Synthesis of branched tri- to pentasaccharides representative of fragments of Shigella flexneri serotypes 3a and/or X O-antigens

Article abstract of DOI:10.1016/j.tet.2008.08.080

Fragments of the {2)-[α-d-Glcp-(1→3)]-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-[Ac→2]-α-l-Rhap-(1→3)-β-d-GlcpNAc-(1→}_n ((E)AB_AcCD)_n polymer were synthesized. D(E)A, CD(E)A, _AcCD(E)A were obtained according to a linear strategy, whereas BCD(E)A and B_AcCD(E)A were derived from the condensation of appropriate BC and D(E)A building blocks. Oligosaccharides were synthesized as their propyl glycoside, relying on (i) the efficient trichloroacetimidate chemistry, (ii) a common EA allyl glycoside, and (iii) a 2-trichloroacetamido-d-glucopyranose precursor to residue D. Final Pd/C-mediated deprotection, run under a high pressure of hydrogen, ensured O-acetyl stability. All targets are parts of the O-antigen of Shigella flexneri 3a, a prevalent serotype. Non-O-acetylated oligosaccharides are shared by the S. flexneri serotype X O-antigen.

Full text of DOI:10.1016/j.tet.2008.08.080

Tetrahedron 64 (2008) 10558–10572
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of branched tri- to pentasaccharides representative of fragments
of Shigella flexneri serotypes 3a and/or X O-antigens
,
,
Julien Boutet a b, Catherine Guerreiro a, Laurence A. Mulard a
*
a Institut Pasteur, Unite´ de Chimie des Biomole´cules (CNRS URA 2128), 28 rue du Dr Roux, F-75015 Paris, France
b Universite´ Paris Descartes, 12 rue de l’Ecole de Me´decine, F-75006 Paris, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 24 June 2008
Received in revised form 26 August 2008
Accepted 27 August 2008
Available online 3 September 2008
Fragments of the {2)-[a-D-Glcp-(1/3)]-a-L-Rhap-(1/2)-a-L-Rhap-(1/3)-[Ac/2]-a-L-Rhap-(1/3)-
b-D-GlcpNAc-(1/}n ((E)ABAcCD)n polymer were synthesized. D(E)A, CD(E)A, AcCD(E)A were obtained
according to a linear strategy, whereas BCD(E)A and BAcCD(E)A were derived from the condensation of
appropriate BC and D(E)A building blocks. Oligosaccharides were synthesized as their propyl glycoside,
relying on (i) the efficient trichloroacetimidate chemistry, (ii) a common EA allyl glycoside, and (iii) a 2-
trichloroacetamido-D-glucopyranose precursor to residue D. Final Pd/C-mediated deprotection, run un-
Keywords:
der a high pressure of hydrogen, ensured O-acetyl stability. All targets are parts of the O-antigen of
Shigella flexneri 3a, a prevalent serotype. Non-O-acetylated oligosaccharides are shared by the S. flexneri
serotype X O-antigen.
Oligosaccharide
Glycosylation
N-Trichloroacetyl
Shigella
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
serotype Y. Additional serotype-specificity is associated to the
presence of branched a-D-glucopyranosyl (E) and O-acetyl (O-Ac)
Shigellosis, or bacillary dysentery, is an invasive infection of the
human colon which in its most classical expression is characterized
by a triad of fever, intestinal cramps and bloody diarrhea.1 This
highly contagious infection, associated with increased antibiotic-
resistance,1,2 is endemic worldwide. In the absence of a vaccine,3
shigellosis remains a major health concern especially in the pedi-
atric population living in the most impoverished areas.2–4 Shigella is
divided into 4 different species. Shigella sonnei (1 serotype) and
Shigella flexneri account for the endemic disease. The latter which,
by far, prevails in developing countries and in children below five
years of age,2,4 is divided into 15 serotypes. Importantly, a wide
range of S. flexneri serotypes, whose geographical distribution is
somewhat heterogeneous, are isolated from patients, emphasizing
the need for a multivalent vaccine providing broad serotype cov-
erage.2,4,3 Serotypes are defined on the basis of the carbohydrate
repeating unit of the S. flexneri O-antigen (O-Ag), that is, the poly-
saccharide part of the bacterial lipopolysaccharide (LPS), the major
surface antigen, and well-known virulence factor.5 Interestingly in
the case of S. flexneri, all serotypes but one share a linear backbone,
decorations (Fig. 1).5 Interestingly, it was recently demonstrated in
the case of S. flexneri serotype 1a, 2a, and 5a, two of which are well
studied in the laboratory,6–9 that LPS glucosylation promotes both
bacterial invasion and survival from the intense inflammatory re-
sponse associated with host innate immunity.10 Clearly, glucosy-
lation affects S. flexneri 5a O-Ag conformation, resulting in
shortened length, crucially impacting on the type III secretion
system exposure at the cell surface, and consequently on bacterial
virulence.10 On the other hand, clinical Shigella infection protects
against subsequent exposure to homologous serotypes, pointing to
the O-Ag as the major target of the host adaptive immunity.11,12 The
key role played by S. flexneri O-Ags in bacterial virulence, resistance
to innate immunity, added to the high resemblance amongst
known S. flexneri O-Ag repeating units, a number of which are
simple regioisomers, associated to the high burden of shigellosis
and broad heterogeneous distribution of S. flexneri isolates en-
couraged us to investigate additional serotype-specific glucosyla-
tion patterns. Herein, focus is on S. flexneri 3a, one of the most
prevalent Shigella serotypes. Interestingly, it was suggested that
a bivalent S. flexneri 2a/S. flexneri 3a vaccine might confer protection
against other serotypes.13 Taking advantage of our experience on S.
flexneri 2a and S. flexneri 5a, we reasoned that probing the role of O-
Ag structure on bacterial properties might be best performed by
use of well-defined synthetic fragments of the O-Ag. In this context,
the following reports on the synthesis of fragments of S. flexneri
serotype X and 3a O-Ags, which are defined by the branched
defined by a tetrasaccharide composed of 3
a-linked
L-rhamnosyl
residues (A, B, C) and a 2-acetamido-2-deoxy-
b-D
-glucopyranosyl
residue (D). Tetrasaccharide ABCD (I) is the basic repeating unit of
* Corresponding author. Tel.: þ33 1 40 61 38 20; fax: þ33 1 45 68 84 04.
E-mail address: laurence.mulard@pasteur.fr (L.A. Mulard).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.08.080

J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
10559
A
B
C
D
2)-α-L-Rhap-(1−>2)-α-L-Rhap-(1−>3)-α-L-Rhap-(1−>3)-β-D-GlcpNAc-(1−>
(I)
E
A
B
C
D
2)-[α-D-Glcp-(1−>3)]-α-L-Rhap-(1−>2)-α-L-Rhap-(1−>3)-α-L-Rhap-(1−>3)-β-D-GlcpNAc-(1−>
(II)
E
A
B
AcC
D
2)-[α-D-Glcp-(1−>3)]-α-L-Rhap-(1−>2)-α-L-Rhap-(1−>3)-[2-OAc]-α-L-Rhap-(1−>3)-β-D-GlcpNAc-(1−>
(III)
Figure 1. Repeating units of the O-Ags of S. flexneri serotypes Y (I), X (II), and 3a (III).
pentasaccharides (E)ABCD (II) and (E)ABAcCD (III),5 respectively
(Fig. 1). Noteworthy, S. flexneri X O-Ag is the non-O-acetylated form
of S. flexneri 3a O-Ag.
OMe
OMe
Me
R1O
O
Me
BnO
O
a
O
O
R1O
O
OH
R1O
BnO
BnO
BnO
R1O
NHR2
O
O
2. Results and discussion
O
OBn
9
OR1
AcO
AcO
AcO
O
OTCA
NHCl3 Ac
10
Following extensive synthetic work and investigation on
S. flexneri Y O-Ag reported by others,14,15 we focused on O-Ag
fragments bearing serotype-specific substitutions.
R3O
OR3
R3O
R2 = Cl3Ac R3 = Ac
2 = Cl3Ac R3 = H
11 R1 = Bn
12 R1 = Bn
13 R1 = Bn
14 R1 = Bn
2 R1 = H
b
c
Di- to pentasaccharides 3 (EA), 4 (D(E)A), 5 (AcCD(E)A), 6
(CD(E)A), 7 (BAcCD(E)A), 8 (BCD(E)A), all bearing rhamnoside A at
their reducing end were synthesized as their propyl glycosides.
Indeed, blocking the reducing end of the oligosaccharide targets in
a form mimicking the natural linkages found in the O-Ag was
thought important. Besides as a general rule, based on our previous
experience in the S. flexneri 2a and 5a series,16,8 all glycosylation
steps relied on the highly efficient trichloroacetimidate (TCA)
chemistry.17 Since this mode of activation requires temporary
masking of the anomeric hydroxyl, all fully protected intermediates
were isolated as their allyl glycoside. This protecting pattern was
selected for three reasons: (i) it is introduced in one high-yielding
R
R2 = H
R2 = Ac
R2 = Ac
R3 = H
R3 = H
R3 = H
Scheme 1. Synthesis of the methyl glycoside 4: (a) cat. TMSOTf, 4 Å MS, CH2Cl2,
ꢀ30 ꢁC/rt, 91%; (b) MeONa, CH2Cl2/MeOH, 89%; (c) (i) Pd/C, H2, HCl, EtOH; (ii) Pd/C,
H2, Et3N, EtOH, 53%.
between 9 and 10 was run in CH2Cl2 to give the fully protected
trisaccharide 11 (91%). NMR analysis (3J1,2 (H-1D)¼8.9 Hz) ascer-
tained the b-stereoselectivity of the coupling. Subsequent trans-
esterification using MeONa in CH2Cl2/MeOH resulted in two
products, one of which was the target triol 12 (89%). The aminotriol
13 issued from concomitant N-deprotection was clearly identified
as a more polar side-product reacting with ninhydrin (ESI-MS:
Fisher glycosylation step on commercially available L-rhamnose, (ii)
it is fully orthogonal to most other conventional protecting groups
used in glycochemistry, in particular O-acetyl, which was thought
to be an essential parameter in the S. flexneri 3a series, and (iii) it is
smoothly converted into propyl upon concomitant Pd/C-mediated
benzyl hydrogenolysis. In addition, in order to ascertain the pos-
sible interference of the propyl aglycon with antibody binding, the
methyl glycoside 2 (D(E)A) was synthesized in complement to di-
saccharide 1 (EA), previously isolated in the course of our study on
S. flexneri 5a (Fig. 2).
C
54H65NO14 952.1084, found m/z 952.4432 [MþH]þ). Although
opening an alternate route to target 2 via acetamide 14, the tri-
chloroacetamide to amine conversion was not investigated further
at this stage. Alternatively, triol 12 was submitted to benzyl
hydrogenolysis, followed by Pd/C-mediated hydrodechlorination
under slightly basic medium,9 as planned, to give 2 in 53% yield
over two steps following HPLC purification. In fact, the present
strategy is an alternative to the existing ones.20,21 Both the glyco-
sylation chemistry and glucosamine N-protection pattern we have
selected differ from those previously reported. Interestingly, both
orders of glycosylation at O-2 and O-3 of rhamnoside A were in-
2.1. Synthesis of trisaccharide 2 (Scheme 1)
The synthetic strategy to methyl glycoside 2 derived from that
developed early on when studying other S. flexneri serotypes. It
relied on the condensation of the known disaccharide acceptor
916 and the known trichloroacetimidate donor 10,18 bearing
a N-trichloroacetyl protecting group, which was previously found
efficient in terms of accessibility, condensation yield, and
deprotection.
vestigated successfully, even though the late 3-O-
suffered from poor stereoselectivity yielding a mixture of tri-
saccharides, which could be separated only in their free form.21 For
that reason, we chose to introduce the -glucosyl residue first.
a-D-glucosylation
a/b
a-D
Interestingly, the yield of acceptor 9 is identical to that previously
reported,20 but the subsequent steps involving the glucosamine
residue offer additional perspectives.
The latter was prepared from
D-glucosamine hydrochloride
according to the alternative protocol we recently disclosed (four
steps, 76% overall yield).19 The TMSOTf-promoted condensation
2.2. Retrosynthetic analysis of propyl glycosides 3, 4, 5, and 6
(Scheme 2)
OMe
Since targets 3, 4, 5, 6, and 8 are simply fragments of target 7, the
retrosynthetic analysis privileging a convergent approach focused
on pentasaccharide 7. More readily available intermediates, not
necessarily compatible with chain elongation, were used to access
shorter targets whenever relevant. Thus, tri- and tetrasaccharides,
4 and 5, 6, respectively, derived from the sequential introduction of
each residue, whereas the synthesis of pentasaccharides 7 and 8
Me
HO
O
O
OH
HO
HO
HO
O
OH
1
Figure 2. Structure of disaccharide 1.

10560
J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
OTCA
OPr
OPr
Me
BnO
O
OTCA
Me
HO
Me
HO
O
O
O
Me
BnO
OAc
O
O
O
O
O
HO
HO
Me
AcO
BnO
O
OAc
17
HO
HO
HO
HO
NHAc
O
NHAc
O
O
O
AcO
OAc
16
OH
OH
OAll
+
+
Me
O
HO
O
HO
O
BnO
HO
O
HO
O
O
O
Me
Me
HO
BnO
HO
BnO
BnO
NHCl3Ac
HO
AcCD(E)A 5
O
O
O
OAc/OH
OAc/OH
OBn
Me
HO
O
CD(E)A
6
O
OH
HO
OH
BAcCD(E)A 7
O
OPr
15
BCD(E)A
8
Me
HO
O
OPr
O
O
OAl
l
HO
Me
O
HO
HO
HO
NHAc
Me
BnO
O
O
O
R2O
R1O
AcO
O
+
OH
O
OH
HO
O
OTCA
NHCl3Ac
HO
HO
OH
BnO
O
BnO
BnO
HO
OH
HO
D(E)A 4
OH
O
10 R1,R2 = Ac, Ac
OBn
(E)A 3
18 R1,R2 = iPr
19
Scheme 2. Retrosynthetic analysis of propyl glycosides 3, 4, 5, 6, 7, and 8.
was through a convergent approach. Analogously to 9 for the
synthesis of 2, disaccharide 19,22 benzylated at all positions but OH-
2A, served as key precursor to the EA moiety involved in all targets.
Relying on our recent study on precursors to 2-N-acetyl-3-O-gly-
when running the condensation in a mixture of Et2O and CH2Cl2.22
The yield of 19 reached 61% when working on larger amounts, such
as 8 g of key diol 20, but could not be increased any further in
contrast to that described by others.29 Lastly, conventional Pd/C-
mediated hydrogenolysis of 19 gave target 3 (83%). Interestingly,
taking advantage of its crystalline form, diol 20 was made readily
available in four steps involving one single crystallization. Overall,
the 78% isolated yield obtained when starting from 20 g of
cosylated-b-D-glucopyranosyl residues, trichloroacetimidate do-
nors 10 and 18,19 both N-trichloroacetylated, served as precursors
to residue D. Trichloroacetimidate 17,23 featuring benzyl groups at
position 3 and 4 and the critical serotype 3a-specific 2-O-acetyl
moiety, which could serve advantageously for anchimeric assis-
tance, was an ideal precursor to residue C involved in targets 5 and
6. Finally, in the absence of any need for chain extension of the
target pentasaccharides 7 and 8, the tetra-O-acetyl rhamnobiose 16
was selected as an appropriate precursor to the BC fragment.
L
-rhamnose compares favorably with the previously reported 46%
obtained following a closely related procedure.28 The improvement
mostly derived from the efficiency of the allylation process. Indeed,
relying on the in situ generation of hydrogen chloride by action of
allyl alcohol on acetyl chloride,30 the allyl
L-rhamnopyranoside was
isolated in 98% yield as a clean 9:1
chromatography.
a/b mixture, following column
2.3. Synthesis of disaccharide 3 (Scheme 3)
Disaccharide 19 was previously used successfully in the course
of our study on S. flexneri 5a oligosaccharides.22 It was synthesized
accordingly. Briefly, crystalline trichloroacetimidate 22, easily
obtained in one step from commercially available 2,3,4,6-tetra-
2.4. Synthesis of trisaccharide 4 (Scheme 3)
The strategy to 4 followed that developed to obtain analogue 2.
Indeed, TMSOTf-promoted condensation of disaccharide acceptor
19 and tri-O-acetyl donor 10 provided intermediate 2319 in an ex-
cellent 92% yield. Subsequent transesterification using catalytic
MeONa in MeOH was carefully controlled to avoid trichloroacetyl
migration, and consequently unwanted N-deprotection. The
resulting triol 24 (94%) was next submitted to conventional hydro-
genolysis and subsequent Pd/C-mediated 2D-trichloroacetamide
reduction into the target acetamide 4 (69%) under slightly basic
conditions.
O-benzyl-
crude allyl
D
-glucopyranose (76%),24,25 was condensed with the
a-L
-rhamnoside acceptor 2126 prepared from diol 2027,28
by conventional regioselective ring-opening of the intermediate
orthoester into the kinetically favored axial acetate. The resulting
85:15 mixture of a- and b-condensation products was best sepa-
rated after transesterification. Under the best conditions used
(TMSOTf, toluene/CH2Cl2), alcohol 19 was isolated in 58% yield from
diol 20, a result which fully supports that previously described
OAll
OAll
OR1
OR1
R2 = Cl3Ac
R4 = Bn
R2 = Cl3Ac
23 R1 = All
R3 = Ac
24 R1 = All
Me
Me
R4O
Me
R2O
c
Me
BnO
b
O
e
O
O
O
BnO
f
O
HO
O
HO
OAc
21
O
OH
OH
R4O
R2O
R4O
R4O
20
R2O
R2O
10
R
R
4 = Bn
2 = Ac
R3 = H
g
NHR2
O
OBn
O
O
O
a
4 R1 = Pr
OR4
OR2
OH
BnO
BnO
R3 = R4 = H
OTCA
19 R1 = All, R2 = Bn
3 R1 = Pr R2 = H
Me
HO
O
d
OBn
R3O
OR3
22
HO
R3O
OH
Scheme 3. Synthesis of the propyl glycosides 3 and 4: (a) (i) AllOH, AcCl; (ii) Me2C(OMe)2, APTS, acetone; (iii) NaH, BnBr, DMF; (iv) 80% aq AcOH, 60 ꢁC, 78%; (b) (i) MeC(OMe)3,
APTS, CH3CN; (ii) 80% aq AcOH; (c) (i) cat. TMSOTf, ꢀ78 ꢁC/rt, toluene/CH2Cl2; (ii) MeONa, MeOH, 50 ꢁC, 61%; (d) Pd/C, H2, AcOH, EtOH, 83%; (e) cat. TMSOTf, 4 Å MS, ꢀ78 ꢁC/rt,
CH2Cl2, 92%; (f) MeONa, MeOH, rt, 94%; (g) (i) Pd/C, H2, HCl, EtOH; (ii) Pd/C, H2, Et3N, EtOH, 69%.

