Structure of Curcumenol

Curcumenol, C15H22O2, a new sesquiterpenic constituent of zedoary, Curcuma zedoaria (Zingiberaceae), has been shown to be represented by formula I on the basis of the following evidence. Chemical and physico-chemical properties of curcumenol and its derivatives indicate that curcumenol has a secondary methyl, a vinylic methyl on a trisubstituted double bond in which the carbon bearing a vinyl hydrogen is a to a quaternary carbon, an isopropylidene, and a hemiketal linkage whose carbon terminal is carrying no hydrogen. The carbon skeleton and the location of the hemiketal system have been established by the transformation to S-guaiazulene (V) and to the five-membered ring ketones (VII and VIII), respectively.