Synthesis of celecoxib analogues possessing a N-difluoromethyl-1,2- dihydropyrid-2-one 5-lipoxygenase pharmacophore: Biological evaluation as dual inhibitors of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity

Article abstract of DOI:10.1021/jm8015188

A novel class of 1-(4-methanesulfonylphenyl and 4-aminosulfonylphenyl)-5- [4-(1-difluoromethyl-1,2- dihydropyrid-2-one)]-3-trifluoromethyl-1 H-pyrazole hybrid cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-LOX) inhibitory anti-inflammatory agents was designed. Replacement of the tolyl ring present in celecoxib by the N-difluoromethyl-1,2-dihydropyrid-2-one moiety provided compounds showing dual selective COX-2/5-LOX inhibitory activities. 1-(4-Aminosulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-dihydropyrid-2-one)] -3-trifluoromethyl-1 H-pyrazole exhibited good anti-inflammatory (AI) activity (ED₅₀ = 27.7 mg/kg po) that compares favorably with the reference drugs celecoxib (ED₅₀ = 10.8 mg/kg po) and ibuprofen (ED₅₀ = 67.4 mg/kg po). The N-difluoromethyl-1,2-dihydropyridin-2-one moiety provides a novel 5-LOX pharma- cophore for the design of cyclic hydroxamic mimetics for exploitation in the development of COX-2/5-LOX inhibitory AI drugs.

Full text of DOI:10.1021/jm8015188

J. Med. Chem. 2009, 52, 1525–1529
1525
Articles
Synthesis of Celecoxib Analogues Possessing a N-Difluoromethyl-1,2-dihydropyrid-2-one
5-Lipoxygenase Pharmacophore: Biological Evaluation as Dual Inhibitors of Cyclooxygenases
and 5-Lipoxygenase with Anti-Inflammatory Activity
Morshed A. Chowdhury, Khaled R. A. Abdellatif, Ying Dong, Dipankar Das, Mavanur R. Suresh, and Edward E. Knaus*
Faculty of Pharmacy and Pharmaceutical Sciences, UniVersity of Alberta, Edmonton, Alberta, T6G 2N8, Canada
ReceiVed December 2, 2008
A novel class of 1-(4-methanesulfonylphenyl and 4-aminosulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-
dihydropyrid-2-one)]-3-trifluoromethyl-1H-pyrazole hybrid cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-
LOX) inhibitory anti-inflammatory agents was designed. Replacement of the tolyl ring present in celecoxib
by the N-difluoromethyl-1,2-dihydropyrid-2-one moiety provided compounds showing dual selective COX-
2/5-LOX inhibitory activities. 1-(4-Aminosulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-dihydropyrid-2-one)]-
3-trifluoromethyl-1H-pyrazole exhibited good anti-inflammatory (AI) activity (ED50 ) 27.7 mg/kg po) that
compares favorably with the reference drugs celecoxib (ED50 ) 10.8 mg/kg po) and ibuprofen (ED50
)
67.4 mg/kg po). The N-difluoromethyl-1,2-dihydropyridin-2-one moiety provides a novel 5-LOX pharma-
cophore for the design of cyclic hydroxamic mimetics for exploitation in the development of COX-2/5-
LOX inhibitory AI drugs.
Introduction
Arachidonic acid (AAa), the most abundant polyunsaturated
fatty acid present in cell membranes, is metabolized after its
release by the cyclooxygenase (COX-1, -2, -3) and lipoxygenase
(5-LOX, 8-, 12-, -15) enzyme families. Proinflammatory pros-
taglandins (PGs) produced via the COX pathway, and leukot-
rienes (LTs) produced via the LOX pathway, are implicated in
physiological processes such as inflammation, fever, arthritis,
and bronchospasm.1,2 PGs that cause contraindicated inflam-
mation, fever, and pain are formed via the inducible COX-2
isozyme, whereas PGs that regulate beneficial gastrointestinal
cytoprotection and renal effects are produced via the constitutive
COX-1 isozyme.1-3 Alternatively, 5-LOX is associated with
the production of LTs that cause inflammatory, bronchocon-
strictor, hypersensitivity, anaphylactic, and asthmatic actions.
