An operation similar to that of Example 461-5 was performed 3 times using 2-{[4-(carboxymethyl)-1,3-thiazol-2-yl]thio}-2-methylpropionic acid resin obtained in Example 461-4 and 4-aminophenylacetic acid ethyl ester. To a suspension of the obtained resin in dimethylformamide (30 mL) were added HOBT monohydrate (0.92 g), diisopropylcarbodiimide (0.93 ml) and 4-aminophenylacetic acid ethyl ester (1.1 g), and the mixture was stirred at room temperature overnight. The resin was collected by filtration from the reaction mixture, washed once each with dimethylformamide and methanol, twice with dimethylformamide, once with methanol, three times with tetrahydrofuran and finally once with methanol, and vacuum dried to give the title pale-brown resin (3.1 g).
