Method and intermediate for preparing carboprost and carboprost tromethamine, and carboprost tromethamine prepared therefrom

Abstract

The present invention relates to a method for preparing carboprost or carboprost tromethamine, an intermediate obtained by the method, and carboprost or carboprost tromethamine free of the 5,6-trans isomer obtained therefrom. The present invention also relates to a novel crystalline form of carboprost tromethamine.

Description

Technical Field

[0001] The present invention relates to a novel method and intermediates for preparing carboprost and carboprost tromethamine, and novel high-melting-point crystals of carboprost tromethamine obtained thereby. Background Art

[0002] As shown in the following Scheme A, carboprost and carboprost tromethamine (INN, trade name Hemabate, Tham) are both synthetic prostaglandin analogs of PGF2α (specifically, 15-methyl-PGF2α) with oxytocin properties. Carboprost and carboprost tromethamine can induce uterine contractions and induce abortion in early pregnancy, and can also reduce postpartum hemorrhage.

[0003] Process A

[0004]

[0005] Despite increasingly stringent regulations limiting the amount of impurities or impurities in active pharmaceutical ingredients (APIs), nearly all commercially available carboprost and carboprost tromethamine still contain approximately 3% of the 5,6-trans isomer and approximately 2% of the 15(R)-epimer. Scheme B below shows the chemical structures of carboprost and its isomers, namely, 5,6-trans carboprost and the 15-epimer carboprost. However, industrial methods for the large-scale production of carboprost or carboprost tromethamine present several challenges, particularly regarding the spatial orientation of the cis-double bond at the C5-C6 position and the tertiary alcohol at the C15 position of carboprost or carboprost tromethamine. Furthermore, current purification methods for removing impurities from carboprost or carboprost tromethamine are ineffective and require improvement.

[0006] Process B

[0007]

[0008] C15-(R / S)-selectivity

[0009] Carboprost tromethamine is an original product of Upjohn. The first large-scale synthesis of carboprost tromethamine was disclosed by Upjohn's chemists (Yankee et al., J. Am. Chem. Soc, 96 (18), 5865-5876, 1974). As shown in the following process C (1), the 15-methyl substituent is constructed from the benzoyl γ-lactone-enone of formula a with trimethylaluminum or with methylmagnesium bromide. However, in both cases the selectivity of the 15(S)-product is only 50%, meaning that this method is not selective. WO2008 / 081191 discloses that the alkylation of the triethylsilyl γ-lactone-enone of formula b with methylmagnesium chloride can obtain the 15(S)-product with a maximum selectivity of 70%, as shown in the following process C (2). WO 2017 / 093770 discloses that the alkylation of p-phenylbenzoyl γ-lactone-enone of formula c with methylmagnesium bromide can yield the 15(S)-product with a selectivity of only 55%. WO 2017 / 093770 also discloses the use of various chiral additives to increase the selectivity of the 15(S)-product, and found that the addition of (S)-Taddol can increase the selectivity to 70%, as shown in the following Scheme C (3). However, the highest selectivity disclosed in WO 2017 / 093770 is at most the same as the selectivity disclosed in WO 2008 / 081191.

[0010] Process C

[0011]

[0012] C5,6-(trans / cis)-selectivity

[0013] WO 2008 / 081191 discloses that the Wittig reaction, as disclosed by Yankee et al., at ambient temperature and in a dimethyl sulfoxide (DMSO) solvent, produces 6% to 8% of the undesired 5,6-trans-isomer, as shown in Scheme D(1) below. WO 2008 / 0181191 further discloses that the reaction at low temperature (i.e., between 5°C and +5°C) can reduce the content of the 5,6-trans-isomer to about 3%, as shown in Scheme D(2) below. In view of the above, since all commercially available carboprost and carboprost tromethamine contain about 3% of the 5,6-trans isomer, it seems that changing the reaction conditions of the Wittig reaction is not useful in further reducing the content of the 5,6-trans isomer produced therefrom.

[0014] Process D

[0015]

[0016] Removal of 15(R)-epimer and trans-isomer by purification of carboprost methyl ester

[0017] As disclosed by Yankee et al. and in Eur. J. Pharm. Sci. 3, 27-38 (1995), the allylic tertiary alcohol at the C15 position of carboprost is extremely unstable; therefore, even small amounts of acid or minimal heat can rapidly produce a large amount of the 15(R)-epimer via epimerization. For this reason, current industrial methods for mass-producing carboprost or carboprost tromethamine do not establish the stereochemistry of the allylic tertiary alcohol in the intermediates formed in the early stages of the process, as the stereochemistry of the allylic tertiary alcohol is difficult to maintain until the final product structure is formed, or establish the stereochemistry of the allylic tertiary alcohol in the intermediates formed in the later stages of the process, or remove the undesired 15(R)-epimer and trans-isomer after the final product is formed.

[0018] Although the final product, carboprost tromethamine, is a crystalline solid at room temperature, it is still extremely difficult to purify it by crystallization alone to effectively remove both the 15(R)-epimer and the trans-isomer. Furthermore, due to the extreme polarity of carboprost, it is even more difficult to remove both the 15(R)-epimer and the trans-isomer from carboprost by chromatography.

[0019] Therefore, the isomers produced during the preparation of carboprost or carboprost tromethamine cannot be effectively removed, and in the prior art methods, there are no late-stage intermediates suitable for separating and removing isomers. In order to purify the final product, two additional steps are required to produce late-stage intermediates suitable for separating and removing isomers. As disclosed in conventional references such as J. Am. Chem. Soc., 96(18), 5865-5876, 1974, WO 2008 / 081191, WO 2017 / 093770, CN 111777537, and CN 102816099, carboprost must be esterified to form carboprost methyl ester, followed by removal of the 15(R)-epimer and trans-isomer of the carboprost methyl ester by chromatography, and hydrolysis of the carboprost methyl ester to form carboprost with higher purity. However, the yield and purity of this method are far from satisfactory. CN 1136938 C discloses the use of expensive and specialized simulated moving bed (SMB) chromatography to separate and remove isomers of carboprost methyl ester, but the purity of the final product is still insufficient. CN 102816099 discloses separation using an analytical-grade HPLC column chromatography packing (5 μm), but the trans isomer cannot be completely removed. In addition, due to the small separation capacity of the method disclosed in CN 102816099, this method is difficult to use for industrial-scale mass production. Summary of the Invention

[0020] In view of the above, it is necessary to research and develop a method for preparing high-purity carboprost or carboprost tromethamine, which can significantly reduce the formation of impurities or isomers including 15(R)-dimer and trans isomer, and can also effectively remove the generated impurities or isomers.

[0021] The object of the present invention is to provide an effective method for forming carboprost or carboprost tromethamine. The method includes a macrolide lactonization step, which can effectively remove the 5,6-trans isomer. The method also includes a methylation step of the macrolide-enone to construct the orientation of the tertiary alcohol at the C15 position of carboprost. In all previous examples, the 15(S)-selectivity of the methylation of the macrolide-enone is much higher than the selectivity of the methylation of the γ-lactone-enone. The present invention also provides a novel purification method that can effectively remove all isomers and can more efficiently produce carboprost and carboprost tromethamine, thereby forming a final product with high purity, high melting point and good stability.

[0022] One aspect of the present invention provides a method for preparing high-purity carboprost or carboprost tromethamine containing no more than about 1% of total isomers from a compound of formula 1a containing about 1% to 10% of the 5,6-trans isomer:

[0023]

[0024] in for or a carbonyl protecting group; and P1 and P2 are H or a hydroxyl protecting group.

[0025] The present invention further provides a method for preparing high-purity carboprost or carboprost tromethamine containing no more than about 1% of total isomers from a compound of formula 1b containing about 1% to 10% of the 5,6-trans isomer.

[0026]

[0027] Wherein P1 and P2 are H or hydroxyl protecting groups.

[0028] The present invention further provides a method for purifying carboprost, which can effectively purify low-purity carboprost containing a large amount of isomers (such as about 1% to 10% of the 5,6-trans isomer and about 1% to 50% of the 15(R)-epimer) into high-purity carboprost containing no more than about 1% of the total isomers.

