O,O-Dimethylthiophosphonosulfenyl bromide-silver triflate: A new powerful promoter system for the preactivation of thioglycosides

Article abstract of DOI:10.1039/c0ob00380h

O,O-Dimethylthiophosphonosulfenyl bromide (DMTPSB) in combination with silver triflate provides a powerful thiophilic promoter system. Both "armed" and "disarmed" thioglycoside glycosyl donors can be activated to form glycosidic linkages efficiently by th

Full text of DOI:10.1039/c0ob00380h

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PAPER
O,O-Dimethylthiophosphonosulfenyl bromide-silver triflate: a new powerful
promoter system for the preactivation of thioglycosides†‡
Peng Peng and Xin-Shan Ye*
Received 5th July 2010, Accepted 1st October 2010
DOI: 10.1039/c0ob00380h
O,O-Dimethylthiophosphonosulfenyl bromide (DMTPSB) in combination with silver triflate provides
a powerful thiophilic promoter system. Both “armed” and “disarmed” thioglycoside glycosyl donors
can be activated to form glycosidic linkages efficiently by the pre-activation protocol. The usefulness of
this new promoter is illustrated by a successful iterative one-pot oligosaccharide assembly.
towards glycosylations.15 However, only limited promoters have
been used in pre-activation approach. The widely-used promot-
ers for thioglycoside activation (e.g. NIS/TfOH; NIS/AgOTf;
Introduction
Oligosaccharides and glycoconjugates play an important role in
many biological processes.1 However, understanding the functions
NIS/TESOTf) cannot be used in pre-activation one-pot oligosac-
of carbohydrates is hampered by the lack of general methods for
charide synthesis, due to the formation of succinimide by-products
the preparation of this class of compounds. In the past decades,
which may result in the complication of coupling products
and decrease the efficacy of glycosylations.5b,16 The promoters
currently used in pre-activation protocol mainly include benzene-
sulfinyl piperidine/triflic anhydride (BSP/Tf2O),15h diphenyl sul-
foxide/triflic anhydride (DPSO/Tf2O),15i p-toluenesulfinyl chlo-
ride/silver triflate (p-TolSCl/AgOTf),6 and benzenesulfinyl mor-
pholine/triflic anhydride (BSM/Tf2O).15l Recently, methyl triflate
(MeOTf) and Me3OBF4 have also been used for pre-activation
of thioglycosides.17 In spite of the promoters available, they still
have some disadvantages. For instance, p-TolSCl is unstable and
it needs to be distilled under an inert atmosphere before use;
BSP and BSM are not efficient for the activation of some low-
reactive “disarmed” donors, and they as well as DPSO would
produce an unfavorable S-thioalkyl sulfonium by-product18 which
would decompose the coupling product in one-pot oligosaccharide
synthesis. Therefore, new and powerful promoters for the pre-
activation of thioglycosides, especially for the “disarmed” donors,
are in great demand.
O,O-Dimethylthiophosphonosulfenyl bromide (DMTPSB, 1,
Fig. 1), prepared from tetramethyl thioperoxydiphosphate (2) and
bromine, is a “soft” electrophilic reagent and easily binds to the
“soft” sulfur atom. Since it was first synthesized by Michalski and
co-workers,19 DMTPSB has attested considerable interest in the
field of organic chemistry, due to its easy preparation and low cost.
However, DMTPSB has never been applied to the glycosylation
reaction. Herein, we report DMTPSB as a new promoter for the
pre-activation of thioglycoside donors.
many advances on oligosaccharide synthesis have been achieved,
including solid-phase strategy,2 solution-phase protocol,3 and
chemo-enzymatic method.4 Among these strategies, the one-
pot multi-step glycosylation approach5 is very attractive. The
reactivity-based one-pot sequential glycosylation relies on the
relative reactivities of glycosyl donors. To obtain glycosyl donors
with suitable anomeric reactivities, extensive protective group
manipulations must be carried out, making the synthetic process
complicated and the overall efficiency decreased. Our recently
developed preactivation-based iterative one-pot glycosylation6
conceptually overcomes the shortages of reactivity-based glyco-
sylation. Furthermore, since the acceptor is absent in the process
of donor activation and reacts with the “activated donor” (the
intermediate resulting from the reaction of donor and promoter),
the stereochemistry7–11 and reaction capacity6,12,13 of pre-activation
glycosylation could be different from the traditional glycosylation
protocol. Because of these advantages, pre-activation strategy
holds the potential for the assembly of oligosaccharide library
and automated synthesis.
In pre-activation one-pot glycosylation, the widely-used glyco-
syl donors are thioglycosides, which are convenient in preparation
and stable in many functional group transformations. The thioac-
etal functionality combines the role of an anomeric protective
group and an efficient leaving group.14 So far there are many
promoter systems available for the activation of thioglycosides
State Key Laboratory of Natural and Biomimetic Drugs, Peking University,
and School of Pharmaceutical Sciences, Peking University, Xue Yuan Rd
No. 38, Beijing, 100191, China. E-mail: xinshan@bjmu.edu.cn; Fax: +86-
10-82802724; Tel: +86-10-62014949
† Electronic supplementary information (ESI) available: NMR spectra for
compounds. See DOI: 10.1039/c0ob00380h
‡ Dedicated to Professor Henry N. C. Wong on the occasion of his 60th
birthday.
Fig. 1 O,O-Dimethylthiophosphonosulfenyl bromide (DMTPSB, 1).
