Synthesis and structure-activity relationship study of antidiabetic penta-O-galloyl-D-glucopyranose and its analogues

Article abstract of DOI:10.1021/jm060087k

The rapid increase of obesity-associated diabetes has created urgent demands for more effective antidiabetic therapies and pharmaceuticals that are able to address the problems of hyperglycemia and weight gain simultaneously. Our previous studies indicated that the α- and β-anomers of penta-O-galloyl-D-glucopyranose (PGG), 2 and 3, act as insulin mimetics that bind to and activate the insulin receptor, stimulate glucose transport in adipocytes, and reduce blood glucose and insulin levels in diabetic and obese animals. In addition, they inhibit differentiation of preadipocytes into adipocytes. These activities suggest that 2 and 3 may reduce blood glucose without increasing adiposity. To investigate the structure-activity relationship of 2 and 3, four series of novel compounds were prepared and their glucose transport stimulatory activities were measured using a radioactive glucose uptake bioassay. The assay results indicate that both the glucose and the galloyl groups are critical to the activity of 2 and 3. It appears that the glucose core provides an optimal scaffold to present the galloyl groups with the correct spatial orientation to induce activity. Moreover, the galloyl groups linked to the 1, 2, 3, and 4 positions of glucose are essential, while the galloyl group connected to the 6 position of 2 is unnecessary for the induction of activity. The discovery that two related novel compounds, 6-deoxytetra-O-galloyl-α-D-glucopyranose (43) and tetra-O-galloyl-α- D-xylopyranose (59), also possess glucose transport stimulatory activity suggests that 2 may be further modified around position 6 to modulate and enhance its efficacy. To test this hypothesis, we developed a new synthetic method that allows for the stereoselective preparation of derivatives of 2 that are modified on C-6. We found that 6-chloro-6-deoxy-1,2,3,4-tetra-O-galloyl- α-D-glucopyranose (80) exhibits a significantly higher glucose transport stimulatory activity than 2. Its activity is comparable to that of insulin.

Full text of DOI:10.1021/jm060087k

J. Med. Chem. 2006, 49, 2829-2837
2829
Synthesis and Structure-Activity Relationship Study of Antidiabetic
Penta-O-galloyl-D-glucopyranose and Its Analogues
Yulin Ren,†,| Klaus Himmeldirk,‡,| and Xiaozhuo Chen†,‡,§,
*
Edison Biotechnology Institute, Department of Chemistry & Biochemistry, and Department of Biomedical Sciences,
Molecular and Cellular Biology Program, Ohio UniVersity, Athens, Ohio 45701
ReceiVed January 25, 2006
The rapid increase of obesity-associated diabetes has created urgent demands for more effective antidiabetic
therapies and pharmaceuticals that are able to address the problems of hyperglycemia and weight gain
simultaneously. Our previous studies indicated that the R- and â-anomers of penta-O-galloyl-D-glucopyranose
(PGG), 2 and 3, act as insulin mimetics that bind to and activate the insulin receptor, stimulate glucose
transport in adipocytes, and reduce blood glucose and insulin levels in diabetic and obese animals. In addition,
they inhibit differentiation of preadipocytes into adipocytes. These activities suggest that 2 and 3 may reduce
blood glucose without increasing adiposity. To investigate the structure-activity relationship of 2 and 3,
four series of novel compounds were prepared and their glucose transport stimulatory activities were measured
using a radioactive glucose uptake bioassay. The assay results indicate that both the glucose and the galloyl
groups are critical to the activity of 2 and 3. It appears that the glucose core provides an optimal scaffold
to present the galloyl groups with the correct spatial orientation to induce activity. Moreover, the galloyl
groups linked to the 1, 2, 3, and 4 positions of glucose are essential, while the galloyl group connected to
the 6 position of 2 is unnecessary for the induction of activity. The discovery that two related novel
compounds, 6-deoxytetra-O-galloyl-R-D-glucopyranose (43) and tetra-O-galloyl-R-D-xylopyranose (59), also
possess glucose transport stimulatory activity suggests that 2 may be further modified around position 6 to
modulate and enhance its efficacy. To test this hypothesis, we developed a new synthetic method that allows
for the stereoselective preparation of derivatives of 2 that are modified on C-6. We found that 6-chloro-6-
deoxy-1,2,3,4-tetra-O-galloyl-R-D-glucopyranose (80) exhibits a significantly higher glucose transport
stimulatory activity than 2. Its activity is comparable to that of insulin.
Introduction
cemic agents. Mechanistic studies have shown that the transport
of blood glucose into cells is largely induced and regulated by
the circulating insulin through interaction with the insulin
receptors (IR) located primarily in the plasma membrane of
adipocytes and muscle cells.12,13 IR is a heterotetrameric protein
consisting of two R- and two â-subunits.12,13 The two extra-
cellular R-subunits form the insulin binding domain,13,14 and
the two â-subunits, covalently linked to the R-subunits and to
each other by disulfide bonds, function as both the transmem-
brane and intracellular tyrosine kinase domains of IR.12-14 The
binding of insulin to the extracellular insulin binding site triggers
a conformation change of the IR.12-14 This induces the intra-
cellular tyrosine kinase activity of the â-subunits, resulting
sequentially in autophosphorylation of the tyrosine residues of
the â-subunits, activation of intracellular protein factors PI-3K,
Akt, and GLUT4, and finally transport of glucose into the target
cells.15 All protein factors involved in this insulin-mediated
signaling pathway, including IR, can be potential pharmaceutical
targets for diabetes treatment.4,16
IR has been a prime target for the development of antidiabetes
pharmaceutics.16-18 However, a high-resolution crystal structure
of IR has not been established, and consequently the detailed
information on insulin-IR binding is unavailable. Increased IR-
mediated signaling is needed for the control of the blood glucose
level in both types of diabetes.19 Insulin has been the most
frequently used antidiabetic agent that targets IR. However,
insulin is a polypeptide that has to be invasively introduced
(injected). Furthermore, it promotes adiposity and weight gain.
Therefore, the discovery and development of nonpeptidyl,
nonadiposity-promoting insulin supplements or replacements are
highly desirable.19-21
Diabetes mellitus, which is classified into type I diabetes
(T1D) and type II diabetes (T2D), has become a serious health
problem worldwide, particularly in developed countries.1,2
Increasing attention has been focused on the elucidation of the
disease mechanisms in order to develop new and more effective
therapies.3,4 T1D is an autoimmune disease characterized by a
decrease in pancreatic secretion of insulin, while T2D is a result
of insulin resistance and decreased insulin action.1,5 The
deficiency in insulin signaling in both types of diabetes leads
to hyperglycemia.1,5,6
Visceral adiposity is associated with significantly increased
risks for T2D,7,8 and up to 90% of the T2D patients in the United
States are either overweight or obese. Therefore, reducing
adiposity, a major contributor to obesity, is beneficial for the
prevention and treatment of T2D. Most current T2D drugs are
both hypoglycemic and weight-gain-promoting, alleviating one
problem (hyperglycemia) while aggravating another (weight
gain).4 Developing innovative antidiabetic therapeutics that
simultaneously combat both hyperglycemia and overweight is
highly desirable.9-11
Current treatments of diabetes are focused on reducing the
blood glucose level with the help of insulin and other hypogly-
* To whom correspondence should be addressed. Address: Edison
Biotechnology Institute, 109 Konneker Research Laboratories, The Ridges,
Ohio University, Athens, Ohio 45701. Phone: 740-593-9699. Fax:740-593-
4795. E-mail: chenx@ohiou.edu.
† Edison Biotechnology Institute.
| Both authors contributed equally to this work.
‡ Department of Chemistry and Biochemistry.
§ Department of Biomedical Sciences, Molecular and Cellular Biology
Program.
