Preparation method for 3[alpha],7[alpha]-dihydroxyl-6[alpha]-ethyl cholanic acid

The invention belongs to the technical field of pharmaceutical synthesis, and discloses a preparation method for 3[alpha],7[alpha]-dihydroxyl-6[alpha]-ethyl cholanic acid. The method comprises the steps: with 3[alpha]-hydroxyl-7-carbonyl cholanic acid as a raw material, carrying out methyl esterification, and under alkaline and low temperature conditions and with estersil as a catalyst, carrying out a reaction with halogenated silane to obtain 3[alpha],7-di(trimethyl siloxy)-6-en-methyl cholanate; then under conditions of low temperature and boron trifluoride acetonitrile, carrying out a reaction with Mukaiyama aldol, to obtain 3[alpha]-hydroxyl-6-ethidene-7-carbonyl methyl cholanate; and then with palladium carbon as a catalyst, carrying out catalytic hydrogenation and deprotection reaction in an alkaline alcohol/aqueous solution, acidifying to obtain 3[alpha]-hydroxyl-6[alpha]-ethyl-7-carbonyl cholanic acid; and finally reducing with sodium borohydride to obtain the target product. The method has the advantages of simple synthesis process, mild conditions and high yield, and is suitable for industrialization.