Full text of DOI:10.1016/j.carres.2018.03.006

Carbohydrate Research 461 (2018) 32e37
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis of bidesmosidic lupane saponins e comparison of batch and
continuous-flow methodologies
Anna Korda, Zbigniew Pakulski*, Piotr Cmoch, Katarzyna Gwardiak, Romuald Karczewski
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of lupane bidesmosides was optimized. The title compounds were obtained by glycosylation of
3-O- or 28-O-substituted betulin monodesmosides with Schmidt donors catalyzed by TMSOTf. Classical
batch procedure and microreactor technique were used and compared in the above synthesis. Experi-
mental results clearly showed that both methods are comparable, although any particular outcome
strongly depends on the structure of the reagents. Undesired allobetulin derivatives formed by the
Wagner-Meerwein rearrangement were usually isolated in minute amounts. In the case of batch reac-
tion, shorter reaction time significantly decreased formation of side-products.
Received 28 February 2018
Accepted 13 March 2018
Available online 15 March 2018
Keywords:
Lupane bidesmosides
Glycosylation
© 2018 Elsevier Ltd. All rights reserved.
Betulin
The Wagner-Meerwein rearrangement
Microreactors
1. Introduction
a century, continues to be a synthetic challenge due to the fact that
numerous factors affect the outcome of the process (stereo-
Betulin and betulinic acid e pentacyclic triterpenoids belonging
to the lupane family and easily accessible from bark of Betula spe-
cies e are regarded as interesting bioactive natural compounds and
valuable starting materials in synthesis [1,2]. Nevertheless, their
pharmacological use is often limited due to the poor solubility in
water. These problems can be addressed by introduction of polar
moieties at the C-3 and/or C-28 positions, e.g. by glycosylation to
form saponins. Saponins, owing to their broad range of medicinal
and biological properties, attract attention of numerous research
groups and their chemical synthesis has been recently reviewed
[3e6]. Monodesmosidic saponins of betulin were synthesized and
their structure-activity relationship studies were reported [7e10].
In contrast, the betulin bidesmosides persist as a difficult to prepare
target (Fig. 1). When the hydroxyl group at the C-28 position in
lupane skeleton is targeted during glycosylation process, the
Wagner-Meerwein rearrangement (Scheme 1) leading to allobe-
tulin derivatives usually predominates [11e15], although some
exceptions are known [16,17]. Since the bidesmosidic saponins are
considered to be less haemolytic than monodesmosidic congeners,
it is worthwhile to develop a general and efficient method of their
synthesis [18,19].
electronic effects, conformation and stereochemistry of reagents,
concentration, temperature, reaction time, to name few).
a
Recently, flow reactors became available in laboratory environment
and they can offer advantage over traditional batch reactors, due to
the differences in reagent contact time, mixing characteristics and
heat transport [20,21]. In the recent example of oligosaccharide
synthesis, flow reactor proved to be superior over traditional flask
methodology because better control of the contact of the reagents
minimized side reaction [22e28].
As stated earlier, synthesis of lupane saponins by glycosylation
of the 28-OH group of betulin derivatives 1 is often accompanied by
the Wagner-Meerwein rearrangement, promoted by the Lewis
acids, leading to allobetulin derivatives 2 (Scheme 1) [29]. In the
case of betulin glycosylated at the 28-O-position (3), the recently
observed sugar migration induced by the Wagner-Meerwein rear-
rangement leading to 3-O-glycosylated allobetulin 4 derivatives
must also be considered as potentially high-yielding side-reaction
(Scheme 2) [30].
Herein, we report on the synthesis of bidesmosidic betulin sa-
ponins by the glycosylation of monodesmosides and side-by-side
comparison of the batch and flow methodologies. Two ap-
proaches to the bidesmosides were proposed, differing in order of
attaching sugar moieties to the betulin core. In the first approach,
monodesmoside 5 [30] substituted at the 28-O position was gly-
cosylated at the 3-OH position in reaction with the tri-
chloroacetimidate sugar donors under Schmidt's procedure [31,32].
Glycosylation reaction, although universally performed for over
* Corresponding author.
E-mail address: zbigniew.pakulski@icho.edu.pl (Z. Pakulski).
https://doi.org/10.1016/j.carres.2018.03.006
0008-6215/© 2018 Elsevier Ltd. All rights reserved.

A. Korda et al. / Carbohydrate Research 461 (2018) 32e37
33
Fig. 1. Lupane type triterpenoids and saponins.
