Synthesis of phenylacetic acid regioisomers possessing an N-substituted 1,2-dihydropyrid-2-one pharmacophore - Evaluation as inhibitors of cyclooxygenases and 5-lipoxygenase

Article abstract of DOI:10.1139/v11-048

The Suzuki-Miyaura cross-coupling reaction provides a useful method for the synthesis of methyl 2-(2-chloropyridyl or 2-methoxypyridyl)phenylacetates. The 2-chloropyridyl or 2-methoxypyridyl ring system can be readily elaborated to N-substituted (OH, Me, CHF₂, H) 1,2-dihydropyrid-2-one ring systems that are useful synthons for use in bioorganic and medicinal chemistry applications.

Full text of DOI:10.1139/v11-048

617
Synthesis of phenylacetic acid regioisomers
possessing an N-substituted 1,2-dihydropyrid-2-
one pharmacophore — Evaluation as inhibitors of
cyclooxygenases and 5-lipoxygenase
Gang Yu, Morshed A. Chowdhury, Zhangjian Huang, Khaled R. A. Abdellatif, and
Edward E. Knaus
Abstract: The Suzuki–Miyaura cross-coupling reaction provides a useful method for the synthesis of methyl 2-(2-chloropyridyl
or 2-methoxypyridyl)phenylacetates. The 2-chloropyridyl or 2-methoxypyridyl ring system can be readily elaborated to
N-substituted (OH, Me, CHF2, H) 1,2-dihydropyrid-2-one ring systems that are useful synthons for use in bioorganic
and medicinal chemistry applications.
Key words: Suzuki–Miyaura cross-coupling reaction, 1,2-dihydropyrid-2-ones, cyclooxygenase (COX) and 5-lipoxygenase
(5-LOX) inhibition.
Résumé : La réaction de couplage croisé de Suzuki–Miyaura est une méthode utile pour la synthèse d’esters 2-(2-chloropyri-
dyl)- ou de 2-(méthoxypyridyl)phénylacétates. Ce système cyclique, portant des groupes 2-chloropyridyle ou 2-méthoxypyridyle,
peut facilement être transformé en systèmes cycliques à base de 1,2-dihydropyrid-2-one N-substituée (OH, Me, CHF2,
H), des synthons utiles dans des applications de chimie bioorganique ou médicinale.
Mots‐clés : réaction de couplage croisé de Suzuki–Miyaura, 1,2-dihydropyrid-2-ones, inhibition de la cycclooxygénase
(COX) et de la 5-lipoxygénase (5-LOX).
[Traduit par la Rédaction]
a group of arylacetic acids possessing an N-substituted (OH,
Me, CHF2, H) 1,2-dihydropyrid-2-one moiety, and their evalu-
ation as inhibitors of the COX-1, COX-2, and 5-LOX en-
zymes.
Introduction
Biotransformation of arachidonic acid gives rise to prosta-
glandin and leukotriene inflammatory mediators that are
produced via their respective cyclooxygenase (COX) and
lipoxygenase (LOX) pathways.1 Dual inhibition of the LOX
and COX enzymatic pathways2 provides a rational approach
for the design of superior anti-inflammatory agents with a
better safety profile relative to ulcerogenic nonsteroidal anti-
inflammatory drugs (NSAIDs) or selective COX-2 inhibitors
that increase the incidence of adverse cardiovascular throm-
botic effects.3,4 The most successful effort to develop 5-LOX
inhibitors was focused on N-hydroxyureas such as zileuton
(1, see structure in Fig. 1), which is believed to chelate iron
present in the 5-LOX enzyme.5,6 In earlier studies, we
showed that linear acetylenes possessing cyclic hydroxamic
acid, N-hydroxy-1,2-dihydropyrid-2-one (2),7 or N-difluoro-
methyl-1,2-dihydropyrid-2-one (3,8 49) 5-LOX pharmaco-
phores exhibited dual COX and 5-LOX inhibitory activities.
In a continuation of our ongoing program to design novel
anti-inflammatory agents and acquire additional structure–
activity relationship data, we now describe the synthesis of
Results and discussion
Reaction of methyl 2-iodophenylacetate (5)9 with a 4- or
5-pyridineboronic acid (6a–6c) using a Suzuki–Miyaura10,11
cross-coupling reaction in the presence of the tetrakis(triphe-
nylphosphine)palladium (0) catalyst and 2 mol/L aqueous so-
dium carbonate furnished the respective diaryl products 7a–
7c in good yields (58%–77%) (Scheme 1). Oxidation of 7a
and 7c using m-chloroperbenzoic acid (m-CPBA) in dichloro-
methane afforded the target methyl 2-(1-oxido-2-chloropyri-
din-4-yl)phenylacetate (8a, 42%) or methyl 2-(1-oxido-2-
methoxypyridin-5-yl)phenylacetate (8c, 59%). Hydrolysis of
the methyl ester 8a using 2 N sodium hydroxide at reflux
for 24 h afforded the target phenylacetic acid product 9a in
41% yield. Reaction of the N-oxide 8c with acetyl chloride
at reflux, and then methanolysis, afforded the N-hydroxy-
1,2-dihydropyrid-2-one 9c in 96% yield.12 Subsequent depro-
Received 3 November 2010. Accepted 22 February 2011. Published at www.nrcresearchpress.com/cjc on 3 May 2011.
