Method for synthesizing UDCA by taking 4-AD as raw material

Abstract

The invention provides a method for synthesizing UDCA by taking 4-AD as a raw material, and belongs to the technical field of organic chemistry and medicine synthesis. The ursodesoxycholic acid is synthesized by taking 4-AD as a raw material through the steps of selective protection of 3, 17-carbonyl, bile acid side chain construction, 7-site oxidation, one-step reduction of 4-ene-3-ketone into a 3alpha-hydroxy-5beta-hydrogen A / B cis structure and the like. The method has the advantages of cheap and easily available raw materials, mild reaction conditions, green and safe reagents, simple post-treatment, low cost and high yield, and has certain industrial application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemistry and drug synthesis, and in particular to a method for synthesizing UDCA using 4-AD as a raw material. Background Art

[0002] Ursodeoxycholic acid (UDCA), chemical name 3α,7β-dihydroxy-5β-cholan-24-oic acid, CAS No. 128-13-2, molecular formula C 24 H 40 O4, molecular weight 392.56, white powder, odorless, bitter, melting point 203 ~ 204 ℃. Ursodeoxycholic acid is a natural hydrophilic bile acid derived from cholesterol. It can reduce the saturation of cholesterol by inhibiting the reabsorption of cholesterol in the intestine and reducing the secretion of cholesterol into bile. It is mainly used clinically for the treatment of cholelithiasis, cholestatic liver disease, bile reflux gastritis, primary sclerosing cholangitis, etc. The structural formula of UDCA is:

[0003]

[0004] Bear bile in traditional Chinese medicine is made by cutting the gallbladder of bears, which has limited sources and violates animal protection. my country now adopts artificial breeding and extracting UDCA alive, but the steps are numerous, the cycle is long, the yield is low, it cannot meet medical requirements, and it is also inhumane; therefore, artificial synthesis of UDCA has far-reaching significance. Given that the natural bile acid structure of many animals has the A / B cis 3α-hydroxy-5β structural unit in UDCA, the current chemical synthesis method mainly uses pig, chenodeoxycholic acid, bile acid, etc. as raw materials to synthesize UDCA through semi-synthetic method.

[0005] The synthesis reports of ursodeoxycholic acid mainly include the following methods: (1) Using hyodeoxycholic acid as the raw material, ursodeoxycholic acid was synthesized with a total yield of 15% through 7 steps of reaction (Journal of the Chemical Society Perkin Transactions, 1990, 1: 1-3.). The raw materials used in this route are cheap and easy to obtain, but the steps are complicated and the yield is low. At the same time, the last step of the reaction uses lithium-liquid ammonia reduction, which is more dangerous. (2) Using hyodeoxycholic acid as the raw material, ursodeoxycholic acid was synthesized with a total yield of 16% through 9 steps of reaction (Synthesis, 2016, 48: 588-594.). The raw materials used in this route are cheap and easy to obtain, but the steps are too complicated and the yield is low. Similarly, metallic sodium is used during the reduction, the reaction is violent, and the risk is relatively high. (3) Using bile acid as the raw material, ursodeoxycholic acid was synthesized with a total yield of 15% through 7 steps of reaction (Acta Chem Scand, 1963, 17: 173-186.). This route uses Wolff-Kishner reaction reduction, which has a low safety factor due to the high toxicity and easy explosion of hydrazine. (4) Using chenodeoxycholic acid as the raw material, ursodeoxycholic acid was synthesized with a total yield of 64% through 2 steps of reaction (Bioorganic & Medicinal Chemistry, 2016, 24: 3986-3993). This route is shorter and has a relatively high yield, but the raw material chenodeoxycholic acid is more expensive.

[0006] Currently, the reported methods for synthesizing ursodeoxycholic acid mostly use animal bile acid as raw material. The extraction and purification steps are cumbersome and inhumane. Not only is it relatively expensive, but its safety is also worrying. Therefore, some scholars have also explored methods for synthesizing ursodeoxycholic acid based on plant-based raw materials. For example: using BA as raw material, ursodeoxycholic acid (steroids.2020.108600.) was synthesized with a total yield of 59% after 6 steps of reaction. This method has cheap raw materials and high yields, but almost every step of the reaction post-processing requires column chromatography separation and purification, and the last step of reduction also requires high temperature and high pressure. There is room for optimization in industrial production.

