Dioxasampsones A and B, Two Polycyclic Polyprenylated Acylphloroglucinols with Unusual Epoxy-Ring-Fused Skeleton from Hypericum sampsonii

Dioxasampsones A and B (1 and 2), two new polycyclic polyprenylated acylphloroglucinols with an unusual epoxy-ring-fused skeleton by new ways of cyclization, along with a new nor-PPAPs hypersampson R (3) with the loss of C-31–33 in isopentenyl, were isolated from the aerial parts of Hypericum sampsonii. 1 possessed an unexpected hexacyclic skeleton with a rare 2,7-dioxabicyclo[2.2.1]­heptane moiety, and 2 featured a unique tetrahydrofuro­[3,4-b]­furan-fused tricycle­[4.3.1.1^5,7]­undecane skeleton. The gross structures of the new compounds were determined by extensive NMR spectroscopic methods. Their absolute configurations were deduced by single-crystal X-ray diffraction and ECD calculations.