Synthesis and biological evaluation of some 5-ethoxycarbonyl-6-isopropylamino-4-(substitutedphenyl)aminopyrimidines as potent analgesic and anti-inflammatory agents

Article abstract of DOI:10.1016/j.bmcl.2006.11.035

Synthesis and biological evaluation of some 5-ethoxycarbonyl-6-isopropylamino-4-(substitutedphenyl)aminopyrimidines have been achieved by cyclization of N-[2-ethoxycarbonyl-2-cyano-1-(isopropylamino)vinyl] formamidine in presence of dry HCl in dioxane fol

Full text of DOI:10.1016/j.bmcl.2006.11.035

Bioorganic & Medicinal Chemistry Letters 17 (2007) 1022–1024
Synthesis and biological evaluation of some 5-ethoxycarbonyl-6-
isopropylamino-4-(substitutedphenyl)aminopyrimidines as potent
analgesic and anti-inflammatory agents
Mahesh T. Chhabria,a,* Hardik G. Bhatt, Hitesh G. Raval and Pratik M. Oza
b
c
c
a
L. M. College of Pharmacy, Navrangpura, Ahmedabad 380 009, India
Institute of Pharmacy, NIRMA University of Science and Technology, Chharodi, Ahmedabad 382 481, India
b
c
Anand Pharmacy College, Anand 388 001, India
Received 18 July 2006; revised 7 November 2006; accepted 13 November 2006
Available online 16 November 2006
Abstract—Synthesis and biological evaluation of some 5-ethoxycarbonyl-6-isopropylamino-4-(substitutedphenyl)aminopyrimidines
have been achieved by cyclization of N-[2-ethoxycarbonyl-2-cyano-1-(isopropylamino)vinyl] formamidine in presence of dry HCl in
dioxane followed by nucleophilic substitution of 4-chloro group with substituted aromatic amine or phenoxide. Target compounds
were evaluated for their analgesic and anti-inflammatory potential by known experimental models. Some of the compounds emerged
out as more potent than standard drugs. Very low ulcer index was observed for the potent compounds.
Ó 2006 Elsevier Ltd. All rights reserved.
1
,2
Non-steroidal anti-inflammatory drugs (NSAIDs) are
widely used in the treatment of pain and inflammation.
Most currently used NSAIDs have limitations for ther-
apeutic use since they cause gastrointestinal and renal
side effects, which are inseparable from their pharmaco-
logical activities. These compounds non-selectively
inhibit the two isoforms of the cyclooxygenase (COX-1
and COX-2) and thus prevent the metabolism of cellular
arachidonic acid (AA) and the upregulation of prosta-
glandin formation, which otherwise lead to an increase
of vascular permeability, edema, hyperalgesia, pyrexia,
and inflammation. Therefore, the synthesis of new mol-
ecules devoid of these toxicities has been of prime inter-
est for medicinal chemists in recent years. In addition to
COX, the 5- lipoxygenase (5-LO) enzyme is another key
enzyme which is involved in the AA cascade. Leukotri-
enes, produced through the 5-LO enzyme pathway, may
also contribute to both inflammation and NSAID-in-
duced side effects. For these reasons, compounds that
are dual inhibitors of both COX and 5-LO are being
studied as potential analgesic and anti-inflammatory
agents with an improved safety profile in comparison
to NSAIDs. Currently, various chemical families of
dual COX/5-LO inhibitors can be found in the scientific
literatures.
3
In continuation of our work to get potent and safe
pyrimidine NSAID, some 5-ethoxycarbonyl-6-isopro-
pylamino-4-(substitutedphenyl)aminopyrimidines have
been designed. Earlier work from our laboratory sug-
gested that isopropylamino group at C-6 and ethoxy-
carbonyl group at C-5 position are essential for
potent analgesic and anti-inflammatory activity. As
most of the NSAIDs contain aryl ring, it was thought
of interest to incorporate aryl group at C-4 position
through imino (–NH) or ethereal(–O–) linkage. Starting
material was synthesized as per Scheme 1. Target
compounds were synthesized by cyclization of N-[2-eth-
oxycarbonyl-2-cyano-1-(isopropylamino)vinyl] form-
4
amidine in presence of dry HCl in dioxane to afford
5-ethoxycarbonyl-4-chloro-6-isopropylaminopyrimi-
5
,6
dines (Table 1).
