Diaryl dihydropyrazole-3-carboxamides with significant in vivo antiobesity activity related to CB1 receptor antagonism: Synthesis, biological evaluation, and molecular modeling in the homology model

Article abstract of DOI:10.1021/jm061490u

A number of analogues of diaryl dihydropyrazole-3-carboxamides have been synthesized. Their activities were evaluated for appetite suppression and body weight reduction in animal models. Depending on the chemical modification of the selected dihydropyrazole scaffold, the lead compounds - the bisulfate salt of (±)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3- carboxylic acid morpholin-4-ylamide 26 and the bisulfate salt of (-)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3- carboxylic acid morpholin-4-ylamide 30-showed significant body weight reduction in vivo, which is attributed to their CB1 antagonistic activity and exhibited a favorable pharmacokinetic profile. The molecular modeling studies also showed interactions of two isomers of (±)-5-(4-chlorophenyl)-1-(2,4- dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid morpholin-4-ylamide 9 with CB1 receptor in the homology model similar to those of N-piperidino-5-(4- chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide (rimonabant) 1 and 4S-(-)-3-(4-chlorophenyl)-N-methyl-N′-[(4-chlorophenyl) -sulfonyl]-4-phenyl-4,5-dihydro-1H-pyrazole-1-carboxamidine (SLV-319) 2.

Full text of DOI:10.1021/jm061490u

J. Med. Chem. 2007, 50, 5951-5966
5951
Diaryl Dihydropyrazole-3-carboxamides with Significant In Vivo Antiobesity Activity Related to
CB1 Receptor Antagonism: Synthesis, Biological Evaluation, and Molecular Modeling in the
Homology Model†
Brijesh Kumar Srivastava,* Amit Joharapurkar, Saurin Raval, Jayendra Z. Patel, Rina Soni, Preeti Raval, Archana Gite,
Amitgiri Goswami, Nisha Sadhwani, Neha Gandhi, Harilal Patel, Bhupendra Mishra, Manish Solanki, Bipin Pandey,
Mukul R. Jain, and Pankaj R. Patel
Zydus Research Centre, Sarkhej-BaVla N. H. 8A, Moraiya, Ahmedabad 382210, India
ReceiVed December 30, 2006
A number of analogues of diaryl dihydropyrazole-3-carboxamides have been synthesized. Their activities
were evaluated for appetite suppression and body weight reduction in animal models. Depending on the
chemical modification of the selected dihydropyrazole scaffold, the lead compoundssthe bisulfate salt of
(()-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid morpholin-4-
ylamide 26 and the bisulfate salt of (-)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-
3-carboxylic acid morpholin-4-ylamide 30sshowed significant body weight reduction in vivo, which is
attributed to their CB1 antagonistic activity and exhibited a favorable pharmacokinetic profile. The molecular
modeling studies also showed interactions of two isomers of (()-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-
4,5-dihydro-1H-pyrazole-3-carboxylic acid morpholin-4-ylamide 9 with CB1 receptor in the homology model
similar to those of N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide
(rimonabant) 1 and 4S-(-)-3-(4-chlorophenyl)-N-methyl-N′-[(4-chlorophenyl)-sulfonyl]-4-phenyl-4,5-dihydro-
1H-pyrazole-1-carboxamidine (SLV-319) 2.
Introduction
agonist in humans and rodents, indicating the role of CB1
receptor in regulation of energy balance.4,6 Thus, CB1 receptor
antagonists/inverse agonists represent a promising new approach
for reducing body weight and decreasing the co-morbidities
associated with excessive adiposity.7
Rimonabant hydrochloride 1 (Figure 1) is the first therapeuti-
cally relevant, potent, and selective CB1 receptor inverse
agonist, recently approved in Europe as an antiobesity drug,
which belongs to the diaryl pyrazole family.8
Since the discovery of rimonabant, several classes of CB1
receptor antagonist with diverse chemical structures have been
disclosed.9-11 Solvay pharmaceuticals has disclosed the 3,4-
diaryl dihydropyrazole class of compound 2 (Figure 1) as a CB1
antagonist, which has elicited potent in vitro12 and in vivo13
activities.
More recently, there has been a surge of interest in this area,
and several research groups are actively working with a view
to generate diverse structures with desired activity. These studies
have provided more insight into pivotal receptor-ligand interac-
tions and eventually led to the diverse chemical structures,10
although very limited in vivo studies of body weight regulation
by these CB1 antagonists are published. 8-Chloro-1-(2,4-
dichlorophenyl)-N-piperidin-1-yl-1,4,5,6-tetrahydrobenzo-[6,7]-
cyclohepta-[1,2-c]-pyrazole-3-carboxamide 3 (Figure 1) was
found to be a very potent CB1 antagonist in cell-based in vitro
assays and ex vivo screens.14 However, the molecule had poor
in vivo efficacy and oral bioavailability.15 Demonstration of in
vivo efficacy in appropriate animal models of obesity and
appetite suppression is an important criterion for selection of
CB1 antagonists for further development.
Obesity is one of the greatest health threats of this century.1
Obesity is usually defined using the body mass index [BMI )
weight (kg)/height (m)2]. People with BMI of 30 and above
(27 and above for Chinese and Asian people) possess great risk
of co-morbid diseases such as hypertension, type 2 diabetes,
and dyslipidaemia.2
The worldwide explosion of obesity and related disorders are
generally attributed to Western dietary habits (high sugar, high
fat diet). The benefits of a controlled dietary intake can be
profound for the management of obesity. Hence, it has been a
goal of research to develop antiobesity drugs that are effective
and safe in targeting appetite suppression.3
The endocannabinoid system (ECB) has an important con-
served evolutionary role in regulation of energy balance.4 The
ECB system comprises of at least two cannabinoid receptors
(CB1 and CB2), endogenous lipid-like ligands (endocannab-
inoids), and the enzymes involved in their formation and
breakdown.5
CB1 receptors are found primarily in brain and neuronal
tissues, while CB2 receptors are found predominantly in immune
cells and tissues. Both cannabinoid receptors belong to the
G-protein coupled receptor family, sharing approximately 48%
homology in their amino acid sequences. Both CB1 and CB2
receptors are coupled to mitogen-activated protein kinase and
adenylyl cyclase signaling systems.5
It has been found clinically and experimentally that the
endocannabinoid system is hyperactive in obese subjects.6 Both
exogenous and endogenous cannabinoids stimulate food intake,
which is attenuated by pretreatment with CB1 antagonist/inverse
Recently Lange et al. have emphasized bioisosteric replace-
ment in the cannabinoid research,16 wherein the thiazoles,
triazoles, and imidazoles have replaced the pyrazole moiety of
rimonabant. The resulting imidazole compounds have shown
impressive potency in pharmacological in vivo activities in both
† ZRC communication #186.
* Corresponding author. Tel.: +91-2717-250801. Fax: +91-2717-
250606. E-mail:
yahoo.com.
brijeshsrivastava@zyduscadila.com, bksri2000@
10.1021/jm061490u CCC: $37.00 © 2007 American Chemical Society
Published on Web 11/03/2007

5952 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
SriVastaVa et al.
Figure 1.
a CB agonist-induced hypertension model and a CB agonist-
induced hypothermia model.16
Similarly, Christopher et al. have published an imidazole
surrogate related to the pyrazole rimonabant and an optimized
series for compounds that are orally bioavailable with good
pharmacokinetic properties and that have shown efficacy in
obese rats both by reducing food intake and overall body
weight.17
Scheme 1a
a Reagents and conditions: (a) KOH, MeOH, 0-10 °C, 10-15 h; (b) EtI, DMF, 72-75 °C, 4-6 h; (c) EtOH, 26-28 °C, 2-4 h, AcOH, 108-110 °C,
18-22 h; (d) KOH(aq), MeOH, 65-68 °C, 2-3 h; (e) R3NH2, HOBt‚H2O, EDC‚HCl, NEt3, CH2Cl2, 26-28 °C, 30-50 min.

Diaryl Dihydropyrazole-3-carboxamides
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5953
Chemistry
A series of proprietary compounds 4-33 based on the
structural similarities with rimonabant 1 were synthesized in
convergent approach as shown in Schemes 1-4. The dihydro
analogues 4-14 were prepared by condensing the corresponding
acids 49-54 with cyclic amines R3-NH2 under usual peptide
(amide) bond formation chemistry using [1-(3-dimethylamino-
propyl)-3-ethylcarbodiimide] hydrochloride and 1-hydroxyben-
zotriazole hydrate. The synthesis of acids 49-54 involved usual
basic hydrolysis of corresponding esters 43-48 which in turn
were prepared by condensing R,â-unsaturated keto esters 38
and 39 with suitably substituted phenyl hydrazines 40-42 under
acidic conditions. The construction of R,â-unsaturated keto
esters involved the usual condensation of corresponding alde-
hydes 34 and 35 with pyruvic acid under basic conditions
followed by esterification with ethyl iodide. The formation of
a diversity of compounds 15-24 (Formula F, Scheme 2) in this
series was ensued by varying aldehydes 55-64 (Formula A,
Scheme 2). The aldehydes 34 and 35 were procured from Sigma-
Aldrich, and aldehydes 55-64 were synthesized as per literature
procedure.20 Although there is sufficient literature evidence
available for synthesis of R,â-unsaturated keto esters, the present
Figure 2.
Using bioisosteric replacement in a rational approach, in
conjunction with molecular modeling studies, we synthesized
several diaryl dihydropyrazole carboxamide derivatives18 4-33
(Figure 2) and evaluated their efficacy in a 5% sucrose solution
intake model at a single dose. A few selected compounds were
tested for efficacy with a chronic dose for food consumption
and body weight reduction in genetically obese rodent models.
The pharmacokinetic parameters and tissue distribution of se-
lected compound were also evaluated. The selected compounds
were used for molecular modeling studies in the homology
model.19
Scheme 2a
a Reagents and conditions: (a) KOH, MeOH, 0-10 °C, 10-15 h; (b) EtI, DMF, 72-75 °C, 4-6 h; (c) EtOH, 26-28 °C, 2-4 h, AcOH, 108-110 °C,
18-22 h; (d) KOH(aq), MeOH, 65-68 °C, 2-3 h; (e) R3NH2, HOBt‚H2O, EDC‚HCl, NEt3, CH2Cl2, 26-28 °C, 30-50 min.

5954 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
SriVastaVa et al.
Scheme 3a
a Reagents and conditions: (a) for (+)-enantiomer: S-(-)-R-methyl benzylamine, CH3CN:(CH3)2CO (1:1), 26-28 °C, 2-4 h; for (-)-enantiomer: R-(+)-
R-methyl benzylamine, CH3CN:(CH3)2CO (1:1), 26-28 °C, 2-4 h; (b) dil. HCl, 5-10 °C, 5-10 min; (c) morpholin-4-ylamine, HOBt‚H2O, EDC‚HCl,
NEt3, CH2Cl2, 26-28 °C, 30-50 min.
Scheme 4a
a Reagents and conditions: (a) ethereal HCl, MeOH, 0-15 °C, 10-15 min; (b) HX, MeOH, 60-65 °C, 30-40 min.
set of conditions afforded compounds 38, 39, and 75-84 in
better yields and are scalable.21-28
ability to reduce the consumption of sucrose solution in
genetically obese Zucker fa/fa rats. The cannabinoid agonists
are reported to enhance sucrose consumption in rodents.29 On
the other hand, the selective central CB1 receptor antagonist
markedly and selectively reduces sucrose feeding and drinking
in rodents.30 Obese Zucker rats have elevated hypothalamic
levels of the endocannabinoid 2-arachidonoyl glycerol as
compared to lean controls.31,32 The higher endocannabinoid tone
in these obese animals may result in higher sensitivity for a
CB1 blockade.
N-Aminopiperidine derivative 4, which structurally mimics
rimonabant, exerted moderate appetite suppression in a single-
dose 5% sucrose solution intake model in genetically obese
Zucker fa/fa rats (Table 1). We have replaced the N-amino-
piperidine side chain of compound 4 by various amino deriva-
tives such as pyrrolidine derivative 5, azabicyclo derivative 6,
homopiperidine derivative 7, N-methyl piperazine derivative 8,
and morpholine derivative 9. Aminopyrrolidine 5 having one
carbon less than the six-membered aminopiperidine was found
to have greatly reduced efficacy. A similar trend was seen for
azabicyclo derivative 6 as well as by seven-membered homo-
piperidine derivative 7. For the carboxamide derivative with
one more heteroatom, i.e., N-amino-N-methyl piperazine 8, the
efficacy was revived to some extent whereas the N-aminomor-
pholine derivative 9 exhibited an efficacy closer to that shown
by rimonabant 1 (Table 1).
As dihydropyrazole analogues 4-24 contained a chiral center
at position 5, the above synthesis provides a target compound
in the form of racemic mixture. To further explore the
stereochemical (chiral) requirements/consequences for binding
to the CB1 receptor, the key compound 9 was synthesized as a
chiraly pure moiety by introducing resolution at suitable stage.
Thus dihydropyrazole-3-carboxylic acid 49 was resolved by
employing S-(-)-R-methyl benzylamine and R-(+)-R-methyl
benzylamine to furnish the corresponding diastereomeric salts.
Removal of resolving agent by 10% HCl solution afforded the
corresponding chiraly pure carboxylic acid as two chiral
antipodes (+)-carboxylic acid 49a and (-)-carboxylic acid 49b,
respectively (Schemes 3). Chiral purity of these carboxylic acids
was confirmed by chiral HPLC and specific optical rotation.
Subsequently various salts 25-33, e.g., hydrochloride, bisulfate,
oxalate, mesylate, and besylate, were prepared with a view to
examine the pharmacodynamic and pharmacokinetic profiles.
Results and Discussion
The present synthetic design was based on the bioisosteric
replacement of the pyrazole moiety of rimonabant 1 by
dihydropyrazole. In this context, we synthesized several diaryl
dihydropyrazoles 4-33. Our strategy in evaluating newly
synthesized cannabinoid antagonists was first to determine their

