Synthesis and evaluation of stilbene derivatives as a potential imaging agent of amyloid plaques

Article abstract of DOI:10.1016/j.bmc.2010.06.044

Fluorescence probes that can detect Aβ (β-amyloid peptide) plaque are important tools for diagnosis of Alzheimer's disease (AD), and 4-N-methylamino-4′-hydroxystilbene (SB-13) is one of the promising candidate molecules. We report here the synthesis of SB-13 derivatives that consist of various electron donating/withdrawing moieties and distinct size of N-substituents. The synthesized compounds were screened for detection of Aβ40 fibrils in vitro. Four compounds exhibited more than sixfold intensity increase, and they were further analyzed for detail bindings and Aβ plaque imaging. Among these molecules, compound 42 meets two critical requirements for imaging agent; high fluorescence responsiveness and strong binding affinity. This compound showed more than 25-fold increase with the dissociation constant of 1.13 ± 0.37 μM. In AD mouse brain tissue, 42 selectively stained Aβ plaque, more specifically peripheral regions of Aβ plaque. This finding demonstrated its potential use as brain-imaging agents for AD studies.

Full text of DOI:10.1016/j.bmc.2010.06.044

Bioorganic & Medicinal Chemistry 18 (2010) 7724–7730
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and evaluation of stilbene derivatives as a potential imaging agent
of amyloid plaques
Myeng Chan Hong a,c, Yun Kyung Kim b,f, Jae Yong Choi d, Si Qiang Yang e, Hakjune Rhee c, Young Hoon Ryu d,
Tae Hyun Choi a, Gi Jeong Cheon a, Gwang Il An a, Hye Yun Kim g, Youngsoo Kim g, Dong Jin Kim g,
a,
Jun-Seok Lee b,f, Young-Tae Chang b,e, , Kyo Chul Lee
*
*
a Molecular Imaging Research Center, Korea Institute of Radiological and Medical Sciences, 215-4, Seoul 139-706, Republic of Korea
b Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
c Department of Chemistry and Applied Chemistry, Hanyang University, 1271 Sa-3-Dong Sanrgok-Gu, Ansan, Kyunggi-Do 426-791, Republic of Korea
d Department of Nuclear Medicine, Yonsei University College of Medicine, Gangnam Severance Hospital, 612 Eonjuro, Kangnam-Gu, Seoul 135-720, Republic of Korea
e Laboratory of Bioimaging Probe Development, Singapore Bioimaging Consortium, Agency for Science, Technology and Research (AꢀSTAR), Biopolis, Singapore 138667, Singapore
f Life/Health Division, Integrated Omics Center, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
g Life/Health Division, Neuro-medicine Center, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Fluorescence probes that can detect Ab (b-amyloid peptide) plaque are important tools for diagnosis of
Alzheimer’s disease (AD), and 4-N-methylamino-40-hydroxystilbene (SB-13) is one of the promising can-
didate molecules. We report here the synthesis of SB-13 derivatives that consist of various electron donat-
ing/withdrawing moieties and distinct size of N-substituents. The synthesized compounds were screened
for detection of Ab40 fibrils in vitro. Four compounds exhibited more than sixfold intensity increase, and
they were further analyzed for detail bindings and Ab plaque imaging. Among these molecules, compound
42 meets two critical requirements for imaging agent; high fluorescence responsiveness and strong bind-
ing affinity. This compound showed more than 25-fold increase with the dissociation constant of
Received 29 December 2009
Revised 10 June 2010
Accepted 15 June 2010
Available online 19 June 2010
Keywords:
Alzheimer’s disease (AD)
b-Amyloid peptide (Ab)
Fluorescence imaging probe
1.13 0.37 lM. In AD mouse brain tissue, 42 selectively stained Ab plaque, more specifically peripheral
regions of Ab plaque. This finding demonstrated its potential use as brain-imaging agents for AD studies.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
emission tomography (PET) imaging of Ab plaques in AD patients.
Also, IMPY (6-iodo-2-(40-dimethylamino)phenyl-imidazo[1,2-
Alzheimer’s disease (AD) is a common neurological disease of
chronic dementia, memory loss, and cognitive impairment. Central
to the neuropathology of AD is the deposition of polymeric pep-
tide/protein deposits, composed of b-amyloid peptide (Ab) and tau
protein.1 The fibrillar aggregates of amyloid peptides, Ab40 and
Ab42, are major metabolic peptides derived from amyloid precursor
protein found in senile plaques and cerebrovascular amyloid depos-
its in AD patients.2 For these reasons, an effective detection of Ab pla-
ques will be an important tool for AD diagnosis.3,4 The Ab imaging
probes have been provided a way for monitoring Ab plaque burden
following the disease progression. Several 11C-, 18F- and 123I-labeled
tracers, such as benzothiazole derivative, 6-OH-BTA-1 ([N-methyl-]
2-(40-methylaminophenyl)-6-hydroxybenzothiazole, 11C), and
stilbene derivative, SB-13 (4-N-methylamino-40-hydroxystilbene,
11C) FDDNP (2-(1-{6-[(2-[18F]fluoroethyl)(methyl)amino]2-naph-
thyl}ethylidene)malononitrile, 18F) have been reported for positron
a]pyridine) and TZDM (2-[40-dimethylaminophenyl]-6-iodobenzo-
thiazole) for radio-iodinated probes have been reported for single-
photon emission computed tomography (SPECT) imaging.5–14
Among them, stilbene derivatives showed a broad range of biologi-
cal responses such as anti-leukemic, anti-bacterial, anti-fungal, anti-
platelet aggregation, coronary vasodilator activities and anti-cancer
activities.15 SB-13 is one of the promising lead compound for Ab pla-
que detection, however, its application has been limited in PET
imaging due to its strong binding affinity to amyloid aggregates
and low fluorescence responses.7c,16 In this report, we describes sys-
tematic modification of SB-13 and their biological assays to discover
a fluorescence turn-on sensor using Ab40 fibrils and AD mouse brain
sections (Fig. 1).
HO
A
B
CH3
N
* Corresponding authors. Tel.: +82 2 970 1369; fax: +82 2 970 2409 (K.C.L.); tel.:
+65 6516 6774; fax: +65 6779 1691 (Y.-T.C.).
H
E-mail addresses: chmcyt@nus.edu.sg (Y.-T. Chang), kyochul@kirams.re.kr (K.C.
Lee).
Figure 1. Structure of the lead compound SB-13.
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.06.044

M. C. Hong et al. / Bioorg. Med. Chem. 18 (2010) 7724–7730
7725
Table 1
2. Results and discussion
2.1. Chemical synthesis
Decoding table of compounds; *marked stilbene compounds are reported here first
time
Compound
R1
R2
Compound
R1
R2
The stilbene derivatives (13–44) were prepared by a Wads-
worth–Emmons reaction with preference of trans-stilbenes as prod-
ucts (Scheme 1).17 Various diethyl phosphates derivatives (1–12)
were prepared in high yield by the condensation of bromo benzyl
derivatives and triethyl phosphite at 80 °C for 17 h. N,N-Dimethyl
stilbene derivatives (13–24) were prepared conjugation of diethyl
phosphates derivatives (1–12) and 4-(dimethylamino)benzalde-
hyde using sodium hydride, giving the desired products with
8–95% yields.
