Synthesis and biological evaluation of salicylic acid and N-acetyl-2-carboxybenzenesulfonamide regioisomers possessing a N-difluoromethyl-1,2-dihydropyrid-2-one pharmacophore: Dual inhibitors of cyclooxygenases and 5-lipoxygenase with anti-inflammatory ac

Article abstract of DOI:10.1016/j.bmcl.2009.10.083

A novel class of salicylic acid and N-acetyl-2-carboxybenzenesulfonamide regioisomers possessing a N-difluoromethyl-1,2-dihydropyrid-2-one pharmacophore attached to its C-4 or C-5 position was designed for evaluation as anti-inflammatory (AI) agents. Repl

Full text of DOI:10.1016/j.bmcl.2009.10.083

Bioorganic & Medicinal Chemistry Letters 19 (2009) 6855–6861
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and biological evaluation of salicylic acid and
N-acetyl-2-carboxybenzenesulfonamide regioisomers possessing
a N-difluoromethyl-1,2-dihydropyrid-2-one pharmacophore: Dual inhibitors
of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity
Morshed A. Chowdhury, Khaled R. A. Abdellatif, Ying Dong, Dipankar Das, Gang Yu, Carlos A. Velázquez,
*
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 novel class of salicylic acid and N-acetyl-2-carboxybenzenesulfonamide regioisomers possessing a N-
difluoromethyl-1,2-dihydropyrid-2-one pharmacophore attached to its C-4 or C-5 position was designed
for evaluation as anti-inflammatory (AI) agents. Replacement of the 2,4-difluorophenyl ring in diflunisal
by the N-difluoromethyl-1,2-dihydropyrid-2-one moiety provided compounds showing dual selective
cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-LOX) inhibitory activities. AI structure–activity studies
showed that the C-4 (14a) and C-5 (14b) salicylate regioisomers were 1.4- and 1.6-fold more potent than
aspirin, and the C-5 N-acetyl-2-carboxybenzenesulfonamide regioisomer (22b) was 1.3- and 2.8-fold
more potent than ibuprofen and aspirin, respectively. In vivo ulcer index (UI) studies showed that the
4- and 5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)salicylic acids (14a and 14b) were completely
non-ulcerogenic since no gastric lesions were present (UI = 0) relative to aspirin (UI = 57) at an equivalent
Received 25 September 2009
Revised 16 October 2009
Accepted 20 October 2009
Available online 23 October 2009
Keywords:
Salicylic acid NSAIDs
N-Difluoromethyl-1,2-dihydropyrid-2-one
5-lipoxygenase pharmacophore
Cyclooxygenase and 5-lipoxygenase
inhibition
lmol/kg oral dose. The N-difluoromethyl-1,2-dihydropyridin-2-one moiety provides a novel 5-LOX phar-
Non-ulcerogenic
Anti-inflammatory activity
macophore for the design of cyclic hydroxamic mimetics for exploitation in the development of dual
COX-2/5-LOX inhibitory AI drugs.
Ó 2009 Elsevier Ltd. All rights reserved.
Salicylic acid derivatives are widely used for treatment of vari-
ous diseases. For example, acetylsalicylic acid (aspirin, 1) is one of
the most extensively used nonsteroidal anti-inflammatory drugs
(NSAIDs) (see structure in Fig. 1). The complex biological actions
exhibited by the simple salicylate class of compounds have at-
tracted ongoing attention for more than a century. In this context,
the moderately active anti-inflammatory (AI) and non-narcotic
analgesic agent acetylsalicylic acid (1) continues to be a frequent
first choice drug in the treatment of some arthritic disorders. How-
ever, these beneficial actions of aspirin may also be accompanied
by adverse effects that include tinnitus, hypersensitization, and
contraindicated gastrointestinal irritation, bleeding and/or ulcera-
tion.1 The ability of aspirin to inhibit blood platelet aggregation
is now viewed as a clinically useful prophylactic action that can
reduce the incidence of thrombus formation in individuals with
cardiovascular disease. The search for a clinical replacement for
aspirin resulted in the development of the nonacetylating salicylic
acid derivative diflunisal (2) that is a more potent AI and analgesic
agent with a longer duration of action and is less ulcerogenic than
aspirin.2 The subsequent discovery3,4 of two cyclooxygenase iso-
zymes COX-1 and COX-2 provided the basis for the drug design
concept that selective COX-2 inhibitors such as celecoxib5 elicit
effective AI activity devoid of the ulcerogenic effect associated with
the use of NSAIDs such as aspirin that inhibit both COX-1 and COX-
2. Some of aspirin’s beneficial therapeutic effects arise from acety-
lation of COX-2, whereas its antithrombotic and ulcerogenic effects
result from acetylation of COX-1. These observations were
exploited in the design of the aspirin analog o-(acetoxyphe-
nyl)hept-2-ynyl sulfide (APHS, 3) that is a selective COX-2 inhibi-
tor.6–8 On the other hand, dual inhibitors of cyclooxygenase-2
(COX-2) and 5-lipoxygenase (5-LOX) represent an attractive safer
alternative to selective COX-2 inhibitors. This view is based on a
potentially greater AI efficacy due to their ability to synergistically
block both metabolic pathways of the arachidonic acid (AA) cas-
cade.9 Proinflammatory prostaglandins (PGs) produced via the
COX pathway, and leukotrienes (LTs) produced via the LOX path-
way, are implicated in physiological processes such as inflamma-
tion, fever, arthritis and bronchospasm.10,11 PGs that cause
contraindicated inflammation, fever, and pain are formed via the
inducible COX-2 isozyme whereas, PGs that regulate beneficial
gastrointestinal cytoprotection and renal effects are produced via
* 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 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.10.083

6856
M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6855–6861
F
F
It is known that the SO2NHCOCH3 moiety is a 105–106 more
reactive acetylating agent of enzyme serine hydroxyls than simple
amides.25 In an earlier study, it was shown that the incorporation
of a para-N-acetylsulfonamido substituent on the C-3 phenyl ring
of a rofecoxib regioisomer provided a highly potent and selective
COX-2 inhibitor that has the potential to acetylate the COX-2 iso-
zyme.26 After acetylation of the COX-2 Ser530 OH by a N-acety-
lsulfonamido compound, a free SO2NH2 compound would be
released that could also exhibit COX-2 inhibitory activity. This
rationale is based on the observation that the water soluble non-
narcotic analgesic agent parecoxib sodium27 is a prodrug to the
selective COX-2 inhibitor valdecoxib.28 Accordingly, the SO2NHC-
OCH3 pharmacophore could serve the dual role of acetylating agent
and prodrug.
It was anticipated that replacement of the 2,4-difluorophenyl
moiety in the salicylic acid derivative diflunisal (2) by a N-difluoro-
methyl-1,2-dihydropyrid-2-one moiety may provide a hitherto un-
known class of dual COX-2/5-LOX inhibitory anti-inflammatory
agents. As part of our ongoing research program to design dual
COX/5-LOX inhibitors, we describe herein the synthesis of a new
class of salicylic acid analogs (14a–b) and N-acetyl-2-carboxyben-
CO2H
CO2H
OH
O
C
O
Me
Aspirin (1)
Diflunisal (2)
SC C(CH2)3Me
HO
NH2
O
N
O
C
O
Me
S
Me
Zileuton (4)
APHS (3)
O
Me
N
N
MeO
N
OH
zenesulfonamides (22a–b) possessing
a N-difluoromethyl-1,2-
Cl
Tepoxalin (5)
dihydropyrid-2-one moiety attached to its C-4 or C-5 position that
may represent a new 5-LOX-inhibiting pharmacophore, their
in vitro evaluation as COX-1/COX-2, 5-LOX inhibitors, in vivo
assessment as AI agents, and results from ulcerogenicity studies
for the two salicylic acid regioisomers (14a–b).
CF3
R2
4
CO2H
N
R1
N
N
O
5
A Suzuki–Miyaura cross-coupling reaction29,30 was used to syn-
thesize the biaryl compounds 12a and 18a, and their respective
regioisomers 12b and 18b. Reaction of methyl 4- or 5-iodo-2-
methoxybenzoate (10a or 10b) with 2-chloropyridine-4-boronic
acid (11) in the presence of tetrakis(triphenylphosphine)palla-
dium(0) catalyst and 2 M aqueous Na2CO3 in THF afforded methyl
4- or 5-(2-chloropyridin-4-yl)-2-methoxybenzoate (12a, 12b) in
71% and 85% yield, respectively. In contrast, the Suzuki cross-cou-
pling reaction of 4- or 5-bromo-2-methoxycarbonylbenzenesulf-
onamide (17a or 17b) with 11 afforded 5- or 6-(2-chloropyridin-
4-yl)-1,2-benzisothiazol-3(2H)-one-1,1-dioxide (18a or 18b) in
65–90% yields. The saccharin ring system present in the bicyclic
compounds (18a–b) arises via an intramolecular cyclization
involving the CO2Me and SO2NH2 substituent present in 17a–b.
