Synthesis of water soluble glycosides of pentacyclic dihydroxytriterpene carboxylic acids as inhibitors of α-glucosidase

Article abstract of DOI:10.1016/j.carres.2016.02.009

A series of compounds were synthesized by glycosylation of maslinic acid (MA) and corosolic acid (CA) with monosaccharides and disaccharides, and the structures of the derivatives were elucidated by standard spectroscopic methods including ¹H NMR, ¹³C NMR and HRMS. The α-glucosidase inhibitory activities of all the novel compounds were evaluated in vitro. The solubility and inhibitory activity of α-glucosidase assays showed that the bis-disaccharide glycosides of triterpene acids possessed higher water solubility and α-glucosidase inhibitory activities than the bis-monosaccharide glycosides. Among these compounds, maslinic acid bis-lactoside (8e, IC₅₀ = 684 μM) and corosolic acid bis-lactoside (9e, IC₅₀ = 428 μM) had the best water solubility, and 9e exhibited a better inhibitory activity than acarbose (IC₅₀ = 478 μM). However, most of glycosylated derivatives possessed lower inhibitory activities than the parent compounds, although their water solubility was enhanced obviously. Moreover, the kinetic inhibition studies indicated that 9e was a non-competitive inhibitor, and structure-activity relationships of the derivatives are also discussed.

Full text of DOI:10.1016/j.carres.2016.02.009

Carbohydrate Research 424 (2016) 42–53
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis of water soluble glycosides of pentacyclic
dihydroxytriterpene carboxylic acids as inhibitors of α-glucosidase
Jiancong Xu a, Xuliang Nie a, Yanping Hong a,*, Yan Jiang a, Guoqiang Wu a, Xiaoli Yin b,
Chunrong Wang a, Xiaoqiang Wang a,c
a Jiangxi Key Laboratory of Natural Product and Functional Food, College of Food Science and Engineering, Jiangxi Agricultural University,
Nanchang 330045, China
b Library of Jiangxi Agricultural University, Nanchang 330045, China
c Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States
A R T I C L E
I N F O
A B S T R A C T
Article history:
Received 27 January 2016
Received in revised form 21 February 2016
Accepted 23 February 2016
Available online 2 March 2016
A series of compounds were synthesized by glycosylation of maslinic acid (MA) and corosolic acid (CA)
with monosaccharides and disaccharides, and the structures of the derivatives were elucidated by stan-
dard spectroscopic methods including 1H NMR, 13C NMR and HRMS. The α-glucosidase inhibitory activities
of all the novel compounds were evaluated in vitro. The solubility and inhibitory activity of α-glucosidase
assays showed that the bis-disaccharide glycosides of triterpene acids possessed higher water solubil-
ity and α-glucosidase inhibitory activities than the bis-monosaccharide glycosides. Among these compounds,
maslinic acid bis-lactoside (8e, IC50 = 684 μM) and corosolic acid bis-lactoside (9e, IC50 = 428 μM) had the
best water solubility, and 9e exhibited a better inhibitory activity than acarbose (IC50 = 478 μM). However,
most of glycosylated derivatives possessed lower inhibitory activities than the parent compounds, al-
though their water solubility was enhanced obviously. Moreover, the kinetic inhibition studies indicated
that 9e was a non-competitive inhibitor, and structure–activity relationships of the derivatives are also
discussed.
Keywords:
Pentacyclic dihydroxytriterpene acids
Glycosylation
Water solubility
α-Glucosidase inhibitor
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
levels. Due to the rigid skeleton and hydrophobic structure, MA and
CA do not dissolve well in water. Their poor water solubility and
Diabetes mellitus affects approximately 382 million people world-
wide according to the report of the International Diabetes Federation
(IDF)1 and type II diabetes mellitus accounts for the most. Therapy
for the type II diabetes relies mainly on several approaches intend-
ed to suppress the hyperglycemia. It is effective to control elevated
glucose level in blood through suppressing the activity of
α-glucosidase,2,3 glycogen phosphorylase (GP)4,5 and protein tyro-
sine phosphatase-1B (PTP-1B).6,7 α-Glucosidase is a membrane-
bound enzyme at the epithelium of the small intestine, catalyzes
the cleavage of glycosidic bonds in disaccharides and oligosaccha-
rides and therefore gives rise to an increase blood glucose
concentration. Inhibition of the activity of α-glucosidase is consid-
ered as an important means for managing type II diabetes.8
Maslinic acid (MA) and corosolic acid (CA) are triterpene acids
found in a wide variety of plants such as Olea europaea L9 and
Lagerstroemia speciosa.10 It is reported that MA9 and CA10–13 (Fig. 1)
exhibited a glucose-lowering effect on postchallenge plasma glucose
low bioavailability, however, are the key factors to limit their clin-
ical applications as therapeutic agents. It has been demonstrated
that encapsulation using cyclodextrins,14,15 phosphorylation16
and introduction of polar groups (e.g. glycosidic-17/amino
acid-18/N-heterocyclic19 residues) was an effective way to achieve
enhancement of water solubility for triterpenoid compounds and
other parent compounds. It has been reported that triterpenoid sa-
ponins synthesized or isolated from plants exhibit good water
solubility and biological activities (e.g. antiviral activity,20 antitu-
mor activity,21,22 anti-inflammatory activity23). In addition, the water
solubility of the derivatives is tightly correlated with the number
and the type of sugars in the glycosides, and it has been shown that
the water solubility improvement may be an effective way to enhance
the bioactivities of bioactive compounds.18,24,25 So far, there have been
only a few studies focused on the α-glucosidase inhibition prop-
erties of MA and CA derivatives. Here, we synthesized a series of
glycoside derivatives of MA and CA by introducing the polar sugar
moieties into their rigid skeleton at the C (2α)-OH and C (3β)-OH
positions. They exhibited better water solubility than the parent com-
pounds. Their α-glucosidase inhibitory activities were also evaluated.
The results of the preliminary studies on the structure-activity re-
lationship and the inhibitory mechanism have also been discussed.
*
Corresponding author. Jiangxi Key Laboratory of Natural Product and Functional
Food, College of Food Science and Engineering, Jiangxi Agricultural University,
Nanchang 330045, China. Tel.: +86 791 83813863; fax: +86 791 83813863.
E-mail address: xyqcjx@163.com (Y. Hong).
http://dx.doi.org/10.1016/j.carres.2016.02.009
0008-6215/© 2016 Elsevier Ltd. All rights reserved.

J. Xu et al./Carbohydrate Research 424 (2016) 42–53
43
2. Results and discussion
2.1. Chemistry
R2
R1
19
20
12
MA and CA have three glycosylation sites, i.e. C (2α)-OH, C (3β)-
OH and COOH (28β). It has been reported that the carboxyl group
at C28 is very important for the hypoglycemic activity of these
triterpenes.26,27 Therefore, a series of derivatives were prepared by
glycosylating MA and CA at C (2α)-OH and C (3β)-OH with D-glucose,
D-xylose, L-arabinose, D-ribose, lactose and maltose, and the C28-
carboxylic group unchanged. The synthetic route has been shown
in Scheme 1.
13
COOH
2
HO
HO
28
3
maslinic acid R1=H, R2=CH3
corosolic acid
Reagents and reaction conditions: (i) BnBr, K2CO3, DMF, 85 °C;
(ii) TMSOTf, 4Å MS, CH2Cl2, rt; (iii) H2, Pd-C (5%), EtOAc, reflux; (iv)
NaOMe, MeOH, rt.
R1=CH3, R2=H
Fig. 1. The structures of maslinic acid and corosolic acid.
R2
R1
R2
R1
ii
i
COOBn
COOH
CCl3
NH
R3
O
H
HO
HO
H
HO
HO
H
H
H
H
MA (R1=H, R2=CH3)
CA (R1=CH3, R2=H )
1 (R1=H, R2=CH3)
2 (R1=CH3, R2=H)
(R =N1-N6)
3a-3f
3
R2
H
R2
R1
R2
R1
R1
COOH
COOH
R4O
iv
H
R3O
R3O
COOBn
iii
H
H
H
R3O
R3O
H
H
H
H
R4O
8a-8f (R1=H, R2=CH3, R4=M1-M6)
9a-9f (R1=CH3, R2=H, R4=M1-M6)
6a-6f (R1=H, R2=CH3, R3=N1-N6)
7a-7f (R1=CH3, R2=H, R3=N1-N6)
4a-4f (R1=H, R2=CH3, R3=N1-N6)
5a-5f (R1=CH3, R2=H, R3=N1-N6)
OBz
OBz
BzO
BzO
O
O
O
O
BzO
BzO
BzO
BzO
OBz
OBz
N3
OBzOBz
N4
OBz
N1
N2
OBz
OBz
OBz
OBz
O
OBz
O
O
BzO
BzO
BzO
O
O
O
BzO
BzO
OBz
OBz
OBz
OBz
N5
N6
OH
OH
HO
HO
O
O
O
HO
HO
O
HO
HO
OH
OH
OH
OH OH
M4
M1
M2
M3
OH
OH
OH
OH
OH
O
O
HO
HO
O
O
O
O
HO
HO
HO
OH
OH
OH
OH
M5
M6
Scheme 1. Synthesis of 2α, 3β-diglycosides of maslinic acid (or corosolic acid).

44
J. Xu et al./Carbohydrate Research 424 (2016) 42–53
The carboxyl group at C28 was critical for the hypoglycemic ac-
The 1H NMR spectra of derivatives showed signals for hydro-
gens on the benzoyl (8.2–7.0 ppm), hydrogens on the sugar and the
triterpenoid moieties (6.0–1.0 ppm), and seven methyl groups
(<1.0 ppm). Due to the removal of benzyl group through catalytic
hydrogenolysis, the integral values of the aromatic proton
were changed between 4 (or 5) and 6 (or 7) at 5.0–4.9 ppm and
8.2–7.0 ppm concurrent with the disappearance of the benzylic
methylene proton signals. The final products (8 and 9) had no proton
absorption signals between 8.2 and 7.0 ppm with the removal of the
benzoyl. The NMR data were generally consistent with those re-
ported in the literature.30
tivity of these triterpenes, and benzyl (Bn) is already known to be
an excellent protective group for COOH group.28,29 Therefore, MA (or
CA) was first converted into its benzyl ester 1 (or 2). The interme-
diate 4 (or 5) was prepared via glycosylation at C (2α)-OH and C
(3β)-OH of 1 (or 2) with TMSOTf as catalyst according to a re-
ported method.30,31 However, the yield of 4 (or 5) with diglycosidic
chains was less than 10%; large amounts of the by-product ob-
tained was attributed to the regioselective reaction.32 The result of
thin layer chromatography showed that there were two main spots
1
of product, and the H NMR spectroscopic data indicated that the
by-product was a mixture of monoglycosylated derivative of 1 (or
2) with only one sugar moiety at C (2α)-OH or C (3β)-OH, since the
fourteen methyl and two hydroxyl distinct proton signals were ob-
served. Therefore, the two by-products with single saccharide chain
possessed a spot with the same value of Rf and the target product
was the other spot in the TLC. The glycosylation reaction (ii) con-
ditions were modified by ensuring stoichiometric excess of the
saccharide donors and under a nitrogen atmosphere, and the yield
of 4 (or 5) was enhanced from 10% to 50%. Then benzyl could be
conveniently removed through catalytic hydrogenolysis in a high
yield. Therefore, a series of derivatives with free carboxylic acids 6
and 7 were prepared. Finally, compounds 8 and 9 were synthe-
sized by removal of the benzoyl protection through transesterification
in NaOMe-MeOH. The structures of the intermediate and the
final compounds were elucidated and confirmed by NMR spectral
studies. In addition, the key NMR signals of typical derivatives
with diglucosides (or monoglucosides) have been listed in
Tables 1 and 2.
With the introduction of the sugar moieties, the water solubil-
ity of these triterpene acids was improved dramatically. The water
solubility of their derivatives is correlated with the number and type
of sugars in the glycosides. Among the derivatives, the bis-
disaccharide glycosides of triterpene acids could be dissolved in water
completely due to the four polar sugar moieties in the two disac-
charide chains. Although bis-monosaccharide glycosides of triterpene
acids were less soluble than the bis-disaccharide glycosides, their
water solubility is still much better than that of the parent com-
pounds. When the concentration is less than 1 mg/mL, all the bis-
monosaccharide glycosides of triterpene acids could disperse well
in water except 8d and 9d (the ribosides). To prepare solutions of
the derivatives with high concentrations, addition of a certain
amount of ethanol into water was necessary. While 8b and 9b (the
glucosides) dissolved completely in 10% ethanol, 8a and 9a (the
xylosides) and 8c and 9c (the arabinosides) required 30% ethanol
for complete dissolution. The worst water solubility was for 8d and
9d which could be dissolved completely in 50% ethanol.
