*2.2. Crystallization of Enrofloxacin Anhydrate*

Enrofloxacin Anhydrate (**1**): Enrofloxacin (230 mg, 0.64 mmol) was added to 4 mL of an ethanol/dichloromethane mixed solvent (1:1 *v*/*v*) for crystallization. The **1** crystals in the suspension were then filtered and dried in air (yield: 77%).
