WO2021113922A1 - Improved method for preparing n-(benzenesulfonyl)-l-prolyl- l-o-(1-pyrrolidinylcarbonyl)tyrosine - Google Patents

Abstract

The present invention relates to an improved synthetic process for preparing N-(benzenesulfonyl)-L-prolyl-L-O-(1-pyrrolidinylcarbonyl)tyrosine. The present invention is also directed to individual steps in this process and individual intermediates used in this process.

Description

Improved method for preparingN-(benzenesulfonyl)-L-prolyl- L-O-(1-pyrrolidinylcarbonyl)tyrosine

Technical Field

The present invention generally relates to an improved synthetic process for preparing N- (benzenesulfonyl)-L-prolyl-L-O-(1-pyrrolidinylcarbonyl)tyrosine. The present invention is also directed to individual steps of this process and individual intermediates used in this process.

Background N-(Benzenesulfonyl)-L-prolyl-L-O-(1-pyrrolidinylcarbonyl)tyrosine (BOP; Compound 1) is a potent inhibitor of the α₄β₁ and α₉β₁ integrins which are expressed by hematopoietic stem cells (HSC) and play a role in retaining HSC in the bone marrow (R. B. Pepinksy, et al., Biochem. 2002, 41, 7125; L. L. Chang, et. al., Bioorg. Med. Chem. Lett. 2002, 12, 159; WO 2016/090434).

The transplantation of mobilized peripheral blood (PB) haematopoietic stem cells (HSC) into patients undergoing treatment for blood diseases has essentially replaced traditional bone marrow (BM) transplants. Some clinical practices for HSC mobilization are achieved with an extended course of recombinant granulocyte-colony stimulating factor (G-CSF), which is believed to stimulate the production of proteases that cleave CXCR4/SDF-1 interactions. However, G-CSF is ineffective in a large cohort of patients and is associated with several side effects such as bone pain, spleen enlargement and on rare occasions, splenic rupture, myocardial infarction and cerebral ischemia.

These inherent disadvantages of G-CSF have driven efforts to identify alternate mobilization strategies based on small molecules. As an example, the FDA-approved CXCR4 antagonist AMD3100 (Plerixafor; Mozobil™) has been shown to rapidly mobilize HSC with limited toxicity issues. Nevertheless, clinical mobilization with AMDS 100 is only effective in combination with G-CSF and the search for rapid, selective and G-CSF independent mobilization regimens remains a topic of clinical interest. Although clinically G-CSF is the most extensively used mobilization agent, its drawbacks further include potentially toxic side effects, a relatively long course of treatment (5-7 days of consecutive injections), and variable responsiveness of patients.

It has been shown that targeting α9β1/α4β1 integrins with a single dose of BOP rapidly mobilizes long-term multi-lineage reconstituting HSC (B Cao, et al. Nature Communications, 2016, 7, 11007). Synergistic engraftment augmentation is observed when BOP is co-administered with AMD3100. Impressively, HSC in equal volumes of peripheral blood (PB) mobilized with this combination effectively out-competes PB mobilized with G-CSF. The enhanced mobilization observed using BOP and AMD3100 is recapitulated in a humanized NODSCIDIL2Rγ^-/- model, demonstrated by a significant increase in PB CD34⁺ cells. As such, BOP has potential application in the mobilisation for autologous stem cell transplants in patients where G-CSF cannot be safely used (e.g., sickle cell disease), mobilisation of stem cells for allogeneic transplantation, and chemosensitisation of drug resistant minimal residual disease in blood cancers including acute lymphoblastic leukaemia (ALL), acute myeloid leukaemia (AML), multiple myeloma (MM) and lymphoma.

The known synthetic route for producing BOP comprises 6 linear steps starting with the preparation of a custom made and protected diamino building block. Synthesis includes 5 chromatographic purification steps and the late stage use of a palladium, leading to potential concerns around metal product contamination. Accordingly, there is a need for an improved synthetic process that is amenable to commercial scale up.

Summary

The present invention is directed to a novel synthetic process for preparing N- (benzenesulfonyl)-L-prolyl-L-O-(1-pyrrolidinylcarbonyl)tyrosine (BOP; Compound 1) using the synthetic steps described herein.

N-(Benzenesulfonyl)-L-prolyl-L-O-(1-pyrrolidinylcarbonyl)tyrosine (BOP; Compound 1)

The present invention is also directed to individual steps of this process and particular intermediates used in this process.

In one aspect, the present invention is directed to a process for preparing a compound of formula (I):

or a salt thereof, comprising coupling a compound of formula (v):

or a salt thereof, with a compound of formula (vi):

or a salt thereof, to provide a compound of formula (vii):

or a salt thereof, and converting the compound of formula (vii) to a compound of formula (I) or a salt thereof; wherein R¹ is a protecting group. In another aspect, the present invention provides a process for preparing a compound of formula (v):

or a salt thereof, with a compound of formula (iv):

or a salt thereof; wherein R¹ is a protecting group; and R² is selected from OH, Cl or F.

In a further aspect, the present invention is directed to a process for preparing a compound of formula (vii):

or a salt thereof, comprising coupling a compound of formula (v):

or a salt thereof; wherein R¹ is a protecting group.

In yet another aspect, the present invention provides a process for preparing a compound of formula (I):

or a salt thereof, comprising coupling a compound of formula (iii):

or a salt thereof, with a compound of formula (iv):

or a salt thereof, to provide a compound of formula (v):

or a salt thereof, coupling the compound of formula (v) with a compound of formula (vi):

or a salt thereof, to provide a compound of formula (vii):

or a salt thereof, and converting the compound of formula (vii) to a compound of formula

(I); wherein R¹ is a protecting group; and R² is selected from OH, Cl or F.

The present invention also provides a compound of formula (II):

or a salt thereof, wherein

R¹ is a protecting group; and

R³ is selected from H and a protecting group. These and other aspects of the present invention will become more apparent to the skilled addressee upon reading the following detailed description in connection with the accompanying examples and claims.

Detailed Description The previously reported synthesis of N-(Benzenesulfonyl)-L-prolyl-L-O(1- pyrrolidinylcarbonyl)tyrosine (BOP; Compound 1) was achieved via a linear process as illustrated in Scheme 1 below, starting from custom made and protected dipeptide building block a. As it is not economically viable to source this material commercially on a large scale, it was prepared via a peptide coupling of the commercially available starting materials. This added an additional step to the process comprising 6 linear steps and 5 purifications. Protected proline and tyrosine building blocks are coupled to give a, which is then deprotected in the presence of TFA to give free phenol b. Phenol b is coupled with pyrolidinecarbonyl chloride to give c, which is deprotected in the presence of hydrogen to give free amine d. Coupling with benzenesulfonyl chloride followed by cleavage of the methyl ester liberates BOP.

In total, the process involves 6 linear steps, 5 chromatographic purifications and the late stage use of palladium leading to potential concerns around metal product contamination. This process also used a number of inefficient protecting groups which necessitated additional steps for their removal. Further, the use of pyrollidine carbonyl chloride was not suitable for scale-up as this material is unstable, prohibitively expensive and hard to source on anything other than a very small scale. As it stands, this process is not suitable for the production of even relatively low amounts of material (grams).

Scheme 1. Known synthesis of BOP

For the purposes of large scale synthesis a more convergent approach with an alternative protecting group strategy was devised. This new four step sequential process (Scheme 2) displays much higher atom efficiency by removing two of the bulky protecting groups (and the need for their removal) from the previous synthetic approach. Additionally, there is no requirement for chromatographic purification throughout the synthesis compared to 5 chromatography steps in the previous route. Furthermore, no heavy metals are used in the synthesis.

The overall weight yield of the new process is 200% (i.e. 1kg of starting material will deliver 2kg of final product), compared to 58% for the previously reported synthesis (1kg starting material = 580g final product). Synthesis also provides the target compound in high purity (98% HPLC purity).

