Differential recognition of mannose-based polysaccharides by tripodal receptors based on a triethylbenzene scaffold substituted with trihydroxybenzoyl moieties

Article abstract of DOI:10.1002/ejoc.201201239

The tripodal receptors 1 and 2 based on a triethylbenzene scaffold substituted with trihydroxybenzoyl groups have been synthesised. The conformational preferences and carbohydrate-binding ability of 1 and 2 have been examined by NMR spectroscopy and model

Full text of DOI:10.1002/ejoc.201201239

FULL PAPER
DOI: 10.1002/ejoc.201201239
Differential Recognition of Mannose-Based Polysaccharides by Tripodal
Receptors Based on a Triethylbenzene Scaffold Substituted with
Trihydroxybenzoyl Moieties
Paula Carrero,[a] Ana Ardá,[b] Mónica Alvarez,[c] Elisa G. Doyagüez,[a] Eva Rivero-Buceta,[a]
Ernesto Quesada,[a] Alicia Prieto,[d] Dolores Solís,[c,e] María José Camarasa,[a]
María Jesús Peréz-Pérez,[a] Jesús Jiménez-Barbero,*[b] and Ana San-Félix*[a]
Keywords: Carbohydrates / Molecular recognition / Receptors / Conformational analysis
The tripodal receptors 1 and 2 based on a triethylbenzene
scaffold substituted with trihydroxybenzoyl groups have
been synthesised. The conformational preferences and
carbohydrate-binding ability of 1 and 2 have been examined
by NMR spectroscopy and modelling procedures. The results
reveal that the particular structural pre-organisation of 2 fa-
cilitates the recognition, in a highly competitive medium
(DMSO), of a mannose-based polysaccharide consisting of a
linear saccharide chain continuously decorated by α(1Ǟ2)-
linked branching mannose moieties. By contrast, other
α(1Ǟ2)-substituted polysaccharides or different monosac-
charides are not bound, revealing the selectivity of the inter-
action. Due to the importance of α(1Ǟ2) mannosides, which
are abundantly present on the glycan shield of several patho-
gens, the results reported here open attractive prospects for
the potential application of 2 or its derivatives in future anti-
infective strategies.
ing opportunities for different practical applications, includ-
ing biomedicine and analytical chemistry.[2] In terms of bio-
medical applications, synthetic receptors could potentially
be used in diagnostic methods to detect carbohydrate bio-
markers of disease,[3] or to develop future antiinfective ther-
apies aimed at avoiding infection by pathogens (viruses,
bacteria, parasites, and fungi).[4]
Two main classes of artificial carbohydrate receptors
have been developed to date. The first one involves the ex-
ploitation of nonnatural bonding interactions, and relies on
boron-based systems that operate through covalent bond
formation. These systems have been relatively successful,
even recognising carbohydrates in aqueous solution.[5] The
second class of carbohydrate receptors include compounds
that act through noncovalent interactions.[6] Such systems
are of special interest because they better reproduce the
noncovalent carbohydrate–receptor interactions observed
in nature. But although several carbohydrate receptors in
this second group showed good degrees of affinity and
selectivity in organic solvents, only a few tolerated signifi-
cant quantities of protic cosolvents. One exception is a par-
ticularly powerful family of receptors developed by Davis
et al. that exhibits outstanding recognition properties for
Introduction
Molecular recognition of carbohydrates is crucial in
many relevant physiological processes, starting from fertili-
sation, embryogenesis, tissue maturation, and immune re-
sponse, and extending to different pathologies such as mi-
crobial infections and tumor metastasis.[1] Different syn-
thetic carbohydrate receptors have been developed over the
past few years as model systems to investigate the basic mo-
lecular features that govern carbohydrate recognition in
natural systems. These synthetic receptors present interest-
[a] Instituto de Química Médica (IQM-CSIC),
Juan de la Cierva 3, 28006 Madrid, Spain
Fax: +34-915644853
E-mail: anarosa@iqm.csic.es
Homepage: http://www.iqm.csic.es
[b] Chemical and Physical Biology, Centro de Investigaciones
Biológicas (CIB-CSIC),
Ramiro de Maeztu 9, 28040 Madrid, Spain
Fax: +34-915360432
E-mail: jjbarbero@cib.csic.es
Homepage: http://www.cib.csic.es
[c] Instituto de Química Física Rocasolano (IQFR-CSIC),
Serrano 119, 28006 Madrid, Spain
Fax: +34-915642431
E-mail: d.solis@iqfr.csic.es
Homepage: http://www.iqfr.csic.es
[d] Enviromental Biology, Centro de Investigaciones Biológicas carbohydrates with all-equatorial stereochemistry (β-gluc-
ose, β-glucosides, cellobiose, etc.), even in water.[2,7]
(CIB-CSIC),
Ramiro de Maeztu 9, 28040 Madrid, Spain
Among the numerous artificial receptors that have been
designed to interact with carbohydrates through noncova-
lent interactions, tripodal receptors based on the 2,4,6-tri-
ethylbenzene scaffold occupy a prominent position. It has
[e] Centro de Investigación Biomédica en Red de Enfermedades
Respiratorias (CIBERES),
Bunyola, Mallorca, Illes Balears, Spain
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201239.
Eur. J. Org. Chem. 2013, 65–76
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
65

