An efficient conversion of N-acetyl-d-glucosamine to N-acetyl-d- galactosamine and derivatives

Article abstract of DOI:10.1016/j.carres.2010.09.008

2-Acetamido-2-deoxy-d-galactose (d-GalNAc) is an important monosaccharide widely distributed in nature. However, unlike its 4-epimer, the 2-acetamido-2-deoxy-d-glucose (d-GlcNAc), d-GalNAc is very expensive to obtain from commercial sources. Herein we rep

Full text of DOI:10.1016/j.carres.2010.09.008

Carbohydrate Research 345 (2010) 2450–2457
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
An efficient conversion of N-acetyl-D-glucosamine to N-acetyl-D-galactosamine
and derivatives
⇑
Jianhao Feng, Chang-Chun Ling
Alberta Ingenuity Center for Carbohydrate Science, Department of Chemistry, University of Calgary, Calgary Alberta, Canada T2N 1N4
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 July 2010
Received in revised form 2 September 2010
Accepted 8 September 2010
Available online 16 September 2010
2-Acetamido-2-deoxy-
ure. However, unlike its 4-epimer, the 2-acetamido-2-deoxy-
D
-galactose (
D
-GalNAc) is an important monosaccharide widely distributed in nat-
-glucose ( -GlcNAc), -GalNAc is very
expensive to obtain from commercial sources. Herein we report an efficient transformation that allows
for the conversion of -GlcNAc to a -GalNAc derivative 7 in three steps and in 58.4–75% overall yields.
D
D
D
D
D
The process was carried out on a greater than 20-g scale without the need of chromatography. The ver-
satility of compound 7 was demonstrated by the synthesis of several useful monosaccharides and thiodi-
Keywords:
saccharides containing a
D
-GalNAc residue.
N-Acetyl-
N-Acetyl-
Synthesis
D
-glucosamine
-galactosamine
Ó 2010 Elsevier Ltd. All rights reserved.
D
Pivalation
Thioglycosides
1. Introduction
OH
O
OR2
Selective
protections
O
HO
HO
HO
R2O
OH
OR1
Glycosides containing 2-acetamido-2-deoxyhexoses are widely
distributed in nature.1,2 Two amino sugars, 2-acetamido-2-deoxy-
NHAc
D-GlcNAc
NHAc
Activation
D
-glucose (
-GalNAc), are the ones most commonly found. As the constitu-
ents of glycoproteins, glycolipids, and polysaccharides, they play
many important roles in biology.1 However, unlike
-GlcNAc which
can be readily obtained by the hydrolysis of chitin, -GalNAc is
very expensive to obtain from commercial sources. There has been
considerable interest in developing viable strategies to convert
GlcNAc to -GalNAc (Fig. 1).
The common strategy involves a selective protection of OH
groups at C-1, C-3, and C-6 of -GlcNAc, leaving the OH-4 unpro-
D-GlcNAc) and the 2-acetamido-2-deoxy-D-galactose
(D
R3
O
HO
Inversion &
deprotections
OR2
O
O
D
OH
O
S
D
O
OR1
OH
HO
R2O
D
-
NHAc
D-GalNAc
NHAc
D
Figure 1. Common strategies to convert
D
-GlcNAc to
D-GalNAc.
D
tected for subsequent epimerization. Since the first attempt
reported by Gross et al. in 1967,3 several approaches have been
published in the literature.4,5 These can be classified into two strat-
egies by comparing the protective group used for the anomeric
center. The first involved the use of an alkyl group to protect the
anomeric OH group.3,5 Methyl or benzyl groups were commonly
used for this purpose. This strategy usually suffers from long reac-
tion sequences, leading to poor overall yields. Since the anomeric
position was protected with a stable group, it was difficult to deriv-
atize the anomeric center further. The second involved the use of
an acyl group to protect the anomeric center.4 This strategy is
the most desirable as the three OH groups at C-1, C-3, C-6 can be
selectively protected in one step to provide an intermediate with
a 4-OH group that can be further activated. One additional advan-
tage is that the acyl group at the anomeric center can be removed
and replaced with other groups in a relatively easy manner to
allow further transformations. However, this strategy has usually
suffered from poor regioselectivity that required tedious separa-
tion of other unwanted by-products. Chaplin et al.4a reported an
elegant enzymatic method to selectively remove a 6-O-acetyl
group from the peracetylated D-GlcNAc to furnish an intermediate
with a free 6-OH group. A subsequent acid treatment resulted in a
migration of the acetyl group from O-4 to O-6 to generate the
desired derivative with a free 4-OH group. The authors subse-
quently synthesized the 4-triflate, which was displaced with
⇑
Corresponding author. Tel.: +1 403 220 2768; fax: +1 403 289 9488.
E-mail address: ccling@ucalgary.ca (C.-C. Ling).
cesium acetate to obtain the peracetylated D-GalNAc. The entire
0008-6215/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2010.09.008

J. Feng, C.-C. Ling / Carbohydrate Research 345 (2010) 2450–2457
2451
process took six steps from
an efficient three-step synthesis of a
Scheme 1) from -GlcNAc using pivalate as a protecting group. Our
methodology is suitable for both small and large scales and pro-
vides a versatile -GalNAc intermediate that is conveniently pro-
D
-GlcNAc to
D
-GalNAc. Here we report
studies. The two less polar compounds, isolated in 8.2% yield, were
found to be /b anomers of 1,3,4,6-tetrapivalate 4. The most polar
D-GalNAc intermediate (7, see
a
D
compound was found to be the 3,6-dipivalate 2, which was isolated
in small amounts (3.1% yield). The reaction could be reproduced in a
20-g scale. We found that compound 2 had a significant solubility in
water, as the majority of 2 formed during the reaction were removed
by water extraction during the workup.
D
tected for further transformations.
We attempted to apply the same conditions to the acetylation
and benzoylation of D-GlcNAc (Scheme 1), using 3.05 equiv of either
2. Results and discussion
acetyl chloride or benzoyl chloride as a reagent. The acetylation
gave a complex mixture, while the benzoylation led to the forma-
tion of a major product at Rf 0.37 (95:5 CH2Cl2–MeOH) that could
be isolated in 48.6% yield after a column chromatography on silica
gel. NMR spectroscopy confirmed that the major benzoylated prod-
The 3,6-dipivalation of D-GlcNAc glycosides has been reported
before.5a–c,f In general, the reaction was very selective to afford
the corresponding 3,6-dipivalate in high selectivity and high yield.
This was usually followed by a triflation of the 4-OH group, and
subsequently an inversion of the C-4 center to provide the corre-
uct was 3,4,6-tribenzoylated
D-GlcNAc 5. Clearly, the pivalation of
sponding
D-GalNAc glycoside. Usually, in the formed D-GalNAc
D-GlcNAc was the most selective. The differences in the three acyla-
glycoside, the 3-O-pivaloyl group was observed to undergo a
migration to the neighboring O-4 position;5a,b,f in one report,
Jacquinet’s group5c also observed the formation of a mixture of
tions could be explained by their relative reactivities: the least
reactive and most bulky reagent (pivaloyl chloride) provided the
highest regioselectivity, while the most reactive but least bulky
reagent (acetyl chloride) exhibited the poorest regioselectivity.
The discovery that compound 2 had a significant solubility in
water was very important for the development of a practical syn-
benzyl
ivalate as well as the migrated 3,4-dipivalate.
For -GlcNAc, which has a unprotected anomeric center, its
selective pivalation has also been studied. In 1988, Ljevakovic
et al.6 reacted
-GlcNAc with 4.8 equiv of pivaloyl chloride in anhy-
D-GalNAc glycosides containing the non-migrated 3,6-dip-
D
´
thesis for
D-GalNAc from D-GlcNAc, as this indicated that after
D
removing compound 2 from the reaction mixture, it should be pos-
sible to carry the crude product on to the next step without the
need of chromatographic separation. In addition, between the
remaining compounds 3 and 4, since only 3 had an alcohol func-
tionality, the mixture could be used for activation. Indeed, after
the pivalation and working up of the reaction mixture as above,
the crude product was directly esterified with triflic anhydride at
ꢀ10 °C in a 1:1 mixture of anhydrous pyridine–dichloromethane
to afford the triflate 6, which was detected by thin-layer chroma-
tography. Water was added to the reaction mixture after 2 h at
0 °C, and the reaction was continued at 60 °C overnight. A major
product with Rf 0.28 (95:5 CH2Cl2–MeOH) was obtained. At a 5-g
scale, we isolated the major compound by recrystallization from
drous pyridine, and obtained a complex mixture containing the
1,3,6-tripivalate (28% yield) and the 1,3,4,6-tetrapivalate (7.5%
yield), together with the 3,4,6-tripivalate (6.7%) and the 3,6-dipiv-
alate (21% yield). All compounds were obtained as an a/b-mixture.
