Synthetic construction of a fucosyl chitobiose as an allergen-associated carbohydrate epitope and the glycopolymer involving highly clustered trisaccharidic sequences

Article abstract of DOI:10.1016/j.tetlet.2010.03.004

Synthetic construction of fucosyl chitobiose [GlcNAcβ1→4(Fucα1→3)GlcNAc] as an allergy-associated carbohydrate epitope was accomplished from three building blocks. The trisaccharidic unit was further transformed into a carbohydrate monomer and polymerization of the glycomonomer proceeded smoothly to provide a series of glycopolymers having various carbohydrate densities. In addition to the organic syntheses, biological evaluations of the glycomonomer and the polymers were carried out and sugar-clustering effects were observed.

Full text of DOI:10.1016/j.tetlet.2010.03.004

Tetrahedron Letters 51 (2010) 2529–2532
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthetic construction of a fucosyl chitobiose as an allergen-associated
carbohydrate epitope and the glycopolymer involving highly clustered
trisaccharidic sequences
*
Koji Matsuoka , Hiroki Yamaguchi, Tetsuo Koyama, Ken Hatano, Daiyo Terunuma
Area for Molecular Function, Division of Material Science, Graduate School of Science and Engineering, Saitama University, Sakura, Saitama 338-8570, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthetic construction of fucosyl chitobiose [GlcNAcb1?4(Fuca1?3)GlcNAc] as an allergy-associated car-
Received 17 February 2010
Revised 24 February 2010
Accepted 1 March 2010
Available online 3 March 2010
bohydrate epitope was accomplished from three building blocks. The trisaccharidic unit was further trans-
formed into a carbohydrate monomer and polymerization of the glycomonomer proceeded smoothly to
provide a series of glycopolymers having various carbohydrate densities. In addition to the organic synthe-
ses, biological evaluations of the glycomonomer and the polymers were carried out and sugar-clustering
effects were observed.
Keywords:
Ó 2010 Elsevier Ltd. All rights reserved.
Plant carbohydrate chains
Fucosyl chitobiose
Glycosides
Glycopolymers
Glycoclusters
Fucosyl chitobiose [GlcNAcb1?4(Fuc
a
1?3)GlcNAc] is known
biological evaluations of the glycomonomer and the glycopolymers
were performed.
as an extremely valuable core structure of glycoconjugates such
as N-linked glycoproteins in plants,1 and the trisaccharide struc-
ture is suspected to be one of epitopes of allergy.2 A regioisomeric
structure of the trisaccharide is also a fucosyl chitobiose having
In our previous study, synthetically efficient construction of an
Lex determinant [Galb1?4(Fuc
a
1?3)GlcNAc] was accomplished
using a convergent synthetic strategy from -galactose (Gal), -fu-
-mannose (Man) as key starting materials, and
D
L
[GlcNAcb1?4(Fuca1?6)GlcNAc], and this trisaccharidic structure
cose (Fuc), and D
is a well-known core structure ubiquitously found as N-linked gly-
coproteins in mammalians.3 Synthetic assembly of the trisaccha-
OH
O
OH
O
O
ride of Fuc
Nishimura et al. using a chitobiosyl derivative as the key starting
material.4 Synthetic assembly of the trisaccharide of Fuc
1?3-
a1?6-linked-type was efficiently accomplished by
HO
HO
O
O
O
N
H
NHAc
NHAc
a
Me
O
OH
1
linked-type was, however, achieved more than 30 years ago by Tej-
ima and co-workers using a convergent strategy.5 The chitobiose
moiety was prepared by means of acid-promoted glycosidation
of the oxazoline derived from GlcNAc and the 1,6-anhydro GlcNAc
derivative in 41% yield. Further introduction of Fuc into the chito-
biose moiety was attempted by using Lemieux’s conditions,6 such
as a halide ion-catalyzed glycosidation in 47% yield. It seems that
since suitable amounts of the trisaccharide and the derivatives
were not obtained, the results of biological evaluations of the tri-
saccharide and derivatives have not been reported. In this Letter,
we describe efficient preparation of trisaccharidic glycomonomer
1 from three building blocks 2, 3, and 4 and chemical conversion
into a highly clustered glycopolymer. In addition to the syntheses,
OH
OH
O
OAc
O
OBn
SLau
OBn
Me
O
O
AcO
SLau
OBn
OBn
AcO
2 NHTroc
OH4 N
3
3
Building block A
Building block B
Building block C
OH
OH
O
OH
OH
O
Me
O
OH
HO
HO
OH
OH
OH
HO
HO
OH
NH2 HCl
L-Fuc
D-GlcN·HCl
D-Man
* Corresponding author. Tel./fax: +81 48 858 3099.
