阅读说明：本技术 一种分离卡前列素15位异构体的方法 (Method for separating carboprost 15-position isomer ) 是由 王方道 王东 王猛 吴伟锋 于 2020-12-21 设计创作，主要内容包括：本发明公开了一种卡前列腺素15位异构体杂质分离技术方法,属于药物化学分离技术领域。将带有15位羟基叔醇化合物B,通过PG保护得到15位S型卡前列素D和15位R型卡前列素E(组成15位羟基叔醇化合物C),分离后得到15位卡前列素D或15位卡前列素E纯品。在此基础上,本发明还提供了一种适合工业化放大的制备卡前列素系列产品的方法。本发明方法通过合适的保护基衍生后,采用普通硅胶柱层析即可分离异构体,操作简单,得到产物的质量满足要求,大大降低生产成本,提高产品的综合效益。(The invention discloses a separation technical method of 15-bit isomer impurities of caprostaglandin, belonging to the technical field of medicinal chemistry separation. And (3) performing PG protection on the compound B with 15-site hydroxyl tertiary alcohol to obtain 15-site S-type carboprost D and 15-site R-type carboprost E (forming a 15-site hydroxyl tertiary alcohol compound C), and separating to obtain a pure product of the 15-site carboprost D or the 15-site carboprost E. On the basis, the invention also provides a method for preparing carboprost series products suitable for industrial scale-up. The method can separate isomers by adopting common silica gel column chromatography after being derived by a proper protecting group, has simple operation, meets the requirement on the quality of the obtained product, greatly reduces the production cost and improves the comprehensive benefit of the product.)

1. A method for separating the 15 th isomer of carboprost, comprising the steps of: and (3) performing PG protection on the compound B with 15-site hydroxyl tertiary alcohol to obtain 15-site S-type carboprost D and 15-site R-type carboprost E (forming a 15-site hydroxyl tertiary alcohol compound C), and separating to obtain a 15-site S-type carboprost D pure product and a 15-site R-type carboprost E pure product. The corresponding structure is as follows:

wherein, R is THP, TES, TBS, Bz and Bn.

2. The method of separating carboprost 15 isomer of claim 1, wherein: the PG protection is selected from benzoyl, trityl, triethyl silicon, acetyl, p-toluenesulfonyl or benzyl.

3. The method of separating carboprost 15 isomer of claim 1, wherein: the difference value of the separation Rf is more than 0.05, and column chromatography, a thin-layer color plate or an HPLC preparative column is adopted for separation.

4. A preparation method of carboprost 1 is characterized in that the reaction equation is represented as follows:

wherein, R is THP, TES, TBS or Bz;

the method comprises the following steps: carrying out addition reaction on the compound A and a methyl Grignard reagent at low temperature to obtain a compound B; protecting the compound B with acetyl to obtain a compound C1; separating the compound C1 by column chromatography to obtain 15S carboprost D1; 15S carboprost D1 to obtain compound F; the compound F is subjected to a Witig reaction to obtain carboprost 1.

5. The method of claim 4, wherein the carboprost 1 is prepared by: the first step methyl grignard reagent is selected from methyl magnesium chloride, methyl magnesium bromide or methyl magnesium iodide.

6. The method of claim 4, wherein the carboprost 1 is prepared by: the first step reaction solvent is one or more of THF, 2-MeTHF or toluene; the reaction temperature is below 0 ℃.

7. The method of claim 4, wherein the carboprost 1 is prepared by: the second acetyl protection is carried out by using acetyl chloride or acetic anhydride under the condition of triethylamine, pyridine or diisopropylethylamine.

8. The method of claim 4, wherein the carboprost 1 is prepared by: and in the third step, DIBAL-H is adopted for reduction, and acetyl is also removed at the same time without additional hydrolysis.

9. The method of claim 4, wherein the carboprost 1 is prepared by: the third step reaction solvent is 2-MeTHF or THF; the reaction temperature is below 0 ℃.

