The title compounds (1a-i) have been synthesized starting with ethyl 1-cyclopropyl-6,7-difluoro-4-quinolone-3-carboxylate (2). The 7-cyclopropyl and 7-vinyl derivative (1e and 1i) exhibited potent in vitro antibacterial activities against both gram-positive and gram-negative bacteria, being equipotent with ciprofloxacin (CPFX) except for the activity against Pseudomonas aeruginosa. The two compounds were significantly less toxic than CPFX in terms of convulsion-induction as determined by intracerebral administration to mice, but showed lower urinary recoveries on intravenous administration.