A New Bisabolene from Stevia tomentosa

The new sesquiterpene (1R,2R,3R,6R,7S)-1-acetoxy-2,3-dihydroxy-2,3-dihydrobisabolene (3) together withten known terpenes and three known flavonoids were isolated from the aerial parts and from the roots of Steviatomentosa. The structure of 3 follows from spectral studies, the relative chirality at C-3 follows from (1)H NMR couplingconstants comparison with the corresponding calculated values obtained by applying a generalized Karplus-typerelationship to the dihedral angles of model compounds, and the absolute configuration is assumed in analogy to known(2R,3R,6R,7S)-2,3-epoxy-2,3-dihydrobisabolen-1-one (2).