Synthesis of celecoxib analogs that possess a N-hydroxypyrid-2(1H)one 5-lipoxygenase pharmacophore: Biological evaluation as dual inhibitors of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity

Article abstract of DOI:10.1016/j.bmcl.2008.10.009

A hitherto unknown class of celecoxib analogs was designed for evaluation as dual inhibitors of the 5-lipoxygenase/cyclooxygenase-2 (5-LOX/COX-2) enzymes. These compounds possess a SO₂Me (11a), or SO₂NH₂ (11b) COX-2 pharmacophore at the para-position of the N¹-phenyl ring in conjunction with a 5-LOX N-hydroxypyrid-2(1H)one iron-chelating moiety in place of the celecoxib C-5 tolyl group. The title compounds 11a-b are weak inhibitors of the COX-1 and COX-2 isozymes (IC₅₀ = 7.5-13.2 μM range). In contrast, the SO₂Me (11a, IC₅₀ = 0.35 μM), and SO₂NH₂ (11b, IC₅₀ = 4.9 μM), compounds are potent inhibitors of the 5-LOX enzyme comparing favorably with the reference drug caffeic acid (5-LOX IC₅₀ = 3.47 μM). The SO₂Me (11a, ED₅₀ = 66.9 mg/kg po), and SO₂NH₂ (11b, ED₅₀ = 99.8 mg/kg po) compounds exhibited excellent oral anti-inflammatory (AI) activities being more potent than the non-selective COX-1/COX-2 inhibitor drug aspirin (ED₅₀ = 128.9 mg/kg po) and less potent than the selective COX-2 inhibitor celecoxib (ED₅₀ = 10.8 mg/kg po). The N-hydroxypyridin-2(1H)one moiety constitutes a novel pharmacophore for the design of cyclic hydroxamic mimetics capable of chelating 5-LOX iron for exploitation in the design of 5-LOX inhibitory AI drugs.

Full text of DOI:10.1016/j.bmcl.2008.10.009

Bioorganic & Medicinal Chemistry Letters 18 (2008) 6138–6141
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of celecoxib analogs that possess a N-hydroxypyrid-2(1H)one
5-lipoxygenase pharmacophore: Biological evaluation as dual inhibitors
of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity
Morshed Alam Chowdhury, Khaled R. A. Abdellatif, Ying Dong, Dipankar Das,
*
Mavanur R. Suresh, Edward E. Knaus
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alta., Canada T6G 2N8
a r t i c l e i n f o
a b s t r a c t
Article history:
A hitherto unknown class of celecoxib analogs was designed for evaluation as dual inhibitors of the 5-
lipoxygenase/cyclooxygenase-2 (5-LOX/COX-2) enzymes. These compounds possess a SO2Me (11a), or
SO2NH2 (11b) COX-2 pharmacophore at the para-position of the N1-phenyl ring in conjunction with a
5-LOX N-hydroxypyrid-2(1H)one iron-chelating moiety in place of the celecoxib C-5 tolyl group. The title
Received 18 September 2008
Revised 1 October 2008
Accepted 2 October 2008
Available online 7 October 2008
compounds 11a–b are weak inhibitors of the COX-1 and COX-2 isozymes (IC50 = 7.5–13.2
contrast, the SO2Me (11a, IC50 = 0.35 M), and SO2NH2 (11b, IC50 = 4.9 M), compounds are potent inhib-
itors of the 5-LOX enzyme comparing favorably with the reference drug caffeic acid (5-LOX
IC50 = 3.47 M). The SO2Me (11a, ED50 = 66.9 mg/kg po), and SO2NH2 (11b, ED50 = 99.8 mg/kg po) com-
lM range). In
l
l
Keywords:
Celecoxib analogs
N-Hydroxypyridin-2(1H)ones
Cyclooxygenase-1, cyclooxygenase-2 and 5-
lipoxygenase inhibition
Anti-inflammatory activity
l
pounds exhibited excellent oral anti-inflammatory (AI) activities being more potent than the non-selec-
tive COX-1/COX-2 inhibitor drug aspirin (ED50 = 128.9 mg/kg po) and less potent than the selective COX-2
inhibitor celecoxib (ED50 = 10.8 mg/kg po). The N-hydroxypyridin-2(1H)one moiety constitutes a novel
pharmacophore for the design of cyclic hydroxamic mimetics capable of chelating 5-LOX iron for exploi-
tation in the design of 5-LOX inhibitory AI drugs.