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synthesis. Indeed, this promoter system worked well, by using
nearly equimolar promoter to minimize the formation of by-
products. As exemplified in Scheme 1, the thiogalactoside donor
9 was pre-activated by DMTPSB/AgOTf at -72 ◦C, followed by
the addition of building block 16. After the coupling reaction
was completed, the newly formed disaccharide without isolation
was activated again with DMTPSB/AgOTf, then followed by the
addition of acceptor 10, providing the final trisaccharide 30 in 60%
isolated yield and with good stereoselectivity. This demonstrated
that this new promoter system can be used in the preactivation-
based one-pot assembly of oligosaccharides.
Results and discussion
Firstly, to test the activating capability of DMTPSB, the gly-
cosylation reaction of benzoylated thioglycoside donor 3 with
glucoside acceptor 10 was investigated by the use of pre-activation
protocol. Through a preliminary screening of conditions, we
found that DMTPSB alone was unable to activate donor 3.
However, when the combination of DMTPSB and AgOTf was
used, donor 3 was activated promptly at low temperature. We
proposed that DMTPSB may react with silver triflate to produce a
more electrophilic reagent (MeO)2P(S)SOTf, which can activate
the thioglycosides easily. Thus, donor 3 was quickly activated
(monitored by TLC) after the addition of the mixture of DMTPSB
and AgOTf at -72 ◦C. Subsequently, acceptor 10 was added to
the reaction mixture, and the coupling reaction was completed
smoothly, providing the disaccharide 17 in 90% isolated yield as a
pure b-isomer (Table 1, entry 1). Under the DMTPSB/AgOTf pre-
activation conditions, a variety of glycosyl donors and acceptors
were employed to evaluate the efficacy and scope of this new
promoter (Table 1). As shown, the “disarmed” thioglycoside 3,
activated by DMTPSB-AgOTf, reacted readily with the glucoside
acceptors 11, 12, and 13 having a free hydroxyl group exposed
at the C-3, C-4, and C-2 positions, respectively, affording the
corresponding disaccharides 18, 19, and 20 in high yields (entries
2–4). The low-reactive benzoyl-protected acceptor 14 also coupled
smoothly with 3 to obtain disaccharide 27 in 95% isolated
yield (entry 11). Other “disarmed” donors, such as thioglucoside
5 (entries 6, 7), thiomannoside 7 (entry 9), and glucosamine
derivative 8 (entry 10), were also activated quickly and efficiently
at -72 ◦C and the coupling products were obtained in high
yields.
The “disarmed” donor 9 underwent the glycosylation reaction
with the “armed” thioglycoside acceptor 15 to provide the
coupling product 28 in an acceptable yield (entry 12), whereas
this reaction was unable to be realized by the reactivity-based
chemoselective method.5b The donor 9 also reacted with the
low-reactive benzoyl-protected thioglycoside acceptor 16 giving
disaccharide 29 in a good yield (entry 13).
All the disaccharides formed above were completely single
anomers. Most glycosylations (entries 1–4, 6, 7, 9, 11, 12, 13)
afforded 1,2-trans stereoselectivity because of the neighboring
group participation at C-2, whereas the glucosamine donor 8
(entry 10) showed 1,2-cis stereoselectivity owing to the special
protective group and an excess of AgOTf.10,20
Conclusion
In summary, DMTPSB as a new and highly powerful promoter for
the glycosylation reactions has been identified. The combination
of DMTPSB and AgOTf works as an efficient promoter system
for the pre-activation of thioglycosides. Both “disarmed” and
“armed” glycosyl donors can be activated smoothly at low
temperature, and the coupling reactions proceed very well with
a range of acceptors in high yields. This reagent overcomes some
limitations of the current promoters for the pre-activation protocol
and can be employed in iterative one-pot oligosaccharide assembly.
Experimental
General
All chemicals were purchased as reagent grade and used without
further purification, unless otherwise noted. Dichloromethane
(CH2Cl2) was distilled over calcium hydride (CaH2), carbon tetra-
chloride was distilled over calcium chloride (CaCl2). All reactions
were performed in flame-dried modified Schlenk (Kjeldahl shape)
flasks fitted with a glass stopper or rubber septa under a positive
pressure of argon or nitrogen. Analytical TLC was performed
on silica gel 60-F254 precoated on aluminium plates (E. Merck),
with detection by UV (254 nm) and/or by staining with acidic
ceric ammonium molybdate. Solvents were evaporated under
reduced pressure and below 35 ◦C (bath). Organic solutions
of crude products were dried over anhydrous Na2SO4. Optical
rotations were measured with a AA-10R automatic polarimeter.
Column chromatography was performed employing Silica Gel
200–300 mesh. 1H NMR spectra were recorded on a JEOL
AL-300, Varian ◦INOVA-500 or Advance DRX Bruker-400 spec-
trometers at 25 C. Chemical shifts (in ppm) were referenced to
tetramethylsilane (d = 0 ppm) in deuterated chloroform. 13C NMR
spectra were obtained by using the same NMR spectrometers
and were calibrated with CDCl3 (d = 77.00 ppm). High-resolution
mass spectra were recorded on a Bruker APEX IV. Low-resolution
mass spectra were recorded on Finnigan TRACE 2000 MS. IR was
measured with a Thermo Nicolet Nexus 470.
