[OH:1][C@@H:2]1[CH2:6][CH2:5][N:4]([CH:7]2[CH2:12][CH2:11][N:10]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:9][CH2:8]2)[C:3]1=[O:20].C(N(CC)CC)C.[CH3:28][S:29](Cl)(=[O:31])=[O:30]>C1COCC1>[CH3:28][S:29]([O:1][C@@H:2]1[CH2:6][CH2:5][N:4]([CH:7]2[CH2:8][CH2:9][N:10]([C:13]([O:15][C:16]([CH3:17])([CH3:19])[CH3:18])=[O:14])[CH2:11][CH2:12]2)[C:3]1=[O:20])(=[O:31])=[O:30](R)-tert-Butyl 4-(3-hydroxy-2-oxopyrrolidin-1-yl)piperidine-1-carboxylate (20.5 g, 72.1 mmol) was dissolved in THF (500 mL) and triethylamine (20.1 mL, 144 mmol) and methanesulfonyl chloride (6.74 mL, 86.5 mmol) were added to the reaction and stirred at ambient temperature for 1 hour. The reaction was partitioned between saturated aqueous NaHCO3 and EtOAc, dried over Na2SO4, filtered and concentrated. The residue was purified over silica gel to afford (R)-tert-butyl 4-(3-(methylsulfonyloxy)-2-oxopyrrolidin-1-yl)piperidine-1-carboxylate (Preparation D; 25.5 g, 70.4 mmol, 98% yield) as a white solid. 1H NMR CDCl3 5.2 ppm (t, 1H), 4.3 ppm (m, 2H), 4.1 ppm (m, 1H), 3.4 ppm (m, 1H), 3.3 ppm (m, 1H), 3.3 ppm (s, 3H), 2.8 ppm (m, 2H), 2.6 ppm (m, 1H), 2.3 ppm (m, 1H), 1.7 ppm (m, 2H, 1.6 ppm (m, 2H), 1.5 ppm (s, 9H).
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