Treatment of 18a or 18b with methanolic-HCl opened the saccha-
rin ring31 to furnish the desired 4-(2-chloropyridin-4-yl)-2-meth-
oxycarbonylbenzenesulfonamide (19a, 81%) or its regioisomer
19b (80%). Subsequent transformation of the 2-chloropyridin-4-yl
compound 12a–b or 19a–b to the target 4- or 5-(N-difluoro-
methyl-1,2-dihydropyrid-2-one-4-yl)salicylic acid (14a or 14b) or
N-acetyl-4- or 5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-
2-carboxybenzenesulfonamide (22a or 22b) were carried out using
the synthetic strategies shown in Schemes 1 and 2. Reaction of
12a–b, or 19a–b, with 2,2-difluoro-2-(fluorosulfonyl)acetic acid
(FSO2CF2COOH)32 afforded methyl 4- or 5-(N-difluoromethyl-1,2-
dihydropyrid-2-one-4-yl)-2-methoxybenzoates (13a–b) in 54–
61% yield or 4- or 5-(N-difluoromethyl-1,2-dihydropyrid-2-one-
4-yl)-2-methoxycarbonylbenzenesulfonamides (20a–b) in 35–
38% yield. Treatment of 13a–b with BBr3 in dichloromethane33 at
ꢀ78 °C resulted in simultaneous deprotection of the OMe and
CO2Me substitutents to afford the target 4- or 5-(N-difluoro-
methyl-1,2-dihydropyrid-2-one-4-yl)salicylic acid regioisomers
(14a or 14b) in quantitative yield. On the other hand, N-acetylation
of 20a and 20b using silica–sulfuric acid (SiO2–OSO2H) and acetyl
chloride in chloroform–acetonitrile34 furnished the respective reg-
ioisomer 21a and 21b in 13% and 57% yields, respectively. Depro-
tection of the CO2Me group in 21a and 21b with aqueous 2 M
lithium hydroxide in methanol-tetrahydrofuran33 furnished the
target N-acetyl-4- or 5-(N-difluoromethyl-1,2-dihydropyrid-2-
SO2NHCOMe F2HC
6, R1 = H, F, SO 2Me, OPr-i; R2 = H, F
SO2R1
7, R1 = Me, NH2
CHF2
R1O2S
N
C
C
O
8, R1 = Me, NH2
Figure 1. Chemical structures of some representative cyclooxygenase (COX)
inhibitors (1–3), iron-chelating 5-LOX inhibitors (4–5), COX inhibitors (6), and the
COX/5-LOX inhibitors (7–8).
the constitutive COX-1 isozyme.10–12 Alternatively, 5-LOX is associ-
ated with the production of LTs that cause inflammatory, broncho-
constrictor, 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.13,14 There is a general belief that a dual inhibitor of the LOX/
COX enzymatic pathways15 constitutes a rational approach for the
design of more effective AI agents with a superior safety profile rel-
ative to ulcerogenic NSAIDs, and selective COX-2 inhibitors that in-
crease the incidence of adverse cardiovascular thrombotic
effects.16,17 It has been pointed out that inhibition of only one of
the COX/LOX pathways could shift the metabolism of AA towards
the other pathway, thereby inducing potential side effects.18 One
of the more successful strategies to develop 5-LOX inhibitors uti-
lized hydroxamic acids and related N-hydroxyureas that act by
chelation of iron present in the 5-LOX enzyme.19 Two representa-
tive examples of iron-chelating 5-LOX inhibitors include zileuton
(4)20 and tepoxalin (5)19 (see structures in Fig. 1). Previously, we
showed that the SO2NHCOMe pharmacophore present in N-acet-
yl-2-carboxybenzenesulfonamides (6) is a suitable bioisostere for
the acetoxy (OCOMe) group in aspirin (1).21 In recent studies, we
described a novel class of dual COX/5-LOX inhibitors of celecoxib22
analogs (7)23 and 1,2-diarylacetylene regioisomers (8)24 that pos-
sess a N-difluoromethyl-1,2-dihydropyrid-2-one 5-LOX pharma-
cophore.

M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6855–6861
Cl
Me
6857
N
CO2H
OH
OMe
4
5
4
5
4
4
a
a
b
I
I
Br
5
Br
5
SO2NHAc
SO2NHAc
CO2Me
Me
CO2
15a, 4-Br
15b, 5-Br
16a, 4-Br
16b, 5-Br
9a, 4-I; 9b, 5-I
10a, 4-I; 10b, 5-I
B(OH)2
11
O
3
NH 2
Cl
b
4
CO2Me
4
5
5
6
c
Cl
O
N
Br
N
4
OMe
OMe
4
S
1
SO2NH2
c
O
N
F2HC
17a, 4-Br
17b, 5-Br
O
5
5
18a, 5-chloropyridyl
18b, 6-chloropyridyl
CO2Me
CO2Me
13a, 4-(pyridinone)
13b, 5-(pyridinone)
12a, 4-(chloropyridyl)
12b, 5-(chloropyridyl)
Cl
CO2Me
e
4
5
d
d
N
O
N
SO2NH2
OH
19a, 4-chloropyridyl
19b, 5-chloropyridyl
4
5
F2HC
O
CO2H
CO2Me
4
5
f
14a, 4-(pyridinone)
14b, 5-(pyridinone)
F2HC
F2HC
F2HC
N
SO2NH2
Scheme 1. Reagents and conditions: (a) MeI, K2CO3, DMF, 2 h, 25 °C; (b) Pd(PPh3)4,
Na2CO3, THF, reflux, 16 h; (c) FSO2CF2COOH, NaHCO3, reflux, 16 h; (d) BBr3, CH2Cl2,
ꢀ78 °C for 1 h, and then 25 °C for 16 h.
20a, 4-pyridinone
20b, 5-pyridinone
O
CO2Me
g
4
5
N
one-4-yl)-2-carboxybenzenesulfonamide regioisomers (22a and
22b) in 72% and 79% yields, respectively.
SO2NHAc
21a, 4-pyridinone
21b, 5-pyridinone
The rational for the design of the 4- or 5-(N-difluoromethyl-1,2-
dihydropyrid-2-one-4-yl)salicylic acids (14a–b) and N-acetyl-4- or
5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-carboxyben-
zenesulfonamides (22a–b) was based on the expectation that
replacement of a 2,4-difluorophenyl ring in the salicylic acid deriv-
ative (diflunisal, 2) by a N-difluoromethyl-1,2-dihydropyrid-2-one
moiety may provide a hitherto unknown class of compounds with
dual COX-2/5-LOX inhibitory activities. The CONCHF2 fragment of
the N-difluoromethyl-1,2-dihydropyrid-2-one ring present in
14a–b and 22a–b can be viewed as a cyclic hydroxamic acid mi-
metic. These N-difluoromethyl-1,2-dihydropyrid-2-ones 14a–b
and 22a–b could inhibit the 5-LOX enzyme by two possible mech-
anisms. In this regard 14a–b and 22a–b, like acyclic hydroxamic
acids, may act as effective iron chelators to exhibit 5-LOX inhibi-
tory activity. It has been reported that there is a substantial
build-up of negative potential around the two fluorine atoms of a
CHF2 group.35 Despite this high electron-density, an aliphatic fluo-
rine seldom acts as a hydrogen-bond acceptor, presumably due to
its high electronegativity and low polarizability.36,37 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.38 In addition, these cyclic N-difluoromethyl-1,2-
dihydropyrid-2-ones, unlike acyclic hydroxamic acids which un-
dergo 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 rel-
atively flat diene portion of this quasi-planar ring system has the
potential to serve as a suitable replacement for the 2,4-difluoro-
phenyl group present in diflunisal (2) resulting in retention of
selective COX-2 inhibitory activity.
