Method for preparing deoxycholic acid

Abstract

The invention discloses a method for preparing deoxycholic acid. Specifically, the preparation method comprises the following steps: step 1, in the presence of a solvent and N-bromosuccinimide, carrying out oxidation reaction on a compound 2 to prepare a compound 3; 2, under the condition of a solvent, the compound 3 and p-toluenesulfonhydrazide are subjected to a condensation reaction, and a compound 4 is prepared; 3, in the presence of a solvent and sodium borohydride, the compound 4 is subjected to a reduction reaction, and deoxycholic acid is prepared. The method is mild in reaction condition, environmentally friendly, high in efficiency, low in cost and suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the field of pharmaceutical organic synthesis, and in particular to a method for preparing deoxycholic acid. Background Art

[0002] Deoxycholic acid (DCA) is a bile acid lacking a hydroxyl group at the C-7 position. It is a free bile acid derived from bile acid by losing an oxygen atom. DCA has strong surface activity and, after local injection, can precisely destroy the cell membranes of fat cells, causing them to rupture and be engulfed by macrophages. However, tissue cells such as skin and muscle are not lysed because their cell membranes contain a large amount of protein, thereby reducing the dissolution of subcutaneous fat in a small area. It is used in various fields of human medicine. For example, it is used to emulsify fat for intestinal absorption. In 2015, deoxycholic acid injection developed by Kythera was approved by the U.S. Food and Drug Administration as a drug for injectable lipolysis. The trade name is Kybella, and it is used to improve the bulge or fullness of moderate to severe submental fat in adults (double chin).

[0003]

[0004] Currently, deoxycholic acid is mainly derived from animal carcasses. Although the cost is relatively low, there is a risk that it may contain animal pathogens and other harmful factors.

[0005] The prior art has disclosed a method for preparing deoxycholic acid by chemical synthesis.

[0006] CN106083969A discloses a total synthesis of deoxycholic acid, as shown in Scheme 1 below. This method uses chromium trioxide as an oxidant during the synthesis of intermediate 24. This oxidant is highly toxic, highly polluting, and carcinogenic. While the total yield reported in the literature is 22.5%, the yield in actual preparations is less than 10%.

[0007]

[0008] Option 1

[0009] CN107011401 discloses a method for preparing deoxycholic acid, the synthetic route of which is shown in Scheme 2. This method employs an oxidation system of tert-butyl peroxide (TBHP) and sodium hypochlorite in the synthesis of intermediate 2.4, avoiding the use of chromium trioxide. Pyridinium chlorochromate (PCC) is used in the preparation of compound 2.5; byproducts are generated during the preparation of 2.5, resulting in a low yield. To improve the reaction yield, byproducts 2.6 and 2.7 are further oxidized with pyridinium chlorochromate to obtain 2.5.

[0010]

[0011] Option 2

[0012] CN106146593 discloses a method for preparing deoxycholic acid, and the synthetic route is shown in Scheme 3. In the process of preparing intermediates 4 to 4a and 4 to 5, pyridinium chlorochromate is also required to be used as an oxidant to improve the conversion of byproducts to the target intermediates, thereby improving the yield of these two steps.

[0013]

[0014] Option 3

[0015] Existing processes use heavy metal oxidation methods such as chromium trioxide / pyridine (PCC oxidation) and potassium dichromate / pyridine (PDC oxidation), and high-pressure reduction methods such as H2 / Pd, which are associated with significant pollution, dangerous reactions, and high costs. Therefore, for environmental and production cost considerations, it is necessary to develop a method that does not use heavy metal catalysts. Summary of the Invention

[0016] The technical problem to be solved by the present invention is to overcome the defects of the prior art in preparing deoxycholic acid, such as high cost, the need to use highly toxic oxidants and low yield, and to provide a method for preparing deoxycholic acid. The method does not require the use of heavy metal catalysts, is environmentally friendly, has low cost, high yield, low risk factor, and is suitable for industrial application.

