Tunable fluorescent sensing of cysteine and homocysteine by intramolecular charge transfer

Article abstract of DOI:10.1080/10610271003759139

An amphiphilic oligo p-phenylene derivative (DCHO bearing electron-donating group (-NH(CH₂)₂OH) and electron-withdrawing group (-CHO has been synthesised and characterised. The sensing characteristics of this probe (DCHO for cysteine (Cys and homocysteine (Hcy are studied in a mixture solution of DMSO-HEPES by UV-vis and fluorescence spectra. ¹H NMR, MALDI-TOF and UV-vis titration experiments proved that thiazolidine and thiazinane derivatives were formed. The highly Cys/Hcy-selective fluorescence hypsochromic shift (> 110 nm can be observed due to the switching of intramolecular charge transfer, leading to potential fabrication of ratiometric fluorescent detection of Cys/Hcy.

Full text of DOI:10.1080/10610271003759139

Supramolecular Chemistry
Vol. 22, No. 6, June 2010, 380–386
Tunable fluorescent sensing of cysteine and homocysteine by intramolecular charge transfer
Yiting Wanga, Jinchong Xiaoa,b*, Sujuan Wanga, Bo Yangb and Xinwu Baa
b
aCollege of Chemistry and Environment Science, Hebei University, Baoding 071002, P.R. China; Laboratory of Chemical Biology,
Department of Chemistry, Hebei University, Baoding 071002, P.R. China
(Received 18 October 2009; final version received 8 March 2010)
An amphiphilic oligo p-phenylene derivative (DCHO) bearing electron-donating group (ZNH(CH2)2OH) and electron-
withdrawing group (ZCHO) has been synthesised and characterised. The sensing characteristics of this probe (DCHO) for
cysteine (Cys) and homocysteine (Hcy) are studied in a mixture solution of DMSO–HEPES by UV–vis and fluorescence
spectra. 1H NMR, MALDI-TOF and UV–vis titration experiments proved that thiazolidine and thiazinane derivatives were
formed. The highly Cys/Hcy-selective fluorescence hypsochromic shift (.110 nm) can be observed due to the switching of
intramolecular charge transfer, leading to potential fabrication of ratiometric fluorescent detection of Cys/Hcy.
Keywords: fluorescence sensor; amino acid; molecular recognition
Introduction
such as photosynthesis was also studied based on the D–
p–A compounds, which led to increasing significance (7).
Oligo-, poly-p-phenylene and their derivatives are the
subjects of tremendous investigations because of their
interesting optical and electrochemical properties. These
compounds often have high extinction coefficients, high
fluorescence quantum yields and high stability against
light and chemical reactions, and can be modified by
various substituents, which might tune their absorption and
emission spectra (8). Thus, the study of the compounds has
attracted significant interest due to their potential
applications on catalysts and optoelectronic devices (9).
To date, many studies on recognition of analytes have been
focused on poly-p-phenylene derivatives (10). In order to
efficiently recognise the biologically important amino
acids, we are encouraged to develop a new D–p–A probe
based on oligo p-phenylene chromophores.
The design and construction of chemosensors with high
selectivity and sensitivity for amino acids has received
particular interest because amino acids play the essential
biological roles in living systems. Their deficiency might
cause a lot of severe human health problems (1) such as
slow growth, hair depigmentation, muscle and fat loss,
skin lesions and weakness (2). Specially, deficiency in
homocysteine (Hcy) is more dangerous and is believed to
cause Alzheimer’s, cardiovascular diseases and osteo-
porosis (3). Therefore, it is very important to develop
highly sensitive and selective assays for cysteine (Cys) or
Hcy. In recent years, several groups have reported that
Cys/Hcy analyses could be performed with high-
performance liquid chromatography, capillary electro-
phoresis, electrochemical detection, Fourier transform
infrared (FT-IR) detection and mass spectrometry identi-
fication (4). Moreover, there are a few chemosensors with
UV–vis and fluorescence turn-on sensing and bioimaging
of Cys/Hcy in mixed solvents (5). Although many
techniques and reaction mechanisms have been developed
for assaying Cys and Hcy, there is still much room for
improvement in terms of rapidity, sensitivity, selectivity
and cost-effectiveness to recognise those biologically
important organic molecules such as amino acids.
