Solid-phase synthesis of oligosaccharides using novel alkyne-type linkers: Selection of reactive sites on the support by Sonogashira reaction

Article abstract of DOI:10.1055/s-2002-33605

Two new alkyne-type linkers having alkynylmethyloxy moieties were elaborated for solid-phase synthesis of oligosaccharides. A propargyl glycoside-type linker between a sugar residue and a solid support was formed by the Sonogashira reaction of a propargyl glycoside with polymer-supported iodobenzene. A propargyl ester-type linker was also constructed by the same reaction of a 4-(proparygyloxycarbonyl)benzyl glycoside with the latter. Both linkers are stable against acids such as TFA but can be readily cleaved with this acid after conversion to the corresponding alkyne-cobalt complex by treatment with C0₂(CO)₈. The latter ester linker is generally advantageous in that mild cleavage liberates a product as its carboxybenzyl glycoside which is readily purified. The Sonogashira reaction was found to proceed only at spatially reactive sites on the solid support where the reagent accesses readily, so that the subsequent reactions including glycosylation on solid phase proceeded smoothly to result in high total yields of the desired oligosaccharides.

Full text of DOI:10.1055/s-2002-33605

LETTER
1409
Solid-phase Synthesis of Oligosaccharides Using Novel Alkyne-type Linkers:
Selection of Reactive Sites on the Support by Sonogashira Reaction
Solid-phase
O
ligosacc
i
n
Synthesis
U
o
r
L
inkersu Izumi, Koichi Fukase,* Shoichi Kusumoto
Department of Chemistry, Graduate School of Science, Osaka University 1-1 Machikaneyama, Toyonaka, Osaka 560-0043
E-mail: koichi@chem.sci.osaka-u.ac.jp
Received 6 June 2002
Indeed, heterogeneity of resins is a common problem for
Abstract: Two new alkyne-type linkers having alkynylmethyloxy
solid-phase oligosaccharide synthesis. Glycosylation on
solid support sometimes does not proceed quantitatively.
moieties were elaborated for solid-phase synthesis of oligosaccha-
rides. A propargyl glycoside-type linker between a sugar residue
and a solid support was formed by the Sonogashira reaction of a
Selective loading on the reactive regions of a solid support
propargyl glycoside with polymer-supported iodobenzene. A pro-
( = readily accessible regions by reagents) should solve
pargyl ester-type linker was also constructed by the same reaction
this problem. In the present study, we propose two novel
of a 4-(proparygyloxycarbonyl)benzyl glycoside with the latter.
alkynyl-type linkers suitable for the purpose of introduc-
ing a starting monosaccharide component to the reactive
sites on the solid support by the Sonogashira reaction.
Both linkers are stable against acids such as TFA but can be readily
cleaved with this acid after conversion to the corresponding alkyne-
cobalt complex by treatment with Co2(CO)8. The latter ester linker
is generally advantageous in that mild cleavage liberates a product
as its carboxybenzyl glycoside which is readily purified. The Sono-
gashira reaction was found to proceed only at spatially reactive sites
on the solid support where the reagent accesses readily, so that the
subsequent reactions including glycosylation on solid phase pro-
ceeded smoothly to result in high total yields of the desired oli-
gosaccharides.
Previously, we reported propargyloxycarbonyl and prop-
argyloxy groups are stable to neat TFA but are readily
cleaved at ambient temperature by treatment with
Co2(CO)8 and TFA in CH2Cl2 via formation of an alkyne-
cobalt complex (Figure 1).14,15 In view of its chemical be-
havior, the propargyloxy group was expected to formulate
Key words: oligosaccharides, solid-phase synthesis, carbohy- a useful linker for solid-phase synthesis if the alkyne ter-
drates, glycosylations, cross-coupling
minal could be immobilized to the polymer support.
O
(CO)3
Co
O
Co2(CO)8
Co(CO)3
R'
H+
Synthesis of oligosaccharides and glycoconjugates has
played important roles in investigation of their biological
functions such as recognition in cellular trafficking, cell-
cell adhesion, and chronic inflammation, receptors for
bacterial toxin, immunostimulation, and so on. Solid-
phase synthesis of oligosaccharides has been extensively
investigated in order to establish practical and convenient
methods for oligosaccharide synthesis.1–11
R
X
O
R
X
O
R
XH
R'
X = O, NH
R' = H, Ph
Figure 1 Cleavage of propargyloxycarbonyl group.
A propargyl glycoside-type linker was first investigated,
since we already reported its use for anomeric protec-
tion.15 Two routes were examined for introduction of pro-
pargyl glycosides to solid supports as shown in Figure 2.
In route 1, Sonogashira coupling between propargyl gly-
cosides and p-iodobenzoate was first carried out to afford
monosaccharides with a linker moiety, which were then
introduced to aminomethylated polystyrene support by
amide bond formation. In route 2, propargyl glycosides
were introduced by the Sonogashira reaction to polymer-
support.16 In the present study, we used ArgoPoreTM-NH2
and SynPhaseTM Lantern-NH2 as supports in order to as-
sess the general applicability of the method. SynPhase
Lanterns are surface-grafted polymers optimized for sol-
id-phase synthesis of small organic molecules and pep-
We have also reported solid-phase oligosaccharide syn-
thesis by using macroporous polystyrene resin (ArgoPo-
reTM)12 as a support.13 Since the macroporous polystyrene
resin has constant ability for the uptake of organic sol-
vents, a wide range of solvents including protic solvents
and ether can permeate easily into the pores and be used
for solid-phase synthesis. -Selective glycosylation on the
macroporous polystyrene support was hence accom-
plished by virtue of the solvent effect of diethyl ether. A
problem in macroporous polystyrene resin is the large het-
erogeneity in pore sizes. Dry ArgoPoreTM resin has an av-
erage pore size of approximately 90 Å but also many
smaller pores (<10 Å) are known to be present. Due to the
space-demanding ionic reaction intermediate of glycosy-
lation that consists of an oxocarbenium ion and a counte-
rion, glycosylation may not proceed in small pores.
tides.17
A
polystyrene graft, which has similar
performance characteristics to conventional polystyrene
resins, was used in the present study. Each SynPhaseTM
Lantern-NH2 (D-series, 5 mm
12.5 mm) has 35 mol
of an amino group in the polystyrene graft.
