Fluorometric sensing of biogenic amines with aggregation-induced emission-active tetraphenylethenes

Article abstract of DOI:10.1002/chem.201003285

A fluorometric sensor for detection and identification of biogenic amines with carboxylic acid modified tetraphenylethenes (TPEs) based on aggregation-induced emission (AIE) is reported. A mixture of the carboxylic acid substituted TPE and biogenic amines

Full text of DOI:10.1002/chem.201003285

DOI: 10.1002/chem.201003285
Fluorometric Sensing of Biogenic Amines with Aggregation-Induced
Emission-Active Tetraphenylethenes
Mitsutaka Nakamura, Takanobu Sanji,* and Masato Tanaka*[a]
Abstract: A fluorometric sensor for de-
tection and identification of biogenic
amines with carboxylic acid modified
tetraphenylethenes (TPEs) based on
aggregation-induced emission (AIE) is
reported. A mixture of the carboxylic
acid substituted TPE and biogenic
amines displayed a blue emission on
aggregation, which serves as a “turn-
on” fluorescent sensor for the amines,
the degree of fluorescence enhance-
ment being dependent on the amine.
The chromic responses were utilized to
distinguish the amines. A fluorometric
sensor array of three TPEs with car-
boxylic acid groups was shown to iden-
tify accurately 10 different amines, in-
cluding biogenic amines. The response
patterns were systematically classified
by using linear discriminant analysis
(LDA) with 98% classification accura-
cy. Additional information on the con-
centration of histamine in a “tuna fish
matrix” as an example was assessed by
the further analysis of the fluorescence
intensity, demonstrating a test for food
freshness and quality.
Keywords: aggregation-induced
emission · biogenic amines · biosen-
sors · fluorescence · tetraphenyle-
thenes
Introduction
the detection and identification of amines by using carboxyl-
ic acid functionalized poly(thiophene).[14] The chromic re-
sponses resulting from the nonspecific interaction between
the polymer and amines were utilized to distinguish amines
by using statistical analysis. A sensor array based on ana-
lyte-specific patterns arising from the differential binding af-
finity of a set of nonspecific receptors is attractive, because
this sensing approach simplifies the sensor design.[15,16]
Recently, we[17] and others[18] have demonstrated that ag-
gregation-induced emission (AIE)-active materials, first re-
ported by Tang and co-workers,[19] have potential utility in
the sensing fields.[20] AIE-active molecules show no emission
in solution but an intense emission when aggregated or in
the solid state because of the restriction of intramolecular
rotations that prevent nonradiative deactivation for fluores-
cence quenching.[21] Based on the state (aggregation)-depen-
dent fluorescence, AIE-active molecules can be used as an
alternative sensing element for biomolecular species, in
which they aggregate via multivalent interactions, resulting
in an intense emission. Here, we show fluorometric sensing
for detection and identification of biogenic amines by using
AIE-active tetraphenylethenes (TPEs) with carboxylic acid
moieties 1–3 (Scheme 1).
Biologically relevant amines, biogenic amines, which are
produced by decarboxylation of amino acids, are found in
virtually all living organisms and play a significant role in
regulating cell growth and differentiation.[1,2] An elevated
level of biogenic amines, for example, is caused by abnormal
cell proliferation,[3] which can be used for markers of health
risks, including cancer and bacterial infections.[4,5] In addi-
tion, a series of biogenic amines, such as histamine, putres-
cine, and cadaverine, are associated with spoilage of raw
and processed foods, which cause food poisoning.[6] In this
context, the detection and identification of biogenic amines
are important issues for health and food safety.
