Oxazaborolidine-catalyzed enantioselective reduction of α-methylene ketones was efficiently carried out by using borane− diethylaniline as a stoichiometric reducing agent. The combination of this method and subsequent hydrogenation of thus-formed allylic alcohol improved stereoselectivity in the reduction of 24-oxocholesteryl ester to 24-(R)- hydroxycholesteryl ester.
