N-Acylation of Sulfonamide – DMAP as Catalyst

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1. A solution of [5-(cyclopentyloxycarbonyl)amino-1-methylindol-3-ylmethyl]-3-methoxybenzoic acid (6.0 g), benzene sulfonamide (2.34 g), DMAP (1.84 g), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (2.86 g) in dichloromethane (100 mL) is prepared under a nitrogen a®osphere.
2. The solution is stirred at room temperature for 18 h.
3. The reaction mixture is quenched by pouring into 1 M hydrochloric acid (100 mL), the aqueous layer separated and extracted with dichloromethane (2 x 100 mL).  The combined organic extracts are washed with water, brine, then dried with anhydrous magnesium sulfate and the filtered solution evaporated.  The residual oil is purified by flash chromatography on silica gel (700 mL) eluting with hexane:dichloromethane:ethyl acetate (45:50:5 v/v/v) to give N-[4-[5-(cyclopentyloxycarbonyl)amino-1-methylindol-3-ylmethyl]-3-methoxylbenzoyl]benzenesulfonamide (7.82 g, 98%).