Otherstilbenederivatives(25–41) werealso preparedin a similar
manner by conjugation of diethyl phosphates derivatives (1–12)
with 4-(N-methyl-N-2-hydroxyethyl) benzaldehyde or 4-(N-methyl
-N-2-cyanoethyl) benzaldehyde giving the products with 20–48%
yields. While most of the products were obtained as expected struc-
tures, weobservedhydrolyzedproductsfromthreereactionswith4-
(N-methyl-N-2-cyanoethyl) benzaldehyde (42–44). Among 32 stil-
bene derivatives, 22 compounds are newly reported in Table 1).
1
2
3
4
5
6
7
8
9
10
11
12
13*
14
15
16
I
II
23
24
XI
XII
X
A
A
B
C
B
C
B
C
B
C
B
C
B
C
B
B
B
C
B
D
D
D
III
IV
V
VI
VII
VIII
IX
X
25*
26*
27*
28*
29*
30
31
32
33*
34*
35*
36*
37
38
39
40
X
XI
XI
XII
XII
VII
VII
VIII
VIII
IX
IX
I
III
IV
IV
VI
IX
I
*
*
*
XI
XII
I
A
A
A
A
A
A
A
A
A
A
II
*
*
*
*
III
IV
V
VI
VII
VIII
IX
X
*
17
18
19*
20
21
22
41*
42*
43*
44
II
2.2. Screening against Ab plaques and AD mouse brain
The synthesized 32 stilbene derivatives were tested with syn-
thetic Ab40 aggregates for their fluorescence response. Among
tested 32 compounds, four compounds showed over sixfold in-
FAb/F0 >111) and higher fluorescence emission increment than
BTA-1 (FAb/F0 = 4.1, KD = 0.30 M) in our measurement.
l
Encouraged by these outstanding properties, we further tested
the applicability of compound 42 in the fluorescence tissue imaging
using AD mouse brain sections. As compound 42 displays blue fluo-
rescence, ThT (green) was used for counter staining of amyloid pla-
ques. Compound 42 specifically stained at Ab plaque sites and
showed good colocalization with ThT-labeling in 98 plaques assayed
in two brain sections (Fig. 2C). It is also noteworthy that compound
42 stains slightly broader regions than ThT and it is better imaging
crease at 30 lM concentrations of Ab40 fibril and further tested
for their binding constants against Ab40. The spectroscopic prop-
erties of selected compounds were summarized in Table 2. Prom-
isingly, one of the compounds, compound 42, meets two critical
requirements for fluorescence imaging probe; high fluorescence
responsiveness (FAb/F0 >25-fold) and strong binding affinity
(1.13 0.37
lM). Compared with the conventional Ab probes,
compound 42 exhibited stronger bindings than ThT (KD = 2.3
lM,
Scheme 1. Reaction scheme for synthesis of stilbene derivatives. Reagents and conditions: (a) triethylphosphite, 80 °C, 17 h; (b) NaH, benzaldehyde (4-(dimethyl-
amino)benzaldehyde, 4-(N-methyl-N-2-hydroxyethyl) benzaldehyde, or 4-(N-methyl-N-2-cyanoethyl) benzaldehyde), THF, 80 °C, 5 h.

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M. C. Hong et al. / Bioorg. Med. Chem. 18 (2010) 7724–7730
Table 2
Structure and properties of primary hit compounds from in vitro screening
Code
Structure
kex (nm)
kem (nm)
Fold (FAb/F0)a
KD (mean SD) (l
m)b
33
350
450
8.91
2.89 2.42
35
42
44
350
350
350
440
440
440
15.7
25.8
9.30
1.84 0.95
1.13 0.37
17.9 7.66
a
Fold changes values were calculated using fluorescence emission intensity at kem of each dye (10
measurement).
lM dye and 30 lM amyloid fibril were used for fold change
b
A non-linear regression analysis was performed in GraphPad Prism fitting a one-site binding model to the binding data (5 replication experiments, N = 5).
Figure 2. A fluorescent imaging probe for Ab plaque. (A) Fluorescence spectra of compound 42 with Ab40 fibril. (B) Non-linear regression analysis at emission maxima
(440 nm). The apparent dissociation constant, KD, was determined to be 1.13 0.37
lM. (C) Labeling of amyloid deposits in a AD mouse brain section with compound 42
(cyanine) and (D) A magnified image of an amyloid deposit labeled with compound 42 (cyanine) and ThT (green).
agent than ThT for peripheral regions of Ab plaque (Fig. 2D). There-
rescence response (over 25-fold) and binding affinity (1.13 lM) to
fore, we believe it would be a useful imaging tool for AD study.
Ab40 aggregates. Compound 42 demonstrated its excellent capa-
bility of imaging Ab fibrils in AD mouse brain with good colocaliza-
tion with ThT. Based on their delicately high binding affinity to
Ab40 aggregates, this novel stilbene analogue can be a good alter-
native candidate for a fluorescence imaging agent to study Alzhei-
mer’s disease.
3. Conclusions
We synthesized 32 stilbene derivatives of the Ab plaque ligand,
SB13, and identified compound 42, which exhibited a strong fluo-

M. C. Hong et al. / Bioorg. Med. Chem. 18 (2010) 7724–7730
7727
m-nitrobenzylalcohol): Calcd for C11H16FO3P: 247.0899. Found:
247.0900 (+0.1 ppm deviation).
4. Experimental
4.1. Chemistry
4.1.2.6. 4-Fluoro-1-diethylphosphonomethyl-benzene (6). Yield:
98%; 1H NMR (300 MHz, CDCl3): d 7.05 (m, 2H), 6.77 (m, 2H), 3.79
(m, 4H), 2.89 (d, J = 21.3 Hz, 2H), 1.01 (t, J = 7.1 Hz, 6H); 13C NMR
(75 MHz, CDCl3): 161.58 (J = 243.8 Hz), 130.56, 126.76, 114.54,
61.29 (J = 6.7 Hz), 32.46 (J = 138.2 Hz), 15.42; HRMS (FAB+, m-
4.1.1. General
Solvents and starting materials for synthesis were purchased
from Aldrich and used as received without purification. 1H NMR
spectra were recorded on Bruker Advance (1H NMR: 300 MHz)
spectrometer, and chemical shifts are reported in parts per million
downfield from internal tetramethylsilane. Mass spectra were re-
corded on a JEOL, JMS-AX505WA and melting points were deter-
mined on a Barnstead International 1002D.
nitrobenzylalcohol): Calcd for
247.0900 (+0.1 ppm deviation).
