Synthesis of symmetric difucopyranose dianhydrides

Abstract

By activation of methyl 3,4-O-isopropylidene-1-methyl thio-β-L-fucopyranoside (1) with copper bromide–tetrabutylammonium bromide, bis(3,4-O-isopropylidene-α-L->fucopyranose)-1,2′∶1′,2->dianhydride (2) with almost> C₂-symmetry was obtained. Starting with the monosaccharide precursors 3 and 4 a corresponding activation led to the disaccharide derivative 5 which in turn was converted into the mixed D,L-dianhydride 7 employing an intramolecular imidate glycosylation.