Reduction method of carbonyl conjugated double bonds in steroid ring

Abstract

The invention relates to the technical field of organic synthesis, in particular to a reduction method of carbonyl conjugated double bonds in a steroid ring, which comprises the following steps: blending a conjugated double bond intermediate, a metal catalyst, a reaction additive and a solvent, and carrying out pressurized reaction with hydrogen to generate a reduction product. The method is mild in reaction condition, simple to operate, high in conversion rate, easy to purify and short in whole production period, and the production cost can be reduced by at least 40% compared with the prior art; therefore, compared with the prior art, the method has the advantages that significant progress is made, and the method has significant value in preparation of the steroid compound.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for reducing a conjugated double bond of a carbonyl group within a steroid ring. Background Art

[0002] Steroids are a class of natural compounds widely found in nature, including plant sterols, bile acids, C21 steroids, insect allergens, cardiac glycosides, steroidal saponins, steroidal alkaloids, toad venom ligands, etc. Steroid compounds have one thing in common in structure, that is, they have the basic skeleton structure of cyclopentane polyhydrogen phenanthrene. In addition, the cyclopentane polyhydrogen phenanthrene mother nucleus usually has two angular methyl groups (C-10, C-13) and a side chain or oxygen-containing group with different numbers of carbon atoms, such as hydroxyl, carbonyl, etc. (C-17). The application of steroid compounds involves medicine, agriculture, animal husbandry and other aspects, and plays an important role in the life activities of animals and plants. At present, steroid compounds mainly rely on extraction from natural organisms. With the sharp increase in the demand for steroid drugs, they are gradually turning to artificial total synthesis. The extraction, separation, synthesis and application research of steroid compounds have become a very active field in drug development.

[0003] Deoxycholic acid, also known as deoxycholate and cholanic acid, is an injectable cytolytic drug. It was first developed by Kaiser Biopharmaceuticals and approved for marketing by the U.S. FDA on April 29, 2015, under the trade name Belkyra. Deoxycholic acid injection can destroy cell membranes when injected into body tissues, causing cell lysis. It is used to improve moderate to severe contour protrusion or excessive facial fullness in submandibular fat in adults. The currently reported deoxycholic acid synthesis strategies all use 9-hydroxyandrostenedione as the raw material. In the process of constructing the chiral hydroxyl group at the 12th position, a carbonyl group is first introduced at the 12th position, and the carbonyl conjugated double bond is reduced by hydrogenation, and then chiral reduction is performed.

[0004] In WO2008157635, R1 is acetyl, R2 is methyl intermediate, and dry palladium carbon is directly hydrogenated, temperature is 50 ℃, hydrogen pressure is 50psi. In the experiment, it is found that this condition will have a large amount of raw material remaining, and there are also more by-products of carbonyl reduction and carbonyl double bond reduction at the same time. The reaction system is more messy, the conversion rate is low, and it is difficult to purify. In CN106146593A, benzoyl is used to replace acetyl, which is convenient for detection. And the reduction by-products have been studied, and an oxidation process has been developed to oxidize the by-products into raw materials and target products, which can be basically completely converted after 3 repetitions. Although this process can solve the problem of hydrogenation by-products, it is equivalent to a minimum of 6 steps of continuous reaction required for one conversion after multiple reduction-oxidation processes, and the production cost is high, the production cycle is long, a large amount of Pd / C catalysts are consumed, and more chromium-containing wastewater is produced. After many experiments, it was found that in actual production, this process requires 4-6 repeated reduction-oxidation processes to obtain a good conversion rate. Due to the high temperature and high pressure conditions, more benzene ring reduction by-products will be generated, which are difficult to purify and have large losses. The actual yield is much lower than the reported yield.