A variety of detection methods for biogenic amines are
available. For example, chromatographic techniques, such as
gas and liquid chromatography, are employed for the screen-
ing and quantification of biogenic amines.[7] These instru-
mental techniques are highly sensitive, but often require
sample pretreatment and relatively long analysis times,
which are not suitable for routine use. Other methods for
biogenic amine detection, including the use of enzymes,[8]
antibodies,[9] molecular imprinted polymers,[10] and fluores-
cent molecules,[11–13] have been reported. Alternatively, Lav-
igne et al. recently demonstrated a colorimetric method for
Results and Discussion
[a] M. Nakamura, Dr. T. Sanji, Prof. M. Tanaka
Chemical Resources Laboratory, Tokyo Institute of Technology
4259-R1-13 Nagatsuta, Midori-ku
Yokohama 226-8503 (Japan)
Design: The design for sensing biogenic amines is illustrated
schematically in Scheme 1c. TPE, which shows no emission
in solution but an intense emission in a state of aggregation,
that is, it is AIE active and is used as a basic sensor element.
Because amines interact with a carboxylic acid through hy-
drogen bonding and/or electrostatic interactions, TPEs inte-
grated with carboxylic acid moieties 1–3 are seen to display
Fax : (+81)45-924-5279
E-mail: sanji@res.titech.ac.jp
m.tanaka@res.titech.ac.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201003285.
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Chem. Eur. J. 2011, 17, 5344 – 5349

FULL PAPER
Scheme 3.
Scheme 4.
prepared from 6 as a starting material (Scheme 4). The
products were fully characterized by spectroscopic methods.
TPEs 1–3 have a different linking unit with carboxylic acid
groups, in which the binding ability to amines could be de-
pendent on the length and degree of flexibility of the tether.
Amine sensing: To demonstrate the sensing ability of TPEs
containing carboxylic acid groups for biogenic amines, the
fluorescence spectral change of TPE 1 (10 mm) upon addi-
tion of 1,4-butanediamine (BDA, putrescine) in dichlorome-
thane was monitored (Figure 1). As designed, a dichlorome-
thane solution of 1 was practically nonluminescent, with a
Scheme 1. Chemical structures of a) carboxylic acid modified TPEs 1–3
and b) amines used as analytes. c) A schematic drawing of fluorescence
“turn-on” sensing of amines with TPEs.
an emission, that is, “turn-on” fluorescence, when they rec-
ognize amines and then form aggregates. The aggregation is
associated with the binding affinity of the carboxylic acid
with the amine through multivalent interactions, and hence
the fluorescence response could be used to differentiate the
amines.
Synthesis: TPE 1 was synthesized by the reaction of lithiat-
ed TPE derived from 4 and dry ice followed by hydrolysis
(Scheme 2). TPE 2 with carboxylic acid groups linked by a
tetramethylene unit was also synthesized, as shown in
Scheme 3. TPE 3, containing a diethylene glycol unit, was
Figure 1. Fluorescence spectra of 1 (10 mm) upon addition of BDA in di-
chloromethane (lex =350 nm). The inset shows photographs of 1 (10 mm)
and the mixture with BDA (10 mm) in a dichloromethane solution under
irradiation with UV light at a wavelength of 365 nm.
Scheme 2.
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5345

T. Sanji, M. Tanaka and M. Nakamura
quantum yield of 0.21% (relative to quinine sulfate as a
standard). However, after addition of BDA to the solution,
the emission intensity at 480 nm increased gradually.[22] The
fluorescence intensity at 480 nm ([BDA]=50 mm) represent-
ed an approximately 80-fold increase relative to the original
value, with a quantum yield of 18.6%. As shown in the inset
in Figure 1, the intense emission of the solution of TPE 1
after addition of BDA was easily confirmed by the naked
eye. The detection limit of BDA was estimated to be at the
parts per billion (ppb) level, which is noticeably more sensi-
tive than previously reported colorimetric sensors.[14]
The dramatic enhancement in the fluorescence intensity
upon addition of BDA is rationalized in terms of aggrega-
tion triggered by divalent interactions of BDA with 1 ap-
pending carboxylic acid groups, as illustrated in Scheme 1c.
Indeed, after filtration with an 0.45 mm pore size membrane,
the solution returned to being nonluminescent.
