Synthesis, characterization, and urease inhibition of 5-substituted-8- methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-diones

Article abstract of DOI:10.1007/s00044-010-9491-2

5-Substituted-8-methyl-2H-pyrido[1,2-a]pyrimidine- 2,4(3H)-dione and its anilines, amino pyridines and hydrazides derivatives were prepared in a good to excellent yields. In the first step 8-methyl-2H-pyrido[1,2-a]pyrimidine- 2,4(3H)-dione (1) was prepared by reacting 4-methyl- 2-aminopyridine, with diethylmalonate. Compounds substituted pyrido[1,2-a]pyrimidine-2,4(3H)-diones (PPMDO) (2)-(17) were prepared by condensing 8-methyl-2H-pyrido[1,2-a] pyrimidine-2,4(3H)-dione in the presence of triethylorthoformte (TEF) and dimethylformamide (DMF), with respective amino components viz. 2-aminoacetophenone, 3-aminoacetophenone, 4-aminoacetophenone, 2,4,6-trimethylaniline, 2-fluoroaniline, 3-fluoroaniline, 4-fluoroaniline, 2-aminothiophenol, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-5-nitropyridine, Benzoic hydrazide, 4-nitrobenzoic hydrazide, 4-bromobenzoic hydrazide, 4-chlorobenzoic hydrazide and 4-hydroxybenzoic hydrazide, respectively. The chemical structures of all the compounds were elucidated by IR, ¹H-NMR, ¹³C-NMR and elemental analysis data. The synthesized compounds were screened for their in vitro urease inhibition activity, by the phenol hypochlorite method. These compounds were found to exhibit either no or low to moderate or significant activity. The compounds (9) and (14) showed comparatively much higher activity. However, the compound (9) was found to be the most active one. Springer Science+Business Media, LLC 2010.

Full text of DOI:10.1007/s00044-010-9491-2

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:60–74
DOI 10.1007/s00044-010-9491-2
ORIGINAL RESEARCH
Synthesis, characterization, and urease inhibition
of 5-substituted-8-methyl-2H-pyrido[1,2-a]pyrimidine-2,
4(3H)-diones
•
Abdul Rauf Sumaira Liaqat Ashfaq M. Qureshi
•
•
•
Muhammad Yaqub Aziz U. Rehman Mahmood U. Hassan
•
•
•
Zahid H. Chohan Faiz U. H. Nasim T. Ben Hadda
•
Received: 31 July 2010 / Accepted: 28 October 2010 / Published online: 25 November 2010
Ó Springer Science+Business Media, LLC 2010
Abstract 5-Substituted-8-methyl-2H-pyrido[1,2-a]pyrimi-
dine-2,4(3H)-dione and its anilines, amino pyridines and
hydrazides derivatives were prepared in a good to excellent
yields. In the first step 8-methyl-2H-pyrido[1,2-a]pyrimi-
dine-2,4(3H)-dione (1) was prepared by reacting 4-methyl-
2-aminopyridine, with diethylmalonate. Compounds substituted
pyrido[1,2-a]pyrimidine-2,4(3H)-diones (PPMDO) (2)–(17)
were prepared by condensing 8-methyl-2H-pyrido[1,2-a]
pyrimidine-2,4(3H)-dione in the presence of triethylortho-
formte (TEF) and dimethylformamide (DMF), with respective
amino components viz. 2-aminoacetophenone, 3-aminoace-
tophenone, 4-aminoacetophenone, 2,4,6-trimethylaniline,
2-fluoroaniline, 3-fluoroaniline, 4-fluoroaniline, 2-amino-
thiophenol, 2-amino-4-methylpyridine, 2-amino-5-meth-
ylpyridine, 2-amino-5-nitropyridine, Benzoic hydrazide,
4-nitrobenzoic hydrazide, 4-bromobenzoic hydrazide,
4-chlorobenzoic hydrazide and 4-hydroxybenzoic hydra-
zide, respectively. The chemical structures of all the
were screened for their in vitro urease inhibition activity,
by the phenol hypochlorite method. These compounds
were found to exhibit either no or low to moderate or
significant activity. The compounds (9) and (14) showed
comparatively much higher activity. However, the com-
pound (9) was found to be the most active one.
Keywords Anti-urease ꢀ Pyridopyrimidines ꢀ
Dimroth rearrangement ꢀ Virtual screening
Introduction
Pyridopyrimidine has wide range of biological activity,
particularly in cancer and virus research (Berthelot, 1859;
Mamouni et al., 2003; David et al., 1997). The pyrido-
pyrimidine is of interest as inhibitor of dihydrofolate
reductase (Mihailo et al., 2009) but also for its antibacte-
rial, antifungal (Miller et al., 2009; Sayed et al., 2005),
antitumor (Cockerill et al., 2001), adenosine kinase
inhibitors (Gfesser et al., 2003; Cowart et al., 2001)
activities and recently as excellent potent Akt1/2 Inhibitors
(Wu et al., 2008). Furthermore, pathologies associated with
the biological system of PDE4 represent some of the more
currently important therapeutic targets such as asthma
(Finan and Thomas, 2004). Moreover, it has been proved
that some of the urea derivatives that have established
potent activity over a wide spectrum of tumor cell lines
exhibited a good profile for preclinical antitumor investi-
gations (Mounneto et al., 2001).
1
compounds were elucidated by IR, H-NMR, 13C-NMR
and elemental analysis data. The synthesized compounds
A. Rauf (&) ꢀ S. Liaqat ꢀ A. U. Rehman ꢀ F. U. H. Nasim
Department of Chemistry, The Islamia University
of Bahawalpur, Bahawalpur 63100, Pakistan
e-mail: lecorganic@yahoo.com
A. M. Qureshi (&) ꢀ M. Yaqub ꢀ Z. H. Chohan
Department of Chemistry, Bahauddin Zakariya University,
Multan 60800, Pakistan
e-mail: shamashfaq@yahoo.com
M. U. Hassan
Department of Chemistry, Government S. E. College,
Bahawalpur 63100, Pakistan
Keeping in view the historical importance and present
prospects of pyridopyrimidines, we were inspired and thus
report a novel class of compounds which we prepared,
characterized and screened for in vitro urease inhibition.
This study is an extension to deal with the synthesis of
T. Ben Hadda
Department of Chemistry, The Mohammed First University,
Oujda 30000, Morocco
123

Med Chem Res (2012) 21:60–74
61
8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione and its
aminopyridine, aniline and hydrazide derivatives.
The results provide an unprecedented opportunity for
detailed comparison of 2/3/4-aminoacetophenones, 2,4,6-
trimethylaniline, 2/3/4-fluoroanilines, 2-aminothiophenol,
2-amino-4/5-methylpyridines, 2-amino-5-nitropyridine and
4-Cl/Br/OH/NO2-benzoic hydrazides, functionalization in
position N of amino group (–NHR) of the same pharma-
cophore (PPMDO).
In the past, intensive attention was mainly devoted to the
Imidazo[1,2-a]pyridines (IP), Imidazo[1,2-a]pyrimidines
(IPM), (Elkakmaoui et al., 1994; Gudmundsson and Johns,
2007; Liang et al., 2007; Scribner et al., 2007; Hayakawa
et al., 2007; Warshakoon et al., 2006); Imidazo[1,2-a]thi-
azoles (IT) and Imidazo[1,2-a]thiazoles (ISO) (Andreani
et al., 1995, 1996, 1999, 2000, 2001, 2005) bioactivity
(Scheme 1). However, from a chemical point of view, a
second isomeric structure is possible. For the development
of binding approaches for (IPM) and its analogs (2)–(17) in
the environment, the identification of the active pyrido[1,2-a]
pyrimidine-2,4(3H)-diones (PPMDO) structures present is
important. Neither experimental nor theoretical data is
available for the identification of water-solved (PPMDO)
species. Theoretically, NMR spectroscopy could be useful
for identifying chemical structures. Theoretical ab initio
studies could supplement these measurements. In addi-
tion, calculations of energetics, atomic charges, minimum
energy structures, geometry, and partial p-charge of het-
eroatoms (Petra) could indicate the electronic density dis-
tribution of each atom. Finally, by taking Petra results
showing the presence of Nd?=C–Nd- dipolar system in
consideration, realistic Lewis structures can be determined.
These systematic data, regarding the variation of molecular
properties, are important for the chemical structure and
could therefore provide first insights into the still poorly
understood chemical opening/closing pyridine or pyrimi-
dine of (IP), (IPM), and (PPMDO) systems.
In brief, the objective of this study is to investigate the
potential pharmacophore sites of (PPMDO) species using
anti-urease screening dependence on pH and comparison
with the calculated molecular properties. To verify these
structures, further Osiris/Molinspiration (OM) analyses
were carried out for example calculation of toxicity
risks, solubility, drug-likeness, drug-scor, and lipophicity.
Finally, to investigate the anti-urease bioactivity of the
(PPMDO) species, tautomeric structure were performed.
Chemistry
Synthesis of compounds (1)–(17)
Three methods were adopted for the synthesis of 8-methyl-
2H-Pyrido[1,2-a]pyrimidine-2,4(3H)dione (1). In the first
method, the reaction of 4-methyl-2-aminopyridine and
diethylmalonate was carried out in 2-butanol (as a solvent)
and catalytic amount of glacial acetic acid. The product
was collected in low yield, i.e., 28% in pure state. In the
second method, the same reaction of 4-methyl-2-amino-
pyridine and diethylmalonate was carried out in glacial
acetic acid (as solvent). The product in this reaction was
obtained in 25% yield. However, in the third method, the
reaction of 4-methyl-2-amino pyridine and diethylmalonate
was carried out without solvent. The product in this reac-
tion was obtained in 72% yield. Direct condensation of
4-methyl-2-aminopyridine with diethyl malonate gave
product in good yield (Scheme 2).
N
O
H3
C
NH
N
R
O
(PPMDO)
Compounds (2)–(17) were prepared by refluxing equi-
molar quantities of 8-methyl-2H-Pyrido[1,2-a] pyrimidine-
2,4(3H)dione (1) with respective anilines, aminopyridines,
or hydrazides in the presence of triethylorthoformate
(Scheme 2). The structures of all the synthesized com-
N
S
X
N
R2
N
R2
N
N
N
R1
(IT)
R1
(IP) and (IPM)
1
pounds were established through H-NMR and elemental
analysis data, and 13C NMR were recorded for compounds
O
O
(2), (10), and (13).
N
S
R2
N
Pharmacology
R1
(ISO)
Scheme 1 Molecules subjected to possible Dimroth opening/closing
heterocyclic rings (X = N,CH). (IP): Imidazo[1,2-a]pyridines (X =
CH); (IPM): Imidazo[1,2-a]pyrimidines (X = N); (IT): Imidazo[1,2-a]-
thiazoles (X = S); (ISO): Imidazo[1,2-a]thiazoles (X = N). (PPMDO):
pyrido[1,2-a]pyrimidine-2,4(3H)-diones
Biological activity: urease inhibition (in vitro)
Compounds (1)–(17) were tested for their urease inhibition
potential in concentration range from 100 lM to 0.01 lM
123