Synlett 2002, No. 9, Print: 02 09 2002.
Art Id.1437-2096,E;2002,0,09,1409,1416,ftx,en;U02402ST.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214
The process of loading a monosaccharide to a polymer via
route 1 is shown in Scheme 1. Propargyl 4,6-O-ben-

1410
M. Izumi et al.
LETTER
1) PropargylOH
TMSCl,
r.t., 72 h
O
O
HO
HO
HO
Ph
O
(RO)n
route 1
O
route 2
O
O
HO
OH
HO
2) PhCH(OMe)2
TsOH, CH3CN
r.t., 5 h
I
HO
O
2
1
OMe
70%
O
I
O
OMe
Pd(0)
O
BnBr, NaH
Ph
O
4
O
BnO
DMF, r.t., 3 h
90%
O
BnO
I
Pd(PPh3)4 , CuI,
THF / TEA = 1/1, r.t.,
O
3
(RO)n
NH
12 h
90%
O
O
O
Ph
O
O
Pd(0)
OMe
NaOH, H2O
BnO
BnO
O
Acetone, r.t., 3 h
quant
O
5
OMe
NH2
O
O
O
Ph
O
Argopore™-NH2
O
(RO)n
BnO
SynPhase™Lanterns-NH2
BnO
O
O
NH2
6
NH
OH
DIC, HOBt
O
O
CH2Cl2, r.t., 3 d
Figure 2 Methods for introduction of propargyl glycosides to the
supports.
O
Ph
O
Ac2O, TEA
CH2Cl2, 1 h
O
BnO
BnO
O
7
zylidene glucopyranoside 2 was readily prepared by treat-
ment of glucose 1 with propargyl alcohol and TMSCl
followed by benzylidenation.15 Benzylation of 2 gave 3.18
Sonogashira coupling of 3 with methyl 4-iodobenzoate
(4) gave the coupling product 5 in a good yield.19 After
cleavage of the methyl ester of 5, the resulting 6 was at-
tached to a polymer support by using diisopropylcarbodi-
imide (DIC) and 1-hydroxybenzotriazole (HOBt) to give
the desired monosaccharide-loaded polymer 7.20
NH
O
Scheme 1
introduced to the region where Co2(CO)8 was unable to
access.
In the case of route 2 (entries 4–6), the yields of 10 were
the sum of the two reaction steps, i.e., Sonogashira reac-
tion and cleavage from the resins. Since cleavage yields of
ArgoPoreTM-NH2 and SynPhaseTM-NH2 were not so dif-
ferent as observed in entries 2 and 3 (Table 1), the differ-
ence in the yields of 10 is attributed to the Sonogashira
reaction step. When ArgoPoreTM-HL resin was used, the
total yield of Sonogashira coupling and the cleavage steps
The same glucose-loaded polymer 7 was also prepared via
the alternative route 2 (Scheme 2).21 Iodobenzoic acid 8
was first introduced to a polymer support. Sonogashira
coupling on the solid support was carried out by the use of
propargyl glycoside 3, polymer-supported iodobenzene 9,
Pd(PPh3)4, CuI, and TEA in THF to give 7.22
In the case of route 1, the loading yields were estimated by
measuring the residual amino groups. Cleavage of the
propargyl glycoside linker was then carried out
(Scheme 3). The modified resin 7 was first treated with
1.5 equiv of Co2(CO)8 and then excess Co2(CO)8 was re-
moved. Then, 10% TFA in CH2Cl2–H2O (10:1) was added
to the resin.23 The liberated monosaccharide 10 was puri-
fied by silica gel TLC and weighed. The results are shown
in Table 1. The yields of 10 (entries 1–3) represent cleav-
age yields from the resins. The loading yield on ArgoPo-
reTM-NH2-HL (high load) was lower than that on
ArgoPoreTM-NH2-LL (low load; entries 1 and 2). This re-
sult indicates that a higher ratio of amino groups exist on
less reactive regions on ArgoPoreTM-NH2-HL. Since the
cleavage of propargyl glycosides in solution proceeded
quantitatively,15 some of monosaccharide 6 was probably
O
OH
I
8
(2 eq)
I
DIC (2 eq), HOBt (5 eq)
CH2Cl2, r.t., 3 days
NH2
NH
Argopore™-NH2
O
9
SynPhase™Lanterns-NH2
O
O
Ph
O
Ph
O
O
O
BnO
BnO
BnO
BnO
O
O
3
(2 eq)
7
Pd(PPh3)4 (0.1 eq), CuI
(0.2 eq), THF / TEA=1/1,
r.t.
