A partial reductive-cleavage study of the capsular polysaccharide of Escherichia coli K57

Trideuteriomethylated and methylated derivatives of the capsular polysaccharide of Escherichia coli K57 were partially cleaved by Et3SiH, using Me3SiOSO2Me and Me3SiOSO2CF3 as catalysts, to produce oligosaccharide-anhydroalditols. The structures of the trideuteriomethylated trisaccharide- and tetrasaccharide-anhydroalditols isolated were established by FABMS and NMR spectroscopy. Although conditions for the selective production of the tetrasaccharide-anhydroalditol could not be established, oligosaccharide-anhydroalditols were isolated in sufficiently high yield to make this an attractive approach for the structural elucidation of the repeating units of bacterial polysaccharides.