[CH3:1][C:2]1[CH:3]=[C:4]([CH:18]=[C:19]([CH3:21])[CH:20]=1)[O:5][CH2:6][C:7]([NH:9][CH2:10][CH2:11][CH2:12][CH2:13][CH2:14][C:15]([OH:17])=[O:16])=[O:8].[N+:22]([C:25]1[CH:26]=[C:27]([S:31]([CH2:34][CH2:35]O)(=[O:33])=[O:32])[CH:28]=[CH:29][CH:30]=1)([O-:24])=[O:23].O.C1(C)C=CC(S(O)(=O)=O)=CC=1.O>C1(C)C=CC=CC=1>[N+:22]([C:25]1[CH:26]=[C:27]([S:31]([CH2:34][CH2:35][O:16][C:15](=[O:17])[CH2:14][CH2:13][CH2:12][CH2:11][CH2:10][NH:9][C:7](=[O:8])[CH2:6][O:5][C:4]2[CH:18]=[C:19]([CH3:21])[CH:20]=[C:2]([CH3:1])[CH:3]=2)(=[O:33])=[O:32])[CH:28]=[CH:29][CH:30]=1)([O-:24])=[O:23]A mixture of 6-[2-(3,5-dimethyl-phenoxy)acetylamino]hexanoic acid (Intermediate 15, 3.0 g, 10.2 mmol), 2-(m-nitrobenzenesulfonyl)ethanol (available from Aldrich 2.3 g, 10.0 mmol), and p-toluenesulfonic acid hydrate (0.5 g) in 100 mL of toluene was refluxed overnight with Dean-Stark trap. Then water was added and the mixture was extracted with CH2Cl2. The combined organic layers were washed with saturated NaHCO3 solution two times, dried over anhydrous MgSO4, and concentrated under reduced pressure. The resulting residual oil was purified by column chromatography (1% MeOH in CH2Cl2) to give Intermediate 16 (4.8 g, 89%) as a yellowish thick oil.
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