Synthesis of two natural betulinic acid saponins containing α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranose and their analogues

Article abstract of DOI:10.1016/j.tet.2008.05.029

A concise synthesis of naturally occurring betulinic acid saponins bearing an α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranoside moiety at the C-3 position is described. Betulinic acid 3β-O-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl- (1→4)]-α-l-arabinopyr

Full text of DOI:10.1016/j.tet.2008.05.029

Tetrahedron 64 (2008) 7386–7399
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of two natural betulinic acid saponins containing
a-
L-rhamnopyranosyl-(1/2)-
a- -arabinopyranose and their analogues
L
*
´
Charles Gauthier, Jean Legault, Serge Lavoie, Simon Rondeau, Samuel Tremblay, Andre Pichette
`
Laboratoire d’Analyse et de Se´paration des Essences Ve´ge´tales, De´partement des Sciences Fondamentales, Universite´ du Que´bec a Chicoutimi,
555 boul. de l’Universite´, Chicoutimi, Que´bec, Canada G7H 2B1
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 April 2008
Received in revised form 3 May 2008
Accepted 8 May 2008
Available online 11 May 2008
A concise synthesis of naturally occurring betulinic acid saponins bearing an
a
-
L
-rhamnopyranosyl-(1/
2)-
anosyl-(1/2)-[
28-O- -glucopyranosyl betulinic acid 3
a
-
L
-arabinopyranoside moiety at the C-3 position is described. Betulinic acid 3
-glucopyranosyl-(1/4)]- -arabinopyranoside isolated from Pulsatilla koreana and
-O- -rhamnopyranosyl-(1/2)- -arabinopyranoside iso-
b-O-a-L-rhamnopyr-
b
-
D
a-L
a
b
-
D
b
-
L
a-L
lated from Schefflera rotundifolia were easily synthesized for the first time using a stepwise glycosidation
approach. The overall syntheses involved eight linear steps starting from allyl betulinate and commer-
Keywords:
Betulinic acid
Lupane-type saponin
a-L-Rhamnopyranosyl-(1/2)-a-L-
arabinopyranose
Anticancer
cially available
glycoside analogues containing an
the synthesis of various lupane-type saponin derivatives as potentially bioactive compounds.
Ó 2008 Elsevier Ltd. All rights reserved.
L
-arabinose,
L-rhamnose and
D-glucose. The syntheses of betulin and betulinic acid O-
a-L-arabinose moiety are also reported. These results open the way to
1. Introduction
Betulin (1) and its C-28 carboxylic derivative betulinic acid (2)
(Fig. 1) are naturally occurring pentacyclic lupane-type triterpe-
noids that possess multiple pharmacological activities.14,15 Betu-
linic acid (2) has the ability to inhibit the growth of various
cancerous cell lines in vitro without affecting normal cells.16 The in
vivo antitumour activity of betulinic acid (2) was also confirmed
whereas no other toxicity was observed on tumour-bearing mice at
doses of 500 mg/kg body weight after intraperitoneal in-
jections.17,18 Thus, due to the selective cytotoxicity and favourable
therapeutic index, which are in contrast with the majority of
antitumour agents actually used in chemotherapy, betulinic acid (2)
is considered a promising anticancer agent.19,20 Nonetheless, fur-
ther clinical development of betulin (1), betulinic acid (2) and
lupane-type analogues is strongly hampered since they are virtu-
Natural products (NPs) have attracted increased attention over
the last century as an important source of new drug leads for the
pharmaceutical industry.1–4 In the domain of cancer research, 47%
of antitumour compounds approved from 1940 to 2006 are either
NPs or their semi-synthetic derivatives.5 Saponins are a specific
class of NPs widely distributed in the plant kingdom, which consist
of a triterpenoid or steroid skeleton bearing one or more sugar
chains.6 They exhibit numerous pharmacological and biological
properties such as anti-inflammatory,7 haemolytic,8 cytotoxic and
antitumour9 activities. Since many commonly used traditional
Chinese drugs are rich in saponins,10 some authors considered
them responsible along with polyphenols for the majority of bi-
ological effects observed in the Chinese medical literature.11 How-
ever, the isolation of saponins from plant extracts is often a long
and fastidious process and usually only small amounts of products
are obtained in a pure and homogeneous form.12 Therefore,
chemical syntheses are needed and appear to be a realistic way to
gain access to a broad library of saponin glycoforms in order to
study the structure–activity relationships (SARs) of this important
class of NPs.13
ally insoluble in water (0.02 m
g/mL for 2)21,22 and possess high
partition coefficient values (log P>6), which complicate the prep-
aration of injectable formulations for biological assays and decrease
their bioavailability in the organism.23 The introduction of polar
groups at either C-3 or C-28 positions such as phthalates,24 amino
acids25,26 or sugar moieties27,28 is an interesting avenue to increase
the hydrosolubility of lupane-type triterpenoids 1 and 2. Recently,
our preliminary SAR studies have shown that adding an
a-
L-rhamnopyranose moiety at the C-3 position of 2 resulted in a sig-
nificant increase of both thewatersolubilityandthe invitro cytotoxic
activity against human lung carcinoma (A549) and human colon
adenocarcinoma (DLD-1) cancer cell lines.27 Therefore, it was
* Corresponding author. Tel.: þ1 418 545 5011; fax: þ1 418 545 5012.
E-mail address: andre_pichette@uqac.ca (A. Pichette).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.05.029

C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
7387
29
2. Results and discussion
20
13
19
30
To our knowledge, the synthesis of betulinic acid saponins
bearing unique -rhamnopyranosyl-(1/2)- -arabinopyr-
a
a
-L
a-L
25
26
R
anosyl moiety at the C-3 position such as natural saponins 3 and 4
has never been reported until now. Two general synthetic ap-
proaches exist in the literature for this particular type of intersugar
linkage.13 One strategy consists in preparing the disaccharide donor
followed by coupling with the triterpene or steroid aglycone.44,45
Since, in this case, the arabinose residue does not contain a neigh-
bouring participating group at the C-2 position, the main in-
convenience of this convergent glycosidation is the formation of an
28
9
3
27
5
HO
1 R = CH2OH
2 R = COOH
23
24
OH
OH
O
a/b anomeric mixture, which complicates the further purification
HO
HO
1'''
of intermediates.13,44,45 In this work, we adopted the stepwise
glycosidation approach in which the arabinose residue containing
a C-2 neighbouring participating group was first coupled with the
aglycone. This linear strategy was shown to form a stereospecific
1,2-trans glycosidic bond13 usually found in the linkage of natural
triterpenoid saponins.12 Moreover, stepwise extension of the sugar
chain allows the preparation of a great variety of analogues by
simply altering the monosaccharide donors.46 Thus, such an ap-
proach to provide saponin glycoforms may be of further interest for
studies regarding the SAR of natural and non-natural saponins and
their development as pharmaceutical or biological agents.
O
O
OH
HO
O
O
3
O
1'
1''
O
3
HO
HO
OH
OH
HO
OH
CH2OH
O
28
O
O
1'''
OH
HO
O
O
3
Saponins 3 and 4 can be retrosynthetically (Fig. 2) disconnected
into distinct fragments: the natural lupane-type betulinic acid (2)
O
1'
4
and the commercially available monosaccharides
L-arabinose,
1''
O
L
-rhamnose and -glucose. As shown in Figure 2, the benzoyl par-
D
HO
ticipating groups were selected as protecting groups for the sugar
donors 5–8 since they avoid the formation of trans-esterification
products47,48 in comparison with the acetyl groups and can be
easily removed under alkaline conditions without hydrolysis of the
C-28 ester in the aglycone.49 In addition, the anomeric position of
sugar donors 5, 6 and 8 was activated by the trichloroacetimidate
(TCA) group, which was first devised by R.R. Schmidt in the early
1980s50 and shown to be ideal donors for the coupling with steroids
and triterpenoids using various Lewis acids as promoters such as
trimethylsilyl trifluoromethanesulfonate (TMSOTf) or boron tri-
fluoride diethyl etherate (BF3$OEt2).51 While TCA donors are usu-
ally used for the preparation of ether-glycosides,13,47 we planned to
employ the sugar donor bromide 752 in order to selectively glyco-
sylate the C-28 carboxylic acid function and produce the ester-
glycoside at a later stage of the synthesis after assembly of the
disaccharide.53
HO
OH
Figure 1. Structures of betulin (1), betulinic acid (2) and natural betulinic acid sapo-
nins (3, 4).
postulated that betulinic acid saponins represent an interesting class
of potent anticancer agents and require additional investigations.
Lupane-type saponins having betulin (1) or betulinic acid (2) as
aglycones are rarely isolated from a natural source29–31 and their
chemical syntheses are very scarce in the literature.27,28,32–37
Betulinic acid
3
b
-O-
a-L-rhamnopyranosyl-(1/2)-[b-D-glucopyr-
anosyl-(1/4)]-a-L-arabinopyranoside (3) (Fig. 1) is a naturally
occurring monodesmosidic saponin isolated from the roots of
Pulsatilla koreana, which is a plant widely used in Chinese tradi-
tional medicine for the treatment of malaria, amoebic dysentery
and various cancers.31 Saponin 3 exhibited moderate in vitro cy-
totoxicity against A549, SK-OV-3, SK-MEL-2 and HCT15 cancer cell
lines and significant in vivo anticancer activity against BDF1 mice
bearing Lewis lung carcinoma (LLC).38,39 The particular tri-
saccharide chain at the C-3 position of saponin 3 has been shown to
be a nontoxic moiety, which would increase the activity and water
solubility once conjugated to NPs.40 Another similar naturally oc-
As depicted in Scheme 1, the starting point of our synthesis
consisted in the preparation of the known 2,3,4-tri-O-benzoyl-
arabinopyranosyl trichloroacetimidate (8).51,54 Accordingly, the
commercial -arabinose was subjected to perbenzoylation with
b-L-
L
benzoyl chloride (BzCl) using a catalytic amount of 4-dimethyl-
aminopyridine (DMAP) at 60 ꢀC. The crude residue was then bro-
minated (33% HBr/HOAc) at the anomeric position, hydrolyzed with
silver carbonate (Ag2CO3) in an acetone/water 20:1 solution and
activated using trichloroacetonitrile (CCl3CN) and 1,8-diaza-
bicyclo[5.4.0]undec-7-ene (DBU) to furnish 8 in 38% yield after four
curring bidesmosidic saponin, 28-O- -glucopyranosyl betulinic
acid 3 -O- -rhamnopyranosyl-(1/2)-a-L-arabinopyranoside (4)
b
-D
b
a
-L
(Fig. 1) isolated from the aerial parts of Schefflera rotundifolia,
a plant used as folk remedies for the treatment of pain, rheumatic
arthritis and lumbago in Asian countries, exhibited noticeable
antiproliferative activity against J774.A1, WEHI-164 and HEK-293
cancer cell lines (IC50 0.32–0.79
and 23-hydroxybetulinic acid saponins bearing an
pyranosyl-(1/2)- -arabinopyranose moiety at the C-3 position
steps. However, two anomeric protons signals at d 6.67 ppm (s) and
6.82 ppm (d, J1,2 3.0 Hz) were visualized in the 1H NMR spectrum
m
M).30 Furthermore, betulinic acid
-rhamno-
indicating that, unexpectedly, the resulting product was an in-
a
-L
separable mixture of 8 and 2,3,5-tri-O-benzoyl-a-L-arabinofur-
a
-
L
anosyl trichloroacetimidate (9)55 (Rf 0.67, hexanes/EtOAc 3:1) in
have already been isolated from Pulsatilla chinensis, which is one of
the most well-known plants used in traditional Chinese medi-
cine.29,41–43 Hence, as part of our efforts to prepare lupane-type
saponins as anticancer agents,27,28 this report describes the first
synthesis of two naturally occurring betulinic acid saponins (3, 4).
The syntheses of betulin (15a,15b, 23a) and betulinic acid (19a, 19b,
a 5:1 ratio. The strong HMBC cross-peaks between the proton H-1
(d 6.67 ppm) and the carbon C-4 (d 84.3 ppm) confirmed the
presence of the TCA 9 in the mixture. It was further postulated that
the furanosyl form of the arabinose residue was produced during
the benzoylation step since the conversion of pyranose to furanose
in hot pyridine is not unprecedented.56 To confirm this hypothesis,
23b) saponin analogues containing
a-
L-arabinose are also reported.
in a separate experiment, L-arabinose was perbenzoylated under

7388
C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
4
3
OAll
OH
OH
HO
O
O
O
O
O
O
O
O
O
O
O
O
BzO
BzO
BzO
BzO
OBz
OBz
OAll
O
O
O
O
O
OH
O
CCl3
OBz
O
BzO
BzO
O
NH
NH
CCl3
BzO
BzO
BzO
O
OBz
6
5
Betulinic acid (2)
OBz
BzO
OBz
O
O
BzO
BzO
NH
CCl3
BzO
BzO
Br
O
7
8
Figure 2. Retrosynthetic analysis of betulinic acid 3
b-O-a-L-rhamnopyranosyl-(1/2)-[b-D-glucopyranosyl-(1/4)]-a-L-arabinopyranoside (3) and 28-O-b-D-glucopyranosyl betu-
linic acid 3 -O- -L-rhamnopyranosyl-(1/2)- -L-arabinopyranoside (4).
b
a
a
the previously mentioned conditions but keeping the temperature
under 25 ꢀC throughout the overnight reaction to afford 1,2,3,4-
betulin (1) was treated with tert-butyldiphenylsilyl chloride
(TBDPSCl) in the presence of imidazole and DMAP in refluxing
tetrahydrofuran (THF) to yield the new compound 13 (90%) pro-
tected at the C-28 primary alcohol position by the most robust
among silyl groups.57 The regioselectivity of the silylation reaction
was confirmed from the upfield shift in the 1H NMR signal of the
tetra-O-benzoyl-
tetra-O-benzoyl-
b
a
-
-
L
-arabinopyranose (10, 91%) along with 1,2,3,5-
L
-arabinofuranose (11)56 in only 1% yield. This
time, the purification by silica gel (SiO2) column chromatography
allowed the separation because both products 10 and 11 presented
a significant difference in their retention factors according to TLC
(hexanes/EtOAc 3:1). Afterwards, 10 was brominated and hydro-
lyzed to furnish 12 (73%, two steps), which was activated with
proton H-28 (d 3.81 ppm in 1 to 3.68 ppm in 13). For the in-
troduction of the arabinose moiety, we chose to use the mixture of
TCA donors 8 and 9 in order to obtain both arabinopyranoside and
arabinofuranoside saponins, which could be of further interest for
SAR investigations. Indeed, although the isolation of natural sapo-
CCl3CN and DBU to yield 8 (80%) as a pure
any trace of 9.
b-anomeric form without
With TCA sugar donor 8 in hand, the next task was its linkage to
the 3-OH of the lupane core of betulin (1) and betulinic acid (2). As
previously described, pure 1 (>95%, GC–MS) was obtained by ex-
haustive extractions in dichloromethane (CH2Cl2) of the external
bark of Betula papyrifera followed by recrystallization.28 The natural
carboxylic derivative 2 was then synthesized from 1 following
known methodologies.28 Here, the choice of the protecting groups
at the C-28 position of triterpenoids 1 and 2 was crucial for the
synthetic strategy since benzoyl groups have to be removed under
basic conditions without affecting this position. Thus, as revealed in
Scheme 2, we planned to temporarily protect the C-28 carboxylic
acid position of betulinic acid (2) with an allyl ester as already
reported by our laboratory in an earlier publication.27 In addition,
nins bearing an a-L-arabinofuranosyl residue was already repor-
ted,58,59 studies regarding their synthesis are scarce.60–62
Consequently, according to Scheme 2, coupling of the acceptor 13
with a mixture of donors 8 and 9 under the catalytic promotion of
TMSOTf in dry CH2Cl2 followed by subsequent removal of benzoyl
groups using 0.25 N NaOH in a solution of MeOH/THF/H2O 1:2:1
afforded the C-28 protected betulin 3
b
-O-
a-
L-arabinopyranoside
16a (84%, two steps) along with the 3
b
-O-a-L-arabinofuranoside
16b (13%, two steps). Moreover, similar treatment of acceptor 17,
i.e., coupling with donors 8 and 9 and deprotection of the benzoyl
groups, furnished allyl betulinate 3
67%, two steps) together with the 3
(11%, two steps). The non-natural betulinic acid saponins 19a and
b-O-
a-
L-arabinopyranoside (18a,
b-O-
a-L-arabinofuranoside 18b

