[CH2:1]([C@H:8]1[CH2:12][O:11][C:10](=[O:13])[NH:9]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[CH2:14]([Li])[CH2:15][CH2:16]C.[O:19]1[CH2:23][CH2:22]NC1=O>C1COCC1>[O:19]=[C:23]([N:9]1[C@@H:8]([CH2:1][C:2]2[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=2)[CH2:12][O:11][C:10]1=[O:13])[CH2:22][CH2:16][CH:15]=[CH2:14]In a separate flask, a solution of 17.7 g (100 mmol) of (S)-4-benzyl-2-oxazolidinone in 120 mL of THF was cooled to -78° C. whereupon 63.1 mL (101 mmol) of 1.6 M n-butyllithium in hexanes was added slowly. This solution was stirred for 10 min at -78° C. The flask containing the mixed anhydride was cooled to -78° C. and the lithiated oxazolidinone was cannulated into the mixed anhydride. After stirring at -78° C. for 15 min, the reaction mixture was warmed to 0° C. and stirred for 30 min. After quenching with water, the layers were separated and the aqueous layer was washed with ether. The combined organic layers were washed with brine, dried, filtered and concentrated. The residue was purified by filtration through a pad of silica gel (3:1 hexanes: ethyl acetate) to give 25.88 g (100%) of the title compound as a colorless oil. 1H NMR (CDCl3) δ 2.42 (m,2H); 2.72 (dd, J=9.7, 13 Hz, 1H); 3.03 (m, 2H; 3.29 (dd, J=13, 4 Hz, 1H); 4.15 (m, 2H); 4.65 (m,1H); 5.07 (m,2H); 5.86 (m, 1H); 7.12-7.37 (m, 5H). 13C NMR (CDCl3) δ 28.17, 34.78, 37.9, 55.14, 66.2, 115.7, 127.3, 128.9, 129.4, 135.2, 136.7, 153.4, 172.5. IR (film) 1790, 1708, 1390 cm-1 [α]24D+64.22° (c=0.83, CHCl3) Anal: Calcd. for C15H17O3N: C, 69.48; H, 6.61; N, 5.40. Found: C, 69.20; H, 6.65; N, 5.33.
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