Calicheamicin gamma(I)(1) and phenyl tert-butyl nitrone (PBN): observation of a kinetic isotope effect by an ESR study

ESR study of enediyne calicheamicin gamma(I)(1) with phenyl tert-butyl nitrone (PBN) gave a significant kinetic isotope effect (k(H)/k(D) = 1.8) for the formation of the phenyl radical PBN monoadducts.