Synthesis of 4- O-glycosylated 1,5-anhydro- d-fructose and of 1,5-anhydro- d-tagatose from a common intermediate 2,3- O-isopropylidene- d-fructose

Four novel disaccharides of glycosylated 1,5-anhydro- d-ketoses have been prepared: 1,5-anhydro-4- O-β- d-glucopyranosyl- d-fructose, 1,5-anhydro-4- O-β- d-galactopyranosyl- d-fructose, 1,5-anhydro-4- O-β- d-glucopyranosyl- d-tagatose, and 1,5-anhydro-4- O-β- d-galactopyranosyl- d-tagatose. The common intermediate, 1,5-anhydro-2,3- O-isopropylidene-β- d-fructopyranose, was prepared from d-fructose and was converted into the d-tagatose derivative by oxidation followed by stereoselective reduction to the 4-epimer. The anhydroketoses thus prepared were glycosylated and deprotected to give the disaccharides.