Sulfoxide and sulfone derivatives of thiocarbazates as synthons for azapeptides synthesis and process of using same

Abstract

Provided for herein are sulfoxide and sulfone derivatives of thiocarbazates that have the formula (I): wherein A, R, R1, R2, and n are defined herein. The compounds may be used as synthons in the synthesis of azaeptides and other aza- amino acid conjugates.

Description

SULFOXIDE AND SULFONE DERIVATIVES OF THIOCARBAZATES AS SYNTHONS FOR AZAPEPTIDES SYNTHESIS AND PROCESS OF USING SAME RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 609,975 filed on December 14, 2023, the entire contents of which are herein incorporated by reference in its entirety. INCORPORATION BY REFERENCE

[0002] All publications cited in this specification as well as the publications cited in said publications are hereby incorporated by reference. The discussion of these publications herein is intended merely to summarize the assertions made by applicant and no admission is made that any publication constitutes prior art. REFERENCE TO AN ELECTRONIC SEQUENCE LISTING

[0003] The contents of the electronic sequence listing (9081013_Sequence12Dec2024.xml; Size: 54000 bytes; and Date of Creation: December 12, 2024) is herein incorporated by reference in its entirety. FIELD OF THE INVENTION

[0004] This disclosure relates to novel and inventive sulfoxide and sulfone derivatives of thiocarbazates; processes for making the sulfoxide and sulfone derivatives of thiocarbazates; uses of the sulfoxide and sulfone derivatives of thiocarbazates as synthons in the synthesis of azapeptides and other aza-amino acid conjugates; and processes that use the sulfoxide and sulfone derivatives of thiocarbazates to synthesize azapeptides and other aza-amino acid conjugates. BACKGROUND OF THE INVENTION

[0005] Peptides are made up of chains of amino acids from 2 to 200 residues long, linked together by amide (peptide) bonds (“-NH-CHR-C(O)-”), and play a critical role in a variety ofbiological processes, including, e.g., inter- and intracellular signaling, as well as in the regulation of physiological functions.

[0006] Peptide-based drugs have become increasingly popular in the pharmaceutical industry because they may have several advantages over small molecules, including, for example, a larger surface area for specific target recognition, a potential for enhanced efficacy and increased selectivity / specificity, and a lower toxicity. These features make peptide-based drugs an attractive option for treating an array of conditions including, but not limited to, cancer, autoimmune diseases, and neurodegenerative disorders.

[0007] The field of peptide therapeutics began with the first medical application of insulin in 1922. As of today, there are more than 80 peptide-based drugs on the global market, and hundreds of peptide-based compounds are in various stages of preclinical testing and clinical development. Despite their advantages, many potential therapeutic peptides have not been approved or have been discontinued by the FDA often because of their poor physicochemical characteristics.

[0008] As active pharmaceuticals, peptides have certain limitations. These limitations include, for example, their short biological half-lives (seconds to minutes). This is because, once administered to a patient, peptides may be rapidly degraded by proteolytic enzymes. To circumvent their shortcomings, researchers have developed chemically modified peptides known as peptidomimetics. These compounds mimic the three-dimensional structure and biological activities of natural peptides, while being engineered to possess improved pharmacokinetic properties.

[0009] Different modification strategies have been developed to overcome the limitations of using peptides as therapeutic peptides and to enhance stability and biological activity of therapeutic peptides. These strategies include: 1) N- or C-terminus modifications / conjugations; 2) macrocyclization; 3) side chain modifications; and 4) backbone modifications, which can potentially improve proteolytic stabilities and extend the plasma half-lives of peptide drugs.

[0010] Unlike natural amino acids, aza-amino acids are not stable and are easily decarboxylated, making them not ideal synthons to use in traditional peptide synthesis strategies.

[0011] Azapeptides are a class of peptidomimetics, where one or more α-carbons in the peptide backbone are replaced by a trivalent nitrogen atom. The replacement of one or more α-carbons in the peptide backbone with a trivalent nitrogen atom results in a more rigid trigonal or achiral geometry. This replacement eliminates chirality at the α-position, decreases the electrophilicity of the carbonyl group, and provides a semicarbazide with two adjacent nitrogen atoms. Further, incorporating aza-amino acids into a peptide sequence increases the number of intramolecular hydrogen bonds and stabilizes β-turns and polyproline-type II helices. Hence, aza-amino acid substitution(s) has the potential to affect the conformation and stability of peptides, which in turn potentially could impact their biological activity.

[0012] Since the first synthesis of azaVal3angiotensin II in 1963, azapeptides have shown biological effects on several therapeutic targets. For example, azapeptides have been used as enzyme inhibitors, receptor ligands (antagonist and agonist), and stabilizers for triple-helical collagen peptides.

[0013] Several azapeptide derivatives have been discovered and advanced as therapeutic agents. For example, in 1989, the aza-Gly peptide analog, Goserelin (Zoladex®), was approved by the FDA for the treatment of prostate and breast cancers. Later, in 2003, the non-native side chain azapeptide analog, Atazanavir (Reyataz®), was approved by the FDA for the treatment of HIV infection. Peptidomimetic small molecules modeled after HMGB1 antagonist tetramer peptides that have been stabilized with at least one azatide bond are provided in US 11,471,507 B2, US 2020 / 0000908 A1, US 2020 / 0354418 A1, and US 11,471,508 B2.

[0014] Over the years there have been various methods developed for azapeptide synthesis and discovery, such as customized solid-phase peptide synthesis (“SPPS”), and submonomer azapeptide synthesis.

[0015] Typically, the synthesis of azapeptides involves a combination of hydrazine chemistry and traditional peptide synthesis in the presence of a carbonyl group source. Conventional azapeptide synthetic strategies-activation of N'-alkyl-N-protected-hydrazines is depicted in Figure 1.

[0016] The most common strategy for incorporating aza amino acid residues into peptide sequences is to prepare N'-alkylated hydrazine derivatives, to activate them using an appropriatecarbonyl donating reagent, and to couple the activated intermediate to the growing resin-bound peptide (Figure 1). See, e.g., K.F. Cheng, et al., “A History of Synthetic Milestones and Key Examples”, Curr. Med. Chem., 29, 6336-6358 (2022) and D. Boeglin, et al., “Aza-Amino Acid Scanning of Secondary Structure Suited for Solid-Phase Peptide Synthesis with Fmoc Chemistry and Aza-Amino Acids with Heteroatomic Side Chains”, J. Comb. Chem.,7, 864-878 (2005).

[0017] Various reagents, such as p-nitrophenyl chloroformate, bis(2,4-dinitrophenyl) carbonate, carbonyl-diimidazole (“CDI”) and 1,1'-carbonyl-di-(1,2,4-triazole) (“CDT”), have been used as carbonyl donors to activate hydrazines. Despite the active nature of resulting intermediates like nitrophenylcarbazates and imidazolides, their exceptional stability prevents effective coupling with resin-bound peptides. Other coupling reagents, such as bis(pentafluorophenyl) carbonate or N,N'-disuccinimidyl carbonate (“DSC”), have faced similar issues related to their reduced reactivity. Consequently, these intermediates suffer from complicated side reactions, poor reaction yields, and / or prolonged reaction times.

[0018] Until recently, the activation of N-(Fmoc)-N'-alkyl hydrazines with phosgene was the most effective protocol for incorporating aza motifs into peptide chains. This approach generally provides azapeptides in good yields but using phosgene-based reagents can create challenges in terms of stability and toxicity. These reagents must be freshly prepared and require specialist organic chemists to perform the reactions. Moreover, during the synthesis, side products like hydantoin, oxadiazalone, or symmetric urea may form, which can reduce the yield.

[0019] While these developed strategies have enriched the field, they are synthetically cumbersome, which limits their clinical application.

[0020] Other classes of synthons that improve azapeptide synthesis have been invented. For example, US 10,919,882 B2 and US 11,414,505 B2 provide for O-benzotriazole and O- imidazole synthons that can be used in the preparation of azapeptides. In addition, dimers that may be used as synthons are provided for in WO 2021 / 226431 A1. Additional synthons are provided in US 2020 / 0354404 A1.

[0021] A more recent approach to synthesizing azapeptides utilizes a thiocarbazate platform, which is summarized in Figure 2. This approach is described in more detail in US 11,440,881 B2 and US 2022 / 0306577 A1, which provide for thiosemicarbazates and their use in azapeptidesynthesis. See also, A. Altiti, et al., “Thiocarbazate Building Blocks Enable the Construction of Azapeptides for Rapid Development of Therapeutic Candidates”, Nature Communications 13:7127 (2022). As can be seen, while a vast improvement over previous approaches, the thiocarbazate synthons still require an activation to form the chloroformate intermediate.

[0022] Despite azapeptites’ limited successes and their potential as therapeutic agents for an unlimited array of diseases, and conditions, in addition to their potential use as diagnostic reagents, azapeptides use has been limited. This is mainly due to the difficulties and intricacies of azapeptide peptide synthesis.

[0023] Therefore, more general, high-yielding, and efficient synthetic protocols are needed.

[0024] Hence, in view of the foregoing, an object of the present invention is to provide synthons with improved physio-chemical properties that may be used as synthons to synthesize azapeptides and other aza-amino acid conjugates in an efficient manner, as well as methods to prepare azapeptides, other aza-amino acid conjugates and other peptidomimetics. These and other objectives achieved by the present invention are discussed below. SUMMARY OF THE INVENTION

[0025] This invention provides for novel and inventive derivatives of thiocarbazates, which may be used as synthons in synthesis of azapeptides and other aza-amino acid conjugates. These derivatives of thiocarbazates are sulfoxide and sulfone thiocarbazate compounds that are stable enough to be stored for months and, at the same time, are reactive enough such that they can be used to efficiently prepare azapeptides, other aza-amino acid conjugates and other peptidomimetics.

[0026] The sulfoxide and sulfone thiocarbazate compounds of the invention exhibit excellent compatibility with reaction conditions and solvents commonly employed in peptide and azapeptide synthesis and make efficient synthesis of azapeptides and other aza-amino acid conjugates feasible.

[0027] Unlike previously known synthons which required activation using phosphagene, triphosgene, TCCA / TBACl, p-nitrophenylchloroformate, bis(2,4-dinitrophenyl) carbonate, bis(pentafluorophenyl) carbonate, N,N'-disuccinimidyl carbonate (DSC), carbonyldiimidazole,and carbonyl-diimidazole (CDI), and 1,1'-carbonyl-di-(1,2,4-triazole) (“CDT”), the sulfoxide and sulfone thiocarbazate compounds of the invention are active reagents that readily couple with the N-terminal end of an amino acid, an aza-amino acid, a peptide, or an azapeptide under reaction conditions and solvents commonly employed in peptide and azapeptide synthesis without such activation. For example, the sulfoxide and sulfone thiocarbazate compounds of the invention readily couple with the N-terminal end of an amino acid, an aza-amino acid, a peptide, or an azapeptide under reaction conditions and solvents commonly employed in peptide and azapeptide synthesis without first being activated by conversion to a chloride intermediate.

