[N:1]1[C:5]2[CH:6]=C(C(O)=O)[C:8]([C:10]([OH:12])=[O:11])=[CH:9][C:4]=2[NH:3][CH:2]=1.C[CH2:17][O:18][CH2:19][CH3:20].C[Si](C=[N+]=[N-])(C)C.[OH2:28].[CH3:29]O>CCOC(C)=O>[CH3:17][O:18][C:19]([C:20]1[C:8]([C:10]([O:12][CH3:29])=[O:11])=[CH:9][C:4]2[N:3]=[CH:2][NH:1][C:5]=2[CH:6]=1)=[O:28]To a solution of 200 mg of 5,6-benzimidazoledicarboxylic acid dissolved in 2.0 mL of MeOH and 2.0 mL of diethyll ether was added 4 mL of trimethylsilyldiazomethane [2.0 M in hexanes]. The resulting solution was stirred for 1 hour before dilution with 20 mL of H2O and extraction with 2×10 mL of EtOAc. the organic phases were dried over MgSO4 and concentrated under reduced pressure. Column chromatography (SiO2, 5% MeOH in CH2Cl2) yielded 210 mg of the title compound as a yellow oil. Mass Spectrum (ESI) 231 (M+1).
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