62
Med Chem Res (2012) 21:60–74
CH3
9
O
H3C
N
O
H
H3C
N
O
(i)
(ii)
N
7
N
N
R
N
NH2
6
O
_
(1)
(2) (17)
CH3
O
O
CH3
H3C
2'
6'
3'
3'
5'
3'
3'
5'
3'
5'
2'
6'
O
4'
(3)
(7)
R =
CH3
(2)
(6)
(5)
R =
R =
R =
4'
4'
(4)
R =
CH3
5'
6'
5'
3'
5'
H3C
HS
F
F
2'
6'
2'
4'
R =
R =
4'
F
(9)
R =
R =
(8)
R =
5'
6'
5'
6'
6'
3'
CH3
3'
3'
4'
3'
4'
2'
6'
O
O
N+
5'
CH3
4'
(13)
(12)
R =
(11)
R =
(10)
R'
NH
N
N
O-
N
6'
5'
6'
6'
3'
3'
5'
2'
6'
2'
6'
O
2'
6'
2'
6'
3'
3'
5'
O
O
O
O
N+
R =
(17)
R =
Br
Cl
OH
(15) R =
(14) R =
(16)
O-
NH
NH
NH
NH
5'
5'
Scheme 2 Synthesis of compounds (1)–(17). (i) Diethylmalonate/reflux (4 h); (ii) R-NH2/Ethylorthoformate/Dimethylformamide/reflux (4 h)
(Table 1). Compound (9) showed the highest inhibitory
potential at the 100 lM concentration followed by com-
pounds 9 [ 14 [ 2[15 [ 11 [ 6[12 [ 3[16 [(1 = 17)
C 8C 10 [ 7[13 [ 4. The extent inhibition was con-
centration-dependent. Compound (5) at all the concentra-
tions tested and compounds (8), (10), (15), and (16) at
some lower concentrations did not inhibit activity of the
enzyme. This effect could be attributed to the lower
effective concentration of the test compound and to the
nature of the test compound and the corresponding func-
tional groups present therein (see below). These observa-
tions suggest that compounds (9) and (14) are strong
inhibitors; compounds (2), (6), (11), and (15) are moderate
urease inhibitors; while compounds (1), (3), (4), (7), (8),
(10), (12), (13), (16), and (17) are weak inhibitors of the
urease enzyme.
material which belongs to the weak urease inhibitor group
of molecules. Compounds (9), (14), (2), (15), (11), (6),
(12), (3), and (16) are more potent inhibitors than the
starting material whereas the compounds (17), (8), (10),
(7), (13), and (4) are less potent inhibitors. These derivatives
were synthesized by treating 8-methyl-2H-pyrido[1,2-a]
pyrimidine-2,4(3H)-dione (1) with 2-aminothiophenol,
4-nitobenzoichydrazide, 2-aminoacteophenone, 4-bromoben-
zoichydrazide, 2-amino-5-methylpyridine, 2-fluoroaniline,
2-amino-5-nitropyridine, 3-aminoacetophenone, 4-chloro-
benzoichydrazide, 4-hydroxybenzoic hydrazide, 4-fluoro-
aniline, 2-amino-4-methyl-pyridine, 3-fluoroaniline,
benzoichydrazide, and 4-aminoacetophenone, respectively.
Since Urease is a metallo-enzyme requiring two Ni?2
ions for its activity the presence of a metal chelating group
like the –SH group [compound (9)] would result in sig-
nificant inhibition of the enzyme activity whereas the
absence of such a group or the introduction of a non-che-
lator group would tend to decrease the metal chelating
Effect of various substitutions can be assessed by
comparing the inhibitory characteristic of the derived
compounds with that of the compound (1), the starting
123

Med Chem Res (2012) 21:60–74
63
7.32–7.43. The C-9 protons experienced deshielding due to
the only inductive effect of the (=N–C=O) and were
recorded downfield as singlet at d 7.42–7.59 as compared to
C-7 protons, which are experiencing less deshielding by
virtue of its position and nature of bonding. The C-6 protons
being deshielded due to the inductive effect of (–N–C=O)
functionality and on the other side electron withdrawing
effect of the (=N–C=O) functionality of the pyrimidine-2,
4-dione, appeared further downfield as double doublet at d
7.70–7.85. In all compounds, a very little difference in the
chemical shifts of C-6 protons, C-7 protons, and C-9 pro-
tons was observed, which was due to the very small
inductively electron withdrawing or donating effect of
substituted anilino or pyridinyl or benzohydrazide func-
tionalities, which are far away from pyrimidine-2,4-dione
ring. Similarly a very little difference in the chemical shifts
of methyl protons present on the pyrimidine-2,4-dione ring
was observed and appeared as singlet at d 2.18–2.27.
Table 1 Urease inhibition of 8-methyl-2H-pyrido[1,2-a]pyrimidine-
2,4(3H)-dione (1) and functionalized derivatives (2)–(17)
Compound % Inhibition in concentration range from 100 to 0.01 lM
100 lM
10 lM
1 lM
0.1 lM
0.01 lM
1
39
69
45
18
0.2
57
28
35
97
33
57
48
26
87
57
43
39
26
54
28
5
12
32
8
6
19
3
1
11
-1
-3
-16
3
2
3
4
1
-2
-6
10
-30
6
5
-8
44
3
-1
26
-25
14
60
16
24
23
6
6
7
-25
1
8
21
73
20
48
36
13
60
23
14
22
21
9
28
6
22
1
10
11
12
13
14
15
16
17
11
6
3
3
1
-1
6
1
The H NMR spectrum of compound (2) demonstrated
54
3
21
-2
-2
-1
8
C-30 proton, ortho to acetyl and meta to amino group
experiencing deshielding due to resonance and inductive
effect of acetyl group appeared downfield as double dou-
blet at d 7.50. The C-50 proton para to acetyl and meta to
amino group experiencing deshielding due to electron
withdrawing effect of acetyl group but experiencing less
inductive effect by virtue of its position, resonated slightly
upfield as double of double doublet at d 7.35. Whereas C-60
proton appeared upfield as compared to C-50 proton as
double doublet because of the shielding effect of the amino
functionality. The acetylanilino C-40 proton appeared fur-
ther upfield as compared to C-50 proton as double of double
doublet at d 7.20, being shielded due to the resonance
effect of amino group and experiencing less inductive
effect due to acetyl and amino functionalities by virtue of
its position.
-8
-4
-5
8
6
7
Thiourea 94
15
property of the compound being synthesized. Reaction with
2,4,6-trimethylaniline did not modify the base line urease
inhibition activity of the starting material.
Results and discussion
Spectroscopic characterization of compounds (1)–(17)
IR spectra
1
The H NMR spectrum of compound (3) demonstrated
C-20 proton, ortho to acetyl and amino groups experiencing
deshielding due to electron withdrawing nature of acetyl
functionality, however, being shielded by the electron
donating effect of amino group, appeared as singlet at d
7.69. The C-40 proton ortho to acetyl and para to N–H
functions experiencing deshielding due to electron
attracting effect of acetyl functional group, however, being
shielded by the electron donating effect of amino func-
tionality but experiencing less inductive effect by virtue of
its position, resonated slightly upfield as double doublet at
d 7.58. The acetylanilino C-60, experiencing a deshielding
effect due to the electron withdrawing effect of acetyl
group, however, being shielded due to the electron donat-
ing effect of amino group. This in turn experiences less
inductive effect by these two functional groups and
appeared upfield as double doublet at d 7.36. The C-50
proton meta to acetyl and NH functions appeared further
The IR spectra of (2)–(17) also help to confirm the coex-
istence, in solution, of their tautomeric structures by
showing, example for compound (2), two bands at 3211/
3060 cm-1 for aminic N–H group of (-RN-H), two bands
at 1723/1685 cm-1 for carbonyl C = O stretching. The IR
data of (2) support the absence of hydrogen on oxygen
atoms of two carbonyl groups by showing no O–H absor-
bance at 3400–3450 cm-1, which confirms the idea that
some tautomeric forms are favored than others (Table 2).
Interestingly we observe, in selected 1H NRM data
(Table 1), the coexistence of Z and E isomers controlled by
Dimroth process (Table 2).
1H NMR spectra
The 1H NMR spectra of all the compounds (2)–(17),
pyrimidine-2,4-dione C-7 protons appeared as doublet at d
123

