Investigation of the intramolecular Diels–Alder reactions of 6-fumaryl 1, 3, 8-nonatrienes, substituted at the C5 by a vinyl group, to afford the B-ring of FR182877 are reported. The synthesis of the required 1, 3, 8-nonatriene was achieved quickly and in high yield. 6- Fumaryl 1, 3, 8-nonatrienes substituted at the C5 by a vinyl group were found to undergo competing tandem sigmatropic rearrangement/Diels–Alder cyclisation when heated under ...