On the other hand, 15-LOX is implicated in atherosclerosis
because it catalyzes the oxidation of lipoproteins (LDL, HDL)
to atherogenic forms.4,5
There is a general belief that a dual inhibitor of the LOX/
COX enzymatic pathways6 constitutes a rational approach for
the design of more effective anti-inflammatory agents with a
superior safety profile relative to ulcerogenic nonsteroidal anti-
inflammatory drugs (NSAIDs) and selective COX-2 inhibitors
that increase the incidence of adverse cardiovascular thrombotic
effects.7,8 It has been pointed out that inhibition of only one of
the COX/LOX pathways could shift the metabolism of AA
toward the other pathway, thereby inducing potential side
effects.9 One of the more successful strategies to develop 5-LOX
inhibitors utilized hydroxamic acids and related N-hydroxyureas
Figure 1. Chemical structures of some representative iron-chelating
5-LOX inhibitors (1, 2), a COX-2/5-LOX inhibitor (3), the selective
COX-2 inhibitor celecoxib (4), and the COX/5-LOX inhibitors (5).
that act by chelation of iron present in the 5-LOX enzyme.10
Two representative examples of iron chelating 5-LOX inhibitors
include zileuton (1)11 and tepoxalin (2)10 (see structures in
Figure 1). A potent hybrid COX-2/5-LOX inhibitor (3) in which
the C-3 trifluoromethyl substituent present in the COX-2
inhibitor celecoxib (4) was replaced by a nonredox competitive
4-(3-fluoro-5-oxymethyl)phenyl-4-methoxytetrahydropyran 5-LOX
pharmacophore was reported by Henichart et al.2 In a recent
study we described a novel class of dual COX/5-LOX inhibitor
* To whom correspondence should be addressed. Phone: (780) 492-5993.
Fax: (780) 492-1217. E-mail: eknaus@pharmacy.ualberta.ca.
a Abbreviations: AA, arachidonic acid; AI, anti-inflammatory; COX-1,
cyclooxygenase-1; COX-2, cyclooxygenase-2; HDL, high density lipopro-
tein; LTs, leukotrienes; LDL, low density lipoprotein; 5-LOX, 5-lipoxy-
genase; PGs, prostaglandins; NSAIDs, nonsteroidal anti-inflammatory drugs.
10.1021/jm8015188 CCC: $40.75
2009 American Chemical Society
Published on Web 02/18/2009

1526 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6
Chowdhury et al.
Scheme 1a
pyridin-4-yl)but-2-en-1-one (8, 91%).15 The subsequent con-
densation of 8 with either 4-(methylsulfonylphenyl)hydrazine-
HCl (9a) or 4-(aminosulfonylphenyl)hydrazine-HCl (9b) afforded
the respective 1,5-diarylpyrazole 10a (40%) or 10b (28%).
Reaction of 10a or 10b with 2,2-difluoro-2-(fluorosulfonyl)acetic
acid (FSO2CF2COOH)16 afforded the target 1-difluoromethyl-
1,2-dihydropyrid-2-one products (11a,b) in 46-52% yields
(Scheme 1).
Results and Discussion
The rational for the design of the 1-(4-methanesulfonylphenyl
and 4-aminosulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-dihy-
dropyrid-2-one)]-3-trifluoromethyl-1H-pyrazoles (11a,b) was
based on the expectation that replacement of a tolyl moiety in
celecoxib (4) or replacement of the N-hydroxy-1,2-dihydropy-
ridin-2-one moiety present in the hybrid compounds 5 would
furnish a novel class of compounds with dual COX-2/5-LOX
inhibitory activities. The CONCHF2 fragment of the N-difluo-
romethyl-1,2-dihydropyrid-2-one ring present in 11a,b can be
viewed as a cyclic hydroxamic acid mimetic. These N-difluo-
romethyl-1,2-dihydropyrid-2-ones 11a,b could inhibit the 5-LOX
enzyme by two possible mechanisms. In this regard 11a,b, like
acyclic hydroxamic acids, may act as effective iron chelators
to exhibit 5-LOX inhibitory activity. It has been reported that
there is a substantial buildup of negative potential around the
two fluorine atoms of a CHF2 group.17 Despite this high electron
density, an aliphatic fluorine seldom acts as a hydrogen-bond
acceptor, presumably because of its high electronegativity and
low polarizability.18,19 Therefore, it is also plausible that the
CHF2 group may interact with a positively charged region on
the enzyme that may contribute to enhanced affinity and
competitive reversible inhibition of the COX and/or 5-LOX
enzymes.20 In addition, these cyclic N-difluoromethyl-1,2-
dihydropyrid-2-ones, unlike acyclic hydroxamic acids that
undergo facile biotransformation to the acids, are expected to
have a greater metabolic stability with increased oral efficacy.
