A new compound [C_(19)H_(19)N_3O_3F_2Cl·C_4H_3O_4·H_2O] (I), (7-((7S)-7-aminospiro[2.4]heptan- 5-yl)-8-chloro-6-fluoro-1-((1R,2S)-2-fluorocyclopropyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid fumaric acid monohydrate), was synthesized and structurally characterized by single-crystal X-ray diffraction, ~1H NMR, 14C spectra and mass spectra. I crystallizes in monoclinic, space group P2_1/c with a = 8.495(2), b = 12.545(3), c = 11.832(3) A, β = 103.37(1)°, V = 1226.8(5) A~3, Z = 2, M_r = 543.90, D_c = 1.472 g/cm~3, F(000) = 564, μ = 0.225...