Synthesis and biologic evaluation of new 3-phenoxyazetidin-2-one derivatives as selective cyclooxygenase-2 inhibitors

Article abstract of DOI:10.1007/s00044-012-0387-1

A new series of 3-phenoxyazetidin-2-ones (β-lactams) were designed and synthesized for the evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. In vitro COX-1 and COX-2 inhibition studies showed that all compounds were selective inhibitors of the COX-2 isozyme with IC₅₀ values in the 0.054-0.095 μM range, and COX-2 selectivity indexes in the 228.47-355.6 range. Among the synthesized compounds, 1-(4-methoxyphenyl)-4-(4- (methylsulfonyl)phenyl)-3-phenoxyazetidin-2-one (4j) possessing methoxy group at the para position of N-1 phenyl ring exhibited the highest COX-2 inhibitory selectivity and potency even more potent than the reference drug celecoxib. Molecular modeling studies indicated that the methylsulfonyl pharmacophore group can be inserted into the secondary pocket of COX-2 active site.

Full text of DOI:10.1007/s00044-012-0387-1

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:3881–3887
DOI 10.1007/s00044-012-0387-1
ORIGINAL RESEARCH
Synthesis and biologic evaluation of new 3-phenoxyazetidin-2-one
derivatives as selective cyclooxygenase-2 inhibitors
•
H. Arefi A. Zarghi
Received: 30 May 2012 / Accepted: 4 December 2012 / Published online: 15 December 2012
Ó Springer Science+Business Media New York 2012
Abstract A new series of 3-phenoxyazetidin-2-ones
(b-lactams) were designed and synthesized for the evalu-
ation as selective cyclooxygenase-2 (COX-2) inhibitors.
In vitro COX-1 and COX-2 inhibition studies showed that
all compounds were selective inhibitors of the COX-2
isozyme with IC50 values in the 0.054–0.095 lM range,
and COX-2 selectivity indexes in the 228.47–355.6 range.
Among the synthesized compounds, 1-(4-methoxyphenyl)-
4-(4-(methylsulfonyl)phenyl)-3-phenoxyazetidin-2-one (4j)
possessing methoxy group at the para position of N-1 phe-
nyl ring exhibited the highest COX-2 inhibitory selectivity
and potency even more potent than the reference drug
celecoxib. Molecular modeling studies indicated that the
methylsulfonyl pharmacophore group can be inserted into
the secondary pocket of COX-2 active site.
COX-3. COX-1 is constitutively expressed in most of the
tissues and has an important role in maintaining the
homeostasis. On the other hand, COX-2 is inducible under
pathologic conditions and is involved in the inflammatory
processes (Vane and Botting, 1998). In addition to COX-1
and COX-2, the third isoform of COX enzyme (COX-3)
has been also identified. It is considered to play a key role
in the biosynthesis of prostanoids known to be important
mediators in pain and fever (Botting, 2003). However,
because NSAIDs act by the blockade of prostaglandin
synthesis through non-selective inhibition of COX isoen-
zymes, they cause side effects associated with gastroin-
testinal ulcers and renal function suppression. Thus, it was
thought that more selective COX-2 inhibitors would have
reduced side effects. For this purpose, a number of selec-
tive COX-2 inhibitors were developed as safer NSAIDs
with improved gastric safety profile. In addition, the rec-
ognition of new avenues for selective COX-2 inhibitors
such as cancer (Kawamori et al., 1998; Katori and Majima,
2000; Srinath et al., 2003; Takkouche et al., 2008) and
neurodegenerative diseases such as Parkinson (Van Gool
et al., 2003) and Alzheimer’s (Teismann et al., 2003)
diseases has kindled the interest in these compounds.
