Synthesis of a regio-isomer of kealiiquinone, a marine benzimidazole alkaloid

Abstract

Treatment of 1,3-dialkyl-2-(phenylthio)benzimidazolium salts 3 and 1,3-dialkyl-2-phenylthio-1H-imidazolium salts 7 with aq. K₂CO₃ gives 1,3-dialkyl-1,3-dihydrobenzimidazol-2-ones 4 and 1,3-dialkyl-1,3-dihydroimidazol-2-ones 8, respectively, in 22–94% yield. A regio-isomer 17 of kealiiquinone, a marine benzimidazole alkaloid, where the 4-methoxyphenyl group at the 4-position migrates to the 9-position, is synthesized by application of the reaction. Cytotoxity of 17 and kealiiquinone against 39 human cancer cells is evaluated. They have weak activity but a unique mechanism of action.