Collect. Czech. Chem. Commun. 1979, 44, 226-233

Participation of the methoxyl group in the cleavage of some 19-substituted steroid epoxides. A case of competition between internal and external nucleophile attack

Pavel Kočovský and Václav Černý

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


Acid cleavage of two steroid epoxides III and IV, bearing a methoxy group in position 19, with aqueous perchloric acid or hydrobromic acid gives two types of products, i.e. diols or bromohydrins VI, VII, IX and X as products of the normal reaction course and cyclic ethers V and VIII formed by participation of the 19-methoxy group. Discussed is similarity of these reactions with electrophilic additions to the related 19-methoxy olefins I and II, the mechanism, and the difference in behavior of both epoxides III and IV. Also discussed is the dependence of product ratios on the nucleophility of the attacking species.