CRYSTAL AND MOLECULAR-STRUCTURE OF METHYL ALPHA-D-GALACTOPYRANOSIDE 3-(SODIUM SULFATE) MONOHYDRATE

The crystal and molecular structure of methyl alpha-D-galactopyranosid e 3-(sodium sulfate) monohydrate has been determined by X-ray diffract ion. The molecular structure has a distorted chair conformation C-4(1) . The conformation of the hydroxymethyl,group is gauche-cis and the me thyl group is gauche-trans with respect to the pyranoid ring. The dist orted sodium ion environment has seven closest oxygens of two differen t molecules. Coordination with (O-5, O-4, O-6) and (O-1, O-2), related by translational symmetry along the a axis, together with water oxyge n O-1W and O-9 of the sulfate group, completes the first coordination sphere of sodium. A complex hydrogen-bond pattern involves all oxygens of the sulfate group as accepters, linking molecules in [100] through O-7. The hydroxyl groups on C-2 and C-4 also participate in the bondi ng pattern. The complex packing by hydrogen bonds and ion coordination results in relevant differences with respect to the structure of othe r sulfate pyranosides.