[N+:1]([C:4]1[C:12]2[N:11]=[CH:10][NH:9][C:8]=2[CH:7]=[CH:6][CH:5]=1)([O-:3])=[O:2].C(=O)([O-])[O-].[K+].[K+].Cl.Cl[CH2:21][C:22]1[CH:27]=[CH:26][N:25]=[CH:24][CH:23]=1>CN(C=O)C>[N+:1]([C:4]1[C:12]2[N:11]=[CH:10][N:9]([CH2:21][C:22]3[CH:27]=[CH:26][N:25]=[CH:24][CH:23]=3)[C:8]=2[CH:7]=[CH:6][CH:5]=1)([O-:3])=[O:2]A 500-mL round-bottomed flask equipped with a magnetic stirrer and nitrogen inlet is charged with compound 3b (3.30 g, 30.6 mmol), potassium carbonate (8.95 g, 64.8 mmol), anhydrous DMF (200 mL) and 4-chloromethylpyridine hydrochloride (3.98 g, 24.3 mmol) and the mixture is then stirred under nitrogen for 24 h at ambient temperature. After such time the reaction is partitioned between water (200 mL) and ethyl acetate (200 mL). The aqueous layer is separated and extracted with ethyl acetate (6×250 mL). The combined organic extracts are dried with sodium sulfate, and the drying agent is filtered off. The filtrate is then concentrated under vacuum to give a brown solid, which is purified by column chromatography to afford compound 3c as a yellow solid.
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