Methods for Producing Macrocyclic Peptides

Abstract

The present invention relates to a compound of formula (I) TIFF2025505521000081.tif4769 (in the formula, PG 1 , P.G. 2 and P.G. 3 is an amino protecting group. or a salt thereof. The process according to the invention is particularly suitable for large-scale production under GMP conditions.

Description

[Technical field]

[0001] The present invention relates to a compound of formula (I): [ka] (In the formula, PG 1 , P.G. 2 and P.G. 3 is an amino protecting group. The present invention relates to a novel process for preparing the compound of formula (I) or a salt thereof. The process according to the invention is particularly suitable for large-scale production under GMP conditions. [Background technology]

[0002] The compounds of formula (Ia) are important precursors in the synthesis of novel antibiotics 1. [ka]

[0003] For marketing products, drugs need to be manufactured in large quantities and in accordance with Good Manufacturing Practice ("GMP") standards, so a high-yielding, inexpensive, safe and reproducible synthesis is paramount.

[0004] WO2019206853 discloses a laboratory-scale synthesis of the compound of formula (Ia) that relies on solid-phase synthesis of a particular tripeptide. However, it has been found that said solid-phase synthesis is not suitable for industrial-scale production of the compound of formula (Ia) due to various problems such as low yields, long reaction times and epimerization of certain stereocenters.

[0005] Therefore, there is a high unmet need for new methods for preparing compounds of formula (Ia). Summary of the Invention

[0006] The present invention provides a solution phase process for preparing compounds of formula (I) that overcomes the problems outlined above. The present invention also provides certain intermediates useful in this new process. Finally, the present invention provides a new method for the Fmoc deprotection of Fmoc protected amines. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] definition It should be understood that features, integers, characteristics, compounds, chemical moieties or groups described in connection with a particular aspect, embodiment or example of the invention are applicable to any other aspect, embodiment or example described herein, except where inconsistent therewith. All of the features disclosed herein (including any accompanying claims and abstracts), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the foregoing embodiments. The invention extends to any novel or any novel combination of features disclosed herein (including any accompanying claims and abstracts), or any novel or any novel combination of steps of any method or process so disclosed.

[0008] The term "protecting group" (PG) refers to a group that selectively blocks a reactive site in a polyfunctional compound so that a chemical reaction can be selectively carried out at an otherwise unprotected reactive site in the relevant conventional sense of synthetic chemistry. The protecting group can be removed at the appropriate time. Exemplary amino protecting groups are Boc (tert-butoxycarbonyl), benzyl, 4-methoxybenzyl, benzhydryl, Fmoc (fluorenylmethoxycarbonyl), Cbz (benzyloxycarbonyl), Moz (p-methoxybenzyloxycarbonyl), Troc (2,2,2-trichloroethoxycarbonyl), Teoc (2-(trimethylsilyl)ethoxycarbonyl), Adoc (adamantoxycarbonyl), formyl, acetyl, and cyclobutoxycarbonyl. Further specific amino protecting groups are tert-butoxycarbonyl (Boc) and fluorenylmethoxycarbonyl (Fmoc). Exemplary carboxylic acid protecting groups are allyl and 9-fluorenylmethyl (Fm). Exemplary amino and carboxylic acid protecting groups and their use in organic synthesis are described, for example, in "Protective Groups in Organic Chemistry", TW Greene and PG M Hutts, 5th Edition, 2014, John Wiley & Sons, New York, which is incorporated herein by reference in its entirety.

[0009] The term "salt" as used herein refers to any type of salt formed by reacting a compound disclosed herein with an inorganic acid, such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, etc., particularly hydrochloric acid, and an organic acid, such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid, N-acetylcysteine, etc. When a compound disclosed herein contains a free acidic moiety, a salt can also be prepared by adding an inorganic or organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, sodium salts, potassium salts, lithium salts, ammonium salts, calcium salts, magnesium salts, etc. Salts derived from organic bases include, but are not limited to, salts of primary, secondary and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, lysine, arginine, N-ethylpiperidine, piperidine, polyimine resins, and the like.

[0010] Manufacturing method In a first aspect, the present invention provides a compound of formula (I) [ka] or a salt thereof, comprising: (a)(i) HOAt and DIC, (ii) HODhat and DIC; (iii) HOPO and DIC, (iv) HOPO and DCC; and (v) HOPO and EDC, using a reagent selected from the group consisting of a carboxylic acid of formula (II) [ka] with a secondary amine of formula (III) [ka] React with Compound of formula (IV) [ka] (In the formula, PG 1 , P.G. 2 , P.G. 3 and P.G. 4 is an amino protecting group, PG 5 is a carboxylic acid protecting group. The method includes forming a

[0011] In one embodiment, PG 1 , P.G. 2 , P.G. 3 and P.G. 4 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, and PG 5 is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl.

[0012] The coupling of carboxylic acids (II) with secondary amines (III) has been shown to be highly susceptible to epimerization, as illustrated in Comparative Example 6. The specific reaction conditions according to the present invention provide high yields with very low levels of epimerization.

[0013] In a preferred embodiment, the present invention provides a process as disclosed herein, wherein the mixture used in step (a) is a mixture of HOAt and DIC.

[0014] In a particularly preferred embodiment, the present invention provides the process disclosed herein, wherein the reagent used in step (a) is a mixture of HOPO and DIC.

[0015] In one embodiment, the present invention relates to a process as disclosed herein, wherein step (a) comprises: (i) a mixture of tert-butyl methyl ether, n-heptane and dimethylacetamide; (ii) isopropyl acetate, with or without 1,3-dimethyl-2-imidazolidinone; (iii) tert-butyl methyl ether, with or without 1,3-dimethyl-2-imidazolidinone; (iv) dichloromethane with or without 1,3-dimethyl-2-imidazolidinone; (v) THF with or without 1,3-dimethyl-2-imidazolidinone; (vi) 2-methyl-THF with or without 1,3-dimethyl-2-imidazolidinone; (vii) toluene with or without 1,3-dimethyl-2-imidazolidinone, and (viii) Acetonitrile The process is carried out in a solvent selected from the group consisting of:

[0016] In a preferred embodiment, the present invention provides a process as disclosed herein, wherein in step (a), the reagent used is a mixture of HOAt and DIC, and the solvent is a mixture of tert-butyl methyl ether, n-heptane and dimethylacetamide.

[0017] In a preferred embodiment, the present invention relates to the process disclosed herein, wherein in step (a), the reagent used is a mixture of HOPO and DIC, and the solvent is (i) isopropyl acetate, with or without 1,3-dimethyl-2-imidazolidinone; (ii) tert-butyl methyl ether, with or without 1,3-dimethyl-2-imidazolidinone; (iii) dichloromethane with or without 1,3-dimethyl-2-imidazolidinone; (iv) THF with or without 1,3-dimethyl-2-imidazolidinone; (v) 2-methyl-THF with or without 1,3-dimethyl-2-imidazolidinone, and (vi) toluene with or without 1,3-dimethyl-2-imidazolidinone; The present invention provides a method of manufacturing a semiconductor device, comprising the steps of:

[0018] In a preferred embodiment, the present invention relates to the process disclosed herein, wherein in step (a), the reagent used is a mixture of HOPO and DIC, and the solvent is (i) isopropyl acetate, with or without 1,3-dimethyl-2-imidazolidinone; (ii) tert-butyl methyl ether, with or without 1,3-dimethyl-2-imidazolidinone; (iii) 2-methyl-THF with or without 1,3-dimethyl-2-imidazolidinone, and (iv) toluene with or without 1,3-dimethyl-2-imidazolidinone; The present invention provides a method of manufacturing a semiconductor device, comprising the steps of:

[0019] In a particularly preferred embodiment, the present invention provides a process as disclosed herein, wherein in step (a), the reagent used is a mixture of HOPO and DIC, and the solvent is a mixture of isopropyl acetate and 1,3-dimethyl-2-imidazolidinone.

[0020] In a particularly preferred embodiment, the present invention provides a process as disclosed herein, wherein in step (a), the reagent used is a mixture of HOPO and DIC, and the solvent is a mixture of tert-butyl methyl ether and 1,3-dimethyl-2-imidazolidinone.

[0021] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (b1)PG 4 The compound of formula (IV), wherein is Fmoc, is reacted with N-acetylcysteine ​​and tAmNH2 to give a compound of formula (V): [ka] and forming (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; The method of manufacturing further comprises:

[0022] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (b1)PG 4 The compound of formula (IV), wherein is Fmoc, is reacted with N-acetylcysteine ​​and tAmNH2 or tBuNH2 to give a compound of formula (V): [ka] (In the formula, PG 1 , P.G. 2 and P.G. 3 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, and PG 5 is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl. and forming (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; The method of manufacturing further comprises:

[0023] In a preferred embodiment, the basic aqueous solution is an aqueous solution of KHCO3 and / or K2CO3.

[0024] In a particularly preferred embodiment, step (b2) comprises: (b2a) washing the reaction mixture obtained in (b1) with an aqueous solution of KHCO3; (b2b) washing the reaction mixture obtained in (b2a) with an aqueous solution of K2CO3.