Scheme 2. Improved synthesis of BOP

The process of general Scheme 2 comprises the following steps: reacting the compound of formula (ii) with benzenesulfonyl chloride under conditions suitable to yield the compound of formula (iii); coupling the compound of formula (iii) with the compound of formula (iv) under conditions suitable to yield the compound of formula (v); coupling the compound of formula (v) with the compound of formula (vi) under conditions suitable to yield a compound of formula (vii); and converting the compound of formula (vii) to a compound of formula (I).

In general Scheme 2:

R¹ is a protecting group; and R² is selected from OH, Cl or F.

In this specification a number of terms are used which are well known to a skilled addressee. Nevertheless for the purposes of clarity a number of terms will be defined. The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

As used herein, the singular forms “a,” “an,” and “the” designate both the singular and the plural, unless expressly stated to designate the singular only.

The term “about” and the use of ranges in general, whether or not qualified by the term about, means that the number comprehended is not limited to the exact number set forth herein, and is intended to refer to ranges substantially within the quoted range while not departing from the scope of the invention. As used herein, “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art given the context in which it is used, "about" will mean up to plus or minus 10% of the particular term.

The term “at least about” as used herein, for example, the expression “at least about 8 hours” in relation to a reaction time, will be understood by the skilled addressee to mean the reaction is allowed to continue for a period of time that is not limited to 8 hours but is in the range of 8 hours, for example, 8 hours ± 20%, ± 15%, ± 10%, ± 5% or ± 2%.

All percentages (%) referred to herein are percentages by weight (w/w or w/v), unless otherwise indicated.

As used herein the term “allowed to” in the context of reaction steps, for example, “allowed to stir overnight”, “allowed to cool”, “allowed to warm”, etc. will be understood to mean that the reaction is located in a suitable and safe environment to achieve to desired result with periodic monitoring as required. As an example, if a reaction is “allowed to cool”, any heat source will be removed from the reaction vessel and the reaction temperature will be monitored until it reaches the desired temperature. If a reaction is allowed to stir overnight the reaction will be located in a safe and secure environment such as in a fume hood and may be monitored periodically for completeness of the reaction.

As used herein the term “overnight” will be understood to mean a period of time of at least about 8 hours, for example, about 8 hours to about 24 hours, about 8 hours to about 20 hours, about 8 hours to about 18 hours, about 8 hours to about 16 hours, about 8 hours to about 14 hours, about 8 hours to about 12 hours, about 8 hours to about 10 hours.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The term “protecting group,” as used herein, refers to a labile chemical moiety which is known in the art to protect reactive groups including hydroxyl and amino groups, against undesired reactions during synthetic procedures. Protecting groups are typically used selectively and/or orthogonally to protect sites during reactions at other reactive sites and can then be removed to leave the unprotected group as is or available for further reactions. Protecting groups as known in the art are described generally in Greene and Wuts, Protective Groups in Organic Synthesis, 3rd edition, John Wiley & Sons, New York (1999). Generally, groups are protected or present as a precursor that will be inert to reactions that modify other areas of the parent molecule for conversion into their final groups at an appropriate time. Further representative protecting or precursor groups are discussed in Agrawal, et al., Protocols for Oligonucleotide Conjugates, Eds, Humana Press; New Jersey, 1994; Vol. 26 pp. 1-72. For the synthesis defined herein, protecting groups are hydroxyl protecting groups. In certain embodiments, the hydroxyl protecting group is selected from C₁-C₆alkyl, C₁-C₆alkenyl, phenyl, benzyl, silyl and oxazoline protecting groups. In some embodiments the C₁-C₆alkyl is selected from, but not limited to, methyl, ethyl, propyl, butyl, t-butyl, pentyl and hexyl.

Examples of suitable protecting groups include, but are not limited to, t-butyl, t- butoxymethyl, methoxymethyl, tetrahydropyranyl, 1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 2-trimethylsilylethyl, p-chlorophenyl, 2,4-dinitrophenyl, benzyl, 2,6-dichlorobenzyl, diphenyl-methyl, p-nitrobenzyl, triphenylmethyl, trimethylsilyl, triethylsilyl, t- butyldimethylsilyl, t-butyldiphenylsilyl (TBDPS), triphenylsilyl, benzoylformate, acetate, chloroacetate, trichloroacetate, trifluoroacetate, pivaloate, benzoate, p-phenylbenzoate, 9- fluorenylmethyl carbonate, mesylate and tosylate.

The term “couple” or “coupled” as used herein denotes a chemical reaction in which two moieties such as intermediate compounds or compound fragments are joined together. Examples of coupling reaction include, but are not limited to, amide coupling between a carboxylic acid and a base, Suzuki coupling between organoboronic acid and halides, Stille coupling between stannanes and halides or pseudohalides, Heck coupling between aryl halides or vinyl halides and activated alkenes, Hiyama coupling between aryl, alkenyl, or alkyl halides or pseudohalides and organosilanes, Negishi coupling between an organic halide or triflate and an organozinc compound, or coupling via a Grignard reaction between an organomagnesium halide Grignard reagent and a ketone or aldehyde to form a tertiary or secondary alcohol.

Coupling reactions are often aided by the use of a catalyst or, in the case of amide coupling, a coupling reagent. The term “coupling reagent” as used herein will be understood by the skilled addressee to denote a reagent that activates a carboxyl moiety by formation of a highly electrophilic intermediate, for example, a halide, azide or an anhydride, which is then attacked by the nucleophilic a-amino group to form an amide bond. A number of coupling reagents are known in the art, including, but are not limited to, isobutyl chloroformate, BOP, PyBOP, AOP, PyAOP, HBTU, TBTU, HATU, HCTU, HOBt, HO At, DCC, EDC1, 1-t-butyl-3-ethylcarbodiimide, N,N'-di-tert-butylcarbodiimide, DIC, 1-[3-(Dimethylamino)propyl]-3-ethylcarbodiimide methiodide, 1,3-di-p- tolylcarbodiimide, BOP-C1, TFFH, Brop, PyBrop, EEDQ, IIDQ, CIP, DPPA, COMU, PyOxim, T3P, CDI and combinations thereof. In a particular embodiment, the coupling reagent is isobutylchloroformate.

As used herein, the term "alkyl", used either alone or in compound words, denotes straight chain or branched alkyl. Prefixes such as "C₂-C₁₀" are used to denote the number of carbon atoms within the alkyl group (from 2 to 10 in this case). Examples of straight chain and branched alkyl include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-pentyl, hexyl, heptyl, 5-methylheptyl, 5-methylhexyl, octyl, nonyl, decyl, undecyl, dodecyl and docosyl (C₂₂).

As used herein, the term "alkenyl", used either alone or in compound words, denotes straight chain or branched hydrocarbon residues containing at least one carbon to carbon double bond including ethylenically mono-, di- or polyunsaturated alkyl groups as previously defined. Prefixes such as "C₂-C₁₀" are used to denote the number of carbon atoms within the alkenyl group (from 2 to 10 in this case). Examples of alkenyl include vinyl, allyl, 1-methylvinyl, butenyl, iso-butenyl, 3-methyl-2-butenyl, 1-pentenyl, 1- hexenyl, 3-hexenyl, 1-heptenyl, 3-heptenyl, 1-octenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl, 1- decenyl, 3-decenyl, 1,3-butadienyl, 1,4-pentadienyl, 1,3-hexadienyl, 1,4-hexadienyl and 5- docosenyl (C₂₂).

It will be understood that the compounds of the invention may exist in a plurality of equivalent tautomeric forms and all such tautomeric forms are considered within the scope of the invention. For the sake of clarity, the compounds have been depicted as single tautomers.

The structures of some of the compounds of the invention may include asymmetric carbon atoms. It is to be understood accordingly that the isomers arising from such asymmetry (e.g., all enantiomers, stereoisomers, rotamers, tautomers, diastereomers, or racemates) are included within the scope of this invention. The present invention includes within its scope all of these stereoisomeric forms either isolated (in, for example, enantiomeric isolation), or in combination (including racemic mixtures and diastereomic mixtures).