Scheme 1. The Wagner-Meerwein rearrangement of betulin derivatives.
Scheme 2. Sugar migration induced by the Wagner-Meerwein rearrangement.
In the second approach, compound 16 [11] substituted at the 3-O
position was used as a starting material. Classical flask technique
and microflow methodology were compared to identify the best
conditions for the preparation of lupane bidesmosides.
bidesmoside 10 was observed for reaction performed at ꢁ40 ꢂC
(87%, Table 1, entry 4). In most cases, allobetulin glycoside 11 was
also isolated in low to moderate yield (11e31%) as a by-product.
Reaction of 5 with -mannopyranosyl trichloroacetimidate 7
D
[35] performed at ꢁ40 ꢂC was selective and afforded required
bidesmoside 12 as the only product (Table 1, entries 8, 10, and 12).
Under flow conditions, even at 0 ꢂC, rearrangement rate was low
and allobetulinyl mannoside 13 [30] was obtained in 6e14% yield,
only (Table 1, entries 9, 11). Under optimal conditions bidesmoside
12 was isolated in 78e80% yield (Table 1, entries 7 and 9).
2. Results and discussion
In the initial batch experiment, monodesmosidic saponin 5
glycosylated at the 28-O position was reacted with L-rhamnopyr-
anosyl trichloroacetimidate 6 [33] under standard conditions
(Scheme 3) [34]. Expected bidesmoside 10 [17] was obtained in 67%
yield together with allobetulin glycoside 11 [30] which was isolated
in 28% yield (Table 1, entry 1). Shorter reaction time inhibited for-
mation of the rearranged product 11, but at the cost of lower yield
of desired product 10 (Table 1, entry 2, 46%).
Next, the microreactor was used to carry out the same reaction
(Fig. 2). Flow experiments were performed in a coil reactor (PTFE
microtube, OD ꢀ ID ꢀ L, 1/16” ꢀ 0.040” ꢀ 2 m) equipped with two
Y-connectors and immersed in a cooling bath as described in pre-
vious paper [27]. Preliminary experiments allowed to determine
the optimal residence time and concentration that resulted in a full
conversion of the starting materials. The highest yield of
Similarly, glycosylation of
5
with
D-idopyranosyl tri-
chloroacetimidate 8 [16] gave bidesmoside 14 in high yield
(86e88%; Table 1, entries 13, 16, and 18). Allobetulinyl idopyrano-
side 15, i.e. a by-product, was observed at a low yield (5e23%).
In the second step, monodesmosidic saponin 16, with sugar
moiety at the 3-O position was used as a starting material (Scheme
4, Table 2). Its reaction with
L
-rhamnopyranosyl donor 6 at ꢁ40 ꢂC
was highly selective towards bidesmosidic saponin 17 which was
isolated in approx. 83% from batch experiments (Table 2, entries 1,
2), and in 95% from microflow reaction (Table 2, entry 4). At 0 ꢂC
moderate amount (18e20%) of allobetulin 21 [30] was also ob-
tained (Table 2, entries 3, 5). Reaction with -manno derivative 7
D

34
A. Korda et al. / Carbohydrate Research 461 (2018) 32e37
Scheme 3. i: Glycosyl donor (6-8), CH2Cl2, TMSOTf.
Table 1
Synthesis of bidesmosidic saponins by glycosylation of monodesmoside 5.
Entry
Glycosyl donor
Reaction mode
Time (min)
Temp. (ꢂC)
TMSOTf
Bidesmosidic Saponin (isolated yield, %)
Allobetulin glycoside (isolated yield, %)
1
2
3
4
5
6
6
6
6
6
6
6
batch
batch
flow
flow
flow
flow
30
5
4
4
4
ꢁ40
ꢁ40
0
60 mol%
60 mol%
0.01 M
0.01 M
0.003 M
0.003 M
10 (67)
10 (46)
10 (49)
10 (87)
10 (56)
10 (57)
11 (28)
e
11 (31)
11 (11)
11 (12)
e
ꢁ40
0
4
ꢁ40
7
8
9
10
11
12
7
7
7
7
7
7
batch
batch
flow
flow
flow
flow
30
5
4
4
4
ꢁ40
ꢁ40
0
60 mol%
60 mol%
0.01 M
0.01 M
0.003 M
0.003 M
12 (78)
12 (57)
12 (80)
12 (51)
12 (56)
12 (53)
13 (16)
e
13 (14)
e
ꢁ40
0
13 (6)
e
4
ꢁ40
13
14
15
16
17
18
8
8
8
8
8
8
batch
batch
flow
flow
flow
flow
30
5
4
4
4
ꢁ40
ꢁ40
0
60 mol%
60 mol%
0.01 M
0.01 M
0.003 M
0.003 M
14 (86)
14 (73)
14 (50)
14 (87)
14 (37)
14 (88)
15 (8)
e
15 (23)
15 (12)
15 (5)
e
ꢁ40
0
4
ꢁ40
yield was obtained in batch experiments (79e81%, Table 2, entries
19 and 20), whereas in microflow reaction the isolated yield and
selectivity were slightly lower (71% in best run, Table 2, entry 23).
