High-purity 2'-deoxy-2',2'-difluorotetrahydrouridine and its production method

Abstract

The present invention relates to a method for synthesizing 2'-deoxy-2',2'-difluorotetrahydrouridine with increased purity and uniform particle size distribution. In particular, the method of the present invention includes providing a crystallization and separation procedure of a synthetic reaction intermediate. The present invention further includes a composition comprising a final compound in a high purity form, which includes a lower number of impurities and lower levels of individual and total impurities.

Description

[0001] Priority declaration

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 62 / 912,317, filed on October 8, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a method for synthesizing 2'-deoxy-2',2'-difluorotetrahydrouridine with increased purity and uniform particle size distribution. In particular, the method of the present invention includes crystallization and isolation procedures that provide synthetic reaction intermediates as well as final compounds in high purity form. Background Art

[0004] Several important chemotherapeutic compounds are analogs of the nucleotide cytidine, including decitabine, gemcitabine, 5-azacytidine, ara-C, tezacitabine, 5-fluoro-2'-deoxycytidine, and cytchlor. As analogs of cytidine, these compounds are subject to degradation by the enzyme cytidine deaminase (CDA), which degrades the compounds into inactive metabolites. The presence of CDA limits the effectiveness of cytidine analogs, requiring administration of higher and / or more frequent doses of the analogs to achieve therapeutic benefit.

[0005] One way to overcome this problem is to co-administer a CDA inhibitor with a cytidine analog, thereby blocking the degradation of the analog. One class of CDA inhibitors is 2'-deoxy-2',2'-difluorotetrahydrouridine compounds. U.S. Pat. No. 8,268,800 (incorporated herein by reference in its entirety) discloses such compounds, including Compound 1:

[0006]

[0007] There exists a need for more efficient methods for producing CDA inhibitors, such as 2'-deoxy-2',2'-difluorotetrahydrouridine, for use in methods of treating cancer and other disorders. Summary of the invention

[0008] The present invention relates to the development of a more efficient method for synthesizing 2'-deoxy-2',2'-difluorotetrahydrouridine compounds and intermediates involved in the synthesis. Previous synthesis methods in the art were inconvenient due to the use of inefficient transfer hydrogenation processes and the use of preparative HPLC to separate the final compound. The inventors of the present invention have developed a synthesis method with improved efficiency, which realizes the ability to purify the final compound by precipitation or crystallization, such as crystallization-induced diastereoselective transformation (CIDT), which converts a mixture of diastereomers into the desired compound, and thus results in an increase in the yield of the desired diastereomer (see WO 2015 / 066162). The present invention improves the method by reducing impurities, improving yields, shortening reaction times and / or otherwise improving conditions for industrial-scale production.

[0009] Another aspect of the present invention relates to a method for producing compound 1 (named (4R)-1-[(2R,4R,5R)-3,3-difluoro-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl]-4-hydroxytetrahydropyrimidin-2(1H)-one) or a salt thereof:

[0010]

[0011] The following steps are involved:

[0012] (a) hydrogenating a starting compound of formula IV:

[0013]

[0014] Wherein R is a hydroxyl protecting group,

[0015] To produce a compound of formula IIa:

[0016]

[0017] (b) reducing the compound of formula IIa to produce a compound of formula IIIa:

[0018]

[0019] (c) deprotecting the compound of formula IIIa to produce compound 2:

[0020] as well as

[0021] (d) precipitating or crystallizing compound 2 in the presence of a catalyst to produce compound 1:

[0022]

[0023] or its salts;

[0024] The method comprises one or more of the following, in any combination:

[0025] (i) wherein the hydrogenation step (a) is carried out under a hydrogen atmosphere using a palladium catalyst;

[0026] (ii) wherein the reducing step (b) is carried out at a temperature of about -12°C to about -5°C;

[0027] (iii) wherein the deprotection step (c) is carried out in the presence of an organic base; and / or

[0028] (iv) wherein the post-treatment of the deprotected compound from the deprotection step (c) is carried out under non-aqueous conditions. In some embodiments, the present invention further comprises a step wherein the final product is recrystallized, and the recrystallization is carried out at a pH of about 6.0 to about 7.4, and by dissolving the final product at a temperature of about 50° C. to about 55° C. to produce a solution and then cooling the solution to about 5° C.

[0029] Additional aspects of the invention relate to highly pure Compound 1 (e.g., Compound 1 having a purity of at least about 80%, such as at least about 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9%):

[0030]

[0031] or a salt thereof. High purity Compound 1 can be produced by the method of the present invention. Other aspects of the present invention relate to Compound 1 comprising a lower number of impurities and / or lower levels of individual and total impurities compared to Compound 1 produced by prior methods. DETAILED DESCRIPTION

[0032] The invention will now be described hereinafter with reference to the accompanying examples, in which embodiments of the invention are shown. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. The terms used in the description of the invention herein are only for the purpose of describing specific embodiments and are not intended to limit the invention.

[0034] Unless the context indicates otherwise, the various features of the invention described herein are specifically intended to be used in any combination. In addition, the present invention also contemplates that in some embodiments of the present invention, any feature or combination of features set forth herein may be excluded or omitted. For illustration, if the specification states that a composition includes components A, B, and C, it is specifically intended that any one or combination of A, B, or C may be omitted and abandoned, alone or in any combination.

[0035] For the purposes of this article, if there is any ambiguity between the written chemical name and the drawn chemical structure, the drawn chemical structure will be constrained.

[0036] definition

[0037] As used herein, "a", "an", or "the" may mean one or more than one. For example, a compound may mean a single compound or a plurality of compounds.

[0038] Also as used herein, "and / or" refers to and encompasses any and all possible combinations of one or more of the associated listed items, as well as the lack of a combination when interpreted as an alternative ("or").

[0039] As used herein, the term "about" when referring to a measurable value such as an amount of a dose (e.g., an amount of a compound), is meant to encompass variations of ±10%, ±5%, ±1%, ±0.5%, or even ±0.1% of the specified amount.

[0040] As used herein, the terms “comprise,” “comprises,” and “comprising” specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0041] As used herein, the transitional phrase "consisting essentially of" means that the scope of the claim should be interpreted to encompass the specified materials or steps recited in the claim and those that do not materially affect one or more basic and novel characteristics of the claimed invention. Therefore, when used in a claim or description of the present invention, the term "consisting essentially of" is not intended to be interpreted as being equivalent to "comprising".

[0042] As used herein, the terms "increase," "increases," "increased," "increasing" and similar terms mean an increase of at least about 25%, 50%, 75%, 100%, 150%, 200%, 300%, 400%, 500% or more.

[0043] As used herein, the terms "reduce", "reduces", "reduced", "reduction" and the like mean a decrease of at least about 5%, 10%, 15%, 20%, 25%, 35%, 50%, 75%, 80%, 85%, 90%, 95%, 97% or more. In specific embodiments, the reduction results in no or substantially no (i.e., a negligible amount, e.g., less than about 10% or even 5%) detectable activity or amount.

[0044] The term "salt thereof" includes pharmaceutically acceptable salts. The term "pharmaceutically acceptable salt" should mean the non-toxic salt of the compound used in the present invention, which is usually prepared by reacting a free acid with a suitable organic or inorganic base or a free base with a suitable organic or inorganic acid. Examples of such salts include, but are not limited to, acetate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, calcium, calcium edetate, camphorsulfonate, carbonate, chloride, clavulanate, citrate, dihydrochloride, edetate, edisylate, estolate, ethanesulfonate, fumarate, glucoheptonate, gluconate, glutamate, glycolyl p-aminophenylarsonic acid salt (glycollylarsanilate), hexylresorcinate (hexylresorcinate), hydrabamine (hydrabamine), hydrobromide, hydrochloride, hydroxynaphthoate (hydroxynaphthoate)

[0013] The invention also includes but is not limited to the following: sodium, potassium, potassium, sodium, stearate, sodium subacetate, sodium succinate, sodium tartrate, sodium iodide, sodium thiocyanate ...

[0045] As used herein, the term "Bronsted-Lowry base" refers to a substance having the ability to accept a proton.

