CS(C)=O.C(Cl)(=O)C(Cl)=O.[CH2:11]([O:18][C:19]([N:21]1[C@@H:25]([CH2:26][CH2:27][OH:28])[CH2:24][O:23][C:22]1([CH3:30])[CH3:29])=[O:20])[C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=1.CCN(CC)CC>C(Cl)Cl>[CH2:11]([O:18][C:19]([N:21]1[C@@H:25]([CH2:26][CH:27]=[O:28])[CH2:24][O:23][C:22]1([CH3:30])[CH3:29])=[O:20])[C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=1A solution of dimethyl sulfoxide (6.39 g, 81.8 mmol) in DCM (25 mL) was added at −70° C. to a solution of oxalyl chloride (5.59 g, 44.1 mmol) in DCM (90 mL), then after 15 min a solution of (S)-4-(2-hydroxy-ethyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid benzyl ester (8.79 g, 31.5 mmol) in DCM (45 mL) was added dropwise. After 60 min Et3N (15.9 g, 157 mmol) was added, then after 20 min the cooling bath was removed and the reaction mixture was stirred for 2 h. The reaction mixture was poured onto water and extracted five times with DCM. The combined organic phases were dried (MgSO4), filtered, and evaporated. Chromatography (SiO2; heptane/EtOAc 1:1) produced the title compound (8.52 g, 98%) as light yellow liquid.
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