64
Med Chem Res (2012) 21:60–74
1
Table 2 Selected IR and H NMR data of compounds (2)–(17)
1
Selected H NMR data
Compd.
Selected IR data (t, cm-1
)
(–RN–H)1
(–RN–H)2
(C=O)1
(C=O)2
(=CH–N)1, (=CH–N)2
(=C–NH)1, (=C–NH)2
2
3291 (m)
3098 (m)
1723 (s)
1685 (m)
9.10 (1H, d, J 12.7)
9.32 (1H, d, J 13.6)
9.0 (1H, d, J 12.9)
9.20 (1H, d, J 13.4)
8.98 (1H, d, J 13.0)
9.22 (1H, d, J 13.6)
8.88 (1H, d, J 13.5)
9.15 (1H, d, J 13.3)
8.92 (1H, d, J 13.4)
9.20 (1H, d, J 13.8)
8.83 (1H, d, J 13.5)
9.10 (1H, d, J 13.4)
8.75 (1H, d, J 13.2)
9.0 (1H, d, J 13.5)
9.62 (1H, d, J 13.8)
9.90 (1H, d, J 13.5)
8.72 (1H, d, J 12.8)
9.32 (1H, d, J 13.1)
8.82 (1H, d, J 12.3)
9.30 (1H, d, J 12.9)
8.91 (1H, d, J 12.3)
9.45 (1H, d, J 13.2)
8.45 (1H, d, J 13.4)
8.75 (1H, d, J 13.2)
12.32 (1H, d, J 13.4)
13.25 (1H, d, J 12.7)
12.90 (1H, d, J = 13.3)
13.18 (1H, d, J 12.9)
12.92 (1H, d, J 13.2)
13.22 (1H, d, J 13.0)
11.32 (1H, d, J 13.1)
12.45 (1H, d, J 13.5)
11.45 (1H, d, J 13.6)
12.88 (1H, d, J 13.4)
11.50 (1H, d, J 13.3)
12.80 (1H, d, J 13.5)
11.44 (1H, d, J 13.0)
12.76 (1H, d, J 13.2)
11.22 (1H, d, J 13.2)
12.35 (1H, d, J 13.8)
12.21 (1H, d, J 12.9)
13.42 (1H, d, J 12.8)
12.19 (1H, d, J 12.7)
13.41 (1H, d, J 12.3)
12.72 (1H, d, J 12.9)
13.68 (1H, d, J 12.3)
11.35 (1H, d, J 13.8)
11.96 (1H, s)
3
3211 (m)
3209 (m)
3279 (m)
3211 (m)
3259 (m)
3260 (m)
3270 (m)
3288 (m)
3269 (m)
3267 (m)
3275 (m)
3060 (m)
3060 (m)
3080 (m)
3029 (m)
3064 (m)
3042 (m)
3007 (m)
3010 (m)
3010 (m)
3034 (m)
3021 (m)
1700 (s)
1703 (s)
1700 (s)
1709 (s)
1710 (s)
1725 (s)
1716 (s)
1706 (s)
1730 (s)
1706 (s)
1718 (s)
1645(m)
1645 (m)
1685 (m)
1675 (m)
1645 (m)
1640 (m)
1660 (m)
1680 (m)
1685 (m)
1665(m)
1651 (m)
4
5
6
7
8
9
10
11
12
13
12.45 (1H, d, J 13.4)
12.0 (1H, s)
14
15
16
17
3235 (m)
3290 (m)
3210 (m)
3275 (m)
3010 (m)
3010 (m)
3011 (m)
3013 (m)
1720 (s)
1735 (s)
1718 (s)
1710 (s)
1685 (m)
1670 (m)
1666 (m)
1665 (m)
8.82 (1H, d, J 12.2)
9.45 (1H, d, J 12.8)
12.55 (1H, d, J 12.5)
13.40 (1H, d, J 12.2)
8.56 (1H, d, J 13.7) 8.85 (1H, d, J 14.2)
8.60 (1H, d, J 13.6) 8.90 (1H, d, J 13.9)
8.44 (1H, d, J 13.8) 8.83 (1H, d, J 14.2)
11.40 (1H, d, J 13.9)
11.93 (1H, s)
12.65 (1H, d, J 13.7)
11.50 (1H, d, J 13.7)
11.94 (1H, s)
12.67 (1H, d, J 13.6)
11.42 (1H, d, J 14.0)
11.88 (1H, s)
12.60 (1H, d, J 13.8)
upfield as compared to C-60 proton as double doublet at
d 7.23, being not shielded or deshielded by both func-
tionalities and experiencing only inductive effect (-I) due to
acetyl and amino group by virtue of its position.
The C-20, C-60 protons are magnetically equivalent and
ortho to amino and meta to acetyl group and being shielded
due to electron donating effect of amino group and reso-
nated upfield as triplet at d 7.32. In all the three compounds
(2–4), acetyl methyl protons appeared at d 3.21–3.24.
The 1H NMR spectrum of compound (5) displayed three
methyl protons present on the anilino ring para to amino
functionality as singlet at d 2.16; however, six methyl
protons ortho to amino group appeared slightly downfield
1
The H NMR spectrum of compound (4) verified acet-
ylanilino C-30 and C-50 protons are equivalent protons,
ortho to acetyl and meta to amino functionalities experi-
encing deshielding due to resonance and inductive effect of
acetyl functionality, appeared downfield as triplet at d 7.62.
123

Med Chem Res (2012) 21:60–74
65
1
at d 2.18. In both cases electron donating effect due to
amino functionality is same but ortho methyl groups
experiencing more inductive effect as compared to para
methyl group due to amino group. As far as the exhibition
of C-30, C-50 equivalent protons is concerned, experiencing
no shielding or deshielding due to amino group, however,
being shielded by the inductively electron donating effect
of methyls and appeared as singlet at d 7.0.
The H NMR spectrum of compound (9) demonstrated
sulfanyl aniline C-30, C-40, C-50, and C-60 protons appeared
as multiplet at d 7.10–7.22. As for as the exposition of the
sulfanyl (S–H) group is concerned, appeared as singlet at
d 4.22.
The 1H NMR spectrum of compound (10) demonstrated
C-60 proton, being deshielded by strong electron with-
drawing effect of pyridinyl nitrogen both by resonance and
inductive effect, appeared downfield as double at d 8.20.
The pyridinyl C-30 proton again deshielded by strong
electron withdrawing effect of pyridinyl nitrogen by reso-
nance and experiencing less inductive effect as compared
to C-60 proton, appeared slightly upfield as singlet at
d 7.88. As for as the display of C-50 proton is concerned it
experiencing deshielding due to only inductive effect of
nitrogen by virtue of its position, appeared further upfield
as singlet at d 7.48. The methyl protons present on the
pyridinyl ring appeared as singlet at d 2.30.
The 1H-NMR spectrum of compound (6) confirmed C-30
proton, ortho to fluoro and meta to amino group experi-
encing deshielding due to the inductive effect of fluorine,
appeared downfield as double doublet at d 7.30. The C-50
proton para to fluoro and meta to amino group experiencing
less inductive effect by virtue of its position, resonated
slightly upfield as double of double doublet at d 7.24. As far
as the exhibition of C-60 proton is concerned, it was recorded
upfield as compared to C-50 proton as double doublet at d
7.18 because of the shielding effect of the amino function-
ality. The fluoroanilino C-40 proton appeared further upfield
as compared to C-60 proton as double of double doublet at d
7.10, being shielded due to the resonance effect of amino
functionality and experiencing less inductive effect due to
fluoro and amino functionalities by virtue of its position.
1
The H NMR spectrum of compound (11) confirmed
C-60 proton, being deshielded by strong electron with-
drawing effect of pyridinyl nitrogen both by resonance and
inductive effect, appeared as singlet at d 8.10, slightly
upfield in comparison with compound (10) due to the
position of methyl group on the ring. The pyridinyl C-40
proton again deshielded by strong electron withdrawing
effect of pyridinyl nitrogen by resonance and experiencing
less inductive effect as compared to C-60 proton, appeared
slightly upfield as singlet at d 7.96. As for as the display of
C-30 proton is concerned, it experiencing deshielding only,
due to inductive effect of the nitrogen, appeared further
upfield as singlet at d 7.48. The methyl protons present on
the pyridinyl ring appeared, slightly downfield as because
of closeness to pyridinyl nitrogen compared to compound
(10) as singlet at d 2.32.
1
The H NMR spectrum of compound (7) demonstrated
C-50 proton meta to fluoro and amino functionalities, being
not shielded by both functional groups and experiencing
only inductive effect (-I) due to these groups appeared
downfield as double doublet at d 7.34. The fluoroanilino
C-20 proton, ortho to fluoro and amino groups experiencing
deshielding due to inductively electron withdrawing nature
of fluoro function, however, being shielded by the electron
donating effect of amino group, appeared upfield as singlet
at d 7.27. The C-40 proton ortho to fluoro and para to amino
functionalities experiencing deshielding due to inductively
electron withdrawing effect of fluorine, however, being
shielded by the electron donating effect of amino group but
experiencing less inductive effect as compared to C-20
proton by virtue of its position, resonated slightly upfield as
double doublet at d 7.19. The fluoroanilino C-60 proton,
being shielded due to the electron donating effect of amino
functionality, which in turn is experiencing less inductive
effect by these two functional groups appeared further
upfield as double doublet at d 7.12.
The 1H NMR spectrum of compound (12) demonstrated
C-60 proton, being deshielded by strong electron with-
drawing effect of pyridinyl nitrogen and nitro functional
groups by resonance effect, as well as by strong inductive
effect, appeared much downfield as singlet at d 9.21. The
pyridinyl C-40 proton, again deshielded by strong electron
withdrawing effect of pyridinyl nitrogen and nitro group by
resonance and experiencing less inductive effect as com-
pared to C-60 proton, appeared as doublet at d 8.88. As for
as the exhibition C-30 proton is concerned, it experiencing
deshielding due to only inductive effect of the nitrogen as
well as nitro groups, appeared as doublet at d 8.20. The
methyl protons present on the pyridinyl ring appeared,
slightly downfield as because of closeness to pyridinyl
nitrogen‘ compared to compound (10) as singlet at d 2.32.
The 1H NMR spectrum of compound (13) verified
benzohydrazide C-20, C-60 equivalent protons, ortho to
(–NH–C=O) functionality experiencing deshielding due to
resonance and inductive effect of that functionality,
1
The H NMR spectrum of compound (8) verified flu-
oroanilino C-30 C-50 equivalent protons, ortho to fluoro and
meta to amino functionalities experiencing deshielding
inductive effect of fluorine, appeared downfield as doublet
at d 7.25. The C-20 C-60 proton ortho to amino and meta to
fluoro group being shielded due to electron donating effect
of amino group, resonated upfield as doublet at d 7.11.
Which was due to the difference in the inductively electron
withdrawing influence of the fluorine atom present on the
anilino ring.
123