10.1021/jm060087k CCC: $33.50 © 2006 American Chemical Society
Published on Web 04/08/2006

2830 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Ren et al.
to discover that both 2 and 3 exhibit glucose transport
stimulatory and adipogenesis inhibitory activities in adipocytes.38
The combination of the two biological activities suggests that
2 and 3 may be lead compounds for the development of novel
antidiabetic therapeutics that are able to combat hyperglycemia
and adiposity in T1D and/or T2D patients. Our signal pathway
studies indicated that 2 binds to the R-subunit of the IR and
induces IR autophosphorylation. It also activates PI-3K, Akt,
GLUT4, protein factors and effectors in the cascade of IR-
mediated signaling pathway, and the stimulation of glucose
transport.38 The results indicate that 2 is an insulin mimetic,
and IR is the molecular target of 2 for its glucose transport
stimulatory activity. However, a detailed study of the structural
features of 2 and 3 required for activity have not been performed.
We hypothesized that the glucose core and the individual
galloyl groups of 2 and 3 constitute important structural elements
responsible for the induction of glucose transport into adipo-
cytes. Several series of novel analogues of 2 and 3 were designed
and synthesized to test this hypothesis. The glucose transport
stimulatory activities of the new compounds were evaluated with
a radioactive glucose uptake assay.22,25,38
Figure 1. Structure of gallotannins and the two anomers of PGG, 2
and 3.
In searching for new antidiabetic agents, we found that the
extract of Lagerstroemia speciosa L. (also called Banaba)
exhibits both glucose transport stimulatory activity and adipocyte
differentiation-inhibitory activity in 3T3-L1 adipocytes.22 Other
groups also showed that the Banaba extract (BE) reduces blood
glucose and adiposity of diabetic mice.23,24 Our continued study
led to the discovery that tannic acid (TA), a component of BE,
exhibits the same activities.25 This finding was consistent with
a report showing that TA-related ellagitannins from BE exhibit
a glucose transport stimulatory activity.26 TA consists mainly
of a group of structurally related polyphenolic compounds
known as gallotannins (Figure 1) that possess a large variety
of health-beneficial effects.27-33 It is widely distributed in plant-
based foods and in traditional medicinal herbs.34-37
Recently, we have identified penta-O-galloyl-â-D-glucopy-
ranose (3), one of the major components of TA, as the most
active compound in TA to induce the glucose transport
stimulatory activity.38 Two anomers of penta-O-galloyl-D-
glucopyranose, 2 and 3, exist in nature.38 Both are composed
of five gallic acid molecules (4) that are esterified with
D-glucopyranose (Figure 1). Because of its potential health-
beneficial bioactivities and abundant occurrence in nature,39-43
3 has been studied before. However, it was not previously
known that 3 possesses anti-diabetic activity. We were the first
Chemical Synthesis
The key step in the known synthesis of 2 and 3 is the Steglich
esterification of R-D-glucopyranose (9) with 3,4,5-tribenzyloxy-
benzoic (8) acid using dicyclohexylcarbodiimide (DCC) and
N,N-(dimethylamino)pyridine (DMAP) as the coupling agents.44,45
The procedure leads to epimerization at C-1 of the glucose ring.
A mixture that contains approximately equal proportions of ben-
zyl protected R- and â-anomers 10 and 11 forms (Scheme 1).
The procedure contains two steps that limit the scale of the
synthesis to milligram quantities. A separation of the protected
anomers 10 and 11 by column chromatography with pure
dichloromethane as the eluent and a final purification of the
individual deprotected products 2 and 3 by HPLC are needed
to obtain pure products.44 In our hands, the column chroma-
tography with dichloromethane led to poor separations. We
improved the process by adding toluene and ethyl acetate to
the eluent. The best separation of the anomers was achieved
Scheme 1. Improved Synthesis of 2 and 344,a
a Reagents and conditions: (a) KI, K2CO3, acetone, reflux; (b) NaOH, ethanol, reflux; (c) HCl, water; (d) DCC, DMAP, CH2Cl2, 40 °C; (e) silica gel,
dichloromethane/toluene/ethyl acetate (75:25:1); (f) H2, THF, 10% Pd/C, 40 °C.

PGG and Its Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2831
Table 1. Glucose Transport Stimulatory Activity of 2 and 3 and Their
The peripheral position of the galloyl groups in 2 and 3 led
us to speculate about their significance for the interaction with
the insulin receptor and the subsequent stimulation of glucose
transport. To test the functional importance, we investigated a
series of compounds that contain the glucose core without
galloyl groups or with a reduced number of phenolic hydroxyl
groups (Chart 1). Compounds 4 and 12-14 were commercially
available, while compounds 15-26 were synthesized by esteri-
fication of glucose with a variety of protected phenolic acids
using the method shown in Scheme 1.
Analoguesa
compd
act.c
compd act.c compd
act.c
compd
act.c
posb 183 ( 8
negb 30 ( 1
22
24
26
4
20 ( 1
16 ( 0
30 ( 0
31 ( 3
20 ( 0
27 ( 1
5 ( 1
29 ( 2
15 ( 1
11 ( 0
7 ( 1
39
41
43
45
47
49
51
53
55
57
59
28 ( 1
30 ( 1
115 ( 5d
15 ( 1
22 ( 4
19 ( 4
23 ( 1
34 ( 4
20 ( 0
19 ( 2
124 ( 11d
61
63
65
67
69
71
73
77
80
21 ( 1
23 ( 0
14 ( 0
10 ( 0
12 ( 1
21 ( 1
7 ( 0
2
145 ( 5d
107 ( 9d
34 ( 2
31 ( 1
24 ( 1
34 ( 3
30 ( 1
27 ( 0
10 ( 0
3
9
5
12
13
14
16
18
20
27
29
31
33
35
37
143 ( 10d
181 ( 9d
To investigate the importance of the glucose core for the
bioactivity of 2 and 3, we tested several commercially available
gallic acid derivatives without a glucose core (Chart 2).
a All benzyl protected analogues failed to induce glucose uptake. The
results are not shown. b In the glucose uptake assay, insulin-treated samples
served as positive control (pos) and mock-treated (no compound) cell
samples served as negative control (neg). c act. ) activity for [1-3H]-2-
deoxy-D-glucose uptake, in Bq ( SE (SE ) standard error). d P < 0.001
compared to negative control using unpaired t-test.
The functional importance of each individual galloyl group
in 2 and 3 was tested in a third series of compounds consisting
of monodeoxy-D-glucopyranose derivatives (Chart 3). Again,
the procedure used for the synthesis of anomers 2 and 3 (Scheme
1) could be applied to prepare all compounds shown.
with a solvent mixture consisting of dichloromethane, toluene,
and ethyl acetate in a ratio 75:25:1 (v/v/v).
A final series of compounds were synthesized to test the
dependence of activity on the spatial orientations of the galloyl
groups in 2 and 3 and its analogues. Hexo- and pentopyranoses
with one stereocenter inverted relative to the D-glucopyranose
ring in 2 and 3 were prepared (Chart 4) from commercially
available carbohydrates. In summary, 66 protected and unpro-
tected analogues of 2 and 3 were synthesized with the help of
our improved synthetic procedure. The only compounds previ-
ously known were 2, 3, 10, 1144 and 25, 26.46
The hydrogenolysis of 10 and 11 led to 2 and 3, respectively.
Our second improvement of the reported procedure consisted
of the purification of the final product by crystallization. The
R-isomer could be crystallized from water. A final purification
by HPLC described in the original procedure44 was unnecessary.
A third enhancement of the known synthesis was achieved
by modifying the preparation of the benzyl protected gallic acid
(8) utilized for the coupling reaction. The new procedure leads
to a yield of 94% of 3,4,5-tribenzylgallic acid (8) starting from
the commercially available methyl ester of gallic acid (5)
(Scheme 1).
The improved chromatographic procedure was applicable in
the synthesis of all derivatives of 2 and 3 shown in Charts 1-4.
The crystallization of the final products succeeded for most
R-isomers shown in Table 1. Only a few derivatives had to be
purified by semipreparative HPLC (see Experimental Section).