As expected, the stereoselectivity of glycoside bond formation
was governed by the presence of benzoyl protecting groups in
sugar donors [37]. In all cases, the 1,2-trans linkage was formed
exclusively as confirmed by the chemical shifts of anomeric protons
and carbon atoms as well as J1,2 coupling constants. Observed
rearrangement of -arabinopyranoside 16 to the allobetulin glyco-
L
side 21 was expected. It is well known that due to the presence of
free 28-OH group such compounds are prone to the Wagner-
Merweein rearrangement. On the other hand, the loss of the ara-
binopyranosyl fragment from the 28-O position and rearrangement
to allobetulin during glycosylation of saponin 5 leading to glyco-
sides 11, 13, and 15 was observed for the first time. Recently we
described a similar transformation where the sugar migration from
the 28-O to 3-O position was forced by the Wagner-Meerwein
rearrangement [30]. It required, however, a much longer reaction
time, higher temperature and relatively high concentration of the
Lewis acid. Here, the loss of a sugar moiety was complete within
minutes. Interestingly, migration of the arabinopyranosyl fragment
from the 28-O to 3-O position was not observed. It may suggest that
glycosylation of acceptor 5 in the 3-O position by external Schmidt
donor is much faster than migration of sugar fragment from 28-O
position.
Fig. 2. Coil microreactor.
was, however, less selective. Disubstituted product 18 was isolated
in 54% yield under batch technique (Table 2, entry 8), and in 79%
yield under flow conditions; allobetulin 21 was isolated in 7%
(Table 2, entry 10).
The highest yield of -idopyranoside 19 was observed under
D
classical conditions (93%, Table 2, entry 13); minute amounts of
allobetulinyl derivative 21 (5%) were also isolated. Both yield and
selectivity were lower in microreactor, reaching 72% yield of the
expected bidesmoside 19 at ꢁ40 ꢂC (Table 2, entry 16). Similarly,
bis-
L
-arabinoside 20 was prepared by glycosylation of 16 with the
known
L
-arabinopyranosyl trichloroacetimidate 9 [36]. The highest

A. Korda et al. / Carbohydrate Research 461 (2018) 32e37
35
Scheme 4. i: Glycosyl donor (6-9), CH2Cl2, TMSOTf.
Table 2
Synthesis of bidesmosidic saponins by glycosylation of monodesmoside 16.
