Construction of the ABCD ring system of (−)-FR182877 via the intramolecular Diels–Alder (IMDA) reaction and the highly diastereoselective intramolecular hetero-Diels–Alder (IMHDA) reaction is described. The IMHDA reactions of the substrates incorporating the oxabutadiene with the E- or Z-alkene were examined, revealing that the sole product was obtained from both substrates and the E-alkene geometry