[0028] The sulfoxide and sulfone thiocarbazate compounds of the invention are prepared by oxidation of an N-protected thiocarbazate compound. For example, a sulfoxide thiocarbazate compound may be prepared by reacting 1 eq of an N-protected thiocarbazate compound with about 1.0 to about 1.5 eq of meta-chloroperoxybenzoic acid (mCPBA). A sulfone thiocarbazate compound may, e.g., be prepared by reacting 1 eq of an N-protected thiocarbazate compound with about 1.5 to about 2.5 eq of mCPBA. These reactions may, for example, be carried out at temperatures from about 0ºC to about 30ºC. In an embodiment, the reaction is started at 0ºC and then, as the reaction progresses, the temperature is increased up to about 25ºC.

[0029] This invention further provides for an improved synthetic method to prepare azapeptides, other aza-amino acid conjugates, azatides, and additional peptidomimetics. The method comprises coupling of a sulfoxide or a sulfone thiocarbazate compound of the invention to N-terminal end of an amino acid, a peptide or an azapeptide and thereby forming an azapeptide or another aza-amino acid conjugate, without first activating the sulfoxide or a sulfone thiocarbazate compound of the invention with phosphagene, triphosgene, TCCA / TBACl, p-nitrophenylchloroformate, bis(2,4-dinitrophenyl) carbonate, bis(pentafluorophenyl) carbonate, N,N'-disuccinimidyl carbonate (DSC), carbonyldiimidazole, carbonyl-diimidazole (CDI), or 1,1'- carbonyl-di-(1,2,4-triazole) (“CDT”).

[0030] The unique stability and reactivity balance of the inventive sulfoxide and sulfone thiocarbazate compounds permits one, for example, to use the sulfoxide and sulfone thiocarbazate compounds of the invention to synthesize azapeptides and other aza amino acid conjugates via full automation solid-phase peptide synthesis techniques.

[0031] It is noted that in this disclosure and particularly in the claims and / or paragraphs, terms such as “comprises”, “comprised”, “comprising”, and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of’ and “consists essentially of’ have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the invention.

[0032] Except where stated otherwise, the following definitions apply throughout the present specification and claims. These definitions apply regardless of whether a term is used by itself or in combination with other terms. Hence the definition of “alkyl” applies to “alkyl” as well as to the “alkyl” portions of “alkoxy”, “cycloalkyl” and so forth.

[0033] As used above, and throughout the specification, the following terms, unless otherwise indicated, shall be understood to have the following meanings:

[0034] The term “about” in the present specification means a value within 15% (±15%) of the value recited immediately after the term “about,” including the value equal to the upper limit (i.e., +15%) and the value equal to the lower limit (i.e., −15%) of this range. For example, the phrase “about 100” encompasses any numeric value that is between 85 and 115, including 85 and 115.

[0035] “Alkyl” means an aliphatic hydrocarbon group which may be straight or branched and comprising about 1 to about 20 carbon atoms in the chain. Preferred alkyl groups contain about 1 to about 12 carbon atoms in the chain. More preferred alkyl groups contain about 1 to about 6 carbon atoms in the chain. Branched means that one or more lower alkyl groups such as methyl, ethyl or propyl, are attached to a linear alkyl chain. “Lower alkyl” means a group having about 1 to about 6 carbon atoms in the chain which may be straight or branched. The term “substituted alkyl” means that the alkenyl group may be substituted by one or more substituents (e.g., 1 to 3 substituents) which may be the same or different, each substituent being independently selected from the group consisting of halo, aryl, cycloalkyl, cyano, hydroxy, alkoxy, alkylthio, amino, — NH(alkyl), —NH(cycloalkyl), —N(alkyl)2, carboxy and —C(O)O—alkyl.

[0036] “Alkylene” means a difunctional group obtained by removal of a hydrogen atom from an alkyl group that is defined above. Non-limiting examples of alkylene include methylene and ethylene.

[0037] “Alkenyl” means an aliphatic hydrocarbon group containing at least one carbon-carbon double bond and which may be straight or branched and comprising about 2 to about 15 carbon atoms in the chain. Preferred alkenyl groups have about 2 to about 12 carbon atoms in the chain; and more preferably about 2 to about 6 carbon atoms in the chain. Branched means that one or more lower alkyl groups such as methyl, ethyl or propyl, are attached to a linear alkenyl chain. “Lower alkenyl” means about 2 to about 6 carbon atoms in the chain which may be straight or branched. The term “substituted alkenyl” means that the alkenyl group may be substituted by one or more substituents which may be the same or different, each substituent being independently selected from the group consisting of halo, alkyl, aryl, cycloalkyl, cyano, alkoxy and —S(alkyl). Non-limiting examples of suitable alkenyl groups include ethenyl, propenyl, n-butenyl, 3- methylbut-2-enyl, n-pentenyl, octenyl and decenyl.

[0038] “Alkynyl” means an aliphatic hydrocarbon group containing at least one carbon-carbon triple bond and which may be straight or branched and comprising about 2 to about 15 carbon atoms in the chain. Preferred alkynyl groups have about 2 to about 12 carbon atoms in the chain; and more preferably about 2 to about 4 carbon atoms in the chain. Branched means that one or more lower alkyl groups such as methyl, ethyl or propyl, are attached to a linear alkynyl chain. “Lower alkynyl” means about 2 to about 6 carbon atoms in the chain which may be straight or branched. Non-limiting examples of suitable alkynyl groups include ethynyl, propynyl, 2- butynyl and 3-methylbutynyl. The term “substituted alkynyl” means that the alkynyl group may be substituted by one or more substituents which may be the same or different, each substituent being independently selected from the group consisting of alkyl, aryl and cycloalkyl.

[0039] “Aryl” means an aromatic monocyclic or multicyclic ring system comprising about 6 to about 14 carbon atoms, preferably about 6 to about 10 carbon atoms. The aryl group can be optionally substituted with one or more “ring system substituents” which may be the same or different and are as defined herein. Non-limiting examples of suitable aryl groups include phenyl and naphthyl.

[0040] “Arylene” means a difunctional group obtained by removal of a hydrogen atom from an aryl group that is defined above. Non-limiting examples of arylene include phenylene and naphthylene.

[0041] “Heteroaryl” means an aromatic monocyclic or multicyclic ring system comprising about 5 to about 14 ring atoms, preferably about 5 to about 10 ring atoms, in which one or more of the ring atoms is an element other than carbon, for example nitrogen, oxygen or sulfur, alone or in combination. Preferred heteroaryls contain about 5 to about 6 ring atoms. The “heteroaryl” can be optionally substituted by one or more “ring system substituents” which may be the same or different and are as defined herein. The prefix aza, oxa or thia before the heteroaryl root name means that at least a nitrogen, oxygen or sulfur atom respectively, is present as a ring atom. A nitrogen atom of a heteroaryl can be optionally oxidized to the corresponding N-oxide. Non- limiting examples of suitable heteroaryls include pyridyl, pyrazinyl, furanyl, thienyl, pyrimidinyl, pyridone (including N-substituted pyridones), isoxazolyl, isothiazolyl, oxazolyl, thiazolyl, pyrazolyl, furazanyl, pyrrolyl, pyrazolyl, triazolyl, 1,2,4-thiadiazolyl, pyrazinyl, pyridazinyl, quinoxalinyl, phthalazinyl, oxindolyl, imidazo[1,2-a]pyridinyl, imidazo[2,1- b]thiazolyl, benzofurazanyl, indolyl, azaindolyl, benzimidazolyl, benzothienyl, quinolinyl, imidazolyl, thienopyridyl, quinazolinyl, thienopyrimidyl, pyrrolopyridyl, imidazopyridyl, isoquinolinyl, benzoazaindolyl, 1,2,4-triazinyl, benzothiazolyl and the like. The term “heteroaryl” also refers to partially saturated heteroaryl moieties such as, for example, tetrahydroisoquinolyl, tetrahydroquinolyl and the like.

[0042] “Aralkyl” or “arylalkyl” means an aryl-alkyl-group in which the aryl and alkyl are as previously described. Preferred aralkyls comprise a lower alkyl group. Non-limiting examples of suitable aralkyl groups include benzyl, 2-phenethyl and naphthalenylmethyl. The bond to the parent moiety is through the alkyl.

[0043] “Alkylaryl” means an alkyl-aryl-group in which the alkyl and aryl are as previously described. Preferred alkylaryls comprise a lower alkyl group. Non-limiting example of a suitable alkylaryl group is tolyl. The bond to the parent moiety is through the aryl.

[0044] “Cycloalkyl” means a non-aromatic mono- or multicyclic ring system comprising about 3 to about 10 carbon atoms, preferably about 5 to about 10 carbon atoms. Preferred cycloalkylrings contain about 5 to about 7 ring atoms. The cycloalkyl can be optionally substituted with one or more “ring system substituents” which may be the same or different and are as defined above. Non-limiting examples of suitable monocyclic cycloalkyls include cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl and the like. Non-limiting examples of suitable multicyclic cycloalkyls include 1-decalinyl, norbornyl, adamantyl and the like, as well as partially saturated species such as, for example, indanyl, tetrahydronaphthyl and the like.

[0045] “Cycloalkylene” means a difunctional group obtained by removal of a hydrogen atom from a cycloalkyl group that is defined above. Non-limiting examples of cycloalkylene include cyclobutylene and cyclopropylene.

[0046] “Halo” means fluoro, chloro, bromo or iodo. Preferred are fluoro, chloro and bromo.

[0047] “Ring system substituent” means a substituent attached to an aromatic or non-aromatic ring system which, for example, replaces an available hydrogen on the ring system. Ring system substituents may be the same or different, each being independently selected from the group consisting of —CF3, alkyl, alkenyl, alkynyl, aryl, heteroaryl, aralkyl, alkylaryl, heteroaralkyl, heteroarylalkenyl, heteroarylalkynyl, alkylheteroaryl, hydroxy, hydroxyalkyl, alkoxy, aryloxy, aralkoxy, acyl, aroyl, halo, nitro, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, aralkoxycarbonyl, alkylsulfonyl, arylsulfonyl, heteroarylsulfonyl, alkylthio, arylthio, heteroarylthio, aralkylthio, heteroaralkylthio, or cycloalkyl.