Ó 2008 Elsevier Ltd. All rights reserved.
Arachidonic acid (AA) is metabolized by two major enzyme
families that include the lipoxygenases (5-, 8-, 12- and 15-LOX)
and the cyclooxygenases (COX-1, -2 and -3). Proinflammatory leu-
kotrienes (LTs) produced via the LOX pathway, and prostaglandins
(PGs) produced via the COX pathway, are associated with adverse
physiologic processes such as inflammation, fever, arthritis, bron-
chospasm1 and the etiology of cancer.2 Two of the three major iso-
forms (5-, 12- and 15-LOX) observed in humans cause undesirable
physiological effects. In this regard, 5-LOX is implicated in the pro-
duction of LTs that are associated with inflammatory, bronchocon-
strictor, hypersensitivity, anaphylactic and asthmatic actions.1,3 In
contrast, 15-LOX is implicated in atherosclerosis since it catalyzes
the oxidation of lipoproteins (LDL, HDL) to atherogenic forms.4
Alternatively, PGs that induce undesirable inflammation,
fever and pain are produced via the inducible COX-2 isozyme
whereas PGs that regulate desirable gastrointestinal cytoprotective
and renal functions are produced via the constitutive COX-1
isozyme.1,5
safety profile relative to ulcerogenic non-steroidal anti-inflamma-
tory drugs (NSAIDs), and selective COX-2 inhibitors that increase
the incidence of adverse cardiovascular thrombotic effects.7,8 Heni-
chart et al.1 described a potent hybrid COX-2/5-LOX inhibitor in
which the C-3 trifluoromethyl substituent present in COX-2 inhib-
itor celecoxib was replaced by a non-redox competitive 4-(3-
fluoro-5-oxymethyl)phenyl-4-methoxytetrahydropyran 5-LOX
pharmacophore.1 Hydroxamic acids and related N-hydroxyureas
that act by chelation of iron present in the 5-LOX enzyme have pro-
vided one of the most successful strategies to develop 5-LOX inhib-
itors.9 Some representative examples of iron-chelating 5-LOX
inhibitors such as zileuton (1)10 and tepoxalin (2)9 are shown in
Figure 1. In a recent study, we described a novel class of acyclic
1-(benzenesulfonamido)-2-[5-(N-hydroxypyridin-2(1H)-one)]-
acetylene regioisomeric 5-LOX inhibitors (3).11 Accordingly, it was
anticipated that replacement of the tolyl ring present in the selec-
tive COX-2 inhibitor celecoxib (4)12 by
a N-hydroxypyridin-
2(1H)one moiety, that has the potential to chelate iron, may pro-
vide a hitherto unknown class of dual 5-LOX/COX-2 inhibitory
anti-inflammatory agents. Accordingly, we now describe the syn-
thesis of a novel class of celecoxib analogs that possess a N-hydrox-
ypyrid-2(1H)one 5-lipoxygenase pharmacophore (11a–b), their
in vitro evaluation as 5-LOX, COX-1/COX-2 inhibitors, and in vivo
assessment as anti-inflammatory (AI) agents.
It is generally agreed that a dual inhibitor of the LOX/COX enzy-
matic pathways6 constitutes a rational concept for the design of
more efficacious anti-inflammatory agents with an improved
* Corresponding author. Tel.: +1 780 492 5993; fax: +1 780 492 1217.
E-mail address: eknaus@pharmacy.ualberta.ca (E.E. Knaus).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.10.009

M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6138–6141
6139
methyl-5-[4-(1-hydroxy-1,2-dihydropyrid-2-one]-1H-pyrazole
11a (94%), or 11b (71%).