10. A preparation method of carboprost methyl ester 2 and carboprost tromethamine 3 is characterized in that: carboprost 1 is synthesized by the method of any of claims 4-8, and then carboprost 1 is converted to carboprost methyl ester 2 and carboprost tromethamine 3 according to the literature or patent.

Technical Field

The invention relates to the technical field of medicinal chemical separation, in particular to a novel technical method for separating impurities of a caprostaglandin 15-position tertiary alcohol R isomer.

Background

Prostaglandins (PGs) are important endogenous products with a wide range of physiological activities. PGs are present in almost all mammalian tissues, play an important role in the reproductive, digestive, respiratory and cardiovascular systems, and are involved in physiological and pathological processes such as thermoregulation, inflammatory responses, glaucoma, pregnancy, hypertension, ulcers and asthma.

The structural characteristics of PGs are as follows: has a five-membered alicyclic ring and two side chains, wherein the upper chain generally has 7 carbons, and the lower side chain has 8 carbons to form 20-carbon unsaturated fatty acid and the like. PGs were first discovered and named by Von Eluer, american scholars, in 1930, and Bergstorm, 1962, extracted two pure forms of PG (PGFl and PGF2) and determined their chemical structures. In 1969 Willis first proposed that PGs is an inflammatory mediator in the body. Subsequently, various physiological activities and pharmacological activities of PGs were intensively studied.

Prostaglandins have the defects of few natural sources, difficult extraction, rapid in vivo metabolism, poor stability and the like, so scientists synthesize a series of prostaglandin substances or analogues successively and completely to meet clinical requirements.

The traditional Chinese medicine composition is successfully applied to induced labor, induction of birth and induced abortion in clinic at present, and the marketed medicines comprise: carboprost (1), carboprost methyl ester (2), carboprost tromethamine (3), etc., whose structures are represented as follows:

the synthesis strategy of carboprost is to utilize a key intermediate Corey lactone to respectively graft an upper side chain and a lower side chain at alpha and omega positions, and a typical synthesis reaction route is as follows:

in 1974, carboprost methyl ester was first synthesized by Ernest W.yankee (J.Am.chem.Soc.,1974,96, 5865-; similar synthetic methods are also reported in Pranav Patel (j. org. chem.2008,73, 7213-: separation of 15R isomers of carglactin methyl ester is carried out by performing high-efficiency preparative chromatography column chromatography in the penultimate step, so that the capacity is greatly limited, and the production efficiency is influenced; in WO2017093770 a1, however, it was reported that 15R isomer was removed by column chromatography using chromatoreexmb type silica gel having a particle size of 40 to 70 μm, with a yield of only 57%. The chiral filler in the method is expensive, the production cost is greatly increased, and the industrial large-scale application of the chiral filler is limited. Patent CN 1136938C discloses the use of simulated moving bed chromatography (SMBC for short) to separate cardprost methyl ester, the method has high equipment investment, is not suitable for industrial production, and the separation purity is only 90%, which cannot meet the requirements of pharmacopoeia on isomers.

Patent CN110746333A in 2019 reports that separation is carried out by using D-camphorsulfonyl chloride as a chiral resolving agent, and the reaction equation is as follows:

the selectivity of hemiacetal hydroxyl and 15-site tertiary hydroxyl is to be verified, and meanwhile, the biphenyl formyl exists in the molecule and the chiral camphor sulfonyl is introduced, so that the whole molecule is more complex, the yield of three steps is only about 17%, and the difficulty and uncertainty are brought to subsequent industrial mass production.

Along with the expansion of the drug effect of the carboplatin, the carboplatin is favored by more and more manufacturers, and has great market potential. Therefore, the existing synthesis process is optimized, the yield is improved, the cost is reduced, and great practical significance and economic value are achieved; meanwhile, a more simple and feasible large-scale production process is designed, market first opportunity is obtained, the method is one of the focuses of researching the prostaglandin synthesis process, and the method has extremely important significance in filling up the process blank and creating economic value.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: after a proper protecting group is introduced into the 15-position hydroxyl isomer produced by the prior art, the 15-position hydroxyl isomer can be removed by a simple purification method (such as column chromatography) so as to remarkably improve the yield and the degree of difficulty in operation and improve the product quality, thereby enhancing the competitiveness of products of companies. On the basis, the invention also provides a method for preparing carboprost series products suitable for industrial scale-up.

