1,3-Diarylcycloalkanopyrazoles and diphenyl hydrazides as selective inhibitors of cyclooxygenase-2

Article abstract of DOI:10.1016/S0960-894X(00)00041-X

Novel 1,3-diarylcycloalkanopyrazoles 1, and diphenyl hydrazides 2 were identified as selective inhibitors of cyclooxygenase-2. The 1,3-diaryl substitution pattern of the pyrazole ring in 1 differentiates these compounds from most of the known selective COX-2 inhibitors that contain two aryl rings at the adjacent positions on a heterocyclic or a phenyl ring. Similarly, the two phenyl rings in 2 are also separated by three atoms. SAR of both phenyl rings in 1 and 2, and the aliphatic ring in 1 will be discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.

Full text of DOI:10.1016/S0960-894X(00)00041-X

Bioorganic & Medicinal Chemistry Letters 10 (2000) 601±604
1,3-Diarylcycloalkanopyrazoles and Diphenyl Hydrazides as
Selective Inhibitors of Cyclooxygenase-2
Zhihua Sui,* Jihua Guan, Michael P. Ferro, Kathy McCoy, Michael P. Wachter,
William V. Murray, Monica Singer, Michele Steber, Dave M. Ritchie
and Dennis C. Argentieri
The R.W. Johnson Pharmaceutical Research Institute, 1000 Route 202, Raritan, NJ 08869, USA
Received 29 November 1999; accepted 13 January 2000
AbstractÐNovel 1,3-diarylcycloalkanopyrazoles 1, and diphenyl hydrazides 2 were identi®ed as selective inhibitors of cyclooxy-
genase-2. The 1,3-diaryl substitution pattern of the pyrazole ring in 1 di€erentiates these compounds from most of the known
selective COX-2 inhibitors that contain two aryl rings at the adjacent positions on a heterocyclic or a phenyl ring. Similarly, the two
phenyl rings in 2 are also separated by three atoms. SAR of both phenyl rings in 1 and 2, and the aliphatic ring in 1 will be dis-
cussed. # 2000 Elsevier Science Ltd. All rights reserved.
The principal pharmacological e€ects of nonsteroidal
anti-in¯ammatory drugs (NSAIDs) are due to their
ability to inhibit prostaglandin synthesis by blocking
cyclooxygenase activities.1±7 The gastrointestinal (GI)
and renal side e€ects of NSAIDs, however, frequently
limit their therapeutic use. These side e€ects were
believed to be inseparable from the pharmacological
e€ects since prostaglandins have cytoprotective e€ects
in the gastrointestinal tract and also regulate renal
blood ¯ow. The discovery of two isozymes, cyclooxy-
genase-1 (COX-1) and cyclooxygenase-2 (COX-2), that
catalyze the second step in prostaglandin synthesis has
provided the possibility of separating the pharmacolo-
gical e€ects from the side e€ects of NSAIDs. Research
results suggest that COX-1 and COX-2 belong to sepa-
rate prostaglandin-forming systems. COX-1 is expressed
constitutively in most cells and tissues.8±10 The COX-1-
dependent pathway can respond instantaneously and
produces prostaglandins that regulate acute events such
as vascular homeostasis. The synthesis of prosta-
glandins by COX-1 also helps maintain normal stomach
and renal function. COX-2 is only expressed following
mitogenic or in¯ammatory stimuli. Since it is not
expressed in most resting tissues and must be induced,
prostaglandins produced by COX-2 are probably
involved only secondarily in chronic physiological reac-
tions. This discovery suggests that the gastrointestinal
and renal side e€ects of the nonsteroidal antiin-
¯ammatory drugs might be avoided.
Recently, many COX-2 selective inhibitors have been
reported, including Celebrex and Vioxx, the ®rst COX-2
inhibitors on the market. The pharmacophore for most
of these inhibitors consists of a central template, most
commonly cyclic (®ve- or six-membered, carbocyclic or
heterocyclic), which is 1,2-disubstituted by aryl moieties.
We wish to report that the 1,3-disubstitution pattern,
such as in structures 1 and 2, is also an e€ective phar-
macophore for selective COX-2 inhibition.11
Compounds 1 were synthesized in two ways. The ®rst
synthetic route is based on conventional 1,3-dipolar
cycloaddition chemistry (Scheme 1).12 Thus, com-
pounds 2 were prepared from the corresponding benzoic
acids by standard procedures and transformed to a-
chlorohydrazones with phorsphorus pentachloride.
Cycloaddition of the nitrileimines generated from 3 to
cycloalkenes 4 gave the precursors 5 which underwent
oxidation to provide the desired products 1. The second
method involves the condensation of b-diketones 8 with
arylhydrazines. The intermediates 8 were prepared by
*Corresponding author. Tel.: +1-908-704-5778; fax: +1-908-526-
6469.
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00041-X

