A mixture of N-(t-butyloxycarbonyl)-4-benzyloxy-L-phenylalanine cyclohexylamide (0.68 g) obtained in Example 4, palladium black (0.10 g), cyclohexene (4 ml), and ethanol (20 ml) was allowed to react under reflux of ethanol for one hour, while stirring. After cooling, the solid was filtered off and the filtrate was concentrated under reduced pressure to obtain N-(t-butyloxycarbonyl-4-hydroxy-L-phenylalanine cyclohexylamide (I) (0.54 g). The compound (I) (0.54 g) was dissolved, without purification, in N,N-dimethylformamide (10 ml), followed by adding sodium hydride (0.06 g) thereto. The mixture was stirred at room temperature for 30 minutes. To this solution was added a solution of phenacyl bromide (0.30 g) in N,N-dimethylformamide (5 ml). The reaction was carried out at room temperature for 4 hours, followed by adding ice-water thereto. The resultant oily product was extracted with ethyl acetate. After a conventional post-treatment, N-(t-butyloxycarbonyl)-4-phenacyloxy-L-phenylalanine cyclohexylamide (II) (0.61 g) was obtained. From the compound (II), N-(trans-4-aminomethylcyclohexylcarbonyl)-4-phenacyloxy-L-phenylalanine cyclohexylamide hydrochloride (0.38 g) was obtained, following the procedure of Example 7.
