N(C(OCC)=O)=NC(OCC)=O.[OH:13][C@@H:14]1[CH2:18][CH2:17][N:16]([C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[CH2:15]1.O[N:27]1[C:35](=[O:36])[C:34]2[C:29](=[CH:30][CH:31]=[CH:32][CH:33]=2)[C:28]1=[O:37].C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1>O1CCCC1>[O:37]=[C:28]1[C:29]2[C:34](=[CH:33][CH:32]=[CH:31][CH:30]=2)[C:35](=[O:36])[N:27]1[O:13][C@H:14]1[CH2:18][CH2:17][N:16]([C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[CH2:15]1Diethyl azodicarboxylate (17.4 g, 100 mmol) was added to a solution of (R)-tert-butyl 3-hydroxypyrrolidin-1-carboxylate (9.40 g, 50.0 mmol), 2-hydroxyisoindoline-1,3-dione (8.16 g, 50.0 mmol) and triphenylphosphine (26.2 g, 100 mmol) in tetrahydrofuran (100 ml) at 0° C. The reaction mixture was stirred at room temperature for 17 hours and concentrated in vacuo. The residue was purified by column chromatography (ethyl acetate/petroleum ether: 5/95 to 12.5/87.5) to give (S)-tert-butyl 3-(1,3-dioxoisoindoline-2-yloxy)pyrrolidin-1-carboxylate (6.74 g, 41%) as a white solid: LCMS: 277 [M−55]+.
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