Synthesis of 4 manipulated Lewis X trisaccharide analogues

Article abstract of DOI:10.3762/bjoc.8.126

Three analogues of the Le^x trisaccharide antigen (β-D-Galp(1→4)[α-L-Fucp(1→3)]-D-GlcNAcp) in which the galactosyl residue is modified at O-4 as a methyloxy, deoxychloro or deoxyfluoro, were synthesized. We first report the preparation of the modified 4-OMe, 4-Cl and 4-F trichloroacetimidate galactosyl donors and then report their use in the glycosylation of an N-acetylglucosamine glycosyl acceptor. Thus, we observed that the reactivity of these donors towards the BF₃OEt ₂-promoted glycosylation at O-4 of the N-acetylglucosamine glycosyl acceptors followed the ranking 4-F > 4-OAc ≈ 4-OMe > 4-Cl. The resulting disaccharides were deprotected at O-3 of the glucosamine residue and fucosylated, giving access to the desired protected Lex analogues. One-step global deprotection (Na/NH3) of the protected 4 -methoxy analogue, and two-step deprotections (removal of a p-methoxybenzyl with DDQ, then Zemplen deacylation) of the 4 -deoxychloro and 4 -deoxyfluoro protected Lex analogues gave the desired compounds in good yields.

Full text of DOI:10.3762/bjoc.8.126

Synthesis of 4” manipulated
Lewis X trisaccharide analogues
Christopher J. Moore and France-Isabelle Auzanneau*
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2012, 8, 1134–1143.
Department of Chemistry, University of Guelph, 50 Stone Rd. East,
Guelph, Ontario, N1G 2W1, Canada
doi:10.3762/bjoc.8.126
Received: 25 April 2012
Accepted: 29 June 2012
Published: 23 July 2012
Email:
France-Isabelle Auzanneau* - fauzanne@uoguelph.ca
* Corresponding author
This article is part of the Thematic Series "Synthesis in the
glycosciences II".
Keywords:
chlorodeoxygalactose; fluorodeoxygalactose; Lewis X analogues;
oligosaccharide synthesis
Guest Editor: T. K. Lindhorst
© 2012 Moore and Auzanneau; licensee Beilstein-Institut.
License and terms: see end of document.
Abstract
Three analogues of the Lex trisaccharide antigen (β-D-Galp(1→4)[α-L-Fucp(1→3)]-D-GlcNAcp) in which the galactosyl residue is
modified at O-4 as a methyloxy, deoxychloro or deoxyfluoro, were synthesized. We first report the preparation of the modified
4-OMe, 4-Cl and 4-F trichloroacetimidate galactosyl donors and then report their use in the glycosylation of an N-acetyl-
glucosamine glycosyl acceptor. Thus, we observed that the reactivity of these donors towards the BF3·OEt2-promoted glycosyl-
ation at O-4 of the N-acetylglucosamine glycosyl acceptors followed the ranking 4-F > 4-OAc ≈ 4-OMe > 4-Cl. The resulting
disaccharides were deprotected at O-3 of the glucosamine residue and fucosylated, giving access to the desired protected Lex
analogues. One-step global deprotection (Na/NH3) of the protected 4”-methoxy analogue, and two-step deprotections (removal of a
p-methoxybenzyl with DDQ, then Zemplén deacylation) of the 4”-deoxychloro and 4”-deoxyfluoro protected Lex analogues gave
the desired compounds in good yields.
Introduction
A glycolipid displaying the dimeric Lex hexasaccharide saccharide (β-D-Galp(1→4)[α-L-Fucp(1→3)]-D-GlcNAcp), at
(dimLex) has been identified as a cancer associated carbohy- the nonreducing end, and this antigenic determinant is also
drate antigen, particularly prevalent in colonic and liver adeno- present at the surface of many normal cells and tissues, which
carcinomas. In addition, an association between the fucosyla- include kidney tubules, gastrointestinal epithelial cells, and cells
tion of internal GlcNAc residues in polylactosamine chains, and of the spleen and brain [7-11]. Indeed, anti-Lex monoclonal
metastasis and tumor progression in colorectal cancers has been antibodies (e.g., FH3, SH1) have been shown to recognize this
suggested [1-6]. Unfortunately, dimLex displays the Lex tri- Lex antigenic determinant as it exists in the hexasaccharide
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Beilstein J. Org. Chem. 2012, 8, 1134–1143.
[1-6]. Therefore, as our group embarks on the development of a It was discovered that the Lex analogue 2, with a glucose unit in
therapeutic anticancer vaccine utilizing the Tumor Associated place of the galactose residue (Figure 1), did not bind to the
Carbohydrate Antigen (TACA) dimLex as a target, an impor- SH1 mAb, even at high concentrations [15]. This discovery
tant factor to consider is an expected autoimmune response to suggests that, to conserve cross-reactivity with the natural Lex
the native Lex antigen. Fortunately an internal epitope displayed antigen, the nonreducing end galactose is essential, and that
by dimLex was discovered when monoclonal antibodies (mAbs) modifying this residue, particularly at O-4, may lead to the
FH4 and SH2, raised against dimLex, were isolated. Indeed, complete loss of this cross-reactivity [15]. Currently, it is not
these mAbs were shown to bind to the dimLex and trimLex anti- known what the reason for this observed loss of binding is,
gens but only weakly recognise Lex trisaccharide antigen [1-6]. since the binding affinities between proteins and carbohydrates
With this in mind, we focus our research on the discovery of are the result of a combination of factors [25-29]. One of the
analogues of dimLex that can be used as safe vaccine candi- main interactions is the formation of hydrogen bonds, either
dates. Ideally, these analogues should display the internal direct or water-mediated, between the amino acid residues of
epitopes that are recognized by anti-dimLex SH2-like anti- the protein and the key binding hydroxy groups of the ligand,
bodies while being free of those that are recognized by anti-Lex which are arranged in clusters presented by different monosac-
SH1-like antibodies.
charide units. Other factors include favourable interactions of
the nonpolar amino acid residues with the hydrophobic patches
In order to abolish cross-reactivity with the Lex antigen, we exhibited by the ligand, as well as high-energy water molecules
have prepared [12-14] several analogues in an attempt to iden- being favourably displaced from the combining site. Binding
tify a suitable replacement for the nonreducing end Lex tri- affinity is therefore a result of combined enthalpic, entropic and
saccharide. In turn, we have compared the conformational solvation effects, frequently leading to a balance between
behaviour of these analogues to that of the natural Lex-OMe 1 favourable enthalpic and unfavourable entropic contributions
(Figure 1) through a mixture of stochastic searches and NMR [25-29]. Thus, only additional competitive ELISA studies with
analyses [15]. The results pointed toward the preferential adop- Lex-OMe analogue inhibitors containing strategic manipula-
tion, by all of analogues, of the stacked conformation that has tions at the 4” site will provide further insight into specific
been assigned for the Lex trisaccharide [16-21]. The relative binding interactions [15]. The synthesis of a 4”-deoxy Lex tri-
affinity of the anti-Lex monoclonal antibody SH1 [6] for the saccharide analogue was reported recently by Dong et al. [30].
native Lex antigen 1 and our Lex analogues [12-14] was exam- Here, we report the synthesis of 4”-methyloxy, 4”-deoxychloro
ined by competitive ELISA experiments using a Lex-BSA and 4”-deoxyfluoro Lex-OMe analogue inhibitors 3–5.
glycoconjugate as the immobilized ligand [15,22-24].
