Cl.[C:2]([CH:5]1[CH2:10][CH:9]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH2:8][CH2:7][NH:6]1)(=[O:4])[NH2:3].CCN(C(C)C)C(C)C.[C:25](Cl)(=[O:34])[O:26][CH2:27][C:28]1[CH:33]=[CH:32][CH:31]=[CH:30][CH:29]=1>ClCCl>[C:2]([CH:5]1[CH2:10][CH:9]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH2:8][CH2:7][N:6]1[C:25]([O:26][CH2:27][C:28]1[CH:33]=[CH:32][CH:31]=[CH:30][CH:29]=1)=[O:34])(=[O:4])[NH2:3]Ethyl 2-carbamoylpiperidine-4-carboxylate hydrochloride (2 g, 7.86 mmol) was slurried in dichloromethane (25 mL) and DIPEA (3.43 mL, 19.65 mmol) was added followed by benzyl carbonochloridate (1.161 mL, 8.25 mmol) dropwise. The reaction was stirred for 1 h then washed with 25 mL of 2 M HCl and water, dried over Na2SO4 and evaporated. The crude product was purified on a 100 g Biotage column with heptane/EtOAc over 4 CV followed by 100% EtOAc over 10 CV. 1-Benzyl 4-ethyl 2-carbamoylpiperidine-1,4-dicarboxylate (1.99 g, 76%) was isolated. 1H NMR (400 MHz, dmso) δ 1.16 (t, 3H), 1.57-1.69 (m, 1H), 1.81-1.92 (m, 1H), 1.95-2.07 (m, 1H), 2.21-2.32 (m, 1H), 2.58-2.67 (m, 1H), 3.29-3.45 (m, 1H), 3.69-3.77 (m, 1H), 3.92-4.06 (m, 2H), 4.34 (t, 1H), 4.99-5.08 (m, 2H), 6.95 (s, 1H), 7.25-7.38 (m, 6H). MS m/z 335 (M+H)+
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