Synthesis of a β-cyclodextrin derivate and its molecular recognition behavior on modified glassy carbon electrode by diazotization

Article abstract of DOI:10.1016/j.tet.2010.07.052

A novel β-cyclodextrin (β-CD) derivative containing mono-phenylamino (MPA-β-CD) was newly synthesized by classical Mitsunobu reaction in good yield, and its structure has been confirmed by ¹H NMR, ¹³C NMR and electrospray ionization

Full text of DOI:10.1016/j.tet.2010.07.052

Tetrahedron 66 (2010) 7815e7820
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Tetrahedron
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Synthesis of a
b-cyclodextrin derivate and its molecular recognition behavior
on modified glassy carbon electrode by diazotization
*
*
Xiuhua Wang, Hao Fan, Fan Zhang, Yantao Qi, Wenwei Qiu, Fan Yang, Jie Tang , Pingang He
Department of Chemistry, East China Normal University, Shanghai 20062, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 May 2010
Received in revised form 19 July 2010
Accepted 20 July 2010
Available online 29 July 2010
A novel
b
-cyclodextrin (
b
-CD) derivative containing mono-phenylamino (MPA-
b
-CD) was newly syn-
thesized by classical Mitsunobu reaction in good yield, and its structure has been confirmed by 1H NMR,
13C NMR and electrospray ionization mass spectra. The compound MPA-
glassy carbon electrode (GCE) by diazotization, and with this modified electrode the binding behavior of
MPA- -CD for ferrocene (Fc) was investigated qualitatively, and the comparison of differential pulse
voltammetry before and after immersion in ferrocene solution indicated that the MPA- -CD immobilized
GCE exhibited the molecular recognition behavior between -CD and ferrocene.
Ó 2010 Elsevier Ltd. All rights reserved.
b-CD was immobilized onto
b
b
Keywords:
Cyclodextrins
Ferrocene
b
Diazotization
Molecular recognition
Mitsunobu reaction
1. Introduction
primary side of CDs by reversible silylation, because the protected
compounds can be readily purified by flash chromatography. Conse-
quently, here, we report a monosubstituted b-Cyclodextrin derivative
Cyclodextrin(CDs),1a class of cyclic oligosaccharides with 6e8
D
-glucose units, gained prominence in recent years in diverse fields,
with mono-phenylamino group by Mitsunobu reaction in good yield.
In the former work, the studies on the abilities of native or
modified cyclodextrin were extensively carried out in some special
kind of solutions by differential circular dichroism spectroscopy or
spectrofluorometric titration in combination with computational
methods.15,18,19 Simultaneously, The functionalization of surfaces is
of considerable interest in applications, such as sensors and bio-
compatible surfaces. Consequently, many researchers have suc-
cessfully prepared a variety of mercaptocyclodextrin derivatives
and studied the host-guest molecular recognition through their
immobilization on gold surfaces, which was achieved by the oxi-
dative adsorption of thiols covalent SeAu bond.20e23Recent reports
showed that the electrochemical reduction of aryl diazonium salts
is proven to be an excellent method to irreversibly attach molecules
to some special conducting substrates.24 Firstly, it avoids the use of
oxidative conditions, which can lead to the detrimental oxidation
of the carbon substrate, moreover because it allows the presence of
selected functional groups on the aryl groups. Lastly, diazonium
salts are easily and rapidly prepared in one step from a wide range
of anilines and its reduction takes place within seconds to minutes.
However, until now, there have not been literatures about the
such as molecular reactors,2drug delivery systems,3artificial enzy-
mes,4catalysis,5 molecular machines,6or supramolecular sensing.7
Cyclodextrins, in their native state, are rigid molecules, and offer
limited utility in terms of size, shape, and availability of chemically
useful functional groups. Cyclodextrins have thus been called
structural and functional straightjackets.8 Consequently, in the past
few decades a great deal of effort has been directed toward
conversion of hydroxyl groups of cyclodextrins to other useful
functional groups.9e12
The modification of cyclodextrins offers both enormous oppor-
tunities and challenges for chemists. Among all the possible types of
modifications, Monomodifications of cyclodextrins to give selectively
2-, 3-, or 6-substituted product is a challenging task because of the
number of hydroxyl groups that can potentially react with the in-
coming reagent.13,14 Many researchers have been accustomed to
prepare monosubstituted cyclodextrins derivatives by the tosylation
of native cyclodextrins extensively,10,15,16,17 However, by this method,
the desired products are painstakingly separated out from other
isomers and homologues bychromatographic methods and always in
the poor yield. A way to overcome this problem is to protect the
studies on the electrochemical immobilization of
surface by diazotizatin.
