2-(3,4-Diaminophenyl)propanoic acid (436 mg, 2.42 mmol) in DMF (5 mL) was added 4-t-butylbenzylamine (399 mg, 2.44 mmol), EDC (702 mg, 3.66 mmol), HOBt (496 mg, 3.67 mmol), triethylamine (617 mg, 6.10 mmol) at 0° C. The reaction mixture was stirred for 16 hours at room temperature, and then the mixture was added water (50 mL) and extracted with methylene chloride. The organic layer was dried with MgSO4 and filtered. Methylene chloride was removed by evaporation. The residue was purified by column chromatography eluting with CH2Cl2/MeOH=20/1.