Entry Glycosyl donor Reaction mode Time (min) Temp. (ꢂC) TMSOTf Bidesmosidic saponin (isolated yield, %) Allobetulin glycoside 21 (isolated yield, %)
1
2
3
4
5
6
6
6
6
6
6
6
batch
batch
flow
flow
flow
flow
30
5
4
4
4
ꢁ40
ꢁ40
0
60 mol% 17 (83)
60 mol% 17 (82)
e
e
0.01 M
0.01 M
17 (71)
17 (95)
(20)
e
ꢁ40
0
0.003 M 17 (61)
0.003 M 17 (67)
(18)
e
4
ꢁ40
7
8
9
10
11
12
7
7
7
7
7
7
batch
batch
flow
flow
flow
flow
30
5
4
4
4
ꢁ40
ꢁ40
0
60 mol% 18 (47)
60 mol% 18 (54)
(15)
e
0.01 M
0.01 M
18 (39)
18 (79)
(20)
(7)
(13)
(4)
ꢁ40
0
0.003 M 18 (57)
0.003 M 18 (53)
4
ꢁ40
13
14
15
16
17
18
8
8
8
8
8
8
batch
batch
flow
flow
flow
flow
30
5
4
4
4
ꢁ40
ꢁ40
0
60 mol% 19 (93)
60 mol% 19 (40)
(5)
e
0.01 M
0.01 M
19 (52)
19 (72)
(37)
(10)
(18)
e
ꢁ40
0
0.003 M 19 (43)
0.003 M 19 (63)
4
ꢁ40
19
20
21
22
23
24
9
9
9
9
9
9
batch
batch
flow
flow
flow
flow
30
5
4
4
4
ꢁ40
ꢁ40
0
60 mol% 20 (81)
60 mol% 20 (79)
(19)
e
0.01 M
0.01 M
20 (63)
20 (56)
(20)
e
ꢁ40
0
0.003 M 20 (71)
0.003 M 20 (54)
(20)
e
4
ꢁ40
3. Conclusions
somewhat unpredictable. The exact results depend on the structure
of the starting materials and products, thus optimization of the
reaction conditions is highly advisable in every case. In our opinion,
development of a general method for lupane bidesmosides syn-
thesis is being hindered by unusual chemical properties of betulin
and betulin saponins. The above problems may be perfectly
concluded with the famous Paulsen's observation, that "each
oligosaccharide synthesis remains an independent problem, whose
resolution requires considerable systematic research and a good deal
of know-how. There are no universal reaction conditions for oligo-
saccharide syntheses" [38].
Herein we described the first synthesis of betulin bidesmosides
in a microfluidic system and compared the flow methodology with
the classical batch technique. A series of saponins were synthesized
by a glycosylation of monodesmosides with Schmidt donors. Pre-
sented results demonstrate that the synthesis of betulin bidesmo-
sides can be efficiently realized using either the classical batch or
the flow methodologies, but a very careful control of the reaction
conditions is necessary to limit formation of undesired allobetulin
derivatives. The target bidesmosides were isolated in a high yield.
In some cases, the easy to separate products of the Wagner-
Meerwein rearrangement were also isolated as by-products. Usu-
ally, the higher yield and/or better selectivity toward bidesmosides
were observed for the reactions carried out in microreactor. In
batch experiments, the shorter reaction time restricted formation
of allobetulin derivatives.
4. Experimental
General procedures. Silica gel HF254 was used for TLC and
preparative TLC. Silica gel 230e400 mesh was used for column
chromatography. 1H and 13C NMR spectra were recorded at 298 K
with a Varian NMR-vnmrs600 or vnmrs500 spectrometers, using
standard experimental conditions and Varian software (ChemPack
4.1). Configurational assignments were based on the NMR mea-
surements, generated using two-dimensional techniques like COSY
Presented methodologies may be considered as highly effective
synthetic methods for the preparation of lupane bidesmosides.
However, according to our experience, susceptibility of lupane
monodesmosides to the Wagner-Meerwein rearrangement is

36
A. Korda et al. / Carbohydrate Research 461 (2018) 32e37
and 1H-13C gradient selected HSQC (g-HSQC), as well as 1H-13
C
28), 3.34 (dd, 1 H, J 4.3, 11.7 Hz, H-3), 2.34e2.38 (m, 1 H, H-19),
1.96e2.01 (m, 2 H, H-21, H-22), 1.82e1.85 (m, 2 H, H-1, H-2), 1.66 (s,
3 H, H-30), 1.62 (H-12), 1.57 (H-13), 1.49 (H-18), 1.45 (H-2), 1.39 (H-
15), 1.38 (H-6), 1.37 (H-21), 1.35 (H-11), 1.28 (H-6), 1.24 (H-16), 1.14
(H-7, H-11), 1.12 (H-9), 1.04 (H-7, H-16), 1.02 (s, 3 H, H-23), 1.00 (H-
22), 0.99 (H-12), 0.88 (s, 3 H, H-26), 0.87 (s, 3 H, H-27), 0.76 (s, 3 H,
H-25), 0.70 (s, 3 H, H-24), 0.70 (H-1), 0.64 (H-15), 0.52 (H-5). 13C
gradient selected HMBC (g-HMBC). Internal TMS was used as the 1H
and 13C NMR chemical shift standard. J values are given in Hertz.
High-resolution mass spectra (HRMS ESI) were acquired with
Mariner and MaldiSYNAPT G2-S HDMS (Waters) mass spectrome-
ters. Optical rotations were recorded on a Jasco P-2000 automatic
polarimeter.