In the sensing studies of amines, five a,w-diamines: 1,2-
ethylenediamine (EDA), 1,3-propanediamine (PrDA),
BDA, 1,5-pentanediamine (PeDA, cadaverine), and 1,6-hex-
anediamine (HDA), two polyamines: spermidine (SpermD)
and spermine (SperM), and three aromatic amines, hista-
mine (HistA), tryptamine (TryptA), and phenethylamine
(PhenA), a total 10 amines, were chosen as sensing targets
(Scheme 1b). Addition of each amine (10 mm) to a dichloro-
methane solution of 1 (10 mm) turned on the fluorescence of
the solution, but the extent of the fluorescence change was
dependent on the amines (Figure 2). For instance, addition
of the a,w-diamines, except for HDA, which differ only by a
methylene unit, increased the fluorescence with increasing
chain length of the amines. On the other hand, 1 showed a
high fluorescence response to the polyamines. Upon addi-
tion of the aromatic amines, however, only a weak fluores-
cence was observed. The unique chromic responses from 1
toward the amines resulted from multiple inter- and intra-
molecular contacts between the carboxylic acid side chains
on the TPE and the amine through electrostatic and/or hy-
drogen-bonding interactions, which seem to be associated
with the pKa value of each amine. The fluorescence respons-
es of 1 toward the amines were visually evident to the
naked eye, as shown in the inset in Figure 2a.
The fluorescence response patterns at 480 nm for TPEs 1–
3 against the 10 amines are shown in Figure 2b.[23] The three
TPEs exhibited different response patterns against the
amines resulting from the different interactions with the
amines. Therefore, we expected that these different fluores-
cence responses of the three TPEs against the amines could
be used to discriminate the amines. To illustrate the capabil-
ity of this approach, we performed a statistical analysis of
the fluorescence-response pattern. Linear discriminant anal-
ysis (LDA) is a statistical method to find the linear combi-
nation of features that best separates two or more classes of
objects.[24] The optical responses from the three TPEs 1–3
were monitored upon addition of the 10 different amines at
two different concentrations (10 and 50 mm). Eight replicates
were assayed for each amine at each concentration, for a
total of 48 measurements for each amine. Thus, 480 meas-
Figure 2. a) Fluorescence spectra of 1 (10 mm) upon addition of EDA,
PrDA, BDA, PeDA, HDA, SpermD, SperM, HistA, TryptA, and PhenA
in dichloromethane (lex =350 nm). The inset shows photographs of 1
(10 mm) and the mixture with BDA, SpermD, and HistA (10 mm, from left
to right) in a dichloromethane solution under irradiation with UV light
at a wavelength of 365 nm. b) Fluorescence-response patterns of TPEs 1–
3 (10 mm) monitored at 480 nm fluorescence intensity against the amine
analytes (10 mm) and pKa values of the amines. The assay 1 was per-
formed in dichloromethane, and the assays 2 and 3 were performed in di-
chloromethane/hexane (v/v 1:1). c) Canonical scores plot for the first two
factors of fluorescence-response patterns of TPEs 1–3 (10 mm) against the
amine analytes.
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Fluorometric Sensing of Biogenic Amines
FULL PAPER
urements overall (3 TPEsꢁ10 analytesꢁ2 concentrationsꢁ8
replicates) were analyzed by using LDA. Figure 2c shows
the projection of the LDA results in two dimensions. The
first two canonical factors contained 80.1 and 16.9% of the
variation, respectively, representing 97.0% in total. The can-
onical patterns were clustered into 10 different groups, al-
though the groupings were subtle for some amines. In this
plot, the a,w-diamines except EDA and the polyamines are
at the middle right and top right, respectively, whereas the
aromatic amines are at the left. The LDA analysis was even
able to differentiate the 10 amines. The leave-one-out clas-
sification was used to estimate the predictive ability of the
LDA model and showed the classification accuracy to be
98%, correctly identifying 78 out of the 80 samples.
Quantification of histamine concentration: The LDA plot
yielded only a qualitative assessment to classify the analytes.
We next demonstrated that the fluorescence response can
be used to quantify the amount of the biogenic amine pres-
ent in a fish sample. HistA is the most prevalent biogenic
amine in tuna fish and potentially hazardous to health.
