Convergent synthesis of the pentasaccharide repeating unit of the biofilms produced by Klebsiella pneumoniae

A pentasaccharide repeating unit containing alpha-linked D-glucuronic acid, beta-linked D-mannose, corresponding to the repeating unit of biofilms produced by Klebsiella pneumoniae, has been synthesized using a stereoselective [2 + 3] convergent glycosylation strategy. The beta-D-mannosidic moiety has been synthesized using a D-mannose-derived thioglycoside by a two-step activation process. Late stage TEMPO-mediated oxidation of the pentasaccharide derivative using phase-transfer reaction conditions furnished the target compound in satisfactory yield.