To confirm our preliminary results that suggested that
derivatives of the R-anomer of glucopyranose retain activity if
the structure around C-6 of 2 is changed, we developed a new
synthesis for a derivative that contains all galloyl groups except
for the one at C-6. The procedure is shown in Scheme 2. For
the esterification, the acid chloride of protected gallic acid 74
was found to lead to the best yield. 74 was easily prepared from
acid 8 by reaction with oxalyl chloride in the presence of
catalytic amounts of dimethylformamide.
Chart 1. Analogues of 2 and 3 with Modified Galloyl Groups

2832 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Ren et al.
Chart 2. Structure of Commercially Available Gallic Acid
Derivatives
than with 9. Only R-anomer 79 could be detected by NMR
spectroscopy of the product of the esterification. Final depro-
tection and crystallization from water afforded pure 6-chloro-
6-deoxy-1,2,3,4-tetra-O-galloyl-R-D-glucopyranose (80).
Results and Discussion
After modification of the known chemical synthesis as
described in the chemistry section of this article (Scheme 1),
the improved procedure was found to allow for the efficient
preparation of 2 and 3 and its analogues. We successfully
synthesized all our target compounds as shown in Charts 1, 3,
and 4 using the same method with minor modifications. The
glucose transport stimulatory activities of the target compounds
in 3T3-L1 adipocytes were screened with an established glucose
uptake bioassay that has been used extensively in diabetes
studies49,50 and previous research into 2 and 3.22,25,38
Since 2 and 3 consist of D-glucopyranose connected to five
gallic acid molecules (Figure 1), we assumed that both chemical
components might be important for activity. In addition, the
stereochemical arrangement of the galloyl groups was expected
to have an influence as well. Evaluation of the target compounds
confirmed previous results38 that compounds 2 and 3 stimulate
glucose transport in adipocytes in an insulin-like fashion (Table
1). The R-anomer 2 was found to be more active than â-anomer
3. This key observation indicates that subtle structural differ-
ences have a significant impact on the glucose transport
stimulatory activity of our lead compounds. In contrast, both
protected precursor compounds 10 and 11 are inactive (Table
1), which suggests that unprotected hydroxyl functions on the
galloyl groups are critical for activity.
Glucose (9) itself was found to be inactive. Commercially
available acetates (12 and 13) and benzoates (14) of glucose
were also inactive (Chart 1, Table 1). These results further
emphasize the importance of the galloyl groups. Compounds
15-26 are esters of glucose and phenolic acids with only one
or two hydroxyl groups. The observation that all compounds
were inactive in our assay suggests that all three phenolic
hydroxyl groups are required for activity.
Our bioassay results reveal that gallic acid (4), methyl galloate
(5), and ellagic acid (27) are inactive (Table 1). These
commercially available compounds contain galloyl groups
without a glucose core. The fact that all three compounds are
inactive suggests that the glucose core is required as a scaffold
to present one or more galloyl groups in a certain spatial
arrangement to interact with and induce the receptor target.
The primary hydroxyl group at C-6 of glucopyranose was
selectively protected with trityl chloride (TrCl).47 Without
isolating the product, all remaining hydroxyl groups were
esterified with acid chloride 74. The two-step procedure led to
the epimerization of the anomeric center of the carbohydrate.
The trityl protecting group of the mixture of R- and â-isomers
75 was removed with hydrobromic acid, and the anomers were
separated by column chromatography. The benzyl protecting
groups of the R-isomer were removed by hydrogenolysis, and
the product was purified by crystallization from water.
We were interested in developing a synthesis that allows for
an easy preparation of multigram quantities of derivatives of 2
needed for animal studies. Since commercially available glucose
consists mostly of crystalline R-D-glucopyranose 9, our goal
was to find conditions that prevent or minimize the isomerization
(mutarotation) of the R-configuration of the starting material
to its â-form before the esterification can take place. We were
successful by using the protected galloyl chloride 74 for the
coupling reaction (Scheme 3). It was found that the selection
of the solvent was crucial for the retention of the R-configuration
during the transformation. Among the solvents tested, acetoni-
trile led to the best results. An R/â ratio of 96:4 could be
obtained. After deprotection, the R-anomer could be further
enriched to a purity >99% by crystallization from water. The
new procedure does not need any chromatographic separation
step. Gram quantities of 2 are easily synthesized.
The new synthetic approach was further tested by using the
easily accessible 6-chloro-6-deoxy-R-D-glucopyranose 7848 as
the carbohydrate starting material (Scheme 3). The R-selectivity
of the transformation with acid chloride 74 was even higher
Chart 3. Analogues of 2 and 3 with Four Galloyl Groups

PGG and Its Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2833
Chart 4. Analogues of 2 and 3 with Modified Stereochemistry of the Carbohydrate Core
Scheme 2. Synthesis of 1,2,3,4-Tetra-O-galloyl-R-D-glucopyranose 77a
a Reagents and conditions: (a) (COCl)2, DMF (cat.), toluene; (b) TrCl, pyridine, 40 °C; (c) 74, DMAP, CH3CN; (d) HBr, AcOH; (e) chromatography;
(f) H2, THF, 10% Pd/C, 40 °C; (g) crystallization.
Scheme 3. Selective Synthesis of Derivatives of 2a
a Reagents and conditions: (a) DMAP, CH3CN; (b) H2, THF, 10% Pd/C, 40 °C; (c) crystallization.
Compounds 28-45 (Chart 3) are analogues containing one
galloyl group less than 2 and 3. Among these compounds, only
43 (6-deoxy-tetra-O-galloyl-R-D-glucopyranose) is active. The
removal of a galloyl group from position 1, 2, 3, or 4 of glucose
resulted in a complete loss of glucose transport stimulation.
However, activity was retained when a galloyl group linked to
position 6 was removed and the R-configuration at C-1 was
present. These results suggest that the galloyl groups linked to

2834 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Ren et al.
position 1, 2, 3, or 4 of glucose in 2 are functionally important,
while the galloyl group bound to C-6 is not. On the other hand,
3 requires all five galloyl groups to induce activity.
mice by the gavage method (data not shown). In summary, our
data suggest that the active compounds presented in this study
may provide the molecular model for the design and develop-
ment of new antidiabetic leads.
The final series of novel hexa- and pentapyranoses, 46-76
(Chart 4) tested the dependence of activity on the stereochemical
arrangement of the galloyl groups attached to the carbohydrate
core. The configuration at one of the positions C-2, C-3, or C-4
of the corresponding R- or â-glucopyranose (2 or 3) was inverted
for 46-57 and 61-73 and retained for 58-61. The only active
compound was found to be 1,2,3,4-tetragalloyl-R-D-xylopyra-
nose 59. Its structure shows the same configuration at C-2, C-3,
and C-4 as found in 2 and 3. The fact that all other compounds
in this series were inactive (Table 1) shows that, among the
different monosaccharides tested, the pyranose ring of glucose
with its equatorial substituents at C-2, C-3, and C-4 provides
the best spatial orientations for the galloyl groups to couple to
and to present themselves to the IR in order to induce glucose
transport. It indicates that the spatial arrangement of galloyl
groups in 2 and 3 greatly impacts glucose transport stimulation.
Conclusion
We have designed and synthesized a series of novel gallo-
tannin analogues by modifying the structure of our lead com-
pounds 2 and 3. We measured the glucose transport stimulatory
activities of these compounds in 3T3-L1 adipocytes. The study
shows that both the glucose core and the galloyl substituents
with their three phenolic hydroxyl groups are essential for
activity. In 2 the glucopyranose ring provides an optimal scaffold
for the galloyl groups on C-1, C-2, C-3, and C-4 to present
themselves in a conformation needed for the induction of
activity. C-6 and the galloyl group attached to it are not crucial
for the induction of activity. Our results demonstrate that more
potent and efficacious derivatives of 2, such as 80, may be
accessible by changing the structure around this part of the
molecule. On the other hand, 3 was the only activity-inducing
compound with an equatorial galloyl group attached to C-1. This
study provides the basis for our ongoing efforts to discover new
potent insulin mimetics and to elucidate the mechanism of the
potentially antidiabetic activities of 2 and 3.
