Design and chemical behavior of novel pyrimidine derivatives and their evaluation of cytotoxicity

Article abstract of DOI:10.1080/00397911.2020.1735444

Diphenyl-4-thioxo-1,4-dihydropyrimidin-5-yl)ethan-1-one 4 was obtained upon the reaction of (phenylamino)but-2-enethioyl)benzamide 3 with sodium hydroxide. The reactions of 4 with several active species such as benzaldehyde, urea, malononitrile, ethyl cyanoacetate, hydrazine, and carbon disulfide were studied. The antitumor activities of some selective compounds were examined against two cell lines: Mammalian cell lines: A-549 cells (human lung cancer cell line) and MRC-5 cells (normal human lung fibroblast cell line); some of the compounds were highly efficient; compound 13 has the most effective anticancer activity.

Full text of DOI:10.1080/00397911.2020.1735444

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Design and chemical behavior of novel pyrimidine
derivatives and their evaluation of cytotoxicity
Alaa R. Sakr, Mohamed G. Assy & Youssra S. ELasaad
To cite this article: Alaa R. Sakr, Mohamed G. Assy & Youssra S. ELasaad (2020): Design and
chemical behavior of novel pyrimidine derivatives and their evaluation of cytotoxicity, Synthetic
Communications, DOI: 10.1080/00397911.2020.1735444
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https://doi.org/10.1080/00397911.2020.1735444
Design and chemical behavior of novel pyrimidine
derivatives and their evaluation of cytotoxicity
Alaa R. Sakr, Mohamed G. Assy, and Youssra S. ELasaad
Department of Chemistry, Faculty of Science, Zagazig University, Zagazig City, Egypt
ABSTRACT
ARTICLE HISTORY
Received 12 November 2019
Diphenyl-4-thioxo-1,4-dihydropyrimidin-5-yl)ethan-1-one 4 was obtained
upon the reaction of (phenylamino)but-2-enethioyl)benzamide 3
with sodium hydroxide. The reactions of 4 with several active
species such as benzaldehyde, urea, malononitrile, ethyl cyanoace-
tate, hydrazine, and carbon disulfide were studied. The antitumor
activities of some selective compounds were examined against
two cell lines: Mammalian cell lines: A-549 cells (human lung can-
cer cell line) and MRC-5 cells (normal human lung fibroblast cell
line); some of the compounds were highly efficient; compound
13 has the most effective anticancer activity.
KEYWORDS
Enamine; benzoyl
isothiocyanate; pyrimidine;
pyran; antitumor assay
GRAPHICAL ABSTRACT
Introduction
Enaminone derivatives are useful for synthetic precursors and their utilization in
organic synthesis due to the presence of the nucleophilic character of the enamine moi-
ety and the electrophilic character of the enone moiety.[1–3]
The synthesis of pyrimidine and condensed pyrimidines has attracted the attention of
medicinal chemists because of their potential pharmacodynamic properties. Numerous
CONTACT Alaa R. Sakr
Alaasakr81@yahoo.com
Department of Chemistry, Faculty of Science, Zagazig University,
Zagazig City 44519, Egypt.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2020 Taylor & Francis Group, LLC

