Naturally occurring enediyne antibiotics1 are o en hailed as the most potent family of anticancer agents discovered to date.2 ese molecules were developed by microorganisms as the most powerful chemical warfare targeting cellular DNA with astounding eciency. e key step in the chemical mechanism responsible for this activity is the transformation of the enediyne moiety to a reactive p-didehydrobenzene diradical (p-benzyne). is step, the simplest version of which is given in Scheme 23.1, is a cycloaromatization reaction called the Bergman cyclization.3 e simultaneous formation of two radical centers is important because it results in the abstraction of two hydrogen atoms (one from each strand of a double-stranded (ds) DNA), which, a er a sequence of reactions, ultimately leads to ds DNA cleavage.4