Preparation method of 7-ketolithocholic acid

Abstract

The invention discloses a preparation method of 7-ketolithocholic acid, which comprises the following steps: by taking 3alpha-adamantane formyloxy-5, 6-alkene-7-carbonyl lithocholic acid methyl ester as a raw material, hydrogenating 5, 6-olefinic bonds under the condition of a metal reduction catalyst, preparing a 5beta-hydrogen intermediate with high stereoselectivity, and then preparing the 7-ketolithocholic acid through hydrolysis reaction. According to the method, 3-hydroxyl is protected by adamantane formyl, the steric hindrance of a system can be effectively increased, the stereoselectivity of a reduction reaction is improved, and the proportion of 5 beta-hydrogen reaches 99.5%. The method disclosed by the invention has the characteristics of simplicity, high efficiency, safety in operation, high stereoselectivity and convenience in product purification, can realize efficient preparation of 7-ketolithocholic acid, and has wide application prospect and practical value.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthetic chemistry. Specifically, it relates to a preparation method of 7-ketolithocholic acid. Background Art

[0002] 7-Ketolithocholic acid, with CAS number 4651-67-6, has the molecular formula C 24 H 38 O 4 , and a molecular weight of 390.56. Its structural formula is shown as formula (A):

[0003]

[0004] 7-Ketolithocholic acid is an important pharmaceutical intermediate. From it, chenodeoxycholic acid (Tetrahedron Letters Volume 24, Issue 24, 1983, Pages 2487-2490), ursodeoxycholic acid (J. Org. Chem. 1993, 58, 499-501), obeticholic acid (J. Med. Chem. 2002, 45, 17, 3569–3572), etc. can be synthesized, as shown in reaction formula (a).

[0005]

[0006] Currently, most production processes of ursodeoxycholic acid and obeticholic acid are methods based on 7-ketolithocholic acid as the raw material. Therefore, the effective acquisition of 7-ketolithocholic acid is particularly important. The reported syntheses of 7-ketolithocholic acid include the following methods:

[0007] I. Using cholic acid as the raw material

[0008] WO2014020024A1 reports using cholic acid as the raw material. Through esterification of the acid in the side chain with hydrochloric acid methanol, double protection of the 3,7-hydroxy groups with acetic anhydride, oxidation of the 12-hydroxy group to a ketone with sodium hypochlorite, reduction of the 12-ketone with Huang Minglong reaction, and finally selective oxidation of the 7-hydroxy group to a ketone with sodium hypobromite to obtain the target compound 7-ketolithocholic acid. The entire process uses the Huang Minglong reaction with a very high temperature. This step of the reaction has a relatively high temperature, hydrazine hydrate is toxic and explosive, and has relatively high requirements for equipment, as shown in reaction formula (b).

[0009]

[0010] II. Using chenodeoxycholic acid as the raw material

[0011] CN106046095 reported a method for obtaining 7-ketolithocholic acid by oxidizing chenodeoxycholic acid with NBS in acetone and water, as shown in reaction formula (c). However, the price of chenodeoxycholic acid is relatively high, which limits its application.

[0012]

[0013] III. Using hyodeoxycholic acid as the raw material

[0014] Patent document CN110423261 A reported a preparation method using hyodeoxycholic acid as the raw material. The disadvantages of this scheme are as follows: 1. Chromium reagents such as Jones reagent are used, resulting in a lot of pollution and great environmental protection pressure; 2. Some reagents such as lithium iodide and TBSCl are expensive, and the overall cost of the route is high; 3. Pyridine is used as the solvent in the third step, which has a strong smell and relatively high toxicity, as shown in reaction formula (d).

[0015]

[0016]

[0017] From the perspective of chemical synthesis, all these three methods utilize the 5β-hydrogen structure of the animal-derived raw materials themselves and perform functional group transformation at other sites to prepare 7-ketolithocholic acid, without involving the direct construction of 5β-hydrogen.

