[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([C:8]2[CH:9]=[C:10]([CH:14]=[C:15]([C:17]([CH3:19])=[CH2:18])[CH:16]=2)[C:11]([OH:13])=[O:12])=[N:6][CH:7]=1.CS(O)(=O)=[O:22].C(=O)([O-])[O-].[Na+].[Na+]>O>[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([C:8]2[CH:9]=[C:10]([CH:14]=[C:15]([C:17]([OH:22])([CH3:19])[CH3:18])[CH:16]=2)[C:11]([OH:13])=[O:12])=[N:6][CH:7]=1To a solution of 3-(5-chloropyridin-2-yl)-5-isopropenylbenzoic acid (0.18 g, 0.46 mmol) in water (4.6 mL) was added methanesulfonic acid (1.5 mL, 23.1 mmol). The mixture was heated to 50° C. After 18 h, the mixture was cooled to ambient temperature and sodium carbonate was added to adjust pH to 3-4. The mixture was extracted with ethyl acetate (3×). The combined organic extracts were washed with brine, dried over magnesium sulfate, filtered and concentrated. Purification by reverse phase chromatography (C-18, 100% water/acetonitrile→25% water/acetonitrile with 0.1% trifluoroacetic acid) gave the title compound (80 mg). MS 292.1 (M+1).
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