Diaryl Dihydropyrazole-3-carboxamides
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5955
Table 1. In Vivo Efficacy of Dihydro Diarylpyrazoles 4-14 in 5%
Sucrose Solution Intake Model in Female Zucker fa/fa Rats at a Single
Oral Dose of 10 mg/kg
rimonabant 1 (Table 2). Replacement of the aryl ring at position
5 of dihydropyrazole by heterocycles such as pyridin-3-yl
derivative 20, thiophen-2-yl analogue 21, furan-2-yl derivative
22, 5-methylthiophen-2-yl analogue 23, and 5-chlorothiophen-
2-yl derivative 24 gave compounds whose efficacies tend to
remain inferior to rimonabant 1 as well as 9 (Table 2).
None of the compounds 15-24 were found suitable for
imparting efficacy comparable to 1 in the 5% sucrose solution
intake model in female Zucker fa/fa rats (Table 2). On the basis
of the efficacy observed in the 5% sucrose solution intake model
in female Zucker fa/fa rats, the compound 9 was selected as a
reasonably good candidate for further studies.
The resolution of 9 was done at the pyrazole carboxylic acid
stage 49 (Scheme 3). The racemic compound 9 and both the
enantiomers 9a and 9b in the form of their hydrochloride salts
25, 27, and 29, respectively, were compared in the 5% sucrose
solution intake model in female Zucker fa/fa rats (Table 3). The
hydrochloride salt of (-)-enantiomer 29 showed superior
efficacy to 1, 9, 25, and 27. Since different pharmaceutically
acceptable salts do exhibit different kinetics, few other salts such
as bisulfate, oxalate, methane sulfonate, and benzene sulfonate
salts were synthesized for 9b and evaluated (Scheme 4 and Table
3) for differences in their efficacy profile in the 5% sucrose
model. The oxalate salt 31, methane sulfonate salt 32, and
benzene sulfonate salt 33 exhibited lower potency as compared
to 1 in female Zucker fa/fa rats. The bisulfate salt of racemic
compound 26 was found to be equiefficacious to 1, while the
bisulfate salt of (-)-enantiomer 30 was found to be much
superior than the bisulfate salt of (()-26, the bisulfate salt of
(+)-enantiomer 28, and 1, demonstrating that bisulfate salt is
probably more bioavailable than its hydrochloride salt. On the
basis of the superior efficacy shown by 30 (Table 3), the
compound was studied for a long term (60 days) repeat dose
regime. The results (Figure 3) indicate a favorable response by
30 without developing tolerance, and a similar trend has been
observed for the cumulative food intake by the animals (Figure
4). Furthermore, the inhibitory effect on body weight gain was
accompanied by a significant reduction in serum triglyceride
levels (Figure 5).
a Values indicate mean ( SEM for n ) 6 in 4 h. *P < 0.05, when
compared with compound 1, one-way ANOVA followed by Dunnett’s
multiple comparison test.
The pharmacokinetic profile of compound 30 was evaluated
in fasted female Zucker fa/fa rats and compared with 1 (Table
4). The AUC0- for 30 was found to be inferior to 1. The tissue
and plasma distribution of compound 30 (Table 5), when
compared to compound 1, revealed a higher availability of drug
in the brain (1.61 ( 0.20 µg/mL) for 30 as compared to 1 (0.15
( 0.01 µg/mL). Similarly the concentration of compound 30
was found to be higher in white adipose tissues (2.10 ( 0.40
µg/mL) as compared to 1 (1.40 ( 0.22 µg/mL). The in vitro
binding affinity33 to hCB1 receptor for the compound 30 was
confirmed using CHO cells stably transfected with hCB1
receptors (Table 6). The highest CB1 receptor affinity (0.150
µM) was found for the bisulfate salt of (-)-enantiomer 30. The
(+)-enantiomer 28 showed threefold less affinity than 30,
indicating that these chiral ligands bind stereoselectively to the
CB1 receptor. The results from Table 6 reveal that highest
CB1/CB2 receptor selectivity (∼163) was found in the most
active compound 30, which is even fourfold higher than the
CB1/ CB2 selectivity (42) for compound 1. The CB1 antago-
nistic activity of 30 was further evaluated using mouse tetrad
models34,35 to confirm its efficacy through the cannabinoid
mechanism (Table 7). Compound 30 showed a dose dependent
CB1 antagonism in this model.
After optimizing the R3 substituent (Table 1), we changed
the substituents R, R1, and R2 on the phenyl ring at positions 1
and 5 (Table 1). The removal of 2-chloro from the phenyl ring
at position N-1 gave compound 10 with low efficacy. The
removal of both the chlorine atoms gave compound 11, and it
was found to be inactive in the 5% sucrose solution intake model
(Table 1). Subsequently, the removal of the chlorine atom from
the phenyl ring at position 5 and removal of the 2-chloro from
the phenyl ring at position N-1 showed a drastic drop in efficacy
for compound 12 (Table 1). Furthermore, with removal of the
chlorine atom of the phenyl ring at position 5 and both chlorine
atoms from the phenyl ring at position 1, 13 also did not improve
the efficacy. Similarly removal of the chlorine atom of the
phenyl ring at position 5 and substitution of 2,4-dichlorophenyl
on N-1 resulted in compound 14, which showed percent inhibi-
tion of sucrose solution comparable to compound 1. Since the
2,4-dichlorophenyl substitution on N-1 of dihydropyrazole and
N-aminomorpholine appeared to be optimal for in vivo efficacy,
we made some more changes at position 5 of the dihydropy-
razole system such as 4-pentylphenyl derivative 15, 4-butoxy-
phenyl derivative 16, 4-methoxyphenyl derivative 17, benzo-
[1,3]dioxol-5-yl derivative 18, 4-bromophenyl and derivative
19, which elicited much inferior in vivo efficacy than that of
Since the dihydropyrazole class of compounds exhibited a
significant potency and efficacy we have studied the binding

5956 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
SriVastaVa et al.
Table 2. In Vivo Efficacy of Dihydro Diarylpyrazoles 15-24 in 5% Sucrose Solution Intake Model in Female Zucker fa/fa Rats at a Single Oral Dose
of 10 mg/kg
a Values indicate mean ( SEM for n ) 6 in 4 h. *P < 0.05, when compared with compound 1, one-way ANOVA followed by Dunnett’s multiple
comparison test.
Table 3. In Vivo Efficacy of Different Salts of Dihydro Diarylpyrazoles
9 and Its Enantiomers in 5% Sucrose Solution Intake Model in Female
Zucker fa/fa Rats at a Single Oral Dose of 10 mg/kg
compd
salts prepared
% inhibition vs controla
25
26
27
28
29
30
31
32
33
9
HCl
H2SO4
HCl
H2SO4
HCl
H2SO4
(COOH)2
CH3SO3H
PhSO3H
free base
34.5 ( 2.4
36.4 ( 1.2
30.1 ( 5.8
15.4 ( 2.6*
42.2 ( 7.1
58.6 ( 6.8*
20.4 ( 1.9
19.2 ( 2.3*
17.1 ( 3.2*
34.2 ( 2.8
36.7 ( 5.3
1
a Values indicate mean ( SEM for n ) 6 in 4 h. *P < 0.05, when
compared with compound 1, one-way ANOVA followed by Dunnett’s
multiple comparison test.
Figure 3. Effect of Compounds 26, 30, and 1 on body weight gain in
female obese Zucker fa/fa rats. Values represent the mean and standard
deviation for six animals in each group. *P < 0.01. Significant
differences with the control group were found.
mode of 9 using modeling techniques. Automated docking of
energy-minimized structures of 1 and 2 was performed using
Ligandfit Software in the active site formed by aromatic residues
in transmembrane helices (TMH) 3-4-5-6.19 It was observed that
the oxygen atom of group SO2 in 2 forms a H bond with Asp
366-Lys 192 and an additional bond with Ser 383 (Figure 7).
Taking a clue from these modeling studies we have taken two
isomers R and S (9a, 9b) of diaryl dihydropyrazole 9 for CB1
receptor interaction and studied them in silico using the same
homology model (Figure 8). On the basis of the reconstructed
model (in order to reproduce the interaction pattern described
in the literature) for the binding of 1 in the CB1 receptor (Figure
6), the target compounds 2 and both enantiomers R and S (9a,
9b) were automatically docked into the receptor using Monte
Carlo simulations implemented in DS SBD.19 Binding of 1 was
characterized by aromatic stacking interactions between the two
aromatic rings of 1 and the aromatic residue rich region in TMH
3-4-5-6.36 A general CB1 inverse agonist pharmacophore model
required for crucial receptor-ligand interaction has been
proposed on the basis of the CB1 receptor modeling.10 However,
it is possible that our docked CB1-ligand model may vary from
other published CB1 models37-39 due to the possible differences
and/or similarities of modeling techniques and different con-
formations of the CB1 ligands.40-42
In the Figures 6-8 the resulting docked conformations of 2
and both enantiomers R and S (9a, 9b) of the compound 9 have
slightly different orientations as compared with that of 1. They
exhibit a hydrogen bond interaction with Lys192, and the
framework of aromatic rings forming aromatic stacking interac-
tions with aromatic residues in the binding pocket of the receptor
is nicely retained. Binding of 9a and 9b is further enhanced by

Diaryl Dihydropyrazole-3-carboxamides
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5957
Figure 4. Effect of compounds 26, 30, and 1 on food intake in female
obese Zucker fa/fa rats. Values represent the mean and standard
deviation for six animals in each group. *P < 0.01. Significant
differences with the control group (n ) 6) were found.
Figure 5. Effect of compounds 26, 30, and 1 on serum triglycerides
level after 60 days treatment in female Zucker fa/fa rats. *P < 0.01,
ANOVA followed by Dunnett’s test. Significant differences with the
same-day control group (n ) 6) were found.
Table 4. Mean Pharmacokinetic Parameters of 30 and 1 in Fasted
Female Zucker fa/fa Ratsa
dose
Tmax
(h)
Cmax
(µg/mL)
T1/2
(h)
AUC(0-
)
compd route (mg/kg)
(h‚µg/mL)
30 oral
oral
30
30
3.70 ( 1.10 0.51 ( 0.14 17.61 ( 6.10 10.00 ( 1.40
2.60 ( 1.30 1.92 ( 0.31 26.55 ( 7.23 41.20 ( 3.65
1
a Values indicate mean ( SD for n ) 6 rats.
Table 5. Tissue and Plasma Distribution of 30 and 1 in Fasted Female
Zucker fa/fa Rat at 3 h after Oral Dose of 30 mg/kga
drug concn
in brain
drug concn in
white adipose tissue
drug concn
in plasma
compd
µg/mL
µg/g
µg/mL
µg/g
µg/mL
30 1.61 ( 0.20 4.86 ( 0.55 2.10 ( 0.40 6.31 ( 1.20 1.40 ( 0.10
0.15 ( 0.01 0.45 ( 0.03 1.40 ( 0.22 4.25 ( 0.70 0.40 ( 0.05
a Values indicate mean ( SEM for n ) 6 rats.
1
Figure 6. Docking of 1 in the homology model of CB1: (a) key
interactions such as H bond with Lys 192 and aromatic stacking of the
phenyl rings with Phe 200, Trp 255, Tyr 275, Phe 278, Trp 279, and
Trp 356; (b) intramolecular H bond in the docked conformer.
Table 6. Radioligand Binding Data of Compounds 26, 28, 30, and 133
CB1 Ki
(µM)a
CB2 Ki
(µM)a
compd
for imparting the antiobesity effect. Similar interactions of diaryl
dihydropyrazol-3-carboxamides have been observed in the
homology models of CB1 receptor as those with 1 and 2. The
diaryl dihydropyrazole-3-carboxamide class of compounds
possesses a promising therapeutic potential as a CB1 receptor
antagonist to treat obesity and needs further exploration.
26
28
30
1
0.334
0.475
0.150
0.047
21.7
26.4
24.5
1.99
a Values indicate the mean of at least two independent experiments
performed.
Experimental Section
an additional intramolecular H-bond involving the hydrogen of
the amidic nitrogen with the nitrogen atom of the dihydropy-
razole ring as shown in Figure 7. In the absence of crystallized
receptor-ligand complexes, our model still gave valuable
information on the receptor-ligand interactions.
Chemistry. Melting points were recorded on a scientific melting
point apparatus and are uncorrected. IR spectra were recorded as
neat (for oils) or on KBr pellet (for solid) on FT-IR 8300 Shimadzu
and are expressed in ν (cm-1). All H spectral data are recorded
1
1
on a 300 MHz H NMR spectrometer (M-300) using DMSO-d6,
CDCl3, or D2O as solvent with tetramethylsilane (TMS) as an
internal standard. Chemical shifts are given in δ downfield from
tetramethylsilane. Multiplicities are recorded as a s (singlet), br s
(broad singlet), d (doublet), t (triplet), q (quartet), dd (doublet of
doublets), or m (multiplet). Coupling constants (J) are expressed
in hertz. Mass spectra are recorded on Perkin-Elmer Sciex API
3000. HPLC analysis were carried out at λmax 220 nm using column
Conclusion
The optimization of the diaryl dihydropyrazol-3-carboxamides
4-33 has led to the compound 30 as a potent cannabinoid CB1
receptor antagonist with a significant antiobesity effect in animal
models. In the dihydropyrazole motif, the N-aminomorpholine
is the optimal side chain, and bisulfate salt is more bioavailable
Table 7. Effect of Compound 30 in the Mouse Tetrad Modela
compd, 30
(mg/kg, po)
locomotor
activityb
change in
body temp (°C)
analgesic
effectd
compd
catalepsyc
WIN-55212-2 (1 mg/kg, iv)
0 (control)
1
3
10
30
7.60 ( 7.00
0.40 ( 0.40
3.00 ( 2.00
13.25 ( 5.30
25.00 ( 3.00*
-4.30 ( 0.35
-4.24 ( 0.25
-2.10 ( 0.30*
-0.15 ( 0.40*
0.15 ( 0.25*
86.10 ( 2.80
85.20 ( 3.04
33.75 ( 7.00*
14.20 ( 7.30*
18.23 ( 7.00*
74.20 ( 8.60
24.00 ( 6.20
12.00 ( 1.50*
-0.15 ( 1.43*
11.50 ( 4.32*
a Values indicate the mean ( SEM for n ) 6. b Number of squares crossed in 5 min. c Percent immobility. d Percent MPE on hot plate. *P < 0.05.
Significant differences with the WIN 55212-2-treated control group.