G. Yu,* M.A. Chowdhury, Z. Huang, K.R.A. Abdellatif, and E.E. Knaus. Faculty of Pharmacy and Pharmaceutical Sciences,
University of Alberta, Edmonton, AB T6G 2N8, Canada.
Corresponding author: Edward E. Knaus (e-mail: eknaus@pharmacy.ualberta.ca).
*Present address: Jiangsu Academy Agricultural Sciences, Nanjing, Jiangsu, 210014, China.
Can. J. Chem. 89: 617–622 (2011)
doi:10.1139/V11-048
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Can. J. Chem. Vol. 89, 2011
Fig. 1. Structures of the iron-chelating 5-LOX inhibitor zileuton (1)
and dual inhibitors of the COX and LOX enzymes that possess an
N-hydroxy-1,2-dihydropyrid-2-one (2) or N-difluoromethyl-1,2-di-
hydropyrid-2-one (3, 4) 5-LOX pharmacophore.
Scheme 1. Synthesis of N-hydroxy-1,2-dihydropyrid-2-one deriva-
tives of phenylacetic acid. Reagents and conditions: (a) Pd(PPh3)4,
2 mol/L Na2CO3 (6a and 6b, reflux in THF for 16 h; 6c, reflux in
1,4-dioxane for 4 h); (b) m-CPBA, CH2Cl2, 25 °C, 48 h; (c) 2 N
NaOH, reflux, 24 h (8a); (d) (i) AcCl, reflux, 1 h, (ii) MeOH, 25 °C,
16 h (8c); (e) 2 N LiOH, MeOH–THF–H2O (1:1:1, v/v/v), reflux,
3 h.
HO
NH2
3 SO2NH2
2
N
4
O
O
C C
S
N
HO
1
2
R1
R1
CO2H
O
N
4
CO2H
5
3
2
F2HC
O
N
3
4
CHF2
3, R1 = H, Me
4, R1 = H, Me
tection of the methyl ester group present in 9c using lithium
hydroxide in MeOH and tetrahydrofuran (THF) at reflux
temperature afforded the target phenylacetic acid product
10c in 74% yield.
The 2-chloropyridine compounds 7a and 7b were con-
verted to their respective N-methylpyridinium methylsulfate
salts (11a and 11b) upon reaction with dimethyl sulfate at re-
flux in acetonitrile (see Scheme 2).13 Subsequent treatment of
the salts 11a and 11b with 2 N aqueous lithium hydroxide at
reflux proceeded smoothly, resulting in simultaneous hydrol-
ysis of the methyl ester and conversion of the N-methyl-2-
chloropyridinium ring to an N-methyl-1,2-dihydropyrid-2-
one ring, to furnish the corresponding target products 12a
and 12b in 70%–89% yield.14 Alternatively, reaction of the
2-chloropyridyl compound 7b with FSO2CF2CO2H15 in the
presence of NaHCO3 afforded the N-difluoromethyl-1,2-dihy-
dropyrid-2-one product 13 in 53% yield. Selective hydrolysis
of the methyl ester group in 13 using 2 N LiOH in a MeOH–
THF–H2O (1:1:1, v/v/v) solvent system afforded the phenyl-
acetic acid product 14.14 In contrast, hydrolysis of 13 under
more basic reaction conditions using aqueous 2 N NaOH
and a longer reaction time of 5 h resulted in concomitant
cleavage of the methyl ester substituent and removal of the
N-difluoromethyl substituent to afford 2-(2-oxo-1,2-dihydro-
pyridin-5-yl)phenylacetic acid (15) in 65% yield.
The N-hydroxy-1,2-dihydropyrid-2-one cyclic hydroxamic
acid mimetics 9a and 10c were designed with the expecta-
tion7 that they would act as iron chelators to inhibit the 5-
LOX enzyme. Although the C-5 regioisomer 10c did exhibit
weak COX-2 inhibition (IC50 = 10.1 µmol/L), 9a and 10c
were both inactive as inhibitors of the 5-LOX enzyme (see
data in Table 1). Similar enzyme inhibition studies showed
that the C-4 (12a) and C-5 (12b) N-methyl-1,2-dihydropyrid-
2-one regioisomers were inactive as inhibitors of the 5-LOX
and COX-2 enzymes (IC50 > 100 µmol/L), but the C-4 re-
gioisomer 12a exhibited weak inhibition (IC50 = 52.4 µmol/L)
of the COX-1 enzyme. In spite of its weak in vitro COX-1
inhibitory activity, 12a showed good in vivo anti-inflamma-
tory activity in a rat model, where a 45% reduction in inflam-
mation was observed for a 100 mg/kg oral dose relative to
the reference drug ibuprofen, which furnished a 50% reduc-
tion in inflammation for a 67 mg/kg oral dose. The struc-
turally related N-difluoromethyl-1,2-dihydropyrid-2-one 14
and 1,2-dihydropyrid-2-one 15 compounds, which failed to in-
hibit the COX-1 and 5-LOX enzymes (IC50 > 100 µmol/L),
showed weak inhibition of the COX-2 enzyme relative to the
reference drugs aspirin and ibuprofen. In view of their weak
COX-2 inhibitory potency and failure to inhibit 5-LOX, the
anti-inflammatory activities for 14 and 15 were not determined.
