Synthesis of the sialylated pentasaccharide repeating unit of the capsular polysaccharide of Streptococcus group B type VI.

An efficient synthetic strategy has been developed for the synthesis of the sialic acid containing pentasaccharide repeating unit of the cell wall O-antigen of Streptococcus group B type VI strain involving stereoselective α-glycosylation of sialic acid thioglycoside derivative. Stereoselective glycosylation of glycosyl trichloroacetimidate derivatives and thioglycosides were carried out using perchloric acid supported over silica (HClO-SiO) as a solid acid catalyst. A panel of sialic acid donors has been screened for achieving satisfactory yield and stereochemical outcome of the glycosylation reaction.