Concise synthesis and antidiabetic effect of three natural triterpenoid saponins isolated from Fadogia ancylantha (Makoni tea)

Article abstract of DOI:10.1002/hlca.201500061

The first concise synthesis of the bidesmosidic oleanolic acid saponins 1-3 isolated from Fadogia ancylantha (Makoni tea) have been accomplished through a 'one-pot sequential glycosylation' strategy with two glycosyl 1-(trichloroacetimidate)s as glycosyl donors. The synthesized natural products 1-3 were then evaluated for their inhibitory activities against α-glucosidase, α-amylase, and lipase. Among the assayed compounds 1-3, compound 1 showed strong α-glucosidase and α-amylase inhibition, with IC₅₀ values of 160 and 180 μM, respectively. Moreover, compounds 2 and 3 showed strong inhibition against α-glucosidase and lipase, with the respective IC₅₀ values of 170 and 190 μM, and 190 and 200 μM.

Full text of DOI:10.1002/hlca.201500061

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Helvetica Chimica Acta – Vol. 98 (2015)
Concise Synthesis and Antidiabetic Effect of Three Natural Triterpenoid
Saponins Isolated from Fadogia ancylantha (Makoni tea)
by Zi-Li Fenga)d)1), Shao-Ping Wuc)1), Wen-Hong Li*a), Tian-Tian Guoa), Qing-Chao Liu*a)b)
a) Department of Pharmaceutical Engineering, Northwest University, Xiꢀan 710069, Shaanxi,
P. R. China (fax: þ 86-29-88305682; e-mail: liuqc21@nwu.edu.cn)
b) Department of Applied Biology & Chemical Technology, The Hong Kong Polytechnic University,
Kowloon, Hong Kong, P. R. China
c) Sorbonne UniversitØs, UPMC Univ. Paris 06, CNRS UMR 8232, IPCM, 4 place Jussieu, FR-75005
Paris
d) School of Bioscience and Engeering, Shaanxi University of Technology, Hanzhong 732001, Shaanxi,
P. R. China
The first concise synthesis of the bidesmosidic oleanolic acid saponins 1 – 3 isolated from Fadogia
ancylantha (Makoni tea) have been accomplished through a ꢁone-pot sequential glycosylationꢀ strategy
with two glycosyl 1-(trichloroacetimidate)s as glycosyl donors. The synthesized natural products 1 – 3
were then evaluated for their inhibitory activities against a-glucosidase, a-amylase, and lipase. Among
the assayed compounds 1 – 3, compound 1 showed strong a-glucosidase and a-amylase inhibition, with
IC50 values of 160 and 180 mm, respectively. Moreover, compounds 2 and 3 showed strong inhibition
against a-glucosidase and lipase, with the respective IC50 values of 170 and 190 mm, and 190 and 200 mm.
Introduction. – For individuals with postprandial hyperglycemia, there is a growing
health risk, such as coronary heart disease, angina pectoris, myocardial infarction, and
other cardiovascular diseases. In order to reduce the incidence of the cardiovascular
diseases associated with high blood glucose level, the conventional approach to treat
diabetic patients and individuals with impaired glucose tolerance focuses on the control
of blood glucose level [1]. a-Glucosidase is a glucohydrolase enzyme at the brush-
border surface membrane of intestinal cells, that hydrolyses the cleavage of d-glucose
of disaccharides and oligosaccharides from dietary complex carbohydrates. a-
Glucosidase inhibitors postpone the digestion of dietary complex carbohydrates into
monosaccharides in the intestine and reduce the postprandial insulin and glucose level
[2][3]. Consequently, synthetic a-glucosidase inhibitors, such as acarbose, voglibose,
and miglitol effectively make up defective early phase insulin release through inhibiting
post-prandial absorption of monosaccharides, and have been formulated and launched
for clinical use of the treatment of type 2 diabetes in the last two decades [4 – 6].
Considerable efforts have been made in the development of potent and effective
small-molecule a-glucosidase inhibitors from natural products and artificial synthetic
compounds for the treatment of type 2 diabetes [7 – 15]. Our program was carried out
with carbohydrate-based modification on natural products. In a series of studies on in
vitro a-glucosidase-inhibiting principles from synthetic natural products and deriva-
1
)
Zi-Li Feng and Shao-Ping Wu contributed equally to this work.
ꢂ 2015 Verlag Helvetica Chimica Acta AG, Zürich

Helvetica Chimica Acta – Vol. 98 (2015)
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tives, we previously reported four hederagenin glycosides, two natural benzophenone
O-glycosides, and ten derivatives by efficient artificial synthesis. The structureÀactivity
relationships (SAR) of these carbohydrate-based modifications on hederagenin and
benzophenone showed that the sugar moiety strongly influenced a-glucosidase
inhibitory activity[16][17].
Glycosides of oleanolic acid with one sugar chain attached through an ester linkage
at C(28) and another through an ether linkage at C(3), constitute more than half of the
triterpeniod saponins, which are widely distributed in plants and in some marine
organisms [18 – 20]. They have been reported to possess important biological and
pharmacological activities, including anti-inflammatory [21], anti-HIV [22], antifungal
[23], antitumor [24 – 26], and inhibition against a-glucosidase [12][27 – 29]. The plant,
Fadogia ancylantha Hiern. (Rubiaceae), commonly known as ꢁMakoniꢀ or ꢁmarangeꢀ,
is a wild perennial shrub growing in the Eastern Highlands area of Zimbabwe. Its leaves
are used as a folk medicine for the treatment of topical ulcers. By investigating the
chemical constituents of Makoni tea, Mencherini et al. recently reported the isolation
and structural characterization of three oleanolic acid saponins 1 – 3 (Fig.) [30].
Attracted by the specific structure and potent biological properties of oleanolic acid
saponins 1 – 3, we report here a facile synthesis of these metabolites. The three saponins
1 – 3 were also evaluated for in vitro inhibition activities against a-glucosidase, a-
Figure. Structures of oleanolic acid saponins 1 – 3 and Acarbose

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Helvetica Chimica Acta – Vol. 98 (2015)
amylase, and lipase. These investigations would be useful for designing and preparing
novel stronger a-glucosidase inhibitors and elucidate the structureÀactivity relation-
ship in the inhibition process of a-glucosidase for the treatment of type 2 diabetes.
Results and Discussion. – Recently, we have successfully completed the synthesis of
several bidesmosidic oleanolic acid saponins via applying the ꢁone-pot sequential
glycosylationꢀ strategy [17][31 – 35]. Encouraged by these accomplishments, we
decided to adopt the similar strategy with two glycosyl 1-(trichloroacetimidate)s as
glycosyl donors to synthesize the new bidesmosidic oleanolic acid saponins 1 – 3 in the
present study.
Synthesis of Target Compounds 1 – 3. Firstly, the two trichloroacetimidate donors 4
and 5 were prepared as depicted in Scheme 1, respectively. Treatment of the known
1,2,3,4,6-penta-O-acetyl-a/b-d-glucopyranose 6 [36] or 1,2,3,4,6-penta-O-acetyl-a/b-d-
galactopyranose 7 [37] with 33% HBr in AcOH in the presence of lutidine afforded
3,4,6-tri-O-acetyl-1,2-O-(1-methoxyethylidene)-a-d-glucopyranose 8 (95%) and 3,4,6-
tri-O-acetyl-1,2-O-(1-methoxyethylidene)-a-d-galactopyranose 9 (94%), respectively.
Removal of the Ac groups with MeONa in CH2Cl2/MeOH, followed by benzoylation
with BzCl in pyrdine, gave 3,4,6-tri-O-benzoyl-1,2-O-(1-methoxyethylidene)-a-d-
glucopyranose 10 (80%) or 3,4,6-tri-O-benzoyl-1,2-O-(1-methoxyethylidene)-a-d-
galactopyranose 11 (83%). Treatment of 10 or 11 with AcOH afforded the desired
1,2-di-O-acetyl-3,4,6-tri-O-benzoyl-a/b-d-glucopyranose 12 (97%) or 1,2-di-O-acetyl-
3,4,6-tri-O-benzoyl-a/b-d-galactopyranose 13 (96%). Then, regioselective removal of
Scheme 1
a) 33% HBr in AcOH, lutidine, MeOH/CH2Cl2, 95% for 8, 94% for 9. b) MeONa, MeOH/CH2Cl2.
c) BzCl, pyrdine, 80% for 10 (two steps), 83% for 11 (two steps). d) AcOH, 97% for 12, 96% for 13.
e) NH2NH2 · AcOH, DMF. f) CNCCl3, DBU, CH2Cl2, 78% for 4 (two steps), 81% for 5 (two steps).