[0005] In the synthesis of deoxycholic acid, cholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and obeticholic acid, the modification of the steroidal parent ring involves the reduction of the carbonyl conjugated double bond. Developing a reduction condition with mild reaction conditions, high conversion rate, low cost, and easy industrial production will not only help the industrial production of deoxycholic acid APIs, but will also be of great help to the synthesis of drugs with steroidal structures. Summary of the invention

[0006] The present invention provides a method for reducing a conjugated double bond of a carbonyl group within a steroid ring, comprising: mixing a conjugated double bond intermediate, a metal catalyst, a reaction additive and a solvent, reacting with hydrogen under pressure, and post-processing to generate a reduction product; the structural formula of the conjugated double bond intermediate is shown in Formula I;

[0007]

[0008] Reaction formula of the present invention is as follows:

[0009]

[0010] As a preferred embodiment, R1 is selected from any one of hydrogen, acetyl, benzoyl, and p-methylbenzoyl.

[0011] As a preferred embodiment, R2 is selected from any one of hydrogen, methyl, ethyl, and isopropyl.

[0012] As a preferred embodiment, the catalyst is selected from at least one of wet palladium carbon, anhydrous palladium carbon, Pd(OH)2 / C, PtO2 / C, and Raney nickel.

[0013] As a preferred embodiment, the reaction additive is selected from at least one of acetic acid, formic acid, methanesulfonic acid, p-toluenesulfonic acid, triethylamine, N,N-diisopropylethylamine, triethylamine hydrochloride, ammonium formate, and ammonium acetate.

[0014] As a preferred embodiment, the organic solvent is selected from at least one of ethyl acetate, tetrahydrofuran, methanol, ethanol, isopropanol, DMF and NMP.

[0015] As a preferred embodiment, the molar ratio of the conjugated double bond intermediate to the catalyst is 1:(0.05-1).

[0016] As a preferred embodiment, the molar ratio of the conjugated double bond intermediate to the reaction additive is (1:0.1-0.5).

[0017] As a preferred embodiment, the pressure of the pressurized reaction is 0.5-3 MPa.

[0018] As a preferred embodiment, the temperature of the pressurized reaction is 25-65°C.

[0019] As a preferred embodiment, the ratio of the solvent to the conjugated double bond intermediate is (5-30) mL: 1 g.

[0020] The present invention screens the protective groups of the hydroxyl and carboxyl groups in the steroid structure and tries different additives and reducing agents, thereby improving the catalytic activity and selectivity under acidic or weakly acidic conditions and obtaining a main double bond reduction product.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The method of the present invention not only has mild reaction conditions, simple operation and high conversion rate, but also is easy to purify and has a short entire production cycle, thereby effectively reducing the overall production cost. Therefore, the present invention has made significant progress compared to the prior art and has significant value in achieving the preparation of steroidal compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the HPLC spectrum of the product prepared in Example 1.

[0024] Figure 2 This is the HPLC spectrum of the product prepared in Example 2.

[0025] Figure 3 This is the HPLC spectrum of the product prepared in Example 3.

[0026] Figure 4 This is the HPLC spectrum of the product prepared in Example 4.

[0027] Figure 5 This is the HPLC spectrum of the product prepared in Example 5.

[0028] Figure 6 This is the HPLC spectrum of the product prepared in Example 6.

[0029] Figure 7 This is the HPLC spectrum of the product prepared in Example 7.

[0030] Figure 8 This is the HPLC spectrum of the product prepared in Example 8.

[0031] Fig. 9 This is the HPLC spectrum of the product prepared in Example 9. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In all the embodiments of the present invention, R1 in the conjugated double bond intermediate is hydrogen, acetyl, benzoyl, p-methylbenzoyl, and R2 is hydrogen, methyl, ethyl, isopropyl. The reaction process is as follows:

[0034]

[0035] Example 1: Preparation of 3α-acetoxy-5β-cholan-12-one-24-oic acid methyl ester

[0036] This example provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring, and the conjugated double bond intermediate is 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-oic acid methyl ester (CAS: 4472-02-0).

