A mixture of 5-hydroxy-1H-indole-2-carboxylic acid ethyl ester (1 g, 5 mmol), 2-chloro-N,N-diethylacetamide (1 mL, 7.5 mmol) and cesium carbonate (5 g, 15 mmol) in dimethylformamide (10 mL) was stirred at room temperature for 6 hours. The reaction was diluted with ethyl acetate (160 mL), washed with water (5×50 mL) and brine, dried and concentrated. The residue was recrystallized from ethyl acetate and hexane to give 0.52 g of 5-diethylcarbamoylmethoxy-1H-indole-2-carboxylic acid ethyl ester as an off-white solid.
