Synthesis of 2-[4-(imidazolin-2-ylideneamino)benzyl]-Indan-1-ones as novel potent prostacyclin antagonists

Article abstract of DOI:10.1002/jccs.200800126

Prostacyclin is involved in many pathological conditions, such as sensitization of inflammation induced pain and isovolumetic distention. Therefore, antagonism of prostacyclin action may be useful in the alleviation of these conditions. In this study, nov

Full text of DOI:10.1002/jccs.200800126

846
Journal of the Chinese Chemical Society, 2008, 55, 846-853
Synthesis of 2-[4-(Imidazolin-2-ylideneamino)benzyl]-indan-1-ones as
Novel Potent Prostacyclin Antagonists
Ching-Yuh Cherna (
Yu-Lin Chenc (
), Yung-Lee Yekb (
) and Wai-Ming Kanc* (
),
)
aDepartment of Applied Chemistry, National Chiayi University, Chiayi, Taiwan, R.O.C.
bSin Lau Hospital, Tainan, Taiwan, R.O.C.
cDepartment of Pharmacology, National Cheng Kung University, Tainan 70101, Taiwan, R.O.C.
Prostacyclin is involved in many pathological conditions, such as sensitization of inflammation in-
duced pain and isovolumetic distention. Therefore, antagonism of prostacyclin action may be useful in the
alleviation of these conditions. In this study, novel potent prostacyclin antagonists, 2-[4-(imidazolin-2-
ylideneamino)benzyl]-indan-1-ones were synthesized from their respective substituted indanones in three
steps. The construction of the amino-imidazole moiety of these derivatives is achieved by using in situ
generation of chloro-imidazole and reaction with their respective anilines. Thus, these N-substituted 2-
imidazolines can be prepared safely and efficiently. Moreover, these compounds show potent prostacyclin
antagonistic activity by inhibition of prostacyclin agonist induced ERK1/2 phosphorylation in human
erythroleukemia cells. Moreover, we observed an increase in activity with the increase in electro-donating
property of the substitution on the indanone aromatic ring. Prostacyclin antagonists with increased po-
tency may be designed based on these findings. These compounds may also be invaluable tools for the
study of the physiological functions of prostacyclin.
Keywords: Prostacyclin antagonist; Imidazolines.
INTRODUCTION
Prostacyclin (PGI2) is an arachidonic acid metabolite
also involved in the formation of edema and increase in leu-
kocyte infiltration when PGI2 promotes blood flow to the
inflamed area. Likewise, symptoms of respiratory allergies
such as asthma may also be the result of increased synthesis
of PGI2.5 Moreover, prostacyclin is synthesized quickly af-
ter mechanical injury. The increased PGI2 sensitizes the
pain nerves.6 It has been shown that PGI2 is more potent in
sensitization of sensory neurons than the more widely
known PGE2. In addition, PGI2 is generated locally during
the stretching of detrusor muscle of the bladder, injuries of
the vesicle mucosa, and nerve stimulation.7 Abnormal PGI2
activities have been shown in inflammatory bladder disor-
ders, cystitis with symptoms involving urgency, frequency
and pain.
synthesized sequentially via cyclooxygenase and prosta-
cyclin synthase. It is a labile molecule with a half-life of 1.5
minutes under physiological conditions, when it spontane-
ously hydrolyzes into inactive 6-keto-prostaglandin F1a.1
PGI2 is synthesized in many tissues especially in endothe-
lial cells lining the blood vessels. It is implied in various
physiological and pathological conditions. Prostacyclin is
a potent agent that prevents vasoconstriction, thrombi for-
mation and blood platelet aggregation that are essential to
homeostatic balance.2 In many physiological systems, it
antagonizes the action of thromboxane A2.3 Thus the deli-
cate balance between these two molecules constitutes the
basis of homeostasis.
From the above discussion, therefore, are many po-
tential clinical applications for PGI2 antagonists, such as
for the prevention of massive bleeding in hemophilia and
hemorrhagic conditions, relief of hypotension, reduction of
edema formation during inflammation and use as a pain-re-
liever in inflammation. In addition, PGI2 antagonists may
On the other hand, hyperactivity of PGI2 is involved
in many pathological conditions. During septic shock, a
large quantity of prostacyclin is secreted. The result may be
life-threatening due to the PGI2 induced drop in blood pres-
sure.4 An abnormal, excessive amount of prostacyclin is
* Corresponding author. Tel: +886-6-235-3535 ext. 5469; Fax: +886-6-274-9296; E-mail: vincent@mail.ncku.edu.tw

Substituted Indan-1-one as IP Antagonists
J. Chin. Chem. Soc., Vol. 55, No. 4, 2008 847
also be useful in the treatment of respiratory allergies such
as asthma where PGI2 production is increased in response
to the presence of allergens.
ylamines are more potent than phenylpropionic acids. The
objective of this study was to examine whether these PGI2
antagonists could accommodate a more rigid structural
modification while the PGI2 antagonistic activity could be
retained or even enhanced. In this study, we used indanone
as the basic structural core in place of the benzyl moiety
and studied its effect on PGI2 antagonistic activity. The ef-
fect of the substitutions on the indanone aromatic ring on
pharmacological activities was also studied.
