Process for the preparation of clindamycin hydrochloride impurities

Abstract

The present application relates to a preparation method of clindamycin hydrochloride impurities, and belongs to the field of medicines.The technical problem to be solved by the present application is that there is a lack of a method for efficiently preparing 7-epiclinamycin and 7-epiclinamycin hydrochloride reference substances of clindamycin hydrochloride impurities in the prior art.The present application provides a preparation method of a clindamycin hydrochloride impurity intermediate shown in formula II: the intermediate is prepared from a compound shown in formula I and R1COOH through a Mitsunobu substitution reaction, and amine and / or a nitrogen-containing aromatic heterocyclic compound are added to the reaction solution.The present application further provides a complete synthesis method of 7-epiclinamycin and 7-epiclinamycin hydrochloride: starting from lincomycin, the method comprises the following steps: protecting a group on silicon, selectively deprotecting, Mitsunobu substitution reaction, hydrolysis reaction to obtain 7-epiclinamycin, and further chlorination reaction to obtain 7-epiclinamycin hydrochloride.

Description

Technical Field

[0001] This invention relates to a method for preparing impurities in clindamycin hydrochloride, and belongs to the field of pharmaceuticals. Background Technology

[0002] Clindamycin hydrochloride, chemically known as 6-(1-methyl-trans-4-propyl-L-2-pyrrolidinecarboxamido)-1-thio-7(S)-chloro-6,7,8-trideoxy-L-threo-α-D-galactopyranoside hydrochloride, is a lincosamide antibiotic and a 7-deoxy-7-chloro derivative of lincomycin. Clindamycin was first synthesized in 1966 by Magerlein et al. by substituting the 7th hydroxyl group in the lincomycin molecule with chloro. It was first marketed in the United States in the early 1970s by Upjohn, and subsequently in the United Kingdom and other European countries. Compared to lincomycin, clindamycin has a broader antibacterial spectrum and stronger antibacterial activity, being 4-8 times more potent. It is also more completely absorbed from the gastrointestinal tract and is not affected by food, resulting in fewer adverse reactions. Since its introduction to China, clindamycin hydrochloride has gained market recognition for its definite efficacy and stable quality, and has been included in the Chinese Pharmacopoeia. In addition to oral formulations, clindamycin hydrochloride is also available as an injection, and its development prospects are very broad.

[0003] 7-Clindamycin hydrochloride is a byproduct of the SN1 reaction at the 7-position during the synthesis of clindamycin hydrochloride; 7-Clindamycin is a residual impurity of lincomycin or an impurity generated during the synthesis of clindamycin hydrochloride from lincomycin. Both 7-Clindamycin hydrochloride and 7-Clindamycin may remain in the final product of clindamycin hydrochloride, affecting product quality. 7-Clindamycin (free state) is listed in the Chinese Pharmacopoeia, with a standard limit of 1.5%. The structural formulas of the above two impurities are as follows:

[0004]

[0005] Chinese patent applications CN101891778A, CN102702279A, and CN103172683A all report on the impurity 7-clindamycin hydrochloride, but none disclose the synthesis method of this impurity. Furthermore, the residual amounts of 7-clindamycin hydrochloride and 7-clindamycin in clindamycin hydrochloride raw materials are small, and obtaining sufficient quantity and quality of reference standards through chromatographic methods is very costly. Therefore, providing a method for preparing high-purity 7-clindamycin hydrochloride and 7-clindamycin, and obtaining impurity reference standards for quality control of the raw material, is of great significance for the research and control of the finished clindamycin hydrochloride product. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing clindamycin hydrochloride impurities—7-differentiated clindamycin hydrochloride and 7-differentiated lincomycin, in order to solve the problem of the lack of efficient methods for preparing the above-mentioned impurity reference standards in the prior art.

[0007] The method provided by this invention uses lincomycin as raw material, and obtains 7-contrast lincomycin through silicon protecting group addition, selective deprotection, Mitsunobu substitution reaction, and hydrolysis reaction; further, through chlorination reaction and other processes, 7-contrast clindamycin hydrochloride is prepared.

[0008] In the Mitsunobu substitution reaction, the inventors unexpectedly discovered that the tertiary amine functional groups present in the reactants themselves, when forming salts with R1COOH, interfered with the progress of the Mitsunobu substitution reaction. The yield of this step could be increased by adding amines and / or nitrogen-containing aromatic heterocyclic compounds. Without the addition of amines and / or nitrogen-containing aromatic heterocyclic compounds, the target product could not be obtained.

[0009] Moreover, the inventors discovered that the crude product prepared by the above-mentioned Mitsunobu substitution reaction has high purity and can be directly used in the next reaction without intermediate purification steps. The process is simple and conducive to industrial production.

[0010] This invention includes the following aspects:

[0011] In a first aspect, the present invention provides a method for preparing the clindamycin hydrochloride impurity intermediate shown in Formula II:

[0012] The compound shown in Formula I and R1COOH were used as raw materials and prepared via a Mitsunobu substitution reaction, with amines and / or nitrogen-containing aromatic heterocyclic compounds added to the reaction solution.

