General procedure for the synthesis of tert-butyl (S)-2-piperidone-3-carbamate from (S)-5-amino-2-((tert-butoxycarbonyl)amino)pentanoic acid: 64 g (2.75 mmol) of BOC-L-ORN-OH was dissolved in 275 mL of DMF at 0 °C. To this solution 1.22 g (2.75 mmol) of BOP reagent and 1.16 g (20.0 mmol) of sodium bicarbonate were added. The reaction mixture was stirred at room temperature for 12 hours. Upon completion of the reaction, the mixture was concentrated under reduced pressure to about 5 mL. The concentrated mixture was diluted with 100 mL of water and saturated sodium bicarbonate solution (1:1) and subsequently extracted with three 100 mL portions of ethyl acetate (EtOAc). The organic phases were combined, washed sequentially with 300 mL of water and 300 mL of brine, dried over anhydrous sodium sulfate (Na2SO4), filtered, and concentrated under reduced pressure to afford the target product (S)-tert-butyl (S)-piperidin-2-one-3-carbamate (133) as a colorless solid in 0.37 g (62%) yield. The product was analyzed by silica gel thin layer chromatography (TLC) with an Rf value of 0.55 (unfolding agent: dichloromethane-methanol = 10:1). Nuclear magnetic resonance hydrogen spectra (1H NMR, CDCl3) showed δ 1.32 (s, 9H), 1.45-1.64 (m, 1H), 1.65-1.84 (m, 2H), 2.10-2.30 (m, 1H), 3.15-3.25 (m, 2H), 3.79-4.05 (m, 1H), 5.62 (br s, 1H) and 6.99 (br s, 1H). Nuclear magnetic resonance carbon spectra (13C NMR, CDCl3) showed δ 27.7, 28.2, 36.56, 36.61, 41.5, 51.0, 79.5, 156.0 and 172.3.
