The first conventional and C-ring isomerised profisetinidins with a dihydroflavanol as nucleophilic entity

The diversity and complexity of the plant-metabolic pool were recomfirmed during an investigation of the core wood Burkea africana. In this study monomeric flavenoids and biflavenoids were isolated. High resolution (300 MHz) 1H nmr was used for the structure determination of flavenoids. Nuclear Overhauser effect and spin-spin-decoupling experiments were also used. Two flavenols, myrecitin (3,3',4',5,5',7-hexahydroxyflavonol) and robinetin (3,3',4',5',7-pentahydroxyflavanol) of which the 1H nmr-spectra are characterised by the absence of any heterocyclic protons, were isolated. The 3-0-galloylester of (-)-robinetinidol and the dihydroflavenol (+)-ampelopsin (3,3',4',5,5',7-hexahydroxydihydroflavonol) was isolated