In this paper, we describe the design and construction
of a class of colorimetric and fluorometric probe to
specifically detect the presence of Cys/Hcy over a wide
range of other amino acids and glucose. To achieve this
goal, a modular molecule (DCHO, Scheme 1) is
synthesised that is composed of oligo p-phenylene
fluorophore which possesses interesting spectroscopic
properties. Electron-donating group (ZNH(CH2)2OH) and
electron-withdrawing unit (ZCHO) that graft into the
chromophore through a covalent bond to create a D–p–A
system, which makes the ICT from the donor to the
acceptor, proceed upon excitation. This process might
induce changes in two-channel output signals (colour
change and fluorescence variation), which is convenient
for practical utilisation.
A molecule containing conjugated electron donor (D)
and electron acceptor (A) usually undergoes an intramo-
lecular charge transfer (ICT) upon electronic excitation
(6). The ICT and hence an elongation of the p electron
conjugation occurring upon Franck–Condon exciton
contributes to the absorption profile. The process of ICT
fluorescence playing a key role in the biological systems
*Corresponding author. Email: jcxiao@hbu.edu.cn
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2010 Taylor & Francis
DOI: 10.1080/10610271003759139
http://www.informaworld.com

Supramolecular Chemistry
381
Figure 1 and Table 1. The electron-withdrawing substituent
(ZCHO) can induce a remarkable red shift of the absorption
maximum, the origin of which can be attributed to the ICT
state for a strong push–pull system. The broader absorption
band of DCHO might be assigned to electronic transitions
delocalised throughout the whole molecule (12). The
solvatochromic shift of DCHO is observed due to the large
difference in dipole moment of the Franck–Condon excited
state and the ground state, which is induced by the formyl
group (7d). In addition, the fluorescence spectrum of DCHO
in DMSO exhibits pronounced red shift, indicative of an ICT
characteristic of the fluorescence states. The emission
maximum of DCHO with two formyl substituents extends
from 483 nm in toluene to 565 nm in DMSO, and the
solvatochromic shift becomes as large as 82nm on change
from toluene to DMSO, while the fluorescence maximum of
RDPh ranges from 419 nm (in toluene) to 443 nm (in
DMSO). The results show that the magnitude of the
solvatochromism effect also depends on electron-with-
drawing groups, and that DCHO has low dipole moments in
the ground state, but much higher dipole moments in the first
excited singlet state, which was better stabilised by polar
solvents. Itshouldbenotedthatit wasdifficult tomeasurethe
fluorescence quantum yields in ethanol due to the low
intensity. Considering the solvatochromic effect and the
strong fluorescence quenching in protonic solvent (ethanol),
a mixture of DMSO and HEPES (v/v, 19:1) was chosen for
the further study.
HO
DCHO
RDPh
NH
OHC
CHO
HO
NH
Scheme 1. Chemical structure of DCHO and the reference
compound RDPh.
Results and discussion
Compound DCHO and the reference compound RDPh
were readily prepared via Suzuki cross-coupling reactions
of N-hydroxyethyl-2,5-dibromoaniline and 4-formyl-
benzeneboronic acid pinacol ester or benzeneboronic
acid pinacol ester, respectively, in the presence of
Pd(PPh3)4 and NaHCO3 in THF/H2O solution according
to the reported method (Scheme 2) (11). It should be noted
that the hydroxyethyl group was introduced in DCHO to
increase the hydrophile. The resulting molecules were
characterised by FT-IR, H NMR, 13C NMR and mass
1
spectroscopy, which were shown to be in full agreement
with the structures presented.
