Design, synthesis, and biological evaluation of new thiazolo[5,4-: D] pyrimidine derivatives as potent antiproliferative agents

Article abstract of DOI:10.1039/c7md00165g

A series of thiazolo[5,4-d]pyrimidine derivatives were synthesized and evaluated for their antiproliferative activities against several human cancer cell lines. Structure-activity relationship studies were carried out, showing that most of the target compounds had good inhibition against the tested cell lines. Among them, compound 7i exhibited potent inhibition against human gastric cancer cells MGC-803 and HGC-27 with IC₅₀ values of 4.64 and 5.07 μM, respectively and around 12-fold selectivity between MGC-803 and GES-1, indicating a relatively low toxicity to normal cells. The potency and low toxicity of compound 7i make the thiazolo[5,4-d]pyrimidine an attractive scaffold for designing new derivatives selectively targeting MGC-803 cells.

Full text of DOI:10.1039/c7md00165g

View Article Online
View Journal
MedChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: B. Yu, H. Liu, Z. Li,
X. Liu, P. Geng, J. Ma, T. Zhao and H. Wei, Med. Chem. Commun., 2017, DOI: 10.1039/C7MD00165G.
Volume 7 Number 1 January 2016 Pages 1–204
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
MedChemComm
Broadening the field of opportunity for medicinal chemists
www.rsc.org/medchemcomm
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
Themed issue: Antibiotic Resistance
ISSN 2040-2503
rsc.li/medchemcomm

Page 1 of 9
MedChemComm
View Article Online
DOI: 10.1039/C7MD00165G
Design, synthesis, and biological evaluation of new thiazolo[5,4-d]pyrimidine
derivatives as potent antiproliferative agents
1
1
Zhong-Hua Li , Xue-Qi Liu , Peng-Fei Geng, Jin-Lian Ma, Tao-Qian Zhao,
Hao-Ming Wei, Bin Yu*, Hong-Min Liu*
Collaborative Innovation Center of New Drug Research and Safety Evaluation, Henan
Province; Key Laboratory of Technology of Drug Preparation (Zhengzhou University),
Ministry of Education of China; Key Laboratory of Henan Province for Drug Quality and
Evaluation; School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou 450001,
PR China
Corresponding Author: Prof. Hong-Min Liu & Dr. Bin Yu
Zhengzhou University, Zhengzhou, 450001, PR China
E-mail: liuhm@zzu.edu.cn (Hong-Min Liu) & zzuyubin@hotmail.com (Bin Yu)
ABSTRACT:
A series of thiazolo[5,4-d]pyrimidine derivatives were synthesized and evaluated for
their antiproliferative activities against several human cancer cell lines. The
structure-activity relationship studies were carried out, showing that most of the target
compounds had good inhibition against the tested cell lines. Among them, compound
7
i exhibited potent inhibition against human gastric cancer cells MGC-803 and
HGC-27 with the IC50 values of 4.64 and 5.07 µM, respectively and around 12-fold
selectivity between MGC-803 and GES-1, indicating relatively low toxicity to normal
cells. The potency and low toxicity of compound 7i make the
thiazolo[5,4-d]pyrimidine an attractive scaffold for designing new derivatives
selectively targeting MGC-803 cells.
KEYWORDS: Thiazolo[5,4-d]pyrimidine, Antiproliferative activity, Low toxicity
The scaffold diversity has been highly pursued in the construction of small-molecule
library, highlighting the importance of molecular scaffolds in the identification of new
1
-4
drugs. Of particular interest are the heterocyclic scaffolds, which are prevalent in
drugs and natural products. Modifications on the biologically privileged scaffolds

