Three novel C-glycosidic ellagitannins, rhoipteleanins H, I, and J, from rhoiptelea chiliantha

Three novel C-glycosidic ellagitannins named rhoipteleanins H (1), I (2), and J (3) were isolated from the fruits and bark of Rhoiptelea chiliantha Diels et Hand.-Mazz. (Rhoipteleaceae), and the structures were elucidated on the basis of detailed spectroscopic analysis and chemical evidence. Rhoipteleanin H possesses a unique cyclopentenone carboxyl moiety, which is probably formed by oxidation and subsequent rearrangement of an aromatic ring of a usual C-glycosidic ellagitannin. Rhoipteleanin I is the first ellagitannin having a hydroxynaphthalene glucoside moiety. Rhoipteleanin J is a dimeric ellagitannin generated by dehydrative coupling between two molecules of a monomeric C-glycosidic ellagitannin and subsequent oxidation of an aromatic ring. From a chemotaxonomic viewpoint, presence of these characteristic ellagitannins in this plant provides a further support for the establishment of the order Rhoipteleales comprising Rhoipteleaceae as the only family.