New Cyclic Diarylheptanoids from the Marine Sponge Tedania ignis

Diarylheptanoids (DHs) are a class of natural products mainly found in terrestrial plants of the families Betulaceae, Aceraceae, Myricaceae, Zingiberaceae and Dioscoreaceae. They have been reported to have various biological activities, including leishmanicidal and antiprotozoal, antitumor, antioxidant, anti-ischemic, anti-inflammatory, and inhibitory against nitric oxide production. In addition to the more common linear DHs, there are a smaller number of cyclic diarylheptanoids, which are formed from the corresponding linear type by phenolic oxidative coupling, either C–C coupling leading to meta,meta-bridged biaryls, or C–O coupling leading to bridged biaryl ethers. The isolation and structural elucidation of new cyclic diarylheptanoids (e.g. the diaryl ether 1) from the marine sponge Tedania ignis will be presented. This represents the first report of diarylheptanoids from marine organisms. Structure of compound 1 was established by NMR spectroscopy and ESI mass spectrometry. The NMR studies, carried out at temperatures comprised between 80°C and -70°C, demonstrated that the compound is present as a mixture of two slowly interconvertible enantiomeric confomers.