Synthesis of a terbenzimidazole topoisomerase I poison via iterative borinate ester couplings

A concise, efficient synthesis is described for a terbenzimidazole that acts as a potent topoisomerase I poison. The strategy involves iterative palladium-catalyzed borinate ester cross-couplings and should be applicable to the synthesis of analogs containing heterocycles other than benzimidazole.