p-Methoxybenzylidene-tethered β-mannosylation for stereoselective synthesis of asparagine-linked glycan chains

Article abstract of DOI:10.1002/(sici)1521-3765(19981102)4:11<2182::aid-chem2182>3.0.co;2-u

One of the main obstacles in the chemical synthesis of Asn-linked glycoprotein oligosaccharides has been the formation of β-manno glycoside linked to the 4 position of N-acetylglucosamine. Addressing this fundamental problem, we previously developed the u

Full text of DOI:10.1002/(sici)1521-3765(19981102)4:11<2182::aid-chem2182>3.0.co;2-u

FULL PAPER
p-Methoxybenzylidene-tethered b-Mannosylation for Stereoselective
Synthesis of Asparagine-Linked Glycan Chains
Akihito Dan, Matthias Lergenmüller, Masayuki Amano, Yoshiaki Nakahara,
Tomoya Ogawa, and Yukishige Ito*
Abstract: One of the main obstacles in
the chemical synthesis of Asn-linked
glycoprotein oligosaccharides has been
the formation of b-manno glycoside
linked to the 4 position of N-acetylglu-
cosamine. Addressing this fundamental
problem, we previously developed the
use of a 2-O-p-methoxybenzyl-protect-
ed mannosyl donor as a new variant of
intramolecular aglycon delivery (IAD).
Now, the flexibility of this approach is
demonstrated in the synthesis of fucose-
containing hexasaccharide, which con-
stitutes the core structure of biomedi-
cally significant glycoproteins, in its
reducing end-protected (1a) and Asn-
linked (1b) forms. The key transforma-
tion is the stereoselective b-mannosyla-
tion of the disaccharide donor 5b, which
was treated with 10 to form trisaccharide
12. Further conversion into trichloro-
acetimidate 15, coupling with disacchar-
ide segment 17, and introduction of a-
linked mannose residue afforded hexa-
saccharides 26a and 26b, which were
transformed into 1a and 1b.
Keywords: glycosides ´ intramolec-
ular aglycon delivery ´ oligosacchar-
ides
´
saccharide chemistry
´
stereoselectivity
Introduction
OH
HO
O
NHAc
HO
OH
O
AcHN
HO
HO
Asparagine-linked glycoprotein oligosaccharides (Figure 1)
have been revealed to play various important roles in
numerous biological events, including cell differentiation,
malignant transformation, cell adhesion, and intra- and
intercellular protein transport. They are also functional
constituents of proteins, defining three dimensional struc-
tures, stabilizing proteins under physiological conditions,
tuning enzymatic activities, and so on.[1] They are usually
divided into three major subgroups, high-mannose type,
hybrid type, and complex type, and each of them consists of
diverse structures, which result from the presence of a variable
degree of branching as well as additional terminal and
nonterminal modifications such as sialylation, fucosylation,
polylactosaminylation, sulfation, and phosphorylation.[2] In
spite of such diversity, all members of this family share a
common pentasaccharide unit, in which the trimannosyl unit
is linked to chitobiose (GlcNAcb1 !4GlcNAc), which in turn
O
-
OH
OH
O
O
O
OH
OH
HO
HO
HO
O
O
CO2
Me
OH
HO
HO
OH
O
O
O
H
O
NHAc
HO
Asn
N
O
OH
O
HO
O
OH
O
NHAc
OH
-
HO
HO
CO2
OH
O
HO
AcHN
O
O
OH
O
O
OH
OH
O
HO
O
NHAc
HO
OH
Fucα1
1
X
Manα1→6
Manα1→3
6
a
b
Manβ1→4GlcNAcβ1→4GlcNAcβ1→X
OMP
Asn
"Core" Pentasaccharide
Figure 1. Typical structure of Asn-linked glycan chain.
is connected to the protein backbone through an N-glycosidic
linkage to an Asn residue.
With the aim of the chemical synthesis of this biologically
important class of molecules, the main obstacle has been the
formation of b-manno (Man) glycoside[3] linked to the
4 position of N-acetylglucosamine (GlcNAc). b-Manno glyco-
side has been considered to be one of the most difficult types
of O-glycoside to synthesize selectively. This derives from its
unique structural feature (1,2-cis equatorial glycoside) that
makes neither stereoelectronic control (i.e., by an anomeric
effect) nor neighboring group participation available. Ad-
dressing these problems, a number of intriguing approaches
‡
[*] Dr. Y. Ito, Dr. A. Dan, M. Lergenmüller, Dr. T. Ogawa
The Institute of Physical and Chemical Research
(RIKEN) and CREST
Japan Science and Technology Corporation (JST)
2-1 Hirosawa, Wako-shi, Saitama 351-0198 (Japan)
Fax: (‡81)48-462-4680
E-mail: yukito@postman.riken.go.jp
M. Amano, Dr. Y. Nakahara
Department of Industrial Chemistry, Tokai University
1117 Kitakaname, Hiratsuka-shi, Kanagawa 259-1292 (Japan)
‡
[ ] Recipient of STA fellowship award (1995 ± 1997).
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2182±2190
have been investigated. However, it would be most fair to
mention that the classical insoluble silver salt approach[4] is
still competitive with more recently developed methods in
terms of its practicality. Although this method has been
successfully applied to the synthesis of glycoprotein-related
glycans and glycolipids, the stereoselectivity is critically
dependent upon the reactivity of the acceptor and the nature
of protecting groups of the mannosyl donor.[5] As a result, it is
often observed that b-selectivity quickly diminishes once
applied to a sterically demanding acceptor. In addition, the
use of unstable bromide required in this approach eliminates
the possibility to accommodate modern glycosylation tech-
nologies[6] (glycosyl fluoride, trichloroacetimidate, thioglyco-
side etc.), which have been demonstrated to be well-adapted
for block condensation of oligosaccharide fragments.
The intramolecular aglycon delivery (IAD) approach,
which was introduced by Baressi and Hindsgaul,[7] and later
by Stork and co-workers,[8] is endowed with an evident
advantage over others, because it guarantees the exclusive
formation of the correct anomer as a result of the geometrical
constraint. As a newer variant of this approach, we have
reported the use of the 2-O-p-methoxybenzyl (PMB) pro-
tected mannose donor 2.[9] Starting from 2, treatment with
DDQ in the presence of aglycon affords mixed acetal 3,
presumably via quinonemethide like species, which serves as a
tethered intermediate in the forthcoming IAD process
(Scheme 1). Subsequent activation of the anomeric position
then triggers IAD to afford b-manno glycoside 4. In order to
apply this methodology into the synthesis of biologically
relevant oligosaccharides, especially asparagine-linked com-
plex-type glycans, appropriately protected mannosyl donors
(5a,b) have been examined.[9b] Most significantly, exclusive
formation of b-manno glycoside at the oligosaccharide block-
condensation stage was realized for the first time.[9b,c]
is a frequently observed structural modification in complex- and
hybrid-type glycans.[10] This also has a biomedical significance
in connection with intracellular trafficking of certain types of
glycoproteins and malignant transformations.[11]
Glycosyl donor 5b was strategically designed, so that
various types of Asn-linked glycans can be synthesized based
on the PMB-assisted b-mannosylation protocol. To be more
precise, the expected b-mannoside product has an available
hydroxy group at C-2 and an acetal protected diol at C-4 and
C-6. Therefore, all hydroxy groups on this particular mannose
residue can be differentiated from others by selective
manipulation of protective groups in combination with the
well established reactivity order[12] that favors the reaction at
C-6 position (vide infra).
Preparation of 5b was performed as depicted in Scheme 2.
Thus, starting from the known methyl thiomannoside 6,[13]
deacetylation ± benzylidenation afforded 4,6-O-protected 7.
OAc
AcO
OR1
O
Ph
AcO
O
a,b
AcO
O
O
SMe
R2O
SMe
R2
6
R1
H
7
H
H
8a
8b
8c
PMB
H
OAc
O
PMB
Ac
BnO
BnO
PMB
BnO
Cl
9
c
8a
5b
Scheme 2. Preparation of dimannosyl donor. a) PhCH(OMe)2, CSA/
DMF, 77%; b) p -MeOC6H4CH2Cl, Bu4NHSO4, aq NaOH/CH2Cl2, 50%;
c) AgOTf, 2,6-di-tert-butyl-4-methylpyridine, MS 4A/CH2Cl2, 81%.
Regioselective alkylation was performed under phase-trans-
fer conditions[14] to afford 8a as a major product, together with
the corresponding regioisomer 8b. The introduction of the
PMB group onto the C-2 position of 8a was confirmed by
NMR analysis of acetylated 8c. Stereoselective incorporation
of an a-linked mannose residue onto 8a was performed by use
of chloride 9[15] as a glycosyl donor to afford disaccharide 5b.
Having the designed dimannoside donor in hand, we
performed the b-mannosylation by using the latent GlcNAc
component 10[16] as an acceptor (Scheme 3).
Results
As a demonstration of the versatility of our PMB-assisted
approach, we disclose here the synthesis of the fucose-
containing core structure (Fuc) of Asn-linked glycans in
reducing end-protected (1a) and Asn-linked (1b) forms.
Addition of a Fuc residue onto C-6 of the innermost GlcNAc
OMe
OMe
Initial transformation into mixed acetal 11 was
effected by DDQ[17] according to our standard
H
O
O
OH
O
O
O
O
RO
a)
b)
protocol. This material was purified by size
RO
RO
RO
RO
RO
RO
O
O
RO
O
RO
exclusion chromatography into a spectroscopi-
cally homogeneous form (86% yield), although
IAD proceeded in a nearly equal efficiency via
nonpurified 11.[18] 1H NMR analysis of 11 revealed
that it consists of a single isomer, within the
detection limit of a 270 MHz NMR spectrometer,
indicating that the mixed acetal formation pro-
ceeds with a high degree of stereoselectivity.
Characteristic low-field shifts of H-1Man (dH ˆ
5.71) and one of the benzylic protons (dH ˆ 5.40)
X
X
2
3
4
OMe
OMe
Ph
O
O
O
O
O
Ph
O
O
O
O
SMe
BnO
BnO
BnO
TBDPSO
O
OAc
SMe
5b
5a
allowed us to assign the configuration of acetalic
Scheme 1. Intramolecular aglycon delivery via p-methoxybenzylidene acetal. a) Agly-
carbon as S.[19]
con, DDQ. b) IAD.
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Y. Ito et al.