DCHO in DMSO/H2O (v/v, 19:1) solution
(2.2 £ 1025 M) at room temperature exhibited absorption
spectra with lmax at 386 nm and other two peaks at 280 and
304 nm, respectively. The absorption maximum of DCHO
has about a 47 nm red shift in comparison to the reference
compound RDPh, which was attributed to the efficient
ICT process from the donor nitrogen atom – the one that
conjugated to oligo p-phenylene – to the acceptor group
(Figure 2(A)). In comparison, the emission spectra of
DCHO (2.2 £ 1025 M) in DMSO/H2O (v/v, 19:1) solution
at room temperature were showed at 442 and 565 nm with
excitation wavelength at 386 nm (Figure 3(A)), and the
quantum yield (Ff) of DCHO in DMSO was measured as
Ff ¼ 0.02 with quinine sulphate as standard at 258C
(Table 1). Figure 2(A) shows the UV–vis spectral changes
of DCHO as a function of the Cys concentration in a
DMSO/H2O solution (v/v, 19:1, 10 mM HEPES buffer, pH
6.7) at room temperature. The addition of Cys (0–
3.2 £ 1023 M) to DCHO solution (2.2 £ 1025 M) led to a
decrease in the intensities of the initial bands at 310 and
386 nm with the concomitant growth of intensity at 343 nm
(Figure 2(A)). These results suggest that thiazolidine
DCHO-a was formed (Scheme 3). The coordination of the
Cys to DCHO reduced the electron-withdrawing ability of
the formyl group, thus the ICT progress is not possible any
more and the red shift in absorption spectra is suppressed.
A similar blue shift was also found for Hcy. As shown
Compounds DCHO and RDPh exhibit good solubility
in CH2Cl2, CHCl3, THF, CH3CN, EtOH, DMF and
DMSO. Typical UV–vis absorption spectra of DCHO and
RDPh in differentsolventsatroomtemperatureareshownin
HO
NH2
2-chloroethanol
NH
Br
K2CO3, 100°C
16 h, 59%
Br
Br
Br
1
2
HO
O
DCHO
B
CHO
NH
O
2
OHC
CHO
Ph(PPh3)4, NaHCO3
THF/H2O, 12 h, 61 %
3
HO
O
B
O
RDPh
NH
2
Ph(PPh3)4, NaHCO3
THF/H2O, 12 h, 57 %
4
Scheme 2. Synthesis of conjugated compounds DCHO and
RDPh.

382
Y. Wang et al.
Figure 1. (A) UV–vis absorption and (B) normalised fluorescence spectra of DCHO (2.2 £ 1025 M) in (a) toluene, (b) CHCl3, (c) THF,
(d) EtOH, (e) DMF and (f) DMSO.
in Figure 2(B), upon addition of Hcy, the absorption
intensity of DCHO at 386 nm decreased with a blue shift
band at 354 nm, which is indicative of the formation of
thiazinane DCHO-b.
resulted in a colour change from yellow to blue as shown
in Scheme 3. This visible emission allows DCHO-a or -b
to be readily distinguished by the naked eye under UV
light. No obvious colour changes were observed upon
addition of other amino acids or glucose.
Note that a fluorometric detection of Cys/Hcy is also
possible for compound DCHO. In the fluorescence
spectra, DCHO exhibits characteristic emission bands at
443 and 565 nm when excited at 386 nm (Figure
3(A),(B)). Upon addition of Cys/Hcy to the solution of
DCHO, a significant decrease in the 565 nm emission
band was observed with the concomitant growth of the
blue-shifted band centred at 443 nm. The obvious blue
shift and the resolved emission peaks make it possible to
obtain a clear I449/I565 46-fold enhancement for Cys and
I449/I565 220-fold enhancement for Hcy. The highly
Cys/Hcy-sensitive UV–vis and fluorescence hypsochro-
mic shift showed more obvious than those in the reported
methods (13). These observations might also suggest that
reaction of Cys/Hcy with the formyl group that was
conjugated to the oligo-phenylene core suppressed the ICT
progress (Scheme 3). It should be noted that the low
concentration of Cys/Hcy did not affect distinctly the ICT
emission due to its unstable formation of thianolidine or
thiazinane derivatives from the reaction ability of DCHO
to Cys/Hcy in the emission spectral analysis. Importantly,
the large Cys/Hcy-induced blue shift in emission spectra
To verify specificity, the optical response experiments
were investigated with other amino acids and glucose,
such as Phe, Pro, Gly, Lys, glucose (Glu), Ser, Thr, Asp,
Val and His. As shown in Figure 4(A), under the identical
condition to Cys/Hcy, no changes were observed in the
UV–vis spectra of DCHO (2.2 £ 1025 M) upon addition
of 90 equiv. of Phe, Pro, Gly, Lys, Glu, Ser, Thr, Asp, Val
and His. This might result from the specific reaction of the
aldehyde group and the b- or g-aminoalkylthio moieties.
