The synthesis of pennogenin 3-O-β-D-glucopyranosyl-(1 → 3)- [α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranoside

Article abstract of DOI:10.1080/10286020.2011.653348

Pennogenin 3-O-β-D-glucopyranosyl-(1 → 3)-[α-L- rhamnopyranosyl-(1 → 2)]-β-D-glucopyranoside, a monodesmosidic saponin isolated from Paris polyphylla Smith var. yunnanensis with promised antitumor activities, was firstly synthesized from glucoside thiol v

Full text of DOI:10.1080/10286020.2011.653348

Journal of Asian Natural Products Research
Vol. 14, No. 4, April 2012, 314–321
The synthesis of pennogenin 3-O-b-D-glucopyranosyl-(1 ! 3)-
[a-L-rhamnopyranosyl-(1 ! 2)]-b-D-glucopyranoside
Xin-Feng Luoa, Fan Leia, Yi Hea, Shu-Chen Peia, Li Haia, Shan Qianb and Yong Wua*
aKey Laboratory of Drug Targeting and Drug Delivery Systems of the Education Ministry,
West China School of Pharmacy, Sichuan University, Chengdu 610041, China;
bBioengineering College, Xihua University, Chengdu 610039, China
(Received 29 September 2011; final version received 22 December 2011)
Pennogenin 3-O-b-D-glucopyranosyl-(1 ! 3)-[a-L-rhamnopyranosyl-(1 ! 2)]-b-D-
glucopyranoside, a monodesmosidic saponin isolated from Paris polyphylla Smith
var. yunnanensis with promised antitumor activities, was firstly synthesized from
glucoside thiol via nine steps and with 27% overall yield.
Keywords: pennogenin; a-L-rhamnopyranoside; b-D-glucopyranoside; antitumor
activity; synthesis
1. Introduction
with IC50 value of 2.25 mg/ml, using
hydroxycamptothecin as positive control
(IC50 ¼ 2.15 mg/ml). In order to further
study the anticancer activity of saponin 1,
saponin 1 was first synthesized.
Spirostanol glycosides constitute a large
group of steroidal saponins and have a
broad range of interesting bioactivities [1].
Among the spirostanol glycosides, saponin
1 (pennogenin 3-O-b-D-glucopyranosyl-
(1 ! 3)-[a-L-rhamnopyranosyl-(1 ! 2)]-
b-D-glucopyranoside; Figure 1) was iso-
lated firstly from the dried rhizome of
Paris axialis H. Li, and it also exists widely
in nature, in plants used in traditional
Chinese herbal medicine, such as Rhizoma
Paridis (‘Chonglou’ in Chinese) [2]. This
saponin exhibits potent antitumor activity
with the IC50 values ranging from 0.5 to
5.1 mg/ml against human promyelocytic
leukemia HL-60 cells [2a]. On the other
hand, cytometric analysis indicated that
saponin 1 caused a concentration- and
time-dependent apoptosis of L1210 cell
(EC50 ¼ 5 mM) [2b]. Recently, we have
also isolated it from P. polyphylla var.
yunnanensis, which shows strong antitu-
mor activity against human HepG 2 cells
2. Results and discussion
This monodesmosidic saponin 1 bears
three 1,2-trans-pyranosidic linkages,
which could be constructed stereo-selec-
tively by stepwise glycosylation with a
sugar donor equipped with a participating
group at its 2-OH. However, employing
this strategy, the aglycone participating in
reactions continuously must be consumed
heavily unavoidably. Herein, the aglycone
(pennogenin) is very precious, which was
isolated from the rhizome of Paris
polyphylla Smith var. yunnanensis (Pyun-
nanensis) [3]. So we select to prepare a
suitably protected and activated oligosac-
charide donor first, and then attach it to the
aglycone. Compound 1 was synthesized as
shown in Schemes 1 and 2.
*Corresponding author. Email: wyong@scu.edu.cn
ISSN 1028-6020 print/ISSN 1477-2213 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10286020.2011.653348
http://www.tandfonline.com

Journal of Asian Natural Products Research
315
O
HO
O
HO
HO
O
O
HO
HO
O
O
O
OH
HO
HO
HO
O
OH
Figure 1. Structure of compound 1.
OH
Ph
O
Ph
O
b
O
a
O
O
O
SPh
HO
HO
O
SPh
SPh
TBSO
HO
OH
OH
OH
4
3
2
c
Ph
O
O
Ph
O
Ph
O
O
O
O
O
O
O
d
AcO
AcO
O
O
O
SPh
SPh
SPh
e
O
HO
TBSO
OAc
AcO
AcO
AcO
AcO
AcO
O
O
AcO
O
AcO
OAc
OAc
OAc
8
9
5
Scheme 1. Synthesis of intermediate 9. Reagents and conditions: (a) PhCH(OMe)2, TsOH, DMF,
˚
608C, 2 h, 100%; (b) TBDMSCl, imidazole, CH2Cl2, 408C, 4 h, 95%; (c) 6, BF3·Et2O, 4 A MS,
˚
CH2Cl2, 2788C, 3 h, 89%; (d) TBAF, THF, r.t., 6 h, 80%; (e) 7, BF3·Et2O, 4 A MS CH2Cl2, 2788C,
5 h, 64%.
