Synthesis of gallotannins

Article abstract of DOI:10.1016/S0008-6215(01)00236-1

As a contribution to the synthesis of gallotannins, four O-galloyl-D-glucoses (3-O-, 6-O-, 3,6-di-O-, 3,4,6-tri-O-galloyl-D-glucose) have been prepared by the reaction of tri-O-benzylgalloyl chloride and partially protected glucose derivatives (1,2-O-, an

Full text of DOI:10.1016/S0008-6215(01)00236-1

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Carbohydrate Research 335 (2001) 245–250
Synthesis of gallotannins
Qiang He, Bi Shi,* Kai Yao, Yi Luo, Zhihong Ma
The Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan Uni6ersity,
Chengdu 610065, P.R. China
Received 29 May 2001; accepted 18 August 2001
Abstract
As a contribution to the synthesis of gallotannins, four O-galloyl-
loyl- -glucose) have been prepared by the reaction of tri-O-benzylgalloyl chloride and partially protected glucose
derivatives (1,2-O-, and 1,2:5,6-di-O-isopropylidene-a- -glucofuranose), followed successively by catalytic debenzyla-
D-glucoses (3-O-, 6-O-, 3,6-di-O-, 3,4,6-tri-O-gal-
D
D
tion (Pd–C) and controlled acid hydrolysis. Their structures were established from their behavior on TLC and from
1
their H and 13C NMR spectra. © 2001 Published by Elsevier Science Ltd.
Keywords: Gallotannin; 3-O-Galloyl-D-glucose; 6-O-Galloyl-D-glucose; 3,6-Di-O- galloyl-D-glucose; 3,4,6-Tri-O-galloyl-D-glucose
the glucose core. Thus, it has been shown that
an increase in the number of galloyl groups
enhances the association of proteins and gal-
loylglucoses,2 and also increases the ability of
gallotannins to scavenge 1,1-diphenyl-2-picryl-
hydrazyl (DPPH) radicals.3 The same seems to
pertain to interaction with biological entities
and enzymes, and the inhibitory effect of gal-
lotannins on glucosyltransferase from Strepto-
coccus mutans follows the sequence,
1. Introduction
O-Galloyl- -glucoses (see Scheme 1) occur
D
naturally in some plants. Such ‘gallotannins’
exhibit various useful properties.1 For exam-
ple, these compounds serve as radical
scavengers and antioxidants and figure impor-
tantly in protein precipitation and enzyme in-
hibition. There are several reports that these
properties are dependent largely on the num-
ber of galloyl groups and their positions on
PGG\TeGG\TriGG\DiGG4
The activity is dependent on other factors
such as the position of the galloyl groups.5
The importance of the placement of the gal-
loyl groups on the glucose core was indicated
by a study of the inhibitory effects of 1,2,6-,
1,3,6- and 3,4,6-TriGG on lipid peroxidation
in mitochondria and microsomes of liver
where the greatest antioxidative effect was
exhibited by 1,3,6-TriGG and the least effect
by 3,4,6-TriGG.6 More recently, it was shown
that 1,2,3,6-TeGG had a strong effect on the
affinity of gallotannins to galloyltransferase,
whereas 1,3,4,6-TeGG was inactive.7
Scheme 1. The model structure of gallotannins [MoGG, one
of R1–R5 is a galloyl group (G); DiGG, two of R1–R5 are G;
TriGG, three of R1–R5 are G; TeGG, four of R1–R5 are G;
PGG, R1–R5 are G].
* Corresponding author. Tel.: +86-28-5405508; fax: +86-
28-5405237.
E-mail address: shibi@pridns.scu.edu.cn (B. Shi).
0008-6215/01/$ - see front matter © 2001 Published by Elsevier Science Ltd.
