Resin acids. XXI. Synthesis of methyl podocarp-8(14)-en-13-on-15-oate from the levopimaric acid-formaldehyde adduct

Abstract

The transformation of the readily available levopimaric acid-formaldehyde adduct 3a to the title compound lb by a convenient five-step sequence is described. Four of the steps proceed in quantitative or nearly quantitative yield. The first step involves an unusual oxidation of a cyclic ether to a 6 lactone in the presence of a secondary hydroxyl group. In the last step three reactions, reductive elimination of an aeetoxy group, (3 elimination of an acyloxy function, and decarboxylation, are effected at once.