New $N$-4 piperazinyl derivatives of norfloxacin: design, synthesis, and correlation of calculated physicochemical parameters with antibacterial activity

摘要

A group of $N-$4 piperazinyl derivatives of norfloxacin was synthesized and identified by different spectroscopic techniques. The $N-$4 piperazinyl substituent in target compounds 2a-2k, 3a-3c , and 4a and 4b was designed to have different electronic, steric, and physicochemical properties. The antibacterial activity of the newly synthesized compounds was evaluated against Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus strains using norfloxacin as a reference. Results showed that most of the tested compounds had higher activity against E. coli and K. pneumoniae than norfloxacin, whereas only five derivatives were more active against P. aeruginosa . On the other hand, all derivatives were less active than norfloxacin against S. aureus . The biological activity of the target compounds, expressed in log MIC, is correlated with lipophilicity, polarizability, and topology parameters. Results showed that none of the calculated parameters could determine the biological activity. Consequently, the total volume of the molecule, bulkiness at C-7, electronic factors, and lipophilicity are important factors that should be considered in the design of new fluoroquinolones.