Hydrochloric Acid → 3-Carboxymethyl-6-benzyl-2,5-diketopiperazine

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Reaction Steps

In 1,000 l of a 50% aqueous methanol solution was suspended 55 g of the 5-benzyl-3,6-dioxo-2-piperazine acetic acid methyl ester obtained in Example 1, and 42 g of a 20% aqueous sodium hydroxide solution was added to the suspension at room temperature under stirring. Then, the hydrolysis was conducted at room temperature for two hours to form an aqueous solution. Thereafter, conc. hydrochloric acid was added dropwise to the aqueous solution, which had been removed with methanol under reduced pressure by distillation, to adjust its pH at 1. The resulting mixture was stirred at room temperature for one hour and the crystal thereby deposited was filtered, washed with water and dried to obtain 5-benzyl-3,6-dioxo-2-piperazine acetic acid.

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