C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
7389
Inseparable mixture
1:1 under reflux57 was sluggish affording the target saponins 15a
and 15b in unoptimized 42% and 37% yields, respectively. Thus, in
order to increase the overall yields, the known acceptor 28-acetyl
betulin (14)27 was coupled with the donors 8 and 9 in a separate
experiment and deprotected using the above mentioned method-
ology to access 15a (73%, two steps) and 15b (15%, two steps). As
expected, the coupling constant data on the 1H NMR spectra con-
ratio 5:1 (8/9)
O
CCl3
NH
BzO
O
a
L-Arabinose
L-Arabinose
8
+
BzOH2C
OBz
firmed the a-anomeric configuration of the glycosidic linkage for all
saponins (Arap, d, J1,2 6.1–6.5 Hz, H-10; Araf, br s, H-10).
9
Separable mixture
In order to achieve the Rhap(1/2)Arap intersugar linkage, the
synthesis started with the regioselective protection of 30- and 40-OH
of the arabinose moiety (Scheme 3). Accordingly, the treatment of
16a under the catalytic action of pyridinium p-toluenesulfonate
(PPTs) in conjunction with 2,2-dimethoxypropane (2,2-DMP)48
afforded the isopropylidinated glycoside 20a in 60% yield. The
treatment of the arabinoside 18a under similar reaction conditions
furnished 20b (74%). We first attempted to glycosylate the equa-
OBz
OBz
BzO
O
b
O
+
BzO
BzOH2C
BzO
10
OBz
OBz
11
c
torial 20-OH of 20b with the known 2,3,4-tri-O-benzoyl-
a-L-rham-
OBz
BzO
nopyranosyl trichloroacetimidate (6)27 using TMSOTf as the
promoter at ꢁ10 ꢀC to room temperature. Unfortunately, the re-
action was sluggish providing the target disaccharide glycoside 21b
in an unsatisfactory 22% yield. One possible explanation for the
moderate yield was the rupture of the isopropylidene group, which
led to the formation of a complex mixture of products.63 Thus, by
modifying the reaction conditions, it was found that the sugar
donor 6 could be coupled with the acceptor 20b under the
promotion of the Lewis acid BF3$OEt2 in CH2Cl2 at a cryogenic
O
OH
OBz
12
d
8
Scheme 1. Synthesis of L-arabinosyl donors (8, 9). Reagents and conditions: (a) (i) BzCl
(6.5 equiv), DMAP (0.01 equiv), Py, rt to 60 ꢀC, overnight; (ii) HBr/HOAc 33%, CH2Cl2, rt,
2 h; (iii) Ag2CO3 (1.35 equiv), acetone/H2O 20:1, rt, 1.5 h; (iv) CCl3CN (8.0 equiv), DBU
(0.5 equiv), CH2Cl2, rt, 4 days, 38% (four steps); (b) BzCl (6.5 equiv), DMAP (0.01 equiv),
Py, rt, overnight, 91% for 10; 1% for 11; (c) (i) HBr/HOAc 33%, CH2Cl2, rt, 2 h; (ii) Ag2CO3
(1.35 equiv), acetone/H2O 20:1, rt, 1.5 h, 73% (two steps); (d) CCl3CN (8.0 equiv), DBU
(0.5 equiv), CH2Cl2, rt, 45 min, 80%.
temperature of ꢁ78 ꢀC in
a nearly quantitative yield (99%).
Glycosidation of the acceptor 20a with 6 using the same conditions
proceeded smoothly to give the protected disaccharide saponin 21a
in a good yield (78%). Desilylation of 21a (1 M TBAF/HOAc 1:1, THF,
reflux, overnight) and deallylation of 21b [Pd0(PPh3)4, PPh3, pyr-
rolidine, THF, room temperature] were then performed under
standard experimental conditions to provide C-28 deprotected
derivatives 22a (72%) and 22b (85%), respectively. The non-natural
19b were obtained in good yields (66% and 71%, respectively) by the
subsequent deprotection of the allylic ester in 18a and 18b using
betulin and betulinic acid saponins 23a and 23b bearing an
a-L-
freshly
prepared
tetrakistriphenylphosphine
palladium(0)
[Pd0(PPh3)4], triphenylphosphine (PPh3) and pyrrolidine in dry
THF.44 On the other hand, the overnight desilylation of 16a and 16b
by the action of 1 M tetrabutylammonium fluoride (TBAF) in HOAc
rhamnopyranosyl-(1/2)- -arabinopyranosyl moiety at the C-3
a-L
position were successfully obtained after the deprotection of the
isopropylidene group using p-toluenesulfonic acid monohydrate
OR
OR
OR
c
OH
[8+9]
+
O
O
HO
O
HO
1 R = H
OH
a
HO
b
13 R = TBDPS
14 R = Ac
15a R = H
16a R = TBDPS
15b R = H
16b R = TBDPS
O
d
d
HOH2C
OH
OR
OR
+
OR
O
c
OH
HO
O
O
[8+9]
O
O
O
HO
2 R = H
OH
e
HO
17 R = All
O
18a R = All
19a R = H
18b R = All
19b R = H
f
f
HOH2C
OH
Scheme 2. Synthesis of 3b-O-a-L-arabinopyranosides (15a, 19a) and 3b-O-a-L-arabinofuranosides (15b, 19b). Reagents and conditions: (a) TBDPSCl (1.5 equiv), imidazole (2.5 equiv),
DMAP (0.1 equiv), THF, reflux, overnight, 90%; (b) Ac2O (1.05 equiv), Py, DMAP (0.1 equiv), rt, 2 h, 73%; (c) (i) TCA (1.5 equiv), TMSOTf (0.1 equiv), 4 Å MS, CH2Cl2, rt, 2 h; (ii) NaOH
(20 equiv), MeOH/THF/H2O 1:2:1, rt, overnight, 73% for 15a (two steps); 15% for 15b (two steps); 84% for 16a (two steps); 13% for 16b (two steps); 67% for 18a (two steps); 11% for
18b (two steps); (d) 1 M TBAF/HOAc 1:1, THF, reflux, overnight, 42% for 15a; 37% for 15b; (e) AllBr (2.0 equiv), K2CO3 (3.0 equiv), DMF, 55 ꢀC, 7 h, 84%; (f) Pd0(PPh3)4 (0.3 equiv), PPh3
(0.6 equiv), pyrrolidine (2.0 equiv), THF, rt, 4 h, 66% for 19a; 71% for 19b.

7390
C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
16a
18a
a
a
OTBDPS
OAll
O
O
O
O
O
O
O
O
O
20a
20b
OH
OH
b
6
b
6
OR
OR
O
O
O
O
O
O
O
O
O
O
O
21a R = TBPDS
22a R = H
21b R = All
22b R = H
c
d
e
e
O
O
BzO
BzO
BzO
BzO
OBz
OBz
OH
OH
OH
HO
OH
HO
O
O
O
O
O
O
O
23a
23b
O
O
HO
HO
HO
HO
OH
OH
-L-rhamnopyranosyl-(1/2)-a-L-arabinopyranosides 23a and 23b. Reagents and conditions: (a) PPTs (0.1 equiv), 2,2-DMP (10 equiv), acetone, rt,
Scheme 3. Synthesis of 3
b-O-a
overnight and 60% for 20a; 3.5 h and 74% for 20b; (b) TCA (1.5 equiv), BF3$OEt2 (0.7 equiv), 4 Å MS, CH2Cl2, ꢁ78 ꢀC, 1.5 h, 78% for 21a; 99% for 21b; (c) 1 M TBAF/HOAc 1:1, THF,
reflux, overnight, 72% for 22a; (d) Pd0(PPh3)4 (0.3 equiv), PPh3 (0.6 equiv), pyrrolidine (2.0 equiv), THF, rt, 4 h, 85% for 22b; (e) (i) TsOH$H2O (0.7 equiv), CH2Cl2/MeOH 1:2, rt,
overnight; (ii) NaOH (20 equiv), MeOH/THF/H2O 1:2:1, rt, 4.5 h, 84% for 23a (two steps); 61% for 23b (two steps).
(TsOH$H2O) in a dry CH2Cl2/MeOH 1:2 solution63 followed by re-
moval of the benzoyl groups (NaOH, MeOH/THF/H2O 1:2:1) in 84%
and 61% yields, respectively, over two steps. As expected, regarding
saponins 23a and 23b, the two anomeric proton signals on the 1H
deprotection reactions, which would increase the number of steps
of the synthesis.40,63 Therefore, as shown in Scheme 4, the acceptor
24 was coupled with the known donor 2,3,4,6-tetra-O-benzoyl-a-D-
glucopyranosyl trichloroacetimidate (5)27 under the promotion of
TMSOTf (0.1 equiv) in CH2Cl2 at low temperature (ꢁ10 ꢀC) to pro-
vide the desired protected 25 in 50% corrected yield along with the
unreacted 24 (15%). The regioselectivity of this reaction was clearly
proved by 2D NMR HMBC analyses, which showed a strong corre-
NMR spectra indicated the
nopyranosyl (
6.19 ppm, br s, H-100 for 23a;
H-100 for 23b) and arabinopyranosyl ( 4.94 ppm, d, J1,2 5.4 Hz, H-10
a
-anomeric configuration of the rham-
d
d
5.10 ppm, d, J1,2 1.1 Hz,
d
for 23a;
d
4.54 ppm, d, J1,2 4.6 Hz, H-10 for 23b) moieties, which
correspond to the natural 1,2-trans glycosidic linkage.64 Moreover,
the HMBC correlations between the proton H-100 of the rhamnose
lation between the proton H-1% of the glucopyranose (
d 5.12 ppm,
d, J1,2 7.9 Hz) and the carbon C-40 of the arabinose (
d
76.0 ppm). It is
moiety and the carbon C-20 of the arabinose (
d
76.4 ppm for 23a;
76.8 ppm for 23b) clearly proved the (1/2) intersugar linkage.
At this stage of the synthesis, we wished to prepare the natural
worth noting that the arabinose moiety of the protected saponin 25
adopted the unusual 1C4 chair conformation as revealed by the
small coupling constant of the proton H-10
(d 4.65 ppm, d, J1,2
d
betulinic acid saponin 3 starting from the fully protected derivative
21b. According to Scheme 4, the deisopropylidination was achieved
by treatment of 21b with TsOH$H2O (0.7 equiv) in a dry CH2Cl2/
MeOH 1:2 solution to afford 24 in 70% yield. Surprisingly, the 1H
NMR spectrum of 24 showed that, once the isopropylidene was
removed, the arabinopyranosyl moiety underwent a ring-flipping
to adopt preferentially the 1C4 chair conformation rather than the
usual 4C1 one.46 Indeed, the coupling constant of the proton H-10
was relatively small (J1,2 3.3 Hz) in comparison with 21b (J1,2 7.5 Hz).
Recently, this unusual 1C4 chair conformation was reported in the
3.8 Hz). Subsequent removal of the allyl and benzoyl groups of
protected derivative 25 using the above mentioned methodology
afforded the natural betulinic acid saponin 3 (60%, two steps) in
which the arabinose residue retrieved the typical 4C1 conformation
(d
4.79 ppm, d, J1,2 6.1 Hz, H-10). The overall yield for the synthesis
was 10% over eight linear steps from allyl betulinate (17). The
physical and analytical data (1H NMR, 13C NMR and [ 25) of 3 were
a]
D
all consistent with those reported for the natural product isolated
from the roots of P. koreana.31
The last step of our work was to incorporate a glucopyranosyl
moiety at the C-28 position of 22b with the aim of synthesizing the
natural betulinic acid saponin 4. As depicted in Scheme 5, the free
carboxylic acid derivative 22b was coupled with the known sugar
literature for saponins containing an a-L-arabinopyranose moiety
with a bulky group at the C-20.44–46,65 In the 1C4 conformation, the
40-OH is in the equatorial position while the 30-OH is in the axial
position. Since it is known that the equatorial hydroxyl groups are
more reactive than the axial ones,66 we planned to directly glyco-
sylate this position in order to avoid tedious protection–
donor 2,3,4,6-tetra-O-benzoyl-a-D
-glucopyranosyl bromide (7)52
under phase-transfer conditions67 using potassium carbonate
(K2CO3)and tetrabutylammoniumbromide(Bu4NBr)inaCH2Cl2/H2O

C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
7391
21b
not consistent with those reported for the natural product isolated
from the aerial part of S. rotundifolia.30 High-resolution electrospray
ionization mass spectra (HR-ESI-MS) and extensive 1D and 2D NMR
analyses (1H, 13C, DEPT-135, COSY, HSQC, HMBC, J-resolved, TOCSY,
NOESY) on a 700 MHz NMR equipped with a cryogenic probe further
proved that the structure of the synthetic saponin 4 was correct
(Fig. 3).
a
OAll
The 1H NMR spectra of saponin 4 showed that the coupling
O
constant of the proton H-10 (
d
4.53 ppm, d, J1,2 4.6 Hz) in the ara-
binopyranose moiety was not characteristic of the standard 4C1
conformation (
4.79 ppm, d, J1,2 6.1 Hz, H-10 for 3). This particu-
larity was also observed for saponins 23a and 23b bearing the same
O
HO
O
24
d
O
HO
b
5
O
disaccharide residue at the C-3 position (d 4.52 ppm, d, J1,2 4.6 Hz,
H-10 in MeOD). In the course of this work, regarding the prepara-
tion of the sugar donor 8, we found that using K2CO3 as a base
instead of DBU led to the preferential formation of the known
BzO
BzO
OBz
OAll
2,3,4-tri-O-benzoyl-
(27)44 (Table 1). The proton H-10 of 27 was visualized like a broad
singlet on the 1H NMR spectrum (
6.33 ppm) as already reported in
a-L
-arabinopyranosyl trichloroacetimidate-1C4
O
d
O
OBz
O
the literature for arabinose,44–46,52,65 xylose68,69 and fucose65
adopting this unusual 1C4 conformation. Hence, a J1,2 coupling
constant midway between 4C1 and 1C4 conformation suggested that
the arabinose residue in saponins 4, 23a and 23b were in a high
conformational mobility.70,71 It is worth noting that such a phe-
nomenon was recently observed for naturally occurring saponins
isolated from Stryphnodendron fissuratum having a terminal arabi-
nose moiety.72 In order to verify this hypothesis of conformational
mobility, we performed a 1H NMR analysis of saponin 4 in which
the temperature was increased from 0 to 100 ꢀC. As shown in
Figure 4, the coupling constant values of the proton H-10 decreased
(J1,2 5.9–4.1 Hz) with an increase of the temperature. In comparison,
the coupling constant values of the proton H-1% of the
HO
BzO
BzO
O
25
O
OBz
O
c
O
3
BzO
BzO
OBz
Scheme 4. Completion of the synthesis of natural betulinic acid saponin 3. Reagents
and conditions: (a) TsOH$H2O (0.7 equiv), CH2Cl2/MeOH 1:2, rt overnight, 70%; (b) TCA
(1.5 equiv), TMSOTf (0.1 equiv), 4 Å MS, CH2Cl2, ꢁ10 ꢀC to rt, 3 h, 50%; (c) (i) Pd0(PPh3)4
(0.3 equiv), PPh3 (0.6 equiv), pyrrolidine (2.0 equiv), rt, 4.5 h; (ii) NaOH (20 equiv),
MeOH/THF/H2O 1:2:1, rt, 6 h, 60% (two steps).
1:1 solution to give the fully protected derivative 26 (78%). Modifying
the reaction conditions such as using the TCA sugar donor 5 in con-
junction with TMSOTf or BF3$OEt2 as the promoter did not increase
the yield and led to a complex mixture of rearrangement products
(data not shown). As expected, the strong HMBC correlation between
OH
the proton H-1% of the glucopyranose (d 6.03 ppm, d, J1,2 9.7 Hz) and
HO
OH
OH
the carbon C-28 of the aglycone ( 174.1 ppm) revealed that the
d
28
O
O
O
1'''
reaction took place at the C-28 carboxylic acid position. The target
naturalbetulinicacidsaponin4wasfinallyobtainedaftertheremoval
of isopropylidene (TsOH$H2O, dry CH2Cl2/MeOH 1:2) and benzoyl
groups (NaOH, MeOH/THF/H2O 1:2:1) in an excellent 82% yield (two
steps). The overall yield for the synthesis was 27% over eight linear
steps from allyl betulinate (17). Surprisingly, it was found that the
OH
HO
3
O
O
O
1'
1''
O
HO
HO
physical and analytical data (1H NMR, 13C NMR and [
a]
25) of 4 were
OH
D
Figure 3. Selected key COSY (
) and HMBC (1H/13C) correlations of saponin 4.
▬
22b
a
7
Table 1
Synthesis of 2,3,4-tri-O-benzoyl-
and 1C4 (27)a
L
-arabinopyranosyl trichloroacetimidates 4C1 (8)
OBz
O
CCl3
NH
OBz
BzO
CCl3CN, base
O
OBz
BzO
O
12
NH
CCl3
O
+
O
CH2OBz
BzO
BzO
CH2Cl2
BzO
O
O
OBz
O
27
8
O
O
O
O
26
Entry
Base (equiv)
Yield (%)
O
b
8
27
BzO
1
2
3
4
DBU (0.5)
Cs2CO3 (0.2)
NaH (0.8)
80
79
42
20
d
11
42
66
BzO
OBz
4
Scheme 5. Completion of the synthesis of natural betulinic acid saponin 4. Reagents
and conditions: (a) sugar donor (1.5 equiv), K2CO3 (2.5 equiv), Bu4NBr (0.4 equiv),
CH2Cl2/H2O 1:1, reflux, 6 h, 78%; (b) (i) TsOH$H2O (0.7 equiv), CH2Cl2/MeOH 1:2, rt,
overnight; (ii) NaOH (20 equiv), MeOH/THF/H2O 1:2:1, rt, 4 h, 82% (two steps).
K2CO3 (1.0)
a
Reactions were performed overnight at room temperature with 8.0 equiv of
CCl3CN and 8 mL/mmol of CH2Cl2 at 0.22 mmol scale.