NH
O
Scheme 2
Synlett 2002, No. 9, 1409–1416 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Solid-phase Oligosaccharides Synthesis Using Alkyne Linkers
1411
Table 1 Cleavage of Alkyne Glycoside Linker with Co2(CO)8 and
TFA
were only 4% (entry 4). The yield of 10 (8%) was some-
how improved by repeating the Sonogashira coupling step
(entry 5). The yield of coupling was improved by using
SynPhaseTM resin (entry 6). In any case, the yields of the
Sonogashira reaction on solid-supports in the present
study were lower than those reported.16 A space-demand-
ing intermediate having many protective groups probably
reacted with only the polymer-supported iodobenzene lo-
cated on the reactive sites of the polymer. The low yields
at this step were hence expected to be preferable for the
next glycosylation step.
Entry
Resin
Loading Yielda
Yield of
10
Route 1
1
7
ArgoPoreTM-NH2-LL
(0.28 mmol/g)
83% b
75%c
70%c
79%c
2
3
ArgoPoreTM-NH2-HL 43% b
(1.16 mmol/g)
SynPhaseTM-NH2
(35 mol/g)
70% b
O
Ph
O
O
BnO
BnO
Route 2
4
9
O
ArgoPoreTM-NH2-HL
(1.16 mmol/g)
93% d
4%e
7
NH
O
5f
6
ArgoPoreTM-NH2-HL
(1.16 mmol/g)
93% d
8%e
Co2(CO)8
(1.5 eq)
TFA, H2O
HO
HO
BnO
O
OH
CH2Cl2, r.t.,
1 h
CH2Cl2, r.t.,
BnO
SynPhaseTM-NH2
(35 mol/g)
quant.d
20%e
12 h
10
a Loading yield was estimated by measuring the amount of residual
amino groups with the Gisin method after introduction of 6.24
b Loading yield in 7.
Scheme 3
The benzylidene group on the resin 7 was cleaved to give c Yield of 10 from 7.
d Loading yield of the iodobenzoyl moiety in 9.
11. The glycosylation reaction was then carried out by us-
ing the benzylated glycosyl trichloroacetimidate donor 12
(3 equiv to the solid supported acceptor 11)23 and TMS-
OTf (0.2 equiv to 10) in CH2Cl2 (room temperature, 3 h)
(Scheme 4, Table 2).25 When 11 (ArgoPoreTM-HL resin)
prepared via route 1 was used, the desired disaccharide 14
was obtained in 14% yield along with 30% of monosac-
charide 10 after cleavage from the resin (Table 2. entry
1):26 the latter was derived from the unreacted acceptor.
The yield of 14 (51%) was improved (Table 2, entry 2),
when 11 (SynPhaseTM resin) was used. Thereby, only a
small amount of monosaccharide 6 was observed.
e Yield of 10 from 9.
f Sonogashira reaction was carried out twice.
By contrast, the glycosylation reaction of the acceptor 11
prepared via the Sonogashira reaction on solid-phase pro-
ceeded quantitatively on both ArgoPoreTM and Syn-
PhaseTM (Table 2, entries 3 and 4). No monosaccharide 10
was observed in each case. In the case of SynPhaseTM, the
cleavage reaction also proceeded in a good yield. These
results indicated that the Sonogashira reaction of the
alkyne in the protected propargyl glycoside with polymer-
O
HO
O
Ph
O
O
HO
BnO
5% TFA,
1% H2O
BnO
BnO
BnO
O
O
CH2Cl2, r.t.,
12 h
7
11
NH
NH
O
O
NH
CCl3
(3 eq)
BnO
BnO
BnO
BnO
BnO
BnO
O
O
O
O
O
BnO
BnO
HO
12
BnO
BnO
O
TMSOTf, CH2Cl2,
MS4A, r.t., 3 h
NH
O
BnO
BnO
BnO
Co2(CO)8
(1.5 eq)
O
TFA, H2O
CH2Cl2, r.t., 12 h
HO
HO
BnO
O
O
HO
BnO
O
+
BnO
14
OH
CH2Cl2, r.t.,
1 h
BnO
OH
BnO
10
Scheme 4
Synlett 2002, No. 9, 1409–1416 ISSN 0936-5214 © Thieme Stuttgart · New York

1412
M. Izumi et al.
LETTER
Table 2 Glycosylation on Solid Support Using Trichloroacetimidate as Donor
Entry
Route 1
1
Resin
Loading Amount of 11
Yield : 14
Yield : 10
ArgoPoreTM-NH2-HL
(1.16 mmol/g of NH2)
31 mol /100 mg
19 mol /lantern
14%
51%
30%
trace
2
SynPhaseTM-NH2
(35 mol/lantern of NH2)
Route 2
3a
ArgoPoreTM-NH2-HL
(1.16 mmol/g of NH2)
8.6 mol /100 mgb
7.1 mol /lanternb
72%
n.d.c
n.d.c
4
SynPhaseTM-NH2
quant
(35 mol/lantern of NH2)
a Modified resin 11 prepared via route 2 (Table 1, entry 5) was used.
b The loading amount was calculated from the cleavage yield of 10 in Table 1.
c Not detected.
supported iodobenzene can select reactive regions on the sugars were also introduced to SynPhaseTM by Sonogash-
polymer supports.
ira coupling in ca. 20% yields as determined similarly
(Table 3, entries 2–4).