NMR (CDCl3) d: 166.1,165.7,165.6,165.3,165.2,165.1,164.7,150.3 (C-
4.1. Glycosylation of saponins 5 and 16
20), 128.2e133.5 (CAr), 109.7 (C-29), 101.6 (C-10), 93.7 (C-100), 82.9
(C-3), 70.5 (C-30), 70.0 (C-20), 68.6 (C-28), 68.4 (C-40), 68.1 (C-200),
67.2 (C-300 or C-400), 66.8 (C-300 or C-400), 64.6 (C-500), 63.6 (C-600), 62.5
(C-50), 55.8 (C-5), 50.3 (C-9), 48.7 (C-18), 47.9 (C-19), 47.0 (C-17),
42.6 (C-14), 40.7 (C-8), 38.4 (C-4), 38.2 (C-1), 37.6 (C-13), 37.0 (C-
10), 34.8 (C-22), 33.8 (C-7), 29.7 (C-21), 29.2 (C-16), 28.5 (C-23), 27.0
(C-15), 25.1 (C-12), 21.5 (C-2), 20.8 (C-11), 19.0 (C-30), 18.1 (C-6),
16.2 (C-24), 16.0 (C-25), 15.8 (C-26), 14.9 (C-27). HR-MS (ESI) calc.
for C90H96NaO18 [MþNa]þ: 1487.6494. Found: 1487.6497.
Method A e batch methodology. A solution of glycosyl donor (6-9,
0.10 mmol) and acceptor 5 or 16 (71 mg, 0.08 mmol) in dichloro-
methane (8 mL) was stirred for 20 min at room temperature over
molecular sieves (4 Å, 300 mg, finely ground), then cooled
to ꢁ40 ꢂC, TMSOTf (10
mL, 0.06 mmol) was added, and the mixture
was stirred (see Tables for details), quenched with Et3N (0.5 mL),
and the solvents were removed under diminished pressure. Col-
umn chromatography (hexaneeethyl acetate, 40: 1 /5: 1) of the
residue yielded the protected saponins as white foam.
4.1.3. 3
b
-O-(2,3,4,6-Tetra-O-benzoyl-
a
-D-idopyranosyl) allobetulin
Method B e microflow technique. Syringe A (Fig. 2) was filled
with solution of a glycosyl donor (0.10 mmol) and the corre-
sponding acceptor (0.08 mmol) in dry dichloromethane (5 mL).
Syringe B contained solution of TMSOTf (0.01 M or 0.003 M in
dichloromethane, 6 mL). The reagents were then fed into the
microreactor filled with dichloromethane via a double syringe
pump and the residence time was adjusted to 4 min by controlling
the pumping rate. Reaction was quenched by injection of 5% solu-
tion of triethylamine in dichloromethane placed in syringe C into
the reaction stream at the bath temperature. Reaction mixture
leaving microreactor was collected, concentrated and the residue
was purified by column chromatography as described in Method A.
(15)
20
[
a
]
70.5 (c 0.2, chloroform). 1H NMR (CDCl3)
d
: 7.15e8.17 (m,
D
20 H, HAr), 5.59 (br s, 1 H), 5.41 (br s, 1 H), 5.32 (br s, 1 H) 5.20 (br s,
1 H), 4.97e5.00 (m, 1 H, H-50), 4.68 (dd, 1 H, J6,5 8.2, J6,6 11.5 Hz, H-
0
60), 4.59 (dd, 1 H, J6,5 4.3, J6,6 11.5 Hz, H-6 ), 3.78 (d, 1 H, J 7.6, H-28),
3.53 (s, 1 H, H-19), 3.45 (d, 1 H, J 7.6, H-28), 3.36 (dd, 1 H, J 4.3,
11.7 Hz, H-3), 0.56e1.88 (m, 24 H, lupane protons), 1.02 (s, 3 H, CH3),
0.95 (s, 3 H, CH3), 0.94 (s, 3 H, CH3), 0.92 (s, 3 H, CH3), 0.81 (s, 3 H,
0
0
CH3), 0.80 (s, 3 H, CH3), 0.70 (s, 3 H, CH3). 13C NMR (CDCl3)
d: 166.1,
165.3, 165.2, 164.7, 133.5, 133.2, 128.2e130.2 (CAr), 93.9 (C-10), 87.9
(C-19), 83.1 (C-3), 71.2 (CH2), 68.2, 67.2, 66.8, 64.6, 63.7 (CH2), 56.0,
51.0, 46.8, 41.5 (C), 40.7 (C), 40.6 (C), 38.4 (CH2), 37.1 (C), 36.8 (CH2),
36.3 (C), 34.1, 33.9 (CH2), 32.7 (CH2), 28.8, 28.5, 26.4 (CH2), 26.3
(CH2), 24.5, 21.6 (CH2), 21.0 (CH2), 18.2 (CH2), 16.4, 16.2, 15.7, 13.6.