5958 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
SriVastaVa et al.
ether (330 mL) to afford 36 as a yellow solid (161 g, 77%): 95.92%
purity by HPLC; mp 280 °C; IR (KBr) 3338, 3066, 1676, 1604,
1
1587 cm-1; H NMR (300 MHz, DMSO-d6) δ 7.68 (d, J ) 8.52
Hz, 2H), 7.45 (d, J ) 8.48 Hz, 2H), 7.36 (d, J ) 16.39 Hz, 1H),
6.73 (d, J ) 16.35 Hz, 1H); ESI-MS 211.5 [M + H]+.
Potassium 2-Oxo-4-phenyl-but-3-enoate (37). Compound 37
was prepared in 43% yield from benzaldehyde and pyruvic acid
by the same procedure as described for 36: 97.61% purity by
HPLC; mp 248 °C; ESI-MS 214.9 [M + H]+.
Potassium 2-Oxo-4-(4-pentylphenyl)-but-3-enoate (65). Com-
pound 65 was prepared in 48% yield from 4-n-pentylbenzaldehyde
and pyruvic acid by the same procedure as described for 36:
97.26% purity by HPLC; mp 217 °C; ESI-MS 285.2 [M + H]+.
Potassium 4-(4-Butoxyphenyl)-2-oxo-but-3-enoate (66). Com-
pound 66 was prepared in 72% yield from 4-butoxybenzaldehyde
and pyruvic acid by the same procedure as described for 36:
95.39% purity by HPLC; mp 220 °C; ESI-MS 286.8 [M + H]+.
Potassium 4-(4-Methoxyphenyl)-2-oxo-but-3-enoate (67). Com-
pound 67 was prepared in 58% yield from 4-methoxybenzaldehyde
and pyruvic acid by the same procedure as described for 36:
95.16% purity by HPLC; mp 248 °C; ESI-MS 244.8 [M + H]+.
Potassium 4-Benzo[1,3]dioxol-5-yl-2-oxo-but-3-enoate (68).
Compound 68 was prepared in 70% yield from 4-piperonal and
pyruvic acid by the same procedure as described for 36: 95.69%
purity by HPLC; mp 250 °C; ESI-MS 258.7 [M + H]+.
Potassium 4-(4-Bromophenyl)-2-oxo-but-3-enoate (69). Com-
pound 69 was prepared in 42% yield from 4-bromobenzaldehyde
and pyruvic acid by the same procedure as described for 36:
99.24% purity by HPLC; mp 233 °C; ESI-MS 294.9 [M + H]+.
Potassium 2-Oxo-4-pyridin-3-yl-but-3-enoate (70). Compound
70 was prepared in 34% yield from 3-pyridinecarboxaldehyde and
pyruvic acid by the same procedure as described for 36: 95.78%
purity by HPLC; mp 239 °C; ESI-MS 216.1 [M + H]+.
Potassium 2-Oxo-4-thiophen-2-yl-but-3-enoate (71). Com-
pound 71 was prepared in 69% yield from 2-thiophenecarboxal-
dehyde and pyruvic acid by the same procedure as described for
36: 98.18% purity by HPLC; mp 260.8 °C; ESI-MS 220.8 [M +
H]+.
Potassium 4-Furan-2-yl-2-oxo-but-3-enoate (72). Compound
72 was prepared in 33% yield from furfuraldehyde and pyruvic
acid by the same procedure as described for 36: 95.86% purity by
HPLC; mp 240 °C; ESI-MS 204.8 [M + H]+.
Figure 7. Docking of 2 in the homology model of CB1 receptor: (a)
key interactions such as H bond with Lys 192 and aromatic stacking
of the phenyl rings with Phe 200, Trp 255, Tyr 275, Phe 278, Trp 279,
and Trp 356; (b) intramolecular H bond in the docked conformer.
ODS C-18, 150 mm × 4.6 mm × 4 µm on AGILENT 1100 series.
Chiral HPLC analysis were carried out at λmax 220 nm using
columns CHIRALCEL OJ-H, 250 mm × 4.6 mm × 5 µm on
SHIMADZU LCVp 10AVp. Optical rotations ([R]D) were measured
on an a JASCO P-1030 polarimeter. Specific rotations are given
as deg/dm; the concentration values are reported as g/100 mL of
the specified solvent and were recorded at 25 °C. Elemental analyses
were performed on a Thermo Quest EA 1110 CHNS. All reactions
involving air or moisture sensitive compounds were performed
under argon atmosphere. Thin layer chromatography (TLC) was
performed on aluminum sheets precoated with silica gel 60 F254
,
and spots were visualized with UV light. Flash chromatography
(FC) was performed using silica gel 230-400 mesh.
Synthesis of Potassium 4-(4-Chlorophenyl)-2-oxo-but-3-
enoate (36). To 4-chlorobenzaldehyde (117 g, 832.1 mmol) in
methanol (117 mL) was added pyruvic acid (146.4 g, 166.2 mmol),
and the mixture was cooled to 10 °C under the atmosphere of argon.
To this was added a solution of KOH (109.8 g, 166.2 mmol) in
methanol (234 mL) dropwise at 15-20 °C over a period of 30
min. The temperature of the reaction mixture increased from 20
°C to 35-40 °C. The reaction mixture was stirred at this
temperature for 3 h and then maintained at 10 °C for 10 h. The
solid separated out was filtered on a Buchner funnel under suction
and washed with chilled methanol (330 mL) followed by diethyl
Figure 8. Docking of the both isomers R and S (9a, 9b) for compound 9 in the homology model of the CB1 receptor: (a, b) key interactions of
R and S isomers, respectively, such as the H bond with Lys 192 and aromatic stacking of the phenyl rings with Phe 200, Trp 255, Tyr 275, Phe
278, Trp 279, and Trp 356; (c, d) intramolecular H bond in the docked conformer of both R and S isomers.

Diaryl Dihydropyrazole-3-carboxamides
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5959
Potassium 4-(5-Methylthiophen-2-yl)-2-oxo-but-3-enoate (73).
Compound 73 was prepared in 64% yield from 5-methyl-2-
thiophenecarboxaldehyde and pyruvic acid by the same procedure
as described for 36: 98.47% purity by HPLC; mp 242 °C; ESI-
MS 234.6 [M + H]+.
Potassium 4-(5-Chlorothiophen-2-yl)-2-oxo-but-3-enoate (74).
Compound 74 was prepared in 71% yield from 5-chloro-2-
thiophenecarboxaldehyde and pyruvic acid by the same procedure
as described for 36: 97.49% purity by HPLC; mp 280 °C; ESI-
MS 255.6 [M + H]+.
and dried to afford the title compound as an orange solid: 96.27%
purity by HPLC; mp 70-72 °C; ESI-MS 206.0 [M + H]+.
2-Oxo-4-thiophen-2-yl-but-3-enoic Acid Ethyl Ester (81).
Compound 81 was prepared from 71 in 74% yield by the same
procedure as described for 38. The solid obtained was triturated in
di-isopropyl ether. It was filtered on a Buchner funnel under suction
and dried to afford the title compound as an orange solid: 95.38%
purity by HPLC; mp 49-50 °C; ESI-MS 210.8 [M + H]+.
4-Furan-2-yl-2-oxo-but-3-enoic Acid Ethyl Ester (82). Com-
pound 82 was prepared from 72 in 89% yield by the same procedure
as described for 38. The solid obtained was triturated in di-isopropyl
ether. It was filtered on a Buchner funnel under suction and dried
to afford the title compound as a pale yellow solid: 96.58% purity
by HPLC; mp 56-57 °C; ESI-MS 194.8 [M + H]+.
4-(5-Methylthiophen-2-yl)-2-oxo-but-3-enoic acid Ethyl Ester
(83). Compound 83 was prepared from 73 in 88% yield by the
same procedure as described for 38. The solid obtained was
triturated in di-isopropyl ether. It was filtered on a Buchner funnel
under suction and dried to afford the title compound as an orange
solid: 98.49% purity by HPLC; mp 42-43 °C; ESI-MS 224.8 [M
+ H]+.
Synthesis of 4-(4-Chlorophenyl)-2-oxo-but-3-enoic Acid Ethyl
Ester (38). To a solution of 36 (30 g, 120 mmol) in dimethylfor-
mamide (100 mL) was added ethyl iodide (16.5 mL, 204 mmol),
and the mixture was stirred at 72-75 °C for 4 h under the argon
atmosphere. The progress of the reaction was monitored by TLC
using 40% EtOAc in petroleum ether as a mobile phase. The
reaction mixture was cooled to 27-28 °C, diluted with water (400
mL), and extracted with ethyl acetate (3 × 100 mL). The ethyl
acetate layer was separated and washed with water (2 × 200 mL)
followed by aqueous NaHCO3 solution (2 × 200 mL). The organic
layer was separated and dried over anhydrous Na2SO4, and solvents
were evaporated on a rotary evaporator under reduced pressure.
The solid obtained was further triturated in di-isopropyl ether (100
mL), filtered on a Buchner funnel under suction, and dried to afford
38 as a pale yellow solid (8.7 g, 30.1%): 95.49% purity by HPLC;
4-(5-Chlorothiophen-2-yl)-2-oxo-but-3-enoic Acid Ethyl Ester
(84). Compound 84 was prepared from 74 in 97% yield by the
same procedure as described for 38. The solid obtained was
triturated in di-isopropyl ether. It was filtered on a Buchner funnel
under suction and dried to afford the title compound as a pale yellow
solid: 96.89% purity by HPLC; mp 79-81 °C; ESI-MS 245.8 [M
+ H]+.
1
mp 69-71 °C; IR (KBr) 3371, 1720, 1689 cm-1; H NMR (300
MHz, CDCl3) δ 7.80 (d, J ) 16.11 Hz, 1H), 7.57 (d, J ) 8.11 Hz,
2H), 7.38 (d, J ) 8.52 Hz, 2H), 7.29 (d, J ) 14.67 Hz, 1H), 4.43-
4.36 (q, 2H), 1.41 (t, 3H); ESI-MS 239.1 [M + H]+.
Synthesis of 5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-
dihydro-1H-pyrazole-3-carboxylic Acid Ethyl Ester (43). To 38
(20.0 g, 83.79 mmol) in ethanol (200 mL) was added 2,4-
dichlorophenyl hydrazine hydrochloride 40 (17.9 g, 83.79 mmol),
and the reaction mixture was stirred at 28-31 °C over a period of
2 h under argon atmosphere. To the reaction mixture was added
acetic acid (50 mL), and the mixture refluxed for 18 h. The progress
of the reaction was monitored by TLC using 10% EtOAc in
petroleum ether as a mobile phase. The reaction mixture was cooled
to 27-28 °C, poured into water (300 mL), and extracted with ethyl
acetate (3 × 100 mL). The combined ethyl acetate layers were
washed with water (2 × 200 mL) followed by aqueous NaHCO3
solution (2 × 200 mL). The organic layer was separated, dried over
anhydrous Na2SO4, and the solvents were evaporated on a rotatory
evaporator under reduced pressure. The residue obtained was
triturated in methanol (100 mL) to afford a solid which was filtered
on a Buchner funnel under suction and dried to afford 43 as a yellow
solid (4.3 g, 57%): 96.79% purity by HPLC; mp 120-122 °C; IR
2-Oxo-4-phenyl-but-3-enoic Acid Ethyl Ester (39). Compound
39 was prepared from 37 in 94% yield by the same procedure as
described for 38. The residue was purified by column chromatog-
raphy using petroleum ether/EtOAc (9.5:1.5) as an eluent to afford
the title compound as a yellow oil: 97.58% purity by HPLC; ESI-
MS 205.1 [M + H]+.
2-Oxo-4-(4-pentylphenyl)-but-3-enoic Acid Ethyl Ester (75).
Compound 75 was prepared from 65 in 62% yield by the same
procedure as described for 38. The residue was purified by column
chromatography using petroleum ether/EtOAc (9.5:1.5) as an eluent
to afford the title compound as a brown oil: 95.27% purity by
HPLC; ESI-MS 274.9 [M + H]+.
4-(4-Butoxyphenyl)-2-oxo-but-3-enoic Acid Ethyl Ester (76).
Compound 76 was prepared from 66 in 84% yield by the same
procedure as described for 38. The residue was purified by column
chromatography using petroleum ether/EtOAc (9.5:1.5) as an eluent
to afford the title compound as a brown oil: 94.28% purity by
HPLC; ESI-MS 277.1 [M + H]+.
4-(4-Methoxyphenyl)-2-oxo-but-3-enoic Acid Ethyl Ester (77).
Compound 77 was prepared from 67 in 77% yield by the same
procedure as described for 38. The solid obtained was triturated in
di-isopropyl ether. It was filtered on a Buchner funnel under suction
and dried to afford the title compound as a pale yellow solid:
96.39% purity by HPLC; mp 49-51 °C; ESI-MS 234.8 [M + H]+.
4-Benzo[1,3]dioxol-5-yl-2-oxo-but-3-enoic Acid Ethyl Ester
(78). Compound 78 was prepared from 68 in 78% yield by the
same procedure as described for 38. The solid obtained was
triturated in di-isopropyl ether. It was filtered on a Buchner funnel
under suction and dried to afford the title compound as an orange
solid: 98.66% purity by HPLC; mp 73-75 °C; ESI-MS 248.8 [M
+ H]+.
1
(KBr) 2981, 1737, 1706, 1575, 1556, 1479 cm-1; H NMR (300
MHz, CDCl3) δ 7.27 (d, J ) 8.27 Hz, 2H), 7.21 (d, J ) 2.29 Hz,
1H), 7.08-7.05 (dd, J ) 8.47 and 2.29 Hz, 4H), 5.88-5.82 (dd, J
) 12.54 and 5.94 Hz, 1H), 4.40-4.33 (q, 2H), 3.74-3.64 (dd, J
) 18.05 and 12.841 Hz, 1H), 3.30-3.22 (dd, J ) 18.05 and 5.94
Hz, 1H), 1.38 (t, 3H); ESI-MS 398.3 [M + H]+.
1,5-Bis-(4-chlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxy-
lic Acid Ethyl Ester (44). Compound 44 was prepared from 38
and 4-chlorophenyl hydrazine hydrochloride 41 in 87% yield by
the same procedure as described for 43. The residue was purified
by column chromatography using petroleum ether/EtOAc (9.5:1.5)
as an eluent to afford the title compound as a brown oil: 99.67%
purity by HPLC; ESI-MS 364.0 [M + H]+.
5-(4-Chlorophenyl)-1-phenyl-4,5-dihydro-1H-pyrazole-3-car-
boxylic Acid Ethyl Ester (45). Compound 45 was prepared from
38 and phenylhydrazine hydrochloride 42 in 69% yield by the same
procedure as described for 43. The residue obtained was triturated
in methanol to afford a solid, which was filtered on a Buchner
funnel under suction and dried to afford the title compound as a
yellow solid: 97.88% purity by HPLC; mp 120-122 °C; ESI-MS
329.3 [M + H]+.
1-(4-Chlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-3-car-
boxylic Acid Ethyl Ester (46). Compound 46 was prepared from
39 and 4-chlorophenyl hydrazine hydrochloride 41 in 70% yield
by the same procedure as described for 43. The residue obtained
4-(4-Bromophenyl)-2-oxo-but-3-enoic Acid Ethyl Ester (79).
Compound 79 was prepared from 69 in 65% yield by the same
procedure as described for 38. The solid obtained was triturated in
di-isopropyl ether. It was filtered on a Buchner funnel under suction
and dried to afford the title compound as an orange solid: 95.19%
purity by HPLC; mp 70 °C; ESI-MS 283.7 [M + H]+.
2-Oxo-4-pyridin-3-yl-but-3-enoic Acid Ethyl Ester (80). Com-
pound 80 was prepared from 70 in 89% yield by the same procedure
as described for 38: The solid obtained was triturated in di-
isopropyl ether. It was filtered on a Buchner funnel under suction

