STEREOSELECTIVE SYNTHESIS OF THE C1-C5 DIENOIC SUBUNIT OF BAFILOMYCINS VIA A GAMMA-SULFONYL-DELTA-LACTONE INTERMEDIATE

A convergent and highly diastereoselective route for the synthesis of the (E,E)-2-methoxypent-2,4-dienoic ester sub-unit of bafilomycins has been developed through a Julia-Lythgoe olefination strategy. Condensa tion of an easily available gamma-dimethoxy delta-carboxy secondary su lfone precursor on model aldehydes was shown to deliver either acyclic hydroxyesters or delta-lactones depending on the quenching conditions . The subsequent reductive elimination reaction was studied on both ty pes of condensation products using Na/Hg as well as SmI2/HMPA conditio ns and proved highly stereoselective, particularly with Na/Hg.