To a solution of 2-{[1-(cyclopropylmethyl)-2-(2,2-dimethylpropyl)-1H-benzimidazol-5-yl]sulfonyl}-2-methylpropan-1-amine (Step K of Example 13, 177 mg, 0.469 mmol) and triethylamine (131 μL, 0.938 mmol) in dichloromethane (4 mL) was added p-nitrophenyl chloroformate (104 mg, 0.516 mmol) at room temperature. After stirring for 30 min, methylamine (40% aqueous solution, 3 mL) was added to the mixture and the whole was stirred for 2 h. To the resulting mixture was added ethyl acetate and 2 mol/L sodium hydroxide aqueous solution. The organic layer was dried over sodium sulfate and concentrated under reduced pressure. The residue was purified by HPLC (ODS, gradient elution with Acetonitrile 10.01% aq. NH3=4:96 to 96:4, by volume; flow rate 40 mL/min) to afford the title compound (34 mg, 17%) as an amorphous.