J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
10561
2.5. Synthesis of tetrasaccharides 5 and 6 (Scheme 4)
tetrasaccharide 26 was not observed when reacting 15 and 17 in
this solvent in the presence of a catalytic amount of TMSOTf.
However, to our satisfaction, the target tetrasaccharide 26 and diol
27 were isolated in 58% and 21% yield, respectively, in the absence
of any observed 29, when the condensation between 15 and 17 was
run in toluene (not described). Interestingly, our findings on the
input of this solvent on the stereochemical outcome of the con-
densation support those reported for a closely related mannosyl
trichloroacetimidate donor.36 Besides, none of the regioisomers of
27 was isolated, ensuring that the isopropylidene hydrolysis oc-
curred post coupling. Limiting any exaggerated loss of the acetal
protecting group was the next step. This was best achieved by
maintaining the reaction temperature at ꢀ78 ꢁC to give 26 and 27
in 72% and 5% yield, respectively.
Considering the basic/acidic conditions involved, we reasoned
that the two-step allyl reduction/hydrogenolysis-hydro-
dechlorination process used to convert triol 24 into target 4 was not
appropriate to ensure the transformation of 27 into mono-O-
acetylated 5. Thus, in order to limit the risk of deacetylation at 2C,
Pd/C-mediated benzyl removal, allyl reduction, and concomitant
trichloroacetamide conversion into acetamide were run in the ab-
sence of Et3N at 45 bar under a hydrogen atmosphere. Completion
of the hydrodechlorination step required 10 days, a duration which
was demonstrated to be necessary at the pentasaccharide level (see
below, synthesis of 7). The mono-O-acetylated tetrasaccharide 5
was isolated as a mixture whereby the 2C- and 3C-O-acetyl isomers
(76%) coexisted in a 70:30 equilibrium, based on NMR data. This
result was anticipated, although exceptions do exist.40 Alterna-
tively, treatment of diol 27 in refluxing methanolic sodium meth-
oxide gave triol 28 (85%), which was converted to target 6 (71%) as
described for the preparation of 5.
Taking advantage of the various ways allowing tri-
chloroacetamide to acetamide conversion, the N-acetyl route was
considered as a possible alternative to get 6, possibly facilitating
the final deprotection steps. For that reason, trichloroacetamide
23 was fully deacylated and converted to the acetamidotriol 31
(90%). Thus, taking into account our observations on the input of
CH2Cl2 on the outcome of the deacylation process (see above,
synthesis of 2), the combination of reaction duration, amount of
methanolic sodium methoxide, and CH2Cl2 volume providing the
highest yielding transformation was investigated. Our findings
outlined on this example the crucial importance of the CH2Cl2/
0.5 M methanolic MeONa ratio, which was set to 8:1. Subsequent
4,6-O-isopropylidenation gave the acetamido acceptor 32 (85%).
However, the latter reacted poorly when treated with donor 17
under the successful conditions set up for the trichloroacetamide
The simplest version involved regioselective acetalation of the
available triol 24 into the corresponding 4,6-O-isopropylidene de-
rivative 15 by use of 2-methoxypropene and CSA. However, con-
sidering the yield of the acetalation step (76%), we reasoned that
the regioselective 4,6-O-protection could be introduced at an early
stage. To our utmost satisfaction, coupling of acceptor 19 with the
recently disclosed 4,6-O-isopropylidene glucosamine donor19 18,
prepared from diacetate19 18a (80%), provided the pre-equipped
trisaccharide 2519 in high yield (90%). Selective removal of the
isolated acetate in 25 providing 15 (84%) was best performed using
0.2 equiv of methanolic sodium methoxide. Interestingly, tri-
saccharide 15, having a free hydroxyl at position 3D, proved to be
rather sensitive to slightly acidic media resulting in partial loss of
the isopropylidene acetal, as found out during NMR analysis.
Clearly, 1H NMR investigation suggested the in situ formation of an
equilibrium between acceptor 15 and the resulting triol 24, co-
existing in a 65:35 ratio. Interestingly, identical treatment did not
affect the fully protected precursor 25. Running the two routes to 15
on a 5 g scale allowed their comparison. Both provided 15 in
comparable overall yields starting from 19 (86% over three steps
and 87% over two steps using donor 10 and donor 18, respectively).
Condensation of trisaccharide 15 and the readily available
rhamnosyl trichloroacetimidate 17 required optimization. Running
the condensation in CH2Cl2 allowed the isolation of three products,
among which the fully protected a-linked tetrasaccharide 26 (40%,
1JC,H (C-1C)¼169.1 Hz) and the corresponding diol 27 (22%, JC,H
(C-1C)¼169.8 Hz) due to isopropylidene loss post condensation.
Formation of 27 was ascertained from HMBC-NMR analysis, and
confirmed following 50% aq TFA-mediated acetal removal of 26
(88%), which provided a diol whose spectral characteristics were
identical to that of the above-mentioned 27. Most interestingly,
transesterification of the second side-product, migrating closely to
1
the expected 26, gave tetrasaccharide 30 having a
b-CD inter-
glycosidic linkage (1JC,H (C-1C)¼156.6 Hz). Thus, formation of the
fully protected b-C-linked isomer 29 occurred upon condensation
of 15 and 17 in CH2Cl2 despite the presence of the acetate group at
C-2C thought to ensure -selectivity. The lack of anchimeric assis-
a
tance from 2-O-acetyl groups is not without precedents. Clearly
addressed in various reports,31–36 it may have several origins
whether electronic, steric, or simply reaction conditions.37,38 We
reasoned that the solvent could play a critical role on the conden-
sation outcome. Alternatives were thus investigated. Contrary to
previous successful uses of Et2O as solvent in glycosylation re-
actions involving 17 as donor,39 formation of the expected
OR1
OAll
OAll
Me
R3O
Me
BnO
Me
O
O
O
BnO
O
O
O
O
O
O
R3O
BnO
BnO
b
e
R3O
R3O
OTCA
BnO
BnO
BnO
BnO
19
NHR2
O
NHCl3Ac
O
O
O
NHCl3Ac
O
O
+
OR3
OBn
OBn
O
Me
O
O
O
BnO
R6O
O
O
OR
NHCl3Ac
O
OR
AcO
O
O
BnO
R4O
O
O
OAc
17
Me
18 R = TCA
18a R = Ac
O
R3O
a
R3O
RO
Me
OR5
25 R = Ac
15 R = H
d
c
OBn
OBn
24
R4, R6 = iPr
R4, R6 = H,H
R4, R6 = H,H
R4, R6 = H,H
R4, R6 = H,H
R2 = Cl3Ac R3 = Bn
R5 = Ac
R5 = Ac
R5 = Ac
R5 = H
R5 = H
26 R1 = All
27 R1 = All
5 R1 = Pr
28 R1 = All
6 R1 = Pr
f
g
R
R
R
2 = Cl3Ac R3 = Bn
2 = Ac
R3 = H
2 = Cl3Ac R3 = Bn
R3 = H
29 R = Ac
30 R = H
j
h
i
R2 = Ac
Scheme 4. Synthesis of tetrasaccharides 5 and 6: (a) (i) ethylenediamine/AcOH, THF; (ii) CCl3CN, DBU, ꢀ5 ꢁC, DCE (80%); (b) cat. TMSOTf, 4 Å MS, ꢀ78 ꢁC/rt, CH2Cl2, 90%; (c)
MeONa, MeOH, rt, 84%; (d) H2C]C(OMe)Me, CSA, DMF, 76%; (e) cat. TMSOTf, 4 Å MS, toluene, ꢀ78 ꢁC/rt, 72%; (f) 50% aq TFA, CH2Cl2, 0 ꢁC, 88%; (g) Pd/C, H2, 45 bar, EtOH, 76%; (h)
MeONa, MeOH, 50 ꢁC, 85%; (i) Pd/C, H2, 45 bar, EtOH, 71%; (j) MeONa, MeOH.

10562
J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
OAll
OAll
Me
BnO
Me
BnO
O
O
Me
BnO
O
O
O
O
c
O
a
O
BnO
BnO
23
+
BnO
BnO
BnO
BnO
BnO
OAc
NHAc
O
NHAc
OBn
OBn
O
O
O
OBn
17
OBn
O
Me
AcO
33
O
R2O
OH
OH
O
R1O
31 R1,R2 = H, H
32 R1,R2 = iPr
32
b
Scheme 5. Synthesis and attempted condensation of acceptor 32: (a) MeONa, CH2Cl2/MeOH, 90%; (b) H2C]C(OMe)Me, CSA, DMF, 85%; (c) cat. TMSOTf, 4 Å MS, ꢀ78 ꢁC/rt, CH2Cl2.
analogue 15. Interestingly, in addition to unreacted 32 (46%) and
hydrolyzed donor, disaccharide 33 (22%) resulting from the do-
nor autocondensation was isolated among other products
(
d
¼5.90 ppm) upon treatment of 35 in methanolic K2CO3. Conse-
quently, 35 was deallylated according to the cationic iridium based
two-step process:46 (i) isomerization of the allyl group under ca-
talysis with 1,5-cyclooctadienebis(methyldiphenyl-phosphine)iri-
dium hexafluorophosphate complex, and (ii) subsequent hydrolysis
of the resulting prop-1-enyl ether.47 The resulting hemiacetal 38
(91%) was readily converted into trichloroacetimidate 16 (89%) by
reaction with trichloroacetonitrile in the presence of 1,8-dia-
zabicyclo[5.4.0]undec-7-ene (DBU). Analogously to our observa-
tions at the tetrasaccharide level, TMSOTf-mediated condensation
of trisaccharide 15 and donor 16, run at ꢀ78 ꢁC in toluene, gave the
fully protected 39 (1JC,H (C-1C)¼170.5 Hz) and diol 40 in a 9:1 ratio
(87%), illustrating once more the high efficiency of the coupling
conditions despite the sensitivity of the 4D,6D-O-isopropylidene to
the acidic medium. As above, HMBC NMR analysis of 40 ensured
that the condensation had taken place at OH-3D, an observation
also confirmed upon subsequent re-acetalation. As expected,
treatment of 39 with K2CO3 in methanol provided triol 41 (85%) and
tetraol 42 (7%). The improved 9:1 triol/tetraol ratio obtained at the
pentasaccharide stage, in comparison to the 7:3 ratio seen at the
disaccharide level, most probably reflects the increased steric
hindrance at 2C in 39 versus 35. Acidic hydrolysis of 41 gave pentaol
43 (95%), which was subsequently converted to 2C-O-acetylated
pentasaccharide 7 (75%) upon treatment with Pd/C under 45 bar of
hydrogen for 10 days. Although somewhat unusual, this duration
was required for completion of the trichloroacetamide trans-
formation. Indeed, NMR and mass spectrometry follow-up of the
later indicated a two-step kinetics. Total conversion into the cor-
responding chloroacetamide 44 (ESI-MS MW¼940.3429, found m/z
(Scheme 5, not described). The (b1/a1)-linkage in 33 was
1
ascertained based on the JC,H coupling constants and HMBC
1
NMR analysis (1JC,H (C-1C)¼159.1 Hz, JC,H (C-1C )¼170.0 Hz). We
0
have previously reported the successful condensation of 4-O-
benzyl-2,3-di-O-acetyl-
(2-acetamido-2-deoxy-4,6-O-isopropylidene-
(1/2)-3,4-di-O-benzyl-
-rhamnopyranoside,22 and at this
L-rhamnosyl trichloroacetimidate and allyl
b-D-glucopyranosyl)-
a-L
point we have no clear explanation for the strong difference
observed in the behavior of acceptors 15 and 32. This route was
not investigated any further.
2.6. Synthesis of pentasaccharides 7 and 8 (Scheme 6)
Looking for the simplest precursor to residue B, we reasoned
that in the absence of any requirement for chain elongation at this
residue, we could take advantage of the known resistance of iso-
lated 2-O-acetyl groups to Zemplen deacetylation conditions,41 and
´
therefore consider a regioselective transesterification step in the
final deprotection process. Accordingly, the readily accessible tri-
acetate 3442 was selected as an ideal rhamnosyl donor. TMSOTf-
mediated condensation of 34 with allyl glycoside 21 gave rham-
nobioside 35 (95%).
Preliminary investigation of various conditions allowing the
regioselective transesterification of 35 (Table 1, not described)
supported the use of the latter as precursor to residue B. Indeed,
based on 1H NMR estimation of the 36/37 ratio, triol 36
940.3425, dCH Cl¼4.10 ppm) was observed after
2 days. The
(d
¼2.15 ppm) was obtained as a 7:3 mixture with tetraol 37
2
OAll
a
Me
BnO
O
21
35 R1 = R2 = Ac
36 R1 = Ac R2 = H
37 R1 = R2 = H
c
b
O
OR1
OTCA
Me
R2O
O
Me
AcO
O
R2O
OR2
OR1
AcO
OAc
34
Me
R3O
O
O
O
R4, R6 = iPr
R4, R6 = H,H
R4, R6 = iPr
R4, R6 = iPr
R4, R6 = H,H
R4, R6 = H,H
R4, R6 = H,H
R4, R6 = H,H
R4, R6 = H,H
R
R
R
R
2 = Cl3Ac R3 = Bn
R5 = Ac R7 = Ac
R5 = Ac R7 = Ac
R5 = H
7 = Ac
R5 = H R7 = H
39 R1 = All
40 R1 = All
41 R1 = All
42 R1 = All
43 R1 = All
44 R1 = Pr
7 R1 = Pr
OR
R3O
R3O
R3O
2 = Cl3Ac
R3 = Bn
f
Me
BnO
O
NHR2
O
O
2 = Cl3Ac R3 = Bn
2 = Cl3Ac R3 = Bn
R
OR3
e
O
g
OAc
Me
AcO
R6O
R2 = Cl3Ac R3 = Bn
3 = H
R3 = H
2 = Cl3Ac R3 = Bn
2 = Ac
R3 = H
R
R
5 = H R7 = Ac
5 = H
O
O
R4O
O
15
g
h
R
R2 = ClAc
R7 = Ac
AcO
Me
OAc
R3O
R
R
R
2 = Ac
R5 = H R7 = Ac
R5 = H
7 = H
R5 = H R7 = H
O
R
45 R1 = All
8 R1 = Pr
38 R = H
16 R = TCA
OR7
h
d
Me
R5O
O
R5O
OR5
Scheme 6. Synthesis of pentasaccharides 7 and 8: (a) cat. TMSOTf, 4 Å MS, ꢀ78 ꢁC/rt, CH2Cl2, 95%; (b) K2CO3, MeOH; (c) (i) cat. [Ir(COD){PCH3(C6H5)2}2]þPF6ꢀ, THF, rt; (ii) I2, THF/
H2O, rt, 91%; (d) CCl3CN, DBU, DCE, ꢀ5 ꢁC, 15 min, 89%; (e) cat. TMSOTf, 4 Å MS, ꢀ78 ꢁC, toluene, 15 min, 87%; (f) K2CO3, MeOH, 25 min, 85% 41, 7% 42; (g) 50% aq TFA, CH2Cl2, 0 ꢁC,
95%; (h) Pd/C, H2, 45 bar, EtOH, 75% 7, 71% 8.

J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
10563
Table 1
containing 0.1% formic acid ESI-TOF spectrometer-solution. Melting
points were determined in capillary tubes with an electrothermal
apparatus and are uncorrected. Anhydrous dichloromethane
(CH2Cl2) and 1,2-dichloroethane (DCE) sold on molecular sieves
were used as such. Powder molecular sieves (4 Å) were activated
before use by heating at 250 ꢁC under vacuum. Additional solvents
commonly cited in the text are abbreviated as Chex (Cyclohexane)
and Tol (Toluene).
Regioselective de-O-acetylation of 35 into 36
Entry
Conditions
Temperature/time
Ratio 36/37
141
2
NaOMe/MeOH 0.2 equiv
NaOMe/MeOH 0.2 equiv
NEt3/MeOH/H2O 3.8 equiv
K2CO3/MeOH 1 equiv
K2CO3/MeOH 1 equiv
HBF4/Et2O/MeOH 6.4 equiv
rta/2 h 30 min
0 ꢁC/2 days
0 ꢁC/2 days
rt/15 min
0 ꢁC/1 h 30 min
rt/7 days
60:40
n.d.b
55:45
70:30
65:35
n.d.
343
444
5
645
a
rt: room temperature.
n.d.: not determined.
4.2. Methyl (3,4,6-tri-O-acetyl-2-deoxy-2-trichloroacetamido-
b-D-glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-a-D-
b
glucopyranosyl-(1/3)]-4-O-benzyl-a-L-
rhamnopyranoside (11)
conversion of the later into target 7 was much slower. Interestingly,
the successful Pd/C-mediated trichloroacetamide to acetamide
conversion under medium pressure of hydrogen was reported
previously.48 Finally, tetraol 42 was treated analogously to 43
to give first the hexaol intermediate 45 (95%) and then target 8
(71%).
TMSOTf (14
(321 mg, 406
487
m
L, 81
mmol) was added to a solution of disaccharide
9
mmol) and trichloroacetimidate 10 (314 mg,
m
mol) in CH2Cl2 (2.2 mL) containing 4 Å molecular sieves
(400 mg), stirred at ꢀ30 ꢁC. The reaction mixture allowed to come
back to rt, at which time TLC (Chex/EtOAc, 7:3) showed the com-
3. Conclusion
plete disappearance of acceptor 9. Et3N (500 mL) was added. The
mixture was filtered and concentrated to dryness. Chromatography
of the residue (Chex/EtOAc, 9:1) gave the condensation product 11
(450 mg, 91%). Trisaccharide 11 had Rf¼0.35 (Chex/EtOAc, 7:3); 1H
The high yielding synthesis of seven di- to pentasaccharide
fragments of S. flexneri 3a O-Ag, all bearing residue A at their re-
ducing end and sharing the
a-D-glucosyl-(1/3)-a-L-rhamnosyl
NMR (CDCl3): d 7.41–7.04 (m, 26H, NHNTCA, CHPh), 5.16 (br s, 3H, H-
(EA) serotype-specific branching pattern is disclosed. The efficiency
of the strategy relied on the combined use of (i) the tri-
chloroacetimidate chemistry and its compatibility with the 4,6-O-
isopropylidene moiety provided that glycosylation reactions are
run at ꢀ78 ꢁC to minimize acetal hydrolysis, (ii) toluene as solvent
for the glycosylation reactions, (iii) the allyl aglycone as temporary/
permanent anomeric protection, and (iv) the trichloroacetyl moiety
as the N-protecting pattern of the glucosamine residue D, and its
convenient conversion to the N-acetyl group under Pd-mediated
neutral hydrodechlorination conditions run at 45 bar of hydrogen.
These oligosaccharides represent the first set of tools required to
investigate the fine specificity of S. flexneri 3a O-Ag recognition by
protective antibodies.
1E, 2HBn), 5.05 (s, 2H, HBn), 5.02 (pt, 1H, J3,4¼9.7 Hz, H-4D), 4.81 (dd,
1H, J2,3¼9.5 Hz, H-3D), 4.79 (d, 1H, J1,2¼8.9 Hz, H-1D), 4.76 (d, 1H,
J¼11.0 Hz, HBn), 4.69 (doverlapped, 1H, H-1A), 4.68 (doverlapped, 1H,
H
Bn), 4.55 (d, 2H, J¼11.6 Hz, HBn), 4.45 (d, 1H, J¼11.0 Hz, HBn), 4.29
(d, 1H, J¼11.9 Hz, HBn), 4.20 (m, 1H, H-2D), 4.15–4.03 (m, 5H, H-3A,
H-3E, H-5E, H-6aD, H-6bD), 3.96 (dd, 1H, H-2A), 3.90 (dd, 1H, J1,2¼3.6
Hz, J2,3¼9.7 Hz, H-2E), 3.77 (dd, 1H, J4,5¼10.0 Hz, H-4E), 3.68 (dq, 1H,
J4,5¼9.4 Hz, H-5A), 3.44 (pt, 1H, J3,4¼9.5 Hz, H-4A), 3.38 (m, 2H, H-
6aE, H-6bE), 3.36 (s, 3H, OMe), 2.93 (m, 1H, J5,6a¼2.7 Hz,
J5,6b¼4.2 Hz, H-5D), 2.12, 2.03, 2.02 (3s, 9H, HAc), 1.41 (d, 3H,
J5,6¼6.2 Hz, H-6A); 13C NMR (CDCl3):
d 171.0, 179.5 (3C, CAc), 162.4
(CNTCA), 139.0–127.7 (CPh), 101.3 (C-1D), 100.2 (C-1A), 95.0 (C-1E),
93.1 (CCl3), 83.8 (C-3E), 80.1 (C-4A), 79.4 (C-2E), 79.0 (C-4E), 76.4,
75.6, 75.3 (3C, CBn), 75.0 (C-3A), 74.8 (C-2A), 74.3, 73.8 (2C, CBn), 73.6
(C-3D), 72.0 (C-5D), 70.2 (C-5E), 68.4, 68.3 (2C, C-5A, C-4D), 68.2 (C-
6E), 62.0 (C-6D), 56.0 (C-2D), 54.9 (OMe), 21.1, 21.0 (3C, CAc), 18.3 (C-
6A).
4. Experimental
4.1. General methods
TLC was performed on precoated slides of silica gel 60 F254
(Merck). Detection was effected when applicable, with UV light
and/or by charring in orcinol (35 mM) in 4 N aq sulfuric acid and
ethanol (95:5). Preparative chromatography was performed by
elution from columns of silica gel 60 (particle size 0.040–
0.063 mm). NMR spectra were recorded at 30 ꢁC for solutions in
CDCl3 or D2O (400 MHz for 1H, 100 MHz for 13C). Residual CHCl3
(7.28 ppm for 1H and 77.0 ppm for 13C), and HOD (4.79 ppm) were
used as internal references for solutions in CDCl3 and D2O, re-
spectively. Proton-signal assignments were made by first-order
analysis of the spectra, as well as analysis of 2D 1H–1H correlation
maps (COSY). Of the two magnetically non-equivalent geminal
protons at C-6, the one resonating at lower field is denoted H-6a
and the one at higher field is denoted H-6b. The 13C NMR assign-
ments were supported by 2D 13C–1H correlations maps (HMBC and
HSQC). Interchangeable assignments are marked with an asterisk in
the listing of signal assignments. Sugar residues are serially lettered
according to the lettering of the repeating unit of the S. flexneri 3a
O-SP and identified by a subscript in the listing of signal assign-
ments. Additional abbreviation in the listing of signal assignments
includes NTCA, which stands for trichloroacetamide whereas in the
schemes OTCA stands for trichloroacetimidate. Electrospray Ioni-
zation-Time of flight (ESI-TOF) mass spectra were recorded in the
4.3. Methyl (2-deoxy-2-trichloroacetamido-
glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-
glucopyranosyl-(1/3)]-4-O-benzyl-a-L-
rhamnopyranoside (12)
b-D-
a-D-
A 0.5 M methanolic solution of sodium methoxide (900
mL) was
added to a solution of 11 (358 mg, 292 mol) in MeOH/CH2Cl2 (2:3,
m
6.5 mL). The mixture was stirred at rt over 48 h. TLC showed the
complete disappearance of starting 11 (Chex/EtOAc, 7:3) and the
presence of one major more polar product (CH2Cl2/MeOH, 19:1),
together with a minor one, which reacted when charring with
ninhydrin. Neutralization with Dowex X8-200 ion exchange resin
(Hþ) was followed by filtration and concentration of the filtrate.
Column chromatography of the residue (CH2Cl2/MeOH, 19:1/9:1)
gave 12 (188 mg, 89%). Trichloroacetamide 12 had Rf¼0.34 (CH2Cl2/
MeOH, 19:1); 1H NMR (CDCl3):
d 7.45–7.06 (m, 26H, NHNTCA, CHPh),
5.10 (d, 1H, J1,2¼3.6 Hz, H-1E), 5.08 (d, 1H, J¼11.2 Hz, HBn), 5.03 (d,
1H, HBn), 5.00 (d, 1H, J¼12.2 Hz, HBn), 4.89 (d, 1H, HBn), 4.78 (d, 1H,
J¼11.2 Hz, HBn), 4.77 (br s, 1H, H-1A), 4.73 (d, 1H, J¼10.2 Hz, HBn),
4.68 (d, 1H, J1,2¼8.2 Hz, H-1D), 4.57 (d, 1H, J¼12.0 Hz, HBn), 4.55 (d,
1H, J¼10.4 Hz, HBn), 4.47 (d, 1H, J¼11.1 Hz, HBn), 4.31 (d, 1H,
J¼12.0 Hz, HBn), 4.14–4.07 (m, 3H, H-3A, H-3E, H-5E), 4.03 (dd, 1H,
H-2A), 3.88–3.74 (m, 5H, H-2D, H-6aD, H-6bD, H-2E, H-4E), 3.68 (dq,
1H, J4,5¼9.4 Hz, H-5A), 3.56 (pt, 1H, H-4D), 3.56 (pt, 1H, J3,4¼9.6 Hz,
positive-ion mode using
a 1:1 acetonitrile (CH3CN)/water

