Synthesis, molecular docking and evaluation of thiazolyl-pyrazoline derivatives as EGFR TK inhibitors and potential anticancer agents

Article abstract of DOI:10.1016/j.bmcl.2011.07.010

Fourty-two thiazolyl-pyrazoline derivatives were synthesized to screen for their EGFR kinase inhibitory activity. Compound 4-(4-chlorophenyl)-2-(3-(3,4- dimethylphenyl)-5-p-tolyl-4,5-dihydro-1H-pyrazol-1-yl)thiazole (11) displayed the most potent EGFR TK inhibitory activity with IC₅₀ of 0.06 μM, which was comparable to the positive control. Molecular docking results indicated that compound 11 was nicely bound to the EGFR kinase. Compound 11 also showed significant antiproliferative activity against MCF-7 with IC ₅₀ of 0.07 μM, which would be a potential anticancer agent.

Full text of DOI:10.1016/j.bmcl.2011.07.010

Bioorganic & Medicinal Chemistry Letters 21 (2011) 5374–5377
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis, molecular docking and evaluation of thiazolyl-pyrazoline
derivatives as EGFR TK inhibitors and potential anticancer agents
⇑
Peng-Cheng Lv , Dong-Dong Li , Qing-Shan Li, Xiang Lu, Zhu-Ping Xiao, Hai-Liang Zhu
State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 February 2011
Revised 3 July 2011
Accepted 6 July 2011
Available online 14 July 2011
Fourty-two thiazolyl-pyrazoline derivatives were synthesized to screen for their EGFR kinase inhibitory
activity. Compound 4-(4-chlorophenyl)-2-(3-(3,4-dimethylphenyl)-5-p-tolyl-4,5-dihydro-1H-pyrazol-1-
yl)thiazole (11) displayed the most potent EGFR TK inhibitory activity with IC50 of 0.06 lM, which was
comparable to the positive control. Molecular docking results indicated that compound 11 was nicely
bound to the EGFR kinase. Compound 11 also showed significant antiproliferative activity against
MCF-7 with IC50 of 0.07
l
M, which would be a potential anticancer agent.
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
Thiazolyl-pyrazoline derivatives
Molecular docking
EGFR TK
Inhibitors
Anticancer
Protein kinases catalyze the phosphorylation of tyrosine and
serine/threonine residues in various proteins involved in the regu-
lation of all functions.1 They can be broadly classified as receptor
kinases such as EGFR, and non-receptor kinases. Inappropriate or
uncontrolled activation of many of these kinases has been shown
to result in uncontrolled cell growth.2 The EGFR PTKs have been
identified as interesting targets for medicinal chemistry programs
especially in cancer therapy.3–6 Compounds that inhibit the kinase
activity of EGFR after binding its cognate ligand are of potential
interest as new therapeutic antitumor agents.7,8
Thiazoles and their derivatives have attracted continuing inter-
est over the years because of their varied biological activities,9,10
recently found applied in drug development for the treatment of
allergies,11 inflammation,12 schizophrenia,13 bacterial,14 HIV infec-
tions,15 and more recently for the treatment of cancer.16
Lin et al. reported that 2,7-diamino-thiazolo[4,5-d]pyrimidines
analogues showed modest to potent EGFR TK inhibitory activity,
with IC50 values ranging from micromolar to single digit nanomo-
lar.17 Many pyrazole derivatives are acknowledged to possess a
wide range of bioactivities. The pyrazole motif makes up the core
structure of numerous biologically active compounds. Thus, some
representatives of this heterocycle exhibit anti-viral/anti-
tumor,18–20 antibacterial,21,22 antiinflamatory,23 analgesic,24 fungi-
static25 and anti-hyperglycemic activity.26 Robert D. Hubbard et al.
have discovered a series of EGFR TK inhibitors with pyrazolopyrim-
idine scaffold.27
Herein, in continuation to extend our research on anticancer
compounds with EGFR TK inhibitory activity,28 we report in the
present work the synthesis and structure–activity relationships
of a series of thiazolyl-pyrazoline derivatives as anticancer agents.
Biological evaluation indicated that some of the synthesized
compounds are potent inhibitors of EGFR TK. Compound 11 dis-
played the most potent EGFR TK inhibitory activity with IC50 of
0.06
(IC50 = 0.03
l
M, which was comparable to the positive control erlotinib
M). Docking simulations were performed using the
l
X-ray crystallographic structure of the EGFR TK in complex with
an inhibitor to explore the binding modes of these compounds at
the active site.
The synthesis of thiazolyl-pyrazoline derivatives 4–45 followed
the general pathway outlined in Scheme 1. Firstly, the chalcones
(compound 2) were obtained by direct condensation between the
aromatic aldehydes and the substituted acetophenone, using 20%
potassium hydroxide as catalyst. Secondly, cyclization of different
chalcones with thiosemicarbazide under basic condition leads to
the formation of pyrazole derivatives containing thiourea skeleton
(compound 3). Finally, thiazolyl-pyrazoline derivatives 4–45 were
obtained by reacting compound 3 with substituted 2-bromoaceto-
phenone. All of the synthetic compounds gave satisfactory analyt-
ical and spectroscopic data, which were in full accordance with
their depicted structures. The general synthetic procedure and
spectroscopic data of compounds 4–45 can be found in the Supple-
mentary data. Most of the synthetic compounds are soluble in
DMSO and CHCl3.
⇑
Corresponding author. Tel./fax: +86 25 8359 2672.
E-mail address: zhuhl@nju.edu.cn (H.-L. Zhu).
These authors contributed equally.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.07.010