The compounds of the invention may be in crystalline form or as solvates (e.g. hydrates), and it is intended that both forms are within the scope of the present invention. The term "solvate" is a complex of variable stoichiometry formed by a solute (in this invention, a compound of the invention) and a solvent. Such solvents should preferably not interfere with the biological activity of the solute. Solvents may be, by way of example, water, acetone, ethanol or acetic acid. Methods of solvation are generally known within the art.

Where a compound or intermediate comprises one or more functional groups that may be protonated or deprotonated (for example at physiological pH) the compound may be prepared and/or isolated as a salt. It will be appreciated that the compound may be zwitterionic at a given pH. The salt may be a pharmaceutically acceptable salt of a given compound, wherein the salt is suitable for administration as a pharmaceutical. Such salts may be formed, for example, by the reaction of an acid or a base with an amine or a carboxylic acid group respectively.

Acid addition salts may be prepared from inorganic and organic acids. Examples of inorganic acids include hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like. Examples of organic acids include acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, malic acid, malonic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid and the like.

Base addition salts may be prepared from inorganic and organic bases. Corresponding counter ions derived from inorganic bases include metal salts. Organic bases include primary, secondary and tertiary amines, substituted amines including naturally-occurring substituted amines, and cyclic amines, including isopropylamine, trimethyl amine, diethylamine, triethylamine, tripropylamine, ethanolamine, 2-dimethylaminoethanol, tromethamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, ethylenediamine, glucosamine, N-alkylglucamines, theobromine, purines, piperazine, piperidine, and N-ethylpiperidine.

Metal salts refer to salts wherein the cation is a metal, such as those formed when an acidic proton present in a compound is replaced by either a metal ion, e.g., an alkali metal ion, an alkaline earth ion, or an aluminium ion; or a metal ion coordinates with an organic base such as diethanolamine, triethanolamine, N-methylglucamine and the like.

The metal can be an alkali metal, alkaline earth metal, transition metal, or main group metal. Non-limiting examples of suitable metals include lithium, sodium, potassium, cesium, cerium, magnesium, manganese, iron, calcium, strontium, cobalt, titanium, aluminum, copper, cadmium and zinc.

Non-limiting examples of suitable metal salts include a lithium salt, a sodium salt, a potassium salt, a cesium salt, a cerium salt, a magnesium salt, a manganese salt, an iron salt, a calcium salt, a strontium salt, a cobalt salt, a titanium salt, an aluminum salt, a copper salt, a cadmium salt, and a zinc salt.

“Pharmaceutically acceptable salt” refers to a salt of a compound that is pharmaceutically acceptable and that possesses (or can be converted to a form that possesses) the desired pharmacological activity of the parent compound. Examples of “pharmaceutically acceptable salts” of the compounds disclosed herein include salts derived from an appropriate base, such as an alkali metal (for example, sodium), an alkaline earth metal (for example, magnesium), ammonium and NX4⁺ (wherein X is C₁-C₄ alkyl). Pharmaceutically acceptable salts of a nitrogen atom or an amino group include for example salts of organic carboxylic acids such as acetic, benzoic, camphorsulfonic, citric, glucohep tonic, gluconic, lactic, fumaric, tartaric, maleic, malonic, malic, mandelic, isethionic, lactobionic, succinic, 2-napththalenesulfonic, oleic, palmitic, propionic, stearic, and trimethylacetic acids; organic sulfonic acids, such as methanesulfonic, ethanesulfonic, benzenesulfonic and p-toluenesulfonic acids; and inorganic acids, such as hydrochloric, hydrobromic, sulfuric, nitric, phosphoric and sulfamic acids. Pharmaceutically acceptable salts of a compound of a hydroxy group include the anion of said compound in combination with a suitable cation such as Na⁺ and NX4⁺ (wherein X is independently selected from H or a C₁-C₄ alkyl group). Pharmaceutically acceptable salts also include salts formed when an acidic proton present in the parent compound is replaced by either a metal ion, e.g., an alkali metal ion, an alkaline earth ion, or an aluminum ion; or coordinates with an organic base such as diethanolamine, triethanolamine, N- methylglucamine and the like. Also included in this definition are ammonium and substituted or quatemized ammonium salts. Representative non-limiting lists of pharmaceutically acceptable salts can be found in S.M. Berge et al., J. Pharma Sci., 66(1), 1-19 (1977), and Remington: The Science and Practice of Pharmacy, R. Hendrickson, ed.,

21st edition, Lippincott, Williams & Wilkins, Philadelphia, PA, (2005), at p. 732, Table 38-5, both of which are hereby incorporated by reference herein.

In one embodiment, the invention provides a compound of formula (II):

or a salt thereof, wherein

R¹ is a protecting group as defined herein; and

R³ is selected from H and a protecting group. The compound of formula (II) is a valuable intermediate in the improved process disclosed herein.

Embodiments of the invention are directed to the general schemes described below. Scheme 3

In one embodiment, the present invention provides the multistep synthetic process described below in Scheme 3.

Scheme 3. Synthesis of BOP

The process illustrated in Scheme 3 comprises the following steps: coupling a compound of formula (v), or a salt thereof, with a compound of formula (vi), or a salt thereof, under conditions suitable to yield a compound of formula (vii); and converting the compound of formula (vii) to a compound of formula (I).

In General Scheme 3: R¹ is a protecting group.

In one embodiment, the compound of formula (v), or salt thereof, is coupled with a compound of formula (vi), or a salt thereof, in the presence of a base. In some embodiments, the base is selected from an organic amine base or an inorganic base. Exemplary organic amine bases and inorganic bases include, but not limited to, ethylamine, diethylamine, triethylamine, diisopropylamine, morpholine, 4- methylmorpholine, N-ethylmorpholine, piperidine, N-methylpiperidine, N-methyl pyrrolidine, ammonium, ammonium carbonate, ammonium hydroxide, barium carbonate, calcium carbonate, calcium hydroxide, cesium carbonate, cesium hydroxide, lithium amide, lithium carbonate, lithium hydroxide, magnesium carbonate, magnesium hydroxide, potassium carbonate, potassium hydroxide, and combinations thereof.

In one embodiment, the compound of formula (v), or salt thereof, is coupled with a compound of formula (vi), or a salt thereof, in a polar aprotic solvent. Suitable polar aprotic solvents include, but not limited to, dichloromethane, dichloroethane, chloroform, N-methylpyrrolidone, tetrahydrofuran, 2-methyltetrahydrofuran, ethyl acetate, dimethylformamide, acetonitrile, acetone, dimethyl sulfoxide, propylene carbonate, dimethyl acetamide and combinations thereof.

In certain embodiments, the compound of formula (vii) is converted to the compound of formula (I) in the presence of a metal salt selected from a hydroxide, sulphate, carbonate, sulphide, phosphate, borate, silicate or trimethylsilanolate. In some embodiments the metal is selected from sodium, potassium, lithium, ammonium, calcium and magnesium.

In some embodiments, the compound of formula (vii) is converted to the compound of formula (I) by ester hydrolysis of the compound of formula (vii).

In one embodiment, the compound of formula (I) is Compound 1:

Scheme 4 Certain embodiments are directed to the synthetic process described below in Scheme 4.

Scheme 4. Synthesis of a compound of formula (v)

The process of general Scheme 4 comprises coupling a compound of formula (iii), or a salt thereof, with a compound of formula (iv), or a salt thereof, under conditions suitable to yield a compound of formula (v).

In Scheme 4:

R¹ is a protecting group; and R² is selected from OH, Cl or F.

In certain embodiments the compound of formula (iii), or salt thereof, is coupled with a compound of formula (iv), or a salt thereof, in the presence of a coupling reagent. Suitable coupling reagents include, but are not limited to, isobutyl chloroformate, BOP, PyBOP, AOP, PyAOP, HBTU, TBTU, HATU, HCTU, HOBt, HOAt, DCC, EDC1, 1-t-butyl-3- ethylcarbodiimide, N,N'-di-tert-butylcarbodiimide, DIC, 1-[3-(Dimethylamino)propyl]-3- ethylcarbodiimide methiodide, 1,3-di-p-tolylcarbodiimide, BOP-C1, TFFH, Brop, PyBrop, EEDQ, IIDQ, CIP, DPPA, COMU, PyOxim, T3P, CDI and combinations thereof. In a particular embodiment, the coupling reagent is isobutylchloroformate.

