CAMEROONANE, PRENOPSANE AND NOPSANE, 3 NEW TRICYCLIC SESQUITERPENE SKELETONS

The strong patchouli-like and woody smelling essential oil of the rhiz omes of Echinops giganteus var. Ielyi C. D. Adams (Compositae) contain s only sesquiterpenes, which are mainly triquinanes. Besides the known tricyclic compounds, silphiperfol-5-(1, 3) and -6-ene (4), modhephen- 2-ene (5), alpha-(6) and beta-isocomene (7), silphiperfolan-7 beta-ol (12), presilphiperforan-8-ol (13), silphiperfol-6-en-5-one (14) and 7- epi-silphiperfolan-6 beta-ol (20), the following compounds, three of w hich (15, 17, 18) have new skeletons, were found, for the first time, occurring naturally: presilphiperfol-7-ene (2), cameroonan-7-ol (15), an 11(7-->8)-abeo-presilphiperfolan-7-ol, prenopsan-8-ol (17), a 1(8-- >7)-abeo-cameroonan-8-ol, and napsan-4-ol (18), a 3(4-->8)-abeo-prenop san-4-ol, three diastereomers of silphiperfolan-6-ol (19, 21, 22), mod heph-2-en-8-ol (23) and silphiperfola-4,7(14)-diene (24). All structur es were elucidated by NMR spectroscopy. A biogenetic pathway from pres ilphiperfolane cation C to the cameroonane K, prenopsane L and nopsane M cations is shown. Cameroonanol (15) and prenopsanol (17) are the ma in contributors to the fragrance of the total oil.