10564
J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
H-4A), 3.43 (m, 2H, H-6aE, H-6bE), 3.35 (s, 3H, OMe), 3.02 (m, 1H,
4.6. Allyl (3,4,6-tri-O-acetyl-2-deoxy-2-trichloroacetamido-
b-
J5,6a¼3.1 Hz, J5,6b¼3.4 Hz, J4,5¼9.5 Hz, H-5D), 2.65 (m, 1H, H-3D), 1.41
D
-glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-
a-D-
(d, 3H, J5,6¼6.2 Hz, H-6A); 13C NMR (CDCl3):
d
164.1 (CNTCA), 138.9–
glucopyranosyl-(1/3)]-4-O-benzyl-a-L-rhamno-
pyranoside (23)
127.7 (CPh), 101.3 (C-1D), 100.4 (C-1A), 94.9 (C-1E), 93.0 (CCl3), 83.6
(C-3E), 80.2 (C-4A), 79.4, 79.0 (2C, C-2E, C-4E), 76.5 (CBn), 73.6 (C-3D),
75.7 (2C, C-5D, CBn), 75.3 (2C, CBn), 74.8 (C-3A), 74.2 (C-2A), 73.8
(CBn), 71.3 (C-4D), 70.2 (C-5E), 68.5 (C-5A), 68.3 (C-6E), 62.2 (C-6D),
58.5 (C-2D), 55.0 (OMe),18.3 (C-6A); HRMS (ESIþ) for C56H64Cl3NO18
([MþH]þ, 1096.3419) found m/z 1270.3423 ([MþNH4]þ, 1115.3674)
found m/z 1115.3638.
The side-product, identified as 13, had Rf¼0.2 (CH2Cl2/MeOH,
19:1), HRMS (ESIþ) for C54H65NO14 ([MþH]þ, 952.4483) found m/z
952.4432.
TMSOTf (40 mL, 230 mmol, 0.2 equiv) was added to a solution of
disaccharide 1922 (0.92 g, 1.13 mmol) and trichloroacetimidate 1018
(0.8 g, 1.35 mmol, 1.2 equiv) in CH2Cl2 (24 mL) containing 4 Å mo-
lecular sieves (1 g), stirred at ꢀ78 ꢁC. The reaction mixture was
stirred for 3 h. TLC (Chex/EtOAc, 7:3) showed the complete disap-
pearance of acceptor 19.22 Et3N (1 mL) was added. The mixture was
filtered and concentrated to dryness. Chromatography of the resi-
due (Chex/EtOAc, 8:2/7:3) gave the condensation product 23
(1.3 g, 92%) as a white foam. Trisaccharide 23 had Rf¼0.2 (Chex/
EtOAc, 7:3); 1H NMR (CDCl3):
d 7.40–7.03 (m, 26H, NHNTCA, CHPh),
4.4. Methyl (2-acetamido-2-deoxy-b-D-glucopyranosyl)-(1/
5.88 (m, 1H, CH]), 5.29 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.20 (m, 1H,
Jcis¼10.4 Hz, ]CH2), 5.22–5.16 (m, 3H, H-1E, 2HBn), 5.06 (s, 2H, HBn),
5.01 (pt, 1H, J3,4¼9.7 Hz, H-4D), 4.85 (d, 1H, J1,2¼1.5 Hz, H-1A), 4.86–
4.75 (m, 3H, H-1D, H-3D, HBn), 4.72 (d, 1H, J¼10.1 Hz, HBn), 4.55 (m,
2H, HBn), 4.45 (d, 1H, J¼10.9 Hz, HBn), 4.30 (d, 1H, J¼12.0 Hz, HBn),
4.25–4.12 (m, 4H, H-2D, H-3A, H-3E, HAll), 4.07–3.99 (m, 3H, H-6aD,
H-6bD, H-5E), 3.98–3.90 (m, 2H, H-2A, HAll), 3.91 (dd,1H, J1,2¼3.6 Hz,
H-2E), 3.80 (pt, 1H, J3,4¼9.2 Hz, H-4E), 3.71 (m, 1H, H-5A), 3.45 (pt,
1H, J3,4¼9.8 Hz, H-4A), 3.37 (m, 2H, H-6aE, H-6bE), 2.94 (m, 1H, H-
5D), 2.12, 2.02 (2s, 9H, HAc), 1.40 (d, 3H, J5,6¼6.2 Hz, H-6A); 13C NMR
2)-[ -glucopyranosyl-(1/3)]- -rhamnopyranoside (2)
a
-
D
a-L
A solution of 12 (114 mg, 104
mmol), in 95% EtOH (10 mL) con-
taining 1 M HCl (80 L) was hydrogenated in the presence of Pd/C
m
(80 mg) for 2 h at rt, at which time TLC (i-PrOH/NH3/H2O, 4:1:2)
showed the complete disappearance of the triol. The mixture was
filtered and concentrated. A solution of the residue in 95% EtOH
(10 mL) and Et3N (80
catalyst (80 mg) for 2 h at rt. The mixture was filtered and con-
centrated. RP-HPLC purification of the residue (Kromasil 5 m C18
mL) was hydrogenated in the presence of Pd/C
m
(CDCl3):
d 170.6, 170.5, 169.1 (3C, CAc), 161.9 (CNTCA), 138.5–
100 Å 10ꢂ250 mm column, 215 nm, 0–20% linear gradient over
137.6 (CPh), 133.7 (CH]), 128.9–127.2 (CHPh), 117.2 (]CH2), 100.8
20 min of CH3CN in 0.01 M aq TFA at 1 mL/min flow rate) provided
1
1
(C-1D, JCH¼161.0 Hz), 98.1 (C-1A, JCH¼172.2 Hz), 94.5 (C-1E,
1JCH¼165.5 Hz), 92.7 (CCl3), 83.4 (C-3E), 79.6 (C-4A), 78.9 (C-2E),
78.5 (C-4E), 76.0, 75.1, 74.8 (3C, CBn), 74.6 (C-3A), 74.4 (C-2A), 73.9,
73.3 (2C, CBn), 73.1 (C-3D), 71.6 (C-5D), 69.8 (C-5E), 68.1 (C-5A), 67.9
(CAll), 67.8 (C-4D), 67.7 (C-6E), 61.6 (C-6D), 55.5 (C-2D), 20.7, 20.6,
2 as a freeze-dried powder (30 mg, 53%). 1H NMR (D2O):
d 8.09 (d,
1H, J2,NH¼9.7 Hz, NH), 5.10 (d, 1H, J1,2¼3.1 Hz, H-1E), 4.80 (br sover-
lapped, 1H, H-1A), 4.79 (doverlapped, 1H, J1,2¼7.7 Hz, H-1D), 4.23 (br s,
1H, H-2A), 4.00 (m, 1H, H-5E), 3.88 (br d, 1H, J6a,6b¼12.4 Hz, H-6aE),
3.83 (pt, 1H, H-3A), 3.80 (pt, 1H, H-3E), 3.78–3.61 (m, 7H, H-2D, H-
6aD, H-6bD, H-2E, H-6bE, H-5A), 3.46 (pt, 1H, J3,4¼J4,5¼9.5 Hz, H-4E),
3.40–3.36 (m, 3H, H-3D, H-4D, H-5D), 3.35 (s, 3H, OMe), 3.32 (pt, 1H,
J3,4¼J4,5¼9.6 Hz, H-4A), 2.07 (s, 3H, HAc), 1.26 (d, 3H, J5,6¼6.0 Hz, H-
20.5 (3C,
C
Ac), 17.8 (C-6A); HRMS (ESIþ) for C64H72Cl3NO18
([MþNa]þ, 1270.3713) found m/z 1270.3662, ([MþNH4]þ,
1265.4159) found m/z 1265.4180.
6A); 13C NMR (D2O):
d 174.5 (CAc), 101.9 (C-1D), 99.9 (C-1A), 94.7 (C-
4.7. Allyl (2-deoxy-2-trichloroacetamido-
b-D-
1E), 76.0 (C-4D), 74.3 (C-3D), 74.0 (2C, C-2A, C-3A), 73.1 (C-3E), 71.5
(C-5E), 71.3 (C-2E), 70.9 (C-4A), 69.8 (C-5D), 69.4 (C-4E), 68.8 (C-5A),
60.7 (C-6D), 60.3 (C-6E), 55.7 (C-2D), 54.8 (OMe), 22.7 (CAc), 16.8 (C-
6A). HRMS (ESIþ) for C21H37NO15 ([MþH]þ, 544.2241) found m/z
544.2259.
glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-
a-D-
glucopyranosyl-(1/3)]-4-O-benzyl-a-L-rhamno-
pyranoside (24)
Methanolic MeONa (0.5 M, 0.16 mL, 0.08 mmol, 0.2 equiv) was
added to a solution of 23 (0.5 g, 0.4 mmol) in MeOH (3 mL), and the
mixture was stirred for 30 min. TLC (CH2Cl2/MeOH, 9.5:0.5) showed
the complete disappearance of the triacetate and the presence of
a single more polar product. The mixture was neutralized by ad-
dition of Dowex X8-200 ion exchange resin (Hþ) and filtered.
Evaporation of the filtrate gave a syrup, which was chromato-
graphed (CH2Cl2/MeOH, 99:1/96:4) to give compound 24 (0.42 g,
94%) as a white foam. Triol 24 had Rf¼0.3 (CH2Cl2/MeOH, 7:3); 1H
4.5. Propyl
pyranoside (3)
a-D-glucopyranosyl-(1/3)-a-L-rhamno-
The benzylated disaccharide 19 (500 mg, 0.61 mmol) was dis-
solved in a 9:1 EtOH/acetic acid mixture (24 mL), treated with 10%
Pd/C catalyst (420 mg), and the suspension was stirred at rt for 1
night under a hydrogen atmosphere. At this time, TLC (i-PrOH/H2O/
NH3, 4:1:0.5) showed that 19 had been transformed into a major
polar product. The suspension was filtered on a bed of Celite and
the filtrate was concentrated. Reverse phase chromatography (H2O/
CH3CN, 100:0/70:30) of the residue, followed by freeze-drying,
gave target 3 (187 mg, 83%) as a white foam. Disaccharide 3 had
NMR (CDCl3):
d 7.38–7.06 (m, 26H, NH, CHPh), 5.88 (m, 1H, CH]),
5.29 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.20 (m, 1H, Jcis¼10.4 Hz, ]CH2),
5.10 (d, 1H, J1,2¼3.7 Hz, H-1E), 5.07 (m, 3H, J¼10.0 Hz, HBn), 4.90–
4.87 (m, 2H, H-1A, HBn), 4.79–4.70 (m, 2H, J¼11.0 Hz, HBn), 4.62 (d,
1H, J1,2¼8.3 Hz, H-1D), 4.61–4.46 (m, 3H, J¼11.0 Hz, HBn), 4.30 (d,
1H, J¼12.0 Hz, HBn), 4.17–4.09 (m, 4H, H-3A, H-5E, HAll, H-3E), 4.01
(m, 2H, H-2A, HAll), 3.84–3.78 (m, 5H, H-2E, H-4E, H-2D, H-6aD, H-
6bD), 3.63 (m, 1H, H-5A), 3.51 (pt, H, J3,4¼9.2 Hz, H-4D), 3.44 (m, 3H,
H-4A, H-6aE, H-6bE), 3.01 (m, 2H, H-5D, OH), 2.57 (pt, 1H,
J2,3¼9.6 Hz, H-3D), 2.56 (br s,1H, OH),1.40 (d, 3H, J5,6¼6.2 Hz, H-6A);
Rf¼0.6 (i-PrOH/H2O/NH3, 7:1:2);
d d 5.03 (d, 1H,
1H NMR (D2O):
J1,2¼3.8 Hz, H-1E), 4.81 (d, 1H, J1,2¼1.6 Hz, H-1A), 4.10 (dd, 1H,
J2,3¼2.2 Hz, H-2A), 3.92 (m, 1H, H-5E), 3.80–3.70 (m, 5H, H-3A, H-3E,
H-6aE, H-6bE, H-5A), 3.62 (m, 1H, HPr), 3.56–3.45 (m, 3H, H-2E, H-4A,
HPr), 3.42 (pt, 1H, J3,4¼9.3 Hz, H-4E), 1.63 (m, 2H, CH2), 1.27 (d, 3H,
J5,6¼6.2 Hz, H-6A), 0.88 (t, 3H, J¼7.4 Hz, CH3); 13C NMR (D2O):
d
99.6
13C NMR (CDCl3):
d 164.4 (CNTCA), 138.9–137.8 (CPh), 129.5 (CH]),
1
1
(C-1A, JCH¼170.2 Hz), 95.9 (C-1E, JCH¼172.7 Hz), 76.1 (C-3A), 73.3
(C-3E), 72.1 (C-5E), 71.8 (C-2E), 70.7 (C-4A), 70.0 (CPr), 69.8 (C-4E),
69.0 (C-5A), 67.3 (C-2A), 60.7 (C-6E), 22.4 (CH2), 17.1 (C-6A), 10.3
(CH3); HRMS (ESIþ) for C15H28NO10 ([MþNa]þ, 391.1580) found m/z
391.1556.
129.1–127.7 (CHPh), 117.7 (]CH2), 101.3 (C-1D, 1JCH¼160.3 Hz), 98.6
1
1
(C-1A, JCH¼171.6 Hz), 94.8 (C-1E, JCH¼166.4 Hz), 92.9 (CCl3), 83.6
(C-3E), 80.2 (C-4A), 79.5, 79.0 (2C, C-2E, C-4E), 76.6 (CBn), 76.0 (C-3D),
75.6 (CBn), 75.5 (C-5D), 75.4, 75.3 (2C, CBn), 74.8 (C-3A), 74.6 (C-2A),
73.8 (CBn), 71.6 (C-4D), 70.3 (C-5E), 68.7 (C-5A), 68.3 (CAll), 66.2 (C-

