Synthesis and anticancer activity of novel 2-alkylthio-4-amino-5-(thiazol-2-YL)pyrimidines

Article abstract of DOI:10.1080/00397911.2021.1939383

A series of new fist-time synthesized of thiazolyl-substituted 4-aminopyrimidine was obtained on the basis of a two-stage process including thioamidation of 4-amino-5-cyanopyrimide followed by one-pot acylation and Hantzsch synthesis in good yield (52–77%

Full text of DOI:10.1080/00397911.2021.1939383

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Synthesis and anticancer activity of novel 2-
alkylthio-4-amino-5-(thiazol-2-YL)pyrimidines
Alexander S. Bunev, Dmitry A. Khochenkov, Yulia A. Khochenkova, Yulia S.
Machkova, Elena V. Varakina, Rovshan E. Gasanov, Marina A. Troshina & Olga
S. Avdyakova
To cite this article: Alexander S. Bunev, Dmitry A. Khochenkov, Yulia A. Khochenkova, Yulia S.
Machkova, Elena V. Varakina, Rovshan E. Gasanov, Marina A. Troshina & Olga S. Avdyakova
(2021) Synthesis and anticancer activity of novel 2-alkylthio-4-amino-5-(thiazol-2-YL)pyrimidines,
Synthetic Communications, 51:16, 2521-2527, DOI: 10.1080/00397911.2021.1939383
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2021, VOL. 51, NO. 16, 2521–2527
https://doi.org/10.1080/00397911.2021.1939383
Synthesis and anticancer activity of novel 2-alkylthio-4-
amino-5-(thiazol-2-YL)pyrimidines
Alexander S. Buneva , Dmitry A. Khochenkova,b, Yulia A. Khochenkovab, Yulia S.
Machkovab, Elena V. Varakinaa, Rovshan E. Gasanova, Marina A. Troshinaa, and
Olga S. Avdyakovaa
b
aMedicinal Chemistry Center, Togliatti State University, Togliatti, Russian Federation; Laboratory of
Biomarkers and Mechanisms of Tumor Angiogenesis, N. N. Blokhin National Medical Research Center of
Oncology, Moscow, Russian Federation
ABSTRACT
ARTICLE HISTORY
Received 9 April 2021
A series of new fist-time synthesized of thiazolyl-substituted 4-amino-
pyrimidine was obtained on the basis of a two-stage process includ-
ing thioamidation of 4-amino-5-cyanopyrimide followed by one-pot
acylation and Hantzsch synthesis in good yield (52–77%). All synthe-
sized compounds showed a good anticancer effect in antiprolifera-
tive assay (end point) on three tumor lines A431, A549 b HT-1080
KEYWORDS
Cancer cell lines; cytotoxic
activity; Hantzsch synthesis;
heterocyclization; nitriles;
pyrimidines; thia-
GRAPHICAL ABSTRACT
zoles; thioamides
NH2
NH2
CN
Alk
N
N
N
N
S
NH
S
Alk
S
N
R
O
Alk = Me, Et, Pri, Prn, MeOCH2CH2
R = Alk, Ar, Het
Yield 52-77%
Introduction
The production of new target-type antitumor compounds remains one of the most
important tasks of modern medicinal chemistry. The design of this kind of compounds
is mainly based on the synthetic modification of various heterocyclic compounds.[1–5]
Recently, pyrimidine-based compounds such as cediranib, pazopanib, tandutinib,
dasatinib, and vandetanib have been identified as promising agents to treat cancer and
have already advanced to clinical trials.[6] Furthermore, pyrimidine-based compounds
can be found in many commercially available anticancer drugs, which are used to treat
breast, ovarian, pancreatic, bladder, colon, esophageal, stomach, cervical, kidney, gastric,
lung, chronic lymphocytic leukemia, and colorectal cancer.[7–9] Hence, witnessing the
recent advancement of pyrimidine compounds in cancer treatment and their versatility
CONTACT Alexander S. Bunev
a.s.bunev@gmail.com; a.bunev@tltsu.ru
Medicinal Chemistry Center, Togliatti State
University, Togliatti, Russian Federation.
Supplemental data for this article can be accessed on the publisher's website
ß 2021 Taylor & Francis Group, LLC