As described, the new alkyne-type linker can be readily
cleaved by treatment with Co2(CO)8 and TFA in CH2Cl2 The alkynyl ester-linker was also cleaved by treatment of
via formation of an alkyne-cobalt complex. The cleavage Co2(CO)8 and TFA. Treatment of 23 with Co2(CO)8 gave
of the above linker affords a 1-hydroxy sugar, which can 29, which was then reacted with TFA to afford the acid 30
be used as a glycosyl donor for further glycosylation. in 14% from 9 (Scheme 6). The cleavage yield was lower
Purification of the 1-hydroxy sugar is, however, some- than that by NaOMe treatment.
times difficult owing to the equilibrium between - and -
anomers. We, therefore, investigated another alkyne-type
linker consisting of an alkynyl ester and a benzyl glyco-
side functionality. This alkynyl ester-linker was prepared
by the Sonogashira reaction of 4-(propargyloxycarbon-
yl)benzyl glycoside with a polymer-supported iodoben-
zene derivative. This linker was stable under the acidic
conditions of conventional glycosylation reactions but
was readily cleaved from the polymer support via conver-
sion of the alkyne function to the corresponding alkyne-
cobalt complex and then with TFA. The ester linkage can
also be cleaved by conventional alkaline treatment.
O
Ph
O
BzCl, Pyridine
O
HO
Glucose
HO
CH2Cl2, 0 °C
then r.t.,90%
OAllyl
15
BF3•Et2O
Et3SiH
BnO
HO
BzO
O
Ph
O
O
O
BzO
BzO
BzO
CH2Cl2, 0°C
90%
OAllyl
OAllyl
16
17
FmocCl
Pyridine
1) Ir complex,
H2, THF
BnO
FmocO
BzO
O
2) I2, H2O, THF,
r.t., 98%
O
CH2Cl2, 0 °C
then r.t.,98%
BzO
OAllyl
18
Synthesis of the monosaccharide 21 attached to the sup-
port via the alkynyl ester linker is shown in Scheme 5. The
allyl 4,6-O-benzylidene glucopyranoside 15 was prepared
from glucose according to the method given in litera-
ture.15 Benzoylation of 15 and then reductive opening of
the benzylidene ring27 with Et3SiH and BF3 OEt2 gave 4-
O-free sugar 17.28 The fluorenylmethyloxycarbonyl
(Fmoc) group5e was introduced to 17 to give 18, of which
the allyl group was then removed. The resultant reducing
sugar was then changed to trichloroacetimidate 19.29 Gly-
cosylation of propargyl 4-(hydroxymethyl)benzoate with
19 afforded 20.30 Sonogashira reaction of monosaccharide
20 was then carried out with polymer-supported iodoben-
zene 9 (SynPhaseTM) in a manner similar to the prepara-
tion of 7 to give Fmoc-glucose-loaded polymer 21. The
loading yield (20%) was determined by the yield of the
monosaccharide 22 that was obtained by NaOMe treat-
ment of 21 with NaOMe (Table 3, entry 1). Other alkyne
O
NH
CCl3
Cl3CCN
Cs2CO3
HO
BnO
FmocO
BzO
O
(1.5 eq)
O
BzO
TMSOTf, CH2Cl2,
0 °C, 64%
CH2Cl2, r.t.,
quant
19
Pd(PPh3)4 (0.05 eq),
CuI (0.1 eq), THF, TEA
O
O
BnO
FmocO
9 (0.5 eq)
O
O
r.t., 12 h
BzO
BzO
20
O
O
BnO
FmocO
NH
O
O
O
BzO
BzO
21
Scheme 5
Synlett 2002, No. 9, 1409–1416 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Solid-phase Oligosaccharides Synthesis Using Alkyne Linkers
1413
Table 3 Introduction of Alkyne Sugars on Solid Support by Sonogashira Coupling
OMe
O
O
CH3ONa
O
RO
RO
RO
RO
RO
RO
NH
O
O
O
O
MeOH
O
OR
OR
Entry
1
Compounda
Product
Yieldb
20%
O
X
CO2Me
CO2Me
BnO
HO
HO
O
BnO
FmocO
BzO
O
O
O
O
OH
BzO
22
21
2
3
4
21%
17%
19%
O
X
BnO
BnO
BnO
O
BnO
BnO
O
O
O
O
BnO
BnO
BnO
24
23
O
X
CO2Me
Ph
O
O
O
Ph
O
O
O
O
BnO
O
O
BnO
BnO
BnO
26
25
O
X
CO2Me
BnO
HO
BnO
O
BnO
HO
BnO
O
O
BnO
O
O
BnO
28
27
a
O
NH
X =
b The yields are based on the isolated products. The values denoted the sum of the two-step conversions: coupling to the resin and cleavage.
the trisaccharide 33. The desired trisaccharide 34 was ob-
O
tained quantitatively after cleavage from the resin.31
O
NH
BnO
BnO
O
The trisaccharide GlcN (1 3)Gal (1 4)Glc (40) was
prepared from 31 as shown in Scheme 8. The 3-O-Fmoc
galactosyl donor 35 was prepared according to Schmidt’s
method.5e The N-Troc glucosaminyl donor 38 was pre-
pared from the intermediate for the synthesis of lipid A.32
The reactions proceeded quantitatively at all the reaction
steps, i.e., two glycosylation steps, Fmoc deprotection
step, and cleavage steps to give trisaccharide 40 in a quan-
titative yield.
O
O
BnO
Co2(CO)8
CH2Cl2
BnO
23
Co(CO)3
Co(CO)3
O
O
NH
BnO
BnO
BnO
O
O
O
BnO
TFA, H2O, CH2Cl2
CO2H
29
As described above, two alkyne-type linkers were devel-
oped for solid-phase oligosaccharide synthesis. Monosac-
charide components having an alkyne moiety were
introduced to polymer supports by the Sonogashira coup-
ling reaction. Since the alkynyl copper intermediate of the
Sonogashira reaction, which has many protective groups,
is polarized and space-demanding, it may reach only reac-
tive sites on the polymer supports. The subsequent reac-
tions including glycosylation proceeded smoothly,
resulting in high total yields of the synthesis. The present
concept, selection of reactive sites on polymer supports by
a particular reaction, is expected to be generally applica-
ble to solid-phase organic synthesis.
