Several N (oxoalky1) norfloxacin derivatives (3a-g) were synthesized and evaluated for antibacterial activity in vitro and in vivo. Most of the compounds exhibited in vitro activity comparable to that of norfloxacin for Gram-positive bacteria, whereas their activity was lower than for Gram-negative bacteria. N-(2-Oxopropyl) norfloxacin (3b) liberated norfloxacin in the blood after oral administration in mice, and the serum level of norfloxacin was about% ...