In order to synthesize the target compounds, substi-
tuted indanones were used as starting materials. Retrosyn-
thetic analysis suggested that the molecules could be con-
structed by alkylation of the respective indanones with
4-nitrobenzyl halides that served as the precursors to N-
4,5-dihydrohydro-imidazolines. Reduction of the phenyl
nitrates by selective catalytic hydrogenation allowed the
preparation of anilines. Although the preparation of 4,5-di-
hydroimidazoline is well documented, most of the proce-
dures require the use of hazardous starting materials.10 The
most effective method requires the preparation of chloro-
imidazoline from chloride gas.11 Milder methods are very
limited. Previously, we devised an alternative preparation
of chloro-imidazoline in situ. From our previous study,12
chloro-imidazoline could be synthesized in situ by the re-
action of chlorophosphate with substituted urea. Thus di-
hydroimidazoles can be prepared efficiently under mild
conditions. On the other hand, derivatives with different
indanone substitutions can be synthesized by using the re-
spective substituted indanones available commercially or
obtained from chemical synthesis. The synthesis of the tar-
get derivatives is illustrated in Scheme I, as exemplified by
the synthesis of compound 7. Other derivatives were syn-
thesized similarly.
Although some attempts have been made to design
and synthesize PGI2 antagonists, they have been unsuc-
cessful until recently. May-Frances Jett et al.8 describe the
pharmacology of RO 1138452 and RO 3244794. RO1138452
is a N-(4,5-dihydro-1H-imidazolyl)-benzylphenylamine 1
that is a potent PGI2 antagonist. Although it is active at
nanomolar concentrations, it also cross reacts with platelet
activation factor (PAF) receptors and imidazole (I2) recep-
tors. Thus, it is not very selective. However, RO 3244794 is
a substituted phenyl-propionic acid derivative 2 that is very
selective, but it is almost two orders of magnitude less po-
tent than the aforementioned compound. Nakae et al.9 re-
ported the pharmacology of compounds A and B which are
also substituted phenyl-propionic acid derivatives. These
derivatives are active at submicromolar concentrations.
In this study, we reported the design and synthesis of
a series of novel indanone containing derivatives that
showed potent PGI2 antagonistic activities.
Fluoro-indanone 3 was used as the starting material.
Heating 4-fluoroindanone with morpholine in DMSO re-
sulted in 4-morpholinyl-indanone 4 in excellent yield after
chromatographic purification. When compound 4 and 4-
nitrobenzyl bromide underwent SN2 reaction, we isolated
about 70% of product 5. In order to improve the efficiency
of the reaction, we studied the effect of LiBr and HMPA on
the yield of 5. We found that the addition of one equivalent
of HMPA to the reaction mixture gave the optimal yield of
90% of product 5. Alkylation using LDA at low tempera-
ture and 4-nitrobenzyl bromide afforded only mono-al-
kylated product 5 in 92% yield after purification. Careful
reductive hydrogenation in THF using Pd/C as a catalyst at
RESULTS AND DISCUSSION
From a recent literature review, we found that there
are basically two classes of PGI2 antagonists reported. One
of them is (N-4,5-dihydro-1H-imidazo-2-yl)benzyl-phen-
ylamine while the other is phenylpropionic acid. Both
classes of PGI2 antagonists possess their distinct merits.
Since subsequent quantitative-structure-activity-relation-
ship studies require biological data from more rigid mole-
cules, we avoided target molecules with flexible structures.
As a result, we chose benzylphenylamines over phenyl-
propionic acids as our starting point for the design and syn-
thesis of novel PGI2 antagonists. In addition, benzylphen-

848 J. Chin. Chem. Soc., Vol. 55, No. 4, 2008
Chern et al.
Scheme I
ambient temperature provided the desired aniline 6 in 93%
yield as the only isolated product. No benzylated alcohol
was observed. The putative 2-choloro-imidazole was pre-
pared in situ as reported previously. Optimum result can be
obtained by reaction of 3 equivalents of dimethyl chloro-
phate and Et3N with imidazolidin-2-one in dichlorometh-
ane at 35 °C for 5 hours. Addition of the appropriate aniline
to the above mixture afforded the target compound 7. The
result of the preparation of other derivatives is summarized
in Scheme II. As observed from the result, this method of
preparation of N-4,5-dihydro-imidazolyl-amine from ani-
lines is indeed superior to most reported methods using
hazardous starting materials using chlorine gas. The syn-
thesis of mesylated morpholinyl derivative 16 is shown in
Scheme II.
The most potent derivatives 11b and 7 are at least two orders
of magnitudes more potent than 11d. In our ERK1/2 phos-
phorylation assay, they are at least as potent as RO1138452.
However, N-mesylated pyrazine 16 is significantly less
potent than the reference compound. The affinity of com-
pound 7 towards the PGI2 receptors endogenously ex-
pressed in human erythorleulemia cells is about 8.4 nM. It
compares favorably versus the benchmark compound
RO1138452.
