15.29 g of N-tert-butoxycarbonyltyrosine and 12.73 g of N-benzyloxycarbonylhomopiperazine were dissolved in 280 ml of tetrahydrofuran, to the solution were added 8.09 g of 1-hydroxybenzotriazole hydrate and 11.77 g of DCC at a room temperature with stirring, and the reaction mixture was stirred for 16 hours. The reaction mixture was evaporated to remove the solvent under a reduced pressure, to the residue was added benzene, and insoluble matter was filtered by suction and washed with benzene. The benzene layers were combined and evaporated off under a reduced pressure. The resulting residue was applied to a silica gel column and eluted with chloroform/methanol (100:1), to obtain 26.42 g of the title compound in colorless amorphous form.
