Method for producing peptide compound using two or more additives

Abstract

Provided is a method for producing a peptide compound or a salt thereof. The method comprises a step (linking step) for linking an amino group of a first amino acid or peptide and a carboxy group of a second amino acid or peptide, wherein: a condensation agent and two or more additives are used in the linking step; and the pKa of the additives is between 0 and 10.0.

Description

Method for producing peptide compounds using two or more additives

[0001] The present invention relates to a method for producing a peptide compound using two or more additives.

[0002] In recent years, it has been found that the metabolic stability and membrane permeability of peptides can be improved by using unnatural amino acids, such as cyclic peptides (Non-Patent Documents 1 and 2). Among these, cyclic peptide compounds containing N-substituted amino acids have been suggested to be particularly useful for the development of inhibitors of protein-protein interactions due to their drug-like properties, such as metabolic stability and membrane permeability (Patent Document 1 and Non-Patent Document 3).

[0003] As peptide compounds have come to be attracting attention as pharmaceuticals, methods for producing them have also become important (Non-Patent Document 4). Peptide compound synthesis is generally carried out by repeatedly linking the C-terminal carboxyl group of an amino acid to the N-terminal amino group of another amino acid or a peptide, thereby extending the peptide chain. Examples of known methods for extending peptide chains include a method using a phosphate ester-based condensing agent as a condensing agent, a method using HOPO (2-hydroxypyridine-N-oxide) as an additive (Non-Patent Document 5), and a method using Oxyma (ethyl 2-cyano-2-(hydroxyimino)acetate) (Non-Patent Document 6). Another known method uses two additives, HOPO and Oxyma, and a carbodiimide as a condensing agent (Patent Document 2). However, all of these methods involve sequentially subjecting amino acids, one residue at a time, to an amide bond formation reaction.

[0004] Meanwhile, a method for elongating peptide chains, called fragment coupling, in which peptide fragments consisting of multiple amino acid residues are subjected to an amide bond formation reaction, is also known. Fragment coupling has the advantage of increasing the overall yield of the final product, and this advantage becomes even more pronounced as the number of amino acid residues in the desired peptide compound increases. However, under conventional amide bond formation conditions, impurities increase due to factors such as racemization at the α-position of amino acid residues, resulting in a significant decrease in the yield and purity of the target product, making purification more difficult and resulting in increased production time and effort. Furthermore, when the N-terminus or C-terminus is an N-substituted amino acid and serves as the reaction site for the amide bond formation reaction in fragment coupling, reduced reactivity has been an issue (Non-Patent Document 7). Therefore, when synthesizing peptide compounds containing N-substituted amino acids, synthesis methods have been limited to either sequentially subjecting amino acids one by one to the amide bond formation reaction or fragment coupling at residues that do not undergo epimerization.

[0005] International Publication No. WO 2013 / 100132 International Publication No. WO 2023 / 117904

[0006] Acc. Chem. Res., 2008, 41, 1331-1342.Angew. Chem. Int. Ed., 2013, 52, 254-269.Chem. Rev., 2019, 119, 10360-10391.Amino Acids, Peptides and Proteins in Organic Chemistry: Building Blocks, Catalysis and Coupling Chemistry., 2011, 3.Tetrahedron Letters., 2020, 152299.Tetrahedron Letters., 2021, 153462.J. Peptide Res., 2005, 65, 153-166.

[0007] The present invention has been made in view of these circumstances. In one aspect, an object is to establish a novel method for synthesizing peptide compounds. In one aspect, an object is to establish a novel synthesis method suitable for fragment coupling of peptide compounds. In one aspect, an object is to establish a synthesis method in which all amino acid residues constituting a peptide compound maintain high diastereoselectivity even in fragment coupling. In one aspect, an object is to establish a method for synthesizing peptide compounds in high yield even in fragment coupling. In one aspect, an object is to establish a method for synthesizing peptide compounds in high yield by fragment coupling, while preventing racemization of the α-carbon of the carboxy group of the reaction substrate. In one aspect, an object is to establish a synthesis method suitable for fragment coupling of peptide compounds containing N-substituted amino acids at the N-terminus or C-terminus. In one aspect, an object is to establish a synthesis method suitable for fragment coupling of peptide compounds in which the nitrogen atom bonded to the α-carbon of the carboxy group of the reaction substrate is substituted with an alkyl.

[0008] As a result of intensive investigations to solve the above-mentioned problems, the present inventors have found a method for solving at least one of the above-mentioned problems by carrying out an amide bond formation reaction in a reaction system containing a condensing agent and two or more additives. Furthermore, the present inventors have found reaction conditions that can suppress the formation of by-products in the condensation reaction.

[0009] In a non-limiting specific embodiment, the present invention includes the following: [1] A method for producing a peptide compound or a salt thereof, comprising a step of linking an amino group of a first amino acid or peptide with a carboxy group of a second amino acid or peptide via an amide bond (linking step), wherein a condensing agent and two or more additives are used in the linking step, and the pKa of the additives is between 0 and 10.0. [1-1] A method for producing a peptide compound or a salt thereof, comprising a step of linking an amino group of a first amino acid or peptide with a carboxy group of a second amino acid or peptide via an amide bond (linking step), wherein a condensing agent and two or more additives are used in the linking step. [2] The method according to [1] or [1-1], wherein the condensing agent is a phosphorus-based condensing agent. [3] The method according to [1] or [1-1], wherein the phosphorus-based condensing agent is a compound represented by the following formula (1): (In the formula, R １ is C １ -C ６ Alkoxy, C ６ -C １０ Aryloxy, C ６ -C １０ Aryl or diC １ -C ６ alkylamino, R ２ is C １ -C ６ Alkoxy, C ６ -C １０ Aryloxy, C ６ -C １０ Aryl or diC １ -C ６ alkylamino, R ３ is halogen, optionally substituted C ６ -C １０ [4] The method according to [2], wherein R is an aryloxy or an azide. １ is ethoxy, phenyloxy, phenyl, or dimethylamino; R ２ is ethoxy, phenyloxy, phenyl, or dimethylamino; R ３[5] The method according to any one of [2] to [4], wherein the phosphorus-based condensing agent is at least one selected from the group consisting of diphenyl chlorophosphate (DPPC), diethyl chlorophosphate (DEPC), dimethyl chlorophosphate, diisopropyl chlorophosphate, dibenzyl chlorophosphate, diphenylphosphoric acid azide (DPPA), pentafluorophenyl diphenylphosphinate (FDPP), 2-chloro-2-oxo-1,3,2-disoxaphosphorane, dimethylphosphinic acid chloride, diethylphosphinic acid chloride, dicyclohexylphosphinic acid chloride, and diphenylphosphinic acid chloride (PhP(O)Cl). [5-1] The method according to any one of [2] to [5], wherein the phosphorus-based condensing agent is at least one selected from the group consisting of diphenyl chlorophosphate (DPPC), diethyl chlorophosphate (DEPC), diphenylphosphoric acid azide (DPPA), pentafluorophenyl diphenylphosphinate (FDPP), and diphenylphosphinic chloride (PhP(O)Cl). [6] The method according to any one of [2] to [5-1], wherein the phosphorus-based condensing agent is at least one selected from the group consisting of diphenyl chlorophosphate (DPPC) and diethyl chlorophosphate (DEPC). [7] The method according to any one of [1] to [6], wherein the condensing agent is used in an amount of 0.5 to 5.0 molar equivalents relative to the first amino acid or peptide. [8] The method according to any one of [1] to [7], wherein the additive is a nucleophilic species that reacts with the carboxy group to form an activated ester.[8-1] The additive is 2-hydroxypyridine-N-oxide (HOPO), a HOPO derivative, 1-hydroxy-7-azabenzotriazole (HOAt), 1-hydroxybenzotriazole (HOBt), 3,4-dihydro-3-hydroxy-4-oxobenzotriazine (HOOBt), ethyl 1-hydroxy-1H-1,2,3-triazole-4-carboxylate (HOCt), 2,2,3,3,3-pentafluoro-1-propanol (PfpOH), ethyl The method according to any one of [1] to [8], wherein the hydroxyimino compound is two or more selected from the group consisting of 2-cyano-2-(hydroxyimino)acetate (Oxyma), 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6-(1H,3H,5H)-trione (Oxyma-B), 4-nitrophenol, pentafluorophenol, potassium salt of (hydroxyimino)cyanoacetate (K-Oxyma), 4,6-dimethoxy-1,3,5-triazin-2-ol, 2-hydroxypyridine, trimethylsilanol, and 2-hydroxy-5-nitropyridine. [8-2] The method according to any one of [1] to [8-1], wherein the additive is two or more selected from the group consisting of 2-hydroxypyridine-N-oxide (HOPO), a HOPO derivative, 3,4-dihydro-3-hydroxy-4-oxo-benzotriazine (HOOBt), 2,2,3,3,3-pentafluoro-1-propanol (PfpOH), ethyl 2-cyano-2-(hydroxyimino)acetate (Oxyma), 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6-(1H,3H,5H)-trione (Oxyma-B), and pentafluorophenol. [8-3] The method according to [8], [8-1], or [8-2], wherein the additive is two or more. [9] The method according to any one of [1] to [8-3], wherein one of the additives is HOPO or a HOPO derivative. [9-1] The method according to any one of [1] to [8-3], wherein one of the additives is HOPO.[9-2] The method according to any one of [1] to [8-3], wherein one of the additives is HOPO and the other one or more are selected from the group consisting of Oxyma, HOAt, HOOBt, HOCt, PfpOH, Oxyma-B, pentafluorophenol, and K-Oxyma. [9-3] The method according to any one of [1] to [8-3], wherein one of the additives is Oxyma. [9-4] The method according to any one of [1] to [8-3], wherein one of the additives is Oxyma and the other one or more are selected from the group consisting of HOPO, a HOPO derivative, HOOBt, HOCt, Oxyma-B, pentafluorophenol, PfpOH, 4,6-dimethoxy-1,3,5-triazin-2-ol, 2-hydroxypyridine, and 2-hydroxy-5-nitropyridine. [9-5] The method according to any one of [1] to [8-3], wherein one of the additives is Oxyma and the other one or more are selected from the group consisting of HOPO, HOOBt, HOCt, Oxyma-B, and pentafluorophenol. [9-6] The method according to any one of [1] to [8-3], wherein the additives are Oxyma and HOPO. [9-7] The method according to any one of [8-1] to [9], wherein the HOPO derivative is selected from the group consisting of 5-F-HOPO, 5-Cl-HOPO, 5-Br-HOPO, 5-CF3-HOPO, 5-CO2Me-HOPO, and 4-Br-HOPO.

[10] The method according to any one of [1] to [9-7], wherein each of the one or more additives is used in an amount of 0.1 to 5.0 molar equivalents relative to the first amino acid or peptide.

[11] The method according to any one of [1] to

[10] , wherein the second amino acid or peptide is a peptide containing two or more amino acid residues.

[12] The amino group containing a nitrogen atom located at the β-position of the carboxy group of the second amino acid or peptide is represented by the formula: -NR. ５ - (wherein, R ５ is a hydrogen atom, linear C １ -C ６ Alkyl, branched C ３ -C ６ Alkyl, or C ３ -C ８

[13] The method according to any one of [1] to

[11] , wherein the amino group containing a nitrogen atom located at the β-position of the carboxy group of the second amino acid or peptide is represented by the formula: -NR ５ - (wherein, R ５ is a hydrogen atom or a linear C １ -C ４

[14] The method according to any one of [1] to

[12] , wherein the amino group containing a nitrogen atom located at the β-position of the carboxy group of the second amino acid or peptide is represented by the formula: -NR ５ - (wherein, R ５

[15] The method according to any one of [1] to

[14] , wherein the first amino acid or peptide is a peptide containing two or more amino acid residues.

[16] The method according to any one of [1] to

[14] , wherein the amino group of the first amino acid or peptide is represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a hydrogen atom, linear C １ -C ６ Alkyl, branched C ３ -C ６ Alkyl, or C ３ -C ８

[17] The method according to any one of [1] to

[15] , wherein the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a hydrogen atom or a linear C １ -C ４

[18] The method according to any one of [1] to

[16] , wherein the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７

[19] The method according to any one of [1] to

[17] , wherein the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７

[20] The method according to any one of [1] to

[18] , wherein the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７

[21] The method according to any one of [1] to

[19] , wherein the α-carbon of the carboxy group of the second amino acid or peptide is an amino group represented by the formula: -CR ８ R ９ - (wherein, R ８ and R ９ are the same or different and represent a hydrogen atom, a linear C １ -C ４ Alkyl, optionally substituted branched C ３ -C ６ Alkyl, optionally substituted phenyl C １ -C ２ Alkyl or optionally substituted 5- to 6-membered heteroaryl C １ -C ２

[22] The method according to any one of [1] to

[20] , wherein the α-carbon of the carboxy group of the second amino acid or peptide is represented by the formula: -CR ８ R ９ - (wherein, R ８ and R ９ are the same or different and represent a hydrogen atom, a linear C １ -C ３

[23] The method according to any one of [1] to

[21] , wherein the α-carbon of the carboxy group of the second amino acid or peptide is represented by the formula: -CR ８ R ９ - (wherein, R ８ is a hydrogen atom, and R ９is a hydrogen atom, methyl, benzyl, or p-fluorobenzyl).

[24] The method of any of [1] to

[23] , wherein the carboxy group of the first amino acid or peptide is protected.

[25] The method of any of [1] to

[24] , wherein the amino group of the second amino acid or peptide is protected.

[26] The method of any of [1] to

[25] , wherein a base is used in the linking step.

[27] The method of

[26] , wherein the pKa of the conjugate acid of the base used in the linking step is between 0 and 15.0, more preferably between 3 and 13.0, and even more preferably between 5 and 11.5. [27-1] The method of any of [1] to

[27] , wherein the pKa is an actually measured value as the pKa when water at 25°C is used as the solvent.

[28] The method of

[26] or

[27] , wherein the base used in the linking step is an organic base. [28-1] The method according to

[28] , wherein the organic base used in the linking step is at least one selected from the group consisting of dicyclohexylmethylamine, diisopropylethylamine, triethylamine, 1-methylpiperidine, N-methylmorpholine, 4-N,N-dimethylaminopyridine, 2,6-lutidine, 2,4,6-collidine, N-methylimidazole, 1,8-diazabicyclo[5.4.0]-7-undecene, 1,5-diazabicyclo[4.3.0]-5-nonene, 1,1,3,3-tetramethylguanidine, 2-tert-butyl-1,1,3,3-tetramethylguanidine, and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. [28-2] The method according to

[28] or [28-1], wherein the organic base used in the linking step is at least one selected from the group consisting of dicyclohexylmethylamine, diisopropylethylamine, triethylamine, 1-methylpiperidine, and 2-tert-butyl-1,1,3,3-tetramethylguanidine.

[29] The method according to

[26] or

[27] , wherein the base used in the linking step is an inorganic base, preferably an alkali metal carbonate or an alkali metal phosphate. [29-1] The method according to

[29] , wherein the inorganic base used in the linking step is potassium carbonate or potassium phosphate.[29-2] The method of any one of

[28] to [29-1], wherein the organic base or inorganic base used in the linking step is used in an amount of 1.1 to 10.0 molar equivalents, preferably 2.0 to 9.0 molar equivalents, and more preferably 3.0 to 8.0 molar equivalents, relative to the first amino acid or peptide.

[30] The method of any one of [1] to

[29] , wherein the linking step is carried out by liquid phase synthesis.

[31] The method of

[30] , wherein the liquid phase synthesis is carried out in an organic solvent.

[32] The method of

[31] , wherein the organic solvent used in the linking step is at least one selected from the group consisting of acetonitrile, isopropyl acetate, ethyl acetate, butyl acetate, methyl t-butyl ether, diethyl ether, dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, α,α,α-trifluorotoluene, toluene, hexane, and cyclopentyl methyl ether, or a mixed solvent thereof.

[33] The method according to

[32] , wherein the organic solvent used in the linking step is at least one selected from the group consisting of acetonitrile, isopropyl acetate, methyl t-butyl ether, dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, α,α,α-trifluorotoluene, toluene, and cyclopentyl methyl ether, or a mixed solvent thereof. [33-1] The method according to

[32] or

[33] , wherein the organic solvent used in the linking step is at least one selected from the group consisting of isopropyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, α,α,α-trifluorotoluene, and toluene, or a mixed solvent thereof. [33-2] The method according to any one of

[32] to [33-1], wherein the organic solvent used in the linking step is at least one selected from the group consisting of 2-methyltetrahydrofuran, α,α,α-trifluorotoluene, and toluene, or a mixed solvent thereof. [33-3] The method according to any one of

[32] to [33-2], wherein the organic solvent used in the linking step is used at 50 to 100 mg / mL relative to the first amino acid or peptide.

[34] The method of any of [1] to

[33] , further comprising a deprotection step.

[35] The method of any of [1] to

[34] , wherein the linking step is repeated two or more times.

[36] The method of any of [1] to

[35] , wherein the peptide compound or a salt thereof produced contains 8 to 20 amino acid residues.

[37] The method of any of [1] to

[36] , wherein the peptide compound or a salt thereof produced contains 11 to 14 amino acid residues.

[38] The method of any of [1] to

[37] , wherein the peptide compound produced contains at least one unnatural amino acid residue.

[39] The method of any of [1] to

[38] , wherein the peptide compound produced contains at least four unnatural amino acid residues.

[40] The method of any of [1] to

[39] , wherein the peptide compound produced contains at least five unnatural amino acid residues.

[41] The method of any of

[38] to

[40] , wherein the unnatural amino acid residue is an N-methyl amino acid residue.

[42] The method of any one of [1] to

[41] , wherein the produced peptide compound or a salt thereof comprises a cyclic portion composed of four or more amino acid residues, and the cyclic portion comprises 1 to 7 amide bonds linking the amino group of a first amino acid or peptide with the carboxy group of a second amino acid or peptide.

[43] The method of any one of [1] to

[42] , wherein the method is carried out using a flow reactor.

[44] The peptide compound or a salt thereof produced by the method of any one of [1] to

[43] .

[45] A pharmaceutical composition comprising the peptide compound or a salt thereof produced by the method of any one of [1] to

[43] .

[46] A linking agent for use in a step of linking the amino group of a first amino acid or peptide with the carboxy group of a second amino acid or peptide via an amide bond, the linking agent comprising a condensing agent and two or more additives.

[47] The amino group of the first amino acid or peptide is represented by the formula: -NR. ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a hydrogen atom, linear C １ -C ６ Alkyl, branched C ３ -C ６ Alkyl, or C ３ -C８ the α carbon of the carboxy group of the second amino acid or peptide is represented by the formula: -CR ８ R ９ - (wherein, R ８ and R ９ are the same or different and represent a hydrogen atom, a linear C １ -C ４ Alkyl, optionally substituted branched C ３ -C ６ Alkyl, optionally substituted phenyl C １ -C ２ Alkyl or optionally substituted 5- to 6-membered heteroaryl C １ -C ２

[48] ​​The linking agent according to

[47] , wherein the amino group of the first amino acid or peptide is represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a hydrogen atom or a linear C １ -C ４

[49] The linking agent according to

[47] , wherein the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７

[50] The linking agent according to

[47] or

[48] , wherein the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７

[51] The linking agent according to any one of

[47] to

[49] , wherein the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７

[52] The linking agent according to any one of

[47] to

[50] , wherein the α-carbon of the carboxy group of the second amino acid or peptide is an amino group represented by the formula: -CR ８ R ９ - (wherein, R ８ and R ９ are the same or different and represent a hydrogen atom, a linear C １ -C ３

[53] The linking agent according to any one of

[47] to

[51] , wherein the α-carbon of the carboxy group of the second amino acid or peptide is represented by the formula: -CR ８ R ９ - (wherein, R ８ is a hydrogen atom, and R ９ is a hydrogen atom, methyl, benzyl, or p-fluorobenzyl). In the above numbering, the numbers cited in the dependent claims include their subnumbers unless otherwise specified. For example, [1] cited in the dependent claims indicates that it includes not only [1] but also its subnumber [1-1]. The same applies to other numbering schemes.

[0010] According to the present invention, peptide compounds can be synthesized with high diastereoselectivity and in high yield even by fragment coupling.

[0011] The abbreviations used in this specification are listed below. 2-MeTHF: 2-methyltetrahydrofuran IPAC: Isopropyl acetate EtOAc: Ethyl acetate MeCN: Acetonitrile THF: Tetrahydrofuran MeOH: Methanol MTBE: Methyl tert-butyl ether MTHP: 4-methyltetrahydropyran CPME: Cyclopentyl methyl ether DCM: Dichloromethane DMF: N,N-dimethylformamide DMA: N,N-dimethylacetamide DMI: 1,3-dimethyl-2-imidazolidinone NMP: N-methylpyrrolidone DMSO: Methyl sulfoxide DBN: 1,5-diazabicyclo[4.3.0]-5-nonene DBU: 1,8-diazabicyclo[5.4.0]-7-undecene DIPEA: N,N-Diisopropylethylamine TEA: Triethylamine NMM: N-methylmorpholine NMI: N-methylimidazole Cy2NMe: Dicyclohexylmethylamine DMAP: 4-N,N-dimethylaminopyridine T3P: Propylphosphonic anhydride HATU: O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate or 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate COMU: (1-cyano-2-ethoxy-2-oxoethylideneaminooxy)dimethylaminomorpholinocarbenium hexafluorophosphate or ethyl 2-cyano-2-((dimethylimino)(morpholino)methyloxyimino)acetate hexafluorophosphate DEPC: diethyl chlorophosphate DPPC: diphenyl chlorophosphate DPPA: diphenylphosphoric acid azide FDPP: pentafluorophenyl diphenylphosphinate Ph2P(O)Cl: diphenylphosphinic chloride HOPO: 1-hydroxypyridin-2-one 3-Cl-5-CF3-HOPO: 3-chloro-1-hydroxy-5-(trifluoromethyl)pyridin-2-one 5-F-HOPO: 5-fluoro-1-hydroxypyridin-2-one 5-Cl-HOPO: 5-chloro-1-hydroxypyridin-2-one 5-Br-HOPO: 5-bromo-1-hydroxypyridin-2-one 5-CF3-HOPO: 1-hydroxy-5-(trifluoromethyl)pyridin-2-one 5-CO2Me-HOPO: 1-hydroxy-5-(methoxycarbonyl)pyridin-2-one 4-Br-HOPO: 4-bromo-1-hydroxypyridin-2-one H3PO4: phosphoric acid NaCl: sodium chloride Na2CO3: sodium carbonate K2CO3: potassium carbonate NaHCO3: sodium bicarbonate NaHSO4: sodium hydrogen sulfate Na2SO4: sodium sulfate H2O: water TFA: trifluoroacetic acid HMDS: hexamethyldisilazane TMSOTf: trimethylsilyl trifluoromethanesulfonate Pd / C: palladium on carbon HOAt: 1-hydroxy-7-azabenzotriazole (HOAt) HOBtv: 1-hydroxybenzotriazole HOOBt: 3-hydroxy-1,2,3-benzotriazin-4-one HOCt: Ethyl 1-hydroxy-1H-1,2,3-triazole-4-carboxylate HOSu: N-hydroxysuccinimide HONB: N-hydroxy-5-norbornene-2,3-dicarboximide HOPht: N-hydroxyphthalimide EDC·HCl: 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride DIC: N,N'-Diisopropylcarbodiimide CDI: 1,1'-Carbonyldiimidazole MNBA: 2-Methyl-6-nitrobenzoic anhydride TCFH: Chloro-N,N,N',N'-tetramethylformamidinium hexafluorophosphate DEPBT: 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3H)-one TDBTU: O-(3,4-Dihydro-4-oxo-1,2,3-benzotriazin-3-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate DPPA: Diphenylphosphoryl azide FDPP: Pentafluorophenyl diphenylphosphinate p-TsCl: para-Toluenesulfonyl chloride HOTU: O-[(Ethoxycarbonyl)cyanomethylenamino]-N,N,N',N'-tetramethyluronium hexafluorophosphate Oxyma: Ethyl 2-cyano-2-(hydroxyimino)acetate Oxyma-B: 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6-(1H,3H,5H)-trione K-Oxyma: Potassium salt of (hydroxyimino)cyanoacetate PfpOH: 2,2,3,3,3-Pentafluoro-1-propanol TMG: 1,1,3,3-Tetramethylguanidine MTBD: 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene BTMB: 2-tert-butyl-1,1,3,3-tetramethylguanidine

[0012] Definitions of functional groups, etc. (The terms exemplified below are merely examples and are not intended to be particularly limiting and are commonly understood by those skilled in the art.)

[0013] As used herein, "halogen atom" is exemplified by fluorine, chlorine, bromine, and iodine. In addition, in the specification, F represents fluorine, Cl represents chlorine, Br represents bromine, and I represents iodine. Examples of halogen include fluorine, chlorine, and bromine, and preferred examples are fluorine and chlorine.

[0014] In this specification, "alkyl" refers to a linear or branched monovalent saturated hydrocarbon group derived from an aliphatic saturated hydrocarbon by removing any one hydrogen atom, and does not contain heteroatoms (atoms other than carbon and hydrogen atoms) or unsaturated carbon-carbon bonds in the skeleton, but has a hydrocarbyl or hydrocarbon group structure subset containing hydrogen atoms and carbon atoms. Alkyl includes not only linear ones but also branched ones. Specific examples of alkyl include alkyls having 1 to 20 carbon atoms (C １ -C ２０ , hereinafter referred to as “C ｐ -C ｑ " means that the number of carbon atoms is p to q), and preferably C １ -C １０ Alkyl, more preferably C １ -C ６ Specific examples of alkyl include methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, isobutyl (2-methylpropyl), n-pentyl, s-pentyl (1-methylbutyl), t-pentyl (1,1-dimethylpropyl), neopentyl (2,2-dimethylpropyl), isopentyl (3-methylbutyl), 3-pentyl (1-ethylpropyl), 1,2-dimethylpropyl, 2-methylbutyl, n-hexyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1,1,2,2-tetramethylpropyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, and 2-ethylbutyl. １ -C ６ Specific examples of alkyl include methyl, ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl. １ -C ３ Specific examples of alkyl include methyl, ethyl, and n-propyl. ３ -C ６Specific examples of alkyl include i-propyl, s-butyl, t-butyl, isobutyl (2-methylpropyl), s-pentyl (1-methylbutyl), t-pentyl (1,1-dimethylpropyl), neopentyl (2,2-dimethylpropyl), isopentyl (3-methylbutyl), 3-pentyl (1-ethylpropyl), 1,2-dimethylpropyl, 2-methylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1,1,2,2-tetramethylpropyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, and the like.

[0015] As used herein, "alkenyl" refers to a straight-chain or branched-chain monovalent unsaturated hydrocarbon group having one or more carbon-carbon double bonds (bonds between two adjacent sp2 carbon atoms). Depending on the configuration of the atom or atomic group bonded to the sp2 carbon atom, the geometry of the double bond can be entgegen (E) or zusammen (Z), cis or trans. Examples of alkenyl include C ２ -C １０ alkenyl, C ２ -C ８ Alkenyl is preferred, C ２ -C ７ Alkenyl is more preferred, C ２ -C ６ Alkenyl is most preferred, and examples thereof include ethenyl (vinyl), 1-propenyl, 2-propenyl (allyl), isopropenyl, 1-butenyl, 2-butenyl (including cis and trans), 3-butenyl, pentenyl, and hexenyl.

[0016] As used herein, the term "alkynyl" refers to a linear or branched monovalent unsaturated hydrocarbon group having one or more carbon-carbon triple bonds (bonds between two adjacent sp carbon atoms). Examples of alkynyl include C ２ -C １０ alkynyl, C ２ -C ８ Alkynyl is preferred, C ２ -C ７Alkynyl is more preferred, C ２ -C ６ Alkynyl is most preferred. Specific examples of alkynyl include ethynyl, 1-propynyl, propargyl (2-propynyl), 1-butynyl, 2-butynyl, 3-butynyl, pentynyl, and hexynyl.

