[NH2:1][C:2]1([C:15]([O:17][CH3:18])=[O:16])[CH2:7][CH2:6][N:5]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:4][CH2:3]1.N1C=CC=CC=1.[Cl:25][CH2:26][CH2:27][CH2:28][C:29](Cl)=[O:30]>C(Cl)Cl>[CH3:18][O:17][C:15]([C:2]1([NH:1][C:29](=[O:30])[CH2:28][CH2:27][CH2:26][Cl:25])[CH2:3][CH2:4][N:5]([C:8]([O:10][C:11]([CH3:12])([CH3:13])[CH3:14])=[O:9])[CH2:6][CH2:7]1)=[O:16]To a solution of methyl 4-amino-1-BOC-piperidine-4-carboxylate (2.0 g, 6.78 mmol) in DCM (15 mL) and pyridine (2.10 mL, 20.35 mmol), 4-chlorobutyryl chloride (0.84 mL, 7.5 mmol) in DCM (5 mL) was added slowly at 0° C. The reaction mixture was gradually warmed to room temperature and stirred for 16 hours. The reaction mixture was diluted with DCM (40 mL), and quenched with saturated NaHCO3 (30 mL). The organic layer was separated and the aqueous layer was extracted twice with DCM. The combined organic layers were then washed with saturated aqueous NaHCO3 and brine, dried over MgSO4, filtered and concentrated to give 4-(4-chloro-butyrylamino)-piperidine-1,4-dicarboxylic acid 1-tert-butyl ester 4-methyl ester which was used further without purification.
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