SYNTHETIC STUDIES TOWARDS PSEUROTIN-A .3. SYNTHESIS OF A RELATED HIGHLY FUNCTIONALIZED GAMMA-LACTONE

A new general concept for the total synthesis of pseurotin A (1), a se condary metabolite of Psertrleurotium ovalis STOLK, which possesses a highly substituted 1-oxa-7-azaspiro[4.4]nonane skeleton, is presented. A key intermediate of the planned reaction sequence is the functional ized gamma-lactone 8. The corresponding protected compound 52 was prep ared using (S)-O,O-isopropylideneglyceraldehyde (13) and the bromoacet al 14 as starting material. gamma-lactone 52 was obtained in enantiome rically pure state in ten steps. It possesses the desired configuratio n.