Two synthetic antigens related to Streptococcus pneumoniae type 3 capsular polysaccharide

The synthesis of the allyl β-glycosides ( 8 and 20, respectively) of β- d-Gl cpA-(1→4)- d-Gl cp and β- d-Gl cp-(1→3)- d-Gl cpA (overlapping disaccharide fragments A and B) in the linear chain of the capsular polysaccharide (S3) from Streptococcus pneumoniae type 3 is described. Oxidation of allyl 2,3,6,2′,3′,4′-hexa- O-acetyl-β-cellobioside with chromic acid and saponification of the product gave 8. The synthesis of 20 involved glycosylation of methyl-5- O-acetyl-1,2- O-isopropylidene-α- d-glucofuranuronate or its 3- O-trityl derivative and subsequent furanose → pyranose transformation. The derivatives 8 and 20 were each copolymerised with acrylamide. In serological tests (enzyme immunoassay and passive hemagglutination), the resulting antigens exhibited the specificity of S3. It was concluded that fragment A was a much stronger immunodeterminant than fragment B.