[0017] The present invention provides a method for preparing deoxycholic acid, which comprises the following steps:

[0018] Step 1: In the presence of a solvent and N-bromosuccinimide, compound 2 undergoes oxidation reaction to prepare compound 3;

[0019]

[0020] Step 2: Compound 3 undergoes a condensation reaction with p-toluenesulfonylhydrazine under solvent conditions to prepare compound 4;

[0021]

[0022] Step 3, in the presence of a solvent and sodium borohydride, compound 4 undergoes a reduction reaction to prepare deoxycholic acid;

[0023]

[0024] In one embodiment, in step 1, the solvent is a mixed solvent of an organic solvent and water; the organic solvent may be a ketone solvent, such as acetone. Preferably, the volume ratio of the water to the organic solvent is 1:(1-6), preferably 1:3.

[0025] In one embodiment, in step 1, the molar ratio of the compound 2 to the N-bromosuccinimide is 1:(1-3); preferably 1:1.45.

[0026] In one embodiment, in step 1, the mass volume ratio of the compound 2 to the solvent is 1 g: (20-24) ml; preferably 1 g: 22 ml.

[0027] In one embodiment, in step 1, the reaction temperature of the oxidation reaction is 10-60° C., preferably room temperature.

[0028] In one embodiment, in step 1, the reaction time of the oxidation reaction is based on the completion of the reaction monitored by TLC, and is preferably 1 to 4 hours, more preferably 2 to 3 hours.

[0029] In one embodiment, in step 1, the oxidation reaction is carried out under light-shielding conditions.

[0030] In one embodiment, the following order of adding raw materials may be used in step 1:

[0031] N-bromosuccinimide was added to compound 2 under light shielding conditions.

[0032] In one embodiment, step 1 further includes the following post-treatment steps: quenching the reaction (for example, using sodium bisulfite to quench the reaction), removing the solvent (for example, evaporating acetone under reduced pressure), extracting (for example, extracting with water and ethyl acetate), washing (for example, washing with a saturated sodium chloride solution), drying (for example, drying with anhydrous sodium sulfate), concentrating (for example, concentrating under reduced pressure), and purifying (for example, separating by column chromatography).

[0033] In one embodiment, in step 2, the solvent is an ether solvent, preferably tetrahydrofuran, more preferably anhydrous tetrahydrofuran.

[0034] In one embodiment, in step 2, the molar ratio of the compound 3 to the p-toluenesulfonyl hydrazide is 1:(1-4), preferably 1:2 or 1:1.5; more preferably 1:1.5.

[0035] In one embodiment, in step 2, the mass volume ratio of the compound 3 to the solvent is 1 g: (4-10) ml, preferably 1 g: 6 ml.

[0036] In one embodiment, in step 2, the reaction temperature of the condensation reaction is 50-80°C, preferably 70°C or 55°C; more preferably 55°C.

[0037] In one embodiment, in step 2, the reaction time of the condensation reaction is based on the completion of the reaction monitored by TLC, and is preferably 1 to 8 h, more preferably 2 to 5 h, and even more preferably 4 to 5 h.

[0038] In one embodiment, in step 2, the condensation reaction is carried out under an inert gas condition, and the inert gas may be nitrogen.

[0039] In one embodiment, the following order of adding raw materials can be used in step 2:

[0040] Compound 3, p-toluenesulfonyl hydrazide and anhydrous tetrahydrofuran solution were added in sequence.

[0041] In one embodiment, step 2 further includes the following post-processing steps: concentration (eg, concentration under reduced pressure) and purification (eg, separation by column chromatography).

[0042] In one embodiment, in step 3, the solvent is glacial acetic acid or a mixed solvent of glacial acetic acid and a halogenated alkane solvent (e.g., dichloromethane), preferably glacial acetic acid and a halogenated alkane solvent. The volume ratio of the glacial acetic acid to the halogenated alkane solvent is preferably 1:(1-3), preferably 2:3.

