To a solution of 1-[9-chloro-1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]propan-1-ol (100 mg, 0.243 mmol), 2-methyl-2-(methylsulfonyl)propanoic acid (65.6 mg, 0.395 mmol) and triphenylphosphine (104 mg, 0.397 mmol) in tetrahydrofuran (5.0 mL) was added a solution of diethylazodicarboxylate in toluene (2.2 M, 0.18 mL, 0.396 mmol) at 0° C. After stirring at room temperature for 20 hr, the mixture was concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with a 25-60% ethyl acetate/n-hexane gradient mixture to give the title compound (83.0 mg, 0.149 mmol, 61%) as a colorless amorphous.
