[CH3:1][C:2]1([CH2:7][CH2:8][CH2:9][CH:10]([CH2:19][CH:20]=C)[C:11]([N:13]2[CH2:17][CH2:16][O:15][C:14]2=[O:18])=[O:12])[O:6][CH2:5][CH2:4][O:3]1.[O:22]=[O+][O-].C1C=CC(P(C2C=CC=CC=2)C2C=CC=CC=2)=CC=1>C(Cl)Cl>[CH3:1][C:2]1([CH2:7][CH2:8][CH2:9][CH:10]([C:11]([N:13]2[CH2:17][CH2:16][O:15][C:14]2=[O:18])=[O:12])[CH2:19][CH:20]=[O:22])[O:3][CH2:4][CH2:5][O:6]1To a stirred solution of 2-4 (4.0 g, 13.5 mmol), sudan III (10 mg) and CH2Cl2 (350 mL) at -78° C. under argon was bubbled ozone until red solution changed to yellow-orange. The solution was purged with argon for 30 minutes. PPh3 (5.28 g, 20.3 mmol) was added followed by the removal of the cooling bath. After 3.0 h, the reaction was concentrated. Flash chromatography (silica, 20%-50% EtOAc/hexanes) gave 2-5 as a yellow oil.
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