(2R)-2-(N-(tert-Butoxycarbonyl)-N-methylamino)-3-phenylpropionic acid (11.2 g, 40 mmol), 1-hydroxy-7-azabenzotriazole (5.4 g, 40 mmol) and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (7.7 g, 40 mmol) were dissolved in dichloromethane (100 mL). The reaction mixture was stirred for 15 min. Ethyidiisopropylamine (6.85 mL, 40 mmol) and 2-(2-methylaminoethyl)pyridine (5.54 mL, 40 mmol) were added. The reaction mixture was stirred for 16 h. The reaction mixture was washed with sat. aqueous sodium hydrogen carbonate solution (3×150 mL). The organic layer was dried over magnesium sulfate. The solvent was removed in vacuo. The crude product was purified by flash chromatography on silica (400 g), using ethyl acetate as eluent, to give 10.9 g of N-methyl-N{(1R)-1-[N-methyl-N-(2-(2-pyridyl)ethyl)carbamoyl]-2-phenylethyl}carbamic acid tert-butyl ester.
