[N+:1]([C:4]1[CH:17]=[CH:16][C:7]([CH2:8][N:9]2[C:13](=[O:14])[CH2:12][NH:11][C:10]2=[O:15])=[CH:6][CH:5]=1)([O-:3])=[O:2].C([O-])([O-])=O.[K+].[K+].[CH2:24](Br)[C:25]1[CH:30]=[CH:29][CH:28]=[CH:27][CH:26]=1>CN(C=O)C>[CH2:24]([N:11]1[CH2:12][C:13](=[O:14])[N:9]([CH2:8][C:7]2[CH:16]=[CH:17][C:4]([N+:1]([O-:3])=[O:2])=[CH:5][CH:6]=2)[C:10]1=[O:15])[C:25]1[CH:30]=[CH:29][CH:28]=[CH:27][CH:26]=1A solution of the product from step (a) (5.9 g) in DMF (15 ml) was added under N2 to a stirred suspension of anhy. K2CO3 (3.5 g) in DMF (15 ml), followed by the addition of benzyl bromide (4.3 g, Aldrich). After additions were complete, the mixture was stirred at room temperature for 16 hours, then poured into ice-water and extracted with ethyl acetate (×3). The combined extracts were washed with brine, dried over MgSO4 and evaporated to give a yellow oil which was flash chromatographed through a silica column using ethyl acetate to give the desired product as a yellow oil (7.0 g).
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