222 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Cedrol CH20H Primary cedrol Figure 30. •OH Widderol Distillation yields two main fractions, the hydrocarbon fraction is the so-called 'Cedrene' of commerce, impure cedrol is obtained as the alcohol cut. Pure cedrol can be obtained by recrystallization of the alcohol fractions and is used in perfumery. Cedrenol is a mixture of cedrol and its isomers, widdrol and some ketonic compounds. Acetylation of this mixture yields cedrenyl acetate. Cedryl acetate is also made by esterification of the alcohol and a number of qualities are sold they range from the pure recrystallized acetate to acetate mixtures containing almost 50•o hydrocarbons. Epoxy-cedrene has been manufactured by epoxidation of cedrene-rich hydrocarbon fractions followed by recrystallization (Fig. 31). One of the most interesting cedarwood derivatives is the complex mixture of ketones known as 'acetyl cedrene' obtained by acetylation of the hydrocarbon fraction. This has a woody, warm-ambergris and musky odour (94), and is sold under a number of trade names. A number of investigations have been made to find the odour constituents of the mixture. The hydro- carbon cut used in the manufacture has two main components, cedrene and thujopsene. The acetylation product of the purified cedrene is said to have little odour. The reaction of thujopsene under these conditions is much more complex. With acid catalysts thujopsene isomerizes into a large number of hydrocarbons and it is thought that this isomerization precedes the acety- lation step in the production of acetyl cedrene. At least seven Cx7H•60 ketones have been observed in the acetylation mixture but the structures of only two are known and these account for

SESQUITERPENES IN THE PERFUMERY INDUSTRY 223 Distilled oil Crude Cedarwood oil Distillation Grades of Cedrene (Hydrocarbon mixtures) / • epoxy cedrane Epoxidation A••. acetyl cedrane ( Ci7H260 ketones) Distilled cedrol • Cedrol crystals fication Cedryl acetate Cedrenol Esterification (alcohol cut' • cedrol and % Cendrenyl acetate other alcohols Figure 31. Perfumery materials from cedarwood oil (93). Acetic Anhydride Catalyst Figure 32. some 605/o of the reaction product. The major ketone is thought to be the active odour constituent of acetyl cedrene. It is said to have a powerful woody, musk-ambergris odour far greater in intensity than any of the other isomers. This acetyl thujopsene isomer has an interesting odour-structure relationship since, although it has a strong musk odour, it has no aromatic ring as have most other tricyclic musks possessing an acetyl group. Patchouli oil has wide application in the perfumery industry and more extensive use would be made of this essential oil if it were in greater supply. Much effort has been devoted to the analysis of the oil and a number of constituents have been identified. No single compound has the total patchouli odour and any effort to formulate a reconstructed patchouli oil will require the synthesis of a number of sesquiterpene alcohols, ketones and hydrocarbons. The main alcohol constituent of patchouli oil is patchouli alcohol. A synthesis of this alcohol from homocamphor has been reported (101) but