[0029] The present invention further provides a macrolide-enone intermediate of formula 2a', which is a novel intermediate for preparing carboprost or carboprost tromethamine.

[0030]

[0031] Wherein P1 is H or a hydroxyl protecting group.

[0032] The present invention further provides a method for preparing a macrolide tertiary alcohol of formula 3 from a macrolide-enone of formula 2a' and a methylating agent, which is an intermediate for preparing carboprost or carboprost tromethamine.

[0033]

[0034] Wherein P1 is H or a hydroxyl protecting group.

[0035] The present invention further provides a high melting point (106.4±1°C) crystal of carboprost tromethamine, which has an X-ray powder diffraction (XRPD) pattern exhibiting characteristic peaks at the following 2θ reflection angles: 6.9±0.2°, 10.3±0.2°, 18.8±0.2°, and 21.9±0.2°.

[0036] The present invention further provides a method for preparing high melting point crystals of carboprost tromethamine, which comprises using anhydrous acetonitrile as a solvent.

[0037] Simple diagram description

[0038] Figure 1 The X-ray powder diffraction (XRPD) pattern of the carboprost tromethamine crystals of the present invention is shown.

[0039] Figure 2 The differential scanning calorimetry (DSC) thermogram of the carboprost tromethamine crystals of the present invention is shown.

[0040] Figure 3 Shown are X-ray powder diffraction (XRPD) patterns of five different batches of carboprost tromethamine crystals according to the present invention.

[0041] Figure 4 Differential Scanning Calorimetry (DSC) thermograms of five different batches of carboprost tromethamine crystals according to the present invention are shown.

[0042] Figure 5 Shown is a differential scanning calorimetry (DSC) thermogram of the carboprost tromethamine crystals prepared in Example 9 of the present invention.

[0043] Figure 6 The differential scanning calorimetry (DSC) thermogram of the carboprost tromethamine crystals prepared in Example 10 of the present invention is shown. DETAILED DESCRIPTION

[0044] definition

[0045] When used in conjunction with the term "comprising" in the claims and / or the specification, the use of the words "a" or "an" can mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one." Although the present invention supports definitions referring only to alternatives and "and / or," the use of the term "or" in the claims is intended to mean "and / or" unless explicitly indicated as referring only to alternatives or unless the alternatives are mutually exclusive. Throughout this application, the term "about" is used to indicate that a value includes the inherent variation in error for the device, the method used to determine the value, or the variation that exists among the study subjects.

[0046] As used in this specification and claims, the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include"), or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0047] In the depictions of compounds given in this specification, wedge-shaped bold bonds Meaning a key that projects above the plane of the paper; a wedge-shaped hash key means a key that projects below the plane of the paper; and a wavy key By this is meant a key that projects almost half above and half below the plane of the paper.

[0048] As used herein, the term "high purity carboprost or carboprost tromethamine," "high purity carboprost," or "high purity carboprost tromethamine" means that the referenced carboprost and / or carboprost tromethamine contains no more than about 1% total isomers, preferably no more than about 0.8% total isomers or no more than about 0.5% total isomers, and more preferably no more than about 0.3% total isomers. The isomers, impurities, or impurities indicated herein include the 5,6-trans isomer, the 15(R)-epimer, and any other stereoisomers.

[0049] As used herein, the term substantially free of the 5,6-trans isomer or the like means that the referenced compound contains no more than about 0.5%, no more than about 0.3%, no more than about 0.2%, no more than about 0.1%, no more than about 0.05%, or no more than about 0.03% of an impurity or isomer such as the 5,6-trans isomer, or contains an undetectable amount of an impurity or isomer such as the 5,6-trans isomer as measured by HPLC, for which the limit of detection does not exceed about 0.03%.

[0050] Unless otherwise specified, the term "hydroxy protecting group" has the meaning conventionally defined in organic synthetic chemistry, i.e., a group capable of protecting a hydroxyl group or moiety of a compound from attack by chemical reactions. Examples of hydroxy protecting groups include, but are not limited to, methoxymethyl, methoxythiomethyl, 2-methoxyethoxymethyl, bis(2-chloroethoxy)methyl, tetrahydropyranyl, tetrahydrothiopyranyl, 4-methoxytetrahydropyranyl, 4-methoxytetrahydrothiopyranyl, tetrahydrofuranyl, tetrahydrothiofuranyl, 1-ethoxyethyl, 1-methyl-1-methoxyethyl, trityl, allyl, benzyl, substituted benzyl, acetyl, substituted acetyl, benzoyl, substituted benzyl, and SiRaRbRc, wherein Ra, Rb, and Rc are each independently unsubstituted or substituted alkyl or unsubstituted or substituted aryl, such as C 1-4 alkyl, phenyl, benzyl, substituted phenyl, and substituted benzyl.

[0051] Unless otherwise specified, the term "carbonyl protecting group" has the meaning conventionally defined in organic synthetic chemistry, i.e., a group capable of protecting the carbonyl group or moiety of a compound from attack by chemical reactions. Examples of carbonyl protecting groups include, but are not limited to, dialkyl ketals, diaralkyl ketals, diacetyl ketals, dithioketals, 1,3-dithioketals, Alkanes, 1,3-dioxolanes, 1,3-dithiazoles (1,3-dithiane), 1,3-dithiolane and 1,3-oxathiolane. Preferred carbonyl protecting groups include dialkyl ketals, 1,3-dithiolane, Alkanes and 1,3-dioxolane.

[0052] Each of the above-mentioned groups, such as alkyl and aryl, may be optionally substituted with one or more substituents selected from the group consisting of halogen, alkyl, aryl, alkoxy, aryloxy, thioalkoxy, thioaryloxy, alkylamino, arylamino, cyano, alkoxycarbonyl, arylcarbonyl, arylaminocarbonyl, alkylaminocarbonyl, and carbonyl, or a heterocyclic group selected from the group consisting of pyridyl, thienyl, furyl, imidazolyl, morpholinyl, As used herein, the term "alkyl" refers to a straight or branched hydrocarbon group containing 1 to 8, 1 to 6, or 1 to 4 carbon atoms, such as methyl, ethyl, isopropyl, tertiary butyl, and the like; or a cyclic saturated hydrocarbon group having 3 to 10 or 3 to 8 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, and the like. As used herein, the term "aryl" refers to a monocyclic or polycyclic aromatic hydrocarbon group having 6 to 20, 6 to 18, or 6 to 12 carbon atoms, such as phenyl, naphthyl, anthracenyl, phenanthrenyl, and the like.

[0053] Synthesis of high-purity carboprost from known prostaglandin intermediates of formula 1a or formula 1b

[0054] According to the present invention, high-purity carboprost or carboprost tromethamine can be prepared according to the reactions shown in Scheme 1 and Scheme 2:

[0055] Process 1

[0056]

[0057] Process 2

[0058]

[0059] The compound of formula 1a in Scheme 1, wherein for Or carbonyl protecting group; and P1 and P2 are hydroxy protecting groups, which are well known prostaglandin F 2α Intermediate. The compound of formula 1b in process 2, wherein P1 and P2 are hydroxyl protecting groups, is the well-known 15-methyl prostaglandin F 2α Intermediates. Both prostaglandin intermediates can be prepared from the well-known intermediate Corey lactone via the Wetté reaction. Due to the different reaction conditions of the Wetté reaction, both prostaglandin intermediates almost entirely contain about 1% to about 10% of the 5,6-trans isomer.

[0060] As shown in step (1) of Scheme 1 and step (1) of Scheme 2, the macrolactonization reaction may involve activation of the carboxyl or / and hydroxyl functional groups. In this approach, the macrolactonization reaction comprises initial formation of a thioester with a suitable reagent including, but not limited to, S-pyridin-2-yl chloromethanethioate, 2,2'-bipyridyl disulfide / triphenylphosphine, or 4-tert-butyl-2-(2-(4-tert-butyl-1-isopropyl-1H-imidazol-2-yl)disulfide)-1-isopropyl-1H-imidazole / triphenylphosphine.

