Isolation and structure elucidation of an intermediate in the photodegradation of ciprofloxacin

Ciprofloxacin decomposes photochemically in aqueous solutions at acidic pH forming two major degradation products. One of the products, isolated from irradiated solutions by flash chromatography, was 7-[(2-aminoethyl)amino]-1-cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-3-quinoline carboxylic acid. The compound was an intermediate in the photochemical process, which degraded after longer exposure with a high-pressure mercury lamp to an aromatic amino-compound, 7-amino-1-cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-3-quinoline carboxylic acid. The structure of the intermediate was elucidated on the basis of information from ultraviolet, mass and nuclear magnetic resonance spectra.