Model studies for the synthesis of clavulactone

A synthesis of the 5,6-bicyclic lactone core of clavulactone is described. The key step involves a tandem reaction of 3-methyl cyclopentenone with allyl p-tolyl sulfoxide and an aldehyde. The relative stereochemistry of the 5,6-bicyclic lactones 13a and 13b was confirmed by NMR studies.