SESQUITERPENE$ IN THE PERFUMERY INDUSTRY 211 •:-Elemene •-- E f emene S -- E lemene ••OH E I emol Figure 11. seed oil (38, 39), whereas the alcohol [Peudesmol occurs in eucalyptus oil (40). a-Selinene has a mild, sweet-woody, and slightly peppery odour, the [Pisomer has a similar but warmer and more herbaceous odour (13). Eudesmol which finds some use as a fixative offers a delicate, sweet-woody and warm odour. The corresponding acetate ester is also interesting for its linalyl acetate type odour combined with much better tenacity. Both a-- Selinene /3-Selinene /•- Eudesmol Figure 12. selinene and [Peudesmol have been synthesized by Marshall, Pike and Carroll (41). Cyperene and a-cyperone also offer interesting structural systems, the latter being the main constituent of the oil of Cyperus rotandus (42). Penfold, Robinson and Simonsen (44) speculated a 1,2-alkyl shift in eudesmanes to generate the commercially important group of compounds known as eremophilanes (44). Eremophilene is present in a number of essential oils and has been a subject of several publications and a recent review by Pinder (43). The ketone Eremophilone is a constituent of Eremo- phiIIa mitcheIIi (44). The most commercially important members of the group are valencene, nootkatene, and nootkatone. Valencene has been isolated from orange juice oil and orange peel oil (45), and its structure and absolute configuration has been related to nootkatene, a t-butyl chromate oxidation product of'

212 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS C yperene rr-Cyperone 0 Eremophilene Eremophilone Figure 13. valencene. Nootkatone itself is an important flavour chemical isolated from grapefruit oil (46). Nootkatene or dehydrovalencene is readily obtainable from wood of Chamaecyparis nootkatensis by steam distillation and can be converted in high yield into nootkatone by hydrochlorination followed by oxidation (47). Therefore, the commercial importance of valencene and nootkatene lies in being readily available starting materials for a convenient synthesis of nootkatone. Nootkatone has an extremely powerful, sweet and citrusy odour of good tenacity and hence in addition to its well established use in flavour, it could undoubtedly find use in certain perfume formula- tions. Its further detection in other oils such as bergamot, lemon, lime, and tangerine emphasizes its importance in flavour and perfumery (45). Valencene Nootkatene Nootkatone 0 o rn- Oi hyd rocarvone Nootkatone Figure 14.