Molecular structures of new ciprofloxacin derivatives

Two new derivatives from the ciprofloxacin fluoroquinoline family, 7-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-methylcarbamate and 1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-(3-oxopyrazolo)[4,3-c]quinoline, were synthesised, tested for antibacterial activity and crystallised. Their molecular and crystal structures were determined. Tests in vitro reveal lower activities than for ciprofloxacin. Characteristic structural features of these compounds are comparable to data for other known fluoroquinolines. The bicyclic quinoline ring is planar in both compounds; the carbamate side chain and five-membered pyrazolo ring are almost coplanar with it. A piperazinyl ring exhibits a chair conformation. In the crystal packing of the carbamate analogue, two C-H...O interactions form a dimer. The pyrazolo derivative crystallises as solvate with 1.5 water molecules per quinoline molecule. In its crystal structure donor and acceptor functionalities form dimers, via hydrogen bonds, which are connected into an infinite pattern through hydrogen bonded water molecules. (C) 2002 Elsevier Science B.V. All rights reserved.