C11H16FO3P: 247.0899. Found:
4.1.2.7. 2-Bromo-1-diethylphosphonomethyl-benzene (7). Yield:
93%; 1H NMR (300 MHz, CDCl3): d 7.56 (d, J = 8.0 Hz, 1H), 7.46 (m,
1H), 7.27 (m, 1H), 7. 11 (m, 1H), 4.05 (m, 4H), 3.41 (d, J = 21.9 Hz,
2H), 1.26 (t, J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 132.89
(J = 2.9 Hz), 131.84 (J = 8.9 Hz), 131.62 (J = 5.0 Hz), 128.45
(J = 3.5 Hz), 127.43 (J = 3.3 Hz), 124.85 (J = 8.8 Hz), 62.20 (J = 6.6 Hz),
33.39 (J = 138.1 Hz), 16.30 (J = 6.0 Hz); HRMS (FAB+, m-nitrobenzylal-
cohol): Calcd for C11H16BrO3P: 307.0099. Found: 307.0100 (+0.5 ppm
deviation).
4.1.2. Preparation of diethylphosphonomethyl-benzene (1–12)
Benzyl bromide derivatives (3.35 mmol) were added to tri-
ethylphosphite (2.57 mmol) in the 50 mL round bottom flask at
room temperature. The reaction mixture was heated to 80 °C for
17 h. After cooling to room temperature, the resulting crude prod-
uct was fractional distillated to remove triethylphosphite in vacuo.
Purification by silica gel column chromatography (70% EtOAc/hex-
ane) gave a product as colorless oil.
4.1.2.8. 3-Bromo-1-diethylphosphonomethyl-benzene (8). Yield:
93%; 1H NMR (300 MHz, CDCl3): d 7.45 (m, 1H), 7.39 (m, 1H), 7.23
(m, 1H), 7.19 (m, 1H), 4.03 (m, 4H), 3.11 (d, J = 21.7 Hz, 2H), 1.26 (t,
J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 133.98 (J = 8.8 Hz), 132.68
(J = 6.7 Hz), 129.98 (J = 3.2 Hz), 128.39 (J = 3.9 Hz), 122.39
(J = 3.5 Hz), 62.22 (J = 6.7 Hz), 33.38 (J = 137.6 Hz), 16.33 (J = 5.9 Hz);
HRMS (FAB+, m-nitrobenzylalcohol): Calcd for C11H16BrO3P:
307.0099. Found: 307.0108 (+0.3 ppm deviation).
4.1.2.1. 2-Methoxy-1-diethylphosphonomethyl-benzene (1). Yield:
80%; 1H NMR (300 MHz, CDCl3): d 7.31 (m, 1H), 7.22 (m, 1H), 6.89
(m, 2H), 4.02 (m, 4H), 3.83 (s, 3H), 3.25 (d, J = 21.7 Hz, 2H), 1.23 (t,
J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 157.15, 131.19, 128.12,
120.51, 120.19 (J = 7.7 Hz), 110.50, 61.86 (J = 6.4 Hz), 55.43, 26.61
(J = 137.9 Hz), 16.30 (J = 5.6 Hz); HRMS (FAB+, m-nitrobenzylalco-
hol): Calcd for C12H19H4P: 259.1099. Found: 259.1098 (ꢁ0.6 ppm
deviation).
4.1.2.9. 4-Bromo-1-diethylphosphonomethyl-benzene (9). Yield:
93%; 1H NMR (300 MHz, CDCl3): d 7.63 (d, J = 7.9 Hz, 2H), 7.04 (dd,
J = 8.3 Hz, 2.5 Hz, 2H), 4.0 (m, 4H), 3.08 (d, J = 21.7 Hz, 2H), 1.25 (t,
J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 137.58 (J = 2.9 Hz), 131.69
(J = 6.5 Hz), 131.41 (J = 9.1 Hz), 92.31 (J = 4.7 Hz), 62.20 (J = 6.7 Hz),
33.35 (J = 137.6 Hz), 16.36 (J = 5.9 Hz); HRMS (FAB+, m-nitrobenzylal-
cohol): Calcd for C11H16BrO3P: 307.0099. Found: 307.0090 (ꢁ2.9 ppm
deviation).
4.1.2.2. 3-Methoxy-1-diethylphosphonomethyl-benzene (2). Yield:
95%; 1H NMR (300 MHz, CDCl3): d 7.21 (m, 1H), 6.87 (m, 2H), 6.79
(m, 1H), 4.01 (m, 4H), 3.80 (s, 3H), 3.13 (d, J = 21.6 Hz, 2H), 1.26 (t,
J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 159.51 (J = 2.8 Hz), 132.90
(J = 8.9 Hz), 129.34 (J = 2.6 Hz), 122.05 (J = 6.6 Hz), 115.18
(J = 6.4 Hz), 112.40 (J = 3.3 Hz), 62.00 (J = 6.7 Hz), 55.05, 33.69
(J = 137.3 Hz), 16.26 (J = 6.0 Hz); HRMS (FAB+, m-nitrobenzylalcohol):
Calcd for
deviation).
C
12H19H4P: 259.1099. Found: 259.1097 (ꢁ0.9 ppm
4.1.2.10. 2-Iodo-1-diethylphosphonomethyl-benzene (10). Yield:
92%; 1H NMR (300 MHz, CDCl3): d 7.84 (d, J = 8.0 Hz, 1H), 7.47 (m,
1H), 7.30 (m, 1H), 6.92 (m, 1H), 4.05 (m, 4H), 3.41 (d, J = 22.0 Hz,
2H), 1.26 (t, J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 139.39
(J = 2.9), 135.10 (J = 8.7 Hz), 130.41 (J = 5.0 Hz), 128.31 (J = 3.5 Hz),
128.06 (J = 3.2 Hz), 101.04 (J = 9.3 Hz), 61.99 (J = 6.75 Hz), 38.08
(J = 137.5 Hz), 16.12 (J = 6.0 Hz); HRMS (FAB+, m-nitrobenzylalcohol):
4.1.2.3. 4-Methoxy-1-diethylphosphonomethyl-benzene (3). Yield:
94%; 1H NMR (300 MHz, CDCl3): d 7.22 (d, J = 2.4 Hz, 1H), 7.19 (d,
J = 2.4 Hz, 1H), 6.84 (d, J = 8.1 Hz, 2H), 4.00 (m, 4H), 3,78 (s, 3H),
3.08 (d, J = 21.0 Hz, 2H), 1.24 (t, J = 7.1 Hz, 6H); 13C NMR (75 MHz,
CDCl3): 158.52 (J = 3.3 Hz), 130.71 (J = 6.5 Hz), 123.40 (J = 9.2 Hz),
113.96 (J = 2.6 Hz), 62.03 (J = 6.8 Hz), 55.21, 32.74 (J = 138.2 Hz),
16.37 (J = 5.9 Hz); HRMS (FAB+, m-nitrobenzylalcohol): Calcd for
Calcd for
deviation).