5960 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
SriVastaVa et al.
was triturated in methanol to afford a solid, which was filtered on
a Buchner funnel under suction and dried to afford the title
compound as a yellow solid: 98.56% purity by HPLC; mp 109-
111 °C; ESI-MS 329.3 [M + H]+.
1,5-Diphenyl-4,5-dihydro-1H-pyrazole-3-carboxylic Acid
Ethyl Ester (47). Compound 47 was prepared from 39 and phenyl
hydrazine hydrochloride 42 in 77% yield by the same procedure
as described for 43. The residue obtained was triturated in methanol
to afford a solid, which was filtered on a Buchner funnel under
suction and dried to afford the title compound as an off-white
solid: 97.25% purity by HPLC; mp 83-85 °C; ESI-MS 295.0 [M
+ H]+.
1-(2,4-Dichlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-3-
carboxylic Acid Ethyl Ester (48). Compound 48 was prepared
from 39 and 2,4-dichlorophenyl hydrazine hydrochloride 40 in 63%
yield by the same procedure as described for 43. The residue
obtained was triturated in methanol to afford a solid, which was
filtered on a Buchner funnel under suction and dried to afford the
title compound as a yellow solid: 99.67% purity by HPLC; mp
65-67 °C; ESI-MS 364.1 [M + H]+
1-(2,4-Dichlorophenyl)-5-furan-2-yl-4,5-dihydro-1H-pyrazole-
3-carboxylic Acid Ethyl Ester (92). Compound 92 was prepared
from 82 and 2,4-dichlorophenyl hydrazine hydrochloride 40 in 82%
yield by the same procedure as described for 43. The residue was
purified by column chromatography using petroleum ether/EtOAc
(9.5:1.5) as an eluent to afford the title compound as a yellow oil:
95.79% purity by HPLC; ESI-MS 354.3 [M + H]+.
1-(2,4-Dichlorophenyl)-5-(5-methylthiophen-2-yl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Ethyl Ester (93). Compound 93
was prepared from 83 and 2,4-dichlorophenyl hydrazine hydro-
chloride 40 in 67% yield by the same procedure as described for
43. The residue was purified by column chromatography using
petroleum ether/EtOAc (9.5:1.5) as an eluent to afford the title
compound as a yellow oil: 99.34% purity by HPLC; ESI-MS 384.9
[M + H]+.
5-(5-Chlorothiophen-2-yl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Ethyl Ester (94). Compound 94
was prepared from 84 and 2,4-dichlorophenyl hydrazine hydro-
chloride 40 in 69% yield by the same procedure as described for
43. The residue was purified by column chromatography using
petroleum ether/EtOAc (9.5:1.5) as an eluent to afford the title
compound as a yellow oil: 97.38% purity by HPLC; ESI-MS 378.9
[M + H]+.
Synthesis of 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-
dihydro-1H-pyrazole-3-carboxylic Acid (49). To a solution of 43
(4.2 g, 10.57 mmol) in methanol (35 mL) was added a solution of
KOH (1.183 g, 21.14 mmol) in water (35 mL), and the mixture
was refluxed at 65-68 °C for 2 h. The progress of the reaction
was monitored by TLC using 5% MeOH in CHCl3 as a mobile
phase. The reaction mixture was cooled to 27-28 °C, poured into
ice cold water (150 mL), acidified to pH 4 using 10% HCl solution,
and extracted with ethyl acetate (3 × 50 mL). The ethyl acetate
layers were pooled and washed with water (100 mL). The organic
layer was separated, dried over anhydrous Na2SO4, and the solvents
were evaporated on a rotatory evaporator under reduced pressure.
The residue was triturated in petroleum ether (25 mL) to afford a
solid. The solid was filtered on a Buchner funnel under suction
and dried to afford 49 as a yellow solid (2.9 g, 74%): 99.23%
purity by HPLC; mp 99-102 °C; IR (KBr) 3433, 2927, 2582, 1685,
1571, 1479 cm-1; 1H NMR (300 MHz, DMSO-d6) δ 13.21 (s, 1H),
7.49 (d, J ) 1.98 Hz, 1H), 7.41-7.38 (m, 1H), 7.35-7.32 (m,
3H), 7.25-7.20 (m, 2H), 5.90-5.84 (dd, J ) 12.03 and 6.66 Hz,
1H), 3.72-3.62 (dd, J ) 17.91 and 12.44 Hz, 1H), 3.08-3.01 (dd,
J ) 18.0 and 6.75 Hz, 1H); ESI-MS 370.1 [M + H]+.
1,5-Bis-(4-chlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxy-
lic Acid (50). Compound 50 was prepared from 44 in 79% yield
by the same procedure as described for 49: 97.18% purity by
HPLC; mp 165-167 °C; ESI-MS 336.0 [M + H]+.
5-(4-Chlorophenyl)-1-phenyl-4,5-dihydro-1H-pyrazole-3-car-
boxylic Acid (51). Compound 51 was prepared from 45 in 98%
yield by the same procedure as described for 49: 98.93% purity
by HPLC; mp 179-181 °C; ESI-MS 301.4 [M + H]+.
1-(4-Chlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-3-car-
boxylic Acid (52). Compound 52 was prepared from 46 in 85%
yield by the same procedure as described for 49: 99.68% purity
by HPLC; mp 173-175 °C; ESI-MS 301.3 [M + H]+.
1,5-Diphenyl-4,5-dihydro-1H-pyrazole-3-carboxylic Acid (53).
Compound 53 was prepared from 47 in 78% yield by the same
procedure as described for 49: 99.35% purity by HPLC; mp 195-
197 °C; ESI-MS 267.0 [M + H]+.
1-(2,4-Dichlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-3-
carboxylic Acid (54). Compound 54 was prepared from 48 in 80%
yield by the same procedure as described for 49: 99.09% purity
by HPLC; mp 248-250 °C; ESI-MS 336.2 [M + H]+.
1-(2,4-Dichlorophenyl)-5-(4-pentylphenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid (95). Compound 95 was prepared from
85 in 91% yield by the same procedure as described for 49: 97.84%
purity by HPLC; mp 175-176 °C; ESI-MS 406.0 [M + H]+.
5-(4-Butoxyphenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid (96). Compound 96 was prepared from
1-(2,4-Dichlorophenyl)-5-(4-pentylphenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Ethyl Ester (85). Compound 85 was
prepared from 75 and 2,4-dichlorophenyl hydrazine hydrochloride
40 in 73% yield by the same procedure as described for 43. The
residue was purified by column chromatography using petroleum
ether/EtOAc (9.5:1.5) as an eluent to afford the title compound as
a brown oil: 96.88% purity by HPLC; ESI-MS 434.0 [M + H]+.
5-(4-Butoxyphenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Ethyl Ester (86). Compound 86 was
prepared from 76 and 2,4-dichlorophenyl hydrazine hydrochloride
40 in 73% yield by the same procedure as described for 43. The
residue was purified by column chromatography using petroleum
ether/EtOAc (9.5:1.5) as an eluent to afford the title compound as
a brown oil: 97.92% purity by HPLC; ESI-MS 437.3 [M + H]+.
1-(2,4-Dichlorophenyl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Ethyl Ester (87). Compound 87 was
prepared from 77 and 2,4-dichlorophenyl hydrazine hydrochloride
40 in 45% yield by the same procedure as described for 43. The
residue was purified by column chromatography using petroleum
ether/EtOAc (9.5:1.5) as an eluent to afford the title compound as
a yellow oil: 97.47% purity by HPLC; ESI-MS 393.8 [M + H]+.
5-Benzo[1,3]dioxol-5-yl-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Ethyl Ester (88). Compound 88
was prepared from 78 and 2,4-dichlorophenyl hydrazine hydro-
chloride 40 in 86% yield by the same procedure as described for
43. The residue was purified by column chromatography using
petroleum ether/EtOAc (9.5:1.5) as an eluent to afford the title
compound as a brown oil: 98.38% purity by HPLC; ESI-MS 408.1
[M + H]+.
5-(4-Bromophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Ethyl Ester (89). Compound 89 was
prepared from 79 and 2,4-dichlorophenyl hydrazine hydrochloride
40 in 78% yield by the same procedure as described for 43. The
residue obtained was triturated in methanol to afford a solid, which
was filtered on a Buchner funnel under suction and dried to afford
the title compound as a yellow solid: 95.92% purity by HPLC;
mp 117-118 °C; ESI-MS 442.9 [M + H]+.
1-(2,4-Dichlorophenyl)-5-pyridin-3-yl-4,5-dihydro-1H-pyra-
zole-3-carboxylic Acid Ethyl Ester (90). Compound 90 was
prepared from 80 and 2,4-dichlorophenyl hydrazine hydrochloride
40 in 81% yield by the same procedure as described for 43. The
residue was purified by column chromatography using petroleum
ether/EtOAc (9.5:1.5) as an eluent to afford the title compound as
a brown oil: 97.25% purity by HPLC; ESI-MS 365.0 [M + H]+.
1-(2,4-Dichlorophenyl)-5-thiophen-2-yl-4,5-dihydro-1H-pyra-
zole-3-carboxylic Acid Ethyl Ester (91). Compound 91 was
prepared from 81 and 2,4-dichlorophenyl hydrazine hydrochloride
40 in 72% yield by the same procedure as described for 43. The
residue was purified by column chromatography using petroleum
ether/EtOAc (9.5:1.5) as an eluent to afford the title compound as
a brown oil: 99.08% purity by HPLC; ESI-MS 370.4 [M + H]+.

