ethyl 4-(6-acetamido-3-nitropyridin-2-yl)piperazine-1-carboxylate

ethyl 7-(4-(ethoxycarbonyl)piperazin-1-yl)-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylate

ethyl 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(4-ethoxycarbonyl-1-piperazinyl)-1,8-naphthyridine-3-carboxylate

diethyl N-[2-(4-ethoxycarbonyl-1-piperazinyl)-3-fluoro-6-pyridinyl]aminomethylenemalonate