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Ac group at C(1) of 12 or 13 with NH2NH2 · AcOH in DMF, followed by
trichloroacetimidation (CNCCl3, DBU), furnished the trichloroacetimidate donors 4
(78%) and 5 (81%) over two steps.
With oleanolic acid aglycon acceptor 14 [38] and trichloroacetimidate donors 4, 5,
and 15 in hand, we next turned our attention to a ꢁone-pot sequential glycosylationꢀ
strategy for the efficient synthesis of natural oleanolic acid saponins 1 – 3 using two
glycose 1-(trichloroacetimidate) donors (Scheme 2). Herein, condensation of oleanolic
ester 14 with 2,3,4,6-tetra-O-benzoyl-a-d-glucopyranosyl trichloroacetimidate 15
under the promotion of trimethylsilyl trifluoromethanesulfonate (TMSOTf, 0.3 equiv.)
at À 788 for 30 min afforded the desired intermediate. Removal of the trityl group by
warming to ambient temperature for 30 min led to the expected product. After addition
of a CH2Cl2 solution of trichloroacetimidate 4 or 5 to the above mixture at 08, the
desired product 18 or 19 was obtained. Removal of the Ac group of compound 18 or 19
using 1% AcCl in MeOH/CH2Cl2 furnished the required product 20 or 21, respectively.
Glycosylation between acceptor 20 (or 21) and the known donor, 15, 2,3,4-tri-O-
benzoyl-a-l-rhamnopyranosyl trichloroacetimidate 16, or the peracetyl apioside donor
17 with the promotion of the reaction by TMSOTf generated the desired product 22, 23,
or 24 in satisfactory yield. Finally, removal of the Bz and Ac groups on the sugar
residues with MeONa in MeOH and CH2Cl2 afforded the expected natural products
1 – 3 in satisfactory yields, whose analytical data were identical with those reported in
the literature [30].
Inhibition of a-Glucosidase, a-Amylase, and Lipase. The inhibitory activities of the
synthesized compounds 1 – 3 against a-glucosidase, a-amylase, and lipase were
evaluated, and the results are summarized in the Table. The data indicated that three
bidesmosidic oleanolic acid saponins were active. Among the assayed triterpenoids,
compound 1 showed strong a-glucosidase and a-amylase inhibition, with IC50 values of
160 and 180 mm, respectively. Notably, the a-glucosidase inhibitory activity of saponin 1
was three-fold stronger than acarbose, a widely used clinically useful drug, used as a
positive control. Compounds 2 and 3 showed strong inhibition against a-glucosidase
and lipase, with the respective IC50 values of 170, 190 mm and 190, 200 mm, however,
exhibited no inhibitory activity against a-amylase. In this study, compound 1 showed
weaker inhibitory activity against lipase. These results demonstrated that a-l-rhamno-
pyranosyl moiety with glycosyl fragment is favorable to enhance the inhibitory activity
Table. Inhibitory Activities of Compounds 1 – 3 for a-Glucosidase, a-Amylase, and Lipase
Compounds
IC50 [mm]a)
a-Glucosidase
a-Amylase
Lipase
1
2
3
160 Æ 19
170 Æ 25
190 Æ 24
450 Æ 40
–
180 Æ 19
NAb)
NA
790 Æ 49
190 Æ 25
200 Æ 27
–c)
Acarbosed)
Orlistatd)
600 Æ 31
–
140 Æ 25
a) The IC50 values in mm were calculated from the dose response curve of six concentrations of each test
compound in triplicate. b) NA: not active. c) ꢁ – ꢀ: not determined. d) Positive control.

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Scheme 2
a) TMSOTf, CH2Cl2, À 788; 08, CH2Cl2, 89% for 18, 87% for 19. b) 08, CH2Cl2. c)1% AcCl in MeOH,
CH2Cl2, 90% for 20, 91% for 21. d) TMSOTf, CH2Cl2, 08, 87% for 22, 90% for 23, 89% for 24. e) MeONa,
MeOH/CH2Cl2, 93% for 1, 90% for 2, 91% for 3.

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against a-amylase, and the specific configuration of apioside seems to have a beneficial
effect on the lipase inhibitory activities.
Conclusions. – In conclusion, a concise synthesis of the bidesmosidic oleanolic acid
saponins 1 – 3 isolated from Fadogia ancylantha (Makoni tea) has been accomplished,
and their inhibitory activities against a-glucosidase, a-amylase, and lipase were
evaluated. On the basis of our results, the synthetic compounds 1 – 3 exhibited positive
response against a-glucosidase, a-amylase, and lipase. In terms of structureÀactivity
relationships, we can conclude that: i) the a-l-rhamnopyranosyl moiety with glycosyl
fragment is favorable to enhance their inhibitory activity against a-amylase; ii) the
specific configuration of apioside seems to have a beneficial effect on the lipase
inhibitory activities. Thus, our study indicates that bidesmosidic oleanolic acid saponins
represent an interesting class of compounds for further pharmacological studies and
preclinical developments.
Experinental Part
General. Commercial reagents were used without further purification unless specialized. Solvents
were dried and redistilled prior to use in the usual way. Thin-layer chromatography (TLC): precoated E.
Merck Silica Gel 60 F254 plates. Flash column chromatography: silica gel (SiO2; 200 – 300 mesh). Optical
1
rotations: PerkinElmer Model 241 MC polarimeter. H- and 13C-NMR spectra: JEOL JNM-ECP 600
spectrometer with tetramethylsilane as the internal standard, and chemical shifts are recorded in d values.
Mass spectra: Q-TOF Global mass spectrometer.
Compounds 8 and 9: Typical Procedure. To a soln. of 6 or 7 (2.43 g, 6.23 mmol) in dry CH2Cl2 (20 ml)
was added a soln. of 33% HBr in glacial AcOH (6.6 ml). The mixture was stirred for 1 h at ambient temp.
The mixture was poured into a 100 ml beaker containing crushed ice and diluted with CH2Cl2, and
neutralized with a sat. aq. NaHCO3 soln. The aq. soln. was extracted with CH2Cl2, and the org. extract
was successively washed with NaHCO3 soln. and brine. The org. layer was dried over Na2SO4, filtered,
and concentrated under reduced pressure to provide the bromide as light yellow syrup. The crude
bromide was immediately dissolved in dry CH2Cl2 (8 ml) and dry MeOH (8 ml), and 2,6-lutidine (1.2 ml)
was added over the course of 5 min. The mixture was stirred at ambient temp. for 12 h. The soln. was
diluted with CH2Cl2 and washed with a cold sat. aq. NaHCO3 soln., a sat. aq. CuSO4 soln. and brine. The
org. layer was dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude solid was
recrystallized from Et2O to afford the colorless crystalline 8 or 9.
3,4,6-Tri-O-acetyl-1,2-O-(1-methoxyethylidene)-a-d-glucopyranose (8). Colorless crystalline. Yield
95%. 1H-NMR (CDCl3, 600 MHz): 5.75 (d, J ¼ 3.0, 1 H, HÀC(1)); 5.18 (t, J ¼ 9.6, 1 H, HÀC(3)); 4.93 (dd,
J ¼ 9.6, 2.8, 1 H, HÀC(2)); 4.54 (t, J ¼ 9.6, 1 H, HÀC(4)); 4.37 (dd, J ¼ 11.9, 3.6, 1 H, HaÀC(6)); 4.22 – 4.24
(m, 1 H, HÀC(5)); 3.97 (dd, J ¼ 11.9, 5.7, 1 H, HbÀC(6)); 3.27 (s, 3 H, MeO); 2.13, 2.09, 2.07 (3s, 3 H each,
3 Me); 1.71 (s, 3 H, Me). HR-ESI-MS: 385.1147 ([M þ Na]þ, C15H22NaO1þ0 ; calc. 385.1105).
3,4,6-Tri-O-acetyl-1,2-O-(1-methoxyethylidene)-a-d-galactopyranose (9). Colorless crystalline. Yield
1
94%. H-NMR (CDCl3, 600 MHz): 5.87 (d, J ¼ 4.7, 1 H, HÀC(1)); 5.41 (dd, J ¼ 9.3, 4.8, 1 H, HÀC(2));
5.09 (dd, J ¼ 9.3, 3.7, 1 H, HÀC(3)); 4.58 (t, J ¼ 3.6, 1 H, HÀC(4)); 4.39 – 4.42 (m, 1 H, HÀC(5)); 4.21 (dd,
J ¼ 11.3, 4.6, 1 H, HaÀC(6)); 4.08 (dd, J ¼ 11.3, 5.7, 1 H, HbÀC(6)); 3.25 (s, 3 H, MeO); 2.09, 2.01, 1.99 (3s,
3 H each, 3 Me); 1.63 (s, 3 H, Me); HR-ESI-MS: 385.1139 ([M þ Na]þ, C15H22NaO1þ0 ; calc. 385.1105).
Compounds 10 and 11: Typical Procedure. MeONa (140 mg, 2.48 mmol) was added to a stirred soln.
of 8 or 9 (3.0 g, 0.82 mmol) in MeOH (20 ml). The mixture was stirred for 1 h and then concentrated
under reduced pressure to afford the triol, quantitatively, which was used in the next step without further
purification. The triol and DMAP (cat.) were dissolved in dry pyridine (5 ml) and BzCl (6 equiv.,
0.04 mol, 5 ml) was added at 08 and stirring was continued for 12 h. The mixture was poured into ice
water. The precipitate was dissolved in CH2Cl2, and was washed sequentially with 1 mol/l aq. HCl soln.,

