Asymmetric Total Synthesis of Dibenzocyclooctadiene Lignan Natural Products

Full details of the asymmetric total syntheses of the dibenzocyclooctadiene lignans interiotherin
A, angeloylgomisin R, gomisin O, and gomisin E (epigomisin O) are presented. The syntheses were
based on a unified synthetic strategy involving a novel crotylation using the Leighton auxiliary
that occurred with excellent asymmetric induction (>98:2 enantiomeric ratio), a diastereoselective
hydroboration/Suzuki−Miyaura coupling reaction sequence, and an atropdiastereoselective biarylcuprate coupling, both of which occurred with total (>20:1) stereocontrol. The syntheses were
achieved in six to eight steps from simple aromatic precursors.