[0007] The existing methods have the disadvantages of expensive raw materials, complicated construction of chiral centers, and harsh conditions. Therefore, it is necessary to explore a method for synthesizing ursodeoxycholic acid that uses plant sources as raw materials, is easy to operate, and has mild conditions. Summary of the invention

[0008] In view of this, the present invention aims to provide a method for synthesizing ursodeoxycholic acid using 4-androsten-3,17-dione (4-AD) as a raw material, through selective protection of 3, 17-carbonyl groups, construction of bile acid side chains, oxidation at position 7, and one-step reduction of 4-ene-3-one to 3α-hydroxy-5β-hydrogen A / B cis structure. The method has cheap and readily available raw materials, mild reaction conditions, green and safe reagents, simple post-treatment, low cost, high yield, and has certain industrial application prospects.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A method for synthesizing UDCA using 4-AD as a raw material comprises the following steps:

[0011] Step 1, 4-AD, triethyl orthoformate and acid are subjected to enol ether protection reaction in ethanol to obtain compound 1;

[0012] Step 2, the compound 1 is subjected to Wittig reaction with triphenylethylphosphonium bromide under alkaline conditions, and then the protecting group is removed by acid hydrolysis to obtain compound 2;

[0013] Step 3, the compound 2, p-toluenesulfonic acid, triethyl orthoformate and ethylene glycol undergo 3-carbonyl ketal protection reaction to obtain compound 3;

[0014] Step 4, in the presence of a Lewis acid catalyst, the compound 3 and methyl propiolate undergo an ene condensation reaction, and the 17-side chain is extended to obtain compound 4;

[0015] Step 5, under the action of catalyst Pd / C, the compound 4 undergoes reduction reaction 1 with hydrogen to obtain compound 5;

[0016] Step 6, under the action of a catalyst such as tert-butyl peroxide or N-hydroxyphthalimide, the compound 5 undergoes an oxidation reaction with an oxidant to obtain a compound 6;

[0017] Step 7, the compound 6 is subjected to hydrolysis reaction 1 under acidic conditions to obtain compound 7;

[0018] Step 8, under the action of catalyst Pd / C, the compound 7 undergoes reduction reaction 2 with hydrogen to obtain compound 8;

[0019] Step 9, the compound 8 undergoes a reduction reaction 3 with cuprous chloride and sodium borohydride to obtain a compound 9;

[0020] Step 10, the compound 9 undergoes hydrolysis reaction 2 under alkaline conditions to obtain the UDCA (ursodeoxycholic acid, 10).

[0021] The general reaction formula is:

[0022]

[0023] In some embodiments of the present invention, in step 1, the acid is p-toluenesulfonic acid and / or pyridine p-toluenesulfonate, preferably pyridine p-toluenesulfonate; in the present invention, p-toluenesulfonic acid and pyridine p-toluenesulfonate are used as catalysts. The molar ratio of 4-AD, triethyl orthoformate and acid is 1:(1-2):(0.01-1), preferably 1:1.2:0.03; the reaction temperature of the enol ether protection reaction is 0-60°C, and the reaction time is 2-24h. Preferably, the reaction temperature of the enol ether protection reaction is 25°C, and the reaction time is 14h.

[0024] In some embodiments of the present invention, in step 2, the base used in the alkaline condition is at least one of sodium tert-butoxide, potassium tert-butoxide and sodium hydrogen, preferably potassium tert-butoxide; the molar ratio of the compound 1, triphenylethylphosphonium bromide and the base is 1:(1-3):(1-4), preferably 1:2:3; the reaction temperature of the Wittig reaction is 25-100°C, and the reaction time is 1-12h, preferably, the reaction temperature of the Wittig reaction is 80°C, and the reaction time is 6h; the acid used for the acid hydrolysis to remove the protecting group is at least one of sulfuric acid, hydrochloric acid and p-toluenesulfonic acid, preferably sulfuric acid.

[0025] In some embodiments of the present invention, the solvent used in the reaction system of step 2 is benzene, tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether or N,N-dimethylformamide, preferably 2-methyltetrahydrofuran.

[0026] In some embodiments of the present invention, in step 3, the molar ratio of compound 2, p-toluenesulfonic acid, triethyl orthoformate and ethylene glycol is 1:(0.01-1):(0-1.5):(1-50), preferably 1:0.1:1.1:30; the reaction temperature of the ethylene glycol ketal protection reaction is 0-150°C, and the reaction time is 2-24h, preferably, the reaction temperature of the ethylene glycol ketal protection reaction is 50°C, and the reaction time is 12h.

