[C:1]([O:5][C:6]([N:8]1[CH2:12][CH2:11][CH2:10][C@H:9]1[C:13](=[O:17])[CH:14]=[N+]=[N-])=[O:7])([CH3:4])([CH3:3])[CH3:2].[C:18]([OH:21])(=[O:20])[CH3:19]>>[C:1]([O:5][C:6]([N:8]1[CH2:12][CH2:11][CH2:10][C@H:9]1[C:13](=[O:17])[CH2:14][O:21][C:18](=[O:20])[CH3:19])=[O:7])([CH3:4])([CH3:3])[CH3:2]A solution of 1.00 g of the diazoketone product of Example 1 in acetic acid (15 ml) was refluxed for 10 minutes. The mixture was cooled, filtered and the acetic acid removed under reduced pressure to give (S)-1-t-butoxycarbonyl-2-(2-acetoxy-1-oxoethyl)-pyrrolidine, which was purified by chromatography on silica gel eluting with 3:1-hexane; ethyl acetate (Rf =0.3).
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