[H-].[Na+].[CH3:3][O:4][C:5]1[CH:6]=[C:7]([NH:13][S:14]([C:17]2[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=2)(=[O:16])=[O:15])[CH:8]=[CH:9][C:10]=1[O:11][CH3:12].Br[CH2:24][C:25]([O:27][CH2:28][CH3:29])=[O:26].Cl>CN(C)C=O>[CH3:3][O:4][C:5]1[CH:6]=[C:7]([N:13]([CH2:24][C:25]([O:27][CH2:28][CH3:29])=[O:26])[S:14]([C:17]2[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=2)(=[O:15])=[O:16])[CH:8]=[CH:9][C:10]=1[O:11][CH3:12]Under ice-cooling, 296 mg of sodium hydride was added to an N,N-dimethylformamide solution (30 ml) of 1.99 g N-(3,4-dimethoxyphenyl)benzene sulfonamide and stirred at room temperature for 30 minutes, and then 0.75 ml of ethyl bromoacetate was added thereto and stirred for 2 hours. The reaction liquid was poured into ice water, acidified by adding 1 M hydrochloric acid and then extracted with ethyl acetate. The organic layer was washed with saturated brine, dried with anhydrous sodium sulfate and then concentrated under a reduced pressure. The thus obtained residue was purified by a silica gel column chromatography using ethyl acetate:n-hexane (1:2) as the elution solvent, thereby obtaining 2.47 g of ethyl [(3,4-dimethoxyphenyl)(phenylsulfonyl)amino]acetate as a pale yellow oily substance.
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