7-​Chloro-​1-​ethyl-​6-​fluoro-​1,​4-​dihydro-​4-​oxo-3-​quinolinecarboxylic Acid Ethyl-d5 Ester is the未標(biāo)記form of 7-​Chloro-​1-​ethyl-​6-​fluoro-​1,​4-​dihydro-​4-​oxo-3-​quinolinecarboxylic Acid Ethyl Ester (C315510), which is an impurity of Norfloxacin (N681000), an antibacterial agent and a contaminant of emerging concern (CECs). 7-​Chloro-​1-​ethyl-​6-​fluoro-​1,​4-​dihydro-​4-​oxo-3-​quinolinecarboxylic Acid Ethyl-d5 Ester is also an intermediate in the synthesis of Norfloxacin-d5 (N681003).