7392
C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
4. Experimental
4.1. General methods
Chemical reagents were purchased from Sigma–Aldrich Co.
Canada or Alfa Aesar Co. and were used as received. The usual
solvents were obtained from VWR International Co. and were used
as received. Air and water sensitive reactions were performed in
flame-dried glassware under argon atmosphere. Moisture sensitive
reagents were introduced via a dry syringe. Dichloromethane
(CH2Cl2) and acetone were distilled from anhydrous CaH2 under an
argon atmosphere. Tetrahydrofuran (THF) was distilled from so-
dium/benzophenone ketyl under an argon atmosphere. Methanol
(MeOH) was distilled from Mg and I2 under an argon atmosphere.
Analytical thin-layer chromatography was performed with silica gel
´
60 F254, 0.25 mm pre-coated TLC plates (Silicycle, Quebec, Canada).
Compounds were visualized using UV254 and cerium molybdate
(2 g Ce(SO4)4(NH4)4, 5 g MoO4(NH4)2, 200 mL H2O, 20 mL H2SO4)
with charring. Flash column chromatography was carried out using
60–230 mesh silica gel (Silicycle, Que´bec, Canada) or high perfor-
mance flash chromatography system (HPFC-Analogix F12-40)
equipped with a silica gel column (F12-M, 8 g). All of the chemical
yields generally represent the highest result obtained for three
independent experiments. Nuclear magnetic resonance (NMR)
spectra were recorded on a Bruker Avance spectrometer at
400 MHz (1H) and 100 MHz (13C), equipped with a 5 mm QNP
probe. Elucidations of chemical structures were based on 1H, 13C,
COSY, TOCSY, HMBC, HSQC, J-resolved, NOESY and DEPT-135 ex-
periments. Signals are reported as m (multiplet), s (singlet),
d (doublet), t (triplet), dd (doublet of doublet), dq (doublet of
quadruplet), ddd (doublet of doublet of doublet), ddt (doublet of
doublet of triplet), br s (broad singlet) and coupling constants are
reported in hertz (Hz). The chemical shifts are reported in parts per
Figure 4. Temperature dependence of the H-10 anomeric signal of the arabinopyr-
anosyl moiety of saponin 4 suggesting its high conformational mobility (1H NMR
500 MHz, C5D5N).
million (d) relative to residual solvent peak or TMS. The labile OH
NMR signals appearing sometimes were not listed. Optical rota-
tions were obtained using sodium D line at ambient temperature
on a Rudolph Research Analytical Autopol IV automatic polarime-
ter. High-resolution electrospray ionization mass spectra (HR-ESI-
MS) and high field NMR analyses (500 and 700 MHz) were obtained
glucopyranose moiety were quite similar over the tested temper-
ature range (J1,2 8.2–8.0 Hz). With regards to the saponin 4, these 1H
NMR data suggested that the equilibrium between the 4C1 and 1C4
conformations of the arabinopyranose moiety tend to shift towards
the 1C4 conformation if the temperature is raised and vice versa.
´
´
´
at the Department of Chemistry, Universite de Montreal, Quebec,
Canada.
4.2. 2,3,4-Tri-O-benzoyl-
trichloroacetimidate (8) and 2,3,5-tri-O-benzoyl-
-arabinofuranosyl trichloroacetimidate (9)
b-L-arabinopyranosyl
3. Conclusion
a-L
In summary, this is the first report of the synthesis of naturally
To a cooled solution (ice/water bath) of L-arabinose (10.0 g,
occurring lupane-type saponins bearing an
(1/2)- -arabinopyranose sugar moiety. In this work, betulinic
acid -O- -rhamnopyranosyl-(1/2)-[ -glucopyranosyl-(1/
4)]- -arabinopyranoside (3) and 28-O- -glucopyranosyl betu-
linic acid -O- -rhamnopyranosyl-(1/2)- -arabinopyrano-
a
-
L
-rhamnopyranosyl-
66.6 mmol) in anhydrous pyridine (140 mL) with DMAP (81 mg,
0.67 mmol) as catalyst was slowly added BzCl (46 mL, 400 mmol)
over 30 min. The mixture was stirred overnight at 60 ꢀC and then
quenched with MeOH (20 mL). Then, the solvents were evaporated
under reduced pressure to afford a yellow oily residue, which was
taken up in EtOAc, washed with 10% HCl (4ꢂ), saturated NaHCO3
solution and brine. The solvents of the dried solution (MgSO4) were
evaporated under reduced pressure to give a residue, which was
used immediately for the next reaction without further purifica-
tion. To a solution of the crude benzoylated arabinose derivative
(32.5 g, 57.4 mmol) in anhydrous CH2Cl2 (168 mL) was added HBr/
HOAc (40.2 mL, 33%) under an argon atmosphere. The mixture was
stirred at room temperature for 2 h, then washed with saturated
NaHCO3 solution (3ꢂ) and brine. The solvents of the dried solution
(MgSO4) were evaporated under reduced pressure and the result-
ing residue was taken up in acetone (264 mL) and water (10.3 mL).
Ag2CO3 (21.4 g, 77.4 mmol) was added portionwise and the hy-
drolysis was performed for 1 h at room temperature with constant
stirring. The mixture was subsequently filtered through a bed of
a-L
b
3
a
-
L
b-D
b-D
a
-
L
3
b
a
-L
a-L
side (4) were synthesized using a stepwise glycosidation approach
in 10% and 27% yields, respectively, over eight linear steps starting
from allyl betulinate (17). It is noteworthy that the arabinose
moiety of saponin 4 was in a high conformational mobility between
4C1 and 1C4 chair conformations as reflected by the unusual
anomeric coupling constant of the proton H-10. These results open
the way for concise and efficient syntheses of a wide range of
betulinic acid saponin analogues as pharmaceutical and/or bi-
ological agents that can be of further interest in the elaboration of
meaningful SAR studies. Work is currently in progress in our lab-
oratory in order to evaluate the in vitro haemolytic, anticancer and
anti-inflammatory activities of these natural saponins (3, 4) and
their analogues (15a, 15b, 19a, 19b, 23a, 23b) and results will be
reported in due course.

C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
7393
CeliteÒ and the solvents of the dried solution (MgSO4) were evap-
4.5. 2,3,4-Tri-O-benzoyl-
trichloroacetimidate-4C1 (8) and 2,3,4-tri-O-benzoyl-
-arabinopyranosyl trichloroacetimidate-1C4 (27)
b-L-arabinopyranosyl
orated under reduced pressure. The resulting crude residue was
dissolved in wet CH2Cl2 (459 mL), then DBU (4.3 mL, 29 mmol) and
CCl3CN (46.0 mL, 459 mmol) were added sequentially. The mixture
was stirred for 4 days at room temperature and the solvents were
evaporated under reduced pressure to give a dark red oily residue,
which was purified by flash chromatography (isocratic hexanes/
EtOAc 9:1) to afford an inseparable mixture of 8 and 9 (15 g, 38%,
four steps) as a white crystalline powder in a 5:1 ratio as confirmed
by NMR. Rf 0.67 (hexanes/EtOAc 3:1). 1H and 13C NMR spectral data
of 844 and 955 in the mixture were in agreement with those pub-
lished in the literature.
a-L
To a solution of 12 (100 mg, 0.216 mmol) in wet CH2Cl2 (1.7 mL)
was added DBU (16 L, 0.108 mmol) followed by CCl3CN (173 L,
m
m
459 mmol). The mixture was stirred for 45 min at room tempera-
ture, then the solvents were evaporated under reduced pressure to
give a dark red oily residue, which was purified by flash chroma-
tography (hexanes/EtOAc 9:1 to 4:1) to furnish 8 (105 mg, 80%) as
a white foam. If the reaction was performed overnight using K2CO3
(30 mg, 0.22 mmol) as a base instead of DBU, the TCA 27 (87 mg,
66%) was obtained as the major product (white amorphous pow-
der) along with 8 (26 mg, 20%).
4.3. 1,2,3,4-Tetra-O-benzoyl-
b-L-arabinopyranose (10) and
1,2,3,5-tetra-O-benzoyl- -arabinofuranose (11)
a-L
4.5.1. Compound 8
25
To a cooled solution (ice/water bath) of
L-arabinose (1.00 g,
Rf 0.67 (hexanes/EtOAc 3:1); [
a
]
þ229.2 (c 0.1, CHCl3). 1H and
D
6.66 mmol) in anhydrous pyridine (15.3 mL) with DMAP (8 mg,
0.07 mmol) as catalyst was slowly added BzCl (5.0 mL, 43 mmol)
over 30 min. The mixture was stirred overnight at room tempera-
ture and then quenched with MeOH (2 mL) while keeping the
temperature at 0 ꢀC. Then, the solvents were evaporated under
reduced pressure to afford a yellow oily residue, which was taken
up in EtOAc, washed with 10% HCl (4ꢂ), saturated NaHCO3 solution
and brine. The solvents of the dried solution (MgSO4) were evap-
orated under reduced pressure to give a residue, which was puri-
fied by flash chromatography (hexanes/EtOAc 9:1 to 7:3) to furnish
10 (3.44 g, 91%) as a white foam along with 11 (43 mg, 1%) as
a colourless solid.
13C NMR spectral data of 844 were in agreement with those pub-
lished in the literature. HR-ESI-MS m/z 628.0298 [MþNa]þ (calcd
for C28H22Cl3NO8Na: 628.0303).
4.5.2. Compound 27
þ94.0 (c 0.1, CHCl3). 1H and 13
C
25
Rf 0.37 (hexanes/EtOAc 3:1); [
a]
D
NMR spectral data of 2744 were in agreement with those published
in the literature. HR-ESI-MS m/z 628.0296 [MþNa]þ (calcd for
C28H22Cl3NO8Na: 628.0303).
4.6. 28-O-tert-Butyldiphenylsilyl betulin (13)
To a cooled (ice/water bath) solution of 1 (2.00 g, 4.52 mmol),
imidazole (769 mg, 11.3 mmol) and DMAP (55 mg, 0.45 mmol) in
anhydrous THF (13.2 mL) was added dropwise TBDPSCl (1.8 mL,
6.8 mmol) under an argon atmosphere. The mixture was refluxed
overnight or until TLC (hexanes/EtOAc 4:1) showed the disap-
pearance of the initial product. Then, the solvents were evaporated
under reduced pressure to give a residue, which was purified by
flash chromatography (hexanes/Et2O 19:1 to 4:1) to furnish 13
4.3.1. Compound 10
25
Rf 0.50 (hexanes/EtOAc 3:1); [
a
]
þ291.2 (c 0.1, CHCl3). 1H NMR
D
(CDCl3, 400 MHz)
d
: 8.17–7.27 (m, 20H, H–Ar), 6.87 (br s, 1H, H-1),
6.07 (s, 2H, H-2, H-3), 5.90 (s, 1H, H-4), 4.41 (d, J¼13.1 Hz, 1H, H-5),
4.19 (dd, J¼13.4, 1.8 Hz, 1H, H-5). 13C NMR (CDCl3, 100 MHz)
d:
165.8–164.7 (4ꢂCO), 133.8–128.4 (C–Ar), 91.1 (C-1), 69.5 (C-4), 68.2
(C-3), 67.8 (C-2), 65.0 (C-5). HR-ESI-MS m/z 589.1464 [MþNa]þ
(calcd for C33H26O9Na: 589.1469).
(2.762 g, 90%) as a white crystalline powder. Rf 0.59 (hexanes/EtOAc
25
3:1); [
a]
ꢁ11.2 (c 1.0, CHCl3). 1H NMR (CDCl3, 400 MHz)
d: 7.68–
D
4.3.2. Compound 11
7.39 (m, 10H, H–Ar), 4.59 (br s, 1H, H-29), 4.52 (br s, 1H, H-29), 3.68
(d, J¼9.8 Hz,1H, H-28), 3.32 (d, J¼9.8 Hz,1H, H-28), 3.16 (dd, J¼10.9,
4.4 Hz, 1H, H-3), 2.26 (td, J¼10.6, 5.6 Hz, 1H, H-19), 2.17–2.09 (m,
2H), 1.64 (s, 3H, H-30), 1.61–1.10 (m, 15H), 1.06 (s, 9H, C(CH3)3), 0.96
(s, 3H, H-23), 0.93 (s, 3H, H-27), 0.76 (s, 3H, H-25), 0.75 (s, 3H, H-
24), 0.70 (s, 3H, H-26), 0.64 (d, J¼8.8 Hz, 1H, H-5). 13C NMR (CDCl3,
25
Rf 0.58 (hexanes/EtOAc 3:1); [
(CDCl3, 400 MHz)
a
]
ꢁ12.8 (c 0.1, CHCl3). 1H NMR
D
d: 8.17–7.27 (m, 20H, H–Ar), 6.77 (br s, 1H, H-1),
5.82 (d, J¼0.6 Hz, 1H, H-2), 5.68 (dt, J¼3.5, 0.9 Hz, 1H, H-3), 4.84 (m,
2H, H-4, H-5), 4.74 (dd, J¼12.7, 6.5 Hz, 1H, H-5). 13C NMR (CDCl3,
100 MHz)
d
: 166.2–164.6 (4ꢂCO), 133.8–128.3 (C–Ar), 99.8 (C-1),
83.9 (C-4), 80.9 (C-2), 77.5 (C-3), 63.7 (C-5). HR-ESI-MS m/z
589.1466 [MþNa]þ (calcd for C33H26O9Na: 589.1469).
100 MHz) d: 150.8 (C-20), 135.7–127.6 (C–Ar), 109.4 (C-29), 78.9 (C-
3), 61.0 (C-28), 55.2 (C-5), 50.3 (C-9), 48.4 (C-18), 48.4 (C-17), 47.8
(C-19), 42.6 (C-14), 40.7 (C-8), 38.8 (C-4), 38.6 (C-1), 37.2 (C-13), 37.1
(C-10), 34.5 (C-22), 34.1 (C-7), 29.8 (C-21), 29.5 (C-16), 28.0 (C-23),
27.4 (C-2), 27.0 (C-15), 26.9 (C(CH3)3), 25.1 (C-12), 20.7 (C-11), 19.4
(C(CH3)3),19.1 (C-30),18.3 (C-6),16.1 (C-25),15.7 (C-26),15.4 (C-24),
14.7 (C-27). HR-ESI-MS m/z 703.4906 [MþNa]þ (calcd for
4.4. 2,3,4-Tri-O-benzoyl-a,b-L-arabinopyranose (12)
To a solution of 10 (3.00 g, 5.30 mmol) in anhydrous CH2Cl2
(12.7 mL) was added HBr/HOAc (2.9 mL, 33%) under an argon at-
mosphere. The mixture was stirred at room temperature for 2 h,
then washed with saturated NaHCO3 solution (3ꢂ) and brine. The
solvents of the dried solution (MgSO4) were evaporated under re-
duced pressure and the resulting residue was taken up in acetone
(24.4 mL) and water (1.0 mL). Ag2CO3 (1.97 g, 7.15 mmol) was
added portionwise and the hydrolysis was performed for 1 h at
room temperature with constant stirring. The mixture was sub-
sequently filtered through a bed of CeliteÒ and the solvents of the
dried solution (MgSO4) were evaporated under reduced pressure.
The resulting oily residue was purified by flash chromatography
(hexanes/EtOAc 4:1 to 3:2) to afford 12 (1.78 g, 73%, two steps) as
C46H68O2SiNa: 703.4881).
4.7. 28-O-tert-Butyldiphenylsilyl betulin 3
pyranoside (16a) and 28-O-tert-butyldiphenylsilyl
betulin 3 -O- -arabinofuranoside (16b)
b-O-a-L-arabino-
b
a-L
The acceptor 13 (1.400 g, 2.055 mmol) and a mixture of donors 8
and 9 (1.871 g, 3.082 mmol, ratio 5:1) were stirred in anhydrous
CH2Cl2 (41.0 mL) with 4 Å MS under an argon atmosphere for
60 min. Then, the promoter TMSOTf (37 mL, 0.20 mmol) was
injected in the medium via a dry syringe at room temperature while
keeping rigorous anhydrous conditions. The reaction mixture was
stirred for 2 h at room temperature and quenched by addition of
Et3N (1.15 mL, 8.22 mmol). The solvents were evaporated under
a white crystalline powder. Rf 0.24 and 0.14 (hexanes/EtOAc 3:1);
25
[
a]
þ291.4 (c 0.1, CHCl3). HR-ESI-MS m/z 485.1206 [MþNa]þ (calcd
D
for C26H22O8Na: 485.1207).

