Synthesis of (R)-Ofloxacin

Significance

The key step in the small-scale synthesis of (R)-ofloxacin depicted here is the first step, a chiral Brønsted acid catalyzed transfer ­hydrogenation in which the hydride source is the dihydropyridine C. These reactions give excellent enantiofacial discrimination with low catalyst loadings under mild conditions. A synthesis of the simpler fluoroquinolone antibiotic flumequine is also described.