On catalytic hydrogenation of Delta (9)-steroids (e.g. 3 beta -hydroxy-5-methyl-19-nor-5 beta -androst-9-en-17-one), four isomers were formed: 9 alpha ,10 alpha-, 9 alpha ,10 beta-, 9 beta ,10 alpha- and 9 beta ,10 beta -adducts. The product distribution was affected by the nature of the C-3 substituent. A chair conformation of A, B, and C rings was found in all of the products with the exception of the 9 alpha ,10 alpha -adduct whose B ring adopts a twist boat conformation. The products were utilized for the synthesis of dihydrotestosterone analogues. (C) 2002 Elsevier Science Inc. All rights reserved.