As expected, the “armed” donors were able to be activated
more easily. The glycosylations of benzylated thioglycosides 4 and
6 with acceptor 11 having a secondary hydroxyl group exposed
proceeded smoothly. The coupling reaction of thiogalactoside
donor 4 and glucoside acceptor 11 (entry 5) displayed good a-
selectivity, whereas the reaction of thioglucoside donor 6 and
acceptor 11 resulted in a poor anomeric selectivity (entry 8).
To check the efficiency of this new promoter, the glycosylation
reactions promoted by DMTPSB/AgOTf and p-TolSCl/AgOTf,
respectively, were investigated, and the similar yields of glycosy-
lations were obtained.21 Although it seemed that the yields of the
former are a little lower, DMTPSB is more readily prepared and
can be stored.
Compound 2 was prepared as described in the literature22 as
◦
white crystals: m.p. 53 C (from methanol) (lit22a 51 ◦C); 1H
NMR (300 MHz, CDCl3) d 3.89 (s, 6H), 3.83 (s, 6H); 31P NMR
(121.5 MHz, CDCl3, 85% H3PO3 as external standard) d 96.1 (lit22b
89.5); m/z (EI) 314 (M+), 125 ((MeO)2P+S); The spectroscopic data
coincide with the previous report.22
The next issue was to determine if DMTPSB/AgOTf could be
applied to a preactivation-based iterative one-pot oligosaccharide
O,O-Dimethylthiophosphonosulfenyl bromide (1) was pre-
pared as described in the literature.19 A solution of Br2 (0.51 g,
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Table 1 Glycosylations promoted by DMTPSB-AgOTf under pre-activation conditions
Entry
1
Donor
Acceptor
Product
Yield
90%
a : b
b only
2
3
3
3
89%
91%
b only
b only
4
5
6
7
3
84%
85%
89%
92%
b only
5.5 : 1a
b only
b only
11
12
10
5
8
11
11
10
83%
93%
75%
1.4 : 1
9
a only
a only
10
11
12
3
95%
63%
b only
b only
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Table 1 (Contd.)
Entry
13
Donor
Acceptor
Product
Yield
73%
a : b
9
b only
a Determined by 1H NMR analysis.
Scheme 1 Preactivation-based iterative one-pot assembly of 30.
3.2 mmol) in CCl4 (1.0 mL) was added to a stirred solution of 2
(1.0 g, 3.2 mmol) in CCl4 (4.0 mL) at -25 ◦C, the mixture was
stirred for 10 min. The solution was used as the promoter directly
without purification. The solution can be stored for several weeks
avoided from moisture in fridge.
3.90 (t, 1H, J = 9.3 Hz), 3.75 (d, 2H, J = 9.0 Hz), 3.37–3.42 (m,
2H), 3.20 (s, 3H, OMe). The spectroscopic data coincide with the
previous report.23
Methyl
3-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyranosyl)-
2-O-benzyl-4,6-O-benzylidene-a-D-glucopyranoside (18). Com-
pound 1815e (16.5 mg, 89% yield as a semisolid) was prepared
according to the general procedure for pre-activation glycosylation
from donor 3 (15.0 mg, 21 mmol) and acceptor 11 (7.1 mg, 19 mmol)
and purified by column◦chromatography (petroleum ether/ethyl
acetate = 5 : 1). [a]D27: +4 (c = 1 in CDCl3), (lit15e [a]D25: +3.5◦ (c =
1.5 in CDCl3)); vmax(KBr)/cm-1: 3065, 3033, 1731, 1602, 1585,
General procedure for pre-activation glycosylation
A mixture of AgOTf (18.5 mg, 72 mmol) and activated molecular
˚
sieves (4 A powder, 300 mg) in dry CH2Cl2 (3 mL) was cooled
to -72 ◦C under argon atmosphere. After stirring for 5 min,
DMTPSB (23 mL, 1.23 M in CCl4 solution, 28 mmol) and
donor 3 (15.5 mg, 22 mmol) were added via a micro-syringe.
After TLC detection indicated that donor 3 was completely
consumed, acceptor 10 (10.5 mg, 19 mmol) was added. The
reaction was further stirred for 15 min and warmed gradually to
room temperature. The reaction was quenched by triethylamine
(0.2 mL) and the precipitate was filtered off through a pad of
Celite. The filtrate was concentrated and the residue was purified
by column chromatography on silica gel (petroleum ether/ether
acetate = 5 : 1), affording 17 (17.7 mg, 90%) as a semisolid.
1
1493, 1452, 1267, 1093, 1071, 1027, 710; H NMR (300 MHz,
CDCl3): d 8.04–8.06 (m, 2H), 7.93–7.97 (m, 5H), 7.75–7.78 (m,
2H), 7.51–7.58 (m, 5H), 7.37–7.48 (m, 8H), 7.20–7.32 (m, 15H),
7.08–7.11 (m, 2H), 5.95 (d, 1H, J = 3.3 Hz, 4¢-H), 5.88 (dd, 1H,
J = 10.5, 7.8 Hz, 2¢-H), 5.58–5.63 (m, 2H, 3¢-H, PhCH), 5.22 (d,
1H, J = 8.1 Hz, 1¢-H), 4.61 (d, 1H, J = 12.3 Hz, PhCH2), 4.22–4.43
(m, 6H), 4.13 (t, 1H, J = 7.5 Hz), 3.61–3.80 (m, 3H, OMe), 3.46
(dd, 1H, J = 9.6, 3.9 Hz), 3.28 (s, 3H). 13C NMR (75 MHz,
CDCl3): d 165.78, 165.60, 165.47, 165.39, 138.13, 137.36, 133.41,
133.18, 129.95, 129.76, 129.39, 129.15, 128.91, 128.81, 128.57,
128.35, 128.24, 128.17, 127.84, 127.71, 125.95, 101.35, 101.09,
99.01, 79.79, 79.24, 77.40, 73.99, 71.95, 70.91, 70.37, 68.97, 67.99,
62.29, 61.42, 55.24. HRMS (ESI) calcd for C55H50NaO15 [M +
Na]+: 973.3042, found 973.3031.
