Boc-phenylglycine (0.25 g) was dissolved in acetonitrile (10 ml). HOBt (0.23 g), WSC (0.29 g), triethylamine (0.2 ml) and 5-methyl-2-(4-piperidinyl)-1,2-dihydro-3H-imidazo[1,5-c]imidazol-3-one dihydrochloride (0.29 g) were added thereto, and mixed at room temperature for 15 hours. The solvent was distilled off under reduced pressure, and the residue was dissolved in ethyl acetate. The ethyl acetate solution was washed with a saturated aqueous sodium hydrogen carbonate solution and dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure to obtain the title compound as a green oil (0.43 g, 95%).
