Geijerone (3‐Isopropenyl‐4‐methyl‐4‐vinylcyclohexanone), a New, Naturally Occurring C12 Terpenoid

In the essential oil of Juniperus communis L. (fruit), the title compound (trans‐ isomer) has been identified; its structure being confirmed by synthesis from elemol. The optical rotation of the natural compound was nearly the same as the synthetic sample, suggesting that it is not an artefact formed from a ten‐membered ring precursor during the isolation.