Benzofused N-substituted cyclic enediynes: activation and DNA-cleavage potential

The effect of electron withdrawal on the reactivity of N-substituted cyclic enediynes has been studied. These were synthesized via an intramolecular Mitsunobu reaction. The electron withdrawing effect of the nitro groups or the positive charge on the free ammonium salts was found to lower the cyclization temperature for Bergman cyclization. The ammonium salts cleave ds-DNA at nanomolar concentrations