Conformational flexibility in highly sulfated β-d-glucopyranoside derivatives

Triggered by findings on heparin-like disaccharides, the conformation of sulfated glucopyranosides was investigated. Sodium (methyl 2,3,4-tri-O-sulfonato-β-d-glucopyranosid)uronate tetrasodium salt is in a conformational equilibrium, to which a non-chair conformation contributes. The same is true for methyl (methyl 2,3,4-tri-O-sulfonato-β-d-glucopyranosid)uronate trisodium salt, methyl 2,3,4,6-tetra-O-sulfonato-β-d-glucopyranoside tetrasodium salt, and octa-O-sulfonato-β,β-trehalose octasodium salt, with less obvious non-chair contributions. The effect is charge related. The conformational effect, which does not occur in analogous α-d-glucopyranoside derivatives, is discussed in terms of the anomeric effect.