C11H16IO3P: 354.9960. Found: 354.9965 (+1.4 ppm
C
12H19H4P: 259.1099. Found: 259.1096 (ꢁ1.3 ppm deviation).
4.1.2.11. 3-Iodo-1-diethylphosphonomethyl-benzene (11). Yield:
91%; 1H NMR (300 MHz, CDCl3): d 7.64 (m, 1H), 7.59 (m, 1H), 7.29
(m, 1H), 7.05 (t, J = 7.8 Hz, 1H), 4.03 (m, 4H), 3.08 (d, J = 21.7 Hz,
2H), 1.26 (t, J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 137.99
(J = 6.6 Hz, 135.32 (J = 3.6 Hz), 133.57 (J = 9.1 Hz), 129.62 (J = 3.0 Hz),
128.51 (J = 6.3 Hz), 93.73 (J = 3.6 Hz), 61.63 (J = 6.7 Hz), 32.62
(J = 137.3 Hz), 15.86; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for
4.1.2.4. 2-Fluoro-1-diethylphosphonomethyl-benzene (4). Yield:
92%; 1H NMR (300 MHz, CDCl3): d 7.36 (m, 1H), 7.22 (m, 1H), 7.07
(m, 2H), 4.05 (m, 4H), 3.20 (d, J = 21.1 Hz, 2H), 1.25 (t, 7.1 Hz, 6H);
13C NMR (75 MHz, CDCl3): 160.82 (J = 244.7 Hz), 131.81
(J = 4.4 Hz), 128.67, 124.11 (J = 3.2 Hz), 119.11, 115.31, 62.18
(J = 6.6 Hz), 27.18 (J = 139.7 Hz), 16.29 (J = 6.1 Hz); HRMS (FAB+,
m-nitrobenzylalcohol): Calcd for C11H16FO3P: 247.0899. Found:
247.0903 (+1.4 ppm deviation).
C11H16IO3P: 354.9960. Found: 354.9970 (+2.8 ppm deviation).
4.1.2.12. 4-Iodo-1-diethylphosphonomethyl-benzene (12). Yield:
98%; 1H NMR (300 MHz, CDCl3): d 7.62 (d, J = 8.1 Hz, 2H), 7.04 (d,
J = 8.3 Hz, 2H), 4.01 (m, 4H), 3.07 (d, J = 21.7 Hz, 2H), 1.24 (t,
J = 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3): 137.20 (J = 2.6 Hz), 131.39
(J = 6.5 Hz), 131.10 (J = 9.2 Hz), 92.02 (J = 4.6 Hz), 61.82 (J = 6.6 Hz),
32.97 (J = 137.3 Hz), 16.09 (J = 5.9 Hz); HRMS (FAB+, m-nitrobenzylal-
cohol): Calcd for C11H16IO3P: 354.9960. Found: 354.9960 (+0.1 ppm
deviation).
4.1.2.5. 3-Fluoro-1-diethylphosphonomethyl-benzene (5). Yield:
96%; 1H NMR (300 MHz, CDCl3): d 7.28 (m, 1H), 7.03 (m, 3H), 4.03
(m, 4H), 3.13 (d, J = 21.6 Hz, 2H), 1.25 (t, J = 7.1 Hz, 6H); 13C NMR
(75 MHz, CDCl3): 162.71 (J = 244.6 Hz), 134.03, 129.92
(J = 8.1 Hz), 125.46 (J = 3.9 Hz), 116.70, 113.86 (J = 20.9 Hz), 62.20
(J = 6.7 Hz), 33.54 (J = 137.9 Hz), 16.32 (J = 5.9 Hz); HRMS (FAB+,

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M. C. Hong et al. / Bioorg. Med. Chem. 18 (2010) 7724–7730
4.1.3. Preparation of styrylbenzene derivatives (13–44)
A sodium hydride (60 w/w, 4.70 mmol) was added to the mix-
ture of diethylphosphonomethyl-benzene derivatives (1–12) and
4-(dimethylamino)benzaldehyde or 4-(N-methyl-N-2-hydroxy-
ethyl)benzaldehyde or 4-(N-methyl-N-2-cyanoethyl)benzaldehyde
in dry THF (30 mL). The reaction mixture was refluxed for 5 h and
cooled to room temperature. The crude product was quenched by
adding water (2 mL), followed by evaporation of solvent in vacuo.
Purification by silica gel column chromatography (16% EtOAc/hex-
ane) gave a product as yellow colored powder.
4.1.3.7. 4-N,N-Dimethyl-20-bromo-stilbene (19). Yield: 17%; mp
107.5–108.7 °C; 1H NMR (300 MHz, CDCl3): d 7.65 (dd, J = 1.5 Hz,
7.9 Hz, 1H), 7.56 (dd, J = 1.2 Hz, 8.0 Hz, 1H), 7.46 (d, J = 8.8 Hz,
2H), 7.30 (m, 1H), 7.24 (s, 1H), 7.05 (dt, J = 1.6 Hz, 7.5 Hz, 1H),
6.99 (d, J = 16.1 Hz, 1H), 6.72 (d, J = 8.8 Hz, 2H), 2.99 (s, 6H); 13C
NMR (75 MHz, CDCl3): 150.37, 137.82, 132.96, 131.50, 127.95,
127.81, 127.41, 126.16, 125.37, 123.70, 122.92, 112.32, 40.41;
HRMS (FAB+, m-nitrobenzylalcohol): Calcd for C16H16BrN:
301.0466. Found: 301.0473 (+2.3 ppm deviation).
4.1.3.8. 4-N,N-Dimethyl-30-bromo-stilbene (20). Yield: 27%; mp
149.9–150.5 °C; 1H NMR (300 MHz, CDCl3): d 7.62 (t, J = 7.4 Hz,
1H), 7.41 (m, 2H), 7.31 (m, 2H), 7.18 (t, J = 7.8 Hz, 1H), 7.04 (d,
J = 16.2 Hz, 1H), 6.81 (d, J = 16.2 Hz, 1H), 6.71 (m, 2H), 2.99 (s,
6H); 13C NMR (75 MHz, CDCl3): 150.29, 140.41, 130.22, 130,01,
129,31, 128.63, 127.76, 125.02, 124.60, 122.78, 122.55, 112.30,
40.37; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for C16H16BrN:
301.0466. Found: 301.0467 (+0.2 ppm deviation).
4.1.3.1. 4-N,N-Dimethyl-20-methoxy-stilbene (13). Yield: 17%;
mp 87.4–88.6 °C; 1H NMR (300 MHz, CDCl3): d 7.58 (d, J = 7.2 Hz,
1H), 7.44 (d, J = 8.6 Hz, 2H), 7.29 (d, J = 16.6 Hz, 1H), 7.19 (t,
J = 7.2 Hz, 1H), 7.05 (d, J = 16.4 Hz, 1H), 6.96 (d, J = 7.4 Hz, 1H),
6.88 (d, J = 8.2 Hz, 1H), 6.71 (d, J = 8.6 Hz, 2H), 3.88 (s, 3H), 2.95
(s, 6H); 13C NMR (75 MHz, CDCl3): 156.53, 149.98, 129.22,
127.64, 127.59, 127.28, 126.53, 125.84, 120.71, 119.06, 112.44,
110.88, 55.52, 40.51; HRMS (FAB+, m-nitrobenzylalcohol): Calcd
for C17H20NO: 253.1467. Found: 253.1466 (ꢁ0.3 ppm deviation).
