Tannins and Related Compounds. CII. : Structures of Terchebulin, an Ellagitannin Having a Novel Tetraphenylcarboxylic Acid(Terchebulic Acid)Moiety, and Biogenetically Related Tannins from Terminalia chebula RETZ.

Abstract

A chemical examination of mylobalans (the fruits of Terminalia chebula RETZ., Combretaceae) has led to the isolation and characterization of punicalagin (1), terflavin A (2) and a new ellagitannin named terchebulin (3), which possesses a anovel tetraphynylcarboxylic acid (terchebulic acid) moiety. Furthermore, from the leaves of T. chebula, a series of biogenetically related hydrolyzable tannins, terflavins B (7), C (9) and D (10), punicalagin (1) and punicalin (8), have been isolated and structurally elucidated. The concomitant isolation of terflavins A (2) and B (7) provides biogenetic evidence that the tervhebulic acid moiety is derived by an oxidative carbon-oxygen coupling of adjacent flavogallonic acid and gallic acid esters.