Although there is some distortion from planarity at the N1-
nitrogen atom of the N-difluoromethyl-1,2-dihydropyrid-2-one
ring system, the relatively flat diene portion of this quasi-planar
ring system has the potential to serve as a suitable replacement
for the tolyl group present in celecoxib (4), resulting in retention
of selective COX-2 inhibitory activity.
In vitro COX-1 and COX-2 enzyme inhibition studies showed
that the celecoxib analogues (10a,b) having a respective SO2Me
and SO2NH2 COX-2 pharmacophore in conjunction with a
2-chloropyridyl ring substituent exhibited potent and selective
COX-2 inhibitory activity (COX-1 IC50 ) 8.3-258 µM; COX-2
IC50 ) 0.19-0.73 µM) that compared favorably to the reference
drug celecoxib (COX-1 IC50 ) 7.7 µM; COX-2 IC50 ) 0.07
µM). In addition, the 2-chloropyridyl compounds 10a,b also
exhibited unexpected potent 5-LOX inhibition (IC50 ) 0.39-0.47
µM) that was 9- to 10-fold more potent than that of the reference
drug caffeic acid (IC50 ) 4.0 µM) (see data in Table 1).
Elaboration of the 2-chloropyridyl ring in 10a,b to a 1-difluo-
romethyl-1,2-dihydropyrid-2-one moiety (11a,b) resulted in a
9-fold reduction in COX-2 inhibition for the SO2Me compound
11a (IC50 ) 1.82 µM). In contrast, the SO2NH2 compound 11b
(IC50 ) 0.69 µM) was equipotent with the 2-chloropyridyl
compound 10b (IC50 ) 0.73 µM). The equipotent 1-difluorom-
ethyl-1,2-dihydropyrid-2-ones 11a,b exhibited comparable 5-LOX
inhibitory activity (IC50 ) 4.4-5.0 µM) to the reference drug
caffeic acid.
a Reagents and conditions: (a) MeMgI, Et2O, 25 °C, 20 h; (b) NaOMe,
CF3CO2Et, Et2O, -5 to 0 °C, 2 h; (c) ethanol (95%), reflux, 20 h; (d)
FSO2CF2COOH, NaHCO3, reflux, overnight.
celecoxib analogues (5) that possess a N-hydroxy-1,2-dihydro-
pyrid-2-one 5-LOX pharmacophore.12 Accordingly, it was
anticipated that replacement of the tolyl ring present in the
selective COX-2 inhibitor celecoxib (4)13 by a N-difluoromethyl-
1,2-dihydropyrid-2-one moiety may provide a hitherto unknown
class of dual 5-LOX/COX-2 inhibitory anti-inflammatory agents.
Accordingly, we now describe the synthesis of a novel class of
celecoxib analogues that possess a potentially novel N-difluoro-
methyl-1,2-dihydropyrid-2-one moiety that may represent a new
5-LOX pharmacophore (11a,b), their in vitro evaluation as
COX-1/COX-2, 5-LOX inhibitors, and in vivo assessment as
AI agents.