The invention relates to a method for separating carboprost 15 isomer, which is technically characterized in that: and (3) performing PG protection on the compound B with 15-site hydroxyl tertiary alcohol to obtain 15-site S-type carboprost D and 15-site R-type carboprost E (forming a 15-site hydroxyl tertiary alcohol compound C), and separating to obtain a 15-site S-type carboprost D pure product and a 15-site R-type carboprost E pure product.

Wherein, R is THP, TES, TBS, Bz and Bn.

Further, in the above technical scheme, the PG protection is selected from benzoyl, trityl, triethylsilicon, acetyl, p-toluenesulfonyl, benzyl, and the like. Under the optimized condition, the acetyl is most ideal in separation effect.

Further, in the above technical scheme, the Rf difference during the separation is above 0.05, and column chromatography, thin-layer chromatography, HPLC preparative column, etc. are used for the separation. Preferably, column chromatography is used for separation.

On the basis of the separation scheme, the invention also provides a preparation method of carboprost, which comprises the following steps: carrying out addition reaction on the compound A and a methyl Grignard reagent at low temperature to obtain a compound B; protecting the compound B with acetyl to obtain a compound C1; separating the compound C1 by column chromatography to obtain 15S carboprost D1; 15S carboprost D1 to obtain compound F; the compound F is subjected to a Witig reaction to obtain carboprost 1. The following equation is used:

further, in the above technical solution, the first step methyl grignard reagent is selected from methyl magnesium chloride, methyl magnesium bromide or methyl magnesium iodide.

Further, in the technical scheme, the first-step reaction solvent is one or more of THF, 2-MeTHF or toluene; the reaction temperature is 0 ℃ or lower, preferably-50 ℃ or lower.

Further, in the above technical scheme, the acetyl protection in the second step is performed by using acetyl chloride or acetic anhydride under the condition of triethylamine, pyridine or diisopropylethylamine.

Furthermore, in the technical scheme, DIBAL-H is adopted for reduction in the third step, acetyl is also removed at the same time, and additional hydrolysis is not needed.

Further, in the technical scheme, the third step reaction solvent is 2-MeTHF or THF; the reaction temperature is 0 ℃ or lower, preferably-50 ℃ or lower.

In the process of practical experiments, the intermediate B tertiary alcohol is obtained by adding carbonyl in the compound A, and the tertiary alcohol has two configurations of R and S and an original chiral structure in a molecule, so that the molecule belongs to epimers (diastereoisomers) and can be separated theoretically. In the experimental process, when TLC detection is carried out, different developing agents are tried to be adopted, and separation signs cannot be seen all the time; separation by HPLC seems to be evident, but it is always difficult to separate at baseline, and thus separation efficiency is usually very low for this intermediate by preparative chromatography.

Then, the newly produced tertiary alcohol is derivatized, for example, with benzoyl, trityl, triethylsilane, acetyl, p-toluenesulfonyl, benzyl, etc. for protection, and after screening, it is found that when acetyl protection is employed, the tertiary alcohol is completely reacted, and two points of reduced polarity (Rf difference of 0.05 or more) are formed by TLC detection, and the R isomer can be efficiently separated by ordinary silica gel column chromatography, and the target S configuration intermediate D1 can be obtained in high yield.