Results and Discussion
There are numerous reports in the literature of the chemical
preparation of Lex analogues [30-55], including one recent
report of the synthesis of a Lex pentasaccharide 4-deoxy at the
nonreducing end galactosyl residue [30]. These syntheses
follow one of three strategies: (1) the galactosylation then fuco-
sylation of a glucosamine acceptor [30-47]; (2) the fucosylation
then galactosylation of a glucosamine acceptor [48-53]; or (3)
the fucosylation at O-3 of a lactosamine derivative prepared
from lactose [54,55]. Our synthetic approach to prepare
analogues 3–5 followed the first strategy [30-47] and involved
the use of N-acetylglucosamine glycosyl acceptors 6 [14] and 8,
galactosyl donors 9–11, and known fucosyl donors 12 [56] and
13 [12] (Figure 2).
Synthesis of monosaccharide building blocks
8–11
Glucosamine acceptor 8 was prepared in two steps from the
known [14] benzylidene 7: the benzylidene acetal was first
hydrolyzed, and then the resulting diol (79%) was selectively
benzoylated at O-6 (BzCl-collidine) giving acceptor 8 in 62%
Figure 1: Structure of Lex and analogues 2–5.
yield.
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Beilstein J. Org. Chem. 2012, 8, 1134–1143.
14 was stirred in a mixture of pyridine and dichloromethane at
−10 °C and treated with 3.1 equivalents of pivaloyl chloride.
Under these conditions the α-tripivaloate 15, selectively
acylated at O-2, O-3 and O-6, was obtained pure and free of
β-anomer (64%). The free hydroxy group in alcohol 15 was
then deprotonated with sodium hydride and allowed to react
with methyl iodide, yielding the 4-OMe galactoside 16 in very
good yield. In turn, trichloroethyl galactoside 16 was converted
to the trichloroacetimidate donor 9 in two steps: the anomeric
trichloroethyl group was removed (Zn/AcOH), and then the
resulting hemiacetal was treated with trichloroacetonitrile in the
presence of DBU giving the desired α-trichloroacetimidate in
good yield.
Figure 2: Monosaccharide building blocks 6–13.
A Lattrell-Dax nitrite mediated inversion [58-60] of the 4-OH
The syntheses of trichloroacetimidate donors 9–11 are in galactoside 15 provided the glucoside 17, which was used as
described on Scheme 1; they were all prepared from the known the common precursor to analogues 18 and 19. Treatment with
trichloroethyl galactoside 14 [57]. Galactoside 14 was first sulfuryl chloride [61] gave the 4-chloro galactoside 18 in good
prepared in three steps from galactose: (1) peracetylation yield, whereas triflation at O-4 followed by SN2 displacement
(Ac2O-pyridine); (2) BF3·OEt2 activation of the anomeric of the triflate by using tetrabutylammonium fluoride [62,63]
acetate and glycosidation with trichloroethanol; and (3) gave the 4-fluoro galactoside analogue 19 in excellent yields.
Zemplén deacetylation. This sequence of reactions gave the As described above for the preparation of donor 9 from glyco-
desired galactoside 14 in 78% yield and as a 9:1 α/β mixture, as side 16, trichloroethyl galactosides 18 and 19 were, in turn,
assessed by 1H NMR. It is important to point out that the converted in two steps (Zn/AcOH then Cl3CCN/DBU) to the
second step in this sequence of reactions used conditions very trichloroacetimidate donors 10 and 11, respectively, which were
similar to those used by Risbood et al. to prepare peracetylated obtained in acceptable yields over the two steps.
trichloroethyl galactopyranoside from peracetylated galactose.
Galactosylation at O-4 of N-acetyl-
Indeed, in agreement with their work [57], the ratio of α-anomer
isolated here suggests a late anomerization of the β-glycoside glucosamine acceptors
during our extended reaction time (20 h) at reflux. The It has been well established that the hydroxy group at C-4 of
4-methyloxy trichloroacetimidate donor 9 was then prepared in N-acetylglucosamine is a poor nucleophile, with reduced
four steps from the anomeric mixture of galactoside 14. Tetraol reactivity toward glycosylation [64-66]. However, we have
Scheme 1: Synthesis of trichloroacetimidate donors 9–11.
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Beilstein J. Org. Chem. 2012, 8, 1134–1143.
reported the successful O-4 glycosylation of an N-acetyl-
glucosamine monosaccharide acceptor using peracetylated
gluco- and galactopyranose α-trichloroacetimidate donors under
activation with 2 equivalents of BF3·OEt2 at room temperature
or 40 °C [14,67]. We applied similar conditions to prepare
disaccharides 20–22 (Table 1). Glycosylation of methyl glyco-
side 6 with the 4-methoxy donor 9 gave the best results when
the reaction was carried out at 40 °C and left to proceed for
2 hours. Under these conditions, the desired disaccharide 20
was isolated in acceptable yields (Table 1, entries 1 and 2). Our
attempts to reduce the number of equivalents of donor 9 used in
the reaction always resulted in a lower yield of the desired
disaccharide. Glycosylation of acceptor 8 with the 4-chloro
galactosyl donor 10 appeared to be slower (Table 1, entries 3–5)
than that of acceptor 6 with donor 9. The best results were
obtained when the reaction was left to proceed for 3 rather than
2 hours (Table 1, entry 4), and the desired disaccharide 21 was
then obtained in acceptable yield. Increasing the temperature to
60 °C did not increase the yield, presumably due to the degrad-
ation of the glycosyl donor at this higher temperature (Table 1,
entry 5). Of the three glycosylations considered here, the
coupling of acceptor 8 with the 4-fluoro donor 11 gave the
Table 1: Glycosylation at O-4 of glucosamine with donors 9–11.a
Entry
Acc. Don. T (°C)
Time (h)
Product (%)
1
2
3
4
5
6
7
6
6
8
8
8
8
8
9
rtb
2
2
2
3
2
2
2
20 (65)
20 (70)
21 (55)
21 (63)
21 (62)
22 (77)
22 (73)
9
40b
40b
40b
60c
40b
60c
10
10
10
11
11
aReagents and conditions: BF3·Et2O (2 equiv), donor 9–11 (5 equiv);
bsolvent: CH2Cl2; csolvent: 1,2-dichloroethane.