BnO
BnO
O
O
BnO
BnO
14% from 9
30
Scheme 6
Solid-phase oligosaccharide synthesis was then investi-
gated by the use of the alkynyl-ester linker. After removal
of the Fmoc group, glycosylation of 31 was carried out us-
ing 3 equiv of trichloroacetimidate donor 19 and TMSOTf
(0.2 equiv to 31) in CH2Cl2 (room temperature, 3 h) to
give 32 (Scheme 7). The Fmoc group of 32 was removed,
and the second glycosylation was then carried out to give
Synlett 2002, No. 9, 1409–1416 ISSN 0936-5214 © Thieme Stuttgart · New York

1414
M. Izumi et al.
LETTER
Scheme 7
Scheme 8
Future’ Program No. 97L00502 from the Japan Society for the Pro-
motion of Science and by Special Coordination Funds and Grant-in-
Aid for Creative Scientific Research ‘In vivo Molecular Science for
Discovery of New Biofunctions and Pharmaceutical Drugs’ No.
13NP0401 from the Ministry of Education, Culture, Sports, Science
and Technology, Japan.
Acknowledgement
The authors are grateful to Dr. Andrew Bray of Mimotopes Pty Ltd.
for the generous gift of SynPhaseTM lantern and for his kind discus-
sions. The present work was financially supported in part by Grants-
in-Aid for Scientific Research No. 11558080 and ‘Research for the
Synlett 2002, No. 9, 1409–1416 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Solid-phase Oligosaccharides Synthesis Using Alkyne Linkers
1415
(13) (a) Egusa, K.; Kusumoto, S.; Fukase, K. Synlett 2001, 777.
(b) Egusa, K.; Fukase, K.; Nakai, Y.; Kusumoto, S. Synlett
2000, 27. (c) Fukase, K.; Nakai, Y.; Egusa, K.; Porco, J. A.
Jr.; Kusumoto, S. Synlett 1999, 1074.
(14) Fukase, Y.; Fukase, K.; Kusumoto, S. Tetrahedron Lett.
1999, 40, 1169.
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Y.; Beebe, X. X.; Danishefsky, S. J. J. Am. Chem. Soc. 1998,
120, 3915.
(3) (a) Doi, T.; Sugiki, M.; Yamada, H.; Takahashi, T.; Porco, J.
A. Jr. Tetrahedron Lett. 1999, 40, 2141. (b) Takahashi, T.;
Inoue, H.; Yamamura, Y.; Doi, T. Angew. Chem. Int. Ed.
2001, 40, 3230. (c) Takahashi, T.; Okano, A.; Amaya, T.;
Tanaka, H.; Doi, T. Synlett 2002, 911.
(4) (a) Yan, L.; Taylor, C. M.; Goodnow, R. Jr.; Kahne, D. J.
Am. Chem. Soc. 1994, 116, 6953. (b) Liang, R.; Yan, L.;
Loebach, J.; Ge, M.; Uozumi, Y.; Sekanina, K.; Horan, N.;
Gildersleeve, J.; Thompson, C.; Smith, A.; Biswas, K.; Still,
W. C.; Kahne, D. Science 1996, 274, 1520.
(15) Izumi, M.; Fukase, K.; Kusumoto, S. Biosci. Biotechnol.
Biochem. 2002, 66, 211.
(16) Sonogashira coupling on solid support: (a) Park, C.;
Burgess, K. J. Comb. Chem. 2001, 3, 257. (b) Liao, Y.;
Fathi, R.; Reitman, M.; Zhang, Y.; Yang, Z. Tetrahedron
Lett. 2001, 42, 1815. (c) Pattarawarapan, M.; Burgess, K.
Angew. Chem. Int. Ed. 2000, 39, 4299. (d) Dyatkin, A. B.;
Rivero, R. A. Tetrahedron Lett. 1998, 39, 3647. (e) Tan, D.
S.; Foley, M. A.; Shair, M. D.; Schreiber, S. L. J. Am. Chem.
Soc. 1998, 120, 8565.
(17) Commercially available from Mimotopes Pty. Ltd. (http://
www.mimotopes.com). Solid-phase oligosaccharide
synthesis on SynPhase Crown see ref.3b and ref.7
(18) 3: Mp: 98 °C; [ ]D22 = +13 (c 1.10, CHCl3); ESI-Mass
(positive) m/z 509.3 [(M + Na)+]; 1H NMR (CDCl3)
=
7.48–7.24 (15 H, m, PhCH 3), 5.54 (1 H, s, PhCH), 5.05 (1
H, d, J = 3.0 Hz, H-1), 4.93–4.73 (4 H, m, PhCH2 2), 4.51
(1 H, t, J = 9.0 Hz, H-3), 4.30 (2 H, d, J = 3.0 Hz, OCH2-
CCH), 4.26 (1 H, dd, J = 10.4, 5.2 Hz, H-6a), 3.88–3.86 (1
H, m, H-5), 3.75–3.72 (2 H, m, H-2 and H-4), 3.62 (1 H, d,
J = 5.2 Hz, H-6b), 2.47 (1 H, t, J = 3.0 Hz, OCH2-CCH).
Found: C, 73.79; H, 6.11%. Calcd for C30H30O6: C, 74.06; H,
6.21%.
