Biology Reference
In-Depth Information
Chapter 5
Strategies for the Synthesis of Ellagitannins
Karamali Khanbabaee
University of Paderborn, Faculty of Science, Department of Chemistry,
Warburgerstr. 100, D-33098 Paderborn, Germany;
kkh@zitmail.uni-paderborn.de
As a result of recent insights in the molecular structures and medicinal
uses of tannins, this class of natural products has enjoyed renewed
scientific interest. This is reflected, on the one hand, in the enormously
increased number of publications reporting on the isolation,
characterisation and biological activity of tannins, and on the other hand,
in the steadily growing number of papers reporting on tannin syntheses.
In this chapter, the most recent advances and effective concepts in the
total synthesis of ellagitannins are discussed. In nature, ellagitannins
occur usually only as the (
R
)- or only as the (
S
)-configured atropisomer,
with the corresponding opposite atropisomers seldom found. The
configuration of the HexaHydroxyDiPhenoyl units (HHDPs) found in
ellagitannins is usually determined by the linkage position of the HHDPs
on their polyol core. Those ellagitannins that have their HHDPs linked to
the 2,3- or 4,6-positions of
D
-glucopyranose have the (
S
)-configuration,
whereas the corresponding 3,6-HHDP-bearing ellagitannins are (
R
)-
configured. Very few exceptions are known in which both atropisomeric
HHDPs co-exist (Schmidt
et al.
, 1965, Gupta
et al.
, 1982).
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