Total Synthesis of Triplinones A and O

The first total synthesis of triplinones A and O, along with the one-carbon truncated triplinones A/O, has been accomplished from a known advanced intermediate. During the addition of the terminal styrene unit by cross-metathesis, on a large scale, the migration of the olefine and subsequent cross-metathesis led to the formation of a one-carbon truncated cross-metathesis product in minor quantities. The Z-selective Wittig–Horner homologation followed by acid-catalyzed lactonization forged the right-hand side 5,6-dihydro-δ-pyrone unit.