[0025] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (c) reacting said compound of formula (V) with a compound of formula (VI): [ka] (In the formula, PG 6 is an amino protecting group. in the presence of (i) a reducing agent selected from NaBHCN and NaBH(OAc) and (ii) a carboxylic acid selected from acetic acid and propionic acid to produce a compound of formula (VII): [ka] (In the formula, PG 1 , P.G. 2 , P.G. 3 and P.G. 6 is an amino protecting group, PG 5 is a carboxylic acid protecting group. The method further comprises forming

[0026] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (c) reacting said compound of formula (V) with a compound of formula (VI): [ka] (In the formula, PG 6 is an amino protecting group selected from BOC, Adoc, Moz and Fmoc. in the presence of (i) a reducing agent selected from NaBHCN and NaBH(OAc) and (ii) a carboxylic acid selected from acetic acid and propionic acid to produce a compound of formula (VII): [ka] (In the formula, PG 1 , P.G. 2 , P.G. 3 and P.G. 6 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, and PG 5is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl. The method further comprises forming

[0027] In one embodiment, the present invention provides a process as disclosed herein, wherein in step (c), the reducing agent is NaBH(OAc)3 and the carboxylic acid is acetic acid.

[0028] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (d)PG 5 is an allyl group, reacting the compound of formula (VII) with a transition metal catalyst in the presence of a secondary amine to give a compound of formula (IX): [ka] (In the formula, PG 1 , P.G. 2 , P.G. 3 and P.G. 6 is an amino protecting group. The method further comprises forming

[0029] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (d)PG 5 is an allyl group, reacting the compound of formula (VII) with a transition metal catalyst in the presence of a secondary amine to give a compound of formula (IX): [ka] (In the formula, PG 1 , P.G. 2 and P.G. 3 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc. The method further comprises forming

[0030] In one embodiment, the transition metal catalyst used in step (d) is a palladium catalyst.

[0031] In a preferred embodiment, the transition metal catalyst used in step (d) is palladium. (0) It is a catalyst.

[0032] In a particularly preferred embodiment, the transition metal catalyst used in step (d) is (PPh3)4Pd.

[0033] In a particularly preferred embodiment, the secondary amine used in step (d) is Et2NH.

[0034] In a particularly preferred embodiment, the secondary amine used in step (d) is Et2NH and the transition metal catalyst is (PPh3)4Pd.

[0035] In one embodiment, the present invention relates to the process disclosed herein, wherein step (d) is carried out in acetonitrile, and the reaction mixture obtained from step (d) comprises: (d2) adding N-acetylcysteine ​​to the reaction mixture obtained from step (d); (d3) adding CyNH to the reaction mixture resulting from step (d2); (d4) distilling off the secondary amine from step (d); and (d5) filtering the reaction mixture obtained from step (d4). The method further comprises post-treating the polymer by

[0036] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (e) reacting said compound of formula (IX) with (i) a mixture of HOBt and EDCI; (ii) a mixture of DIC and oxyma; (iii) COMU; (iv) 2,4,6-trichloro-1,3,5-triazine (TCT), or (v) 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM), to form a compound of formula (I).

[0037] In one embodiment, the present invention relates to a method of manufacturing as disclosed herein, comprising: (e) reacting said compound of formula (IX) with (i) a mixture of HOBt and EDCI, or (ii) a mixture of DIC and oxyma, or (iii) COMU; to form a compound of formula (I).

[0038] In one aspect, the present invention provides a process for preparing a compound of formula (I), or a salt thereof, comprising: [ka] (a)(i) HOAt and DIC, or (ii) HODhat and DIC; or (iii) HOPO and DIC, or (iv) HOPO and DCC; or (v) HOPO and EDC, using a reagent selected from the group consisting of a carboxylic acid of formula (IIb) [ka] (In the formula, PG 1 and P.G. 2 is an amino protecting group. with a secondary amine of formula (IIIb) [ka] (In the formula, PG 3 is an amino protecting group. React with Compound of formula (IVb) [ka] and forming (b1) reacting the compound of formula (IVb) with N-acetylcysteine ​​and tAmNH2 to obtain a compound of formula (Vb): [ka] and forming (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; (c) reacting said compound of formula (Vb) with a compound of formula (VIa): [ka] in the presence of (i) a reducing agent selected from NaBHCN and NaBH(OAc) and (ii) a carboxylic acid selected from acetic acid and propionic acid to produce a compound of formula (VIIb): [ka] and forming (d) reacting said compound of formula (VIIb) with a transition metal catalyst in the presence of a secondary amine to produce a compound of formula (IX): [ka] Forming The reaction mixture obtained from (d) is then (d2) adding N-acetylcysteine ​​to the reaction mixture obtained from step (d); (d3) adding CyNH to the reaction mixture resulting from step (d2); (d4) distilling off the secondary amine from step (d); and (d5) filtering the reaction mixture obtained from step (d4). and post-processing by (e) reacting said compound of formula (IX) with (i) a mixture of HOBt and EDCI, or (ii) a mixture of DIC and oxyma, or (iii) COMU to form a compound of formula (I); The present invention provides a method comprising:

[0039] In one aspect, the present invention provides a process for preparing a compound of formula (IVb) or a salt thereof as described herein, comprising: (a)(i) HOAt and DIC, (ii) HODhat and DIC; (iii) HOPO and DIC, (iv) HOPO and DCC; and (v) HOPO and EDC, reacting a carboxylic acid of formula (IIb) as described herein with an amine of formula (IIIb) as described herein using a reagent selected from forming said compound of formula (IVb).

[0040] In one aspect, the present invention provides a process for preparing a compound of formula (Vb) as described herein or a salt thereof, comprising: (a)(i) HOAt and DIC, (ii) HODhat and DIC, (iii) HOPO and DIC, (iv) HOPO and DCC; and (v) HOPO and EDC, reacting a carboxylic acid of formula (IIb) as described herein with an amine of formula (IIIb) as described herein using a reagent selected from forming a compound of formula (IVb) as described herein; (b1) reacting the compound of formula (IVb) with N-acetylcysteine ​​and tAmNH2 to form the compound of formula (Vb); (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; The present invention provides a method comprising:

[0041] In one aspect, the present invention provides a process for preparing a compound of formula (VIIb) or a salt thereof as described herein, comprising: (a)(i) HOAt and DIC, (ii) HODhat and DIC, (iii) HOPO and DIC, (iv) HOPO and DCC; and (v) HOPO and EDC, reacting a carboxylic acid of formula (IIb) as described herein with an amine of formula (IIIb) as described herein using a reagent selected from forming a compound of formula (IVb) as described herein; (b1) reacting the compound of formula (IVb) with N-acetylcysteine ​​and tAmNH2 to form the compound of formula (Vb); (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; (c) reacting said compound of formula (Vb) with a compound of formula (VIa) as described herein in the presence of (i) a reducing agent selected from NaBHCN and NaBH(OAc)3, and (ii) a carboxylic acid selected from acetic acid and propionic acid to form said compound of formula (VIIb); The present invention provides a method comprising:

[0042] In one aspect, the present invention provides a process for preparing a compound of formula (IX) or a salt thereof as described herein, comprising: (a)(i) HOAt and DIC, (ii) HODhat and DIC, (iii) HOPO and DIC, (iv) HOPO and DCC; and (v) HOPO and EDC, reacting a carboxylic acid of formula (IIb) as described herein with an amine of formula (IIIb) as described herein using a reagent selected from forming a compound of formula (IVb) as described herein; (b1) reacting the compound of formula (IVb) with N-acetylcysteine ​​and tAmNH2 to form the compound of formula (Vb); (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; (c) reacting said compound of formula (Vb) with a compound of formula (VIa) as described herein in the presence of (i) a reducing agent selected from NaBHCN and NaBH(OAc)3, and (ii) a carboxylic acid selected from acetic acid and propionic acid to form said compound of formula (VIIb); (d) reacting said compound of formula (VIIb) with a transition metal catalyst in the presence of a secondary amine to form said compound of formula (IX). The present invention provides a method comprising:

[0043] In one aspect, the present invention provides a process for preparing a compound of formula (IX) or a salt thereof as described herein, comprising: (a)(i) HOAt and DIC, (ii) HODhat and DIC, (iii) HOPO and DIC, (iv) HOPO and DCC; and (v) HOPO and EDC, reacting a carboxylic acid of formula (IIb) as described herein with an amine of formula (IIIb) as described herein using a reagent selected from forming a compound of formula (IVb) as described herein; (b1) reacting the compound of formula (IVb) with N-acetylcysteine ​​and tAmNH2 to form the compound of formula (Vb); (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; (c) reacting said compound of formula (Vb) with a compound of formula (VIa) as described herein in the presence of (i) a reducing agent selected from NaBHCN and NaBH(OAc)3, and (ii) a carboxylic acid selected from acetic acid and propionic acid to form said compound of formula (VIIb); (d) reacting said compound of formula (VIIb) with a transition metal catalyst in the presence of a secondary amine to form said compound of formula (IX), and then (d2) adding N-acetylcysteine ​​to the reaction mixture obtained from step (d); (d3) adding CyNH to the reaction mixture resulting from step (d2); (d4) distilling off the secondary amine from step (d); and (d5) filtering the reaction mixture obtained from step (d4). working up the reaction mixture obtained from step (d) by The present invention provides a method comprising:

[0044] In a particularly preferred embodiment, the present invention relates to a process for preparing a compound of formula (Ia), comprising the steps of: [ka] [ka] [ka] [ka] The present invention provides a method for

[0045] In one aspect, the present invention provides a compound of formula (I) as described herein, or a salt thereof, when prepared according to the method of the present invention. [ka] to provide.