(19) 5: Mp: 162 °C; [ ]D22 = +37 (c 1.00, CHCl3); ESI-Mass
(positive) m/z 629.3 [(M + Na)+]; 1H NMR (CDCl3) = 8.00
(2 H, m, CC6H4CO2Me), 7.50–7.21 (17 H, m, PhCH 3 +
CC6H4CO2Me), 5.56 (1 H, s, PhCH), 5.10 (1 H, d, J = 3.6
Hz, H-1), 4.93–4.73 (4 H, m, PhCH2 2), 4.54 (2 , d, J = 3.0
Hz, OCH2-CCH), 4.26 (1 H, dd, J = 10.3, 4.9 Hz, H-6a), 4.09
(1 H, t, J = 9.1 Hz, H-3), 3.95–3.92 (1 H, m, H-5), 3.92 (3 H,
s, CC6H4CO2Me), 3.71 (1 H, d, J = 10.3 Hz, H-6b), 3.65–
3.61 (2 H, m, H-2 and H-4). Found: C, 72.92; H, 5.75%.
Calcd for C38H36O8 1/2H2O: C, 72.48; H, 5.92%.
(5) (a) Rademann, J.; Schmidt, R. R. Tetrahedron Lett. 1996, 37,
3989. (b) Rademann, J.; Schmidt, R. R. J. Org. Chem. 1997,
62, 3650. (c) Rademann, J.; Geyer, A.; Schmidt, R. R.
Angew. Chem., Int. Ed. Engl. 1988, 37, 1241. (d) Knerr, L.;
Schmidt, R. R. Eur. J. Org. Chem. 2000, 2803. (e) Roussel,
F.; Knerr, L.; Grathwohl, M.; Schmidt, R. R. Org. Lett. 2000,
2, 3043. (f) Roussel, F.; Knerr, L.; Schmidt, R. R. . Eur. J.
Org. Chem. 2001, 2067. (g) Roussel, F.; Takhi, M.;
Schmidt, R. R. J. Org. Chem. 2001, 66, 8540.
(6) (a) Shimizu, H.; Ito, Y.; Kanie, O.; Ogawa, T. Bioorg. Med.
Chem. Lett. 1996, 6, 2841. (b) Manabe, S.; Nakahara, Y.;
Ito, Y. Synlett 2000, 1241. (c) Manabe, S.; Ito, Y. Chem.
Pharm. Bull. 2001, 49, 1234.
(7) Rodebaugh, R.; Joshi, S.; Fraser–Reid, B.; Geysen, H. M. J.
Org. Chem. 1997, 62, 5660.
(8) (a) Nicolaou, K. C.; Winssinger, N.; Pastor, J.; Deroose, F.
J. Am. Chem. Soc. 1997, 119, 449. (b) Nicolaou, K. C.;
Watanabe, N.; Li, J.; Pastor, J.; Winssinger, N. Angew.
Chem. Int. Ed. 1998, 37, 1559.
(9) (a) Kanemitsu, T.; Kanie, O.; Wong, C.-H. Angew. Chem.
Int. Ed. 1998, 37, 3415. (b) Kanemitsu, T.; Wong, C.-H.;
Kanie, O. J. Am. Chem. Soc. 2002, 124, 3591.
(10) (a) Melean, L. G.; Haase, W.-C.; Seeberger, P. H.
Tetrahedron Lett. 2000, 41, 4329. (b) Plante, O. J.;
Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, 1523.
(c) Plante, O. J.; Palmacci, E. R.; Andrade, R. B.; Seeberger,
P. H. J. Am. Chem. Soc. 2001, 123, 9545. (d) Palmacci, E.
R.; Plante, O. J.; Seeberger, P. H. Eur. J. Org. Chem. 2002,
595.
(20) 6: ESI-Mass (negative) m/z 605.2 [(M – H)–]; 1H NMR
(CDCl3) = 8.00 (2 H, m, CC6H4CO2H), 7.50–7.21 (17 H,
m, PhCH 3 + CC6H4CO2H), 5.56 (1 H, s, PhCH), 5.10 (1
H, d, J = 3.6 Hz, H-1), 4.93–4.73 (4 H, m, PhCH2 2), 4.54
(2 H, d, J = 3.0 Hz, OCH2-CCH), 4.26 (1 H, dd, J = 10.3, 4.9
Hz, H-6a), 4.09 (1 H, t, J = 9.1 Hz, H-3), 3.95–3.92 (1 H, m,
H-5), 3.71 (1 H, d, J = 10.3 Hz, H-6b), 3.65–3.61 (2 H, m,
H-2 and H-4). Found: C, 72.24; H, 5.78%. Calcd for
C37H34O8 1/2H2O: C, 72.18; H, 5.73%. A typical procedure
for introduction of a monosaccharide 6 on solid support.
ArgoPore resin (NH2-LL: 0.28 mmol/g) (100mg, 28.0 mol)
was placed in a polypropylene tube (Varian) fitted with a
filter, and washed with 5% diisopropylamine in CH2Cl2 and
then CH2Cl2. Compound 6 (38.9 mg, 56.0 mol), HOBt
(18.9 mg, 140 mol), CH2Cl2 (3.0 mL), and DIC (8.8 L,
56.0 mol) were added to the tube, successively. The
reaction mixture was shaken for 3 d with Rotator RT-50
(Taitech) and filtered. The resin was washed with CH2Cl2
and the residual amino groups on the resin were then capped
with acetic anhydride (1.0 mL) and triethylamine (1.0 mL)
in CH2Cl2 (2.0 mL) by shaking for 30 min. The resin was
washed successively with DMF, MeOH, and CH2Cl2.
