Dioxasampsones A and B, Two Polycyclic Polyprenylated
Acylphloroglucinols with Unusual Epoxy-Ring-Fused Skeleton from Hypericum sampsonii
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Abstract
Dioxasampsones A and B (<b>1</b> and <b>2</b>), 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 (<b>3</b>) with the loss of C-31–33
in isopentenyl, were isolated from the aerial parts of Hypericum sampsonii. <b>1</b> possessed an
unexpected hexacyclic skeleton with a rare 2,7-dioxabicyclo[2.2.1]heptane
moiety, and <b>2</b> featured a unique tetrahydrofuro[3,4-<i>b</i>]furan-fused tricycle[4.3.1.1<sup>5,7</sup>]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