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

Methyl beta-D-mannopyranosyl-(1 -> 4)-beta-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 phi' torsion angle (O5'(Man)-C1'(Man)-O1'(Man)-C4(Xyl); Man is mannose and Xyl is xylose) of -88.38 (17)degrees and a psi' torsion angle (C1'(Man)-O1'(Man)-C4(Xyl)-C5(Xyl)) of -149.22 (15)degrees, whereas the corresponding torsion angles in molecule (IB) are -89.82 (17) and -159.98 (14)degrees, 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 beta-Xylp and beta-Manp residues, respectively. By comparison, the internal glycosidic linkage in the major disorder component of the structurally related disaccharide, methyl beta-D-galactopyranosyl-(1 -> 4)-beta-D-xylopyranoside), (II) [Zhang, Oliver & Serriani (2012). Acta Cryst. C68, o7-o11], is characterized by phi' = -85.7 (6)degrees and psi' = -141.6 (8)degrees. Inter-residue hydrogen bonding is observed between atoms O3(Xyl) and O5'(Man) in both (IA) and (IB) [O3(Xyl)center dot center dot center dot O5'(Man) internuclear distances = 2.7268 (16) and 2.6920 (17) angstrom, respectively], analogous to the inter-residue hydrogen bond detected between atoms O3(Xyl) and O5'(Gal) in (II). Exocyclic hydroxymethyl group conformation in the beta-Manp residue of (IA) is gauche-gauche, whereas that in the beta-Manp residue of (IB) is gauche-trans.