66
Med Chem Res (2012) 21:60–74
appeared downfield as doublet at d 7.88. The C-40 proton
para to same functional group experiencing deshielding
due to resonance effect but less inductive effect by virtue of
its position appeared as triplet at d 7.51. The C-30, C-50
proton meta to –NH–C=O functional group being not
deshielded due to electron withdrawing effect of same
group resonated upfield as doublet at d 7.37. The 1H NMR
spectra of compounds (15)–(17) demonstrated benzohyd-
razide C-20, C-60 equivalent protons, ortho to –NH–C=O
and meta to –Br, Cl, and OH functional groups, experi-
encing deshielding due to resonance and inductive effect of
amide function, appeared as doublet at d 7.90–7.94. The
C-30, C-50 protons meta to –NH–C = O functionality being
not deshielded due to electron withdrawing effect of amide
group but experiencing shielding due electron donating
effect of Br, Cl, and OH functional groups, resonated
upfield as doublet at d 7.39–7.45. The –N–NH protons
appeared as singlet at d 11.92–11.94. In addition, In the
case of compound (17), hydroxylic (OH) proton was
appeared as singlet at d 9.75.
31.3; again the upfield signal was due to acetyl methyl
group whereas downfield was due to methyl group attached
with the ring. 13C NMR of (10) recorded fifteen signals
altogether, d 167.1 and 164.2 accounted for the two amide
carbonyls and there were four more quaternary carbons as
well recorded at d 155.4, 148.3, 147.1, and 107.7. Two
methyl groups were observed at d 23.0 and 22.6 along with
seven methine carbons which accounted for the methine
aromatic carbons and vinylic carbon, respectively. Simi-
larly, 13C NMR of (13) was in good agreement with the
proposed structure as it displayed three carbonyls of the
amides at d 174.2, 160.7, and 153.5. Three quaternary
carbons observed at d 143.8, 136.3, and 107.3 along with
nine methine carbons which represented aromatic and
vinylic carbons. A signal at 20.5 accounted for the methyl
group present at the aromatic ring. All the 13C NMR data
effectively favored the proposed structures which was
complemented with 1H NMR and elemental analysis
records.
The 1H NMR spectrum of compound (14) demonstrated
benzohydrazide C-20, C-60 equivalent protons, ortho to
–NH–C=O and meta to nitro (–NO2) groups, experiencing
deshielding due to electron withdrawing nature of amide
and inductively (-I) of amide and nitro groups, appeared as
doublet at d 8.21. The C-30, C-50 proton meta to –NH–C=O
and ortho to nitro groups being deshielded more due to
strong electron withdrawing effect of the nitro group both
by resonance and inductive effects, displayed further
downfield as doublet at d 8.32. Similarly, –N–NH proton
appeared downfield as singlet at d 12.0 as compared to
compounds (15)–(17).
Molecular properties calculations
Tautomerism of (PPMDO) compounds (2)–(17)
For substituted Imidazo[1,2-a]pyridine (-pyimidine) (IP)
and (IPM) and certainly for their analogs (2)–(17),
depending on the pH, two major possible (PPMDO) con-
formations can be described for the neutral form. This
isomerism is governed by the mechanism of Dimroth pro-
cess. These relevant structures are sketched in Scheme 3.
On the other hand, the two isomeric forms (A) and (G),
depending on the pH, four principal possible tautomeric
limit forms can be described for the neutral parent form.
This tautomerism is governed by the bond dissociation
energies of bonds (O–HN and OH–N=C), sigma charge
distribution, p-charge distribution of aromatic bicyclic
system (PPMDO), inductive effect of substituent R of
amine (–NH–R), resonance effect and delocalization
energies and polarizability effect. So the partial p-charge of
the two oxygen atoms of carbonyl groups and the elec-
tronic nature of substituent R of amine (–NH–R) are
strongly involved in the leading to the most stable tauto-
mer. These relevant structures are sketched in (Scheme 4).
Current thinking in the generation of specific drug leads
embodies the concept of achieving high molecular diver-
sity within the boundaries of reasonable drug-like proper-
ties (Koehn and Carter, 2005). Natural and semi-natural
products have high chemical diversity, biochemical speci-
ficity and other molecular properties that make them
favorable as lead and standard reference (SR) structures for
drug discovery, and which serve to differentiate them from
libraries of synthetic and combinatorial compounds. Vari-
ous investigators have used computational methods to
1
The H NMR spectra of compounds (2)–(17) exhibited
split doublets between d 11.22–12.92 and d 12.35–13.42
and between d 8.44–9.10 and d 8.75–9.90 ascribed to
=C–NH and (=CH–N) protons, respectively. The splitting
was due to the existence of Z and E isomers (Hamdi et al.,
1992; Skaellariou et al., 1990). 13C NMR of reference
compounds is also reported. The elemental analysis data
agree well with calculated values.
13C NMR spectra
13C NMR spectra of (2–17) were recorded; however, (2),
(10), and (13) which are representative compounds of each
series are discussed here and found to be consistent with
the proposed structures at each instance. Compound (2)
clearly gave three carbonyl carbons at d 158.8, 169.4 and
201.7, the first two accounts for the carbonyl at the ring and
last one markedly upfield due to the acetyl carbonyl car-
bon. There were eight quaternary and eight methine (CH)
carbons were traced in total, which justified the structure
suggested. Two methyl peaks were also evident at 24.1 and
123

Med Chem Res (2012) 21:60–74
67
O1
O
9
9
H
N
9
H
N
H3C
N
H3C
O
H3C
O
H+
H
N
H2O
-H+
H
N
H
N
N+
N
N
6
7
7
R
7
R
R
6
6
OH
O
O
O
O2
(B)
(C)
(enol Tautomer)
(A)
7
7
6
OH
6
O
H3C
H3C
O1
O
9
H
N
9
H
N
N
H3C
O
H3C
N
O
O
9
9
H
N
H
H
N
N
N
6
N
N
7
N
7
R
R
R
O
O
O
N
O
O
H
R
O2
(D)
(E)
(aldehydeTautomer)
(F)
(G)
Scheme 3 Dimroth process: opening/closing pyridine ring
H3C
N
O
O
H3C
N
O
O
H3C
N
O
O
H
H
N
N
N
N
N
N
R
R
R
(T-3)
H
(T-1)
(T-2)
Dimroth
process
N
O
O
H3C
N
O
H3C
N
O
H3C
H
N
N
N
O
N
N
O
N
H
H
(T-4) or (T-2)
(T-5) or (T-3)
R
(T-6)
R
R
Scheme 4 Phenomenon of tautomerism
understand differences between natural products and other
sources of drug leads (Carroll et al., 2006). Modern drug
discovery is based in large part on high throughput
screening of small molecules against macromolecular dis-
ease targets requiring that molecular screening libraries
contain drug-like or lead-like compounds. We have ana-
lyzed known standard references (SR) for drug-like and
lead-like properties. With this information in hand, we
have established a strategy to design specific drug-like or
lead-like (PPMDO) (2)–(17).
favor of an anti-urease activity, more, and this is in good
´
agreement with the mode of thermodynamic stabilite of
metal complexes [(5c,5c) [ (5c,6c) [ (4c,6c) [ (6c,6c)]
according angle of Bits. It was hypothesized that potential
Nickel chelatation of ligands may facilitate the inhibition
of urease, more than non-chelator ligands. It is further
found that the activity increases with increase in negative
charge of heteroatoms of the common pharmacophore
fragment of the potential tautomers (T-1 and T-6). The
presence of conformation/tautomerism phenomena in aza-
bicyclic analogs was presented previously since 1999, in
few articles by some rare authors (Hamdouchi et al., 1999;
Jaramillo et al., 2006) (Scheme 6).
The series (2)–(17) have been subjected to tautomer-
ization and charge-delocalization using ACD method of the
amino-hydrogen atom (Scheme 5), obtained from the
proton-transfer of the amino group (-NHR), have been used
to model the bioactivity against urease. We give here, as
example, the compounds (2), (9), (10–12), and (13–17).
It is found that the ligands containing 5/6 bonded-
coordination pseudo-cycles of (9) contribute positively in
The structural parameters indicate a stereodynamics of
Ar–C=O rotation and conformational preferences of
2-amino-3-(2,4-difluorobenzoyl)-imidazo[1,2-a]pyridine
(Jaramillo et al., 2006). The main differences between the
three tautomeric forms lie in the intramolecular hydrogen
123