Compound 2 was afforded through
three steps from D-glucose [4], which was
converted to diol 3 by protection of the
40,60-OH with an O-benzylidene group [5].
Reaction of 3 with tert-butyldimethylsilyl
(TBDMS) chloride in the presence of
imidazole resulted in a totally regioselec-
tive silylation at C-3, affording compound
4 in high yield [6]. Compound 4, having its
20-OH free, was glycosylated by 2,3,4-tri-
O-acetyl-a-L-rhamnopyranosyl trichloroa-
cetimidate 6 [7]. In the presence of
borontrifluoride ether complex, compound
5 was provided [8,9]. Desilylation of 5
under tetrabutylammonium fluoride
(TBAF) gave 8 (80% yield) with 30-OH
free [10,11], which was treated with
2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl
trichloroacetimidate 7 [12] in the presence
of borontrifluoride ether complex to
furnish triosaccharide 9 in 64% yield.
Subsequently, thiosaccharide 9 was
used as a glycosyl donor to transfer to
aglycone by standard glycosylation.
Unfortunately, direct glycosylation of
pennogenin with 9 under the promotion
of N-iodosuccinimide (NIS)–TfOH was
troublesome [13]. The reaction resulted in
a complex mixture of products and the
desired protected glycoside resulted in a
poor yield. A detailed evaluation of the
result suggested that thioglycoside 9 was
not an active glycosyl donor matching
3-OH of pennogenin aglycone in this
glycosylation.
To circumvent this problem, com-
pound 9 was converted into more efficient
trichloroacetimidate 12 in 86% yield in

316
X.-F. Luo et al.
O
Ph
O
Ph
O
O
O
O
O
O
O
AcO
O
Pennogenin
f
Pennogenin
O
AcO
AcO
SPh
O
O
AcO
AcO
OAc
AcO
AcO
OAc
AcO
AcO
AcO
O
O
OAc
OAc
9
11
NH
CCl3
g
O
O
O
Ph
O
Ph
O
O
O
O
i Pennogenin
O
AcO
AcO
h
O
O
AcO
OH
O
AcO
AcO
O
AcO
OAc
AcO
AcO
OAc
AcO
AcO
NH
O
O
OAc
O
CCl3
OAc
10
12
O
AcO
AcO
OAc
O
Ph
O
O
O
AcO
j
6
O
Pennogenin
NH
CCl3
O
1
AcO
AcO
AcO
AcO
AcO
O
OAc
AcO
O
O
O
AcO
AcO
OAc
7
11
˚
Scheme 2. Synthesis of saponin 1. Reagents and conditions: (f) NIS, TfOH, 4 A MS, CH2Cl2;
(g) NBS, acetone–H2O, 08C ! r.t., 2 h, 93%; (h) CNCCl3, DBU, CH2Cl2, 08C ! r.t., 3 h, 92%;
˚
(i) TMSOTf, 4 A MS, CH2Cl2, 08C ! r.t., 87%; (j) 80% HOAc, 3 h, 708C; NaOMe/MeOH, r.t.,
overnight, 84% (two steps).
two steps as follows: (i) N-bromosuccini-
mide (NBS) promoted chemoselective
hydrolysis of thioglycoside 9 in acetone–
H2O co-solvent system to get compound
10 [14]; (ii) trichloroacetimidate activation
of anomeric carbon using trichloroaceto-
nitrile (CCl3CN) and 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU) in dichloro-
methane. As expected, trisaccharide imi-
date 12 was successfully and efficiently
transformed to the aglycone in the
presence of TMSOTf at 08C to afford the
corresponding protected glycose 11 in
87% yield [15–17].
under 80% HOAc, followed by deacetyla-
tion under NaOMe in MeOH, furnished
the naturally existing saponin 1 [10,18].
3. Experimental
3.1 General experimental procedures
Melting points were observed in an open
capillary tube and are uncorrected.