In good agreement with the changes in the absorption, the
emission spectra also displayed a significant change upon
addition of Cys/Hcy (Figure 4(B)). In comparison, no
visible variations were observed upon addition of other
amino acids or glucose. To further explore the utility of
DCHO as a selective fluorescence probe for Cys/Hcy, the
competition experiments were conducted. Figure 5 depicts
the fluorescence responses of DCHO to the presence of 90
equiv. of Cys or Hcy and 40 equiv. of Phe, Pro, Gly, Lys,
Glu, Ser, Thr, Asp, Val and His. The addition of other
amino acids and glucose showed nearly no changes in
emission spectra, indicative of the sensitive and selective
detection of Cys/Hcy under competition from other related
analytes.
Table 1. Photophysical properties of DCHO and RDPh.
The formation of thiazolidine DCHO-a and thiazinane
1
DCHO-b was demonstrated by H NMR spectroscopic
UV–vis
)
PL
(lmax
Stokes shift
(nm)
Sample
Solvent
(lmax
)
Ff
studies in DMSO-d6. Figure 6 shows the 1H NMR
spectra in the absence and presence of Cys. The
concentration of DCHO (2.9 £ 1022 M) was kept
constant, and the aldehyde signal at 10.05 ppm disap-
peared after 30 min upon addition of 10 equiv. Cys to
DCHO. Meanwhile, the new peaks centred at 5.74 and
5.54 ppm (for Cys) and 5.32 ppm (for Hcy) (Figure S1 of
the Supplementary Material) appeared, which might be
assigned to the methine protons of the thiazolidine and
thiazinane diastereomer, respectively. The MALDI-TOF
DCHO Toluene
CHCl3
THF
370
370
377
373
383
386
329
339
483
503
510
513
555
565
419
443
113
133
133
140
172
179
80
0.23
0.36
0.46
a
EtOH
DMF
DMSO
Toluene
DMSO
–
0.08
0.02
0.49
0.50
RDPh
104
aIt was difficult to measure this value due to the low intensity. All emission spectra
were measured at each UV–vis (lmax, nm). The Ff values for DCHO and RDPh are
relative to those of quinine sulphate (0.53 in 0.1 N H2SO4) (14).

Supramolecular Chemistry
383
Figure 2. UV–vis absorption spectral changes of DCHO (2.2 £ 1025 M) upon addition of increasing concentration (0–140 equiv.) of
(A) Cys and (B) Hcy in DMSO/H2O (v/v, 19:1): (a) 0, (b) 4 £ 1024 M, (c) 8 £ 1024 M, (d) 1.2 £ 1023 M, (e) 1.6 £ 1023 M,
(f) 2 £ 1023 M, (g) 2.4 £ 1023 M, (h) 3.2 £ 1023 M; pH 6.7. Each spectrum is recorded after 30 min incubation in a 458C water bath after
Cys/Hcy addition.
mass spectrograms of DCHO with Cys and Hcy also
showed clear dimeric complex of the peaks at 552.3 and
580.3, respectively (Figures S2 and S3 of the Supplemen-
tary Material, available online). The results also strongly
suggest that the thiazolidine DCHO-a and thiazinane
DCHO-b are formed through the interaction of the
aldehyde group and Cys or Hcy.
Experimental section
Materials and methods
Most of the chemicals were purchased from Alfa Aesar
(Karlsruhe, Germany) or Aldrich Corporation (Steinheim,
Germany), and used as received. Column chromatography
was performed on silica gel (200–300 mesh). Melting points
were taken on a TX-4 hot-stage apparatus and are
uncorrected. IR spectra were measured on a Nicolet 380
instrument. UV–vis spectra were recorded on a Shimadzu
UV-2550 spectrometer, and fluorescence spectra were
Conclusion
measured on an RF5300PC spectrofluorometer. 1H and 13
C
In summary, we have developed a new class of
colorimetric and fluorometric probe of DCHO for
Cys/Hcy detection with high selectivity and sensitivity
on the basis of the tuning of the ICT process. The DCHO
molecule with N-hydroxyethylaniline component renders
a straightforward preparation and good solubility in
aqueous media. Meanwhile, a highly Cys/Hcy fluor-
escence enhancing in conjunction with remarkable blue-
shift property can be observed. This D–p–A constitution
demonstrated in this study might serve as a protocol for the
future development of a multi-stage chemosensor for the
possible analyte.