Chemistry
The target 1-(4-methanesulfonylphenyl and 4-aminosulfo-
nylphenyl)-5-[4-(1-difluoromethyl-1,2-dihydropyrid-2-one)]-3-
trifluoromethyl-1H-pyrazoles (11a,b) were prepared using the
reaction sequence illustrated in Scheme 1. Accordingly, reaction
of 2-chloroisonicotinonitrile (6) with methylmagnesium iodide,
using a literature method for elaboration of cyano to acetyl,
furnished 1-(2-chloropyridin-4-yl)ethanone (7, 81%).14 The base
catalyzed condensation of the acetyl compound 7 with ethyl
trifluoroacetate afforded 4,4,4-trifluoro-3-hydroxy-1-(2-chloro-
The oral AI activities (ED50 values) exhibited by the 2-chlo-
ropyridyl compounds 10a,b and the 1-difluoromethyl-1,2-

Celecoxib Analogues
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6 1527
Table 1. In Vitro COX-1, COX-2, 5-LOX Enzyme Inhibition and in
Vivo Anti-Inflammatory Activity Data for Celecoxib Analogues Having
a 2-Chloropyridyl (10a,b), 1-Difluoromethyl-1,2-dihydropyrid-2-one
(11a,b), or N-Hydroxy-1,2-dihydropyrid-2-one (5a-b) Moiety
drugs celecoxib (ED50 ) 10.8 mg/kg po) and ibuprofen (ED50
) 67.4 mg/kg po).
Conclusions
A hitherto unknown class of 1-(4-methanesulfonylphenyl and
4-aminosulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-dihydropy-
rid-2-one)]-3-trifluoromethyl-1H-pyrazoles (11a,b) was designed
for evaluation as dual 5-LOX and COX-1/COX-2 isozyme
inhibitors of inflammation. The structure-activity data acquired
indicate that (i) compounds 11a,b exhibit acceptable in vitro
COX-2 isozyme inhibitory potency and selectivity in conjunc-
tion with potent inhibition of the 5-LOX enzyme, (ii) the relative
AI potency order with respect to the COX-2 pharmacophore is
SO2NH2 > SO2Me, (iii) the 1-difluoromethyl-1,2-dihydropyrid-
2-one moiety provides a novel 5-LOX pharmacophore for the
design of cyclic hydroxamic mimetics, and (iv) the dual acting
compounds 11a,b exhibit AI activity that is dependent upon
inhibition of proinflammatory prostaglandin and leukotriene
biosyntheses in the respective cyclooxygenase and lipoxygenase
pathways.
COX-1 IC50 COX-2 IC50 5-LOX IC50 AI activityc
compd
10a
10b
R1
(µM)a
(µM)a
(µM)b
ED50 (mg/kg)
SO2Me
SO2NH2
SO2Me
SO2NH2
SO2Me
SO2NH2
258
8.3
7.8
13.1
13.2
10.2
7.7
0.19
0.73
1.82
0.69
7.5g
7.5g
0.12
1.1g
0.47
0.39
4.4
5.0
0.35
4.90
<150d
<150e
42.9
27.7
66.9
99.8
10.8
67.4
11a
11b
5af
5bf
celecoxib
ibuprofen
caffeic acid
2.9
4.0
a The in vitro test compound concentration required to produce 50%
inhibition of ovine COX-1 or human recombinant COX-2. The result (IC50,
µM) is the mean of two determinations acquired using the enzyme
immunoassay kit (catalog no. 560131, Cayman Chemicals Inc., Ann Arbor,
MI), and the deviation from the mean is <10% of the mean value. b The in
vitro test compound concentration required to produce 50% inhibition of
potato 5-LOX (Cayman Chemicals Inc. catalog no. 60401). The result (IC50,
µM) is the mean of two determinations acquired using a LOX assay kit
(catalog no. 760700, Cayman Chemicals Inc., Ann Arbor, MI), and the
deviation from the mean is <10% of the mean value. c Inhibitory activity
in a carrageenan-induced rat paw edema assay. The results are expressed
as the ED50 value (mg/kg) at 3 h after oral administration of the test
compound. d 43.1% reduction in inflammation at a 150 mg/kg po dose.
e 33.3% reduction in inflammation at a 150 mg/kg po dose. f Data taken
from the literature.12 g Data acquired using ovine COX-2 (catalog no.
560101, Cayman Chemicals Inc.).