4.1.3.9. 4-N,N-Dimethyl-40-bromo-stilbene (21). Yield: 11%; mp
234.5–235.6 °C; 1H NMR (300 MHz, CDCl3): d 7.45 (m, 1H), 7.42
(m, 2H), 7.39 (m, 1H), 7.34 (m, 1H), 7.31 (m, 1H), 7.03 (d,
J = 16.3 Hz, 1H), 6.83 (d, J = 16.3 Hz, 1H), 6.71 (d, J = 8.7 Hz, 2H),
3.00 (s, 6H); 13C NMR (75 MHz, CDCl3): 150.22, 137.13, 131.59,
129.51, 127.65, 127.44, 125.26, 122.94, 120.08, 112.36, 40.41;
HRMS (FAB+, m-nitrobenzylalcohol): Calcd for C16H16BrN:
301.0466. Found: 301.0467 (+0.2 ppm deviation).
4.1.3.2. 4-N,N-Dimethyl-30-methoxy-stilbene (14). Yield: 95%;
mp 90.2–91.3 °C; 1H NMR (300 MHz, CDCl3): d 7.41 (m, 2H), 7.25
(m, 2H), 7.08 (m, 1H), 7.02 (s, 1H), 6.89 (d, J = 16.2 Hz, 1H), 6.75
(m, 3H), 3.85 (s, 3H), 2.99 (s, 6H); 13C NMR (75 MHz, CDCl3):
159.82, 150.12, 139.63, 129.48, 129.09, 127.59, 125.57, 124.19,
118.76, 112.38, 111.13, 55.19, 40.43; HRMS (FAB+, m-nitrobenzyl-
alcohol): Calcd for
(ꢁ0.7 ppm deviation).
C17H20NO: 253.1467. Found: 253.1465
4.1.3.10. 4-N,N-Dimethyl-20-iodo-stilbene (22). Yield: 23%; mp
85.6–86.4 °C; 1H NMR (300 MHz, CDCl3): d 7.84 (dd, J = 1.1 Hz,
8.0 Hz, 1H), 7.60 (dd, J = 1.5 Hz, 7.8 Hz, 1H), 7.45 (m, 2H), 7.31
(m, 1H), 7.11 (d, J = 15.9 Hz, 1 Hz), 6.90 (m, 2H), 67.3 (m, 2H),
2.99 (s, 6H); 13C NMR (75 MHz, CDCl3): 150.38, 140.99, 139.53,
131.71, 128.29, 128.07, 127.95, 125.72, 125.30, 112.34, 100.22,
40.41; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for C16H16IN:
349.0327. Found: 349.0333 (+1.6 ppm deviation).
4.1.3.3. 4-N,N-Dimethyl-40-stilbene (15). Yield: 20%; mp 171.9–
173.4 °C; 1H NMR (300 MHz, CDCl3): d 7.40 (t, J = 8.1 Hz, 4H),
6.89 (m, 4H), 6.72 (d, J = 8.6 Hz, 2H), 3.82 (s, 3H), 2.94 (s, 6H);
13C NMR (75 MHz, CDCl3): 158.66, 149.92, 131.05, 127.27,
127.15, 126.82, 126.22, 124.06, 114.07, 112.57, 55.33, 40.55; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C17H20NO: 253.1467.
Found: 253.1461 (ꢁ2.2 ppm deviation).
4.1.3.11. 4-N,N-Dimethyl-30-iodo-stilbene (23). Yield: 32%; mp
161.6–162.2 °C; 1H NMR (300 MHz, CDCl3): d 7.83 (m, 1H), 7.51
(m, 1H), 7.40 (m, 3H), 7.06 (d, J = 7.8 Hz, 1H), 7.01 (d, J = 8.1 Hz,
1H), 6.78 (d, J = 16.2 Hz, 1H), 6.71 (m, 2H), 2.99 (s, 6H); 13C NMR
(75 MHz, CDCl3): 150.27, 140.49, 135.27, 134.68, 130.17, 130.10,
127.74, 125.17, 125.04, 122.41, 112.29, 94.80, 40.37; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C16H16IN: 349.0327.
Found: 349.0328 (+0.1 ppm deviation).
4.1.3.4. 4-N,N-Dimethyl-20-fluoro-stilbene (16). Yield: 57%; mp
122.8–123.7 °C; 1H NMR (300 MHz, CDCl3): d 7.59 (m, 1H), 7.43
(m, 2H), 7.14 (m, 1H), 7.09 (m, 3H), 7.03 (m, 1H), 6.72 (d,
J = 9.0 Hz, 2H), 2.99 (s, 6H); 13C NMR (75 MHz, CDCl3): 160.15
(J = 246.8 Hz), 150.32, 130.94 (J = 4.4 Hz), 127.75, 127.59, 126.47
(J = 3.8 Hz), 126.00 (J = 11.9 Hz), 125.58, 124.08 (J = 3.4 Hz),
116.32 (J = 3.8 Hz), 115.62 (J = 22.1 Hz), 112.33, 40.41; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C16H16FN: 241.1267.
Found: 241.1264 (ꢁ1.3 ppm deviation).
4.1.3.12. 4-N,N-Dimethyl-40-iodo-stilbene (24). Yield: 8%; mp
251.6–252.5 °C; 1H NMR (300 MHz, CDCl3): d 7.63 (m, 2H), 7.40
(m, 2H), 7.21 (m, 2H), 7.03 (d, J = 16.3 Hz, 1H), 6.81 (d,
J = 16.3 Hz, 1H), 6.71 (m, 2H), 2.99 (s, 6H); 13C NMR (75 MHz,
CDCl3): 150.27, 137.74, 137.55, 129.62, 127.73, 127.69, 125.20,
123.00, 112.35, 91.35, 40.40; HRMS (FAB+, m-nitrobenzylalcohol):
4.1.3.5. 4-N,N-Dimethyl-30-fluro-stilbene (17). Yield: 49%; mp
148.9–149.7 °C; 1H NMR (300 MHz, CDCl3): d 7.41 (d, J = 8.8 Hz,
2H), 7.30 (m, 1H), 7.21 (m, 2H), 7.05 (d, J = 16.3 Hz, 1H), 6.89 (m,
2H), 6.72 (d, J = 8.7 Hz, 2H), 3.00 (s, 6H); 13C NMR (75 MHz, CDCl3):
163.22 (J = 242.9 Hz), 150.32, 140.63 (J = 7.8 Hz), 130.11, 129.89
(J = 8.5 Hz), 127.75, 125.12, 123.03 (J = 2.4 Hz), 121.89 (J = 2.1 Hz),
113.30 (J = 21.4 Hz), 112.34, 112.02, 40.38; HRMS (FAB+, m-nitro-
benzylalcohol): Calcd for C16H16FN: 241.1267. Found: 241.1268
(+0.7 ppm deviation).