FULL PAPER
OMe
OMe
H
OBn
O
Ph
O
Ph
NPhth
OH
O
O
O
Ph
O
O
O
O
O
O
BnO
O
b
OMP
O
O
O
O
OMP
BnO
SMe
a
O
O
O
O
NPhth
SMe
HO
BnO
BnO
BnO
BnO
BnO
BnO
OBn
BnO
BnO
BnO
O
OAc
OAc
12
11
OBn
O
OAc
5b
OMP
BnO
NPhth
10
Ph
NPhth
OAc
O
O
BnO
O
O
X
O
O
O
c, d, e or f
BnO
BnO
BnO
OBn
X
OMP
OH
F
OAc
13a
13b
14
(Fragment B)
OC(NH)CCl3
15
Scheme 3. Preparation of trisaccharides. a) DDQ, MS 4A/
Fucα1
CH2Cl2; b) MeOTf, 2,6-di-tert-butyl-4-methylpyridine,
Manα1→6
6
MS 4A/CH2Cl2, 53% over
DMAP/MeCN; d) Ce(NH4)2(NO3)6/toluene/MeCN/H2O,
77% over steps; e) Et2NSF3/CH2Cl2, 76% (14);
f) CCl3CN, DBU/CH2Cl2, 82% (15).
2 steps; c) Ac2O, Et3N,
Manβ1→4GlcNAcβ1→4GlcNAcβ1→Asn
Manα1→3
2
B
A
IAD was effected by exposure of 11 to MeOSO2CF3
(MeOTf[20]) and 2,6-di-tert-butyl-4-methylpyridine (DBMP)
in 1,2-dichloroethane to afford the b-manno glycoside product
12 (53% yield), which corresponds to the backbone trisac-
charide structure (aMan1 !3bMan1 !4GlcNAc; frag-
ment B) of Asn-linked glycan chains . Further transforma-
tions into fluoride 14 and trichloroacetimidate 15 were
performed via 13a and 13b in a standard manner.
afforded 16a/b. Alternatively, azide 19b was prepared from
tetraacetate 22, in a similar manner as described by Kunz and
co-workers.[24] Namely, 22 was first converted into glycosyl
azide 23 (TMSN3, TMSOTf/MeCN), which was then subjected
to a three step sequence [a): NaOMe/MeOH; b): PhCH(OMe)2,
CSA/MeCN; c): PhCH2Br, NaH/DMF] to afford 19b via 21.
Fucosylation was performed by use of the thioglycoside 18 under
in situ anomerization-like[25] conditions (CuBr2, Bu4NBr/
CH2Cl2/DMF[26]) to afford 17a (78%) and 17b (73%).
Critical fragment coupling of 17a/b with 15 was successfully
performed by the action of Me3SiOSO2CF3 (TMSOTf) and
pentasaccharides 24a and 24b were obtained in 71% and
79% yield, respectively (Scheme 5). Fluoride 14 proved less
effective for this purpose even under the conditions optimized
for the strongest activation (AgOTf, Cp2HfCl2[27]/CH2Cl2,
39% 24a).
Since the benzylated fucose residue is known to be acid
labile,[28] subsequent debenzylidenation of 24a/b required
carefully controlled conditions. This transformation was best
achieved by treatment with dilute trifluoroacetic acid in CH2Cl2
to afford 25a (88%) and 25b (94%). Regioselective introduc-
tion of an a-mannose residue was achieved by use of the chlo-
ride 9 (AgOTf/CH2Cl2) to afford 26a (77%) and 26b (74%).
Deprotection of 26a was performed as follows. Removal of
phthalimide groups (ethylenediamine[29]/EtOH) followed by
N-acetylation afforded 27a (Scheme 5). Somewhat surpris-
ingly, the acetyl group of the b-linked mannose residue mostly
remained intact, while those of a-linked mannose residues
were cleaved. Compound 27a was further deprotected [a): H2,
Pd-C; b): aq NaOH] into 1a via 28.
The designed fucosyl glucosamine component (17a/b;
fragment A) was synthesized by regioselective glycosylation
of the 4,6-diol 16a/b with fucose donor 18 (Scheme 4).[21]
BnO
OBn
BnO
Me
OBn
OBn
O
OBn
SMe
O
Me
OH
O
O
(Fragment A)
O
X
HO
BnO
X
18
HO
NPhth
X
BnO
NPhth
CuBr2-Bu4NBr
CH2Cl2-DMF
17
a
16
a
X
OMP
N3
OMP
N3
b
b
OAc
O
Ph
O
O
O
AcO
AcO
X
X
RO
NPhth
NPhth
X
R
X
19a
19b
20
OMP
N3
Bn
Bn
Bn
H
OAc
N3
22
23
OC(NH)CCl3
N3
21
Scheme 4. Synthesis of fucosyl glucosamine.
On the other hand, azide-carrying 26b was converted into
glycosyl asparagine 1b as follows. Dephthaloylation ± acety-
lation afforded 27b, which was de-O-acetylated to give 29
(Scheme 6). Compound 29 was then subjected to the con-
ditions for chemoselective reduction of an azide group with a
Lindlar catalyst to produce the corresponding glycosylamine,
Requisite 16a/b were prepared from 4,6-benzylidene protect-
ed 19a, which was reported previously. Thus, transformation
into trichloroacetimidated 20 [a): CAN[22]; b): CCl3CN, DBU]
followed by introduction of an azide group[23] afforded 19b.
Subsequent acidic removal of benzylidene groups from 19a/b
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Intramolecular Aglycon Delivery
2182±2190
BnO
OBn
OBn
O
Me
O
9
O
HO
BnO
Me
BnO
Me
X
OBn
O
BnO
OBn
O
TFA
OBn
OBn
NPhth
17
a
X
TMSOTf
Ph
AgOTf
DBMP
O
O
O
O
O
OH
NPhth
O
HO
HO
OAc
O BnO
NPhth
O
OMP
N3
O
O BnO
O
X
O
X
O
BnO
O
OBn
BnO
b
O
O
OBn
NPhth
NPhth
BnO
BnO
BnO
BnO
BnO
BnO
R1O
R1O
O
OR2
O
OR1
O
O
OR1
OAc
OAc
R1O
(Fragment B-A)
R1O
Me
25
a
24
a
X
X
Ph
O
OR3
O
OAc
O BnO
OMP (88%)
NR4R5
O
OR1
NPhth
O
O
HO
O
OMP (71%)
N3 (79%)
O
R1O
O
O
OC(NH)CCl3
O
b
b
R1O
N3
(94%)
X
O
O
OBn
O
NR4R5
R1O
BnO
BnO
BnO
15
O
R1
O
O
OR2
OAc
R1O
R3
Ac
Ac
Ac
Ac
Ac
H
R4R5
X
R2
Ac
Ac
H
R1
Bn
Bn
Bn
Bn
H
Scheme 5. Coupling of fragments A and B.
26a
Phth
Phth
H,Ac
H,Ac
H,Ac
H,Ac
H,Ac
OMP
N3
b
27a
b
OMP
N3
H
28
29
1a
OMP
N3
H
Bn
H
H
H
OMP
H
R1O
OH
the stereochemistry of the mixed acetal 3 was recently
solved.[19] Namely, it is now clear that mixed acetal formation
proceeds with a high degree of stereoselectivity to afford 3
with S- configuration at the acetalic carbon (see Scheme 1).
An elegant synthetic approach to asparagine linked glycans
has been reported by Unverzagt.[32] In this case, the b-
mannosylation protocol developed by Kunz was used as the
key transformation, in which the b-gluco-configurated glyco-
sylation product was transformed into b-manno glycoside by
intramolecular SN2 type replacement.[33] Our IAD based
methodology would be able to provide more flexible synthetic
route, with respect to the substitution pattern at the C-3
position. For instance, in our case the mannose donor that has
an additional sugar residue at C-3 (i.e., 5b) can be used to
provide building blocks for a more convergent synthetic
approach to Asn-linked glycans.
On the other hand, efficient methods for the stereoselective
introduction of sialic acid (NeuAc) residue, which was
considered as another challenge in synthetic carbohydrate
chemistry, have been developed by various approaches
utilizing either chemical[34] or enzymatic means.[35] Taking all
of these aspects together, it is now possible to conceive highly
stereocontrolled synthetic routes to a wide range of Asn-
linked glycans.
R1O
Me
OR1
OR1
R1O
O
1) (Z-Asp-OBn)2,
Lindler cat., H2 (91%)
2) H2, Pd / C (97%)
R1O
O
OH
O
O
O
O
HO
NHAc
R1O
O
H
29
N
COOR1
NHR2
O
O
R1O
O
OR1
NHAc
R1O
O
R1O
O
R1O
OH
R2
Cbz
H
R1
Bn
H
30
1b
Scheme 6. Synthesis of hexasaccharide.
which was trapped in situ with a Cbz-Asp-OBn derived acid
anhydride[30] to give 30 in 91% yield. Deprotection of 30 was
performed in a standard manner to afford hexaglycosyl
asparagine 1b.
Discussion
The utility of PMB-tethered b-mannosylation in Asn-linked
glycans is clearly demonstrated in the synthesis of 1a/b. Now,
the fully stereocontrolled construction of b-manno glycoside
is possible in a practical manner. The following features make
our PMB-based strategy clearly distinct from others; a) b-
manno glycoside can be formed with complete stereochemical
control, b) it is applicable to oligosaccharide condensation,
and c) a variety of protecting group patterns can be
accommodated (i.e., acetyl, benzyl, benzylidene, silyl, p-
methoxyphenyl, phthalimide). From these results, it can be
concluded that the IAD approach has gained practical utility
in synthetic studies on Asn-linked glycans.
Experimental Section
General Procedures: Melting points were determined with a Yanagimoto
micro melting-point apparatus and are not corrected. Optical rotations
were measured with a JASCO DIP 370 polarimeter at ambient temperature
(20 Æ 38C). NMR spectra were recorded with a JEOL EX-270 or GX-400
spectrometers. Me4Si (d ˆ 0.00) and tBuOH (d ˆ 1.23 ppm) were used as
internal standards for 1H NMR in CDCl3 and D2O, respectively. 13C NMR
spectra in CDCl3 were measured with the solvent peaks as an internal
standard adjusted to d ˆ 77.0. 1,4-Dioxane (d ˆ 67.2) was used as an internal
standard for 13C NMR spectra in D2O. TLC on silica gel 60 F254 (Merck,
Darmstadt) was used to monitor the reactions and to ascertain the purity of
Recently, the efficiency of PMB-assist-
ed b-mannosylation was further improved
by the use of 4,6-cyclohexylidene-protect-
ed mannosyl donor 31, which now realizes
OMe
O
O
O
the formation of the b-Man1 !4bGlcNAc
O
TBDPSO
equivalent in as high as >80% yield.[31]
SMe
31
Furthermore, the question with regard to
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Y. Ito et al.