HO
NH2
O
Me
N
MeO
Cl
N
N
N
OH
The rational for the design of the 1-[4-methyl(or amino)sulfo-
nylphenyl]-3-trifluoromethyl-5-[4-(1-hydroxy-1,2-dihydropyrid-
2-one]-1H-pyrazoles (11a–b) was based on the expectation that
replacement of the tolyl substituent in celecoxib (4) by a N-
hydroxypyridin-2(1H)one moiety would furnish a novel class of
compounds with dual 5-LOX/COX-2 inhibitory activities. The CON-
OH part of the N-hydroxypyrid-2(1H)-one ring present in 11a–b
can be viewed as a cyclic hydroxamic acid mimetic. These N-
hydroxypyridin-2(1H)-ones, like acyclic hydroxamic acids, are ex-
pected to serve as effective iron chelators to exhibit 5-LOX inhibi-
tory activity. However, these cyclic N-hydroxypyridin-2(1H)-ones,
unlike acyclic hydroxamic acids which undergo facile biotransfor-
mation to the acids, are expected to have a greater metabolic sta-
bility with improved oral efficacy. Although, there is some
distortion from planarity at the N1-nitrogen atom of the N-
hydroxypyridin-2(1H)-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 in celecoxib resulting
in retention of selective COX-2 inhibitory activity.
S
O
Tepoxalin (2)
Zileuton (1)
CF3
N
N
3
2
R1
4
Me
O
C
C
N
HO
SO2NH2
(3), R1 = 2-, 3-, 4-SO2NH2
Celecoxib (4)
Figure 1. Some representative iron-chelating 5-LOX inhibitors (1–3) and the
selective COX-2 inhibitor celecoxib (4).
The target 1-[4-methyl(or amino)sulfonylphenyl]-3-trifluoro-
methyl-5-[4-(1-hydroxy-1,2-dihydropyrid-2-one]-1H-pyrazoles
(11a–b) were prepared using the reaction sequence illustrated in
Scheme 1. Accordingly, reaction of 2-methoxyisonicotinonitrile
(5) with methyllithium, using a literature method for elaboration
of cyano to acetyl,13 furnished 1-(2-methoxypyridin-4-yl)ethanone
(6, 72%). The base catalyzed condensation14 of the acetyl com-
pound 6 with ethyl trifluoroacetate afforded 4,4,4-trifluoro-3-hy-
droxy-1-(2-methoxypyridin-4-yl)-but-2-en-1-one (7, 74%). The
subsequent condensation of 7 with either 4-(methylsulfonylphe-
nyl)hydrazine-HCl (8a), or 4-(aminosulfonylphenyl)hydrazine-HCl
(8b), afforded the respective 1,5-diarylpyrazole 9a (37%), or 9b
(38%). Oxidation of the 2-methoxypyridine moiety present in com-
pounds 9a–b using meta-chloroperbenzoic acid in dichlorometh-
ane15 afforded the respective 1-oxido-2-methoxypyridine
derivative 10a (51%) or 10b (59%). Finally, reaction of the 1-oxi-
do-2-methoxypyridyl compounds 10a–b with acetyl chloride at re-
flux, followed by methanolysis in place of hydrolysis,15 furnished
the target 1-[4-methyl(or amino)sulfonylphenyl]-3-trifluoro-
In vitro COX-1 and COX-2 enzyme inhibition studies showed
that the N-hydroxypyridin-2(1H)-ones (11a–b) were much weaker
inhibitors (COX-1 IC50 = 10.2–3.2
than the selective COX-2 inhibitor celecoxib (COX-1 IC50 = 7.7
COX-2 IC50 = 0.07
l
M range; COX-2 IC50 = 7.5
l
l
M)
M;
l
M). The SO2Me (11a) and SO2NH2 (11b) com-
pounds exhibited similar COX-1/COX-2 inhibitory activity (see
data in Table 1). In contrast, the SO2Me compound (11a) was a
much more potent in vitro inhibitor of the potato 5-LOX enzyme
(5-LOX IC50 = 0.35
lM) than the SO2NH2 compound (11b, 5-LOX
IC50 = 4.9 M). In comparison, the SO2Me compound (11a) was
l
about 10-fold more potent, and the SO2NH2 compound (11b) was
a slightly less potent, 5-LOX inhibitor than the reference drug caf-
feic acid (5-LOX IC50 = 3.47 lM).
The oral AI activities (ED50 values) exhibited by the cyclic N-
hydroxypyridin-2(1H)-ones 11a–b were determined using a carra-
geenan-induced rat foot paw edema model (see data in Table 1).