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NaHCO3 (sat.) soln., NaCl (sat.) soln., dried (Na2SO4), and filtered. The solvent was evaporated to yield
orange syrup. Recrystallization from AcOEt/hexane gave the tribenzoate 10 (or 11) as colorless
crystalline.
3,4,6-Tri-O-benzoyl-1,2-O-(1-methoxyethylidene)-a-d-glucopyranose (10). Colorless crystalline.
1
Yield 80%. H-NMR (CDCl3, 600 MHz): 7.35 – 8.02 (m, 15 arom. H); 5.95 (t, J ¼ 9.6, 1 H, HÀC(4));
5.83 (t, J ¼ 9.6, 1 H, HÀC(3)); 5.76 (d, J ¼ 2.9, 1 H, HÀC(1)); 4.87 (dd, J ¼ 9.6, 2.9, 1 H, HÀC(2)); 4.67 (dd,
J ¼ 12.0, 3.2, 1 H, HaÀC(6)); 4.45 (dd, J ¼ 12.0, 4.9, 1 H, HbÀC(6)); 4.15 – 4.18 (m, 1 H, HÀC(5)); 3.26 (s,
3 H, MeO); 1.73 (s, 3 H, Me). HR-ESI-MS: 571.1593 ([M þ Na]þ, C30H28NaO1þ0 ; calc. 571.1575).
3,4,6-Tri-O-benzoyl-1,2-O-(1-methoxyethylidene)-a-d-galactopyranose (11). Colorless crystalline.
Yield 83%. 1H-NMR (CDCl3, 600 MHz): 7.37 – 8.01 (m, 15 arom. H), 5.97 (dd, J ¼ 9.7, 3.7, 1 H,
HÀC(3)); 5.83 (t, J ¼ 3.6, 1 H, HÀC(4)); 5.79 (d, J ¼ 4.9, 1 H, HÀC(1)); 5.53 (dd, J ¼ 9.6, 4.9, 1 H,
HÀC(2)); 4.71 (dd, J ¼ 12.1, 4.8, 1 H, HaÀC(6)); 4.53 (dd, J ¼ 12.1, 3.7, 1 H, HbÀC(6)); 4.29 – 4.33 (m, 1 H,
HÀC(5)); 3.27 (s, 3 H, MeO); 1.65 (s, 3 H, Me). HR-ESI-MS: 571.1553 ([M þ Na]þ, C30H28NaO1þ0 ; calc.
571.1574).
Compounds 12 and 13: Typical Procedure. Compound 10 or 11 (3.2 g, 6 mmol) was dissolved in
glacial AcOH (20 ml). The soln. was stirred for 1 h at r.t., and then partitioned between AcOEt and H2O.
The org. layer was dried with Na2SO4, filtered, and concentrated under reduced pressure to yield 12 or 13
as yellow oil.
1,2-Di-O-acetyl-3,4,6-tri-O-benzoyl-a/b-d-glucopyranose (12). Yellow oil. Yield 97%. Data of the a-
Anomer: 1H-NMR (CDCl3, 600 MHz): 7.33 – 8.05 (m, 15 arom. H); 6.47 (d, J ¼ 3.3, 1 H, HÀC(1)); 5.97 (t,
J ¼ 9.7, 1 H, HÀC(3)); 5.71 (t, J ¼ 9.7, 1 H, HÀC(4)); 5.37 (dd, J ¼ 9.7, 3.6, 1 H, HÀC(2)); 4.65 (dd, J ¼ 12.1,
3.3, 1 H, HaÀC(6)); 4.47 (dd, J ¼ 12.1, 5.1, 1 H, HbÀC(6)); 4.37 – 4.40 (m, 1 H, HÀC(5)); 2.25, 1.97 (2s, 3 H
each, 2 Me). 13C-NMR (CDCl3, 150 MHz): 169.7; 168.7; 166.1; 165.9; 165.2; 133.7; 133.5; 133.3; 133.1;
132.5; 132.1; 132.0; 130.5; 130.3; 130.1; 129.9; 129.8; 129.7; 129.5; 129.1; 128.9; 128.7; 89.7; 70.8; 70.5; 69.7;
69.3; 62.8; 21.8; 20.6. HR-ESI-MS: 599.1551 ([M þ Na]þ, C31H28NaO1þ1 ; calc. 599.1524).
1,2-Di-O-acetyl-3,4,6-tri-O-benzoyl-a/b-d-galactopyranose (13). Yellow oil. Yield 96%. Data of the
a-Anomer: 1H-NMR (CDCl3, 600 MHz): 7.35 – 8.03 (m, 15 arom. H); 6.51 (d, J ¼ 3.7, 1 H, HÀC(1)); 5.93
(dd, J ¼ 9.9, 3.6, 1 H, HÀC(3)); 5.75 (t, J ¼ 3.6, 1 H, HÀC(4)); 5.41 (dd, J ¼ 9.9, 3.7, 1 H, HÀC(2)); 4.71
(dd, J ¼ 12.3, 3.5, 1 H, HaÀC(6)); 4.45 – 4.47 (m, 1 H, HÀC(5)); 4.41 (dd, J ¼ 12.3, 5.5, 1 H, HbÀC(6)); 2.21,
1.93 (2s, 3 H each, 2 Me). 13C-NMR (CDCl3, 150 MHz): 170.1; 168.9; 166.0; 165.9; 165.1; 133.9; 133.5;
133.2; 133.1; 132.7; 132.1; 131.9; 130.6; 130.3; 130.1; 130.0; 129.9; 129.8; 129.7; 129.3; 129.1; 128.9; 128.5;
89.3; 70.7; 70.6; 69.9; 69.1; 62.5; 21.9; 20.3. HR-ESI-MS: 599.1543 ([M þ Na]þ, C31H28NaO11þ; calc.
599.1524).
Compounds 4 and 5: Typical Procedure. To a soln. of 12 or 13 (1.00 g, 1.74 mmol) in DMF (10 ml)
was added NH2NH2 · AcOH (321 mg, 3.48 mmol), and the mixture was stirred for 3 h. Then, the mixture
was concentrated to syrup, which was used in the next step without further purification. The syrup was
dissolved in CH2Cl2 (20 ml) and then cooled to 08. To this soln. was added CNCCl3 (1.67 ml, 16.6 mmol)
and DBU (5 drops). The mixture was stirred for 4 h at 08, then concentrated. The residue was purified by
SiO2 CC (petroleum ether (PE)/AcOEt) to afford the product 4 or 5.
2-O-Acetyl-3,4,6-tri-O-benzoyl-a-d-glucopyranosyl Trichloroacetimidate (¼2-O-Acetyl-3,4,6-tri-O-
benzoyl-1-O-(2,2,2-trichloroethanimidoyl)-a-d-glucopyranose; 4). Amorphous white solid. Yield 78%.
[a]2D7 ¼ 17.0 (c ¼ 0.8, CHCl3). 1H-NMR (CDCl3, 600 MHz): 8.57 (br. s, 1 H, NH); 7.23 – 7.97 (m, 15 arom.
H); 6.75 (d, J ¼ 3.6, 1 H, HÀC(1)); 6.20 (t, J ¼ 9.9, 1 H, HÀC(3)); 5.75 (t, J ¼ 9.9, 1 H, HÀC(4)); 5.41 (dd,
J ¼ 9.9, 3.6, 1 H, HÀC(2)); 4.57 (dd, J ¼ 12.3, 3.1, 1 H, HaÀC(6)); 4.51 – 4.54 (m, 1 H, HÀC(5)); 4.41 (dd,
J ¼ 12.3, 5.0, 1 H, HbÀC(6)); 2.01 (s, 3 H, Me). 13C-NMR (CDCl3, 150 MHz): 169.3 (MeCO); 165.9;
165.3; 165.1; 160.3 (C¼N); 133.6; 133.3; 133.1; 129.9; 129.8; 129.5; 129.3; 128.3; 128.1; 127.9; 127.7; 127.5;
93.3 (C(1)); 70.6; 70.4; 70.2; 68.7; 62.3; 20.9. HR-ESI-MS: 700.0531 ([M þ Na]þ, C31H26Cl3NNaO1þ0 ; calc.
700.0515).
2-O-Acetyl-3,4,6-tri-O-benzoyl-a-d-galactopyranosyl Trichloroacetimidate (¼2-O-Acetyl-3,4,6-tri-
O-benzoyl-1-O-(2,2,2-trichloroethanimidoyl)-a-d-galactopyranose; 5). Amorphous white solid. Yield
1
81%. [a]2D7 ¼ 23.5 (c ¼ 1.3, CHCl3). H-NMR (CDCl3, 600 MHz): 8.69 (s, 1 H, NH); 7.25 – 8.09 (m, 15
arom. H); 6.81 (d, J ¼ 3.6, 1 H, HÀC(1)); 6.19 (t, J ¼ 3.7, 1 H, HÀC(4)); 6.01 (dd, J ¼ 10.0, 3.7, 1 H,
HÀC(3)); 5.76 (dd, J ¼ 10.0, 3.6, 1 H, HÀC(2)); 4.76 – 4.80 (m, 1 H, HÀC(5)); 4.60 (dd, J ¼ 12.1, 4.6, 1 H,