Experimental Section
General. Melting points were determined on a Thomas-Hoover
capillary apparatus and are uncorrected. Unless otherwise noted,
infrared (IR) spectra were recorded as films on NaCl plates using
1
a Nicolet 550 series II Magna FT-IR spectrometer. H NMR and
13C NMR spectra were measured on a Bruker AM-300 spectrometer.
Microanalyses (MicroAnalytical Service Laboratory, Department
of Chemistry, University of Alberta) of compounds 11a,b were
performed for C, H, and N and were within (0.4% of theoretical
values for all elements listed. Compounds 10a,b showed a single
spot on Macherey-Nagel Polygram Sil G/UV254 silica gel plates
(0.2 mm) using a low, medium, and highly polar solvent system,
and no residue remained after combustion, indicating a purity of
>95%. Silica gel column chromatography was performed using
Merck silica gel 60 ASTM (70-230 mesh). 4-(Methylsulfonylphe-
nyl)hydrazine-HCl (9a) was synthesized in 53% yield starting from
1-chloro-4-methanesulfonylbenzene,21 which was prepared by the
Fridel-Crafts reaction of methanesulfonyl chloride with chloroben-
zene.22 4-(Aminosulfonylphenyl)hydrazine-HCl (9b) was synthe-
sized in 84% yield starting from sulfanilamide.23 All other reagents,
purchased from the Aldrich Chemical Co. (Milwaukee, WI), were
used without further purification. The in vivo anti-inflammatory
assay was carried out using a protocol approved by the Health
Sciences Animal Welfare Committee at the University of Alberta.
dihydropyrid-2-ones 11a,b were determined using a carrageenan-
induced rat foot paw edema model (see data in Table 1). In
spite of the fact that the 2-chloropyridyl compounds 10a,b are
more potent in vitro inhibitors of the 5-LOX enzyme than the
1-difluoromethyl-1,2-dihydropyrid-2-ones 11a,b, the in vivo AI
structure-activity data acquired showed that 11a (SO2Me, AI
ED50 ) 42.9 mg/kg po) and 11b (SO2NH2, AI ED50 ) 27.7
mg/kg po) are more potent AI agents than the 2-chloropyridyl
compounds 10a and 10b which showed a respective 43.1% and
33.3% reduction in inflammation for a 150 mg/kg po dose. This
superior AI activity exhibited by the 1-difluoromethyl-1,2-
dihydropyrid-2-ones 11a,b could be due to a number of factors
that include oral bioavailability, biodistribution, and/or metabolic
stability. A comparison of the AI activities for the 1-difluo-
romethyl-1,2-dihydropyrid-2-ones 11a,b to the previously re-
ported N-hydroxy-1,2-dihydropyrid-2-one compounds 5a,b12
shows that compounds 11a,b exhibit greater oral AI activity
than compounds 5a,b. The more potent AI activity exhibited
by 11a,b, relative to 5a,b, could be due to their superior
adsorption, distribution, metabolism, and/or excretion (ADME)
properties. These AI data suggest that the 1-difluoromethyl-
1,2-dihydropyrid-2-one moiety may be a superior 5-LOX
pharmacophore relative to the N-hydroxy-1,2-dihydropyrid-2-
one group for the design of hybrid COX-2/5-LOX inhibitory
AI drugs. The most potent compound 1-(4-aminosulfonylphe-
nyl)-5-[4-(1-difluoromethyl-1,2-dihydropyrid-2-one)]-3-triflu-
oromethyl-1H-pyrazole (11b) exhibited good AI activity (ED50
) 27.7 mg/kg po) that compares favorably with the reference
General Procedure for the Synthesis of 1-(4-Methanesulfo-
nylphenyl or 4-aminosulfonylphenyl)-5-(2-chloropyridin-4-yl)-3-
trifluoromethyl-1H-pyrazoles (10a,b). A solution of 4-(methylsul-
fonylphenyl)hydrazine-HCl (9a) or 4-(aminosulfonylphenyl)hydrazine-
HCl (9b) (20 mmol) and 4,4,4-trifluoro-3-hydroxy-1-(2-chloropyridin-
4-yl)but-2-en-1-one (8, 4.58 g, 18.20 mmol) in 95% ethanol (225
mL) was heated at reflux with stirring for 20 h. After cooling to 25
°C, the reaction mixture was concentrated in vacuo to give a crude
solid which was purified by silica gel column chromatography using
hexanes-acetone (2:1, v/v) as eluent to furnish the respective title
compound 10a or 10b. Some physical and spectroscopic data for
10a and 10b are listed below.
