[CH2:1]([C:8]1[N:12]=[C:11]([CH:13]=[CH:14][C:15]2[CH:20]=[CH:19][C:18]([O:21]C)=[C:17]([O:23]C)[CH:16]=2)[O:10][N:9]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.B(Br)(Br)Br.C(=O)([O-])[O-].[Na+].[Na+]>ClCCl.CO.C(Cl)(Cl)Cl>[CH2:1]([C:8]1[N:12]=[C:11]([CH:13]=[CH:14][C:15]2[CH:16]=[C:17]([OH:23])[C:18]([OH:21])=[CH:19][CH:20]=2)[O:10][N:9]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1
3-Benzyl-5-[2-(3,4-dimethoxy-phenyl)-vinyl-]-[1,2,4]oxadiazole (compound of Example 4, Method A, Step 1; 0.180 g, 0.55 mmol) was dissolved in dichloromethane (7 mL) and cooled to −78° C. A solution of boron tribromide (0.41 mL, 4.40 mmol) in dichloromethane (4 mL), which was cooled to 0° C., was added slowly over a period of 15 min. After 3 h, the reaction mixture was warmed to room temperature and stirred for 3 h. After completion of the reaction, the mixture was quenched by dropwise addition of methanol (15 mL) at 0° C. and stirred for 20 min at room temperature. The solvent was evaporated and the residue obtained was redissolved in 10% methanol in chloroform at 0° C., followed by stirring with solid sodium carbonate to maintain pH ˜8. The solvent was evaporated and the crude product obtained was purified by column chromatography (silica gel, 0.5% methanol in chloroform) to afford the title compound.
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