3-Deoxy-β-D-ribo-hexopyranose (3-deoxy-β-D-glucopyranose)

The beta- pyranose form, ( III), of 3- deoxy- D- ribo- hexose ( 3- deoxy- D- glucose), C6H12O5, crystallizes from water at 298 K in a slightly distorted C-4(1) chair conformation. Structural analyses of ( III), beta- D- glucopyranose, ( IV), and 2- deoxy- beta- D-arabinohexopyranose ( 2- deoxy- beta- D- glucopyranose), ( V), show significantly different C - O bond torsions involving the anomeric carbon, with the H - C - O - H torsion angle approaching an eclipsed conformation in ( III) (. 10.9 degrees) compared with 32.8 and 32.5 degrees in ( IV) and ( V), respectively. Ring carbon deoxygenation significantly affects the endo- and exocyclic C - C and C - O bond lengths throughout the pyranose ring, with longer bonds generally observed in the monodeoxygenated species ( III) and ( V) compared with ( IV). These structural changes are attributed to differences in exocyclic C - O bond conformations and/ or hydrogenbonding patterns superimposed on the direct ( intrinsic) effect of monodeoxygenation. The exocyclic hydroxymethyl conformation in ( III) ( gt) differs from that observed in ( IV) and ( V) ( gg).