PII: S0008-6215(01)00236-1

246
Q. He et al. / Carbohydrate Research 335 (2001) 245–250
Scheme 2. Synthetic route for the compounds 3, 7, 8 and 9. Reagents and conditions: (i) tri-O-benzylgalloyl chloride, pyridine,
CHCl3, 60 °C, 11 h (7, 8 and 9), 8 h (3); (ii) Pd–C, H2, THF, 7 h (7, 8 and 9), 3 h (3); (iii) HCl, H2O, 90 °C, 50 min.
More recently, O-galloyl-
D
-glucoses are
The first exploration was designed to intro-
duce one galloyl group into a specific site of
glucose. For this purpose, 1,2:5,6-di-O-iso-
mainly isolated from hydrolysates of extracts
from sources like Chinese gall nuts and Turk-
ish gall,8 but only few natural galloylated
furanoses have been isolated.9 Dependence on
natural materials in short supply, and
difficulties in the isolation and purification
have limited the research work and the practi-
cal utilization of gallotannins. Thus chemical
synthesis is desirable, and some methods have
been developed for the synthesis of gallotan-
nins.10–12 A programme to develop such syn-
thesis with the galloyl groups located at
propylidene-
-glucofuranose14 was condensed
D
in equimolar amount with tri-O-benzylgalloyl
chloride in pyridine–chloroform to afford
compound 1. Without purification, 1 was hy-
drogenated over 10% Pd–C in tetra-
hydrofuran to cleave the benzyl groups to give
compound 2, which was purified by chro-
matography on a column of Sephadex LH-20.
The compound gave a positive test for a
polyphenol with potassium ferricyanide–ferric
chloride solution. On partial acid hydrolysis (1
M HCl, 90 °C, 50 min) the O-isopropylidene
specified sites in
D
-glucose is being under-
taken, and as part of this work the prepara-
tion of four O-galloyl- -glucoses is reported
herein.
D
groups were cleaved to afford 3-O-galloyl- -
D
glucose (3) as a 2:1 mixture of a and b
1
anomers as shown by H NMR spectroscopy.
1,2-O-Isopropylidene-a-
-glucofuranose,15
D
2. Results and discussion
having three hydroxyl groups (3,5,6-) reactive
for esterifying, was used to explore the
method of introducing additional galloyl
groups to predicted sites of glucose based on
the same procedures described for 3. Reaction
of tri-O-benzylgalloyl chloride and 1,2-O-iso-
Synthetic route.—The phenolic hydroxyl
groups of gallic acid were protected by benzy-
lation. Reaction of tri-O-benzylgalloyl
chloride13 with
D
-glucose in pyridine–chloro-
form and debenzylation of the product gave a
mixture (TLC) showing no selectivity for the
galloylation. Therefore, O-isopropylidenation
of glucose was employed to protect a number
of the hydroxyl groups (Scheme 2).
propylidene-a- -glucofuranose in a molar ra-
D
tio of 3:1 and debenzylation of the product
afforded compounds 4, 5 and 6 in yields of
40.8, 30.2 and 11.8%, respectively, after purifi-

Q. He et al. / Carbohydrate Research 335 (2001) 245–250
247
well-known proof for a and b anomers in a
glucopyranose spectrum. The ratio of the a
and b anomers as determined by the peak
areas was 2:1, which is in agreement with the
TLC analysis. In the 13C NMR spectrum of
compound 3 [(75 MHz, CD3COCD3) l 63.7
(d, a-C-6), 64.3 (d, b-C-6), 70.8, 71.9, 73.2,
73.8, 74, 74.7, 76 (C-2, C-3, C-4, C-5), 93.4 (d,
a-C-1), 96.6 (d, b-C-1), 110.2 (d, galloyl C-2,
C-6), 121.3 (s, galloyl C-1), 138.6 (s, galloyl
C-4), 145.8 (s, galloyl C-3, C-5), 166.9 (s,
ꢀCOOꢀ)], CH3 isopropylidene peaks disap-
peared whilst C-1 shifted from 104.3 to 93.4–
96.6 compared to that in compound 2, which
is further evidence of the reversion of 2 to 3.