Further, in the above technical scheme, the synthesis process is typically as follows: the reactor was charged with the compound A synthesized as described in paragraph 0166 and 0178 of patent CN 108602769A. Then dissolving the mixture by toluene, cooling the mixture to below-50 ℃, dropwise adding methyl magnesium chloride Grignard reagent to obtain epimeric tertiary alcohol B, dropwise adding acetic anhydride in the presence of triethylamine, stirring the mixture at room temperature to complete the conversion into acetyl protected tertiary alcohol ester C1, and detecting the ester by TLC as two points with small polarity (developing agent PE/EA is 2/1, Rf is 0.6 and 0.7). Purifying by common silica gel column chromatography to obtain small polar target molecule D1 and slightly larger polar isomer E1. Then DIBAL-H reduces lactone, acetyl is removed at the same time, key intermediate F is obtained in one step, and carboprost 1 is obtained through wittig reaction.

Further, in the above-mentioned technical solution, carboprost 1 is converted into carboprost methyl ester 2 and carboprost amine butanetriol 3 according to the existing literature or patent.

The invention has the positive effects

The invention successfully develops a method for removing the 15R hydroxyl isomer of the carboprost, removes the carboprost 15R hydroxyl isomer in time when the chiral isomer is introduced, avoids the high-efficiency liquid phase separation of the 15R isomer by the final carboprost methyl ester, avoids the two hydroxyl selectivity potential risks and low yield in industrial amplification production caused by using the D-camphorsulfonyl chloride as a resolving agent, separates the carboprost methyl ester by the common silica gel column chromatography, has simple operation, meets the quality requirement of the obtained product, greatly reduces the production cost and improves the comprehensive benefit of the product.

The industrial preparation method of the carboprost { comprising the currently marketed carboprost (1), carboprost methyl ester (2) and carboprost amine butanetriol (3) } has simple operation and high yield, avoids the potential toxic risk of high-activity substances to operators caused by separation at a high-activity stage, improves the product quality, greatly reduces the requirements on production equipment, and improves the product competitiveness.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions. The following examples are given for R ═ TBS, TES and Bz. The reagents and starting materials used in the present invention are commercially available.

Example 1 example with protecting agent R ═ TBS

The first step is as follows: 60g of compound A was synthesized as a white solid in a yield of 95% as described in paragraph 0166 and 0178 of CN 108602769A.

The second step is that: in a 2L three-necked flask, compound A (55.0g,145mmol) was added, followed by 800mL of toluene, followed by cooling to-50 ℃ or below under nitrogen, 3M MeMgCl tetrahydrofuran solution (120mL) was added dropwise, and the reaction was stopped when the starting material was completely disappeared by TLC. The reaction mixture was warmed to 0 ℃ and 500mL of a saturated aqueous ammonium chloride solution was slowly added dropwise thereto, followed by addition of a 3M aqueous hydrochloric acid solution dropwise until the pH became 3 to 4. The organic layer was separated, the aqueous layer was extracted with 200mL of ethyl acetate, and the organic layers were combined, washed successively with a saturated aqueous sodium bicarbonate solution and a saturated brine, and dried over anhydrous sodium sulfate. Filtering, vacuum distilling to obtain crude product, silica gel column flash column chromatography to obtain 55.1g pale yellow viscous liquid B with 96% yield.

In the third step, intermediate B (55g,139mmol) was dissolved in 300mL of dichloromethane under nitrogen, and triethylamine (21.0g,200mmol) was added. Stirring was started, acetic anhydride (18.0g, 176mmol) was added dropwise, and the reaction was stirred at room temperature for 24 hours after the addition. TLC detection, the material disappeared completely, two small polar spots were formed. Concentrating under reduced pressure, washing with half saturated salt water, and drying. The crude product obtained by filtration was subjected to silica gel column chromatography with ethyl acetate/petroleum ether as the mobile phase and subjected to rapid separation to obtain a small-polarity product as a pale yellow oily liquid D1, 36.5g, yield 60%.

