RECENT DEVELOPMENTS IN ESSENTIAL OILS 295 Additional work has been done on the structural formulas of the cur- cumenes (20, 144) (VIII, IX, X). c•-Curcumene /%Curcumene •-Curcumene (VIII) (IX) (X) The same is true of/-bisabolol, a sesquiterpene alcohol isolated from German chamomile oil (162), and of its d-isomer, observed in oil of Popu- /us ba/samifera (161). Bisabolol (XI) occurs also in Brazilian Louro Inhamuy oil (106). /OH Bisabolol (XI) gorm and Herout, who did the work on bisabolol, established the con- figurations of calacorene (XII)--a sesquiterpene C•5H20 (154)--and of calamenene (160) (XIII)--a sesquiterpene C•sH2=--both present in cala- mus oil, while Treibs suggested a structural formula for the diol calameone (calamenediol) (64, 177) (XIV), a bicyclic direfriary sesquiterpene alcohol also occurring in calamus oil. /OH NOH Cal acorene Calamenene Calamenediol (Calameone) (XlI) (XIII) (XIV)

296 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The configuration of lanceol (XV), a primary sesquiterpene alcohol present in oil of Santalum lanceolatum, remained doubtful for a long time, but recently a tentative formula, based upon •-bisabolene, has been as- signed to it (24, 55, 101,144). I•CH•OH Lanceol (xv) Metrosiderene (XVI), a hydrocarbon present in oils of Metrosideros umbellata and Dacrydium biforme, is now considered a sesquiterpene of the cadinene type, but the position of the double bonds has not yet been clearly explained (42). Metrosiderene (xvi) Carotol (XVII), a bicyclic sesquiterpene alcohol and chief component of carrot seed oil, has also been found to belong to the cadinene type (144). Carotol (XVII) Zingiberene (XVIII), which is present in ginger root oil, has been re- examined (108) and its absolute configuration now appears clear (9, 54). I Zingiberene (XVlii)