Chemistry of the Podocarpaceae. XXXVII. Oxidative degradations of phyllocladene and isophyllocladene : conversion of isophyllocladene into (+)-Podocarp-8(14)-en-13-one

Abstract

The ozonolysis of phyllocladene (2) and isophyllocladene (12) has been carried out under a number of different conditions and the ozonide (34) of isophyllocladene has been isolated and characterized. Conversion of phyllocladene (2) into the diacid (20) has been accomplished by several routes from the norketone (3). Isophyllocladene (12) has been converted into (+)-podocarp-8(14)-en-13-one (1), an optically active relay which is useful in synthesis. The route involves ozonolysis of isophyllocladene, Baeyer-Villiger oxidation of the keto aldehyde (25), lithium aluminium hydride reduction of the ester (27), and chromium trioxide-pyridine oxidation of the resulting keto aldehyde (32) which gives the keto acid (30) in 26% overall yield. Oxidative decarboxylation then affords the enone (1) in 14% yield.