[0061] The macrolactonization reaction can alternatively be used to initially form a mixed anhydride with a suitable reagent in the presence or absence of a base or Lewis acid. Suitable reagents for forming mixed anhydrides include, but are not limited to, 2,4,6-trichlorobenzoyl chloride, 2-nitro-6-nitrobenzoic anhydride, p-nitrofluoromethylbenzoic anhydride, p-nitrobenzoic anhydride, and the like. Examples of suitable bases include 4-(dimethylamino)pyridine, pyridopyridine, triethylamine, N,N-diisopropylethylamine, and isopropyldiethylamine. Examples of suitable Lewis acids include Sc(OTf), TiCl, AgClO, trimethylsilyl chloride (TMSCl), and TiCl(OTf).

[0062] The macrolactonization reaction can also be achieved using a condensation reagent and a base in an appropriate solvent. Suitable condensation reagents include, but are not limited to, N,N'-dicyclohexylcarbodiimide, 2-chloro-1-methyl-pyridinium iodide, 2-chloro-4,5-dihydro-1,3-dimethyl-1H-imidazolium chloride, N,N-diphenylchlorophenylmethyleneammonium chloride, cyanuric chloride, 1,3-dimethyl-2-chloroimidazolium chloride, N,N,N,N-tetramethylchloroformamidine chloride, and the like. Examples of suitable bases include pyridine, triethylamine, diisopropylethylamine, 4-dimethylaminopyridine (DMAP), and the like. Suitable solvents for the condensation reaction include dichloromethane, tetrahydrofuran, 1,2-dichloroethane, and mixtures thereof.

[0063] When the resulting compound of Formula 2a, 2a', 2b, 3, or 4 was analyzed by HPLC or UPLC, it was unexpectedly found that the resulting compound of Formula 2a, 2a', 2b, 3, or 4 contained no more than about 0.1% or less of the 5,6-trans isomer, confirming that the macrolactonization reaction exhibited cis-selectivity; that is, the 5,6-cis compound of Formula 1a or 1b dominated the macrolactonization reaction, while the 5,6-trans compound of Formula 1a or 1b hardly underwent the macrolactonization reaction.

[0064] Step (2) of Scheme 1 involves the removal of P2 and / or P1 at the ω-side chain of a compound of formula 2a (wherein for ) deprotection and oxidation. The conditions for carrying out the deprotection reaction will be apparent to those skilled in the art. For example, a macrolide of Formula 2a, wherein P1 and P2 are tetrahydropyranyl protecting groups, is dissolved in a suitable solvent (such as methanol or a solvent mixture of acetone and water in a volume ratio of 5:1); treated with a deprotecting agent (such as hydrogen chloride, p-toluenesulfonic acid, or pyridinium p-toluenesulfonate); and stirred at room temperature for 10 minutes to 10 hours. The reaction is quenched with a base (such as ammonium hydroxide or the like), and the work-up procedure is carried out in a conventional manner. The deprotected product of Formula 2a, wherein P1 and P2 are H, is oxidized with a suitable oxidant (such as MnO2 or 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)) to form a macrolide-enone of Formula 2a', wherein P1 is H.

[0065] For example, a macrolide of Formula 2a, wherein P1 is a tetrahydropyranyl protecting group and P2 is a tertiary butyldimethylsilyl protecting group, is dissolved in a suitable solvent such as tetrahydrofuran (THF); treated with a deprotecting agent such as tetrabutylammonium fluoride (TBAF); and stirred at room temperature for 10 minutes to 10 hours. The reaction is allowed to proceed in a conventional manner. The deprotected product of Formula 2a, wherein P1 is a tetrahydropyranyl protecting group and P2 is H, is then oxidized with a suitable oxidant such as Collins oxidant, Swern oxidant, PCC oxidant, PDC oxidant, and TEMPO oxidant, preferably TEMPO oxidant, to form a macrolide-enone of Formula 2a', wherein P1 is a tetrahydropyranyl protecting group.

[0066] Step (2) of Scheme 1 also involves a compound of formula 2a (wherein The conditions for carrying out the deprotection reaction are obvious to those skilled in the art. For example, 1,3-di A macrolide of Formula 2a wherein the alkyl protecting group and P1 is H is dissolved in a suitable solvent such as THF or acetone, treated with a deprotecting agent such as 1 M HCl solution, and stirred at room temperature for 10 minutes to 10 hours. The reaction is quenched with a base (e.g., saturated NaHCO3 solution or the like) and worked up in a conventional manner to form a macrolide-enone of Formula 2a' wherein P1 is H.

[0067] Furthermore, step (2) of Scheme 2 involves deprotection of a compound of formula 2b (wherein P2 is a hydroxy protecting group) by removing P2 and / or P1 at the ω-side chain. The conditions for carrying out the deprotection reaction will be apparent to those skilled in the art.

[0068] Step (3) of Scheme 1 shows the methylation of a macrolide-enone of formula 2a' wherein P1 is a hydroxy protecting group to form a macrolide tertiary alcohol of formula 3a. According to the present invention, the methylating agent includes, but is not limited to, MeLi, MeMgCl, MeMgBr, MeMgI, Me3Al, or a mixture thereof. Preferably, the methylating agent is MeMgCl, MeMgBr, MeMgI, MeLi, or a mixture thereof. Optimally, the methylating agent is MeLi. Non-limiting suitable solvents used in the reaction may be selected from tetrahydrofuran, ether, toluene, hexane, or a mixture thereof. The reaction is carried out at a temperature ranging from about -120°C to room temperature, preferably from about -100°C to about -40°C. The amount of methylating agent used may allow the reactants to react completely, as monitored by thin layer chromatography (TLC).

[0069] It was unexpectedly found that the reaction of macrolide-enone and methyl Grignard reagent as a methylating agent exhibited a 15(S)-selectivity of up to about 65%. However, as shown in Scheme A(1), the 15(S)-selectivity of the reaction of γ-lactone-enone and methyl Grignard reagent was only 50%. It seems that the structure of the macrolide contributes to the 15(S)-selectivity compared to the γ-lactone. In addition, the present invention unexpectedly found that using low-cost and more suitable MeLi as a methylating agent, the methylation of macrolide-enone can have a 15(S)-selectivity of about 75% or more, which is extremely high and cannot be achieved even when using a chiral additive in the γ-lactone reaction (WO 2017 / 093770, using (S)-Taddol, the highest selectivity is only 70%).

[0070] Step (4) of Scheme 1 and step (3) of Scheme 2 involve purification of the macrolide tertiary alcohol of Formula 3 to remove the 15(R)-diamer. Generally, separation of isomers of cardioprost is the most expensive and time-consuming step in the mass production of cardioprost. However, the cost of separating the isomers of the present invention is much lower than that of the prior art, such as J. Am. Chem. Soc., 96(18), 5865-5876, 1974; WO 2008 / 081191; WO 2017 / 093770; CN 111777537 and CN102816099A. The reasons are as follows:

[0071] (a) In the prior art, carboprost must be esterified to form the intermediate carboprost methyl ester, which is suitable for removing isomers. The isomers of carboprost methyl ester can then be removed by chromatography purification. However, it was unexpectedly discovered that the late-stage intermediate of Formula 3 is a suitable intermediate for removing isomers; therefore, an additional esterification reaction is unnecessary in the present invention.

[0072] (b) When chromatographic purification is used to remove the 5,6-trans isomer and 15(R)-epimer of a carboprost intermediate, the 5,6-trans isomer (HPLC, 0.93) is generally more difficult to separate than the 15(R)-epimer (HPLC, RRT 0.88). CN 102816099 even used analytical-grade HPLC with a filler (5 μm) to remove the 5,6-trans isomer of carboprost methyl ester (RRT 0.93). In contrast, the intermediate of Formula 3 and the compound of Formula 2a' formed after macrolactonization are substantially free of the 5,6-trans isomer. Therefore, chromatography on a standard silica gel column, which is commercially available in large quantities, can be simply used to separate the more easily removed 15(R)-epimer.

[0073] (c) The methylation of the macrolide-enone of the present invention exhibits higher selectivity, so the 15(R)-epimer is produced in smaller amounts and can be more easily removed.

