An effective sialylation method using N-Troc- and N-Fmoc-protected β-thiophenyl sialosides and application to the one-pot two-step synthesis of 2,6-sialyl-T antigen

Article abstract of DOI:10.1055/s-2004-817759

We describe an efficient sialylation method using β-thiosialosides with various N-protecting groups. Modification of the C-5 amino group of β-thiosialosides into N-Fmoc and N-Troc derivatives enhanced their reactivity in glycosidation. In addition, a minimum amount of MS-3 A? was effective to improve the yield of α-linked sialoside. Branched type one-pot glycosylation initiating glycosidation of the N-Troc-protected β-thiophenyl sialoside at a primary alcohol provided the protected 2,6-sialyl-T antigen in good yield, which was converted to the fully deprotected glycosyl amino acid.

Full text of DOI:10.1055/s-2004-817759

LETTER
609
An Effective Sialylation Method Using N-Troc- and N-Fmoc-protected
b-Thiophenyl Sialosides and Application to the One-pot Two-step Synthesis
of 2,6-Sialyl-T Antigen
O
ne-pot Two-step Syn
a
thesis of 2, 6
s
-Sialyl-T
a
Antigen atsu Adachi, Hiroshi Tanaka, Takashi Takahashi*
Department of Applied Chemistry, Tokyo Institute of Technology, Ookayama, Meguro, Tokyo 152-8552, Japan
Fax +81(3)57342884; E-mail: thiroshi@apc.titech.ac.jp
Received 4 December 2003
Chemical syntheses of the sialo-containing glycosyl ami-
no acids require a-selective glycosidation of sialyl donors.
However, a-selective sialylation is a problematic step in
chemical oligosaccharide synthesis.5 Most of the existing
Abstract: We describe an efficient sialylation method using b-thio-
sialosides with various N-protecting groups. Modification of the
C-5 amino group of b-thiosialosides into N-Fmoc and N-Troc deriv-
atives enhanced their reactivity in glycosidation. In addition, a
minimum amount of MS-3 Å was effective to improve the yield of sialyl donors often have relatively low anomeric reactivi-
a-linked sialoside. Branched type one-pot glycosylation initiating
glycosidation of the N-Troc-protected b-thiophenyl sialoside at a
primary alcohol provided the protected 2,6-sialyl-T antigen in good
yield, which was converted to the fully deprotected glycosyl amino
acid.
ties. Furthermore, the sialylation reaction proceeds with
low yield, low a-selectivity and generates significant un-
desirable glycals via elimination. The reasons are as fol-
lows: (1) the sterically hindered tertiary anomeric center,
(2) the presence of an electron-withdrawing carboxyl
group, and (3) the lack of a participating auxiliary substit-
uent adjacent to the anomeric center.6 Therefore, an effec-
tive sialylation method is required for the synthesis of
various sialo-glycosyl amino acids. In 1998, Boons et al.
reported that di-N-acetyl-protected thiosialoside was ef-
fective for glycosidation in terms of reactivity in compar-
ison with N-acetyl thiosialoside.7 Recently, modification
of the C-5 amino group of the sialyl donor into an azido
group8 and N-trifluoroacetyl (N-TFA) group9 has been re-
ported to improve their reactivity in glycosidation. Herein
we report an effective sialylation method using an N-Troc
and N-Fmoc-protected b-thiophenyl sialosides and an
application to the synthesis of a 2,6-sialyl-T antigen by a
one-pot two-step glycosylation.10
Key words: sialic acids, one-pot glycosylation, glycopeptides, gly-
cosyl amino acids, thioglycosides
Sialic acids such as Neu5Ac, Neu5Glc and KDN, are
often located at the non-reducing end of glycoconjugates
on the cell surface through a-glycosidic bonds, and play a
central role in cell surface recognition phenomena.1 For
example, 2,6-sialyl-T antigen composed of Galb(1→3)-
[Neu5Aca(2→6)]-GalNAca(1→3)-Ser (1a) or -Thr (1b)
is one of the glycoforms contained in mucin glycopro-
teins, and are important tumor-associated antigens
(Figure 1).2 Different glycoforms composed of the 6-sia-
lylated galactoside are found in the related antigens.3
However, elucidation of the biological roles of each gly-
coform would be difficult as glycoproteins with these oli-
gosaccharides attached often contain several different
glycoforms. Therefore, pure sialo-glycosides related to
the glycosyl amino acids are required as effective chemi-
cal probes.4
We first investigated glycosidation of b-thiophenyl sialo-
sides 2a–i varying the N-protecting group (Scheme 1 and
Table 1). Although b-thiophenyl sialosides are less reac-
tive in glycosidation than a-thiophenyl sialosides, they
can be simply prepared from N-acetylneuraminic acid.11
Thiosialosides 2b–h were synthesized by removal of all
acetyl groups of the N-acetyl thiosialoside 2a under acidic
conditions,12 followed by selective acylation of the amino
group with various acid derivatives13,14 and acetylation of
the remaining hydroxyl groups. All compounds 2b–d and
2f–h except for N-Fmoc derivative 2e were obtained in
good yields (63–89% in 3 steps). Glycosylation of the pri-
mary alcohol of 3 with donors 2a–i was examined. Aceto-
nitrile was used as a solvent because it is known to
improve a-selectivity in sialylation.15 The sialyl donors
2a–i were treated with 1.5 equivalents of acceptor 3 in the
presence of NIS (1.20 equiv)/TfOH (0.20 equiv)16 and
MS-3 Å (10 g/mmol) in CH3CN at –35 °C. Glycosidation
of N-TFA derivative 2g provided disaccharide 4g in the
best yield (92%, a/b = 92:8). The N-Fmoc and N-Troc de-
rivatives 2e and 2f17 were converted to disaccharide 4e
and 4f in excellent yields with acceptable a-selectivity
1
OH CO2H
HO
HO
O
O
3
AcHN
5
HO
OH
HO
HO
HO
O
O
O
NH2
O
AcHN
HO
O
OH
1a : R1 = H
1b : R1 = Me
R1
Figure 1 Structure of 2,6-sialyl-T antigen.
