Hexahydroxydiphenoyl group

It is interesting to note that the same conclusions regarding the chirality of hexahydroxydiphenoyl groups bound to D-glucopyranose follow from theoretical considerations. Two assumptions are necessary ... 

The presence of a hexahydroxydiphenoyl group in a polyphenolic metabolite is readily defined by spectroscopic means (41, 43, 103, 104). The chirality (and hence their probable position of attachment to the D-glucose core) may be determined by cd spectra (43, 103, 104). 

It is interesting to note that the same conclusions, regarding the chirality of hexahydroxydiphenoyl groups bound to D-glucopyranose, follow from theoretical considerations. Two assumptions are necessary (i) that the ester carbonyl groups of the hexahydroxydiphenoyl residue have, like other ester groups (22, 107, 108), a preference for the... 

Biogenetically one important and perhaps unexpected variation of the hexahydroxydiphenoyl ester group found in a limited number of metabolites is the dehydro hexahydroxydiphenoyl ester (45) first identified by Schmidt °> and later noted in other metabolites of the families Gerania-ceae, Euphorbiaceae and Aceraceae. Isomerization occurs in solution and leads to an equilibrium mixture of internal hemi-acetal forms (45a, 45b) he attainment of... 

Hexahydroxydiphenoyl esters (2B, 2C). A very widely distributed metabolic fingerprint is that in which 3-penta-Q-galloyl-Erglucose (40) - it is assumed - is further transformed by oxidative coupling of pairs of adjacent galloyl ester groups (2, 3 and 4, 6) on the 3-D-glucopyra-nose core (Fig. 15, 2B). Some details of this pattern of metabolism were hinted at in earlier work by Hillis and Siekel, by Jurd, by Wilkins and Bohm, and Schmidt. 

In chemical terms a perhaps unexpected but biosynthetically interesting variant of the hexahydroxydiphenoyl ester group first noted by Schmidt is its dehydro-derivative (22). It was identified by Schmidt as a structural component of brevilagin 1 and 2, polyphenols from the fruit pods of Caesalpinia brevifolia (133, 134). Subsequent work has shown the ester to be present in the structure of other plant polyphenols, notably geraniin (51) in plants of the Geraniaceae (Thble 7.2.9). 

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