30 ml of a diethylaluminum cyanide solution (1 N, in toluene) are added to a solution of 3.82 g cholesta-4,8-dien-3-one in 60 ml tetrahydrofuran at 0° C. The reaction mixture is warmed to room temperature and stirred for 4 hours. 20 ml of a sodium hydroxide solution (1 N) are added before the mixture is extracted with diethyl ether. The organic layer is separated, dried over anhydrous sodium sulphate and filtered. After evaporation of the solvent the residue is chromatographed with a mixture of hexane and ethyl acetate to give 1.46 g 5-cyano-5β-cholest-8-en-3-one and 1.76 g 5-cyano-5α-cholest-8-en-3-one as pale yellow crystals.
