Phosphotungstic acid as a novel acidic catalyst for carbohydrate protection and glycosylation

Article abstract of DOI:10.1039/c9ra06170c

This work demonstrates the utilization of phosphotungstic acid (PTA) as a novel acidic catalyst for carbohydrate reactions, such as per-O-acetylation, regioselective O-4,6 benzylidene acetal formation, regioselective O-4 ring-opening, and glycosylation. These reactions are basic and salient during the synthesis of carbohydrate-based bioactive oligomers. Phosphotungstic acid's high acidity and eco-friendly character make it a tempting alternative to corrosive homogeneous acids. The various homogenous acid catalysts were replaced by the phosphotungstic acid solely for different carbohydrate reactions. It can be widely used as a catalyst for organic reactions as it is thermally stable and easy to handle. In our work, the reactions are operated smoothly under ambient conditions; the temperature varies from 0 °C to room temperature. Good to excellent yields were obtained in all four kinds of reactions.

Full text of DOI:10.1039/c9ra06170c

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PAPER
Phosphotungstic acid as a novel acidic catalyst for
carbohydrate protection and glycosylation†
Cite this: RSC Adv., 2019, 9, 33853
Jyun-Siao Chen,‡a Arumugam Sankar,‡a Yi-Jyun Lin,a Po-Hsun Huang,a
a
Chih-Hsiang Liao,b Shen-Shen Wu,c Hsin-Ru Wud and Shun-Yuan Luo
*
This work demonstrates the utilization of phosphotungstic acid (PTA) as a novel acidic catalyst for
carbohydrate reactions, such as per-O-acetylation, regioselective O-4,6 benzylidene acetal formation,
regioselective O-4 ring-opening, and glycosylation. These reactions are basic and salient during the
synthesis of carbohydrate-based bioactive oligomers. Phosphotungstic acid's high acidity and eco-
friendly character make it
a tempting alternative to corrosive homogeneous acids. The various
Received 8th August 2019
Accepted 11th October 2019
homogenous acid catalysts were replaced by the phosphotungstic acid solely for different carbohydrate
reactions. It can be widely used as a catalyst for organic reactions as it is thermally stable and easy to
handle. In our work, the reactions are operated smoothly under ambient conditions; the temperature
varies from 0 ꢀC to room temperature. Good to excellent yields were obtained in all four kinds of reactions.
DOI: 10.1039/c9ra06170c
rsc.li/rsc-advances
It could be installed by using acid or base12b such as cam-
Introduction
phorsulfonic acid (CSA),12c p-toluenesulfonic acid (TsOH),12d
12e
SnCl4 and TCT.12f Nevertheless, the formation of 4,6-O-ben-
Carbohydrates are present throughout living organisms and are
structurally richer than other biopolymers.1 They are involved in
a vast range of crucial biological operations and are potential
drug targets.2,3 They are available as mixtures from natural
sources.4 Pure forms of carbohydrates are essential for under-
standing their biological activity5a and disease-related infor-
mation.5b A few strategies for minimizing the number of steps
and achieving oligosaccharides in good yields through chemical
synthesis are available.6 The synthesis of oligosaccharides
requires the preparation of glycosyl acceptors and glycosyl
donors,7a which upon glycosylation, produce stereo-selective
and regio-selective glycosidic bonds.7b Hence, new techniques
for synthesizing oligosaccharides are essential.8
zylidene acetals and its yields are limited by side-products and
the requirement of severe acidic medium.12g Selective O-4 ring
opening is also an important reaction of carbohydrates as it
affords free hydroxyl group at C-4 position. This reaction
proceeds in the presence of triuoroacetic acid and triethylsi-
lane12h,i or sodium cyanoborohydride.13 However, this reaction
provides low yield14a and sodium cyanoborohydride is danger-
ous,14b so new mediators for this reaction must be found to
increase the yield. Finally, the glycosylation reaction requires an
acid catalyst to build the oligosaccharides and it requires acid
catalysts such as FeCl3/C,15a Cu(OTf)2,15b BF3$OEt2 or TMSOTf.15c
However, no common acid catalyst for all of these reactions has
been identied.
Hence, we would like to replace these different homogenous
corrosive acid catalysts by using a sole acid catalyst for impor-
tant reactions of carbohydrates. Furthermore, that acid catalyst
must be eco-friendly, acidity must be strong enough, should not
be corrosive and affordable. Fortunately, all of this require-
ments were fullled by the phosphotungstic acid. Thence, in
this work, we have used phosphotungstic acid (H3[P(W3O10)4])
catalyst for basic reactions namely per-O-acetylation, regiose-
lective O-4,6 benzylidene acetal formation, regioselective O-4
reductive ring-opening, and glycosylation reactions. All of these
reactions were underwent smoothly in the presence of PTA
under ambient reaction condition.
Acetylation is a common reaction in carbohydrate chemistry.
It can proceed in the presence of Cu(OTf)2,9a HClO4,9b FeCl3,10a
10b
11b
V(O)(OTf)3,
pyridine,11a Dy(OTf)3,
and Zn4(OCOCF3)6O.11c
However, mineral acid is corrosive and pyridine is harmful,11d
so new ways to conduct this reaction are sought. 4,6-O-benzy-
lidene acetal is an important moiety in the synthesis of poly-
saccharides as one can reductively open the acetal either at O-4
or O-6 position of monosaccharide,12a by tuning of the reaction
conditions and give a free hydroxyl group selectively at C4 or C6.
aDepartment of Chemistry, National Chung Hsing University, Taichung 402, Taiwan.
E-mail: syluo@dragon.nchu.edu.tw
bTaichung Municipal Feng Yuan Senior High School, Taichung 420, Taiwan
cNational Hsinchu Girls' Senior High School, Hsinchu 300, Taiwan
dInstrumentation Center, National Tsing Hua University, MOST, Hsinchu 300, Taiwan
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra06170c
PTA is a heteropolyacid,16a and a solid inorganic sub-
stance,16b it is following Keggin's structure.16c Phosphotungstic
acid is non-toxic,17a eco-friendly,17b and the strongest heteropoly
acid18a than common mineral acid such as H2SO4, HCl, and
‡ J.-S. Chen and A. Sankar contributed equally.
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HNO3.18b It has a good chemical stability, thermal stability,
reuse, and recycling.19–21 Phosphotungstic acid extensively used
in well known organic reactions, including Prins cyclization,22a
Claisen–Schmidt condensation,22b Schiff-bases synthesis,23
Pinacol-pinacolone rearrangements,24 Beckman rearrange-
ments,25 bio-diesel synthesis in industries,26a–c and quinolone
synthesis.27
Table 1 Phosphotungstic acid catalyzed per-O-acetylation
Neverthless, its impact in carbohydrate eld is quite low and
a few groups have been employed it as a catalyst for carbohy-
drate reactions.28a,b To the best of our knowledge, the applica-
tions of PTA in carbohydrates eld is inadequate. Accordingly,
our group extended the utilization of PTA to carbohydrates
principle reactions, and obtaining good to excellent yields and
will discuss in next part. These general reactions are depicted in
Fig. 1.
Results and discussion
Acetylation
H3[P(W3O10)4]
(equiv.)
Entry
SM
Product (a/b)
Yield
Table 1 presents the results of the phosphotungstic acid-
catalyzed per-O-acetylation reaction. D-glucose 1a was used as
the initial substrate to test phosphotungstic acid as a catalyst of
per-O-acetylation. To test per-O-acetylation, the reaction was
conducted under solvent-free conditions with D-glucose 1a,
phosphotungstic acid (0.05 equiv.) and acetic anhydride (10
equiv.) in an atmosphere of nitrogen at room temperature. Aer
24 hours, the starting material was disappeared on the TLC
plate and the desired product D-glucose pentaacetate 2a was
obtained in 66% (a/b ¼ 5/1) isolated yield (Table 1, entry 1). In
an effort to increase the yield of the per-O-acetylated product,
the amount of phosphotungstic acid was reduced to 0.01
equivalent. This change remarkably increased the yield of 2a to
88% (a/b ¼ 5/1) without changing other reaction conditions
(Table 1, entry 2). When 0.02 equivalent of phosphotungstic
acid was used, the desired product 2a was afforded in good yield
93% (a/b ¼ 5/1) (Table 1, entry 3).