highest yields (Table 1, entries 6 and 7). Indeed the desired TMSOTf activation at low temperature (−30 °C). Under these
disaccharide 22 was obtained in very good yields when the conditions, the desired trisaccharide 26 was isolated in 78%
reaction was allowed to proceed for 2 hours at 40 °C. Once yield but as an 8:2 mixture of the α and β-anomers as estimated
again, increasing the temperature to 60 °C offered no advan- by 1H NMR. Although the desired anomer 26α could be
tage and in fact led to a lower yield of the desired product.
obtained pure upon purification by HPLC, it was isolated in a
less than desirable yield of 48%. We thus attempted the
From these three reactions, it is clear that the substituent at O-4 coupling of acceptor 23 and donor 12 under activation with
of a galactosyl donor impacts the outcome of glycosylation at excess MeOTf (5 equiv). Indeed, we have reported that such
O-4 of N-acetylglucosamine acceptors. Indeed, we have previ- conditions allow glycosylation at O-4 of N-acetylglucosamine
ously observed that galactosylations of such acceptors [68,69] acceptors through the in situ formation of the corresponding
usually result in lower yields (~70%) than those for analogous N-methylimidate, temporarily masking the N-acetyl group in the
glucosylations, which usually provided around 90% of the acceptor [70,71]. Thus, we expected a similar in situ formation
desired disaccharides [14,67]. The results described here indi- of the methyl imidate in acceptor 23, which would further
cate that 4-OAc galactosyl donors perform better than the 4-Cl undergo fucosylation at O-3. However, since methylimidates
donor 10, whereas the 4-OMe donor 9 performs as well as the are unstable when purified on silica gel, they were converted
4-OAc analogues. In addition, of all of the galactosyl donors back to the acetamido before purification. Thus, once TLC had
employed thus far in such reactions, the 4-fluorinated analogue shown that all of the acceptor had been consumed, the reaction
seemed to perform the best. Thus the reactivity of galactosyl was worked up and the crude mixture was treated with
trichloroacetimidate donors towards the BF3·OEt2-promoted Ac2O–AcOH prior to purification by chromatography [70,71].
glycosylation at O-4 of N-acetylglucosamine glycosyl accep- Under these conditions, the desired trisaccharide 26α was
tors seems to follow the ranking 4-F > 4-OAc ≈ 4-OMe > 4-Cl. obtained pure and free of the β-anomer in 77% yield.
Preparation of the protected Lex tri-
saccharide analogues
Similar reaction conditions were applied for the glycosylation
of acceptors 24 and 25 with ethylthioglycoside 13. Interestingly,
The synthesis of protected trisaccharide intermediates 26–28 is these fucosylation reactions proved to be slower and required
described in Scheme 2. First, acceptors 23–25 were prepared in additional equivalents of donor 13 to proceed. However, after
good yields through the selective removal of the chloroacetate treatment of the reaction mixtures with AcOH–Ac2O, the
(thiourea) in disaccharides 20–22. Fucosylation of acceptor 23 desired trisaccharides 27 and 28 were isolated in good yields
with ethylthioglycoside 12 was first attempted under NIS and (Scheme 2) and exclusively as the α-fucosylated trisaccharides.
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Beilstein J. Org. Chem. 2012, 8, 1134–1143.
Scheme 2: Synthesis of trisaccharides 26–28 and deprotection reactions giving 3–5.
As previously observed for other similar analogues [66,72,73], pectively, over the two steps. The structures of the final depro-
careful analysis of the 1H NMR spectra acquired for trisaccha- tected trisaccharides 3–5 were confirmed by HR–ESI mass
rides 26α, 27, 28 indicated that the glucosamine residue adopted spectrometry and NMR.
a conformation distorted from the usual 4C1 chair conformation.
The distorted conformations of the N-acetylglucosamine ring in Conclusion
analogues 26α, 27, 28 were characterized by vicinal coupling We describe here the efficient synthesis of three Lex methyl
constants of 6.2–6.6 Hz measured between the ring hydrogens glycoside derivatives (3–5) in which the galactosyl 4-hydroxy
H-2 to H-5 of this residue, rather than the expected values of group is either methylated (3) or replaced by a chlorine (4) or
8.0–8.3 Hz as observed, when measurable, for the same hydro- fluorine (5). Our results seem to indicate that galactosylation at
gens in disaccharides 20–25. In addition, although signal O-4 of an N-acetylglucosamine acceptor under activation with
overlap precluded its measurement in trisaccharides 26α and 28, excess BF3·OEt2 can be significantly affected by the nature of
the vicinal coupling constant measured between H-1 and H-2 in the substituent present at C-4 of the galactosyl donor. Indeed,
trisaccharide 27 (5.2 Hz) also supported a distorted con- the best results were obtained with the 4-fluoro galactosyl
formation for this residue (compare to the same coupling donor, whereas the 4-chloro donor reacted less efficiently than
constant in compounds 23–25, ~7.4 Hz).
the 4-O-methyl or 4-O-acetyl donors. Overall, this study also
confirms our observation [68], that galactosylations at position
4 of N-acetylglucosamine acceptors are usually less successful
Deprotection of trisaccharides 26–28
As described previously, the removal of various protecting than glucosylations [14,67]. The final Lex-OMe analogues will
groups, such as pivaloyl and benzyl groups here, can be accom- be used as competitive inhibitors in future ELISA experiments
plished efficiently in one step under Birch reduction conditions to provide a better understanding of the binding process
[15,68,69,74,75]. Thus, treatment of trisaccharide 26α with between the anti-Lex monoclonal antibody SH1 and the Lex
sodium in liquid ammonia at −78 °C was followed by neutrali- antigen.
zation of the reaction mixture with AcOH and purification by
gel permeation chromatography on a Biogel P2 column (water) Experimental
to give the desired deprotected 4”-methoxy trisaccharide General Methods: 1H (400.13 MHz) and 13C NMR
analogue 3 pure in 83% yield. Since such conditions were not (100.6 MHz) spectra were recorded for compounds solubilized
compatible with the 4-chloro and 4-fluoro substituents in trisac- in CDCl3 (internal standard, for 1H: residual CHCl3 δ 7.24; for
charides 27 and 28, these intermediates were converted in two 13C: CDCl3 δ 77.0), DMSO-d6 (internal standard, for 1H:
steps to the desired deprotected analogues 4 and 5, respectively. residual DMSO δ 2.54; for 13C: DMSO-d6 δ 40.45),
Thus, removal of the p-methoxybenzyl group with DDQ in CD3OD (internal standard, for 1H: residual MeOD δ 3.31;
CH2Cl2/H2O (15:1 v/v) was followed by Zemplén deacylation, for 13C: CD3OD δ 49.15) or D2O [external standard
giving the target Lex analogues 4 and 5 in 78% and 75%, res- 3-(trimethylsilyl)propionic acid-d4, sodium salt (TSP) for
1138

Beilstein J. Org. Chem. 2012, 8, 1134–1143.
