Synthetic and mechanistic studies on the antitumor antibiotics esperamicin A1 and calicheamicin delta1: synthesis of 2-ketobicyclo(7.3.1) enediyne and 13-ketocyclo(7.3.1) enediyne cores mediated by eta2 dicobalt hexacarbonyl alkyne complexes. Cycloaromatization rate studies

The bicyclo(7.3. 1)tridecenediyne core structure of the antitumor antibiotics esperamicin and calicheamicin can be constructed via the complexation of the 10,11-acetylenic bond as its derived eta2 Co(CO)6 adduct. This complexation results in the cation being aligned axially to the enol pi-system in the cyclohexanone ring, with the products unable to undergo cycloaromatization. Cyclohexane-1,2-dione yields 13-ketobicyclo(7.3.1)tridecenediyne in ten steps. The Co2(CO)6-eta2 propargylic cation methodology may also be used in the preparation of the core structures of dynemicin and neocarzinostatin.