In another attempt, Santoyo-González’s group4b prepared a very
mild pivalation reagent, the N-pivaloylimidazole, and reacted 4
equivalents of the reagent with
D
-GlcNAc in DMF at 55 °C for
18 h; two partially protected pivalates: the 1,4,6- and 1,3,6-tripiv-
alate were obtained in 28% and 61% yield, respectively, together
with the 1,3,4,6-tetrapivalate, which was obtained in 10% yield.
The 1,3,6-tripivalated product was subsequently converted on a
small scale to a
D-GalNAc derivative containing a 4-OH group.
We attempted to repeat the pivalation of
D
-GlcNAc using piva-
a mixture of ethyl acetate–hexane in 75% overall yield from D-Glc-
loyl chloride as the reagent (Scheme 1). However, under slightly
modified conditions, we obtained different results compared to
NAc. When the reaction was carried out at a 20-g scale, we found
that the major product could also be isolated by crystallization,
although in slightly lower yield (58.4% for three steps); the highest
yield was obtained by chromatography on silica gel (62.7%) using
24% ethyl acetate–hexane as the eluent. The structure of the major
product was confirmed to be compound 7 by NMR studies and
high-resolution mass spectrometry. The migration of the pivaloyl
group from O-3 to O-4 was consistent with the previous finding
on the glycosides.5a,b,f According to the literature reports,7,8 the dis-
placement of the 4-triflate in 6 was most probably the result of an
intramolecular nucleophilic attack by the carbonyl oxygen of the
´
those of Ljevakovic et al. The D-GlcNAc was first stirred in a 1:2
mixture of anhydrous pyridine–dichloromethane overnight; after
cooling to ꢀ10 °C, pivaloyl chloride (3.05 equiv) was added, and
the reaction was stirred at room temperature for two days. We
observed the formation of a major product with Rf 0.40 (95:5
CH2Cl2–MeOH,), together with some less polar products at Rf 0.59
and 0.50. Another more polar product that had an Rf 0.25 was also
obtained. The major product was isolated in pure form in 79.5% yield
by column chromatography, and it was characterized as the b
anomer of the 1,3,6-tripivalate of
D
-GlcNAc 3, as shown by NMR
OPiv
OH
O
OPiv
O
OPiv
O
O
HO
HO
a
HO
PivO
PivO
PivO
HO
OPiv
OPiv
+
OH
+
PivO
AcHN
1
AcHN
2
NHAc
NHAc
OH
3
4
c
b
d or e
PivO
HO
OBz
O
OPiv
O
OPiv
O
mixtures
of partially
acetylated
products
BzO
BzO
TfO
OPiv
OPiv
PivO
OH
AcHN
NHAc
NHAc
5
6
7
Scheme 1. Selective acylations of
D
-GlcNAc and the conversion of
D
-GlcNAc to
D
-GalNAc. Reagents and conditions: (a) (CH3)3CCOCl (3.5 equiv)/CH2Cl2-Py (2:1), ꢀ10 °C?rt,
two days; (b) AcCl (3.05 equiv)/CH2Cl2-Py (2:1), ꢀ10 °C?rt, two days; (c) PhCOCl (3.05 equiv)/CH2Cl2-Py (2:1), ꢀ10 °C?rt, two days; (d) Tf2O/CH2Cl2-Py (1:1), ꢀ10?0 °C, 2 h;
(e) Tf2O/CH2Cl2-Py (1:1), ꢀ10?0 °C, 2 h; then H2O, 60 °C, overnight.

2452
J. Feng, C.-C. Ling / Carbohydrate Research 345 (2010) 2450–2457
neighboring 3-pivalate to form an orthoacid, which was in the end
hydrolyzed to regioselectively place the pivaloyl group at the O-4
position.
Compound 7 had a free alcohol at C-3 and an ester group at the
anomeric center. This suggested that it could be a very useful syn-
thetic intermediate. To demonstrate the versatility of compound 7
as well as other intermediates, we carried out the syntheses of
some mono- and disaccharides containing GalNAc.
OPiv
O
AcO
S
PivO
OPiv
O
a
6
AcHN
PivO
15
11
+
OPiv
AcHN
PivO
AcO
OPiv
As shown in Scheme 2, the crude triflate 6 was subjected to SN2
nucleophilic substitutions with different nucleophiles. When
potassium thioacetate was used, compound 8, which had a galacto
O
S
OPiv
O
a
AcHN
AcO
13
6
+
configuration, was obtained in 88% from D-GlcNAc, and when so-
OPiv
dium azide was used, the 4-azido compound 9 was obtained in
77% yield over two steps. The labile anomeric pivalate in both
compounds 3 and 7 was converted to a glycosyl chloride by the
AcHN
16
OAc
O
treatment with acetyl chloride to furnish the corresponding a-gly-
AcO
AcO
OAc
copyranosyl chlorides 10 and 12 in almost quantitative yields,
according to the proton NMR spectra of the crude materials. In
both cases, the free hydroxyl groups that existed in the starting
S
OPiv
O
O
a
a
AcO
AcO
OAc
AcO
6
6
+
+
SAc
OPiv
OPiv
OAc
materials were acetylated in situ. The a-chlorides 10 and 12 were
AcHN
18
17
converted to the corresponding b-thioacetate 11 and 13 in very
good yields. Additionally, we also converted 12 to the p-chloro-
phenyl b-thioglycoside 14 in 62.8% yield. The stable thioglycoside
14 could be derivatized further for glycosylations.9
AcO
AcO
OAc
O
AcO OAc
O
S
OPiv
O
With several functionalized monosaccharides in hand, we pro-
ceeded to synthesize four disaccharides containing a GalNAc unit
(Scheme 3). The coupling of 4-triflate 6 with 11 in DMF provided
disaccharide 15 in 63.4% yield using diethylamine as a base.10
Compound 15 is a thio analog of the bGlcNAc-(1?4)-GalNAc
sequence found in the lipopolysaccharide (LPS) expressed by
Escherichia coli O48:H21.11 Similarly, the coupling of 4-triflate 6 with
13 in an analogous fashion provided thiodisaccharide 16 in 70%
yield. The disaccharide 16 contains two bGalNAc residues linked
together via the b-(1?4)-thio linkage; its natural O-glycoside is
present in the LPS structure of E. coli 87/D2.12 Additionally, we also
prepared two other disaccharides 18 and 20 using triflate 6 to react
with the previously known 1713 and 19,14 respectively. The O-glyco-
side counterparts of disaccharides 18 and 20 were, respectively,
OAc
AcO
SAc
AcO
OAc
AcHN
20
19
Scheme 3. Syntheses of thio analogs of disaccharides 15, 16, 18, and 20. Reagents
and condition: (a) Et2NH/DMF, ꢀ5 °C, overnight.
found in the LPS structures of S. Dakar serotype O:2815 and in the
capsular polysaccharide of S. pneumoniae serotype 10A.16
Additionally, since compound 7 had a free hydroxyl group
which can act as an acceptor, and its anomeric center was pro-
tected with an acyl group, which can act as a donor, we were inter-
ested in probing its behavior in carrying out self-condensations
when treated with a Lewis acid such as ferric chloride.17 As shown
in Scheme 4, after treating compound 7 with 1.2 equiv of ferric
chloride in 1,2-dichloroethane overnight, no self-condensed oligo-
saccharides were isolated; however, compound 21 was obtained in
27% yield.
N3
AcS
PivO
OPiv
O
OPiv
O
a
b
6
OPiv
OPiv
PivO
NHAc
Clearly, compound 21 was the result of an intramolecular glyco-
sylation between OH-4 and the anomeric center. Its structure was
confirmed by a series of 1D and 2D NMR experiments: for example,
in the 1H NMR spectra, the coupling constants J1,2, J2,3, J3,4, and J4,5
were consistently small, indicating that the conformation of the
original 4C1 chair in 7 has been changed; an 2D 1H–13C HMBC
experiment revealed a strong correlation between H-1 and C-4.
Since from a normal HMBC experiment, we can only observe
heteronuclear correlations up to three bonds apart; however, in a
normal chair conformation of a pyranoside, C-4 is four bonds away
from H-1. Thus the observed strong correlation between H-1 and
C-4 can only be explained by the formation of a linkage between
C-1 and O-4, which brings the distance to three bonds between
H-1 and C-4. The structure of compound 21 was also confirmed
by high-resolution mass spectrometry.
NHAc
9
8
OPiv
O
OPiv
c
d
O
AcO
PivO
AcO
3
SAc
PivO
AcHN
AcHN
11
Cl
10
PivO
PivO
AcO
OPiv
O
OPiv
O
c
d
7
SAc
AcO
AcHN
AcHN
13
Cl
12
e
PivO
AcO
OPiv
O
PivO
O
OPiv
O
PivO
PivO
S
a
O
OPiv
HO
AcHN
14
AcHN
Cl
NHAc
7
21
Scheme 2. Syntheses of useful intermediates. Reagents and conditions: (a) KSAc/
DMF, 65 °C, 2 h; (b) NaN3/DMF, 65 °C, 2 h; (c) AcCl/MeOH; (d) KSAc/acetone,
0 °C?rt, overnight; (e) p-ChPhSH/KOBu-t/DMF–THF, overnight.