J. Jiménez-Barbero, A. San-Félix et al.
FULL PAPER
been demonstrated that this scaffold is able to preorganise central scaffold by amide bonds. The choice of amide
the binding elements, and so improve the binding affinity groups as spacers was made on account of the double hy-
of supramolecular hosts.[8] In this context, the research drogen-bonding donor–acceptor nature of this functional
groups of Roelens,[9] Mazik,[6d,6e,10] Abe,[11] and group. Consequently, these groups could provide “extra”
Schmuck,[12] demonstrated that compounds with a tripodal hydrogen-bonding interactions with the polar groups of
1,3,5-substituted 2,4,6-triethylbenzene scaffold, bearing on carbohydrates.
the side arms three carbohydrate-recognition units, are able
to bind different monosaccharides and even short oligosac-
charides in organic media with significant affinities and
selectivities.
The design of this second group of artificial receptors
has been at least partially inspired by lectins, carbohydrate-
binding proteins that are the most common class of natural
carbohydrate receptors. X-ray crystallographic structures of
lectin–carbohydrate complexes have revealed that carbo-
hydrate recognition is generally established through mul-
tiple noncovalent forces, mainly hydrogen bonding between
the sugar hydroxy groups and polar residues of the protein,
but also hydrophobic interactions between sugar CH
groups and nonpolar residues of the protein.[13] Interest-
ingly, these nonpolar residues are frequently aromatic,
which suggests the presence of CH–π interactions between
sugar CH groups and aromatic amino acids.[14–17] In par-
ticular, the importance of the aromatic amino acids has
been confirmed using a variety of experimental techniques,
including site-directed mutagenesis.[14b,15] Depending on the
particular system, either hydrogen bonds or CH–π interac-
tions may drive the molecular recognition process, although
typically both are simultaneously operative.
It should be said that although some noncovalent recep-
tors showing a preference for disaccharides over monosac-
charides[18] or even the capacity to distinguish tetrasac-
charides from their lower (mono-, di-, and trisaccharide)
homologues have been described,[19] reports of the selective
recognition of oligosaccharides by this type of receptor are
still scarce.
On the other hand, it is known that natural polyphenols
are amphipathic molecules having both hydrophobic aro-
matic rings and hydrophilic hydroxy groups, which allows
Figure 1. Structures of 1 and 2.
them to bind simultaneously at several sites on the surface
The carbohydrate-binding ability of 1 and 2 was exam-
of different types of macromolecules, including polysaccha- ined by UV/Vis and NMR spectroscopy. As an unde-
rides.[20,21] Their complexation with these macromolecules manding technique (with respect to sample concentration),
involves both hydrophobic effects, which are considered to UV/Vis spectroscopy appears to be an appropriate method-
be the main driving force in the association, and hydrogen ology to screen a set of carbohydrates in aqueous media.
bonding.[22] Factors such as molecular size, conformation, Such a pre-evaluation of the interaction of 1 and 2 indicated
and the number and position of free phenolic hydroxy that both compounds showed a preference for a certain
groups affect the binding capacity and selectivity of poly- mannose-based polysaccharide. Further analysis by NMR
phenols.[20]
spectroscopy in a highly competitive medium (DMSO) re-
Based on all these precedents, two tripodal receptors 1 vealed that tripodal receptor 2 showed a unique selectivity
and 2 (Figure 1) based on a triethylbenzene scaffold substi- for a certain type of α(1Ǟ2) mannose polysaccharide that
tuted with trihydroxybenzoyl groups have been synthesised. resembles those abundantly present on the glycan shield of
We hypothesised that the central and phenolic aromatic several pathogens.[4a,23] Interaction with this type of poly-
rings of these compounds might establish stabilising CH–π saccharide has recently been envisaged as an original thera-
interactions with the sugar CH groups of polysaccharides, peutic concept for the treatment of various pathogenic in-
while the acidic phenolic OH groups might give additional fections.[4]
hydrogen-bonding interactions with the polar groups (OH
The selectivity found for 2, with three 2,3,4-trihydroxy-
groups and oxygen of the glycosidic linkage) of carbo- benzoyl moieties on a triethylbenzene scaffold, contrasts
hydrates. The phenolic entities have been connected to the with that of 1, with three gallic acid (3,4,5-trihydroxy-
66
www.eurjoc.org
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 65–76

Recognition of Mannose-Based Polysaccharides
benzoyl) moieties as substituents (Figure 1). To explore the UV Spectroscopic Evaluation of the Carbohydrate-Binding
1
origin of this selectivity, additional H NMR spectroscopy Ability of 1 and 2
and molecular modelling studies were performed.
The carbohydrate-binding ability of the compounds syn-
thesised was initially evaluated by scrutinising possible
changes in their UV spectra in the absence and presence of
different mono- and polysaccharides in aqueous media. As
expected, 1 and 2 gave similar spectra characterised by a
Results and Discussion
Synthesis
Target compounds 1 and 2 were prepared following the band centred at 265 nm and a trough at 243/247 nm (for 1/
synthetic pathway shown in Scheme 1. 2, respectively). No changes in the spectra were visible in
The central scaffold, 1,3,5-trisamine-2,4,6-triethylbenz- the presence of mannose, galactose, or glucose at
ene (3), was prepared in three steps from commercially 12 mgmL–1, or even at a higher 18 mgmL–1 (0.1 m) mono-
available 1,3,5-triethylbenzene following previously re- saccharide concentration. However, isosbestic points were
ported procedures.[24] Subsequently, 3 was treated with the observed in the presence of 12 mgmL–1 mannan (Figure 2),
respective benzyl-protected trihydroxybenzoic acids (i.e., a mannose-based polysaccharide, together with some sig-
4[25] and 6[26]) in the presence of BOP and triethylamine to nificant changes. In particular, the absorbance intensity of
afford 5 and 7 in 70 % and 63 % yields, respectively. the band at 265 nm decreased noticeably while the trough
Attempts to conduct the reaction with the unprotected tri- minimum was slightly red-shifted. There were no percepti-
hydroxybenzoic acids failed, giving intractable mixtures un- ble changes in the presence of 12 mgmL–1 dextran (a gluc-
der several conditions. The alternative protection of the ose-based polysaccharide). Altogether, the results were
phenolic hydroxy groups as methyl ethers also proved to be taken as a hint of the existence of a selective interaction of
unsuitable, as their subsequent deprotection required harsh 1 and 2 with mannan in aqueous solvent. Taking into ac-
conditions.
count the fact that mannan from Saccharomyces cerevisae
Deprotection of the benzyl groups of 5 and 7 by catalytic is composed of a linear α(1Ǟ6)-linked mannose chain with
hydrogenation in the presence of 10 % Pd/C gave the corre- α(1Ǟ3)-linked mannose branches, and with varying
sponding phenol-deprotected derivatives 1 (99 %) and 2 amounts of mannose α(1Ǟ2)-linked to the α(1Ǟ3)
(76 %) in excellent yields (Scheme 1).
branching units, three different DMSO-soluble mannose-
Scheme 1. Synthesis of 1 and 2.
Eur. J. Org. Chem. 2013, 65–76
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
67

J. Jiménez-Barbero, A. San-Félix et al.
FULL PAPER
based polysaccharides with similar connectivities were se- vents such as CDCl3 in which hydrogen-bonding interac-
lected for NMR analysis.
tions are enhanced, often dramatically, compared to water
and other competitive polar media.[10d,10e] In our case, ti-
trations monitored by 1H NMR spectroscopy were per-
formed in [D6]DMSO, a competitive solvent.
First, polysaccharides with general structures A and C
(Figure 3) consisting of a main linear α(1Ǟ6)-linked mann-
ose chain continuously decorated by α(1Ǟ2)-linked glucose
(polysaccharide A) or α(1Ǟ2)-linked mannose (polysac-
charide C) units were used. In addition, polysaccharide B,
in which an α(1Ǟ2)-linked mannose unit is attached to
every third residue of the main chain, was also investigated.
The addition of polysaccharide C (23 mg/mL) to a [D6]-
DMSO solution (0.7 mm) of 2 caused significant broaden-
ing of its aromatic H-5 and H-6 signals, thus indicating the
participation of these groups in an interaction with the
sugar (see Figure 4 and Figure 5, left). Broadening of the
signals of the NH and OH groups of 2 was also observed.
When the reverse titration was performed,[28] i.e., polysac-
charide C was titrated with 2, no unambiguous confirm-
ation of the interaction could be obtained. This can be ex-
plained by the heterogeneity of the polysaccharide, whose
molecular weight range encompasses several kDa, following
a Gaussian distribution. Thus, upon titration of C with the
“small” receptor 2, the effects are diluted among the dif-
ferent units of the polysaccharide, resulting in very tiny
chemical shift variations that are below experimental error.
This also explains the success of the direct experiment: a
single polysaccharide molecule can accommodate several
receptor molecules, thereby allowing detection of the effect.
In contrast, in the presence of polysaccharides A and B,
broadening of the proton signals of 2 was not observed in
analogous 1H NMR experiments, underlining the selectivity
of the interaction between polysaccharide C and receptor
2.
Figure 2. Mannan-induced changes in the UV spectra of com-
pounds 1 and 2. The spectra of 2.42ϫ10–4 m solutions of 1 (upper
panel) and 2.46ϫ10–4 m of 2 (lower panel) in water containing
30 % acetonitrile and 10 mm DTT, were recorded in the absence
(solid lines) and presence (dotted lines) of 12 mgmL–1 mannan.
A rough estimate of the binding affinity between 2 and
polysaccharide C was made by measuring the variations in
intensity and linewidth (which is related to the transverse
relaxation rate, 1/T2*) of protons H-5 and H-6 of 2 upon
stepwise additions (5 μL) of polysaccharide C (Figure 4).
1H NMR Analysis of the Carbohydrate-Binding Ability of
1 and 2
The interaction of different monosaccharides with simple As described by Shortridge et al.,[29] an estimated Kd was
aromatic moieties has been investigated by NMR spec- calculated from these values, using Equation (1)
troscopy previously.[27] Changes in the relaxation properties
or in chemical shifts of the different protons of the inter-
acting partners were monitored to provide unambiguous
evidence of the existence of an interaction. Similar method-
ologies have been used to study the interaction of simple
(1)
glycosides with synthetic receptors.[9,10] With this precedent,
and prompted by the indications from UV spectroscopy of
selective compound–sugar interactions, we also used NMR where [P]T is the total polysaccharide concentration, Iobs
experiments to evaluate the binding of the tripodal recep- and I0 are the intensities of 2 in the presence and absence
tors, 1 and 2, to different mannose-containing polysac- of polysaccharide C, and the nondimensional parameter c
charides with different chemical architectures. In addition, is defined as c = (υB/υF – 1), where υF and υB are the line-
the interaction with different monosaccharides was scruti- widths of free and bound 2, respectively. An estimated Kd
nised in polar solvents.
Most studies to determine the carbohydrate-binding was obtained.
properties of synthetic receptors have used NMR spec- On the other hand, in the case of 1, no changes were
troscopy measurements using noncompetitive organic sol- observed in the aromatic region of the H NMR spectrum
(averaged between the values for H-5 and H-6) of 6Ϯ4 mm
1
68
www.eurjoc.org
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 65–76