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HaÀC(6)); 4.43 (dd, J ¼ 12.1, 5.9, 1 H, HbÀC(6)); 2.03 (s, 3 H, Me). 13C-NMR (CDCl3, 150 MHz): 169.9
(MeCO); 165.9; 165.6; 165.3; 160.5 (C¼N); 133.9; 133.7; 133.3; 133.2; 129.9; 129.8; 129.7; 129.4; 128.9;
128.7; 128.1; 127.9; 127.8; 127.3; 93.9 (C(1)); 69.9; 68.7; 68.5; 67.7; 62.3; 21.3. HR-ESI-MS: 700.0542 ([M þ
Na]þ, C31H26Cl3NNaO10þ; calc. 700.0515).
Compounds 18 and 19: Typical Procedure. A mixture of oleanolic ester 14 (200 mg, 0.29 mmol),
trichloroacetimidate 15 (0.35 mmol, 1.2 equiv.), and powdered 4 Š molecular sieves in dry CH2Cl2 (8 ml)
were stirred for 30 min at r.t. and then cooled to 08. TMSOTf (15 ml, 0.09 mmol, 0.3 equiv.) was added
slowly. After being stirred at À 788 for 30 min, the mixture was warmed up to r.t. for 30 min, and then
cooled to 08. A soln. of 4 or 5 (298 mg, 0.44 mmol, 1.5 equiv.) in dry CH2Cl2 (10 ml) was injected slowly.
The mixture was stirred at 08 for 30 min, and then warmed up to r.t. for another 30 min. The reaction was
quenched by addition of Et3N and then filtered. The filtrate was concentrated and purified by SiO2 CC
(PE/AcOEt) to afford the product 18 or 19.
2-O-Acetyl-3,4,6-tri-O-benzoyl-1-O-{(3b)-28-oxo-3-[(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)-
27
oxy]olean-12-en-28-yl}-b-d-glucopyranose (18). Amorphous white solid. Yield 89%. [a]D ¼ 16.9 (c ¼
1
1.1, CHCl3). H-NMR (CDCl3, 600 MHz): 7.33 – 8.05 (m, 35 arom. H); 5.99 (t, J ¼ 9.6, 1 H, HÀC(3’’));
5.93 (d, J ¼ 8.7, 1 H, HÀC(1’’)); 5.89 (t, J ¼ 9.9, 1 H, HÀC(3’)); 5.75 (t, J ¼ 9.6, 1 H, HÀC(4’’)); 5.69 (dd, J ¼
9.6, 8.7, 1 H, HÀC(2’’)); 5.60 (t, J ¼ 9.9, 1 H, HÀC(4’)); 5.55 (dd, J ¼ 9.9, 7.8, 1 H, HÀC(2’)); 5.27 (t, J ¼ 3.6,
1 H, HÀC(12)); 4.87 (d, J ¼ 7.8, 1 H, HÀC(1’)); 4.61 (dd, J ¼ 11.9, 3.2, 1 H, HaÀC(6’)); 4.55 (dd, J ¼ 11.9,
2.8, 1 H, HaÀC(6’’)); 4.51 (dd, J ¼ 11.9, 6.7, 1 H, HbÀC(6’)); 4.47 (dd, J ¼ 11.9, 5.0, 1 H, HbÀC(6’’)); 4.22 –
4.25 (m, 1 H, HÀC(5’’)); 4.16 – 4.19 (m, 1 H, HÀC(5’)); 3.10 (dd, J ¼ 11.9, 4.6, 1 H, HÀC(3)); 2.91 (dd, J ¼
13.7, 3.7, 1 H, HÀC(18)); 2.01 (s, 3 H, Me), 0.93, 0.85, 0.81, 0.76, 0.71, 0.62, 0.45 (7s, 3 H each, 7 Me).
13C-NMR (CDCl3, 150 MHz): 178.1 (C(28)); 169.9 (MeCO); 165.9; 165.8; 165.5; 165.3; 163.7; 163.5;
163.1; 143.5 (C(13)); 138.5; 138.3; 138.1; 137.9; 137.5; 136.7; 136.3; 136.1; 133.6; 133.3; 132.9; 129.9; 129.8;
129.7; 128.5; 128.3; 122.4 (C(12)); 105.1 (C(1’)); 97.1 (C(1’’)); 89.6 (C(3)); 78.5; 77.5; 71.9; 70.6; 70.0; 67.3;
66.7; 66.1; 65.9; 62.7; 55.9; 47.9; 41.7; 39.3; 36.7; 33.6; 31.9; 27.8; 26.7; 25.9; 24.7; 21.2; 17.6; 17.1; 15.6. HR-
ESI-MS: 1573.6501 ([M þ Na]þ, C93H98NaO2þ1 ; calc. 1573.6493).
2-O-Acetyl-3,4,6-tri-O-benzoyl-1-O-{(3b)-28-oxo-3-[(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)-
oxy]olean-12-en-28-yl}-b-d-galactopyranose (19). Amorphous white solid. Yield 87%. [a]2D7 ¼ 41.7 (c ¼
1.9, CHCl3). 1H-NMR (CDCl3, 600 MHz): 7.31 – 8.03 (m, 35 arom. H); 5.96 (dd, J ¼ 9.9, 3.7, 1 H,
HÀC(3’’)); 5.91 (d, J ¼ 8.3, 1 H, HÀC(1’’)); 5.87 (t, J ¼ 9.9, 1 H, HÀC(3’)); 5.71 (t, J ¼ 3.7, 1 H, HÀC(4’’));
5.66 (dd, J ¼ 9.9, 8.3, 1 H, HÀC(2’’)); 5.61 (t, J ¼ 9.9, 1 H, HÀC(4’)); 5.57 (dd, J ¼ 9.9, 7.7, 1 H, HÀC(2’));
5.29 (t, J ¼ 3.6, 1 H, HÀC(12)); 4.89 (d, J ¼ 7.7, 1 H, HÀC(1’)); 4.65 (dd, J ¼ 12.1, 3.3, 1 H, HaÀC(6’)); 4.55
(dd, J ¼ 11.9, 2.9, 1 H, HaÀC(6’’)); 4.51 (dd, J ¼ 12.1, 5.7, 1 H, HbÀC(6’)); 4.44 (dd, J ¼ 11.9, 5.1, 1 H,
HbÀC(6’’)); 4.25 – 4.28 (m, 1 H, HÀC(5’’)); 4.17 – 4.21 (m, 1 H, HÀC(5’)); 3.12 (dd, J ¼ 11.9, 3.7, 1 H,
HÀC(3)); 2.89 (dd, J ¼ 13.7, 4.3, 1 H, HÀC(18)); 2.00 (s, 3 H, Me), 0.93, 0.87, 0.81, 0.76, 0.70, 0.62, 0.49 (7s,
3 H each, 7 Me). 13C-NMR (CDCl3, 150 MHz): 177.9 (C(28)); 170.1 (MeCO); 165.9; 165.7; 165.5; 165.1;
163.7; 163.6; 163.1; 143.3 (C(13)); 138.9; 138.5; 138.1; 137.9; 137.6; 136.7; 136.3; 136.1; 133.6; 133.1; 132.9;
129.9; 129.8; 129.6; 128.5; 128.1; 122.3 (C(12)); 104.9 (C(1’)); 96.7 (C(1’’)); 89.7 (C(3)); 78.3; 77.5; 72.3;
70.6; 69.9; 67.3; 66.9; 66.3; 65.6; 63.0; 55.9; 47.9; 41.7; 39.5; 36.7; 33.6; 31.7; 27.8; 26.7; 25.9; 24.7; 21.0; 17.6;
17.3; 15.6. HR-ESI-MS: 1573.6479 ([M þ Na]þ, C93H98NaO2þ1 ; calc. 1573.6493).
Compounds 20 and 21: Typical Procedure. To a soln. of compound 18 or 19 (180 mg, 0.12 mmol) in
dry CH2Cl2 (10 ml) was added 1% AcCl in MeOH (1 ml). The mixture was stirred for 5 h, and then, the
reaction was quenched by addition of Et3N. The mixture was concentrated and purified by SiO2 CC
(PE/AcOEt) to afford the product 20 or 21.
3,4,6-Tri-O-benzoyl-1-O-{(3b)-28-oxo-3-[(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)oxy]olean-
12-en-28-yl}-b-d-glucopyranose (20). Amorphous white solid. Yield 90%. [a]2D7 ¼ 13.8 (c ¼ 1.6, CHCl3).
1H-NMR (CDCl3, 600 MHz): 7.31 – 8.07 (m, 35 arom. H); 5.97 (t, J ¼ 9.7, 1 H, HÀC(3’’)); 5.93 (d, J ¼ 8.3,
1 H, HÀC(1’’)); 5.88 (t, J ¼ 9.9, 1 H, HÀC(3’)); 5.73 (t, J ¼ 9.9, 1 H, HÀC(4’’)); 5.63 (t, J ¼ 9.7, 1 H,
HÀC(4’)); 5.57 (dd, J ¼ 9.9, 8.3, 1 H, HÀC(2’’)); 5.53 (dd, J ¼ 9.7, 7.7, 1 H, HÀC(2’)); 5.27 (t, J ¼ 3.7, 1 H,
HÀC(12)); 4.89 (d, J ¼ 7.7, 1 H, HÀC(1’)); 4.63 (dd, J ¼ 12.3, 3.9, 1 H, HaÀC(6’)); 4.55 (dd, J ¼ 12.1, 2.8,
1 H, HaÀC(6’’)); 4.50 (dd, J ¼ 12.3, 6.5, 1 H, HbÀC(6’)); 4.43 (dd, J ¼ 12.1, 5.3, 1 H, HbÀC(6’’)); 4.25 – 4.28
(m, 1 H, HÀC(5’’)); 4.17 – 4.21 (m, 1 H, HÀC(5’)); 3.11 (dd, J ¼ 11.9, 3.7, 1 H, HÀC(3)); 2.89 (dd, J ¼ 13.7,
4.3, 1 H, HÀC(18)); 0.97, 0.85, 0.80, 0.76, 0.73, 0.62, 0.49 (7s, 3 H each, 7 Me). 13C-NMR (CDCl3,