Table 1
The key 1H NMR signals of representative compounds (400 MHz, TMS, δ ppm)
Compounds
H-C12
PhCH2
H-C3
H-C2
H-anomeric carbon
1′
1″
1‴
1′′′′
4b (CDCl3)
R1 = H, R2 = CH3
5b (CDCl3)
5.17-5.16
5.14-5.12
4.98-4.92
4.93-4.88
3.07
3.07
2.85
2.21
5.04-5.01
4.84-4.82
5.14-5.02
4.85-4.82
R1 = CH3, R2 = H
6b (CDCl3)
R1 = H, R2 = CH3
7b (CDCl3)
5.26-5.23
5.24-5.22
3.15
3.15
2.84
2.21
5.02
5.01
4.93-4.90
4.95-4.92
R1 = CH3, R2 = H
8b (DMSO)
R1 = H, R2 = CH3
9b (DMSO)
5.15
5.13
3.21
3.20
2.74-2.71
2.13-2.10
4.90
4.90
4.78-4.75
4.78-4.76
R1 = CH3, R2 = H
4e (CDCl3)
R1 = H, R2 = CH3
5e (CDCl3)
5.11-5.07
5.12-5.10
5.03-4.94
5.10-4.93
2.95
3.00
2.83
2.25
4.79-4.77
4.97-4.92
4.53-4.50
4.63-4.60
4.40-4.36
4.50-4.45
4.22-4.17
4.23
R1 = CH3, R2 = H
6e (CDCl3)
R1 = H, R2 = CH3
7e (CDCl3)
5.16-5.11
5.12
3.01
3.01
2.82-2.78
2.17
4.80-4.78
4.85
4.59-4.56
4.63-4.60
4.48-4.44
4.53-4.48
4.29-4.24
4.27-4.22
R1 = CH3, R2 = H
8e (DMSO)
R1 = H, R2 = CH3
9e (DMSO)
5.12
5.10
3.13-3.08
3.12-3.06
2.76-2.75
2.13-2.12
4.50-4.45
4.47
4.20-4.15
4.18-4.15
4.37-4.35
4.36
4.20-4.15
4.18-4.15
R1 = CH3, R2 = H

J. Xu et al./Carbohydrate Research 424 (2016) 42–53
45
Table 2
The key 13C NMR signals of representative compounds (100 MHz, TMS, δ ppm)
Compounds
C(28)
C(13)
C(12)
C(3)
C(2)
Anomeric carbon
1′
1″
1‴
1′′′′
4b(CDCl3)
R1 = H, R2 = CH3
5b(CDCl3)
177.3
177.1
143.7
138.3
122.0
125.1
89.3
89.0
65.9
66.0
97.4
101.6
97.7
101.7
R1 = CH3, R2 = H
6b(CDCl3)
R1 = H, R2 = CH3
7b(CDCl3)
184.0
183.8
143.6
138.0
122.1
125.2
89.2
88.9
64.2
64.2
97.3
97.5
101.6
101.6
R1 = CH3, R2 = H
8b(DMSO)
R1 = H, R2 = CH3
9b(DMSO)
178.6
178.3
144.0
138.3
121.3
124.4
86.9
87.1
61.5
61.6
98.9
98.7
103.6
103.6
R1 = CH3, R2 = H
4e(CDCl3)
R1 = H, R2 = CH3
5e(CDCl3)
177.3
177.1
143.4
138.1
122.1
125.2
89.4
89.0
65.9
63.1
98.5
98.9
102.1
102.1
100.7
100.6
100.9
100.9
R1 = CH3, R2 = H
6e(CDCl3)
R1 = H, R2 = CH3
7e(CDCl3)
183.0
183.0
143.3
137.9
122.2
125.3
89.3
89.1
67.3
63.1
98.4
98.8
102.0
102.0
100.8
100.7
100.9
100.9
R1 = CH3, R2 = H
8e(DMSO)
R1 = H, R2 = CH3
9e(DMSO)
175.3
176.2
144.6
138.8
120.9
124.0
87.0
87.2
68.2
68.2
98.7
98.3
104.0
104.1
103.2
103.3
103.2
103.3
R1 = CH3, R2 = H
2.2. Bioactivity
that the bis-disaccharide glycosides of the same triterpene acid pos-
sessed higher α-glucosidase inhibitory activities than the bis-
monosaccharide glycosides (e.g. 8e vs 8a and 8b; 9e vs 9a and 9b).
Both 8f (IC50 = 2940 μM) and 9f (IC50 = 2447 μM) were less active than
8e (IC50 = 684 μM) and 9e (IC50 = 428 μM), suggesting that the in-
troduction of lactose group at C-2 and C-3 resulted in a better
enhancement of water solubility and inhibitory activity. Among bis-
monosaccharide glycosides of triterpene acids MA and CA, D-glucose
group (9b, IC50 = 3437 μM) was the most favorite sugar moiety to
be introduced for enhancing solubility and inhibitory activity
(9b vs 9a, 9c and 9d).
In order to screen for the potent antidiabetic compounds which
may be used in clinic, we chose the low toxicity ethanol–water
system to dissolve samples instead of the common solvent (DMSO).
However, unlike the derivatives, the parent compounds (MA and
CA) could not be dissolved completely in the same solvent system
and it was hard to perform the bioactivity assay for them and
compare the inhibitory activity of α-glucosidase with the deriva-
tives. Therefore, twelve glycosylated derivatives of pentacyclic
dihydroxytriterpene acids, together with acarbose (as a positive
control), were dissolved in ethanol–water (1:1) and their inhibito-
ry activities against α-glucosidase were evaluated in vitro. In addition,
we explored the effect of ethanol on α-glucosidase and found the
activity of α-glucosidase was not affected when the volume of
ethanol was less than 10% in the reaction mixture. To eliminate the
influence from ethanol, we controlled the volume of ethanol added
to the reaction system strictly. The results are summarized in Table 3.
Because of the poor water solubility, 8d and 9d could not be dis-
solved well in ethanol–water (1:1) at high concentrations for
determining their inhibitory activity. As shown in Table 3, most of
the tested derivatives exhibited inhibitory activity, and the 8e
(IC50 = 684 μM) and 9e (IC50 = 428 μM) glycosylated at C (2α)-OH and
C (3β)-OH with lactose moiety showed the highest α-glucosidase
inhibitory activity. Under the same experimental conditions, 9e ex-
hibited lower IC50 than the positive control (acarbose, IC50 = 478 μM).
On the other hand, the glycosides of CA showed better potency than
the corresponding MA derivatives (e.g. 9e vs 8e; 9f vs 8f; 9b vs 8b).
In addition, the inhibitory activity of α-glucosidase analysis indicated
To further analyze the inhibitory activities of α-glucosidase of
the parent compounds and their derivatives under identical con-
ditions, the parent compounds (MA, CA) and their derivatives with
the highest α-glucosidase inhibitory activity (8e, 9e) and with the
Table 3
IC50 values (μM) of the final compounds for the inhibition of α-glucosidase
a
Compounds
IC50
Compounds
IC50
8a
8b
8c
8d
8e
8f
Acarbose
7865 53
5362 41
7837 161
b NI
9a
9b
9c
9d
9e
9f
5966 21
3437 17
7434
NI
6
684 23
428
5
2940
478
6
5
2447 13
a
Values are the mean of four experiments.
NI = no inhibition.
b

46
J. Xu et al./Carbohydrate Research 424 (2016) 42–53
Table 4
bis-monosaccharide glycosides. In addition, the derivatives of CA
exhibited better inhibitory activity (IC50) than the corresponding de-
rivatives of MA. Moreover, the study of the kinetic inhibition
indicated that the synthesized glycoside inhibitors (i.e., 9e) utilize
a non-competitive inhibition mechanism. Glycosylation of the
pentacyclic dihydroxytriterpene carboxylic acids (such as MA or CA)
can improve their solubility obviously; however, the studies of
α-glucosidase inhibition in vitro showed that the glycosylated de-
rivatives possessed lower inhibitory activities than the parent
compounds (MA or CA).
IC50 values (μM) of the final compounds (dissolved in DMSO) for the inhibition of
α-glucosidase
a
Compounds
IC50
Compounds
IC50
8e
8d
MA
Acarbose
705
bNI
103
449
6
9e
9d
CA
448
NI
71
4
1
1
6
a
Values are the mean of four treatments.
NI = no inhibition.
b
160
4. Experimental section
9e (0.821 mM)
9e (1.642 mM)
9e (2.463 mM)
4.1. Chemicals and general methods
9e (0.000 mM)
120
All chemicals and solvents used were of reagent grade. Boiling
range of petroleum ether was 60−90 °C. Analytical TLC was per-
formed on Merck silica-gel 60 F254 plates and spots were visualized
with ultraviolet light (254 nm) followed by spraying with a solu-
tion of H2SO4 (10 mL) in ethanol (90 mL) and heating. The melting
points were measured with Tektronix X4 microscopic melting point
apparatus and are uncorrected. Optical rotations were deter-
mined with a Perkin-Elmer 241 polarimeter at room temperature.
1H NMR and 13C NMR spectra were recorded on a Bruker 400 MHz
spectrometer in CDCl3 or DMSO-d6 with the tetramethylsilane as
inner reference. High resolution mass spectral analysis (HRMS) was
performed on Finnigan MAT 95 XP mass spectrometer (Thermo Elec-
tron Corporation). 4-Nitrophenyl-α-D-glucopyranoside (PNPG) and
acarbose were purchased from Sigma. α-Glucosidase from Saccha-
romyces cerevisiae (product number: G5003, CAS: 9001-42-7) was
also purchased from Sigma.
80
40
-1
0
1
2
3
4
5
1/s (mM)-1
Fig. 2. Lineweaver–Burk plot of 9e.
4.2. Synthesis
worst water solubility (8d, 9d) were dissolved in DMSO. The
α-glucosidase inhibitory activities were measured using the same
method described above for α-glucosidase inhibition assay (ethanol–
water system), and the results are presented in Table 4. MA
(IC50 = 103 μM) and CA (IC50 = 71 μM) exhibited better activities than
their derivatives. These indicated that introducing sugar moieties
on the parent compounds by glycosylation can be detrimental to
their α-glucosidase activity (e.g. MA vs 8e; CA vs 9e), although the
water solubility of derivatives were enhanced obviously.
The kinetic studies were also further performed to explore the
inhibition mechanism of the active compounds which inhibited the
α-glucosidase. Considering the similarities in the structure of these
derivatives, 9e with the highest inhibitory activity was selected for
the kinetic analysis. The kinetic constants and modes of inhibition
for 9e were determined based on Lineweaver–Burk plots (Fig. 2),
and 9e exhibited a non-competitive inhibition mechanism because
increasing substrate concentrations resulted in a series of lines with
different slopes, but the same x-intercept. Km (1.76 0.02 mM) was
obtained from the -(x) value at the intersection of the three straight
lines.
4.2.1. Saccharide donors (3) were prepared according to the reported
33–35
methods
Maslinic acid, corosolic acid, benzyl-2α, 3β-dihydroxyolean-12-
en-28-oic acid (1) and benzyl-2α, 3β-dihydroxyurs-12-en-28-oic acid
(2) were synthesized by using the reported methods.13,36
4.2.2. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-xylosyloxy)-benzyl
maslinate (4a)
Powdered 4Å molecular sieves (500 mg) and TMSOTf (50 μL) were
added to a solution of 3a (xylosyl trichloroacetimidate, 2.40 g,
3.95 mmol) in dry CH2Cl2 at rt while stirring. The reaction mixture
was stirred for 5 min followed by addition of 1 (1.00 g, 1.80 mmol)
under the nitrogen atmosphere. After 2 h, Et3N (0.20 mL) was added
to terminate the reaction. The mixture was then filtered and the
filtrate was concentrated and purified by a silica gel-column chro-
matography (6:1, petroleum ether-EtOAc) to give 4a as a white solid
(1.41 g, 67.5%). [α]D25 = −18° (c = 0.1, CDCl3); mp: 150–151 °C; 1H NMR
(400 MHz, CDCl3): δ 8.04–7.98 (m, 5H), 7.94–7.83 (m, 10H), 7.50–
7.29 (m, 16H), 7.24–7.18 (m, 4H), 5.87 (t, 1H, J = 9.3 Hz), 5.69 (t, 1H,
J = 6.3 Hz), 5.39–5.36 (m, 4H), 5.20–5.15 (m, 1H), 5.04–4.95 (m, 3H),
4.84–4.81 (m, 2H), 4.42–4.37 (m, 1H), 3.89–3.80 (m, 2H), 3.60 (t,
1H, J = 10.5 Hz), 3.09 (d, 1H, J = 9.3 Hz), 2.85 (d, 1H, J = 12.1 Hz), 1.97–
1.95 (m, 1H), 1.90–1.84 (m, 1H), 1.79–1.70 (m, 3H), 1.62–1.56 (m,
3H), 1.51–1.46 (m, 2H), 1.36–1.34 (m, 1H), 1.32–1.28 (m, 2H), 1.16–
1.04 (m, 7H), 0.90 (s, 3H), 0.88 (s, 3H), 0.84 (s, 3H), 0.79 (s, 6H), 0.55
(s, 3H), 0.45 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 177.3, 165.8, 165.7,
165.4, 165.3, 165.2, 164.9, 143.6, 136.3, 133.4, 133.3, 133.1, 133.0,
129.9, 129.8, 129.7, 129.5, 129.4, 129.1, 129.0, 128.3, 128.2,128.1,
128.0, 127.9, 122.0,101.0, 99.0, 89.2, 74.7, 72.4, 72.2, 70.2, 69.0, 68.4,
67.9, 65.9, 63.1, 61.2, 54.6, 47.2, 46.6, 46.0, 44.3, 41.6, 41.3, 40.7, 39.1,
3. Conclusion
In summary, a series of glycosylated derivatives of maslinic acid
and corosolic acid with monosaccharides or disaccharides were syn-
thesized and their α-glucosidase inhibitory activities were evaluated.
Among all of the compounds, 9e (IC50 = 428 μM) with the best water
solubility exhibited a better inhibitory activity than the positive ref-
erence (acarbose, IC50 = 478 μM). Analyses of the solubility and the
inhibitory activities of α-glucosidase showed that the bis-
disaccharide glycosides of triterpene acids possessed better water
solubility and higher α-glucosidase inhibitory activities than the

J. Xu et al./Carbohydrate Research 424 (2016) 42–53
47
37.3, 33.8, 33.1, 32.4, 32.2, 30.6, 28.3, 27.4, 26.8, 25.4, 23.7, 23.4, 22.9,
18.0, 17.5, 16.7, 16.3.