HR-MS (ESI) calc. for C64H76NaO11 [MþNa]þ: 1043.5285. Found:
1043.5283.
4.1.1. 28-O-20,30,40-Tri-O-benzoyl-
a
-
L
-arabinopyranosylbetulin 3
-mannopyranoside (12)
64.2 (c 0.3, chloroform). 1H NMR (CDCl3)
d: 7.27e8.10 (m,
D
b-
O-200,300,400,600-tetra-O-benzoyl-
a-D
20
[a
]
35 H, HAr), 6.09 (t, 1 H, J4,3 ¼ J4,5 ¼10.1 Hz, H-400), 5.91 (dd, 1 H, J3,2
3.2, J3,4 10.1 Hz, H-300), 5.73 (dd, 1 H, J2,1 6.2, J2,3 8.6 Hz, H-20),
5.68e5.70 (m, 1 H, H-40), 5.61e5.64 (m, 2 H, H-200, H-30), 5.27 (d, 1 H,
J1,2 1.2 Hz, H-100), 4.71 (d, 1 H, J1,2 6.2 Hz, H-10), 4.65e4.69 (m, 2 H, H-
4.1.4. 3
O-200,300,400-tri-O-benzoyl-
20 107.0 (c 0.3, chloroform). 1H NMR (CDCl3)
d: 7.23e8.11 (m,
b
-O-20,30,40-Tri-O-benzoyl-
-rhamnopyranoside (17)
a-L-arabinopyranosylbetulin 28-
a-L
[
a
]
D
600, H-29), 4.52e4.56 (m, 2 H, H-500, H-29), 4.47 (dd, 1 H, J6,5 5.0, J6,6
30 H, HAr), 5.79 (dd, 1 H, J3,2 3.4, J3,4 10.0 Hz, H-300), 5.76 (dd, 1 H, J2,1
6.4, J2,3 8.9 Hz, H-20), 5.69 (dd, 1 H, J2,1 1.6, J2,3 3.4 Hz, H-200),
5.67e5.68 (m, 1 H, H-40), 5.66 (t, 1 H, J4,3 ¼ J4,5 ¼10.0 Hz, H-400), 5.59
(dd, 1 H, J3,2 8.9, J3,4 3.6 Hz, H-30), 4.96 (d, 1 H, J1,2 1.6 Hz, H-100), 4.78
(d, 1 H, J1,2 6.4 Hz, H-10), 4.73 (br s, 1 H, H-29), 4.61 (br s, 1 H, H-29),
0
0
12.0 Hz, H-600), 4.33 (dd, 1 H, J5,4 4.1, J5,5 12.7 Hz, H-5 ), 3.92 (dd, 1 H,
0
0
0
J5,4 1.9, J5,5 12.7 Hz, H-5 ), 3.68 (d, 1 H, J 8.8 Hz, H-28), 3.59 (d, 1 H, J
8.8 Hz, H-28), 3.33 (dd, 1 H, J 4.3, 11.7 Hz, H-3), 2.34e2.39 (m, 1 H),
1.95e2.02 (m, 2 H), 1.79e1.85 (m, 2 H), 0.63e1.70 (m, 20 H, lupane
protons), 1.66 (s, 3 H, CH3), 1.10 (s, 3 H, CH3), 0.95 (s, 3 H, CH3), 0.92
4.33 (dd, 1 H, J5,4 3.9, J5,5 12.9 Hz, H-50), 4.14 (dq, 1 H, J5,4 10.0, J5,6
0
(s, 3 H, CH3), 0.87 (s, 3 H, CH3), 0.85 (s, 3 H, CH3). 13C NMR (CDCl3)
d:
6.3 Hz, H-500), 3.87 (dd, 1 H, J5,4 2.0, J5,5 12.9 Hz, H-5 ), 3.60 (d, 1 H, J
9.3 Hz, H-28), 3.56 (d, 1 H, J 9.3 Hz, H-28), 3.14 (dd, 1 H, J 4.7, 11.7 Hz,
H-3), 2.47e2.51 (m, 1 H), 2.04e2.09 (m, 2 H), 1.96e2.02 (m, 1 H),
1.83e1.86 (m, 1 H), 0.63e1.81 (m, 20 H, lupane protons), 1.72 (s, 3 H,
CH3), 1.38 (d, 3 H, J 6.3 Hz, H-600), 0.99 (s, 3 H, CH3), 0.98 (s, 3 H, CH3),
0.80 (s, 3 H, CH3), 0.77 (s, 3 H, CH3), 0.64 (s, 3 H, CH3). 13C NMR
0
0
166.1, 165.8, 165.6, 165.6, 165.5, 165.1, 150.4 (C-20), 128.3e133.4
(CAr), 109.7 (C-29), 101.7 (C-10), 94.3 (C-100), 84.2 (C-3), 71.6, 70.5,
70.2, 70.0, 69.4, 68.6 (C-28), 68.5, 67.0, 63.1 (C-600), 62.6 (C-50), 55.6