FULL PAPER
the products. Silica-gel column chromatography was performed with Merck
silica gel 60 (63 ± 200 mm) or Cica silica gel 60N (spherical, 40 ± 100 or 100 ±
210 mm). Molecular sieves were activated by heating to 1808C in vacuo for
24 h prior to use. All reactions require anhydrous conditions were
performed under atmosphere of N2 or Ar.
aromatic), 5.61 (s, 1H; benzylidene CH), 5.60 (dd, J ˆ 3.3, 2.0 Hz, 1H;
H-22), 5.30 (d, J ˆ 2.0 Hz, 1H; H-12), 5.15 (d, J ˆ 1.0 Hz, 1H; H-11), 4.89 ±
4.55 (m, 4H; benzylic CH2), 3.96 (dd, J ˆ 8.6, 3.3 Hz, 1H; H-32), 3.67 (m,
1H; H-42), 3.63 (s, 3H; OMe), 2.09 and 2.07 (2s, each 3H; SMe, Ac); 13C
NMR (67.5 MHz, CDCl3, 258C): d ˆ 101.6 (benzylidene CH), 99.2 (C-12),
85.2 (C-11), 79.5, 78.7, 78.3, 75.4, 74.7, 73.7, 73.6, 72.9, 72.5, 71.9, 69.2, 68.9,
68.5, 64.8, 55.4; C51H56O12S (893.07): calcd C 68.59, H 6.32; found C 68.34, H
6.34.
Methyl 4,6-O-benzylidene-1-thio-a-d-mannopyranoside (7): A mixture of
compound 6 (10.0 g, 47.6 mmol), benzaldehyde dimethylacetal (7.85 mL,
52.3 mmol), and dl-camphorsulfonic acid (330 mg, 1.4 mmol) in DMF
(150 mL) was stirred at room temperature under vacuum (ꢀ15 mmHg) for
4 h. An additional amount of benzaldehyde dimethylaectal (1.4 mL,
9.3 mmol) was added and stirring was continued for 3 h. The reaction
was quenched with triethylamine (3 mL) and diluted with ether/dichloro-
methane (1:1). The solution was washed three times with water, and the
combined aqueous layers were extracted with AcOEt. The combined
organic layers were washed with brine and dried (MgSO4), and the solvent
was evaporated in vacuo. The residue was crystallized from AcOEt/EtOH
to afford 6.09 g of 7. The mother liquor was evaporated in vacuo and
purified by silica-gel column chromatography (hexane/AcOEt 5:1 ± 1:3) to
afford an additional 4.85 g of 7. Total yield 10.94 g (77%). M.p. 173 ± 1758C;
p-Methoxyphenyl O-(2-O-acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-
(1 !3)-O-(4,6-O-benzylidene-b-d-mannopyranosyl)-(1 !4)-3,6-di-O-ben-
zyl-2-deoxy-2-phthalimido-b-d-glucopyranoside (12) via mixed acetal 11:
Compounds 5b (43 mg, 0.048 mmol) and 10 (20.8 mg, 0.035 mmol) as a
solution in CH2Cl2 (1.3 mL) were added to an ice-cold mixture of DDQ
(14 mg, 0.062 mmol), molecular sieves 4A (0.2 g) in CH2Cl2 (0.5 mL). The
mixture was stirred at room temperature for 3 h and quenched with an
aqueous solution of ascorbic acid (0.7%)/citric acid (1.3%)/NaOH (0.9%)
(2 mL). The resulting solution was stirred for 10 min to form a lemon-
yellow suspension, that was subsequently diluted with AcOEt and filtered
through Celite. The filtrate was washed with water, aq NaHCO3, and brine
successively, and dried over MgSO4. The solvent was then evaporated in
vacuo, and the residue was subjected to size-exclusion column chromatog-
raphy with Bio-Beads S-X4 (toluene). Fractions containing mixed acetal 11
were collected, concentrated, and, after brief exposure to high vacuum,
added as a solution in 1,2-dichloroethane (5 mL) to a flask containing
molecular sieves 4A (0.2 g) and DBMP (39 mg, 0.19 mmol). Methyl
trifluoromethanesulfonate (MeOTf; 20 ml, 0.18 mmol) was added, and the
mixture was stirred at 408C for 14 h. The reaction was quenched with Et3N
(0.2 mL; RT, 10 min), diluted with AcOEt/water, and filtered through
Celite. The filtrate was washed with water and brine successively, and dried
over MgSO4; the solvent was then evaporated in vacuo. The residue was
purified by chromatography with Bio-Beads S-X4 (toluene) and then with
silica gel (hexane/AcOEt 1:3) to afford 24.3 mg (53%) of compound 12.
[a]D ˆ ‡24.1 (c ˆ 0.8 in chloroform); 1H NMR (270 MHz, CDCl3, 258C,
TMS): d ˆ 7.61 ± 6.61 (m, 38H; aromatic), 5.52 (d, J ˆ 8.3 Hz, 1H; H-11),
5.40 (s, 1H; benzylidene CH), 5.04 (d, J ˆ 1.3 Hz, 1H; H-13), 4.59 (s, 1H;
H-12), 4.31 (dd, J ˆ 8.3, 3.7 Hz, 1H), 3.97 (dd, J ˆ 9.2, 3.3 Hz, 1H; H-33),
3.89 (t, J ˆ 9.6 Hz, 1H; H-42), 3.64 (s, 3H; OMe), 3.07 (ddd, J ˆ 9.6, 4.6,
4.6 Hz, 1H; H-52), 2.80 (d, J ˆ 3 Hz, 1H; OH), 2.05 (s, 3H; Ac); 13C NMR
1
[a]D ˆ ‡171.5 (c ˆ 1.1 in chloroform); H NMR (270 MHz, CDCl3, 258C,
TMS): d ˆ 5.57 (s, 1H; benzylidene CH), 5.25 (s, 1H; H-1), 2.16 (s, 3H;
SMe); 13C NMR (67.5 MHz, CDCl3, 258C): d ˆ 102.1 (benzylidene CH),
83.9 (C-1), 79.7, 79.5, 72.7, 68.9, 68.6, 63.9, 55.3; C14H18O5S (298.4): calcd C
56.36, H 6.08, S 10.75; found C 56.62, H 6.03, S 10.35.
Methyl 4,6-O-benzylidene-2-O-p-methoxybenzyl-1-thio-a-d-mannopyra-
noside (8a): p-Methoxybenzyl chloride (1.0 mL, 7.4 mmol), Bu4NHSO4
(240 mg, 0.71 mmol), and 5% aq NaOH (5 mL) were added to a solution
of compound 7 (1.08 g, 3.62 mmol) in CH2Cl2 (60 mL), and the whole was
stirred vigorously and heated under reflux for 2 days. The mixture was
washed with water and brine successively, and dried over MgSO4; the solvent
was then evaporated in vacuo. The residue was separated by silica-gel
column chromatography (toluene/AcOEt 4:1) to afford 758 mg (50%) of
compound 8a as well as the corresponding regioisomer 8b (222 mg, 15%).
Compound 8a: 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.55 ± 6.84 (m,
9H; aromatic), 5.56 (s, 1H; benzylidene CH), 5.26 (s, 1H; H-1), 3.81 (s, 3H;
OMe), 2.13 (s, 3H; SMe); 13C NMR (67.5 MHz, CDCl3, 258C): d ˆ 102.1
(benzylidene CH), 83.9 (C-1), 79.7, 79.5, 72.7, 68.9, 68.6, 63.9, 55.3;
C22H26O6S (418.5): calcd C 63.14, H 6.26; found C 63.01, H 6.29.
(67.5 MHz, CDCl3, 258C): d ˆ 101.4 (benzylidene CH), 100.6 (C-12, 1JCH
ˆ
The regiochemistry of 8a was confirmed by converting into corresponding
acetate 8c: [a]D ˆ ‡59.6 (c ˆ 1.0 in chloroform); 1H NMR (270 MHz,
CDCl3, 258C, TMS): d ˆ 7.32 ± 7.48 (m, 5H; C6H5CH), 6.89 and 7.28 (2 d,
each 2H; CH3OC6H4CH2), 5.56 (s, 1H; C6H5CH), 5.21 (dd, J ˆ 3.6, 9.6 Hz,
1H; 3-H), 5.20 (d, J ˆ 1.3 Hz, 1H; H-1), 4.48 and 4.63 (ABq, J ˆ 11.9 Hz,
each 1H; MeOC6H4CH2), 4.21 ± 4.31 (m, 2H; H-5, H-6b), 4.18 (dd, J ˆ 9.7,
9.6 Hz, 1H; H-4), 4.05 (dd, J ˆ 1.3, 3.6 Hz, 1H; H-2), 3.89 (m, 1H; H-6a),
3.81 (s, 3H; CH3OC6H4CH2), 2.13 and 2.01 (2s, each 3H; MeS, Ac);
C24H28O7S (460.5): calcd C 62.59, H 6.13; found C 62.73, H 6.13.
161 Hz), 98.8 (C-13), 97.7 (C-11), 78.7, 77.9, 77.2, 77.1, 75.6, 74.7, 74.4, 73.6,
73.5, 71.9, 71.8, 70.6, 69.4, 68.5, 68.4, 68.3, 66.8, 55.6, 55.5; C77H77NO19
(1320.47): calcd C 68.59, H 6.32, N 1.06; found C 69.90, H 5.90, N 0.95.
In a separate experiment, mixed acetal 11 was prepared with a slight excess
amount of 10 and was more rigorously purified into a spectroscopically
pure form. To be brief, compounds 5b (44.1 mg, 0.0494 mmol) and 10
(38.3 mg, 0.0643 mmol) were treated with DDQ (13.5 mg, 0.0593 mmol) in
CH2Cl2 (0.4 mL) in the presence of molecular sieves 4A (0.1 g) at room
temperature for 3 h. The mixture was processed as described above and
purified by a column of Bio-Beads S-X4 (toluene) to afford 63.2 mg (86%)
of 11. 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 5.71 (s, 1H; H-12), 5.66
(d, J ˆ 8.3 Hz, 1H; H-11), 5.63 (brs, 2H; mixed acetal CH and H-23), 5.40
(d, J ˆ 11.2 Hz, 1H; benzylic CH2), 5.26 (d, J < 1 Hz, 1H; H-13), 4.85 (s, 1H;
benzylidene CH), 3.78 (s, 3H; OMe), 3.25 (s, 3H; OMe), 2.08 and 1.99 (2s,
each 3H; SMe, Ac); 13C NMR (67.5 MHz, CDCl3, 258C): d ˆ 100.5, 99.4,
98.1, 97.5 (C-11, C-13, benzylidene CH, mixed acetal CH), 82.1, 78.6, 78.4,
77.8, 77.2, 76.1, 76.0, 75.3, 75.2, 74.4, 74.0, 73.5, 73.2, 71.8, 71.2, 68.5, 68.1,
64.9, 55.9, 55.6, 54.8, 21.0 (Ac), 13.5 (SMe).
