Use of 'click chemistry' for the synthesis of carbohydrate-porphyrin dendrimers and their multivalent approach toward lectin sensing

Article abstract of DOI:10.1016/j.tetlet.2016.03.031

Multivalent carbohydrate dendrimers having 12 and 36 α-d-mannose units on the periphery of a porphyrin-cored dendritic scaffold have been synthesized using 'click chemistry'. Synthesized dendrimers were characterized by ¹H and ¹³C NM

Full text of DOI:10.1016/j.tetlet.2016.03.031

Accepted Manuscript
Use of ‘click chemistry’ for the synthesis of carbohydrate-porphyrin dendrimers
and their multivalent approach towards lectin sensing
Rituparna Das, Balaram Mukhopadhyay
PII:
S0040-4039(16)30253-2
DOI:
http://dx.doi.org/10.1016/j.tetlet.2016.03.031
TETL 47419
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
31 January 2016
8 March 2016
9 March 2016
Please cite this article as: Das, R., Mukhopadhyay, B., Use of ‘click chemistry’ for the synthesis of carbohydrate-
porphyrin dendrimers and their multivalent approach towards lectin sensing, Tetrahedron Letters (2016), doi: http://
dx.doi.org/10.1016/j.tetlet.2016.03.031
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a
a
Rituparna Das,* Balaram Mukhopadhyay*
Fluorescent
porphyrin core
Aromatic
Triazole
Mannose

1
Tetrahedron Letters
jo u r n a l h o m e p a g e : w w w . e ls e v ie r . c o m
Use of ‘click chemistry’ for the synthesis of carbohydrate-porphyrin dendrimers and
their multivalent approach towards lectin sensing
a
a
Rituparna Das,* Balaram Mukhopadhyay*
a
Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, Nadia 741246, India
E-mail: ritu_iiser@yahoo.com (RD), sugarnet73@hotmail.com (BM)
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Multivalent carbohydrate dendrimers having 12 and 36 a-D-mannose units on the periphery of a
porphyrin-cored dendritic scaffold have been synthesized using “click chemistry”. Synthesized
1
13
dendrimers were characterized by H and C NMR, UV, IR and MALDI-TOF MS. The
fluorescence behavior of the glycodendrimers was examined and they were used successfully for
the detection of mannose binding lectin (MBL) Concanavalin A.
Available online
2
009 Elsevier Ltd. All rights reserved.
Keywords:
Carbohydrate dendrimer
lectin
porphyrin
click chemistry
sensor
Introduction
scaffold. In addition to their high photostability, the rigidity
offered by the porphyrin architecture also aids in fine tuning the
carbohydrate epitopes directly grafted on the scaffolds and thus
exhibiting strong potential to act as selective inhibitors capable of
discriminating between lectins of similar sequence. Porphyrins
are capable of generating singlet oxygen upon shining light of
specific wavelength which is lethal to the tumor cells. The
multivalent approach with the porphyrin dendrimeric
glycoconjugates thus plays a crucial role in photodynamic
Lectins are the proteins that interact with carbohydrates with
high specificity and play an integral role in establishing various
cell-cell interactions. These non-covalent interactions act as a
mediator in a range of biological events like cell growth, cell
agglutination, interaction of bacteria/viruses and cell signaling.
Naturally, lectins responsible for definite recognition are often
found in aggregates offering multiple binding sites to the
carbohydrates. This multivalency or technically “the glycoside
1
2
6
therapy (PDT) of tumors. Although porphyrin glycodendrimers
3
cluster” effect poses as a perfect solution to the low binding
7
8
have been synthesized and used as various photosensitizers,
affinities provided by monovalent interactions or that predicted
from the sum of constitutive interactions. This enhanced binding
of lectins with carbohydrates is at present an attractive area of
research by virtue of its pivotal role in diverse biological
processes like promoting inflammatory response, functioning of
the immune system in malignancy, metastasis and apoptosis.
Proper and significant elucidation of the key characteristics of
these interactions may facilitate the development of various
therapeutic strategies. The concept of natural multivalency has
been explored by various research groups and several multivalent
ligands have been synthesized to modulate the biological
9
their capability to act as fluorescent markers is less explored.