[0027] In some embodiments of the present invention, the reaction system of step 3 is carried out in the absence of solvent or under solvent conditions, preferably in the absence of solvent conditions; when carried out under solvent conditions, the solvent used is at least one of benzene, toluene, dichloromethane, ethyl acetate, tetrahydrofuran and hexane.

[0028] In some embodiments of the present invention, in step 4, the Lewis acid is diethylaluminum chloride; the molar ratio of the compound 3, diethylaluminum chloride and methyl propiolate is 1:(1-6):(1-5), preferably 1:4:3; the reaction temperature of the olefin condensation reaction is 25-64.5°C, and the reaction time is 10-36h, preferably, the reaction temperature of the olefin condensation reaction is 25°C, and the reaction time is 24h.

[0029] In some embodiments of the present invention, the solvent used in the reaction system of step 4 is dichloromethane and / or dichloroethane, preferably dichloromethane.

[0030] In some embodiments of the present invention, in step 5, the mass ratio of the compound 4 to palladium carbon is 1:(0.1-5), preferably 1:0.1; the reaction temperature of the reduction reaction 1 is 0-50°C, and the reaction time is 1-10h, preferably, the reaction temperature of the reduction reaction 1 is 25°C, and the reaction time is 6h.

[0031] In some embodiments of the present invention, the solvent used in the reaction system in step 5 is at least one of tetrahydrofuran, 2-methyltetrahydrofuran, isopropanol, tert-butanol, methanol and ethanol, preferably 2-methyltetrahydrofuran.

[0032] In some embodiments of the present invention, in step 6, the oxidant is at least one of chromium trioxide, pyridinium chlorochromate, pyridinium dichromate, sodium hypochlorite and sodium chlorite, preferably sodium chlorite; the molar ratio of the compound 5, the catalyst and the oxidant is 1:(0.1-1):(1-3), preferably 1:0.1:1.5; the reaction temperature of the oxidation reaction is 25-120°C, and the reaction time is 4-24h, preferably, the reaction temperature of the oxidation reaction is 50°C, and the reaction time is 8h.

[0033] In some embodiments of the present invention, the solvent used in the reaction system of step 6 is at least one of toluene, acetone, acetonitrile, water, dichloromethane, N,N-dimethylformamide, ethyl acetate and tert-butanol; preferably a mixed solvent of acetonitrile and water in a volume ratio of 2:1.

[0034] In some embodiments of the present invention, in step 7, the acid used in the acidic condition is at least one of sulfuric acid, hydrochloric acid and p-toluenesulfonic acid, preferably sulfuric acid.

[0035] In some embodiments of the present invention, the solvent used in the reaction system of step 7 is at least one of methanol, ethanol, tetrahydrofuran and water, preferably a mixed solvent of ethanol and water in a volume ratio of 9:1.

[0036] In some embodiments of the present invention, in step 8, the mass ratio of the compound 7 and Pd / C is 1:(0.1-5); the reaction temperature of the reduction reaction 2 is 0-25°C, and the reaction time is 0-2h. Preferably, the reaction temperature of the reduction reaction 2 is 25°C, and the reaction time is 1h.

[0037] In some embodiments of the present invention, the solvent used in the reaction system of step 8 is at least one of tetrahydrofuran, 2-methyltetrahydrofuran, isopropanol, tert-butanol, methanol and ethanol, preferably a mixed solvent of 2-methyltetrahydrofuran and isopropanol in a volume ratio of 1:1.

[0038] In some embodiments of the present invention, in step 9, the molar ratio of compound 8, cuprous chloride and sodium borohydride is 1:(1-5):(1-4), preferably 1:4:3; the reaction temperature of the reduction reaction 3 is 0-80°C, and the reaction time is 0-6h, preferably, the reaction temperature of the reduction reaction 3 is 25°C, and the reaction time is 2h.

[0039] In some embodiments of the present invention, the solvent used in the reaction system of step 9 is at least one of methanol, ethanol, isopropanol, tetrahydrofuran and 2-methyltetrahydrofuran, preferably ethanol.

[0040] In some embodiments of the present invention, in step 10, the base used in the alkaline condition is sodium hydroxide and / or potassium hydroxide, preferably potassium hydroxide.

