280 mg (1.14 mmol) of t-butoxycarbonyl-N-methyl-L-leucine, 204 mg (1.06 mmol) of 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride, 271 mg (1.04 mmol) of 3-(5H-dibenzo[a,d][7]annulen-5-ylidene)-N-methyl-1-propanamine and 0.15 ml (1.08 mmol) of triethylamine were stirred in 10 ml of dichloromethane at room temperature overnight. Saturated aqueous sodium hydrogencarbonate solution was added to the reaction mixture. After extracting with dichloromethane, the organic layer was dried over anhydrous sodium sulfate and then concentrated under reduced pressure. The residue was purified by the silica gel chromatography (hexane:ethyl acetate=82:18) to obtain the title compound.