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Helvetica Chimica Acta – Vol. 98 (2015)
150 MHz): 178.3 (C(28)); 165.9; 165.8; 165.7; 165.3; 163.9; 163.5; 163.3; 163.1; 143.3 (C(13)); 138.6;
138.3; 138.0; 137.9; 137.7; 136.7; 136.3; 136.0; 133.6; 133.2; 132.9; 129.9; 129.8; 129.7; 128.5; 128.3; 122.3
(C(12)); 105.3 (C(1’)); 97.3 (C(1’’)); 89.7 (C(3)); 78.9; 77.3; 71.7; 70.6; 69.7; 67.3; 66.7; 66.3; 65.6; 62.7;
55.7; 47.9; 41.7; 39.3; 36.7; 33.6; 31.9; 27.8; 26.7; 25.9; 24.6; 17.6; 17.1; 15.3. HR-ESI-MS: 1531.6399 ([M þ
Na]þ, C91H96NaO2þ0 ; calc. 1531.6387).
3,4,6-Tri-O-benzoyl-1-O-{(3b)-28-oxo-3-[(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)oxy]olean-
12-en-28-yl}-b-d-galactopyranose (21). Amorphous white solid. Yield 91%. [a]2D7 ¼ 27.6 (c ¼ 1.8, CHCl3).
1H-NMR (CDCl3, 600 MHz): 7.35 – 8.01 (m, 35 arom. H); 5.97 (dd, J ¼ 9.7, 3.7, 1 H, HÀC(3’’)); 5.89 (d,
J ¼ 8.5, 1 H, HÀC(1’’)); 5.85 (t, J ¼ 9.7, 1 H, HÀC(3’)); 5.73 (t, J ¼ 3.7, 1 H, HÀC(4’’)); 5.65 (dd, J ¼ 9.7, 8.5,
1 H, HÀC(2’’)); 5.60 (t, J ¼ 9.7, 1 H, HÀC(4’)); 5.55 (dd, J ¼ 7.9, 9.9, 1 H, HÀC(2’)); 5.31 (t, J ¼ 3.6, 1 H,
HÀC(12)); 4.87 (d, J ¼ 7.9, 1 H, HÀC(1’)); 4.66 (dd, J ¼ 12.3, 3.5, 1 H, HaÀC(6’)); 4.57 (dd, J ¼ 12.0, 3.1,
1 H, HaÀC(6’’)); 4.51 (dd, J ¼ 12.3, 5.3, 1 H, HbÀC(6’)), 4.44 (dd, J ¼ 12.1, 5.7, 1 H, HbÀC(6’’)); 4.21 – 4.25
(m, 1 H, HÀC(5’’)); 4.15 – 4.18 (m, 1 H, HÀC(5’)); 3.10 (dd, J ¼ 11.9, 4.3, 1 H, HÀC(3)); 2.87 (dd, J ¼ 13.7,
3.7, 1 H, HÀC(18)); 0.97, 0.89, 0.80, 0.73, 0.69, 0.61, 0.51 (7s, 3 H each, 7 Me). 13C-NMR (CDCl3,
150 MHz): 178.1 (C(28)); 165.9; 165.7; 165.6; 165.0; 163.9; 163.6; 163.5; 143.7 (C(13)); 138.7; 138.5;
138.3; 137.9; 137.5; 136.7; 136.3; 136.1; 133.9; 133.6; 133.3; 132.9; 129.9; 129.8; 129.5; 128.3; 128.0; 122.4
(C(12)); 104.7 (C(1’)); 96.9 (C(1’’)); 89.3 (C(3)); 78.1; 76.9; 72.1; 70.9; 69.6; 67.1; 66.5; 66.1; 65.6; 63.1;
55.9; 47.9; 41.7; 39.5; 36.9; 33.6; 31.5; 27.8; 26.7; 25.9; 24.7; 17.6; 17.5; 15.6. HR-ESI-MS: 1531.6361 ([M þ
Na]þ, C91H96NaO2þ0 ; calc. 1531.6387).
Compounds 22 – 24: Typical Procedure. A mixture of 20 or 21 (100 mg, 0.07 mmol), trichloroace-
timidate 15, 16, or 17 (0.084 mmol, 1.20 equiv.) and powdered 4 Š molecular sieves in dry CH2Cl2 (5 ml)
were stirred for 30 min at r.t. and then cooled to 08. TMSOTf (5 ml, 0.02 mmol, 0.3 equiv.) was added
slowly. After being stirred at 08 for 1 h, the mixture was warmed up to r.t. for 30 min. The reaction was
quenched by addition of Et3N, and then filtered. The filtrate was concentrated and purified by a SiO2 CC
(PE/AcOEt) to afford the products 22 – 24.
3,4,6-Tri-O-benzoyl-1-O-{(3b)-28-oxo-3-[(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)oxy]olean-
12-en-28-yl}-2-O-(2,3,4-tri-O-benzoyl-6-deoxy-a-l-mannopyranosyl)-b-d-glucopyranose (22). Amor-
1
phous white solid. Yield 87%. [a]2D7 ¼ 56.1 (c ¼ 0.83, CHCl3). H-NMR (CDCl3, 600 MHz): 7.27 – 8.09
(m, 50 arom. H); 5.95 (t, J ¼ 9.9, 1 H, HÀC(3’’)); 5.91 (d, J ¼ 8.5, 1 H, HÀC(1’’)); 5.88 (dd, J ¼ 10.1, 3.2,
1 H, HÀC(3’’’)); 5.85 (t, J ¼ 9.9, 1 H, HÀC(3’)); 5.81 (dd, J ¼ 5.0, 1.8, 1 H, HÀC(2’’’)); 5.77 (br. s, 1 H,
HÀC(1’’’)); 5.74 (t, J ¼ 9.9, 1 H, HÀC(4’’)); 5.67 (t, J ¼ 10.1, 1 H, HÀC(4’’’)); 5.61 (t, J ¼ 9.9, 1 H, HÀC(4’));
5.55 (dd, J ¼ 9.9, 8.5, 1 H, HÀC(2’’)); 5.51 (dd, J ¼ 9.9, 7.9, 1 H, HÀC(2’)); 5.23 (t, J ¼ 3.7, 1 H, HÀC(12));
4.89 (d, J ¼ 7.9, 1 H, HÀC(1’)); 4.65 (dd, J ¼ 12.1, 3.3, 1 H, HaÀC(6’)); 4.57 (dd, J ¼ 12.0, 3.1, 1 H,
HaÀC(6’’)), 4.50 – 4.55 (m, 2 H, HÀC(5’’’), HbÀC(6’)); 4.41 (dd, J ¼ 12.0, 5.6, 1 H, HbÀC(6’’)); 4.23 – 4.27
(m, 2 H, HÀC(5’), HÀC(5’’)); 3.21 (dd, J ¼ 11.9, 4.6, 1 H, HÀC(3)); 2.91 (dd, J ¼ 13.1, 3.2, 1 H, HÀC(18));
1.36 (d, J ¼ 6.0, 3 H, HÀC(6’’’)); 1.13, 0.95, 0.89, 0.80, 0.76, 0.73, 0.63 (7s, 3 H each, 7 Me). 13C-NMR
(CDCl3, 150 MHz): 177.6 (C(28)); 165.9; 165.8; 165.7; 165.3; 163.7; 163.5; 163.3; 163.1; 143.8 (C(13));
138.7; 138.5; 138.3; 138.0; 137.9; 137.8; 136.7; 136.5; 136.1; 133.6; 133.2; 132.9; 129.9; 129.8; 129.7; 128.5;
128.2; 128.1; 122.5 (C(12)); 104.9 (C(1’)); 97.7 (C(1’’’)); 97.1 (C(1’’)); 89.9 (C(3)); 80.9; 78.1; 75.3; 72.1;
70.7; 70.3; 69.5; 67.3; 66.7; 66.3; 65.9; 65.6; 62.7; 56.0; 47.9; 41.7; 41.5; 39.3; 36.7; 33.6; 31.9; 27.8; 26.7; 25.9;
23.6; 19.3; 17.6; 17.1; 15.3. HR-MALDI-MS: 1989.7771 ([M þ Na]þ, C118H118NaO2þ7 ; calc. 1989.7753).
3,4,6-Tri-O-benzoyl-2-O-{(2S,3R,4S)-3,4-bis(acetyloxy)-4-[(acetyloxy)methyl]tetrahydrofuran-2-yl}-
1-O-{(3b)-28-oxo-3-[(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)oxy]olean-12-en-28-yl}-b-d-glucopyr-
anose (23). Amorphous white solid. Yield 90%. [a]2D7 ¼ 95.3 (c ¼ 1.2, CHCl3). 1H-NMR (CDCl3,
600 MHz): 7.33 – 8.01 (m, 35 arom. H); 5.99 (t, J ¼ 9.9, 1 H, HÀC(3’’)); 5.95 (d, J ¼ 8.1, 1 H, HÀC(1’’));
5.87 (t, J ¼ 9.7, 1 H, HÀC(3’)); 5.73 (t, J ¼ 9.9, 1 H, HÀC(4’’)); 5.60 (t, J ¼ 9.7, 1 H, HÀC(4’)); 5.53 (dd, J ¼
9.9, 8.1, 1 H, HÀC(2’’)); 5.50 (dd, J ¼ 9.7, 7.9, 1 H, HÀC(2’)); 5.29 (s, 1 H, HÀC(1’’’)); 5.21 (t, J ¼ 3.6, 1 H,
HÀC(12)); 4.93 (d, J ¼ 7.9, 1 H, HÀC(1’)); 4.67 (dd, J ¼ 12.3, 3.7, 1 H, HaÀC(6’)); 4.53 (dd, J ¼ 11.9, 3.3,
1 H, HaÀC(6’’)); 4.50 (d, J ¼ 12.5, 1 H, HaÀC(3’’’)); 4.47 (dd, J ¼ 12.3, 5.8, 1 H, HbÀC(6’)); 4.45 (d, J ¼ 12.5,
1 H, HbÀC(3’’’)), 4.40 (dd, J ¼ 11.9, 5.3, 1 H, HbÀC(6’’)); 4.35 (d, J ¼ 10.7, 1 H, HaÀC(4’’’)); 4.27 – 4.31 (m,
1 H, HÀC(5’)); 4.19 – 4.22 (m, 1 H, HÀC(5’’)); 4.17 (d, J ¼ 10.7, 1 H, HbÀC(4’’’)); 3.19 (dd, J ¼ 11.9, 4.3,
1 H, HÀC(3)); 2.89 (dd, J ¼ 13.3, 3.7, 1 H, HÀC(18)); 2.17, 2.00, 1.91 (3s, 3 H each, 3 Me), 1.12, 0.97, 0.89,
0.83, 0.76, 0.71, 0.62 (7s, 3 H each, 7 Me). 13C-NMR (CDCl3, 150 MHz): 177.9 (C(28)); 170.1; 169.7; 169.3