[0018] The 2017 patent WO 2017 / 019524A1 reported a method for preparing 7-ketolithocholic acid, as shown in reaction formula (e). The synthetic strategy of this patent starts from diosgenin as the starting material, prepares compound 15 through 12 steps of reaction, then hydrogenates the double bond using a metal catalyst to obtain compound 19, and finally prepares 7-ketolithocholic acid by removing the protecting group. This reaction route is lengthy, and the ratio of 5α to 5β is not reported.

[0019]

[0020] The currently reported synthetic routes of 7-ketocholic acid have problems such as overly cumbersome steps, low yield, large pollution, and expensive raw materials. Therefore, it is of great significance and industrial value to develop an efficient synthetic method for 7-ketolithocholic acid. Summary of the Invention

[0021] To address the deficiencies of the existing technology, the objective of the present invention is to provide a method for preparing 7-ketolithocholic acid. The preparation method of 7-ketolithocholic acid in the present invention uses methyl 3α-adamantanecarbonyloxy-5,6-ene-7-carbonyl lithocholate as a raw material (this raw material can be obtained by referring to the preparation methods in Biosci. Biotechnol. Biochem., 68(6), 1332–1337, 2004 and Bulletin of the Georgian National Academy of Sciences (2021), 15(3), 65-71). Under the condition of a metal reduction catalyst, the 5,6-ene bond is hydrogenated to obtain a 5β-hydro intermediate with high stereoselectivity, and then 7-ketolithocholic acid is obtained through a hydrolysis reaction. In the method of the present invention, the adamantanecarbonyl group is used to protect the 3-hydroxy group, which can effectively increase the steric hindrance of the system and improve the stereoselectivity of the reduction of the 5,6-double bond. The selectivity of 5β-hydrogen reaches 99.5%. This reaction has the characteristics of simplicity, high efficiency, safe operation, high stereoselectivity, and convenient product purification, and can effectively prepare 7-ketolithocholic acid.

[0022] The present invention provides a method for preparing 7-ketolithocholic acid, which uses methyl 3α-adamantanecarbonyloxy-5,6-ene-7-carbonyl lithocholate as a raw material, hydrogenates the 5,6-ene bond under the condition of a metal reduction catalyst to prepare a 5β-hydro intermediate with high stereoselectivity, and then prepares 7-ketolithocholic acid through a hydrolysis reaction;

[0023] The reaction process of the method is shown in Reaction Scheme (I):

[0024]

[0025] The preparation method of 7-ketolithocholic acid in the present invention includes the following steps:

[0026] Step (1) Reduction reaction: Dissolve the compound of formula (1) in a first solvent, add a metal reduction catalyst, and under the condition of hydrogen, carry out a hydrogenation reaction to prepare the compound of formula (2). The reaction process is shown in Reaction Scheme (A):

[0027]

[0028] Step (2) Hydrolysis reaction: Dissolve the compound of formula (2) obtained in step (1) in a second solvent, and under alkaline conditions, carry out a hydrolysis reaction to prepare 7-ketolithocholic acid. The reaction process is shown in Reaction Scheme (B):

[0029]

[0030] In step (1) of the present invention, the hydrogenation reaction is specifically as follows: The compound of formula (1) is dissolved in a first solvent, a metal reduction catalyst is added, and under a hydrogen atmosphere, a hydrogenation reaction occurs at a certain reaction temperature to prepare the compound of formula (2).

[0031] Among them, the weight ratio of the compound of formula (1): the reduction metal catalyst: the first solvent is 1:(0.01 - 0.5):(5 - 20); preferably, it is 1:0.05:10;

[0032] Among them, the temperature of the hydrogenation reaction is 25 - 75 °C; preferably, it is 50 °C;

[0033] Among them, the time of the hydrogenation reaction is 6 - 48; preferably, it is 24.

[0034] Among them, the reduction metal catalyst is any one or more of palladium on carbon, palladium carbonate, palladium hydroxide, platinum oxide, etc.; preferably, it is platinum oxide;

[0035] Among them, the first solvent is any one or more of methanol, ethanol, isopropanol, ethyl acetate, tetrahydrofuran, etc.; preferably, it is ethanol;

[0036] In step (2) of the present invention, the hydrolysis reaction is specifically as follows: The compound of formula (2) is dissolved in a second solvent, and under alkaline conditions, a hydrolysis reaction occurs at a certain reaction temperature to prepare 7-ketolithocholic acid.