[0013]

[0014] Wherein, R1 is an optionally substituted aryl or alkyl group;

[0015] R2 is R3, R4, and R5 are independently selected from alkyl groups.

[0016] The amines described in this invention are products of ammonia molecules in which one or more hydrogen atoms are replaced by hydrocarbon groups, including aliphatic amines and aromatic amines. In some embodiments of this invention, the amines and / or nitrogen-containing aromatic heterocyclic compounds are tertiary amines and / or six-membered ring nitrogen-containing aromatic heterocyclic compounds;

[0017] Preferably, the tertiary amine is one or more of trimethylamine, triethylamine, triethanolamine, triallylamine, and N,N-diisopropylethylamine, and the nitrogen-containing aromatic heterocyclic compound of the six-membered ring is pyridine, 4-dimethylaminopyridine, or a mixture thereof.

[0018] Preferably, the amine and / or nitrogen-containing aromatic heterocyclic compound is one or more of triethylamine, diisopropylethylamine, and pyridine.

[0019] In some embodiments of the present invention, R1 is an optionally substituted 5-14 aryl group or a C1-C6 alkyl group, and R3, R4, and R5 are independently selected from C1-C6 alkyl groups; preferably, R1 is an optionally substituted phenyl group or a C1-C4 alkyl group, and R3, R4, and R5 are independently selected from C1-C4 alkyl groups; more preferably, R1 is p-nitrophenyl, and R3, R4, and R5 are all methyl groups.

[0020] In some embodiments of the present invention, the preparation method includes the following steps: adding the compound shown in Formula I, R1COOH, phosphine reagent, and amine and / or nitrogen-containing aromatic heterocyclic compound to a reaction solvent, then slowly adding azodicarboxylic acid ester, controlling the temperature of the reaction solution below 30°C, and after the reaction is completed, the clindamycin impurity intermediate shown in Formula II is obtained.

[0021] In some embodiments of the present invention, the preparation method satisfies at least one of the following:

[0022] The phosphine reagent is triarylphosphine; preferably, the phosphine reagent is triphenylphosphine.

[0023] The azodicarboxylic acid ester is diisopropyl azodicarboxylate, diethyl azodicarboxylate, or a mixture thereof;

[0024] The reaction solvent is one or more of toluene, dichloromethane, and tetrahydrofuran;

[0025] Before adding azodicarboxylic acid ester, the temperature of the reaction solution is controlled below 30°C; preferably, the temperature of the reaction solution is controlled between 10°C and 30°C.

[0026] The concentration (g:ml) of the compound shown in Formula I in the reaction solvent is (1:2) to (1:100); the preferred concentration (g:ml) is 1:30.

[0027] The molar ratio of the compound shown in reaction formula I: R1COOH: phosphine reagent: azodicarboxylic acid ester: amine and / or nitrogen-containing aromatic heterocyclic compound is 1:(1-5):(1-5):(1-5):(1-5); preferably, the molar ratio of the compound shown in reaction formula I: R1COOH: phosphine reagent: azodicarboxylic acid ester: amine and / or nitrogen-containing aromatic heterocyclic compound is 1:2:2:2:2.

[0028] Secondly, the present invention provides a method for preparing the clindamycin hydrochloride impurity shown in Formula IV, comprising one or more of the following steps:

[0029] a. The hydroxyl group of compound 1 is protected with a silicon reagent to obtain compound 2:

[0030]

[0031] R2 is R3, R4, and R5 are independently selected from alkyl groups;

[0032] b. Compound 2 undergoes selective removal of the silicon protecting group in the presence of acid to obtain the compound shown in Formula I:

[0033]

[0034] c. Prepare the intermediate of Formula II according to the preparation method of the clindamycin hydrochloride impurity intermediate shown in Formula II;

[0035] d. The intermediate of formula II undergoes a hydrolysis reaction to obtain the clindamycin hydrochloride impurity shown in formula IV:

[0036]

[0037] In some embodiments of the present invention, R3, R4, and R5 are independently selected from C1 to C6 alkyl groups; preferably, R3, R4, and R5 are independently selected from C1 to C4 alkyl groups; most preferably, R3, R4, and R5 are all methyl groups.

[0038] In some embodiments of the present invention, the acid in step b is one or more of formic acid, acetic acid, and propionic acid; preferably, the acid in step b is acetic acid.

