CCN(C(C)C)C(C)C.[C:10]([O:14][C:15]([N:17]1[CH2:22][CH2:21][CH:20]([C:23]([O:25][CH2:26][CH3:27])=[O:24])[CH2:19][CH2:18]1)=[O:16])([CH3:13])([CH3:12])[CH3:11].I[CH2:29][CH:30]([CH3:32])[CH3:31]>C1COCC1.CCCCCC>[CH2:26]([O:25][C:23]([C:20]1([CH2:29][CH:30]([CH3:32])[CH3:31])[CH2:21][CH2:22][N:17]([C:15]([O:14][C:10]([CH3:13])([CH3:12])[CH3:11])=[O:16])[CH2:18][CH2:19]1)=[O:24])[CH3:27]4.7 g (47 mmol) DIPEA in THF at −5° C. was treated slowly with 29.1 mL (47 mmol) n-Buli (1.6N in hexane) and stirred for 30 min at −5° C. and subsequently cooled to −75° C. and stirred for 2 h. A solution of 10 g (39 mmol) ethyl 1-tert-butoxycarbonylpiperidine-4-carboxylate (commercially available) in THF was added and the mixture was stirred for 2 h at −75° C. 8.51 g (47 mmol) 1-iodo-2-methylpropane was added and the mixture was allowed to stir to room temperature over night. The mixture was quenched at 0° C. with citric acid 10% aq. and extracted with ethyl acetate. The combined organic layers were washed with NaCl aq. sat., dried with Na2SO4, filtered and evaporated. The residue was purified by column chromatography on silica eluting with a gradient formed heptane and t-butyl-methylether. The combined product fractions were evaporated to yield 10.2 g (84%) of the title compound as light yellow oil. MS (m/e): 331.2 (M+NH4+).
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