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(MeCO); 165.9; 165.7; 165.5; 165.3; 163.9; 163.5; 163.3; 163.0; 143.5 (C(13)); 138.5; 138.2; 138.0; 137.9;
136.7; 136.5; 136.0; 133.5; 133.1; 132.9; 129.9; 129.7; 128.5; 128.1; 122.3 (C(12)); 106.7 (C(1’’’)); 104.3
(C(1’)); 97.8 (C(1’’)); 89.7 (C(3)); 83.9; 80.3; 78.5; 76.1; 75.3; 73.0; 72.1; 70.5; 69.5; 67.3; 66.4; 65.9; 65.6;
63.1; 56.1; 47.9; 41.9; 41.5; 39.5; 36.7; 33.6; 31.9; 27.9; 26.7; 25.9; 23.6; 20.9; 20.5; 20.1; 19.3; 17.6; 17.1; 15.2.
HR-MALDI-MS: 1789.7143 ([M þ Na]þ, C102H110NaO2þ7 ; calc. 1789.7127).
3,4,6-Tri-O-benzoyl-1-O-{(3b)-28-oxo-3-[(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)oxy]olean-
12-en-28-yl}-2-O-(2,3,4,6-tetra-O-benzoyl-b-d-glucopyranosyl)-b-d-galactopyranose (24). Amorphous
white solid. Yield 89%. [a]2D7 ¼ 87.9 (c ¼ 0.9, CHCl3). 1H-NMR (CDCl3, 600 MHz): 7.29 – 8.11 (m, 55
arom. H); 5.97 (dd, J ¼ 9.9, 3.6, 1 H, HÀC(3’’)); 5.91 (d, J ¼ 8.3, 1 H, HÀC(1’’)); 5.85 (t, J ¼ 9.9, 1 H,
HÀC(3’)); 5.83 (t, J ¼ 9.9, 1 H, HÀC(3’’’)); 5.75 (t, J ¼ 3.6, 1 H, HÀC(4’’)); 5.65 (dd, J ¼ 9.9, 8.3, 1 H,
HÀC(2’’)); 5.59 (t, J ¼ 9.9, 1 H, HÀC(4’’’)); 5.56 (t, J ¼ 9.9, 1 H, HÀC(4’)); 5.51 (dd, J ¼ 9.9, 7.9, 1 H,
HÀC(2’)); 5.44 (t, J ¼ 9.1, 1 H, HÀC(2’’’)); 5.30 (t, J ¼ 3.7, 1 H, HÀC(12)); 5.01 (d, J ¼ 8.2, 1 H, HÀC(1’’’));
4.89 (d, J ¼ 7.9, 1 H, HÀC(1’)); 4.61 (dd, J ¼ 12.1, 3.7, 1 H, HaÀC(6’)); 4.53 (dd, J ¼ 12.0, 3.5, 1 H,
HaÀC(6’’)); 4.49 (dd, J ¼ 12.1, 5.7, 1 H, HbÀC(6’)); 4.45 (dd, J ¼ 12.0, 5.0, 1 H, HbÀC(6’’)); 4.18 – 4.23 (m,
2 H, HÀC(5’’), HaÀC(6’’’)); 4.13 – 4.16 (m, 1 H, HÀC(5’)); 3.81 – 3.85 (m, HÀC(5’’’), HbÀC(6’’’)); 3.12 (dd,
J ¼ 11.9, 3.7, 1 H, HÀC(3)); 2.85 (dd, J ¼ 13.7, 4.6, 1 H, HÀC(18)); 1.13, 0.97, 0.83, 0.79, 0.76, 0.69, 0.62 (7s,
3 H each, 7 Me). 13C-NMR (CDCl3, 150 MHz): 178.3 (C(28)); 165.9; 165.7; 165.5; 165.0; 164.9; 163.9;
163.7; 163.5; 163.1; 143.9 (C(13)); 138.9; 138.7; 138.5; 138.3; 137.9; 137.7; 136.7; 136.3; 136.0; 133.9; 133.7;
133.6; 133.3; 132.9; 129.9; 129.8; 129.5; 128.3; 128.0; 127.9; 122.3 (C(12)); 104.1 (C(1’)); 99.9 (C(1’’’)); 96.7
(C(1’’)); 89.6 (C(3)); 78.1; 77.3; 76.9; 74.5; 72.1; 70.9; 70.3; 69.6; 67.5; 67.1; 66.5; 66.1; 65.6; 63.1; 62.9; 55.6;
47.9; 41.7; 39.5; 36.9; 33.6; 32.9; 31.5; 27.8; 26.7; 25.9; 24.7; 17.7; 17.5; 15.6. HR-MALDI-MS: 2109.7981
([M þ Na]þ, C125H122NaO2þ9 ; calc. 2109.7964).
Compounds 1 – 3: Typical Procedure. To a soln. of fully protected oleanolic acid glycosides 22 – 24
(50 mg) in dry 1:2 CH2Cl2/MeOH (10 ml) was added a newly prepared MeONa in MeOH soln. (1.0 mol/
l, 0.20 ml). The mixture was stirred at r.t. for 5 h and neutralized with Dowex Hþ resin to pH 7 and then
filtered. The filtrate was concentrated, and the resulting residue was subjected to SiO2 CC to give the
