Crystal structure of a nucleoside analog, 2′,3′-dideoxy-3′-azido-5-chlorocytidine

The title compound, l-(2,3-dideoxy-3-azido-β-D-erythro pentofuranos-1-yl)-5-chlorocytosine, crystallizes in the orthorhombic space group P212121 with a=5.840(1), b=13.780(1), c=15.396(2)Å, Z=4. The structure was solved by direct methods and refined by full-matrix least-squares calculations to a final R value of 0.033 for 1688 unique observed reflections. The N-glycosidic torsion angle χ has a value of -160.8(1)°, in the and range. The sugar pucker is23T with P=180(1)° and ψ=34(1)°. The C4′-C5′ conformation is +sc with γ=50.8(2)°. The azido group is nonlinear and oriented trans to the C3′-C4′ bond. The molecular packing in the crystalline space is stabilized by N-H⋯N, N-H⋯O, O-H⋯O hydrogen bonds and C-H⋯O close contacts. © 1993 Plenum Publishing Corporation.