Regioisomer 8b: 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 5.61 (s, 1H;
benzylidene CH), 5.22 (s, 1H; H-1), 2.14 (s, 3H; SMe). Corresponding
1
acetate: H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.68 ± 7.32 (m, 5H;
Ar), 7.26 (m, 2H; Ar), 6.84 (m, 2H; Ar), 5.62 (s, 1H; benzylidene CH), 5.45
(dd, J ˆ 3.4, 1.3 Hz, 1H; H-2), 5.14 (d, J ˆ 1.3 Hz, 1H; H-1), 4.63 and 4.56
(each ABq, J ˆ 11.6 Hz, 1H; MeOC6H4CH2), 4.25 (dd, J ˆ 9.7, 4.9 Hz, 1H;
H-6), 4.19 (ddd, J ˆ 9.5, 4.9, 4.9 Hz, 1H; H-5), 4.08 (dd, J ˆ 9.6, 9.5 Hz, 1H;
H-4), 3.95 (dd, J ˆ 9.6, 3.4 Hz, 1H; H-3), 3.87 (m, 1H; H-6'), 3.79 (s, 3H;
OMe), 2.14 and 2.17 (2s, each 3H; SMe, Ac).
Methyl O-(2-O-acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)-4,6-
O-benzylidene-2-O-p-methoxybenzyl-1-thio-a-d-mannopyranoside (5b):
Methyl thiomannopyranoside 8a (1.15 g, 2.75 mmol) and 2,6-di-t-butyl-4-
methylpyridine (DBMP, 1.02 g, 4.95 mmol) were dissolved in anhydrous
CH2Cl2 (25 mL) and stirred for 30 min under Ar and exclusion of light with
AgOTf (1.27 g, 4.95 mmol) over freshly activated molecular sieves 4A
(5.0 g). After cooling to 158C, 9 (1.97 g, 3.85 mmol) was added as a
solution in CH2Cl2 (15 mL). The mixture was gradually warmed up to room
temperature, stirred for 90 min, and diluted with CH2Cl2 (100 mL). The
suspension was filtered through Celite and the filtrate was washed with
satd. NaHCO3 solution (30 mL) and 10% Na2S2O3 solution (30 mL), and
dried (Na2SO4). Removal of the solvent in vacuo gave a colorless foam
(3.79 g), which was purified by elution from silica gel with toluene/AcOEt
10:1 to afford 2.10 g (86%) of 5 as a colorless foam. [a]D ˆ ‡57.0 (c ˆ 1.1,
CHCl3); 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.64 ± 6.70 (m, 24H;
O-(2-O-Acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)-O-(2-O-
acetyl-4,6-O-benzylidene-b-d-mannopyranosyl)-(1 !4)-3,6-di-O-benzyl-2-
deoxy-2-phthalimido-b-d-glucopyranose (13b): Compound 12 (65.6 mg,
0.0497 mmol) was dissolved in acetonitrile (1.5 mL), and triethylamine
(21 ml, 0.15 mmol), N,N-dimethylaminopyridine (DMAP; 0.3 mg,
0.003 mmol), and acetic anhydride (7 ml, 0.07 mmol) were added succes-
sively. The mixture was stirred at room temperature overnight and
quenched with MeOH. Volatiles were removed in vacuo, and the residue
was co-evaporated successively with ethanol and toluene to afford the
acetylated product 13a, which was then diluted with toluene/acetonitrile/
water (3:4:3; 4 mL). Ceric ammnonium nitrate (CAN; 82 mg, 0.15 mmol)
was added, and the mixture was stirred at room temperature for 2 h. An
additional amount of CAN (40 mg, 0.073 mmol) was added and stirring was
continued for 2 h. The resulting mixture was diluted with AcOEt, washed
2186
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
0947-6539/98/0411-2186 $ 17.50+.50/0
Chem. Eur. J. 1998, 4, No. 11

Intramolecular Aglycon Delivery
2182±2190
with water, 5% aq NaOH, and brine successively, and dried over MgSO4;
the solvent was then evaporated in vacuo. The residue was purified by
silica-gel column chromatography (hexane/AcOEt 10:1 ± 5:1) to afford
48.2 mg (77%) of compound 13b.
Compound 13a: [a]D ˆ ‡26.4 (c ˆ 0.9 in chloroform); 1H NMR (270 MHz,
CDCl3, 258C, TMS): d ˆ 7.68 ± 6.67 (m, 38H; aromatic), 5.58 (d, J ˆ 8.3 Hz,
1H; H-11), 5.50 (s, 1H; benzylidene CH), 5.46 (dd, J ˆ 3.3, 1.7 Hz, 1H;
H-23), 5.37 (brs, 1H; H-22), 5.22 (d, J ˆ 1.7 Hz, 1H; H-13), 4.67 (d, J < 1 Hz,
1H; H-12), 3.71 (s, 3H; OMe); 13C NMR (67.5 MHz, CDCl3, 258C): d ˆ
101.2 (benzylidene CH), 99.2, 98.6 (C-12, C-13), 97.6 (C-11), 78.7, 78.6, 76.5,
74.7, 74.7, 74.6, 74.1, 73.4, 73.4, 72.7, 72.1, 71.7, 70.7, 68.9, 68.5, 68.3, 68.0, 66.4,
55.6; C79H79NO20 (1362.51): calcd C 69.94, H 5.84, N 1.03; foumd C 69.46, H
5.85, N 1.16.
Compound 13b: 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.69 ± 6.93
(m, 34H; aromatic), 5.49 (s, 1H; benzylidene CH), 5.46 (dd, J ˆ 2.6, 1.6 Hz,
1H; H-23), 5.33 (br, 1H; H-22), 5.27 (d, J ˆ 8.6 Hz, 1H; H-11), 5.21 (d, J ˆ
1.6 Hz, 1H; H-13), 2.88 (d, J ˆ 8.6 Hz, 1H; OH), 2.09 and 2.04 (2s, each 3H;
Ac);13C NMR (67.5 MHz, CDCl3, 258C): d ˆ 99.0, 98.6 (C-12, C-13), 93.0
(C-11), 78.6, 78.4, 74.5, 74.4, 74.1, 73.5, 73.4, 72.7, 72.1, 71.7, 70.6, 68.9, 68.5,
68.3, 68.1, 66.4, 57.5.
solution of 19a (520 mg, 0.88 mmol) in toluene/MeCN/H2O (3:4:3; 10 mL),
and the mixture stirred at room temperature. After 3 h, additional amounts
of toluene/MeCN/H2O (3:4:3; 10 mL) and CAN (961 mg, 1.75 mmol) were
added. After being stirred for additional 30 min, the mixture was diluted
with AcOEt, washed successively with water, 5% aq NaOH, and brine, and
dried over MgSO4; the solvent was then evaporated in vacuo. The residue
was triturated with hexane/AcOEt and a solid material was collected by
filtration to afford 343 mg of compound 19c. The mother liquor was
concentrated to dryness and purified by silica-gel column chromatography
(10 ± 30% AcOEt in hexane) to afford additional 67 mg of 19c. Total yield
410 mg (96%). 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.71 ± 6.79 (m,
14H; aromatic), 5.63 (s, 1H; benzylidene CH), 5.42 (brt, J ˆ 8 Hz, 1H;
H-1), 4.81 and 4.53 (ABq, J ˆ 12.2 Hz, each 1H; benzyl CH2), 4.52 (dd, J ˆ
10.2, 8.9 Hz, 1H; H-3), 4.14 (dd, J ˆ 10.2, 8.6 Hz, 1H; H-2), 3.84 (m, 2H;
H-6), 3.70 (m, 1H; H-5), 3.21 (d, J ˆ 7.6 Hz, 1H; OH).
3-O-Benzyl-4,6-O-benzylidene-2-deoxy-2-phthalimido-b-d-glucopyranosyl
trichloroacetimidate (20): DBU (5 ml, 0.03 mmol) was added to an ice-cold
solution of compound 19c (195 mg, 0.40 mmol) and trichloroacetonitrile
(0.4 mL, 4.0 mmol) in 1,2-dichloroethane (4 mL), and the mixture was
stirred for 1.5 h. The mixture was subjected to a column of silica gel, which
was eluted with 10 ± 30% AcOEt in toluene to afford 228 mg (91%) of
compound 20. 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 8.57 (s, 1H;
O-(2-O-Acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)-O-(4,6-O-
benzylidene-b-d-mannopyranosyl)-(1 !4)-3,6-di-O-benzyl-2-deoxy-2-
phthalimido-b-d-glucopyranosyl fluoride (14): Dimethylaminosulfur tri-
fluoride (DAST; 2.4 ml, 0.018 mmol) was added to a precooled ( 208C)
solution of compound 13b (16.5 mg, 0.0131 mmol) in CH2Cl2 (1 mL). The
mixture was stirred at this temperature for 30 min and quenched with ice-
cold aq NaHCO3. After being diluted with AcOEt, the layers were
separated. The organic layer was washed with aq NaHCO3 and brine
successively, and dried over MgSO4; the solvent was then evaporated in
vacuo. The residue was purified by silica-gel column chromatography
(toluene/AcOEt 20:1 ± 10:1) to afford 12.5 mg (76%) of compound 14. 1H
NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.74 ± 6.90 (m, 34H; aromatic),
5.81 (dd, 1J(H,F) ˆ 53.8 Hz, J ˆ 7.7 Hz, 1H; H-11), 5.49 (s, 1H; benzylidene
CH), 5.46 (dd, J ˆ 2.2, 1.7 Hz, 1H; H-23), 5.34 (brs, 1H; H-22), 5.22 (d, J ˆ
1.7 Hz, 1H; H-13), 2.09 and 2.04 (2s, each 3H; Ac).
ˆ
C NH), 7.70 ± 6.85 (m, 14H; aromatic), 6.49 (d, 1H, J ˆ 8.6 Hz; H-1), 5.65
(s, 1H; benzylidene CH), 4.82 and 4.53 (ABq, J ˆ 12.2 Hz, each 1H; benzyl
CH2), 4.59-4.47 (m, 3H; H-2, H-3, H-4), 3.89 (m, 3H; H-5, H-6).
3,4,6-Tri-O-acetyl-2-deoxy-2-phthalimido-b-d-glucopyranosyl azide (23):
Trimethylsilyl triflate (38 ml, 0.21 mmol) was added to a solution of
compound 22 (1.00 g, 2.1 mmol) and trimethylsilyl azide (420 mmL,
3.16 mmol) in acetonitrile (20 mL), and the solution was stirred at room
temperature for 4 h. The resulting mixture was diluted with AcOEt and
washed with ice-cold water, aq NaHCO3, and brine, successively. The
organic layer was dried over MgSO4 and the solvent was evaporated in
vacuo. The residue was purified by silica-gel column chromatography
(toluene/AcOEt 2:1) to afford 0.817 g (84%) of compound 23. M.p. 135 ±
1388; 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.90 ± 7.75 (m, 4H;
Phth), 5.74 (dd, J ˆ 10.6, 9.2 Hz, 1H; H-3 ), 5.66 (d, J ˆ 9.2 Hz, 1H; H-1),
5.20 (t, J ˆ 9.6 Hz, 1H; H-4), 4.36 (dd, J ˆ 12.5, 4.6 Hz, 1H; H-6), 4.25 (dd,
J ˆ 12.5, 2.3 Hz, 1H; H-6'), 4.24 (dd, J ˆ 10.6, 9.2 Hz, 1H; H-2), 3.98 (m,
1H; H-5), 2.14, 2.05 and 1.87 (s, 3H; Ac); C20H20N4O9 (460.40): calcd C
52.18, H 4.38, N 12.17; found C 52.18, H 4.33, N 12.01.