These enzyme inhibition structure–activity data show that none
of the compounds investigated in this study exhibited the de-
sired dual inhibition of the COX-2 and 5-LOX enzymes.
Conclusion
The Suzuki–Miyaura cross-coupling reaction of methyl
2-iodophenylacetate with a 2-chloro- or 2-methoxypyridine-
Published by NRC Research Press

Yu et al.
619
Scheme 2. Synthesis of N-substituted (Me, CHF2, H) 1,2-dihydropyrid-2-one derivatives of phenylacetic acid. Reagents and conditions: (a)
Me2SO4, MeCN, reflux, 6 h; (b) 2 N LiOH, MeOH–THF–H2O (1:1:1, v/v/v), reflux, 2 h; (c) FSO2CF2CO2H, MeCN, NaHCO3, reflux under
argon, 12 h; (d) 2 N NaOH, reflux, 5 h.
Table 1. In vitro COX-1, COX-2, and 5-LOX enzyme inhibition
data for N-substituted (OH, Me, CHF2, H) 1,2-dihydropyrid-2-one
Experimental
derivatives of phenylacetic acid.
Instrumentation, analysis, and starting material
Melting points were determined on a Thomas Hoover
capillary apparatus and are uncorrected. IR spectra were re-
corded as films on NaCl plates using a Nicolet 550 Series II
COX-1 IC50
(µmol/L)a
—
>100
52.4
>100
>100
>100
0.2
COX-2 IC50
(µmol/L)a
—
5-LOX IC50
(µmol/L)b
Entry
Compound
9a
10c
12a
12b
14
15
Aspirin
Ibuprofen
Zileuton
1
2
3
4
5
6
7
8
9
>100
>100
>100
>100
>100
>100
—
1
Magna FT–IR spectrometer. H NMR spectra were measured
10.1
>100
>100
187
18.2
2.4c
1.1c
—
on a Bruker AM-300 spectrometer in CDCl3 or DMSO-d6
with TMS as the internal standard. Compounds 7–8, 9c, 10c,
11, and 13 showed a single spot on Macherey–Nagel Poly-
gram Sil G/UV254 silica gel plates (0.2 mm) using a low,
medium, or highly polar solvent system; no residue remained
after combustion, indicative of high purity. Microanalyses for
all other compounds were performed for C, H, and N (Micro
Analytical Service Laboratory, Department of Chemistry,
University of Alberta) and were within 0.4% of theoretical
values. Silica gel column chromatography was performed us-
ing Merck silica gel 60 ASTM (70–230 mesh). All reagents
were purchased from the Sigma-Aldrich Chemical Company
(Milwaukee, Wisconsin), with the exception of 2-chloropyri-
dine-4-boronic acid, purchased from Combi-Blocks Inc., and
were used without further purification.
2.9
—
—
1.1
aThe in vitro test compound concentration required to produce 50% in-
hibition of ovine COX-1 or human recombinant COX-2. The result (IC50,
µmol/L) is the mean of two determinations acquired using an enzyme im-
munoassay kit (catalog No. 560131, Cayman Chemicals Inc., Ann Arbor,
Michigan), and the deviation from the mean is <10% of the mean value.
bThe in vitro test compound concentration required to produce 50% in-
hibition of potato 5-LOX (Cayman Chemicals Inc. catalog No. 60401).
The result (IC50, µmol/L) is the mean of two determinations acquired using
a LOX assay kit (catalog No. 760700, Cayman Chemicals Inc.), and the
deviation from the mean is <10% of the mean value.
cData taken from a previous report (ref. 16). COX-2 inhibition was de-
termined using ovine COX-2.
General Suzuki–Miyaura cross-coupling synthesis of 7a–7c
Methyl 2-iodophenylacetate (5, 1.20 g, 4.35 mmol) and a
pyridineboronic acid (6a–6c, 4.35 mmol) were dissolved in a
polar solvent (THF, 50 mL for 6a and 6b or 1,4-dioxane,
50 mL for 6c). Aqueous 2 mol/L Na2CO3 (6.5 mL,
13.05 mmol) and then Pd(PPh3)4 (115 mg, 0.10 mmol) were
added. The reaction was allowed to proceed at reflux under
argon (16 h for 6a and 6b and 4 h for 6c) and then cooled
to 25 °C; water (50 mL) was added, and the mixture was ex-
tracted with EtOAc (3 × 50 mL). The combined EtOAc
extracts were washed with water (2 × 30 mL), the organic
boronic acid provides a useful method for the synthesis of
methyl 2-(pyridinyl)phenylacetates. The 2-chloropyridyl and
2-methoxypyridyl ring systems present in this group of com-
pounds can be readily elaborated to N-hydroxy-1,2-dihydro-
pyrid-2-one (a cyclic hydroxamic acid), N-methyl-1,2-
dihydropyrid-2-one, and 1,2-dihydropyrid-2-one ring systems
that may serve as useful synthons in bioorganic and medici-
nal chemistry applications.
