[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH2:11][CH:10]([CH2:14][NH2:15])[CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].[Cl:16][CH2:17][C:18](Cl)=[O:19].C(N(C(C)C)CC)(C)C>C(Cl)Cl.C(OCC)(=O)C>[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH2:11][CH:10]([CH2:14][NH:15][C:18](=[O:19])[CH2:17][Cl:16])[CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2]3-Aminomethyl-piperidine-1-carboxylic acid tert-butyl ester 1c (5.0 g, 23.4 mmol) in 20 mL CH2Cl2 was added dropwise to a cold (−10→0° C.) solution of chloroacetylchloride (2.8 mL, 35 mmol, 1.5 equiv) and diisopropylethylamine (6.1 mL, 35 mmol, 1.5 equiv) in 60 mL CH2Cl2 under N2. After being left overnight (−10° C.→rt), the mixture was diluted with ethyl acetate and washed briefly with water and brine, dried (Na2SO4), and concentrated to give 3-[(2-chloroacetylamino)-methyl]-piperidine-1-carboxylic acid tert-butyl ester 1d as a dark brown oil. The crude product was used without further purification.
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