[0074] In step (4) of Scheme 1 and step (3) of Scheme 2, chromatographic purification can be performed using esters, ethers, ketones, halogenated solvents, or the like, or mixtures thereof. For mixtures of dichloromethane and acetone, good separation can also be achieved using ethyl acetate, isopropyl acetate, methyl tertiary butyl ether, acetone, methyl ethyl ketone, or mixtures thereof. Chromatography can reduce the amount of the undesired 15(R)-epimer to a specified limit, i.e., < about 0.5%, < about 0.3%, < about 0.2%, < about 0.1%, or less.

[0075] As shown in step (5) of Scheme 1 and step (4) of Scheme 2, the macrolide tertiary alcohol of Formula 3 is hydrolyzed to a methanol solution containing carboprost by treatment with a lithium hydroxide solution. Acidification to obtain carboprost must be performed quickly to avoid epimerization reactions in the acidic medium.

[0076] Therefore, the present invention provides a process for preparing carboprost containing not more than 1% of total isomers, said process comprising the steps of:

[0077] (1) Macrolactonization of a compound of formula 1a containing 1% to 10% of the 5,6-trans isomer

[0078]

[0079] in for Or a carbonyl protecting group; and P1 and P2 are H or a hydroxy protecting group, to form a compound of formula 2a:

[0080]

[0081] in P1 and P2 are as defined above for Formula 1a;

[0082] (2) When When is a carbonyl protecting group, removing the carbonyl protecting group of the compound of formula 2a; or when for When P2 is removed and / or the compound of formula 2a is oxidized to form a compound of formula 2a':

[0083]

[0084] Wherein P1 is H or a hydroxyl protecting group;

[0085] (3) methylating the compound of formula 2a' with a methylating agent to form a compound of formula 3:

[0086]

[0087] Wherein P1 is H or a hydroxyl protecting group;

[0088] (4) separating the compound of formula 3 by chromatography to remove isomers;

[0089] (5) hydrolyzing the compound of formula 3 to form a compound of formula 4:

[0090]

[0091] wherein P1 is H or a hydroxyl protecting group; and

[0092] (6) When P1 is a hydroxy protecting group, a deprotection reaction of the compound of Formula 2a, 2a', 3 or 4 is optionally performed to form a compound of Formula 2a, 2a', 3 or 4, wherein P1 is H.

[0093] The present invention also provides a method for preparing high-purity carboprost containing no more than 1% of total isomers, the method comprising the following steps:

[0094] (1) macrolactonizing a compound of formula 1b containing 1% to 10% of the 5,6-trans isomer and 1% to 50% of the 15(R)-epimer,

[0095]

[0096] Wherein P1 and P2 are H or hydroxyl protecting groups to form a compound of formula 3a:

[0097]

[0098] wherein P1 and P2 are as defined above;

[0099] (2) when P1 is H or a hydroxy protecting group and P2 is a hydroxy protecting group, performing a deprotection reaction of the compound of formula 3a to form a compound of formula 3a, wherein P1 is H or a hydroxy protecting group and P2 is H;

[0100] (3) separating the compound of formula 3a, wherein P1 is H or a hydroxy protecting group and P2 is H, by chromatography to remove isomers;

[0101] (4) hydrolyzing the compound of formula 3a to form a compound of formula 4:

[0102]

[0103] wherein P1 is H or a hydroxyl protecting group; and

[0104] (5) When P1 is a hydroxy protecting group, a deprotection reaction of the compound of Formula 3a or 4 is optionally performed to form a compound of Formula 3a or 4, wherein P1 is H.

[0105] Purification of low-purity carboprost containing excess isomers

[0106] Crude carboprost obtained from conventional reactions or due to overreaction of epimerization reactions often contains a large or excessive amount of one isomer. The inventors of the present invention have discovered that carboprost containing an excess of one isomer can be further purified by using the method of the present invention. The method of the present invention comprises providing low-purity carboprost containing at least about 1% to 10% of the 5,6-trans isomer and about 1% to 50% of the 15(R)-epimer; macrolactonizing the low-purity carboprost to form a macrolide tertiary alcohol; chromatographically separating the excess isomer of the macrolide tertiary alcohol; and hydrolyzing the macrolide tertiary alcohol to form high-purity carboprost containing no more than about 1% of total isomers.

[0107] Therefore, the present invention provides a method for purifying carboprost, comprising the following steps:

[0108] (1) macrolactonizing low-purity carboprost containing 1% to 10% of the 5,6-trans isomer and 1% to 50% of the 15(R)-epimer to form a compound of formula 3b:

[0109]

[0110] (2) separating the isomers of the compound of formula 3b by chromatography; and

[0111] (3) Hydrolyzing the compound of formula 3b to form high-purity carboprost containing no more than 1% of total isomers.

[0112] Forms carboprost salt with tromethamine

[0113] In order to form carboprost tromethamine from carboprost, the method of the present invention further comprises forming a salt with tromethamine, and crystallization of carboprost tromethamine. The salt formation and crystallization steps can follow the methods disclosed in CN102336693 or WO 2017 / 093770. In general, carboprost can first be dissolved in a suitable solvent, such as acetone, acetonitrile, methanol, ethanol, isopropanol, and combinations thereof; then a suitable solvent containing tromethamine (such as water, methanol, ethanol, isopropanol, and combinations thereof) can be added to the solution; and the mixture can be heated to about 85°C for about 1 hour to form a homogeneous solution. Subsequently, the homogeneous solution can be cooled to about 60°C, and a white solid slowly begins to precipitate. The reaction mixture can be further cooled to room temperature and then filtered to obtain white crystals of carboprost tromethamine. The melting point of the white crystals thus obtained is typically about 95°C to 105°C, as originally disclosed by Pfizer (e.g., provided by Pfizer). Prescribing Information).

[0114] In the case of Example 1 of CN 102336693, about 1.20 g of carboprost tromethamine was precipitated from a mixture of 100 ml of acetonitrile and 0.5 ml of water during temperature reduction, and the melting point of the white crystals was measured to be 103.97° C. (see Figure 2 The inventors of the present invention repeated Example 1 of CN 102336693 and found that the melting point of the obtained carboprost tromethamine crystals was measured to be 103.41°C.

[0115] In Example 1g of WO 2017 / 093770, approximately 593 g of carboprost tromethamine was precipitated from a mixture of isopropyl alcohol and acetone. WO 2017 / 093770 does not disclose the melting point of the carboprost tromethamine crystals obtained in Example 1g. The present inventors repeated Example 1g of WO 2017 / 093770 and found that the melting point of the obtained carboprost tromethamine crystals was measured to be 97.49°C.

[0116] The melting point of the above-mentioned known carboprost tromethamine crystals ranges from about 97°C to about 104°C, which is actually within the range (95°C to 105°C) as originally provided by Pfizer.

[0117] Recrystallization of Carboprost Tromethamine

[0118] Recrystallization of carboprost tromethamine may have an effect on reducing the content of the 15(R)-isomer. Methods for recrystallizing carboprost tromethamine have been disclosed in CN 102336693 and WO 2017 / 093770. The inventors of the present invention repeated the method disclosed in CN 102336693 using water and acetone and found that the recrystallized carboprost tromethamine had a measured melting point of 103.85°C. The inventors of the present invention also repeated the method disclosed in WO 2017 / 093770 using isopropyl alcohol and acetone and found that the recrystallized carboprost tromethamine had a measured melting point of 99.46°C.

[0119] Unexpectedly, it has been discovered that specific high-melting-point carboprost tromethamine crystals can be obtained by recrystallizing carboprost tromethamine using a specific solvent of anhydrous acetonitrile. The high-melting-point carboprost tromethamine crystals thus formed exhibit a differential scanning calorimetry (DSC) thermogram including an endothermic peak with a peak maximum of 106.4±1.0°C. This peak maximum is significantly higher than the upper limit of the melting point range originally provided by Pfizer and disclosed in the prior art for the aforementioned carboprost tromethamine crystals.

[0120] Preparation of high melting point carboprost tromethamine crystals

[0121] The present invention provides a method for preparing a high melting point crystalline form of carboprost tromethamine, comprising the following steps:

[0122] a. Carboprost tromethamine is added to anhydrous acetonitrile to form a mixture, wherein the amount of anhydrous acetonitrile is from about 80 ml to 250 ml per 1 g of carboprost tromethamine;

[0123] b. heating the mixture to a temperature in the range of about 70 ℃ to 90 ℃ to obtain a homogeneous solution;

[0124] c. allowing the homogeneous solution to cool to form the crystalline form of carboprost tromethamine; and

[0125] d. Isolate the crystalline product as appropriate.

