Crystal and molecular structures of substituted α- d-glucopyranosides

Abstract

The crystal and molecular structures of methyl 2,4,6-tri- O-pivaloyl-α- d-glucopyranoside ( 1), methyl 4,6- O-( R)-benzylidene-2- O-pivaloyl-α- d-glucopyranoside ( 2), and methyl 4,6- O-( R)-benzylidene-2,3-di- O-pivaloyl-α- d-glucopyranoside ( 3) were determined by X-ray analysis. Crystals of 1 are orthorhombic, space group P2 12 12 1 with the unit cell a = 13.026(2), b = 16.832, c = 11.929(2) Å, Z = 4. Crystals of 2 are monoclinic, space group P2 1. The unit-cell parameters are a = 6.519(1), b = 14.664(4), c = 10.635(4) Å, β = 93.18(1)°, Z = 2. Crystals of 3 are orthorhombic, space group P2 12 12 1 with a = 10.006(3), b = 13.874(3), c = 18.527(5) Å, Z = 4. The structures were solved by MULTAN and refined by a full-matrix procedure to final values of R = 0.084 ( 1), 0.048 ( 2), and 0.069 ( 3). The pyranose ring in each compound adopts the 4 C 1 conformation. The 1,3-dioxane rings in 2 and 3 show a chair conformation. The molecular packing in 1 is through the hydrogen bonds involving HO-3 and the 6- O-pivaloyl carbonyl group [HO-3 ⋯ O-9, 2.855(8) Å], which connect the molecules into a chain along ▪. The endocyclic oxygen atom is involved in an intermolecular hydrogen-bond with HO-3 [2.848(4) Å], joining molecules of 2 into the chains along ▪. There are no free hydroxyl groups in 3 and molecular packing reflects van der Waals interactions only.