The observation that 43 and 59 are active indicates that
variations of the structure around C-6 of the glucopyranose core
of 2 are tolerated. This suggested that it might be possible to
enhance the glucose transport activity of 2 by changing the
groups bound to C-5 or C-6 of the glucopyranose ring. To test
this hypothesis, we developed two novel syntheses (Schemes 2
and 3) to access specifically derivatives of 2 that are modified
at C-6. 1,2,3,4-Tetra-O-galloyl-R-D-glucopyranose 77 shows an
activity very similar to that of 2. 6-Chloro-6-deoxy-1,2,3,4-tetra-
O-galloyl-R-D-glucopyranose 80 was found to be ∼30% more
active than 2. Even more remarkable, 80 is as active as insulin
(Table 1).
Experimental Section
All procedures were carried out using anhydrous solvents
purchased from commercial sources and used without further
purification. 1-Deoxy-D-glucose, 2-deoxy-D-glucose, and 3-deoxy-
D-glucose were purchased from Toronto Research Chemicals,
Canada. 4-Deoxy-D-glucose was purchased from CMC Chemicals,
England. 6-Deoxy-D-glucose was purchased from Sigma. Ellagic
acid (27) was purchased from Acros Chemical. Gallic acid (4),
methyl galloate (5), R-D-glucose (9), R-D-glucopyranose penta-
acetate (12), â-D-glucopyranose pentaacetate (13), R-D-glucopyra-
nose pentabenzoate (14), and all other reagents were purchased from
Aldrich. Chromatographic separations were performed on silica gel
using the solvent systems indicated. Solvent systems are reported
as v/v percent ratios. All reactions were monitored by TLC using
precoated silica gel plates. Yields refer to chromatographically and
spectroscopically pure compounds except when otherwise indicated.
Product analysis by HPLC indicated that purities of all synthesized
and purchased target compounds were greater than 98%.
Melting points were determined on a Mel-Temp II apparatus
(Laboratory Devices) and are uncorrected. Proton nuclear magnetic
resonance spectra were recorded at 500 MHz with a Varian INOVA-
500 spectrometer, and chemical shifts are expressed in δ (parts per
million, ppm). Coupling constants (J) were expressed in Hz. The
splitting patterns are abbreviated as follows: s (singlet), d (doublet),
t (triplet), q (quartet), m (multiplet), br (broad singlet). IR spectra
were recorded on a Shimadzu Advantage FTIR 8400S spectrometer.
Optical rotations were measured on an AUTOPOL IV (Rudolph
Research Analytical) polarimeter at 20 °C and 589 nm. Mass spectra
were recorded on a Micromass Q-TOF II (Micromass, Wythen-
shawe, U.K.). Silica gel thin-layer chromatography was performed
on precoated Kieselgel 60F254 (Merck KGaA, Germany) plates. For
column chromatography, silica gel (ACROS Organics) with par-
ticles size of 0.035-0.070 mm was used.
Little was known about the antidiabetic activity of 2 and 3
and their analogues before this study. SAR investigations of
gallotannins were only conducted in other biomedical areas. 3
was shown to have higher fatty acid synthase inhibitory activity
than other tannin compounds.39 Gallotannins were found to
possess anticancer and anti-inflammatory activities.40,41 The
number of galloyl groups in gallotannins was found to be
important for their antiherpetic42 and antioxidant43 activities.
In addition, the presence of all three unprotected phenolic
hydroxyl groups was shown to be crucial for antioxidant
activity.43 Some of our experimental results are consistent with
the studies described above.
Our previous mechanistic studies showed that 2 binds to the
R-subunit of IR and activates the IR-mediated signaling pathway
for glucose transport activity.38 The present study indicates that
at least four galloyl groups of 2 are critical for the activity of
the compound. These results lead to the hypothesis that binding
of 2 to IR is responsible for the glucose transport stimulatory
activity. The glucose core appears to provide a near-optimal
spatial arrangement for the galloyl groups to form proper
chemical interactions with the amino acid residues of the IR
located in the binding site. Our previous studies38 suggest that
the R-subunit of the IR forms the binding site for 2 and its
analogues. Since the removal of phenolic hydroxyl groups leads
to loss of activity, the interaction may take place primarily
through the peripheral hydroxyl groups in the form of hydrogen
bonding. The shape and polarity of the residue-linked C-6 may
also affect the binding. Currently a more detailed characteriza-
tion of the binding between 2 and IR is under investigation.
Our in vivo studies established that 2 effectively reduces blood
glucose and insulin levels in diabetic mice.38 A preliminary
pharmacokinetic study indicates that 2 is orally bioavailable
because it can be detected in blood 1 h after delivering it into
HPLC was performed on a Beckman (Beckman Coulter) HPLC
instrument with a model 118 pump, model 7725i injector, and a
Beckman 168 photodiode array detector. Chromatograms were
recorded using System Gold 32 Karat software (Beckman). Solvent
A of the mobile phase of was made of deionized water (Ultrapure
Water, Dubuque, IA) and trifluoroacetic acid (Fisher Scientific)
(999:1). Solvent B consisted of acetonitrile (Sigma-Alderich) and
trifluoroacetic acid (999:1). A linear gradient was applied from
80:20 A/B to 50:50 A/B over 15 min at a flow rate of 1 mL/min
for the analytical column and at 3 mL/min for the semipreparative

PGG and Its Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2835
column. Detection wavelength was at 280 nm, and analyses were
conducted at 20 °C. Analytical HPLC was carried out on a Beckman
Ultrasphere ODS column (250 mm × 4.6 mm i.d., 5 µm) used
together with an Ultrasphere ODS precolumn (4 mm × 4.6 mm
i.d.) using an injector with a 10 µL loop. Preparative HPLC was
carried out on a Beckman Ultrasphere ODS column (250 mm ×
10 mm i.d., 5 µm) used together with an Ultrasphere ODS
precolumn (4 mm × 4.6 mm i.d.) using an injector with a 100 µL
loop.
3T3-L1 preadipocytes were purchased from American Type
Culture Collection (ATCC, Rockville, MD). Dulbecco’s modified
Eagle’s medium (DMEM), Dulbecco’s PBS (DPBS), fetal bovine
serum (FBS), and calf bovine serum (CBS) were purchased from
Cellgro, Inc.. Kerbs-Ringer-HEPES (KRP) buffer had the following
composition: 136 mM NaCl, 4.7 mM KCl, 1.25 mM CaCl2, 1.25
mM MgSO4, and 10 mM sodium phosphate buffer at pH 7.4.
3-Isobutyl-1-methylxanthine (IBMX), dexamethasone (DEX), and
bovine insulin were purchased from Sigma Chemical (St. Louis,
MO). 2-Deoxy-[1-3H]-D-glucpse (1 mCi/mL) was purchased from
Amersham. Radioactive glucose taken up by the cells was measured
by a LS 6500 multipurpose scintillation counter from Beckman
Coulter.
3,4,5-Tribenzyloxybenzoate (8). A mixture of 10.00 g (54.3
mmol) of methyl 3,4,5-trihydroxybenzoate, 4.00 g (24 mmol) of
potassium iodide, and 44.00 g (318 mmol) of anhydrous powdered
potassium carbonate in 500 mL of acetone was stirred at room
temperature for 20 min. Then 22.00 g (174 mmol) of benzyl chloride
dissolved in 100 mL of acetone was added. The suspension was
refluxed for 18 h. TLC shows full conversion of the starting material
and a single product spot (Rf ) 0.30; hexanes/ethyl acetate ) 8:2).