O
N
CO2H
4
5
SO2NHAc
22a, 4-pyridinone
22b, 5-pyridinone
Scheme 2. Reagents and conditions: (a) KMnO4, 0.5 N NaOH, 60 °C, 16 h; (b) MeOH,
concd H2SO4, reflux, 16 h; (c) 2-chloropyridin-4-boronic acid (11), Pd(PPh3)4,
Na2CO3, THF, reflux, 16 h; (d) methanolic-HCl, ꢀ5 °C, 1 h, reflux, 1 h; (e)
FSO2CF2CO2H, NaHCO3, reflux, 16 h; (f) SiO2–OSO3H, THF–MeCN, CH3COCl, reflux,
16 h; (g) LiOH, THF–MeOH–H2O, reflux, 1 h.
and the C-5 regioisomer was a more potent, COX-2 inhibitor than
the reference drugs ibuprofen and aspirin. These COX-1/COX-2 iso-
zyme inhibition data indicate that attachment of a N-difluoro-
methyl-1,2-dhydropyrid-2-one moiety to salicylic acid confers
COX-2 selectivity relative to the COX-1 selective aspirin (see data
in Table 1). The N-acetylbenzenesulfonamide regioisomers (22a–
b) did not inhibit COX-1 (IC50 >100
regioisomer (22a) was a weaker COX-2 inhibitor (IC50 = 17.6
than the C-5 regioisomer (IC50 = 2.6 M) that exhibited an inhibi-
tory potency approaching that of the reference drugs aspirin
(IC50 = 2.4 M) and ibuprofen (IC50 = 1.1 M).
l
M). In comparison, the C-4
l
M)
l
l
l
In vitro 5-LOX inhibition studies showed that the point of
attachment of the N-difluoromethyl-1,2-dihydropyrid-2-one moi-
ety was a determinant of activity where the C-5 regioisomer was
more potent than the corresponding C-4 regioisomer (14b > 14a;
22b P 22a). In this regard, the 5-LOX inhibition potency of the less
potent salicylic acid regioisomer (14a) (IC50 = 4.7
favorably to the reference drug caffeic acid (IC50 = 4.0
the more potent C-5 regioisomers 14b and 22b with respective 5-
LOX IC50 values of 0.37 and 0.28 M were 11- and 14-fold more po-
l
M) compared
l
M) whereas
In vitro COX-1 and COX-2 enzyme inhibition studies (see data in
Table 1) showed that the salicylic acid regioisomers (14a–b) exhib-
ited a more potent inhibition, and hence selectively, for the COX-2
l
tent than the reference drug caffeic acid.
isozyme (COX-1 IC50 = 15.4 to >100
l
M range; COX-2 IC50 = 0.98–
The oral AI activities (ED50 values) exhibited by the N-difluoro-
methyl-1,2-dihydropyrid-2-one-4-yl derivatives of the salicylic
4.4 M range). In this regard, the C-4 regioisomer was a less potent,
l

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M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6855–6861
Table 1
In vitro COX-1, COX-2, 5-LOX enzyme inhibition, and in vivo anti-inflammatory activity, data for salicylic acid (14a–b), and N-acetyl-2-carboxybenzenesulfonamide (22a–b),
regioisomers possessing a N-difluoromethyl-1,2-dihydropyrid-2-one moiety
R1
O
N
R1
O
N
R2
F2HC
R2
F2HC
22a-b
14a-b
R1
R2
IC50
COX-1
(l
M)
COX-2 S.I.b
5-LOX IC50
(lM)
AI activityd ED50
(lmol/kg)
a
c
Compd
COX-2
14a
14b
22a
22b
Ibuprofen
Aspirin
Diflunisal
Caffeic acidf
OH
CO2H
CO2H
SO2NHAc
—
—
—
—
CO2H
OH
SO2NHAc
CO2H
—
—
—
—
>100
15.4
>100
>100
2.9
0.35
—
—
4.4
0.98
17.6
2.6
1.1e
2.4e
—
>22
>15
>5
>38
>2
0.15
—
—
4.7
0.37
0.32
0.28
—
—
—
4.0
497
434
Inactive
258
327
716
68
—
—
a
The in vitro test compound concentration required to produce 50% inhibition of ovine COX-1 or human recombinant COX-2. The result (IC50, lM) 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
In vitro COX-2 selectivity index (COX-1 IC50/COX-2 IC50).
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
c
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.
d
Inhibitory activity in a carrageenan-induced rat paw edema assay. The results are expressed as the ED50 value (lmol/kg) at 3 h after oral administration of the test
compound.
e
f
Data acquired using ovine COX-2 (Catalog No. 560101, Cayman Chemicals Inc.).
Caffeic acid: 3,4-dihydroxycinnamic acid.
Table 2
Ulcer index assay data for the salicylates 14a and 14b
acids (14a–b), and the N-acetyl-2-carboxybenzenesulfonamides
(22a–b), were determined using a carrageenan-induced rat foot
paw edema model (see data in Table 1). AI structure–activity data
acquired showed that the salicylic acid regioisomers 14a (AI
Compound
Dose (mmol/kg)
Ulcer indexa
14a
14b
1.38
1.38
1.38
—
0
0
ED50 = 497
more potent AI agents than the reference drug aspirin (AI
ED50 = 716 mol/kg po). The C-5 2-carboxybenzenesulfonamide
regioisomer 22b (AI ED50 = 258 mol/kg po), unlike the inactive
lmol/kg po) and 14b (AI ED50 = 434 lmol/kg po) are
Aspirin (1)
57.4 3.1b
0
Control groupb,c
l
a
l
Calculated by adding the total length (in mm) of individual lesion (ulceration)
in each stomach and averaging over the number of animals (n = 4) in each group.
Data are presented as mean total length SEM at 6 h after oral administration of the
test compound.
C-4 regioisomer (22a) that is an extremely weak inhibitor of
COX-2, is a more potent AI agent than the reference drugs ibupro-
fen (AI ED50 = 327 lmol/kg po) and aspirin. This superior AI activ-
ity exhibited by the N-difluoromethyl-1,2-dihydropyrid-2-ones
14a–b relative to aspirin, and 22b relative to both aspirin and ibu-
profen, could be due to a number of factors which include oral bio-
b
Data taken from the literature.39
c
1.0% Methyl cellulose solution.
availability,
biodistribution,
and/or
metabolic
stability.
conjunction with potent inhibition of the 5-LOX enzyme, (ii) the
relative AI potency order43 with respect to the point of attachment
of the N-difluoromethyl-1,2-dihydropyrid-2-one moiety is C-5 > C-
4 regioisomer, (iii) the N-difluoromethyl-1,2-dihydropyrid-2-one
moiety provides a novel 5-LOX-inhibiting pharmacophore for the
design of cyclic hydroxamic mimetics, and (iv) the non-ulcero-
genic44 dual acting compounds 14a–b, 22b exhibit AI activity that
is dependent upon inhibition of proinflammatory prostaglandin
and leukotriene biosyntheses in the respective cyclooxygenase
and lipoxygenase pathways.
Compounds 14a–b, 22b bearing a N-difluoromethyl-1,2-dihydro-
pyrid-2-one 5-LOX pharmacophore were less potent AI agents than
diflunisal 2 (AI ED50 = 68 lmol/kg po) having a 2,4-difluorophenyl
moiety.
The most common side effects associated with the long-term
administration of NSAIDs are gastric erosions, ulcer formation,
and sometimes severe bleeding. Therefore, the potential of the
salicylates 14a and 14b to induce adverse gastric ulcerogenicity
was determined in comparison to the reference NSAID aspirin (Ta-
ble 2). It is significant that the two salicylate regioisomers (14a–b)
were completely devoid of any gastric ulcerogenicity [ulcer index
(UI) = 0] relative to aspirin (UI = 57) at equivalent 1.38 mmol/kg
oral doses.
In conclusion, a hitherto unknown class of 4- and 5-(N-difluoro-
methyl-1,2-dihydropyrid-2-one-4-yl)salicylic acids (14a–b), and
N-acetyl 4- and 5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-
yl)carboxybenzenesulfonamides (22a–b), was synthesized40 for
evaluation as dual 5-LOX41 and COX-1/COX-242 isozyme inhibitors
of inflammation. The structure–activity data acquired indicate that
(i) compounds 14a–b and 22a–b exhibit weak to moderate in vitro
COX-2 isozyme inhibitory potency and good COX-2 selectivity in
Acknowledgment
We are grateful to the Canadian Institutes of Health Research
(Grant No. MOP-14712) for financial support of this research.
References and notes
1. The Salicylates; Smith, M. J. H., Smith, P. K., Eds.; Wiley-Interscience: New York,
1966. and references cited therein.
2. Hannah, J.; Ruyle, W. V.; Jones, H.; Matzuk, A. R.; Kelly, K. W.; Witzel, B. E.;
Holtz, W. J.; Houser, R. A.; Shen, T. Y.; Sarett, L. H. J. Med. Chem. 1978, 21, 1093.

M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6855–6861
6859
3. Fu, J. Y.; Masferrer, J. L.; Seibert, K.; Raz, A.; Needleman, P. J. Biol. Chem. 1990,
265, 16737.
General procedure for the synthesis of methyl 4- or 5-iodo-2-methoxybenzoates
(10a–b): solution of methyl 4- or 5-iodosalicylate (9a or 9b) (3 g,
A
4. Xie, W.; Chipman, J.; Robertson, D. L.; Erikson, R. L.; Simmons, D. L. Proc. Natl.
Acad. Sci. U.S.A. 1991, 88, 2692.