1H δ 0.00; for 13C δ 0.00]. Chemical shifts and coupling (39 mg, 0.0347 mmol) and DDQ (12 mg, 1.5 equiv) in CH2Cl2
constants were obtained from a first-order analysis of one- (350 μL) and H2O (20 μL, 6% v/v) was stirred at room tempera-
dimensional spectra. Assignments of proton and carbon reso- ture for 2 h. The mixture was filtered over Celite and the solids
nances were based on COSY and 13C–1H heteronuclear corre- were washed with CH2Cl2 (5 mL). The combined filtrate and
lated experiments. 1H NMR data are reported with standard washings were washed with aq saturated NaHCO3 (10 mL), the
abbreviations: singlet (s), doublet (d), triplet (t), doublet of aq layer was re-extracted with CH2Cl2 (3 × 5 mL), and the
doublet (dd), doublet of doublet of doublet (ddd), broad singlet combined organic layers were dried and concentrated. Flash
(bs), broad triplet (bt), broad doublet of doublet (bdd) and chromatography (EtOAc/hexanes, 1:1 → 7:3) of the residue
multiplet (m). Mass spectra were obtained with electrospray gave a white solid (27 mg, 0.0269 mmol, 78%), which was
ionization (ESI) on a high-resolution mass spectrometer. TLC dissolved in a methanolic solution of NaOMe (1 mL, 0.13 M)
were performed on precoated aluminum plates with Silica Gel and stirred for 3 h at 50 °C. The reaction mixture was diluted
60 F254 and detected with UV light and/or by charring with a with MeOH (5 mL) and de-ionized with DOWEX H+ resin. The
solution of 10% H2SO4 in EtOH. Compounds were purified by resin was filtered off and washed with MeOH (5 mL), and the
flash chromatography with Silica Gel 60 (230–400 mesh) unless combined filtrated and washings were concentrated. The crude
otherwise stated. Solvents were distilled and dried according to product was dissolved in Milli Q water and washed with
standard procedures [76], and organic solutions were dried over CH2Cl2 (5 mL). After freeze drying, the deprotected 4”-deoxy-
Na2SO4 and concentrated under reduced pressure below 40 °C. chloro Lex analogue 4 (15.1 mg, 0.0269 mmol, 78%) was
HPLC purifications were run with HPLC grade solvents.
obtained pure as an amorphous solid. [α]D = −123 (c = 0.7,
H2O); 1H NMR (400 MHz, D2O, 295 K) δ 4.97 (d, 1H, J =
Methyl 2-acetamido-2-deoxy-3-O-(α-L-fucopyranosyl)-4-O- 4.0 Hz, H-1’), 4.61 (m, 1H, H-5’), 4.38–4.30 (m, 3H, H-1,
(4-methoxy-β-D-galactopyranosyl)-β-D-glucopyranoside (3). H-1”, H-4”), 3.88 (dd, J = 1.9, 12.3 Hz, 1H, H-6a), 3.82 (dd, J =
A solution of the protected trisaccharide 26α (50 mg, 3.8, 9.7 Hz, 1H, H-3”), 3.77–3.70 (m, 7H, H-2, H-3, H-4, H-6b,
0.043 mmol) dissolved in THF (5 mL) was added to a solution H-3’, H-4’, H-5”), 3.66 (dd, J = 7.1, 11.7 Hz, 1H, H-6a”),
of liquid NH3 (ca. 20 mL) containing Na (72 mg, 3.13 mmol, 3.59–3.53 (m, 2H, H-2’, H-6b”), 3.45 (m, 1H, H-5), 3.38–3.33
73 equiv) at −78 °C. After 1 h the reaction was quenched with (m, 4H, H-2”, OCH3), 1.88 (s, 3H, C(O)CH3), 1.05 (d, J =
MeOH (5 mL) and the ammonia was allowed to evaporate at rt. 6.6 Hz, 3H, H-6’); 13C NMR (100 MHz, D2O, 295 K) δ 174.4
The remaining solution was neutralized with AcOH (220 μL, (C=O), 102.2 (C-1”), 101.7 (C-1), 98.5 (C-1’), 75.2 (C-5), 74.4
ca. 1.2 equiv to Na), and the mixture was concentrated. The (C-3), 73.7 (C-4), 73.6 (C-5”), 71.9 (C-4’), 71.5 (C-3”), 70.8
resulting solid was dissolved in water and passed through a (C-2”), 69.3 (C-3’), 67.6 (C-2’), 66.6 (C-5’), 62.2 (C-4”), 61.6
Biogel P2 column eluted with H2O. After freeze drying, the (C-6”), 59.5 (C-6), 57.1 (OCH3), 55.7 (C-2), 22.2 (C(O)CH3),
deprotected 4”-methoxy-Lex analogue 3 (20 mg, 0.0359 mmol, 15.2 (C-6’); HRMS–ESI (m/z): [M + Na]+ calcd for
83%) was obtained pure as a white solid. [α]D = −75 (c 0.3, C21H36ClNNaO14, 584.1722; found, 584.1733.
