Toward the total synthesis of methyl isosartortuoate: construction of the backbone of the diene unit

The backbone of diene precursor in the proposed biogenesis of methyl isosartortuoate through a Diels–Alder reaction has been constructed via dehydration to establish the conjugated system; and double cyclization by using Horner–Wittig–Emmons reaction and the chiral epoxy ring opening.