C-13 NMR AND SINGLE-CRYSTAL X-RAY STRUCTURAL INVESTIGATION OF THE FLUOROQUINOLONE ANTIMICROBIAL DRUG NORFLOXACIN 2DCLD2O

The sites of deuteronation of the molecule norfloxacin.2DCl.D2O have b een investigated by C-13 n.m.r. and a single-crystal structure determi nation. The C-13 n.m.r. spectrum of norfloxacin (3 m DCl) displays 14 lines, seven of which display F-19-C-13 coupling. The observation of F -19-C-13 coupling for the resonance at 171.0 ppm (J 3.9 Hz) allows pos itive assignment of this resonance to the keto carbon atom. The positi on of this resonance was found to be sensitive to [D+]. The crystals o f norfloxacin.2DCl.D2O are monoclinic, space group P2(1)/c, with a 8.5 36(2), b 14.379(3), c 14.985(4) angstrom, beta 93.40(2)-degrees, V 183 6.0(7) angstrom3, and Z = 4. The structure was refined to R 0.039 and R(omega) 0.041. The n.m.r. study, combined with the structural analysi s, permits assignment of the sites of deuteronation for this molecule as an oxygen of the carboxylic acid, the external nitrogen of the pipe razine ring and the keto oxygen atom.