Synthesis and NMR study of a linear pentasaccharide fragment of the Shigella Flexneri 5a O-specific polysaccharide

Laurence A Mulard (1) , Marie-Jeanne Clement (2) , Fabienne Ségat-Dioury (1) , Muriel Delepierre (2)

1 Chimie Organique
2 Résonance Magnétique Nucléaire des Biomolécules

A convergent chemical synthesis of the methyl glycoside of the linear epitope α-d-Glcp-(1→3)-α-l-Rhap-(1→3)-α-l-Rhap-(1→3)-β-d-GlcNAcp-(1→2)-α-l-Rhap (EBCDA) corresponding to the ramification of the O-antigen of Shigella flexneri serotype 5a is described. The strategy relies on the preparation of a key EB trichloroacetimidate donor and that of an appropriate CDA trisaccharide acceptor. Trichloroacetimidate chemistry was used for the construction of all glycosidic linkages except that of DA, where a bromide donor was preferred. In depth analysis of the pentasaccharide EBCDA 1H and 13C NMR spectra shows that its conformation approaches that of the corresponding fragment in the native polysaccharide. A convergent synthesis of pentasaccharide 1 is described. NMR analysis shows that its conformation approaches that of the related fragment in the native polysaccharide.

Mots clés: bacterial oligosaccharides; Shigella flexneri; chemical glycosylation

Domaines: Sciences du Vivant [q-bio]

Laurence A Mulard, Marie-Jeanne Clement, Fabienne Ségat-Dioury, Muriel Delepierre. Synthesis and NMR study of a linear pentasaccharide fragment of the Shigella Flexneri 5a O-specific polysaccharide. Tetrahedron, 2002, 58 (13), pp.2953-2604. ⟨10.1016/S0040-4020(02)00148-5⟩. ⟨pasteur-00371338⟩