Hydrochloric Acid → 1-{[4-({[(3-isopropyl-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl)carbonyl]amino}methyl)piperidin-1-yl]methyl}cyclopentanecarboxylic acid

A mixture of Methyl 1-{[4-({[(3-isopropyl-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl)carbonyl]amino}methyl)piperidin-1-yl]methyl}cyclopentanecarboxylate (1.33 g, 2.90 mmol, Step 4) in 4N-HCl (6 mL) and acetic acid (6 mL) was stirred at reflux for 18 h . After cooling, the reaction mixture was concentrated and basified with sat. NaHCO3 aq. (100 mL), extracted with CH2Cl2 (150 mL) for three times. The combined extracts were dried over Na2SO4, filtered and concentrated. The residue was chromatographed on a column of silica gel eluted with MeOH/CH2Cl2 (1:10) to give 1.12 g (85%) of title compound as white solid. The crude compound was recrystallized from EtOAc×2 and dried in vacuo at 50° C. for 2 days to give 610 mg of title compound as white crystal.