[0041] In some embodiments of the present invention, the solvent used in the reaction system of step 10 is at least one of methanol, ethanol, tetrahydrofuran and water, preferably a mixed solvent of tetrahydrofuran and water in a volume ratio of 9:1.

[0042] The present invention discloses the following technical effects:

[0043] The raw material 4-AD used in the present invention is derived from plants and can be obtained from industrial wastes such as sugar making and papermaking waste liquid, edible oil refining residue, etc. through microbial fermentation and degradation, turning waste into treasure, being cheap and easy to obtain, and solving the problem of pathogenic bacteria and virus infection of animal raw materials; the synthesis method provided by the present invention is simple and mild in conditions, and provides a feasible route for the process synthesis of ursodeoxycholic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 This is the X-ray diffraction structure diagram of the crystal of ursodeoxycholic acid prepared in Example 10. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0051] In the present invention, room temperature means 20-30°C.

[0052] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0053] The raw material 4-androstene-3,17-dione (4-AD) includes but is not limited to that obtained by biological fermentation or chemical synthesis.

[0054] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0055] Example 1

[0056] Preparation of 3-ethoxy-androsta-3,5-dien-17-one (1)

[0057] 4-AD (30 g, 104.74 mmol), pyridine p-toluenesulfonic acid (265 mg, 1.05 mmol), triethyl orthoformate (21 mL, 127.39 mmol), ethanol (100 mL), stirred at room temperature for 14 h, TLC monitored the completion of the reaction, added 40 mL of saturated sodium bicarbonate solution to quench the reaction, filtered under reduced pressure, and the filter cake was recrystallized in petroleum ether and ethyl acetate (volume ratio) 20:1 to obtain compound (1) (31.86 g, white solid), with a molar yield of 96.73%. mp: 146-147°C. 1 H-NMR (400MHz, CDCl3) δ5.26(s,1H,H-4),5.16(s,1H,H-5),3.73-3.84(m,2H,-O CH 2CH3),1.34(t,3H,J=7.0Hz,-OCH2 CH 3),1.03(s,3H,H-19),0.95(s,3H,H-18).ESIMS C 21 H 30 O2 m / z 315.2[M+H] + .

[0058]

[0059] Example 2

[0060] Preparation of 4,17-pregnadien-3-one (2)

[0061] Take triphenylethylphosphonium bromide (47.8 g, 128.75 mmol), potassium tert-butoxide (21.2 g, 188.93 mmol), add 2-methyltetrahydrofuran (180 mL), stir at room temperature for 30 min under anhydrous and oxygen-free conditions, add compound (1) (20 g, 63.6 mmol), heat to 80 ° C and reflux for 6 h. After TLC monitoring, the reaction is complete, cool to room temperature naturally, add water (20 mL), adjust pH to 1-3 with concentrated sulfuric acid, and stir for 1 h. TLC monitoring shows that the hydrolysis is complete, adjust pH to neutral with saturated sodium bicarbonate solution, extract with ethyl acetate (40 mL × 3), combine the organic phases and wash with saturated sodium chloride solution (60 mL), dry with anhydrous sodium sulfate, concentrate under reduced pressure, dissolve in petroleum ether under reflux, filter while hot, and recrystallize to obtain compound (2) (15.42 g, white solid), with a molar yield of 74.25%. 1 H-NMR (400MHz, CDCl3) δ5.76(s,1H,H-4),5.17(qt,J=7.1,2.1Hz,1H)),1.69(dt,J=7.2,2.0Hz,3H),1.23(s,3H,H-19),0.96(s,3H,H-18).ESIMS C 21 H 30 Om / z 299.2[M+H] + .

[0062]

[0063] Example 3

[0064] Preparation of 3-cyclic ethylenedioxy-17-ethylidene-androst-5-ene (3)

[0065] Compound (2) (10 g, 33.5 mmol), p-toluenesulfonic acid (637 mg, 3.35 mmol), triethyl orthoformate (8.36 mL, 50.26 mmol), ethylene glycol (56 mL, 1 mol) were added, and the mixture was reacted at 45°C for 12 h. After the reaction was completed by TLC monitoring, the mixture was naturally cooled to room temperature, and the reaction solution was poured into 500 mL of ice water and stirred to precipitate. The mixture was filtered under reduced pressure, and the filter cake was recrystallized in ethanol to obtain compound (3) (9.86 g, white solid), with a molar yield of 85.9%. mp: 160-162°C. 1 H-NMR(400MHz, CDCl3)δ5.36(s,1H,H-6),5.13(m,1H,H-20),4.01-3.87(m,4H ,-OCH2CH2O-),1.66(m,3H,H-21),1.04(s,3H,H-19),0.89(s,3H,H-18).ESIMS C 23 H 34O2 m / z 243.2[M+H] + .