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A. R. SAKR ET AL.
publications describe the synthesis of condensed pyrimidines possessing a variety of
pharmacological activities such as anticonvulsant[4] and antifertility activities.[5] In con-
junction with the work on the synthesis of pyrimidinethione derivatives for biological
evaluations,[6–9] A series involving synthesis and reaction pyrimidinthione moiety
is described.
Acyl isothiocyanates[10] are bifunctional compounds containing an acyl group and
thiocyanate group. Its reactivity determined by three active centers: the nucleophilic
nitrogen atom, the electrophilic carbon atoms of the carbonyl and the thiocarbonyl
groups, which make them capable of participating in diverse types of addition and cyc-
lization reactions. Isothiocyanates are a key reagent in heterocyclic chemistry because
they are very useful in the synthesis of such functionalized thiazoles, thiadiazoles, tria-
zoles, imidazoles, oxazolines, triazines, oxazines, and pyrimidine compounds. They have
been shown to exhibit anti-cancer activity in animals treated with chemical carcinogens
due to their inhibition of carcinogenic metabolic activation.[11]
Result and discussion
In continuation of our work in the synthesis of pyrimidines, this paper describes the
preparation of some pyrimidines from simply available laboratory reagents.[12,13]
Enamine of type 1 added its reactive nucleophilic carbon to activated heteroallene
carbon of benzoyl isothiocyanate to provide the acyclic thioamide derivative 3 (Scheme
1). Infrared (IR) spectrum of compound 3 absorption peaks at 3275, 1670, and
1
1257 cmꢀ1 for NH, C¼O, and C¼S groups, respectively. H NMR of the same com-
pound showed downfield signals at 12.63 and 11.57 ppm for NH protons in addition to
aromatic multiplet signal. 13C NMR for the acyclic compound 3 contained sp2 carbon
for C¼S and 2 C¼O at 201.43, 193.50, and 179.59 ppm in addition to aliphatic sp3 car-
bon signal. Intramolecular cyclization of acyclic compound 3 was achieved by heating
in base mediated alcoholic solution to furnish pyrimidinthione 4, also absorption fre-
quencies for C¼S and C¼O sp2 carbon.
Acetylpyrimidinthione 4 undergoes cyclization with benzaldehyde to form qunazoline
derivative 7. The reaction may be started with the formation of cinnamoyl derivative 5
that cyclized intramolecularity via the addition of the activated methyl to a, b-unsatur-
ated system, dehydrogenated and finally enolized to stable enolic form. IR spectrum of
target condensed compound 7 showed OH peaks at 3344 cmꢀ1 and C¼S at 1261 cmꢀ1
.
1H NMR displayed of deshielded signal at d10.24 together multiplet signal for aromatic
protons. 13C NMR provided C¼N carbon at 166.12 ppm. When compound 7 was sub-
jected to condensation with hydrazine, it resulted in the cyclization of pyrazole to pro-
vide polyheterocyclic compound 8, compound 8 contained downfield signal for NH
(Scheme 1).
Keeping a mixture of benzaldehyde, compound 4 provided the polycyclic compound
9 presumably via formation 7 that condensed with thiourea to give pyrimidine ring 9
1
(Scheme 1). IR spectrum was in agreement with the expected structure 9. H NMR
revealed signal at 10.25 ppm in addition to aromatic multiplet. 13C NMR showed sp2
carbon of C¼S at 166.11 ppm.

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Scheme 1. Synthesis and reaction of pyrimidinethione 4 with amine derivatives and benzaldehyde.
Urea was also condensed with pyrimidinethione 4 under similar above reaction condition
to provide compound 10 (Scheme 1). IR spectrum of compound 10 provided stretching fre-
1
quencies at 3275 and 1670cmꢀ1 for OH and C¼O groups, respectively. H NMR revealed
that the compound 10 present in equimolar amounts of keto/enol form at d12.44ppm for
OH and NH at 11.57ppm, respectively. 13C provided C¼O carbon signal at d174; com-
pound 4 undergoes base cyclization with benzaldehyde and malononitrile to provide pyri-
dine 13. The reaction may proceed via the formation of nonisolable cinnamoyl derivative 5,
then forming nonisolable adduct 11 via Michael addition of malononitrile with 5,

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A. R. SAKR ET AL.
Scheme 2. Reaction of pyrimidinethione 4 with malononitrile.
compound 11 cyclized to pyran derivative 12 which rearranged to give compound 13
(Scheme 2). IR spectrum of 13 showed CN in addition to the carbonyl group. Also 1H NMR
showed the lactam lactim equilibrium. Contrary to the above reaction conditions, when the
reaction was carried out in acidic medium, it showed the pyran derivative 14, which dehy-
drogenated and hydrolyzed yielding pyran derivative 15 (Scheme 2). The absence of CN
group in IR spectrum of 15 potentiates the structure. 1H NMR contained two deshielded sig-
nals at 12.62 and 11.57 ppm for NH2 and CONH2 protons, respectively. 13C NMR provided
sp2 carbon signal for C¼S and C¼O at 179.69 and 169.79ppm, respectively.
A ternary mixture of 4, benzaldehyde, ethyl cyanoacetate, and TEA resulted in pyran ring
followed by transformation affording compound 18. Compound 18 revealed stretching fre-
quencies at 3271, 1670, 1604, and 1246cmꢀ1 for NH, C¼O, C¼N, and C¼S, respectively. It
also showed keto-enol form equilibrium in 1H NMR as two downfield signals at 12.63 and
11.57 for OH and NH protons. Pyrimidinthione 4 was condensed with hydrazine in ethanol
to produce the hydrazone derivative 19. IR spectrum showed the presence of NH and C¼O
1
at 3342cmꢀ1and 1658 cmꢀ1, respectively. H NMR displayed downfield signal at 10.25,
while 13C NMR provide signal at 166.11ppm for carbonyl carbon (Scheme 3).
Acetyl pyrimidinethione 4 added its activated methyl ketone group to carbon disul-
fide in the presence of alcoholic KOH to produce bicyclic compound 22 presumably
through the nonisolable compound 20 which cyclized via loss of H2S to give 21, which
dehydrogenated to give the final product 22 (Scheme 4).