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Can. J. Chem. Vol. 89, 2011
fraction was dried (MgSO4), and the solvent was removed in
vacuo. The residue obtained was purified by silica gel col-
umn chromatography using hexanes–EtOAc (3:1, v/v) as elu-
ent to afford the respective products 7a–7c. Some
spectroscopic data for 7a–7c are listed below.
Methyl 2-(1-oxido-2-methoxypyridin-5-yl)phenylacetate (8c)
Yield, 59%; pale yellow oil. IR (film): 2961, 1740, 1438,
1
1257 cm–1. H NMR (CDCl3) d: 3.58 (s, 2H, CH2), 3.67 (s,
3H, OMe), 4.14 (s, 3H, pyridyl-OMe), 6.96 (d, J = 8.5 Hz,
1H, pyridyl H-3), 7.23–7.39 (overlapping multiplets, 4H to-
tal, phenyl H-3, H-4, H-5, H-6), 7.32 (dd, J = 8.5, 1.8 Hz,
1H, pyridyl H-4), 8.29 (d, J = 1.8 Hz, 1H, pyridyl H-6). 13C
NMR (CDCl3) d: 38.5, 52.2, 57.4, 107.3, 127.7, 128.8,
129.0, 130.1, 130.8, 132.1, 136.0, 139.9, 157.8, 171.6.
Methyl 2-(2-chloropyridin-4-yl)phenylacetate (7a)
Yield, 74%; yellow oil. IR (film): 2920, 1736, 1536 cm–1.
1H NMR (CDCl3) d: 3.72 (s, 2H, CH2), 3.73 (s, 3H, OMe),
7.39–7.55 (overlapping multiplets, 6H total, phenyl H-3,
H-4, H-5, H-6, pyridyl H-3, H-5), 8.44 (d, J = 5.5 Hz, 1H,
pyridyl H-6). 13C NMR (CDCl3) d: 41.0, 52.2, 120.5, 122.1,
125.8, 128.0, 129.5, 130.6, 135.1, 137.2, 150.0, 151.2, 152.2,
171.5.
2-(1-Hydroxy-2-oxo-1,2-dihydropridin-4-yl)phenylacetic
acid (9a)
A mixture of methyl 2-(1-oxido-2-chloropyridin-4-yl)phe-
nylacetate (8a, 0.75 mmol) and 2 N NaOH (3.0 mL,
6.0 mmol) was refluxed for 24 h. The reaction mixture was
cooled to 25 °C and washed with CH2Cl2 (30 mL). The
water phase was then acidified to pH 2 by addition of 3 N
hydrochloric acid prior to extraction with EtOAc (3 ×
50 mL). The combined EtOAc extracts were washed with
water and then brine, the organic fraction was dried
(MgSO4), and the solvent was removed in vacuo. The crude
product was purified by flash silica gel column chromatogra-
phy using EtOAc–MeOH (9:1, v/v) as eluent to furnish 9a in
a 41% yield as an off-white solid, mp >335 °C. IR (film):
Methyl 2-(2-chloropyridin-5-yl)phenylacetate (7b)
Yield, 58%; pale yellow oil. IR (film): 2918, 1734,
1
1590 cm–1. H NMR (CDCl3) d: 3.56 (s, 2H, CH2), 3.64 (s,
3H, OMe), 7.24 (d, J = 6.1 Hz, 1H, phenyl H-6), 7.36–7.41
(overlapping multiplets, 3H, phenyl H-3, H-4, H-5), 7.37 (d,
J = 8.5 Hz, 1H, pyridyl H-3), 7.68 (dd, J = 8.5, 2.4 Hz, 1H,
pyridyl H-4), 8.37 (d, J = 2.4 Hz, 1H, pyridyl H-6). 13C
NMR (CDCl3) d: 38.6, 52.1, 123.7, 127.6, 128.7, 130.3,
130.7, 132.1, 135.6, 137.3, 139.5, 149.7, 150.5, 171.7.
1
3084, 3018, 2922, 1722, 1651, 1575, 1229 cm–1. H NMR
(DMSO-d6) d: 3.56 (s, 2H, CH2), 6.63 (dd, J = 6.7, 1.8 Hz,
pyridone H-5), 6.85 (dd, J = 6.7, 1.8 Hz, 1H, pyridone H-3),
7.18–7.34 (overlapping multiplets, 4H total, phenyl H-3, H-4,
H-5, H-6), 8.02 (d, J = 6.7 Hz, 1H, pyridone H-6), 8.65 (br s,
2H, NOH and COOH). Anal. Calcd for C13H11NO4·1/8H2O: C,
63.03; H, 4.55; N, 5.65. Found: C, 63.21; H, 4.64; N, 5.62.
