From toluene to triquinanes: Formal total syntheses of the sesquiterpenoid natural products (-)-hypnophilin and (-)-coriolin

The enantiomerically pure cis-1,2-dihydrocatechol 6, which is readily obtained via the whole-cell biotransformation of toluene, has been converted into the linear triquinane 3 using a reaction sequence involving Diels-Alder cycloaddition and oxa-di-π-methane rearrangement reactions as key steps. Compound 3 is an advanced intermediate associated with several previously reported total syntheses of the sesquiterpenoid natural products (-)-hypnophilin (1) and (-)-coriolin (2). Related chemistry has provided the tetracyclic compound 5, another established precursor to (-)-coriolin (2).