Collect. Czech. Chem. Commun. 1980, 45, 3030-3038

Participation of 19-substituents in hypobromous acid addition to 3,4- and 4,5-unsaturated steroids

Pavel Kočovský and Václav Černý

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


Participation of a 19-substituent (hydroxyl, methoxyl, acetoxyl) in hypobromous acid addition to 3- and 4-cholestenes was investigated. All three 3,4-unsaturated compounds Ia-Ic yielded exclusively the cyclic ether VI as a product of 5(O)n participation. Contrasting with this behavior, the isomeric 4-cholestenes react differently depending on the substituent at C(19): Either exclusively (IIaXI) or predominantly (IIbXI) with 5(O)n participation or with 6(O)π,n participation (IIcXIVc). These results are compared with those of 19-substituted 6- and 5-cholestenes III and IV.