[0046] As used herein, the term "hydroxy protecting group" can be any suitable hydroxy protecting group, i.e., an unstable chemical moiety known in the art to protect a hydroxy group from undesirable reactions during a synthesis procedure. After one or more of the synthesis procedures, the blocking group as described herein can be selectively removed. See, for example, A.Isidro-Llobet et al., Amino Acid-Protecting Groups, Chem.Rev.109:2455–2504 (2009) and T.Greene and P.Wuts, Protective Groups in Organic Synthesis (3dEd.1999). In some embodiments, the hydroxy protecting group is an acid-stable hydroxy protecting group. Examples of hydroxy protecting groups include, but are not limited to, alkyl, cycloalkyl, arylalkyl, aryl, ether, ester, cyclic ether, cyclic ester, acetal, cyclic acetal, ketal, and cyclic ketal groups, etc., which can be removed under acidic or alkaline conditions to remove the protecting group and replace it with a hydrogen atom. Specific hydroxyl protecting groups include, but are not limited to, methyl, ethyl, acetate, ethyl acetate, propionate, ethylene glycol, propylene glycol, 4-methoxybenzyl, benzyl, trityl, trimethylsilyl, tetrahydropyranyl, and benzoyl. Other hydroxyl protecting groups include, but are not limited to, methoxymethyl (MOM), methylthiomethyl (MTM), tert-butylthiomethyl, (phenyldimethylsilyl)methoxymethyl (SMOM), benzyloxymethyl (BOM), p-methoxybenzyloxymethyl (PMBM), (4-methoxyphenoxy)methyl (p-AOM), guaiacolmethyl (GUM), tert-butoxymethyl, 4-pentenyloxymethyl (POM), silanyloxymethyl, 2-methoxyethoxymethyl (MEM), 2,2,2-trichloroethoxymethyl, bis(2-chloroethoxy)methyl, 2-(trimethylsilyl)ethoxymethyl (SEMOR), tetrahydropyranyl (THP), 3-bromotetrahydropyranyl, tetrahydrothiopyranyl, 1-methoxy Cyclohexyl, 4-methoxytetrahydropyranyl (MTHP), 4-methoxytetrahydrothiopyranyl, 4-methoxytetrahydrothiopyranyl S,S-dioxide, 1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin-4-yl (CTMP), 1,4-dioxane-2-yl, tetrahydrofuranyl, tetrahydrothiofuranyl, 2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-yl, 1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 1-methyl-1-methoxyethyl, 1-methyl-1-benzyloxyethyl, 1-methyl-1-benzyloxy-2-fluoroethyl, 2,2,2-Trichloroethyl, 2-trimethylsilylethyl, 2-(phenylseleno)ethyl, tert-butyl, allyl, p-chlorophenyl, p-methoxyphenyl, 2,4-dinitrophenyl, benzyl, p-methoxybenzyl, 3,4-dimethoxybenzyl, o-nitrobenzyl, p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl, p-phenylbenzyl, 2-picolyl, 4-picolyl, 3-methyl-2-picolyl N-oxide N-oxido), diphenylmethyl, p,p'-dinitrodiphenylmethyl, 5-dibenzosuberyl, triphenylmethyl, α-naphthyldiphenylmethyl, p-methoxyphenyldiphenylmethyl, di(p-methoxyphenyl)phenylmethyl, tri(p-methoxyphenyl)methyl, 4-(4'-bromophenacyloxyphenyl)diphenylmethyl, 4,4',4"-tris(4,5-dichlorophthalimidophenyl)methyl, 4,4',4"-tris(levulinyloxyphenyl)methyl 1-(4-methoxyphenyl)-1'-pyrenylmethyl, 1,1-bis(4-methoxyphenyl)-1'-pyrenylmethyl, 9-anthryl, 9-(9-phenyl)xanthenyl, 9-(9-phenyl-10-oxydeoxyphenyl)-1'-anthryl, 1,3-benzodithiolan-2-yl, S,S-dioxide benzisothiazolyl, trimethylsilyl (TMS), triethylsilyl (TES), triisopropylsilyl (TIPS), dimethylisothiazolyl Propylsilyl (IPDMS), diethylisopropylsilyl (DEIPS), dimethylethylsilyl, tert-butyldimethylsilyl (TBDMS), tert-butyldiphenylsilyl (TBDPS), tribenzylsilyl, tri-p-xylylsilyl, triphenylsilyl, diphenylmethylsilyl (DPMS), tert-butylmethoxyphenylsilyl (TBMPS), formates, benzoylformates, acetates, chloroacetates, dichloroacetates, trichloroacetates, trifluoroacetates, methoxyacetates, triphenylmethoxyethyl Acid ester, phenoxyacetate, p-chlorophenoxyacetate, 3-phenylpropionate, 4-oxypentanoate (levulinic acid ester), 4,4-(ethylenedithio)pentanoate (levulinic acid dithioacetal), pivalate, adamantanoate (adamantoate), crotonate, 4-methoxycrotonate, benzoate, p-phenylbenzoate, 2,4,6-trimethylbenzoate (mesitoate), alkyl methyl carbonate, 9-fluorenylmethyl carbonate (Fmoc), alkyl ethyl carbonate, alkyl 2,2,2-Trichloroethyl (Troc), 2-(trimethylsilyl)ethyl carbonate (TMSEC), 2-(phenylsulfonyl)ethyl carbonate (Psec); 2-(triphenylphosphine)ethyl carbonate (Peoc), alkyl isobutyl carbonate, alkyl ethylene carbonate, alkyl allyl carbonate, alkyl p-nitrophenyl carbonate, alkyl benzyl carbonate, alkyl p-methoxybenzyl carbonate, alkyl 3,4-dimethoxybenzyl carbonate, alkyl o-nitrobenzyl carbonate, alkyl p-nitrobenzyl carbonate, alkyl S-benzyl thiocarbonate, 4-ethoxy-1-naphthyl carbonate, methyl dithiocarbonate, 2-iodobenzoate, 4-azidobutyrate, 4-nitro-4-methylvalerate, o-(dibromomethyl)benzoate, 2-formylbenzenesulfonate, 2-(methylthiomethoxy)ethyl, 4 -(methylthiomethoxy)butyrate, 2-(methylthiomethoxymethyl)benzoate, 2,6-dichloro-4-methylphenoxyacetate, 2,6-dichloro-4-(1,1,3,3-tetramethylbutyl)phenoxyacetate, 2,4-bis(1,1-dimethylpropyl)phenoxyacetate, chlorodiphenylacetate, isobutyrate, monosuccinate, (E)-2-methyl-2-butenoate, o-(methoxycarbonyl)benzoate, α-naphthoate, nitrate, alkyl N,N,N',N'-tetramethylphosphonodiamidate, alkyl N-phenylcarbamate, borate, dimethylphosphonothioate, alkyl 2,4-dinitrophenylsulfenate, sulfate, methanesulfonate (mesylate), benzylsulfonate and tosylate (Ts). Methods for protecting and deprotecting hydroxyl groups are well known and can be found, for example, in Protective Groups in Organic Synthesis (T. Green and P. Wuts; 3rd Edition; John Wiley and Sons, 1999).

[0047] Depend on The identified key either exists or does not exist.

[0048] Depend on The bonds identified are those that include mixtures of stereochemistry.

[0049] As used herein, the term "g / g" refers to grams per gram of substrate. The substrate is defined as 1 equivalent in each step, and all other aspects in that step are defined relative to the substrate.

[0050] The term "enantiomer" refers to stereoisomers of a compound that are mirror images of each other and are non-superimposable. In this application, unless otherwise mentioned or indicated, the chemical designation of a compound denotes the mixture of all possible stereochemically isomeric forms.

[0051] The term "diastereomers" refers to stereoisomers of compounds that have different configurations at one or more stereocenters, but which are not mirror images of each other (and therefore are not enantiomers).

[0052] The term "diamers" refers to two diastereomers that differ from each other at only one stereocenter.

[0053] The term "alkyl" refers to a straight or branched hydrocarbon chain containing 1-12 carbon atoms, such as 1-6 or 1-4 carbon atoms. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and the like.

[0054] The term "aryl" refers to an aromatic 5-8 membered monocyclic or 8-12 membered bicyclic ring system. The term also includes aromatic bicyclic ring systems in which hydrogen atoms have been added to one, two or three ring carbons in one ring (e.g., partially saturated rings). Examples of aryl groups include phenyl, naphthyl, etc.

[0055] The term "acyl" refers to an alkyl or aryl group attached to a carbonyl group. Examples of acyl groups include formyl, acetyl, propionyl, acryloyl, benzoyl, and the like.

