A strategic approach to [6,6]-bicyclic lactones: application towards the CD fragment of DHβE.

We report an effective synthetic protocol to access [6,6]-bicyclic lactone moieties through a regio-and stereoselective intramolecular Mizoroki-Heck cross-coupling reaction followed by a 6 pi-electrocyclization. This method enabled the first synthesis of the elusive CD fragment of the Erythrina alkaloid DH beta E. Preliminary pharmacological evaluations support the notion that the key pharmacophores of DH beta E are located in the A and B rings.