Facile synthesis of three bidesmosidic oleanolic acid saponins with strong inhibitory activity on pancreatic lipase

Article abstract of DOI:10.1016/j.carres.2009.04.024

The first synthesis of scabiosaponins E (1), F (2), and G (3), three new oleanolic acid saponins with strong inhibitory activity on pancreatic lipase isolated from the Chinese traditional medicinal herb Scabiosa tschiliensis, was efficiently achieved in an one-pot strategy under the combined use of glycosyl trichloroacetimidates and p-toluene 1-thioglycosides (STol) as donors.

Full text of DOI:10.1016/j.carres.2009.04.024

Carbohydrate Research 344 (2009) 1167–1174
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Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Facile synthesis of three bidesmosidic oleanolic acid saponins with strong
inhibitory activity on pancreatic lipase
*
Tiantian Guo, Qingchao Liu, Peng Wang, Lei Zhang, Wei Zhang, Yingxia Li
Key Laboratory of Marine Drugs, The Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The first synthesis of scabiosaponins E (1), F (2), and G (3), three new oleanolic acid saponins with strong
inhibitory activity on pancreatic lipase isolated from the Chinese traditional medicinal herb Scabiosa
tschiliensis, was efficiently achieved in an one-pot strategy under the combined use of glycosyl trichloro-
acetimidates and p-toluene 1-thioglycosides (STol) as donors.
Received 24 March 2009
Received in revised form 13 April 2009
Accepted 21 April 2009
Available online 24 April 2009
Ó 2009 Published by Elsevier Ltd.
Keywords:
Scabiosaponins
Bidesmosidic oleanolic acid saponins
One-pot sequential glycosylation
Trichloroacetimidates
p-Toluenethioglycosides
1. Introduction
Herein we report the first, convenient synthesis of the three bides-
mosidic oleanolic acid saponins, which overcomes the problem of
Saponins, glycosides of steroids and triterpenes, which are
widely distributed in plants and in some marine organisms,1,2 pos-
sess a broad spectrum of interesting biomedical activities, includ-
ing antitumor, anti-HIV, anti-inflammatory, antifungal, ion
channel-blocking, and immune-stimulating activities.3–5 Besides,
it has been reported that oleanane-type, lupine-type, and damma-
rane-type triterpenoid saponins exhibit inhibitory activity upon
pancreatic lipase and prevent the increase of body weight because
of a high-fat diet.6–8 Obesity is widely recognized as a major public
health problem, which can result in cardiovascular-related dis-
eases such as type II diabetes, hypertension, hyperlipidemia, and
coronary heart disease (CHD).9 The application of a pancreatic li-
pase inhibitor has been considered as an effective therapeutic
means for diet-induced obesity in humans. Orlistat, first approved
in 1998, is a pancreatic lipase inhibitor that suppresses the devel-
opment of obesity and hyperlipidemia.10,11
Scabiosaponins E–G (1–3), three new bidesmosidic oleanolic acid
saponins (Fig. 1), were isolated from Sacbiosa tschiliensis Grun. (Dip-
sacaceae), aperennialherbusedforthetreatmentof headache, fever,
cough, and jaundice in Inner Mongolia, and they showed remarkable
inhibition activity against pancreatic lipase.12 The formidable task of
isolatingthese compoundsturnsouttobe a great obstacle forfurther
pharmacological research, so it is worthwhile to exploit an efficient
approach to afford this kind of saponin for further SAR investigation.
the scarceness of this type of saponins in nature.
2. Results and discussion
So far few facile synthetic approaches toward bidesmosidic ole-
anane-type saponins bearing the distinctive disaccharide, the a-L-
O
O
O
1'
OH
O
O
HO
HO
O
1'''
O
HO
HO
O
1''''
1''
O
HO
OH
HO
HO
RO
OH
HO
Scabiosaponin E (1): R = Xyl
Scabiosaponin F (2): R = Glc
Scabiosaponin G (3): R = Glc (1
4) Glc
* Corresponding author. Tel.: +86 532 82032150; fax: +86 532 82033054.
E-mail address: liyx417@ouc.edu.cn (Y. Li).
Figure 1. Structures of scabiosaponins E–G (1–3).
0008-6215/$ - see front matter Ó 2009 Published by Elsevier Ltd.
doi:10.1016/j.carres.2009.04.024

1168
T. Guo et al. / Carbohydrate Research 344 (2009) 1167–1174
Scabiosaponins 1-3
O
BzO
BzO
NH
CCl
BzO
O
O
O
3
5
O
OBz
STol
O
O
O
O
BzO
BzO
NH
CCl
BzO
BzO
O
AcO
OBz
O
BzO
BzO
HO
HO
OAc
3
8
BzO
6
7
O
OBz
BzO
BzO
4
BzO
BzO
BzO
BzO
O
O
BzO
O
NH
CCl
BzO
BzO
BzO
O
3
BzO
BzO
BzO
O
O
O
BzO
BzO
NH
CCl
O
O
BzO
NH
CCl
BzO
OTr
LevO
BzO
O
3
BzO
O
3
HO
11
9
10
Scheme 1. Retrosynthesis of scabiosaponins 1–3.
rhamnopyranosyl-(1?2)-b-
D
-xylopyranosyl moiety, have been re-
3- and 28-glycosyl residues in the target compounds. Such an ap-
proach would allow us to rapidly obtain a variety of structural ana-
logues of bidesmosidic oleanolic acid saponin.
As shown in Scheme 1, saponins 1–3 were retrosynthetically
disconnected into three glycosyl trichloroacetimidate donors 5,17
6,18 and 7,19 a thioglycoside acceptor 8,20 and a triterpene saponin
acceptor 4. The latter could be assembled from three readily acces-
sible building blocks 9, 1015h, and 11 through two successive glyco-
sylation steps in a one-pot reaction.
ported.13 Fortunately, the successful synthesis of many natural
saponins has provided us with a gratifying experience,14 especially
since the application of a one-pot protocol makes the synthetic
route more concise and efficient.15 The one-pot approach with
the combined use of glycosyl trichloroacetimidates and thioglyco-
sides was developed by Takahashi et al.,16 and then Yu and co-
workers applied it to the synthesis of natural saponins.15g,15i In this
approach, thioglycosides employed by them were either ethyl 1-
thioglycosides or phenyl 1-thioglycosides; herein we decided to
adopt the one-pot sequential glycosylation strategy employing
the p-toluene 1-thioglycosides to complete the assembly of the
Disaccharide trichloroacetimidatedonor11was readilyprepared
ina straightforwardmannerasdepictedinScheme2. Herein, 1,2,3,4-
tetra-O-benzoyl-6-O-trityl-
a,b-D
-glucopyranoside (12)15h was
BzO
BzO
TrO
BzO
BzO
O
O
BzO
BzO
c,d
O
a,b
O
BzO
BzO
O
BzO
BzO
OBz
OAc
O
O
BzO
BzO
NH
CCl
BzO
O
OBz
BzO
BzO
BzO
BzO
g
13
11
12
O
3
O
O
O
h
e, f
AcO
AcO
BzO
BzO
BzO
HO
HO
STol
STol
STol
BzO
LevO
AcO
14
HO
HO
15
16
17
i, d
O
BzO
BzO
NH
LevO
O
CCl
3
9
Scheme 2. Reagents and conditions: (a) FeCl3ꢀ6H2O, CH2Cl2, 88%; (b) 6, TMSOTf (0.1 equiv), CH2Cl2, 4 Å MS, 0 °C, 94%; (c) CH3NH2–HOCH3, THF, 94%; (d) CNCCl3, DBU, CH2Cl2,
87% (for 11); 79% (for 9); (e) p-thiocresol, BF3ꢀEt2O, CH2Cl2, 0 °C? rt, 85%; (f) MeONa, MeOH, rt, 99%; (g) Bu2SnO, toluene, reflux; then BzCl (2.0 equiv), 0 °C, 94%; (h) levulinic
acid, DCC, DMAP, CH2Cl2, rt, 85%; (i) NBS, 9:1 CH3COCH3–H2O, ꢁ20 °C, 78%.