When tested in a “tuna fish matrix”, extracting with di-
chloromethane/hexane (v/v 1:1) from canned tuna fish,
spiked with HistA, addition of 2 increased the fluorescence
at 480 nm (Figure 3a). As shown in the inset in Figure 3b,
the “turn-on” fluorescence was clearly observable by the
naked eye even at a HistA concentration of 50 ppm. The
fluorescence intensity at 480 nm increased linearly with the
HistA concentration in the range of 0–100 ppm (Figure 3b),
in which the line obtained could be used for a calibration
curve for quantification of the amount of HistA in the ana-
lyte. Because the U.S. Food and Drug Administration
(FDA) set a safe concentration level of HistA at 50 ppm
Figure 3. a) Fluorescence spectra of 2 (10 mm) upon addition of HistA in
a “tuna fish matrix” of dichloromethane/hexane (v/v 1:1) (lex =350 nm).
b) Changes of the fluorescence intensities at 480 nm of 2 upon addition
of HistA. The inset shows photographs of 2 (10 mm) and the mixture with
HistA (0, 20, 50, and 100 mm, from left to right) in a “tuna fish matrix” of
dichloromethane/hexane (v/v 1:1) under irradiation with UV light with a
wavelength of 365 nm.
ACHTUNGTRENNUNG
Experimental Section
Conclusion
Measurements: 1H and 13C NMR spectra were recorded by using a
Bruker AVANCE DPX 300 FT-NMR spectrometer at 300 and
75.4 MHz, respectively. 1H and 13C chemical shifts were referenced to sol-
vent residues. FAB mass spectra were obtained with a JEOL JMS-700
mass spectrometer. Melting points were measured on a Micro melting
point apparatus As-One IA9100. UV/Vis spectra were recorded by using
an Agilent 8453 diode array spectrometer. Fluorescence spectra were re-
corded by using a Hitachi F-4500 spectrometer.
We have demonstrated a fluorometric sensing array for de-
tection and identification for biogenic amines by using car-
boxylic acid modified TPEs 1–3 based on the AIE mecha-
nism. In the sensing studies, the three TPEs 1–3 revealed
unique fluorescence response patterns against 10 amines, in-
cluding biogenic amines. The response patterns were classi-
fied by using LDA with 98% classification accuracy for the
amines. Additional information about HistA concentration
as an example was assessed by the further analysis of the
fluorescence intensity in a “tuna fish matrix”, demonstrating
a test for food freshness and quality. This sensing array is a
highly sensitive and convenient detection method for bio-
genic amines at hazardous levels. Their detection could be
used advantageously, for example, for health and food
safety, which are particularly attractive for on-site use. Fur-
ther experiments are required to demonstrate the practical
use of this assay, for example, testing in a more complex en-
vironment. Further study is in progress.
Materials: All manipulations involving air and moisture-sensitive com-
pounds were carried out under an atmosphere of dry nitrogen. All sol-
vents and reagents were of reagent quality, purchased from commercial
sources and used without further purification, unless otherwise noted
below. DMF was dried and distilled from calcium sulfate. Tuna used for
the sensing study was purchased from a local supermarket and was di-
rectly used.
