Ethyl cyanoacetate → HCID 20076766, compound

5.2 g of 1-cyclopropyl-6-fluoro-8-chloro-7-(3-t-butoxycarbonylaminopyrrolidin-1-yl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid imidazolide and 6.9 g of potassium carbonate were put into 200 ml of acetonitrile, and 5.66 g of ethyl cyanoacetate was added thereto, and then refluxed under heating for 5 hours. Acetonitrile was distilled off under reduced pressure, and then water and ethyl acetate were added thereto. The pH of the reaction mixture was adjusted to about 3 with 1N-HCl, and then the organic layer was separated. The organic layer was dehydrated with anhydrous MgSO4, and the solvent was distilled off under reduced pressure. The residue was purified on a silica gel column chromatography, and 50 ml of 10% HCl-ethyl acetate was added to the purified compound. The reaction mixture was stirred for 30 minutes, and the resulting solid was filtered, and then dried to obtain 3.4 g of the object compound