Methyl 2-(2-methoxypyridin-5-yl)phenylacetate (7c)
Yield, 77%; pale yellow syrup. IR (film): 2919, 1736,
1
1086 cm–1. H NMR (CDCl3) d: 3.60 (s, 2H, CH2), 3.65 (s,
3H, OMe), 3.99 (s, 3H, pyridyl-OMe), 6.80 (d, J = 8.5 Hz,
1H, pyridyl H-3), 7.23–7.39 (overlapping multiplets, 4H to-
tal, phenyl H-3, H-4, H-5, H-6), 7.57 (dd, J = 8.5, 1.8 Hz,
1H, pyridyl H-4), 8.12 (d, J = 1.8 Hz, 1H, pyridyl H-6). 13C
NMR (CDCl3) d: 38.7, 52.0, 53.5, 110.2, 127.2, 127.4,
127.9, 129.7, 130.4, 132.3, 138.7, 139.6, 146.6, 163.3, 172.0.
Methyl 2-(1-hydroxy-2-oxo-1,2-dihydropridin-5-yl)
phenylacetate (9c)
Acetyl chloride (5 mL) was added to methyl 2-(1-oxido-2-
methoxypyridin-5-yl)phenylacetate (8c, 82 mg, 0.30 mmol)
and the reaction 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 for 16 h. Methanol was
removed in vacuo to afford 9c; yield, 96%; pale yellow oil.
IR (film): 3026, 2961, 2921, 1746, 1656, 1582, 1168 cm–1.
1H NMR (CDCl3) d: 3.61 (s, 2H, CH2), 3.68 (s, 3H, OMe),
6.87 (d, J = 9.1 Hz, 1H, pyridyl H-3), 7.23–7.37 (overlap-
ping multiplets, 4H total, phenyl H-3, H-4, H-5, H-6), 7.49
(dd, J = 9.1, 2.4 Hz, 1H, pyridyl H-4), 7.90 (d, J = 2.4 Hz,
1H, pyridyl H-6), 8.67 (br s, 1H, N-OH). 13C NMR (CDCl3)
d: 38.7, 52.2, 116.8, 119.8, 127.7, 128.7, 130.4, 130.6, 130.7,
132.4, 136.3, 139.5, 156.7, 171.9.
General procedure for the synthesis of methyl 2-(1-oxido-
2-chloropyridin-4-yl)phenylacetate (8a) and methyl 2-(1-
oxido-2-methoxypyridin-5-yl)phenylacetate (8c)
m-Chloroperoxybenzoic acid (77% maximum purity)
(12 mmol) was added to a stirred solution of a pyridine (7a
or 7c, 3.0 mmol) in CH2Cl2 (30 mL), and the reaction was
allowed to proceed with stirring at 25 °C for 48 h. The sol-
vent was washed with a saturated solution of aqueous
NaHCO3 (2 × 20 mL), then washed with water (40 mL) and
brine, and the organic fraction was dried (MgSO4). Removal
of the solvent from the organic fraction in vacuo gave a resi-
due that was purified by silica gel column chromatography
using methanol–EtOAc (10:1, v/v) as eluent to afford the re-
spective product 8a or 8c. Some physical and spectroscopic
data for 8a and 8c are listed below.
2-(1-Hydroxy-2-oxo-1,2-dihydropridin-5-yl)phenylacetic
acid (10c)
Methyl 2-(1-oxido-2-chloropyridin-4-yl)phenylacetate (8a)
A mixture of 9c (0.75 mmol) and 2 N LiOH (3.0 mL,
6.0 mmol) in THF (3.0 mL) and MeOH (3.0 mL) was stirred
at reflux temperature for 3 h. The reaction mixture was
cooled to 25 °C and washed with CH2Cl2 (30 mL). The
water phase was acidified to pH 2 by addition of 3 N hydro-
chloric acid prior to extraction with EtOAc (3 × 50 mL). The
combined EtOAc extracts were washed with water and then
brine, the organic fraction was dried (MgSO4), and the sol-
vent was removed in vacuo. The crude product was purified
Yield, 42%; pale yellow oil. IR (film): 3060, 3030, 2955,
1
1741, 1461, 1267 cm–1. H NMR (CDCl3) d: 3.59 (s, 2H,
CH2), 3.69 (s, 3H, OMe), 7.26 (dd, J = 6.7, 2.4 Hz, 1H, pyr-
idyl H-5), 7.27–7.55 (overlapping multiplets, 4H total, phenyl
H-3, H-4, H-5, H-6), 7.55 (d, J = 2.4 Hz, 1H, pyridyl H-3),
8.40 (d, J = 6.7 Hz, 1H, pyridyl H-6). 13C NMR (CDCl3) d:
38.5, 52.3, 124.7, 127.6, 127.9, 129.3, 129.5, 131.1, 131.5,
137.1, 139.5, 139.9, 141.6, 171.5.