SYNLETT 2004, No. 4, pp 0609–0614
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9.
0
3.
2
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Advanced online publication: 10.02.2004
DOI: 10.1055/s-2004-817759; Art ID: U26903ST
© Georg Thieme Verlag Stuttgart · New York

610
M. Adachi et al.
LETTER
(91%, a/b = 86:14, for 4e, and 91%, a/b = 89:11 for 4f).
The anomeric configurations of these sialosides were de-
termined by NMR measurement based on the chemical
shift of H-3eq and H-4, coupling constant of J7,8, and value
of Dd{H-9¢-H-9}, which were in accordance with the em-
pirical rules to define the anomeric configuration of N-
acetyl sialic acid glycosides.18,19 Removal of the Troc
group of the separated a- and b-disaccharides 4f, followed
by acetylation provided the corresponding a- and b-N-
acetyl disaccharides 4a. To adapt the sialylation to the
synthesis of glycosyl amino acids and peptides, removal
of the C-5 protecting group without racemization of the
amino acid is needed. However, deprotection of the N-
TFA group requires relatively strongly basic conditions,
in which racemization of amino acids would occur. On the
other hand, the N-Fmoc and N-Troc groups can be con-
verted to various N-acyl groups under mildly acidic or ba-
sic conditions. Therefore, the N-Fmoc and N-Troc-
protected b-thiophenyl sialosides 2e and 2f would be suit-
able for the synthesis of glycosyl amino acids and glyco-
peptides. Recently, Kiso and Ando et al. have reported the
effectiveness of an N-Troc-protected a-thiophenyl sialo-
side for the synthesis of sialo-glycosides.20
OAc
O
OAc
O
AcO
AcO
AcO
AcO
SPh
CO2Me
SPh
CO2Me
a, b, d
R3R2N
AcHN
or
a, c, d
AcO
2b-i
AcO
2a
OAc
CO2Me
AcO
AcO
O
OH
O
R3R2N
AcO
O
BnO
BnO
O
BnO
BnO
BnO
BnO
OMe
OMe
3
4a-i
+
e
OAc
AcO
AcO
CO2Me
O
R3R2N
AcO
5a-i
Scheme 1 Reagents and conditions: (a) MsOH, MeOH, 60 °C, 12
h; (b) Z-OSu, Alloc-OSu, Fmoc-OSu, Troc-OSu, or (Boc)2O, Et3N,
CH3CN/H2O, r.t., 5.5 h, for 2b–f; (c) CF3CO2Me or CCl3CO2Me,
Et3N, MeOH, r.t., 1 h, for 2g–h; (d) Ac2O, pyridine, DMAP; (e) 2a–i
(1.00 equiv), 3 (1.50 equiv), NIS (1.20 equiv), TfOH (0.20 equiv),
CH3CN, MS-3 Å (10 g/mmol), –35 °C, 1 h.
In order to demonstrate the feasibility of the sialylation
method, we planned a one-pot two-step synthesis of 2,6-
sialyl-T antigen (1a). One-pot glycosylation involving se-
quential formation of glycosidic bonds in a vessel, is one
of the most effective solution-phase methodologies, not
only for the high speed synthesis of target oligosaccha-
rides, but also for the parallel synthesis of oligosaccharide
libraries.21–25 We have investigated the one-pot glycosyla-
tion methodology on the basis of selective-activation of
glycosyl donors attached with different leaving groups us-
ing appropriate activators, and have accomplished an
efficient one-pot synthesis of a di-branched heptasaccha-
ride,26 and a combinatorial synthesis of linear and
branched trisaccharide libraries.27 Most of the reported
syntheses of 2,6-sialyl-T antigen are based on a traditional
step-wise glycosylation strategy.28 If the one-pot glyco-
sylation approach involving glycosidation of sialyl donors
can be achieved, it should be effective for the synthesis of
related antigens.