J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
10565
6E), 62.4 (C-6D), 58.6 (C-2D), 18.3 (C-6A); HRMS (ESIþ) for
Camphorsulfonic acid (CSA, 24 g, 103 mmol) was added to
a suspension of the crude trichloroacetamide (54 mmol) in a mix-
ture of DMF (185 mL) and 2-methoxypropene (10.3 mL, 108 mmol,
2 equiv), and the suspension was stirred at rt. After 2 h, the formed
methanol was evaporated under reduced pressure, and more
2-methoxypropene (2 mL, 21.6 mmol, 0.4 equiv) was added. After
1 h, TLC (DCM/MeOH, 8:2 and Chex/EtOAc, 1:1) showed the pres-
ence of a less polar product. Et3N (2 mL) was added and volatiles
were evaporated to give the corresponding 2-deoxy-4,6-O-iso-
C
58H66Cl3NO15 ([MþNa]þ, 1144.3396) found m/z 1144.3389,
([MþNH4]þ, 1139.3842) found m/z 1139.3890.
4.8. Propyl (2-acetamido-2-deoxy-b-D-glucopyranosyl)-(1/
2)-[ -glucopyranosyl-(1/3)]- -rhamnopyranoside (4)
a
-D
a-L
The benzylated trisaccharide 24 (412 mg, 0.36 mmol) was dis-
solved in 95% EtOH (30 mL) containing 1 M aq HCl (200 L), treated
m
propylidene-2-trichloroacetamido-a/b-D-glucopyranose as a crude
with 10% Pd/C catalyst (280 mg), and the suspension was stirred at
rt for 1 night under a hydrogen atmosphere. At this time, TLC (i-
PrOH/H2O/NH3, 4:1:0.5) showed that 24 had been transformed into
a major polar product. The suspension was filtered on a bed of
Celite and the filtrate was concentrated. A solution of the residue in
yellow foam (30 g). The
NMR (DMSO-d6):
a
anomer had Rf¼0.3 (Chex/EtOAc, 1:1); 1H
d
8.37 (d, 1H, JNH,2¼7.8 Hz, NHNTCA), 6.88 (d, 1H,
J1,2¼3.9 Hz, H-1), 5.0 (m, 2H, OH), 3.77 (m, 1H, H-3), 3.71–3.65 (m,
4H, H-2, H-5, H-6a, H-6b), 3.50 (m, 1H, H-4), 1.44 (s, 3H, Hi-Pr), 1.25
(s, 3H, Hi-Pr); 13C NMR (DMSO-d6):
d 162.4 (CNTCA), 99.9 (Ci-Pr), 93.3
EtOH (30 mL) and Et3N (153 mL, 1.1 mmol, 3 equiv) was treated with
(CCl3), 91.2 (C-1, 1JCH¼168.2 Hz), 75.0 (C-4), 67.5 (C-3), 63.9 (C-5),
10% Pd/C catalyst (280 mg), and the suspension was stirred at rt for
1 night under a hydrogen atmosphere. TLC (i-PrOH/H2O/NH3,
4:1:0.5) showed that the intermediate trichloroacetamide had been
transformed into a major polar product. The suspension was fil-
tered on a bed of Celite and the filtrate was concentrated. Reverse
phase chromatography (H2O/CH3CN, 100:0/70:30) of the residue,
followed by freeze-drying, gave target 4 (144 mg, 69%) as a white
62.3 (C-6), 58.0 (C-2), 29.8 (Ci-Pr), 21.6 (Ci-Pr); HRMS (ESIþ) for
C
11H16NO6Cl3 ([MþNa]þ, 385.9941) found m/z 385.9962.
Acetic anhydride (100 mL) was added dropwise to a solution
of the crude 4,6-O-isopropylidene acetal (30.0 g, from 54 mmol of
-glucosamine) in anhydrous pyridine (100 mL) stirred at 0 ꢁC.
D
After overnight stirring at rt, TLC (Chex/EtOAc, 1:1) showed the
presence of two less polar products. Volatiles were eliminated by
repeated coevaporation with toluene under reduced pressure. The
residue was purified by column chromatography (Chex/EtOAc,
foam. Trisaccharide 4 had Rf¼0.45 (i-PrOH/H2O/NH3, 7:1:2);
d
1H
5.10 (d, 1H, J1,2¼3.7 Hz, H-1E), 4.89 (d, 1H, J1,2¼1.8 Hz,
NMR (D2O):
d
H-1A), 4.79 (d, 1H, J1,2¼8.5 Hz, H-1D), 4.23 (dd, 1H, J2,3¼2.3 Hz, H-
2A), 4.01 (m, 1H, H-5E), 3.89–3.86 (m, 2H, H-3A, H-6aD), 3.80 (pt, 1H,
J3,4¼9.7 Hz, H-3E), 3.78–3.64 (m, 6H, H-6bD, H-6aE, H-6bE, H-2D, H-
2E, H-5A), 3.60 (m, 1H, HPr), 3.50–3.44 (m, 2H, H-4E, HPr), 3.42–3.38
(m, 3H, H-5D, H-3D, H-4D), 3.32–3.34 (pt, 1H, J3,4¼9.7 Hz, H-4A), 2.10
(s, 3H, HAc), 1.57 (m, 2H, CH2), 1.24 (d, 3H, J5,6¼6.2 Hz, H-6A),
8:2/7.5:2.5) to give a 1:1 inseparable mixture of
(17.0 g, 70%) as a white solid. The
anomer had Rf¼0.7 (Chex/EtOAc,
1:1); 1H NMR (CDCl3):
a/b anomers 18a
a
d
7.01 (d, 1H, JNH,2¼8.4 Hz, NH), 6.23 (d, 1H,
J1,2¼3.9 Hz, H-1), 5.30 (pt, 1H, J2,3¼J3,4¼9.5 Hz, H-3), 4.28 (ddd, 1H,
H-2), 3.93–3.83 (m, 2H, H-4, H-6a), 3.79–3.74 (m, 2H, H-5, H-6b),
2.16, 2.09 (2s, 6H, HAc), 1.51 (s, 3H, Hi-Pr), 1.39 (s, 3H, Hi-Pr); 13C NMR
0.87 (t, 3H, J¼7.4 Hz, CH3); 13C NMR (D2O):
d 174.8 (CNAc), 102.3
(CDCl3):
d 172.2, 169.4 (2C, CAc), 162.4 (CNTCA), 100.4 (Ci-Pr), 92.2
1
1
(C-1D, JCH¼163.4 Hz), 99.6 (C-1A, JCH¼171.3 Hz), 95.1 (C-1E,
1JCH¼169.5 Hz), 76.3 (C-4D), 74.6 (2C, C-2A, C-3D), 74.5 (C-3A), 73.5
(C-3E), 71.8 (C-5E), 71.7 (C-2E), 71.3 (C-4A), 70.2 (C5-D), 70.0 (CPr),
69.8 (C-4E), 69.3 (C-5A), 61.0 (C-6D), 60.7 (C-6E), 56.0 (C-2D), 23.0
(CNAc), 22.4 (CH2), 17.1 (C-6A), 10.3 (CH3); HRMS (ESIþ) for
(CCl3), 90.5 (C-1, 1JCH¼178.6 Hz), 71.8 (C-4), 70.0 (C-3), 66.4 (C-5),
62.2 (C-6), 53.8 (C-2), 29.2 (Ci-Pr), 21.2, 21.1 (2C, CAc), 19.4 (Ci-Pr). The
b
anomer had Rf¼0.75 (Chex/EtOAc, 1:1); mp¼207 ꢁC (Chex/
EtOAc); 1H NMR (CDCl3):
d
7.03 (d, 1H, JNH,2¼9.7 Hz, NHNTCA), 5.78
(d, 1H, J1,2¼8.7 Hz, H-1), 5.24 (pt, 1H, J2,3¼J3,4¼9.6 Hz, H-3), 4.25 (m,
1H, H-2), 4.01 (m, 1H, H-6a), 3.88–3.83 (m, 2H, H-4, H-6b), 3.55 (m,
1H, H-5), 2.11 (s, 3H, HAc), 2.09 (s, 3H, HAc), 1.52 (s, 3H, Hi-Pr), 1.45 (s,
C
23H41NO15 ([MþNa]þ, 594.2374) found m/z 594.2379.
4.9. 1,3-Di-O-acetyl-2-deoxy-4,6-O-isopropylidene-2-
trichloroacetamido- -glucopyranose (18a)
3H, Hi-Pr); 13C NMR (CDCl3)
d 171.8, 169.5 (2C, CAc), 162.8 (CNTCA),
a
/b-
D
100.5 (Ci-Pr), 93.2 (C-1), 92.2 (CCl3), 71.6 (C-4), 71.3 (C-3), 69.1 (C-5),
62.1 (C-6), 55.9 (C-2), 30.1 (Ci-Pr), 21.2, 21.1 (2C, CAc), 19.3 (Ci-Pr);
HRMS (ESIþ) for C15H20NO8Cl3 ([MþNa]þ, 470.0152) found m/z
470.0123.
Methanolic NaOMe (25%, 16.1 mL, 58.1 mmol, 2.5 equiv) was
slowly added to a solution of -glucosamine hydrochloride (5.0 g,
D
23.2 mmol) in methanol (100 mL) stirred at 0 ꢁC. After 10 min,
trichloroacetic anhydride (6.4 mL, 34.9 mmol, 1.5 equiv) was added
dropwise. The mixture was stirred at this temperature for 1 h,
when TLC (i-PrOH/H2O/NH3, 4:1:0.5) showed the complete disap-
pearance of the starting material and the presence of a single less
polar product. The mixture was carefully neutralized by addition of
Dowex X8-200 ion exchange resin (Hþ) and filtered. Evaporation of
4.10. 3-O-Acetyl-2-deoxy-4,6-O-isopropylidene-2-
trichloroacetamido-a/b-D-glucopyranosyl
trichloroacetimidate (18)
Glacial acetic acid (840
mL, 14.5 mmol, 1.4 equiv) was added
dropwise to a solution of ethylenediamine (920
m
L, 12.5 mmol,
the filtrate gave crude 2-deoxy-2-trichloroacetamido-
D
-glu-
1.2 equiv) in THF (200 mL), resulting in the immediate formation of
a precipitate, which remained until aqueous work-up. Diacetate
18a (4.65 g, 10.4 mmol) was added and the mixture was stirred at rt
for 24 h. TLC (CH2Cl2/MeOH, 95:5 and Chex/EtOAc, 1:1) showed the
complete disappearance of the starting materials and the presence
of a more polar product. The reaction mixture was diluted with
water and EtOAc, then washed with saturated aq NaHCO3, saturated
aq NaCl, and finally water. The organic layer was dried on Na2SO4,
filtered, and concentrated under reduced pressure. Crude 3-
copyranose18 as a foam. The trichloroacetamide, isolated as a 60:40
a
/
b
mixture, had Rf¼0.6 (i-PrOH/H2O/NH3, 4:1:0.5); 1H NMR
(DMSO-d6):
d
8.59 (d, 1H, JNH,2¼8.5 Hz, NHNTCAb), 8.13 (br s, 1H,
NHNTCAa), 5.06 (d, 1H, J1,2¼3.5 Hz, H-1a), 4.99 (br s, 1H, OH-4a), 4.95
(br s, 1H, OH-4b), 4.90 (br s, 1H, OH-2a), 4.82 (br s, 1H, OH-3a), 4.65
(d, 1H, J1,2¼7.6 Hz, H-1b), 4.50 (br s, 1H, OH-6b), 4.43 (br s, 1H, OH-
6a), 3.73 (m, 1H, H-3a), 3.68 (m, 1H, H-6ab), 3.64 (m, 1H, H-6a), 3.61
(m, 1H, H-5a), 3.56 (m, 1H, H-2a), 3.53 (m, 1H, H-6ba), 3.50 (m, 1H,
H-5b), 3.46 (m, 1H, H-6bb), 3.41 (m, 1H, H-2b), 3.18 (m, 2H, H-3, H-
O-acetyl-2-deoxy-4,6-O-isopropylidene-2-trichloroacetamido-a/b-
4b), 3.16 (pt, 1H, J3,4¼8.6 Hz, H-4a); 13C NMR (DMSO-d6):
d
162.3
D-glucopyranose was directly engaged in the next step without
(CNTCAa), 162.1 (CNTCAb), 95.4 (C-1b, 1JCH¼157.0 Hz), 94.3 (CCl3b), 93.5
(CCl3a), 90.5 (C-1a, 1JCH¼167.4 Hz), 77.7 (C-4b), 74.2 (C-5b), 73.1 (C-
5a), 72.0 (C-3b), 71.6 (C-4a), 70.7 (C-3a), 62.0 (C-6b), 61.8 (C-6a), 59.9
(C-2b), 57.8 (C-2a).
purification (4.2 g). Relying on an analytical sample, the
a
anomer
had Rf¼0.5 (Chex/EtOAc, 1:1); 1H NMR (CDCl3):
d 7.11 (d, 1H,
JNH,2¼8.9 Hz, NHNTCA), 5.37–5.34 (m, 2H, H-1, H-3), 4.20 (ddd, 1H,
J1,2¼3.7 Hz, J2,3¼9.5 Hz, J2,OH¼1.8 Hz, H-2), 4.02 (ddd, 1H, H-5), 3.91

10566
J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
(dd, 1H, J5,6a¼5.2 Hz, J6a,6b¼10.6 Hz, H-6a), 3.86–3.77 (m, 2H,
J3,4¼10.6 Hz, H-4, H-6b), 2.09 (s, 3H, HAc), 1.53 (s, 3H, Hi-Pr), 1.45 (s,
and 2-methoxypropene (85 mL, 0.89 mmol, 2 equiv). After stirring
for 2 h at rt, TLC (Chex/EtOAc, 1:1 and CH2Cl2/MeOH, 9.6:0.4)
showed the complete disappearance of the starting material and
the presence of a less polar product. Et3N (0.2 mL) was added and
the reaction mixture was concentrated to dryness. Chromatography
of the residue (Chex/EtOAc, 9:1/1:1) gave 15 (0.39 g, 76%) as
a white foam.
3H, Hi-Pr); 13C NMR (CDCl3):
d 171.8 (CAc), 162.5 (CNTCA), 100.4 (Ci-Pr),
92.4 (CCl3), 92.1 (C-1, 1JCH¼173.5 Hz), 72.0 (C-4), 70.2 (C-3), 64.3 (C-
5), 62.6 (C-6), 55.3 (C-2), 29.3 (Ci-Pr), 21.3 (CAc), 19.4 (Ci-Pr); HRMS
(ESIþ) for C13H18Cl3NO7 ([MþNa]þ, 428.0047) found m/z 428.0048.
The crude hemiacetal (4.2 g, 10.4 mmol) was dissolved in DCE
(30 mL), placed under argon, and cooled at ꢀ5 ꢁC. Tri-
chloroacetonitrile (4.5 mL, 44.6 mmol, 4.3 equiv) and then DBU
Alternatively, starting from acceptor 1922 (1.5 g, 1.83 mmol)
and donor 1018 (1.31 g, 2.19 mmol), the condensation, trans-
esterification, and acetalation steps were run without any in-
termediate purification. Column chromatography (Chex/EtOAc,
9:1/1:1) of the residue gave the expected 15 (1.8 g, 86%) over three
steps.
(434 mL, 2.9 mmol, 0.28 equiv) were added. The mixture was stirred
at ꢀ5 ꢁC for 10 min. TLC (Chex/EtOAc, 7:3) showed the complete
disappearance of the hemiacetal and the presence of a single less
polar product. Direct chromatography (Chex/EtOAc, 7:3) gave do-
nor 18 (4.6 g, 80%) as a white foam. The
a
anomer had Rf¼0.5 (Chex/
Route b. 0.5 M MeONa (108 mL, 54 mmol, 0.2 equiv) was added to
EtOAc, 7:3); 1H NMR (CDCl3):
d
8.78 (s, 1H, ]NH), 7.10 (d, 1H,
a solution of compound 25 (328 mg, 0.27 mmol) in MeOH (5 mL),
and the mixture was stirred for 4 h. TLC (Chex/EtOAc, 1:1 and Chex/
EtOAc, 7:3) showed the complete disappearance of the starting
material and the presence of a single more polar product. The
mixture was neutralized by addition of Dowex X8-200 ion
exchange resin (Hþ) and filtered. Evaporation of the filtrate gave a
syrup, which was chromatographed (Chex/EtOAcþNEt3, 7:3/6:4)
to give 15 (241 mg, 76%) as a white foam.
JNH,2¼8.5 Hz, NHNTCA), 6.45 (d, 1H, J1,2¼3.7 Hz, H-1), 5.40 (pt, 1H,
J2,3¼9.2 Hz, H-3), 4.39 (m, 1H, H-2), 3.98–3.91 (m, 3H, H-4, H-5, H-
6a), 3.81 (m,1H, H-6b), 2.11 (s, 3H, HAc),1.54 (s, 3H, Hi-Pr),1.43 (s, 3H,
H
i-Pr); 13C NMR (CDCl3):
d 171.9 (CAc), 162.5 (CNTCA), 160.7 (C]NH),
100.5 (Ci-Pr), 94.7 (C-1, 1JCH¼180.1 Hz), 92.2, 91.0 (2C, 2CCl3), 71.4 (C-
4), 69.9 (C-3), 67.0 (C-5), 62.3 (C-6), 55.0 (C-2), 29.3 (Ci-Pr), 21.2
(CAc), 19.4 (Ci-Pr).
Alternatively, starting from acceptor 1922 (3.65 g, 4.5 mmol)
and donor 18 (3.5 g, 6.3 mmol), the condensation and trans-
esterification steps were run without any intermediate purifica-
tion. Column chromatography (Chex/EtOAc, 9:1/1:1) of the
residue gave the expected 15 (4.5 g, 87%) over two steps. Acceptor
4.11. Allyl (3-O-acetyl-2-deoxy-4,6-O-isopropylidene-2-
trichloroacetamido-
tetra-O-benzyl- -glucopyranosyl-(1/3)]-4-O-benzyl-
rhamnopyranoside (25)
b-D-glucopyranosyl)-(1/2)-[2,3,4,6-
a
-D
a-L-
15 had Rf¼0.45 (Chex/EtOAc, 6:4); 1H NMR (CDCl3):
d 7.42–7.08
TMSOTf (59
mL, 330
mmol, 0.3 equiv) was added to a solution of
(m, 26H, NH, CHPh), 5.89 (m, 1H, CH]), 5.29 (m, 1H,
Jtrans¼15.6 Hz, ]CH2), 5.21 (m, 1H, Jcis¼10.4 Hz, ]CH2), 5.10 (d,
1H, J1,2¼3.6 Hz, H-1E), 5.15–4.91 (m, 3H, HBn), 4.90 (d, 1H,
disaccharide 1922 (0.90 g, 1.1 mmol) and donor 18 (0.85 g, 1.5 mmol,
1.4 equiv) in CH2Cl2 (10 mL) containing 4 Å MS (0.9 g), stirred at
ꢀ78 ꢁC. The reaction mixture was stirred for 3 h. TLC (Chex/EtOAc,
7:3) showed the complete disappearance of acceptor 19.22 Et3N
(1 mL) was added. The mixture was filtered and concentrated to
dryness. Chromatography of the residue (Chex/EtOAc, 8:2/7:3)
gave the glycosylation product 25 (1.2 g, 90%) as a white foam.
Trisaccharide 25 had Rf¼0.35 (Chex/EtOAc, 7:3); 1H NMR (CDCl3):
J¼12.1 Hz,
HBn), 4.82–4.79 (m, 2H, H-1A, HBn), 4.74 (d, 1H,
J¼10.0 Hz, HBn), 4.62–4.49 (m, 4H, HBn, H-1D, 2HBn), 4.34 (d, 1H,
J¼10.9 Hz, HBn), 4.18–4.11 (m, 4H, H-3A, H-5E, HAll, H-3E), 4.02 (br
s, 1H, H-2A), 4.01 (m, 1H, HAll), 3.91–3.82 (m, 4H, H-2E, H-4E, H-2D,
H-6aD), 3.76–3.71 (m, 2H, H-6bD, H-5A), 3.51–3.42 (m, 4H, H-4A,
H-6aE, H-6bE, H-4D), 2.84 (m, 2H, H-5D, OH), 2.48 (pt, 1H,
J2,3¼9.4 Hz, H-3D), 1.51 (s, 3H, Hi-Pr), 1.50 (s, 3H, Hi-Pr), 1.40 (d, 3H,
d
7.42–7.04 (m, 26H, NHNTCA, CHPh), 5.89 (m, 1H, CH]), 5.28 (m, 1H,
Jtrans¼17.2 Hz, ]CH2), 5.19 (m, 1H, Jcis¼10.4 Hz, ]CH2), 5.13–5.10
(m, 3H, J1,2¼3.3 Hz, 2HBn, H-1E), 5.04 (d, 2H, HBn), 4.79–4.74 (m, 3H,
H-3D, H-1A, HBn), 4.71 (m, 2H, H-1D, HBn), 4.58–4.51 (m, 2H, HBn),
4.45 (d, 1H, J¼10.9 Hz, HBn), 4.29 (d, 1H, J¼12.0 Hz, HBn), 4.18–4.10
(m, 4H, H-3A, H-3E, HAll, H-2D), 4.07 (m, 1H, H-5E), 3.97 (br s, 1H, H-
2A), 3.94 (m, 1H, HAll), 3.91–3.83 (m, 2H, H-2E, H-6aD), 3.78 (pt, 1H,
J3,4¼9.4 Hz, H-4E), 3.75–3.64 (m, 3H, H-6bD, H-5A, H-4D), 3.43 (pt,
1H, J3,4¼9.6 Hz, H-4A), 3.41 (m, 2H, H-6aE, H-6bE), 2.71 (m, 1H, H-
5D), 2.07 (s, 3H, HAc), 1.45 (s, 3H, Hi-Pr), 1.40 (s, 3H, Hi-Pr), 1.39 (d, 3H,
J5,6¼6.2 Hz, H-6A); 13C NMR (CDCl3):
d 164.1 (CNTCA), 138.8–137.8
(CPh), 134.2 (CH]), 129.3–127.7 (CHPh), 117.6 (]CH2), 101.5 (C-1D,
1JCH¼163.6 Hz), 100.1 (Ci-Pr), 98.7 (C-1A, 1JCH¼174.0 Hz), 94.5 (C-1E,
1JCH¼167.5 Hz), 92.9 (CCl3), 83.6 (C-3E), 80.2 (C-4A), 80.1 (C-2E),
79.1 (C-4E), 76.6, 75.8, 75.7, 75.3 (4C, CBn), 74.7 (C-3A), 74.4 (C-4D),
74.0 (C-2A), 73.8 (CBn), 73.4 (C-3D), 70.2 (C-5E), 68.7 (C-5A), 68.2
(2C, CAll, C-6E), 67.4 (C-5D), 62.3 (C-6D), 59.1 (C-2D), 27.3 (Ci-Pr),
19.3 (Ci-Pr), 18.3 (C-6A); HRMS (ESIþ) for C61H70Cl3NO15 ([MþNa]þ,
1184.3709) found m/z 1184.3669, ([MþNH4]þ, 1179.4155) found m/
z 1179.4165.
J5,6¼6.2 Hz, H-6A); 13C NMR (CDCl3):
d 171.2 (CAc), 162.5 (CNTCA),
138.8–137.8 (CPh), 134.1 (CH]), 129.5–127.7 (CHPh), 117.6 (]CH2),
101.8 (C-1D, 1JCH¼164.4 Hz), 100.1 (Ci-Pr), 98.7 (C-1A, 1JCH¼173.7 Hz),
94.9 (C-1E, 1JCH¼168.6 Hz), 93.1 (CCl3), 83.8 (C-3E), 80.1 (C-4A), 78.9
(2C, C-2E, C-4E), 76.5, 75.5, 75.3 (3C, CBn), 74.7 (C-3A), 74.6 (C-2A),
74.4, 73.8 (2C, CBn), 72.8 (C-3D), 71.5 (C-4D), 70.1 (C-5E), 68.6 (C-5A),
68.2 (2C, CAll, C-6E), 67.6 (C-5D), 62.4 (C-6D), 56.8 (C-2D), 29.4 (Ci-Pr),
21.3 (CAc), 19.3 (Ci-Pr), 18.3 (C-6A); HRMS (ESIþ) for C63H72Cl3NO16
([MþNa]þ, 1226.3814) found m/z 1226.3860, ([MþNH4]þ,
1221.4260) found m/z 1221.4227, ([MþK]þ, 1242.3553) found m/z
1242.3586.
4.13. Allyl (2-O-acetyl-3,4-di-O-benzyl-
rhamnopyranosyl)-(1/3)-(2-deoxy-4,6-O-isopropylidene-2-
trichloroacetamido- -glucopyranosyl)-(1/2)-[2,3,4,6-
tetra-O-benzyl- -glucopyranosyl-(1/3)]-4-O-benzyl-
rhamnopyranoside (26)
a-L-
b-D
a-
D
a-L-
TMSOTf (24 mL, 131 mmol, 0.3 equiv) was added to a solution of
15 (0.51 g, 0.44 mmol) and trichloroacetimidate 1739 (0.35 g,
0.66 mmol, 1.5 equiv) in toluene (11 mL) containing 4 Å MS
(0.9 g), stirred at ꢀ78 ꢁC. The reaction mixture was stirred for
30 min at ꢀ78 ꢁC. TLC (Chex/EtOAc, 7.5:2.5 and Chex/EtOAc, 6:4)
showed the complete disappearance of the starting materials and
the presence of a major more polar product. Et3N (1 mL) was
added and the mixture was filtered, and concentrated to dryness.
Chromatography of the residue (Chex/EtOAc, 6.5:3.5/1:1) gave
firstly fully protected 26 (480 mg, 72%) as a white foam and next,
diol 27 (33 mg, 5%). The former, 26, had Rf¼0.7 (Chex/EtOAc, 6:4);
4.12. Allyl (2-deoxy-4,6-O-isopropylidene-2-
trichloroacetamido-b-D-glucopyranosyl)-(1/2)-[2,3,4,6-
tetra-O-benzyl- -glucopyranosyl-(1/3)]-4-O-benzyl-a-L-
a
-D
rhamnopyranoside (15)
Route a. CSA (10 mg, 23 mmol, 0.1 equiv) was added to a sus-
pension of triol 24 (0.5 g, 0.45 mmol) in a mixture of DMF (3 mL)