The AI structure–activity data acquired showed that the SO2Me
NHNH2.HCl
O
Me
O
OH
CF3
CN
a
b
+
N
OMe
N
OMe
N
OMe
SO2R1
8a, R1 = Me
5
6(72%)
7 (74%)
8b, R1 = NH2
c
CF3
CF3
CF3
d
e
N
N
N
N
N
N
N
N+
MeO
N
HO
O
O
MeO
SO2R1
SO2R1
SO2R1
11a, R1 = Me (94%)
9a, R1 = Me (37%)
10a, R1 = Me (51%)
11b, R1 = NH2 (71%)
9b, R1 = NH2 (38%)
10b, R1 = NH2 (59%)
Scheme 1. Reagents and conditions: (a) i—MeLi, THF, À78 °C ? 25 °C, 2.5 h; ii—3 N HCl; iii—Na2CO3; (b) i—NaOMe, CF3CO2Et, reflux, 6 h; ii—CH3CO2H; (c) ethanol (95%),
reflux, 20 h; (d) meta-chloroperbenzoic acid, CH2Cl2, 25 °C, 12 h; (e) i—acetyl chloride, reflux, 1 h, ii—MeOH, 25 °C, 12 h.

6140
M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6138–6141
8. Dogné, J.-M.; Supuran, C. T.; Pratico, D. J. Med. Chem. 2005, 48, 2251.
Table 1
9. Muri, E. M. F.; Nieto, M. J.; Sindelar, R. D.; Williamson, J. S. Curr. Med. Chem.
2002, 9, 1631.
10. Carter, G. W.; Young, P. R.; Albert, D. H.; Bouska, J.; Dyer, R.; Bell, R. L.;
Summers, J. B.; Brooks, D. W. J. Pharmacol. Exp. Ther. 1991, 256, 929.
11. Chowdhury, M. A.; Chen, H.; Abdellatif, K. R.; Dong, Y.; Petruk, K. C.; Knaus, E. E.
Bioorg. Med. Chem. Lett. 2008, 18, 4195.
In vitro COX-1, COX-2, 5-LOX enzyme inhibition, and in vivo anti-inflammatory
activity, data for the 1-[4-methyl(or amino)sulfonylphenyl]-3-trifluoromethyl-5-[4-
(1-hydroxy-1,2-dihydropyrid-2-one]-1H-pyrazoles (11a–b)
Compound COX-1 IC50
M)a
COX-2 IC50
M)a
5-LOX IC50
M)b
AI activityc
ED50 (mg/kg)
(l
(
l
(
l
12. Penning, T. D.; Tally, J. J.; Bertenshaw, S. R.; Carter, J. S.; Collins, P. W.; Doctor,
S.; Graneto, M. J.; Lee, L. F.; Malecha, J. W.; Miyashiro, J. M.; Rogers, R. S.; Rogier,
D. J.; Yu, S. S.; Anderson, G. D.; Burton, E. G.; Cogburn, J. N.; Gregory, S. A.;
Koboldt, C. M.; Perkins, W. E.; Seibert, K.; Veenhuizen, A. W.; Zhang, Y. Y.;
Isakson, P. C. J. Med. Chem. 1997, 40, 1347.
13. Huang, H.-C.; Li, J. J.; Garland, D. J.; Chamberlain, T. S.; Reinhard, E. J.; Manning,
R. E.; Seibert, K.; Koboldt, C. M.; Gregory, S. A.; Anderson, G. D.; Veenhuizen, A.
W.; Zhang, Y.; Perkins, W. E.; Burton, E. G.; Cogburn, J. N.; Isakson, P. C.; Reitz,
D. B. J. Med. Chem. 1996, 39, 253.
11a
11b
Celecoxib
Aspirin
Caffeic
acid
13.2
10.2
7.7
0.35
—
7.5
7.5
0.07
2.4
—
0.35
4.90
>10
—
66.9
99.8
10.8
128.7
—
3.47
a
The in vitro test compound concentration required to produce 50% inhibition of
M) is the mean of two determinations acquired
COX-1 or COX-2. The result (IC50, l
14. Levine, R.; Sneed, J. K. J. Am. Chem. Soc. 1951, 73, 4478.
15. Choi, H.-Y.; Yoon, S.-H. Bull. Korean Chem. Soc. 1999, 20, 857.
16. Experimental procedures and spectral data for compounds 6–7, 9–11.
1-(2-Methoxypyridin-4-yl)ethanone (6): Methyllithium (8.75 mL of 1.6 M in
Et2O, 14 mmol) was added to a stirred solution of 2-methoxyisonicotinonitrile
(5, 1.5 g, 11.19 mmol) in THF (20 mL) under nitrogen at À78 °C with stirring.
