The chemistry of triterpenes and related compounds. Part XLVII. Crystal and molecular structure of ‘compound B’, a triterpene dimethyl ester ε-lactone from dammar resin

Abstract

A triterpenoid dimethyl ester ε-lactone (‘compound B’) isolated from dammar resin has been shown by X-ray crystallographic examination to be 23-hydroxy-2,3-secours-12-ene-2,3,28-trioic acid (2 → 23)-lactone 3,28-di-methyl ester (I). The crystals are triclinic, space group P1, with a= 7·01, b= 9·16, c= 11·72 Å, α= 90·62, β= 92·03, γ= 100·42°, and Z= 1. The crystal structure was solved by numerical non-centrosymmetric direct methods involving the systematic examination of 32 alternative phase sets. The lactone is probably formed biogenetically by the oxidation of asiatic acid (II).