Synthesis of 1,3-diphenyl-2-propen-1-one derivatives and evaluation of their biological activities

Article abstract of DOI:10.1016/j.bmc.2007.03.077

A simple synthesis and biological properties of 1,3-diphenyl-2-propen-1-ones 18-22 and 25-26 are described. The key synthetic strategies involve Grignard reaction of aldehyde 2 and oxidation reaction of 8-12 in high yields. The prepared compounds 18-22 an

Full text of DOI:10.1016/j.bmc.2007.03.077

Bioorganic & Medicinal Chemistry 15 (2007) 4098–4105
Synthesis of 1,3-diphenyl-2-propen-1-one derivatives
and evaluation of their biological activities
Soyong Jang,a Jae-Chul Jungb and Seikwan Oha,*
aDepartment of Neuroscience and Medical Research Institute, School of Medicine, Ewha Womans University,
Seoul 158-710, South Korea
bDepartment of Medicinal Chemistry, School of Pharmacy, University of Mississippi, PO Box 1848, University,
MS 38677-1848, USA
Received 5 December 2006; revised 22 March 2007; accepted 26 March 2007
Available online 30 March 2007
Abstract—A simple synthesis and biological properties of 1,3-diphenyl-2-propen-1-ones 18–22 and 25–26 are described. The key
synthetic strategies involve Grignard reaction of aldehyde 2 and oxidation reaction of 8–12 in high yields. The prepared compounds
18–22 and 25–26 were evaluated for free-radical scavenging, suppression of LPS-induced NO generation, and anti-excitotoxicity
in vitro. It was found that a couple of compounds, especially 21 and 26, were potent suppressors of NO generation and demon-
strated anti-excitotoxicity with the concentration range 10–20 lM in vitro.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
vates the glutamate receptor. Overactivation of the
receptors may induce elevation of intracellular Ca2+ lev-
els resulting in activation of Ca2+ dependent proteases
and kinases. High intracellular Ca2+ may also activate
nitric oxide synthase, resulting in excessive production
of nitric oxide (NO) and cytotoxicity. Although many
reagents, such as glutamate receptor antagonists, cal-
cium channel antagonists, anti-inflammatory agents,
and nitric oxide synthase (NOS) inhibitors, have neuro-
protective effects, their serious side effects limit clinical
application. Antioxidants also play an important role
in biological defense mechanisms. According to the
accumulated research data, activated oxygen is thought
to be a major factor in cytotoxicity. Therefore, research
was undertaken to search for novel compounds with
better neuroprotective effects and less neurotoxicity. It
is known that 4-hydroxy-3-methoxycinnamaldehyde
has antioxidant properties and its analogues, 4-hydro-
xy-3-methoxycinnamic acid (ferulic acid), could be
applicable in neurodegenerative diseases.11
The naturally occurring Yakuchinones A and B or re-
lated 1,3-diphenyl-2-propen-1-ones exhibit a wide range
of intriguing biological activities1 such as anti-inflamma-
tory,2 antitumor,3 antibacterial,4 antiviral,5 and gastric
protective activities.6 Recently, the Ryu group1a de-
scribed that the optimal length of linker between two
aryl groups played an important role for the biological
activity. The Deck and Vander Jagt group1d reported
the curcumin and related enones having significant
anti-oxidant activities based on the formation of stable
carbon centered-radicals. The Yakuchinones and their
analogues are interesting due to their scavenging effect
of active oxygen,7 nematocidal activity,8 inhibition of li-
pid peroxidation,9 and inhibition of acyl-CoA10 (Fig. 1).
Furthermore, accumulating evidence implicates that
endogenous excitatory amino acids, especially gluta-
mate, play an important role in the neuronal degenera-
tion associated with some neurological diseases such as
ischemia, Parkinson’s disease, Alzheimer’s disease, and
Huntington’s disease. In these neurodegenerative dis-
eases, glutamate is excessively released and then acti-
In the context of our medicinal chemistry program
dealing with the development of new Yakuchinone
derivatives, we have introduced aromatic substrates
having electron-withdrawing groups or electron-donat-
ing groups in order to generate antioxidant agents
and anti-excitotoxicity compounds. Our previous
work has examined the biological properties of
Keywords: 1,3-Diphenyl-2-propen-1-ones; Grignard reaction; NO-
generation; Anti-excitotoxicity.
*
Corresponding author. Tel.: +82 2 2650 5749; fax: +82 2 2653
8891; e-mail: skoh@ewha.ac.kr
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.03.077

S. Jang et al. / Bioorg. Med. Chem. 15 (2007) 4098–4105
4099
O
O
O
Ph
Ph
R1
R2
4
4
HO
HO
HO
OMe
Yakuchinone B
Figure 1. Structures of Yakuchinone A, Yakuchinone B, and 1,3-diphenyl-2-propen-1-ones.
OMe
R3
OMe
R1, R2, R3 = H, Me, F, or OMe
Yakuchinone A
benzylideneacetophenone derivatives.12 We wish to
report herein the synthesis and biological activities of
1,3-diphenyl-2-propen-1-ones 18–22 and 25–26 for free-
radical scavenging, suppression of LPS-induced NO
generation in vitro, and anti-excitotoxicity starting from
4-hydroxy-3-methoxy cinnamaldehyde (1) via Grignard
reaction of aldehyde 2 and oxidation reaction of 8–12 in
high yields.