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A. S. BUNEV ET AL.
Table 1. Cytotoxicity of the synthesized compounds against human cancer cell line.
Survival,a %
Survival, %
Compounds
A431
A549
HT-1080
Compounds
A431
A549
HT-1080
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
8k
13.5 9.3
22.9 3.2
23.2 7.0
10.2 5.1
15.7 8.2
21.7 4.1
23.2 8.2
21.2 4.7
44.5 8.8
17.3 1.1
30.9 7.2
47.7 1.3
1.8 2.7
67.7 9.3
66.6 3.2
60.3 7.0
77.0 5.1
88.7 8.2
54.0 4.1
79.1 8.2
75.9 4.2
70.1 4.7
74.5 8.8
52.6 7.6
75.5 1.1
6.1 3.2
40.1 4.7
54.5 8.8
62.6 7.6
55.5 1.1
63.3 7.2
43.9 1.3
54.0 8.5
53.1 6.0
84.6 7.5
41.8 7.3
75.8 5.0
73.3 6.2
3.9 1.3
8m
8n
8o
8p
8q
8r
8s
8t
8u
23.9 8.5
36.6 3.7
32.0 1.2
25.9 3.5
28.4 6.8
62.5 1.9
71.1 7.5
74.0 7.3
62.9 5.0
61.1 6.2
32.1 5.2
41.2 2.7
1.8 2.7
73.3 7.2
83.9 1.3
74.0 8.5
53.1 6.0
88.2 3.7
75.8 6.6
27.4 0.5
75.8 6.6
63.4 2.9
64.0 2.0
83.9 5.2
83.3 4.5
6.1 3.2
71.4 5.2
63.5 2.7
95.7 10.1
79.7 4.7
50.2 3.7
77.1 2.2
53.9 8.4
107.1 2.2
98.5 4.6
105.6 3.7
100.9 9.3
107.3 12.9
3.9 1.3
8v
8w
8x
8l
Gefitinib
Gefitinib
aAdd 50 lM test compound, incubation 72 h.
as anticancer drugs promoted us to use pyrimidine as the core structural unit of our
target bioactive compounds.
Among various heterocycles that have been explored for developing pharmaceutically
important molecules, thiazoles, fused thiazoles, and thiazoles linked to various hetero-
cyclic rings through different linkages have recently attracted great attention. They were
found to be associated with a wide range of chemotherapeutic activities including anti-
microbial,[10–14] antifungal,[15] antiparasitic,[16] and antiviral[17] activities. On the other
hand, thiazole-containing compounds were reported to contribute to a variety of anti-
cancer potentials including antitumor,[18,19] cytotoxic,[20,21] antiproliferative,[22] DNA-
cleaving,[23] and angiogenesis inhibiting[24] activities. Interest in the chemotherapeutic
activity of thiazoles was potentiated after the discovery of the natural antineoplastic
antibiotics tiazofurin[25,26] bleomycin, netropsin, and thiazole netropsin.
Consequently, to exploit the potentialities of thiazoles toward cancer treatment and
also considering the remarkable anticancer properties of pyrimidines, we intended to
conjugate these subunits in one structural frame.
Results and discussion
The presented work demonstrates a synthetic strategy for combining two pharmaco-
logically active scaffolds, which consists in the transformation of 4-amino-5-cyanopyri-
midine derivatives into the corresponding thioamides, followed by the
Hantzsch reaction.
The target 4-amino-5-cyanopyrimidines 3a–e were obtained on the basis of (1-ethox-
yethylidene)malonitrile 1 and S-alkylisothiourea salt 2 (hydroiodide, hydrobromide or
mesylates). Thioamides of pyrimidine series 4a–e, previously not described in the litera-
ture, were obtained in the course of the thioamidation of nitriles 3 under the action of
hydrogen sulfide in pyridine (Scheme 1).[27–29]
Target compounds 8a–x were obtained by the Hantzsch reaction between thioamides
4a–e and the corresponding N-acylated 3-aminophenacyl bromide 7. It is noteworthy
that the acylation of 3-aminophenacyl bromide and the Hantzsch reaction were success-
fully carried out in the one pot format. Activated CDI carboxylic acid 6 was introduced

