Methyl β-D-galactopyranosyl-(1→4)-β-D-allopyranoside tetrahydrate

Abstract

The title compound, C13H24O11·4H2O, (I), crystallized from water, has an inter­nal glycosidic linkage conformation having φ′ (O5Gal—C1Gal—O1Gal—C4All) = −96.40 (12)° and ψ′ (C1Gal—O1Gal—C4All—C5All) = −160.93 (10)°, where ring-atom numbering conforms to the convention in which C1 denotes the anomeric C atom, C5 the ring atom bearing the exocyclic hydroxymethyl group, and C6 the exocyclic hy­droxy­methyl (CH2OH) C atom in the βGalp and βAllp residues. Inter­nal linkage conformations in the crystal structures of the structurally related disaccharides methyl β-lactoside [methyl β-d-galactopyranosyl-(1→4)-β-d-gluco­pyran­oside] methanol solvate [Stenutz, Shang & Serianni (1999). Acta Cryst. C55, 1719–1721], (II), and methyl β-cello­bioside [methyl β-d-gluco­pyran­osyl-(1→4)-β-d-gluco­pyran­oside] methanol solvate [Ham & Williams (1970). Acta Cryst. B26, 1373–1383], (III), are characterized by φ′ = −88.4 (2)° and ψ′ = −161.3 (2)°, and φ′ = −91.1° and ψ′ = −160.7°, respectively. Inter-residue hydrogen bonding is observed between O3Glc and O5Gal/Glc in the crystal structures of (II) and (III), suggesting a role in determining their preferred linkage conformations. An analogous inter-residue hydrogen bond does not exist in (I) due to the axial orientation of O3All, yet its inter­nal linkage conformation is very similar to those of (II) and (III).