[0043] In one embodiment, in step 3, the molar ratio of the compound 4 to the sodium borohydride is 1:(4-30), preferably 1:20 or 1:6; more preferably 1:6.

[0044] In one embodiment, in step 3, the mass volume ratio of the compound 4 to the solvent is 1 g:(8-12) ml, preferably 1 g:10 ml.

[0045] In one embodiment, in step 3, the reaction temperature of the reduction reaction is 0-70°C, preferably 0-50°C, and more preferably room temperature.

[0046] In one embodiment, in step 3, the reaction time of the reduction reaction is based on the completion of the reaction monitored by TLC, and is preferably 2 to 12 h, more preferably 2 h or 8 h; and more preferably 8 h.

[0047] In one embodiment, the following order of adding raw materials may be used in step 3:

[0048] Sodium borohydride is added to a mixed solution of compound 4, glacial acetic acid and dichloromethane; preferably, the sodium borohydride is added at 0 to 50° C. (preferably 0 to 15° C.).

[0049] In one embodiment, step 3 further includes the following post-treatment steps: quenching the reaction (for example, using ice water to quench the reaction), extraction (for example, using dichloromethane to extract), washing (for example, using saturated sodium chloride solution to wash), and concentration (for example, concentration under reduced pressure).

[0050] In the present invention, the room temperature may be 20-30°C.

[0051] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

[0052] The reagents and raw materials used in the present invention are commercially available.

[0053] The positive progress of the present invention is that: the method of the present invention uses low-cost raw materials, avoids the use of expensive palladium, is simple to operate, has optimized conditions, high conversion rate, and high yield; under the existing technology, it can avoid high-pressure hydrogenation reaction, effectively reduce energy consumption while reducing costs, and the key conditions used are more suitable for industrial production.

[0054] Furthermore, the present invention avoids the serious pollution caused by the use of heavy metal reagents such as chromium trioxide / pyridine (PCC oxidation) and potassium dichromate pyridine (PDC oxidation), effectively reduces the use and recovery costs of heavy metal catalysts, and is more environmentally friendly. DETAILED DESCRIPTION

[0055] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0056] Example 1

[0057] Synthesis of compound of formula 3

[0058]

[0059] At room temperature, compound 2 (5 g, 12.24 mmol) and a mixture of acetone and water (110 ml) (water:acetone = 1:3, v / v) were added to a three-necked flask and stirred until the solution became clear. The flask was wrapped with aluminum foil and N-bromosuccinimide (3.16 g, 17.74 mmol) was slowly added under light-shielding conditions. After the addition was complete, the reaction was allowed to react at room temperature for 3 h. After completion, sodium bisulfite (3.69 g, 35.48 mmol) was added to quench the reaction. The acetone in the mixture was evaporated under reduced pressure, and water (25 ml) was added and allowed to stand for 30 min. The product was then extracted with ethyl acetate (3 x 25 ml). The organic phases were combined, washed with saturated sodium chloride solution (50 ml), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain the crude product. The crude product was purified by column chromatography to afford compound 3 (4.12 g, 82.81%, HPLC purity: 100.00%) as a white solid. mp:121.3~123.5℃, ESI-MS m / z 405.39[MH] - . 1H NMR(400MHz,MeOD)δ3.98(s,1H),3.56–3.46(m,1H),2.97(dd,J=12.4,5.9Hz, 1H), 2.55 (t, J = 11.5Hz, 1H), 1.21 (s, 3H), 1.01 (d, J = 6.4Hz, 3H), 0.72 (s, 3H).