7394
C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
reduced pressure and the resulting residue was immediately dis-
solved in a solution of MeOH/THF/H2O 1:2:1 (140 mL) to which was
added NaOH (1.65 g, 41.1 mmol). The reaction mixture was stirred
overnight at room temperature or until TLC (hexanes/EtOAc 2:3)
showed the complete disappearance of the benzoylated products
and then acidified to pHz4 with 10% aqueous HCl. The solvents
were evaporated under reduced pressure to give a solid residue,
which was purified by flash chromatography (hexanes/EtOAc 2:3 to
100% EtOAc, then CH2Cl2/MeOH 9:1) to afford 16a (1.404 g, 84%,
two steps) and 16b (225 mg, 13%, two steps) as white crystalline
powders.
in agreement with those published in the literature. HR-ESI-MS m/z
497.3985 [MþH]þ (calcd for C33H53O3: 497.3995).
4.9. Allyl betulinate 3 -O-
b
a-L-arabinopyranoside (18a) and
allyl betulinate 3 -O-a-L-arabinofuranoside (18b)
b
These compounds were prepared from the acceptor 17 (1.250 g,
2.516 mmol) and a mixture of donors 8 and 9 (2.290 g, 3.774 mmol,
ratio 5:1) in the same manner as that described for compounds 16a
and 16b. Purification by flash chromatography (hexanes/EtOAc 2:3
to 100% EtOAc) gave 18a (1.065 g, 67%, two steps) as a white crys-
talline powder and 18b (176 mg, 11%, two steps) as a white amor-
phous powder.
4.7.1. Compound 16a
25
Rf 0.62 (CH2Cl2/MeOH 9:1); [
(CDCl3, 400 MHz)
a]
ꢁ10.2 (c 0.5, CHCl3). 1H NMR
D
d: 7.74–7.34 (m, 10H, H–Ar), 4.59 (br s, 1H, H-29),
4.9.1. Compound 18a
25
4.52 (br s, 1H, H-29), 4.26 (d, J¼5.6 Hz, 1H, H-10), 3.90 (m, 1H, H-40),
3.88 (m, 1H, H-50), 3.74 (m, 1H, H-20), 3.68 (m, 1H, H-28), 3.63 (m,
1H, H-30), 3.46 (m, 1H, H-50), 3.32 (d, J¼9.2 Hz, 1H, H-28), 3.07 (m,
1H, H-3), 2.26 (m, 1H, H-19), 2.19–2.08 (m, 2H), 1.90–1.72 (m, 2H),
1.64 (s, 3H, H-30), 1.62–1.11 (m, 13H), 1.05 (s, 9H, C(CH3)3), 0.95 (s,
3H, H-23), 0.91 (s, 3H, H-27), 0.76 (s, 3H, H-24), 0.74 (s, 3H, H-25),
0.70 (s, 3H, H-26), 0.63 (d, J¼7.4 Hz, 1H, H-5). 13C NMR (CDCl3,
Rf 0.54 (CH2Cl2/MeOH 9:1); [
1H NMR (CDCl3, 400 MHz)
Allyl), 5.34 (dq, J¼17.2, 1.1 Hz, 1H, H-3Allyl), 5.23 (dq, J¼10.3, 1.1 Hz,
a]
þ4.0 (c 0.5, CHCl3/MeOH 1:1).
D
d
: 5.93 (ddt, J¼17.2, 10.5, 5.7 Hz, 1H, H-
2
1H, H-3Allyl), 4.74 (d, J¼1.4 Hz, 1H, H-29), 4.60 (m, 1H, H-29), 4.59
(m, 2H, H-1Allyl), 4.27 (d, J¼6.5 Hz, 1H, H-10), 3.92 (m, 1H, H-40), 3.90
(m, 1H, H-50), 3.75 (t, J¼8.1 Hz, 1H, H-20), 3.65 (dd, J¼8.4, 2.1 Hz, 1H,
H-30), 3.48 (d, J¼11.3, 1H, H-50), 3.09 (dd, J¼11.3, 4.1 Hz, 1H, H-3),
3.02 (td, J¼11.1, 4.9 Hz, 1H, H-19), 2.31–2.17 (m, 2H), 1.96–1.74 (m,
3H),1.69 (s, 3H, H-30),1.66–0.99 (m,16H), 0.96 (s, 3H, H-23), 0.95 (s,
3H, H-27), 0.89 (s, 3H, H-26), 0.80 (s, 3H, H-25), 0.77 (s, 3H, H-24),
100 MHz) d: 150.7 (C-20), 135.6–127.6 (C–Ar), 109.4 (C-29), 105.2
(C-10), 89.6 (C-3), 72.9 (C-30), 71.4 (C-20), 67.9 (C-40), 65.0 (C-50), 61.0
(C-28), 55.5 (C-5), 50.2 (C-9), 48.4 (C-18), 48.4 (C-17), 47.8 (C-19),
42.5 (C-14), 40.7 (C-8), 39.1 (C-4), 38.7 (C-1), 37.1 (C-13), 36.7 (C-
10), 34.4 (C-22), 34.1 (C-7), 29.8 (C-21), 29.5 (C-16), 27.9 (C-23), 27.0
(C-15), 26.9 (C(CH3)3), 26.0 (C-2), 25.1 (C-12), 20.7 (C-11), 19.3
(C(CH3)3),19.1 (C-30),18.1 (C-6),16.4 (C-24),16.0 (C-25),15.7 (C-26),
14.6 (C-27). HR-ESI-MS m/z 835.5292 [MþNa]þ (calcd for
0.66 (d, J¼9.7 Hz, 1H, H-5). 13C NMR (CDCl3, 100 MHz)
d: 175.7 (C-
28), 150.5 (C-20), 132.5 (C-2Allyl), 118.1 (C-3Allyl), 109.6 (C-29), 105.2
(C-10), 89.7 (C-3), 72.8 (C-30), 71.4 (C-20), 67.8 (C-40), 65.0 (C-50), 64.6
(C-1Allyl), 56.5 (C-17), 55.6 (C-5), 50.5 (C-9), 49.4 (C-18), 46.9 (C-19),
42.3 (C-14), 40.7 (C-8), 39.1 (C-4), 38.7 (C-1), 38.2 (C-13), 37.0 (C-
22), 36.8 (C-10), 34.3 (C-7), 32.1 (C-16), 30.6 (C-21), 29.6 (C-15), 27.9
(C-23), 26.0 (C-2), 25.5 (C-12), 20.8 (C-11), 19.4 (C-30), 18.1 (C-6),
16.4 (C-24), 16.1 (C-25), 15.9 (C-26), 14.6 (C-27). HR-ESI-MS m/z
651.4221 [MþNa]þ (calcd for C38H60O7Na: 651.4231).
C
51H76O6SiNa: 835.5303).
4.7.2. Compound 16b
Rf 0.69 (CH2Cl2/MeOH 9:1); [
(CDCl3, 400 MHz) d
: 7.72–7.35 (m, 10H, H–Ar), 5.10 (br s, 1H, H-10),
25
a
]
ꢁ41.5 (c 0.5, CHCl3). 1H NMR
D
4.59 (d, J¼2.0 Hz, 1H, H-29), 4.52 (br s, 1H, H-29), 4.19 (m, 1H, H-40),
4.03 (br s, 1H, H-30), 3.99 (br s, 1H, H-20), 3.89 (dd, J¼11.7, 2.2 Hz, 1H,
H-50), 3.83 (dd, J¼11.7, 1.4 Hz, 1H, H-50), 3.68 (d, J¼9.9 Hz, 1H, H-28),
3.32 (d, J¼9.9 Hz, 1H, H-28), 3.10 (dd, J¼11.8, 4.8 Hz, 1H, H-3), 2.27
(td, J¼10.7, 5.4 Hz, 1H, H-19), 2.17–2.09 (m, 2H), 1.89–1.75 (m, 2H),
1.65 (s, 3H, H-30), 1.63–1.10 (m, 13H), 1.06 (s, 9H, C(CH3)3), 0.93 (s,
3H, H-27), 0.92 (s, 3H, H-23), 0.75 (s, 3H, H-25), 0.72 (s, 3H, H-24),
4.9.2. Compound 18b
25
Rf 0.59 (CH2Cl2/MeOH 9:1); [
a
]
ꢁ44.4 (c 0.5, CHCl3/MeOH 1:1).
D
1H NMR (CDCl3/CD3OD 1:1, 400 MHz)
d
: 5.94 (ddt, J¼16.7, 11.1,
5.6 Hz, 1H, H-2Allyl), 5.35 (d, J¼17.2 Hz, 1H, H-3Allyl), 5.25 (d, J¼10.5,
1H, H-3Allyl), 4.99 (br s, 1H, H-10), 4.73 (br s, 1H, H-29), 4.60 (m, 1H,
H-29), 4.59 (m, 2H, H-1Allyl), 4.04 (q, J¼4.0 Hz, 1H, H-40), 4.00 (m,
1H, H-20), 3.89 (m, 1H, H-30), 3.77 (dd, J¼11.9, 2.5 Hz, 1H, H-50), 3.68
(dd, J¼11.4, 3.7 Hz, 1H, H-50), 3.09 (dd, J¼11.6, 4.3 Hz, 1H, H-3), 3.00
(td, J¼11.3, 5.4 Hz, 1H, H-19), 2.32–2.17 (m, 2H), 1.96–1.76 (m, 3H),
1.70 (s, 3H, H-30), 1.67–1.00 (m, 16H), 0.99 (s, 3H, H-27), 0.95 (s, 3H,
H-23), 0.92 (s, 3H, H-26), 0.84 (s, 3H, H-25), 0.76 (s, 3H, H-24), 0.72
0.69 (s, 3H, H-26). 13C NMR (CDCl3, 100 MHz)
d: 150.9 (C-20), 135.7–
127.6 (C–Ar), 110.4 (C-10), 109.4 (C-29), 87.9 (C-3), 87.2 (C-40), 78.2
(C-20), 78.1 (C-30), 62.0 (C-50), 61.0 (C-28), 55.4 (C-5), 50.2 (C-9), 48.4
(C-18), 48.4 (C-17), 47.8 (C-19), 42.6 (C-14), 40.7 (C-8), 38.8 (C-4),
38.5 (C-1), 37.2 (C-13), 36.8 (C-10), 34.5 (C-22), 34.1 (C-7), 29.8 (C-
21), 29.5 (C-16), 28.0 (C-23), 27.0 (C-15), 26.9 (C(CH3)3), 25.9 (C-2),
25.1 (C-12), 20.7 (C-11), 19.4 (C(CH3)3), 19.1 (C-30), 18.2 (C-6), 16.1
(C-24), 16.0 (C-25), 15.7 (C-26), 14.7 (C-27). HR-ESI-MS m/z
835.5283 [MþNa]þ (calcd for C51H76O6SiNa: 835.5303).
(d, J¼9.5 Hz, 1H, H-5). 13C NMR (CDCl3/CD3OD 1:1, 100 MHz)
d:
176.6 (C-28), 150.7 (C-20), 132.8 (C-2Allyl), 118.4 (C-3Allyl), 110.7 (C-
10), 109.9 (C-29), 88.1 (C-3), 85.0 (C-40), 81.4 (C-20), 77.8 (C-30), 65.1
(C-1Allyl), 62.0 (C-50), 57.1 (C-17), 56.0 (C-5), 51.0 (C-9), 49.8 (C-18),
47.5 (C-19), 42.8 (C-14), 41.1 (C-8), 39.3 (C-4), 39.1 (C-1), 38.7 (C-13),
37.3 (C-22), 37.3 (C-10), 34.7 (C-7), 32.5 (C-16), 30.9 (C-21), 30.0 (C-
15), 28.1 (C-23), 26.2 (C-2), 25.9 (C-12), 21.3 (C-11), 19.4 (C-30), 18.6
(C-6), 16.4 (C-25), 16.4 (C-24), 16.2 (C-26), 14.9 (C-27). HR-ESI-MS
m/z 651.4222 [MþNa]þ (calcd for C38H60O7Na: 651.4231).
4.8. Allyl betulinate (17)
Allyl bromide (0.19 mL, 2.2 mmol) and K2CO3 (454 mg,
3.28 mmol) were added to a solution of 2 (501 mg, 1.10 mmol) in
DMF (7 mL). The reaction mixture was stirred for 7 h at 55 ꢀC. After
cooling, EtOAc was added and the organic layer was washed with
1 N HCl. The aqueous layer was extracted with EtOAc (3ꢂ) and the
combined organic layers were washed with saturated NaHCO3 and
brine. After the solution was dried (MgSO4), the solvents were
evaporated under reduced pressure. The resulting residue was
purified by flash chromatography (100% CH2Cl2) to give 8 as a white
4.10. Betulin 3
b-O-a-L-arabinopyranoside (15a) and betulin
3b
-O- -arabinofuranoside (15b)
a-L
These compounds were prepared from the acceptor 14 (150 mg,
0.309 mmol) and a mixture of donors 8 and 9 (282 mg, 0.464 mmol,
ratio 5:1) in the same manner as that described for compounds 16a
and 16b. Purification by C-18 reversed phase flash chromatography
(MeOH/H2O 4:1 to 100% MeOH) gave pure 15a (139 mg, 73%, two
steps) as a white amorphous powder and pure 15b (26 mg, 15%, two
steps) as a white crystalline powder.
crystalline powder (458 mg, 84%). Rf 0.58 (CH2Cl2/MeOH 99:1);
20
[
a]
þ3.9 (c 1.00, CHCl3). 1H and 13C NMR spectral data of 1727 were
D

