SYNTHESIS OF SYMMETRICAL DIFUCOPYRANOSE DIANHYDRIDES

By activation of methyl 3,4-O-isopropylidene-1-methyl thio-beta-L-fuco pyranoside (1) with copper bromide-tetrabutylammonium bromide, bis(3,4 -O-isopropylidenea-alpha-L-fucopyranose)-1 ,2': 1',2-dianhydride (2) w ith almost C-2-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-dianhydri de 7 employing an intramolecular imidate glycosylation.