Methyl 3-O-α-L-fucopyranosyl α-D-gal­acto­pyran­oside: a synchrotron study

The title compound, C₁₃H₂₄O₁₀ is the methyl glycoside of a structural element α-L-Fucp-(1→ 3)-α-D-Galp making up two thirds of the repeating unit in the capsular polysaccharide of Klebsiella K63. The conformation of the title compound is described by the glycosidic torsion angles φ_H = 55 (1)° and ψ_H = −24 (1)°. The hy­droxy­methyl group in the galactose residue is present in the gauche–trans conformation. In the crystal, O—H...O hydrogen bonds connect the disaccharide units into chains along the a-axis direction and further hydrogen bonds cross-link the chains.

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 φ2 = 48 (1)°, ψ2 = −29 (1)°, φ3 = 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.

Methyl 3-O-α-L-fucopyranosyl β-D-glucopyran­oside tetra­hydrate

The title compound, C₁₃H₂₄O₁₀·4H₂O, is the methyl glycoside of a disaccharide structural element present in the backbone of the capsular polysaccharide from Klebsiella K1, which contains only three sugars and a substituent in the polysaccharide repeating unit. The conformation of the title disaccharide is described by the glycosidic torsion angles φ_H = 51.1 (1)° and ψ_H = 25.8 (1)°. In the crystal, a number of O—H...O hydrogen bonds link the methyl glycoside and water mol­ecules, forming a three-dimensional network. One water mol­ecule is disordered over two positions with occupancies of 0.748 (4) and 0.252 (4).