Published by NRC Research Press

Yu et al.
621
by flash silica gel column chromatography using EtOAc–
MeOH (9:1, v/v) as eluent to yield 10c; yield, 74%; pale yel-
low solid, mp 147–149 °C. IR (film): 3081, 3041, 2924,
9.2, 2.4 Hz, 1H, pyridone H-4), 7.46 (d, J = 1.8 Hz, 1H, pyr-
idone H-6), 10.1 (br s, 1H, COOH). Anal. Calcd for
C14H13NO3: C, 69.12; H, 5.39; N, 5.76. Found: C, 68.78; H,
5.51; N, 5.55.
1
2859, 1703, 1663, 1562 cm–1. H NMR (DMSO-d6) d: 3.70
(s, 2H, CH2), 6.57 (d, J = 6.7 Hz, pyridone H-3), 7.24–7.39
(overlapping multiplets, 5H total, phenyl H-3, H-4, H-5, H-6
and pyridone H-4), 7.88 (d, J = 2.4 Hz, 1H, pyridone H-6),
12.22 (br s, 2H, NOH and COOH). Anal. Calcd for
C13H11NO4·1/10H2O: C, 63.21; H, 4.57; N, 5.67. Found: C,
63.25; H, 4.55; N, 5.61.
Methyl 4-(1-difluoromethyl-2-oxo-1,2-dihydropyridin-5-yl)
phenylacetate (13)
To a solution of 7b (522 mg, 2.0 mmol) in acetonitrile
(15 mL) was added FSO2CF2CO2H (1.12 g, 6.0 mmol) fol-
lowed by NaHCO3 (186 mg, 2.2 mmol). This mixture was
heated at reflux under argon for 12 h and cooled to 25 °C; a
saturated solution of aqueous NaHCO3 (40 mL) was added
and the mixture was extracted with CH2Cl2 (3 × 40 mL).
The organic fraction was washed with water (50 mL) and
then brine, and the organic fraction was dried (MgSO4). Re-
moval of the solvent from the organic fraction in vacuo af-
forded 13 in 53% yield; pale yellow oil. IR (film): 3010,
General procedure for the synthesis of 2-(1-methyl-2-oxo-
1,2-dihydropyridyl)phenylacetic acids (12a–12b)
Dimethyl sulfate (420 mg, 3.33 mmol) in MeCN (10 mL)
was added to a solution of 7a or 7b (290 mg, 1.11 mmol) in
MeCN (10 mL). The mixture was stirred at reflux for 6 h.
Removal of excess dimethyl sulfate and MeCN in vacuo af-
forded the respective 1-methylpyridinium methylsulfate salt
1
2966, 1744, 1694, 1619, 1153 cm–1. H NMR (CDCl3) d:
1
3.60 (s, 2H, CH2), 3.67 (s, 3H, OMe), 6.61 (d, J = 9.1 Hz,
1H, pyridone H-3), 7.23–7.39 (overlapping multiplets, 4H,
phenyl H-3, H-4, H-5, H-6), 7.43 (dd, J = 9.1, 2.4 Hz, 1H,
pyridone H-4), 7.48 (d, J = 2.4 Hz, 1H, pyridone H-6), 7.74
(t, J = 60.4 Hz, 1H, CHF2). 13C NMR (CDCl3) d: 38.7, 52.2,
107.5 (t, J = 250 Hz), 120.4, 121.1, 127.8, 128.5, 128.8,
130.0, 130.8, 132.4, 136.3, 143.3, 160.2, 171.8.
11a or 11b. Compound 11a, H NMR (DMSO-d6) d: 3.62
–
(s, 3H, MeSO4 ), 3.67 (s, 2H, CH2), 3.68 (s, 3H, OMe), 4.53
(s, 3H, NMe), 7.41–7.47 (overlapping multiplets, 4H total,
phenyl H-3, H-4, H-5, H-6), 7.98 (dd, J = 6.7, 1.8 Hz, 1H,
pyridyl H-5), 8.09 (d, J = 1.8 Hz, 1H, pyridyl H-3), 9.19 (d,
1
J = 6.7 Hz, 1H, pyridyl H-6). Compound 11b, H NMR
–
(DMSO-d6) d: 3.65 (s, 3H, OMe), 3.67 (s, 3H, MeSO4 ),
3.68 (s, 2H, CH2), 4.46 (s, 3H, NMe), 7.34–7.50 (overlap-
ping multiplets, 4H total, phenyl H-3, H-4, H-5, H-6), 8.07
(d, J = 8.5, Hz, 1H, pyridyl H-3), 8.48 (dd, J = 8.5, 1.8 Hz,
1H, pyridyl H-4), 9.12 (d, J = 1.8 Hz, 1H, pyridyl H-6). A
solution of the 1-methylpyridinium methylsulfate 11a or 11b
in THF (3.0 mL) and MeOH (3.0 mL) was added to 2 N
LiOH (3.0 mL, 6.0 mmol), and the mixture was stirred at re-
flux temperature for 2 h. The reaction mixture was cooled to
25 °C and washed with CH2Cl2 (30 mL). The water phase
was then acidified to pH 4 by addition of 3 N hydrochloric
acid prior to extraction with EtOAc (3 × 50 mL). The com-
bined EtOAc extracts were washed with water and then brine,
the organic fraction was dried (MgSO4), and the solvent was
removed in vacuo. The crude product was purified by flash
silica gel column chromatography using EtOAc–MeOH (9:1,
v/v) to yield the respective product 12a or 12b. Some physi-
cal and spectral data of 12a and 12b are listed below.