b-CD on electrode
In this work, we demonstrate for the first time the synthesis of
a novel -cyclodextrin derivative containing one phenylamino by
* Corresponding authors. Tel./fax: þ86 21 62232764; e-mail address: jtang@
b
chem.ecnu.edu.cn (J. Tang).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.07.052

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X. Wang et al. / Tetrahedron 66 (2010) 7815e7820
Mitsunobu reaction, at the same time, we prepared a MPA-
b
-CD-
During the course of the preparation of the target compound 5.
The Mitsunobu reaction is a key step. In recent years, the scope of
the Mitsunobu reaction in natural products synthesis has been
extensively discussed and reviewed.25The application of this clas-
sical reaction is the synthesis of some types of ethers.26In this nu-
cleophilic substitution reaction, we tried a variety of reaction
conditions, such as ratio of the reactants, reaction time, the adding
sequence, and finally we got the optimal condition as described in
the Experiment section. The Monosubstitution was in good yield
under the optimal condition. More importantly the selectivity of
this reaction was well controlled according to the final product.
modified electrode by the electrochemical reduction of aryl di-
azonium salts on glassy carbon electrode. Furthermore, with the
modified electrode we investigated qualitatively the binding
behavior of MPA-b-CD for ferrocene, which was detected by dif-
ferential pulse voltammetry in Fc solution.
2. Results and discussion
2.1. Synthesis
The special structure of the target compound MPA-b-CD was
confirmed by 1H NMR, 13C NMR, and ESI-Mass. Judging by the ra-
The synthesis of MPA-b-CD was shown schematically in
tion of the aromatic protons in the aminophenoxy group at
Scheme 1. Hydroxyl groups present at the 2-, 3-, and 6-positions
compete for the reagent and make selective modification extremely
difficult, and thereby, the synthesis of monofunctionalization of
native cyclodextrin involves in sequence (1) protection of the pri-
mary side with silyl groups, (2) protection of the secondary side
with acetyl groups, (3) desilylation of the primary side, (4) Mitsu-
nobu reaction, monosubstitution of the primary hydroxyl group of
7.14e7.40 and the proton of
b-cyclodextrin at the C-5, only one
hydroxyl group of -cyclodextrin at the 6-position was substituted
b
by aminophenoxy group. In addition, ESI-Mass spectra also showed
the presence of monosubstitution.
2.2. Immobilization of MPA-b-CD on GCE
b-cyclodextrin was achieved. Although the process was slightly
long, the purification of every step reaction was easily achieved by
flash chromatography. In this strategy, each reaction is carefully
chosen to give a high yield and the products were easily separable
and purifiable by flash column chromatography.
The formation of MPA-
which occurred via diazotization of MPA-
diazonium in aqueous acidic medium. The diazonium cations
b
-CD diazonium was shown in Scheme 2,
b
-CD to form the aryl
generated in situ from MPA-b-CD was investigated by cyclic
OH
OH
CbzCl,Na2CO3
THF/H2O
NH2
NHCbz
A
OH
O
OTBS
OTBS
O
O
Ac2O,DMAP
Pyridine
TBSCl,imidazole
OH
OH
OAc
O
O
DMF,
O
OH
OH
OAc
7
7
7
1
2
OH
O
NHCbz
O
1
OAc
BF3
DCM
Pd(OH)2
MeOH
O
A
, DIAD, PPh3
OAc
O
O
THF
OAc
OAc
7
7
3
4
NH2
O
1
O
OAc
O
OAc
7
5
Scheme 1. Schematic representation of MPA-b-CD.