2 h, under argon atmosphere according to a literature
procedure]10 gave racemic secondary alcohols 8–12 in
high yields.
Oxidation of 8–12 was accomplished by manganese
dioxide (MnO2) condition to give 13–17 in good yields.
In this stage, oxidation of 8–12 was also investigated using
Dess–Martin periodinane (DMP),13 tetrapropylammoni-
um perruthenate (TPAP)/N-methylmorpholine (NMO),14
and Swern[(COCl)2, DMSO, TEA] conditions.15 Although
these latter conditions were more convenient for scale-up
due to shorter reaction time and ease of handing, manga-
nese dioxide oxidation afforded a superior yield. Subse-
quent deprotecting of 13–17 was accomplished with 2
equivalents of tetrabutyl ammonium fluoride (TBAF)
in THF at room temperature to give 1,3-diphenyl-2-
propen-1-ones 18–22 in good yields (Scheme 1).
2. Results and discussion
2.1. Chemistry
A series of benzylideneacetophenones 18–22 was pre-
pared from commercially available 4-hydroxy-3-meth-
oxy cinnamaldehyde (1) as a starting material, which
was protected with tert-butyldimethylsilyl trifluorome-
thanesulfonate (TBSOTf) in the presence of 2,6-lutidine
to give aldehyde 2 in 95% yield. Grignard reaction of 2
with freshly prepared several phenyl magnesium halides
3–7 [phenylbromides were treated with activated
magnesium (Mg) in 1,2-dichloroethane at 150 ꢁC for
On the other hand, 4-hydroxycoumarin (23) was treated
with aldehyde 2 in ethanol to yield 24 which was subse-
quently oxidized using MnO2 in n-pentane to give 25 in
75% yields in two steps. Removal of TBS group of 25
was achieved with 20% TFA in dichloromethane at
OH
R2
O
H
b
R1O
TBSO
OMe
R2-MgBr
OMe
1 R1 = H
2 R1 = TBS
8
9
R2 = 4-Trimethylsilylpheny
R2 = 3,4-(Methylenedioxy)phenyl (89
3 R2 = 4-Trimethylsilylphenyl
4 R2 = 3,4-(Methylenedioxy)phenyl
5 R2 = 4-Trifluoromethylphenyl
6 R2 = 3,4,5-Trifluorophenyl
a
10 R2 = 4-Trifluoromethylphenyl (90
11 R2 = 3,4,5-Trifluorophenyl (8
)
12 R2 = 3-Fluoro-4-methoxyphenyl (8
7 R2 = 3-Fluoro-4-methoxyphenyl
c
O
O
R2
R2
d
TBSO
OMe
HO
OMe
13 R2 = 4-Trimethylsilylph
14 R2 = 3,4-(M
15 R2 = 4-Trifluoromethylphenyl (9
16 R2 = 3,4,5-Trifluorophenyl (8
17 R2 = 3-Fluoro-4-methoxyph
)
18 R2 = 4-Trimethylsilylphenyl (9
19 R2 = 3,4-(Methylenedioxy)ph
20 R2 = 4-Trif
21 R2 = 3,4,5-Trifluorophenyl (9
22 R2 = 3-Fluoro-4-methoxyphenyl (8
)
)
)
)
)
)
)
Scheme 1. Reagents and conditions: (a) TBSOTf (1.5 equiv), 2,6-lutidine (2.0 equiv), CH2Cl2, 0 ꢁC, 30 min, 95%; (b) 3–7 (2.0 equiv), THF, ꢀ78 ꢁC,
20 min, then ꢀ78 ꢁC–rt, 30 min, (82–90%); (c) MnO2 (10.0 equiv), n-pentane, reflux, 2 h, (85–92%); or Dess–Martin periodinane, CH2Cl2, rt, 30 min,
(87% for 13); or TPAP (5 mol %), NMO (1.5 equiv), molecular sieves (powder), CH2Cl2, 0 ꢁC, 15 min, (88% for 13); or DMSO (2.4 equiv), (COCl)2
(1.2 equiv), TEA (4.8 equiv), CH2Cl2, ꢀ78 ꢁC, 1 h, (85% for 13); (d) TBAF (2.0 equiv), THF, rt, 10 min, (86–95%).

4100
S. Jang et al. / Bioorg. Med. Chem. 15 (2007) 4098–4105
OH
O
OH
OH
O
O
OH
O
a
b
O
TBSO
O
O
RO
OMe
OMe
c
25 R = TBS
26 R = H
23
24
Scheme 2. Reagents and conditions: (a) 2, EtOH, reflux, 30 min, (81%); (b) MnO2 (10.0 equiv), n-pentane, reflux, 2 h, (84%); (c) 20% TFA, CH2Cl2,
0 ꢁC, 1 h, (85%).
Table 1. Rate of scavenging DPPH radical of 18–22 and 25–26
25–26 have been described. Compounds 18–22 and 25–
26 show the similar free radical scavenging activity.
However, compounds 19, 21, and 26 showed better sup-
pression effect on NO generation after LPS stimulation
in microglial cells. In addition, compounds 21 and 26
showed inhibitory action on glutamate-induced neuro-
toxicity in cultured neurons.
Compound
IC50 (DPPH) (lM)
18
19
20
21
22
25
26
1a
52.8
46.0
43.8
53.2
52.5
45.5
52.5
64.6
4. Experimental
4.1. General
a Compound 1 was 4-hydroxy-3-methoxycinnamaldehyde as a com-
pared material.
