Inter- and Intramolecular Photochemical Reactions of Fleroxacin

Abstract

In the cation formed by photoinduced C-F bond cleavage in fleroxacin, intramolecular reaction with the N-ethyl chain is prevented by the electron-withdrawing effect of fluorine and intermolecular attack by nucleophiles is facilitated.

Pulse radiolysis study on several fluoroquinolones

“…The different methods employed for the detection of the DNA-photodamage mediated by FQs have been reported, including gel electrophoresis (with whole cells, isolated DNA, and oligonucleotides) and chromatographic analysis (especially HPLC with electrochemical and MS/MS detection). A number of reports have shown that 6,8-difluoroquinolones are more phototoxic than the 6-monofluoroquinolones under anaerobic conditions, due to the formation of reactive aryl cations (Albini and Monti, 2003;Cuquerella et al, 2006a,b;Fasani et al, 2009;. The phototoxicity of the 6,8-difluoroquinolones is less affected by O 2 .…”

“…Beyond these concerns, from a strictly photochemical point of view, photochemists are interested in the photodefluorination (Fasani et al, 1997;Martinez et al, 1997;Fasani et al, 1999a,b;Albini and Monti, 2003;Cuquerella et al, 2004;Fasani et al 2004;Cuquerella et al, 2006a,b;Fasani et al, 2009) of many FQs, a very uncommon process in a wide area of fluoroaromatic photochemistry, due to the strength of the C-F bond (dissociation energy ca. 533 kJ mol À 1 ).…”

“…The triplet states of the 6-monofluoroquinoloes defluorinate through a photosubstitution reaction of the fluorine atom by OH À , such as in enoxacin (ENX), norfloxacin (NFX), and ciprofloxacin (CPX) (Fasani et al, 1999a,b;Vermeersch et al, 1991;Mella et al, 2001). The 6,8-difluoroquinolone derivatives are defluorinated at position 8, with the formation of an aryl cation that plays an important role in their phototoxicity (Martinez et al, 1997;Fasani et al 2004;Cuquerella et al, 2006a,b;Fasani et al, 2009). …”

“…In recent years, the photodefluorination of some 6,8-difluoroquinolones derivatives has been studied in detail (Albini and Monti, 2003;Fasani et al 2004;Cuquerella et al, 2006a,b;Fasani et al, 2009). Apart from this reaction, other photochemical properties of FQs, such as decarboxylation, side-chain degradation, the effect of medium, and pH dependence of FQ excited states were also investigated by photochemists, and have also been reported in detail (Albini and Monti, 2003;Bilski et al, 1996;Bilski et al, 1998;Fasani et al, 1998;Sortino et al, 1998;Fasani et al, 1999a,b;Sortino et al, 1999;Bazin et al, 2000;Park et al, 2000;Sortino et al, 2000;Fasani et al, 2001;Monti and Sortino 2002;Park et al, 2002a,b;Viola et al, 2004;Lorenzo et al, 2008a,b;Lorenzo et al, 2009;Ge et al, 2010).…”

Enhanced Photostability of Fluoroquinolone Antibacterials Capped on Silver Nanoparticles

“…Many of these drugs are indeed characterized by uncommonly high photolability, which is responsible for effective photosensitivity side effects such as phototoxicity and photocarcinogenicity. [3][4][5][6][7][8][9][10][11][12][13][14][15] Over the last decade, an intense research activity has been devoted to the characterization of both stable and transient species involved in the FQs photochemistry and overviews illustrating the unsuspected facets characterizing the photoreactivity of structurally related FQs can be found in excellent review papers. [16,17] Due to the ionization of the carboxylic group and the 4 0 -amino of the piperazinyl ring, many FQs are amphoteric substrates and thus, they may exist as neutral or differently charged species, possessing distinct absorption, and emission properties, depending on pH.…”