[0046] In one aspect, the present invention provides a process for preparing a compound of formula (1), or a salt thereof, comprising: [ka] Methods are provided, including any of the methods described herein.

[0047] In one aspect, the present invention provides a compound of formula (1) [ka] or a salt thereof.

[0048] In one embodiment, in the methods and compounds disclosed herein, PG 1 is BOC.

[0049] In one embodiment, in the methods and compounds disclosed herein, PG 2 is BOC.

[0050] In one embodiment, in the methods and compounds disclosed herein, PG 3 is BOC.

[0051] In one embodiment, in the methods and compounds disclosed herein, PG 4 is Fmoc.

[0052] In one embodiment, in the methods and compounds disclosed herein, PG 5 is an allyl.

[0053] In one embodiment, in the methods and compounds disclosed herein, PG 6 is Fmoc.

[0054] In one embodiment, in the methods and compounds disclosed herein, PG 1 is BOC, PG 2 is the BOC, and PG 4 is Fmoc.

[0055] In one embodiment, in the methods and compounds disclosed herein, PG 3 is the BOC, and PG 5 is an allyl.

[0056] In one embodiment, in the methods and compounds disclosed herein, PG 1 is BOC, PG 2 is BOC, PG 3 is BOC, PG 4 is Fmoc, and PG 5 is an allyl.

[0057] In one embodiment, in the methods and compounds disclosed herein, PG 1 is BOC, PG 2 is BOC, PG 3 is the BOC, and PG 5 is an allyl.

[0058] In one embodiment, in the methods and compounds disclosed herein, PG 1 is BOC, PG 2 is BOC, PG 3 is BOC, PG 5 is an aryl group, and PG 6 is Fmoc.

[0059] In one embodiment, in the methods and compounds disclosed herein, PG 1 is BOC, PG 2 is the BOC, and PG 3 is BOC.

[0060] In one aspect, the present invention provides a compound of formula (II) [ka] or a salt thereof, wherein: 1 , P.G. 2 and P.G. 4 is an amino protecting group.

[0061] In one embodiment, the present invention provides a method for the preparation of a PG 1 , P.G. 2 and P.G. 4 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, or a salt thereof.

[0062] In a preferred embodiment, the present invention relates to a compound of formula (II) having the formula (IIa) [ka] or a salt thereof.

[0063] In one aspect, the present invention provides a compound of formula (III) [ka] or a salt thereof, wherein: 3 is an amino protecting group, PG 5 is a carboxylic acid protecting group.

[0064] In one embodiment, the present invention provides a method for the preparation of a PG 3 is an amino protecting group selected from BOC, Adoc, Moz and Fmoc, and PG 5 is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

[0065] In a preferred embodiment, the present invention relates to a compound of formula (III) having the formula (IIIa) [ka] or a salt thereof.

[0066] In one aspect, the present invention provides a compound of formula (IV) [ka] or a salt thereof, wherein: 1 , P.G. 2 , P.G. 3 and P.G. 4 is an amino protecting group, PG 5 is a carboxylic acid protecting group.

[0067] In one embodiment, the present invention provides a method for the preparation of a PG 1 , P.G. 2 , P.G. 3 and P.G. 4 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, and PG 5 is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

[0068] In a preferred embodiment, the present invention relates to a compound of formula (IV) having the formula (IVa) [ka] or a salt thereof.

[0069] In one aspect, the present invention provides a compound of formula (V) [ka] or a salt thereof, wherein: 1 , P.G. 2 and P.G.3 is an amino protecting group, PG 5 is a carboxylic acid protecting group.

[0070] In one embodiment, the present invention provides a method for the preparation of a PG 1 , P.G. 2 and P.G. 3 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, and PG 5 is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

[0071] In a preferred embodiment, the present invention provides a hemiphosphate salt of the compound of formula (V) described herein.

[0072] In a preferred embodiment, the present invention relates to a compound of formula (V) having the formula (Va) [ka] or a salt thereof.

[0073] In a preferred embodiment, the present invention provides a hemiphosphate salt of the compound of formula (Va) described herein.

[0074] In one aspect, the present invention provides a compound of formula (VI) as described herein [ka] or a salt thereof.

[0075] In one embodiment, the present invention provides a method for the preparation of a PG 6 is an amino protecting group selected from BOC, Adoc, Moz and Fmoc, or a salt thereof.

[0076] In a preferred embodiment, the present invention relates to a compound of formula (VI) having the formula (VIa) [ka] or a salt thereof.

[0077] In one aspect, the present invention provides a compound of formula (VII) [ka] or a salt thereof, wherein: 1 , P.G. 2 , P.G. 3 and P.G. 6 is an amino protecting group, PG 5 is a carboxylic acid protecting group.

[0078] In one embodiment, the present invention provides a method for the preparation of a PG 1 , P.G. 2 , P.G. 3 and P.G. 6 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, and PG 5 is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

[0079] In a preferred embodiment, the present invention relates to a compound of formula (VII) having the formula (VIIa) [ka] or a salt thereof.

[0080] In one aspect, the present invention provides a compound of formula (VIII) [ka] or its salt (PG 1 , P.G. 2 and P.G. 3 and P.G. 6 is an amino protecting group.

[0081] In one embodiment, the present invention provides a method for the preparation of a PG 1 , P.G. 2 and P.G. 3 and P.G. 6 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, or a salt thereof.

[0082] In a preferred embodiment, the present invention relates to a compound of formula (VIII) having the formula (VIIIa) [ka] or a salt thereof.

[0083] In one aspect, the present invention provides a compound of formula (IX) [ka] or a salt thereof, wherein: 1 , P.G. 2 and P.G. 3 is an amino protecting group.

[0084] In one embodiment, the present invention provides a method for the preparation of a PG 1 , P.G. 2 and P.G. 3 is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc, or a salt thereof.

[0085] In a preferred embodiment, the present invention relates to a compound of formula (IX) having the formula (IXa) [ka] or a salt thereof.

[0086] A novel method for Fmoc deprotection U.S. Pat. No. 9,334,302 discloses a method for removing the Fmoc protecting group from an amine which involves adding a mercaptocarboxylic acid to the dibenzofulvene (DBF) Fmoc deprotection by-product, followed by removal of the adduct by a basic aqueous wash. [ka]

[0087] This process may not be applicable, for example, if the desired product contains an acidic functional group (R2 = H), as it will be carried into the aqueous phase along with the DBF-mercaptocarboxylic acid adduct, and performing a basic aqueous extraction may be inconvenient when carried out on an industrial scale.

[0088] Thus, the present invention provides a novel method for Fmoc deprotection whereby the by-product is removed by simple filtration rather than washing with aqueous basic solution.

[0089] Surprisingly, it has been found that t-amylamine and dicyclohexylamine can form salts with DBF-N-acetylcysteine ​​adducts, and that these salts exhibit low solubility in selected organic solvents, such as MeCN. [ka]

[0090] More specifically, the Fmoc protecting group is removed by reacting the Fmoc protected amine with a base such as diethylamine, dicyclohexylamine or t-amylamine. The dibenzofulvene by-product formed in this reaction is then trapped by forming an adduct with N-acetylcysteine. If the base used to remove the Fmoc protecting group was a base other than dicyclohexylamine or t-amylamine, the adduct is subsequently reacted with dicyclohexylamine or t-amylamine. This forms an insoluble salt that precipitates from the reaction mixture and can be conveniently filtered off.

[0091] If the base used to perform the Fmoc deprotection is an amine other than dicyclohexylamine or t-amylamine, such as diethylamine, the base may also form a salt with the N-acetylcysteine ​​DBF adduct that does not precipitate from the reaction mixture. Thus, the presence of such a base may prevent the desired removal of the adduct salt by filtration. Therefore, it may be desirable to remove the excess of this amine reagent by distillation to shift the equilibrium toward the adduct dicyclohexylamine or t-amylamine salt, thus maximizing the precipitation of the corresponding dicyclohexylamine or t-amylamine salt.

[0092] Examples 10, 11 and 13 demonstrate the applicability and efficiency of the novel method for Fmoc deprotection according to the present invention, which is further illustrated by the following reaction scheme: [ka]

[0093] Indeed, in this particular case, product IXa contains a carboxylic acid functionality that precludes simple basic aqueous washes to remove the DBF-mercaptocarboxylic acid adduct by-product.

[0094] In one aspect, the present invention provides a method for removing an Fmoc protecting group from a compound that contains an Fmoc-protected amine, comprising the steps of: (a) reacting said compound containing an Fmoc-protected amine with a base; (b) adding N-acetylcysteine ​​to the reaction mixture resulting from step (a); (c) if the base in step (a) is not CyNH or t-amylamine, adding a base selected from CyNH and t-amylamine to the reaction mixture resulting from step (b); (d) optionally distilling off the base from step (a); and (e) filtering the reaction mixture resulting from step (b), (c) or (d); The present invention provides a method comprising:

[0095] It should be understood that steps (a) and (b) need not be performed sequentially, but may be performed simultaneously, i.e., in a "one-pot" manner. Thus, in one embodiment, the present invention provides a method for removing an Fmoc protecting group, comprising: (a) reacting a compound containing an Fmoc-protected amine with a reagent mixture containing a base and N-acetylcysteine; (b) if the base in step (a) is not CyNH or t-amylamine, adding a base selected from CyNH and t-amylamine to the reaction mixture resulting from step (a); (c) optionally distilling off the base from step (a); and (d) filtering the reaction mixture resulting from step (a), (b) or (c); The present invention provides a method comprising:

[0096] In a preferred embodiment, the process is carried out in acetonitrile as the solvent.

