Synthesis of Lewis X and three Lewis X trisaccharide analogues in which glucose and rhamnose replace N-acetylglucosamine and fucose, respectively

Article abstract of DOI:10.1016/j.carres.2008.04.017

Three analogues of the Le^x trisaccharide: α-l-Fucp-(1→3)-[β-d-Galp-(1→4)]-d-GlcNAcp as well as the Le^x trisaccharide itself were synthesized as methyl glycosides. In the analogues, either only the fucose residue is replaced by rhamnose or both the N-acetylglucosamine and the fucosyl residues are replaced by glucose and rhamnose, respectively. Our synthetic strategy relied on the use of lactoside and 2-azido lactoside derivatives as disaccharide acceptors, which were submitted to either fucosylation or rhamnosylation. Our results confirm that the reactivity of lactose in protection and glycosylation reactions is greatly affected by (1) the structure of the aglycone and (2) the presence of an azido substituent at C-2 of the glucose moiety. Thus, a methyl lactoside acceptor was easily glycosylated at O-3 with perbenzylated β-thiophenyl fucoside and rhamnoside to give anomerically pure α-fucosylated and α-rhamnosylated trisaccharides, respectively. In contrast, the same reactions on a 2-azido methyl lactoside acceptor led to the formation of anomeric mixtures. While the α- and β-fucosylated 2-azido trisaccharides could be separated by RP-HPLC, such separation was not possible for the rhamnosylated anomers. The desired rhamnosylated trisaccharide was finally obtained anomerically pure using an isopropylidene-protected rhamnosyl donor. The deprotection sequences also showed that the presence of a 2-azido substituent at C-2 of the glucose residue conferred stability to the vicinal fucosidic linkage at C-3. To test their relative affinity for anti-Le^x Abs the Le^x analogues will be used as competitive inhibitors against methyl Le^x. In addition, their conformational behavior will be studied by NMR spectroscopy and molecular modeling experiments.

Full text of DOI:10.1016/j.carres.2008.04.017

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 1653–1664
Synthesis of Lewis X and three Lewis X trisaccharide analogues
in which glucose and rhamnose replace N-acetylglucosamine
and fucose, respectively
Ari Asnani and France-Isabelle Auzanneau*
Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Received 14 March 2008; received in revised form 8 April 2008; accepted 13 April 2008
Available online 22 April 2008
Abstract—Three analogues of the Lex trisaccharide: a-L-Fucp-(1?3)-[b-D-Galp-(1?4)]-D-GlcNAcp as well as the Lex trisaccharide
itself were synthesized as methyl glycosides. In the analogues, either only the fucose residue is replaced by rhamnose or both the N-
acetylglucosamine and the fucosyl residues are replaced by glucose and rhamnose, respectively. Our synthetic strategy relied on the
use of lactoside and 2-azido lactoside derivatives as disaccharide acceptors, which were submitted to either fucosylation or rham-
nosylation. Our results confirm that the reactivity of lactose in protection and glycosylation reactions is greatly affected by (1) the
structure of the aglycone and (2) the presence of an azido substituent at C-2 of the glucose moiety. Thus, a methyl lactoside acceptor
was easily glycosylated at O-3 with perbenzylated b-thiophenyl fucoside and rhamnoside to give anomerically pure a-fucosylated
and a-rhamnosylated trisaccharides, respectively. In contrast, the same reactions on a 2-azido methyl lactoside acceptor led to
the formation of anomeric mixtures. While the a- and b-fucosylated 2-azido trisaccharides could be separated by RP-HPLC, such
separation was not possible for the rhamnosylated anomers. The desired rhamnosylated trisaccharide was finally obtained anomer-
ically pure using an isopropylidene-protected rhamnosyl donor. The deprotection sequences also showed that the presence of a
2-azido substituent at C-2 of the glucose residue conferred stability to the vicinal fucosidic linkage at C-3. To test their relative
affinity for anti-Lex Abs the Lex analogues will be used as competitive inhibitors against methyl Lex. In addition, their conforma-
tional behavior will be studied by NMR spectroscopy and molecular modeling experiments.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Lewis X analogues; Oligosaccharide synthesis; Reversed-phase HPLC; Lactosides; 2-Azido lactosides
1. Introduction
sues while they only weakly recognized the Lex trisac-
charide antigen.3a,f The observation that these MAbs
are able to distinguish between the polyfucosylated type
2 chains, such as dimeric Lex, accumulating in cancer
cells and the monofucosylated type 2 chains displaying
Lex and present in normal cells opens the possibility of
using dimeric Lex as a vaccine candidate. However, if
used directly as a vaccine candidate, the dimLex hexa-
saccharide is likely to trigger anti-dimLex antibodies,
as well as antibodies binding to the non-reducing trisac-
charide Lex.
Because such reactions could lead to the destruction
of normal cells displaying Lex,2 we are proposing to
investigate as vaccine candidates analogues of hexasac-
charide 1 in which one of the sugar units defining
the Lex epitope is replaced by other sugar residues,
Since it was first characterized,1 the Lex antigenic deter-
minant: a-L-Fucp-(1?3)-[b-D-Galp-(1?4)]-D-GlcNAcp
has been found on numerous normal cells and tissues
such as kidney tubules, gastrointestinal epithelial cells,
and cells of the spleen and brain.2 In contrast, the hexa-
saccharide dimLex 1 (Chart 1) has been identified as a
tumor associated carbohydrate antigen (TACA).3 Inter-
estingly, monoclonal antibodies raised and selected
against dimLex (1) were shown to bind specifically to
epitopes displayed by dimLex on colorectal tumor tis-
*
Corresponding author. Tel.: +1 519 824 4120x53809; fax: +1 519 766
1499; e-mail: fauzanne@uoguelph.ca
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.04.017

1654
A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
OH
HO
HO
OH
HO
OH
OH
O
O
O
O
O
O
O
O
OH
O
OH
NHAc
NHAc
O
OH
O
OH
OH
HO
OH
HO
1
OH
HO
HO
OH
OH
HO
HO
OH
O
O
R
O
O
O
O
OCH3
O
OH
OCH3
O
OH
R
O
OH
O
HO
OH
HO
OH
OH
R = OH
2 R = OH
4
3
R = NHAc
5 R = NHAc
Chart 1.
i.e., N-acetylglucosamine (A0) by glucose, fucose (B0) by
rhamnose, or galactose (C0) by glucose. These analogues
are expected to retain the internal epitopes presented on
the surface of colorectal cancer cells by dimLex but no
longer possess epitopes associated with the Lex trisac-
charide. To identify analogues that loose cross-reactivity
with the natural Lex antigen, we have first embarked on
the chemical synthesis of trisaccharide analogues to be
used in competitive binding experiments with the Lex
antigen (3). We are reporting here the chemical synthesis
of three trisaccharide analogues of Lex (2, 4, 5) in which
either only the N-acetylglucosamine is replaced by glu-
cose or in which both the N-acetylglucosamine and the
fucosyl residues are replaced by glucose and rhamnose,
respectively. Numerous syntheses of Lex analogues and
Lex intermediate building blocks have been reported in
the literature.4–6 These syntheses usually follow one of
three synthetic strategies: (1) a stepwise approach
involving the successive galactosylation then fucosyla-
tion of a glucosamine acceptor;4 (2) a stepwise approach
in which the sequence of glycosylation of the glucosa-
mine acceptor is reversed, that is, the fucosylation is fol-
lowed by the galactosylation;5 (3) a block approach in
which a lactosamine derivative prepared from lactose
is subjected to fucosylation at O-3.6 Expanding on our
previous work that used an allyl b-lactoside as key inter-
mediate in the synthesis of allyl Lex analogues,7 we
report here the preparation of the methyl trisaccharides
2 and 4 from methyl b-lactoside. Similarly, applying the
2. Results and discussion
The lactose containing analogues 2 and 4 were prepared
from the known9 30,40-O-isopropylidene methyl lact-
oside 6 (Scheme 1).
Lactoside 6 was treated with benzoyl chloride using
the conditions established by Tsukida et al. for the selec-
tive benzoylation of benzyl or thiophenyl lactosides.10
While the benzyl and phenyl lactosides gave a high yield
of the analogous tetra-benzoates,10 the desired methyl
lactoside acceptor 7 was isolated in only 53% yield. This
mediocre yield was explained by the concomitant forma-
tion of the known11 penta-benzoate 8, which was iso-
lated in 22% yield. Thus it appears that the presence
of a methyl group at the anomeric position increased
the reactivity of the lactoside toward benzoylation thus
reducing the selectivity of the reaction. However, since
enough acceptor 7 was obtained, this reaction was not
investigated further.
The disaccharide acceptor 7 was glycosylated with the
known thiophenyl fucoside12 9 and thiophenyl rhamn-
oside13 10 under NIS–TfOH promotion. To prevent the
degradation of the reactants and products, these reac-
tions were allowed to proceed for 15 min at ꢀ30 °C in
˚
anhydrous chloroform containing activated 4 A pow-
dered molecular sieves. In these conditions and after
HPLC purification as we previously described for similar
compounds,7 the fucosylated trisaccharide 11 and
rhamnosylated trisaccharide 13 were isolated in 73%
and 70% yields, respectively. The configuration of
the fucosidic linkage in trisaccharide 11 was estab-
lished using the vicinal coupling constant measured
between H-10 and H-20 (3.8 Hz) that corresponded to
an axial–equatorial relative orientation of these hydro-
strategy developed by Windmuller and Schmidt,6a we
¨
report here the synthesis of the known5e methyl Lex tri-
saccharide 3 and that of the rhamnosylated analogue 5
via the glycosylation of a methyl 2-azido-2 deoxy b-lac-
toside acceptor that was prepared from lactal.8

