Removal of the E-Olefin Barrier of Humulene Leading to Unnatural Terpenoid-like Skeletons.

An unnatural terpenoid scaffold containing a bicyclo[5.4.0]undecane moiety, as well as a salvialane skeleton based on an intramolecular C-C bond formation strategy were synthesized. Such a strategy was made possible by the removal of strained E-olefin conformations of the humulene skeleton. Some compounds were identified to show PPARα antagonist activity.