E-mail address: koji@fms.saitama-u.ac.jp (K. Matsuoka).
Figure 1. Synthetic plan for the construction of fucosyl chitobiose [Glc-
NAcb1?4(Fuc 1?3)GlcNAc] derivative.
a
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.03.004

2530
K. Matsuoka et al. / Tetrahedron Letters 51 (2010) 2529–2532
OAc
O
i)
AcO
AcO
2
OAc
NHTroc
5
O
O
OBn
OR2
O
O
ii)
iii)
vii)
OAc
O
OAc
O
+
2
4
AcO
AcO
O
NHAc
O
N3
3
AcO
AcO
NHTroc
6
NHR1
7 : R1 = Troc, R2 = Bn
8 : R1 = H, R2 = Bn
9 : R1 = Ac, R2 = Bn
10 : R1 = Ac, R2 = H
iv)
v)
vi)
O
O
OAc
O
OAc
O
OAc
O
OAc
O
O
OAc
O
AcO
AcO
AcO
O
O
OAc
O
O
AcO
O
x)
xi)
AcO
O
NHAc
NHAc
NHAc
NHAc
Me
O
N
AcO
Me
NHAc
O
O
Me
OAc
OAc
Me
OAc
OAc
OR
OAc
OAc
OR
OR
11 : R = Bn
12 : R = H
13 : R = Ac
14
15
viii)
ix)
OAc
O
OH
OAc
O
OH
O
O
AcO
AcO
HO
HO
OR
OR
O
O
O
O
xii)
xiv)
NHAc
NHAc
NHAc
NHAc
Me
O
Me
O
OAc
OH
OAc
OH
OAc
OH
O
O
O
N
16 : R =
17 : R =
1 : R =
N
H
xiii)
xv)
H
O
18 : R =
N
H
N
H
Scheme 1. Reagents and conditions: (i) BF3ꢀOEt2, CH3(CH2)11SH, ClCH2CH2Cl, 0 °C to rt, 2.5 h, 97%; (ii) NIS/TMSOTf, CH2Cl2, MS 4A, ꢂ20 °C, 3 h, 81%; (iii) AcSH, Pyr, 0 °C to rt,
on, 100%; (iv) Zn, AcOH, rt, on; (v) Ac2O, Pyr, rt, 1 day, 98% (two steps); (vi) Pd/C, H2, EtOAc, rt, 1 day, 100%; (vii) NIS/TMSOTf, CH2Cl2, MS 4A, ꢂ30 °C, 2.5 h, 74%; (viii) Pd/C, H2,
EtOAc, rt, 1 day; (ix) Ac2O, Pyr, rt, 94%(two steps); (x) BF3ꢀOEt2, Ac2O, 0 °C, 4 h, 98%; (xi) TMSOTf, ClCH2CH2Cl, 50 °C, 5 h, 97%; (xii) 6-acrylamidohexan-1-ol, PPTS, ClCH2CH2Cl,
reflux, 2 h, 68%; (xiii) Pd/C, H2, MeOH, rt, 5 h, 98%; (xiv) NaOMe, MeOH, rt, on, 96%; (xv) Pd/C, H2, MeOH, rt, 4 h, 99%.