Recently, Bley et al.8 reported the pharmacological
study of PGI2 antagonists RO1138452 and RO 3244794
while Nakae et al.9 reported the characterization of PGI2
antagonists “compounds A” and “B” (named according to
Nakae et. al.). RO1138452 belongs to the class of N-[4-
(benzylphenyl)-4,5-dihydro-1H-imidazol-2-amine. On the
other hand, RO3244794, compounds A and B are substi-
tuted propanoic acids. RO1138452 has a pKi value of 9.2 in
human platelet PGI2 receptors, while the latter group is at
least 10 times less potent. However, RO1138452 suffers
from lack of specificity. It also binds to PAF receptor (pKi
7.9) and imidazole I2 receptor (pKi 8.3) in addition to its
PGI2 antagonistic activities. Therefore, more studies are re-
quired to understand the structural requirement for potent
and selective PGI2 antagonists. In this study, we reported
that substituted a-benzyl-indanones are potent PGI2 antag-
onists with biological activities comparable to the most po-
tent PGI2 antagonists reported. The indanone skeleton of
the derivatives is well tolerated. We also observed that sub-
stitutions on the indanone aromatic ring have a major im-
pact on its activity. These results may shed light on the de-
In addition, for the preparation of 11b, starting mate-
rial 8b was synthesized from 3-methylcinnamic acid. 3-
Cinnamic acid was hydrogenated using Pd/C catalyzed hy-
drogenation. After reaction with oxalyl chloride, it under-
went self Friedel-Craft reaction to give 80% of 8b and 20%
of 1-methylindanenone.
In order to screen for PGI2 antagonistic activity, we
designed an assay based on PGI2 agonist’s ability to induce
ERK1/2 phosphorylation in human erythroleukemia cells.
RO1138452 was used as the standard for comparison. It
was found that the substitution at the indanone signifi-
cantly affects the biological activity. In general, com-
pounds with electro-donating substitutions such as in com-
pounds 7, 11b, and 11c are more potent than those with
electro-withdrawing substitutions such as compound 11d.

Substituted Indan-1-one as IP Antagonists
J. Chin. Chem. Soc., Vol. 55, No. 4, 2008 849
Scheme II

850 J. Chin. Chem. Soc., Vol. 55, No. 4, 2008
Chern et al.
sign of novel PGI2 antagonists.
(CDCl3) d: 205.0, 157.7, 155.8, 128.2, 124.9, 114.0, 109.7,
66.4, 47.6, 36.3, 25.8; EI-MS m/z (rel. int. %): 217 (M+,
88), 159 (100), 131 (11), 103 (9); HRMS Calcd for
C13H15NO2: 217.1103. Found: 217.1107.
EXPERIMENTAL
Proton NMR spectra were recorded at 300 MHz on a
Varian Mercury-300. Carbon NMR spectra were recorded
at 75 MHz on a Varian Mercury-300. Proton and carbon
chemical shifts are reported on the scale as parts per million
(ppm) downfield from tetramethylsilane (TMS) as internal
reference. Mass spectra were measured with a VG Analyti-
cal Model 70-250s Spectrometer. All reagents were used as
obtained commercially.
5-Morpholino-2-(4-nitrobenzyl)-2,3-dihydro-1H-inden-
1-one 5
A 2.0 M THF solution of LDA (2 mL) was added
dropwise to a solution of compound 4 (0.5 g, 2.3 mmol) in
dry THF (10 mL) and HMPA (1.3 mL, 2.3 mmol) at -78 °C
under argon for 5 min. After stirring for 1 h, a solution of
4-nitrobenzyl bromide (1.49 g, 6.9 mmol) in dry THF (20
mL) was added and the reaction mixtures were kept at -78
°C under argon. On completion of the reaction (TLC), the
reaction was then quenched with saturated aqueous NH4Cl,
and extracted with CH2Cl2 (20 ´ 4 mL). The organic layers
were combined, dried over MgSO4 and concentrated under
reduced pressure. The product was isolated on silica gel
(50% EtOAc/hexanes) (92%); 1H-NMR (CDCl3) d: 8.14
(2H, dd, J = 1.8, 8.7 Hz), 7.68 (1H, d, J = 8.7 Hz), 7.40 (2H,
d, J = 8.7 Hz), 6.89 (1H, dd, J = 2.1, 8.7 Hz), 6.73 (1H, d, J
= 2.1 Hz), 3.85 (4H, t, J = 4.8 Hz), 3.41 (1H, dd, J = 4.2,
13.8 Hz), 3.33 (4H, t, J = 5.1 Hz), 3.11 (1H, dd, J = 7.5,
16.8 Hz), 3.03-2.95 (1H, m), 2.85 (1H, dd, J = 9.6, 13.8
Hz), 2.71 (1H, dd, J = 3.6, 16.8 Hz); 13C-NMR (CDCl3) d:
204.4, 156.2, 155.7, 147.8, 146.6, 129.8, 127.1, 125.5,
123.6, 114.3, 109.4, 66.4, 48.2, 47.5, 37.0, 31.9; EI-MS m/z
(rel. int. %): 352 (M+, 100), 335 (18), 274 (15), 216 (13),
158 (81); HRMS Calcd for C20H20N2O4: 352.1423. Found:
352.1426.