Selective COX-2 inhibitors such as celecoxib (Penning
et al., 1997) and rofecoxib (Prasit et al., 1999) (COXIBs)
frequently belong to a class of vicinal diaryl hetero or
carbocyclic central ring system having a characteristic
methanesulfonyl, sulfonamide, or azido group on one of
the aryl rings that play a key role on COX-2 selectivity
(Chakraborti et al., 2010). However, observation of
increased cardiovascular risks associated with the use of
Keywords Cyclooxygenase-2 inhibition ꢀ
3-Phenoxyazetidin-2-ones ꢀ Molecular modeling
Introduction
Non-steroidal anti-inflammatory drugs (NSAIDs) are a
diverse group of compounds used for the treatment of
inflammation, pain, and fever. They exert their action by
the preventing of prostaglandins biosynthesis. Cyclooxy-
genase (COX) was identified as the molecular target for
NSAIDs by Vane in 1971 (Vane, 1971). Three COX iso-
forms have been identified so far: COX-1, COX-2, and
H. Arefi ꢀ A. Zarghi (&)
´
some COX-2 inhibitors such as rofecoxib (Dogne et al.,
Department of Medicinal Chemistry, School of Pharmacy,
Shahid Beheshti University of Medical Sciences,
P.O. Box 14155-6153, Tehran, Iran
2005) led to withdrawal of some COXIBs from the market.
In addition, some studies have suggested that rofecoxib
adverse cardiac events may not be a class effect, but rather
e-mail: azarghi@yahoo.com
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Med Chem Res (2013) 22:3881–3887
Me
an intrinsic chemical property related to its metabolism.
Based upon this, the researchers are interested to introduce
new scaffolds for COX-2 inhibitory activities to evaluate
their biologic effects and may improve the safety profiles.
For this reason, new template with high selectivity for
COX-2 inhibition requires to be found and evaluated for
their biologic activities. In this regard, ring contraction to
smaller carbocycles such as cyclobutenes (see compounds
A and B) leads to potent COX-2 inhibitors as well as an
insertion of 5- and 6-membered carbocyclic or heterocyclic
groups (Fig. 1) (Friesen et al., 1996). Therefore, it is
interesting to synthesize new COX-2 inhibitors having the
b-lactam scaffold as a 4-membered heterocyclic central
ring to evaluate their COX-2 inhibitory activities. b-
Lactam ring has been widely used as an active moiety for
design and development of antibiotics (Mata et al., 2003),
anti-tumors (Veinberg et al., 2004), thrombin inhibitors
(Han et al., 1995), antihyperglycemic (Goel et al., 2004),
anti-HIV (Sperka et al., 2005), and analgesic agents (Sat-
urnino et al., 2000) due to its safety and activity. As a part
of our research program, aimed at discovering new selec-
tive COX-2 inhibitors, we focused our attention on the
synthesis, COX inhibitory, and some molecular modeling
studies of 3-phenoxyazetidin-2-ones possessing a methyl-
sulfonyl COX-2 pharmacophore at the para position of the
C-4 phenyl ring and different substituents at the N-1 central
ring. The rational for the design of these compounds was
based on the application of 3-phenoxyazetidin-2-one moi-
ety as a new scaffold for developing new selective COX-2
inhibitors.