Recognition of Mannose-Based Polysaccharides
Figure 3. Structure of polysaccharides A, B, and C.
Figure 4. From bottom to top: 1H NMR spectra of 2 in [D6]DMSO alone and after stepwise additions (5 μL) of polysaccharide C solution
(23 mg/mL). The lower panel shows an enlargement of the aromatic region, highlighting the broadening of the signals corresponding to
the H-5 and H-6 protons.
Eur. J. Org. Chem. 2013, 65–76
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
69

J. Jiménez-Barbero, A. San-Félix et al.
FULL PAPER
Figure 5. (left) Aromatic region of 2 in [D6]DMSO after stepwise additions (5 μL) of polysaccharide C solution (23 mg/mL), showing the
broadening of the signals corresponding to the H-5 and H-6 protons (᭹); (right) broadening of the signals corresponding to the H-5 and
1
H-6 protons (᭹) was not observed in an analogous H NMR experiment using N-benzyl-2,3,4-trihydroxybenzamide.
upon addition of any of the three polysaccharides A, B, Conformational Studies of 1 and 2 Using NMR
or C. Furthermore, the NMR spectrum of N-benzyl-2,3,4- Spectroscopy and Molecular Modelling
trihydroxybenzamide, used as model compound,[26] did not
show significant changes either in chemical shifts or in line
The conformational preferences of compounds 1 and 2
broadening in the presence of polysaccharide C (20–25 mg/ were studied by NMR spectroscopy and molecular model-
mL), which suggests that no interaction occurs under these ling. Previous work has shown that preorganisation of
experimental conditions (Figure 5, right). Therefore, NMR ortho-hydroxy (o-OH) substituted benzamides on trieth-
experimental evidence of the interaction in solution was se- ylbenzene scaffolds exists in the solid state and is main-
lectively achieved for a unique receptor–ligand pair. Only tained in polar solutions, through the establishment of in-
receptor 2 was able to recognise polysaccharide C, which tramolecular hydrogen bonding between the o-OH proton
shows a linear saccharide chain continuously decorated by of the benzamide group and the CO moiety.[30]
1
α(1Ǟ2) mannose branched moieties. A smaller degree of
The H NMR spectra of compounds 1 and 2 in [D6]-
branching, or the substitution of mannose by glucose, did DMSO allowed the detection of all the exchangeable OH
not result in an interaction. and NH protons as sharp singlet peaks. A first hint of the
In parallel, the binding abilities of 1 and 2 towards a set possible participation of the o-OH proton of 2 in intramo-
of mono- and disaccharides were also investigated in [D6]- lecular hydrogen bonding was its remarkable downfield
DMSO at T = 298 K. The monosaccharide glycosides, shift (δ = 12.5 ppm at 294 K), as it appeared much further
methyl α-d-glucopyranoside, methyl β-d-glucopyranoside, downfield than the signals for the meta- and para-hydroxy
methyl α-d-galactopyranoside, methyl β-d-galactopyran- protons (Figure S9, Supporting Information). In contrast,
oside, and methyl α-d-mannopyranoside, the monosaccha- for 1, such a large difference between the chemical shifts of
ride N-acetylglucosamine, and the disaccharide α,α-tre- the different OH protons was not observed. The tempera-
halose were used at 20–25 mg/mL. The NMR spectra of 1 ture coefficients[31] (Δδ/ΔT) of each exchangeable OH and
and 2 did not show significant changes either in chemical NH proton for both 1 and 2 were calculated by acquiring
shifts or in line broadening in the presence of these sugars, 1H NMR spectra at different temperatures (T = 294–328 K)
which suggests that no interaction occurs in DMSO solu- (Table 1). The lower temperature coefficient observed for
tion under these experimental conditions, as was similarly the o-OH proton in 2, in comparison with those for the
concluded from the UV spectroscopy analysis under other hydroxy protons, supports its participation in hydro-
aqueous conditions.
gen bonding.
Overall, NMR spectroscopic data indicate that the inter-
In addition, 2D NOE (NOESY) studies were performed
action in [D6]DMSO of the polyphenolic compounds with in [D6]DMSO at 294 K. For 2, strong NOE cross-peaks be-
the mannose-containing polysaccharides studied here is tween the amide NH/aromatic H-6 and aromatic H-6/H-5
fairly selective, that it depends on the chemical nature of protons were observed (Figure 6 and Figure S9 Supporting
the substitution of the central benzene unit (only 2, and not Information). In addition, weak, but noticeable, NOEs be-
1, shows any interaction), and, additionally, on the presen- tween the amide NH and the aromatic H-5 proton, amide
tation of the mannose units of the polysaccharide. The NH/ethyl CH3 and H-6/ethyl CH3 were observed. It should
differential recognition by compounds 1 and 2 of mannose- be mentioned that the observed NOE between the amide
based polysaccharides justified the analysis of the confor- NH and the aromatic H-6 proton was even stronger than
mational preferences of the two compounds.
those observed between the two adjacent H-6 and H-5 aro-
70
www.eurjoc.org
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 65–76