Considering these potential applications, in this paper we report
the synthesis of novel tetra-substituted mannosyl moiety
appended dendrimeric metalloporphyrins (Figure 1).
4
systems. However, glycodendrimers go a long way in achieving
the multivalent platform in the cellular processes. Many
glycodendrimers have been reported in order to initiate lectin
5
recognition by virtue of their inherent optical, photophysical and
electronic properties.
Metallated porphyrins are natural scaffolds that constitute
various biologically relevant macromolecules like haemoglobin,
myoglobin and most of the cytochromes. Porphyrin
glycoconjugates are gaining much interest as they open up the
scope of exploring the photochemical behavior of the core
Fluorescent
porphyrin core
Aromatic
Triazole
Mannose

2
Tetrahedron
Figure 1. Representative structure of the proposed mannose conjugated
porphyrin-dendrimer
functionality was employed followed by reaction with the freshly
prepared TfN in the presence of triethylamine and CuSO to
afford the desired azide-functionalized generation
glycodendron 12 in 75% yield over two steps (Scheme 2).
3
4
nd
2
10
Concanavalin A (Con A, Canavalia ensiformis), a mannose
binding lectin (MBL) has been chosen as the protein model to
explore the capability of the synthesized carbohydrate dendrimers
as potential fluorescent sensors and the studies have revealed
promising insight to the specific and efficient binding affinities
of such carbohydrate dendrimers over natural porphyrin
biomolecules due to multivalent ConA-mannose interaction.
O
Propargyl
bromide
O
HO
HO
HO
HO
O
Boc2O
93%
NH2
N
H
O
N
H
O
KOH
O
67%
HO
HO
O
4
5
3
To explore the influence of the multivalency on carbohydrate
lectin interaction, we aimed at the synthesis of first and second
generation mannose conjugated zinc(II)porphyrin dendrimers by
the use of mild and environment friendly, regioselective Cu(I)
catalyzed ‘click reaction’. Tris(hydroxymethyl)aminomethyl
group was implemented as the branching platform and the
potential linker for the carbohydrate appendages connected to the
porphyrin architecture. The flexible linker was strategically
employed to introduce relatively high degrees of freedom and
adaptability to chelate with the binding sites of the protein with
the optimized affinity enhancements. For the effective synthesis
of the 1 and 2 generation carbohydrate dendrimers, a divergent
approach was chosen as the better route wherein an ‘inside-out’
strategy was employed. The porphyrin functionalized
zinc(II)porphyrin core was synthesized followed by the insertion
of the separately constructed azide functionalized mannose
conjugated dendrimeric building blocks. Starting with the
synthesis of the carbohydrate dendrimeric wedges, we started
OAc
O
AcO
AcO
AcO
OAc
O
AcO
AcO
AcO
O
B
N
N
N
AcO
AcO
AcO
OAc
A
O
C
O
N3
N
D
6
O
N
N
O
R
CuSO4, Na-ascorbate
87%
O
OAc
O
O
AcO
AcO
AcO
N
N
N
O
TFA 7 R = NHBoc
8 R = NH2
st
nd
TfN3, Et3N, CuSO4
9 R = N3
7
6%
Scheme 1. Synthesis of the first generation azide-functionalized
glycodendron 9
with
the
commercially
available
tris-
AcO
OAc
O
AcO
(hydroxymethyl)aminomethane (3), commonly known as TRIS.