MeO2S
H2NO2S
N
N
O
O
CF3
Celecoxib
Rofecoxib
MeO2S
MeO2S
O
A
B
MeO2S
O
N
R
O
Designed molecules
Fig. 1 Chemical structures of celecoxib, rofecoxib, lead compounds
(A, B), and our designed molecules
was prepared from the appropriately substituted acetic acid
and imine precursors using an acid-activating agent such as
p-toluene-sulfonyl chloride (TsCl). As illustrated in
Scheme 1, 4-(methylsulfonyl)benzaldehyde 1 and appro-
priate amine 2 were treated in dry DMF in the presence of
molecular sieve under argon atmosphere at room tempera-
ture to obtain imine 3. Then, the resulting imine was reacted
with phenoxyacetic acid, tosyl chloride, and triethylamine in
dry DMF to give 3-phenoxyazetidin-2-ones 4a–j (yield:
50–70 %). Geometrical assignments of b-lactam isomers
Chemistry
The target b-lactams (4a–j) were synthesized by the Stau-
dinger reaction. Accordingly, the b-lactam ring scaffold
1
were carried out essentially on the basis of their HNMR
MeO2S
Scheme 1 Reagents and
conditions: a dry DMF, 25 °C,
MeO2S
24 h; b dry DMF, TEA,
phenoxy acetic acid, TsCl,
25 °C, 24 h
N
a
+
R
NH2
R
CHO
1
2
3a-j
MeO2S
4a; R= Pr
4b; R= iPr
4c; R= Butyl
4d; R= Pentyl
4e; R= cyclohexyl
4f; R= phenyl
4g; R= 4-F-phenyl
4h; R= 4-Cl-phenyl
4i; R= 4-Me-phenyl
4j; R= 4-OMe-phenyl
R
O
b
N
O
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Med Chem Res (2013) 22:3881–3887
3883
Table 1 In vitro COX-1 and COX-2 enzyme inhibition assay data
SO2Me
O
O
N
R
Compound
R
IC50 (lM)a
Selectivity index (SI)b
COX-1
COX-2
4a
Pr
21.7
21.8
20.9
21.2
19.51
19.85
19.0
18.3
18.1
19.2
24.30
0.095
0.084
0.080
0.070
0.057
0.072
0.056
0.068
0.060
0.054
0.06
228.4
259.5
261.2
302.8
342.3
275.7
339.3
269.1
320.0
355.6
405
4b
iPr
4c
Bu
4d
Pentyl
4e
Cyclohexyl
Phenyl
4f
4g
4F-phenyl
4Cl-phenyl
4Me-phenyl
4-OMe-phenyl
4h
4i
4j
Celecoxib
a
Values are means of two determinations acquired using an ovine COX-1/COX-2 assay kit and the deviation from the mean is \ 5 % of the
mean value
b
In vitro COX-2 selectivity index (COX-1 IC50/COX-2 IC50
)
the cis and J3,4 C 3.0 Hz for the trans stereoisomers) (Banik
et al., 2005).
Results and discussion
A new group of 3-phenoxyazetidin-2-one having different
substituents at the N-1 of azetidin-2-one ring was prepared
to investigate the effect of different substituents on COX-2
selectivity and potency. Several synthetic methods have
been developed for the preparation of the b-lactam ring
(Stein and Gellman, 1992). The Staudinger reaction is
regarded as the most important method for the synthesis of
b-lactam core and is used for the synthesis of a large
number of b-lactams (Staudinger, 1907). Based upon this,
we used a modified Staudinger reaction that leads to b-
lactam with cis selectivity. The coupling constant of H-3
and H-4 was used for the indication of stereochemistry of
b-lactams (J3,4 [ 4.0 Hz). The series of b-lactam analogs
of 4a–j were evaluated for their COX inhibitory activity by
an enzyme chemiluminescent assay. The result of COX-1/
COX-2 inhibition is summarized in Table 1. SAR data
(IC50 values) acquired by the determination of the in vitro
ability of the title compounds to inhibit the COX-1 and
COX-2 isozymes showed that all compounds were potent
Fig. 2 Docking 1-(4-methoxyphenyl)-4-(4-(methylsulfonyl)phenyl)-
3-phenoxyazetidin-2-one (4j) (in red) in the active site of murine
COX-2. Hydrogen atoms have been removed to improve clarity
(Color figure online)
data according to literature (Banik et al., 2003). In general,
the coupling constant of H-3 and H-4 is used for the indi-
cation of stereochemistry of b-lactams (J3,4 [ 4.0 Hz for
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Med Chem Res (2013) 22:3881–3887
and selective inhibitors of the COX-2 isozyme with IC50
