Revised Structure, Total Synthesis, and Absolute Configuration of Kopeolin and Kopeolone

An enantioselective total synthesis
of two sesquiterpenoids, kopeolin
and kopeolone, has been achieved. Using the diastereoselective addition
of an organocerate as a key step, we controlled the absolute stereochemistry
of a crucial stereocenter present in these natural products. This
approach allowed us to confirm a structural revision that we previously
proposed (Chem.Eur.
J. 2013, 19, 10632−10642) and to fully characterize
these natural products while elucidating their absolute stereochemistry.