X. Wang et al. / Tetrahedron 66 (2010) 7815e7820
7817
(OAc)14
O
(OAc)14
(OAc)14
O
(OAc)14
O
N2
e-
+
i
ii
O
iii
NH2
N+
N
Scheme 2. Schematic illustration of MPA-b-CD-modified GCE via diazotization.
voltammetry. The whole procedure involved: (i) the diazotation of
the compound MPA- -CD, (ii) the electroreduction of diazonium
b
cation, and (iii) the covalent linkage to the GCE surface.
As shown in Figure 1, the first cycle exhibited a well-defined,
reproducible, and irreversible reduction peak at ꢀ700 mV, corre-
sponding to the reduction of the aryl diazonium salt, generating the
radical. During the second and subsequent cycles, the redox peak
disappears and the cyclic voltammogram exhibits only a small re-
duction current. This feature gave an evidence of electrode surface
saturation, simultaneously showed that a monolayer of fixed mol-
ecules was achieved.
Figure 2. Cyclic voltammogram at a scan rate of 100 mV/s for a 1 mM K3Fe(CN)6
solution before (a) and after grafting of the MPA- -CD diazonium (b).
b
Figure 1. Cyclic voltammogram of MPA-b-CD diazonium in 1.0 M HCl. Potential
scanned from 0 to ꢀ1 V versus GCE. Four cycles were performed at a scan rate of
100 mV/s.
The cyclic voltammogram of soluble electroactive species pro-
vides a convenient tool to study the presence of grafted films and
their blocking properties. The influence of the glassy carbon elec-
trode modification conditions on the cyclic voltammetric response
of Fe(CN)36ꢀ/4ꢀ oxido-reduction was investigated for different layers
grafted by electrochemical reduction of the in situ generated
diazonium cations. Figure 2 shows the cyclic voltammogram
Figure 3. FT-IR spectra of GCE (a), MPA-
diazonium salt of MPA- -CD film (c).
b-CD (b), GCE modified by grafting aryl
b
recorded at bare glassy carbon electrode and MPA-b-CD-modified
electrodes. The voltammogram of the Fe(CN)36ꢀ/4ꢀ redox system
presents a quasireversible behavior at the bare electrode with an
apparent redox potential of 0.23 V. However, the MPA-
b
-CD-mod-
both MPA-
about between 1155 and 1042 cmꢀ1 correspond to the antisym-
metric glycosidic a(CeOeC) vibrations, and the coupled (CeC/
b-CD and the diazonium/CNTs share two intense band at
ified electrodes exhibit a significant blocking behavior for the
oxidation and reduction reactions of the Fe(CN)36ꢀ/4ꢀ redox system.
n
n
Therefore, in this case, this feature can be explained that MPA-
CD-modified electrodes have been successfully prepared.
b
-
CeO) stretch vibration. On the other hand, the peak seen at 2928
and 2931 cmꢀ1 for them, which is attributed to the asymmetric
methylene stretches. The OeH vibrational band at about 3435 cmꢀ1
is broadened in figure b and c spectra, presumably due to inter- and
FT-IR spectra were used to confirm surface attachment to elec-
trodes, as shown in the spectra of MPA- -CD (Fig. 3). Compared
with the FT-IR spectrum of pristine GCE (Fig. 3a), the spectrum of
b
intramolecular hydrogen bonding. The deformation vibrations
d

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X. Wang et al. / Tetrahedron 66 (2010) 7815e7820
(CeH) and d(OeH) of the CH2 and OH groups between 1460 and
1299 cmꢀ1 and the characteristic ring vibrations at 945 and
705 cmꢀ1 are seen in figure b and c spectra. Furthermore, of note is
the sharp peak at 1754 cmꢀ1 common to both MPA-
b
-CD and its
GCE/diazonium film spectrum. This absorption stretch is charac-
teristic of 14 carbonyl groups at the 2- and 3-position of MPA- -CD.
