Rare Sesquiterpenoids from the Shed Trunk Barks of the Critically Endangered Plant Abies beshanzuensis and Their Bioactivities

Two rare rearranged cuparane‐type sesquiterpenoid C‐10 epimers [beshanzuenones A (1) and B (2)] and two bisabolane‐type sesquiterpenoid spirolactones [beshanzuenones C (3) and D (4)] featuring an unusual [6/6/5]‐fused tricyclic ring system were isolated from the shed trunk barks of Abies beshanzuensis, one of the critically endangered plant species in the world. The structures of these four new enone‐containing sesquiterpenoids were determined by spectroscopic analyses and single‐crystal X‐ray diffraction or electronic circular dichroism (ECD) calculations. Compounds 1 and 2 showed considerable activity against the H3N2 virus, whereas 3 and 4 exhibited significant inhibition on PTP1B. Two rare rearranged cuparane‐type sesquiterpenoid C‐10 epimers [beshanzuenones A (1) and B (2)] and two bisabolane‐type sesquiterpenoid spirolactones [beshanzuenones C (3) and D (4)] featuring an unusual [6/6/5]‐fused tricyclic ring system were isolated from the shed trunk barks of Abies beshanzuensis, one of the critically endangered plant species in the world.