The general procedure for the synthesis of Cbz-D-aspartic acid from D-aspartic acid and benzyl chloroformate is as follows:
1. 6 M NaOH solution was added to 500 mL of distilled water at 0 °C and the pH of the solution was adjusted to 13. Subsequently, 65 g (489 mmol) of (R)-aspartic acid was added.
2. 141 g (831 mmol, 1.7 eq.) of benzyl chloroformate was slowly added to the above solution under magnetic stirring.
3. The reaction mixture was stirred at room temperature for 2 days. 4.
4. After completion of the reaction, the mixture was washed with ether and the aqueous phase was acidified with 6 N HCl to pH < 2. 5.
5. The acidified aqueous phase was extracted with ethyl acetate (AcOEt) and the organic phases were combined.
6. The organic phase was dried with anhydrous Na2SO4, filtered, and concentrated in a rotary evaporator to give 80 g of a clear, colorless gelatinous product in 59% yield.
Product Characterization:
- MS (ESI) m/e (MH+): 266
- 1H-NMR (CDCl3, 400 MHz): δ 7.21-7.21 (m, 5H), 6.14 (d, J = 8.4 Hz, 1H), 5.05 (s, 2H), 4.60 (m, 1H), 2.99 (m, 1H), 2.75 (m, 1H).
