Synthesis of methyl 2-acetamido-2-deoxy-3-O-(?-d-galactopyranosyl)-?-d-galactopyranoside from a corresponding thioglycoside derivative

Synthesis of the methyl glycosides of a tri- and a tetra-saccharide related to heparin and heparan sulphate

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

Synthesis of mono- and disaccharide amino-acid derivatives for use in solid phase peptide synthesis

N-Fluorenylmethyloxycarbonyl-protected serine and threonine derivatives, carrying O-glycosidically alpha- or beta-linked peracetylated beta-D-Galp-(1-3)-D-GalNAcp carbohydrate chains, were prepared. These derivatives are intended for use in solid phase glycopeptide synthesis. Suitably protected mono- and disaccharide thioglycosides were used as carbohydrate intermediates. These were activated by treatment with bromine to give the glycosyl bromides, which were then used in silver triflate-promoted glycosidations of N-fluorenylmethyloxycarbonyl amino-acid phenacyl esters. Removal of the phenacyl esters with zinc gave the target free acids.