MedChemComm
Page 2 of 9
View Article Online
DOI: 10.1039/C7MD00165G
have been recognized as an important strategy to search new bioactive compounds for
the treatment of diseases. Compounds bearing the bicyclic thiazolo[5,4-d]pyrimidine
scaffold have been proved to possess diverse biological activities such as
5
-9
10
11
12
anti-tumor,
antimicrobial, anti-inflammatory, antinociceptive
and human
13
cytomegalovirus inhibitory. For example, compound A as a TRPV1 (vanilloid
receptor 1) antagonist is orally active and exerts reversal of carrageenan-induced
1
4
thermal hyperalgesia model in rats. And compound B is a highly potent and
selective hA AR (human adenosine A receptor) antagonist with the hA AR Ki value
reaching 18 nM. Moreover, 7-thia-8-oxoguanosine C is a guanosine analogue
3
3
3
15
1
6, 17
showing immunostimulatory activity both in vivo and in vitro,
in addition to a
18-20
broad-spectrum antiviral activity.
Also, thiazolidinone D was reported to be active
21
against HEPG2 (human liver carcinoma cell line) targeting thymidylate synthase.
Therefore, modifications based on this scaffold may be a viable strategy for designing
new antiproliferative agents. Our previous work has demonstrated that the
thiazolo[5,4-d]pyrimidine scaffold could be used for designing apoptosis-inducing
22
agent. Following our previous work, herein we report the synthesis and
antiproliferative activity of a series of thiazolo[5,4-d]pyrimidine derivatives against
three human cancer cell lines. We also explored the selectivity of such compounds to
MGC-803 cells over GES-1 cells.
Fig. 1. Pharmaceutically important thiazole-pyrimidine derivatives.
The general synthetic route was illustrated in Scheme 1. The intermediate derivatives
23
5
a~b were synthesized following the previously reported procedure. Then the
isothiocyanate analogs reacted with 5a~b under alkaline conditions (cesium carbonate)
24
in acetonitrile to give the key active intermediates 6a~f. The target compounds 7a-j

Page 3 of 9
MedChemComm
View Article Online
DOI: 10.1039/C7MD00165G
were readily obtained by refluxing indicated amines with 6 and triethylamine in
isopropanol.
Scheme 1. Reagent and conditions: (a) alkyl bromide, TEA, methanol, reflux, 2 h; (b) fuming
o
nitric acid, AcOH, 25~45 C, 1 h; (c) POCl
3
, DMA, reflux, 2 h; (d) Fe, AcOH, methanol, rt~reflux;
2
(
e) R SCN, Cs
2
CO
3
, acetonitrile, rt, overnight; (f) TEA, isopropanol, reflux, 6 h.
All the target compounds were screened for their antiproliferative activities against
human gastric cancer cell lines (MGC-803 and HGC-27) and human lung cancer cell
line (H1650) by the MTT assay (the cells were purchased from Cell Bank, Shanghai
Institutes for Biological Sciences, Shanghai, China), and 5-fluorouracil (5-FU) was
25
employed as the reference drug. The antiproliferative results were summarized in
Table 1. Generally, most of the synthesized compounds presented moderate to good
inhibition toward the tested cancer cell lines, and especially were more sensitive to
MGC-803 cell line than the other two cell lines with the IC50 values of less than 10
µM. For MGC-803 cells, compounds 7a, 7c, and 7i showed the best inhibitory effect
with the IC50 values of around 5 µM, comparable to that of 5-FU. For HGC-27 and
H1650 cells, this series of compounds displayed decreased inhibitory activity with the
IC50 values of more than 10 µM. Only compound 7i showed slightly better
antiproliferative activity than 5-FU. For H1650 cells, a similar trend was observed,