[0126] In some embodiments, the mixture can be heated to about 80° C. to completely dissolve the carboprost tromethamine; the homogeneous solution can then be slowly cooled, and a white solid slowly begins to precipitate; and the mixture can be further cooled to room temperature, and then filtered and dried to obtain a crystalline form of carboprost tromethamine.

[0127] In some embodiments, the amount of anhydrous acetonitrile used in step a ranges from about 80 ml to 250 ml, about 100 ml to 220 ml, or about 150 ml to 200 ml per 1 g of carboprost tromethamine; the water content (w / w) of the anhydrous acetonitrile is less than about 0.05%, less than about 0.01%, less than about 0.005%, or less than about 0.001%; and the method is preferably carried out without adding water. The crystalline form of carboprost tromethamine prepared by the method has a differential scanning calorimetry (DSC) thermogram comprising an endothermic peak with a peak maximum of 106.4 ± 1.0 ° C, and the peak maximum is higher than another known crystalline form of carboprost tromethamine. Since the carboprost tromethamine crystals obtained by the present invention have the highest melting point compared to all other known carboprost tromethamine crystals, it is the most stable crystalline form of carboprost tromethamine.

[0128] Furthermore, the high-melting-point carboprost tromethamine crystals of the present invention have an X-ray powder diffraction (XRPD) pattern exhibiting characteristic peaks at the following 2θ reflection angles: 6.9±0.2°, 10.3±0.2°, 18.8±0.2°, and 21.9±0.2°, which are significantly different from the 2θ reflection angles of 6.6±0.2°, 9.9±0.2°, 18.5±0.2°, and 21.6±0.2° of the crystals disclosed in CN 102336693. This indicates that the high-melting-point carboprost tromethamine crystals are a novel crystalline form of carboprost tromethamine.

[0129] In one embodiment of the present invention, the carboprost tromethamine crystals have an XRPD pattern exhibiting characteristic peaks at the following 2θ reflection angles: 6.9±0.2°, 10.3±0.2°, 18.8±0.2°, and 21.9±0.2°. In a preferred embodiment, the XRPD pattern further comprises characteristic peaks at the following 2θ reflection angles: 9.1±0.2°, 9.5±0.2°, 11.0±0.2°, and 20.5±0.2°. More preferably, the XRPD pattern of the carboprost tromethamine crystals is Figure 1 Specific data for carboprost tromethamine crystals are shown in Table 1.

[0130] Table 1

[0131]

[0132]

[0133] In one embodiment, the present invention provides a Figure 1 The XRPD pattern of the crystalline form of carboprost tromethamine is shown in FIG.

[0134] In one embodiment, the present invention provides XRPD patterns of carboprost tromethamine crystals from five different batches (a) to (e), as shown in FIG. Figure 3 The specific data of the four main isolated characteristic peaks are clearly marked and shown in Table 2. The average positions of the characteristic peaks are located at approximately 6.9°, 10.3°, 18.8° and 21.9°, respectively.

[0135] Table 2

[0136]

[0137]

[0138] Compared with 6.6±0.2°, 9.9±0.2°, 18.5±0.2° and 21.6±0.2° disclosed in CN102336693, the XRPD characteristic peak positions of the carboprost tromethamine crystals of the present invention are located at higher 2θ (2-theta) angles (6.9±0.2°, 10.3±0.2°, 18.8±0.2° and 21.9±0.2°). The characteristic peak at 6.621° of the carboprost tromethamine disclosed in CN102336693 indicates On the other hand, the characteristic peak at 6.92° of the carboprost tromethamine of the present invention represents d-spacing. Greater than The difference in d-spacing is a clear evidence that the molecular packing is different in the lattice structure. This result shows that carboprost tromethamine crystals are a novel crystalline form with a more stable and tightly ordered packing structure compared to the prior art.

[0139] In one embodiment, the present invention provides carboprost tromethamine crystals having a DSC thermogram comprising an endothermic peak with a peak onset temperature of approximately 103.9° C. and a peak maximum of approximately 106.4±1.0° C. In a preferred embodiment, the present invention provides carboprost tromethamine crystals having substantially Figure 2 The DSC thermogram of the crystalline form of carboprost tromethamine is shown in FIG.

[0140] In one embodiment, the present invention provides DSC thermograms of carboprost tromethamine crystals from five different batches (a) to (e), as shown in FIG. Figure 4 Specific data for the peak maxima of the individual endothermic peaks are clearly marked and shown in Table 3. The average peak maximum of these endothermic peaks is about 106.4°C.

[0141] Table 3

[0142] sample Peak maximum (℃) (a) 106.27 (b) 106.63 (c) 106.44 (d) 106.34 (e) 106.40 average value 106.42

[0143] The DSC peak maximum temperature of approximately 106.4°C of the carboprost tromethamine crystals of the present invention far exceeds the disclosed melting point of 95°C to 105°C for carboprost tromethamine (as originally provided by Pfizer) and the peak maximum temperature of 103.97°C disclosed in CN 102336693, indicating that the carboprost tromethamine crystals of the present invention are novel crystals with higher thermal stability compared to the prior art. It is well known to those skilled in the art that the crystal with the highest melting point is the most thermodynamically stable crystalline form; therefore, compared to the prior art, the novel carboprost tromethamine crystals of the present invention are the most stable.

[0144] The United States Pharmacopeia recommends that carboprost tromethamine be stored in a refrigerator (-20°C). In contrast, the present invention demonstrates that the high-melting-point crystalline form of carboprost tromethamine is extremely stable even after 6 months at 20°C, 18 months at 5°C, and 3 days at 80°C. Thus, the stability of the carboprost tromethamine crystals of the present invention is significantly improved.

[0145] Although the word "about" is added before the minimum and maximum values within the range, unless otherwise expressly indicated, the use of numerical values in the multiple quantitative values specified in this application is an approximation. In this way, slight changes in the numerical values can be used to achieve substantially the same results as the numerical values. In addition, the scope of the present disclosure is intended to be a continuous range, including each numerical value between the minimum and maximum values and any range that can be formed by such numerical values. Also disclosed herein are any and all ratios (and ranges of any such simulated ratios) that can be formed by dividing the stated numerical values into any other stated numerical values. Accordingly, those skilled in the art will understand that many of the ratios, ranges, and ranges of ratios can be clearly derived from the numerical values proposed herein, and the ratios, ranges, and ranges of ratios described in all examples represent multiple embodiments of the present invention.

[0146] All compounds and / or methods disclosed and claimed herein can be made and executed in accordance with the present invention without undue experimentation. Although the compounds and methods of the present invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the art that variations may be applied to the compositions and / or methods and to the steps or sequence of steps of the methods described herein without departing from the concept, spirit, and scope of the present invention. All such similar substitutions and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the present invention as defined by the appended claims.

[0147] Examples

[0148] X-ray powder diffraction (XRPD) analysis: XRPD patterns were collected on a Bruker D2 PHASER diffractometer with a fixed divergence slit and a 1D LYNXEYE detector. The sample (approximately 100 mg) was placed flat on the sample holder. A CuK2 ionization was used at 10 mA and 30 kV. α The prepared samples were analyzed with radiation in the range of 5° to 40° 2θ with a step size of 0.02 degrees and a step time of 1 second. CuK β radiation.

[0149] Differential Scanning Calorimetry (DSC) Analysis: DSC thermograms were collected on a TA DISCOVERY DSC25 instrument. Samples were weighed into aluminum pans with crimped aluminum lids. The prepared samples were analyzed under a nitrogen flow (approximately 50 ml / min) at a scan rate of 10°C / min from 25°C to 150°C. Melting temperatures and heats of fusion were calibrated with indium (In) prior to measurement. The melting points of all samples were determined by the peak maximum of the endothermic peak during the DSC measurement.