ERK1/2 Phosphorylation Assay
ERK1/2 can be activated by PGI2 agonist treatment in
human erythroleukemia (HEL) cells.13 ERK1/2 activation
required phosphorylation at residues Thr202/Tyr204 and
Thr185/Tyr187, respectively. Therefore, by using poly-
conal antibodies specific for the phosphorylated form of
ERK1/2 at Thr202/Tyr204 and Thr185/Tyr187 (New Eng-
land Biolabs) for immunoblot analysis, ERK1/2 activation
can be quantitated. Atypical assay is as follows. Subconfluent
HEL cells were incubated in RPMI in the absence of serum
overnight at 37 °C. HEL cells were incubated with vehicle
or antagonists for 30 minutes before activation with PGI2
agonist, 1 mM beraprost. After stimulation, cells were rap-
idly lysed by sample buffer [62.5 mM Tris-HCl (pH 6.5 at
25 °C), 2% w/v SDS, 10% glycerol, 50 mM dithiothreitol,
0.1 w/v bromophenol blue] at 4 °C. Total cell lysates (100
mg protein) were separated by gel electrophoresis (10%
acrylamide gel) and transferred onto PVDF membrane.
The membrane was blotted with anti-phospho-ERK1/2 anti-
body (1:1000) overnight and then probed with peroxidase-
conjugated secondary antibody (1:2000), followed by vi-
sualization with ECL Western Blotting reagents. The re-
sults were quantitated by densitometry using the software
SigmaGelÒ.
2-(4-Aminobenzyl)-5-morpholino-2,3-dihydro-1H-
inden-1-one 6
One-tenth of a gram (0.28 mmol) of compound 5 was
dissolved in 10 mL of THF. After the addition of 0.1 g of
5% Pd-C, the mixture was hydrogenated for 3 hours. After
hydrogen consumption had ceased, the solution was fil-
tered through Celite and concentration afforded a residue.
Product 6 was obtained in 93% yield (0.085 g); 1H-NMR
(CDCl3) d: 7.63 (1H, d, 8.4 Hz), 6.98 (2H, d, J = 8.4 Hz),
6.82 (1H, dd, J = 1.8, 8.4 Hz), 6.71 (1H, d, J = 1.8 Hz), 6.59
(2H, d, J = 8.4 Hz), 3.82 (4H, t, J = 4.8 Hz), 3.30 (4H, t , J =
4.8 Hz), 3.21 (1H, dd, J = 4.2, 14.1 Hz), 3.00 (1H, dd, J =
7.5, 17.4 Hz), 2.91-2.85 (1H, m), 2.73 (1H, dd, J = 5.3, 16.8
Hz), 2.53 (1H, dd, J = 10.2, 13.8 Hz); 13C-NMR (CDCl3) d:
206.0, 156.3, 155.8, 144.5, 129.5, 129.4, 127.5, 125.1,
115.0, 114.0, 109.5, 66.3, 49.1, 47.3, 36.3, 31.9; EI-MS m/z
(rel. int. %): 322 (M+, 32), 217 (49), 159 (11), 106 (100);
HRMS Calcd for C20H22N2O2: 322.1681. Found: 322.1680.
5-Morpholino-2,3-dihydro-1H-inden-1-one 4
A mixture of 5-fluoro-inden-1-one 3 (1.0 g, 6.66
mmol) and morpholine (1.7 mL, 19.98 mmol) in anhydrous
DMSO (15 mL) was stirred at 100-110 °C. After stirring
for 3 h, the solution was treated with and extracted with
EtOAc (10 mL ´ 3). The organic layers were then com-
bined, washed with brine, dried over anhydrous MgSO4,
filtered, and concentrated. The residue was purified on sil-
1
ica gel (30% EtOAc/hexanes) (96%); H-NMR (CDCl3)
d:7.64 (1H, d, J = 8.7 Hz), 6.88 (1H, dd, J = 2.1, 8.7 Hz),
6.82 (1H, s), 3.86 (4H, t, J = 4.8 Hz), 3.34 (4H, t, J = 4.8
Hz), 3.06-2.99 (2H, m), 2.66-2.62 (2H, m); 13C-NMR

Substituted Indan-1-one as IP Antagonists
J. Chin. Chem. Soc., Vol. 55, No. 4, 2008 851
2-(4-Nitrobenzyl)-2,3-dihydro-1H-inden-1-one 9a
The complex was prepared similarly as compound 5
(94%); 1H-NMR (CDCl3) d: 8.18 (2H, dd, J = 1.8, 6.6 Hz),
7.78 (1H, d, J = 7.5 Hz), 7.63-7.55 (1H, m), 7.43-7.38 (4H,
m), 3.45 (1H, dd, J = 3.9, 13.8 Hz), 3.23 (1H, dd, J = 7.8,
17.1 Hz), 3.08-2.99 (1H, m), 2.91-2.79 (2H, m); HRMS
Calcd for C16H13NO3: 267.0895. Found: 267.0892.
5-Methyl-2-(4-nitrobenzyl)-2,3-dihydro-1H-inden-1-
one 9b
Hz), 2.95-2.79 (2H, m), 2.57 (1H, dd, J = 9.6, 13.8 Hz);
13C-NMR (CDCl3) d: 208.1, 153.7, 144.6, 136.5, 134.6,
129.6, 129.1, 127.2, 126.4, 123.7, 115.1, 49.0, 36.0, 31.9;
EI-MS m/z (rel. int. %): 237 (M+, 24), 106 (100); HRMS
Calcd for C16H15NO: 237.1151. Found: 237.1152.