1-(4-Methanesulfonylphenyl)-5-(2-chloropyridin-4-yl)-3-trifluoro-
methyl-1H-pyrazole (10a). This compound was obtained as a pale-
yellow solid in 40% yield, mp 220-222 °C; IR 1299, 1155 (SO2)
cm-1 1H NMR (CDCl3) δ 3.15 (s, 3H, SO2Me), 7.28 (s, 1H,
;
pyrazole H-4), 7.66 (dd, J ) 5.5, 1.2 Hz, 1H, pyridyl H-5), 7.80
(d, J ) 1.2 Hz, 1H, pyridyl H-3), 7.82 (dd, J ) 6.7, 1.8 Hz, 2H,
phenyl H-2, H-6), 8.15 (dd, J ) 6.7, 1.8 Hz, 2H, phenyl H-3, H-5),
8.49 (d, J ) 5.5 Hz, 1H, pyridyl H-6); 13C NMR (CDCl3) δ 44.5,
108.1, 118.8, 119.2, 120.6, 126.0, 128.8, 134.8, 141.4, 141.5, 142.8,
148.9, 150.4, 152.5.

1528 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6
Chowdhury et al.
1-(4-Aminosulfonylphenyl)-5-(2-chloropyridin-4-yl)-3-trifluoro-
methyl-1H-pyrazole (10b). This compound was obtained as a white
solid in 28% yield, mp 235-237 °C; IR 3365, 3272 (NH2), 1330,
evaluated using the in vivo carrageenan-induced rat foot paw edema
model reported previously.25
1
1162 (SO2) cm-1; H NMR (CDCl3 + DMSO-d6) δ 6.89 (s, 2H,
Acknowledgment. We are grateful to the Canadian Institutes
of Health Research (Grant No. MOP-14712) for financial
support of this research. We also thank Dr. M. Rahman for
recording rat paw volumes acquired in the anti-inflammatory
assays.
SO2NH2 that exchanges with D2O), 6.91 (s, 1H, pyrazole H-4),
6.94 (dd, J ) 5.5, 1.2 Hz, 1H, pyridyl H-5), 7.25 (d, J ) 1.2 Hz,
1H, pyridyl H-3), 7.38 (dd, J ) 8.5, 1.8 Hz, 2H, phenyl H-2, H-6),
7.94 (dd, J ) 8.5, 1.8 Hz, 2H, phenyl H-3, H-5), 8.31 (d, 1H, J )
5.5 Hz, pyridyl H-6); 13C NMR (CDCl3 + DMSO-d6): δ 107.4,
120.3, 121.2, 122.8, 125.0, 126.9, 138.5, 140.0, 140.3, 143.2, 144.2,
149.7, 151.4.
Supporting Information Available: Table of combustion data
for compounds 11a and 11b. This material is available free of
charge via the Internet at http://pubs.acs.org.
General Procedure for the Synthesis of 1-(4-Methanesulfo-
nylphenyl or 4-aminosulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-
dihydropyrid-2-one)]-3-trifluoromethyl-1H-pyrazole (11a,b). To a
stirred solution of 1-(4-methanesulfonylphenyl or 4-aminosulfo-
nylphenyl)-5-(2-chloropyridin-4-yl)-3-trifluoromethyl-1H-pyra-
zole (10a or 10b) (6 mmol) in dry acetonitrile (45 mL) was added
FSO2CF2COOH (3.28 g, 18 mmol) and NaHCO3 (0.51 g, 6 mmol),
and the mixture was heated at reflux overnight under argon. After
cooling to 25 °C, the reaction mixture was concentrated in vacuo
and a solution of saturated NaHCO3 (50 mL) was added. This
mixture was extracted with EtOAc (3 × 50 mL). The combined
organic phases were concentrated to about 25 mL and washed with
10 N hydrochloric acid (1 × 25 mL) to remove unreacted starting
material 10a or 10b. The organic phase was washed successively
with water and brine and dried (MgSO4). Filtration and then removal
of the solvent in vacuo from the organic fraction afforded the impure
product which was purified by silica gel column chromatography.
