The general procedure for the synthesis of Fmoc-N-(2-Boc-aminoethyl)glycine from 9-fluorenylmethyl-N-succinimidyl carbonate and 2-((2-((tert-butoxycarbonyl)amino)ethyl)amino)acetic acid was as follows: 10.9 g (50 mmol) of 2-((2-((tert-butoxycarbonyl)amino)ethyl)amino)acetic acid was mixed and stirred with 50 mL of water, adding 11.3 g (135 mmol) sodium bicarbonate and 50 mL of tetrahydrofuran. Subsequently, 24.3 g (72 mmol) of 9-fluorenylmethyl-N-succinimidyl carbonate was added. The reaction mixture was stirred at room temperature for 20 h. After completion of the reaction, the resulting salt was removed by filtration. The filtrate was acidified to separate the phases and the organic phase was subsequently concentrated to afford the product N-(2-tert-butoxycarbonylaminoethyl)-N-(9-fluorenylmethoxycarbonyl)aminoacetic acid in 21.0 g (99%) yield.