The fourth step: to a 500mL reaction flask, compound D1(36.5g,83.2mmol) and 100mL tetrahydrofuran were added, cooled to below-50 ℃ under nitrogen, and a 1.6M DIBAL-H toluene solution (260mL,416mmol) was started dropwise while maintaining the reaction temperature at no more than-50 ℃. After the addition was complete, the reaction was continued for 10 minutes with stirring at this temperature and the starting material was completely lost by TLC to give a slightly more polar product (EA/PE: 1/1, Rf: 0.5). Pouring the reaction solution into a rapidly stirred 1M cold hydrochloric acid aqueous solution, and adding acid while pouring so as to keep the reaction solution in an acidic environment all the time. After the addition, the pH was adjusted to 3-4, the mixture was transferred to a separatory funnel, extracted twice with ethyl acetate, and the organic phases were combined, washed with a saturated aqueous sodium bicarbonate solution and a saturated saline solution in this order, dried over anhydrous sodium sulfate, filtered and concentrated to dryness to obtain 36.5g of a pale yellow oily liquid as an intermediate F. The next reaction was carried out without further purification.

The fifth step: under the protection of nitrogen, 4-carboxybutyltriphenylphosphonium bromide (100g,225mmol) and 300mL of tetrahydrofuran were added to a 3L reaction flask with mechanical stirring, the temperature was reduced to-10 deg.C, potassium tert-butoxide (73.0g,0.65mol) was added, and then the mixture was stirred for 10 minutes at-5 deg.C. The temperature was controlled at-5 ℃ to-10 ℃, and a solution of intermediate F (36.5g,0.128mol) in 300mL of tetrahydrofuran was added dropwise to the reaction mixture. After dropping, the reaction was stopped by keeping the temperature for 12 hours. 500mL of water was added to the reaction system. The mixture was extracted with 300mL of ethyl acetate, the pH of the aqueous phase was adjusted to 4 to 5 by adding citric acid, and the mixture was extracted with 300mL of ethyl acetate and dried over anhydrous sodium sulfate. Filtration, concentration and column chromatography purification gave 24.5g of a pale yellow viscous oily liquid as casstaglandin 1 with an HPLC purity of 98.1% and a two-step yield of 66.7%.

And a sixth step: carboprost (24.5g,66.8mmol) was dissolved in filtered 135mL isopropanol, tromethamine (8.5g,70.2mmol) was added and the reaction mixture was stirred at room temperature for 1 hour. Filtering, concentrating, adding isopropanol and acetone, stirring at 20 deg.C for crystallization, and filtering to obtain wet product 30.0 g. Dissolving the wet product in isopropanol, filtering, removing mechanical impurities, concentrating most of the solvent, adding acetone, crystallizing, filtering, and drying at 40 deg.C to obtain 25.2g white solid. HPLC purity 98.7%, no 15R isomer. The yield thereof was found to be 77.0%.

Example 2 example with protecting agent R ═ TES

The first step is as follows: 6.0g of Compound A was synthesized as a white solid in a yield of 95% as described in paragraph 0166 and 0178 of CN 108602769A.

The second step is that: in a 2L three-necked flask, compound A (5.5g,14.5mmol) was added, followed by addition of 80mL of toluene, followed by cooling to-50 ℃ or below under nitrogen, 3M MeMgCl tetrahydrofuran solution (12mL) was added dropwise, and the reaction was stopped when the starting material was completely disappeared by TLC detection. The reaction mixture was warmed to 0 ℃ and 50mL of a saturated aqueous ammonium chloride solution was slowly added dropwise thereto, followed by addition of a 3M aqueous hydrochloric acid solution dropwise until the pH became 3 to 4. The organic layer was separated, the aqueous layer was extracted with 20mL of ethyl acetate, and the organic layers were combined, washed successively with a saturated aqueous sodium bicarbonate solution and a saturated brine, and dried over anhydrous sodium sulfate. Filtering, vacuum distilling to obtain crude product, silica gel column flash column chromatography to obtain 5.5g pale yellow viscous liquid B with 96% yield.

In the third step, intermediate B (5.5g,13.9mmol) was dissolved in 30mL of dichloromethane under nitrogen, and triethylamine (2.1g,20mmol) was added. Stirring was started, acetic anhydride (1.8g, 17.6mmol) was added dropwise, and the reaction was stirred at room temperature for 24 hours after the addition was completed. TLC detection, the material disappeared completely, two small polar spots were formed. Concentrating under reduced pressure, washing with half saturated salt water, and drying. The crude product obtained by filtration was subjected to silica gel column chromatography with ethyl acetate/petroleum ether as the mobile phase and subjected to rapid separation to obtain a small-polarity product as a pale yellow oily liquid D1, 3.60g, yield 59%.