Recognition of Mannose-Based Polysaccharides
Table 1. Chemical shifts (δ values, ppm) and temperature coefficients (Δδ/ΔT, ppb/K) of the exchangeable OH and NH protons of 1 and
2.
2
1
T [K]
o-OH
m-OH
p-OH
NH
p-OH
2 m-OH
NH
294
298
303
308
313
318
323
328
Δδ/ΔT
12.541
12.521
12.496
12.471
12.447
12.421
12.395
12.368
5.100
8.442
8.414
8.379
8.344
8.309
8.273
8.238
8.202
6.500
9.523
9.497
9.465
9.432
9.400
9.368
9.335
9.302
7.100
8.422
8.403
8.397
8.355
8.331
8.306
8.282
8.256
5.000
8.648
8.619
8.583
8.547
8.511
8.476
8.440
8.405
7.200
8.999
8.973
8.943
8.911
8.879
8.848
8.816
8.785
6.300
7.715
7.691
7.662
7.632
7.602
7.572
7.541
7.511
6.000
matic protons. This indicates that the distance between the
amide NH and the aromatic H-6 is very short and, there-
fore, that the H-6 proton should be orientated towards the
amide NH. Consequently, the o-OH proton faces the amide
1
CO moiety. In conclusion, the H NMR spectroscopic data
obtained for compound 2 are consistent with the idea that
the phenol ring and the amide bond are in the same plane,
and at an appropriate distance for the formation of an in-
tramolecular hydrogen bond between the o-OH proton and
the amide carbonyl oxygen.
Figure 6. Observed NOEs for compound 2. NOEs between H-6/H-
5, NH/H-6, and NH/H-5 define the preferred conformation in
which the distance NH/H-5 is shorter than the distance H-5/H-6.
Figure 7. Compound 2: top) Structure of the global minimum ge-
ometry and bottom) local minimum conformation as deduced by
the MMFFs force field. The dotted lines represent the intramolecu-
lar hydrogen bond between the o-OH proton and the amide carb-
onyl oxygen.
Molecular modelling calculations were performed
through a Monte Carlo conformational search using the
MMFFs force field to provide three-dimensional structures
of these molecules in solution. This protocol (see Exp. Sec-
tion) yielded for 2 a structure adopting a so-called ababab It should be noticed that, in this conformation, the poly-
disposition as the lowest energy conformation (Figure 7, phenolic rings are orientated with the three phenolic OH
top). In this geometry, the three polyphenolic rings (arms) groups pointing out of the molecule, while the two aromatic
and the three ethyl groups (legs) are alternately orientated protons (H-5 and H-6) point inwards.
above (a) and below (b) the benzene ring. This alternating
However, some observed weak NOEs (amide NH/ethyl
geometrical pattern agrees with what has been reported for CH3 and H-6/ethyl CH3) cannot be satisfactorily explained
other tripodal receptors,[8–10] and orientates all of the poly- by considering this unique structure. Thus, it was necessary
phenolic rings to the same upper side of the central benzene to consider the involvement of a second conformational
core.
family (Figure 7, bottom). In this second family, one of the
Another key feature of this geometry was the formation polyphenolic arms is orientated differently from the other
of an intramolecular hydrogen bond between the o-OH pro- two arms with respect to the central benzene ring. In this
ton and the amide carbonyl oxygen, thus resulting in a conformation, distances of 2.71 and 2.51 Å were measured
nearly planar disposition of the phenolic ring. In this struc- between the corresponding NH/ethyl CH3 and H-6/ethyl
ture, the distance between the amide NH and H-6 proton CH3 proton pairs, which can explain the observed NOEs.
is 2.23 Å, while the H-5/H-6 distance is 2.45 Å, consistent Thus, the existence of a minor population of conformers of
with the corresponding observed relative NOE intensities. this type must be assumed.
Eur. J. Org. Chem. 2013, 65–76
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
71

J. Jiménez-Barbero, A. San-Félix et al.
FULL PAPER
Regarding compound 1, the NMR spectroscopic data
suggested that no phenolic OH groups were involved in hy-
drogen bonds. The observed NOEs are consistent with the
minimum energy structure obtained from the conforma-
tional search using the MMFFs force field shown in Fig-
ure 8, top. For this structure, the alternating ababab pattern
is observed. The distances between NH/ethyl CH3 (4.62 Å),
NH/(CH2)NH (2.77 Å) and NH/CHaromatic (2.16 Å) protons
agree with the observed NOEs.
Figure 9. Structure of 1 adopting an alternative conformation to
the ababab arrangement.
Therefore, from the conformation search protocol, it can
be concluded that compound 2 has a clear preference for
the adoption of a global conformation in which the orienta-
tion of the substituents (polyphenol rings) attached to the
central skeleton (triethylbenzene) is controlled. Therefore,
in compound 2, a well-defined structure is energetically fa-
voured. In contrast, for 1, a much larger degree of confor-
mational mobility takes place.
With the aim of explaining the interaction observed by
1H NMR spectroscopy between 2 and polysaccharide C,
additional molecular modelling studies were performed. A
Manα(1Ǟ2)Man disaccharide was taken as a model of the
branch of polysaccharide C. The global minimum obtained
(Figure 10) revealed that the cavity provided by 2 offers the
correct shape and size for the encapsulation of the mannose
side-chain of polysaccharide C. In the structure obtained,
the branching α(1Ǟ2)-linked mannose is located within the
cleft formed by the three phenolic arms of the receptor,
Figure 8. Compound 1: top) Structure of the global minimum ge-
ometry. bottom) Superimposition of different energy minima struc-
tures obtained from the molecular modelling protocol. The poly-
phenolic benzene rings may adopt different orientations.
Nevertheless, the molecular modelling protocol sug-
gested that the torsion angles between the phenolic moieties
and the carbonyl oxygen may be different (Figure 8, bot-
tom). These results are in contrast with those mentioned
above for 2. In that molecule, the presence of the intramo-
lecular hydrogen bond already described significantly re-
stricts the motion around this linkage. A corresponding hy-
drogen bond does not exist in 1, and therefore more confor-
mations are possible.
Compound 1 also showed a set of weak NOEs between
the aromatic CH protons of the phenolic moieties and the
ethyl groups attached to the central benzene unit that can-
not arise from the ababab conformation (in which these
protons are at a distance of 6.50 Å). However, they can be
explained by considering the additional flexibility around
the C(benzene)–CH2CH3 and C(benzene)–CH2NHCO
bonds, which can give rise to conformations different from
the ababab arrangement. This is the case for the local mini-
mum (destabilised by 6.3 kJ/mol) shown in Figure 9, where
the distance between the aromatic CH protons and the ethyl
CH3 is 2.69 Å.
Figure 10. Minimum energy conformer for the complex of 2 with
Manα(1Ǟ2)Man from the conformational search with MMFFs
force field. In this structure, the branching α(1Ǟ2)-linked mannose
is located within the cleft formed by the receptor, whereas the back-
bone mannose residue is orientated in such a way that the O-1
anomeric and O-6 atoms point outside the cleft.
72
www.eurjoc.org
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 65–76

