Synthetic and theoretical studies on the Bergman cycloaromatization of cyclic enediynes

1 Synthetic and Theoretical Studies on the Bergman Cycloaromatization of Cyclic Enediynes 

IbUe 7-4 Calculated c-d distances and stabilities of cyclic enediynes 

A number of other strategies have been reported for constructing the enediyne core of the calicheamicin aglycone. These include the oxidative formation of the enediyne unit from a 

5-diyne precursor [213], base-induced elimination in a 3-OMs-l,5-hexadiyne system to generate the enediyne unit [214, 215], and an intramolecular Pd(0)-catalyzed coupling of a terminal acetylene with a (Z)-chloroenyne to generate an 11-membered enediyne bridging ring [216]. 

7 Total synthesis of the calicheamicin aglycone (Danishefsky and co-workeis). 

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