Sodium Hydroxide → 4-[4-(4-Carboxy-oxazol-5-yl)-phenyl]-2,2-dimethyl-piperazine-1-carboxylic acid tert-butyl ester

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Reaction Steps

To a solution of 4-[4-(4-ethoxycarbonyl-oxazol-5-yl)-phenyl]-2,2-dimethyl-piperazine-1-carboxylic acid tert-butyl ester (2.4 g, 5.6 mmol) in 20 mL THF and 20 mL methanol was added 2N aqueous sodium hydroxide solution (11.2 mL, 22.4 mmol). The mixture was stirred at room temperature for 16 hrs and organic solvent was then removed in vacuo. The remaining aqueous mixture was adjusted to pH 4˜5 by the addition of 1N aqueous hydrogen chloride. The mixture was freeze-dried to yield 3 g of 4-[4-(4-carboxy-oxazol-5-yl)-phenyl]-2,2-dimethyl-piperazine-1-carboxylic acid tert-butyl ester as an off-yellow powder, which was used in the next step directly.

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