Synthesis of Branched Polysaccharides Having Hypoglycaemic Activity

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2,4-Di-O-benzyl- (1*6) -alpha-D-glucopyranan which was prepared by cationic ring-opening polymerization of an anhydro glucose derivative was xylosylated at the C-3 position to give xylopyranosyl glucopyranan derivatives. Stereoselectivity of the xylosylation with xylopyranosyl trichloroacetimidate as glycosylating reagent was low. Glucosyl branches were introduced into curdlan ((1*3)-beta-D-glucopyranan) for the purpose of improvement of physical properties of natural polysaccharides. Curdlan was protected by regioselective tritylation at C-6 position, followed by phenylcarbamoylation at C-2 and C-4. Selectively deprotected (detritylated) curdlan was glucosylated to give (1*3) -beta-D-glucopyranan derivative with glucopyranosyl branches. Deprotections of the obtained branched polysaccharide were also attempted. Natural polysaccharide curdlan was then dimethoxytritylated, phenylcarbamoylated, and dedimethoxytritylated in order to prepare a regioselectively protected polysaccharide. The regioselectively protected curdlan was subsequently glucosylated with glucopyranosyl trichloroacetimidate.