Methyl α-l-rhamnosyl-(1→2)[α-l-rhamnosyl-(1→3)]-α-l-rhamnoside pentahydrate: synchrotron study

The title hydrate, C19H34O13·5H2O, contains a vicinally disubstituted trisaccharide in which the two terminal rhamnosyl sugar groups are positioned adjacent to each other. The conformation of the trisaccharide is described by the glycosidic torsion angles 2 = 48 (1)°, ψ2 = 29 (1)°, 3 = 44 (1)° and ψ3 = 4 (1)°, whereas the ψ2 torsion angle represents a conformation from the major state in solution, the ψ3 torsion angle conformation may have been caught near a potential energy saddle-point when compared to its solution structure, in which at least two but probably three conformational states are populated. Extensive intermolecular O—H...O hydrogen bonding is present in the crystal and a water-containing channel is formed along the b-axis direction.