Total Synthesis of (-)-Merochlorin A.

The first asymmetric total synthesis of the meroterpenoid (-)-merochlorin A is described. The route features enantiospecific gold-catalyzed tandem 1,3-acyloxy migration/Nazarov/aldol reaction sequence to furnish the bicyclo[3.3.0]octane core in a single step from a linear propargylic 1,3-enyne aldehyde. After completion of the central skeleton by reductive enol lactone rearrangement, late stage Diels-Alder cycloaddition/aromatization sequence installed the resorcinol. An additional salient feature of the synthesis is the assignment of the absolute configuration, which had not been determined previously.