A series of novel 7-(3-amino-6,7-dihydro-2-methyl-2H-pyrazolo[4,3-c]pyridin- 5(4H)-yl)fluoroquinolone derivatives were designed, synthesized and characterized by ¹H-NMR, MS and HRMS. These fluoroquinolones were evaluated for their in vitro antibacterial activity against representative Gram-positive and Gram-negative strains. Results reveal that most of the target compounds exhibit good growth inhibitory potency against methicillin-resistant Staphylococcus epidermidis (MRSE) (MIC: 0.25–4 μg/mL) and Streptococcus pneumoniae (MIC: 0.25–1 μg/mL). In addition, compound 8f is 8–128 fold more potent than the reference drugs gemifloxacin (GM), moxifloxacin (MX), ciprofloxacin (CP) and levofloxacin (LV) against methicillin-resistant Staphylococcus aureus 10-05 and Streptococcus hemolyticus 1002 and 2–64 fold more active against methicillin-sensitive Staphylococcus aureus 10-03 and 10-04.

A series of amino acid and dipeptide prodrugs of IMB-070593, a fluoroquinolone candidate discovered in our lab, were synthesized and evaluated for their water solubility and then antibacterial activity. Our results reveal that four amino acid prodrugs 4a,b,e,f and two dipeptide prodrugs 4k,l have much greater solubility (>85 mg/mL) than IMB-070593 mesylate (22.5 mg/mL). Compounds 4a and 4k show good in vivo efficacy against MSSA 12-1 (p.o./i.v., 5.32–7.68 mg/kg) and S. pneumoniae12-10 (p.o., 18.39–23.13 mg/kg) which is 1.19–1.50 fold more active than the parent drug.