Compound 5 was prepared in 91% yield from 2-chloroisonicotinonitrile (Peters,
R.; Althaus, M.; Diolez, C.; Rolland, A.; Manginot, E.; Veyrat, M. J. Org. Chem.
2006, 71, 7583). The resulting solution was warmed to 25 °C and stirring was
continued for 2.5 h. The reaction mixture was quenched with 3 N HCl and the
mixture as stirred for 1 h at 25 °C. After washing with EtOAc, the aqueous
fraction was neutralized with Na2CO3 and extracted with EtOAc (3Â 25 mL).
The combined organic fractions were washed successively with water and
brine, and dried (MgSO4). After filtration, the solvent from the organic fraction
was removed in vacuo to give 6 as a brown syrup in 72% yield; 1H NMR (CDCl3)
d 2.59 (s, 3H, COMe), 3.98 (s, 3H, OMe), 7.18 (d, J = 1.2 Hz, 1H, pyridyl H-3), 7.31
(dd, J = 5.5, 1.2 Hz, 1H, pyridyl H-5), 8.31 (d, J = 5.5 Hz, 1H, pyridyl H-6).
using an ovine COX-1/COX-2 assay kit (Catalog No. 560101, Cayman Chemicals Inc.,
Ann Arbor, MI, USA) 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, lM) is
the mean of two determinations acquired using a LOX assay kit (Catalog No.
760700, Cayman Chemicals Inc., Ann Arbor, MI, USA) 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.
(11a, ED50 = 66.9 mg/kg po) and SO2NH2 (11b, ED50 = 99.8 mg/kg
po), compounds exhibited AI activities between that of the refer-
ence drugs celecoxib (ED50 = 10.8 mg/kg po) and aspirin
(ED50 = 128.7 mg/kg po). The in vitro and in vivo structure–activity
data acquired suggest that the N-hydroxypyridin-2(1H)-ones 11a–
b, that are very weak inhibitors of the COX-1 and COX-2 isozymes,
exhibit their AI activity primarily by preventing the biosynthesis of
proinflammatory leukotrienes (LTs) produced via the LOX
pathway.
In conclusion, a hitherto unknown class of 1-[4-methyl(or
amino)sulfonylphenyl]-3-trifluoromethyl-5-[4-(1-hydroxy-1,2-
dihydropyrid-2-one]-1H-pyrazoles (11a–b)16 was designed for
evaluation as dual 5-LOX17 and COX-1/COX-2 isozyme18 inhibitors
of inflammation. The structure–activity data acquired indicate that
(i) the SO2Me compound (11a) is a 14-fold more potent inhibitor of
5-LOX than the SO2NH2 compound (11b), (ii) the N-hydroxypyrid-
2(1H)-one moiety provides a novel 5-LOX pharmacophore for the
design of cyclic hydroxamic mimetics and (iii) the title compounds
11a–b, that are very weak inhibitors of the COX-1/COX-2 isozymes,
exhibit anti-inflammatory activity19 predominately via inhibition
of proinflammatory leukotriene biosynthesis in the lipoxygenase
pathway.
4,4,4-Trifluoro-3-hydroxy-1-(2-methoxypyridin-4-yl)-but-2-en-1-one
(7):
A
mixture of 1-(2-methoxypyridin-4-yl)ethanone (6, 1.21 g, 8.01 mmol),
sodium methoxide (1.73 mL of a 25% w/v solution in MeOH, 8.01 mmol) and
ethyl trifluoroacetate (0.95 mL, 8.01 mmol) was refluxed for 6 h. The reaction
mixture was cooled to 25 °C and glacial acetic acid (0.46 mL, 8.01 mmol) was
added. Water (15 mL) was added, the reaction mixture was extracted with
CHCl3 (3Â 25 mL), the organic phase was washed successively with water and
then brine, and the organic fraction was dried (MgSO4). After filtration, the
solvent from the organic fraction was removed in vacuo to give product 7 as a
brown syrup in 74% yield; 1H NMR (CDCl3) d 4.00 (s, 3H, OMe), 6.55 [s, 1H,
CF3C(OH)@CHCO–], 7.21 (d, J = 1.2 Hz, 1H, pyridyl H-3), 7.29 (dd, J = 5.5, 1.2 Hz,
1H, pyridyl H-5), 8.34 (d, J = 5.5 Hz, 1H, pyridyl H-6), 14.25 (br s, 1H, OH).