602
Z. Sui et al. / Bioorg. Med. Chem. Lett. 10 (2000) 601±604
Scheme 1.
reactions of cycloalkanones 6 with benzoyl chlorides 7
using similar procedures reported by our laboratory
(Scheme 2).13 Both regioisomers were isolated in the
condensation reactions. The activities of the regioisomer
with the adjacent diaryl substitution (9) will be dis-
cussed elsewhere.
versus COX-1. In addition, none of the dihydropyrazole
precursors (5) showed inhibitory activity against COX-2.
Furthermore, we studied the SAR of the alkane ring
modi®cations. A series of 5-substituted cyclohexano-
pyrazoles were synthesized from the 5-keto precursor.
As shown in Table 2, substitution of the cyclohexane
ring with ¯uoro did not change the activity pro®le (1q).
Replacing the ¯uoro with OH increased the activity
against COX-2 and hence enhanced the selectivity (1r).
While substitution with N-acetylhydroxylamino did not
signi®cantly alter the activity, O-acetylhydroxylamino
abolished the activity against COX-2 (1s and 1t).
In general, the cycloalkanopyrazoles possess potent
inhibitory activity against COX-2 and are selective ver-
sus COX-1 except when both phenyl rings are unsub-
stituted (Table 1). Seven-membered cycloalkanes (n=3)
were most potent against COX-2, followed by the six-
membered ring compounds. Five-membered cyclo-
alkanes were the least active series (IC50: 1a>1d>1h,
1b>1e>1i). While substitution of the A-ring with chlo-
ro at the 4-position did not signi®cantly change the
activity against COX-2 (1b, 1e and 1i), an additional
substitution with chloro at 4-position of B-ring abol-
ished activity (1c and 1j). The most common combina-
tion of substituents of 1,2-diarylsubstituted selective
COX-2 inhibitors in the literature,14 Cl/MeSO2 or F/
MeSO2, did not show inhibition in the 1,3-diaryl com-
pounds synthesized in our study (1f, 1g and 1n). When
X=Cl, Y=Me or OMe, the compounds (1k and 1m)
showed potent COX-2 activity and moderate selectivity
Surprisingly, the diphenylhydrazides, intermediates for
the synthesis of the cycloalkanopyrazoles, showed
potent inhibition of COX-2 and are also selective versus
COX-1 (Table 3). The comparative SAR of the diphe-
nylhydrazides to that of the cycloalkanopyrazoles sug-
gests that the two series share similar binding mode.
Analogous to the cycloalkanopyrazole series, substitu-
tion on one or both phenyl rings with chloro, methyl or
methoxy generally provided potent and selective COX-2
inhibitors (except 2m). When methylsulfonyl is present on
B-ring, the activity was abolished. The best compound in
Scheme 2.

