Synthesis of 4-substituted pyrido[2,3-d]pyrimidin-4(1H)-one as analgesic and anti-inflammatory agents

Article abstract of DOI:10.1016/j.bmcl.2009.05.044

4-Substituted-pyrido[2,3-d]pyrimidin-4(1H)-ones 4a-c were synthesized by oxidation of 4-substituted-dihydropyrido[2,3-d]pyrimidin-4(1H)-ones 3a-c which were in turn prepared from arylidenemalononitriles 1a-c and 6-aminothiouracil 2. The reactivity of comp

Full text of DOI:10.1016/j.bmcl.2009.05.044

Bioorganic & Medicinal Chemistry Letters 19 (2009) 3392–3397
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of 4-substituted pyrido[2,3-d]pyrimidin-4(1H)-one as analgesic
and anti-inflammatory agents
*
Abdel-Rahman B. A. El-Gazzar , Hend N. Hafez
National Research Centre, Photochemistry Department (Heterocyclic and Nucleoside Unit), Dokki, Giza, 12622 Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
4-Substituted-pyrido[2,3-d]pyrimidin-4(1H)-ones 4a–c were synthesized by oxidation of 4-substituted-
dihydropyrido[2,3-d]pyrimidin-4(1H)-ones 3a–c which were in turn prepared from arylidenemalononitr-
iles 1a–c and 6-aminothiouracil 2. The reactivity of compounds 4a–c towards some reagents such as
formamide, carbon disulfide, urea, thiourea, formic and acetic acids were studied. All the synthesized
compounds were characterized by spectroscopic means and elemental analysis. Compound 4c exhibited
64% and 72% analgesic activity. Also, compound 4b showed 50% and 65% anti-inflammatory activity.
Interestingly these compounds showed one-third of ulcer index of the reference aspirin and diclofenac.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 30 January 2009
Revised 23 April 2009
Accepted 12 May 2009
Available online 18 May 2009
Keywords:
Pyrido[2,3-d]pyrimidines
Anti-inflammatory
Analgesic activity
Ulcerogenicity
Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly
prescribed for the treatment of acute and chronic inflammation,
pain and fever. However, long-term clinical usage of NSAIDs is
associated with significant side effects such as gastrointestinal le-
sions, bleeding, and nephrotoxicity. Therefore, discovery of new
safer anti-inflammatory drugs represents a challenging goal in a
research area.1–3 In our ongoing medicinal chemistry research
program, we found that pyrimidines and condensed pyrido[2,3-
d]pyrimidines exhibit potent central nervous system (CNS)
activity, including analgesic, anti-inflammatory and anticonvulsant
behavior.4,5 Pyridopyrimidines with 7-(6-morpholin-4-ylpyridin-
3-yl)-substitutions are reported to possess significant analgesic,
anti-inflammatory and anticonvulsant activitiy.6,7 We have earlier
documented that some lead 2-pyrazolyl-pyridopyrimidines,8 2-
thioxopyridipyrimidines, 2-thioxopyrimidoquinolines exhibited
good analgesic and anti-inflammatory properties.9,10
Both pyrimidine and heterocyclic uracil structural analogues
such as 2-thioxo-pyrido[2,3-d]pyrimidin-4-one and pyrrolo[2,3-
d]pyrimidines have shown a wide range of biological applications.
The use of Sangivamicine or Toyocamicine as antibiotics is well
known, and the antiviral application of their analogues has been
reported.11 Besides, other pyrido[2,3-d]pyrimidine ring system is
present in a number of biologically active compounds which in-
cludes antipyretic,12 bactericides,13 medicinal,14 and antitu-
moral,15 antihistaminic,16 diuretic,17,18 activities and can even be
used in the treatment of neuronal diseases.19
In this work, we present the synthesis of several pyrido[2,3-
d]pyrimidine derivatives from 6-aminouracil and arylidenemalon-
onitrile derivatives. These reactions have two points of interest:
first, to obtain new derivatives with potential biological applica-
tions, and second to explore into the reactivity of 6-aminouracil
with electron-deficient alkenyl compounds; these reactions, as
we previously reported in the case of electron-deficient a,b-unsat-
urated dienophiles,20–22 could evolve through two different ways
via a Michael addition at the C(5) atom of the pyrimidine ring.23
The synthesis of pyrido[2,3-d]pyrimidine derivatives from 6-
aminouracil and ketones, DMFDMA,24
a
,b-unsaturated ketones,25
and via Mannich bases (arylalkanone),26 has been reported. In
our case we have used arylidenemalononitrile derivatives 1 as
electron-deficient reactants with 6-aminouracil 2.
6-Aminothiouracil 2 was reacted with an equimolar amount of
arylidenemalononitrile 1a–c according to the reported proce-
dure.20 We performed this reaction under dry conditions and
refluxing for long time in order to prevent the formation of the
1,4-dihydropyrido[2,3-d]pyrimidin-4-ones 3a–c, thus it was not
necessary to purified the reaction mixture by column chromatog-
raphy. The most probable mechanism to afford pyridopyrimidines
3, which is shown in Scheme 1, involves two steps, the first a Mi-
chael addition reaction of the pyrimidine ring C-5 carbon atom to 1
to give, via zwitterionic structure I, the intermediate II, which then
undergoes ring closing resulting in product 3. The prolonged dura-
tion reaction is required to furnish the oxidized form 4a–c.
Various 7-amino-6-cyano-5-sbstituted-2-thioxopyrido[2,3-d]pyr-
imidin-4(1H)-ones (4a–c, Scheme 2) were synthesized by
condensation of arylidenemalononitriles 1a–c and 6-aminothio-
uracil 2 as reported in the literature.9 6-Aminothiouracil on
* Corresponding author. Tel.: +20 237318830.
E-mail address: profelgazzar@yahoo.com (A.-R.B.A. El-Gazzar).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.05.044

A.-R.B.A. El-Gazzar, H. N. Hafez / Bioorg. Med. Chem. Lett. 19 (2009) 3392–3397
3393
O
Ar
O
O
Ar
O
Ar
H
Ar
CN
CN
N
-
CN
HN
HN
HN
HN
+
+
S
N
H
NH2
NC
CN
S
N
H
N
H
NH2
S
N
H
NH2
S
N
H
NH2 NH
1
I
II
2
3
Scheme 1. Mechanism postulated for the reaction of 6-aminouracil and arylidenemalononitrile.
X
X
X
N
N
N
O
DMF
+
NH
O
O
H
CN H2N
N
H
S
CN
CN
H
HN
HN
H
N
CN
1a-c
S
N
H
S
N
H
N
NH2
NH2
2
X
X
X = CH2, O, N-CH3
N
N
O
O
1-1.5 h
3-5 h
H
CN
CN
HN
HN
S
N
H
N
NH2
S
N
H
N
4a-c
NH2
H
3a-c
Scheme 2. Reaction of 6-aminouracil with arylidenemalononitriles 1a–c.
refluxing with arylidenemalononitrile 1a in dimethylformamide
for 3–5 h gave condensed product 4a after usual workup. Com-
pound 4a was purified by crystallization from dioxane to give pure
7-amino-6-cyano-5-[4-(1-piperidinyl)-phenyl]-2-thioxopyrido [2,3-
d]pyrimidin-4(1H)-ones (4a) in 78% yield. 1H NMR (500 MHz;
DMSO-d6) of 4a showed signals at d 1.56 (br s, 6H, piperidinyl 3
CH2), 3.25 (br s, 4H, piperidinyl 2 NCH2), 6.88 (AA0BB0, 2H, Ar–H,
J = 8.6 Hz), 7.10 (AA0BB0, 2H, Ar–H, J = 8.6 Hz), 7.62 (br s, 2H, NH2),
8.45 (br s, H, NH), 12.05 (br s, H, NH). Also, 13C NMR (500 MHz;
DMSO-d6) of 4a showed signals at d 23.86, 25.09, 25.81 (3 CH2),
48.15, 48.67 (2 NCH2), 107.68 (CN), 113.63, 114.83, 115.64,
117.12, 120.83, 121.92, 129.18, 151.4, 153.07, 167.30, 160.98 (11
signals for 11 sp2 carbon), 172.7 (C@O), 183.05 (C@S). IR spectra
show absorption band at 3450 (NH’s), 2218 (CN) and 1680 (C@O)
cmꢀ1. Spectral data of 4a fully support the structure assigned to
it. Similarly the others –(4-morpholinyl) and –(4-methylpiperazi-
nyl), that is, 4b,c (Scheme 2) were synthesized and purified by
crystallization. Spectral and analytical data of compounds 4a–c re-
ported in Reference and notes of this Letter fully support the struc-
tures assigned to them.