MedChemComm
Page 4 of 9
View Article Online
DOI: 10.1039/C7MD00165G
compounds 7b and 7e were slightly more potent than 5-FU with the IC50 values of
.49 and 5.79 µM, respectively. In general, this series of compounds did not show
8
remarkable structure-activity relationships, highlighting the importance of the
thiazolo[5,4-d]pyrimidine scaffold for the activity observed. The prioritized one is the
compound 7i, which potently inhibited growth of MGC-803 and HGC27 cells and
will be subject to further mechanistic studies.
Table 1
Antiproliferative activities of thiazolo-pyrimidine derivatives against three cancer cell
lines.
a
IC50 (µM)
1
2
3
Compound
R
R
R N
MGC-803
5.13±0.71
HGC27
H1650
7
7
a
Propyl
Propyl
Propyl
Propyl
Propyl
Ph
16.17±1.20
13.36±1.12
b
Ph
Ph
9.84±0.99
4.81±0.68
14.50±0.65
6.07±0.78
12.26±1.50
18.90±1.27
27.56±0.87
10.30±1.01
8.49±0.92
21.73±1.65
36.93±3.06
5.79±0.86
7
c
7
d
3,4,5-triMeO-Ph
2-Cl-Ph
7
e
7
f
Propyl
Propyl
2-Cl-Ph
7.78±0.89
8.63±0.96
10.62±1.02
10.23±0.79
12.95±2.16
13.13±2.01
7
7
g
h
Propyl
Bn-
30.80±1.48
13.50±1.13
18.73±2.66
13.83±1.14
7
i
Ph
4.64±0.66
5.07±0.70
7
j
Bn-
-
Ph
-
9.91±0.99
6.56±0.31
>64
15.73±0.36
12.52±1.53
5
-FU
-
8.22±0.98
a
Inhibitory activity was assayed by exposure for 72 h to substrate and expressed as concentration
required to inhibit tumor cell proliferation by 50 % (IC50). Data are presented as the means ± SDs
of three independent experiments.

Page 5 of 9
MedChemComm
View Article Online
DOI: 10.1039/C7MD00165G
The potent inhibition of compounds 7a and 7i against MGC-803 cells promoted us to
explore the selectivity between MGC-803 cells and GES-1 cells. As shown in Table 2,
these two compounds showed good selectivity with the SI values of >12.5 and 12.0,
respectively, indicating low toxicity (IC50 > 55 µM against GES-1 cells). The potency
and low toxicity of compounds 7a and 7i make the thiazolo[5,4-d]pyrimidine an
attractive scaffold for designing new derivatives selectively targeting MGC-803 cells.
Table 2
Selectivity of compounds 7a and 7i between MGC-803 and GES-1.
a
IC50 (µM)
b
Compound
SI
MGC-803
5.13±0.71
GES-1
>64
7a
>12.5
12.0
7
i
4.64±0.66
55.84±0.99
a
Inhibitory activity was assayed by exposure for 72 h to substance and expressed as concentration
required to inhibit tumor cell proliferation by 50% (IC50). Data are presented as the means ± SDs
of three independent experiments.
b
The selectivity index (SI) was calculated based on the IC50 (GES-1) and IC50 (MGC803) data.
In light of the acceptable cytotoxicity and low toxicity of compounds 7a and 7i,
molecular properties of compounds 7a and 7i were calculated online using the free
molecular calculation services provided by Molsoft (http://molsoft.com/mprop). As
shown in Table 3, compounds 7a and 7i exhibited acceptable molecular properties
with the MolLogP value slightly higher than the desirable value.
Table 3
a
Molecular properties of 7a and 7i
2
3
Compound
MW HBA HBD MolLogP MolPSA (A ) MV (A )
Desirable value <500
<10
<5
<5
<140
---
7
a
486.19
448.15
7
1
5.82
62.61
476.71
7
i
6
1
5.47
43.92
411.88
a
MW: Molecular weight; HBA: Number of hydrogen bond acceptors; HBD: Number of hydrogen
bond donors; MolLogP: LogP value predicted by molsoft; MolPSA: Topological polar surface
area; MV: Molecular volume.