H2O); 1H NMR (400 MHz, D2O, 295 K) δ 4.95 (d, J = 4.0 Hz,
1H, H-1’), 4.67 (m, 1H, H-5’), 4.32 (d, J = 8.2 Hz, 1H, H-1), Methyl 2-acetamido-2-deoxy-4-O-(4-deoxy-4-fluoro-β-D-
4.27 (d, J = 7.7 Hz, 1H, H-1”), 3.85 (dd, J = 2.0, 12.2 Hz, 1H, galactopyranoside)-3-O-(α-L-fucopyranosyl)-β-D-glucopy-
H-6a), 3.78–3.68 (m, 5H, H-2, H-3, H-4, H-3’, H-6b), ranoside (5). Trisaccharide 28 (30 mg, 0.0271 mmol) was
3.63–3.60 (m, 3H, H-4’, H-6ab”), 3.55–3.50 (m, 2H, H-2’, deprotected in two steps as described above for the preparation
H-3”), 3.47–3.44 (m, 2H, H-5, H5”), 3.39 (d, J = 3.4 Hz, 1H, of trisaccharide 4. After freeze drying, the deprotected
H-4”), 3.35 (s, 3H, OCH3), 3.32 (s, 3H, OCH3), 3.29 (m, 1H, 4”-deoxyfluoro Lex analogue 5 (11.1 mg, 0.0203 mmol, 75%)
H-2”), 1.88 (s, 3H, C(O)CH3), 1.03 (d, J = 6.6 Hz, 3H, H-6’); was obtained pure as an amorphous solid. [α]D = −85 (c 0.5,
13C NMR (100 MHz, D2O, 295 K) δ 174.4 (C=O), 101.7 (C-1), H2O); 1H NMR (400 MHz, D2O, 295 K) δ 4.95 (d, J = 4.0 Hz,
101.6 (C-1”), 98.7 (C-1’), 78.6 (C-4”), 75.3, 75.1, 75.0 (C-5, 1H, H-1’), 4.66 (m, 1H, H-5’), 4.65 (bdd, J = 2.7 Hz, JH,F =
C-5”, C-3), 73.3 (C-4), 72.9 (C-3”), 71.9 (C-4’), 71.5 (C-2”), 50.4 Hz, 1H, H-4”), 4.39 (d, J = 7.8 Hz, 1H, H-1”), 4.33 (d, J =
69.2 (C-3’), 67.7 (C-2’), 66.7 (C-5’), 61.1 (OCH3), 61.0 (C-6”), 8.0 Hz, 1H, H-1), 3.86 (dd, J = 2.0, 12.3 Hz, 1H, H-6a),
59.7 (C-6), 57.1 (OCH3), 55.6 (C-2), 22.2 (C(O)CH3), 15.2 3.81–3.66 (m, 6H, H-2, H-3, H-4, H-6b, H-3’, H-3”), 3.64–3.58
(C-6’); HRMS–ESI (m/z): [M + Na]+ calcd for C22H39NNaO15, (m, 4H, H-4’, H-5”, H-6ab”), 3.54 (dd, J = 4.0, 10.4 Hz, 1H,
580.2217; found, 580.2223.
H-2’), 3.45 (m, 1H, H-5), 3.37–3.33 (m, 4H, H-2”, OCH3), 1.88
(s, 3H, C(O)CH3), 1.02 (d, J = 6.6 Hz, 3H, H-6’); 13C NMR
Methyl 2-acetamido-2-deoxy-4-O-(4-chloro-4-deoxy-β-D- (100 MHz, D2O, 295 K) δ 174.4 (C=O), 101.7 (C-1), 101.4
galactopyranoside)-3-O-(α-L-fucopyranosyl)-β-D-glucopy- (C-1”), 98.7 (C-1’), 89.3 (d, JC,F = 177.7 Hz, C-4”), 75.2 (C-5),
ranoside (4). A solution of the protected trisaccharide 27 74.9 (C-3), 73.4 (C-4), 73.2 (d, JC,F 17.6 Hz, C-5”), 71.9 (C-4’),
1139

Beilstein J. Org. Chem. 2012, 8, 1134–1143.
71.2 (C2”), 71.1 (d, JC,F = 18.5 Hz, C-3”), 69.2 (C-3’), 67.6 3.91 (t, J = 8.3 Hz, 1H, H-4), 3.83 (bt, J = 6.2 Hz, 1H, H-5’),
(C-2’), 66.5 (C-5’), 60.0 (C-6”), 59.6 (C-6), 57.1 (OCH3), 55.6 3.72 (m, 1H, H-5), 3.45 (s, 3H, OCH3), 1.97 (s, 3H, C(O)CH3),
(C-2), 22.2 (C(O)CH3), 15.3 (C-6’); HRMS–ESI (m/z): 1.16, 1.14, 1.13 (3s, 27H, 3 × C(CH3)3); 13C NMR (100 MHz,
[M + Na]+ calcd for C21H36FNO14, 568.2018; found, 568.2023. CDCl3, 295 K) δ 177.8, 177.6, 176.3, 170.3, 167.3, 166.0
(C=O), 133.5, 129.6, 129.4, 128.7, 128.4 (Ar), 101.7 (C-1),
Methyl 2-acetamido-6-O-benzyl-3-O-chloroacetyl-2-deoxy- 100.4 (C-1’), 73.5 (C-3), 73.4 (C-4), 72.5 (C-5), 71.6 (C-3’),
4-O-(4-O-methyl-2,3,6-tri-O-pivaloyl-β-D-galactopyranosyl)- 71.2 (C-5’), 68.3 (C-2’), 62.6 (C-6), 62.6 (C-6’), 57.2 (C-4’),
β-D-glucopyranoside (20). A solution of acceptor 6 (215 mg, 56.8 (OCH3), 52.6 (C-2), 40.7 (CH2Cl), 38.9, 38.8, 38.7
0.535 mmol) and trichloroacetimidate donor 9 (1.58 g, (C(CH3)3), 27.6, 27.1, 27.0, 26.9, 26.7 (C(CH3)3), 23.3
5.0 equiv) in CH2Cl2 (30 mL) was stirred at 40 °C, and (C(O)CH3); HRMS–ESI (m/z): [M + H]+ calcd for
BF3·OEt2 (134 μL, 2.0 equiv) was added. The reaction was C39H56Cl2NO15, 848.3027; found, 848.3009.
