ELLAGITANNIN CHEMISTRY, PREPARATIVE AND MECHANISTIC STUDIES OF THE BIOMIMETIC OXIDATIVE COUPLING OF GALLOYL ESTERS

The construction of strictly the (S)-hexahydroxydiphenyl (HHDP) unit v ia biomimetic cyclization of suitably protected glucose-derived digall oyl esters has been achieved in good yield. Studies on substrates of i ncreasing complexity utilizing a range of oxidants (Pb(OAc)(4), VOF3, Tl2O3) have helped define the scope and limitations of this approach t o ellagitannin synthesis. Computer modeling of key cyclization precurs ors helped elucidate the molecular-level structural details which unde rgird the Haslam/Schmidt biosynthesis model for this class of naturall y occurring secondary plant metabolites.