J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
10567
1H NMR (CDCl3):
d
7.45–7.10 (m, 35H, CHPh), 6.98 (d, 1H,
4.15. Allyl (3,4-di-O-benzyl-
deoxy-2-trichloroacetamido-
[2,3,4,6-tetra-O-benzyl- -glucopyranosyl-(1/3)]-4-O-
benzyl- -rhamnopyranoside (28)
a
-
L
-rhamnopyranosyl)-(1/3)-(2-
JNH,2¼8.6 Hz, NH), 5.92 (m, 1H, CH]), 5.37 (m, 1H, H-2C), 5.29 (m,
1H, Jtrans¼16.9 Hz, ]CH2), 5.21 (m, 1H, Jcis¼10.6 Hz, ]CH2), 5.17
(d, 1H, J1,2¼3.6 Hz, H-1E), 5.05–4.90 (m, 3H, HBn), 4.83–4.69 (m,
6H, H-1C, 2HBn, H-1A, 2HBn), 4.64–4.50 (m, 7H, 3HBn, H-1D, 3HBn),
4.34 (d, 1H, J¼12.0 Hz, HBn), 4.17–4.14 (m, 3H, H-3E, HAll, H-3A),
4.12–4.03 (m, 3H, H-5E, H-5C, H-2D), 4.00 (br s, 1H, H-2A), 3.99–
3.89 (m, 2H, HAll, H-3C), 3.90–3.86 (m, 2H, H-2E, H-6aD), 3.84 (pt,
1H, J3,4¼9.8 Hz, H-4E), 3.74–3.69 (m, 2H, H-6bD, H-5A), 3.50 (pt,
1H, J3,4¼9.4 Hz, H-4D), 3.49–3.41 (m, 3H, H-4A, H-6aE, H-6bE), 3.40
(pt, 1H, J3,4¼9.5 Hz, H-4C), 2.84–2.76 (m, 2H, H-5D, H-3D), 2.16
b-D-glucopyranosyl)-(1/2)-
a-D
a-L
MeONa (0.5 M, 102
lution of compound 27 (69 mg, 46.2
m
L, 50.8
m
mol, 1.1 equiv) was added to a so-
mol) in MeOH (3 mL), and the
m
mixture was stirred for 2 h at 50 ꢁC. TLC (Chex/EtOAc, 6:4) showed
the complete disappearance of the starting material and the pres-
ence of a single more polar product. The mixture was neutralized by
addition of Dowex X8-200 ion exchange resin (Hþ) and filtered.
Evaporation of the filtrate gave a syrup, which was chromato-
graphed (Chex/EtOAc, 6:4/1:1) to give 28 (57 mg, 85%) as a white
foam. Triol 28 had Rf¼0.2 (Chex/EtOAc, 6:4); 1H NMR (CDCl3):
(s, 3H,
HAc), 1.51 (s, 3H, Hi-Pr), 1.50 (s, 3H, Hi-Pr), 1.41 (d,
3H, J5,6¼6.2 Hz, H-6A), 1.41 (d, 3H, J5,6¼6.2 Hz, H-6C); 13C
NMR (CDCl3):
d 170.1 (CAc), 162.2 (CNTCA), 139.0–137.8 (CPh),
134.3 (CH]), 129.8–127.7 (CHPh), 117.5 (]CH2), 101.7 (C-1D,
d
7.41–7.07 (m, 35H, CHPh), 6.93 (d, 1H, JNH,2¼7.7 Hz, NH), 5.89 (m,
1JCH¼161.0 Hz), 99.9 (Ci-Pr), 98.9 (C-1C, JCH¼169.1 Hz), 98.8 (C-1A,
1H, CH]), 5.29 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.23 (m, 1H,
Jcis¼10.4 Hz, ]CH2), 5.21 (d, 1H, J1,2¼3.7 Hz, H-1E), 5.13–4.88 (m,
5H, HBn), 4.84 (d, 1H, J1,2¼1.7 Hz, H-1A), 4.79 (d, 1H, J¼11.0 Hz, HBn),
4.73–4.67 (m, 3H, HBn), 4.62 (m, 1H, HBn), 4.58 (d, 1H, J1,2¼8.5 Hz, H-
1D), 4.58 (m, 1H, HBn), 4.55 (m, 1H, H-1C), 4.51 (d, 2H, J¼11.0 Hz,
1
1JCH¼171.2 Hz), 94.6 (C-1E, 1JCH¼167.6 Hz), 93.5 (CCl3), 83.5 (C-3E),
80.6 (C-2E), 80.2 (C-4C), 80.1 (C-4A), 79.1 (C-4E), 79.0 (C-3D), 78.5
(C-3C), 76.5, 75.7, 75.6, 75.3, 75.2 (5C, CBn), 74.8 (C-3A), 74.1 (C-2A),
73.8 (CBn), 73.0 (C-4D), 72.2 (CBn), 70.3 (C-5E), 69.7 (C-2C), 68.7 (C-
5A), 68.3 (C-6E), 68.3 (C-5C), 68.2 (CAll), 67.4 (C-5D), 62.5 (C-6D),
57.8 (C-2D), 29.5 (Ci-Pr), 21.5 (CAc), 19.3 (Ci-Pr), 18.4, 18.3 (C-6A, C-
6C); HRMS (ESIþ) for C83H94Cl3NO20 ([MþNa]þ, 1552.5332) found
m/z 1552.5293, ([MþNH4]þ, 1547.5779) found m/z 1547.5818,
([MþK]þ, 1568.5072) found m/z 1568.5120.
H
Bn), 4.34 (d, 1H, J¼12.0 Hz, HBn), 4.19–4.11 (m, 4H, H-3A, HAll, H-3E,
H-5E), 4.03–4.00 (m, 3H, H-2A, H-2C, HAll), 3.96 (m, 1H, H-2D), 3.93–
3.87 (m, 3H, H-5C, H-3C, H-6aD), 3.85 (m, 1H, H-2E), 3.83 (m, 1H, H-
4E), 3.77 (m, 1H, H-6bD), 3.73 (m, 1H, H-5A), 3.50–3.44 (m, 4H, H-4C,
H-6aE, H-6bE, H-4A), 3.38 (pt, 1H, J3,4¼8.9 Hz, H-4D), 3.08 (m, 1H, H-
5D), 2.30 (m, 1H, J3,4¼8.8 Hz, H-3D), 1.40 (d, 3H, J5,6¼6.2 Hz, H-6A),
1.32 (d, 3H, J5,6¼6.2 Hz, H-6C); 13C NMR (CDCl3):
d 162.0 (CNTCA),
4.14. Allyl (2-O-acetyl-3,4-di-O-benzyl-
rhamnopyranosyl)-(1/3)-(2-deoxy-2-trichloroacetamido-
-glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-
a-
L-
138.7–138.2 (CPh), 134.3 (CH]), 129.7–127.6 (CHPh), 117.8 (]CH2),
b
-
101.4 (C-1D, 1JCH¼161.7 Hz), 101.0 (C-1C, 1JCH¼168.3 Hz), 98.6 (C-1A,
1
D
a-
D-
1JCH¼168.3 Hz), 94.3 (C-1E, JCH¼17.6 Hz), 93.7 (CCl3), 87.1 (C-3D),
glucopyranosyl-(1/3)]-4-O-benzyl-
pyranoside (27)
a
-L
-rhamno-
83.5 (C-3E), 80.8 (C-2E), 80.2 (C-4A), 79.5 (C-4C), 79.4 (C-3C), 79.3 (C-
4E), 76.6, 75.7, 75.6, 75.5, 75.3 (5C, CBn), 75.3 (C-5D), 74.5 (2C, C-2A,
C-3A), 73.8, 72.2 (2C, CBn), 71.1 (C-4D), 70.3 (C-5E), 69.5 (C-5C), 68.9
(C-2C), 68.8 (C-5A), 68.4 (C-6E), 68.1 (CAll), 63.3 (C-6D), 55.9 (C-2D),
21.4 (CAc), 18.3, 18.2 (2C, C-6A, C-6C); HRMS (ESIþ) for C78H88Cl3NO19
([MþNa]þ, 1470.4913) found m/z 1470.5050, ([MþNH4]þ,
1465.5360) found m/z 1465.5448, ([MþK]þ, 1486.4653) found m/z
1486.4777.
Aq TFA (50%, 1.6 mL) was added, at 0 ꢁC, to a solution of tet-
rasaccharide 26 (79 mg, 52 mol) in CH2Cl2 (4 mL), and the bi-
m
phasic mixture was stirred vigorously at rt for 1 h. TLC (Chex/
EtOAc, 6:4) showed the complete disappearance of the starting
material and the presence of a major more polar product. Re-
peated coevaporation with toluene and chromatography of the
residue (Chex/EtOAc, 7:3/6:4) provided diol 27 (68 mg, 88%) as
a white foam. Compound 27 had Rf¼0.3 (Chex/EtOAc, 6:4); 1H
4.16. Allyl (3,4-di-O-benzyl-
deoxy-4,6-O-isopropylidene-2-trichloroacetamido-
glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-a-D-
b-L-rhamnopyranosyl)-(1/3)-(2-
b-D-
NMR (CDCl3):
d
7.40–7.07 (m, 35H, CHPh), 6.99 (d, 1H,
JNH,2¼8.3 Hz, NH), 5.91 (m, 1H, CH]), 5.31 (m, 1H, H-2C), 5.29 (m,
1H, Jtrans¼16.9 Hz, ]CH2), 5.25–5.23 (m, 2H, ]CH2, H-1E), 5.12
(m, 2H, HBn), 5.08 (d, 1H, J¼12.6 Hz, HBn), 4.99–4.91 (m, 2H, HBn),
4.85 (d, 1H, J1,2¼1.5 Hz, H-1A), 4.82 (d, 1H, J¼11.1 Hz, HBn), 4.73 (d,
1H, J¼10.1 Hz, HBn), 4.67 (d, 1H, J¼11.4 Hz, HBn), 4.62–4.51 (m, 6H,
2HBn, H-1D, 3HBn), 4.49 (d, 1H, J1,2¼1.8 Hz, H-1C), 4.35 (d, 1H,
J¼11.9 Hz, HBn), 4.22–4.13 (m, 5H, OH-4D, H-3A, H-3E, HAll, H-5E),
4.04–4.01 (m, 3H, HAll, H-2A, H-3C), 3.98 (m, 1H, H-2D), 3.96 (m,
1H, H-5C), 3.87–3.82 (m, 3H, H-6aD, H-2E, H-4E), 3.80–3.70 (m,
2H, H-6bD, H-5A), 3.52–3.49 (m, 3H, H-4A, H-6aE, H-6bE), 3.46 (pt,
1H, J3,4¼9.4 Hz, H-4C), 3.39 (pt, 1H, J3,4¼9.4 Hz, H-4D), 3.09 (m,
1H, H-5D), 2.09 (m, 4H, HAc, H-3D), 1.41 (d, 3H, J5,6¼6.2 Hz, H-6A),
glucopyranosyl-(1/3)]-4-O-benzyl-a-L-rhamno-
pyranoside (29)
TMSOTf (25 mL, 140 mmol, 0.5 equiv) was added to a solution of
15 (0.3 g, 0.26 mmol) and trichloroacetimidate 1739 (0.19 g,
0.36 mmol, 1.4 equiv) in CH2Cl2 (4 mL) containing 4 Å MS (0.4 g),
stirred at ꢀ78 ꢁC. The reaction mixture was stirred for 30 min,
while slowly coming back to rt. TLC (Chex/EtOAc, 7:3) showed the
complete disappearance of the starting materials and the presence
of several products. Et3N (1 mL) was added and the mixture was
filtered and concentrated to dryness. Chromatography of the resi-
due (Chex/EtOAc, 6.5:3.5/1:1) gave first fully protected 26
(170 mg, 40%) as a white foam, then, the side-product 29 (80 mg,
20%), which had Rf¼0.65 (Chex/EtOAc, 6:4) and finally diol 27
(85 mg, 22%). MeONa (0.5 M, 0.8 mL, 0.4 mmol) was added to
a solution of 29 (25 mg) in MeOH (1 mL). After stirring for 4 h at rt,
TLC (Chex/EtOAc, 6:4) showed the presence of a single more polar
product. The mixture was neutralized by addition of Dowex X8-200
ion exchange resin (Hþ) and filtered. Evaporation of the filtrate gave
a syrup, which was chromatographed (Chex/EtOAc, 8:2/6:4) to
give trichloroacetamide 30 (8 mg) as a white foam. Tetrasaccharide
1.34 (d, 3H, J5,6¼6.2 Hz, H-6C); 13C NMR (CDCl3):
d 170.5 (CAc),
162.3 (CNTCA), 138.8–137.8 (CPh), 134.3 (CH]), 129.7–127.8
1
(CHPh), 117.8 (]CH2), 101.4 (C-1D, JCH¼158.6 Hz), 99.5 (C-1C,
1JCH¼169.8 Hz), 98.6 (C-1A, 1JCH¼174.0 Hz), 94.3 (C-1E,
1JCH¼169.3 Hz), 93.7 (CCl3), 87.3 (C-3D), 83.4 (C-3E), 81.0 (C-2E),
80.2 (C-4A), 79.6 (C-4C), 79.2 (C-4E), 77.5 (C-3C), 76.6, 75.7, 75.6,
75.5, 75.3 (5C, CBn), 75.2 (C-5D), 74.6 (C-3A), 74.3 (C-2A), 73.8, 72.2
(2C, CBn), 71.2 (C-4D), 70.3 (C-5E), 69.8 (C-5C), 69.4 (C-2C), 68.8 (C-
5A), 68.3 (C-6E), 68.1 (CAll), 63.3 (C-6D), 55.6 (C-2D), 21.4 (CAc), 18.4
(C-6A), 18.2 (C-6C); HRMS (ESIþ) for C80H90Cl3NO20 ([MþNa]þ,
1512.5019) found m/z 1512.4950, ([MþNH4]þ, 1507.5465) found
m/z 1507.5507.
30 had Rf¼0.5 (Chex/EtOAc, 6:4); 1H NMR (CDCl3):
d 7.40–7.03 (m,
35H, CHPh), 5.88 (m, 1H, CH]), 5.26 (m, 1H, Jtrans¼17.2 Hz, ]CH2),
5.18 (m, 1H, Jcis¼10.4 Hz, ]CH2), 5.10–5.05 (m, 3H, HBn, H-1E, HBn),

