Studies on Synthesis and Biological Evaluation of Some Substituted Fluoroquinolones'

In the present study the synthesis of Fluoroquinolone nucleus, 7-chloro-6-fluoro-1, 4dihydro-4-oxoquinoline-3-ethyl carboxylate has been reported by the microwave-assisted condensation of 3-chloro-4-fluoro aniline and diethyl (ethoxymethylene) malonate (EMME) under solvent free conditions. The microwave-assisted synthesis of Fluoroquinolone nucleus was successfully standardized and optimized making the method easy, more convenient & less time –consuming and eco-friendly requiring less chemicals and reagents and with better yield making the process more economic than other conventional methods. N1-alkyl / aryl/arylsulphonyl substituted and C7 piperazinyl derivatives of the title compounds have been synthesized to identify newer fluoroquinolones which have better efficacy, lesser side-effects and well tolerability than Akhiles Roy et al /Int.J. ChemTech Res.2009,1(1) 35 the already available ones. The biological evaluation of the synthesized fluoroquinolone derivatives was carried out using disc method and compounds V2,VP2, V3, VP3A, V5, VP5 V10,VP10 were found to be active against both Gram-positive and Gram-negative bacteria having activity comparable to that of standard drug i.e. Ciprofloxacin.(5 μg/disc) Comparison of activity of the test compounds indicates that benzenesulphonamido moiety at N1 position and piperazine moiety at C7 position possibly contributes to activity either due to stronger binding with the receptor or better hydrophilic lipophillic balance of the overall molecule. It is clear from the results that replacement of 7-chloro substituent by piperazine improves the spectrum of activity of fluoroquinolones, showing activity against Pseudomonas species as well as Gram-positive and Gram-negative bacteria whereas the 7-chloroquinolones are active against Gram-positive and Gramnegative bacteria.