C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
7395
4.10.1. Compound 15a
4.12. Betulinic acid 3b-O-a-L-arabinofuranoside (19b)
25
Rf 0.47 (CH2Cl2/MeOH 9:1); [
a
]
þ12.4 (c 0.4, CHCl3/MeOH 1:1).
D
1H NMR (CDCl3/CD3OD 1:1, 400 MHz)
d
: 4.68 (d, J¼1.6 Hz,1H, H-29),
This compound was prepared from 18b (75 mg, 0.119 mmol) in
the same manner as that described for compound 19a. Purification
by flash chromatography (100% CH2Cl2 to CH2Cl2/MeOH 47:3) gave
4.57 (br s, 1H, H-29), 4.33 (d, J¼6.1 Hz, 1H, H-10), 3.87 (m, 1H, H-50),
3.86 (m, 1H, H-40), 3.75 (d, J¼11.0 Hz, 1H, H-20), 3.64 (dd, J¼8.3,
6.2 Hz,1H, H-28), 3.57 (dd, J¼8.3, 2.9 Hz,1H, H-30), 3.53 (m,1H, H-50),
3.28 (d, J¼11.0 Hz, 1H, H-28), 3.14 (dd, J¼11.4, 4.5 Hz, 1H, H-3), 2.41
(td, J¼10.6, 5.7 Hz, 1H, H-19), 2.01–1.71 (m, 5H), 1.69 (s, 3H, H-30),
1.68–1.07 (m, 14H), 1.05 (s, 3H, H-26), 1.02 (s, 3H, H-23), 0.99 (s, 3H,
H-27), 0.85 (s, 3H, H-25), 0.82 (s, 3H, H-24), 0.74 (d, J¼12.2 Hz, 1H,
pure 19b (50 mg, 71%) as a white amorphous powder. Rf 0.54
25
(CH2Cl2/MeOH 9:1); [
a]
ꢁ41.9 (c 0.2, CHCl3/MeOH 1:1). 1H NMR
D
(CDCl3/CD3OD 1:1, 400 MHz) d
: 4.99 (br s, 1H, H-10), 4.72 (m, 1H,
H-29), 4.59 (br s, 1H, H-29), 4.04 (m, 1H, H-40), 4.01 (dd, J¼3.0,
1.6 Hz, 1H, H-20), 3.88 (dd, J¼5.1, 3.2 Hz, 1H, H-30), 3.77 (dd, J¼11.9,
3.2 Hz, 1H, H-50), 3.68 (dd, J¼11.9, 4.1 Hz, 1H, H-50), 3.09 (dd, J¼11.8,
4.8 Hz, 1H, H-3), 3.02 (td, J¼11.0, 4.8 Hz, 1H, H-19), 2.31–2.22 (m,
2H), 2.01–1.89 (m, 2H), 1.81 (m, 1H, H-2), 1.70 (s, 3H, H-30), 1.68–
1.01 (m, 16H), 0.99 (s, 3H, H-27), 0.96 (s, 3H, H-23), 0.95 (s, 3H,
H-26), 0.85 (s, 3H, H-25), 0.77 (s, 3H, H-24), 0.73 (d, J¼10.2 Hz, 1H,
H-5). 13C NMR (CDCl3/CD3OD 1:1, 100 MHz)
d: 151.1 (C-20), 109.9
(C-29),105.9 (C-10), 90.2(C-3), 73.3 (C-30), 71.8(C-20), 68.1 (C-40), 65.1
(C-50), 60.0 (C-28), 56.2 (C-5), 51.0 (C-9), 49.3 (C-18), 48.4 (C-19), 48.2
(C-17), 43.2 (C-14), 41.5 (C-8), 39.7 (C-4), 39.3 (C-1), 37.9 (C-13), 37.4
(C-10), 34.7 (C-7), 34.5 (C-22), 30.2 (C-21), 29.7 (C-16), 28.1 (C-23),
27.5 (C-15), 26.5 (C-2), 26.1 (C-12), 21.4 (C-11),19.3 (C-30),18.7 (C-6),
16.5 (C-24), 16.5 (C-25), 16.2 (C-26), 15.0 (C-27). HR-ESI-MS m/z
597.4114 [MþNa]þ (calcd for C35H58O6Na: 597.4126).
H-5). 13C NMR (CDCl3/CD3OD 1:1, 100 MHz)
d: 179.6 (C-28), 151.2
(C-20), 110.9 (C-10), 109.9 (C-29), 88.3 (C-3), 85.1 (C-40), 81.7 (C-20),
78.0 (C-30), 62.2 (C-50), 56.8 (C-17), 56.2 (C-5), 51.2 (C-9), 49.8 (C-
18), 47.6 (C-19), 43.0 (C-14), 41.3 (C-8), 39.5 (C-4), 39.3 (C-1), 38.9
(C-13), 37.6 (C-22), 37.5 (C-10), 34.9 (C-7), 32.8 (C-16), 31.1 (C-21),
30.2 (C-15), 28.2 (C-23), 26.4 (C-2), 26.1 (C-12), 21.5 (C-11), 19.5 (C-
30), 18.8 (C-6), 16.5 (C-25), 16.5 (C-24), 16.3 (C-26), 15.0 (C-27). HR-
ESI-MS m/z 611.3898 [MþNa]þ (calcd for C35H58O7Na: 611.3918).
4.10.2. Compound 15b
25
Rf 0.57 (CH2Cl2/MeOH 9:1); [
a
]
ꢁ32.2 (c 0.1, CHCl3/MeOH 1:1).
D
1H NMR (CDCl3, 400 MHz)
d
: 5.11 (br s, 1H, H-10), 4.68 (d, J¼1.8 Hz,
1H, H-29), 4.58 (br s, 1H, H-29), 4.20 (d, J¼1.2 Hz, 1H, H-40), 4.04 (s,
1H, H-30), 4.01 (br s, 1H, H-20), 3.89 (dd, J¼11.8, 2.2 Hz, 1H, H-50),
3.84 (dd, J¼11.8, 1.4 Hz, 1H, H-50), 3.81 (d, J¼10.8 Hz, 1H, H-28), 3.34
(d, J¼10.8 Hz, 1H, H-28), 3.12 (dd, J¼11.5, 4.4 Hz, 1H, H-3), 2.39 (td,
J¼10.5, 5.7 Hz, 1H, H-19), 2.03–1.71 (m, 4H), 1.69 (s, 3H, H-30), 1.68–
1.02 (m, 17H), 1.01 (s, 3H, H-26), 0.98 (s, 3H, H-27), 0.93 (s, 3H, H-
23), 0.82 (s, 3H, H-25), 0.73 (s, 3H, H-24). 13C NMR (CDCl3, 100 MHz)
4.13. 28-O-tert-Butyldiphenylsilyl betulin 3
b-O-3,4-O-
isopropylidene- -arabinopyranoside (20a)
a-L
To
a cooled (ice/water bath) solution of 16a (1.000 g,
1.230 mmol) in anhydrous acetone (14.7 mL) were added PPTs
(31 mg, 0.122 mmol) and 2,2-dimethoxypropane (1.52 mL,
12.3 mmol) under an argon atmosphere. The reaction mixture was
stirred overnight at room temperature or until TLC (hexanes/EtOAc
7:3) showed the disappearance of the initial product. Then, the
solvents were evaporated under reduced pressure and the resulting
residue was taken up in CH2Cl2 and washed with saturated NaHCO3
solution and brine. The organic solvents of the dried solution
(MgSO4) were evaporated under reduced pressure to give a residue,
which was purified by flash chromatography (hexanes/EtOAc 9:1 to
d
: 150.5 (C-20), 110.4 (C-10), 109.7 (C-29), 87.9 (C-3), 87.3 (C-40), 78.2
(C-20), 78.1 (C-30), 62.0 (C-50), 60.5 (C-28), 55.4 (C-5), 50.3 (C-9),
48.7 (C-18), 47.8 (C-19), 47.7 (C-17), 42.7 (C-14), 40.9 (C-8), 38.9 (C-
4), 38.6 (C-1), 37.3 (C-13), 36.8 (C-10), 34.1 (C-22), 33.9 (C-7), 29.7
(C-16), 29.1 (C-21), 28.0 (C-23), 27.0 (C-15), 25.9 (C-2), 25.1 (C-12),
20.8 (C-11), 19.1 (C-30), 18.2 (C-6), 16.1 (C-24), 16.1 (C-25), 15.9 (C-
26), 14.7 (C-27). HR-ESI-MS m/z 597.4116 [MþNa]þ (calcd for
C
35H58O6Na: 597.4126).
4.11. Betulinic acid 3
b
-O-
a
-
L
-arabinopyranoside (19a)
4:1) to give 20a (626 mg, 60%) as a white crystalline powder. Rf 0.38
25
(hexanes/EtOAc 3:1); [
a
]
þ1.7 (c 1.0, CHCl3). 1H NMR (CDCl3,
D
To a solution of 18a (75 mg, 0.119 mmol) and PPh3 (19 mg,
400 MHz)
d
: 7.72–7.35 (m, 10H, H–Ar), 4.60 (d, J¼2.4 Hz, 1H, H-29),
0.072 mmol) in anhydrous THF (0.84 mL) was added Pd0(PPh3)4
4.53 (br s, 1H, H-29), 4.20 (m, 3H, H-10, H-40, H-50), 4.06 (dd, J¼7.6,
5.7 Hz, 1H, H-30), 3.75 (dd, J¼13.8, 3.5 Hz, 1H, H-50), 3.68 (d,
J¼9.9 Hz, 1H, H-28), 3.63 (t, J¼7.7 Hz, 1H, H-20), 3.32 (d, J¼9.9 Hz,
1H, H-28), 3.09 (dd, J¼11.7, 4.6 Hz, 1H, H-3), 2.26 (td, J¼11.0, 5.7 Hz,
1H, H-19), 2.17–2.08 (m, 2H), 1.91–1.66 (m, 3H), 1.65 (s, 3H, H-30),
1.54 (s, 3H, (CH3)2C), 1.36 (s, 3H, (CH3)2C), 1.06 (s, 9H, C(CH3)3), 0.96
(s, 3H, H-23), 0.92 (s, 3H, H-27), 0.80 (s, 3H, H-24), 0.76 (s, 3H, H-
25), 0.69 (s, 3H, H-26), 0.66 (m, 1H, H-5). 13C NMR (CDCl3, 100 MHz)
(41 mg, 0.036 mmol) followed by pyrrolidine (20 mL, 0.239 mmol)
at room temperature under an argon atmosphere. The reaction
mixture was stirred in the dark overnight or until TLC (CH2Cl2/
MeOH 9:1) showed the disappearance of the initial product. Then,
the solvents were evaporated under reduced pressure to give a red-
yellow powder, which was purified by flash chromatography (100%
CH2Cl2 to CH2Cl2/MeOH 47:3) to afford pure 19a (46 mg, 66%) as
25
a white amorphous powder. Rf 0.46 (CH2Cl2/MeOH 9:1); [
a
]
þ5.2
d: 150.8 (C-20), 135.7–127.6 (C–Ar), 110.0 ((CH3)2C), 109.4 (C-29),
D
(c 0.2, CHCl3/MeOH 1:1). 1H NMR (CDCl3/CD3OD 1:1, 400 MHz)
d
:
104.3 (C-10), 89.0 (C-3), 78.1 (C-30), 74.3 (C-20), 73.2 (C-40), 63.1 (C-
50), 61.0 (C-28), 55.5 (C-5), 50.3 (C-9), 48.4 (C-18), 48.4 (C-17), 47.8
(C-19), 42.6 (C-14), 40.8 (C-8), 39.1 (C-4), 38.7 (C-1), 37.2 (C-13),
36.8 (C-10), 34.5 (C-22), 34.1 (C-7), 29.8 (C-21), 29.5 (C-16), 28.2 (C-
23), 28.0 ((CH3)2C), 27.0 (C-15), 26.9 (C(CH3)3), 26.1 ((CH3)2C), 26.1
(C-2), 25.1 (C-12), 20.7 (C-11), 19.4 (C(CH3)3), 19.1 (C-30), 18.1 (C-6),
16.5 (C-24), 16.1 (C-25), 15.7 (C-26), 14.7 (C-27). HR-ESI-MS m/z
875.5648 [MþNa]þ (calcd for C54H80O6SiNa: 875.5616).
4.72 (d, J¼1.6 Hz, 1H, H-29), 4.59 (br s, 1H, H-29), 4.33 (d, J¼6.0 Hz,
1H, H-10), 3.88 (m, 1H, H-50), 3.87 (m, 1H, H-40), 3.64 (dd, J¼8.1,
6.1 Hz, 1H, H-20), 3.58 (dd, J¼8.1, 3.0 Hz, 1H, H-30), 3.53 (dd, J¼13.8,
3.7 Hz, 1H, H-50), 3.13 (dd, J¼11.6, 4.5 Hz, 1H, H-3), 3.03 (td, J¼10.5,
4.3 Hz,1H, H-19), 2.31–2.21 (m, 2H), 2.01–1.72 (m, 3H),1.70 (s, 3H, H-
30), 1.68–1.04 (m, 15H), 1.01 (s, 3H, H-23), 0.98 (s, 3H, H-27), 0.95 (s,
3H, H-26), 0.84 (s, 3H, H-25), 0.81 (s, 3H, H-24), 0.74 (d, J¼9.7 Hz,1H,
H-5). 13C NMR (CDCl3/CD3OD 1:1,100 MHz)
d: 179.5 (C-28),151.2 (C-
20),109.8 (C-29),105.7 (C-10), 90.2 (C-3), 73.2 (C-30), 71.7 (C-20), 67.9
(C-40), 64.9 (C-50), 56.7 (C-17), 56.2 (C-5), 51.1 (C-9), 49.7 (C-18), 47.5
(C-19), 42.9 (C-14), 41.2 (C-8), 39.6 (C-4), 39.2 (C-1), 38.8 (C-13), 37.6
(C-22), 37.4 (C-10), 34.8 (C-7), 32.7 (C-16), 31.0 (C-21), 30.1 (C-15),
28.1 (C-23), 26.4 (C-2), 26.0 (C-12), 21.4 (C-11),19.5 (C-30),18.6 (C-6),
16.4 (C-25), 16.4 (C-24), 16.2 (C-26), 14.9 (C-27). HR-ESI-MS m/z
611.3901 [MþNa]þ (calcd for C35H56O7Na: 611.3918).
4.14. Allyl betulinate 3
b-O-3,4-O-isopropylidene-
a-L-arabinopyranoside (20b)
This compound was prepared from 18a (800 mg, 1.27 mmol) in
the same manner as that described for compound 20a. Purification
by flash chromatography (hexanes/EtOAc 9:1 to 4:1) gave 20b
(630 mg, 74%) as a white crystalline powder. Rf 0.34 (hexanes/EtOAc

7396
C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
25
3:1); [
a
]
D
þ18.0 (c 1.0, CHCl3). 1H NMR (CDCl3, 400 MHz)
d: 5.93
manner as that described for compound 21a. Purification by flash
chromatography (hexanes/EtOAc 9:1 to 17:1) gave 21b (873 mg,
(ddt, J¼17.2, 10.3, 5.7 Hz,1H, H-2Allyl), 5.34 (dq, J¼17.2, 1.6 Hz,1H, H-
3
Allyl), 5.24 (dq, J¼10.3, 1.2 Hz, 1H, H-3Allyl), 4.74 (d, J¼2.1 Hz, 1H, H-
99%) as a white crystalline powder. Rf 0.51 (hexanes/EtOAc 3:1);
25
29), 4.60 (m, 1H, H-29), 4.59 (m, 2H, H-1Allyl), 4.21 (d, J¼7.6 Hz, 1H,
H-10), 4.20 (m, 2H, H-40, H-50), 4.06 (dd, J¼7.6, 5.7 Hz, 1H, H-30), 3.76
(dd, J¼13.8, 3.5 Hz, 1H, H-50), 3.63 (t, J¼7.6 Hz, 1H, H-20), 3.10 (dd,
J¼11.4, 4.6 Hz, 1H, H-3), 3.02 (td, J¼11.3, 4.8 Hz, 1H, H-19), 2.29–2.17
(m, 2H), 1.95–1.75 (m, 2H), 1.69 (s, 3H, H-30), 1.54 (s, 3H, (CH3)2C),
1.37 (s, 3H, (CH3)2C), 0.96 (s, 3H, H-23), 0.95 (s, 3H, H-27), 0.90 (s,
3H, H-26), 0.82 (s, 3H, H-25), 0.80 (s, 3H, H-24), 0.69 (d, J¼8.9 Hz,
[a
]
þ81.5 (c 0.5, CHCl3). 1H NMR (CDCl3, 400 MHz)
d: 8.13–7.21 (m,
D
15H, H–Ar), 5.93 (ddt, J¼17.2, 10.3, 5.8 Hz, 1H, H-2Allyl), 5.87 (dd,
J¼10.0, 3.5 Hz, 1H, H-300), 5.75 (dd, J¼3.3, 1.6 Hz, 1H, H-200), 5.66 (t,
J¼10.1 Hz, 1H, H-400), 5.61 (d, J¼1.3 Hz, 1H, H-100), 5.35 (dq, J¼17.3,
1.6 Hz, 1H, H-3Allyl), 5.24 (dq, J¼10.5, 1.3 Hz, 1H, H-3Allyl), 4.75 (d,
J¼2.2 Hz, 1H, H-29), 4.61 (m, 1H, H-29), 4.58 (m, 2H, H-1Allyl), 4.51
(dd, J¼9.4, 5.8 Hz, 1H, H-500), 4.47 (d, J¼7.5 Hz, 1H, H-10), 4.26 (m,
2H, H-30, H-40), 4.16 (dd, J¼13.0, 1.9 Hz, 1H, H-50), 3.90 (t, J¼7.3 Hz,
1H, H-20), 3.81 (dd, J¼13.0, 3.0 Hz, 1H, H-50), 3.16 (dd, J¼11.9, 4.8 Hz,
1H, H-3), 3.03 (td, J¼11.3, 4.5 Hz, 1H, H-19), 2.31–2.18 (m, 2H), 1.96–
1.72 (m, 4H), 1.70 (s, 3H, H-30), 1.55 (s, 3H, (CH3)2C), 1.35 (d,
J¼5.8 Hz, 3H, H-600), 1.34 (s, 3H, (CH3)2C), 1.23 (s, 3H, H-23), 0.98 (s,
3H, H-27), 0.93 (s, 3H, H-24), 0.92 (s, 3H, H-26), 0.84 (s, 3H, H-25),
1H, H-5). 13C NMR (CDCl3, 100 MHz)
d: 175.7 (C-28), 150.6 (C-20),
132.6 (C-2Allyl), 118.2 (C-3Allyl), 110.1 ((CH3)2C), 109.6 (C-29), 104.3
(C-10), 89.1 (C-3), 78.2 (C-30), 74.4 (C-20), 73.3 (C-40), 64.6 (C-1Allyl),
63.2 (C-50), 56.6 (C-17), 55.7 (C-5), 50.6 (C-9), 49.5 (C-18), 46.9 (C-
19), 42.4 (C-14), 40.8 (C-8), 39.2 (C-4), 38.8 (C-1), 38.2 (C-13), 37.0
(C-22), 36.9 (C-10), 34.3 (C-7), 32.1 (C-16), 30.6 (C-21), 29.6 (C-15),
28.2 (C-23), 28.1 ((CH3)2C), 26.1 ((CH3)2C), 26.1 (C-2), 25.6 (C-12),
20.9 (C-11), 19.4 (C-30), 18.2 (C-6), 16.5 (C-24), 16.2 (C-25), 16.0
(C-26), 14.7 (C-27). HR-ESI-MS m/z 691.4538 [MþNa]þ (calcd for
0.77 (d, J¼9.4 Hz, 1H, H-5). 13C NMR (CDCl3, 100 MHz)
d: 175.8 (C-
28), 165.8–165.4 (3ꢂCO), 150.6 (C-20), 133.4–133.0 (C–Ar), 132.6
(C-2Allyl), 130.0–128.2 (C–Ar), 118.1 (C-3Allyl), 110.4 ((CH3)2C), 109.6
(C-29), 103.3 (C-10), 95.2 (C-100), 89.2 (C-3), 79.2 (C-30), 75.3 (C-20),
73.4 (C-40), 72.0 (C-400), 70.6 (C-200), 69.9 (C-300), 66.5 (C-500), 64.6 (C-
C
41H64O7Na: 691.4544).
4.15. 28-O-tert-Butyldiphenylsilyl betulin 3
b-O-2,3,4-tri-O-
1
Allyl), 62.7 (C-50), 56.6 (C-17), 56.0 (C-5), 50.6 (C-9), 49.5 (C-18),
benzoyl- -rhamnopyranosyl-(1/2)-3,4-O-isopropylidene-
a
-
L
47.0 (C-19), 42.4 (C-14), 40.8 (C-8), 39.3 (C-4), 39.0 (C-1), 38.3 (C-
13), 37.0 (C-22), 37.0 (C-10), 34.4 (C-7), 32.2 (C-16), 30.6 (C-21), 29.7
(C-15), 28.1 (C-23), 27.8 ((CH3)2C), 26.3 (C-2), 26.1 ((CH3)2C), 25.6
(C-12), 20.9 (C-11), 19.4 (C-30), 18.2 (C-6), 17.6 (C-600), 16.6 (C-24),
16.2 (C-25), 16.0 (C-26), 14.7 (C-27). HR-ESI-MS m/z 1149.5898
[MþNa]þ (calcd for C68H86O14Na: 1149.5910).
a
-L-arabinopyranoside (21a)
The acceptor 20a (500 mg, 0.586 mmol) and the donor 6
(546 mg, 0.879 mmol) were stirred in anhydrous CH2Cl2 (8.8 mL)
with 4 Å MS under an argon atmosphere for 40 min. The temper-
ature was lowered to ꢁ78 ꢀC with an ice CO2/acetone bath, then the
promoter BF3$Et2O (52 mL, 0.41 mmol) was injected in the medium
via a dry syringe while keeping rigorous anhydrous conditions. The
4.17. Betulin 3
(1/2)-3,4-O-isopropylidene-a-L
b
-O-2,3,4-tri-O-benzoyl-
a-L-rhamnopyranosyl-
reaction mixture was stirred for 1.5 h at ꢁ78 ꢀC and quenched by
-arabinopyranoside (22a)
addition of Et3N (327 mL, 2.34 mmol). The solvents were evaporated
under reduced pressure to give a residue, which was purified by
flash chromatography (hexanes/EtOAc 47:3 to 17:1) to afford 21a
To a solution of 21a (250 mg, 0.191 mmol) in anhydrous THF
(2.08 mL) was added HOAc (120 L, 2.10 mmol) and 1 M TBAF in
m
(600 mg, 78%) as a white crystalline powder. Rf 0.57 (hexanes/EtOAc
THF (2.08 mL) at room temperature under an argon atmosphere.
The reaction mixture was refluxed overnight or until TLC (CH2Cl2/
MeOH 9:1) showed the disappearance of the initial product. Then,
the mixture was diluted with CH2Cl2, washed with H2O, dried over
anhydrous MgSO4, filtered and the solvents were evaporated under
reduced pressure. The resulting residue was purified by flash
chromatography (hexanes/EtOAc 9:1 to 7:3) to furnish 22a (125 mg,
25
3:1); [
a
]
þ59.2 (c 0.5, CHCl3). 1H NMR (CDCl3, 400 MHz)
d: 8.13–
D
7.21 (m, 25H, H–Ar), 5.87 (dd, J¼10.2, 3.5 Hz, 1H, H-300), 5.75 (dd,
J¼3.5, 1.7 Hz, 1H, H-200), 5.67 (t, J¼10.0 Hz, 1H, H-400), 5.61 (d,
J¼1.5 Hz, 1H, H-100), 4.60 (d, J¼2.1 Hz, 1H, H-29), 4.53 (m, 1H, H-29),
4.51 (m, 1H, H-500), 4.46 (d, J¼7.5 Hz, 1H, H-10), 4.25 (m, 2H, H-30, H-
40), 4.15 (dd, J¼13.3, 1.9 Hz, 1H, H-50), 3.90 (t, J¼7.1 Hz, 1H, H-20),
3.79 (dd, J¼12.6, 2.6 Hz, 1H, H-50), 3.71 (d, J¼9.9 Hz, 1H, H-28), 3.32
(d, J¼9.9 Hz, 1H, H-28), 3.15 (dd, J¼11.7, 4.5 Hz, 1H, H-3), 2.26 (td,
J¼10.9, 6.0 Hz, 1H, H-19), 2.18–2.09 (m, 2H), 1.88–1.68 (m, 3H), 1.66
(s, 3H, H-30), 1.55 (s, 3H, (CH3)2C), 1.35 (d, J¼6.5 Hz, 3H, H-600), 1.33
(s, 3H, (CH3)2C), 1.23 (s, 3H, H-23), 1.06 (s, 9H, C(CH3)3), 0.95 (s, 3H,
72%, corrected yield) as a white amorphous powder along with 21a
25
(28 mg, 11%, recovery yield). Rf 0.20 (hexanes/EtOAc 3:1); [a]
D
þ91.2 (c 0.5, CHCl3). 1H NMR (CDCl3, 400 MHz)
d: 8.14–7.21 (m, 15H,
H–Ar), 5.87 (dd, J¼10.2, 3.5 Hz, 1H, H-300), 5.75 (dd, J¼3.3, 1.6 Hz, 1H,
H-200), 5.66 (t, J¼10.0 Hz, 1H, H-400), 5.57 (d, J¼1.1 Hz, 1H, H-100), 4.69
(d, J¼1.4 Hz, 1H, H-29), 4.59 (br s, 1H, H-29), 4.51 (dq, 10.0, 6.3 Hz,
1H, H-500), 4.47 (d, J¼7.5 Hz, 1H, H-10), 4.27 (m, 1H, H-30), 4.26 (m,
1H, H-40), 4.16 (d, J¼13.4 Hz, 1H, H-50), 3.90 (t, J¼7.0 Hz, 1H, H-20),
3.85 (m, 1H, H-28), 3.84 (m, 1H, H-50), 3.34 (d, J¼10.8 Hz, 1H, H-28),
3.16 (dd, J¼11.9, 4.6 Hz, 1H, H-3), 2.40 (td, J¼10.7, 5.7 Hz, 1H, H-19),
2.04–1.80 (m, 4H), 1.69 (s, 3H, H-30), 1.55 (s, 3H, (CH3)2C), 1.35 (d,
J¼6.2 Hz, 3H, H-600), 1.34 (s, 3H, (CH3)2C), 1.24 (s, 3H, H-23), 1.03 (s,
3H, H-26), 0.99 (s, 3H, H-27), 0.93 (s, 3H, H-24), 0.85 (s, 3H, H-25),
H-27), 0.93 (s, 3H, H-24), 0.79 (s, 3H, H-25), 0.74 (s, 3H, H-26). 13
NMR (CDCl3, 100 MHz)
C
d
: 165.8–165.4 (3ꢂCO), 150.9 (C-20), 135.7–
127.6 (C–Ar), 110.4 ((CH3)2C), 109.4 (C-29), 103.3 (C-10), 95.3 (C-100),
89.2 (C-3), 79.2 (C-30), 75.4 (C-20), 73.4 (C-40), 72.0 (C-400), 70.6 (C-
200), 69.9 (C-300), 66.5 (C-500), 62.7 (C-50), 61.1 (C-28), 55.9 (C-5), 50.4
(C-9), 48.5 (C-18), 48.4 (C-17), 47.8 (C-19), 42.6 (C-14), 40.8 (C-8),
39.3 (C-4), 38.9 (C-1), 37.2 (C-13), 36.9 (C-10), 34.5 (C-22), 34.2 (C-
7), 29.9 (C-21), 29.5 (C-16), 28.1 (C-23), 27.8 ((CH3)2C), 27.1 (C-15),
26.9 (C(CH3)3), 26.3 (C-2), 26.1 ((CH3)2C), 25.2 (C-12), 20.8 (C-11),
19.4 (C(CH3)3), 19.1 (C-30), 18.2 (C-6), 17.6 (C-600), 16.5 (C-24), 16.2
(C-25), 15.8 (C-26), 14.7 (C-27). HR-ESI-MS m/z 1333.6971 [MþNa]þ
(calcd for C81H102O13SiNa: 1333.6982).
0.77 (d, J¼10.0 Hz, 1H, H-5). 13C NMR (CDCl3, 100 MHz)
d: 165.8–
165.4 (3ꢂCO), 150.5 (C-20), 133.4–128.2 (C–Ar), 110.4 ((CH3)2C),
109.7 (C-29), 103.3 (C-10), 95.2 (C-100), 89.2 (C-3), 79.2 (C-30), 75.3
(C-20), 73.4 (C-40), 72.0 (C-400), 70.6 (C-200), 69.9 (C-300), 66.5 (C-500),
62.7 (C-50), 60.6 (C-28), 55.9 (C-5), 50.4 (C-9), 48.8 (C-18), 47.8 (C-
19), 47.8 (C-17), 42.7 (C-14), 41.0 (C-8), 39.3 (C-4), 39.0 (C-1), 37.3
(C-13), 36.9 (C-10), 34.2 (C-22), 34.0 (C-7), 29.8 (C-21), 29.2 (C-16),
28.1 (C-23), 27.8 ((CH3)2C), 27.0 (C-15), 26.3 (C-2), 26.1 ((CH3)2C),
25.2 (C-12), 20.8 (C-11), 19.1 (C-30), 18.2 (C-6), 17.5 (C-600), 16.5 (C-
24), 16.2 (C-25), 16.0 (C-26), 14.7 (C-27). HR-ESI-MS m/z 1095.5798
[MþNa]þ (calcd for C65H84O13Na: 1095.5804).
4.16. Allyl betulinate 3
b-O-2,3,4-tri-O-benzoyl-
a
-L-rhamnopyranosyl-(1/2)-3,4-O-isopropylidene-
a
-L-arabinopyranoside (21b)
This compound was prepared from the acceptor 20b (500 mg,
0.747 mmol) and the donor 6 (696 mg, 1.12 mmol) in the same

