Non‐Enzymatic Oxidation of a Pentagalloylglucose Analogue into Members of the Ellagitannin Family

Abstract

The occurrence of more than 1000 structurally diverse ellagitannins has been hypothesized to begin with the oxidation of penta-O-galloyl-b-d-glucose (b-PGG) for the coupling of the galloylg roups.H owever,t he non-enzymatic behavior of b-PGG in the oxidation is unknown. Disclosed herein is whichgalloylgroups tended to couple and whichaxial chirality was predominant in the derived hexahydroxydiphenoyl groups when an analogue of b-PGG was subjected to oxidation. The galloylg roups coupled in the following order: at the 4,6-, 1,6-, 1,2-, 2,3-, and 3,6-positions with respective S-, S-, R-, S-, and R-axial chirality.A mong them, the most preferred 4,6-coupling reflected the what was observed for natural ellagitannins.Anew finding was that the second best coupling occured at the 1,6-positions.W ith the detection of a3 ,6-coupled product, this work demonstrated that even ellagitannin skeletons with an axial-richg lucose core may be generated non-enzymatically.