7
Nucleophilic substitution of 4-chloro group by aromat-
8
9
ic amine or phenoxide provided target compounds
Scheme 2).
(
Keywords: Aminopyrimidines; Analgesic; Anti-inflammatory; Cyclo-
oxygenase; NSAIDs.
*
Corresponding author. Tel.: +91 79 26302736; fax: +91 79
6304865; e-mail: mt_chhabria@icenet.net
All compounds were tested for analgesic activity using
model—inhibition in acetic acid-induced writhings in
2
0
960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2006.11.035

M. T. Chhabria et al. / Bioorg. Med. Chem. Lett. 17 (2007) 1022–1024
1023
H C O C
CN
5
2
2
KOH, DMF
H C O C
CN
5
2
2
CS , DMS
2
H CS
SCH3
3
NH2
H C
CH3
3
H C O C
CN
N
NH
5
2
2
H C O C
CN
5
2
2
NH2
H
NH
2
HN
HN
SCH3
H
H C
CH3
3
H C
CH3
3
I
Scheme 1.
Table 1. Physical data of 5-ethoxycarbonyl-6-isopropylamino-4-(substitutedphenyl)aminopyrimidines (IIIa–IIIe, IV)
a
R
Compound
Melting point (°C)
% Yield
Molecular formula
IIIa
IIIb
IIIc
IIId
IIIe
IV
p-Cl–C
6
H
4
112–114
135–138
145–148
75–78
72.9
78.0
62.2
55.5
61.2
87.5
C
C
C
C
C
C
16
H
16
H
17
H
17
H
16
H
16
H
4 2
19ClN O
p-NO
p-CH
p-OCH
p-SO NH
–OC
2
–C
–C
–C
6
H
4
19
N
22
N
22
N
21
N
19
N
5
4
4
5
3
O
4
3
6
H
4
O
2
O
3
O
4
O
3
3
6
H
4
2
2
–C
6
H
4
149–154
60–64
S
6 5
H
a
Solvent for recrystallization: methanol.
1
0
albino mice. Statistically significant results were
obtained with compound IIId, being more potent than
Cl
N
H C OOC
CN
N
5
2
H C OOC
diclofenac sodium. Acute anti-inflammatory activity
1
5
2
1
NH2
N
was determined using known experimental models.
Ulcerogenic potential of the potent compounds was also
HN
1
2
evaluated. Significant anti-inflammatory activity with
very low ulcer index was observed with compounds IIIc
and IIIe (Table 2).
HN
H
H C
CH3
3
H C
CH3
3
I
II
In summary, compounds with potent analgesic and anti-
inflammatory activities with very low ulcerogenic poten-
Table 2. Analgesic activity, anti-inflammatory activity and ulcerogenic
potential of 5-ethoxycarbonyl-6-isopropylamino-4-(substitutedphenyl)
aminopyrimidines
O
HN
R
Compound
% Inhibition % Inhibition of Ulcer Index
a
H C OOC
a
5
2
H C OOC
of writhing
inflammation
a
± SEM
± SEM
5
2
N
N
IIIa
IIIb
IIIc
IIId
IIIe
IV
70.23
77.38
72.02
85.11
72.61
70.23
30.85 ± 3.58
84.56 ± 0.61
89.69 ± 0.03
62.72 ± 4.57
87.65 ± 3.26
55.50 ± 3.20
—
—
—
HN
N
HN
N
0.290 ± 0.024
—
H C
CH3
0.241 ± 0.104
—
3
H C
CH3
III
3
Diclofenac sodium 77.98
Celecoxib
0.805 ± 0.120
0.104 ± 0.005
IV
—
82.09 ± 4.31
a
Scheme 2.
n = 5, dose = 50 mg/kg po.

1024
M. T. Chhabria et al. / Bioorg. Med. Chem. Lett. 17 (2007) 1022–1024
tial are reported in the present study. Compounds IIIb,
IIIc, and IIIe showed potent anti-inflammatory activity
with very low ulcerogenic potential when compared with
that of the standard drugs celecoxib and diclofenac sodi-
um, respectively. However, ulcerogenic potential was
remarkably more than celecoxib. Compound IIId exhib-
ited greater analgesic activity than the reference stan-
dard diclofenac sodium. This series opened new doors
for possible modifications of the pharmacophoric
requirements of NSAIDs and future exploitations.