In some embodiments, the compound of formula (iii), or salt thereof, is coupled with a compound of formula (iv), or a salt thereof, in the presence of a coupling reagent and a base. In some embodiments the base is selected from, but not limited to, ethylamine, diethylamine, triethylamine, diisopropylamine, morpholine, 4-methylmorpholine, N- ethylmorpholine, piperidine, N-methylpiperidine, N-methyl pyrrolidine, ammonium, ammonium carbonate, ammonium hydroxide, barium carbonate, calcium carbonate, calcium hydroxide, cesium carbonate, cesium hydroxide, lithium amide, lithium carbonate, lithium hydroxide, magnesium carbonate, magnesium hydroxide, potassium carbonate, potassium hydroxide and combinations thereof.

In some embodiments, the base is selected from N-methylmorpholine, morpholine, N- ethylmorpholine, piperidine, N-methylpiperidine, N-methyl pyrrolidine and combinations thereof. In a particular embodiment, the base is N-methylmorpholine.

In a further embodiment, the compound of formula (iii), or salt thereof, is coupled with a compound of formula (iv), or a salt thereof, in a polar aprotic solvent.

In some embodiments, the polar aprotic solvent is selected from, but not limited to, dichloromethane, dichloroethane, chloroform, N-methylpyrrolidone, tetrahydrofuran, 2- methyltetrahydrofuran, ethyl acetate, dimethylformamide, acetonitrile, acetone, dimethyl sulfoxide, propylene carbonate, dimethyl acetamide and combinations thereof. In one embodiment, the polar aprotic solvent is dichloromethane.

Scheme 5

Certain embodiments are directed to the synthetic process described below in Scheme 5.

Scheme 5. Synthesis of a compound of formula (vii) The process of general Scheme 5 comprises coupling a compound of formula (v), or a salt thereof, with a compound of formula (vi), or a salt thereof, under conditions suitable to yield a compound of formula (vii). In General Scheme 5:

R¹ is a protecting group.

Suitable conditions are as explained above for Scheme 3. Scheme 6

Certain embodiments are directed to the multistep synthetic process described below in Scheme 6.

Scheme 6. Synthesis of a compound of formula (v)

The process of general Scheme 6 comprises the following steps: reacting the compound of formula (ii) with benzenesulfonyl chloride under conditions suitable to yield the compound of formula (iii); and coupling a compound of formula (iii), or a salt thereof, with a compound of formula (iv), or a salt thereof, under conditions suitable to yield a compound of formula (v).

In General Scheme 6:

R¹ is a protecting group; and R² is selected from OH, Cl or F.

In certain embodiments R² is selected from OH, Cl or F. In a particular embodiment R² is

OH.

General Schemes - individual steps

Additional embodiments of the invention are directed to the individual steps of the general synthetic methods described above, namely Schemes 2 to 6. These individual steps and intermediates of the present invention are described in detail below. All substituent groups in the steps described below are as defined above.

A. Preparation of a compound of formula (iii)

Scheme 7. Preparation of a compound of formula (iii)

In one embodiment, about 1 equivalent of benzenesulfonyl chloride is reacted with L- proline that is dissolved in a solvent with a suitable base. The reaction occurs at about 15 °C to about 60 °C and is allowed to continue until sufficiently complete. The reaction mixture is then washed and acidified by the addition of a suitable acid. Once the pH is confirmed, the compound is extracted into an organic solvent, washed, filtered and evaporated to dryness to give the compound of formula (iii).

In certain embodiments, the suitable base is an amine base, an aromatic base, inorganic carbonate, a metal hydride, an alkoxide, or mixtures thereof. Exemplary amine bases include, but are not limited to, triethylamine, N,N-diisopropylethylamine, quinuclidine, 1,4-diazabicyclo[2.2.2]octane, 1,8-diazabicyclo[5.4.0]undec-7-ene, tripropylamine, and tributylamine. Exemplary aromatic amine bases include, but are not limited to, pyridine. Exemplary inorganic carbonates include, but are not limited to, lithium carbonate, sodium carbonate, potassium carbonate, or cesium carbonate. Exemplary metal hydrides, include, but are not limited to, sodium hydride or potassium hydride. Exemplary alkoxides include, but are not limited to, sodium methoxide, sodium tert-butoxide or lithium tert-butoxide. In still further embodiments, the base is a mixture comprising at least one of the preceding bases, for example, in certain embodiments the base is a mixture of up to three, or up to two, amine bases. In certain embodiments, the base is a mixture of up to three, or up to two, aromatic bases. In certain embodiments, the base is a mixture of up to three, or up to two, inorganic carbonates. In certain embodiments, the base is a mixture of up to three, or up to two, metal hydrides. In certain embodiments, the base is a mixture of up to three, or up to two, alkoxides. In certain embodiments, the base is a mixture of up to three, or up to two, bases from the group consisting of triethylamine, N,N-diisopropylethylamine, quinuclidine, 1 ,4-diazabicyclo [2.2.2] octane, 1 ,8-diazabicyclo [5.4.0] undec-7 -ene, tripropylamine, tributylamine, pyridine, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium hydride, potassium hydride, sodium methoxide, sodium tert-butoxide and lithium tert-butoxide. In a particular embodiment, the base is sodium carbonate.

In some embodiments, the reaction occurs in a solvent selected from the group consisting of water, acetonitrile, ethanol, isopropanol, methyl ethyl ketone, isopropyl acetate, dioxane, a mixture of water and a water-miscible organic solvents such as ethanol and isopropanol, an halogenated solvent such as dichloromethane and chloroform. In certain embodiments, the solvent is water or isopropanol or a mixture thereof. In a particular embodiment, the solvent is water.

In certain embodiments, the reaction mixture is washed at least once in a suitable organic solvent such as diethyl ether or ethyl acetate and acidified with a suitable acid.

Suitable acids include, but are not limited to, an inorganic acid, an organic acid, or a halogenated organic acid. Exemplary inorganic acids, include, but are not limited to hydrochloric acid, hydrobromic acid, hydroiodic acid. Exemplary organic acids, include, but are not limited to, formic acid and acetic acid. In yet other embodiments the organic acid is a halogenated organic acid. Exemplary halogenated organic acids include, but are not limited to, trifluoromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and perfluoropropionic acid. In certain embodiments, the acid is trifluoroacetic acid. In still further embodiments, the acid is a mixture comprising one or more organic acids and one or more inorganic acids. In certain embodiments, the acid is a mixture comprising up to three, or up to two, organic acids. In certain embodiments, the acid is a mixture comprising up to three, or up to two, halogenated organic acids. In certain embodiments, the acid is a mixture comprising up to three, or up to two, inorganic acids. In a certain embodiment, the acid is a mixture of up to three, or up to two, acids selected from the group consisting of hydrochloric acid, hydrobromic acid, hydroiodic acid, formic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and perfluoropropionic acid. In a particular embodiment, the acid is concentrated hydrochloric acid.

In a particular embodiment, the crude residue is dissolved in an organic solvent, such as ethyl acetate, and the organic layer is washed with saturated sodium bicarbonate solution, and the combined bicarbonate washes are back extracted with an organic solvent such as ethyl acetate. Total combined organic layers are filtered through phase separation filter paper and concentrated under reduced pressure.

B. Preparation of a compound of formula (v)

Scheme 8. Preparation of a compound of formula (v)

In particular embodiments, the compound of formula (iii) is suspended in a first solvent, about 1 equivalent of a base is added, and the reaction mixture is cooled to about 0 °C to - 20 °C under nitrogen. Once cooled, about 1 to 2 equivalents of a suitable coupling reagent is added over about 10 to about 20 minutes while maintaining the reduced temperature and the mixture is left to stir for around 10 minutes. The compound of formula (iv) is then added as a steady stream while maintaining the reduced temperature. After the addition is complete, a second solvent is added and the reaction is allowed to warm to an ambient temperature. The reaction is allowed to stir for at least about 8 hours.

