An improved synthesis of levofloxacin

Abstract

The benzoxazinecarboxylic acid (8), a precursor of levofloxacin (1), was prepared from (S)-2-amino-1-propanol (2) in 4 steps in good overall yield. The synthesis is characterized by one pot construction of 8 from the useful benzoylacrylates (7) which are effectively prepared in three steps. The key intermediates (7) were obtained from 2-nitrobenzoyl derivative (6a) and 2-fluorobenzoyl derivative (6b) through acylation of the acrylates (5), respectively.