(OAc)14
(OAc)14
(OAc)14
b
The peak assignments for the various CeH, CeO, and CeC vibra-
tions could not be determined, owing in part to the difficulty in
determining the dipole moment of the cyclodextrin ring, and in
part to the added complication of the spacer units in the derivatized
cyclodextrin. Nevertheless, all the above information of the spec-
trum to some extent provided strong evidence for the presence of
Fe
O
O
O
MPA-
b
-CD at GCE. The peak at 1251 cmꢀ1 attributed to the aryl CeN
-CD, while in the diazonium/GCE this
stretch vibration in MPA-
b
peak disappeared, which is indicative of surface attachment by
reduction of the aryl diazonium cation.
glassy carbon electrode
Scheme 3. Schematic illustration of inclusion of MPA-
b-CD for Fc in 1 mM Fc solution
onto the GCE.
2.3. Host-guest including behavior for Fc on the MPA-b-CD-
modified electrode
Furthermore, in order to further investigate the ability of bind-
ing of the MPA- -CD for Fc, based on the above comparison
experiment, we conducted a series of experiments with the MPA-
b
b
-
The formation of inclusion complexes between b-cyclodextrin
CD-modified GCE by varying the immersion time in the same
concentration of Fc solution. One is differential pulse voltammetry,
and the other is the peak current dependence of immersion time in
Fc solution. The results were shown in Figure 4 and 5. As can be
seen from the Figure 4, compared to the bare electrode, after im-
mersion in the Fc solution, a distinct current increased was found.
In addition, as seen from the Figure 5, the response of the peak
current was enhanced gradually with time increased from 5 to
70 min until the equilibrium was obtained, which indicated that
and Fc has been widely reported, and the structural nature of
such complexes has been successfully used to the study of the
modified electrode with cyclodextrins and their deriva-
tive.27Therefore, in order to further investigate the characteristic
of molecular recognition on the MPA-
we carried out the research of binding interactions between fer-
rocene and MPA- -CD-modified GCE. MPA- -CD-modified GCE
b-CD-modified electrode,
b
b
was immersed in a solution of 1 mM ferrocene (Fc) in ethanol for
30 min. After a washing procedure, differential pulse voltamme-
try was performed from ꢀ0.2 to 0.6 V at a scan rate of 100 mV/s in
PBS buffer. The result was shown in Figure 4. By contrast with the
bare electrode, an obvious peak current was obtained, and the
potential response was recorded at 0.27 V, which falls within
the typical redox potential range of Fc. Furthermore, a slight
current wave was observed in the Figure 4a, which was explained
that a small quantity of adsorption occurred between Fc and the
bare electrode after immersion in the Fc solution. This adsorption
was reported in the previous research.28Therefore, in this case,
surface binding of Fc by the MPA-b-CD monolayer reached the
equilibrium at the same concentration of Fc solution. Similarly
under the same condition the insert of peak current dependence of
immersion time showed that the peak current was linear versus
immersion time. Still the eventual equilibrium was observed.
Herein, we could draw a conclusion that a large amount of Fc was
included in the MPA-b-CD cavity by host-guest molecular recog-
nition, simultaneously, this kind of binding of host-guest would
reach the equilibrium at the definite condition, the explanation
about, which was reported in the previous literature.29
during the course of the inclusion of MPA-
trochemical response becomes the sum of contributions both
from the Fc in solution and Fc included in MPA- -CD cavity, as
b-CD for Fc, the elec-
b
shown in the Scheme 3. For all this, compared to the bare elec-
trode, just by the distinct increase of the peak current, we could
draw a qualitative conclusion that large numbers of Fc were in-
cluded in the b-CD cavity except a small adsorption.
Figure 5. Differential pulse voltammetry curves for the MPA-b-CD-modified glassy
carbon electrode with varying immersion time (5e70 min) in 1 mM Fc. Insert is re-
sponse cure of peak current with the immerse time in 1 mM Fc solution. Potential
recorded from ꢀ0.2 to 0.6 V. Scan rate 100 v/s.
3. Conclusions
Figure 4. Comparison of differential pulse voltammetry curves for 1 mM Fc in Ethanol,
recorded using a bare GCE (a) and MPA- -CD-modified electrode (b) after immersion
in 1 mM Fc for 30 min, respectively. Scan rate 100 v/s.
