West African timbers. Part XIX. The structure of methyl angolensate, a ring-B-seco tetranor-tetracyclic triterpene of the meliacin family

Abstract

Methyl angolensate, C₂₇H₃₄O₇, isolated from Entandrophragma angolense and related species of the Meliaceae family, has been shown to be a ring-B-seco tetranor-tetracyclic triterpene of the meliacin group. It contains a β-substituted furan, a lactone ring, a ketone group, a cyclic ether linkage, and an exocyclic methylene group. The results described lead to a structure for methyl angolensate. This structure can be obtained by a rational biogenetic route from simpler meliacins.