Step 1: Preparation of piperazine-2-carboxylic acid: pyrazine-2-carboxylic acid (102.7 g, 0.827 mol) was dissolved in water (600 mL), sodium hydroxide (66 g, 1.65 mol) and 20% palladium/carbon catalyst (5.0 g) were added. The hydrogenation reaction was carried out under hydrogen atmosphere for 15 hours. Upon completion of the reaction, the catalyst was removed by filtration and the filtrate was concentrated. Concentrated hydrochloric acid was added to the concentrate and a white precipitate precipitated. The solid was washed with cold water, collected by filtration and dried under vacuum to give 137.2 g of piperazine-2-carboxylic acid hydrochloride (99.6% yield). Mass spectrum (MS): m/z 131 (corresponding to C5H10N2O2, [M+H]+).
[1] Tetrahedron Letters, 1989, vol. 30, # 39, p. 5193 - 5196
[2] Bioorganic and Medicinal Chemistry Letters, 1999, vol. 9, # 8, p. 1121 - 1126
[3] Patent: US6251919, 2001, B1