1
2
3
4
5
6
7
8
1a
1a
1a
1b
1c
1d
1e
1f
0.05
0.01
0.02
0.02
0.02
0.02
0.02
0.02
2a (5/1)
2a (5/1)
2a (5/1)
2b (5/1)
2c (a only)
2d (a only)
2e (5/1)
66%
88%
93%
81%
88%
88%
99%
96%
2f (5/1)
mannose pentaacetate 2c in 88% (a only 1), 2d in 88% (a only),
D-xylose tetraaacetate 2e in 99% (a/b ¼ 5/1) and lactose octaa-
cetate 2f in 96% (a/b ¼ 5/1) yields (Table 1, entries 4–8). The
various carbohydrates underwent reactions smoothly with ace-
tic anhydride in the presence of phosphotungstic acid and the
yields of acetylated products were excellent. These favorable
ndings help in solving problems such as the separation and
corrosiveness of high-boiling-point liquid acids. Importantly,
Therefore, under the improved reaction conditions of per-O-
acetylation by phosphotungstic acid, different substrates were
screened. Unprotected sugars, such as D-galactose 1b, D-
mannose 1c, methyl alpha-D-glucopyranoside 1d, D-xylose 1e
and lactose 1f also participated in the reaction, which pro-
ceeded reaction smoothly under the same reaction conditions
and producing D-galactose pentaacetate 2b in 81% (a/b ¼ 5/1), D-
we developed
a new method for per-O-acetylation with
comparatively low cost PTA and it afforded good yield as
Cu(OTf)2 and HClO4 wich are expensive catalysts.9a,b
Acetalization
Phosphotungstic acid is used for the regioselective 4,6-O-benzy-
lidene acetalization, as presented in Table 2. The reaction of 4,6-
O-benzylidene acetalization started with 1d, phosphotungstic
acid (0.5 equiv.), and benzaldehyde dimethyl acetal (2.0 equiv.) in
acetonitrile. Aer 12 hours, the desired product 4a was obtained
in 71% isolated yield (Table 2, entry 1). Initial attempts were
made to nd a suitable equivalent of phosphotungstic acid to
enhance the yields of the desired product 4a. Notably, lowering
the amount of phosphotungstic acid catalyst to 0.2 equivalent
reduced the yield of 4a to 58% (Table 2, entry 2).
Therefore, the amount of phosphotungstic acid was not
reduced any further. When 0.25 equivalent of H3[P(W3O10)4] was
used with 1d, the yield of product 4a changed the yield remark-
ably to 69% (Table 2, entry 3). When the amount of catalyst was
Fig. 1 Reactions of carbohydrates with phosphotungstic acid as the
catalyst.
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Table 2 Phosphotungstic acid catalyzed benzylidene acetal formation
reaction was considered. First, methyl 2,3-di-O-benzyl-4,6-O-
benzylidene-a-D-glucopyranoside 5a was used as the optimal
substrate. At the outset, 5a, phosphotungstic acid (0.05 equiv.)
ꢀ
and triethylsilane (11.0 equiv.) were used in DCM at 0 C. The
expected product 6a was formed and its O-4 silylated side
product also observed on the TLC plate. To cleave the silyl group
at the O-4 position, the reaction mixture was treated with tetra-
n-butyl ammonium uoride (TBAF, 11.0 equiv.) and acetic acid
(AcOH, 11.0 equiv.) at room temperature for 30 minutes,
providing 6a in 31% isolated yield (Table 3, entry 1). For further
optimization, the amount of H3[P(W3O10)4] was increased to 0.1
equivalent, signicantly changing the yield of 6a to 80% (Table
3, entry 2). Further increasing the amount of catalyst to 0.2
equivalent did not have a considerable effect in 79% yield (Table
3, entry 3).
Based on these results, the various substrate for the O-4 ring
opening reaction was investigated. The b-thio D-glucoside
derivatives 5b and 5c underwent the reaction readily, giving 6b
in 82% yield and 6c in 86% yield, respectively (Table 3, entries
4–5). The b-thio-D-galactose derivative 5d gave 6d in a similar
yield 79% (Table 3, entry 6). Importantly, aer the completion of
the reaction of 5e, TBAF and AcOH were used to cleave its O-4
silylated group. However, under TBAF and AcOH condition,
H3[P(W3O10)4]
(equiv.)
Entry
SM
Product
Yield
1
2
3
4
5
6
7
8
9
1d
1d
1d
1d
1d
3b
3c
0.5
0.2
4a
4a
4a
4a
4a
4b
4c
4d
4e
71%
58%
69%
72%
69%
84%
82%
65%
86%
0.25
0.3a
0.3b
0.3
0.15
0.3
Table 3 Phosphotungstic acid catalyzed regio-selective O-4 ring
opening reactions
3d
3e
0.3
a
b
The benzaldehyde dimethyl acetal was used 2.0 equivalents. The
benzaldehyde dimethyl acetal was used 3.0 equivalents.
increased to 0.3 equivalent, the desired product 4a was obtained
in a slightly higher yield 72% (Table 2, entry 4). Ultimately, 0.3
equivalent of phosphotungstic acid was determined to be the
optimal amount for the regioselective 4,6-O-benzylidene acetali-
zation reaction. Increasing the amount of benzaldehyde dimethyl
acetal to 3.0 equivalent did not signicantly affect the yield of 4a,
which remained 69% (Table 2, entry 5). Therefore, various
substrates were examined under optimized reaction conditions.
b-Thio-D-glucoside derivative 3b was reacted with benzaldehyde
dimethyl acetal in presence of phosphotungstic acid. The starting
material was consumed in 6 hours and 4b was obtained in 84%
yield (Table 2, entry 6). Aer 3c underwent the reaction, and the
desired product 4c was obtained in 82% yield (Table 2, entry 7).
3d and 3e underwent the reaction, and afforded 4d yield in 65%
and 4e in 86% yield, respectively (Table 2, entries 8–9). It has
produced better yield than PTSA12d catalyst and similar yield as
CSA. PTA only required less amount than CSA to bring better
yield of benzylidene acetal.
H3[P(W3O10)4]
(equiv.)
Entry
SM
Product
Yield
1
2
3
4
5
6
7
8
5a
5a
5a
5b
5c
5d
5e
5f
0.05
0.1
0.2
0.1
0.1
0.1
0.1
0.1
6a
6a
6a
6b
6c
6d
6e
6f
31%
80%
79%
82%
86%
79%
69%
80%
Regioselective reductive ring opening of benzylidene acetals
Following the successful per-O-acetylation and regioselective
benzylidene ring formation, the O-4 selective ring opening
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Table 4 Phosphotungstic acid catalyzed glycosylation with various
donors and acceptors
-OTBS was also removed, producing corresponding diol 6e in
69% (a/b ¼ 3/2) yield (Table 3, entry 7). Finally, 4-methylphenyl
3-O-acetyl-4,6-O-benzylidene-2-deoxyl-2-phthalimido-1-thio-b-D-
glucopyranoside 5f freely underwent the reaction, giving the
corresponding product 6f in 80% yield (Table 3, entry 8). The
PTA is little higher cost than TFA. However, PTA brought better
yield than TFA12i catalysed O-4 reductive ring-opening reaction.
Glycosylation reactions
Obtaining highly stereo-selective glycosidic linkages is one of
the most challenges in carbohydrate synthesis, as it is affected
by solvent effect, neighboring group effect, anomeric effect,
temperature effect and promoter effect. Use of phosphotungstic
acid which is a large catalyst may lead to increased selectivities
in glycosylations. Phosphotungstic acid was used in the glyco-
sylation to synthesize biologically important disaccharide
molecules. Chitosan plays a crucial role in tissue repair,
angiogenesis, tumor growth and drug delivery.29 The disaccha-
ride of chitosan contains b-D-GlcNH2(1 / 4)-D-GlcNH2 7. Lipid
A is a lipophilic portion of bacterial lipopolysaccharides and has
a b-D-GlcNH2(1 / 6)-D-GlcNH2 backbone 8.30 Hyaluronic acid is
another important biological molecule,31 which is involved in
cell-migration, tumor inhibition, adhesion and other processes.
It consists of a b-D-GlcA (1 / 3)-D-GlcNH2 disaccharide
repeating unit 9 (Fig. 2).
During the glycosylation reaction, the acid-sensitive group
such as the benzylidene ring was stable and exhibited good
tolerance of the phosphotungstic acid catalyst. The catalyst was
used as a promoter in the preparation of a disaccharide 13. With
donor 5f and acceptor 6g. The reaction proceeded conveniently
to provide compound 13 in 82% yield (Table 4, entry 1). The
derivatives of lipid A have immune-modulator characteristic.