0 ꢁC to generate 4-hydroxycoumarin moiety 26 in 85%
yield (Scheme 2).
Reactions requiring anhydrous conditions were per-
formed with the usual precautions for rigorous exclu-
sion of air and moisture. Thin layer chromatography
(TLC) was performed on precoated silica gel G and
GP uniplates from Analtech and visualized with a
254-nm UV light. Flash chromatography was carried
out on silica gel 60 [Scientific Adsorbents Incorporated
2.2. Biological activities
2.2.1. Radical scavenging activity. DPPH radicals are
widely used for the preliminary screening of compounds
capable of scavenging activated oxygen species since
they are much more stable and easier to handle than
oxygen free radicals. The test results of the scavenging
ratio of DPPH radicals of each compound are shown
in Table 1. By employing the DPPH radical test, favor-
able scavenging ratios were found in all of compounds
18–22 and 25–26 ranging from 43.8 to 53.2 lM in
IC50. We have found that the compounds 18–22 and
25–26 exhibited the similar DPPH scavenging activity.
(SAI), particle size 32–63 lm, pore size 60 A]. 1H
˚
NMR and 13C NMR spectra were recorded on a Bru-
ker DRX 500 at 500 MHz and 125 MHz, respectively.
The chemical shifts are reported in parts per million
(ppm) downfield from tetramethylsilane, and J-values
are in Hz. Infrared (IR) spectra were obtained on an
ATI Mattson FT/IR spectrometer. Mass spectra were
recorded with a Waters Micromass ZQ LC-Mass sys-
tem and high resolution mass spectra (HRMS) were
measured with a Bruker BioApex FTMS system by di-
rect injection using an electrospray interface (ESI).
When necessary, chemicals were purified according to
the reported procedures.16
2.2.2. Suppression of NO-generation and anti-neurotox-
icity. NO production from activated microglial cells was
determined by measuring the amount of nitrite after
incubation with or without LPS (1 lg/mL) in the pres-
ence or absence of various concentrations of compounds
for 24 h. Compounds 18–22 and 25–26 (1, 5, 10, 20 lM)
showed considerable suppression of LPS-induced NO
generation (Fig. 2). Exposure of cortical cell cultures
to 300 lM NMDA (prototype of glutamate receptor
agonist) resulted in a rapid swelling of the neuronal cell
body within 2 h, and caused 90–100% neuronal death
over the next day. The 60 lM of glutamate induced
50% of neurotoxicity after 24 h exposure in cultured
neurons. These excitotoxic neuronal deaths were pre-
vented by inclusion of 5 and 10 lM of compounds 19,
21, and 26 (Fig. 3).
4.2. General procedure for the preparation of 8–12
To a stirred solution of 2 (2.9 g, 10.0 mmol) in dry THF
(30 mL) were added dropwise freshly prepared Grignard
reagents 3–7 (20.0 mmol) at ꢀ78 ꢁC. The reaction mix-
ture was stirred at same temperature for a further
20 min and then stirred to room temperature for
30 min. The reaction mixture was quenched by addition
of sat’d aqueous NH4Cl solution (20 mL) at 5 ꢁC and di-
luted with ethyl acetate (30 mL). The organic phase was
separated, and the aqueous phase was extracted with
ethyl acetate (20 mL). The combined organic phases
were washed with brine (30 mL). The organic layer
was dried over anhydrous MgSO4, filtered, and concen-
trated under reduced pressure followed by purification
of the crude products by flash column chromatography
(silica gel, 10–15% ethyl acetate/hexanes) affording the
desired compounds 8–12.
3. Conclusion
In conclusion, an efficient preparation and biological
evaluation of 1,3-diphenyl-2-propen-1-ones 18–22 and

S. Jang et al. / Bioorg. Med. Chem. 15 (2007) 4098–4105
4101
25
20
1μM
15
10
5μM
10μM
20μM
5
0
Sham
LPS
LPS+18 LPS+19 LPS+20
LPS+21 LPS+22 LPS+25
LPS+26
Figure 2. Suppression of NO production in LPS-treated microglia. The cells were treated with 1 lg/mL of LPS only or LPS plus different
concentrations (1, 5, 10, 20 lM) of compounds 18–22 and 25–26 at 37 ꢁC for 24 h. At the end of incubation, 50 lL of the medium was removed to
measure nitrite production. All values represent mean SE of three-independent experiments performed in triplicate.
120
100
80
1
5
μ
μ
M
M
60
40
20
0
10μM
Sham
Glu
Glu+18
Glu+19
Glu+20
Glu+21
Glu+22
Glu+25 Glu+26
Figure 3. Inhibition of glutamate-induced neurotoxicity in cultured cortical neurons. Glutamate (60 lM), compounds 18–22 and 25–26 were applied
for 24 h at 37 ꢁC. After incubation of neurons with WST-1 for 2 h, its quantified spectrophotometrically. All values represent mean SE of three-
independent experiments performed in triplicate.
4.2.1. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-[4–(trimethylsilyl)phenyl]prop-2-en-1-ol (8).