Our strategy for the synthesis of 1a by a branched type
one-pot glycosylation is shown in Scheme 2. 3,6-Dihy-
droxyl glycosylated serine derivative 6 was used as a gly-
cosyl acceptor.28d–e,29 N-Troc-protected b-thiophenyl
Table 1 Preparation and Glycosidation of b-Thiophenyl Sialosides 2a–i Having Various N-Protecting Groups at the C-5 Position
Entry
R3R2N
Donor
2a
Yield of 2 (%)a
Disaccharide
Yield of 4 (%) / a:bb
47 / 85:15
68 / 84:16
–
Glycal
5a
Yield of 5 (%)
1
2
3
4
5
6
7
8
9
AcHN
–
4a
4b
4c
4d
4e
4f
28
8
ZHN
2b
2c
63
76
68
27
89
77
70
–
5b
5c
AllocHN
BocHN
FmocHN
TrocHN
TFAHN
CCl3COHN
Ac2N
–
2d
2e
44 / 88:12
91 / 86:14
91 / 89:11
92 / 92:8
5d
5e
20
7
2f
5f
6
2g
4g
4h
4i
5g
5
2h
2i
83 / 91:9
5h
5i
4
65 / 62:38
23
a Yield was estimated from the N-acetyl thiosialoside 2a in 3 steps.
b The a/b ratio was determined by HPLC analysis.
Synlett 2004, No. 4, 609–614 © Thieme Stuttgart · New York

LETTER
One-pot Two-step Synthesis of 2,6-Sialyl-T Antigen
611
sialoside 2f was selected as the glycosyl donor because
accessibility of 2f from N-acetylneuraminic acid was bet-
ter than that of the N-Fmoc derivative 2e. Regioselective
glycosylation of the primary alcohol of 6 at the 6-position
with the N-Troc derivative 2f, followed by glycosylation
at the 3-position with galactoside 7 would provide protect-
ed 2,6-sialyl-T antigen. Transformation of the azido and
the N-Troc group to the N-acetyl group, followed by
deprotection of all protecting groups should be achieved
without racemization of the amino acid to provide the
fully deprotected 2,6-sialyl-T antigen (1a).
OAc
AcO
AcO
CO2Me
O
O
TrocHN
AcO
BnO
+
5f
a
O
6
R4O
NHZ
N3
O
OBn
O
8 : R4 = H
9 : R4
c
OAc
O
AcO
AcO
CO2Me
=
One-pot
Glycosylation
TrocHN
AcO
OAc
AcO
AcO
SPh
O
CO2Me
OAc
O
TrocHN
AcO
AcO
CO2Me
AcO
1)
OH
6
2f
O
TrocHN
BnO
1a
AcO
BnO OBn
b
d
BnO
O
2)
HO
O
NHZ
O
3
O
OBn
O
BnO
BnO
N3
O
O
BnO
NHZ
O
OBn
BzO
N3
O
X
6
OBn
BzO
7a : X = SPh
7b : X = F
10
OAc
O
Scheme 2 Strategy for the one-pot two-step synthesis of 1a.
AcO
CO2Me
AcO
AcHN
O
Stepwise synthesis of the protected trisaccharide 10 was
conducted (Scheme 3). We first examined glycosylation
of a primary alcohol of 6 with an equivalent of N-Troc-
protected b-thiophenyl sialoside 2f (Table 2). Treatment
of diol 6 with an equivalent of the sialyl donor 2f in the
presence of NIS (1.20 equiv), TfOH (0.20 equiv) and MS-
3 Å (10 g/mmol) in CH3CN (10 mL/mmol) at –35 °C for
1 hour provided disaccharide 8 in moderate yield (57%, a/
b = 84:16) along with the di-sialyl trisaccharide 9 in 4%
yield and glycal 5f in 20% yield (entry 1).30,31 Further op-
timization of the reaction revealed that the quantity of
MS-3 Å and concentration of the substrates influenced the
efficiency of the glycosidation. Glycosylation of 6 with an
equivalent of 2f in the presence of MS-3 Å (0.50 g/mmol)
in CH3CN (5 mL/mmol) provided disaccharide 8 in 75%
yield (a/b = 80:20) along with the di-sialyl-trisaccharide 9
in 4% yield and glycal 5f in 8% yield, respectively (entry
7). Use of propionitrile as a solvent requires higher reac-
tion temperature (–25 °C) and longer reaction time (3 h),
and resulted in a reduced yield of 8 (58%, a/b = 82:18)
(entry 8). Finally, minimization of the remaining acceptor
6 and the side-products 9 and 5f was accomplished by gly-
cosidation of 1.2 equivalents of the sialyl donor 2f with
NIS (1.44 equiv), TfOH (0.10 equiv) and MS-3 Å (0.50 g/
mmol) in CH3CN (5 mL/mmol) at –35 °C to provide di-
saccharide 8 in 93% yield (a/b = 78:22) along with tri-
saccharide 9 (6%) and glycal 5f (12%) (entry 9).