Elemental analyses were carried out by
Atlantic Microlab (Atlanta, GA, USA). 1H
and 13C NMR spectra were acquired on a
Bruker AC-E 200 (13C NMR) or a Varian
INOVA-400/54 (1H NMR) spectrometer
in CDCl3, with TMS as an internal
standard. Mass spectra were recorded on
an Agilent 1946B ESI-MS instrument. All
starting materials were commercially
available and of analytical grade. All
reactions were carried out under inert gas
(argon). Reaction progress was monitored
by TLC, performing on precoated silica
gel GFA254 plates (0.2 mm; Chemical
Industry Institute, Yantai, China). Column
chromatography was performed using
The aglycone with trisaccharide imi-
date will always provide the a and b
glycoside; interestingly, the stereo-selec-
tivity of this glycosylation was predomi-
nantly b stero-controlled without the
neighboring group participation effect of
donor 12, which was adjusted by the
coupling constant 7.8 Hz of the glucopyr-
1
anosyl H-1 in H NMR spectrum and in
13C NMR spectrum the chemical shift of
C-1 at d 99.9. Debenzylidenation of 11

Journal of Asian Natural Products Research
317
silica gel (10–40 mm; Qingdao Sea
Chemical Factory, Qingdao, China).
petroleum ether–EtOAc); 1H NMR
(400MHz, CDCl3) d: 7.60–7.58 (m, 2H,
Ar), 7.48–7.46 (m, 2H, Ar), 7.41–7.35 (m,
6H, Ar), 5.52 (s, 1H, PhCH), 4.66 (d, 1H,
J1,2 ¼ 9.6 Hz, H-1), 4.37 (dd, 1H,
J4,5 ¼ 4.0 Hz, J3,4 ¼ 10.4Hz, H-4), 3.80–
3.76 (m, 2H, H2-6), 3.50–3.41 (m, 3H, H-2,
H-3, H-5), 1.27 (s, 6H, 2 £ CH3), 0.87 (s,
9H, 3 £ CH3);13C NMR(100 MHz, CDCl3)
d: 137.3, 133.5, 131.8, 129.6, 129.3, 128.6,
128.5, 126.6, 101.9, 89.0, 80.6, 74.9, 73.0,
71.1, 67.0, 31.1, 26.3, 24.85, 24.21;
elemental analysis: Found: C, 63.26%, H,
7.22%; calcd for C25H34O5SSi: C, 63.20%,
H, 7.19%; ESI-MS: m/z 475 [M þ H]þ.
3.2 Preparation of key intermediates
and compound 1
3.2.1 4,6-O-benzylidene-1-thio-b-D-
glucopyranoside (3)
To a solution of 2 (1.69 g, 6.2 mmol) and
PhCH(OMe)2 (2 ml, 13.3 mmol) in dry
DMF (30 ml) was added p-TsOH (until the
pH of the solution reached 2–3). The
resulting mixture, stirred at 608C under
reduced pressure for 3 h, was neutralized by
Et3N (3.0 ml), diluted with EtOAc (50 ml),
then washed with brine, dried over
anhydrous Na2SO4, and concentrated.
Chromatography of the residue on a silica
gelcolumn(20:1, petroleumether–EtOAc)
afforded 3 as a white solid (2.22 g, 100%);
Rf 0.15 (CH2Cl2/MeOH: 50/1); mp: 172–
1748C; 1H NMR (400 MHz, CDCl3) d:
7.54–7.52 (m, 2H, Ar), 7.48–7.46 (m, 2H,
Ar), 7.34–7.32 (m, 6H, Ar), 5.50 (s, 1H,
PhCH), 4.59 (d, 1H, J1,2 ¼ 10.0 Hz, H-1),
4.35 (dd, J4,5 ¼ 4.4 Hz, J3,4 ¼ 10.8 Hz,
H-4), 3.81–3.71 (m, 2H, H2-6), 3.51–
3.41 (m, 3H, H-2, H-3, H-5); 13C NMR
(100 MHz, CDCl3) d: 136.7, 132.9, 131.2,
129.1, 128.9, 128.1, 128.0, 126.1, 101.5,
88.4, 80.0, 74.4, 72.4, 70.5, 66.4; elemental
analysis: Found: C, 63.32%, H, 5.59%;
calcd forC19H20O5S: C, 62.25%, H, 5.50%;
ESI-MS: m/z 361 [M þ H]þ.