[0066]

[0067] Example 4

[0068] Preparation of 3-Cyclic ethylenedioxy-cholestane-5,16,22-triene-24-oic acid methyl ester (4)

[0069] Compound (3) (3 g, 8.76 mmol) was added with dichloromethane (60 mL), diethylaluminum chloride (1.0 M solution in Hexanes, 35 mL), and methyl propiolate (3 mL, 26.28 mmol) in sequence. The mixture was stirred at room temperature for 24 h. After the reaction was completed by monitoring by TLC, the reaction solution was poured into 100 mL of ice water and filtered under reduced pressure. The filtrate was extracted with dichloromethane (60 mL × 3). The organic phases were combined and washed with saturated sodium chloride solution (60 mL), dried over anhydrous sodium sulfate, concentrated under reduced pressure, and recrystallized from acetonitrile to obtain compound (4) (3.08 g, white solid) with a molar yield of 82.43%. mp: 133-136 °C. 1 H-NMR (400MHz, CDCl3) δ6.93 (dd, J=15.7, 7.8Hz, 1H, H-22), 5.81 (dd, J=15.6, 1.2Hz, 1H, H-23), 5.41 (dt ,J=2.9,1.4Hz,1H,H-16),5.30(dd,J=4.8,2.4Hz,1H,H-6),3.73(s,3H,-OCH3),3.70(t,J=5.0Hz,2H,-O CH 2CHO2O-),3.45(t,J=5.0Hz,2H,-OCH2 CH 2O-),3.02(m,1H,H-20),2.34(m,1H),1.18(d,J=6.9Hz,3H,H-21),1.05(s,3H,H-19),0.78(s,3H,H-18).ESIMS C 27 H 38 O4 m / z327.3[M+H] + .

[0070]

[0071] Example 5

[0072] Preparation of 3-cycloethylenedioxy-cholestane-5-ene-24-oic acid methyl ester (5)

[0073] Compound (4) (2 g, 4.69 mmol) and 5% Pd / C (0.3 g) were added with tetrahydrofuran (20 mL) and stirred at room temperature for 6 h under H2 atmosphere. The reaction was completed by TLC monitoring, and Pd / C was removed by filtration. The mixture was concentrated under reduced pressure to obtain compound (5) (1.98 g, white solid) with a molar yield of 98.1%. mp: 121-123°C. 1 H-NMR(400MHz, CDCl3)δ5.29(m,1H,H-6),3.71(m,2H,-O CH 2CHO2O-),3.67(m,3H,-OCH3),3.45(m,2H,-OCH2 CH 2O-),2.38-0.70(m,26H),1.08(m,3H,H-21),1.02(m,3H,H-19),0.77(m,3H,H-18).ESIMS C 27 H 42 O4 m / z 431.3[M+H] + .

[0074]

[0075] Example 6

[0076] Preparation of 3-Cyclic ethylenedioxy-cholestane-5-ene-24-oic acid methyl ester-7-one (6)

[0077] Compound (5) (2.0 g, 4.64 mmol), N-hydroxyphthalamide (76 mg, 0.46 mmol), sodium chlorite (630 mg, 6.97 mmol) were added with 12 mL of acetonitrile and 4 mL of water, and the mixture was stirred at 50 °C for 8 h. The reaction was complete when detected by TLC. The reaction was quenched with saturated ammonium chloride solution (20 mL), extracted with ethyl acetate (20 mL × 3), and the organic phases were combined and washed with saturated sodium chloride solution (60 mL), dried over anhydrous sodium sulfate, concentrated under reduced pressure, and recrystallized from acetonitrile to obtain compound (6) (1.58 g, white solid) with a molar yield of 76.5%. 1 H-NMR(400MHz, CDCl3)δ5.68(m,1H,H-6),3.72(m,2H,-O CH 2CHO2O-),3.66(m,3H,-OCH3),3.47(m,2H,-OCH2 CH 2O-),1.22(m,3H,H-21),0.93(m,3H,H-19),0.79(m,3H,H-18).ESIMS C 27 H 40 O5 m / z 445.7[M+H] + .

