[CH3:1][C:2]([NH:10][C:11](=[O:20])[O:12][CH2:13][C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)([CH3:9])[C:3](=[O:8])[NH:4][CH2:5][CH:6]=O.C1C=CC(P(C2C=CC=CC=2)C2C=CC=CC=2)=CC=1.II.CCN(CC)CC>C(Cl)Cl.O>[O:8]1[CH:6]=[CH:5][N:4]=[C:3]1[C:2]([NH:10][C:11](=[O:20])[O:12][CH2:13][C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)([CH3:9])[CH3:1]
A solution of benzyl 2-methyl-1-oxo-1-(2-oxoethylamino)propan-2-ylcarbamate (2.23 g, 8 mmol) in methylene chloride (50 mL) was added to a freshly prepared solution of PPh3 (3.15 g, 12 mmol), I2 (3.05 g, 12 mmol) and Et3N (2.43 g, 24 mmol) in methylene chloride (100 mL). The resulting mixture was stirred at room temperature until TLC showed the reaction was completed. Then water (150 mL) was added. The organic layer was washed with 5% sodium bisulfite (150 mL×2), brine (150 mL) and dried over anhydrous sodium sulfate. Removal of the solvent under reduced pressure left a yellow oil which was purified by column chromatography (silica gel, 50 g, eluting with 25% ethyl acetate in petroleum ether) to yield the title compound (0.63 g, 30%) as colorless oil; MS: m/e 261.2 [M+H]+. 1H NMR (300 MHz, CDCl3): δ 7.57 (s, 1H), 7.37-7.33 (m, 5H), 7.05 (s, 1H), 5.06 (s, 2H), 1.74 (s, 6H).
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