A mixture of 1-[4-(2-{(tert-butoxycarbonyl)[(tert-butoxycarbonyl)oxy]amino}ethyl)phenyl]-5,6-dichloro-2-ethyl-1H-benzimidazole (step 1, 174 mg, 0.3 mmol) and 2N hydrochloric acid (3 mL) in ethyl acetate (20 mL) was stirred at room temperature for 1 day. The reaction mixture was poured into water (100 mL), neutralized with saturated aqueous sodium bicarbonate, and extracted with ethyl acetate (100 mL). The organic layer was washed with brine (50 mL), dried (Na2SO4), and concentrated to afford 162 mg (quant.) of the title compound as a yellow oil: 1H-NMR (CDCl3) δ 10.35 (2H, br.s), 7.89 (1H, s), 7.46-7.50 (2H, m), 7.29 (2H, d, J=6.8 Hz), 7.17 (1H, s), 3.37 (2H, t, J=6.9 Hz), 3.12 (2H, t, J=6.9 Hz), 2.80 (2H, q, J=6.9 Hz), 1.34 (3H, m).