Rf = 0.4 (10% ethyl acetate/hexanes); IR (neat, NaCl)
3356, 3001, 2956, 2887, 1651, 1619, 1577, 1513, 1466,
1
1281, 1255, 1126, 1067 cmꢀ1; H NMR (CDCl3) d 7.65
(d, J = 8.0 Hz, 2H), 7.58 (d, J = 8.0 Hz, 2H), 6.92 (s,
1H), 6.86 (d, J = 8.5 Hz, 1H), 6.83 (d, J = 8.5 Hz, 1H),
6.63 (d, J = 16.0 Hz, 1H), 6.23 (dd, J = 6.0, 6.0 Hz,
1H), 5.43 (d, J = 6.5 Hz, 1H), 3.83 (s, 3H), 2.44 (br s,
1H), 1.03 (s, 9H), 0.19 (s, 6H); 13C NMR (CDCl3) d
150.9, 146.6, 145.3, 131.6, 129.9, 128.7, 127.0, 126.4,
125.4, 120.9, 120.0, 115.4, 109.9, 74.9, 55.7, 26.1, 18.9,
ꢀ4.2; HRMS Calcd for C23H30O3F3Si: 439.1916
[M+H]+, found: 439.1922.
3356, 3016, 2955, 2858, 1652, 1511, 1464, 1281, 1249,
1086 cmꢀ1 1H NMR (CDCl3) d 7.62–7.43 (m, 4H),
;
6.98 (d, J = 5.5 Hz, 1H), 6.92 (d, J = 8.5 Hz, 1H), 6.87
(d, J = 8.0 Hz, 1H), 6.68 (d, J = 16.0 Hz, 1H), 6.31
(dd, J = 6.5, 6.5 Hz, 1H), 5.41 (d, J = 6.5 Hz, 1H), 3.86
(s, 3H), 2.47 (br s, 1H), 1.09 (s, 9H), 0.36 (s, 9H), 0.25
(s, 6H); 13C NMR (CDCl3) d 150.9, 145.0, 143.5,
139.8, 133.6, 133.2, 130.6, 129.6, 128.7, 127.7, 125.6,
120.9, 120.0, 115.0, 75.5, 55.7, 26.2, 26.1, 18.9, ꢀ0.3,
ꢀ0.6, ꢀ4.1; HRMS Calcd for C25H39O3Si2: 443.2438
[M+H]+, found: 443.2421.
4.2.4. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-(3,4,5-trifluorophenyl)prop-2-en-1-ol (11). Rf =
0.5 (15% ethyl acetate/hexanes); mp 97–98 ꢁC. IR (neat,
NaCl) 3335, 3039, 2987, 2885, 1660, 1609, 1545, 1471,
4.2.2. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-[(3,4-methylenedioxy)phenyl]prop-2-en-1-ol (9).
Rf = 0.5 (15% ethyl acetate/hexanes); IR (neat, NaCl)
3526, 3074, 2956, 2858, 1664, 1505, 1436, 1240,
1277, 1245, 1142, 1082 cmꢀ1 1H NMR (CDCl3) d
;
7.13–7.06 (m, 2H), 6.90 (s, 1H), 6.86 (d, J = 8.0 Hz,
1H), 6.82 (d, J = 8.0 Hz, 1H), 6.59 (d, J = 16.0 Hz,
1H), 6.10 (dd, J = 6.0, 6.0 Hz, 1H), 5.28 (d, J = 6.5 Hz,
1H), 3.83 (s, 3H), 2.34 (br s, 1H), 1.02 (s, 9H), 0.18 (s,
6H); 13C NMR (CDCl3) d 150.9, 145.4, 132.1, 129.6,
128.0, 121.0, 120.0, 110.2, 110.1, 109.9, 74.1, 55.7,
26.1, 18.9, ꢀ4.2; HRMS Calcd for C22H28O3F3Si:
425.1760 [M+H]+, found: 425.1772.
1039 cmꢀ1 1H NMR (CDCl3) d 7.02–7.71 (m, 6H),
;
6.58 (d, J = 7.0 Hz, 1H), 6.45 (d, J = 7.0 Hz, 1H), 5.95
(s, 2H), 4.96 (d, J = 8.5 Hz, 1H), 3.81 (s, 3H), 2.37 (br
s, 1H), 1.02 (s, 9H), 0.18 (s, 6H); 13C NMR (CDCl3) d
150.8, 147.3, 146.2, 130.3, 125.5, 124.9, 120.8, 119.7,
118.8, 107.6, 106.9, 101.0, 76.1, 55.7, 26.1 18.9, ꢀ4.1;
HRMS Calcd for C23H31O5Si: 415.1941 [M+H]+, found:
415.1957.
4.2.5. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-(3-fluoro-4-methoxyphenyl)prop-2-en-1-ol (12).
Rf = 0.5 (10% ethyl acetate/hexanes); mp 94–95 ꢁC. IR
(neat, NaCl) 3351, 3006, 2985, 2878, 1649, 1545, 1455,
4.2.3. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-[4-(trifluoromethyl)phenyl]prop-2-en-1-ol (10).