NMR spectra were obtained on Bruker 400 spectrometers
using CDCl3 or DMSO-d6 as a solvent with tetramethylsi-
lane (TMS) as the internal standard. MALDI-TOF mass
spectrometric measurements were performed on Bruker
Biflex MALDI-TOF. Elemental analyses were carried out on
a Carlo Erba 1106 elemental analyser.
N-(2-Hydroxyethyl)-2,5-dibromoaniline (2)
A mixture of 2,5-dibromoaniline (1.50 g, 6.0 mmol), 2-
chloroethanol (36 ml) and K2CO3 (2.48 g, 18.0 mmol) was
Figure 3. Fluorescence spectral changes (excitation at 386 nm) of DCHO (2.2 £ 1025 M) upon addition of increasing concentration
(0–140 equiv.) of (A) Cys and (B) Hcy in DMSO/H2O (v/v, 19:1): (a) 0, (b) 4 £ 1024 M, (c) 8 £ 1024 M, (d) 1.2 £ 1023 M, (e)
1.6 £ 1023 M, (f) 2 £ 1023 M, (g) 2.4 £ 1023 M, (h) 3.2 £ 1023 M; pH 6.7. Each spectrum is recorded after 30 min incubation in a 458C
water bath after Cys/Hcy addition. The inset shows the curves I449/I565 with the addition of Cys and Hcy (colour online).

384
Y. Wang et al.
Scheme 3. Reaction of DCHO with Cys or Hcy to afford thiazolidine (DCHO-a) or thiazinane (DCHO-b) and the change in fluorescent
colour on excitation at 365 nm using UV light at room temperature.
stirred at 1008C for 16 h under an atmosphere of nitrogen.
The reaction was then cooled to ambient temperature,
brine was added (100 ml) and the solution was extracted
with CH2Cl2 (3£ 50 ml). The combined organic phase was
collected and dried over Na2SO4, and filtered. The solvent
was removed under reduced pressure and the crude
product was purified by column chromatography (silica
gel) with petroleum–CH2Cl2 (v/v, 10:3) as the eluent to
give white solid 2 (1.03 g, 59%).
temperature, the mixture was filtered and concentrated
under reduced pressure. The residue was purified by silica
gel column chromatography with CH2Cl2–CH3CO2Et
(v/v, 50:8) as the eluent to give white solid 3 (170 mg,
61%).
Mp: 170–1718C; IR (KBr): 3413, 2957, 2872, 2729,
1727, 1693, 1599, 1553, 1386, 1291, 1209, 1165, 1069,
1
834, 802, 697 cm21; H NMR (400 MHz, CDCl3, 298 K,
TMS): d ¼ 10.01 (s, 2H), 7.98 (t, J ¼ 8.8 Hz, 4H), 7.79 (d,
J ¼ 7.6 Hz, 2H), 7.67 (d, J ¼ 7.6 Hz, 2H), 7.22 (d,
J ¼ 7.6 Hz, 1H), 7.08 (d, J ¼ 7.6 Hz, 1H), 6.99 (s, 1H),
4.36 (br, 1H), 3.86 (t, J ¼ 4.0 Hz, 2H), 3.40 (t, J ¼ 4.0 Hz,
2H), 1.59 (br, 1H); 13C NMR (100 MHz, CDCl3, 298 K,
TMS): 192.2, 147.7, 145.8, 145.7, 141.5, 135.8, 135.7,
131.3, 130.8, 130.6, 130.2, 128.0, 127.2, 117.2, 110.3,
61.4, 46.4; MS (EI): 345 [M]þ; Anal. Calcd for
C22H19NO3 (345.14): C, 76.50; H, 5.54; N, 4.06. Found:
C, 75.82; H, 5.69; N, 3.88.