Elution with hexanes-acetone (2:1, v/v) furnished the respective
1-(4-methanesulfonylphenyl or 4-aminosulfonylphenyl)-5-[4-(1-
difluoromethyl-1,2-dihydropyrid-2-one)]-3-trifluoromethyl-1H-pyra-
zole (11a or 11b). The spectral and microanalytical data for
compounds 11a and 11b are listed below.
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1-(4-Methanesulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-dihy-
dropyrid-2-one)]-3-trifluoromethyl-1H-pyrazole (11a). This com-
pound was obtained as a pale-yellow solid in 46% yield, mp
1
200-202 °C; IR 1678 (CO), 1327, 1152 (SO2) cm-1; H NMR
(CDCl3) δ 3.12 (s, 3H, SO2Me), 6.02 (dd, J ) 7.5, 1.8 Hz, 1H,
pyridone H-5), 6.56 (d, J ) 1.8 Hz, 1H, pyridone H-3), 6.93 (s,
1H, pyrazole H-4), 7.46 (d, J ) 7.5 Hz, 1H, pyridone H-6), 7.64
2
(dd, J ) 6.7, 1.8 Hz, 2H, phenyl H-2, H-6), 7.65 (t, JHCF ) 60
Hz, 1H, CHF2), 8.07 (dd, J ) 6.7, 1.8 Hz, 2H, phenyl H-3, H-5);
13C NMR (CDCl3): δ 44.4, 106.5, 107.2, 108.2, 120.4, 120.9, 125.6,
129.1, 130.5, 140.7, 141.0, 141.1, 142.5, 144.8, 159.9. Anal.
(C17H12F5N3O3S) C, H, N.
1-(4-Aminosulfonylphenyl)-5-[4-(1-difluoromethyl-1,2-dihydro-
pyrid-2-one)]-3-trifluoromethyl-1H-pyrazole (11b). This compound
was obtained as a white solid in 52% yield, mp 190-192 °C; IR
1
3260 (broad NH2), 1680 (CO), 1347, 1169 (SO2) cm-1; H NMR
(CDCl3 + DMSO-d6) δ 6.03 (dd, J ) 7.5, 1.8 Hz, 1H, pyridone
H-5), 6.42 (s, 1H, pyridone H-3), 6.92 (s, 1H, pyrazole H-4), 7.08
(s, 2H, SO2NH2 that exchanges with D2O), 7.45 (d, J ) 7.5 Hz,
1H, pyridone H-6), 7.47 (d, J ) 8.5 Hz, 2H, phenyl H-2, H-6),
7.57 (t, 2JHCF ) 60 Hz, 1H, CHF2), 7.97 (d, J ) 8.5 Hz, 2H, phenyl
H-3, H-5); 13C NMR (CDCl3 + DMSO-d6): δ 106.0, 106.6, 107.1,
119.7, 119.9, 124.5, 126.8, 129.7, 139.9, 140.3, 143.1, 143.9, 159.1.
Anal. (C16H11F5N4O3S) C, H, N.
Cyclooxygenase Inhibition Assays. The ability of the test
compounds listed in Table 1 to inhibit ovine COX-1 and human
recombinant COX-2 (IC50 value, µM) was determined using an
enzyme immunoassay (EIA) kit (catalog no. 560131, Cayman
Chemical, Ann Arbor, MI) according to our previously reported
method.24
5-Lipoxygenase Inhibition Assay. The ability of the test com-
pounds listed in Table 1 to inhibit potato 5-LOX (catalog no. 60401,
Cayman Chemical, Ann Arbor, MI) (IC50 values, µM) were
determined using an enzyme immunoassay (EIA) kit (catalog no.
760700, Cayman Chemical, Ann Arbor, MI) according to our
previously reported method.12
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and the reference drugs celecoxib, ibuprofen, and aspirin were

Celecoxib Analogues
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6 1529
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