Synthesis of (+)-SclareolideBased on a Cyclic Enol Ether Ring Contraction Inducedby Peroxy Acids

(+)-Sclareolide has been synthesised from (+)-sclareol oxide in one step in high yield, by treatment with peroxy acids under very mild conditions. The reaction pathway does not follow the usual oxidative cleavage of the double bond of (+)-sclareol oxide, but the key intermediate is a five-membered ring hemiketal. The direct conversion of a six-membered cyclic enol ether into a gamma-lactone is described for the first time.