Spin-trapping of the p-benzyne intermediates from ten-membered enediyne calicheamicin γ1

In the presence of thiols, the ten-membered-ring enediyne calicheamicin gamma(l)(1) generates a p-benzyne biradical that initiates oxidative cleavage of double-stranded DNA. Application of spin-trapping has successfully provided ESR and mass spectroscopic evidence for the formation of the monoadducts with phenyl tert-butyl nitrone (PBN).