General procedure for the synthesis of 1-[4-methyl(amino)sulfonylphenyl]-3-
trifluoromethyl-5-(2-methoxypyridin-4-yl)-1H-pyrazoles (9a–b):
A solution of
the hydrazine hydrochloride 8a or 8b (6.46 mmol) and the ketone
7
(1.45 g, 5.87 mmol) in 95% ethanol (75 mL) was heated at reflux for 20 h.
Compound 8a was synthesized in 53% yield starting from 1-chloro-4-
methanesulfonylbenzene2 which was prepared by the Fridel–Crafts reaction
of methanesulfonyl chloride with chlorobenzene (Truce, W. E.; Vriesen, C. W. J.
Am. Chem. Soc. 1953, 75, 5032), and compound 8b was synthesized in 84% yield
starting from sulfanilamide (Soliman, R. J. Med. Chem. 1979, 22, 321). After
cooling to 25 °C, the reaction mixture was concentrated in vacuo to yield a
gummy mass. The crude product 9a, or 9b, was purified by silica gel column
chromatography using acetone-hexane (1:2, v/v) as eluent to furnish the
respective product 9a or 9b. Some physical and spectroscopic data for 9a–b are
listed below.
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-(2-methoxypyridin-4-yl)-1H-
pyrazole (9a): Product 9a was obtained as dark brown syrup in 37% yield; IR
Acknowledgments
(neat) 1380, 1160 (SO2) cmÀ1 1H NMR (CDCl3) d 3.09 (s, 3H, SO2Me), 3.95 (s,
;
3H, OMe), 6.61–6.68 (m, 2H, pyridyl H-3, H-5), 6.87 (s, 1H, pyrazol H-4), 7.57
(d, J = 9.0 Hz, 2H, phenyl H-2, H-6), 8.00 (d, J = 9.0 Hz, 2H, phenyl H-3, H-5),
8.17 (d, J = 6.0 Hz, 1H, pyridyl H-6). Anal. Calcd for C17H14F3N3O3S: C, 51.38; H,
3.55. Found: C, 51.46; H, 3.94.
We are grateful to the Canadian Institutes of Health Research
(CIHR) (MOP-14712) for financial support of this research.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(2-methoxypyridin-4-yl)-1H-
pyrazole (9b): Product 9b was obtained as a white solid in 38% yield, mp 175–
References and notes
177 °C; IR (film) 3350, 3280 (NH2), 1325, 1165 (SO2) cmÀ1 1H NMR (DMSO-d6)
;
d 3.85 (s, 3H, OMe), 6.79–6.91 (m, 2H, pyridyl H-3, H-5), 7.45 (s, 1H, pyrazol H-
4), 7.57 (s, 2H, SO2NH2 that exchanges with D2O), 7.62 (d, J = 8.5 Hz, 2H, phenyl
H-2, H-6), 7.91 (d, J = 8.5 Hz, 2H, phenyl H-3, H-5), 8.19 (d, 1H, J = 6.1 Hz,
pyridyl H-6). Anal. Calcd for C16H13F3N4O3S: C, 48.24; H, 3.29. Found: C, 47.93;
H, 3.43.
General procedure for the synthesis of 1-[4-methyl(amino)sulfonylphenyl]-3-
trifuoromethyl-5-(1-oxido-2-methoxypyridin-4-yl)-1H-pyrazoles (10a–b): meta-
Chloroperoxybenzoic acid (77% max) (6 mmol) was added to a stirred solution
of either 9a or 9b (2 mmol) in dry CH2Cl2 (25 mL), and the reaction was
allowed to proceed with stirring at 25 °C overnight. The solvent (CH2Cl2) was
removed in vacuo to give a residue which was purified by silica gel column
chromatography using methanol–EtOAc (1:3, v/v) as eluent to afford the
respective product 10a or 10b. Some physical and spectroscopic data for 10a–b
are listed below.
1. (a) Charlier, C.; Michaux, C. Eur. J. Med. Chem. 2003, 38, 645; (b) Barbey, S.;
Goossens, L.; Taverne, T.; Cornet, J.; Choesmel, V.; Rouaud, C.; Gimeno, G.;
Yannic-Arnoult, S.; Michaux, C.; Charlier, C.; Houssin, R.; Henichart, J.-P. Bioorg.
