Synthetic Studies on Sesquiterpenoids from D-Glucose

Total Syntheses of (+) -Eremantholide A and (-) -Verrucarol

Abstract

Enantiospecific total syntheses of (+) -eremantholide A (6) and (-) -verrucarol (41) are described. Both total syntheses began with our enantiopure building block 1, which was prepared from D-glucose. The total synthesis of 6 features (1) regio- and stereoselective radical carbocyclization applied to 16, and (2) nine-membered ring formation by the coupling reaction of the A/B ring equivalent 35 with 3 (2H) -furanone 8 followed by a vinylogous aldol reaction applied to 38. The key steps for the total synthesis of 41 are (1) intramolecular Knoevenagel cyclization applied to 48, (2) construction of the consecutive quaternary carbon center by sequential alkylation and aldol reaction applied to γ-lactone 54, and (3) a skeletal rearrangement applied to 68β for the trichothecene ring system construction.