Syntheses of the biological repeating units of Salmonella serogroups A, B, and D1 O-antigenic polysaccharides

Abstract

The immunogenic polysaccharide part of the Salmonella lipopolysaccharide of the cell walls of Salmonella bacteria belonging to serogroups A, B, and D₁ is depicted below. [graphic omitted] Syntheses of the following three tetrasaccharides are described : p-trifluoroacetamidophenyl O-(3,6-dideoxy-α-D-hexopyranosyl)-(1 → 3)-O-α-D-mannopyranosyl-(1 → 4)-O-α-L-rhamnopyranosyl-(1 → 3)O-α-D-galactopyranoside, in which the 3,6-dideoxyhexopyranosyl group is abequosyl (28), paratosyl (29), and tyvelosyl (30), respectively. The three tetrasaccharides were made from a common trisaccharide precursor, a derivative (24) of p-trifluoroacetamidophenyl O-α-D-mannopyranosyl-(1 → 4)-O-α-L-rhamnopyranosyl-(1 → 3)-O-α-D-galactopyranoside with all hydroxy-groups protected but the one at C-3 in the mannosyl unit. In the various glycosylations, halide-ion catalysis or silver triflate-promotion was used in the construction of 1,2-cis-glycosidic bonds from glycosyl halides with a non-participating group in the 2-position. Silver triflate was used as promotor in the construction of 1,2-trans-glycosidic bonds from glycosyl halides carrying a participating acyl group in the 2-position.