"The enediyne group is often called a warhead because it is ready to cyclize, forming benzene via a highly reactive 1,4 benzeniod diradical intermediate. This diradical intermediate is responsible for the oxidative DNA cleavage. This cyclization process is named the Bergman cycloaromatization reaction. The enediyne group readily cyclizes via a diradical intermediate that cleaves the DNA, giving rise to enediynes’ powerful antitumor activity".
http://jlstasal.myweb.uga.edu/