Conformational studies of tedarenes, two cyclic diarylheptanoids from the sponge Tedania ignis

Diarylheptanoids (DHs) are an unusual class of natural products composed of two aromatic rings linked by a C7 chain. They showed interesting biological activities, including leishmanicidal and antiprotozoal,1 antitumor, antioxidant, anti-ischemic, anti-inflammatory, and inhibitory against NO production. In addition to the more common linear DHs, there is a smaller number of cyclic DHs, formed from the linear type by phenolic oxidative coupling.3 The isolation and structural elucidation of two new cyclic diarylheptanoids (the diaryl ether 1 and the diphenyl 2) from the marine sponge Tedania ignis will be presented. Compound 1, but not compound 2, inhibits NO production. The conformational equilibria of the two molecules, which made their apparently simple structure elucidation a challenging process, will be discussed.