The solid was filtered, and the filtrate was evaporated. The residue
was taken up in 400 mL of dichloromethane. The suspension was
filtered through Celite, and the filtrate was evaporated. After the
mixture was dried for 1 h under vacuum, methyl 3,4,5-tribenzy-
loxybenzoate 7 was obtained as a white solid that was used for the
next step without further purification.
Crude 7 (26.52 g) was suspended in 500 mL of 95% ethanol.
An amount of 3.54 g (88.5 mmol) of sodium hydroxide was added.
The mixture was heated at reflux for 2 h. The hot solution was
poured into 525 mL of 0.6 M hydrochloric acid. A thick,
voluminous suspension formed. The hot mixture was stirred for
10 min before the solid was filtered off. The product was washed
successively with a 1:1 mix of 95% ethanol and water (100 mL),
pure water (100 mL), 95% ethanol (100 mL), methanol (2 × 50
mL), and tert-butyl methyl ether (2 × 50 mL). The solid was dried
overnight under vacuum to yield 22.6 g (94%) of colorless crystals.
Mp 191-194 °C (lit.51 196-196.5 °C).
cm-1; HRMS (ESI) (C146H122O26), m/z calculated M + Na+
1
2313.8122, measured M + Na+ 2313.8203 (3.5 ppm); H NMR
(CDCl3) δ 4.41 (1H, dd, J ) 6.5, 12.5), 4.49 (1H, m), 4.81 (1H,
m), 4.96-5.20 (30H, m), 5.79 (1H, t, J ) 10.0), 5.88 (1H, dd, J )
8.0, 10.0), 6.10 (1H, t, J ) 10.0), 6.26 (1H, d, J ) 8.0), 7.20-7.50
(85H, m).
r-D-Glucopyranose Pentakis[3,4,5-tris(phenylmethoxy)ben-
zoate] (10) via Esterification with Acid Chloride 74 (Scheme
3). A suspension of 459 mg (1.0 mmol) of acid chloride 74 and 36
mg (0.2 mmol) of finely powdered D-glucose in 10 mL of
acetonitrile was stirred at room temperature. Then an amount of
128 mg (1.05 mmol) of DMAP was added, and the mixture was
stirred at room temperature. After 18 h, the solvent was evaporated.
The residue was taken up in 5 mL of toluene at 60 °C. After the
mixture was cooled to room temperature, the solution was filtered
through a layer of silica gel (250 mg, 1.2 cm thick). The silica gel
was washed with 5 mL of a mix of toluene and ethyl acetate (100:
4). The solvent was evaporated. An amount of 455 mg (99%) of
74 was obtained as a highly viscous oil after drying in a vacuum
for 5 h (for analytical data, see above).
R-D-Glucopyranose Pentakis(3,4,5-trihydroxybenzoate) (2) (R-
PGG). A suspension of 332 mg (0.145 mmol) of 10 and 31.8 mg
(0.30 mmol) of palladium (10 wt % on activated carbon) in 30 mL
of dry THF was stirred at 40 °C under a hydrogen gas atmosphere
for 16 h. The reaction mixture was cooled and filtered through
Celite filter-aid, and the filtrate was evaporated. The residue was
crystallized from water. Compound 2 (85.0 mg, 62.2%) was
obtained as colorless crystals. Mp >210 °C (dec); [R]24D +167.06°
(c 0.17, CH3COCH3); IR (KBr) 3390, 1699, 1612, 1535 cm-1
;
HRMS (ESI) (C41H32O26), m/z calculated M - H+ 939.1104,
measured M - H+ 939.1107 (0.3 ppm); 1H NMR (CD3COCD3) δ
4.38 (1H, dd, J ) 4.0, 13.0), 4.5 (1H, dd, J ) 1.5, 11.0), 4.66 (1H,
d, J ) 9.5), 5.45 (1H, dd, J ) 3.5, 9.0), 5.76 (1H, t, J ) 10.5),
6.16 (1H, t, J ) 10.5), 6.72 (1H, d, J ) 3.5), 6.90 (2H, s), 6.91
(2H, s), 7.02 (2H, s), 7.18 (2H, s), 7.22 (2H, s).
â-D-Glucopyranose Pentakis(3,4,5-trihydroxybenzoate) (3) (â-
PGG). A suspension of 314 mg (0.137 mmol) of 11 and 31.8 mg
(0.30 mmol) of palladium (10 wt % on activated carbon) in 30 mL
of dry THF was stirred at 40 °C under a hydrogen gas atmosphere
for 16 h. The reaction mixture was cooled and filtered through
Celite filter-aid, and the filtrate was evaporated. The residue was
dissolved in water at 60 °C. When the mixture was cooled,
compound 3 precipitated. After filtration and drying under vacuum
for 20 h, an amount of 79.0 mg (61.7%) of a white solid was
obtained. [R]24 +17.14° (c 0.14, CH3COCH3); IR (KBr) 3392,
D
1708, 1616, 1535 cm-1; HRMS (ESI) (C41H32O26), m/z calculated
1
M - H+ 939.1104, measured M - H+ 939.1075 (3.1 ppm); H
r- and â-D-Glucopyranose Pentakis[3,4,5-tris(phenylmethoxy)-
benzoate] 10 and 11 via Steglich Esterification (Scheme 1). A
suspension of 0.21 g (1.17 mmol) of D-glucose, 3.77 g (8.57 mmol)
of 3,4,5-tribenzyloxybenzoic acid, 2.2 g (10.68 mmol) of dicyclo-
hexylcarbodiimide (DCC), and 1.2 g (9.84 mmol) of N,N-(di-
methylamino)pyridine (DMAP) in 135 mL of dry dichloromethane
was refluxed for 18 h. After the mixture was cooled to room
temperature, the urea byproduct was filtered and the filtrate was
evaporated. The resulting residue was purified by column chro-
matography on silica gel, using a 75:25:1 mixture of dichloro-
methane, toluene, and ethyl acetate as the eluent. The product
fraction was evaporated, and the residue was precipitated from
toluene. Compounds 10 (337 mg, 14.7%) and 11 (319 mg, 11.7%)
were obtained.
NMR (CD3COCD3) δ 4.36 (1H, dd, J 5.0, 13.0), 4.52 (1H, m),
4.54 (1H, m), 5.60 (1H, t, J 9.5), 5.64 (1H, t, J 10.0), 5.99 (1H, t,
J 10.0), 6.30 (1H, d, J 8.5), 6.95 (2H, s), 6.99 (2H, s), 7.04 (2H,
s), 7.09 (2H, s), 7.16 (2H, s).
3,4,5-Tribenzyloxybenzoyl Chloride (74). A suspension of
11.57 g (26.26 mmol) of 3,4,5-tribenzyloxybenzoic acid 8 in 120
mL of toluene and 0.2 mL of DMF was stirred at room temperature.
Via a dropping funnel, a solution of 5 g (39.4 mmol) of oxalyl
chloride in 17 mL of toluene was added over a period of 10 min.
After being stirred at room temperature for an additional 20 min,
the mixture was heated to 50 °C. The ceasing of gas evolution
indicated the end of the reaction after about 1 h. The yellow solution
was evaporated. The residue was taken up in 50 mL of toluene at
70 °C. A yellow, highly viscous, sticky side product remained
undissolved. The product solution was decanted. The chloride was
precipitated by adding 55 mL of cyclohexane to the hot toluene
solution. Crystallization started within a few minutes. The solid
was filtered and washed with cyclohexane. The product, 9.46 g
(78%), was obtained as a white solid. Mp 116-117 °C (lit.52 115-
116 °C).