C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
7397
4.18. Betulinic acid 3
b
-O-2,3,4-tri-O-benzoyl-
27.1 (C-2), 26.1 (C-12), 21.4 (C-11),19.6 (C-30),19.0 (C-600),18.9 (C-6),
17.2 (C-24), 16.8 (C-25), 16.5 (C-26), 15.3 (C-27). HR-ESI-MS m/z
743.4696 [MþNa]þ (calcd for C41H68O10Na: 743.4705).
a
-L-rhamnopyranosyl-(1/2)-3,4-O-isopropylidene-
a
-L-arabinopyranoside (22b)
This compound was prepared from 21b (100 mg, 0.089 mmol) in
the same manner as that described for compound 19a. Purification
by flash chromatography (hexanes/EtOAc 9:1 to 100% EtOAc) gave
4.20. Betulinic acid 3
b-O-a-L-rhamnopyranosyl-(1/2)-
a-L-arabinopyranoside (23b)
22b (82 mg, 85%) as a white amorphous powder. Rf 0.28 (hexanes/
This compound was prepared from 22b (50 mg, 0.046 mmol) in
the same manner as that described for compound 23a. Purification
by C-18 reversed phase flash chromatography (MeOH/H2O 4:1 to
9:1) gave pure 23b (20 mg, 61%, two steps) as a white amorphous
25
EtOAc 3:1); [
a]
þ70.2 (c 0.5, CHCl3). 1H NMR (CDCl3, 400 MHz)
d:
D
8.13–7.20 (m, 15H, H–Ar), 5.86 (dd, J¼10.2, 3.5 Hz, 1H, H-300), 5.75
(dd, J¼3.3, 1.6 Hz, 1H, H-200), 5.66 (t, J¼10.0 Hz, 1H, H-400), 5.60 (d,
J¼1.2 Hz, 1H, H-100), 4.76 (br s, 1H, H-29), 4.62 (br s, 1H, H-29), 4.50
(m, 1H, H-500), 4.47 (d, J¼7.5 Hz, 1H, H-10), 4.26 (m, 2H, H-30, H-40),
4.16 (d, J¼12.9 Hz, 1H, H-50), 3.90 (m, 1H, H-20), 3.80 (d, J¼12.2 Hz,
1H, H-50), 3.16 (dd, J¼11.5, 4.3 Hz, 1H, H-3), 3.01 (td, J¼10.6, 4.4 Hz,
1H, H-19), 2.31–2.14 (m, 2H), 2.05–1.80 (m, 3H), 1.71 (s, 3H, H-30),
1.55 (s, 3H, (CH3)2C), 1.34 (s, 3H, (CH3)2C), 1.33 (d, J¼6.0 Hz, 3H, H-
600), 1.23 (s, 3H, H-23), 0.99 (s, 3H, H-27), 0.95 (s, 3H, H-26), 0.92 (s,
3H, H-24), 0.84 (s, 3H, H-25), 0.77 (d, J¼9.4 Hz, 1H, H-5). 13C NMR
25
powder. Rf 0.86 (CH2Cl2/MeOH 3:1); [
a
]
ꢁ37.7ꢀ (c 0.1, MeOH). 1H
D
NMR (CD3OD, 400 MHz)
d
: 5.10 (d, J¼1.1 Hz, 1H, H-100), 4.70 (br s,
1H, H-29), 4.56 (br s, 1H, H-29), 4.52 (d, J¼4.6 Hz, 1H, H-10), 3.88
(dd, J¼3.2, 1.6 Hz, 1H, H-200), 3.84 (m, 1H, H-50), 3.81 (m, 1H, H-500),
3.79 (m,1H, H-40), 3.76 (m,1H, H-20), 3.74 (m,1H, H-400), 3.69 (m,1H,
H-300), 3.48 (dd, J¼11.4, 2.4 Hz, 1H, H-50), 3.38 (t, J¼9.5 Hz, 1H, H-30),
3.10 (m, 2H, H-3, H-19), 2.43 (td, J¼12.1, 2.7 Hz, 1H, H-13), 2.25 (dt,
J¼12.6, 3.0 Hz, 1H, H-16), 2.00–1.78 (m, 3H), 1.69 (s, 3H, H-30), 1.23
(d, J¼6.2 Hz, 3H, H-600), 1.00 (s, 6H, H-23, H-27), 0.99 (s, 3H, H-26),
(CDCl3, 100 MHz)
d
: 181.4 (C-28), 165.8–165.4 (3ꢂCO), 150.5 (C-20),
133.4–128.2 (C–Ar), 110.4 ((CH3)2C), 109.7 (C-29), 103.3 (C-10), 95.3
(C-100), 89.2 (C-3), 79.2 (C-30), 75.4 (C-20), 73.4 (C-40), 72.0 (C-400),
70.6 (C-200), 69.9 (C-300), 66.6 (C-500), 62.7 (C-50), 56.4 (C-17), 56.0 (C-
5), 50.6 (C-9), 49.3 (C-18), 46.9 (C-19), 42.5 (C-14), 40.8 (C-8), 39.3
(C-4), 39.0 (C-1), 38.4 (C-13), 37.1 (C-22), 37.0 (C-10), 34.4 (C-7),
32.2 (C-16), 30.6 (C-21), 29.7 (C-15), 28.1 (C-23), 27.8 ((CH3)2C), 26.3
(C-2), 26.1 ((CH3)2C), 25.6 (C-12), 20.9 (C-11), 19.4 (C-30), 18.2 (C-6),
17.5 (C-600), 16.5 (C-24), 16.2 (C-25), 16.0 (C-26), 14.7 (C-27). HR-ESI-
MS m/z 1109.5589 [MþNa]þ (calcd for C65H82O14Na: 1109.5597).
0.87 (s, 3H, H-25), 0.82 (s, 3H, H-23), 0.75 (d, J¼9.4 Hz, 1H, H-5). 13
C
NMR (CD3OD, 100 MHz) d: 181.9 (C-28), 152.5 (C-20), 109.8 (C-29),
104.8 (C-10), 102.0 (C-100), 90.6 (C-3), 76.8 (C-20), 73.9 (C-30), 73.1 (C-
400), 72.2 (C-300), 72.1 (C-200), 70.2 (C-500), 68.4 (C-40), 63.8 (C-50), 58.1
(C-17), 57.2 (C-5), 52.1 (C-9), 50.7 (C-18), 48.5 (C-19), 43.6 (C-14),
42.0 (C-8), 40.4 (C-4), 40.2 (C-1), 39.5 (C-13), 38.6 (C-22), 38.1 (C-
10), 35.6 (C-7), 33.9 (C-16), 31.9 (C-21), 31.0 (C-15), 28.5 (C-23), 27.2
(C-2), 27.0 (C-12), 22.2 (C-11), 19.6 (C-30), 19.3 (C-6), 18.0 (C-600),
16.9 (C-24), 16.9 (C-25), 16.8 (C-26), 15.2 (C-27). HR-ESI-MS m/z
757.4488 [MþNa]þ (calcd for C41H66O11Na: 757.4497).
4.19. Betulin 3
b-O-a-L-rhamnopyranosyl-(1/2)-
a-L-arabinopyranoside (23a)
4.21. Allyl betulinate 3
b-O-2,3,4-tri-O-benzoyl-
To a solution of 22a (65 mg, 0.061 mmol) in anhydrous CH2Cl2/
a-
L-rhamnopyranosyl-(1/2)-a-L
-arabinopyranoside (24)
MeOH 1:2 (5.2 mL) was added TsOH$H2O (9.0 mg, 0.048 mmol) at
room temperature under an argon atmosphere. The reaction mix-
ture was stirred overnight at room temperature or until TLC (hex-
anes/EtOAc 7:3) showed the complete disappearance of the initial
To a solution of 21b (200 mg, 0.046 mmol) in anhydrous CH2Cl2/
MeOH 1:2 (13.3 mL) was added TsOH$H2O (23 mg, 0.12 mmol) at
room temperature under an argon atmosphere. The reaction mix-
ture was stirred overnight at room temperature or until TLC (hex-
anes/EtOAc 7:3) showed the complete disappearance of the initial
product. Then, the mixture was quenched with Et3N (124 mL,
0.887 mmol) and the solvents were evaporated under reduced
pressure to give a solid residue, which was purified by flash chro-
product. Then, the mixture was quenched with Et3N (49 mL,
0.35 mmol) and the solvents were evaporated under reduced
pressure. The resulting residue was immediately dissolved in a so-
lution of MeOH/THF/H2O 1:2:1 (4.2 mL) to which was added NaOH
(49 mg, 1.2 mmol). The reaction mixture was stirred for 4.5 h at
room temperature or until TLC (CH2Cl2/MeOH 9:1) showed the
complete disappearance of the benzoylated products and then
acidified to pHz4 with 10% aqueous HCl. The solvents were
evaporated under reduced pressure to give a solid residue, which
was purified by C-18 reversed phase flash chromatography (MeOH/
matography (hexanes/EtOAc 4:1 to 2:3) to furnish 24 (133 mg, 70%)
25
as a white crystalline powder. Rf 0.15 (hexanes/EtOAc 3:1); [a]
D
þ52.5 (c 0.2, CHCl3). 1H NMR (CDCl3, 400 MHz)
d: 8.12–7.23 (m, 15H,
H–Ar), 5.93 (ddt, J¼17.2, 10.4, 5.7 Hz, 1H, H-2Allyl), 5.83 (dd, J¼10.2,
3.4 Hz, 1H, H-300), 5.71 (m, 1H, H-200), 5.69 (m, 1H, H-400), 5.38 (d,
J¼1.3 Hz, 1H, H-100), 5.34 (dq, J¼17.2, 1.5 Hz, 1H, H-3Allyl), 5.24
(dq, J¼10.4, 1.3 Hz, 1H, H-3Allyl), 4.80 (d, J¼3.3 Hz, 1H, H-10), 4.74 (d,
J¼2.1 Hz, 1H, H-29), 4.61 (m, 1H, H-29), 4.58 (m, 2H, H-1Allyl), 4.36
(ddt, J¼9.7, 6.3, 6.2 Hz, 1H, H-500), 4.03 (m, 1H, H-40), 4.01 (m, 1H, H-
30), 3.99 (m, 1H, H-20), 3.83 (dd, J¼11.8, 7.6 Hz, 1H, H-50), 3.68 (dd,
J¼11.7, 4.2 Hz, 1H, H-50), 3.15 (dd, J¼11.5, 4.5 Hz, 1H, H-3), 3.02 (td,
J¼11.1, 4.2 Hz, 1H, H-19), 2.30–2.18 (m, 2H), 1.95–1.83 (m, 3H), 1.69
(s, 3H, H-30), 1.34 (d, J¼6.3 Hz, 3H, H-600), 1.04 (s, 3H, H-23), 0.96 (s,
3H, H-27), 0.92 (s, 3H, H-26), 0.83 (s, 6H, H-23, H-25), 0.72 (d,
H2O 4:1 to 9:1) to afford pure 23a (42 mg, 84%, two steps) as a white
25
amorphous powder. Rf 0.84 (CH2Cl2/MeOH 3:1); [
a
]
ꢁ32.8 (c 0.1,
D
MeOH). 1H NMR (C5D5N, 400 MHz)
d
: 6.19 (s, 1H, H-100), 4.94 (d,
J¼5.4 Hz, 1H, H-10), 4.90 (br s, 1H, H-29), 4.79 (br s, 1H, H-200), 4.74
(br s, 1H, H-29), 4.66 (m, 1H, H-300), 4.62 (m, 1H, H-500), 4.59 (m, 1H,
H-20), 4.34 (m, 1H, H-400), 4.33 (m, 1H, H-50), 4.31 (m, 1H, H-30), 4.30
(m, 1H, H-40), 4.10 (dd, J¼10.2, 4.3 Hz, 1H, H-28), 3.84 (d, J¼10.0 Hz,
1H, H-50), 3.69 (dd, J¼10.5, 4.7 Hz, 1H, H-28), 3.28 (dd, J¼11.7,
4.1 Hz, 1H, H-3), 2.64 (td, J¼10.8, 5.9 Hz, 1H, H-19), 2.52–2.40 (m,
2H), 2.23–2.11 (m, 2H), 1.97–1.85 (m, 2H), 1.77 (s, 3H, H-30), 1.66 (d,
J¼6.1 Hz, 3H, H-600), 1.20 (s, 3H, H-23), 1.10 (s, 3H, H-24), 1.09 (s, 3H,
H-27), 0.98 (s, 3H, H-26), 0.82 (s, 3H, H-25), 0.75 (d, J¼10.8 Hz, 1H,
J¼8.9 Hz, 1H, H-5). 13C NMR (CDCl3, 100 MHz)
d: 175.7 (C-28),
165.8–165.5 (3ꢂCO), 150.5 (C-20), 133.5–133.1 (C–Ar), 132.5 (C-
2
Allyl), 129.9–128.3 (C–Ar), 118.1 (C-3Allyl), 109.6 (C-29), 102.1 (C-10),
H-5). 13C NMR (C5D5N, 100 MHz)
d
: 151.6 (C-20), 110.3 (C-29), 105.2
98.2 (C-100), 90.3 (C-3), 76.2 (C-20), 71.6 (C-400), 70.9 (C-30), 70.7 (C-
200), 69.8 (C-300), 67.2 (C-500), 65.6 (C-40), 64.6 (C-1Allyl), 61.3 (C-50),
56.5 (C-17), 55.6 (C-5), 50.5 (C-9), 49.4 (C-18), 46.9 (C-19), 42.4 (C-
14), 40.7 (C-8), 39.2 (C-4), 38.8 (C-1), 38.2 (C-13), 37.0 (C-22), 36.9
(C-10), 34.2 (C-7), 32.1 (C-16), 30.6 (C-21), 29.6 (C-15), 28.0 (C-23),
26.0 (C-2), 25.5 (C-12), 20.9 (C-11), 19.4 (C-30), 18.2 (C-6), 17.5
(C-10), 102.2 (C-100), 89.2 (C-3), 76.4 (C-20), 74.5 (C-400), 74.2 (C-30),
73.0 (C-300), 72.8 (C-200), 70.3 (C-500), 69.1 (C-40), 65.1 (C-50), 59.8 (C-
28), 56.3 (C-5), 51.0 (C-9), 49.5 (C-18), 48.9 (C-17), 48.7 (C-19), 43.3
(C-14), 41.5 (C-8), 40.0 (C-4), 39.5 (C-1), 37.9 (C-13), 37.5 (C-10), 35.2
(C-22), 34.9 (C-7), 30.8 (C-21), 30.4 (C-16), 28.3 (C-23), 27.9 (C-15),