T. Guo et al. / Carbohydrate Research 344 (2009) 1167–1174
1169
treated with FeCl3ꢀ6H2O in CH2Cl2 at room temperature,21 to afford
in CH2Cl2 to introduce the 4-tolylthio group,23 and subsequently
the acetyl groups were deprotected by treatment with a catalytic
amount of sodium methoxide in methanol to afford p-tolyl
1,2,3,4-tetra-O-benzoyl-D-glucopyranoside, which was coupled
with 2,3,4,6-tetra-O-benzoyl-a-D-glucopyranosyl trichloroacetimi-
date (6) in anhydrousCH2Cl2 in the presenceof trimethylsilyltrifluo-
romethanesulfonate (TMSOTf) to provide the corresponding
b-selective disaccharide 13 in 94% yield. Treatment of 13 with
MeNH2 in CH3OH, followed by trichloroacetonitrile (Cl3CCN) and
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in dry CH2Cl2, afforded
the corresponding imidate 11 in a yield of 87% over two steps. The
1H NMR data for compound 11 were in good agreement with those
from the natural product.19 The product’s integrity was further sub-
stantiated by the observation of a single spot by TLC analysis.
The preparation of donor 9 began with acetyl-protected xylo-
side 14.22 The latter was treated with p-thiocresol and BF3ꢀEt2O
1-thio-b-D
-xylopyranoside (15)24 in 84% overall yield. Typically,
the regioselectivity is difficult to control due to the similar reactiv-
ity of the secondary 2-, 3- and 4-hydroxyl groups in xylose.
Although a series of useful techniques for access to differentially
protected xylose building blocks have been developed, the labori-
ous protecting manipulation results in notoriously low yieds.14e,f,25
We completed the synthesis of compound 16 with satisfactory reg-
ioselectivity achieved by employing a dibutyltin oxide-mediated
reaction26 that gave no traces of monosubstituted, 2,3- or 2,4-
disubstituted byproducts. In the 1H NMR spectrum of 16, the H-3
and H-4 signals all appeared downfield at d 5.56 and 5.27, which
O
O
BzO
NH
+
BzO
OTr
LevO
O
CCl
3
HO
9
10
a
O
OH
O
O
BzO
BzO
LevO
18
b
TrO
BzO
O
NH
CCl
BzO
11
BzO
O
3
O
O
6, c
O
O
O
O
O
O
O
O
BzO
BzO
BzO
BzO
OBz
TrO
BzO
O
OBz
LevO
RO
BzO
BzO
BzO
19
O
OBz
BzO
BzO
BzO
20 R = Lev
4 R = OH
d
Scheme 3. Reagents and conditions: (a) TMSOTf (0.3 equiv), CH2Cl2, 4 Å MS, ꢁ78 °C?rt; (b) 11 (1.6 equiv), CH2Cl2, 4 Å MS, 0 °C, 66% (overall yields based on 10); (c) catalyst
(1.5 equiv), CH2Cl2, 4 Å MS; (d) NH2NH2ꢀHOAc, 1:1CH2Cl2–CH3OH, 83%.

1170
T. Guo et al. / Carbohydrate Research 344 (2009) 1167–1174
clearly proved the selectivity. As it was desirable to have a distin-
guishable 2-O-protecting group that would allow selective cleav-
age in the presence of an acyl-protecting group and at the same
time ensure stereoselectivity in forming the 1,2-trans glycosidic
linkages, the levulinoyl (Lev) group27 was chosen. The Lev group
was introduced by treatment of 16 with levulinic acid and DCC–
DMAP to prepare 17 in 85% yield. The anomeric 4-tolylthio group
of 17 was removed with NBS in 9:1 acetone–H2O in 15 min to ob-
tain the hemiacetal, which was then converted into the corre-
sponding trichloroacetimidate donor 9 in satisfactory yield.
The key intermediate 4 was efficiently prepared as shown in
Scheme 3. The initial focus of this work was to employ three suc-
cessive glycosylation steps based on Yu’s methodology15h for the
synthesis of 4. Herein, condensation of oleanolic ester 10 with tri-
chloroacetimidate 9 under the promotion of TMSOTf in ꢁ78 °C for
30 min provided the desired product, which was then transformed
into compound 18 by warming to ambient temperature for 30 min.
Following addition of a CH2Cl2 solution of 2,3,4-tri-O-benzoyl-6-O-
we then turned our attention to the reaction conditions, including
alteration of the amount of reagents, temperature, and catalysts
(BF3ꢀEt2O and TfOH). We also tried other known donors, such as
2,3,4,6-tetra-O-acetyl-a-D
-glucopyranosyl trichloroacetimidate,28
p-tolyl 2,3,4,6-tetra-O-acetyl-1-thio-b-
p-tolyl 2,3,4,6-tetra-O-benzoyl-1-thio-b-
D
-glucopyranoside,29 and
-glucopyranoside.30 Fi-
D
nally, we found that the catalyst amount had a key effect on the
reaction. If the amount of catalyst had decreased, Tr was not totally
deprotected, while if the amount of catalyst was increased, Lev was
cleaved to generate a free OH, which could be coupled with donors,
providing the undesired by-products. For this reason, we decided
to utilize the two sequential glycosylation steps for the synthesis
of 4. With the above-synthesized 11 in hand, we added the CH2Cl2
solution of 11 to the reaction mixture of 18 in the presence of
TMSOTf at 0 °C, and after 30 min the desired glycoside 20 was
smoothly obtained. Removing the Lev protecting group by treat-
ment with NH2NH2ꢀHOAc in CH2Cl2–CH3OH finished the synthesis
of 4 in 83% yield.
