Triethylamine (1.5 ml) was added to a solution of N-(t-butyloxycarbonyl)-4-benzyloxy-L-phenylalanine (I) (2 g) dissolved in dry tetrahydrofuran (30 ml) and ethyl chlorocarbonate (0.65 g) was added under ice-cooling, followed by stirring for 30 minutes. To this solution was added 4-trifluoromethylaniline (0.65 g) and the mixture was stirred at room temperature for 10 hours. Post-treatment was carried out in the same manner as in Example 1 to obtain 1.3 g of N-(t-butyloxycarbonyl)-4-benzyloxy-L-phenylalanine 4-trifluoromethylanilide (II). to the above compound (II) (0.5 g) was added under ice-cooling 4N-hydrogen chloride/dioxane solution (3 ml) and the mixture was stirred at room temperature for 30 minutes. Post-treatment conducted in the same manner as in Example 1 gave quantitatively 4-benzyloxy-L-phenylalanine 4-trifluoromethylanilide (III). On the other hand, trans-4-(t-butyloxycarbonyl)aminomethylcyclohexylcarboxylic acid (0.25 g) and triethylamine (0.2 ml) were added, and ethylchlorocarbonate (0.1 g) was added under ice-cooling, followed by stirring for 30 minutes. To this solution were added the above compound (III) (0.42 g) and triethylamine (1 ml), and the mixture was stirred at room temperature for 3 hours. After extraction with chloroform, according to the same post-treatment as in Example 1, 0.28 g of N-[trans-4-(t-butyloxycarbonyl)aminomethylcyclohexylcarbonyl]-4-benzyloxy-L-phenylalanine 4-trifluoromethylanilide (IV) was obtained. To the above compound (IV) (0.28 g) was added 4N-hydrogen chloride/dioxane solution (2 ml) and, after stirring at room temperature for 30 minutes, following the same procedure as in Example 1, 0.15 g of N-(trans-4-aminomethylcyclohexylcarbonyl)-4-benzyloxy-L-phenylalanine 4-trifluoromethylanilide hydrochloride was obtained.