[0056] As used herein, the term "benzoyl" refers to the acyl group of benzoic acid (attached through the carbonyl carbon) and has the following structure.

[0057]

[0058] Compound

[0059] One aspect of the invention relates to Compound 1 (or a salt thereof) produced by the methods of the invention, particularly Compound 1 in free base form having high purity (e.g., dimeric purity or low amounts of impurities, solvents, reaction byproducts, and / or degradation products). Another aspect of the invention relates to Compound 1 having a purity of at least about 80%, e.g., at least about 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9% or more by weight. In some embodiments, Compound 1 contains less than about 20%, e.g., less than about 15%, 10%, 5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% by weight of impurities, solvents, reaction byproducts, and / or degradation products, such as those shown in Tables 1 and 4 below. In some embodiments, Compound 1 contains less than about 20%, such as less than about 15%, 10%, 5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2% or 0.1% by weight of its corresponding enantiomer and / or diastereomer. Additional aspects of the invention relate to compound 1 having a molar ratio of the desired epimer (compound 1) to another epimer (compound 6) of at least about 60:40 by weight, e.g., at least about 70:30, 80:20, 90:10, 95:5, 96:4, 97:3, 98:2, 99:1 or more, e.g., an epimeric purity of at least about 60%, e.g., at least about 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99% or more, e.g., 99.5% or 99.9%.

[0060] In some embodiments, compound 1 (or its salt) produced by the method of the present invention contains less than 20 different measurable impurities, such as less than 15 impurities, such as less than 15, 14, 13, 12, 11, 10, 9, 8, 7 or 6 impurities, such as 5 or less impurities. As used herein, measurable impurities refer to impurities that can be detected by methods conventionally used in the art for testing chemical purity (e.g., HPLC or mass spectrometry). Measurable impurities are impurities present in an amount greater than 0.03 wt%.

[0061] In some embodiments, compound 1 (or a salt thereof) produced by the methods of the present invention contains less than about 4.0% by weight of the diastereomer compound 6, for example, less than about 3.5%, 3.0%, 2.5%, 2.0%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1% or 1.0%.

[0062] In some embodiments, compound 1 (or its salt) produced by the methods of the present invention contains less than about 2.5% by weight of total impurities excluding the diastereomer compound 6, for example, less than about 2.0%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1.0%, 0.9%, 0.8%, 0.7%, 0.6% or 0.5%.

[0063] In some embodiments, Compound 1 (or its salt) produced by the methods of the present invention contains less than about 1.0% by weight of any single impurity, including or excluding the diastereomer Compound 6, for example, less than about 1.0%, 0.95%, 0.9%, 0.85%, 0.8%, 0.75%, 0.7%, 0.65%, 0.6%, 0.55%, 0.5%, 0.45%, 0.4%, 0.35%, 0.3%, 0.25%, 0.2%, 0.15% or 0.1%.

[0064] Certain compounds described herein contain one or more chiral centers, or may additionally be capable of existing as multiple stereoisomers. The scope of the present invention includes pure stereoisomers and mixtures of stereoisomers, such as purified enantiomers / diastereomers / epimers, mixtures enriched in enantiomers / diastereomers / epimers, or racemates. In some embodiments, the compound has a stereochemical purity of at least about 80%, for example at least about 85%, 90%, 95%, 96%, 97%, 98%, 99% or more.

[0065] In certain cases, the compounds of the invention may also exist as tautomers, such as amide / iminol tautomers. Although only one delocalized resonance structure may be depicted, all such forms are contemplated as being within the scope of the invention.

[0066] As mentioned above, the compounds disclosed herein can be prepared in the form of their pharmaceutically acceptable salts. Pharmaceutically acceptable salts are salts that retain the desired biological activity of the parent compound and do not impart undesired toxicological effects. Examples of such salts are (a) acid addition salts formed with inorganic acids, such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, etc.; and salts formed with organic acids, such as, for example, acetic acid, oxalic acid, tartaric acid, succinic acid, maleic acid, fumaric acid, gluconic acid, citric acid, malic acid, ascorbic acid, benzoic acid, tannic acid, palmitic acid, alginic acid, polyglutamic acid, naphthalenesulfonic acid, methanesulfonic acid, p-toluenesulfonic acid, naphthalenedisulfonic acid, polygalacturonic acid, etc.; (b) salts formed by elemental anions such as chlorine, bromine and iodine, and (c) salts derived from bases, such as ammonium salts, alkali metal salts such as sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, and salts with organic bases such as dicyclohexylamine and N-methyl-D-glucosamine. In one embodiment, the compounds disclosed herein are prepared in the form of free bases.

[0067] It is also understood that the compositions herein include compounds in combination with stoichiometric or non-stoichiometric amounts of water (eg, in a hydrate) or other components (eg, in a solvate).

[0068] Synthesis method

[0069] Another aspect of the present invention relates to a method for producing compound 1 or a salt thereof:

[0070]

[0071] The method comprises precipitating or crystallizing compound 1 from a solution of compound 2 in the presence of a catalyst:

[0072]

[0073] In one embodiment, the method produces Compound 1.

[0074] The method utilizes crystallization-induced diastereoselective transformation (CIDT) to provide an increase in the production of the desired epimer (compound 1). Any suitable catalyst can be used in the method. The term "catalyst" as used herein with respect to the precipitation or crystallization step refers to a compound that promotes the balance between compound 6 and compound 1 when present in a substoichiometric amount relative to compound 2. Without being limited by the mechanism, it is believed that compound 1 and its epimer compound 6 are in equilibrium with the opened aldehyde structure of the compound as an intermediate. The catalyst is believed to work by promoting the opening of compound 6 into the aldehyde form, thereby increasing the conversion of one epimer to another and balancing the amount of compound 1 and compound 6 in the solution, because when using an appropriate solvent, compound 1 is preferentially precipitated or crystallized from the solution. The catalyst is present in a catalytically effective amount. In some embodiments, the catalyst can be an acid, such as an inorganic acid, such as an organic acid, such as acetic acid or trifluoroacetic acid. In other embodiments, the catalyst can be a base, such as a Bronsted-Lowry base, such as a weak base (a base that is not completely ionized in an aqueous solution). In other embodiments, the catalyst can be diisopropylethylamine or ammonium hydroxide. In some embodiments, the base has a basicity of 10 or more in the solvent. In some embodiments, the base has a pKa of 10 or more in a solvent such as DMSO, such as reported in: Bordwell, Acc. Chem. Res. 21: 456 1988); Crampton, J. Chem. Res. (S) 22 (1997); Kaliurand et al., J. Org. Chem. 65 (19): 6202 (2000); Kaljurand et al, J. Org. Chem. 70 (3): 1019 (2005). In some embodiments, the catalyst is a strong base. In some embodiments, the catalyst is a strong base, such as a sterically hindered strong base, such as a strong base of a weak nucleophile. In some embodiments, the catalyst is 1,8-diazabicyclo (5.4.0) undec-7-ene (DBU). DBU can be present in any effective amount, for example, from about 1 mol% to about 20 mol%, for example, from about 2 mol% to about 15 mol%, for example, from about 5 mol% to 10 mol%, for example, about 5 mol%, or for example, about 10 mol%, for example, about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mol%. In some embodiments, DBU can be present in 1 mol% to 20 mol%, for example, from 2 mol% to 15 mol%, for example, from 5 mol% to 10 mol%, for example, 5 mol%, or for example, 10 mol%, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mol%.

[0075] Any solvent or combination of solvents that causes compound 1 to precipitate or crystallize preferentially relative to compound 6 can be used. In one embodiment, the solvent is a solvent in which compound 6 has a greater solubility than compound 1. In some embodiments, the solution used to form a solution of compound 2 includes an organic solvent, consists essentially of an organic solvent, or consists of an organic solvent. In some embodiments, the solution includes water or an aqueous solvent, consists essentially of water or an aqueous solvent, or consists of water or an aqueous solvent. In some embodiments, the solvent is a protic solvent. In some embodiments, the solvent is a solvent miscible with water. In a specific embodiment, the solution is acetonitrile, acetone, tetrahydrofuran, dimethyl sulfoxide, or methanol. In a specific embodiment, the solution is an acetonitrile aqueous solution, an acetone aqueous solution, an tetrahydrofuran aqueous solution, an dimethyl sulfoxide aqueous solution, or an aqueous methanol solution. In a specific embodiment, the solution is an acetonitrile aqueous solution.