Compounds 4a–c as a typical b-enaminonitrile derivative,
reacted with formamide and aliphatic acids namely, formic and
acetic acids, afforded 5-substituted-pyrido[2,3-d:6,5-d]dipyrimi-
dine-4,6-dione derivatives (5a–c, 7a–f), respectively. The IR
spectra of compounds
5 displayed absorption bands around
3500 cmꢀ1 (NH, NH2) and around 1685 cmꢀ1 for carbonyl group,
However the IR spectra of compounds 7 displayed absorption
bands around 3450 cmꢀ1 (NH) and around 1670, 1685 cmꢀ1 for
two carbonyl groups. The 1H NMR (DMSO-d6) spectrum of 5b
showed the signals at
d 3.29 (t, 4H, morpholinyl 2 NCH2,
J = 5.0 Hz), 3.90 (t, 4H, morpholinyl 2 OCH2, J = 5.0 Hz), 6.98
(AA0BB0, 2H, Ar–H, J = 8.7 Hz), 7.18 (AA0BB0, 2H, Ar–H, J = 8.7 Hz),
7.75 (br, s, 2H, NH2), 8.06 (s, 1H, pyrimidine-H), 8.65 (br s, H,
NH), 12.30 (br s, H, NH). Also, the 1H NMR (DMSO-d6) spectrum
of compound 7b as an example showed signals at 1.60 (br, s, 6H,
piperidinyl 3 CH2), 2.26 (s, 3H, pyrimidine-CH3), 3.32 (br s, 4H,

3394
A.-R.B.A. El-Gazzar, H. N. Hafez / Bioorg. Med. Chem. Lett. 19 (2009) 3392–3397
piperidinyl 2 NCH2), 7.10 (d, 2H, Ar–H, J = 8.6 Hz), 7.25 (d, 2H, Ar–
H, J = 8.6 Hz), 8.50 (br s, H, NH), 9.70 (br s, 1H, NH), 11.80 (br s, H,
NH).
at 3 h (Table 1). Compound 4b with morpholine substituent
showed good activity; with the increased lipophilicity (N-methyl-
piprazine group, compound 4c) showed increased in activity.
Replacement of N-methylpiprazine group with piperidinyl group
(compound 4a) retains the activity. 4-Aminopyrimidine ring for-
mation at C-2 and C-3 (compounds 5a–c) leads to moderate de-
crease in activity. Imino-pyrimido[1,3]thiazine formation and
pyrimidin-4-one formations (compounds 6a–c and 7a–c) also re-
sults in decreasing activity. 2-Thioxopyrimidines ring formation
(compound 8a–c) leads to further decrease of activity. Compound
7-amino-6-cyano-5-[4-(4-methylpiperazinyl)-phenyl]-2-thioxo-
pyrido[2,3-d]pyrimidin-4(1H)-one (4c) emerged as the most active
analgesic agent and it is moderately more potent when compared
to the reference standard diclofenac sodium.
Also, when compound 4a–c was heated with carbon disulfide in
pyridine, 6-Imino-5-substituted-2-thioxopyrimido[40,50:2,3]pyr-
ido[6,5-d][1,3]thiazin-13-one (6a–c), was obtained. The 1H NMR
(DMSO-d6) spectrum of 6c showed signals at d 2.29 (s, 3H, piperaz-
inyl NCH3), 2.57 (br s, 4H, piperazinyl 2 CH3NCH2), 3.38 (br s, 4H,
piperazinyl 2 ArNCH2), 7.18 (AA0BB0, 2H, Ar–H, J = 8.6 Hz), 7.42
(AA0BB0, 2H, Ar–H, J = 8.6 Hz), 8.45 (br s, H, NH), 8.90 (s, 1H, NH),
9.25 (br s, H, NH), 11.80 (br s, H, NH).
Finally, compound 4a–c reacted with thiourea or urea at 180 °C,
it gave 6-amino-5-substituted-2,8-dithiopyrido[2,3-d:6,5-d]dipyr-
imidin-4-one (8a,c,e), and 6-amino-5-substituted-2-thiopyri-
do[2,3-d:6,5-d]dipyrimidine-4,8-dione
(8b,d,f),
respectively,
Anti-inflammatory activity was evaluated by carrageenan-in-
duced paw edema test in rats.27 The anti-inflammatory activity
data (Table 2) indicated that all the test compounds protected rats
from carrageenan-induced inflammation moderately at 30 min of
reaction time; the activity increased at 1 h and it reached to peak
level at 2 h. Declining in activity was observed at 3 h. The com-
pound with morpholine substituent 4b showed moderately more
potent anti-inflammatory activity when compared to the reference
standard diclofenac sodium. The compound 7-amino-6-cyano-5-
[4-(4-methylpiperazinyl)-phenyl]-2-thioxopyrido[2,3-d]pyrimi-din-
4(1H)-one (4c) showed equipotent anti-inflammatory activity
when compared to the reference standard diclofenac sodium.
The ulcer index of the test compounds (Table 2) reveals that the
2-amino-3-cyano-pyrido[2,3-d]pyrimidines 4a–c and 6-amino-5-
(Scheme 3). The 1H NMR (DMSO-d6) spectrum of 8f, as an example,
showed signals at 2.26 (s, 3H, piperazinyl NCH3), 2.58 (br, s, 4H,
piperazinyl 2 CH3NCH2), 3.39 (br s, 4H, piperazinyl 2 ArNCH2),
7.07 (AA0BB0, 2H, Ar–H, J = 9.0 Hz), 7.33 (AA0BB0, 2H, Ar–H,
J = 9.0 Hz), 8.23 (br s, 2H, NH2), 8.70 (br s, H, NH), 9.37 (br s, H,
NH), 11.82 (br s, H, NH). Also, its IR spectra for the compounds 8
displayed absorption bands around 3500 (NH, NH2) and 1670,
1685 cmꢀ1 (2 C@O).
Test for analgesic activity was performed by tail-flick technique
using Wistar albino mice. The results of analgesic activity indicate
that test compounds exhibited moderate analgesic activity at
30 min of reaction time; the activity increased at 1 h, further it
reached to peak level at 2 h and declining in activity was observed
X
X
N
N
O
NH
O
NH2
CS2
HN
S
HN
N
4a-c
S
N
H
N
N
H
S
S
N
H
N
N
6a-c
5a-c
X
X
5,6, a, X = CH2
b, X = O
c, X = N-CH3
N
N
Urea or
Thiourea
O
NH2
O
O
N
HCOOH or
AcOH
HN
N
HN
NH
S
N
H
N
N
H
Y
S
N
H
N
7a-f
R
8a-f
8b, Y = O, X = CH2
8d, Y = O, X = O
8f,Y = O, X = N-CH3
7b, X = CH2 , R = CH3
7d, X = O , R = CH3
7f, X = N-CH3 , R = CH3
7a, X = CH2 , R = H
7c, X = O , R = H
7e, X = N-CH3 , R = H
8a, Y = S, X = CH2
8c,Y = S, X = O
8e,Y = S, X = N-CH3
Scheme 3. Reactions of 2-aminopyrido[2,3-d]pyrimidine-3-carbonitriles 4a–c with some reagents.

