Enantioselective Formal Synthesis of (−)-Englerin A via a Rh-Catalyzed [4 + 3] Cycloaddition Reaction

An enantioselective formal synthesis of (-)-englerin A (1) is reported. Key to the strategy is a Rh-catalyzed [4 + 3] cycloaddition reaction between furan 10 and diazo ester 11 that, following an intramolecular aldol condensation, produces the tricyclic scaffold of englerin. This strategy also provides a rapid, efficient, and stereoselective access to the biologically significant core motif of the guaiane sesquiterpenes.