[0076] Precipitation or crystallization can be carried out for a long enough time to form a suitable amount of compound 1, for example, about 0.5 days to 14 days, for example, about 1-4 days, for example, about 2-3 days, for example, about 3-10 days, for example, about 4-6 days. Precipitation or crystallization can be carried out at any suitable temperature, for example, at about room temperature, optionally subsequently at a temperature of about 0°C to about 10°C. After precipitation or crystallization is complete, the precipitate can be collected, for example, by filtration, and washed, for example, with acetonitrile aqueous solution and / or acetonitrile, optionally cooled to a temperature of about 0°C to about 10°C. The precipitate can then be dried, for example, under vacuum, for example, at a temperature below about 45°C. The progress of the reaction can be monitored, for example, by sampling the supernatant of the reaction mixture and determining the ratio of compound 1 to compound 6. The completion of the reaction is indicated by the presence of a 50:50 mixture of compound 1 and compound 6 in the supernatant. If this ratio is not reached, additional catalysts can be added and the reaction is continued until completion.

[0077] After precipitation or crystallization, compound 1 is optionally further purified by recrystallization or slurrying, for example, from an acetonitrile aqueous solution, optionally with the addition of an acid, such as trifluoroacetic acid. For example, the precipitate can be resuspended in a ratio of about 1:2 to about 1:10 (v / v) water: acetonitrile, heated to about 35-45°C, and then cooled to about 0°C. The resulting precipitate can be washed in a ratio of about 1:2 to about 1:10 (v / v) water: acetonitrile, and then washed in acetonitrile, optionally cooled to a temperature of about 0°C to about 10°C. In certain embodiments, compound 1 is optionally further purified by other methods known in the art such as HPLC.

[0078] In some embodiments, compound 1 is further purified by recrystallization in acetone and water, and the pH is adjusted to about 6.0 to about 7.4 (e.g., about 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3 or 7.4 or any value or range thereof), for example, using aqueous formic acid alone or in combination with aqueous DBU. In some embodiments, the mixture is further heated, for example, heated to a temperature of about 50°C to about 55°C, for example at a rate of 0.5 to 1.5°C / min, until complete dissolution is observed, filtered, washed with a mixture of acetone and water, and then cooled, for example, cooled to a temperature of about 33°C to about 43°C, for example at a rate of 0.1 to 0.5°C / min, then seeded and further cooled, for example, cooled to a temperature of about -10°C to about 0°C, for example at a rate of 0.1 to 0.5°C / min, and allowed to stand, and then further prepared as known in the art (e.g., filtered, washed, and dried). In some embodiments, the recrystallization mixture is further heated to about 53°C, clarified filtered, and then cooled to a temperature of about 35°C, seeded, cooled to a temperature of about -5°C, and allowed to stand (e.g., aged) for about 12 to about 16 hours (e.g., about 12, 13, 14, 15 or 16 hours or any value or range therein). The inventors of the present invention have found that specific recrystallization parameters, such as higher temperatures and / or specific pH ranges, as disclosed herein, produce products of higher purity, improve particle size distribution, and avoid dimerization impurities. In some embodiments, the present method produces a compound having a more uniform particle size distribution, such as a unimodal particle size distribution, such as a particle size distribution centered at about 100-200 μm (e.g., about 130 μm). In some embodiments, at least 50% of the particles have a size of 20 μm to 300 μm, for example, at least 60%, 70%, 80% or 90%.

[0079] The molar ratio of compound 1 (i.e., the desired epimer) to the epimer of compound 1 (e.g., compound 6) after precipitation or crystallization can be at least about 60:40, such as at least about 70:30, 80:20, 90:10, 95:5, or 98:2 or higher. After the second purification step (e.g., recrystallization or slurry), the molar ratio of the desired epimer (compound 1) to the other epimer (compound 6) can be at least about 80:20, such as at least about 90:10, 95:5, or 98:2 or higher.

[0080] Another aspect of the present invention relates to a method for producing compound 1 or a salt thereof:

[0081]

[0082] The following steps are involved:

[0083] (a) hydrogenating a starting compound of formula IV:

[0084]

[0085] Wherein R is a hydroxyl protecting group,

[0086] To produce a compound of formula IIa:

[0087]

[0088] (b) reducing the compound of formula IIa to produce a compound of formula IIIa:

[0089]

[0090] (c) deprotecting the compound of formula IIIa to produce compound 2:

[0091] as well as

[0092] (d) precipitating or crystallizing compound 2 in the presence of a catalyst to produce compound 1:

[0093]

[0094] or its salts;

[0095] The method comprises one or more of the following, in any combination:

[0096] (i) wherein the hydrogenation step (a) is carried out under a hydrogen atmosphere using a palladium catalyst;

[0097] (ii) wherein the reducing step (b) is carried out at a temperature of about -12°C to about -5°C;

[0098] (iii) wherein the deprotection step (c) is carried out in the presence of an organic base; and / or

[0099] (iv) wherein the post-treatment of the deprotected compound from the deprotection step (c) is carried out under non-aqueous conditions. In some embodiments, the present invention further comprises a step wherein the final product is recrystallized, and the recrystallization is carried out at a pH of about 6.0 to about 7.4, and by dissolving the final product at a temperature of about 50° C. to about 55° C. to produce a solution and then cooling the solution to about 5° C.

[0100] Starting compounds of Formula IV can be obtained commercially, for example, from Aurora Fine Chemicals (San Diego, CA), or synthesized by known methods, for example as disclosed in Wheeler et al., J. Labeled Compounds Radiopharm. 29:583 (1991) and Chou et al., Synthesis 6:565 (1992), which are incorporated herein by reference in their entirety.

[0101] In step (a), the hydrogenation of the compound of formula IV to produce the compound of formula IIa can be carried out by methods known in the art, for example, as disclosed in U.S. Patent No. 8,268,800 and / or patent publication WO 2015 / 066162, the disclosure of which is incorporated herein by reference in its entirety. For example, this step can be carried out under catalytic transfer hydrogenation conditions, for example, in the presence of palladium on carbon (Pd / C), for example, in the presence of about 5% Pd / C. The amount of the catalyst used in the hydrogenation step (a), for example, Pd / C, can be any catalytically effective amount, for example, a catalytic amount of no more than 0.1 parts by weight of the compound of formula IV per 1 part by weight. In some embodiments, the amount of Pd / C used in the hydrogenation step (a) can be, for example, about 0.025 to about 0.05 parts of Pd / C per 1 part by weight of the compound of formula IV. Hydrogenation can be carried out by heating the compound of formula IV to reflux, for example with formic acid and hydrochloric acid or with hydrogen (for example, at about 2 to about 4 bar hydrogen pressure) and optionally with acetic acid) in a solvent such as ethyl acetate aqueous solution. Hydrogenation can be carried out at a temperature of about 0°C to about 100°C, for example, about 50°C to about 80°C, for example, about 63°C to about 77°C, for example, about 68°C for about 0.5-48 hours, for example, about 5 to about 24 hours, about 10 to about 20 hours, about 15 to about 20 hours, or any value or range therein, for example, about 24 hours. Reagents (for example, palladium and charcoal) used to affect hydrogenation can be added after the reaction mixture reaches an elevated temperature (for example, about 50°C to about 80°C, or about 68°C). After completion, the catalyst can be removed, for example, by filtering at, for example, about 60°C to about 70°C, and washed, for example, with ethyl acetate. After separation of the organic layer, it can be washed with, for example, aqueous potassium carbonate solution, aqueous sodium bicarbonate solution and / or aqueous NaCl solution. The volume of the organic layer can be reduced (e.g., by distillation), and the residue heated (e.g., at about 70°C) until dissolved and cooled (e.g., to about 45°C to about 55°C), seeded with the product and stirred, for example, for about 1 hour, for example, at about 45°C to about 55°C. The volume of the reaction mixture can be reduced (e.g., by distillation), and methyl tert-butyl ether can be slowly added at a temperature of about 40°C to about 50°C, and the reaction mixture can be slowly cooled to about 0°C to about 10°C. The resulting suspension can be stirred, for example, for about 2 to about 16 hours, and then filtered. The filtrate can be washed with, for example, methyl tert-butyl ether, optionally cooled to about 0°C to about 10°C.