[0060] Example 2

[0061] Synthesis of compound of formula 3

[0062]

[0063] At room temperature, compound 2 (9 g, 22.03 mmol) and a mixture of acetone and water (200 ml) (water:acetone = 1:3, v / v) were added to a three-necked flask and stirred until the solution became clear. The flask was wrapped in aluminum foil and N-bromosuccinimide (5.68 g, 31.94 mmol) was slowly added under light-shielding conditions. After the addition was complete, the reaction was allowed to react at room temperature for 2 h. After completion, sodium bisulfite (6.65 g, 63.88 mmol) was added to quench the reaction. The acetone in the mixture was evaporated under reduced pressure, and water (50 ml) was added and allowed to stand for 30 min. The product was then extracted with ethyl acetate (3 x 50 ml). The organic phases were combined, washed with saturated sodium chloride (100 ml), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain the crude product. Column chromatography of the crude product afforded compound 3 (7.58 g, 84.64%) as a white solid. mp:121.3~123.5℃, ESI-MS m / z 405.39[MH] - .

[0064] Example 3

[0065] Synthesis of compound of formula 3

[0066]

[0067] At room temperature, compound 2 (18 g, 44.06 mmol) and a mixture of acetone and water (400 ml) (water:acetone = 1:3, v / v) were added to a three-necked flask and stirred until the solution became clear. The flask was wrapped in aluminum foil and N-bromosuccinimide (11.37 g, 63.88 mmol) was slowly added under light-shielding conditions. After the addition was complete, the reaction was allowed to react at room temperature for 2 h. After completion, sodium bisulfite (13.30 g, 127.76 mmol) was added to quench the reaction. The acetone in the mixture was evaporated under reduced pressure, and water (100 ml) was added and allowed to stand for 30 min. The product was then extracted with ethyl acetate (3 x 100 ml). The organic phases were combined, washed with saturated sodium chloride (100 ml), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain the crude product. Column chromatography of the crude product afforded compound 3 (15.63 g, 87.26%) as a white solid. mp:121.3~123.5℃, ESI-MS m / z 405.39[MH] - .

[0068] Example 4

[0069] Synthesis of compound of formula 3

[0070]

[0071] At room temperature, compound 2 (100.00 g, 244.75 mmol) and a mixture of acetone and water (2200 ml) (water:acetone = 1:3, v / v) were added to a three-necked flask and stirred until the solution became clear. The flask was wrapped in aluminum foil and N-bromosuccinimide (63.16 g, 354.89 mmol) was slowly added under light-shielding conditions. After the addition was complete, the reaction was allowed to react at room temperature for 2 h. After completion, sodium bisulfite (73.85 g, 709.78 mmol) was added to quench the reaction. The acetone in the mixture was evaporated under reduced pressure, and water (550 ml) was added and allowed to stand for 30 min. The product was then extracted with ethyl acetate (3 x 550 ml). The organic phases were combined, washed with saturated sodium chloride (2 x 500 ml), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain the crude product. Column chromatography of the crude product afforded compound 3 (84.51 g, 84.93%) as a white solid. mp:121.3~123.5℃, ESI-MS m / z 405.39[MH] - .

[0072] Example 5

[0073] Synthesis of compound of formula 4

[0074]

[0075] Under a nitrogen atmosphere, compound 3 (5.00 g, 12.30 mmol), p-toluenesulfonyl hydrazide (4.58 g, 24.60 mmol), and anhydrous tetrahydrofuran solution (50 ml) were added to a three-necked flask in this order. The mixture was heated to 70°C with stirring under reflux for 2 h. After completion of the reaction as monitored by TLC, the mixture was slowly cooled to room temperature and concentrated under reduced pressure to remove tetrahydrofuran. The mixture was separated by column chromatography to obtain a beige solid compound 4 (5.62 g, 79.51%, HPLC purity: 97.40%). mp: 111.6-113.2°C, ESI-MS m / z 575.44 [M+H] + . 1 H NMR (400MHz, MeOD) δ7.78(d,J=8.3Hz,2H),7.36(d,J=8.1Hz,2H),3.93(s,1H),3.49(dq,J=11.1,5.5 Hz, 1H), 2.57 (dd, J = 13.4, 1.8 Hz, 1H), 2.42 (s, 3H), 1.05 (s, 3H), 1.00 (d, J = 6.1Hz, 3H), 0.64 (s, 3H).

