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

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