values in the highly potent 0.054–0.095 lM range, and
COX-2 selectivity indexes in the 228.4–355.6 range. Our
results showed that the COX inhibition was affected by the
type of substituent on the N-1 central ring. Accordingly,
compounds possessing larger alkyls (4d and 4e) were more
potent and selective COX-2 inhibitors compared with other
analogs 4a–c which had smaller ones. These results indi-
cated that the increase the lipophilicity of N-1 alkyl group
may improve both selectivity and potency for COX-2
inhibitory activity. Our results also indicated that replace-
ment of cyclohexyl group (4e) with phenyl substituent
decreased the COX-2 inhibitory activity. However, the
introduction of suitable substituents such as F (4g) or OMe
(4j) at the para position of N-1 phenyl ring increased the
selectivity and potency for COX-2 inhibitory activity in
comparison of unsubstituted analog (4f). In addition,
compounds having Cl substituent (4h) showed less selec-
tivity and potency for COX-2 isozyme which may be
explained by steric parameter for interaction with COX-2
active binding site. These data showed that the nature and
size of substituent attached to N-1 phenyl ring can influ-
ence both selectivity and potency for COX-2 inhibitory
activity. Our results indicated that 1-(4-methoxyphenyl)-4-
(4-(methylsulfonyl) phenyl)-3-phenoxyazetidin-2-one 4j
showed the highest COX-2 selectivity (S.I. = 355.6)
among the synthesized compounds which may be due to
better interaction with the COX-2 active site. It was almost
equipotent potent (IC50 = 0.054 lM) as celecoxib
(IC50 = 0.060 lM; S.I. = 405) in terms of COX-2 inhib-
itory activity, but showed less selectivity. Accordingly, the
binding interactions of the most selective COX-2 inhibitor
(4j) within the COX-2 binding site were studied. Docking
the selective and potent COX-2 inhibitor 4j into the COX-2
binding site (Fig. 2) shows that the para-SO2Me sub-
stituent inserts into the secondary pocket present in COX-2
(Arg513, Phe518, and Val523). One of the O-atoms of the
SO2Me moiety forms a H-bond with the NH of Arg513
at N-1 of azetidin-2-one ring (iii) 1-(4-methoxyphenyl)-4-
(4-(methylsulfonyl)phenyl)-3-phenoxyazetidin-2-one (4j)
exhibited highly COX-2 inhibitory potency and selectivity
even more potent than celecoxib.
Experimental section
All chemicals and solvents used in this study were pur-
chased from Merck AG and Aldrich Chemical. Melting
points were determined using a Thomas–Hoover capillary
apparatus. Infrared spectra were acquired using a Perkin
Elmer Model 1420 spectrometer. A Bruker FT-500 MHz
instrument (Brucker Biosciences, USA) was used to
1
acquire HNMR spectra with TMS as an internal standard.
Chloroform-D was used as solvents. Coupling constant
(J) values are estimated in hertz (Hz) and spin multiples are
given as s (singlet), d (double), t (triplet), q (quartet), m
(multiplet), and br (broad). The mass spectral measure-
ments were performed on an 6410Agilent LCMS triple
quadrupole mass spectrometer (LCMS) with an electro-
spray ionization (ESI) interface. Microanalyses, deter-
mined for C and H, were within 0.4 % of theoretic
values.
General procedure for the one-pot preparation
of azetidin-2-one
A mixture of 4-(methylsulfonyl)benzaldehyde 1 (20 mmol)
and appropriate amine 2 (20 mmol) in dry DMF in the
presence of molecular sieve was stirred under argon
atmosphere at 25 °C for 24 h. The imine 3 was not iso-
lated. To this mixture, triethylamine (100 mmol), tosyl-
chloride (30 mmol), and phenoxy acetic acid (30 mmol)
was added and stirred at room temperature for 24 h. After
this time, water was added and the precipitate was re-
crystallized in appropriate solvent (yield 50–70 %).
