title: Methyl 4-O-beta-D-galactopyranosyl alpha-D-glucopyranoside (methyl alpha-lactoside).
abstract: Methyl alpha-lactoside, C13H24O11, (I), is described by glycosidic torsion angles varphi (O5gal-C1gal-O1gal-C4glc) and psi (C1gal-O1gal-C4glc-C5glc), which have values of -93.52 (13) and -144.83 (11) degrees, respectively, where the ring atom numbering conforms to the convention in which C1 is the anomeric C atom and C6 is the exocyclic hydroxymethyl (-CH2OH) C atom in both residues. The linkage geometry is similar to that observed in methyl beta-lactoside methanol solvate, (II), in which varphi is -88.4 (4) degrees and psi is -161.3 (4) degrees. As in (II), an intermolecular O3glc-H...O5gal hydrogen bond is observed in (I). The hydroxymethyl group conformation in both residues is gauche-trans, with torsion angles omegagal (O5gal-C5gal-C6gal-O6gal) and omega(glc) (O5glc-C5glc-C6glc-O6glc) of 69.15 (13) and 72.55 (14) degrees, respectively. The latter torsion angle differs substantially from that found for (II) [-54.6 (2) degrees; gauche-gauche]. Cocrystallization of methanol, which is hydrogen bonded to O6glc in the crystal structure of (II), presumably affects the hydroxymethyl conformation in the Glc residue in (II).
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556-5670, USA.
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Pan
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Noll
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Serianni
mesh_terms: D002236:Carbohydrate Conformation; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008759:Methylglycosides / Q000737:chemistry*; D008958:Models, Molecular
chemical_list: D008759:Methylglycosides; C034207:methyl lactoside