The invention provides a method for synthesizing difluprednate from a
sterol fermentation product. The
sterol fermentation product, namely 9 Alpha-hydroxyl-
androstane-1,4-
diene-3,17-
diketone (9 Alpha-OH-AD) obtained by fermenting
phytosterol of which the content in byproducts of the
grease industry is very high, serves as a starting
raw material. The method comprises the following 15 reaction steps in total: dehydrating steride 9-hydroxyl to form a double-bond; adding 17-carbonyl with
acetylene; dehydrating; producing 21-
copper carbonyl under an acid condition; epoxidizing 16,17-
double bond; oxidizing periodide and introducing 21-hydroxyl; performing ring opening on 16,17 Alpha-
epoxy hydrobromate; hydrogenating for removing 16 Beta
bromine; forming a ring on
orthoester; performing ring opening; esterifying; epoxidizing 9,11-
double bond-Beta; enolizing and esterifying; performing ring opening on 6-electrophilic fluoro; and performing ring opening on 9,11-
epoxy fluoro. According to the method, steride 17 Alpha and 21-dyhydroxyl are efficiently built by means of periodide oxidization,
epoxide ring-opening and debromination and an important
intermediate type 11 compound is obtained; in the whole process, a large quantity of heavy
metal pollutant chromium which is generated when producing corticoid medicines in the traditional industry is effectively avoided, so that the method is green, environment-friendly and suitable to industrialized production.