´
˚
(distance = 3.9 A), whereas the other O-atom is close to
´
4-(4-(Methylsulfonyl)phenyl)-3-phenoxy-
the NH of His90 (distance = 2.5 A). The oxygen atom of
1-propyl-azetidin-2-one (4a)
˚
the phenoxy group of C-3 is almost close to the NH of
´
Arg120 (distance = 4.0 A), and therefore may form
Yield; 57 %; white crystalline powder; mp: 135–137 °C;
IR (KBr): m (cm-1) 1755 (C=O), 1322, 1161 (SO2);
1HNMR (CDCl3): d ppm 0.97 (t, 3H, CH3), 1.58 (m, 2H,
CH2), 2.99 (m, 2H, CH2), 3.05 (s, 3H, SO2CH3), 3.54 (m,
1H, CH2), 5.07 (d, 1H, CH, J = 4.5 Hz), 5.55 (d, 1H, CH,
J = 4.5 Hz), 6.76 (d, 2H, phenoxy H2 and H6, J =
7.9 Hz), 6.94 (t, 1H, phenoxy H4), 7.17 (t, 2H, phenoxy H3
and H5), 7.59 (d, 2H, 4-methylsulfonyl phenyl H2 and H6,
J = 8.3 Hz), 7.92 (d, 2H, 4-methylsulfonyl phenyl H3 and
H5, J = 8.3 Hz); LCMS (ESI): 360.1 (M?1)?(100); Anal.
Calcd. for C19H21NO4S: C, 63.49; H, 5.89; N, 3.90. Found:
C, 63.77; H, 6.01; N, 3.74.
˚
hydrogen bond with this amino acid. These data together
with COX-2 inhibition results may explain the in vitro
potency and selectivity of designed compounds.
Conclusions
This study indicates that (i) 3-phenoxy-azetidin-2-one
is a suitable template to design COX-1/-2 inhibitors, (ii)
COX-1/-2 inhibition is sensitive to the type of substituent
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Med Chem Res (2013) 22:3881–3887
3885
1-Isopropyl-4-(4-(methylsulfonyl)phenyl)-
(CDCl3): d ppm 1.11–1.30 (m, 4H, CH2), 1.57-1.60 (m, 4H,
CH2), 1.83–1.85 (m, 2H, CH2), 3.04 (s, 3H, SO2CH3),
3.57–3.59 (m, 1H, CH), 5.09 (d, 1H, CH, J = 4.58 Hz), 5.45
(d, 1H, CH, J = 4.59 Hz), 6.73 (d, 2H, phenoxy H2 and H6,
J = 7.88 Hz), 6.93 (t, 1H, phenoxy H4), 7.14–7.17 (t, 2H,
phenoxy H3 and H5), 7.63 (d, 2H, 4-methylsulfonyl phenyl
H2 and H6, J = 8.33 Hz), 7.90 (d, 2H, 4-methyl sulfonyl
phenyl H3 and H5, J = 8.35 Hz); LCMS (ESI): 400.2
(M?1)?(100); Anal. Calcd. for C22H25NO4S: C, 66.14; H,
6.31; N, 3.51. Found: C, 66.29; H, 6.09; N, 3.67.
3-phenoxy-azetidin-2-one (4b)
Yield; 60 %; white crystalline powder; mp: 142–143 °C; IR
(KBr): m (cm-1) 1740 (C=O), 1313, 1152 (SO2); HNMR
1
(CDCl3): d ppm 1.14 (t, 3H, CH3), 1.36 (m, 3H, CH3), 3.04 (s,
3H, SO2CH3), 5.07 (d, 1H, CH, J = 4.6 Hz), 5.46 (d, 1H,
CH, J = 4.6 Hz), 6.74 (d, 2H, phenoxy H2 and H6,
J = 8.1 Hz), 6.92 (t, 1H, phenoxy H4), 7.16 (d, 2H, phenoxy
H3 and H5, J = 8.1 Hz), 7.65 (d, 2H, 4-methylsulfonyl
phenyl H2 and H6, J = 8.3 Hz), 7.90 (d, 2H, 4-methylsul-
fonyl phenyl H3 and H5, J = 8.3 Hz); LCMS (ESI): 360.1
(M?1)?(100); Anal. Calcd. for C19H21NO4S: C, 63.49; H,
5.89; N, 3.90. Found: C, 63.74; H, 6.06; N, 3.99.
