Biomimetic Sequential Tautomerization/Dehydration/Addition Cascade Reactions: Facile Access to Proanthocyanidin Analogues Driven by Heating

Abstract

An acid-catalyzed, biomimetic cascades strategy for the synthesis of proanthocyanidin analogues is reported. The method lays in the structural transformations of 2-hydroxychalcone strongly affecting by pH and in situ generated flavylium salt intermediate could facile couping with π-nucleophile to form the proanthocyanidin-type product. A proposed bioinspired cascade reaction pathway based on control experiments were also provided. These results are of interest for developing the total synthesis of proanthocyanidin natural products.