[0039] Thirdly, the present invention provides a method for preparing the clindamycin hydrochloride impurity shown in Formula III, which further includes the following steps:

[0040] e. According to the preparation method of clindamycin hydrochloride impurity shown in Formula IV, clindamycin hydrochloride impurity shown in Formula IV is prepared;

[0041] f. Prepare the clindamycin hydrochloride impurity shown in Formula IV as a hydrochloride salt, and then perform a chlorination reaction to obtain the clindamycin hydrochloride impurity shown in Formula III:

[0042]

[0043] In some embodiments of the present invention, the chlorination reaction in step f is carried out under the following conditions: a chloroform solution of triphosgene is added to a mixed solvent of chloroform and N,N-dimethylformamide, and the reaction is allowed to proceed until Vilsmeier reagent is generated. Then, hydrochloride of formula IV is added, and the reaction is completed to obtain the product.

[0044] In some embodiments of the present invention, the silicon reagent in step a is a trialkyl halosilane and a hexaalkyldisilazane, wherein the halogen group in the trialkyl halosilane and the hexaalkyldisilazane is selected from Cl, Br, or I, preferably Cl, and the alkyl group is preferably methyl.

[0045] In some embodiments of the present invention, step a: adding a silicon protecting group, lincomycin hydrochloride (compound 1), trimethylchlorosilane, hexamethyldisilazane, and pyridine are added to a three-necked flask and reacted at 0-25°C for 8 hours. The reaction solution is then post-treated to obtain compound 2. In some embodiments of the present invention, step b: selective deprotection, the obtained compound 2 is added to a reaction flask, followed by the addition of methanol and acetic acid. The reaction solution is reacted at a temperature not exceeding 30°C for 18 hours. The reaction solution is then post-treated to obtain the compound shown in formula I.

[0046] In some embodiments of the present invention, step c: Mitsunobu substitution reaction, compound I purified in step b and toluene are added to a reaction flask, followed by triphenylphosphine, p-nitrobenzoic acid, amine and / or nitrogen-containing aromatic heterocyclic compound, and diisopropyl azodicarbonate. The reaction solution temperature does not exceed 30°C, and the reaction is carried out for 20 hours. The reaction solution is then concentrated to obtain the compound shown in formula II.

[0047] In some embodiments of the present invention, step d: hydrolysis reaction, the compound II obtained in step c is dissolved in methanol, potassium carbonate is added, the temperature of the reaction solution does not exceed 30°C, and the mixture is stirred overnight. After post-treatment, compound IV, namely 7-anazolincomycin, is obtained.

[0048] In some embodiments of the present invention, step f preferably uses the Vilsmeier reagent generated by triphosgene / DMF as the chlorinating agent.

[0049] In some embodiments of the present invention, step f: chlorination reaction, compound IV obtained in step d is converted into compound IV hydrochloride; chloroform, N,N-dimethylformamide and triphosgene are added to the reaction flask, and then compound IV hydrochloride is added, and the reaction is carried out at 0-60°C. After post-treatment, clindamycin hydrochloride impurity of formula III is obtained.

[0050] More preferably, in some embodiments of the present invention, the method for synthesizing the clindamycin hydrochloride impurity includes the following steps:

[0051] Step a: At room temperature, compound 1 and pyridine were stirred in a three-necked flask until basically dissolved. Hexamethyldisilazane and trimethylchlorosilane were added sequentially, and the temperature of the reaction solution was controlled at 2-10°C using an ice-water bath. After the addition was completed, the ice-water bath was removed, and the reaction was carried out at room temperature for 8 hours. The reaction solution was extracted, dried, concentrated, and subjected to column chromatography to obtain compound 2.

[0052] Step b: Compound 2 was dissolved in methanol under room temperature conditions, and then acetic acid solution was added. The temperature of the reaction solution did not exceed 30°C. The reaction was carried out for 18 hours. The reaction solution was washed with water, dried, filtered, and concentrated to obtain the compound shown in Formula I.

[0053] Step c: At room temperature, add the compound shown in Formula I and toluene to the reaction flask, and then add triphenylphosphine, p-nitrobenzoic acid, amine and / or nitrogen-containing aromatic heterocyclic compound, and diisopropyl azodicarbonate in sequence. Stir until homogeneous, and control the temperature of the reaction solution to not exceed 30°C. Stir for 20 hours. Wash the reaction solution with sodium bicarbonate solution and purified water, and concentrate the organic phase to obtain the compound shown in Formula II.

[0054] Step d: At room temperature, add the compound shown in Formula II, methanol, and potassium carbonate to the reaction flask, control the temperature of the reaction solution to not exceed 30°C, stir for 20 hours, and then wash, extract, concentrate, and precipitate the reaction solution by column chromatography to obtain compound IV, namely 7-diatomocytin.

[0055] Step f: Compound IV was prepared into compound IV hydrochloride at room temperature. Chloroform and N,N-dimethylformamide were added to the reaction flask, stirred until homogeneous, and then cooled in an ice-water bath. Then, a chloroform solution of triphosgene was added to the system, and the reaction was carried out at a temperature not exceeding 5°C for 0.5 hours. Compound IV hydrochloride was then added in batches, and the reaction was carried out at a temperature not exceeding 5°C for 1.5 hours. The reaction system was then carried out at room temperature and 40°C for 0.5 hours each, and finally moved to 60°C for 20 hours. After post-treatment, clindamycin hydrochloride impurity as shown in Formula III was obtained.