A.-R.B.A. El-Gazzar, H. N. Hafez / Bioorg. Med. Chem. Lett. 19 (2009) 3392–3397
3395
Table 1
Table 2
Percent analgesic activity of the synthesized compounds (tail-flick technique)
Percent anti-inflammatory activity of the synthesized compounds (Carrageenan-
induced paw oedema test in rats)
Compound
Percent analgesic activity
Compound Dose
(mg/kg)
Percent protection
1 h 28 h
Ulcer index
Dose (mg/kg) 30 min
1 h
2 h
55 1.26**
3 h
30 min
3 h
4a
4b
4c
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
46 1.39*
63 1.54***
45 1.69*
59 1.51***
53 1.79**
67 1.91***
41 1.71*
55 1.62**
38 1.57*
55 1.25**
39 1.71*
50 1.93*
38 172*
51 1.83*
39 1.23*
49 1.74*
32 1.72*
42 1.11*
32 1.62*
40 1.31*
37 1.09*
48 1.22*
30 1.69*
44 1.93*
38 1.39*
43 1.92*
39 1.71*
48 1.93*
42 1.76*
48 1.25*
51 1.73*
39 1.25*
64 1.26*** 69 1.73*** 47 1.37*
4a
10
35 1.96* 37 1.36* 45 1.54* 29 1.26* 0.58 1.39*
45 1.08* 49 1.32** 51 1.58** 36 1.27*
47 1.32*
63 1.67*** 66 1.59*** 43 1.38*
60 1.73** 64 1.32*** 44 1.36*
68 1.57*** 72 1.51*** 52 1.58*
53 1.15**
31 1.92*
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
10
20
4b
4c
41 1.21* 48 1.39* 50 1.30** 36 1.72* 0.54 1.56*
50 1.52** 61 1.54*** 63 1.52*** 47 1.96*
39 1.26* 40 1.54* 46 1.63* 31 1.63* 0.51 1.47*
48 1.32** 55 1.62*** 60 1.39*** 37 1.35*
49 1.24*
57 1.93**
43 1.90*
57 1.84**
43 1.72*
58 1.66**
42 1.28*
53 1.73**
41 1.28*
53 1.84*
35 1.23*
46 1.70*
36 1.81*
50 1.32*
43 1.83*
56 1.24*
38 1.74*
47 1.24*
43 1.53*
49 1.24**
43 1.82*
51 1.28*
45 1.62*
49 1.63*
52 1.64*
59 1.93**
46 1.73*
58 1.66**
45 1.56*
58 1.25*
48 1.71*
56 1.58**
44 1.90*
56 1.26**
38 1.23*
49 1.58*
45 1.26*
55 1.36**
48 1.39*
56 1.58**
45 1.18*
53 1.23*
46 1.26*
52 1.35*
46 1.71*
53 1.63**
49 1.57*
55 1.29**
32 1.66*
38 1.90*
27 1.73*
36 1.56*
36 1.96*
43 1.71*
34 1.23*
39 1.73*
32 1.44*
44 1.52*
29 1.41*
38 1.89*
33 1.32*
39 1.82*
35 1.32*
42 1.71*
29 1.71*
36 1.56*
34 1.29*
41 1.31*
33 1.71*
44 1.93*
33 1.63*
46 1.51*
5a
33 1.31* 39 1.57* 40 1.37* 32 1.63* 0.58 1.39*
42 1.29* 45 1.53* 48 1.71* 39 1.23*
5b
5c
35 1.28* 40 1.18* 42 1.39* 30 1.71* 0.70 1.37*
43 1.34* 47 1.74* 49 1.22** 38 1.36*
35 1.28* 37 1.32* 38 1.37* 31 1.29* 0.69 1.17*
43 1.34* 48 1.18* 50 1.56* 38 1.37*
6a
33 1.28* 38 1.57* 39 1.73* 25 1.91* 0.73 1.34*
37 1.71* 40 1.31* 46 1.32* 33 1.24*
6b
6c
25 1.73* 28 1.91* 31 1.72* 21 1.41* 0.89 1.62*
30 1.26* 34 1.57* 42 1.74* 30 1.30*
31 1.27* 32 1.18* 37 1.31* 22 1.33* 0.85 1.32*
39 1.93* 40 1.21* 46 1.28* 31 1.47*
7a
30 1.71* 34 1.53* 38 1.61
27 1.18* 0.89 1.41*
35 1.60* 41 1.27* 44 1.71* 32 1.73*
7b
7c
29 1.71* 33 1.73* 34 1.64* 26 1.61* 0.90 1.51*
36 1.83* 39 1,72* 41 1.25* 34 1.74*
31 1.29* 36 1.57* 38 1.22* 29 1.51 0.86 1.33*
39 1.33* 42 1.26* 46 1.36* 36 1.30*
8a
35 1.27* 37 1.42* 40 1.97* 28 1.71* 0.69 1.27*
41 1.31* 47 1.56* 51 1.23* 39 1.69*
8b
8c
33 1.26* 39 1.62* 43 1.73* 29 1.31* 0.72 1.61*
40 1.83* 46 1.51** 48 1.62** 35 1.70*
33 1.54* 40 1.72* 43 1.11* 29 1.25* 0.67 1.23*
39 1.26* 46 1.60* 49 1.29** 38 1.56*
Control
Diclofenac
2
0.35
6
0.49
4
0.59
45 0.94*
62 1.49*** 39 1.13*
4
0.91
10
20
37 1.69*
46 0.95*
43 1.42*
55 1.16**
33 0.96*
Control
Diclofenac 10
20
5.1 0.29 6.1 0.27 5.7 0.32 3.2 0.93 0.15 0.32**
32 0.63* 38 1.58* 39 1.97* 33 0.93*
45 1.63** 52 0.92*** 60 1.52*** 42 1.36** 1.65 0.59**
1.73 0.41*
Each value represents the mean SEM (n = 6).
Aspirin
—
—
—
—
—
Significance levels *p < 0.5, **p < 0.01 and ***p < 0.001 as compared with the
respective control.
Each value represents the mean SEM (n = 6).
Significance levels *p < 0.5, **p < 0.01 and ***p < 0.001 as compared with the
respective control.
[4-(1-piperidinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d] dipyrimidine
(5a) showed negligible ulcer index, whereas compounds 5b,c, 6a
and 8a–c exhibited little increase in ulcer index and the compounds
6b,c and 7a–c exhibited higher ulcer index over other test com-
pounds. When compared to the reference standard aspirin (ulcer in-
dex 1.73 0.41) and diclofenac (ulcer index 1.6 0.59) the test
compounds exhibited about 35–50% of the ulcer index of reference
standards. Compounds 5-[4-(4-methylpiperazinyl)-phenyl]-2-thi-
oxopyrido[2,3-d]pyrimidine (4c) and 5-[4-(4-morpholinyl)-phe-
nyl]-2-thioxopyrido-[2,3-d]pyrimidine (4b) exhibited least ulcer
index (0.54 1.56 and 0.51 1.47, respectively)among the test
compounds, which is about one-third of the ulcer index of reference
standards aspirin and diclofenac. The compound 5-[4-(1-piperidi-
nyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-4,6-dione
(7a) showed the highest ulcer index (0.90 1.51) among the test
compounds which is about 50% of the ulcer index of reference stan-
dards aspirin and diclofenac.