Diaryl Dihydropyrazole-3-carboxamides
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5961
86 in 82% yield by the same procedure as described for 49: 99.47%
purity by HPLC; mp 108-110 °C; ESI-MS 408.1 [M + H]+.
1-(2,4-Dichlorophenyl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid (97). Compound 97 was prepared from
87 in 79% yield by the same procedure as described for 49: 97.63%
purity by HPLC; mp 178-180 °C; ESI-MS 366.0 [M + H]+.
5-Benzo[1,3]dioxol-5-yl-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid (98). Compound 98 was prepared
from 88 in 89% yield by the same procedure as described for 49:
96.78% purity by HPLC; mp 157-158 °C; ESI-MS 380.0 [M +
H]+.
5-(4-Bromophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid (99). Compound 99 was prepared from
89 in 84% yield by the same procedure as described for 49: 99.49%
purity by HPLC; mp 92-93 °C; ESI-MS 415.7 [M + H]+.
1-(2,4-Dichlorophenyl)-5-pyridin-3-yl-4,5-dihydro-1H-pyra-
zole-3-carboxylic Acid (100). Compound 100 was prepared from
90 in 75% yield by the same procedure as described for 49: 98.29%
purity by HPLC; ESI-MS 336.8 [M + H]+.
1-(2,4-Dichlorophenyl)-5-thiophen-2-yl-4,5-dihydro-1H-pyra-
zole-3-carboxylic Acid (101). Compound 101 was prepared from
91 in 86% yield by the same procedure as described for 49: 99.37%
purity by HPLC; mp 137-138 °C; ESI-MS 342.1 [M + H]+.
1-(2,4-Dichlorophenyl)-5-furan-2-yl-4,5-dihydro-1H-pyrazole-
3-carboxylic Acid (102). Compound 102 was prepared from 92 in
89% yield by the same procedure as described for 49: 97.38%
purity by HPLC; mp 140-141 °C; ESI-MS 326.2 [M + H]+.
1-(2,4-Dichlorophenyl)-5-(5-methylthiophen-2-yl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid (103). Compound 103 was pre-
pared from 93 in 84% yield by the same procedure as described
for 49: 99.94% purity by HPLC; mp 148-150 °C; ESI-MS 355.7
[M + H]+.
NMR (300 MHz, CDCl3) δ 7.25 (m, 2H), 7.21 (d, J ) 1.93 Hz,
1H), 7.19 (s, 1H), 7.09 (d, J ) 8.65 Hz, 3H), 5.95-5.89 (dd, J )
12.68 and 6.14 Hz, 2H), 3.77-3.67 (dd, J ) 18.06 and 12.14 Hz,
1H), 3.32-3.24 (dd, J ) 18.10 and 6.18 Hz, 1H); ESI-MS 370.9
[M + H]+.
(+)-5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid (49a). The resolution of 49 to (+)-
enantiomer 49a was done using the same procedure described for
compound 49b. Compound 49 was reacted with S-(-)-R-methyl
benzylamine to get the S-(-)-R-methyl benzylamine salt of (+)-
5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-
3-carboxylic acid as an off-white solid (18 g, 35%): 99.95% purity
by HPLC, 99.6% chiral purity by HPLC (99.2% ee), [RD] ) +407°,
c ) 0.2, DMSO; mp 160-161 °C; IR (KBr) 3033, 2943, 2881,
1
1571, 1475 cm-1; H NMR (300 MHz, DMSO-d6) δ 7.45-7.41
(m, 2H), 7.38-7.33 (m, 5H), 7.23 (d, J ) 8.38 Hz, 2H), 7.20-
7.16 (dd, J ) 8.74 and 2.33 Hz, 1H), 7.11 (d, J ) 8.41 Hz, 2H),
5.69-5.64 (dd, J ) 11.29 and 4.95 Hz, 1H), 4.36-4.29 (q, 1H),
3.55-3.45 (dd, J ) 17.19 and 12.22 Hz, 1H), 2.97-2.90 (dd, J )
17.01 and 5.07 Hz, 1H), 1.43 (d, 3H) ESI-MS 492.7 [M + H]+.
The S-(-)-R-methyl benzylamine salt of (+)-5-(4-chlorophenyl)-
1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid
was converted into free acid 49a as an off-white solid (11.5 g,
28%): 99.86% purity by HPLC, 99.66% chiral purity by HPLC
(99.2% ee), [RD] ) +187°, c ) 0.2, DMSO; mp 180-181 °C; IR
(KBr) 3425, 1689, 1575, 1555 cm-1; 1H NMR (300 MHz, DMSO-
d6) δ 13.01 (br s, 1H), 7.48 (d, J ) 2.19 Hz, 1H), 7.35-7.28 (m,
4H), 7.20 (d, J ) 8.49 Hz, 2H), 5.90-5.84 (dd, J ) 12.15 and
6.69 Hz, 2H), 3.72-3.62 (dd, J ) 17.91 and 12.57 Hz, 1H), 3.08-
3.01 (dd, J ) 18.03 and 6.78 Hz, 1H); ESI-MS 370.9 [M + H]+.
Synthesis of 5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-
dihydro-1H-pyrazole-3-carboxylic Acid Morpholin-4-ylamide
(9). To a solution of 49 (2.5 g, 6.66 mmol) in dichloromethane (30
mL) were added 1-hydroxybenzotriazole hydrate (1.825 g, 13.32
mmol) and [1-(3-dimethylaminopropyl)-3-ethylcarbodiimide] hy-
drochloride (1.945 g, 9.99 mmol), and the mixture was stirred for
5-7 min at 26-27 °C. To this mixture N-aminomorpholine (0.755
g, 7.326 mmol) was added followed by triethylamine (1.78 mL,
13.32 mmol). The reaction mixture was stirred at 28-29 °C for 30
min. The progress of the reaction was monitored by TLC using
5% MeOH in CHCl3 as a mobile phase. The reaction mixture was
poured in water (80 mL) and extracted with dichloromethane (2 ×
50 mL). The dichloromethane layer was separated and dried over
anhydrous Na2SO4, and the solvents were evaporated on a rotatory
evaporator under reduced pressure to get crude brown oil. The crude
oil was purified through flash column chromatography petroleum
ether:EtOAc (9: 1) as an eluent. The fractions were pooled and
solvents were evaporated on a rotatory evaporator under reduced
pressure to afford oil. The oil was triturated in petroleum ether (15
mL) to afford 9 as a white solid (1.1 g, 34%): 99.94% purity by
HPLC, [RD] ) +0.28°, c ) 0.2, DMSO; mp 172-174 °C; IR (KBr)
3421, 3246, 1662, 1583, 1477 cm-1; 1H NMR (300 MHz, CDCl3)
δ 7.49 (s, 1H), 7.18 (d, J ) 8.40 Hz, 2H), 7.12 (d, J ) 8.61 Hz,
2H), 7.09-7.04 (m, 3H), 5.76-5.69 (dd, J ) 12.18 and 6.36 Hz,
1H), 3.87-3.84 (br s, 4H), 3.74-3.63 (dd, J ) 18.33 and 12.46
Hz, 1H), 3.37-3.29 (dd, J ) 18.36 and 6.36 Hz, 1H), 2.95-2.92
(br s, 4H); ESI-MS 454.9 [M + H]+.
5-(5-Chlorothiophen-2-yl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid (104). Compound 104 was pre-
pared from 94 in 81% yield by the same procedure as described
for 49: 99.06% purity by HPLC; mp 82-84 °C; ESI-MS 377.4
[M + H]+.
Typical Procedure for the Resolution of 5-(4-Chlorophenyl)-
1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid
(49). (-)-5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid (49b). To a solution of 49 (64 g,
0.17 mole) in acetone (320 mL) was added R-(+)-R-methyl
benzylamine (20.9 mL, 0.17 mol) at 26-28 °C, and the mixture
was stirred for 10-15 min. To this was added acetonitrile (320
mL), and the mixture was stirred at 26-28 °C for another 2 h. The
solid salt separated out was filtered on a Buchner funnel under
suction and washed with chilled acetonitrile to afford the R-(+)-
R-methyl benzylamine salt of (-)-5-(4-chlorophenyl)-1-(2,4-dichlo-
rophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid as an off-
white solid salt (34 g, 40%): 99.3% purity by HPLC, 99.8% chiral
purity by HPLC (99.6% ee), [RD] ) -407°, c ) 0.2, DMSO; mp
1
164-165 °C; IR (KBr) 3413, 2977, 1569, 1477, 1307 cm-1; H
NMR (300 MHz, DMSO-d6) δ 7.45 (d, J ) 6.93 Hz, 2H), 7.40-
7.37 (m, 3H), 7.35-7.31 (m, 2H), 7.27 (d, J ) 8.43 Hz, 2H), 7.21-
7.19 (dd, J ) 8.76 and 2.34 Hz, 1H), 7.12 (d, J ) 8.43 Hz, 2H),
5.71-5.65 (dd, J ) 11.34 and 6.63 Hz, 1H), 4.33-4.27 (q, 1H),
3.56-3.47 (dd, J ) 17.82 and 11.82 Hz, 1H), 2.99-2.91 (dd, J )
17.88 and 5.43 Hz, 1H), 1.45 (d, 3H) ESI-MS 492.7 [M + H]+.
The R-(+)-R-methyl benzylamine salt of (-)-5-(4-chlorophenyl)-
1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid
(34.0 g) was taken in ice cold water (100 mL) and acidified to pH
3 using 10% HCl solution. The solution was extracted with
dichloromethane (2 × 200 mL), and the organic layer was washed
with water (3 × 200 mL). The organic layer was separated and
dried over anhydrous Na2SO4, and the solvents were evaporated
on a rotatory evaporator under reduced pressure. The residue was
triturated in petroleum ether to get a solid. The solid was filtered
on a Buchner funnel under suction and dried to afford 49b as an
off-white solid (20 g, 31%): 99.90% purity by HPLC, 99.8% chiral
purity by HPLC (99.6% ee), [RD] ) -187°, c ) 0.2, DMSO; mp
5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Piperidin-1-ylamide (4). Compound
4 was prepared from 49 and N-aminopiperidine in 38% yield by
the same procedure as described for 9: 99.46% purity by HPLC,
[RD] ) -0.78°, c ) 0.2, DMSO; mp 176-177 °C; IR (KBr) 3422,
3219, 1649, 1587, 1475 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.48
(s, 1H), 7.25 (d, J ) 3.82 Hz, 1H), 7.17 (d, J ) 8.47 Hz, 2H), 7.11
(d, J ) 8.65 Hz, 1H), 7.08-7.04 (m, 3H), 5.74-5.68 (dd, J )
12.12 and 6.24 Hz, 1H), 3.73-3.63 (dd, J ) 18.34 and 12.63 Hz,
1H), 3.37-3.29 (dd, J ) 18.34 and 6.28 Hz, 1H), 2.85-2.82 (br s,
4H), 1.79-1.75 (br s, 4H), 1.46-1.42 (br s, 2H); ESI-MS 452.6
[M + H]+.
5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Pyrrolidin-1-ylamide (5). Compound
1
144-146 °C; IR (KBr) 3413, 2925, 1685, 1571, 1479 cm-1; H