30
their biological responses against plant lectin were confirmed.7
similar synthetic plan for the construction of a fucosyl chitobiose
[GlcNAcb1?4(Fuc 1?3)GlcNAc] structure was selected because
A
graphic purification, which was recrystallized from EtOH, ½aꢁD
ꢂ18.3° (c 1.00, CHCl3), mp 108.8–109.5 °C, 1H NMR (CDCl3) d 5.16
(d, 1H, J2,NH = 9.3 Hz, NH), 4.62 (d, 1H, J1,2 = 10.3 Hz, H-1).
a
of ready access of the key building blocks. Thus, a monosaccharide
unit of the reducing end as the pivotal building block C 4 for Glc-
NAc residue was derived from 1,6-anhydro-b-mannose8 as shown
in Figure 1. Our synthetic plan for the fucosyl chitobiose structure,
Since three building blocks were prepared, we turned our atten-
tion to the construction of each building block. A synthetic assem-
bly of the trisaccharide is illustrated in Scheme 2. TMSOTf-
mediated glycosidation of thioglycoside in the presence of appro-
priate amounts of NIS13 in CH2Cl2 at ꢂ20 °C allowed condensation
of N-Troc donor 2 and an azido acceptor 4 to give the precursor 6 of
the chitobiose moiety involving a newly formed b-glycosidic link-
age in 81% yield, in which the azide moiety at C-2 was converted
into acetamide by means of chemoselective reduction using thio-
acetic acid—pyridine14 at rt to furnish the corresponding acetam-
therefore, was convergent methodology using
D-glucosamine
hydrochloride (GlcNꢀHCl), -fucose (Fuc), and -mannose (Man)
L
D
as key starting materials. Building block B 39 was derived by step-
wise syntheses from Fuc according to Lewis acid-mediated glycos-
idation with 1-dodecanethiol (lauryl mercaptan).10 Building block
C 4 was derived from 1,6-anhydro-b-Man by the method previ-
ously reported.8 Scheme 1 shows the preparation of building block
A 2 from known 5.11 Since an N-Troc protective group at the C-2
position in glucosamine promises formation of b-glycosidic linkage
with high stereoselectivity reported by Magnusson and Ellervik12
we chose the N-Troc-protected donor as the building block in this
study. Thus, a b-acetate 5 was treated with 3 molar equivalents of
lauryl mercaptan by means of mediation of 2 molar equivalents of
BF3–OEt2 to afford b-thioglycoside 2 in 97% yield after chromato-
ide 7 in a quantitative yield, ½a D32
ꢁ
ꢂ75.2° (c 1.00, CHCl3), IR (KBr)
1751 (mC@O), 1654 (m ,
C@O, amide I), 1530 (dN–H, amide II) cmꢂ1 1H
0
0
NMR (CDCl3) d 6.59 (d, 1H, J2 ,NH = 8.0 Hz, NH), 5.28 (s, 1H, H-1),
4.53 (d, 1H, J1 ,2 = 8.0 Hz, H-10), 13C NMR (CDCl3) d 101.03 (C-1),
100.10 (C-10). Selective removal of the N-Troc moiety was per-
formed in AcOH in the presence of Zn dust at rt overnight to afford
the amine 8, which was successively acetylated in the usual man-
ner. Chromatographic purification of the reactant gave the diaceta-
mide 95 in 97% yield in two steps. Reductive removal of the benzyl
group in 9 was carried out using typical hydrogenolysis with Pd/C
in EtOAc under hydrogen atmosphere and the reaction proceeded
0
0
All new compounds with specific rotation data gave satisfactory results of
elemental analyses.

K. Matsuoka et al. / Tetrahedron Letters 51 (2010) 2529–2532
2531
meric configuration was estimated to be
a
/b = 3:2 on the basis of
OH
O
OH
O
O
the results of 1H NMR. Treatment of the anomeric mixture 14 with
TMSOTf16 produced the unstable oxazoline derivative 15 in 97%
yield, which has a characteristic coupling constant in 1H NMR at
d 5.93 (d, 1H, J1,2 = 6.42 Hz, H-1). Because of the accessibility and
appropriate methylene chain length, 6-acrylamidohexan-1-ol17
was selected as an alcoholic candidate for the glycosidation. Thus,
PPTS-catalyzed glycosidation18 of the oxazoline 13 with the alco-
hol proceeded in dichloroethane to afford the corresponding b-gly-
HO
HO
O
O
O
N
H
i)
NHAc
NHAc
1
Me
O
OH
19
29
OH
OH
Scheme 2. Reagents and conditions: (i) APS, TEMED, H2O/EtOH (1:1, v/v), rt, 6 h,
86%.