[0097] In a preferred embodiment, the base used in step (a) is diethylamine.

[0098] In a preferred embodiment, the base used in step (c) is Cy2NH.

[0099] In a preferred embodiment, the method for removing an Fmoc protecting group according to the present invention comprises step (d), distilling off the base from step (a).

[0100] In one embodiment, the reaction mixture obtained in step (b) is heated to from 30° C. to reflux.

[0101] In one embodiment, the reaction mixture obtained in step (b) is heated to a temperature between 30°C and 70°C.

[0102] In a preferred embodiment, the reaction mixture obtained in step (b) is heated to 40°C to 60°C.

[0103] In a particularly preferred embodiment, the reaction mixture obtained in step (b) is heated to 50°C.

[0104] Surprisingly, it has been found that if 10 or more equivalents of base are used in step (a) of the method according to the invention, the Fmoc deprotection proceeds smoothly at room temperature. Thus, in a preferred embodiment, 10 or more equivalents of base relative to the compound containing the Fmoc-protected amine are used in step (a) of the method according to the invention. In a further preferred embodiment, steps (a) to (c) of the method according to the invention are carried out at room temperature. In a further preferred embodiment, 10 or more equivalents of base relative to the compound containing the Fmoc-protected amine are used in step (a) of the method according to the invention, and steps (a) to (c) of the method according to the invention are carried out at room temperature.

[0105] In a preferred embodiment, the method for removing an Fmoc protecting group according to the present invention comprises the steps of: (a) reacting a compound containing an Fmoc-protected amine with EtNH in acetonitrile; (b) adding N-acetylcysteine ​​to the reaction mixture obtained from (a); (c) adding CyNH to the reaction mixture obtained from (b); (d) distilling off EtNH; (e) filtering the reaction mixture obtained from step (d); Includes.

[0106] In a preferred embodiment, the method for removing an Fmoc protecting group according to the present invention comprises the steps of: (a) reacting a compound containing an Fmoc-protected amine with CyNH and a base selected from t-amylamine in acetonitrile; (b) adding N-acetylcysteine ​​to the reaction mixture obtained from (a); (c) filtering the reaction mixture obtained from step (b); Includes.

[0107] In a preferred embodiment, the method for removing an Fmoc protecting group according to the present invention comprises the steps of: (a) reacting a compound containing an Fmoc-protected amine with a reagent mixture containing N-acetylcysteine ​​and a base selected from CyNH and t-amylamine in acetonitrile; (b) filtering the reaction mixture obtained from step (a); Includes.

[0108] In one embodiment, the reagent mixture used in step (a) further comprises seed crystals of the DBF-N-acetylcysteine ​​adduct Cy2NH or t-amylamine salt.

[0109] As mentioned above, the basic aqueous washes described in US Patent No. 9,334,302 may not be applicable, for example, when the desired product contains an acidic functional group, since it would be washed away into the aqueous phase along with the DBF-mercaptocarboxylic acid adduct by-product.Thus, in a preferred embodiment, the Fmoc-protected amine-containing compound used in the method according to the present invention further comprises at least one carboxylic acid moiety, preferably one to three carboxylic acid moieties, most preferably one carboxylic acid moiety.

[0110] Working Example The present invention will be more fully understood by reference to the following examples, which should not, however, be construed as limiting the scope of the claims to the examples. The following abbreviations are used in the text: All = allyl; Boc = tert-butoxycarbonyl; BOP-Cl = bis(2-oxo-3-oxazolidinyl)phosphine chloride; COMU = (1-cyano-2-ethoxy-2-oxoethylideneaminooxy)dimethylamino-morpholine-carbenium hexafluorophosphate; Cy2NH: dicyclohexylamine; DBF = dibenzofulvene; DCM = dichloromethane; DIPEA = diisopropylethylamine; DIC = N,N'-diisopropylamine Propylcarbodiimide;DMAP=4-Dimethylaminopyridine;DMF=N,N-Dimethylformamide;DMSO=Dimethylsulfoxide;DMTMM=4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride;EDCI=1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride;Fmoc=Fluorenylmethoxycarbonyl;HATU=2-(7-aza-1H-benzotriazol-1-yl )-1,1,3,3-Tetramethyluronium hexafluorophosphate;HOAt=1-Hydroxy-7-azabenzotriazole;HOBt=1-Hydroxybenzotriazole;HODhat=3-Hydroxypyrido[3,2-d][1,2,3]triazin-4(3H)-one;HOPO=2-Hydroxypyridine-N-oxide;IPC=In-Process Control;KFT=Karl Fischer titration;NMM=N-Methylmorpholine;Oxyma=Cyanohydroxy Ethyl iminoacetate; PyBrop = bromo-tris-pyrrolidino-phosphonium hexafluorophosphate; Su = succinimide; T = temperature; T3P = propylphosphonic anhydride; TBTU = N,N,N',N'-tetramethyl-O-(benzotriazol-1-yl)uranium tetrafluoroborate; THF = tetrahydrofuran; TOTT = S-(1-oxido-2-pyridyl)-N,N,N',N'-tetramethylthiuronium tetrafluoroborate.

[0111] Analysis method [Table 1] [Table 2] [Table 3] [Table 4] [Table 5]

[0112] Example 1 Preparation of Fmoc-Orn(Boc)-Lys(Boc)-OH (IIa) Process 1: Fmoc-Orn(Boc)-OSu Fmoc-Orn(Boc)-OH (50.0 g, 0.11 mol), N-hydroxysuccinimide (13.9 g, 0.12 mol) and THF (200 mL) were charged into a reaction vessel. A solution of dicyclohexylcarbodiimide (26.1 g, 0.13 mol) in THF (50 mL) was added at 20 °C within 2 h. The reaction mixture was stirred for another 21 h. The precipitate was filtered off and washed twice with THF (30 mL). The filtrate was concentrated to 125 mL at 40-45 °C. EtOAc (150 mL) was added and the mixture was concentrated to 165 mL at 40-45 °C. Isopropyl alcohol (500 mL) was added at room temperature within 1 h. The suspension was stirred at room temperature for 10 h. The solid was filtered off, washed twice with isopropyl alcohol (50 mL) and dried at 40° C. for 8 h to give Fmoc-Orn(Boc)-OSu as a white solid, typically in a yield of 85%.

[0113] Step 2: Fmoc-Orn(Boc)-Lys(Boc)-OH(IIa) H-Lys(Boc)-OH (66.0 g, 0.27 mol) and THF (960 mL) were charged to a reaction vessel. Bis(trimethylsilyl)acetamide (79.3 g, 0.39 mol) was added over 1 h at 20 °C. The mixture was stirred at 40-45 °C for 2 h (solid should be completely dissolved) and cooled to 20-25 °C (= solution A). In a separate reaction vessel, Fmoc-Orn(Boc)-OSu (120 g, 0.22 mol) was dissolved in THF (480 mL) (approximately 30 min) and the solution was cooled to 14-16 °C. Solution A was added within 1-2 h, keeping the internal temperature at a maximum of 15 °C. The reaction mixture was stirred for an additional 5 h. The reaction mixture was added to water (1200 mL) cooled to 5-10 °C over 2 h and the mixture was further stirred at 5-10 °C for 30 min. Ethyl acetate (600 mL) was added. The pH was adjusted to 2-3 by adding 15% aqueous HCl (10-11 g) while maintaining the temperature at 5-10 °C. The phases were separated. The organic layer was washed five times with 1.6% aqueous NaCl (600 g). Ethyl acetate (600 mL) was added and the mixture was concentrated to 780-820 g. This operation was repeated four times by adding ethyl acetate (480 mL). After the last addition, the mixture was concentrated to 960-1000 g. The suspension was heated to 40 °C. n-heptane (1500 mL) was added over 1 h. The suspension was stirred for another 1 h, cooled to 25 °C and stirred at this temperature for 3 h. The precipitate was filtered off, washed three times with n-heptane (300 mL) and dried at 45 °C to give IIa as a white solid. Typically, the yield was about 90%. LCMS: 705.35 (M+Na + )

[0114] Example 2 Preparation of N-Me-Trp(Boc)-OAll oxalate (IIIa) Process 1: N-NBS-Trp-OAll HN-Trp-OAll hydrochloride (105.0 g, 374.0 mmol), 2-nitrobenzenesulfonyl chloride (83.7 g, 377.8 mmol) and ethyl acetate (1050 mL) were charged to a reaction vessel and the mixture was cooled to 0-5°C. Water (315 mL) was charged over 30 min. Then, keeping the temperature below 5°C and pH=8-9, KOH 15% aqueous solution (338.0 g) was charged over 4 h. The reaction mixture was stirred at 0-5°C for an additional 5 h and the pH was adjusted to 5-6 with 15% aqueous HCl. The mixture was brought to room temperature and the phases were separated. The organic layer was washed with water (260 mL). The biphasic mixture was polish filtered through Celite. The phases were separated and the organic phase was concentrated under reduced pressure to approximately 300 g. Ethyl acetate (540 mL) was added and the solution was concentrated under reduced pressure to approximately 300 g. Karl Fischer titration was performed and the water level should be ≦0.05% w / w. Typically, the yield was about 98%.

