Yield:190319-95-0 99%

Reaction Conditions:

with triethylamine in methanol at 20; for 2 h;

Steps:

5.1 Step 1: (S)-3-(5-bromothiophen-2-yl)-2-((tert-butoxycarbonyl)amino)propanoic acid (5B)

5A (10g, 40.3mmol) was dissolved in methanol (200mL), triethylamine (12.2g, 120.9mmol) was added, di-tert-butyl dicarbonate (10.5g, 48.36mmol) was added to the reaction at room temperature for 2 hours, after concentration, dilute hydrochloric acid (1N) was adjusted pH = 6 ~ 7, and after extraction and then concentration of dichloromethane, silica gel column chromatography was purified (methanol: dichloromethane (v/v) = 1:100 ~ 1: 1: 1: 100 ~ 1: 1: 100) to obtain the title compound (5B), Yellow solid (14 g, yield 99%).

References:

WO2022/42591,2022,A1 Location in patent:Page/Page column 41-42