[0076] Example 6

[0077] Synthesis of compound of formula 4

[0078]

[0079] Under a nitrogen atmosphere, compound 3 (10 g, 24.60 mmol), p-toluenesulfonyl hydrazide (6.87 g, 36.89 mmol), and anhydrous tetrahydrofuran solution (60 ml) were added to a three-necked flask in this order. The mixture was heated to 55°C and stirred for 4 h. After completion of the reaction as monitored by TLC, the temperature was slowly lowered to room temperature and the tetrahydrofuran was removed by concentration under reduced pressure. The mixture was separated by column chromatography to obtain compound 4 (11.55 g, 81.70%) as a beige solid. mp: 111.6-113.2°C, ESI-MS m / z 575.44 [M+H] + .

[0080] Example 7

[0081] Synthesis of compound of formula 4

[0082]

[0083] Under a nitrogen atmosphere, compound 3 (84.00 g, 206.61 mmol), p-toluenesulfonyl hydrazide (57.72 g, 309.92 mmol), and anhydrous tetrahydrofuran solution (504 ml) were added to a three-necked flask in this order. The mixture was heated to 55°C and stirred for 4 h. After completion of the reaction, the temperature was slowly lowered to room temperature and the tetrahydrofuran was removed by concentration under reduced pressure. The residue was separated by column chromatography to obtain compound 4 (99.17 g, 83.51%) as a beige solid. mp: 111.6-113.2°C, ESI-MS m / z 575.44 [M+H] + .

[0084] Example 8

[0085] Synthesis of deoxycholic acid

[0086]

[0087] At room temperature, compound 4 (5 g, 8.70 mmol) and glacial acetic acid solution (50 ml) were added to a three-necked flask and stirred until the solution became clear. Sodium borohydride (3.58 g, 173.98 mmol) was then slowly added portionwise, controlling the temperature not to exceed 50°C. After the addition of the ingredients, the reaction was stirred for 2 h. After completion of the reaction, the mixture was cooled in an ice-water bath. Stirring in the ice bath, ice water was slowly added dropwise to quench the mixture, maintaining the temperature below 45°C. The liquids were separated, the aqueous phase was extracted with dichloromethane, and the organic phases were combined and washed with saturated sodium chloride solution. The organic phases were evaporated under reduced pressure and then column chromatographed to obtain DCA (1.54 g, 45.09%, HPLC purity: 100.00%) as a white solid. mp: 171.8-172.0°C, ESI-MS m / z 415.30 [M+Na] + . 1 H NMR(400MHz,CD3OD)δ3.95(t,J=2.7Hz,1H),3.57–3.47(m,1H),2.34(ddd,J=15.1,9 .8,5.1Hz,1H),2.25–2.15(m,1H),1.00(d,J=6.5Hz,3H),0.93(s,3H),0.71(s,3H).

[0088] Example 9

[0089] Synthesis of deoxycholic acid

[0090]

[0091] At room temperature, a mixed solution of compound 4 (10.00 g, 17.40 mmol), glacial acetic acid and dichloromethane (100 ml) was added to a three-necked flask (glacial acetic acid: dichloromethane = 2:3, V / V). The mixture was stirred until the solution was clear, placed in an ice-water bath, cooled to below 15°C, and sodium borohydride (3.95 g, 104.39 mmol) was slowly added in batches, controlling the temperature not to exceed 15°C. After the addition was completed, the mixture was moved to room temperature and reacted for 8 hours. After the reaction was completed, the mixture was cooled in an ice-water bath, stirred in an ice bath, and slowly quenched with ice water dropwise, maintaining the temperature below 15°C. The liquid was separated, the aqueous phase was extracted with dichloromethane, the organic phases were combined, the organic phases were washed with saturated sodium chloride aqueous solution, distilled under reduced pressure, and then column chromatography was performed to obtain DCA (5.61 g, 82.14%) as a white solid. mp: 171.8~172.0℃, ESI-MSm / z 415.30[M+Na] + .

