[CH:1]([C:3]1[C:18]([O:19][CH3:20])=[CH:17][C:6]([O:7][CH2:8][CH2:9][CH2:10][CH2:11][C:12]([O:14]CC)=[O:13])=[CH:5][C:4]=1[O:21][CH3:22])=[O:2].[OH-].[Na+]>CO>[CH:1]([C:3]1[C:4]([O:21][CH3:22])=[CH:5][C:6]([O:7][CH2:8][CH2:9][CH2:10][CH2:11][C:12]([OH:14])=[O:13])=[CH:17][C:18]=1[O:19][CH3:20])=[O:2]To a solution of ethyl 5-(4-formyl-3,5-dimethoxyphenoxy)valerate (37 g, 119 mmol) in methanol (200 mL) was added 4 N sodium hydroxide (200 mL) and the mixture was stirred for 2 h. The methanol was removed in vacuo, water (100 mL) was added and the mixture was washed with ethyl acetate (100 mL) and dichloromethane (2×100 mL). The aqueous layer was acidified with 12 N hydrochloric acid until pH˜3 and extracted with ethyl acetate (2×200 mL). The combined organic layers were washed with brine (2×50 mL), dried (magnesium sulfate) and concentrated in vacuo. The obtained product was recrystallized from ethanol to give 26 g of 5-(4-formyl-3,5-dimethoxyphenoxy)valeric acid.
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