CH(CH
2
3
)
2
0
), 4.41–4.45 (q, 2H, –COOCH
0
2
0
CH
0
3
), 7.2–7.3 (d,
H, Ar-2 ,6 -H), 7.50–7.53 (d, 2H, Ar-3 ,5 -H), 7.92–7.93
(
d, 1H, –NH–CH(CH ) ; D O exchangeable), 8.21 (s, 1H,
3 2 2
C–H), 10.26 (s, 1H, –NH–C
2
6
4
H ; D
2
O exchangeable); LC-
4 2
19ClN O ,
+
MS m/z 334.8 (M ), 336.8 (M+2) (C16
H
1
required 333.81). Compound IIIb: H NMR (400 MHz,
CDCl ): d 1.25–1.28 (m, 6H, –NH–CH(CH ) ), 1.48–1.51
3
3 2
(
t, 3H, –COOCH
CH ), 4.37–4.42 (m, 1H, –NH–
2 3
3 2 2 3
CH(CH ) ), 4.43–4.49 (q, 2H, –COOCH CH ), 7.86–7.91
0
0
0
0
(d, 2H, Ar-2 ,6 -H), 7.97–7.99 (d, 2H, Ar-3 ,5 -H), 8.16–
8.18 (d, 1H, –NH–CH(CH ) ; D O exchangeable), 8.27 (s,
3
2
2
2
1
H, C–H), 10.88 (s, 1H, –NH–C
H
6 4
; D
, required 345.36).
Compound IIIc: H NMR (60 MHz, CDCl ): d 0.5–1.7
2
O exchangeable);
+
19 5 4
LC-MS m/z 346.2 (M , C16H N O
1
References and notes
3
(
m, 10H, –NH–CH(CH
CH(CH ), 2.37 (s, 3H, p-CH
COOCH CH ), 7.1–7.4 (m, 4H, p-CH
H, –NH–CH(CH ) ; D O exchangeable), 8.47 (s, 1H, C–
3
)
2
,
COOCH
–C ), 4.4–4.6 (q, 2H,
–C ), 8.20 (s,
2
CH
3
,
–NH–
3
)
2
3
6 4
H
1
2
. Charlier, C.; Michaux, C. Eur. J. Med. Chem. 2003, 38,
45.
. Unangst, P. C.; Connor, D. T.; Centenko, W. A.; Sorenson,
R. J.; Kostlan, R. K.; Sircar, J. C.; Wright, C. D.; Schrier, D.
J.; Dyer, R. D. J. Med. Chem. 1994, 37, 322.
2
3
3
6 4
H
6
2
1
3
2
2
H), 10.51 (s, 1H, –NH–C
m/z 315.0 (M , C17H N O , required 314.39). Compound
H
6 4
; D
2
O exchangeable); LC-MS
+
22 4 2
1
IIId: H NMR (60 MHz, CDCl ): 0.8–1.5 (m, 10H, –NH–
3
3
4
5
6
. de Leval, X.; Delarge, J. J.; Pirotte, B.; Dogne, J. M. Curr.
Med. Chem. 2002, 9, 941.
. Shishoo, C. J.; Chhabria, M. T.; Gandhi, T. P.; Bangaru,
R. A. Arzneim.-Forsch./Drug Res. 1997, 47, 35.
. Chhabria, M. T. Ph. D. Thesis, Gujarat University, India,
May 1998.
CH(CH ) , COOCH CH , –NH–CH(CH ) ), 2.67 (s, 3H,
3 2
3
2
2
3
p-OCH
m, 4H, p-OCH
D O exchangeable), 8.17 (s, 1H, C–H), 9.96 (s, 1H, –NH–
3
–C
6 4
H ), 4.3–4.5 (q, 2H, COOCH
2 3
CH ), 7.3–7.5
(
3
–C ), 7.97 (s, 1H, –NH–CH(CH
6
H
4
3 2
) ;
2
2
+
C
C
6
H
4
; D
2
O exchangeable); LC-MS m/z 331.0 (M ,
1
17
H
22
N
4
O
3
,
required 330.39). Compound IIIe:
): d 1.25–1.27 (m, 6H, –NH–
CH(CH ) ), 1.47–1.50 (t, 3H, –COOCH CH ), 4.36–4.40
H
. Chhabria, M. T.; Shishoo, C. J. Heterocycles 1999, 51,
NMR (400 MHz, CDCl
3
2723.
