Five New Sesquiterpenoids from Parasenecio petasitoides

Abstract From the whole plants of Parasenecio petasitoides , five new sesquiterpenoids were isolated, ( E , E )‐3 α ,9 β ‐dihydroxy‐6 β H,11 β H‐13‐norgermacra‐1(10),4‐dien‐11,6‐carbolactone ( 2 ), ( E , E )‐2 α ,9 β ‐dihydroxy‐6 β H,11 β H‐13‐norgermacra‐1(10),4‐dien‐11,6‐carbolactone ( 3 ), ( E , E )‐2 α ,9 β ‐dihydroxy‐6 β H,11 α H‐13‐norgermacra‐1(10),4‐dien‐11,6‐carbolactone ( 4 ), ( E )‐15‐hydroxy‐2‐oxo‐6 β H,11 α H‐13‐norguaia‐3‐ene‐11,6‐carbolactone ( 7 ), and ( E )‐11 β ,15‐dihydroxy‐2‐oxo‐6 β H‐13‐norguaia‐3‐ene‐11,6‐carbolactone ( 8 ), together with three known compounds, deacetyl herbolide A ( 1 ), jacquilenin ( 5 ), and ( E )‐15‐hydroxy‐2‐oxo‐6 β H,11 β H‐13‐norguaia‐3‐ene‐11,6‐carbolactone ( 6 ). The structures of these natural products were elucidated spectroscopically, especially by 1D‐ and 2D‐NMR techniques, in combination with high‐resolution mass spectroscopy.