Once the reaction has been allowed to stir, the reaction mixture is cooled to about -5 to about 0 °C and a suitable acid is added over about 10 minutes while maintaining the temperature at about less 2 °C. After the acid addition is complete, the solution is allowed to warm to ambient temperature and the aqueous phase is removed. The organic phase is washed, dried, filtered and evaporated to dryness. The product is recrystallised from a suitable solvent such as ethyl acetate.

In certain embodiments, the mother liquor is reduced in volume under pressure, heated to reflux to redissolve and then allowed to cool to ambient temperature and stand overnight at ambient temperature.

In some embodiments, the coupling reaction is performed with 1 to 2 equivalents of the compound of formula (vi), or salt thereof, such as 1.25 equivalents, 1.5 equivalents or 1.75 equivalents.

In some embodiments, the first solvent is a polar aprotic solvent. In certain embodiments, the second solvent is also a polar aprotic solvent. Exemplary polar aprotic solvents include, but are not limited to, dichloromethane, dichloroethane, chloroform, N- methylpyrrolidone, tetrahydrofuran, 2-methyltetrahydrofuran, ethyl acetate, dimethylformamide, acetonitrile, acetone, dimethyl sulfoxide, propylene carbonate, dimethyl acetamide, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, N- methylpyrrolidinone, dimethoxyethane, methyl t-butyl ether and cyclopentyl methyl ether. In a particular embodiment, the first solvent is tetrahydrofuran. In a particular embodiment, the second solvent is dichloromethane.

In some embodiments, the base is an organic amine or an inorganic base. In certain embodiments, the base is selected from, but not limited to, ethylamine, diethylamine, triethylamine, diisopropylamine, N,N-diisopropylethylamine, quinuclidine, 1,4- diazabicyclo[2.2.2]octane, 1,8-diazabicyclo[5.4.0]undec-7-ene, tripropylamine, tributylamine, morpholine, 4-methylmorpholine, N-ethylmorpholine, piperidine, N- methylpiperidine, N-methyl pyrrolidine, ammonium, ammonium carbonate, ammonium hydroxide, barium carbonate, calcium carbonate, calcium hydroxide, cesium carbonate, cesium hydroxide, lithium amide, lithium carbonate, lithium hydroxide, magnesium carbonate, magnesium hydroxide, potassium carbonate, potassium hydroxide, sodium hydroxide, sodium carbonate and combinations thereof.

In further embodiments, the base is selected from N-methylmorpholine, morpholine, N- ethylmorpholine, piperidine, N-methylpiperidine, N-methyl pyrrolidine and combinations thereof. In a particular embodiment, the base is N-methylmorpholine.

In certain embodiments, the coupling reagent is selected from, but not limited to, isobutyl chloroformate, BOP, PyBOP, AOP, PyAOP, HBTU, TBTU, HATU, HCTU, HOBt, HOAt, DCC, EDC1, 1-t-butyl-3-ethylcarbodiimide, N,N'-di-tert-butylcarbodiimide, DIC, l-[3- (Dimethylamino)propyl]-3-ethylcarbodiimide methiodide, 1,3-di-p-tolylcarbodiimide, BOP-C1, TFFH, Brop, PyBrop, EEDQ, IIDQ, CIP, DPPA, COMU, PyOxim, T3P, CDI and combinations thereof. In a particular embodiment, the coupling reagent is isobutyl chloroformate.

In some embodiments the acid is selected from, but not limited to, an inorganic acid, an organic acid, or a halogenated organic acid. Exemplary inorganic acids, include, but are not limited to, hydrochloric acid, hydrobromic acid, hydroiodic acid. Exemplary organic acids include, but are not limited to, formic acid and acetic acid. In yet other embodiments the organic acid is a halogenated organic acid. Exemplary halogenated organic acids include, but are not limited to, trifluoromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and perfluoropropionic acid. In certain embodiments, the acid is trifluoroacetic acid. In still further embodiments, the acid is a mixture comprising one or more organic acids and one or more inorganic acids. In certain embodiments, the acid is a mixture comprising up to three, or up to two, organic acids. In certain embodiments, the acid is a mixture comprising up to three, or up to two, halogenated organic acids. In certain embodiments, the acid is a mixture comprising up to three, or up to two, inorganic acids. In a certain embodiment, the acid is a mixture of up to three, or up to two, acids selected from the group consisting of hydrochloric acid, hydrobromic acid, hydroiodic acid, formic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and perfluoropropionic acid. In a particular embodiment, the acid is hydrochloric acid.

In certain embodiments, the organic phase comprising the compound of formula (v) is sequentially washed with hydrochloric acid, saturated NaHCO₃ and saturated NaCl, then dried over Na₂SO₄, filtered and evaporated to dryness. The product is then recrystallised from a suitable solvent such as ethyl acetate.

C. Preparation of a compound of formula (vi)

Scheme 9. Preparation of a compound of formula (vi)

In certain embodiments, the compound of formula (vi) is prepared by dissolving pyrrolidine in a polar aprotic solvent and adding about 1 to 1.5 equivalents of 1,1- carbonyldiimidazole dissolved in a polar aprotic solvent at reflux over about 60 minutes to about 100 minutes. Upon completion, the solvent is removed under pressure and the residue is dissolved in a second solvent, then washed, filtered and evaporated to dryness.

In a particular embodiment, pyrrolidine and 1,1-carbonyldiimidazole are dissolved in tetrahydrofuran. In certain embodiments, the second solvent is also a polar aprotic solvent such as dichloromethane, dichloroethane, chloroform, N-methylpyrrolidone, tetrahydrofuran, 2- methyltetrahydrofuran, ethyl acetate, dimethylformamide, acetonitrile, acetone, dimethyl sulfoxide, propylene carbonate, dimethyl acetamide, N,N-dimethylformamide, N,N- dimethylacetamide, 1,4-dioxane, N-methylpyrrolidinone, dimethoxyethane, methyl t-butyl ether and cyclopentyl methyl ether. In a particular embodiment, the second solvent is dichloromethane .

The residue is then dissolved in a suitable solvent such as a polar non-protic solvent and iodomethane is added. The reaction is allowed to stir for about 12 to 30 hours at a temperature of about 15 to 50 °C. The solvent is then removed under reduced pressure to give the compound of formula (vi). Exemplary polar non-protic solvents include, but are not limited to, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, or N-methyl-2-pyrrolidinone. In a particular embodiment, the polar non-protic solvent is acetonitrile.

D. Preparation of a compound of formula ( vii )

Scheme 10. Preparation of a compound of formula (vii)

In certain embodiments, the compound of formula (v) is dissolved in a suitable solvent and about 1 equivalent of base is added followed by about 1 equivalent of a compound of formula (vi) at a temperature of about 10 °C to about 60 °C. The reaction is allowed to continue for about 5 to 80 hours. The reaction mixture is then washed and dried.

In some embodiments, the compound of formula (v) is dissolved in a polar aprotic solvent such as dichloromethane, dichloroethane, chloroform, N-methylpyrrolidone, tetrahydrofuran, 2-methyltetrahydrofuran, ethyl acetate, dimethylformamide, acetonitrile, acetone, dimethyl sulfoxide, propylene carbonate, dimethyl acetamide, N,N- dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, N-methylpyrrolidone, dimethoxyethane, methyl t-butyl ether and cyclopentyl methyl ether. In a particular embodiment, the compound of formula (v) is dissolved in dichloromethane. In certain embodiments, the base is an organic amine or an inorganic base. In certain embodiments, the base is selected from, but not limited to, ethylamine, diethylamine, triethylamine, diisopropylamine, N,N-diisopropylethylamine, quinuclidine, 1,4- diazabicyclo[2.2.2]octane, 1,8-diazabicyclo[5.4.0]undec-7-ene, tripropylamine, tributylamine, morpholine, 4-methylmorpholine, N-ethylmorpholine, piperidine, N- methylpiperidine, N-methyl pyrrolidine, ammonium, ammonium carbonate, ammonium hydroxide, barium carbonate, calcium carbonate, calcium hydroxide, cesium carbonate, cesium hydroxide, lithium amide, lithium carbonate, lithium hydroxide, magnesium carbonate, magnesium hydroxide, potassium carbonate, potassium hydroxide, sodium hydroxide, sodium carbonate and combinations thereof. In a particular embodiment, the base is triethylamine.