AcO
The use of tris hydrochloride was avoided as it demanded an
additional step of neutralizing the compound. The free amine of 3
was initially protected with tert-butyloxycarbonyl (Boc)
functionality using di-tert-butyl dicarbonate to give the N-Boc
protected derivative 4 in 93% yield. The hydroxyl groups were
then propargylated to furnish the tris-propargyl derivative 5 in
O
OAc
O
AcO
AcO
AcO
B
A
N
N
11
O
N
AcO
OAc
O
N
N
C
AcO
N
AcO
O
D
O
N
N
O
N
N
N
67% isolated yield. Alkylation with propargyl bromide in the
N
N
E
AcO
OAc
O
O
presence of KOH provided the best possible yield compared to
alkylation in the presence of NaH at -55 ºC which gave yield of
AcO
F
O
AcO
N
R
O
N
N
O
4
2
5%. Derivative 5 was then coupled with known 2-azidoethyl
CuSO4,
N
O
12
Na-ascorbate
OAc
O
,3,4,6-tetra-O-acetyl-a-D-mannopyranoside (6) using CuSO
4
AcO
AcO
AcO
N
5
+ 9
O
st
THF-H O (1:1)
N
N
N
2
and sodium L-ascorbate to afford the
1
generation
6
1%
N
O
N
O
O
mannosylated dendron 7 in 87% yield. The formation of the
desired dendron was assured from the characteristic triazole peak
at d 7.66 respective to the anomeric proton at d 4.76 and
complete disappearance of the acetylenic signals (d 2.42), in the
N
N
N
N
AcO
O
N
O
N
O
N
AcO
AcO
O
O
N
O
AcO
N
N
1
13
N
H NMR spectrum. In the C NMR spectrum, peaks at d 145.1
N
O
N
O
AcO
and 123.7 for the triazole and 97.4 for the anomeric-α-carbon
further supported the formation of the desired product. Next,
TFA mediated selective deprotection of the N-Boc followed by
O
AcO
AcO OAc
O
O
AcO
AcO
AcO
AcO
reaction with freshly prepared TfN
3
in the presence of Et
3
N and
OAc
AcO
OAc
AcO
13
CuSO
4
gave the desired azide-functionalized dendron 9 in 76%
yield over two steps (Scheme 1). The disappearance of the strong
TFA, Py 10 R = NHBoc
11 R = NH2
1
singlet at d 1.35 in H NMR spectrum for the tert-butyloxy group
TfN3, CuSO4, Et3N
1
2 R = N3
13
7
5%
and corresponding carbonyl peak at d 154.7 in C NMR
confirmed the complete removal of the Boc functionality.
Scheme 2. Preparation of the second generation azide-functionalized
dendrimeric wedge 12
The second generation glycodendrons were prepared with the
synthesized azido-functionalized first generation dendritic
wedges (9) by clicking them on Boc protected tris-propargyl
The synthesis of tetra-substituted porphyrins has always been
challenging for the synthetic chemists because of its low yield.
Based on the known protocols and methodologies, the propargyl
functionalized porphyrin derivative 13 was synthesized in a
4
derivative 5 using CuSO in the presence of Na-ascorbate. The
nd
formation of the 2 generation glycodendrons (10) was similarly
confirmed by two sets of triazole signals at d 7.82 and d 7.68 in
14
1:3 ratio with the disappearance of the acetylenic signals (δ 2.42),
modest 40% yield employing Lindsey type condensation
between 4-O-propargyl benzaldehyde and pyrrole. It was
3
followed by metalation using Zn-acetate in refluxing CHCl -
and the corresponding mannoside anomeric signal at d 4.79 in the
1
H spectrum. Usual TFA-catalyzed deprotection of the NHBoc

3
MeOH mixture to give propargyl functionalized Zn-porphyrin
derivative (14) in 98% yield (Scheme 3). The introduction of
zinc was confirmed by the disappearance of the characteristic NH
The propargyl-functionalized Zn-porphyrin core (14) was
coupled with the glycodendrons 9 and 12 separately employing
click chemistry’ to afford the 1 generation and 2 generation
1
st
nd
signal at d -2.76 in the H NMR spectrum.
‘
Zn-porphyrin glycodendrimers 1a and 2a respectively (Schemes
4
2
and 5). After chromatographic purification, compound 1a and
a were isolated in 69% and 65% yields indicating that the
O
influence of the sterically crowded glycodendrons is insignificant
for the coupling reaction. The symmetrically tetra-substituted
porphyrin carbohydrate dendrimers were fully characterized by
O
NH
N
N
BF3.Et2O
chloranil
1
13
+
O
O
H and C NMR, IR and MALDI-TOF MS. Complete absence of
N
H
HN
4
0%
the characteristic azide peak in the IR spectra confirmed the
O
H
1
purity of the final glycodendrimers (Figure S1 and S2). In the H
NMR of 1a, peaks at d 8.15 and d 7.68 for the formed triazoles
in 4:12 ratio and the anomeric signal at d 4.78 confirmed the
O
1
3
formation of the symmetrical glycodendrimer. C NMR showed
the new anomeric signal at d 97.5 which confirmed the
O
1
3
1
formation of the α-mannosides. Similarly, for compound 2a, H
NMR showed signals at d 8.10 , d 7.68 and d 7.50 in 9:36:4
Zn-acetate
8%
1
N
N
N
N
ratio in its H spectrum and the new anomeric signal at d 97.5 in
9
O
Zn
O
13
C spectrum.
