Cl.[CH3:2][O:3][C:4](=[O:11])[C@@H:5]1[CH2:9][C@@H:8]([OH:10])[CH2:7][NH:6]1.C(N(CC)CC)C.CC1C=C(C)N=C(S[C:28]([O:30][CH2:31][C:32]2[CH:37]=[CH:36][C:35]([N+:38]([O-:40])=[O:39])=[CH:34][CH:33]=2)=[O:29])N=1>C(Cl)(Cl)Cl>[CH3:2][O:3][C:4](=[O:11])[C@@H:5]1[CH2:9][C@@H:8]([OH:10])[CH2:7][N:6]1[C:28]([O:30][CH2:31][C:32]1[CH:33]=[CH:34][C:35]([N+:38]([O-:40])=[O:39])=[CH:36][CH:37]=1)=[O:29]To a clear solution of L-hydroxyproline methyl ester hydrochloride (27.2 g, 0.15 mol) and triethylamine (50 ml, 0.36 mol) in chloroform (500 ml) was added 4,6-dimethyl-2-(4-nitrobenzyloxycarbonylthio)pyrimidine (40.7 g, 0.13 mol) and then the resulting solution was stirred at room temperature for 12 hours, sequentially washed with H2O (200 ml), 0.5N NaOH (400 ml) and brine (200 ml) and dried (MgSO4). Concentration followed by silicagel column chromatography (Wakogel® C-300, ethyl acetate) afforded (2S, 4R)-4-hydroxy-N-(4-nitrobenzyloxycarbonyl)proline methyl ester (34.5 g, 70.9% yield) as an oil.
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