[0056] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, the molar ratio of clindamycin hydrochloride (compound 1), hexamethyldisilazane, and trimethylchlorosilane in step a is 1:1:2 to 1:5:10, preferably 1:3:7.

[0057] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, the specific post-processing steps in step a are as follows: the reaction solution is poured into dichloromethane, the organic phase is washed with water, dried, concentrated, and eluted by column chromatography. After elution, the product is washed with water to remove pyridine, yielding compound 2. The eluent is n-hexane and ethyl acetate in a volume ratio of 5:1-20:1; preferably, the volume ratio is 12:1.

[0058] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, in step b, the concentration of the acetic acid solution is 36%-98%, preferably 80%.

[0059] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, in step b, the temperature of the reaction solution for vacuum concentration is 25-40°C, preferably 30°C.

[0060] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, in step d, the molar ratio of the compound shown in Formula II to potassium carbonate is 1:1 to 1:5; preferably, the molar ratio is 1:1.5.

[0061] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, the post-processing steps in step d are as follows: the reaction solution is concentrated under reduced pressure, separated by solvent, extracted, dried, concentrated, and eluted by column chromatography to obtain compound IV; the eluent is dichloromethane and methanol in a volume ratio of 5:1-30:1; preferably 15:1.

[0062] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, step f specifically involves the following method for synthesizing the hydrochloride salt of compound IV: at room temperature, a mixture of compound IV, ethanol hydrochloride, and anhydrous ethanol is stirred for 10 hours, and then concentrated under reduced pressure to obtain crude hydrochloride salt of compound IV, wherein the volume ratio of ethanol hydrochloride to ethanol is 1:5-1:20; preferably 1:8.

[0063] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, in step f, the molar ratio of crude hydrochloride of compound IV to triphosgene is 1:1-1:5; preferably, the molar ratio is 1:2.

[0064] In some embodiments of the present invention, in the method for synthesizing clindamycin hydrochloride impurities, the post-processing steps in step f are as follows: the reaction solution is cooled to below 20°C, sodium hydroxide solution is added to adjust the pH to >11.0, and the mixture is stirred at room temperature for 2 hours; then the system is cooled again to below 10°C, concentrated hydrochloric acid is added to adjust the pH to <1.0, the organic phase is separated and extracted, the pH of the aqueous phase is adjusted to >11.0, and then extracted, dried, concentrated, and frozen for preservation; finally, the crude product is eluted by column chromatography, salted, and recrystallized to obtain compound III, with dichloromethane and methanol as the eluent in a volume ratio of 10:1-40:1; preferably 20:1.

[0065] This invention provides an intermediate of clindamycin hydrochloride impurity as shown in Formula II, or a salt thereof:

[0066]

[0067] R1 is an optionally substituted aryl or alkyl group; R2 is... R3, R4, and R5 are independently selected from alkyl groups.

[0068] In some embodiments of the present invention, R1 is an optionally substituted 5-14 aryl group or a C1-C6 alkyl group, and R3, R4, and R5 are independently selected from C1-C6 alkyl groups.

[0069] Preferably, R1 is an optionally substituted phenyl or C1-C4 alkyl group, and R3, R4, and R5 are independently selected from C1-C4 alkyl groups.

[0070] More preferably, R1 is p-nitrophenyl, and R3, R4, and R5 are all methyl.

[0071] The present invention also provides the use of the clindamycin hydrochloride impurity intermediate of Formula II in the preparation of 7-differentiated clindamycin hydrochloride of Formula III and / or 7-differentiated lincomycin of Formula IV.

[0072] In the context of this specification, the following abbreviations have the following meanings; for undefined abbreviations, they have generally accepted meanings:

[0073] DMF = N,N-dimethylformamide

[0074] TMSCl = Trimethylchlorosilane

[0075] (TMS)2NH=hexamethyldisilazane

[0076] TEA = Triethylamine

[0077] Py = pyridine

[0078] DIPEA = N,N-Diisopropylethylamine

[0079] DIAD = diisopropyl azodicarbonate

[0080] Ph3P = Triphenylphosphine

[0081] MeOH = methanol

[0082] PhMe = Toluene

[0083] AcOH = Acetic acid

[0084] EtOH-HCl = hydrochloric acid ethanol solution

[0085] The amines described in this invention are products of ammonia molecules in which one or more hydrogen atoms are replaced by hydrocarbon groups, including aliphatic amines and aromatic amines.