3.2.3 2,3,4-Tri-O-acetyl-a-L-
rhamnopyranosyl-(1 ! 2)-3-O-
butyldimethysilyl-4,6-O-benzylidene-1-
thio-b-D-glucopyranoside (5)
To a solution of 4 (1.28 g, 2.7 mmol) and
˚
4 A MS (2g) in dry CH2Cl2 (30 ml) at
2788C under Ar was added borontrifluor-
ide–ether complex (0.65 ml, 5.28mmol),
then a solution of 6 (3.6g, 8.3 mmol) in
CH2Cl2 (10 ml). The mixture, warmed up
naturally to room temperature (r.t.) and
allowed to stir for another 3 h, was then
neutralized with Et3N (1ml), filtered, and
concentrated. The residue was chromato-
graphed on a silica gel column (25:1,
petroleum ether–EtOAc) to afford 5 as a
white solid (1.79 g, 89%); 1H NMR
(400MHz, CDCl3) d: 7.57–7.54 (m, 2H,
Ar), 7.47–7.44 (m, 2H, Ar), 7.40–7.31 (m,
6H, Ar), 5.52 (s, 1H, PhCH), 5.40–5.30 (m,
3H, H-10, H-20, H-30), 5.14 (t, J ¼ 9.6 Hz,
1H, H-40), 4.71 (d, 1H, J ¼ 10Hz, H-1),
4.52–4.41 (m, 1H, H-50), 4.35 (dd, 1H,
J6a,5 ¼ 4.4 Hz, J6a,6b ¼ 10.6 Hz, H-6a),
3.93 (t, J ¼ 8.8 Hz, 1H, H-3), 3.79–3.71
(m, 1H, H-6b), 3.66 (t, J ¼ 8.4 Hz, 1H, H-
2), 3.48–3.41 (m, 2H, H-4, H-5), 2.15 (s,
3H), 2.07 (s, 3H), 2.01 (s, 3H), 1.29 (d, 3H,
J ¼ 6.8 Hz), 0.89 (s, 9H), 0.11 (s, 3H), 0.04
(s, 3H); 13C NMR (100 MHz, CDCl3) d:
170.4, 137.5, 133.7, 131.9, 129.8, 129.5,
128.8, 128.6, 126.7, 106.1, 101.9, 91.1,
3.2.2 3-O-butyldimethysilyl-4,6-O-
benzylidene-1-thio-b-D-glucopyranoside
(4)
To a solution of 3 (1.0g, 2.78mmol) in dry
CH2Cl2 (20 ml), TBDMS chloride (0.617g,
4.17 mmol) and imidazole (0.378 g,
5.56mmol) were added under an argon
atmosphere and the mixture was refluxed
overnight. After dilution with EtOAc
(50 ml), the crude was submitted to standard
work-up and purified by silica gel column
(35:1, petroleum ether–EtOAc) to afford 4
as a colorless oil (1.25 g, 95%); Rf 0.7 (8:1,

318
X.-F. Luo et al.
86.3, 82.4, 79.1, 78.7, 71.1, 71.1, 70.9, 69.0,
68.2, 31.0, 26.1, 21.1, 17.0, 22.1; elemen-
tal analysis: Found: C, 59.50%, H, 6.75%;
calcd for C37H50O12SSi: C, 59.48%, H,
6.71%; ESI-MS: m/z 748 [M þ H]þ.
2788C under Ar was added borontrifluor-
ide–ether complex (0.15 ml, 1.17 mmol),
then a solution of 7 (0.76 g, 1.75 mmol) in
CH2Cl2 (5 ml). The mixture, warmed up
naturally to r.t. and allowed to stir for
another 8 h, was then neutralized with
Et3N (1 ml), filtered, and concentrated.
The residue was chromatographed on a
silica gel column (25:1, petroleum ether–
EtOAc) to afford 9 as a colorless oil
(0.36 g, 64%); 1H NMR (400 MHz,
CDCl3) d: 7.53–7.33 (m, 10H, 2 £ Ph),
5.50 (s, 1H, PhCH), 5.40–5.39 (m, 1H),
5.36 (s, 1H), 5.28 (dd, 1H, J ¼ 4.4,
10.6 Hz), 5.20 (t, 1 H, J ¼ 9.6 Hz), 5.14
(t, 1H, J ¼ 9.2 Hz), 5.05–4.98 (m, 2H),
4.85 (d, 1H, J ¼ 8.0 Hz), 4.72 (d, 1H,
J ¼ 6.0 Hz), 4.59–4.52 (m, 1H), 4.18–
4.11 (m, 2H), 3.97 (dd, 1H, J ¼ 4.8,
10.0 Hz), 3.85 (t, 1H, J ¼ 8.8 Hz), 3.74 (t,
1H, J ¼ 9.6 Hz), 3.64–3.59 (m, 2H),
3.47–3.41 (m, 1H), 2.24 (s, 3H), 2.06 (s,
3H), 2.02 (s, 3H), 2.00 (s, 3H), 1.99 (s,
3H), 1.98 (s, 3H), 1.95 (s, 3H), 1.23 (d,
J ¼ 6.3 Hz, CH3-60); 13C NMR (100 MHz,
CDCl3) d: 170.1, 137.5, 133.5, 131.7,
129.9, 129.0, 128.8, 128.5, 126.6, 106.7,
106.0, 101.8, 91.0, 86.2, 82.3, 79.0, 78.6,
74.8, 72.6, 71.0, 71.0, 70.8, 69.3, 68.9,
68.1, 62.7, 30.6, 21.0, 16.7; elemental
analysis: Found: C, 56.13%, H, 5.65%;
calcd for C45H54O21S: C, 56.02%, H,
5.56%; ESI-MS: m/z 963 [M þ H]þ.
3.2.4 2,3,4-Tri-O-acetyl-a-L-
rhamnopyranosyl-(1 ! 2)-4,6-O-
benzylidene-1-thio-b-D-glucopyranoside
(8)
To a solution of 5 (0.67 g, 0.90 mmol) in
dry THF (10 ml) was added a solution of
BU4NF in THF (0.7 g, 2.7 mmol, 0.5 M).
