Molecular and crystal structure of galactinol dihydrate [1-O-(alpha-D-galactopyranosyl)-myo-inositol dihydrate]

The crystal structure of galactinol dihydrate has been determined by X-ray diffraction. The crystal belongs to the orthorhombic system, space group P2 (1)2(1)2, a = 15.898(6), b = 19.357(5), c = 5.104(4) Angstrom, and Z = 4. T he structure was refined to R = 0.044 for 1818 observed structure amplitude s. The primary hydroxyl group exhibits twofold orientational disorder. The linkage conformation is close to those of alpha-(1 --> 4) linkages in methy l alpha-maltotrioside tetrahydrate and erlose trihydrate. Although there is no interring hydrogen bond in galactinol, an indirect interring hydrogen b ond including a water molecule is present. The observed conformation is add itionally stabilized by the indirect interring hydrogen bond. The global mi nimum in the relaxed-residue energy map based on the MM3(92) force-field is close to the observed conformation in the crystal structure. All hydroxyl, ring and water oxygen atoms are involved in a complex three-dimensional hy drogen-bonding network. (C) 2000 Elsevier Science Ltd. All rights reserved.