SESQUITERPENES IN THE PERFUMERY INDUSTRY 225 o - Patchoulene /• -- Patchoulene 7'- Patchoulene o- Guaiene Caryophyllene B -- Guaiene Patchouli alcohol , Figure 35. Some constituents of patchouli oil. the synthesis involves a large number of steps. [3-Patchoulene is first syn- thesized and then converted to the a-patchoulene structure and hence patchouli alcohol. No commercial synthesis of this alcohol appears possible at the present. Patchouli oil is interesting as it is one of the few oils obtained by steam distillation and is found to contain sesquiterpene alkaloids (102). These alkaloids are formed from the sesquiterpene structures of two hydrocarbons found in patchouli oil, [I-patchoulene and a-gauiene thus they have been called patchoulipyridine and epiguaipyridine. The structures of these products, present in the oil to the extent of 0'1•o were determined by physical organic techniques (102) and confirmed by the synthesis of pat- choulipyridine and dihydro-epiguaipyridine. Patchoulipyridine was syn- thesized from [•-patchoulene by the action of hydrazoic acid and dehydro- genation of the resulting product. Dihydro-a-guaiene was synthesized (102) from guaiol and subjected to the same reaction steps to yield dihydro- epiguaipyridine. No odour descriptions have been given for these two alkaloids. An alternative synthesis (103) of patchoulipyridine has been developed by

226 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS /•- Patchoule13e HN& --H 2 Patchoulipyr[dine Guaiol H Dihydro -- a --guaiene dihydroepig uaipyridine Figure 36 French workers who started from homocamphor. This was converted in a number of steps to a diketone which was then transferred into the pyridine. Some of the hydrocarbons found in guaiacwood oil have also been found in patchouli oil (104). The main constituents of guaiacwood oil are the two sesquiterpene alcohols guiaol and bulnesol. Treatment of these alcohols with a small quantity (0.01 ta) of sulphuric acid produces a number of the hydrocarbons found in patchouli oil. These are obtained as a mixture and isolation of the desired hydrocarbons is difficult (see Fig. 37). A total synthesis (105) of guaiol has been reported but as guaiacwood oil is one of the cheaper sesquiterpene containing essential oils, this work appears to be of academic interest only. Treatment of guaiol with sulphuric acid, para-toluenesulphonic acid or iodine yields a cyclic ether guaioxide (Fig. 38). This ether has been claimed