The mixture, which was stirred at r.t. for
5 h, was diluted with EtOAc, washed with
brine, dried over anhydrous Na2SO4, and
concentrated. The residue was chromato-
graphed on silica gel column (6:1,
petroleum ether–EtOAc) to give 8 as a
colorless oil (0.45 g, 80%); 1H NMR
(400 MHz, CDCl3) d: 7.57–7.54 (m, 2H,
Ar), 7.47–7.44 (m, 2H, Ar), 7.40–7.31 (m,
6H, Ar), 5.49 (s, 1H, PhCH), 5.37–5.30
(m, 3H, H-10, H-20, H-30), 5.12 (t,
J ¼ 9.6 Hz, 1H, H-40), 4.70 (d, 1H,
J ¼ 10.0 Hz, H-1), 4.47–4.40 (m, 1H,
H-50), 4.33 (dd, 1H, J6a,5 ¼ 4.4 Hz,
J6a,6b ¼ 10.6 Hz, H-6a), 3.90 (t,
J ¼ 8.4 Hz, 1H, H-3), 3.75–3.70 (m, 1H,
H-6b), 3.65 (t, J ¼ 8.8 Hz, 1H, H-2),
3.46–3.42 (m, 2H, H-4, H-5), 2.14 (s,
3H), 2.06 (s, 3H), 2.00 (s, 3H), 1.27 (d, 3H,
J ¼ 8.0 Hz); 13C NMR (100 MHz, CDCl3)
d: 170.3, 137.4, 133.6, 131.8, 129.7, 129.4,
128.7, 128.5, 126.6, 106.0, 101.8, 91.0,
86.2, 82.3, 79.0, 78.6, 71.0, 71.0, 70.8,
68.9, 68.1, 30.9, 21.1, 16.9; elemental
analysis: Found: C, 58.85%, H, 5.74%;
calcd for C31H36O12S: C, 58.70%, H,
5.66%; ESI-MS: m/z 633 [M þ H]þ.
3.2.6 2,3,4-Tri-O-acetyl-a-L-
rhamnopyranosyl-(1 ! 2)-[(2,3,4,6-tetra-
O-acetyl-b-D-glucopyranosyl)-(1 ! 3)]-
4,6-O-benzylidene-b-D-glucopyranoside
(10)
A solution of 9 (100 mg, 0.1 mmol) in 50:1
acetone–H2O (15 ml) was added to NBS
(140 mg, 0.8 mmol) at 08C. The mixture,
warmed up naturally to r.t. and allowed to
stir for another 1 h, was then neutralized
with Na2S2O3 (100 mg). The solvent was
removed under vacuum to give a residue,
which was dissolved in CH2Cl2 (20 ml),
washed with brine and water, dried over
3.2.5 2,3,4-Tri-O-acetyl-a-L-
rhamnopyranosyl-(1 ! 2)-[(2,3,4,6-tetra-
O-acetyl-b-D-glucopyranosyl)-(1 ! 3)]-
4,6-O-benzylidene-1-thio-b-D-
glucopyranoside (9)
To a solution of 8 (0.36 g, 0.58 mmol) and
˚
4 A MS (1.2 g) in dry CH2Cl2 (10 ml) at

Journal of Asian Natural Products Research
319
anhydrous Na2SO4, and concentrated. The
residue was chromatographed on silica gel
column (4:1, petroleum ether–EtOAc) to
give 10 as a colorless oil (84 mg, 93%); 1H
NMR (400 MHz, CDCl3) d: 7.51–7.48 (m,
2H, Ar), 7.37–7.29 (m, 3H, Ar), 5.38 (s,
1H, PhCH), 5.33 (s, 1H), 5.30–5.23 (m,
2H), 5.15–5.06 (m, 2H), 5.03–4.97 (m,
1H), 4.89 (d, 1H, J ¼ 7.6 Hz), 4.66 (d, 1H,
J ¼ 7.2 Hz), 4.52–4.48 (m, 1H), 4.27–
4.22 (m, 1H), 4.18–4.14 (m, 1H), 3.92–
3.88 (m, 2H), 3.83–3.80 (m, 2H), 3.73–
3.69 (m, 1H), 3.56 (s, 1H), 3.47 (t, 1H,
J ¼ 8.0 Hz), 3.36–3.31 (m, 1H), 2.24 (s,
3H, CH3CO), 2.09 (s, 3H, CH3CO), 2.07
(s, 3H, CH3CO), 2.07 (s, 3H, CH3CO),
2.04 (s, 3H, CH3CO), 2.03 (s, 3H,
CH3CO), 1.98 (s, 3H, CH3CO), 1.21 (d,
J ¼ 6.0 Hz, 3H, CH3); 13C NMR
(100 MHz, CDCl3) d: 170.7, 137.7,
129.5, 128.5, 126.4, 106.5, 106.1, 101.9,
97.8, 86.3, 82.4, 79.1, 78.7, 74.9, 72.7,
71.1, 71.1, 70.9, 69.4, 68.9, 68.2, 62.8,
30.7, 21.1, 16.6; elemental analysis:
Found: C, 53.79%, H, 5.79%; calcd for
C39H50O22: C, 53.59%, H, 5.81%; ESI-
MS: m/z 871 [M þ H]þ.