4.2.6. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-lactosyloxy)-
benzyl maslinate (4e)
It was prepared as a white solid from 1 and 3e (lactosyl
trichloroacetimidate) by using the method established for 4a (1.46 g,
50.6%). [α]D25 = +38° (c = 0.1, CDCl3); mp: 171–172 °C; 1H NMR
(400 MHz, CDCl3): δ 8.08–8.06 (m, 2H), 7.97–7.79 (m, 25H), 7.70–7.66
(m, 4H), 7.58–7.31 (m, 28H), 7.20–7.09 (m, 16H), 5.73–5.62 (m, 6H),
5.44–5.36 (m, 2H), 5.32–5.30 (m, 1H), 5.27–5.22 (m, 1H), 5.11–5.07
(m, 1H), 5.03–4.94 (m, 2H), 4.79–4.64 (m, 6H), 4.53–4.50 (m, 1H),
4.40–4.36 (m, 1H). 4.20 (t, 1H, J = 9.2 Hz), 3.89–3.83 (m, 4H), 3.70
(m, 4H), 3.82 (m, 1H), 3.35 (t, 1H, J = 11.7 Hz), 2.95 (d, 1H, J = 9.0 Hz),
2.83 (d, 1H, J = 11.6 Hz), 1.86–1.73 (m, 5H), 1.65–1.55 (m, 4H),
1.47–1.40 (m, 3H), 1.24–1.18 (m, 2H), 1.10–0.99 (m, 2H), 0.90 (s, 3H),
0.88 (s, 3H), 0.83 (s, 3H), 0.68 (s, 3H), 0.61 (s, 3H), 0.39 (s, 6H). 13C
NMR (100 MHz, CDCl3): δ 177.3, 165.9, 165.8, 165.4, 165.2, 164.9,
164.7, 143.4, 136.3, 133.4, 133.2, 133.1, 133.0, 132.8, 130.1, 130.0,
129.9, 129.8, 129.7, 129.6, 129.5, 129.4, 129.3, 128.9, 128.8, 128.7,
128.5, 128.4, 128.3, 128.2, 128.1, 127.9, 122.1, 102.1, 100.7, 98.5, 89.4,
75.9, 74.1, 73.6, 73.2, 72.9, 72.7, 72.0, 71.8, 71.7, 71.1, 70.8, 69.9, 67.5,
67.3, 65.9, 63.1, 60.7, 60.2, 54.5, 47.2, 46.6, 44.0, 41.6, 41.3, 40.3, 39.1,
37.1, 33.1, 32.3, 30.6, 28.2, 27.4, 25.5, 23.7, 23.2, 22.9, 17.9, 17.4, 16.6,
16.1.
4.2.3. 2-α,3-β-di-(2, 3, 4, 6-tetra-O-benzoyl-glucosyloxy)-benzyl
maslinate (4b)
It was prepared as a white solid from 1 and 3b (glucosyl
trichloroacetimidate) by using the method established for 4a
(1.56 g, 51%). [α]D25 = +55° (c = 0.1, CDCl3); mp: 143–144 °C; 1H NMR
(400 MHz, CDCl3): δ 7.97–7.92 (m, 6H), 7.86–7.80 (m, 6H),
7.76–7.74 (m, 4H), 7.43–7.30 (m, 10H), 7.28–7.13 (m, 19H), 5.93–5.86
(m, 2H), 5.80–5.74 (m, 2H), 5.58 (t, 1H, J = 7.7 Hz), 5.49 (t, 1H,
J = 7.9 Hz), 5.20–5.14 (m, 2H), 5.04–4.92 (m, 3H), 4.84–4.82 (m,
1H), 4.68–4.63 (m, 2H), 4.56–4.52 (m, 1H), 4.38–4.32 (m, 1H),
4.22–4.13 (m, 1H), 4.10–4.0 (m, 1H), 3.07 (d, 1H, J = 8.9 Hz), 2.85
(d, 1H, J = 13.1 Hz), 2.00 (d, 1H, J = 10.6 Hz), 1.87 (t, 1H, J = 13.1 Hz),
1.68–1.47 (m, 9H), 1.30–1.03 (m, 9H), 0.89 (s, 6H), 0.87 (s, 3H),
0.71 (s, 6H), 0.60 (s, 3H), 0.44 (s, 3H). 13C NMR (100 MHz, CDCl3): δ
177.3, 166.1, 165.9, 165.8, 165.2, 165.1, 165.0, 143.7, 136.3, 133.2,
133.0, 132.9, 132.8, 132.7, 129.9, 129.8, 129.7, 129.6, 129.2, 129.1,
129.0, 128.4, 128.3, 128.2, 128.1, 127.9, 122.0, 101.6, 97.4, 89.2,
73.7, 73.6, 73.4, 73.2, 72.7, 72.4, 71.3, 70.8, 70.2, 65.9, 64.2, 63.7,
54.5, 47.3, 46.6, 45.9, 43.1, 41.6, 41.3, 40.1, 39.1, 37.2, 33.8, 33.1,
32.3, 32.3, 30.6, 28.4, 27.4, 25.6, 23.7, 23.4, 23.0, 18.0.
4.2.7. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-
4.2.4. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-arabinosyloxy)-benzyl
maslinate (4c)
maltosyloxy)-benzyl maslinate (4f)
It was prepared as a white solid from 1 and 3f (maltosyl
trichloroacetimidate) by using the method established for 4a (1.75 g,
52.1%). [α]D25 = +56° (c = 0.1, CDCl3); mp: 158–159 °C; 1H NMR
(400 MHz, CDCl3): δ 8.23–8.21 (m, 2H), 8.16–8.13 (m, 2H), 8.05–8.00
(m, 4H), 7.89–7.87 (m, 2H), 7.84–7.83 (m, 2H), 7.79–7.76 (m, 5H),
7.73–7.70 (m, 7H), 7.63–7.61 (m, 2H), 7.54–7.45 (m, 6H), 7.43–7.37
(m, 15H), 7.36–7.28 (m, 13H), 7.25–7.22 (m, 6H), 7.20–7.16 (m, 5H),
7.15–7.11 (m, 4H), 6.14–6.05 (m, 2H), 5.79–5.73 (m, 2H), 5.71–5.63
(m, 3H), 5.51 (d, 1H, J = 3.8 Hz), 5.43–5.39 (m, 1H), 5.31–5.22 (m,
4H), 5.11–4.94 (m, 6H), 4.85 (d, 1H, J = 7.8 Hz), 4.69–4.65 (m, 1H),
4.63–4.56 (m, 3H), 4.50–4.47 (m, 1H), 4.44–4.40 (m, 1H), 4.33–4.28
(m, 2H), 4.25–4.22 (m, 1H), 4.19–4.10 (m, 2H), 3.96–3.90 (m, 1H),
3.06 (d, 1H, J = 9.3 Hz), 2.93–2.88 (m, 1H), 1.97–1.90 (m, 2H), 1.76–1.72
(m, 1H), 1.69–1.60 (m, 7H), 1.56–1.53 (m, 2H), 1.34–1.27 (m, 2H),
1.25–1.16 (m, 4H), 1.13–1.08 (m, 2H), 0.96 (s, 3H), 0.93 (s, 6H), 0.74
(s, 3H), 0.72 (s, 3H), 0.54 (s, 3H), 0.48 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 177.3, 166.2, 166.1, 165.9, 165.7, 165.6, 165.5, 165.4, 165.1,
165.0, 164.9, 164.8, 143.6, 136.3, 133.4, 133.2, 133.1, 133.0, 132.9,
132.8, 132.7, 130.1, 130.0, 129.9, 129.8, 129.7, 129.6, 129.5, 129.1,
129.0, 128.9, 128.8, 128.7, 128.6, 128.5, 128.4, 128.3, 128.2, 128.1,
128.0, 127.9, 122.1, 101.6, 97.3, 97.0, 96.1, 89.0, 75.6, 75.2, 75.1, 73.7,
73.4, 72.5, 70.9, 70.8, 70.1, 69.1, 68.7, 65.9, 64.3, 62.5, 62.4, 54.5, 47.3,
46.7, 45.9, 43.4, 41.6, 41.3, 40.2, 39.1, 37.2, 33.8, 33.1, 32.4, 32.3, 30.6,
28.4, 27.4, 25.6, 23.7, 23.4, 23.0, 18.0, 17.5, 16.7, 16.2.
It was prepared as a white solid from 1 and 3c (arabinosyl
trichloroacetimidate) and by using the method established for 4a
(1.65 g, 63.2%). [α]D25 = +109° (c = 0.1, CDCl3); mp: 160–161 °C; 1H
NMR (400 MHz, CDCl3): δ 7.98–7.92 (m, 7H), 7.83–7.79 (m, 4H),
7.76–7.74 (m, 2H), 7.46–7.39 (m, 8H), 7.34–7.30 (m, 5H), 7.24–7.18
(m, 9H), 5.72 (t, 1H, J = 8.7 Hz), 5.63–5.49 (m, 6H), 5.20 (s, 1H),
5.01–4.95 (m, 3H), 4.80 (d, 1H, J = 7.6 Hz), 4.60–4.53 (m, 1H), 4.26
(d, 1H, J = 13.4 Hz), 4.01–3.93 (m, 2H), 3.83 (d, 1H, J = 13.3 Hz),
3.07 (d, 1H, J = 9.3 Hz), 2.86 (d, 1H, J = 13.1 Hz), 2.03–1.97 (m, 1H),
1.87–1.83 (m, 1H), 1.72–1.68 (m, 2H), 1.64–1.56 (m, 4H), 1.51–1.45
(m, 2H), 1.35 (s, 1H), 1.30–1.27 (m, 2H), 1.15–1.03 (m, 7H), 0.90 (s,
3H), 0.88 (s, 3H), 0.83 (s, 3H), 0.79 (s, 3H), 0.74 (s, 3H), 0.61 (s,
3H), 0.45 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 177.2, 165.7, 165.6,
165.5, 165.3, 165.2, 143.7, 136.3, 133.3, 133.2, 133.1, 133.0, 132.9,
130.0, 129.8, 129.7, 129.6, 129.5, 129.4, 129.1, 128.9, 128.4, 128.3,
128.1, 128.0, 127.9, 122.0, 101.2, 98.7, 90.1, 75.0, 71.4, 70.7, 70.4,
69.2, 67.7, 65.9, 64.2, 54.6, 47.2, 46.6, 46.0, 44.1, 41.6, 41.4, 40.5,
39.1, 37.2, 33.8, 33.1, 32.4, 32.2, 30.6, 28.4, 27.3., 26.8, 25.4, 23.7,
23.4, 23.0, 18.0, 17.7, 16.7, 16.2.
4.2.5. 2-α,3-β-di-(2, 3, 5-tri-O-benzoyl-ribosyloxy)-benzyl
maslinate (4d)
It was prepared as a white solid from 1 and 3d (ribosyl
trichloroacetimidate) by using the method established for 4a (1.37 g,
57.1%). [α]D25 = −40° (c = 0.1, CDCl3); mp: 161–162 °C; 1H NMR
(400 MHz, CDCl3): δ 8.04–7.96 (m, 10H), 7.81–7.77 (m, 2H), 7.56–
7.37 (m, 9H), 7.34–7.27 (m, 10H), 7.25–7.21 (m, 4H), 6.17 (s, 1H), 6.08
(s, 1H), 5.67 (s, 2H), 5.55 (s, 1H), 5.45 (s, 2H), 5.27 (d, 2H, J = 16.4 Hz),
5.09–5.01 (m, 2H), 4.72 (d, 1H, J = 12.5 Hz), 4.59 (d, 1H, J = 10.0 Hz),
4.22–4.18 (m, 1H), 4.09 (d, 1H, J = 12.6 Hz), 4.00–3.96 (m, 1H), 3.42
(d, 1H, J = 9.4 Hz), 2.90 (d, 1H, J = 12.4 Hz), 2.19 (d, 1H, J = 10.0 Hz),
2.00–1.94 (m, 1H), 1.88–1.86 (m. 2H), 1.72–1.54 (m, 9H), 1.43–1.38
(m, 2H), 1.33–1.25 (m, 3H), 1.15 (s, 3H), 1.09 (s, 3H), 0.93 (s, 3H),
0.91 (s, 3H), 0.89 (s, 3H), 0.77 (s, 3H), 0.57 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 177.1, 166.1, 166.0, 165.5, 165.3, 165.0, 143.7, 136.3, 133.2,
132.9, 132.8, 130.2, 130.0, 129.9, 129.8, 129.7, 129.6, 128.4, 128.3,
128.2, 128.0, 127.9, 122.1, 101.0, 93.8, 89.6, 70.7, 69.6, 69.4, 68.3, 68.1,
67.5, 66.3, 65.9, 62.4, 61.6, 55.0, 47.5, 46.7, 45.8, 42.3, 41.4, 40.7, 39.3,
37.5, 33.8, 33.1, 32.6, 32.3, 30.6, 28.5, 26.9, 25.7, 23.6, 23.4, 23.0, 18.2,
17.5, 16.8, 16.4.