[0115] Process 2: N-NBS-N-Me-Trp-OAll A 20% solution of N-NBS-Trp-OAll (600 g, 279.4 mmol), potassium carbonate (57.9 g, 418.9 mmol) and tetrabutylammonium bromide (9.01 g, 27.1 mmol) was charged into the reaction vessel. Methyl iodide (47.6 g, 335.4 mmol) was added within 30 min at room temperature. The reaction mixture was stirred at 30-35 °C for 15 h and then cooled to 0-5 °C. Water (480 mL) was added over 1 h and the biphasic mixture was stirred for 30 min. The phases were separated and the organic layer was washed twice with 5% aqueous NaCl solution (240 mL). The organic layer was concentrated under reduced pressure to 200-230 g. Ethyl acetate (300 mL) was added and the solution was concentrated to 200-230 g. This operation was repeated once more. Karl Fischer titration was performed and the water level should be ≦0.05% w / w. Microfiltration was performed to remove salts. Typically, the yield was about 97-98% with an assay of 22.5-23.0% w / w.

[0116] Step 3: N-NBS-N-Me-Trp(Boc)-OAll N-NBS-N-Me-Trp-OAll (529 g, 272.0 mmol) 22.8% w / w in ethyl acetate, ethyl acetate (200 mL) and DMAP (6.65 g, 54.4 mmol) were charged to a reaction vessel. The reaction mixture was heated to 27 °C and di-tert-butyl dicarbonate (71.2 g, 326.2 mmol) dissolved in ethyl acetate (64.5 mL) was added over 1.5 h. The reaction mixture was stirred at 27 °C for another 2 h, then heated to 70 °C and cooled to 30 °C over 2 h. The reaction mixture was concentrated to about 305 g under reduced pressure at 40-45 °C and cooled to room temperature. Methanol (845 mL) was charged within 1 h and the mixture was stirred for 3 h. The precipitate was filtered off, washed three times with methanol (100 mL), and dried under reduced pressure at 45 °C for 6 h to give 133 g (90%) of N-NBS-N-Me-Trp(Boc)-OAll as a pale yellow oil. Purification: The obtained yellow oil was dissolved in ethyl acetate (789 mL) at 70 °C and cooled to 30 °C within 2 h. The mixture was concentrated to about 277 g under reduced pressure at 40 °C, and the obtained suspension was cooled to 20-25 °C. Methanol (931 mL) was added within 1 h, and the suspension was stirred for another 3 h. The precipitate was filtered off, washed three times with methanol (67 mL), and dried under reduced pressure at 45 °C for 6 h to give 127.7 g (96%) of N-NBS-N-Me-Trp(Boc)-OAll as a pale yellow solid.

[0117] Step 4: N-Me-Trp(Boc)-OAll oxalate (IIIa) N-NBS-N-Me-Trp(Boc)-OAll (171 g, 314.6 mmol) and DMF (684 mL) were charged to the reaction vessel, the system was inerted and cooled to -5 °C. Thiophenolate (65.0 g, 491.8 mmol) was added over 30 min at -5 to 0 °C. The reaction mixture was stirred at -5 °C for 4 h. tert-Butyl methyl ether (1.03 L) was added followed by water (1.28 L) at -5 to 0 °C (typically for 30 to 60 min). The reaction mixture was then brought to 20 °C and stirred for 2 h. The layers were separated. The organic layer was washed three times with water (513 mL) and concentrated under reduced pressure to 264 g below 35 °C. Acetone (850 mL) was added. The solution was polish filtered. The solution was cooled to 7° C. and a solution of oxalic acid dihydrate (39.2 g, 310.9 mmol) in acetone (342 mL) was added. The mixture was stirred at 7° C. for 2 h. The precipitate was filtered off, washed three times with acetone (375 mL) and dried under reduced pressure at 35° C. for 3 h to give 130 g (92%) of N-Me-Trp(Boc)-OAll as a yellowish solid. LCMS: 359.19 (M+H + )

[0118] Example 3 Preparation of tert-butyl 3-[(2S)-3-allyloxy-2-[[(2S)-6-(tert-butoxycarbonylamino)-2-[[(2S)-5-(tert-butoxycarbonylamino)-2-(9H-fluoren-9-ylmethoxycarbonylamino)pentanoyl]amino]hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (IVa) HN-Me-Trp(Boc)-OAll oxalate (IIIa oxalate, 150 g, 334.5 mmol) and tert-butyl methyl ether (1.1 kg) were charged to the reactor, water (1.95 kg) was added, followed by NaOH 28% aqueous solution (119.5 kg) within 5 min (slight gas evolution). The two-phase system was stirred at room temperature for 60 min and the phases were separated. The organic phase was washed with water (750 g), evaporated under reduced pressure and dried under high vacuum. The residue was dissolved in n-heptane (513 g) and the solution was completely evaporated. The residue was dissolved in n-heptane (257 g) and the resulting solution was set aside (Solution A). Fmoc-Orn(Boc)-Lys(Boc)-OH (IIa, 228.5 g, 334.6 mmol) and tert-butyl methyl ether (1.1 kg) were charged to the reactor. HOAt (22.75 g, 167.2 mmol) was added and the addition funnel was rinsed with tert-butyl methyl ether (50 g). Dimethylacetamide (155 g) was added and the addition funnel was rinsed with tert-butyl methyl ether (100 g). The mixture was cooled to 0-5 °C and diisopropylcarbodiimide (44.5 g, 352.6 mmol) was added within 10 min. The addition funnel was rinsed with tert-butyl methyl ether (200 g). The reaction mixture was stirred for 120 min at -2-2 °C. Solution A was added over 30 min and the dropping line was rinsed with n-heptane (68 g). Stirring was continued for 40 min. The reaction mixture was warmed to room temperature within 180-240 min and stirred for another 15 h. A solution of citric acid (103 g) and water (1.95 kg) was added within 30 min at T = < 25 °C. The dropping funnel was rinsed with water (200 g). The extraction mixture was stirred for 90 min, filtered through a glass filter, the reactor was rinsed with n-heptane (298 g), and the filter cake was washed with a mixture of tert-butyl methyl ether (340 g) and n-heptane (157 g). The biphasic filtrate was stirred for another 10 min, then the phases were separated. The organic layer was washed with a solution of NaHCO3 (56.5 g) and water (1.25 kg), and three times with a mixture of methanol (871 g) and water (1.1 kg). The organic layer was concentrated under reduced pressure to a volume of about 900 mL (the solution becomes more viscous). DMSO (2.43 kg) was added, and the solution was dried under high vacuum at <40 °C for 60-120 min.The yield was considered 100% and the solution was carried on directly to the next step (approximately 12.3% w / w solution).Chiral purity (Method A; % a / a): LLL: 97.2%; LLD: not detected; LDL: 2.80%; DLL: not detected.

[0119] Example 4 Preparation of tert-butyl 3-[(2S)-3-allyloxy-2-[[(2S)-6-(tert-butoxycarbonylamino)-2-[[(2S)-5-(tert-butoxycarbonylamino)-2-(9H-fluoren-9-ylmethoxycarbonylamino)pentanoyl]amino]hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (IVa) HN-Me-Trp(Boc)-OAll oxalate (IIIa oxalate, 80 g, 178.4 mmol) and tert-butyl methyl ether (587 g) were charged to a reactor and water (1.04 kg) was added followed by 30% aqueous NaOH (59.5 g) within 5 min (slight gas evolution). The biphasic system was stirred at room temperature for 60 min and the phases were separated. The organic phase was washed with water (400 g), evaporated under reduced pressure and dried under high vacuum. The residue was dissolved in heptane (275 g) and evaporated completely under reduced pressure to give HN-MeTrp(Boc)OAll (IIIa, 64.6 g, 100%) as a yellow oil.

[0120] Fmoc-Orn(Boc)-Lys(Boc)-OH (IIa, 20.5 g, 30.0 mmol), 2-hydroxypyridine-N-oxide ("HOPO", 1.67 g, 15 mmol), and 1,3-dimethyl-2-imidazolidinone ("DMI", 64.9 g) were charged to a reaction vessel. After dissolution was complete, a solution of HN-Me-Trp(Boc)-OAll (IIIa, 11.1 g, 30.9 mmol) in tert-butyl methyl ether (40 g) was added. The reaction mixture was diluted with tert-butyl methyl ether (91 g). A solution of diisopropylcarbodiimide ("DIC", 4.17 g, 33 mmol) in tert-butyl methyl ether (11.0 g) was added over 20 minutes. The dropping funnel was rinsed with tert-butyl methyl ether (10.0 g) and stirring was continued for 22 h at room temperature. n-heptane (47.0 g) was added to the reaction mixture followed by a solution of citric acid (11.53 g, 60 mmol) in water (220 g) within 10 min. The mixture was stirred for 1 h. The precipitate was filtered off. The filter cake was washed with a mixture of tert-butyl methyl ether (57 g) and n-heptane (18 g). The phases of the filtrate were separated. The organic layer was washed with a solution of citric acid (11.5 g, 60 mmol) in water (220 g), a solution of sodium bicarbonate (2.5 g) in water (47.5 g) and three times with a mixture of methanol (79 g) and water (100 g). The organic phase was concentrated under reduced pressure and dried under high vacuum to give IVa (29.3 g, 95.6%) as an oil. Chiral purity (Method A; %a / a): LLL: 98.8%; LLD: not detected; LDL: 1.2%; DLL: not detected.