[0037] Among them, the base is selected from one or more of LiOH, KOH, NaOH, K 2 CO 3 etc.; preferably, it is potassium hydroxide (KOH);

[0038] Among them, the mass ratio of the compound of formula (2): the base: the second solvent is 1:(1 - 4):(5 - 20); preferably, it is 1:1:10;

[0039] Among them, the second solvent is selected from one or two of water, methanol, ethanol, isopropanol, etc.; preferably, it is ethanol;

[0040] Among them, the temperature of the hydrolysis reaction is 10 - 75 °C; preferably, it is 50 °C;

[0041] Among them, the time of the hydrolysis reaction is 1 - 12 h; preferably, it is 12 h.

[0042] Among them, the configuration of the compound of formula (2) has extremely high stereoselectivity, and the selectivity of 5β is greater than 99%.

[0043] The innovations and beneficial effects of the present invention include: The preparation method of the present invention uses methyl 3α-adamantanecarbonyloxy-5,6-ene-7-carbonylcholate as a raw material, hydrogenates the 5,6-ene bond under the condition of a metal reduction catalyst to prepare a 5β-hydrogen intermediate with high stereoselectivity, and then prepares 7-ketocholic acid through a hydrolysis reaction.

[0044] The preparation method of 7-ketocholic acid provided by the present invention uses adamantanecarbonyl to protect the 3-hydroxy group, which can effectively increase the steric hindrance of the system and improve the stereoselectivity of the reduction of the 5,6-double bond. The selectivity of 5β-hydrogen reaches 99.5%. This reaction has the characteristics of simplicity, high efficiency, safe operation, high stereoselectivity, and convenient product purification, and can effectively prepare 7-ketocholic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0046] Figure 1 It is a single crystal structure diagram of ursodeoxycholic acid. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] Combined with the following specific embodiments and drawings, the invention will be further described in detail. The processes, conditions, experimental methods, etc. for implementing the present invention, except for the specifically mentioned content below, are all common knowledge and well-known common sense in the art, and the present invention has no special limiting content. For those embodiments where specific experimental steps or conditions are not described, the operations can be carried out according to the conventional experimental methods described in the publicly available texts in the art. For reagents or equipment whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0048] The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0049] In all the examples shown and discussed here, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0050] The present invention discloses a method for preparing 7-ketolithocholic acid. Using methyl 3α-adamantanecarbonyloxy-5,6-ene-7-carbonyl lithocholate as a raw material, the 5,6-ene bond is hydrogenated under the condition of a metal reduction catalyst to prepare a 5β-hydro intermediate with high stereoselectivity, and then 7-ketolithocholic acid is prepared through a hydrolysis reaction. The method of the present invention uses an adamantanecarbonyl group to protect the 3-hydroxy group, which can effectively increase the steric hindrance of the system and improve the stereoselectivity of the reduction reaction. The proportion of 5β-hydro is up to 99.5%. The method of the present invention has the characteristics of simplicity, high efficiency, safe operation, high stereoselectivity, and convenient product purification, can achieve the efficient preparation of 7-ketolithocholic acid, and has broad application prospects and practical value.

[0051] Unless otherwise specified, the test materials used in the examples are all conventional biochemical reagents.

[0052] Example 1: Hydrogenation reaction and hydrolysis reaction (palladium on carbon, ethanol)

[0053] Dissolve the compound of formula (1) (1.0 g, 1.77 mmol) in 10 g of ethanol, add 0.05 g of palladium on carbon, heat up to 50 °C, and keep the reaction under a hydrogen atmosphere. React for 24 h, take samples, and detect by liquid phase. After the raw material reaction is completed, cool to 20 °C, filter, and concentrate to obtain the hydrogenation crude product. Dissolve 1.0 g of the crude product in 10 g of ethanol, add solid potassium hydroxide (1.0 g, 17.8 mmol), stir at 50 °C for 12 h. After the raw material reaction is completed, cool to 20 - 25 °C. Add 100 g of water, add hydrochloric acid, adjust the pH value of the system to acidic, and white solid precipitates. Filter and dry to obtain the crude product of 7-ketolithocholic acid. The crude product is recrystallized with methanol to obtain 0.58 g of the refined product of 7-ketolithocholic acid, with a molar yield of 85%. The configuration ratio of 5β to 5α is 70:30.