A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
1655
OH
OBz
O
O
O
OH
OBz
O
O
O
O
O
a
O
O
OMe
OMe
HO
RO
OH
OBz
OH
OBz
6
7
R = H
8 R = Bz
OBz
O
O
OBz
O
SPh
OBn
O
O
O
b
7 +
OMe
O
c
OBn
OBn
BzO
2
BzO
O
9
OR
OR
RO
d
e
11 R = Bn
12 R = Ac
OBz
O
OBz
O
O
b
SPh
O
c
O
O
+
7
BnO
4
O
OMe
OBn
BzO
OBn
BzO
O
10
BnO
OBn
OBn
13
˚
Scheme 1. Reagents and conditions: (a) 8 equiv BzCl, toluene, C5H5N, 0 °C, 2.5 h, 7 53% and 8 22%; (b) NIS, TfOH, CHCl3, MS 4 A, ꢀ30 °C, 11
(73%) and 13 (70%); (c) (1) MeONa, MeOH; (2) 90% aq AcOH 80 °C, 1 h; (3) 10% Pd–C, H2(g); 2 (45%) and 4 (75%); (d) (1) 10% Pd–C, H2(g) 100 psi;
(2) Ac2O, C5H5N; (e) (1) 90% aq AcOH 80 °C, 3 h; (2) MeONa, MeOH; 2 (85% from 10).
gens consistent with an a-fucosidic bond. The configura-
tion of the newly formed glycosidic linkage in the rham-
nosylated trisaccharide 13 was deduced from the JC,H
coupling constant at C-1 of rhamnose (169 Hz) that
was consistent with that of an a linkage.7,14 It is impor-
tant to point out that while preparing trisaccharides 11
and 13, we did not observe nor detect any formation of
the b-fucosylated or b-rhamnosylated trisaccharide
analogues.
Because methyl 2-azido-2-deoxy-lactoside (14) is easily
available from lactose via the azido-nitration of peracet-
ylated lactal,8 it was chosen as a precursor to make tri-
saccharides 3 and 5 (Scheme 2). While lactoside
derivatives can be selectively protected at the 30 and
40-hydroxyl groups of the galactose residue through the
formation of thermodynamically more stable 30,40-O-iso-
propylidenes,9,16 it has been observed that such reactions
are more difficult to achieve on 2-azido lactosides,4l,17,18
which often lead to considerable amounts of the kinetic
40,60-protected isomers. However, we found that the
known18 30,40-O-isopropylidene derivative 15 could be
obtained in a 66% yield when the reaction was carried
out at 80 °C in DMF adding 2,2-dimethoxypropane
(up to 6 equiv) and camphorsulfonic acid (up to 5 mg/
mL) portion-wise over a 24-hour reaction time. This re-
sult constitutes a considerable improvement over the
47% yield reported by Zhu et al.18 for the synthesis of
15. Selective benzoylation of disaccharide 15, once again
employing the conditions developed by Tsukida et al.,10
gave the 2-azido-2-deoxy-lactoside acceptor 16 in 67%
yield; a considerably higher yield than that reported
above for the synthesis of lactoside 7 (53%). Thus, it ap-
pears that the presence of the azido substituent at C-2 of
the glucose residue in disaccharide 15 impacts greatly the
reactivity of lactoside derivatives.
Deprotection of trisaccharides 11 and 13 was first
´
attempted in three steps: Zemplen deacylation was
followed by the acid hydrolysis (AcOH aq) of the
isopropylidene group and subsequent hydrogenolysis
of the benzyl groups. While the deprotected rhamnosy-
lated trisaccharide 4 was isolated in 75% over three
steps, the final fucosylated analogue was only obtained
in 45% yield. Indeed, TLC analysis during the isopropyl-
idene hydrolysis showed a considerable amount of deg-
radation consistent with the loss of the fucosyl residue.
Thus the deprotection strategy for trisaccharide 11 was
revised and accomplished in four steps. Hydrogenolysis
of the benzyl protecting groups was followed by the
acetylation of the fucosyl hydroxyl groups to stabilize
the fucosidic linkage.7,15 In turn, the trisaccharide
intermediate 12 was first submitted to acid hydrolysis
´
of the isopropylidene group then deacylated in Zemplen
conditions. Following this deprotection sequence, the
desired trisaccharide 2 was isolated pure in 85% yield
over four steps.
Acceptor 16 was glycosylated with the thiophenyl
glycoside donors 9 and 10 using the same conditions
as described above for the synthesis of trisaccharides

1656
A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
OH
HO
HO
OR
OH
O
OR
a
O
O
O
O
O
O
O
OMe
HO
14
OMe
HO
HO
RO
b
N3
N3
15 R = H
16
R = Bz
OBz
O
OBz
O
O
c or d
O
O
b
3
OMe
16
9
O
+
BzO
N3
O
OBn
OBn
BnO
17
α
17β
OBz
O
OBz
O
O
b
O
O
16
10
+
OMe
O
BzO
N3
O
BnO
OBn
OBn
18
α/β
OBz
O
O
OBz
O
O
O
OMe
O
SPh
O
BzO
e
b
N3
AcO
5
16
+
O
O
O
AcO
O
O
19
20
Scheme 2. Reagents and conditions: (a) 2–6 equiv DMP, CSA (2–5 mg/mL), DMF, 80 °C, 1.5 d, 66%; (b) 6 equiv BzCl, toluene, C5H5N, 0 °C, 4 h,
˚
67%; (b) NIS, TfOH, CHCl3, MS 4 A, ꢀ30 °C, 15–30 min, 17 (74%, a/b = 7:3), 18 (70%, a/b = 65:35), 20 (95%); (c) (1) 10% Pd–C, H2(g) 100 psi; (2)
Ac2O, C5H5N; (3) 90% aq AcOH 80 °C, 3 h; (4) MeONa, MeOH; 3 (55% from 17a); (d) (1) MeONa, MeOH; (2) 90% aq AcOH 80 °C, 1 h; (3) 10% Pd–
C, H2(g); 3 (76% from 17a); (e) (1) 10% Pd–C, H2(g) then in situ Ac2O, C5H5N; 2. 90% aq AcOH 80 °C, 18 h; (3) MeONa, MeOH; 5 (72% from 20).
11 and 13. Once again showing the impact of the 2-azido
substituent on the chemistry and reactivity of acceptor
16 versus that of acceptor 8, the outcome of these reac-
tions was unexpected. Indeed, in both fucosylation and
rhamnosylation, we observed the formation of both a-
and b-anomers in essentially identical ratios assessed
Although RP-HPLC7 was successfully used to separate
the a- and b-fucosylated trisaccharide 17a and 17b, the
rhamnolsylated anomers 18a,b could not be separated.
Thus we attempted to glycosylate acceptor 16 with the
known7 rhamnosyl donor 19 hoping for a better stereo-
selectivity. Indeed, in the same glycosylation condi-
tions as used for the preparation of trisaccharide
18a,b, the coupling of 16 with 19 gave the rhamnosylat-
ed trisaccharide 20 in 95% yield and as one single a
rhamnoside confirmed by NMR as described above
1
by H NMR of 7:3 in favor of the a-anomers. Hence,
the mixture of the fucosylated anomers 17a,b was
isolated in 74% yield while the anomeric mixture of
the rhamnosylated anomers was obtained in 70% yield.
The structure of the newly formed fucosidic bonds in
trisaccharides 17a and 17b was established using the
vicinal coupling constants measured between H-10 and
H-20 and that corresponded to an axial–equatorial
(3.6 Hz) relative orientations of these hydrogens for
17a and to a trans-diaxial orientation (8.4 Hz) for 17b.
0
0
ðJC-1 ;H-1 ¼ 172 HzÞ.
Having in hand the pure trisaccharides 17a and 20,
these were submitted to deprotection reactions to
provide the desired trisaccharides 3 and 5, respectively.
Given the lability of the benzylated fucosidic residue
observed in the deprotection of trisaccharide 11, we first
attempted to deprotect trisaccharide 17a in four steps.
Hydrogenolysis of the benzyl groups and reduction of
the azido group were first accomplished with H2(g)
(100 psi) and 10% Pd–C catalyst and the intermediate
0
0
Measurements of the JC-1 ;H-1 coupling constants for
each product formed in the rhamnosylation reaction
confirmed7,14 that these indeed were the aðJC-1 ;H-1
¼
0
0
0
0
171 HzÞ and bðJC-1 ;H-1 ¼ 161 HzÞ anomers 18a,b.