[0048] “Acyl” means an H—C(O)—, alkyl-C(O)— or cycloalkyl-C(O)—, group in which the various groups are as previously described. The bond to the parent moiety is through the carbonyl. Preferred acyls contain a lower alkyl. Non-limiting examples of suitable acyl groups include formyl, acetyl and propanoyl.

[0049] “Aroyl” means an aryl-C(O)— group in which the aryl group is as previously described. The bond to the parent moiety is through the carbonyl. Non-limiting examples of suitable groups include benzoyl and 1-naphthoyl.

[0050] Alkoxy” means an alkyl-O— group in which the alkyl group is as previously described. Non-limiting examples of suitable alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy and n-butoxy. The bond to the parent moiety is through the ether oxygen.

[0051] An “azpeptide” means a peptide in which one or more α-carbons are replaced by nitrogen trivalent atoms.

[0052] An “azatide” means a peptide in which the α-carbons of two adjacent amino acids are replaced by nitrogen trivalent atoms.

[0053] An “α-nitrogen” means a nitrogen atom bonded to a carbonyl group in an azapeptide or an azatide. The carbon atom next to the α-nitrogen is called the β-carbon.

[0054] An “aza-amino acid” is defined as an amino acid where the chiral α-carbon atom is replaced by a nitrogen atom.

[0055] An “azapeptide analogue” means a compound which differs from a peptide that it is an analogue of in that one or more α-carbon atoms of the peptide have been replaced by a nitrogen atom with or without additional structural modification(s) to the side chain(s) of the amino acid residues of the peptide. The one or more α-carbon atoms of the peptide may, e.g., be at the N- termini of the peptide (i.e., the first residue of the peptide), at the second residue of the peptide, the C-termini of the peptide (i.e., the last residue of the peptide), the residue covalently bound to the C-termini of the peptide, and / or at another residue of the peptide (e.g., at the site of hydrolysis of the peptide). Despite having a backbone different from the peptide, the azapeptide analogue preserves, extends and / or improves functional activity of the peptide. The azapeptide analogue is often more resistant to degradation than the peptide and / or has an improved therapeutic activity than the peptide and / or has an improved selectivity for a biological receptor than the peptide and / or improved affinity to a biological receptor and / or reversed activity at a biological receptor (agonistic activity instead of antagonist activity or antagonistic activity instead of agonistic activity).

[0056] An “amine” in the process of the invention may, e.g., be an amino ester, an ester of an amino acid, an amino ester of an aza-amino acid, a peptide, or an aza-peptide, an amino acid, an aza-amino acid, provided that, if the amino ester, the ester of an amino acid, the amino ester of the aza-amino acid, the peptide, the aza-peptide, the amino acid, or the aza-amino acid contains a group selected from amino, amide, guanidino N, carboxyl, sulfhydryl, carboxyl, hydroxyl, indole, imidazole phenol, the group is protected with a protecting group selected from tert- butoxycarbonyl (Boc), 9-fluorenylmethoxycarbonyl (Fmoc), or 2-(3,5-dimethoxyphenyl)propan-2-yloxycarbonyl (Ddz), phthalimide (Phth), carboxybenzyl (Cbz), 2,2,4,6,7-pentamethyl- dihydrobenzofuran-5-sulfonyl (Pbf), trityl or triphenylmethyl (Trt), t-butyl ester (OtBu), t-butyl ether (tBu), allyloxycarbonyl (Aloc), methoxytrimethylbenzene sulfonyl (Mtr), 4,4- dimethyloxybenzhydryl (Mbh), 2,2,5,7,8-pentamethyl-chroman-6-sulfonyl chloride (Pmc), 2,4,6- trimethoxybenzyl (Tmob), allyl ester (OAT), acetamidomethyl (Acm), and the like. The amino ester may, e.g., be t-butyl, p-methoxy benzyl ester, glycine ethyl ester, etc.

[0057] The term “heteroaryl” includes all aryl compounds with atoms other than C and H.

[0058] The term “protected” as it is used herein means that one or more group(s) (e.g., —OH) in an amino acid, an aza-amino acid, a peptide, an azapeptide, or a compound is protected with a protecting group (e.g., Phth, Boc, Ddz, etc.). Unless otherwise indicated, the term “protecting group” or “protective group,” when used to refer to part of a molecule subjected to a chemical reaction, means a chemical moiety that is not reactive under the conditions of that chemical reaction, and which may be removed to provide a moiety that is reactive under those conditions. Protecting groups include, for example, nitrogen protecting groups and hydroxy-protecting groups. Examples of protective groups include, e.g., benzyl, diphenylmethyl, trityl, Cbz, Boc, Fmoc, methoxycarbonyl, ethoxycarbonyl, Phth, Ddz, as well as other protective groups known to those skilled in the art.

[0059] The abbreviation “Phth” means “phthalimidyl”: .

[0060] The term “phthaloyl” or “phthaloyl group” means:.

[0061] The abbreviation “Boc” m onyl.

[0062] The abbreviation “Fmoc” means “9-fluorenylmethoxycarbonyl.”

[0063] The abbreviation “Ddz” means “2-(3,5-dimethoxyphenyl)propan-2-yloxycarbonyl.”

[0064] The abbreviation “HOBt” means “1-OH-Benzotriazole.”

[0065] The abbreviation “Cbz” means “carboxybenzyl.”

[0066] The abbreviation “mCPBA” means meta-chloroperoxybenzoic acid.

[0067] The abbreviation “Pbf” means “2,2,4,6,7-pentamethyl-dihydrobenzofuran-5-sulfonyl.”

[0068] In peptide chemistry, “deprotection” refers to a process of removing the protecting groups (e.g., phthaloyl, Boc, Cbz, Fmoc, etc.) by a chemical agent. For example, Boc protecting group could be removed under acidic conditions (e.g., 4 M HCl, or neat trifluoroacetic acid TFA); Fmoc protecting group could be removed under basic conditions when pH is higher than 12 (20% piperidine / DMF or DCM); and Phthaloyl group can be cleaved, e.g., under basic conditions or by the use of hydrazine.

[0069] The “amino acid side chain radical(s)” in the compounds of Formulae (I)-(V) may be a side chain radical of natural amino acid or a side chain radical of unnatural amino acid. The following table shows the definitions of the abbreviations for certain natural, unnatural and aza- amino acids: Abbreviation Definition G GlycineA Alanine I Isoleucine L Leucine V Valine C Cysteine M Methionine S Serine T Threonine N Asparagine Q Glutamine F Phenylalanine W Tryptophan P Proline D Aspartic acid E Glutamic acid Y Tyrosine R Arginine K Lysine H Histidine Aib 2-aminoisobutyric acid aG Aza GlycineaA Aza Alanine aI Aza Isoleucine aL Aza Leucine aV Aza Valine aC Aza Cysteine aM Aza Methionine aS Aza Serine aT Aza Threonine aN Aza Asparagine aQ Aza Glutamine aF Aza Phenylalanine aW Aza Tryptophan aP Aza Proline aD Aza Aspartic acid aE Aza Glutamic acid aY Aza Tyrosine aR Aza Arginine aK Aza Lysine aH Aza Histidine

[0070] Non-limiting examples of natural amino acids include aspartic acid, phenylalanine, alanine, histidine, glutamic acid, tryptophan, valine, leucine, lysine, methionine, tyrosine,isoleucine (including, R-isoleucine, S-isoleucine and RS-isoleucine), arginine, glycine, asparagine, and glutamine.

