General synthetic approach to bicyclo[9.3.0]tetradecenone: a versatile intermediate to clavulactone and clavirolides

An efficient and stereoselective approach to the bicyclo[9.3.0]tetradecenone core structure of clavulactone starting from readily and abundantly available 2-methyl-1,3-cyclopentandione employing microbial desymmetrization and cyanohydrin alkylation as the key steps is described. The synthetic route described herein is applicable to the syntheses of the core structures of Clavirolides A–F.