The title compounds 2-substituted phenyl-3-{1-cyclopropyl-6-fluoro-7-[4-(4-methoxyphenylpiperazin-1-yl]-4-oxo-1,4-dihydroquinoline} carboxamido-1, 3-thiazolidin-4-ones 6a-j have been synthesized from lead molecule 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid 1; this reacted with thionyl chloride to give acid chloride 2 and with hydrazine hydrate to afford hydrazide 3. The hydrazide 3 on condensation with substituted aromatic aldehydes a-j gave Schiff base; these on reaction with N-(4-methoxyphenyl) piperazine and thioglycolic acid furnished title compounds 6a-j. All of the synthesized compounds have been established by elemental analysis. IR and NMR spectral data and have been screened for antifungal and antibacterial activities.
In this study, we report the antimicrobial evaluation of newly synthesized amides of pyridoquinolones from substituted aniline, substituted phenyl thioureas and 4-amino-N-(substitutedphenyl)benzenesulfonamide. Structures of selected compounds have been established by IR and 1 H NMR spectra and elemental analysis. The structureactivity releationships have been studied by screening of antimicrobial activity over S. aureus, B. subtilis, E. coli, P. aeruginosa, and C. albicans using cup-plate method.
The title compounds VIa -j have been prepared from the lead molecule 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid I. The lead molecule was converted to hydrazide III via acid chloride II, which on reaction with different substituted aromatic aldehydes a -j afforded Schiff base, and on further structural variation of the Schiff base furnished the final compounds VIa -j (Scheme I).The synthesized compounds were tested for their antibacterial and antifungal activity (MIC) in vitro against two Gram-positive bacteria, S. aureus and S. pyogenes, and two Gram-negative bacteria E. coli and P. aeruginosa, and fungi C. albicans, A. niger, and A. clavatus, taking gentamycin, ampicillin, chloramphenicol, ciprofloxacin, norfloxacin, nystatin, and griseofulvin as standard drugs. All the synthesized compounds have been established by elemental analysis amd IR and NMR spectral data. Quinolones are extensively investigated as broad spectrum antibacterial [1, 2], antidiabetic [3], anticancer [4], antiviral [5], and anti-HIV [6] agents. Thiazolidinones possess antibacterial [7], antiinflammatory [8], antitubercular [9], anticancer [10], antitumor [11], anti HIV [12], antifungal [13], anesthetic [14], anti-viral [15], anticonvulsant [16], diuretic [17], nematicidal [18], and antihistaminic [19] activity.We have also synthesized some amide derivatives [20 -22] of quinolones and tested their activity. We observed that some of the compounds were potent and hence we initiated this work with a Schiff base and tried to synthesize more potent antimicrobial agents in addition to thiazolidinone with priority at C-3 and N-methylpiperazine at C-7.The 1 H NMR spectra of the lead molecule contained signals from the -OH of carboxylic acid at 13.59, a multiplet signal from N-CH proton at 3.77 -3.87, a multiplet signal from the cylcopropane proton at 0.85 -1.42, and peaks for three protons of the quinolone ring at 7.98 -8.84. These signals remained similar during further structural variation at C-3 and C-7 of the quinolone ring, with disappearance of the carboxylic acid group peak. The 1 H NMR of the hydrazide contained two singlet for NH at 8.64 and NH 2 at 5.72. The Schiff base contained signals for the -CH-proton at 5.13 -7.73 and a singlet for CONH similar to hydrazide. A multiplet at 2.77 -3.20 for the piperazin-1-yl group and a singlet for >N-CH 3 at 1.87 -1.95 were also observed; a singlet at 3.27 -4.07 for -CH 2 -and 5.67 -6.20 for the proton at C-2 of the cyclized thiazolidinone containing the aromatic ring at 7.67 for -OH was also observed.The IR spectra of the lead molecule contained absorption bands for >C=O of the quinolone ring at 1747 cm -1 , for carboxylic acid at 1725 cm -1 , and 2856 -2960 cm -1 for the cyclopropyl group. A band for the amide of the hydrazide at 1622 cm -1 and for the Schiff base for >N=CH-at 1615 cm -1 band were observed. In addition to the piperazine-1-yl group, an absorption band was observed at 1031 -1047 cm -1 for N-CH; for the thiazolidinone derivatives, the absorption ban...
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