L-Aspartic acid 4-tert-butyl ester

In a 3000 mL three-necked bottle, add 1000 mL of dichloromethane, cool down to -5C, add 344 g of anhydrous p-toluenesulfonic acid and 133 g of aspartic acid, pass through 448 g of isobutene, and maintain the reaction at -5C for 50 hours; and then adjust the pH to 7 with a 10% aqueous solution of Na2CO3, separate the liquid, the aqueous layer was left to stand, and evaporate it under reduced pressure to produce Asp(OtBu)2, _ x000D_ Asp(OtBu) and Asp-OtBu oily mixture, the oily layer and the aqueous layer combined to be used, the yield was 58.4%.

The resulting mixture was transferred to a 3000 mL three-necked flask, 125 g of CuSO4-5H2O was added, and the was adjusted with concentrated hydrochloric acid. pH 3, stirring to raise the temperature to 40 C, the reaction for 16 hours to produce Cu[Asp(OtBu)]x (x = 1 ~ 2); then reduced to room temperature, add 186.3 g Na2EDTA-2H2O and 400mL dioxane, and adjust the pH to 8~9 with triethylamine to produce L-aspartic acid-4-tert-butyl ester.