68
Med Chem Res (2012) 21:60–74
Scheme 5 Potential mode of
metal-coordination of
M
O
N
H3C
M
O
N
O
H C
compounds (2), (9), (10–12),
and (13–17), leading ligands to
be organized in situ as different
tridentate sites of coordination
(O,N,O) for (2) and (13)–(17);
(O,N,S) for (9); and (O,N,N) for
(10)–(12)
3
CH
O
3
6c
4c
6c
N
N
N
6c
N
N
H
CH3
H
O
(10)-(12)
(2)
O
N
O
H3C
O
M
N
H C
M
3
H
O
S
6c
6c
5c
5c
N
N
N
H
N
N
H
H
O
R
(9)
(13)-(17)
Scheme 6 Conformation/
tautomerism phenomena in aza-
bicyclic analogs
N
N
N
NH+2
NH2
NH2
+
N
N
N
O-
O-
F
F
F
O
F
F
F
bonding and the relative orientation of the carbonyl group.
Attractive intermolecular interactions occur and are
responsible for the value of diahedral angle (C2–C3–C=O).
This has a direct impact on bioactivity of compounds
(Hamdouchi et al., 1999; Scheme 5). Potential mode of
metal-coordination of compounds (2), (9), (10–12), and
(13–17), leading ligands to be organized in situ as different
tridentate sites of coordination (O,N,O) for (2) and (13)–(17);
(O,N,S) for (9); and (O,N,N) for (10)–(12).
With our recent publication of the drug design combi-
nation of various pharmacophore sites by using spiro-
heterocyclic structure, it is now possible to predict activity
and/or inhibition with increasing success in two targets
(bacteria and HIV virus). This is done using a combined
electronic/structure docking procedure and an example will
be given here. The remarkably well behaved mutagenicity
of divers synthetic molecules classified in data base of
CELERON Compagny of Swiss can be used to quantify the
role played by various organic groups in promoting or
interfering with the way a drug can associate with DNA.
Toxicity risks (mutagenicity, tumorogenicity, irritation,
and reproduction) and physic-chemical properties (ClogP,
solubility, drug-likness, and drug-scor) of tautomers of
compound (9) are calculated by the methodology devel-
oped by Molinspiration as a sum of fragment-based con-
tributions and correction factors (Table 3).
Osiris calculations1
Structure-based design is now fairly routine but many
potential drugs fail to reach the clinic because of ADME-
Tox liabilities. One very important class of enzymes,
responsible for many ADMET problems, is the cyto-
chromes P450. Inhibition of these or production of
unwanted metabolites can result in many adverse drug
reactions. Of the most important program, Osiris is already
available online.
Molinspiration calculations
CLogP (octanol/water partition coefficient) is calculated by
the methodology developed by Molinspiration (Ertl et al.,
2000) as a sum of fragment-based contributions and cor-
rection factors (Table 4).
1
The OSIRIS Property Explorer shown in this page is an integral part
of Actelion’s inhouse substance registration system. It lets you draw
chemical structures and calculates on-the-fly various drug-relevant
properties whenever a structure is valid. Prediction results are valued
and color coded. Properties with high risks of undesired effects like
mutagenicity or a poor intestinal absorption are shown in red.
Whereas a green color indicates drug-conform behavior. http://www.
organic-chemistry.org/prog/peo/.
The method is very robust and is able to process prac-
tically all organic, and most organometallic molecules.
Molecular Polar Surface Area TPSA is calculated based on
the methodology published by Ertl et al. as a sum of
123

Med Chem Res (2012) 21:60–74
69
Table 3 Osiris calculations of tautomers of compound (9)
Tautomer
Toxicity risks
MUT
Osiris calculations
TUMO
IRRI
REP
MW
CLP
S
D-L
D-S
T-1
T-2
T-6
T3
311
311
311
311
1.20
0.73
1.20
0.96
-3.75
-3.33
-3.75
-4.69
1.48
1.84
1.48
1.63
0.76
0.81
0.76
0.68
* Within suitable limits for drugs
Table 4 Molinspiration calculations of tautomers of compound (9)
Tautomer
Molinspiration calculations
Drug-likeness
GPCRL
MW
CLP
TPSA
OH–NH
NV
VOL
ICM
KI
NRL
T-1
T-2
T-6
T-3
311
313
311
313
2.48
2.30
2.48
2.08
63
67
63
67
1
2
1
1
0
0
0
0
265
271
265
271
-1.25
-1.12
-1.25
-0.90
-1.52
-0.66
-1.52
-1.07
-0.90
-1.36
-0.90
-1.41
-1.75
-1.61
-1.75
-1.22
fragment contributions. O- and N-centered polar fragments
are considered. PSA has been shown to be a very good
descriptor characterizing drug absorption, including intes-
tinal absorption, bioavailability, Caco-2 permeability, and
blood–brain barrier penetration. Prediction results of com-
pound (9) molecular properties (TPSA, GPCR ligand, and
ICM) are valued (Table 4).
Experimental protocols
Materials and methods
All reagents and solvents were used as obtained from the
supplier or recrystallized or redistilled as necessary. Thin-
Layer chromatography was performed using aluminum
sheets (Merck) coated with silica gel 60 F254. IR spectra
were recorded in the range 4000–6000 nm using an IR
Perkin-Elmer Spectrum 1 FTIR spectrophotometer and
peaks are reported max(neat)/cm-1 which refer to the mmax
in wave numbers. Proton magnetic resonance spectra were
recorded in d6-DMSO with Bruker AM 300 and AM 400
spectrometers (Rheinstetten–Forchheim, Germany) oper-
ating at 300 and 400 MHz, respectively. The 13C NMR
spectra were recorded in d6-DMSO with Bruker AM 100
spectrometer operating at 100 MHz. Tetramethyl-silane
was used as an internal standard. Elemental analysis for
C, H, N, and S were recorded with Perkin-Elmer 2400
Series II CHN Analyzer. Melting points were recorded on a
GallenKamp apparatus and are uncorrected.
Conclusions
Of the synthesized compounds (2)–(17), two compounds
(9) and (14) were found to be significantly more potent
inhibitors of urease activity than the starting compound (1).
The same two compounds also exhibited anti-urease
activity comparable to thiourea, a standard urease inhibitor
used in this study as a reference. While at 100 lM con-
centration thiourea reduces activity of the urease enzyme
by a factor of 94%, compounds (9) and (14) reduce activity
of this enzyme by a factor of 96 and 86%, respectively. The
compounds are potent inhibitors of the urease enzyme even
at lower concentrations. While at 0.01 lM concentration
the standard urease inhibitor thiourea reduces enzyme
activity by a factor of 8% only, compound (9) at the same
concentration reduces enzyme activity by a factor of 22%.
The study being submitted suggests that of all the com-
pounds synthesized during the present investigation, those
bearing sulfanylanilino and 4-nitrobenzohydrazide moie-
ties possess significant urease inhibition activity. These
compounds may have more tendencies to chelate with the
nickel ions required for the activity of the enzyme.
Procedure for establishing urease inhibition (in vitro)
Urease inhibition was determined by a combination of the
protocol adopted by (Pervez et al., 2009 and Weatherburn,
1967). A clear solution of 5 lL (0.1 mM) of the test
sample was incubated along with 25 lL of enzyme (Jack
bean urease) and 55 lL of buffer containing 100 mM urea
in a well plate at 30°C for 15 min. Urease inhibition was
determined by measuring the ammonia production using
123

