Stereoselective Syntheses of Four Diastereomers of 3,9,12-Trihydroxycalamenene via a Benzobicyclo[3.3.1] Intermediate

The highly stereoselective syntheses of four diastereomers of natural 3,9,12-trihydroxycalamenene are described. The syntheses highlight the utility of an unusual framework of benzobicyclo[3.3.1] lactones, which were accomplished via an intramolecular Friedel Crafts-type Michael addition of alpha,beta-unsaturated lactones.