[C:1]([O:5][C:6]([N:8]1[C@@H:12]([CH2:13][CH:14]=[O:15])[CH2:11][O:10][C:9]1([CH3:17])[CH3:16])=[O:7])([CH3:4])([CH3:3])[CH3:2].[CH3:18][Mg]Br>O1CCCC1.C(OCC)C>[C:1]([O:5][C:6]([N:8]1[C@@H:12]([CH2:13][C@@H:14]([OH:15])[CH3:18])[CH2:11][O:10][C:9]1([CH3:17])[CH3:16])=[O:7])([CH3:4])([CH3:3])[CH3:2]To a cooled solution of (S)-2,2-dimethyl-4-(2-oxo-ethyl)-oxazolidine-3-carboxylic acid t-butyl ester (2.05 g, 8.43 mmol) in dry tetrahydrofuran (25 mL) was added 1.4M methyl magnesium bromide in diethyl ether (6.02 mL) at −78° C. The mixture was stirred at −78° C. for 30 min and then warmed to −5° C. The mixture was extracted with diethyl ether and ammonium chloride solution. The organic layer was dried and concentrated. The crude mixture was purified by ISCO flash chromatography (0 to 60% ethyl acetate/hexanes) to give two fractions. The first fraction afforded (S)-4-((S)-2-hydroxy-propyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid t-butyl ester as a colorless oil (870 mg): 1H NMR (300 MHz, CDCl3) δ ppm 1.20 (d, J=6.0 Hz, 3H), 1.42-1.60 (m, 1H), 1.50 (s, 12H), 1.55 (s, 3H), 1.68-1.88 (m, 1H), 3.66 (d, J=8.8 Hz, 1H), 3.69-3.80 (m, 1H), 3.94-4.08 (m, 1H), 4.17-4.30 (m, 1H), 4.62 (br. s., 1H); The second fraction afforded (S)-4-((R)-2-hydroxy-propyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid t-butyl ester as a white solid (740 mg): 1H NMR (300 MHz, CDCl3) δ ppm 1.22 (d, J=6.0 Hz, 3H), 1.49 (s, 12H), 1.58 (br. s., 3H), 1.75-1.90 (m, 2H), 2.56 (br. s., 1H), 3.75-3.93 (m, 2H), 3.95-4.05 (m, 1H), 4.03-4.20 (m, 1H).
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