3
2
2
3
7
8
. Taylor, E. C.; Gillespie, P. J. Org. Chem. 1992, 57, 5757.
. General synthetic procedure and analytical data for II,
IIIa–IIIe: To N-[2-ethoxycarbonyl-2-cyano-1-(isopropyla-
mino)vinyl]formamidine (0.01 mol), dioxane (30 ml) satu-
rated with dry hydrogen chloride gas was added and
stirred for 3 h. The reaction mixture was allowed to stand
at room temperature for 12 h and poured into ice. The
solid obtained was filtered, triturated with saturated
sodium bicarbonate solution, filtered, washed with water,
and dried. Crystallization of the crude product from n-
(
COOCH CH ), 5.16 (s, 2H, –NH–C
m, 1H, –NH–CH(CH
3
)
2
), 4.43–4.47 (q, 2H,
–
2
3
6
0
H
4
0
– SO
2
NH
2
, D
exchangeable), 7.74–7.77 (d, 2H, Ar-2 ,6 -H), 7.82–7.85 (d,
2
O
0
0
2H, Ar-3 ,5 -H), 7.90–7.91 (s, 1H, –NH–CH(CH ) ; D O
exchangeable), 8.24 (s, 1H, C–H), 10.61 (s, 1H, –NH–
3
2
2
2
+
C
C H N O S, required 379.44).
H
6 4
; D
2
O exchangeable); LC-MS m/z 380.2 (M ,
1
6
21
5
4
9
. Synthetic procedure and analytical data for IV: A mixture
of II (0.01 mol) and potassium phenoxide (0.01 mol) in
dimethylformamide (15 ml) was refluxed for 3 h. The
reaction mixture was allowed to cool to room temperature
and poured into ice. The solid so obtained was filtered,
washed with excess of water, and dried. Crystallization of
hexane afforded colorless crystalline product II. Com-
1
pound II: H NMR (60 MHz, CDCl ): d 0.9–1.8 (m, 10 H,
3
–
NH–CH(CH
3
)
2
, COOCH
.5 (q, 2H, COOCH CH ), 8.12 (s, 1H, –NH–CH(CH ) ;
2 3 3 2
CH , –NH–CH(CH ) ), 4.3–
4
D O exchangeable), 8.47 (s, 1H, C–H); LC-MS m/z 244.4
2
3
3 2
2
crude product from methanol yielded colorless crystalline
product (87.5% yield). H NMR (60 MHz, CDCl ): d 1.2–
2
1
+
3
(
M , C H ClN O , required 243.67); A mixture of II
10 14 3 2
1
.4 (m, 10H, –NH–CH(CH
CH(CH ), 4.3–4.5 (q, 2H, COOCH
H, –OC H ), 8.20 (s, 1H, –NH–CH(CH3)2; D O
3
)
2
, COOCH
2 3
CH , –NH–
(
0.01 mol), substituted amine (0.01 mol), and catalytic
3
)
2
2
CH ), 7.0–7.5 (m,
3
amount of concentrated HCl in isopropylalcohol (15 ml)
was refluxed for 3 h. The reaction mixture was allowed to
cool to room temperature and poured into ice. The crude
solid product so obtained was filtered, washed with excess
of water, and dried. Recrystallization of crude product
5
6
5
2
2
exchangeable), 8.40 (s, 1H, C–H); LC-MS m/z 302.0
(
+
19 3 3
M , C16H N O , required 301.35).
1
1
0. Greenhouse, D. D. J. Pharm. Exp. Ther. 1969, 169, 29.
1. Winter, C. A.; Risley, E. A.; Nuss, G. W. Proc. Soc. Expt.
Biol. Med. 1962, 111, 544.
from methanol yielded colorless crystalline product in
1
good yields (60–90%). Compound IIIa:
400 MHz, CDCl
.45–1.49 (t, 3H, –COOCH CH ), 4.3–4.4 (m, 1H, –NH–
H
NMR
1
2. Scibert, K.; Zhang, Y. Proc. Natl. Acad. Sci. U.S.A. 1994,
9
(
1
3
): d 1.21–1.27 (m, 6H, –NH–CH(CH
3
)
2
),
1, 12013.
2
3