[0086] This invention provides a method for preparing clindamycin hydrochloride impurity —7-differentiated clindamycin hydrochloride, which mainly has the following beneficial effects:

[0087] 1. This invention uses lincomycin as a raw material and, through silicon protecting group addition, selective deprotection, Mitsunobu substitution reaction, hydrolysis reaction, and chlorination reaction, can prepare 7-clindamycin hydrochloride in an overall yield of 23%. The synthesized high-purity 7-clindamycin hydrochloride can be used as an impurity standard in the detection and analysis of finished clindamycin hydrochloride, thereby improving the accuracy of qualitative and quantitative analysis of impurities, facilitating the control of this impurity, and ultimately improving the quality of the finished clindamycin hydrochloride product.

[0088] 2. The synthetic route for clindamycin hydrochloride impurities provided by this invention can not only obtain 7-clindamycin hydrochloride, but also another impurity, 7-clindamycin. This route can synthesize both impurities simultaneously with a high yield, which is unmatched by existing methods.

[0089] 3. This invention uses Vilsmeier reagent generated from triphosgene / DMF as the chlorinating agent. Triphosgene is a solid and is stable in properties during production, transportation, and storage. In the reaction of step f, the reactivity of triphosgene is much greater than that of chlorinating agents such as phosphorus oxychloride, which enables the reaction to proceed more thoroughly. The wastewater generated by the reaction is reduced by half compared to the use of chlorinating agents such as phosphorus oxychloride, which reduces the cost of waste treatment and is more suitable for industrial production.

[0090] 4. This invention uses Formula II intermediates to prepare 7-differentiated clindamycin hydrochloride and 7-differentiated lincomycin, which not only reduces production costs but also provides an efficient method for preparing clindamycin hydrochloride impurity reference standards, solving the problems of low yield and high content of by-products and impurities in the preparation of 7-differentiated clindamycin hydrochloride in the prior art. Detailed Implementation

[0091] The raw materials and equipment used in the specific embodiments of the present invention are all known products, obtained by purchasing commercially available products.

[0092] The technical solution of the present invention will be further illustrated by the following embodiments.

[0093] In a preferred embodiment of the present invention, the synthetic routes for 7-clindamycin hydrochloride and 7-clindamycin are as follows:

[0094]

[0095] Example 1 Compound 2-A

[0096]

[0097] At room temperature, 50.07 g of lincomycin hydrochloride (compound 1) and 500 ml of pyridine were added to a three-necked flask and stirred until a uniform, translucent solution was obtained. The three-necked flask was then placed in an ice-water bath to cool down, with the internal temperature controlled between 2-10 °C. 75.0 ml of hexamethyldisilazane was added dropwise. When the solution turned white and turbid, 86.0 ml of trimethylchlorosilane was added dropwise. The internal temperature was controlled to not exceed 10 °C using an ice-water bath. After the addition was completed, the ice-water bath was removed, and the system was slowly heated to room temperature and reacted for 8 hours.

[0098] During the reaction, TLC plate monitoring was used (dichloromethane to methanol volume ratio of 10:1) until no reactants remained. The reaction solution was then poured into 1500 ml of dichloromethane, stirred until clear, and the organic phase was washed three times with 500 ml of water. The organic phase was dried with 75.05 g of anhydrous sodium sulfate, filtered, and evaporated to dryness to obtain 75.91 g of a yellow oil. The oil was separated by column chromatography (n-hexane to ethyl acetate volume ratio of 12:1) to obtain the title compound 2-A (69.31 g, yield: 89%).

[0099] MS (m / z): 695.3 [M+1] +

[0100] 1 H NMR (400MHz, CDCl3) δ7.82(d,J=8.9Hz,1H),5.17(d,J=5.6Hz,1H),4.43(d,J=2.4Hz,1H),4.19(dd,J=9.4,5. 6Hz,1H),4.16-4.07(m,2H),3.96(d,J=9.3Hz,1H),3.70(dd,J=9.4,3.3Hz,1H),3.60(s,1H),3.15(q,J=4.0H z,1H),2.96(dd,J=10.7,4.5Hz,1H),2.36(s,3H),2.08(s,2H),2.06-2.03(m,1H),1.97-1.89(m,2H),1.58(d ,J=4.1Hz,3H),1.31-1.20(m,5H),0.89(t,J=6.9Hz,3H),0.14(s,9H),0.13(s,9H),0.10(s,9H),0.07(s,9H).

[0101] Example 2 Compound 3

[0102]

[0103] At room temperature, 69.31 g of compound 2-A was mixed with 1400 ml of methanol and stirred to dissolve. Then, 70 ml of 80% acetic acid solution was slowly added, and the internal temperature was controlled not to exceed 30 °C. The mixture was stirred for 18 hours. After confirming the completeness of the reaction by TLC plate detection, the reaction solution was evaporated to dryness at 30 °C. Then, 600 ml of dichloromethane was added, and the organic phase was washed three times with 100 ml of sodium bicarbonate aqueous solution with pH 8.0. Finally, the mixture was dried, filtered, and concentrated to obtain title compound 3 (55.52 g, yield: 90%).