Rf = 0.5 (15% ethyl acetate/hexanes); IR (neat, NaCl)
1
1279, 1163, 1045 cmꢀ1; H NMR (CDCl3) d 7.20 (d,

4102
S. Jang et al. / Bioorg. Med. Chem. 15 (2007) 4098–4105
J = 12.0 Hz, 1H), 7.13 (d, J = 8.5 Hz, 1H), 7.01–6.89 (m,
2H), 6.83 (dd, J = 8.0, 8.0 Hz, 2H), 6.57 (d, J = 16.0 Hz,
1H), 6.20 (dd, J = 6.5, 6.5 Hz, 1H), 5.30 (d, J = 6.5 Hz,
1H), 3.90 (s, 3H), 3.82 (s, 3H), 2.25 (br s, 1H), 1.07 (s,
9H), 0.19 (s, 6H); 13C NMR (CDCl3) d 150.8, 146.9,
145.0, 136.0, 130.8, 130.2, 129.1, 127.6, 124.2, 121.9,
120.9, 119.9, 114.2, 113.3, 74.5, 56.4, 55.7, 26.1, 18.9,
ꢀ4.1; HRMS Calcd for C23H32O4FSi: 419.2054
[M+H]+, found: 419.2062.
4.3.4. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-[3,4,5-trifluorophenyl]-2-propen-1-one (16).
Rf = 0.5 (5% ethyl acetate/hexanes); mp 105 ꢁC. IR
(neat, NaCl) 3008, 2981, 2857, 1718, 1549, 1453, 1287,
1163, 1061 cmꢀ1
; d 7.81 (d,
1H NMR (CDCl3)
J = 15.5 Hz, 1H), 7.68 (t, J = 7.5 Hz, 2H), 7.24 (d,
J = 15.5 Hz, 1H), 7.19 (d, J = 8.0 Hz, 1H), 7.14 (s,
1H), 6.91 (d, J = 8.5 Hz, 1H), 3.91 (s, 3H), 1.03 (s,
9H), 0.22 (s, 6H); 13C NMR (CDCl3) d 186.2, 151.2,
148.4, 146.7, 128.1, 123.0, 121.2, 118.0, 112.9, 112.7,
111.5, 55.8, 26.0, 18.9, ꢀ4.1; HRMS Calcd for
C22H25O3F3SiNa: 445.1423 [M+Na]+, found: 445.1438.
4.3. General procedure for the preparation of 13–17
To a stirred solution of 8–12 (5.9 mmol) in n-pentane
(120 mL) was added portionwise manganese dioxide
(59.0 mmol) and the mixture was refluxed for 2 h. The
reaction mixture was cooled to room temperature and
filtered through Celite and then washed successively
with n-pentane (2times 10 mL). The filtrate was evapo-
rated under reduced pressure to yield crude enones,
which were purified by flash column chromatography
(silica gel, 5% ethyl acetate/hexanes) to give the desired
compounds 13–17.
4.3.5. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-(3-fluoro-4-methoxyphenyl)-2-propen-1-one (17).
Rf = 0.5 (5% ethyl acetate/hexanes); mp 145–146 ꢁC. IR
(neat, NaCl) 3010, 2959, 2868, 1722, 1538, 1465, 1272,
1154, 1050 cmꢀ1 1H NMR (CDCl3) d 7.86–7.74 (m,
;
3H), 7.35 (d, J = 15.5 Hz, 1H), 7.17 (d, J = 8.5 Hz,
1H), 7.14 (s, 1H), 7.05 (t, J = 8.5 Hz, 1H), 6.90 (d,
J = 8.0 Hz, 1H), 3.98 (s, 3H), 3.90 (s, 3H), 1.03 (s,
9H), 0.21 (s, 6H); 13C NMR (CDCl3) d 187.4, 151.3,
147.8, 144.8, 131.5, 128.6, 125.5, 122.6, 121.4, 119.1,
116.2, 112.4, 111.5, 56.5, 55.8, 26.0, 18.9, ꢀ4.1; HRMS
Calcd for C23H30O4FSi: 417.1897 [M+H]+, found:
417.1881.
4.3.1. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-(4-trimethylsilylphenyl)-2-propen-1-one (13).
Rf = 0.5 (5% ethyl acetate/hexanes); IR (neat, NaCl)
3011, 2968, 2875, 1722, 1586, 1462, 1267, 1144,
;
1081 cmꢀ1
1H NMR (CDCl3) d 7.99 (t, J = 7.5 Hz,
4.4. General procedure for the preparation of 1,3-diphenyl-
2-propen-1-ones (18–22)
1H), 7.78 (dd, J = 4.0, 4.0 Hz, 1H), 7.68 (t, J = 8.0 Hz,
2H), 7.46–7.38 (m, 3H), 7.17 (d, J = 8.5 Hz, 1H), 6.91
(dd, J = 4.0, 4.0 Hz, 1H), 3.91 (s, 3H), 1.04 (s, 9H),
0.34 (s, 9H), 0.28 (s, 3H), 0.22(s, 3H); 13C NMR
(CDCl3) d 190.5, 151.1, 147.7, 146.3, 145.0, 138.5,
133.4, 133.1, 128.7, 127.3, 125.0, 122.6, 121.2, 120.3,
111.5, 55.7, 26.0, 18.9, ꢀ0.64, ꢀ0.80, ꢀ4.1; HRMS
Calcd for C25H37O3Si2: 441.2281 [M+H]+, found:
441.2268.
