A mixture of 4-(1-methylethyl)benzohydrazide (2194 mg), HOBt.H2O (2073 mg), EDCI HCl (2595 mg) and 2-aminopyridine-3-carboxylic acid (1700 mg) in dehydrated DMF (50 mL) was stirred at 60° C. overnight. The reaction mixture was added to a saturated aqueous sodium hydrogen carbonate solution, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated aqueous sodium hydrogen carbonate solution and saturated brine, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was crystallized from a mixture of ethyl acetate and diisopropyl ether to give the title compound (2.4489 g) as a white solid. The mother liquor was purified by silica gel column chromatography (ethyl acetate/hexane) to give the title compound (276.1 mg) as a white solid.