Mp: 59–608C; IR (KBr): 3376, 3242, 2930, 2879,
1
1588, 1504, 1456, 1408, 1286, 1060, 825, 782 cm21; H
NMR (400 MHz, CDCl3, 298 K, TMS): d ¼ 7.25 (d,
J ¼ 8.0 Hz, 1H), 6.76 (s, 1 H), 6.99 (d, J ¼ 8.0 Hz, 1H),
4.69 (br, 1H), 3.86 (s, 2H), 3.32 (s, 2H), 1.89 (br, 1H); 13
C
NMR (100 MHz, CDCl3, 298 K, TMS): 146.0, 133.4,
122.3, 120.6, 114.1, 108.4, 60.7, 45.6; MS (EI): 295 [M]þ.
N-(2-Hydroxyethyl)-2,5-di(4-formylphenyl)aniline (3)
A mixture of N-(2-hydroxyethyl)-2,5-dibromoaniline (2,
238 mg, 0.8 mmol), 4-formylbenzeneboronic acid pinacol
ester (428 mg, 1.84 mmol), Pd(PPh3)4 (45 mg, 0.04 mmol)
and NaHCO3 (400 mg, 4.76 mmol) in THF/H2O
(44 ml/4 ml, v/v, 10:1) was stirred for 12 h at refluxing
temperature under nitrogen. After cooling to room
N-(2-Hydroxyethyl)-2,5-diphenylaniline (4)
A mixture of N-(2-hydroxyethyl)-2,5-dibromoaniline (2,
100 mg, 0.33 mmol), benzeneboronic acid pinacol ester
(135 mg, 0.66 mmol), Pd(PPh3)4 (15 mg, 0.01 mmol) and
NaHCO3 (200 mg, 2.38 mmol) in THF/H2O (44 ml/4 ml,
Figure 4. (A) UV–vis absorption and (B) fluorescence spectra (excitation at 386 nm) of DCHO (2.2 £ 1025 M) with or without amino
acids, and glucose (90 equiv.) in DMSO/HEPES (v/v, 19:1); pH 6.7.

Supramolecular Chemistry
385
Figure 5. Fluorescence spectral changes of DCHO (1.1 £ 1025 M) upon addition of (A) Cys (90 equiv.), (a) Cys, (b) Cys þ Phe,
(c) Cys þ Pro, (d) Cys þ Gly, (e) Cys þ Lys, (f) Cys þ Glu, (g) Cys þ Ser, (h) Cys þ Thr, (i) Cys þ Asp, (j) Cys þ Val, (k) Cys þ His;
(B) Hcy (90 equiv.), (a) Hcy, (b) Hcy þ Phe, (c) Hcy þ Pro, (d) Hcy þ Gly, (e) Hcy þ Lys, (f) Hcy þ Glu, (g) Hcy þ Ser, (h) Hcy þ Thr,
(i) Hcy þ Asp, (j) Hcy þ Val, (k) Hcy þ His and subsequent addition of different amino acids and glucose (40 equiv.) in DMSO/HEPES
(v/v, 19:1); pH 6.7.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (20574016) and the Science Research
Project of Hebei University (2007-103).
References
(1) (a) Czarnik, A.W., Ed. Fluorescent Chemosensors for Ion
and Molecule Recognition; American Chemistry Society:
Washington, DC, 1992. (b) Rohman, I.; MacNee, W. Free
Radic. Biol. Med. 2000, 28, 1405–1420. (c) Carmel, R.,
Jacobsen, D.W., Eds. Homocysteine in Health and Disease;
Cambridge University Press: Cambridge, UK, 2001. (d)
¨
Wood, Z.A.; Schroder, E.; Harris, J.R.; Poole, L.B. Trends
Biochem. Sci. 2003, 28, 32–40. (e) Jolliffe, K.A. Supra-
molecular Chemistry 2005, 17, 81–86.
(2) (a) Shahrokhian, S. Anal. Chem. 2001, 73, 5972–5978. (b)
Rusin, O.; Luce, N.N.S.; Agbaria, R.A.; Escobeda,
J.O.; Jiang, S.; Warner, I.M.; Dawan, F.B.; Lian, K.;
Strongin, R.M. J. Am. Chem. Soc. 2004, 126, 438–439.