5. Goldstein, J. L.; Silverstein, F. E.; Agrawal, N. M.; Hubbard, R. C.; Kaiser, J.;
Maurath, C. I.; Verburg, K. M.; Geis, G. S. Am. J. Gastroenterol. 2000, 95, 1681.
6. Kalgutkar, A. S.; Crews, B. C.; Rowlinson, S. W.; Garner, C.; Seibert, K.; Marnett,
L. J. Science 1998, 280, 1268.
10.79 mmol), methyl iodide (3.06 g, 21.58 mmol) and potassium carbonate
(5.97 g, 43.16 mmol) in N,N0-dimethylformamide (75 mL) was stirred at 25 °C
for 2 h.33 Water (200 mL) was added, the mixture was extracted with ethyl
acetate (3 ꢁ 75 mL), the combined organic extracts were washed successively
with 5% HCl (2 ꢁ 75 mL), water and brine, and the organic fraction was dried
(MgSO4). Filtration and then removal of the solvent from the organic fraction in
vacuo afforded the product (10a or 10b). The spectral data for compounds 10a
and 10b are listed below.
7. Kalgutkar, A. S.; Kozak, K. R.; Crews, B. C.; Hochgesang, G. P., Jr.; Marnett, L. J. J.
Med. Chem. 1998, 41, 4800.
8. Hochgesang, G. P., Jr.; Nemeth-Cawley, J. F.; Rowlinson, S. W.; Caprioli, R. M.;
Marnett, L. J. Arch. Biochem. Biophys. 2003, 409, 127.
Methyl 4-iodo-2-methoxybenzoate (10a): This compound was obtained as a pale
brown liquid in 100% yield; IR 1730 (C@O) cmꢀ1 1H NMR (CDCl3) d 3.88 (s, 3H,
;
9. Fiorucci, S.; Meli, R.; Bucci, M.; Cirino, G. Biochem. Pharmacol. 2001, 62, 1433.
10. Charlier, C.; Michaux, C. Eur. J. Med. Chem. 2003, 38, 645.
11. 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.
OCH3), 3.89 (s, 3H, OCH3), 7.31 (d, J = 1.8 Hz, 1H, phenyl H-3), 7.34 (dd, J = 7.9,
1.8 Hz, 1H, phenyl H-5), 7.50 (d, J = 7.9 Hz, 1H, phenyl H-6).
Methyl 5-iodo-2-methoxybenzoate (10b): This compound was obtained as a
white solid in 97% yield; mp 56–58 °C (lit.46 57 °C); IR 1731 (C@O) cmꢀ1 1H
;
NMR (CDCl3) d 3.88 (s, 6H, 2 ꢁ OCH3), 6.76 (d, J = 9.1 Hz, 1H, phenyl H-3), 7.73
(dd, J = 9.1, 2.4 Hz, 1H, phenyl H-4), 8.07 (d, J = 2.4 Hz, 1H, phenyl H-6).
General procedure for the synthesis of N-acetyl-4- or 5-bromo-2-carboxy-
12. Dannhardt, G.; Laufer, S. Curr. Med. Chem. 2000, 7, 1101.
13. Vila, L. Med. Res. Rev. 2004, 24, 399.
14. Zhao, L.; Funk, C. D. Trends Cardiovasc. Med. 2004, 14, 191.
15. Rao, P. N. P.; Chen, Q.-H.; Knaus, E. E. J. Med. Chem. 2006, 49, 1668. and
references cited therein.
benzenesulfonamide (16a–b): KMnO4 (6.5 g, 41.1 mmol) was added to a
solution of N-acetyl-4- or 5-bromo-2-methylbenzenesulfonamide (15a or
15b) (2.0 g, 6.85 mmol) in aqueous 0.5 N NaOH (82 mL), and the reaction
was allowed to proceed at 60 °C with stirring for 6 h prior to quenching with
acetone. The insoluble material was removed by filtration, and the filtrate was
diluted with H2O (300 mL) prior to acidification to pH 3 using 5% HCl. This
mixture was extracted with EtOAc (3 ꢁ 150 mL) and the combined organic
phases were washed successively with water and brine, and dried (MgSO4).
Filtration and then removal of the solvent from the organic fraction in vacuo
afforded the product (16a or 16b). The spectral data for compounds 16a and
16b are listed below.
16. Scheen, A. J. Rev. Med. Liege 2004, 59, 565.
17. Dogné, J.-M.; Supuran, C. T.; Pratico, D. J. Med. Chem. 2005, 48, 2251.
18. Asako, H.; Kubes, P.; Wallace, J.; Gaginella, T.; Wolf, R. E.; Granger, N. Am. J.
Physiol. Gastrointest. Liver Physiol. 1992, 262, 903.
19. Muri, E. M. F.; Nieto, M. J.; Sindelar, R. D.; Williamson, J. S. Curr. Med. Chem.
2002, 9, 1631.
20. 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.
21. Chen, Q.-H.; Rao, P. N. P.; Knaus, E. E. Bioorg. Med. Chem. 2005, 13, 2459.
22. Penning, T. D.; Talley, J. J.; Bertenshaw, S. R.; Carter, J. S.; Collins, P. W.; Docter,
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.
23. Chowdhury, M. A.; Abdellatif, K. R. A.; Dong, Y.; Das, D.; Suresh, M. R.; Knaus, E.
E. J. Med. Chem. 2009, 52, 1525.
24. Chowdhury, M. A.; Abdellatif, K. R. A.; Dong, Y.; Rahman, M.; Das, D.; Suresh, M.
R.; Knaus, E. E. Bioorg. Med. Chem. Lett. 2009, 19, 584.
N-Acetyl-4-bromo-2-carboxybenzenesulfonamide (16a): This compound was
obtained as a white solid in 76% yield; mp 170–172 °C; IR 1722 (CO), 1368,
1166 (SO2) cmꢀ1 1H NMR (CDCl3 + DMSO-d6) d 1.95 (s, 3H, SO2NHCOCH3), 6.75
;
(br s, 1H, SO2NHCOCH3 that exchanges with D2O), 7.65 (dd, J = 8.5, 1.8 Hz, 1H,
phenyl H-5), 7.74 (d, J = 1.8 Hz, 1H, phenyl H-3), 8.00 (d, J = 8.5 Hz, 1H, phenyl
H-6), 11.38 (br s, 1H, COOH that exchanges with D2O); 13C NMR
(CDCl3 + DMSO-d6) d 23.0, 127.4, 131.8, 132.4, 132.5, 134.4, 135.2, 166.4, 168.6.
N-Acetyl-5-bromo-2-carboxybenzenesulfonamide (16b): This compound was
obtained as a white solid in 66% yield; mp 195–197 °C; IR 3270 (NH), 1715
(CO), 1373, 1166 (SO2) cmꢀ1 1H NMR (CDCl3 + DMSO-d6)
; d 1.96 (s, 3H,
25. Sykes, N. O.; Macdonald, S. J. F.; Page, M. I. J. Med. Chem. 2002, 45, 2850.
26. Zarghi, A.; Rao, P. N. P.; Knaus, E. E. Bioorg. Med. Chem. Lett. 2004, 14, 1957.
27. Boyer-Joubert, C.; Lorthiois, E.; Moreau, F. Annu. Rep. Med. Chem. 2003, 38, 347.
28. Talley, J. J.; Brown, D. L.; Carter, J. S.; Graneto, M. J.; Koboldt, C. M.; Masferrer, J.
L.; Perkins, W. E.; Rogers, R. S.; Shaffer, A. F.; Zhang, Y. Y.; Zweifel, B. S.; Seibert,
K. J. Med. Chem. 2000, 43, 775.
SO2NHCOCH3), 6.87 (br s, 1H, SO2NHCOCH3 that exchanges with D2O), 7.53 (d,
J = 7.9 Hz, 1H, phenyl H-3), 7.71 (dd, J = 7.9, 1.8 Hz, 1H, phenyl H-4), 8.24 (d,
J = 1.8 Hz, 1H, phenyl H-6), 11.48 (br s, 1H, COOH that exchanges with D2O);
13C NMR (CDCl3 + DMSO-d6): d 23.0, 124.5, 129.7, 133.3, 134.3, 135.5, 143.1,
166.7, 168.6.
General procedure for the synthesis of 4- or 5-bromo-2-methoxycarbonyl-
29. Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
benzenesulfonamide (17a–b): Concentrated H2SO4 (2 mL) was added to a
30. Stanforth, S. P. Tetrahedron 1998, 54, 263.
31. Loev, B.; Kormendy, M. J. Org. Chem. 1962, 27, 1703.
32. Ando, M.; Wada, T.; Sato, N. Org. Lett. 2006, 8, 3805.
33. Adamski-Werner, S. L.; Palaninathan, S. K.; Sacchettini, J. C.; Kelly, J. W. J. Med.
Chem. 2004, 47, 355.
