To a mixture of 5-(2-hydroxy-ethyl)-2-methyl-1H-indole-3-carboxylic acid benzyl ester (1.02 g, 3.3 mmol) and triethylamine (0.92 mL, 6.6 mmol) in dry THF (10 mL) was added methanesulfonyl chloride (0.26 mL, 3.3 mmol) under nitrogen atmosphere at room temperature. The mixture was stirred at room temperature for 3 hours and then partitioned between ethyl acetate and water. The organic phase was washed with water and brine, dried over Na2SO4 and filtered. The filtrate was concentrated in vacuo to give 1.27 g (99%) of the desired product as a white solid: mp 122-124° C.; MS(APCI−): m/z 386.0 (M−H); Anal. Calcd for C20H21N1O5S1: C, 62.00; H, 5.46; N, 3.62; S, 8.28. Found: C, 61.95; H, 5.61; N, 3.54; S, 8.32.