[0017] As used herein, the term "cycloalkyl" refers to a saturated or partially saturated cyclic monovalent non-aromatic hydrocarbon ring group (alicyclic ring group). The carbon atoms constituting the ring may be oxidized to include a carbonyl. The cycloalkyl may be selected from the group consisting of a monocyclic ring, a fused ring, and a spiro ring. As used herein, a cycloalkyl containing a monocyclic ring is referred to as a monocyclic cycloalkyl, i.e., a monocyclic alicyclic ring group; a cycloalkyl containing a fused ring is referred to as a fused ring cycloalkyl, i.e., a fused ring alicyclic ring group; and a cycloalkyl containing a spiro ring is referred to as a spirocyclic cycloalkyl, i.e., a spirocyclic alicyclic ring group. A cycloalkyl may form a fused ring with a saturated alicyclic ring such as a cyclopentane ring or a cyclohexane ring, an unsaturated alicyclic ring such as a cyclopentene ring or a cyclohexene ring, or an aromatic hydrocarbon ring such as a benzene ring or a naphthalene ring. A cycloalkyl may form a spiro ring with a saturated alicyclic ring such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, or a cyclohexane ring. Examples of cycloalkyl include C ３ -C １０ is cycloalkyl, and C ３ -C ８ Cycloalkyl is preferred, C ３ -C ７ Cycloalkyl is more preferred, C ３ -C ６ Cycloalkyl is most preferred. Specific examples of cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, bicyclo[2.2.1]heptyl, spiro[3.3]heptyl, cyclohexenyl, and the like.

[0018] In the present specification, the term "aryl" refers to a monovalent aromatic hydrocarbon ring group consisting of a single ring or fused rings that exhibits monovalent aromaticity. In the present specification, an aryl consisting of a single ring is referred to as a monocyclic aryl, and an aryl consisting of a fused ring is referred to as a fused ring aryl. Examples of aryl include C ６ -C １４ aryl, C ６ Aryl, C １０ Aryl and C １４ Aryl is preferred, C ６ Aryl and C １０ Aryl is more preferred, C ６ Aryl is most preferred. Specific examples of aryl include phenyl, 1-naphthyl, 2-naphthyl, tolyl, and xylyl.

[0019] As used herein, the term "heterocyclyl" refers to a heterocyclic group containing, in addition to carbon atoms, preferably 1 to 5, and more preferably 1 to 3, heteroatoms selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms as ring-constituting atoms, and which may have a double and / or triple bond within the ring. A carbon atom within the heterocyclyl ring may be oxidized to form a carbonyl. As used herein, a heterocyclyl containing a single ring is referred to as a monocyclic heterocyclyl, a heterocyclyl containing a fused ring is referred to as a fused-ring heterocyclyl, and a heterocyclyl containing a spiro ring is referred to as a spirocyclic heterocyclyl. A heterocyclyl may form a fused ring or a spiro ring with, for example, a saturated alicyclic ring such as a cyclopentane ring or a cyclohexane ring, or a saturated heterocycle such as a tetrahydropyran ring, a dioxane ring, or a pyrrolidine ring. The number of atoms constituting the heterocyclyl ring is, for example, 3 to 14 (3- to 14-membered heterocyclyl), preferably 3 to 12 (3- to 12-membered heterocyclyl), more preferably 3 to 10 (3- to 10-membered heterocyclyl), and most preferably 4 to 7 (4- to 7-membered heterocyclyl). Specific examples of heterocyclyl include azetidinyl, oxiranyl, oxetanyl, thietanyl, tetrahydrofuranyl, pyrrolidinyl, pyrazolidinyl, imidazolidinyl, oxazolidinyl, isoxazolidinyl, thiazolidinyl, isothiazolidinyl, thiadiazolidinyl, oxazolidonyl, dioxolanyl, tetrahydropyranyl, morpholinyl, thiomorpholinyl, 4-oxopyrrolidinyl, piperidinyl, 4-oxopiperidinyl, piperazinyl, dioxanyl, and rings in which one or more single bonds in these saturated heterocycles are replaced with double bonds or triple bonds.

[0020] As used herein, the term "heteroaryl" refers to a monovalent aromatic heterocyclic group that contains at least one heteroatom in addition to carbon atoms and is composed of a monocyclic or fused ring that exhibits aromaticity. In this specification, a heteroaryl composed of a single ring is referred to as a monocyclic heteroaryl, and a heteroaryl composed of a fused ring is referred to as a fused-ring heteroaryl. The number of atoms constituting the heteroaryl ring is, for example, 5 to 14 (5- to 14-membered heteroaryl), preferably 5 to 13 (5- to 13-membered heteroaryl), more preferably 5 to 10 (5- to 10-membered heteroaryl), and most preferably 5 to 7 (5- to 7-membered heteroaryl). Specific examples of heteroaryl include 5-membered heteroaryls such as furyl, thienyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, oxazolyl, triazolyl, and tetrazolyl; 6-membered heteroaryls such as pyridyl, pyrimidyl, pyridazinyl, pyrazinyl, and triazinyl; 9-membered heteroaryls such as benzofuranyl, benzothienyl, benzothiazolyl, benzimidazolyl, benzotriazolyl, indolyl, indazolyl, and pyrazolopyridyl; and 10-membered heteroaryls such as quinolyl, isoquinolyl, cinnolinyl, quinazolinyl, and quinoxalinyl.

[0021] As used herein, "alkoxy" refers to a group in which an "alkyl" as defined herein is bonded to an oxygen atom (-OR (R is alkyl)). Examples of alkoxy include C １ -C ２０ Alkoxy, C １ -C １０ Alkoxy is preferred, C １ -C ８ Alkoxy is more preferred, C １ -C ６ Alkoxy is most preferred, and specific examples of alkoxy include methoxy, ethoxy, 1-propoxy, 2-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, pentyloxy, and 3-methylbutoxy.

[0022] As used herein, "alkenyloxy" refers to a group in which an "alkenyl" as defined herein is bonded to an oxygen atom (-OR (R is alkenyl)). Examples of alkenyloxy include C２ -C １０ alkenyloxy, C ２ -C ８ Alkenyloxy is preferred, C ２ -C ７ Alkenyloxy is more preferred, C ２ -C ６ Alkenyloxy is most preferred. Specific examples of alkenyloxy include ethenyl(vinyl)oxy, 1-propenyloxy, 2-propenyl(allyl)oxy, isopropenyloxy, 1-butenyloxy, 2-cis-butenyloxy, 2-trans-butenyloxy, 3-butenyloxy, pentenyloxy, and hexenyloxy.

[0023] As used herein, "cycloalkoxy" refers to a group in which a "cycloalkyl" as defined herein is bonded to an oxygen atom (-OR (R is cycloalkyl)). Examples of cycloalkoxy include C ３ -C １０ cycloalkoxy, C ３ -C ８ Cycloalkoxy is preferred, C ３ -C ７ Cycloalkoxy is more preferred, C ３ -C ６ Cycloalkoxy is most preferred. Specific examples of cycloalkoxy include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and the like.

[0024] As used herein, "aryloxy" refers to a group in which an "aryl" as defined herein is bonded to an oxygen atom (-OAr (Ar is aryl)). Examples of aryloxy include C ６ -C １４ aryloxy, C ６ Aryloxy, C １０ Aryloxy and C １４ Aryloxy is preferred, C ６ Aryloxy and C １０ Aryloxy is more preferred, C ６Aryloxy is most preferred. Specific examples of aryloxy include phenoxy, 1-naphthyloxy, 2-naphthyloxy, tolyloxy, and xylyloxy.

[0025] As used herein, "amino" refers to -NRR', where N represents a nitrogen atom, and R and R' are each independently selected from the group consisting of a hydrogen atom, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl, or R and R' are groups that form a ring together with the nitrogen atom to which they are attached. ２ , Mono C １ -C ６ Alkylamino, DiC １ -C ６ Examples thereof include alkylamino and 4- to 8-membered cyclic amino.

[0026] As used herein, "monoalkylamino" refers to a group in which R is a hydrogen atom and R' is an "alkyl" in the "amino (-NRR')" defined herein. Examples of monoalkylamino include monoC １ -C ２０ alkylamino, mono C １ -C １５ Alkylamino is preferred, mono C １ -C １０ Alkylamino is more preferred, and mono C １ -C ６ Alkylamino is most preferred. Specific examples of monoalkylamino include methylamino, ethylamino, n-propylamino, i-propylamino, n-butylamino, s-butylamino, and t-butylamino.

[0027] As used herein, "dialkylamino" refers to a group in which R and R' are each independently "alkyl" within the "amino (-NRR')" defined herein. Examples of dialkylamino include diC １ -C ２０ alkylamino, diC １ -C １５ Alkylamino is preferred, diC １ -C１０ Alkylamino is more preferred, diC １ -C ６ Alkylamino is most preferred. Specific examples of dialkylamino include dimethylamino, diethylamino, and methylethylamino.

[0028] As used herein, "cyclic amino" refers to the "amino (-NRR')" defined herein, in which R and R' form a ring together with the nitrogen atom to which they are bonded. Examples of cyclic amino include 3- to 14-membered cyclic amino, preferably 3- to 12-membered cyclic amino, more preferably 3- to 10-membered cyclic amino, and most preferably 4- to 7-membered cyclic amino. Specific examples of cyclic amino include 1-azetidyl, 1-pyrrolidyl, 1-piperidyl, 1-piperazyl, 4-morpholinyl, 3-oxazolidyl, 1,1-dioxidethiomorpholinyl-4-yl, 3-oxa-8-azabicyclo[3.2.1]octan-8-yl, and the like.

[0029] As used herein, the term "protected amino" refers to an amino group protected with any protecting group. Specific examples of the protected amino include amino protected with a protecting group such as Boc (tert-butoxycarbonyl), Fmoc (9-fluorenylmethyloxycarbonyl), Cbz (benzyloxycarbonyl), Troc (2,2,2-trichloroethoxycarbonyl), Alloc (allyloxycarbonyl), Teoc (2-(trimethylsilyl)ethoxycarbonyl), or trifluoroacetyl.

[0030] As used herein, "aminocarbonyl" refers to a group in which an "amino" as defined herein is bonded to the carbon atom of a carbonyl. It may also be called an amide. Examples of aminocarbonyl include -CONH ２ , Mono C １ -C ６ Alkylaminocarbonyl, diC １ -C ６ alkylaminocarbonyl, and 4- to 8-membered cyclic aminocarbonyl. Specific examples of aminocarbonyl include -CONH ２methylaminocarbonyl, ethylaminocarbonyl, dimethylaminocarbonyl, diethylaminocarbonyl, 1-azetidinylcarbonyl, 1-pyrrolidinylcarbonyl, 1-piperidinylcarbonyl, 1-piperazinylcarbonyl, 4-morpholinylcarbonyl, 3-oxazolidinylcarbonyl and the like.

[0031] As used herein, "alkenyloxycarbonyl" refers to a carbonyl group to which "alkenyloxy" as defined herein is bonded. Examples of alkenyloxycarbonyl include C ２ -C １０ alkenyloxycarbonyl, C ２ -C ８ Alkenyloxycarbonyl is preferred, C ２ -C ７ Alkenyloxycarbonyl is more preferred, C ２ -C ６ Alkenyloxycarbonyl is most preferred. Specific examples of alkenyloxycarbonyl include ethenyl(vinyl)oxycarbonyl, 1-propenyloxycarbonyl, 2-propenyl(allyl)oxycarbonyl, isopropenyloxycarbonyl, 1-butenyloxycarbonyl, 2-cis-butenyloxycarbonyl, 2-trans-butenyloxycarbonyl, 3-butenyloxycarbonyl, pentenyloxycarbonyl, and hexenyloxycarbonyl.

[0032] As used herein, "alkylsulfonyl" refers to a sulfonyl group to which an "alkyl" as defined herein is bonded. Examples of alkylsulfonyl include C １ -C ２０ alkylsulfonyl, C １ -C １０ Alkylsulfonyl is preferred, C １ -C ８ Alkylsulfonyl is more preferred, C １ -C ６Specific examples of alkylsulfonyl include methylsulfonyl, ethylsulfonyl, 1-propylsulfonyl, 2-propylsulfonyl, n-butylsulfonyl, i-butylsulfonyl, s-butylsulfonyl, t-butylsulfonyl, pentylsulfonyl, and 3-methylbutylsulfonyl.

[0033] As used herein, "hydroxyalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with a hydroxy group. Preferred hydroxyalkyl groups are those in which one hydrogen atom of an alkyl is substituted with a hydroxy group. Examples of hydroxyalkyl include hydroxy C １ -C ２０ alkyl, and hydroxy C １ -C １０ Alkyl is preferred, and hydroxy C １ -C ８ Alkyl is more preferred, and hydroxy C １ -C ６ Alkyl is most preferred. Specific examples of hydroxyalkyl include hydroxyethyl, 1-hydroxyethyl, 2-hydroxyethyl, 2-hydroxy-2-methylpropyl, and 5-hydroxypentyl.

[0034] As used herein, "haloalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with halogen. As the haloalkyl, a group in which 1 to 6 hydrogen atoms, which are allowed to be substituted, are substituted with halogen is preferred. Examples of haloalkyl include haloC １ -C ２０ alkyl and haloC １ -C １０ Alkyl is preferred, haloC １ -C ８ Alkyl is more preferred, haloC １ -C ６ Alkyl is most preferred. HaloC １ -C ６The alkyl is, for example, a group in which 1 to 6 hydrogen atoms, which are permissible for substitution, are substituted with fluorine, preferably a group in which 1 to 5 hydrogen atoms are substituted with fluorine, more preferably a group in which 1 to 4 hydrogen atoms are substituted with fluorine, and most preferably a group in which 1 to 3 hydrogen atoms are substituted with fluorine. Specific examples of haloalkyl include difluoromethyl, trifluoromethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3,3-difluoropropyl, 4,4-difluorobutyl, 5,5-difluoropentyl, etc.

[0035] As used herein, "cyanoalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with cyano. Preferred cyanoalkyl groups include alkyl groups in which one hydrogen atom is substituted with cyano. Examples of cyanoalkyl include cyanoC １ -C ２０ alkyl and cyano C １ -C １０ Alkyl is preferred, and cyano C １ -C ８ Alkyl is more preferred, and cyano C １ -C ６ Alkyl is most preferred. Specific examples of cyanoalkyl include cyanomethyl and 2-cyanoethyl.

[0036] As used herein, "aminoalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with "amino". As the aminoalkyl, a group in which one hydrogen atom of an alkyl is substituted with amino is preferred. Examples of aminoalkyl include amino C １ -C ２０ alkyl and amino C １ -C １０ Alkyl is preferred, and amino C １ -C ８ Alkyl is more preferred, and amino C １ -C ６Alkyl is most preferred. Specific examples of aminoalkyl include aminomethyl, aminoethyl, 4-aminobutyl, methylaminomethyl, dimethylaminomethyl, methylaminoethyl, and dimethylaminoethyl.

[0037] As used herein, "carboxyalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with "carboxy". Preferred carboxyalkyl groups are those in which one hydrogen atom of an alkyl is substituted with carboxy. Examples of carboxyalkyl include carboxyC １ -C ２０ alkyl and carboxy C １ -C １５ Alkyl is preferred, and carboxy C １ -C １０ Alkyl is more preferred, and carboxy C １ -C ６ Alkyl is most preferred. Specific examples of carboxyalkyl include carboxymethyl and carboxyethyl.

[0038] As used herein, "alkenyloxycarbonylalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with "alkenyloxycarbonyl". As the alkenyloxycarbonylalkyl, a group in which one hydrogen atom of an alkyl is substituted with alkenyloxycarbonyl is preferred. Examples of alkenyloxycarbonylalkyl include C ２ -C １０ Alkenyloxycarbonyl C １ -C ６ alkyl, C ２ -C ８ Alkenyloxycarbonyl C １ -C ６ Alkyl is preferred, C ２ -C ７ Alkenyloxycarbonyl C １ -C ６ Alkyl is more preferred, C ２ -C ６ Alkenyloxycarbonyl C １ -C ６Specific examples of alkenyloxycarbonylalkyl include ethenyl(vinyl)oxycarbonylmethyl, 1-propenyloxycarbonylethyl, 2-propenyl(allyl)oxycarbonylmethyl, isopropenyloxycarbonylmethyl, 1-butenyloxycarbonylethyl, 2-cis-butenyloxycarbonylmethyl (including cis and trans), 2-trans-butenyloxycarbonylmethyl, 3-butenyloxycarbonylethyl, pentenyloxycarbonylmethyl, and hexenyloxycarbonylethyl.

[0039] As used herein, "alkoxyalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with "alkoxy". Preferred alkoxyalkyl groups are those in which one hydrogen atom of an alkyl is substituted with alkoxy. Examples of alkoxyalkyl include C １ -C ６ Alkoxy C １ -C ２０ alkyl, C １ -C ６ Alkoxy C １ -C １５ Alkyl is preferred, C １ -C ６ Alkoxy C １ -C １０ Alkyl is more preferred, C １ -C ６ Alkoxy C １ -C ６ Specific examples of alkoxyalkyl include methoxymethyl, ethoxymethyl, 1-propoxymethyl, 2-propoxymethyl, n-butoxymethyl, i-butoxymethyl, s-butoxymethyl, t-butoxymethyl, pentyloxymethyl, 3-methylbutoxymethyl, 1-methoxyethyl, 2-methoxyethyl, and 2-ethoxyethyl.

[0040] As used herein, "cycloalkylalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with a "cycloalkyl". As the cycloalkylalkyl, a group in which one hydrogen atom of an alkyl is substituted with a cycloalkyl is preferred. Examples of cycloalkylalkyl include C ３ -C １０ Cycloalkyl C １ -C ２０ alkyl, C ３ -C １０ Cycloalkyl C １ -C ６ Alkyl is preferred, C ３ -C ８ Cycloalkyl C １ -C ６ Alkyl is more preferred, C ３ -C ６ Cycloalkyl C １ -C ２ Alkyl is most preferred. Specific examples of cycloalkylalkyl include cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl, cyclohexylmethyl, cyclohexylethyl, and cyclohexylpropyl.

[0041] As used herein, "cycloalkoxyalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with "cycloalkoxy". As the cycloalkoxyalkyl, a group in which one hydrogen atom of an alkyl is substituted with cycloalkoxy is preferred. Examples of cycloalkoxyalkyl include C ３ -C １０ Cycloalkoxy C １ -C ６ alkyl, C ３ -C ８ Cycloalkoxy C １ -C ６ Alkyl is preferred, C ３ -C ７ Cycloalkoxy C １ -C ６ Alkyl is more preferred, C ３ -C ６ Cycloalkoxy C １ -C ６Alkyl is most preferred. Specific examples of cycloalkoxyalkyl include cyclopropoxymethyl, cyclobutoxymethyl, cyclopentyloxymethyl, and the like.

[0042] As used herein, "heterocyclylalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with a "heterocyclyl". Preferred heterocyclylalkyl groups are those in which one hydrogen atom of an alkyl is substituted with a heterocyclyl. Examples of heterocyclylalkyl include 3- to 14-membered heterocyclyl C １ -C ６ alkyl and 3- to 12-membered heterocyclyl C １ -C ６ Alkyl is preferred, and 3- to 10-membered heterocyclyl C １ -C ４ Alkyl is more preferred, and 4- to 7-membered heterocyclyl C １ -C ３ Specific examples of heterocyclylalkyl include azetidin-1-ylmethyl, oxetan-3-ylmethyl, 2-(tetrahydrofuran-3-yl)ethyl, (1-methylpyrrolidin-3-yl)methyl, 2-morpholinoethyl, 3-(1-piperidinyl)propyl, and 3-(4-methylpiperazin-1-yl)propyl.

[0043] As used herein, "alkylsulfonylalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with "alkylsulfonyl". As the alkylsulfonylalkyl, a group in which one hydrogen atom of an alkyl is substituted with alkylsulfonyl is preferred. For example, C １ -C ２０ Alkylsulfonyl C １ -C ４ alkyl, C １ -C １０ Alkylsulfonyl C １ -C ４ Alkyl is preferred, C １ -C ８ Alkylsulfonyl C １ -C ４ Alkyl is more preferred, C １ -C６ Alkylsulfonyl C １ -C ４ Specific examples of alkylsulfonylalkyl include methylsulfonylmethyl, methylsulfonylpropyl, methylsulfonylbutyl, ethylsulfonylethyl, 1-propylsulfonylmethyl, 2-propylsulfonylethyl, n-butylsulfonylpropyl, i-butylsulfonylmethyl, s-butylsulfonylmethyl, t-butylsulfonylmethyl, pentylsulfonylmethyl, and 3-methylbutylsulfonylmethyl.

[0044] As used herein, "aminocarbonylalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with an "aminocarbonyl" as defined herein. As the aminocarbonylalkyl, a group in which one hydrogen atom of an alkyl is substituted with an aminocarbonyl is preferred. As the aminocarbonylalkyl, for example, aminocarbonyl C １ -C １０ alkyl, and aminocarbonyl C １ -C ６ Alkyl is preferred, and aminocarbonyl C １ -C ４ Alkyl is more preferred, and aminocarbonyl C １ -C ２ Alkyl is most preferred. Specific examples of aminocarbonylalkyl include -CH ２ CONH ２ , methylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethylaminocarbonylpropyl, diethylaminocarbonylmethyl, 1-azetidinylcarbonylmethyl, 1-pyrrolidinylcarbonylethyl, 1-piperidinylcarbonylpropyl, 1-piperazinylcarbonylbutyl, 4-morpholinylcarbonylmethyl, 3-oxazolidinylcarbonylethyl and the like.

[0045] As used herein, "aryloxyalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with an "aryloxy" as defined herein. ６ -C１０ Aryloxy C １ -C ６ Alkyl is preferred, C ６ -C １０ Aryloxy C １ -C ２ Alkyl is more preferred. Specific examples of aryloxyalkyl include phenoxymethyl and 2-phenoxyethyl.

[0046] As used herein, "aralkyl (arylalkyl)" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with an "aryl" as defined herein. Examples of aralkyl include C ７ -C ２０ aralkyl, C ７ -C １８ Aralkyl is preferred, C ７ -C １６ Aralkyl is more preferred, C ７ -C １４ Aralkyl is most preferred. ７ -C ２０ Examples of aralkyl include C ６ -C １０ Aryl C １ -C １０ alkyl, C ６ -C １０ Aryl C １ -C ８ Alkyl is preferred, C ６ Aryl C １ -C ８ Alkyl or C １０ Aryl C １ -C ８ Alkyl is more preferred, C ６ Aryl C １ -C ８ Alkyl is most preferred. ７ -C １８ Examples of aralkyl include C ６ -C １０ Aryl C １ -C ８ alkyl, C ６ -C １０ Aryl C １ -C ６Alkyl is preferred, C ６ Aryl C １ -C ６ Alkyl or C １０ Aryl C １ -C ６ Alkyl is more preferred, C ６ Aryl C １ -C ６ Alkyl is most preferred. ７ -C １６ As the aralkyl, for example, C ６ -C １０ Aryl C １ -C ６ alkyl, C ６ -C １０ Aryl C １ -C ４ Alkyl is preferred, C ６ Aryl C １ -C ４ Alkyl or C １０ Aryl C １ -C ４ Alkyl is more preferred, C ６ Aryl C １ -C ４ Alkyl is most preferred. ７ -C １４ As the aralkyl, for example, C ６ -C １０ Aryl C １ -C ４ alkyl, C ６ -C １０ Aryl C １ -C ３ Alkyl is preferred, C ６ Aryl C １ -C ３ Alkyl or C １０ Aryl C １ -C ３ Alkyl is more preferred, C ６ Aryl C １ -C ３ Alkyl is most preferred. Specific examples of aralkyl include benzyl, phenethyl, and 3-phenylpropyl.

[0047] As used herein, "aralkoxy" refers to a group in which the alkyl moiety of an "aralkyl" defined herein is bonded to an oxygen atom (-O-R-Ar (R is alkylene)). Examples of aralkoxy include C ７ -C ２０ Aralkoxy, C ７ -C １８ Aralkoxy is preferred, C ７ -C １６ Aralkoxy is more preferred, C ７ -C １４ Aralkoxy is most preferred. ７ -C ２０ Examples of aralkoxy include C ６ -C １０ Aryl C １ -C １０ Alkoxy, C ６ -C １０ Aryl C １ -C ８ Alkoxy is preferred, C ６ Aryl C １ -C ８ Alkoxy or C １０ Aryl C １ -C ８ Alkoxy is more preferred, C ６ Aryl C １ -C ８ Alkoxy is most preferred. ７ -C １８ Examples of aralkoxy include C ６ -C １０ Aryl C １ -C ８ Alkoxy, C ６ -C １０ Aryl C １ -C ６ Alkoxy is preferred, C ６ Aryl C １ -C ６ Alkoxy or C １０ Aryl C １ -C ６ Alkoxy is more preferred, C ６ Aryl C １ -C ６ Alkoxy is most preferred. ７ -C１６ As the aralkoxy, for example, C ６ -C １０ Aryl C １ -C ６ Alkoxy, C ６ -C １０ Aryl C １ -C ４ Alkoxy is preferred, C ６ Aryl C １ -C ４ Alkoxy or C １０ Aryl C １ -C ４ Alkoxy is more preferred, C ６ Aryl C １ -C ４ Alkoxy is most preferred. ７ -C １４ As the aralkoxy, for example, C ６ -C １０ Aryl C １ -C ４ Alkoxy, C ６ -C １０ Aryl C １ -C ３ Alkoxy is preferred, C ６ Aryl C １ -C ３ Alkoxy or C １０ Aryl C １ -C ３ Alkoxy is more preferred, C ６ Aryl C １ -C ３ Alkoxy is most preferred. Specific examples of aralkoxy include benzyloxy, phenethyloxy, and 3-phenylpropoxy.

[0048] As used herein, "aralkoxyalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with an "aralkoxy" as defined herein. Aralkoxyalkyl includes C ７ -C １４ Aralkoxy C １ -C ６ Alkyl is preferred, C ７ -C １４ Aralkoxy C １ -C２ Alkyl is more preferred. Specific examples of aralkoxyalkyl include benzyloxymethyl and 1-(benzyloxy)ethyl.

[0049] As used herein, "heteroarylalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with a "heteroaryl". As the heteroarylalkyl, a group in which one hydrogen atom of an alkyl is substituted with a heteroaryl is preferred. Examples of heteroarylalkyl include 5- to 10-membered heteroaryl C １ -C ６ alkyl and 5-10 membered heteroaryl C １ -C ４ Alkyl is preferred, and 5- to 10-membered heteroaryl C １ -C ３ Alkyl is more preferred, and 5- to 10-membered heteroaryl C １ -C ２ Specific examples of heteroarylalkyl include 2-pyridylmethyl, 3-pyridylmethyl, 4-pyridylmethyl, 2-furanylmethyl, 2-thienylmethyl, 3-thienylmethyl, and 4-thiazolylmethyl.

[0050] As used herein, "heteroarylalkoxy" refers to a group in which the alkyl moiety of "heteroarylalkyl" as defined herein is bonded to an oxygen atom. Examples of heteroarylalkoxy include 5- to 10-membered heteroaryl C １ -C ６ alkoxy and 5-10 membered heteroaryl C １ -C ４ Alkoxy is preferred, and 5- to 10-membered heteroaryl C １ -C ３ Alkoxy is more preferred, and 5- to 10-membered heteroaryl C １ -C ２ Alkoxy is most preferred. Specific examples of heteroarylalkoxy include 2-pyridylmethoxy, 3-pyridylmethoxy, 4-pyridylmethoxy, 2-furanylmethoxy, 2-thienylmethoxy, 3-thienylmethoxy, and 4-thiazolylmethoxy.