e, f
AcO
BnO OBn
1a
BnO
O
O
O
BnO
NHZ
AcHN
BzO
O
OBn
11
O
Scheme 3 Reagents and conditions: (a) 2f (1.20 equiv), NIS (1.44
equiv), TfOH (0.10 equiv) CH3CN (5 mL/mmol), MS-3 Å (0.50 g/
mmol), –35 °C, 93%, a/b = 78:22; (b) 7a (1.50 equiv), NIS (2.00
equiv), TfOH (0.20 equiv) CH2Cl2/CH3CN (9:1, 5 mL/mmol), MS-3
Å (0.50 g/mmol), –30 °C, 82%, a/b = 6:94; (c) 2f (1.20 equiv), 6
(1.00 equiv), NIS (1.44 equiv), TfOH (0.10 equiv) CH3CN (5 mL/
mmol), MS-3 Å (0.50 g/mmol), –35 °C, then 7a (1.80 equiv) NIS
(2.70 equiv), TfOH (0.20 equiv), CH2Cl2 (45 mL/mmol), –30 °C,
77%, a/b = 78:22; (d) Zn dust, THF, HOAc, Ac2O, 0 °C, 1 h, 92%;
(e) Pd(OH)2, THF, MeOH, HOAc, H2O, 2 h; (f) 0.1 N NaOH, MeOH,
then H2O, 85% in 2 steps.
thiogalactoside 7a in the presence of NIS/TfOH in
CH3CN at room temperature provided trisaccharide 10 in
60% yield with poor b-selectivity (a/b = 19:81).32,33 Ga-
lactosyl fluoride 7b was not completely activated with
ZrCp2Cl2/AgOTf34 in CH3CN. After optimization of the
reaction conditions, we found that treatment of disaccha-
ride 8-a with 7a (1.50 equiv) in CH2Cl2/CH3CN (9:1) at
–30 °C afforded trisaccharide 10 in 82% yield with
acceptable selectivity (a/b = 6:94).
Next, glycosylation of the remaining secondary alcohol of
8 with galactoside 7 was examined. In the one-pot glyco-
sylation, the galactosylation should be achieved after the
sialylation. Therefore, we first examined glycosylation of
8-a with 7 in CH3CN. Treatment of disaccharide 8-a with
One-pot glycosylation using 2f, 6, and 7a was examined.
Treatment of diol 6 with the N-Troc-protected b-thiophe-
nyl sialoside 2f under the above described conditions pro-
vided disaccharide 8. Dilution of the reaction mixture
Synlett 2004, No. 4, 609–614 © Thieme Stuttgart · New York

612
M. Adachi et al.
LETTER
Table 2 Optimization of Regioselective Sialylation of Diol 6 with the N-Troc-protected b-Thiophenyl Sialoside 2fa
Entry
Donor
(equiv)
TfOH
(equiv)
Concentration MS-3 Å
Yield of 8
(%) / a:bb
Yield of
9
Yield of
5f
(mL/mmol)
10 (CH3CN)
10 (CH3CN)
10 (CH3CN)
10 (CH3CN)
10 (CH3CN)
5 (CH3CN)
5 (CH3CN)
5 (EtCN)
(g/mmol)
1
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.1
0.1
10
57 / 84:16
65 / 78:22
55 / 79:21
71 / 80:20
69 / 81:19
70 / 79:21
75 / 80:20
58 / 82:18
93 / 78:22
4
5
4
4
5
5
4
6
6
20
12
17
12
10
17
8
2
5.0
3
2.5
4
0.50
0.25
0.50
0.50
0.50
0.50
5
6
7
8c
9d
25
12
5 (CH3CN)
a Conditions: NIS (1.2 equiv based on 2f) and TfOH at –35 °C for 1 h.
b The a/b ratio was determined by HPLC analysis.
c The reaction was carried out at –25 °C for 3 h.
d 1.44 equiv of NIS was used.
with CH2Cl2, followed by addition of thioglactoside 7a of all protecting groups without racemization of the a-po-
and additional NIS/TfOH afforded the protected tri- sition of the amino acid was accomplished to provided
saccharide 10 as two diastereomers in 77% yield (a/ sialo-glycosyl amino acid. Application of the glycosyla-
b = 78:22) in 2 steps. The ratio was determined by HPLC tion method to the synthesis of an oligosaccharide library
analysis based on refractive index detection. The mixture is in progress.
10 was easily separated by column chromatography on
1
silica gel. H NMR analysis of the separated isomers
shows that the major is the desired trisaccharide 10-a and
the minor is b-sialoside 10-b.
Acknowledgment
This work was supported by a Grand-in Aid for Scientific Research
on Priority Area (S) from the Ministry of Education, Culture,
Sports, Science, and Technology (Grant-in-aid No.14103013).
Transformation of 10-a to 1a is as follows. The simulta-
neous reduction of the azido and Troc groups of 10-a,35
followed by acetylation, provided the corresponding N-
References
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the benzoate, acetyl and methyl ester to provide the fully
deprotected 2,6-sialyl-T serine (1a) in 85% overall yield.