Calcd for
deviation).
C16H16IN: 349.0327. Found: 349.0334 (+2.0 ppm
4.1.3.13. 4-[N-Methyl-N-(2-hydroxyethyl)]-20-iodo-stilbene (25).
Yield: 40%; 1H NMR (300 MHz, CDCl3): d 7.86 (m, 1H), 7.83 (m,1H),
7.46 (d, 2H), 7.34 (m,2H), 7.15 (d, J = 16.3 Hz, 1H), 6.90 (m, 2H),
6.76 (m, 2H), 3.83 (m, 2H), 3.51 (m, 2H), 3.01 (s, 1H); 13C NMR
(75 MHz, CDCl3): 149.75, 140.91, 139.58, 128.43, 128.36, 128.22,
128.09, 125. 89, 125.80, 112.71, 100.30, 60.23, 55.07, 38.92; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C17H18INO: 379.0433.
Found: 349.0438 (+1.3 ppm deviation).
4.1.3.6. 4-N,N-Dimethyl-40-fluoro-stilbene (18). Yield: 17%; mp
198.6–199.5 °C; 1H NMR (300 MHz, CDCl3): d 7.41 (m, 4H), 7.02
(t, J = 8.9 Hz, 2H), 6.91 (d, J = 12.6 Hz, 2H), 6.72 (d, J = 8.7 Hz, 2H),
2.99 (s, 6H); 13C NMR (75 MHz, CDCl3): 161.81 (J = 244.2 Hz),
150.15, 134.36 (J = 3.1 Hz), 128.58, 127.51, 127.36 (J = 7.8 Hz),
125.59, 123.18, 115.46 (J = 21.5 Hz), 112.45, 40.48; HRMS (FAB+,
m-nitrobenzylalcohol): Calcd for
241.1261 (ꢁ2.2 ppm deviation).
C16H16FN: 241.1267. Found:
4.1.3.14. 4-[N-Methyl-N-(2-cyanoethyl)]-20-iodo-stilbene (26).
Yield: 42%; mp 66.5–67.5 °C; 1H NMR (300 MHz, CDCl3): d 7.86

M. C. Hong et al. / Bioorg. Med. Chem. 18 (2010) 7724–7730
7729
(m, 1H), 7.60 (m, 1H), 7.44 (m, 2H), 7.39 (d, 2H), 7.33 (t, 1H), 7.18
(d, J = 15.9 Hz, 1H), 6.92 (m, 2H), 6.71 (d, 2H), 3.72 (t, 2H), 3.06 (s,
3H), 2.57 (t, 2H); 13C NMR (75 MHz, CDCl3): 147.44, 140.75,
139.62, 131.30, 128.96, 128.44, 128.34, 126.55, 125.89, 118.38,
112.50, 100.38, 48.81, 38.80, 15.38; HRMS (FAB+, m-nitrobenzylal-
cohol): Calcd for C18H17IN2: 388.0436. Found: 388.0443 (+1.6 ppm
deviation).
127.88, 125.71, 124.68, 122.99, 122.84, 112.71, 60.26, 55.08,
38.85; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for
C
17H18BrNO: 331.0572. Found: 331.0570 (ꢁ0.5 ppm deviation).
4.1.3.22. 4-[N-Methyl-N-(2-cyanoethyl)]-30-bromo-stilbene (34).
Yield: 43%; mp 107.7–108.9 °C; 1H NMR (300 MHz, CDCl3): d 7.62
(m, 1H), 7.38 (m, 4H), 7.05 (d, 1H), 6.86 (d, J = 16.3 Hz, 1H), 6.70
(m, 2H), 3.74 (t, 2H), 3.06 (s, 3H), 2.59 (t, 2H); 13C NMR (75 MHz,
CDCl3): 147.39, 130.10, 129.79, 129.65, 128.80, 128.13, 126.43,
124.77, 123.59, 112.48, 48.82, 38.77, 15.38; HRMS (FAB+, m-nitro-
benzylalcohol): Calcd for C18H17BrN2: 340.0571. Found: 340.0578
(+0.9 ppm deviation).
4.1.3.15. 4-[N-Methyl-N-(2-hydroxyethyl)]-30-iodo-stilbene (27).
Yield: 37%; mp 108.5–109.5 °C; 1H NMR (300 MHz, CDCl3): d 7.82
(m, 1H), 7.52 (d, 1H), 7.40 (m, 3H), 7.03 (m, 2H), 6.78 (m, 3H),
3.83 (t, 2H), 3.51 (t, 2H), 3.01 (s, 3H); 13C NMR (75 MHz, CDCl3):
149.73, 140.43, 135.44, 134.78, 130.22, 129.94, 127.87, 125.71,
125.26, 122.84, 112.69, 94.81, 60.23, 55.06, 38.85; HRMS (FAB+,
m-nitrobenzylalcohol): Calcd for C17H18INO: 379.0433. Found:
379.0437 (+0.9 ppm deviation).
4.1.3.23. 4-[N-Methyl-N-(2-hydroxyethyl)]-40-bromo-stilbene
(35). Yield: 36%; mp 183.4–184.9 °C; 1H NMR (300 MHz, CDCl3):
d 7.42 (m, 6H), 6.99 (d, 1H), 6.78 (m, 3H), 3.84 (m, 2H), 3.53 (t,
2H), 3.01 (s, 3H); 13C NMR (75 MHz, CDCl3): 149.67, 137.05,
131.64, 129.31, 127.50, 125.91, 123.34, 120.24, 112.75, 60.25,
55.11, 38.84; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for
4.1.3.16. 4-[N-Methyl-N-(2-cyanoethyl)]-30-iodo-stilbene (28).
Yield: 34%; mp 94.6–96.0 °C; 1H NMR (300 MHz, CDCl3): d 7.82 (m,
1H), 7.71 (m, 1H), 7.42 (m, 4H), 7.07 (m, 2H), 6.82 (d, 1H), 6.67
(m, 3H) 3.73 (t, 2H), 3.06 (s, 3H), 2.58 (t, 2H); 13C NMR (75 MHz,
CDCl3): 147.38, 140.25, 135.62, 132.31, 130.28, 129.68, 128.12,
126.42, 125.36, 123.44, 112.48, 94.85, 48.81, 38.77, 15.39; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C18H17IN2: 388.0436. Found:
388.0432 (ꢁ1.1 ppm deviation).