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Scheme 1. Reagents and conditions: (i) Pri2EtN, EtOH, reflux, 8 h; (ii) H2S, Et3N, Py, r.t.,12 h.
Scheme 2. Reagents and conditions: (i) CDI (1.2 equiv.), MeCN, r.t., 1 h, then 5 (1.0 equiv.), r.t., 5 h;
(ii) 4 (1 equiv.), reflux, 12 h, then solution NaHCO3.
into the acylation reaction of amine 5, followed by prolonged reflux (12 h) with thioa-
mide 4 (Scheme 2).
The structure of all the synthesized compounds 3a–e, 4a–e, and 8a–x were confirmed
by nuclear magnetic resonance (NMR) analysis. All the final compounds showed a char-
acteristic chemical shift to a proton substitute and carbon on the pyrimidine ring.
Spectral analysis data are provided as Supplementary Information.
The synthesized 4-amino-5-cyanopyrimidine derivatives were evaluated for cytotoxic
activities by MTT assay against human lung adenocarcinoma cell line A549, human epi-
dermoid carcinoma cell line A431, and human sarcoma cell line HT-1080 (Table 1).
The synthesized compounds exhibited cytotoxicity activities against A431 cell lines.
Based on cell viability data we selected compounds 8d and 8e for further study. The
low activity of compounds 8t–x is partly due to the poor solubility of these compounds.
Conclusion
In conclusion, a straightforward and efficient protocol for the first-time synthesis of
novel functionalized pyrimidines derivatives has been developed. Mild reaction

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A. S. BUNEV ET AL.
conditions, good yields, operational simplicity and the absence of tedious separation
procedures, clean reaction profiles, high atom economy, inexpensive starting materials
are the key advantages of the present protocol. Most of the compounds possessed cyto-
toxicity effects on all the tested cell lines.
Experimental
General
All reagents and solvents were purchased from commercial sources and used without
further purification.[1]  and13‘ NMR spectra were acquired on a Bruker Avance spec-
trometer (600 and 150 MHz, respectively) in DMSO-d6, internal standard was TMS. 19F
NMR spectra were recorded on the Bruker Avance III 500 spectrometer, operating at
471 MHz. 19F chemical shifts was measured relative to CFCl3 as an external standard.
Elemental analysis was performed on a vario EL cube analyzer. Melting points were
determined on a Boetius hot stage and were not corrected. All compounds reported in
this communication are at least 95þ% pure judged by HPLC UV detection (Agilent
Technologies 1220 Infinity LC) and optionally NMR.
Synthesis of 4-amino-2-alkylthiopyrimidine-5-carbonitriles (typical procedure)
A mixture (1-ethoxyethylidene)malonitrile 1 (50 mmol), S-alkylisothiourea salt 2 (hydro-
iodide, hydrobromide or mesylates) (50 mmol), Pri2EtN (60 mmol) and ethanol
(250 mL) was reacted under reflux conditions for approximately 8 h. When the reaction
was complete (TLC monitoring, hexane/EtOAc 7:3), the reaction mixture was poured
into water (400 mL), then washed thoroughly with water. The product was isolated by
filtration, dried, and recrystallized from 95% ethanol.
Synthesis of 4-amino-2-alkylthiopyrimidine-5-carbothiamide (typical procedure)
A mixture of compound 3 (10 mmol) and Et3N (20 mmol) in 50 ml of pyridine is satu-
rated with H2S for 2 h while cooling on ice. Then the mixture is left for 12 h. After the
product is precipitated with water, filtered off, dried and recrystallized from DMF.
Synthesis of pyrimidines 8a–x (typical procedure)
CDI (2.2 mmol) was added to a solution of the corresponding carboxylic acid 6
(2.1 mmol) in 20 mL of anhydrous MeCN, and the mixture was stirred for an hour at
room temperature. Next, phenacyl bromide 5 (2 mmol) is added to the resulting imida-
zolide and stirring is continued for 5 h. Then the corresponding thioamide 4 (2 mmol)
in 25 mL of MeCN is added to the resulting solution. The resulting mixture was
refluxed for 12 h, neutralized with 20% NaHCO3 solution, and the reaction mixture was
diluted with water. The precipitated product was filtered off, dried in air, and recrystal-
lized from DMF.

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N-(3-(2-(4-Amino-2-(methylthio)pyrimidin-5-yl)thiazol-4-yl)phenyl)acetamide (8a)
Yield 74%, mp 213–214 ꢀC. Found, %: C 54.01; H 4.63; N 19.66. C16H15N5OS2.
1
Calculated, %: C 53.76; H 4.23; N 19.59. H NMR (500 MHz, DMSO-d6): 10.12 (s, 1H),
8.65 (s, 1H), 8.43 (s, 2H), 8.19 (s, 1H), 8.04 (s, 1H), 7.68–7.58 (m, 2H), 7.40 (t,
J ¼ 7.9 Hz, 1H), 2.51 (s, 2H), 2.08 (s, 3H). 13C NMR (126 MHz, DMSO-d6): 171.8, 169.0,
164.8, 158.8, 155.3, 154.3, 140.4, 134.3, 129.8, 121.2, 119.5, 117.1, 113.3, 106.0,
24.5, 13.9.
ORCID
Alexander S. Bunev
http://orcid.org/0000-0001-6408-8329
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