coside 16 in 68% yield, 1H NMR (CDCl3)
d 6.33 (dd, 1H,
Jtrans = 17.0 Hz and Jgem = 1.4 Hz, –CH@CHHtrans), 6.18 (dd, 1H,
Jcis = 10.2 Hz, –CH@CHHcis), 5.66 (dd, 1H, –CH@), 13C NMR (CDCl3)
d 130.99 (@CH2), 126.28 (–CH@), 100.98 (C-1), 100.09 (C-10),
95.15 (C-100). Since the aglycon of 16 was highly polymerizable
by itself, elemental analysis was performed after reductive treat-
ment of the terminal C@C double bond to yield the corresponding
smoothly to afford the corresponding mono alcohol 10 in a quan-
titative yield, ½a D31
ꢁ
ꢂ99.2° (c 1.00, CHCl3), IR (neat) 3306 (
m
O–H),
,
1747 (
m
C@O), 1659 (
m
C@O, amide I), 1537 (dN–H, amide II) cmꢂ1
1H
NMR (CDCl3) d 6.90 (d, 1H, J2 ,NH = 10.0 Hz, NH0), 6.18 (d, 1H,
0
0
0
0
J2,NH = 9.2 Hz, NH), 5.32 (s, 1H, H-1), 4.55 (d, 1H, J1 ,2 = 8.4 Hz, H-
propanamide 17, ½a D28
ꢂ105.6° (c 0.37, CHCl3). Transesterification
ꢁ
10), 13C NMR (CDCl3) d 101.59 (C-1), 99.76 (C-10). Since the glycosyl
of 16 by the Zemplén manner19 was performed and gave the acryl-
amide alcohol 1 as a white powder after lyophilization in 96% yield,
which was further transformed into the corresponding propana-
mide 18 in the same manner as that described for 16 to give 18
donor 3 and the acceptor 10 were prepared, a-stereoselective gly-
cosidation of Fuc for constructing trisaccharide 14 was performed
using the fucosyl donor 3 and the acceptor 10 by means of condi-
tions similar to those used for the production of disaccharide 6 to
give crystalline 11 having an
a
-fucosyl linkage in 74% yield, ½a D28
ꢁ
in 99% yield, ½a 3D0
ꢁ
ꢂ77.3° (c 0.41, CH3OH), 13C NMR (CD3OD) d
ꢂ89.0° (c 1.00, CHCl3), mp 160.2–164.7 °C, 1H NMR (CDCl3) d
102.93 (C-1), 102.42 (C-10), 100.13 (C-100).