Compound 10: white solid, Rf (94% toluene/6% ethyl acetate),
0.55; [R]24D +43.53° (c 0.17, CH2Cl2); IR (KBr) 1724, 1589, 1499
cm-1; HRMS (ESI) (C146H122O26), m/z calculated M + Na+
1
2313.8122, measured M + Na+ 2313.8152 (1.2 ppm); H NMR
(CDCl3) δ 4.36 (1H, dd, J ) 6.0, 12.5), 4.64 (1H, m), 4.83 (1H,
dd, J ) 2.5, 12.5), 4.89-5.16 (30H, m), 5.65 (1H, dd, J ) 3.5,
10.0), 5.81 (1H, t, J ) 10.0), 6.40 (1H, t, J ) 10.0), 6.88 (1H, d,
J ) 3.0), 7.20-7.53 (85H, m).
r-D-Glucopyranose
1,2,3,4-Tetrakis(3,4,5-tri-O-benzyl-
galloate) (76). A solution of 500 mg (2.78 mmol) of R-D-
glucopyranose and 836 mg (3.00 mmol) of trityl chloride in 6 mL
of dry pyridine was stirred for 8 h at 40 °C. The mixture was cooled
Compound 11: white solid, Rf (94% toluene/6% ethyl acetate),
0.57; [R]24D -0.59° (c 0.17, CH2Cl2); IR (KBr) 1727, 1589, 1499

2836 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Ren et al.
to room temperature, and 5.35 g (11.66 mmol) of 3,4,5-tribenz-
yloxybenzoyl chloride (74), 1.9 g (15.55 mmol) of DMAP, and an
additional 12 mL of pyridine were added. The mixture was stirred
for 2 days at room temperature. Solid material was filtered off and
washed with 20 mL of toluene. The filtrate was evaporated to
dryness and redissolved in toluene, and the solution was evaporated
again. The dissolving and evaporation was repeated once more.
The residue was purified by column chromatography on silica gel
with an eluent consisting of toluene and ethyl acetate (100:1). An
amount of 4.75 g of a clear, colorless, highly viscous oil was
obtained. The NMR spectrum showed a mixture of R and â products
(1:1).
COCH3); IR (KBr) 3428, 1714, 1617, 1534 cm-1; HRMS (ESI)
C34H27O21Cl, calculated M - H 805.0655, measured M - H
1
805.0623 (4.0 ppm); H NMR (CD3COCD3) δ 3.78 (1H, dd, J )
5.0, 12.5 Hz), 3.86 (1H, dd, J ) 2.5, 12.5 Hz), 4.61 (1H, m), 5.45
(1H, dd, J ) 4.0, 10.5 Hz), 5.63 (1H, t, J ) 10.0 Hz), 6.12 (1H, t,
J ) 9.5 Hz), 6.71 (1H, d, J ) 3.5 Hz), 6.98 (2H, s), 7.07 (2H, s),
7.26 (2H, s).
Glucose Uptake Assay. 3T3-L1 preadipocytes grown in 24-well
plates were induced by MDI (IBMX-DEX-insulin) into adipocytes,
which were washed twice and incubated with 0.5 mL of serum-
free DMEM in 10% CO2 at 37 °C for 2 h. The cells were washed
with 0.45 mL of KRP buffer three times and then incubated at 37
°C for 30 min. Insulin was added to the cells at a final concentration
of 1 µM. Alternatively, 2 or 3 or their analogues were added to the
cells at a final concentration of 30 µM. The adipocytes were
incubated at 37 °C for 15 min. Glucose uptake was initiated by
addition of 0.1 mL of KRP buffer with 1 µCi/mL [1-3H]-2-deoxy-
D-glucose and 1 mM cold glucose as the final concentration. The
glucose uptake was terminated with addition and then removal of
ice-cold PBS buffer. Finally, the cells were lysed with 0.45 mL of
1% Triton X-100 at 37 °C for 20 min. The radioactivity taken up
by the cells was measured in a solution of 0.4 mL of the cell lysates
and 5 mL of scintillation liquid using a scintillation counter. Assay
data were analyzed statistically using the Student’s t-test by
comparison of experimental samples or of positive samples (insulin)
with the negative control. To compensate for the multiple t-test, P
< 0.01 was set as the level of significant difference. In the assay,
insulin-treated samples served as positive controls while untreated
samples were used as negative controls. The assay for each com-
pound was performed twice, and each condition was in duplicate.
A compound with the activity statistically significantly higher than
that of the negative control was considered active.
The mixture was dissolved in 100 mL of acetic acid at 70 °C.
After the mixture was cooled to room temperature, a suspension
formed. An amount of 4.3 mL (23.74 mmol) of a 33% solution of
hydrogen bromide in acetic acid was added. After exactly 2 min,
an amount of 90 mL of ice-cold water was added. It was extracted
with dichloromethane (3 × 150 mL). The combined extracts were
washed with ice-cold water (3 × 150 mL) and with 100 mL of
brine. After the mixture was dried over sodium sulfate, the solvent
was evaporated. The residue was purified by column chromatog-
raphy on silica gel using a mixture of toluene and ethyl acetate
(100:8) as the eluent. The product (764 mg, 0.41 mmol, 15%) was
obtained as a clear, colorless, highly viscous oil. [R]25 +47.70°
D
(c 1.00, CH3COCH3); IR (KBr) 1724, 1589, 1499 cm-1; HRMS
(ESI) C118H100O22, m/z calculated M + H+ 1891.6604, measured
M + H+ 1891.6671 (3.5 ppm); 1H NMR (CDCl3) δ 3.68 (1H, dd,
J ) 2.9, 13.2 Hz), 3.78 (1H, dd, J ) 1.4, 13.2 Hz), 4.08 (1H, d, J
) 10.1 Hz), 4.72-5.08 (24 H, m), 5.52 (1H, t, J ) 10.1 Hz), 5.55
(1H, dd, J ) 3.5, 10.1 Hz), 6.31 (1H, t, J ) 10.1 Hz), 6.77 (1H, d,
J ) 3.6 Hz), 7.05-7.42 (68H, m).
1,2,3,4-Tetra-O-galloyl-r-D-glucopyranose (77). A suspension
of 300 mg (0.160 mmol) of 77 and 30 mg (0.29 mmol) of palladium
(10 wt % on activated carbon) in 15 mL of dry THF was stirred at
40 °C under a hydrogen gas atmosphere for 16 h. The reaction
mixture was cooled and filtered through Celite filter-aid, and the
filtrate was evaporated. The residue was crystallized from water.
Compound 77 (81 mg, 64%) was obtained as colorless crystals.
Mp >203 °C (dec); white crystals; [R]25D +142.55° (c 0.55, CH3-
COCH3); IR (KBr) 3400, 1723, 1612, 1539 cm-1; HRMS (ESI)
C34H28O22, m/z calculated M - H+ 787.0994, measured M - H+
787.0992 (0.3 ppm); 1H NMR (CD3COCD3) δ 3.57-3.67 (2H, m),
4.19 (1H, ddd, J ) 2.4, 3.9, 10.0 Hz), 5.31 (1H, dd, J ) 3.6 and
10.3 Hz), 5.49 (1H, t, J ) 10.0 Hz), 6.02 (1H, t, J ) 10.0 Hz),
6.58 (1H, d, J ) 3.6 Hz), 6.87 (2H, s), 6.89 (2H, s), 6.96 (2H, s),
7.14 (2H, s).
6-Chloro-6-deoxy-1,2,3,4-tetra-O-galloyl-r-D-glucopyranose
(80). A suspension of 7.133 g (15.5 mmol) of acid chloride 74 and
0.771 g (3.89 mmol) of 6-chloro-6-deoxy-R-D-glucopyranose48 78
in 150 mL of acetonitrile was stirred at room temperature. Finally,
1.99 g (16.3 mmol) of DMAP was added, and the mixture is stirred
at room temperature. After 18 h, the solvent was evaporated. The
residue was suspended in 100 mL of toluene at 60 °C. A total of
5 g of silica gel was added. After an additional 10 min of stirring,
the mixture was cooled to room temperature and then filtered
through a layer of silica gel (10 g, ∼1.5 cm thick). The filtrate was
evaporated, and the residue was dried in high vacuum. Crude 79
was obtained as a highly viscous, colorless oil.