Recognition of Mannose-Based Polysaccharides
whereas the backbone mannose residue is orientated in such
Thus, 2 displays the basic features in terms of functional
a way that the O-1 anomeric and O-6 atoms point outside groups and structural pre-organisation requirements to be
the cleft. Thus, the linear Manα(1Ǟ6)Man polysaccharide able to recognise, in a highly competitive medium (DMSO),
backbone should not interfere with the interaction, al- a certain α(1Ǟ2)-linked mannose polysaccharide that mim-
though it provides the proper orientation of the branching ics the mannose composition of the high-mannose oligosac-
residue to interact with the receptor. Also, the two aromatic charide chains found in the glycoproteins of several patho-
protons H-5/H-6 of the trihydroxybenzoyl moieties are ori- gens. This property could be of interest for the potential
entated inside this cavity, allowing an interaction with the application of compound 2 in future antiinfective strategies.
bound carbohydrate.
In any case, the monovalent interaction is expected to be
very weak, as is commonly observed for protein–carbo-
hydrate interactions in nature.[32] Indeed, no interaction
Experimental Section
could be detected for the single Man monosaccharide,
either as its α- or β-methyl glycoside. Only the presence of
many branched Man units in the polysaccharide generated
detectable interaction signals.
Chemical Synthesis
General Methods: Commercially available reagents and solvents
were used as received from the suppliers without further purifica-
tion unless otherwise stated. Dichloromethane was dried prior to
use by distillation from CaH2, and was stored over Linde-type acti-
vated molecular sieves (4 Å). Analytical thin-layer chromatography
(TLC) was performed on aluminium plates pre-coated with silica
gel 60 (F254, 0.25 mm). Products were visualised on TLC plates by
exposure to ultraviolet light (254 nm) or by heating on a hot plate
(approx. 200 °C), directly or after treatment with a 5 % solution
of phosphomolybdic acid or vanillin in ethanol. Separations were
performed by preparative Centrifugal Circular Thin-Layer
Chromatography (CCTLC) (Kieselgel 60 PF254 gipshaltig, layer
thickness of 1 mm, flow rate 4 mLmin–1). For HPLC analysis, an
Alliance 2695 (Waters) equipped with a PDA (Photo Diode Array)
detector Waters 2996 was used. Acetonitrile with 0.08 % formic
acid was used as mobile phase A, and water with 0.1 % formic acid
was used as mobile phase B at a flow rate of 1 mLmin–1. Two
different methods were used, one on an XBridge C18
(2.1ϫ100 mm, 3.5 μm) column with 5–80 % of solvent A, which is
denoted tR(X), and the other on a SunFire C18 (4.6ϫ50 mm,
3.5 μm) column with 0–100 % of solvent A, which is denoted
tR(S). All retention times are quoted in minutes. Melting points
were measured with a Reichert–Jung Kofler apparatus. Standard
NMR (1H and 13C) spectra were recorded with 300 MHz (Inova
300) and 400 MHz (Inova 400) spectrometers, using CDCl3 or
CD3OD as solvents at room temperature. Chemical shift values
are reported in parts per million (δ) using as internal standards
Conclusions
The tripodal receptors 1 and 2 based on a triethylbenz-
ene scaffold substituted with trihydroxybenzoyl groups have
been prepared.
Compound 2 mainly adopts a well-defined conformation
in polar ([D6]DMSO) solution, in which the phenol rings
and the amide bonds are in the same plane. This places the
ortho-hydroxy proton and the amide carbonyl oxygen at a
distance appropriate for the formation of an intramolecular
hydrogen bond. This is not the case for compound 1, which
is much more flexible and does not show the corresponding
intramolecular hydrogen bonds. On this basis, molecular
modelling studies showed, for compound 2, a well defined
major structure in which the ortho-hydroxy protons are
strongly hydrogen-bonded to the amide carbonyl oxygen,
resulting in the outward projection of the phenolic OH
groups and the inward presentation of the aromatic pro-
tons. In contrast, 1 may adopt a large variety of conforma-
tions, which results in the lack of a well-defined geometry.
UV spectroscopic measurements indicated a selective re-
cognition of mannan by 1 and 2 in water containing 30 %
acetonitrile, over dextran (a glucose-based polysaccharide)
and different monosaccharides. Mannan from Saccharo-
myces cerevisae consists of a linear α(1Ǟ6)-linked mannose
chain with branching α(1Ǟ3)-linked mannose units, and
variable amounts of mannose α(1Ǟ2)-linked to these
α(1Ǟ3) branching units. Furthermore, evidence from NMR
1
tetramethylsilane (TMS) in H, and CDCl3 (δ = 77.0 ppm) in 13C
NMR spectra. Coupling constants (J values) are reported in Hertz
(Hz), and spin multiplicities are indicated by the following symbols:
s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet). Mass
spectra were recorded with a quadrupole mass spectrometer 1100
equipped with an electrospray source. Microanalyses were obtained
with a Heraeus CHN-O-RAPID instrument.
General Procedure for the Reaction of Trisamine 3 with Benzoic
spectroscopy revealed that 2 discriminated between dif- Acids: Benzotriazol-1-yloxytris(dimethylamino)phosphoniumhexa-
fluorophosphate (BOP) (3.3 equiv.) was added to a solution of the
corresponding benzoic acid (3.3 equiv.) in dry dichloromethane
(5 mL). After 5 min, trisamine 3[24] (0.05 g, 1 equiv.) and triethyl-
amine (3.3 equiv.) were added. The mixture was stirred at room
temperature overnight. The solvent was evaporated, and the residue
was treated with ethyl acetate (10 mL) and washed successively with
saturated solutions of citric acid (3ϫ 30 mL), NaHCO3 (3ϫ
30 mL), and brine (1ϫ 30 mL). The organic phase was dried
(Na2SO4) and filtered, and the solvents were evaporated to dryness.
The residue was purified by CCTLC using dichloromethane/meth-
anol, (9:1) as eluent.
ferent mannose-based polysaccharides and recognised poly-
saccharide C, a mannan consisting of a linear saccharide
chain continuously decorated by α(1Ǟ2)-linked branching
mannose moieties. A significant selectivity for the presence
of branching mannose residues was deduced from these
studies. From the receptor’s perspective, pre-organisation
seems to be required for the recognition process with poly-
saccharide C, since there are no major changes in the orien-
tation of the phenolic aromatic rings between the free and
bound states of 2.
Eur. J. Org. Chem. 2013, 65–76
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
73

