CONCISE SYNTHESES OF NATURAL GAMMA-BUTYROLACTONES, (+)-TRANS-WHISKY LACTONE, (+)-TRANS-COGNAC LACTONE, (-)-METHYLENOLACTOCIN, (+)-NEPHROSTERANIC ACID, AND (+)-ROCCELLARIC ACID USING NOVEL CHIRAL BUTENOLIDE SYNTHONS

cis-4-Hydroxy-5-(iodomethyl)-4,5-dihydro-2(3H)-furanones (1 and ent-1) were converted by cross-coupling with several Grignard-derived cuprates followed by benzoylation and base-induced elimination into new chiral butenolides 12, 14, ent-14, 20, and 27. The sequential conjugate addition-quenching of these butenolides under complete stereocontrol provided several polysubstituted gamma-butyrolactones including flavor components [(+)-trans-whisky lactone (3) and (+)-trans-cognac lactone (4)], the antitumor antibiotic lactone (-)-methylenolactocin (5), and lichen components [(+)-nephrosteranic acid (7) and (+)-roccellaric acid (8)].