Collect. Czech. Chem. Commun. 1980, 45, 3023-3029

Participation of 19-substituents in electrophilic additions. influence of 3β-substitution on hypobromous acid addition to 5,6-unsaturated steroids

Pavel Kočovský and Václav Černý

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6


Reactions of 19-hydroxy-, methoxy- and acetoxy-5-cholestenes Ia, IIa, IIIa were studied and compared with those previously obtained with analogous 3β-acetoxy-19-substituted 5-cholestenes Ib, IIb, IIIc. A marked difference was found in 19-acetoxy derivatives where the 3-unsubstituted compound IIIa yields exclusively the bromohydrin XVIa as a product of 6(O)π,n participation while the 3β-acetoxy derivative IIIb gives, apart from the analogous bromohydrin XVIb, also products of competing reactions: The epoxide XIIb and the bromohydrin XIIIb.