[N:1]1([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:6][CH2:5][CH:4]([C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH2:3][CH2:2]1.[Li+].[CH3:20]C([N-]C(C)C)C.CI>C1COCC1>[CH3:20][C:4]1([C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH2:3][CH2:2][N:1]([C:12]([O:14][C:15]([CH3:17])([CH3:16])[CH3:18])=[O:13])[CH2:6][CH2:5]1A solution of O1-tert-butyl O4-ethyl piperidine-1,4-dicarboxylate (1.5 g, 5.84 mmol) in THF (25 mL) was cooled to −78° C. followed by dropwise addition of LDA (1.80 M in THF, 6.5 mL, 11.68 mmol) at −78° C. The resulting mixture was stirred at −78° C. for 45 min followed by addition of methyl iodide (1.2 mL, 17.52 mmol). The temperature was slowly raised up to RT and left at RT for 6 h. The reaction was cooled to 0° C. and quenched by the dropwise addition of saturated NH4Cl solution (50 mL). The reaction was extracted with EtOAc (3×100 mL). The combined organics were washed with brine, dried (Na2SO4), filtered and concentrated in vacuo. Purification by chromatography on silica eluting with 2% EtOAc in hexane gave i (1.0 g, 65%).
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