[0071] Non-limiting examples of unnatural amino acids include aza-imidazole derivatives and Phth-protected carbamoyl aza-benzotriazole derivatives of β-amino acids (e.g., L-β- homotyrosine, β-alanine, L-β-homoasparagine, L-β-homoalanine, L-β-homophenylalanine, L-β- homoproline, L-β-holysine, L-β-homoarginine, L-β-proline, etc.), aliphatic amino acids (e.g., 6- aminohexanoic acid, 2-amino-3-methoxybutanoic acid, 1-aminocyclopentane-1-carboxylic acid, 2-(aminooxy)acetic acid, 6-aminohexanoic acid, 2-[2-(amino)-ethoxy]-ethoxy}acetic acid), β- cyclohexyl-L-alanine, 6-aminohexanoic acid, L-α,β-diaminopropionic acid, L-propargylglycinel, L-α,β-diaminopropionic acid, α-aminoisobutyric acid, β-(2-pyridyl)-L-alanine, β-(3-pyridyl)-L- alanine, β-cyclopropyl-L-alanine, β-t-butyl-L-alanine, (2,4-dinitrophenyl))-L-α,β- diaminopropionic acid, (allyloxycarbonyl)-L-α,β-diaminopropionic acid, D-α,β- diaminopropionic acid, L-α,β-diaminopropionic acid, (N-γ-1-(4,4-dimethyl-2,6-dioxocyclohex- 1-ylidene)ethyl)-L-α,γ-diaminobutyric acid, (N-γ-4-methyltrityl)-L-α,γ-diaminobutyric acid, L- α,γ-diaminobutyric acid, 4-fluoro-L-phenylglycine, 5,5,5-trifluoro-DL-leucine, epsilon- aminohexanoic-OH, L-α-t-butylglycine, L-2-amino-3-(dimethylamino)propionic acid, L-2- aminocaproic acid, L-allylglycine, lysine azide, (Nδ-4-methyltrityl)-L-ornithine, Arg(Me)(Pbf)- OH, dimethyl-L-arginine (symmetrical and unsymmetrical), L-2-amino-3-guanidinopropionic acid, L-citrulline, ε-acetyl-L-lysine, Lys(ivDde)-OH, Lys(Me)2-OH.HCl, Lys(Me3)— OHchloride, α-methyl-DL-glutamic acid, γ-carboxy-L-glutamic acid γ,γ-di-t-butyl ester, (N-γ- ethyl)-L-glutamine, 2,6-diaminopimelic acid, Glu(OAll)-OH, L-cysteic acid, α-methyl-DL- methionine, DL-buthionine, L-cysteic acid, L-selenomethionine, S-[2-(4-pyridyl)ethyl]-L- cysteine, S-[2-(4-pyridyl)ethyl]-L-cysteine, S-diphenylmethyl-L-cysteine, S-trityl-L- homocysteine, S-trityl-L-enicillamine, (Se-p-methoxybenzyl)-L-selenocysteine, β- hydroxyphenylalanine, 2-cyano-L-phenylalanine, L-thyroxine, O-methyl-L-tyrosine, β-methyl- DL-phenylalanine, 2-cyano-L-phenylalanine, L-thyroxine, O-methyl-L-tyrosine, β-methyl-DL- phenylalanine, 2-cyano-L-phenylalanine, 3,4-dichloro-L-phenylalanine, 3,4-difluoro-L- phenylalanine, 3,4-dihydroxy-L-phenylalanine, 3,4-dihydroxy-phenylalanine, 3-amino-L- tyrosine, 3-chloro-L-tyrosine, 3-fluoro-DL-tyrosine, 3-nitro-L-tyrosine, 4-amino-L- phenylalanine, 4-aminomethyl-L phenylalanine, 4-(phosphonomethyl)-phenylalanine, 4-benzoyl- D-phenylalanine, 4-bis(2-chloroethyl)amino-L-phenylalanine, 4-cyano-L-phenylalanine, 4-fluoro-L-phenylalanine, 4-iodo-L-phenylalanine, DL-m-tyrosine, 2,6-dimethyl-tyrosine, L- homophenylalanine, O-methyl-L-tyrosine, Phe(4-guanidino) OH, O-benzyl-L-phosphotyrosine, (2S,3R)-3-phenylpyrrolidine-2-carboxylic acid, (2S,4S)-4-phenyl-pyrrolidine-2-carboxylic acid, (2S,3aS,7aS)-Octahydro-1H-indole-2-carboxylic acid, (2S,3R)-3-phenylpyrrolidine-2-carboxylic acid, (2S,4R) (−)-4-t-butoxypyrrolidine-2-carboxylic acid, trans-4-Fluoro-L-proline, (3S,4S)-4- amino-3-hydroxy-6-methylheptanoic acid, 4-amino-3-hydroxybutanoic acid, L-α-methylserine, (2S,3S)-2-amino-3-methoxybutanoic acid, Thr(β-D-GlcNAc(Ac)3)-OH, O-benzyl-L- phosphoserine, O-benzyl-D-phosphothreonine, O-benzyl-L-phosphothreonine, 4-methyl-DL- tryptophan, 6-fluoro-DL-tryptophan, 6-methyl-DL-tryptophan, DL-7-azatryptophan, (R)-7- Azatryptophan, 5-benzyloxy-DL-tryptophan, 5-bromo-DL-tryptophan, 5-chloro-DL-tryptophan, 5-fluoro-DL-tryptophan, 5-hydroxy-L-tryptophan, 5-methoxy-L-tryptophan, 6-chloro-L- tryptophan, 6-methyl-DL-tryptophan, 7-methyl-DL-tryptophan, DL-7-azatryptophan, 5-azido- pentanoic acid, 2-Amino-N-(3-azidopropyl)-3-mercaptopropionamide, 2-Amino-N-(3- azidopropyl)-3-mercaptopropionamide, Azidohomoalanine, L-propargylglycine-DCHA, azidolysine, p-azidophenylalanine, Azidohomoalanine, D-propargylglycine, L-propargylglycine, azidolysine, Tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine, 2-(7′-octenyl) alanine, 2-(4′- pentenyl) alanine, 2-(4′-pentenyl)glycine, 2-(7′-octenyl) alanine, [5-((2- Aminoethyl)amino)naphthalene-1-sulfonic acid], L-glutamic acid-γ-[2-(1-sulfonyl-5-naphthyl)- aminoethylamide], N-ε-(5-carboxyfluorescein)-L-lysine, N-ε-(5 / 6-carboxyfluorescein)-L-lysine, N-ε-(4,4-dimethylazobenzene-4′carbonyl)-L-lysine, Nε-2,4-dinitrophenyl-L-lysine, N-ε-[(7- methoxycoumarin-4-yl)-acetyl-L-lysine, glycosylated amino acids (e.g., Ser(β-D-GlcNAc(Ac)3) —OH, Thr(β-D-GlcNAc(Ac)3) —OH), 3-azabicyclo[3.1.0]hexane-2-carboxylic acid; 4-amino- (1-carboxymethyl) piperidine, 4-phenylpiperidine-4-carboxylic acid, Nα-methyl-N-im-trityl-L- histidine, Na-methyl-O-benzyl-L-serine dicyclohexylammonium salt, Nalpha-methyl-Nomega- (4-methoxy-2,3,6-trimethylbenzenesulfonyl)-L-arginine, Nalpha-methyl-L-leucine, Nalpha- methyl-L-norvaline, Nalpha-methyl-L-phenylalanine, Nalpha-methyl-N-im-trityl-L-histidine, Nalpha-methyl-O-t-butyl-L-serine, Nalpha-methylglycine, 21-amino-4,7,10,13,16,19- hexaoxaheneicosanoic acid, {2-[2-(amino)-ethoxy]-ethoxy}acetic acid, 6-Amino-4-oxohexanoic acid, 5-Amino-3-Oxapentamoic Acid, NH-(PEG)10-CH2CH2COOH, NH-(PEG)12— CH2CH2COOH, 9-Amino-4; 7-Dioxanonanoic acid, 9-Amino-4; 7-Dioxanonanoic acid, 12- amino-4,7,10-trioxadodecanoic acid, 15-amino-4,7,10,13-tetraoxapentadecacanoic acid, 18-amino-4,7,10,13,16-pentaoxaoctadecanoic acid, 21-amino-4,7,10,13,16,19- hexaoxaheneicosanoic acid, NH-(PEG)8-CH2CH2COOH, 11-amino-3,6,9-trioxaundecanoic acid, N-(Fmoc-8-amino-3,6-dioxa-octyl)succinamic acid, —N-ε-acetyl-L-lysine, L-citrulline, Arg(Me)(Pbf)-OH, Nω,ω-dimethyl-L-arginine (asymmetrical and symmetrical), Lys(Me)2-OH chloride, N-ε,ε-t-methyl-L-lysine, Lys(Me3)—OH chloride, O-benzyl-L-phosphoserine, O- benzyl-D-phosphothreonine, O-benzyl-L-phosphothreonine, O-benzyl-L-phosphotyrosine.

[0072] Amino acids which can be used in the present invention include L and D-amino acids.

[0073] Substituents for the natural and unnatural amino acids are halo, –ORa, –S(O)mRa, – NRaRb, –C(O)Rc, –C(O)ORa, C1-C6 haloalkyl, and a protecting group, wherein Ra is H, C1-C6 alkyl, or C1-C6haloalkyl, Rbis H, C1-C6alkyl, or C1-C6haloalkyl, Rcis C1-C6alkyl, or C1-C6haloalkyl, m is 0, 1, or 2.

[0074] Unless otherwise specified, “substituted” means that one or more hydrogens of the compound is replaced with a substituent selected from a group consisting of halo, –ORa, – S(O)mRa, –NRaRb, –C(O)Rc, –C(O)ORa, C1-C6haloalkyl, and a protecting group, wherein Rais H, C1-C6 alkyl, or C1-C6 haloalkyl, Rb is H, C1-C6 alkyl, or C1-C6 haloalkyl, Rc is C1-C6 alkyl, or C1-C6 haloalkyl, m is 0, 1, or 2.

[0075] A “protecting group” includes tert-butoxycarbonyl, 9-fluorenylmethoxycarbonyl, carboxybenzyl, 2-(3,5-dimethoxyphenyl)propan-2-yloxycarbonyl, 2,2,4,6,7,-pendamethyl- dihydrobenzofuran-5-sulfonyl, triphenylmethyl, tert-butylcarbonyl, t-butoxy, allyloxycarbonyl, methoxytrimethylbenzene sulfonyl, 4,4-dimethoxy benzhydryl, 2,2,5,7,8-pentamethylchroman- 6-sulfonyl, 2,4,6-trimethoxybenzyl, allylcarbonyl, acetamidomethyl, phthaloyl, phthalimidyl, and its derivatives.

[0076] The term “solid-phase peptide synthesis” or “SSPS” means a method in which molecules (e.g., amino acids, aza-amino acids, etc.) are covalently bound on a solid support material and synthesized step-by-step in a single reaction vessel utilizing selective protecting group chemistry. In this method, building blocks are typically protected at all reactive functional groups. The order of functional group reactions can be controlled by the order of deprotection. For example, in an aza-peptide synthesis, an amino-protected amino acid or an amino-protected aza-amino acid is bound to a solid phase material (e.g., low cross-linked polystyrene beads),forming a covalent bond between the carbonyl group and the resin, e.g., an amido or an ester bond. Then the amino group is deprotected and reacted with the carbonyl group of the next amino-protected amino acid or amino-protected aza-amino acid. This cycle is repeated to form the desired peptide or aza-peptide chain. After all reactions are complete, the synthesized peptide or aza-peptide is cleaved from the bead.

[0077] The terms “solution phase synthesis” and “liquid phase synthesis” means a method in which molecules (e.g., amino acids, aza-amino acids, etc.) are synthesized in a solution without being covalently bound on a solid support material.

[0078] The term “synthon” means a synthetic building block.

[0079] The term “ambient temperature” means 18-28°C.

[0080] A “halogenating agent” in a reagent that forms the active intermediate through halogenation and includes reagents such as phosgene, trichloroisocyanuric acid (“TCCA), or a combination of tetrabutyl ammonium chloride (“TBACl”) with tetrabutyl ammonium chloride (“TBACl”).

[0081] These and embodiments are disclosed or are obvious from and encompassed by the following Detailed Description. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The following detailed description, given by way of example, but not intended to limit the invention solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings.

[0083] Fig. 1 summarizes conventional azapeptide synthetic strategies-activation of N'-alkyl- N-protected-hydrazines.

[0084] Fig. 2 summarizes thiocarbazate-based azapeptide synthetic platform. DETAILED DESCRIPTION OF THE INVENTION

[0085] This invention provides for a compound of the formula:wherein: A is an amine protecting group; R1is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or A and R1together form phthaloyl group: ; R2isalkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkoxyalkylene, an optionally protected alkyl amine, or a side chain radical of an amino acid, which is substituted or unsubstituted, or R1and R2together joined by –(CH2)-(CH2)-(CH2)–; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 1 or 2; or a salt thereof.

[0086] Another embodiment of the present invention is compounds of Formula I, which have the formula: wherein:A is an amine protecting group; R1is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or A and R1together form phthaloyl group: ;unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkoxyalkylene, an optionally protected alkyl amine, or a side chain radical of an amino acid, which is substituted or unsubstituted, or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or a salt therof.

[0087] Another embodiment of the present invention is compounds of Formula I, which have the formula: wherein:A is an amine protecting group; R1is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or A and R1together form phthaloyl group: ; R2is H, a substituted oror unsubstituted alkoxy, a substituted or unsubstituted alkoxyalkylene, an optionally protected alkyl amine, or a side chain radical of an amino acid, which is substituted or unsubstituted, or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or a salt thereof.

