Synthesis of a hexasaccharide fragment of the capsular polysaccharide of Streptococcus pneumoniae type 3

In the framework of the development of a new generation of neoglycoconjugate vaccines against Streptococcus pneumoniae, the synthesis is described of a spacer-containing hexasaccharide fragment related to the capsular polysaccharide of S. pneumoniae type 3. Hexasaccharide - D -GlcpA-(1 4)- - D -Glcp-(1 3)- - D -GlcpA-(1 4)- - D - Glcp-(1 3)- - D -GlcpA-(1 4)- - D -Glcp-(1 O-(CH 2 ) 3 NH 2 ) ( 1 ), comprised of three repeating units, was synthesized via a blockwise strategy employing suitably protected disaccharide building blocks. Carboxylic groups were introduced by selective oxidation with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) in the last reaction steps. Deprotection afforded target hexasaccharide 1 .Key words: oligosaccharide synthesis, Streptococcus pneumoniae type 3, TEMPO oxidation.