[0102] Alternatively, the filtrate from the hydrogenation reaction can be washed (e.g., with acetic acid), heated (e.g., to about 80° C.) to dissolve and water added (e.g., preheated to about 80° C.) After cooling, the precipitate can be collected by filtration, washed (e.g., with water and ethanol) and dried.

[0103] The solvent used for hydrogenation step (a) herein can be any conventional solvent that does not cause adverse effects in the reaction.The limiting examples of such solvent for hydrogenation include water, alcohol (such as methanol, ethanol, isopropanol, n-butanol, trifluoroethanol, ethylene glycol), ether (such as tetrahydrofuran, dioxane, diethyl ether, diglyme), ester (such as methyl acetate, ethyl acetate), other organic solvents and / or a mixed solvent of two or more solvents as disclosed herein.Reaction can be preferably carried out in the presence of organic acid such as formic acid, acetic acid, oxalic acid, maleic acid, fumaric acid, malic acid, tartaric acid, citric acid, succinic acid and / or benzoic acid.In some embodiments, hydrogenation can be carried out in a mixed solvent including ethyl acetate, acetic acid and water.

[0104] In some embodiments, hydrogenation can be carried out under increased pressure (relative to ambient pressure), such as an increased pressure of about 0.1 to about 1 MPa (MPa), such as about 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.96, 0.97, 0.98, 0.99 or 1MPa or any value or range therein. In some embodiments, hydrogenation step (a) can be carried out under ambient pressure (e.g., atmospheric pressure, e.g., normal pressure). In some embodiments, hydrogenation step (a) can be carried out under an increased pressure of about 0.1 to about 0.85MPa, or about 0.15 to about 0.73MPa, or about 0.1 to about 0.5MPa.

[0105] The reduction of the compound of formula IIa in step (b) to the compound of formula IIIa can be carried out by methods known in the art, for example, as disclosed in U.S. Patent No. 8,268,800 and / or patent publication WO 2015 / 066162. For example, it can be reduced with a reducing agent such as sodium borohydride in an organic solvent such as a mixture of dichloromethane and ethanol. The reduction can be carried out at any suitable temperature, for example, about -5°C to about 10°C, for example, about 0°C to about 5°C, for about 0.5 to 3 hours, for example, about 1.5 hours.

[0106] In some embodiments, the reduction can be carried out at a temperature of about -12°C to about -3°C, for example, about -12, -11, -10, -9, -8, -7, -6, -5, -4 or -3°C or any value or range thereof. In some embodiments, the reduction can be carried out at a temperature of about -11°C to about -3°C, about -12°C to about -5°C, about -11°C to about -5°C or about -10 to about -6°C, or at a temperature of about -8°C. The present invention is based in part on the following unexpected discovery: abnormally cold conditions (e.g., a temperature of about -11°C to about -5°C) minimize the formation of impurities such as but not limited to DPU and DCU and indirect CYU (which is produced by conversion of DCU in a subsequent step) that cannot be further removed well in the production of compound 1. The structures of exemplary impurities are shown in Table 1.

[0107] Table 1: Examples of impurity reduction (Bz = benzoyl)

[0108]

[0109]

[0110] Reduction can be optionally carried out in the presence of cerium trichloride. In one embodiment, the amount of cerium chloride is about 50mol% (e.g., 50mol%). In another embodiment, the amount of cerium chloride is about 20mol% or about 10mol% (e.g., 20mol% or 10mol%). After adding cerium chloride (III), the reaction can be heated (e.g., to about 15°C to about 25°C) for example about 20 minutes before cooling.

[0111] After reduction, the reaction can be quenched, for example, with acetone, and the solution can be neutralized with an acid, such as citric acid. The organic layer of the compound comprising formula IIIa can be separated and washed, for example, with water. The organic layer can be heated (for example, to about 20°C to about 30°C) and the pH can be adjusted with an acid (for example, citric acid), and the steps are repeated until the pH is stable. The organic phase can be washed, for example, with sodium bicarbonate at a temperature of about 20°C to about 35°C, and then washed with water at a temperature of about 0°C to about 10°C. The volume of the organic phase can be reduced (for example, by distillation), methyl tert-butyl ether can be added, and the resulting precipitate can be collected, washed with methyl tert-butyl ether cooled to about 0°C to about 10°C, and dried.

[0112] The compound of formula IIIA may be deprotected in step (c) to produce compound 2 by methods known in the art, such as methods disclosed in U.S. Pat. No. 8,268,800 and / or patent publication WO2015 / 066162. For example, the deprotection may be carried out in the presence of a weak base such as ammonium hydroxide in a solvent such as methanol. In some embodiments, the deprotection may be carried out in the presence of an organic base, such as one or more bases selected from the group consisting of DBU, trimethylamine, N,N-dimethyl-4-aminopyridine (DMAP) and 1,3-diazabicyclo[2.2.2]octane (DABCO). In some embodiments, the deprotection may be carried out in the presence of ammonia in a solvent such as methanol, for example at a temperature of about 20°C to about 30°C. The amount of the organic base used for deprotection should not be limited as long as it is the necessary amount and does not cause any adverse effects, for example, does not cause side reactions. In some embodiments, the amount of the organic base used for deprotection can be about 0.01 to about 2.2 moles per mole of the compound of Formula IIIa (e.g., about 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.15, 2.16, 2.17, 2.18, 2.19 or 2.2 moles per mole of the compound of Formula IIIa, or any value or range thereof). For example, in some embodiments, the deprotection step (c) can be carried out in the presence of about 0.01 to about 2.2 moles of organic base per mole of compound of formula IIIa, or about 0.05 to about 2.0 moles of organic base per mole of compound of formula IIIa, or about 1.0 to about 1.9 moles of organic base per mole of compound of formula IIIa. The deprotection can be carried out for about 12-48 hours, for example, about 24 hours. After deprotection, the mixture can be concentrated, dissolved in an aqueous solvent such as water, and washed with an organic solvent such as ethyl acetate.

[0113] In some embodiments, after deprotection, post-treatment can be carried out under non-aqueous conditions, for example, using an evaporative solvent exchange process. The inventors of the present invention have found that the use of a non-aqueous evaporative solvent exchange process forms a non-sticky solid and avoids hydrolytic instability and dimer formation. In some embodiments, deprotection can be further followed by additional grinding to remove impurities, such as genotoxic impurities, such as but not limited to benzamide. In some embodiments, deprotection in non-aqueous post-treatment can be carried out with isopropanol and / or acetonitrile.

[0114] In some embodiments, non-aqueous post-treatment can be performed by reducing the volume of the reaction mixture (e.g., by distilling under reduced pressure), adding methanol and continuing to reduce the volume, adding isopropanol and acetonitrile and continuing to reduce the volume, then adding acetonitrile and continuing to reduce the volume. The reaction can then be cooled, for example, to about 0°C to about 10°C, for example, over 1-2 hours, and maintained for example 1-6 hours. The solid product can be collected and washed with acetonitrile.

[0115] The precipitation or crystallization of compound 2 to produce compound 1 in step (d) can be carried out as described above.

[0116] In some embodiments, the precipitation or crystallization of Compound 2 to produce Compound 1 in step (d) can be performed by suspending the compound in the presence of DBU, acetic acid, trifluoroacetic acid, diisopropylethylamine and / or ammonium hydroxide, optionally under cooling.

[0117] In some embodiments, the method of the present invention may include steps (a) to (d), wherein the reduction step (b) is carried out at a temperature of about -12°C to about -3°C, thereby minimizing the formation of DCU and DPU and indirect CYU. CYU is not well purged from the rest of the synthesis. In some embodiments, the method of the present invention may further include post-treatment of the deprotected compound from the deprotection step (c) under non-aqueous conditions (e.g., evaporative solvent exchange) to produce a non-sticky solid and / or avoid hydrolytic instability and / or dimer formation. In some embodiments, the method of the present invention may further include, wherein the deprotection step (c) further includes a grinding step to remove genotoxic impurities such as benzamide. In some embodiments, the method of the present invention may further include recrystallization of the final product, wherein the recrystallization is carried out at a pH of about 6.0 to about 7.4 and a temperature of about 50°C to about 55°C.

