CRYSTAL-STRUCTURE OF A NUCLEOSIDE ANALOG - 2',3'-DIDEOXY-3'-FLUORO-5-BROMOCYTIDINE

The title compound crystallizes in the orthorhombic space group P2(1)2 (1)2(1) with a = 5.084(1), b = 14.322(3), c = 16.065(2) angstrom, Z = 4. The structure was solved by the heavy atom method and refined by fu ll-matrix least-squares calculations to a final R value of 0.033 for 1 106 unique observed reflections. The N-glycosidic torsion angle chi ha s a value of -153.7(4)degrees, in the anti-range. The sugar pucker is 2T3 with P = 175(1)degrees and psi = 30(1)degrees. The C4'-C5' conform ation is + sc with gamma = 46.7(7)degrees. The structure is stabilized by N-H...N, N-H...O and O-H...O hydrogen bonds and C-H...O close cont acts.