Abstract: The synthesis of substance S acetate (Ⅵ) from 16α, 17α-epoxypregn-5-en-3β-ol-20-one (Ⅰ) by a 5-step process was improved to give an overall yield of 45 per cent. For the debromination of the bromohydrin (Ⅲb), hydrogenolysis was carried out under ordinary pressure in an alcoholic solution in the presence of a moderate amount of Raney nickel catalyst. An alcoholic solution of ammonium acetate which served as buffer was dropped into the mixture at a steady rate. Thus, the course of reaction was under control, and, at the same time, hydrogenation made selective.