allowed to proceed for 2 h at 40 °C and then quenched with
Et3N (179 μL, 2.4 equiv), and the mixture was diluted with Methyl 2-acetamido-6-O-benzoyl-3-O-chloroacetyl-2-deoxy-
CH2Cl2 (70 mL). The mixture was washed with aq saturated 4-O-(4-deoxy-4-fluoro-2,3,6-tri-O-pivaloyl-β-D-galactopyra-
NaHCO3 (100 mL), the aq layer was re-extracted with CH2Cl2 nosyl)-β-D-glucopyranoside (22). Glycosylation of acceptor 8
(20 mL × 3), and the combined organic layers were dried and (91.5 mg, 0.220 mmol) with trichloroacetimidate 11 (637 mg,
concentrated. Flash chromatography (EtOAc/hexanes, 2:8 → 5.0 equiv) was performed under BF3·OEt2 (134 μL, 2.0 equiv)
6:4) of the residue gave disaccharide 20 (312 mg, 0.375 mmol, activation as described above for the synthesis of disaccharide
70%) pure as a colourless glass. [α]D = −11 (c 0.6, CH2Cl2); 20. Work-up, as described above, and flash chromatography
1H NMR (400 MHz, CDCl3, 296 K) δ 7.29 (m, 5H, Harom), (EtOAc/hexanes, 2:8 → 6:4) of the residue gave disaccharide
5.95 (d, J = 9.2 Hz, 1H, NH), 5.08–4.99 (m, 2H, H-3, H-2’), 22 (143 mg, 0.172 mmol, 77%) pure as a colourless glass. [α]D
4.71–4.68 (m, 2H, H-3’, CHHPh), 4.40 (d, J = 12.1 Hz, 1H, = +9 (c 2.2, CH2Cl2); 1H NMR (400 MHz, CDCl3, 295 K) δ
CHHPh), 4.38 (d, J = 7.4 Hz, 1H, H-1), 4.24–4.19 (m, 2H, 7.98–7.46 (m, 5H, Harom), 6.00 (d, J = 9.3 Hz, 1H, NH),
H-1’, H-6a’), 4.13–4.07 (m, 2H, H-6b’, CHHCl), 4.01 (d, J = 5.21–5.16 (m, 2H, H-3, H-2’), 4.82 (ddd, J = 2.6, 10.3 Hz, JH,F
15.1 Hz, 1H, CHHCl), 3.96–3.92 (m, 2H, H-4, H-2), 3.71 (m, = 26.9 Hz, 1H, H-3’), 4.70 (dd, J = 2.6 Hz, JH,F = 42.9 Hz, 1H,
2H, H-6ab), 3.50–3.40 (m, 3H, H-5, H-4’, H-5’), 3.43, 3.41 (2s, H-4’), 4.62 (m, 1H, H-6a), 4.51–4.46 (m, 3H, H-1, H-6b, H-1’),
6H, 2 × OCH3), 1.94 (s, 3H, C(O)CH3), 1.30, 1.15, 1.10 (3s, 4.29 (dd, J = 7.6, 11.4 Hz, 1H, H-6a’), 4.16 (dd, J = 5.6,
27H, 3 × C(CH3)3); 13C NMR (100 MHz, CDCl3, 296 K) δ 11.5 Hz, 1H, H-6b’), 4.09–4.00 (m, 3H, H-2, CH2Cl), 3.92 (t, J
177.9, 177.7, 176.2, 170.3, 167.3 (C=O), 137.7, 128.6, 128.1, = 8.2 Hz, 1H, H-4), 3.72 (m, 1H, H-5), 3.66 (dt, J = 6.4 Hz,
128.0 (Ar), 101.7 (C-1), 99.2 (C-1’), 76.3 (C-4’), 74.2 (C-5), JH,F = 25.8 Hz, 1H, H-5’), 3.44 (s, 3H, OCH3), 1.97 (s, 3H,
73.9 (C-3), 73.5 (CH2Ph), 73.4 (C-3’), 72.1 (C-4), 72.0 (C-5’), OCH3), 1.16, 1.13 (2s, 27H, 3 × C(CH3)3); 13C NMR
69.5 (C-2’), 67.7 (C-6), 61.7 (C-6’), 61.5 (OCH3), 56.6 (OCH3), (100 MHz, CDCl3, 295 K) δ 177.8, 177.6, 176.5, 170.46, 167.3,
52.6 (C-2), 40.8 (CH2Cl), 38.8, 38.7, 38.6 (C(CH3)3), 27.2, 27.1 165.9 (C=O), 133.5, 129.5, 129.4, 128.6 (Ar), 101.6 (C-1), 99.9
(C(CH3)3), 23.3 (C(O)CH3); HRMS–ESI (m/z): [M + H]+ calcd (C-1’), 85.3 (d, JC,F = 186.4 Hz, C-4’), 73.5 (C-3), 73.4 (C-4),
for C40H61ClNO15, 830.3730; found, 830.3735.
72.4 (C-5), 71.2 (d, JC,F = 18.0 Hz, C-3’), 71.1 (d, JC,F =
18.0 Hz, C-5’), 68.6 (C-2’), 62.6 (C-6), 61.2 (C-6’), 56.8
Methyl 2-acetamido-6-O-benzoyl-3-O-chloroacetyl-4-O-(4- (OCH3), 52.5 (C-2), 40.6 (CH2Cl), 38.8, 38.8, 38.7 (C(CH3)),
chloro-4-deoxy-2,3,6-tri-O-pivaloyl-β-D-galactopyranosyl)- 27.1, 26.9 (C(CH3)), 23.2 (C(O)CH3); HRMS–ESI (m/z):
2-deoxy-β-D-glucopyranoside (21). Glycosylation of acceptor [M + H]+ calcd for C39H56ClFNO15, 832.3323; found,
8 (97 mg, 0.233 mmol) with trichloroacetimidate 10 (694 mg, 832.3344.
5.0 equiv) was performed under BF3·OEt2 (59 μL, 2.0 equiv)
activation as described above for the synthesis of disaccharide Methyl 2-acetamido-6-O-benzyl-3-O-(2,3,4-tri-O-benzyl-α-
20. Work-up, as described above, and flash chromatography L-fucopyranosyl)-2-deoxy-4-O-(4-O-methyl-2,3,6-tri-O-
(EtOAc/hexanes, 2:8 → 6:4) of the residue gave disaccharide pivaloyl-β-D-galactopyranosyl)-β-D-glucopyranoside (26). A
21 (125 mg, 0.147 mmol, 63%) pure as a colourless glass. [α]D mixture of disaccharide acceptor 23 (30 mg, 0.0398 mmol),
= +9 (c 0.9, CH2Cl2); 1H NMR (400 MHz, CDCl3, 295 K) δ known [56] thioethyl fucopyranoside 12 (76 mg, 0.159 mmol,
8.00–7.41 (m, 5H, Ar), 5.87 (d, J = 9.3 Hz, 1H, NH), 5.27–5.16 4.0 equiv), and activated powdered 4 Å molecular sieves
(m, 2H, H-2’, H-3), 4.86 (dd, J = 3.9, 10.1 Hz, 1H, H-3’), 4.61 (0.25 g) in Et2O (3.0 mL, 0.13 M), was stirred for 1 h at rt
(dd, J = 2.9, 12.0 Hz, 1H, H-6a), 4.51–4.47 (m, 3H, H-1, H-6b, under N2. Then, MeOTf (23 μL, 5.0 equiv) was added, the reac-
H-1’), 4.38 (d, J = 3.5 Hz, 1H, H-4’), 4.35–4.30 (dd, J = 7.2, tion mixture was stirred for 30 min, and the reaction quenched
11.5 Hz, 1H, H-6a’), 4.16–4.02 (m, 4H, H-2, H-6b’, CH2CCl3), with Et3N (33 μL, 6.0 equiv). Solids were filtered off on Celite
1140

Beilstein J. Org. Chem. 2012, 8, 1134–1143.