2-(4-Aminobenzyl)-5-methyl-2,3-dihydro-1H-inden-1-
one 10b
The complex was prepared similarly as compound 6
(95%); 1H-NMR (CDCl3) d: 7.64 (1H, d, J = 7.8 Hz), 7.17-
7.14 (2H, m), 7.01 (2H, d, J = 8.1 Hz), 6.60 (2H, d, J = 8.1
Hz), 3.45 (2H, bs, -NH2), 3.21 (1H, dd, J = 4.2, 13.8 Hz),
3.07 (1H, dd, J = 7.5, 17.1 Hz), 2.95-2.89 (1H, m), 2.77
(1H, dd, J = 3.6, 16.8 Hz), 2.56 (1H, dd, J = 9.9, 13.8 Hz),
2.41 (3H, s, -CH3); 13C-NMR (CDCl3) d: 207.4, 154.2, 145.8,
144.6, 134.3, 129.6, 129.4, 128.5, 126.8, 123.6, 115.2,
49.2, 36.1, 31.8, 21.9; EI-MS m/z (rel. int. %): 251 (M+,
27), 106 (100); HRMS Calcd for C17H17NO: 251.1310.
Found: 251.1316.
The complex was prepared similarly as compound 5
(80%); 1H-NMR (CDCl3) d: 8.16 (2H, d, J = 8.7 Hz), 7.68
(1H, d, J = 7.8 Hz), 7.42 (2H, d, J = 8.7 Hz), 7.31 (1H, d, J =
8.7 Hz), 7.21 (1H, s), 3.43 (1H, dd, J = 4.2, 13.8 Hz), 3.18
(1H, dd, J = 7.5, 16.8 Hz), 3.08-2.99 (1H, m), 2.88 (1H, dd,
J = 9.6, 13.8 Hz), 2.78 (1H, dd, J = 3.9, 13.8 Hz), 2.45 (3H,
s, -CH3); 13C-NMR (CDCl3) d: 206.2, 153.6, 147.5, 146.4,
129.7, 129.2, 128.9, 126.9, 123.9, 123.7 (2C), 48.2, 36.7,
31.7, 22.0; HRMS Calcd for C17H15NO3: 281.1052. Found:
281.1055.
2-(4-Aminobenzyl)-5-methoxy-2,3-dihydro-1H-inden-1-
one 10c
5-Methoxy-2-(4-nitrobenzyl)-2,3-dihydro-1H-inden-1-
one 9c
The complex was prepared similarly as compound 6
(92%); 1H-NMR (CDCl3) d: 7.65 (1H, d, J = 8.7 Hz), 6.95
(2H, d, J = 8.1 Hz), 6.85-6.80 (1H, m), 6.76 (1H, d, J = 0.9
Hz), 6.57 (2H, d, J = 8.1 Hz), 3.78 (3H, s, -OCH3), 3.53
(2H, bs, -NH2), 3.18 (1H, dd, J = 3.9, 13.8 Hz), 3.01 (1H,
dd, J = 6.6, 15.6 Hz), 2.91-2.82 (1H, m), 2.74 (1H, dd, J =
3.6, 16.8 Hz), 2.53 (1H, dd, J = 9.9, 13.8 Hz); 13C-NMR
(CDCl3) d: 206.2, 165.0, 156.6, 144.6, 130.6, 129.3, 128.8,
125.1, 115.0, 114.8, 109.3, 55.2, 48.9, 35.9, 31.7; EI-MS
m/z (rel. int. %): 267 (M+, 11), 106 (100); HRMS Calcd for
C17H17NO2: 267.1251. Found: 267.1255.
The complex was prepared similarly as compound 5
(86%); 1H-NMR (CDCl3) d: 8.13 (2H, d, J = 8.7 Hz), 7.69
(1H, d, J = 8.4 Hz), 7.40 (2H, d, J = 8.4 Hz), 6.91 (1H, dd, J
= 1.8, 8.4 Hz), 6.81 (1H, d, J = 1.8 Hz), 3.86 (3H, s,
-OCH3), 3.40 (1H, dd, J = 4.2, 13.8 Hz), 3.14 (1H, dd, J =
9.3, 17.1 Hz), 3.05-2.95 (1H, m), 2.84 (1H, dd, J = 9.3, 13.5
Hz), 2.73 (1H, dd, J = 3.9, 17.1 Hz); 13C-NMR (CDCl3) d:
204.9, 165.6, 156.1, 147.6, 130.9, 129.8, 125.8, 123.7, 123.4,
115.6, 109.6, 55.6, 48.3, 36.8, 31.9; EI-MS m/z (rel. int.
%): 297 (M+, 44), 161 (100); HRMS Calcd for C17H15NO4:
297.0989. Found: 297.0995.
2-(4-Aminobenzyl)-5-chloro-2,3-dihydro-1H-inden-1-
one 10d
5-Chloro-2-(4-nitrobenzyl)-2,3-dihydro-1H-inden-1-one
9d
The complex was prepared similarly as compound 6
(94%); 1H-NMR (CDCl3) d: 7.78 (1H, d, J = 7.5 Hz), 7.57
(1H, t, J = 7.5 Hz), 7.40 (1H, m), 7.03 (2H, d, J = 7.8 Hz),
6.62 (2H, d, J = 7.8 Hz), 3.24 (1H, dd, J = 3.9, 13.8 Hz),
3.15 (1H, dd, J = 7.5, 16.8 Hz), 2.98-2.82 (2H, m), 2.59
(1H, dd, J = 9.9, 13.8 Hz); 13C-NMR (CDCl3) d: 208.2,
153.8, 144.5, 136.6, 134.7, 129.8, 129.6, 127.3, 126.6,
123.9, 115.4, 49.2, 36.1, 32.1; EI-MS m/z (rel. int. %): 273
(M++2, 0.7), 271 (M+, 2), 237 (17), 106 (100), 77 (9);
HRMS Calcd for C16H14ClNO: 271.0764. Found: 271.0769.
