Piperazine-2-carboxylic acid dihydrochloride can be used as a pharmaceutical synthesis intermediate. The reaction proceeds as follows: Piperazine-2-carboxylic acid dihydrochloride (2 g, 9.8 mmol) and (Boc)₂O (8.6 g, 39.4 mmol) are dissolved in THF (40 mL) and water (40 mL). Sodium bicarbonate (8.31 g, 79.8 mmol) is added. The reaction mixture is magnetically stirred at room temperature for 4 hours, then ethyl acetate is added. The mixture is separated using a separatory funnel. The separated organic phase is washed with saturated brine, dried over anhydrous sodium sulfate, concentrated under reduced pressure, and then separated by silica gel column chromatography. 2.5 g of 1,4-di-tert-butoxycarbonylpiperazine-2-carboxylic acid (13-2) was obtained after purification, with a yield of 78%. LC-MS (ESI): m/z (M+1) 331.2.
