Color reactions for identification of nalidixic acid
Görlitzer, K.; Badia, G.; Jones, P.G.; Fischer, A.K.
Die Pharmazie 55(1): 17-21
2000
ISSN/ISBN: 0031-7144 PMID: 10683865 Document Number: 512780
Nalidixic acid (1) gives with 2-naphthol a yellow charge-transfer complex. The 7-methyl group of 1 condenses with vanillin (2) and Ehrlich's reagent (4) to the coloured (E)-benzylidene compounds 3 and 5. Treating 1 with thionyl chloride and subsequent reaction with aminopyrazolone (6) and sodium acetate leads to a mixture of trichloronalidixic acid (7) and its 3-carboxamide 8. The trichloromethyl group of 7 is converted with 6 in pyridine to form the amide 9. Nalidixic acid reacts with 1,3-dimethylbarbituric acid (10) in acetanhydride/acetic acid to yield the polymethine dyes 11-13, whose structures are confirmed by X-ray crystal structure analysis. The dyes 3 and 12 inhibit the growth of staphylococcus aureus and Escherichia coli, respectively.