A chemical synthesis has been achieved for beta-D-ManNAc-(1-->4)-alpha-D-Glc-(1-->3)-L-Rha, a trisacchariderepeatingunit of the capsular polysaccharide of Streptococcuspneumoniae serotype 19A, by stepwise link-up of the suitably functionalized, constituent sugar units. A beta-selective glycosylation of trimethylsilylethyl glucoside having free 4-OH with 2-(benzoyloxyimino)-2-deoxyglycosyl bromide