4-(4-(Methylsulfonyl)phenyl)-3-phenoxy-
1-phenylazetidin-2-one (4f)
Yield; 70 %; bright brown crystalline powder; mp:
197–198 °C; IR (KBr): m (cm-1) 1744 (C=O), 1352, 1126
(SO2); 1HNMR (CDCl3): d ppm 3.05 (s, 3H, SO2CH3), 5.54
(d, 1H, CH, J = 5.0 Hz), 5.7 (d, 1H, CH, J = 5.0 Hz), 6.82
(d, 2H, phenoxy H2 and H6, J = 8.0 Hz), 6.99–7.17 (t, 1H,
phenoxy H4), 7.18–7.20 (t, 1H, phenyl H4), 7.22–7.24 (t, 2H,
phenoxy H3 and H5), 7.34–7.38 (m, 4H, phenyl), 7.62 (d, 2H,
4-methyl sulfonyl phenyl H2 and H6, J = 8.3 Hz), 7.91 (d,
2H, 4-methylsulfonyl phenyl H3 and H5, J = 8.3 Hz);
LCMS (ESI): 394.1 (M?1)? (100); Anal. Calcd. for
C22H19NO4S: C, 67.16; H, 4.87; N, 3.56. Found: C, 67.33; H,
4.59; N, 3.74.
1-Butyl-4-(4-(methylsulfonyl)phenyl)-
3-phenoxyazetidin-2-one (4c)
Yield; 56 %; white crystalline powder; mp: 158–159 °C; IR
(KBr): m (cm-1) 1748 (C=O), 1312, 1153 (SO2); HNMR
1
(CDCl3): d ppm 0.95 (t, 3H, CH3), 1.38 (m, 2H, CH2), 1.55
(m, 2H, CH2), 3.01 (m, 1H, CH2), 3.05 (s, 3H, SO2CH3), 3.59
(m, 1H, CH2), 5.06 (d, 1H, CH, J = 4.5 Hz), 5.53 (d, 1H,
CH, J = 4.5 Hz), 6.76 (d, 2H, phenoxy H2 and H6,
J = 7.94 Hz), 6.94 (t, 1H, phenoxy H4), 7.16 (t, 2H, phenoxy
H3 and H5), 7.59 (d, 2H, 4-methylsulfonyl phenyl H2 and H6,
J = 8.3 Hz), 7.92 (d, 2H, 4-methylsulfonyl phenyl H3 and
H5, J = 8.3 Hz); LCMS (ESI): 347.1 (M?1)?(100); Anal.
Calcd. for C20H23NO4S: C, 64.32; H, 6.21; N, 3.75. Found:
C, 64.55; H, 6.39; N, 3.55.
1-(4-Fluorophenyl)-4-(4-(methylsulfonyl)phenyl)-
3-phenoxyazetidin-2-one (4g)
Yield; 52 %; bright brown crystalline powder; mp:
198–199.5 °C; IR (KBr): m (cm-1) 1757 (C=O), 1317,
1155 (SO2); 1HNMR (CDCl3): d ppm 3.06 (s, 3H,
SO2CH3), 5.52 (d, 1H, CH, J = 4.90 Hz), 5.7 (d, 1H, CH,
J = 4.89 Hz), 6.82 (d, 2H, phenoxy H2 and H6,
J = 7.89 Hz), 6.98–7.10 (t, 1H, phenoxy H4), 7.03–7.06 (t,
2H, phenoxy H3 and H5), 7.21–7.24 (t, 2H, 4-F phenyl H3
and H5), 7.34–7.36 (dd, 2H, 4-F phenyl H2 and H6), 7.61
(d, 2H, 4-methylsulfonyl phenyl H2 and H6, J = 8.30 Hz),
7.92 (d, 2H, 4-methylsulfonyl phenyl H3 and H5,
J = 8.34 Hz); LCMS (ESI): 412.1 (M?1)? (100); Anal.
