Oligomeric ellagitannins

Li, H. Tanaka, T. Zhang, Y.J. Yang, C.R. Kouno, I. 2007. Rubusuaviins A-F, Monomeric and oligomeric ellagitannins from Chinese sweet tea and their alpha-amylase inhihitory activity. Chem. Pharm. Bull. 55 1325-1331. 

PHYSICAL METHODS FOR STRUCTURAL ELUCIDATION OF OLIGOMERIC ELLAGITANNINS... 

The DOG type units are also subdivided into their meta and para variants. In these units, a HHDP unit is 0-C-linked to a G unit. The m-DOG type unit that is also referred to as the valoneoyl unit is found in numerous oligomeric ellagitannins (Okuda et al, 1993), as well as in some monomeric ellagitannins such as the aforementioned type III+ mallotusinic acid (15, Fig. 4.4). The dimer oenothein B (20, Hatano et al, 1990a), isolated in... 

Fig. 4,5 Examples of Okuda s GOG and GOGOG type oligomeric ellagitannins.

Fig. 4.6 Typical examples of DOG type oligomers, including macrocyclic and higher oligomeric ellagitannins.

Fig. 4,8 Examples of C-O-coupled D(OG)2 type and C-C-coupled DG type oligomeric ellagitannins.

Fig. 64.12 Putative pathway from monomeric C-glycosidic ellagitaimins to oligomeric and glycosilated C-glycosidic ellagitannins as well as to llavano-ellagitannins. Acid-catalyzed condensation reactions of C-glycosidic ellagitannins via benzylic-type carbocation intermediates...

Fig. 4.12 The melasquanins, a series of related oligomeric C-glucosidic ellagitannins.

Pig. 4.14 The pentamer castaneanin D, the laigest oligomeric C-glucosidic ellagitannin known to date. 

The largest identified oligomeric C-glucosidic ellagitannin to date is a vescalagin/ castalagin-based pentamer, called castaneanin D (54, Fig. 4.14), which has been isolated by Kouno and associates coworkers (Tanaka et al, 1996) from the heartwood of the fagaceous Japanese chestnut tree (i.e., Castanea crenata SIEB. et ZUCC., Japanese name Kuri). 

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