Figure 6. 1H NMR spectra of DCHO in DMSO-d6 in the
(A) absence and (B) presence of Cys at 298 K. The concentration
of DCHO was kept constant at 2.9 £ 1022 M.
˚
(3) (a) Refsum, H.; Ueland, P.M.; Nygard, O.; Vollset, S.E.
Annu. Rev. Med. 1989, 49, 31–62. (b) Seshadri, S.; Beiser,
A.; Selhub, J.; Jacques, P.F.; Rosenberg, I.H.; D’Agostino,
R.B.; Wilson, P.W.F. New Engl. J. Med. 2002, 346, 476–
483.
v/v, 10:1) was stirred for 12 h at refluxing temperature
under nitrogen. After cooling to room temperature, the
mixture was filtered and concentrated under reduced
pressure. The residue was purified by silica gel column
chromatography with petroleum–CH2Cl2 (v/v, 1:2) as the
eluent to give yellow solid 4 (56 mg, 57%).
(4) (a) Chwatko, G.; Bald, E. Talanta 2000, 52, 509–515. (b)
Inoue, T.; Kirchhoff, J.R. Anal. Chem. 2000, 72, 5755–5760.
(c) Fei, S.D.; Chen, J.H.; Yao, S.Z.; Deng, G.H.; He,
D.L.; Kuang, Y.F. Anal. Biochem. 2005, 339, 29–35. (d) Sato,
Y.; Iwata, T.; Tokutomi, S.; Kandori, H. J. Am. Chem. Soc.
2005, 127, 1088–1089. (e) Burford, N.; Eelman,
M.D.; Mahony, D.E.; Morash, M. Chem. Commun. 2003,
146–147.
Mp: 113–1148C; IR (KBr): 3405, 3254, 3025, 2928,
1606, 1557, 1485, 1415, 1257, 1041, 848, 758, 700 cm21
;
1H NMR (400 MHz, CDCl3, 298 K, TMS): d ¼ 7.63 (d,
J ¼ 7.2 Hz, 2H), 7.45 (t, J ¼ 7.2 Hz, 6H), 7.36 (t, 2H),
7.19 (d, J ¼ 7.6 Hz, 1H), 7.04 (d, J ¼ 7.6 Hz, 1H), 6.97 (s,
1H), 4.41(br, 1H), 3.81 (t, J ¼ 4.0 Hz, 2H), 3.38 (t, 2H),
1.61 (br, 1H); 13C NMR (100 MHz, CDCl3, 298 K, TMS):
142.1, 141.8, 138.7, 131.1, 129.4, 129.2, 128.9, 127.7,
127.5, 127.3, 61.5, 47.3; MS (EI): 289 [M]þ; Anal. Calcd
for C20H19NO (289.15); C, 83.01; H, 6.62; N, 4.84. Found:
C, 83.01; H, 6.75; N, 4.63.
(5) (a) Tanaka, F.; Mase, N.; Barbas, C.F., III. Chem. Commun.
2004, 1762–1763. (b) Shao, N.; Jin, J.Y.; Cheung,
S.M.; Yang, R.H.; Chan, W.H.; Mo, T. Angew. Chem. Int.
Ed. 2006, 45, 4944–4948. (c) Zhang, D.Q.; Zhang, M.; Liu,
Z.Q.; Yu, M.X.; Li, F.Y.; Yi, T.; Huang, C.H. Tetrahedron
Lett. 2006, 47, 7093–7096. (d) Zhang, M.; Yu, M.X.; Li,
F.Y.; Zhu, M.W.; Li, M.Y.; Gao, Y.H.; Li. L.; Liu,
Z.Q.; Zhang, J.P.; Zhang, D.Q.; Yi, T.; Huang, C.H. J. Am.
Chem. Soc. 2007, 129, 10322–10323. (e) Duan, L.P.; Xu,
Y.F.; Qian, X.H.; Wang, F.; Liu, J.W.; Cheng, T.Y.
Tetrahedron Lett. 2008, 49, 6624–6627. (f) Lin,

386
Y. Wang et al.
W.Y.; Long, L.L.; Yuan, L.; Cao, Z.M.; Chen, B.B.; Tan, W.