C
17H18BrNO: 331.0572. Found: 331.0568 (ꢁ1.1 ppm deviation).
4.1.3.24. 4-[N-Methyl-N-(2-cyanoethyl)]-40-bromo-stilbene (36).
Yield: 39%; mp 190.4–192.0 °C; 1H NMR (300 MHz, CDCl3): d 7.43
(m, 6H), 7.04 (d, J = 16.3 Hz, 1H), 6.87 (d, J = 16.3 Hz, 1H), 6.70 (m,
2H), 3.74 (t, 2H), 3.06 (2, 3H), 2.59 (t, 2H); 13C NMR (75 MHz, CDCl3):
147.27, 136.88, 131.68, 129.04, 128.00, 127.57, 126.64, 123.96,
120.46, 118.26, 112.52, 48.85, 38.77, 15.36; HRMS (FAB+, m-nitro-
benzylalcohol): Calcd for C18H17BrN2: 340.0571. Found: 340.0575
(ꢁ0.1 ppm deviation).
4.1.3.17. 4-[N-Methyl-N-(2-hydroxyethyl)]-40-iodo-stilbene (29).
Yield: 31%; mp 201.2–202.8 °C; 1H NMR (300 MHz, CDCl3): d 7.63
(m, 2H), 7.40 (m, 2H), 7.21 (m, 2H), 7.05 (d, J = 16.2 Hz, 1H), 6.78
(m, 3H), 3.84 (t, 2H), 3.51 (t, 2H), 3.02 (s, 3H); 13C NMR (75 MHz,
CDCl3): 149.69, 137.64, 137.59, 129.41, 127.80, 127.78, 125.85,
123.40, 112.74, 91.51, 60.25, 55.10, 38.84; HRMS (FAB+, m-nitroben-
4.1.3.25. 4-[N-Methyl-N-(2-hydroxyethyl)]-20-methoxy-stilbene
(37). Yield: 30%; mp 78.7–79.8 °C; 1H NMR (300 MHz, CDCl3): d
7.58 (m, 1H), 7.44 (m, 2H), 7.23 (m, 2H), 6.96 (m, 3H), 6.78 (m,
2H), 3.83 (m, 5H), 3.50 (t, 2H), 3.00 (s, 3H); 13C NMR (75 MHz,
CDCl3): 156.58, 149.39, 129.01, 127.78, 127.70, 127.17, 125.91,
120.73, 119.49, 112.88, 110.91, 60.23, 55.54, 55.28, 38.86; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C18H21NO2: 283.1572.
Found: 283.1567 (ꢁ1.9 ppm deviation).
zylalcohol): Calcd for
(+0.5 ppm deviation).
C17H18INO: 379.0433. Found: 379.0435
0
4.1.3.18. 4-[N-Methyl-N-(2-cyanoethyl)]-4 -iodo-stilbene (30). Yield:
28%; mp 194.8–196.0 °C; 1H NMR (300 MHz, CDCl3): d 7.65 (m, 2H),
7.43 (m, 2H), 7.25 (m, 2H), 7.05 (d, J = 16.3 Hz, 1H), 7.00 (d, 1H), 6.86
(d, 1H), 6.70 (m, 2H), 3.77 (t, 2H), 3.06 (s, 3H), 2.59 (t, 2H); 13C NMR
(75 MHz, CDCl3): 147.28, 137.63, 137.46, 129.13, 128.03, 127.84,
126.60, 124.04, 118.25, 112.50, 91.75, 48.85, 38,78, 15.36; HRMS (FAB+,
m-nitrobenzylalcohol): Calcd for C18H17IN2: 388.0436. Found: 388.0445
(+2.2 ppm deviation).
4.1.3.26. 4-[N-Methyl-N-(2-hydroxyethyl)]-40-methoxy-stilbene
(38). Yield: 36%; mp 153.4–154.9 °C; 1H NMR (300 MHz, CDCl3):
d 7.39 (m, 4H), 6.82 (m, 6H), 3.82 (m, 5H), 3.56 (t, 2H), 2.99 (s,
3H); 13C NMR (75 MHz, CDCl3): 158.72, 149.30, 130.90, 127.35,
127.18, 126.85, 126.56, 124.42, 114.07, 112.97, 60.23, 55.32,
55.29, 38.84; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for
0
4.1.3.19. 4-[N-Methyl-N-(2-hydroxyethyl)]-2 -bromo-stilbene (31). Yield:
42%; mp 87.9–89.0 °C; 1H NMR (300 MHz, CDCl3): d 7.66 (m, 1H), 7.58
(m, 1H), 7.46 (m, 2H), 7.28 (m, 2H), 7.06 (m, 2H), 6.78 (m, 2H), 3.82 (t,
2H), 3.50 (t, 2H), 3.01 (s, 3H); 13C NMR (75 MHz, CDCl3): 149.76, 137.77,
133.02, 131.37, 128.11, 127.95, 127.49, 126.25, 123.78, 123.28, 112.68,
60.21, 55.04, 38.90; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for
C17H18BrNO: 331.0572. Found: 331.0573 (+0.5 ppm deviation).
C18H21NO2: 283.1572. Found: 283.1579 (+2.5 ppm deviation).
4.1.3.27. 4-[N-Methyl-N-(2-hydroxyethyl)]-20-fluoro-stilbene
(39). Yield: 48%; mp 95.2–96.5 °C; 1H NMR (300 MHz, CDCl3): d
7.60 (m, 1H), 7.43 (m, 2H), 7.10 (m, 5H), 6.80 (m, 2H), 3.82 (m,
2H), 3.51 (t, 2H), 3.01 (s, 3H); 13C NMR (75 MHz, CDCl3): 158.52
(J = 987.9 Hz), 149.70, 130.72 (J = 17.7 Hz), 127.87, 127.84
(J = 34.8 Hz), 126.51 (J = 80.7 Hz), 125.85 (J = 48.3 Hz), 124.06
(J = 13.8 Hz), 116.75 (J = 15.3 Hz), 115.52 (J = 88.2 Hz), 112.73,
60.24, 55.11, 38.86; HRMS (FAB+, m-nitrobenzylalcohol): Calcd
for C17H18FNO: 271.1372. Found: 271.1373 (+0.1 ppm deviation).
0
4.1.3.20. 4-[N-Methyl-N-(2-cyanoethyl)]-2 -bromo-stilbene (32). Yield:
38%; mp 73.7–74.9 °C; 1H NMR (300 MHz, CDCl3): d7.66 (m, 1H), 7.63 (m,
1H), 7.49 (m, 2H), 7.28 (m, 2H), 7.09 (m,1H), 6.99 (d, J = 16.3 Hz 1H), 6.71
(m, 2H), 3.75 (t, 2H), 3.07 (s, 3H), 2.59 (t, 2H); 13C NMR (75 MHz, CDCl3):
149.70, 137.77, 133.03, 127.19, 125.21, 122.48, 122.28, 121.65, 120.47,
118.15, 117.99, 106.66, 43.02, 32.95, 9.5; HRMS (FAB+, m-nitrobenzylalco-
hol): Calcd for C18H17BrN2: 340.0575. Found: 340.0571 (ꢁ1.3 ppm
deviation).
