A strategy for the one-pot synthesis of sialylated oligosaccharides

A new strategy has been developed for the synthesis of branched sialylated oligosaccharides using one-pot technology. Sialyl donors are in general too weak in reactivity to be used as the first glycosyl donors in the one-pot synthesis. When sialic acid is linked to a different sugar such as galactose, the reactivity is, however, significantly enhanced and can be tuned to enable the one-pot synthesis. A combination of NIS–TfOH–AgOTf was used for activation of the thioglycosides to improve the glycosylation yield when a hindered acceptor was used, as illustrated in the one-pot assembly of sialylated hexasaccharide.Key words: one-pot synthesis, sialyl oligosaccharides, new activation.