A suspension of methyl 4-chloro-3-{[(3,5-dichloropyridin-2-yl)carbamothioyl]amino}-2-[(4-hydroxybutyl)amino]benzoate (2.76 g, 5.78 mmol), triethylamine (886 μL, 6.36 mmol), and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (1.22 g, 6.36 mmol) in tetrahydrofuran (25 mL) was stirred at 50° C. for 1 h. The reaction mixture was diluted with ethyl acetate, washed with water and brine, dried over sodium sulfate, filtered and concentrated in vacuo. The resulting solid was washed with diisopropyl ether to give the title compound as a pale yellow solid (2.45 g, 5.52 mmol, 96%).