2-(1-Difluoromethyl-2-oxo-1,2-dihydropyridin-5-yl)
phenylacetic acid (14)
A mixture of methyl 2-(1-difluoromethyl-2-oxo-1,2-dihy-
dropyridin-5-yl)phenylacetate (13, 0.75 mmol) and 2 N
LiOH (3.0 mL, 6.0 mmol) in THF (3.0 mL) and MeOH
(3.0 mL) was stirred at reflux temperature for 2 h. The reac-
tion mixture was cooled to 25 °C and washed with CH2Cl2
(30 mL). The water phase was then acidified to pH 2 by ad-
dition of 3 N hydrochloric acid prior to extraction with
EtOAc (3 × 50 mL). The combined EtOAc extracts were
washed with water and then brine, the organic fraction was
dried (MgSO4), and the solvent was removed in vacuo. The
crude product was purified by flash silica gel column chro-
matography using EtOAc–MeOH (9:1, v/v) as eluent to fur-
nish 14 in 90% yield; pale yellow gum. IR (film): 3063,
1
2948, 1737, 1692, 1592, 1152 cm–1. H NMR (CDCl3) d:
3.64 (s, 2H, CH2), 6.68 (dd, J = 7.3, 1.8 Hz, 1H, pyridone
H-3), 7.25–7.42 (overlapping multiplets, 4H total, phenyl H-
3, H-4, H-5, H-6), 7.47 (dd, J = 7.3, 2.4 Hz, 1H, pyridone
H-4), 7.56 (d, J = 2.4 Hz, 1H, pyridone H-6), 7.75 (t, J =
60.4 Hz, 1H, CHF2), 10.2 (br s, 1H, COOH). Anal. Calcd
for C14H11F2NO3: C, 60.22; H, 3.97; N, 5.02. Found: C,
59.94; H, 4.30; N, 4.79.
2-(1-Methyl-2-oxo-1,2-dihydropridin-4-yl)phenylacetic acid
(12a)
Yield, 89%; off-white solid, mp 182–184 °C. IR (film):
3068, 2943, 1723, 1658, 1558 cm–1. 1H NMR (CDCl3
+
DMSO-d6) d: 3.52 (s, 3H, NMe), 3.53 (s, 2H, CH2), 6.22
(dd, J = 6.7, 1.8 Hz, 1H, pyridone H-5), 6.52 (d, J =
1.8 Hz, 1H, pyridone H-3), 7.15–7.33 (overlapping multip-
lets, 5H total, phenyl H-3, H-4, H-5, H-6, pyridone H-6),
9.98 (br s, 1H, COOH). Anal. Calcd for C14H13NO3: C,
69.12; H, 5.39; N, 5.76. Found: C, 68.64; H, 5.42; N, 5.66.
2-(2-Oxo-1,2-dihydropyridin-5-yl)phenylacetic acid (15)
A mixture of 13 (0.75 mmol) and 2 N NaOH (3.0 mL,
6.0 mmol) was heated at reflux for 5 h. The reaction mixture
was cooled to 25 °C and washed with CH2Cl2 (30 mL). The
water phase was then acidified to pH 2 by addition of 3 N
hydrochloric acid prior to extraction with EtOAc (3 ×
50 mL). The combined EtOAc extracts were washed with
water and then brine, the organic fraction was dried
(MgSO4), and the solvent was removed in vacuo. The crude
product was purified by flash silica gel column chromatogra-
phy using EtOAc–MeOH (9:1, v/v) as eluent to afford 15;
2-(1-Methyl-2-oxo-1,2-dihydropridin-5-yl)phenylacetic acid
(12b)
Yield, 70%; pale yellow solid, mp 171–173 °C. IR (film):
3075, 2941, 1719, 1659, 1564 cm–1. 1H NMR (CDCl3
+
DMSO-d6) d: 3.47 (s, 3H, NMe), 3.48 (s, 2H, CH2), 6.46 (d,
J = 9.2 Hz, 1H, pyridone H-3), 7.12–7.28 (overlapping mul-
tiplets, 4H total, phenyl H-3, H-4, H-5, H-6), 7.34 (dd, J =
Published by NRC Research Press

622
Can. J. Chem. Vol. 89, 2011
(6) 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.