They are therefore used as adjuvants for vaccinations and
treatments for many diseases. Two protected disaccharides 14
(83%) and 15 (53%) were synthesized using phosphotungstic
acid (Table 4, entries 2–3). Eventually, phosphotungstic acid
was used to synthesize 1,3-linked disaccharide with acceptor 4c
Entry
Donor
Acceptor
T ꢀC
Product (a/b)
Yield
1
2
3
4
5
5f
5f
5f
5f
10
6g
11
12
4c
4c
25
0
ꢁ40
25
25
13 (b only)
14 (b only)
15 (b only)
16 (b only)
17 (b only)
82%
83%
53%
86%
67%
and protected donors 5f and 10. The expected products 16 and group. All of the reactions proceeded smoothly in the presence
17 were obtained in good yields (Table 4, entries 4–5). Three of phosphotungstic acid as the catalyst. The glycosylation pro-
biologically important disaccharide backbones were prepared ceeded even at room temperature in the presence of PTA while
exclusively in b-form with the participation of the neighbouring other catalyst such as BF3.THF, TMSOTf and Ag(OTf)2 required
lower temperature.
Conclusions
We have successfully established that the phosphotungstic acid
was a convenient candidate to replace the corresponding
homogeneous acids for various carbohydrates reactions. It
could effectively catalyze per-O-acetylation, 4,6-O-benzylidene
acetal formation, regioselective O-4 ring-opening, and glyco-
sylation. Notably, the glycosylation reactions brought biologi-
cally important disaccharide unites like chitosan, hyaluronic
acid and lipid A in ambient condition. The different protecting
groups such as benzylidene acetal, –OAc, –NPhth, –OBn, 2-
Naph, –OTBS and azido were well tolerated during the reaction.
It provides moderate to excellent yields under optimal reaction
Fig. 2 Structures of the disaccharide of chitosan 7, lipid A 8 and
hyaluronic acid 9.
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conditions. Phosphotungstic acid is a useful acidic catalyst for 0.2H), 5.33 (t, J ¼ 1.4 Hz, 2H), 5.09–5.05 (m, 0.2H), 4.34 (td, J ¼
various reactions of carbohydrates.
6.8, 1.2 Hz, 1H), 4.14 (t, J ¼ 7.0 Hz, 0.4H), 4.10 (d, J ¼ 3.3 Hz, 1H),
4.09 (d, J ¼ 3.4 Hz, 1H), 4.07–4.05 (m, 0.3H), 2.17 (m, 0.6H), 2.16
(s, 3H), 2.16 (s, 3H), 2.12 (s, 0.6H), 2.05 (s, 0.5H), 2.04 (s, 3H),
2.02 (s, 3H), 2.01 (s, 3H), 1.99 (s, 0.5H); 13C NMR (100 MHz,
CDCl3) d 170.0, 169.9, 169.8, 169.6, 168.6, 89.4, 68.5, 67.2, 67.1,
66.2, 61.0, 20.6, 20.5, 20.4, 20.3; HRMS (ESI, M + Na+) calcd for
Experimental section
General information
The reactions were conducted in ame-dried glassware, under
the nitrogen atmosphere. Acetonitrile and dichloromethane
were puried and dried from a safe purication system con-
taining activated Al2O3. All reagents obtained from commercial
sources were used without purication unless otherwise
mentioned. Flash column chromatography was carried out on
Silica Gel 60. TLC was performed on pre-coated glass plates of
Silica Gel 60 F254 detection was executed by spraying with
a solution of Ce(NH4)2(NO3)6 (0.5 g), (NH4)6Mo7O24 (24.0 g) and
H2SO4 (28.0 mL) in water (500.0 mL) and subsequent heating on
a hot plate. Optical rotations were measured at 589 nm (Na), 1H,
13C NMR, DEPT, 1H–1H COSY, 1H–13C COSY, and NOESY
spectra were recorded with 400 MHz instruments. Chemical
shis are in ppm from Me4Si generated from the CDCl3 lock
signal at d 7.26. IR spectra were taken with a FT-IR spectrometer
using NaCl plates. Mass spectra were analyzed on orbitrap
instrument with an ESI source.
C
16H22O11Na 413.1060, found 413.1056.
1,2,3,4,6-Penta-O-acetyl-a-D-mannopyranose (2c). Prepared
according to the general procedure discussed above: colorless
oil (380 mg, 88%); Rf 0.60 (EtOAc/Hex ¼ 1/1); [a]2D9 +50.3 (c 1.0,
DCM); IR (NaCl) n 2106, 1749, 1645, 1371 cmꢁ1; H NMR (400
1
MHz, CDCl3) d 6.08 (s, 1H), 5.34–5.33 (m, 2H), 5.25 (s, 1H), 4.28
(dd, J ¼ 12.0, 4.8 Hz, 1H), 4.08 (dd, J ¼ 12.6, 1.8 Hz, 2H), 2.17 (s,
3H), 2.16 (s, 3H), 2.09 (s, 3H), 2.05 (s, 3H), 2.00 (s, 3H); 13C NMR
(100 MHz, CDCl3) d 170.3, 169.7, 169.4, 169.3, 167.8, 90.3, 70.3,
68.5, 68.0, 65.2, 61.8, 20.5, 20.4, 20.3, 20.29, 20.26; HRMS
(ESI, M + Na+) calcd for C16H22O11Na 413.1060, found 413.1054.
Methyl
2,3,4,6-tetra-O-acetyl-a-D-glucopyranoside
(2d).
Prepared according to the general procedure discussed above:
white soild (330 mg, 88%); Rf 0.60 (EtOAc/Hex ¼ 1/2); mp 51–
53 ꢀC; [a]2D9 +46.7 (c 1.0, DCM); IR (NaCl) n 2960, 1750, 1648,
1371, 1225 cmꢁ1; 1H NMR (400 MHz, CDCl3) d 5.47 (dd, J ¼ 10.1,
9.5 Hz, 1H), 5.07 (dd, J ¼ 10.2, 9.4 Hz, 1H), 4.95 (d, J ¼ 3.7 Hz,
1H), 4.90 (dd, J ¼ 10.2, 3.7 Hz, 1H), 4.26 (dd, J ¼ 12.3, 4.6 Hz,
1H), 4.12–4.08 (m, 1H), 3.98 (ddd, J ¼ 10.2, 4.5, 2.3 Hz, 1H), 3.41
Acetylation
General procedure for per-O-acetylation reaction. A round (s, 3H), 2.10 (s, 3H), 2.08 (s, 3H), 2.03 (s, 3H), 2.01 (s, 3H); 13C
bottom ask equipped with a magnetic stirrer bar was charged NMR (100 MHz, CDCl3) d 170.4, 169.9, 169.8, 169.4, 96.6, 70.6,
with 1a–1f (200 mg for 1a–1e, 500 mg for 1f, 1.0 equiv.) and to 69.9, 68.3, 67.0, 61.7, 55.3, 20.5, 20.46, 20.4; HRMS (ESI, M +
this were added phosphotungstic acid (0.02 equiv.) and acetic Na+) calcd for C15H22O10Na 385.1111, found 385.1111.
anhydride (10.0 equiv.) under nitrogen atmosphere. The reac-
1,2,3,5-Tetra-O-acetate-D-xylopyranose
(2e).