Scheme 4. The treatment of compound 7 with FeCl3. Reagents and condition: (a)
FeCl3/1,2-dichloroethane, 90 °C, overnight.

J. Feng, C.-C. Ling / Carbohydrate Research 345 (2010) 2450–2457
2453
H
+
Cl3Fe
O
O
O
O
OPiv
O
OPiv
OPiv
O
-
-
Cl3FeO
Cl Fe
O
O
3
+
OPiv
OPiv
OPiv
HO
O
O
H
AcHN
AcHN
AcHN
7
-
O
FeCl3
O
H
O
HO
OPiv
O
+
HO
PivO
OPiv
O
PivO
PivO
O
O
FeCl3
PivO
O
-
OFeCl3
NH
23
O
O
NHAc
O
+
HN
FeCl3
OH
O
O
PivO
PivO
O
NHAc
22
Scheme 5. Proposed mechanism for the formation of compound 21 from 7.
The formation of 21 was intriguing because the free hydroxyl
group in compound 7 was at C-3. The only way to explain the for-
mation would be a migration of the pivaloyl group from O-4 to O-3
with the assistance of a Lewis acid. As shown in Scheme 5, after
coordination of ferric chloride to the carbonyl oxygen of the
4-pivalate, it was possible that an equilibrium would have been
established between 7 and intermediate 22 which underwent an
intramolecular glycosylation to generate the observed 1,4-anhydro
sugar 21.
enced to residual CHCl3 (dH 7.24 and dC 77.0). 1H and 13C NMR
spectra were assigned with the assistance of GCOSY, GHSQC, or
GHMBC spectra. High-resolution ESI-QTOF mass spectra were
recorded on an Agilent 6520 Accurate Mass Quadrupole Time-
of-Flight LC/MS spectrometer. All the data were obtained by the
analytical services of the Department of Chemistry, University of
Calgary.
4.2. O-Pivalation of 2-acetamido-2-deoxy-
D
-glucose
2-Acetamido-2-deoxy- -glucose (N-acetyl-
D
D-glucosamine, 1,
3. Conclusions
20.0 g, 90.4 mmol) was added to a mixture of anhyd CH2Cl2
(100 mL) and pyridine (50 mL) and the mixture was stirred over-
night. After cooling the reaction mixture to ꢀ10 °C, trimethylacetyl
chloride (34.0 mL, 276.3 mmol) was added, and the reaction was
allowed to warm up to room temperature. After 2 days, the solu-
tion was diluted with CH2Cl2 (150 mL), and the organic phase
was washed with H2O (2 ꢂ 100 mL), brine (1 ꢂ 100 mL), and dried
over anhyd Na2SO4. After evaporation, the crude residue could be
used directly for the next step. We also attempted to carry out
the purification of the mixture by column chromatography on sil-
ica gel using 25% EtOAc–hexane as the eluent to give first a mixture
of 3 and 4 (ꢃ8.8 g), and subsequently pure compound 3 (29.5 g,
68.9% yield) as a single b anomer. By increasing the polarity of
the eluent to 45% EtOAc–hexane, a small amount of compound 2
We have developed a viable method to convert
protected -GalNAc derivative. The entire process required a
three-step transformation which required no chromatography to
isolate the desired -GalNAc derivative in 75% overall yield on a
small scale and 58.4% on a larger scale. This is so far the most
efficient method reported in the literature. The versatility of the
D-GlcNAc to a
D
D
D
-GalNAc derivative so obtained and the other intermediates has
been illustrated by thesynthesis of several mono- and disaccharides.
4. Experimental
4.1. General methods
was obtained as an
a/b mixture (1.1 g, 3.1% yield, a/b 25:1). The
mixture of 3 and 4 was subjected to another column chromatogra-
phy using 5% acetone–hexane as the eluent to give compound 4 as
Optical rotations were determined in a 5-cm cell at 25 2 °C.
½
a 2D5 values are given in units of 10ꢀ1 deg cm2 gꢀ1. Analytical TLC
ꢁ
an inseparable
a/b mixture (4.1 g, 8.2% yield, a/b 1:2) and more
was performed on Silica Gel 60-F254 (E. Merck, Darmstadt) with
detection by quenching of fluorescence and/or by charring with
5% sulfuric acid in water or with a ceric ammonium molybdate
dip. All commercial reagents were used as supplied unless other-
wise stated. Column chromatography was performed on Silica
Gel 60 (Silicycle, Ontario). Organic solutions from extractions were
dried with anhyd Na2SO4 prior to concentration under vacuum at
<40 °C (bath). 1H NMR spectra were recorded at 300 or 400 MHz
on Bruker spectrometers. The first-order proton chemical shifts
dH and dC are reported in d (ppm) for solutions in CDCl3 and refer-
pure compound 3 (4.5 g, 10.5%). Compound 3 was obtained in a
combined yield of 79.4%.
4.2.1. 2-Acetamido-2-deoxy-3,6-di-O-pivaloyl-
a
,b-D-
glucopyranose (2)
Rf: 0.25 (5:95 MeOH–CH2Cl2). 1H NMR for 2
a (400 MHz, CDCl3):
dH 6.55 (d, 1H, J = 9.5 Hz, NH), 5.24 (dd, 1H, J = 10.7, 9.4 Hz, H-3),
5.18 (dd, 1H, J = 3.6, 3.6 Hz, H-1), 5.10 (d, 1H, J = 3.0 Hz, OH-1),
4.35–4.31 (m, 2H, H-6a + H-6b), 4.20 (ddd, 1H, J = 10.0, 10.0,

2454
J. Feng, C.-C. Ling / Carbohydrate Research 345 (2010) 2450–2457
2.9 Hz, H-2), 4.13–4.05 (m, 1H, H-5), 3.56 (ddd, 1H, J = 7.0, 9.6,
9.6 Hz, H-4), 3.27 (d, J = 6.9 Hz, 1H, OH-4), 1.93 (s, 3H, NHAc),
white solid. Rf: 0.37 (5:95 MeOH–CH2Cl2). 1H NMR for
5a
(400 MHz, 2:1 CDCl3–CD3OD): dH 8.02–7.97 (m, 2H, Bz), 7.89–
7.84 (m, 4H, Bz), 7.56–7.51 (m, 1H Bz), 7.50–7.44 (m, 2H, Bz),
7.42–7.36 (m, 2H, Bz), 7.36–7.29 (m, 4H, Bz), 5.77 (dd, 1H, J = 9.6,
10.7 Hz, H-3), 5.61 (dd, 1H, J = 9.8, 9.8 Hz, H-4), 5.25 (d, 1H,
J = 3.5 Hz, H-1), 4.60 (ddd, 1H, J = 3.6, 3.6, 10.0 Hz, H-5), 4.55 (dd,
1H, J = 3.1 Hz, H-6a, overlapped), 4.50 (dd, 1H, J = 3.5, 10.8 Hz, H-
2), 4.41 (dd, 1H, J = 4.2, 12.1 Hz, H-6b), 1.84 (s, 3H, NHAc). 13C
1.20 (s, 9H, Piv), 1.17 (s, 9H, Piv). 13C NMR for 2
a (100 MHz, CDCl3):
dC 180.09 (Piv), 179.46 (Piv), 170.64 (NHAc), 91.72 (C-1), 73.07 (C-
3), 69.97 (C-5), 69.25 (C-4), 62.96 (C-6), 51.90 (C-2), 38.99
(C(CH3)3 ꢂ 2), 27.16 (C(CH3)3), 26.98 (C(CH3)3), 22.90 (NHAc). HRE-
SIMS: Calcd for
390.2115.
C
18H32NO8 (M+H+): m/z 390.2122. Found:
NMR for 10
a (100 MHz, 2:1 CDCl3–CD3OD): dC 171.76 (NHAc),
4.2.2. 2-N-Acetamido-2-deoxy-1,3,6-tri-O-pivaloyl-b-
D
-
166.84 (Bz), 166.68 (Bz), 165.61 (Bz), 133.37 (Ph), 133.30 (Ph),
133.15 (Ph), 129.58 (Ph), 129.57 (Ph), 129.01 (Ph), 128.91 (Ph),
128.31 (Ph), 128.29 (Ph), 91.55 (C-1), 71.76 (C-3), 70.10 (C-4),
67.28 (C-5), 63.25 (C-6), 52.46 (C-2), 22.02 (NHAc). HRESIMS: Calcd
for C29H28NO9 (M+H+): m/z 534.1758. Found: 534.1754.
glucopyranose (3)
Rf: 0.40 (5:95 MeOH–CH2Cl2). [
a]
D ꢀ3.5 (c 12.5, CHCl3). 1H NMR
(400 MHz, CDCl3): dH 5.91 (d, 1H, J = 9.8 Hz, NH), 5.62 (d, 1H,
J = 8.8 Hz, H-1), 5.08 (dd, 1H, J = 10.7, 9.1 Hz, H-3), 4.46 (dd, 1H,
J = 12.2, 4.6 Hz, H-6a), 4.34 (dd, 1H, J = 12.2, 2.4 Hz, H-6b), 4.31–
4.20 (m, 1H, H-2), 3.68 (ddd, 1H, J = 9.8, 4.5, 2.4 Hz, H-5), 3.56
(ddd, 1H, J = 9.4, 5.5 Hz, H-4), 3.24 (d, 1H, J = 5.5 Hz, OH), 1.88 (s,
3H, NHAc), 1.23 (s, 9H, Piv), 1.21 (s, 9H, Piv), 1.19 (s, 9H, Piv). 13C
NMR (100 MHz, CDCl3): dC 179.78 (Piv), 179.21 (Piv), 177.06
(Piv), 169.86 (NHAc), 92.58 (C-1), 74.85 (C-5), 74.74 (C-3), 69.01
(C-4), 62.75 (C-6), 52.62 (C-2), 38.94 (C(CH3)3), 38.91 (C(CH3)3),
38.68 (C(CH3)3), 27.08 (C(CH3)3), 26.95 (C(CH3)3), 26.70 (C(CH3)3),
22.91 (NHAc). HRESIMS: Calcd for C23H39NO9SNa (M+Na+): m/z
496.2517. Found: 496.2514. Anal. Calcd for C23H39NO9: C, 58.33;
H, 8.30; N, 2.96. Found: C, 58.02; H, 8.20; N, 2.86.