[0121] Example 5 Alternative preparation of tert-butyl 3-[(2S)-3-allyloxy-2-[[(2S)-6-(tert-butoxycarbonylamino)-2-[[(2S)-5-(tert-butoxycarbonylamino)-2-(9H-fluoren-9-ylmethoxycarbonylamino)pentanoyl]amino]hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (IVa) HN-Me-Trp(Boc)-OAll oxalate (IIIa oxalate, 150 g, 334.5 mmol) and tert-butyl methyl ether (1.1 kg) were charged to the reactor, water (1.95 kg) was added, followed within 5 min by NaOH 28% aqueous solution (119.5 g) (slight gas evolution). The two-phase system was stirred at room temperature for 60 min and the phases were separated. The organic phase was washed with water (750 g), evaporated under reduced pressure and dried under high vacuum. The residue was dissolved in heptane (513 g) and the solution was completely evaporated under reduced pressure. The residue was dissolved in heptane (356 g) (= solution A).

[0122] Fmoc-Orn(Boc)-Lys(Boc)-OH (IIa, 228.0 g, 334.5 mmol), 1-hydroxy-7-azabenzotriazole (22.8 g, 167.1 mmol), dimethylacetamide (155 g) and tert-butyl-methyl ether (1.25 kg) were charged into the reaction vessel. To the resulting suspension, cooled to 0° C., diisopropylcarbodiimide (44.5 g, 352.6 mmol) and tert-butyl methyl ether (200 g) were added. The reaction mixture was stirred at 0° C. for 2 h. Solution A was added within 30 min. The addition funnel was rinsed with n-heptane (68 g). The reaction mixture was stirred for 40 min, then warmed to 22° C. within 3.5 h and stirred at this temperature for 16 h. A solution of citric acid (103 g, 536 mmol) in water (2.15 kg) was added within 30 min. The reaction mixture was stirred for 90 min, diluted with heptane (297 g) and filtered. The precipitate was washed with a mixture of tert-butyl methyl ether (340 g) and heptane (157 g). The phases of the filtrate were separated. The organic layer was washed with a solution of sodium bicarbonate (56.5 g) in water (1.25 kg) and then washed three times with a mixture of methanol (871 g) and water (1.1 kg). The organic phase was concentrated under reduced pressure to a volume of about 900 mL, diluted with DMSO (2.43 kg) and dried under high vacuum to give IVa as a 12.3 wt% solution in DMSO. Chiral purity (Method A; % a / a): LLL: 97.2%; LLD: not detected; LDL: 2.8%; DLL: not detected.

[0123] Comparative Example 6 Table 1 shows a screen of reaction conditions for the coupling of amines IIIa with carboxylic acids IIa (see also Examples 4 and 5 above). [Table 6-1] [Table 6-2]

[0124] Example 7 tert-Butyl 3-[(2S)-3-allyloxy-2-[[(2S)-2-[[(2S)-2-amino-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (Va) A solution of tert-butyl 3-[(2S)-3-allyloxy-2-[[(2S)-6-(tert-butoxycarbonylamino)-2-[[(2S)-5-(tert-butoxycarbonylamino)-2-(9H-fluoren-9-ylmethoxycarbonylamino)pentanoyl]amino]hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (IVa, 2.43 kg, 334.2 mmol) in DMSO from Example 5 was charged to the reactor. N-acetyl-cysteine ​​(71.0 g, 435.1 mmol, 1.3 equiv.) was added and the addition funnel was rinsed with DMSO (100 g). tert-Amylamine (75.8 g, 869.0 mmol, 2.6 equiv) was added (slightly exothermic) and the addition funnel was rinsed with DMSO (85 g). The reaction mixture was stirred at 19-21 °C for 90 min and a solution of acetic acid (52.18 g, 869.0 mmol, 2.6 equiv) in water (680 g) was added dropwise while maintaining T = < 22 °C (exothermic). The quenched reaction mixture was added to a solution of KHCO3 (87.0 g, 869.0 mmol, 2.6 equiv) in water (2.91 kg) and tert-butyl methyl ether (2.0 kg) while maintaining the temperature = < 25 °C. After stirring for 30 min, the phases were separated. The organic layer was washed with a solution of K2CO3 (92.4 g, 668.5 mmol, 2.0 equiv) in water (2.84 kg) and with water (1.7 kg). The organic phase was concentrated under reduced pressure to a volume of 870 mL. Toluene (865 g) was added and the solution was concentrated to 870 mL and diluted with toluene (216.2 g). The yield was 93.6% based on the assay of the solution (31.86% w / w). Chiral purity (Method B; % a / a): LLL: 97.42%; LLD: not detected; LDL: 2.58%; DLL: not detected.

[0125] Example 8 Alternative preparation of tert-butyl 3-[(2S)-3-allyloxy-2-[[(2S)-2-[[(2S)-2-amino-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (Va) A reaction vessel was charged with a solution of Fmoc-Orn(Boc)-Lys(Boc)-N(Me)-Trp(Boc)-OAll (IVa, 177.2 g, 173.2 mmol) and 1093 mL of DMSO at room temperature. N-acetyl-cysteine ​​(36.7 g, 1.3 equiv.) was added and the funnel was rinsed with DMSO (100 mL). The reaction mixture was stirred until the solids were completely dissolved. A solution of tert-butylamine (32.9 g, 2.6 equiv.) in DMSO (47 mL) was added over 30-60 min while maintaining the temperature at 18-22 °C. The reaction mixture was stirred at 18-22 °C for 90 min. tert-Butyl methyl ether (1400 mL) was added. The mixture was cooled to 10-15 °C. A solution of acetic acid (27.1 g, 2.6 equiv.) in water (354 mL) was added dropwise while keeping the temperature below 20 °C. The quenched reaction mixture was stirred for 30 min and a solution of potassium bicarbonate (38.0 g, 2.2 equiv.) in water (1220 mL) was added while keeping the temperature below 20 °C. After stirring for 30 min, the phases were separated. The organic layer was washed with a solution of potassium carbonate (47.6 g, 2.0 equiv.) in water (1452 mL) and then with water (708 mL). The organic layer was dried over MgSO4 (104 g). The solid was filtered off and washed with tert-butyl methyl ether (138 mL). The filtrate was concentrated to about 2.0 volumes. The residue was diluted with tert-butyl methyl ether (416 mL) and n-heptane (416 mL) was added (= solution A). The solution was cooled to 0-5 °C. A solution of phosphoric acid (85%, 8.45 g, 0.43 equiv.) in tert-butyl methyl ether (138.5 ml) was prepared at 5-10 °C and cooled to 0-5 °C. The phosphoric acid solution was added to solution A while maintaining the temperature at 0-5 °C (approximately 1-1.5 h). The suspension was stirred at 0-5 °C for another 2 h. Cold n-heptane (3050 mL) was added slowly and stirring was continued at 0-5 °C for 1 h. The precipitate was filtered off, washed with cold n-heptane (277 mL) and dried under reduced pressure at 25 °C to give Orn(Boc)-Lys(Boc)-N(Me)-Trp(Boc)-OAll hemiphosphate (Va) as a yellowish solid (112.0 g, 76.2% over two steps).

[0126] Example 9 tert-Butyl 3-[(2S)-3-allyloxy-2-[[(2S)-2-[[(2S)-2-[[2-[3-bromo-2-[(9H-fluoren-9-ylmethoxycarbonylamino)methyl]phenyl]sulfanyl-3-pyridyl]methylamino]-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (VIIa) 3-[(2S)-3-Allyloxy-2-[[(2S)-2-[[(2S)-2-amino-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-keto-propyl]indole-1-carboxylic acid tert-butyl ester (Va, 209 g, 260.9 mmol, 1.0 equiv) dissolved in toluene (447.3 g, 656.3 g solution) was charged to the reaction vessel and the solution was diluted with toluene (1.11 kg, 1.28 L) to give a clear yellow solution. N-[2-bromo-6-[(3-formyl-2-pyridyl)thio]benzyl]carbamic acid 9H-fluoren-9-ylmethyl ester (142.32 g, 260.9 mmol, 1 equiv.) was added at room temperature and the addition funnel was rinsed with toluene (144.52 mL). This resulted in a pale yellow suspension. Acetic acid (34.47 g, 574.05 mmol, 2.2 equiv.) was added at room temperature and the funnel was rinsed with toluene (24.12 mL). At Ti=45-50 °C and 100-150 mbar, 836 mL of toluene was distilled off (azeotropic water removal) for about 2 h. At about 45 °C the suspension turns into a solution. Acetic acid (15.67 g, 260.9 mmol, 1.0 equiv) was added at room temperature followed by sodium triacetoxyborohydride (110.6 g, 521.86 mmol, 2.0 equiv). The addition funnel was rinsed with toluene (836 mL). The reaction mixture was stirred at 40° C. for 3 h. The reaction mixture was then added to a solution of sodium bicarbonate (131.52 g, 1565.58 mmol, 6 equiv) and water (1.92 L) over 15 min. Gas evolution and bubbling were observed during the addition. The extraction mixture was heated to 50° C. and stirred for 40 min (gas evolution and bubbling; pH=7), then kept at room temperature overnight without stirring. The layers were separated. The organic layer was washed with water (1.28 L). The organic phase was concentrated under reduced pressure and dried under high vacuum at 40° C. for 4 h to give the title compound VIIa (371 g) as a yellow foam. The yield was assumed to be 100% for the next step.