(21) A typical procedure for introduction of 4-iodobenzoic acid 8
on solid support. SynPhaseTM resin (NH2-HL: 35.0 mol)
was placed in a polypropylene tube (Varian) fitted with a
filter, and washed with 5% diisopropylamine in CH2Cl2 and
then CH2Cl2. Compound 8 (17.4 mg, 70.0 mol), HOBt
(23.6 mg, 175 mol), CH2Cl2 (3.0 mL), and DIC (11.0 L,
(11) Belogi, G.; Zhu, T.; Boons, G.-J. Tetrahedron Lett. 2000, 41,
6969.
(12) Commercially available from Argonaut Technologies, San
Carlos, California (http://www.argotech.com/resins/
index.htm). For investigations of other highly crosslinked
macroporous resins, see: Hori, M.; Gravert, D. J.;
Wentworth, P. Jr.; Janda, K. D. Bioorganic Med. Chem. Lett.
1998, 8, 2363.
Synlett 2002, No. 9, 1409–1416 ISSN 0936-5214 © Thieme Stuttgart · New York

1416
M. Izumi et al.
LETTER
70.0 mol) were added to the tube, successively. The
reaction mixture was shaken for 3 d with Rotator RT-50
(Taitech) and filtered. The resin was washed with CH2Cl2
and the residual amino groups on the resin were then capped
with acetic anhydride (1.0 mL) and triethylamine (1.0 mL)
in CH2Cl2 (2.0 mL) by shaking for 30 min. The resin was
washed successively with DMF, MeOH, and CH2Cl2.
9.6 Hz, H-3), 5.05 (1 H, d, J = 3.6 Hz, H-1), 4.93–4.73 (4 H,
m, PhCH2 and OCH2CH=CH2), 4.26 (1 H, dd, J = 10.4, 5.2
Hz, H-6a), 3.88–3.86 (1 H, m, H-5), 3.75–3.72 (1 H, m, H-
4), 3.62 (1 H, d, J = 5.2 Hz, H-6b).
(29) 18: ESI-Mass (positive) m/z 763.2 [(M + Na)+]; 1H NMR
(CDCl3) = 8.00–7.24 [24 H, m, PhCO 2, PhCH2, and
C13H9-CH2-OCO(Fmoc)], 5.94–5.88 (1 H, m,
(22) A typical procedure for Sonogashira coupling of
monosaccharide 3 on solid support. SynPhaseTM resin 9
(NH2: 35.0 mol) was placed in a polypropylene tube
(Varian) fitted with a filter, and washed with THF. CuI (2.6
mg, 14.0 mol), Pd(PPh3)4 (8.1 mg, 7.0 mol), THF (2.5
mL), TEA (2.5 mL) and 3 (34.1 mg, 70.0 mol) were added
to the tube, successively. The reaction mixture was shaken
for 24 h with Rotator RT-50 (Taitech) and filtered. The resin
was washed with DMF, MeOH and CH2Cl2 to give 7.
(23) A typical cleavage reaction of alkynylmethyloxy linker: The
ArgoPoreTM resin 7 (100 mg of ArgoPoreTM resin) was
shaken with a mixture of Co2(CO)8 (14.4 mg, 42.0 mol) in
CH2Cl2 (3.0 mL) at room temperature for 1 h. After the
reaction mixture was filtered, the resin was washed with
DMF and CH2Cl2 (3.0 mL). The resin was shaken with TFA
(0.5 mL) in CH2Cl2 (4.0 mL) and water (0.5 mL) at room
temperature for 12 h and then filtered. The resin was then
washed with ethyl acetate. The organic layer was combined,
washed with saturated NaHCO3 solution and brine, dried
over MgSO4, and concentrated in vacuo. The residue was
purified with preparative silica gel TLC (CHCl3–MeOH =
5:1) to give colorless solid 10. Yield 5.1 mg (75%). ESI-
Mass (positive) m/z 383.1 [(M + Na)+]; 1H NMR (CDCl3)
= 7.35–7.24 (10 H, m, PhCH 2), 5.24 (1 H, d, J = 3.63 Hz,
H-1), 4.93–4.63 (4 H, m, PhCH2 2), 4.26 (1 H, dd, J = 10.4,
5.2 Hz, H-6a), 3.84–3.73 (2 H, m, H-6b), 3.71–3.62 (1 H, m,
H-5), 3.57–3.52 (2 H, m, H-2 and H-4), 2.19 (2 H, d, J = 8.3
Hz, OH 2).
OCH2CH=CH2), 5.75 (1 H, d, J = 9.6 Hz, H-2), 5.56 (1 H,
dd, J = 9.6, 7.9 Hz, H-4), 5.37–5.26 (2 H, m,
OCH2CH=CH2), 5.24 (1 H, t, J = 9.6 Hz, H-3), 5.05 (1 H, d,
J = 3.6 Hz, H-1), 4.93–4.73 (4 H, m, PhCH2 and
OCH2CH=CH2), 4.26 (1 H, dd, J = 10.4, 5.2 Hz, H-6a), 3.94
[1 H, d, J = 10.3 Hz, C13H9-CH2-OCO(Fmoc)], 3.88–3.86 (1
H, m, H-5), 3.75–3.72 (1 H, m, H-4), 3.62 (1 H, d, J = 5.2
Hz, H-6b).