A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
1657
was N-acetylated in situ. After work-up, the triol was O-
acetylated (Ac2O–pyridine) to stabilize the fucosidic
bond7,15 and the triacetate was submitted to acid hydro-
lysis (AcOH aq) to remove the isopropylidene group.
After silica gel chromatography, the diol was submitted
a-fucosidic and rhamnosidic bonds, while the azido
group at C-2 of acceptor 16 led to the formation of
anomeric mixtures in both reactions.
Given the fact that the b-thiophenyl glycosyl donors
were activated by iodonium ions using only a catalytic
amount of TfOH, we propose that the glycosylation of
the 2-benzoate acceptor 8 with donors 9 and 10 pro-
ceeded mostly through fast SN2-type displacements of
the activated thiophenyl groups leading exclusively to
a glycosidic bonds. In contrast, we propose that the
2-azido substituent at C-2 of acceptor 16 significantly
reduced the reactivity of OH-3 and allowed the glycosyl-
ations to proceed through slower SN1-type processes
that led to the intermediate formation of oxocarbenium
ions, which in turn gave anomeric mixtures of the de-
sired trisaccharides. These results may be rationalized
by the fact that, based on field inductive parameters,19
the azido substituent is more inductively electron with-
drawing than both hydroxyl and O-benzoyl groups. This
greater inductive withdrawing effect may explain the
reduced nucleophilicity of the 3-OH group toward
benzoylation and glycosylation in the 2-azido lactoside
7 and 2-azido acceptor 16, respectively. It also may
explain the greater stability of the fucosidic bond toward
acid hydrolysis in the deprotection of the 2-azido trisac-
charide 17a.
´
to a Zemplen trans-esterification of the acyl groups and
gave the deprotected Lex trisaccharide 3 in 55% yield
after Biogel P2 gel exclusion chromatography. We ex-
plain this relatively poor yield by the difficulties encoun-
tered in the first step (H2, Pd–C), which required an
extended reaction time and only proceeded to an accept-
able degree following multiple work-ups and addition of
fresh palladium catalyst.
To increase the yield of deprotection of trisaccharide
17a, we attempted a three-reaction deprotection se-
quence. The benzoyl groups were first removed by
trans-esterification, the isopropylidene was hydrolyzed,
and the benzyl groups were removed by hydrogenolysis
with the concomitant reduction of the azido group and
the in situ acetylation of the resulting amino group.
Following this sequence of reactions the deprotected
Lex trisaccharide 3 was obtained pure in 76% yield,
and its analytical data were in total agreement with
those reported in the literature.5e Although the depro-
tection of trisaccharide 11 following the same sequence
of reactions (Scheme 1) led to some loss of the benzyl-
ated fucosidic residue during the aqueous hydrolysis, it
is interesting to mention that we did not observe such
degradation when deprotecting the azido trisaccharide
17a. This result once again supports the assertion that
the azido group at C-2 of the glucose residue confers a
noticeably different reactivity to the molecule. The pro-
tected rhamnosylated trisaccharide 20 was easily depro-
tected in three steps. Reduction of the azido group (H2,
10% Pd–C) and in situ acetylation of the amino group
was followed by the acid catalyzed hydrolysis of the iso-
propylidene substituents and, finally, the O-acyl groups
To test their relative affinity for the anti-Lex monoclo-
nal antibody SH1,3f the trisaccharide analogues 2, 4, and
5 will be used as competitive inhibitors with the methyl
Lex analogue 3. In addition, the conformational behav-
ior of these Lex analogues will be studied by NMR spec-
troscopy and molecular modeling experiments.20 The
results obtained in these studies will be reported in due
time and, hopefully, will lead to the discovery of an ana-
logue of the TACA dimLex (1) that can be safely used in
the design of an anti-cancer vaccine.
´
were removed in Zemplen conditions to give trisaccha-
ride 5, which was isolated pure in 72% yield after gel per-
meation chromatography.
3. Experimental
The synthetic work described here illustrates some of
the effects that an azido group at C-2 of a methyl lacto-
side derivative may have on its reactivity. When
comparing the results obtained for the selective benzoyl-
ation of methyl lactoside 5 to that of the 2-azido 2-deoxy
analogue 7, it is reasonable to suggest that the azido
substituent allowed a better selectivity of the reaction
by reducing the reactivity at OH-3 of the lactoside.
When comparing the deprotection of trisaccharide 11
to that of the 2-azido analogue 17a, it appeared that,
in contrast to a hydroxyl group, the 2-azido substituent
reduced the lability of the fucosidic bond toward acid
hydrolysis. In the glycosylation reactions using perbenz-
ylated b-thiophenyl fuco- and rhamnoside donors, it
appeared that the O-benzoyl group at C-2 of lactose in
acceptor 8 favored the exclusive formation of the
3.1. General methods
1H NMR (400.13 and 600.13 MHz) and 13C NMR (75.5,
100.6 and 150.9 MHz) spectra were recorded in CDCl3
1
(internal standard, for H residual CHCl3 d 7.26; for
13C: CDCl3 d 77.0), CD3OD (internal standard, for H
1
residual CH3OD d 3.30; for 13C: CD3OD d 49.0), or
D2O [external standard 3-(trimethylsilyl)-propionic
acid-d4, sodium salt (TSP) for 1H d 0.00, for 13C d
0.00]. 1H NMR and 13C NMR chemical shifts are
reported in parts per million (ppm). Coupling constants
(J) are reported in Hertz (Hz). Chemical shifts and
coupling constants were obtained from a first-order
analysis of one-dimensional spectra. Assignments of pro-
ton and carbon resonances were based on two-dimen-
sional 1H–1H and 13C–1H correlation experiments.

1658
A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
Multiplicities are abbreviated as follows: singlet (s), dou-
blet (d), triplet (t), quartet (q), multiplet (m), and broad-
ened (br). All NMR spectra were recorded at 300 K. All
reagents were purchased from commercial suppliers and
used without further purification. TLC was performed
on precoated aluminum plates with Silica Gel 60 F254
and detected with UV light and/or charred with a solu-
tion of 10% H2SO4 in ethanol. Compounds were purified
by flash chromatography with Silica Gel 60 (230–400
mesh) unless otherwise stated. Solvents were distilled
and dried according to standard procedures,21 and or-
ganic solutions were dried over Na2SO4 and concen-
trated below 40 °C, under reduced pressure. Reversed-
phase HPLC purifications were carried out on a Prep
then acceptor 7 (2.19 g, 53%), both pure as a white
powders.
3.2.2.1. Analytical data for 7. [a]D +28.3 (c 1.2,
1
CHCl3); H NMR (400 MHz, CDCl3): d 8.08–7.27 (m,
20H, Ar), 5.37 (t, 1H, J = 7.8 Hz, H-20), 5.24 (dd, 1H,
J = 9.5, 8.1 Hz, H-2), 4.87 (dd, 1H, J = 12.5, 2.5 Hz,
H-6a0), 4.67 (d, 1H, J = 8.2 Hz, H-10), 4.64 (d, 1H,
J = 1.4 Hz, OH), 4.47 (d, 1H, J = 8.1 Hz, H-1), 4.42–
4.38 (m, 3H, H-6a, H-6b0, H-30), 4.29–4.25 (m, 2H,
H-40, H-50), 4.21 (dd, 1H, J = 12.1, 4.3 Hz, H-6b), 4.01
(br t, 1H, J = 8.7, 1.1 Hz, H-3), 3.75 (t, 1H, J =
9.8 Hz, H-4), 3.74 (m, 1H, H-5), 3.40 (s, 3H, OCH3),
1.64, 1.62 (2s, 6H, C(CH3)2); 13C NMR (100.6 MHz,
CDCl3): d 166.5, 165.5, 165.2 (CO), 133.4–128.2 (Ar),
111.2 (C(CH3)2), 101.6 (C-1), 101.5 (C-10), 82.3 (C-4),
76.6 (C-30), 73.4 (C-3, C-40), 72.9 (C-20), 72.8 (C-2),
72.0 (C-5, C-50), 63.6 (C-60), 62.5 (C-6), 56.7 (OCH3),
27.6, 26.2 (C(CH3)2). ESIMS: [M+Na]+ calcd for
C44H44O15, 835.2578; found, 835.2629.
Nova PakÒ HR C18, 6 lm 60 A (25 ꢁ 100 mm) column
˚
using mixtures of acetonitrile and water as eluants. Gel
permeation purifications were carried out on a Biogel
P2 column (100 ꢁ 1 cm) eluted with water. High-resolu-
tion electrospray-ionization mass spectra (ESIMS) were
recorded at the McMaster Regional Centre for Mass
Spectrometry.
3.2.2.2. Analytical data for 8. 1H NMR (400 MHz,
CDCl3): d 8.13–7.27 (m, 25H, Ar), 5.73 (t, 1H,
J = 9.5 Hz, H-3), 5.41 (dd, 1H, J = 9.6, 7.8 Hz, H-2),
5.14 (t, 1H, J = 7.3 Hz, H-20), 4.65–4.54 (m, 3H, H-1,
H-10, H-6a0), 4.47 (dd, 1H, J = 12.2, 4.2 Hz, H-6b0),
4.28–4.18 (m, 3H, H-4, H-6a, H-30), 4.07 (dd, 1H,
J = 5.6, 2.0 Hz, H-40), 3.81 (m, 2H, H-5, H-50), 3.65
(dd, 1H, J = 11.4, 7.6 Hz, H-6b), 3.43 (s, 3H, OCH3),
1.52, 1.25 (2s, 6H, C(CH3)2); 13C NMR (100.6 MHz,
CDCl3): d 165.8, 165.6, 165.2, 164.9 (CO), 133.4–128.1
(Ar), 110.8 (C(CH3)2), 101.9 (C-1), 100.1 (C-10), 76.9
(C-30), 75.3 (C-4), 73.6 (C-20), 73.1 (C-40), 72.9 (C-5 or
C-50), 72.6 (C-3), 71.8 (C-2), 71.3 (C-5 or C-50), 62.6
(C-6, C-60), 57.1 (OCH3), 27.4, 26.1 (C(CH3)2). ESIMS:
[M+NH4]+ calcd for C51H48O16, 934.3265; found,
934.3286.
3.2. Methyl 2,6-di-O-benzoyl-4-O-(2,6-di-O-benzoyl-3,4-
O-isopropylidene-b-D-galactopyranosyl)-b-D-glucopyran-
oside (7)
3.2.1. Methyl 4-O-(3,4-O-isopropylidene-b-D-galactopyr-
anosyl)-b-D-glucopyranoside (6). b-Methyl lactoside
(2.02 g, 5.6 mmol)9,22 was dissolved in 2,2-dimethoxy-
propane (45 mL) containing anhydrous pTsOH
(253 mg). The mixture was stirred at room temperature
for 39 h, and then diluted with MeOH (50 mL). Water
(15 mL) was added to the mixture and the clear solution
obtained was neutralized with Et3N (1 mL). The solu-
tion was concentrated to produce isopropylidene deriv-
ative 6 (2.01 g, 89%). NMR data were in agreement
with those reported previously,9 and disaccharide 6
was used directly in the next reaction.
3.3. Methyl 2,6-di-O-benzoyl-4-O-(2,6-di-O-benzoyl-3,4-
O-isopropylidene-b-D-galactopyranosyl)-3-O-(2,3,4-tri-
O-benzyl-a-L-fucopyranosyl)-b-D-glucopyranoside (11)
3.2.2. Methyl 2,6-di-O-benzoyl-4-O-(2,6-di-O-benzoyl-
3,4-O-isopropylidene-b-D-galactopyranosyl)-b-D-glucopyr-
anoside (7) and methyl 2,3,6-tri-O-benzoyl-4-O-(2,6-di-O-
benzoyl-3,4-O -isopropylidene-b-D-galactopyranosyl)-b-D-
glucopyranoside (8). Benzoyl chloride (4.6 mL, 0.04
mol) was added to a solution of the isopropylidene
derivative 6 (2.01 g, 5.1 mmol) in anhydrous pyridine
(30 mL) and toluene (40 mL) stirred at 0 °C. After stir-
ring at 0 °C for 2.5 h, the reaction was quenched with
MeOH (0.1 mL) and the mixture was concentrated.
The residue was dissolved in EtOAc (150 mL) and
washed sequentially with water, satd aq NaHCO3, M
HCl, and water. The aqueous phases were re-extracted
with EtOAc (2 ꢁ 100 mL), and the combined organic
solutions were dried and concentrated. Flash chromato-
graphy (1:5, EtOAc–toluene) of the residue produced
first the known11 penta-benzoate 8 (1.05 g, 22%) and
A mixture of the known thiophenyl glycoside12
9
(278 mg, 523 lmol) and acceptor 7 (254 mg, 312 lmol)
˚
in anhydrous CHCl3 (3 mL) containing activated 4 A
powdered molecular sieves (484 mg) was stirred under
N2 for 3 h at room temperature. The mixture was cooled
to ꢀ30 °C and N-iodosuccinimide (158 mg, 700 lmol)
followed by TfOH (22 lL, 248 lmol) was added. The
reaction mixture was stirred for 15 min at ꢀ30 °C and
the reaction was quenched with triethylamine (130 lL).
The solids were filtered off and washed with CH2Cl2.
The combined filtrate and washing were washed succes-
sively with satd aq NaHCO3, satd aq Na2S2O3, and
water. The aqueous phases were re-extracted twice with
CH2Cl2, and the combined organic solutions were dried

