Hydrochloric Acid → 3-[4-(5-Bromo-3,3-dimethyl-2-oxo-2,3-dihydroindol-1-ylmethoxy)phenyl]hex-4-ynoic acid

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730 mg of methyl 3-[4-(5-bromo-3,3-dimethyl-2-oxo-2,3-dihydroindol-1-ylmethoxy)phenyl]-hex-4-ynoate were dissolved in a mixture of THF/MeOH/2N NaOH=1:1:1 (5 ml of each) and stirred at room temperature. After 1 hour, the mixture was acidified to pH 1 by addition of 2N HCl. 50 ml of water were added, the mixture was extracted three times with 50 ml each time of ethyl acetate. The combined organic phases were dried over MgSO4, then concentrated under reduced pressure and purified on silica gel with the n-heptane/ethyl acetate solvent mixture as a linear gradient of 100% n-heptane=>100% ethyl acetate. This gave 620 mg of 3-[4-(5-bromo-3,3-dimethyl-2-oxo-2,3-dihydroindol-1-ylmethoxy)phenyl]-hex-4-ynoic acid.

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