Phlobatannins via facile ring isomerizations of profisetinidin and prorobinetinidin condensed tannin units
Abstract
[4,8]-2,3-trans-3,4-trans-(–)-Fisetinidol-2,3-trans-(+)-catechin and its (–)-robinetinidol homologue are to a varying degree subject to facile ring isomerizations (also when preceded by induced positional isomerization) in NaHCO3–Na2CO3 buffer solution under nitrogen, with liberation of reactive nucleophilic resorcinol units to form a range of bifunctional phlobatannins.