5-[4-(Methansulfonyl)pPGI2erazin-1-yl]-2,3-dihydro-
1H-inden-1-one 13
The complex was prepared similarly as compound 5.
It was quantified by 1H NMR (with CH2Cl2 as internal stan-
dard) (75%); 1H-NMR (CDCl3) d: 8.17 (2H, td, J = 2.1, 8.7
Hz), 7.74-7.69 (1H, m), 7.42-7.35 (2H, m), 7.31-7.27 (2H,
m), 3.42 (1H, dd, J = 4.5, 13.8 Hz), 3.21 (1H, dd, J = 7.8,
17.1 Hz), 3.08-3.01 (1H, m), 2.87 (1H, m), 2.81 (1H, dd, J
= 4.2, 17.1 Hz).
2-(4-Aminobenzyl)-2,3-dihydro-1H-inden-1-one 10a
The complex was prepared similarly as compound 6
(98%); 1H-NMR (CDCl3) d: 7.76 (1H, d, J = 7.8 Hz), 7.54
(1H, td, J = 1.2, 7.8 Hz), 7.38-7.30 (2H, m), 7.01 (2H, d, J =
8.4 Hz), 6.60 (2H, dd, J = 4.8, 8.4 Hz), 3.53 (2H, bs, -NH2),
3.23 (1H, dd, J = 3.9, 13.8 Hz), 3.12 (1H, dd, J = 7.5, 16.8
The complex was prepared similarly as compound 4,
while morpholine was used instead of pPGI2erazine. After

852 J. Chin. Chem. Soc., Vol. 55, No. 4, 2008
Chern et al.
reaction, the resulting solution was concentrated under
pressure without any further purification. The product was
a light yellow liquid and it was quantified by 1H NMR (with
CH2Cl2 as internal standard) (78%); 1H-NMR (CDCl3) d:
7.64 (1H, d, J = 8.7 Hz), 6.90 (1H, dd, J = 2.4, 8.7 Hz), 6.85
(1H, d, J = 9.3 Hz), 3.50-3.29 (8H, m), 3.06 (2H, t, J = 6.6
Hz), 2.83 (3H, s, -CH3), 2.69-2.16 (2H, t, J = 6.6 Hz);
13C-NMR (CDCl3) d: 205.0, 157.8, 155.2, 155.1, 125.2,
115.3, 111.0, 47.9, 45.4, 36.4, 34.6, 25.9.
2-[4-(4,5-Dihydro-1H-imidazol-2-ylamino)benzyl]-5-
morpholin-2,3-dihydro-1H-inden-1-one 7
The complex was prepared by as described in the pre-
vious section (86%); 1H-NMR (CDCl3) d: 7.66 (1H, d, J =
8.4 Hz), 7.42 (2H, d, J = 8.4 Hz), 7.17 (2H, d, J = 8.7 Hz),
6.86 (1H, dd, J = 2.1, 8.4 Hz), 6.7 (1H, d, J = 2.1 Hz), 4.86
(1H, s, -NH), 4.06 (2H, t, J = 7.5 Hz), 3.85 (4H, t, J = 4.8
Hz), 3.55 (2H, t, J = 7.5 Hz), 3.32 (5H, t, J = 4.8 Hz), 3.05
(1H, dd, J = 4.8, 16.8 Hz), 2.98-2.89 (1H, m), 2.75 (1H, dd,
J = 3.3, 16.5 Hz), 2.62 (1H, dd, J = 10.2, 13.8 Hz); 13C-
NMR (CDCl3) d: 205.9, 158.5, 156.3, 155.9, 150.7, 135.9,
135.0, 129.4, 125.4, 119.9, 114.3, 109.8, 66.5, 48.9, 47.7,
42.1, 36.6, 32.0, 29.7; EI-MS m/z (rel. int. %): 349 (M+-
C2H3N, 20), 348 (82), 216 (100), 158 (40), 132 (52);
HRMS Calcd for C23H26N4O2-C2H3N: 349.1790. Found:
349.1788.
5-[4-(Methansulfonyl)pPGI2erazin-1-yl]-2-(4-nitroben-
zyl)-2,3-dihydro-1H-inden-1-one 14
The complex was prepared similarly as compound 5.