[0088] One embodiment of the present invention provides for compounds of Formula I, II, and III, where A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, carboxybenzyl, 2-(3,5-dimethoxyphenyl)propan-2-yloxycarbonyl, 2,2,4,6,7,-pendamethyl-dihydrobenzofuran-5-sulfonyl, triphenylmethyl, tert-butylcarbonyl, t- butoxy, allyloxycarbonyl, methoxytrimethylbenzene sulfonyl, 4,4-dimethoxy benzhydryl, 2,2,5,7,8-pentamethylchroman-6-sulfonyl, 2,4,6-trimethoxybenzyl, allylcarbonyl, phthalimidyl, and acetamidomethyl.

[0089] Another embodiment of the present invention provides for compounds of Formula I, Formula II, or Formula III, wherein A is selected from the group consisting of tert- butoxycarbonyl, 9-fluorenylmethoxycarbonyl, and carboxybenzyl.

[0090] Another embodiment of the present invention provides for compounds of Formula I, Formula II, or Formula III, wherein A and R1 together form phthaloyl group.

[0091] Another embodiment of the present invention provides for Formula I, Formula II, or Formula III, wherein: A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted; or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; and R is a C1to C4alkyl; or a salt thereof.

[0092] Another embodiment of the present invention provides for Formula I, Formula II, or Formula III, wherein: A is 9-fluorenylmethoxycarbonyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted; or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; and R is a C1 to C4 alkyl; or a salt thereof.

[0093] Another embodiment of the present invention provides for Formula I, Formula II, or Formula III, wherein: A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1and R2together joined by –(CH2)-(CH2)-(CH2)–; and R is a C1 to C4 alkyl; or a salt thereof.

[0094] Another embodiment of the present invention provides for Formula I, Formula II, or Formula III, wherein A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine, cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; and R is a C1to C4alkyl; or a salt thereof.

[0095] Another embodiment of the present invention provides for Formula I, Formula II, or Formula III, wherein A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is an unnatural amino acid; and R is a C1 to C4 alkyl; or a salt thereof.

[0096] Another embodiment of the present invention provides for Formula I, Formula II, or Formula III, wherein A is 9-fluorenylmethoxycarbonyl;R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is an unnatural amino acid; and R is a C1to C4alkyl; or a salt thereof.

[0097] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: wherein:A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0098] Another embodiment of the present invention provides for compounds of Formula I, which has the formula:(IV) wherein: A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine, cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H or a substituted or unsubstituted C1-C10alkyl; or a salt thereof.

[0099] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: O Rwherein: R2is a side chain radical of a natural amino acid; R is H, or a substituted or unsubstituted C1-C10 alkyl; n is 1 or 2; or a salt thereof.

[0100] Another embodiment of the present invention provides for compounds of Formula I, which has the formula:O R2 R wherein:R2is a side chain radical of an unnatural amino acid; R is H, or a substituted or unsubstituted C1-C10 alkyl; n is 1 or 2; or a salt thereof.

[0101] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: O Rwherein: R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine, cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; R is H, or a substituted or unsubstituted C1-C10 alkyl; n is 1 or 2; or a salt thereof.

[0102] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: O R2 R wherein:R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine, cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; R is H or a substituted or unsubstituted C1-C10alkyl; n is 1; or a salt thereof.

[0103] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: O Rwherein:R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine, cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; R is H or a substituted or unsubstituted C1-C10 alkyl; n is 2; or a salt thereof.

[0104] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: wherein:A is 9-fluorenylmethoxycarbonyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine, cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0105] Another embodiment of the present invention provides for compounds of Formula I, which has the formula:wherein: A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is an unnatural amino acid; or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0106] Another embodiment of the present invention provides for compounds of Formula I, which has the formula:wherein: A is 9-fluorenylmethoxycarbonyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is an unnatural amino acid;or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0107] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: wherein:A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0108] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: AR2Rwherein: A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl;R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, or R1 and R2 together joined by –(CH2)-(CH2)-(CH2)– ; R is H or a substituted or unsubstituted C1-C10alkyl; or a salt thereof.

[0109] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: AR2R wherein:A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; and A and R1together form phthaloyl group: ; R2is a side chain radical ofor unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine,cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0110] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: AR2O R wherein:A is 9-fluorenylmethoxycarbonyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is selected from a group consisting of glycine, alanine, isoleucine, leucine, valine, cysteine, methionine, serine, threonine, asparagine, glutamine, phenylalanine, tryptophan, aspartic acid, glutamic acid, tyrosine, arginine, lysine, and histidine; R is H or a substituted or unsubstituted C1-C10alkyl; or a salt thereof.

[0111] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: AR2R(V) wherein: A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is an unnatural amino acid; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0112] Another embodiment of the present invention provides for compounds of Formula I, which has the formula: AR2R wherein:A is 9-fluorenylmethoxycarbonyl; R1is H; R2is a side chain radical of an amino acid, which is substituted or unsubstituted, wherein the amino acid is an unnatural amino acid; R is H or a substituted or unsubstituted C1-C10alkyl; or a salt thereof.

[0113] Another embodiment of the present invention provides for compounds of Formula I, which has the formula:A R2O R wherein:A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, and carboxybenzyl; R1and R2together joined by –(CH2)-(CH2)-(CH2)–; R is H or a substituted or unsubstituted C1-C10 alkyl; or a salt thereof.

[0114] Another embodiment of the invention is directed to for compounds of Formula I, which has the formula: wherein:A is an amine protecting group; R1is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or A and R1together form phthaloyl group:; R2is m R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 1 or 2; or a salt thereof.

[0115] Another embodiment of the invention is directed to for compounds of Formula I, which has the formula: wherein:A is selected from the group consisting of tert-butoxycarbonyl, 9- fluorenylmethoxycarbonyl, carboxybenzyl, 2-(3,5-dimethoxyphenyl)propan-2- yloxycarbonyl, 2,2,4,6,7,-pendamethyl-dihydrobenzofuran-5-sulfonyl, triphenylmethyl, tert-butylcarbonyl, t-butoxy, allyloxycarbonyl, methoxytrimethylbenzene sulfonyl, 4,4- dimethoxy benzhydryl, 2,2,5,7,8-pentamethylchroman-6-sulfonyl, 2,4,6- trimethoxybenzyl, allylcarbonyl, acetamidomethyl, and phthalimidyl;R1is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or A and R1together form phthaloyl group: ; R2isR is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 1 or 2; or a salt thereof.

[0116] Another embodiment of the present invention provides for compounds of Formula I, Formula II, Formula III, Formula IV, or Formula V in the embodiments described above, wherein R is an optionally substituted C1-C10 alkyl, wherein the optional substituents are selected from the group consisting of halo, –ORa, –S(O)mRa, –NRaRb, –C(O)Rc, –C(O)ORa, and C1-C6haloalkyl, wherein Ra is H, C1-C6 alkyl, or C1-C6 haloalkyl, Rb is H, C1-C6 alkyl, or C1-C6 haloalkyl, Rc is C1-C6 alkyl, or C1-C6 haloalkyl, and m is 0, 1, or 2.

[0117] Another embodiment of the present invention provides for compounds of Formula I, Formula II, Formula III, Formula IV, or Formula V in the embodiments described above, wherein R2is a side chain radical of a natural amino acid, which is substituted or unsubstituted.

[0118] Another embodiment of the present invention provides for compounds of Formula I, Formula II, Formula III, Formula IV, or Formula V in the embodiments described above, wherein the amino acid is selected from the group consisting of aspartic acid, phenylalanine, alanine, histidine, glutamic acid, tryptophan, valine, leucine, lysine, methionine, tyrosine,isoleucine, arginine, glycine, asparagine, serine, and glutamine, which are unsubstituted or substituted by one or more substituents selected from the group consisting of halo, –ORa, – S(O)mRa, –NRaRb, –C(O)Rc, –C(O)ORa, C1-C6 haloalkyl, and a protecting group, wherein Ra is H, C1-C6alkyl, or C1-C6haloalkyl, Rbis H, C1-C6alkyl, or C1-C6haloalkyl, Rcis C1-C6alkyl, or C1-C6 haloalkyl, m is 0, 1, or 2.

[0119] Another embodiment of the present invention provides for compounds of Formula I, Formula II, Formula III, Formula IV, or Formula V in the embodiments described above, wherein R2is a side chain radical of an unnatural amino acid, which is unsubstituted or substituted by one or more substituents selected from the group consisting of halo, –ORa, – S(O)mRa, –NRaRb, –C(O)Rc, –C(O)ORa, C1-C6haloalkyl, and a protecting group, wherein Rais H, C1-C6alkyl, or C1-C6haloalkyl, Rbis H, C1-C6alkyl, or C1-C6haloalkyl, Rcis C1-C6alkyl, or C1-C6 haloalkyl, m is 0, 1, or 2.

[0120] Compounds of Formula I, Formula II, Formula III, Formula IV, and Formula V may be prepared, e.g., by oxidizing compounds described in U.S. Patent No. 11,480,881, Thiosemicarbazates and Uses Thereof. The oxidation could, e.g., from about 0.5 to about 2.5 eq of meta-chloroperoxybenzoic acid (mCPBA). The sulfoxide thiocarbazate compounds may be formed by oxidation with about 0.5 to about 1.5 eq of meta-chloroperoxybenzoic acid (mCPBA); the sulfone thiocarbazate compounds may, e.g., be formed by oxidation with about 1.5 to about 2.5 eq of mCPBA.

[0121] This invention also provides for a compound of the formula: O R(VI), wherein A is an amine protecting group;R1and R2is each independently H, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkoxyalkylene, an optionally protected alkyl amine, or a chain radical of an amino acid; A1is H or absent; A2is H or absent; Z1 and Z2 is each independently C or N, provided that at least one of Z1 and Z2 is N; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 1 or 2; or a salt thereof.

[0122] This invention also provides for a compound of the formula: O R, wherein A is an amine protecting group; R1and R2is each independently H, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkoxyalkylene, an optionally protected alkyl amine, or a chain radical of an amino acid; A1is H or absent; A2is H or absent;Z1and Z2is each independently C or N, provided that at least one of Z1and Z2is N; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 1; or a salt thereof.

[0123] This invention also provides for a compound of the formula: O A1 R, wherein A is an amine protecting group; R1and R2is each independently H, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkoxyalkylene, an optionally protected alkyl amine, or a chain radical of an amino acid; A1is H or absent; A2is H or absent; Z1and Z2is each independently C or N, provided that at least one of Z1and Z2is N; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 2;or a salt thereof.

[0124] The sulfoxide and sulfone derivates of the present invention have utility in synthesis of aza analogues of therapeutic peptides. As compared to the therapeutic peptides, the aza analogues of therapeutic peptides are more resistant to degradation by serum and / or digestive proteases.