(30) 20: Mp: 144 °C; [ ]D 24 = +134 (c 1.00, CHCl3); ESI-Mass
(positive) m/z 895.2 [(M + Na)+]; 1H NMR (CDCl3) = 8.01
(2 H, m, OCH2C6H4CO2CH2-CCH), 7.48–7.25 (17 H, m,
PhCH2 3, and OCH2C6H4CO2CH2-CCH), 4.71 (1 H, d, J =
8.6 Hz, H-1), 4.88–4.45 (8 H, m, PhCH2 3 and
OCH2C6H4CO2H), 4.51 (1 H, t, J = 9.1 Hz, H-3), 4.26 (1 H,
dd, J = 10.4, 5.2 Hz, H-6a), 3.91 (2 H, d, J = 3.0 Hz,
OCH2C6H4CO2CH2-CCH), 3.88–3.86 (1 H, m, H-5), 3.72 (1
H, d, J = 10.3 Hz, H-6b), 3.65–3.57 (2 H, m, H-2 and H-4),
2.47 (1 H, t, J = 3.0 Hz, OCH2C6H4CO2CH2-CCH).
(31) A typical procedure for solid-phase glycosylation using a
glycosyl trichloroacetimidate: The 4-O-Fmoc resin 21 (21%
loading) (SynPhaseTM-NH2; 7.7 mol) was washed with
CH2Cl2 (3.0 mL). To the resin was added 25% piperidine in
CH2Cl2 (3.0 mL). The reaction mixture was shaken with
Rotator RT-50 (Taitech) at room temperature for 30 min.
The solution was removed by filtration and the resin was
washed with CH2Cl2, DMF and MeOH. The resin was then
washed with 5% TMSOTf in dry CH2Cl2 and then dry
CH2Cl2 (3 mL). Trichloroacetimidate 19 (19.5 mg, 23.1
mol), dry CH2Cl2 (3.0 mL), and TMSOTf (0.3 L, 1.5
mol) were added. The reaction mixture was shaken with
Rotator RT-50 (Taitech) at room temperature for 30 min to
give resin-linked disaccharide 32.
(24) Gisin, B. F. Anal. Chim. Acta 1972, 58, 248.
(25) The typical procedure for glycosylation on solid-support:
The monosaccharide resin 11 (62% loading) (100 mg of
ArgoPoreTM resin) was washed with dry CH2Cl2 (3 mL). To
the resin were added Molecular Sieves 4A beads, 8–12 mesh
(200 mg), a solution of a glycosyl trichloroacetimidate 12
(38.9 mg, 56.0 mol) in dry CH2Cl2 (3.0 mL), and TMSOTf
(8.8 L, 56.0 mol), successively. The reaction mixture was
shaken with Rotator RT-50 (Taitech) at room temperature
for 3 h. The solution was removed by filtration and the resin
was washed with CH2Cl2 and ether. After Molecular Sieves
4Å beads were removed by picking with forceps, the resins
were washed with DMF and CH2Cl2.
Typical procedure of cleavage from solid support by alkali.
SynPhase resin linked with disaccharide via alkynyl ester
linker was shaken with a mixture of 28% CH3ONa in MeOH
(1.0 mL), MeOH (1.0 mL) and CH2Cl2 (2.0 mL) at room
temperature for 12 h. After the reaction mixture was filtered,
EtOAc and 0.1 N aqueous HCl were added to the filtrate.
The organic layer was combined, washed with saturated
NaHCO3 solution and brine, dried over MgSO4, and
concentrated in vacuo. The residue was purified with
preparative silica gel TLC (CHCl3–MeOH = 5:1) to give the
desired compound.
34: Yield 7.2 mg (quant.). ESI-Mass (positive) m/z 945.5
[(M + Na)+]; 1H NMR (CDCl3) = 7.84–7.21 (19 H, m,
PhCH2 3 and OCH2C6H4CO2Me), 4.83–4.43 (10 H, m,
PhCH2 3, OCH2C6H4CO2Me, H-1 , H-1 , and H-1 ),
3.93 (3 H, s, OCH2C6H4CO2Me), 3.84–3.60 (12H, m, H-2,
H-3, H-4, H-5, H-2 , H-3 , H-4 , H-5 , H-2 , H-3 , H-4 and
H-5 ), 3.57–3.37 (4 H, m, H-6, H-6 , and H-6 ), 2.50 (4 H, s,
OH 7).
(26) 14: ESI-Mass (positive) m/z 905.4 [(M + Na)+]; 1H NMR
(CDCl3) = 7.34–7.21 (30 H, m, PhCH 6), 5.01 (1/2 H, d,
J = 3.2 Hz, H-1 ), 4.93–4.43 (14 H, m, PhCH2 6, H-1 , H-
1 , H-1 ), 3.84–3.73 (4 H, m, H-2, H-3, H-3 , and H-4 ),
3.76–3.62 (4 H, m, H-4, H-5, H-2 , and H-5 ), 3.57–3.37 (4
H, m, H-6, and H-6 ), 2.50 (2 H, s, OH 2).
(27) (a) DeNinno, M. P.; Etienne, J. B.; Duplantier, K. C.
Tetrahedron Lett. 1995, 36, 669. (b) Debenham, S. D.;
Toone, E. J. Tetrahedron: Asymmetry 2000, 11, 385.
(28) 17: ESI-Mass (positive) m/z 541.1 [(M + Na)+]; 1H NMR
(CDCl3) = 7.48–7.24 (15 H, m, PhCO 2 and PhCH2),
5.94–5.88 (1 H, m, OCH2CH=CH2), 5.75 (1 H, d, J = 9.6 Hz,
H-2), 5.37–5.26 (2 H, m, OCH2CH=CH2), 5.24 (1 H, t, J =
(32) Fukase, Y.; Zhang, S.-Q.; Iseki, K.; Oikawa, M.; Fukase, K.;
Kusumoto, S. Synlett 2001, 1693.
Synlett 2002, No. 9, 1409–1416 ISSN 0936-5214 © Thieme Stuttgart · New York