and washed with CH2Cl2 (20 mL), and the combined filtrate NH), 5.32–5.24 (m, 3H, H-3’, H-4’, H-2”), 5.18 (d, J = 3.6 Hz,
and washings were washed with aq saturated NaHCO3 (15 mL). 1H, H-1’), 4.90 (dd, J = 3.8, 10.0 Hz, 1H, H-3”), 4.80 (d, J =
The aq layer was re-extracted with CH2Cl2 (3 × 10 mL), and the 5.2 Hz, 1H, H-1), 4.72 (dd, J = 3.6, 11.9 Hz, 1H,H-6a),
combined organic layers were dried and concentrated. The 4.65–4.52 (m, 5H, H-6b, H-5’, H-1”, CH2Ph), 4.42 (bd, J =
residue was dissolved in 25% AcOH in Ac2O (5 mL), and the 3.4 Hz, 1H, H-4”), 4.39–4.34 (m, 2H, H-6ab”), 4.20 (t, J =
solution was stirred at rt for 12 h and co-concentrated with 6.6 Hz, 1H, H-3), 3.96 (t, J = 6.4 Hz, 1H, H-4), 3.89 (dd, J =
toluene (3 × 10 mL). Flash chromatography (EtOAc/hexanes, 3.7, 10.4 Hz, 1H, H-2’), 3.81–3.76 (m, 2H, H-5, H-5”), 3.76 (s,
2:8 → 1:1) of the residue gave trisaccharide 26 (35.7 mg, 3H, OCH3), 3.58 (m, 1H, H-2), 3.34 (s, 3H, OCH3), 2.11, 1.95,
0.0305 mmol, 77%) pure as a colourless glass. [α]D = −56 (c 1.86 (3s, 9H, 3 × C(O)CH3), 1.15–1.14 (m, 30H, H-6’, 3 ×
0.7, CH2Cl2); 1H NMR (400 MHz, CDCl3, 296 K) δ 7.32–7.17 C(CH3)3); 13C NMR (100 MHz, CDCl3, 295 K) δ 177.6, 177.5,
(m, 20H, Harom), 5.96 (d, J = 7.6 Hz, 1H, NH), 5.14 (dd, J = 170.5, 170.4, 169.7, 166.0, 159.2 (C=O), 133.4, 130.4, 129.7,
8.1, 10.4 Hz, 1H, H-2”), 5.04 (d, J = 3.6 Hz, 1H, H-1’), 4.89 (d, 129.5, 128.9, 128.7 (Ar), 100.4 (C-1), 100.0 (C-1”), 96.1 (C-1’),
J = 11.7 Hz, 1H, CHHPh), 4.78–4.66 (m, 6H, H-1, H-3”, 2 × 73.3 (C-4, C-2’), 72.6 (CH2Ph), 72.2 (C-5”), 71.7 (C-4’, C-3,
CH2Ph), 4.60 (d, J = 11.7 Hz, 1H, CHHPh), 4.56 (d, J = C-5), 71.5 (C-3”), 70.4 (C-3’), 68.0 (C-2”), 65.0 (C-5’), 63.7
12.1 Hz, 1H, CHHPh), 4.31 (m, 2H, H-1”, CHHPh), 4.21 (m, (C-6), 62.2 (C-6”), 57.6 (C-4”), 56.6, 55.3 (OCH3), 53.5 (C-2)
1H, H-5’), 4.10–4.00 (m, 4H, H-4, H-2’, H-6ab”), 3.89 (t, J = 38.9, 38.8, 38.7 (C(CH3)3), 27.1, 27.0, 27.0 (C(CH3)3), 23.2,
6.3 Hz, 1H, H-3), 3.86 (dd, J = 2.6, 10.1 Hz, 1H, H-3’), 3.79 20.9, 20.7 (C(O)CH3), 15.9 (C-6’); HRMS–ESI (m/z): [M + H]+
(dd, J = 4.9, 10.1 Hz, 1H, H-6a), 3.69 (dd, J = 3.7, 10.1 Hz, 1H, calcd for C55H77ClNO21, 1122.4677; found, 1122.4626.
H-6b), 3.59 (bd, J = 1.4 Hz, 1H, H-4’), 3.46–3.40 (m, 4H, H-2,
H-5, H-4”, H-5”), 3.29, 3.26 (2s, 6H, 2 × OCH3), 1.73 (s, 3H, Methyl 2-acetamido-3-O-(3,4-di-O-acetyl-2-O-p-methoxy-
C(O)CH3), 1.14–1.08 (m, 30H, H-6’, 3 × C(O)C(CH3)3); benzyl-α-L-fucopyranosyl)-6-O-benzoyl-2-deoxy-4-O-(4-
13C NMR (100 MHz, CDCl3, 296 K) δ 177.7, 177.6, 176.8, deoxy-4-fluoro-2,3,6-pivaloyl-β-D-galactopyranosyl)-β-D-
170.3 (C=O), 139.1, 139.0, 138.7, 138.0, 128.5–127.0 (Ar), glucopyranoside (28). A mixture of disaccharide acceptor 25
100.4 (C-1), 98.8 (C-1”), 96.2 (C-1’), 79.7 (C-3’), 77.0 (C-4’), (24 mg, 0.0318 mmol), known [12] thiophenyl fucopyranoside
76.5 (C-4), 76.2 (C-4”), 74.7 (CH2Ph), 73.4 (C-5”), 73.3 (C-3”), 13 (44 mg, 0.0953 mmol, 3.0 equiv) and activated powdered
73.0, 72.6, 72.2 (3 × CH2Ph), 72.0 (C-3), 71.8 (C-2’), 71.6 4 Å molecular sieves (0.15 g) in Et2O (1.5 mL) was stirred for
(C-5), 69.1 (C-2”), 68.8 (C-6), 66.6 (C-5’), 61.5 (C-6”), 61.3 1 h at rt under N2. MeOTf (18 μL, 5.0 equiv) was added and the
(OCH3), 56.5 (OCH3), 53.5 (C-2) 38.8, 38.7 (C(CH3)3), 27.2, reaction was allowed to proceed for 30 min at rt. More donor 13
27.1 (C(CH3)3), 23.1 (C(O)CH3), 16.6 (C-6’); HRMS–ESI (44 mg, 3.0 equiv) was added and the reaction was allowed to
(m/z): [M + H]+ calcd for C65H88NO18, 1170.6001; found, proceed for an additional 2 h at rt before being quenched with
1170.6033.