[0051] As used herein, "heteroarylalkoxyalkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are substituted with a "heteroarylalkoxy" as defined herein. As the heteroarylalkoxyalkyl, a group in which one hydrogen atom of an alkyl is substituted with a heteroarylalkoxy is preferred. As the heteroarylalkoxyalkyl, for example, a 5- to 10-membered heteroaryl C １ -C ６ Alkoxy C １ -C ６ alkyl and 5-10 membered heteroaryl C １ -C ４ Alkoxy C １ -C ６ Alkyl is preferred, and 5- to 10-membered heteroaryl C １ -C ３ Alkoxy C １ -C ６ Alkyl is more preferred, and 5- to 10-membered heteroaryl C １ -C ２ Alkoxy C １ -C ６ Specific examples of heteroarylalkoxyalkyl include 2-pyridylmethoxymethyl, 3-pyridylmethoxymethyl, 4-pyridylmethoxymethyl, 2-furanylmethoxymethyl, 2-thienylmethoxymethyl, 3-thienylmethoxymethyl, and 4-thiazolylmethoxymethyl.

[0052] As used herein, "heterocycloalkylidenealkyl" refers to a group in which one or more hydrogen atoms of an "alkyl" as defined herein are replaced with a "heterocycloalkylidene" as defined herein. Heterocycloalkylidenealkyl includes 4- to 7-membered heterocycloalkylidene C １ -C ６ Alkyl is preferred, and 4- to 7-membered heterocycloalkylidene C １ -C ２ Specific examples of heteroarylalkoxyalkyl include tetrahydro-4H-pyran-4-ylidenemethyl, azetidin-3-ylidenemethyl, and the like.

[0053] As used herein, "alkoxyalkenyl" refers to a group in which one or more hydrogen atoms of an "alkenyl" as defined herein are substituted with "alkoxy". As the alkoxyalkenyl, a group in which one hydrogen atom of an alkenyl is substituted with alkoxy is preferred. Examples of the alkoxyalkenyl include C １ -C ６ Alkoxy C ２ -C １０ alkenyl, C １ -C ６ Alkoxy C ２ -C ８ Alkenyl is preferred, C １ -C ６ Alkoxy C ２ -C ７ Alkenyl is more preferred, C １ -C ６ Alkoxy C ２ -C ６ Alkenyl is most preferred. Specific examples of alkoxyalkenyl include (E)-4-methoxybut-2-en-1-yl.

[0054] As used herein, "aminocarbonylalkenyl" refers to a group in which one or more hydrogen atoms of an "alkenyl" as defined herein are substituted with "aminocarbonyl". As the aminocarbonylalkenyl, a group in which one hydrogen atom of an alkenyl is substituted with aminocarbonyl is preferred. As the aminocarbonylalkenyl, for example, aminocarbonyl C ２ -C １０ alkenyl, and aminocarbonyl C ２ -C ８ Alkenyl is preferred, and aminocarbonyl C ２ -C ６ Alkenyl is more preferred, and aminocarbonyl C ２ -C ４ Alkenyl is most preferred. Specific examples of aminocarbonylalkenyl include (E)-3-(dimethylaminocarbonyl)-prop-2-en-1-yl.

[0055] The term "haloalkoxy" as used herein refers to a group in which one or more hydrogen atoms of an "alkoxy" as defined herein are substituted with halogen. The haloalkoxy is preferably a group in which 1 to 6 hydrogen atoms of an alkoxy that are allowed to be substituted are substituted with halogen. For example, haloC １ -C ２０ Alkoxy and haloC １ -C １０ Alkoxy is preferred, haloC １ -C ８ Alkoxy is more preferred, haloC １ -C ６ Alkoxy is most preferred. HaloC １ -C ６ The alkoxy is, for example, a group in which 1 to 6 hydrogen atoms of an alkoxy, which are permissible for substitution, are substituted with fluorine, preferably a group in which 1 to 5 hydrogen atoms are substituted with fluorine, more preferably a group in which 1 to 4 hydrogen atoms are substituted with fluorine, and most preferably a group in which 1 to 3 hydrogen atoms are substituted with fluorine. Specific examples of haloalkoxy include difluoromethoxy, trifluoromethoxy, 2,2-difluoroethoxy, 2,2,2-trifluoroethoxy, 3-fluoropropoxy, 2,2-difluoropropoxy, etc.

[0056] As used herein, "alkylene" refers to a divalent group derived from an "alkyl" as defined herein by further removing one optional hydrogen atom. １ -C ８ Alkylene is preferred, C ４ -C ８ Alkylene is more preferred. Specific examples of alkylene include —CH ２ -, -(CH ２ ) ２ -, -(CH ２ ) ３ -, -CH(CH ３ ) CH ２ -, -C(CH ３ ) ２ -, -(CH ２ ) ４ -, -CH(CH ３ ) CH ２CH ２ -, -C(CH ３ ) ２ CH ２ -, -CH ２ CH (CH ３ ) CH ２ -, -CH ２ C(CH ３ ) ２ -, -CH ２ CH ２ CH (CH ３ ) -, -CH ２ CH (CH ２ CH ３ ) -, -(CH ２ ) ５ -, -CH(CH ３ ) CH(CH ２ CH ３ ) -, -(CH ２ ) ６ -, -(CH ２ ) ７ -, -(CH ２ ) ８ - and others.

[0057] As used herein, an "alicyclic ring" refers to a saturated or partially saturated non-aromatic hydrocarbon ring. The carbon atoms constituting the ring may be oxidized to include a carbonyl. The alicyclic ring may be selected from the group consisting of a monocyclic ring, a fused ring, and a spiro ring. As used herein, an alicyclic ring containing a monocyclic ring is referred to as a monocyclic alicyclic ring, an alicyclic ring containing a fused ring is referred to as a fused alicyclic ring, and an alicyclic ring containing a spiro ring is referred to as a spirocyclic alicyclic ring. The alicyclic ring may form a fused ring with a saturated alicyclic ring such as a cyclopentane ring or a cyclohexane ring, an unsaturated alicyclic ring such as a cycloheptene ring or a cyclohexene ring, or an aromatic hydrocarbon ring such as a benzene ring or a naphthalene ring. The alicyclic ring may form a spiro ring with a saturated alicyclic ring such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, or a cyclohexane ring. Examples of alicyclic rings include C ３ -C １０ is an alicyclic ring, ３ -C ８ An alicyclic ring is preferred, and C ３ -C ７ An alicyclic ring is more preferred, and C ３ -C６ Alicyclic rings are most preferred. Specific examples of alicyclic rings include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a bicyclo[2.2.1]heptane ring, and a cyclohexene ring.

[0058] The term "saturated heterocycle" as used herein refers to a "heterocycle" that does not have an unsaturated bond within the ring. The number of atoms constituting the ring of the saturated heterocycle is 3 to 14 (3- to 14-membered heterocycle), preferably 3 to 12 (3- to 12-membered heterocycle), more preferably 3 to 10 (3- to 10-membered heterocycle), and most preferably 4 to 7 (4- to 7-membered heterocycle). Specific examples of saturated heterocycles include an azetidine ring, an epoxy ring, an oxetane ring, a thietane ring, a tetrahydrofuran ring, a pyrrolidine ring, a pyrazolidine ring, an imidazolidine ring, an oxazolidine ring, an isoxazolidine ring, a thiazolidine ring, an isothiazolidine ring, a thiadiazolidine ring, an oxazolidone ring, a dioxolane ring, a tetrahydropyran ring, a morpholine ring, a thiomorpholine ring, a 4-oxopyrrolidine ring, a piperidine ring, a 4-oxopiperidine ring, a piperazine ring, and a dioxane ring.

[0059] As used herein, the term "peptide compound" refers to a compound in which two or more amino acids are linked by amide bonds. As long as two or more amino acids are linked by amide bonds, the peptide chain may contain other bonds (e.g., ester bonds, thioester bonds, etc.). The number of amino acid residues contained in the peptide is, for example, 5 to 30. The peptide may be linear, branched, or cyclic.

[0060] As used herein, the term "peptide chain" refers to a chain-like portion of a peptide in which two or more amino acids are linked by amide bonds. As long as two or more amino acids are linked by amide bonds, the peptide chain may contain other bonds (e.g., ester bonds, thioester bonds, etc.). The number of amino acid residues contained in the peptide chain is, for example, 5 to 30 residues.

[0061] As used herein, the term "optionally substituted" means that a certain group and / or a certain atom may be substituted with any substituent and / or any atom. That is, either a state in which the certain group and the certain atom are not substituted with any substituent or any atom, or a state in which the certain group and / or the certain atom are substituted with any substituent and / or any atom, can be selected. Each of the certain group and / or the certain atom may be further substituted with any substituent and / or any atom. That is, either a state in which the certain group and the certain atom are not substituted with any substituent or any atom, or a state in which the certain group and / or the certain atom are substituted with any substituent and / or any atom, can be selected. The certain group and the certain substituent are not limited and may be freely selected, for example, from groups containing atoms selected from the group consisting of hydrogen atoms, halogen atoms, carbon atoms, oxygen atoms, sulfur atoms, nitrogen atoms, boron atoms, silicon atoms, and phosphorus atoms. The certain atom and the optional atom are not limited and may be freely selected from, for example, a halogen atom, a carbon atom, an oxygen atom, a sulfur atom, a nitrogen atom, a boron atom, a silicon atom, or a phosphorus atom. Examples of the optional substituent include alkyl, alkoxy, fluoroalkyl, fluoroalkoxy, oxo, aminocarbonyl, alkylsulfonyl, alkylsulfonylamino, cycloalkyl, aryl, heteroaryl, heterocyclyl, arylalkyl, heteroarylalkyl, halogen, nitro, amino, monoalkylamino, dialkylamino, cyano, carboxyl, alkoxycarbonyl, formyl, etc.

[0062] As used herein, the term "optionally protected" means that a group may be protected by any protecting group.

[0063] As used herein, "one or more" means one or more than one. When "one or more" is used in the context of substituents on a group, the term means a number from one to the maximum number of substituents permitted by that group. Specific examples of "one or more" include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and / or more.

[0064] The compounds or salts thereof described herein may be solvates thereof. Examples of salts of the compounds include hydrochlorides, hydrobromides, hydroiodides, phosphates, phosphonates, sulfates, sulfonates such as methanesulfonates and p-toluenesulfonates, carboxylates such as acetates, citrates, malates, tartrates, succinates, and salicylates, alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, and ammonium salts such as ammonium salts, alkylammonium salts, dialkylammonium salts, trialkylammonium salts, and tetraalkylammonium salts. These salts can be produced, for example, by contacting the compound with an acid or a base. In this specification, the term "solvate" refers to a compound that forms a molecular group together with a solvent, and is not particularly limited as long as it is a solvate formed with a solvent that is acceptable for ingestion accompanying the administration of a drug. Specific examples of solvates include solvates with a single solvent such as water, alcohol (ethanol, methanol, 1-propanol, 2-propanol, etc.), dimethyl sulfoxide, etc., as well as solvates formed with multiple solvents per molecule of the compound, or solvates formed with multiple types of solvents per molecule of the compound. For example, a solvate formed with water of a compound is called a hydrate. As the solvate of the compound of the present invention, hydrates are preferred. Specific examples of such hydrates include mono- to 20-hydrates, more preferably mono- to deca-hydrates, even more preferably mono- to penta-hydrates, and most preferably mono- to tri-hydrates.

[0065] As used herein, "amino acid" includes natural amino acids and unnatural amino acids (sometimes referred to as amino acid derivatives). Furthermore, as used herein, "amino acid" may refer to an amino acid residue. As used herein, "natural amino acid" refers to any L-amino acid selected from the group consisting of Gly (glycine), L-Ala (alanine), L-Ser (serine), L-Thr (threonine), L-Val (valine), L-Leu (leucine), L-Ile (isoleucine), L-Phe (phenylalanine), L-Tyr (tyrosine), L-Trp (tryptophan), L-His (histidine), L-Glu (glutamic acid), L-Asp (aspartic acid), L-Gln (glutamine), L-Asn (asparagine), L-Cys (cysteine), L-Met (methionine), L-Lys (lysine), L-Arg (arginine), and L-Pro (proline). As used herein, "unnatural amino acid" refers to an amino acid other than natural amino acids. Examples of unnatural amino acids include β-amino acids, γ-amino acids, D-amino acids, N-substituted amino acids other than Pro, α,α-disubstituted amino acids, and amino acids whose side chains differ from those of natural amino acids. The amino acids referred to herein may have any configuration. The side chains of the amino acids are not particularly limited and may be freely selected from groups such as alkyl, alkenyl, alkynyl, aryl, heteroaryl, aralkyl, heteroaralkyl, cycloalkyl, and spiro-linked cycloalkyl, and / or atoms such as hydrogen atoms. Each of these groups and / or atoms may be further substituted. In a non-limiting embodiment, the amino acids referred to herein may be compounds having a carboxy group and an amino group in the same molecule. Even in this case, amino acids also include proline, hydroxyproline, azetidine-2-carboxylic acid, and the like, in which the nitrogen atom of the amino group and any atom in the side chain of the amino acid form a ring.

[0066] The main chain amino group of the amino acid is unsubstituted (NH ２group), and may be substituted (i.e., an —NHR group: R represents an alkyl, alkenyl, alkynyl, aryl, heteroaryl, aralkyl, or cycloalkyl group which may have a substituent, and one or two non-adjacent methylene groups in these groups are replaced by an oxygen atom, a carbonyl group (—CO—), or a sulfonyl group (—SO ２ -), or, as in proline, the carbon chain bonded to the N atom may form a ring with the carbon atom at the α-position.) The substituent of R is selected in the same manner as the substituent in the amino acid side chain described above. When the main chain amino group is substituted, R is included in the "amino acid side chain" in this specification. An amino acid in which such a main chain amino group is substituted is referred to as an "N-substituted amino acid" in this specification. As used herein, the "N-substituted amino acid" is preferably an N-alkyl amino acid, an N-C １ ~C ６ Alkyl amino acids, N-C １ ~C ４ Examples include, but are not limited to, alkyl amino acids and N-methyl amino acids.

[0067] As used herein, "amino acid" includes all corresponding isotopes. An isotope of an "amino acid" is one in which at least one atom is replaced with an atom having the same atomic number (number of protons) but a different mass number (sum of the number of protons and neutrons) in an abundance ratio different from the natural abundance ratio. Examples of isotopes included in "amino acids" as used herein include hydrogen atoms, carbon atoms, nitrogen atoms, oxygen atoms, phosphorus atoms, sulfur atoms, fluorine atoms, and chlorine atoms, each of which is 2 H, 3 H, 13 C. 14 C. 15 N, 17 O. 18 O. 32 P, 35 S, 18 F, 36 Cl, etc. Compounds herein containing all proportions of radioactive or non-radioactive isotopes are within the scope of the present invention.

[0068] As used herein, the term "substituent derived from halogen" includes fluoro (-F), chloro (-Cl), bromo (-Br), iodo (-I), and the like.

[0069] As used herein, examples of a "substituent containing an oxygen atom" include hydroxy (-OH), oxy (-OR), oxo (=O), carbonyl (-C(=O)-R), carboxy (-COH), oxycarbonyl (-C(=O)-OR), carbonyloxy (-OC(=O)-R), thiocarbonyl (-C(=O)-SR), carbonylthio group (-SC(=O)-R), aminocarbonyl (-C(=O)-NHR), carbonylamino (-NH-C(=O)-R), oxycarbonylamino (-NH-C(=O)-OR), sulfonylamino (-NH-SO-R), aminosulfonyl (-SO-NHR), sulfamoylamino (-NH-SO-NHR), thiocarboxy (-C(=O)-SH), and carboxycarbonyl (-C(=O)-COH).

[0070] Examples of oxy (—OR) include alkoxy, cycloalkoxy, alkenyloxy, alkynyloxy, aryloxy, heteroaryloxy, aralkyloxy, etc. Alkoxy includes C １ ~C ４ Alkoxy, C １ ~C ２ Alkoxy is preferred, and methoxy or ethoxy is particularly preferred.

[0071] Examples of carbonyl (-C(=O)-R) include formyl (-C(=O)-H), alkylcarbonyl, cycloalkylcarbonyl, alkenylcarbonyl, alkynylcarbonyl, arylcarbonyl, heteroarylcarbonyl, aralkylcarbonyl, and the like.

[0072] Examples of oxycarbonyl (-C(=O)-OR) include alkyloxycarbonyl, cycloalkyloxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl, aryloxycarbonyl, heteroaryloxycarbonyl, aralkyloxycarbonyl, and the like.

[0073] Examples of carbonyloxy (-OC(=O)-R) include alkylcarbonyloxy, cycloalkylcarbonyloxy, alkenylcarbonyloxy, alkynylcarbonyloxy, arylcarbonyloxy, heteroarylcarbonyloxy, and aralkylcarbonyloxy.

[0074] Examples of thiocarbonyl (-C(=O)-SR) include alkylthiocarbonyl, cycloalkylthiocarbonyl, alkenylthiocarbonyl, alkynylthiocarbonyl, arylthiocarbonyl, heteroarylthiocarbonyl, aralkylthiocarbonyl, and the like.

[0075] Examples of carbonylthio (-SC(=O)-R) include alkylcarbonylthio, cycloalkylcarbonylthio, alkenylcarbonylthio, alkynylcarbonylthio, arylcarbonylthio, heteroarylcarbonylthio, and aralkylcarbonylthio.

[0076] Examples of aminocarbonyl (-C(=O)-NHR) include alkylaminocarbonyl (e.g., C １ ~C ６ or C １ ~C ４ Examples thereof include alkylaminocarbonyl, specifically ethylaminocarbonyl, methylaminocarbonyl, etc.), cycloalkylaminocarbonyl, alkenylaminocarbonyl, alkynylaminocarbonyl, arylaminocarbonyl, heteroarylaminocarbonyl, aralkylaminocarbonyl, etc. In addition to these, examples thereof include groups in which the H atom bonded to the N atom in —C(═O)—NHR is further substituted with an alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, or aralkyl.

[0077] Examples of carbonylamino (-NH-C(=O)-R) include alkylcarbonylamino, cycloalkylcarbonylamino, alkenylcarbonylamino, alkynylcarbonylamino, arylcarbonylamino, heteroarylcarbonylamino, aralkylcarbonylamino, etc. In addition to these, groups in which the H atom bonded to the N atom in -NH-C(=O)-R is further substituted with alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, or aralkyl are also included.

[0078] Examples of oxycarbonylamino (-NH-C(=O)-OR) include alkoxycarbonylamino, cycloalkoxycarbonylamino, alkenyloxycarbonylamino, alkynyloxycarbonylamino, aryloxycarbonylamino, heteroaryloxycarbonylamino, aralkyloxycarbonylamino, etc. In addition to these, groups in which the H atom bonded to the N atom in -NH-C(=O)-OR is further substituted with alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, or aralkyl are also included.

[0079] Examples of sulfonylamino (-NH-SO2-R) include alkylsulfonylamino, cycloalkylsulfonylamino, alkenylsulfonylamino, alkynylsulfonylamino, arylsulfonylamino, heteroarylsulfonylamino, aralkylsulfonylamino, etc. In addition to these, groups in which the H atom bonded to the N atom in -NH-SO2-R is further substituted with alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, or aralkyl are also included.

[0080] Examples of aminosulfonyl (-SO2-NHR) include alkylaminosulfonyl, cycloalkylaminosulfonyl, alkenylaminosulfonyl, alkynylaminosulfonyl, arylaminosulfonyl, heteroarylaminosulfonyl, aralkylaminosulfonyl, etc. In addition to these, groups in which the H atom bonded to the N atom in -SO2-NHR is further substituted with alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, or aralkyl are also included.

[0081] Examples of sulfamoylamino (-NH-SO-NHR) include alkylsulfamoylamino, cycloalkylsulfamoylamino, alkenylsulfamoylamino, alkynylsulfamoylamino, arylsulfamoylamino, heteroarylsulfamoylamino, aralkylsulfamoylamino, etc. Furthermore, the two H atoms bonded to the N atom in -NH-SO-NHR may be substituted with substituents independently selected from the group consisting of alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, and aralkyl, and these two substituents may form a ring.

[0082] As used herein, examples of a "substituent containing a sulfur atom" include thiol (-SH), thio (-SR), sulfinyl (-S=OR), sulfonyl (-S(O)2-R), sulfo (-SO3H), pentafluorosulfanyl (-SF5), and disulfanyl (-SSR).

[0083] Examples of thio (-SR) are selected from alkylthio, cycloalkylthio, alkenylthio, alkynylthio, arylthio, heteroarylthio, aralkylthio, and the like.

[0084] Examples of sulfinyl (-S=OR) include alkylsulfinyl, cycloalkylsulfinyl, alkenylsulfinyl, alkynylsulfinyl, arylsulfinyl, heteroarylsulfinyl, aralkylsulfinyl, and the like.

[0085] Examples of sulfonyl (-S(O)2-R) include alkylsulfonyl, cycloalkylsulfonyl, alkenylsulfonyl, alkynylsulfonyl, arylsulfonyl, heteroarylsulfonyl, aralkylsulfonyl, and the like.

[0086] Examples of a "substituent containing a nitrogen atom" in this specification include azide (-N3, also referred to as an "azido group"), cyano (-CN), primary amino (-NH2), secondary amino (-NH-R), tertiary amino (-NR(R')), amidino (-C(=NH)-NH2), substituted amidino (-C(=NR)-NR'R''), guanidino (-NH-C(=NH)-NH2), substituted guanidino (-NR-C(=NR''')-NR'R''), and aminocarbonylamino (-NR-CO-NR'R'').

[0087] Examples of secondary amino (-NH-R) include alkylamino, cycloalkylamino, alkenylamino, alkynylamino, arylamino, heteroarylamino, and aralkylamino.

[0088] Examples of tertiary amino (—NR(R′)) include an amino group having any two substituents independently selected from alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, aralkyl, etc., such as alkyl(aralkyl)amino, and these two substituents may form a ring.

[0089] Examples of substituted amidino (-C(=NR)-NR'R'') include groups in which the three substituents R, R', and R'' on the N atom are each independently selected from alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, and aralkyl, such as alkyl(aralkyl)(aryl)amidino.

[0090] Examples of substituted guanidino (-NR-C(=NR''')-NR'R'') include groups in which R, R', R'', and R''' are each independently selected from alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, and aralkyl, or groups in which these groups form a ring.

[0091] Examples of aminocarbonylamino (-NR-CO-NR'R'') include groups in which R, R', and R'' are each independently selected from a hydrogen atom, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, and aralkyl, or groups in which these groups form a ring.

[0092] In this specification, the "amino acid residues" that constitute a peptide compound may be simply referred to as "amino acids".

[0093] In this specification, the term "to" indicating a numerical range includes both ends of the range. For example, "A to B" means a numerical range that is equal to or greater than A and equal to or less than B.

[0094] As used herein, the term "about" when used in conjunction with a numerical value means a range of values ​​of plus or minus 10% of that numerical value.

[0095] As used herein, the term "and / or" includes any combination of "and" and "or." Specifically, for example, "A, B, and / or C" includes the following seven variations: (i) A, (ii) B, (iii) C, (iv) A and B, (v) A and C, (vi) B and C, and (vii) A, B, and C.

[0096] Method for Producing Peptide Compounds In one aspect, the present invention relates to a method for producing a peptide compound or a salt thereof, the method comprising a step of linking an amino group of a first amino acid or peptide with a carboxy group of a second amino acid or peptide via an amide bond (linking step), wherein a condensing agent and two or more additives are present in a reaction system in the linking step, and the pKa of the additives is expressed in the range of 0 to 10.0, more preferably 0 to 8.0, even more preferably 0 to 5.0, and most preferably 1 to 5.0 (hereinafter also referred to as "Aspect 1").

[0097] In one aspect, the present invention relates to a method for producing a peptide compound or a salt thereof, the method comprising a step of linking an amino group of a first amino acid or peptide with a carboxy group of a second amino acid or peptide via an amide bond (linking step), wherein a condensing agent and two or more additives are used in the linking step, and the pKa of the additives is expressed in the range of 0 to 10.0, more preferably 0 to 8.0, even more preferably 0 to 5.0, and most preferably 1 to 5.0 (hereinafter also referred to as "Aspect 2").

