Racemic Meroterpenoid with a 6/6/4/6/6/10/3 Skeleton via [2 + 2] and [4 + 2] Coupling of Sesquiterpenoid and Pyrone Units

Hypbeaone A (1), a pair of racemic meroterpenoids featuring a 6/6/4/6/6/10/3 heptacyclic core, along with its biogenic precursor, hypermonone A (2), were isolated from Hypericum beanii. Compound 1 represented the first trimeric meroterpenoid that should be biosynthesized through intermolecular [2 + 2] and [4 + 2] cycloadditions of two pyrones and one sesquiterpenoid unit. Its structure was unequivocally determined by spectroscopic analysis and X-ray crystallography. Both compounds (±)-1 and 2 exhibited potential α-glucosidase inhibitory activities.