Synthesis of (3aS,4S,6aR)-2-Oxo-3,3a,4,6a-tetrahydro-2H-cyclopenta[b]furan-4-yl Acetate as a Key Synthon for (–)-Galiellalactone

Abstract

The synthesis of a bicyclic allyl acetate, a promising precursor of (–)-galiellalactone, is performed. The synthetic approach is based on separation of the diastereomeric carboxamides prepared by the amidation of racemic gem-dichloro-substituted Grieco lactone with (+)-α-methylbenzylamine. The subsequent steps of transformation of an individual diastereomer involve complete reductive dechlorination, construction of an allyl alcohol fragment in the ring part by stereo- and regiospecific bromohydroxylation with NBS in aqueous THF, and dehydrobromination.