[CH2:1]([O:4][C:5]([N:7]1[CH2:11][CH2:10][CH2:9][C@H:8]1[C:12]([OH:14])=[O:13])=[O:6])[CH:2]=[CH2:3].[C:15](=O)([O-])[O-].[K+].[K+].CI.C(OCC)(=O)C>CN(C)C=O.O>[CH2:1]([O:4][C:5]([N:7]1[CH2:11][CH2:10][CH2:9][C@H:8]1[C:12]([O:14][CH3:15])=[O:13])=[O:6])[CH:2]=[CH2:3]
To a solution of (2S)-1-allyloxycarbonyl-2-carboxypyrrolidine (72.4 g) in N,N-dimethylformamide (250 ml) were added potassium carbonate (57.6 g) and methyl iodide (43.2 ml) at ° C. with stirring. The resulting mixture was allowed to warm to ambient temperature and stirring was continued for additional 1 hour. The reaction mixture was taken up into a mixture of ethyl acetate (1.2 l) and water (0.6 l). The organic layer was separated, washed in turn with water (1l×3), brine (1l), dried over magnesium sulfate, and evaporated to give (2S)-1-allyloxycarbonyl-2-methoxycarbonylpyrrolidine (66.21 g).
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