[0118] In some embodiments, the method of the present invention may include the steps of (a) to (d), wherein the hydrogenation step (a) is carried out using a palladium catalyst under a hydrogen atmosphere, and / or wherein the deprotection step (c) is carried out in the presence of an organic base. In particular, with respect to step (a), WO 2015 / 066162, as an improved method disclosed in U.S. Patent No. 8,268,800, successfully carried out high-yield hydrogenation by protecting a hydroxyl group, and then by carrying out a hydrogenation step with a large amount of formic acid in the presence of considerable Pd / C, but from the perspective of industrial production, the improved step of WO 2015 / 066162 still has other disadvantages, such as the large-scale use of expensive Pd / C, and the large-scale use of formic acid that is not suitable as an industrial production reagent. The present invention is carried out by carrying out the hydrogenation step (a) in a hydrogen atmosphere in the presence of a catalytic amount of a palladium catalyst, so that the hydrogenation step can be carried out with high yield and high purity. In addition, the deprotection reaction in WO 2015 / 066162 requires a long time with ammonia, which is troublesome for industrial-scale production and produces impurities that are difficult to remove. Compared with U.S. Patent No. 8,268,800, the hydrogenation step is carried out in the presence of a large amount of expensive rhodium catalyst under unprotected hydroxyl groups, resulting in, for example, high manufacturing costs, low product purity and difficulty in purification by chromatography. The problems of the above-mentioned WO 2015 / 066162 and U.S. Patent No. 8,268,800 are overcome by the invention as disclosed herein.

[0119] use

[0120] Compound 1 or a pharmaceutically acceptable salt thereof produced by the present invention can be used to inhibit CDA activity. Compound 1 or a pharmaceutically acceptable salt thereof can be in the form of a pharmaceutical composition, for example, together with a pharmaceutically acceptable excipient. In some embodiments, Compound 1 or a pharmaceutically acceptable salt thereof can be used in combination with a CDA substrate drug, such as a CDA substrate drug that can be used to treat cancer, in a method for treating cancer in a subject in need thereof. Examples of CDA substrate drugs include, but are not limited to, decitabine, 5-azacytidine, gemcitabine, ara-C, tezacitabine, 5-fluoro-2'-deoxycytidine, and cytochlor. In some embodiments, the cancer can be selected from the group consisting of a blood cancer and a solid cancer. In certain embodiments, the blood cancer can be myelodysplastic syndrome or a leukemia, such as acute myeloid leukemia or chronic myeloid leukemia. In certain embodiments, the solid cancer can be pancreatic cancer, ovarian cancer, peritoneal cancer, non-small cell lung cancer, metastatic breast cancer, bladder cancer, squamous cell carcinoma, transitional cell carcinoma, adenocarcinoma, gynecological cancer, fallopian tube cancer, liver cancer, hepatocellular carcinoma, lung cancer, cervical cancer, genitourinary tract cancer or gastrointestinal cancer. In some embodiments, Compound 1 or a pharmaceutically acceptable salt thereof can be administered substantially simultaneously with a CDA substrate drug, before a CDA substrate drug, or after a CDA substrate drug, optionally in a single unit dosage form or in a plurality of separate unit dosage forms. Embodiments according to the present invention are described below in non-limiting examples.

[0121] Example

[0122] Example 1. Hydrogenation step (a)

[0123] The hydrogenation of the compound of formula IV (1 equivalent) to produce the compound of formula IIa in step (a) is carried out at least 12 hours in the presence of Pd / C (5%, 0.05 g / g) in water (1.98 g / g) at a temperature of 63° C. to 77° C. with hydrogen and acetic acid (80%, 2.62 g / g) under 2 to 4 bar hydrogen pressure in ethyl acetate (8.97 g / g). After completion, the catalyst is removed by filtration, and the filter cake is washed with ethyl acetate (6.73 g / g). After cooling, the filtrate is washed with potassium carbonate aqueous solution. The organic phase is washed with sodium bicarbonate aqueous solution (7% w / w, 5.38 g / g) and with NaCl aqueous solution (10% w / w, 3 g / g). The organic layer is distilled to a residual volume of about 8 volumes, and the residue is heated to 70° C. until dissolved and cooled to 45° C. to 55° C. The reaction was seeded with a compound of formula IIa, and the reaction mixture was distilled to a residual volume of about 2 volumes, and methyl tert-butyl ether (4.44 g / g) was slowly added at a temperature of 40°C to 50°C. After the mixture was cooled, the precipitated crystals were collected on a filter, washed with methyl tert-butyl ether (1.48 g / g) cooled to 0°C to 10°C, and the product was dried to obtain formula IIa. Yield: 86%. Chemical purity: 98.9%.

[0124] Example 2. Reduction of impurities during reduction step (b)

[0125] The compound of formula IIa (1 equivalent) is dissolved in dichloromethane (14.6 g / g) and stirred. Ethanol (5.83 g / g) is added, and the reaction mixture is cooled to -5°C to 5°C. Cerium (III) chloride heptahydrate (0.08 g / g) is added, and the reaction is heated to 15°C to 25°C. Water (0.68 g / g) is then added, and the reaction is stirred for at least 20 min, and then cooled to 0°C to -11°C. Keeping the temperature at 0°C to -11°C, sodium borohydride (0.11 g / g) is added in batches, and the reaction is stirred until completed. Keeping the temperature at 0°C to -11°C, acetone (0.73 g / g) is added. An aqueous solution of citric acid (3.7 to 4.4% w / w) is slowly added until a pH of 6.5 to 7.5 is reached. Each phase is settled and the aqueous phase is separated. The organic phase is washed with an aqueous solution of sodium bicarbonate, and then further washed with water. Separate the phases and further wash the organic phase with water. The organic phase is vacuum distilled at ≤35°C until the volume is about 2 volumes, then methyl tert-butyl ether (7.38g / g) is added and vacuum distilled at ≤35°C until the volume is 4.8 volumes. A second portion of methyl tert-butyl ether (3.7g / g) is added and vacuum distilled at ≤30°C until the volume is 4.8 volumes. Additional methyl tert-butyl ether (2.67g / g) is added, and the reaction mixture is cooled to 0°C to 10°C in ≥4h. Additional methyl tert-butyl ether (0.89g / g) is added, and the reaction mixture is stirred at this temperature, and then the solid product is separated and washed with methyl tert-butyl ether (1.46g / g) precooled to 0°C to 10°C, and the product is dried to obtain Formula IIIa. Yield: 76%. Chemical purity: 93%.

[0126] The process of entries 1-5 was carried out in a similar manner as described above, except that the reduction temperature was changed to 0°C, -3°C, -5°C, -8°C and -11°C, respectively. As shown in Table 2, the lower temperature minimized the formation of DCU, DPU and CYU. The structures of the impurities are shown in Table 1.

[0127] Table 2

[0128]

[0129] Example 3. Improvement during the deprotection step (c)

[0130] Deprotection was performed in a solution of ammonia (0.87 g / g) in methanol (4.95 g / g). Compound of formula IIIa (1 equivalent) and additional methanol (1.58 kg / kg) were added. The reaction mixture was adjusted to 20°C to 30°C and stirred at this temperature until completion. Post-treatment was performed by distilling the reaction mixture under reduced pressure until the residual volume was about 3 volumes. Methanol (1.58 g / g) was added and distillation continued under reduced pressure until the residual volume was about 3 volumes. Isopropanol (1.92 g / g) was added, followed by acetonitrile (3.93 g / g), and distillation continued under reduced pressure until the residual volume was about 3 volumes. Acetonitrile (5.51 g / g) was added and distilled under reduced pressure until a residual volume of 5 volumes was reached. Additional acetonitrile (1.58 g / g) was added and distilled under reduced pressure until a residual volume of about 5 volumes was reached. After cooling the mixture, the solid product was separated and washed with acetonitrile (1.56 g / g) precooled to 0°C to 10°C. The wet product was mixed with acetonitrile (2.37 g / g). After the mixture was cooled, the wet product was then dried to obtain Compound 2. Yield: 87%. Chemical purity: 97%.

[0131] Reference Example 4. Original Deprotection Step (c)

[0132] Deprotection was performed by treatment with ammonia (7.0 M in methanol, 25 equivalents). The mixture was stirred at 25 ° C for 27 h, and then concentrated under reduced pressure. The residue was dissolved in water (6.3 volumes) and washed twice with ethyl acetate (5.7 volumes each time). The aqueous layer was concentrated under reduced pressure at a temperature below 35 ° C to give compound 2 (95% yield).