Synthesis of 1:[26] n-Butyllithium (1.65m in hexane, 2.70 mL, 4.46 mmol)
was added to a THF solution (15 mL) of 4[27] (1.00 g, 2.04 mmol) at
À788C and stirred for 30 min at this temperature. The mixture was
added to dry ice (ca. 50 g) and stirred for 2 h. H2SO4 (1.5m, 10 mL) was
added to the mixture and the solution was extracted with ethyl acetate
(70 mLꢁ3). The organic layer was washed with a saturated aqueous solu-
tion of NaCl (70 mL) and dried over anhydrous Na2SO4. After filtration
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T. Sanji, M. Tanaka and M. Nakamura
and removal of the solvent, ethyl acetate (150 mL) was added to the resi-
due. The organic layer was washed with a saturated aqueous solution of
NaHCO3 (150 mL). The aqueous layer was made acid with 15% HCl and
the solution was extracted with ethyl acetate (70 mLꢁ3). The organic
layer was washed with a saturated aqueous solution of NaCl (70 mL) and
dried over anhydrous Na2SO4. After filtration and removal of the solvent,
1 (cis/trans mixture) was obtained (0.663 g, 1.58 mmol, 77%). Pale-yellow
solid; m.p. 242.0–3408C (decomp.); 1H NMR (300 MHz, [D6]acetone):
d=7.06–7.09 (m, 8H; ArH), 7.15–7.20 (m, 20H; ArH), 7.81 (AA’BB’,
J=8.4 Hz, 4H; ArH), 7.82 ppm (AA’BB’, J=8.4 Hz, 4H; ArH);
13C NMR (75 MHz, [D6]acetone): d=127.9, 128.0, 128.8, 128.9, 129.6,
129.7, 130.0, 130.1, 131.87, 131.90, 131.98, 132.03, 142.38, 142.42, 143.6,
143.7, 149.0, 149.1, 167.27, 167.31 ppm; HRMS (FAB, matrix=3-nitro-
benzyl alcohol): m/z: calcd for C28H20O4: 420.1362 [M]+; found: 420.1364.
solution of NaCl (50 mLꢁ2) and dried over anhydrous MgSO4. After fil-
tration and removal of the solvent, the residue (0.822 g) was purified by
chromatography (SiO2, CH2Cl2/ethyl acetate 10:1) to give 8 (cis/trans
mixture, 0.612 g, 0.864 mmol, 63%). Yellow oil; 1H NMR (CDCl3,
300 MHz): d=1.42 (s, 9H; tBu), 1.43 (s, 9H; tBu), 2.50 (t, J=6.3 Hz, 4H;
CH2COO), 2.51 (t, J=6.3 Hz, 4H; CH2COO), 3.72–3.78 (m, 16H;
CH2CH2COO+ArOCH2CH2), 4.00 (t, J=6.0 Hz, 4H; ArOCH2), 4.01 (t,
J=6.6 Hz, 4H; ArOCH2), 6.62 (AA’BB’, J=8.7 Hz, 8H; Ar), 6.89
(AA’BB’, J=8.7 Hz, 8H; Ar), 6.96–7.10 ppm (m, 20H; ArH); 13C NMR
(75 MHz, CDCl3): d=28.1 (ꢁ2), 36.2 (ꢁ2), 67.0 (ꢁ2), 69.43, 69.44, 80.6
(ꢁ2), 113.6, 113.7, 126.1 (ꢁ2), 127.5, 127.6, 131.3, 131.4, 132.43, 132.45,
136.48, 136.50, 139.6 (ꢁ2), 144.1, 144.2, 157.1 (ꢁ2), 170.8 ppm (ꢁ2);
HRMS (FAB, matrix=3-nitrobenzyl alcohol): m/z: calcd for C44H52O8:
708.3662 [M]+; found: 708.3658.
Synthesis of 2: A THF solution (10 mL) of 5[18a] (2.00 g, 3.15 mmol) was
added to Mg (0.459 g, 18.9 mmol) in THF (1.5 mL). After refluxing for
30 min, the solution was added via syringe to dry ice (ca. 50 g) and the
mixture was stirred for 2 h. H2SO4 (1.5m, 20 mL) was added to the mix-
ture and the solution was extracted with ethyl acetate (100 mLꢁ3). The
organic layer was washed with a saturated aqueous solution of NaCl
(100 mL) and dried over anhydrous Na2SO4. After filtration and removal
of the solvent, ethyl acetate (100 mL) was added to the residue (1.70 g).
The organic layer was washed with a saturated aqueous solution of
NaHCO3 (100 mL). The aqueous layer was made acid with 15% HCl
(50 mL) and the solution was extracted with ethyl acetate (70 mLꢁ3).