[0098] In one embodiment, the additive used in the linking step has a pKa between 0 and 10.0, more preferably between 0 and 8.0, even more preferably between 0 and 5.0, and most preferably between 1 and 5.0. The "pKa" herein can be measured using water as a solvent. As the pKa herein, an actual measured value that has already been reported as the pKa when water is used as a solvent may be used. As the actual measured pKa value, a value measured at 25°C is applied. If the actual measured pKa value is not available, it may be calculated using ADMETPredictor (Simulations Plus Inc., ver. 8.0), and the value may be used as the pKa herein. The pKa of representative additives contemplated in this embodiment are listed below: HOAt (pKa = 3.28; Chem. Eur. J. 2009, 15, 9394-9403); HOBt (pKa = 4.60; Chem. Eur. J. 2009, 15, 9394-9403); oxyma (pKa = 4.60; Chem. Eur. J. 2009, 15, 9394-9403); tert-Butyl 2-cyano-2-(hydroxyimino)acetate (pKa = 4.60; ACS Omega. 2022, 7, 6007-6023); (2,2-Dimethyl0-1,3-dioxolan-4-yl)methyl2-cyano-2-(hydroxyimino)acetate (pKa=4.5; ACS Omega. 2022, 7, 6007-6023); 2-Amino-N-hydroxy-oxoacetimidoylcyanide (pKa=6.3; ACS Omega. 2022, 7, 6007-6023); 2-(Ethylamino)-N-hydroxy-2-oxoacetimidoylcyanide (pKa=6.3; ACS Omega. 2022, 7, 6007-6023); 2-(Dimethylamino)-N-ydroxy-2-oxoacetimidoylcyanide (pKa=6.3; ACS Omega.2022, 7, 6007-6023); N-Hydroxy-2-oxo-2-(Piperidin-1-yl)acetimidoyl cyanide(pKa=6.3;ACS Omega. 2022, 7, 6007-6023); N-Hydroxy-2-morpholino-2-oxoacetimidoylcyanide(pKa=6.1;ACS Omega. 2022, 7, 6007-6023); Oxyma-B (5-(Hydroxyimino)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione)(pKa=8.2;ACS Omega. 2022, 7, 6007-6023); Oxyma-T (1,3-diethyl-5-hydroxyimino-2-thioxo-hexahydropyrimidine-4,6-dione)(pKa=8.2;ACS Omega. 2022, 7, 6007-6023); Hydroxyimino-2-phenylacetonitrile(pKa=8.2;ACS Omega. 2022, 7, 6007-6023); Hydroxyimino-2-(4-chloro)phenylacetonitrile(pKa=8.0;ACS Omega. 2022, 7, 6007-6023); Hydroxypicolinimidoyl cyanide(pKa=8.2;ACS Omega. 2022, 7, 6007-6023); Hydroxyimino-2-(1-naphytyl)phenylacetonitrile(pKa=8.2;ACS Omega. 2022, 7, 6007-6023); Hydroxycarbonimidoyl dicyanide(pKa=3.8;ACS Omega. 2022, 7, 6007-6023); 1-Ethyl-3-methyl-2-(hydroxyamino)malonate(pKa=7.2;ACS Omega. 2022, 7, 6007-6023); Diethyl 2-(hydroxyamino)malonate(pKa=7.2;ACS Omega.2022, 7, 6007-6023); Diisopyrplyl 2-(hydroxyimino)malonate(pKa=7.2;ACS Omega. 2022, 7, 6007-6023); HONM (5-(Hyrdoxyimino)-2,2-dimethyl-1,3-dioxane-4,6-dione)(pKa=6.1;ACS Omega. 2022, 7, 6007-6023); HOSu (1-Hydroxypyrrolidine-2,5-dione)(pKa=7.7;ACS Omega. 2022, 7, 6007-6023); HONB ((4S,7S)-2-Hydroxy-3a,4,7,7a-tetrahydro-1H-4,7-methanoisoindole-1,3-(2H)-dione)(pKa=7.7;ACS Omega. 2022, 7, 6007-6023); HOBI (2-Phenyl-1H-benzo[d]imidazoyl-1-ol)(pKa=7.7;ACS Omega. 2022, 7, 6007-6023); 6-Cl-HOBI (6-Chloro-2-phanyl-1H-benzo[dimidazol]-1-ol)(pKa=7.1;ACS Omega. 2022, 7, 6007-6023); HODhad (3-Hydroxypyrido[3,2-d]pyrimidin-4(3H)-one)(pKa=5.8;ACS Omega. 2022, 7, 6007-6023); 2H-Tetrazol-2-ol(pKa=8.2;ACS Omega. 2022, 7, 6007-6023); HOI (1-Hydroxyindolin-2-one)(pKa=8.3;ACS Omega. 2022, 7, 6007-6023); 2-(Hydroxyimino)-2-(pyrazin-2-yl)acetamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); Ethyl-2-(hydroxyimino)-2-(pyrazin-2-yl)acetate(pKa=9.4;ACS Omega.2022, 7, 6007-6023); Ethyl-2-(furan-2-yl)-2-(hydroxyimino)acetate(pKa=9.6;ACS Omega. 2022, 7, 6007-6023); 2-(Furan-2-yl)-2-(hydroxyimino)acetamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)-2-(thianol-2-yl)acetate (pKa=8.7;ACS Omega. 2022, 7, 6007-6023); 2(Hydroxyimino)-2-(thiazol-2-yl)acetamide(pKa=8.7;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)-2-(pyrimidin-2-yl)acetate (pKa=9.6;ACS Omega. 2022,7, 6007-6023); 2-(Hydroxyimino)-2-(pyrimidin-2-yl)acetamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); 2-(Hydroxyimino)-2-(pyrimidin-2-yl)ethanethioamide(pKa=10.5;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(furan-2-yl)-2-(hydroxyimino)acetate (pKa=9.6;ACS Omega. 2022, 7, 6007-6023); 2-(Hydroxyimino)-2-(1H-pyrrol-2-yl)acetamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); 2-(Hydroxyimino)-2-(thiophen-2-yl)acetamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)-(1H-pyrrol-2-yl)acetate(pKa=9.6;ACS Omega.2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)-2-(thiophen-2-yl)acetate (pKa=9.6;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)-2-(pyridine-2-yl)acetate (pKa=9.6;ACS Omega. 2022, 7, 6007-6023); Ehyl2-(hydroxyimino)-2-(pyridine-4-yl)acetate (pKa=9.6;ACS Omega. 2022, 7, 6007-6023); 2-(Hydroxyimino)but-3-ynamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)but-3-ynoate (pKa=9.6;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyamino)-2-nitroacetate(pKa=4.7;ACS Omega. 2022, 7, 6007-6023); Dinitromethanoneoxime (pKa=2.7;ACS Omega. 2022, 7, 6007-6023); Nitro(phenyl)methanoneoxime(pKa=7.6;ACS Omega. 2022, 7, 6007-6023); 1-Nitro-3-phenylpropan-1-oneoxime (pKa=7.4;ACS Omega. 2022, 7, 6007-6023); 1-(Hydroxyimino)-N,N-dimethyl-1-phenylmethanesulfinamide(pKa=7.4;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)-2-sulfamoylacetate(pKa=5.8;ACS Omega. 2022, 7, 6007-6023); (Hydroxyimino)(methylsulfonyl)methanesulfinamide(pKa=9.4;ACS Omega.2022, 7, 6007-6023); 2-(Hydroxyimino)-2-(methylsulfonyl)acetamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); Ethyl 2-(hydroxyimino)-2-((trifluoromethyl)sulfonyl)acetate (pKa=4.2;ACS Omega. 2022, 7, 6007-6023); 2-Ethoxy-N-hydroxy-2-oxoacetimidictrifluoromethaneslfonic anhydride (pKa=7.74;ACS Omega. 2022, 7, 6007-6023); Diphenylmethaneoxime (pKa=11.1;ACS Omega. 2022, 7, 6007-6023); 2-((Hydroxyimino)(pyridin-2-yl)methyl)-1-methylpyridin-1-iumiodide (pKa=5.6;ACS Omega. 2022, 7, 6007-6023); 9H-Fluoren-9-oneoxime (pKa=11.1;ACS Omega. 2022, 7, 6007-6023); Anthracene-9,10-dionedioxime (pKa=7.1;ACS Omega. 2022, 7, 6007-6023); Pyrido[3,4-g]isoquinoline-5,10-dioxime(pKa=5.5;ACS Omega. 2022, 7, 6007-6023); Imidazolidin-2-oneoxime (pKa=12.5;ACS Omega. 2022, 7, 6007-6023); 1,3-Dihydro-2H-imidazol-2-oneoxime (pKa=8.2;ACS Omega. 2022, 7, 6007-6023); Oxazolidin-2-oneoxime (pKa=12.5;ACS Omega. 2022, 7, 6007-6023); Oxazol-2(3H)-oneoxime (pKa=6.6;ACS Omega.2022, 7, 6007-6023); 2-(Hydroxyimino)malonamide(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); N’,N’-Dihydroxy-2-(hydroxyamino)malonamide(pKa=7.7;ACS Omega. 2022, 7, 6007-6023); Butane-2,3-dionedioxime (pKa=12.1;ACS Omega. 2022, 7, 6007-6023); N’-Hydroxypyrazine-2-carboximidamide(pKa=12.5;ACS Omega. 2022, 7, 6007-6023); 3-Methyl-1,2,4-oxadiazole-5-carbaldehydeoxime (pKa=8.0;ACS Omega. 2022, 7, 6007-6023); 3-(Hydroxyimino)-1-phenylindoline-2-one(pKa=9.0;ACS Omega. 2022, 7, 6007-6023); 3-(Hydroxyimino)-1-methylindolin-2-one(pKa=9.4;ACS Omega. 2022, 7, 6007-6023); 2-((Hydroxyimino)methyl)-1-methylpyridine-1-ium(pKa=8.0;ACS Omega. 2022, 7, 6007-6023); 2,3,4,5,6,-Pentafluorophenol(pKa=4.9;ACS Omega. 2022, 7, 6007-6023); 2,3,5-Trichlorophenol(pKa=6.4;ACS Omega. 2022, 7, 6007-6023); 4-Nitrophenol(pKa=7.2;ACS Omega. 2022, 7, 6007-6023); Phenol (pKa=10.0;ACS Omega. 2022, 7, 6007-6023); HFIP (1,1,1,3,3,3-Hexafluoropropan-2-ol)(pKa=9.3;Tetrahedron Asymmetry, 2012, 23, 1023-1027).

[0099] In Aspects 1 and 2, the condensing agent and two or more additives may be added to a reaction system containing a first amino acid or peptide and a second amino acid or peptide, or the first amino acid or peptide and the second amino acid or peptide may be added to reaction systems containing the condensing agent and two or more additives separately.

[0100] In some embodiments of Aspects 1 and 2, the condensing agent is a phosphorus-based condensing agent. Here, the phosphorus-based condensing agent is not particularly limited as long as it is a compound that has a phosphorus atom in the molecule and promotes the linkage (condensation reaction) between an amino group and a carboxy group, and examples thereof include compounds represented by the following formula (1): (In the formula, R １ is C １ -C ６ Alkoxy, C ６ -C １０ Aryloxy, C ６ -C １０ Aryl or diC １ -C ６ alkylamino, R ２ is C １ -C ６ Alkoxy, C ６ -C １０ Aryloxy, C ６ -C １０ Aryl or diC １ -C ６ alkylamino, R ３ is halogen, optionally substituted C ６ -C １０ In the phosphorus-based condensing agent represented by formula (1), R １ is ethoxy, phenyloxy, phenyl, or dimethylamino; R ２ is ethoxy, phenyloxy, phenyl, or dimethylamino; R ３ is preferably chloro, pentafluorophenyloxy, or azido.

[0101] In some embodiments of Aspects 1 and 2, specific examples of the phosphorus-based condensing agent include diphenyl chlorophosphate (DPPC), diethyl chlorophosphate (DEPC), dimethyl chlorophosphate, diisopropyl chlorophosphate, dibenzyl chlorophosphate, diphenylphosphoric acid azide (DPPA), pentafluorophenyl diphenylphosphinate (FDPP), 2-chloro-2-oxo-1,3,2-disoxaphosphorane, dimethylphosphinic acid chloride, diethylphosphinic acid chloride, dicyclohexylphosphinic acid chloride, diphenylphosphinic acid chloride (PhP(O)Cl), etc. Among these, diphenyl chlorophosphate (DPPC), diethyl chlorophosphate (DEPC), diphenylphosphoric acid azide (DPPA), pentafluorophenyl diphenylphosphinate (FDPP), and diphenylphosphinic acid chloride (PhP(O)Cl) are preferred, and diphenyl chlorophosphate (DPPC) and diethyl chlorophosphate (DEPC) are more preferred.

[0102] In embodiments 1 and 2, the additive is a nucleophilic species that reacts with a carboxy group to form an active ester, preferably 2-hydroxypyridine-N-oxide (HOPO), a HOPO derivative, 1-hydroxy-7-azabenzotriazole (HOAt), 1-hydroxybenzotriazole (HOBt), 3,4-dihydro-3-hydroxy-4-oxobenzotriazine (HOOBt), ethyl 1-hydroxy-1H-1,2,3-triazole-4-carboxylate (HOCt), 2,2,3,3,3-pentafluoro-1-propanol (PfpOH), ethyl Two or more selected from the group consisting of 2-cyano-2-(hydroxyimino)acetate (Oxyma), 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6-(1H,3H,5H)-trione (Oxyma-B), 4-nitrophenol, pentafluorophenol, potassium salt of (hydroxyimino)cyanoacetate (K-Oxyma), 4,6-dimethoxy-1,3,5-triazin-2-ol, 2-hydroxypyridine, trimethylsilanol, and 2-hydroxy-5-nitropyridine are more preferred, and 2-hydroxypyridine-N-oxide (HOPO), HOPO derivatives, 3,4-dihydro-3-hydroxy-4-oxo-benzotriazine (HOOBt), 2,2,3,3,3-pentafluoro-1-propanol (PfpOH), ethyl acetate, ... The HOPO derivatives are two or more selected from the group consisting of 2-cyano-2-(hydroxyimino)acetate (Oxyma), 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6-(1H,3H,5H)-trione (Oxyma-B), and pentafluorophenol. Specific examples of the HOPO derivatives include 5-F-HOPO, 5-Cl-HOPO, 5-Br-HOPO, 5-CF-HOPO, 5-COMe-HOPO, and 4-Br-HOPO.

[0103] In the embodiments 1 and 2, the number of additives is preferably two.

[0104] In some embodiments of Embodiments 1 and 2, the condensing agent is used in an amount of 0.1 to 5.0 molar equivalents relative to the first amino acid or peptide, more preferably 0.5 to 3.0 molar equivalents, even more preferably 0.5 to 2.6 molar equivalents, and most preferably 0.5 to 2.0 molar equivalents.

[0105] In certain embodiments of Aspects 1 and 2, one of the two or more additives is HOPO and the other one or more is selected from the group consisting of Oxyma, HOAt, HOOBt, HOCt, PfpOH, Oxyma-B, pentafluorophenol, and K-Oxyma.

[0106] In another embodiment of Aspects 1 and 2, one of the two or more additives is Oxyma and the other one or more are selected from the group consisting of HOPO, a HOPO derivative, HOOBt, HOCt, Oxyma-B, pentafluorophenol, PfpOH, 4,6-dimethoxy-1,3,5-triazin-2-ol, 2-hydroxypyridine, and 2-hydroxy-5-nitropyridine. In this embodiment, it is preferred that one of the two or more additives is Oxyma and the other one or more are selected from the group consisting of HOPO, HOOBt, HOCt, Oxyma-B, and pentafluorophenol, and more preferably both Oxyma and HOPO.

[0107] In some embodiments of Embodiments 1 and 2, the additive is used in an amount of 0.1 to 5.0 molar equivalents relative to the first amino acid or peptide, more preferably 0.3 to 3.0 molar equivalents, even more preferably 0.5 to 2.6 molar equivalents, and most preferably 0.5 to 2.0 molar equivalents.

[0108] In one embodiment, the coupling step can be carried out by stirring the reaction mixture for 10 minutes to 24 hours at a reaction temperature of, for example, −50° C. to 30° C., preferably −20° C. to 20° C., more preferably −18° C. to 20° C., and most preferably 0° C. to 15° C.

[0109] A method is also known in which only peptide components bound to dissolved tags are selectively dissolved in a specific phase during liquid phase separation, thereby separating them from other unnecessary components (hereinafter referred to as the "liquid-phase tagging method"). This method allows unnecessary components to be separated without solidification, thereby contributing to the rapid and simplified reaction process. Examples of liquid-phase tagging methods using hydrophobic tags include (Y. Okada, H. Suzuki, T. Nakae, S. Fujita, H. Abe, K. Nagano, T. Yamada, N. Ebata, S. Kim and K. Chiba, Tag-Assisted Liquid-Phase Peptide Synthesis Using Hydrophobic Benzyl Alcohols as Supports, J. Org. Chem., 2013, 78, 320-327, or S. Yano et al., Molecules 2021, 26(12), 3497).

[0110] In some embodiments, the linking step may be performed by solid-phase synthesis or liquid-phase synthesis, preferably liquid-phase synthesis. When the linking step is performed by liquid-phase synthesis, the liquid-phase synthesis may be performed in an organic solvent, and a liquid-phase tagging method may be used.

[0111] In one embodiment, specific examples of organic solvents used in the linking step include acetonitrile, isopropyl acetate, ethyl acetate, butyl acetate, methyl t-butyl ether, diethyl ether, dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, α,α,α-trifluorotoluene, toluene, hexane, cyclopentyl methyl ether, and mixed solvents thereof. Among these, at least one selected from the group consisting of acetonitrile, isopropyl acetate, methyl t-butyl ether, dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, α,α,α-trifluorotoluene, toluene, and cyclopentyl methyl ether, or a mixed solvent thereof, is preferred, at least one selected from the group consisting of isopropyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, α,α,α-trifluorotoluene, and toluene, or a mixed solvent thereof is more preferred, and at least one selected from the group consisting of 2-methyltetrahydrofuran, α,α,α-trifluorotoluene, and toluene, or a mixed solvent thereof is more preferred. As the mixed solvent, a mixed solvent of isopropyl acetate and methyl t-butyl ether or a mixed solvent of isopropyl acetate and acetonitrile is preferred.

[0112] In one embodiment, the organic solvent is used at 10 to 1000 mg / mL, preferably 20 to 500 mg / mL, and more preferably 50 to 200 mg / mL relative to the first amino acid or peptide.

[0113] In some embodiments, a base is used in the ligation step.

[0114] In one embodiment, the base used in the linking step has a conjugate acid having a pKa of 15.0 or less, more preferably 13.0 or less, and even more preferably 11.5 or less. In one embodiment, the base used in the linking step has a conjugate acid having a pKa of 0 or more, preferably 3 or more, and even more preferably 5 or more. In one embodiment, the base used in the linking step has a conjugate acid having a pKa of 0 to 15.0, preferably 0 to 11.5, more preferably 3 to 11.5, even more preferably 5 to 11.5, and most preferably 6 to 11.5. The "pKa" used herein can be measured using water as a solvent. As the pKa used herein, an actual measured value that has already been reported as the pKa when water is used as a solvent may be used. The actual pKa value is measured at 25°C. If the measured value of pKa is not available, it may be calculated using ADMETPredictor (Simulations Plus Inc., ver. 8.0), and the calculated value may be used as the pKa in this specification.The pKa of representative reagents is listed below: conjugate acid of DBU (pKa=11.9; R. Srivastava, J. Mol. Catal. A: Chem. 264 (2007) 146-152); conjugate acid of piperidine (pKa=11.22; Hall, HK, Jr. JA Am Chem. Soc. 1957, 79, 5441); conjugate acid of triethylamine (pKa=10.65; Hall, HK, Jr. JA Am Chem. Soc. 1957, 79, 5441); conjugate acid of diisopropylethylamine (pKa=11.44; Chemical and Pharmaceutical Bulletin, 1995, 43, 1872-1877); The conjugate acid of 2,4,6-collidine (pKa = 7.48; Clarke, K., Rothwell, K.J. Chem. Soc. 1960, 1885); the conjugate acid of 2,6-lutidine (pKa = 6.77; Clarke, K., Rothwell, K.J. Chem. Soc. 1960, 1885); the conjugate acid of N-methylmorpholine (pKa = 7.38; Analytical Sciences, 1996, vol. 12); the conjugate acid of pyridine (pKa = 5.21; D.H. Ripin, D.A. Evans, pKa's of Nitrogen Acids, [online], [retrieved September 22, 2023]); HCl (pKa = -8.0; D.H. Ripin, D.A. Evans, pKa's of Inorganic and Oxo-Acids, [online], [Retrieved December 5, 2017], Internet<URL: http: / / evans.rc.fas.harvard.edu / pdf / evans_pKa_table.pdf> ); HFIP(1,1,1,3,3,3-Hexafluoropropane-2-ol) (pKa=9.3; Tetrahedron Asymmetry, 2012, 23, 1023-1027).

[0115] In some embodiments, the base used in the linking step is an organic base, such as dicyclohexylmethylamine, diisopropylethylamine, triethylamine, 1-methylpiperidine, N-methylmorpholine, 4-N,N-dimethylaminopyridine, 2,6-lutidine, 2,4,6-collidine, N-methylimidazole, 1,8-diazabicyclo[5.4.0]-7-undecene, 1,5-diazabicyclo[4.3.0]-5-nonene, 1,1,3,3-tetramethylguanidine, 2-tert-butyl-1,1,3,3-tetramethylguanidine, and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. The organic base used in the linking step is preferably one selected from the group consisting of dicyclohexylmethylamine, diisopropylethylamine, triethylamine, 1-methylpiperidine, and 2-tert-butyl-1,1,3,3-tetramethylguanidine.

[0116] In one embodiment, the base used in the linking step is an inorganic base, preferably an alkali metal carbonate or an alkali metal phosphate. Examples of alkali metal carbonates include sodium carbonate, potassium carbonate, and cesium carbonate. Examples of alkali metal phosphates include sodium phosphate and potassium phosphate. Preferred inorganic bases used in the linking step are potassium carbonate and potassium phosphate.

[0117] In one embodiment, the organic or inorganic base used in the linking step is used in an amount of 1.1 to 10.0 molar equivalents, preferably 2.0 to 9.0 molar equivalents, more preferably 3.0 to 8.0 molar equivalents relative to the first amino acid or peptide.

[0118] As used herein, the terms "first amino acid" and "second amino acid" are used solely to distinguish the reactive sites between amino acids that are substrates in the ligation step. Specifically, a "first amino acid" refers to an amino acid whose reactive site is an amino group, and a "second amino acid" refers to an amino acid whose reactive site is a carboxy group.

[0119] In some embodiments, the first amino acid or peptide is a peptide comprising two or more amino acid residues.

[0120] In some embodiments, the amino group of the first amino acid or peptide has the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a linear C １ -C ６ Alkyl, branched C ３ -C ６ Alkyl, or C ３ -C ８ In certain embodiments, the amino group of the first amino acid or peptide is represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a hydrogen atom or a linear C １ -C ４ In certain embodiments, the amino group of the first amino acid or peptide is an amino group represented by the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a hydrogen atom, methyl, or ethyl. In certain embodiments, the amino group of the first amino acid or peptide is an amino group of the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is a hydrogen atom or methyl. In certain embodiments, the amino group of the first amino acid or peptide is an amino group of the formula: -NR ６ R ７ (In the formula, R ６ is a hydrogen atom, and R ７ is methyl).

[0121] In some embodiments, the carboxyl group of the first amino acid or peptide may be protected with a protecting group. Any protecting group known in the art may be used as the protecting group for the carboxyl group, as long as it does not reduce the solubility of the peptide in a solvent. Specific examples of such a protecting group for the carboxyl group include methyl, ethyl, t-butyl, trityl, cumyl, benzyl, and allyl groups, with t-butyl being preferred.

[0122] In some embodiments, the second amino acid or peptide is a peptide comprising two or more amino acid residues.

[0123] In some embodiments, the α-carbon of the carboxy group of the second amino acid or peptide is optionally substituted. In some embodiments, the α-carbon of the carboxy group of the second amino acid or peptide is substituted with a group of the formula: -CR ８ R ９ - (wherein, R ８ and R ９ are the same or different and represent a hydrogen atom, a linear C １ -C ４ Alkyl, optionally substituted branched C ３ -C ６ Alkyl, optionally substituted phenyl C １ -C ２ Alkyl or optionally substituted 5- to 6-membered heteroaryl C １ -C ２ R is an alkyl group. １ or R ２ is branched chain C ３ -C ６ When the branched C ３ -C ６ The alkyl may be substituted with one or more halogens. 1 or R ２ Phenyl C １ -C ２ When the phenyl C is alkyl, １ -C ２ The alkyl may be substituted with one or more selected from the group consisting of methyl, ethyl, propyl, halogen, methoxy, ethoxy, and trifluoromethyl.１ or R ２ is a 5- to 6-membered heteroaryl C １ -C ２ When it is alkyl, the 5- to 6-membered heteroaryl C １ -C ２ The alkyl may be substituted with one or more selected from the group consisting of methyl, ethyl, propyl, halogen, methoxy, ethoxy and trifluoromethyl.

[0124] In certain embodiments, the alpha carbon of the carboxy group of the second amino acid or peptide has the formula: -CR ８ R ９ - (wherein, R ８ and R ９ are the same or different and represent a hydrogen atom, a linear C １ -C ３ R is alkyl, isopropyl, or optionally substituted benzyl. 1 or R ２ When is benzyl, the benzyl or phenethyl may be substituted with one or more selected from the group consisting of fluorine, methyl, ethyl, methoxy, ethoxy and trifluoromethyl.

[0125] In certain embodiments, the alpha carbon of the carboxy group of the second amino acid or peptide has the formula: -CR ８ R ９ - (wherein, R ８ is a hydrogen atom, and R ２ is a hydrogen atom, methyl, benzyl, or p-fluorobenzyl).

[0126] In some embodiments, the amino group containing the nitrogen atom located β to the carboxy group of the second amino acid or peptide has the formula: -NR ５ - (wherein, R ５ is a hydrogen atom, linear C １ -C ６ Alkyl, branched C ３ -C ６ Alkyl, or C ３ -C ８ is cycloalkyl).

[0127] In certain embodiments, the amino group comprising the nitrogen atom located β to the carboxy group of the second amino acid or peptide has the formula: -NR ５ - (wherein, R ３ is a hydrogen atom or a linear C １ -C ４ alkyl).

[0128] In certain embodiments, the amino group comprising the nitrogen atom located β to the carboxy group of the second amino acid or peptide has the formula: -NR ５ - (wherein, R ３ is a hydrogen atom or methyl).

[0129] In some embodiments, the amino group of the second amino acid or peptide may be protected with a protecting group. Any protecting group known in the art may be used as the amino group protecting group, as long as it does not reduce the solubility of the peptide in a solvent. Specific examples of such amino group protecting groups include Cbz, p-nitrobenzyloxycarbonyl, 2-naphthylmethyloxycarbonyl, diphenylmethyloxycarbonyl, 9-anthrylmethyloxycarbonyl, Teoc, Fmoc, Boc, Alloc, trifluoroacetyl, triphenylmethyl, and methoxycarbonyl. Of these, Cbz, Teoc, Fmoc, Boc, Alloc, and trifluoroacetyl are preferred.

[0130] In one embodiment, the peptide compound or salt thereof produced by the method of the present invention comprises 8 to 20 amino acid residues, preferably 11 to 14 amino acid residues, more preferably 11 to 13 amino acid residues, and most preferably 11 amino acid residues.

[0131] In certain embodiments, the peptide compound or salt thereof produced by the method of the invention can comprise at least 1, at least 2, at least 3, at least 4, or at least 5 unnatural amino acid residues. In particular embodiments, the unnatural amino acid residue contained in the peptide compound or salt thereof produced by the method of the invention is an N-methyl amino acid residue.

[0132] In one embodiment, the peptide compound produced by the method of the present invention can be a linear peptide compound. In another embodiment, the peptide compound produced by the method of the present invention can be a cyclic peptide compound. In one embodiment, the linear or cyclic peptide compound may contain a cyclic structure (cyclic portion) as a partial structure. Specific examples of cyclic structures include a structure in which the side chain of one amino acid residue is linked to the side chain of another amino acid residue, a structure in which the N-substituent of one amino acid residue is linked to the side chain of another amino acid residue, or a structure in which the N-substituent of one amino acid residue is linked to the N-substituent of another amino acid residue. The two amino acid residues involved in the linkage for the cyclic structure may be adjacent, or there may be any number of amino acid residues between them, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 amino acid residues. The size of the ring formed by the cyclic structure is not particularly limited, and examples include a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring, an 8-membered ring, a 9-membered ring, a 10-membered ring, an 11-membered ring, a 12-membered ring, a 13-membered ring, a 14-membered ring, a 15-membered ring, a 16-membered ring, a 17-membered ring, an 18-membered ring, a 19-membered ring, a 20-membered ring, a 21-membered ring, a 22-membered ring, a 23-membered ring, a 24-membered ring, a 25-membered ring, a 26-membered ring, a 27-membered ring, a 28-membered ring, a 29-membered ring, a 30-membered ring, a 31-membered ring, a 32-membered ring, a 33-membered ring, a 34-membered ring, or a 35-membered ring. Preferably, the ring is a 5-, 6-, 7-, 8-, 9-, 10-, 11-, 12-, 13-, 14-, 15-, 16-, 17-, 18-, 19-, or 20-membered ring, more preferably a 10-, 11-, 12-, 13-, 14-, 15-, 16-, 17-, or 18-membered ring, and most preferably an 11-, 12-, 13-, or 14-membered ring. When a peptide compound has a cyclic structure, the number of cyclic structures is not limited, but it is preferred that one, two, three, four, or five cyclic structures be present.

[0133] In certain aspects, the peptide compound or salt thereof produced by the method of the present invention can comprise a cyclic portion composed of 4 or more, 6 or more, 8 or more, or 11 or more amino acid residues. In certain embodiments, the peptide compound or salt thereof produced by the method of the present invention is a cyclic peptide compound or salt thereof, and comprises a cyclic portion composed of 4 to 14 amino acid residues, preferably 6 to 14 amino acid residues, more preferably 8 to 14 amino acid residues, and most preferably 11 to 14 amino acid residues. In certain embodiments, the peptide compound or salt thereof produced by the method of the present invention is a cyclic peptide compound or salt thereof, and comprises a cyclic portion composed of 11 amino acid residues. In these aspects, the cyclic portion comprises one, two, three, four, five, six, or seven amide bonds linking the amino group of a first amino acid or peptide with the carboxy group of a second amino acid or peptide.

[0134] In certain embodiments, the method of the present invention may further comprise a step of removing / deprotecting the protecting groups of the amino and carboxy groups derived from the second amino acid or peptide and / or the protecting groups of the amino and carboxy groups derived from the first amino acid or peptide in the peptide compound obtained in the linking step (deprotection step) immediately before, immediately after, and / or during the linking step. The deprotection step can be carried out using a method known in the art, for example, using reagents and conditions described in "Greene's Protective Groups in Organic Synthesis, Fifth Edition, 2014."

