Facile synthesis of a pentasaccharide repeating unit corresponding to the common O-antigen of Salmonella enterica O57 and Escherichia coli O51

A concise chemical synthetic strategy has been developed for the synthesis of a pentasaccharide present in the O-antigen of Salmonella enterica O57 and Escherichia coli O51 strains. A sequential glycosylation strategy has been adopted for the synthesis of the target pentasaccharide. All intermediate steps are high yielding and the glycosylation steps are stereoselective. A number of recently developed methodologies have been used in the synthesis.