Synthesis
GENERAL STEPS: A solution of (S)-2-aminobutyric acid (11.2 g, 109 mmol) in THF (200 mL) and 2M aqueous sodium carbonate (65.2 mL, 130 mmol) was slowly added dropwise to benzyl chloroformate (17.06 mL, 119 mmol) at 0 °C. After the dropwise addition was completed, the reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, the separation was carried out by extraction with H2O/TBME (water/tert-butyl methyl ether). The aqueous layer was acidified to pH=2 with 2M HCl aqueous solution and subsequently extracted with EtOAc (ethyl acetate). The organic layers were combined, dried with anhydrous Na2SO4, filtered and the filtrate was concentrated to afford (R)-2-(((benzyloxy)carbonyl)amino)butanoic acid (22.8 g, 77% yield) as a colorless oil. The product could be used for subsequent reaction without further purification.LC-MS analysis: [M-H]? m/z 236.2; retention time (Rt) 0.76 min (LCMS method 1).
References
[1] Chemical and Pharmaceutical Bulletin, 1994, vol. 42, # 9, p. 1927 - 1930
[2] Patent: US2014/135330, 2014, A1. Location in patent: Paragraph 0230
[3] Journal of the American Chemical Society, 1964, vol. 86, p. 4991 - 4999
[4] Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1964, p. 635 - 640
[5] Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1964, # 4, p. 685 - 692