Prepared
tion mixture was stirred at 28 ꢀC for 24 hours. Aer completion according to the general procedure discussed above: colorless
of the reaction, the reaction mixture was diluted with ethyl oil (424 mg, 99%); Rf 0.55 (EtOAc/Hex ¼ 1/1); [a]2D9 +51.8 (c 1.0,
acetate and extracted with water (50.0 mL ꢂ 3). The combined DCM); IR (NaCl) n 2924, 1743, 1649, 1370, 1211 cmꢁ1; 1H NMR
organic layers were dried over anhydrous MgSO4, ltered and (400 MHz, CDCl3) d 6.25 (d, J ¼ 3.6 Hz, 1H), 5.70 (d, J ¼ 6.8 Hz,
concentrated. The crude product was puried by column 0.18H), 5.46 (t, J ¼ 9.9 Hz, 1H), 5.36 (t, J ¼ 5.0 Hz, 0.33H), 5.30–
chromatography on silica gel to give the desired product 2a–2f. 5.23 (m, 0.28H), 5.19 (t, J ¼ 8.4 Hz, 0.26H), 5.06–5.00 (m, 2H),
1,2,3,4,6-Penta-O-acetyl-D-glucopyranose (2a). Prepared 4.35 (dd, J ¼ 12.0, 4.0 Hz, 0.22H), 4.24 (d, J ¼ 6.0 Hz, 0.15H), 4.14
according to the general procedure discussed above: white solid (dd, J ¼ 12.4, 4.8 Hz, 0.24H), 3.99 (dd, J ¼ 12.0, 6.0 Hz, 0.23H),
(405 mg, 93%); Rf 0.53 (EtOAc/Hex ¼ 1/1); mp 109–113 ꢀC; 3.93 (dd, J ¼ 11.2, 5.9 Hz, 1H), 3.70 (t, J ¼ 11.0 Hz, 1H), 3.52 (dd,
[a]2D9 +62.5 (c 1.0, DCM); IR (NaCl) n 1752, 1647, 1371, 1221, J ¼ 12.0, 8.4 Hz, 0.2H). 2.17 (s, 3H), 2.13–2.05 (m, 9H), 2.05 (s,
1147 cmꢁ1; 1H NMR (400 MHz, CDCl3) d 6.33 (d, J ¼ 3.6 Hz, 1H), 3H), 2.04 (s, 3H), 2.02 (s, 3H); 13C NMR (100 MHz, CDCl3)
5.71 (d, J ¼ 8.4 Hz, 0.2H), 5.50–5.45 (m, 1H), 5.25 (t, J ¼ 9.2 Hz, d 170.0, 169.7, 169.6, 168.9, 89.1, 69.2, 69.16, 68.5, 60.5, 20.8,
0.2H), 5.16–5.14 (m, 1H), 5.11 (d, J ¼ 4.0 Hz, 1H), 5.09 (d, J ¼ 20.6, 20.6, 20.4; HRMS (ESI, M + Na+) calcd for C13H18O9Na
4.0 Hz, 0.5H), 4.29–4.28 (m, 0.5H), 4.25 (d, J ¼ 4.4 Hz, 1H), 4.14– 341.0849, found 341.0842.
4.10 (m, 2H), 4.07 (d, J ¼ 2.4 Hz, 0.4H), 2.18 (s, 3H), 2.12 (s,
1,2,3,6-Tetra-O-acetate-4-O-(2,3,4,6-tetra-O-acetyl-b-D-gal-
0.6H), 2.10 (s, 3H), 2.09 (s, 0.7H), 2.04 (s, 3H), 2.04 (s, 0.5H), 2.03 actopyranosyl)-D-glucopyranose (2f). Prepared according to the
(s, 0.5H), 2.03 (s, 3H), 2.02 (s, 3H), 2.01 (s, 0.6H); 13C NMR (100 general procedure discussed above: white solid (950 mg, 96%);
MHz, CDCl3) d 170.6, 170.2, 169.6, 169.4, 168.7, 89.0, 69.8, 69.2, Rf 0.44 (EtOAc/Hex ¼ 3/2); mp 85–87 ꢀC; [a]D22 +55.8 (c 1.0, DCM);
67.9, 61.4, 20.9, 20.7, 20.6, 20.5, 20.4; HRMS (ESI, M + Na+) calcd IR (NaCl) n 2981, 2943, 1753, 1649, 1434, 1371 cmꢁ1; H NMR
1
for C16H22O11Na 413.1060, found 413.1050.
(400 MHz, CDCl3) d 6.25 (d, J ¼ 3.6 Hz, 1H), 5.67 (d, J ¼ 8.4 Hz,
1,2,3,4,6-Penta-O-acetyl-D-galactopyranose (2b). Prepared 0.2H), 5.46 (t, J ¼ 9.6 Hz, 1.2H), 5.35 (d, J ¼ 3.6 Hz, 1.2H), 5.27–
according to the general procedure discussed above: white soild 5.21 (m, 0.3H), 5.12 (dd, J ¼ 10.4, 7.6 Hz, 1H), 5.09–5.03 (m,
(353 mg, 81%); Rf 0.50 (EtOAc/Hex ¼ 1/2); mp 70–80 ꢀC; 0.4H), 5.00 (dd, J ¼ 10.3, 3.6 Hz, 1H), 4.96 (dd, J ¼ 10.2, 3.4 Hz,
[a]2D9 +80.8 (c 1.0, DCM); IR (NaCl) n 1751, 1648, 1373 cmꢁ1; H 1H), 4.48 (d, J ¼ 8.0 Hz, 1H), 4.43 (s, 1H), 4.18–4.05 (m, 4H), 4.00
1
NMR (400 MHz, CDCl3) d 6.38 (d, J ¼ 1.6 Hz, 1H), 5.69 (d, J ¼ (ddd, J ¼ 10.0, 3.6, 1.6 Hz, 1H), 3.88 (t, J ¼ 6.8 Hz, 1H), 3.81 (t, J ¼
8.4 Hz, 0.2H), 5.50 (d, J ¼ 1.2 Hz, 1H), 5.42 (dd, J ¼ 3.2, 1.0 Hz, 9.7 Hz, 1H), 2.18 (s, 3H), 2.16 (s, 2H), 2.15 (s, 1H), 2.13 (s, 3H),
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2.12 (s, 1H), 2.09 (s, 1H), 2.06 (s, 2H), 2.06 (s, 2H), 2.05 (s, 3H), 7.47 (m, 2H), 7.41–7.35 (m, 3H), 5.50 (s, 1H), 4.59 (d, J ¼ 8.0 Hz,
2.05 (s, 1H), 2.04 (s, 1H), 2.03 (s, 1H), 2.01 (s, 2H), 1.97 (s, 3H); 1H), 4.26 (t, J ¼ 4.0 Hz, 1H), 3.74 (t, J ¼ 10.0 Hz, 1H), 3.59–3.46
13C NMR (100 MHz, CDCl3) d 170.28, 170.24, 170.08, 170.01, (m, 2H), 3.31–3.25 (m, 2H), 3.18 (br, 1H), 0.97 (s, 9H), 0.18 (s,
169.87, 169.56, 169.07, 168.88, 101.13, 88.87, 75.72, 70.91, 6H); 13C NMR (100 MHz, CDCl3) d 136.8, 129.2, 128.3, 126.3,
70.61, 69.50, 69.31, 69.01, 66.49, 61.36, 60.70, 20.91, 20.80, 101.8, 97.4, 80.7, 71.5, 68.9, 68.4, 66.2, 25.5, 17.8, ꢁ4.4, ꢁ5.3;
20.61, 20.46; HRMS (ESI, M + Na+) calcd for C28H38O19Na HRMS (ESI, M + Na+) calcd for C19H29N3O5SiNa 430.1774, found
701.1905, found 701.1902.
430.1770.
4-Methylphenyl 4,6-O-benzylidene-1-thio-b-D-glucopyrano-
side (4d). Prepared according to the general procedure dis-
cussed above: white solid. (126 mg, 65%); Rf 0.62 (EtOAc); mp
Acetalization
General procedure for benzylidene formation. A solution of 177–178 ꢀC; [a]D25 ꢁ161.30 (c 1.0, DCM); IR (NaCl) v 3442, 2870,
1d, 3b–3e (150 mg for 1d, 3b, 3d, and 3e, 140 mg for 3c, and 2088, 1643, 1493, 1454, 1381, 1265, 1214, 1165, 1085, 1030,
120 mg for 3e, 1.0 equiv.) and activated 4 A MS in anhydrous 1005, 974 cmꢁ1; 1H NMR (400 MHz, CDCl3) d 7.48–7.42 (m, 4H),
ꢀ
acetonitrile (2 mL) was stirred for 30 minutes under nitrogen 7.38–7.35 (m, 3H), 7.15 (d, J ¼ 8.0 Hz, 2H), 5.52 (s, 1H), 4.57 (d, J
atmosphere at rt. Then the ask was placed into an ice bath. ¼ 9.6 Hz, 1H), 4.39 (dd, J ¼ 10.4, 4.4 Hz, 1H), 3.85 (t, J ¼ 8.4 Hz,
Aer 3 minutes, benzaldehyde dimethyl acetal (2.0 equiv.) and 1H), 3.78 (t, J ¼ 7.4 Hz, 1H), 3.52–3.47 (m, 2H), 3.43 (t, J ¼ 9.0 Hz,
dried phosphotungstic acid (0.3 equiv. for 1d, 3b, 3d, and 3e 1H), 2.80 (bs, 1H), 2.65 (bs, 1H), 2.36 (s, 3H); 13C NMR (100 MHz,
and 0.15 equiv. for 3c) were added to the reaction mixture at CDCl3) d 138.6, 136.8, 133.4, 129.7, 129.2, 128.2, 127.3, 126.2,
0 ꢀC. Aer completion of the reaction, the reaction mixture was 101.7, 88.5, 80.0, 74.3, 72.3, 70.3, 68.4, 21.1; HRMS (ESI, M +
passed through the Celite and extracted with water (25 mL) and Na+) calcd for C20H22O5SNa 397.1086, found 397.1084.
ethyl acetate (50 mL ꢂ 2). The combined organic layers were
4-Methylphenyl 4,6-O-benzylidene-1-thio-b-D-galactopyrano-
washed with brine, dried over anhydrous MgSO4, ltered and side (4e). Prepared according to the general procedure dis-
concentrated under reduced pressure. The crude product was cussed above: white solid (135 mg, 86%); Rf 0.34 (EtOAc); mp
puried by column chromatography on silica gel to afford 4a– 145–146 ꢀC; [a]D25 ꢁ175.30 (c 1.0, DCM); IR (NaCl) v 3440, 2920,
4e.