34. Massah, A. R.; Adibi, H.; Khodarahmi, R.; Abiri, R.; Majnooni, M. B.; Shahidi, S.;
Asadi, B.; Mehrabib, M.; Zolfigol, M. A. Bioorg. Med. Chem. 2008, 16, 5465.
35. Narjes, F.; Koehler, K. F.; Koch, U.; Gerlach, B.; Colarusso, S.; Steinkühler, C.;
Brunetti, M.; Altamura, S.; De Francesco, R.; Matassa, V. G. Bioorg. Med. Chem.
Lett. 2002, 12, 701. and references cited therein.
solution of N-acetyl-4- or 5-bromo-2-carboxybenzenesulfonamide (16a or
16b) (1.42 g, 4.41 mmol) in MeOH (30 mL) and the mixture was refluxed for
16 h. The mixture was then concentrated in vacuo to remove excess MeOH, and
a saturated solution of aqueous Na2CO3 (25 mL) was added. After extraction
with EtOAc (3 ꢁ 30 mL), the combined organic extracts were successively
washed with water and brine, and dried (MgSO4). Filtration and then removal
of the solvent from the organic fraction in vacuo afforded the product (17a or
17b). The spectral data for compounds 17a and 17b are listed below.
4-Bromo-2-methoxycarbonylbenzenesulfonamide (17a): This compound was
obtained as a white solid in 53% yield; mp 130–132 °C; IR 3339, 3257 (NH2),
36. Dunitz, J. D.; Taylor, R. Chem. -A Eur. J. 1997, 3, 89.
1715 (CO), 1346, 1167 (SO2) cmꢀ1 1H NMR (CDCl3) d 4.00 (s, 3H, OCH3), 5.75
;
37. Howard, J. A. K.; Hoy, V. J.; O’Hagan, D.; Smith, G. T. Tetrahedron 1996, 52,
12613.
38. Chavatte, P.; Yous, S.; Marot, C.; Baurin, N.; Lesieur, D. J. Med. Chem. 2001, 44,
3223.
39. Velázquez, C.; Rao, P. N. P.; Knaus, E. E. J. Med. Chem. 2005, 48, 4061.
40. Experimental procedures and spectral data for compounds 10, 12–14, 17–22.
(br s, 2H, SO2NH2 that exchanges with D2O), 7.78 (dd, J = 8.5, 1.8 Hz, 1H, phenyl
H-5), 7.99 (d, J = 1.8 Hz, 1H, phenyl H-3), 8.00 (d, J = 8.5 Hz, 1H, phenyl H-6);
13C NMR (CDCl3) d 53.7, 127.0, 129.9, 131.3, 133.7, 135.0, 140.5, 166.6.
5-Bromo-2-methoxycarbonylbenzenesulfonamide (17b): This compound was
obtained as a white solid in 93% yield; mp 185–187 °C; IR 3346, 3255 (NH2),
1704 (CO), 1348, 1167 (SO2) cmꢀ1 1H NMR (CDCl3 + DMSO-d6) d 3.98 (s, 3H,
;
General. Melting points were determined on
a
Thomas-Hoover capillary
OCH3), 6.66 (br s, 2H, SO2NH2 that exchanges with D2O), 7.70–7.80 (m, 2H,
phenyl H-3, H-4), 8.28 (d, J = 1.2 Hz, 1H, phenyl H-6); 13C NMR (CDCl3) d 53.1,
126.0, 128.1, 131.0, 131.8, 134.6, 143.4, 166.7.
apparatus and are uncorrected. Unless otherwise noted, infrared (IR) spectra
were recorded as films on NaCl plates using a Nicolet 550 Series II Magna FT-IR
spectrometer. 1H NMR and 13C NMR spectra were measured on a Bruker AM-
300 spectrometer. Microanalyses (MicroAnalytical Service Laboratory,
Department of Chemistry, University of Alberta) were performed for C, H and
General procedure for the synthesis of methyl 4- or 5-(2-chloropyridin-4-yl)-2-
methoxybenzoate (12a–b) and 5- or 6-(2-chloropyridin-4-yl)-1,2-benzisothiazol-
3(2H)-one-1,1-dioxide (18a–b): 2-Chloropyridine-4-boronic acid (11) (0.47 g,
3 mmol) and an aryl halide (10a, 10b, 17a or 17b, 2.0 mmol) were dissolved in
THF (30 mL). Aqueous 2 M Na2CO3 (3.0 mL) and then tetrakis(triphenyl-
phosphine)palladium (70 mg, 0.06 mmol) were added. The reaction was
allowed to proceed at reflux for 16 h, cooled to 25 °C, water (150 mL) was
added, the mixture was acidified to pH 3 using 5% w/v HCl, and this mixture
was extracted with EtOAc (3 ꢁ 100 mL). The combined organic extracts were
successively washed with water (3 ꢁ 50 mL) and brine, and the organic
fraction was dried (MgSO4). Filtration and then removal of the solvent from the
organic fraction in vacuo afforded the crude product. The product 12a or 12b
was purified by silica gel column chromatography using hexanes–acetone (2:1,
v/v) as eluent. On the other hand, 5- or 6-(2-chloropyridin-4-yl)-1,2-
benzisothiazol-3(2H)-one-1,1-dioxide (18a or 18b) were purified by washing
the respective crude solid with Et2O. Some physical and spectroscopic data for
12a–b and 18a–b are listed below.
N
and were within 0.4% of theoretical values for all elements listed.
Compounds 12a–b, 13a–b, 18a–b, 19a–b, 20a–b and 21a–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. Silica gel column chromatography was performed using Merck
Silica Gel 60 ASTM (70–230 mesh). Methyl 5-iodosalicylate (9b) was
synthesized in 81% yield by esterification of 5-iodosalicylic acid with MeOH
in the presence of concd H2SO4. 2-Chloropyridine-4-boronic acid (11) was
purchased from Combi-Blocks, Inc. (San Diego, CA). N-Acetyl-4- or 5-bromo-2-
methylbenzenesulfonamide (15a or 15b) were prepared according to
a
previously reported procedure.21 Silica–sulfuric acid (SiO2–OSO2H) was
readily prepared by mixing silica gel with chlorosulfonic acid.45 All other
reagents, purchased from the Aldrich Chemical Company (Milwaukee, WI),
were used without further purification. The in vivo anti-inflammatory and
ulcerogenesis assays were carried out using protocols approved by the Health
Sciences Animal Welfare Committee at the University of Alberta.
Methyl 4-(2-chloropyridin-4-yl)-2-methoxybenzoate (12a): This compound was
obtained as a pale yellow solid in 71% yield; mp 111–113 °C; IR 1727 (CO)

6860
cmꢀ1
M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6855–6861
;
1H NMR (CDCl3) d 3.93 (s, 3H, OCH3), 4.00 (s, 3H, OCH3), 7.15 (d,
pyridone H-3), 7.12 (d, J = 1.8 Hz, 1H, phenyl H-3), 7.22 (dd, J = 7.9, 1.8 Hz, 1H,
phenyl H-5), 7.55 (d, J = 7.3 Hz, 1H, pyridone H-6), 7.73 (t, J = 60 Hz, 1H, CHF2),
7.89 (d, J = 7.9 Hz, 1H, phenyl H-6); 13C NMR (CDCl3) d 52.2, 56.2, 106.9, 107.4,
110.3, 118.3, 118.5, 121.5, 129.6, 132.4, 141.6, 152.3, 159.4, 161.0, 165.9.
J = 1.8 Hz, 1H, phenyl H-3), 7.22 (dd, J = 7.9, 1.8 Hz, 1H, phenyl H-5), 7.44 (dd,
J = 4.9, 1.2 Hz, 1H, pyridyl H-5), 7.56 (d, J = 1.2 Hz, 1H, pyridyl H-3), 7.92 (d,
J = 7.9 Hz, 1H, phenyl H-6), 8.48 (d, J = 4.9 Hz, 1H, pyridyl H-6); 13C NMR
(CDCl3) d 52.3, 56.3, 110.6, 118.9, 120.6, 121.1, 122.3, 132.6, 141.9, 150.1,
150.6, 152.3, 159.6, 166.0.
Methyl
(13b): This compound was obtained as a pale yellow solid in 61% yield; mp
125–127 °C; IR 1732, 1675 (CO) cmꢀ1 1H NMR (CDCl3) d 3.93 (s, 3H, OCH3),
5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxybenzoate
Methyl 5-(2-chloropyridin-4-yl)-2-methoxybenzoate (12b): This compound was
;
obtained as a pale yellow solid in 85% yield; mp 93–95 °C; IR 1731 (CO) cmꢀ1
;
3.98 (s, 3H, OCH3), 6.59 (dd, J = 7.3, 1.2 Hz, 1H, pyridone H-5), 6.74 (d, J = 1.2 Hz,
1H, pyridone H-3), 7.09 (d, J = 9.2 Hz, 1H, phenyl H-3), 7.52 (d, J = 7.3 Hz, 1H,
pyridone H-6), 7.72 (t, J = 60 Hz, 1H, CHF2), 7.73 (dd, J = 9.2, 2.4 Hz, 1H, phenyl
H-4), 8.07 (d, J = 2.4 Hz, 1H, phenyl H-6); 13C NMR (CDCl3) d 52.3, 56.3, 106.5,
107.5, 112.7, 116.5, 120.6, 128.1, 129.3, 130.3, 131.7, 151.5, 160.6, 161.2, 165.8.