J. Jiménez-Barbero, A. San-Félix et al.
FULL PAPER
1,3,5-Tris(3,4,5-tribenzyloxybenzamidomethyl)-2,4,6-triethylbenzene
(5): Trisamine derivative 3[24] (0.05 g, 0.20 mmol) and 4[25] (0.32 g,
0.72 mmol) were coupled according to the general procedure to
give 5 (0.21 g, 70 %) as a white solid: m.p. 178–180 °C. HPLC: tR(X)
order to prevent any potential oxidation. The measured solutions
had concentrations in the range of 10–4 m. To test the effect of the
monosaccharides and polysaccharides, solutions of 1 and 2 at the
appropriate concentration were added to the undissolved sugars,
and the spectra of the resulting mixtures were compared to the one
1
= 20.44. H NMR (CDCl3, 300 MHz): δ = 1.18 (t, J = 6.9 Hz, 9
H, CH3-CH2), 2.73 (q, J = 6.7 Hz, 6 H, CH3-CH2), 4.61 (s, 6 H, obtained for the pure tripodal receptor.
CH2-NH), 4.99 (s, 18 H, CH2-Ph), 5.66 (s, 3 H, NH), 6.93 (s, 6 H,
NMR Spectroscopy: NMR titrations of 1 and 2 with polysac-
H-Ar), 7.18–7.25 (m, 45 H, H-Ar) ppm. 13C NMR (CDCl3,
75 MHz): δ = 17.15 (CH3), 23.78 (CH2), 39.18 (CH2), 72.09 (CH2),
75.63 (CH2), 107.76 (CH), 127.96–129.78 (CH), 132.78 (C), 136.96
(C), 137.68 (C), 142.11 (C), 145.22 (C), 153.25 (C), 167.20 (CO)
ppm. MS (ES+): m/z = 1517 [M + H]+, 1539 [M + Na]+.
charides A, B, and C were performed at 500 MHz with a Bruker
AVANCE spectrometer, at 298 K, unless otherwise stated. The ex-
periments were performed in [D6]DMSO. Experiments with the
free species were recorded at 2.1 mm for 1, and at 1.2 mm for 2.
Besides regular 1D 1H NMR spectra, TOCSY (35 ms mixing time)
and NOESY (500 ms mixing time) experiments, using standard
BRUKER sequences, were also acquired.
1,3,5-Tris(2,3,4-tribenzyloxybenzamidomethyl)-2,4,6-triethylbenzene
(7): Trisamine derivative 3[24] (0.05 g, 0.20 mmol) and 6[26] (0.29 g,
0.66 mmol) were coupled according to the general procedure to
give 7 (0.19 g, 63 %) as a yellow oil. HPLC: tR(S) = 5.74. 1H NMR
(CDCl3, 300 MHz): δ = 1.03 (t, J = 7.3 Hz, 9 H, CH3-CH2), 2.47
(q, J = 7.3 Hz, 6 H, CH3-CH2), 4.53 (s, 6 H, CH2-NH), 4.83 (s, 6
H, CH2-Ph), 4.84 (s, 6 H, CH2-Ph), 5.12 (s, 6 H, CH2-Ph), 6.8–7.4
(m, 48 H, H-Ar), 7.73 (t, J = 4.4 Hz, 3 H, NH), 7.91 (d, J = 8.9 Hz,
3 H, H-Ar) ppm. 13C NMR (CDCl3, 75 MHz): δ = 16.27 (CH3),
22.84 (CH2), 37.88 (CH2), 70.88 (CH2), 75.52 (CH2), 76.49 (CH2),
109.25 (C), 119.68 (C), 126.78 (CH), 127.54–128.06 (CH), 132.34
(C), 135.73 (C), 136.14 (C), 136.88 (C), 141.05 (C), 143.90 (C),
151.42 (C), 155.72 (C), 164.42 (C=O) ppm. MS (ES+): m/z = 1517
[M + H]+, 1539 [M + Na]+.
For the titrations, stepwise additions (5 μL) of a concentrated poly-
saccharide solution (ca. 23 mg/mL) were made to solutions of 1 or
2 (0.7 mm), and NMR spectra of the resulting mixtures were re-
corded and monitored, looking for chemical shift changes or line
broadening in the signals of 1 or 2.
Molecular Modelling Procedures: Compounds 1 and 2 were built
using Maestro[33] and minimised using conjugate gradients with the
AMBER* force field,[34] and a dielectric constant of 37.5 Debyes
with extended cut-off to treat remote interactions. A maximum of
5000 iterations were used with the PRCG scheme until the conver-
gence energy threshold was 0.05 kJ/mol. Once the optimum geome-
tries had been achieved, a conformational search protocol was
adopted for both compounds, using a Monte Carlo torsional sam-
pling method (MCMM) with automatic setup during the calcula-
tion, energy window of 50 kJ/mol, maximum number of steps of
1000, and 100 steps per torsion to be rotated. The best structures
obtained from this calculation in terms of energy were chosen, and
then models of a mannose monosaccharide and a Manα(1Ǟ2)
ManαOMe disaccharide were manually docked within the cavity
and further minimised. Different complexes were found to be
stable. Of those that had the sugar inside the receptor cavity, the
most stable was submitted to additional Conformational Search
calculations.
General Procedure for Benzyl Group Deprotection: A solution of
the corresponding benzyl-protected derivative (1 mmol) in THF/
methanol (1:1; 100 mL) containing Pd (10 % on C; 30 wt.-%) was
hydrogenated at 2.85 atm (42 psi) at 30 °C overnight. The Pd/C was
removed by filtration through Whatman® filter paper 42, and the
solvent was removed under reduced pressure to give the corre-
sponding deprotected derivatives as single products.
1,3,5-Tris(3,4,5-trihydroxybenzamidomethyl)-2,4,6-triethylbenzene
(1): Following the deprotection procedure, benzyl derivative 5
(0.10 g, 0.07 mmol) gave 1 (0.05 g, 99 %) as a white solid: m.p. 178–
180 °C. HPLC: tR(X) = 3.04. 1H NMR (CD3OD, 300 MHz): δ =
1.21 (t, J = 7.3 Hz, 9 H, CH3-CH2), 2.90 (q, J = 7.1 Hz, 6 H, CH3-
CH2), 4.61 (s, 6 H, CH2-NH), 6.80 (s, 6 H, H-Ar), 7.82 (wide s, 3
H, NH) ppm. 13C NMR (CD3OD, 100 MHz): δ = 15.56 (CH3),
22.90 (CH2), 38.64 (CH2), 106.75 (CH), 124.83 (C), 131.74 (C),
136.93 (C), 144.52 (C), 145.43 (C), 169.32 (C=O) ppm. MS (ES+):
m/z = 706 [M + H]+, 728 [M + Na]+. C36H39N3O12 (705.72): calcd.
C 61.27, H 5.57, N 5.95; found C 61.00, H 5.60, N 5.98.
Polysaccharides: Polysaccharides A, B, and C were obtained as de-
scribed previously.[35,36] Mannan from Saccharomyces cerevisiae
(Sigma) and dextran T40 (Pharmacia) were used without further
purification.
Supporting Information (see footnote on the first page of this arti-
cle): Copies of the 1H and 13C NMR spectra for all key intermedi-
ates and final products are included, as well as the NOESY spec-
trum of 2 and the 1H NMR control experiment with N-benzyl-
2,3,4-trihydroxybenzamide.
1,3,5-Tris(2,3,4-trihydroxybenzamidomethyl)-2,4,6-triethylbenzene
(2): Following the deprotection procedure, benzyl derivative 7
(0.19 g, 0.12 mmol) gave 2 (0.07 g, 76 %) as a white solid: m.p. 154–
156 °C. HPLC: tR(S) = 3.62. 1H NMR (CD3OD, 300 MHz): δ =
1.21 (t, J = 7.3 Hz, 9 H, CH3-CH2), 2.88 (q, J = 7.0 Hz, 6 H, CH3-
CH2), 4.66 (s, 6 H, CH2-NH), 6.33 (d, J = 8.8 Hz, 3 H, H-Ar), 7.17
(d, J = 8.8 Hz, 3 H, H-Ar) ppm. 13C NMR (CD3OD, 75 MHz): δ
= 16.64 (CH3), 24.04 (CH2), 39.16 (CH2), 108.09 (C), 109.47 (CH),
120.36 (CH), 132.87 (C), 133.75 (C), 145.83 (C), 150.44 (C), 150.66
(C), 170.73 (C=O) ppm. MS (ES+): m/z = 706 [M + H]+, 728 [M
+ Na]+. C36H39N3O12 (705.72): calcd. C 61.27, H 5.57, N 5.95;
found C 60.98, H 5.63, N 6.12.
Acknowledgments
The Spanish Ministerio de Educación y Ciencia (MEC/MCINN)
(project number SAF 2009-13914-C02-01), the Spanish Consejo
Superior de Investigaciones Científicas (project number PIF08-
022), the Spanish Comunidad Autónoma de Madrid (CAM) (pro-
ject number BIPEDD 2-CM-S2010/BMD-2457) and the Spanish
Institute of Health Carlos III (ISCIII) (CIBER of Respiratory Dis-
eases, CIBERES) are acknowledged for their financial support.
UV/Vis Spectroscopy: UV/Vis spectra were measured with a
CARY/1E/UV/Vis Spectrophotometer (Varian, Cary winUV soft-
ware) at room temperature and 600 nm/min, with a 2 nm slit.
Quartz cells with a path-length of 0.1 cm were used. Stock solu-
[1] a) A. Varki, Glycobiology 1993, 3, 97; b) H.-J. Gabius, H.-C.
Siebert, S. André, J. Jimenez-Barbero, H. Rüdiger, ChemBi-
oChem 2004, 5, 740–764; c) H.-J. Gabius (Ed.), The Sugar
Code: Fundamentals of Glycosciences, Wiley-VCH, Weinheim,
tions of 1 and 2 were prepared at a concentration of around 10–3
m
in water containing 30 % acetonitrile. DTT (10 mm) was used in
74
www.eurjoc.org
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 65–76

