Isolation and characterization of an impurity obtained during the synthesis of the antibiotic drug sparfloxacin

Abstract

During the synthesis of Sparfloxacin, a fluoroquinolone antibiotic drug, an unknown impurity (SF5-IMP) was identified in the fifth stage of the synthetic process. The impurity has been isolated from the mother liquor of intermediate SF5. The mother liquor was concentrated to dryness added dichloromethane and stirred for 1 h and filtered to generate SF5-IMP and the molecular structure was elucidated as 7-amino-1-cyclopropyl-5,6,8-trifluoro-4-oxo-1,4-dihydro- quinoline-3-carboxylic acid by 19F NMR and single crystal X-ray diffraction studies. The structural features of SF5-IMP and SF5 have been discussed here.