A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
1659
and concentrated. Flash chromatography (7:3 hexanes–
2 ꢁ C(CH3)2); 13C NMR (100.6 MHz, CDCl3):
d
166.2, 164.9, 164.78 (CO), 133.6–126.7 (Ar), 110.9,
104.1 (2 ꢁ C(CH3)2), 101.1 (1JC–H = 169 Hz, C-10),
99.8 (C-100), 99.1 (C-1), 80.39 (C-40 or C-500), 79.9
(C-30), 77.3 (C-3 or C-300), 76.8 (C-20), 76.4 (C-3 or
C-300), 75.1 (CH2Ph), 74.8 (C-2), 74.7 (C-4), 73.5
(C-400), 73.2 (C-40 or C-500), 72.9 (C-200), 72.8 (CH2Ph),
71.9 (C-5), 71.3 (CH2Ph), 68.2 (C-50), 62.9 (C-600), 62.3
(C-6), 56.9 (OCH3), 27.6, 26.2 (2 ꢁ C(CH3)2), 17.6
(C-60). ESIMS: [M+Na]+ calcd for C71H72O19,
1251.4590; found, 1251.4503.
EtOAc) of the residue followed by RP-HPLC (20 mL/
min; 9:1 CH3CN–H2O) produced pure trisaccharide 11
(281 mg, 73%); [a]D +6.7 (c 1.2, CHCl3); 1H NMR
(400 MHz, CDCl3): d 8.23–6.99 (m, 20H, Ar), 5.49 (d,
1H, J = 3.8 Hz, H-10), 5.46 (t, 1H, J = 8.0 Hz, H-200),
5.29 (t, 1H, J = 8.0 Hz, H-2), 5.0 (d, 1H, J = 11.6 Hz,
CHHPh), 4.94 (m, 1H, H-50), 4.87–4.75 (m, 3H, H-6a00,
2CHHPh), 4.71 (d, 1H, J = 11.6 Hz, CHHPh), 4.62 (br
d, 1H, J = 11.7 Hz, H-6a), 4.55 (m, 2H, H-1, H-6b),
4.40 (m, 2H, H-100, CHHPh), 4.30 (m, 5H, H-3, H-30,
H-300, H-6b00, CHHPh), 4.20 (br d, 1H, H-400), 4.17 (t,
1H, J = 9.3 Hz, H-4), 3.98 (dd, 1H, J = 10.1, 3.7 Hz,
H-20), 3.88 (m, 1H, H-500), 3.83 (br s, 1H, H-40), 3.56
(m, 1H, H-5), 3.41 (s, 3H, OCH3) 1.55, 1.36 (2s, 6H,
C(CH3)2), 1.37 (d, 3H, J = 7.4 Hz, H-60); 13C NMR
(100.6 MHz, CDCl3): d 166.2, 166.0, 164.6, 164.5 (CO),
133.5–126.7 (Ar), 110.8 (C(CH3)2), 102.8 (C-1), 100.1
(C-100), 97.3 (C-10), 79.0, 77.4, 74.1 (C-3, C-30, C-300),
78.2 (C-40), 75.6 (C-20), 74.8 (CH2Ph), 74.8 (C-200), 73.3,
73.2 (C-2, C-5, C-400), 72.6, 72.5 (2 ꢁ CH2Ph), 71.4 (C-
500), 66.4 (C-50), 62.5 (C-600), 62.3 (C-6), 56.8 (OCH3),
27.7, 26.2 (C(CH3)2), 16.8 (C-60). ESIMS: [M+NH4]+
calcd for C71H72O19, 1246.5012; found, 1246.5020.
3.5. Methyl 3-O-a-L-fucopyranosyl-4-O-b-D-galactopyr-
anosyl-b-D-galactopyranoside (2)
3.5.1. Method A. The protected trisaccharide 11
(158 mg, 128 lmol) was dissolved in 0.4 M methanolic so-
dium methoxide (15 mL). The mixture was stirred at
room temperature overnight, diluted with MeOH
(10 mL), and deionized with Dowex 50 (H+) resin. The re-
sin was filtered off, rinsed with MeOH, and the combined
filtrate and washings were concentrated. Chromatogra-
phy (hexanes then 1:9 MeOH–CHCl3) of the residue pro-
duced the corresponding polyol (98 mg, 94%) that was
dissolved in 90% aqueous acetic acid (10 mL). The solu-
tion was stirred at 80 °C for 1 h and co-concentrated with
toluene. The dry residue was dissolved in MeOH (10 mL),
10% Pd–C (100 mg) was added, and the stirred mixture
was subjected overnight at room temperature to hydrog-
enolysis under H2 atmosphere. Additional 10% Pd–C
(100 mg) was added and the mixture was again submitted
to hydrogenolysis overnight. The catalyst was filtered off
on Celite and the solids were rinsed thoroughly with
MeOH. The combined filtrate and washings were concen-
trated and silica gel chromatography (0.5:3:6.5 H2O–
MeOH–EtOAc) followed by RP-HPLC (10 mL/min;
7:3 CH3CN–H2O) produced the pure trisaccharide 2
(29 mg, 45 % from 13), which was isolated as an amor-
phous powder after freeze-drying.
3.4. Methyl 2,6-di-O-benzoyl-4-O-(2,6-di-O-benzoyl-3,4-
O-isopropylidene-b-D-galactopyranosyl)-3-O-(2,3,4-tri-
O-benzyl-a-L-rhamnopyranosyl)-b-D-glucopyranoside (13)
A mixture of the known13 thiophenyl rhamnoside 10
(115 mg, 218 lmol) and acceptor 7 (102 mg, 126 lmmol)
˚
in anhydrous CHCl3 (1.5 mL) containing activated 4 A
powdered molecular sieves (165 mg) was stirred under
N2 for 3 h at room temperature. The mixture was cooled
to ꢀ30 °C, then N-iodosuccinimide (64 mg, 280 lmol)
and TfOH (9 lL, 100 lmol) were added to the mixture.
After the reaction was stirred for 15 min, triethylamine
(90 lL) was added to quench the reaction and the
work-up of the reaction was performed as described
for the preparation of 11. Flash chromatography (7:3,
hexanes–EtOAc) followed by RP-HPLC (20 mL/min;
9:1 CH3CN–H2O) gave trisaccharide 13 (107 mg, 70%)
pure as an amorphous glass. [a]D +65.6 (c 0.9, CHCl3);
1H NMR (400 MHz, CDCl3): d 8.16–6.87 (m, 30H, Ar),
5.36 (dd, 1H, J = 8.0, 9.2 Hz, H-2), 5.32 (t, 1H,
J = 8.0 Hz, H-200), 5.21 (d, 1H, J = 1.2 Hz, H-10), 4.95
(d, 1H, J = 11.5 Hz, CHHPh), 4.84 (dd, 1H, J = 3.6,
11.7 Hz, H-6a00), 4.78 (m, 1H, H-50), 4.70–4.59 (m, 3H,
H-6a, H-6b00, CHHPh), 4.49 (dd, 1H, J = 3.8, 12.0 Hz,
H-6b), 4.47 (d, 1H, J = 8.8 Hz, H-100), 4.41 (d, 1H,
J = 7.9 Hz, H-1), 4.35 (d, 1H, J = 11.8 Hz, CHHPh),
4.23–4.17 (m, 3H, H-3, H-300, CHHPh), 4.12 (dd, 1H,
J = 2.2, 5.1 Hz, H-400), 4.09–4.00 (m, 3H, H-4, H-30,
CHHPh), 3.81 (m, 2H, H-500, CHHPh), 3.74 (m, 1H,
H-20), 3.55 (m, 2H, H-40, H-500), 3.37 (s, 3H, OCH3),
1.48 (d, 3H, J = 6.1 Hz, H-60), 1.47, 1.29 (2s, 6H,
3.5.2. Method B
3.5.2.1. Methyl 2,6-di-O-benzoyl-3-O-(2,3,4-tri-O-
acetyl-a-L-fucopyranosyl)-4-O-(2,6-di-O-benzoyl-3,4-O-
isopropylidene-b-D-galactopyranosyl)-b-D-glucopyrano-
side (12). The protected trisaccharide 11 (20 mg,
16 lmol) was dissolved in EtOAc (2 mL), and 10% Pd–
C (42 mg) was added. The reaction mixture was submit-
ted to hydrogenolysis at 100 psi of H2 overnight at room
temperature. The catalyst was filtered off and rinsed
thoroughly with a mixture of MeOH and EtOAc (1:1,
10 mL) followed by pure MeOH (10 mL). The combined
filtrate and washings were concentrated, and the crude
alcohol (12.3 mg) was submitted to acetylation overnight
at room temperature in a 1:1 mixture of Ac2O and pyri-
dine (2 mL). The reaction mixture was co-concentrated

