Methyl 4-O-β-D-mannopyranosyl β-D-xylopyran­oside

Methyl β-D-mannopyranosyl-(1→4)-β-D-xylopyran­oside, C₁₂H₂₂O₁₀, (I), crystallizes as colorless needles from water, with two crystallographically independent mol­ecules, (IA) and (IB), comprising the asymmetric unit. The inter­nal glycosidic linkage conformation in mol­ecule (IA) is characterized by a φ′ torsion angle (O5′_Man—C1′_Man—O1′_Man—C4_X­yl; Man is mannose and Xyl is xylose) of −88.38 (17)° and a ψ′ torsion angle (C1′_Man—O1′_Man—C4_Xyl—C5_Xyl) of −149.22 (15)°, whereas the corresponding torsion angles in mol­ecule (IB) are −89.82 (17) and −159.98 (14)°, respectively. Ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hy­droxy­methyl (–CH₂OH) C atom in the β-Xylp and β-Manp residues, respectively. By comparison, the inter­nal glycosidic linkage in the major disorder component of the structurally related disaccharide, methyl β-D-galactopyranosyl-(1→4)-β-D-xylo­pyran­oside), (II) [Zhang, Oliver & Serriani (2012). Acta Cryst. C68, o7–o11], is characterized by φ′ = −85.7 (6)° and ψ′ = −141.6 (8)°. Inter-residue hydrogen bonding is observed between atoms O3_Xyl and O5′_Man in both (IA) and (IB) [O3_Xyl...O5′_Man inter­nuclear distances = 2.7268 (16) and 2.6920 (17) Å, respectively], analogous to the inter-residue hydrogen bond detected between atoms O3_Xyl and O5′_Gal in (II). Exocyclic hy­droxy­methyl group conformation in the β-Manp residue of (IA) is gauche–gauche, whereas that in the β-Manp residue of (IB) is gauche–trans.