Methyl
6-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyranosyl)-
2,3,4-tri-O-benzyl-a-D-glucopyranoside (17). Compound 1723
(17.7 mg, 90% yield as a semisolid) was prepared according
to the general procedure for pre-activation glycosylation from
donor 3 (15.5 mg, 22 mmol) and acceptor 10 (10.5 mg, 19 mmol)
and purified by column chromatography (petroleum ether/ethyl
Methyl
4-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyranosyl)-
1
acetate = 5 : 1). H NMR (300 MHz, CDCl3): d 8.00–8.09 (m,
2,3,6-tri-O-benzyl-a-D-glucopyranoside (19). Compound 1924
(18.1 mg, 91% yield as a semisolid) was prepared according
to the general procedure for pre-activation glycosylation from
donor 3 (15.0 mg, 21 mmol) and acceptor 12 (10.5 mg, 19 mmol)
and purified by column chromatography (petroleum ether/ethyl
4H), 7.88 (d, 2H, J = 6.9 Hz), 7.76 (d, 2H, J = 6.9 Hz), 7.37–7.63
(m, 9H), 7.19–7.33 (m, 18H, aromatic), 7.11–7.13 (m, 2H), 5.97
(d, 1H, J = 3.3 Hz, 4¢-H), 5.85 (dd, 1H, J = 10.2, 7.8 Hz, 2¢-H),
5.59 (dd, 1H, J = 10.2, 3.3 Hz, 3¢-H), 4.90 (d, 1H, J = 11.1 Hz,
PhCH2), 4.64–4.77 (m, 4H, 1¢-H, 6¢-H, PhCH2¥2), 4.49–4.60
(m, 3H, 1-H, PhCH2¥2), 4.35–4.43 (m, 2H), 4.18–4.27 (m, 2H),
1
acetate = 4 : 1). H NMR (300 MHz, CDCl3): d 8.02 (d, 2H, J =
7.2 Hz), 7.93 (d, 2H, J = 7.2 Hz), 7.85 (d, 2H, J = 7.2 Hz), 7.74
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(d, 2H, J = 7.2 Hz), 7.18–7.56 (m, 31H), 5.84 (d, 1H, J = 3.6 Hz),
5.69 (dd, 1H, J = 10.2, 8.1 Hz), 5.29 (dd, 1H, J = 10.5, 3.3 Hz),
5.17 (d, 1H, J = 11.1 Hz), 4.90 (d, 1H, J = 11.4 Hz), 4.73–4.81
(m, 3H), 4.64 (d, 1H, J = 12.0 Hz), 4.57 (d, 1H, J = 3.3 Hz),
4.39 (dd, 1H, J = 11.4, 6.3 Hz), 4.31 (d, 1H, J = 12.3 Hz), 4.18
(dd, 1H, J = 11.1, 7.5 Hz), 4.02 (t, 1H, J = 9.6 Hz), 3.88–3.94
(m, 2H), 3.69–3.70 (m, 1H), 3.41–3.55 (m, 3H), 3.30 (s, 3H). The
spectroscopic data coincide with the previous report.24
4.89 (d, 1H, J = 11.1 Hz), 4.82 (d, 1H, J = 7.8 Hz, 1¢-H), 4.73 (d,
1H, J = 12.0 Hz), 4.68 (d, 1H, J = 10.8 Hz), 4.57–4.61 (m, 2H),
4.47–4.54 (m, 3H), 4.27 (d, 1H, J = 11.4 Hz), 4.06–4.16 (m, 2H),
3.88 (t, 1 H, J = 9.0 Hz), 3.70–3.76 (m, 2H), 3.34–3.45 (m, 2H),
3.20 (s, 3H). The spectroscopic data coincide with the previous
report.26
Methyl 3-O-(2,3,4,6-tetra-O-benzyl-D-glucopyranosyl)-4,6-O-
benzylidene-2-O-benzyl-a-D-glucopyranoside (24). Compound
2415o was prepared according to the general procedure for
pre-activation glycosylation from donor 6 (15.0 mg, 23 mmol)
and acceptor 11 (7.1 mg, 19 mmol) and purified by column
chromatography (petroleum ether/ethyl acetate = 6 : 1).
Methyl
2-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyranosyl)-
3-O-benzyl-4,6-O-benzylidene-a-D-glucopyranoside (20). Com-
pound 2025 (15.5 mg, 84% yield as a semisolid) was prepared
according to the general procedure for pre-activation glycosylation
from donor 3 (15.0 mg, 21 mmol) and acceptor 13 (7.1 mg, 19 mmol)
and purified by column chromatography (petroleum ether/ethyl
For 24-a (8.0 mg, 47% yield as a semisolid): 1H NMR (300 MHz,
CDCl3): d 7.06–7.41 (m, 36H), 6.91 (d, 2H, J = 6.9 Hz), 5.59 (d,
1H, J = 3.6 Hz, 1¢-H), 5.47 (s, 1H), 5.00 (d, 1H, J = 10.8 Hz), 4.80
(dd, 2H, J = 11.1, 2.4 Hz), 4.71 (d, 1H, J = 3.6 Hz), 4.65 (d, 1H,
J = 11.4 Hz), 4.54–4.61 (m, 3H), 4.18–4.41 (m, 6H), 3.97 (t,, 1H,
J = 9.6 Hz), 3.63–3.88 (m, 5H), 3.45–3.53 (m, 3H), 3.41 (s, 3H).