[0135] In one embodiment, the deprotection step of the amino-protecting group can be carried out by catalytic hydrogenation, for example, when the protecting group is Cbz, p-nitrobenzyloxycarbonyl, 2-naphthylmethyloxycarbonyl, diphenylmethyloxycarbonyl, or 9-anthrylmethyloxycarbonyl. Any catalyst known in the art can be used for catalytic hydrogenation. Specific examples of the catalyst include Pd / C, Pd(OH) / C, and PtO, with Pd / C being preferred.

[0136] In some embodiments, the deprotection step of the amino protecting group can be carried out using a reagent such as TBAF, LiBH4, piperidine, trifluoroacetic acid, or methanesulfonic acid when the protecting group is Teoc, Fmoc, Boc, Alloc, or trifluoroacetyl.

[0137] In one embodiment, the deprotection step of the carboxy protecting group can be carried out under acidic conditions in the presence of a deprotecting reagent, for example, when the protecting group is a methyl group, an ethyl group, a t-butyl group, a trityl group, a cumyl group, a benzyl group, or an allyl group.

[0138] In some embodiments, the method of the present invention may further comprise a step of linking / condensing a third amino acid or peptide to the peptide compound obtained in the linking step or deprotection step (linking step A). ​​That is, the method of the present invention may comprise repeating the linking step two or more times.

[0139] In one embodiment, the method of the present invention may further comprise a step of linking / condensing the amino group and the carboxy group in the peptide compound obtained in the linking step or the deprotection step (linking step B). In this case, the peptide compound obtained in linking step B is a cyclic peptide compound.

[0140] In some embodiments, the ligation steps A and B can be carried out in the presence or absence of, for example, a condensation reagent, such as T3P, EDCI, HATU, COMU, BEP, PyBOP, DMT-MM, or PyOxim.

[0141] In one embodiment, the method of the present invention is carried out using a flow reactor. As used herein, the term "flow reactor" refers to a device that continuously supplies raw materials to a tubular reactor, mixes and reacts them to produce a target compound. The flow reactor may be a commercially available flow reactor (e.g., the Africa flow chemistry system or the Asia flow chemistry system manufactured by Syrris), or may be a device that combines a tubular reactor with a syringe pump.

[0142] Peptide Compound In one aspect, the present invention relates to a peptide compound or a salt thereof produced by the above-mentioned "method for producing a peptide compound." In one aspect, the present invention relates to a pharmaceutical composition comprising a peptide compound or a salt thereof produced by the above-mentioned "method for producing a peptide compound."

[0143] All references cited herein, including patent applications and publications, are hereby incorporated by reference in their entirety, including the following: WO 2013 / 100132, WO 2018 / 225851, WO 2018 / 225864, WO 2019 / 117274, WO 2020 / 111238, WO 20201 2 / 2182, WO 2021 / 075478, WO 2021 / 090856, WO 2021132545, WO 2021246471, WO 2022 / 097540, WO 2022 / 138891, WO 20221 / 45444, WO 2022 / 234864, WO 2023 / 127869.

[0144] The present invention is further illustrated by the following examples, but is not limited thereto. Unless otherwise specified, starting materials, starting materials, solvents, and reagents were obtained from commercial suppliers or synthesized using known methods. In these examples, "OxymaPure" refers to the name of ethyl 2-cyano-2-(hydroxyimino)acetate (Oxyma) obtained from a commercial supplier. K2CO3 fine powder and K3PO4 fine powder were obtained from commercial suppliers.

[0145] 1 ​H-NMR spectra were measured using a JNM-ECZ500 nuclear magnetic resonance spectrometer (JEOL Ltd.). The chemical shift of tetramethylsilane, used as an internal standard, was set at 0 ppm, and the deuterium lock signal from the sample solvent was used as the reference. The chemical shifts of the analyte signals were expressed in ppm. Signal splitting was abbreviated as follows: s: singlet, brs: broad singlet, d: doublet, t: triplet, q: quartet, dd: double doublet, and m: multiplet. Signal splitting widths were expressed in J values ​​(Hz). Signal integration was calculated based on the ratio of the area intensities of each signal.

[0146] HPLC analysis was performed using a Waters H-Class system with a PDA detector at a wavelength of 210 nm. The reactivity, selectivity, and purity of each substrate used in the examples were evaluated using the analytical methods shown in Table 1 below. LCMS analysis was performed using an SQD2 or QDa detector.

[0147]

[0148] Unless otherwise specified in the experimental section, HPLC samples were prepared in the following manner: Condensation step: 3-10 μL of the reaction mixture was dissolved in MeCN (1.0 mL) and azetidine or 1-propylamine (0.1 mL).

[0149] The conversion rate and diastereomeric ratio of the condensation reaction were calculated using the HPLC area values ​​of each component in the reaction mixture according to the following formula. In the formula, "substrate" refers to the substrate with the smaller molar amount of the two substrates to be condensed. Conversion rate = [(desired product + epimer) / (substrate + desired product + epimer)] x 100 Diastereomeric ratio = desired product / epimer

[0150] In the table, a horizontal line (-) indicates that no calculation was performed, negligible indicates that a trace amount of a by-product was detected, and many indicates that multiple by-products were detected.

[0151] (Example 1) Condensation reaction of Cbz-MeLeu-MePhe(4-F)-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0152] Reaction procedure: HOPO (134.6 mg, 1.211 mmol, 2.0 equiv.), OxymaPure (86.1 mg, 0.606 mmol, 1.0 equiv.), a 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (129.0 mg / mL, 2.60 mL, 335.0 mg, 0.731 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (150.0 mg / mL, 3.00 mL, 450.0 mg, 0.606 mmol, 1.0 equiv.), and DIPEA (738 μL, 4.24 mmol, 7.0 equiv.) were sequentially added to a vial containing a stir bar. The reaction mixture was cooled to 10°C while stirring. DPPC (250 μL, 1.211 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 14 hours. HPLC analysis of the reaction mixture confirmed the progress of the reaction. Conversion: 99.5% Diastereomer ratio (dr): 99.9 / 0.1

[0153] Post-treatment step: 5% Na2CO3 aqueous solution (2.2 mL) was added to the reaction mixture and stirred for 1.5 hours. NMI (48 μL, 0.606 mmol) was added and stirred for an additional 1.5 hours. The aqueous layer was removed, and 5% Na2CO3 aqueous solution (2.0 mL) was added to the resulting organic layer and stirred for 4 hours. The aqueous layer was removed, and the resulting organic layer was washed three times with 10% citric acid aqueous solution (2.0 mL x 3) and twice with 5% Na2CO3 aqueous solution (2.0 mL x 2). The resulting organic layer was concentrated to dryness to obtain 650.0 mg of the desired product. Yield: 91% Purity: 97.0% Measurement method: HPLC Method A Retention time: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 10.2 min, desired product: 18.8 min, epimer: 19.0 min Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.07 ([M+H] + ),desired product: m / z 1206.52 ([M+Na] + ), epimer: m / z 1206.35 ([M+Na] + )

[0154] (Example 2) Condensation reaction of Cbz-MeLeu-MePhe(4-F)-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0155] Under the conditions shown in Table 2, additive-1, additive-2, a 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (concentration: 129.0 mg / mL, 0.300 mL, 38.7 mg, 0.084 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (concentration: 142.9 mg / mL, 0.245 mL, 35.0 mg, 0.070 mmol, 1.0 equiv.), and DIPEA (85.0 μL, 0.487 mmol, 7.0 equiv.) were sequentially added to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DPPC (28.8 μL, 0.139 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 3 h. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.4 min, desired product: 17.5 min, epimer: 17.8 min. Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.81 ([M+H] + ),desired product: m / z 944.14 ([M+H] + ), epimer: m / z 944.14 ([M+H] + )

[0156]

[0157] As shown in Table 2, it was found that the target product was obtained with the highest conversion, diastereomeric ratio, and purity under the conditions where both HOPO and OxymaPure were added.

[0158] Comparative experiment using HATU. A 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (concentration: 129.0 mg / mL, 0.300 mL, 38.7 mg, 0.084 mmol), a MeCN solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (concentration: 200.0 mg / mL, 0.175 mL, 35.0 mg, 0.069 mmol), and DIPEA (24.3 μL, 0.139 mmol) were added sequentially to a vial containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (52.8 mg, 0.139 mmol) was added. The mixture was stirred for 5 h. Conversion: 99.7%. Diastereomeric ratio: 90.5 / 9.5.

[0159] (Example 3) Condensation reaction of Cbz-MeLeu-MePhe(4-F)-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0160] Additive-1, Additive-2, a 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (concentration: 129.0 mg / mL, 0.260 mL, 33.5 mg, 0.073 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (concentration: 150.0 mg / mL, 0.300 mL, 45.0 mg, 0.061 mmol, 1.0 equiv.), and DIPEA (73.8 μL, 0.424 mmol, 7.0 equiv.) were sequentially added to a test tube containing a stir bar under the conditions shown in Table 3. The reaction mixture was cooled to 10 °C with stirring. DPPC (25.0 μL, 0.121 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 10 hours. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 10.3 min, desired product: 18.9 min, epimer: 19.1 min. Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.07 ([M+H] + ),desired product: m / z 1206.23 ([M+Na] + ), epimer: m / z 1206.35 ([M+Na] + )

[0161]

[0162] As shown in Table 3, it was found that the target product was obtained with the highest conversion, diastereomeric ratio, and purity under the conditions where both HOPO and OxymaPure were added.

[0163] Comparative experiment using HATU. A 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (concentration: 129.0 mg / mL, 0.260 mL, 33.5 mg, 0.073 mmol), a MeCN solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (concentration: 170.0 mg / mL, 0.265 mL, 45.1 mg, 0.061 mmol), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a vial containing a stir bar. The reaction mixture was cooled to 10 °C, and HATU (46.5 mg, 0.121 mmol) was added and stirred for 5 h. Conversion: 99.6%. Diastereomeric ratio: 79.5 / 20.5.

[0164] (Example 4) Condensation reaction of Cbz-MeLeu-MePhe-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0165] Under the conditions shown in Table 4, additive-1, additive-2, a 2-MeTHF solution of Cbz-MeLeu-MePhe-OH (concentration: 169.5 mg / mL, 0.210 mL, 35.6 mg, 0.081 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (concentration: 170.0 mg / mL, 0.295 mL, 50.2 mg, 0.067 mmol, 1.0 equiv.), and DIPEA (82.1 μL, 0.471 mmol, 7.0 equiv.) were sequentially added to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DPPC (27.8 μL, 0.135 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 10 h. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 10.1 min, desired product: 18.7 min, epimer: 19.0 min. Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.12 ([M+H] + ),desired product: m / z 1188.73 ([M+Na] + ), epimer: m / z 1188.33 ([M+Na] + )

[0166]

[0167] As shown in Table 4, it was found that the target product was obtained with the highest conversion, diastereomeric ratio, and purity under the conditions where both HOPO and OxymaPure were added.

[0168] Comparative experiment using HATU: A 2-MeTHF solution of Cbz-MeLeu-MePhe-OH (concentration: 169.5 mg / mL, 0.210 mL, 35.6 mg, 0.081 mmol), a MeCN solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (concentration: 170.0 mg / mL, 0.295 mL, 50.2 mg, 0.067 mmol), and DIPEA (23.4 μL, 0.135 mmol) were added sequentially. The reaction mixture was cooled to 10 °C, and HATU (50.8 mg, 0.134 mmol) was added. The mixture was stirred for 5 h. Conversion: 99.5%. Diastereomeric ratio: 76.5 / 23.5.

[0169] (Example 5) Condensation reaction of Cbz-MeLeu-MePhe-OH and H-MeGly(cPent)-MeAsp(OtBu)-NMe2

[0170] Under the conditions shown in Table 5, additive-1, additive-2, a 2-MeTHF solution of Cbz-MeLeu-MePhe-OH (concentration: 169.5 mg / mL, 0.210 mL, 35.6 mg, 0.081 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeGly(cPent)-MeAsp(OtBu)-NMe2 (concentration: 129.6 mg / mL, 0.210 mL, 27.2 mg, 0.068 mmol, 1.0 equiv.), and DIPEA (82.6 μL, 0.474 mmol, 7.0 equiv.) were sequentially added to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DPPC (28.0 μL, 0.135 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 10 h. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: 5.7 min, desired product: 17.8 min, epimer: 18.2 min. Mass spectrometry: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: m / z 370.82 ([M+H] +), desired product: m / z 748.28 ([M-NMe2] + ), epimer: m / z 748.06([M-NMe2] + )

[0171]

[0172] As shown in Table 5, it was found that the target product was obtained with the highest conversion, diastereomeric ratio, and purity when both HOPO and OxymaPure were added.

[0173] Comparative experiment using HATU. HATU (78.0 mg, 0.206 mmol), an IPAC solution of Cbz-MeLeu-MePhe-OH (160.0 mg / mL, 0.300 mL, 48.0 mg, 0.109 mmol), an MeCN solution of H-MeGly(cPent)-MeAsp(OtBu)-NMe2 (75.7 mg / mL, 0.500 mL, 37.9 mg, 0.103 mmol), and DIPEA (90.0 μL, 0.514 mmol) were added sequentially to a vial containing a stir bar and stirred for 3.5 hours. Conversion: 100.0% Diastereomeric Ratio: 35.5 / 64.5

[0174] (Example 6) Condensation reaction of Cbz-MeLeu-MeAla-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0175] Cbz-MeLeu-MeAla-OH (23.9 mg, 0.066 mmol, 1.1 equiv.), HOPO (13.3 mg, 0.119 mmol, 2.0 equiv.), OxymaPure (8.5 mg, 0.060 mmol, 1.0 equiv.), H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (30.0 mg, 0.060 mmol, 1.0 equiv.), 2-MeTHF (0.300 mL), and DIPEA (72.8 μL, 0.418 mmol, 7.0 equiv.) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DEPC (17.2 μL, 0.119 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 30 h. Conversion: 98.4% Diastereomeric ratio: 99.2 / 0.8 Epimer synthesis: The epimer was synthesized according to the above conditions, except for using Cbz-MeLeu-D-MeAla-OH instead of Cbz-MeLeu-MeAla-OH. Measurement method: HPLC Method A Retention times: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.0 min, desired product: 15.6 min, epimer: 15.9 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.36 ([M+H] + ),desired product: m / z 849.69 ([M+H] + ), epimer: m / z 849.50 ([M+H] + )

[0176] (Example 7) Condensation reaction of Cbz-MeLeu-MeAla-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0177] Cbz-MeLeu-MeAla-OH (27.0 mg, 0.074 mmol, 1.1 equiv.), HOPO (15.0 mg, 0.135 mmol, 2.0 equiv.), OxymaPure (9.6 mg, 0.067 mmol, 1.0 equiv.), H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (50.0 mg, 0.067 mmol, 1.0 equiv.), 2-MeTHF (0.300 mL), and DIPEA (81.1 μL, 0.471 mmol, 7.0 equiv.) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DPPC (27.9 μL, 0.135 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 30 h. Conversion: 99.0% Diastereomer ratio: 99.5 / 0.5 Epimer synthesis: The epimer was synthesized according to the above conditions, except for using Cbz-MeLeu-D-MeAla-OH instead of Cbz-MeLeu-MeAla-OH. Measurement method: HPLC Method A Retention times: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 9.9 min, desired product: 17.4 min, epimer: 17.7 min Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 743.63 ([M+H] + ),desired product: m / z 1089.78 ([M+H] + ), epimer: m / z 1089.95 ([M+H] + )

[0178] (Example 8) Condensation reaction of Cbz-MeLeu-MeAla-OH and H-MeGly(cPent)-MeAsp(OtBu)-NMe2

[0179] Cbz-MeLeu-MeAla-OH (27.1 mg, 0.074 mmol, 1.1 equiv.), HOPO (15.0 mg, 0.135 mmol, 2.0 equiv.), OxymaPure (9.6 mg, 0.068 mmol, 1.0 equiv.), 2-MeTHF (0.152 mL), a 2-MeTHF solution of H-MeGly(cPent)-MeAsp(OtBu)-NMe2 (170.0 mg / mL, 0.147 mL, 25.0 mg, 0.068 mmol, 1.0 equiv.), and DIPEA (81.5 μL, 0.474 mmol, 7.0 equiv.) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DEPC (19.6 μL, 0.068 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 30 hours. Conversion: 96.6% Diastereomer ratio: 99.5 / 0.5 Epimer synthesis: The epimer was synthesized according to the above conditions, except for using Cbz-MeLeu-D-MeAla-OH instead of Cbz-MeLeu-MeAla-OH. Measurement method: HPLC Method A Retention times: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: 5.5 min, desired product: 16.1 min, epimer: 16.3 min Mass spectrometry: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: m / z 370.31 ([M+H] + ),desired product: m / z 738.53 ([M+Na] + ), epimer: m / z 738.35 ([M+Na] + )

[0180] (Example 9) Evaluation of Additive-1

[0181] To a test tube containing a stir bar, additive-1 (0.139 mmol, 2.0 equiv.), OxymaPure (9.90 mg, 0.070 mmol, 1.0 equiv.), a 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (129.0 mg / mL, 0.300 mL, 38.7 mg, 0.084 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (142.9 mg / mL, 0.245 mL, 35.0 mg, 0.070 mmol, 1.0 equiv.), and DIPEA (85.0 μL, 0.487 mmol, 7.0 equiv.) were sequentially added under the conditions shown in Table 6. The reaction mixture was cooled to 10 °C with stirring. DPPC (28.8 μL, 0.139 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 3 hours. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.5 min, desired product: 17.6 min, epimer: 17.9 min. Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.98 ([M+H] + ), desired product: m / z 944.14 ([M+H] + ), epimer: m / z 944.14 ([M+H] + )

[0182]

[0183] As shown in Table 6, HOOBt, Oxyma-B, and pentafluorophenol gave results similar to those of HOPO.

[0184] (Example 10) Evaluation of Additive-2

[0185] HOPO (15.5 mg, 0.139 mmol, 2.0 equiv.), additive-2 (0.070 mmol, 1.0 equiv.), a 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (129.0 mg / mL, 0.300 mL, 38.7 mg, 0.084 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (142.9 mg / mL, 0.245 mL, 35.0 mg, 0.070 mmol, 1.0 equiv.), and DIPEA (85.0 μL, 0.487 mmol, 7.0 equiv.) were sequentially added to a test tube containing a stir bar under the conditions shown in Table 7. The reaction mixture was cooled to 10 °C with stirring. DPPC (28.8 μL, 0.139 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 3 hours. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.4 min, desired product: 17.5 min, epimer: 17.8 min. Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.98 ([M+H] + ), desired product: m / z 944.14 ([M+H] + ), epimer: m / z 944.14 ([M+H] + )

[0186]

[0187] As shown in Table 7, HOAt, Oxyma-B, and K-Oxyma gave results similar to OxymaPure.

[0188] (Example 11) Evaluation of condensing agents other than DPPC and DEPC

[0189] Cbz-MeLeu-MeAla-OH (27.1 mg, 0.074 mmol, 1.1 equiv.), HOPO (15.0 mg, 0.135 mmol, 2.0 equiv.), OxymaPure (9.6 mg, 0.068 mmol, 1.0 equiv.), 2-MeTHF (0.152 mL), a 2-MeTHF solution of H-MeGly(cPent)-MeAsp(OtBu)-NMe2 (170.0 mg / mL, 0.147 mL, 25.0 mg, 0.068 mmol, 1.0 equiv.), and DIPEA (81.5 μL, 0.474 mmol, 7.0 equiv.) were sequentially added to a test tube containing a stir bar under the conditions shown in Table 8. The reaction mixture was cooled to 10 °C with stirring. A condensing agent (0.135 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 5 hours. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: 5.5 min, desired product: 16.1 min, epimer: 16.3 min. Mass spectrometry: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: m / z 370.31 ([M+H] + ), desired product: m / z 738.54 ([M+Na] + ), epimer: m / z 738.41 ([M+Na] + )

[0190]

[0191] As shown in Table 8, DPPA, FDPP, and Ph2P(O)Cl gave results similar to those of DPPC, and the other condensing agents gave significantly lower results in either the conversion rate, diastereomeric ratio, or amount of by-products.

[0192] (Example 12) Evaluation of bases

[0193] To a test tube containing a stir bar, HOPO (13.5 mg, 0.121 mmol, 2.0 equiv.), OxymaPure (8.6 mg, 0.061 mmol, 1.0 equiv.), a 2-MeTHF solution of Cbz-MeLeu-MePhe(4-F)-OH (concentration: 129.0 mg / mL, 0.260 mL, 33.5 mg, 0.073 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (concentration: 150.0 mg / mL, 0.300 mL, 45.0 mg, 0.061 mmol, 1.0 equiv.), and base (0.424 mmol, 7.0 equiv.) were sequentially added under the conditions shown in Table 9. The reaction mixture was cooled to 10°C with stirring. DPPC (25.0 μL, 0.121 mmol, 2.0 equiv.) was added to the reaction mixture and stirred for 10 hours. The reaction mixture was analyzed by HPLC to evaluate the conversion rate, diastereomeric ratio, and amount of by-products. Measurement method: HPLC Method A. Retention times: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 10.3 min, desired product: 18.9 min, epimer: 19.1 min. Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.07 ([M+H] + ),desired product: m / z 1206.23 ([M+Na] + ), epimer: m / z 1206.35 ([M+Na] + )

[0194]

[0195] As shown in Table 9, TEA and 1-methylpiperidine gave results equivalent to those of DIPEA.

[0196] (Example 13) Condensation reaction of Cbz-Gly-MePhe-OH and H-MePhe-MeAsp(OtBu)-NMe

[0197] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (10.5 mg, 0.074 mmol), HOPO (16.4 mg, 0.148 mmol), H-MePhe-MeAsp(OtBu)-NMe2 (30.0 mg, 0.074 mmol), 2-MeTHF (0.300 mL), a 2-MeTHF / DMI solution of Cbz-Gly-MePhe-OH (182.6 mg / mL, 0.170 mL, 31.0 mg, 0.088 mmol), and Cy2NMe (110.0 μL, 0.518 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to -5 °C with stirring. DPPC (30.6 μL, 0.148 mmol) was added to the reaction mixture, which was then warmed to 10 °C and stirred for 12 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0198] Comparative experiment using HATU: H-MePhe-MeAsp(OtBu)-NMe2 (30.0 mg, 0.074 mmol), MeCN (0.300 mL), a 2-MeTHF / DMI solution of Cbz-Gly-MePhe-OH (182.6 mg / mL, 0.170 mL, 31.0 mg, 0.088 mmol), and DIPEA (25.8 μL, 0.148 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (56.3 mg, 0.148 mmol) was added and stirred for 12 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MePhe-MeAsp(OtBu)-NMe2: 7.2 min, desired product: 15.6 min, epimer: 16.1 min Mass spectrometry: H-MePhe-MeAsp(OtBu)-NMe2: m / z 392.77 ([M+H] + ), desired product: m / z 700.00 ([M-NMe2] + ), epimer: m / z 699.95 ([M-NMe2] + )

[0199]

[0200] As shown in Table 10, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0201] (Example 14) Condensation reaction of Cbz-MeAla-MeLeu-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0202] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (8.6 mg, 0.061 mmol), HOPO (13.5 mg, 0.121 mmol), a 2-MeTHF solution of Cbz-MeAla-MeLeu-OH (170.0 mg / mL, 0.160 mL, 27.0 mg, 0.073 mmol), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (150.0 mg / mL, 0.300 mL, 45.0 mg, 0.061 mmol), and Cy2NMe (90.0 μL, 0.424 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (25.0 μL, 0.121 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 11 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0203] Comparative experiment using HATU. A 2-MeTHF solution of Cbz-MeAla-MeLeu-OH (170.0 mg / mL, 0.160 mL, 27.0 mg, 0.073 mmol), a MeCN solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (170.0 mg / mL, 0.270 mL, 45.9 mg, 0.061 mmol), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (46.1 mg, 0.121 mmol) was added and stirred for 5 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 11.1 min, desired product: 18.7 min, epimer: 19.0 min Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.18 ([M+H] + ), desired product: m / z 945.34 ([M-Sar-OtBu] + ), epimer: m / z 945.28 ([M-Sar-OtBu] + )

[0204]

[0205] As shown in Table 11, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0206] (Example 15) Condensation reaction of Cbz-MeAla-MeLeu-OH and H-MeGly(nPr)-Ile-Pro-OtBu

[0207] Experiments using DPPC, HOPO, and OxymaPure: H-MeGly(nPr)-Ile-Pro-OtBu (24.1 mg, 0.061 mmol), OxymaPure (8.6 mg, 0.061 mmol), HOPO (13.5 mg, 0.121 mmol), 2-MeTHF (0.200 mL), a 2-MeTHF solution of Cbz-MeAla-MeLeu-OH (170.0 mg / mL, 0.160 mL, 27.0 mg, 0.073 mmol), and Cy2NMe (90.0 μL, 0.424 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to -5 °C with stirring. DPPC (25.0 μL, 0.121 mmol) was added to the reaction mixture, which was then warmed to 10 °C and stirred for 10 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0208] Comparative experiment using HATU: H-MeGly(nPr)-Ile-Pro-OtBu (24.1 mg, 0.073 mmol), MeCN (0.200 mL), a 2-MeTHF solution of Cbz-MeAla-MeLeu-OH (170.0 mg / mL, 0.160 mL, 27.0 mg, 0.073 mmol), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (46.1 mg, 0.121 mmol) was added and stirred for 10 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeGly(nPr)-Ile-Pro-OtBu: 8.6 min, desired product: 18.0 min, epimer: 18.1 min Mass spectrometry: H-MeGly(nPr)-Ile-Pro-OtBu: m / z 398.81 ([M+H] + ), desired product: m / z 745.09 ([M+H] + ), epimer: m / z 745.15 ([M+H] + )

[0209]

[0210] As shown in Table 12, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0211] (Example 16) Condensation reaction of Cbz-MeLeu-MePhe-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0212] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (8.5 mg, 0.060 mmol), HOPO (13.3 mg, 0.119 mmol), a 2-MeTHF solution of Cbz-MeLeu-MePhe-OH (200.0 mg / mL, 0.160 mL, 32.0 mg, 0.072 mmol), a 2-MeTHF solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (143.3 mg / mL, 0.210 mL, 30.0 mg, 0.060 mmol), and Cy2NMe (88.7 μL, 0.418 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (24.7 μL, 0.119 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 10 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0213] Comparative experiment using HATU. A 2-MeTHF solution of Cbz-MeLeu-MePhe-OH (200.0 mg / mL, 0.160 mL, 32.0 mg, 0.072 mmol), a MeCN solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (200.0 mg / mL, 0.150 mL, 30.0 mg, 0.060 mmol), and DIPEA (20.8 μL, 0.119 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (45.4 mg, 0.119 mmol) was added and stirred for 5 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.0 min, desired product: 17.0 min, epimer: 17.3 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.37 ([M+H] + ), desired product: m / z 780.50 ([M-Sar-OtBu] + ), epimer: m / z 780.50 ([M-Sar-OtBu] + )

[0214]

[0215] As shown in Table 13, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0216] (Example 17) Condensation reaction of Cbz-MeLeu-D-MePhe-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0217] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (8.5 mg, 0.060 mmol), HOPO (13.3 mg, 0.119 mmol), a 2-MeTHF solution of Cbz-MeLeu-D-MePhe-OH (200.0 mg / mL, 0.160 mL, 32.0 mg, 0.072 mmol, 1.2 equiv.), a 2-MeTHF solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (143.3 mg / mL, 0.210 mL, 30.0 mg, 0.060 mmol, 1.0 equiv.), and Cy2NMe (88.7 μL, 0.418 mmol, 7.0 equiv.) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (24.7 μL, 0.119 mmol, 2.0 equiv.) was added to the reaction mixture, which was then heated to 10° C. and stirred for 10 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0218] Comparative experiment using HATU. A 2-MeTHF solution of Cbz-MeLeu-D-MePhe-OH (200.0 mg / mL, 0.160 mL, 32.0 mg, 0.072 mmol, 1.2 equiv.), a MeCN solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (200.0 mg / mL, 0.150 mL, 30.0 mg, 0.060 mmol, 1.0 equiv.), and DIPEA (20.8 μL, 0.119 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (45.4 mg, 0.119 mmol) was added and stirred for 5 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.0 min, desired product: 17.3 min, epimer: 17.0 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.37 ([M+H] +), desired product: m / z 780.48 ([M-Sar-OtBu] + ), epimer: m / z 780.57 ([M+H] + )