The physicochemical and spectral data of 3
were identical with those of the naturally oc-
curring sample.16
cation on Sephadex LH-20. The yields indi-
cated that the C-6 hydroxyl group of 1,2-O-
isopropylidene-a- -glucofuranose has the
D
highest esterification activity, while the C-5
hydroxyl group has the lowest. On partial
hydrolysis, the furanose ring of 4, 5 and 6 was
reverted to the pyranose form and corre-
spondingly afforded the O-galloyl- -glucoses
D
7, 8 and 9. For compound 6, the reversion
(6“9) occurred with the migration of one
galloyl group from the 5-O to 4-O-position of
glucose. Like 3, compounds 7, 8 and 9 all
occurred as a mixture of a and b anomers in a
ratio of 3:2 as determined by 1H NMR
spectroscopy.
Characterization of compounds 2–9 — Com-
1
pound 2. The H NMR spectrum (300 MHz,
CDCl3) of compound 2 indicated the presence
of one galloyl group [l 7.16 (s, 2 H)] and two
O-isopropylidene groups [l 1.1–1.4 (4 s, 12
H, 4×CH3), 3.5 (t, 1 H, J2,3 3.3 Hz, H-3),
4.1–4.5 (5 H, H-2,4,5,6,6%), 5.88 (d, 1 H, J1,2
3.7 Hz, H-1)] in the molecule. Furthermore, as
H-3 was shown to be downfield compared to
1
Compound 4. The H NMR spectrum (300
MHz, CDCl3) of compound 4 indicated the
presence of one galloyl group [l 7.10 (s, 2 H)]
and one isopropylidene group [l 1.31–1.48 (2
s, 6 H, 2×CH3), 3.2 (t, 1 H, J2,3 3 Hz, H-3),
4–4.32 (m, 2 H, H-4,5), 4.38 (t, 1 H, J1,2 3.7
Hz, H-2), 4.41–4.56 (2 H, H-6,6%), 5.90 (d, 1
H, H-1)] in the molecule. Furthermore, as H-6
and H-6% are shifted downfield compared to
that of 1,2:5,6-di-O-isopropylidene-a- -gluco-
D
fucanose [1H NMR spectrum (300 MHz,
CDCl3) l 1.31–1.40 (4 s, 12 H, CH3-iso), 2.91
(dd, 1 H, H-3), 3.93–4.52 (5 H, H-2,4,5,6,6%),
5.88–5.93 (d, 1 H, H-1)] due to the influence
of the galloyl group, one could conclude that
the glucofuranose moiety is acylated at C-3.
The structure of 3-O-galloyl-1,2:5,6-di-O-iso-
those resonances of 1,2-O-isopropylidene-a- -
D
glucofuranose [1H NMR spectrum (300 MHz,
CDCl3) l 1.29–1.40 (2 s, 6 H, 2×CH3), 3.0 (t,
1 H, H-3), 3.4–3.6 (dd, 2 H, H-6,6%), 4.04 (t, 1
H, H-4), 4.31 (t, 1 H, H-5), 4.43 (t, 1 H, H-2),
5.90 (d, 1 H, H-1)] due to the influence of the
galloyl group, one could conclude that the
glucofuranose moiety is acylated at C-6. The
structure of 6-O-galloyl-1,2-O-isopropylidene-
propylidene-a- -glucofuranose (2) was further
D
supported by its 13C NMR spectrum [(75
MHz, CDCl3) l 25.2, 26.3, 26.5, 26.6 (4×
CH3), 64.3 (C-6), 68.9 (C-5), 78.8 (C-4), 81.1,
82.5 (C-2, C-3), 104.3 (C-1), 110 (2 C, galloyl
C-2, C-6), 111.9, 112.8 (2 C-iso), 121.1 (galloyl
C-1), 138.5 (galloyl C-4), 145.9 (2 C, galloyl
C-3,C-5), 166.9 (ꢀCOOꢀ)].
a- -glucofuranose (4) was further confirmed
D
by its 13C NMR spectrum [(75 MHz, CDCl3)
l 26.1, 26.6 (2 C, CH3-iso), 66 (C-6), 69.5
(C-5), 79.5, 82.7, 83.5 (C-2, C-3, C-4), 105
(C-1), 109.8 (2 C, galloyl C-2, C-6), 112.1
(C-iso), 121 (galloyl C-1), 138.5 (galloyl C-4),
144.9 (2 C, galloyl C-3,C-5), 167.2 (ꢀCOOꢀ)].