trityl-
a
-
D
-glucopyranosyl trichloroacetimidate to the above
With an effective synthetic access to the key intermediate 4, we
then set about our final assembly of the target natural products,
scabiosaponins 1–3 by a one-pot sequential glycosylation with
the combined use of glycosyl trichloroacetimidates and p-toluene
1-thioglycosides (STol) donors (Scheme 4). Readily accessible tri-
chloroacetimidates 5–7 and p-toluene 1-thioglycoside 8 were,
respectively, coupled with promotion by TMSOTf at ꢁ78 °C, afford-
mixture at 0 °C, the glycoside 19 was obtained. After the next tri-
chloroacetimidate 6 was subsequently added to the reaction mix-
ture in the presence of TMSOTf and N-iodosuccinimide (NIS) at
0 °C,
a complicated mixture of products was unfortunately
observed by TLC. The spots were close to each other, and were
inseparable by column chromatography. To address the problem,
O
O
O
O
O
O
BzO
BzO
BzO
BzO
NH
CCl3
OBz
O
BzO
BzO
STol
OH
BzO
O
O
O
5
O
OBz
BzO
BzO
OBz
AcO
4
HO
O
OAc
BzO
BzO
BzO
NH
CCl3
8
BzO
a
b
6
BzO
BzO
BzO
BzO
O
O
O
NH
CCl3
BzO
BzO
BzO
O
7
O
BzO
BzO
21
O
R =
c
c
1
BzO
O
OBz
O
O
O
22
2
O
BzO
BzO
BzO
BzO
OBz
O
BzO
BzO
O
BzO
O
OBz
OBz
O
23
3
O
O
O
BzO
c
BzO
BzO
OBz
BzO
BzO
AcO
RO
BzO
BzO
OAc
BzO
Scheme 4. Reagents and conditions: (a) TMSOTf (0.2 equiv), CH2Cl2, 4 Å MS, ꢁ78 °C; (b) ꢁ10 °C, NIS (1.0 equiv), 30 min, 68% for 21, 65% for 22, 65% for 23; (c) NaOMe, 1:1
CH2Cl2–CH3OH, 89% for 1, 87% for 2, 90% for 3.

T. Guo et al. / Carbohydrate Research 344 (2009) 1167–1174
1171
ing the corresponding three glycosides. These products were then
glycosylated in order with saponin 4 dissolved in a CH2Cl2 solution
under the presence of TMSOTf and NIS at ꢁ10 °C, and the fully pro-
tected saponin derivatives 21–23 were obtained in good yields
(60–70%). Finally, removal of the acetyl and benzoyl groups with
NaOMe in MeOH–CH2Cl2 afforded the target scabiosaponins 1–3
in 87–90% yields. All the analytical data for the synthesized triter-
pene saponins 1–3 are identical in all respects to those reported in
the literature.12
In summary, the completion of the first synthesis of scabiosapo-
nins 1–3 was reported in an efficient, practical one-pot sequential
glycosylation, which paves the way to easy access to bidesmosidic
triterpene saponins and their diversified analogues.
ether–EtOAc); IR (KBr) mmax 3066, 2949, 2867, 1719, 1603, 1490,
1447, 1264, 1147, 1089, 1061, 813, 707 cmꢁ1 1H NMR (CDCl3): d
;
7.15–8.01 (m, 14H, Ph-H), 5.62 (t, 1H, J 7.8 Hz, H-3), 5.20–5.24
(m, 1H, H-4), 5.17 (t, 1H, J 7.8 Hz, H-2), 4.93 (d, 1H, J 7.8 Hz, H-
1), 4.55 (dd, 1H, J 11.9, 4.1 Hz, H-5-1), 3.63–3.67 (m, 1H, H-5-2),
2.49–2.69 (m, 4H, CH3COCH2CH2–), 2.36 (s, 3H, Ph–CH3), 2.06 (s,
3H, CH3CO–); 13C NMR (CDCl3): d 205.9, 171.4, 165.6, 139.2,
133.8, 133.6, 130.2, 130.1, 130.0, 129.9, 129.2, 128.6, 86.6 (C-1),
71.9, 70.0, 69.1, 62.0, 38.0, 29.8, 28.1, 21.4; HRESIMS: Calcd for
C31H30O8NaS [M+Na+]: m/z 585.1559; found: m/z 585.1563.
3.4. 3,4-Di-O-benzoyl-2-O-levulinoyl-b-D-xylopyranosyl
trichloroacetimidate (9)
To a solution of compound 17 (622 mg, 1.05 mmol) in 10 mL of
9:1 acetone–H2O, NBS (487 mg, 2.74 mmol) was added at ꢁ20 °C.
The mixture was stirred for 5 min, and quenched with satd aq
NaHCO3.The reaction mixture was concentrated, and the residue
was diluted with EtOAc (20 mL), washed with satd aq NaHCO3
(2 ꢃ 5 mL), brine (2 ꢃ 5 mL), dried over Na2SO4, and concentrated.
3. Experimental
3.1. General methods
Solvents were purified in the usual way. TLC was performed
on precoated E. Merck Silica Gel 60 F254 plates. Flash column
chromatography was performed on silica gel (200–300 mesh,
Qingdao, China). Optical rotations were determined with a JASCO
P-1020 polarimeter. Melting points were determined with a
Yanaco apparatus and were uncorrected. NMR spectra were re-
corded on a Jeol JNM-ECP 600-MHz spectrometer with Me4Si as
the internal standard, and chemical shifts are reported as d val-
ues. Mass spectra were obtained on a Q-TOF GIOBAL mass
spectrometer.
A
solution of the above-obtained product, CNCCl3 (0.52 mL,
5.30 mmol) and DBU (0.12 mL, 0.33 mmol) in dry CH2Cl2 (8 mL)
was stirred for 3 h at room temperature, then the solvent was
evaporated in vacuo to give a residue, which was purified by silica
gel flash column chromatography (3:1 petroleum ether–EtOAc) to
afford 9 as a colorless oil (261 mg, 66% two steps): ½a D23
ꢁ8.7
ꢂ
(ꢁ2.25, CHCl3); Rf = 0.57 (1:1 petroleum ether–EtOAc); 1H NMR
(CDCl3): d 8.73 (s, 1H, NH), 7.39–7.98 (m, 10H, Ph-H), 6.58 (d, 1H,
J 3.3 Hz, H-1), 6.05 (t, 1H, J 9.9 Hz, H-3), 5.41 (ddd, 1H, J 9.9, 6.0,
4.4 Hz, H-4), 5.35 (dd, 1H, J 9.9, 3.3 Hz, H-2), 4.24 (dd, 1H, J 11.5,
6.0 Hz, H-5-1), 3.98 (dd, 1H, J 11.5, 4.0 Hz, H-5-2), 2.58–2.69 (m,
2H, Lev-CH2), 2.44–2.52 (m, 2H, Lev-CH2), 1.58 (s, 3H, Lev-CH3);
13C NMR (CDCl3): d 206.0, 171.9, 165.8, 165.7, 161.1, 133.7,
133.6, 130.1, 130.0, 129.3, 128.6, 93.6 (C-1), 70.3, 69.8, 69.7, 61.3,
37.8, 29.8, 27.9; HRESIMS: Calcd for C26H25O9NCl3 [M+H+]: m/z
600.0595; found: m/z 600.0583.
3.2. p-Tolyl 3,4-di-O-benzoyl-1-thio-b-D-xylopyranoside (16)
Compound 15 (2.56 g, 10 mmol) and dibutyltin oxide (2.50 g,
1.03 equiv) were suspended in benzene (350 mL), and the mixture
was stirred at reflux overnight with the azeotropic removal of
water. The resulting hazy-to-clear solution was cooled under N2
in an ice-water bath and stirred while BzCl (2.4 mL, 2.05 equiv)
was added via a syringe. After addition was complete, the flask
was removed from the ice-water bath and was allowed to reach
room temperature. After completion of the reaction (monitored
by TLC), the reaction mixture was quenched with CH3OH, concen-
trated under reduced pressure, and the crude mixture was purified
by column chromatography (5:1 petroleum ether–EtOAc) to afford
3.5. 3-O-(3,4-Di-O-benzoyl-2-O-levulinoyl-b-
oleanolic acid, 2,3,4,6-tetra-O-benzoyl-b- -glucopyranosyl-
(1?6)-2,3,4-tri-O-benzoyl-b- -glucopyranosyl ester (20)
D-xylopyranosyl)-
D
D
A mixture of 10 (200 mg, 0.29 mmol), 9 (206 mg, 0.34 mmol,
1.2 equiv), and 4 Å MS (400 mg) in dry CH2Cl2 (3 mL) was stirred
at room temperature for 30 min and then cooled to ꢁ78 °C.