CuSO4, Na-ascorbate
1
2 + 14
O
THF-H2O
5%
6
RO OR
RO
RO OR
OR
OR
OR
RO
OR
RO OR
OR
OR
OR RO
RO
OR
O
OR
RO
O
RO
OR
OR
1
4
OR
OR
O
OR RO
RO OR
RO
O
RO
O
O
O
O
O
OR
OR
O
N
O
RO
RO
O
RO OR
RO
O
O
N
N
N
O
N
N
O
N
N
N
O
Scheme 3. Synthesis of the propargyl derivative of Zn-porphyrin core 14
A
N
N
OR
N
N
N
N
N
N
O
O
O
B
N
RO
O
N
N
N
N
N
N
O
N
RO
OR
OR
N
O
N
O
N
O
C
O
N
RO OR
RO
N
O
O
O
N
O
D
O
N
N
O
OR
RO
O
N
N
It is worth noting that the pre-metalation of the free porphyrin
is essential prior to the Cu-catalyzed “click reaction” to prevent
insertion of Cu in the porphyrin core. The choice of zinc as the
insertion metal was triggered by the fact that it was often inert to
insertion by other heavy metals at room temperature. The size
affinity of the heavy metals towards porphyrin core is in the
RO
O
N
N
O
N
OR
OR
O
O
N
N
OR
N
N
N
OR
RO
RO
RO
N
N
O
E
N
N
N
N
N
O
N
N
O
N
O
O
N
O
O
F
N
N
N
N
O
OR
N
O
N
O
O
O
O
N
OR
OR
OR
RO
O
N
N
N
N
N
N
N
N
O
O
O
RO
RO
RO
N
O
N
O
N
N
N
O
N
N
G
N
O
OR
N
O
O
RO
O
OR
RO OR
O
RO
15
RO OR
N
order Zn(II)~Cu(II)>>Mg(II). Moreover the introduction of
N
N
Zn
N
RO OR
OR
heavy metals in dyes promoting inter-system crossing has also
RO OR
1
6
RO
O
been of high interest.
O
O
O
OR
O
N
N
RO
O
O
O
O
N
N
OR
OR
OR
N
O
N
N
N
N
RO
RO
RO
N
O
N
O
N
N
N
N
N
N
O
O
N
N
O
RO
N
N
N
O
O
O
N
OR
N
O
O
9
N
O
O
N
N
N
O
N
OR
OR
OR
O
O
N
N
N
CuSO4, Na-ascorbate
N
N
O
RO
RO
RO
N
N
N
N
N
RO
14
O
N
N
N
O
THF-H2O
OR
N
N
N
N
N
O
OR
O
N
O
6
9%
RO
O
O
N
O
OR
RO OR
O
OR
RO
RO
O
N
O
O
O
O
N
N
N
RO O R
OR
OR
OR
N
N
O
O
N
OR
RO
O
RO
O
N
N
N
N
N
N
N
N
O
OR
OR
RO OR
RO
O
N
O
N
N
N
N
N
N
N
N
O
RO
O
N
N
O
O
A
O
N
O
N
O
O
N
RO
RO
O
O
B
RO
RO
O
N
OR
OR
N
N
OR
O
RO
O
N
N
N
N
O
O
O
N
N
O
RO
O
O
RO
RO
OR
OR
ROOROR
OR
O
OR
RORO
O
RO
OR RO
C
O
O
N
O
OR
RO
OR
RO OR
OR
RO OR
RO
RO
RO
D
OR
RO OR
OR
N
N
E
RO OR
OR
O
Zn
O
2a R = Ac
2b R = H
O
N
OR
NaOMe, MeOH
RO OR
RO
O
N
N
N
RO
O
O
N
Scheme 5. Synthesis of the Zn-porphyrin dendrimer 2b
O
N
N
N
N
O
O
N
O RO R
OR
N
N
N
N
N
N
O
O
RO
O
O
O
O
N
O
N
N
N
N
The acetate groups of the per-O-acetylated dendrimers 1a and
2a were quantitatively removed by using NaOMe in MeOH by
implementing Zémplen de-O-acetylation method to afford the
water soluble dendrimers 1b and 2b (Schemes 4 and 5). The
compositions of the de-O-acetylated derivatives were confirmed
by MALDI-TOF MS only. The extensive use of ‘click chemistry’
for the entire synthetic route marks the easy applicability of the
said process.