1660
A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
with toluene to produce the crude triacetate 12 (20 mg)
that was used directly in the next reaction. H NMR
and the reaction was allowed to proceed overnight at
rt. Work-up and purification by chromatography were
carried out as described in Section 3.5.1 for the depro-
tection of trisaccharide 11 following method A. The
intermediate polyol (51 mg, 93%) was then dissolved in
90% aqueous acetic acid (5 mL) and the hydrolysis as
well as work-up of the reaction and subsequent hydrog-
enolysis of the remaining benzyl groups (H2, 10% Pd–C)
were also carried out as described in Section 3.5.1. Puri-
fication by chromatography (0.5:3:6.5, H2O–MeOH–
EtOAc) followed by RP-HPLC (10 mL/min; 7:3,
CH3CN–H2O) gave the pure trisaccharide 3 (25 mg,
75% from 13), which was isolated as an amorphous
powder upon freeze-drying. [a]D ꢀ33.5 (c 0.5, MeOH);
1H NMR (600 MHz, D2O): d 5.14 (d, 1H, J = 1.5 Hz,
H-10), 4.29 (m, 1H, H-50), 4.26 (d, 1H, J = 7.9 Hz,
H-100), 4.23 (d, 1H, J = 8.0 Hz, H-1), 3.83 (dd, 1H, J =
1.75, 3.3 Hz, H-20), 3.81 (dd, 1H, J = 2.0, 12.3 Hz, H-
6a), 3.73 (dd, 1H, J = 3.4, 9.7 Hz, H-30), 3.71 (br d,
1H, J = 3.5 Hz, H-400), 3.69 (t, 1H, J = 9.3 Hz, H-3),
3.67–3.61 (m, 3H, H-4, H-6b, H-6a00), 3.58 (dd, 1H,
J = 4.2, 11.9 Hz, H-6b00), 3.49 (br dd, 1H, J = 4.0,
8.1 Hz, H-500), 3.45 (dd, 1H, J = 3.4, 9.9 Hz, H-300),
3.40 (m, 1H, H-5), 3.38 (s, 3H, OCH3), 3.25 (m, 2H,
H-2, H-200), 3.21 (t, 1H, J = 9.7 Hz, H-40), 1.09 (d, 3H,
J = 6.3 Hz, H-60); 13C NMR (150.9 MHz, D2O): d
103.0 (C-1), 102.3 (C-100), 99.7 (C-10), 76.3 (C-3), 75.3,
75.2 (C-5, C-500), 74.4 (C-2), 72.9 (C-4), 72.9 (C-4),
72.5 (C-300), 72.3 (C-40), 71.4 (C-200), 70.1 (C-20), 69.9
(C-30), 68.9 (C-400), 68.2 (C-50), 61.1 (C-600), 59.5 (C-6),
57.2 (OCH3), 16.0 (C-60). ESIMS: [M + H]+ calcd for
C19H34O15, 503.1976; found, 503.1978.
1
(400 MHz, CDCl3): d 8.25–7.30 (m, 20H, Ar), 5.45–
5.32 (m, 3H, H-11, H-30, H-40 H-200), 5.27 (dd, 1H,
J = 7.5, 8.5 Hz, H-2), 5.18 (m, 1H, H-50), 5.10 (dd, 1H,
J = 4.0, 10.1 Hz, H-20), 4.98 (dd, 1H, J = 4.1,
12.1 Hz, H-6a00), 4.80 (dd, 1H, J = 8.9, 11.9 Hz,
H-6b00), 4.61 (dd, 1H, J = 1.3, 12.1 Hz, H-6a), 4.51 (d,
1H, J = 8.7 Hz, H-100), 4.44 (dd, 1H, J = 3.4, 12.3 Hz,
H-6b), 4.35 (d, 1H, J = 7.9 Hz, H-1), 4.29–4.10 (m, 4H,
H-3, H-4, H-300, H-400), 3.84 (m, 1H, H-500), 3.53 (m,
1H, H-5), 3.34 (s, 3H, OCH3), 2.13, 1.87, 1.86 (3s,
3 ꢁ 3H, 3CH3CO), 1.60, 1.35 (2s, 2 ꢁ 3H, C(CH3)2),
1.35 (d, 3H, H-60).
3.5.2.2. Methyl 3-O-a-L-fucopyranosyl-4-O-b-D-galac-
topyranosyl-b-D-galactopyranoside (2). The crude tri-
acetate 12 was dissolved in 90% aqueous AcOH
(2 mL), stirred at 80 °C for 3 h, and co-concentrated
with toluene to give the corresponding crude diol which
was dissolved in methanolic (0.4 M) sodium methoxide
(2 mL). The solution was stirred overnight at room tem-
perature and deionized with Dowex 50 (H+) resin. The
resin was filtered off, rinsed with MeOH, and the com-
bined filtrate and washings were concentrated. Gel per-
meation chromatography of the residue on a Biogel P2
column eluted with water produced the pure trisaccha-
ride 2 (7 mg, 85% from 11), which was isolated as an
amorphous powder after freeze-drying.
3.5.3. Analytical data for trisaccharide 2. [a]D ꢀ5.3 (c
0.3, MeOH); 1H NMR (600 MHz, D2O): d 5.29 (d,
1H, J = 3.9 Hz, H-10), 4.68 (m, 1H, H-50), 4.29 (d, 1H,
J = 7.8 Hz, H-100), 4.24 (m, 1H, J = 8.0 Hz, H-1), 3.86
(dd, 1H, J = 2.0, 12.3 Hz, H-6a), 3.81 (dd, 1H, J =
3.7. Methyl 2-azido-6-O-benzoyl-4-O-(2,6-di-O-benzoyl-
3,4-O-isopropylidene-b-D-galactopyranosyl)-2-deoxy-b-D-
glucopyranoside (16)
3.3, J3 ;4 10.4 Hz, H-30), 3.75 (br d, 1H, J = 3.3 Hz,
H-400), 3.71 (t, 1H, J = 9.5 Hz, H-4), 3.68 (dd, 1H, J =
4.8, 12.3 Hz, H-6b), 3.66–3.62 (m, 3H, H-3, H-20,
H-40), 3.61–3.55 (m, 2H, H-6a00, H-6b00), 3.50 (dd, 1H,
J = 3.3, 10.4 Hz, H-300), 3.45–3.43 (m, 2H, H-5, H-500),
3.42 (s, 3H, OCH3), 3.37–3.33 (m, 2H, H-2, H-200),
1.03 (d, 3H, J = 6.6 Hz, H-60); 13C NMR (150.9 MHz,
D2O): d 103.6 (C-1), 101.8 (C-100), 98.8 (C-10), 77.3
(C-3 or C-20 or C-40), 75.3, 75.0 (C-5, C-500), 74.5 (C-
2), 72.8 (C-40), 72.5 (C-300), 72.0 (C-3 or C-20 or C-40),
71.2 (C-200), 69.3 (C-30), 68.4 (C-400), 68.1 (C-3 or C-20
or C-40), 66.6 (C-50), 61.7 (C-600), 59.8 (C-6), 57.5
(OCH3), 15.2 (C-60). ESIMS: [M+Na]+ calcd for
C19H34O15, 525.1801; found, 525.1792.
0
0
3.7.1. Methyl 2-azido-4-O-(3,4-O -isopropylidene-b-D-
galactopyranosyl)-2-deoxy-b-D-glucopyranoside
(15).
The known8 methyl 2-azido lactoside 14 (224 mg,
590 lmol) was dissolved in DMF (3 mL) containing
CSA (3 mg). The mixture was stirred at 80 °C for
5 min, and then 2,2-dimethoxypropane (150 lL, 1.2
mmol) was added to the mixture. The stirring was con-
tinued overnight and additional CSA (total 14.5 mg)
and 2,2-dimethoxypropane (total 450 lL) were added
portion-wise over the next 24 h. The reaction was
quenched with triethylamine (30 lL) and the mixture
was co-concentrated with toluene. Chromatography
(1:9 MeOH–CHCl3) of the residue produced the
known18 isopropylidene derivative 15 (163 mg, 66%),
which was taken directly to the next step. 1H NMR
(400 MHz, D2O): d 4.49 (d, 1H, J = 8.4 Hz, H-10), 4.47
(d, 1H, J = 8.3 Hz, H-1), 4.34 (dd, 1H, J = 1.7, 5.3 Hz,
H-40), 4.21 (dd, 1H, J = 5.5, 7.5 Hz, H-30), 4.08 (m,
1H, H-50), 3.96 (dd, 1H, J = 2.3, 12.4 Hz, H-6a), 3.87–
3.6. Methyl 4-O-b-D-galactopyranosyl-3-O-a-L-rhamno-
pyranosyl-b-D-galactopyranoside (3)
The protected trisaccharide 13 (82 mg, 60 lmol) was dis-
solved in 0.4 M methanolic sodium methoxide (5 mL)

