A new route to D-xylo-hexos-5-ulose and some of its selectively protected derivatives from D-galactose

A new approach to d - xylo -hexos-5-ulose, a useful synthetic intermediate, is described, starting from methyl β- d -galactopyranoside and involving as the key step an epoxidation/methanolysis of 3- O -protected methyl 2,6- di -O- benzyl-4-deoxy-α- l -threo- hex-4-enopyranosides , to produce bis-glycosides of the parent dicarbonylic sugar, which can be obtained free or selectively protected through hydrogenolytic and/or hydrolytic procedures. The diastereo- and regioselectivity of the epoxidation and solvolysis steps are investigated and tentatively interpreted, and new products characterized by NMR techniques.