For 24-b (6.2 mg, 36% yield as a semisolid): 1H NMR (300 MHz,
CDCl3): d 7.14–7.42 (m, 30H, aromatic), 5.47 (s, 1H), 5.07 (d, 1H,
J = 11.4 Hz), 4.87–4.93 (m, 2H), 4.70–4.80 (m, 4H), 4.45–4.51 (m,
5H), 4.36 (t, 1H, J = 9.0 Hz), 4.21 (dd, 1H, J = 9.6, 4.2 Hz), 3.80
(dd, 1H, J = 9.9, 4.5 Hz), 3.46–3.71 (m, 8H), 3.35 (s,3H), 3.23–
3.25 (m, 1H). The spectroscopic data coincide with the previous
report.15o
1
acetate = 5 : 1). H NMR (300 MHz, CDCl3): d 8.11 (d, 2H, J =
7.2 Hz), 8.02 (d, 2H, J = 7.2 Hz), 7.88 (d, 2H, J = 6.9 Hz), 7.77 (d,
2H, J = 7.2 Hz), 7.38–7.66 (m, 11H), 7.32–7.34 (m, 3H), 7.20–7.26
(m, 8H), 7.10–7.16 (m, 3H), 6.99–7.03 (m, 2H), 5.93–6.00 (m,
2H), 5.59 (dd, 1H, J = 10.5, 3.6 Hz), 5.50 (s, 1H), 5.18 (d, 1H, J =
8.1 Hz), 5.02 (d, 1H J = 3.6 Hz), 4.42–4.66 (m, 4H), 4.25–4.36 (m,
2H), 3.97 (t, 1H, J = 9.0 Hz), 3.80–3.88 (m, 2H), 3.70 (t, 1H, J =
10.2 Hz), 3.55 (t, 1H, J = 9.0 Hz), 3.45 (s, 3H). The spectroscopic
data coincide with the previous report.25
Methyl
2-O-benzyl-4,6-O-benzylidene-3-O-(2,3,4,6-tetra-O-
(21). Com-
benzyl-D-galactopyranosyl)-a-D-glucopyranoside
pound 2115o (16.0 mg, 85% yield, a/b inseparable mixture as
an oil) was prepared according to the general procedure for
pre-activation glycosylation from donor 4 (15.0 mg, 23 mmol)
and acceptor 11 (7.8 mg, 21 mmol) and purified by column
chromatography (petroleum ether/ethyl acetate = 6 : 1). 1H NMR
(300 MHz, CDCl3): d 7.01–7.40 (m, 45H), 5.61 (d, 1.0H, J =
3.3 Hz), 5.50 (s, 0.17H), 5.43 (s, 1H), 4.69–5.03 (m, 6.6 H),
4.19–4.60 (m, 13.6 H), 3.53–3.98 (m, 12.7H), 3.33–3.43(m, 4.6H).
The spectroscopic data coincide with the previous report.15o
Methyl 3-O-(2,3,4,6-tetra-O-acetyl-a-D-mannopyranosyl)-2-O-
benzyl-4,6-O-benzylidene-a-D-glucopyranoside (25). Compound
25 (24.2 mg, 93% yield as a white amorphous solid) was
prepared according to the general procedure for pre-activation
glycosylation from donor 7 (20.0 mg, 44 mmol) and acceptor
11 (13.7 mg, 37 mmol) and purified by column chromatography
(petroleum ether/ethyl acetate = 4 : 1). [a]2D7: +26◦ (c = 1 in CDCl3);
v
max(KBr)/cm-1: 3067, 3036, 2993, 2918, 2876, 1750, 1604, 1454,
1371, 1231, 1141, 1088, 1047, 980, 753, 701; 1H NMR (300 MHz,
CDCl3): d 7.31–7.39 (m, 11H), 5.52 (s, 1H, PhCH), 5.33–5.38 (m,
3H, 1¢-H, 2¢-H, 3¢-H), 5.26 (t, 1H, J = 9.9 Hz, 4¢-H), 4.62–4.71 (m,
3H, 1-H, PhCH2), 4.20–4.36 (m, 3H, 5¢-H, 6a-H, 3-H), 3.97–4.01
(m, 2H, 6¢-H), 3.61–3.84 (m, 3H, 5-H, 6b-H, 4-H), 3.54 (dd, 1H,
J = 9.6, 3.6 Hz, 2-H), 3.39 (s, 3H, OMe), 2.09 (s, 6H, OAcX2), 1.99
(s, 6H, OAcX2). 13C NMR (75 MHz, CDCl3): d 170.79, 170.04,
169.79, 169.63, 137.49, 136.91, 128.83, 128.54, 128.26, 128.13,
128.04, 125.96, 101.12, 98.40, 97.55, 82.31, 77.60, 73.18, 72.91,
69.29, 69.23, 68.84, 68.31, 65.68, 61.84 ¥ 2, 55.28, 20.78, 20.71.
HRMS (ESI) calcd for C35H42NaO15 [M + Na]+: 725.2416, found
725.2400; C35H43O15 [M + H]+: 703.2596, found 703.2591.
