C(OC(=O)N=NC(OC(C)(C)C)=O)(C)(C)C.[Si:17]([O:34][C@H:35]([CH2:45][CH2:46]O)[C:36]([NH:38][C:39]1[CH:44]=[CH:43][CH:42]=[CH:41][CH:40]=1)=[O:37])([C:30]([CH3:33])([CH3:32])[CH3:31])([C:24]1[CH:29]=[CH:28][CH:27]=[CH:26][CH:25]=1)[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1>C1COCC1>[Si:17]([O:34][C@@H:35]1[CH2:45][CH2:46][N:38]([C:39]2[CH:40]=[CH:41][CH:42]=[CH:43][CH:44]=2)[C:36]1=[O:37])([C:30]([CH3:33])([CH3:32])[CH3:31])([C:24]1[CH:25]=[CH:26][CH:27]=[CH:28][CH:29]=1)[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1To a solution of tert-butyl-N-tert-butoxycarbonyliminocarbamate (2.44 g, 10.61 mmol) in THF (17.25 mL) at 0° C. was added n-tributylphosphine (2.15 g, 2.64 mL, 10.61 mmol) dropwise, the cooling bath was removed and the reaction mixture stirred at RT for 20 min. The reaction mixture was then cooled to 0° C. and a solution of (R)-2-(tert-butyldiphenylsilyloxy)-4-hydroxy-N-phenylbutanamide (1.15 g, 2.65 mmol) in THF (17.25 mL) was added slowly, the cooling bath removed and the reaction mixture stirred at RT for 45 min. The reaction mixture was poured into water and extracted with EtOAc (3×). The combined organics were washed with water (2×), brine, dried over MgSO4 and evaporated to dryness. Purification by silica gel chromatography (1-10% EtOAc in hexane) afforded (R)-3-(tert-butyldiphenylsilyloxy)-1-phenylpyrrolidin-2-one (1.1 g, 96%) as an oil. 1H-NMR (400 MHz, DMSO-d6) δ 7.81 (dd, J=1.5, 7.7 Hz, 2H), 7.72-7.66 (m, 4H), 7.51-7.36 (m, 8H), 7.15 (m, 1H), 4.51 (dd, J=8.1, 9.2 Hz, 1H), 3.72-3.59 (m, 2H), 2.26-2.21 (m, 1H), 2.03-1.98 (m, 1H) and 1.06 (s, 9H) ppm. LC/MS (10%-99% CH3CN (0.035% TFA)/H2O (0.05% TFA)), m/z: M+1 obs=416.7; tR=2.40 min.
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