The type XXVIIStreptococcus pneumoniae(pneumococcus) capsular polysaccharide contains equimolar amounts ofD-glucose,D-galactose,L-rhamnose, 2-amino-2-deoxy-D-glucose, acetyl, pyruvic acid, phosphate, and choline. Structural investigations involving methylation studies and characterization of oligosaccharides obtained by three different degradations indicate the structure of the complete repeating unit to be