Methyl
4-O-(2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl)-
2,3,6-tri-O-benzyl-a-D-glucopyranoside (22). Compound 2224
(20.9 mg, 89% yield as a foam) was prepared according to the
general procedure for pre-activation glycosylation from donor
5 (20.0 mg, 29 mmol) and acceptor 12 (11.0 mg, 23 mmol) and
purified by column chromatography (petroleum ether/ethyl
acetate = 5 : 1). 1H NMR (300 MHz, CDCl3): d 7.96 (d, 1H,
J = 7.2 Hz), 7.87 (d, 4H, J = 7.8 Hz), 7.79 (d, 2H, J = 7.2 Hz),
7.17–7.52 (m, 34H), 5.43–5.64 (m, 3H), 5.07 (d, 1H, J = 11.1 Hz,
1¢-H), 4.72–4.81 (m, 4H), 4.58 (d, 1H, J = 12.0 Hz), 4.54 (d,
1H, J = 3.6 Hz), 4.39 (dd, 1H, J = 12.3, 3.6 Hz), 4.34 (d, 1H,
J = 12.3 Hz), 4.25 (dd, 1H, J = 12.3, 5.1 Hz), 3.84–3.99 (m,
2H), 3.67–3.74 (m, 2H), 3.40–3.51 (m, 3H), 3.27 (s, 3H). The
spectroscopic data coincide with the previous report.24
Methyl
6-O-(N-acetyl-2-amino-2,3-N,O-carbonyl-4,6-di-O-
acetyl-2-deoxy-a-D-glucopyranosyl)-2,3,4-tri-O-benzyl-a-D-gluco-
pyranoside (26). Compound 2610a (18.1 mg, 75% yield as
an oil) was prepared according to the general procedure for
pre-activation glycosylation from donor 8 (15.0 mg, 34 mmol)
and acceptor 10 (14.3 mg, 31 mmol) and purified by column
chromatography (petroleum ether/ethyl acetate = 3 : 1). 1H NMR
(400 MHz, CDCl3): d 7.24–7.38 (m, 18H), 5.78 (d, 1H, J = 2.8 Hz,
1¢-H), 5.26 (t, 1H, J = 10.0 Hz), 5.01 (d, 1H, J = 10.8 Hz), 4.87 (d,
1H, J = 11.6 Hz), 4.76–4.81 (m, 2H), 4.68 (d, 1H, J = 12.0 Hz),
4.47–4.58 (m, 3H), 4.11–4.14 (m, 2H), 3.99 (t, 1H, J = 9.2 Hz),
3.70–3.88 (m, 5H), 3.52 (dd, 1H, J = 9.6, 3.2 Hz), 3.36 (s, 3H),
Methyl
6-O-(2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl)-
2,3,4-tri-O-benzyl-a-D-glucopyranoside (23). Compound 2326
(22.0 mg, 92% yield as a semisolid) was prepared according
to the general procedure for pre-activation glycosylation from
donor 5 (20.0 mg, 29 mmol) and acceptor 10 (11.0 mg, 23 mmol)
and purified by column chromatography (petroleum ether/ethyl
1
acetate = 5 : 1). H NMR (300 MHz, CDCl3): d 7.99 (d, 2H, J =
7.2 Hz), 7.81–7.90 (m, 6H), 7.03–7.52 (m, 31H), 5.89 (t, 1H, J =
9.6 Hz), 5.67 (t, 1H, J = 9.6 Hz), 5.59 (dd, 1H, J = 9.6, 8.1 Hz),
620 | Org. Biomol. Chem., 2011, 9, 616–622
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(petroleum ether/ethyl acetate = 2 : 1). [a]2D7: +50◦ (c = 1 in
CDCl3); vmax(KBr)/cm-1: 3065, 3034, 2925, 2868, 1732, 1601,
1584, 1493, 1452, 1402, 1368, 1316, 1277, 1179, 1094, 1069, 1026,
3.31 (t, 1H, J = 9.2 Hz), 2.40 (s, 3H), 2.11 (s, 3H), 2.03 (s, 3H).
The spectroscopic data coincide with the previous report.10a
Methyl
6-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyranosyl)-
1
999, 806, 755, 709; H NMR (300 MHz, CDCl3): d 7.98–8.04
2,3,4-tri-O-benzoyl-a-D-glucopyranoside (27). Compound 2727
(18.0 mg, 95% yield as a foam) was prepared according to the
general procedure for pre-activation glycosylation from donor 3
(15.0 mg, 21 mmol) and acceptor 14 (8.5 mg, 17 mmol) and purified
by column chromatography (petroleum ether/ethyl acetate = 4 : 1).
[a]2D7: +72◦ (c = 1 in CDCl3), (lit27 [a]D20: +78.1◦ (c = 1 in CDCl3));
(m, 2H), 7.91–7.95 (m, 4H), 7.83–7.86 (m, 2H), 7.72–7.75 (m,
2H), 7.21–7.60 (m, 28H), 7.10 (d, 2H, J = 7.8 Hz), 5.88 (dd, 1H,
J = 10.5, 8.1 Hz, 2¢-H), 5.75 (t, 1H, J = 9.3 Hz, 3-H), 5.53 (s,
1H, PhCH), 5.25–5.35 (m, 3H, 3¢-H, 2-H, 4-H), 4.94 (d, 1H, J =
8.1 Hz, 1¢-H), 4.79 (d, 1H, J = 10.2 Hz, 1-H), 4.60 (d, 1H, J =
3.0 Hz, 4¢-H), 4.30 (d, 1H, J = 11.4 Hz, 6¢-H), 3.89–4.11 (m, 4H,
5-H, 6a-H, 6b-H, 6b¢-H), 3.63 (s, 1H, 5¢-H), 2.30 (s, 3H, SPhMe).
