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can be classified as depsides. Total substitution degrees of 10-12 galloyl
units attached to the central glucose moiety have been determined for
Chinese gallotannin. Many variations of these fundamental structural
principles have been discovered in higher plants, but their discussion is
beyond the scope of this chapter.
HO
HO
COOH
OH
OH
HO
OH
HO
OH
O
OH
1
HO
O
O
HO
OH
OH
OH
O
O
O
OH
2
HO
O
O
O
O
O
OH
O
HO
OH
O
O
OH
HO
OH
HOOC
OH
HO
OH
OH
3
O
O
OH
OH
COOH
HO
OH
HO
OH
HO
OH
OH
5
HO
HO
OO
O
OH
HO
6
O
OH
O
O
HO
OH
O
O
O
O
HO
O
OH
HO
O
O
OH
OH
O
4
O
O
OH
OH
7
OH
HO
OH
OH
OH
Fig. 3.1 Structures of important components related to hydrolyzable tannins: ( 1 ) Gallic
acid (3,4,5-trihydroxybenzoic acid), the principal phenolic unit; ( 2 ) β-glucogallin (1- O -
galloyl-β- D -glucopyranose; ( 3 ) 1,2,3,4,6-penta- O -galloyl-β- D -glucopyranose; ( 4 )
tellimagrandin II, a typical monomeric ellagitannin; ( 5 ) 3,4,5,3',4',5'-
hexahydroxydiphenic acid (usually abbreviated as HHDP), the typical constituent of
ellagitannins; ( 6 ) ellagic acid, the dilactone of 5 ; ( 7 ) meta -digalloyl residue, the
characteristic moiety of gallotannins.
HO
It is not surprising that increasing knowledge of these chemical
structures was suitable to stimulate considerations on the biogenetic
routes to hydrolyzable tannins. Plausible pathways were proposed on this
 
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