1) At room temperature, 3-hydroxypiperidine (5.00 g) was dissolved in methanol (50 mL), to which a methanol (50 mL) solution of triethylamine (15.2 mL) and di-tert-butyl dicarbonate (11.9 g) were sequentially added. The reaction mixture was stirred for 15 hours. After completion of the reaction, the solvent was removed by evaporation under reduced pressure and the resulting residue was purified by silica gel column chromatography (eluent: ethyl acetate-chloroform) to afford tert-butyl 3-hydroxypiperidine-1-carboxylate as a white solid (9.86 g, 99% yield). The product was characterized by 1H-NMR (400 MHz, CDCl3) and EI-MS: 1H-NMR δ: 1.36-1.55 (2H, m), 1.45 (9H, s), 1.71-1.78 (1H, m), 1.88 (1H, m), 3.02-3.13 (2H, m), 3.52 (1H, m), 3.72-3.76 (2H, m); EI-MS m/z: 201 (M+).
