[C:1]([O:5][C:6]([N:8]1[CH2:12][CH2:11][CH2:10][C@H:9]1[CH2:13][C:14]([OH:16])=[O:15])=[O:7])([CH3:4])([CH3:3])[CH3:2].[C:17](#N)C.C(N(CC)C(C)C)(C)C.C[Si](C=[N+]=[N-])(C)C>CO.C(OCC)(=O)C>[C:1]([O:5][C:6]([N:8]1[CH2:12][CH2:11][CH2:10][C@H:9]1[CH2:13][C:14]([O:16][CH3:17])=[O:15])=[O:7])([CH3:4])([CH3:2])[CH3:3]A solution of (S)-2-carboxymethyl-pyrrolidine-1-carboxylic acid tert-butyl ester (2.00 g) in methanol (1.32 ml)/acetonitrile (40 ml) was treated with N,N-diisopropylethylamine (1.78 ml). Trimethylsilyldiazomethane (2M, 8.73 ml) was added dropwise and the resulting mixture was stirred at room temperature, under argon for 24 h. The mixture was diluted with ethyl acetate, washed with 2M HCl, saturated aqueous sodium hydrogen carbonate, brine then dried (magnesium sulfate). The solvent was removed under reduced pressure to afford the title compound (2.10 g)
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