In certain embodiments the compound of formula (v), or salt thereof, is coupled with the compound of formula (vi), or salt thereof, at a temperature of about 10 to 60 °C, about 15 to 50 °C, about 18 to 40 °C, about 21 to 35 °C, about 21 to 28 °C. In certain embodiments, the reaction is performed at ambient temperature.

In certain embodiments, the reaction is stirred for about 5 to 80 hours, for about 10 to 50 h, for about 12 to 30h, for about 20 to 26h.

In certain embodiments, the reaction mixture is washed with 10% citric acid, 1M NaOH, H2O and saturated NaCl, dried over Na₂SO₄ and evaporated to dryness. E. Conversion of a compound of formula ( vii ) to a compound of formula (I)

Scheme 11. Preparation of a compound of formula (I) In certain embodiments the compound of formula (vii) is dissolved in a suitable solvent and an aqueous solution of a metal salt is added over about 15 to about 45 minutes maintaining the temperature at about less than 25 °C. The reaction is allowed to stir for at least about 8 hours.

In some embodiments the reaction vessel is placed in a water bath at ambient temperature during the above reaction to aid in heat dissipation.

The solvent is removed by evaporation and the resulting aqueous phase is washed with a suitable solvent such as diethyl ether. The aqueous phase is then removed by freeze-drying to give the compound of formula (I).

In certain embodiments, the reaction occurs in a solvent selected from the group consisting of acetonitrile, ethanol, isopropanol, methyl ethyl ketone, isopropyl acetate, dioxane, a mixture of water and a water-miscible organic solvents such as ethanol and isopropanol, an halogenated solvent such as dichloromethane and chloroform. In a particular embodiment, the solvent is ethanol.

In some embodiments, the compound of formula (vii) is converted to the compound of formula (I) in the presence of a metal salt selected from a hydroxide, sulphate, carbonate, sulphide, phosphate, borate, silicate or trimethylsilanolate.

In some embodiments, the metal is selected from sodium potassium, lithium, ammonium, calcium and magnesium. In a particular embodiment, the metal salt is sodium hydroxide. Examples

In order for this invention to be more fully understood, the following examples are set forth. These examples are for the purpose of illustrating embodiments, and are not to be construed as limiting the scope of this disclosure in any way. The reactants used in the examples below may be obtained either as described herein, or if not described herein, are themselves either commercially available or may be prepared from commercially available materials by methods known in the art. Analytical conditions

NMR

NMR experiments were performed on a Bruker Av400 or Av500 NMR spectrometer. Solutions for analysis by NMR were prepared by dissolving each sample in 0.6 ml of deuterated solvent. NMR experiments were performed with the sample held at 25+0.1°C. Chemical shifts for ¹H experiments are referenced to the residual solvent signal; ¹³C spectra are referenced to the solvent signal. UPLC-MS (with QDa)

Samples were dissolved in 1ml of HPLC-grade methanol or acetonitrile.

The Chromatographic conditions were as follows:

Column: Acquity UPLC BEH C₁₈ (50 × 2.1 mm, 1.7 μm particle size) Mobile Phase A: 100% Milli-Q Water with 0.1% formic acid

Mobile Phase B: 100% Acetonitrile with 0.1% formic acid

Gradient: 95% A to 100% B over 4.50 min. Hold at 100% B for 1 min. Change to 95% A over 0.5 min, then hold for 1 min. MS is collecting data for the complete 7 min run. Spectral analysis was from 190 to 350 nm with chromatograms extracted using a wavelength of 254 nm.

Flow Rate: 0.400 ml / min Column Temperature: 30°C Sample Injection Volume: 1 μl Mass spectrometric analyses were performed on a Waters Acquity UPLC i-Class with QDa mass detector with adjustment-free atmospheric pressure ionisation (API) electrospray (ES) interface for reliability. Positive and negative ions were recorded simultaneously with full scan analysis in m/z range 100 to 1000. High purity nitrogen (>95%) nebulizing/desolvation gas is used for vaporization with the pressure regulated at 650 - 700k Pa. The Probe temperature was set at 600°C, the source temperature at 120 °C, the cone voltage was 10V whilst the capillary voltage was 0.8kV for both positive and negative ions.

Example 1. Synthesis of (1H-imidazol-1-yl)(pyrrolidin-1-yl)methanone

Pyrrolidine (45.1 mL, 0.55 mol, 1 eq) in THF (124 mL) was added over 80 mins to CDI (98 g, 0.60 mol, 1.1 eq) in THF (371 mL) at reflux. The reaction was then stirred at reflux overnight. The THF was removed under reduced pressure and the residue was dissolved in DCM (350 mL). The organic solution was washed with H₂O (3 x 150 mL) filtered through phase separation filter paper and evaporated to dryness to obtain a golden oil which solidified on standing to give 60.6 g of a golden-brown solid (67% yield). This was used without purification in the next step (it is possible to recrystallise from DCM to give white crystals). ¹H NMR (400 MHz, CDCl₃) δ 8.04 (s, 1H), 7.37 (s, 1H), 7.10 (s, 1H), 3.73-3.57 (m, 4H), 2.08-1.94 (m, 4H).

¹³C NMR (100 MHz, CDCl₃) δ 149.8, 136.9, 129.6, 117.8, 49.1, 25.6.

Example 2. Synthesis of 3-methyl-1-(pyrrolidine-1-carbonyl)-1H-imidazol-3-ium iodide

Iodomethane (137.6 mL, 2.21 mmol, 4 eq) was added to (1H-imidazol-1-yl)(pyrrolidin-1- yl)methanone (91.3 g) in MeCN (552 mL) and stirred at ambient temperature for 24 h. The volatiles were then removed under reduced pressure to give the target compound as a tan solid (168.2 g, quantitative recovery), which was used without further purification. ¹H NMR (400 MHz, CDCl₃) δ 10.51 (br s, 1H), 7.84 (br tr, J = 1.8 Hz, 1H), 7.53 (br tr, J = 1.8 Hz, 1H), 4.34 (s, 3H), 4.04 (br s, 2H), 3.70 (br s, 2H), 2.15-2.01 (m, 4H).

¹³C NMR (100 MHz, CDCl₃) δ 144.8, 136.7, 123.6, 121.1, 51.0, 59.5, 38.2, 26.5, 24.3.

Example 3. Synthesis of (phenylsulfonyl)-L-proline

Benzenesulfonyl chloride was added to a stirring solution of L-proline (60 g, 0.52mol, leq) and Na₂CO₃ (165.7g, 1.56mol, 3eq) in H2O (682 mL). The resulting milky mixture was stirred at ambient temperature overnight. The (still milky) reaction mixture was then washed with diethyl ether (3 × 100 mL) and acidified to pH 1 by the careful addition of cone. HCl (~225 mL; CAUTION - gas evolution; the milkiness dissipated at ~ pH 5, while a solid formed at lower pH). After stirring for 30min the pH was confirmed and the compound was extracted into ethyl acetate (3 × 300 mL), washed with saturated NaCl (250 mL), filtered through phase separation filter paper and evaporated to dryness to give 123.6 g of a white solid (93% yield); >99% by UPLC-MS, t_R 1.80min, M+1 = 210 (target -CO₂), 256 (target), 353 (unknown). ¹H NMR (500 MHz, CDCl₃) δ 7.92-7.87 (m, 2H), 7.66-7.60 (m, 1H), 7.59-7.53 (m, 2H), 4.33-4.26 (m, 1H), 3.57-3.51 (m, 1), 3.33-3.25 (m, 1H), 2.21-2.12 (m, 1H), 2.02-1.91 (m,

2H), 1.82-1.72 (m, 1H).

