OLIGOMERIC FLAVANOIDS. PART 13. SYNTHESIS OF PROFISETINIDINS BASED ON (-)-ROBINETINIDOL AND (+)-EPIFISETINIDOL

Article abstract of DOI:10.1016/S0040-4020(01)85799-9

Acid-catalyzed condensation of (+)-mollisacacidin<(2R,3S,4R)-2,3-trans-3,4-trans-flavan-3,3',4,4',7-pentaol> with an excess of (-)-robinetinidol<(2R,3S)-2,3-trans-flavan-3,3',4,4',5',7-pentaol> afforded a novel series of bi-, tri-, and tetraflavanoid profisetinidins.They are accompanied by (-)-fisetinidol-(4α,2')-(-)-robinetinidol which results from the pyrogallol B-ring of (-)-robinetinidol serving as nucleophile competing with its resorcinol A-ring in coupling with a C-4 carbocationic intermediate.Similar condensation with (+)-epifisetinidol<(2S,3S)-2,3-cis-flavan-3,3',4',7-tetraol> led to the exclusive formation of <4,6>-interflavanyl bonds, these units being 'linearly' arranged in the tetraflavanoid analogue in contrast to the 'branched' nature of the (-)-robinetinidol homologue.