Hyperuralones A and B, new acylphloroglucinol derivatives with intricately caged cores from Hypericum uralum.

Hyperuralone A (1), a polycyclic polyprenylated acylphloroglucinol possessing an unprecedented tetracyclo-[5.3.1.1(4,9).0(4,11)]-dodecane core, was characterized from Hypericum uralum together with hyperuralone B (2), a congener with another complex caged skeleton. Their structures were determined by extensive spectroscopic analysis and ECD calculations. A plausible biosynthetic pathway of their intriguing architectures via intramolecular Diels-Alder reactions was also proposed. Compound 1 exhibited obviously cytotoxic activities against five human cancer cell lines in vitro (IC50 4.6-14.4 μM).