Z. Sui et al. / Bioorg. Med. Chem. Lett. 10 (2000) 601±604
603
Table 1. Inhibitory activities of representative compounds against
COX-1 and COX-2
this series (2h) has an IC50 of 10 nM against COX-2 and
greater than 1000 fold selectivity versus COX-1.
In summary, 1,3-diarylpyrazoles fused with a cyclo-
alkane were identi®ed as selective COX-2 inhibitors.
SAR revealed the importance of the size and substitu-
tion of the cycloalkane ring. N0-Phenylarylhydrazides
were also found to be potent and selective COX-2 inhi-
bitors. The best compound 2h has an IC50 of 10 nM
against COX-2 and >10,000 nM against COX-1. The
two phenyl rings displayed distinct SARs from those in
1,2-diphenyl substituted analogues found in most of the
selective COX-2 inhibitors reported in the literature.
The results indicate that the 1,3-diarylsubstitution pat-
tern is an alternative pharmacophore to the more com-
mon 1,2-diarylsubstitution pattern. The fact that none
of the dihydro precursors (5) demonstrates activity
indicates the importance of the planarity of the designed
compounds.
Cmpd
X
Y
n
COX-215
IC50 (mM)
COX-116
IC50 (mM)
1a
1b
1c
1d
1e
1f
1g
1h
1i
H
Cl
Cl
H
Cl
Cl
F
H
H
Cl
H
1
1
1
2
2
2
2
3
3
3
3
3
3
3
6.20
2.59
>10
0.57
0.62
>10
>10
0.17
0.14
10
>10
10
>10
0.49
10
>10
>10
0.12
1.0
>10
>10
>10
10
H
SO2Me
SO2Me
H
H
Cl
Me
OMe
SO2Me
H
H
Cl
Cl
Cl
Cl
Cl
OMe
1j
1k
1m
1n
1p
0.64
1.56
>10
1.24
Acknowledgement
10
The authors thank Dr. Mark Macielag for his support
and discussion.
Table 2. Examples of cycloalkane ring modi®cations
References and Notes
1. Carter, J. S. Exp. Opin. Ther. Patents 1997, 8, 21.
2. O'Neill, G. P.; Mancini, J. A.; Kargman, S.; Yergey, J.;
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1994, 46, 205.
4. Laneuville, O.; Breuer, D. K.; DeWitt, D. L.; Hla, T.; Funk,
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5. Meade, E. A.; Smith, W. L.; DeWitt, D. L. J. Lipid Media-
tors 1993, 6, 119.
Cmpda
X
Y
R
COX-2
IC50 (mM)
COX-1
IC50 (mM)
1m
1q
1r
1s
1t
Cl
Cl
Cl
Cl
Cl
OMe
OMe
OMe
OMe
OMe
H
F
1.56
2.10
0.46
2.40
>10
>10
>10
>10
>10
OH
-N(OH)Ac
-NHOAc
>10
6. Michell, J. A.; Akarasereenont, P.; Thiemermann, C.;
Flower, R. J.; Vane, J. R. Proc. Natl. Acad. Sci. USA 1993, 90,
11693.
aCompounds 1q±1t are racemic.
7. Rome, L. H.; Lands, W. E. M. Proc. Natl. Acad. Sci. USA
1975, 72, 4863.
8. Seibert, K.; Zhang, Y.; Leahy, K.; Hauser, S.; Masferrer, J.;
Perkins, W.; Lee, L.; Isakson, P. Proc. Natl. Acad. Sci. USA
1994, 91, 12013.
Table 3. Inhibitory activities of representative hydrazides against
COX-1 and COX-2
9. O'Neill, G. P.; Ford-Hutchinson, A. W. FEBS Lett. 1993,
330, 156.
10. Kargman, S.; Chan, S.; Evans, J.; Vickers, P.; O'Neill, G.
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RWJ
X
Y
COX-2
IC50 (mM)
COX-1
IC50 (mM)
2a
2b
2c
2d
2e
2f
2g
2h
2i
H
Cl
Cl
H
H
H
H
Cl
Cl
Cl
OMe
OMe
H
H
Cl
Me
10
0.33
0.34
0.33
0.53
>10
0.18
0.01
0.13
>10
0.47
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
Cl
SO2Me
OMe
Me
OMe
SO2Me
Cl
2j
2k
2m
H

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Z. Sui et al. / Bioorg. Med. Chem. Lett. 10 (2000) 601±604
15. Human cyclooxygenase type II whole cell assay: ECV-304
(human, endothelial, umbilical cord) cells are maintained in
culture in a suitable medium, and are trypsinized and plated at
a density of 9Â104 cells per well of a 96 well plate prior to
assay. Approximately 28 hours later, 50 mg/mL PMA and
1 mM ionomycin (both ®nal concentrations) are added to each
well. Approximately 24 hours later, cells are incubated in the
presence of vehicle or drug and the presence of PGE2 is
determined via RIA after the addition of 30 mM arachidonic
acid. The % inhibition of products as compared to vehicle is
calculated.
16. Human cyclooxygenase type I whole cell assay: Peripheral
blood is drawn in heparinized tubes and platelet-rich plasma
(PRP) collected by centrifugation (200Âg) for 20 min at room
temperature. The PRP is removed and diluted 1:20 in 0.9%
NaCl. Test compound or vehicle is added to a 180 mL aliquot
in a 96-well plate. After a 15 min incubation at 37 ꢀC, 27 mM
calcium ionophore A-23187 (free acid) is added and the sam-
ples are incubated at 37 ꢀC for another 15 min. Following the
incubation, the samples are placed on ice for 5 min. An aliquot
of the supernatant is assayed for the presence of thromboxane
B2 by standard radioimmunoassay techniques.