Structural studies of the capsular polysaccharide from Streptococcus pneumoniae type 1

The capsular polysaccharide from Streptococcus pneumoniae type 1 is composed of D-galactopyranosyluronic acid residues and 2-acetamido-4-amino-2,4,6-trideoxy-D-galactopyranosyl residues. The latter sugar, previously unknown in Nature, was not isolated but was identified from the products obtained on deamination of the polymer. Using n.m.r. spectroscopy, methylation analysis, and Smith degradation as the principal methods of structural investigation, it is concluded that the polysaccharide is composed of trisaccharide repeating-units having the structure: leads to 3)-alpha-Sugp-(1 leads to 4)-alpha-D-GalpA-(1 leads to 3)-alpha-D-GalpA-(1 leads to, in which Sug denotes the new sugar.