Template-directed intramolecular C-glycosidation. Formation of tetrahydrofurans and application to the synthesis of a higher-order sugar

Abstract Cation-mediated cyclisation reactions of silyl enol ether-containing thioglycosides give bicyclic ketotetrahydrofurans. Cyclisation of an analogous 3-phenyl-2-propenyl ether-containing substrate gives an intermediate in the total synthesis of the higher-order sugar 2,3-dideoxy- d - manno -2-octulopyranosonic acid.