70
Med Chem Res (2012) 21:60–74
3-[(3-Acetylanilino)methylidene]-8-methyl-2H-pyrido[1,2-a]-
pyrimidine-2,4-dione (3) Light yellow powder. Mp =
158–160°C. Yield: 78%; IR (m neat)/cm-1) 3211(m),
3060(m), 1700 (s), 1645(m); 1H NMR (d6-DMSO, d, ppm):
2.23 (s, CH3-pyrimidine-2,4-dione), 3.24 (3H, s,0 CH3CO),
7.23 (1H, dd, J 7.85, 8.12 Hz, acetylanilino C5 -H), 7.36
the indophenol method and percentage inhibitions were
calculated at each instance. Thiourea was employed as the
standard.
Synthesis of compounds (1)–(17)
0
(1H, dd, J 8.1, 2.2 Hz, acetylamino C6 -H), 7.38 (1H, d,
J 7.4 Hz, pyrimidine-2,4-dione C7-H), 7.53 (1H, s, J 7.4,
pyrimidine-2,4-dione C9-H), 7.58 (1H, dd, J = 7.8, 2.2 Hz,
Preparation of 8-methyl-2H-pyrido[1,2-a]pyrimidine-
2,4(3H)-dione (1)
0
0
acetylanilino C4 -H), 7.69 (1H, s, acetylanilino C2 -H), 7.80
(1H, d, J 7.4 Hz, pyrimidine-2,4-dione C6-H), 9.0 (1H, d,
J 12.9, = CH–N-), 9.20 (1H, d, J 13.4, = CH–N–), 12.90
(1H, d, J = 13.3, = C-NH-), 13.18 (1H, d, J 12.9,
= C–NH–); 13C NMR (d6-DMSO, d, ppm): 23.8 (CH3),
31.7 (CH3), 104.0 (C), 110.4 (CH), 117.4 (CH), 117.5
(CH), 124.0 (CH), 125.1 (CH), 128.4 (CH), 129.0 (CH),
131.3 (C), 140.8 (C), 147.6 (CH), 151.3 (C), 153.5 (C),
158.4 (C = O), 169.8 (C = O), 200.9 (C = O). SM
[C18H15N3O3] [321.33]. Elemental analyses Found
(Calcd.): C, 66.71 (67.28); H, 4.85 (4.71); N, 13.45 (13.08).
4-Methyl-2-aminopyridine (10 g, 92 mmol) was dissolved in
diethyl malonate (16 g, 92 mmol) and the resultant mixture
was then heated under reflux for 4 h. Upon completion, the
reaction mixture was kept at room temperature for further 1 h
till the precipitates appeared. The precipitates were collected
by suction filtration and washed several times with diethyl
ether which furnished the light yellow product in 72%
yield (Scheme 1). The purity of the prepared compounds
was checked by Thin-Layer Chromatography and m.p.
268–270°C (Tschitschibabin, 1924; Stadlbauer et al., 2001).
General procedure for the synthesis of compounds (2)–(17)
3-[(4-Acetylanilino)methylidene]-8-methyl-2H-pyrido[1,2-
a]pyrimidine-2,4-dione (4) Light yellow powder. Mp =
208–210°C. Yield: 76%; IR (m neat)/cm-1) 3209(m),
3060(m), 1703 (s), 1645(m); 1H NMR (d6-DMSO, d, ppm):
2.24 (3H, s, CH3- pyrimidine-2,4-dione), 3.21 (03H, s,
CH3CO), 7.32 (2H, d, J 8.24 Hz, acetlanilino C2 ,60-H),
7.40 (1H, d, J 7.43 Hz, pyrimidine-2,4-dione C7-H), 7.54
(1H, s, pyrimidin0e-02,4-dione C9-H), 7.62 (2H, d, J 8.24 Hz,
acetylanilino C 3 ,5 -H), 7.81 (1H, d, J 7.4 Hz, pyrimidine-
2,4-dione C6-H), 8.98 (1H, d, J 13.0, =CH–N–), 9.22 (1H,
d, J 13.6, =CH–N–), 12.92 (1H, d, J 13.2, = C-NH-), 13.22
(1H, d, J 13.0, =C–NH–); 13C NMR (d6-DMSO, d, ppm):
24.4 (CH3), 33.0 (CH3), 103.1 (C), 109.6 (CH), 119.0
(CH), 119.2 (CH), 121.3 (CH), 128.9 (CH), 130.5 (C),
139.9 (C), 148.0 (CH), 150.8 (C), 154.0 (C), 154.6 (C=O),
170.4 (C=O), 201.8 (C=O). SM [C18H15N3O3] [321.33].
Elemental analyses Found (Calcd.) C, 67.65 (67.28); H,
4.35 (4.71); N, 12.92 (13.08).
To a hot stirred solution of (1) (0.5 g, 2.8 mmol) and DMF
(7 g, 95 mmol) was added appropriate amount of aniline or
aminopyridine or hydrazides followed by the addition of
triethylorthoformate (0.42 g, 2.8 mmol). The resultant
reaction mixture was heated under reflux for 4 h. After
completion of reaction, the volume was reduced to one-
third. The reaction mixture was allowed to stand for 1 h at
room temperature. The contents were poured in distilled
water, and the solid thus obtained was collected by suction
filtration in pure state (Scheme 2).
3-[(2-Acetylanilino)methylidene]-8-methyl-2H-pyrido[1,2-a]-
pyrimidine-2,4-dione(2) White powder. Mp = 306–308°C.
Yield 80%. IR (m neat)/cm-1) 3291(m), 3098(m), 1723 (s),
1685(m); 1H NMR (d6-DMSO, d, ppm): 2.25 (3H, s, CH3-
pyrimidine-2,4-dione), 3.22(3H, s, CH3CO–), 7.20(1H, ddd,
0
J 7.9, 7.5, 2.1 Hz, acetylanilino C4 -H), 7.26 (1H, dd, J 8.1,
0
2.1 Hz, acetylanilino C6 -H), 7.35 (1H, ddd, J 7.5, 8.1,
0
3-[(Mesitylamino)methylidene]-8-methyl-2H-pyrido[1,2-
a]pyrimidine-2,4-dione (5) White powder. Mp = 238–
240°C. Yield 70%; IR (m neat)/cm-1) 3279(m), 3080(m),
2.2 Hz, acetylanilino C5 -H), 7.40 (1H, d, J 7.4, pyrimidine-
2,4-dione C7-H), 7.50 (1H, dd, J 7.9, 2.2 Hz, acetylanilino
0
C3 -H), 7.55 (1H, s, pyrimidine-2,4-dione C9-H), 7.82 (1H, d,
1
1700 (s), 1685(m); H NMR (d6-DMSO, d, ppm): 2.16
J 7.4 Hz, pyrimidine-2,4-dione C6-H), 9.10 (1H, d, J 12.7,
=CH–N–), 9.32 (1H, d, J 13.6, =CH–N–), 12.32 (1H, d,
J 13.4, = C-NH-), 13.25 (1H, d, J 12.7, =C–NH–). 13C NMR
(d6-DMSO, d, ppm): 24.1 (CH3), 31.3 (CH3), 102.4 (C),
112.2 (CH), 116.4 (CH), 117.3 (CH), 123.5 (CH), 125.6
(CH), 128.1 (CH), 129.2 (CH), 132.2 (C), 140.3 (C), 148.2
(CH), 150.2 (C), 154.5 (C), 158.8 (C=O), 169.4 (C = O),
201.7 (C=O). SM [C18H15N3O3] [321.33]. Elemental anal-
yses Found (Calcd.) C, 66.75 (67.28); H, 4.62 (4.71); N,
13.51 (13.08).
(3H, s, p-CH3), 2.18 (6H, s, 2 9 o-CH3), 2.20 (3H, s, CH3-
0
0
pyrimidine-2,4-dione), 7.00 (2H, s, mesitylamino C3 ,5 -H),
7.35 (1H, d, J 7.5 Hz, pyrimidine-2,4-dione C7-H), 7.44
(1H, s, pyrimidine-2,4-dione C9-H), 7.72 (1H, d, J 7.5 Hz,
pyrimidine-2,4-dione C6-H), 8.88 (1H, d, J 13.5, =CH–
N–), 9.15 (1H, d, J 13.3, =CH–N–), 11.32 (1H, d,
J 13.1, = C–NH–), 12.45 (1H, d, J 13.5, =C–NH–);13C
NMR (d6-DMSO, d, ppm): 18.5(CH3), 20.8(2 9 CH3),
23.3 (CH3), 103.9 (C), 111.6 (CH), 115.0 (CH), 130.2
123

