Synthesis of di- to penta-saccharides related to the O-specific polysaccharide of Shigella dysenteriae type 1, and their nuclear magnetic resonance study

Abstract

The syntheses of oligosaccharide fragments of the O-specific polysaccharide of the lipopolysaccharide of Shigella dysenteriae type 1 are described, including disaccharides methyl O-α- d-mannopyranosyl-(1→2)-α- d-galactopyranoside ( 1), and methyl O-(2-deoxy-2-propionamido-α- d-glucopyranosyl)-(1→3)-α- l-rhamnopyranoside ( 2), trisaccharide methyl O-α- d-galactopyranosyl-(1→3)- O-(2-acetamido-2-deoxy-α- d-glucopyranosyl)-(1→3)-α- l-rhamnopyranoside ( 3), tetrasaccharide methyl O-α- l-rhamnopyranosyl-(1→2)- O-α- d-galactopyranosyl-(1→3)- O-(2-acetamido-2-deoxy-α- d-glucopyranosyl)-(1→3)-α- l-rhamno-pyranoside ( 4), and pentasaccharide methyl O-α- l-rhamnopyranosyl-(1→3)- O-α- l-rhamnopyranosyl-(1→2)- O-α- d-galactopyranosyl-(1→3)- O-(2-acetamido-2-deoxy-α- d-glucopyranosyl)-(1→3)-α- l-rhamnopyranoside ( 5). The following monosaccharide building blocks were used as starting compounds: methyl 6- O- tert-butyldiphenylsilyl-3,4- O-isopropylidene-α- d-galactopyranoside ( 8), methyl 3,4,6-tri- O-benzyl-2- O-(4-methoxybenzyl)-1-thio-β- d-galactopyranoside ( 11), methyl 3,4,6-tri- O-acetyl-2-azido-2-deoxy-1-thio-α- d-glucopyranoside ( 16), methyl 2-azido-4,6- O-benzylidene-2-deoxy-1-thio-α- d-glucopyranoside ( 18), methyl 2,4-di- O-benzyl-α- l-rhamnopyranoside ( 21), methyl 2,3,4-tri- O-benzoyl-1-thio-α- l-rhamnopyranoside ( 22), 2,3,4-tri- O-benzoyl-α- l-rhamnopyranosyl bromide ( 23), and methyl 4- O-benzyl-α- l-rhamnopyranoside ( 24). Nuclear magnetic resonance data indicate that oligosaccharides 4 and 5 partially mimic the conformation of the O-specific polysaccharide of S. dys. type 1.