Compound 3. That the glucose ring in com-
pound 3 had reverted to the a, b pyranose
1
form was shown by TLC and the H NMR
spectrum [(300 MHz, CD3COCD3) l 3.55–
4.52 (m, 5 H, H-2,4,5,6,6%), 4.74 (d, 0.33 H,
J1,2 8 Hz, b anomer, H-1), 5.21 (t, 0.67 H, J2,3
Compound 7. The 6-O-galloyl- -glucose
D
structure with a and b anomers of compound
1
7 was confirmed by the H NMR spectrum
9 Hz, a anomer, H-3), 5.30 (d, 0.67 H, J1,2
3
[(300 MHz, CD3COCD3) l 3.12–4.41 (m, 4 H,
H-2,3,4,5), 4.50–4.63 (m, 2 H, H-6, 6%), 4.86
(d, 0.4 H, J1,2 8 Hz, b anomer, H-1), 5.20 (d,
0.6 H, J1,2 3 Hz, a anomer, H-1), 7.13 (s, 2 H,
galloyl)] and the 13C NMR spectrum [(75
Hz, a anomer, H-1), 5.50 (t, 0.33 H, b
anomer, H-3), 7.25 (s, 2 H, galloyl). The pres-
ence of both a smaller coupling constant (J1,2
3 Hz) and a larger one (J1,2 8 Hz) of H-1 is a

248
Q. He et al. / Carbohydrate Research 335 (2001) 245–250
C-3, C-5), 166.6, 166.9 (ꢀCOOꢀ) based on
elucidations similar to those used for com-
pound 3. The ratio of the a and b anomers, as
determined by peak areas was 3:2, which is in
agreement with the TLC analysis. The behav-
MHz, CD3COCD3) l 64.5 (C-6), 70.2, 70.9,
71.1, 73.0, 74.1, 74.5, 75.5, 77.0 (C-2, C-3,
C-4, C-5), 93.2 (d, a-C-1), 96.9 (d, b-C-1),
109.7 (galloyl C-2, C-6), 121 (s, galloyl C-1),
138.7 (s, galloyl C-4), 145.6 (galloyl C-3, C-5),
167.1 (s, ꢀCOOꢀ)] based on elucidations simi-
lar to those used for compound 3. The ratio of
the a and b anomers as determined by peak
areas was 3:2, which is in agreement with the
TLC analysis. The behavior of 7 was identical
ior of 8 is identical to 3,6-di-O-galloyl- -glu-
D
cose obtained as a hydrolysate of extracts
from Chinese gall nuts.18
1
Compound 6. The H NMR spectrum (300
MHz, CDCl3) of compound 6 indicated the
presence of three galloyl groups [l 7.08 (s, 2
H), 7.14 (s, 2 H), 7.17 (s, 2 H)] and one
isopropylidene group [l 1.30–1.47 (2 s, 6 H,
CH3-iso), 4.21 (t, 1 H, J4,5 8 Hz, H-4), 4.43 (t,
1 H, J1,2 4 Hz, H-2), 4.56–4.85 (m, 3 H,
H-5,6,6%), 5.32 (t, 1 H, J2,3 3.7 Hz, H-3), 5.80
(d, 1 H, H-1)] in the molecule. Furthermore,
as H-6, H-6%, H-5 and H-3 are shifted
downfield compared to the corresponding res-
to 6-O-galloyl- -glucose by direct comparison
D
with the report by Nonaka and Nishioka.17
1
Compound 5. The H NMR spectrum (300
MHz, CDCl3) of compound 5 indicated the
presence of two galloyl groups [l 7.10 (s, 2 H),
7.23 (s, 2 H)] and one O-isopropylidene group
[l 1.33–1.45 (2 s, 6 H, 2×CH3), 4.20–4.34
