Synthesis of Methyl 12S- and 12R-Hydroxylabd-8(17)-en-19-oates

Abstract

A formal total synthesis using podocarpic acid as the relay of methyl 12S- and 12R-hydroxylabd-8(17)-en-19-oates, 7 and 8 respectively, has been achieved. Carbons 13 → 16 of the labdane side chain were formed by the nucleophilic addition of s-butyllithium to the bicyclic acid 5a or the aldehyde 4, and the configuration of the alcohols assigned from a consideration of product distributions and physical and spectroscopic properties. The spectroscopic properties of the synthetic alcohols were in agreement with those reported for two alcohols isolated from JuniperusphoeniceaL. and assigned structures 7 and 8.