4-(N-Difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxycarbonylbenzenesul-
fonamide (20a): This compound was obtained as a pale yellow solid in 38%
1H NMR (CDCl3) d 3.94 (s, 3H, OCH3), 3.98 (s, 3H, OCH3), 7.11 (d, J = 9.2 Hz, 1H,
phenyl H-3), 7.44 (dd, J = 4.9, 1.2 Hz, 1H, pyridyl H-5), 7.54 (d, J = 1.2 Hz, 1H,
pyridyl H-3), 7.76 (dd, J = 9.2, 2.4 Hz, 1H, phenyl H-4), 8.10 (d, J = 2.4 Hz, 1H,
phenyl H-6), 8.43 (d, J = 4.9 Hz, 1H, pyridyl H-6); 13C NMR (CDCl3) d 52.3, 56.3,
112.8, 119.8, 120.8, 121.4, 128.5, 130.4, 131.8, 149.9, 150.0, 152.2, 160.2, 166.0.
5-(2-Chloropyridin-4-yl)-1,2-benzisothiazol-3(2H)-one-1,1-dioxide (18a): This
compound was obtained as a white solid in 90% yield; mp 260–262 °C; IR
yield; mp 215–217 °C; IR 3338 (NH2), 1725, 1674 (CO) 1348, 1166 (SO2) cmꢀ1
;
3306 (NH), 1736 (CO), 1322, 1113 (SO2) cmꢀ1
;
1H NMR (CDCl3 + DMSO-d6) d
1H NMR (CDCl3 + DMSO-d6)
d
3.90 (s, 3H, OCH3), 6.67 (d, J = 7.4 Hz, 1H,
7.47 (dd, J = 4.9, 1.2 Hz, 1H, pyridyl H-5), 7.57 (d, J = 1.2 Hz, 1H, pyridyl H-3),
7.97 (d, J = 7.9 Hz, 1H, saccharinyl H-7), 8.05 (dd, J = 7.9, 1.8 Hz, 1H, saccharinyl
H-6), 8.14 (d, J = 1.8 Hz, 1H, saccharinyl H-4), 8.45 (d, J = 4.9 Hz, 1H, pyridyl H-
6); 13C NMR (CDCl3 + DMSO-d6) d 120.5, 121.4, 121.9, 126.8, 129.1, 133.2,
139.9, 142.0, 148.0, 150.0, 151.6, 160.1.
pyridone H-5), 6.76 (s, 1H, pyridone H-3), 7.11 (br s, 2H, SO2NH2 that
exchanges with D2O), 7.69 (d, J = 7.4 Hz, 1H, pyridone H-6), 7.70 (t, J = 60 Hz,
1H, CHF2), 7.89 (d, J = 8.5 Hz, 1H, phenyl H-5); 7.91 (s, 1H, phenyl H-3), 8.10 (d,
J = 8.5 Hz, 1H, phenyl H-6); 13C NMR (CDCl3 + DMSO-d6) d 52.9, 105.9, 107.5,
117.9, 127.7, 128.5, 129.3, 130.1, 130.8, 139.3, 142.6, 149.9, 160.0, 166.8.
5-(N-Difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxycarbonylbenzenesul-
fonamide (20b): This compound was obtained as a pale yellow solid in 35%
yield; mp 205–207 °C; IR 3371, 3262 (NH2), 1734, 1675 (CO) 1340, 1140 (SO2)
6-(2-Chloropyridin-4-yl)-1,2-benzisothiazol-3(2H)-one-1,1-dioxide (18b): This
compound was obtained as a white solid in 65% yield; mp >360 °C; IR 1739
(CO) 1317, 1122 (SO2) cmꢀ1 1H NMR (CDCl3 + DMSO-d6) d 7.69 (dd, J = 4.9,
;
1.2 Hz, 1H, pyridyl H-5), 7.81 (d, J = 1.2 Hz, 1H, pyridyl H-3), 8.05 (d, J = 7.9 Hz,
1H, saccharinyl H-4), 8.17 (dd, J = 7.9, 1.8 Hz, 1H, saccharinyl H-5), 8.42 (d,
J = 1.8 Hz, 1H, saccharinyl H-7), 8.46 (d, J = 4.9 Hz, 1H, pyridyl H-6); 13C NMR
(CDCl3 + DMSO-d6) d 119.6, 120.6, 122.0, 125.2, 128.0, 132.7, 140.4, 142.8,
147.7, 150.0, 151.6, 159.7.
cmꢀ1 1H NMR (CDCl3 + DMSO-d6) d 3.90 (s, 3H, OCH3), 6.65 (d, J = 7.4 Hz, 1H,
;
pyridone H-5), 6.77 (s, 1H, pyridone H-3), 7.06 (br s, 2H, SO2NH2 that
exchanges with D2O), 7.67 (d, J = 7.4 Hz, 1H, pyridone H-6), 7.68 (t, J = 60 Hz,
1H, CHF2), 7.78 (d, J = 8.0 Hz, 1H, phenyl H-3); 7.85 (d, J = 8.0 Hz, 1H, phenyl H-
4), 8.25 (s, 1H, phenyl H-6); 13C NMR (CDCl3 + DMSO-d6) d 52.7, 105.6, 107.4,
117.7, 125.8, 129.5, 129.9, 131.1, 131.5, 138.5, 142.5, 149.9, 160.0, 166.8.
General procedure for the synthesis of 4- or 5-(N-difluoromethyl-1,2-dihydropyrid-
2-one-4-yl)salicylic acid (14a–b): A solution of BBr3 (5.24 mL of a 1 M solution
General procedure for the synthesis of 4- or 5-(2-chloropyridin-4-yl)-2-
methoxycarbonylbenzenesulfonamide (19a–b): Hydrogen chloride gas was
passed into a suspension of the saccharin derivative (18a or 18b) (1.16 g,
3.94 mmol) in MeOH (100 mL) at ꢀ5 °C for 1 h. The mixture was then heated at
reflux for 1 h, the mixture was cooled to 25 °C and the excess MeOH was
removed in vacuo. A saturated solution of aqueous NaHCO3 (25 mL) was added
to the residue and the mixture was extracted with EtOAc (3 ꢁ 50 mL). The
combined organic phases were successively washed with water (50 mL) and
brine, and the organic fraction was dried (MgSO4). Filtration and then removal
of the solvent from the organic fraction in vacuo afforded the crude product
which was purified by silica gel column chromatography using hexanes–ethyl
acetate (1:3, v/v) as eluent to furnish the respective title compound 19a or 19b.
Some physical and spectroscopic data for 19a–b are listed below.
in CH2Cl2, 5.24 mmol) was added to
difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxybenzoate
a
solution of
a
methyl 4- or 5-(N-
(13a–b)
(0.81 g, 2.62 mmol) in CH2Cl2 (15 mL) at ꢀ78 °C with stirring for 1 h under
argon. The mixture was then warmed to 25 °C, the mixture was stirred for
another 16 h, quenched with water (50 mL), and the mixture was extracted
with CH2Cl2 (3 ꢁ 25 mL). The combined CH2Cl2 extracts were successively
washed with water (50 mL) and brine, and the organic fraction was dried
(MgSO4). Filtration and then removal of the solvent from the organic fraction in
vacuo afforded the respective product 14a or 14b. The spectral and
microanalytical data for compounds 14a and 14b are listed below.
4-(2-Chloropyridin-4-yl)-2-methoxycarbonylbenzenesulfonamide (19a): This
compound was obtained as a white solid in 80% yield; mp 138–140 °C; IR
4-(N-Difluoromethyl-1,2-dihydropyrid-2-one-4-yl)salicylic acid (14a): This
compound was obtained as a white solid in 100% yield; mp 255–257 °C; IR
3359, 3273 (NH2), 1724 (CO), 1349, 1169 (SO2) cmꢀ1
;
1H NMR (CDCl3) d 4.06 (s,
1679 (CO) cmꢀ1 1H NMR (CDCl3 + DMSO-d6) d 6.54 (dd, J = 7.3, 1.8 Hz, 1H,
;
3H, OCH3), 5.81 (br s, 2H, SO2NH2 that exchanges with D2O), 7.47 (dd, J = 4.9,
1.2 Hz, 1H, pyridyl H-5), 7.59 (d, J = 1.2 Hz, 1H, pyridyl H-3), 7.89 (dd, J = 8.0,
1.9 Hz, 1H, phenyl H-5), 8.09 (d, J = 1.9 Hz, 1H, phenyl H-3), 8.30 (d, J = 8.0 Hz,
1H, phenyl H-6), 8.54 (d, J = 4.9 Hz, 1H, pyridyl H-6); 13C NMR (CDCl3) d 53.3,
120.1, 121.8, 129.0, 129.1, 129.9, 130.5, 140.5, 142.0, 148.1, 150.1, 152.2, 166.8.