[0150] Example 1

[0151] (8aR,9R,10R,11aS,Z)-10-((tert-butyldimethylsilyl)oxy)-9-((S,E)-3-((tert-butyldimethyl-silyl)oxy)oct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxecin-2(3H)-one

[0152]

[0153] At ambient temperature under nitrogen, 1.4 kg of 7-((1R,2R,3R,5S)-3-((tert-butyldimethylsilyl)oxy)-2-((S,E)-3-((tert-butyldimethylsilyl)oxy)oct-1-en-1-yl)-5-hydroxycyclopentyl)hept-5(Z)-enoic acid (which included approximately 6.5% of the 5,6-trans isomer as determined by detection of its deprotected product in HPLC analysis) and 475 g of pyridine were dissolved in 6.5 L of dichloromethane. Next, 843 g of benzoyl chloride was added to the mixture and stirred for one hour. The reaction mixture was checked by TLC to confirm the completion of the reaction. The mixture was quenched with 6 L of saturated aqueous sodium bicarbonate solution and stirred for 10 minutes. The solution was allowed to stand to separate into two phases, and the organic layer was collected. The organic layer was further evaporated. The concentrated residue was diluted with 6 L of toluene and washed with 0.1 N aqueous hydrochloric acid and brine, respectively. The organic layer was collected and evaporated to obtain the crude silyl-protected 1,9-lactone compound. The crude compound was further purified by silica gel chromatography using a gradient eluent of hexane and ethyl acetate. The yield of the silyl-protected 1,9-lactone obtained was 1.0 kg (74%).

[0154] 0.1 g of the product was further treated with hydrolysis and deprotection to obtain a crude product. HPLC analysis showed that no 5,6-trans isomer was detected for the crude compound.

[0155] 1 H-NMR (CDCl3): δ5.156~5.595(m,5H),4.067(q,1H),3.809(q,1H),1.247~2.532(m,20H),0.852~0.898(m,21H),-0.005~0.034(m,12H); 13 C-NMR(CDCl3): δ173.620,136.520,131.169,129.135,127.890,72.809,72.088,55.345,44.567,41.599,38.669,36.134,31.831, 26.730,26.571,25.895,25.835,25.349,25.136,22.624,18.222,18.063,14.047,-4.252,-4.556,-4.579,-4.768; MS(m / z,EI): C 32 H 60 O4Si2Na(M + ) was calculated to be 587.4 and the experimental value was 587.5.

[0156] Example 2

[0157] (8aR,9R,10R,11aS,Z)-9-((S,E)-3-((tributyldimethylsilyl)oxy)oct-1-en-1-yl)-10-((tetrahydro-2H-pyran-2-yl)oxy)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one

[0158]

[0159] At ambient temperature under nitrogen, 2.0 g of 7-((1R,2R,3R,5S)-2-((S,E)-3-((tributyldimethylsilyl)oxy)oct-1-en-1-yl)-5-hydroxy-3-((tetrahydro-2H-pyran-2-yl)oxy)cyclopentyl)hept-5(Z)-enoic acid (containing 1.8% of the 5,6-trans isomer as determined by detection of its deprotected compound in HPLC analysis) and 0.72 g of pyridine were dissolved in 20 ml of dichloromethane. Then, 1.27 g of benzoyl chloride was added to the mixture and stirred for 30 minutes. The reaction mixture was checked by TLC to confirm the completion of the reaction. The mixture was quenched with 15 ml of saturated aqueous sodium bicarbonate solution and stirred for 10 minutes. The solution was allowed to stand to separate into two phases, and the organic layer was collected. The organic layer was evaporated to give the crude ether-protected 1,9-lactone compound. The crude compound was purified by silica gel chromatography using a gradient eluent of a mixture of hexane and ethyl acetate. The yield of the ether-protected 1,9-lactone obtained was 1.35 g (70%).

[0160] 0.1 g of the product was further treated with hydrolysis and deprotection to obtain a crude product. HPLC analysis showed that no 5,6-trans isomer was detected for the crude compound.

[0161] 1 H-NMR(CDCl3): δ5.172~5.630(m,5H),4.813~4.944(m,1H),3.428~4.091( m,4H),1.230~2.619(m,26H),0.845~0.879(m,12H),0.012~0.038(m,6H); 13C-NMR(CDCl3): δ173.635(173.559),136.778(136.619),131.260,129.666,(129.507),127.640,9 5.390(94.623),81.933(77.910),73.159,62.457(61.106),53.971(53.106),44.962(44.855),39. 618,38.662(38.578),37.417,31.816(31.778),30.639(30.601),26.730,25.417,25.319,24.962, 22.601,19.732(19.573),18.237(18.222),14.009,-4.252,-4.267,-4.806,-4.844; MS(m / z,EI): C 31 H 54 O5SiNa(M + ) was calculated to be 557.4 and the experimental value was 557.4.

[0162] Example 3

[0163] (8aR,9R,10R,11aS,Z)-9-((E)-3-oxooct-1-en-1-yl)-10-((tetrahydro-2H-pyran-2-yl)oxy)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one

[0164]

[0165] At ambient temperature under nitrogen, 1.5 g of 7-((1R,2R,3R,5S)-5-hydroxy-2-((E)-3-oxooct-1-en-1-yl)-3-((tetrahydro-2H-pyran-2-yl)oxy)cyclopentyl)hept-5(Z)-enoic acid and 0.68 g of pyridine were dissolved in 15 ml of dichloromethane. Then, 1.21 g of benzoyl chloride was added to the mixture and stirred for 30 minutes. The reaction mixture was checked by TLC to confirm the completion of the reaction. The mixture was quenched with 10 ml of saturated aqueous sodium bicarbonate solution and stirred for 10 minutes. The solution was allowed to stand to separate into two phases, and the organic layer was collected. The organic layer was evaporated to obtain a crude 1,9-lactone compound. The crude compound was purified by silica gel chromatography using a mixture of hexane and ethyl acetate as a gradient eluent. The yield of 1,9-lactone obtained was 1.02 g (71%).

[0166] 1H-NMR(CDCl3): δ6.688(ddd,1H),6.235(dd,1H),5.326(dt,1H),5.197(br s,2H),4.592(t,0.5H),4.550(t,0.5H),4.060(dd,0.5H),3.952(dd,0.5H),3 .692~3.800(m,1H),3.388~3.447(m,1H),1.236~2.684(m,26H),0.887(t,3H); 13 C-NMR(CDCl3): δ200.466(200.299),173.499(173.408),146.569(146.417),131.951,131.7 84,126.873,96.321(96.612),81.386(78.790),72.445(72.111),62.646(61.736),54.130(5 3.546),45.030(44.939),40.582(40.309),39.808(38.024),35.998,31.451(31.421),30.67 7(30.601),26.715,25.364(25.303),23.952,22.442,19.550,18.988,13.895; MS(m / z,EI): C 25 H 38 O5Na(M+Na + ) is calculated to be 441.3 and the experimental value is 441.3.

[0167] Example 4

[0168] (8aR,9R,10R,11aS,Z)-10-hydroxy-9-((S,E)-3-hydroxyoct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one

[0169]

[0170] At ambient temperature, 480 g of (8aR,9R,10R,11aS,Z)-10-((tert-butyldimethylsilyl)oxy)-9-((S,E)-3-((tert-butyldimethyl-silyl)oxy)oct-1-en-1-)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one (from Example 1) was dissolved in 4.5 L of tetrahydrofuran. Then, 775 g of tetrabutylammonium fluoride trihydrate was added to the solution. The homogeneous solution was heated at 45 ° C and stirred for 6 hours. The reaction mixture was checked by TLC to confirm the completion of the reaction. The mixture was cooled at ambient temperature and then quenched with 8 L of saturated sodium bicarbonate aqueous solution. The solution was allowed to stand to separate into two phases, and the organic layer was collected. The organic layer was evaporated to obtain a crude 1,9-lactone diol compound. The crude compound was purified by silica gel chromatography using a mixture of hexane and ethyl acetate as a gradient eluent. The diol compound was then further crystallized in a mixed solvent of ethyl acetate and hexane. The yield of the obtained crystals of the diol compound was 259 g (91%).