The organic layer was washed with a saturated aqueous solution of NaCl
(100 mL) and dried over anhydrous Na2SO4. After filtration and removal
of the solvent, 2 (cis/trans mixture) was obtained (1.07 g, 1.90 mmol,
60%). Pale-yellow solid; m.p. 56.5–78.88C; 1H NMR (CDCl3, 400 MHz):
d=1.77–1.81 (m, 16H; OCH2CH2 +CH2CH2COOH), 2.41 (t, J=5.1 Hz,
4H; CH2COOH), 2.42 (t, J=5.1 Hz, 4H; CH2COOH), 3.87 (t, J=4.5 Hz,
4H; OCH2), 3.90 (t, J=4.5 Hz, 4H; OCH2), 6.58 (AA’BB’, J=6.6 Hz,
4H; ArH), 6.62 (AA’BB’, J=6.6 Hz, 4H; ArH), 6.88 (AA’BB’, J=
6.6 Hz, 4H; ArH), 6.91 (AA’BB’, J=6.6 Hz, 4H; ArH), 6.98–7.09 (m,
20H; ArH), 11.06 ppm (brs, 4H, COOH); 13C NMR (75 MHz, CDCl3):
d=21.3 (ꢁ2), 28.5 (ꢁ2), 33.6 (ꢁ2), 67.0 (ꢁ2), 113.4, 113.5, 126.1 (ꢁ2),
127.5, 127.6, 131.3, 131.4, 132.5 (ꢁ2), 136.3 (ꢁ2), 139.6 (ꢁ2), 144.2 (ꢁ2),
157.2 (ꢁ2), 180.0 ppm (ꢁ2); elemental analysis calcd for C36H36O6: C
76.57, H 6.43; found: C 76.49, H 6.24; HRMS (FAB, matrix=3-nitroben-
zyl alcohol): calcd for C36H36O6: 564.2512 [M]+; found: 564.2513.
Synthesis of 3: A mixture of 8 (1.9 g, 2.79 mmol) and formic acid (40 mL)
was stirred at RT for 7 h. After evaporation, 3 (cis/trans mixture) was ob-
tained (1.63 g, 2.73 mmol, 98%). Yellow gumlike solid; H NMR (CDCl3,
1
300 MHz): d=2.63 (t, J=6.3 Hz, 8H; CH2COO), 3.77–3.83 (m, 16H;
CH2CH2COO+ArOCH2CH2), 4.01 (t, J=5.7 Hz, 8H; ArOCH2), 4.02 (t,
J=6.6 Hz, 4H; ArOCH2), 6.61 (AA’BB’, J=8.7 Hz, 4H; Ar), 6.64
(AA’BB’, J=8.7 Hz, 4H; Ar), 6.88 (AA’BB’, J=8.7 Hz, 4H; Ar), 6.89
(AA’BB’, J=8.7 Hz, 4H; Ar), 6.99–7.08 (m, 20H; ArH), 8.99 ppm (brs,
4H; COOH); 13C NMR (75 MHz, CDCl3): d=34.8, 34.9, 66.4 (ꢁ2), 66.9,
67.1, 69.4, 69.5, 113.6, 113.7, 126.2 (ꢁ2), 127.5, 127.6, 131.32, 131.34,
132.4, 132.5, 136.59, 136.64, 139.6, 139.7, 144.0, 144.1, 156.97, 157.02,
177.0, 177.5 ppm; HRMS (FAB, matrix=3-nitrobenzyl alcohol): m/z:
calcd for C36H36O8: 596.2410; found: 596.2406.
Sample preparation for sensing studies: A typical example is as follows:
A solution (5 mL) of a mixture of 1 (10 mm) and histamine (0–50 mm) in
CH2Cl2, prepared from stock solutions of 1 and histamine in CH2Cl2
(100 mm) was vigorously stirred for 3 min. After standing for 10 min, the
solution was subjected to the fluorescence measurement (lex =350 nm,
scan speed=15 nmminÀ1).
Data analysis: Fluorescence data was analyzed by using LDA with Systat
(Systat Software, 2009, ver. 13.00.05).