4-(2-Chloropyridin-4-yl)-2-methoxycarbonylbenzenesulfonamide (19a): This
compound was obtained as a white solid in 80% yield; mp 138–140 °C; IR
pyridone H-5), 6.65 (d, J = 1.8 Hz, 1H, pyridone H-3), 7.01 (dd, J = 8.5, 1.8 Hz,
1H, phenyl H-5), 7.07 (d, J = 1.8 Hz, 1H, phenyl H-3), 7.52 (d, J = 7.3 Hz, 1H,
pyridone H-6), 7.63 (t, J = 60 Hz, 1H, CHF2), 7.87 (d, J = 8.5 Hz, 1H, phenyl H-6),
11.32 (br s, 1H, COOH that exchanges with D2O); 13C NMR (CDCl3) d 106.0,
106.8, 113.4, 114.6, 116.4, 117.3, 128.9, 130.5, 142.2, 151.2, 160.1, 161.2, 171.2.
Anal. Calcd for C13H9F2NO4: C, 55.52; H, 3.23; N, 4.98. Found: C, 55.83; H, 3.44;
N, 4.89.
3359, 3273 (NH2), 1724 (CO), 1349, 1169 (SO2) cmꢀ1
;
1H NMR (CDCl3) d 4.06 (s,
5-(N-Difluoromethyl-1,2-dihydropyrid-2-one-4-yl)salicylic acid (14b): This
compound was obtained as a white solid in 100% yield; mp 258–260 °C; IR
3H, OCH3), 5.81 (br s, 2H, SO2NH2 that exchanges with D2O), 7.47 (dd, J = 4.9,
1.2 Hz, 1H, pyridyl H-5), 7.59 (d, J = 1.2 Hz, 1H, pyridyl H-3), 7.89 (dd, J = 8.0,
1.9 Hz, 1H, phenyl H-5), 8.09 (d, J = 1.9 Hz, 1H, phenyl H-3), 8.30 (d, J = 8.0 Hz,
1H, phenyl H-6), 8.54 (d, J = 4.9 Hz, 1H, pyridyl H-6); 13C NMR (CDCl3) d 53.3,
120.1, 121.8, 129.0, 129.1, 129.9, 130.5, 140.5, 142.0, 148.1, 150.1, 152.2, 166.8.
5-(2-Chloropyridin-4-yl)-2-methoxycarbonylbenzenesulfonamide (19b): This
compound was obtained as a white solid in 81% yield; mp 180–182 °C; IR
1677 (CO) cmꢀ1 1H NMR (CDCl3 + DMSO-d6) d 6.55 (dd, J = 7.9, 1.8 Hz, 1H,
;
pyridone H-5), 6.61 (d, J = 1.8 Hz, 1H, pyridone H-3), 6.97 (d, J = 9.2 Hz, 1H,
phenyl H-3), 7.48 (d, J = 7.9 Hz, 1H, pyridone H-6), 7.63 (t, J = 60 Hz, 1H, CHF2),
7.64 (dd, J = 9.2, 2.4 Hz, 1H, phenyl H-4), 8.07 (d, J = 2.4 Hz, 1H, phenyl H-6),
11.50 (br s, 1H, COOH that exchanges with D2O); 13C NMR (CDCl3) d 104.9,
106.3, 112.1, 114.1, 116.9, 125.4, 127.6, 128.3, 132.1, 150.2, 159.4, 161.9, 170.5.
Anal. Calcd for C13H9F2NO4: C, 55.52; H, 3.23; N, 4.98. Found: C, 55.53; H, 3.34;
N, 4.87.
General procedure for the synthesis of N-acetyl-4- or 5-(N-difluoromethyl-1,2-
dihydropyrid-2-one-4-yl)-2-methoxycarbonylbenzenesulfonamide (21a–b): Acetyl
chloride (0.14 mL, 2 mmol), and then SiO2–OSO3H (8 mg), was added to a
solution of a 4- or 5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-metho-
xycarbonylbenzenesulfonamide (20a or 20b, 0.36 g, 1 mmol) in CHCl3 (10 mL)
and CH3CN (3 mL). The reaction was allowed to proceed at reflux for 16 h under
argon. The mixture was filtered and the solvent was removed in vacuo. The
crude residue was purified by silica gel column chromatography using
hexanes–ethyl acetate (1:2, v/v), and then ethyl acetate, as eluent to furnish
the respective title product 21a or 21b. Some physical and spectroscopic data
for 21a–b are listed below.
1716 (CO), 1363, 1122 (SO2) cmꢀ1 1H NMR (CDCl3 + DMSO-d6) d 3.91 (s, 3H,
;
OCH3), 6.94 (br s, 2H, SO2NH2 that exchanges with D2O), 7.50 (dd, J = 5.5,
1.2 Hz, 1H, pyridyl H-5), 7.59 (d, J = 1.2 Hz, 1H, pyridyl H-3), 7.80–7.90 (m, 2H,
phenyl H-3, H-4), 8.28 (s, 1H, phenyl H-6), 8.43 (d, J = 5.5 Hz, 1H, pyridyl H-6);
13C NMR (CDCl3 + DMSO-d6) d 52.8, 120.3, 121.6, 126.2, 129.9, 130.0 130.8,
138.8, 142.6, 148.3, 150.1, 151.6, 167.0.
General procedure for the synthesis of methyl 4- or 5-(N-difluoromethyl-1,2-
dihydropyrid-2-one-4-yl)-2-methoxybenzoates (13a–b), or 4- or 5-(N-difluoro-
methyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxycarbonylbenzenesulfonamides
(20a–b): FSO2CF2CO2H (1.92 g, 10.84 mmol), and then NaHCO3 (0.30 g,
3.60 mmol), was added to a solution of a methyl 4- or 5-(2-chloropyridin-4-
yl)-2-methoxybenzoate (12a or 12b) (1.0 g, 3.60 mmol), or 4- or 5-(2-
chloropyridin-4-yl)-2-methoxycarbonylbenzenesulfonamide (19a or 19b)
(1.18 g, 3.60 mmol) in acetonitrile (25 mL). The mixture was then heated at
reflux under argon for 16 h, cooled to 25 °C, a saturated solution of aqueous
NaHCO3 (25 mL) was added, and the mixture was extracted with CHCl3
(3 ꢁ 30 mL). The combined organic extracts were successively washed with
10 N HCl (30 mL) to remove some unreacted starting material, water (50 mL)
and brine, and the organic fraction was dried (MgSO4). Filtration and then
removal of the solvent from the organic fraction in vacuo afforded the
respective title product (13a–b, 20a–b). Some physical and spectroscopic data
for 13a–b and 20a–b are listed below.
N-Acetyl-4-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxycarbonylben-
zenesulfonamide (21a): This compound was obtained as a pale yellow solid in
13% yield; mp 218–220 °C; IR 1715, 1670 (CO) 1362, 1166 (SO2) cmꢀ1 1H NMR
;
(CDCl3 + DMSO-d6) d 2.15 (s, 3H, COCH3), 4.00 (s, 3H, OCH3), 6.56 (dd, J = 7.3,
1.8 Hz, 1H, pyridone H-5), 6.82 (d, J = 1.8 Hz, 1H, pyridone H-3), 7.60 (d,
J = 7.3 Hz, 1H, pyridone H-6), 7.72 (t, J = 60 Hz, 1H, CHF2), 7.85 (dd, J = 8.6,
1.8 Hz, 1H, phenyl H-5); 7.98 (d, J = 1.8 Hz, 1H, phenyl H-3), 8.42 (d, J = 8.6 Hz,
1H, phenyl H-6), 9.00 (br s, 1H, NH that exchanges with D2O); 13C NMR (DMSO-
d6) d 23.2, 53.3, 105.8, 107.5, 117.8, 128.9, 129.8, 131.4, 132.1, 133.0, 137.0,
137.8, 149.8, 160.0, 166.3, 169.0.
