General procedure for the synthesis of ethyl 1-(tert-butoxycarbonyl)-4-aminomethylpiperidine-4-carboxylate from 1-tert-butyl 4-ethyl 4-cyanopiperidine-1,4-dicarboxylate: At 21°C, platinum(IV) oxide (0.724 g, 3.19 mmol) and 1-tert-butyl 4-ethyl 4-cyanopiperidine-1,4-dicarboxylate (9 g, 31.88 mmol) were ) were dissolved in acetic acid (100 ml) and stirred at 25°C for 1 day under hydrogen atmosphere (5 bar). After completion of the reaction, the crude product was filtered through diatomaceous earth and the filtrate was purified by ion exchange chromatography using SCX column. The target product ethyl 1-(tert-butoxycarbonyl)-4-aminomethylpiperidine-4-carboxylate was eluted from the column using 7 M NH3/MeOH solution, and the pure grades were collected and evaporated to dryness to give a colorless oily product (7.59 g, 83% yield). The structure of the product was confirmed by 1H NMR (400.13 MHz, CDCl3): δ 1.27-1.28 (3H, m), 1.30-1.37 (2H, m), 1.41 (2H, s), 1.45 (9H, s), 2.10 (2H, d), 2.78 (2H, s), 2.91-2.97 (2H, m), 3.89 (2H , s), 4.21 (2H, q).