It was quantified by 1H NMR (with CH2Cl2 as internal stan-
dard) (82%); 1H-NMR (CDCl3) d: 8.13 (2H, d, J = 8.7 Hz),
7.67 (1H, d, J = 8.7 Hz), 7.39 (2H, d, J = 8.7 Hz), 6.90 (1H,
dd, J = 6.6, 8.7 Hz), 6.75 (1H, d, J = 1.5 Hz), 3.50-3.36 (8H,
m), 3.11 (1H, dd, J = 7.8, 17.1 Hz), 3.04-2.97 (1H, m),
2.92-2.85 (1H, m), 2.84-2.80 (1H, m), 2.83 (3H, s), 2.71
(1H, dd, J = 3.6, 10.5 Hz); 13C-NMR (CDCl3) d: 205.2,
154.5, 148.0, 147.0, 141.7, 129.8, 129.3, 128.6, 126.8,
125.2, 123.8, 48.3, 45.2, 36.9, 36.5, 31.7, 29.6.
2-[4-(4,5-Dihydro-1H-imidazol-2-ylamino)benzyl]-2,3-
dihydro-1H-inden-1-one 11a
The complex was prepared by as described in the pre-
vious section (87%); 1H-NMR (CDCl3) d: 10.16 (1H, bs,
-NH), 7.79 (1H, d, J = 7.8 Hz), 7.57 (1H, td, J = 1.2, 8.7
Hz), 7.44-7.34 (4H, m), 7.18 (2H, d, J = 8.4 Hz), 4.95 (1H,
bs, -NH), 4.06 (2H, t, J = 7.8 Hz), 3.56 (2H, t, J = 8.4 Hz),
3.37 (1H, dd, J = 4.2, 14.1 Hz), 3.17 (1H, dd, J = 7.2, 17.1
Hz), 3.02-2.94 (1H, m), 2.85 (1H, dd, J = 4.2, 17.4 Hz),
2.65 (1H, dd, J = 9.9, 13.8 Hz); 13C-NMR (CDCl3) d:
207.9, 158.5, 153.7, 150.7, 136.5, 136.1, 134.8, 129.4,
127.4, 126.6, 124.0, 120.0, 48.9, 42.1, 36.7, 36.4, 32.1;
EI-MS m/z (rel. int. %): 264 (M+-C2H3N, 5), 263 (15), 218
(100), 132 (99), 106 (17); HRMS Calcd for C19H19N3O-
C2H3N: 264.1263. Found: 264.1260.
2-(4-Aminobenzyl)-5-[4-(methansulfonyl)pPGI2erazin-
1-yl]-2-(4-nitrobenzyl)-2,3-dihydro-1H-inden-1-one 15
The complex was prepared similarly as compound 6
(95%); 1H-NMR (CDCl3) d: 7.64 (1H, d, J = 8.7 Hz), 7.00
(2H, d, J = 8.4 Hz), 6.86 (1H, d, J = 8.7 Hz), 6.74 (1H, s),
6.60 (2H, d, J = 8.7 Hz), 3.45-3.37 (8H, m), 3.18 (1H, dd, J
= 6.6, 17.4 Hz), 3.03 (1H, dd, J = 7.8, 17.1 Hz), 2.92-2.85
(1H, m), 2.82 (3H, s, -CH3), 2.82-2.70 (1H, m), 2.52 (1H,
dd, J = 9.6, 13.8 Hz); 13C-NMR (CDCl3) d: 206.0, 156.4,
155.2, 144.5, 129.7, 129.6, 128.4, 125.4, 115.2, 115.1,
110.8, 49.2, 45.3, 36.3, 34.3, 32.0, 29.6; EI-MS m/z (rel.
int. %): 399 (M+, 47), 320 (27), 294 (55), 215 (29), 106
(100), 56 (28); HRMS Calcd for C21H25N3O3S: 399.1617.
Found: 399.1619.
2-[4-(4,5-Dihydro-1H-imidazol-2-ylamino)benzyl]-5-
methyl-2,3-dihydro-1H-inden-1-one 11b
The complex was prepared by as described in the pre-
vious section (85%); 1H-NMR (CDCl3) d: 10.15 (1H, bs,
-NH), 7.64 (1H, d, J = 8.4 Hz), 7.42 (2H, d, J = 7.8 Hz),
7.18-7.15 (4H, m), 5.46 (1H, bs, -NH), 4.04 (2H, t, J = 8.4
Hz), 3.53 (2H, t, J = 8.4 Hz), 3.31 (1H, dd, J = 3.9, 13.8
Hz), 3.09 (1H, dd, J = 7.8, 17.1 Hz), 2.99-2.91 (1H, m),
2.79 (1H, dd, J = 3.5, 17.1 Hz), 2.63 (1H, dd, J = 9.9, 13.8
Hz), 2.41 (3H, s); 13C-NMR (CDCl3) d: 207.4. 158.6.
154.2. 150.8. 146.0. 136.0. 134.9. 129.4. 128.7. 126.9.
123.8. 119.9. 49.0. 42.1. 36.6. 36.4. 31.9. 22.0; EI-MS m/z
(rel. int. %): 278 (M+-C2H3N, 4), 277 (9), 218 (100), 145
(41), 132 (88), 106 (15); HRMS Calcd for C20H21N3O-
C2H3N: 278.1419. Found: 278.1422.