RO
RO
RO
N
N
N
N
O
O
O
OR
N
N
O
RO
OR
O
N
OR
OR
RO
O
OR
RO
RO
N
N
N
O
O
O
N
N
N
N
N
N
N
N
RO
O
N
O
O
O
RO
RO OR
O
O
RO
RO
OR
OR
OR
RO OR
RO
The effect of the dendritic environment on the
metalloporphyrin behavior was examined by the absorption and
emission studies on the protected dendrimers 1a and 2a. The
visible purple colour of the carbohydrate porphyrin dendrimers is
1
1
a R = Ac
b R = H
NaOMe, MeOH
Scheme 4. Synthesis of the Zn-porphyrin dendrimer 1b

4
Tetrahedron
due to the absorption(s) within the porphyrin ligand involving
the excitation of electrons from π to π* porphyrin ring orbitals.
The UV-Vis spectra of 1a and 2a in dichloromethane showed
typical metalloporphyrin behavior having Soret or B bands in the
4
23-429 nm range representing strong transition to the second
excited state (S ® S ) and Q-bands in the 549-562 nm and 592-
03 nm ranges representing weak transitions to the first excited
state (S ® S ). When compared with the UV-Vis spectrum of
0
2
6
0
1
the Zn-porphyrin derivative 14, slight red shifts from 14 to 1a
and 1a to 1b were observed (Figure 2a). Next, the fluorescence
behavior of the acetylated dendrimers 1a and 2a were studied and
compared with that of the Zn-prophyrin derivative 14. No
significant difference was observed in the emission behavior of
the dendrimers due to the dendritic environment (Figure 2b).
Figure 3. Increase of fluorescence upon binding of ConA with dendrimer 1b
Once the carbohydrate dendrimers were characterized
satisfactorily, we focused our attention to see the potential of the
carbohydrate functionalized Zn-porphyrin dendrimers for the
detection of lectins. The dendrimers were purposefully decorated
with mannose so that they can be utilized for the interaction
experiments with the mannose-binding lectin Concanavalin A
(
ConA). The tetrameric ConA has four carbohydrate binding
domains and thus, it can form aggregated networks when
exposed to multivalent mannose conjugates. The tetrasubstituted
st
nd
1
and 2 generation carbohydrate dendrimers portray an ideal
aggregration platform to the four equivalent and diverged
carbohydrate binding sites of the lectin. The fluorescence
intensity of water soluble Zn-porphyrin dendrimers remains
moderate in the buffer solution having high dielectric constant.
However, upon interaction with the lectins when the aggregates
are formed, it creates a hydrophobic microenvironment around
the dendrimer resulting considerable enhancement of the
fluorescence intensity. ConA which exists as a tetramer at pH>7
can ideally bind with mannose derivatives on all four wedges of
our synthesized molecules by virtue of their tetrasubstituted
nature, Therefore, the extent of binding to the lectin can be
titrated by measuring the increase of fluorescence intensity.
2
a
-6
Based on this 0.5×10 molar solutions of dendrimer 1b and 2b in
TRIS buffer (0.1M, pH 7.4) containing 0.1 mM CaCl and 0.1
mM MnCl were separately mixed with varied concentrations of
2
2
ConA in the same buffer and the fluorescence was measured. The
concentration of the ConA solution was gradually increased until
the fluorescence intensity enhancement became constant
suggesting maximum binding of ConA with the first and second
generation dendrimers (Figure 3 and 4 respectively).