4.4. 2-Acetamido-2-deoxy-1,4,6-tri-O-pivaloyl-b-D-galactopyran-
ose (7)
4.4.1. Small-scale procedure
N-Acetyl-D-glucosamine (1, 5.0 g, 22.6 mmol) was reacted with
trimethylacetyl chloride (8.5 mL, 69.1 mmol) in a mixture of anhyd
CH2Cl2 (30 mL) and pyridine (15 mL) as above. After workup, the
crude mixture was dissolved in a mixture of anhyd CH2Cl2
(20 mL) and pyridine (20 mL). Trifluoromethanesulfonic anhydride
(5.3 mL, 31.6 mmol) was added at ꢀ10 °C, and the reaction mixture
was stirred at 0 °C for 2 h. H2O (5.0 mL) was added, and the reac-
tion mixture was heated to 60 °C overnight. The solution was di-
luted with CH2Cl2 (40 mL) and washed with H2O (2 ꢂ 30 mL),
then brine (1 ꢂ 30 mL). The organic solution was dried over anhyd
Na2SO4 and evaporated. The residue was recrystallized from a mix-
ture of EtOAc–hexane to afford the desired compound 7 (8.0 g,
75.0% yield over three steps).
4.2.3. 2-Acetamido-2-deoxy-1,3,4,6-tetra-O-pivaloyl-a,b-D-
glucopyranose (4)
Rf: 0.59 for 4
a
, 0.50 for 4b (5:95 MeOH–CH2Cl2). 1H NMR for
4a (400 MHz, CDCl3): dH 6.17 (d, 1H, J = 3.7 Hz, H-1), 5.41 (d,
1H, J = 9.0 Hz, NH), 5.31–5.22 (m, 2H, H-3 + H-4), 4.56–4.48 (m,
1H, H-2), 4.20–4.08 (m, 2H, H-6a + H-6b), 3.99 (ddd, J = 9.8, 3.4,
3.4 Hz, 1H, H-5), 1.90 (s, 3H, NHAc), 1.30 (s, 9H, Piv), 1.21 (s,
9H, Piv), 1.18 (s, 9H, Piv), 1.15 (s, 9H, Piv). 1H NMR for 4b
(400 MHz, CDCl3): dH 5.64 (d, 1H, J = 9.9 Hz, NH), 5.60 (d, 1H,
J = 8.8 Hz, H-1), 5.22–5.11 (m, 2H, H-4 + H-3), 4.48–4.37 (m, 1H,
H-2), 4.20–4.08 (m, 2H, H-6a + H-6b), 3.83 (ddd, 1H, J = 9.5, 4.2,
2.6 Hz, H-5), 1.87 (s, 3H, NHAc), 1.22 (s, 9H, Piv), 1.19 (s, 9H,
4.4.2. Large-scale procedure
N-Acetyl-D-glucosamine (1, 20.0 g, 90.4 mmol) was reacted
with trimethylacetyl chloride (34.0 mL, 276.3 mmol) in a mixture
of anhyd CH2Cl2 (100 mL) and pyridine (50 mL) as above. After
workup, the crude mixture was dissolved in a mixture of anhyd
CH2Cl2 (50 mL) and pyridine (50 mL). Trifluoromethanesulfonic
anhydride (21.3 mL, 126.6 mmol) was added at ꢀ10 °C, and the
reaction mixture was stirred at 0 °C for 2 h. H2O (20.0 mL) was
added, and the mixture was heated to 60 °C overnight. The solution
was diluted with CH2Cl2 (150 mL) and washed with H2O
(2 ꢂ 100 mL), then brine (1 ꢂ 100 mL). The organic solution was
dried over anhyd Na2SO4 and evaporated. The residue could be
recrystallized from a mixture of EtOAc–hexane to afford compound
7 (25.0 g, 58.4% yield over three steps). Alternatively, the residue
was purified by column chromatography on silica gel using 24%
EtOAc–hexane as the eluent to give compound 7 (26.8 g, 62.7%
yield over three steps).
Piv), 1.16 (s, 9H, Piv), 1.14 (s, 9H, Piv). 13C NMR for
4a
(100 MHz, CDCl3): dC 179.48 (Piv), 178.00 (Piv), 177.06 (Piv),
175.80 (Piv), 169.53 (NHAc), 90.47 (C-1), 70.34 (C-5), 70.24 (C-
3), 66.82 (C-4), 61.59 (C-6), 51.72 (C-2), 39.32 (C(CH3)3), 38.99
(C(CH3)3), 38.83 (C(CH3)3), 38.76 (C(CH3)3), 27.11 (C(CH3)3),
27.08 (C(CH3)3), 27.03 (C(CH3)3), 27.00 (C(CH3)3), 22.94 (NHAc).
13C NMR for 4b (100 MHz, CDCl3): dC 178.85 (Piv), 178.06 (Piv),
177.06 (Piv), 176.18 (Piv), 169.40 (NHAc), 92.70 (C-1), 73.08 (C-
5), 72.25 (C-3), 67.23 (C-4), 61.45 (C-6), 52.80 (C-2), 38.92
(C(CH3)3), 38.87 (C(CH3)3), 38.76 (C(CH3)3), 38.74 (C(CH3)3),
27.06 (C(CH3)3), 27.01 (C(CH3)3 ꢂ 2), 26.74 (C(CH3)3), 23.02
(NHAc). HRESIMS: Calcd for C28H48NO10 (M+H+): m/z 558.3273.
Found: 558.3269.
4.4.3. 2-Acetamido-2-deoxy-1,4,6-tri-O-pivaloyl-b-D-galacto-
4.3. 2-Acetamido-3,4,6-tri-O-benzoyl-2-deoxy-
glucopyranose (5)
a-
D
-
pyranose (7)
Rf: 0.28 (5:95 MeOH–CH2Cl2). [a]
D +0.56 (c 1.8, CHCl3). 1H NMR
(400 MHz, CDCl3): dH 5.83 (d, 1H, J = 7.8 Hz, NH), 5.66 (d, 1H,
J = 8.8 Hz, H-1), 5.32 (dd, 1H, J = 3.3, 0.8 Hz, H-4), 4.20–4.04 (m,
3H, H-2 + H-6a + H-6b), 4.01 (ddd, 1H, J = 6.3, 6.3, 1.0 Hz, H-5),
3.89 (ddd, 1H, J = 10.8, 4.5, 3.6 Hz, H-3), 3.54 (d, 1H, J = 4.7 Hz,
OH-3), 1.99 (s, 3H, Ac), 1.30 (s, 9H, Piv), 1.23 (s, 9H, Piv), 1.18 (s,
9H, Piv). 13C NMR (100 MHz, CDCl3): dC 178.02 (Piv), 177.93 (Piv),
177.82 (Piv), 172.24 (NHAc), 92.58 (C-1), 72.64 (C-3), 72.17 (C-5),
68.02 (C-4), 61.33 (C-6), 53.51 (C-4), 39.28 (C(CH3)3), 38.90
(C(CH3)3), 38.70 (C(CH3)3), 27.22 (C(CH3)3), 27.01 (C(CH3)3), 26.81
(C(CH3)3), 23.10 (NHAc). HRCIMS: Calcd for C23H40NO9 (M+H+):
m/z 474.2703. Found: 474.2686. Anal. Calcd for C23H39NO9: C,
58.33; H, 8.30; N, 2.96. Found: C, 58.04; H, 8.30; N, 2.82.
