1. An aqueous solution of sodium hydroxide (8.4 g, 0.110 mol) was prepared by dissolving sodium hydroxide (8.4 g, 0.110 mol) in water (53 mL) at room temperature. 2. The above solution was cooled down to 5-10 °C. 3. To the cooled aqueous solution of sodium hydroxide was added sequentially D-serine (10.5 g, 0.100 mol) and di-tert-butyl dicarbonate (26.2 g, 0.120 mol), while the temperature was maintained at ≤ 10 °C. 4. 26.2 g, 0.120 mol). 4. The reaction mixture was heated to 30-35 °C and stirred at this temperature for 20 h. 5. Upon completion of the reaction, an aqueous solution of compound I (BOC-L-serine) was obtained in 100% yield, with 99.1% HPLC purity and 99.4% chiral purity. 6. The aqueous solution of compound I did not need to be further purified and could be used directly in the subsequent synthetic step. 7. The aqueous solution of compound I can be used directly in the subsequent synthesis steps.
[1] Journal of the American Chemical Society, 1994, vol. 116, # 18, p. 8402 - 8403
[2] Journal of the American Chemical Society, 2008, vol. 130, # 7, p. 2351 - 2364
[3] Advanced Synthesis and Catalysis, 2016, vol. 358, # 1, p. 34 - 40
[4] Patent: CN104030943, 2016, B. Location in patent: Paragraph 0095; 0096
[5] Beilstein Journal of Organic Chemistry, 2014, vol. 10, p. 1114 - 1120