2
b
Figure 2. a. UV-Vis spectra of 1a, 2a and 14 in CH
2 2
Cl , b. emission spectra
of 1a, 2a and 14 in CH Cl
2
2
The conjugation of the carbohydrates onto the hydrophobic
porphyrin core renders the required water-solubility to make it
available in the biological media. The UV-Vis spectra for the de-
O-acetylated dendrimers 1b and 2b were recorded in Tris buffer
(pH 7.4) at room temperature. Prominent Soret and Q-bands
indicated good solubility of the deprotected dendrimers in water
due to effective shielding of the hydrophobic porphyrin and
aromatic core by the hydrophilic sugar units in the periphery.
However, significant broadening of the Soret band suggests
significant aggregation arising from hydrophobic interactions in
water (Figure S3, ESI).
Figure 4. Increase of fluorescence upon binding of ConA with dendrimer 2b
st
nd
By comparing the 1 and 2 generation dendrimers (Figure
5
), it can be seen that greater aggregation is achieved with the
first generation dendrimer 1b with an overall change in emission
of 3800 a.u. from dispersed to fully aggregated condition upon

5
addition of ConA, as compared to 1000 a.u. obtained with the
Acknowledgments
second generation dendrimer 2b. 1b display a dynamic linear
-
7
range from 0-350×10 M concentration of ConA compared to
RD is thankful to IISER Kolkata for postdoctoral fellowship.
SERB, DST, India is gratefully acknowledged for funding
through grant SB/S1/OC-48/2013 to BM. We acknowledge the
help of Dr. Subhajit Bandyopadhyay for binding constant
determination and Mr. Atiur Rahaman for fluorescence
measurements.
-7
that of only 0-50×10 M for 2b. It is clear that the first generation
dendrimer 1b provides superior aggregation with ConA,
displaying a greater change in emission along a larger linear
range. The quicker saturation of the second generation dendrimer
2
b may be explained by the much higher peripheral carbohydrate
density that sterically hinders the possibility of interaction with
incoming ConA. The obtained observations are also in sync with
the various studies done in the past to state that higher number of
epitopes doesn’t necessary indicate enhanced binding potency
towards proteins. The titration data of the fluorescence intensity
against the concentration of ConA displayed non-linearity
indicating some degree of cooperativity in the binding process.
Therefore, the non-linear equation (Equation S1, ESI) was used
References and notes
1.
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Baum, L. G.; Brewer, C. F. Biochemistry 2001, 40, 3009-3015.
Lis, H., Sharon, N. Chem. Rev. 1998, 98, 637-634.
17
2
3
4
.
.
.
Lee, Y. C.; Lee, R. T. Acc. Chem. Res. 1995, 28, 321-327.
(a) Brandehorst, H. M., Kooij, R.; Salminen, A.; Jongeneel, L. H.;
Arnusch, C. J., Liskamp, R. M. J.; Finne, J.; Pieters, R. J. Org.
Biomol. Chem. 2008, 6, 1425–1434. (b) Pukin, A. V.;
Brandehorst, H. M.; Sisu, C.; Weijers, C. A. G. M.; Gilbert, M.;
Liskamp, R. M. J.; Visser, G. M.; Zuilhof, H.; Pieters, R. J.
ChemBioChem 2007, 8, 1500–1503.
to fit the titration data to incorporate the factor for the
st
cooperative behavior. The binding constant logK
b
with 1
generation dendrimer 1b was found to be 5.46 with the value of
nd
n=1.30. The same with the 2 generation dendrimer 2b found to
be 5.91 with the value of n=1.82 (Figure S4 and S5). Further, to
judge the specificity of the mannose modified carbohydrate
dendrimer towards the MBL ConA, first generation dendrimer
similar to that of 1b was synthesized with galactose in the
periphery (compound F, Scheme S1, ESI). When it was
subjected to titration with ConA, no enhancement of fluorescence
was observed suggesting no binding with ConA (Figure 5).
Thus, the specific nature of the carbohydrate-lectin interaction is
established.
5
.