5962 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
SriVastaVa et al.
5 was prepared from 49 and N-aminopyrrolidine in 30% yield by
the same procedure as described for 9: 99.14% purity by HPLC,
[RD] ) +0.63°, c ) 0.2, DMSO; mp 140-142 °C; IR (KBr) 3425,
3220, 1654, 1595, 1490 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.36
(s, 1H), 7.26-7.24 (m, 2H), 7.18 (d, J ) 8.43 Hz, 2H), 7.12 (d, J
) 8.67 Hz, 1H), 7.08-7.04 (m, 2H), 5.74-5.68 (dd, J ) 12.09
and 6.21 Hz, 1H), 3.74-3.64 (dd, J ) 18.33 and 12.45 Hz, 1H),
3.36-3.30 (dd, J ) 18.34 and 6.22 Hz, 1H), 2.99-2.96 (br s, 4H),
1.92-189 (br s, 4H); ESI-MS 438.8 [M + H]+.
-0.63°, c ) 0.2, DMSO; mp 197-198 °C; IR (KBr) 3433, 3222,
1739, 1651, 1596, 1494 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.46
(s, 1H), 7.33-7.30 (m, 3H), 7.18 (d, J ) 6.49 Hz, 2H), 7.13 (d, J
) 8.95 Hz, 2H), 6.92 (d, J ) 8.94 Hz, 2H), 5.34-5.27 (dd, J )
12.94 and 7.35 Hz, 1H), 3.88-3.85 (br s, 4H), 3.81-3.70 (dd, J )
18.45 and 12.49 Hz, 1H), 3.15-3.06 (dd, J ) 18.45 and 7.38 Hz,
1H), 2.97-2.94 (br s, 4H); ESI-MS 385 [M + H]+.
1,5-Diphenyl-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Mor-
pholin-4-ylamide (13). Compound 13 was prepared from 53 and
N-aminomorpholine in 62% yield by the same procedure as
described for 9: 99.09% purity by HPLC, [RD] ) -0.18°, c )
0.2, DMSO; mp 212-214 °C; IR (KBr) 3421, 3213, 1737, 1651,
5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid (Hexahydrocyclopenta[c]pyrrol-2-
yl)-amide (6). Compound 6 was prepared from 49 and 3-amino-
3-azabicyclo[3.3.0]octane hydrochloride in 34% yield by the same
procedure as described for 9: 99.69% purity by HPLC, [RD] )
+0.28°, c ) 0.2, DMSO; mp 80 °C (fuses); IR (KBr) 3409, 3234,
1
1598, 1498 cm-1; H NMR (300 MHz, CDCl3) δ 7.49 (s, 1H),
7.26-7.23 (m, 2H), 7.21-7.08 (br s, 4H), 7.06-7.01 (br s, 2H),
6.87 (br s, 1H), 5.38-5.31 (dd, J ) 11.95 and 6.95 Hz, 1H), 3.87-
3.84 (br s, 4H), 3.73-3.70 (dd, J ) 17.7 and 12.28 Hz, 1H), 3.12-
3.09 (dd, J ) 17.70 and 6.96 Hz, 1H), 2.97-2.94 (br s, 4H); ESI-
MS 247.3 [M + H]+.
1
1671, 1585, 1477 cm-1; H NMR (300 MHz, CDCl3) δ 7.52 (s,
1H), 7.26-7.24 (m, 2H), 7.16 (d, J ) 8.43 Hz, 2H), 7.12 (d, J )
7.06 Hz, 1H), 7.07-7.03 (m, 2H), 5.74-5.68 (dd, J ) 12.12 and
6.15 Hz, 1H), 3.73-3.63 (dd, J ) 18.33 and 12.58 Hz, 1H), 3.38-
3.31 (dd, J ) 18.35 and 6.17 Hz, 1H), 3.29-3.27 (m, 2H), 2.71-
2.68 (br s, 2H), 2.46-2.35 (m, 2H), 1.68-1.63 (m, 3H), 1.56-
1.50 (m, 3H); ESI-MS 478.9 [M + H]+.
1-(2,4-Dichlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-3-
carboxylic Acid Morpholin-4-ylamide (14). Compound 14 was
prepared from 54 and N-aminomorpholine in 28% yield by the same
procedure as described for 9: 99.49% purity by HPLC, [RD] )
-0.48°, c ) 0.2, DMSO; mp 184 °C; IR (KBr) 3411, 3228, 1685,
5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Azepan-1-ylamide (7). Compound 7
was prepared from 49 and N-aminohomopiperidine in 9% yield by
the same procedure as described for 9: 98.25% purity by HPLC,
[RD] ) -1.18°, c ) 0.2, DMSO; mp 190-191 °C; IR (KBr) 3424,
3224, 1649, 1585, 1490 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.84
(s, 1H), 7.26-7.24 (m, 2H), 7.18 (d, J ) 8.37 Hz, 2H), 7.08-7.04
(m, 3H), 5.74-5.68 (dd, J ) 12.09 and 6.24 Hz, 1H), 3.73-3.63
(dd, J ) 18.30 and 12.35 Hz, 1H), 3.37-3.29 (dd, J ) 18.33 and
6.27 Hz, 1H), 3.14-3.11 (br s, 4H), 1.75-1.72 (br s, 4H), 1.67-
1.64 (br s, 4H); ESI-MS 466.2 [M + H]+.
5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid (4-Methylpiperazin-1-yl)-amide (8).
Compound 8 was prepared from 49 and N-amino-4-methylpipera-
zine in 26% yield by the same procedure as described for 9: 99.18%
purity by HPLC, [RD] ) +0.02°, c ) 0.2, DMSO; mp 80 °C (fuses);
IR (KBr) 3425, 3261, 1658, 1583, 1480 cm-1; 1H NMR (300 MHz,
CDCl3) δ 7.41 (s, 1H), 7.25 (s, 1H), 7.18 (d, J ) 8.30 Hz, 2H),
7.10 (d, J ) 7.36 Hz, 1H), 7.09-7.03 (m, 3H), 5.76-5.70 (dd, J
) 12.42 and 6.45 Hz, 1H), 3.73-3.63 (dd, J ) 18.43 and 12.57
Hz, 1H), 3.37-3.29 (dd, J ) 18.33 and 6.21 Hz, 1H), 2.98-2.95
(br s, 4H), 2.72-2.69 (br s, 4H), 2.37 (s, 3H); ESI-MS 468 [M +
H]+.
1,5-Bis-(4-chlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxy-
lic Acid Morpholin-4-ylamide (10). Compound 10 was prepared
from 50 and N-aminomorpholine in 29% yield by the same
procedure as described for 9: 99.76% purity by HPLC, [RD] )
+0.32°, c ) 0.2, DMSO; mp 216-217 °C; IR (KBr) 3438, 3235,
1737, 1651, 1598, 1476 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.44
(s, 1H), 7.31 (d, J ) 8.44 Hz, 2H), 7.19-7.12 (m, 4H), 6.89 (d, J
) 8.91 Hz, 2H), 5.30-5.24 (dd, J ) 12.87 and 7.38 Hz, 1H), 3.87-
3.84 (br s, 4H), 3.76-3.73 (dd, J ) 18.45 and 12.45 Hz, 1H), 3.09-
3.06 (dd, J ) 18.48 and 7.41 Hz, 1H), 2.85-2.82 (br s, 4H); ESI-
MS 419 [M + H]+.
1
1647, 1569, 1481 cm-1; H NMR (300 MHz, DMSO-d6) δ 9.54
(s, 1H), 7.51 (d, J ) 8.77 Hz, 1H), 7.43 (d, J ) 2.33 Hz, 1H),
7.29-7.25 (dd, J ) 8.83 and 2.21 Hz, 1H), 7.23-7.19 (m, 3H),
7.14-7.11 (m, 2H), 5.84-5.77 (dd, J ) 12.23 and 6.15 Hz, 1H),
3.72-3.62 (br s, 4H), 3.40-3.37 (dd, J ) 18.75 and 12.78 Hz,
1H), 3.06-3.01 (dd, J ) 18.75 and 5.76 Hz, 1H), 2.90-2.87 (br s,
4H); ESI-MS 421 [M + H]+.
1-(2,4-Dichlorophenyl)-5-(4-pentylphenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Morpholin-4-ylamide (15). Com-
pound 15 was prepared from 95 and N-aminomorpholine in 33%
yield by the same procedure as described for 9: 99.18% purity by
HPLC, [RD] ) -0.33°, c ) 0.2, DMSO; mp 210 °C; IR (KBr)
3309, 3136, 1691, 1577, 1479 cm-1; 1H NMR (300 MHz, DMSO-
d6) δ 9.47 (s, 1H), 7.47 (d, J ) 8.76 Hz, 1H), 7.41 (d, J ) 2.28
Hz, 1H), 7.26-7.25 (dd, J ) 8.73 and 2.21 Hz, 1H), 7.07-7.01
(br s, 4H), 5.78-5.72 (dd, J ) 11.67 and 5.55 Hz, 1H), 3.77-3.64
(br s, 5H), 3.09-3.01 (dd, J ) 18.01 and 12.51 Hz, 1H), 2.87-
2.84 (br s, 4H), 2.43-2.40 (br s, 2H), 1.49-1.42 (m, 2H), 1.22-
1.13 (br s, 4H), 0.80 (t, 3H); ESI-MS 491 [M + H]+.
5-(4-Butoxyphenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Morpholin-4-ylamide (16). Com-
pound 16 was prepared from 96 and N-aminomorpholine in 30%
yield by the same procedure as described for 9: 99.75% purity by
HPLC, [RD] ) -0.18°, c ) 0.2, DMSO; mp 195 °C; IR (KBr)
3423, 3254, 1685, 1510, 1479 cm-1; 1H NMR (300 MHz, DMSO-
d6) δ 9.52 (s, 1H), 7.47 (d, J ) 8.74 Hz, 1H), 7.42 (d, J ) 2.28
Hz, 1H), 7.28-7.24 (dd, J ) 8.72 and 2.29 Hz, 1H), 7.01 (d, J )
8.55 Hz, 2H), 6.73 (d, J ) 8.59 Hz, 2H), 5.76-5.71 (dd, J ) 11.70
and 5.33 Hz, 1H), 3.83 (t, 2H), 3.60-3.57 (br s, 4H), 3.40-3.37
(br s, 1H), 3.08-3.01 (dd, J ) 17.43 and 12.13 Hz, 1H), 2.88-
2.85 (br s, 4H), 1.62-1.57 (m, 2H), 1.39-1.21 (m, 2H), 0.87 (t,
3H); ESI-MS 492.1 [M + H]+.
1-(2,4-Dichlorophenyl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Morpholin-4-ylamide (17). Com-
pound 17 was prepared from 97 and N-aminomorpholine in 7%
yield by the same procedure as described for 9: 98.46% purity by
HPLC, [RD] ) +0.58°, c ) 0.2, DMSO; mp 176-178 °C; IR (KBr)
3423, 1685, 1610, 1577 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.50
(s, 1H), 7.11-7.02 (m, 5H), 6.70 (d, J ) 8.28 Hz, 2H), 5.73-5.67
(dd, J ) 11.76 and 6.03 Hz, 1H), 3.86-3.79 (br s, 4H), 3.72 (s,
3H), 3.66-3.60 (dd, J ) 18.16 and 11.95 Hz, 1H), 3.39-3.31 (dd,
J ) 18.15 and 6.0 Hz, 1H), 2.96-2.85 (br s, 4H); ESI-MS 450.2
[M + H]+.
5-Benzo[1,3]dioxol-5-yl-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Morpholin-4-ylamide (18). Com-
pound 18 was prepared from 98 and N-aminomorpholine in 45%
yield by the same procedure as described for 9: 99.48% purity by
HPLC, [RD] ) +0.62°, c ) 0.2, DMSO; mp 174-176 °C; IR (KBr)
5-(4-Chlorophenyl)-1-phenyl-4,5-dihydro-1H-pyrazole-3-car-
boxylic Acid Morpholin-4-ylamide (11). Compound 11 was
prepared from 51 and N-aminomorpholine in 10% yield by the same
procedure as described for 9: 98.89% purity by HPLC, [RD] )
+0.28°, c ) 0.2, DMSO; mp 201-202 °C; IR (KBr) 3424, 3228,
1
1687, 1596, 1468 cm-1; H NMR (300 MHz, DMSO-d6) δ 9.42
(s, 1H), 7.39 (d, J ) 7.43 Hz, 2H), 7.23 (d, J ) 7.90 Hz, 2H), 7.17
(s, 2H), 7.04 (d, J ) 6.61 Hz, 2H), 6.82-6.79 (m, 1H), 5.57-5.49
(dd, J ) 11.69 and 5.57 Hz, 1H), 3.65-3.62 (br s, 4H), 3.51-3.49
(dd, J ) 18.05 and 12.02 Hz, 1H), 3.16-3.13 (dd, J ) 18.07 and
5.77 Hz, 1H), 2.89-2.86 (br s, 4H); ESI-MS 385 [M + H]+.
1-(4-Chlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-3-car-
boxylic Acid Morpholin-4-ylamide (12). Compound 12 was
prepared from 52 and N-aminomorpholine in 29% yield by the same
procedure as described for 9: 99.35% purity by HPLC, [RD] )

