β-lactam fused enediynes have been successfully synthesized by intramolecular Kinugasa reaction in moderate yields. DSC studies indicated significant influence of the β-lactam ring upon the reactivity of enediynes. None of the β-lactam fused enediynes (under ring opening conditions) as well as the 11-membered monocyclic enediyne as the tosylate salt showed any cleavage of plasmid DNA. Interestingly, the 10-membered enediyne as the tosylate salt cleaved both single and double strands of plasmid DNA at micromolar concentration