5.30 (s, 1H, H-1), 5.14 (d, 1H, J1 ,2 = 4.0 Hz, H-100), 4.52 (d, 1H,
00 00
Given the success of the preparation of the polymerizable fuco-
syl chitobiose 1, our attention turned to polymerization ability of
the carbohydrate monomer 1. In our previous synthetic study of
artificial glycoconjugates, bioactive carbohydrate moieties were
incorporated into the polymer chain as pendant-type epitopes
using linear polymers.7,20 Therefore, the same strategy as that used
for making macromolecules having carbohydrate chains21 was ap-
plied to the glycomonomer 1. Thus, the homopolymerization of 1
was initially tried and the reaction proceeded efficiently in an
aqueous media to afford white powdery glycopolymer 19 in 86%
yield after chromatographic purification by Sephadex G-50 fol-
lowed by lyophilization, Mn 13 kDa; Mw 21 kDa; Mw=Mn1:6, 1H
NMR d (D2O) 5.11 (br s, 1H, H-100), 4.52 (br s, 1H, H-1), 4.48 (br s,
13
J1 ,2 = 8.0 Hz, H-10), C NMR (CDCl3) d 101.18 (C-1), 99.76 (C-10),
95.98 (C-100). Exchange of the protections in the fucose moiety in
11 from the benzyl group to acetyl group proceeded in EtOAc in
the presence of Pd/C under hydrogen atmosphere, followed by
the usual acetylation to yield acetate 13 in 94% yield in two steps,
0
0
½
a 2D7
ꢁ
ꢂ144.5° (c 0.67, CHCl3), mp 298.4–300.6 °C (dec.), 1H NMR
(CDCl3) d 5.38 (d, 1H, J1 ,2 = 3.8 Hz, H-100), 5.23 (s, 1H, H-1), 4.54
00 00
(d, 1H, J1 ,2 = 8.2 Hz, H-10), 13C NMR (CDCl3) d 101.08 (C-1), 99.80
(C-10), 93.39 (C-100). The next step was the fission of the 1,6-anhy-
dro ring in 13 involving a highly acid-labile fucosidic bond. In order
to avoid such trouble, we used BF3–OEt2 as a Lewis acid source for
fission of the 1,6-anhydro ring.15 Thus, acetolysis of 13 gave the
corresponding acetate 14 as an anomeric mixture, in which ano-
0
0
13
1H, H-10), C NMR (D2O) d 100.87 (C-1), 100.35 (C-10), 98.48
0.35
(A)
(B)
0.3
0.25
0.2
0
0.15
/F
0.1
0.05
0
0
0.5
1
1.5
2
2.5
3
3.5
[S] (μM)
0.6
0.4
0.2
0
(C)
F
-0.2
-0.4
-0.6
-0.8
-1
F
F
-1.2
-6.4
-6.2
-6
-5.8
-5.6
310
335
360
385
410
435
460
log [S]
Wavelength (nm)
Figure 2. (A) Changes in fluorescence emission spectra of WGA (0.65
wavelength (kex) was used at 295 nm. (B) Plots of F/F0 versus [S], where
of WGA alone, and [S] is total ligand concentration. (C) Hill plots of log [
l
D
D
M) upon the addition of 20-
F is change in the intensity at 348 nm of WGA with various concentrations of 19, F0 is the intensity
F/( FMAX F)] versus log [S].
lL aliquots of glycopolymer 19 (69.1 lM) at 5 °C. The excitation
D
D
ꢂ
D

2532
K. Matsuoka et al. / Tetrahedron Letters 51 (2010) 2529–2532
(C-100). From the weight-average molecular weight ðMwÞ of the gly-
copolymer 19, the degree of polymerization was estimated to be
29. Biological activity of the glycopolymer 19 against a plant lectin
as a model protein was preliminarily examined on the basis of fluo-
rescence measurement using wheat germ agglutinin (WGA), which
2. (a) Ogawa, H.; Hikijima, A.; Amano, M.; Kojima, K.; Fukushima, H.; Ishizuka, I.;
Kurihara, Y.; Matsumoto, I. Glycoconjugate J. 1996, 13, 555–566; (b) Ueda, H.;
Ogawa, H. Trend Glycsci. Glycotech. 1999, 11, 413–428. and references cited
therein.
3. For example, see: Kornfeld, R.; Kornfeld, S. Ann. Rev. Biochem. 1985, 54, 631–
664. and references cited therein.
4. Nishimura, S.-I.; Kurita, K.; Kuzuhara, H. Chem. Lett. 1990, 1611–1614.
5. Oguri, S.; Ishihara, H.; Tejima, S. Chem. Pharm. Bull. 1980, 28, 3196–3202.
6. Lemieux, R. U.; Hendriks, K. B.; Stick, R. V.; James, K. J. Am. Chem. Soc. 1975, 97,
4056–4062.
binds to an N-acetyl-D
-glucosamine and its oligomers.22 Figure 2
shows fluorescence emission of WGA and of its complexes with
various concentrations of glycopolymer 19. When the protein
was saturated with the glycopolymer 19, the maximum fluores-
cence intensity was enhanced by 35% and the emission maximum
was downfield-shifted from 347 nm to 341 nm (ꢂ6 nm). The
results suggested that the environment of tryptophan residues
located at or near the binding sites of WGA is altered from hydro-
philic to relatively more hydrophobic upon interaction with the
7. Matsuoka, K.; Kohzu, T.; Hakumura, T.; Koyama, T.; Hatano, K.; Terunuma,
D. Tetrahedron Lett. 2009, 50, 2593–2596. The Lex trisaccharide is
composed of Galb1?4(Fuca1?3)GlcNAc and the synthetic construction of
the trisaccharidic unit was achieved by means of Gabriel amine synthesis
as the key reaction.
