Synthesis of the Tetrasaccharide Repeating Unit of the Antigen from Klebsiella TYPE 83

Starting from D-galactose, D-glucose and L-rhamnose, methyl 2-O- benzy 1-3-O-(3-O-ally 1-2,4,6-tri-O-benzy 1-α-D-galactopyranosyl)-4-O-(2,3,4,6-tetra-O-benzyl-β-D-galactopyranosyl)-α-L-rhamnopyranoside (9) and methyl 2-O-benzyl-3-O-[2,4, 6-tri-O-benzyl-3-O-(methyl 2,3,4-tri-O-benzyl-α-D-glucopyranosyluronate)-α-D-galactopyranosyl]-4-O-(2,3,4,6-tetra-O-benzyl-β-D-galactopyranosyl)-α-L-rhamnopyranoside (13A) have been synthesised. Removal of protecting groups from 9 and 13A gave the trisaccharide (11) and the tetrasaccharide repeating unit of the antigen type 83 in the form of its methyl ester methyl glycoside (14A) respectively.