Synthesis of the Putative Structure of 15-Oxopuupehenoic Acid

Synthesis of the putative structure of the marine natural 15-oxopuupehenoic acid has been achieved starting from commercial (-)-sclareol. Key steps of the synthetic sequence are the Robinson annulation of a beta-ketoester and methyl vinyl ketone and an unprecedented cyclization of the resulting a,beta-enone, which is mediated by tin(IV) chloride in the presence of N-phenylselenophthalimide. The physical properties of the synthetic compound are somewhat different from those reported for the natural product.