Their analytical data (1H NMR, optical rotation) were
identical with those previously reported.27,36
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of glycosyl amino acids by one-pot glycosylation was
demonstrated. Branched type one-pot two-step glycosyla-
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thiophenyl sialoside 2f at a primary alcohol of acceptor 6
provided the protected Galb(1→3)-[Neu5Aca(2→6)]-
GalNAca(1→3)-Ser (1a) in good yield. Modification of
the N-Troc group to N-acetyl group, followed by removal
Synlett 2004, No. 4, 609–614 © Thieme Stuttgart · New York

LETTER
One-pot Two-step Synthesis of 2,6-Sialyl-T Antigen
613
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(d = 2.72 ppm), H-4 (d = 4.98 ppm), Dd{H-9¢-H-9} = 0.27
ppm. For 4f-b-isomer: H-3eq (d = 2.54 ppm), H-4 (d = 5.25
ppm), J7,8 = 4.8 Hz, Dd{H-9¢-H-9} = 0.91 ppm. For 4g-a-
isomer: H-3eq (d = 2.70 ppm), H-4 (d = 4.99 ppm), J7,8 = 8.8
Hz, Dd{H-9¢-H-9} = 0.30 ppm. For 4g-b-isomer: H-3eq
(d = 2.45 ppm), H-4 (d = 5.21 ppm), Dd{H-9¢-H-9} = 0.91
ppm.
(20) Ando, H.; Koike, Y.; Ishida, H.; Kiso, M. Tetrahedron Lett.
2003, 44, 6883.
(21) Seeberger, P. H.; Haase, W.-C. Chem. Rev. 2000, 100, 4349.
(22) Raghavan, S.; Kahne, D. J. Am. Chem. Soc. 1993, 115, 1580.
(23) (a) Yamada, H.; Harada, T.; Miyazaki, H.; Takahashi, T.
Tetrahedron Lett. 1994, 35, 3979. (b) Yamada, H.; Harada,
T.; Takahashi, T. J. Am. Chem. Soc. 1994, 116, 7919.
(c) Yamada, H.; Kato, T.; Takahashi, T. Tetrahedron Lett.
1999, 40, 4581.
(24) Douglas, N. L.; Ley, S. L.; Lücking, U. L.; Warriner, S. L. J.
Chem. Soc., Perkin Trans. 1 1998, 51.
(25) Zang, Z.; Ollmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov,
T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
(26) (a) Yamada, H.; Takimoto, H.; Ikeda, T.; Tsukamoto, H.;
Harada, T.; Takahashi, T. Synlett 2001, 1751. (b) Tanaka,
H.; Adachi, M.; Tsukamoto, H.; Ikeda, T.; Yamada, H.;
Takahashi, T. Org. Lett. 2002, 4, 4213; and references
therein.
(27) Takahashi, T.; Adachi, M.; Matsuda, A.; Doi, T.
Tetrahedron Lett. 2000, 41, 2599.
(28) (a) Iijima, H.; Ogawa, T. Carbohydr. Res. 1989, 186, 95.
(b) Qiu, D.; Gandhi, S. S.; Koganty, R. R. Tetrahedron Lett.
1996, 37, 595. (c) Sames, D.; Chen, X.-T.; Danishefsky, S.
J. Nature (London) 1997, 389, 587. (d) Schwarz, J. B.;
Kuduk, S. D.; Chen, X.-T.; Sames, D.; Glunz, P. W.;
Danishefsky, S. J. J. Am. Chem. Soc. 1999, 121, 2662.
(e) Brocke, C.; Kunz, H. Synlett 2003, 2052.
(29) For the related approaches using GalNAca(1→3)-Ser or
-Thr derivatives as building blocks, see: (a) Nakahara, Y.;
Iijima, H.; Ogawa, T. Tetrahedron Lett. 1994, 35, 3321.
(b) Liebe, B.; Kunz, H. Tetrahedron Lett. 1994, 35, 8777.
(c) Meinjohanns, E.; Meldal, M.; Paulsen, H.; Schleyer, A.;
Bock, K. J. Chem. Soc., Perkin Trans. 1 1996, 985.
(d) Liebe, B.; Kunz, H. Angew. Chem. Int. Ed. 1997, 36,
2830. (e) Chen, X.-T.; Sames, D.; Danishefsky, S. J. J. Am.
Chem. Soc. 1998, 120, 7760.
(11) Marra, A.; Sinäy, P. Carbohydr. Res. 1989, 187, 35.
(12) (a) Sugita, T.; Higuchi, R. Tetrahedron Lett. 1996, 37, 2613.
(b) Sugita, T.; Kan, Y.; Nagaregawa, Y.; Miyamoto, T.;
Higuchi, R. J. Carbohydr. Chem. 1997, 16, 917.
(13) (a) Paguet, A. Can. J. Chem. 1982, 60, 976. (b) Lapatsanis,
L.; Milias, G.; Froussios, K.; Kolovos, M. Synthesis 1983,
671.
(30) The a/b ratio was determined by HPLC analysis based on
refractive index detection (Eluent: hexane/2-propanol =
90:10, 3.0 mL/min; Retention time: a-isomer 10.7 min, b-
isomer 11.7 min). The anomeric configuration of
disaccharide 8 was determined by 1H NMR measurement of
the isolated isomers according to empirical rule.
(14) Byramova, N. E.; Tuzikov, A. B.; Bovin, N. V. Carbohydr.
Res. 1992, 237, 161.
(15) Hasegawa, A.; Nagahama, T.; Ohki, H.; Hotta, K.; Ishida,
H.; Kiso, M. J. Carbohydr. Chem. 1991, 10, 493.
(16) (a) Konradsson, P.; Udodong, U.; Fraser-Reid, B.
