Approaches towards the synthesis of a sulfur analog of ergosterol peroxide

Abstract

In an analogous fashion to the preparation of ergosterol peroxide from singlet oxygen, the preparation of its sulfur analog was attempted via the Diels–Alder addition of diatomic sulfur to ergosterol. Two of the recently reported methods for generating and trapping diatomic sulfur were employed as well as "activated" sulfur. Although the desired target was not obtained, several interesting steroidal products were isolated including 3,5-cyclo-6,8(14),22-ergostatriene (12), ergosta-5,7,22-trien-3-thiol (13), and ergosta-4,6,8(14),22-tetraen-3-one (16). Mechanistic aspects are discussed. Keywords: diatomic sulfur, ergosterol, sulfur analog of ergosterol peroxide, ergosta-6,22-dien-5a,8a-epidisulfide-3-ol, ergosterol peroxide, 3,5-cyclo-6,8(14),22-ergostatriene, ergosta-5,7,22-trien-3-thiol, ergosta-4,6,8(14),22-tetraen-3-one.