[0078]

[0079] Example 7

[0080] Preparation of 7-hydroxy-cholestane-4,6-diene-24-carboxylate-3-one (7)

[0081] Compound (6) (18 g, 40.48 mmol) was added with 50 mL of methanol and 4 mL of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h. The reaction was complete when detected by TLC. Saturated sodium bicarbonate solution was added to adjust the pH to neutral. The mixture was extracted with ethyl acetate (30 mL × 3). The organic phases were combined and washed with saturated sodium chloride solution (60 mL), dried over anhydrous sodium sulfate, concentrated under reduced pressure, and recrystallized from ethanol to obtain compound (7) (15.7 g, yellow solid). The molar yield was 96.8%. 1 H-NMR(400MHz,CDCl3)δ5.88(s,1H,H-4),5.56(s,1H,H-6),3.66(s,3H,-OCH3),1.08(d,3H,H-21),0.93(d,3H,H-19),0.70(s,3H,H-18).ESIMSC 25 H 36 O4 m / z 401.3[M+H] + .

[0082]

[0083] Example 8

[0084] Preparation of 7-hydroxy-cholestane-4-ene-24-carboxylate-3-one (8)

[0085] Take compound (7) (15 g, 37.45 mmol), 5% Pd / C (3 g), add 2-methyltetrahydrofuran (15 mL), isopropanol (15 mL), stir and react at 25 ° C under H2 atmosphere for 1 h. After the reaction is completed, monitor the completion of the reaction by TLC, filter out Pd / C, and concentrate under reduced pressure to obtain compound (8) (14.3 g, white solid) with a molar yield of 94.9%. 1 H-NMR (400MHz, CDCl3) δ5.64(s,1H,H-4),3.66(s,3H,-OCH3),3.65(m,1H,H-7),1.15(m,3H,H-21),0.93(m,3H,H-19),0.67(m,3H,H-18).ESIMS C 25 H 38 O4 m / z 403.3[M+H] + .

[0086]

[0087] Example 9

[0088] Preparation of 3α,7β-dihydroxy-5β-cholestane-24-carboxylate (9)

[0089] Compound (8) (8 g, 19.87 mmol) and cuprous chloride (7.87 g, 79.49 mmol) were added with ethanol (20 mL). After stirring at room temperature for 1 h, sodium borohydride (2.26 g, 59.62 mmol) was slowly added. After 2 h, the reaction was completed as monitored by TLC. The mixture was filtered, concentrated under reduced pressure, and purified by column chromatography (petroleum ether / ethyl acetate = 10 / 1, v / v) to obtain compound (9) (5.13 g, white solid) with a molar yield of 63.49%. 1 H-NMR (400MHz, CDCl3) δ3.63(s,3H,-OCH3),3.66-3.52(m,2H,H-3,H-6),0.94(s,3H,H-21),0.92(d,J=6.3Hz,3H,H-19),0.67(s,3H,H-18).ESIMS C 25 H 42 O4 m / z407.3[M+H] + .

[0090]

[0091] Example 10

[0092] Preparation of 3α,7β-dihydroxy-5β-cholestane-24-oic acid (UDCA)

[0093] Compound (9) (6 g, 14.76 mmol) and potassium hydroxide (1.24 g, 22.13 mmol) were added with tetrahydrofuran (16 mL) and refluxed for 6 h. The reaction was completed after TLC monitoring. The mixture was cooled to room temperature and the pH was adjusted to acidic by adding hydrochloric acid. The reaction solution was poured into ice water for precipitation and filtered. The solid was recrystallized in ethanol to obtain ursodeoxycholic acid (5.46 g, white solid) with a molar yield of 94.25%. mp: 202-203°C. 1 H-NMR (400MHz, CD3OD) δ3.44-3.54(m,2H,H-3,H-7),0.96(m,6H,H-19,H-21),0.72(m,3H,H-18).ESIMS C 24 H 40 O4 m / z 415.2[M+Na] + .