[0219]

[0220] As shown in Table 14, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0221] (Example 18) Condensation reaction of Cbz-Leu-MePhe-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0222] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (8.6 mg, 0.061 mmol), HOPO (13.5 mg, 0.121 mmol), Cbz-Leu-MePhe-OH (31.0 mg, 0.073 mmol), 2-MeTHF (0.200 mL), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (150.0 mg / mL, 0.300 mL, 45.0 mg, 0.061 mmol), and Cy2NMe (90.0 μL, 0.424 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (25.0 μL, 0.121 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 10 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0223] Comparative experiment using HATU: Cbz-Leu-MePhe-OH (31.0 mg, 0.073 mmol), MeCN (0.200 mL), a MeCN solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (170.0 mg / mL, 0.270 mL, 45.9 mg, 0.061 mmol), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (46.1 mg, 0.121 mmol) was added and stirred for 5 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 9.9 min, desired product: 17.9 min, epimer: 18.6 min Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.24 ([M+H] + ), desired product: m / z 1007.53 ([M-Sar-OtBu] + ), epimer: m / z 1007.24 ([M-Sar-OtBu] + )

[0224]

[0225] As shown in Table 15, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0226] (Example 19) Condensation reaction of Cbz-Leu-D-MePhe-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0227] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (8.6 mg, 0.061 mmol), HOPO (13.5 mg, 0.121 mmol), Cbz-Leu-D-MePhe-OH (31.0 mg, 0.073 mmol), 2-MeTHF (0.200 mL), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (150.0 mg / mL, 0.300 mL, 45.0 mg, 0.061 mmol), and Cy2NMe (90.0 μL, 0.424 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (25.0 μL, 0.121 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 5 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0228] Comparative experiment using HATU: Cbz-Leu-D-MePhe-OH (31.0 mg, 0.073 mmol), MeCN (0.200 mL), a MeCN solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (170.0 mg / mL, 0.270 mL, 45.9 mg, 0.061 mmol), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (46.1 mg, 0.121 mmol) was added and stirred for 4 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 9.9 min, desired product: 18.6 min, epimer: 17.9 min Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.24 ([M+H] + ), desired product: m / z 1007.24 ([M-Sar-OtBu] +), epimer: m / z 1007.35 ([M-Sar-OtBu] + )

[0229]

[0230] As shown in Table 16, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0231] (Example 20) Condensation reaction of Cbz-D-Leu-MePhe-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0232] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (8.6 mg, 0.061 mmol), HOPO (13.5 mg, 0.121 mmol), Cbz-D-Leu-MePhe-OH (31.0 mg, 0.073 mmol), 2-MeTHF (0.200 mL), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (150.0 mg / mL, 0.300 mL, 45.0 mg, 0.061 mmol), and Cy2NMe (90.0 μL, 0.424 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (25.0 μL, 0.121 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 5 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0233] Comparative experiment using HATU: Cbz-D-Leu-MePhe-OH (31.0 mg, 0.073 mmol), MeCN (0.200 mL), a MeCN solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (170.0 mg / mL, 0.270 mL, 45.9 mg, 0.061 mmol), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (46.1 mg, 0.121 mmol) was added. The reaction mixture was stirred for 4.5 hours. HPLC analysis was performed to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 9.9 min, desired product: 18.1 min, epimer: 18.2 min Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.24 ([M+H] + ), desired product: m / z 1007.30 ([M-Sar-OtBu] + ), epimer: m / z 1007.30 ([M-Sar-OtBu] + )

[0234]

[0235] As shown in Table 17, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0236] (Example 21) Condensation reaction of Cbz-MeLeu-MeSer(OtBu)-OH and H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0237] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (11.0 mg, 0.077 mmol), HOPO (17.0 mg, 0.153 mmol), a 2-MeTHF solution of Cbz-MeLeu-MeSer(OtBu)-OH (166.5 mg / mL, 0.240 mL, 40.0 mg, 0.092 mmol), a 2-MeTHF solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (150.0 mg / mL, 0.380 mL, 57.0 mg, 0.077 mmol), and Cy2NMe (114.0 μL, 0.537 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (31.7 μL, 0.153 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 10 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0238] Comparative experiment using HATU: A 2-MeTHF solution of Cbz-MeLeu-MeSer(OtBu)-OH (166.0 mg / mL, 0.240 mL, 40.0 mg, 0.092 mmol), a MeCN solution of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (170.0 mg / mL, 0.340 mL, 57.8 mg, 0.077 mmol), and DIPEA (26.8 μL, 0.153 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (58.4 mg, 0.153 mmol) was added and stirred for 5 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 10.0 min, desired product: 18.9 min, epimer: 19.4 min Mass spectrometry: H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 744.01 ([M+H] +), desired product: m / z 1017.67 ([M-Sar-OtBu] + ), epimer: m / z 1017.27 ([M-Sar-OtBu] + )

[0239]

[0240] As shown in Table 18, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0241] (Example 22) Condensation reaction of Cbz-MeLeu-MeSer(OtBu)-OH and H-MeGly(cPent)-MeAsp(OtBu)-NMe2

[0242] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (11.0 mg, 0.077 mmol), HOPO (17.0 mg, 0.153 mmol), a 2-MeTHF solution of Cbz-MeLeu-MeSer(OtBu)-OH (166.0 mg / mL, 0.240 mL, 40.0 mg, 0.092 mmol), a 2-MeTHF solution of H-MeGly(cPent)-MeAsp(OtBu)-NMe (129.7 mg / mL, 0.215 mL, 27.9 mg, 0.077 mmol), and CyNMe (114.0 μL, 0.536 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (31.7 μL, 0.153 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 24 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0243] Comparative experiment using HATU. A 2-MeTHF solution of Cbz-MeLeu-MeSer(OtBu)-OH (166.0 mg / mL, 0.240 mL, 40.0 mg, 0.092 mmol), a MeCN solution of H-MeGly(cPent)-MeAsp(OtBu)-NMe2 (75.8 mg / mL, 0.360 mL, 27.3 mg, 0.077 mmol), and DIPEA (26.8 μL, 0.153 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (58.4 mg, 0.153 mmol) was added and stirred for 2 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: 5.7 min, desired product: 17.9 min, epimer: 18.3 min Mass spectrometry: H-MeGly(cPent)-MeAsp(OtBu)-NMe2: m / z 370.71 ([M+H] + ), desired product: m / z 744.07 ([M-NMe2] + ), epimer: m / z 743.95 ([M-NMe2] + )

[0244]

[0245] As shown in Table 19, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0246] (Example 23) Condensation reaction of Cbz-Aze-EtPhe(4-Me)-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0247] Experiments using DPPC, HOPO, and OxymaPure: OxymaPure (8.6 mg, 0.061 mmol), HOPO (13.5 mg, 0.121 mmol), Cbz-Aze-EtPhe(4-Me)-OH (31.0 mg, 0.073 mmol), 2-MeTHF (0.200 mL), a 2-MeTHF solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (143.3 mg / mL, 0.210 mL, 30.1 mg, 0.061 mmol), and Cy2NMe (90.0 μL, 0.425 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to −5 °C with stirring. DPPC (25.0 μL, 0.121 mmol) was added to the reaction mixture, which was then heated to 10° C. and stirred for 24 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio.

[0248] Comparative experiment using HATU: Cbz-Aze-EtPhe(4-Me)-OH (31.0 mg, 0.073 mmol), MeCN (0.200 mL), a MeCN solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (200.0 mg / mL, 0.150 mL, 30.0 mg, 0.060 mmol), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (46.1 mg, 0.121 mmol) was added and stirred for 10 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.1 min, desired product: 15.8 min, epimer: 15.9 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.81 ([M+H] + ), desired product: m / z 766.01 ([M-Sar-OtBu] + ), epimer: m / z 765.95 ([M-Sar-OtBu] + )

[0249]

[0250] As shown in Table 20, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0251] (Example 24) Condensation reaction of Fmoc-MeAlGly-MeAlGly-OH and H-MeGly(nPr)-Ile-Pro-OtBu

[0252] Experiments using DPPC, HOPO, and OxymaPure: H-MeGly(nPr)-Ile-Pro-OtBu (24.1 mg, 0.061 mmol), Fmoc-MeAlGly-MeAlGly-OH (33.6 mg, 0.073 mmol), OxymaPure (8.6 mg, 0.061 mmol), HOPO (13.5 mg, 0.121 mmol), 2-MeTHF (0.400 mL), and DIPEA (73.9 μL, 0.424 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to -5 °C with stirring. DPPC (25.1 μL, 0.121 mmol) was added to the reaction mixture, which was then heated to 10 °C and stirred for 10 h. The reaction mixture was analyzed by HPLC to assess the reaction conversion and diastereomeric ratio.

[0253] Comparative experiment using HATU: H-MeGly(nPr)-Ile-Pro-OtBu (24.1 mg, 0.061 mmol), Fmoc-MeAlGly-MeAlGly-OH (33.6 mg, 0.073 mmol), MeCN (0.400 mL), and DIPEA (21.1 μL, 0.121 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring, and HATU (46.1 mg, 0.121 mmol) was added and stirred for 10 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeGly(nPr)-Ile-Pro-OtBu: 8.7 min, desired product: 19.3 min, epimer: 19.4 min Mass spectrometry: H-MeGly(nPr)-Ile-Pro-OtBu: m / z 398.81 ([M+H] + ), desired product: m / z 865.19 ([M+Na] + ), epimer: m / z 865.08 ([M+Na] + )

[0254]

[0255] As shown in Table 21, it was found that condition A using DPPC, HOPO, and OxymaPure gave a higher diastereomeric ratio than condition B using HATU as a condensing agent.

[0256] (Example 25) Investigation of solvents in the condensation reaction of Cbz-MeLeu-MeIle-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0257] Cbz-MeLeu-MeIle-OH (38.2 mg, 0.092 mmol), H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (38.6 mg, 0.077 mmol), OxymaPure (11.0 mg, 0.077 mmol), HOPO (17.1 mg, 0.154 mmol), solvent (0.500 mL), and DIPEA (93.6 μL, 0.538 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DEPC (22.2 μL, 0.154 mmol) was added to the reaction mixture and stirred for 24 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.3 min, desired product: 17.6 min, epimer: 18.1 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.98 ([M+H] + ), desired product: m / z 914.21 ([M+Na] + ), epimer: m / z 914.27 ([M+Na] + )

[0258]

[0259] As shown in Table 22, it was found that α,α,α-trifluorotoluene and toluene gave particularly high reaction conversion rates and diastereomeric ratios.

[0260] (Example 26) Examination of organic bases in the condensation reaction of Cbz-MeLeu-MeIle-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0261] Cbz-MeLeu-MeIle-OH (38.2 mg, 0.092 mmol), H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (38.6 mg, 0.077 mmol), OxymaPure (11.0 mg, 0.077 mmol), HOPO (17.1 mg, 0.154 mmol), toluene (0.500 mL), and DIPEA (93.6 μL, 0.538 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DEPC (22.2 μL, 0.154 mmol) was added to the reaction mixture and stirred for 3 h. Additional base (0.538 mmol) was added to the reaction mixture, and stirring was continued for an additional 21 h. The reaction mixture was analyzed by HPLC to assess the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.3 min, desired product: 17.6 min, epimer: 18.1 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.81 ([M+H] + ), desired product: m / z 914.21 ([M+Na] + ), epimer: m / z 913.99 ([M+Na] + )

[0262]

[0263] As shown in Table 23, it was found that Cy2NMe and BTMG gave high reaction conversion rates and diastereomeric ratios.

[0264] (Example 27) Examination of inorganic bases in the condensation reaction of Cbz-MeLeu-MeIle-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0265] OxymaPure (11.0 mg, 0.077 mmol), HOPO (17.1 mg, 0.154 mmol), a toluene solution of Cbz-MeLeu-MeIle-OH (164.0 mg / mL, 0.240 mL, 39.4 mg, 0.096 mmol), a toluene solution of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (169.0 mg / mL, 0.230 mL, 38.9 mg, 0.077 mmol), and Cy2NMe (114.0 μL, 0.538 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DEPC (22.2 μL, 0.154 mmol) was added to the reaction mixture and stirred for 5 h. An additional inorganic base (0.538 mmol) was added to the reaction mixture, and stirring was continued for an additional 19 hours. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A. Retention times: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.3 min, desired product: 17.6 min, epimer: 18.1 min. Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.98 ([M+H] + ), desired product: m / z 914.21 ([M+Na] + ), epimer: m / z 914.27 ([M+Na] + )

[0266]

[0267] As shown in Table 24, it was found that K3PO4 and K2CO3 gave high reaction conversion and diastereomeric ratio.

[0268] (Example 28) Investigation of the equivalent ratio of HOPO to OxymaPure in the condensation reaction of Cbz-MeLeu-MeIle-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0269] Cbz-MeLeu-MeIle-OH (38.2 mg, 0.092 mmol), H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (38.6 mg, 0.077 mmol), HOPO (x mmol), OxymaPure (y mmol), toluene (0.500 mL), and DIPEA (93.6 μL, 0.538 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DEPC (22.2 μL, 0.154 mmol) was added to the reaction mixture and stirred for 5 h. DIPEA (93.6 μL, 0.538 mmol) was added to the reaction mixture and stirring was continued for an additional 19 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.3 min, desired product: 17.6 min, epimer: 18.1 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.98 ([M+H] + ), desired product: m / z 914.21 ([M+Na] + ), epimer: m / z 914.27 ([M+Na] + )

[0270]

[0271] As shown in Table 25, the equivalent ratio of HOPO to OxymaPure has little effect on the diastereomeric ratio.

[0272] (Example 29) Examination of hydroxypyridine derivatives in the condensation reaction of Cbz-MeLeu-MeIle-OH and H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0273] Cbz-MeLeu-MeIle-OH (38.2 mg, 0.092 mmol), H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu (38.6 mg, 0.077 mmol), OxymaPure (11.0 mg, 0.077 mmol), HOPO derivative (0.154 mmol), toluene (0.500 mL), and DIPEA (187.0 μL, 1.080 mmol) were added sequentially to a test tube containing a stir bar. The reaction mixture was cooled to 10 °C with stirring. DEPC (22.2 μL, 0.154 mmol) was added to the reaction mixture, and the mixture was stirred for 24 h. The reaction mixture was analyzed by HPLC to evaluate the reaction conversion and diastereomeric ratio. Measurement method: HPLC Method A Retention time: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: 8.3 min, desired product: 17.6 min, epimer: 18.1 min Mass spectrometry: H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu: m / z 503.98 ([M+H] + ), desired product: m / z 914.21 ([M+Na] + ), epimer: m / z 914.27 ([M+Na] + )

[0274]

[0275] As shown in Table 26, the addition of 5-Br-HOPO or 5-CO2Me-HOPO resulted in high conversion rates and diastereomeric ratios. The diastereomeric ratios for Run 2 were not shown because the conversion rate was significantly low.

[0276] (Raw material synthesis 1) Synthesis of Cbz-MeLeu-MePhe-OH

[0277] Cbz-MePhe-OtBu (6.50 g, 17.59 mmol) was dissolved in 2-MeTHF (50 mL) and added to a pressure reactor. 5% Pd / C (3.76 g, 0.88 mmol on Pd metal basis) was added to the pressure reactor, and the atmosphere was purged with nitrogen and hydrogen. The mixture was stirred under hydrogen pressure (3-4 atm) for 6 hours. The reaction mixture was filtered, and the Pd / C was washed with 2-MeTHF. The filtrate and washings were combined and concentrated under reduced pressure to give H-MePhe-OtBu (4.13 g, 17.55 mmol). Cbz-MeLeu-OH (4.62 g, 16.54 mmol) was added to a flask equipped with a stir bar. A solution of H-MePhe-OtBu in MeCN (concentration: 0.10 g / mL, 37.0 mL, 3.70 g, 15.72 mmol) and NMM (5.2 mL, 47.20 mmol) were added to the flask, sequentially. HATU (8.97 g, 23.58 mmol) was added to the reaction mixture, and stirring was continued at room temperature. Stirring was continued for 1 hour, and completion of the reaction was confirmed by HPLC analysis. CPME (50.0 mL), 5% aqueous K2CO3 solution (50.0 mL), and NMI (1.25 mL, 15.72 mmol) were added to the reaction mixture, and stirring was continued for 1.5 hours. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The organic layer was washed three times with 2.5% aqueous ammonia (50 mL x 3), twice with 5% aqueous NaHSO4 (50 mL x 2), and once with 5% aqueous Na2CO3 (40 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-MeLeu-MePhe-OtBu (6.90 g, 13.89 mmol). Cbz-MeLeu-MePhe-OtBu (6.90 g, 13.89 mmol), 2-MeTHF (70 mL), and HMDS (15.0 mL, 69.50 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (10.1 mL, 55.60 mmol). After stirring for 2 h, HMDS (2.9 mL) and TMSOTf (2.5 mL) were added to the reaction mixture. After stirring for an additional 1.5 h, HMDS (6.0 mL) and TMSOTf (5.0 mL) were added to the reaction mixture.HPLC analysis confirmed that the conversion rate reached 94%. The flask was cooled, and 5% aqueous NaHCO3 (70 mL) was added dropwise while maintaining the reaction mixture at 33 °C or below. The entire contents of the flask were transferred to a separatory funnel, and 5% aqueous NaHCO3 (30 mL) and 2-MeTHF (30 mL) were used for rinsing. After HPLC analysis of the organic and aqueous layers, the organic layer was removed. 2-MeTHF (100 mL) was added to the resulting aqueous layer, and 85% H3PO4 (7.5 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (50 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-MePhe-OH (5.00 g, 11.35 mmol). Yield: 72% (over 2 steps starting from H-MePhe-OtBu) Purity: 100% Measurement method: HPLC Method A, retention time: 13.9 min Mass spectrometry: m / z 441.78 ([M+H]. + )

[0278] (Raw Material Synthesis 2) Synthesis of Cbz-MeLeu-MePhe(4-F)-OH

[0279] A flask containing a stir bar was charged with Fmoc-MePhe(4-F)-OH (4.98 g, 11.87 mmol), cyclohexane (15 mL), and DCM (40 mL). tert-Butyl 2,2,2-trichloroacetimidate (4.3 mL, 23.80 mmol) was then added. Boron trifluoride diethyl etherate (0.15 mL, 1.19 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 4.5 hours. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (40 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (40 mL x 2). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Fmoc-MeLeu-MePhe(4-F)-OtBu (5.30 g, 11.10 mmol). To a flask equipped with a stir bar, Fmoc-MeLeu-MePhe(4-F)-OtBu (5.30 g, 11.10 mmol) and MeCN (40 mL) were added. DBU (1.7 mL, 11.10 mmol) was added to the flask and stirred for 30 min. After confirming completion of the reaction by HPLC analysis, TEA (6.2 mL, 44.60 mmol) and water (2.0 mL, 111.00 mmol) were added to the reaction mixture. Sodium bisulfite (2.90 g, 27.90 mmol) was added to the flask while cooling in an ice bath, and the mixture was stirred at room temperature for 2 h. MTBE (100 mL) and 10% aqueous ammonia (50 mL) were added to the reaction mixture, and the entire contents of the flask were transferred to a separatory funnel. The aqueous layer was removed, and the resulting organic layer was washed three times with 10% aqueous ammonia (50 mL x 3) and once with 5% aqueous NaCl (50 mL x 1). The resulting organic layer was concentrated under reduced pressure to give H-MePhe(4-F)-OtBu. A flask containing a stir bar was charged with H-MePhe(4-F)-OtBu, MeCN (30 mL), Cbz-MeLeu-OH (3.41 g, 12.30 mmol), and NMM (3.7 mL, 33.40 mmol).While cooling the flask in an ice bath, HATU (5.53 g, 14.50 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 2 h. After confirming completion of the reaction by HPLC analysis, CPME (50 mL), 5% aqueous K2CO3 (30 mL), and NMI (0.88 mL, 11.10 mmol) were added to the reaction mixture, and stirring was continued for 1.5 h. The contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The resulting organic layer was washed three times with 2.5% aqueous ammonia (50 mL x 3), two times with 5% aqueous NaHSO4 (50 mL x 2), one time with 5% aqueous Na2CO3 (50 mL x 1), and one time with 5% aqueous NaCl (50 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4, and the desiccant was removed by filtration. The filtrate was concentrated under reduced pressure to give Cbz-MeLeu-MePhe(4-F)-OtBu (5.37 g, 10.40 mmol). Cbz-MeLeu-MePhe(4-F)-OtBu (5.37 g, 10.40 mmol), 2-MeTHF (50 mL), and HMDS (10.9 mL, 52.20 mmol) were added to a flask containing a stir bar, followed by the dropwise addition of TMSOTf (7.5 mL, 41.70 mmol). After stirring for 2 h, HMDS (5.0 mL) and TMSOTf (3.0 mL) were added to the reaction mixture. Stirring was continued for an additional 4 h, and HPLC analysis confirmed that the conversion had reached 97%. The flask was cooled, and 5% aqueous NaHCO3 (70 mL) was added dropwise while maintaining the reaction temperature below 25 °C. The entire contents of the flask were transferred to a separatory funnel, and 5% aqueous NaHCO3 (30 mL) and 2-MeTHF (20 mL) were used for rinsing. The organic and aqueous layers were analyzed by HPLC, and the organic layer was removed. 2-MeTHF (100 mL) was added to the resulting aqueous layer, and 85% H3PO4 (10 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (30 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-MePhe(4-F)-OH (4.00 g, 8.72 mmol).Yield: 73% (over 4 steps starting from Fmoc-MePhe(4-F)-OH) Purity: 98.3% Assay: HPLC Method A, Retention Time: 14.04 min Mass Spectrometry: m / z 459.80 ([M+H]. + )

[0280] (Raw material synthesis 3) Synthesis of Cbz-MeLeu-MeAla-OH

[0281] A flask containing a stir bar was charged with Cbz-MeLeu-OH (10.50 g, 37.59 mmol), H-MeAla-OtBu·HCl (7.00 g, 35.77 mmol), 2-MeTHF (70 mL), MeCN (50 mL), and NMM (11.8 mL, 107 mmol). The flask was cooled, and HATU (20.40 g, 53.65 mmol) was added to the reaction mixture while maintaining the reaction temperature below 30 °C. Stirring was continued for 3 h, and completion of the reaction was confirmed by HPLC analysis. IPAC (50 mL), 5% aqueous Na2CO3 solution (70 mL), and NMI (2.84 mL, 35.81 mmol) were added to the reaction mixture, and stirring was continued for 30 min. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The organic layer was washed three times with 2.5% aqueous ammonia (50 mL x 3), twice with 5% aqueous NaHSO4 (50 mL x 2), once with 5% aqueous Na2CO3 (50 mL), and once with 10% aqueous NaCl (50 mL). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-MeLeu-MeAla-OtBu (14.35 g, 34.12 mmol). 2-MeTHF (140 mL) and HMDS (49.9 mL, 238.9 mmol) were added to the concentrate, followed by the dropwise addition of TMSOTf (37.7 mL, 204.7 mmol). Stirring was continued for 3.5 h, and completion of the reaction was confirmed by HPLC analysis. The flask was cooled, and 5% aqueous Na2CO3 (70 mL) was added dropwise while maintaining the reaction mixture below 30 °C. The entire contents of the flask were transferred to a separatory funnel, and 2-MeTHF (30 mL) and 5% aqueous Na2CO3 (30 mL) were added. The aqueous layer was removed. 2-MeTHF (100 mL) was added, followed by the slow addition of 85% H3PO4 (15 mL). The aqueous layer was removed, and the organic layer was washed once with 10% aqueous NaCl (50 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-MeAla-OH (9.74 g).Yield: 75% (over 2 steps) Purity: 98.2% Assay: HPLC Method A, Retention time: 11.3 min Mass Spectrometry: m / z 365.08 ([M+H]. + )

[0282] (Synthesis of analytical standard 2) Synthesis of Cbz-MeLeu-D-MeAla-OH

[0283] A flask containing a stir bar was charged with Cbz-MeLeu-OH (2.25 g, 8.05 mmol), HD-MeAla-OtBu·HCl (1.50 g, 7.67 mmol), MeCN (20 mL), and NMM (2.53 mL, 23.0 mmol). The flask was cooled, and HATU (4.37 g, 11.5 mmol) was added to the reaction mixture while maintaining the reaction temperature below 30 °C. Stirring was continued for 6 h, and completion of the reaction was confirmed by HPLC analysis. IPAC (20 mL), 5% aqueous Na2CO3 (20 mL), and NMI (0.608 mL, 7.67 mmol) were added to the reaction mixture, and stirring was continued for 30 min. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The organic layer was washed three times with 2.5% aqueous ammonia (15 mL x 3), twice with 5% aqueous NaHSO4 (15 mL x 2), once with 5% aqueous Na2CO3 (15 mL), and once with 10% aqueous NaCl (15 mL). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-MeLeu-D-MeAla-OtBu (3.18 g, 7.56 mmol). 2-MeTHF (30 mL) and HMDS (11.1 mL, 52.9 mmol) were added to the concentrate, followed by the dropwise addition of TMSOTf (8.36 mL, 45.4 mmol). Stirring was continued for 4 hours, and completion of the reaction was confirmed by HPLC analysis. The flask was cooled, and 5% aqueous Na2CO3 (15 mL) was added dropwise while maintaining the reaction mixture below 30 °C. The entire contents of the flask were transferred to a separatory funnel, and 2-MeTHF (10 mL) and 5% aqueous Na2CO3 (10 mL) were added. The aqueous layer was removed. 2-MeTHF (20 mL) was added, followed by the slow addition of 85% H3PO4 (3.0 mL). The aqueous layer was removed, and the organic layer was washed once with 10% aqueous NaCl (15 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-D-MeAla-OH (2.54 g). Yield: 91% (over 2 steps). Purity: 99.7%. Measurement method: HPLC Method A. Retention time: 11.4 min. Mass spectrometry: m / z 365.20 ([M+H] +)

[0284] (Raw Material Synthesis 4) Synthesis of H-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0285] It was synthesized according to the method described in WO 2023 / 127869.

[0286] (Raw Material Synthesis 5) Synthesis of H-MeLeu-Ile-MeAla-Aze-EtPhe(4-Me)-Sar-OtBu

[0287] The L-tartrate salt of the title compound obtained by the method described in WO 2023 / 127869 was desalted and synthesized.

[0288] (Raw Material Synthesis 6) Synthesis of H-MeGly(cPent)-MeAsp(OtBu)-NMe2

[0289] The hydrochloride salt of the title compound obtained by the method described in WO 2023 / 127869 was desalted and synthesized.