Med Chem Res (2012) 21:60–74
71
(CH), 131.3 (CH), 132.7 (C), 136.9 (C), 138.9 (CH), 150.5
(C), 151.9 (C), 160.8 (C=O), 166.7 (C=O). SM [C19H19N3O2]
[321.37]. Elemental analyses Found (Calcd.) C, 69.50
(71.01); H, 6.22 (5.96); N, 12.72 (13.08).
4-dione C7–H), 7.49 (1H, s, pyrimidine-2,4-dione C9–H),
7.76 (1H, d, J 7.4, pyrimidine-2,4-dione C6–H), 8.75 (1H,
d, J 13.2, = CH–N–), 9.0 (1H, d, J 13.5, = CH–N–), 11.44
(1H, d, J 13.0, = C–NH–), 12.76 (1H, d, J 13.2, = C–NH–);
13C NMR (d6-DMSO, d, ppm): 22.11(CH3), 104.7(C),
110.3(CH), 115.8 (CH), 116.1 (CH), 117.9 (CH), 132.0
(CH), 136.3 (C), 148.2 (CH), 153.8 (C), 156.3(C), 156.9(C),
160.6 (C = O), 166.2 (C = O). SM [C16H12FN3O2] [297.28].
Elemental analyses Found (Calcd.) C, 64.92 (64.64); H,
3.77 (4.07); N, 13.69 (14.13).
3-[(2-Fluoroanilino)methylidene]-8-methyl-2H-pyrido[1,2-a]-
pyrimidine-2,4-dione (6) Maroon powder. Mp = 114–
116°C. Yield 68%; IR (m neat)/cm-1) 3211(m), 3029(m),
1
1709 (s), 1675(m); H NMR (d6-DMSO, d, ppm): 2.21
(3H, s, CH3-pyrimidine-2,40-dione), 7.10 (1H, ddd, J 7.7,
7.4, 2.1 Hz fluoroanilino C4 –H), 7.18 (1H, dd, J 7.8, 2.15,
fluoroanilino C6 –H),7.24 (1H, ddd, J 7.8, 7.4, 2.1 fluoro-
0
8-Methyl-3-[(2-sulfanylanilino)methylidene]-2H-pyrido[1,
2-a]pyrimidine-2,4-dione (9) Light green powder. Mp =
218–220°C. Yield 75%; IR (m neat)/cm-1) 3270(m),
3007(m), 1716 (s), 1660(m); 1H NMR (d6-DMSO, d, ppm):
2.18 (3H, s, CH3-pyrimidine-2,4-dione), 4.22 (1H, s, –SH),
0
anilino C5 –H), 7.30 (dd, 1H, J 7.7, 2.1 Hz, fluoroanilino
0
C3 –H), 7.37 (s, J 7.37, pyrimidine-2,4-dione C7–H),
7.52 (1H, s, pyrimidine-2,4-dione C9–H), 7.79 (2H, d,
J 7.3, pyrimidine-2,4-dione C6,7–H), 8.92 (1H, d, J 13.4, =
CH–N–), 9.20 (1H, d, J 13.8, = CH–N–), 11.45 (1H, d,
J 13.6, = C–NH–), 12.88 (1H, d, J 13.4, = C–NH–); 13C
NMR (d6-DMSO, d, ppm): 23.2(CH3), 105.6(C), 111.0
(CH), 115.1 (CH), 115.7 (CH), 115.8 (CH), 124.2 (CH),
124.3 (CH), 125.9 (C), 132.03 (CH), 142.5 (CH),
153.8 (C), 154.7(C), 156.7(C)161.4 (C = O), 166.4
(C = O). SM [C16H12FN3O2] [297.28]. Elemental analyses
Found (Calcd.) C, 65.01 (64.64); H, 3.83 (4.07); N, 13.65
(14.13).
0
0 0
7.10–7.22(3H, m, sulfanylanilino C3 ,4 ,6 –H), 7.32 (1H, d,
J 7.5, pyridopyrimidine-2,4-dione C7–H), 7.42 (1H, s,
pyridopyrimidine-2,4-dione C9–H), 7.70 (1H, d, J 7.5,
pyridopyrimidine-2,4-dione C6–H), 8.62 (1H, d, J 13.8, =
CH–N–), 9.90 (1H, d, J 13.5, = CH–N–), 11.22 (1H, d,
J 13.2, = C–NH–), 12.35 (1H, d, J 13.8, = C–NH–)
13C NMR (d6-DMSO, d, ppm): 21.5(CH3), 105.8(C),
110.0(CH), 114.3 (CH), 115.8 (CH), 118.3 (C), 118.4
(CH), 127.0 (CH), 131.9 (CH), 133.0 (CH), 147.3 (C),
151.8 (C), 155.3(CH), 156.9(C), 162.5 (C = O), 167.2
(C = O). SM [C16H13N3O2S] [311.36]. Elemental analyses
Found (Calcd.) C, 62.10 (61.72); H, 3.88 (4.21); N, 13.21
(13.50).
3-[(3-Fluoroanilino)methylidene]-8-methyl-2H-pyrido[1,2-a]-
pyrimidine-2,4-dione (7) Yellowish Brown powder.
Mp = 174–176°C. Yield 69%; IR (m neat)/cm-1) 3259(m),
3064(m), 1710 (s), 1645(m); 1H NMR (d6-DMSO, d, ppm):
2.20 (3H, s, CH3-pyrimidine-2,4-dione), 7.12 (1H, dd,
8-Methyl-3-{[(4-methyl-2-pyridinyl)amino]methylidene}-2H-
pyrido[1,2-]pyrimidine-2,4-dione (10) Shiny brown
0
J 7.65, 2.20 Hz, fluoroanilino C6 –H), 7.19 (1H, dd, J 7.6,
0
2.20 HZ, fluoroanilino C4 –H), 7.27 (1H, s, fluoroanilino
crystals. Mp = 168–170°C. Yield 66%; IR (m neat)/cm-1
)
C2 –H), 7.34 (1H, dd, J 7.6, 7.6 HZ, fluoroanilino C5 –H),
7.36 (1H, d, J 7.39, pyrimidine-2,4-dione C7–H), 7.51 (1H,
s, pyrimidine-2,4-dione C9–H), 7.78 (1H, d, J 7.3, pyrim-
idine-2,4-dione C6–H), 8.83 (1H, d, J 13.5, = CH–N–),
9.10 (1H, d, J 13.4, = CH–N–), 11.50 (1H, d, J 13.3, = C–
NH–), 12.80 (1H, d, J 13.5, = C–NH–); 13C NMR (d6-
DMSO, d, ppm): 22.11(CH3), 106.2(C), 110.0(CH), 110.7
(CH), 112.3 (CH), 115.8 (CH), 127.3 (CH), 127.9 (CH),
132.1 (CH), 138.8 (C), 148.3 (CH), 153.8 (C), 156.3(C),
156.7(C), 160.9 (C = O), 165.8 (C = O). SM [C16H12FN3O2]
[297.28]. Elemental analyses Found (Calcd.) C, 64.23
(64.64); H, 4.44 (4.07); N, 13.75 (14.13).
3288(m), 3010(m), 1706 (s), 1680(m); 1H NMR (d6-
DMSO, d, ppm): 2.26 (3H, s, CH3-pyrimidine-2,4-dione),
2.30 (3H, s, pyridinyl CH3), 7.42 (1H, d, J 7.48 HZ,
pyrimidine-2,4-dione C7–H), 7.48 (1H, d, J 7.5, pyridinyl
0
0
0
C5 –H), 7.57 (1H, s, pyrimidine-2,4-dione C9–H), 7.84 (1H,
d, J 7.4 HZ, pyrimidine-2,4-dione C6–H), 7.808 (1H, s,
0
pyridinyl C3 –H), 8.20 (1H, d, J 7.5, pyridinyl C6 –H), 8.72
(1H, d, J 12.8, = CH–N–), 9.32 (1H, d, J 13.1, = CH–N–),
12.21 (1H, d, J 12.9, = C–NH–), 13.42 (1H, d, J 12.8,
= C–NH–). 13C NMR (d6-DMSO, d, ppm): 21.8 (CH3),
23.0 (CH3), 107.7 (C), 115.3 (CH), 119.7 (CH), 121.8 (CH),
123.4 (CH), 124.0 (CH), 134.3 (CH), 143.9 (CH), 147.1 (C),
148.3 (C), 152.8(C), 155.4 (C), 164.2 (C = O), 167.1
(C = O). SM [C16H14N4O2] [294.31]. Elemental analyses
Found (Calcd.) C, 64.74 (65.3); H, 5.31 (4.79); N, 19.55
(19.04).
3-[(4-Fluoroanilino)methylidene-8-methyl-2H-pyrido[1,2-a]
pyrimidine-2,4-dione (8) Shiny dirty green powder.
Mp = 132–134°C. Yield 81%; IR (m neat)/cm-1) 3260(m),
3042(m), 1725 (s), 1640(m); 1H NMR (d6-DMSO, d, ppm):
2.18 (3H, s, CH3-pyrimidine-2,4-dione), 7.11 (2H, d, J 7.2
8-Methyl-3-{[(5-methyl-2-pyridinyl)amino] methylidene}-
2H-pyrido[1,2-]pyrimidine-2,4-dione (11) Shiny light
0
0
HZ, fluoroanilino0 C 2 ,6 –H), 7.25 (2H, d, J 7.23 HZ, flu-
oroanilino C 3 ,5 –H), 7.33 (1H, d, J 7.4, pyrimidine-2,
yellow. Mp = 179–181°C. Yield 68%; IR (m neat)/cm-1
)
0
123

