Asymmetric Total Synthesis of (+)-Waihoensene

The asymmetric total synthesis of
(+)-waihoensene, which has a cis-fused [6,5,5,5]
tetracyclic core bearing an angular
triquinane, a cis-fused six-membered ring, and four
contiguous quaternary carbon atoms, was achieved through a sequence
of chemical reactions in a stereochemically well-defined manner. The
total synthesis features the following: (1) Cu-catalyzed asymmetric
conjugated 1,4-addition; (2) diastereoselective Conia-ene type reaction;
(3) diastereoselective intramolecular Pauson–Khand reaction;
(4) Ni-catalyzed diastereoselective conjugated 1,4-addition; and (5)
radical-initiated intramolecular hydrogen atom transfer (HAT). Control
experiments and density functional theory calculations support the
proposed HAT process.