MPA-
b-CD has been successfully synthesized via Mitsunobu
b
reaction in good yield and its structure has been confirmed by 1H

X. Wang et al. / Tetrahedron 66 (2010) 7815e7820
7819
NMR, 13C NMR, and ESI-MS. Specially, for the studied object MPA-
b-
8 g crude product. The crude product was purified by silica gel
column chromatography (eluted by dichloromethane and metha-
nol 10/1,v/v) to give a pure product (5.6 g, 82.4%). 1H NMR
CD, we achieved in both facilitating our synthetic work and
enhancing the solubility of the derivative in common organic sol-
vents, especially for the molecular recognition process, good solu-
bility of host molecular to some extent promotes the forming of the
inclusion.
(500 MHz, CDCl3, ppm)
7H), 4.00(t, J¼15 Hz, 7H), 3.90(d, J¼10 Hz, 7H), 3.72e3.58(m, 28H),
d
6.73(s, 7H), 5.27(s, 7H), 4.89(d, J¼5.00 Hz,
0.87(s, 63H), 0.03(d, J¼20 Hz, 42H). Mp 299e302 ꢁC (dec)31
In the study for application of this derivative in electrochemis-
try, here, we achieved in immobilizing MPA-
b
-CD on the GCE via
4.3.3. Acetylated heptakis(6-O-tert-butyldimethylsilyl)-
b-CD (2).
diazotization. Finally using the MPA- -CD-modified electrode we
b
Heptakis (6-O-tert-butyldimethylsilyl)- -CD(5 g, 2.58 mmol) was
b
investigated the binding ability for Fc by host-guest molecular
recognition. The results showed that we have obtained a practical
analyte-responsive modified electrode, furthermore, the applica-
dissolved in 20 mL of dry pyridine. Acetic anhydride (12 mL) and
94 mg of 4-dimethylamino pyridine were added, and then the
mixture was stirred at room temperature overnight. The solvent was
distilled off in vacuo to give a slurry. The residue was dissolved in
ethyl acetate (50 mL), washed with aqueous HCl (0.2 M, 50 mLꢂ3),
then washed with saturated NaHCO3 solution (50 mLꢂ3), finally
with brine. The combined organic layer was dried over anhydrous
Na2SO4 and concentrated in vacuo to give a crude as a white solid.
The crude was purified by silica gel column chromatography (eluted
by dichloromethane and methanol) to yield the desired product
(5.8 g, 89%). It is unnecessary for the purification of this step.1H NMR
tion of this MPA-b-CD-modified electrode has been in progress in
our group.
4. Experimental section
4.1. Materials
Reagent grade
b-cyclodextrin was recrystallized twice from
water and dried in vacuo at 100 ꢁC for 24 h prior to use. N,N-dime-
thylformamide, dichloromethane, tetrahydrofuran, pyridine, acetic
anhydride, diisopropyl azodicarboxylate, triphenylphosphine, 4-
Aminophenol, benzyl carbonochloridate, imidazole, potassium fer-
ricyanide, hydrochloric acid, ferrocene, potassium chloride, were
commercially available and used without further purification.
(500 MHz, CDCl3, ppm)