4.2.8. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-xylosyloxy)-benzyl
corosolate (5a)
It was prepared as a white solid from 2 and 3a by using the
method established for 4a (1.37 g, 65.6%). [α]D25 = −27° (c = 0.1, CDCl3);
mp: 153–154 °C; 1H NMR (400 MHz, CDCl3): δ 8.04–8.00 (m, 4H),
7.94–7.85 (m, 8H), 7.51–7.27 (m, 16H), 7.25–7.16 (m, 7H), 5.85 (t,
1H, J = 9.3 Hz), 5.70–5.65 (m, 1H), 5.40–5.33 (m, 1H), 5.14 (s, 1H),
5.07–5.01 (m, 1H), 4.97 (s, 1H), 4.90–4.81 (m, 3H), 4.41–4.37 (m,
1H), 3.89–3.80 (m, 2H), 3.59 (t, 1H, J = 10.4 Hz), 3.09 (d, 1H, J = 9.3 Hz),
2.20 (d, 1H, J = 10.9 Hz), 1.98–1.74 (m, 3H), 1.70–1.52 (m, 7H),
1.43–1.40 (m, 1H), 1.35–1.09 (m, 9H), 0.89 (s, 3H), 0.82 (s, 12H), 0.56
(s, 3H), 0.48 (s, 3H). 13C NMR (100 MHz, CDCl3) : δ 177.2, 165.8, 165.7,
165.4, 165.3, 164.9, 138.5, 136.3, 133.3, 133.2, 133.1, 133.0, 130.1,
130.0, 129.9, 129.8, 129.6, 129.5, 129.2, 128.4, 128.3, 128.2, 128.1,
128.0, 125.1, 101.0, 99.1, 89.1, 74.7, 72.5, 12.0, 70.4, 70.3, 70.2, 69.5,
66.0, 63.2, 61.2, 54.7, 52.8, 48.0, 47.3, 44.2, 42.0, 40.9, 39.5, 39.1, 38.8,

48
J. Xu et al./Carbohydrate Research 424 (2016) 42–53
37.5, 36.6, 32.7, 30.6, 28.4, 27.9, 24.1, 23.4, 23.3, 21.2, 18.1, 17.5, 17.2,
16.9, 16.6.
mp: 172–173 °C; 1H NMR (400 MHz, CDCl3): δ 8.13–8.11 (m, 2H),
8.04–8.02 (m, 2H), 8.01–7.92 (m, 15H), 7.92–7.84 (m, 6H), 7.76–7.72
(m, 4H), 7.64–7.54 (m, 4H), 7.53–7.43 (m, 13H), 7.41–7.28 (m, 20H),
7.24–7.16 (m, 9H), 5.77–5.68 (m, 6H), 5.50–5.29 (m, 4H), 5.12–5.07
(m, 2H), 4.97–4.92 (m, 1H), 4.83–4.60 (m, 7H), 4.50–4.45 (m, 1H),
4.23 (t, 1H, J = 9.3 Hz), 3.92–3.64 (m, 9H), 3.42–3.37 (m, 1H), 3.00
(d, 1H, J = 9.2 Hz), 2.25 (d, 1H, J = 11.0 Hz), 2.00–1.85 (m, 2H), 1.69–1.61
(m, 8H), 1.55–1.43 (m, 3H), 1.27–1.09 (m, 7H), 0.96 (s, 3H), 0.87 (s,
6H), 0.75 (s, 3H), 0.69 (s, 3H), 0.49 (s, 3H), 0.44 (s, 3H). 13C NMR
(100 MHz, CDCl3): δ 177.1, 165.8, 165.4, 165.3, 165.2, 164.9, 164.6,
138.1, 136.2, 133.4, 133.2, 133.1, 133.0, 132.9, 132.8, 130.2, 129.9,
129.8, 129.7, 129.6, 129.5, 129.4, 129.3, 128.9, 128.8, 128.7, 128.5,
128.4, 128.3, 128.2, 128.1, 128.0, 127.9, 125.2, 102.1, 100.9, 100.6,
98.9, 89.0, 76.0, 74.3, 73.6, 73.4, 73.2, 72.8, 71.9, 71.8, 71.7, 71.0, 70.8,
69.9, 69.8, 67.4, 67.2, 65.9, 63.1, 60.6, 60.2, 54.5, 52.7, 48.0, 47.3, 44.2,
41.8, 40.4, 39.3, 39.0, 38.8, 37.1, 36.5, 32.6, 30.6, 28.2, 27.7, 24.1, 23.3,
23.0, 21.1, 17.9, 17.2, 17.0, 16.7, 16.3.
4.2.9. 2-α,3-β-di-(2, 3, 4, 6-tetra-O-benzoyl-glucosyloxy)-benzyl
corosolate (5b)
It was prepared as a white solid from 2 and 3b by using the
method established for 4a (1.71 g, 55.2%). [α]D25 = +60° (c = 0.1, CDCl3);
mp: 134–135 °C; 1H NMR (400 MHz, CDCl3): δ 7.95–7.90 (m, 6H),
7.86–7.84 (m, 4H), 7.81–7.79 (m, 2H), 7.75–7.73 (m, 4H), 7.44–7.36
(m, 5H), 7.35–7.27 (m, 9H), 7.25–7.08 (m, 15H), 5.92–5.85 (m, 2H),
5.80–5.73 (m, 2H), 5.59–5.49 (m, 2H), 5.20–5.10 (m, 2H), 5.06–5.00
(m, 1H), 4.93–4.82 (m, 3H), 4.70–4.53 (m, 3H), 4.37–4.28 (m, 1H),
4.2–4.14 (m, 1H), 4.05–3.99 (m, 1H), 3.07 (d, 1H, J = 9.2 Hz), 2.21 (d,
1H, J = 11.1 Hz), 2.01–1.87 (m, 2H), 1.75–1.55 (m, 8H), 1.44–1.41 (m,
1H), 1.24–1.08 (m, 9H), 0.90 (s, 3H), 0.85 (s, 6H), 0.72 (s, 6H), 0.58
(s, 3H), 0.47 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 177.2, 166.2, 166.1,
165.9, 165.3, 165.1, 165.0, 138.3, 136.3, 133.2, 133.1, 133.0, 132.8,
132.7, 129.9, 129.8, 129.7, 129.6, 129.3, 129.1, 129.0, 128.4, 128.3,
128.2, 128.1, 128.0, 125.2, 101.7, 97.8, 89.0, 73.9, 73.6, 73.4, 73.3, 71.4,
70.9, 70.3, 66.0, 64.2, 63.8, 54.6, 52.8, 48.0, 47.4, 43.3, 42.0, 40.3, 39.4,
39.1, 38.8, 37.3, 36.6, 32.6, 30.6, 28.4, 27.8, 24.1, 23.4, 23.2, 21.1, 18.0,
17.6, 17.1, 16.8, 16.4.
4.2.13. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-
maltosyloxy)-benzyl corosolate (5f)
It was prepared as a white solid from 2 and 3f by using the
method established for 4a (1.92 g, 50.0%). [α]D25 = +48° (c = 0.1, CDCl3);
mp: 156–157 °C; 1H NMR (400 MHz, CDCl3): δ 8.12–8.06 (m, 2H),
8.04–7.96 (m, 2H), 7.92–7.87 (m, 4H), 7.76–7.73 (m, 2H), 7.72–7.68
(m, 2H), 7.66–7.55 (m, 13H), 7.46–7.44 (m, 2H), 7.40–7.31 (m, 8H),
7.25–6.97 (m, 40H), 5.99–5.91 (m, 2H), 5.64–5.49 (m, 5H), 5.37–5.33
(m, 1H), 5.28 (t, 1H, J = 8.1 Hz), 5.16–5.05 (m, 4H), 4.98–4.79 (m, 6H),
4.71 (d, 1H, J = 7.8 Hz), 4.57–4.53 (m, 1H), 4.47–4.38 (m, 3H),
4.35–4.33 (m, 1H), 4.28–4.26 (m, 1H), 4.19–4.15 (m, 2H), 4.08–3.99
(m, 3H), 3.80–3.74 (m, 1H), 2.92 (d, 1H, J = 9.3 Hz), 2.13 (d, 1H,
J = 11.2 Hz), 1.85–1.79 (m, 2H), 1.65–1.48 (m, 9H), 1.36 (d, 1H,
J = 11.1 Hz), 1.16–1.09 (m, 6H), 1.01–0.97 (m, 2H), 0.83 (s, 3H), 0.76
(s, 6H), 0.61 (s, 6H), 0.39 (s, 3H), 0.38 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 177.1, 166.2, 166.1, 165.8, 165.7, 165.6, 165.5, 165.4, 165.1,
165.0, 164.9, 164.8, 138.2, 136.3, 133.4, 133.2, 133.2, 133.1, 133.0,
132.9, 132.8, 132.7, 130.0, 129.9, 129.8, 129.7, 129.6, 129.5, 129.4,
129.0, 128.9, 128.8, 128.7, 128.6, 128.5, 128.3, 128.2, 128.1, 128.0,
127.9, 125.2, 101.6, 97.6, 96.9, 96.1, 88.8, 75.6, 75.2, 74.9, 74.0, 73.5,
73.4, 73.3, 72.5, 72.4, 71.2, 70.9, 70.8, 70.1, 69.1, 69.0, 68.7, 65.9, 64.2,
62.4, 54.5, 52.8, 48.0, 47.3, 43.5, 41.9, 40.3, 39.4, 39.0, 38.8, 37.2, 36.5,
32.6, 30.6, 28.3, 27.8, 24.1, 23.4, 23.2, 21.1, 18.0, 17.4, 17.0, 16.8, 16.4.
4.2.10. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-arabinosyloxy)-benzyl
corosolate (5c)
It was prepared as a white solid from 2 and 3c by using the
method established for 4a (1.80 g, 69.0%). [α]D25 = +120° (c = 0.1,
CDCl3); mp: 163–164 °C; 1H NMR (400 MHz, CDCl3): δ 7.98–7.91 (m,
6H), 7.81–7.76 (m, 4H), 7.73–7.71 (m, 2H), 7.46–7.35 (m, 7H),
7.33–7.29 (m, 6H), 7.25–7.18 (m, 10H), 5.72 (t, 1H, J = 8.7 Hz),
5.58–5.50 (m, 5H), 5.16 (s, 1H), 5.06–5.01 (m, 1H), 4.95–4.88 (m,
2H), 4.79 (d, 1H, J = 7.5 Hz), 4.65–4.56 (m, 2H), 4.25 (d, 1H, J = 13.4 Hz),
4.01–3.93 (m, 2H), 3.82 (d, 1H, J = 13.4 Hz), 3.07 (d, 1H, J = 9.3 Hz),
2.21 (d, 1H, J = 11.1 Hz), 2.04–2.00 (m, 1H), 1.90–1.54 (m, 9H),
1.44–1.08 (m, 8H), 0.89 (s, 3H),0.82 (s, 9H), 0.75 (s, 3H), 0.61 (s, 3H),
0.45 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 177.1, 165.6, 165.4, 165.3,
165.2, 138.5, 136.2, 133.3, 133.2, 133.1, 133.0, 132.9, 130.0,
129.7,129.6, 129.5, 129.4, 129.3, 129.1, 128.9, 128.3, 128.1, 128.0,
127.9, 125.0, 101.1, 98.7, 90.2, 74.9, 71.4, 70.7, 70.2, 69.2, 67.6, 65.9,
64.2, 54.6, 52.8, 47.9, 47.2, 43.9, 41.9, 40.6, 38.8, 37.4, 36.5, 32.6, 30.5,
28.4, 27.8, 26.8, 24.0, 23.4, 23.3, 21.1, 18.1, 17.6, 17.2, 16.8, 16.5.
4.2.11. 2-α,3-β-di-(2, 3, 5-tri-O-benzoyl-ribosyloxy)-benzyl
corosolate (5d)
4.2.14. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-xylosyloxy)-maslinic acid
(6a)
It was prepared as a white solid from 2 and 3d by using the
method established for 4a (1.71 g, 64.0%). [α]D25 = −53° (c = 0.1, CDCl3);
mp: 161–162 °C; 1H NMR (400 MHz, CDCl3): δ 7.99–7.96 (m, 4H),
7.93–7.91 (m, 6H), 7.74–7.72 (m, 2H), 7.52–7.33 (m, 9H), 7.30–7.26
(m, 2H), 7.25–7.17 (m, 12H), 6.12 (s, 1H), 6.03 (s, 1H), 5.61 (s, 2H),
5.49 (s, 1H), 5.41 (s, 2H) 6.03 (s, 1H), 5.61 (s, 2H), 5.49 (s, 1H), 5.41
(s, 2H), 5.24 (s, 1H), 5.15 (s, 1H), 5.07–5.01 (m, 1H), 4.93–4.88 (m,
1H), 4.67 (d, 1H, J = 12.7 Hz), 4.53 (d, 1H, J = 11.0 Hz), 4.17–4.12 (m,
1H), 4.04 (d, 1H, J = 12.4 Hz), 3.96–3.88 (m, 1H), 3.37 (d, 1H, J = 9.5 Hz),
2.23–2.12 (m, 2H), 1.96–1.55 (m, 9H), 1.47–1.37 (m, 5H), 1.35–1.17
(m, 5H), 1.10 (s, 3H), 0.99 (s, 3H), 0.88 (s, 6H), 0.81 (s, 3H), 0.72 (s,
3H), 0.54 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 177.2, 166.1, 165.5,
165.3, 165.0, 138.2, 136.3, 133.2, 133.1, 133.0, 132.8, 130.2, 130.0,
129.9, 129.8, 129.7, 129.6, 128.4, 128.3, 128.2, 128.1, 127.9, 125.3,
101.0, 93.8, 89.5, 70.6, 69.6, 69.4, 68.3, 68.1, 67.5, 66.2, 65.9, 62.4,
61.6, 55.0, 52.8, 48.0, 47.5, 42.4, 42.0, 40.7, 39.5, 39.0, 38.8, 37.5, 36.6,
32.8, 30.6, 28.6, 26.8, 24.2, 23.4, 23.3, 21.1, 18.2, 17.6, 17.0, 16.9, 16.5.
A mixture of 4a (1.33 g, 0.92 mmol) and 5% Pd/C (0.80 g) in EtOAc
(50 mL) was stirred at 85 °C under H2 at atmospheric pressure for
4 h. The reaction mixture was filtered and concentrated in vacuo
to give 6a as a white solid (1.1 g, 88.0%). [α]D25 = −19° (c = 0.1, CDCl3);
mp: 184–186 °C; 1H NMR (400 MHz, CDCl3): δ 8.11–8.09 (m, 2H),
8.07–8.05 (m, 2H), 8.01–7.99 (m, 2H), 7.96–7.93 (m, 6H), 7.57–7.53
(m, 1H), 7.52–7.45 (m, 4H), 7.44–7.42 (m, 2H), 7.40–7.37 (m, 4H),
7.35–7.33 (m, 3H), 7.32–7.30 (m, 2H), 7.28–7.27 (m, 1H), 7.25–7.24
(m, 1H), 5.97–5.92 (m, 1H), 5.79–5.75 (m, 1H), 5.50–5.44 (m, 3H),
5.25–5.19 (m, 1H), 5.10–5.05 (m, 1H), 4.94–4.88 (m, 2H), 4.48–4.44
(m, 1H), 4.13–4.08 (m, 1H), 3.92–3.89 (m, 2H), 3.69–3.64 (m, 1H),
3.18–3.15 (m, 1H), 2.83 (d, 1H, J = 13.6 Hz), 2.04–2.00 (m, 2H),
1.93–1.88 (m, 1H), 1.86–1.70 (m, 2H), 1.66–1.55 (m, 5H), 1.41–1.35
(m, 2H), 1.29–1.21 (m, 4H), 1.19–1.07 (m, 4H), 0.97 (s, 3H), 0.95 (s,
3H), 0.91 (s, 3H), 0.87 (s, 3H), 0.85 (s, 3H), 0.65 (s, 3H), 0.58 (s, 3H).