A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
1661
1
3.77 (m, 3H, H-6b, H-6a0, H-6b0), 3.71–3.47 (m, 8H,
H-3, H-4, H-5, H-20, H-50, OCH3), 3.34 (br t, 1H,
H-2), 1.53, 1.38 (2s, 2 ꢁ 3H, C(CH3)2).
(17a,b, 232 mg, 74%) as assessed by H NMR. The two
anomers were eventually separated by RP-HPLC (8:2
CH3CN–H2O). The wanted trisaccharide 17a was iso-
lated pure in 48% yield (150 mg) while trisaccharide
17b was isolated in 8% yield (31 mg).
3.7.2. Methyl 2-azido-6-O-benzoyl-4-O-(2,6-di-O-benz-
oyl-3,4-O-isopropylidene-b-D-galactopyranosyl)-2-deoxy-
b-D-glucopyranoside (16). Benzoyl chloride (270 lL,
2.3 mmol) was added to a solution of the isopropylidene
derivative 15 (163 mg, 0.39 mmol) in anhydrous pyri-
dine (2.4 mL) and toluene (3.3 mL) stirred at 0 °C. After
stirring at 0 °C for 4 h, the reaction was quenched with
MeOH (0.1 mL), concentrated, and the work-up was per-
formed as described for the synthesis of acceptor 7. Puri-
fication of the residue by centrifugal chromatography (7:3
hexanes–EtOAc) gave the 2-azido acceptor 16 (189 mg,
3.8.1. Analytical data for 17a. [a]D +0.001 (c 0.8,
CHCl3); H NMR (400 MHz, CDCl3): d 8.15–7.23 (m,
1
30H, Ar), 5.63 (d, 1H, J = 3.6 Hz, H-10), 5.22 (dd, 1H,
J = 7.5, 8.5 Hz, H-200), 5.02 (d, 1H, J = 11.6 Hz,
CHHPh), 4.93–4.78 (m, 5H, 2 CH2Ph, H-50), 4.71 (m,
2H, CHHPh, H-6a00), 4.54 (dd, 1H, J = 1.6, 12.3 Hz,
H-6a), 4.49 (d, 1H, J = 8.7 Hz, H-100), 4.45 (dd, 1H,
J = 3.6, 12.3 Hz, H-6b), 4.39 (dd, 1H, J = 7.6, 11.2 Hz,
H-6b00), 4.24 (dd, 1H, J = 2.6, 10.3, H-30), 4.19 (d, 1H,
J = 7.9 Hz, H-1), 4.19–4.15 (m, 3H, H-20, H-300, H-400),
3.92–3.85 (m, 2H, H-4, H-500), 3.81 (br s, 1H, H-40),
3.69 (t, 1H, J = 9.5 Hz, H-3), 3.48 (s, 3H, OCH3), 3.43
(dd, 1H, J = 8.1, 9.9 Hz, H-2), 3.37 (m, 1H, H-5),
1.51, 1.31 (2s, 6H, C(CH3)2), 1.29 (d, 3H, J = 6.5 Hz,
H-60); 13C NMR (100.6 MHz, CDCl3): d 166.0, 165.9
164.6 (CO), 139.2–126.9 (Ar), 110.7 (C(CH3)2), 103.4
(C-1), 101.1 (C-100), 97.3 (C-10), 79.4 (C-30), 78.1 (C-40),
77.0, 76.0 (2 of C-20, C-300, C-400), 74.8 (CH2Ph), 74.7
(C-4 or C-500), 73.9 (C-3), 73.3 (CH2Ph), 73.2 (C-20 or
C-300 or C-400), 73.0 (C-4 or C-500), 72.6 (CH2Ph), 71.1
(C-4 or C-500), 66.5 (C-2), 66.3 (C-50), 62.7 (C-600), 62.3
(C-6), 57.2 (OCH3), 27.7, 26.2 (C(CH3)2), 16.8 (C-60).
ESIMS: [M+Na]+ calcd for C64H67O17N3, 1172.4368;
found, 1172.4379.
1
67%) as a white powder. [a]D +28.3 (c 1.2, CHCl3); H
NMR (400 MHz, CDCl3): d 8.18–7.26 (m, 15H, Ar),
5.34 (t, 1H, J = 7.5 Hz, H-20), 4.92 (dd, 1H, J = 2.8,
12.3 Hz, H-6a0), 4.63 (br s, 1H, OH), 4.62 (d, 1H,
J = 7.9 Hz, H-10), 4.49 (dd, 1H, J = 8.9, 12.2, H-6b0),
4.39 (dd, 1H, J = 5.4, 7.1 Hz, H-30), 4.32–4.26 (m, 3H,
H-6a, H-40, H-50), 4.20 (dd, 1H, J = 4.0 12.0 Hz,
H-6b), 4.13 (d, 1H, J = 8.2 Hz, H-1), 3.69 (dd, 1H,
J = 7.7, 9.6 Hz, H-3), 3.55–3.47 (m, 2H, H-4, H-5),
3.48 (s, 3H, OCH3), 3.25 (dd, 1H, J = 8.3, 9.7 Hz,
H-2), 1.64, 1.36 (2s, 2 ꢁ 3H, C(CH3)2); 13C NMR
(100.6 MHz, CDCl3): d 166.5, 165.5, 165.1 (CO),
133.4–128.3 (Ar), 111.3 (C(CH3)2), 102.2 (C-1), 101.4
(C-10), 81.7 (C-4 or C-5), 76.8 (C-30), 73.9 (C-3), 73.3
(C-40 or C-50), 72.8 (C-20), 72.0, 72.0 (C-4 or C-5 and
C-40 or C-50), 65.5 (C-2), 63.6 (C-60), 62.5 (C-6), 57.1
(OCH3), 27.5, 26.2 ((C(CH)3)2). ESIMS: [M+NH4]+
calcd for C37H39O13N3, 751.2827; found, 751.2860.
3.8.2. Analytical data for 17b. 1H NMR (400 MHz,
CDCl3): d 8.10–7.20 (m, 30H, Ar), 5.15 (t, 1H,
J = 8.0 Hz, H-200), 5.01 (d, 1H, J = 10.9 Hz, CHHPh),
4.97 (d, 1H, J = 10.8 Hz, CHHPh), 4.92 (d, 1H,
J = 8.4 Hz, H-100), 4.86 (d, 1H, J = 11.2 Hz, CHHPh),
4.85 (d, 1H, J = 7.5 Hz, H-10), 4.78, 4.72 (2d, 2H,
CH2Ph), 4.61 (m, 2H, CHHPh, H-6a00), 4.53 (m, 2H,
H-6a, H-6b00), 4.24 (dd, 1H, J = 4.9, 11.9 Hz, H-6b),
4.15 (d, 1H, J = 7.7 Hz, H-1), 4.12 (m, 1H, H-500), 4.07
(t, 1H, J = 9.4 Hz, H-4), 4.00 (t, 1H, J = 9.5 Hz, H-3),
3.85 (dd, 1H, J = 7.7, 9.6 Hz, H-20), 3.80 (dd, 1H,
J = 2.1, 5.2 Hz, H-400), 3.62–3.51 (m, 4H, H-2, H-5,
H-30, H-300), 3.48 (br s, 1H, H-40), 3.39 (s, 3H, OCH3),
3.37 (m, 1H, H-50), 1.36, 1.21 (2s, 2 ꢁ 3H, C(CH3)2),
1.22 (d, 3H, J = 5.8 Hz, H-60); 13C NMR (100.6 MHz,
CDCl3): d 165.7, 165.0 (CO), 139.0–127.0 (Ar), 110.4
(C(CH3)2), 102.5 (C-1), 101.2 (C-100), 98.9 (C-10), 83.1
(C-5 or C-300), 79.8 (C-20), 79.2 (C-3), 77.0 (C-30), 76.7
(C-40), 76.3 (C-4), 75.2, 74.7 (2 CH2Ph), 74.0 (C-200),
73.3 (C-400), 73.0 (CH2Ph), 72.6 (C-5 or C-300), 70.6 (C-
500), 70.4, (C-50), 64.5 (C-2), 63.2 (C-600), 62.9 (C-6),
56.9 (OCH3), 27.3, 26.2 (C(CH3)2), 16.8 (C-60). ESIMS:
[M+H]+ calcd for C64H67O17N3, 1150.4549; found,
1150.4554.
3.8. Methyl 2-azido-4-O-(2,6-di-O-benzoyl-3,4-O-isopro-
pylidene-b-D-galactopyranosyl)-6-O-benzoyl-3-O-(2,3,4-
tri-O-benzyl-a-L-fucopyranosyl)-2-deoxy-b-D-glucopyran-
oside (17a) and methyl 2-azido-4-O-(2,6-di-O-benzoyl-
3,4-O-isopropylidene-b-D-galactopyranosyl)-6-O-benzoyl-
3-O-(2,3,4-tri-O-benzyl-b-L-fucopyranosyl)-2-deoxy-b-D-
glucopyranoside (17b)
A mixture of known12 donor 9 (257 mg, 490 lmol,
1.8 equiv) and acceptor 16 (201 mg, 275 lmol) in anhy-
˚
drous CHCl3 (4 mL) containing activated 4 A powdered
molecular sieves (345 mg) was stirred under N2 for 3 h at
room temperature. The mixture was cooled to ꢀ30 °C,
then N-iodosuccinimide (161 mg, 710 lmol) and TfOH
(23 lL, 260 lmol) were added to the mixture. The reac-
tion was stirred at ꢀ30 °C for 15 min and quenched with
triethylamine (150 lL). Work-up of the reaction was
performed as described for the preparation of 11. Flash
chromatography followed by centrifugal chromatogra-
phy (2:8 then 7:3, hexanes–EtOAc) produced the desired
trisaccharide 17a contaminated with 30% b-anomer 17b

