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

Abstract

Methyl β-D-mannopyranosyl-(1→4)-β-D-xylopyranoside, C(12)H(22)O(10), (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 (-CH(2)OH) 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.