[CH3:1][O:2][C:3]1[CH:4]=[C:5]([CH:10]=[CH:11][C:12]=1[C:13]1[C:17]([CH3:18])=[CH:16][S:15][CH:14]=1)[C:6]([O:8]C)=[O:7].[OH-].[Na+]>CCO.O>[CH3:1][O:2][C:3]1[CH:4]=[C:5]([CH:10]=[CH:11][C:12]=1[C:13]1[C:17]([CH3:18])=[CH:16][S:15][CH:14]=1)[C:6]([OH:8])=[O:7]To a solution of methyl 3-methoxy-4-(4-methyl-3-thienyl)benzoate obtained in step 1 (2.30 g; 8.77 mmol) in EtOH (70 mL), was added at RT an aqueous solution of sodium hydroxide (5 M; 5.26 mL; 26.31 mmol). The reaction mixture was stirred at 60° C. for one hour. The reaction mixture was concentrated under vacuum to give a brown solid. It was taken up in water and the aqueous phase was washed twice with EtOAc. Aqueous phase was acidified with concentrated HCl (2 mL) to pH 2. Then it was concentrated under vacuum until a precipitate was formed (⅓ of volume). The suspension was filtered off and dried under vacuum, affording the title compound as a brown solid (1.81 g, 83% for 2 steps). 1H NMR: (DMSO-d5) δ 13.05 (s, 1H), 7.62-7.59 (m, 2H), 7.40-7.39 (d, J=3.23 Hz, 1H), 7.32-7.29 (d, J=7.48 Hz, 1H), 7.25-7.23 (m, 1H), 3.82 (s, 3H), 2.99 (s, 3H). LC/MS (Method A): 248.8 (M+H)+; 246.9 (M−H)−. HPLC (Method A) Rt 3.99 min (Purity: 97.4%).
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