1662
A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
3.9. Methyl 2-azido-4-O-(2,6-di-O-benzoyl-3,4-O-isopro-
pylidene-b-D-galactopyranosyl)-6-O-benzoyl-3-O-(2,3,4-
tri-O-benzyl-a/b-L-rhamnopyranosyl)-2-deoxy-b-D-gluco-
pyranoside (18a/b)
8.05 Hz, H-200), 4.89 (dd, 1H, J = 8.3, 10.3 Hz, H-40),
4.77 (dd, 1H, J = 3.9, 11.7 Hz, H-6a00), 4.70–4.61 (m,
2H, H-50, H-6b00), 4.52 (m, 2H, H-6a, H-6b), 4.46 (d,
1H, J = 8.7 Hz, H-100), 4.24 (m, 2H, H-30, H-300), 4.18
(m, 2H, H-1, H-400), 4.18 (br d, 1H, J = 8.7 Hz, H-20),
3.99 (m, 1H, H-500), 3.76–3.67 (m, 2H, H-3, H-4), 3.48
(s, 3H, OCH3), 3.38 (m, 1H, H-5), 3.27 (br t, 1H,
J = 9.1 Hz, H-2), 2.16 (s, 3H, COCH3), 1.59, 1.56, (2s,
2 ꢁ 3H, C(CH3)2), 1.34 (1s, 3H, CCH3), 1.28 (d, 1H,
J = 6.2 Hz, H-60), 1.26 (1s, 3H, CCH3); 13C NMR
(100.6 MHz, CDCl3): d 170.2, 166.07, 165.8, 164.6
(CO), 133.5–128.5 (Ar), 110.8, 109.5 (2 ꢁ C(CH3)2),
102.8 (C-1), 100.4 (C-100), 96.6 (1JC,H = 172.4 Hz,
C-10), 77.3 (C-30 or C-300), 76.0 (C-20), 75.6 (C-3 or
C-4), 75.5 (C-30 or C-300), 74.5 (C-40), 73.8 (C-3 or
C-4), 73.5 (C-400), 73.0 (C-5), 72.8 (C-200), 71.5 (C-500),
66.9 (C-2), 64.1 (C-50), 63.1 (C-600), 62.4 (C-6), 57.2
(OCH3), 27.8, 27.6, 26.3 (2 ꢁ C(CH3)2), 21.0 (COCH3),
16.6 (C-60). ESIMS: [M+NH4]+ calcd for C48H55O18N3,
979.3824; found, 979.3862.
A mixture of known13 donor 10 (149 mg, 283 lmol,
2 equiv) and acceptor 16 (100 mg, 136 lmol) in anhy-
˚
drous CHCl3 (1.5 mL) containing activated 4 A pow-
dered molecular sieves (170 mg) was stirred under N2
for 3 h at room temperature. The mixture was cooled
to ꢀ30 °C, then NIS (81 mg, 359 lmol) and TfOH
(11 lL, 127 lmol) were added to the mixture. The reac-
tion was stirred at ꢀ30 °C for 30 min and quenched with
triethylamine (100 lL). Work-up of the reaction was
performed as described for the preparation of 11. Flash
chromatography (7:3, hexanes–EtOAc) produced a mix-
ture of the anomeric trisaccharides 18a,b that could not
be distinguished by TLC (109 mg, 70%). The a/b ratio
1
was estimated to be 65:35 by H NMR.
Selected NMR data for 18a: 1H NMR (400 MHz,
CDCl3): d 5.62 (d, 1H, J = 3.7 Hz, H-10), 5.21 (dd, 1H,
J = 7.6, 8.5, H-200), 4.8 (H-50), 4.48 (H-100), 4.18 (H-1),
3.48 (s, 3H, OCH3), 1.50, 1.30 (2s, 2 ꢁ 3H, C(CH3)2),
1.29 (d, 3H, J = 6.6 Hz, H-60); 13C NMR (100.6 MHz,
3.11. Methyl 2-acetamido-2-deoxy-3-O-a-L-fucopyranos-
yl-4-O-b-D-galactopyranosyl-b-D-galactopyranoside 3
CDCl3): d 103.4 (1JC–H = 161 Hz, C-1), 100.2 (1JC–H
=
3.11.1. Method A. The protected trisaccharide 17a
(21 mg, 19 lmol) was dissolved in EtOAc (2 mL)
and 10% Pd–C (41 mg) was added. The reaction mixture
was submitted to hydrogenolysis at 100 psi of H2 48 h at
room temperature. The catalyst was centrifuged down,
the supernatant decanted, and the catalyst rinsed thor-
oughly through re-suspension/centrifugation/decanta-
tion with a mixture of MeOH and EtOAc. After
concentration of the combined supernatant and wash-
ings, the crude residue was submitted to hydrogenolysis
a second time in the same conditions described above.
Once again the catalyst was centrifuged down and
washed carefully with MeOH and EtOAc. After concen-
tration of the combined supernatant and washings, the
residue was this time dissolved in a mixture of EtOAc
and MeOH (2:1, 2 mL), Ac2O (200 lL) and 10% Pd–C
(63 mg) were added and the mixture was submitted to
hydrogenolysis at 100 psi for 2 days at room tempera-
ture. Work-up and hydrogenolysis were carried out as
described immediately above one more time for an addi-
tional 2 days at room temperature. Work-up as above
gave a crude residue (13 mg) that was submitted to acet-
ylation overnight at room temperature in a 1:1 mixture
of Ac2O and pyridine (3 mL). The reaction mixture
was co-concentrated with toluene to produce the crude
acetylated intermediate (13 mg) that was used directly
in the next reaction. It was dissolved in 90% aqueous
AcOH (2 mL), the mixture was stirred at 80 °C for
4 h, and co-concentrated with toluene to give the corre-
sponding crude diol (13 mg) which was submitted to
flash chromatography (7:3 EtOAc–hexanes). The puri-
fied diol was dissolved in methanolic (0.4 M) sodium
159 Hz, C-100), 97.3 (1JC–H = 171.5 Hz, C-10), 57.2
(OCH3), 27.7, 26.2 (C(CH3)2), 16.9 (C-60).
Selected NMR data for 18b: 1H NMR (400 MHz,
CDCl3): d 5.15 (t, 1H, J = 8.0, H-200), 4.92 (H-100), 4.85
(H-10), 4.14 (H-1), 3.40 (s, 3H, OCH3), 3.36 (H-50),
1.35, 1.22 (2s, 2 ꢁ 3H, C(CH3)2), 1.23 (d, 3H,
J = 6.0 Hz, H-60); 13C NMR (100.6 MHz, CDCl3): d
102.5 (1JC–H = 160 Hz, C-1), 101.3 (1JC–H = 161 Hz,
C-10), 99.0 (1JC–H = 163 Hz, C-100), 56.9 (OCH3), 27.7,
26.2 (C(CH3)2), 16.8 (C-60).
3.10. Methyl 2-azido-4-O-(2,6-di-O-benzoyl-3,4-O-iso-
propylidene-b-D-galactopyranosyl)-6-O-benzoyl-2-deoxy-
3-O-(2,3-O-isopropylidene-4-O-acetyl-a-L-rhamnopyr-
anosyl)-b-D-glucopyranoside (20)
A mixture of the known7 rhamnosyl donor 19 (91 mg,
269 lmol) and acceptor 16 (100 mg, 136 lmol) in anhy-
˚
drous CHCl3 (1.5 mL) containing activated 4 A pow-
dered molecular sieves (173 mg) was stirred under N2
for 3 h at room temperature. The mixture was cooled
to ꢀ35 °C and NIS (81 mg, 360 lmol) followed by
TfOH (12 lL, 135 lmol) was added to the mixture.
The reaction mixture was stirred for 30 min at ꢀ35 °C,
and triethylamine (150 lL) was added to quench the
reaction. The work-up of the reaction was performed
as described for the preparation of 11. Flash chromato-
graphy (8:2 hexanes–EtOAc) of the residue produced
the pure trisaccharide 20 (124 mg, 95 %). [a]D +19.1 (c
1
1.9, CHCl3); H NMR (400 MHz, CDCl3): d 8.13–7.39
(m, 15H, Ar), 5.60 (br s, 1H, H-10), 5.25 (t, 1H, J =

