SYNTHESIS OF THE METHYL GLYCOSIDES OF A TRISACCHARIDE AND A TETRASACCHARIDE RELATED TO HEPARIN AND HEPARAN-SULFATE

The methyl glycoside of a tetrasaccharide isolated from heparin, methy l O-(alpha-L-idopyranosyluronic acid)-(1 --> -O-(2-acetamido-2-deoxy-a lpha-D-glucopyranosyl)-(1 --> 4)-O-(beta-D-glucopyranosyluronic acid)- (1 --> 3)-O-beta-D-galactopyranoside disodium salt and a trisaccharide derivative thereof, methyl O-(alpha-L-idopyranosyluronic acid)-(1 --> -O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-(1 --> 4)-O-beta-D-gl ucopyranosyluronic acid disodium salt, were synthesized using a block- type strategy. A suitable protected disaccharide block of iduronic aci d and glucosamine (IdoA-GlcN) was used as a key intermediate for the s yntheses and was glycosidated with a protected galactose derivative an d a disaccharide block of glucuronic acid and galactose (GlcA-Gal) to give tri- and tetra-saccharide derivatives, respectively. Deprotection gave the target compounds.