[0037] The reduction method comprises: dissolving 70 g of 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-acid methyl ester in 1.4 L of methanol, adding 1.4 mL of glacial acetic acid, transferring the reaction solution to a reaction kettle, adding 35 g of 10% dry palladium carbon, replacing the nitrogen and then replacing the hydrogen three times, pressurizing the hydrogen to 2.0 MPa, heating to 60° C. and reacting for 16 hours. Sampling HPLC (ELSD) detection shows that the remaining raw material is 3.68%, and the product purity is 73.5%.

[0038] The specific steps of the post-treatment are: cooling to 20°C, filtering, eluting with 140mL methanol, concentrating the mother liquor under reduced pressure until no fraction flows out, adding 140mL isopropanol and concentrating under reduced pressure until no fraction flows out, to obtain an off-white solid. The solid is added to 350mL isopropanol, heated until dissolved, 70mL water is added dropwise, the temperature is slowly lowered, a white solid is precipitated, the temperature is lowered to 10°C, stirred for 2h, filtered, the solid is eluted with 35mL cold isopropanol / water (5 / 1) solution, and dried with air at 45°C to obtain 43g of the product (white solid), with a yield of 61.3% and a HPLC (ELSD) purity of 96.04%.

[0039] The HPLC spectrum of the product is shown in Figure 1 .

[0040] Example 2: Preparation of 3α-acetoxy-5β-cholan-12-one-24-oic acid methyl ester

[0041] This example provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring, and the conjugated double bond intermediate is 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-oic acid methyl ester (CAS: 4472-02-0).

[0042] The reduction method comprises: dissolving 70 g of 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-acid methyl ester in 1.4 L of methanol, adding 1.4 g of triethylamine hydrochloride, transferring the reaction solution to a reaction kettle, adding 35 g of 10% dry Pd(OH)2 / C, replacing the nitrogen and then replacing the hydrogen three times, pressurizing the hydrogen to 2.0 MPa, heating to 60° C. and reacting for 16 hours. Sampling HPLC (ELSD) detection shows that the remaining raw material is 1.55%, and the product purity is 61.2%.

[0043] The specific steps of the post-treatment are: cooling to 20°C, filtering, eluting with 140mL methanol, concentrating the mother liquor under reduced pressure until no fraction flows out, adding 140mL isopropanol and concentrating under reduced pressure until no fraction flows out, to obtain an off-white solid. The solid is added to 350mL isopropanol, heated until dissolved, 70mL water is added dropwise, the temperature is slowly lowered, a white solid is precipitated, the temperature is lowered to 10°C, stirred for 2h, filtered, the solid is eluted with 35mL cold isopropanol / water (5 / 1) solution, and dried with air at 45°C to obtain 38.5g of the product (white solid), with a yield of 54.9% and a HPLC (ELSD) purity of 98.51%.

[0044] The HPLC spectrum of the product is shown in Figure 2 .

[0045] Example 3: Preparation of 3α-acetoxy-5β-cholan-12-one-24-oic acid methyl ester

[0046] This example provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring, and the conjugated double bond intermediate is 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-oic acid methyl ester (CAS: 4472-02-0).

[0047] The reduction method comprises: dissolving 70 g of 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-acid methyl ester in 3.5 L of methanol, adding 3.5 mL of glacial acetic acid, transferring the reaction solution to a reaction kettle, adding 10% PtO2 / C21 g, replacing the gas with nitrogen and then replacing the gas with hydrogen three times, pressurizing the gas with hydrogen to 2.0a, and reacting at 30°C for 16 hours. The remaining raw material is 2.23% detected by sampling HPLC (ELSD), and the purity of the product is 88.65%.

[0048] The specific steps of the post-treatment are: filtering, eluting with 140 mL of methanol, concentrating the mother liquor under reduced pressure until no fraction flows out, adding 140 mL of isopropanol and concentrating under reduced pressure until no fraction flows out, to obtain an off-white solid. The solid is added to 350 mL of isopropanol, heated until dissolved, 70 mL of water is added dropwise, the temperature is slowly lowered, a white solid precipitates, the temperature is lowered to 10° C., stirred for 2 hours, filtered, the solid is rinsed with 35 mL of cold isopropanol / water (5 / 1) solution, and dried with air at 45° C. to obtain 57.2 g of the product (white solid), with a yield of 81.6% and a HPLC (ELSD) purity of 98.96%.

