Further investigations of the stereochemistry of electrophilic addition reactions of the steroidal C-22 double bond

Abstract

Three kinds of electrophilic addition reactions, viz. peracid epoxidation, hydroboration, and iodoacetoxylation, of both the trans- and cis-isomers of 6β-methoxy-3α,5-cyclo-5α-cholest-22-enes (1) and (2) were examined. The observed stereoselectivity can be explained on the basis of the product-like model for the transition states. The preferred conformation of the transition state is determined by the difference in steric interaction between the C-16 hydrogens and reacting species or C-23 alkyl moiety.