Methyl 4-O-β-L-galactopyranosyl-β-D-glucopyranoside (methyl β-L-lactoside)

Methyl beta-L-lactoside, C13H24O11, (II), is described by glycosidic torsion angles phi (O5(Gal) - C1(Gal) - O4(Glc) - C4(Glc)) and psi (C1(Gal) - O1(Gal) - C4(Glc) - C5(Glc)) of 93.89 (13) and -127.43 (13) 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 ( Gal is galactose and Glc is glucose). Substitution of L-Gal for D-Gal in the biologically relevant disaccharide, methyl beta-lactoside [Stenutz, Shang & Serianni ( 1999). Acta Cryst. C55, 1719 - 1721], ( I), significantly alters the glycosidic linkage interface. In the crystal structure of ( I), one inter-residue ( intramolecular) hydrogen bond is observed between atoms H3O(Glc) and O5(Gal). In contrast, in the crystal structure of ( II), inter-residue hydrogen bonds are observed between atoms H6O(Glc) and O5(Gal), H6O(Glc) and O6(Gal), and H3O(Glc) and O2(Gal), with H6O(Glc) serving as a donor with two intramolecular acceptors.