To a stirred solution of 13–17 (5.0 mmol) in dry THF
(80 mL) was added dropwise TBAF (10.0 mmol, 1 M
solution in THF) at room temperature under argon
atmosphere and the mixture was stirred at room temper-
ature for 10 min. The reaction mixture was diluted with
EtOAc (30 mL) and washed with brine (70 mL). The or-
ganic phase was separated, and the aqueous phase was
extracted with EtOAc (2· 30 mL). The combined organ-
ic phases were washed with brine (50 mL), dried over
anhydrous MgSO4, filtered, and concentrated under re-
duced pressure to yield alcohols, which were purified by
flash column chromatography (silica gel, 20–30% ethyl
acetate/hexanes) to give 18–22.
4.3.2. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-[(3,4-methylenedioxy)phenyl]-2-propen-1-one
(14). Rf = 0.5 (5% ethyl acetate/hexanes); IR (neat,
NaCl) 3008, 2981, 2883, 1715, 1544, 1465, 1268, 1185,
1042 cmꢀ1 1H NMR (CDCl3) d 7.09–6.75 (m, 6H),
;
6.58 (dd, J = 7.0, 7.0 Hz, 1H), 6.35 (dd, J = 6.5,
6.5 Hz, 1H), 6.02 (s, 2H), 3.86 (s, 3H), 1.03 (s, 9H),
0.24(s, 6H); 13C NMR (CDCl3) d 189.3, 151.5, 146.8,
146.0, 145.2, 138.4, 133.3, 128.6, 127.7, 125.1, 121.9,
121.2, 120.3, 112.1, 101.8, 55.8, 26.0, 18.8, ꢀ4.1; HRMS
Calcd for C23H29O5Si: 413.1784 [M+H]+, found:
413.1774.
4.4.1. (2E)-3-[4-Hydroxy-3-(methoxyphenyl)]-1-(4-trimeth-
ylsilylphenyl)-2-propen-1-one (18). Rf = 0.3 (30% ethyl
acetate/hexanes); IR (neat, NaCl) 3374, 3070, 3018, 2956,
1
2857, 1654, 1579, 1512, 1430, 1272, 1185, 1032 cmꢀ1; H
NMR (CDCl3) d 8.00 (d, J = 8.5 Hz, 2H), 7.81 (d,
J = 15.5 Hz, 1H), 7.69 (t, J = 7.5 Hz, 2H), 7.38 (d,
J = 8.5 Hz, 1H), 7.25 (d, J = 8.5 Hz, 1H), 7.17 (s, 1H),
6.98 (dd, J = 4.5, 4.5 Hz, 1H), 3.98 (s, 3H), 0.36 (s, 9H);
13C NMR (CDCl3) d 190.7, 148.4, 146.8, 146.4, 145.2,
138.5, 133.4, 127.3, 123.4, 119.8, 115.0, 110.1, 56.2,
ꢀ0.79; HRMS Calcd for C19H22O3SiNa: 349.1236
[M+Na]+, found: 349.1248.
4.3.3. (2E)-3-[(4-tert-Butyldimethylsilyloxy)-3-methoxy-
phenyl]-1-(4-trifluoromethylphenyl)-2-propen-1- one (15).
Rf = 0.5 (5% ethyl acetate/hexanes); IR (neat, NaCl)
3006, 2979, 2856, 1720, 1551, 1476, 1285, 1164,
1062 cmꢀ1 1H NMR (CDCl3) d 8.11 (d, J = 7.5 Hz,
;
2H), 7.78 (d, J = 8.0. Hz, 3H), 7.35 (d, J = 15.5 Hz,
2H), 7.19 (d, J = 7.5 Hz, 1H), 7.16 (s, 1H), 3.91 (s,
3H), 1.04 (s, 9H), 0.22 (s, 6H); 13C NMR (CDCl3) d
187.5, 151.9, 147.8, 145.5, 131.0, 128.2, 126.1, 122.3,
120.4, 119.0, 115.8, 112.9, 111.3, 55.8, 26.0, 18.9, ꢀ4.2;
HRMS Calcd for C23H28O3F3Si: 437.1760 [M+H]+,
found: 437.1785.
4.4.2. (2E)-3-[4-Hydroxy-3-(methoxyphenyl)]-1-[(3,4-methy-
lenedioxy)phenyl]-2-propen-1-one (19). Rf = 0.3 (30%
ethyl acetate/hexanes); IR (neat, NaCl) 3349, 3007, 2955,
1
2876, 1645, 1554, 1477, 1243, 1186, 1045 cmꢀ1; H NMR
(CDCl3) d 7.11–6.72 (m, 7H), 6.59 (dd, J = 7.5, 7.0 Hz,
1H), 6.38 (dd, J = 7.0, 7.0 Hz, 1H), 6.05 (s, 2H), 3.88

S. Jang et al. / Bioorg. Med. Chem. 15 (2007) 4098–4105
4103
(s, 3H); 13C NMR (CDCl3) d 188.9, 151.1, 147.0, 146.3,
145.7, 138.3, 133.5, 127.9, 126.5, 125.4, 122.1, 121.4, 120.5,
112.1, 102.5, 55.9; HRMS Calcd for C17H15O5: 299.0919
[M+H]+, found: 299.0928.