General procedure for the synthesis of compound 7,
11, and 16
Dimethyl chlorophosphate (3 equiv) and Et3N (3
equiv) was added into a solution of the imidazolidin-2-one
in CH2Cl2 at room temperature under nitrogen. The reac-
tion mixture was stirred at 35 °C for 5 h. The appropriate
amine (1 equiv) was dissolved in CH2Cl2 and added drop-
wise into the reaction mixture. The progress of the reaction
was monitored by TLC. After an aqueous work up the sol-
vent was evaporated under reduced pressure and the resi-
due was purified on silica gel (50% EtOAc/hexanes).

Substituted Indan-1-one as IP Antagonists
J. Chin. Chem. Soc., Vol. 55, No. 4, 2008 853
2-[4-(4,5-Dihydro-1H-imidazol-2-ylamino)benzyl]-5-
methoxy-2,3-dihydro-1H-inden-1-one 11c
Hz), 3.55 (2H, t, J = 8.1 Hz), 3.48-3.41 (4H, m), 3.38-3.36
(4H, m), 3.28 (1H, dd, J = 3.9, 13.8 Hz), 3.03 (1H, dd, J =
7.8, 16.8 Hz), 2.94-2.85 (1H, m), 2.82 (3H, s), 2.76 (1H,
dd, J = 3.9, 15.9 Hz), 2.65 (1H, dd, J = 9.6, 13.8 Hz);
13C-NMR (CDCl3) d: 205.8, 158.5, 156.4, 155.3, 136.0,
135.0, 129.5, 128.3, 125.5, 119.9, 115.3, 110.9, 53.8, 49.0,
47.8, 45.4, 36.6, 34.6, 32.0, 29.7; EI-MS m/z (rel. int. %):
426 (M+-C2H3N, 4), 347 (17), 321 (29), 242 (20), 215
(100), 106 (69); HRMS Calcd for C24H29N5O3S-C2H3N:
426.1726. Found: 426.1730.
The complex was prepared by as described in the pre-
vious section (80%); 1H-NMR (CDCl3) d: 7.67 (1H, d, J =
8.4 Hz), 7.42 (2H, d, J = 8.4 Hz), 7.16 (2H, d, J = 8.4 Hz),
6.89 (1H, dd, J = 8.4, 2.4 Hz), 6.82 (1H, d, J = 2.4 Hz), 5.22
(2H, bs, -NH2), 4.05 (2H, t, J = 8.4 Hz), 3.85 (3H, s, -OCH3),
3.54 (2H, t, J = 8.4 Hz), 3.31 (1H, dd, J = 3.9, 13.8 Hz),
3.09 (1H, dd, J = 7.8, 16.8 Hz), 3.02-2.90 (1H, m), 2.78
(1H, dd, J = 3.0, 16.8 Hz), 2.62 (1H, dd, J = 10.5, 14.1 Hz);
13C-NMR (CDCl3) d: 206.1, 165.4, 158.5, 156.7, 136.0,
134.9, 129.8, 129.4, 125.6, 119.9, 115.5, 109.6, 55.6, 49.0,
42.1, 36.7, 36.5, 32.1; EI-MS m/z (rel. int. %): 294 (M+-
C2H3N, 7), 293 (13), 218 (100), 161 (38), 132 (56); HRMS
Calcd for C20H21N3O2-C2H3N: 294.1368. Found: 294.1371.
2-[4-(4,5-Dihydro-1H-imidazol-2-ylamino)benzyl]-5-
chloro-2,3-dihydro-1H-inden-1-one 11d
Received July 10, 2007.
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The complex was prepared by as described in the pre-
vious section (72%); 1H-NMR (CDCl3) d: 10.16 (1H, bs,
-NH), 7.77 (1H, d, J = 7.5 Hz), 7.57 (1H, t, J = 7.2 Hz),
7.45-7.34 (3H, m), 7.17 (2H, d, J = 8.4 Hz), 4.05 (2H, t, J =
7.8 Hz), 3.54 (2H, t, J = 8.4 Hz), 3.33 (1H, dd, J = 3.9, 13.8
Hz), 3.17 (1H, dd, J = 7.8, 17.1 Hz), 3.02-2.93 (1H, m),
2.85 (1H, dd, J = 3.9, 17.1 Hz), 2.65 (1H, dd, J = 10.2, 14.1
Hz); 13C-NMR (CDCl3) d: 207.9, 158.5, 153.7, 151.0,
136.6, 136.1, 134.8, 129.4, 127.4, 126.6, 123.9, 120.0,
48.9, 42.1, 36.7, 36.3, 32.1; EI-MS m/z (rel. int. %): 339
(M+-C2H3N, 5), 263 (14), 218 (22), 132 (100), 106 (16), 77
(11); HRMS Calcd for C19H17ClN3O-C2H3N: 339.1138.
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2-[4-(4,5-Dihydro-3H-imidazol-2-ylamino)-benzyl]-5-
(4-methansulfonyl-pPGI2erazin-1-yl)-2,3-dihydro-1H-
inden-1-one 16
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The complex was prepared by as described in the pre-
vious section (81%); 1H-NMR (CDCl3) d: 10.15 (1H, bs,
-NH), 7.67 (1H, d, J = 8.7 Hz), 7.41 (2H, d, J = 8.4 Hz),
7.15 (2H, d, J = 8.4 Hz), 6.87 (1H, dd, J = 1.8, 8.7 Hz), 6.75
(1H, d, J = 1.8 Hz), 4.90 (1H, bs, -NH), 4.06 (2H, t, J = 7.8
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