13C NMR (75 MHz, CDCl3): d 166.19, 165.63, 165.40, 165.36,
164.94, 138.65, 137.39, 133.71, 133.45, 133.35, 133.22, 133.11,
132.98, 129.78, 129.24, 129.09, 128.87, 128.77, 128.60, 128.38,
128.26, 128.19, 128.07, 127.60, 126.19, 101.10, 100.76, 85.97,
78.54, 74.12, 73.48, 72.91, 70.35, 69.29, 68.92, 68.83, 67.73, 66.55,
21.16. HRMS (ESI) calcd for C61H52KO15S [M + K]+: 1095.2653,
found 1095.2655; C61H52NaO15S [M + Na]+: 1079.2919, found
1079.2927.
v
max(KBr)/cm-1: 3067, 2936, 1731, 1602, 1452, 1270, 1105, 1069,
1
1028, 710; H NMR (300 MHz, CDCl3): d 7.77–8.07 (m, 14H),
7.21–7.60 (m, 25H), 6.08 (t, 1H, J = 9.9 Hz, 3-H), 5.99 (d, 1H,
J = 3.3 Hz, 4¢-H), 5.84 (dd, 1H, J = 10.5, 7.8 Hz, 2¢-H), 5.63
(dd, 1H, J = 10.5, 3.6 Hz, 3¢-H), 5.33 (t, 1H, J = 10.5 Hz, 4-H),
5.06 (dd, 1H, J = 10.5, 3.9 Hz, 2-H), 4.95 (d, 1H, J = 7.8 Hz,
1¢-H), 4.91 (d, 1H, J = 3.6, 1-H), 4.61 (dd, 1H, J = 10.8, 6.3 Hz,
6a¢-H), 4.16–4.43 (m, 4H, 6b¢-H, 5¢-H, 5-H, 6a-H), 3.79 (dd, 1H,
J = 11.4, 7.8 Hz, 6b-H), 3.10 (s, 3H, OMe). 13C NMR (75 MHz,
CDCl3): d 165.98, 165.65, 165.54, 165.49, 165.45, 165.34, 133.54,
133.46, 133.26, 133.04, 129.99, 129.85, 129.78, 129.61, 129.38,
129.19, 129.01, 128.73, 128.58, 128.49, 128.35, 128.26, 102.24,
96.39, 71.96, 71.55, 71.35, 70.28, 69.72, 69.57, 69.17, 68.68, 68.01,
61.79, 55.00. HRMS (ESI) calcd for C62H52NaO18 [M + Na]+:
1107.3046, found: 1107.3027.
Methyl
6-O-(6-O-(2,3-di-O-benzoyl-4,6-O-benzylidene-b-D-
galactopyranosyl)-2,3,4-tri-O-benzoyl-b-D-glucopyranosyl)-2,3,4-
tri-O-benzyl-a-D-glucopyranoside (30). A mixture of AgOTf
˚
(53 mg, 204 mmol) and activated molecular sieves (500 mg, 4 A
powder) in dry CH2Cl2 (5 mL) was cooled to -72 ◦C under argon
atmosphere. After stirring for 5 min, DMTPSB (36 mL, 1.23 M
in CCl4 solution, 44 mmol) and donor 9 (20.0 mg, 34 mmol)
were added via a micro-syringe. After TLC detection indicated
that donor 9 was completely consumed, acceptor 16 (18.3 mg,
31 mmol) was added. The reaction mixture was warmed to room
temperature and further stirred for 15 min before cooling down
back to -72 ◦C. Subsequently, DMTPSB (29 mL, 1.23 M in
CCl4 solution, 35 mmol) was added to the reaction mixture.
After the newly formed disaccharide was consumed by TLC
detection, acceptor 10 (13.0 mg, 28 mmol) was added. The reaction
mixture was stirred and gradually warmed to room temperature.
The reaction was quenched by triethylamine (0.2 mL) and
the precipitate was filtered off through a pad of Celite. The
filtrate was concentrated and the residue was purified by column
chromatography on silica gel (petroleum ether/ether acetate =
1.5 : 1), affording trisaccharide 30 (24.0 mg, 60%) as a semisolid.