1705, 1640, 1457, 1286, 1125, 1064 cmꢀ1cmꢀ1
;
1H
NMR (CDCl3) d 8.39 (dd, J = 11.0, 12.0 Hz, 1H), 8.09
(d, J = 8.0, 8.0 Hz, 1H), 7.64 (t, J = 7.0 Hz, 1H), 7.52
(dd, J = 7.0, 7.0 Hz, 1H), 7.25 (dd, J = 6.0, 7.0 Hz,
4H), 6.91 (d, J = 8.0 Hz, 2H), 3.91 (s, 3H), 1.01 (s,
9H), 0.22 (s, 6H); 13C NMR (CDCl3) d 186.7, 178.5,
160.2, 151.1, 149.8, 144.2, 138.9, 128.8, 127.2, 125.4,
123.9, 122.2, 120.9, 112.3, 101.2, 56.3, 26.1, 18.9, ꢀ4.1;
HRMS Calcd for C25H29O6Si: 453.1733 [M+H]+, found:
453.1741.
4.4.3. (2E)-3-[4-Hydroxy-3-(methoxyphenyl)]-1-(4-trifluo-
romethylphenyl)-2-propen-1-one (20). Rf = 0.3 (30% ethyl
acetate/hexanes); IR (neat, NaCl) 3384, 3011, 2964,
2876, 1658, 1585, 1512, 1452, 1323, 1272, 1125,
1033 cmꢀ1 1H NMR (CDCl3) d 8.09 (d, J = 8.0 Hz,
;
2H), 7.76 (dd, J = 6.5, 6.5 Hz, 3H), 7.34 (d, J = 16.0, Hz,
1H), 7.23 (dd, J = 7.5, 7.5 Hz, 1H), 7.15 (d, J = 7.5 Hz,
1H), 6.97 (d, J = 8.0 Hz, 1H), 5.66 (br s, 1H), 3.96 (s,
3H); 13C NMR (CDCl3) d 189.6, 149.4, 146.1, 145.9,
145.0, 138.5, 133.2, 128.3, 126.8, 124.1, 120.0, 115.6,
111.4, 56.1; HRMS Calcd for C17H13O3F3Na: 345.0714
[M+Na]+, found: 345.0725.
4.6. (2E)-4-Hydroxy-3-[3-(4-hydroxy)-3-(methoxy-
phenyl)prop-2-enoyl]-2H-chromen-2-one (26)
To a solution of 25 (0.3 g, 2.5 mmol) in dry dichloro-
methane (10 mL) was added dropwise TFA (2.6 g,
20% solution in dichloromethane) at 0 ꢁC under argon
atmosphere and the mixture was stirred at this tempera-
ture for 1 h. The reaction mixture was diluted with
dichloromethane (10 mL) and treated with sat’d aque-
ous NaCl solution (20 mL). The organic layer was sepa-
rated, and the aqueous phase was extracted with
dichloromethane (2· 20 mL). The combined organic
phases were washed with saturated aqueous Na2SO4
solution (20 mL), brine (50 mL), dried over anhydrous
MgSO4, filtered, and concentrated under reduced pres-
sure to give alcohols, which were purified by flash col-
umn chromatography (silica gel, 20–30% ethyl acetate/
hexanes) to afford 26. Rf = 0.4 (30% ethyl acetate/hex-
anes); IR (neat, NaCl) 3521, 3345, 2976, 2845, 1710,
4.4.4. (2E)-3-[4-Hydroxy-3-(methoxyphenyl)]-1-[3,4,5-tri-
fluorophenyl]-2-propen-1-one (21). Rf = 0.3 (30% ethyl
acetate/hexanes); IR (neat, NaCl) 3350, 3005, 2985,
2858, 1657, 1550, 1448, 1262, 1153, 1081 cmꢀ1 1H
;
NMR (CDCl3) d 7.83 (d, J = 16.0 Hz, 1H), 7.66
(t, J = 8.0 Hz, 2H), 7.22 (d, J = 16.0 Hz, 1H), 7.20
(d, J = 8.5 Hz, 1H), 7.15 (s, 1H), 6.93 (d, J = 8.0 Hz,
1H), 5.58 (br s, 1H), 3.90 (s, 3H); 13C NMR (CDCl3)
d 187.3, 151.0, 148.2, 146.5, 132.2, 128.3, 122.9,
121.7, 119.3, 113.1, 112.2, 111.9, 55.8. HRMS
Calcd for C16H12O3F3: 309.0739 [M+H]+, found:
309.0745.
1645, 1464, 1265, 1133, 1072 cmꢀ1cmꢀ1 1H NMR
;
4.4.5. (2E)-3-[4-Hydroxy-3-(methoxyphenyl)]-1-(3-fluoro-
4-methoxyphenyl)-2-propen-1-one (22). Rf = 0.3 (40%
ethyl acetate/hexanes); IR (neat, NaCl) 3359, 2987,
(CDCl3) d 13.2 (br s, 1H), 8.36 (dd, J = 11.0, 11.0 Hz,
1H), 8.11 (d, J = 8.5, 8.5 Hz, 1H), 7.61 (t, J = 7.5 Hz,
1H), 7.50 (d, J = 6.5, 6.5 Hz, 1H), 7.23 (d, J = 7.0 Hz,
4H), 6.92 (d, J = 8.0 Hz, 2H), 3.90 (s, 3H); 13C NMR
(CDCl3) d 183.6, 176.1, 159.8, 150.4, 149.5, 145.3,
138.2, 133.1, 128.3, 126.9, 124.5, 123.0, 121.1, 115.4,
108.4, 56.3; HRMS Calcd for C19H15O6: 339.0869
[M+H]+, found: 339.0876.