[0171] 1 H-NMR (CDCl3): δ5.203~5.642(m,5H),4.409(q,1H),3.800(q,1H),3.304(br s,1H),1.281~2.608(m,21H),0.868(t,3H); 13 C-NMR(CDCl3): δ173.437,136.785,131.973,131.411,127.464,76.065,73.158,71.936,56.201,45. 074,40.285,37.196,36.050,31.655,26.722,26.532,25.272,25.158,22.562,13.971; MS(m / z,EI): C 20 H 30 O4(M + ) is calculated to be 336.2 and the experimental value is 336.2.

[0172] Example 5

[0173] (8aR,9R,10R,11aS,Z)-10-hydroxy-9-((E)-3-oxooct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one

[0174]

[0175] At ambient temperature, 300 g of (8aR,9R,10R,11aS,Z)-10-hydroxy-9-((S,E)-3-hydroxyoct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one (from Example 4) was dissolved in 3 L of tetrahydrofuran, and 2,3-dichloro-5,6-di-cyano-1,4-benzoquinone was added. The reaction mixture was heated at 55°C and stirred for 2 hours. After the reaction was complete, the mixture was cooled at ambient temperature and evaporated. The dark brown residue was then diluted with dichloromethane, and a yellow solid precipitated. The mixture was filtered, and the filtrate was further concentrated to obtain the crude ketone compound. The crude compound was purified by silica gel chromatography using a mixture of hexane and ethyl acetate as a gradient eluent. The yield of 15-keto-1,9-lactone obtained was 276 g (93%).

[0176] 1 H-NMR (CDCl3): δ5.183~6.686(m,5H), 3.991~4.062(m,1H), 1.251~2.642(m,21H), 0.887(t,3H); 13 C-NMR(CDCl3): δ200.101,173.316,145.536,132.064,131.737,126.865,76.383,72.406,56.239 ,45.591,40.983,40.839,36.027,31.435,26.729,25.302,23.754,22.433,13.895; MS(m / z,EI): C 20 H 30 O4(M + ) is calculated to be 334.2144 and the experimental value is 334.2130.

[0177] Example 6

[0178] (8aR,9R,10R,11aS,Z)-10-hydroxy-9-((S,E)-3-hydroxy-3-methyloct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one

[0179]

[0180] Method A: 275 g of (8aR, 9R, 10R, 11aS, Z) -10-hydroxy-9- ((E) -3- oxooct-1-en-1-yl) -4,5,8,8a,9,10,11,11a- octahydrocyclopenta [b] oxin-2 (3H) -one (from Example 5) was dissolved in 4.5 L of tetrahydrofuran and cooled at -70 ° C. 1.0 L of methyl lithium (2 M in ether) was slowly added to the reaction mixture at -70 ° C. and the reaction was checked by TLC. After the reaction was complete, the mixture was quenched with saturated aqueous ammonium chloride solution and stirred for 10 minutes. Then, 1 L of ethyl acetate was added to the reaction mixture and allowed to warm at ambient temperature. The mixture was allowed to stand to separate into two phases, and the organic layer was collected and dried over anhydrous sodium sulfate. Subsequently, the solid was filtered off and the filtrate was evaporated. A crude 15-methyl compound mixture was obtained and tested by HPLC. The 15-R / 15-S ratio of the crude compound was approximately 25 / 75. The crude compound was further purified by silica gel chromatography using a gradient eluent of dichloromethane and acetone. The yield of pure 15-methyl compound obtained was 163 g (57%).

[0181] Method B: 2 g of (8aR,9R,10R,11aS,Z)-10-hydroxy-9-((E)-3-oxooct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one (from Example 5) was dissolved in 20 ml of tetrahydrofuran at ambient temperature under nitrogen and cooled at -70°C. Then, 21 ml of methylmagnesium bromide (1 M in THF) was slowly added to the reaction mixture at -70°C and warmed to 0°C. The mixture was checked by TLC to confirm the reaction was complete. The reaction mixture was sampled to check that the 15-R / 15-S ratio of the product was approximately 35 / 65.

[0182] 1 H-NMR (CDCl3): δ5.203~5.713(m,5H),3.787(q,1H),1.167~2.535(m,25H),0.859(t,3H); 13 C-NMR(CDCl3): δ173.399,140.709,131.336,127.556,127.526,76.331,72.840,72.187,56.233,45.281, 42.875,40.317,36.029,32.173,27.520,26.693,26.579,25.274,23.801,22.541,13.950; MS(m / z,EI): C 21 H 32 O3(M+ The calculated value for NH-H2O) is 332.2351 and the observed value is 332.2349.

[0183] Example 7

[0184] (8aR,9R,10R,11aS,Z)-10-((tert-butyldimethylsilyl)oxy)-9-((S,E)-3-hydroxy-3-methyloct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one

[0185]

[0186] At ambient temperature, 2.0 g of (8aR,9R,10R,11aS,Z)-10-((tributyldimethylsilyl)oxy)-9-((E)-3-oxooct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one was dissolved in 20 ml of tetrahydrofuran and cooled at -70°C. 3.5 ml of methyllithium (2 M in diethyl ether) was slowly added to the reaction mixture at -70°C and the reaction was checked by TLC. After the reaction was complete, the mixture was quenched with saturated aqueous ammonium chloride solution and stirred for 10 minutes. 1 ml of ethyl acetate was then added to the reaction mixture and allowed to warm at ambient temperature. The mixture was phase separated and the organic layer was dried over anhydrous sodium sulfate. The solid was then filtered off and the filtrate was evaporated to obtain a crude 15-methyl mixture compound. The crude compound was purified by silica gel chromatography using a mixture of dichloromethane and acetone as a gradient eluent. The yield of the pure 15-methyl compound obtained was 1.05 g (51%).

[0187] 1 H-NMR (CDCl3): δ5.168~5.689(m,5H),3.807(q,1H),1.258~2.551(m,24H),0.857~0.944(m,12H),0.011(s,6H); 13 C-NMR(CDCl3): δ173.582,140.368,131.275,127.746,127.678,76.954,72.938,72.005,55.610,44.483,42.844,4 1.569,36.127,32.279,28.081,26.738,26.487,25.789,23.839,22.579,18.070,14.040,-3.592,-4.518,-4.624.

[0188] MS (m / z, EI): C 27 H 48 O4SiNa(M+Na + ) was calculated to be 487.3 and the experimental value was 487.3.

[0189] Example 8

[0190] (Z)-7-((1R,2R,3R,5S)-3,5-dihydroxy-2-((S,E)-3-hydroxy-3-methyloct-1-en-1-yl)cyclopentyl)hept-5-enoic acid, carboprost

[0191]

[0192] 143 g of (8aR,9R,10R,11aS,Z)-10-hydroxy-9-((S,E)-3-hydroxy-3-methyloct-1-en-1-yl)-4,5,8,8a,9,10,11,11a-octahydrocyclopenta[b]oxin-2(3H)-one (from Example 6) was dissolved in 750 ml of methanol, and 1.5 L of 1N aqueous lithium hydroxide solution was added. The reaction mixture was heated at 60° C. for 2 hours. After the reaction was complete, the mixture was cooled to room temperature, and the pH of the solution was adjusted to approximately 8.5. The mixture was concentrated to remove the methanol, and the residue was further purified by acid-base extraction. The yield of carboprost obtained was 129 g.

[0193] 1 H-NMR (CDCl3): δ5.278~5.610(m,7H), 4.112~4.133(m,1H), 3.866~3.911(m,1H), 1.252~2.298(m,23H), 0.843(t,3H);

[0194] 13 C-NMR(CDCl3): δ177.316,138.903,129.431,129.226,128.839,77.599,73.333,72.339,55.292,5 0.427,42.731,42.488,33.031,32.257,26.966,26.245,25.099,24.507,23.809,22.610,14.063;

[0195] MS (m / z, EI): C 21 H 34 O4(M + The calculated value for NH-H2O) is 350.2 and the found value is 350.3.