72
Med Chem Res (2012) 21:60–74
3269(m), 3010(m), 1730 (s), 1685(m); 1H NMR (d6-
DMSO, d, ppm): 2.26 (3H, s, CH3-pyrimidine-2,4-dione),
2.32 (3H, s, pyridinyl CH3), 7.41 (1H, d, J 7.4 Hz,
pyrimidine-2,4-dione C7–H), 7.56 (1H, s, pyrimidine-2,4-
(C = O). SM [C17H14N4O3] [322.32]. Elemental analyses
Found (Calcd.) C, 62.89 (63.35); H, 4.75 (4.38); N, 17.11
(17.38).
0
dione C9–H), 7.76 (1H, d, J 7.5 Hz, pyridinyl C3 –H), 7.84
(1H, d, J 7.4 Hz, pyrimidine-2,4-dione C6–H), 7.96 (10H, d,
4-Nitro-N0-{[8-methyl-2,4-dioxo-2H-pyrido[1,2-a]pyrimidin-
3(4H)-ylidene]methyl} benzohydrazide (14) Orange brown
powder. Mp = 196–198°C. Yield 74%; IR (m neat)/cm-1)
0
J 7.5 Hz, pyridinyl C4 –H), 8.10 (1H, s, pyridinyl C6 –H),
1
8.82 (1H, d, J 12.3, = CH–N–), 9.30 (1H, d, J 12.9, =
CH–N–), 12.19 (1H, d, J 12.7, = C–NH–), 13.41 (1H, d,
J 12.3, = C–NH–); 13C NMR (d6-DMSO, d, ppm): 18.4
(CH3), 21.7 (CH3), 105.2 (C), 111.0(CH), 112.3 (CH),
114.6 (CH), 123.5 (C), 130.4 (CH), 135.6 (CH), 143.8
(CH), 152.7 (CH), 152.8 (C), 153.0 (C), 154.5(C), 164.2
(C = O), 167.1 (C = O). SM [C16H14N4O2] [294.31].
Elemental analyses Found (Calcd.) C, 65.70 (65.30); H,
5.11 (4.79); N, 18.87 (19.04).
3235(m), 3010(m), 1720 (s), 1685(m); H NMR (DMSO-
d6, d, ppm): 2.25 (3H, s, CH3-pyrimidine-2,4-dione),7.41
(1H, d, J 7.70, pyrimidine-2,4-dione C7–H), 7.52 (1H, s,
pyrimidine-2,4-dione C9–H), 7.82 (1H, d, J 7.70 Hz,
pyrimidine-2,4-dione C6–H), 8.21 (2H, d, J 7.5 Hz, ben-
0
0
zohydrazide C2 ,6 –H), 8.32 (2H, d, J 7.5 Hz, benzohyd-
0
0
razide C3 ,5 –H), 8.82 (1H, d, J 12.2, = CH–N–), 9.45 (1H,
d, J 12.8, = CH–N–), 12.0 (1H, s, –N–NH–C = O), 12.55
(1H, d, J 12.5, = C–NH–N–C = O), 13.40 (1H, d,
J 12.2, = C–NH–N–C = O); 13C NMR (d6-DMSO, d,
ppm): 20.1 (CH3), 107.5 (C), 109.8 (CH), 114.6 (CH),
124.7 (CH), 127.0 (CH), 133.6 (CH), 139.6 (C), 146.0(CH),
151.0 (C), 152.6 (C), 156.0 (C), 159.8 (C = O), 161.3
(C = O), 173.1 (C = O). SM [C17H13N5O5] [367.32]. Ele-
mental analyses Found (Calcd.) C, 55.22 (55.59); H, 3.98
(3.57); N, 20.33 (19.07).
8-Methyl-3-{[(5-nitro-2-pyridinyl)amino] methylidene}-
2H-pyrido[1,2-a]pyrimidine-2,4-dione (12) Golden Yel-
low powder. Mp = 156–158°C. Yield 72%; IR (m neat)/
cm-1) 3267(m), 3034(m), 1706 (s), 1665(m); 1H NMR
(d6-DMSO, d, ppm): 2.27 (3H, s, CH3-pyrimidine-2,
4-dione), 7.43 (1H, d, J 7.4 Hz, pyrimidine-2,4-dione C7–H),
7.59 (1H, s, pyrimidine-2,4-dione C9–H), 7.85 (1H,
d, J 7.4 Hz, pyrimidine-2,4-dione C6–H), 8.20 (1H, d,
4-Bromo-N0-{[8-methyl-2,4-dioxo-2H-pyrido[1,2-a]pyrimi-
din-3(4H)-ylidene]methyl}benzohydrazide (15) White
crystals. Mp = 212–214°C. Yield 70%; IR (m neat)/cm-1)
3290(m), 3010(m), 1735 (s), 1670(m); 1H NMR (d6-
DMSO, d, ppm): 2.22 (3H, s, CH3-pyrimidine-2,4-dione),
7.34 (1H, d, J 7.72 Hz, pyrimidine-2,4-dione C7–H), 7.43
0
J 7.4 Hz, pyridinyl C3 –H), 8.88 (1H, d, J 7.45 Hz,
0
0
pyridinyl C4 –H), 9.21 (1H, s, pyridinyl C6 –H), 8.91 (1H,
d, J 12.3, = CH–N–), 9.45 (1H, d, J 13.2, = CH–N–),
12.72 (1H, d, J 12.9, = C–NH–), 13.68 (1H, d, J 12.3,
= C–NH–); 13C NMR (d6-DMSO, d, ppm): 18.6 (CH3), 21.0
(CH3), 104.6 (C), 110.2 (CH), 110.8 (CH), 115.8(CH), 132.1
(CH), 134.9(CH), 139.1 (C), 146.8 (CH), 147.7 (CH), 153.8
(C), 156.7(C), 158.9(C), 164.2 (C = O), 167.1 (C = O). SM
[C15H11N5O4] [325.28]. Elemental analyses Found (Calcd.)
C, 55.02 (55.39); H, 3.66 (3.41); N, 20.16 (21.53).
0
0
(2H, d, J 7.42 Hz, benzohydrazide C3 ,5 –H), 7.45 (1H, s,
pyrimidine-2,4-dione C9–H), 7.74 (1H, d, J 7.72 Hz,
pyrimidine-2,4-dione C6–H), 7.90 (2H, d, J 7.4 Hz, ben-
0
0
zohydrazide C2 ,6 –H), 8.56 (1H, d, J 13.7, = CH–N–),
8.85 (1H, d, J 14.2, = CH–N–), 11.40 (1H, d, J 13.9, = C–
NH–N–C = O), 11.93 (1H, s, –N–NH–C = O), 12.65 (1H,
d, J 13.7, = C–NH–N–C = O); 13C NMR (d6-DMSO, d,
ppm): 20.1 (CH3), 107.0 (C), 112.0 (CH), 116.0 (CH),
127.2 (C), 129.5 (CH), 129.8(C), 130.6(CH), 132.2 (CH),
148.0(CH), 154.1 (C), 156.9 (C), 158.7 (C = O), 162.6
(C = O), 170.0 (C = O). SM [C17H13BrN3O3] [401.21].
Elemental analyses Found (Calcd.) C, 50.39 (50.89); H,
3.40 (3.27); N, 13.51 (13.96).
N’-{[8-Methyl-2,4-dioxo-2H-pyrido[1,2-a]pyrimidin-3(4H)-
ylidene]methyl}-benzo-hydrazide (13) White crystals.
Mp = 182–184°C. Yield 78%; IR (m neat)/cm-1) 3275(m),
3021(m), 1718 (s), 1651(m); 1H NMR (d6-DMSO, d, ppm):
2.23 (3H, s, CH3-pyrimidine-2,4-dion0e), 7.33 (2H, dd,
0
J 7.35, 7.42 Hz, benzohydrazide C3 ,5 -H), 7.38 (1H, d,
J 7.67 Hz, pyrimidine-2,4-dione C7–H),7.48 (1H, s, pyrim-
idine-2,4-dione C9–H),7.51 (1H, t, J 7.4, 2.0 Hz,
0
benzohydrazide C4 –H),7.78 (1H, d, J 7.6 Hz, pyrimidine-
2,4-dione 0C6–H), 7.88 (2H, dd, J 7.35, 2.0 Hz, benzohydr-
4-Chloro-N0-{[8-methyl-2,4-dioxo-2H-pyrido[1,2-a]pyrimi-
din-3(4H)-ylidene]methyl}benzohydrazide (16) White
powder. Mp = 198–200°C. Yield 98% as white solid; IR
0
azideC2 ,6 –H), 8.45 (1H, d, J 13.4, = CH–N–), 8.75 (1H, d,
1
J 13.2, = CH–N–), 11.35 (1H, d, J 13.8, = C–NH–N–
C = O), 11.96 (1H, s, –N–NH–C = O), 12.45 (1H, d,
J 13.4, = C–NH–N–C = O). 13C NMR (d6-DMSO, d,
ppm): 20.5 (CH3), 107.3 (C), 112.4 (CH), 113.7 (CH), 122.4
(CH), 122.8 (CH), 124.2 (CH), 126.7 (CH), 128.0 (CH),
136.3 (C), 143.8 (C), 153.5 (C = O), 160.7 (C = O), 174.2
(m neat)/cm-1) 3210(m), 3011(m), 1718 (s), 1666(m); H
NMR (d6-DMSO, d, ppm): 2.23 (3H, s, CH3-pyrimidine-
2,4-dione), 7.37 (1H, d, J 7.68 Hz pyrimidine-2,4-dione
0
C7–H), 7.45 (2H, d, J 7.4 Hz, benzohydrazide C3 ,50–H),
7.48 (1H, s, pyrimidine-2,4-dione C9–H), 7.76 (1H, d,
J 7.6 Hz, pyrimidine-2,4-dione C6–H), 7.92 (2H, d,
123

Med Chem Res (2012) 21:60–74
73
0
J 7.4 Hz, benzohydrazide C2 ,60–H), 8.60 (1H, d, J 13.6, =
CH–N–), 8.90 (1H, d, J 13.9, = CH–N–), 11.50 (1H, d,
J 13.7, = C–NH–N–C = O), 11.94 (1H, s, –N–NH–
C = O), 12.67 (1H, d, J 13.6, = C–NH–N–C = O); 13C
NMR (d6-DMSO, d, ppm): 23.0 (CH3), 106.6 (C), 112.3
(CH), 116.0 (CH), 127.9(CH), 128.2 (CH), 129.0(CH),
132.1(C), 142.2(C), 145.6(CH), 150.7 (C), 154.4 (C), 159.6
(C = O), 163.5 (C = O), 172.6 (C = O). SM
[C17H13ClN4O3] [356.76]. Elemental analyses Found
(Calcd.) C, 56.88 (57.23); H, 3.79 (3.67); N, 15.23 (15.70).
Andreani A, Granaiola M, Guardigli M, Leoni A, Locatelli A, Morigi
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4-Hydroxy-N0-{[8-methyl-2,4-dioxo-2H-pyrido[1,2-a]pyr-
imidin-3(4H)-ylidene]methyl}benzohydrazide (17) White
crystals. Mp = 210–212°C. Yield 78%; IR (m neat)/cm-1
)
3275(m), 3013(m), 1710 (s), 1665(m); 1HNMR (d6-
DMSO, d, ppm): 2.21 (3H, s, CH3-pyrimidine-2,4-dione),
7.32 (1H, d, J 7.73 Hz pyrimidine-2,04-0dione C7-H), 7.39
(2H, d, J 7.5 Hz, benzohydrazide C3 ,5 –H), 7.44 (1H, s,
pyrimidine-2,4-dione C9–H), 7.73 (1H, d, J 7.73 Hz,
pyrimidine-2,4-0di0one C6–H), 7.94 (2H, d, J 7.5 Hz, ben-
zohydrazide C2 ,6 –H), 9.75 (1H, s, benzohydrazide –OH),
8.44 (1H, d, J 13.8, = CH–N–), 8.83 (1H, d, J 14.2, =
CH–N–), 11.42 (1H, d, J 14.0, = C–NH–N–C = O), 11.88
(1H, s, –N–NH–C = O), 12.60 (1H, d, J 13.8, = C–NH–
N–C = O); 13C NMR (d6-DMSO, d, ppm): 23.1 (CH3),
110.0 (C), 110.3 (CH), 115.7 (CH), 115.8(CH), 129.4(C),
128.1 (CH), 128.7(CH), 142.4(CH), 154.3 (C), 156.0 (C),
162.3 (C = O), 163.1(C), 165.7 (C = O), 170.2 (C = O).
SM [C17H14N4O4] [338.32]. Elemental analyses Found
(Calcd.) C, 59.88 (60.35); H, 4.35 (4.17); N, 16.19 (16.56).
Acknowledgments One of the authors (Prof. A. Rauf) is thankful to
H.E.J. Research Institute of Chemistry—University of Karachi,
Pakistan for carrying out spectroscopic and elemental analyses. Prof.
T. Ben Hadda would like to thank the ACTELION, the Biopharma-
ceutical Company of Swiss, for the molecular properties calculations.
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