4.1.3.28. 4-[N-Methyl-N-(2-cyanoethyl)]-20-fluoro-stilbene (40). Yield:
1
40%; mp 65.8–67.0 °C; H NMR (300 MHz, CDCl3): d 7.61 (m, 1H), 7.47
(m, 2H), 7.09 (m, 5H), 6.71 (m, 2H), 3.77 (t, 2H), 3.07 (s, 3H), 2.59 (t,
2H), 13C NMR (75 MHz, CDCl3): 158.52 (J = 247.1 Hz), 147.28, 130.49
(J = 4.5 Hz), 128.11 (J = 4.5 Hz), 127.94, 126.95, 126.62 (J = 9.0 Hz),
125.82 (J = 11.3 Hz), 124.14 (J = 3.45 Hz), 118.29, 117.39 (J = 3.75 Hz),
115.85 (J = 22.1 Hz), 112.48, 48.86, 38.79, 15.34; HRMS (FAB+, m-nitro-
benzylalcohol): Calcd for C18H17FN2: 280.1376. Found: 280.1382
(+2.2 ppm deviation).
4.1.3.21. 4-[N-Methyl-N-(2-hydroxyethyl)]-30-bromo-stilbene
(33). Yield: 36%; mp 104.9–105.9 °C; 1H NMR (300 MHz, CDCl3):
d 7.62 (m, 1H), 7.61 (m, 4H), 7.29 (m, 1H), 7.84 (d, J = 16.3 Hz,
1H), 6.78 (m, 3H), 3.83 (t, 2H), 3.52 (t, 2H), 3.01 (s, 3H); 13C
NMR (75 MHz, CDCl3): 149.76, 140.35, 130.05, 129.47, 128.73,

7730
M. C. Hong et al. / Bioorg. Med. Chem. 18 (2010) 7724–7730
4.1.3.29.
4-[N-Methyl-N-(2-hydroxyethyl)]-40-fluoro-stilbene
4.2.4. Imaging of AD mouse brain
(41). Yield: 42%; mp 111.3–112.2 °C; 1H NMR (300 MHz, CDCl3):
d 7.42 (m, 4H), 7.05 (m,1H), 6.92 (d, 2H), 6.71 (d, 2H), 3.74 (t,
2H), 3.06 (s, 3H), 2.54 (t, 2H); 13C NMR (75 MHz, CDCl3): 160.32
(J = 978.9 Hz), 147.09, 134.04 (J = 12.9 Hz), 128.09, 127.83, 127.54
(J = 31.2 Hz), 126.90, 124.14, 118.30, 115.66 (J = 86.1 Hz), 112.55,
48.89, 38.77, 15.33; HRMS (FAB+, m-nitrobenzylalcohol): Calcd
for C18H17FN2: 280.1376. Found: 280.1375 (ꢁ0.1 ppm deviation).
Brain sections of Tg2576 mice were stained with compound 42
(1 lM) and ThT (5 lM) in PBS (Phosphate Buffered Saline). After
30 min of incubation, the brain sections were washed with PBS
and imaged using a Nikon Ti microscope.
Acknowledgements
This study was supported by Korea Science and Engineering
Foundation (KOSEF) (M20702010001-07N0201-00110) and Minis-
try of Science and Technology (MOST), Republic of Korea, through
its National Nuclear Technology Program. Also this work was sup-
ported by and intramural funding from AꢀSTAR Biomedical Re-
search Council and National University of Singapore Young
Investigator Award (R-143-000-353-123). J.-S. Lee thanks for the
generous support of the POSCO TJ Park Foundation (TJ Park Besse-
mer Science Fellowship).
4.1.3.30. 4-N-Methyl-40-bromo-stilbene (42). Yield: 23%; mp
214.3–215.8 °C; 1H NMR (300 MHz, CDCl3): d 7.41 (m, 6H), 7.03
(d, J = 16.3 Hz, 1H), 6.84 (d, J = 16.3 Hz, 1H), 6.60 (m, 2H), 3.81
(bs, 1H), 2.86 (s, 3H); 13C NMR (75 MHz, CDCl3): 149.22, 137.12,
131.63, 129.63, 128.02, 127.84, 127.48, 126.24, 123.0, 120.17,
112.43, 30.62; HRMS (FAB+, m-nitrobenzylalcohol): Calcd for
C15H14BrN: 287.0310. Found: 280.0313 (+1.3 ppm deviation).
4.1.3.31. 4-N-Methyl-20-methoxy-stilbene (43). Yield: 24%; mp
87.9–89.3 °C; 1H NMR (300 MHz, CDCl3): d 7.40 (m, 3H), 7.27 (m,
3H), 6.88 (m, 2H), 6.53 (m, 2H), 3.83 (s, 3H), 2.80 (s, 3H); 13C
NMR (75 MHz, CDCl3): 159.87, 149.08, 139.64, 129.53, 129.23,
127.81, 126.54, 124.25, 118.81, 112.44, 111.21, 55.24, 30.66; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C15H14BrN: 239.1310.
Found: 239.1314 (+1.5 ppm deviation).
Supplementary data
Supplementary data (Detail NMR characterizations of all com-
pounds) associated with this article can be found, in the online ver-
sion, at doi:10.1016/j.bmc.2010.06.044.
References and notes
4.1.3.32. 4-N-Methyl-30-methoxy-stilbene (44). Yield: 20%; mp
62.8–63.9 °C; 1H NMR (300 MHz, CDCl3): d 7.39 (m, 3H), 7.25 (m,
3H), 6.90 (m, 2H), 6.61 (m, 2H), 3.84 (s, 3H), 2.86 (s, 3H); 13C
NMR (75 MHz, CDCl3): 159.87, 149.08, 139.64, 129.53, 129.23,
127.81, 126.54, 124.25, 118.81, 112.44, 111.21, 55.24, 30.66; HRMS
(FAB+, m-nitrobenzylalcohol): Calcd for C15H14BrN: 239.1310.
Found: 239.1309 (ꢁ0.5 ppm deviation).
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10–50 lM of Ab40 fibril in PBS buffer solution were used in the
experiments. Generally, the kmax of emission was determined by
scanning a fixed excitation first, and the kmax of excitation was
determined by scanning emission spectrum with a fixed kem. Detail
protocols were reported in elsewhere.19
4.2.3. Measurement of binding affinity (KD)
Ab40 fibrils of 50 lM concentration solution were titrated by a
series concentration of compounds 42, 44, 33, 35 and ThT. A non-
linear regression analysis was performed in GraphPad Prism fitting
a one-site binding model to the binding data. The dissociation con-
stants (KD) were obtained from the best-fitted curve of each tested
compound.