Et3N (27 μL, 6.0 equiv). Work up of the reaction and treatment
of the crude product in 25% AcOH in Ac2O (4 mL), as well as
Methyl 2-acetamido-3-O-(3,4-acetyl-2-O-paramethoxy- the subsequent work-up, were carried out as described above for
benzyl-α-L-fucopyranosyl)-6-O-benzoyl-4-O-(4-chloro-4- the synthesis of trisaccharide 26. Flash chromatography
deoxy-2,3,6-pivaloyl-β-D-galactopyranosyl)-2-deoxy-β-D- (EtOAc/hexanes, 2:8 → 6:4) of the residue gave trisaccharide
glucopyranoside (27). A mixture of disaccharide acceptor 24 28 (22.8 mg, 0.0206 mmol, 65%) pure as a colourless glass.
(48 mg, 0.0622 mmol), known [12] thiophenyl fucopyranoside [α]D = −37 (c 1.2, CH2Cl2); 1H NMR (400 MHz, CDCl3,
13 (86 mg, 0.187 mmol, 3.0 equiv) and activated powdered 4 Å 295 K) δ 8.00–6.84 (m, 9H, Harom), 6.08 (d, J = 7.9 Hz, 1H,
molecular sieves (0.3 g) in Et2O (2.0 mL) was stirred 1 h at rt NH), 5.30–5.22 (m, 3H, H-3’, H-4’, H-2”), 5.19 (d, J = 3.6 Hz,
under N2. MeOTf (35 μL, 5.0 equiv) was added and the reac- 1H, H-1’), 4.87 (ddd, J = 2.4, 10.3 Hz, JH,F = 27.1 Hz, 1H,
tion was allowed to proceed for 3 h at rt. More donor 13 H-3”), 4.79–4.53 (m, 7H, H-1, H-6ab, H-1”, H-4”, CH2Ph),
(43 mg, 1.5 equiv) was added and the reaction was allowed to 4.47 (m, 1H, H5’), 4.36–4.33 (m, 2H, H-6ab”), 4.14 (t, J =
proceed for an additional 1 h at rt before being quenched with 6.2 Hz, 1H, H-3), 3.97 (t, J = 6.1 Hz, 1H, H-4), 3.90–3.83 (m,
Et3N (52 μL, 6.0 equiv). Work up of the reaction and treatment 2H, H-5, H-2’), 3.76 (s, 3H, OCH3), 3.69–3.61 (m, 2H, H-2,
of the crude product in 25% AcOH in Ac2O (6 mL), as well as H-5”), 3.34 (s, 3H, OCH3), 2.11, 1.95, 1.87 (3s, 9H, 3 ×
the subsequent work-up, were carried out as described above for C(O)CH3), 1.17–1.14 (m, 30H, H-6’, 3 × C(CH3)3); 13C NMR
the synthesis of trisaccharide 26. Flash chromatography (100 MHz, CDCl3, 295 K) δ 177.6, 177.0, 170.5, 170.4, 169.8,
(EtOAc/hexanes, 2:8 → 6:4) of the residue gave trisaccharide 166.0, 159.2 (C=O), 133.3, 130.3, 129.7, 129.5–128.6, 113.8
27 (42.5 mg, 0.0379 mmol, 61%) pure as a colourless glass. (Ar), 100.5 (C-1’), 99.2 (C-1”), 95.9 (C-1), 85.4 (d, JC,F =
[α]D = –21 (c 0.8, CH2Cl2); 1H NMR (400 MHz, CDCl3, 186.3 Hz, C-4”), 73.3 (C-2’), 72.9 (C-4), 72.6 (CH2Ph), 72.1
295 K) δ 8.00–6.84 (m, 9H, Harom), 6.01 (d, J = 7.6 Hz, 1H, (C-3), 71.6 (C-5), 71.1 (d, JC,F = 18.1 Hz, C-5”), 70.9 (d, JC,F =
1141

Beilstein J. Org. Chem. 2012, 8, 1134–1143.
13.Asnani, A.; Auzanneau, F.-I. Carbohydr. Res. 2008, 343, 1653–1664.
doi:10.1016/j.carres.2008.04.017
18.5 Hz , C-3”), 70.5 (C-3’, C-4’), 68.5 (C-2”), 64.9 (C-5’),
63.8 (C-6), 60.7 (C-6”), 56.6, 55.2 (OCH3), 52.7 (C-2), 38.9,
38.8, 38.7 (C(CH3)3), 23.1 (C(CH3)3), 20.9, 20.7 (C(O)CH3),
15.8 (C-6’); HRMS–ESI (m/z): [M + H]+ calcd for
C55H77FNO21, 1106.4972; found, 1106.4956.
14.Hendel, J. L.; Cheng, A.; Auzanneau, F.-I. Carbohydr. Res. 2008, 343,
2914–2923. doi:10.1016/j.carres.2008.08.025
15.Wang, J.-W.; Asnani, A.; Auzanneau, F.-I. Bioorg. Med. Chem. 2010,
18, 7174–7185. doi:10.1016/j.bmc.2010.08.040
16.Thøgersen, H.; Lemieux, R. U.; Bock, K.; Meyer, B. Can. J. Chem.
1982, 60, 44–57. doi:10.1139/v82-009
Supporting Information
17.Imberty, A.; Mikros, E.; Koča, J.; Mollicone, R.; Oriol, R.; Pérez, S.
Glycoconjugate J. 1995, 12, 331–349. doi:10.1007/BF00731336
18.Reynolds, M.; Fuchs, A.; Lindhorst, T. K.; Pérez, S. Mol. Simul. 2008,
34, 447–460. doi:10.1080/08927020701713878
Supporting Information File 1
Experimental procedures and characteristics for compounds
8–11, 14–19, 23–25.
19.Miller, K. E.; Mukhopadhyay, C.; Cagas, P.; Bush, C. A. Biochemistry
1992, 31, 6703–6709. doi:10.1021/bi00144a009
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10705–10714. doi:10.1021/ja011156h
21.Pérez, S.; Mouhous-Riou, N.; Nifant’ev, N. E.; Tsvetkov, Y. E.;
Bachet, B.; Imberty, A. Glycobiology 1996, 6, 537–542.
doi:10.1093/glycob/6.5.537
Supporting Information File 2
1H NMR and 13C NMR for compounds 3–5, 8–11, 14–28.
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-8-126-S2.pdf]
22.Bundle, D. R. Pure Appl. Chem. 1989, 61, 1171–1180.
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Acknowledgements
We thank the National Science and Engineering Research
doi:10.1016/S0008-6215(00)91000-0
25.Bundle, D. R. Recognition of Carbohydrate Antigens by Antibody
Binding Sites. In Bioorganic Chemistry: Carbohydrates; Hecht, S. M.,
Ed.; Oxford University Press: New York, 1999; pp 370–440.
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Council for financial support of this work.
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