Calcd. For C22H18FNO4S: C, 64.22; H, 4.41; N, 3.40.
Found: C, 64.52; H, 4.58; N, 3.44.
4-(4-(Methylsulfonyl)phenyl)-1-pentyl-
3-phenoxyazetidin-2-one (4d)
Yield; 60 %; bright brown crystalline powder; mp:
118–120 °C; IR (KBr): m (cm-1) 1756 (C=O), 1317, 1157
(SO2); 1HNMR (CDCl3): d ppm 0.92 (t, 3H, CH3), 1.35 (m,
4H, CH2), 1.59 (m, 2H, CH2), 2.97-3.03 (m, 1H, CH2), 3.05
(s, 3H, SO2CH3), 3.55–3.61 (m, 1H, CH2), 5.06 (d, 1H,
CH, J = 4.5 Hz), 5.53 (d, 1H, CH, J = 4.5 Hz), 6.76 (d,
2H, phenoxy H2 and H6, J = 7.9 Hz), 6.92 (t, 1H, phenoxy
H4), 7.7 (d, 2H, phenoxy H3 and H5, J = 7.9 Hz), 7.58 (d,
2H, 4-methylsulfonyl phenyl H2 and H6, J = 8.3 Hz), 7.92
(d, 2H, 4-methylsulfonyl phenyl H3 and H5, J = 8.3 Hz);
LCMS (ESI): 388.2 (M?1)?(100); Anal. Calcd. for
C21H25NO4S: C, 65.09; H, 6.60; N, 3.61. Found: C, 65.21;
H, 6.84; N, 3.75.
1-(4-Chlorophenyl)-4-(4-(methylsulfonyl)phenyl)-
3-phenoxyazetidin-2-one (4h)
Yield; 53 %; white crystalline powder; mp: 246–247 °C;
IR (KBr): m (cm-1) 1753 (C=O), 1315, 1158 (SO2);
1HNMR (CDCl3): d ppm 3.06 (s, 3H, SO2CH3), 3.80 (s,
3H, OCH3), 5.52 (d, 1H, CH, J = 4.64 Hz), 5.71 (d, 1H,
CH, J = 4.59 Hz), 6.81 (d, 2H, phenoxy H2 and H6,
J = 7.95 Hz), 7.0 (t, 1H, phenoxy H4), 7.21–7.24 (t, 2H,
1-Cyclohexyl-4-(4-(methylsulfonyl)phenyl)-
3-phenoxyazetidin-2-one (4e)
Yield; 54 %; white crystalline powder; mp: 208–209 °C; IR
(KBr): m (cm-1) 1740 (C=O), 1317, 1154 (SO2); HNMR
1
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Med Chem Res (2013) 22:3881–3887
phenoxy H3 and H5), 7.30–7.31 (m, 4H, chlorophenyl H2,6
and H3,5), 7.61 (d, 2H, methoxyphenyl H2 and H6,
J = 8.03 Hz), 7.93 (d, 2H, 4-methylsulfonyl phenyl H3 and
H5, J = 8.15 Hz); LCMS (ESI): 428.1 (M?1)? (100);
Anal. Calcd. for C22H18ClNO4S: C, 61.75; H, 4.24; N,
3.27. Found: C, 61.99; H, 4.36; N, 3.41.
PDB file 1cx2 after which SC-558 was deleted. The pur-
pose of docking is to search for favorable binding config-
uration between the small flexible ligands and the rigid
˚
protein. Protein residues with atoms greater than 7.5 A
from the docking box were removed for efficiency. These
docked structures were very similar to the minimized
structures obtained initially. The quality of the docked
structures was evaluated by measuring the intermolcular
energy of the ligand-enzyme assembly (Morris et al., 1998;
Kurumbail et al., 1996).