16 as a white solid (4.35 g, 94%): ½a D23
ꢁ106.6 (c 1.90, CHCl3); Rf
ꢂ
0.45 (3:1 petroleum ether–EtOAc); IR (KBr) mmax 3486, 3066,
2957, 2860, 1731, 1606, 1494, 1447, 1276, 1077, 805, 707 cmꢁ1
;
TMSOTf (15 lL, 0.09 mmol, 0.3 equiv) was added slowly. After stir-
1H NMR (CDCl3): d 7.17–8.02 (m, 14H, Ph-H), 5.56 (t, 1H, J 8.4 Hz,
H-3), 5.27 (td, 1H, J 9.0, 4.8 Hz, H-4), 4.71 (d, 1H, J 8.4 Hz, H-1),
4.45 (dd, 1H, J 11.4, 4.8 Hz, H-5-1), 3.72 (t, 1H, J 8.4 Hz, H-2),
3.58 (dd, 1H, J 11.4, 9.0 Hz, H-5-2), 2.38 (s, 3H, SPhCH3); 13C NMR
(CDCl3): d 166.4, 165.7, 139.5, 134.2, 134.0, 130.2, 130.1, 129.9,
129.8, 128.7, 128.6, 89.3 (C-1), 74.5, 70.5, 69.5, 66.2, 21.4; HRE-
SIMS: Calcd for C26H24O6NaS [M+Na+]: m/z 487.1191; found: m/z
487.1210.
ring at ꢁ78 °C for 30 min, the reaction mixture was warmed to
room temperature for 30 min, and then cooled to 0 °C. A solution
of 11 (520 mg, 0.43 mmol, 1.5 equiv) in dry CH2Cl2 (3 mL) was
added slowly by injection. The reaction mixture was stirred at
0 °C for 30 min, and then warmed up to room temperature for
another 30 min. The reaction was quenched by addition of Et3N
(0.3 mL), and then filtered. The filtrate was concentrated and puri-
fied by a silica gel column chromatography (3:1 petroleum ether–
EtOAc) to afford 20 (370 mg, 66% based on acceptor 10): mp
133–135 °C; ½a 2D3
ꢂ
+16.6 (c 3.16, CHCl3); Rf 0.35 (2:1 petroleum
ether–EtOAc); IR (KBr) mmax 3065, 2949, 1735, 1598, 1450, 1260,
3.3. p-Tolyl 3,4-di-O-benzoyl-2-O-levulinoyl-1-thio-b-D-
xylopyranoside (17)
1061, 711 cmꢁ1 1H NMR (CDCl3): d 7.25–8.16 (m, 45H, Ph-H),
;
5.86 (d, 1H, J 8.0 Hz, H-10), 5.84 (t-like, 1H, J 9.9, 9.6 Hz, H-3000),
5.81 (t-like, 1H, J 8.8, 8.5 Hz, H-30), 5.62 (t-like, 1H, J 8.8, 8.4 Hz,
H-300), 5.57 (dd, 1H, J 9.9, 8.4 Hz, H-20), 5.54 (t-like, 1H, J 9.5,
9.2 Hz, H-40), 5.46 (dd, 1H, J 9.5, 8.0 Hz, H-2000), 5.39–5.42 (m, 1H,
H-5000-1), 5.35 (t-like, 1H, J 4.4, 4.0 Hz, H-12), 5.24–5.28 (m, 1H,
H-500), 5.21 (dd, 1H, J 8.8, 7.0 Hz, H-200), 5.06 (d, 1H, J 8.0 Hz, H-
1000), 4.66 (d, 1H, J 6.6 Hz, H-100), 4.56 (dd, 1H, J 12.1, 3.3 Hz, H-60-
1), 4.46 (dd, 1H, J 12.1, 5.5 Hz, H-60-2), 4.31–4.36 (m, 2H, H-400,
H-600-1), 4.05–4.10 (m, 1H, H-4000), 3.99–4.03 (m, 1H, H-50), 3.93–
To a solution of compound 16 (300 mg, 0.61 mmol) in dry
CH2Cl2 (5 mL), levulinic acid (142 mg, 1.22 mmol), DCC (252 mg,
1.22 mmol), and DMAP (7.5 mg, 0.06 mmol) were added under ar-
gon. The mixture was stirred for 5 h, diluted with CH2Cl2 (20 mL),
washed with H2O (5 mL), 1 M HCl (2 ꢃ 5 mL), satd aq NaHCO3
(2 ꢃ 5 mL), and brine (2 ꢃ 5 mL), dried over Na2SO4, and concen-
trated. The residue was purified by silica gel column chromatogra-
phy (2:1 petroleum ether–EtOAc) to give 17 (307 mg, 85%) as a
white solid: ½a 2D3
ꢁ77.9 (c 2.15, CHCl3); Rf 0.30 (2:1 petroleum
ꢂ

1172
T. Guo et al. / Carbohydrate Research 344 (2009) 1167–1174
3.98 (m, 1H, H-5000-2), 3.47 (dd, 1H, J 14.0, 7.0 Hz, H-600-2), 3.11 (dd,
1H, J 11.3, 4.4 Hz, H-3), 2.89 (dd, 1H, J 14.3, 4.0 Hz, H-18), 0.96,
0.90, 0.87, 0.87, 0.85, 0.74, 0.48 (s each, 3H each, CH3 ꢃ 7); 13C
NMR (CDCl3): d 205.9, 175.6 (C-28), 171.2, 166.1, 165.7, 165.6,
165.5, 165.3, 165.2, 165.1, 164.6 (C@O), 142.9 (C-13), 133.4,
133.2, 133.1, 133.0, 130.1, 129.9, 129.8, 129.7, 129.6, 129.4,
129.2, 129.1, 128.9, 128.8, 128.7, 128.4, 128.3, 128.2, 122.8 (C-
12), 102.8 (C-100), 100.1 (C-1000), 91.9 (C-10), 89.9 (C-3), 75.3, 72.9,
72.7, 72.2, 71.8, 71.7, 71.3, 70.3, 69.9, 69.7, 69.3, 66.5, 63.1, 62.0,
55.4, 47.5, 46.8, 45.7, 41.5, 41.0, 38.9, 38.4, 37.8, 36.7, 33.8, 32.9,
31.9, 31.7, 30.5, 29.6, 27.8, 25.8, 25.7, 25.4, 23.6, 23.4, 22.6, 18.1,
16.4, 15.3; HRMALDI-MS: Calcd for [M+Na]+ C115H118O28: m/z
1969.7682; found: m/z 1969.7702.
yields of the saponin products were calculated based on saponin
accepter 4.