10568
J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
5.00–4.92 (m, 3H, HBn), 4.86 (d, 1H, J¼12.1 Hz, HBn), 4.76 (m, 1H,
J1,2¼1.5 Hz, H-1A), 4.75–4.69 (m, 4H, HBn, H-1D, 2HBn), 4.66–4.50 (m,
4H, 3HBn, H-1C), 4.45 (d, 1H, J¼10.9 Hz, HBn), 4.30 (d, 1H, J¼11.9 Hz,
H-6aE, H-6bE), 3.65–3.59 (m, 4H, H-6bD, H-3C, H-5A, H-2E), 3.52 (m,
1H, HPr), 3.42–3.28 (m, 6H, H-4E, HPr, H-4D, H-5D, H-3D, H-4C), 3.23
(pt, 1H, J3,4¼9.7 Hz, H-4A), 2.01 (s, 3H, HNAc), 1.49 (sex, 2H, CH2), 1.16
(d, 3H, J5,6¼6.2 Hz, H-6A), 1.12 (d, 3H, J5,6¼6.3 Hz, H-6C), 0.80
H
Bn), 4.17–4.02 (m, 6H, H-3E, H-3A, HAll, H-5E, H-2C, H-2D), 3.99 (m,
1H, H-2A), 3.91 (m,1H, HAll), 3.85–3.68 (m, 5H, H-6aD, H-2E, H-4E, H-
6bD, H-5A), 3.62 (pt, 1H, J3,4¼9.4 Hz, H-4D), 3.52–3.39 (m, 6H, H-4C,
H-3D, H-4A, H-3C, H-6aE, H-6bE), 3.24 (m, 1H, H-5C), 2.72 (m, 1H, H-
5D), 1.45 (s, 6H, Hi-Pr), 1.40 (d, 3H, J5,6¼6.3 Hz, H-6A), 1.18 (d, 3H,
(t, 3H, J¼7.4 Hz, CH3); 13C NMR (D2O):
d 174.5 (CNAc), 101.8 (C-1D,
1JCH¼160.3 Hz), 101.6 (C-1C, 1JCH¼170.5 Hz), 99.0 (C-1A,
1JCH¼172.7 Hz), 94.8 (C-1E, 1JCH¼169.8 Hz), 81.7 (C-3D), 76.4 (C-4D),
74.7 (C-2A), 74.1 (C-3A), 73.5 (C-3E), 72.2 (C-4C), 71.7 (C-5E), 71.6 (C-
2E), 71.2 (C-2C), 71.0 (C-4A), 70.5 (C-3C), 70.0 (CPr), 69.6 (C-5D), 69.3
(C-5C), 69.1 (C-5A), 68.6 (C-4E), 60.9 (C-6D), 60.6 (C-6E), 55.9 (C-2D),
22.8 (CNAc), 22.3 (CH2), 17.0, 16.7 (C-6A, C-6C), 10.2 (CH3); HRMS
(ESIþ) for C29H51NO19 ([MþNa]þ, 740.2953) found m/z 740.2941.
J5,6¼6.3 Hz, H-6C); 13C NMR (CDCl3):
d 163.2 (CNTCA), 138.8–137.8
(CPh), 134.2 (CH]), 129.5–127.6 (CHPh), 117.6 (]CH2), 101.8 (C-1D,
1JCH¼160.3 Hz), 99.8 (Ci-Pr), 99.1 (C-1C, JCH¼156.6 Hz), 98.7 (C-1A,
1
1JCH¼172.7 Hz), 95.0 (C-1E, 1JCH¼166.1 Hz), 93.4 (CCl3), 83.8 (C-3E),
81.7 (C-3C), 80.1 (C-4A), 79.7 (C-4C), 79.1 (C-4E), 78.5 (C-2E), 77.1 (C-
3D), 76.5, 75.8, 75.5, 75.1 (4C, CBn), 75.1 (C-3A), 74.6 (C-4D), 74.4
(C-2A), 74.3, 73.8 (2C, CBn), 71.7 (C-5C), 71.1 (CBn), 70.7 (C-5E), 68.7
(C-5A), 68.2 (C-2C), 68.2, 68.1 (2C, C-6E, CAll), 67.1 (C-5D), 62.4 (C-6D),
56.6 (C-2D), 29.4 (Ci-Pr), 19.5 (Ci-Pr), 18.5 (C-6C), 18.2 (C-6A).
4.19. Allyl (2-acetamido-2-deoxy-
[2,3,4,6-tetra-O-benzyl- -glucopyranosyl-(1/3)]-4-O-
benzyl- -rhamnopyranoside (31)
b-D-glucopyranosyl)-(1/2)-
a-D
a-L
Methanolic MeONa (0.5 M, 4.8 mL, 2.4 mmol, 6 equiv) was
added to a solution of 23 (0.5 g, 0.4 mmol) in CH2Cl2 (38 mL), and
the mixture was stirred for 9 h. TLC (CH2Cl2/MeOH, 92:8) showed
the complete disappearance of the triacetate and the presence of
a single more polar product. MeOH (77 mL) and acetic anhydride
4.17. Propyl (2/3-O-acetyl-
acetamido-2-deoxy- -glucopyranosyl)-(1/2)-[
glucopyranosyl-(1/3)]- -rhamnopyranoside (5)
a-L-rhamnopyranosyl)-(1/3)-(2-
b-D
a-D-
a-L
Tetrasaccharide 27 (0.34 g, 0.323 mmol) was dissolved in EtOH
(30 mL), treated with 10% Pd/C catalyst (300 mg), and the suspen-
sion was stirred at rt for 10 days, under a hydrogen atmosphere (45
bar). TLC (i-PrOH/H2O/NH3, 4:1:0.5 and Chex/EtOAc, 6:4) showed
that 27 had been transformed into a major polar product. The
suspension was filtered on Acrodisc LC 25 mm and the filtrate was
concentrated. Reverse phase chromatography (H2O/CH3CN,
100:0/70:30) of the residue, followed by freeze-drying, gave 5 as
a mixture of the non separable 2C- and 3C-O-acetyl isomers
(132 mg, 76%). Compound 5, isolated as a white foam, had Rf¼0.5
(300 mL) were added. After 2 h, TLC (CH2Cl2/MeOH, 92:8) showed
the complete disappearance of the aminotriol intermediate. Evap-
oration of the filtrate gave a syrup, which was purified by chro-
matography (CH2Cl2/MeOH, 98:2/95:5) to give compound 31
(371 mg, 90%) as a white foam. Triol 31 had Rf¼0.4 (CH2Cl2/MeOH,
92:8); 1H NMR (CDCl3):
d 7.41–7.08 (m, 26H, NH, CHPh), 5.88 (m, 1H,
CH]), 5.29 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.21 (m, 1H, Jcis¼10.4 Hz,
]CH2), 5.09–5.06 (m, 2H, H-1E, HBn), 5.01–4.96 (m, 2H, H-1A, HBn),
4.91–4.87 (m, 2H, HBn), 4.81–4.76 (m, 2H, J¼10.3 Hz, HBn), 4.63–
4.58 (m, 2H, HBn), 4.50 (d, 1H, J¼10.9 Hz, HBn), 4.62 (m, 1H, H-1D),
4.34 (m, 1H, HBn), 4.19–4.08 (m, 4H, H-3A, H-5E, HAll, H-3E), 4.01 (m,
1H, HAll), 3.91 (br s, 1H, H-2A), 3.87–3.81 (m, 5H, H-2E, H-4E, H-2D,
H-6aD, H-6bD), 3.72 (m, 1H, H-5A), 3.51 (pt, 1H, J3,4¼9.0 Hz, H-4D),
3.51–3.45 (m, 3H, H-4A, H-6aE, H-6bE), 3.13 (m, 1H, H-5D), 2.80
(pt, 1H, J2,3¼9.2 Hz, H-3D), 2.21 (s, 3H, HNAc), 1.40 (d, 3H,
(i-PrOH/H2O/NH3, 4:1:0.5); 1H NMR (D2O):
d (partial) 5.05 (m, 1H,
H-1E), 4.83–4.72 (m, 4H, H-1A, H-1C, H-1D, H-2C), 4.17 (m, 1H, H-2A),
3.93 (m, 1H, H-5E), 3.82–3.79 (m, 2H, H-3A, H-5C), 3.73–3.52 (m,
10H, H-2D, H-6aD, H-3E, H-6aE, H-6bE, H-6bD, H-3C, H-5A, H-2E, HPr),
3.42–3.32 (m, 6H, H-4E, HPr, H-5D, H-4C, H-4D, H-3D), 3.21 (pt, 1H,
J3,4¼9.7 Hz, H-4A), 2.07–2.01 (m, 6H, HAc, HNAc), 1.48 (m, 2H, CH2),
1.17–1.11 (d, 6H, H-6A, H-6C), 0.80 (t, 3H, J¼7.4 Hz, CH3); 13C NMR
J5,6¼6.2 Hz, H-6A); 13C NMR (CDCl3):
d 173.3 (CNAc), 138.6–137.5
(CPh), 134.2 (CH]), 129.5–127.8 (CHPh), 117.8 (]CH2), 103.0
1
1
(D2O): (partial)
d
174.9, 174.5, 174.1, 173.6 (CNAc, CAc), 101.8 (C-1D),
(C-1D, JCH¼155.6 Hz), 98.5 (C-1A, JCH¼174.8 Hz), 94.6 (C-1E,
1JCH¼167.9 Hz), 83.7 (C-3E), 80.2 (C-4A), 79.2, 79.0 (2C, C-2E, C-4E),
77.1 (C-3D), 76.9 (C-2A), 76.5, 75.8 (2C, CBn), 75.7 (C-5D), 75.6, 75.3
(2C, CBn), 74.6 (C-3A), 73.8 (CBn), 71.8 (C-4D), 70.3 (C-5E), 68.7 (C-5A),
68.3 (CAll), 68.2 (C-6E), 62.7 (C-6D), 57.4 (C-2D), 23.6 (CNAc), 18.2 (C-
6A); HRMS (ESIþ) for C58H70NO15 ([MþH]þ, 1020.4745) found m/z
1020.4739, ([MþH]þ, 1042.4565) found m/z 1042.4545.
101.5, 101.2 (C-1C), 99.0, 98.8 (C-1A), 94.8, 94.7 (C-1E), 82.6, 81.7 (C-
3D), 76.4 (C-4D), 74.7 (C-2A), 74.3–73.9 (C-3A, C-2C, C-3C), 73.5, 73.3
(C-3E), 72.4 (C-4C), 71.7, 71.6 (C-5E, C-2E), 71.0 (C-4A), 70.0 (CPr),
69.6–68.5 (C-4E, C-5A, C-5C, C-5D), 60.9 (C-6D), 60.6 (C-6E), 55.8 (C-
2D), 23.1, 22.8 (CNAc), 22.3 (CH2), 20.8, 20.6 (CAc), 17.1–16.6 (C-6A, C-
6C), 10.2 (CH3); HRMS (ESIþ) for C31H53NO20 ([MþNa]þ, 782.3058)
found m/z 782.3066.
4.20. Allyl (2-acetamido-2-deoxy-4,6-O-isopropylidene-
glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-
glucopyranosyl-(1/3)]-4-O-benzyl-a-L-rhamno-
b-D-
4.18. Propyl
deoxy- -glucopyranosyl)-(1/2)-[
3)]- -rhamnopyranoside (6)
a
-
L
-rhamnopyranosyl-(1/3)-(2-acetamido-2-
a-D-
b-D
a
-
D-glucopyranosyl-(1/
a
-L
pyranoside (32)
Tetrasaccharide 28 (0.412 g, 0.36 mmol) was dissolved in EtOH
(30 mL), treated with 10% Pd/C catalyst (300 mg), and the suspen-
sion was stirred at rt for 2 days, under a hydrogen atmosphere (45
bar). TLC (i-PrOH/H2O/NH3, 4:1:0.5 and Chex/EtOAc, 6:4) showed
that 28 had been transformed into a major polar product. The
suspension was filtered on Acrodisc LC 25 mm and the filtrate was
concentrated. Reverse phase chromatography (H2O/CH3CN,
100:0/70:30) of the residue, followed by freeze-drying, gave
target 6 (119 mg, 71%) as a white foam. Tetrasaccharide 6 had
CSA (6.2 mg, 26
(270 mg, 0.26 mmol) in a mixture of DMF (3 mL) and 2-methoxy-
propene (76 L, 0.79 mmol, 3 equiv). After stirring for 2 h at rt, TLC
mmol) was added to a suspension of triol 31
m
(Chex/EtOAc, 1:1 and CH2Cl2/MeOH, 92:8) showed the complete
disappearance of the triol and the presence of a less polar product.
Et3N (0.2 mL) was added and concentrated to dryness. Chroma-
tography of the residue (Chex/EtOAc, 1:1) gave 32 (240 mg, 85%) as
a white foam. Compound 32 had Rf¼0.35 (Chex/EtOAc, 1:1); 1H
NMR (CDCl3):
d 7.31–6.96 (m, 26H, NH, CHPh), 5.88 (m, 1H, CH]),
Rf¼0.65 (i-PrOH/H2O/NH3, 4:1:0.5); 1H NMR (D2O):
d
5.06 (d, 1H,
5.29 (m, 1H, Jtrans¼17.3 Hz, ]CH2), 5.21 (m, 1H, Jcis¼10.4 Hz, ]CH2),
J1,2¼3.7 Hz, H-1E), 4.83 (d, 1H, J1,2¼1.6 Hz, H-1A), 4.76 (d, 1H,
J1,2¼1.3 Hz, H-1C), 4.73 (d, 1H, J1,2¼8.6 Hz, H-1D), 4.18 (m, 1H, H-2A),
3.95 (m, 1H, H-5E), 3.88 (m, 1H, H-5C), 3.83–3.79 (m, 2H, H-3A, H-
6aD), 3.74 (m, 1H, H-2D), 3.72 (m, 1H, H-3E), 3.70–3.67 (m, 3H, H-2C,
5.09–5.06 (m, 2H, J1,2¼5.6 Hz, H-1E, HBn), 4.98 (m, 1H, J¼11.9 Hz,
H
Bn), 4.86 (m, 2H, HBn), 4.84 (br s, 1H, J1,2¼1.7 Hz, H-1A), 4.80–4.74
(m, 2H, HBn), 4.63–4.57 (m, 2H, J¼11.9 Hz, HBn), 4.50 (m, 1H,
J¼9.6 Hz, HBn), 4.37–4.30 (m, 2H, J1,2¼8.3 Hz, HBn, H-1D), 4.19–4.07

J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
10569
(m, 4H, H-3A, H-5E, HAll, H-3E), 3.96 (m, 1H, HAll), 3.89–3.70 (m, 7H,
H-2A, H-6aD, H-2E, H-4E, H-2D, H-5A, H-6bD), 3.53 (pt, 1H,
J3,4¼9.3 Hz, H-4D), 3.51 (m, 2H, H-6aE, H-6bE), 3.45 (pt, 1H,
J3,4¼9.6 Hz, H-4A), 2.87 (m, 1H, H-5D), 2.81 (pt, 1H, J2,3¼9.2 Hz, H-
3D), 2.20 (s, 3H, HNAc), 1.52 (s, 3H, Hi-Pr), 1.48 (s, 3H, Hi-Pr), 1.39 (d,
d 7.33–7.26 (m, 5H, CHPh), 5.34 (m, 1H, H-2B), 5.25 (m,1H, H-3B), 5.18
(m, 1H, H-2C), 5.10 (s, 1H, H-1C), 5.05 (pt, 1H, J3,4¼9.9 Hz, H-4B), 5.04
(d,1H, J1,2¼1.7 Hz, H-1B), 4.80 (d,1H, J¼10.9 Hz, HBn), 4.65 (d,1H, HBn),
4.19 (m,1H, H-3C), 4.01–3.91 (m, 2H, H-5C, H-5B), 3.58 (s,1H, OH), 3.49
(pt, 1H, J3,4¼9.5 Hz, H-4C), 2.21, 2.08, 2.07, 1.99 (4s, 12H, HAc), 1.31 (d,
3H, J5,6¼6.2 Hz, H-6C), 1.19 (d, 3H, J5,6¼6.3 Hz, H-6B); 13C NMR
3H, J5,6¼6.2 Hz, H-6A); 13C NMR (CDCl3):
d 173.3 (CNAc), 138.5–137.5
(CPh), 134.2 (CH]), 129.5–127.7 (CHPh), 117.7 (]CH2), 102.8 (C-1D,
1JCH¼155.2 Hz), 100.1 (Ci-Pr), 98.6 (C-1A, 1JCH¼172.4 Hz), 94.6 (C-1E,
1JCH¼169.1 Hz), 83.7 (C-3E), 80.2 (C-4A), 79.9 (C-2E), 79.1 (C-4E), 76.6
(C-2A), 76.5, 76.1, 75.8, 75.4 (4C, CBn), 74.8 (C-3A), 74.6 (C-3D), 74.5
(C-4D), 73.8 (CBn), 70.4 (C-5E), 68.8 (C-5A), 68.3 (CAll), 68.2 (C-6E),
67.3 (C-5D), 62.3 (C-6D), 58.9 (C-2D), 29.5 (Ci-Pr), 23.6 (CNAc), 19.3 (Ci-
Pr), 18.2 (C-6A); HRMS (ESIþ) for C58H70NO15 ([MþH]þ, 1060.5058)
found m/z 1060.5066, ([MþH]þ, 1082.4878) found m/z 1082.4875.
(CDCl3): d 171.7, 171.0, 170.6, 170.3 (4C, CAc), 138.3–137.9 (CPh), 128.8–
128.1 (CHPh), 99.7 (C-1B, 1JCH¼172.7 Hz), 92.3 (C-1C, 1JCH¼170.5 Hz),
81.1 (C-4C), 76.6 (C-3C), 75.9 (CBn), 72.9 (C-2C), 71.1 (C-4B), 70.2 (C-2B),
69.5 (C-3B), 68.2 (C-5C), 67.6 (C-5B), 21.4, 21.2, 21.1, 21.0 (4C, CAc),18.3
(C-6C), 17.6 (C-6B); HRMS (ESIþ) for C27H36O13 ([MþNa]þ, 591.2054)
found m/z 591.2037, ([MþK]þ, 607.1793) found m/z 607.1838.
4.23. (2,3,4-Tri-O-acetyl-a-L-rhamnopyranosyl)-(1/3)-2-O-
acetyl-4-O-benzyl- -rhamnopyranose
a/b-L
4.21. Allyl (2,3,4-tri-O-acetyl-
a
-L
-rhamnopyranosyl)-(1/3)-2-
trichloroacetimidate (16)
O-acetyl-4-O-benzyl- -rhamnopyranoside (35)
a-L
Hemiacetal 38 (1.0 g, 1.7 mmol) was dissolved in DCE (15 mL),
placed under argon, and cooled to ꢀ5 ꢁC. Trichloroacetonitrile
TMSOTf (125 mL, 0.7 mmol, 0.3 equiv) was added to a solution of
21 (780 mg, 2.3 mmol) and trichloroacetimidate 34 (1.5 g,
3.5 mmol, 1.5 equiv) in CH2Cl2 (60 mL) containing 4 Å MS (2 g),
stirred at ꢀ78 ꢁC. The reaction mixture was stirred for 6 h while
slowly coming back to rt. TLC (Tol/EtOAc, 8:2) showed the complete
disappearance of the acceptor and the presence of a major more
polar product. Et3N (1 mL) was added and the mixture was filtered
and concentrated to dryness. Chromatography of the residue (Tol/
EtOAc, 9:1/8:2) gave 35 (1.34 g, 95%) as a white foam. Di-
saccharide 35 had Rf¼0.35 (Tol/EtOAc, 8:2); 1H NMR (CDCl3):
(2.15 mL, 21.5 mmol, 12 equiv) and then DBU (75 mL, 0.5 mmol,
0.28 equiv) were added. The mixture was stirred at ꢀ5 ꢁC for
10 min. TLC (Chex/EtOAcþEt3N, 7:3) showed the complete disap-
pearance of 38 and the presence of a single less polar product. The
mixture was directly chromatographed (Chex/EtOAcþ5% Et3N,
9:1/7:3) to give 16 (1.13 g, 89%) as
a yellow syrup. Tri-
chloroacetimidate 16 (
a
anomer) had Rf¼0.5 (Chex/EtOAc, 6:4); 1H
NMR (CDCl3):
d
8.70 (s, 1H, NH), 7.33–7.27 (m, 5H, CHPh), 6.18 (d, 1H,
J1,2¼1.7 Hz, H-1C), 5.35 (m, 2H, H-2B, H-2C), 5.22 (m, 1H, H-3B), 5.08
(s, 1H, J1,2¼1.5 Hz, H-1B), 5.07 (pt, 1H, J3,4¼9.9 Hz, H-4B), 4.80 (d, 1H,
J¼10.8 Hz, HBn), 4.68 (d, 1H, HBn), 4.23 (m, 1H, H-3C), 4.00–3.92 (m,
2H, H-5C, H-5B), 3.62 (pt, 1H, J3,4¼9.6 Hz, H-4C), 2.26, 2.08, 2.07, 1.99
(4s, 12H, HAc), 1.37 (d, 3H, J5,6¼6.3 Hz, H-6C), 1.19 (d, 3H, J5,6¼6.3 Hz,
d
7.34–7.02 (m, 5H, CHPh), 5.87 (m, 1H, CH]), 5.33 (m, 1H, H-2B),
5.28 (m, 1H, ]CH2), 5.25 (m, 1H, H-3B), 5.20 (m, 1H, ]CH2), 5.18 (m,
1H, H-2C), 5.07 (pt, 1H, J3,4¼9.9 Hz, H-4B), 5.04 (d, 1H, J1,2¼1.5 Hz, H-
1B), 4.82 (d, 1H, J¼10.8 Hz, HBn), 4.75 (d, 1H, J1,2¼1.6 Hz, H-1C), 4.67
(d, 1H, HBn), 4.17–4.12 (m, 2H, H-3C, HAll), 4.00–3.91 (m, 2H, HAll, H-
5B), 3.77 (m, 1H, H-5C), 3.51 (pt, 1H, J3,4¼9.5 Hz, H-4C), 2.21, 2.08,
2.07, 1.99 (4s, 12H, HAc), 1.34 (d, 3H, J5,6¼6.2 Hz, H-6C), 1.21 (d, 3H,
H-6B); 13C NMR (CDCl3):
d 170.6, 170.5, 170.4, 170.2 (4C, CAc), 164.0
(C]NH), 137.8 (CPh), 128.8–128.3 (CHPh), 99.6 (C-1B, 1JCH¼173.4 Hz),
95.1 (C-1C, 1JCH¼178.6 Hz), 91.2 (CCl3), 80.5 (C-4C), 76.2 (CBn), 75.6
(C-3C), 71.3 (C-5C), 70.9 (C-4B), 70.7 (C-2C), 70.0 (C-2B), 69.4 (C-3B),
67.8 (C-5B), 21.3, 21.2, 21.1, 21.0 (4C, CAc), 18.3 (C-6C), 17.7 (C-6B).
J5,6¼6.3 Hz, H-6B); 13C NMR (CDCl3):
d 170.9, 170.4, 170.3, 170.2 (4C,
C
Ac), 138.3 (CPh), 133.8 (CH]), 129.4–128.1 (CHPh), 117.9 (]CH2),
1
1
99.8 (C-1B, JCH¼173.0 Hz), 96.8 (C-1C, JCH¼170.0 Hz), 81.1 (C-4C),
77.2 (C-3C), 75.6 (CBn), 72.5 (C-2C), 71.1 (C-4B), 70.2 (C-2B), 69.5 (C-
3B), 68.5 (CAll), 68.3 (C-5C), 67.6 (C-5B), 21.4, 21.2, 21.1, 21.0 (4C, CAc),
18.3 (C-6C), 17.7 (C-6B); HRMS (ESIþ) for C30H40O13 ([MþNa]þ,
631.2367) found m/z 631.2368, ([MþK]þ, 647.2106) found m/z
647.2124.
4.24. Allyl (2,3,4-tri-O-acetyl-
(2-O-acetyl-4-O-benzyl- -rhamnopyranosyl)-(1/3)-(2-
deoxy-4,6-O-isopropylidene-2-trichloroacetamido-
glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl-
a-L-rhamnopyranosyl)-(1/3)-
a-L
b-D-
a-D-
glucopyranosyl-(1/3)]-4-O-benzyl-a-L-rhamno-
pyranoside (39)
4.22. (2,3,4-Tri-O-acetyl-
a-L-rhamnopyranosyl)-(1/3)-2-O-
acetyl-4-O-benzyl- -rhamnopyranose (38)
a
-
L
TMSOTf (50 mL, 280 mmol, 0.3 equiv) was added to a solution of
15 (1.09 g, 935 mmol) and trichloroacetimidate 16 (935 mg,
1.3 mmol,1.4 equiv) in toluene (10 mL) containing 4 Å MS (765 mg),
stirred at ꢀ78 ꢁC. The reaction mixture was stirred for 15 min at this
temperature. TLC (Tol/EtOAc, 7:3) showed the complete disap-
pearance of 15 and the presence of a major more polar product.
Et3N (0.5 mL) was added and the mixture was filtered, and con-
centrated to dryness. Chromatography of the residue (Tol/EtOAc,
9:1/4:6) gave first the fully protected 39 (1.3 g, 80%) as a white
foam and next, diol 40 (Rf¼0.24, Tol/EtOAc, 7:3, 108 mg, 7%) slightly
contaminated by the hydrolyzed donor 38. The former, 39, had
1,5-Cyclooctadiene-bis(methyldiphenylphosphine)iridium hexa-
fluorophosphate (170 mg) was dissolved in THF (30 mL) and the
resulting red solution was degassed under an argon stream. Hydro-
genwas bubbled through the solution, causing the color to change to
yellow. The solutionwas then degassed again underan argon stream.
A solution of 35 (1.34 g, 2.2 mmol) in THF (8 mL) was added. The
mixture was stirred overnight at rt and TLC (Tol/EtOAc, 8:2) showed
thecomplete disappearance of thestartingmaterialandthepresence
of a single less polar product. The mixturewas treated with a solution
of iodine (1.12 g, 4.4 mmol) in THF/water (15 mL, 4:1 v/v) and stirred
for 1 h at rt. TLC (Tol/EtOAc, 8:2 and CH2Cl2/MeOH, 9.5:0.5) showed
the complete disappearance of the intermediate and the presence of
a single more polar product. Excess iodine was destroyed by adding
a solution of freshly prepared 5% aq sodium bisulphite. CH2Cl2
(100 mL) was added and the organic phase was washed with brine
(3ꢂ30 mL), water (3ꢂ30 mL), dried on Na2SO4, filtered, and con-
centrated to dryness. Chromatography of the residue (CH2Cl2/MeOH,
99:1/9:1) gave compound 38 (1.14 g, 91%) as a yellow syrup.
Hemiacetal38hadRf¼0.55(CH2Cl2/MeOH, 9.5:0.5); 1H NMR (CDCl3):
Rf¼0.55 (Tol/EtOAc, 7:3); 1H NMR (CDCl3):
d 7.48–7.12 (m, 30H,
CHPh), 6.95 (d, 1H, JNH,2¼8.8 Hz, NH), 5.92 (m, 1H, CH]), 5.38 (m,
1H, H-2B), 5.29 (m, 1H, Jtrans¼16.9 Hz, ]CH2), 5.28 (m, 1H, H-3B),
5.22 (d, 1H, J1,2¼4.1 Hz, H-1E), 5.21 (m, 1H, Jcis¼10.6 Hz, ]CH2), 5.17
(m, 1H, H-2C), 5.15 (m, 4H, H-1B, H-4B, 2HBn), 5.05 (d, 1H, J¼12.2 Hz,
H
Bn), 4.95 (d, 1H, J¼12.2 Hz, HBn), 4.86–4.82 (m, 3H, H-1A, 2HBn),
4.76–4.70 (m, 3H, HBn, H-1C, HBn), 4.62–4.53 (m, 4H, 2HBn, H-1D,
Bn), 4.36 (d, 1H, J¼12.0 Hz, HBn), 4.22–4.14 (m, 6H, H-3E, HAll, H-3C,
H-3A, H-5B, H-5E), 4.09–4.04 (m, 3H, H-2D, H-5C, H-2A), 3.99 (m, 1H,
All), 3.93–3.88 (m, 2H, H-2E, H-6aD), 3.85 (pt, 1H, J3,4¼9.6 Hz,
H
H

