A series of substituted 2-(4-methoxyphenyl)-1H-benzimidazoles were synthesized and evaluated as inhibitors of topoisomerase I. The presence of a 5-formyl-, 5-(aminocarbonyl)-, or 5-nitro group (ie, substituents capable of acting as hydrogen bond acceptors) correlated with the potential of select derivatives to inhibit topoisomerase I. In contrast to bi-and terbenzimidazoles, the substituted benzimidazoles that were active as topoisomerase I ...