Bicyclic enediyne core

An alternative approach to the bicyclic enediyne core of esperamicin utilizing an intramolecular Diels-Alder reaction was reported by Schreiber and co-workers (Scheme 7-45) [195-197]. This approach was initially hampered by an unfavorable regiochemical outcome in the Diels-Alder reaction (195 - 196), but was successfully corrected by a clever maneuver involving a Tsuchihashi pinacol rearrangement [198, 199] with concomitant diastereoselective acyloin shift to secure the desired bicyclic ring skeleton (197 - 198 - 199). 

Audrain, H. Skrydstrup, T. Ulibarri, G. Riche, C. Chiaroni, A. Grierson, D.S. Application and mechanistic studies of the [2,3]-Wittig rearrangement an approach to the bicyclic core structure of the enediyne antitumor antibiotics calicheamicin y/ and esperamicin-Ai. Tetrahedron 1994, 50, 1469-1502. 

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