To a mixture containing anhyd CH2Cl2 (4 mL) and pyridine
(2 mL), was added N-acetyl- -glucosamine (1, 500 mg, 2.3 mmol),
and the suspension was stirred overnight. After cooling to
L, 6.8 mmol) was added, and
D
ꢀ10 °C, benzoyl chloride (787.7
l
the reaction mixture was allowed to warm up to room tempera-
ture. After two days, the solution was diluted with CH2Cl2
(15 mL) and washed with H2O (2 ꢂ 10 mL), then brine
(1 ꢂ 10 mL); the organic phase was dried over anhyd Na2SO4 and
evaporated. The residue was purified by column chromatography
on silica gel using 2.5% MeOH–CH2Cl2 as the eluent to give com-
pound 518 as an
a/b mixture (586 mg, 48.6% yield, a/b 16:1) as

J. Feng, C.-C. Ling / Carbohydrate Research 345 (2010) 2450–2457
2455
4.5. 2-Acetamido-2-deoxy-1,3,6-tri-O-pivaloyl-4-O-
trifluoromethanesulfonyl-b- -glucopyranose (6)
4.8. 2-Acetamido-3-O-acetyl-2-deoxy-4,6-di-O-pivaloyl-
glucopyranosyl chloride (10) and 2-acetamido-4-O-acetyl-1-S-
acetyl-2-deoxy-3,6-di-O-pivaloyl-1-thio-b- -glucopyranose (11)
a-D-
D
D
Compound 3 (400 mg, 0.845 mmol) was dissolved in a mixture
of anhyd CH2Cl2 (2 mL) and anhyd pyridine (2 mL). Trifluorometh-
Compound 3 (500 mg, 1.06 mmol) was dissolved in AcCl (3 mL).
Anhyd MeOH (400 L) was added at 0 °C, and the reaction mixture
anesulfonic anhydride (285.4
lL, 1.69 mmol) was slowly added at
l
ꢀ10 °C, and the reaction mixture was stirred at 0 °C for 1.5 h. Then
the solution was diluted by CH2Cl2 (10 mL) and washed with
HCl (1 N, 2 ꢂ 10 mL), satd aq NaHCO3 (1 ꢂ 10 mL) and H2O (1 ꢂ
10 mL), followed by evaporation to dryness. The crude triflate 6
was used for the following reactions without purification. 1H
NMR (400 MHz, CDCl3): dH 5.95 (d, 1H, J = 9.9 Hz, NH), 5.68 (d,
1H, J = 8.8 Hz, H-1), 5.48 (dd, 1H, J = 10.8, 9.2 Hz, H-3), 5.12 (dd,
1H, J = 9.4, 9.4 Hz, H-4), 4.50–4.37 (m, 2H, H-6a + H-2), 4.11–4.00
(m, 2H, H-6a + H-5), 1.88 (s, 3H, Ac), 1.24 (s, 9H, Piv), 1.23 (s, 9H,
Piv), 1.18 (s, 9H, Piv).
was kept at room temperature overnight. The solution was evapo-
rated to dryness and the crude chloride 10 was dissolved in ace-
tone (5 mL) containing 4 Å molecular sieves (500 mg). Potassium
thioacetate (165 mg, 1.38 mmol) was added to the solution at
0 °C, and the reaction mixture was kept at room temperature
overnight. The solution was then evaporated, and the residue
was purified by column chromatography on silica gel using 28%
EtOAc–hexane as eluent to give compound 11 (325 mg, 62.9%
yield) as a yellow solid.
4.8.1. 2-Acetamido-3-O-acetyl-2-deoxy-4,6-di-O-pivaloyl-a-D-
glucopyranosyl chloride (10)
4.6. 2-Acetamido-4-S-acetyl-2-deoxy-1,3,6-tri-O-pivaloyl-4-
1H NMR (400 MHz, CDCl3): dH 6.17 (d, 1H, J = 3.7 Hz, H-1), 5.81
(d, 1H, J = 8.8 Hz, NH), 5.34 (dd, 1H, J = 9.7, 9.7 Hz, H-3), 5.26 (dd,
1H, J = 9.8, 9.8 Hz, H-4), 4.56 (ddd, 1H, J = 10.5, 9.0, 3.7 Hz, H-2),
4.29 (ddd, 1H, J = 10.0, 3.0, 3.0 Hz, H-5), 4.25–4.16 (m, 2H, H-
6a + H-6b), 2.04 (s, 3H, Ac), 1.97 (s, 3H, Ac), 1.24 (s, 9H, Piv), 1.15
(s, 9H, Piv).
thio-b-D-galactopyranose (8)
The crude triflate 6 (512 mg, 0.845 mmol) was dissolved in
DMF (4 mL). KSAc (193 mg, 1.69 mmol) was added, and the reac-
tion mixture was refluxed at 65 °C for 2 h. The solution was di-
luted with EtOAc (20 mL) and washed with H2O (3 ꢂ 25 mL). The
organic solution was dried over anhyd Na2SO4 and evaporated.
The residue was purified by column chromatography on silica
gel using 20% EtOAc–hexane as the eluent to give compound 8
(395 mg, 88.0% yield over two steps) as a yellow solid. Rf: 0.68
4.8.2. 2-Acetamido-3-O-acetyl-1-S-acetyl-2-deoxy-4,6-di-O-
pivaloyl-1-thio-b-
D
-glucopyranose (11)
Rf: 0.52 (4:6 EtOAc–toluene). [
a
]
D
+7.2 (c 3.4, CHCl3). 1H NMR
(MeOH/CH2Cl2 5:95).
[a
]
D
ꢀ17.2 (c 2.3, CHCl3). 1H NMR
(400 MHz, CDCl3): dH 6.12 (d, 1H, J = 9.8 Hz, NH), 5.28–5.10 (m,
3H, H-3 + H-4 + H-1), 4.39 (ddd, 1H, J = 10.5, 9.0, 3.7 Hz, H-2),
4.21–4.09 (m, 2H, H-6a + H-6b), 3.83 (ddd, 1H, J = 9.5, 4.0, 3.1 Hz,
H-5), 2.37 (s, 3H, SAc), 2.04 (s, 3H, OAc), 1.89 (s, 3H, NHAc), 1.21
(s, 9H, Piv), 1.15 (s, J = 9.4, 9H, Piv). 13C NMR (100 MHz, CDCl3):
dC 193.27 (SAc), 179.31 (Piv), 178.09 (Piv), 169.69 (NHAc), 168.92
(OAc), 81.69 (C-1), 76.64 (C-5), 73.95 (C-3), 67.78 (C-4), 61.86 (C-
6), 51.82 (C-2), 38.93 (C(CH3)3), 38.84 (C(CH3)3), 30.75 (SAc),
27.05 (C(CH3)3), 26.85 (C(CH3)3), 22.99 (NHAc), 20.52 (OAc). HRE-
SIMS: Calcd for C22H35NO9SNa (M+Na+): m/z 512.1925. Found:
512.1924.
(400 MHz, CDCl3): dH 5.60–5.51 (m, 2H, H-1 + NH), 5.23 (dd,
1H, J = 4.4, 11.0 Hz, H-3), 4.33–4.22 (m, 3H, H-4 + H-2 + H-6a),
4.18 (ddd, 1H, J = 1.5, 6.2, 6.2 Hz, H-5), 4.10 (dd, 1H, J = 6.1,
10.8 Hz, H-6b), 2.36 (s, 3H, SAc), 1.86 (s, 3H, NHAc), 1.17 (s,
9H, Piv), 1.16 (s, 9H, Piv), 1.11 (s, 9H, Piv). 13C NMR (100 MHz,
CDCl3): dC 193.15 (SAc), 178.09 (Piv), 177.93 (Piv), 177.09 (Piv),
169.49 (NHAc), 93.35 (C-1), 72.40 (C-5), 70.55 (C-3), 62.66 (C-
6), 51.49 (C-2), 45.84 (C-4), 38.90 (C(CH3)3), 38.76 (C(CH3)3),
38.71 (C(CH3)3), 30.70 (SAc), 27.01 (C(CH3)3), 26.80 (C(CH3)3),
26.77 (C(CH3)3), 23.08 (NHAc). HREIMS: Calcd for C20H32NO8S
(MꢀPiv+): m/z 446.1849. Found: 446.1838. Anal. Calcd for
C25H41NO9S: C, 56.48; H, 7.77; N, 2.63. Found: C, 56.29; H,
4.9. 2-Acetamido-3-O-acetyl-2-deoxy-4,6-di-O-pivaloyl-
a-D-
7.53; N, 2.46.
galactopyranosyl chloride (12) and 2-acetamido-3-O-acetyl-1-S-
acetyl-2-deoxy-4,6-di-O-pivaloyl-1-thio-b-D-galactopyranose
(13)
4.7. 2-Acetamido-4-azido-2,4-dideoxy-1,3,6-tri-O-pivaloyl-a,b-
D
-galactopyranose (9)
Compound 7 (500 mg, 1.06 mmol) was dissolved in AcCl (3 mL).