[0290] (Raw Material Synthesis 7) Synthesis of Cbz-Gly-MePhe-OH

[0291] A flask containing a stir bar was charged with Cbz-MePhe-OH (10.00 g, 31.90 mmol), cyclohexane (80 mL), and DCM (30 mL). tert-Butyl 2,2,2-trichloroacetimidate (11.4 mL, 63.70 mmol) was added to the flask. Boron trifluoride diethyl etherate (0.4 mL, 3.19 mmol) was added dropwise while cooling the flask in an ice bath, and the mixture was stirred at room temperature for 2 hours. tert-Butyl 2,2,2-trichloroacetimidate (3.0 mL, 16.76 mmol) was added to the flask, and the mixture was stirred for an additional 30 minutes. The reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (50 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (50 mL x 2). The resulting organic layer was concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MePhe-OtBu (9.84 g, 26.6 mmol). Cbz-MePhe-OtBu (9.50 g, 25.70 mmol), 2-MeTHF (70 mL), and 5% Pd / C (5.50 g, 1.29 mmol on Pd metal basis) were sequentially added to a pressure-resistant reaction vessel equipped with a stirrer. The atmosphere in the reaction vessel was purged with nitrogen and then hydrogen, and the reaction mixture was stirred under a hydrogen atmosphere (3-4 atm) for 5 hours. The reaction mixture was filtered, and the Pd / C was washed with 2-MeTHF. The filtrate and washings were combined and concentrated under reduced pressure to give H-MePhe-OtBu (6.02 g, 25.60 mmol). To a flask containing a stir bar, H-MePhe-OtBu (1.33 g, 5.52 mmol), MeCN (16.0 mL), Cbz-Gly-OH (1.29 g, 6.08 mmol), and NMM (2.4 mL, 21.80 mmol) were added sequentially. While the flask was cooled in an ice bath, HATU (4.20 g, 11.05 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 2 hours. After confirming completion of the reaction by HPLC analysis, CPME (20 mL), 5% aqueous Na2CO3 (15 mL), and NMI (0.45 mL, 5.65 mmol) were added sequentially to the reaction mixture, and stirring was continued for 2 hours.The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The mixture was washed three times with 2.5% aqueous ammonia (25 mL x 3), twice with 5% aqueous NaHSO (25 mL x 2), and once with 5% aqueous KCO (25 mL x 1). The resulting organic layer was dried over anhydrous NaSO. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-Gly-MePhe-OtBu (2.36 g, 5.52 mmol). A flask containing a stir bar was charged with Cbz-Gly-MePhe-OtBu (2.36 g, 5.52 mmol), 2-MeTHF (25.0 mL), and HMDS (6.1 mL, 29.10 mmol), followed by the dropwise addition of TMSOTf (4.3 mL, 23.76 mmol). Stirring was continued for 1.5 h. During this time, 2-MeTHF (10.0 mL) was added to the reaction mixture to improve its fluidity. After confirming the completion of the reaction by HPLC analysis, the flask was cooled, and 5% aqueous NaHCO3 (25 mL) was added dropwise while maintaining the reaction mixture at 25°C or below. The entire contents of the flask were transferred to a separatory funnel. 2-MeTHF (50 mL) was added to the separatory funnel, and 85% H3PO4 (3.0 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (30 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-Gly-MePhe-OH (1.77 g, 4.78 mmol). Purity: 100.0%. Measurement method: HPLC Method A. Retention time: 11.3 min. Mass spectrometry: m / z 371.62 ([M+H]). + )

[0292] (Raw Material Synthesis 8) Synthesis of Cbz-MeAla-MeLeu-OH

[0293] A flask containing a stir bar was charged with Cbz-MeLeu-OH (2.00 g, 7.20 mmol), cyclohexane (16 mL), and DCM (6 mL). tert-Butyl 2,2,2-trichloroacetimidate (2.6 mL, 14.53 mmol) was added to the flask. Boron trifluoride diethyl etherate (90 μL, 0.72 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 1 hour. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (16 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (16 mL x 2). The resulting organic layer was concentrated under reduced pressure to give Cbz-MeLeu-OtBu (2.38 g, 7.10 mmol). To a flask equipped with a stir bar, Cbz-MeLeu-OtBu (2.38 g, 7.10 mmol), 2-MeTHF (24 mL), and 5% Pd / C (1.51 g, 0.36 mmol on Pd metal basis) were added sequentially. The atmosphere in the flask was purged with nitrogen and then hydrogen, and the reaction mixture was stirred under a hydrogen atmosphere (1 atm) for 1 h. The reaction mixture was filtered, and the Pd / C was washed with 2-MeTHF. The filtrate and washings were combined and concentrated under reduced pressure to give H-MeLeu-OtBu (1.39 g, 6.90 mmol). To a flask equipped with a stir bar, H-MeLeu-OtBu (1.39 g, 6.90 mmol), MeCN (14.0 mL), Cbz-MeAla-OH (1.80 g, 7.60 mmol), and NMM (1.5 mL, 13.64 mmol) were added sequentially. While the flask was cooled in an ice bath, COMU (3.55 g, 8.29 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 3 hours. Completion of the reaction was confirmed by HPLC analysis, and 2-MeTHF (42 mL), 5% aqueous K2CO3 solution (21 mL), and NMI (0.55 mL, 6.90 mmol) were added sequentially to the reaction mixture, and stirring was continued for 1 hour. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed.The organic layer was washed once with 5% K2CO3 aqueous solution (35 mL x 1), three times with 2.5% ammonia solution (35 mL x 3), twice with 5% NaHSO4 aqueous solution (35 mL x 2), once with 5% K2CO3 aqueous solution (35 mL x 1), and once with 5% NaCl aqueous solution (35 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-MeAla-MeLeu-OtBu (2.70 g, 6.42 mmol). Cbz-MeAla-MeLeu-OtBu (2.70 g, 6.42 mmol), 2-MeTHF (27.0 mL), and HMDS (5.8 mL, 27.67 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (3.6 mL, 19.89 mmol). After stirring for 3 h, HMDS (2.9 mL, 13.84 mmol) and TMSOTf (1.8 mL, 9.95 mmol) were added to the reaction mixture. After stirring for an additional 1.5 h, HMDS (1.4 mL, 6.68 mmol) and TMSOTf (0.95 mL, 5.25 mmol) were added to the reaction mixture. After HPLC analysis confirmed that the conversion had reached 93%, the flask was cooled and 5% aqueous NaHCO3 (32 mL) was added dropwise while maintaining the reaction temperature below 13 °C. The contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (65 mL) was added to the resulting aqueous layer, and 85% H3PO4 (4.8 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (32 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeAla-MeLeu-OH (1.73 g, 4.74 mmol). Purity: 99.3%. Measurement method: HPLC Method A. Retention time: 12.6 min. Mass spectrometry: m / z 365.64 ([M+H]). + )

[0294] (Raw Material Synthesis 9) Synthesis of Cbz-MeLeu-MePhe-OH

[0295] A flask containing a stir bar was charged with Cbz-MePhe-OH (4.50 g, 14.00 mmol), cyclohexane (36 mL), and DCM (14 mL). tert-Butyl 2,2,2-trichloroacetimidate (5.0 mL, 27.94 mmol) was added to the flask. Boron trifluoride diethyl etherate (0.18 mL, 1.43 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 1.5 hours. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (36 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (36 mL x 2). The resulting organic layer was concentrated under reduced pressure to give Cbz-MePhe-OtBu (5.18 g, 14.00 mmol). To a flask containing a stir bar, Cbz-MePhe-OtBu (5.18 g, 14.00 mmol), 2-MeTHF (52 mL), and 5% Pd / C (2.98 g, 0.70 mmol on Pd metal basis) were added sequentially. The atmosphere in the flask was purged with nitrogen and then hydrogen, and the reaction mixture was stirred under a hydrogen atmosphere (1 atm) for 2 hours. The reaction mixture was filtered, and the Pd / C was washed with 2-MeTHF. The filtrate and washings were combined and concentrated under reduced pressure to give H-MePhe-OtBu (3.20 g, 13.60 mmol). To a flask containing a stir bar, H-MePhe-OtBu (3.20 g, 13.60 mmol), MeCN (32.0 mL), Cbz-MeLeu-OH (4.19 g, 15.00 mmol), and NMM (4.5 mL, 40.93 mmol) were added sequentially. While the flask was cooled in an ice bath, COMU (7.57 g, 17.68 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 4 hours. Completion of the reaction was confirmed by HPLC analysis, and 2-MeTHF (96 mL), 5% aqueous K2CO3 solution (48 mL), and NMI (1.1 mL, 13.80 mmol) were added sequentially to the reaction mixture, and stirring was continued for 30 minutes. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed.The organic layer was washed once with 5% K2CO3 aqueous solution (80 mL x 1), three times with 2.5% ammonia solution (80 mL x 3), twice with 5% NaHSO4 aqueous solution (80 mL x 2), once with 5% K2CO3 aqueous solution (80 mL x 1), and once with 5% NaCl aqueous solution (80 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-MeLeu-MePhe-OtBu (7.14 g, 14.40 mmol). Cbz-MeLeu-MePhe-OtBu (6.75 g, 13.60 mmol), 2-MeTHF (68.0 mL), and HMDS (20.0 mL, 95.42 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (15.0 mL, 82.88 mmol). After stirring for 5.5 hours, HPLC analysis confirmed that the conversion rate had reached 95%. The flask was cooled, and 5% aqueous NaHCO3 (68 mL) was added dropwise while maintaining the reaction mixture at 20°C or below. The entire contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (100 mL) was added to the resulting aqueous layer, and 85% H3PO4 (10.0 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (68 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-MePhe-OH (5.08 g, 11.50 mmol). Purity: 99.2%. Measurement method: HPLC Method A. Retention time: 13.4 min. Mass spectrometry: m / z 441.33 ([M+H]). + )

[0296] (Raw Material Synthesis 10) Synthesis of Cbz-MeLeu-D-MePhe-OH

[0297] A flask containing a stir bar was charged with Fmoc-D-MePhe-OH (2.01 g, 4.98 mmol), cyclohexane (16 mL), and DCM (22 mL). tert-Butyl 2,2,2-trichloroacetimidate (0.9 mL, 5.03 mmol) was added. While cooling the flask in an ice bath, boron trifluoride diethyl etherate (0.06 mL, 0.478 mmol) was added dropwise, and the mixture was stirred at room temperature for 1 hour. Additional tert-butyl 2,2,2-trichloroacetimidate (0.9 mL, 5.03 mmol) was added to the flask, and the mixture was stirred for 2 hours. Additional tert-butyl 2,2,2-trichloroacetimidate (0.9 mL, 5.03 mmol) was added to the flask, and the mixture was stirred for 1 hour. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (14 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (14 mL x 2). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Fmoc-D-MePhe-OtBu (2.79 g, 6.09 mmol). To a flask equipped with a stir bar, Fmoc-D-MePhe-OtBu (2.28 g, 4.98 mmol) and MeCN (18 mL) were added. DBU (0.74 mL, 4.95 mmol) was added to the flask and stirred for 1 h. After confirming the completion of the reaction by HPLC analysis, TEA (2.8 mL, 20.09 mmol) and water (1.0 mL, 55.49 mmol) were added to the reaction mixture. While cooling the flask in an ice bath, sodium bisulfite (1.30 g, 12.49 mmol) was added and the mixture was stirred at room temperature for 1 hour. MTBE (60 mL) and 10% aqueous ammonia (30 mL) were added to the reaction mixture, and the entire contents of the flask were transferred to a separatory funnel. The aqueous layer was removed, and the resulting organic layer was washed three times with 10% aqueous ammonia (30 mL x 3) and once with 5% aqueous NaCl (15 mL x 1). The resulting organic layer was concentrated under reduced pressure to give HD-MePhe-OtBu (0.98 g).HD-MePhe-OtBu (0.98 g), MeCN (12 mL), Cbz-MeLeu-OH (1.29 g, 4.60 mmol), and NMM (1.4 mL, 12.73 mmol) were added to a flask containing a stir bar. COMU (2.33 g, 5.44 mmol) was added to the reaction mixture while cooling the flask in an ice bath, and stirring was continued at room temperature for 2 hours. After confirming completion of the reaction by HPLC analysis, 2-MeTHF (30 mL), 5% aqueous K2CO3 (15 mL), and NMI (0.33 mL, 4.14 mmol) were added to the reaction mixture, and stirring was continued for 30 minutes. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The resulting organic layer was washed once with 5% K2CO3 aqueous solution (25 mL x 1), three times with 2.5% ammonia solution (25 mL x 3), twice with 5% NaHSO4 aqueous solution (25 mL x 2), once with 5% K2CO3 aqueous solution (25 mL x 1), and once with 5% NaCl aqueous solution (50 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4, and the drying agent was removed by filtration. The filtrate was concentrated under reduced pressure to give Cbz-MeLeu-D-MePhe-OtBu (2.05 g, 4.12 mmol). Cbz-MeLeu-D-MePhe-OtBu (2.05 g, 4.12 mmol), 2-MeTHF (20 mL), and HMDS (6.0 mL, 28.63 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (4.6 mL, 25.42 mmol). After stirring for 4.5 hours, completion of the reaction was confirmed by HPLC analysis. The flask was cooled, and 5% aqueous NaHCO3 (20 mL) was added dropwise while maintaining the reaction mixture at 18 °C or below. The entire contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (30 mL) was added to the resulting aqueous layer, and 85% H3PO4 (3.0 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (20 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-D-MePhe-OH (1.36 g, 3.09 mmol).Purity: 99.2% Determination method: HPLC Method A, retention time: 13.6 min Mass analysis: m / z 441.28 ([M+H]. + )

[0298] (Synthesis of raw materials 11) Synthesis of Cbz-Leu-MePhe-OH

[0299] A flask containing a stir bar was charged with Cbz-MePhe-OH (4.98 g, 16.00 mmol), cyclohexane (40 mL), and DCM (15 mL). tert-Butyl 2,2,2-trichloroacetimidate (5.8 mL, 32.41 mmol) was added to the flask. Boron trifluoride diethyl etherate (0.20 mL, 1.59 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 2.5 hours. tert-Butyl 2,2,2-trichloroacetimidate (1.4 mL, 7.82 mmol) and boron trifluoride diethyl etherate (0.20 mL, 1.59 mmol) were added to the reaction mixture, and the mixture was stirred for 1 hour. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (40 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (40 mL x 2). The resulting organic layer was concentrated under reduced pressure to give Cbz-MePhe-OtBu (5.02 g, 13.59 mmol). Cbz-MePhe-OtBu (5.02 g, 13.59 mmol), 2-MeTHF (50 mL), and 5% Pd / C (2.88 g, 0.68 mmol on Pd metal basis) were added sequentially to a flask equipped with a stir bar. The atmosphere in the flask was purged with nitrogen and then hydrogen, and the reaction mixture was stirred under a hydrogen atmosphere (1 atm) for 1.5 hours. The reaction mixture was filtered, and the Pd / C was washed with 2-MeTHF. The filtrate and washings were combined and concentrated under reduced pressure to give H-MePhe-OtBu (3.19 g, 13.55 mmol). H-MePhe-OtBu (2.01 g, 8.50 mmol), MeCN (20.0 mL), Cbz-Leu-OH (2.48 g, 9.35 mmol), and NMM (1.9 mL, 17.28 mmol) were sequentially added to a flask containing a stir bar. COMU (4.37 g, 10.20 mmol) was added to the reaction mixture while cooling the flask in an ice bath, and stirring was continued at room temperature for 3 h.After confirming the completion of the reaction by HPLC analysis, 2-MeTHF (30.0 mL), 5% aqueous K2CO3 (20.0 mL), and NMI (0.67 mL, 8.41 mmol) were added to the reaction mixture, followed by stirring for 45 minutes. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The organic layer was washed three times with 2.5% aqueous ammonia (25 mL x 3), two times with 5% aqueous NaHSO4 (25 mL x 2), and once with 5% aqueous Na2CO3 (25 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-Leu-MePhe-OtBu (4.13 g, 8.56 mmol). Cbz-Leu-MePhe-OtBu (4.13 g, 8.56 mmol), 2-MeTHF (41.0 mL), and HMDS (13.0 mL, 62.02 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (9.5 mL, 52.49 mmol). After stirring for 2 h, HPLC analysis confirmed that the conversion had reached 94%. The flask was cooled, and 5% aqueous NaHCO3 (40 mL) was added dropwise while maintaining the reaction mixture below 23 °C. The entire contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (50 mL) was added to the resulting aqueous layer, and 85% H3PO4 (4.5 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (30 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-Leu-MePhe-OH (2.49 g, 5.84 mmol). Purity: 98.7%. Measurement method: HPLC Method A. Retention time: 12.7 min. Mass spectrometry: m / z 427.71 ([M+H]). + )

[0300] (Raw Material Synthesis 12) Synthesis of Cbz-D-Leu-MePhe-OH

[0301] A flask containing a stir bar was charged with Cbz-MePhe-OH (4.98 g, 16.00 mmol), cyclohexane (40 mL), and DCM (15 mL). tert-Butyl 2,2,2-trichloroacetimidate (5.8 mL, 32.41 mmol) was added to the flask. Boron trifluoride diethyl etherate (0.20 mL, 1.59 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 2.5 hours. tert-Butyl 2,2,2-trichloroacetimidate (1.4 mL, 7.82 mmol) and boron trifluoride diethyl etherate (0.20 mL, 1.59 mmol) were added to the reaction mixture, and the mixture was stirred for 1 hour. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (40 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (40 mL x 2). The resulting organic layer was concentrated under reduced pressure to give Cbz-MePhe-OtBu (5.02 g, 13.59 mmol). Cbz-MePhe-OtBu (5.02 g, 13.59 mmol), 2-MeTHF (50 mL), and 5% Pd / C (2.88 g, 0.68 mmol on Pd metal basis) were added sequentially to a flask equipped with a stir bar. The atmosphere in the flask was purged with nitrogen and then hydrogen, and the reaction mixture was stirred under a hydrogen atmosphere (1 atm) for 1.5 hours. The reaction mixture was filtered, and the Pd / C was washed with 2-MeTHF. The filtrate and washings were combined and concentrated under reduced pressure to give H-MePhe-OtBu (3.19 g, 13.55 mmol). H-MePhe-OtBu (1.16 g, 4.93 mmol), MeCN (12.0 mL), Cbz-D-Leu-OH (1.44 g, 5.42 mmol), and NMM (1.1 mL, 10.01 mmol) were sequentially added to a flask containing a stir bar. COMU (2.53 g, 5.91 mmol) was added to the reaction mixture while cooling the flask in an ice bath, and stirring was continued at room temperature for 2 h.After confirming completion of the reaction by HPLC analysis, 2-MeTHF (20.0 mL), 5% aqueous K2CO3 (20.0 mL), and NMI (0.39 mL, 4.89 mmol) were added sequentially to the reaction mixture and stirred for 30 min. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The organic layer was washed once with 5% aqueous Na2CO3 (15 mL x 1), three times with 2.5% aqueous ammonia (15 mL x 3), two times with 5% aqueous NaHSO4 (15 mL x 2), and once with 5% aqueous Na2CO3 (15 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The desiccant was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-D-Leu-MePhe-OtBu (2.47 g, 5.12 mmol). Cbz-D-Leu-MePhe-OtBu (2.47 g, 5.12 mmol), 2-MeTHF (25.0 mL), and HMDS (7.5 mL, 35.78 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (5.6 mL, 30.94 mmol). After stirring for 3 h, HPLC analysis confirmed that the conversion had reached 97%. The flask was cooled, and 5% aqueous NaHCO3 (30 mL) was added dropwise while maintaining the reaction mixture below 24 °C. The entire contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (30 mL) was added to the resulting aqueous layer, and 85% H3PO4 (2.5 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (20 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-D-Leu-MePhe-OH (1.44 g, 3.38 mmol). Purity: 99.1%. Measurement method: HPLC Method A. Retention time: 12.9 min. Mass spectrometry: m / z 427.71 ([M+H]). + )

[0302] (Raw Material Synthesis 13) Synthesis of Cbz-Leu-D-MePhe-OH

[0303] A flask containing a stir bar was charged with Fmoc-D-MePhe-OH (2.00 g, 4.98 mmol), cyclohexane (16 mL), and DCM (6 mL). tert-Butyl 2,2,2-trichloroacetimidate (2.7 mL, 15.09 mmol) was added to the flask. Boron trifluoride diethyl etherate (0.06 mL, 0.478 mmol) was added dropwise while the flask was cooled in an ice bath, and stirring was continued at room temperature for 1 hour. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (14 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (14 mL x 2). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Fmoc-D-MePhe-OtBu (2.62 g, 5.72 mmol). To a flask equipped with a stir bar, Fmoc-D-MePhe-OtBu (2.28 g, 4.98 mmol) and MeCN (18 mL) were added. DBU (0.74 mL, 4.95 mmol) was added to the flask and stirred for 1 h. After confirming completion of the reaction by HPLC analysis, TEA (2.8 mL, 20.09 mmol) and water (1.0 mL, 55.49 mmol) were added to the reaction mixture. Sodium bisulfite (1.30 g, 12.49 mmol) was added to the flask while cooling in an ice bath, and the mixture was stirred at room temperature for 1 h. MTBE (60 mL) and 10% aqueous ammonia (30 mL) were added to the reaction mixture, and the entire contents of the flask were transferred to a separatory funnel. The aqueous layer was removed, and the resulting organic layer was washed three times with 10% aqueous ammonia (30 mL x 3) and once with 5% aqueous NaCl (15 mL x 1). The resulting organic layer was concentrated under reduced pressure to give HD-MePhe-OtBu (1.08 g, 4.59 mmol). A flask containing a stir bar was charged with HD-MePhe-OtBu (1.08 g, 4.59 mmol), MeCN (14 mL), Cbz-Leu-OH (1.45 g, 5.48 mmol), and NMM (1.6 mL, 14.6 mmol).While cooling the flask in an ice bath, COMU (2.78 g, 6.49 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 1 hour. After confirming completion of the reaction by HPLC analysis, 2-MeTHF (30 mL), 5% aqueous K2CO3 (15 mL), and NMI (0.39 mL, 4.89 mmol) were added to the reaction mixture, and stirring was continued for 30 minutes. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The resulting organic layer was washed once with 5% aqueous K2CO3 (25 mL x 1), three times with 2.5% aqueous ammonia (25 mL x 3), twice with 5% aqueous NaHSO4 (25 mL x 2), once with 5% aqueous K2CO3 (25 mL x 1), and once with 5% aqueous NaCl (50 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-Leu-D-MePhe-OtBu (2.35 g, 4.87 mmol). Cbz-Leu-D-MePhe-OtBu (2.35 g, 4.87 mmol), 2-MeTHF (24 mL), and HMDS (7.1 mL, 33.87 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (5.4 mL, 29.84 mmol). Stirring was continued for 3 h, and completion of the reaction was confirmed by HPLC analysis. The flask was cooled, and 5% aqueous NaHCO3 (24 mL) was added dropwise while maintaining the reaction mixture below 25 °C. The entire contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (36 mL) was added to the resulting aqueous layer, and 85% H3PO4 (3.5 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (24 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-Leu-D-MePhe-OH (1.40 g, 3.28 mmol). Purity: 99.8%. Measurement method: HPLC Method A. Retention time: 12.9 min. Mass spectrometry: m / z 427.71 ([M+H]). + )

[0304] (Raw Material Synthesis 14) Synthesis of Cbz-MeLeu-MeSer(OtBu)-OH

[0305] A flask containing a stir bar was charged with Fmoc-MeSer(OtBu)-OH (1.80 g, 4.53 mmol), cyclohexane (14.4 mL), and DCM (5.4 mL). tert-Butyl 2,2,2-trichloroacetimidate (1.6 mL, 8.94 mmol) was added to the flask. Boron trifluoride diethyl etherate (57 μmL, 0.454 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 3 hours. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (15 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (15 mL x 2). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Fmoc-MeSer(OtBu)-OtBu (2.05 g, 4.52 mmol). To a flask equipped with a stir bar, Fmoc-MeSer(OtBu)-OtBu (2.05 g, 4.52 mmol) and MeCN (16 mL) were added. DBU (0.68 mL, 4.55 mmol) was added to the flask and stirred for 30 min. After confirming completion of the reaction by HPLC analysis, TEA (2.5 mL, 17.94 mmol) and water (0.81 mL, 44.95 mmol) were added to the reaction mixture. Sodium bisulfite (1.19 g, 11.44 mmol) was added to the flask while cooling in an ice bath, and the mixture was stirred at room temperature for 1 h. MTBE (50 mL) and 10% aqueous ammonia (25 mL) were added to the reaction mixture, and the entire contents of the flask were transferred to a separatory funnel. The aqueous layer was removed, and the resulting organic layer was washed three times with 10% aqueous ammonia (25 mL x 3) and once with 5% aqueous NaCl (25 mL x 1). The resulting organic layer was concentrated under reduced pressure to give H-MeSer(OtBu)-OtBu. 2-MeTHF (12.0 mL), Cbz-MeLeu-OH (1.39 g, 4.97 mmol), and NMM (1.5 mL, 13.64 mmol) were added to the flask. COMU (2.52 g, 5.88 mmol) was added to the reaction mixture while cooling the flask in an ice bath, and the mixture was stirred at room temperature for 2 hours.After confirming completion of the reaction by HPLC analysis, 2-MeTHF (30 mL), 5% aqueous K2CO3 (15 mL), and NMI (0.36 mL, 4.52 mmol) were added to the reaction mixture, followed by stirring for 30 min. The contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The organic layer was washed once with 5% aqueous K2CO3 (25 mL x 1), three times with 2.5% aqueous ammonia (25 mL x 3), twice with 5% aqueous NaHSO4 (25 mL x 2), once with 5% aqueous K2CO3 (25 mL x 1), and once with 5% aqueous NaCl (25 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The desiccant was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-MeLeu-MeSer(OtBu)-OtBu (1.98 g, 4.02 mmol). Cbz-MeLeu-MeSer(OtBu)-OtBu (1.98 g, 4.02 mmol), 2-MeTHF (20 mL), and HMDS (6.0 mL, 28.63 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (4.4 mL, 24.31 mmol). Stirring was continued for 2.5 h, and the reaction was confirmed to be complete by HPLC analysis. The flask was cooled, and 5% aqueous NaHCO3 (20 mL) was added dropwise while maintaining the reaction mixture below 24 °C. The entire contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (30 mL) was added to the resulting aqueous layer, and 85% H3PO4 (2.25 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (20 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-MeSer(OtBu)-OH (0.69 g, 1.59 mmol). Purity: 99.7%. Measurement method: HPLC Method A. Retention time: 14.0 min. Mass spectrometry: m / z 437.74 ([M+H]). + )

[0306] (Raw Material Synthesis 15) Synthesis of Cbz-Aze-EtPhe(4-Me)-OH

[0307] A flask containing a stir bar was charged with Fmoc-EtPhe(4-Me)-OH (5.02 g, 11.60 mmol), cyclohexane (40 mL), and DCM (15 mL). tert-Butyl 2,2,2-trichloroacetimidate (4.2 mL, 23.47 mmol) was added to the flask. Boron trifluoride diethyl etherate (0.15 mL, 1.19 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 1 hour. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (40 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (40 mL x 2). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Fmoc-EtPhe(4-Me)-OtBu (6.13 g, 12.60 mmol). To a flask equipped with a stir bar, Fmoc-EtPhe(4-Me)-OtBu (5.65 g, 11.60 mmol) and MeCN (45 mL) were added. DBU (1.80 mL, 12.04 mmol) was added to the flask and stirred for 30 min. After confirming completion of the reaction by HPLC analysis, TEA (6.5 mL, 46.64 mmol) and water (2.1 mL, 116.54 mmol) were added to the reaction mixture. Sodium bisulfite (3.03 g, 29.12 mmol) was added to the flask while cooling in an ice bath, and the mixture was stirred at room temperature for 1 h. MTBE (140 mL) and 10% aqueous ammonia (85 mL) were added to the reaction mixture, and the entire contents of the flask were transferred to a separatory funnel. The aqueous layer was removed, and the resulting organic layer was washed three times with 10% aqueous ammonia (85 mL x 3) and once with 5% aqueous NaCl (85 mL x 1). The resulting organic layer was concentrated under reduced pressure to give H-EtPhe(4-Me)-OtBu (3.06 g, 11.60 mmol). A flask containing a stir bar was charged with H-EtPhe(4-Me)-OtBu (3.06 g, 11.60 mmol), 2-MeTHF (28 mL), Cbz-Aze-OH (3.28 g, 13.90 mmol), and DIPEA (16.0 mL, 91.85 mmol).While cooling the flask in an ice bath, T3P solution (50% in 2-MeTHF, 21.0 mL, 11.1 g, 34.9 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 2 h. After confirming the completion of the reaction by HPLC analysis, 5% aqueous Na2CO3 solution (28 mL) was added to the reaction mixture. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The resulting organic layer was washed once with 4% aqueous H2SO4 (28 mL x 1), once with 10% aqueous KHSO4 (28 mL x 1), once with 5% aqueous Na2CO3 (28 mL x 1), and once with 5% aqueous NaCl (28 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4, and the desiccant was removed by filtration. The filtrate was concentrated under reduced pressure to give Cbz-Aze-EtPhe(4-Me)-OtBu (5.42 g, 11.30 mmol). Cbz-Aze-EtPhe(4-Me)-OtBu (5.42 g, 11.30 mmol), 2-MeTHF (54 mL), and HMDS (9.5 mL, 45.32 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (6.5 mL, 35.91 mmol). Stirring was continued for 4 h, and completion of the reaction was confirmed by HPLC analysis. The flask was cooled, and 5% aqueous NaHCO3 (65 mL) was added dropwise while maintaining the reaction mixture below 24 °C. The entire contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (108 mL) was added to the resulting aqueous layer, and 85% H3PO4 (8.2 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (65 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-Aze-EtPhe(4-Me)-OH (1.67 g, 3.93 mmol). Purity: 99.0%. Measurement method: HPLC Method A. Retention time: 11.9 min. Mass spectrometry: m / z 425.72 ([M+H]). + )

