Antibacterial Activity of Naphthyridone Derivatives Containing 8-Alkoxyimino-1,6-dizaspiro[3,4]octane Scaffolds

We report herein in vitro antibacterial activity of a series of novel naphthyridone derivatives containing 8-alkoxyimino-1,6-dizaspiro[ 3.4] octane scaffolds, the position isomers of the side chain at the C-7 position of zabofloxacin. Our results revealed that the target compounds were generally less active than the reference against the tested Gram-positive and Gram-negative strains with few exceptions, but compounds 1-5 and 7 showed good activity against MSSA and P. aeruginosa (MICs: 0.25-1 mu g/mL). Especially, compounds 3 and 7 (MICs: 0.25 mu g/mL) were found to be 4 times more potent than or comparable to levofloxacin against P. aeruginosa, the important conditioned pathogen on hospital infection. Simple structure-activity relationship was also discussed in this paper.