The racemic sesquiterpenes isocomene 1 and β-isocomene 22 have been synthesized starting from 1, 7-octadien-3-one 10 in a stereoselective manner. In the key step 12→ 13 (Scheme 5) the C-7, C-8-bond was formed by an intramolecular thermal ene reaction. Further transformations of 13 (Scheme 6) involved successively ring contraction 18→ 19, elimination 21→ 22 and olefin isomerization 22→ 1.
