To a solution of 2-imidazolidone-4-carboxylic acid (12 mg, 0.093 mmol) in dichloromethane (1 mL) was added 1-(cyclopropylmethyl)-2-neopentyl-5-(piperidin-4-ylmethylsulfonyl)-1H-benzo[d]imidazole (STEP D of Example 5, 25 mg, 0.062 mmol), triethylamine (13 microL, 0.093 mmol) and 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (35 mg, 0.093 mmol) at room temperature, then stirred. After 15 h, 2-imidazolidone-4-carboxylic acid (12 mg, 0.093 mmol) was added to the mixture and stirred at room temperature. After 2 days, the mixture was washed with water (0.5 mL). The organic layer was mounted to a strong cationic exchange column (SCX) which was preconditioning with methanol (4 mL). SCX was washed with methanol (4 mL). Finally SCX was washed with 1 mol/L ammonia in methanol (5 mL), the product was collected a collection tube and concentrated at under reduced pressure by centrifugal concentrator. The residue (25 mg) was purified by prep-LC-MS(“process A”).