¹³C NMR (125 MHz, CDCl₃) δ 175.5, 137.5, 133.3, 129.4, 127.7, 60.6, 49.0, 30.7, 24.8. Example 4. Synthesis of methyl (phenylsulfonyl)-L-prolyl-L-tyrosinate

NMM (70.4 mL, 640.3 mmol, 1.0 eq) was added to (phenylsulfonyl)-L-proline (163.5 g, 640.3 mmol, 1.0 eq) in THF (1.875 L) and the mixture cooled to below -15 °C (dry ice / acetone bath) under N₂. Isobutyl chloroformate (99.7 mL, 768.4 mmol, 1.2 eq) was added over 20 mins maintaining the temperature below -15 °C, the reaction solution was then stirred at -15 °C for 10 mins. Solid H-Tyr-OMe^a (125.0 g, 640.3 mmol, 1.0 eq), was then added as a steady stream maintaining the temperature below -10 °C. After the addition was complete, DCM (750 mL) was added, the reaction was allowed to warm to ambient temperature and stirred at ambient temperature under N2 overnight.

The reaction was cooled to 0 °C and HCl (1M, 500 mL) was added over 10 mins maintaining the temperature below 2 °C. After the HCl addition was complete, the solution was allowed to warm to ambient temperature and the aqueous phase was removed. The organic phase was washed with HCl (1M, 2 x 500 mL), sat. NaHCO₃ (3 × 675 mL) and sat. NaCl (500 mL), dried over Na₂SO₄, filtered and evaporated to dryness to give a thick brown oil (310.3 g). The product was recrystallised from EtOAc (465 mL), to give 155 g of the target compound (56% yield) as golden-brown crystals; UPLC-MS /R 2.25min 93.9% M+1=433 (target), 2.43 min, 5.2% M+1=447 (target as Et ester). The mother liquor was reduced in volume (RotaVap) until solid appeared on the flask, heated to reflux to redissolve and then allowed to cool to ambient temperature and stand overnight at ambient temperature. A further 10.6g (2.6%) of target was obtained as golden-brown crystals, UPLC-MS t_R 2.25 min, 93.9%, M+1=433 (target), 2.43 min, 4.9% M+1=447 (Et ester of the target due to impure H-Tyr-OMe).

The two crops of crystals were combined to give 165.5 g (60% yield) of golden-brown crystals. UPLC-MS t_R 2.25 min, 94.1% M+1=433 (target), 2.43 min, 4.4% M+1=447 (target as Et ester). ¹H NMR (400 MHz, d₆-DMSO) δ 9.23 (s, 1H), 8.23 (d, J=8.3Hz, 1H), 7.84-7.78 (m, 2H), 7.74-7.67 (m, 1H), 7.64-7.57 (m, 2H), 7.05-6.99 (m, 2H), 6.69-6.63 (m, 2H), 4.48-4.39 (m, 1H), 4.15-4.10 (m, 1H), 3.61 (s, 3H), 3.40- 3.34 (m, 1H, obscured), 3.18-3.10 (m, 1H), 2.98-2.85 (m, 2H), 1.68-1.50 (m, 3H), 1.49-1.38 (m, 1H).

¹³C NMR (100Mz, d₆-DMSO) δ 171.7, 171, 156.0, 136.8, 133.2, 130.1, 129.4, 127.3, 127.0, 115.0, 61.1, 53.6, 51.9, 49.0, 35.8, 30.5, 23.8. a. H-Tyr-OMe is a commercial compound that contains ~3% ethyl ester by ¹H NMR, as such, the presence of the ethyl ester was carried through the rest of the synthesis.

Example 5. Synthesis of 4-((S)-3-methoxy-3-oxo-2-((S)-1-(phenylsulfonyl)pyrrolidine-2- carboxamido)propyl)phenyl pyrrolidine-1-carboxylate

Et₃N (62.5 mL, 449 mmol, 1 eq), followed by v (194 g, 449 mmol, 1 eq) was added to methyl (phenylsulfonyl)-L-prolyl-L-tyrosinate (172 g, 561 mmol, 1.25 eq) dissolved in DCM (897 mL) at ambient temperature. The reaction was stirred at ambient temperature for 44 h^b, then washed with 10% citric acid (3 × 300 mL), 1M NaOH (300 mL), H₂O (300 mL) and saturated NaCl (300 mL), dried over Na₂SO₄ and evaporated to dryness. (CAUTION extreme foaming during evaporation) to give 198 g of a tan foam (82% yield). UPLC-MS, t_R=2.82min, 92.9%, M+1=530 (target), 2.99min, 4.5%, M+1=544 (target as Et ester). ¹H NMR (400MHz, MeOD) δ 7.89-7.82 (m, 2H), 7.72-7.65 (m, 1H), 7.65-7.56 (m, 2H), 7.28-7.21 (m,2H), 7.07-7.00 (m, 2H), 4.73 (dd J = 8.2, 5.4Hz, 1H), 4.11 (dd, J =8.0, 3.8 Hz, 1H), 3.60-3.52 (m, 2H), 3.48-3.37 (m, 3H), 3.27-3.15 (m, 2H), 3.08 (dd, J = 14.0, 8.2 Hz, 1H), 2.03-1.88 (m, 4H), 1.82-1.58 (m, 3H), 1.58-1.44 (m, 1H). (The quartet and triplet associated with the Et ester were observed at 4.18 and 1.26 respectively). ¹³C NMR (100MHz, MeOD) δ 174.2, 172.9, 155.1, 151.8, 138.1, 135.2, 134.5, 131.4, 130.5, 128.9, 122.9, 61.2, 54.9, 52.8, 51.6, 47.5, 37.5, 31.8, 26.7, 25.9, 25.4 b. Reaction monitoring by UPLC-MS showed 86% conversion. Due to time constraints the reaction was worked-up. The yield may improve by extending the reaction time.

Example 6. Synthesis of sodium (S)-2-((S)-1-(phenylsulfonyl)pyrrolidine-2- carboxamido)-3-(4-((pyrrolidine-1-carbonyl)oxy)phenyl)propanoate ( Compound 1 )

4-((S)-3-methoxy-3-oxo-2-((S)-1-(phenylsulfonyl)pyrrolidine-2-carboxamido)propyl) phenyl pyrrolidine-1-carboxylate (188 g, 345.4 mmol^c, 1 eq) was dissolved^d in EtOH (690 mL) and placed in a water bath at ambient temperature to aid in heat dissipation. Aqueous NaOH (0.5 M, 670 mL, 335 mmol, 0.97 eq) was added over 30 mins maintaining the temperature at below 25°C. The reaction was allowed to stir overnight at ambient temperature. The ethanol was removed by evaporation at 30 °C and the resulting aqueous phase was washed with Et₂O (9 x 400 mL)^e. The water was then removed by freeze- drying to give the sodium salt of Compound 1 as a pale tan solid (177 g^f,g, 98% yield). UPLC-MS t_R 2.52 min, 97.8%, M+1=516.4 (target). ¹H NMR (500 MHz) d 7.91-7.84 (m, 2H), 7.72-7.65 (m, 1H), 7.65-7.57 (m, 2H), 7.28-7.21 (m, 2H), 7.00-6.94 (m, 2H), 4.47-4.41 (m, 1H) 4.08 (dd, J = 8.8, 3.5 Hz, 1H), 3.60-3.51 (m, 2H), 3.45-3.38 (m, 2H), 3.38-3.24 (m, 2H, obscured by MeOD), 3.22-3.15 (m, 1H), 3.11 (dd, J = 13.6, 5.8 Hz, 1H), 2.02-1.89 (m, 4H), 1.88-1.80 (m, 1H), 1.72-1.44 (m, 3H).