Recognition of Mannose-Based Polysaccharides
Germany, 2009; d) B. Ernst, W. Hart, P. Sinay (Eds.), Carbo-
hydrates in Chemistry and Biology, Wiley-VCH, Weinheim,
Germany, 2000, part I, vol. 2, and part II, vol. 4; e) T. K. Lind-
horst, Essentials of Carbohydrate Chemistry and Biochemistry
Wiley-VCH, Weinheim, Germany, 2000; f) C. R. Bertozzi, L. L.
Kiessling, Science 2001, 291, 2357–2364; g) R. A. Dwek, T. D.
Butters, Chem. Rev. 2002, 102, 283–284; h) H.-J. Gabius, S.
André, J. Jiménez-Barbero, A. Romero, D. Solís, Trends Bio-
chem. Sci. 2011, 36, 298–313.
N. Sharon, Chem. Rev. 1998, 98, 637–674; d) W. I. Weiss, K.
Drickamer, Annu. Rev. Biochem. 1996, 65, 441–473; e) H. Lis,
N. Sharon, Lectins, Kluwer Academic Publishers, Dordrecht,
The Netherlands, 2003; f) H.-J. Gabius, S. André, J. Jiménez-
Barbero, A. Romero, D. Solís, Trends Biochem. Sci. 2011, 36,
298–313.
a) M. Nishio, Y. Umezawa, M. Hirota, Y. Takeuchi, Tetrahe-
dron 1995, 51, 8665–8701; b) M. Nishio, M. Hirota, Y. Umez-
awa, The CH/π Interaction: Evidence, Nature and Consequences,
Wiley-VCH, New York, 1998.
[14]
[2]
[3]
A. P. Davis, R. S. Wareham, Angew. Chem. 1999, 111, 3160–
3179; Angew. Chem. Int. Ed. 1999, 38, 2978–2996.
[15]
[16]
[17]
M. Muraki, K. Harata, N. Sugita, K. Sato, Biochemistry 2000,
39, 292–299.
a) A. Pal, M. Bérubé, D. G. Hall, Angew. Chem. 2010, 122,
1534–1537; Angew. Chem. Int. Ed. 2010, 49, 1492–1495; b)
A. P. Davis, Nature 2010, 464, 169–170.
a) J. Balzarini, Nature Rev. 2007, 5, 583–597; b) J. Balzarini,
Antiviral Chem. Chemother. 2007, 18, 1–11; c) J. Balzarini, Lan-
cet Infect. Dis. 2005, 5, 726–731.
H. Kogelberg, D. Solís, J. Jiménez-Barbero, Curr. Opin. Struct.
Biol. 2003, 13, 646–653.
a) K. K. S. Ng, A. R. Kolatkar, S. Park-Snyder, H. Feinberg,
D. A. Clark, K. Drickamer, W. I. Weis, J. Biol. Chem. 2002,
277, 16088–16095; b) G. Colombo, M. Meli, J. Cañada, J. L.
Asensio, J. Jiménez-Barbero, Carbohydr. Res. 2004, 339, 985–
994.
a) Y. Ferrand, M. P. Crump, A. P. Davis, Science 2007, 318,
619–622; b) U. Neidlein, F. Diederich, Chem. Commun. 1996,
1493–1494; c) M. Mazik, A. C. Buthe, Org. Biomol. Chem.
2009, 7, 2063–2071; d) G. Lecollinet, A. P. Dominey, T. Vela-
sco, A. P. Davis, Angew. Chem. 2002, 114, 4267–4270; Angew.
Chem. Int. Ed. 2002, 41, 4093–4096; e) M. Mazik, A. C. Buthe,
J. Org. Chem. 2007, 72, 8319–8326; f) M. Mazik, H. Cavga, J.
Org. Chem. 2006, 71, 2957–2963; g) M. Mazik, A. C. Buthe,
Org. Biomol. Chem. 2008, 6, 1558–1568.
G. Fukuhara, M. Inouye, Chem. Commun. 2010, 46, 9128–
9130.
C. le Bourvellec, C. M. G. C. Renard, Crit. Rev. Food Sci. Nutr.
2012, 52, 213–248.
a) R. L. Hanlin, M. Hrmova, J. F. Harbertson, M. O. Downey,
Aust. J. Grape Wine Res. 2010, 16, 173–188; b) R. Ficarra, S.
Tommasini, D. Raneri, M. L. Calabro, M. R. Di Bella, C. Rus-
tichelli, M. C. Gamberini, P. Ficarra, J. Pharm. Biomed. Anal.
2002, 29, 1005–1014.
E. Haslam, Practical Polyphenolics: From Structure to Molecu-
lar Recognition and Physiological Action, Cambridge Univer-
sity Press, Cambridge, 1998.
a) B. Wang, G.-J. Boons (Eds.), Carbohydrate Recognition: Bio-
logical Problems, Methods and Applications, John Wiley &
Sons, Hoboken, New Jersey, 2011; b) I. Botos, A. Wlodawer,
Prog. Biophys. Mol. Biol. 2005, 88, 233–282; c) C. A. Bewley,
Structure 2001, 9, 931–940; d) A. J. Bolmstedt, B. R. O’Keefe,
S. R. Shenoy, J. B. McMahon, M. R. Boyd, Mol. Pharmacol.
2001, 59, 949–954.
a) C. Walsdorff, W. Saak, S. Pohl, J. Chem. Res. Synop. 1996,
27, 282–283; b) A. Metzger, V. M. Lynch, E. V. Anslyn, Angew.
Chem. 1997, 109, 911–914; c) A. Metzger, V. M. Lynch, E. V.
Anslyn, Angew. Chem. 1997, 109, 911–914; Angew. Chem. Int.
Ed. Engl. 1997, 36, 862–865; d) K. J. Wallace, R. Hanes, E.
Anslyn, J. Morey, K. Kilway, J. Siegel, Synthesis 2005, 12,
2080–2083.
Belin, P. Barthélémy, K. Ruiz, J. M. Lacombe, B. Pucci, Helv.
Chim. Acta 2003, 86, 247–265.
N. Takashi, K. Kumiko, A. Akiko, M. Kenji, T. Koichiro,
JP8143525 (A), 1996-06-04.
S. Vandenbussche, D. Díaz, M. C. Fernández-Alonso, W. Pan,
S. Vincent, G. Cuevas, J. Cañada, J. Jiménez-Barbero, K. Bar-
tik, Chem. Eur. J. 2008, 14, 7570–7578.
H.-K. Cho, H.-J. Kim, K. H. Lee, J.-I. Hong, Bull. Korean
Chem. Soc. 2004, 25, 1714–1716.
[4]
[5]
a) T. A. Houston, ChemBioChem 2010, 11, 954–957; b) D. G.
Hall (Ed.), Boronic Acids. Preparation and Applications in Or-
ganic Synthesis and Medicine, 1st ed., Wiley-VCH, Weinheim,
Germany, 2005; c) T. D. James, M. D. Phillips, S. Shinkai, Bo-
ronic Acids in Saccharide Recognition, 1st ed., Royal Society of
Chemistry, Cambridge, UK, 2006; d) M. Dowlut, D. G. Hall,
J. Am. Chem. Soc. 2006, 128, 4226–4227; e) S. Jin, Y. Cheng,
S. Reid, M. Li, B. Wang, Med. Res. Rev. 2010, 30, 171–257; f)
T. D. James, S. Shinkai, Top. Curr. Chem. 2002, 218, 159–200;
g) S. Striegler, Curr. Org. Chem. 2003, 7, 81–102.
a) A. P. Davis, T. D. James, in: Functional Synthetic Receptors
(Eds.: T. Schrader, A. D. Hamilton), Wiley-VCH, Weinheim,
Germany, 2005, pp. 45–109; b) D. B. Walker, G. Joshi, A. P.
Davis, Cell. Mol. Life Sci. 2009, 66, 3177–3191; c) A. P. Davis,
Org. Biomol. Chem. 2009, 7, 3629–3638; d) M. Mazik, Chem-
BioChem 2008, 9, 1015–1017; e) M. Mazik, Chem. Soc. Rev.
2009, 38, 935–956; f) S. Penadés (Ed.), Host–Guest Chemistry:
Mimetic Approaches to Study Carbohydrate Recognition, Top.
Curr. Chem. Springer, Berlin, 2002, vol. 218.
a) E. Klein, Y. Ferrand, N. P. Barwell, A. P. Davis, Angew.
Chem. 2008, 120, 2733–2736; Angew. Chem. Int. Ed. 2008, 47,
2693–2696; b) Y. Ferrand, M. P. Crump, A. P. Davis, Science
2007, 318, 619–622; c) Y. Ferrand, E. Klein, N. P. Barwell,
M. P. Crump, J. Jiménez-Barbero, C. Vicent, G. J. Boons, S.
Ingale, A. P. Davis, Angew. Chem. 2009, 121, 1807–1811; An-
gew. Chem. Int. Ed. 2009, 48, 1775–1779.
X. Wang, F. Hof, Beilstein J. Org. Chem. 2012, 8, 1–10.
a) M. Cacciarini, C. Nativi, M. Norcini, S. Staderini, O. Fran-
cesconi, S. Roelens, Org. Biomol. Chem. 2011, 9, 1085–1091; b)
A. Ardá, C. Venturi, C. Nativi, O. Francesconi, G. Gabrielli,
F. J. Cañada, J. Jiménez-Barbero, S. Roelens, Chem. Eur. J.
2010, 16, 414–418; c) A. Vacca, C. Nativi, M. Cacciarini, R.
Pergoli, S. Roelens, J. Am. Chem. Soc. 2004, 126, 16456–16465;
d) M. Cacciarini, E. Cordiano, C. Nativi, S. Roelens, J. Org.
Chem. 2007, 72, 3933–3936; e) C. Nativi, M. Cacciarini, O.
Francesconi, A. Vacca, G. Moneti, A. Lenco, S. Roelens, J.
Am. Chem. Soc. 2007, 129, 4377–4385; f) C. Nativi, O. Fran-
cesconi, G. Gabrielli, I. De Simone, B. Turchetti, T. Mello,
L. D. C. Mannelli, C. Ghelardini, P. Buzzini, S. Roelens, Chem.
Eur. J. 2012, 18, 5064–5072.
[18]
[6]
[7]
[19]
[20]
[21]
[22]
[23]
[8]
[9]
[24]
[25]
[26]
[27]
[10]
a) M. Mazik, RSC Adv. 2012, 2, 2630–2642; b) M. Mazik, A.
Hartmann, P. G. Jones, Chem. Eur. J. 2009, 15, 9147–9159; c)
M. Mazik, H. Bandmann, W. Sicking, Angew. Chem. 2000, 112,
562–565; Angew. Chem. Int. Ed. 2000, 39, 551–554; d) M. Ma-
zik, M. Kuschel, W. Sicking, Org. Lett. 2006, 8, 855; e) M.
Mazik, H. Cavga, P. G. Jones, J. Am. Chem. Soc. 2005, 127,
9045–9052; f) M. Mazik, A. Hartmann, J. Org. Chem. 2008,
73, 7444–7450; g) M. Mazik, A. C. Buthe, J. Org. Chem. 2007,
72, 8319–8326.
H. Abe, Y. Aoyagi, M. Inouye, Org. Lett. 2005, 7, 59–61.
C. Schmuck, M. Schwegmann, Org. Lett. 2005, 7, 3517–3520.
a) F. A. Quiocho, Pure Appl. Chem. 1989, 61, 1293–1306; b)
R. U. Lemieux, Chem. Soc. Rev. 1989, 18, 347–374; c) H. Lis,
[28]
[29]
[30]
[31]
M. D. Shortridge, D. S. Hage, G. S. Harbison, R. Powers, J.
Comb. Chem. 2008, 10, 948–958.
T. D. P. Stack, Z. Hou, K. N. Raymond, J. Am. Chem. Soc.
1993, 115, 6466–6467.
B. Hakkarainen, L. Kenne, M. Lahmann, S. Oscarson, C.
Sandström, Magn. Reson. Chem. 2007, 45, 1076–1080.
[11]
[12]
[13]
Eur. J. Org. Chem. 2013, 65–76
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
75