[0049] The HPLC spectrum of the product is shown in Figure 3 .

[0050] Example 4: Preparation of 3α-benzoyloxy-5β-cholan-12-one-24-oic acid methyl ester

[0051] This embodiment provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring, and the conjugated double bond intermediate is 3α-benzoyloxy-5β-chole-9(11)-ene-12-one-24-oic acid methyl ester (CAS: 2024612-50-6).

[0052] The reduction method comprises: dissolving 70 g of 3α-benzoyloxy-5β-chole-9(11)-ene-12-one-24-acid methyl ester in 3.5 L of tetrahydrofuran solution, adding 3.5 mL of formic acid, transferring the reaction solution to a reaction kettle, adding 21 g of 10% PtO2 / C, replacing the nitrogen and then replacing the hydrogen three times, pressurizing the hydrogen to 1.0 MPa, and reacting at 40° C. for 16 hours. Sampling HPLC detection shows that the remaining raw material is 12.33%, and the product purity is 56.6%.

[0053] The specific steps of the post-treatment are: filtering, eluting with 140 mL of tetrahydrofuran, and concentrating the mother liquor under reduced pressure until no fraction flows out to obtain an off-white waxy crude product. The crude product is purified by silica gel column, and the eluent is petroleum ether / ethyl acetate from 10 / 1 to 3 / 1 to obtain 24.5 g of a white solid product, with a yield of 34.9% and a HPLC purity of 94.37%.

[0054] The HPLC spectrum of the product is shown in Figure 3 .

[0055] Example 5: Preparation of 3α-acetoxy-5β-cholane-12-one-24-acid

[0056] This example provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring, and the conjugated double bond intermediate is 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-oic acid (CAS: 130798-68-4).

[0057] The reduction method comprises: dissolving 60 g of 3α-acetoxy-5β-chole-9(11)-ene-12-one-24-acid in 3 L of ethyl acetate / tetrahydrofuran (1 / 1) mixed solution, adding 3 mL of glacial acetic acid, transferring the reaction solution to a reaction kettle, adding 10% PtO2 / C 18 g, replacing the nitrogen and then replacing the hydrogen three times, pressurizing the hydrogen to 2.0 MPa, and reacting at 30° C. for 16 hours. Sampling HPLC (ELSD) detection shows that the remaining raw material is 3.56%, and the product purity is 86.8%.

[0058] The specific steps of the post-treatment are: filtering, eluting with 140 mL of methanol, concentrating the mother liquor under reduced pressure to about 1 L, adding 1 L of methyl tert-butyl ether and concentrating under reduced pressure to about 1 L, repeating the operation until the methanol content in the solution is less than 1%, continuing to concentrate to a total volume of about 600 mL, and a white solid precipitates, cooling to 10° C., stirring at this temperature for 2 h, filtering, eluting the solid with 35 mL of cold methyl tert-butyl ether, and drying with air at 45° C. to obtain 51.3 g of the product (white solid), with a yield of 85.4% and a HPLC (ELSD) purity of 99.17%.

[0059] The HPLC spectrum of the product is shown in Figure 5 .

[0060] Example 6: Preparation of 3α-benzoyloxy-5β-cholane-12-one-24-acid

[0061] This embodiment provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring. The conjugated double bond intermediate is 3α-benzoyloxy-5β-chole-9(11)-ene-12-one-24-oic acid, which is prepared by reacting 3α-hydroxy-5β-chole-9(11)-ene-12-one-24-oic acid (CAS: 6874-18-6) and benzoyl chloride.