Chi, L.C.; Huang, S.C.; Liao, Y.L.; Liu, Y.H.; Wang, Y. Org.
Lett. 2006, 8, 5029–5032. (c) Yokoyama, A.; Kato, A.;
Mijakoshi, R.; Yokozawa, T. Macromolecules 2008, 41,
7271–7273. (d) Banerjee, M.; Shukla, R.; Rathore, R. J. Am.
Chem. Soc. 2009, 131, 1780–1786.
Org. Lett. 2008, 10, 5577–5580. (g) Ji, S.M.; Yang, J.;
Yang, Q.; Liu, S.S.; Chen, M.D.; Zhao, J.Z. J. Org. Chem.
2009, 74, 4855–4865.
(6) (a) de Silva, A.P.H.; Gunaratne, Q.N.; Gunnlaugsson, T.;
Huxley, A.J.M.; McCoy, C.P.; Rademacher, J.T.; Rice, T.E.
Chem. Rev. 1997, 97, 1515–1566. (b) Valeur, B.; Leray, I.
Coord. Chem. Rev. 2000, 205, 3–40. (c) Rurack, K.
Spectrochim. Acta Part A 2001, 57, 2161–2195.
(10) (a) Ramey, M.B.; Hiller, J.A.; Rubner, M.F.; Tan,
C.Y.; Schanze, K.S.; Reynold, J.R. Macromolecules 2005,
38, 234–243. (b) Pu, K.Y.; Liu, B. Macromolecules 2008,
41, 6636–6640.
(7) (a) Ward, M.D. Chem. Soc. Rev. 1997, 26, 365–375. (b)
Armaroli, N.; Accorsi, G.; Felder, D.; Nierengarten, J.F.
(11) Li, Z.A.; Li, Z.; Di, C.A.; Zhu, Z.C.; Li, Q.Q.; Zeng, Q.;
Zhang, K.; Liu, Y.Q.; Ye, C.; Qin, J.G. Macromolecules
2006, 39, 6951–6961.
(12) Grabowski, Z.R.; Rotkiewicz, K.; Rettig, W. Chem. Rev.
2003, 103, 3899–4032.
(13) (a) Duan, L.P.; Xu, Y.F.; Qian, X.H.; Wang, F.; Liu, J.W.;
Cheng, T.Y. Tetrahedron Lett. 2008, 49, 6624–6627.
(b) Zhang, D.Q.; Zhang, M.; Liu, Z.Q.; Yu, M.X.; Li,
F.Y.; Yi, T.; Huang, C.H. Tetrahedron Lett. 2006, 47, 7093–
7096.
(14) (a) Adams, M.J.; Highfield, J.G.; Kirkbrigh, G.F. Anal.
Chem. 1977, 49, 1850–1852. (b) Xiao, J.C.; Xu, J.L.; Cui,
S.; Liu, H.B.; Wang, S.; Li, Y.L. Org. Lett. 2008, 10, 645–
648.
¨
Chem. Eur. J. 2002, 8, 2314–2323. (c) Jodicke, C.J.; Luthi,
H.P. J. Am. Chem. Soc. 2003, 125, 252–264. (d) Demeter,
¨
´
A.; Berces, T.; Zachariasse, K.A. J. Phys. Chem. A 2001,
105, 4611–4621.
(8) (a) Patil, A.O.; Heeger, A.J.; Wudl, F. Chem. Rev. 1988, 88,
183–200. (b) Hoeben, F.J.M.; Jonkheijm, P.; Meijer,
E.W.; Schenning, A.P.H.J. Chem. Rev. 2005, 105, 1491–
1546. (c) Hong, D.J.; Lee, E.; Lee, J.K.; Zin, W.C.; Han, M.;
Sim, E.; Lee, M. J. Am. Soc. Chem. 2008, 130, 14448–
14449.
(9) (a) Ryu, J.H.; Jang, C.J.; Yoo, Y.S.; Lim, S.G.; Lee, M.
J. Org. Chem. 2005, 70, 8956–8962. (b) Wong, K.T.;

Copyright of Supramolecular Chemistry is the property of Taylor & Francis Ltd and its content may not be
copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written
permission. However, users may print, download, or email articles for individual use.