Pyridine → Phenyl N-(4-(1-(ethylamino)carbonyl-1H-5-indolyl)oxy-2-pyridyl)carbamate

N1-ethyl-5-(2-amino-4-pyridyl)oxy-1H-1-indolecarboxamide (3.168 g, 10.69 mmol) synthesized in Production example 27-1 was dissolved in N,N-dimethylformamide (30 ml) under nitrogen atmosphere. Pyridine (1.25 ml, 15.40 mmol) and phenyl chlorocarbonate (1.61 ml, 12.83 mmol) were sequentially added dropwise while cooled with an ice water bath. The reaction mixture was heated to room temperature while stirred. After 1 hour, the reaction mixture was partitioned between ethyl acetate and water. The organic layer was washed with water and brine, and dried over anhydrous sodium sulfate. The solvent was distilled off, and the crystals were precipitated from ethyl acetate, filtered off, and dried under aeration to yield the title compound (1.530 g, 3.67 mmol, 34.4%) as white crystals.