2875, 1662, 1578, 1455, 1278, 1164, 1086 cmꢀ1 1H
;
NMR (CDCl3)
d 7.85–7.72 (m, 3H), 7.33 (d,
J = 16.0 Hz, 1H), 7.15 (d, J = 8.5 Hz, 1H), 7.13 (s,
1H), 7.04 (t, J = 8.5 Hz, 1H), 6.91 (d, J = 8.0 Hz, 1H),
5.45 (br s, 1H), 3.96 (s, 3H), 3.91 (s, 3H); 13C NMR
(CDCl3) d 189.4, 150.3, 148.7, 145.2, 132.4, 129.6,
124.9, 123.1, 121.8, 119.5, 115.3, 113.2, 111.8, 56.8,
55.9; HRMS Calcd for C17H16O4F: 303.1033 [M+H]+,
found: 303.1020.
4.7. DPPH radical-scavenging effects
To test the free radical-scavenging effects by using
DPPH, compounds were adjusted with ethanol solution
to final concentration of 0.1–100 lM. Acetic acid buffer
(0.1 mM) was added, and the mixture was warmed in
water bath at 25 ꢁC. After 5 min, 1,1-diphenyl-2-pic-
rylhydrazyl (DPPH) radical ethanol solution (1 mL,
0.2 mM) was added. After 30 min, absorbance was mea-
sured with a spectrophotometer (517 nm). The DPPH
radical-scavenging rate of each sample was calculated
and the 50% scavenging concentration based on the
DPPH radical-scavenging rate was also calculated based
on the following formula.
4.5. (2E)-4-Hydroxy-3-[3-(4-tert-butyldimethylsilyloxy)-
3-(methoxyphenyl)prop-2-enoyl]-2H-chromen-2-one (25)
To a stirred solution of 4-hydroxycoumarin (23, 0.62 g,
3.8 mmol) in ethanol (25 mL) was added portionwise 2
(1.1 g, 3.8 mmol) and the mixture was refluxed for
30 min. The reaction mixture was cooled to room tem-
perature and evaporated under reduced pressure to yield
24, which was treated without purification with manga-
nese dioxide (3.9 g, 38.0 mmol) in n-pentane (50 mL)
and the mixture was refluxed for 2 h. The reaction mix-
ture was cooled to room temperature and filtered
through Celite and then washed successively with n-pen-
tane (2· 10 mL). The filtrate was evaporated under re-
duced pressure to yield crude enones, which were
purified by flash column chromatography (silica gel,
10% ethyl acetate/hexanes) to give 25 as a brown solid
(0.5 g, 75%). Rf = 0.4 (10% ethyl acetate/hexanes); mp
129–130 ꢁC; IR (neat, NaCl) 3465, 3012, 2985, 2856,
DPPH radical-scavenging rate (%)
ꢀ
ꢁ
A ꢀ C
¼
1 ꢀ
ꢁ 100
B
where A is the absorbance of the sample when a blank
was substituted for ethanol, B is the absorbance of the
sample when a color-contrast agent was substituted for

4104
S. Jang et al. / Bioorg. Med. Chem. 15 (2007) 4098–4105
ethanol in the 1,1-diphenyl-2-picrylhydrazyl (DPPH)
radical-ethanol solution, and C is the absorbance of
the color-contrast agent alone which is an absorbance
change in order to detect the DPPH radical-scavenging
rate.
of 1:10 in the original conditioned media at 37 ꢁC for 2 h.
After thorough shaking, the formazan produced by the
metabolically active cells in each sample was measured
at a wavelength of 450 nm and a reference wavelength
of 650 nm. Absorbance readings were normalized against
control wells with untreated cells. Neuronal death was
analyzed 24 h later, and the percentage of neurons under-
going actual neuronal death was normalized to the mean
value that is found after a 24-h exposure to 300 lM
NMDA (defined as 0) or a sham control (defined as 100)
(Fig. 3).
4.8. Cell culture
Cerebral cortices were removed from the brains of 15-
day-old fetal mice. The neocortices were triturated and
plated on 24-well plates (with approximately 106 cells/
mL) precoated with 100 lg/mL poly-D-lysine and
4 lg/mL laminine, in Eagle’s minimal essential media
(Earle’s salts, supplied glutamine-free), and supple-
mented with horse serum (5%), fetal bovine serum
(5%), 2 mM glutamine, and 20 mM glucose. Cultures
were maintained at 37 ꢁC in a humidified atmosphere
of 5% CO2. After 6 days in vitro (DIV), the cultures
were shifted to the plating media containing 10 lM
cytosine arabinoside without fetal serum. Cultures were
then fed twice per week. Mixed cortical cell cultures
containing neurons and glia (DIV 16–14) were exposed
to excitatory amino acid, glutamate, in Eagle’s minimal
essential media without serum. The morphology of the
degenerating neurons was observed under a phase con-
trast microscope over the next 24 h. Primary microglia
were prepared from postnatal 1 day Sprague–Dawley
rat as described previously17 with some modifications.
In brief, the rat cortices were triturated into single cells
in minimal essential medium (MEM) containing 10%
FBS and then plated into 75 cm2 T-flask for 10–14
days. To prepare microglia, cells were removed from
the T-flasks by mild shaking. Detached microglia was
plated on 24-well plates (with approximately 5 · 105
cells/mL). Morphology was examined under a phase-
contrast microscopy.
Acknowledgment
This work has been supported by KOSEF Brain Neuro-
biology Grant (2006).
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