target compounds 1 – 3 as white amorphous solids.
2-O-(6-Deoxy-a-l-mannopyranosyl)-1-O-[(3b)-3-(b-d-glucopyranosyloxy)-28-oxoolean-12-en-28-
yl]-b-d-glucopyranose (1). Amorphous white solid. Yield 93%. [a]2D7 ¼ À4.1 (c ¼ 0.17, MeOH). 1H-NMR
(CD3OD, 600 MHz): 5.45 (d, J ¼ 7.6, 1 H, HÀC(1’’)); 5.36 (d, J ¼ 1.4, 1 H, HÀC(1’’’)); 5.26 (t, J ¼ 3.6, 1 H,
HÀC(12)); 4.30 (d, J ¼ 7.7, 1 H, HÀC(1’)); 3.91 (dd, J ¼ 2.1, 1.4, 1 H, HÀC(2’’’)); 3.84 (dd, J ¼ 12.0, 2.6, 1 H,
HaÀC(6’)); 3.80 (dd, J ¼ 12.0, 3.6, 1 H, HaÀ(6’’)); 3.73 – 3.76 (m, 1 H, HÀC(5’’’)); 3.69 (dd, J ¼ 12.0, 4.1,
1 H, HbÀC(6’)); 3.67 (dd, J ¼ 8.5, 2.0, 1 H, HÀC(3’’’)); 3.65 (dd, J ¼ 12.0, 4.5, 1 H, HbÀC(6’’)); 3.55 (dd, J ¼
9.0, 7.5, 1 H, HÀC(2’’)); 3.41 (t, J ¼ 9.0, 1 H, HÀC(3’’)); 3.39 (t, J ¼ 8.5, 1 H, HÀC(4’’’)); 3.37 (t, J ¼ 9.0, 1 H,
HÀC(4’’)); 3.35 (t, J ¼ 9.0, 1 H, HÀC(3’)); 3.30 – 3.33 (m, 1 H, HÀC(5’’)); 3.29 (t, J ¼ 9.0, 1 H, HÀC(4’));
3.23 – 3.26 (m, 1 H, HÀC(5’)); 3.19 (dd, J ¼ 9.0, 7.7, 1 H, HÀC(2’)); 3.16 (dd, J ¼ 11.9, 4.6, 1 H, HÀC(3));
2.83 (dd, J ¼ 14.0, 3.3, 1 H, HÀC(18)); 1.26 (d, J ¼ 6.6, 3 H, HÀC(6’’’)); 1.14, 1.03, 0.95, 0.93, 0.90, 0.85, 0.78
(7s, 3 H each, 7 Me). 13C-NMR (CD3OD, 150 MHz): 177.9 (C(28)); 144.8 (C(13)); 122.9 (C(12)); 105.9
(C(1’)); 101.6 (C(1’’’)); 94.7 (C(1’’)); 90.1 (C(3)); 78.8 (C(2’’)); 78.0 (C(3’’)); 77.8 (C(5’’)); 77.3 (C(3’));
76.9 (C(5’)); 75.3 (C(2’)); 73.4 (C(4’’’)); 71.7 (C(3’’’)); 73.5 (C(2’’’)); 70.7 (C(4’’)); 70.6 (C(4’)); 69.8
(C(5’’’)); 62.2 (C(6’’)); 61.8 (C(6’)); 56.3; 48.3; 47.3; 46.5; 42.3; 40.2; 39.6; 39.1; 37.3; 34.0; 33.3; 32.8; 31.9;
30.7; 28.9; 27.8; 25.6; 25.1; 23.3; 23.2; 22.7; 18.4; 17.9 (C(6’’’)); 16.8; 16.1. HR-ESI-MS: 949.5123 ([M þ
Na]þ, C48H78NaO1þ7 ; calc. 949.5137).
2-O-[(2S,3R,4S)-Tetrahydro-3,4-dihydroxy-4-(hydroxymethyl)furan-2-yl]-1-O-[(3b)-3-(b-d-gluco-
pyranosyloxy)-28-oxoolean-12-en-28-yl]-b-d-glucopyranose (2). Amorphous white solid. Yield 90%.
[a]2D7 ¼ À6.5 (c ¼ 0.12, MeOH). 1H-NMR (CD3OD, 600 MHz): 5.42 (d, J ¼ 2.0, 1 H, HÀC(1’’’)); 5.39 (d,
J ¼ 7.6, 1 H, HÀC(1’’)); 5.25 (t, J ¼ 3.6, 1 H, HÀC(12)); 4.33 (d, J ¼ 7.6, 1 H, HÀC(1’)); 4.01 (d, J ¼ 10.0,
1 H, HaÀC(4’’’)); 3.96 (d, J ¼ 2.0, 1 H, HÀC(2’’’)); 3.83 (dd, J ¼ 12.1, 3.5, 1 H, HaÀC(6’’)); 3.81 (dd, J ¼ 12.1,
2.5, 1 H, HaÀC(6’)); 3.72 (d, J ¼ 10.0, 1 H, HbÀC(4’’’)); 3.67 (dd, J ¼ 12.1, 4.0, 1 H, HbÀC(6’)); 3.64 (dd, J ¼
12.1, 4.5, 1 H, HbÀC(6’’)); 3.53 (dd, J ¼ 9.0, 7.6, 1 H, HÀC(2’’)); 3.51 (br. s, 1 H, HÀC(5’’’)); 3.38 (t, J ¼ 9.0,
1 H, HÀC(3’’)); 3.36 (t, J ¼ 9.0, 1 H, HÀC(4’’)); 3.33 (t, J ¼ 9.0, 1 H, HÀC(3’)); 3.30 – 3.33 (m, 1 H,
HÀC(5’’)); 3.27 (t, J ¼ 9.0, 1 H, HÀC(4’)); 3.22 – 3.26 (m, 1 H, HÀC(5’)); 3.17 (dd, J ¼ 9.0, 7.6, 1 H,
HÀC(2’)); 3.15 (dd, J ¼ 11.9, 4.3, 1 H, HÀC(3)); 2.83 (dd, J ¼ 14.0, 3.7, 1 H, HÀC(18)); 1.14, 1.02, 0.95,

