The general procedure for the synthesis of (R)-4-((3R,5S,8R,9S,10S,13R,14S,17R)-3-hydroxy-10,13-dimethyl-7-oxohexadecahydro-1H-cyclopenta[a]phenanthren-17-yl)pentanoic acid from goose deoxycholic acid was as follows: goose deoxycholic acid (5 g, 12.7 mmol) was placed in a reaction flask and dichloromethane ( 50 mL) as solvent, followed by DMSO (1.12 g, 14.3 mmol) and triethylamine (4.2 g, 41.5 mmol) sequentially. After cooling the reaction system to -30 °C, trifluoroacetic anhydride (3.2 g, 15.2 mmol) was added slowly and dropwise. The reaction mixture was stirred at -30 °C for 1.5 hours. Upon completion of the reaction, the reaction was quenched by the addition of water (10 mL) and the mixture was gradually warmed to room temperature and stirred. Extraction was carried out with methanol (20 mL x 2), the organic phases were combined, washed once with saturated sodium chloride solution, dried over anhydrous sodium sulfate, filtered and the organic phase was concentrated to dryness to give the target product (R)-4-((3R,5S,8R,9S,10S,13R,14S,17R)-3-hydroxy-10,13-dimethyl-7-oxohexadecahydro-1H-cyclopenta[a]phenanthren- 17-yl)pentanoic acid (Compound 2) in a yield of 4.89 g in 98.6%.
