Tricyclic Ortho Ester Formation From Trichloroethylidene Acetals of Sugars Via Ketene Acetals

One step formation of the tricyclic dichloroethylidyne ortho esters from the reaction of trichloroethylidene acetals of D-galactose and D-arabinose with K tert-butoxide are described. The possible intermediate, ie, ketene acetal was prepared separately, from the suitably protected 1,2-O-trichloroethylidene-alpha-D-galactofuranose Stereoselective formation of an ortho ester anhydride, from the ketene acetal is also described