Isoflavonoid derivatives from Lophira alata stem heartwood.

Six isoflavonoid derivatives among which three are new have been isolated from the stem heartwood of Lophira alata. The structures were elucidated from spectroscopic and chemical evidences. Two have unusual carbon skeletons, possibly resulting from a variant of isoflavonoid biogenesis. The two compounds form the first members of a new subclass of flavonoid compounds which we call "isobiflavonoids". The presence of these isoflavonoid compounds in this plant of the Ochnaceae family has important chemotaxonomic implications since it modifies the botanic distribution of isoflavonoid compounds in non-leguminous plants.