[Li+].[CH3:2]C([N-]C(C)C)C.[C:9]([O:13][C:14](=[O:20])[CH2:15][CH2:16][C:17]([OH:19])=[O:18])([CH3:12])([CH3:11])[CH3:10].CI>C1COCC1>[C:9]([O:13][C:14](=[O:20])[CH:15]([CH3:2])[CH2:16][C:17]([OH:19])=[O:18])([CH3:12])([CH3:10])[CH3:11]To a stirred solution of LDA (6.3 mmol, 2M in hexane) in THF (5 mL) at −78° C. is added a solution of succinic acid mono-tert-butyl ester (523 mg, 3 mmol) in THF (2 mL) dropwise. After the addition, the mixture is warmed to −20° C. slowly and stirred at −20° C. for 30 minutes. The solution is re-cooled to −78° C. and MeI (511 mg, 3.6 mmol) is added dropwise. The mixture is warmed to room temperature and stirred for 18 hours. The mixture is quenched with water and extracted with ethyl acetate. The organic layer is washed with water, brine, dried over MgSO4 and filtered. The solvent is removed under reduced pressure to give 2-methyl-succinic acid 1-tert-butyl ester.
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