MedChemComm
Page 6 of 9
View Article Online
DOI: 10.1039/C7MD00165G
In conclusion, a series of thiazolo-pyrimidine derivatives were prepared and evaluated
for the antiproliferative activity toward several human cancer cell lines. Most of the
target compounds showed moderate to good inhibition against the tested cell lines.
Among them, compounds 7a and 7i exhibited potent inhibition against MGC-803
cells with the IC50 values of 5.13 and 4.64 µM, respectively and showed at least
1
2-fold selectivity between MGC-803 and GES-1, indicating low toxicity. These
results indicated that the thiazolo[5, 4-d]pyrimidine scaffold may serve as a template
for designing new anticancer agents.
Acknowledgement
This work was supported by National Key Research Programs of Proteins
(
2016YFA0501800); National Natural Science Foundation of China (Project No.
1430085 and No. 21372206 for H.-M.L.); Key Research Program of Henan Province
No. 1611003110100 for H.-M.L.); The Starting Grant of Zhengzhou University (No.
2210533 for B. Yu)
8
(
3
Conflict of Interest
The authors declare no competing interests.
References
1
.
Wang S, Zhao LJ, Zheng YC, et al. Design, synthesis and biological evaluation of
1,2,4]triazolo[1,5-a]pyrimidines as potent lysine specific demethylase 1 (LSD1/KDM1A) inhibitors.
European journal of medicinal chemistry. 2017;125: 940-951.
Shi XJ, Yu B, Wang JW, et al. Structurally novel steroidal spirooxindole by241 potently inhibits
tumor growth mainly through ROS-mediated mechanisms. Scientific reports6;6: 31607.
Yu B, Qi PP, Shi XJ, et al. Efficient synthesis of new antiproliferative steroidal hybrids using the
molecular hybridization approach. European journal of medicinal chemistry. 2016;117: 241-255.
[
2
.
3
.
4
3
5
.
Yu B, Xing H, Yu DQ, et al. Catalytic asymmetric synthesis of biologically important
-hydroxyoxindoles: an update. Beilstein journal of organic chemistry. 2016;12: 1000-1039.
Lin R, Johnson SG, Connolly PJ, et al. Synthesis and evaluation of 2,7-diamino-thiazolo[4,5-d]
.
pyrimidine analogues as anti-tumor epidermal growth factor receptor (EGFR) tyrosine kinase
inhibitors. Bioorganic & medicinal chemistry letters. 2009;19(8): 2333-2337.
6
.
Fahmy HT, Rostom SA, Saudi MN, et al. Synthesis and in vitro evaluation of the anticancer activity
of novel fluorinated thiazolo[4, 5-d]pyrimidines. Archiv der Pharmazie. 2003;336(4-5): 216-225.