O-(2-O-Acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)-O-(4,6-O-
benzylidene-b-d-mannopyranosyl)-(1 !4)-3,6-di-O-benzyl-2-deoxy-2-
phthalimido-b-d-glucopyranosyl trichloroacetimidate (15): Trichloroaceto-
nitrile (15 ml, 0.15 mmol) was added to a solution of compound 13b
(18.4 mg, 0.0147 mmol) in 1,2-dichloroethane (0.5 mL), and the solution
was cooled down to 08C. DBU (10% in 1,2-dichloroethane; 2 ml,
0.001 mmol) was added and the mixture was stirred for 2 h. The mixture
was applied to a column of silica gel (10 ± 30% AcOEt in hexane) to afford
16.8 mg (82%) of compound 15. 1H NMR (270 MHz, CDCl3, 258C, TMS):
4,6-O-Benzylidene-2-deoxy-2-phthalimido-b-d-glucopyranosyl azide (21):
A
solution of 23 (1.57 g, 4.69 mmol), benzaldehyde dimethylacetal
(1.05 mL, 7.0 mmol), and dl-camphorsulfomic acid (0.11 g, 0.47 mmol) in
acetonitrile (40 mL) was stirred at room temperature for 4 d. The mixture
was made slightly basic with NaOMe (0.5m; phenolphthalein indicator)
and immediately neutralized with a drop of acetic acid. After the solvent
was evaporated in vacuo, purification by silica-gel column chromatography
(toluene/EtOH 19:1) afforded 1.83 g (94%) of compound 21. M.p. 187 ±
1918; 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.90 ± 7.72 (m, 4H;
Phth), 7.57 ± 7.32 (m, 5H; Ph), 5.59 (s, 1H; benzylidene CH), 5.48 (d, J ˆ
9.2 Hz, 1H; H-1), 4.69 (ddd, J ˆ 10.4, 8.9, 3.6 Hz, 1H; H-3), 4.44 (dd, J ˆ
9.9, 4.3 Hz, 1H; H-6), 4.18 (dd, J ˆ 10.4, 9.4 Hz, 1H; H-2), 3.86 (t, J ˆ
10 Hz, 1H; H-6'), 3.76 (m, 1H; H-5), 3.64 (t, J ˆ 8.9 Hz, 1H; H-4).
ˆ
d ˆ 8.54 (s, 1H; NH), 7.67 ± 6.91 (m, 34H; aromatic), 6.36 (d, J ˆ 8.3 Hz,
1H; H-11), 5.50 (s, 1H; benzylidene CH), 5.46 (dd, J ˆ 3.6, 1.6 Hz, 1H;
H-23), 5.36 (brs, 1H; H-22), 5.22 (d, J ˆ 1.6 Hz, 1H; H-13), 2.09 and 2.05 (2s,
each 3H; Ac).
p-Methoxyphenyl O-(2,3,4-tri-O-benzyl-a-d-fucopyranosyl)-(1 !6)-3-O-
benzyl-2-deoxy-2-phthalimido-b-d-glucopyranoside (17a): A mixture of
CuBr2 (69.2 mg, 0.31 mmol), Bu4NBr (100 mg, 0.31 mmol), and molecular
sieves 4A (0.13 g) in CH2Cl2/DMF (2:1, 3 mL) was stirred and cooled over
an ice ± water bath. A solution of comounds 16a (73.0 mg, 0.145 mmol) and
18 (72.0 mg, 0.155 mmol) in CH2Cl2 (4 mL in total) was added dropwise and
the mixture stirred at 08C for 4.5 h. An additional amount of compound 18
(12.0 mg, 0.026 mmol) was added as a solution in CH2Cl2 (0.5 mL) and
stirring was continued overnight at room temperature. The resulting
mixture was quenched with aq NaHCO3 (RT, 10 min), diluted with AcOEt,
and filtered through Celite. The filtrate was washed successively with aq
NaHCO3 and brine, and dried over Na2SO4; the solvent was then
evaporated in vacuo. The residue was purified by silica-gel column
chromatography (4 ± 8% AcOEt in toluene) to afford 104.4 mg (78%) of
3-O-Benzyl-4,6-O-benzylidene-2-deoxy-2-phthalimido-b-d-glucopyranosyl
azide (19b)
From 20: Compound 20 (112 mg, 0.178 mmol) and trimethylsilyl azide
(0.22 mL, 1.7 mmol) were dissolved in CH2Cl2 (1 mL) containing molecular
sieves 4A (0.16 g), and the mixture was cooled down to 788C. A solution
of TMSOTf in 1,2-dichloroethane (0.2m; 50 ml, 0.01 mmol) was added, and
the whole was stirred for 2 h, while being warmed up to 208C. The
reaction was quenched with Et3N (0.2 mL), diluted with AcOEt, and
filtered through Celite. The filtrate was washed successively with water and
brine, and dried over Na2SO4; the solvent was evaporated in vacuo. The
residue was purified by silica-gel column chromatography (10 ± 20%
AcOEt in hexane) to afford 63.7 mg (70%) of 19b. M.p. 129 ± 1318;
[a]D ˆ 37.1 (c ˆ 1.1 in chloroform); 1H NMR (270 MHz, CDCl3, 258C,
TMS): d ˆ 7.83 ± 7.72 (m, 4H; Phth), 7.55 ± 7.37 (m, 5H; Ph), 7.00 ± 6.85 (m,
5H; Ph), 5.64 (s, 1H; benzylidene CH), 5.43 (d, J ˆ 9.6 Hz, 1H; H-1), 4.80
and 4.45 (ABq, J ˆ 12.2 Hz, each 1H; benzyl CH2), 4.49 ± 4.42 (m, 2H; H-3,
H-6), 4.14 (dd, J ˆ 10.2, 9.2 Hz, 1H; H-2), 3.91 ± 3.70 (m, 3H; H-4, H-5,
compound 17a, together with 10.5 mg (8%) of corresponding b-isomer.
1
Compound 17a: [a]D
ˆ
5.1 (c ˆ 0.8 in chloroform); H NMR (270 MHz,
CDCl3, 258C, TMS): d ˆ 7.62 ± 6.58 (m, 28H; aromatic), 5.53 (d, J ˆ 8.3 Hz,
1H; H-11), 4.31 ± 4.13 (m, 2H; H-21, H-31), 3.98 (m, 1H; H-5F), 3.60 (s, 3H;
OMe), 1.00 (d, J ˆ 6.3 Hz, 3H; H-6F); 13C NMR (67.5 MHz, CDCl3): d ˆ
98.5 and 97.8 (anomeric carbons), 79.3, 77.7, 77.2, 76.3, 74.9, 74.3, 74.2, 73.5,
73.3, 72.9, 68.3, 66.9, 55.5, 55.5.
3-O-Benzyl-4,6-O-benzylidene-2-deoxy-2-phthalimido-b-d-glucopyranose
(19c): Ceric ammonium nitrate (CAN; 961 mg, 1.75 mmol) was added to a
Chem. Eur. J. 1998, 4, No. 11
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
0947-6539/98/0411-2187 $ 17.50+.25/0
2187

Y. Ito et al.
FULL PAPER
H-6'); C28H24N4O6 (512.52): calcd C 65.62, H 4.72, N 10.53; found C 65.80,
H 4.73, N 10.53.
Method B (with fluoride 14): A mixture of Cp2HfCl2 (5.1 mg, 0.013 mmol),
AgOTf (6.9 mg, 0.027 mmol), and molecular sieves 4A (0.04 g) in CH2Cl2
(0.2 mL) was stirred at 08C for 10 min and then cooled down to 788C.
Compounds 14 (12.0 mg, 0.0095 mmol) and 17a (26.4 mg, 0.029 mmol)
were added as a solution in CH2Cl2 (0.6 mL), and the whole was stirred for
3 h, while being gradually warmed up to 108C. After being stirred for
From 21: NaH (60%, 792 mg, 20 mmol) was added to an ice-cold solution
of compound 21 (4.60 g, 9.9 mmol) and benzyl bromide (2.35 mL,
19.8 mmol) in DMF, and the mixture was stirred for 19 h, while being
gradually warmed up to room temperature. The solution was quenched
with Et3N, diluted with AcOEt, washed successively with aq NH4Cl and
brine, and dried over Na2SO4; the the solvent was evaporated in vacuo. The
residue was purified by silica-gel column chromatography (toluene/EtOH
19:1) to afford 3.9 g (72%) of compound 19b.
additional 2 h at
108C, additional amounts of Cp2HfCl2 (2.0 mg,
0.005 mmol) and AgOTf (2.8 mg, 0.011 mmol) were added and stirring
was continued at room temperature overnight. The resulting mixture was
quenched with aq NaHCO3 (RT, 10 min), diluted with AcOEt, and filtered
through Celite. The filtrate was washed successively with aq NaHCO3 and
brine, and dried over Na2SO4; the solvent was evaporated in vacuo. The
residue was subjected to a column of Bio-Beads S-X1 (toluene). Fractions
containing pentasaccharide were collected and further purified by prepar-
aetive TLC (hexane/AcOEt 1:1) to afford 8.1 mg (39%) of compound
24a.
3-O-Benzyl-2-deoxy-2-phthalimido-b-d-glucopyranosyl azide (16b): A sol-
ution of 19b (500 mg, 0.98 mmol) and dl-camphorsulfonic acid (21 mg,
0.09 mmol) in MeOH (10 mL) was stirred under heating with oil bath
(508C). After 30 min, CH2Cl2 (2 mL) was added and stirring was continued
at the same temperature for additional 1.5 h. The mixture was processed as
described for 21 and purified by silica-gel column chromatography
(AcOEt/toluene 1:1) to afford 317 mg (83%) of compound 16b. M.p.