[0127] Example 10 (2S)-2-[[(2S)-2-[[(2S)-2-[[2-[2-(aminomethyl)-3-bromo-phenyl]sulfanyl-3-pyridyl]methylamino]-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-(1-tert-butoxycarbonylindol-3-yl)propanoic acid (IXa) 3-[(2S)-3-allyloxy-2-[[(2S)-2-[[(2S)-2-[[2-[[3-bromo-2-[(9H-fluoren-9-ylmethoxycarbonylamino)methyl]phenyl]thio]-3-pyridyl]methylamino]-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-keto-propyl]indole-1-carboxylic acid tert-butyl ester (VIIa, 347.15 g, 0.261 mol) in acetonitrile (1.1 L) was charged to the reaction vessel. Diethylamine (95.42 g, 1.3 mol, 5.0 equiv.) was added at room temperature and the addition funnel was rinsed with acetonitrile (28 mL). Palladium tetrakis(triphenylphosphine) (1.51 g, 0.001 mol, 0.005 equiv.) was added at room temperature (slightly exothermic) and the addition funnel was rinsed with acetonitrile (68 mL). The reaction mixture was stirred at room temperature for 45 min. N-acetyl-cysteine ​​(51.1 g, 0.313 mol, 1.2 equiv.) was added, the addition funnel was rinsed with acetonitrile (435.1 mL) and the reaction mixture was stirred at 50 °C for 2.5 h. The reaction mixture was further stirred at room temperature overnight. Dicyclohexylamine (61.51 g, 0.339 mol, 1.3 equiv.) was added and the addition funnel was rinsed with acetonitrile (28 mL). The reaction mixture was stirred at room temperature for 1 h (after about 10 min, the solution turns into a suspension). At Ti max 35 °C / 180-160 mbar and a constant volume of acetonitrile (2.26 L), diethylamine was removed by azeotropic distillation. The reaction mixture was filtered, and the reactor and filter cake were washed with acetonitrile (1.1 L). The filtrate was evaporated under reduced pressure at 40° C., and the residue was dried under high vacuum for 2 h.

[0128] Example 11 Alternative preparation of (2S)-2-[[(2S)-2-[[(2S)-2-[[2-[2-(aminomethyl)-3-bromo-phenyl]sulfanyl-3-pyridyl]methylamino]-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-(1-tert-butoxycarbonylindol-3-yl)propanoic acid (IXa) Crude tert-butyl 3-[(2S)-3-allyloxy-2-[[(2S)-2-[[(2S)-2-[[2-[3-bromo-2-[(9H-fluoren-9-ylmethoxycarbonylamino)methyl]phenyl]sulfanyl-3-pyridyl]methylamino]-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (VIIa, 43.6 g, 31.2 mmol) was dissolved in acetonitrile (211.6 g). The solution was concentrated under reduced pressure to a volume of 100-110 mL and diluted with acetonitrile (218.0 g). Diethylamine (22.8 g, 10.0 equiv.) was added and the addition funnel was rinsed with acetonitrile (4.2 g). Palladium tetrakis(triphenylphosphine) (180.4 mg, 0.005 equiv.) was added and the addition funnel was rinsed with acetonitrile (2.1 g). The reaction mixture was stirred at room temperature for 1.5 hours. N-acetylcysteine ​​(6.1 g, 1.2 equiv.) was added. The addition funnel was rinsed with acetonitrile (4.2 g) and the reaction mixture was stirred at room temperature for 3 hours. Dicyclohexylamine (7.4 g, 1.3 equiv.) was added and the transfer line was rinsed with acetonitrile (4.2 g). The reaction mixture was distilled at constant volume under reduced pressure at 45° C. while adding acetonitrile (218.0 g). The formed suspension was cooled to room temperature and stirred at room temperature for 1 hour, cooled to 0° C. over 3 hours and stirred at 0° C. for 10 hours. The precipitate was filtered off, washed with cold acetonitrile (54.5 g), the filtrate was evaporated under reduced pressure and dried under high vacuum, the residue was used as is, assuming 100% yield in the next step.

[0129] Example 12 tert-Butyl 3-[[(11S,14S,17S)-22-bromo-14-[4-(tert-butoxycarbonylamino)butyl]-11-[3-(tert-butoxycarbonylamino)propyl]-16-methyl-12,15,18-trioxo-2-thia-4,10,13,16,19-pentaazatricyclo[19.4.0.03,8]pentacosa-1(25),3,5,7,21,23-hexaen-17-yl]methyl]indole-1-carboxylate (Ia) 1-Hydroxybenzotriazole hydrate (79.92 g, 0.522 mol, 4.0 equiv.), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (100.05 g, 0.522 mol, 4.0 equiv.) and dichloromethane (1.07 L) were charged to a reactor at room temperature (endotherm Ti 13° C.). The suspension slowly formed a solution. A solution of (2S)-2-[[(2S)-2-[[(2S)-2-[[2-[[2-(aminomethyl)-3-bromo-phenyl]thio]-3-pyridyl]methylamino]-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-(1-tert-butoxycarbonylindol-3-yl)propionic acid (IXa, 139.36 g, 0.130 mol) in dichloromethane (695 mL) was added at room temperature within 4 h. The addition funnel was rinsed with dichloromethane (92.8 mL). The reaction mixture was stirred at room temperature for an additional 30 min. A solution of sodium bicarbonate (48.95 g, 0.583 mol, 4.47 equiv.) in water (670.0 mL) was added within 30 min (gas evolution) and stirring was continued for 30-40 min. The phases were separated. The organic layer was washed twice with a solution of sodium bicarbonate (48.95 g, 0.583 mol, 4.47 equiv.) in water (670.0 mL) and then with water (670.0 mL). The organic phase was concentrated at 25-35 °C / 700-600 mbar to a volume of 479 mL. Crystals started to precipitate during distillation. At constant volume and 48-52 °C / 600-300 mbar, the solvent was exchanged for ethyl acetate (1.1 L). The resulting fine suspension was cooled to room temperature within 30 min and stirred at room temperature for another hour. n-Heptane (349.15 mL) was added within 60 min and the suspension was stirred at room temperature overnight. The precipitate was filtered off and the filter cake was washed with a mixture of ethyl acetate (157.3 mL) and n-heptane (157.3 mL). The powder was dried under high vacuum at 50 °C to give the title compound Ia (92.8 g, 67.7%) as a beige powder. Chiral purity (Method C; %a / a): 0.02% DLL; 99.18% LLL; 0.52% LDL; 0.29% LLD.

[0130] The product was further purified: the obtained compound Ia (90.63 g) was dissolved in dichloromethane (406 mL) at room temperature and filtered through a charcoal pad. The filter was washed with dichloromethane (362 mL). The filtrate was concentrated under reduced pressure to a volume of 447 mL. Ethyl acetate (555 mL) was added and the solvent was exchanged with ethyl acetate (1590 mL) at a constant volume (1002 mL) under reduced pressure at an internal temperature of 32-65 °C. Ethyl acetate (394 mL) was distilled off under reduced pressure at 60-65 °C. The orange-brown suspension was slowly cooled to room temperature (0.15 K / min) and aged for 16 h. n-heptane (203 mL) was added within 45 min and the suspension was stirred for 2 h. The precipitate was filtered off, washed with a mixture of ethyl acetate (270 mL) and n-heptane (89 mL) (two portions, filtered slowly) and dried under high vacuum at 60° C. to give Ia (62.26 g, 61%) as a white powder. Chiral purity (Method C; %a / a): 100%.

[0131] Example 13 tert-Butyl 3-[(2S)-3-allyloxy-2-[[(2S)-2-[[(2S)-2-amino-5-(tert-butoxycarbonylamino)pentanoyl]amino]-6-(tert-butoxycarbonylamino)hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (Va) A solution of tert-butyl 3-[(2S)-3-allyloxy-2-[[(2S)-6-(tert-butoxycarbonylamino)-2-[[(2S)-5-(tert-butoxycarbonylamino)-2-(9H-fluoren-9-ylmethoxycarbonylamino)pentanoyl]amino]hexanoyl]-methyl-amino]-3-oxo-propyl]indole-1-carboxylate (IVa, 19.5 g, 19.1 mmol, 1 equiv) in MeCN (210 mL) was charged to the reactor. tert-Amylamine (5.32 g, 61 mmol, 3.2 equiv.) and a suspension of N-acetyl-cysteine ​​(4.04 g, 24.8 mmol, 1.3 equiv.) and seeds (of DBF-N-acetylcysteine ​​adduct t-amylamine salt) in MeCN (15 mL) were charged. The addition funnel was washed into the reactor with MeCN (15 mL). The reaction mixture was stirred at room temperature for 20 h (IPC: mostly deprotected) and then at 50 °C for 7 h (complete deprotection and mainly N-acetyl-cysteine-DBF adduct). The reaction mixture was cooled to room temperature and filtered to remove most of the N-acetyl-cysteine-DBF adduct. The filter cake was washed with MeCN (100 mL). The filtrate was concentrated under reduced pressure (50 °C, 300-60 mbar). The residue was redissolved in Me-THF (250 mL) and washed twice successively with a solution of K2CO3 (25 g) in water (225 g) and a solution of NaCl (28 g) in water (200 mL). The solution was concentrated to dryness under reduced pressure (50 °C, 350-15 mbar) to give the product (14.8 g as an oil) in 97% crude yield (85 a% by LC at 230 nm).

