To a solution of (S)-2-(2-Oxo-2,3-dihydro-benzimidazol-1-yl)-pentanoic acid tert-butyl ester (0.1 g, 0.34 mmol) in DMF (2 mL) were added K2CO3 (0.1 g, 0.69 mmol) and trimethyl-(4-methyl-benzo[b]thiophen-3-ylmethyl)-ammonium iodide (0.24 g, 0.69 mmol). The reaction mixture was heated to 80° C. for 5 h. The reaction mixture was then diluted with ethyl acetate and washed with water (×4). The organic phase was dried over Na2SO4 and concentrated. The resulting residue was purified by silica gel prep TLC using 98:2 CH2Cl2:MeOH as an eluent to afford 0.11 g (71%) of the desired product as an oily residue. LCMS (ESMS): m/z 451.33 (M+H+).
