Concise syntheses of natural γ-butyrolactones, (+)-trans-whisky lactone, (+)-trans-cognac lactone, (-)-methylenolactocin, (+)-nephrosteranic acid, and (+)-roccellaric acid using novel chiral butenolide synthons

Article abstract of DOI:10.1021/jo00122a051

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 γ-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)].