Step 3: 10% Pd-C (0.2 equiv) was added to a stirred methanol solution of 0.1 M methyl 1-Cbz-4-Boc-2-piperazinecarboxylate (A2) and the mixture was stirred for 3 hours at room temperature under hydrogen atmosphere. After completion of the reaction, the mixture was filtered, the filter cake was washed with methanol and the filtrate was evaporated under reduced pressure to give methyl 1-BOC-3-piperazinecarboxylate (A3) in 95% yield. The product was characterized as follows: 1H NMR (400 MHz, CDCl3, 300 K) δ 4.02 (1H, m), 3.74 (3H, s), 3.70 (1H, m), 3.43 (1H, m), 3.20 (1H, m), 3.04 (2H, m), 2.75 (1H, m), 2.14 (1H, m), 1.47 (9H, s). s).MS (ES+) C11H20N2O4 theoretical value 244, measured value: 267 (M + Na)+.