8. Sakairi, N.; Takahashi, S.; Wang, F.; Ueno, Y.; Kuzuhara, H. Bull. Chem. Soc. Jpn.
1994, 67, 1756–1758.
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327.
glycopolymer 19. In a plot of
DF/F0 versus [S] based on sugar unit
concentration followed by analyses using the Hill equation,23 asso-
ciation constant Ka was estimated to be 6.9 ꢃ 105 (Mꢂ1). These
results clearly indicated that the lectin showed a higher affinity
for the glycopolymer 19 than that for GlcNAc and oligomeric
GlcNAc.24 In addition, interference of the fucose residue located
on the glucosamine unit of the reducing end was not observed in
this study.
11. Myszka, H.; Bednarczyk, D.; Najder, M.; Kaca, W. Carbohydr. Res. 2003, 338,
133–141.
12. Ellervik, U.; Magnusson, G. Carbohydr. Res. 1996, 280, 251–260.
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Hatano, K.; Terunuma, D. Tetrahedron Lett. 2004, 45, 9383–9386.
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Carbohydr. Chem. 1998, 17, 231–239.
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17. Sarfati, S. R.; Pochet, S.; Neumann, J.-M.; Igolen, J. J. Chem. Soc., Perkin Trans. 1
1990, 1065–1070.
In summary, we have successfully described an efficient prepa-
ration of a fucosyl chitobiose [GlcNAcb1?4(Fuca1?3)GlcNAc]
18. Yoshino, T.; Sato, K.-I.; Wanme, F.; Takai, I.; Ishido, Y. Glycoconjugate J. 1992, 9,
287–291.
19. Zemplén, G.; Pacsu, E. Ber. 1929, 62, 1613–1614.
derivative and its chemical modification to provide a water-soluble
glycomonomer. Homopolymerization using the glycomonomer
was performed to give a water-soluble glycopolymer having Mw
21 KDa in high yield, which displayed highly clustered glycoepi-
topes. Plant lectin binding activity of the glycopolymer was prelim-
inarily examined on the basis of fluorescence measurement and
showed enhancement of the affinity due to a sugar-clustering ef-
fect. Further polymerization conditions including copolymeriza-
tion conditions with acryl amide are now under investigation,
and the biological activities of the glycopolymers as the epitope
for allergy will also be examined. The results of these experiments
will be reported in the near future.
20. (a) Miyagawa, A.; Kurosawa, H.; Watanabe, T.; Koyama, T.; Terunuma, D.;
Matsuoka, K. Carbohydr. Polym. 2004, 57, 441–450; (b) Matsuoka, K.;
Goshu, Y.; Takezawa, Y.; Mori, T.; Sakamoto, J.-I.; Yamada, A.; Onaga, T.;
Koyama, T.; Hatano, K.; Snyder, P. W.; Toone, E. J.; Terunuma, D.
Carbohydr. Polym. 2007, 69, 326–335; (c) Matsuoka, K.; Takita, C.;
Koyama, T.; Miyamoto, D.; Yingsakmongkon, S.; Hidari, K. I. P. J.;
Jampangern, W.; Suzuki, T.; Suzuki, Y.; Hatano, K.; Terunuma, D. Bioorg.
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21. Nishimura, S.-I.; Matsuoka, K.; Kurita, K. Macromolecules 1990, 23, 4182–4184.
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Nishi, N.; Tokura, S. Macromolecules 1994, 27, 4876–4880.
References and notes
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1974, 254, 10715–10719.