1,2-O-(Ethane-1,2-diyl)-α-D-glucofuranose. Crystal Structure, and the Stereochemistry of Related Bicyclic Acetal Analogues

Abstract

Crystalline 1,2-O-(ethane-1,2-diyl)-α-D- glucofuranose (9) is orthorhombic, P 2₁2₁2, with a = 17.702(4), b = 8.892(2), c = 5.6400(9) Ǻ, Z = 4, R = 0.050, and R_w = 0.041. The conformation of the 1,4-dioxan ring in this bicyclic acetal is slightly distorted from ⁷C₁, and that of the glucofuranose ring is intermediate between the ³E and ³T₂ conformations. Extensive intermolecular hydrogen-bonding of exocyclic OH(5) and OH(6) dominates the solid state interactions. In aqueous solution, compound (9) retains close to the same stereochemical characteristics as in the crystal, including those of the exocyclic C(4)-C(5)-C(6) segment of the molecule, according to n.m.r. spectroscopic evidence. These findings provide support for the structures assigned to related bicyclic acetals (7) and (8), which differ from (9) in having a methyl substituent at C(8) on their 1,4-dioxan rings, notably in confirming that the configuration at C(8) is R in (7) and S in (8).