[0104] MS (m / z): 623.3 [M+1] +

[0105] 1 H NMR (400MHz, CDCl3) δ7.44(d,J=9.8Hz,1H),5.22(d,J=5.6Hz,1H),4.34(td,J=9.7,5.0Hz,1H),4.17(dd,J=9 .5,5.6Hz,1H),4.14–4.08(m,1H),4.02(d,J=9.5Hz,1H),3.81(d,J=2.1Hz,1H),3.60(dd,J=9.5,2.4Hz,1H), 3.23–3.13(m,1H),3.09(s,1H),3.01(dd,J=10.9,3.8Hz,1H),2.40(s,3H),2.10(s,3H),2.08–1.94(m,3H),1 .90–1.80(m,1H),1.38-1.25(m,4H),1.22-1.12(m,3H),0.95-0.82(m,3H),0.19(s,9H),0.17–0.13(m,18H).

[0106] Example 3-1 Compound 4

[0107]

[0108] At room temperature, 50 g of compound 3 was dissolved in 1500 ml of toluene. 48.45 g of triphenylphosphine, 26.80 g of p-nitrobenzoic acid, and 27 ml of triethylamine were added, and the mixture was stirred until homogeneous. Then, 32.18 g of DIAD was slowly added, and the reaction solution temperature was controlled below 30°C. After stirring for 20 hours, the reaction was confirmed to be complete by TLC plate analysis. 400 ml of sodium bicarbonate aqueous solution with pH 8.0 was added to the reaction solution, and the mixture was stirred for 0.5 hours. The mixture was allowed to stand and separate into layers. The organic phase was collected, washed with purified water, and dried to obtain a yellow viscous solid. This solid was then directly added to 400 ml of a mixed solvent (hexane to ethyl acetate in a volume ratio of 7:1). The mixture was stirred at room temperature for 2 hours, and the filter cake was removed by filtration. The filtrate was concentrated to obtain the title compound 4 (45 g, yield 72%).

[0109] MS(m / z): 772.3 [M+1] +

[0110] 1 H NMR (400MHz, CDCl3) δ8.32(d,J=8.8Hz,2H),8.17(d,J=8.8Hz,2H),7.68(d,J=10.7Hz,1H),5.56(q,J=6.2Hz,1H),5.15(d,J=5.5 Hz,1H),4.53(t,J=10.2Hz,1H),4.14(dd,J=9.5,5.5Hz,1H),3.93(d,J=9.9Hz,1H),3.78(d,J=2.0Hz,1H),3.54(dd,J=9.5,2.3Hz ,1H),3.26(dd,J=7.2,4.8Hz,1H),3.05(dd,J=10.8,3.9Hz,1H),2.42(s,3H),2.20–1.98(m,3H),1.92(d,J=10.1Hz,1H),1.72(s ,3H),1.35–1.32(m,3H),1.31–1.24(m,3H),1.15(d,J=6.2Hz,1H),0.91(t,J=6.8Hz,3H),0.20(s,9H),0.12(s,9H),0.10(s,9H).

[0111] Example 3-2 Compound 4

[0112]

[0113] At room temperature, 0.551 g of compound 3 was dissolved in 30 ml of dichloromethane, and 0.475 g of triphenylphosphine, 0.320 g of p-nitrobenzoic acid, and 0.3 ml of diisopropylethylamine were added. After stirring until homogeneous, 0.4 ml of DIAD was added, and the internal temperature was controlled below 30°C. After stirring for 20 hours, the title compound 4 (yield 67%) was obtained using the separation method of Example 3-1.

[0114] The mass spectrometry and proton spectrum data are basically the same as those in Example 3-1.

[0115] Example 3-3 Compound 4

[0116]

[0117] At room temperature, 0.506 g of compound 3 was dissolved in 30 ml of tetrahydrofuran, and then 0.433 g of triphenylphosphine, 0.271 g of p-nitrobenzoic acid, and 0.2 ml of pyridine were added. After stirring until homogeneous, 0.3 ml of DIAD was added. The internal temperature was controlled below 30°C, and the mixture was stirred for 20 hours. The title compound 4 (yield 60%) was obtained by the separation method of Example 3-1.

[0118] The mass spectrometry and proton spectrum data are basically the same as those in Example 3-1.

[0119] Example 4: 7-Clincomycin (Compound of Formula IV)

[0120]

[0121] At room temperature, 20 g of compound 4 was dissolved in 500 ml of methanol, and 18.43 g of potassium carbonate was added. The internal temperature was controlled below 30 °C. After stirring for 20 hours, the reaction was confirmed to be complete by TLC plate detection. The reaction solution was then evaporated to dryness to obtain a yellow viscous solid. 200 ml of ultrapure water and 300 ml of ethyl acetate were added directly, and the mixture was stirred for 10 minutes. After standing and separating the layers, the pH of the aqueous phase was adjusted to 10 with 2N KOH solution. The mixture was then extracted twice with 300 ml of ethyl acetate. The organic phases were combined and evaporated to dryness to obtain the crude product. The crude product was eluted by column chromatography (dichloromethane to methanol volume ratio of 15:1) to obtain the title compound IV (9.10 g, yield 86%, HPLC purity 98.4%).