10570
J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
H-4E), 3.77–3.72 (m, 2H, H-5A, H-6bD), 3.57 (pt, 1H, J3,4¼9.2 Hz, H-
4D), 3.52–3.45 (m, 4H, H-4C, H-4A, H-6aE, H-6bE), 2.84–2.80 (m, 2H,
H-5D, H-3D), 2.26, 2.13, 2.11, 2.03 (4s, 12H, HAc), 1.52 (s, 3H, Hi-Pr),
1.50 (s, 3H, Hi-Pr), 1.44 (d, 3H, J5,6¼6.2 Hz, H-6A), 1.37 (d, 3H,
J5,6¼6.2 Hz, H-6B), 1.33 (d, 3H, J5,6¼6.2 Hz, H-6C); 13C NMR (CDCl3):
Tetraol 42 had Rf¼0.25 (CH2Cl2/MeOH, 9.6:0.4); 1H NMR
(CDCl3):
d
7.38–7.04 (m, 30H, CHPh), 6.93 (d, 1H, JNH,2¼8.8 Hz, NH),
5.86 (m, 1H, CH]), 5.26 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.18 (m, 1H,
Jcis¼10.4 Hz, ]CH2), 5.15 (d, 1H, J1,2¼3.5 Hz, H-1E), 5.09–4.95 (m,
4H, H-1B, 3HBn), 4.89 (d, 1H, J¼12.3 Hz, HBn), 4.78 (d, 1H, J¼11.0 Hz,
d
170.6, 170.5, 170.3, 170.2 (4C, CAc), 162.4 (CNTCA), 138.6–137.8 (CPh),
H
H
Bn), 4.75 (d, 1H, J1,2¼1.0 Hz, H-1A), 4.73–4.61 (m, 4H, 2HBn, H-1C,
Bn), 4.57 (d,1H, J¼12.0 Hz, HBn), 4.51–4.47 (m, 2H, HBn), 4.41 (d,1H,
134.3 (CH]), 129.8–127.7 (CHPh), 117.6 (]CH2), 101.6 (C-1D,
1
1JCH¼164.7 Hz), 99.9 (Ci-Pr), 99.2 (C-1B, JCH¼174.2 Hz), 98.8
J1,2¼8.4 Hz, H-1D), 4.32 (d, 1H, J¼12.0 Hz, HBn), 4.14–4.07 (m, 4H,
1
1
(C-1A, JCH¼171.2 Hz), 98.4 (C-1C, JCH¼170.5 Hz), 94.7 (C-1E,
1JCH¼166.9 Hz), 93.4 (CCl3), 83.5 (C-3E), 81.5 (C-4C), 80.7 (C-2E), 80.2
(C-4A), 79.2 (C-4E), 78.7 (C-3D), 76.5 (CBn), 75.6 (C-3C), 75.7, 75.6,
75.4, 75.3 (4C, CBn), 74.9 (C-3A), 74.1 (C-2A), 73.8 (CBn), 72.9 (C-4D),
72.5 (C-2C), 71.2 (C-4B), 70.3 (2C, C-2B, C-5E), 69.6 (C-3B), 68.8 (C-
5A), 68.4 (C-6E), 68.3 (C-5C), 68.2 (CAll), 67.8 (C-5B), 67.4 (C-5D), 62.5
(C-6D), 58.0 (C-2D), 29.6 (Ci-Pr), 21.4, 21.3, 21.2, 21.1 (4C, CAc), 19.5 (Ci-
Pr), 18.5 (C-6C), 18.3 (C-6A), 17.7 (C-6B); HRMS (ESIþ) for
H
All, H-3A, H-3E, H-5E), 4.03 (d, 1H, J1,2¼9.2 Hz, H-2D), 4.00–3.91 (m,
4H, H-5C, H-2A, H-3C, HAll), 3.89–3.79 (m, 6H, H-2C, H-2B, H-2E, H-
6aD, H-4E, H-3B), 3.75–3.64 (m, 3H, H-5B, H-6bD, H-5A), 3.52–3.48
(pt, 2H, J3,4¼9.2 Hz, H-4D, H-4B), 3.44 (m, 2H, H-6aE, H-6bE), 3.48
(pt, 1H, J3,4¼9.9 Hz, H-4C), 3.48 (pt, 1H, J3,4¼9.5 Hz, H-4A), 2.74–2.69
(m, 2H, H-3D, H-5D), 1.46 (s, 3H, Hi-Pr), 1.42 (s, 3H, Hi-Pr), 1.41 (d, 3H,
J5,6¼6.0 Hz, H-6B), 1.37 (d, 3H, J5,6¼6.2 Hz, H-6A), 1.22 (d, 3H,
J5,6¼6.2 Hz, H-6C); 13C NMR (CDCl3):
d 162.3 (CNTCA), 138.8–138.2
(CPh), 134.2 (CH]), 129.8–127.7 (CHPh), 117.6 (]CH2), 102.0 (C-1B,
C
88H104Cl3NO27 ([MþNa]þ, 1734.5759) found m/z 1734.5825,
([MþNH4]þ, 1729.6205) found m/z 1729.6278.
1JCH¼175.6 Hz), 101.4 (C-1D, 1JCH¼162.5 Hz), 100.2 (C-1C,
1JCH¼171.2 Hz), 99.8 (Ci-Pr), 98.7 (C-1A, JCH¼172.0 Hz), 94.4 (C-1E,
1
4.25. Allyl
benzyl- -rhamnopyranosyl)-(1/3)-(2-deoxy-4,6-O-
isopropylidene-2-trichloroacetamido- -glucopyranosyl)-
(1/2)-[2,3,4,6-tetra-O-benzyl- -glucopyranosyl-(1/3)]-4-
O-benzyl- -rhamnopyranoside (41) and allyl -rhamno-
pyranosyl-(1/3)-(4-O-benzyl- -rhamnopyranosyl)-(1/3)-
(2-deoxy-4,6-O-isopropylidene-2-trichloroacetamido-
glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl- -gluco-
pyranosyl-(1/3)]-4-O-benzyl- -rhamnopyranoside (42)
a
-L-rhamnopyranosyl-(1/3)-(2-O-acetyl-4-O-
1JCH¼166.1 Hz), 93.3 (CCl3), 83.5 (C-3E), 80.7 (C-4C), 80.5 (C-2E), 80.1
(C-4A), 79.4 (C-3C), 79.1 (C-4E), 78.0 (C-3D), 76.6, 75.8, 75.6, 75.4,
75.3 (5C, CBn), 74.5 (C-3A), 73.8 (C-4B), 73.7 (CBn), 73.6 (C-2A), 72.5
(C-4D), 72.0 (C-3B), 71.5 (C-2C), 71.4 (C-2B), 70.1 (C-5E), 69.2 (C-5B),
68.7 (C-5A), 68.2 (2C, C-6E, CAll), 68.0 (C-5C), 67.3 (C-5D), 62.4 (C-6D),
a-L
b-D
a-D
a-
L
a-L
a-
L
58.1 (C-2D), 30.1 (Ci-Pr), 19.5 (Ci-Pr), 18.3, 18.2 (C-6A
*
,C-6C), 17.8 (C-6B);
*
b-D
-
HRMS (ESIþ) for C80H96Cl3NO23 ([MþNa]þ, 1566.5337) found m/z
a-D
1566.5404, ([MþNH4]þ, 1561.5782) found m/z 1561.5812.
a-L
4.26. Allyl
benzyl- -rhamnopyranosyl)-(1/3)-(2-deoxy-2-
trichloroacetamido- -glucopyranosyl)-(1/2)-[2,3,4,6-
tetra-O-benzyl- -glucopyranosyl-(1/3)]-4-O-benzyl-
rhamnopyranoside (43)
a-L-rhamnopyranosyl-(1/3)-(2-O-acetyl-4-O-
Anhydrous K2CO3 (42 mg, 0.30 mmol, 1 equiv) was added to
a stirred solution of pentasaccharide 39 (525 mg, 0.30 mmol) in
dry MeOH (20 mL). The mixture was stirred at rt for 25 min, at
which time TLC (CH2Cl2/MeOH, 9.6:0.4 and Tol/EtOAc, 8:2) in-
dicated total conversion of 39 into two products. Neutralization by
addition of Dowex X8-200 ion exchange resin (Hþ), filtration, and
evaporation of the volatiles gave a syrup, which was chromato-
graphed (Chex/Acetone, 6:4/4:6) to give first mono-acetylated 41
(414 mg, 85%), then tetraol 42 (33 mg, 7%), both as white foams.
Triol 41 had Rf¼0.3 (CH2Cl2/MeOH, 9.6:0.4); 1H NMR (CDCl3)
a-L
b-D
a-
D
a-L-
Aq TFA (50%, 2 mL) was added, at 0 ꢁC, to a solution of penta-
saccharide 41 (292 mg, 0.18 mmol) in CH2Cl2 (5 mL), and the bi-
phasic mixture was stirred vigorously at rt for 1 h. TLC (CH2Cl2/
MeOH, 9.5:0.5) showed the complete disappearance of the starting
material and the presence of a major more polar product. Repeated
coevaporation with toluene and chromatography of the residue
(CH2Cl2/MeOH, 95:5/93:7) provided pentaol 43 (274 mg, 95%) as
a white foam. Compound 43 had Rf¼0.3 (CH2Cl2/MeOH, 9.5:0.5); 1H
d
7.42–7.07 (m, 30H, CHPh), 6.95 (d, 1H, JNH,2¼8.8 Hz, NH), 5.92 (m,
1H, CH]), 5.26 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.18 (m, 1H,
Jcis¼10.4 Hz, ]CH2), 5.15 (d, 1H, J1,2¼3.4 Hz, H-1E), 5.09–5.05 (m,
4H, H-2C, H-1B, 2HBn), 4.98 (d, 1H, J¼12.2 Hz, HBn), 4.87 (d, 1H,
J¼12.2 Hz, HBn), 4.80–4.74 (m, 3H, H-1A, 2HBn), 4.70 (d, 1H,
J¼11.2 Hz, HBn), 4.66–4.63 (m, 3H, HBn, H-1C, HBn), 4.56–4.47 (m,
NMR (CDCl3):
d 7.39–7.05 (m, 31H, CHPh, NH), 5.88 (m, 1H, CH]),
5.28 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.22–5.20 (m, 2H, H-1E, ]CH2),
5.11 (m,1H, H-2C), 5.09–5.02 (m, 3H, HBn), 4.98 (m,1H, H-1B), 4.93 (d,
1H, J¼12.5 Hz, HBn), 4.84 (d,1H, J1,2¼1.3 Hz, H-1A), 4.81–4.73 (m, 3H,
3H, 2HBn, H-1D), 4.30 (d, 1H, J¼11.9 Hz, HBn), 4.14–4.05 (m, 5H, HAll
,
H-3E, H-3A, H-5E, H-3C), 4.00–3.94 (m, 4H, H-2D, HAll, H-2A, H-5C),
3.87–3.84 (m, 4H, H-6aD, H-2B, H-5B, H-2E), 3.79 (pt, 1H,
J3,4¼9.1 Hz, H-4E), 3.70–3.65 (m, 3H, H-6bD, H-5A, H-3B), 3.53 (pt,
1H, J3,4¼9.2 Hz, H-4D), 3.46–3.37 (m, 5H, H-4B, H-6aE, H-6bE, H-4C,
H-4A), 2.81–2.71 (m, 2H, H-5D, H-3D), 2.14 (s, 3H, HAc), 1.47 (s, 3H,
HBn), 4.63–4.60 (m, 3H, HBn, H-1D, HBn), 4.57 (m,1H, H-1C), 4.54–4.49
(m, 2H, HBn), 4.33 (d, 1H, J¼12.0 Hz, HBn), 4.17–4.07 (m, 6H, H-3A,
HAll, H-3E, H-5E, H-3C, H-2A), 4.00–3.95 (m, 2H, H-2D, HAll), 3.90 (m,
1H, H-5C), 3.88–3.85 (m, 2H, H-2B, H-6aD), 3.84–3.78 (m, 2H, H-2E,
H-4E), 3.77–3.61 (m, 4H, H-6bD, H-5B, H-3B, H-5A), 3.51–3.41 (m, 5H,
H-4A, H-6aE, H-6bE, H-4C, H-4B), 3.53 (pt,1H, J3,4¼8.9 Hz, H-4D), 3.04
(m, 1H, H-5D), 2.29 (m, 1H, H-3D), 2.19 (s, 3H, HAc), 1.25 (d, 3H,
J5,6¼6.2 Hz, H-6B), 1.36 (d, 3H, J5,6¼6.2 Hz, H-6C), 1.38 (d, 3H,
H
i-Pr), 1.43 (s, 3H, Hi-Pr), 1.38 (d, 3H, J5,6¼5.9 Hz, H-6A), 1.36 (d, 3H,
J5,6¼6.0 Hz, H-6B), 1.25 (d, 3H, J5,6¼6.2 Hz, H-6C); 13C NMR (CDCl3):
d
170.5 (CAc), 162.6 (CNTCA), 138.7–138.1 (CPh), 134.2 (CH]), 129.8–
127.7 (CHPh), 117.7 (]CH2), 101.6 (C-1B, 1JCH¼170.5 Hz), 101.4 (C-1D,
1JCH¼159.5 Hz), 99.9 (Ci-Pr), 98.7 (C-1A, 1JCH¼172.0 Hz), 98.2 (C-1C,
1JCH¼169.1 Hz), 94.6 (C-1E, 1JCH¼166.9 Hz), 93.3 (CCl3), 83.4 (C-3E),
81.3 (C-4C), 80.6 (C-2E), 80.1 (C-4A), 79.1 (C-4E), 78.7 (C-3D), 76.5
(CBn), 76.0 (C-3C), 75.7, 75.6, 75.5, 75.3 (4C, CBn), 74.8 (C-3A), 73.9
(C-2A), 73.8 (C-4B), 73.7 (CBn), 72.9 (C-2C), 72.7 (C-4D), 71.8 (C-3B),
71.4 (C-2B), 70.2 (C-5E), 69.2 (C-5B), 68.7 (C-5A), 68.3 (C-5C), 68.2
(2C, C-6E, CAll), 67.3 (C-5D), 62.4 (C-6D), 57.9 (C-2D), 29.6 (Ci-Pr), 21.6
(CAc), 19.5 (Ci-Pr), 18.4 (C-6A), 18.3 (C-6C), 17.8 (C-6B); HRMS (ESIþ)
for C82H98Cl3NO24 ([MþNa]þ, 1608.5542) found m/z 1608.5582,
([MþNH4]þ, 1603.5889) found m/z 1603.6035, ([MþK]þ, 1624.5182)
found m/z 1624.5436.
J5,6¼6.2 Hz, H-6A); 13C NMR (CDCl3):
d 170.5 (CAc), 162.8 (CNTCA),
138.9–138.2 (CPh), 134.3 (CH]), 129.7–127.8 (CHPh), 117.7
1
1
(]CH2), 102.1 (C-1B, JCH¼167.9 Hz), 101.1 (C-1D, JCH¼164.0 Hz),
1
1
98.7 (C-1C, JCH¼170.3 Hz), 98.6 (C-1A, JCH¼170.3 Hz), 94.5 (C-1E,
1JCH¼167.9 Hz), 93.2 (CCl3), 86.6 (C-3D), 83.4 (C-3E), 80.7 (C-2E), 80.3
(C-4C), 79.9 (C-4A), 79.1 (C-4E), 77.7 (C-3C), 76.6, 75.9, 75.7, 75.4, 75.3
(5C, CBn), 75.2 (C-5D), 74.8 (C-3A), 74.0 (C-2A), 73.8 (C-4B), 73.7 (CBn),
72.5 (C-2C), 71.9 (C-3B), 71.4 (C-2B), 70.9 (C-4D), 70.3 (C-5E), 69.5 (C-
5C), 69.4 (C-5A), 68.8 (C-5B), 68.4 (C-6E), 68.2 (CAll), 63.1 (C-6D), 55.8
(C-2D), 21.4 (CAc),18.4 (C-6C),18.3 (C-6B),17.8 (C-6A); HRMS (ESIþ) for
C
79H94Cl3NO24 ([MþNa]þ, 1568.5129) found m/z 1568.5162,
([MþNH4]þ, 1563.5575) found m/z 1563.5681.

