The stereochemistry and hydrolysis of gibberellin 16,17-epoxides. X-Ray molecular structures of ent-17-acetoxy-1α,10α-epoxy-2β,3α,13,16β-tetrahydroxy-20-norgibberella-7,19-dioic acid 19,2-lactone 7-methyl ester and of ent-17-chloro-1α,10α-epoxy-2β,3α,13,16β-tetrahydroxy-20-norgibberella-7,19-dioic acid 19,2-lactone 7-methyl ester

Abstract

The 16S stereochemistry of the major 16,17-epoxides obtained from methyl gibberellate, its 13-acetate, and the 19,2α-isolactone, has been established by n.O.e. measurements. The structures of the hydrolysis products of the 16-epimeric epoxides were established by X-ray crystallography. Neighbouring group participation by the 13-acetoxy group may play a role in some of the hydrolyses. Unlike the Δ¹-3-hydroxy-19,10-lactones, the ring A double bond of the isomeric Δ¹⁽¹⁰⁾-3-hydroxy-19,2α-lactones was readily epoxidized by m-chloroperbenzoic acid.