(C-5), 50.3, 48.7, 47.9, 47.0 (C), 42.6 (C), 40.8 (C), 38.6 (C), 38.2 (CH2),
37.6, 37.1 (C), 34.8 (CH2), 33.9 (CH2), 29.7 (CH2), 29.2 (CH2), 28.8,
27.0 (CH2), 25.1 (CH2), 22.2 (CH2), 20.8 (CH2), 19.0, 18.2 (CH2), 16.5,
16.1, 15.9, 14.8. HR-MS (ESI) calc. for C90H96NaO18 [MþNa]þ:
1487.6494. Found: 1487.6495.
(CDCl3) d: 165.8, 165.6, 165.6, 165.5,165.2, 150.4 (C-20), 128.2e133.4
(CAr), 109.7 (C-29), 103.0 (C-10), 98.2 (C-100), 90.1 (C-3), 71.8 (C-400),
70.8 (C-200), 70.7 (C-30), 70.2 (C-20, C-300), 68.7 (C-40), 66.9 (C-500, C-
28), 62.6 (C-50), 55.5 (C-5), 50.3, 48.8, 47.9, 47.1 (C), 42.7 (C), 40.9 (C),
39.0 (C), 38.7 (CH2), 37.6, 36.8 (C), 35.1 (CH2), 34.1 (CH2), 30.1 (CH2),
29.8 (CH2), 27.7, 27.1 (CH2), 26.1 (CH2), 25.2 (CH2), 20.8 (CH2), 19.2,
18.1 (CH2), 17.8 (C-600), 16.0, 14.7. HR-MS (ESI) calc. for C83H92NaO16
[MþNa]þ: 1367.6283. Found: 1367.6289.
4.1.2. 28-O-20,30,40-Tri-O-benzoyl-
a
-
L
-arabinopyranosylbetulin 3
-idopyranoside (14)
79.6 (c 0.3, chloroform). 1H NMR (CDCl3)
d: 7.14e8.17 (m,
D
b-
O-200,300,400,600-tetra-O-benzoyl-
a-D
20
[a
]
35 H, HAr), 5.73 (dd, 1 H, J2,1 6.3, J2,3 8.6 Hz, H-20), 5.68e5.69 (m, 1 H,
H-40), 5.63 (dd, 1 H, J3,2 8.6, J3,4 3.5 Hz, H-30), 5.58 (br s, 1 H, H-300 or
H-400), 5.41 (br s, 1 H, H-300 or H-400), 5.32 (br s, 1 H, H-100), 5.19 (br s,
1 H, H-200), 4.97e4.99 (m, 1 H, H-500), 4.70 (d, 1 H, J1,2 6.3 Hz, H-10),
4.65e4.68 (m, 2 H, H-600, H-29), 4.56e4.60 (m, 2 H, H-600, H-29),
4.1.5. 3
b
-O-20,30,40-Tri-O-benzoyl-
a
-
L
-arabinopyranosylbetulin 28-
-mannopyranoside (18)
37.3 (c 0.2, chloroform). 1H NMR (CDCl3)
d: 7.25e8.11 (m,
D
O-200,300,400,600-tetra-O-benzoyl-
a-D
20
[
a
]
4.33 (dd, 1 H, J5,4 4.1, J5,5 12.8 Hz, H-50), 3.91 (dd, 1 H, J5,4 1.9, J5,5
12.8 Hz, H-50), 3.68 (d, 1 H, J 8.8 Hz, H-28), 3.58 (d, 1 H, J 8.8 Hz, H-
35 H, HAr), 6.13 (t, 1 H, J4,3 ¼ J4,5 ¼10.1 Hz, H-400), 5.88 (dd, 1 H, J3,2
0
0
3.3, J3,4 10.1 Hz, H-300), 5.75 (dd, 1 H, J2,1 6.4, J2,3 8.8 Hz, H-20),

A. Korda et al. / Carbohydrate Research 461 (2018) 32e37
37
5.72e5.74 (dd, 1 H, J2,1 1.4, J2,3 3.3 Hz, H-200), 5.66e5.68 (m, 1 H, H-
Acknowledgment
40), 5.59 (dd, 1 H, J3,2 8.8, J3,4 3.6 Hz, H-30), 5.06 (d, 1 H, J1,2 1.4 Hz, H-
100), 4.78 (d, 1 H, J1,2 6.4 Hz, H-10), 4.69e4.71 (m, 2 H, H-600, H-29),
This work was financially supported by the National Science
Centre, Poland (No. 2016/21/B/ST5/02141).
