- Photonucleophilic aromatic substitution of 6-fluoroquinolones in basic media: Triplet quenching by hydroxide anion
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Photoreaction of 1-ethyl-6-fluoro-7-(1-piperazinyl)-1,4-dihydro-4- oxoquinoline-3-carboxylic acid (norfloxacin, NFX) and other 6-fluoroquinolones in aqueous solution gives rise to the corresponding 6-hydroxy derivatives. Although two mechanisms have been proposed for this photonucleophilic aromatic substitution, direct evidence for any of them is still missing. Obtaining such evidence requires work in basic media, where intramolecular electron transfer from the piperazine ring to the quinolone system is the almost exclusive singlet deactivation pathway. To overcome this problem, the 4′-N-acetyl derivative of norfloxacin (ANFX) has been employed in the present paper due to the lower availability of the N lone pair. The photochemical and photophysical properties of ANFX have been studied in aqueous solutions at pH between 7.4 and 13. As expected, fluorescence of ANFX is not significantly quenched in basic media. Furthermore, the excited triplet state (λmax = 620 nm) reacts with hydroxide anions with a rate constant of (0.3 ± 0.1) × 106 M-1 s-1. This supports a direct attack by hydroxide anions to the excited triplet state with subsequent release of fluoride as the operating mechanism. The fact that the reaction is inhibited by the presence of naproxen (a water-soluble naphthalene derivative) as triplet quencher clearly confirms the mechanistic assignment.
- Cuquerella, M. Consuelo,Bosca, Francisco,Miranda, Miguel A.
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- Design, synthesis and antimicrobial evaluation of novel glycosylated-fluoroquinolones derivatives
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Herein we report the design, synthesis and biological evaluation of structurally modified ciprofloxacin, norfloxacin and moxifloxacin standard drugs, featuring amide functional groups at C-3 of the fluoroquinolone scaffold. In vitro antimicrobial testing against various Gram-positive bacteria, Gram-negative bacteria and fungi revealed potential antibacterial and antifungal activity. Hybrid compounds 9 (MIC 0.2668 ± 0.0001 mM), 10 (MIC 0.1358 ± 00025 mM) and 13 (MIC 0.0898 ± 0.0014 mM) had potential antimicrobial activity against a fluoroquinolone-resistant Escherichia coli clinical isolate, compared to ciprofloxacin (MIC 0.5098 ± 0.0024 mM) and norfloxacin (MIC 0.2937 ± 0.0021 mM) standard drugs. Interestingly, compound 10 also exerted potential antifungal activity against Candida albicans (MIC 0.0056 ± 0.0014 mM) and Penicillium chrysogenum (MIC 0.0453 ± 0.0156 mM). Novel derivatives and standard fluoroquinolone drugs exhibited near-identical cytotoxicity levels against L6 muscle cell-line, when measured using the MTT assay.
- Mohammed, Aya A. M.,Okechukwu, Patrick N.,Shehadeh, Mayadah B.,Suaifan, Ghadeer A. R. Y.
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- GLYCOSYLATED 3-SUBSTITUTED FLUOROQUINOLONE DERIVATIVES, PREPARATION METHODS THEREOF, AND THEIR USE IN THE TREATMENT OF ANTIMICROBIAL INFECTIONS
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The present disclosure relates to 3-substituted fluoroquinolone derivatives, and more particularly to glycosylated 3-substitutred fluoroquinolone derivatives, methods of preparation thereof, and uses thereof for treating microbial infections.
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Paragraph 038; 041
(2020/10/20)
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- Substituted quinoline carboxylic acid derivatives
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This invention relates to new compounds of value as antibacterial agents. More particularly, it relates to quinoline carboxylic acid derivatives, the hydrates and the acid or alkali addition salts thereof.
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- Structure-Activity Relationships of Antibacterial 6,7- and 7,8-Disubstituted 1-Alkyl-1,4-dihydro-4-oxoquinoline-3-carboxylic Acids
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Previous quantitative and qualitative structure-activity studies in antibacterial monosubstituted 1-ethyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids prompted us to synthesize the 6,7,8-polysubstituted compounds.In this paper, the preparation and antibacterial activity of the 6,7- and 7,8-disubstituted compounds and their derivatives are described.Among these compounds, 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)quinoline-3-carboxylic acid (34) possessed many significant activities and was more active than oxolinic acid (84) against Gram-positive andGram-negative bacteria.Structure activity relationships are discussed.
- Koga, Hiroshi,Itoh, Akira,Murayama, Satoshi,Suzue, Seigo,Irikura, Tsutomu
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p. 1358 - 1363
(2007/10/02)
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