General procedure: to a stirred solution of benzyloxycarbonyl-L-alanine (250 mg, 1.2 mmol) in dichloromethane at 0 °C, dicyclohexylcarbodiimide (DCC) (296 mg, 1.44 mmol, 1.2 eq.) and hydroxybenzotriazole (HOBt) (195 mg, 1.44 mmol, 1.2 eq.) were sequentially added. The reaction mixture was kept at 0 °C for 1 h and then slowly warmed up to room temperature. Subsequently, methylamine (112 mg, 3.6 mmol, 3 eq.) was added and the reaction mixture continued to be stirred for 12 hours. Upon completion of the reaction, dicyclohexylurea (DCU) was removed by filtration, and the organic layer was washed sequentially with 5% citric acid solution (twice), saturated aqueous sodium bicarbonate solution (twice) and brine, and after drying with anhydrous sodium sulphate, it was concentrated in vacuum to obtain a clarified oil. Finally, the residue was purified by fast column chromatography (eluent: EtOAc/hexane, 8:2) to afford N-Cbz-N'-methyl-L-alaninamide as a white solid in 64% yield.
