Oxalyl chloride (55 ml, 0.63 mol) was added dropwise over 10 minutes to a stirred suspension of 2-methanesulfonyl-benzoic acid (7.1 g, 0.036) in DCM (550 ml) containing DMF (0.5 ml). The solution was then stirred for 2 hours at room temperature. The solution was then evaporated to give a solid that was redissolved in dichloromethane and again evaporated to give a yellow solid. The solid acid chloride was dissolved in DCM (275 ml) and was added over 10 minutes to a stirred solution of the product of Step 3 (11.0 g, 0.033 mol) and triethylamine (15.4 ml, 0.11 mol) in dichloromethane (125 ml). The resultant solution was stirred at room temperature for 16 hours. The solution was then washed with water (500 ml), 1M aq NaOH (500 ml) and water (2×500 ml). The organic phase was dried (MgSO4), filterered and the solvent removed to give a pale yellow foam. The foam was triturated with diethyl ether to give the title compound (12.96 g, 76%).