7398
C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
(C-600), 16.3 (C-24), 16.1 (C-25), 16.0 (C-26), 14.7 (C-27). HR-ESI-MS
(c 0.1, MeOH). 1H NMR (C5D5N, 700 MHz) : 6.21 (br s, 1H, H-100),
d
m/z 1109.5589 [MþNa]þ (calcd for C65H82O14Na: 1109.5597).
5.16 (d, J¼7.9 Hz, 1H, H-1%), 4.94 (m, 1H, H-29), 4.79 (d, J¼6.1 Hz,
1H, H-10), 4.76 (m, 2H, H-200, H-29), 4.65 (m, 1H, H-500), 4.64 (m, 1H,
H-300), 4.53 (m, 1H, H-20), 4.52 (m, 1H, H-6%), 4.42 (dd, J¼12.2,
3.9 Hz, 1H, H-50), 4.40 (dd, J¼12.0, 5.0 Hz, 1H, H-6%), 4.34 (t,
J¼9.4 Hz, 1H, H-400), 4.30 (m, 1H, H-40), 4.28 (t, J¼9.3 Hz, 1H, H-4%),
4.27 (m, 1H, H-30), 4.23 (t, J¼9.0 Hz, 1H, H-3%), 4.07 (t, J¼8.5 Hz, 1H,
H-2%), 3.92 (ddd, J¼9.5, 5.1, 2.3 Hz, 1H, H-5%), 3.81 (d, J¼11.7 Hz,
1H, H-50), 3.57 (td, J¼10.7, 4.5 Hz, 1H, H-19), 3.22 (dd, J¼11.7, 4.2 Hz,
1H, H-3), 2.78 (m, 1H, H-13), 2.66 (m, 1H, H-16), 2.29–2.22 (m, 2H),
2.08 (m, 1H, H-2), 1.95 (m, 1H, H-12), 1.87 (m, 1H, H-15), 1.78 (s, 3H,
H-30), 1.76 (t, J¼11.4 Hz, 1H, H-18), 1.65 (d, J¼6.2 Hz, 3H, H-600),
1.61–1.21 (m, 12H), 1.18 (s, 3H, H-23), 1.10 (s, 3H, H-27), 1.09 (s, 3H,
H-24), 1.02 (s, 3H, H-26), 0.77 (s, 3H, H-25), 0.72 (d, J¼11.9 Hz, 1H,
4.22. Allyl betulinate 3
b
-O-2,3,4-tri-O-benzoyl-
a
-L-rhamnopyranosyl-(1/2)-[2,3,4,6-tetra-O-benzoyl-
b-D
-glucopyranosyl-(1/4)]-a-L-arabinopyranoside (25)
The acceptor 24 (38.5 mg, 0.036 mmol) and the donor 5 (41 mg,
0.055 mmol) were stirred in anhydrous CH2Cl2 (1.5 mL) with 4 Å
MS under an argon atmosphere for 40 min. The temperature was
lowered to ꢁ10 ꢀC with an ice water/acetone bath, then a solution
of TMSOTf in CH2Cl2 (100 mL, 40 mM) was injected in the medium
via a dry syringe while keeping rigorous anhydrous conditions. The
reaction mixture was stirred while the temperature was gradually
raised to room temperature over 3 h and quenched by addition of
H-5). 13C NMR (C5D5N, 175 MHz)
d: 179.6 (C-28), 151.8 (C-20), 110.2
Et3N (21
m
L, 0.15 mmol). The solvents were evaporated under re-
(C-29), 106.7 (C-1%), 105.3 (C-10), 102.1 (C-100), 89.1 (C-3), 80.0 (C-
40), 79.1 (C-5%), 78.8 (C-3%), 76.7 (C-20), 75.8 (C-2%), 74.4 (C-4%),
74.3 (C-400), 72.8 (C-300), 72.6 (C-200), 71.5 (C-30), 70.1 (C-500), 64.9 (C-
50), 62.8 (C-6%), 57.1 (C-17), 56.4 (C-5), 51.1 (C-9), 50.1 (C-18), 48.1
(C-19), 43.1 (C-14), 41.3 (C-8), 39.9 (C-4), 39.4 (C-1), 38.8 (C-13),
38.0 (C-22), 37.4 (C-10), 35.0 (C-7), 33.3 (C-16), 31.6 (C-21), 30.6 (C-
15), 28.2 (C-23), 27.1 (C-2), 26.4 (C-12), 21.5 (C-11), 19.8 (C-30), 19.0
(C-600), 18.8 (C-6), 17.1 (C-24), 16.7 (C-25), 16.7 (C-26), 15.1 (C-27).
HR-ESI-MS m/z 919.5018 [MþNa]þ (calcd for C47H76O16Na:
919.5026).
duced pressure to give a residue, which was purified by flash
chromatography (hexanes/EtOAc 9:1 to 1:1) to afford 25 (20 mg,
50%, corrected yield) as a white crystalline powder along with 24
25
(6 mg,15%, recovery yield). Rf 0.32 (hexanes/EtOAc 3:1); [
a
]
D
þ52.0
(c 0.1, CHCl3). 1H NMR (CDCl3, 400 MHz)
d
: 8.11–7.22 (m, 35H, H–
Ar), 5.93 (m, 1H, H-3%), 5.92 (m, 1H, H-2Allyl), 5.79 (dd, J¼10.2,
3.4 Hz, 1H, H-300), 5.70 (t, J¼9.7 Hz, 1H, H-4%), 5.62 (m, 2H, H-200, H-
400), 5.59 (m, 1H, H-2%), 5.33 (dq, J¼17.2, 1.5 Hz, 1H, H-3Allyl), 5.23
(dq, J¼10.4, 1.3 Hz, 1H, H-3Allyl), 5.19 (d, J¼1.6 Hz, 1H, H-100), 5.12 (d,
J¼7.9 Hz, 1H, H-1%), 4.74 (m, 1H, H-29), 4.71 (m, 1H, H-6%), 4.65 (d,
J¼3.8 Hz, 1H, H-10), 4.60 (m, 1H, H-29), 4.59 (m, 2H, H-1Allyl), 4.51
(m, 1H, H-6%), 4.31 (m, 1H, H-500), 4.25 (m, 1H, H-5%), 4.09 (m, 1H,
H-50), 4.07 (m, 1H, H-40), 3.90 (m, 1H, H-30), 3.83 (m, 1H, H-20), 3.68
(m, 1H, H-50), 3.07 (m, 1H, H-3), 3.02 (m, 1H, H-19), 2.30–2.12 (m,
2H), 1.95–1.70 (m, 3H), 1.69 (s, 3H, H-30), 1.29 (d, J¼6.2 Hz, 3H, H-
600), 1.00 (s, 3H, H-23), 0.94 (s, 3H, H-27), 0.89 (s, 3H, H-26), 0.80 (s,
3H, H-25), 0.78 (s, 3H, H-24), 0.68 (d, J¼9.1 Hz, 1H, H-5). 13C NMR
4.24. 28-O-2,3,4,6-Tetra-O-benzoyl-
betulinic acid 3 -O-2,3,4-tri-O-benzoyl-
(1/2)-3,4-O-isopropylidene- -arabinopyranoside (26)
b-D
-glucopyranosyl
b
a-L-rhamnopyranosyl-
a-L
To a solution of the acceptor 22b (30 mg, 0.028 mmol) and the
donor 7 (27 mg, 0.041 mmol) in CH2Cl2 (0.32 mL) were added H2O
(0.32 mL), K2CO3 (9.5 mg, 0.069 mmol) and Bu4NBr (3.6 mg,
0.011 mmol). The resulting mixture was vigorously stirred and
refluxed for 6 h. Then, the mixture was diluted with CH2Cl2, washed
with H2O and brine. The solvents of the dried (MgSO4) organic
solution were evaporated under reduced pressure to give a brown
residue, which was purified by flash chromatography (hexanes/
(CDCl3, 100 MHz)
133.5–133.1 (C–Ar), 132.6 (C-2Allyl), 129.9–128.3 (C–Ar), 118.1 (C-
Allyl), 109.6 (C-29),102.4 (C-10), 101.9 (C-1%), 97.9 (C-100), 90.3 (C-3),
d: 175.7 (C-28), 166.1–165.1 (7ꢂCO), 150.6 (C-20),
3
76.0 (C-40), 76.0 (C-20), 72.8 (C-3%), 72.3 (C-5%), 72.0 (C-2%), 71.7
(C-400), 70.7 (C-200), 70.6 (C-30), 69.8 (C-300), 69.6 (C-4%), 67.0 (C-500),
64.6 (C-1Allyl), 63.0 (C-6%), 60.6 (C-50), 56.6 (C-17), 55.7 (C-5), 50.6
(C-9), 49.5 (C-18), 46.9 (C-19), 42.4 (C-14), 40.7 (C-8), 39.2 (C-4),
38.8 (C-1), 38.2 (C-13), 37.0 (C-22), 36.9 (C-10), 34.3 (C-7), 32.1 (C-
16), 30.6 (C-21), 29.6 (C-15), 28.1 (C-23), 25.9 (C-2), 25.5 (C-12), 20.9
(C-11), 19.4 (C-30), 18.2 (C-6), 17.5 (C-600), 16.3 (C-24), 16.2 (C-25),
16.0 (C-26), 14.7 (C-27). HR-ESI-MS m/z 1687.7167 [MþNa]þ (calcd
for C99H108O23Na: 1687.7174).
EtOAc 9:1 to 3:2) to afford 26 (36 mg, 78%) as a white amorphous
25
powder. Rf 0.20 (hexanes/EtOAc 3:1); [
NMR (CDCl3, 400 MHz)
a
]
D
þ93.0 (c 0.1, CHCl3). 1H
d
: 8.12–7.22 (m, 35H, H–Ar), 6.03 (d,
J¼9.7 Hz, 1H, H-1%), 6.01 (t, J¼8.3 Hz, 1H, H-3%), 5.86 (dd, J¼10.2,
3.5 Hz, 1H, H-300), 5.76 (t, J¼9.1 Hz, 1H, H-2%), 5.75 (m, 1H, H-200),
5.73 (t, J¼9.7 Hz, 1H, H-4%), 5.67 (t, J¼10.0 Hz, 1H, H-400), 5.61 (d,
J¼1.6 Hz, 1H, H-100), 4.71 (d, J¼1.8 Hz, 1H, H-29), 4.58 (m, 1H, H-29),
4.59 (m, 1H, H-6%), 4.49 (m, 1H, H-6%), 4.51 (m, 1H, H-500), 4.45 (d,
J¼7.5 Hz, 1H, H-10), 4.29 (m, 1H, H-5%), 4.25 (m, 1H, H-40), 4.25 (m,
1H, H-30), 4.15 (dd, J¼13.4, 1.6 Hz, 1H, H-50), 3.89 (m, 1H, H-20), 3.78
(dd, J¼12.7, 2.6 Hz, 1H, H-50), 3.11 (dd, J¼11.5, 4.6 Hz, 1H, H-3), 2.93
(td, J¼11.0, 4.7 Hz, 1H, H-19), 2.17 (m, 1H, H-16), 2.05 (td, J¼12.1,
3.2 Hz,1H, H-13),1.96–1.66 (m, 4H),1.64 (br s, 3H, H-30),1.54 (s, 3H,
(CH3)2C), 1.36 (d, J¼6.2 Hz, 3H, H-600), 1.33 (s, 3H, (CH3)2C), 1.18 (s,
3H, H-23), 0.90 (s, 3H, H-24), 0.80 (s, 3H, H-27), 0.71 (s, 3H, H-25),
0.63 (d, J¼11.9 Hz, 1H, H-5), 0.49 (s, 3H, H-26). 13C NMR (CDCl3,
4.23. Betulinic acid 3 -rhamnopyranosyl-(1/2)-
b
-O-a
-L
[
b-D
-glucopyranosyl-(1/4)]-a-L-arabinopyranoside (3)
To a solution of 25 (17 mg, 0.010 mmol) and PPh3 (2.7 mg,
0.010 mmol) in anhydrous THF (>0.10 mL) was added Pd0(PPh3)4
(5.9 mg, 0.005 mmol) followed by pyrrolidine (2.0 L, 0.024 mmol)
m
at room temperature under an argon atmosphere. The reaction
mixture was stirred for 4.5 h in the dark at room temperature or
until TLC (hexanes/EtOAc 7:3) showed the disappearance of the
initial product. Then, the solvents were evaporated under reduced
pressure and the resulting red-yellow residue was immediately
dissolved in a solution of MeOH/THF/H2O 1:2:1 (0.72 mL) to which
was added NaOH (8.4 mg, 0.21 mmol). The reaction mixture was
stirred for 6 h at room temperature or until TLC (CH2Cl2/MeOH 4:1)
showed the complete disappearance of the benzoylated product
and then acidified to pHz4 with 10% aqueous HCl. The solvents
were evaporated under reduced pressure to give a solid residue,
which was purified by C-18 reversed phase flash chromatography
100 MHz)
d
: 174.1 (C-28), 166.1–164.7 (7ꢂCO), 150.3 (C-20), 133.6–
128.3 (C–Ar), 110.4 ((CH3)2C), 109.6 (C-29), 103.3 (C-10), 95.2 (C-100),
91.4 (C-1%), 89.1 (C-3), 79.2 (C-30), 75.3 (C-20), 73.4 (C-40), 73.0 (C-
5%), 72.9 (C-3%), 72.1 (C-400), 70.6 (C-200), 70.3 (C-2%), 70.0 (C-300),
69.4 (C-4%), 66.5 (C-500), 62.8 (C-6%), 62.7 (C-50), 56.8 (C-17), 55.8
(C-5), 50.4 (C-9), 49.1 (C-18), 46.7 (C-19), 42.2 (C-14), 40.3 (C-8),
39.2 (C-4), 38.9 (C-1), 38.0 (C-13), 36.8 (C-10), 36.3 (C-22), 33.4 (C-
7), 31.5 (C-16), 30.3 (C-21), 29.9 (C-15), 28.1 (C-23), 27.8 ((CH3)2C),
26.2 (C-2), 26.1 ((CH3)2C), 25.5 (C-12), 20.8 (C-11), 19.5 (C-30), 17.9
(C-6), 17.6 (C-600), 16.6 (C-24), 16.1 (C-25), 15.4 (C-26), 14.5 (C-27).
HR-ESI-MS m/z 1687.7157 [MþNa]þ (calcd for C99H108O23Na:
1687.7174).
(MeOH/H2O 3:2 to 4:1) to afford pure 3 (5.4 mg, 60%, two steps) as
a white amorphous powder. Rf 0.68 (CH2Cl2/MeOH 3:1); [
25
a
]
ꢁ24.6
D