147 ± 1498C; [a]D ˆ ‡26.9 (c ˆ 1.1 in chloroform); 1H NMR (270 MHz,
CDCl3, 258C, TMS): d ˆ 7.81 ± 6.92 (m, 9H; aromatic), 5.42 (d, J ˆ 9.2 Hz,
1H; H-1), 5.42 and 4.73 (ABq, J ˆ 12.2 Hz, each 1H; benzyl CH2), 4.31 (dd,
J ˆ 10.6, 8.6 Hz, 1H; H-3), 4.08 (dd, J ˆ 10.6, 9.2 Hz, 1H; H-2), 3.98 (m,
2H; H-6), 3.86 (ddd, J ˆ 9.6, 8.6, 3.6 Hz, 1H; H-4), 3.65 (ddd, J ˆ 9.6, 3.6,
3.6 Hz, 1H; H-5), 3.01 (brd, J ˆ 3.6 Hz, 1H; 4-OH), 2.35 (brs, 1H; 6-OH);
13C NMR (67.5 MHz, CDCl3, 258C): d ˆ 85.8 (C-1), 78.9, 77.2, 74.2, 71.7,
62.1, 55.0; C21H20N4O6 (424.42): calcd C 59.43, H 4.75, N 13.20; found C
59.18, H 4.64, N 13.19.
O-(2-O-Acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1!3)-O-(2-O-ac-
etyl-4,6-O-benzylidene-b-d-mannopyranosyl)-(1!4)-O-(3,6-di-O-benzyl-2-
deoxy-2-phthalimido-b-d-glucopyranosyl)-(1 !4)-O-[(2,3,4-tri-O-benzyl-a-
l-fucopyranosyl)-(1 !6)]-3,6-di-O-benzyl-2-deoxy-2-phthalimido-b-d-glu-
copyranosyl azide (24b): Compounds 15 (34.0 mg, 0.0486 mmol) and 17b
(40.9 mg, 0.0486 mmol) were treated with TMSOTf (1 mmol) and molecular
sieves 4A (0.04 g) in CH2Cl2 (0.6 mL; 78 ± 408C, 1 h) as desribed for
24a, method A. The mixture was processed as described above and purified
by Bio-Beads S-X1 (toluene/AcOEt 1:1) and by silice-gel column
chromatography (10 ± 30% AcOEt in hexane) to afford 40.1 mg (79%)
of compound 24b. [a]D
ˆ
10.8 (c ˆ 1.0 in chloroform); 1H NMR
O-(2,3,4-Tri-O-benzyl-a-d-fucopyranosyl)-(1 !6)-3-O-benzyl-2-deoxy-2-
phthalimido-b-d-glucopyranosyl azide (17b): Compounds 16b (55 mg,
0.13 mmol) and 18 (67 mg, 0.14 mmol) were treated as described for the
preparation of 17a, with the use of CuBr2 (64 mg, 0.29 mmol), Bu4NBr
(93 mg, 0.29 mmol), and molecular sieves 4A (0.2 g) in CH2Cl2/DMF (5:1,
108C ± RT., 17 h) to afford 80.2 mg (73%) of 17b, together with
(400 MHz, CDCl3, 258C, TMS): d ˆ 7.87 ± 6.72 (m, 58H; aromatic), 5.48
(d, J ˆ 8.3 Hz, 1H; H-11), 5.44 (m, 2H; H-24, benzylidene CH), 5.37 (dd,
J ˆ 2.6, <1 Hz, 1H; H-23), 5.22 (d, J ˆ 1.5 Hz, 1H; H-14), 5.11 (d, J ˆ
9.3 Hz, 1H; H-12), 2.07 and 1.74 (2s, each 3H; Ac), 1.02 (d, J ˆ 6.3 Hz,
3H; H-6F); 13C (67.5 MHz, CDCl3): d ˆ 101.1 (benzylidene CH), 99.3, 98.6,
96.9, 96.8 (C-12,3,4,F), 84.9 (C-11), 79.4, 79.1, 78.8, 77.8, 77.6, 77.2, 76.9, 76.0,
76.0, 75.1, 75.0, 74.8, 74.7, 74.6, 74.0, 73.4, 73.3, 73.3, 73.2, 72.7, 72.1, 71.7,
70.4, 68.7, 68.5, 68.3, 67.9, 66.3, 66.1, 63.2, 56.4, 55.4; C120H119N5O28 (2079.30):
calcd C 69.32, H 5.77, N 3.37; found C 69.00, H 5.75, N 3.27.
corresponding b-isomer (7.2 mg, 7%). [a]D
ˆ
34.1 (c ˆ 1.0 in chloroform);
1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.83 ± 6.84 (m, 24H;
aromatic), 5.32 (d, J ˆ 9.6 Hz, 1H; H-11), 3.71 (m, 1H; H-4F), 3.67 (m,
1H; H-51), 1.14 (d, J ˆ 6.4 Hz, 3H; H-6F); 13C NMR (67.5 MHz, CDCl3):
d ˆ 98.7 (C-1F), 85.7 (C-11), 79.2 77.2, 76.8, 76.4, 75.6, 74.9, 74.4, 73.0, 72.8,
67.9, 66.9, 55.0; C48H48N4O10 (840.94): calcd C 68.56, H 5.75, N 6.66; found C
68.21, H 5.67, N 6.49.
p-Methoxyphenyl O-(2-O-acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-
(1 !3)-O-(2-O-acetyl-b-d-mannopyranosyl)-(1 !4)-O-(3,6-di-O-benzyl-2-
deoxy-2-phthalimido-b-d-glucopyranosyl)-(1 !4)-O-[(2,3,4-tri-O-benzyl-a-
l-fucopyranosyl)-(1 !6)]-3,6-di-O-benzyl-2-deoxy-2-phthalimido-b-d-glu-
copyranoside (25a): Compound 24a (12.8 mg, 5.9 mmol) was dissolved in a
precooled (08C) solution of 5% trifluoroacetic acid in CH2Cl2 (1 mL).
After 10 min, the reaction was quenched with aq NaHCO3 and extracted
three times with CHCl3. The combined organic layers were dried over
Na2SO4, and the solvent was evaporated in vacuo. The residue was purified
by preparative TLC (toluene/AcOEt 1:1) to afford 10.8 mg (88%) of
compound 25a. [a]D ˆ ‡2.4 (c ˆ 0.7 in chloroform); 1H NMR (400 MHz,
CDCl3, 258C, TMS): d ˆ 7.87 ± 6.55 (m, 57H; aromatic), 5.46 (d, J ˆ 7.8 Hz,
1H; H-11), 5.39 (d, J ˆ 8.3 Hz, 1H; H-12), 5.32 (dd, J ˆ 3.4, < 1 Hz, 1H;
H-23), 5.23 (brs, 1H; H-14), 5.21 (dd, J ˆ 2.9, 1.5 Hz, 1H; H-23), 3.61 (s, 3H,
OMe), 2.12 and 1.72 (2s, each 3H; Ac); 13C NMR (67.5 MHz, CDCl3): d ˆ
98.5, 98.0, 97.6, 97.0 and 96.9 (anomeric carbons), 79.6, 78.7, 77.7, 77.3, 76.9,
75.5, 75.3, 75.2, 74.8, 74.7, 74.4, 74.3, 74.0, 73.8, 73.4, 73.4, 73.2, 72.7, 71.8,
71.7, 70.9, 69.3, 69.0, 66.9, 65.9, 63.6, 62.3, 56.4, 55.8, 55.5; C120H120N2O30
(2070.29): calcd C 69.55, H 5.93, N 1.35; found C 69.18, H 5.88, N 1.46.
b-Isomer: 1H NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 5.34 (d, J ˆ 9.6 Hz,
1H; H-11), 4.41 (d, J ˆ 7.6 Hz, 1H; H-1F), 1.19 (d, J ˆ 6.3 Hz, 3H; H-6F);
13CNMR (67.5 MHz, CDCl3): d ˆ 103.8 (C-1F), 85.8 (C-11), 82.4, 79.0, 77.2,
76.9, 76.5, 76.2, 75.3, 74.6, 74.4, 73.2, 72.1, 70.7, 68.3, 55.1.
p-Methoxyphenyl O-(2-O-acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-
(1 !3)-O-(2-O-acetyl-4,6-O-benzylidene-b-d-mannopyranosyl)-(1 !4)-O-
(3,6-di-O-benzyl-2-deoxy-2-phthalimido-b-d-glucopyranosyl)-(1 !4)-O-
[(2,3,4-tri-O-benzyl-a-l-fucopyranosyl)-(1 !6)]-3,6-di-O-benzyl-2-deoxy-
2-phthalimido-b-d-glucopyranoside (24a)
Method A (with trichloroacetimidate 15): A solution of TMSOTf (0.2m in
1,2-dichloroethane; 1.5 ml, 0.3 mmol) was added to a precooled ( 788C)
mixture of compounds 15 (16.5 mg, 0.0118 mmol) and 17a (27.1 mg,
0.0294 mmol) in CH2Cl2 (0.3 mL) containing molecular sieves 4A
(0.04 g), and the mixture was stirred at this temperature. After 1 h, an
additional amount of TMSTOf (0.3 mmol) was added and the mixture was
gradually warmed up to 458C (ꢀ1 h) and kept at that temperature for
0.5 h. The reaction mixture was quenched with Et3N, diluted with AcOEt,
and filtered through Celite. The filtrate was washed successively with aq
NaHCO3 and brine, and dried over Na2SO4; the solvent was evaporated in
vacuo. The residue was subjected to a column of Bio-Beads S-X1 (toluene/
AcOEt 1:1) and pentasaccharide-containing fractions were further purified
by silica-gel column chromatography (hexane/AcOEt 1:1) to afford
O-(2-O-Acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)-O-(2-O-ac-
etyl-b-d-mannopyranosyl)-(1!4)-O-(3,6-di-O-benzyl-2-deoxy-2-phthalimi-
do-b-d-glucopyranosyl)-(1 !4)-O-[(2,3,4-tri-O-benzyl-a-l-fucopyranosyl)-
(1 !6)]-3,6-di-O-benzyl-2-deoxy-2-phthalimido-b-d-glucopyranosyl azide
(25b): Compound 24b (27.8 mg, 0.0134 mmol) was treated with 5%
trifluoroacetic acid in CH2Cl2 (08C, 30 min), and the proceedure described
for 25a was followed. Purification by silica-gel column chromatography
(toluene/AcOEt 5:1 ± 3:1) afforded 25.0 mg (94%) of compound 25b.
