Synthesis of four spacer-containing 'tetrasaccharides' that represent four possible repeating units of the capsular polysaccharide of Streptococcus pneumoniae type 6B

Abstract

In the framework of studies towards oligosaccharide-conjugate based vaccines against Streptococcus pneumoniae, the synthesis is reported of four spacer-containing 'tetrasaccharides' that each can be conceived as representing a repeating unit of the capsular polysaccharide of S. pneumoniae serotype 6B, namely, 3-aminopropyl D-ribityl-(5→hydrogen phosphate→2)-α-D-galactopyranosyl-(1→3)-α-D-glucopyranosyl-(1→3)-α-L-rhamnopyranoside, 3-aminopropyl α-L-rhamnopyranosyl-(1→4)-D-ribityl-(5→hydrogen phosphate→2)-α-D-galactopyranosyl-(1→3)-α-D-glucopyranoside, 3-aminopropyl α-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→4)-D-ribityl-(5→hydrogen phosphate→2)-α-D-galactopyranoside, and α-D-galactopyranosyl-(1→3)-α-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→4)-5-O-(3-aminopropyl hydrogen phosphate)-D-ribitol. Phosphorylations were carried out using the H-phosphonate method.