Total Synthesis of (±)-Cochlearol A

Abstract

Total synthesis of (±)-cochlearol A was accomplished, which features a <i>cis</i> 6/6 B/D ring synthesis. A TMSOTf-promoted lactonization of <i>tert</i>-butoxy ketoester produced the desired lactone with quaternary carbon. The <i>cis</i> configuration of the B/E ring is essential for regioselective B/D ring formation. Finally, simple deprotections and transformations gave cochlearol A in 16 steps from known ethyl 4-<i>tert</i>-butoxyacetoacetate.