Synthetic Antibacterials. V. 7-Substituted 1-Ethyl-1, 4-dihydro-4-oxo-1, 8-naphthyridine-3-carboxylic Acids

Abstract

The reaction of nalidixic acid (1) with thionyl chloride afforded 1-ethyl-1, 4-dihydro-4-oxo-7-trichloromethyl-1, 8-naphthyridine-3-carboxylic acid (2) in high yield. Several 7-N-substituted carbamoyl-(3-47) and 7-(5-substituted benzimidazol-2-yl)-1-ethyl-1, 4-dihydro-4-oxo-1, 8-naphthyridine-3-carboxylic acids (48-52) were prepared by treatment of 2 with appropriate amine and o-phenylenediamine, respectively. Alkaline treatment of 2 provided unexpected 7-hydroxy derivative (54), while the action of conc. sulfuric acid gave 3, 7-dicarboxylic acids (53). The in vitro antibacterial activity and structural requirements of these compounds for broad spectrum activity were also discussed.