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Scheme 3. Reaction of pyrimidinethione 4 with hydrazine and benzaldehyde, ethyl cyanoacetate
and TEA.
Compound 22 shows stretching frequency at ꢀ3344, 1654 and 1261 cmꢀ1 for OH,
1
C¼N, and C¼S groups, respectively. H NMR for the same target compound contains a
deshielded signal at d 10.24 ppm due to OH proton in addition to aromatic multiplet
signal. 13C NMR showed C¼S carbon signal at d 166 ppm and another C¼S signal at
139 ppm (due to intramolecular hydrogen bond).
Antitumor evaluation of tested compounds
Compounds were tested for their antitumor activity against mammalian cell lines: A-
549 cells (human lung cancer cell line) and MRC-5 cells (normal human lung fibroblast
cell line) using viability assay method (Table 1).[13,14]
No significant difference was observed between IC50 of compound 13 and doxorubi-
cin; therefore, compound 13 showed the lowest IC50 as compared to other test com-
pounds. Hence, compound 13 has the most effective anticancer activity.
The compound 13 showed the best result more than the doxorubicin. Compound 13
inhibitory is 98.26% with a concentration of 250 mM/ml higher than doxorubicin inhibi-
tory which is 98.02% with a concentration of 1000 mM/ml.

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A. R. SAKR ET AL.
Scheme 4. Reaction of pyrimidinethione 4 with carbon disulfide.
Table 1. Evaluation of cytotoxic effects of tested compounds.[14]
Compound
IC50 mM/mL
CC50 mM/mL
7
9
13
18
288 9.8
215 4.7
6.86 0.2
116 2.9
328 9.2
0.89 0.05
210 5.4
124 3.1
45.8 1.9
382 8.7
214 5.2
22
Doxorubicin
Experimental
Melting points were measured using an Electrothermal IA 9100 apparatus with an open
capillary tube and are uncorrected. The IR spectra (KBr disk) were recorded on a
PyeUnicam Sp-3-300 or a Shimadzu FT-IR 8101 PC IR spectrophotometer. The 1H
NMR and 13C NMR spectra were measured on a JEOL-JNM-LA 400 MHz spectrometer
using DMSO-d6 as a solvent. All chemical shifts were expressed on the d (ppm) scale
using tetramethylsilane (TMS) as an internal standard reference. The coupling constant
(J) values are given in Hz. Analytical data were obtained from the Microanalysis Center
at Cairo University, Giza, Egypt.
General experimental procedure for the preparation of compound: (E)-N-(2-
methyl-3-(phenylamino)but-2-enethioyl)benzamide [3]
A mixture of enamine 1 (0.01 mol, 1.75 g) and benzoyl isothiocyanate 2[15](0.01 mol,
1.63 g) in dioxane (15 mL) was stirred for 30 min. The red precipitate obtained was

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filtered off and crystallized from ethanol to provide red crystals of compound 3 (3.22 g),
1
90% yield. MP 158 ꢁC, IR: 1670 (C¼O), 1604 (C¼N), 1257 (C¼S); H NMR: 12.36
(s, 1H, NH), 11.75 (s, 1H, NH), 8.00 ꢀ 7.26 (m, 9H, ArH’s þ enaminon proton), 2.5
(s, 3H, CH3):13C NMR; 179.59 (C¼S), 168.78 (C¼O), 138.46, 133.60, 132.62, 129.16,
128.92, 126.80, 124.80, 30.93, 17.99, Anal. Calcd for C18H18N2OS (310.41): C, 69.58%;
H, 5.79%; N, 9.02%;S, 10.30, found: C, 69.65%; H, 5.84%;N, 9.02%;S,10.33.
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