Tetrahedron Lett. 1990, 31, 4313. (b) Veeneman, G. H.; van
Leeuwen, S. H.; van Boom, J. H. Tetrahedron Lett. 1990, 31,
1331.
(17) Glycosidation of the N-Troc-protected b-thiophenyl
sialoside 2f with a primary alcohol has already been
reported. However, in this report, improvement of the yield
in glycosidation was not noted. See: Ren, C.-T.; Chen, C.-S.;
Wu, S.-H. J. Org. Chem. 2002, 67, 1376.
(31) Analytical data of 8: For 8-a: [a]D21 +43.4 (c 1.00, CHCl3).
1H NMR (400 MHz, CDCl3): d = 7.30–7.60 (m, 15 H,
aromatic), 5.89 (d, 1 H, Ser-NH, J = 8.3 Hz), 5.40 (ddd, 1 H,
Neu-H-8), 5.36 (dd, 1 H, Neu-H-7, J6,7 = 1.4 Hz, J7,8 = 8.8
Hz), 5.35 (d, 1 H, Jgem = 12.2 Hz), 5.14 (d, 1 H, Jgem = 12.6
Hz), 5.11 (d × 2, 2 H), 5.00 (br dd, 1 H, Neu-H-4, J3ax,4 = 4.9
Hz, J3eq,4 = 10.8 Hz), 4.94 (d, 1 H, Neu-Troc-NH, J = 10.3
Hz), 4.90 (d, 1 H, Jgem = 12.2 Hz), 4.79 (d, 1 H, Jgem = 11.7
Hz), 4.78 (d, 1 H, GalNAc-H-1, J1,2 = 3.4 Hz), 4.65 (d, 1 H,
Jgem = 11.2 Hz), 4.60 (m, 1 H, Ser-a), 4.36 (d, 1 H,
(18) (a) Dabrowski, U.; Friebolin, H.; Brossmer, R.; Supp, M.
Tetrahedron Lett. 1979, 20, 4637. (b) Paulsen, H.; Tietz, H.
Angew. Chem., Int. Ed. Engl. 1982, 21, 927.
Jgem = 12.2 Hz), 4.24 (d, 1 H, Neu-H-9¢, J8,9’ = 1.9 Hz,
Jgem = 12.7 Hz), 4.16 (br d, 1 H, Neu-H-6, J = 10.8 Hz), 4.06
(dd, 1 H, Neu-H-9, J8,9 = 4.9 Hz, Jgem = 12.7 Hz), 3.91–4.01
(m, 3 H, GalNAc-H-6¢, Ser-b), 3.79–3.85 (m, 3 H, GalNAc-
H-3, H-4, H-6), 3.65–3.69 (m, 4 H, Neu-H-5, OMe), 3.52 (br
dd, 1 H, GalNAc-H-5), 3.36 (dd, 1 H, GalNAc-H-2,
(19) Selected 1H NMR assignment of disaccharide 4e–g: For 4e-
a-isomer: H-3eq (d = 2.70 ppm), H-4 (d = 4.90 ppm),
J7,8 = 9.2 Hz, Dd{H-9¢-H-9} = 0.31 ppm. For 4e-b-isomer:
H-3eq (d = 2.54 ppm), H-4 (d = 5.21 ppm), J7,8 = 8.7 Hz,
Dd{H-9¢-H-9} = 0.93 ppm. For 4f-a-isomer: H-3eq
J1,2 = 3.0 Hz, J2,3 = 10.3 Hz), 2.66 (dd, 1 H, Neu-H-3eq,
J3eq,4 = 4.9 Hz, Jgem = 13.2 Hz), 2.25 (d, 1 H, GalNAc-H-3,
Synlett 2004, No. 4, 609–614 © Thieme Stuttgart · New York