(m, 2 H, H-4,5), 4.42 (t, 1 H, J2,3 2.9 Hz, H-2),
4.45–4.61 (2 H, H-6,6%), 5.27 (t, 1 H, J3,4 3.8
Hz, H-3), 5.88 (d, 1 H, J1,2 4 Hz, H-1)] in the
molecule. Furthermore, as H-6, H-6% and H-3
are shifted downfield compared to those reso-
onances of 1,2-O-isopropylidene-a- -gluco-
D
furanose as above due to the influence of the
galloyl group, one can conclude that the glu-
cofuranose moiety is acylated at C-6, C-5 and
C-3. The 3,5,6-tri-O-galloyl-1,2-O-isopropyli-
nances of 1,2-O-isopropylidene-a- -gluco-
D
furanose as above due to the influence of the
galloyl group, one can conclude that the glu-
cofuranose moiety is acylated at C-6 and C-3.
The structure of 3,6-di-O-galloyl-1,2-O-iso-
dene-a- -glucofuranose structure of com-
D
pound 6 was further confirmed by its 13C
NMR spectrum [(75 MHz, CDCl3) l 26.1,
26.2 (CH3-iso), 67.2 (C-6), 70 (C-5), 79.8 (C-
4), 83.5 (C-2), 85.1 (C-3), 105.7 (C-1), 110.1,
110.2 (galloyl C-2, C-6), 112.7 (C-iso), 121.4,
121.5 (galloyl C-1), 138.3, 138.5, 138.7 (galloyl
C-4), 145.5 (galloyl C-3, C-5), 165.6, 166.5
(ꢀCOOꢀ)].
propylidene-a- -glucofuranose (5) was further
D
confirmed by its 13C NMR spectrum [(75
MHz, CDCl3) l 26.1, 26.3 (CH3-iso), 67.1
(C-6), 69.3 (C-5), 79.1 (C-4), 83.3, 84.4 (C-2,
C-3), 105.5 (C-1), 110, 110.2 (galloyl C-2,
C-6), 111.9 (C-iso), 121.2, 121.5 (galloyl C-1),
138.4, 138.6 (galloyl C-4), 145.6, 145.7 (galloyl
C-3, C-5), 166.7–166.8 (ꢀCOOꢀ)].
Compound 9. The 3,4,6-tri-O-galloyl- -glu-
D
cose structure with a and b anomers of com-
1
Compound 8. The 3,6-di-O-galloyl-
D
-glu-
pound 9 was confirmed by the H NMR
cose structure with a and b anomers of com-
pound 8 was confirmed by its 1H NMR
spectrum [(300 MHz, 9:1 CD3COCD3 –D2O) l
3.45 (dd, 0.4 H, J1,2 8, J2,3 9 Hz, b anomer,
H-2), 3.61 (dd, 0.6 H, J1,2 4 Hz, a anomer,
H-2), 3.63–4.28 (m, 2 H, H-4,5), 4.4–4.73 (m,
2 H, H-6,6%), 4.77 (d, 0.4 H, b anomer, H-1),
5.22 (d, 0.6 H, a anomer, H-1), 5.25–5.34 (m,
1 H, H-3), 7.15–7.16 (m, 4 H, galloyl)] and
the 13C NMR spectrum [(75 MHz, 9:1
CD3COCD3–D2O) l 63.9 (C-6), 70.7, 71.0,
72.9, 73.3, 74.0, 75.8 (C-2, C-3, C-4, C-5), 93
(d, a-C-1), 96.3 (d, b-C-1), 110.0, 110.2 (gal-
loyl C-2, C-6), 121.3, 121.5 (galloyl C-1),
138.2, 138.5 (galloyl C-4), 145.8 (d, galloyl
spectrum [(300 MHz, 9:1 CD3COCD3–D2O) l
3.57 (dd, 0.4 H, J1,2 8, J2,3 9 Hz, b anomer,
H-2), 3.69 (dd, 0.6 H, J1,2 3 Hz, a anomer,
H-2), 4.39–4.76 (m, 3 H, H-5,6,6%), 4.84 (d, 0.4
H, b anomer, H-1), 5.43 (d, 0.6 H, a anomer,
H-1), 5.48–5.60 (m, 1 H, H-1), 5.62 (t, 0.4 H,
