C([C@H]1COC(=O)N1[C:14](=[O:25])[C@H:15]([C:17]1[CH:22]=[CH:21][C:20]([O:23][CH3:24])=[CH:19][CH:18]=1)[CH3:16])C1C=CC=CC=1.[O-:26]O.[Li+].O[Li].O.OO>C1COCC1.O.C(OCC)(=O)C>[CH3:24][O:23][C:20]1[CH:19]=[CH:18][C:17]([C@H:15]([CH3:16])[C:14]([OH:25])=[O:26])=[CH:22][CH:21]=1To a mechanically stirred solution of the above amide (27) (56.2 g) in THF (750 mL) and H2O (250 mL) at 0° C. was added a solution of lithium hydroperoxide prepared by adding a solution of LiOH.H2O (10.4 g) in H2O (250 mL) to 30% H2O2 (84 mL). After stirring for 1 h at 0° C. the excess peroxide was destroyed by the slow addition of a solution of Na2SO3 (103 g) in H2O (500 mL) (exothermic!). After removing most of the THF by evaporation the remaining solution was washed with CH2Cl2 twice to remove recoverable (S)-4-benzyl-2-oxazolidinone, acidified to pH ~2 with 3N HCl and extracted twice with ethyl acetate to isolate the product. The ethyl acetate phases were combined, washed with saturated NaCl, dried over MgSO4 and evaporated to give TLC pure product, (28) (29.87 g, 100%). TLC Rf 0.49 (95:4:1 CHCl3 :MeOH:HOAc) Rf 0.33 streaks (98:2 CHCl3 :MeOH); 1H NMR (CDCl3)δ1.5(3H, d, J=7 HZ), 2.25 (2H, br s), 2.78 (3H, s), 4.08 (1H, q), 7.15 (4H, q).
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