[0054] Example 2: Hydrogenation reaction and hydrolysis reaction (palladium hydroxide, ethanol)

[0055] Dissolve the compound of formula (1) (1.0 g, 1.77 mmol) in 10 g of ethanol, add 0.05 g of palladium hydroxide, heat up to 50 °C, and keep the reaction under a hydrogen atmosphere. React for 24 h, take samples, and detect by liquid phase. After the raw material reaction is completed, cool to 20 °C, filter, and concentrate to obtain the hydrogenation crude product. Dissolve 1.0 g of the crude product in 10 g of ethanol, add solid potassium hydroxide (1.0 g, 17.8 mmol), stir at 50 °C for 12 h. After the raw material reaction is completed, cool to 20 - 25 °C. Add 100 g of water, add hydrochloric acid, adjust the pH value of the system to acidic, and white solid precipitates. Filter and dry to obtain the crude product of 7-ketolithocholic acid. The crude product is recrystallized with methanol to obtain 0.54 g of the refined product of 7-ketolithocholic acid, with a molar yield of 78%. The configuration ratio of 5β to 5α is 30:70.

[0056] Example 3: Hydrogenation reaction and hydrolysis reaction (platinum oxide, ethanol)

[0057] Dissolve the compound of formula (1) (1.0 g, 1.77 mmol) in 10 g of ethanol, add 0.05 g of platinum oxide, heat up to 50 °C, keep the temperature for reaction under a hydrogen atmosphere for 24 h, take samples, detect by liquid phase. After the raw materials are completely reacted, cool to 20 °C, filter, and concentrate to obtain the hydrogenation crude product. Dissolve 1.0 g of the crude product in 10 g of ethanol, add solid potassium hydroxide (1.0 g, 17.8 mmol), stir at 50 °C for 12 h. After the raw materials are completely reacted, cool to 20 - 25 °C. Add 100 g of water, add hydrochloric acid, adjust the pH value of the system to acidic, and white solid precipitates. Filter and dry to obtain the crude product of 7-ketolithocholic acid. Recrystallize with methanol to obtain 0.61 g of the refined product of 7-ketolithocholic acid, with a molar yield of 88%, and the configuration ratio of 5β to 5α is 99.5:0.5.

[0058] Example 4: Hydrogenation reaction and hydrolysis reaction (platinum oxide, isopropanol)

[0059] Dissolve the compound of formula (1) (1.0 g, 1.77 mmol) in 10 g of isopropanol, add 0.05 g of platinum oxide, heat up to 50 °C, keep the temperature for reaction under a hydrogen atmosphere for 24 h, take samples, detect by liquid phase. After the raw materials are completely reacted, cool to 20 °C, filter, and concentrate to obtain the hydrogenation crude product. Dissolve 1.0 g of the crude product in 10 g of ethanol, add solid potassium hydroxide (1.0 g, 17.8 mmol), stir at 50 °C for 12 h. After the raw materials are completely reacted, cool to 20 - 25 °C. Add 100 g of water, add hydrochloric acid, adjust the pH value of the system to acidic, and white solid precipitates. Filter and dry to obtain the crude product of 7-ketolithocholic acid. Recrystallize with methanol to obtain 0.60 g of the refined product of 7-ketolithocholic acid, with a molar yield of 87%, and the configuration ratio of 5β to 5α is 99:1.

