[OH-].[K+].[CH3:3][O:4][CH2:5][O:6][C:7]1[CH:16]=[C:15]([O:17][CH2:18][O:19][CH3:20])[C:14]([CH:21]([CH3:23])[CH3:22])=[CH:13][C:8]=1[C:9]([O:11]C)=[O:10]>CO.O>[CH3:3][O:4][CH2:5][O:6][C:7]1[CH:16]=[C:15]([O:17][CH2:18][O:19][CH3:20])[C:14]([CH:21]([CH3:23])[CH3:22])=[CH:13][C:8]=1[C:9]([OH:11])=[O:10]Aqueous potassium hydroxide (50% w/v, 1.0 ml) was added to a mixture of methyl 2,4-bis-(methoxymethyloxy)-5-isopropylbenzoate (560 mg, 1.88 mmol) in methanol (12 ml) and water (4 ml) and the mixture was stirred and held at reflux for 3 hours. Upon cooling to room temperature the organic solvent was removed in vacuo and the residue diluted with water (20 ml) and acidified by the addition of 2M hydrochloric acid (10 ml). The organic material was extracted with dichloromethane (2×20 ml) and the combined organic extracts were evaporated in vacuo. The residue was triturated with a mixture of petroleum ether and diethyl ether to afford 2,4-bis-(methoxymethyloxy)-5-isopropylbenzoic acid (392 mg, 73%) as a colourless solid. 1H NMR (DMSO-d6) 12.38 (1H, br s), 7.59 (1H, s), 6.84 (1H, s), 5.31 (2H, s), 5.20 (2H, s), 3.41 (6H, s), 3.21 (1H, m), 1.18 (6H, d). MS: [M+Na]+ 307.
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