In summary, a new series of pyrido[2,3-d]pyrimidine deriva-
tives has been prepared an fully assigned by analytical and spectral
data.28 The results of the analgesic and anti-inflammatory activi-
ties of the present series showed that moderate enhancement of
the activity. Compound 4c exhibited 64% and 72% analgesic activity
at 10 and 20 mg/kg dose level, respectively, at the reaction time of
2 h. The compound 4b showed 50% and 65% anti-inflammatory
activity at the dose 10 and 20 mg/kg, respectively, at the reaction
time 2 h. Interestingly these compounds showed one-third of ulcer
index of the reference aspirin and diclofenac. Hence this series
could be developed as a novel class of analgesic and anti-inflam-
matory agents. However, further structural modification is planned
to increase the analgesic and anti-inflammatory activities with the
decreased ulcerogenic index.
Acknowledgments
The authors are thankful to the National Research Center for
providing laboratory facilities, Micro-analytical Centre, Cairo Uni-
versity and the Pharmacological Unit National Research Centre,
for microanalyses and pharmacological screening of the
compounds.
References and notes
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2. van Ryn, J.; Trummlitz, G.; Pairet, M. Curr. Med. Chem. 2000, 7, 1145.
3. van Ryn, J. Nat. New Biol. 1971, 231, 232.
4. Gavrilov, M. Y.; Mardanova, I. G.; Kolla, V. E.; Konshin, M. E. Pharm. Chem. J.
1988, 22, 554.
5. Robins, B. R.; Hitciiings, G. J. Am. Chem. Soc. 1958, 80, 3449.
6. Matulenko, M. A.; Lee, C. H.; Jiang, M.; Frey, R. R.; Cowart, M. D.; Bayburt, E. K.;
Didomenico, S., Jr.; Gfesser, G. A.; Gomtsyan, A.; Zheng, G. Z.; McKie, J. A.;
Stewart, A. O.; Yu, K.; Kohlhaas, K. L.; Alexander, K. M.; McGaraughty, S.;
Wismer, C. T.; Mikusa, J.; Marsh, K. M.; Snyder, R. D.; Diehl, M. S.; Kowalk, E. A.;
Jarvis, M. F.; Bhagwat, S. S. Bioorg. Med. Chem. 2005, 13, 3705.
7. Gfesser, G. A.; Bayburt, E. K.; Cowart, M.; DiDomenico, S.; Gomtsyan, A.; Lee, C.
H.; Stewart, A. O.; Jarvis, M. F.; Kowaluk, E. A.; Bhagwat, S. S. Eur. J. Med. Chem.
2003, 38, 245.
8. Hafez, N. H.; Abbas, H. A. S.; El-Gazzar, A. B. A. Acta Pharm. 2008, 58, 359.
9. El-Gazzar, A. B. A.; El-Enany, M. M.; Mahmoud, M. N. Bioorg. Med. Chem. 2008,
16, 3261.
10. El-Gazzar, A. B. A.; Hafez, H. N.; Nawwar, G. W. Eur. J. Med. Chem. 2009, 44,
1427.

3396
A.-R.B.A. El-Gazzar, H. N. Hafez / Bioorg. Med. Chem. Lett. 19 (2009) 3392–3397
11. Renan, T.; Kennedy, C.; Ptak, R.; Breitenbach, J.; Drach, J.; Townsend, L. J. Med.
Chem. 1996, 39, 873.
dioxane, in 67% yield, mp 311–313 °C, IR,
m
max/cmꢀ1: 3485 (br s, NH, NH2),
1.58 (br s, 6H,
3034 (CH aryl), 1680 (CO). 1H NMR (DMSO-d6) ppm:
d
12. Piper, J. R.; McCaleb, G. S.; Montgomery, J. A.; Kisliuk, R. L.; Sirotnaks, F. M. J.
Med. Chem. 1986, 29, 1086.
13. (a) Pathak, U. S.; Sing, S.; Padh, J. Indian J. Chem., Sect. B 1991, 30, 618; (b)
Darias, V.; Abdallah, S. S.; Tello, M. L.; Degado, L. D.; Vega, S. Arch. Pharm. 1994,
327, 779.
piperidinyl 3 CH2), 3.27 (br s, 4H, piperidinyl 2 NCH2), 6.96 (d, 2H, Ar–H,
J = 9.0 Hz), 7.14 (d, 2H, Ar–H, J = 9.0 Hz), 7.80 (br s, 2H, NH2), 8.30 (s, 1H,
pyrimidine-H), 8.68 (br s, H, NH), 11.70 (br s, H, NH); The MS, [M+], m/z 405
(76%); C20H19N7OS (405.4); requires (Found): C, 59.24 (59.21); H, 4.72 (4.69);
N, 24.18 (24.16).
14. (a) Carclunescu, D.; Lopez, A. D.; Iriarte, E. G.; Tina, G.; Gomez, G.; Tena, R.;
Ghirvu, C. Ann. R. Acad. Farm. 1985, 51, 241; (b) Newberry, R. A.; Bushell, B. J.;
U.S. 3, 979, 402 (Cl.260–302R; Co7 D227122).07 Sep. (1976), Brit. Appl. 748,
870, 27 Feb. (1974); C.A. 1977, 86, 29795z.
15. Cordeu, L.; Cubedo, E.; Bandres, E.; Rebollo, A.; Saenz, X.; Chozes, H. M.;
Dominquez, V.; Echeverria, M.; Mendivil, B.; Sanmartin, C.; Palop, J. A.; Font,
M.; Garcia-Foncillas, J. Bioorg. Med. Chem. 2007, 15, 1659.
6-Amino-5-[4-(4-morpholinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-
4-one (5b): It was obtained from 4b, as a yellow powder, crystallized from
dioxane, in 64% yield, mp 269–271 °C, IR, m
max/cmꢀ1: 3500 (br s, NH, NH2),
3039 (CH aryl), 1675 (CO). 1H NMR (DMSO-d6) ppm: d 3.29 (t, 4H, morpholinyl
2 NCH2, J = 5.0 Hz), 3.90 (t, 4H, morpholinyl 2 OCH2, J = 5.0 Hz), 6.98 (d, 2H, Ar–
H, J = 8.7 Hz), 7.18 (d, 2H, Ar–H, J = 8.7 Hz), 7.75 (br s, 2H, NH2), 8.06 (s, 1H,
pyrimidine-H), 8.65 (br s, H, NH), 12.30 (br s, H, NH); The MS, [M+], m/z 407
(100%); C19H17N7O2S (407.4); requires (Found): C, 56.01 (55.98); H, 4.21 (4.19);
N, 24.06 (24.11).
16. Quintela, J. M.; Peinador, C.; Botana, L.; Estevez, M.; Riguera, R. Bioorg. Med.
Chem. 1997, 5, 1543.
17. Monge, A.; Martinez-Merino, V.; Sanmartin, C.; Fernandez, F. J.; Ochoa, M. C.;
Bellver, C. Eur. J. Med. Chem. 1989, 24, 209.
18. Parish, H. A., Jr.; Gilliom, R. D. J. Med. Chem. 1982, 25, 98.
19. Andrus, P.; Fleck, T.; Oostveen, J.; Hall, E. J. Neurosci. Res. 1997, 47, 650.
20. El-Gazzar, A. B. A.; Gaafar, A. M.; Aly, A. S. Phosphorus, Sulfur, Silicon Relat. Elem.
2002, 177, 45.