[0133] When proceeding using typical process conditions, compound 2 generated from the original deprotection conditions generally afforded compound 1 which was generally of lower overall purity and with significantly higher amounts of impurities. See Table 3, entries 1 and 2.

[0134] Example 5. Highly specific crystallization conditions at high temperatures

[0135] Crystallization conditions for Compound 1 were tested for improved purity. Highly specific crystallization conditions were found to produce very pure material, improve particle size distribution control to an optimal (unimodal) range, lower acetonitrile levels, and avoid dimerization impurities. Specific conditions included the use of higher temperatures and adjustments to pH.

[0136] The preferred procedure for recrystallization of compound 1 is carried out by mixing compound 2 (1 equivalent), 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU, 0.028 g / g), acetonitrile (5.02 g / g) and water (0.73 g / g) and stirring at 15°C to 25°C for 2 hours. The mixture is cooled to 0°C to 10°C within ≥1 hour and maintained at this temperature for 1 to 8 hours. The solid product is collected by filtration and washed with acetonitrile:water (0.21 g / g:0.033 g / g) cooled to 0°C to 10°C. The wet product and acetonitrile (2.36 g / g) are stirred at 0°C to 10°C for 30 min to 8 hours. The solid product is collected and washed with acetonitrile (0.78 g / g) cooled to 0°C to 10°C. The wet product is dried to give crude compound 1. Yield: 80%. Chemical purity: 94%.

[0137] Crude compound 1 (1 equivalent), acetone (6.26 g / g) and water (2 g / g) were mixed at a temperature of 20°C to 30°C. The pH of the reaction mixture was adjusted to 6.0 to 7.5 with an aqueous solution of formic acid (0.0076 g / g formic acid in 1.25 g / g water). If necessary, the pH can be adjusted to the target range using an aqueous solution of 1,8-diazabicyclo[5,4,0]undec-7-ene DBU (0.041 g / g DBU in 0.78 g / g water). The reaction mixture was heated to 50°C to 55°C until complete dissolution was observed and filtered into a reactor set to 40°C to 50°C and washed with a mixture of water (0.1 g / g) and acetone (0.31 g / g). The solution was cooled to 33°C to 43°C and seeded with 0.005 g / g of compound 1. The reaction was maintained at this temperature and then cooled to -10°C to 0°C. The suspension was kept at -10°C to 0°C for 12 to 16h and separated by filtration. The product was washed with acetone (0.78g / g) and dried to give compound 1. Yield: 61%. Chemical purity excluding diastereomers: 99.6%. Compound 6 of the following formula, which is a diastereomer of compound 1, was produced in the following ratio. Compound 1: Compound 6 = 99.6: 0.4. (PSD: D(0.9) = 252μm, D(0.5) = 125μm, D(0.1) = 21μm).

[0138] Example 6. Comparison with the original purification process

[0139] Crude compound 1 (1 equivalent) is suspended in a mixture of acetone (2.5ml / g) and water (2.5ml / g) and stirred at 25±2°C for 2 hours. The mixture is cooled to 5±2°C and stirred for 2 hours, and then filtered. The filter cake is rinsed with acetone (2x0.55ml / g), and then vacuum dried at 55°C. Compound 1 is provided in a yield of 67%. Chemical purity excluding diastereomers: 99.4%. Compound 6 of the following formula as a diastereomer of compound 1 is produced in the following ratio. Compound 1: Compound 6 = 98.7: 1.3.

[0140] The overall purity of compound 1 and the ratio to compound 6 were lower in the original process compared to the updated purification process. The impurity profile is shown in Table 3. The structures of the monitored impurities are shown in Table 4.

[0141] Table 3

[0142]

[0143] ND = not detected.

[0144] Table 4

[0145]

[0146] Example 7. Alternative methods for steps (a) and (c)

[0147] Step (a):

[0148]

[0149] A mixture of compound (2-1) (20.0 g, 42.4 mmol), ethyl acetate (200 mL), acetic acid (80 mL) and water (50 mL) was dissolved at 50 to 60 ° C under a nitrogen atmosphere under stirring, and then 0.2 g of Pd / C (10% by weight, 5 wt% on a dry basis, 50% water-wet, NEs-5DR type) was added thereto and the atmosphere in the reaction vessel was replaced with nitrogen. Subsequently, the atmosphere was replaced with hydrogen, and the reaction mixture was stirred at 50 to 60 ° C for 18 hours under an increased hydrogen pressure (0.5 MPa). The reaction mixture was filtered and the residue on the filter was washed with 20 mL of 80% acetic acid. The ethyl acetate (100 Torr, 50 ° C) in the filtrate was removed by vacuum. The residual solution was heated to 80 ° C to dissolve, and 400 mL of water preheated to 80 ° C was added thereto. After cooling the mixture, the precipitated crystals were collected on a filter, washed with water and ethanol, and dried to obtain 19.24 g of compound (3-1) (yield: 95.6%, chemical purity: 98.4%).

[0150] Steps (b) and (c)

[0151]

[0152] Synthesis of compound (4-1): Compound (3-1) (19.0 g, 40.0 mmol) was dissolved in dichloromethane (228 mL) under stirring. Ethanol (152 mL) and cerium (III) chloride heptahydrate (1.49 g, 4.0 mmol) were added to the solution, and the mixture was cooled to a temperature below 6 ° C. A solution of sodium borohydride (3.77 g, 100 mmol) in water (19 mL) was added dropwise to the cooled mixture while keeping its temperature below 6 ° C. After addition, the reaction mixture was reacted at a temperature below 6 ° C for 2 hours. Keeping the temperature of the reaction mixture below 6 ° C, the stirred reaction mixture was quenched with 9.5 mL of acetone, and then 114 mL of 0.5 M hydrochloric acid aqueous solution was added thereto while keeping its temperature below 6 ° C to adjust the quenched mixture to pH 7. After the mixture was warmed to 30 to 40 ° C, 114 mL of saturated sodium bicarbonate aqueous solution was added to the mixture. The mixture was separated with a separatory funnel, the organic layer was washed with 114 mL of water, and the solvent was removed in vacuo (50 Torr, 40° C.) The obtained compound (4-1) was used in the next step without purification.

[0153] Synthesis of compound 5: Methanol (190 mL) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.30 mL, 2.0 mmol) were added to the compound (4-1) obtained in step (b), and the reaction mixture was warmed to 40°C and stirred at 40°C for 3 hours. After the reaction, methanol was removed in a vacuum (50 torr, 40°C), and 95 mL of acetonitrile was added to the residual solution. After cooling, the precipitated crystals were collected on a filter, washed with cooled acetonitrile, and dried to obtain 8.96 g of compound 5 (yield: 83.4%, chemical purity: 97.1%).

[0154] Step (d)

[0155]

[0156] Synthesis of crude compound (1): A mixture of compound (5) (0.9 g, 3.35 mmol), acetonitrile (5.8 mL), water (0.65 mL) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.025 mL, 0.17 mmol) was suspended, and the suspension was stirred at 20 to 30° C. for 48 hours. After cooling, the precipitated crystals were collected on a filter, washed with cooled 90% acetonitrile and acetonitrile, and dried to obtain 0.66 g of compound 1 (yield: 73.0%, chemical purity: 98.3%). Compound 5: Compound 6 (dimer of compound 5) = 98.9: 1.1.

[0157] Purification of crude compound 1: Compound 1 (0.3 g, 1.11 mmol) was suspended in a mixture of acetonitrile (0.96 mL) and water (0.24 mL), and the suspension was stirred at 40 to 50 ° C for two hours. Then, the suspension was stirred at a temperature below 5 ° C for two hours. The resulting precipitate was collected on a filter, washed with cooled 90% acetonitrile and acetonitrile, and dried to give 0.66 g of compound 1 (yield: 73.5%, chemical purity: 99.6%). Compound 6 of the following formula, which is a diastereomer of compound 1, was produced in the following ratio. Compound 1: Compound 6 = 99.7: 0.3.

[0158]

[0159] The total amount of impurities contained in the purified compound 1 is 0.46% (by area percentage). Separately, compound 1 is prepared and purified from the same material by the method disclosed in patent document 2 (WO 2015 / 066162), but the total amount of impurities therein (2.46%) is higher than the total amount of impurities of the above method, which means that the method of the present invention can provide a method for preparing compound 1 with a higher yield.