Diaryl Dihydropyrazole-3-carboxamides
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5963
3429, 3236, 1683, 1548, 1485 cm-1; 1H NMR (300 MHz, DMSO-
d6) δ 9.39 (s, 1H), 7.52 (d, J ) 8.73 Hz, 1H), 7.45 (d, J ) 2.26
Hz, 1H), 7.31-7.27 (dd, J ) 8.72 and 2.33 Hz, 1H), 6.73 (d, J )
7.91 Hz, 1H), 6.65 (s, 1H), 6.60 (d, J ) 7.89 Hz, 1H), 5.93 (d, J
) 4.22 Hz, 2H), 5.74-5.68 (dd, J ) 11.65 and 5.56 Hz, 1H), 3.64-
3.61 (br s, 4H), 3.49-3.43 (br s, 1H), 3.07-2.99 (dd, J ) 18.02
and 11.94 Hz, 1H), 2.86-2.83 (br s, 4H); ESI-MS 464.1 [M +
H]+.
5-(4-Bromophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-
pyrazole-3-carboxylic Acid Morpholin-4-ylamide (19). Com-
pound 19 was prepared from 99 and N-aminomorpholine in 39%
yield by the same procedure as described for 9: 98.88% purity by
HPLC, [RD] ) +0.66°, c ) 0.2, DMSO; mp 156-157 °C; IR (KBr)
3417, 3234, 1645, 1573, 1475 cm-1; 1H NMR (300 MHz, DMSO-
d6) δ 9.41 (s, 1H), 7.50 (d, J ) 8.73 Hz, 1H), 7.42 (d, J ) 8.17
Hz, 3H), 7.29 (d, J ) 8.69 Hz, 1H), 7.08 (d, J ) 8.16 Hz, 2H),
5.81-5.76 (dd, J ) 11.64 and 5.82 Hz, 1H), 3.66-3.60 (br s, 5H),
3.10-3.02 (dd, J ) 18.14 and 11.86 Hz, 1H), 2.85-2.82 (br s,
4H); ESI-MS 498.8 [M + H]+.
1-(2,4-Dichlorophenyl)-5-pyridin-3-yl-4,5-dihydro-1H-pyra-
zole-3-carboxylic Acid Morpholin-4-ylamide (20). Compound 20
was prepared from 100 and N-aminomorpholine in 27% yield by
the same procedure as described for 9: 98.99% purity by HPLC,
[RD] ) -0.38°, c ) 0.2, DMSO; mp 107 °C (fuses); IR (KBr)
3421, 3254, 1654, 1560, 1490 cm-1; 1H NMR (300 MHz, DMSO-
d6) δ 9.75 (s, 1H), 8.68-6.65 (br s, 2H), 7.98-7.81 (m, 2H), 7.69-
7.50 (m, 2H), 7.33 (s, 1H), 6.10-5.98 (dd, J ) 12.17 and 6.90 Hz,
1H), 3.66-3.63 (br s, 4H), 3.56-3.51 (dd, J ) 18.76 and 12.46
Hz, 1H), 3.37-3.29 (dd, J ) 18.76 and 6.90 Hz, 1H), 2.89-2.86
(br s, 4H); ESI-MS 421.5 [M + H]+.
CDCl3) δ 7.43 (s, 1H), 7.33 (d, J ) 1.86 Hz, 1H), 7.19-7.09 (m,
2H), 6.58 (s, 2H), 5.97-5.91 (dd, J ) 11.31 and 4.80 Hz, 1H),
3.87-3.84 (br s, 4H), 3.67-3.57 (dd, J ) 18.21 and 11.90 Hz,
1H), 3.49-3.41 (dd, J ) 18.24 and 4.83 Hz, 1H), 2.95-2.92 (br s,
4H); ESI-MS 461 [M + H]+.
(+)-5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Morpholin-4-ylamide (9a). Com-
pound 9a was prepared from 49a and N-aminomorpholine in 46%
yield by the same procedure as described for 9: 99.15% purity by
HPLC, 99.8% chiral purity by HPLC, [RD] ) + 265°, c ) 0.2,
DMSO; mp 164-165 °C (fuses); IR (KBr) 3410, 3236, 1632, 1568,
1
1549 cm-1; H NMR (300 MHz, DMSO-d6) δ 9.39 (s, 1H), 7.49
(d, J ) 8.73 Hz, 1H), 7.44 (d, J ) 2.17 Hz, 1H), 7.29 (d, J ) 8.36
Hz, 3H), 7.15 (d, J ) 8.35 Hz, 2H), 5.82-5.76 (dd, J ) 11.81 and
5.90 Hz, 1H), 3.65-3.62 (br s, 4H), 3.39-3.35 (dd, J ) 18.08 and
12.14 Hz, 1H), 3.10-3.02 (dd, J ) 18.03 and 5.91 Hz, 1H), 2.85-
2.82 (br s, 4H); ESI-MS 455.2 [M + H]+.
(-)-5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Morpholin-4-ylamide (9b). Com-
pound 9b was prepared from 49b and N-aminomorpholine in 56%
yield by the same procedure as described for 9: 99.85% purity by
HPLC, 100% chiral purity by HPLC [RD] ) -265°, c ) 0.2,
DMSO; mp 181-183 °C (fuses); IR (KBr) 3388, 3238, 1635, 1571,
1
1550 cm-1; H NMR (300 MHz, DMSO-d6) δ 9.39 (s, 1H), 7.49
(d, J ) 8.73 Hz, 1H), 7.44 (d, J ) 2.17 Hz, 1H), 7.29 (d, J ) 8.36
Hz, 3H), 7.15 (d, J ) 8.35 Hz, 2H), 5.82-5.73 (dd, J ) 11.81 and
5.90 Hz, 1H), 3.63-3.60 (br s, 4H), 3.44-3.38 (dd, J ) 18.09 and
12.21 Hz, 1H), 3.10-3.02 (dd, J ) 18.03 and 5.91 Hz, 1H), 2.85-
2.82 (br s, 4H); ESI-MS 455.2 [M + H]+.
Procedure for the Preparation of Hydrochloride Salt. Hy-
drochloride Salt of 5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-
4,5-dihydro-1H-pyrazole-3-carboxylic Acid Morpholin-4-yl-
amide (25). The compound 9 (11.7 g, 25.80 mmol) was taken in
methanol (45 mL), and ethereal HCl (12 mL) was added at 0-5
°C dropwise. The reaction mixture was stirred at 10-15 °C for
10-15 min. Solvent was evaporated on a rotatory evaporator under
reduced pressure. The residue obtained was triturated in EtOAc
(55 mL) at 60-70 °C for 10-15 min to afford an off-white solid
which was filtered on a Buchner funnel under suction and dried to
afford 25 as an off-white solid (10.60 g, 84%): 99.89% purity by
HPLC, [RD] ) -1.9°, c ) 0.2, DMSO; mp 184-185 °C (with
decomposition); IR (KBr) 3423, 2987, 1687, 1571, 1481 cm-1; 1H
NMR (300 MHz, DMSO-d6) δ 9.51 (s, 1H), 7.50 (d, J ) 8.75 Hz,
1H), 7.45 (d, J ) 2.32 Hz, 1H), 7.29 (d, J ) 6.96 Hz, 3H), 7.15
(d, J ) 8.47 Hz, 2H), 5.83-5.77 (dd, J ) 11.88 and 5.80 Hz, 1H),
3.70-3.60 (br s, 5H), 3.10-3.02 (dd, J ) 18.12 and 5.95 Hz, 1H),
2.87-2.84 (br s, 4H); ESI-MS 455 [M + H - HCl]+.
1-(2,4-Dichlorophenyl)-5-thiophen-2-yl-4,5-dihydro-1H-pyra-
zole-3-carboxylic Acid Morpholin-4-ylamide (21). Compound 21
was prepared from 101 and N-aminomorpholine in 83% yield by
the same procedure as described for 9: 98.87% purity by HPLC,
[RD] ) +0.18°, c ) 0.2, DMSO; mp 168-170 °C; IR (KBr) 3435,
1
3209 1670, 1651, 1579, 1473 cm-1; H NMR (300 MHz, CDCl3)
δ 7.49 (s, 1H), 7.31 (d, J ) 1.62 Hz, 1H), 7.11-7.04 (m, 3H),
6.79-6.75 (m, 2H), 6.05-6.04 (dd, J ) 11.19 and 4.92 Hz, 1H),
3.88-3.85 (br s, 4H), 3.69-3.60 (dd, J ) 18.01 and 11.74 Hz,
1H), 3.55-3.47 (dd, J ) 18.15 and 4.86 Hz, 1H), 2.99-2.94 (br s,
4H); ESI-MS 426.3 [M + H]+.
1-(2,4-Dichlorophenyl)-5-furan-2-yl-4,5-dihydro-1H-pyrazole-
3-carboxylic Acid Morpholin-4-ylamide (22). Compound 22 was
prepared from 102 and N-aminomorpholine in 38% yield by the
same procedure as described for 9: 99.18% purity by HPLC, [RD]
) +0.38°, c ) 0.2, DMSO; mp 203-205 °C; IR (KBr) 3417, 3238,
1
1687, 1533, 1477 cm-1; H NMR (300 MHz, DMSO-d6) δ 9.60
(s, 1H), 7.51 (d, J ) 2.05 Hz 1H), 7.42 (s, 1H), 7.39 (d, J ) 8.69
Hz 1H), 7.28-7.25 (dd, J ) 8.67 and 2.11 Hz, 1H), 6.20 (s, 2H),
5.83-5.78 (dd, J ) 11.07 and 4.53 Hz, 1H), 3.67-3.64 (br s, 4H),
3.56-3.46 (dd, J ) 17.75 and 11.83 Hz, 1H), 3.29-3.21 (dd, J )
17.86 and 4.62 Hz, 1H), 2.90-2.87 (br s, 4H); ESI-MS 410.2 [M
+ H]+.
1-(2,4-Dichlorophenyl)-5-(5-methylthiophen-2-yl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Morpholin-4-ylamide (23). Com-
pound 23 was prepared from 103 and N-aminomorpholine in 53%
yield by the same procedure as described for 9: 99.16% purity by
HPLC, [RD] ) +0.34°, c ) 0.2, DMSO; mp 135-138 °C; IR (KBr)
3423, 3230, 1664, 1579, 1475 cm-1; 1H NMR (300 MHz, CDCl3)
δ 7.44 (s, 1H), 7.31 (d, J ) 2.13 Hz, 1H), 7.15-7.06 (m, 2H),
6.57 (d, J ) 3.40 Hz, 1H), 6.39-6.38 (dd, J ) 3.37 and 1.01 Hz,
1H), 6.00-5.94 (dd, J ) 11.12 and 4.87 Hz, 1H), 3.87-3.84 (br s,
4H), 3.64-3.54 (dd, J ) 18.08 and 11.56 Hz, 1H), 3.50-3.42 (dd,
J ) 18.09 and 4.92 Hz, 1H), 2.95-2.92 (br s, 4H), 2.32 (s, 3H);
ESI-MS 440.4 [M + H]+.
Hydrochloride Salt of (+)-5-(4-Chlorophenyl)-1-(2,4-dichlo-
rophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Morpho-
lin-4-ylamide (27). Compound 27 was prepared from 9a in 83%
yield by the same procedure as described for 25: 99.81% purity
by HPLC, 100% chiral purity by HPLC, [RD] ) +233°, c ) 0.2,
DMSO; mp 207-208 °C (with decomposition); IR (KBr) 3413,
1
2858, 1683, 1571, 1483 cm-1; H NMR (300 MHz, DMSO-d6) δ
9.50 (s, 1H), 7.49 (d, J ) 8.74 Hz, 1H), 7.45 (d, J ) 2.24 Hz, 1H),
7.28 (d, J ) 8.22 Hz, 3H), 7.14 (d, J ) 8.40 Hz, 2H), 5.83-5.77
(dd, J ) 11.81 and 5.79 Hz, 1H), 3.74-3.61 (br s, 5H), 3.10-3.02
(dd, J ) 18.05 and 6.05 Hz, 1H), 2.87-2.84 (br s, 4H); ESI-MS
454.8 [M + H - HCl]+.
Hydrochloride Salt of (-)-5-(4-Chlorophenyl)-1-(2,4-dichlo-
rophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Morpho-
lin-4-ylamide (29). Compound 29 was prepared from 9b in 90%
yield by the same procedure as described for 25: 99.92% purity
by HPLC, 100% chiral purity by HPLC, [RD] ) -233°, c ) 0.2,
DMSO; mp 211-212 °C (with decomposition); IR (KBr) 3419,
1
5-(5-Chlorothiophen-2-yl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Morpholin-4-ylamide (24). Com-
pound 24 was prepared from 104 and N-aminomorpholine in 39%
yield by the same procedure as described for 9: 98.36% purity by
HPLC, [RD] ) +0.47°, c ) 0.2, DMSO; mp 76-79 °C (fuses); IR
3229, 1683, 1571, 1550 cm-1; H NMR (300 MHz, DMSO-d6) δ
9.45 (s, 1H), 7.50 (d, J ) 8.73 Hz, 1H), 7.45 (d, J ) 2.24 Hz, 1H),
7.28 (d, J ) 8.47 Hz, 3H), 7.14 (d, J ) 8.42 Hz, 2H), 5.83-5.77
(dd, J ) 11.91 and 5.82 Hz, 1H), 3.64-3.55 (br s, 5H), 3.10-3.02
(dd, J ) 17.91 and 5.94 Hz, 1H), 2.85-2.82 (br s, 4H); ESI-MS
454.9 [M + H - HCl]+.
1
(KBr) 3409, 3244, 1664, 1581, 1477 cm-1; H NMR (300 MHz,