Quantification of histamine concentration: A mixture of canned tuna fish
(54.7 g) in hexane/dichloromethane (v/v 1:1, 200 mL) was ultrasonicated
for 10 min at room temperature. The obtained solution (100 mL) was
centrifuged at 3000 rpm, and the supernatant was filtered with an
0.45 mm pore-size membrane (“tuna fish matrix”). A solution (5 mL) of a
mixture of stock solutions of 2 (0.5 mL, 100 mm) and histamine (0–
2.0 mL, 100 ppm) in hexane/dichloromethane (v/v 1:1) and the “tuna fish
matrix” (1.0 mL) was vigorously stirred for 3 min. After standing for
10 min, the solution was subjected to the fluorescence measurement.
Synthesis of 7: p-Toluene sulfonic acid (56.3 g, 295 mmol) was added to a
mixture of 3-(2-hydroxyethoxy)propionic acid tert-butyl ester[28] (28.0 g,
147 mmol) and pyridine (300 mL) at 08C. The mixture was stirred for 3 h
at RT and poured into HCl (1n, 300 mL). The solution was extracted
with CH2Cl2 (200 mLꢁ3). The organic layer was washed with a saturated
solution of NaCl (200 mLꢁ2) and dried over anhydrous MgSO4. After
filtration and removal of the solvent, the residue was purified by chroma-
tography (SiO2, CH2Cl2/ethyl acetate 10:1) to give 7 (28.6 g, 83.0 mmol,
56%). White solid; m.p. 53.7–55.18C; 1H NMR (CDCl3, 300 MHz): d=
1.41 (s, 9H; tBu), 2.39 (t, J=6.6 Hz, 2H; CH2COO), 2.43 (s, 3H;
ArCH3), 3.61 (t, J=4.8 Hz, 2H; CH2CH2COO), 3.61 (t, J=6.6 Hz, 2H;
TsOCH2CH2), 4.12 (t, J=4.8 Hz; TsOCH2), 7.20 (d, J=8.4 Hz; ArH),
7.77 ppm (d, J=8.4 Hz; ArH); 13C NMR (75 MHz, CDCl3): d=21.6, 28.0,
36.1, 66.9, 68.3, 69.1, 80.7, 128.0, 129.8, 132.9, 144.8, 170.6 ppm; HRMS
(FAB, matrix=3-nitrobenzyl alcohol): m/z: calcd for C16H25O6S: 345.1372
[M+H]+; found: 345.1369.
Acknowledgements
This work was supported in part by the Management Expenses Grants
for National Universities Corporations “Nano-Macro Materials, Devices
and System Research Alliance” from the Ministry of Education, Culture,
Sports, Science and Technology of Japan (MEXT).
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Synthesis of 8:
A 7 (4.68 g,
mixture of 6[18b] (2.25 g, 6.18 mmol),
13.6 mmol), and K2CO3 (5.13 g, 37.1 mmol) in acetone (100 mL) was re-
fluxed for 3 days. After filtration and evaporation, water (200 mL) was
added to the mixture. The solution was extracted with CH2Cl2 (100 mLꢁ
3) and the organic layer was washed with a saturated solution of NH4Cl
(100 mL) and NaCl (100 mL) and dried over anhydrous MgSO4. After fil-
tration and removal of the solvent, the residue (5.17 g) was purified by
chromatography (SiO2, CHCl3/ethyl acetate 30:1) to give a mixture of 7
and 8 (4.53 g). LiBr (2.69 g, 30.9 mmol) was added to the mixture of 7
and 8 (1.00 g) in acetone (10 mL) at À68C and stirred at RT for 21 h.
Water (30 mL) was added to the mixture and the solution was extracted
with CH2Cl2 (50 mLꢁ3). The organic layer was washed with a saturated
5348
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Chem. Eur. J. 2011, 17, 5344 – 5349

Fluorometric Sensing of Biogenic Amines
FULL PAPER
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Received: November 15, 2010
Revised: December 25, 2011
Published online: March 24, 2011
Chem. Eur. J. 2011, 17, 5344 – 5349
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5349