ACID-CATALYZED CLEAVAGE OF SOME 3-SUBSTITUTED 5-ALPHA,6-ALPHA-EPOXY-7-NORANDROSTAN-17-ONES

Crystallographic and spectroscopic studies show that treatment of 3-beta-acetoxy-5-alpha,6-alpha-epoxy-7-norandrostan-17-one with HBr in glacial acetic acid gives 3-beta-acetoxy-6-bromo and 3-beta,6-dibromo-7-norandrost-5-en-17-one and 5-beta-bromo-3-alpha,6-alpha-epoxy-7-norandrostan-17-one. Cleavage of the epoxide with periodic acid gives the 5-beta,6-alpha-diol. The corresponding 3-beta-methanesulphonate gave 3-beta,6-beta-diobromo-5-beta-methyl-7,19-dinorandrost-9-en-17-one and 1-methyl-7-norestra-1,3,5(10)-trien-17-one. The formation of these products is rationalized in terms of the various modes of collapse of a C-5 carbocation.