[0062] The reduction method comprises: dissolving 60 g of 3α-benzoyloxy-5β-chole-9(11)-ene-12-one-24-acid in 3 L of anhydrous ethanol solution, transferring the reaction solution to a reaction kettle, adding 30 g of Raney nickel, replacing the nitrogen and then replacing the hydrogen three times, pressurizing the hydrogen to 2.0 MPa, and reacting at 40° C. for 16 hours. Sampling HPLC detection shows that the remaining raw material is 8.86%, and the product purity is 63.5%.

[0063] The specific steps of the post-treatment are: filtering, rinsing with 180 mL of ethanol, concentrating the mother liquor under reduced pressure to about 1 L, adding 1 L of methyl tert-butyl ether and then concentrating under reduced pressure to about 1 L, repeating the operation until the methanol content in the solution is less than 1%, continuing to concentrate to a total volume of about 600 mL, and a white solid precipitates, cooling to 10° C., stirring at this temperature for 2 h, filtering, rinsing the solid with 35 mL of cold methyl tert-butyl ether, and drying with air at 45° C. to obtain 28.8 g of the product (white solid), with a yield of 47.8% and an HPLC purity of 94.37%.

[0064] The HPLC spectrum of the product is shown in Figure 6 .

[0065] Example 7: Preparation of 3α-p-methylbenzoyloxy-5β-cholan-12-one-24-acid

[0066] This embodiment provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring. The conjugated double bond intermediate is 3α-p-methylbenzoyloxy-5β-chole-9(11)-ene-12-one-24-oic acid, which is prepared by reacting 3α-hydroxy-5β-chole-9(11)-ene-12-one-24-oic acid (CAS: 6874-18-6) and p-methylbenzoyl chloride.

[0067] The reduction method comprises: dissolving 60 g of 3α-p-methylbenzoyloxy-5β-chole-9(11)-ene-12-one-24-acid in 3 L of ethyl acetate solution, adding 3 g of ammonium formate, transferring the reaction solution to a reaction kettle, adding 30 g of 10% dry Pd / C, replacing the nitrogen and then replacing the hydrogen three times, pressurizing the hydrogen to 1.0 MPa, and reacting at 40° C. for 16 hours. Sampling HPLC detection shows that the remaining raw material is 5.65%, and the product purity is 75.6%.

[0068] The specific steps of the post-treatment are: filtering, rinsing with 180 mL of ethyl acetate, concentrating the mother liquor under reduced pressure to about 1 L, adding 1 L of methyl tert-butyl ether and concentrating again under reduced pressure to about 1 L, repeating the operation until the methanol content in the solution is less than 1%, continuing to concentrate to a total volume of about 600 mL, and a white solid precipitates, cooling to 10° C., stirring at this temperature for 2 h, filtering, rinsing the solid with 35 mL of cold methyl tert-butyl ether, and drying with air at 45° C. to obtain 41.2 g of the product (white solid), with a yield of 68.5% and an HPLC purity of 96.7%.

[0069] The HPLC spectrum of the product is shown in Figure 7 .

[0070] Example 8: Preparation of 3α-hydroxy-5β-cholane-12-one-24-acid

[0071] This example provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring, and the conjugated double bond intermediate is 3α-hydroxy-5β-chole-9(11)-ene-12-one-24-oic acid (CAS: 6874-18-6).

[0072] The reduction method comprises: dissolving 45 g of 3α-hydroxy-5β-chole-9(11)-ene-12-one-24-acid in 0.9 L of methanol, adding 1.4 mL of glacial acetic acid, transferring the reaction solution to a reaction kettle, adding 22.5 g of 10% dry Pd / C, replacing the gas with nitrogen and then replacing the gas with hydrogen three times, pressurizing the gas with hydrogen to 2.0 MPa, heating the gas to 60° C. and reacting the gas for 16 hours. The remaining raw material is 0.85% as detected by HPLC (ELSD) of the sample, and the purity of the product is 88.5%.