The fourth step: to a 100mL reaction flask, compound D1(3.6g,8.2mmol) and 10mL tetrahydrofuran were added, cooled to below-50 ℃ under nitrogen, and 1.6M DIBAL-H in toluene (25.6mL,41.0mmol) was added dropwise while maintaining the reaction temperature at no more than-50 ℃. After the addition was complete, the reaction was continued at this temperature for 10 minutes with complete disappearance of starting material by TLC, yielding a slightly more polar product. Pouring the reaction solution into a rapidly stirred 1M cold hydrochloric acid aqueous solution, and adding acid while pouring so as to keep the reaction solution in an acidic environment all the time. After the addition, the pH was adjusted to 3-4, the mixture was transferred to a separatory funnel, extracted twice with ethyl acetate, and the organic phases were combined, washed with a saturated aqueous sodium bicarbonate solution and a saturated saline solution in this order, dried over anhydrous sodium sulfate, filtered and concentrated to dryness to obtain 3.70g of a pale yellow oily liquid as an intermediate F. The next reaction was carried out without further purification.

The fifth step: under the protection of nitrogen, in a 300mL reaction bottle with a mechanical stirrer, 4-carboxybutyltriphenylphosphonium bromide (10g,22.5mmol) and 30mL tetrahydrofuran were added, the temperature was reduced to-10 ℃, potassium tert-butoxide (7.30g,65mmol) was added, and then the mixture was stirred for 10 minutes at-5 ℃. The temperature was controlled at-5 ℃ to-10 ℃, and a solution of intermediate F (3.70g,13.0mmol) in 30mL of tetrahydrofuran was added dropwise to the reaction mixture. After dropping, the reaction was stopped by keeping the temperature for 12 hours. 50mL of water was added to the reaction system. The mixture was extracted with 30mL of ethyl acetate, the pH of the aqueous phase was adjusted to 4 to 5 by adding citric acid, and the mixture was extracted with 30mL of ethyl acetate and dried over anhydrous sodium sulfate. Filtration, concentration and column chromatography purification gave 2.45g of a pale yellow viscous oily liquid as caprostaglandin 1 with an HPLC purity of 98.3% and a two-step yield of 66.8%.

And a sixth step: carboprost (2.45g,6.65mmol) was dissolved in filtered 13.5mL isopropanol, 0.85g tromethamine (7.02mmol) was added and the reaction mixture was stirred at room temperature for 1 hour. Filtering, concentrating, adding isopropanol and acetone, stirring at 20 deg.C for crystallization, and filtering to obtain wet product 3.0 g. Dissolving the wet product in isopropanol, filtering, removing mechanical impurities, concentrating most of the solvent, adding acetone, crystallizing, filtering, and drying at 40 deg.C to obtain 2.5g white solid. HPLC purity 98.8%, no 15R isomer. The yield thereof was found to be 77.0%.

Example 3 is exemplified with the protecting agent R ═ Bz

The first step is as follows: 30g of compound A was synthesized as an oily liquid in a yield of 80% as described in paragraph 0166 and 0178 of CN 108602769A.

The second step is that: in a 1L three-necked flask, compound A (25.0g) was added, followed by addition of 400mL of toluene, followed by cooling to-50 ℃ or below under nitrogen, and 3M MeMgCl tetrahydrofuran solution (60mL) was added dropwise to complete disappearance of the starting materials by TLC detection, thereby stopping the reaction. The reaction mixture was warmed to 0 ℃ and 250mL of a saturated aqueous ammonium chloride solution was slowly added dropwise thereto, followed by addition of a 3M aqueous hydrochloric acid solution dropwise until the pH became 3 to 4. The organic layer was separated, the aqueous layer was extracted with 100mL of ethyl acetate, and the organic layers were combined, washed successively with a saturated aqueous sodium bicarbonate solution and a saturated brine, and dried over anhydrous sodium sulfate. Filtering, vacuum distilling to obtain crude product, silica gel column flash column chromatography to obtain 27.5g pale yellow viscous liquid B, yield 96%.