614
M. Adachi et al.
LETTER
J1,2 = 3.4 Hz), 4.67 (d, 1 H, J = 12.2 Hz), 4.61 (d, 1 H,
OH, J = 8.8 Hz), 1.97, 2.00, 2.09, 2.11 (4 s, 12 H, Ac), 1.92
(dd, 1 H, Neu-H-3ax, J3ax,4 = 10.8 Hz). 13C NMR (100 MHz,
CDCl3): d = 172.0, 170.7, 170.5, 169.8, 166.6, 156.0, 154.5,
138.0, 136.0, 134.9, 128.6, 128.6, 128.5, 128.4, 128.1,
127.9, 127.8, 98.7, 98.2, 95.5, 77.9, 77.2, 75.4, 74.4, 72.3,
71.8, 70.7, 69.2, 68.4, 68.2, 68.1, 67.9, 67.2, 63.3, 62.7, 60.4,
53.8, 52.7, 50.9, 37.0, 20.9, 20.8, 20.7, 20.6. IR (KBr): 3347,
2534, 2109, 1745, 1523, 1369, 1218, 1038, 738, 738, 698
cm–1. Anal. Calcd for C52H60Cl3N5O22: C, 41.47; H, 4.98; N,
J = 11.2 Hz), 4.58 (d, 1 H, J = 11.7 Hz), 4.56 (m, 1 H, Ser-
a), 4.53 (d, 1 H, J = 12.7 Hz), 4.46 (d, 1 H, J = 12.2 Hz), 4.45
(d, 1 H, J = 12.2 Hz), 4.29 (br dd, 1 H, Neu-H-9¢, Jgem = 11.2
Hz), 4.14 (dd, 1 H, Neu-H-9, J8,9 = 4.9 Hz, Jgem = 11.2 Hz),
4.13 (dd, 1 H, Neu-H-6, J5,6 = 9.8 Hz, J6,7 < 1 Hz), 4.05 (br
dd, 1 H, Gal-H-4), 3.89–3.99 (m, 4 H, Ser-b, Gal-H-3, H-6¢),
3.67–3.69 (m, 6 H, GalNAc-H-4, H-6, Gal-H-3, H-5, H-6,
H-6¢), 3.59–3.64 (m, 4 H, Neu-H-5, OMe), 3.50 (dd, 1 H,
GalNAc-H-2, J1,2 = 3.0 Hz, J2,3 = 11.2 Hz), 3.20 (ddd, 1 H,
GalNAc-H-5, J = 4.9 Hz, J = 9.3 Hz), 2.56 (dd, 1 H, Neu-H-
3eq, J3eq,4 = 9.3 Hz, Jgem = 12.7 Hz), 1.97, 1.99, 2.07, 2.11 (4
22
5.77. Found: C, 51.03; H, 5.02; N, 5.47. For 8-b: [a]D
+37.5 (c 1.00, CHCl3). 1H NMR (400 MHz, CDCl3): d =
7.30–7.39 (m, 15 H, aromatic), 6.36 (d, 1 H, Ser-NH, J = 8.8
Hz), 6.22 (d, 1 H, Neu-Troc-NH, J = 10.3 Hz), 5.54 (ddd, 1
H, Neu-H-4, J3ax,4 = 12.2 Hz, J3eq,4 = 4.4 Hz), 5.47 (br s, 1 H,
Neu-H-7), 5.37 (d, 1 H, Jgem = 13.9 Hz), 5.34 (m, 1 H, Neu-
H-8), 5.12 (d, 1 H, Jgem = 13.9 Hz), 5.11 (d × 2, 2 H), 4.96 (br
d, 1 H, Neu-H-9¢, J = 11.2 Hz), 4.89 (d, 1 H, GalNAc-H-1,
J1,2 = 2.9 Hz), 4.76 (m, 1 H, Ser-a), 4.75 (d, 1 H, Jgem = 12.2
Hz), 4.69 (d × 2, 2 H), 4.53 (d, 1 H, Jgem = 11.7 Hz), 4.10 (m,
1 H, Ser-b¢), 4.03 (dd, 1 H, Neu-H-9, J8,9 = 8.8 Hz,
s, 12 H, Ac), 1.84 (dd, 1 H, Neu-H-3ax, J3ax,4 = 12.2 Hz). 13
NMR (100 MHz, CDCl3): d = 170.6, 170.3, 170.1, 169.8,
169.6, 169.6, 167.7, 165.3, 156.0, 154.0, 138.6, 138.5,
137.7, 137.6, 136.2, 135.1, 132.8, 132.8, 130.2, 129.8,
128.7, 128.6, 128.5, 128.5, 128.4, 128.3, 128.2, 128.1,
C
128.0, 127.9, 127.8, 127.7, 127.6, 127.4, 127.3, 102.6, 99.3,
98.4, 95.4, 79.7, 77.2, 76.8, 75.3, 74.5, 74.4, 74.3, 73.6, 73.4,
72.6, 72.1, 72.0, 71.8, 69.8, 68.7, 68.6, 68.4, 68.3, 67.5, 67.1,
63.8, 62.1, 59.4, 54.5, 52.7, 51.5, 37.7, 21.0, 20.7, 20.7. IR
(KBr): 3347, 2952, 2109, 1745, 1520, 1454, 1218, 1040,
737, 698 cm–1.
Jgem = 12.7 Hz), 3.94 (m, 2 H, Neu-H-6, GalNAc-H-5), 3.62
(m, 9 H, Neu-H-5, OMe, GalNAc-H-3, H-4, H-6¢, H-6, Ser-
b), 3.36 (dd, 1 H, GalNAc-H-2, J1,2 = 2.9 Hz, J2,3 = 10.8 Hz),
2.51 (dd, 1 H, Neu-H-3eq, J3eq,4 = 4.4 Hz, Jgem = 13.9 Hz),
1.96 (d, 1 H, GalNAc-H-3-OH), 1.91, 1.97 × 2, 2.01 (3 s, 12
(34) (a) Matsumoto, T.; Maeta, H.; Suzuki, K.; Tsuchihashi, G.
Tetrahedron Lett. 1988, 29, 2567. (b) Suzuki, K.; Maeta,
H.; Matsumoto, T. Tetrahedron Lett. 1989, 3029, 4853.
(35) Windholz, T. B.; Johnston, D. B. R. Tetrahedron Lett. 1967,
8, 2555.
