Solid state and solution conformations of 1 -(β-D-2′,3′-secoribofuranosyl)-5,6-dichlorobenzimidazole, an acyclonucleoside analogue

Abstract

The title compound crystallizes in the monoclinic space group P21, with two independent molecules in the asymmetric unit (Z = 4). The unit cell dimensions are a = 11.861(2), b = 7.897(1), c = 14.527(3) Å, β = 91.28(1)°. X-ray intensity data were measured on a diffractometer, and the crystal structure was determined by direct methods. Least-squares refinement converged at R = 0.036 for 2980 reflections. The glycosidic torsion angle [C(2)—N(1)—C(1′)—O(1′)] is 53.9° in molecule A and 129.8° in molecule B. In both molecules, the orientation of C(1′)—O(1′) to C(2′)—O(2′) is trans. The conformations about C(3′)—C(4′) and C(4′)—C(5′) are different in each of the two molecules. These features are compared with those of acyclonucleoside analogues with antiviral activity. The conformation in aqueous medium was examined with the aid of high-resolution 1H nmr spectroscopy, and the results are compared with those obtained from the X-ray analysis.