4.60 (br s, 1 H, H-29), 4.48 (dd, 1 H, J6,5 3.8, J6,6 12.2 Hz, H-600),
0
4.31e4.38 (m, 2 H, H-50, H-5000), 4.04 (d, 1 H, J 9.2 Hz, H-28), 3.87 (dd,
0
1 H, J5,4 1.8, J5,5 12.8 Hz, H-5 ), 3.25 (d, 1 H, J 9.2 Hz, H-28), 3.13 (dd,
1 H, J 4.6, 11.6 Hz, H-3), 2.38e2.43 (m, 1 H), 1.98e2.11 (m, 3 H),
0.63e1.85 (m, 25 H, lupane protons), 1.70 (s, 3 H, CH3), 0.98 (s, 3 H,
CH3), 0.93 (s, 3 H, CH3), 0.76 (s, 3 H, CH3), 0.75 (s, 3 H, CH3), 0.62 (s,
Appendix A. Supplementary data
Supporting Information Available. Copies of 1H and 13C NMR
spectra of all new compounds are provided.
Supplementary data related to this article can be found at
https://doi.org/10.1016/j.carres.2018.03.006.
3 H, CH3). 13C NMR (CDCl3)
d: 166.1, 165.8, 165.6, 165.5, 165.5, 165.4,
165.2, 150.2 (C-20), 128.3e133.4 (CAr), 109.8 (C-29), 103.0 (C-10),
98.5 (C-100), 90.1 (C-3), 70.7, 70.5, 70.2, 69.2, 68.6, 67.5 (C-28), 66.9,
62.8 (C-50), 55.5 (C-5), 50.3, 48.8, 48.0, 47.0 (C), 42.7 (C), 40.8 (C),
39.0 (C), 38.8 (CH2), 37.6, 36.8 (C), 34.6 (CH2), 34.2 (CH2), 30.1 (CH2),
29.8 (CH2), 27.7, 27.2 (CH2), 26.1 (CH2), 25.2 (CH2), 20.8 (CH2), 18.1
(CH2), 16.0, 14.8. HR-MS (ESI) calc. for C90H96NaO18 [MþNa]þ:
1487.6494. Found: 1487.6482.
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C
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b
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a-L-arabinopyranosylbetulin 28-
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1 H, J5,4 1.8, J5,5 12.9 Hz, H-5 or H-5 ), 3.66 (d, 1 H, J 8.9 Hz, H-28),
3.56 (d, 1 H, J 8.9 Hz, H-28), 3.12 (dd, 1 H, J 4.7, 11.6 Hz, H-3),
2.32e2.37 (m, 1 H), 1.93e2.00 (m, 2 H), 1.75e1.85 (m, 3 H),
0.95e1.62 (m, 18 H, lupane protons), 1.64 (s, 3 H, CH3), 0.86 (s, 3 H,
CH3), 0.84 (s, 3 H, CH3), 0.78 (s, 3 H, CH3), 0.76 (s, 3 H, CH3), 0.65 (s,
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47.0 (C), 42.5 (C), 40.7 (C), 39.0 (C), 38.7 (CH2), 37.6, 36.8 (C), 34.8
(CH2), 33.8 (CH2), 29.7 (CH2), 29.2 (CH2), 27.7, 27.0 (CH2), 26.1 (CH2),
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