A Synthesis of (+)-FR182877, Featuring Tandem Transannular Diels−Alder Reactions Inspired by a Postulated Biogenesis

An efficient biomimetic synthesis of the reported structure of the hexacyclic, cytotoxic secondary metabolite FR182877 is described. The successful route features the synthesis of a 19-membered ring carbocycle using two pi-allyl palladium(II)-mediated C-C bond-forming reactions. This polyunsaturated macrocycle undergoes tandem transannular Diels-Alder reactions that create five rings and seven stereogenic centers in one operation under mild conditions, representing the first double transannular Diels-Alder reaction. The absolute stereochemistry of the natural product is demonstrated to be opposite of that reported previously. Significant quantities of both enantiomers of this microtubule-stabilizing natural product and related structures are now available via this approach.