[0196] Example 9

[0197] Carboprost tromethamine salt formation

[0198] 2-Amino-2-(hydroxymethyl)propane-1,3-diol; (Z)-7-((1R,2R,3R,5S)-3,5-dihydroxy-2-((S,E)-3-hydroxy-3-methyloct-1-en-1-yl)cyclopentyl)hept-5-enoate, carboprost tromethamine

[0199]

[0200] Method A:

[0201] 114 g of carboprost was dissolved in 1.2 L of acetonitrile at 60 ° C, and the solution was heated to 65 ° C. 120 ml of water containing 37.4 g of tromethamine was slowly added to the solution. The reaction mixture was further heated to 85 ° C for reflux for 10 minutes. The homogeneous solution was cooled to 60 ° C, and a white solid slowly began to precipitate. The mixture was further cooled to room temperature and stirred for more than 16 hours. The reaction mixture was filtered to obtain a white crystalline form of carboprost tromethamine (118 g). The melting point of the crystals was measured to be 103.41 ° C by DSC. Figure 5 As shown in (a).

[0202] 1 H-NMR(D2O): δ5.336~5.594(m,4H),4.109(br s,1H),3.819(br s,1H),3.632(s,6H),1.193~2.427(m,23H),0.764(t,3H);

[0203] 13 C-NMR(CDCl3): δ183.433,138.523,130.584,129.203,128.854,75.928,73.576,71.109,71.109,61.257,5 9.451,54.327,41.971,41.902,37.136,31.565,26.601,25.850,25.743,24.779,23.277,21.888,13.288;

[0204] MS (m / z, ESI): C 25 H 48 NO8(MH + ) was calculated to be 490.3374 and the experimental value was 490.3384.

[0205] Method B:

[0206] Carboprost tromethamine crystals were prepared from an acetone / water solution by the method disclosed in Example 3 of CN 102336693. The inventors of this case measured the melting point of the crystals to be 103.22°C. Figure 5 (b) is shown.

[0207] Method C:

[0208] Carboprost tromethamine crystals were prepared from an ether / water solution by the method disclosed in Example 7 of CN 102336693. The inventors of this invention measured the melting point of the crystals to be 103.43°C. Figure 5 (c) is shown.

[0209] Method D:

[0210] Carboprost tromethamine crystals were prepared from an isopropyl alcohol / acetone solution by the method disclosed in Example 1g of WO 2017 / 093770. The inventors of this invention measured the melting point of the crystals to be 97.49°C. Figure 5 (d) is shown.

[0211] Example 10

[0212] Recrystallization of Carboprost Tromethamine

[0213] Method A:

[0214] At 85°C, 10.0 g of carboprost tromethamine was dissolved in 1 L of acetonitrile containing 0.02% water to obtain a homogeneous solution, and then the homogeneous solution was cooled to 60°C, and a white solid slowly began to precipitate. The mixture was further cooled to room temperature. The precipitated crystals were filtered and dried. After recrystallization, the yield of high-purity carboprost tromethamine crystals obtained was 9.0 g. The melting point of the crystals was measured by DSC to be 106.40°C, as shown in FIG. Figure 6 After HPLC analysis, the amount of the 15(R)-epimer was 0.05%, and the 5,6-trans isomer was not detected.

[0215] Method B:

[0216] Carboprost tromethamine crystals were prepared from an acetone / water solution by the method disclosed in Examples 2, 4, 6 or 8 of CN 102336693. The inventors of this invention measured the melting point of the crystals to be 103.85°C. Figure 6 (b) is shown.

[0217] Method C:

[0218] Carboprost tromethamine crystals were prepared from an isopropyl alcohol / acetone solution by the method disclosed in Example 1h of WO2017093770. The inventors of this invention measured the melting point of the crystals to be 99.46°C. Figure 6 (c) is shown.

[0219] Example 11

[0220] Purification of Low-Purity Carboprost Tromethamine

[0221] 3 g of commercially available carboprost tromethamine (containing 2.5% of the 5,6-trans isomer and 1.5% of the 15(R)-epimer) was dissolved in acidic water at pH 3 and extracted with ethyl acetate to yield 2 g of carboprost. A solution of carboprost in 8 ml of anhydrous, oxygen-free xylene was treated with 1.73 g of 2,2'-dipyridyl disulfide and 2.06 g of triphenylphosphine. After stirring at 25°C for 18 hours, the mixture was diluted with 500 ml of xylene and heated under reflux for 4 hours. The reaction mixture was further evaporated to remove the solvent, and the residue was partitioned between cold aqueous sodium bicarbonate solution and ethyl acetate. The organic layer was collected, washed with brine, and dried over anhydrous sodium sulfate. The mixture was filtered and concentrated to yield the crude 1,9-lactone compound. The crude compound was purified by silica gel chromatography using a gradient eluent of dichloromethane and acetone. The yield of 15-methyl 1,9-lactone was 1.67 g.

[0222] The 1,9-lactone product was further treated by hydrolysis to obtain carboprost containing 2.5% of the 15(R)-epimer but no detectable 5,6-trans isomer by HPLC analysis. Carboprost tromethamine was formed from carboprost and tromethamine according to the method of Example 9 and crystallized and recrystallized according to the methods of Examples 10 (Method A) and 11 to obtain high-purity carboprost tromethamine. HPLC analysis revealed a 15(R)-epimer content of 0.15%, and no detectable 5,6-trans isomer.

[0223] Example 12

[0224] Stability of carboprost tromethamine crystals

[0225] The stability data shown in Tables 4 and 5 show that the high-melting-point carboprost tromethamine crystals are stable even after treatment at 20° C. for 6 months, at 5° C. for 18 months, and at 80° C. for 3 days. The high-melting-point carboprost tromethamine crystals are extremely stable at room temperature and even at higher temperatures, making it possible to effectively avoid the formation of degradation impurities.

[0226] Table 4

[0227]

[0228]

[0229] Table 5

[0230]

[0231] On the other hand, the hygroscopicity of the high-melting-point carboprost tromethamine crystals prepared in Example 10 (Method A) and the low-melting-point carboprost tromethamine crystals prepared in Example 10 (Method B) was measured. The samples were placed in glass bottles at 99% RH at 25° C. for 3 hours, and the water content of the samples was measured by Karl Fischer titration, as shown in Table 6. The high-melting-point carboprost tromethamine crystals showed a relatively low rate of water absorption compared to the low-melting-point carboprost tromethamine crystals, indicating that the high-melting-point carboprost tromethamine crystals are more stable and can be stored for a longer period of time under high humidity conditions. Therefore, the high-melting-point carboprost tromethamine crystals are more convenient for product handling, storage, and transportation.

[0232] Table 6

[0233]

[0234] Although the present invention has been described with reference to illustrative examples, it should be understood that any modifications or alterations that may be easily accomplished by those skilled in the art will fall within the scope of the disclosure of the present specification and the appended claims.

Claims

1. A method for preparing carboprost containing not more than 0.5% of the 15(R)-epimer, the method comprising the following steps: (1) Macrolactonization of a compound of formula 1a containing 1% to 10% of the 5,6-trans isomer in for Or a carbonyl protecting group; and P1 and P2 are H or a hydroxy protecting group, to form a compound of formula 2a: in P1 and P2 are as defined above for Formula 1a; (2) When When is a carbonyl protecting group, removing the carbonyl protecting group of the compound of formula 2a; or when for When P2 is removed and the compound of formula 2a is oxidized to form a compound of formula 2a': Wherein P1 is H or a hydroxyl protecting group; (3) methylating the compound of formula 2a' with a methylating agent to form a compound of formula 3: Wherein P1 is H or a hydroxyl protecting group; (4) separating the compound of Formula 3 by chromatography to remove the 15(R)-epimer; (5) hydrolyzing the compound of formula 3 to form a compound of formula 4: wherein P1 is H or a hydroxyl protecting group; and (6) When P1 is a hydroxy protecting group, a deprotection reaction of the compound of Formula 2a, 2a', 3 or 4 is optionally performed to form a compound of Formula 2a, 2a', 3 or 4, wherein P1 is H.

2. The method according to claim 1, which is used for preparing carboprost tromethamine, said method further comprising forming a salt with tromethamine and purifying the carboprost tromethamine by crystallization.

3. The method of claim 1, wherein the methylating agent is selected from the group consisting of MeLi, MeMgBr, MeMgCl, MeMgI, Me3Al, and mixtures thereof. The method of claim 3 , wherein the methylating agent is MeLi.

5. A compound of formula 2a', Wherein P1 is H or a hydroxyl protecting group.

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