J ¼ 8.0 Hz), 4.71–4.65 (m, 2H), 4.54–4.50
(m, 1H), 4.38–4.33 (m, 1H), 4.28–4.23 (m,
1H), 4.19–4.15 (m, 1H), 3.89–3.78 (m,
3H), 3.65 (t, 1H, J ¼ 8.4 Hz), 3.58 (s, 1H),
3.50 (t, 1H, J ¼ 8.2 Hz), 2.24 (s, 3H,
CH3CO), 2.10 (s, 3H, CH3CO), 2.08 (s, 3H,
CH3CO), 2.07 (s, 3H, CH3CO), 2.05 (s, 3H,
CH3CO), 2.04 (s, 3H, CH3CO), 1.98 (s, 3H,
CH3CO), 1.21 (d, 3H, J ¼ 6.0 Hz, CH3);
13C NMR (100MHz, CDCl3) d: 170.5,
161.8, 137.5, 129.4, 128.7, 126.3, 106.3,
106.0, 101.7, 92.7, 86.3, 84.3, 82.2, 79.0,
78.6, 74.8, 72.6, 71.0, 71.1, 70.7, 69.3, 68.7,
68.0, 62.6, 30.5, 21.0, 16.7; elemental
analysis: Found: C, 48.51%, H, 4.96%, Cl,
10.48%,
N,
1.38%;
calcd
for
C41H50Cl3NO22: C, 48.47%, H, 4.81%,
Cl, 10.50%, N, 1.41%; ESI-MS: m/z 1014
[M þ H]þ.
3.2.8 Pennogenin 3-O-[2,3,4-tri-O-
acetyl-a-L-rhamnopyranosyl-(1 ! 2))-
[(2,3,4,6-tetra-O-acetyl-b-D-
glucopyranosyl)-(1 ! 3)]-4,6-O-
benzylidene-D-glucopyranoside (11)
To a mixture of compound pennogenin
(100 mg, 0.23 mmol), 12 (280 mg,
˚
0.28mmol), and powered 4 A molecular
3.2.7 2,3,4-Tri-O-acetyl-a-L-
sieves in dried CH2Cl2 (10 ml) at 08C was
added TMSOTf (4ml, 0.023 mmol). After
stirring at 08C and then at r.t. for 1 h, the
reaction was quenched with Et3N. The solid
was then filtered off. The filtrate was
concentrated under vacuum to give color-
less oil that was purified by column
chromatography (3:1, petroleum ether–
EtOAc) to give 11 as a white solid
(258 mg, 87%); 1H NMR (400 MHz,
CDCl3) d: 7.47–7.37 (m, 5H, Ar), 5.50 (s,
1H, PhCH), 5.40 (d, 1H, H-6), 5.26–5.23
(m, 2H, H-100, H-200), 5.20 (dd,
rhamnopyranosyl-(1 ! 2)-[(2,3,4,6-tetra-
O-acetyl-b-D-glucopyranosyl)-(1 ! 3)]-
4,6-O-benzylidene -a-D –glucopyranosyl
trichloroacetimidate (12)
Trichloroacetonitrile (0.035ml, 0.34mmol)
was added to a solution of trisaccharide 10
(100mg, 0.11mmol) in CH2Cl2 (3ml) at
08C under Ar. After stirring for 30min,
DBU (0.015ml, 0.1 mmol) was added to
the mixture and stirred for 3 h. The mixture
was concentrated under diminished press-
ure, and the residue was purified by silica
gel column chromatography (4:1, pet-
roleum ether–EtOAc) to give 12 as a
colorless oil (107mg, 92%); 1H NMR
(400MHz, CDCl3) d: 7.55–7.53 (m, 2H,
Ar), 7.33–7.28 (m, 3H, Ar), 5.38 (s, 1H,
PhCH), 5.32–5.25 (m, 3H), 5.16–5.08 (m,
2H), 5.02 (t, 1H, J ¼ 8.8 Hz), 4.81 (d, 1H,
J3 ,2 ¼ 3.0 Hz, J3 ,4 ¼ 10.2 Hz, H-300),
00 00
00 00
5.15 (t, J3 ,2 ¼ 9.2 Hz, H-3000), 5.10 (t,
000 000
J ¼ 9.2 Hz, 1H, H-400), 5.03 (t, J ¼ 9.8 Hz,
1H, H-4000), 4.94 (t, J ¼ 9.6 Hz, 1H, H-2000),
4.84 (d, 1H, J1 ,2 ¼ 8.0 Hz, H-1000), 4.61 (d,
000 000
1H, J1 ,2 ¼ 7.8 Hz, H-10), 4.55–4.52 (m,
0
0
1H, H-500), 4.31 (dd, 1H, J6 a,5 ¼ 4.8 Hz,
0
0

320
X.-F. Luo et al.
