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Photochemistry of 1‐Cyclopropyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐ (piperazin‐1‐yl)quinoline‐3‐carboxylic Acid (=Ciprofloxacin) in Aqueous Solutions
Author(s) -
Mella Mariella,
Fasani Elisa,
Albini Angelo
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010919)84:9<2508::aid-hlca2508>3.0.co;2-y
Subject(s) - chemistry , piperazine , flash photolysis , moiety , carboxylic acid , quinoline , aqueous solution , photochemistry , medicinal chemistry , quenching (fluorescence) , stereochemistry , organic chemistry , fluorescence , kinetics , physics , quantum mechanics , reaction rate constant
Abstract The 1‐cyclopropyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(piperazin‐1‐yl)quinoline‐3‐carboxylic acid (=ciprofloxacin; 1 ) undergoes low‐efficiency ( Φ =0.07) substitution of the 6‐fluoro by an OH group on irradiation in H 2 O via the ππ * triplet (detected by flash photolysis, λ max 610 nm, τ 1.5 μs). Decarboxylation is a minor process (≤5%). The addition of sodium sulfite or phosphate changes the course of the reaction under neutral conditions. Reductive defluorination is the main process in the first case, while defluorination is accompanied by degradation of the piperazine moiety in the presence of phosphate. In both cases, the initial step is electron‐transfer quenching of the triplet ( k q =2.3⋅10 8 M −1 s −1 and 2.2⋅10 7 M −1 s −1 , respectively). Oxoquinoline derivative 1 is much more photostable under acidic conditions, and in this case the F‐atom is conserved, and the piperazine group is stepwise degraded ( Φ =0.001).