3.7.1. 3-O-(2,3,4-Tri-O-benzoyl-b-
O-acetyl- -rhamnopyranosyl-(1?2)-3,4-di-O-benzoyl-b-
xylopyranosyl)oleanolic acid, 2,3,4,6-tetra-O-benzoyl-b-
D-xylopyranosyl-(1?3)-2,4-di-
a-
L
D-
D
-
glucopyranosyl-(1?6)-2,3,4-tri-O-benzoyl-b-D-glucopyranosyl
ester (21)
Yield 68%; mp 156–158 °C; ½a D23
ꢁ1.97 (c 2.35, CHCl3); Rf 0.38
ꢂ
(2:1 petroleum ether–EtOAc); IR (KBr) mmax 3062, 2938, 1735,
1603, 1451, 1264, 1093, 707 cmꢁ1
(m, 60H, Ph-H), 5.87 (t, 1H, J 9.7 Hz, H-30), 5.85 (t, 1H, J 9.6 Hz,
H-300), 5.81 (d, 1H, J 8.8 Hz, H-10), 5.53–5.59 (m, 5H, H-3000, H-300000
H-40, H-400, H-4000), 5.46 (dd, 1H, J 9.9, 7.7 Hz, H-2000), 5.41 (t, 1H, J
;
1H NMR (CDCl3): d 7.27–8.06
,
9.6 Hz, H-40000), 5.35 (t, 1H, J 3.7 Hz, H-12), 5.20–5.22 (m, 2H, H-400000
,
3.6. 3-O-(3,4-Di-O-benzoyl-b-
2,3,4,6-tetra-O-benzoyl-b- -glucopyranosyl-(1?6)-2,3,4-tri-O-
benzoyl-b- -glucopyranosyl ester (4)
D-xylopyranosyl)oleanolic acid,
H-5000-1), 5.13–5.16 (m, 2H, H-50, H-500), 5.07 (s, 1H, H-10000), 5.05 (d,
1H, J 7.7 Hz, H-100), 5.04 (t, 1H, J 9.6 Hz, H-30000), 4.79 (d, 1H, J 7.2 Hz,
H-100000), 4.57 (d, 1H, J 8.0 Hz, H-1000), 4.55 (m, 1H, H-500000-1), 4.46
(dd, 1H, J 12.1, 5.5 Hz, H-600-1), 4.39 (dd, 1H, J 13.2, 4.4 Hz, H-60-
D
D
To a stirred solution of 20 (300 mg, 0.16 mmol) in CH2Cl2
(50 mL) and CH3OH (50 mL) was added NH2NH2ꢀHOAc (50 mg,
0.5 mmol). After 2 h, the solution was concentrated, and the resi-
due was purified by silica gel column chromatography (3:1 petro-
leum ether–EtOAc) to afford 4 (250 mg, 83%) as a white solid: mp
1), 4.07–4.10 (m, 2H, H-20, H-20000), 3.99–4.03 (m, 3H, H-500-2, H-50000
,
H-500000-2), 3.93–3.96 (m, 2H, H-200, H-200000), 3.65 (dd, 1H, J 12.6,
6.0 Hz, H-60-2), 3.31 (dd, 1H, J 12.7, 6.1 Hz, H-600-2), 3.11 (dd, 1H,
J 11.5, 4.4 Hz, H-3), 2.87 (dd, 1H, J 14.8, 3.8 Hz, H-18), 2.05, 1.95
(s each, 3H each, Ac ꢃ 2), 1.14 (d, 3H, J 6.6 Hz, H-60000), 0.96, 0.92,
0.91, 0.88, 0.86, 0.71, 0.49 (s each, 3 H each, CH3 ꢃ 7); 13C NMR
(CDCl3): d 175.7 (C-28), 170.0, 169.8, 165.7, 165.6, 165.5, 165.3,
165.2, 142.9 (C-13), 133.5, 133.3, 133.2, 129.9, 129.8, 129.7,
129.5, 128.4, 122.9 (C-12), 102.9 (C-100000), 101.1 (C-1000), 100.3 (C-
100), 97.8 (C-10000), 92.0 (C-10), 89.4 (C-3), 75.9, 75.3, 73.1, 72.8,
72.3, 71.9, 71.3, 70.4, 70.2, 69.9, 69.5, 68.9, 67.2, 63.2, 60.8, 60.5,
55.6, 47.6, 46.9, 45.8, 41.7, 41.1, 39.2, 39.0, 38.7, 36.8, 33.9, 33.1,
32.0, 31.8, 30.6, 29.8, 28.1, 27.9, 25.9, 25.5, 23.7, 23.5, 22.7, 20.9,
20.6, 18.2, 17.5, 16.6, 16.5, 15.6, 14.3. HRMALDI-MS: Calcd for
[M+Na]+ C146H146O39: m/z 2545.9355; found: m/z 2545.9334.
141–143 °C; ½a 2D3
ꢂ
+17.7 (c 3.10, CHCl3); Rf 0.41 (2:1 petroleum
ether–EtOAc); IR (KBr) mmax 3066, 2941, 1731, 1603, 1447, 1264,
1085, 704 cmꢁ1 1H NMR (CDCl3): d 7.22–8.15 (m, 45H, Ph-H),
;
5.86 (t-like, 1H, J 9.9, 9.5 Hz, H-3000), 5.85 (d, 1H, J 8.4 Hz, H-10),
5.82 (t-like, 1H, J 8.5, 8.4 Hz, H-30), 5.59 (t-like, 1H, J 8.5, 8.4 Hz,
H-30), 5.57 (t, 1H, J 9.9 Hz, H-20), 5.54 (t-like, 1H, J 9.5, 9.4 Hz, H-
40), 5.46 (dd, 1H, J 9.9, 8.0 Hz, H-2000), 5.39–5.42 (m, 1H, H-5000-1),
5.35 (t-like, 1H, J 4.4, 3.7 Hz, H-12), 5.27–5.31 (m, 1H, H-500), 5.06
(d, 1H, J 7.7 Hz, H-1000), 4.55 (dd, 1H, J 12.1, 3.3 Hz, H-60-1), 4.53
(d, 1H, J 6.6 Hz, H-100), 4.46 (dd, 1H, J 12.1, 5.5 Hz, H-60-2), 4.29–
4.32 (m, 2H, H-400, H-600-1), 4.05–4.08 (m, 1H, H-4000), 3.94–4.03
(m, 3H, H-50, H-200, H-5000-2), 3.51 (dd, 1H, J 11.7, 9.5 Hz, H-600-2),
3.19 (dd, 1H, J 11.7, 4.4 Hz, H-3), 2.89 (dd, 1H, J 13.9, 4.0 Hz, H-
18), 0.97, 0.96, 0.88, 0.86, 0.85, 0.80, 0.48 (s each, 3H each,
CH3 ꢃ 7); 13C NMR (CDCl3): d 175.6 (C-28), 166.2, 166.1, 165.6,
165.3, 165.1, 164.6 (C@O), 142.9 (C-13), 133.4, 133.2, 133.1,
133.0, 130.1, 129.9, 129.8, 129.7, 129.6, 129.4, 129.1, 128.9,
128.8, 128.7, 128.5, 128.4, 128.2, 122.8 (C-12), 105.2 (C-100),
100.1 (C-1000), 91.9 (C-10), 89.8 (C-3), 75.2, 73.6, 72.9, 72.7, 72.5,
72.2, 71.8, 70.3, 69.9, 69.7, 69.3, 66.5, 63.2, 62.4, 55.4, 47.5, 46.8,
45.7, 41.5, 41.0, 38.9, 38.4, 36.7, 33.8, 32.9, 31.9, 31.7, 30.5, 28.2,
27.9, 25.9, 25.4, 23.6, 23.4, 22.6, 18.1, 16.7, 16.5, 15.4; HRMALDI-
MS: Calcd for [M+Na]+ C110H112O26: m/z 1871.7356; found: m/z
1871.7334.