[0160] Implementation

[0161] Embodiments of the present invention include, but are not limited to, the following.

[0162] 1. A method for producing compound 1 or a salt thereof:

[0163]

[0164] The following steps are involved:

[0165] (a) hydrogenating a compound of formula IV:

[0166]

[0167] Wherein R is a hydroxyl protecting group,

[0168] To produce a compound of formula IIa:

[0169]

[0170] (b) reducing the compound of formula IIa to produce a compound of formula IIIa:

[0171]

[0172] (c) deprotecting the compound of formula IIIa to produce compound 2:

[0173] as well as

[0174] (d) precipitating or crystallizing compound 2 in the presence of a catalyst to produce compound 1:

[0175]

[0176] or its salts;

[0177] The method comprises one or more of the following, in any combination:

[0178] (i) wherein the hydrogenation step (a) is carried out under a hydrogen atmosphere using a palladium catalyst;

[0179] (ii) wherein the reducing step (b) is carried out at a temperature of about -12°C to about -5°C;

[0180] (iii) wherein the deprotection step (c) is carried out in the presence of an organic base; and / or

[0181] (iv) wherein the deprotection step (c) is carried out under non-aqueous conditions.

[0182] 2. The method of embodiment 1, wherein the catalyst is about 1 mol % to about 20 mol % DBU.

[0183] 3. The method of embodiment 2, wherein the catalyst is about 5 mol % to about 10 mol % DBU.

[0184] 4. The method of embodiment 3, wherein the catalyst is about 5 mol% DBU.

[0185] 5. The method of embodiment 1, wherein the catalyst is acetic acid, trifluoroacetic acid, diisopropylethylamine, or ammonium hydroxide.

[0186] 6. The method according to embodiments 1-5, wherein the deprotection step (c) further comprises a grinding step.

[0187] 7. The method according to embodiments 1-6, further comprising recrystallizing or slurrying Compound 1.

[0188] 8. The method of embodiment 7, wherein the recrystallization is performed at a pH of about 6.0 to about 7.4 and a temperature of about 50°C to about 55°C.

[0189] 9. The method according to embodiments 1-8, wherein step (d) is performed in the presence of a solution comprising acetonitrile.

[0190] 10. The method according to embodiments 1-8, wherein step (d) is performed in the presence of a solution comprising acetone or tetrahydrofuran.

[0191] 11. The method according to embodiments 1-10, wherein step (b) is carried out in CeCl 3 In the presence of.

[0192] 12. The method of embodiments 1-11, wherein R is a benzoyl group.

[0193] 13. The method according to embodiments 1-12, wherein the palladium catalyst used in step (i) is palladium on carbon (Pd / C).

[0194] 14. The method according to embodiment 13, wherein the amount of Pd / C used in step (i) is a catalytic amount of no more than 0.1 parts by weight per 1 part by weight of the compound of formula IV.

[0195] 15. The method according to embodiment 13, wherein the amount of the Pd / C used in step (i) is 0.025 to 0.05 parts by weight per 1 part by weight of the compound of formula IV.

[0196] 16. The method according to embodiments 1-15, wherein step (i) is carried out in a mixed solvent comprising ethyl acetate, acetic acid and water.

[0197] 17. The method of embodiments 1-16, wherein step (i) is performed under ambient pressure or increased pressure.

[0198] 18. The method of embodiments 1-17, wherein step (i) is performed under an increased pressure of 0.1 to 0.5 MPa.

[0199] 19. The method according to embodiments 1-18, wherein the organic base used in step (iii) is one or more bases selected from the group consisting of DBU, triethylamine, DMAP and DABCO.

[0200] 20. The method according to embodiments 1-19, wherein the amount of the organic base used in step (iii) is 0.01 to 2.2 moles per mole of the compound of formula IIIa.

[0201] 21. The method according to embodiments 1-20, wherein the organic base used in step (iii) is DBU.

[0202] 22. A composition of compound 1 or a salt thereof:

[0203]

[0204] Contains fewer than 10, 9, 8, 7, 6 or 5 measurable impurities.

[0205] 23. The composition of claim 24, wherein impurities are absent at levels greater than 0.5 wt%, 0.25 wt%, 0.2 wt%, 0.15 wt%, 0.1 wt%, 0.05 wt% or 0.01 wt%.

[0206] 24. A composition of compound 1 or a salt thereof:

[0207]

[0208] There are no impurities present at levels greater than 0.5 wt%, 0.25 wt%, 0.2 wt%, 0.15 wt%, 0.1 wt%, 0.05 wt% or 0.01 wt%.

[0209] 25. The composition of claim 26 comprising less than 10, 9, 8, 7, 6 or 5 measurable impurities.

[0210] The foregoing is illustrative of the present invention and is not to be construed as limiting the present invention. The present invention is defined by the following claims, with equivalents of the claims to be included therein.

[0211] All publications, patent applications, patents, and other references cited herein are incorporated by reference in their entirety for the teachings relevant to the sentence and / or paragraph in which the reference is presented.

Claims

1. A method for producing compound 1 or a salt thereof: The following steps are involved: (a) hydrogenating a compound of formula IV: wherein R is a hydroxy protecting group to produce a compound of formula IIa: (b) reducing the compound of formula IIa to produce a compound of formula IIIa: (c) deprotecting the compound of formula IIIa to produce compound 2: as well as (d) precipitating or crystallizing compound 2 in the presence of a catalyst to produce compound 1: or its salts; The method comprises the following steps: (i) wherein the hydrogenation step (a) is carried out under a hydrogen atmosphere using a palladium catalyst; (ii) wherein the reducing step (b) is carried out at a temperature of -12°C to -6°C; (iii) wherein the deprotection step (c) is carried out in the presence of an organic base, wherein the organic base comprises an amine base in the presence of methanol; (iv) wherein the work-up of the deprotected compound from the deprotection step (c) is carried out under non-aqueous conditions; wherein the non-aqueous conditions of step (iv) are a non-aqueous evaporative solvent exchange process; and The catalyst in step (d) is diazabicyclo(5.4.0)undec-7-ene.

2. The method according to claim 1, wherein the catalyst is 1 mol% to 20 mol% of 1,8-diazabicyclo(5.4.0)undec-7-ene.

3. The method according to claim 2, wherein the catalyst is 5 mol% to 10 mol% of 1,8-diazabicyclo(5.4.0)undec-7-ene.

4. The method according to claim 3, wherein the catalyst is 5 mol% of 1,8-diazabicyclo(5.4.0)undec-7-ene.

5. The method according to claim 1, wherein the deprotection step (c) further comprises a milling step.

6. The method of claim 1, further comprising recrystallizing or slurrying Compound 1.

7. The method according to claim 6, wherein the recrystallization is performed at a pH of 6.0 to 7.4, and is performed by dissolving Compound 1 at a temperature of 50°C to 55°C to produce a solution and then cooling the solution to 5°C.

8. The method of claim 1, wherein step (d) is performed in the presence of a solution comprising acetonitrile.

9. The method of claim 1, wherein step (d) is performed in the presence of a solution comprising acetone or tetrahydrofuran.

10. The method according to claim 1, wherein step (b) is carried out in CeCl 3 In the presence of.

11. The method of claim 1, wherein said R is a benzoyl group.

12. The process according to claim 1, wherein the palladium catalyst used in step (i) is palladium on carbon.

13. The method according to claim 12, wherein the amount of the palladium on carbon used in step (i) is a catalytic amount of no more than 0.1 parts by weight per 1 part by weight of the compound of formula IV.

14. The method according to claim 12, wherein the amount of the palladium on carbon used in step (i) is 0.025 to 0.05 parts by weight per 1 part by weight of the compound of formula IV.

15. The method according to claim 1, wherein step (i) is carried out in a mixed solvent comprising ethyl acetate, acetic acid and water.

16. The method of claim 1, wherein step (i) is performed at ambient pressure or an increased pressure of 0.1 to 1 MPa.

17. The method of claim 1, wherein step (i) is performed under an increased pressure of 0.1 to 0.5 MPa.

18. The method according to claim 1, wherein the amount of the organic base used in step (iii) is 0.01 to 2.2 moles per mole of the compound of formula IIIa.

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