b anomer, H-3), 5.75 (dd, 0.6 H, J3,4 8 Hz, a
anomer, H-3), 7.05–7.21 (6 H, galloyl)] and
the 13C NMR spectrum [(75 MHz, 9:1
CD3COCD3–D2O) l 63.1 (C-6), 71.5, 72.4,
72.6, 73.3, 73.6, 75.0, 75.4, 76.0 (C-2, C-3,
C-4, C-5), 93.1 (d, a-C-1), 95.5 (d, b-C-1),
110.1, 110.3 (galloyl C-2, C-6), 120.7, 121.2,
121.9 (galloyl C-1), 138.2, 138.8 (galloyl C-4),
145.9 (t, galloyl C-3, C-5), 165.5, 166.1, 166.6

Q. He et al. / Carbohydrate Research 335 (2001) 245–250
249
(ꢀCOOꢀ)] based on the analogous elucidations
as for compound 3. This means that one
galloyl group had migrated from the 5-O to
4-O-position of glucose when the furanose
ring of compound 6 reverted to the pyranose
form of compound 9. The ratio of the a and b
anomers, as determined by peak areas, was
3:2, which is in agreement with the TLC
analysis.
h, and the mixture was then filtered, and the
catalyst was washed with a small amount of
THF. The filtrate was concentrated, and the
crude product was purified on a Sephadex
LH-20 column (120×2 cm i.d.). Based on
TLC analysis, purified compound 2 (1.15 g,
2.8 mmol, 63.3%) was obtained as a white
solid: Rf 0.70 (A), Rf 0.24 (B). Anal. Calcd for
C19H24O10: C, 55.32; H, 5.87. Found: C, 55.37;
H, 5.85.
O-Galloyl-1,2-O-isopropylidene-h- -gluco-
D
furanoses (4, 5, and 6).—Based on the route to
synthesize compound 2, a mixture of tri-O-
benzylgalloyl chloride (6.8 g, 15 mmol), 1,2-
3. Experimental
General methods.—Solutions were concen-
trated on a rotary evaporator under reduced
pressure at 30–35 °C. For quantitative analy-
sis, samples were dried at 60 °C (5 mmHg) to
constant weight. The TLC analyses were car-
ried out on DC: Alufolien Cellulose F plates
that were developed at 1292 °C. Samples
were separated into two dimensions with sol-
vent systems: (A) 6:94 AcOH–water; and (B)
14:1:5 n-butanol–AcOH–water. Detection
was first by UV light (260–300 nm) as fluores-
cent spots, and then a color was developed by
spraying with a solution of 1:1 0.1% ferric
O-isopropylidene-a- -glucofuranose (1.1 g, 5
D
mmol), pyridine (6 mL) and CHCl3 (60 mL)
was stirred at 60 °C for 11 h. The product was
debenzylated (7 h) as in the previous example,
and the filtrate was concentrated. Separation
of 2.6 g of the residue by column chromatog-
raphy at a flow rate of 1 mL/min afforded the
following fractions: (1) 400 mL, discarded; (2)
Tubes 12–25, compound 4, 760 mg (white
solid, 40.8%): Rf 0.72 (A), Rf 0.30 (B). Anal.
Calcd for C16H20O10: C, 51.60; H, 5.42.
