1,2-O-(ETHANE-1,2-DIYL)-ALPHA-D-GLUCOFURANOSE - CRYSTAL-STRUCTURE, AND THE STEREOCHEMISTRY OF RELATED BICYCLIC ACETAL ANALOGS

Crystalline 1,2-O-(ethane-1,2-diyl)-alpha-D-glucofuranose (9) is ortho rhombic, P2(1)2(1)2, with a = 17.702(4), b = 8.892(2), c = 5.6400(9) A ngstrom, 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 C-7( 1), and that of the glucofuranose ring is intermediate between the (3) E and T-3(2) conformations. Extensive intermolecular hydrogen-bonding of exocyclic OH(5) and OH(6) dominates the solid state interactions. I n aqueous solution, compound (9) retains close to the same stereochemi cal characteristics as in the crystal, including those of the exocycli c C(4)-C(5)-C(6) segment of the molecule, according to n.m.r. spectros copic evidence. These findings provide support for the structures; ass igned to related bicyclic acetals (7) and (8), which differ from (9) i n having a methyl substituent at C(8) on their 1,4-dioxan rings, notab ly in confirming that the configuration at C(8) is R in (7) and S in ( 8).