13C NMR (100 MHz, CDCl3): δ 183.8, 165.8, 165.7, 165.4, 165.3, 164.9,
143.5, 133.3, 133.2, 133.1, 133.0, 129.8, 129.7, 129.6, 129.4, 129.1,
129.0, 128.3, 128.2, 128.0, 122.1, 100.9, 99.1, 89.2, 74.7, 72.4, 72.2,
70.3, 70.2, 70.1, 69.4, 63.1, 61.1, 60.3, 54.5, 47.3, 46.4, 45.9, 44.3, 41.5,
40.9, 40.7, 39.1, 37.3, 33.7, 33.1, 32.3, 30.6, 28.2, 27.4, 25.5, 23.6, 23.3,
22.8, 20.9, 17.9, 17.4, 16.8, 16.3.
4.2.12. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-
lactosyloxy)-benzyl corosolate (5e)
It was prepared as a white solid from 2 and 3e by using the
method established for 4a (2.8 g, 44.5%). [α]D25 = +50° (c = 0.1, CDCl3);

J. Xu et al./Carbohydrate Research 424 (2016) 42–53
49
4.2.15. 2-α,3-β-di-(2, 3, 4, 6-tetra-O-benzoyl-glucosyloxy)-maslinic
acid (6b)
It was prepared as a white solid from 4b by using the method
4.2.18. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-
lactosyloxy)-maslinic acid (6e)
It was prepared as a white solid from 4e by using the method
established for 6a (1.3 g, 97.7%). [α]D25 = +37° (c = 0.1, CDCl3); mp:
184–185 °C; 1H NMR (400 MHz, CDCl3): δ 8.14–8.12 (m, 2H),
8.03–8.01 (m, 2H), 8.01–7.99 (m, 3H), 7.99–7.95 (m, 10H), 7.94–7.90
(m, 5H), 7.85–7.83 (m, 2H), 7.76–7.73 (m, 4H), 7.64–7.59 (m, 2H),
7.57–7.51 (m, 4H), 7.50–7.47 (m, 5H), 7.46–7.41 (m, 6H), 7.40–7.35
(m, 8H), 7.34–7.27 (m, 7H), 7.25–7.21 (m, 7H), 7.20–7.16 (m, 3H),
5.80–5.69 (m, 6H), 5.51–5.43 (m, 2H), 5.40–5.29 (m, 2H), 5.16–5.11
(m, 1H), 4.87 (d, 1H, J = 7.5 Hz), 4.80–4.65 (m, 5H), 4.60–4.53 (m,
1H), 4.50–4.43 (m, 1H), 4.26 (t, 1H, J = 9.3 Hz), 4.15–4.10 (m, 1H),
3.97–3.87 (m, 4H), 3.83–3.75 (m, 4H), 3.71–3.67 (m, 1H), 3.45–3.39
(m, 1H), 3.01 (d, 1H, J = 9.1 Hz), 2.82–2.78 (m, 1H), 2.05–2.03 (m,
1H), 1.96–1.86 (m, 2H), 1.78–1.65 (m, 2H), 1.83–1.57 (m, 4H),
1.49–1.32 (m, 2H), 1.31–1.20 (m, 4H), 1.19–1.00 (m, 5H), 0.97 (s, 3H),
0.95 (s, 3H), 0.90 (s, 3H), 0.72 (s, 3H), 0.66 (s, 3H), 0.57 (s, 3H), 0.41
(s, 3H). 13C NMR (100 MHz, CDCl3): δ 183.0, 165.9, 165.8, 165.4, 165.2,
165.0, 164.9, 164.7, 143.3, 133.4, 133.3, 133.2, 133.1, 133.0, 132.9,
132.8, 130.1, 129.9, 129.8, 129.7, 129.6, 129.5, 129.4, 129.3, 128.9,
128.8, 128.7, 128.5, 128.4, 128.3, 128.2, 122.2, 102.0, 100.9, 100.8,
96.4, 89.3, 76.0, 74.1, 73.6, 73.4, 73.2, 72.9, 72.7, 72.0, 71.8, 71.7, 71.1,
70.9, 69.9, 67.6, 67.5, 67.3, 63.1, 60.9, 60.7, 60.3, 54.4, 53.7, 47.2, 46.4,
45.9, 44.0, 41.5, 40.8, 40.2, 39.0, 37.1, 33.1, 32.3, 30.6, 28.2, 27.4, 26.9,
25.5, 23.6, 23.2, 22.9, 21.0, 17.8, 17.3, 16.8, 16.1.
established for 6a (0.83 g, 88.2%). [α]D25 = +53° (c = 0.1, CDCl3); mp:
161–162 °C; 1H NMR (400 MHz, CDCl3): δ 8.06–8.05 (m, 2H),
8.01–7.98 (m, 4H), 7.94–7.92 (m, 4H), 7.88–7.87 (m, 2H), 7.84–7.82
(m, 4H), 7.52–7.45 (m, 4H), 7.43–7.39 (m, 6H), 7.35–7.29 (m, 6H),
7.28–7.27 (m, 1H), 7.25–7.22 (m, 7H), 6.00–5.96 (m, 2H), 5.89–5.82
(m, 5H), 5.68–5.65 (m, 1H), 5.59–5.56 (m, 1H), 5.26–5.23 (m, 2H),
5.02 (d, 1H, J = 7.6 Hz), 4.93–4.90 (m, 1H), 4.75–4.70 (m, 2H),
4.63–4.60 (m, 1H), 4.47–4.44 (m, 1H), 4.27–4.24 (m, 1H), 4.15–4.11
(m, 1H), 3.15 (d, 1H, J = 9.2 Hz), 2.85–2.82 (m, 1H), 2.08–2.06
(m, 1H), 1.98–1.94 (m, 1H), 1.81–1.70 (m, 3H), 1.65–1.58 (m, 4H),
1.38–1.14 (m, 11H), 0.97 (s, 3H), 0.96 (s, 3H), 0.95 (s, 3H), 0.77 (s,
3H), 0.76 (s, 3H), 0.64 (s, 3H), 0.63 (s, 3H). 13C NMR (100 MHz, CDCl3):
δ 184.0, 166.1, 165.9, 165.8, 165.3, 165.1, 165.0, 143.6, 133.0, 132.9,
132.8, 132.7, 129.9, 129.8, 129.7, 129.6, 129.3, 129.1, 129.0, 128.3,
128.2, 128.1, 122.1, 101.6, 97.3, 89.2, 73.7, 73.6, 73.4, 73.2, 72.7, 72.4,
71.3, 70.8, 70.2, 64.2, 63.7, 54.5, 47.3, 46.5, 45.9, 43.0, 41.5, 40.8, 40.1,
39.1, 37.3, 33.7, 33.0, 32.3, 30.6, 29.6, 28.4, 27.5, 25.6, 23.6, 23.3, 22.9,
17.9, 17.7, 16.9, 16.2.
4.2.16. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-arabinosyloxy)-maslinic
acid (6c)
It was prepared as a white solid from 4c by using the method
established for 6a (1.30 g, 88.4%). [α]D25 = +112° (c = 0.1, CDCl3);
mp: 195–196 °C; 1H NMR (400 MHz, CDCl3): δ 8.05–8.04 (m, 1H),
8.03–7.99 (m, 5H), 7.90–7.86 (m, 4H), 7.82–7.80 (m, 2H), 7.53–7.49
(m, 2H), 7.48–7.43 (m, 4H), 7.42–7.37 (m, 4H), 7.34–7.33 (m, 2H),
7.32–7.31 (m, 3H), 7.30–7.28 (m, 3H), 5.81–5.77 (m, 1H), 5.69–5.64
(m, 3H), 5.62–5.58 (m, 2H), 5.26–5.25 (m, 1H), 5.03 (d, 1H, J = 5.2 Hz),
4.86 (d, 1H, J = 7.6 Hz), 4.73–4.60 (m, 1H), 4.33–4.30 (m, 1H), 4.07–
3.99 (m, 2H), 3.91–3.88 (m, 1H), 3.14 (d, 1H, J = 9.3 Hz), 2.86–2.82
(m, 1H), 2.10–2.06 (m, 1H), 1.98–1.87 (m, 2H), 1.85–1.73 (m, 2H),
1.70–1.64 (m, 2H), 1.61–1.56 (m, 3H), 1.44–1.42 (m, 1H), 1.39–1.32
(m, 2H), 1.27–1.21 (m, 4H), 1.20–1.15 (m, 3H), 0.98 (s, 3H), 0.96 (s,
3H), 0.91 (s, 3H), 0.87 (s, 3H), 0.82 (s, 3H), 0.66 (s, 3H), 0.65 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 183.9, 165.7, 165.6, 165.4, 165.3,
165.2, 143.6, 133.4, 133.3, 133.1, 132.9, 130.0, 129.8, 129.7, 129.6,
129.5, 129.4, 129.1, 128.9, 128.4, 128.3, 128.1, 128.0, 122.1, 101.0,
98.7, 90.1, 75.0, 71.4, 70.7, 70.4, 69.2, 67.6, 64.2, 61.6, 60.3, 54.6,
47.2, 46.4, 46.0, 44.1, 41.5, 40.9, 40.5, 39.1, 37.3, 33.7, 32.3, 30.6,
28.3, 27.4, 26.8, 25.5, 23.6, 23.3, 22.8, 17.9, 16.9, 16.2.
4.2.19. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-
maltosyloxy)-maslinic acid (6f)
It was prepared as a white solid from 4f by using the method
established for 6a (1.51 g, 93.8%). [α]D25 = +51° (c = 0.1, CDCl3); mp:
173–174 °C; 1H NMR (400 MHz, CDCl3): δ 8.23–8.21 (m, 2H),
8.16–8.14 (m, 2H), 8.05–8.00 (m, 4H), 7.88–7.83 (m, 4H), 7.81–7.77
(m, 2H), 7.77–7.68 (m, 10H), 7.66–7.62 (m, 2H), 7.56–7.49 (m, 2H),
7.49–7.35 (m, 20H), 7.35–7.28 (m, 8H), 7.24–7.18 (m, 9H),
7.16–7.07 (m, 5H), 6.14–6.05 (m, 2H), 5.79–5.63 (m, 5H),
5.55–5.49 (m, 1H), 5.44–5.40 (m, 1H), 5.31–5.21 (m, 4H), 5.06–4.95
(m, 4H), 4.90–4.85 (m, 1H), 4.70–4.56 (m, 4H), 4.49–4.40 (m, 2H),
4.31–4.24 (m, 3H), 4.18–4.11 (m, 2H), 4.00–3.88 (m, 1H), 3.06 (d,
1H, J = 8.8 Hz), 2.87–2.77 (m, 1H), 2.08–2.02 (m, 1H), 2.01–1.91 (m,
2H), 1.80–1.70 (m, 2H), 1.67–1.54 (m, 5H), 1.43–1.34 (m, 1H),
1.32–1.03 (m, 9H), 0.96 (s, 3H), 0.94 (s, 6H), 0.71 (s, 6H), 0.60 (s, 3H),
0.49 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 183.3, 166.2, 165.9, 165.6,
165.5, 165.2, 165.1, 165.0, 164.9, 143.5, 133.4, 133.3, 133.2, 133.1,
133.0, 132.9, 132.8, 130.1, 130.0, 129.9, 129.8, 129.7, 129.6, 129.5,
129.1, 129.0, 128.9, 128.8, 128.7, 128.5, 128.4, 128.3, 128.2, 128.1,
128.0, 122.8, 101.6, 97.3, 97.0, 96.1, 90.8, 75.8, 75.2, 75.1, 73.8, 73.5,
73.4, 73.1, 72.6, 72.5, 72.1, 71.0, 70.8, 70.2, 69.1, 68.8, 64.3, 62.6, 60.8,
60.6, 60.4, 54.5, 52.7, 47.4, 46.5, 41.6, 40.2, 39.1, 37.3, 33.8, 33.1, 32.4,
30.7, 28.6, 28.4, 27.6, 25.7, 23.7, 23.4, 23.0, 18.0, 17.5, 16.9, 16.2.
4.2.17. 2-α,3-β-di-(2, 3, 5-tri-O-benzoyl-ribosyloxy)-maslinic
acid (6d)
It was prepared as a white solid from 4d by using the method
established for 6a (1.1 g, 90.9%). [α]D25 = −40° (c = 0.1, CDCl3); mp:
184–186 °C; 1H NMR (400 MHz, CDCl3): δ 8.06–8.03 (m, 4H),
8.01–7.99 (m, 3H), 7.98–7.97 (m, 3H), 7.81–7.79 (m, 2H), 7.57–7.53
(m, 2H), 7.51–7.45 (m, 4H), 7.43–7.38 (m, 2H), 7.31–7.29 (m, 3H),
7.28–7.27 (m, 4H), 7.25–7.23 (m, 3H), 6.19 (t, 1H, J = 3.8 Hz), 6.11–6.09
(m, 1H), 5.70–5.68 (m, 2H), 5.59–5.57 (m, 1H), 5.48–5.47 (m, 2H),
5.35–5.32 (m, 1H), 5.27–5.23 (m, 1H), 4.74 (d, 1H, J = 12.2 Hz),
4.63–4.59 (m, 1H), 4.25–4.20 (m, 1H), 4.14–4.10 (m, 1H), 4.03–3.97
(m, 1H), 3.45 (d, 1H, J = 9.6 Hz), 2.83–2.79 (m, 1H), 2.24–2.20 (m,
1H), 2.03–1.98 (m, 1H), 1.93–1.91 (m, 2H), 1.75–1.68 (m, 2H),
1.65–1.53 (m, 6H), 1.45–1.36 (m, 2H), 1.34–1.24 (m, 4H), 1.23–1.19
(m, 2H), 1.17 (s, 3H), 1.11 (s, 3H), 0.96 (s, 3H), 0.91 (s, 6H), 0.78 (s,
3H), 0.73 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 183.8, 166.1, 166.0,
165.5, 165.3, 165.0, 143.5, 133.2, 133.0, 132.8, 130.1, 130.0, 129.9,
129.8, 129.7, 129.6, 128.4, 128.3, 128.2, 128.1, 122.2, 101.0, 93.7, 89.6,
70.7, 69.5, 69.4, 68.6, 68.3, 68.1, 67.6, 66.2, 62.4, 61.7, 60.3, 55.0, 47.6,
46.5, 45.7, 42.2, 41.6, 40.9, 40.7, 39.2, 37.5, 33.8, 33.0, 32.5, 32.3, 30.6,
28.5, 27.5, 26.8, 25.7, 23.5, 23.4, 22.9, 18.1, 17.5, 17.0, 16.4.
