Hypatulone A, a Homoadamantane-Type Acylphloroglucinol with an Intricately Caged Core from Hypericum patulum

Hypatulone A (1), an acylphloroglucinol possessing an unprecedented homoadamantane architecture based on a tricyclo-[4.3.1.13,8]-undecane core and a unique 5/5/7/6/6 pentacyclic ring system, together with its biogenetic precursor hyperbeanol B (2), was isolated from Hypericum patulum. The structure of 1 was elucidated by extensive spectroscopic analysis and electronic circular dichroism calculation. Its plausible biosynthetic pathway via Wagner–Meerwein rearrangement was proposed. 1 exhibited nitric oxide inhibitory effect on LPS-induced RAW264.7 cell line (IC50 18.8 ± 1.75 μM).