Diterpene chemistry III. Chemistry of some epoxides derived from methyl pimarate

Abstract

Some chemistry of the α- and β-epoxides derived from a methyl pimarate degradation product (vinyl group transformed into a methoxycarbonyl) is described. The α-epoxide was found to be a very reactive species leading, by an intramolecular process, to a hydroxy-γ-lactone even on standing in hexane solution. A possible explanation for the reactivity is given, based on a conformational argument. The β-epoxide undergoes a cleavage reaction with Lewis acid to give a 'backbone' rearrangement product, although a non-rearranged compound was observed in minor yield.