J6 a,6 b ¼ 10.2Hz, H-60a), 4.10–4.07 (m,
2H, H-30, H-6000a), 3.98 (t, 1H, J ¼ 7.5 Hz,
H-16), 3.96 (dd, 1H, H-6000b), 3.81–3.76 (m,
J ¼ 7.2 Hz), 1.11 (d, 3H, J ¼ 4.4 Hz),
0.99–0.87 (m, 4H), 0.72 (d, 3H,
J ¼ 4.4 Hz); 13C NMR (100MHz, C5D5N)
d: 140.7, 121.8, 109.8, 104.5, 102.1, 99.9,
90.1, 89.9, 89.5, 78.6, 78.4, 77.8, 77.8, 77.6,
77.0, 75.0, 72.4, 72.4, 71.4, 69.5, 69.5, 66.6,
62.4, 62.4, 53.0, 50.2, 45.1, 44.7, 38.6, 37.5,
37.1, 32.3, 32.0, 32.0, 32.0, 31.8, 30.4, 30.0,
28.8, 20.9, 19.4, 18.6, 17.2, 17.1, 9.7;
elemental analysis: Found: C, 59.98%, H,
8.05%; calcd for C45H72O18: C, 59.95%, H,
31.98%; ESI-MS: m/z 901 [M þ H]þ.
0
0
2H, H-20, H-60b), 3.70 (t, 1H, J4 ,3 ¼ 9.2 Hz,
H-40), 3.68–3.62 (m, 1H, H-3), 3.49–3.36
(m, 4H, H-50, H-5000, H-26), 2.22, 2.03, 2.02,
2.00, 1.99, 1.97, 1.95 (7s, 21H, CH3CO),
1.20 (d, 3H, J6 ,5 ¼ 6.0 Hz, CH3-600), 1.04
0
0
00 00
(s, 3H, CH3), 0.99 (d, J ¼ 7.2 Hz, CH3),
0.80 (s, 3H, CH3), 0.79 (s, 3H, CH3); 13C
NMR (100MHz, CDCl3) d: 170.1, 140.8,
137.5, 133.5, 131.7, 129.9, 129.0, 128.8,
128.5, 126.6, 121.4, 110.1, 107.8, 106.7,
106.0, 101.8, 90.9, 90.1, 86.2, 82.3, 79.0,
78.6, 74.8, 72.6, 71.7, 71.0, 71.0, 70.8, 69.3,
68.9, 68.1, 66.8, 62.7, 52.8, 49.8, 44.6, 43.9,
42.5, 37.1, 36.6, 32.0, 31.6, 31.6, 31.2, 30.8,
30.1, 29.7, 28.1, 21.5, 21.0, 20.7,19.4, 17.1,
17.0, 16.7, 8.1; elemental analysis: Found:
C, 61.77%, H, 7.07%; calcd for C66H90O25:
C, 61.55%, H, 6.94%; ESI-MS: m/z 1284
[M þ H]þ.
Acknowledgements
This work was financially supported by the
Scientific Research Fund of Sichuan Provincial
Education Department (11205023).
References
[1] (a) S.B. Mahato, A.N. Ganguly, and
N.P. Sahu, Phytochemistry 21, 959
(1982); (b) K. Hostettmann and
S. Marston, Saponins (Cambridge Uni-
versity Press, Cambridge, 1995),
288–303.
3.2.9 Pennogenin 3-O-b-D-
glucopyranosyl-(1 ! 3)-[a-L-
rhamnopyranosyl-(1 ! 2)]-b-D-
glucopyranoside (1)
[2] (a) M. Yoshihiro, K. Minper, O. Yuusuke,
S. Yutaka, K. Milio, Y. Akira,
N. Noriyuki, W.X. Zhen, M.R. Li, and
A.N. Lao, Nat. Prod. Lett. 14, 357 (2000);
(b) E. Candra, K. Matsunaga, H. Fujiwara,
Y. Mimaki, M. Kuroda, Y. Sashida, and
Y. Ohizumi, J. Pharm. Pharmacol. 54,
257 (2002); (c) M. Yoshihiro, Y. Akihito,
K. Minper, and S. Yutaka, Biol. Pharm.
Bull. 24, 1286 (2001); (d) T. Zhang,
H. Liu, X.T. Liu, D.R. Xu, X.Q. Chen, and
Q. Wang, J. Pharm. Biomed. Anal. 51,
114 (2010); (e) H.S. Yu, B.P. Ma,
L.P. Kang, T. Zhang, F.J. Jiang, J. Zhang,
P. Zou, Y. Zhao, C.Q. Xiong, D.W. Tan,
X.B. Song, and K. Yu, Chem. Pharm.
