1-Ethyl-1,4-dihydro-4-oxo-7-(4-pyridyl)quinoline-3-carboxylic Acid Ethyl Ester is an intermediate in the synthesis of Rosoxacin (R693580), an antibacterial agent used against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pneumoniae.