[0094]

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for synthesizing UDCA using 4-AD as a raw material, characterized in that: The following steps are involved: Step 1, 4-AD, triethyl orthoformate and acid are subjected to enol ether protection reaction in ethanol to obtain compound 1; Step 2, the compound 1 is subjected to Wittig reaction with triphenylethylphosphonium bromide under alkaline conditions, and then the protecting group is removed by acid hydrolysis to obtain compound 2; Step 3, the compound 2, p-toluenesulfonic acid, triethyl orthoformate and ethylene glycol undergo 3-carbonyl ketal protection reaction to obtain compound 3; Step 4, in the presence of a Lewis acid catalyst, the compound 3 and methyl propiolate undergo an ene condensation reaction, and the 17-side chain is extended to obtain compound 4; Step 5, under the action of catalyst Pd / C, the compound 4 undergoes reduction reaction 1 with hydrogen to obtain compound 5; Step 6, under the action of a catalyst such as tert-butyl peroxide or N-hydroxyphthalimide, the compound 5 undergoes an oxidation reaction with an oxidant to obtain a compound 6; Step 7, the compound 6 is subjected to hydrolysis reaction 1 under acidic conditions to obtain compound 7; Step 8, under the action of catalyst Pd / C, the compound 7 undergoes reduction reaction 2 with hydrogen to obtain compound 8; Step 9, the compound 8 undergoes a reduction reaction 3 with cuprous chloride and sodium borohydride to obtain a compound 9; Step 10, the compound 9 undergoes hydrolysis reaction 2 under alkaline conditions to obtain the UDCA; The structural formula of the compound 1 is: The structural formula of the compound 2 is: The structural formula of the compound 3 is: The structural formula of the compound 4 is: The structural formula of the compound 5 is: The structural formula of the compound 6 is: The structural formula of the compound 7 is: The structural formula of the compound 8 is: The structural formula of the compound 9 is:

2. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that In step 1, the acid is p-toluenesulfonic acid and / or pyridine p-toluenesulfonate; the molar ratio of 4-AD, triethyl orthoformate and acid is 1:(1-2):(0.01-1); the reaction temperature of the enol ether protection reaction is 0-60° C., and the reaction time is 2-24 h.

3. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that In step 2, the base used in the alkaline condition is at least one of sodium tert-butoxide, potassium tert-butoxide and sodium hydrogen; the molar ratio of the compound 1, triphenylethylphosphonium bromide and the base is 1:(1-3):(1-4); the reaction temperature of the Wittig reaction is 25-100° C., and the reaction time is 1-12 h; the acid used for the acid hydrolysis to remove the protecting group is at least one of sulfuric acid, hydrochloric acid and p-toluenesulfonic acid.

4. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that In step 3, the molar ratio of the compound 2, p-toluenesulfonic acid, triethyl orthoformate and ethylene glycol is 1:(0.01-1):(0-1.5):(1-50); the reaction temperature of the ethylene glycol ketal protection reaction is 0-150° C., and the reaction time is 2-24 h.

5. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that In step 4, the Lewis acid is diethylaluminum chloride; the molar ratio of the compound 3, diethylaluminum chloride and methyl propiolate is 1:(1-6):(1-5); the reaction temperature of the olefin condensation reaction is 25-64.5° C., and the reaction time is 10-36 h.

6. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that In step 5, the mass ratio of the compound 4 to palladium carbon is 1:(0.1-5); the reaction temperature of the reduction reaction 1 is 0-50° C., and the reaction time is 1-10 h.

7. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that In step 6, the oxidant is at least one of chromium trioxide, pyridinium chlorochromate, pyridinium dichromate, sodium hypochlorite and sodium chlorite; the molar ratio of the compound 5, the catalyst and the oxidant is 1:(0.1-1):(1-3); the reaction temperature of the oxidation reaction is 25-120°C, and the reaction time is 4-24h.

8. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that In step 7, the acid used in the acidic condition is at least one of sulfuric acid, hydrochloric acid and p-toluenesulfonic acid.

9. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that: In step 8, the mass ratio of the compound 7 to Pd / C is 1:(0.1-5); the reaction temperature of the reduction reaction 2 is 0-25° C., and the reaction time is 0-2 h.

10. The method for synthesizing UDCA using 4-AD as raw material according to claim 1, characterized in that: In step 9, the molar ratio of the compound 8, cuprous chloride and sodium borohydride is 1:(1-5):(1-4); the reaction temperature of the reduction reaction 3 is 0-80°C, and the reaction time is 0-6h; in step 10, the base used in the alkaline condition is sodium hydroxide and / or potassium hydroxide.

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