(a) Kikkeri, R.; Kamena, F.; Gupta, T.; Hossain, L. H.;
Boonyarattanakalin, S.; Gorodyska, G.; Beurer, E.; Coullerez, G.,
Textor, M.; Seeberger, P. H. Langmuir 2010, 26 , 1520-1523. (b)
Kikkeri, R.; Rubio, I. G.; Seeberger, P. H. Chem. Commun. 2009,
2
35-237. (c) Khan, S. A.; Adak, A.; Murthy, R. V.; Kikkeri, R.
Inorg. Chim. Acta 2014, 409, 26-33. (d) Kikkeri, R.; Grunstein,
D.; Seeberger, P. H. J. Am. Chem. Soc. 2010, 132, 10230-10232.
(a) Hao, E.; Jensen, T. J.; Vicente, M. G. H.; J. Porphyrins
Phthalocyanines 2009, 13, 51−59. (b) Garcia, G.; Hammerer, F.;
Achelle, F. P. S.; Teulade-Fichou, M.-P.; Maillard, P. Bioorg.
Med. Chem. 2013, 21, 153−165. (c) Garcia, G.; Naud-Martin, D.;
Carrez, D.; Croisy, A.; Maillard, P. Tetrahedron 2011, 67, 4924-
6.
4
932.
(a) Kushwaha, D.; Tiwari, V. K. J. Org. Chem.2013, 78,
184−8190. (b) Makky, A.; Michel, J. P.; Kasselouril, A.; Briand,
7
8
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.
8
E.; Maillard, Ph.; Rosilio, V. Langmuir 2010, 26, 12761-12768.
(a) Figueiraa, F.; Pereiraa, P. M. R.; Silvaa, S.; Cavaleiroa, J. A.
S.; Toméa, J. P. C. Curr. Org. Synth. 2014, 11, 110-126. (b)
Nishiyama, N.; Stapert, H. R.; Zhang, G.; Takasu, D.; Jiang, D. -
L.; Nagano, T.; Aida, T.; Kataoka, K. Bioconjugate Chem.
2
003, 14, 58–66.
9
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Okada, M.; Kishibe, Y.; Ide, K.; Takahashi, T.; Hasegawa, T. Int.
J. Carbohydr. Chem. 2009, 305276, 1−9.
1
1
0. Hardman, K. D.; Ainsworth, C. F. Biochemistry 1972, 11, 4910.
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1
2. Mandal, S.; Das, R.; Gupta, P.; Mukhopadhyay, B. Tetrahedron
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1
1
3. Liu, Q.; Tor, Y. Org. Lett. 2003, 5, 2571-2572.
Figure 5. Comparison of the interaction of ConA with dendrimers 1b, 2b and
4. Lindsey, J. S.; Schreiman, I. C.; Hsu, H. C.; Kearney, P. C.;
Marguerettez, A. M. J. Org. Chem. 1987, 52, 827-836.
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the galactose modified dendrimer
1
Thus, in conclusion, we have developed the synthetic strategy
for the preparation of porphyrin carbohydrate dendrimer with
peripheral mannose ligands using the versatile ‘click reaction’
and established their application as sensors for the detection of
lectins. The lack of significant previous reports employing
porphyrin dendrimers for lectin sensing marks the novelty of our
reported work. The first generation dendrimer displayed greater
aggregation with the lectin ConA compared to that of the second
generation. This is clearly showing that the extent of
carbohydrate-lectin binding depends not only on the number of
peripheral carbohydrate ligands but also the ligand density that
dictates the number of available carbohydrates for effective
binding. This particular application of carbohydrate appended
porphyrin carbohydrate dendrimers for lectin-sensing may
provide the required opening for the further use of porphyrin
based dendrimers as lectin sensors.
16. Plater, M. J.; Aiken, S.; Bourhill, G. Tetrahedron 2002, 58, 2415-
422.
1
2
7. (a) Gargano, J. M.; Ngo, T.; Kim, J. Y.; Acheson, D. W. K.; Lees,
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12169.
Supplementary Material
1
13
Experimental details and copies of the H C and selected
COSY and HSQC NMR spectra.

6
Tetrahedron
Highlights
st
nd
·
·
·
Rational synthesis of 1 and 2 generation
Zn-porphyrin glycodendrimer
Use of water soluble dendrimers for lectin
sensing through fluorescence
st
nd
Insight of the 1 vs 2
generation
efficiency of binding with lectin