2665, 2248, 1644, 1493, 1451, 1402, 1361, 1276, 1245, 1197,
(4a). 1165, 1101, 1070, 1042, 993, 970 cmꢁ1
1H NMR (400 MHz,
Methyl
4,6-O-benzylidene-a-D-glucopyranoside
;
Prepared according to the general procedure discussed above: CDCl3) d 7.45 (d, J ¼ 8.0 Hz, 2H), 7.25 (d, J ¼ 4.0 Hz, 5H), 6.99 (d,
white solid. (157 mg, 72%); Rf 0.35 (EtOAc); mp 161–162 ꢀC; J ¼ 8.0 Hz, 2H), 5.37 (s, 1H), 4.32 (d, J ¼ 8.8 Hz, 1H), 4.25 (d, J ¼
[a]2D5 +117.0 (c 1.0, DCM); IR (NaCl) v 3380, 2915, 2870, 1640, 12.4 Hz, 1H), 4.06 (d, J ¼ 3.2 Hz, 1H), 3.89 (d, J ¼ 12.4 Hz, 1H),
1
1453, 1373, 1192, 1145, 1125, 1076, 1030, 1000 cmꢁ1; H NMR 3.55 (bs, 1H), 3.50 (t, J ¼ 9.2 Hz, 1H), 3.40 (s, 1H), 2.54 (bs, 2H),
(400 MHz, CDCl3) d 7.48–7.45 (m, 2H), 7.37–7.32 (m, 3H), 5.49 2.24 (s, 3H); 13C NMR (100 MHz, CDCl3) d 138.5, 137.5, 134.2,
(s, 1H), 4.73 (d, J ¼ 4.0 Hz, 1H), 4.26 (dd, J ¼ 9.6, 4.4 Hz, 1H), 129.6, 129.2, 128.1, 126.5, 101.3, 86.9, 75.2, 73.7, 69.9, 69.2, 68.6,
3.88 (t, J ¼ 9.2 Hz, 1H), 3.80–3.67 (m, 2H), 3.58 (bs, 1H), 3.44 (t, J 21.2; HRMS (ESI, M + Na+) calcd for C20H22O5SNa 397.1086,
¼ 12.0 Hz, 1H), 3.41 (s, 3H), 3.29 (bs, 1H), 2.65 (bs, 1H); 13C found 397.1086.
NMR (100 MHz, CDCl3) d 137.2, 129.5, 128.6, 126.5, 102.1,
100.0, 81.1, 73.0, 71.8, 69.1, 62.8, 55.8; HRMS (ESI, M + Na+)
calcd for C14H18O6Na 305.1001, found 305.1005.
Regioselective reductive ring opening of benzylidene acetals
4-Methylphenyl 4,6-O-benzylidene-2-deoxyl-1-thio-2-phthali-
General procedure for regio-selective O-4 ring opening
mido-b-D-glucopyranoside (4b). Prepared according to the reaction. A solution of 5a–5f (100 mg for 5a–5e and 200 mg for
ꢀ
general procedure discussed above: white solid (154 mg, 84%); 5f, 1.0 equiv.) and activated 4 A MS (100 mg) in anhydrous
25
ꢀ
Rf 0.46 (EtOAc/Hex ¼ 1/2); mp 121–122 C; [a]D +40.0 (c 0.45, dichloromethane (1.0 mL) was stirred under nitrogen atmo-
DCM); IR (NaCl) v 3443, 2868, 2090, 1775, 1644 cmꢁ1; 1H NMR sphere at room temperature. Then the ask was placed into an
(400 MHz, CDCl3) d 7.91–7.78 (m, 2H), 7.76–7.68 (m, 2H), 7.49– ice bath for 5 minutes and triethylsilane (11 equiv.), phospho-
4.41 (m, 2H), 7.38–7.31 (m, 3H), 7.27–7.24 (m, 2H), 7.05 (d, J ¼ tungstic acid (0.1 equiv.) were added to the reaction mixture at
7.6 Hz, 2H), 5.60 (d, J ¼ 10.8 Hz, 1H), 5.53 (s, 1H), 4.58 (t, J ¼ 0 ꢀC. Then the reaction was allowed to stir at same temperature
8.8 Hz, 1H), 4.36 (dd, J ¼ 10.4, 4.8 Hz, 1H), 4.27 (t, J ¼ 10.0 Hz, for 12 hours. Aer completion of the reaction, were added 1 M
1H), 3.79 (t, J ¼ 10.0 Hz, 1H), 3.68–3.60 (m, 1H), 3.55 (t, J ¼ tetra-n-butyl ammonium uoride (11 equiv.) and acetic acid (11
9.2 Hz, 1H), 2.75 (s, 1H), 2.29 (s, 3H); 13C NMR (100 MHz, CDCl3) equiv.) at 0 ꢀC, and stirred for 30 minutes at 25 ꢀC. The
d 165.7, 165.0, 135.9, 134.3, 131.6, 130.7, 129.1, 127.1, 126.8, molecular sieves were removed by ltration through Celite. The
125.8, 125.2, 123.7, 121.3, 120.8, 99.3, 81.9, 79.3, 67.7, 67.1, 66.0, ltrate was extracted with EtOAc (20 mL ꢂ 3) and water (20 mL).
53.0, 18.6; HRMS (ESI, M + Na+) calcd for C28H25NO6SNa The combined organic layers were dried over anhydrous MgSO4,
526.1301, found 526.1299.
2-Azido-4,6-O-benzylidene-2-deoxyl-1-O-tert-butyldi-methyl-
silyl-b-D-glucopyranoside (4c). Prepared according to the
ltered and concentrated. It was puried by column chroma-
tography on silica gel to give the desired product 6a–6f.
Methyl 2,3-di-O-acetyl-6-O-benzyl-a-D-glucopyranoside (6a).
general procedure discussed above: colorless oil. (106 mg, 82%); Prepared according to the general procedure discussed above:
Rf 0.59 (EtOAc/Hex ¼ 1/2); [a]2D5 ꢁ19.9 (c 0.05, DCM); IR (NaCl) v yellow liquid (88 mg, 80%); Rf 0.35 (EtOAc/Hex ¼ 1/1);
3443, 3039, 2860, 2111 cmꢁ1; 1H NMR (400 MHz, CDCl3) d 7.52– [a]2D6 +109.5 (c 1.0, DCM); IR (NaCl) n 3474, 2919, 2871, 1747,
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1452, 1371 cmꢁ1
;
1H NMR (400 MHz, CDCl3) d 7.37–7.29 (m, ¼ 2.8 Hz, 0.6H), 3.68–3.62 (m, 2H), 3.55 (d, J ¼ 9.5 Hz, 1H), 3.52–
5H), 5.30 (t, J ¼ 10.0 Hz 1H), 4.91 (d, J ¼ 3.6 Hz, 1H), 4.87 (dd, J ¼ 3.49 (m, 1H), 3.34 (dd, J ¼ 10.2, 8.0 Hz, 0.8H), 3.28 (dd, J ¼ 10.5,
10.1, 3.6 Hz, 1H), 4.60 (q, J ¼ 12.0 Hz, 2H), 3.80–3.70 (m, 4H), 3.4 Hz, 1H), 2.16 (s, 3H), 2.15 (s, 2H); 13C NMR (100 MHz, CDCl3)
3.40 (s, 3H), 2.83 (s, 1H), 2.09 (s, 3H), 2.08 (s, 3H).; 13C NMR (100 d 172.0, 171.8, 137.3, 137.2, 128.53, 128.5, 128.02, 127.98, 95.9,
MHz, CDCl3) d 176.8, 171.3, 170.2, 137.7, 128.3, 127.6, 127.5, 91.9, 75.7, 74.6, 73.7, 73.6, 73.5, 70.5, 70.3, 70.1, 69.5, 69.4, 64.5,
96.6, 73.5, 72.9, 70.7, 70.1, 70.0, 69.2, 55.1, 20.8, 20.6; HRMS 61.4, 21.0; HRMS (ESI, M + Na+) calcd for C15H19O6N3Na
(ESI, M + Na+) calcd for C18H24O8Na 391.1369, found 391.1362. 360.1172, found 360.1164.