The intermediate 79 was dissolved in 200 mL of dry THF. A
total of 0.7 g (0.66 mmol) of 10% palladium on carbon was added.
The suspension was stirred vigorously at 40 °C under a hydrogen
gas atmosphere at normal pressure for 18 h. The mixture was cooled
and filtered through Celite, and the filtrate was evaporated. A
slightly pink, highly viscous oil was obtained. It dissolved in 20
mL of water. The mixture was evaporated at <45 °C to remove
residual organic solvent. Once more, the residue was taken up in
20 mL of water and dried by evaporation. Again, the residue was
dissolved in 20 mL of water. The solution was left at room
temperature. After 8 days, the colorless crystals were filtered off,
washed with cold water, and dried in a vacuum. An amount of
1.845 g (58%) of 80 was obtained. [R]24D +111.67° (c 0.12, CH3-
Acknowledgment. We thank Mark McMills for critical
reading of the manuscript and Jaekyung Kim for technical
assistance. This study was supported in part by MetaCor
Pharmaceuticals Inc., Central Ohio Diabetes Association, and
the Edison Program of State of Ohio.
Supporting Information Available: Synthetic procedures and
analytical data for the remaining analogues of 2 and 3. This material
is available free of charge via the Internet at http://pubs.acs.org.
References
(1) Devendra, D.; Liu, E.; Eisenbarth, G. S. Type I diabetes: recent
developments. BMJ 2004, 328, 750-754.
(2) Kahn, B. B.; Flier, J. S. Obesity and insulin resistance. J. Clin. InVest.
2000, 106, 473-481.
(3) Saltiel, A. R.; Kahn, C. R. Insulin signaling and the regulation of
glucose and lipid metabolism. Nature 2001, 414, 799-806.
(4) Moller, D. E. New drug targets for type 2 diabetes and the metabolic
syndrome. Nature 2001, 414, 821-827.
(5) Dominiczak, M. H. Metabolic syndrome. Curr. Opin. Lipidol. 2003,
14, 329-332.
(6) Issa, B. G.; Hanna, F. W. Insulin resistance, the metabolic syndrome
and risk of cardiovascular disease: a complex story. Curr. Opin.
Lipidol. 2003, 14, 405-407.
(7) Kopelman, P. G. Obesity as a medical problem. Nature 2000, 404,
635-643.
(8) Camp, H. S.; Ren, D.; Leff, T. Adipogenesis and fat-cell function in
obesity and diabetes. Trends Mol. Med. 2002, 8, 442-447.
(9) Etgen, G. J.; Oldham, B. A.; Johnson, W. T.; Broderick, C. L.;
Montrose, C. R.; Brozinick, J. T.; Misener, E. A.; Bean, J. S.; Bensch,
W. R.; Brooks, D. A.; Shuker, A. J.; Rito, C. J.; McCarthy, J. R.;
Ardecky, R. J.; Tyhonas, J. S.; Dana, S. L.; Bilakovics, J. M.;
Paterniti, J. R., Jr.; Ogilvie, K. M.; Liu, S.; Kauffman, R. F. A tailored
therapy for the metabolic syndrome: the dual peroxisome proliferator-
activated receptor-[alpha][gamma] agonist LY465608 ameliorates
insulin resistance and diabetic hyperglycemia while improving
cardiovascular risk factors in preclinical models. Diabetes 2002, 51,
1083-1087.
(10) Rieusset, J.; Touri, F.; Michalik, L.; Escher, P.; Desvergne, B.; Niesor,
E.; Wahli, W. A new selective peroxisome proliferators-activated
receptor γ antagonist with antiobesity and antidiabetic activity. Mol.
Endocrinol. 2002, 16, 2628-2644.

PGG and Its Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2837
(11) Rocchi, S.; Pichard, F.; Vamecq, J.; Gelman, L.; Potier, N.; Zeyer,
D.; Dubuquoy, L.; Bac, P.; Champy, M. F.; Plunket, K. D.;
Leesnitzer, L. M.; Blanchard, S. G.; Desreumaux, P.; Moras, D.;
Renaud, J. P.; Auwerx, J. A unique PPAR-γ ligand with potent
insulin-sensitizing yet weak adipogenic activity. Mol. Cell 2001, 8,
737-747.
(12) Kristensen, C.; Anderson, A. S.; Ostergaard, S.; Hansen, P. H.; Brandt,
J. Functional reconstitution of insulin receptor binding site from non-
binding receptor fragments. J. Biol. Chem. 2002, 277, 18340-18345.
(13) Whittaker, J.; Sorensen, H.; Gadsboll, V. L.; Hinrichsen, J. Com-
parison of the functional insulin binding epitopes of the A and B
isoforms of the insulin receptor. J. Biol. Chem. 2002, 277, 47380-
47384.
(14) Ottensmeyer, F. P.; Beniac, D. R.; Luo, R. Z.-T.; Yip, C. C.
Mechanism of transmembrane signaling: insulin binding and the
insulin receptor. Biochemistry 2000, 39, 12103-12112.
(15) Saltiel, A. R.; Pessin, J. E. Insulin signaling pathways in time and
space. Trends Cell Biol. 2002, 12, 65-71.
(16) Zhang, B.; Moller, D. E. New approaches in the treatment of type 2
diabetes. Curr. Opin. Chem. Biol. 2000, 4, 461-467.
(17) Strowski, M. Z.; Li, Z.; Szalkowski, D.; Shen, X.; Guan, X.; Ju¨ttner,
S.; Moller, D. E.; Zhang, B. Small-molecule insulin mimetic reduces
hyperglycemia and obesity in a nongenetic mouse model of type 2
diabetes. Endocrinology 2004, 145, 5259-5268.
(33) Corder, R.; Douthwaite, J. A.; Lees, D. M. Endothelin-1 synthesis
reduced by red wine. Nature 2001, 414, 853-854.
(34) Satoh, K.; Nagai, F.; Ushiyama, K.; Yasuda, I.; Seto, T.; Kano, I.
Inhibition of Na, K,-ATPase by 1,2,3,4,6-penta-O-galloyl-â-D-
glucose, a major constitute of both Mountan cortex and Paeoniae
radix. Biochem. Pharmacol. 1997, 53, 611-614.
(35) Yoshida, T.; Jin, Z. X.; Okuda, T. Taxifolin apioside and davuricin
M1, a hydrolysable tannin from Rosa davurica. Phytochemistry 1989,
28, 2177-2181.
(36) Nishizawa, M.; Yamagishi, T.; Nonaka, G. I.; Nishioka, I.; Ragan,
M. A. Gallotannins of the freshwater green Alga spirogyrasp.
Phytochemstry 1985, 24, 2411-2413.
(37) Kandil, F. E.; El-Sayed, N. H.; Micheal, H. N.; Ishak, M. S.; Mabry,
T. J. Gallotannins and flavonoids from Haematoxylon campechianum.
Phytochemstry 1996, 42, 1243-1245.
(38) Li, Y.; Li, J.; Liu, F.; Liu, X.; Kim, J.; Himmeldirk, K.; Ren, Y.;
Wagner, T. E.; Chen, X. Antidiabetic R-PGG stimulates glucose
transport by activating insulin receptor-mediated signaling pathway.
Biochem. Biophys. Res. Commun. 2005, 336, 430-437.
(39) Li, X. C.; Joshi, A. S.; ElSohly, H. N.; Khan, S. I.; Jacob, M. R.;
Zhang, Z. Z.; Khan, I. A.; Ferreira, D.; Walker, L. A.; Broedel, S.
E.; Raulli, R. E.; Cihlar, R. L. Fatty acid synthase inhibitors from
plants: isolation, structure elucidation, and SAR studies. J. Nat. Prod.
2002, 65, 1909-1914.
(40) Kashiwada, K. Antitumor agents, 129. Tannins and related com-
pounds as selective cytotoxic agents. J. Nat. Prod. 1992, 55, 1033-
1043.