[a]D ˆ ‡10.7 (c ˆ 1.1 in chloroform); 1H NMR (400 MHz, CDCl3, 258C,
TMS): d ˆ 7.88 ± 6.72 (m, 53H; aromatic), 5.46 (d, J ˆ 7.8 Hz, 1H; H-11),
5.32 (brd, J ˆ 3.2 Hz, 1H; H-24), 5.23 (d, J ˆ 1.5 Hz, 1H; H-14), 5.20 (dd,
J ˆ 3.4, 2.0 Hz, 1H; H-23), 5.11 (d, J ˆ 9.3 Hz, 1H; H-12), 2.11 and 1.74 (2s,
each 3H; Ac), 1.02 (d, J ˆ 6.8 Hz, 3H; H-6F); 13C NMR (100 MHz, CDCl3):
d ˆ 98.45, 97.62, 96.94 and 96.19 (C-12,3,4,F), 84.80 (C-11), 79.5, 78.7, 78.6, 77.8,
77.4, 77.4, 76.9, 76.1, 76.0, 75.3, 75.2, 75.2, 74.8, 74.8, 74.8, 74.5, 74.3, 74.0,
73.5, 73.3, 73.2, 72.8, 71.8, 71.7, 70.9, 69.3, 69.0, 67.7, 66.9, 66.1, 63.2, 62.2,
18.0 mg (71%) of compound 24a. [a]D
ˆ
0.5(c ˆ 0.9 in chloroform); 1H
NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.86 ± 6.55 (m, 62H; aromatic),
5.47 (d, J ˆ 8.3 Hz, 1H; H-11), 5.45 (brs, 2H; H-24, benzylidene CH), 5.39
(d, J ˆ 8.3 Hz, 1H; H-12), 5.38 (brs, 1H; H-23), 5.25 (d, J ˆ 1.5 Hz, 1H;
H-14), 3.61 (s, 3H; OMe), 2.08 and 1.74 (2s, each 3H; Ac), 0.86 (d, J ˆ
6.3 Hz, 3H; H-6F); 13C NMR (67.5 MHz, CDCl3, 258C): d ˆ 101.1
(benzylidene CH), 99.3, 98.6, 98.0, 96.94, 96.93 (anomeric carbons), 79.9,
79.2, 78.8, 77.6, 76.4, 75.4, 75.2, 75.0, 74.8, 74.7, 74.6, 74.1, 73.8, 73.4, 72.7,
72.1, 71.7, 70.5, 68.7, 66.3, 66.0, 63.7, 56.5, 55.8, 55.5; C122H120N2O30 (2094.31):
calcd C 70.60, H 5.88, N 1.30; found C 70.13, H 5.82, N 1.19.
2188
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
0947-6539/98/0411-2188 $ 17.50+.50/0
Chem. Eur. J. 1998, 4, No. 11

Intramolecular Aglycon Delivery
2182±2190
56.4, 55.3; C113H115N5O28 (1991.19): calcd C 68.16, H 5.82, N 3.52; found C
67.71, H 5.85, N 3.43.
2-deoxy-b-d-glucopyranosyl]-(1 !4)-O-[(a-l-fucopyranosyl)-(1 !6)]-2-
acetamido-2-deoxy-b-d-glucopyranoside (1a): Compound 27a (10.9 mg,
4.9 mmol) was hydrogenated over 10% Pd-C (6 mg) in MeOH/AcOH/H2O
(7:2:1) at room temperature for 24 h. The mixture was filtered through a
membrane filter and the filtrate was subjected to a column of Bio-Gel P-2
(H2O) to afford 5.3 mg (91%) of 28. 1H NMR (270 MHz, CDCl3, 258C, TMS):
d ˆ 7.01 (m, 4H, aromatic), 5.51 (brd, Jˆ 4 Hz, 1H; H-23), 5.12 (d, Jˆ 1.0 Hz,
1H; H-14), 4.97 (d, J ˆ 8.3 Hz, 1H; H-11), 4.91 (d, J < 1 Hz, 1H;, H-14), 4.83
(d, J ˆ 3.3 Hz, 1H; H-1F), 4.63 (d, J ˆ 7.9 Hz, 1H; H-12), 3.80 (s, 3H; OMe),
2.18, 2.07 and 2.04 (3s, each 3H; Ac), 1.01 (d, 3H, J ˆ 6 Hz; H-6F).
This material was dissolved in 50mm NaOH in D2O and the progress of the
reaction was monitored by 1H NMR. After standing for 2 h, the solution
was neutralized with acetic acid, and the solvent was evaporated in vacuo.
The residue was subjected to a column of Bio-Beads P-2 (H2O) to afford,
p-Methoxyphenyl O-(2-O-acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-
(1 !6)-O-[(2-O-acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)]-
(2-O-acetyl-b-d-mannopyranosyl)-(1 !4)-O-(3,6-di-O-benzyl-2-deoxy-2-
phthalimido-b-d-glucopyranosyl]-(1 !4)-O-[(2,3,4-tri-O-benzyl-a-l-fu-
copyranosyl)-(1 !6)]-3,6-di-O-benzyl-2-deoxy-2-phthalimido-b-d-gluco-
pyranoside (26a): A mixture of compound 25a (20.0 mg, 9.7 mmol), silver
trifluoromethenesulfonate (AgOTf; 4.0 mg, 16 mmol), and molecular sieves
4A (0.03 g) in CH2Cl2 (0.8 mL) was stirred at 08C. Compound 9 (5.4 mg,
11 mmol) was added dropwise as a solution in CH2Cl2 (0.2 ml), and the
mixture was warmed up to room temperature and stirred for 4 h. The
reaction was quenched by aq NaHCO3 (RT, 10 min), diluted with CHCl3,
and filtered through Celite. The filtrate was washed with CHCl3 and the
aqueous layer was back-extracted twice with CHCl3. The combined organic
layers were dried over Na2SO4, and the solvent was evaporated in vacuo.
The residue was purified by preparative TLC (toluene/AcOEt 2:1) to
afford 18.8 mg (77%) of compound 26a together with recovered 25a
(3.2 mg). [a]D ˆ ‡9.5 (c ˆ 1.3 in chloroform); 1H NMR (400 MHz, CDCl3,
258C, TMS): d ˆ 7.99 ± 6.54 (m, 72H; aromatic), 5.43 (d, J ˆ 8.3 Hz, 1H;
H-11), 5.37 (d, J ˆ 8.8 Hz, 1H; H-12), 5.39 and 5.35 (each 1H; H-24, H-24'),
5.24 (brs, 1H; H-23), 3.60 (s, 3H; OMe), 2.10, 1.95 and 1.77 (3s, each 3H;
Ac); 13C NMR (100 MHz, CDCl3): d ˆ 99.3, 99.2, 97.93, 97.75, 96.93 and
96.85 (anomeric carbons), 79.5, 79.4, 78.2, 78.0, 77.7, 77.2, 76.4, 75.4, 75.3,
75.2, 74.7, 74.5, 74.4, 74.2, 74.1, 73.8, 73.4, 73.0, 72.6, 71.9, 71.7, 71.4, 70.8,
68.9, 68.8, 68.6, 68.4, 67.8, 67.0, 66.1, 65.9, 63.8, 56.6, 55.7, 55.4;
C149H152N2O36 ´ H2O (2564.88): calcd C 69.77, H 6.05, N 1.09; found C
69.61, H 6.01, N 1.05.
1
after lyophilization, 5.0 mg (88%) of 1a. H NMR (400 MHz, D2O, 608C,
tBuOH adjusted to d ˆ 1.23): d ˆ 7.01 (m, 4H; aromatic), 5.10 (d, J ˆ
1.0 Hz, 1H; H-14), 4.98 (d, J ˆ 8.3 Hz, 1H; H-11), 4.90 (d, J ˆ 1.5 Hz, 1H;
H-14), 4.84 (d, J ˆ 3.9 Hz, 1H; H-1F), 4.76 (s, 1H; H-13), 4.66 (d, J ˆ 7.8 Hz,
1H; H-12), 4.22 (brs, 1H; H-2), 4.06 (dd, J ˆ 3.4, 1.5 Hz, 1H; H-24), 3.80 (s,
3H; OMe), 2.07 and 2.04 (2s, each 3H; Ac), 1.01 (d, J ˆ 6.8 Hz, 3H; H-6F);
13C NMR (100 MHz, D2O): d ˆ 104.3, 102.8, 102.1 and 101.3 (anomeric
carbons), 82.2, 82.5, 80.6, 76.1, 75.9, 75.3, 75.2, 74.4, 73.9, 73.7, 72.1, 72.0,
71.9, 71.7, 71.6, 71.5, 71.2, 69.8, 68.7, 68.6, 68.5, 68.4, 67.5, 62.9, 62.7, 62.2, 61.7,
57.5, 56.8, 56.6.
O-(3,4,6-Tri-O-benzyl-a-d-mannopyranosyl)-(1 !6)-O-[(3,4,6-tri-O-benzyl-
a-d-mannopyranosyl)-(1 !3)]-(2-O-acetyl-b-d-mannopyranosyl)-(1 !4)-
O-(2-acetamido-3,6-di-O-benzyl-2-deoxy-b-d-glucopyranosyl]-(1 !4)-O-
[(2,3,4-tri-O-benzyl-a-l-fucopyranosyl)-(1 !6)]-2-acetamido-3,6-di-O-be-
nzyl-2-deoxy-b-d-glucopyranoside (29): Compound 26b (20.2 mg,
8.2 mmol) was treated with ethylenediamine (0.3 mL) in EtOH (1 mL)
under reflux for 22 h. The resulting mixture was evaporated in vacuo and
co-evaporated with EtOH and then with toluene, and was dissolved in
MeOH (1.5 mL). The solution was treated at 08C with acetic anhydride
(0.5 mL) for 1 h and evaporated in vacuo to afford crude 27b. This material
was dissolved in 0.2m methanolic NaOMe (1 mL) and stirred at room
temperature for 22 h. The mixture was quenched with acetic acid,
evaporated in vacuo and purified through a column of Sephadex LH-20
O-(2-O-Acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !6)-O-[(2-O-
acetyl-3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)]-(2-O-acetyl-b-d-
mannopyranosyl)-(1 !4)-O-(3,6-di-O-benzyl-2-deoxy-2-phthalimido-b-d-
glucopyranosyl]-(1 !4)-O-[(2,3,4-tri-O-benzyl-a-l-fucopyranosyl)-(1 !6)]-
di-O-benzyl-2-deoxy-2-phthalimido-b-d-glucopyranosyl azide (26b): Com-
pound 25b was transformed into 26b with the procedure described for the
preparation of 26a. Compound 25b (39.6 mg, 0.0199 mmol) was treated
with
9 (11.8 mg, 0.023 mmol) in the presence of AgOTf (10.3 mg,
0.040 mmol), and molecular sieves 4A (0.1 g) (08C ± RT, 4 h). Purification
by silica-gel column chromatography (10 ± 30% AcOEt in toluene)
afforded 36.1 mg (74%) of compound 26b as well as recovered 25b
(6.0 mg). [a]D ˆ ‡4.4 (c ˆ 0.6 in chloroform); 1H NMR (400 MHz, CDCl3,
258C, TMS): d ˆ 7.80 ± 6.71 (m, 68H; aromatic), 5.43 (d, J ˆ 8.3 Hz, 1H;
H-11), 5.38 and 5.35 (each dd, J ˆ 3, 1 Hz, 1H; H-24,4'), 5.24 (brs, 1H; H-23),
5.21 (d, J ˆ 1.5 Hz, 1H; H-14), 2.10, 1.95 and 1.76 (3s, each 3H; Ac); 13C
NMR (67.5 MHz, CDCl3): d ˆ 99.3, 99.2, 97.9, 96.9 and 96.8 (C-12,3,4,4',F), 84.9
(C-11), 79.4, 78.2, 78.0, 77.9, 77.7, 77.2, 76.7, 76.1, 76.0, 75.3, 75.2, 75.0, 74.7,
74.7, 74.6, 74.4, 74.3, 74.1, 73.4, 73.1, 72.7, 71.9, 71.8, 71.4, 70.8, 69.0, 68.8,
68.6, 68.4, 67.9, 67.0, 66.1, 63.3; C142H145N5O34 ´ H2O (2483.77): C 68.67, H
5.97, N 2.82; found C 68.73, H 6.00, N 2.60.
