Norsampsones A–D, Four New Decarbonyl Polycyclic Polyprenylated Acylphloroglucinols from Hypericum sampsonii

Norsampsones A–D (1–4), four new decarbonyl polycyclic polyprenylated acylphloroglucinols, together with a new biogenetically related compound hypersampsone M (5), were isolated from the aerial parts of Hypericum sampsonii. Norsampsones A–D featured an unprecedented carbon skeleton with the loss of C-2 carbonyl in the phloroglucinol ring. All structures were determined by extensive NMR spectroscopic methods, ECD calculation, and single-crystal X-ray diffraction.