In the third step, intermediate B (27.5g) was dissolved in 150mL of dichloromethane under nitrogen and triethylamine (10.5g) was added. Stirring was started, acetic anhydride (9.0g) was added dropwise thereto, and the reaction was stirred at room temperature for 24 hours after the completion of the addition. TLC detection, the material disappeared completely, two small polar spots were formed. Concentrating under reduced pressure, washing with half saturated salt water, and drying. The crude product obtained by filtration was subjected to silica gel column chromatography with ethyl acetate/petroleum ether as the mobile phase and subjected to rapid separation to obtain a small-polarity product as a pale yellow oily liquid D1, 18.2g, yield 59%.

The fourth step: to a 250mL reaction flask, compound D1(18.2g,42.5mmol) and 50mL tetrahydrofuran were added, cooled to below-50 ℃ under nitrogen, and 1.6M DIBAL-H in toluene (187.5mL,300.0mmol) was added dropwise while maintaining the reaction temperature at no more than-50 ℃. After the addition was complete, the reaction was continued at this temperature for 10 minutes with complete disappearance of starting material by TLC, yielding a slightly more polar product. Pouring the reaction solution into a rapidly stirred 1M cold hydrochloric acid aqueous solution, and adding acid while pouring so as to keep the reaction solution in an acidic environment all the time. After the addition, the pH was adjusted to 3-4, the mixture was transferred to a separatory funnel, extracted twice with ethyl acetate, and the organic phases were combined, washed with a saturated aqueous sodium bicarbonate solution and a saturated brine in this order, dried over anhydrous sodium sulfate, filtered and concentrated to dryness to obtain 18.0g of a pale yellow oily liquid as an intermediate F. The next reaction was carried out without further purification.

The fifth step: under the protection of nitrogen, 4-carboxybutyltriphenylphosphonium bromide (50g) and 150mL of tetrahydrofuran were added to a 3L reaction flask with mechanical stirring, the temperature was reduced to-10 ℃, potassium tert-butoxide (36.5g) was added, and then the mixture was stirred for 10 minutes at-5 ℃. The temperature was controlled at-5 ℃ to-10 ℃, and a solution of intermediate F (18.0g,63.4mmol) in 150mL of tetrahydrofuran was added dropwise to the reaction mixture. After dropping, the reaction was stopped by keeping the temperature for 12 hours. 150mL of water was added to the reaction system. The mixture was extracted with 150mL of ethyl acetate, the pH of the aqueous phase was adjusted to 4 to 5 by adding citric acid, and the mixture was extracted with 150mL of ethyl acetate and dried over anhydrous sodium sulfate. Filtration, concentration and column chromatography purification gave 12.2g of a pale yellow viscous oily liquid as casstaglandin 1, with an HPLC purity of 98.0% and a two-step yield of 66.5%.

And a sixth step: carboprost (12.2g,33.1mmol) was dissolved in filtered 70mL isopropanol, tromethamine (4.2g,34.7mmol) was added and the reaction mixture was stirred at room temperature for 1 hour. Filtering, concentrating, adding isopropanol and acetone, stirring at 20 deg.C for crystallization, and filtering to obtain wet product 15.0 g. Dissolving the wet product in isopropanol, filtering, removing mechanical impurities, concentrating most of the solvent, adding acetone, crystallizing, filtering, and drying at 40 deg.C to obtain 12.5g white solid. HPLC purity 98.5% without 15R isomer. The yield thereof was found to be 76.5%.

The foregoing embodiments have described the general principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the present invention, and that various changes and modifications may be made without departing from the scope of the principles of the present invention, and the invention is intended to be covered by the appended claims.