4-Methylphenyl 2,3-di-O-acetyl-6-O-benzyl-1-thio-b-D-gluco-
4-Methylphenyl 3-O-acetyl-6-O-benzyl-2-deoxyl-2-phthalimi-
pyranoside (6b). Prepared according to the general procedure do-1-thio-b-D-glucopyranoside (6f). Prepared according to the
discussed above: yellow oil (83 mg, 82%); Rf 0.25 (EtOAc/Hex ¼ general procedure discussed above: white solid (159 mg,
1/2); [a]2D6 ꢁ37.4 (c 0.8, DCM); IR (NaCl) n 3478, 3030, 2920, 1752, 80%); Rf 0.38 (EtOAc/Hex ¼ 1/1); mp 54–56 C; [a]D +17.0 (c
23
ꢀ
1494, 1373 cmꢁ1
;
1H NMR (400 MHz, CDCl3) d 7.40–7.28 (m, 1.0, DCM); IR (NaCl) n 3478, 3030, 2922, 2855, 1750, 1494,
7H), 7.08 (d, J ¼ 8.4 Hz, 2H), 5.06 (t, J ¼ 9.6 Hz, 1H), 4.90 (dd, J ¼ 1430, 1369 cmꢁ1; H NMR (400 MHz, CDCl3) d 7.89–7.84 (m,
9.6, 9.2 Hz, 1H), 4.63 (d, J ¼ 10.0 Hz, 1H), 4.57 (d, J ¼ 5.2 Hz, 2H), 2H), 7.77–7.72 (m, 2H), 7.40–7.31 (m, 5H), 7.29 (d, J ¼ 8.2 Hz,
3.80 (dd, J ¼ 6.4, 4.8 Hz, 2H), 3.72 (t, J ¼ 9.4 Hz, 1H), 3.58–3.52 2H), 7.03 (d, J ¼ 7.9 Hz, 2H), 5.68–5.61 (m, 2H), 4.60 (q, J ¼
(m, 1H), 2.32 (s, 3H), 2.09 (s, 3H), 2.07 (s, 3H).; 13C NMR (100 11.8 Hz, 2H), 4.26 (t, J ¼ 10.4 Hz, 1H), 3.88–3.72 (m, 4H), 2.91
MHz, CDCl3) d 171.2, 169.5, 138.4, 137.6, 133.4, 129.6, 128.4, (s, 1H), 2.29 (s, 3H), 1.91 (s, 3H); 13C NMR (100 MHz, CDCl3)
128.0, 127.8, 127.6, 85.8, 78.4, 76.7, 73.7, 70.0, 69.9, 69.87, 21.1, d 171.1, 167.8, 167.3, 138.4, 137.7, 134.3, 134.1, 133.5, 131.6,
20.8.; HRMS (ESI, M+Na+) calcd for C24H28O7SNa 483.1453, 131.2, 129.6, 128.4, 127.8, 127.7, 127.5, 123.6, 123.5, 83.2,
1
found 483.1446.
78.3, 74.3, 73.7, 71.0, 70.2, 53.6, 52.6, 21.1, 20.7, 20.5, 13.9;
4-Methylphenyl
2,3,6-tri-O-benzyl-1-thio-b-D-glucopyrano- HRMS (ESI, M + Na+) calcd for C30H29NO7SNa 570.1562,
side (6c). Prepared according to the general procedure dis- found 570.1561.
cussed above: yellow oil (86 mg, 86%); Rf 0.25 (EtOAc/Hex ¼ 1/2);
26
Glycosylation reactions
ꢀ
mp 62–64 C; [a]D ꢁ7.4 (c 0.8, DCM); IR (NaCl) n 3478, 3030,
2920, 1752, 1494, 1373 cmꢁ1; 1H NMR (400 MHz, CDCl3) d 7.46
2-Azido-2-deoxy-3-O-acetyl-6-O-benzyl-1-O-tert-butyldime-
(d, J ¼ 8.1 Hz, 2H), 7.44–7.40 (m, 2H), 7.38–7.27 (m, 13H), 7.05 thylsilyl-4-O-(3-O-ace-tyl-4,6-O-benzylidene-2-deoxy-2-phthali-
(d, J ¼ 7.9 Hz, 2H), 4.93 (d, J ¼ 4.4 Hz, 1H), 4.90 (d, J ¼ 6.0 Hz, mido-b-D-glucopyranosyl)-b-D-glucopyranoside (13). A solution
1H), 4.76 (dd, J ¼ 16.0, 15.2 Hz, 2H), 4.63 (d, J ¼ 9.6 Hz, 1H), 4.57 of acceptor 6g (50 mg, 0.11 mmol), donor 5f (120 mg, 0.22
ꢀ
(d, J ¼ 4.4 Hz, 2H), 3.77 (t, J ¼ 5.0 Hz, 2H), 3.64 (t, J ¼ 9.2 Hz, mmol), and activated 4 A molecular sieves (300 mg) in
1H), 3.53 (t, J ¼ 8.6 Hz, 1H), 3.49–3.42 (m, 2H), 2.55 (s, 1H), 2.31 dichloromethane (1 mL) was stirred for 30 minutes at room
(s, 3H).; 13C NMR (100 MHz, CDCl3) d 138.4, 138.2, 138.1, 138.0, temperature. Aer N-iodosuccinimide (148 mg, 0.66 mmol)
137.9, 137.7, 132.6, 129.7, 129.6, 128.6, 128.4, 128.37, 128.2, and dried phosphotungstic acid (158 mg, 0.055 mmol) were
127.9, 127.7, 87.9, 86.1, 80.4, 78.0, 75.5, 75.3, 73.6, 71.6, 70.3, added, the reaction mixture was stirred for 5 hours. When
21.1; HRMS (ESI, M + Na+) calcd for C34H36O5SNa 579.2181, the reaction was completed, molecular sieves were removed
found 579.2184.
by ltration through Celite. The ltrate was extracted with
4-Methylphenyl
2,3-di-O-acetyl-6-O-benzyl-1-thio-b-D-gal- aqueous sodium thiosulfate (10 mL) and brine (10 mL), and
acopyranoside (6d). Prepared according to the general proce- the organic layer was dried over anhydrous MgSO4, ltered,
dure discussed above: white solid (80 mg, 79%); Rf 0.50 (EtOAc/ and concentrated under vacuum. The residue was puried by
Hex ¼ 1/1); mp 114–115 ꢀC; [a]2D6 +1.8 (c 0.8, DCM); IR (NaCl) n column chromatography on silica gel to give the desired
1
3478, 3030, 2922, 1750, 1494, 1369 cmꢁ1; H NMR (400 MHz, product 13 (79 mg, 82%) as a white soild. Rf 0.47 (EtOAc/Hex
24
ꢀ
CDCl3) d 7.41 (d, J ¼ 8.0 Hz, 2H), 7.36–7.29 (m, 5H), 7.07 (d, J ¼ ¼ 1/2); mp 112–114 C; [a]D ꢁ13.4 (c 1.0, DCM); IR (NaCl) n
8.1 Hz, 2H), 5.27 (t, J ¼ 9.8 Hz, 1H), 4.96 (dd, J ¼ 9.6, 3.0 Hz, 1H), 3479, 2931, 2112, 1751, 1720, 1386, 1227, 1105, 1082 cmꢁ1
;
4.63 (d, J ¼ 10.0 Hz, 1H), 4.56 (d, J ¼ 4.8 Hz, 2H), 4.17 (t, J ¼ 1H NMR (400 MHz, CDCl3) d 7.83 (dd, J ¼ 5.5, 3.1 Hz, 2H),
3.2 Hz, 1H), 3.78 (t, J ¼ 4.4 Hz, 2H), 3.71 (t, J ¼ 5.0 Hz, 1H), 2.64– 7.71 (dd, J ¼ 5.5, 3.0 Hz, 2H), 7.46 (d, J ¼ 4.4 Hz, 1H), 7.44 (d, J
2.59 (m, 1H), 2.31 (s, 3H), 2.08 (s, 3H), 2.07 (s, 3H); 13C NMR (100 ¼ 2.1 Hz, 1H), 7.38–7.35 (m, 3H), 7.32–7.27 (m, 3H), 7.21–
MHz, CDCl3) d 170.2, 169.5, 164.8, 155.2, 138.3, 137.5, 133.3, 7.19 (m, 2H), 5.84 (dd, J ¼ 10.2, 9.4 Hz, 1H), 5.52 (s, 1H), 5.50
129.6, 128.5, 128.3, 127.9, 127.8, 86.5, 76.7, 74.5, 73.8, 69.5, 68.3, (d, J ¼ 8.4 Hz, 1H), 4.90 (dd, J ¼ 10.4, 9.2 Hz, 1H), 4.47 (d, J ¼
67.6, 29.7, 21.2, 20.9; HRMS (ESI, M + Na+) calcd for 8.0 Hz, 1H), 4.39–4.36 (m, 2H), 4.26 (d, J ¼ 12.0 Hz, 1H), 4.21
C
24H28O7SNa 483.1453, found 483.1458.
