Scheme 1. Synthetic route of GMI from maleic and glycine anhydride. The scheme 1 presents the reaction procedure of GMI preparation. GMI was synthesized using the procedure described by Daniel H. Rich. Typically, a solution of maleic anhydride (0.1 mol, 9.8 g) in 50 mL glacial acetic acid was added to a solution of glycine (0.1 mol, 7.5 g) in 100 mL glacial acetic acid. The mixer was stirred at room at room temperature, followed by filtration. The precipitation was washed with cold water and dried in vacuum. N-glycinyl maleamic acid (GMA) (16.8 mmol, 2.91 g) and Et3N (35.1 mmol, 3.55 g) were added to 500 mL toluene. The suspension was refluxed with vigorous stirring for 1.5 hours, meanwhile the byproduct water was removed through a Dean-Stark apparatus. The toluene solution was decanted away from brown-colored oil and the toluene was removed by evaporation to give the triethylammonium salt. The hygroscopic product was acidified to pH 2 with HCl, followed by extraction with ethyl acetate. The organic layer was dried with magnesium sulfate, then the ethyl acetate was evaporated to give GMI.