Concise Syntheses of Natural γ-Butyrolactones, (+)-trans -Whisky Lactone, (+)-trans-Cognac Lactone, (-)-Methylenolactocin, (+)-Nephrosteranic Acid, and (+)-Roccellaric Acid Using Novel Chiral Butenolide Synthons

摘要

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 polysub-stituted 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)].