[0125] Further, the oxidation process to form sulfoxide and sulfone compounds of the invention is unique to thiocarbazates. Unlike thiocarbazates, when a regular thioester is subjected to the same oxidation conditions, only hydrolysis of the thioester occurs. For example, when Fmoc-Phe-Set is oxidized, the corresponding sulfoxide or sulfone is not formed; only Fmoc-Phe- OH is obtained:which comprises coupling N-terminal end of a peptide with a compound of Formula I, Formula II, Formula III, Formula IV, Formula V, Formula VI or Formula VII without first activating the compound of Formula I, Formula II, Formula III, Formula IV, Formula V, Formula VI or Formula VII, with a halogenating agent, without forming a reactive chloride intermediate and without using a reagent selected from a group consisting of phosphagene, triphosgene, TCCA / TBACl, p-nitrophenylchloroformate, bis(2,4-dinitrophenyl) carbonate, bis(pentafluorophenyl) carbonate, N,N'-disuccinimidyl carbonate (DSC), carbonyldiimidazole, and carbonyl-diimidazole (CDI), and 1,1'-carbonyl-di-(1,2,4-triazole) (“CDT”).

[0127] For example, the present invention provides for the preparation of an aza-peptide which comprises coupling N-terminal end of a peptide with a compound of the formula:wherein A is an amine protecting group; R1is H, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; R2is H, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkoxyalkylene, optionally protected alkyl amine, and a side chain radical of an amino acid, which is substituted or unsubstituted, or R1and R2together joined by –(CH2)-(CH2)-(CH2)– ; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 1 or 2. The coupling takes place without activation of the compound of the Formula (I) with reagent selected from the group consisting of phosphagene, triphosgene, TCCA / TBACl, p- nitrophenylchloroformate, bis(2,4-dinitrophenyl) carbonate, bis(pentafluorophenyl) carbonate, N,N'-disuccinimidyl carbonate (DSC), carbonyldiimidazole, and carbonyl-diimidazole (CDI), and 1,1'-carbonyl-di-(1,2,4-triazole) (“CDT”). The coupling also is not through a reactive chloride intermediate.

[0128] In certain embodiments, the method provides for the preparation of an aza-peptide, the preparation comprising coupling a compound according to the Formula (VI) or a compound of Formula (VII) to an amino acid, a peptide or an azapeptide, wherein the coupling takes place without activation of the compound of the Formula (I) with reagent selected from the groupconsisting of phosphagene, triphosgene, TCCA / TBACl, p-nitrophenylchloroformate, bis(2,4- dinitrophenyl) carbonate, bis(pentafluorophenyl) carbonate, N,N'-disuccinimidyl carbonate (DSC), carbonyldiimidazole, and carbonyl-diimidazole (CDI), and 1,1'-carbonyl-di-(1,2,4- triazole) (“CDT”), the coupling is not through a reactive chloride intermediate.

[0129] In certain embodiments, the method provides for the preparation of an aza-peptide, the preparation comprising synthesizing a trimer peptide sulfoxide and / or sulfone synthon and coupling the trimer peptide sulfoxide and / or sulfone synthon to an amino acid, a peptide or an azapeptide, wherein the coupling takes place without activation of the compound of the Formula (I) with reagent selected from the group consisting of phosphagene, triphosgene, TCCA / TBACl, p-nitrophenylchloroformate, bis(2,4-dinitrophenyl) carbonate, bis(pentafluorophenyl) carbonate, N,N'-disuccinimidyl carbonate (DSC), carbonyldiimidazole, and carbonyl-diimidazole (CDI), and 1,1'-carbonyl-di-(1,2,4-triazole) (“CDT”), the coupling is not through a reactive chloride intermediate.

[0130] Target peptides that may benefit from being converted to azapeptides by the inventive process are well known in the art and include peptides that comprise from 2 to 200 carbonyl group(s). For example, the peptide may comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39, 40, 41, 43, 44, 56, or 166 carbonyl groups. In certain embodiments, peptide comprises from 2 to 60 carbonyl groups, from 2 to 50 carbonyl groups, from 2 to 40 carbonyl groups, from 2 to 30 carbonyl groups, from 2 to 25 carbonyl groups, from 2 to 20 carbonyl groups, from 2 to 15 carbonyl groups, from 2 to 12 carbonyl groups, from 2 to 10 carbonyl groups, from 2 to 9 carbonyl groups, from 3 to 40 carbonyl groups, from 3 to 30 carbonyl groups, from 3 to 25 carbonyl groups, from 3 to 20 carbonyl groups, from 3 to 15 carbonyl groups, from 3 to 12 carbonyl groups, from 3 to 10 carbonyl groups, or from 3 to 9 carbonyl groups.

[0131] Many of the target peptides that may benefit from having at least one peptide bond replaced by an azapeptide bond have utility as therapeutics. Such agents include, e.g., GLP-1, glucose-dependent insulinotropic peptide (GIP) and glucagon receptor agonists.

[0132] GLP-1 (1-37) has the following sequence: HAEGTFTSDVSSYLEGQAAKEFIAWLVKGRG (SEQ ID NO: 1).

[0133] GIP have the following sequence: YAEGTFISDYSIAMDKIHQQDFVNWLLAQKGKKNDWKHNITQ (SEQ ID NO: 2).

[0134] Glucagon has the following sequence: HSQGTFTSDYSKYLDSRRAQDFVQWLMNT (SEQ ID NO: 3).

[0135] GLP-1, GIP and glucagon receptor agonists mimic the therapeutic action of GLP-1 and / or both GLP-1 and GIP and / or GLP-1, GIP and glucagon, and may be used to treat disorders including, e.g., type-2 diabetes and obesity.

[0136] GLP-1 receptor agonist that may serve as target peptides are known in art (see, e.g., A. M. Jastreboff et al., Annu. Rev. Med., “New Frontiers in Obesity Treatment: GLP-1 and Nascent Nutrient-Stimulated Hormone-Based Therapeutics”, 74, 125-139 (2023), W. Peng, et al., Aging and Disease, “Novel Insights into the Roles and Mechanisms of GLP-1 Receptor Agonists against Aging-Related Diseases”, 13(2), 468-490 (2022); and T.D. Miller, et al., Molecular Metabolism, 30, 72-130 (2019). Specific peptides that may be target peptides include liraglutide, semaglutide, danuglipron, LY3502970 (Lilly) (GLP-1 receptor agonists); cagrilintide, SP8396 (Zealand Pharma), amylin agonist LA (Eli Lilly), DACRA QWII (Eli Lilly) (endo-pancreatic receptor agonists); tirzepatide, CT388 (Carmot Therapeutics), dapiglutide, AMG133 (Amgen) (entero-endocrine receptor agonists / antagonists); and retratrutide (pancreatic-entero-endocrine receptor).

[0137] Other aza GLP-1-based therapeutic analogues that may be synthesized by the processes provided for herein are disclosed in U.S. Application Serial No. 63 / 609,981, entitled “Aza GLP- 1-Based Therapeutic Analogues” to Yousef Al-Abed and International PCT application entitled “Aza GLP-1-Based Therapeutic Analogues”, filed concurrently herewith.