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Helvetica Chimica Acta – Vol. 98 (2015)
0.93, 0.91, 0.85, 0.76 (7s, 3 H each, 7 Me). 13C-NMR (CD3OD, 150 MHz): 177.8 (C(28)); 144.8 (C(13));
122.9 (C(12)); 106.9 (C(1’)); 110.7 (C(1’’’)); 94.7 (C(1’’)); 90.1 (C(3)); 79.8 (C(3’’’)); 79.1 (C(2’’)); 77.9
(C(3’)); 77.8 (C(2’’’)); 77.3 (C(5’)); 77.1 (C(5’’)); 76.6 (C(3’’)); 75.3 (C(2’)); 74.7 (C(4’’’)); 73.3 (C(4’’)); 71.2
(C(4’)); 64.7 (C(5’’’)); 62.2 (C(6’’)); 62.1 (C(6’)); 56.3; 48.3; 47.2; 46.5; 42.3; 40.1; 39.6; 39.2; 37.3; 34.1;
33.3; 32.8; 31.9; 30.6; 28.9; 27.9; 25.6; 25.1; 23.3; 23.2; 22.7; 18.5; 16.8; 16.1. HR-ESI-MS: 935.5383 ([M þ
Na]þ, C47H76NaO1þ7 ; calc. 935.5361).
2-O-b-d-Glucopyranosyl-1-O-[(3b)-3-(b-d-glucopyranosyloxy)-28-oxoolean-12-en-28-yl]-b-d-gal-
actopyranose (3). Amorphous white solid. Yield 91%. [a]2D7 ¼ À4.1 (c ¼ 0.11, MeOH). 1H-NMR
(CD3OD, 600 MHz): 5.45 (d, J ¼ 7.5, 1 H, HÀC(1’’)); 4.81 (d, J ¼ 7.6, 1 H, HÀC(1’’’)); 5.24 (t, J ¼ 3.7, 1 H,
HÀC(12)); 4.31 (d, J ¼ 7.6, 1 H, HÀC(1’)); 3.91 (dd, J ¼ 12.0, 2.5, 1 H, HaÀC(6’’’)); 3.89 (dd, J ¼ 9.9, 7.5,
1 H, HÀC(2’’)); 3.81 (dd, J ¼ 12.0, 2.5, 1 H, HaÀC(6’)); 3.79 (dd, J ¼ 11.9, 7.5, 1 H, HaÀC(6’’)); 3.69 (dd, J ¼
11.9, 4.5, 1 H, HbÀC(6’’)); 3.67 (dd, J ¼ 9.9, 3.2, 1 H, HÀC(3’’)); 3.65 (dd, J ¼ 12.0, 4.0, 1 H, HbÀC(6’)); 3.62
(dd, J ¼ 12.0, 4.0, 1 H, HbÀC(6’’’)); 3.55 – 3.58 (m, 1 H, HÀC(5’’)); 3.37 (t, J ¼ 9.0, 1 H, HÀC(4’’’)); 3.35 (d,
J ¼ 3.2, 1 H, HÀC(4’’)); 3.31 (d, J ¼ 9.0, 1 H, HÀC(3’)); 3.27 – 3.30 (m, 1 H, HÀC(5’’’)); 3.28 (t, J ¼ 9.0, 1 H,
HÀC(4’)); 3.21 – 3.25 (m, 1 H, HÀC(5’)); 3.21 (t, J ¼ 9.0, 1 H, HÀC(3’’’)); 3.17 (dd, J ¼ 9.0, 7.6, 1 H,
HÀC(2’)); 3.14 (dd, J ¼ 9.0, 7.6, 1 H, HÀC(2’’’)); 3.16 (dd, J ¼ 12.3, 4.3, 1 H, HÀC(3)); 2.81 (dd, J ¼ 14.3,
3.7, 1 H, HÀC(18)); 1.13, 1.02, 0.96, 0.93, 0.91, 0.83, 0.76 (7s, 3 H each, 7 Me). 13C-NMR (CD3OD,
150 MHz): 177.8 (C(28)); 144.7 (C(13)); 122.9 (C(12)); 106.3 (C(1’)); 102.7 (C(1’’’)); 94.4 (C(1’’)); 90.1
(C(3)); 78.1 (C(5’’)); 77.8 (C(3’)); 77.5 (C(5’)); 77.4 (C(2’’)); 77.1 (C(5’’’)); 77.0 (C(3’’’)); 75.2 (C(2’)); 72.9
(C(5’’’)); 71.6 (C(2’’’)); 71.4 (C(4’)); 71.0 (C(3’’)); 70.0 (C(4’’)); 62.7 (C(5’’’)); 62.3 (C(6’)); 61.2 (C(6’’));
56.4; 48.3; 47.2; 46.5; 42.3; 40.0; 39.6; 39.2; 37.2; 34.1; 33.3; 32.8; 31.9; 30.7; 28.9; 27.9; 25.6; 25.1; 23.3; 23.2;
22.7; 18.5; 16.8; 16.1. HR-ESI-MS: 965.5041 ([M þ Na]þ, C48H78NaO1þ8 ; calc. 965.5061).
Assay for a-Glucosidase Inhibitory Activities. Inhibitory a-glucosidase activities were determined
spectrophotometrically in a 96-well microtiter plate based on p-nitrophenyl a-d-glucopyranoside
(PNPG) as a substrate. In brief, 20 ml of enzyme soln. (0.8 U/ml a-glucosidase in 0.01m potassium
phosphate buffer (pH 6.8) containing 0.2% of BSA) and 120 ml of the synthetic compound in 0.5%
DMSO of 0.01m potassium phosphate buffer were mixed, and was preincubated at 378 prior to initiation
of the reaction by adding the substrate. After 15 min of preincubation, PNPG soln. (20 ml) (5.0 mM
PNPG in 0.1m potassium phosphate buffer (pH 6.8) was added and then incubated together at 378. After
15 min of incubation, 0.2m Na2CO3 (80 ml) in 0.1m potassium phosphate buffer was added to the test tube
to stop the reaction. Acarbose was used as positive control. The increment in absorption at 410 nm due to
the hydrolysis of PNPG by a-glucosidase was monitored continuously with an auto multi-functional
microplate reader (BIORAD680).
Assay for a-Amylase Inhibitory Activities. The a-amylase inhibitory activities were measured with
the method reported by Xiao et al. and Yoshikawa et al. with slight modifications [39][40]. Substrate was
prepared by heating starch (250 mg) in 12 ml of 0.4m NaOH soln. for 5 min at 1008, and then cooled to 08
and adjusted to pH 7 with 2m HCl. Sample solns. were prepared by dissolving each soln. in acetate buffer
(pH 6.5). The sample (20 ml) and the substrate (40 ml) were mixed in a microplate well. After
preincubation at 378 for 15 min, 5 mg/ml a-amylase soln. (20 ml) was added and the soln. was incubated
at 378 for 15 min. The reaction was stopped by adding 50 ml 1m HCl, and then 50 ml I2 soln. was added.
The absorbances were measured at 650 nm by a microplate reader. Acarbose was used as positive
control.
Assay for Lipase Inhibitory Activities. Lipase inhibitory activities were measured according to the
method of Han et al. with slight modifications [41]. Substrate was prepared by sonication of a mixture of
glyceryl trioleate (80 mg), lecithin (10 mg), and sodium cholate (5 mg) suspended in 9 ml of 0.1m TES
buffer (pH 7.0). Samples were prepared by dissolving each sample in 0.1m TES buffer. The sample (20 ml)
and the substrate (20 ml) were mixed in microplate wells. After preincubated for 5 min, 10 ml of lipase
soln. (20 mg/ml) was added to each mixture and incubated for 30 min at 378. The amount of released fatty
acid was measured at 405 nm. Inhibition of lipase activity was expressed as the percentage decrease in the
absorbance when porcine pancreatic lipase was incubated with the test compounds. Orlistat was used as
positive control.

Helvetica Chimica Acta – Vol. 98 (2015)
1265
This work was financial supported by the Postdoctoral Science Foundation of Northwest
University (334100018), China Postdoctoral Science Foundation funded project (No. 2012 M512023,
No. 2013T60887, and No. 2015M572596), Hong Kong Scholars Program Foundation (XJ2014014), the
Foundation of Natural Science Basic Research Plan in Shaanxi Province of China (2014JQ2069), the
Doctoral Program Foundation of Institutions of Higher Education of China (No. 20116101120025), the
Northwestern University Outstanding Young Academic Backbone Support Plan and the Scientific
Research Foundation of Northwest University.
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Received March 10, 2015