(41) Feldman, K. S.; Sahasrabudhe, K.; Smith, R. S.; Scheuchenzuber,
W. J. Immunostimulation by plant polyphenols: a relationship
between tumor necrosis factor-R production and tannin structure.
Bioorg. Med. Chem. Lett. 1999, 9, 985-990.
(42) Takechi, M.; Tanaka, Y.; Takehara, M.; Nonaka, G. I.; Nishioka, I.
Structure and antiherpetic activity among the tannins. Phytochemistry
1985, 24, 2245-2250.
(43) Yokozava, T.; Chen, C. P.; Dong, E.; Tanaka, T.; Nonaka, G. I.;
Nishioka, I. Study on the inhibitory effect of tannins and flavonoids
against the 1,1-diphenyl-2-picrylhydrazyl radical. Biochem. Pharmcol.
1998, 56, 213-222.
(44) Khanbabaee, K.; Lotzerich, K. Efficient total synthesis of the natural
products 2,3,4,6-tetra-O-galloyl-D-glucopyranose, 1,2,3,4,6-penta-O-
galloyl-â-D-glucopyranose and the unnatural 1,2,3,4,6-penta-O-
galloyl-R-D-glucopyranose. Tetrahedron 1997, 53, 10725-10732.
(45) Neises, S.; Steglich, W. Simple method for the esterification of
carboxylic acids. Angew. Chem., Int. Ed. Engl. 1978, 17, 522-524.
(46) Feldman, K. S.; Sambandam, A.; Lemon, S. T.; Nicewonger, R. B.;
Long, G. S.; Battaglia, D. F.; Ensel, S. M.; Laci, M. A. Binding
affinities of gallotannin analogs with bovine serum albumin: rami-
fications for polyphenol-protein molecular recognition. Phytochem-
istry 1999, 51, 867-872.
(47) Whistler, R. L.; Doner, L. W.; Kosik, M. 1,2,3,4-Tetra-O-acetyl-â-
D-glucopyranose and Methyl 2,3,4-Tri-O-acetyl-â-D-glucopyranoside.
In Methods in Carbohydrate Chemistry; Whistler, R. L., BeMiller,
J. N., Eds.; Academic Press: New York, 1972; Vol. VI, pp 411-
412.
(18) Zhang, B.; Salituro, G.; Szalkowski, D.; Li, Z.; Zhang, Y.; Royo, I.;
Vilella, D.; Diez, M. T.; Pelaez, F.; Ruby, C.; Kendall, R. L.; Mao,
X.; Griffin, P.; Calaycay, J.; Zierath, J. R.; Heck, J. V.; Smith, R.
G.; Moller, D. E. Discovery of a small molecule insulin mimetic
with antidiabetic activity in mice. Science 1999, 284, 974-977.
(19) Zamanini, A.; Newson, R. B.; Maisey, M.; Feher, M. D. Injection
related anxiety in insulin treated diabetes. Diabetes Res. Clin. Pract.
1999, 46, 239-246.
(20) Amiel, S. A.; Alberti, K. G. Inhaled insulin. BMJ 2004, 328, 1215-
1216.
(21) Wigley, F. M.; Londono, J. H.; Wood, S. H.; Shipp, J. C.; Waldman,
R. H. Insulin across respiratory mucosae by aerosol delivery. Diabetes
1991, 20, 552-557.
(22) Liu, F.; Kim, J.; Li, Y.; Liu, X.; Li, J.; Chen, X. An extract of
Lagerstroemia speciosa L has insulin-like glucose uptake-stimulatory
and adipocyte differentiation-inhibitory activities in 3T3-L1 cells. J.
Nutr. 2001, 131, 2242-2247.
(23) Kakuda, T.; Sakane, I.; Takihara, T.; Ozaki, Y.; Takeuchi, H.;
Kuroyanagi, M. Hypoglycemic effect of extracts from Lagerstroemia
speciosa L. leaves in genetically diabetic KK-AY mice. Biosci.
Biotechnol. Biochem. 1996, 60, 204-208.
(24) Suzuki, Y.; Unno, T.; Ushitani, M.; Hayashi, K.; Kakuda, T.
Antiobesity activity of extracts from Lagerstroemia speciosa L. leaves
on female KK-AY mice. J. Nutr. Sci. Vitaminol. 1999, 45, 791-
795.
(25) Liu, X. Q.; Kim, J. K.; Li, Y. S.; Li, J.; Liu, F.; Chen, X. Tannic
acid stimulates glucose transport and inhibits adipocyte differentiation
in 3T3-L1 cells. J. Nutr. 2005, 135, 165-171.
(26) Hayashi, T.; Maruyama, H.; Kasai, R.; Hattori, K.; Takasuga, S.;
Hazeki, O.; Yamasaki, K.; Tanaka, T. Ellagitannins from lagerstro-
emia speciosa as activators of glucose transport in fat cells. Planta
Med. 2002, 68, 173-175.
(27) Okuda, T.; Yoshida, T.; Hatano, T. Hydrolyzable tannins and related
polyphenols. Fortschr. Chem. Org. Naturst. 1995, 66, 1-117.
(28) Hagerman, A. E.; Carlson, D. M. Biological responses to dietary
tannins and other polyphenols. Recent Res. DeV. Agric. Food Chem.
1998, 2, 689-704.
(29) Hagerman, A. E.; Riedl, K. M.; Jones, J. A.; Sovik, K. N.; Ritchard,
N. T.; Hartzfeld, P. W.; Riechel, T. L. High molecular weight plant
polyphenolics (tannins) as biological antioxidants. J. Agric. Food
Chem. 1998, 46, 1887-1892.
(48) Evans, M. E.; Parrish, F. W. 6-Cloro-6-deoxy-R-D-glucose. In
Methods in Carbohydrate Chemistry; Whistler, R. L., BeMiller, J.
N., Eds.; Academic Press: New York, 1972; Vol. VI, pp 193-196.
(49) Sakoda, H.; Ogihara, T.; Anai, M.; Makoto, F.; Inukai, K.; Katagiri,
H.; Fukushima, Y.; Onishi, Y.; Ono, H.; Yazaki, Y.; Kikuchi, M.;
Oka, Y.; Asano, T. No correlation of plasma cell overexpression with
insulin resistance in diabetic rats and 3T3-L1 adipocytes. Diabetes
1999, 48, 1365-1371.
(50) Herreros, G. A.; Birnbaum, M. J. The acquisition of increased insulin-
responsive hexose transport in 3T3-L1 adipocytes correlates with
expression of novel transporter gene. J. Biol. Chem. 1989, 264,
19994-19999.
(51) Clinton, R. O.; Geissman, T. A. Gallaldehyde tribenzyl ether. J. Org.
Chem. 1943, 65, 85-87.
(30) Oh, G. S.; Pae, H. O.; Oh, H.; Hong, S. G.; Kim, I. K.; Chai, K. Y.;
Yun, Y. G.; Kwon, T. O.; Chung, H. T. In vitro anti-proliferative
effect of 1,2,3,4,6-penta-O-galloyl-beta-D-glucose on human hepa-
tocellular carcinoma cell line, SK-HEP-1 cells. Cancer Lett. 2001,
74, 17-24.
(31) Cowan, M. M. Plant products as antimicrobial agents. Clin. Microbiol.
ReV. 1999, 12, 564-582.
(32) Gin, H.; Rigalleau, V.; Caubet, O.; Masquelier, J.; Aubertin, J. Effects
of red wine, tannic acid, or ethanol on glucose tolerance in non-
insulin-dependent diabetic patients and on starch digestibility in vitro.
Metabolism 1999, 48, 1179-1183.
(52) Schmidt, O. T.; Schach, A. Natural tannins. VIII. Synthesis of
3-galloylglucose, 6-galloylglucose and 3,6-digalloylglucose. Liebigs
Ann. Chem. 1951, 571, 29-41.
JM060087K