3.7.2. 3-O-(2,3,4,6-Tetra-O-benzoyl-b-
2,4-di-O-acetyl- -rhamnopyranosyl-(1?2)-3,4-di-O-benzoyl-
b- -xylopyranosyl)oleanolic acid, 2,3,4,6-tetra-O-benzoyl-b-
D-glucopyranosyl-(1?3)-
a-L
D
D-
glucopyranosyl-(1?6)-2,3,4-tri-O-benzoyl-b-D-glucopyranosyl
ester (22)
Yield 65%; mp 160–162 °C; ½a D23
ꢂ
+27.3 (c 2.10, CHCl3); Rf 0.35
(2:1 petroleum ether–EtOAc); IR (KBr) mmax 3062, 2941, 1727,
1603, 1447, 1264, 1085, 1062, 1027, 704 cmꢁ1 1H NMR (CDCl3):
;
d 7.27–8.08 (m, 65H, Ph-H), 5.87 (t, 1H, J 9.6 Hz, H-300), 5.85 (t,
1H, J 9.6 Hz, H-30000), 5.82 (d, 1H, J 8.2 Hz, H-10), 5.53–5.61 (m, 4H,
H-2000, H-30, H-300000, H-400000), 5.50 (t, 1H, J 9.8 Hz, H-3000), 5.46 (dd,
1H, J 9.9, 7.7 Hz, H-20), 5.41 (t, 1H, J 9.9 Hz, H-200), 5.36–5.39 (br
s, 2H, H-12, H-20000), 5.12–5.16 (m, 2H, H-40, H-40000), 5.06 (s, 1H,
H-10000), 5.05 (d, 1H, J 8.0 Hz, H-100), 4.98 (t, 1H, J 9.6 Hz, H-400),
4.70 (d, 1H, J 5.6 Hz, H-100000), 4.57 (dd, 1H, J 12.4, 3.4 Hz, H-60-1),
4.46 (dd, 1H, J 12.1, 4.0 Hz, H-600-1), 4.34–4.38 (m, 2H, H-600-2, H-
3.7. Typical procedure for the one-pot synthesis of triterpene
saponins 21–23
6
00000-1), 4.28 (d, 1H, J 7.7 Hz, H-1000), 4.24 (dd, 1H, J 12.1, 3.8 Hz,
H-5000-1), 4.04–4.08 (m, 1H, H-4000), 4.01–4.03 (m, 1H, H-500), 3.92–
3.97 (m, 3H, H-400000, H-50000, H-60-2, H-6000000-2), 3.87 (t-like, 1H, J
6.6, 5.5 Hz, H-200000), 3.56 (dd, 1H, J 12.1, 6.6 Hz, H-5000-2), 3.31–
3.34 (m, 1H, H-600000-2), 3.09 (dd, 1H, J 11.6, 4.4 Hz, H-3), 2.89 (dd,
1H, J 13.8, 3.7 Hz, H-18), 2.04, 1.88 (s each, 3H each, Ac ꢃ 2), 1.07
(d, 3H, J 6.0 Hz, H-60000), 0.97, 0.90, 0.87, 0.86, 0.85, 0.72, 0.50 (s
each, 3H each, CH3 ꢃ 7); 13C NMR (CDCl3): d 175.7 (C-28), 170.0,
169.7, 166.1, 165.6, 165.2, 165.0, 164.7, 142.9 (C-13), 133.5,
133.3, 133.2, 129.9, 129.8, 128.5, 128.4, 122.9 (C-12), 103.3 (C-
A solution of thioglycoside 8 (40 mg, 0.11 mmol) and 4 Å MS
(80 mg) in CH2Cl2 (5 mL) was stirred at room temperature under
argon for 30 min and then cooled to ꢁ78 °C. At this temperature,
a solution of TMSOTf (0.2 equiv) in dry CH2Cl2 was injected, and
after 10 min trichloroacetimidate 5, 6, or 7 (2.1 equiv) in dry
CH2Cl2 was added. The resulting mixture was stirred for additional
30 min and then warmed to ꢁ10 °C. To the above mixture was
added a solution of saponin acceptor 4 (200 mg, 0.11 mmol,
1.0 equiv) in CH2Cl2 (2 mL), followed by NIS (50 mg, 0.11 mmol,
2.0 equiv). After stirring for 1 h, the reaction mixture was
quenched with Et3N, and then filtered through a pad of Celite.
The filtrate was concentrated. The residue was purified by silica
gel column chromatography (2.5:1 petroleum ether–EtOAc) to give
the fully protected saponin. The amounts of the reactants and the
1
00000), 101.0 (C-100), 100.3 (C-10000), 97.7 (C-1000), 92.1 (C-10), 89.0 (C-
3), 75.7, 75.3, 72.8, 72.3, 71.9, 71.8, 71.7, 70.4, 70.1, 69.9, 69.6,
69.4, 68.8, 67.0, 66.6, 63.2, 62.4, 60.9, 60.5, 55.6, 47.6, 46.9, 45.8,
41.7, 41.1, 39.1, 39.0, 38.7, 36.8, 33.9, 33.1, 32.0, 31.9, 30.6, 29.8,
28.0, 25.5, 23.7, 23.4, 22.7, 21.2, 20.8, 20.2, 18.2, 17.5, 16.6, 16.4,

T. Guo et al. / Carbohydrate Research 344 (2009) 1167–1174
1173
15.5, 14.2; HRMALDI-MS: Calcd for [M+Na]+ C154H152O41: m/z
2679.9672; found: m/z 2679.9701.
50), 4.05 (t, 1H, J 8.2 Hz, H-200), 3.92 (m, 1H, H-500), 3.78 (d, 1H, J
10.1 Hz, H-500-2), 3.75 (d, 1H, J 9.1 Hz, H-500000-2), 3.36 (dd, 1H, J
11.5, 4.1 Hz, H-3), 3.23 (dd, 1H, J 13.7, 4.1 Hz, H-18), 1.68 (d, 3H,
J 5.9 Hz, H-60000), 1.41, 1.29, 1.27, 1.12, 0.92, 0.91, 0.91 (s each, 3H
each, CH3 ꢃ 7); 13C NMR (C5D5N): d 176.9 (C-28), 144.6 (C-13),
123.2 (C-12), 107.8 (C-100000), 106.4 (C-1000), 105.5 (C-100), 101.7 (C-
3.7.3. 3-O-(2,3,4,6-Tetra-O-benzoyl-b-
2,3,6-tri-O-benzoyl-b- -glucopyranosyl-(1?3)-2,4-di-O-acetyl-
-rhamnopyranosyl-(1?2)-3,4-di-O-benzoyl-b- -xylo-
pyranosyl)oleanolic acid, 2,3,4,6-tetra-O-benzoyl-b- -gluco-
-glucopyranosyl ester (23)
+29.4 (c 2.15, CHCl3); Rf 0.31
D-glucopyranosyl-(1?4)-
D
a-
L
D
D
1
0000), 96.0 (C-10), 88.9 (C-3), 83.2 (C-30000), 80.1, 79.0, 78.8, 78.7,
pyranosyl-(1?6)-2,3,4-tri-O-benzoyl-b-
D
78.6, 78.3, 77.2, 75.9, 75.4, 74.2, 73.2, 72.2, 71.8 (C-3000), 71.4,
71.1, 70.0, 69.6, 67.8, 67.3, 62.9, 56.4, 48.4, 47.3, 46.5, 42.4, 42.0,
40.2, 39.9, 39.3, 37.4, 33.4, 32.8, 31.1, 28.5, 27.2, 26.4, 24.1, 24.0,
18.9, 17.8, 17.6, 16.0; HRESIMS: Calcd for C58H94O25Na [M+Na+]:
m/z 1213.5982; found: m/z 1213.6011.
