Synthesis of optically active butenolides via chromium alkoxycarbene complexes : total synthesis of (+)-tetrahydrocerulenin and two butenolides from the marine sponge Plakortis lita

Optically active butenolides were synthesized from the corresponding cyclobutanones, derived from the photolysis of chromium alkoxycarbene complexes and optically active enecarbamates. The cyclobutanones were oxidized (Baeyer-Villiger) to the corresponding lactones, and subsequent base-induced elimination of the β-oxazolidinone ring provided optically active butenolides efficiently. The butenolides were utilized in the syntheses of (+)-tetrahydrocerulenin and two marine natural products