Synthesis of chondroitin sulfate E hexasaccharide in the repeating region by an effective elongation strategy toward longer chondroitin oligosaccharide

We synthesized chondroitin and its sulfate E hexasaccharides (1 and 2) composed of the trimer of the repeating disaccharide, beta-D-GalNAc(+/-4,6-di-O-SO(3)Na)-(1-->4)-beta-D-GlcA, by employing an efficient synthetic strategy for longer chondroitin oligosaccharide. Successful elongation with the beta-D-GalNAc-(1-->4)-beta-D-GlcA unit instead of the corresponding disaccharide possessing an azide group avoided problematic reduction of the multiple azide groups on the hexasaccharide.