¹³C NMR 177.2, 173.0, 155.1, 151.3, 137.8, 136.3, 134.5, 131.6, 130.5, 129.0, 122.4, 63.5, 56.9, 50.6, 47.5, 47.4, 38.2, 31.6, 26.7, 25.9, 25.3. c. Based on UPLC-MS result indicating 93% Me ester and 4.5% Et Ester. d. The ester initially dissolved, then a fine stirrable suspension formed. e. Washes were performed in sets of 3, after which the aqueous phase was analysed by UPLC-MS. f. Et₂O 1.4% by mass was observed in the ¹H NMR. g. 170 g was isolated directly from the freeze dryer flasks. A further 4% was isolated by rinsing the flasks and evaporation from EtOH.

Example 7. Synthesis of sodium ( S)-2-((S)-1-(phenylsulfonyl)pyrrolidine-2 - carboxamido)-3-(4-((pyrrolidine-1-carbonyl)oxy)phenyl)propanoate ( Compound 1) with sodium trimethylsilanoate.

To a mixture of charcoal (62.5 g) and sodium trimethylsilanoate (10.6 g, 94.3 mmol) in CH₂CI₂ (500 mL) maintained between 15 and 25°C a solution of 4-((S)-3-methoxy-3-oxo- 2-((S)-1-(phenylsulfonyl)pyrrolidine-2-carboxamido)propyl) phenyl pyrrolidine- 1- carboxylate (50 g, 94.3 mmol) in CH₂CI₂ (250 mL) was added, drop wise, and this reaction stirred and the temperature maintained between 15 and 20 5°C for 16 h. The progress of the reaction was monitored by HPLC and upon completion the mixture was filtered through Celite washing with CH₂CI₂ (250 mL). The filtrate was slowly added to MTBE (4.5 L) and precipitated. Under a blanket of N₂, the precipitate was filtered, washed with

MTBE (2 × 50 mL) and dried under vacuum to give the sodium salt of Compound 1 as a pale tan solid (33 g 65% yield). HPLC, 99.2%.

The use of this reagent rather than NaOH helped control chirality and thus increase purity.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A process for preparing a compound of formula (I):

or a salt thereof, comprising coupling a compound of formula (v):

or a salt thereof, with a compound of formula (vi):

or a salt thereof, to provide a compound of formula (vii):

or a salt thereof, and converting the compound of formula (vii) to a compound of formula (I) or a salt thereof; wherein R¹ is a protecting group.

2. The process according to claim 1, wherein the compound of formula (v) is coupled with the compound of formula (vi) in the presence of a base.

3. The process according to claim 2, wherein the base is selected from an organic amine or an inorganic base.

4. The process according to claim 2 or 3, wherein the base is selected from ethylamine, diethylamine, triethylamine, diisopropylamine, N,N-diisopropylethylamine, quinuclidine, 1 ,4-diazabicyclo [2.2.2] octane, 1 ,8-diazabicyclo [5.4.0] undec-7 -ene, tripropylamine, tributylamine, morpholine, 4-methylmorpholine, N-ethylmorpholine, piperidine, N-methylpiperidine, N-methyl pyrrolidine, ammonium, ammonium carbonate, ammonium hydroxide, barium carbonate, calcium carbonate, calcium hydroxide, cesium carbonate, cesium hydroxide, lithium amide, lithium carbonate, lithium hydroxide, magnesium carbonate, magnesium hydroxide, potassium carbonate, potassium hydroxide sodium hydroxide, sodium carbonate and combinations thereof.

5. The process according to claim 4, wherein the base is triethylamine.

6. The process according to any one of claims 1 to 5, wherein the coupling step is performed in a polar aprotic solvent.

7. The process according to claim 6, wherein the polar aprotic solvent is selected from dichloromethane, dichloroethane, chloroform, N-methylpyrrolidone, tetrahydrofuran, 2- methyltetrahydrofuran, ethyl acetate, dimethylformamide, acetonitrile, acetone, dimethyl sulfoxide, propylene carbonate, dimethyl acetamide and combinations thereof.

8. The process according to claim 7, wherein the polar aprotic solvent is dichloromethane .

9. The process according to any one of claims 1 to 8, wherein the compound of formula (vii) is converted to the compound of formula (I) in the presence of a metal salt selected from a hydroxide, sulphate, carbonate, sulphide, phosphate, borate, silicate or trimethylsilanolate.

10. The process according to claim 9, wherein the metal is selected from sodium, potassium, lithium, ammonium, calcium and magnesium.

11. The process according to any one of claims 1 to 10, wherein the compound of formula (I) is in the form of a sodium salt.

12. The process according to claim 11, wherein the compound of formula (I) is Compound 1:

13. The process according to any one of claims 1 to 12, wherein the compound of formula (v):

or the salt thereof, is prepared by coupling a compound of formula (iii):

or a salt thereof, with a compound of formula (iv):

or a salt thereof; wherein R¹ is a protecting group; and R² is selected from OH, Cl or F.

14. A compound of formula (II):

or a salt thereof, wherein

R¹ is a protecting group; and

R³ is selected from H and a protecting group.

15. A compound according to claim 14, wherein the compound is a compound of formula (Ila):

or a salt thereof.

16. A process for preparing a compound of formula (v):

or a salt thereof, comprising coupling a compound of formula (iii):

or a salt thereof, with a compound of formula (iv):

or a salt thereof; wherein R¹ is a protecting group; and R² is selected from OH, Cl or F.

17. A process for preparing a compound of formula (vii):

or a salt thereof, comprising coupling a compound of formula (v):

or a salt thereof, with a compound of formula (vi):

or a salt thereof; wherein R¹ is a protecting group.

18. A process for preparing a compound of formula (I):

or a salt thereof, comprising coupling a compound of formula (iii):

or a salt thereof, with a compound of formula (iv):

or a salt thereof, to provide a compound of formula (v):

or a salt thereof, coupling the compound of formula (v) with a compound of formula (vi):

or a salt thereof, to provide a compound of formula (vii):

or a salt thereof, and converting the compound of formula (vii) to a compound of formula

(i); wherein R¹ is a protecting group; and R² is selected from OH, Cl or F.

19. The process according to any one of claims 1 to 10 or 13 to 18 wherein the protecting group is selected from C₁-C₆alkyl, C₁-C₆alkenyl, phenyl, benzyl, silyl and oxazoline.

20. The process according to any one of claims 13, 15 or 18, wherein the compound of formula (iii) is coupled with the compound of formula (iv) in the presence of a coupling reagent.

21. The process according to any one of claims 13, 15, 18 or 20, wherein the compound of formula (iii) is coupled with the compound of formula (iv) in the presence of a coupling reagent and a base.

22. The process according to claim 20 or 21, wherein the coupling reagent is selected from isobutyl chloroformate, BOP, PyBOP, AOP, PyAOP, HBTU, TBTU, HATU, HCTU, HOBt, HO At, DCC, EDC1, 1-t-butyl-3-ethylcarbodiimide, N,N'-di-tert-butylcarbodiimide, DIC, 1-[3-(Dimethylamino)propyl]-3-ethylcarbodiimide methiodide, 1,3-di-p- tolylcarbodiimide, BOP-C1, TFFH, Brop, PyBrop, EEDQ, IIDQ, CIP, DPPA, COMU, PyOxim, T3P, CDI and combinations thereof.

23. The process according to claim 22, wherein the coupling reagent is isobutyl chloroformate.

24. The process according to any one of claims 21 to 23, wherein the base is selected from N-methylmorpholine, morpholine, N-ethylmorpholine, piperidine, N- methylpiperidine, N-methyl pyrrolidine and combinations thereof.

25. The process according to any one of claims 13, 15, 18 or 20 to 24, wherein the compound of formula (iii) is coupled with the compound of formula (iv) in a polar aprotic solvent.

26. The process according to claim 25, wherein the polar aprotic solvent is dichloromethane .

27. Use of a compound of formula (v):

or a salt thereof, in the preparation of a compound of formula (I):

or a salt thereof; wherein R¹ is a protecting group.

28. A compound of formula (I):

or a salt thereof, prepared by the process of any one of claims 1 to 13 or 18 to 26.