Reaction Steps
To a 100 mL round bottom flask were added the TFA salt of (R)-tert-butyl 3-((S)-4-amino-1-(3-chlorophenyl)-1-hydroxybutyl)piperidine-1-carboxylate (0.8164 g, 1.64 mmol, 1.0 equiv), DMAP (0.542 g), CH2Cl2 (40 mL) and triethylamine (6 mL). The mixture was cooled in an ice bath and a solution of methyl chloroformate (0.550 g, 5.82 mmol, 3.5 equiv) in CH2Cl2 (10 mL) was added. The reaction mixture was allowed to slowly warm to rt and stirred overnight. After the solvents were removed in vacuo, the residue was purified by reversed-phase HPLC (Phenomenex® Luna 5μ C18(2) 100 A, 250×21.20 mm, 5 micron, 70%→90% CH3CN/H2O, 0.1% CF3COOH over 8 min and then 90% CH3CN/H2O, 0.1% CF3COOH over 1.5 min, flow rate 25 mL/min) to give 0.5020 g (69%) of (R)-tert-butyl 3-((S)-4-(methoxycarbonyl-amino)-1′-(3-chlorophenyl)1-hydroxybutyl)piperidine-1-carboxylate. LC-MS (3 min) tR=1.91 min, m/z 463 (MNa+), 441 (MH+), 343 341; 1H NMR (400 MHz, CDCl3) δ 7.37-7.36 (m, 1H), 7.28-7.17 (m, 3H), 4.90 (br s, 2H), 4.37 (d, J=12.0 Hz, 1H), 3.97 (d, J=12.3 Hz, 1H), 3.64 (s, 3H), 3.16-3.04 (m, 2H), 2.58-2.49 (m, 2H), 1.98-1.86 (m, 2H), 1.76-1.70 (m, 1H), 1.61-1.56 (m, 1H), 1.45 (s, 9H), 1.48-1.13 (m, 5H); 13C NMR (100 MHz, CDCl3) δ 157.60, 155.31, 146.51, 134.31, 129.36, 126.72, 125.96, 123.76, 80.08, 77.65, 52.21, 46.45, 44.91, 44.56, 40.91, 35.97, 28.42, 25.33, 25.25, 24.34.