J. Jiménez-Barbero, A. San-Félix et al.
FULL PAPER
[32] a) M. Mammen, S.-K. Choi, G. M. Whitesides, Angew. Chem.
1998, 110, 2908–2953; Angew. Chem. Int. Ed. 1998, 37, 2754–
784; b) S. J. Weiner, P. A. Kollman, D. T. Nguyen, D. A. Case,
J. Comput. Chem. 1986, 7, 230–252.
2794; b) D. R. Bundle, N. M. Young, Curr. Opin. Struct. Biol. [35] J. Jiménez-Barbero, M. Bernabé, J. A. Leal, A. Prieto, B.
1992, 2, 666–673.
Gómez-Miranda, Carbohydr. Res. 1993, 250, 289–299.
[36] J. Jiménez-Barbero, A. Prieto, B. Gómez-Miranda, J. A. Leal,
M. Bernabé, Carbohydr. Res. 1995, 272, 121–128.
Received: September 17, 2012
[33] Maestro, A powerful, all-purpose molecular modelling environ-
ment, version 8.5, Schrödinger, LLC, New York, NY 2008.
[34] a) S. J. Weiner, P. A. Kollman, D. Case, U. C. Singh, G. Ala-
gona, S. Profeta, P. Weiner, J. Am. Chem. Soc. 1984, 106, 765–
Published Online: November 9, 2012
76
www.eurjoc.org
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 65–76