d
5.37e5.31 (m, 7H), 5.15 (d, J¼3.5 Hz, 7H),
4.70 (dd, J¼3.5 and 3.5 Hz, 7H), 4.05e3.70(m, 21H), 2.09e2.04(m,
49H), 0.88(s, 63H), 0.04(d, J¼8.5 Hz, 42H).31
4.3.4. Heptakis(2,3-O-diacetyl)-b-CD (3). To a solution of com-
pound 2 (2 g, 0.79 mmol) in 20 mL of dry dichloromethane was
added dropwise boron trifluoride etherate in ether (48%, 2.9 mL,
33 mmol) at room temperature. The mixture was stirred for about
6 h. The reaction mixture was poured into ice water. The organic
layer was separated and washed with saturated NaHCO3 solution
(20 mLꢂ3) and brine, dried over anhydrous Na2SO4, and concen-
trated in vacuo to give a crude product. The crude product was
purified by silica gel column chromatography to afford 1.2 g of
4.2. Instrumentation
1H NMR and 13C NMR spectra were acquired on a Bruker 500 MHz
spectrometer. ESI-Mass spectrometry experiments were performed
with Bruker microTOfII. Electrochemical experiments were carried
out using a CHI 660A electrochemical workstation (Chen Hua in-
struments Co., Shanghai, China). A three-electrode single-compart-
ment cell was used for cyclic voltammetry. A 4 mm diameter glassy
carbon electrode (GCE) disk was used as the working electrode,
a platinum wire as the counter electrode, and a Ag/AgCl electrode (in
saturated KCl aqueous solution) as the reference electrode. Fourier
transform infrared (FT-IR) spectra were obtained on a Nicolet Nexus
670 FT-IR spectrophotometer (ThermoNicolet, USA).
desired product (88%). 1H NMR (500 MHz, DMSO-d6, ppm)
d 5.25(t,
7H), 5.09 (d, J¼3.4 Hz, 7H), 4.80e4.78 (m, 7H), 4.59 (dd, J¼3.45 and
3.45 Hz, 7H), 3.86e3.80 (m, 21H), 3.62(d, J¼7.15 Hz, 7H). Mp
184e188 ꢁC (dec).31
4.3.5. Mono(6-O-benzyl-4-hydroxyphe-nylcarbamate) heptakis(2,3-
O-diacetyl)-b-CD (4). The compound 4 was synthesized according
to modified literature methods.32 A solution of compound 3
(500 mg, 0.29 mmol), benzyl 4-hydroxyphenylcarbamate (423 mg,
1.74 mmol), and PPh3 (684 mg, 2.61 mmol) was stirred in dry THF
(20 mL) at 0 ꢁC at a nitrogen atmosphere. To this mixture was added
4.3. Synthesis
4.3.1. Benzyl 4-hydroxyphenylcarbamate(A). To a cold solution of
p-aminophenol (5.0 g, 45.82 mmol) and Na2CO3 (7.7, 3.31 mmol)
in a mixed solution (THF/H2O, 50 mL/50 mL) was added dropwise a
solution of benzyl carbonochloridate in THF at ice-bath. After ad-
dition, the reaction mixture was slowly warmed to room temper-
ature. The mixture was extracted with ethyl acetate (100 mLꢂ3),
the combined organic layer was washed with brine, dried over
anhydrous sodium sulfate, filtered, and concentrated by rotary
evaporation. The residue was purified by flash chromatography to
afford the desired product as white solid (10 g, 90%). 1H NMR
dropwise
a solution of diisopropyl azodicarboxylate(5.1 mL,
2.61 mmol) in THF (5 mL) over a period of 30 min, and the reaction
was monitored by TLC. The starting material wasn’t consumed
completely. The reaction mixture was poured into ice water,
extracted with ethyl acetate (30 mLꢂ3), the organic layer was
washed with brine and dried over anhydrous Na2SO4, filtered, and
concentrated in vacuo to give a crude oil. The crude was purified by
flash column chromatography (dichloromethane/methanol) to give
260 mg of the desired product (45.8%). The by-product was a mix-
(400 MHz, DMSO-d6, ppm)
d
9.43 (s, 1H), 9.11(s, 1H), 7.49e7.35 (m,
ture of bi-and tri-substituted at the 6-position of
(500 MHz, DMSO-d6, ppm) 9.59 (s, 1H), 7.34e7.43 (m, 7),
b
-CD. 1H NMR
5H), 7.22 (d, 2H), 6.66e6.68 (d, 2H), 5.11 (s, 2H).30
d
6.85e6.87 (d, 2H), 5.24e5.29 (m, 7H), 5.05e5.13 (m, 9H), 4.55e4.78
(m, 13H), 4.35 (d, J¼0.3 Hz, 1H), 4.22 (d, J¼0.3 Hz, 1H), 4.08 (m, 2H),
3.76e3.83 (m, 16H), 3.63e3.65 (m, 5H), 3.58(m, 2H), 3.29 (d,
J¼0.3 Hz, 1H), 2.00e2.04 (m, 42H). 13C NMR (500 MHz, CDCl3, ppm)
4.3.2. Heptakis(6-O-tert-butyldimethylsi-lyl)-b-CD (1). b-cyclodex-
trin (4 g, 3.52 mmol, dried at 100 ꢁC in vacuum) was dissolved in
60 mL anhydrous DMF, imidazole (3.35 g, 49.28 mmol) was added.