21. El-Gazzar, A. B. A.; Gaafar, A. E. M.; Hafez, H. N.; Aly, A. S. Phosphorus, Sulfur
Silicon Relat. Elem. 2006, 181, 1859.
22. El-Gazzar, A. B. A.; Hossein, H. A. R.; Hafez, H. N. Acta Pharm. 2007, 57, 395.
23. Cobo, J.; Melguizo, M.; Nogueras, M.; Sanchez, A.; Dobado, A.; Monella, M.
Tetrahedron 1996, 52, 13721.
6-Amino-5-[4-(4-methylpiperazinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimi-
dine-4-one (5c): It was obtained from 4c, as a pale yellow powder, crystallized
from ethanol, in 70% yield, mp 261–263 °C, IR, m
max/cmꢀ1: 3445 (br s, NH, NH2),
3025 (CH aryl), 1685 (CO); 1H NMR (DMSO-d6) ppm: d 2.29 (s, 3H, piperazinyl
NCH3), 2.59 (br s, 4H, piperazinyl 2 CH3NCH2), 3.36 (br s, 4H, piperazinyl 2
ArNCH2), 7.12 (d, 2H, Ar–H, J = 8.5 Hz), 7.40 (d, 2H, Ar–H, J = 8.5 Hz), 8.00 (br s,
2H, NH2), 8.32 (s, 1H, pyrimidine-H), 8.90 (br s, H, NH), 11.65 (br s, H, NH); The
MS, [M+], m/z 420 (100%); C20H20N8OS (420.5); requires (Found): C, 57.12
(57.09); H, 4.79 (4.81); N, 26.65 (26.59).
6-Imino-5-substituted-2-thioxopyrimido[40,50:2,3]pyrido[6,5-d][1,3]thiazin-13-
one (6a–c); General procedure: A mixture of compound 4 (10 mmol) and carbon
disulfide (excess 10 mL) was heated under reflux on a water-bath (80 °C) in
40 mL pyridine for 12 h (TLC control). The reaction mixture was allowed to cool
to 0 °C for 12 h the precipitate was filtered off, washed with ethanol (40 mL),
dried and crystallized from the proper solvent.
24. Hassneen, H. M.; Abdallah, T. A. Molecules 2003, 8, 333.
25. Quiroga, J.; Insuasty, B.; Sanchez, A.; Nogueras, M.; Meier, H. J. Heterocycl. Chem.
1992, 29, 1045.
26. Girreser, U.; Heber, D.; Schutt, M. Tetrahedron 2004, 60, 11211.
27. Winter, C. A.; Risley, E. A.; Nuss, G. W. Exp. Biol. Med. 1962, 111, 544.
28. General: All melting points were measured using an Electrothermal IA 9100
apparatus (Shimadzu, Japan). The 1H NMR and 13C NMR spectra were recorded
on JEOL ECA-500 and chemical shifts were expressed as d values against
Si(CH3)4 as internal standard (p-substituted phenyl are assigned as AA0BB0
system). IR spectra were recorded as KBr pellets on a Perkin–Elmer 1430
spectrometer, (National Research Center and Department of Chemistry Cairo
University). Mass spectra were run at 70ev on HP-5988A Mass spectrometer,
Micro-analytical Centre, Cairo University. The pharmacological data were
analyzed in Pharmacological Unit National Research Centre, Egypt. The starting
materials 1a–c were prepared according to the reported procedure.29
6-Imino-5-[4-(1-piperidinyl)phenyl]-2-thioxopyrimido[40,50:2,3]pyrido[6,5-
d][1,3]-thiazin-13-one (6a): It was obtained from 4a, as a dark brown substance
and crystallized from DMF in 65% yield, mp 317–319 °C, IR, m
max/cmꢀ1: 3500
(br s, NH’s), 3036 (CH aryl), 1680 (CO). 1H NMR (DMSO-d6) ppm: d 1.53 (br s,
6H, piperidinyl 3 CH2), 3.24 (br s, 4H, piperidinyl 2 NCH2), 7.02 (d, 2H, Ar–H,
J = 8.7 Hz), 7.14 (d, 2H, Ar–H, J = 8.7 Hz), 8.39 (br s, H, NH), 8.85 (br s, H, NH),
9.50 (br s, H, NH), 11.20 (br s, H, NH); The MS, [M+], m/z 452 (100%);
C20H16N6OS3 (452.5); requires (Found): C, 53.07 (53.02); H, 3.56 (3.54); N,
18.57 (18.49).
6-Imino-5-[4-(4-morpholinyl)phenyl]-2-thioxopyrimido[40,50:2,3]pyrido[6,5-
d][1,3]-thiazin-13-one (6b): It was obtained from 4b, as a dark yellow powder
Synthesis
4(1H)-ones 4a–c; General procedure:
arylidenemalononitrile and 6-aminothiouracil
of
7-amino-6-cyano-5-sbstituted-2-thioxopyrido[2,3-d]pyrimidin-
mixture of equimolar of
(10 mmol) in
and crystallized from DMF in 62% yield, mp 339–341 °C, IR, m
max/cmꢀ1: 3480
A
(br s, NH’s), 3039 (CH aryl), 1676 (CO). 1H NMR (DMSO-d6) ppm: d 3.32 (t, 4H,
morpholinyl 2 NCH2, J = 4.9 Hz), 3.86 (t, 4H, morpholinyl 2 OCH2, J = 4.9 Hz),
7.08 (d, 2H, Ar–H, J = 8.9 Hz), 7.22 (d, 2H, Ar–H, J = 8.9 Hz), 8.20 (br s, H, NH),
8.86 (br s, H, NH), 9.30 (br s, H, NH), 12.10 (br s, H, NH); The MS, [M+], m/z 456
(53%); C19H16N6O2S3 (456.5); requires (Found): C, 49.98 (49.89); H, 3.53 (3.50);
N, 18.41 (18.37).
1
2
dimethylformamide (50 mL) was boiled under reflux for 3–5 h (under TLC
control). The reaction mixture was allowed to cool; the formed precipitate was
filtered off, washed with ethanol and dried, and crystallized from appropriate
solvent to produce 4a–c in good yields.
7-Amino-6-cyano-5-[4-(1-piperidinyl)phenyl]-2-thioxopyrido[2,3-d]pyrimidin-
6-Imino-5-[4-(4-methylpiperazinyl)phenyl]-2-thioxopyrimido[40,50:2,3]pyrido-
[6,5-d][1,3]thiazin-13-one (6c): It was obtained from 4c, as a brown powder and
4(1H)-one (4a): It was obtained from 1a, as a yellow powder, crystallized from
dioxane; in 78% yield, mp 287–289 °C, IR,
m
max/cmꢀ1: 3450 (br s, NH, NH2),
crystallized from DMF in 60% yield, mp 291–293 °C, IR, m
max/cmꢀ1: 3520 (br s,
3028 (CH aryl), 2218 (CN), 1680 (CO); 1H NMR (DMSO-d6) ppm: d 1.56 (br s,
6H, piperidinyl 3 CH2), 3.25 (br s, 4H, piperidinyl 2 NCH2), 6.88 (d, 2H, Ar–H,
J = 8.6 Hz), 7.10 (d, 2H, Ar–H, J = 8.6 Hz), 7.62 (br s, 2H, NH2), 8.45 (br s, H, NH),
12.05 (br s, H, NH); 13C NMR (DMSO-d6) ppm: d 23.86, 25.09, 25.81 (3 CH2),
48.15, 48.67 (2 NCH2), 107.68 (CN), 113.63, 114.83, 115.64, 117.12, 120.83,
121.92, 129.18, 151.4, 153.07, 167.30, 160.98 (11 signals for 11 sp2 carbon),
172.7 (C@O), 183.05 (C@S); The MS, [M+], m/z 378 (67%); C19H18N6OS (378.4);
requires (Found): C, 60.29 (60.26); H, 4.79 (4.77); N, 22.23 (22.19).
