| Popis: |
The structure of the hydrochloride of 5′-chlorocyclocytidine, a potent inhibitor of DNA synthesis, was determined by X-ray crystallography. The nucleoside crystallizes in the orthorhombic space group P212121 with cell dimensions a = 10.413(4), b = 13.236(5), c = 17.064(6) A and with two independent molecules in the asymmetric unit (Z = 8). Atomic parameters were refined by full-matrix least squares to a final value of R = 0.053 for 2490 observed reflections. In both molecules the furanose ring has a C4′ endo/04′ exo (4 T 0) pucker. In molecule A the orientation of the -CH2Cl side chain is gauche. In molecule B the side chain is disordered: in 70% of these molecules the orientation is trans and in 30% it is gauche +. 1H NMR spectra indicate a conformational equilibrium between C4′ exo/04′ endo (4 T 0) and C4′ endo/C3′ exo (4 3 T) with a population ratio of 38:62. All three side chain rotamers occur in solution, the trans orientation contributing most. 1J(C, H) values for C1′ and C2′ are significan... |
