The Smelling Principle of Vetiver Oil, Unveiled by Chemical Synthesis

Vetiver oil, produced on a multiton‐scale from the roots of vetiver grass, is one of the finest and most popular perfumery materials, appearing in over a third of all fragrances. It is a complex mixture of hundreds of molecules and the specific odorant, responsible for its characteristic suave and sweet transparent, woody‐ambery smell, has remained a mystery until today. Herein, we prove by an eleven‐step chemical synthesis, employing a novel asymmetric organocatalytic Mukaiyama–Michael addition, that (+)‐2‐epi‐ziza‐6(13)en‐3‐one is the active smelling principle of vetiver oil. Its olfactory evaluation reveals a remarkable odor threshold of 29 picograms per liter air, responsible for the special sensuous aura it lends to perfumes and the quasi‐pheromone‐like effect it has on perfumers and consumers alike.
Despite the advance of modern analytic techniques, the smelling principle of vetiver oil is still unknown owing to its extremely complex matrix of over 150 compounds. A concise stereoselective total synthesis proves (+)‐2‐epi‐ziza‐6(13)en‐3‐one to be the key to the quasi‐pheromone‐like aura of vetiver that magically resembles the effect of Iso E Super.