NH’s), 3037 (CH aryl), 1678 (CO). 1H NMR (DMSO-d6) ppm: d 2.29 (s, 3H,
piperazinyl NCH3), 2.57 (br s, 4H, piperazinyl 2 CH3NCH2), 3.38 (br s, 4H,
piperazinyl
2 ArNCH2), 7.18 (d, 2H, Ar–H, J = 8.6 Hz), 7.42 (d, 2H, Ar–H,
J = 8.6 Hz), 8.45 (br s, H, NH), 8.90 (s, H, NH), 9.25 (br s, H, NH), 11.80 (br s, H,
NH); The MS, [M+], m/z 469 (58%); C20H19N7OS3 (469.5); requires (Found): C,
51.15 (51.09); H, 4.08 (4.05); N, 20.87 (20.79).
Synthesis of 5-substituted pyrido[2,3-d:6,5-d]dipyrimidine-4,6-dione (7a,c,e);
General procedure: A mixture of compound 4 (10 mmol), formic acid (10 mL)
and a catalytic amount of concentrated hydrochloric acid was heated under
reflux for 16 h. The reaction mixture was allowed to cool to room temperature,
poured into cold water (100 mL). The formed solid was collected by filtration,
washed by ethanol (20 mL), dried and crystallized.
7-Amino-6-cyano-5-[4-(4-morpholinyl)phenyl]-2-thioxopyrido[2,3-d]pyrimidin-
4(1H)-one (4b): It was obtained from 1b, as a yellow powder, crystallized from
dioxane; in 81% yield, mp 303–305 °C, IR, m
max/cmꢀ1: 3430 (br s, NH, NH2),
3045 (CH aryl), 2216 (CN), 1684 (CO); 1H NMR (DMSO-d6) ppm: d 3.25 (t, 4H,
morpholinyl 2 NCH2, J = 5.1 Hz), 3.84 (t, 4H, morpholinyl 2 OCH2, J = 5.0 Hz),
6.92 (d, 2H, Ar–H, J = 8.8 Hz), 7.14 (d, 2H, Ar–H, J = 8.8 Hz), 7.80 (br s, 2H, NH2),
8.39 (br s, H, NH), 12.00 (br s, H, NH); The MS, [M+], m/z 380 (100%);
C18H16N6O2S (380.4); requires (Found): C, 56.83 (56.79); H, 4.24 (4.19); N,
22.09 (22.11).
5-[4-(1-Piperidinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-4,6-dione
(7a): It was obtained from 4a, as a yellow powder, crystallized from DMF in
63% yield, mp 320–323 °C, IR, m
max/cmꢀ1: 3450 (br s, NH’s), 3029 (CH aryl),
1675, 1684 (2 C@O). 1H NMR (DMSO-d6) ppm: d 1.56 (br s, 6H, piperidinyl 3
CH2), 3.31 (br s, 4H, piperidinyl 2 NCH2), 6.94 (d, 2H, Ar–H, J = 8.8 Hz), 7.18 (d,
2H, Ar–H, J = 8.8 Hz), 8.24 (s, 1H, pyrimidine-H), 8.65 (br s, H, NH), 9.30 (br s, H,
NH), 12.10 (br s, H, NH); The MS, [M+], m/z 406 (100%); C20H18N6O2S (406.4);
requires (Found): C, 59.09 (59.11); H, 4.46 (4.41); N, 20.67 (20.64).
7-Amino-6-cyano-5-[4-(4-methylpiperazinyl)phenyl]-2-thioxopyrido[2,3-
d]pyrimi-din-4(1H)-one (4c): It was obtained from 1c, as a yellow powder,
crystallized from ethanol, in 76% yield, mp 273-275 °C, IR, m
max/cmꢀ1: 3430 (br
s, NH, NH2), 3029 (CH aryl), 2215 (CN), 1682 (CO). 1H NMR (DMSO-d6) ppm: d
2.31 (s, 3H, piperazinyl NCH3), 2.57 (br s, 4H, piperazinyl 2 CH3NCH2), 3.34 (br
s, 4H, piperazinyl 2 ArNCH2), 7.06 (d, 2H, Ar- H, J = 8.7 Hz), 7.37 (d, 2H, Ar–H,
J = 8.7 Hz), 7.88 (br s, 2H, NH2), 8.75 (br s, H, NH), 11.80 (br s, H, NH); The MS,
[M+], m/z 393 (100%); C19H19N7OS (393.4); requires (Found): C, 57.99 (57.94);
H, 4.86 (4.79); N, 24.92 (24.96).
5-[4-(4-Morpholinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-4,6-dione
(7c): It was obtained from 4b, as a yellow powder, crystallized from DMF in
57% yield, mp 271–273 °C, IR, m
max/cmꢀ1: 3480 (br s, NH), 3029 (CH aryl), 1678,
1688 (2 C@O). 1H NMR (DMSO-d6) ppm: d 3.27 (t, 4H, morpholinyl 2 NCH2,
J = 4.9 Hz), 3.89 (t, 4H, morpholinyl 2 OCH2, J = 4.9 Hz), 7.03 (d, 2H, Ar–H,
J = 8.4 Hz), 7.31 (d, 2H, Ar–H, J = 8.4 Hz), 8.16 (s, 1H, pyrimidine-H), 8.55 (br s,
H, NH), 9.00 (br s, H, NH), 12.25 (br s, H, NH); The MS, [M+], m/z 408 (49%);
C19H16N6O3S (408.4); requires (Found): C, 55.87 (55.85); H, 3.95 (3.98); N,
20.58 (20.61).
Synthesis of 6-amino-5-substituted pyrido[2,3-d:6,5-d]dipyrimidin-4-one (5a–c);
General procedure: A mixture of compound 4 (10 mmol), formamide (10 mL)
and formic acid (2 mL) was stirred under reflux in DMF (50 mL) for 12 h. The
reaction mixture was allowed to cool to room temperature, poured into water
(100 mL) and neutralized with ammonia solution. The precipitate was
collected by filtration washed with water and ethanol, dried and crystallized.
6-Amino-5-[4-(1-piperidinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-4-
one (5a): It was obtained from 4a, as a pale yellow powder, crystallized from
5-[4-(4-Methylpiperazinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-4,6-
dione (7e): It was obtained from 4c, as a yellow powder, crystallized from
dioxane in 59% yield, mp 263–265 °C, IR, m
max/cmꢀ1: 3465 (br s, NH), 3036 (CH
aryl), 1673, 1682 (2 C@O). 1H NMR (DMSO-d6) ppm: d 2.32 (s, 3H, piperazinyl
NCH3), 2.63 (br, s, 4H, piperazinyl 2 CH3NCH2), 3.38 (br s, 4H, piperazinyl 2

A.-R.B.A. El-Gazzar, H. N. Hafez / Bioorg. Med. Chem. Lett. 19 (2009) 3392–3397
3397
ArNCH2), 7.15 (d, 2H, Ar–H, J = 8.6 Hz), 7.38 (d, 2H, Ar–H, J = 8.6 Hz), 8.28 (s, 1H,
pyrimidine-H), 8.85 (br s, H, NH), 9.35 (br s, H, NH), 12.15 (br s, H, NH); The MS,
[M+], m/z 421(64%); C20H19N7O2S (421.4); requires (Found): C, 56.99 (56.95); H,
4.54 (4.49); N, 23.26 (23.28).