Med. Chem. Lett. 2002, 12, 779.
2. Pommery, N.; Taverne, T.; Telliez, A.; Goossens, L.; Charlier, C.; Pommery, J.;
Goossens, J.-F.; Houssin, R.; Durant, F.; Henichart, J.-P. J. Med. Chem. 2004, 47,
6195. and reference cited therein.
3. (a) McMillan, R. M.; Walker, E. R. H. Trends Pharmacol. Sci. 1992, 13, 323; (b)
Ford-Hutchinson, A. W.; Gresser, M.; Young, R. N. Annu. Rev. Biochem. 1994, 63,
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Cardiovasc. Med. 2004, 14, 191.
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references cited therein.
1-(4-Methylsulfonylphenyl)-3-trifuoromethyl-5-(1-oxido-2-methoxypyridin-4-
yl)-1H-pyrazole (10a): Product 10a was obtained as a white solid in 51% yield,
mp 165–167 °C; IR (film) 1350, 1125 (SO2) cmÀ1 1H NMR (DMSO-d6) d 3.28 (s,
;
7. Scheen, A. J. Rev. Med. Liege 2004, 59, 565.

M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6138–6141
6141
3H, SO2Me), 3.85 (s, 3H, OMe), 6.82 (dd, J = 6.7, 2.4 Hz, 1H, pyridyl H-5), 7.21 (d,
J = 2.4 Hz, 1H, pyridyl H-3), 7.48 (s, 1H, pyrazol H-4), 7.72 (d, J = 8.5 Hz, 2H,
phenyl H-2, H-6), 8.05 (d, J = 8.5 Hz, 2H, phenyl H-3, H-5), 8.21 (d, 1H,
J = 6.7 Hz, pyridyl H-6). Anal. Calcd for C17H14F3N3O4S 1/2H2O: C, 48.34; H,
3.58. Found: C, 48.37; H, 3.53.
dihydropyridyl H-5), 6.53 (d, J = 2.4 Hz, 1H, dihydropyridyl H-3), 7.41 (s, 1H,
pyrazol H-4), 7.57 (s, 2H, SO2NH2 that exchanges with D2O), 7.67 (d, J = 8.5 Hz,
2H, phenyl H-2, H-6), 7.94 (d, J = 8.5 Hz, 2H, phenyl H-3, H-5), 7.96 (d,
J = 7.3 Hz, 1H, dihydropyridyl H-6), 11.90 (br s, 1H, OH); 13C NMR (DMSO-d6) d
103.9, 107.6, 118.9, 121.0, 126.0, 128.9, 136.3, 137.2, 139.4, 142.0, 142.1, 142.3,
156.9; MS (M+1)+ 400.94.
1-(4-Aminosulfonylphenyl)-3-trifuoromethyl-5-(1-oxido-2-methoxypyridin-4-yl)-
1H-pyrazole (10b): Product 10b was obtained as white solid in 59% yield, mp
17. 5-Lipoxygenase inhibition assay: The ability of the test compounds 11a and 11b
to inhibit potato 5-LOX (Catalog No. 60401, Cayman Chemical, Ann Arbor, MI,
220–222 °C; IR (film) 3400–3000 broad (NH2), 1280, 1140 (SO2) cmÀ1 1H NMR
;
(DMSO-d6) d 3.86 (s, 3H, OMe), 6.83 (dd, J = 6.7, 2.4 Hz, 1H, pyridyl H-5), 7.18
(d, J = 2.4 Hz, 1H, pyridyl H-3), 7.48 (s, 1H, pyrazol H-4), 7.54 (s, 2H, SO2NH2
that exchanges with D2O), 7.66 (d, J = 8.5 Hz, 2H, phenyl H-2, H-6), 7.93 (d,
J = 8.5 Hz, 2H, phenyl H-3, H-5), 8.23 (d, 1H, J = 6.7 Hz, pyridyl H-6). Anal. Calcd
for C16H13F3N4O4S: C, 46.38; H, 3.16. Found: C, 46.07; H, 3.42.
General procedure for the synthesis of 1-[4-methyl(amino)sulfonylphenyl]-3-
trifluoromethyl-5-[4-(1-hydroxy-1,2-dihydropyrid-2-one]-1H-pyrazoles (11a–b):
Acetyl chloride (6 mL) was added to either 10a, or 10b (2 mmol), and the
reaction mixture was allowed to proceed at reflux for 1 h. The reaction mixture
was cooled to 25 °C, and excess acetyl chloride was removed in vacuo. The
residue was dissolved in methanol prior to stirring at 25 °C overnight.