5964 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
SriVastaVa et al.
Procedure for Preparation of Salts. Preparation of Bisulfate
Salt of 5-(4-Chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-
1H-pyrazole-3-carboxylic Acid Morpholin-4-ylamide (26). To
a solution of 9 (5.4 g, 11.2 mmol) in methanol (108 mL) was added
concentrated H2SO4 (0.54 mL) at 10-15 °C over period of 5-7
min. The reaction mixture was refluxed at 60-65 °C for 30-40
min. The solvents were evaporated on a rotatory evaporator under
reduced pressure to get a solid. The solid was stirred in diethyl
ether (32 mL) at 26-28 °C for 20-25 min and filtered on a
Buchner funnel under suction to afford 26 as a light yellow solid
(6.51 g, 99%), 99.98% purity by HPLC, [RD] ) +0.3°, c ) 0.2,
DMSO; mp 135-137 °C (fuses); IR (KBr) 3438, 2927, 1679, 1571,
described for 26: 99.80% purity by HPLC, 100% chiral purity by
HPLC, [RD] ) -201.6°, c ) 0.2, DMSO; mp 190-192 °C (with
decomposition); IR (KBr) 3398, 1685, 1654, 1637, 1544 cm-1; 1H
NMR (300 MHz, CDCl3) δ 10.68 (br s, 1H), 7.90 (d, J ) 6.60 Hz,
2H), 7.45-7.39 (m, 4H), 7.21-7.17 (m, 3H), 7.06-7.02 (m, 3H),
5.99-5.92 (dd, J ) 12.66 and 5.46 Hz, 1H), 4.05-3.93 (br s, 4H),
3.74-3.63 (dd, J ) 18.03 and 12.31 Hz, 1H), 3.27-3.19 (dd, J )
18.03 and 5.52 Hz, 1H), 2.48-2.45 (br s, 4H); ESI-MS 612.7 [M
+ C6H5SO3H]+.
Molecular Modeling. All computational experiments were
conducted on a HP Windows workstation. Human CB1 sequence
was retrieved from the SWISS-PROT protein sequence database,44
and structure construction, optimization, and visualization were
carried out using the molecular modeling packages including the
Modeler module of Discovery Studio 1.1.36 The conformations of
the input structures 1 (the conformational properties of 1 are readily
modeled with constraints), 2, and of both enantiomers R and S (9a,
9b) for the compound 9 were generated using corina 3D and cosmic
module of TSAR36 followed by minimization using the PM3
method. The PM3 method has been reported to give the best
approximation of the angle in comparison with other methods for
CB1 receptor antagonists.12
The coordinates of the inactive R-state of the human CB1
cannabinoid receptor were modeled using the 2.8 Å crystal structure
of bovine rhodopsin.45 The residues were aligned and mutated, and
the helices were constructed as mentioned in the experiments
earlier.46-48 The loops were omitted. This model was minimized
with CFF force field, holding the TMH backbones fixed. Subse-
quently, the kink in TMH6 at Pro35848 was introduced to enable
the salt bridge between Lys192 and Asp366, and the model was
further minimized. The stereochemical quality of the resulting
protein structure was tested with the PROCHECK program.49
The ligand 1 was automatically docked into the receptor, using
Ligandfit module of DS SBD 1.2.36 It performs docking of flexible
ligands into proteins with partial flexibility in the neighborhood of
the active site. To take protein flexibility into account, the complex
were then refined using molecular dynamics (CFF force field,
dielectric constant ) 4, 300 °K). The energy minimization process
consists of two sequential steps: the Steepest Descent algorithm,
reaching a final convergence of 10.0 kcal mol-1 Å-1, followed by
the Conjugate Gradient algorithm to reach a final convergence of
0.01 kcal mol-1 Å-1. Constraints including the distance and torsion
angles of aromatic residues and as well as range-constraint of 2.5-
3.0 Å on the N-atom of Lys192 were applied during the run so
that hydrogen-bond formation is favored as reported in earlier
models. The other ligands 2 and both enantiomers R and S (9a,
9b) for the compound 9 were then automatically docked in the
binding site defined by the docked posed of ligand 1. The poses
were ranked with PLP-1, PLP-1, and Dockscore, and the conforma-
tions with the best scores were checked visually.
In Vivo Pharmacological Studies. Animals. All the animals
used in the study were procured from the Animal Breeding Facility
of Zydus Research Center. Institutional Animal Ethical Committee
approved all the study protocols. Female Zucker fa/fa rats (age of
10-12 weeks and 300-350 g of weight) were used for the 5%
sucrose solution intake as well as long term study. The pharma-
cokinetic parameters were also assessed in the obese overnight-
fasted female Zucker fa/fa rats. For the mouse tetrad model,
10-12 weeks old female Swiss Albino Mice (25-30 g) were used.
Drug Preparation and Administration. For in vivo experi-
ments, compounds were suspended with 0.01% Tween 80 plus 5%
DMSO in saline (NaCl 0.9%) for intravenous administration
(particularly for the CB1 agonist WIN-55212-2) or with 0.5%
carboxymethylcellulose sodium salt in distilled water for oral route.
The test compounds were administered at the dose of 10 mg/kg.
All the compounds were administered by oral route in a volume of
2 mL/kg body weight for rats and 10 mL/kg body weight for mice.
WIN-55212-2 was injected intravenous at a dose of 1 mg/kg in
mice in a volume of 10 mL/kg body weight.
1
1477 cm-1; H NMR (300 MHz, DMSO-d6) δ 9.58 (s, 1H), 7.49
(d, J ) 8.73 Hz, 1H), 7.44 (d, J ) 2.17 Hz, 1H), 7.29 (d, J ) 8.36
Hz, 3H), 7.15 (d, J ) 8.35 Hz, 2H), 5.83-5.77 (dd, J ) 11.81 and
5.90 Hz, 1H), 3.71-3.61 (br s, 5H), 3.11-3.03 (dd, J ) 18.03 and
5.92 Hz, 1H), 2.89-2.86 (br s, 4H); ESI-MS 454.9 [M+H-
H2SO4]+.
Bisulfate Salt of (+)-5-(4-Chlorophenyl)-1-(2,4-dichlorophen-
yl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Morpholin-4-
ylamide (28). Compound 28 was prepared from 9a in 99% yield
by the same procedure as described for 26: 99.87% purity by
HPLC, 100% chiral purity by HPLC, [RD] ) +157°, c ) 0.2,
DMSO; mp 162-164 °C (with decomposition); IR (KBr) 3390,
3259 1670, 1577, 1490 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.54
(br s, 1H), 7.32-7.11 (m, 4H), 7.09-7.04 (m, 3H), 5.76-5.70 (dd,
J ) 12.21 and 6.36 Hz, 1H), 3.88-3.85 (br s, 4H), 3.74-3.63 (dd,
J ) 18.30 and 12.68 Hz, 1H), 3.37-3.28 (dd, J ) 18.31 and 6.37
Hz, 1H), 2.99-2.96 (br s, 4H); ESI-MS 454.9 [M + H - H2SO4]+.
Bisulfate Salt of (-)-5-(4-Chlorophenyl)-1-(2,4-dichlorophen-
yl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Morpholin-4-
ylamide (30). Compound 30 was prepared from 9b in 96% yield
by the same procedure as described for 26: 99.77% purity by
HPLC, 100% chiral purity by HPLC, [RD] ) -157°, c ) 0.2,
DMSO; mp 149-151 °C (with decomposition); IR (KBr) 3427,
3219 1685, 1575, 1551 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.46
(br s, 1H), 7.36 (d, J ) 8.67 Hz, 1H), 7.23-7.17 (dd, J ) 7.92 and
2.31 Hz, 2H), 7.12 (d, J ) 2.31 Hz, 1H), 7.09 (d, J ) 8.40 Hz,
3H), 5.85 (dd, J ) 12.54 and 5.91 Hz, 1H), 4.02-3.99 (br s, 4H),
3.75-3.65 (dd, J ) 18.09 and 12.79 Hz, 1H), 3.57-3.54 (br s,
4H), 3.32-3.24 (dd, J ) 18.15 and 6.01 Hz, 1H); ESI-MS 454.9
[M + H - H2SO4]+.
Oxalate Salt of (-)-5-(4-Chlorophenyl)-1-(2,4-dichlorophen-
yl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Morpholin-4-
ylamide (31). Compound 31 was prepared from 9b and oxalic acid
in 60% yield by the same procedure as described for 26: 99.74%
purity by HPLC, 100% chiral purity by HPLC, [RD] ) -213.3°, c
) 0.2, DMSO; mp 170 °C (with decomposition); IR (KBr) 3390,
3249, 1670, 1577, 1554 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.45
(s, 1H), 7.17 (d, J ) 8.45 Hz, 3H), 7.14 (s, 1H), 7.09-7.04 (m,
3H), 5.76-5.70 (dd, J ) 11.38 and 6.34 Hz, 1H), 3.88-3.85 (br s,
4H), 3.74-3.64 (dd, J ) 18.33 and 11.86 Hz, 1H), 3.37-3.29 (dd,
J ) 18.34 and 6.34 Hz, 1H), 2.95-2.92 (br s, 4H); ESI-MS 454.4
[M + H - C2H2O4]+.
Methane Sulfonate Salt of (-)-5-(4-Chlorophenyl)-1-(2,4-
dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Mor-
pholin-4-ylamide (32). Compound 32 was prepared from 9b and
methanesulfonic acid in 95% yield by the same procedure as
described for 26: 99.09% purity by HPLC, 100% chiral purity by
HPLC, [RD] ) -207.2°, c ) 0.2, DMSO; mp 145-147 °C (with
decomposition); IR (KBr) 3425, 3219, 1685, 1575, 1551 cm-1; 1H
NMR (300 MHz, CDCl3) δ 10.68 (br s, 1H), 7.40 (d, J ) 8.71 Hz,
1H), 7.19 (d, J ) 7.99 Hz, 3H), 7.12 (d, J ) 8.71 Hz, 1H), 7.03
(d, J ) 8.40 Hz, 2H), 5.95 (dd, J ) 12.66 and 5.46 Hz, 1H), 4.04-
3.99 (br s, 4H), 3.89 (br s, 3H), 3.74-3.64 (dd, J ) 18.01 and
12.78 Hz, 1H), 3.27-3.20 (dd, J ) 18.09 and 5.46 Hz, 1H), 2.96-
2.93 (br s, 4H); ESI-MS 454.1 [M + H - CH3SO3H]+.
Benzene Sulfonate Salt of (-)-5-(4-Chlorophenyl)-1-(2,4-
dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic Acid Mor-
pholin-4-ylamide (33). Compound 33 was prepared from 9b and
benzene sulfonic acid in 63% yield by the same procedure as
5% Sucrose Solution Intake in Zucker fa/fa Rats. The obese
Zucker fa/fa rats were housed individually and subjected to training

Diaryl Dihydropyrazole-3-carboxamides
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5965
for consuming 5% sucrose solution over 4 h, by allowing access
to the 5% sucrose solution in the bottles. Food and water were
withdrawn during this time. This training was given for six
consecutive days, at the same time of the day. On seventh day, the
animals were randomized into groups of six animals each and
treated with the test compounds. After 1 h of treatment, the animals
were exposed to the 5% sucrose solution for 4 h as that of the
training schedule. The primary pharmacokinetic measurements
indicated the T1/2 of 2-3 h for all the tested compounds (Data not
shown). Accordingly, this duration was selected for sucrose
consumption studies, so that the T1/2 of the compound falls exactly
in between of the study duration. The amount of sucrose solution
consumed by each animal was calculated. Difference between the
control and treatment groups were analyzed by performing one-
way ANOVA followed by Dunnett’s test on sucrose solution
consumption using Graph pad Prism software.
Long-Term Effect on Body Weight and Serum Biochemistry.
Female obese Zucker fa/fa rats were individually housed and
divided into groups of six animals each. All treatments were given
orally, 1 h before the start of the dark phase. Body weight was
recorded daily for 60 days. On day 61, blood samples were collected
from retro-orbital sinus of the animals in the morning, and the serum
was analyzed for triglyceride using Pointe Scientific kit using
SpectraMax190 microplate reader. The difference between groups
was analyzed by performing one-way ANOVA followed by
Dunnett’s test of control and treated groups using Graphpad Prism
software.
Mouse Tetrad Model for Cannabinoid Receptor 1 Antagonist
Activity. Female Swiss albino mice were used for this test. The
test compounds were administered orally, and after 1 h of test
compound administration, WIN-55212-2 (1 mg/kg) was given by
intravenous route. Thirty minutes later, the four tests typically
comprising of tetrad were carried out. Temperature was measured
for evaluation of hypothermia using a lubricated thermometer
inserted into the rectum twice: before and after the treatment. The
hot plate test was carried out using a hot plate at 55 °C as
nociceptive stimulus, immediately after testing the temperature. The
latency was measured before and after the treatment, and analgesia
was quantified as the percentage of maximum possible effect (%
MPE) with a cutoff time of 30 s. The formula for % MPE is as
follows: (latency after treatment - control latency)/(cutoff time
- control latency) × 100. Catalepsy was measured using the “ring
test” 30 min after drug injection for a duration of 5 min.35 The
data is expressed as an immobility index defined as percentage of
total time spent on a ring during which the animal remained
motionless. The Locomotor activity was evaluated after 35 min of
drug injection in a squared open field. The total number of squares
crossed in 5 min was taken as the mobility index.
Pharmacokinetic of Antiobesity Compound. Pharmacokinetic
parameters of 1 and 30 were evaluated by administration of 30
mg/kg dose orally to female obese Zucker fa/fa rats. The oral
suspension of both the compounds was prepared in 0.5% car-
boxymethylcellulose sodium salt in distilled water. A group of six
female obese Zucker fa/fa rats were kept for an overnight fasting
and then administered with a dose of 30 mg/kg orally. Serial blood
samples were collected from retro-orbital of animals at various time
points, i.e., 10, 20,and 40 min and 1.0, 2.0, 4.0, 6.0, 8.0, 24.0, and
48.0 h. The blood samples were subjected to centrifugation for
collection of the plasma.
voltage 1.8 kV, Block and CDL temperature was 200 °C, and
Nebulizer gas was 1.5 L/min. The quantitation was performed using
the known concentration versus response curve. The calibration
standards were obtained by spiking a known concentration in blank
matrix with internal standard; they were processed and analyzed
as for the samples.
The pharmacokinetic parameters, Tmax, Cmax, half-life, and
AUC(0- ) were calculated using WinNolin software version 5.0.1.
The brain to plasma and adipose to plasma ratios were calculated
using plasma (µg/mL) concentration over brain/adipose (µg/g)
concentration.
Radioligand Binding Assay for CB1 and CB2. The radioligand
binding assays were performed at MDS Pharma Services Taiwan
Ltd. (Taiwan, ROC). The measurements were done in duplicate,
and values indicate the mean of at least two independent experi-
ments performed. The CB1 assay was performed using human
recombinant HEK-293 cells. The membranes were incubated at 37
°C with 0.5 nM [3H] CP-55940 in 1 mL of buffer (50 mM Tris-
HCl, pH 7.4, 1 mM EDTA, 3 mM MgO2, 0.5% BSA). The Ki values
were calculated from the equation of Cheng and Prusoff using a
fixed Kd value (1.3 nM) for WIN-55212-2, obtained from inde-
pendent experimental assays. For the CB2 binding assay, a similar
procedure was followed using human recombinant CHO-K1 cells
with 2.4 nM [3H] WIN-55212-2 in 1 mL of buffer (20 mM HEPES,
pH 7.0, 5 mg/mL BSA). Ki values were calculated from the equation
of Cheng and Prusoff using a fixed Kd value (4.9 nM) for WIN-
55212-2. IC50 values were determined by a nonlinear, least-square
regression analysis using Data Analysis Toolbox (MDL Information
Systems, San Leandro, CA).
Acknowledgment. We thank the reviewers for a number of
excellent suggestions and drawing our attention to several
publications, the management of Zydus Cadila Healthcare
Limited for encouragement, Mr. Sandeep A Shedage, Mr.
Shivaji B. Gugale, Mr. Rahul P. Salunke, Mr. Sidhartha Sankar
Kar, and Mr. Amol K. Dhawas for synthesizing some of the
intermediates, and the analytical department for support.
Supporting Information Available: Table of spectroscopic data
(IR and 1H NMR) of compounds 37, 39, 44-48, 50-54, and 65-
104 and a table of microanalytical data of compounds 4-33. This
material is available free of charge via the Internet at http://
pubs.acs.org.
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