Synthesis
The general procedure for the synthesis of 3-[[(1,1-dimethylethoxy)carbonyl]amino]butanoic acid from DL-3-aminobutyric acid (CAS No. [541-48-02], 18.72 g, 176.09 mmol) and di-tert-butyl dicarbonate (39.62 g, 176.09 mmol) is as follows: first, DL-3-aminobutyric acid was dissolved in 96 mL of water, followed by the addition of a 76 mL aqueous solution of di-tert-butyl dicarbonate and NaOH (8.03 g, 200.74 mmol), followed by the addition of tert-butanol (132 mL). The reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the reaction solution was concentrated under vacuum, then diluted with 200 mL of ethyl acetate and acidified by adjusting to pH 3 with dilute hydrochloric acid. After standing and layering, the aqueous phase was extracted with 200 mL of ethyl acetate. The organic phases were combined, dried with magnesium sulfate, filtered and concentrated in vacuum to give 34.5 g of the target compound as a colorless oil in 82% yield. NMR hydrogen spectrum (300MHz, CDCl3, δ, ppm): 1.25 (d, J = 7.0Hz, 3H); 1.45 (s, 9H); 2.55 (m, 2H); 4.04 (m, 1H); 4.93 (broad peak, 1H); 8.41 (broad peak, 1H).
References
[1] Journal of Organic Chemistry, 2001, vol. 66, # 20, p. 6541 - 6544
[2] Organic Letters, 2012, vol. 14, # 1, p. 398 - 401
[3] Patent: WO2017/76998, 2017, A1. Location in patent: Page/Page column 161
[4] Organic Letters, 2005, vol. 7, # 21, p. 4781 - 4784
[5] Synlett, 2004, # 15, p. 2709 - 2712
