Reaction Steps
To a stirred solution of (4S)-4-benzyl-1,3-oxazolidin-2-one (9.31 g, 52.56 mmol) in anhydrous THF (150 mL) is added n-butyllithium (2.5 M in hexanes, 21.05 mL, 52.56 mmol) over 25 min at −78° C. Then a solution of tetrahydro-pyran-2-carbonyl chloride (7.1 g, 47.78 mmol) in anhydrous THF (12 mL) is added dropwise. The reaction is stirred at −70° C. for 0.5 h, then allowed to warm to room temperature and stirred for 2 h. Saturated aqueous NH4Cl solution (20 mL) is added and the reaction mixture is concentrated under reduced pressure. The residue is partitioned between ethyl acetate (200 mL) and water (50 mL). The organic layer is separated, washed with saturated aqueous NaHCO3 solution (2×50 mL), brine (50 mL), dried (MgSO4) and filtered. The filtrate is concentrated under reduced pressure and the mixture of diastereoisomers is separated by multiple column chromatography (silica, eluent: toluene, 0-20% TBME) to afford 3.81 g of (4S)-4-benzyl-3-{[(2S)-oxan-2-yl]carbonyl}-1,3-oxazolidin-2-one (78%, yield: 22%; ES-MS: m/z 290 [M+H]; 1H NMR (500 MHz, CHLOROFORM-d) δ ppm 1.46-1.72 (4H, m), 1.81-1.90 (2H, m), 2.71 (1H, dd, J=13.43, 9.77 Hz), 3.30 (1H, dd, J=13.43, 3.05 Hz), 3.54 (1H, td, J=11.52, 2.14 Hz), 4.06-4.19 (3H, m), 4.60 (1H, m, J=9.88, 6.75, 3.28, 3.28 Hz), 4.97 (1H, dd, J=10.60, 1.91 Hz), 7.12-7.30 (5H, m)) and 1.65 g of (4S)-4-benzyl-3-{[(2R)-oxan-2-yl]carbonyl}-1,3-oxazolidin-2-one (93%, yield: 11%; ES-MS: m/z 290 [M+H]; 1H NMR (500 MHz, CHLOROFORM-d) δ ppm 1.54-1.80 (4H, m), 1.90-2.06 (2H, m), 2.83 (1H, dd, J=13.58, 9.16 Hz), 3.24 (1H, dd, J=13.50, 3.28 Hz), 3.53-3.61 (1H, m), 4.11-4.17 (1H, m), 4.19-4.24 (1H, m), 4.25-4.31 (1H, m), 4.71-4.78 (1H, m), 4.96 (1H, dd, J=10.60, 2.06 Hz), 7.16-7.37 (5H, m))