Synthesis of 8-methyl-5-substituted pyrido[2,3-d:6,5-d]dipyrimidine-4,6-dione
(7b,d,f); General procedure. A mixture of compound 4 (10 mmol) and acetic
acid (80 mL) was heated under reflux for 28 h. The reaction mixture was
allowed to cool to room temperature and poured into cold water (100 mL). The
formed solid was collected by filtration, washed with ethanol (20 mL), dried
and crystallized.
[M+], m/z 423 (100%); C19H17N7O3S (423.4); requires (Found): C, 53.89 (53.91);
H, 4.04 (4.02); N, 23.15 (23.09).
6-Amino-5-[4-(4-methylpiperazinyl)phenyl]-2,8-dithioxopyrido[2,3-d:6,5-
d]dipyrimi-din-4-one (8e): It was obtained from 4c and thiourea, as a yellow
powder and crystallized from DMF, in 64% yield, mp 307–309 °C, IR, m :
max/cmꢀ1
3480 (br s, NH, NH2), 3025 (CH aryl), 1683 (CO). 1H NMR (DMSO-d6) ppm: d
2.23 (s, 3H, piperazinyl NCH3), 2.57 (br s, 4H, piperazinyl 2 CH3NCH2), 3.35 (br
s, 4H, piperazinyl 2 ArNCH2), 7.10 (d, 2H, Ar–H, J = 8.6 Hz), 7.36 (d, 2H, Ar–H,
J = 8.6 Hz), 8.19 (br s, 2H, NH2), 8.62 (br s, H, NH), 9.15 (br s, H, NH), 11.45 (br s,
H, NH); The MS, [M+], m/z 452 (75%); C20H20N8OS2 (452.5); requires (Found): C,
53.07 (53.11); H, 4.45 (4.42); N, 24.76 (24.71).
8-Methyl-5-[4-(1-piperidinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-
4,6-dione (7b): It was obtained from 4a, as a yellow powder, crystallized from
6-Amino-5-[4-(4-methylpiperazinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimi-
dine-4,8-dione (8f): It was obtained from 4c and urea, a yellow powder and
dioxane in 62% yield, mp 289–291 °C, IR,
m
max/cmꢀ1: 3475 (br s, NH), 3026 (CH
aryl), 1668, 1683 (2 C@O). 1H NMR (DMSO-d6) ppm:
d
1.60 (br s, 6H,
crystallized from DMF, in 71% yield, mp 327–329 °C, IR, m
max/cmꢀ1: 3460 (br s,
piperidinyl 3 CH2), 2.26 (s, 3H, pyrimidine-CH3), 3.32 (br s, 4H, piperidinyl 2
NCH2), 7.10 (d, 2H, Ar–H, J = 8.6 Hz), 7.25 (d, 2H, Ar–H, J = 8.6 Hz), 8.50 (br s, H,
NH), 9.70 (br s, H, NH), 11.80 (br s, H, NH); The MS, [M+], m/z 420 (100%);
C21H20N6O2S (420.4); requires (Found): C, 59.98 (59.96); H, 4.79 (4.73); N,
19.99 (19.94).
NH, NH2), 3019 (CH aryl), 1685, 1678 (2C@O). 1H NMR (DMSO-d6) ppm: d 2.26
(s, 3H, piperazinyl NCH3), 2.58 (br s, 4H, piperazinyl 2 CH3NCH2), 3.39 (br s, 4H,
piperazinyl
2 ArNCH2), 7.07 (d, 2H, Ar–H, J = 9.0 Hz), 7.33 (d, 2H, Ar–H,
J = 9.0 Hz), 8.23 (br s, 2H, NH2), 8.70 (br s, H, NH), 9.37 (br s, H, NH), 11.82 (br s,
H, NH); The MS, [M+], m/z 436 (100%); C20H20N8O2S (436.4); requires (Found):
C, 55.03 (55.05); H, 4.61 (4.65); N, 25.67 (25.63).
8-Methyl-5-[4-(4-morpholinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-
4,6-dione (7d): It was obtained from 4b, as a yellow powder, crystallized from
Pharmacology: The synthesized compounds were evaluated for analgesic,
ulcergenic index and anti-inflammatory activities. One-way analysis of
variance (ANOVA) was performed to certain the significance of all the
exhibited activities. The test compounds and the standard drugs were
administered in the form of a suspension (1% carboxy methyl cellulose as a
vehicle) by oral route of administration for analgesic and anti-inflammatory
but for ulcerogenicity studies by intraperitoneally as suspension in 10% v/v
Tween-80. Each group consisted of six animals. The animals were procured
from Animal Home (National Research Center Egypt), and were maintained in
colony cages at 25 2 °C, relative humidity of 45–55%, under a 12-h light and
dark cycle; were fed standard animal feed.30 All the animals were acclimatized
for a week before use. The institutional Animal Ethics Committee approved the
protocol adopted for the experimentation of animals.
Analgesic assay: The analgesic activity was performed by tail-flick technique
using Wister albino mice (25–35 g) pf either sex selected by random sampling
technique.31,32 Diclofenac sodium at a dose level of 10 and 20 mg/kg was
administered orally as reference drug for comparison. The test compounds at
two dose levels (10, 20 mg/kg) were administered orally. The reaction times
were recorded at 30 min, 1, 2 and 3 h after the treatment. And cut-off time was
10 s. The percent analgesic activity (P) was calculated by the following formula.
P = [T2 ꢀ T1/10 ꢀ T1] ꢁ 100; where T1 is the reaction time (s) before treatment,
and T2 is the reaction time (s) after treatment.
Anti-inflammatory activity: Anti-inflammatory activity was evaluated by
carrageenan-induced paw oedema test in rats.27 Diclofenac sodium 10,
20 mg/kg was administered as standard drug for comparison. The test
compounds were administered at two dose levels (10, 20 mg/kg). The paw
volumes were measured using the mercury displacement technique with the
help of plethysmograph (Model PLYAN; Buxco, USA) immediately before and
30 min, 1, 2 and 3 h after carrageenan injection. The percent inhibition of paw
oedema was calculated according to the following formula, (percent inhibition
I = 100[1 ꢀ (a ꢀ x)/(b ꢀ y)] where x is the mean paw volume of rats before the
administration of carrageenan and test compounds or reference compound
(test group), a is the mean paw volume of rats after the administration of
carrageenan in the test group (drug treated), b is the mean paw volume of rats
after the administration of carrageenan in the control group, y is the mean paw
volume of rats before the administration of carrageenan in the control group.
Ulcerogenicity: Ulceration in rats was induced as described by Goyal et al.
Albino rats of wistar strain weighing 150–200 g of either sex were divided into
various groups each of six animals.33 Control group of animals were
administered only with 10% v/v Tween-80 suspension intraperitoneally. One
group was administered with Aspirin intraperitoneally in a dose of 200 mg/kg
once daily for three days. The remaining group of animals was administered
with test compounds intraperitoneally in a dose of 20 mg/kg. On fourth day,
Pylorus was ligated as per the method of Shay et al..34 Animals were fasted for
36 h before the pylorus ligation procedure. Four hours after the ligation,
animals were sacrificed. The stomach was removed and opened along with the
greater curvature. Ulcer index was determined by the method of Ganguly and
Bhatnagar.35
dioxane, mp 253–255 °C, IR,
1686 (2 C@O). 1H NMR (DMSO-d6) ppm: d 2.27 (s, 3H, pyrimidine-CH3), 3.30 (t,
4H, morpholinyl NCH2, J = 5.1 Hz), 3.93 (t, 4H, morpholinyl OCH2,
m
max/cmꢀ1: 3450 (br s, NH), 3029 (CH aryl), 1670,
2
2
J = 5.1 Hz), 7.08 (d, 2H, Ar–H, J = 8.7 Hz), 7.36 (d, 2H, Ar–H, J = 8.7 Hz), 8.80
(br s, H, NH), 9.150 (br s, H, NH), 12.20 (br s, H, NH); The MS, [M+], m/z 410
(39%); C19H18N6O3S (410.4); requires (Found): C, 55.59 (55.46); H, 4.42 (4.39);
N, 20.48 (20.45).