H, Ac), 1.83 (dd, 1 H, Neu-H-3ax, J3ax,4 = 12.2 Hz). 13
C
NMR (100 MHz, CDCl3): d = 170.7, 170.3, 170.0, 169.8,
169.7, 167.7, 156.0, 154.0, 138.0, 156.0, 138.0, 136.1,
135.1, 128.5, 128.5, 128.1, 128.0, 128.0, 127.8, 99.3, 98.4,
95.3, 76.6, 75.1, 74.4, 71.9, 69.6, 69.1, 68.3, 68.0, 67.9, 67.5,
67.3, 67.0, 63.0, 62.2, 60.8, 54.4, 52.8, 51.4, 37.7, 21.0, 20.8,
20.7, 20.6. IR (KBr): 3368, 2955, 2110, 1744, 1530, 1370,
1223, 1036, 944, 736, 696 cm–1.
(36) Analytical data for 1a: [a]D26 +67.0 (c 0.16, H2O). 1H NMR
(400 MHz, D2O, 303 K): d = 4.88 (d, 1 H, GalNAc-H-1,
J1,2 = 3.9 Hz), 4.43 (d, 1 H, Gal-H-1, J1,2 = 7.8 Hz), 4.31 (dd,
1 H, GalNAc-H-2, J1,2 = 3.4 Hz, J2,3 = 11.2 Hz), 4.22 (br d,
GalNAc-H-4, J = 2.9 Hz), 4.10 (dd, 1 H, Ser-b¢, Ja,b¢ = 2.4
Hz, Jgem = 10.7 Hz), 4.04 (dd, 1 H, GalNAc-H-3, J2,3 = 11.2
Hz, J3,4 = 2.9 Hz), 4.01 (m, 1 H, GalNAc-H-5), 3.97 (dd, 1
H, Ser-a, Ja,b¢ = 2.4 Hz, Ja,b = 4.9 Hz), 3.90 (dd, 1 H, Ser-b,
Ja,b = 4.9 Hz, Jgem = 10.7 Hz), 3.61–3.88 (12 H, Neu5Ac-H-
4,5,6,7,8,9¢,9, GalNAc-H-6¢,6, Gal-H-5,6¢), 3.58 (dd, 1 H,
Gal-H-3, J2,3 = 10.3 Hz, J3,4 = 3.9 Hz), 3.55 (dd, 1 H, Gal-H-
6, J5,6 = 1.0 Hz, Jgem = 10.3 Hz), 3.48 (dd, 1 H, Gal-H-2,
(32) The a/b ratio was determined by HPLC analysis based on
refractive index detection (Eluent: hexane/2-propanol =
95:5, 3.0 mL/min; Retention time: a-isomer 12.9 min, b-
isomer 16.1 min).
(33) Selected analytical data of 10: For a-sialoside 10 (a-isomer):
1H NMR (400 MHz, CDCl3): d = 5.61 (dd, 1 H, Gal-H-2,
J1,2 = 3.4 Hz, J2,3 = 10.3 Hz), 5.55 (d, 1 H, Gal-H-1, J1,2 = 3.4
Hz). For a-sialoside 10 (b-isomer): [a]D21 +23.8 (c 1.36,
CHCl3). 1H NMR (400 MHz, CDCl3): d = 8.05 (d, 2 H,
aromatic), 7.13–7.57 (m, 33 H, aromatic), 5.74 (dd, 1 H, Gal-
H-2, J1,2 = 7.3 Hz, J2,3 = 8.2 Hz), 5.74 (d, 1 H, Ser-NH,
J = 6.8 Hz), 5.39 (m, 1 H, Neu-H-8), 5.35 (dd, 1 H, Neu-H-
7, J6,7 < 1 Hz, J7,8 = 8.3 Hz), 5.09–5.17 (m, 4 H), 5.05 (d, 1
H, J = 11.2 Hz), 4.97 (ddd, 1 H, Neu-H-4, J3ax,4 = 12.2 Hz,
J1,2 = 7.8 Hz, J2,3 = 10.3 Hz), 2.70 (dd, 1 H, Neu5Ac-H-3eq,
J3eq,4 = 4.9 Hz, Jgem = 12.7 Hz), 2.00, 2.01 (2 s, 6 H, Ac),
1.65 (dd, 1 H, Neu5Ac-H-3ax, J3ax,4 = 12.2 Hz). 13C NMR
(100 MHz, D2O, acetone-d6): d = 175.8, 175.4, 173.9, 172.0,
105.5, 100.9, 99.1, 77.4, 75.8, 73.5, 73.4, 72.4, 71.4, 70.3,
69.4, 69.3, 69.7, 68.9, 67.3, 64.6, 63.5, 61.8, 54.8, 52.6, 49.2,
40.9, 22.9 × 2. IR (KBr): 3330, 1641, 1572, 1393, 1121,
1055, 930, 669 cm–1. MS (ESI-TOF): Calcd for
J
3aq,4 = 4.9 Hz, J4,5 = 9.6 Hz), 4.94 (d, 1 H, J = 11.7 Hz), 4.90
(d, 1 H, J = 12.7 Hz), 4.87 (d, 1 H, J = 10.8 Hz), 4.77 (d, 1
H, Gal-H-1, J1,2 = 7.8 Hz), 4.69 (d, 1 H, GalNAc-H-1,
C28H47N3O21Na [M + Na]+ 784.3; found: 784.3.
Synlett 2004, No. 4, 609–614 © Thieme Stuttgart · New York