C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.[CH3:20][O:21][C:22]([C@@H:24]1[CH2:28][C@@H:27](O)[CH2:26][N:25]1[C:30]([O:32][C:33]([CH3:36])([CH3:35])[CH3:34])=[O:31])=[O:23].C(Br)(Br)(Br)[Br:38].C(O)C>ClCCl>[CH3:20][O:21][C:22]([C@@H:24]1[CH2:28][C@H:27]([Br:38])[CH2:26][N:25]1[C:30]([O:32][C:33]([CH3:36])([CH3:35])[CH3:34])=[O:31])=[O:23]Add triphenylphosphine (0.88 mol, 231 g) in portions to a solution of (2S,4R)-4-hydroxy-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-methyl ester (0.58 mol, 144 g) and CBr4 (0.88 mol, 292 g) in dry dichloromethane (1.44 L) at 0° C. Upon complete addition, warm the reaction mixture to room temperature and stir for 4 h. Add ethanol (1.44 L) and stir for an additional 2 h. Add diethyl ether (1.44 L) to the reaction mixture, filter the precipitated triphenylphosphine oxide, and concentrate the filtrate under reduced pressure. Purify by column chromatography using 5% ethyl acetate in hexanes as eluent to obtain the title compound (155 g, 85%) as a thick oil. ES-MS m/z 308 [M+1]+.
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