[0122] MS(m / z): 407.2 [M+1] +

[0123] 1H NMR(400MHz, CDCl3) δ7.99(d,J=8.9Hz,1H),5.35(d,J=5.5Hz,1H),5.19(s,1H),4.40(q,J=6.3Hz,1H ),4.13(dd,J=10.0,5.4Hz,1H),4.04(d,J=10.2Hz,1H),3.84(t,J=9.5Hz,1H),3.71–3.58(m,2H),3.1 8(dd,J=7.1,4.5Hz,1H),3.02(dd,J=10.4,4.9Hz,1H),2.94–2.56(m,2H),2.38(s,3H),2.14(s,3H),2 .10–1.98(m,3H),1.97–1.81(m,2H),1.37–1.23(m,4H),1.19(d,J=6.4Hz,3H),0.88(t,J=6.6Hz,3H).

[0124] Example 5: 7-Clindamycin Hydrochloride (Compound of Formula III)

[0125]

[0126] At room temperature, 7.81 g of compound IV was dissolved in 100 ml of anhydrous ethanol, and 12 ml of 8M hydrochloric acid-ethanol solution was added. After stirring for 10 hours, the solution was evaporated to dryness to obtain 8.50 g of compound IV hydrochloride. 10.0 ml of chloroform and 7.0 ml of DMF were added to a three-necked flask, stirred thoroughly, and then cooled in an ice-water bath. 10.13 g of triphosgene was dissolved in 25.0 ml of chloroform and then slowly added dropwise to the three-necked flask, maintaining the internal temperature below 5°C. After reacting for 0.5 hours, 7.40 g of compound IV hydrochloride was added in batches, and the reaction was maintained at this temperature for 1.5 hours. Once the reaction solution became a clear yellow solution, the reaction system was moved to room temperature and reacted for 0.5 hours. Then, the temperature was raised to 40°C and reacted for 0.5 hours, followed by a further increase to 60°C and reacting for 20 hours. The reaction system was then moved to an ice-water bath and cooled, maintaining the internal temperature below 20°C, and concentrated triphosgene was added dropwise. The pH was adjusted to >11.0 with a 50% sodium hydroxide aqueous solution. After stirring at room temperature for 2 hours, the mixture was transferred to an ice-water bath for cooling. The pH was adjusted to <1.0 with 3N concentrated hydrochloric acid. The mixture was then allowed to stand and separate into layers. The aqueous layer was separated, and the organic phase was extracted with 50 ml of pH 1.0 dilute hydrochloric acid. The aqueous phases were then combined. The pH of the aqueous phase was adjusted to >11.0, and the aqueous phase was extracted with 50 ml of dichloromethane. The organic phases were then combined, washed, dried, filtered, and concentrated. The mixture was then eluted by column chromatography (dichloromethane to methanol volume ratio of 20:1) to obtain 5.02 g of yellow solid. 15 ml of ethanol was added to dissolve the solid, followed by 9.5 ml of 8M hydrochloric acid-ethanol solution. The mixture was stirred at room temperature for 2 hours and concentrated at 40 °C to obtain 5.40 g of yellow solid. The solid was then dissolved, stirred, allowed to stand, and filtered at room temperature to obtain compound III (3.54 g, yield 47%, HPLC purity 98.7%).

[0127] MS(m / z): 425.1 [M+1] +

[0128] 1H NMR (400MHz, DMSO) δ9.78 (s, 1H), 9.08 (d, J = 9.6Hz, 1H), 7.55 (s, 1H), 7.43 (s, 1H), 7.30 (s, 1H), 5.17 ( d,J=5.5Hz,1H),4.64(td,J=9.9,2.4Hz,1H),4.41(dd,J=6.7,2.6Hz,1H),4.26(s,1H),4.12–3.84(m, 2H),3.75(s,1H),3.68–3.56(m,1H),3.40(s,1H),3.30(dd,J=10.1,2.8Hz,1H),2.84(s,3H),2.29–2. 15(m,2H),2.11–1.98(m,4H),1.49–1.35(m,5H),1.27(tt,J=12.9,6.5Hz,2H),0.87(t,J=7.2Hz,3H).

[0129] 13 C NMR (101MHz, DMSO) δ167.61,89.27,70.93,69.95,68.09,67.89,67.63,60.65,59.23,53.30,36.04,35.59,34.84,20.93,19.29,14.31,13.66.

[0130] The spectrum of compound III DEPT135 shows that it contains four secondary carbons at 20.46 ppm, 34.37 ppm, 35.12 ppm and 60.18 ppm; nine tertiary carbons at 35.57 ppm, 52.83 ppm, 58.76 ppm, 67.16 ppm, 67.42 ppm, 67.62 ppm, 69.48 ppm, 70.46 ppm and 88.80 ppm; and one quaternary carbon at 167.14 ppm.