Anhyd MeOH (400 L) was added at 0 °C and the reaction mixture
l
The crude triflate 6 (512 mg, 0.845 mmol) was dissolved in an-
was kept at room temperature overnight. The solution was evapo-
rated to dryness and the crude chloride 12 was dissolved in ace-
tone (5 mL) containing 4 Å molecular sieves (500 mg). Potassium
thioacetate (165 mg, 1.38 mmol) was added to the solution at
0 °C, and the reaction mixture was kept at room temperature over-
night. The solution was then evaporated, and the residue was puri-
fied by column chromatography on silica gel using 40% EtOAc–
hexane as the eluent to give compound 13 (370 mg, 71.6% yield)
as a yellow solid.
hyd DMF (4 mL), and NaN3 (109.9 mg, 1.69 mmol) was added. The
reaction was stirred at 65 °C for 2 h. The solution was diluted with
EtOAc (20 mL) and washed with H2O (3 ꢂ 25 mL). The organic
solution was dried over anhyd Na2SO4 and evaporated. The residue
was purified by column chromatography on silica gel using 20%
EtOAc–hexane as the eluent to give compound 9 as an
a/b mixture
(323 mg, 76.7% yield over two steps, /b 1:5). Rf: 0.75 (5:95 MeOH–
a
CH2Cl2). 1H NMR for 9b (400 MHz, CDCl3): dH 5.58 (d, 1H, J = 8.8 Hz,
H-1), 5.51 (m, 1H, NH), 5.22 (m, 1H, H-3), 4.52 (ddd, 1H, J = 19.1,
9.5, 1.1 Hz, H-2), 4.30 (dd, 1H, J = 11.2, 6.3 Hz, H-6a), 4.20 (dd, 1H
J = 11.2, 6.7 Hz, H6-b), 4.00–3.91 (m, 2H, H-5 + H-4), 1.87 (s, 3H,
Ac), 1.24 (s, 9H, Piv), 1.21 (s, 9H, Piv), 1.18 (s, 9H, Piv). 13C NMR
for 9b (100 MHz, CDCl3): dC 178.54 (Piv), 177.92 (Piv), 177.14
(Piv), 169.53 (NHAc), 92.84 (C-1), 72.00 (C-3), 71.65 (C-5), 62.17
(C-6), 60.37 (C-4), 49.95 (C-2), 39.28 (C(CH3)3), 38.79 (C(CH3)3),
38.78 (C(CH3)3), 27.11 (C(CH3)3), 27.03 (C(CH3)3), 26.77 (C(CH3)3),
23.10 (NHAc). HREIMS: Calcd for C23H28N4O8 (M+): m/z 498.2690.
Found: 498.2705.
4.9.1. 2-Acetamido-3-O-acetyl-2-deoxy-4,6-di-O-pivaloyl-a-D-
galactopyranosyl chloride (12)
1H NMR (400 MHz, CDCl3): dH 6.30 (d, 1H, J = 3.6 Hz, H-1), 5.98
(d, 1H, J = 8.8 Hz, NH), 5.48 (dd, 1H, J = 3.0, 1.1 Hz, H-4), 5.31 (dd,
1H, J = 11.3, 3.2 Hz, H-3), 4.78 (ddd, 1H, J = 11.5, 8.9, 3.6 Hz, H-2),
4.54 (ddd, 1H, J = 7.0, 7.0, <1 Hz, H-5), 4.18–4.06 (m, 2H, H-
6a + H-6b), 2.01 (s, 3H, Ac), 2.00 (s, 3H, Ac), 1.27 (s, 9H, Piv), 1.19
(s, 9H, Piv).

2456
J. Feng, C.-C. Ling / Carbohydrate Research 345 (2010) 2450–2457
4.9.2. 2-Acetamido-3-O-acetyl-1-S-acetyl-2-deoxy-4,6-di-O-
pivaloyl-1-thio-b- -galactopyranose (13)
Rf: 0.36 (4:6 EtOAc–toluene). [
+8.5 (c 6.2, CHCl3). 1H NMR
1.9 Hz, GalNAc_H-4), 2.01 (s, 3H, NHAc), 1.99 (s, 3H, NHAc), 1.88
(s, 3H, OAc), 1.24 (s, 9H, Piv), 1.22 (s, 9H, Piv), 1.20 (s, 9H, Piv),
1.18 (s, 9H, Piv), 1.15 (s, 9H, Piv). 13C NMR (100 MHz, CDCl3): dC
178.99 (Piv), 178.31 (Piv), 178.28 (Piv), 178.08 (Piv), 176.96
(Piv), 169.97 (Ac), 169.46 (Ac), 168.77 (Ac), 93.24 (GalNAc_C-1),
84.00 (GlcNAc_C-1), 76.21 (GlcNAc_C-5), 74.32 (GalNAc_C-5),
73.47 (GlcNAc_C-3), 72.10 (GalNAc_C-3), 67.68 (GlcNAc_C-4),
64.41 (GalNAc_C-6), 61.52 (GlcNAc_C-6), 53.67 (GlcNAc_C-2),
50.97 (GalNAc_C-2), 45.63 (GalNAc_C-4), 39.12 (C(CH3)3), 38.95
(C(CH3)3), 38.88 (C(CH3)3), 38.78 (C(CH3)3), 38.73 (C(CH3)3),
27.26 (C(CH3)), 27.08 (C(CH3)3 ꢂ 2), 26.91 (C(CH3)3), 26.84
(C(CH3)3), 23.17 (NHAc), 23.16 (NHAc), 20.53 (OAc). HRESIMS:
Calcd for C43H71N2O16S (M+H+): m/z 903.4519. Found: 903.4522.
D
a]
D
(400 MHz, CDCl3): dH 5.96 (br, 1H, NH), 5.38 (dd, 1H, J = 3.2,
<1 Hz, H-4), 5.24 (d, 1H, J = 10.8 Hz, H-1), 5.10 (dd, 1H, J = 10.8,
3.3 Hz, H-3), 4.42 (ddd, 1H, J = 10.5, 10.5, 10.5 Hz, H-2), 4.13–3.97
(m, 3H, H-5 + H-6a + H-6b), 2.34 (s, 3H, SAc), 1.94 (s, 3H, OAc),
1.89 (s, 3H, NHAc), 1.23 (s, 9H, Piv), 1.13 (s, 9H, Piv). 13C NMR
(100 MHz, CDCl3): dC 193.49 (SAc), 177.80 (Piv), 177.42 (Piv),
170.45 (NHAc), 170.20 (OAc), 81.86 (C-1), 75.03 (C-5), 71.71 (C-
3), 66.16 (C-4), 61.08 (C-6), 48.44 (C-2), 39.16 (C(CH3)3), 38.64
(C(CH3)3), 30.75 (SAc), 27.07 (C(CH3)3), 26.96 (C(CH3)3), 23.15
(NHAc), 20.53 (OAc). HRESIMS: Calcd for C22H35NO9SNa (M+Na+):
m/z 512.1925. Found: 512.1923.
4.12. S-(2-Acetamido-3-O-acetyl-2-deoxy-4,6-di-O-pivaloyl-b-
galactopyranosyl)-(1?4)-2-acetamido-2-deoxy-1,3,6-tri-O-
D-
4.10. p-Chlorophenyl 2-acetamido-3-O-acetyl-2-deoxy-4,6-di-O-
pivaloyl-1-thio-b-
D-galactopyranoside (14)
pivaloyl-4-thio-b-D-galactopyranose (16)
The glycosyl chloride 12 was prepared from compound 7 (4 g,
7.17 mmol) and AcCl (20 mL) as above. The crude 12 was dissolved
in anhyd THF (15 mL), and the solution was added to a DMF solu-
tion (20 mL) containing 4-chlorobenzenethiol (2.1 g, 14.4 mmol)
and t-BuOK (1.45 g, 13.9 mmol). The reaction mixture was stirred
at room temperature overnight. The solution was diluted with
EtOAc (80 mL) and washed with H2O (3 ꢂ 100 mL). The organic
solution was dried over anhyd Na2SO4 and evaporated. The residue
was purified by column chromatography on silica gel using 20%
EtOAc–toluene as the eluent to give the compound 14 (2.96 g,
Thioacetate 13 (170 mg, 0.347 mmol) and the crude triflate 6
(231 mg, 0.382 mmol) were dissolved in anhyd DMF (4 mL). Under
argon, Et2NH (500
l
L) was added at ꢀ5 °C. The reaction mixture
was kept at ꢀ5 °C overnight. The solution was then extracted with
EtOAc (15 mL) and H2O (3 ꢂ 20 mL). The organic layer was dried
over anhyd Na2SO4 and evaporated. The residue was purified by
column chromatography on silica gel using 20% acetone–hexane
as the eluent to give compound 16 (220 mg, 70.2% yield) as a white
solid. Rf: 0.43 (1:1 EtOAc–toluene). [
a
]
D
ꢀ6.2 (c 0.87, CHCl3). 1H
NMR (400 MHz, CDCl3): dH 5.77–5.65 (m, 2H, NH ꢂ 2), 5.55 (d,
1H, J = 8.3 Hz, GalNAc_H-1), 5.37 (dd, 1H, J = 2.8, <1 Hz, Gal-
NAc_H-40), 5.22–5.13 (m, 2H, GalNAc_H-30 + GalNAc_H-3), 4.98
(d, 1H, J = 10.3 Hz, GalNAc_H-10), 4.53 (dd, 1H, J = 12.1, 8.0 Hz, Gal-
NAc_H-6a), 4.45 (ddd, 1H, J = 9.7, 8.5, 8.5 Hz, GalNAc_H-2), 4.22
(dd, 1H, J = 12.1, 3.7 Hz, GalNAc_H-6b), 4.17 (dd, 1H, J = 11.0,
6.6 Hz, GalNAc_H-6a0), 4.10–4.00 (m, 3H, GalNAc_H-20 + Gal-
NAc_H-5 + GalNAc_H-6b0), 3.93–3.84 (m, 1H, GalNAc_H-50), 3.52
(dd, 1H, J = 4.0, 1.8 Hz, GalNAc_H-4), 1.98 (s, 3H, NHAc), 1.95 (s,
3H, OAc), 1.85 (s, 3H, NHAc), 1.24 (s, 9H, Piv), 1.21 (m, 9H, Piv),
1.15 (m, 18H, Piv ꢂ 2), 1.14 (s, 9H, Piv). 13C NMR (100 MHz, CDCl3):
dC 178.28 (Piv ꢂ 2), 177.72 (Piv), 177.42 (Piv), 176.93 (Piv), 170.43
(NHAc), 170.36 (NHAc), 169.60 (OAc), 93.11 (C-1), 83.18 (C-10),
74.45 (C-50), 73.91 (C-5), 72.30 (C-3), 70.95 (C-30), 66.08 (C-40),
64.25 (C-6), 61.03 (C-60), 50.88 (C-2), 50.86 (C-20), 45.25 (C-4),
39.18 (C(CH3)3 ꢂ 2), 39.04 (C(CH3)3), 38.70 (C(CH3)3), 38.66
(C(CH3)3), 27.22 (C(CH3)3), 27.09 (C(CH3)3), 27.04 (C(CH3)3), 27.00
(C(CH3)3), 26.77 (C(CH3)3), 23.33 (NHAc), 23.07 (NHAc), 20.55
(OAc). HRESIMS: Calcd for C43H71N2O16S (M+H+): m/z 903.4519.