4.2.20. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-xylosyloxy)-corosolic
acid (7a)
It was prepared as a white solid from 5a by using the method
established for 6a (0.99 g, 87.6%). [α]D25 = −23° (c = 0.1, CDCl3); mp:
185–187 °C; 1H NMR (400 MHz, CDCl3): δ 8.13–8.08 (m, 5H),
8.03–8.01 (m, 3H), 7.98–7.93 (m, 6H), 7.56–7.54 (m, 1H), 7.51–7.46
(m, 4H), 7.43–7.41 (m, 3H), 7.38–7.34 (m, 5H), 7.31–7.28 (m, 3H),
5.95 (t, 1H, J = 9.2 Hz), 5.80–5.75 (m, 1H), 5.48–5.42 (m, 4H),
5.24–5.18 (m, 1H), 5.07–4.99 (m, 2H), 4.91 (d, 1H, J = 6.7 Hz),
4.50–4.43 (m, 1H), 3.98–3.90 (m, 2H), 3.68 (t, 1H, J = 10.2 Hz), 3.18
(d, 1H, J = 9.1 Hz), 2.20 (d, 1H, J = 10.6 Hz), 2.06–1.94 (m, 3H),
1.92–1.81 (m, 2H), 1.74–1.60 (m, 5H), 1.53–1.50 (m, 1H), 1.42–1.41
(m, 1H), 1.35–1.16 (m, 8H), 0.96 (s, 3H), 0.91 (s, 12H), 0.69 (s, 3H),
0.57 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 183.6, 165.8, 165.7, 165.3,
165.2, 164.9, 138.2, 133.2, 133.1, 133.0, 130.1, 130.0, 129.8, 129.7,
129.4, 129.3, 129.1, 129.0, 128.3, 128.2, 128.1, 128.0, 125.1, 100.8,

50
J. Xu et al./Carbohydrate Research 424 (2016) 42–53
99.2, 89.0, 74.6, 72.5, 72.0, 70.2, 70.1, 69.7, 69.3, 63.1, 60.9, 60.3, 54.6,
52.4, 47.8, 47.2, 44.2, 41.7, 40.9, 39.3, 38.9, 38.7, 37.4, 36.6, 32.5, 30.5,
28.2, 27.8, 26.8, 23.9, 23.4, 23.2, 21.1, 20.9, 18.0, 17.3, 17.1, 16.9, 16.6.
41.9, 40.7, 39.5, 39.0, 38.7, 37.5, 36.6, 32.8, 30.5, 28.8, 27.9, 26.8, 24.0,
23.4, 23.3, 21.1, 18.1, 17.5, 17.0, 16.5.
4.2.24. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-
lactosyloxy)-corosolic acid (7e)
4.2.21. 2-α,3-β-di-(2, 3, 4, 6-tetra-O-benzoyl-glucosyloxy)-corosolic
acid (7b)
It was prepared as a white solid from 5e by using the method
established for 6a (2.13 g, 91.8%). [α]D25 = +47° (c = 0.1, CDCl3); mp:
183–185 °C; 1H NMR (400 MHz, CDCl3): δ 8.13–8.11 (m, 2H), 8.05–
8.03 (m, 2H), 8.01–7.98 (m, 6H), 7.97–7.96 (m, 4H), 7.95–7.92 (m,
4H), 7.91–7.88 (m, 3H), 7.83–7.82 (m, 2H), 7.76–7.73 (m, 4H), 7.64–
7.58 (m, 2H), 7.57–7.53 (m, 2H), 7.52–7.43 (m, 13H), 7.41–7.28 (m,
16H), 7.25–7.16 (m, 10H), 5.81–5.69 (m, 6H), 5.51–5.42 (m, 2H), 5.39–
5.31 (m, 2H), 5.15–5.10 (m, 1H), 4.85 (d, 1H, J = 7.4 Hz), 4.79–4.71
(m, 4H), 4.63–4.60 (m, 1H), 4.53–4.48 (m, 1H), 4.24 (t, 1H, J = 9.2 Hz),
4.15–4.08 (m, 1H), 3.98–3.93(m, 1H), 3.91–3.80 (m, 4H), 3.79–
3.71 (m, 3H), 3.68–3.62 (m, 1H), 3.44–3.38 (m, 1H), 3.01 (d, 1H,
J = 9.0 Hz), 2.17 (d, 1H, J = 11.0 Hz), 2.04–1.87 (m, 4H), 1.75–1.61 (m,
5H), 1.55–1.50 (m, 2H), 1.44–1.42 (m, 1H), 1.36–1.20 (m, 6H), 1.18–
1.13 (m, 2H), 0.98 (s, 3H), 0.88 (s, 6H), 0.73 (s, 3H), 0.69 (s, 3H), 0.59
(s, 3H), 0.41 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 183.0, 165.8, 165.4,
165.3, 165.2, 165.0, 164.9, 164.6, 137.9, 133.4, 133.2, 133.1, 133.0,
132.8, 130.1, 129.9, 129.8, 129.7, 129.6, 129.5, 129.4, 129.3, 128.9,
128.8, 128.7, 128.5, 128.4, 128.2, 125.3, 102.0, 100.9, 100.7, 96.8, 89.1,
76.1, 74.4, 73.6, 73.4, 73.2, 72.8, 71.9, 71.8, 71.7, 71.1, 70.8, 69.9, 67.4,
67.2, 63.1, 60.7, 60.3, 60.2, 54.5, 52.4, 47.8, 47.3, 44.2, 41.8, 40.4, 39.3,
39.0, 38.8, 37.2, 36.6, 32.5, 30.6, 28.2, 27.8, 26.9, 23.3, 23.0, 21.1, 21.0,
17.9, 17.2, 17.1, 16.7, 16.3.
It was prepared as a white solid from 5b by using the method
established for 6a (1.05 g, 85.0%). [α]D25 = +63° (c = 0.1, CDCl3); mp:
168–170 °C; 1H NMR (400 MHz, CDCl3): δ 8.06–8.05 (m, 2H),
8.02–7.99 (m, 2H), 7.95–7.93 (m, 4H), 7.88–7.86 (m, 2H), 7.51–7.50
(m, 1H), 7.49–7.45 (m, 3H), 7.43–7.38 (m, 7H), 7.36–7.30 (m, 7H),
7.28–7.26 (m, 2H), 7.25–7.21 (m, 4H), 6.01–5.97 (m, 2H), 5.90–
5.82 (m, 2H), 5.69–5.66 (m, 1H), 5.61–5.58 (m, 1H), 5.24–5.22 (m,
2H), 5.01(d, 1H, J = 7.5 Hz), 4.79–4.76 (m, 1H), 4.73–4.70 (m, 1H),
4.65–4.62 (m, 1H), 4.46–4.43 (m, 1H), 4.28–4.25 (m, 1H), 4.13–4.09
(m, 1H), 3.15 (d, 1H, J = 9.3 Hz), 2.21 (d, 1H, J = 11.2 Hz), 2.09–2.07
(m, 1H), 2.02–1.97 (m, 1H), 1.82–1.65 (m, 7H), 1.55–1.53 (m, 1H),
1.35–1.26 (m, 6H), 1.20–1.16 (m, 2H), 1.11–1.04 (m, 2H), 0.99 (d, 3H,
J = 6.2 Hz), 0.95 (s, 3H), 0.93 (d, 3H, J = 6.4 Hz), 0.81 (s, 3H), 0.78 (s,
3H), 0.66 (s, 3H), 0.64 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 183.8,
166.1, 165.8, 165.3, 165.0, 138.0, 133.1, 133.0, 132.9, 132.8, 132.6,
129.9, 129.8, 129.7, 129.6, 129.2, 129.1, 129.0, 128.3, 128.2, 128.1,
128.0, 125.2, 101.6, 97.5, 88.9, 73.8, 73.6, 73.3, 73.2, 72.7, 72.3, 71.3,
70.9, 70.2, 64.2, 63.7, 54.5, 52.4, 47.9, 47.3, 43.1, 41.8, 40.2, 39.3, 39.0,
38.8, 37.2, 36.6, 32.5, 30.5, 29.6, 28.4, 27.8, 24.0, 23.4, 23.2, 21.1, 17.9,
17.6, 17.0, 16.8, 16.4.
4.2.22. 2-α,3-β-di-(2, 3, 4-tri-O-benzoyl-arabinosyloxy)-corosolic
acid (7c)
4.2.25. 2-α,3-β-di-(2, 3, 4, 6, 2’, 3’, 4’, 6’-octa-O-benzoyl-
maltosyloxy)-corosolic acid (7f)
It was prepared as a white solid from 5c by using the method
established for 6a (1.25 g, 88.7%). [α]D25 = +122° (c = 0.1, CDCl3); mp:
198–199 °C; 1H NMR (400 MHz, CDCl3): δ 8.05–8.03 (m, 1H),
8.02–7.97 (m, 5H), 7.86–7.80 (m, 4H), 7.75–7.74 (m, 2H), 7.52–7.45
(m, 3H), 7.43–7.39 (m, 4H), 7.38–7.34 (m, 3H), 7.33–7.27 (m, 5H),
7.25–7.22 (m, 3H), 5.77 (t, 1H, J = 8.8 Hz), 5.66–5.55 (m, 5H), 5.25–5.18
(m, 1H), 5.00 (d, 1H, J = 4.5 Hz), 4.85 (d, 1H, J = 7.6 Hz), 4.79–4.65
(m, 1H), 4.28 (d, 1H, J = 12.8 Hz), 4.07–3.97 (m, 2H), 3.89–3.85 (m,
1H), 3.13 (d, 1H, J = 9.4 Hz), 2.18 (d, 1H, J = 11.1 Hz), 2.09–2.06 (m,
1H), 2.01–1.89 (m, 2H), 1.86–1.58 (m, 6H), 1.51–1.49 (m, 1H),
1.40–1.37 (m, 1H), 1.33–1.08 (m, 7H), 0.96 (s, 3H), 0.89 (d, 9H,
J = 7.4 Hz), 0.83 (s, 3H), 0.67 (s, 3H), 0.61 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 183.5, 166.1, 166.0, 165.5, 165.2, 164.9, 137.9, 133.2, 133.0,
132.8, 130.1, 129.9, 129.8, 129.7, 129.6, 128.4, 128.3, 128.2, 128.1,
125.3, 100.9, 93.7, 89.5, 70.6, 69.5, 69.3, 68.3, 68.0, 67.5, 66.2, 62.4,
61.6, 54.9, 52.4, 47.8, 47.4, 42.2, 41.9, 40.7, 39.4, 38.9, 38.7, 37.5, 36.6,
32.7, 30.5, 28.5, 27.9, 26.8, 23.9, 23.4, 23.3, 21.1, 18.1, 17.5, 17.0, 16.5.
It was prepared as a white solid from 5f by using the method
established for 6a (1.84 g, 98.9%). [α]D25 = +48° (c = 0.1, CDCl3); mp:
173–174 °C; 1H NMR (400 MHz, CDCl3): δ 8.24–8.22 (m, 2H), 8.18–
8.16 (m, 2H), 8.07–8.02 (m, 4H), 7.90–7.85 (m, 4H), 7.81–7.79 (m,
2H), 7.75–7.70 (m, 10H), 7.62–7.60 (m, 2H), 7.55–7.51 (m, 2H), 7.50–
7.44 (m, 7H), 7.43–7.37 (m, 13H), 7.36–7.27 (m, 9H), 7.24–7.17 (m,
9H), 7.16–7.09 (m, 4H), 6.15–6.06 (m, 2H), 5.82–5.75 (m, 2H), 5.74–
5.64 (m, 3H), 5.53–5.49 (m, 1H), 5.43 (t, 1H, J = 4.1 Hz), 5.32–5.25
(m, 3H), 5.23–5.18 (m, 1H), 5.07–4.94 (m, 4H), 4.87 (d, 1H, J = 7.5 Hz),
4.73–4.69 (m, 1H), 4.62–4.53 (m, 3H), 4.50–4.46 (m, 1H), 4.45–
4.39 (m, 1H), 4.35–4.30 (m, 2H), 4.27–4.22 (m, 1H), 4.18–4.10 (m,
2H), 3.95–3.93 (m, 1H), 3.06 (d, 1H, J = 9.2 Hz), 2.20 (d, 1H, J = 10.9 Hz),
2.05–1.94 (m, 3H), 1.81–1.64 (m, 6H), 1.55–1.52 (m, 1H), 1.44–1.24
(m, 7H), 1.19–1.05 (m, 3H), 0.99 (s, 3H), 0.92 (s, 6H), 0.76 (s, 3H),
0.74 (s, 3H), 0.65 (s, 3H), 0.51 (s, 3H). 13C NMR (100 MHz, CDCl3): δ
183.4, 166.2, 166.1, 165.8, 165.7, 165.5, 165.4, 165.1, 165.0, 164.9,
164.8, 137.9, 133.4, 133.2, 133.1, 132.9, 132.8, 132.7, 130.0, 129.9,
129.8, 129.7, 129.6, 129.5, 129.4, 129.0, 128.9, 128.7, 128.6, 128.5,
128.3, 128.2, 128.1, 128.0, 127.9, 125.5, 101.5, 97.4, 96.9, 96.1, 88.9,
75.2, 74.9, 73.9, 73.5, 73.4, 73.3, 72.5, 72.4, 70.9, 70.7, 70.1, 69.1, 68.7,
64.2, 62.5, 62.4, 54.4, 52.4, 47.8, 47.3, 43.5, 41.8, 40.2, 39.3, 39.0, 38.8,
37.2, 36.6, 32.5, 30.5, 28.3, 27.8, 26.8, 24.0, 23.4, 21.1, 18.0, 17.4, 17.0,
16.8, 16.3.