(H2O) to afford compound 29. [a]D
ˆ
17.6 (c ˆ 1.1 in chloroform); 1H
NMR (270 MHz, CDCl3, 258C, TMS): d ˆ 7.65 ± 7.09 (m, 60H, aromatic),
5.80 (brd, J ˆ 8.9 Hz, 1H; NHCO), 5.65 (brd, J ˆ 8.6 Hz, 1H; NHCO), 5.12
(brs, 1H; H-14), 2.98 and 2.84 (2brs, each 1H; OH), 2.52 (brs, 2H; 2OH),
1.84 and 1.72 (2s, each 3H; Ac), 1.06 (d, J ˆ 6.6 Hz, 3H; H-6F); 13C NMR
(67.5 MHz, CDCl3): d ˆ 100.8, 100.6, 99.6, 99.4 and 98.0 (C-12,3,4,4',F), 88.3 (C-
11), 82.4, 80.1, 80.8, 79.7, 79.3, 78.2, 76.3, 76.2, 75.9, 75.2, 74.9, 74.4, 73.8, 73.4,
73.0, 72.8, 72.2, 71.7, 71.5, 71.3, 70.3, 69.1, 68.9, 68.1, 66.6, 66.5, 65.3.
N2-Benzyloxycarbonyl-N4-{O-(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-
(1 !3)-O-[(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1!6)]-(b-d-manno-
pyranosyl)-(1 !4)-(2-acetamido-3,6-di-O-benzyl-2-deoxy-b-d-glucopyra-
nosyl)-(1 !4)-O-[(2,3,4-tri-O-benzyl-a-d-fucopyranosyl)-(1 !6)]-2-ace-
tamido-3,6-di-O-benzyl-2-deoxy-b-d-glucopyranosyl}-l-asparagine benzyl
ester (30): DCC (4.8 mg, 0.023 mmol) was added to a solution of Z-Asp-
OBn (16.0 mg) in CH2Cl2 (1 mL), and the mixture was stirred at 08C for
30 min. The precipitate was filtered off, and the filtrate was evaporated in
vacuo to afford the crude anhydride, which was dissolved in AcOEt (1 mL).
A solution of compound 29 (8.0 mg, 3.7 mmol) in MeOH was added
followed by Lindlar catalyst (5 mg). The mixture was stirred under an H2
atmosphere at room temperature for 2 h and then filtered through Celite.
The filtrate was evaporated in vacuo and purified through a column of
p-Methoxyphenyl O-(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !6)-O-
[(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)]-(2-O-acetyl-b-d-man-
nopyranosyl)-(1 !4)-O-(2-acetamido-3,6-di-O-benzyl-2-deoxy-b-d-gluco-
pyranosyl]-(1 !4)-O-[(2,3,4-tri-O-benzyl-a-l-fucopyranosyl)-(1 !6)]-2-
acetamido-3,6-di-O-benzyl-2-deoxy-b-d-glucopyranoside (27a): Com-
pound 26a (14.6 mg, 5.7 mmol) was dissolved in EtOH (2 mL), which
contained ethylenediamine (0.3 mL), and the solution was heated under
reflux for 7 h. Volatiles were removed in vacuo, and the residue was co-
evaporated with toluene. The residue was dissolved in MeOH (3 mL) and
treated at 08C with acetic anhydride (0.5 mL) for 30 min. The mixture was
evaporated in vacuo and purified by preparative TLC (toluene/AcOEt 7:1)
Sephadex LH-20 (MeOH) to afford 8.3 mg (91%) of compound 30. [a]D
ˆ
2.5 (c ˆ 0.5 in chloroform); 1H NMR (270 MHz, CDCl3-D2O, 258C,
TMS): d ˆ 7.35 ± 7.09 (m, 60H; aromatic), 5.11 (m, 2H; H-14, CO2CH2Ph),
5.07 and 5.02 (ABq, J ˆ 12.2 Hz, each 1H; CO2CH2Ph), 2.83 (dd, J ˆ 16.1,
4.9 Hz, 1H; CH2Asn), 2.58 (dd, J ˆ 16.1, 3.9 Hz, 1H; CH2Asn), 1.73 and 1.67
(2s, each 3H; Ac), 1.03 (d, J ˆ 6.3 Hz, 3H, H-6Fuc); 13C NMR (100 MHz,
CDCl3): d ˆ 100.8, 100.6, 99.7, 99.4 and 97.9 (C-12,3,4,4',F), 79.8 (C-11), 82.4,
80.1, 80.0, 80.0, 78.7, 77.2, 76.1, 75.9, 75.1, 74.9, 74.8, 74.4, 73.7, 73.4, 73.1, 72.7,
72.2, 71.7, 71.5, 71.2, 70.3, 69.1, 68.8, 68.6, 68.1, 67.1, 67.1, 66.9, 66.5, 66.2, 65.3;
to afford 10.9 mg (85%) of compound 27a. [a]D
ˆ
25.3 (c ˆ 0.7 in
1
chloroform); H NMR (400 MHz, CDCl3, 258C, TMS): d ˆ 7.37 ± 6.71 (m,
64H; aromatic), 6.51 (brd, J ˆ 9.2 Hz, 1H; NHCO), 5.31 (brd, J ˆ 3.0 Hz,
1H; H-23), 5.27 (d, J ˆ 1.5 Hz, 1H; H-14), 5.10 (brd, J ˆ 8.6 Hz, 1H;
NHCO), 5.04 (d, J ˆ 5.0 Hz, 1H; H-11), 3.71 (s, 3H; OMe), 1.98, 1.94 and
1.64 (3s, each 3H; Ac), 0.88 (d, J ˆ 6.6 Hz, 3H; H-6F); 13C NMR (67.5 MHz,
CDCl3): d ˆ 100.6, 100.4, 99.4, 99.3, 98.6 and 98.0 (anomeric carbons), 80.2,
79.7, 79.5, 78.9, 77.9, 77.2, 76.0, 75.4, 74.8, 74.7, 74.4, 74.3, 74.1, 73.5, 73.4,
73.3, 73.0, 72.8, 72.2, 72.0, 71.7, 71.5, 71.2, 68.9, 68.8, 68.5, 68.3, 68.2, 67.6,
66.7, 66.4, 66.3, 55.6, 55.0, 50.0, 23.4 and 23.2 (NHCOCH3), 21.0 (OCOCH3).
C143H158N4O35 (2492.86): calcd C 68.90, H 6.39, N 2.25; found C 68.41, H
6.53, N 2.28.
p-Methoxyphenyl O-(a-d-mannopyranosyl)-(1 !6)-O-[(a-d-mannopyra-
nosyl)-(1 !3)]-(2-O-acetyl-b-d-mannopyranosyl)-(1 !4)-O-(2-acetamido-
N4-{O-(a-d-mannopyranosyl)-(1 !3)-O-[(-a-d-mannopyranosyl)-(1 !6)]-
(b-d-mannopyranosyl)-(1 !4)-(2-acetamido-2-deoxy-b-d-glucopyranosyl)-
Chem. Eur. J. 1998, 4, No. 11
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0947-6539/98/0411-2189 $ 17.50+.25/0
2189

Y. Ito et al.
FULL PAPER
(1 !4)-O-[(a-d-fucopyranosyl)-(1 !6)]-2-acetamido-2-deoxy-b-d-gluco-
pyranosyl}-l-asparagine (1b): Compound 30 (9.0 mg, 3.6 mmol) was hydro-
genated over 10% Pd-C in MeOH/AcOH/H2O (7:2:1; 1.5 mL) at room
temperature for 44 h. The resulting mixture was filtered through membrane
filter and the filtrate was evaporated and subjected to a column of
Sephadex G-50 (H2O) to afford, after lyophilization, 4.1 mg (97%) of
compound 1b. 1H NMR (400 MHz, D2O, 608C, tBuOH adjusted to d ˆ
1.23): d ˆ 5.10 (d, J ˆ 1.5 Hz, 1H; H-14), 5.06 (d, J ˆ 9.8 Hz, 1H; H-11), 4.90
(d, J ˆ 1.5 Hz, 1H; H-14'), 4.86 (d, J ˆ 3.9 Hz, 1H; H-1F), 4.76 (s, 1H; H-13),
4.67 (d, J ˆ 7.8 Hz, 1H; H-12), 4.22 (brs, 1H; H-23), 4.10 (q, J ˆ 6.8 Hz, 1H;
H-5F), 4.06 (dd, J ˆ 3.4, 1.5 Hz, 1H; H-24), 3.96 (dd, J ˆ 3.4, 1.5 Hz, 1H;
H-24'), 2.88 (dd, J ˆ 16.8, 4.2 Hz, 1H; CH2Asn), 2.74 (dd, J ˆ 16.8, 7.6 Hz, 1H;
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[19] S configuration does not seem to be a critical factor for successful
intramolecular aglycon delivery. Detailed discussion will be reported
in due course. (M. Lergenmüller, T. Nukada, K. Kuramochi, A. Dan,
T. Ogawa, Y. Ito, unpublished results)
CH2Asn), 2.07 and 2.00 (2s, each 3H; Ac), 1.19 (d, 3H, J ˆ 6.6 Hz; H-6F); 13
C
NMR (100 MHz, D2O): d ˆ 104.3, 102.7, 102.1, 101.3 and 101.0 (C-12,3,4,4',F),
79.9 (C-11), 82.2, 81.5, 79.8, 76.9, 76.1, 75.9, 75.2, 74.5, 74.4, 73.7, 73.5, 72.1,
72.0, 71.9, 71.7, 71.6, 71.5, 71.2, 69.9, 68.5, 68.5, 68.2, 67.5, 62.9, 62.7, 61.7, 56.6,
55.3, 53.0.
Received: April 20, 1998 [F1105]
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2190
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Chem. Eur. J. 1998, 4, No. 11