Tetrahedron 2004; 60: 2475-88
The synthesis of the methyl glycoside of the branched pentasaccharide biological repeating unit of the O-antigen of Shigella flexneri serotype 2a is described together with that of the methyl glycoside of the corresponding tetrasaccharide and frame-shifted linear pentasaccharide. All the strategies disclosed herein involve a key disaccharide corresponding to the branching point and otherwise appropriate monosaccharide building blocks activated as their trichloroacetimidate. Our data suggest partial lack of conformational
flexibility at the branched residue.