Synthesis
4.3: After completion of the separation, the reaction mixture was extracted with ethyl acetate to remove the D-isomer to give L-2-amino-4-bromo-4-pentenoic acid. Subsequently, an aqueous solution of 5 L of acetone and 120 g of di-tert-butyl dicarbonate was added to the reaction system and the alkaline environment of the aqueous sodium carbonate solution was maintained. After the reaction was carried out for 5 hours, the reaction mixture was acidified with 3M hydrochloric acid and the product was extracted with ethyl acetate. The organic phase was dried and purified by crystallization to give 64 g of (S)-4-bromo-2-((tert-butoxycarbonyl)amino)pent-4-enoic acid as a solid. The purity of the product was 98.84% and the overall yield was 43.5% by HPLC analysis.
References
[1] Patent: CN107827767, 2018, A. Location in patent: Paragraph 0030; 0036
[2] Tetrahedron Letters, 1993, vol. 34, # 28, p. 4485 - 4488