Page 7 of 9
MedChemComm
View Article Online
DOI: 10.1039/C7MD00165G
7
.
Yu ZQ, Paul R, Bhattacharya C, et al. Structural features facilitating tumor cell targeting and
internalization by bleomycin and its disaccharide. Biochemistry. 2015;54(19): 3100-3109.
Yu ZQ, Schmaltz RM, Bozeman TC, et al. Selective tumor cell targeting by the disaccharide moiety
of bleomycin. Journal of the American chemical society. 2013;135(8): 2883-2886.
Baljinder S, Santosh K, Guru, et al. Synthesis, antiproliferative and apoptosis-inducing activity of
thiazolo[5,4-d]pyrimidines. European journal of medicinal chemistry. 2013;70: 864-874.
0. Jang MY, De Jonghe S, Segers K, et al. Synthesis of novel 5-amino-thiazolo[4,5-d]pyrimidines as E.
coli and S. aureus SecA inhibitors. Bioorganic & medicinal chemistry. 2011;19(1): 702-714.
8
.
9
.
1
1
1
1. Bekhit AA, Fahmy HT, Rostom SA, et al. Design and synthesis of some substituted
H-pyrazolyl-thiazolo[4,5-d]pyrimidines as anti-inflammatory-antimicrobial Agents. European journal
of medicinal chemistry. 2003;38(1): 27-36.
1
2
2. Varano F, Catarzi D, Vincenzi F, et al. Design, synthesis, and pharmacological characterization of
-(2-furanyl)thiazolo[5,4-d]pyrimidine-5,7-diamine derivatives: new highly potent A2A adenosine
receptor inverse agonists with antinociceptive activity. Journal of medicinal chemistry. 2016;59(23):
1
1
0564-10576.
3. Lewis AF, Drach JC, Fennewald SM, et al. Inhibition of human cytomegalovirus in culture by
alkenyl guanine analogs of the thiazolo[4,5-d]pyrimidine ring system. Antimicrob Agents Chemother.
1
1
2
994;38(12): 2889-2895.
4. Lebsack AD, Branstetter BJ, Hack MD, et al. Identification and synthesis of
,7-diamino-thiazolo[5,4-d]pyrimidine derivatives as TRPV1 antagonists. Bioorganic & medicinal
chemistry letters. 2009;19(1): 40-46.
5. Varano F, Catarzi D, Squarcialupi L, et al. Exploring the 7-oxo-thiazolo[5,4-d]pyrimidine core for
1
the design of new human adenosine A3 receptor antagonists. Synthesis, molecular modeling studies
and pharmacological evaluation. European journal of medicinal chemistry. 2015;96: 105-121.
1
6. Colic M, Jandric D, Gasic S, et al. Immunosine (7-thia-8-oxoguanosine) acts as a cofactor for
proliferation of T cells. Fundamental & clinical pharmacology. 2000;14(3): 209-217.
1
7
7. Sharma BS, Mhaskar S, Balazs L, et al. Immunomodulatory activity of a novel nucleoside,
-thia-8-oxoguanosine: I. Activation of natural killer cells in mice. Immunopharmacology and
immunotoxicology. 1992;14(1-2): 1-19.
1
7
1
1
7
2
8. Smee DF, Alaghamandan HA, Cottam HB, et al. Broad-spectrum in vivo antiviral activity of
-thia-8-oxoguanosine, a novel immunopotentiating agent. Antimicrob agents chemother. 1989;33(9):
487-1492.
9. Smee DF, Alaghamandan HA, Cottam HB, et al. Antiviral activity of the novel immune modulator
-thia-8-oxoguanosine. Journal of biological response modifiers. 1990;9(1): 24-32.
0. Smee DF, Alaghamandan HA, Jin A, et al. Roles of interferon and natural killer cells in the antiviral
activity of 7-thia-8-oxoguanosine against Semliki Forest virus infections in mice. Antiviral research.
1
2
990;13(2): 91-102.
1. El-Zahar MI, Adb El-Karim SS, Haiba ME, et al. Synthesis, antitumor activity and molecular
docking study of novel benzofuran-2-yl pyrazole pyrimidine derivatives. Acta poloniae pharmaceutica.
2
2
011;68(3): 357-373.
2. Li ZH, Zhang J, Liu XQ, et al. Identification of thiazolo[5,4-d]pyrimidine derivatives as potent
antiproliferative agents through the drug repurposing strategy. European journal of medicinal
chemistry. 2017;135: 204-212.
2
3. Li ZH, Yang DX, Geng PF, et al. Design, synthesis and biological evaluation of

MedChemComm
Page 8 of 9
View Article Online
DOI: 10.1039/C7MD00165G
[
1,2,3]triazolo[4,5-d]pyrimidine derivatives possessing a hydrazone moiety as antiproliferative agents.
European journal of medicinal chemistry. 2016;124: 967-980.
2
2
4. Liu
J,
Patch
RJ,
Schubert
C,
et
al.
Single-step
syntheses
of
-amino-7-chlorothiazolo[5,4-d]pyrimidines: intermediates for bivalent thiazolopyrimidines. Journal of
organic chemistry. 2005;70(24): 10194-10197.
5. Duan YC, Ma YC, Zhang E, et al. Design and synthesis of novel 1,2,3-triazole-dithiocarbamate
hybrids as potential anticancer agents. European journal of medicinal chemistry. 2013;62: 11-19.
2

Page 9 of 9
MedChemComm
View Article Online
DOI: 10.1039/C7MD00165G
Graphic abstract
A series of thiazolo[5,4-d]pyrimidine derivatives were synthesized and evaluated for
their antiproliferative activities against several cancer cell lines. Among these
compounds, compound 7i exhibited potent inhibition against human gastric cancer
cells MGC-803 and HGC-27 with the IC50 values of 4.64 and 5.07 μM, respectively and
around 12-fold selectivity between MGC-803 and GES-1.