Found: 903.4512.
62.8% yield over two steps). Rf: 0.60 (8:92 MeOH–CH2Cl2). [a]
D
ꢀ25.8 (c 0.73, CHCl3). 1H NMR (400 MHz, CDCl3): dH 7.54–7.46
(m, 2H, Ph), 7.31–7.24 (m, 2H, Ph), 5.80 (d, 1H, J = 9.1 Hz, NH),
5.35 (dd, 1H, J = 3.2, <1 Hz, H-4), 5.23 (dd, 1H, J = 10.7, 3.3 Hz, H-
3), 4.90 (d, 1H, J = 10.3 Hz, H-1), 4.14 (m, 1H, H-6a), 4.10–3.98
(m, 3H, H-2 + H-6b + H-5), 1.98 (s, 3H, NHAc), 1.94 (s, 3H, OAc),
1.17 (m, 18H, Piv ꢂ 2. 13C NMR (100 MHz, CDCl3): dC 177.82
(Piv), 177.29 (Piv), 170.25 (NHAc), 170.09 (OAc), 134.78 (Ph),
134.54 (Ph), 129.97 (Ph), 128.92 (Ph), 85.66 (C-1), 74.52 (C-5),
71.22 (C-3), 66.32 (C-4), 61.52 (C-6), 49.60 (C-2), 39.05 (C(CH3)3),
38.64 (C(CH3)3), 26.98 (C(CH3)3), 26.93 (C(CH3)3), 23.35 (NHAc),
20.52 (OAc). HRCIMS: Calcd for
C
26H37NO8SCl (M+H+): m/z
558.1928. Found: 558.1925. Anal. Calcd for C26H36NO8SCl: C,
55.96; H, 6.50; N, 2.51. Found: C, 56.03; H, 6.55; N, 2.39.
4.11. 4-S-(2-Acetamido-4-O-acetyl-2-deoxy-3,6-di-O-pivaloyl-b-
D-glucopyranosyl)-(1?4)-2-acetamido-2-deoxy-1,3,6-tri-O-
pivaloyl-4-thio-b- -galactopyranose (15)
D
Thioacetate 11 (265 mg, 0.541 mmol) and the crude triflate 6
(361 mg, 0.595 mmol) were dissolved in anhyd DMF (7 mL). Under
4.13. 4-S-(2,3,4,6-Tetra-O-acetyl-b-
amido-2-deoxy-1,3,6-tri-O-pivaloyl-4-thio-b-
(18)
D
-glucopyranosyl)-(1?4)-2-acet-
argon, Et2NH (900
l
L) was added at ꢀ5 °C. The reaction mixture
D-galactopyranose
was kept at ꢀ5 °C overnight. The solution was then extracted with
EtOAc (20 mL) and H2O (3 ꢂ 30 mL). The organic layer was dried
over anhyd Na2SO4 and evaporated. The residue was purified by
column chromatography on silica gel using 15% acetone–hexane
as the eluent to give compound 15 (310 mg, 63.4% yield) as a white
2,3,4,6-Tetra-O-acetyl-1-S-acetyl-1-thio-b-D-glucopyranose
(17) was prepared according to the literature procedure.13 Com-
pound 17 (947 mg, 2.33 mmol) and the crude triflate 6 (1.6 g,
2.69 mmol) were dissolved in anhyd DMF (10 mL). Under argon,
Et2NH (2 mL) was added at ꢀ5 °C, and the reaction mixture was
kept at ꢀ5 °C overnight. The solution was then extracted with
EtOAc (40 mL) and H2O (3 ꢂ 60 mL). The organic layer was dried
over anhyd Na2SO4 and evaporated. The residue was purified by
column chromatography on silica gel using 36% EtOAc–hexane as
the eluent to give compound 18 (917 mg, 43.7% yield over three
solid. Rf: 0.45 (1:1 EtOAc–toluene). [
a]
ꢀ26.7 (c 1.5, CHCl3). 1H
D
NMR (400 MHz, CDCl3): dH 5.58 (d, 1H, J = 9.5 Hz, GlcNAc_NH),
5.57 (d, 1H, J = 8.5 Hz, GalNAc_H-1), 5.41 (d, 1H, J = 9.5 Hz, Gal-
NAc_NH), 5.20 (dd, 1H, J = 9.7, 9.7 Hz, GlcNAc_H-4), 5.16 (dd, 1H,
J = 10.7, 4.6 Hz, GalNAc_H-3), 5.03 (dd, 1H, J = 10.3, 9.7 Hz, Glc-
NAc_H-3), 4.85 (d, 1H, J = 10.4 Hz, GlcNAc_H-1), 4.52 (dd, 1H,
J = 12.2, 7.9 Hz, GalNAc_H-6a), 4.49–4.40 (m, 1H, GalNAc_H-2),
4.36 (dd, 1H, J = 12.5, 2.2 Hz, GlcNAc_H-6a), 4.24 (dd, 1H, J = 12.2,
3.3 Hz, GalNAc_H-6b), 4.21–4.12 (m, 2H, GlcNAc_H-2 + Glc-
NAc_H-6b), 4.05 (ddd, 1H, J = 7.9, 3.3, 2.1 Hz, GalNAc_H-5), 3.61
(ddd, 1H, J = 10.0, 3.8, 2.4 Hz, GlcNAc_H-5), 3.49 (dd, 1H, J = 4.5,
steps). Rf: 0.64 (5:95 MeOH–CH2Cl2). [
a
]
ꢀ5.6 (c 8.4, CHCl3). 1H
D
NMR (400 MHz, CDCl3): dH 5.59 (d, 1H, J = 10.5 Hz, NH), 5.52 (dd,
1H, J = 9.0 Hz, GalNAc_H-1), 5.16 (dd, 1H, J = 10.9, 4.2 Hz, Gal-
NAc_H-3), 5.14–5.03 (m, 2H, Glu_H-3 + Glu_H-4), 4.99 (m, 1H,

J. Feng, C.-C. Ling / Carbohydrate Research 345 (2010) 2450–2457
2457
J = 10.1, 10.1 Hz, Glu_H-2), 4.70 (d, 1H, J = 10.1 Hz, Glu_H-1), 4.43
(ddd, 1H, J = 10.7, 9.3, 9.3 Hz, GalNAc_H-2), 4.34 (dd, 1H, J = 12.2,
7.5 Hz, GalNAc_H-6a), 4.27 (dd, 1H, J = 12.1, 3.5 Hz, GalNAc_H-
6b), 4.21 (dd, 1H, J = 12.4, 2.6 Hz, Glu_H-6a), 4.15 (dd, 1H,
J = 12.5, 4.6 Hz, Glu_H-6b), 4.01 (ddd, 1H, J = 7.3, 3.4, 1.6 Hz, Gal-
NAc_H-5), 3.58 (ddd, 1H, J = 9.5, 4.2, 2.6 Hz, Glu_H-5), 3.44 (dd,
1H, J = 4.2, 1.6 Hz, GalNAc_H-4), 2.10 (s, 3H, OAc), 2.06 (s, 3H,
OAc), 1.99 (s, 3H, OAc), 1.98 (s, 3H, OAc), 1.83 (s, 3H, NAc), 1.22
(s, 9H, Piv), 1.16–1.14 (m, 18H, Piv ꢂ 2). 13C NMR (100 MHz,
CDCl3): dC 178.47 (Piv), 178.30 (Piv), 176.95 (Piv), 170.62 (NHAc),
170.11 (OAc), 169.50 (OAc), 169.43 (OAc), 169.24 (OAc), 93.12
(GalNAc_C-1), 83.69 (Glu_C-1), 75.73 (Glu_C-5), 73.98 (Gal-
NAc_C-5), 73.70 (Glu_C-3), 72.25 (GalNAc_C-3), 70.23 (Glu_C-2),
68.24 (Glu_C-4), 64.69 (GalNAc_C-6), 61.74 (Glu_C-6), 50.74 (Gal-
NAc_C-2), 47.21 (GalNAc_C-4), 39.10 (C(CH3)3), 38.71 (C(CH3)3),
38.66 (C(CH3)3), 27.14 (C(CH3)3), 27.00 (C(CH3)3), 26.76 (C(CH3)3),
23.07 (NHAc), 20.63 (OAc), 20.61 (OAc), 20.53 (OAc), 20.50 (OAc).
