Biology Reference
In-Depth Information
OH
HO
OH
OH
HO
HO
OH
HO
HO
OH
O
O
OH
O
O
HO
OH
OH
O
O
O
O
O
O
OH
OH
O
O
O
O
OH
OH
O
O
O
O
O
O
H
H
HOOC
O
HOOC
O
H
H
HO
OH
HO
OH
OH
OH
O
H
H
O
O
O
Chebulinic acid
Chebulagic acid
OH
OH
OH
HO
O
O
OH
HO
OH
O
O
O
OH
O
O
OH
O
O
O
O
H
H
O
O
HO
HO
O
O
OH
OH
OH
HO
OH
HO
O
OH
OH
O
Terchebin
Ellagitannins can be defined in a narrow sense as
hexahydroxydiphenoyl esters of carbohydrates or cyclitols, while the
definition of ellagitannins in a wider sense also cover compounds derived
from further oxidative transformations, including oligomerization
processes (Okuda
et al
., 1995). It is this latter and wider definition that
will be taken into account throughout this topic.
1.1.3 Stereochemistry of ellagitannins - Absolute configuration of
HHDP, DHHDP and chebuloyl group
Chemical and circular dichroism (CD) spectral studies have shown that
the absolute configuration of the atropisomeric biaryl HHDP groups at
the O-2~O-3 and O-4~O-6 positions of the
D
-glucopyranose core of most
ellagitannins is
S
, such as in the molecule of pedunculagin, whereas the
