A quinolone synthetic antibacterial agent and a therapeutic agent for an infection which exhibit broad spectrum and strong antibacterial activity for both Gram positive and Gram negative bacteria, and which are also highly safe are provided. The compound provided is represented by following formula (I):wherein R1and R2represent hydrogen atom, or the like R3represents an alkyl group containing 1 to 6 carbon atoms, or the like R4and R5independently represents hydrogen atom, an alkyl group containing 1 to 6 carbon atoms, or the like, with the proviso that R4and R5do not simultaneously represent hydrogen atom or the substituents R4and R5together represent (a) a 3- to 6-membered cyclic structure including the carbon atom shared by R4and R5to form a spirocyclic structure with the pyrrolidine ring R6and R7independently represents hydrogen atom, an alkyl group containing 1 to 6 carbon atoms, or the like R8represents a halogen-substituted alkyl group containing 1 to 6 carbon atoms, or the like X1represents hydrogen atom or a halogen atom A represents nitrogen atom or a moiety represented by formula (II):本發明係提供一種喹諾酮系合成抗菌藥以及感染症治療藥,其對於革蘭氏陽性菌及革蘭氏陰性菌顯示廣泛且強力之抗菌活性,且具有高安全性。本發明係提供一種以下述式(I)所表示之化合物、其鹽、或其等之水合物[式中,R1及R2表示氫原子等;R3表示碳數1至6之烷基等;R4及R5分別獨立表示氫原子、碳數1至6之烷基等,其中,R4及R5不同時為氫原子,進而,上述取代基R4及R5亦可一體化,形成吡咯啶環及螺環狀結構,R6及R7分別獨立表示氫原子或碳數1至6之烷基;R8表示碳數1至6之鹵代烷基等;X1表示氫原子或鹵原子;A表示氮原子或以式(II)所表示之部分結構]。