A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
1663
methoxide (1.5 mL) and the solution was stirred over-
night at room temperature and deionized with Dowex
50 (H+) resin. The resin was filtered off, rinsed with
MeOH, and the combined filtrate and washings were
concentrated. Gel permeation chromatography of the
residue on a Biogel P2 column eluted with water pro-
duced the pure trisaccharide 3 (5.7 mg, 55% from 17a),
which was isolated as an amorphous powder after
freeze-drying.
(C-60). ESIMS: [M+Na]+ calcd for C21H37O15N,
566.2061; found, 566.2054.
3.12. Methyl 2-acetamido-2-deoxy-4-O-b-D-galactopyr-
anosyl-3-O-a-L-rhamnopyranosyl-b-D-galactopyranoside
(5)
10% Pd–C (64 mg) was added to a solution of trisaccha-
ride 20 (54 mg, 56 lmol) in EtOAc (2.5 mL). The reac-
tion mixture was stirred at room temperature under
H2 atmosphere overnight. Pyridine (100 lL) and Ac2O
(100 lL) was added to the reaction mixture that was stir-
red at room temperature for 3 h. The catalyst was fil-
tered off and rinsed with EtOAc (20 mL) and MeOH
(10 mL) and the combined filtrate and washings were
concentrated to dryness. The residue was dissolved in
80% aqueous acetic acid (3 mL) and the solution was
stirred at 80 °C overnight. The mixture was co-concen-
trated with toluene and gave a residue (47 mg) that
was dissolved in 0.4 M methanolic sodium methoxide
(3 mL). The mixture was stirred overnight at room tem-
perature and deionized with Dowex 50 (H+) resin. The
resin was filtered off, rinsed with MeOH, and the
combined filtrate and washings were concentrated.
Chromatography (6:3:1 EtOAc–MeOH–H2O) of the
crude product followed by gel permeation chromato-
graphy on Biogel P2 (water) gave trisaccharide 5
(22 mg, 72%) pure, which was isolated as an amorphous
powder upon freeze-drying. [a]D ꢀ43.6 (c 1.1, MeOH);
1H NMR (600 MHz, D2O): d 4.82 (s, 1H, H-10), 4.36
(m, 1H, H-1), 4.32 (d, 1H, J = 7.9 Hz, H-100), 4.32 (m,
1H, H-50), 3.86 (dd, 1H, J = 2.0, 12.3 Hz, H-6a), 3.78–
3.73 (m, 4H, H-2, H-3, H-4, H-400), 3.73–3.68 (m, 3H,
H-6, H-30, H-600), 3.67 (br s, 1H, H-20), 3.60 (dd, 1H,
J = 4.1, 11.9 Hz, H-6b00), 3.53 (m, 1H, H-5), 3.49 (dd,
1H, J = 3.4, 9.9 Hz, H-300), 3.46 (m, 1H, H-5), 3.37 (s,
3H, OCH3), 3.28 (dd, 1H, J = 8.0, 9.8 Hz, H-200), 3.23
(t, 1H, J = 9.7 Hz, H-40), 1.87 (s, 3H, COCH3), 1.12
(d, 3H, J = 6.3 Hz, H-60); 13C NMR (150.9 MHz,
D2O): d 102.3 (C-100), 101. 3 (C-1), 99.8 (C-10), 75.3
(C-5, C-500), 75.2, 73.6 (2 of C-3, C-4, C-400), 72.7
(C-300), 72.3 (C-40), 71.4 (C-200), 70.5 (C-20), 70.0 (C-30),
68.9 (C-3 or C-4 or C-400), 68.4 (C-50), 61.2 (C-600), 59.7
(C-6), 57.2 (OCH3), 55.7 (C-2), 21.8 (COCH3), 16.5
(C-60). ESIMS: [M+H]+ calcd for C21H37O15N,
544.2241; found, 544.2263.
3.11.2. Method B. Trisaccharide 17a (70 mg, 60.9
lmol) was dissolved in 0.4 M methanolic sodium meth-
oxide (5 mL). The mixture was stirred at room temper-
ature overnight, diluted with MeOH (10 mL), and
deionized with Dowex 50 (H+) resin. The resin was fil-
tered off, rinsed with MeOH, and the combined filtrate
and washings were concentrated. Chromatography
(1:9 MeOH–CHCl3) produced the triol intermediate
(46 mg), which was dissolved in 90% aqueous acetic acid
(4 mL). The solution was stirred at 80 °C for 2 h and co-
concentrated with toluene. The residue was dissolved in
MeOH (4 mL), 10% Pd–C (40 mg) was added, and the
mixture was submitted to hydrogenolysis at room tem-
perature for 5 h. Ac2O (16 lL) was added and the mix-
ture was stirred under H2 atmosphere overnight at room
temperature. Additional 10% Pd–C (total 122 mg) and
Ac2O (total 300 lL) were added portion-wise during
the following 2 days while hydrogenolysis at room tem-
perature was continued. Once the reaction was seen to
be complete by TLC (6:1:3 EtOAc–MeOH–H2O) the
catalyst was filtered off, the solids were rinsed thor-
oughly with MeOH, and the combined filtrate and
washings were concentrated. Gel filtration on a Biogel
P2 column eluted with H2O produced trisaccharide 3
pure (25 mg, 76%) that was isolated as an amorphous
white powder upon freeze-drying.
3.11.3. Analytical data for trisaccharide 3. The analyti-
cal data for 3 were in agreement with that reported pre-
viously.5e [a]D ꢀ66.4 (c 0.3, MeOH); 1H NMR
(600 MHz, D2O): d 4.95 (d, 1H, J = 4.0 Hz, H-10), 4.68
(m, 1H, H-50), 4.32 (d, 1H, J = 8.1 Hz, H-1), 4.30 (d,
1H, J = 7.8 Hz, H-100), 3.86 (dd, 1H, J = 2.1, 12.2 Hz,
H-6a), 3.80–3.70 (m, 6H, H-2, H-3, H-4, H-6b, H-30,
H-400), 3.64 (br d, 1H, J = 3.4 Hz, H-40), 3.62–3.56 (m,
2H, H-6a00, H-6b00), 3.54 (dd, 1H, J = 4.0, 10.3 Hz,
H-20), 3.51 (dd, 1H, J = 3.4, 9.9 Hz, H-300), 3.45 (m,
2H, H-5, H-500), 3.35 (m, 4H, H-200, OCH3), 1.87 (s,
3H, COCH3), 1.02 (d, 3H, J = 6.6 Hz, H-60); 13C
NMR (150.9 MHz, D2O): d 174.5 (COCH3), 101.9
(C-100), 101.7 (C-1), 98.7 (C-10), 75.4, 75.0 (2 C, C-5,
C-500), 74.9 (C-4 or C-30 or C-400), 73.5 (C-3), 72.5
(C-300), 71.9 (C-40), 71.1 (C-200), 69.3, 68.4 (2 of C-4,
C-30, C-400), 67.7 (C-20), 66.7 (C-50), 61.5 (C-600), 59.8
(C-6), 57.1 (OCH3), 55.6 (C-2), 22.2 (COCH3), 14.2
Acknowledgments
The authors are grateful for financial support by
NSERC, the Canada Foundation for Innovation, the
Ontario Innovation Trust and Aventis Pasteur Ltd.
A.A. acknowledges the World bank for a fellowship
under the DUE program.

1664
A. Asnani, F.-I. Auzanneau / Carbohydrate Research 343 (2008) 1653–1664
Carbohydr. Res. 2002, 337, 1333–1342; (m) Xia, J.;
Supplementary data
Alderfer, J. L.; Locke, R. D.; Piskorz, C. F.; Matta, K.
L. J. Org. Chem. 2003, 68, 2752–2759.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.carres.
2008.04.017.
5. (a) Toepfer, A.; Schmidt, R. R. Tetrahedron Lett. 1992, 33,
5161–5164; (b) Hummel, G.; Schmidt, R. R. Tetrahedron
Lett. 1997, 38, 1173–1176; (c) Kretzschmar, G.; Stahl, W.
Tetrahedron 1998, 54, 6341–6358; (d) Manzoni, L.; Lay,
L.; Schmidt, R. R. J. Carbohydr. Chem. 1998, 17, 739–758;
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