[OH-].[Li+].C([O:5][C:6]([C:8]1[C:12]([CH2:13][CH2:14][CH2:15][S:16]([CH3:19])(=[O:18])=[O:17])=[C:11]([CH:20]=[O:21])[NH:10][C:9]=1[CH3:22])=[O:7])C.Cl>CO.O>[CH:20]([C:11]1[NH:10][C:9]([CH3:22])=[C:8]([C:6]([OH:7])=[O:5])[C:12]=1[CH2:13][CH2:14][CH2:15][S:16]([CH3:19])(=[O:17])=[O:18])=[O:21]Lithium hydroxide (179.6 mg, 7.5 mmol) was added to a suspension of 5-formyl 4-(3-methanesulfonyl-propyl)2-methyl-1H-pyrrole-3-carboxylic acid ethyl ester (450 mg, 1.5 mmol) in methanol (6 mL) and water (6 mL). The mixture was heated under nitrogen in a 65° C. oil bath for 20 hours. The cooled reaction was adjusted to pH 2 using 1N HCl, the resulted precipitate was collected by vacuum filtration, washed with water and dried to give 356 mg (87%) of 5-formyl-4-(3-methanesulfonyl-propyl)-2-methyl-1H-pyrrole-3-carboxylic acid.
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