Verification of Biaryl-Structure Axial Chirality Produced in Ellagitannins by Chemical Oxidation.

The axial chirality of hexahydroxydiphenoyl (HHDP) groups contained in ellagitannins depends on the bridging position of d-glucose. The 4,6- O -HHDP group predominantly exhibits S- type chirality. This study elucidated the formation of the 4,6- O -( R )-HHDP group and subsequent axial isomerization by means of oxidative coupling of galloyl groups, which resulted in S chirality.