Disorder and conformational analysis of methyl beta-D-galactopyranosyl-(1 -> 4)-beta-D-xylopyranoside

作者：Zhang Wenhui; Oliver Allen G; Serianni Anthony S^*

来源：Acta Crystallographica Section C-Crystal Structure Communications, 2012, 68: O7-O11.

DOI：10.1107/S0108270111048347

Methyl beta-D-galactopyranosyl-(1 -> 4)-beta-D-xylopyranoside, C12H22O10, (II), crystallizes as colorless needles from water with positional disorder in the xylopyranosyl (Xyl) ring and no water molecules in the unit cell. The internal glycosidic linkage conformation in (II) is characterized by a phi' torsion angle (C2(Gal)'-C1(Gal)'-O1(Gal)'-C4(Xyl)) of 156.4 (5)degrees and a psi' torsion angle (C1(Gal)'-O1(Gal)'-C4(Xyl)-C3(Xyl)) of 94.0 (11)degrees, where the ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (-CH2OH) C atoms in the beta-Xyl and beta-Gal residues, respectively. By comparison, the internal linkage conformation in the crystal structure of the structurally related disaccharide, methyl beta-lactoside [methyl beta-D-galactopyranosyl-(1 -> 4)-beta-D-glucopyranoside], (III) [Stenutz, Shang & Serianni (1999). Acta Cryst. C55, 1719-1721], is characterized by phi' = 153.8 (2)degrees and psi' = 78.4 (2)degrees. A comparison of beta-(1 -> 4)-linked disaccharides shows considerable variability in both phi' and psi', with the range in the latter (similar to 38 degrees) greater than that in the former (similar to 28 degrees). Inter-residue hydrogen bonding is observed between atoms O3(Xyl) and O5(Gal)' in the crystal structure of (II), analogous to the inter-residue hydrogen bond detected between atoms O3(Glc) and O5(Gal)' in (III). The exocyclic hydroxymethyl conformations in the Gal residues of (II) and (III) are identical (gauche-trans conformer).

• 出版日期2012-1