Methyl
(13a): This compound was obtained as a pale yellow solid in 54% yield; mp
75–77 °C; IR 1729, 1678 (CO) cmꢀ1 1H NMR (CDCl3) d 3.92 (s, 3H, OCH3), 3.97
(s, 3H, OCH3), 6.57 (dd, J = 7.3, 1.2 Hz, 1H, pyridone H-5), 6.77 (d, J = 1.2 Hz, 1H,
4-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxybenzoate
N-Acetyl-5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-methoxycarbonyl
benzenesulfonamide (21b): This compound was obtained as a pale yellow solid
;
in 57% yield; mp 225–227 °C; IR 1715, 1670 (CO) 1362, 1166 (SO2) cmꢀ1 1H
;

M. A. Chowdhury et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6855–6861
NMR (CDCl3 + DMSO-d6) d 1.96 (s, 3H, COCH3), 3.90 (s, 3H, OCH3), 6.58 (dd, Arbor, MI, USA) (IC50 values,
6861
l
M) were determined using an enzyme immuno
J = 7.3, 1.8 Hz, 1H, pyridone H-5), 6.73 (d, J = 1.8 Hz, 1H, pyridone H-3), 7.55 (d,
J = 7.3 Hz, 1H, pyridone H-6), 7.63 (t, J = 60 Hz, 1H, CHF2), 7.68 (d, J = 8.0 Hz, 1H,
phenyl H-3); 7.80 (dd, J = 8.0, 1.8 Hz, 1H, phenyl H-4), 8.40 (d, J = 1.8 Hz, 1H,
phenyl H-6), 11.70 (br s, 1H, NH that exchanges with D2O); 13C NMR
assay (EIA) kit (Catalog No. 760700, Cayman Chemical, Ann Arbor, MI, USA)
according to our previously reported method.47
42. 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, lM)
(CDCl3 + DMSO-d6)
132.6, 137.3, 138.0, 149.8, 159.9, 165.9, 168.5.
d
22.9, 52.7, 105.8, 107.5, 117.9, 129.5, 129.8, 130.9,
were determined using an enzyme immuno assay (EIA) kit (Catalog No.
560131, Cayman Chemical, Ann Arbor, MI, USA) according to our previously
reported method.48
General procedure for the synthesis of N-acetyl-4- or 5-(N-difluoromethyl-1,2-
dihydropyrid-2-one-4-yl)-2-carboxybenzenesulfonamide (22a–b): Aqueous LiOH
(2 M, 5 mL) was added to a solution of N-acetyl-4- or 5-(N-difluoromethyl-1,2-
dihydropyrid-2-one-4-yl)-2-methoxycarbonylbenzenesulfonamide (21a or
21b, 0.30 g, 0.75 mmol) in MeOH (5 mL) and THF (5 mL), and the reaction
was allowed to proceed at reflux for 1 h. The mixture was cooled to 25 °C, and
acidified to pH 3 using 5% HCl prior to extraction with EtOAc (3 ꢁ 25 mL). The
combined organic extracts were successively washed with water (50 mL) and
brine, and the organic fraction was dried (MgSO4). Filtration and then removal
of the solvent from the organic fraction in vacuo afforded the respective
product 22a or 22b. The spectral and microanalytical data for compounds 22a
and 22b are listed below.
43. Anti-inflammatory assay: The test compounds 14a–b, 22a–b, and the reference
drugs ibuprofen, aspirin and diflunisal were evaluated using the in vivo
carrageenan-induced rat foot paw edema model reported previously.49
44. Acute ulcerogenesis assay: The ability of the test compounds 14a–b to produce
gastric damage (lesions) was evaluated according to reported procedures.50–53
Ulcerogenic activity was evaluated after oral administration of 14a or 14b
(1.38 mmol/kg) at an equimolar to that used for the reference drug aspirin
(1.38 mmol/kg). All drugs were suspended and administered in
a 1%
methylcellulose solution. Food, but not water, was removed 24 h before
administration of test compounds. Six hours after oral administration of the
drug, rats were euthanized in
a CO2 chamber, and their stomachs were
N-Acetyl-4-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-carboxybenzenesul-
removed, cut out along the greater curvature of the stomach, gently rinsed
with water, and placed on ice. The number and the length of ulcers observed in
each stomach were determined by using magnifier lenses. In this assay, the
severity of each gastric lesion is measured along its greatest length (1 mm,
rating of 1; 1–2 mm, rating of 2; and >2 mm, rating according to their length in
millimeter). The UI for each test compound is calculated by adding the total
length (L, in mm) of individual gastric lesions in each stomach and averaging
over the number of animals in each group (n = 4): UI = (L1 + L2 + L3 + L4)/4.
45. Zolfigol, M. A. Tetrahedron 2001, 57, 9509.
fonamide (22a): This compound was obtained as a white solid in 72% yield; mp
210–212 °C; IR 1723, 1672 (CO), 1350, 1169 (SO2) cmꢀ1 1H NMR (CDCl3) d 1.97
;
(s, 3H, COCH3), 6.55 (dd, J = 7.9, 1.8 Hz, 1H, pyridone H-5), 6.69 (d, J = 1.8 Hz, 1H,
pyridone H-3), 7.57 (d, J = 7.9 Hz, 1H, pyridone H-6), 7.64 (t, J = 60 Hz, 1H,
CHF2), 7.73 (dd, J = 8.0, 1.9 Hz, 1H, phenyl H-5); 7.82 (d, J = 1.9 Hz, 1H, phenyl H-
3), 8.24 (d, J = 8.0 Hz, 1H, phenyl H-6), 11.60 (br s, 1H, COOH that exchanges
with D2O); 13C NMR (CDCl3 + DMSO-d6) d 22.8, 105.6, 106.7, 118.0, 127.0, 127.4,
129.5, 131.4, 133.8, 137.2, 140.3, 149.8, 159.8, 166.9, 168.5. Anal. Calcd for
C15H12F2N2O6Sꢂ3/7H2O: C, 45.72; H, 3.29; N, 7.11. Found: C, 46.09; H, 3.67; N,
6.55.
46. Deng, B.-L.; Hartman, T. L.; Buckheit, R. W.; Pannecouque, C.; De Clercq, E.;
Fanwick, P. E.; Cushman, M. J. Med. Chem. 2005, 48, 6140.
N-Acetyl-5-(N-difluoromethyl-1,2-dihydropyrid-2-one-4-yl)-2-carboxybenzenesul-
fonamide (22b): This compound was obtained as a white solid in 79% yield; mp
47. Chowdhury, M. A.; Abdellatif, K. R. A.; Dong, Y.; Das, D.; Suresh, M. R.; Knaus, E.
E. Bioorg. Med. Chem. Lett. 2008, 18, 6138.
48. Rao, P. N. P.; Amini, M.; Li, H.; Habeeb, A.; Knaus, E. E. J. Med. Chem. 2003, 46, 4872.
49. Winter, C. A.; Risley, E. A.; Nuss, G. W. Proc. Soc. Exp. Biol. Med. 1962, 111, 544.
50. Cocco, M. T.; Congiu, C.; Onnis, V.; Morelli, M.; Cauli, O. Eur. J. Med. Chem. 2003,
38, 513.
51. Cocco, M. T.; Congiu, C.; Onnis, V.; Morelli, M.; Felipo, V.; Cauli, O. Bioorg. Med.
Chem. 2004, 12, 4169.
52. Süleyman, H.; Akçay, F.; Altinkaynak, K. Pharmacol. Res. 2002, 45, 155.
53. Verma, M.; Sinha, J. N.; Gujrati, V. R.; Bhalla, T. N.; Bhargava, K. P.; Shanker, K.
Pharmacol. Res. Commun. 1981, 13, 967.
230–233 °C; IR 1723, 1675 (CO), 1352, 1152 (SO2) cmꢀ1
;
1H NMR
(CDCl3 + DMSO-d6) d 1.94 (s, 3H, COCH3), 6.61 (d, J = 7.3 Hz, 1H, pyridone H-
5), 6.72 (s, 1H, pyridone H-3), 7.61 (d, J = 7.3 Hz, 1H, pyridone H-6), 7.65 (t,
J = 60 Hz, 1H, CHF2), 7.72 (d, J = 8.5 Hz, 1H, phenyl H-3); 7.84 (d, J = 8.5 Hz, 1H,
phenyl H-4), 8.33 (s, 1H, phenyl H-6), 11.70 (br s, 1H, COOH that exchanges
with D2O); 13C NMR (CDCl3 + DMSO-d6) d 22.4, 105.3, 106.5, 117.2, 128.6, 128.9,
129.2, 130.1, 133.7, 136.5, 136.9, 149.5, 159.5, 166.5, 168.1. Anal. Calcd for
C15H12F2N2O6Sꢂ1/18H2O: C, 46.51; H, 3.16; N, 7.23. Found: C, 46.85; H, 3.44; N,
6.84.
41. 5-Lipoxygenase inhibition assay: The ability of the test compounds listed in
Table 1 to inhibit potato 5-LOX (Catalog No. 60401, Cayman Chemical, Ann