4.2.23. 2-α,3-β-di-(2, 3, 5-tri-O-benzoyl-ribosyloxy)-corosolic acid
(7d)
It was prepared as a white solid from 5d by using the method
established for 6a (1.01 g, 89.4%). [α]D25 = −52° (c = 0.1, CDCl3); mp:
185–187 °C; 1H NMR (400 MHz, CDCl3): δ 8.05–8.02 (m, 5H),
7.98–7.96 (m, 6H), 7.79–7.77 (m, 2H), 7.56–7.52 (m, 2H), 7.50–7.44
(m, 4H), 7.43–7.37 (m, 3H), 7.30–7.27 (m, 4H), 7.25–7.22 (m, 4H),
6.20–6.17 (m, 1H), 6.11–6.06 (m, 1H), 5.71–5.65 (m, 2H), 5.58–
5.54 (m, 1H), 5.50–5.44 (m, 2H), 5.34–5.30 (m, 1H), 5.23–5.19 (m,
1H), 4.73 (d, 1H, J = 12.3 Hz), 4.63–4.56 (m, 1H), 4.23–4.19 (m, 1H),
4.12–4.09 (m, 1H), 4.02–3.95 (m, 1H), 3.44 (d, 1H, J = 9.4 Hz), 2.24–
2.22 (m, 1H), 2.18–2.15 (m, 1H), 2.02–1.90 (m, 4H), 1.86–1.80 (m,
1H), 1.70–1.59 (m, 4H), 1.55–1.41 (m, 5H), 1.34–1.23 (m, 5H), 1.16
(s, 3H), 1.05 (s, 3H), 0.95 (s, 3H), 0.96 (s, 3H), 0.85 (s, 3H), 0.76 (s,
3H), 0.74 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 183.5, 166.1, 165.5,
165.3, 164.9, 137.9, 132.2, 133.0, 132.9, 132.8, 130.1, 130.0, 129.9,
129.8, 129.7, 129.6, 128.4, 128.3, 128.2, 128.1, 125.3, 101.0, 93.7, 89.5,
70.7, 69.5, 69.3, 68.1, 67.5, 66.2, 62.4, 61.7, 55.0, 52.4, 47.9, 47.5, 42.3,
4.2.26. 2-α,3-β-di-xylosyloxy-maslinic acid (8a)
Sodium methoxide–methanol solution (33%, 1.1 mL) was added
dropwise to a suspension of 6a (920 mg, 0.676 mmol) in MeOH
(20 mL) at room temperature and the mixture was stirred for 5 h.
The reaction was neutralized with Dowex H+ resin to pH 7, filtered
and then concentrated in vacuo. The residue was purified by silica-
gel column chromatography (9:1, CHCl3-MeOH) to give 8a as white
solid (498 mg, 88.3%). [α]D25 = −35° (c = 0.1, DMSO); mp: 253–
255 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.14 (s, 1H), 4.46 (d, 1H,
J = 4.4 Hz), 4.30 (d, 1H, J = 7.1 Hz), 4.02–4.01 (m, 1H), 3.71–3.68 (m,
1H), 3.65–3.62 (m, 2H), 3.54–3.36 (m, 8H), 3.32–3.30 (m, 2H), 3.28–
3.26 (m, 1H), 3.23–3.13 (m, 5H), 3.09–3.06 (m, 1H), 3.05–3.02 (m,

J. Xu et al./Carbohydrate Research 424 (2016) 42–53
51
1H), 2.99–2.95 (m, 1H), 2.74–2.72 (m, 1H), 1.97–1.96 (m, 1H), 1.89–
1.82 (m, 3H), 1.86–1.56 (m, 3H), 1.52–1.45 (m, 3H), 1.42–1.36 (m,
2H), 1.31–1.26 (m, 2H), 1.23–1.21 (m, 1H), 1.07 (s, 3H), 1.02 (s, 3H),
0.87 (s, 3H), 0.86 (s, 3H), 0.85 (s, 3H), 0.79 (s, 3H), 0.69 (s, 3H). 13C
NMR (100 MHz, DMSO-d6): δ 178.8, 144.1, 121.3, 104.4, 96.4, 86.5,
76.5, 73.7, 72.1, 70.5, 70.1, 69.5, 69.3, 65.4, 62.8, 54.3, 52.2, 47.1, 45.8,
45.5, 44.0, 41.4, 40.9, 38.9, 37.3, 33.5, 32.9, 32.4, 32.2, 30.5, 28.1, 25.7,
23.5, 23.2, 22.7, 17.8, 17.7, 16.9, 16.3. HRMS (ESI): Calcd for
C40H64O12Na [M + Na]+: 759.4290; found:759.4259.
(m, 14H), 3.13–3.09 (m, 2H), 2.80–2.70 (m, 1H), 2.07–2.05 (m, 1H),
1.83–1.67 (m, 8H), 1.56–1.39 (m, 8H), 1.29–1.22 (m, 3H), 1.06 (s, 3H),
1.05 (s, 3H), 0.95 (s, 9H), 0.76 (s, 3H), 0.70 (s, 3H). 13C NMR (100 MHz,
DMSO-d6): δ 175.3, 144.6, 120.9, 104.0, 103.2, 98.7, 87.0, 81.3, 80.8,
75.6, 75.2, 74.9, 74.8, 74.0, 73.3, 72.7, 71.6, 70.7, 70.6, 68.2, 60.8, 60.7,
60.5, 54.8, 47.2, 46.1, 45.6, 43.8, 41.5, 41.1, 40.3, 38.9, 37.1, 33.7, 33.0,
32.5, 32.4, 30.5, 28.8, 27.3, 25.6, 23.6, 23.2, 22.9, 18.0, 17.1, 16.1. HRMS
(ESI): Calcd for C54H88O24Na [M + Na]+: 1143.5558; found: 1143.5514.
4.2.31. 2-α,3-β-di-maltosyloxy-maslinic acid (8f)
4.2.27. 2-α,3-β-di-glucosyloxy-maslinic acid (8b)
It was prepared as a white solid from 6f by using the method
established for 8a (530 mg, 80.2%). [α]D25 = +80° (c = 0.1, DMSO); mp:
280–282 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.13 (s, 1H), 5.00–4.95
(m, 2H), 4.44 (d. 1H, J = 7.1 Hz, 1H), 4.34 (d, 1H, J = 6.9 Hz, 1H),
3.92–3.88 (m, 1H), 3.71–3.66 (m, 2H), 3.61–3.59 (m, 3H), 3.55–3.50
(m, 5H), 3.48–3.42 (m, 9H), 3.40–3.34 (m, 7H), 3.31–3.21 (m, 10H),
3.12–3.02 (m, 6H), 2.76–2.73 (m, 1H), 2.12–2.05 (m, 1H), 1.90–1.80
(m, 3H), 1.66–1.39 (m, 9H), 1.30–1.20 (m, 4H), 1.07 (s, 3H), 1.05 (s,
3H), 0.87 (s, 3H), 0.86 (s, 6H), 0.76 (s, 3H), 0.70 (s, 3H). 13C NMR
(100 MHz, DMSO-d6): δ 176.5, 144.4, 121.0, 103.6, 100.9, 96.4, 87.3,
79.9, 79.7, 76.7, 76.2, 75.4, 75.0, 74.0, 73.5, 73.3, 72.8, 72.5, 71.3, 70.0,
69.9, 61.1, 60.9, 60.8, 60.7, 54.8, 47.2, 45.9, 45.6, 43.4, 41.5, 41.0, 40.3,
38.9, 37.1, 33.6, 33.0, 32.5, 32.3, 30.5, 28.6, 27.3, 25.6, 23.5, 23.2, 22.8,
18.0, 17.0, 16.1. HRMS (ESI): Calcd for C54H88O24Na [M + Na]+:
1143.5558; found: 1143.5505.
It was prepared as a white solid from 6b by using the method
established above for 8a (320 mg, 86.7%). [α]D25 = +29° (c = 0.1, DMSO);
mp: 232–233 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.15 (s, 1H), 4.95–
4.83 (m, 3H), 4.80–4.70 (m, 2H), 4.39–4.38 (m, 1H), 4.28 (d, 1H,
J = 7.6 Hz), 4.10–4.03 (m, 1H), 3.89–3.85 (m, 1H), 3.66 (d, 2H,
J = 10.7 Hz), 3.45–3.33 (m, 10H), 3.21 (d, 1H, J = 9.5 Hz), 3.14–3.01
(m, 7H), 2.74–2.71 (m, 1H), 2.07 (d, 1H, J = 9.1 Hz), 1.91–1.83 (m, 3H),
1.65–1.57 (m, 3H), 1.52–1.45 (m, 3H), 1.43–1.38 (m, 2H), 1.32–1.28
(m, 2H), 1.23–1.22 (m, 1H), 1.08 (s, 3H), 1.05 (s, 3H), 0.87 (s, 3H),
0.86 (s, 6H), 0.77 (s, 3H), 0.69 (s, 3H). 13C NMR (100 MHz, DMSO-
d6): δ 178.6, 144.0, 121.3, 103.6, 96.9, 86.9, 77.1, 76.9, 76.6, 76.5, 74.2,
72.9, 71.1, 70.1, 61.5, 61.2, 54.7, 52.1, 47.1, 45.7, 45.5, 43.8, 41.4, 40.9,
40.3, 38.9, 37.1, 33.4, 32.9, 32.4, 32.1, 30.4, 28.5, 27.2, 25.8, 23.4, 23.1,
22.7, 18.0, 16.8, 16.1. HRMS (ESI): Calcd for C42H68O14Na [M + Na]+:
819.4501; found: 819.4464.
4.2.32. 2-α,3-β-di-xylosyloxy-corosolic acid (9a)
4.2.28. 2-α,3-β-di-arabinosyloxy-maslinic acid (8c)
It was prepared as a white solid from 7a by using the method es-
tablished for 8a (400 mg, 86%). [α]D25 = −42° (c = 0.1, DMSO); mp:
241–243 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.12 (s, 1H), 5.00–4.95
(m, 2H), 4.48 (d, 1H, J = 4.3 Hz), 4.31 (d, 1H, J = 7.1 Hz), 4.03–4.01 (m,
1H), 3.72–3.68 (m, 1H), 3.65–3.62 (m, 1H), 3.40–3.34 (m, 6H),
3.32–3.30 (m, 1H), 3.28–3.26 (m, 1H), 3.23–3.15 (m, 5H), 3.09–3.04
(m, 2H), 2.99–2.95 (m, 1H), 2.09 (d, 1H, J = 11.8 Hz), 2.03–2.01 (m,
1H), 1.91–1.85 (m, 3H), 1.80–1.76 (m, 1H), 1.58–1.56 (m, 1H), 1.52–1.48
(m, 4H), 1.43–1.41 (m, 2H), 1.29–1.23 (m, 5H), 1.02 (s, 6H), 0.90 (s,
3H), 0.89 (s, 3H), 0.80 (s, 3H), 0.79 (s, 3H), 0.72 (s, 3H). 13C NMR
(100 MHz, DMSO-d6): δ 178.3, 138.3, 124.4, 104.3, 96.2, 86.4, 76.4,
73.7, 72.0, 70.6, 70.2, 69.5, 69.3, 65.4, 62.7, 54.2, 52.4, 52.1, 47.0, 46.9,
44.0, 41.7, 40.8, 39.1, 38.5, 37.1, 36.3, 32.6, 30.2, 28.1, 27.5, 23.8, 23.2,
23.1, 21.1, 17.7, 17.0, 16.9, 16.4. HRMS (ESI): Calcd for C40H64O12Na
[M + Na]+: 759.4290; found: 759.4263.
It was prepared as a white solid from 6c by using the method es-
tablished for 8a (497 mg, 80.6%). [α]D25 = −27° (c = 0.1, DMSO); mp:
266–268 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.14 (s, 1H), 5.10–5.02
(m, 1H), 4.88 (s, 1H), 4.50 (s, 1H), 4.28 (d, 1H, J = 7.1 Hz), 4.16 (d, 1H,
J = 12.2 Hz), 4.04 (t, 1H, J = 11.0 Hz), 3.92 (d, 1H, J = 10.9 Hz), 3.76–
3.74 (m, 1H), 3.69–3.65 (m, 1H), 3.61–3.59 (m, 1H), 3.52–3.49 (m,
1H), 3.40–3.34 (m, 11H), 3.29–3.27 (m, 1H), 3.25–3.22 (m, 1H), 3.15
(d, 1H, J = 9.8 Hz), 2.74–2.72 (m, 1H), 1.91–1.88 (m, 2H), 1.84–1.83 (m,
2H), 1.66–1.53 (m, 4H), 1.51–1.36 (m, 4H), 1.33–1.26 (m, 2H), 1.24–
1.22 (m, 1H), 1.06 (s, 3H), 1.02 (s, 3H), 0.88 (s, 3H), 0.86 (s, 6H), 0.82
(s, 3H), 0.69 (s, 3H). 13C NMR (100 MHz, DMSO-d6): δ 178.7, 144.0,
121.3, 104.2, 96.2, 85.9, 72.9, 71.2, 70.7, 70.0, 68.0, 64.9, 63.5, 59.1,
54.0, 47.0, 45.7, 45.5, 43.6, 41.4, 41.1, 40.8, 38.9, 37.2, 33.4, 32.8, 32.3,
32.1, 30.4, 28.1, 27.2, 25.6, 23.5, 23.1, 22.6, 17.7, 16.8, 16.3. HRMS (ESI):
Calcd for C40H64O12Na [M + Na]+: 759.4290; found: 759.4257.
