A reinvestigation on the structure of the capsular polysaccharide from Pneumococcus Type IX

Abstract

The capsular polysaccharide of Pneumococcus Type IX (S IX) was subjected to methylation. The methylated derivative was reduced with LiAlH₄ to convert the uronic acid units into neutral sugars, and the native polysaccharide was also reduced with diborane. The uronic acid residues were subjected to base degradation. The uronic acid-reduced product was deacetylated and deaminated. All these products were converted into their methylated derivatives and the methyl sugars in the hydrolysates were characterised and estimated. The polysaccharide was subjected to periodate oxidation followed by Smith degradation. At every stage of the reaction the material was subjected to methylation studies. The fully methylated S IX was hydrolysed using mildly acidic conditions to yield five methyl oligosaccharides. The mixture was re-methylated and then separated into its component. One mixture and three homogeneous fractions were obtained. The methyl sugars in the homogeneous fragments were identified. From these studies a revised structure is assigned to the repeating unit of S IX. Chromium trioxide oxidation studies indicated that all the glycosidic linkages are of the α-type.