Imidazo- and triazoloquinolones as antibacterial agents. Synthesis and structure-activity relationships

4,5-Disubstituted 6-cyclopropyl-6,9-dihydro-9-oxo-1H-imidazo (30-32) and triazolo[4,5-f]quinoline-8-carboxylic acids (33-35) were synthesized starting from 5,6-diaminoquinolones 25. The imidazoquinolones 30-32 were equal or superior to the corresponding triazoloquinolone analogues 33-35 in in vitro antibacterial activity. As for the C-5 substituents, a fluorine atom was the most favorable of the three groups, H, F, and Cl. Among the compounds prepared, 4-(cyclic amino)-5-fluoro-imidazoquinolones 31 a-d showed potent and well-balanced antibacterial activity against both gram-positive and gram-negative bacteria. Structure-activity relationships for the C-4 substituents (cyclic amino groups) were also examined in detail.