4.2.33. 2-α,3-β-di-glucosyloxy-corosolic acid (9b)
4.2.29. 2-α,3-β-di-ribosyloxy-maslinic acid (8d)
It was prepared as a white solid from 7b by using the method
established for 8a (450 mg, 94.7%). [α]D25 = +35° (c = 0.1, DMSO); mp:
236–238 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.13 (s, 1H), 4.89–4.72
(m, 5H), 4.39–4.37 (m, 2H), 4.29 (d, 1H, J = 7.5 Hz), 4.10–4.00 (m,
1H), 3.91–3.87 (m, 1H), 3.66 (d, 2H, J = 10.6 Hz), 3.45–3.30 (m, 8H),
3.20 (d, 1H, J = 9.5 Hz), 3.15–2.99 (m, 8H), 2.13–2.09 (m, 2H), 1.92–1.76
(m, 4H), 1.57–1.41 (m, 6H), 1.28–1.26 (m, 4H), 1.05 (s, 3H), 1.02 (s,
3H), 0.89 (s, 3H), 0.88 (s, 3H), 0.79 (s, 3H), 0.77 (s, 3H), 0.72 (s, 3H).
13C NMR (100 MHz, DMSO-d6): δ 178.3, 138.3, 124.4, 103.6, 98.7, 87.1,
77.2, 76.9, 76.6, 74.3, 73.0, 70.9, 70.2, 70.1, 61.6, 61.3, 54.7, 52.5, 52.1,
47.0, 46.9, 43.8, 41.8, 40.3, 38.5, 37.0, 36.3, 32.7, 30.2, 28.6, 27.5, 23.8,
23.2, 23.1, 21.1, 18.0, 17.0, 16.9, 16.2. HRMS (ESI): Calcd for
C42H68O14Na [M + Na]+: 819.4501; found: 819.4465.
It was prepared as a white solid from 6d by using the method
established for 8a (420 mg, 88.2%). [α]D25 = −54° (c = 0.1, DMSO); mp:
238–241 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.15 (s, 1H), 4.88–
4.77 (m, 4H), 4.70–4.68 (m, 1H), 4.64 (d, 1H, J = 5.1 Hz), 4.06 (d, 1H,
J = 10.4 Hz), 3.82–3.80 (m, 1H), 3.72–3.69 (m, 2H), 3.65–3.63 (m, 1H),
3.55–3.52 (m, 1H), 3.50–3.48 (m, 1H), 3.41–3.32 (m, 10H), 3.07 (d,
1H, J = 9.7 Hz), 2.74–2.72 (m, 1H), 1.99–1.98 (m, 1H), 1.91–1.84 (m,
3H), 1.65–1.53 (m, 3H), 1.53–1.41 (m, 5H), 1.32–1.22 (m, 4H), 1.08
(s, 3H), 0.98 (s, 3H), 0.88 (s, 3H), 0.86 (s, 6H), 0.76 (s, 3H), 0.69 (s,
3H). 13C NMR (100 MHz, DMSO-d6): δ 178.6, 143.9, 121.4, 102.5, 96.4,
87.3, 71.4, 71.0, 69.9, 69.6, 68.5, 68.3, 65.6, 63.9, 63.7, 54.2, 52.1, 47.0,
45.7, 45.0, 42.7, 41.4, 40.8, 40.6, 38.9, 37.1, 33.4, 32.9, 32.3, 32.1, 30.4,
28.4, 27.2, 25.6, 23.4, 23.1, 22.6, 17.9, 17.7, 16.8, 16.2. HRMS (ESI):
Calcd for C40H64O12Na [M + Na]+: 759.4290; found: 759.4265.
4.2.34. 2-α,3-β-di-arabinosyloxy-corosolic acid (9c)
It was prepared as a white solid from 7c by using the method
established for 8a (500 mg, 88.0%). [α]D25 = −25° (c = 0.1, DMSO); mp:
257–260 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.11 (s, 1H), 4.51 (s,
1H), 4.28 (d, 1H, J = 7.0 Hz), 4.03 (t, 1H, J = 10.9 Hz), 3.96–3.89 (m,
1H), 3.75 (d, 1H, J = 10.7 Hz), 3.69–3.63 (m, 2H), 3.60–3.58 (m, 3H),
3.54–3.49 (m, 2H), 3.47–3.44 (m, 2H), 3.40–3.36 (m, 2H), 3.34–
3.28 (m, 4H), 3.25–3.22 (m, 1H), 3.16 (d, 1H, J = 9.8 Hz), 2.10 (d, 1H,
4.2.30. 2-α,3-β-di-lactosyloxy-maslinic acid (8e)
It was prepared as a white solid from 6e by using the method es-
tablished for 8a (390 mg, 70.9%). [α]D25 = +34° (c = 0.1, DMSO); mp:
301–303 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.12 (s, 1H), 4.50–4.45
(m, 1H), 4.37–4.35 (m, 1H), 4.20–4.15 (m, 2H), 3.90–3.85 (m, 3H),
3.76–3.70 (m, 4H), 3.60–3.58 (m, 8H), 3.51–3.46 (m, 9H). 3.35–3.20

52
J. Xu et al./Carbohydrate Research 424 (2016) 42–53
J = 11.2 Hz), 1.95–1.94 (m, 1H), 1.90–1.86 (m, 3H), 1.83–1.79 (m, 1H),
1.57–1.48(m, 6H),1.43–1.41 (m, 2H), 1.30–1.22 (m, 5H), 1.02 (s, 6H),
0.90 (s, 6H), 0.82 (s, 3H), 0.80 (d, 3H, J = 6.2 Hz), 0.72 (s, 3H). 13C NMR
(100 MHz, DMSO-d6): δ 178.6, 138.4, 124.3, 104.2, 96.2, 85.9, 72.9,
71.3, 70.7, 70.6, 70.0, 68.0, 64.9, 63.5, 59.1, 54.0, 52.5, 52.1, 47.0, 46.9,
43.7, 41.8, 41.1, 39.1, 38.6, 38.5, 37.1, 36.4, 32.6, 30.3, 28.1, 27.6, 23.9,
23.2, 23.1, 21.1, 17.7, 17.1, 17.0, 16.4. HRMS (ESI): Calcd for C40H64O12Na
[M + Na]+: 759.4290; found: 759.4258.
5.8 mM 4-nitrophenyl-α-D-glucopyranoside (PNPG). Solution of the
inhibitors, i.e., glycosylated derivatives of dihydroxylpentacyclic
triterpene acids and acarbose (positive control), were prepared with
ethanol–water (1:1) at a series of concentrations. The reaction
mixture was pre-incubated at 37 °C for 15 minutes after addition
of KH2PO4-K2HPO4 buffer, 10 μL α-glucosidase and a certain volume
of inhibitor. A 20 μL aliquot of PNPG solution was then added to the
reaction mixture in a final volume of 250 μL, which was further in-
cubated at 37 °C for 10 minutes, and the absorbance was recorded
by microplate reader at 405 nm. The percentage of inhibition was
calculated using [(A–(A1–A2)) /A] × 100%, where A was the absor-
bance without the derivative, A1 was the absorbance with the
derivative and A2 was background reference of derivative. Each ex-
periment was carried out in four replicates at least. The IC50 value
was determined from a plot of the percentage of inhibition versus
the sample concentration. Acarbose was used as a positive control
and was evaluated under the same procedure. In addition, to further
analyze the inhibitory activity of α-glucosidase of the parent com-
pounds (low water solubility) and their derivatives under the
identical conditions and the structure-activity relationship, DMSO
was also used as the solvent to perform the bioactivity assay. The
method was described above for α-glucosidase inhibition assay
(ethanol–water system).
4.2.35. 2-α,3-β-di-ribosyloxy-corosolic acid (9d)
It was prepared as a white solid from 7d by using the method
established for 8a (440 mg, 75.3%). [α]D25 = −75° (c = 0.1, DMSO); mp:
235–238 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.12 (s, 1H), 4.88–
4.83 (m, 1H), 4.80–4.74 (m, 3H), 4.73–4.69 (m, 2H), 4.65 (d, 1H,
J = 5.0 Hz), 4.05 (d, 1H, J = 10.5 Hz), 3.82–3.79 (m, 1H), 3.73–3.69 (m,
2H), 3.67–3.63 (m, 1H), 3.53–3.49 (m, 2H), 3.40–3.32 (m, 10H), 3.07
(d, 1H, J = 9.6 Hz), 2.09 (d, 1H, J = 11.2 Hz), 2.05–2.02 (m, 1H), 1.93–
1.88 (m, 2H), 1.80–1.76 (m, 1H), 1.58–1.56 (m, 1H), 1.52–1.48 (m,
4H), 1.43–1.41 (m, 2H), 1.28–1.24 (m, 4H),1.03 (s, 3H), 0.98 (s, 3H),
0.90 (s, 3H), 0.89 (s, 3H), 0.80 (d, 3H, J = 6.4 Hz), 0.76 (s, 3H), 0.73
(s, 3H). 13C NMR (100 MHz, DMSO-d6): δ 178.3, 138.3, 124.4, 102.5,
96.3, 87.4, 71.4, 71.0, 69.9, 69.6, 68.5, 68.1, 65.7, 63.9, 63.7, 54.1, 52.4,
52.1, 46.9, 42.8, 41.7, 40.6, 39.1, 38.5, 38.4, 37.0, 36.3, 32.6, 30.2, 28.5,
27.5, 23.8, 23.2, 23.0, 21.1, 17.8, 17.0, 16.9, 16.3. HRMS (ESI): Calcd
for C40H64O12Na [M + Na]+: 759.4290; found: 759.4257.
4.3.2. Measurement of kinetic constants
For kinetic studies of α-glucosidase inhibition by the synthe-
sized glycosides (i.e., 9e), enzyme and inhibitor at various
concentrations (0, 0.821, 1.642, 2.463 mM) were incubated with in-
creasing concentrations of substrate PNPG (0.232, 0.348, 0.464, 0.580,
0.696, 0.812, 0.928 mM). The enzyme activities were measured, and
the kinetic constants and modes of inhibition for active com-
pound were determined based on Lineweaver–Burk plots.39
4.2.36. 2-α,3-β-di-lactosyloxy-corosolic acid (9e)
It was prepared as a white solid from 7e by using the method
established for 8a (510 mg, 70.2%). [α]D25 = +26° (c = 0.1, DMSO); mp:
1
291–293 °C; H NMR (400 MHz, DMSO-d6): δ 5.10 (s, 1H), 4.47 (d,
1H, J = 7.5 Hz), 4.36 (d, 1H, J = 7.0 Hz), 4.18–4.15 (m, 2H), 3.90–3.88
(m, 1H), 3.76–3.74 (m, 2H), 3.62–3.59 (m, 4H), 3.58–3.54 (m, 4H),
3.53–3.50 (m, 4H), 3.49–3.42 (m, 8H), 3.33–3.28 (m, 9H), 3.27–
3.21 (m, 6H), 3.12–3.06 (m, 2H), 2.13–2.12 (m, 2H), 1.91–1.83 (m,
4H), 1.73 (s, 2H), 1.55–1.39 (m, 8H), 1.26–1.21 (m, 5H), 1.05 (s, 3H),
1.01 (s, 3H), 0.88 (s, 6H), 0.79 (s, 3H), 0.76 (s, 3H), 0.74 (s, 3H). 13C
NMR (100 MHz, DMSO-d6): δ 176.2, 138.8, 124.0, 104.1, 103.3, 98.3,
87.2, 81.4, 80.9, 79.2, 75.6, 75.2, 75.0, 74.8, 74.7, 74.1, 73.3, 72.8, 71.5,
70.7, 70.6, 68.2, 60.9, 60.8, 60.5, 54.8, 52.7, 47.1, 47.0, 43.7, 41.8, 40.2,
38.7, 37.0, 36.6, 32.8, 30.5, 28.7, 27.7, 24.1, 23.7, 23.2, 23.1, 21.3, 18.1,
18.0, 17.2, 16.3. HRMS (ESI): Calcd for C54H88O24Na [M + Na]+:
1143.5558; found: 1143.5508.
Acknowledgment
We thank the Jiangxi Province Natural Science Foundation of
China (20132BAB204010) for financial support.
Appendix: Supplementary material
Supplementary data to this article can be found online at
doi:10.1016/j.carres.2016.02.009.
4.2.37. 2-α,3-β-di-maltosyloxy-corosolic acid (9f)
It was prepared as a white solid from 7f by using the method
established for 8a (540 mg, 74.4%). [α]D25 = +41° (c = 0.1, DMSO);
mp: 280–283 °C; 1H NMR (400 MHz, DMSO-d6): δ 5.10 (s, 1H),
4.99–4.95 (m, 2H), 4.44 (d, 1H, J = 7.4 Hz), 4.35 (d, 1H, J = 7.3 Hz),
3.93–3.89 (m, 1H), 3.70 (t, 3H, J = 11.8 Hz), 3.61–3.59 (m, 4H),
3.56–3.49 (m, 4H), 3.46–3.43 (m, 6H), 3.42–3.34 (m, 6H), 3.30–3.27
(m, 2H), 3.26–3.20 (m, 8H), 3.11–3.02 (m, 6H), 2.12 (d, 2H, J = 10.1 Hz),
1.92–1.83 (m, 4H), 1.74 (s, 2H), 1.55–1.39 (m, 8H), 1.26–1.21 (m, 5H),
1.05 (s, 3H), 1.01 (s, 3H), 0.89 (s, 3H), 0.88 (s, 3H), 0.79 (s, 3H), 0.76
(s, 3H), 0.73 (s, 3H). 13C NMR (100 MHz, DMSO-d6): δ 175.5, 138.7,
124.1, 103.6, 100.9, 98.2, 87.6, 80.0, 79.8, 79.2, 76.7, 76.3, 75.5, 75.0,
74.0, 73.5, 73.3, 72.7, 72.5, 71.2, 70.1, 70.0, 61.1, 60.9, 60.7, 54.8, 52.7,
47.1, 47.0, 43.4, 41.8, 40.3, 38.7, 37.0, 36.5, 32.8, 30.5, 28.6, 27.7, 24.0,
23.5, 23.2, 23.1, 21.2, 18.1, 18.0, 17.2, 16.2. HRMS (ESI): Calcd for
C54H88O24Na [M + Na]+: 1143.5558; found: 1143.5501.
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