For the first time, the Bergman reaction of a naturally occurring enediyne, namely dynemicin A, is fully investigated at the DFT level of theory using the B3LYP hybrid functional and VDZ basis sets. The calculated geometry of dynemicin A agrees well with the X-ray structure of deoxydynemicin A. The activation barrier is calculated to be 19.4 kcal/mol, while the reaction energy is exothermic by -2.1 kcal/mol, reflecting the destabilization of the enediyne unit by incorporation into a tricyclic ring system. The energetics of dynemicin A reveal that the enediyne is biologically active at body temperature. (C) 2002 Elsevier Science B.V. All rights reserved.