Claims

1. A process for preparing a compound of formula (I) or a salt thereof, comprising the steps of: 【Chemistry 1】 (a) (i) HOAt and DIC; (ii) HODhat and DIC; (iii) HOPO and DIC; (iv) HOPO and DCC, and (v) HOPO and EDC, using a reagent selected from the group consisting of a carboxylic acid of formula (II) 【Chemistry 2】 with a secondary amine of formula (III) 【Chemistry 3】 React with Compound of formula (IV) 【Chemistry 4】 (In the formula, PG １ , P.G. ２ , P.G. ３ and P.G. ４ is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc; PG ５ is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl. forming a

2. The method further comprising: (i) a mixture of tert-butyl methyl ether, n-heptane and dimethylacetamide; (ii) isopropyl acetate with or without 1,3-dimethyl-2-imidazolidinone; (iii) tert-butyl methyl ether, with or without 1,3-dimethyl-2-imidazolidinone; (iv) dichloromethane with or without 1,3-dimethyl-2-imidazolidinone; (v) THF with or without 1,3-dimethyl-2-imidazolidinone; (vi) 2-methyl-THF with or without 1,3-dimethyl-2-imidazolidinone; (VII) toluene with or without 1,3-dimethyl-2-imidazolidinone, and (viii) acetonitrile The process of claim 1 , wherein the process is carried out in a solvent selected from the group consisting of:

3. (b1) PG ４ The compound of formula (IV), wherein is Fmoc, is reacted with N-acetylcysteine ​​and tAmNH ２ or tBuNH ２ to produce a compound of formula (V): 【Chemistry 5】 (In the formula, PG １ , P.G. ２ and P.G. ３ is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc; PG ５ is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl. and forming (b2) washing the reaction mixture obtained in (b1) with a basic aqueous solution; The method of claim 1 or 2, further comprising:

4. (c) reacting said compound of formula (V) with a compound of formula (VI): 【Chemistry 6】 (In the formula, PG ６ is an amino protecting group selected from BOC, Adoc, Moz and Fmoc. and (i) NaBH ３ CN and NaBH(OAc) ３ and (ii) a carboxylic acid selected from acetic acid and propionic acid to produce a compound of formula (VII): 【Chemistry 7】 (In the formula, PG １ , P.G. ２ , P.G. ３ and P.G. ６ is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc; PG ５ is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl. The method of claim 3 , further comprising forming

5. (d) PG ５ is an allyl group, reacting the compound of formula (VII) with a transition metal catalyst in the presence of a secondary amine to give a compound of formula (IX): 【Chemistry 8】 (In the formula, PG １ , P.G. ２ and P.G. ３ are amino protecting groups independently selected from BOC, Adoc, Moz and Fmoc. The method of claim 4 , further comprising forming

6. The secondary amine is Et ２ NH, and the transition metal catalyst is (PPh ３ ) ４ The method of claim 5, wherein the metal is Pd.

7. Step (d) is carried out in acetonitrile, and the reaction mixture obtained from step (d) is (d2) adding N-acetylcysteine ​​to the reaction mixture obtained from step (d); (d3) Adding Cy to the reaction mixture obtained from step (d2). ２ adding NH; (d4) distilling off the secondary amine from step (d); and (d5) filtering the reaction mixture obtained from step (d4). The method of claim 5 or 6, further comprising post-treating by

8. (e) reacting said compound of formula (IX) with (i) a mixture of HOBt and EDCI; (ii) a mixture of DIC and oxyma; (iii) COMU (iv) 2,4,6-trichloro-1,3,5-triazine (TCT), or (v) 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM); The method of any one of claims 5 to 7, further comprising reacting with to form a compound of formula (I).

9. A compound of formula (II), 【Chemistry 9】 (In the formula, PG １ , P.G. ２ and P.G. ４ is an amino protecting group independently selected from BOC, Adoc, Moz, and Fmoc, or a salt thereof.

10. A compound of formula (III), 【Chemistry 10】 (In the formula, PG ３ is an amino protecting group selected from BOC, Adoc, Moz and Fmoc; PG ５ is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

11. A compound of formula (IV), 【Chemistry 11】 (In the formula, PG １ , P.G. ２ , P.G. ３ and P.G. ４ is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc; PG ５ is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

12. A compound of formula (V), 【Chemistry 12】 (In the formula, PG １ , P.G. ２ and P.G. ３ is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc; PG ５ is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

13. A compound of formula (VII), 【Chemistry 13】 (In the formula, PG １ , P.G. ２ , P.G. ３ and P.G. ６ is an amino protecting group independently selected from BOC, Adoc, Moz and Fmoc; PG ５ is a carboxylic acid protecting group selected from allyl and 9-fluorenylmethyl, or a salt thereof.

14. A compound of formula (VIII), 【Chemistry 14】 (In the formula, PG １ , P.G. ２ and P.G. ３ and P.G. ６ is an amino protecting group independently selected from BOC, Adoc, Moz, and Fmoc, or a salt thereof.

15. A compound of formula (IX), 【Chemistry 15】 (In the formula, PG １ , P.G. ２ and P.G. ３ is an amino protecting group independently selected from BOC, Adoc, Moz, and Fmoc, or a salt thereof.

16. P.G. １ , P.G. ２ and P.G. ３ is BOC, and PG ４ is Fmoc, and PG ５ The method of claim 1 or the compound of formula (IV) of claim 11, wherein is allyl.

17. P.G. １ , P.G. ２ and P.G. ３ is BOC, and PG ５ The method of claim 3 or the compound of formula (V) of claim 12, wherein is allyl.

18. P.G. １ , P.G. ２ and P.G. ３ is BOC, and PG ５ is allyl, and PG ６ The method of claim 4 or the compound of formula (VII) of claim 13, wherein is Fmoc.

19. P.G. １ , P.G. ２ and P.G. ３ is BOC, and PG ６ The method of claim 6 or the compound of formula (VIII) of claim 14, wherein is Fmoc.

20. P.G. １ , P.G. ２ and P.G. ３ The method of claim 7 or the compound of formula (IX) of claim 15, wherein is BOC.

21. A compound that is N-NBS-N-Me-Trp-OAll 【Chemistry 16】 Or its salt.

22. The compound is N-NBS-N-Me-Trp(Boc)-OAll. 【Chemistry 17】 Or its salt.

23. 【Chemical 18】 【Chemistry 19】 【Chemistry 20】 【Chemistry 21】 The method according to any one of claims 1 to 8 and 16 to 20, wherein

24. Compounds of formula (I) 【Chemical 22】 (In the formula, PG １ , P.G. ２ and P.G. ３ is an amino protecting group when prepared according to the method of any one of claims 1 to 8 or 16 to 21, or a salt thereof.

25. A process for preparing a compound of formula (1) or a salt thereof, comprising the steps of: 【Chemistry 23】 22. A method comprising the method of any one of claims 1 to 8 or 16 to 21.

26. Compound of formula (1) 【Chemistry 24】 22. Use of the method according to any one of claims 1 to 8 or 16 or 21 in the preparation of a compound or a salt thereof.

27. 1. A method for removing an Fmoc protecting group from a compound containing an Fmoc-protected amine, comprising: (a) reacting said compound containing an Fmoc-protected amine with a base; (b) adding N-acetylcysteine ​​to the reaction mixture resulting from step (a); (c) the base in step (a) is Cy ２ If it is not NH or t-amylamine, then Cy ２ adding a base selected from NH and t-amylamine to the reaction mixture resulting from step (b); (d) optionally distilling off the base from step (a); and (e) filtering the reaction mixture resulting from step (b), (c) or (d); A method comprising:

28. 28. The method of claim 27, wherein the method is carried out in acetonitrile as a solvent.

29. 29. The process of claim 27 or 28, wherein the base used in step (a) is diethylamine.

30. 30. The method of any one of claims 27 to 29, wherein in step (a) 10 or more equivalents of base are used relative to the compound containing the Fmoc-protected amine.

31. 31. The method of claim 30, wherein steps (a)-(c) are carried out at room temperature.

32. The base used in step (c) is Cy ２ 32. The method of any one of claims 27 to 31, wherein said alkyl group is NH.

33. 33. The process of any one of claims 27 to 32, comprising a step (d) of distilling off the base from step (a).

34. 34. The process according to any one of claims 27 to 29, 32 and 33, wherein the reaction mixture obtained in step (b) is heated to between 30°C and reflux.

35. 35. The process according to claim 34, wherein the reaction mixture obtained in step (b) is heated to 30°C to 70°C.

36. 36. The process according to claim 35, wherein the reaction mixture obtained in step (b) is heated to 40°C to 60°C.

37. 37. The method of claim 36, wherein the reaction mixture obtained in step (b) is heated to 50°C.

38. The method of any one of claims 27 to 37, wherein the compound comprising an Fmoc-protected amine further comprises at least one carboxylic acid moiety.

39. 20. The invention as hereinbefore described.

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