[CH:1](NC(C)C)(C)C.[CH3:8][O:9][C:10]([CH:12]1[CH2:17][CH2:16][N:15]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:14][CH2:13]1)=[O:11].CI>C1COCC1>[CH3:8][O:9][C:10]([C:12]1([CH3:1])[CH2:13][CH2:14][N:15]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:16][CH2:17]1)=[O:11]137 mL Diisopropylamine in 3390 mL THF was cooled to 0° C. and 360 mL n-buthyllithium was added dropwise under nitrogen. The reaction was cooled to −78° C. and a solution of 180 mL piperidine-1,4-dicarboxylic acid 1-tert-butyl ester 4-methyl ester in 1800 mL THF was added dropwise over 1 h. The reaction was stirred at −78° C. for 2 h and then 168 mL methyliodide in 300 mL THF was added in one portion. The mixture was stirred 2 h at −78° C. and then allowed to warm to RT. The reaction was quenched with saturated aqueous sodium sulfate solution, the organig phase was separated, dried and evaporated. The residue was purified by chromatography on silica gel to give 155 g of the desired product.
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