Bull. 57, 1011 (2009); (f) C.X. Cheng and
J. Zhou, Acta Bot. Yunnan. 6, 111 (1984).
[3] C.X. Cheng, Y.T. Zhang, and J. Zhou,
Acta Bot. Yunnan. 5, 91 (1983).
A solution of 11 (130mg, 0.1 mmol) in 80%
HOAc (20 ml) was stirred at 708C for 3 h.
The solvent was removed under vacuum to
give a residue, which was dissolved in the
solution of NaOMe/MeOH (0.4M, 10ml),
and the mixture was stirred overnight. The
solution was neutralized with ion-exchange
resin (Hþ), filtered, and concentrated.
The residue was purified by column
chromatography to afford 1 as a white
1
solid (76 mg, 84%); mp: 300–3028C; H
NMR (400MHz, C5D5N) d: 6.28 (d, 1H,
J1 ,2 ¼ 10.8 Hz, H-100), 5.40 (d, 1H,
00 00
J ¼ 4.0 Hz, H-6), 5.11 (d, 1H, J ¼ 7.8 Hz,
H-1000), 4.94–4.91 (m, 3H, H-200, H-300, H-
400), 4.62–4.54 (m, 3H), 4.46–4.35 (m, 2H),
4.27–4.17 (m, 5H), 4.08–3.90 (m, 6H),
3.61–3.54 (m, 4H), 2.80–2.75 (m, 2H),
2.34–2.28 (m, 2H), 2.17–2.11 (m, 3H),
1.98–1.89 (m, 2H), 1.78–1.73 (m, 6H),
1.61–1.48 (m, 8H), 1.30 (d, 3H,
[4] K.U. Sunil and S.J. Branko, Tetrahedron
Lett. 52, 1835 (2011).
[5] (a) Q. Chen, T. Gong, J. Liu, X.L. Wang,
H.L. Fu, and Z.R. Zhang, J. Drug Target.
17, 318. (2009); (b) F. Roussel, L. Knerr,
M. Grathwohl, and R.R. Schmidt, Org.
Lett. 2, 30 (2000); (c) R.P. Emma and
H.S. Peter, Tetrahedron 660, 7755 (2004).

Journal of Asian Natural Products Research
321
[6] (a) P. Francesco, N. Francesco, P.L.
Colin, M. Fabrizio, S. Pierfausto, and
M.J. Carla, Carbohydr. Chem. 22, 57
(2003); (b) S.J. Hou, P. Xu, L. Zhou,
D.Q. Yu, P.S. Lei, and C.C. Zou,
Chin. Chem. Lett. 17, 183 (2006).
[7] K. Isao, I.B. Nam, O. Kazuyoshi,
S. Masahiro, Y. Masayuki, and
S. Hirotaka, Chem. Pharm. Bull. 37,
1131 (1989).
[8] M. Hiroyuki, I. Tsuyoshi, and N. Toshihiro,
Carbohydr. Res. 342, 2182 (2007).
[9] S.J. Hou, P. Xu, L. Zhou, D.Q. Yu, and
P.S. Lei, Bioorg. Med. Chem. Lett. 16,
2454 (2006).
A.R. Mark, J. Am. Chem. Soc. 131, 1607
(2009).
[12] R.R. Schmidt and J. Michel, Angew.
Chem. Int. Ed. Engl. 19, 731 (1980).
[13] M.S. Cheng, Q.L. Wang, Q. Tian,
H.Y. Song, Y.X. Liu, Q. Li, X. Xu, H.D.
Miao, X.S. Yao, and Z. Yang, J. Org.
Chem. 68, 3685 (2003).
[14] S.M. Mohammed, M. Jan, and
L.M. Birger, J. Carbohydr. Chem. 14,
1279 (1995).
[15] J. Gao, X. Li, G.F. Gu, B. Sun, M. Cui,
M. Ji, and H.X. Lou, Bioorg. Med. Chem.
Lett. 21, 622 (2011).
[16] B. Yu, Y.C. Zhang, and P.P. Tang,
Eur. J. Org. Chem. 31, 5145 (2007).
[17] B. Yu and J.S. Sun, Chem. Asian J. 5, 642
(2009).
[10] C. Li, B. Yu, M.Z. Liu, and Y.Z. Hui,
Carbohydr. Res. 306, 189 (1998).
[11] E.A. Tim, E.S. Mariana, C.H. Bill,
H. Sebastian, H. Georgina, L.K. Mui,
J.O. David, S. Paul, J.S. Peter, and
[18] C.C. Zou, S.J. Hou, Y. Shi, P.S. Lei, and
X.T. Liang, Carbohydr. Res. 338, 721
(2003).

Copyright of Journal of Asian Natural Products Research is the property of Taylor & Francis Ltd and its content
may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express
written permission. However, users may print, download, or email articles for individual use.