[0131] The infrared spectrum of compound III is shown in the table below:

[0132]

[0133] High-resolution mass spectra of compound III, m / z 425.1859 [M+H] + , m / z 447.1678[M+Na] + .

[0134] Comparative Example 1: Compound 4 was prepared without the addition of amines and / or nitrogen-containing aromatic heterocyclic compounds.

[0135] At room temperature, 0.805 g of compound 3 was dissolved in 30 ml of toluene, and 0.690 g of triphenylphosphine and 0.437 g of p-nitrobenzoic acid were added. After stirring evenly, 0.51 ml of DIAD was added. The internal temperature was controlled below 30 °C. After stirring for 20 hours, TLC plate detection showed that the starting material disappeared, the reaction was very disordered, and no compound 4 was formed.

[0136] As can be seen from Comparative Example 1, the target product cannot be prepared without the addition of amines and / or nitrogen-containing aromatic heterocyclic compounds. In Examples 3-1, 3-2 and 3-3 of the present invention, compound 4 can be prepared by adding amines or nitrogen-containing aromatic heterocyclic compounds (e.g., TEA, DIPEA, pyridine) and the yield is high.

[0137] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing the clindamycin hydrochloride impurity intermediate shown in Formula II, characterized in that: The compound shown in Formula I, R1COOH, phosphine reagent, and amine and / or nitrogen-containing aromatic heterocyclic compound are added to the reaction solvent, followed by the slow addition of azodicarboxylic acid ester. The reaction temperature is controlled below 30°C. After the reaction is completed, the clindamycin impurity intermediate shown in Formula II is obtained. The reaction formula is shown below: ； Wherein, R1 is p-nitrophenyl; R2 is R3, R4, and R5 are independently selected from C1-C4 alkyl groups; The amine is one or more of trimethylamine, triethylamine, triethanolamine, triallylamine, and N,N-diisopropylethylamine; The phosphine reagent is triphenylphosphine; The azodicarboxylic acid ester is diisopropyl azodicarboxylate, diethyl azodicarboxylate, or a mixture thereof; The nitrogen-containing aromatic heterocyclic compound is pyridine, 4-dimethylaminopyridine, or a mixture thereof.

2. The preparation method according to claim 1, characterized in that: R3, R4, and R5 are all methyl groups.

3. The preparation method according to claim 1, characterized in that: The reaction solvent is one or more of toluene, dichloromethane, and tetrahydrofuran; and / or Before adding azodicarboxylic acid ester, the temperature of the reaction solution should be controlled below 30℃; and / or The concentration (g: ml) of the compound shown in Formula I in the reaction solvent is (1:2) to (1:100); and / or The molar ratio of the compound shown in Formula I: R1COOH:phosphine reagent: azodicarboxylic acid ester: amine and / or nitrogen-containing aromatic heterocyclic compound is 1: (1~5): (1~5): (1~5): (1~5).

4. The preparation method according to claim 3, characterized in that: Before adding azodicarboxylic acid ester, the temperature of the reaction solution is controlled at 10~30℃.

5. The preparation method according to claim 3, characterized in that: The concentration (g:ml) of the compound shown in Formula I in the reaction solvent is 1:

30.

6. The preparation method according to claim 3, characterized in that: The molar ratio of the compound shown in Formula I: R1COOH:phosphine reagent: azodicarboxylic acid ester: amine and / or nitrogen-containing aromatic heterocyclic compound is 1:2:2:2:

2.

7. A method for preparing the clindamycin hydrochloride impurity shown in Formula IV, characterized in that: Includes the following steps a~d: a. The hydroxyl group of compound 1 is protected with a silicon reagent to give compound 2; the reaction formula is shown below: ； Where R2 is R3, R4, and R5 are independently selected from C1-C4 alkyl groups; b. Compound 2 undergoes selective desilicon protecting group removal in the presence of acid to yield the compound shown in Formula I; the reaction formula is shown below: ； Wherein, the acid mentioned in step b is acetic acid; c. The intermediate of Formula II is prepared by the preparation method according to any one of claims 1 to 5; d. The intermediate of formula II undergoes a hydrolysis reaction to obtain the clindamycin hydrochloride impurity shown in formula IV; the reaction formula is shown below: 。 8. The preparation method according to claim 7, characterized in that: R3, R4, and R5 are all methyl groups.

9. The clindamycin hydrochloride impurity intermediate or its salt as shown in Formula II: ； in, R1 is p-nitrophenyl; R2 is R3, R4, and R5 are independently selected from C1 to C4 alkyl groups.

10. The intermediate or its salt as described in claim 9: R3, R4, and R5 are all methyl groups.

11. Use of the clindamycin hydrochloride impurity intermediate according to claim 9 or 10 in the preparation of 7-diacritic lincomycin of formula IV, wherein the structure of 7-diacritic lincomycin of formula IV is as follows: 。

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