(dd, J ¼ 10.4, 8.4 Hz, 1H), 3.93 (t, J ¼ 9.6 Hz, 1H), 3.79–3.70
3-O-Acetyl-2-azido-6-O-benzyl-2-deoxyl-D-glucopyranoside
(m, 2H), 3.65–3.59 (m, 1H), 3.36–3.33 (m, 1H), 3.30–3.25 (m,
(6e). Prepared according to the general procedure discussed 3H), 2.15 (s, 3H), 1.86 (s, 3H), 0.88 (s, 9H), 0.07 (s, 3H), 0.07
above: colorless liquid (52 mg, 69%), a/b ¼ 3/2; Rf 0.30 (EtOAc/ (s, 3H); 13C NMR (101 MHz, CDCl3) d 170.1, 169.2, 137.8,
Hex ¼ 1/1); [a]2D5 ꢁ5.5 (c 0.6, DCM); IR (NaCl) n 3417, 2923, 2871, 136.6, 134.2, 131.2, 129.1, 128.1, 127.4, 127.3, 126.1, 123.4,
2110, 1720, 1454, 1364 cmꢁ1.; 1H NMR (400 MHz, CDCl3) d 7.37– 101.5, 98.2, 96.7, 78.8, 74.6, 74.2, 72.7, 72.4, 69.5, 68.5, 67.3,
7.27 (m, 8.4H), 5.33 (d, J ¼ 10.0 Hz, 0.7H), 5.30 (d, J ¼ 3.2 Hz, 66.3, 65.8, 55.5, 25.4, 21.1, 20.4, 17.8, ꢁ4.6, ꢁ5.4; HRMS
1H), 4.78 (dd, J ¼ 10.2, 8.7 Hz, 0.9H), 4.58–4.54 (m, 3H), 4.08 (ESI, M + Na+) calcd for C44H52N4O13SiNa 895.31978, found
(ddd, J ¼ 9.2, 5.7, 2.8 Hz, 1H), 3.74 (t, J ¼ 3.1 Hz, 0.8H), 3.72 (d, J 895.3181.
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9.2 Hz, 1H), 4.41–4.35 (m, 2H), 4.27 (d, J ¼ 4 Hz, 2H), 4.00 (d, J ¼
10.4 Hz, 1H), 3.86–3.76 (m, 2H), 3.75–3.69 (m, 2H), 3.48–3.37
(m, 2H), 3.22 (dd, J ¼ 12.8, 8.8 Hz, 1H), 1.97 (s, 3H), 1.89 (s, 3H),
0.86 (S, 9H), 0.07 (s, 3H), 0.01 (s, 3H); 13C NMR (100 MHz,
CDCl3) d 170.1, 169.7, 137.1, 136.8, 134.2, 129.1, 128.3, 128.2,
127.8, 127.5, 126.2, 123.5, 101.6, 98.1, 97.0, 79.1, 76.0, 74.3, 74.0,
73.5, 69.8, 68.6, 67.8, 66.3, 66.2, 55.1, 25.4, 20.8, 20.5, 17.8, ꢁ4.3,
ꢁ5.4; HRMS (ESI, M + Na+) calcd for C44H52N4O13SiNa 895.3197,
found 895.3193.
2-Azido-4-O-benzyl-1-O-tert-butyldimethylsilyl-2-deo-xy-3-O-
(2-naphthylmethyl)-6-O-(3-O-acetyl-4,6-O-be-nzylidene-2-deoxy-
2-phthalimi-do-b-D-glucopyranosyl)-b-D-glucopyranoside (14).
To a solution of acceptor 12 (241 mg, 0.44 mmol), donor 5f
(200 mg, 0.37 mmol), N-iodosuccinimide (90 mg, 0.40 mmol)
ꢀ
and activated 4 A molecular sieves (150 mg) in dichloromethane
(3.0 mL) were stirred for 1 hour at room temperature. Aer
phosphotungstic acid (126 mg, 0.044 mmol) was added at 0 ꢀC,
the reaction mixture was stirred for 12 hours at same temper-
ature. When the reaction was completed, the mixture was
quenched by triethylamine and molecular sieves were removed
by ltration through Celite. The ltrate was extracted with
aqueous sodium thiosulfate (10 mL) and brine (10 mL), and the
organic layer was dried over anhydrous MgSO4, ltered, and
concentrated under vacuum. The residue was puried by
column chromatography on silica gel to give the desired
product 14 (84 mg, 53%) as pali yellow soild. Rf 0.50 (EtOAc/Hex
¼ 1/2); mp 90–93 ꢀC; [a]D25 ꢁ93.63 (c 0.1, DCM); IR (NaCl) v 3414,
2106, 1748, 1718, 1645 cmꢁ1; 1H NMR (400 MHz, CDCl3) d 7.86–
7.79 (m, 3H), 7.75–7.72 (m, 3H), 7.60–7.58 (m, 2H), 7.51–7.45
(m, 5H), 7.39 (d, J ¼ 4.4 Hz, 3H), 7.28–7.24 (m, 4H), 7.03 (d, J ¼
6.0 Hz, 2H), 5.87 (t, J ¼ 10 Hz, 1H), 5.57 (s, 1H), 5.53 (d, J ¼ 8.4,
1H), 5.00 (d, J ¼ 11.2 Hz, 1H), 4.86 (d, J ¼ 11.2 Hz, 1H), 4.60 (d, J
¼ 10.8 Hz, 1H), 4.39 (t, J ¼ 8, 2H), 4.32 (d, J ¼ 10.8 Hz, 1H), 4.23
(d, J ¼ 10 Hz, 1H), 3.88–3.79 (m, 2H), 3.77–3.69 (m, 2H), 3.46–
3.36 (m, 2H), 3.34–3.29 (m, 2H), 1.90 (s, 3H), 0.89 (s, 9H), 0.08 (s,
3H), 0.00 (s, 3H); 13C NMR (100 MHz, CDCl3) d 170.0, 137.4,
136.8, 135.3, 134.0, 133.1, 132.8, 129.0, 128.2, 128.1, 128.0,
127.8, 127.6, 127.5, 127.5, 126.5, 126.1, 125.9, 125.9, 125.8,
123.3, 101.5, 98.0, 97.0, 82.4, 79.0, 77.5, 75.2, 74.7, 74.1, 69.8,
68.5, 68.3, 67.9, 66.1, 55.0, 30.7, 25.4, 20.4, 17.7, ꢁ4.4, ꢁ5.6;
HRMS (ESI, M + Na+) calcd for C53H58N4O12SiNa 993.3718,
found 993.3707.
2-Azido-4,6-O-benzylidene-1-O-tert-butyldimethylsilyl-2-
deoxyl-3-O-(3-O-acetyl-4,6-O-benzylidene-2-deoxyl-2-phtha-lim-
ido-b-D-glucopyranosyl)-b-D-glucopyranoside (16). A solution of
acceptor 4c (100 mg, 0.25 mmol) and dried phosphotungstic
acid (177 mg, 0.062 mmol) inꢀdichloromethane (2.68 mL) was
ꢀ
stirred for 30 minutes at 28 C with activated 4 A molecular
sieves (335 mg). Then N-iodosuccinimide (166 mg, 0.74 mmol)
and donor 5f (235 mg, 0.43 mmol) in dichloromethane (4 mL)
was added, and the reaction mixture was stirred for 8 hours.