(7) Chowdhury, M. A.; Chen, H.; Abdellatif, K. R. A.; Dong, Y.;
Petruk, K. C.; Knaus, E. E. Bioorg. Med. Chem. Lett. 2008 18
(14), 4195. doi:10.1016/j.bmcl.2008.05.071.
(8) Yu, G.; Praveen Rao, P. N.; Chowdhury, M. A.; Abdellatif, K.
R. A.; Dong, Y.; Das, D.; Velázquez, C. A.; Suresh, M. A.;
Knaus, E. E. Bioorg. Med. Chem. Lett. 2010 20 (7), 2168.
doi:10.1016/j.bmcl.2010.02.040.
(9) Yu, G.; Chowdhury, M. A.; Abdellatif, K. R. A.; Dong, Y.;
Praveen Rao, P. N.; Das, D.; Velázquez, C. A.; Suresh, M. A.;
Knaus, E. E. Bioorg. Med. Chem. Lett. 2010 20 (3), 896.
doi:10.1016/j.bmcl.2009.12.073.
yield, 56%; pale yellow solid, mp 242–244 °C. IR (film):
1
3060, 2981, 1663, 1614 cm–1. H NMR (DMSO-d6) d: 3.46
(s, 2H, CH2), 6.43 (d, J = 9.1 Hz, 1H, pyridone H-3), 7.18–
7.33 (overlapping multiplets, 5H total, phenyl H-3, H-4, H-5,
H-6 and pyridone H-6), 7.38 (dd, J = 9.1, 2.4 Hz, 1H, pyri-
done H-4), 7.60 (s, 1H, NH), 10.1 (br s, 1H, COOH). Anal.
Calcd for C13H11NO3: C, 68.11; H, 4.84; N, 6.11. Found: C,
68.23; H, 4.86; N, 5.98.
Cyclooxygenase inhibition assays
The ability of the test compounds listed in Table 1 to in-
hibit ovine COX-1 and human recombinant COX-2 (IC50
value, µmol/L) were determined using an enzyme immunoas-
say kit (catalog No. 560131, Cayman Chemical, Ann Arbor,
Michigan, USA) according to our previously reported
method.17
(10) Miyaura, N.; Suzuki, A. Chem. Rev. 1995 95 (7), 2457. doi:10.
1021/cr00039a007.
(11) Stanforth, S. P. Tetrahedron 1998 54 (3–4), 263. doi:10.1016/
S0040-4020(97)10233-2.
5-Lipoxygenase inhibition assay
(12) Chowdhury, M. A.; Abdellatif, K. R.; Dong, Y.; Das, D.;
Suresh, M. R.; Knaus, E. E. Bioorg. Med. Chem. Lett. 2008 18
(23), 6138. doi:10.1016/j.bmcl.2008.10.009.
(13) Franceschin, M.; Frasca, S.; Alvino, A.; Bianco, A. Lett. Org.
Chem. 2007 4 (2), 86. doi:10.2174/157017807780414217.
(14) Chowdhury, M. A.; Abdellatif, K. R.; Dong, Y.; Das, D.; Yu,
G.; Velázquez, C. A.; Suresh, M. R.; Knaus, E. E. Bioorg.
Med. Chem. Lett. 2009 19 (24), 6855. doi:10.1016/j.bmcl.
2009.10.083.
The ability of the test compounds listed in Table 1 to in-
hibit potato 5-LOX (catalog No. 60401, Cayman Chemical,
Ann Arbor, Michigan, USA) (IC50 values, µmol/L) were de-
termined using an enzyme immunoassay kit (catalog
No. 760700, Cayman Chemical) according to our previously
reported method.18
Acknowledgements
(15) Ando, M.; Sato, N.; Nagase, T.; Nagai, K.; Ishikawa, S.;
Takahasi, H.; Ohtake, N.; Ito, J.; Hirayama, M.; Mitobe, Y.;
Iwaasa, H.; Gomori, A.; Matsushita, H.; Tadano, K.; Fujino,
N.; Tanaka, S.; Ohe, T.; Ishihara, A.; Kanatani, A.; Fukaimi, T.
Bioorg. Med. Chem. 2009 17 (16), 6106. doi:10.1016/j.bmc.
2009.05.069.
(16) Velázquez, C.; Praveen Rao, P. N.; Knaus, E. E. J. Med. Chem.
2005 48 (12), 4061. doi:10.1021/jm050211k .
(17) Rao, P. N. P.; Amini, M.; Li, H.; Habeeb, A. G.; Knaus, E. E.
J. Med. Chem. 2003 46 (23), 4872. doi:10.1021/jm0302391.
(18) Chowdhury, M. A.; Abdellatif, K. R. A.; Dong, Y.; Das, D.;
Suresh, M. R.; Knaus, E. E. Bioorg. Med. Chem. Lett. 2008 18
(23), 6138. doi:10.1016/j.bmcl.2008.10.009.
We are grateful to the Canadian Institutes of Health Research
(CIHR) for financial support of this research (MOP-14712).
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