Yield 65%; mp 161–163 °C; ½a D23
ꢂ
(2:1 petroleum ether–EtOAc); IR (KBr) mmax 3062, 2922, 2852,
1735, 1603, 1451, 1268, 1097, 704 cmꢁ1 1H NMR (CDCl3): d
;
7.23–8.13 (m, 80H, Ph-H), 5.87 (t, 1H, J 9.4 Hz, H-3000000), 5.82 (d,
1H, J 8.8 Hz, H-10), 5.67 (t, 1H, J 9.7 Hz, H-30), 5.58 (dd, 1H, J 9.9,
8.2 Hz, H-20), 5.50–5.56 (m, 3H, H-20000, H-2000000, H-300000), 5.47 (dd,
1H, J 9.9, 7.7 Hz, H-400), 5.41 (t, 1H, J 9.9 Hz, H-300), 5.36–5.38 (m,
2H, H-12, H-10000), 5.31 (t, 1H, J 9.9 Hz, H-40), 5.26 (dd, 1H, J 9.8,
7.7 Hz, H-2000), 5.16 (m, 1H, H-500), 5.06 (d, 1H, J 7.8 Hz, H-100000),
4.90–4.97 (m, 3H, H-200000, H-3000, H-4000), 4.74 (d, 1H, J 8.2 Hz, H-
3.8.2. 3-O-(b-
D
-Glucopyranosyl-(1?3)-
a
-
L
-rhamnopyranosyl-
-glucopyranosyl-
(1?2)-b-
(1?6)-b-
D
-xylopyranosyl)oleanolic acid, b-D
-glucopyranosyl ester (2)
D
Yield 87%; mp 222–224 °C; ½a D25
ꢁ13.1 (c 0.25, CH3OH); Rf 0.29
ꢂ
(1:20:0.1 MeOH–CHCl3–H2O); IR (KBr) mmax 3401, 2938, 1735,
1
000000), 4.68 (d, 1H, J 6.5 Hz, H-100), 4.56 (dd, 1H, J 12.4, 3.3 Hz, H-
1645, 1455, 1365, 1073 cmꢁ1 1H NMR (C5D5N): d 6.55 (br s, 1H,
;
5000-1), 4.46 (dd, 1H, J 12.6, 5.4 Hz, H-5000-2), 4.37 (dd, 1H, J 11.6,
3.3 Hz, H-600-1), 4.26 (m, 2H, H-5000000, H-600000-1), 4.08 (m, 1H, H-
4000), 4.00–4.04 (m, 2H, H-500000, H-6000000-2), 3.94–3.99 (m, 5H, H-1000,
H-60-1, H-40000, H-600000-2, H-6000000-2), 3.89 (dd, 1H, J 9.9, 6.1 Hz, H-
H-10000), 6.30 (d, 1H, J 8.2 Hz, H-10), 5.55 (d, 1H, J 7.8 Hz, H-100000),
5.46 (t, 1H, J 3.6 Hz, H-12), 5.13 (br s, 1H, H-20000), 5.08 (d, 1H, J
7.7 Hz, H-100), 4.93 (dd, 1H, J 9.9, 3.2 Hz, H-30000), 4.86 (d, 1H,
J 6.8 Hz, H-1000), 4.81 (dq, 1H, J 9.6, 5.9 Hz, H-50000), 4.77 (dd, 1H, J
9.6, 4.7 Hz, H-5000-1), 4.60 (t-like, 1H, J 9.7, 9.6 Hz, H-40000), 4.50–
4.55 (m, 2H, H-600-1, H-600000-1), 4.38–4.45 (m, 4H, H-60-1, H-60-2,
H-600-2, H-600000-2), 4.33–4.35 (m, 2H, H-3000, H-4000), 4.30 (t, 1H, J
9.1 Hz, H-40), 4.25–4.28 (m, 3H, H-2000, H-300000, H-400000), 4.14–4.24
(m, 6H, H-20, H-30, H-50, H-300, H-400, H-200000), 4.07 (t-like, 1H, J 8.3,
8.2 Hz, H-200), 4.03 (m, 1H, H-500000), 3.94 (m, 1H, H-500), 3.76 (t, 1H,
J 10.1 Hz, H-5000-2), 3.36 (dd, 1H, J 11.9, 3.7 Hz, H-3), 3.23 (dd, 1H,
J 13.7, 3.7 Hz, H-18), 1.68 (d, 3H, J 5.9 Hz, H-60000), 1.44, 1.30, 1.27,
1.13, 0.94, 0.93, 0.93 (s each, 3H each, CH3 ꢃ 7); 13C NMR
(C5D5N): d 176.9 (C-28), 144.5 (C-13), 123.2 (C-12), 107.1 (C-100000),
106.6 (C-1000), 105.5 (C-100), 101.9 (C-10000), 96.0 (C-10), 89.0 (C-3),
83.5 (C-30000), 79.8, 79.0, 78.8, 78.7, 78.3, 77.5, 76.3, 76.2, 76.1,
75.5, 74.2, 73.3, 71.9 (C-3000), 71.2, 70.1, 69.6, 67.3, 62.9, 62.8,
56.4, 48.4, 47.4, 46.6, 42.5, 42.0, 40.2, 40.0, 39.3, 37.4, 35.3, 33.5,
32.8, 31.1, 28.5, 27.2, 26.4, 24.1, 24.0, 23.7, 19.0, 18.8, 17.8, 17.6,
16.0; HRESIMS: m/z Calcd for C59H96O26Na [M+Na+]: 1243.6088;
found: 1243.6119.
