Stereocontrolled Total Syntheses of Shark Cartilage Chondroitin Sulfate D-Related Tetra- and Hexasaccharide Methyl Glycosides

Expeditious and stereocontrolled syntheses of β-D-GlcpA(2SO4)-(1⇄3)-[β-D-GalpNAc(6-SO4)-(1⇄4)-β-D-GlcpA(2-SO4)(1⇄3)]n-β-D-GalpNAc(6-SO4)-(1⇄OMe) (where n = 1 and 2), which represent structural elements of shark cartilage chondroitin sulfate D, are reported for the first time. The compounds were obtained from a common key disaccharide donor 15, which was used in an iterative way, and in which the 2-deoxy-2-trichloroacetamido group was used as an efficient stereocontrolling auxiliary. The D-glucuronyl donor 7 was easily prepared from D-glucose, whereas the D-galactosaminyl acceptor 11 was synthesized starting from D-glucosamine precursors. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, 2002)