[0092] Example 10

[0093] Synthesis of deoxycholic acid

[0094]

[0095] At room temperature, a mixed solution of compound 4 (99.00 g, 172.24 mmol), glacial acetic acid and dichloromethane (990 ml) (glacial acetic acid: dichloromethane = 2:3, V / V) was added to a three-necked flask and stirred until the solution was clear. The mixture was placed in an ice-water bath and cooled to below 15°C. Sodium borohydride (39.10 g, 1.03 mol) was slowly added in batches, controlling the temperature not to exceed 15°C. After the addition was completed, the mixture was moved to room temperature and reacted for 8 hours. After the reaction was completed, the mixture was cooled in an ice-water bath, stirred in an ice bath and slowly quenched with ice water dropwise, maintaining the temperature below 15°C. The liquid was separated, the aqueous phase was extracted with dichloromethane, the organic phases were combined, the organic phases were washed with saturated sodium chloride aqueous solution, distilled under reduced pressure, and column chromatography was performed to obtain DCA (59.98 g, 88.70%) as a white solid. mp: 171.8~172.0℃, ESI-MSm / z 415.30[M+Na] + .

Claims

1. A method for preparing deoxycholic acid, characterized in that: It includes the following steps: Step 1: In the presence of a solvent and N-bromosuccinimide, compound 2 undergoes oxidation reaction to prepare compound 3; Step 2: Compound 3 undergoes a condensation reaction with p-toluenesulfonylhydrazine under solvent conditions to prepare compound 4; Step 3, in the presence of a solvent and sodium borohydride, compound 4 undergoes a reduction reaction to prepare deoxycholic acid; 2. The method for preparing deoxycholic acid according to claim 1, wherein The step 1 satisfies one or more of the following conditions: (1) In step 1, the solvent is a mixed solvent of an organic solvent and water; (2) In step 1, the molar ratio of compound 2 to N-bromosuccinimide is 1:(1-3); (3) In step 1, the mass volume ratio of the compound 2 to the solvent is 1 g: (20-24) ml; (4) In step 1, the reaction temperature of the oxidation reaction is 10 to 60° C.; (5) In step 1, the reaction time of the oxidation reaction is 1 to 4 hours; (6) In step 1, the oxidation reaction is carried out under light-shielding conditions; (7) Step 1 adopts the following order of adding raw materials: adding N-bromosuccinimide to compound 2 under light-shielding conditions; and (8) Step 1 further includes the following post-processing steps: quenching the reaction, removing the solvent, extracting, washing, drying, concentrating, and purifying.

3. The method for preparing deoxycholic acid according to claim 2, wherein: The step 1 satisfies one or more of the following conditions: (1) In step 1, the organic solvent is a ketone solvent; (2) In step 1, the molar ratio of compound 2 to N-bromosuccinimide is 1:1.45; (3) In step 1, the mass volume ratio of the compound 2 to the solvent is 1 g:22 ml; (4) In step 1, the volume ratio of the water to the organic solvent is 1:(1-6); (5) In step 1, the reaction temperature of the oxidation reaction is room temperature; and (6) In step 1, the reaction time of the oxidation reaction is 2 to 3 hours.

4. The method for preparing deoxycholic acid according to claim 3, wherein The step 1 satisfies one or both of the following conditions: (1) In step 1, the ketone solvent is acetone; and (2) In step 1, the volume ratio of the water to the organic solvent is 1:

3.