Found: C, 51.39; H, 5.43; (3) Tubes 38–43,
compound 5, 791 mg (pale-yellow solid,
30.2%): Rf 0.25 (A), Rf 0.36 (B). Anal. Calcd
for C23H24O14: C, 52.66; H, 4.61. Found: C,
52.55; H, 4.60; (4) Tubes 46–52, compound 6,
402 mg (pale-yellow solid, 11.8%): Rf 0.11 (A),
Rf 0.42 (B). Anal. Calcd for C30H28O18: C,
53.24; H, 4.17. Found: C, 53.40; H, 4.18; (5)
1
chloride–0.1% potassium ferricyanide. H and
13C NMR spectra were recorded using Bruker
AC 300 and AM 300 spectrometers. Spin-de-
coupling experiments were used when neces-
sary for assigning the position of hydrogen
atoms. The purified samples were obtained by
chromatography on a column (120×2 cm
i.d.) of Sephadex LH-20 using 9:1 EtOH–wa-
ter as eluant. Elemental analyses were per-
formed on a Carlo–Erba EA 1108 instrument.
Column
residue,
566
mg,
unknown
composition.
O-Galloyl-
D
-glucoses (3, 7, 8, and 9).—O-
Galloyl-a- -glucofuranoses (2, 4, 5, and 6)
D
3-O-Galloyl-1,2:5,6-di-O-isopropylidene-h- -
D
were each separately stirred in 1 M HCl at
90 °C for 50 min. After evaporation of the
solvent, each residue was purified by Sephadex
LH-20 column chromatography (120×2 cm
glucofuranose (2).—A mixture of tri-O-ben-
zylgalloyl chloride (2.0 g, 4.4 mmol),
1,2:5,6-di-O-isopropylidene-a- -glucofuranose
D
(1.15 g, 4.4 mmol), pyridine (5 mL) and
CHCl3 (50 mL) was stirred, and the pale-yel-
low solution was heated to 60 °C and allowed
to react for 8 h during which time pyridine
hydrochloride was precipitated and the solu-
tion darkened. The cooled mixture was
filtered, and the filtrate was concentrated,
washed with water, and dried to a white pow-
der. This product was reduced by H2 in THF
(50 mL) at rt using 10% Pd–C (0.3 g) as the
catalyst. Hydrogen absorption ceased after 3
i.d.). The purified O-galloyl- -glucose deriva-
D
tives were collected based on TLC analyses.
Traces of gallic acid and glucose could be
detected by TLC on further hydrolysis.
3-O-Galloyl-
light brown solid, yield 81%: Rf 0.76 (A), Rf
0.20 (B). Anal. Calcd for C13H16O10 H2O: C,
44.56; H, 5.18. Found: C, 44.66; H, 5.15;
6-O-galloyl- -glucose (7) was isolated as a
light brown solid, yield 71.7%: Rf 0.75 (A), Rf
D
-glucose (3) was isolated as a
·
D

250
Q. He et al. / Carbohydrate Research 335 (2001) 245–250
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0.26 (B). Anal. Calcd for C13H16O10
44.56; H, 5.18. Found: C, 44.48; H, 5.14;
3,6-Di-O-galloyl-
·
H2O: C,
D
-glucose (8) was isolated as
a buff amorphous solid, yield 66.3%: Rf 0.28
(A), Rf 0.35 (B), lit.18 Rf 0.28 (A), Rf 0.34 (B).
Anal. Calcd for C20H20O14
4.42. Found: C, 47.86; H, 4.43; 3,4,6-Tri-O-
galloyl- -glucose (9) was isolated as a buff
solid, yield 49.5%: Rf 0.13 (A), Rf 0.40 (B).
Anal. Calcd for C27H24O18 0.5 H2O: C, 50.22;
·
H2O: C, 47.80; H,
D
·
H, 3.91. Found: C, 50.27; H, 3.89; All the Rf
data are the average values of two very close-
running zones (a and b anomers).
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Acknowledgements
We thank the Natural Science Foundation
of China for the financial support of this work
(29872025).
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