Sesquiterpenoids from Inula britannica

Phytochemical investigation of the flowers of Inula britannica led to the isolation of nineteen sesquiterpenoids (1-19), including britanlins E-J (2, 3, 5, 8, 13, and 14, respectively) and known sesquiterpenoids (1, 4, 6, 7, 9-12, and 15-19). The structures of these isolates were elucidated by detailed spectroscopic analyses and comparison to the previously reported spectroscopic data. The absolute configurations of compounds 12, 15, 17, and 19 were determined by X-ray single crystal diffraction analyses and chemical transformations.