[0308] (Starting Material Synthesis 16) Synthesis of Fmoc-MeAlGly-MeAlGly-OH

[0309] A flask containing a stir bar was charged with Fmoc-MeAlGly-OH (1.50 g, 4.27 mmol), cyclohexane (12 mL), and DCM (4.5 mL). tert-Butyl 2,2,2-trichloroacetimidate (1.5 mL, 8.38 mmol) was added to the flask. Boron trifluoride diethyl etherate (54 μL, 0.43 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 1.5 hours. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (12 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (12 mL x 2). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to yield Fmoc-MeAlGly-OtBu (1.89 g, 4.64 mmol). To a flask equipped with a stir bar, Fmoc-MeAlGly-OtBu (1.74 g, 4.27 mmol) and MeCN (14 mL) were added. DBU (0.64 mL, 4.28 mmol) was added to the flask and stirred for 30 min. After confirming completion of the reaction by HPLC analysis, TEA (2.4 mL, 17.22 mmol) and water (0.77 mL, 42.73 mmol) were added to the reaction mixture. Sodium bisulfite (1.11 g, 10.67 mmol) was added to the flask while cooling in an ice bath, and the mixture was stirred at room temperature for 30 min. MTBE (44 mL) and 10% aqueous ammonia (24 mL) were added to the reaction mixture, and the entire contents of the flask were transferred to a separatory funnel. The aqueous layer was removed, and the resulting organic layer was washed three times with 10% aqueous ammonia (24 mL x 3) and once with 5% aqueous NaCl (24 mL x 1). The resulting organic layer was concentrated under reduced pressure to give H-MeAlGly-OtBu (0.74 g). MeCN (10.0 mL), Fmoc-MeAlGly-OH (1.65 g, 4.70 mmol), and NMM (1.4 mL, 12.73 mmol) were added sequentially to the flask. COMU (2.20 g, 5.14 mmol) was added to the reaction mixture while cooling the flask in an ice bath, and stirring was continued at room temperature for 2 hours.COMU (0.19 g, 0.44 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 30 min. COMU (0.36 g, 0.84 mmol) was added to the reaction mixture, and stirring was continued at room temperature for another 30 min. After confirming the completion of the reaction by HPLC analysis, 2-MeTHF (24 mL), 5% aqueous K2CO3 (12 mL), and NMI (0.34 mL, 4.27 mmol) were added sequentially to the reaction mixture, and stirring was continued for 30 min. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed. The organic layer was washed four times with 5% aqueous K2CO3 (20 mL x 4), two times with 5% aqueous NaHSO4 (20 mL x 2), one time with 5% aqueous K2CO3 (20 mL x 1), and one time with 5% aqueous NaCl (20 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4, and the desiccant was removed by filtration. The filtrate was concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Fmoc-MeAlGly-MeAlGly-OtBu (2.08 g, 4.01 mmol). To a flask containing a stir bar, Fmoc-MeAlGly-MeAlGly-OtBu (2.08 g, 4.01 mmol), 2-MeTHF (20 mL), and HMDS (3.4 mL, 16.22 mmol) were added, followed by the dropwise addition of TMSOTf (2.2 mL, 12.16 mmol). After stirring for 2 h, the reaction mixture was further treated with HMDS (1.3 mL, 6.20 mmol) and TMSOTf (1.2 mL, 6.63 mmol). The precipitate was dissolved by adding 2-MeTHF (20 mL). After stirring for an additional hour, HMDS (2.1 mL, 10.02 mmol) and TMSOTf (1.9 mL, 10.50 mmol) were added to the reaction mixture. Stirring was continued for an additional hour, and the reaction was confirmed to be complete by HPLC analysis. The flask was cooled, and 5% aqueous NaHCO3 (20 mL) was added dropwise while maintaining the reaction mixture at 13 °C or below. The contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (30 mL) was added to the resulting aqueous layer, and 85% H3PO4 (3.6 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (20 mL) and concentrated under reduced pressure.The resulting concentrate was purified by silica gel column chromatography to give Fmoc-MeAlGly-MeAlGly-OH (1.41 g, 3.05 mmol). Purity: 98.1%. Measurement method: HPLC Method A. Retention time: 14.6 min. Mass spectrometry: m / z 463.79 ([M+H]). + )

[0310] (Raw Material Synthesis 17) Synthesis of Cbz-MeLeu-MeIle-OH

[0311] A flask containing a stir bar was charged with Cbz-MeIle-OH (4.50 g, 16.00 mmol), cyclohexane (36 mL), and DCM (14 mL). tert-Butyl 2,2,2-trichloroacetimidate (5.8 mL, 32.41 mmol) was added to the flask. Boron trifluoride diethyl etherate (0.20 mL, 1.59 mmol) was added dropwise while the flask was cooled in an ice bath, and the mixture was stirred at room temperature for 2 hours. After confirming the completion of the reaction by HPLC analysis, the reaction mixture was filtered, and the filtered solid was washed with cyclohexane. The filtrate and washings were combined and washed five times with 10% aqueous citric acid (36 mL x 5). The resulting organic layer was washed twice with 5% aqueous Na2CO3 (36 mL x 2). The resulting organic layer was concentrated under reduced pressure to give Cbz-MeIle-OtBu (5.11 g, 15.20 mmol). To a flask equipped with a stir bar, Cbz-MeIle-OtBu (5.11 g, 15.20 mmol), 2-MeTHF (51 mL), and 5% Pd / C (3.24 g, 0.76 mmol on Pd metal basis) were added sequentially. The atmosphere in the flask was purged with nitrogen and then hydrogen, and the reaction mixture was stirred under a hydrogen atmosphere (1 atm) for 2 hours. The reaction mixture was filtered, and the Pd / C was washed with 2-MeTHF. The filtrate and washings were combined and concentrated under reduced pressure to give H-MeIle-OtBu (2.73 g, 13.57 mmol). To a flask equipped with a stir bar, H-MeIle-OtBu (2.73 g, 13.57 mmol), MeCN (27.0 mL), Cbz-MeLeu-OH (4.17 g, 14.90 mmol), and NMM (4.5 mL, 40.93 mmol) were added sequentially. While the flask was cooled in an ice bath, COMU (7.55 g, 17.63 mmol) was added to the reaction mixture, and stirring was continued at room temperature for 4 hours. COMU (0.58 g, 1.35 mmol) was added, and stirring was continued at room temperature for 30 minutes. After confirming the completion of the reaction by HPLC analysis, 2-MeTHF (80 mL), 5% aqueous K2CO3 solution (40 mL), and NMI (1.0 mL, 12.55 mmol) were added sequentially to the reaction mixture, and stirring was continued for 30 minutes. The entire contents of the flask were transferred to a separatory funnel, and the aqueous layer was removed.The organic layer was washed once with 5% K2CO3 aqueous solution (40 mL x 1), three times with 2.5% ammonia solution (70 mL x 3), twice with 5% NaHSO4 aqueous solution (70 mL x 2), once with 5% K2CO3 aqueous solution (70 mL x 1), and once with 5% NaCl aqueous solution (70 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give Cbz-MeLeu-MeIle-OtBu (5.99 g, 12.95 mmol). Cbz-MeLeu-MeIle-OtBu (5.99 g, 12.95 mmol), 2-MeTHF (60.0 mL), and HMDS (19.0 mL, 90.64 mmol) were added to a flask equipped with a stir bar, followed by the dropwise addition of TMSOTf (14.0 mL, 77.35 mmol). After stirring for 6 h, HMDS (8.0 mL, 38.17 mmol) and TMSOTf (4.8 mL, 26.52 mmol) were added to the reaction mixture. After stirring for 30 min, HPLC analysis confirmed that the conversion had reached 94%. The flask was cooled, and 5% aqueous NaHCO3 (60 mL) was added dropwise while maintaining the reaction mixture at 24 °C or below. The contents of the flask were transferred to a separatory funnel, and the organic layer was removed. 2-MeTHF (90 mL) was added to the resulting aqueous layer, and 85% H3PO4 (8.5 mL) was slowly added. The aqueous layer was removed, and the resulting organic layer was washed with 5% aqueous NaCl (60 mL) and concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give Cbz-MeLeu-MeIle-OH (3.09 g, 7.59 mmol). Purity: 97.7% Measurement method: HPLC Method A, retention time: 13.8 min Mass spectrometry: m / z 407.70 ([M+H]. + )

[0312] (Starting Material Synthesis 18-1) Synthesis of substituted HOPO

[0313] Synthesis was carried out based on the conditions described in the following literature. Reference 1: Bioorganic & Medicinal Chemistry 2009, 17, 6106-6122. Reference 2: Communications Chemistry 2023, 14, 5790.

[0314] (Raw Material Synthesis 18-2) Synthesis of 5-F-HOPO

[0315] A flask containing a stir bar was charged with 2-chloro-5-fluoropyridine (0.77 g, 5.83 mmol), hydrogen peroxide (1.15 g, 12.24 mmol), and DCM (10 mL) in that order and cooled to -5 °C. TFAA (1.63 mL, 11.66 mmol) was added dropwise to the stirred reaction mixture, which was then stirred at 25 °C for 3.5 h. The flask was cooled to 0 °C, and 10% aqueous NaHSO (5 mL) was added. The contents of the flask were transferred to a separatory funnel, and EtOAc (30 mL) and 10% NaHSO (5 mL) were added. The aqueous layer was removed, and the resulting organic layer was washed twice with saturated aqueous NaHCO (15 mL x 1) and once with 5% aqueous NaCl (10 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give 2-chloro-5-fluoropyridine N-oxide (360 mg). 2-Chloro-5-fluoropyridine N-oxide (360 mg, 2.44 mmol) and MeCN (2.0 mL) were added to a flask equipped with a stir bar. TFAA (4.0 mL) was added dropwise to the stirring reaction mixture, and the mixture was stirred for 4.5 hours. The reaction mixture was concentrated under reduced pressure, and DCM (4 mL) and NaHCO3 (1.4 g) were added. The solid was removed by filtration, and the filtrate was concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give 5-F-HOPO (50 mg, 0.39 mmol). 1 H-NMR (500 MHz, DMSO-d6): δ(ppm) 8.26 (t, J=3.7 Hz, 1H), 7.56-7.52 (m, 1H), 6.54 (dd, J=10.0, 6.0 Hz, 1H)

[0316] (Raw Material Synthesis 18-3) Synthesis of 5-Cl-HOPO

[0317] 2,5-Dichloropyridine (0.86 g, 5.83 mmol), urea hydrogen peroxide (1.15 g, 12.24 mmol), and DCM (10 mL) were sequentially added to a flask containing a stir bar and cooled to -5 °C. TFAA (1.63 mL, 11.66 mmol) was added dropwise to the stirred reaction mixture, which was then stirred at 25 °C for 6 h. The flask was cooled to 0 °C, and 10% aqueous NaHSO (5 mL) was added. The entire contents of the flask were transferred to a separatory funnel, and EtOAc (30 mL) and 10% NaHSO (5 mL) were added. The aqueous layer was removed, and the resulting organic layer was washed twice with saturated aqueous NaHCO (15 mL x 1) and once with 5% aqueous NaCl (10 mL x 1). The resulting organic layer was dried over anhydrous NaSO. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give 2,5-dichloropyridine N-oxide (760 mg). 2,5-Dichloropyridine N-oxide (455 mg, 2.75 mmol) and MeCN (2.0 mL) were added to a flask equipped with a stir bar. TFAA (4.0 mL, mmol) was added dropwise to the stirred reaction mixture, and the mixture was stirred for 5 hours. The reaction mixture was concentrated under reduced pressure, and DCM (4 mL) and NaHCO3 (1.4 g) were added. The solid was removed by filtration, and the filtrate was concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give 5-Cl-HOPO (100 mg, 0.69 mmol). 1 H-NMR (500 MHz, DMSO-d6): δ(ppm) 8.26 (d, J=2.9 Hz, 1H), 7.46 (dd, J=9.7, 2.9 Hz, 1H), 6.55 (d, J=9.2 Hz, 1H)

[0318] (Raw Material Synthesis 18-4) Synthesis of 5-CF3-HOPO

[0319] A flask containing a stir bar was charged with 2-chloro-5-(trifluoromethyl)pyridine (1.06 g, 5.83 mmol), urea hydrogen peroxide (1.15 g, 12.24 mmol), and DCM (10 mL), followed by cooling to -5 °C. TFAA (1.63 mL, 11.66 mmol) was added dropwise to the stirred reaction mixture, which was then stirred at 25 °C for 6 h. The flask was cooled to 0 °C, and 10% aqueous NaHSO3 (5 mL) was added. The contents of the flask were transferred to a separatory funnel, and EtOAc (30 mL) and 10% NaHSO3 (5 mL) were added. The aqueous layer was removed, and the resulting organic layer was washed twice with saturated aqueous NaHCO3 (15 mL x 1) and once with 5% aqueous NaCl (10 mL x 1). The resulting organic layer was dried over anhydrous Na2SO4. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give 2-chloro-5-(trifluoromethyl)pyridine N-oxide (940 mg). 2-Chloro-5-(trifluoromethyl)pyridine N-oxide (542 mg, 2.75 mmol) and MeCN (2.0 mL) were added to a flask equipped with a stir bar. TFAA (4.0 mL, mmol) was added dropwise to the stirring reaction mixture, and the mixture was stirred for 4.5 hours. The reaction mixture was concentrated under reduced pressure, and DCM (4 mL) and NaHCO3 (1.4 g) were added. The solid was removed by filtration, and the filtrate was concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give 5-CF3-HOPO (350 mg, 1.95 mmol). 1 H-NMR (500 MHz, DMSO-d6): δ(ppm) 8.60 (d, J=0.9 Hz, 1H), 7.66 (dd, J=9.5, 2.6 Hz, 1H), 6.66 (d, J=9.2 Hz, 1H)

[0320] (Raw Material Synthesis 18-5) Synthesis of 5-CO2Me-HOPO

[0321] Methyl 6-chloronicotinate (1.01 g, 5.83 mmol), urea hydrogen peroxide (1.15 g, 12.24 mmol), and DCM (10 mL) were added sequentially to a flask containing a stir bar and cooled to -5 °C. TFAA (1.63 mL, 11.66 mmol) was added dropwise to the stirred reaction mixture, which was then stirred at 25 °C for 6 h. The flask was cooled to 0 °C, and 10% aqueous NaHSO (5 mL) was added. The entire contents of the flask were transferred to a separatory funnel, and EtOAc (30 mL) and 10% NaHSO (5 mL) were added. The aqueous layer was removed, and the resulting organic layer was washed twice with saturated aqueous NaHCO (15 mL x 1) and once with 5% aqueous NaCl (10 mL x 1). The resulting organic layer was dried over anhydrous NaSO. The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure to give methyl 6-chloronicotinate N-oxide (540 mg). Methyl 6-chloronicotinate N-oxide (521 mg, 2.75 mmol) and MeCN (2.0 mL) were added to a flask equipped with a stir bar. TFAA (4.0 mL, mmol) was added dropwise to the stirred reaction mixture, and the mixture was stirred for 4.5 hours. The reaction mixture was concentrated under reduced pressure, and DCM (4 mL) and NaHCO3 (1.4 g) were added. The solid was removed by filtration, and the filtrate was concentrated under reduced pressure. The resulting concentrate was purified by silica gel column chromatography to give 5-CO2Me-HOPO (300 mg, 1.77 mmol). 1 H-NMR (500 MHz, DMSO-d6): δ(ppm) 8.50 (d, J=2.3 Hz, 1H), 7.79 (dd, J=9.5, 2.6 Hz, 1H), 6.56 (d, J=9.2 Hz, 1H), 3.78 (s, 3H)

[0322] (Raw Material Synthesis 19) Synthesis of H-MeGly(nPr)-Ile-Pro-OtBu

[0323] Step 19-1: Synthesis of Compound 19-1: tert-butyl (2S)-1-[(2S,3S)-2-(benzyloxycarbonylamino)-3-methyl-pentanoyl]pyrrolidine-2-carboxylic acid

[0324] A nitrogen-purged reactor was charged with tert-butyl(2S)-pyrrolidine-2-carboxylate (18.8 g), (2S,3S)-2-(benzyloxycarbonylamino)-3-methyl-pentanoic acid (20.0 g), and DMF (140 mL) at room temperature and stirred. After confirming complete dissolution, the mixture was cooled to 0°C and DIPEA (52.7 mL) was added. A 50 wt.% propylphosphonic anhydride ethyl acetate solution (58.3 mL) was added to the mixture over 20 minutes at 0°C and stirred at 0°C for 1.5 hours. Water (100 mL) and ethyl acetate (200 mL) were added to the mixture in that order. Aqueous layer 1 and organic layer 1 were separated by liquid-liquid separation, and aqueous layer 1 was set aside. Organic layer 1 was washed with 5% aqueous potassium hydrogen sulfate (100 mL), 5% aqueous sodium carbonate (100 mL), and 10% brine (100 mL). Water (100 mL) and ethyl acetate (200 mL) were added to the separated aqueous layer 1, and the mixture was stirred. After liquid-liquid separation, organic layer 2 was obtained. Organic layer 1 and organic layer 2 were combined and concentrated under reduced pressure to obtain compound 19-1 (33.8 g). LCMS (ESI) of compound 19-1: retention time: 2.75 minutes, m / z=419 [M+H] ＋

[0325] Step 19-2: Synthesis of Compound 19-2: tert-butyl(2S)-1-[(2S,3S)-2-amino-3-methyl-pentanoyl]pyrrolidine-2-carboxylic acid

[0326] Compound 19-1 (31.6 g) obtained in step 19-1 and 2-MeTHF (221 mL) were added to a reaction vessel purged with nitrogen and cooled to 10°C. 5% Pd / C (6.32 g, 50% water content) was added to the mixed solution, followed by triethylsilane (60.3 mL) over 20 minutes. After stirring at an internal temperature of 15°C for 6 hours, the mixture was stirred at room temperature for an additional 17 hours. The mixed solution was filtered, and the filtrate was concentrated under reduced pressure to obtain compound 19-2. Compound 19-2 was used in step 19-3 without further purification. LCMS (ESI) of compound 19-2: retention time: 1.14 minutes, m / z=285 [M+H] ＋

[0327] Step 19-3: Synthesis of Compound 19-3: tert-butyl(2S)-1-[(2S,3S)-2-[[(2S)-2-[9H-fluoren-9-ylmethoxycarbonyl(methyl)amino]pentanoyl]amino]-3-methyl-pentanoyl]pyrrolidine-2-carboxylic acid

[0328] Acetonitrile (221 mL) was added to compound 19-2 obtained in step 19-2 at 5°C, followed by (2S)-2-[9H-fluoren-9-ylmethoxycarbonyl(methyl)amino]pentanoic acid (28.0 g) and DIPEA (39.6 mL). HATU (34.5 g) was slowly added to the mixture at 2.5°C. The mixture was stirred at 2.5°C for 1 hour and then at room temperature for 2.5 hours. 5% aqueous sodium carbonate (189 mL) and water (150 mL) were added to the mixture, in that order. Toluene (80 mL) and 2-MeTHF (140 mL) were added, stirred, and then the liquids were separated. The organic layer was washed with 5% aqueous potassium hydrogen sulfate (190 mL x 2) and 10% brine (190 mL x 2). The resulting organic layer was concentrated under reduced pressure to give compound 19-3. Compound 19-3 was used in step 19-4 without further purification. LCMS (ESI) of compound 19-3: Retention time: 3.43 minutes, m / z=620 [M+H] ＋

[0329] Step 19-4 Compound 19-4: Synthesis of tert-butyl(2S)-1-[(2S,3S)-3-methyl-2-[[(2S)-2-(methylamino)pentanoyl]amino]pentanoyl]pyrrolidine-2-acetate (Synthesis of H-MeGly(nPr)-Ile-Pro-OtBu)

[0330] Compound 19-3 (296 mg), synthesized by a similar method to step 19-3, and toluene (2.07 mL) were added to a nitrogen-purged reactor and stirred. DBU (0.072 mL) was added to the mixed solution and stirred for 30 minutes. Acetonitrile (1.00 mL) was added to the mixed solution, followed by stirring for 30 minutes. DBU (0.072 mL) was added and stirred for an additional 30 minutes. 1 M hydrochloric acid (2.00 mL) and n-heptane (1.00 mL) were added and stirred, after which aqueous layer 1 and organic layer 1 were separated. Organic layer 1 was extracted with 1 M hydrochloric acid (1.00 mL) to obtain aqueous layer 2 containing compound 19-4. Aqueous layers 1 and 2 were combined and extracted with 5% aqueous potassium carbonate (2.00 mL) and toluene (4.00 mL), and the organic layer containing compound 19-4 was separated. The resulting organic layer was washed with 10% brine (2.00 mL) and then concentrated under reduced pressure to give compound 19-4 (166 mg). LCMS (ESI) of compound 19-4: retention time: 1.36 minutes, m / z = 398 [M+H] ＋

[0331] The analytical conditions for compounds 19-1 to 19-4 by LCMS are shown below. Apparatus: Waters UPLC / SQD Column: Ascentis Express RP 90A amide, 2.1 mm ID x 50 mm, 2.7 μm Mobile phase: 0.1% FA / water (A), 0.1% FA / MeCN (B) Elution method: B) 5% (0 min) → 100% (4.5 min) → 100% (5.0 min) → 5% (5.01 min) → 5% (7 min) Flow rate: 0.5 mL / min Column temperature: 40°C Detection wavelength: 210-400 nm (PDA)

[0332] The present invention can provide a method for synthesizing a peptide compound with high diastereoselectivity and high yield even in fragment coupling.

Claims

1. A method for producing a peptide compound or a salt thereof, comprising a step of linking an amino group of a first amino acid or peptide and a carboxy group of a second amino acid or peptide with an amide bond (linking step), wherein a condensing agent and two or more additives are used in the linking step, and the pKa of the additive is represented between 0 and 10.

0.

2. The condensing agent is a phosphorus-based condensing agent, and the phosphorus-based condensing agent is represented by the following formula (1): (In the formula, R １ is C １ -C ６ alkoxy, C ６ -C １０ aryloxy, C ６ -C １０ aryl, or diC １ -C ６ alkylamino, and R ２ is C １ -C ６ alkoxy, C ６ -C １０ aryloxy, C ６ -C １０ aryl, or diC １ -C ６ alkylamino, and R ３ is halogen, optionally substituted C ６ -C １０ aryloxy, or azide.) The method according to claim 1.

3. The method according to claim 1 or 2, wherein the phosphorus-based condensing agent is at least one selected from the group consisting of diphenyl chlorophosphate (DPPC), diethyl chlorophosphate (DEPC), dimethyl chlorophosphate, diisopropyl chlorophosphate, dibenzyl chlorophosphate, diphenylphosphoric acid azide (DPPA), pentafluorophenyl diphenylphosphinate (FDPP), 2-chloro-2-oxo-1,3,2-dioxaphospholane, dimethylphosphinic acid chloride, diethylphosphinic acid chloride, dicyclohexylphosphinic acid chloride, and diphenylphosphinic acid chloride (Ph2P(O)Cl).

4. The method according to any one of claims 1 to 3, wherein the additives are two or more selected from the group consisting of 2-hydroxypyridine-N-oxide (HOPO), 1-hydroxy-7-azabenzotriazole (HOAt), 1-hydroxybenzotriazole (HOBt), 3,4-dihydro-3-hydroxy-4-oxo-benzotriazine (HOOBt), ethyl 1-hydroxy-1H-1,2,3-triazole-4-carboxylate (HOCt), 2,2,3,3,3-pentafluoro-1-propanol (PfpOH), ethyl 2-cyano-2-(hydroxyimino)acetate (Oxyma), 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6-(1H,3H,5H)-trione (Oxyma-B), (hydroxyimino)cyanoacetic acid ethyl potassium salt (K-Oxyma), 4,6-dimethoxy-1,3,5-triazin-2-ol, 2-hydroxypyridine, and 2-hydroxy-5-nitropyridine.

5. The method according to any one of claims 1 to 4, wherein the additives are Oxyma and HOPO.

6. The method according to any one of claims 1 to 5, wherein the one or more additives are used in an amount of 0.5 to 5.0 molar equivalents relative to the first amino acid or peptide.

7. The nitrogen located at the β-position of the carboxy group of the second amino acid or peptide has the formula: -NR ５ -(wherein R ５ is a hydrogen atom, a linear C １ -C ６ alkyl, a branched C ３ -C ６ alkyl, or a C ３ -C ８ cycloalkyl), the method according to any one of claims 1 to 6.

8. The amino group of the first amino acid or peptide has the formula: -NR ６ R ７ (wherein R ６ is a hydrogen atom, and R ７ is a hydrogen atom, a linear C １ -C ６ alkyl, a branched C ３ -C ６ alkyl, or a C ３ -C ８ cycloalkyl), and the method according to any one of claims 1 to 7.

9. The α-carbon of the carboxy group of the second amino acid or peptide is of the formula: -CR ８ R ９ -(wherein R ８ and R ９ are the same or different and are a hydrogen atom, a linear C １ -C ４ alkyl, an optionally substituted branched C ３ -C ６ alkyl, an optionally substituted phenyl C １ -C ２ alkyl, or an optionally substituted 5- to 6-membered heteroaryl C １ -C ２ alkyl), the method according to any one of claims 1 to 8.

10. The method according to any one of claims 1 to 9, wherein the base used in the coupling step is at least one selected from the group consisting of dicyclohexylmethylamine, diisopropylethylamine, triethylamine, 2,6-lutidine, N-methylmorpholine, 4-N,N-dimethylaminopyridine, and 2,4,6-collidine.

11. The method according to any one of claims 1 to 10, wherein the coupling step is carried out by liquid-phase synthesis.

12. The method according to any one of claims 1 to 11, wherein the peptide compound or a salt thereof to be produced contains amino acid residues of 8 to 20 residues.

13. The method according to any one of claims 1 to 12, wherein the peptide compound to be produced contains at least one non-natural amino acid residue.

14. A peptide compound or a salt thereof produced by the method according to any one of claims 1 to 13.

15. A pharmaceutical composition comprising the peptide compound or a salt thereof produced by the method according to any one of claims 1 to 14.

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