At 0e5 ꢁC, tert-butyldimethylsilyl chloride (7.43 g, 49.28 mmol) in
dry DMF was added in 20 min. The mixture was stirred overnight,
then was poured into ice/water (150 mL) and followed by stirring
for 30 min. The white precipitate was filtered and dissolved in ethyl
acetate (100 mL), washed with aqueous HCl (50 mLꢂ2), then
washed with brine (50 mLꢂ2). The combined organic layer was
dried over anhydrous Na2SO4 and concentrated in vacuo yielding
d
170.75, 170.63, 169.34, 162.67, 154.21, 131.55, 128.50, 128.10,
114.73, 96.69, 96.26, 69.82e72.77, 66.77, 60.26e61.25, 53.37, 29.35,
20.63e20.90. MS (ESI) m/z 1970.5893 [MþNa]þ.
4.3.6. Mono(6-O-4-aminophenoxy)heptakis(2,3-O-diacetyl)-b-CD
(5). The compound 4 (200 mg, 0.103 mmol) was dissolved in 10 mL
of methanol, palladium hydroxide (20 mg, 10%m/m) under

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X. Wang et al. / Tetrahedron 66 (2010) 7815e7820
Carmen Ortiz Mellet, C. O.; Baussanne, I.; Defaye, J.; Fernández, J. M. G. J. Am.
Chem. Soc. 2004, 126, 10355e10363.
hydrogen was added to the solution. The mixture was stirred at
room temperature for about 1 h. The reaction mixture was filtered
over Celite, the filtrate was concentrated in vacuo to give the de-
sired product (180 mg, 96.2%) without purification. 1H NMR
4. Villalonga, R.; Cao, R.; Fragoso, A. Chem. Rev. 2007, 107, 3088e3116.
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(500 MHz, DMSO-d6, ppm)
d 6.64e6.66 (d, 2H), 6.51e6.53 (d, 2H),
5.25e5.28 (m, 7H), 5.07e5.11 (m, 7H), 4.52e4.68 (m, 15H), 4.27 (d,
J¼0.3 Hz, 1H), 4.13 (d, J¼0.3 Hz, 1H), 3.93e4.06 (m, 2H), 3.78e3.84
(m, 16H), 3.60e3.67 (m, 7H), 3.36 (d, J¼0.3 Hz, 1H), 1.99e2.02 (m,
42H). 13C NMR (500 MHz, CDCl3, ppm)
d 170.58, 169.50, 117.61,
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4.4.1. Preparation of MPA-b-CD diazonium. The compound MPA-b-
CD (42 mg) was dissolved in 1 mL of aqueous solution containing
1.0 M HCl, the solution was treated by deaerating and cooled to
0 ꢁC, then a solution of 1.4 mg NaNO2 in cold water was added
dropwise to the mixture. The mixture was stirred under argon at
this temperature for about 10 min. The diazonium solution formed
was then immediately used to perform electro-addressing.
4.4.2. Electrodeposition of Diazonium of MPA-b-CD on GCE. The di-
azonium of MPA- -CD formed in the above step was used to modify
b
the prepared GCE by electrodeposition. The surface derivatization
was carried out by electrochemical reduction, in the diazonium
cation-generating solution by scanning from 0 V to ꢀ1.0 V versus
Ag/AgCl at 0.1 V/s for four cycles. After deposition, the carbon
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Acknowledgements
This work was supported by NSF of China (Grant No. 20675031).
Supplementary data
1H NMR of the compound A, 1, 2, and 3, 13C NMR of compound 4
and compound 5, 1H NMR and ESI-MS of the compound 4 and 5.
Supplementary data for this article can be found in the online
version, at doi:10.1016/j.tet.2010.07.052.
References and notes
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