Total Synthesis of (±)-Bisabosqual A

The synthesis of the novel squalene synthase inhibitor,
bisabosqual
A, was completed in 14 steps (longest linear sequence) from commercially
available starting materials. The doubly convergent route employs
a tandem 5-exo, 6-exo radical cyclization as the key step. This reaction
assembles the fully functionalized tetracyclic core and introduces
three stereogenic centers. Other effective transformations are the
regioselective deoxygenation of an advanced enone intermediate and
the chemo- and diastereoselective addition of trimethylaluminum to
a ketone in the presence of esters.