Synthesis of (-)-deoxypukalide, the enantiomer of a degradation product ofthe furanocembranolide pukalide

A convergent stereoselective synthesis of (-)-deoxypukalide is described. T his substance has not yet been found in Nature but is obtained through deox ygenation of pukalide, the first naturally occurring furanocembrane to be s tructurally elucidated. The route features a new intraannular furan synthes is that entails treatment of a 4-oxopropargylic beta -keto ester with silic a gel. The product of this novel reaction, a 3-carboxy 2,5-bridged furan, i s formed in 96% yield. The synthetic strategy was strongly directed by mole cular mechanics calculations, which provided valuable insight into stereode fining steps including double bond stereochemistry and butenolide configura tion.