[0138] In certain embodiments, the sulfoxide and sulfone thiocarbazate compounds and the methods disclosed herein are used to provide a compound selected from a group consisting of: (i) a compound of Formula: X1X2X3GX4X5X6X7X8X9X10X11X12EGX13X14AX15X16X17X18X19X20X21X22X23X24X25X26X27- X28X29X30X31X32X33X34X35,wherein X1is azaH, azaA, AzaG, azaY, azaF, F, Y, A, G, or H; X2is azaA, azaG, aza-D, D, Aib, G, or A; X3 is azaE, E, Q, or azaQ; X4 is azaT, azaS, T or S; X5 is azaF or F; X6 is azaT or T; X7 is azaS or S; X8 is azaD or D; X9 is azaV, azaY, Y or V; X10 is azaS or S; X11 is azaS, azaI, azaL, azaV, azaF, I, L, V, F, or S; X12is azaY, Y, Aib, L, or azaL; X13is azaG, azaK, K or G; X14is azaQ, azaE, azaI, I, K, azaK, Q, or E; X15 is azaA, A, azaE, E, AzaQ, or Q; X16 is azaK, K or Aib; X17 is azaE, azaA, A or E; X18 is azaF or F; X19 is azaI, azaV, V, or I; X20 is azaA, azaQ, Q, E, azaE, or A; X21is AzaW, W, Y, or azaY; X22is azaL, azaV, L, azaL, V, or azaV; X23is azaV, azaI, L, aza L, I, or V; X24 is azaK, azaE, azaR, K, E or R; X25 is azaG or G; X26 is azaG, azaR, G or R; X27 is absent or is azaG, G, azaP, or P; X28 is absent or S; X29 is absent or S; X30 is absent or G; X31is absent or A; X32is absent or P; X33is absent or P; X34is absent or P; X35is absent or S, and wherein X35, if present, is optionally amidated as a C-terminal primary amide (SEQ ID NO: 4); wherein at least one of X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, and X27 is an aza-amino acid; or a pharmaceutically acceptable salt thereof; (ii) a compound of Formula: X1X2X3GX4X5X6X7X8X9X10X11X12EGX13X14AX15X16X17X18X19X20X21X22X23X24X25X26X27, wherein X1is azaH, azaA, AzaG, azaY, azaF, F, Y, A, G, or H; X2is azaA, azaG, aza-D, D, Aib, G, or A; X3 is azaE or E; X4 is azaT, azaS, T or S; X5 is azaF or F; X6 is azaT or T; X7 is azaS or S; X8 is azaD or D; X9 is azaV, azaY, Y or V; X10 is azaS or S; X11 is azaS, azaI, azaL, azaV, azaF, I, L, V, F, or S; X12is azaY, Aib, or Y; X13is azaG, azaK, K or G; X14is azaQ, azaE, azaI, I, Q or E; X15is azaA, azaE, E, or A; X16is azaK or K; X17is azaE, azaA, A or E; X18is azaF or F; X19 is azaI, azaV, V, or I; X20 is azaA, azaQ, Q, or A; X21 is AzaW or W; X22 is azaL, azaV, L or V; X23 is azaV, azaI, I or V; X24 is azaK, azaE, azaR, K, E or R; X25 is azaG or G; X26 is azaG, azaR, G or R; X27is azaG or G (SEQ ID NO: 5); wherein at least one of X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, and X27 is an aza-amino acid; or a pharmaceutically acceptable salt thereof; (iii) a compound of Formula: X1X2X3GX4X5X6X7X8X9X10X11X12EGX13X14AX15X16X17X18X19X20X21X22X23X24X25X26, wherein X1 is azaH, azaA, AzaG, azaY, azaF, F, Y, A, G, or H; X2 is azaA, azaG, aza-D, D, Aib, G, or A; X3 is azaE or E; X4 is azaT, azaS, T or S; X5 is azaF or F; X6 is azaT or T; X7 is azaS orS; X8is azaD or D; X9is azaV, azaY, Y or V; X10is azaS or S; X11is azaS, azaI, azaL, azaV, azaF, I, L, V, F, or S; X12 is azaY, Aib, or Y; X13 is azaG, azaK, K or G; X14 is azaQ, azaE, azaI, I, Q or E; X15 is azaA, azaE, E, or A; X16 is azaK or K; X17 is azaE, azaA, A or E; X18 is azaF or F; X19is azaI, azaV, V, or I; X20is azaA, azaQ, Q, or A; X21is AzaW or W; X22is azaL, azaV, L or V; X23 is azaV, azaI, I or V; X24 is azaK, azaE, azaR, K, E or R; X25 is azaG or G; X26 is azaG, azaR, G or R (SEQ ID NO: 6); wherein at least one of X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, and X26is an aza-amino acid; or a pharmaceutically acceptable salt thereof; (iv) a compound of Formula: X1X2X3GX4X5TSX6VSSX7LEGX8AAX9EX10IAX11X12VX13GX14G, wherein X1is azaH or H; X2is azaA, Aib, or A; X3is azaE or E; X4is T or S; X5is azaF or F; X6is azaD or D; X7 is azaY, K, or Y; X8 is Q or E; X9 is azaK or K; X10 is azaF or F; X11 is azaW, W or K; X12 is L or V; X13 is K, R or E; and X14 is R or G (SEQ ID NO: 7); wherein at least one of X1, X2, X3, X5, X6, X7, X9, X10, and X11is an aza-amino acid; or a pharmaceutically acceptable salt thereof; (v) a compound of Formula: HXEGTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X is Aib (SEQ ID NO: 8); or a pharmaceutically acceptable salt thereof; (vi) a compound of Formula: HX1X2GTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X1is Aib and X2is azaE (SEQ ID NO: 9); or a pharmaceutically acceptable salt thereof; (vii) a compound of Formula: HXEGTFTSDVSSYLEGQAAKEFIAWLVKGRG, wherein X is azaA (SEQ ID NO: 10); or a pharmaceutically acceptable salt thereof; (viii) In an embodiment, the present invention provides a compound of Formula: HXEGTFTSDVSSYLEGQAAKEFIAWLVKGRG, wherein X is azaA (SEQ ID NO: 11); or a pharmaceutically acceptable salt thereof; (ix) a compound of Formula: HAXGTFTSDVSSYLEGQAAKEFIAWLVKGRG,wherein X is azaE (SEQ ID NO: 12); or a pharmaceutically acceptable salt thereof; (x) a compound of Formula: HAXGTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X is azaE (SEQ ID NO: 13); or a pharmaceutically acceptable salt thereof; (xi) a compound of Formula: X1AEGTFTSDVSSYLEGQAAKEFIAWLVKGRG, wherein X1 is azaH (SEQ ID NO: 14); or a pharmaceutically acceptable salt thereof; (xii) a compound of Formula: X1X2X3GTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X1 is azaH; X2 is Aib, and X3 is azaE (SEQ ID NO: 15); or a pharmaceutically acceptable salt thereof; (xiii) a compound of Formula: X1X2EGTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X1 is azaH, and X2 is Aib (SEQ ID NO: 16); or a pharmaceutically acceptable salt thereof; (xiv) a compound of Formula: X1X2EGTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X1 is azaH, and X2 is azaA (SEQ ID NO: 17); or a pharmaceutically acceptable salt thereof; (xv) a compound of Formula: XAEGTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X is azaH (SEQ ID NO: 18); or a pharmaceutically acceptable salt thereof; (xvi) a compound of Formula: X1AX2GTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X1 is azaH, and X2 is AzaE (SEQ ID NO: 19); or a pharmaceutically acceptable salt thereof;(xvii) a compound of Formula: HX1EGTFTSX2VSSX3LEGQAAKEX4IAX5LVKGRG, wherein X1 is AzaA; X2 is AzaD; X3 is azaY; X4 is azaF, and X5 is azaW (SEQ ID NO: 20); or a pharmaceutically acceptable salt thereof; (xviii) a compound of Formula: HX1X2GTFTSDVSSYLEGQAAKEFIAWLVRGRG, wherein X1is Aib; and X2is azaE (SEQ ID NO: 21); or a pharmaceutically acceptable salt thereof; (xix) a compound of Formula: X1X2X3GX4X5TSX6VSSX7LEGX8AAX9EX10IAX11X12VX13GX14,wherein X1is azaH or H; X2is azaA, Aib, or A; X3is azaE or E; X4is T or S; X5is azaF or F; X6is azaD or D; X7 is azaY, K, or Y; X8 is Q or E; X9 is azaK or K; X10 is azaF or F; X11 is azaW, W or K; X12 is L or V; X13 is K, R or E; and X14 is R or G (SEQ ID NO: 22); wherein at least one of X1, X2, X3, X5, X6, X7, X9, X10, and X11, is an aza-amino acid; or a pharmaceutically acceptable salt thereof; (xx) a compound of Formula: HX1EGSX2TSDVSSKLEGEAAX3EX4IAKVVEGG, wherein X1is azaA; X2is azaF; X3is azaK; and X4is azaF (SEQ ID NO: 23); or a pharmaceutically acceptable salt thereof. (xxi) a compound of Formula: X1X2X3GX4X5TSX6VSIX7LDKX8AQX9AX10IEX11X12LX13GX14PSSGAPPPS, wherein X1 is azaH, H, Y, or azaY; X2 is azaA, Aib, or A; X3 is azaE, E, Q, or azaQ; X4 is T or S; X5 is azaF or F; X6 is azaD or D; X7 is azaY, K, L, azaL, azaK, azaA, or Y; X8 is Q, E or K; X9is azaK, K or Aib; X10is azaF or F; X11is azaW, W, Y or K; X12is L or V; X13is K, R or E; and X14is R or G; wherein S at position 39 is optionally amidated as a C-terminal primary amide; ); wherein at least one of X1, X2, X3, X5, X6, X7, X9, X10, and X11, is an aza-amino acid (SEQ ID NO: 24); or a pharmaceutically acceptable salt thereof; (xxii) a compound of Formula: X1X2X3GX4X5TSX6VSIX7LDKX8AQX9AFIEYLLEGFPSSGAPPPS,wherein X1is Y or azaY; X2is Aib; X3is Q or azaQ; X4is T; X5is azaF or F; X6is azaD or D; X7 is L or azaL; X8 is K or azaK; X9 is Aib; and S at position 38 is optionally amidated as a C- terminal primary amide (SEQ ID NO: 25); or a pharmaceutically acceptable salt thereof.

[0139] Non-limiting examples of GLP-1 agonist therapeutics that can be prepared by the inventive process include: azaA8-GLP-1(7-37), azaE9-GLP-1(7-37), [R34, azaA8]-GLP-1(7-37), [R34, Aib8]-GLP-1(7-37), [R34, Aib8, azaH7]-GLP-1(7-37), [R34, Aib8, azaH7]-GLP-1(7-37),[R34, azaE9, azaH7]-GLP-1(7-37).

[0140] Non-limiting examples of bradykinin (RPPGFSPFR) that may be made by the inventive process include RazaP2PGFSPFR, RPPGFSPazaF8R, and RazaP2PGFSPazaF8R.

[0141] Target peptides that may also benefit from having at least one peptide bond replaced by an azapeptide bond also include HMGB1 antagonists, which may be used to treat disorders including, e.g., inflammatory bowel disease and rheumatoid arthritis (see, e.g., US 11,471,507 B2), bradykinin, and RazaP2PGFSPazaF8R, and TFsEws-FL-1.

[0142] Generally, the synthons and processes of the invention allow for the synthesis of azapeptides and aza-peptide conjugates, e.g., in yields of at least about 50% (by weight) (e.g., from about 55% to about 99%, from about 60% to about 95%, or from about 65% to about 95%). Thus, the yield may, e.g., be about 55%, about 60%; about 65%, about 75%, about 80%, about 85%, about 90%, about 95%, about 97%, or about 99%. In certain embodiments, the yield is greater than 85%.

[0143] The compounds of the invention can be used in the form of salts derived from inorganic or organic acids, which include pharmaceutically acceptable salts. For clarity, the term “pharmaceutically acceptable salt[s]” as used herein generally refers to salts prepared from pharmaceutically acceptable acids or bases including inorganic acids and bases and organic acids and bases. Suitable pharmaceutically acceptable base addition salts include, e.g., metallic salts made from aluminum, calcium, lithium, magnesium, potassium, sodium and zinc or organic salts made from lysine, N,N′-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine, ethylenediamine, meglumine (N-methylglucamine) and procaine. Suitable non-toxic acids include inorganic and organic acids such as acetic, alginic, anthranilic, benzenesulfonic, benzoic, camphorsulfonic, citric, ethenesulfonic, formic, fumaric, furoic, galacturonic, gluconic,glucuronic, glutamic, glycolic, hydrobromic-, hydrochloric, isethionic, lactic, maleic, malic, mandelic, methanesulfonic, mucic, nitric, pamoic, pantothenic, phenylacetic, phosphoric, propionic, salicylic, stearic, succinic, sulfanilic, sulfuric, tartaric acid, and p-toluenesulfonic acid. Specific acids include, e.g., hydrochloric, hydrobromic, phosphoric, sulfuric, and methanesulfonic acids. Examples of specific salts include, e.g., hydrochloride and mesylate salts. Others are well-known in the art. See, e.g., Remington's Pharmaceutical Sciences, 18th ed. (Mack Publishing, Easton Pa.: 1990) and Remington: The Science and Practice of Pharmacy, 19th ed. (Mack Publishing, Easton Pa.: 1995). The preparation and use of acid addition salts, carboxylate salts, amino acid addition salts, and zwitterion salts of compounds of the present invention may also be considered pharmaceutically acceptable if they are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response, and the like, are commensurate with a reasonable benefit / risk ratio, and are effective for their intended use. Such salts may also include various solvates and hydrates of the compound of the present invention.

[0144] Certain compounds of the present invention may be isotopically labelled, e.g., with various isotopes of carbon, fluorine, or iodine, as applicable when the compound in question contains at least one such atom. In preferred embodiments, methods of diagnosis of the present invention comprise administration of such an isotopically labelled compound.