5. The method for preparing deoxycholic acid according to claim 1, wherein The step 2 satisfies one or more of the following conditions: (1) In step 2, the solvent is an ether solvent; (2) In step 2, the molar ratio of compound 3 to p-toluenesulfonyl hydrazide is 1:(1-4); (3) In step 2, the mass volume ratio of the compound 3 to the solvent is 1 g: (4-10) ml; (4) In step 2, the reaction temperature of the condensation reaction is 50 to 80°C; (5) In step 2, the reaction time of the condensation reaction is 1 to 8 hours; (6) In step 2, the condensation reaction is carried out under inert gas conditions; (7) Step 2 adopts the following order of adding raw materials: Compound 3, p-toluenesulfonyl hydrazide and anhydrous tetrahydrofuran solution are added in this order; and (8) Step 2 further includes the following post-processing steps: concentration and purification.

6. The method for preparing deoxycholic acid according to claim 5, wherein: The step 2 satisfies one or more of the following conditions: (1) In step 2, the ether solvent is tetrahydrofuran; (2) In step 2, the molar ratio of compound 3 to p-toluenesulfonyl hydrazide is 1:2 or 1:1.5; (3) In step 2, the mass volume ratio of the compound 3 to the solvent is 1 g:6 ml; (4) In step 2, the reaction temperature of the condensation reaction is 70°C or 55°C; (5) In step 2, the reaction time of the condensation reaction is 2 to 5 hours; and (6) In step 2, the inert gas is nitrogen.

7. The method for preparing deoxycholic acid according to claim 6, wherein: The step 2 satisfies one or more of the following conditions: (1) In step 2, the ether solvent is anhydrous tetrahydrofuran; (2) In step 2, the molar ratio of compound 3 to p-toluenesulfonyl hydrazide is 1:1.5; (3) In step 2, the reaction temperature of the condensation reaction is 55°C; and (4) In step 2, the reaction time of the condensation reaction is 4 to 5 hours.

8. The method for preparing deoxycholic acid according to claim 1, wherein The step 3 satisfies one or more of the following conditions: (1) In step 3, the solvent is glacial acetic acid or a mixed solvent formed by glacial acetic acid and a halogenated alkane solvent; (2) In step 3, the molar ratio of compound 4 to sodium borohydride is 1:(4-30); (3) In step 3, the mass volume ratio of the compound 4 to the solvent is 1 g: (8-12) ml; (4) In step 3, the reaction temperature of the reduction reaction is 0 to 70° C.; (5) In step 3, the reaction time of the reduction reaction is 2 to 12 hours; (6) Step 3 may be performed in the following order of adding raw materials: sodium borohydride is added to a mixed solution of compound 4, glacial acetic acid and dichloromethane; and (7) Step 3 further includes the following post-processing steps: quenching the reaction, extraction, washing, and concentration.

9. The method for preparing deoxycholic acid according to claim 8, wherein: The step 3 satisfies one or more of the following conditions: (1) In step 3, the solvent is a mixed solvent formed by glacial acetic acid and a halogenated alkane solvent; (2) In step 3, the molar ratio of compound 4 to sodium borohydride is 1:20; (3) In step 3, the mass volume ratio of the compound 4 to the solvent is 1 g:10 ml; (4) In step 3, the volume ratio of the glacial acetic acid to the halogenated alkane solvent is 1:(1-3); (5) In step 3, the reaction temperature of the reduction reaction is 0-50°C; (6) In step 3, the reaction time of the reduction reaction is 2 h or 8 h; and (7) Step 3 may be carried out in the following order of adding raw materials: sodium borohydride is added at 0-50°C.

10. The method for preparing deoxycholic acid according to claim 9, wherein: The step 3 satisfies one or both of the following conditions: (1) In step 3, the halogenated alkane solvent is dichloromethane; (2) In step 3, the molar ratio of compound 4 to sodium borohydride is 1:6; (3) In step 3, the volume ratio of the glacial acetic acid to the halogenated alkane solvent is 2:3; (4) In step 3, the reaction temperature of the reduction reaction is room temperature; (5) In step 3, the reaction time of the reduction reaction is 8 hours; and (6) Step 3 may be performed in the following order of adding raw materials: sodium borohydride is added at 0-15°C.

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