4-(4-(Methylsulfonyl)phenyl)-3-phenoxy-
1-(p-tolyl)azetidin-2-one (4i)
Yield; 55 %; bright brown crystalline powder; mp:
199–201 °C; IR (KBr): m (cm-1) 1739 (C=O), 1317, 1125
(SO2); 1HNMR (CDCl3): d ppm 2.30 (s, 3H, CH3), 3.05 (s,
3H, SO2CH3), 5.50 (d, 1H, CH, J = 4.8 Hz), 5.69 (d, 1H,
CH, J = 4.8 Hz), 6.80 (d, 2H, phenoxy H2 and H6,
J = 8.05 Hz), 6.83 (d, 2H, methylphenyl H3 and H5,
J = 7.25 Hz), 7.01 (t, 1H, phenoxy H4), 7.23–7.25 (t, 2H,
phenoxy H3 and H5), 7.31 (d, 2H, 4-methylphenyl H2 and
H6, J = 7.51 Hz), 7.61 (d, 2H, 4-methylsulfonyl phenyl H2
and H6, J = 8.22 Hz), 7.9 (d, 2H, 4-methylsulfonyl phenyl
H3 and H5, J = 8.24 Hz); LCMS (ESI): 408.1 (M?1)?
(100); Anal. Calcd. for C23H21NO4S: C, 67.79; H, 5.19; N,
3.44. Found: C, 67.99; H, 5.01; N, 3.40.
In vitro cyclooxygenase (COX) inhibition assays
The assay was performed using an enzyme chemilumi-
nescent kit (Cayman chemical, MI, USA) according to our
previously reported method (Zarghi et al., 2007). The
Cayman chemical chemiluminescent COX (ovine) inhibi-
tor screening assay utilizes the heme-catalyzed hydroper-
oxidase activity of ovine cyclooxygenases to generate
luminescence in the presence of a cyclic naphthalene
hydrazide and the substrate arachidonic acid. Arachido-
nate-induced luminescence was shown to be an index of
real-time catalytic activity and demonstrated the turnover
inactivation of the enzyme. Inhibition of COX activity,
measured by luminescence, by a variety of selective and
nonselective inhibitors showed potencies similar to those
observed with other in vitro and whole cell methods.
1-(4-Methoxyphenyl)-4-(4-(methylsulfonyl)phenyl)-
3-phenoxyazetidin-2-one (4j)
Yield; 50 %; bright brown crystalline powder; mp:
173–175 °C; IR (KBr): m (cm-1) 1744 (C=O), 1352, 1126
1
Acknowledgments We like to thank Deputy of Research, School of
Pharmacy, Shahid Beheshti University of Medical Sciences, for
financial support of this work as part of Ph.D thesis of Hadi Arefi.
(SO2); HNMR (CDCl3): d ppm 3.05 (s, 3H, SO2CH3),
3.80 (s, 3H, OCH3), 5.49 (d, 1H, CH, J = 4.8 Hz), 5.68 (d,
1H, CH, J = 4.8 Hz), 6.82 (d, 2H, phenoxy H2 and H6,
J = 8.0 Hz), 6.87 (d, 2H, phenyl H3 and H5, J = 7.3 Hz),
6.97–7.0 (t, 1H, phenoxy H4), 7.20 (t, 2H, phenoxy H3 and
H5), 7.31 (d, 2H, methoxyphenyl H2 and H6, J = 7.6 Hz),
7.61 (d, 2H, 4-methylsulfonyl phenyl H2 and H6,
J = 8.3 Hz), 7.9 (d, 2H, 4-methylsulfonyl phenyl H3 and
H5, J = 8.3 Hz); LCMS (ESI): 424.1 (M?1)? (100); Anal.
Calcd. for C23H21NO5S: C, 65.23; H, 5.00; N, 3.31. Found:
C, 65.29; H, 5.19; N, 3.17.
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