Methanol was removed in vacuo to give a solid product which was then
mixed with Et2O (10 mL) to form a slurry. Finally, the solid product was filtered
out and dried under vacuum to give the respective product 11a or 11b. Some
physical and spectroscopic data for 11a–b are listed below.
USA) (IC50 values, lM) was determined using an enzyme immuno assay (EIA)
kit (Catalog No. 760700, Cayman Chemical, Ann Arbor, MI, USA) according to
the manufacturer’s instructions. The Cayman Chemical lipoxygenase inhibitor
screening assay detects and measures the hydroperoxides produced in the
lipoxygenation reaction using a purified lipoxygenase. Stock solutions of test
compounds were dissolved in a minimum volume of DMSO and were diluted
using the supplied buffer solution (0.1 M, Tris–HCl, pH 7.4). To a 90
of 5-LOX enzyme in 0.1 M, Tris–HCl, pH 7.4 buffer, 10
concentrations of test drug solutions (0.01, 0.1, and 10
volume of 210 l) were added and the lipoxygenase reaction was initiated by
the addition of 10 l (100 M) of linoleic acid (LA). After maintaining the 96-
well plate on a shaker for 5 min, 100 l of chromogen was added and the plate
l
l solution
of various
in final
l
l
1
lM
a
l
l
l
l
was retained on a shaker for 5 min. The lipoxygenase activity was determined
after measuring absorbance at a wavelength of 500 nm. Percent inhibition was
calculated by the comparison of compound-treated to various control
incubations. The concentration of the test compound causing 50% inhibition
(IC50, lM) was calculated from the concentration–inhibition response curve
(duplicate determinations).
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-[4-(1-hydroxy-1,2-dihydropyrid-
2-one]-1H-pyrazole (11a): Product 11a was obtained as a brown solid in 94%
yield, mp 188–190 °C; IR (film) 3105 broad (OH), 1657 (C@O), 1325, 1154 (SO2)
cmÀ1
;
1H NMR (CDCl3) d 3.12 (s, 3H, SO2Me), 6.08 (dd, J = 7.3, 2.4 Hz, 1H,
18. Cyclooxygenase inhibition assays: The ability of the test compounds listed in
dihydropyridyl H-5), 6.71 (d, J = 2.4 Hz, 1H, dihydropyridyl H-3), 6.90 (s, 1H,
pyrazol H-4), 7.62 (d, J = 8.5 Hz, 2H, phenyl H-2, H-6), 7.82 (d, J = 6.7 Hz, 1H,
dihydropyridyl H-6), 8.05 (d, J = 8.5 Hz, 2H, phenyl H-3, H-5); 13C NMR (DMSO-
d6) d 43.3, 104.0, 107.6, 119.0, 121.0, 126.2, 128.4, 136.4, 137.3, 141.0, 142.0,
142.2, 142.4, 156.9; MS (M+1)+ 399.98.
Table 1 to inhibit ovine COX-1 and COX-2 (IC50 value, lM) was determined
using an enzyme immuno assay (EIA) kit (Catalog No. 560101, Cayman
Chemical, Ann Arbor, MI, USA) according to our previously reported method.
Rao, P. N. P.; Amini, M.; Li, H.; Habeeb, A.; Knaus, E. E. J. Med. Chem. 2003, 46,
4872.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-[4-(1-hydroxy-1,2-dihydropyrid-
2-one]-1H-pyrazole (11b): Product 11b was obtained as brown solid in 71%
yield, mp 235–237 °C; IR (film) 3400–3000 broad (OH, NH2), 1655 (C@O), 1280,
19. In vivo anti-inflammatory assay: The test compounds 11a and 11b and the
reference drugs celecoxib and aspirin were evaluated using the in vivo
carrageenan-induced rat foot paw edema model reported previously. Winter,
C. A.; Risley, E. A.; Nuss, G. W. Proc. Soc. Exp. Biol. Med. 1962, 111, 544.
1140 (SO2) cmÀ1
; d 6.04 (dd, J = 7.3, 2.4 Hz, 1H,
1H NMR (DMSO-d6)