A new route to 2,5-dihydrofurans and tetrahydrofuro[3,2-b]furans via ring contraction of pyranoid C-glycosides

Abstract

Hex-2-enopyranosides featuring a malonate-type C-glycosidic bond and a free hydroxy group at C-4′ undergo, under basic conditions [DBU (20 mol%) in trifluoroethanol], a ring contraction leading to either 2,5-dialkyl-2,5-dihydrofurans or 2-alkylfuro[3,2-b]furans depending on the substitution pattern of the glycosides.