[a]2D7: +26◦ (c = 1 in CDCl3); vmax(KBr)/cm-1: 3064, 3033, 2933,
1733, 1602, 1585, 1495, 1368, 1315, 1277, 1178, 1095, 1069, 1027,
741, 710; 1H NMR (500 MHz, CDCl3): d 7.93–7.96 (m, 4H), 7.87
(dd, 2H, J = 8.0, 1.0 Hz), 7.83 (dd, 2H, J = 8.0, 1.0 Hz), 7.76 (dd,
2H, J = 8.0, 1.0 Hz), 7.21–7.51 (m, 32H), 7.15 (t, 2H, J = 8.0 Hz),
6.98–7.00 (m, 2H), 5.84 (dd, 1H, J = 10.5, 8.0 Hz, 2¢¢-H), 5.74 (t,
1H, J = 9.5 Hz, 3¢-H), 5.50 (s, 1H, PhCH), 5.42 (dd, 1H, J = 9.5,
8.0 Hz, 2¢-H), 5.27–5.34 (m, 2H, 3¢¢-H, 4¢-H), 4.86 (d, 1H, J =
12.0 Hz, PhCH2), 4.84 (d, 1H, J = 8.5 Hz, 1¢¢-H), 4.72 (d, 1H,
J = 12.0 Hz, PhCH2), 4.65 (d, 1H, J = 11.0 Hz, PhCH2), 4.56 (d,
1H, J = 12.0 Hz, PhCH2), 4.51 (m, 2H, 4¢¢-H, 1-H), 4.47 (d, 1H,
J = 8.0 Hz, 1¢-H), 4.37 (d, 1H, J = 11.0 Hz, PhCH2), 4.31 (m,
1H, 6a¢¢-H), 4.17 (d, 1H, J = 11.5 Hz, PhCH2), 4.02–4.06 (m, 2H,
6b¢¢-H), 3.76–3.90 (m, 4H, 5¢-H, 6a¢-H, 6b¢-H), 3.57 (s, 1H, 5¢¢-H),
3.27–3.93 (m, 7H). 13C NMR (75 MHz, CDCl3): d 166.08, 165.69,
165.47, 165.14, 164.82, 138.88, 138.37, 138.18, 137.35, 133.49,
133.37, 133.13, 129.83, 129.66, 129.54, 129.10, 129.02, 128.87,
128.75, 128.40, 128.20, 128,11, 127.79, 127.37, 127.28, 126.13,
p-Tolyl 6-O-(2,3-di-O-benzoyl-4,6-O-benzylidene-b-D-galacto-
pyranosyl)-2,3,4-tri-O-benzyl-1-thio-b-D-glucopyranoside
(28).
Compound 28 (13.5 mg, 63% yield as a semisolid) was
prepared according to the general procedure for pre-activation
glycosylation from donor 9 (15.0 mg, 26 mmol) and acceptor
15 (11.6 mg, 21 mmol) and purified by column chromatography
(petroleum ether/ethyl acetate = 3 : 1). [a]2D5: +44◦ (c = 1 in CDCl3);
v
max(KBr)/cm-1: 3063, 3031, 2924, 2858, 1729, 1601, 1494, 1453,
1402, 1365, 1316, 1275, 1179, 1093, 1069, 1026, 1000, 738, 709,
1
699; H NMR (400 MHz, CDCl3): 8.00 (m, 2H), 7.84 (m, 2H),
7.48–7.53 (m, 5H), 7.22–7.43 (m, 28H), 7.12–7.15 (m, 4H), 5.89
(dd, J = 8.4, 10.4 Hz, 1H, 2¢-H), 5.55 (s, 1H, PhCH), 5.29 (dd,
J = 3.6, 10.4 Hz, 1H, 3¢-H), 4.91 (d, J = 8.0 Hz, 1H, 1¢-H), 4.83 (t,
J = 10.0 Hz, 2H), 4.75 (d, J = 10.8 Hz, 1H, PhCH2), 4.66 (d, J =
10.4 Hz, 1H, PhCH2), 4.65 (d, J = 10.8 Hz, 1H, PhCH2), 4.59 (d,
J = 3.6 Hz, 1H, 4¢-H), 4.51 (d, J = 9.2 Hz, 1H, 1-H), 4.50 (d, J =
10.4 Hz, 1H, PhCH2) 4.40 (d, J = 10.8 Hz, 1H, PhCH2), 4.14(t,
J = 12.4 Hz, 2H), 3.94 (m, 1H), 3.57–3.61(m, 2H), 3.42–3.44
(m, 2H), 3.35 (t, J = 9.2 Hz, 1H, 2-H), 2.25 (s, 3H, SPhMe).
13C NMR (75 MHz, CDCl3): d 166.20, 165.14, 138.37, 138.09,
137.97, 137.84, 137.55, 133.31, 132.90, 129.93, 129.87, 129.64,
129.33, 129.16, 128.87, 128.37, 128.23, 128.18, 128.08, 127.86,
127.79, 127.73, 127.68, 127.60, 126.29, 100.88 ¥ 2, 87.55, 86.55,
80.40, 79.26, 77.48, 75.61, 75.28, 74.90, 73.60, 72.98, 69.05, 68.92,
67.28, 66.58, 21.02. HRMS (ESI) calcd for C61H58KO12S [M +
K]+: 1053.3275, found 1053.3311; C61H62NO12S [M + NH4]+:
1032.3987, found 1032.3987.
p-Tolyl 6-O-(2,3-di-O-benzoyl-4,6-O-benzylidene-b-D-galacto-
pyranosyl)-2,3,4-tri-O-benzoyl-1-thio-b-D-glucopyranoside (29).
Compound 29 (17.0 mg, 73% yield as a semisolid) was
prepared according to the general procedure for pre-activation
glycosylation from donor 9 (15.0 mg, 26 mmol) and acceptor
16 (13.0 mg, 22 mmol) and purified by column chromatography
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101.46, 100.66 ¥ 2, 98.08, 81.80, 79.65, 76.84, 75.37, 74.33, 74.18,
73.52, 73.39, 72.75, 72.45, 71.78, 69.57, 69.39, 69.29, 68.78, 68.20,
67.28, 66.45, 55.28. HRMS (ESI) calcd for C82H76NaO21 [M +
Na]+: 1419.4771, found 1419.4727.
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Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (Grant No. 20732001) and the grant
(2009ZX09501-011) from the Ministry of Science and Technology
of China.
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