The Wittig-cyclization procedure: acid promoted intramolecular formation of 3-C-branched-chain 3,6-anhydro furano sugars via 2′-oxopropylene derivatives

Some olefinic Wittig products, 3-deoxy-5,6-O-isopropylidene-3-C-(2′-oxopropylene)-1,2-O-alkylidene hexofuranose derivatives were converted to the branched-chain 3,6-anhydro-3-C-(2′-oxopropyl) derivatives on treatment with ion exchange resin Amberlite 120 (H+) in methanol–water at room temperature. Hydrolysis of 5,6-isopropylidene groups and intramolecular ring-closures took place in one pot reactions.