Computationally Assisted Assignment of the Kadsuraols, a Class of Chemopreventive Agents for the Control of Liver Cancer

Kadsuraols A-C (1-3), which are tetrahydrocyclobutaphenanthrofuranone-type lignans with a new carbon skeleton comprising a four-membered ring across C-1'-C-8, have been isolated from the roots of Kadsura longipedunculata. Their structures and absolute configurations were unambiguously determined using nuclear magnetic resonance, X-ray diffraction crystallography, DP4+ calculations, and computed and experimental electronic circular dichroism spectra. Kadsuraol C (3) exhibited hepatoprotective activity against N-acetyl-p-aminophenol (APAP)-induced toxicity. The compounds showed no cytotoxicity at 10 mu M in a zone assay.