When the reaction was completed, molecular sieves were
removed by ltration through Celite. The ltrate was extracted
with aqueous sodium thiosulfate (20 mL) and brine (20 mL),
and the organic layers were dried over anhydrous MgSO4,
ltered, and concentrated under vacuum. The residue was
puried by column chromatography on silica gel to give the
desired product 16 (176 mg, 86%) as a white soild. Rf 0.52
(EtOAc/Hex ¼ 1/2); mp 260–262 ꢀC; [a]D24 ꢁ64.3 (c 1.0, DCM); IR
(NaCl) n 3441, 2931, 2112, 1745, 1719, 1387, 1225, 1098 cmꢁ1; 1H
NMR (400 MHz, CDCl3) d 7.85 (dd, J ¼ 5.2, 3.0 Hz, 2H), 7.68 (dd,
J ¼ 5.4, 3.0 Hz, 2H), 7.49–7.43 (m, 4H), 7.39–7.34 (m, 6H), 5.90 (t,
J ¼ 9.8 Hz, 1H), 5.56 (d, J ¼ 8.4 Hz, 1H), 5.50 (d, J ¼ 14.8 Hz, 2H),
4.53 (d, J ¼ 7.6 Hz, 1H), 4.39 (dd, J ¼ 10.2, 8.6 Hz, 1H), 4.24 (dd, J
¼ 10.6, 5.0 Hz, 1H), 4.07 (dd, J ¼ 10.0, 4.4 Hz, 1H), 3.78–3.69 (m,
3H), 3.66 (dd, J ¼ 9.4, 4.2 Hz, 1H), 3.58 (t, J ¼ 9.2 Hz, 1H), 3.48 (t,
J ¼ 9.4 Hz, 1H), 3.31 (td, J ¼ 9.6, 5.0 Hz, 1H), 3.20 (dd, J ¼ 9.6,
7.6 Hz, 1H), 1.88 (s, 3H), 0.85 (s, 9H), 0.07 (s, 3H), 0.06 (s, 3H);
13C NMR (101 MHz, CDCl3) d 170.0, 136.9, 136.8, 134.1, 131.3,
129.0, 128.1, 128.0, 126.2, 125.9, 123.4, 101.5, 101.1, 99.8, 97.7,
80.6, 79.0, 78.9, 69.7, 68.5, 68.2, 67.4, 66.3, 66.0, 55.4, 25.4, 20.5,
17.7, ꢁ4.5, ꢁ5.3; HRMS (ESI, M + H+) calcd for C42H49N4O12Si
829.3116, found 829.3113.
2-Azido-2-deoxy-3-O-acetyl-4-O-benzyl-1-O-tert-butyldime-
thylsilyl-6-O-(3-O-ace-tyl-4,6-O-benzylidene-2-phthalimido-2-
deoxy-b-D-glucopyranosyl)-b-D-gluco-pyranoside (15). To a solu-
tion of acceptor 11 (99 mg, 0.22 mmol), donor 5f (100 mg, 0.18
mmol), N-iodosuccinimide (61 mg, 0.27 mmol) and activated 4
ꢀ
A molecular sieves (200 mg) in dichloromethane (1.5 mL) were
stirred for 1 hour at room temperature. Aer dried phospho-
2-Azido-4,6-O-benzylidene-1-O-tert-butyldimethylsilyl-2-
tungstic acid (158 mg, 0.054 mmol) was added, the reaction
mixture was stirred for 3 hours at ꢁ40 C. When the reaction
ꢀ
deoxyl-3-O-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)-b-D-gluco-
pyranoside (17). A solution of acceptor 4c (100 mg, 0.25 mmol)
and donor 10 (167 mg, 0.37 mmol) in dichloromethane (5.5 mL)
was stirred for 30 minutes at room temperature with activated 4
was completed, it was quenched by triethylamine and molec-
ular sieves were removed by ltration through Celite. The
ltrate was extracted with aqueous sodium thiosulfate (10 mL)
and brine (10 mL), and the organic layer was dried over anhy-
drous MgSO4, ltered, and concentrated under vacuum. The
residue was puried by column chromatography on silica gel to
give the desired product 15 (84 mg, 53%). Rf 0.30 (EtOAc/Hex ¼
ꢀ
A molecular sieves (323 mg). Aer N-iodosuccinimide (166 mg,
0.74 mmol) and phosphotungstic acid (216 mg, 0.075 mmol)
were added, the reaction mixture was stirred for 5 hours at room
temperature. When the reaction was completed, molecular
sieves were removed by ltration through Celite. The ltrate was
extracted with aqueous sodium thiosulfate (10 mL) and brine
(10 mL), and the organic layers were dried over anhydrous
MgSO4, ltered, and concentrated under vacuum. The residue
was puried by column chromatography on silica gel to give the
desired product 17 (123 mg, 67%) as a white soild. Rf 0.51
25
ꢀ
1.5/8.5); mp 175–176 C; [a]D ꢁ152.2 (c 1.0, DCM); IR (NaCl) v
2951, 2931, 2884, 2858, 2111, 1747, 1718, 1645, 1469, 1387,
1312, 1225, 1176, 1104, 1042, 1014, 1001, 970, 917, 872, 840,
1
784, 738, 700 cmꢁ1; H NMR (400 MHz, CDCl3) d 7.76 (s, 2H),
7.65–7.63 (m, 2H), 7.47–7.44 (m, 2H), 7.37–7.35 (m, 3H), 7.22–
7.21 (m, 3H), 6.96–6.94 (m, 2H), 5.84 (t, J ¼ 9.2 Hz, 1H), 5.54 (s,
1H), 5.51 (d, J ¼ 8.4 Hz, 1H), 4.91 (t, J ¼ 8.8 Hz, 1H), 4.54 (d, J ¼
25
ꢀ
(EtOAc/Hex ¼ 3/4); mp 96–98 C; [a]D ꢁ40.4 (c 1.0, DCM); IR
(NaCl) n 3472, 2933, 2860, 2114, 1757, 1371, 1228, 1099,
33860 | RSC Adv., 2019, 9, 33853–33862
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1040 cmꢁ1; 1H NMR (400 MHz, CDCl3) d 7.44 (dd, J ¼ 6.8, 2.9 Hz,
2H), 7.33–7.32 (m, 3H), 5.52 (s, 1H), 5.16 (d, J ¼ 9.6 Hz, 1H),
5.09–5.00 (m, 2H), 4.74 (d, J ¼ 8.0 Hz, 1H), 4.59 (d, J ¼ 8.0 Hz,
1H), 4.25 (dd, J ¼ 10.6, 5.0 Hz, 1H), 4.08 (dd, J ¼ 12.4, 4.0 Hz,
1H), 3.84 (dd, J ¼ 12.4, 2.4 Hz, 1H), 3.77 (t, J ¼ 10.4 Hz, 1H), 3.66
(t, J ¼ 9.2 Hz, 1H), 3.59 (t, J ¼ 9.4 Hz, 1H), 3.47–3.43 (m, 1H), 3.36
(dd, J ¼ 9.6, 4.8 Hz, 1H), 3.31 (dd, J ¼ 9.6, 7.6 Hz, 1H), 2.05 (s,
3H), 1.98 (s, 3H), 1.97 (s, 3H), 1.96 (s, 3H), 0.91 (s, 9H), 0.15 (s,
3H), 0.13 (s, 3H); 13C NMR (101 MHz, CDCl3) d 170.5, 170.2,
169.3, 169.2, 136.9, 129.1, 128.1, 125.9, 101.2, 101.0, 97.5, 79.4,
79.1, 72.7, 71.6, 71.4, 68.4, 68.3, 67.9, 66.4, 61.4, 25.4, 20.6, 20.5,
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N3O14SiNa 760.2725, found 760.2732.
Author contribution
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611; (b) Y. Vohra, V. Mahalakshmi, A. Venot and G. J. Boons,
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S.-Y. L. designed the research. J.-S. C. and S.-S. W. prepared
compounds 2a–2f of Table 1. A. S. prepared compounds 4a–4e
of Table 2. J.-S. C., P.-H. H., and C.-H. L. prepared compounds
6a–6f of Table 3. Y.-J. L. and A. S. prepared compounds 13–17 of
Table 4. H. R. W. analyzed the Mass data. A. S. and S.-Y. L. wrote
the manuscript.
Conflicts of interest
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2003, 68, 8719; (b) J. A. Hyatt and G. W. Tindall,
Heterocycles, 1993, 35, 227.
There are no conicts to declare.
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Res., 1980, 80, 346; (b) C. T. Chen, J. H. Kuo, C. H. Li,
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C. F. Liang, Chem.–Asian J., 2017, 12, 2471; (c) T. W. Lin,
A. K. Adak, H. J. Lin, A. Das, W. C. Hsiao, T. C. Kuan and
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Acknowledgements
The authors thank the Ministry of Science and Technology
(MOST) in Taiwan (MOST 107-2113-M-005-021) and National
Chung Hsing University for nancial support.
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