C. Gauthier et al. / Tetrahedron 64 (2008) 7386–7399
7399
19. Cichewicz, R. H.; Kouzi, S. A. Med. Res. Rev. 2004, 24, 90–114.
20. Eiznhamer, D. A.; Xu, Z.-Q. IDrugs 2004, 7, 359–373.
21. Bang Son, L.; Kaplun, A. P.; Symon, A. V.; Shpilevsky, A. A. Proc. Int. Symp.
Control. Rel. Bioact. Mater. 1998, 25, 419–420.
4.25. 28-O-
b
-
D
-Glucopyranosyl betulinic acid 3
b-O-
a
-L-rhamnopyranosyl-(1/2)-a-L
-arabinopyranoside (4)
22. Ja¨ger, S.; Winkler, K.; Pfu¨ller, U.; Scheffler, A. Planta Med. 2007, 73, 157–162.
23. Krasutsky, P. A. Nat. Prod. Rep. 2006, 23, 919–942.
24. Kvasnica, M.; Sarek, J.; Klinitova, E.; Dzubak, P.; Hajduch, M. Bioorg. Med. Chem.
2005, 13, 3447–3454.
This compound was prepared from 26 (80 mg, 0.048 mmol) in
the same manner as that described for compound 23a. Purification
by C-18 reversed phase flash chromatography (MeOH/H2O 3:2 to
25. Jeong, H.-J.; Chai, H.-B.; Park, S.-Y.; Kim, D. S. H. L. Bioorg. Med. Chem. Lett. 1999,
9, 1201–1204.
26. Saxena, B. B.; Zhu, L.; Hao, M.; Kisilis, E.; Katdare, M.; Oktem, O.; Bomshteyn, A.;
Rathnam, P. Bioorg. Med. Chem. 2006, 14, 6349–6358.
27. Gauthier, C.; Legault, J.; Lebrun, M.; Dufour, P.; Pichette, A. Bioorg. Med. Chem.
2006, 14, 6713–6725.
28. Thibeault, D.; Gauthier, C.; Legault, J.; Bouchard, J.; Dufour, P.; Pichette, A.
Bioorg. Med. Chem. 2007, 15, 6144–6157.
29. Mimaki, Y.; Yokosuka, A.; Kuroda, M.; Hamanaka, M.; Sakuma, C.; Sashida, Y.
J. Nat. Prod. 2001, 64, 1226–1229.
30. Braca, A.; Autore, G.; De Simone, F.; Marzocco, S.; Morelli, I.; Venturella, F.; De
Tommasi, N. Planta Med. 2004, 70, 960–966.
31. Bang, S.-C.; Kim, Y.; Lee, J.-H.; Ahn, B.-Z. J. Nat. Prod. 2005, 68, 268–272.
32. Ohara, S.; Hishiyama, S. Mokuzai Gakkaishi 1994, 40, 444–451.
3:1) afforded pure 4 (35 mg, 82%, two steps) as a white amorphous
25
powder. Rf 0.49 (CH2Cl2/MeOH 3:1); [
a
]
ꢁ36.0 (c 0.1, MeOH); 1H
D
NMR (CD3OD, 400 MHz)
d
: 5.49 (d, J¼8.2 Hz, 1H, H-1%), 5.10 (d,
J¼1.4 Hz,1H, H-100), 4.71 (d, J¼1.6 Hz,1H, H-29), 4.59 (br s,1H, H-29),
4.53 (d, J¼4.6 Hz, 1H, H-10), 3.87 (dd, J¼3.3, 1.7 Hz, 1H, H-200), 3.84
(m, 1H, H-6%), 3.83 (m, 1H, H-50), 3.80 (m, 1H, H-500), 3.78 (m, 1H, H-
40), 3.76 (m,1H, H-20), 3.74 (m,1H, H-30), 3.70 (m,1H, H-6%), 3.69 (m,
1H, H-300), 3.47 (m,1H, H-50), 3.42 (m,1H, H-3%), 3.38 (m,1H, H-5%),
3.38 (m, 1H, H-400), 3.37 (m, 1H, H-4%), 3.32 (m, 1H, H-2%), 3.08 (dd,
J¼11.4, 4.3 Hz,1H, H-3), 3.00 (td, J¼11.0, 4.6 Hz,1H, H-19), 2.39–2.27
(m, 2H), 2.03–1.78 (m, 3H), 1.70 (s, 3H, H-30), 1.21 (d, J¼6.2 Hz, 3H,
H-600), 1.00 (s, 3H, H-27), 0.99 (s, 3H, H-23), 0.96 (s, 3H, H-26), 0.87
(s, 3H, H-25), 0.82 (s, 3H, H-24), 0.74 (d, J¼9.1 Hz, 1H, H-5). 13C NMR
ˇ ˇ
´
´
ˇˇ´
´
33. Klinitova´, E.; Krecek, V.; Klinot, J.; Endova, M.; Eisenreichova, J.; Budesınsky, M.;
ˇ
´
Stıcha, M. Collect. Czech. Chem. Commun. 1997, 62, 1776–1798.
34. Ohara, S.; Ohira, T. J. Wood Sci. 2003, 49, 59–64.
35. Samoshina, N. F.; Denisenko, M. V.; Denisenko, V. A.; Uvarova, N. I. Chem. Nat.
Compd. 2003, 39, 575–582.
(CD3OD, 100 MHz) d: 176.2 (C-28), 151.9 (C-20), 110.3 (C-29), 104.8
(C-10), 102.1 (C-100), 95.2 (C-1%), 90.7 (C-3), 78.8 (C-5%), 78.4 (C-3%),
76.9 (C-20), 74.1 (C-2%), 73.9 (C-400), 73.1 (C-30), 72.2 (C-200), 72.2 (C-
300), 71.1 (C-4%), 70.2 (C-500), 68.4 (C-40), 63.8 (C-50), 62.4 (C-6%), 57.9
(C-17), 57.2 (C-5), 52.0 (C-9), 50.6 (C-18), 48.4 (C-19), 43.6 (C-14),
42.1 (C-8), 40.4 (C-4), 40.2 (C-1), 39.4 (C-13), 38.1 (C-10), 37.5 (C-22),
35.5 (C-7), 32.8 (C-16), 31.5 (C-21), 30.8 (C-15), 28.5 (C-23), 27.2 (C-
2), 26.9 (C-12), 22.1 (C-11), 19.5 (C-30), 19.4 (C-6), 18.0 (C-600), 16.9
(C-24),16.9 (C-25),16.7 (C-26),15.2 (C-27). HR-ESI-MS m/z 919.5022
[MþNa]þ (calcd for C47H76O16Na: 919.5026).
36. Pakulski, Z. Pol. J. Chem. 2005, 79, 361–367.
37. Cmoch, P.; Pakulski, Z.; Swaczynova´, J.; Strnad, M. Carbohydr. Res. 2008, 343,
995–1003.
38. Park, H.-J.; Kwon, S.-H.; Lee, J.-H.; Lee, K.-H.; Miyamoto, K.-I.; Lee, K.-T. Planta
Med. 2001, 67, 118–121.
39. Bang, S.-C.; Lee, J.-H.; Song, G.-Y.; Kim, D.-H.; Yoon, M.-Y.; Ahn, B.-Z. Chem.
Pharm. Bull. 2005, 53, 1451–1454.
40. Bang, S.-C.; Seo, H.-S.; Yun, H.-Y.; Jung, S.-H. Chem. Pharm. Bull. 2007, 55,
1734–1739.
41. Gao, X.-D.; Ye, W.-C.; Yu, A. C. H.; Zhang, Y.; Tan, R.-X.; Li, M.; Hsiao, W. L. W.
Planta Med. 2003, 69, 171–174.
42. Glebko, L. I.; Krasovskaj, N. P.; Strigina, L. I.; Ulanova, K. P.; Denisenko, V. A.;
Dmitrenok, P. S. Russ. Chem. B. 2002, 51, 1945–1950.
43. Ye, W.; Zhang, Q.; Hsiao, W. W. L.; Zhao, S.; Che, C.-T. Planta Med. 2002, 68,
183–186.
Acknowledgements
´
44. Ple, K.; Chwalek, M.; Voutquenne-Nazabadioko, L. Eur. J. Org. Chem. 2004,
We thank Marianne Piochon for her contribution in organic
synthesis and Professor François-Xavier Garneau for his corrections
and helpful commentaries about this manuscript. The financial
1588–1603.
´
45. Ple, K.; Chwalek, M.; Voutquenne-Nazabadioko, L. Tetrahedron 2005, 61,
4347–4362.
46. Yan, M.-C.; Liu, Y.; Lu, W.-X.; Wang, H.; Sha, Y.; Cheng, M.-S. Carbohydr. Res.
2008, 343, 780–784.
47. Pellissier, H. Tetrahedron 2004, 60, 5123–5162.
48. Wang, P.; Li, C.; Zang, J.; Song, N.; Zhang, X.; Li, Y. Carbohydr. Res. 2005, 340,
2086–2096.
49. Peng, W.; Han, X.; Yu, B. Synthesis 2004, 10, 1641–1647.
50. Schmidt, R. R. Adv. Carbohydr. Chem. Biochem. 1994, 50, 21–123.
51. Deng, S.; Yu, B.; Xie, J.; Hui, Y. J. Org. Chem. 1999, 64, 7265–7266.
52. Li, C.-X.; Zang, J.; Wang, P.; Zhang, X.-L.; Guan, H.-S.; Li, Y.-X. Chin. J. Chem. 2006,
24, 509–517.
53. Peng, W.; Sun, J.; Lin, F.; Han, X.; Yu, B. Synlett 2004, 259–262.
54. Yu, B.; Xie, J.; Deng, S.; Hui, Y. J. Am. Chem. Soc. 1999, 121, 12196–12197.
55. Du, Y.; Pan, Q.; Kong, F. Carbohydr. Res. 2000, 323, 28–35.
´
´
support of Fonds Quebecois de la Recherche sur la Nature et les
Technologies (FQRNT, fonds forestier 02) is gratefully acknowl-
`
edged. Charles Gauthier thanks Programme d’Aide Institutionnel a
´
´
`
la Recherche de l’Universite du Quebec a Chicoutimi (PAIR-UQAC),
Fondation de l’UQAC, Association Francophone pour le Savoir
(ACFAS) and FQRNT for graduate scholarships.
References and notes
1. Nisbet, L. J.; Moore, M. Curr. Opin. Biotechnol. 1997, 8, 708–712.
2. Butler, M. S. J. Nat. Prod. 2004, 67, 2141–2153.
´
56. Gandolfi-Donadıo, L.; Gallo-Rodriguez, C.; de Lederkremer, R. M. Can. J. Chem.
2006, 84, 486–491.
3. Balunas, M. J.; Kinghorn, A. D. Life Sci. 2005, 78, 431–441.
4. McChesney, J. D.; Venkataraman, S. K.; Henri, J. T. Phytochemistry 2007, 68,
2015–2022.
57. Zhang, Y.; Li, Y.; Zhu, S.; Guan, H.; Lin, F.; Yu, B. Carbohydr. Res. 2004, 339,
1753–1759.
58. Plaza, A.; Cinco, M.; Tubaro, A.; Pizza, C.; Piacente, X. J. Nat. Prod. 2003, 66,
1606–1610.
59. Voutquenne, L.; Guinot, P.; Froissard, C.; Thoison, O.; Litaudon, M.; Lavaud, C.
Phytochemistry 2005, 66, 825–835.
60. Deng, S.; Yu, B.; Hui, Y.; Yu, H.; Han, X. Carbohydr. Res. 1999, 317, 53–62.
61. Li, B.; Yu, B.; Hui, Y.; Li, M.; Han, X.; Fung, K.-P. Carbohydr. Res. 2001, 331,
1–7.
62. Roy, B.; Pramanik, K.; Mukhopadhyay, B. Glycoconjugate J. 2008, 25, 157–166.
63. Cheng, M.-S.; Yan, M.-C.; Liu, Y.; Zheng, L.-G.; Liu, J. Carbohydr. Res. 2006, 341,
60–67.
5. Newman, D. J.; Cragg, G. M. J. Nat. Prod. 2007, 70, 461–477.
6. Vincken, J.-P.; Heng, L.; de Groot, A.; Gruppen, H. Phytochemistry 2007, 68,
275–297.
7. Sparg, S. G.; Light, M. E.; van Staden, J. J. Ethnopharmacol. 2004, 94, 219–243.
8. Oda, K.; Matsuda, H.; Murakami, T.; Katayama, S.; Ohgitani, T.; Yoshikawa, M.
Biol. Chem. 2000, 381, 67–74.
9. Rao, A. V.; Gurfinkel, D. M. Drug Metabol. Drug Interac. 2000, 17, 211–235.
10. Qin, G.-W. Curr. Org. Chem. 1998, 2, 613–625.
11. Liu, J.; Henkel, T. Curr. Med. Chem. 2002, 9, 1483–1485.
12. Bruneton, J. Pharmacognosie, Phytochimie, Plantes Me´dicinales; Editions
´
64. Agrawal, P. K. Phytochemistry 1992, 31, 3307–3330.
65. Liu, Y.; Ding, N.; Xiao, H.; Li, Y. J. Carbohydr. Chem. 2006, 25, 471–489.
66. Levy, D. E.; Fu¨ gedi, P. The Organic Chemistry of Sugars; CRC: Boca Raton, FL,
2006.
67. Bliard, C.; Massiot, G.; Nazabadioko, S. Tetrahedron Lett. 1994, 35, 6107–6108.
68. Hall, L. D.; Manville, J. F. Carbohydr. Res. 1967, 4, 512–513.
69. Gu, G.; Du, Y.; Linhardt, R. J. J. Org. Chem. 2004, 69, 5497–5500.
70. Piacente, S.; Pizza, C. J. Nat. Prod. 1995, 58, 512–519.
71. Schimmel, J.; Passos Eleute´rio, M. I.; Ritter, G.; Schmidt, R. R. Eur. J. Org. Chem.
2006, 1701–1721.
Technique & Documentation: Paris, 1995.
13. Yu, B.; Zhang, Y.; Tang, P. Eur. J. Org. Chem. 2007, 5145–5161.
14. Yogeeswari, P.; Sriram, D. Curr. Med. Chem. 2005, 12, 657–666.
15. Sami, A.; Taru, M.; Salme, K.; Jari, Y.-K. Eur. J. Pharm. Sci. 2006, 29, 1–13.
16. Kessler, J. H.; Mullauer, F. B.; de Roo, G. M.; Medema, J. P. Cancer Lett. 2007, 25,
132–145.
17. Pisha, E.; Chai, H.; Lee, I.-S.; Chagwedera, T. E.; Farnsworth, N. R.; Cordell, G. A.;
Beecher, C. W. W.; Fong, H. H. S.; Kinghorn, A. D.; Brown, D. M.; Wani, M. C.;
Wall, M. E.; Hieken, T. J.; Das Gupta, T. K.; Pezzuto, J. M. Nat. Med. 1995, 1,
1046–1051.
72. Yokosuka, A.; Kawakami, S.; Haraguchi, M.; Mimaki, Y. Tetrahedron 2008, 64,
1474–1481.
18. Zuco, V.; Supino, R.; Righetti, S. C.; Cleris, L.; Marchesi, E.; Gambacorti-Passerini,
C.; Formelli, F. Cancer Lett. 2002, 175, 17–25.