213318-44-6

5419-55-6

75400-67-8

213318-44-6

Step 2: Synthesis of 1-(tert-butoxycarbonyl)-1H-indole-2-boronic acid Lithium diisopropylammonium (140 mL, 2.0 M in hexane) was slowly added dropwise to a solution of ethoxyethane (500 mL) containing tert-butyl 1H-indole-1-carboxylate (26 g, 119.67 mmol) and triisopropylboronate (30 g, 159.57 mmol) at -70 °C. The progress of the reaction was monitored by thin layer chromatography (TLC, unfolding agent ratio ethyl acetate/petroleum ether = 1:5) during the reaction. Upon completion of the reaction, the reaction was quenched with 200 g of ice-water mixture, followed by adjusting the pH with 10% hydrochloric acid solution to 7. The reaction mixture was extracted with ethyl ether (100 mL x 1), and the organic layers were combined and dried over anhydrous sodium sulfate. Concentration under reduced pressure gave 13 g (67% yield) of the target compound 1-(tert-butoxycarbonyl)-1H-indole-2-boronic acid as a white solid.