8-Methyl-5-[4-(4-methylpiperazinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrim-
idine-4,6-dione (7f): It was obtained from 4c, as a yellow powder, crystallized
from dioxane, mp 259–261 °C, IR, m
max/cmꢀ1: 3445 (br s, NH), 3027 (CH aryl),
1672, 1683 (2 C@O). 1H NMR (DMSO-d6) ppm: d 2.29 (s, 3H, pyrimidine-CH3),
2.34 (s, 3H, piperazinyl NCH3), 2.61 (br s, 4H, piperazinyl 2 CH3NCH2), 3.40 (br
s, 4H, piperazinyl 2 ArNCH2), 7.09 (d, 2H, Ar–H, J = 8.8 Hz), 7.39 (d, 2H, Ar–H,
J = 8.8 Hz), 8.68 (br s, H, NH), 9.23 (br s, H, NH), 12.00 (br s, H, NH); The MS,
[M+], m/z 435 (43%); C21H21N7O2S (435.4); requires (Found): C, 57.91 (57.86);
H, 4.86 (4.79); N, 22.51 (22.49).
Synthesis of 6-amino-5-substituted-2,8-dithiopyrido[2,3-d:6,5-d]dipyrimidin-4-
one (8a,c,e) and 6-amino-5-substituted-2-thiopyrido[2,3-d:6,5-d]dipyrimidine-
4,8-dione (8b,d,f); General procedure: A mixture of compound 4 (0.01 mol)
and thiourea or urea (10 mmol) was heated at 180 °C in a test tube on a sand-
bath for 6 h. The mixture was allowed to cool to room temperature; the
product was solidified by cooling and addition of methanol (50 mL). The
precipitate was collected by filtration and crystallized from the proper solvent.
6-Amino-5-[4-(1-piperidinyl)phenyl]-2,8-dithioxopyrido[2,3-d:6,5-d]dipyrimidin-
4-one (8a): It was obtained from 4a and thiourea, as a yellow powder and
crystallized from DMF, in 63% yield, mp 290–293 °C, IR, m
max/cmꢀ1: 3490 (br s,
NH, NH2), 3031 (CH aryl), 1679 (CO). 1H NMR (DMSO-d6) ppm: d 1.56 (br s, 6H,
piperidinyl 3 CH2), 3.29 (br s, 4H, piperidinyl 2 NCH2), 7.11 (d, 2H, Ar–H,
J = 8.7 Hz), 7.38 (d, 2H, Ar–H, J = 8.7 Hz), 8.05 (br s, 2H, NH2), 8.55 (br s, H, NH),
8.95 (br s, H, NH), 11.05 (br s, H, NH); The MS, [M+], m/z 437 (47%);
C20H19N7OS2 (437.5); requires (Found): C, 54.90 (54.86); H, 4.37 (4.39); N,
22.41 (22.36).
6-Amino-5-[4-(1-piperidinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-
4,8-dione (8b): It was obtained from 4a and urea, as a brown powder and
crystallized from DMF, in 65% yield, mp 268–270 °C, IR, m
max/cmꢀ1: 3500 (br s,
NH, NH2), 3038 (CH aryl), 1684, 1668 (2C@O). 1H NMR (DMSO-d6) ppm: d 1.60
(br s, 6H, piperidinyl 3 CH2), 3.32 (br s, 4H, piperidinyl 2 NCH2), 7.08 (d, 2H, Ar–
H, J = 8.6 Hz), 7.36 (d, 2H, Ar–H, J = 8.6 Hz), 8.15 (br s, 2H, NH2), 8.85 (br s, H,
NH), 9.45 (br s, H, NH), 11.75 (br s, H, NH); The MS, [M+], m/z 421 (100%);
C20H19N7O2S (421.4); requires (Found): C, 56.99 (56.95); H, 4.54 (4.52); N,
23.26 (23.29).
6-Amino-5-[4-(4-morpholinyl)phenyl]-2,8-dithioxopyrido[2,3-d:6,5-
d]dipyrimidin-4-one (8c): It was obtained from 4b and thiourea, as a yellow
powder and crystallized from DMF, in 60% yield, mp 297-300 °C, IR, m :
max/cmꢀ1
3470 (br s, NH, NH2), 3029 (CH aryl), 1680 (CO). 1H NMR (DMSO-d6) ppm: d
3.28 (t, 4H, morpholinyl 2 NCH2, J = 5.2 Hz), 3.94 (t, 4H, morpholinyl 2 OCH2,
J = 5.1 Hz), 7.08 (d, 2H, Ar–H, J = 8.9 Hz), 7.43 (d, 2H, Ar–H, J = 8.9 Hz), 8.25 (br
s, 2H, NH2), 8.86 (br s, H, NH), 9.34 (br s, H, NH), 11.70 (br s, H, NH); The MS,
[M+], m/z 439 (61%); C19H17N7O2S2 (439.5); requires (Found): C, 51.92 (51.87);
H, 3.89 (3.91); N, 22.30 (22.26).
29. Brunskill, J. S. A.; De, A.; Vas, G. M. F. Synth. Commun. 1978, 8, 1.
30. Olfert, E. D.; Cross, B. M.; McWilliam, A. A., editors. Canadian Council of Animal
Care guide to the care and use of experimental animals, vol. 1. 2nd ed. 1993.
31. Kulkarni, S. K. Life Sci. 1980, 27, 185.
6-Amino-5-[4-(4-morpholinyl)phenyl]-2-thioxopyrido[2,3-d:6,5-d]dipyrimidine-
4,8-dione (8d): It was obtained from 4b and urea, a yellow powder and
32. Amour, R. E.; Smith, D. L. J. Pharmacol. Exp. Ther. 1941, 72, 74.
crystallized from DMF, in 58% yield, mp 281–283 °C, IR,
NH, NH2), 3028 (CH aryl), 1686, 1675 (2 C@O). 1H NMR (DMSO-d6) ppm: d 3.30
(t, 4H, morpholinyl NCH2, J = 5.1 Hz), 3.96 (t, 4H, morpholinyl OCH2,
m
max/cmꢀ1: 3510 (br s,
33. Goyal, R. K.; Chakrabarti, A.; Sanyal, A. K. Planta Med. 1985, 29, 85.
34. Shay, M.; Komarov, S. A.; Fels, D.; Meranze, D.; Grunstein, H.; Siplet, H.
Gastroenterology 1945, 5, 43.
2
2
J = 5.1 Hz), 7.07 (d, 2H, Ar–H, J = 8.8 Hz), 7.40 (d, 2H, Ar–H, J = 8.8 Hz), 8.32 (br
35. Ganguly, A. K.; Bhatnagar, O. P. Can. J. Physiol. Pharmacol. 1973, 51, 148.
s, 2H, NH2), 8.95 (br s, H, NH), 9.65 (br s, H, NH), 11.85 (br s, H, NH); The MS,