J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
10571
4.27. Allyl
rhamnopyranosyl)-(1/3)-(2-deoxy-2-trichloroacetamido-
-glucopyranosyl)-(1/2)-[2,3,4,6-tetra-O-benzyl- -gluco-
pyranosyl-(1/3)]-4-O-benzyl- -rhamnopyranoside (45)
a
-
L
-rhamnopyranosyl-(1/3)-(4-O-benzyl-
a
-
L
-
J5,6¼6.1 Hz, H-6A), 1.16 (m, 3H, J5,6¼6.0 Hz, H-6B), 1.15 (d, 3H,
J5,6¼6.4 Hz, H-6C), 0.80 (t, 3H, J¼7.4 Hz, CH3); 13C NMR (D2O):
b
-
D
a-
D
d
174.7 (CNAc), 173.5 (CAc), 103.1 (C-1B, 1JCH¼172.0 Hz), 101.9 (C-1D,
a-
L
1JCH¼163.9 Hz), 99.0 (C-1A, 1JCH¼174.2 Hz), 98.7 (C-1C,
1JCH¼171.2 Hz), 94.7 (C-1E, 1JCH¼170.5 Hz), 83.0 (C-3D), 77.4 (C-3C),
76.4 (C-4D), 74.7 (C-2A), 74.0 (C-3A), 73.5 (C-3E), 72.8 (C-2C), 72.1 (C-
4B), 71.7 (C-5E), 71.6 (C-2E), 71.5 (C-4C), 71.2 (C-4A), 70.5 (C-2B), 70.3
(C-3B), 70.0 (CPr), 69.4 (2C, C-4E, C-5D), 69.2 (C-5C), 69.1 (C-5A), 68.5
(C-5B), 61.0 (C-6D), 60.6 (C-6E), 55.8 (C-2D), 23.1 (CNAc), 22.3 (CH2),
20.6 (CAc), 17.1, 16.9, 16.7 (3C, C-6A, C-6B, C-6C), 10.2 (CH3); HRMS
(ESIþ) for C37H63NO24 ([MþNa]þ, 928.3638) found m/z 928.3630,
([MþH]þ, 906.3818) found m/z 906.3823.
50% aq TFA (2 mL) was added, at 0 ꢁC, to a solution of penta-
saccharide 42 (340 mg, 0.18 mmol) in CH2Cl2 (5 mL), and the bi-
phasic mixture was stirred vigorously at rt for 1 h. TLC (CH2Cl2/
MeOH, 9.4:0.6) showed the complete disappearance of the starting
material and the presence of a major more polar product. Repeated
coevaporation with toluene and chromatography of the residue
(CH2Cl2/MeOH, 95:5/93:7) provided hexaol 45 (314 mg, 95%) as
a white foam. The later had Rf¼0.2 (CH2Cl2/MeOH, 9.4:0.6); 1H NMR
(CDCl3):
d
7.34–7.05 (m, 30H, CHPh), 6.93 (d, 1H, JNH,2¼8.7 Hz, NH),
4.29. Propyl
a-L-rhamnopyranosyl-(1/3)-a-L-
5.86 (m, 1H, CH]), 5.26 (m, 1H, Jtrans¼17.2 Hz, ]CH2), 5.20 (m, 1H,
Jcis¼10.4 Hz, ]CH2), 5.17 (d, 1H, J1,2¼3.6 Hz, H-1E), 5.06 (d, 1H,
J¼11.0 Hz, HBn), 5.02 (m, 1H, H-1B), 5.01–4.97 (m, 2H, HBn), 4.88 (d,
1H, J¼12.3 Hz, HBn), 4.81 (d, 1H, J1,2¼1.4 Hz, H-1A), 4.78–4.69 (m,
rhamnopyranosyl-(1/3)-(2-acetamido-2-deoxy-
b-D-
glucopyranosyl)-(1/2)-[a-D-glucopyranosyl-(1/3)]-a-L-
rhamnopyranoside (8)
3H, HBn), 4.62–4.56 (m, 3H, HBn, H-1D, HBn), 4.51–4.47 (m, 3H, HBn
,
Trichloroacetamide 45 (0.20 g, 0.13 mmol) was dissolved in EtOH
(15 mL), treated with 10% Pd/C catalyst (250 mg), and the suspen-
sion was stirred at rt for 2 days, under a hydrogen atmosphere (45
bar). TLC (i-PrOH/H2O/NH3, 4:1:0.5 and CH2Cl2/MeOH, 9.5:0.5)
showed that 45 had been transformed into a major polar product.
The suspension was filtered on Acrodisc LC 25 mm and the filtrate
was concentrated. Reverse phase chromatography (H2O/CH3CN,
100:0/70:30) of the residue, followed by freeze-drying, gave 8
(81 mg, 71%) as a white foam. Pentasaccharide 8 had Rf¼0.2 (i-PrOH/
H-1C, HBn), 4.32 (d,1H, J¼12.0 Hz, HBn), 4.15–4.13 (m, 2H, H-3A, HAll),
4.11–4.07 (m, 2H, H-3E, H-5E), 4.02 (m, 1H, H-2A), 3.98–3.95 (m, 2H,
H-3C, HAll), 3.93–3.87 (m, 4H, H-2C, H-2D, H-5C, H-2B), 3.84 (m, 1H,
H-6aD), 3.82–3.71 (m, 5H, H-5B, H-2E, H-4E, H-6bD, H-3B), 3.69 (m,
1H, H-5A), 3.48 (pt, 1H, J3,4¼9.2 Hz, H-4B), 3.47–3.37 (m, 5H, H-4C,
H-6aE, H-6bE, H-4A, H-4D), 3.04 (m, 1H, H-5D), 2.38 (pt, 1H,
J3,4¼9.1 Hz, H-3D), 1.27 (d, 3H, J5,6¼6.5 Hz, H-6C), 1.36 (d, 3H,
J5,6¼6.2 Hz, H-6A), 1.37 (d, 3H, J5,6¼6.2 Hz, H-6B); 13C NMR (CDCl3):
H2O/NH3, 4:1:0.5); 1H NMR (D2O):
d
4.94 (d, 1H, J1,2¼3.6 Hz, H-1E),
d
162.4 (CNTCA), 138.2–137.9 (CPh), 134.2 (CH]), 129.2–127.7 (CHPh),
117.7 (]CH2), 101.4 (C-1B, 1JCH¼167.6 Hz), 101.1 (C-1D,
1JCH¼159.5 Hz), 100.9 (C-1C, 1JCH¼168.3 Hz), 98.6 (C-1A,
1JCH¼174.2 Hz), 94.3 (C-1E, 1JCH¼169.1 Hz), 93.3 (CCl3), 85.8 (C-3D),
83.4 (C-3E), 80.6 (C-2E), 80.3 (C-4A), 80.0 (C-4C), 79.2 (C-4E), 78.8 (C-
3C), 76.6, 75.7, 75.6, 75.5 (4C, CBn), 75.3 (C-5D), 75.2 (CBn), 74.5 (C-
3A), 74.0 (C-2A), 73.7 (CBn), 73.6 (C-4B), 71.9 (C-3B), 71.2 (C-2B), 70.9
(C-2C), 70.6 (C-4D), 70.3 (C-5E), 69.4 (2C, C-5B, C-5C), 68.8 (C-5A),
68.3 (C-6E), 68.1 (CAll), 63.0 (C-6D), 56.3 (C-2D), 18.2,18.1, 18.0 (3C, C-
6A, C-6B, C-6C); HRMS (ESIþ) for C77H92Cl3NO23 ([MþNa]þ,
1526.5023) found m/z 1526.5076, ([MþNH4]þ, 1521.5470) found
m/z 1521.5582, ([MþK]þ, 1542.4763) found m/z 1542.4871.
4.78 (br s, 1H, H-1B), 4.71 (br s, 1H, H-1A), 4.63 (br s, 1H, H-1D), 4.61
(br s, 1H, H-1C), 4.07 (m, 1H, H-2A), 3.83–3.78 (m, 3H, H-2B, H-5E, H-
5C), 3.71–3.68 (m, 2H, H-3A, H-6aD), 3.66–3.64 (m, 2H, H-2C, H-2D),
3.62–3.59 (m, 2H, H-3E, H-3B), 3.59–3.52 (m, 5H, H-6aE, H-6bE, H-3C,
H-5B, H-6bD), 3.50–3.39 (m, 2H, H-5A, H-2E), 3.41 (m, 1H, HPr), 3.32–
3.18 (m, 7H, H-4E, H-4C, HPr, H-3D, H-5D, H-4B, H-4D), 3.10 (pt, 1H,
J3,4¼9.7 Hz, H-4A), 1.89 (s, 3H, HNAc), 1.38 (m, 2H, CH2), 1.09 (m, 3H,
J5,6¼6.2 Hz, H-6B), 1.05 (d, 3H, J5,6¼6.2 Hz, H-6A), 1.01 (d, 3H,
J5,6¼6.2 Hz, H-6C), 0.29 (t, 3H, J¼7.4 Hz, CH3); 13C NMR (D2O):
d 174.4
(CNAc),102.8 (C-1B,1JCH¼172.0 Hz),102.0 (C-1D,1JCH¼163.2 Hz),101.7
1
1
(C-1C, JCH¼171.2 Hz), 99.1 (C-1A, JCH¼172.7 Hz), 95.0 (C-1E,
1JCH¼170.5 Hz), 82.1 (C-3D), 78.5 (C-3C), 76.5 (C-4D), 74.8 (C-2A), 74.4
(C-3A), 73.6 (C-3E), 72.5 (C-4B), 71.9 (C-5E), 71.8 (C-2E), 71.7 (C-4C),
71.3 (C-4A), 71.0 (C-2C), 70.7 (C-3B), 70.6 (C-2B), 70.1 (CPr), 69.9 (C-
5D), 69.5 (2C, C-5B, C-5C), 69.3 (C-5A), 68.8 (C-4E), 61.2 (C-6D), 60.8 (C-
6E), 55.9 (C-2D), 23.1 (CNAc), 22.5 (CH2),17.2,17.1,16.9 (3C, C-6A, C-6B,
C-6C),10.3 (CH3); HRMS (ESIþ) for C35H61NO23 ([MþNa]þ, 886.3532)
found m/z 886.3461, ([MþH]þ, 864.3713) found m/z 864.3652.
4.28. Propyl
a-L-rhamnopyranosyl-(1/3)-(2-O-acetyl-a-L-
rhamnopyranosyl)-(1/3)-(2-acetamido-2-deoxy-
b-D-
glucopyranosyl)-(1/2)-[a-D-glucopyranosyl-(1/3)]-a-L-
rhamnopyranoside (7)
The benzylated pentasaccharide 43 (0.27 g, 0.18 mmol) was
dissolved in EtOH (20 mL), treated with 10% Pd/C catalyst (280 mg),
and the suspension was stirred at rt for 10 days, under a hydrogen
atmosphere (45 bar). TLC (i-PrOH/H2O/NH3, 4:1:0.5 and CH2Cl2/
MeOH, 9.5:0.5) showed that starting material had been trans-
formed into a major polar product. The suspension was filtered on
Acrodisc LC 25 mm and the filtrate was concentrated. Reverse
phase chromatography (H2O/CH3CN, 1000/70/30) of the residue,
followed by freeze-drying, gave the target pentasaccharide 7
(111 mg, 70%) as a white foam. Pentasaccharide 7 had Rf¼0.3
Acknowledgements
This work was supported by the ANR (Grant NT05-1_42479), the
Institut Pasteur, and the MENRT (fellowship to J.B.). The authors
thank F. Bonhomme (CNRS URA 2128) for running the NMR and
Mass spectra.
(i-PrOH/H2O/NH3, 4:1:0.5); 1H NMR (D2O):
d 5.04 (d, 1H,
References and notes
J1,2¼3.7 Hz, H-1E), 4.91 (m, 1H, H-2C), 4.90 (d, 1H, J1,2¼1.4 Hz, H-1B),
4.83 (d, 1H, J1,2¼1.7 Hz, H-1A), 4.79 (d, 1H, J1,2¼1.4 Hz, H-1C), 4.72 (d,
1H, H-1D), 4.17 (m, 1H, H-2A), 4.00 (m, 1H, H-5C), 3.96 (m, 1H, H-5E),
3.91 (m, 1H, H-2B), 3.86 (dd, 1H, J2,3¼3.2 Hz, J3,4¼9.7 Hz, H-3C),
3.82–3.79 (m, 2H, H-3A, H-6aD), 3.76 (m, 1H, H-2D), 3.71 (pt, 1H,
J3,4¼9.5 Hz, H-3E), 3.69 (m, 2H, H-6aE, H-6bE), 3.67–3.52 (m, 5H, H-
6bD, HPr, H-5A, H-2E, H-3B), 3.48 (pt, 1H, J3,4¼9.9 Hz, H-4C), 3.44 (m,
1H, H-5B), 3.40 (m, 1H, HPr), 3.38 (m, 1H, H-4E), 3.33 (m, 1H, H-4B),
3.33–3.28 (m, 3H, H-5D, H-4D, H-3D), 3.23 (pt,1H, J3,4¼9.7 Hz, H-4A),
2.07 (s, 3H, HAc), 2.04 (s, 3H, HNAc), 1.49 (m, 2H, CH2), 1.17 (d, 3H,
1. Niyogi, S. K. J. Microbiol. 2005, 43, 133–143.
2. von Seidlein, L.; Kim, D. R.; Ali, M.; Lee, H.; Wang, X.; Thiem, V. D.; Canh do, G.;
Chaicumpa, W.; Agtini, M. D.; Hossain, A.; Bhutta, Z. A.; Mason, C.; Sethabutr,
O.; Talukder, K.; Nair, G. B.; Deen, J. L.; Kotloff, K.; Clemens, J. PLoS Med. 2006,
3, 1556–1568.
3. Levine, M. M.; Kotloff, K. L.; Barry, E. M.; Pasetti, M. F.; Sztein, M. B. Nat. Rev.
Microbiol. 2007, 5, 540–553.
4. Kotloff, K. L.; Winickoff, J. P.; Ivanoff, B.; Clemens, J. D.; Swerdlow, D. L.; San-
sonetti, P. J.; Adak, G. K.; Levine, M. M. Bull. World Health Organ. 1999, 77,
651–666.
5. Lindberg, A. A.; Karnell, A.; Weintraub, A. Rev. Infect. Dis. 1991, 13, S279–S284.
6. Mulard, L. A.; Ughetto-Monfrin, J. J. Carbohydr. Chem. 2000, 19, 193–220.

10572
J. Boutet et al. / Tetrahedron 64 (2008) 10558–10572
7. Cle´ment, M. J.; Imberty, A.; Phalipon, A.; Perez, S.; Simenel, C.; Mulard, L. A.;
Delepierre, M. J. Biol. Chem. 2003, 278, 47928–47936.
8. Mulard, L. A.; Costachel, C.; Sansonetti, P. J. J. Carbohydr. Chem. 2000, 19, 849–877.
25. Schmidt, R. R.; Michel, J. Tetrahedron Lett. 1984, 25, 821–824.
26. Pinto, B. M.; Reimer, K. B.; Tixidre, A. Carbohydr. Res. 1991, 210, 199–219.
27. Gigg, J.; Payne, S.; Conant, R. J. Carbohydr. Chem. 1983, 2, 207–223.
28. Pinto, B. M.; Morissette, D. G.; Bundle, D. R. J. Chem. Soc., PerkinTrans.11987, 9–14.
29. Zhang, K. Q.; Li, S. C.; Mao, J. M.; Chen, H. M.; Cai, M. S. Chem. J. Chin. Univ. 1997,
18, 1469–1473.
´
9. Belot, F.; Wright, K.; Costachel, C.; Phalipon, A.; Mulard, L. A. J. Org. Chem. 2004,
69, 1060–1074.
10. West, N. P.; Sansonetti, P.; Mounier, J.; Exley, R. M.; Parsot, C.; Guadagnini, S.;
Prevost, M. C.; Prochnicka-Chalufour, A.; Delepierre, M.; Tanguy, M.; Tang, C. M.
Science 2005, 307, 1313–1317.
30. Lindhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry; Wiley-
VCH: Weinheim, 2000; p 42.
11. Ferreccio, C.; Prado, V.; Ojeda, A.; Cayyazo, M.; Abrego, P.; Guers, L.; Levine, M. M.
Am. J. Epidemiol. 1991, 134, 614–627.
12. Formal, S. B.; Oaks, E. V.; Olsen, R. E.; Wingfield-Eggleston, M.; Snoy, P. J.; Cogan,
J. P. J. Infect. Dis. 1991, 164, 533–537.
13. Noriega, F. R.; Liao, F. M.; Maneval, D. R.; Ren, S.; Formal, S. B.; Levine, M. M.
Infect. Immun. 1999, 67, 782–788.
14. Pinto, B. M.; Reimer, K. B.; Morissette, D. G.; Bundle, D. R. Carbohydr. Res. 1990,
196, 156–166.
31. Spijker, N. M.; van Boeckel, C. A. A. Angew. Chem., Int. Ed. Engl. 1991, 30, 180–183.
32. Yang, F.; He, H. M.; Du, Y. G.; Lu, M. J. Carbohydr. Res. 2002, 337, 1165–1169.
33. Zeng, Y.; Ning, J.; Kong, F. Z. Tetrahedron Lett. 2002, 43, 3729–3733.
34. Ikeda, T.; Yamauchi, K.; Nakano, D.; Nakanishi, K.; Miyashita, H.; Ito, S.; Nohara,
T. Tetrahedron Lett. 2006, 47, 4355–4359.
35. Fekete, A.; Gyergyoi, K.; Kover, K. E.; Bajza, I.; Liptak, A. Carbohydr. Res. 2006,
341, 1312–1321.
36. Geyer, K.; Seeberger, P. H. Helv. Chim. Acta 2007, 90, 395–403.
37. Adamo, R.; Kovac, P. Eur. J. Org. Chem. 2007, 988–1000.
38. Whitfield, D. M.; Nukada, T. Carbohydr. Res. 2007, 342, 1291–1304.
39. Segat-Dioury, F.; Mulard, L. A. Tetrahedron: Asymmetry 2002, 13, 2211–2222.
40. Das, S. K.; Roy, N. J. Carbohydr. Chem. 1995, 14, 417–428.
41. Szurmai, Z.; Liptak, A.; Snatzke, G. Carbohydr. Res. 1990, 200, 201–208.
42. Kitagawa, I.; Baek, N. I.; Ohashi, K.; Sakagami, M.; Yoshikawa, M.; Shibuya, H.
Chem. Pharm. Bull. 1989, 37, 1131–1133.
15. Tsvetkov, Y. E.; Bairamova, N. E.; Bakinovskii, L. V.; Kochetkov, N. K.; Lankina,
N. F. Bioorg. Khim. 1986, 12, 1213–1224.
16. Mulard, L. A.; Ughetto-Monfrin, J. J. Carbohydr. Chem. 1999, 18, 721–753.
17. Schmidt, R. R.; Kinzy, W. Adv. Carbohydr. Chem. Biochem. 1994, 50, 21–123.
18. Blatter, G.; Beau, J. M.; Jacquinet, J. C. Carbohydr. Res. 1994, 260, 189–202.
19. Boutet, J.; Kim, T. H.; Guerreiro, C.; Mulard, L. A. Tetrahedron Lett. 2008, 49,
5339–5342.
´
20. Bakinovskii, L. V.; Gomtsyan, A. R.; Bairamova, N. E.; Kochetkov, N. K. Bioorg.
Khim. 1984, 10, 79–87.
21. Wessel, H. P.; Bundle, D. R. J. Chem. Soc., Perkin Trans. 1 1985, 2251–2260.
22. Mulard, L. A.; Cle´ment, M. J.; Segat-Dioury, F.; Delepierre, M. Tetrahedron 2002,
58, 2593–2604.
23. Castro-Palomino, J. C.; Hernandez Rensoli, M.; Verez Bencomo, V. J. Carbohydr.
Chem. 1996, 15, 137–146.
24. Schmidt, R. R.; Michel, J.; Roos, M. Liebigs Ann. Chem. 1984, 1343–1357.
43. Lubineau, A.; Basset-Carpentier, K.; Auge, C. Carbohydr. Res. 1997, 300, 161–167.
44. Baeschlin, D. K.; Green, L. G.; Hahn, M. G.; Hinzen, B.; Ince, S. J.; Ley, S. V.
Tetrahedron: Asymmetry 2000, 11, 173–197.
45. Pozsgay, V.; Coxon, B. Carbohydr. Res. 1994, 257, 189–215.
46. Oltvoort, J. J.; van Boeckel, C. A. A.; der Koning, J. H.; van Boom, J. H. Synthesis
1981, 305–308.
47. Nashed, M. A.; Anderson, L. J. Chem. Soc., Chem. Commun. 1982, 1274–1276.
48. Donohoe, T. J.; Logan, J. G.; Laffan, D. D. Org. Lett. 2003, 5, 4995–4998.