Illisimonin A, a Caged Sesquiterpenoid with a Tricyclo[5.2.1.0]decane Skeleton from the Fruits of Illicium simonsii.

Illisimonin A, an unprecedented sesquiterpenoid with a tricyclo[5.2.1.0]decane skeleton, was isolated from the fruits of Illicium simonsii. The structure and absolute configuration of 1 were determined using extensive spectroscopic evidence and electronic circular dichroism (ECD) calculations. It was determined that 1 possesses a caged 2-oxatricyclo[3,3,0,1]nonane ring system fused to a five-membered carbocyclic ring and a five-membered lactone ring. A plausible biogenetic pathway for 1 was proposed, and 1 showed neuroprotective effects against oxygen-glucose deprivation (OGD)-induced cell injury in SH-SY5Y cells with an EC value of 27.72 μM.