5
0000), 3.82–3.87 (m, 2H, H-200, H-5000), 3.68 (m, 1H, H-50), 3.58 (dd,
1H, J 12.1, 5.5 Hz, H-600-2), 3.53 (dd, 1H, J 11.6, 6.6 Hz, H-60-2),
3.10 (dd, 1H, J 12.0, 4.4 Hz, H-3), 2.89 (dd, 1H, J 13.7, 3.9 Hz, H-
18), 2.06, 2.05 (s each, 3H each, Ac ꢃ 2), 1.06 (d, 3H, J 6.0 Hz, H-
6
0000), 0.96, 0.89, 0.88, 0.87, 0.87, 0.67, 0.49 (s each, 3H each,
CH3 ꢃ 7); 13C NMR (CDCl3): d 175.7 (C-28), 169.9, 169.8, 165.8,
165.7, 165.6, 165.5, 165.4, 165.3, 142.9 (C-13), 133.9, 133.5,
133.3, 133.2, 129.9, 129.8, 128.5, 128.4, 122.9 (C-12), 103.3 (C-
100), 100.9 (C-1000), 100.5 (C-1000000), 100.3 (C-100000), 98.1 (C-10000), 92.1
(C-10), 88.9 (C-3), 75.4, 73.1, 73.0, 72.4, 72.3, 71.9, 69.9, 69.5,
67.0, 66.6, 63.2, 62.7, 61.8, 60.9, 60.5, 55.6, 47.6, 46.9, 45.8, 41.7,
41.1, 39.1, 39.0, 38.7, 36.7, 33.9, 33.1, 32.0, 31.9, 30.6, 29.8, 27.9,
26.0, 25.5, 23.7, 23.5, 22.7, 21.2, 20.7, 20.1, 18.2, 17.4, 16.6, 16.3,
15.5, 14.3; HRMALDI-MS: Calcd for [M+Na]+ C181H174O49: m/z
3154.1015; found: m/z 3154.1016.
3.8. Typical procedure for removal of the protecting groups of
triterpene saponins 21–23
3.8.3. 3-O-(b-
D
-Glucopyranosyl-(1?4)-b-
-xylopyranosyl)oleanolic acid, b-
-glucopyranosyl-(1?6)-O-b-D-glucopyranosyl ester (3)
D-glucopyranosyl-(1?3)-
To a solution of fully protected triterpene saponins 21–23
(100 mg) in dry 1:2 CH2Cl2–MeOH (20 mL) was added a newly pre-
pared NaOMe in MeOH solution (1.0 mol/L, 0.20 mL). The mixture
was stirred at rt for 5 h and neutralized with Dowex H+ resin to pH
7 and then filtered. The filtrate was concentrated, and the resulting
residue was subjected to a silica gel column chromatography
(1:20:0.1 MeOH–CHCl3–H2O) to give the natural products 1–3 as
white amorphous solids.
a-L-rhamnopyranosyl-(1?2)-b-D
D
Yield 90%; mp 229–231 °C; ½a D25
ꢁ17.8 (c 1.20, CH3OH); Rf 0.21
ꢂ
(1:20:0.1 MeOH–CHCl3–H2O); IR (KBr) mmax 3416, 2941, 1731,
1638, 1377, 1062 cmꢁ1 1H NMR (C5D5N): d 6.51 (br s, 1H, H-10000),
;
6.28 (d, 1H, J 8.2 Hz, H-10), 5.48 (d, 1H, J 7.8 Hz, H-100000), 5.47 (br s,
1H, H-12), 5.22 (d, 1H, J 7.8 Hz, H-1000000), 5.05 (d, 1H, J 7.8 Hz, H-100),
4.86 (dd, 1H, J 9.6, 3.0 Hz, H-30000), 4.80 (d, 1H, J 7.2 Hz, H-1000), 4.78
(dq, 1H, J 9.6, 5.0 Hz, H-50000), 4.73 (d, 1H, J 10.9 Hz, H-60-1), 4.53–
4.58 (m, 3H, H-40000, H-600000-1, H-6000000-1), 4.50 (dd, 1H, J 9.7,
3.0 Hz, H-600-1), 4.43 (dd, 1H, J 10.1, 3.2 Hz, H-600000-2), 4.35–4.40
(m, 5H, H-40, H-400000, H-5000-1, H-600-2, H-6000000-2), 4.28–4.31 (m,
2H, H-300000, H-3000000), 4.21–4.26 (m, 5H, H-2000, H-30, H-300, H-400, H-
4000), 4.16–4.20 (m, 5H, H-20, H-3000, H-200000, H-50, H-60-2), 4.11–
4.14 (m, 2H, H-2000000, H-3000000), 4.09 (t, 1H, J 7.2 Hz, H-200), 4.03 (m,
1H, H-5000000), 3.96 (m, 1H, H-500000), 3.90 (m, 1H, H-500), 3.72 (t, 1H,
J 9.2 Hz, H-5000-2), 3.32 (dd, 1H, J 11.9, 3.2 Hz, H-3), 3.19 (dd, 1H, J
13.3, 3.7 Hz, H-18), 1.66 (d, 3H, J 5.0 Hz, H-60000), 1.38, 1.27, 1.23,
1.10, 0.90, 0.90, 0.90 (s each, 3H each, CH3 ꢃ 7); 13C NMR
(C5D5N): d 177.0 (C-28), 144.6 (C-13), 122.9 (C-12), 106.7 (C-100000),
106.5 (C-1000), 105.5 (C-100), 105.3 (C-1000000), 101.8 (C-10000), 96.0 (C-
10), 88.9 (C-3), 83.7 (C-30000), 81.5, 79.3, 79.0, 78.8, 78.7, 78.6, 78.3,
77.6, 77.1, 75.7, 75.5, 75.2, 74.3, 73.2, 71.9 (C-3000), 71.2, 70.1,
69.7, 67.4, 64.8, 62.9, 62.8, 62.1, 56.5, 48.5, 47.4, 46.6, 42.5, 42.1,
3.8.1. 3-O-(b-
D-Xylopyranosyl-(1?3)-
a-
L-rhamnopyranosyl-
(1?2)-b- -xylopyranosyl)oleanolic acid, b-
D
D
-glucopyranosyl-
(1?6)-b-d-glucopyranosyl ester (1)
Yield 89%; mp 213–215 °C; ½a D25
ꢁ17.1 (c 0.70, CH3OH); Rf 0.31
ꢂ
(1:20:0.1 MeOH–CHCl3–H2O); IR (KBr) mmax 3401, 2938, 1731,
1642, 1459, 1361, 1050 cmꢁ1 1H NMR (C5D5N): d 6.63 (br s, 1H,
;
H-10000), 6.29 (d, 1H, J 8.3 Hz, H-10), 5.44 (t, 1H, J 3.7 Hz, H-12),
5.42 (d, 1H, J 7.8 Hz, H-100000), 5.07 (d, 1H, J 7.7 Hz, H-100), 5.04 (br
s, 1H, H-20000), 4.86 (d, 1H, J 7.3 Hz, H-1000), 4.84 (dd, 1H, J 9.2,
3.2 Hz, H-30000), 4.81 (dq, 1H, J 9.6, 5.9 Hz, H-50000), 4.75 (dd, 1H, J
11.4, 1.8 Hz, H-60-1), 4.58 (t-like, 1H, J 9.6, 9.2 Hz, H-40000), 4.50
(dd, 1H, J 11.9, 2.3 Hz, H-600-1), 4.36–4.40 (m, 4H, H-5000-1, H-50000
-
1, H-60-2, H-600-2), 4.29 (t-like, 1H, J 8.6, 7.7 Hz, H-2000), 4.26 (m,
1H, H-40), 4.21–4.25 (m, 4H, H-30, H-30, H-400, H-400000), 4.17–4.20
(m, 3H, H-20, H-3000, H-300000), 4.10–4.15 (m, 3H, H-200000, H-4000, H-

1174
T. Guo et al. / Carbohydrate Research 344 (2009) 1167–1174
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Acknowledgment
This work was financial supported by the Natural Science Foun-
dation of China (30701046).
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.carres.2009.04.024.
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