[0073] The specific steps of the post-treatment are: cooling to 30°C, filtering, rinsing with 140mL of methanol, adding 1L of methyl tert-butyl ether and then concentrating under reduced pressure to about 1L, repeating the operation until the methanol content in the solution is less than 1%, continuing to concentrate to a total volume of about 600mL, and a white solid precipitates, cooling to 10°C, stirring at this temperature for 2h, filtering, rinsing the solid with 35mL of cold methyl tert-butyl ether, and drying with air at 45°C to obtain 37.3g of the product (white solid), with a yield of 82.6% and an HPLC purity of 97.5%.

[0074] The HPLC spectrum of the product is shown in Figure 8 .

[0075] Example 9: Preparation of 3α-hydroxy-5β-cholane-12-one-24-acid

[0076] This example provides a method for reducing the conjugated double bond of the carbonyl group within the steroid ring, and the conjugated double bond intermediate is 3α-hydroxy-5β-chole-9(11)-ene-12-one-24-oic acid (CAS: 6874-18-6).

[0077] The reduction method comprises: dissolving 45 g of 3α-hydroxy-5β-chole-9(11)-ene-12-one-24-acid in 0.9 L of tetrahydrofuran, adding 1.4 mL of glacial acetic acid, transferring the reaction solution to a reaction kettle, adding 3.5 g of 10% PtO2 / C1, replacing the nitrogen and then replacing the hydrogen three times, pressurizing the hydrogen to 2.0 MPa, heating to 30° C. and reacting for 16 hours. Sampling HPLC (ELSD) detection shows that the remaining raw material is 0.85%, and the product purity is 92.5%.

[0078] The specific steps of the post-treatment are: cooling to 20°C, filtering, rinsing with 140mL of tetrahydrofuran, adding 1L of methyl tert-butyl ether and then concentrating under reduced pressure to about 1L, repeating the operation until the content of tetrahydrofuran in the solution is less than 1%, continuing to concentrate to a total volume of about 600mL, and a white solid precipitates, cooling to 10°C, stirring at this temperature for 2h, filtering, rinsing the solid with 35mL of cold methyl tert-butyl ether, and drying with air at 45°C to obtain 40.2g of the product (white solid), with a yield of 89.2% and an HPLC purity of 99.03%.

[0079] The HPLC spectrum of the product is shown in Fig. 9 .

[0080] The above is 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 principles 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 reducing the conjugated double bonds of carbonyl groups within a steroid ring, characterized in that: include: The conjugated double bond intermediate, the metal catalyst, the reaction additive and the solvent are mixed, and reacted with hydrogen under pressure, and then post-treated to generate a reduction product; The structural formula of the conjugated double bond intermediate is shown in Formula I; 2. The reduction method according to claim 1, characterized in that: R1 is selected from any one of hydrogen, acetyl, benzoyl and p-methylbenzoyl.

3. The reduction method according to claim 2, characterized in that: R2 is selected from any one of hydrogen, methyl, ethyl and isopropyl.

4. The reduction method according to claim 3, characterized in that: The catalyst is selected from at least one of wet palladium carbon, anhydrous palladium carbon, Pd(OH)2 / C, PtO2 / C, and Raney nickel.

5. The reduction method according to claim 4, characterized in that: The reaction additive is selected from at least one of acetic acid, formic acid, methanesulfonic acid, p-toluenesulfonic acid, triethylamine, N,N-diisopropylethylamine, triethylamine hydrochloride, ammonium formate, and ammonium acetate.

6. The reduction method according to claim 5, characterized in that: The molar ratio of the conjugated double bond intermediate to the catalyst is 1:(0.05-1).

7. The reduction method according to claim 6, characterized in that: The molar ratio of the conjugated double bond intermediate to the reaction additive is 1:(0.1-0.5).

8. The reduction method according to claim 7, characterized in that: The pressure of the pressurized reaction is 0.5-3MPa.

9. The reduction method according to claim 8, characterized in that: The temperature of the pressurized reaction is 25-65°C.

10. The reduction method according to claim 9, characterized in that: The ratio of the solvent to the conjugated double bond intermediate is (5-30) mL: 1 g.

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