Total Synthesis of Asperaculin A.

The racemic total synthesis of asperaculin A, a sesquiterpenoid lactone with an unprecedented structure, has been accomplished in 17 steps from 3-methyl-2-cyclopentenone. Key features of the synthesis are the construction of a central all-carbon quaternary center using the Johnson-Claisen rearrangement, stereocontrolled introduction of a cyano group, and acid-mediated γ-lactonization.