Yield:42002-18-6 73.3%

Reaction Conditions:

with dicyclohexyl-carbodiimide in 1,4-dioxane;dichloromethane at 0 - 5; for 15 h;

Steps:

Preparation of N-Boc-L-Asparagine-N-succinimidyl ester (Boc-Asn-ONHS)

N-hydroxysuccinimide(1.5 g, 12.93 mmol) was added to a solution ofN-tert-butyloxycarboryl-L-asparagine (3.0 g, 12.93 mmol) in 10 mL of anhydrous 1,4-dioxane at 25°C.The reaction mixture was cooled to 0°C, then a solution of DCC (2.67 g, 12.95 mmol) in 3 mL of CH2Cl2was added slowly and stirred at 5°C for 15h. After filtration, the solution was removed under reducedpressure. Another 8 mL of CH2Cl2 was added and the mixture was filtrated again. After the CH2Cl2 wasremoved under reduced pressure, the isolated product was recrystallized from methanol to yieldBoc-Asn-ONHS as a white solid (3.12 g, 73.3%). 1H NMR (400 MHz, DMSO-d6) δ/ppm=1.38(s, 9H),2.61(m, 2H), 2.79(s, 4H), 4.74(m, 1H), 7.01 (s, 1H), 7.43(s, 1H) and 7.51 (d, 2H, J=10 Hz). 13C NMR(100 MHz, DMSO-d6) δ/ppm=170.4, 170.3, 167.0, 155.4, 79.2, 49.0, 36.8, 28.6, 25.9 and 25.7.

References:

Feng, Wenhua;Li, Xiaobao;Liu, Jinwei;Ma, Chunying;Zheng, Yixuan [Molecules,2022,vol. 27,# 6,art. no. 1920] Location in patent:supporting information