mixture was stirred at room temperature for 0.5 h. Anhyd FeCl3
(200 mg, 1.23 mmol) was added to the suspension and the reaction
mixture was refluxed at 90 °C overnight. The mixture was filtered
through Celite and the filtrate was evaporated. The residue was
purified by column chromatography on silica gel using 15% ace-
tone–toluene as the eluent to give compound 21 (105 mg, 26.8%
yield) as a yellow solid. Rf: 0.44 (6:94 MeOH–DCM). [a] +47.1 (c
D
2.2, CHCl3). 1H NMR (400 MHz, CDCl3): dH 5.97 (d, 1H, J = 7.7 Hz,
NH), 5.58 (d, 1H J = 2.6 Hz, H-1), 4.55 (dd, 1H, J = 1.1, <1 Hz, H-4),
4.46 (dd, 1H, J = 1.8, <1 Hz, H-3), 4.24 (dddd, 1H, J = 7.80, 2.80,
1.60, 1.60 Hz, H-2), 4.05 (dd, 1H, J = 11.1, 5.4 Hz, H-6a), 3.92 (dd,
1H, J = 11.1, 6.8 Hz, H-6b), 3.87 (ddd, 1H, J = 6.7, 5.5, <1 Hz, H-5),
1.99 (s, 3H, NHAc), 1.22 (s, 9H, Piv), 1.20 (s, 9H, Piv). 13C NMR
(100 MHz, CDCl3): dC 178.20 (Piv), 178.14 (Piv), 170.15 (NHAc),
99.23 (C-1), 81.86 (C-4), 77.91 (C-3), 73.25 (C-5), 63.25 (C-6),
60.73 (C-2), 38.77 (C(CH3)3), 38.63 (C(CH3)3), 27.12 (C(CH3)3),
26.95 (C(CH3)3), 23.05 (NHAc). HRCIMS: Calcd for C18H30NO7
(M+H+): m/z 372.2022. Found: 372.2010.
HRESIMS: Calcd for
Found: 842.3238.
C
37H57NO17SNa (M+Na+): m/z 842.3239.
Acknowledgments
4.14. 4-S-(2,3,4,6-Tetra-O-acetyl-b-D-galactopyranosyl)-(1?4)-2-
acetamido-2-deoxy-1,3,6-tri-O-pivaloyl-4-thio-b-
ose (20)
D-galactopyran-
We wish to acknowledge the Natural Sciences and Engineering
Research Council of Canada and the University of Calgary for their
support of the current project.
2,3,4,6-Tetra-O-acetyl-1-S-acetyl-1-thio-b-D-galactopyranose
(19) was prepared according to the literature procedure.14 Com-
pound 19 (993 mg, 2.44 mmol) and the crude triflate 6 (1.6 g,
2.69 mmol) were dissolved in anhyd DMF (10 mL). Under argon,
Et2NH (2 mL) was added at ꢀ5 °C, and the reaction was kept at
ꢀ5 °C overnight. The solution was then extracted with EtOAc
(40 mL) and H2O (3 ꢂ 60 mL). The organic layer was dried over an-
hyd Na2SO4 and evaporated. The residue was purified by column
chromatography on silica gel using 36% EtOAc–hexane as the elu-
ent to give compound 20 as a white solid. (777 mg, 37.0% yield over
Supplementary data
Supplementary data (1D and 2D NMR spectra) associated with
this article can be found, in the online version, at doi:10.1016/
j.carres.2010.09.008.
References
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three steps). Rf: 0.64 (5:95 MeOH–CH2Cl2). [
a]
D ꢀ3.5 (c 6.1, CHCl3).
1H NMR (400 MHz, CDCl3): dH 5.47 (d, 1H, J = 8.7 Hz, GalNAc_H-1),
5.39 (dd, 1H, J = 3.3, 0.7 Hz, Gal_H-4), 5.33 (d, 1H, J = 9.9 Hz, Gal-
NAc_NH), 5.22–5.11 (m, 2H, Gal_H-2 + GalNAc_H-3), 4.90 (dd,
1H, J = 10.0, 3.4 Hz, Gal_H-3), 4.66 (d, 1H, J = 10.1 Hz, Gal_H-1),
4.48 (dd, 1H, J = 19.5, 10.0 Hz, GalNAc_H-2), 4.37 (dd, 1H, J = 12.2,
7.4 Hz, GalNAc_H-6a), 4.26 (dd, 1H, J = 12.2, 3.4 Hz, GalNAc_H-
6b), 4.16–4.04 (m, 2H, Gal_H-6a + Gal_H-6b), 3.98 (1H, ddd,
J = 7.2, 3.3, 1.5 Hz, GalNAc_H-5), 3.78 (ddd, 1H, J = 6.6, 6.6, 0.8 Hz,
Gal_H5), 3.41 (dd, 1H, J = 3.9, 1.5 Hz, GalNAc_H4), 2.15 (s, 3H,
OAc), 2.12 (s, 3H, OAc), 2.02 (s, 3H, OAc), 1.95 (s, 3H, OAc), 1.82
(s, 3H, NHAc), 1.21 (s, 9H, Piv), 1.16 (s, 9H, Piv), 1.15 (s, 9H, Piv).
13C NMR (100 MHz, CDCl3): dC 178.78 (Piv), 178.57 (Piv), 177.34
(Piv), 170.63 (NHAc), 170.51 (OAc), 170.30 (OAc), 170.03 (OAc),
169.57 (OAc), 93.46 (GalNAc_C-1), 84.65 (Gal_C-1), 74.61(Gal_C-
5), 74.38 (GalNAc_C-5), 72.75 (GalNAc_C-3), 71.96 (Gal_C-3),
67.67 (Gal_C-2), 67.18 (Gal_C-4), 65.00 (GalNAc_C-6), 61.45
(Gal_C-6), 51.00 (GalNAc_C-2), 47.52 (GalNAc_C-4), 39.37
(C(CH3)3), 38.99 (C(CH3)3), 38.94 (C(CH3)3), 29.89, 27.41
(C(CH3)3), 27.28 (C(CH3)3), 27.00 (C(CH3)3), 23.37 (NHAc), 21.01
(OAc), 20.91 (OAc), 20.83 (OAc), 20.78 (OAc). HRESIMS: Calcd for
8. Binkley, R. W. J. Org. Chem. 1991, 56, 3892–3896.
9. Feng, J.; Ling, C.-C., unpublished results.
10. (a) Kiefel, M. J.; Beisner, B.; Bennett, S.; Holmes, I. D.; von Itzstein, M. J. Med.
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Perkin Trans. 1 2001, 832–837.
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13. MacDougall, J. M.; Zhang, X.-D.; Polgar, W. E.; Khroyan, T. V.; Toll, L.; Cashman,
J. R. J. Med. Chem. 2004, 47, 5809–5815.
C
37H57NO17SNa (M+Na+): m/z 842.3239. Found: 842.3234.
14. Pei, Z.; Dong, H.; Caraballo, R.; Ramström, O. Eur. J. Org. Chem. 2007, 4927–
4934.
15. Kumirska, J.; Szafranek, J.; Czerwicka, M.; Paszkiewicz, M.; Dziadziuszko, H.;
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18. Fiandor, J.; García-López, M. T.; De Las Heras, F. G.; Méndez-Castrillón, P. P.
Synthesis 1985, 1121–1123.
4.15. 2-Acetamido-1,4-anhydro-2-deoxy-3,6-di-O-pivaloyl-b-D-
galactopyranose (21)
Compound 7 (500 mg, 1.06 mmol) was added to 1,2-dichloro-
ethane (7 mL) containing 4 Å molecular sieves (500 mg), and the