[0060] 1H NMR spectrum of product 7-ketolithocholic acid (5β-H): 1 HNMR(400MHz,DMSO-d 6 )δ4.47(t,1H,H-3β),2.90(dd,1H),2.44(t,1H),2.19-2.27(m,1H),2.01-2.13(m,2H),1.89-1.94(m,1H),1.76-1.85(m,2H),1.63-1.73(m,4H),0.98-1.53(m,14H),1.13(s,3H),0.88-0.95(m,1H),0.86(d,3H),0.61(s,3H);

[0061] 1H NMR Spectrum of Isomeric 7-Ketolithocholic Acid (5α-H): 1 H NMR(400MHz,DMSO-d 6 ): δ 3.83 (t, 1H, H-3β), 2.44–2.28 (m, 2H), 2.23 (m, 1H), 2.14–2.02 (m, 2H), 1.95–1.75 (m, 3H), 1.69 (m, 2H), 1.61–1.43 (m, 4H), 1.43–1.13 (m, 9H), 1.10–1.00 (m, 3H), 0.99 (s, 3H), 0.93 (m, 1H), 0.87 (d, 3H), 0.61 (s, 3H).

[0062] Example 5

[0063] Using the refined 7-ketolithocholic acid prepared in Example 3 of the present invention (the configuration ratio of 5β to 5α is 99.5:0.5) as the raw material to prepare ursodeoxycholic acid. After single crystal cultivation and X-ray single crystal diffraction detection, it was determined that the 5-position of the product ursodeoxycholic acid is the 5β-configuration, as shown in the appendix Figure 1 as follows

[0064] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0065] As used in the present invention, the term "comprising" is an open expression, that is, it includes the content specified in the present invention, but does not exclude other aspects.

[0066] As used in the present invention, the term "and / or" includes any one and all combinations of one or more of the related listed items. Although the embodiments of the present specification have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present specification. The scope of the present specification is defined by the appended claims and their equivalents.

Claims

1. A method for preparing 7-ketolithocholic acid, characterized in that: The method uses 3α-adamantanecarbonyloxy-5,6-ene-7-carbonyllithocholic acid methyl ester as a raw material, hydrogenates the 5,6-ene bond under the condition of a metal reduction catalyst, prepares a 5β-hydrogen intermediate with high stereoselectivity, and then prepares 7-ketolithocholic acid through a hydrolysis reaction; the reaction process of the method is shown in reaction formula (I): Reaction formula (I).

2. The method according to claim 1, characterized in that: The method comprises the following steps: Step (1) hydrogenation reaction: dissolving the compound of formula (1) in a first solvent, adding a metal reduction catalyst, and carrying out a hydrogenation reaction under hydrogen conditions to prepare a compound of formula (2); the reaction process is shown in reaction formula (A): Reaction formula (A); Step (2) hydrolysis reaction: dissolving the compound of formula (2) obtained in step (1) in a second solvent, and performing a hydrolysis reaction under alkaline conditions to prepare 7-ketolithocholic acid; the reaction process is shown in reaction formula (B): Reaction formula (B).

3. The method according to claim 2, characterized in that In the step (1), the weight ratio of the compound of formula (1): the reducing metal catalyst: the first solvent is 1: (0.01-0.5): (5-20).

4. The method according to claim 2, characterized in that: In the step (1), the reducing metal catalyst is any one or more of palladium carbon, palladium carbonate, palladium hydroxide, and platinum oxide; and / or the first solvent is any one or more of methanol, ethanol, isopropanol, ethyl acetate, and tetrahydrofuran.

5. The method according to claim 2, characterized in that: In the step (1), the temperature of the hydrogenation reaction is 25-75° C.; and / or the time of the hydrogenation reaction is 6-48 hours.

6. The method according to claim 2, characterized in that In the step (2), the base is selected from one or more of LiOH, KOH, NaOH, and K2CO3.

7. The method according to claim 2, characterized in that: In step (2), the second solvent is selected from one or more of water, methanol, ethanol, and isopropanol.

8. The method according to claim 2, characterized in that: In the step (2), the weight ratio of the compound of formula (2): base: second solvent is 1: (1-4): (5-20).

9. The method according to claim 2, characterized in that: In the step (2), the temperature of the hydrolysis reaction is 10° C. to 75° C.; and / or the time of the hydrolysis reaction is 1 to 12 hours.

10. The method according to claim 1 or 2, characterized in that: The configuration of the compound of formula (2) has extremely high stereoselectivity, and the proportion of 5β is greater than 99%.

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