[0145] Certain compounds of the present invention may exist as stereoisomers wherein, asymmetric or chiral centers are present. These stereoisomers are “R” or “S” depending on the configuration of substituents around the chiral carbon atom. The terms “R” and “S” used herein are configurations as defined in IUPAC 1974 Recommendations for. Section E, Fundamental Stereochemistry, in Pure Appl. Chem., 1976, 45: 13-30. The invention contemplates various stereoisomers and mixtures thereof and these are specifically included within the scope of this invention. Stereoisomers include enantiomers and diastereomers, and mixtures of enantiomers or diastereomers. Individual stereoisomers of compounds of the invention may be prepared synthetically from commercially available starting materials which contain asymmetric or chiral centers or by preparation of racemic mixtures followed by resolution well known to those of ordinary skill in the art. These methods of resolution are exemplified by (1) attachment of a mixture of enantiomers to a chiral auxiliary, separation of the resulting mixture of diastereomersby recrystallization or chromatography and optional liberation of the optically pure product from the auxiliary as described in Furniss, Hannaford, Smith, and Tatchell, “Vogel's Textbook of Practical Organic Chemistry”, 5th edition (1989), Longman Scientific & Technical, Essex CM20 2JE, England, or (2) direct separation of the mixture of optical enantiomers on chiral chromatographic columns or (3) fractional recrystallization methods.

[0146] Certain compounds of the present invention may exist as cis or trans isomers, wherein substituents on a ring may attach in such a manner that they are on the same side of the ring (cis) relative to each other, or on opposite sides of the ring relative to each other (trans). Such methods are well known to those of ordinary skill in the art and may include separation of isomers by recrystallization or chromatography. It should be understood that the compounds of the invention may possess tautomeric forms, as well as geometric isomers, and that these also constitute an aspect of the invention.

[0147] Certain embodiments of the present invention will now be illustrated by the following Examples, which are given for illustration purposes only and are not intended to limit the invention in any way. Example 1 Preparation of Sulfoxide and Sulfone Thiocarbazate Synthons

[0148] The thiocarbazate starting materials for the preparation of sulfoxide and sulfone thiocarbazate synthons are known and are described, for example, in US 11,440,881 B2, US 2022 / 0306577 A1, and A. Altiti, et al., “Thiocarbazate Building Blocks Enable the Construction of Azapeptides for Rapid Development of Therapeutic Candidates”, Nature Communications 13:7127 (2022).

[0149] The sulfoxide and sulfone thiocarbazate synthons were made by oxidizing the corresponding thiocarbazate starting materials as described in detail below. A. General Synthesis of Fmoc-azaAa-SOEt (ethyl sulfoxide)HO1eq mCPBA, DCM HON 1. 0oC to 25oC N N To aadded m- CPBA (0.1mmol) solution in DCM (0.4mL) dropwise. The mixture was stirred at 0°C for 15 min then room temperature for 1 to 2 hours until completely conversion of the starting material by TLC analysis. Then, the reaction mixture was mixed with DCM (5mL) and washed with saturated NaHCO3 (2x3mL) and brine (3mL). Dried over Na2SO4, filtered, and evaporated under vacuum. The crude material was precipitated with EtOAc / Hex and isolated as the white precipitate (“ppt”).

[0150] Table 1 describes the synthesis of sulfoxides that were prepared by the above method:Fmoc-azaHis(Trt)-(SOEt)N Trt1.5h 72% >90% N H Fmoc-azaArg(bis-Boc)-(SOEt)N NHBoc2h 58% >92.4% BocNBoc Fmoc-azaArg(tri-Boc)-(SOEt)N NHBoc2h 65% 90% BocNTable 1 B. General Synthesis and isolation of Fmoc-azaAa-SO2Et (ethyl sulfone)

[0151] To a solution of ethyl thiocarbazate (0.1mmol) in DCM (0.6mL) at room temperature was added mCPBA (0.3mmol) solution in DCM (0.4mL) dropwise. The mixture was stirred at room temperature for 2 hours. Then, the reaction mixture was mixed with DCM (5mL) and washed with saturated NaHCO3(2x3mL) and brine (3mL). Dried over Na2SO4, filtered, and evaporated under vacuum. The crude material was purified on silica gel using gradient of Hexanes / EtOAc and isolated as the white precipitate. Example 2 Comparison of azaF28GLP-1 (28-36) using Fmoc-azaF28-SOEt as described in Scheme 1 with Fmoc-azaF28-SEt using the prior known activation process

[0152] The following scheme illustrates the fully automated solid phase protein synthesis of azapeptides (“Mix & Go”) using an Pg-azaAA-SOEt according to the present invention:R, R’: H, amino acid side chain residue; Xaa, Yaa amino acids; Z: O (Wang resin), NH (Rink amide resin).

[0153] GLP-1 (29-36) was prepared using the Fmoc-azaF28-SOEt in the process described in Scheme 1 using Fmoc-azaF28-SEt and the corresponding thioester synthon in the activation process described in US 11,440,881 B2 and US 2022 / 0306577 A1.

[0154] The results are described in Table 2 below: Table 2 Incorporation of azaPhe to resin bound GLP-1 fragment via thiocarbazate building blocks in solid phaseH H N 36 NH2N 36 Fmo GG E V V K A IFmoc-azaPheBuildingBlocks G G E V V K A IaF28 GLP-1 (29-36) DMF, 25oC azaF28 GLP-1 (28-36) Fmoc-aza building blocks O O FmocHN FmocHN N SEt N SOEt Ph PhActivated by TCCA Mix & go Incorporation of aza-amino Rxn time 1 h 18 h 1 h 18 h acid Crude purity 69% 69% 83% 98%

[0155] As can be seen the solid phase protein synthesis using Fmoc-azaF28-SOEt provided a superior result over the prior activation process that uses Fmoc-azaF28-SOEt. Example 3 Mono- and di-oxidized Thiocarbazate Coupling Activity with Asparagine

[0156] FmocAzaPhe sulfoxide and FmocazaPhe sulfone were prepared from azaPheSEt using the reaction depicted in Scheme 2. O O O OScheme 2: Preparation of AzaPhe sulfoxide and azaPhe sulfone

[0157] FmocAzaPhe sulfoxide, FmocAzaPhe sulfone and FmocAzaPheHOBt were then coupled to asparagine using the reaction depicted in Scheme 3: O FmocHN NSNH2with asparagine

[0158] While illustrative embodiments of the disclosure have been described and illustrated above, it should be understood that these are exemplary of the disclosure and are not intended to be limiting. Additions, deletions, substitutions, and other modifications can be made without departing from the spirit or scope of the disclosure. Accordingly, the disclosure is not to be considered as limited by the foregoing description.

Claims

What is claimed is:

1. A compound of the formula whereinA is an amine protecting group; R1is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; or A and R1together form phthaloyl group: ; 2R is H, a substituted or or unsubstituted alkoxy, a substituted or unsubstituted alkoxyalkylene, an optionally protected alkyl amine, or a side chain radical of an amino acid, which is substituted or unsubstituted, or R1 and R2 together joined by –(CH2)-(CH2)-(CH2)– ; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; andn is 1 or 2.

2. The compound of claim 1, wherein A is selected from the group consisting of tert- butoxycarbonyl, 9-fluorenylmethoxycarbonyl, carboxybenzyl, 2-(3,5-dimethoxyphenyl)propan- 2-yloxycarbonyl, 2,2,4,6,7,-pendamethyl-dihydrobenzofuran-5-sulfonyl, triphenylmethyl, tert- butylcarbonyl, t-butoxy, allyloxycarbonyl, methoxytrimethylbenzene sulfonyl, 4,4-dimethoxy benzhydryl, 2,2,5,7,8-pentamethylchroman-6-sulfonyl, 2,4,6-trimethoxybenzyl, allylcarbonyl, acetamidomethyl, and phthalimidyl.

3. The compound of claim 1, wherein A is selected from the group consisting of tert- butoxycarbonyl, 9-fluorenylmethoxycarbonyl, and carboxybenzyl.

4. The compound of claim 1, wherein R is an optionally substituted C1-C10alkyl, wherein the optional substituents are selected from the group consisting of halo, –ORa, –S(O)nRa, – NRaRb, –C(O)Rc, –C(O)ORa, and C1-C6 haloalkyl, wherein Ra is H, C1-C6 alkyl, or C1-C6 haloalkyl, Rb is H, C1-C6 alkyl, or C1-C6 haloalkyl, Rc is C1-C6 alkyl, or C1-C6 haloalkyl, and n is 0, 1, or 2.

5. The compound of claim 1, wherein R2is a side chain radical of a natural amino acid, which is substituted or unsubstituted.

6. The compound of claim 4, wherein the amino acid is selected from the group consisting of aspartic acid, phenylalanine, alanine, histidine, glutamic acid, tryptophan, valine, leucine, lysine, methionine, tyrosine, isoleucine, arginine, glycine, asparagine, serine, and glutamine, which are unsubstituted or substituted by one or more substituents selected from the group consisting of halo, –ORa, –S(O)nRa, –NRaRb, –C(O)Rc, –C(O)ORa, C1-C6haloalkyl, and a protecting group, wherein Ra is H, C1-C6 alkyl, or C1-C6 haloalkyl, Rb is H, C1-C6 alkyl, or C1-C6 haloalkyl, Rc is C1-C6 alkyl, or C1-C6 haloalkyl, n is 0, 1, or 2, and p is 0 or 1.

7. The compound of claim 1, wherein R2is a side chain radical of an unnatural amino acid, which is substituted or unsubstituted.

8. The compound of claim 1, wherein the compound has the formula9. The compound of claim 1, wherein the compound has the formula:

10. The compound of claim 1,11. The compound of any one of claims 1 to 4 or 6 to 10, wherein R2is the side chain of an amino acid.

12. The compound of claim 11, wherein the amino acid is a natural amino acid.

13. A process for preparing an aza-peptide which comprises coupling N-terminal end of a peptide with a compound of the formula: whereinA is an amine protecting group; R1is H, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; or A and R1together form phthaloyl group: 2R is H, substituted or unsubstituted alkoxy, substituted or unsubstituted alkoxyalkylene, optionally protected alkyl amine, and a side chain radical of an amino acid, which is substituted or unsubstituted, or R1 and R2 together joined by –(CH2)-(CH2)-(CH2)– ; R is H, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and n is 1 or 2;wherein the coupling is without first activating the compound of Formula I with a halogenating agent.

14. The process of claim 13, wherein the aza-peptide is azaF28GLP-1 (28-36) or a salt thereof.

15. The process of claim 13, wherein the aza-peptide is AzaAla8GLP-1(7-37).

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