P.-C. Lv et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5374–5377
5375
i
R1
R2
R1
O
O
1
2
R1
A
ii
B
N
N
R2
S
H2N
3
R1
A
B
N
I
R2
N
iii
II
N
S
C
4-45
R3
Scheme 1. General synthesis of compounds 4–45. Reagents and conditions: (i) Substituted aromatic aldehyde, 40% NaOH, CH3CH2OH; (ii) thiosemicarbazide, NaOH,
CH3CH2OH, reflux; (iii) substituted 2-bromoacetophenone, reflux, 4 h. I and II represent the atom number binding to the amino acid active site.
The synthesized compounds 4–45 were evaluated for their
activity to inhibit the autophosphorylation of EGFR kinases. The
inhibition constants (IC50) of the compounds are summarized in
Table 1. As shown in Table 1, the synthesized compounds showed
fairly good inhibitory activity displaying IC50 values between 0.06
Among compounds 4–17, compounds 11–17 (IC50
0.06–1.04 M) with a chlorine atom substitution on the 4-position
of the C-ring displayed more inhibitory activity than those without
4-position substitution derivatives (compounds 4–10, IC50
1.73–3.85 M). Furthermore, as for compounds 11–17, a compari-
:
l
:
l
and 28.17
l
M. Subsequently SAR studies were performed by
son of the substitution on B-ring demonstrated that the electron-
modification of the parent compound to determine how the
substituents of the subunits affect the EGFR inhibitory activities.
Inspection of the chemical structures of the compounds 4–45
(Table 1 and Scheme 1) suggested that they could be divided into
three subunits: A-, B- and C-rings.
withdrawing substituents at 4-position derivatives (compounds
11–13 and 17, IC50: 0.06–0.63
activities than the electron-donating substituents ones (compounds
14–16, IC50: 0.82–1.04 M). Among the former, compound 11 dis-
played the most potent EGFR inhibitory activity with IC50 of
0.06 M, which was comparable to the positive control erlotinib
(IC50 = 0.03 M).
lM) had more potent EGFR inhibitory
l
As shown in Table 1, structure–activity relationships in
compounds 4–45 demonstrated that compounds bearing one
l
l
methoxy group at 4-position at A-ring (compounds 32–45, IC50
5.07–8.63 M) showed better EGFR inhibitory activity than those
with one bromine atom substituent (compounds 18–31, IC50
8.95–28.17 M) at the same position. After we modified the
substituents on A-ring with two methyl group at 3-position and
4-position (compounds 4–17, IC50: 0.06–3.08 M), the EGFR inhib-
itory activity of compounds 4–17 was remarkably increased com-
pared to compounds 32–45 (IC50: 5.07–8.63 M).
:
To help understand the SARs observed at the EGFR and guide
further SAR studies, molecular docking of the most potent inhib-
itor 11 into ATP binding site of EGFR kinase was performed on the
binding model based on the EGFR complex structure (1M17.pdb).
The binding model of compound 11 and EGFR is depicted in Fig-
ure 1.
l
:
l
l
As shown in Figure 1, compound 11 was nicely bound to the
l
EGFR kinase with three hydrogen bonds: NIÁ Á ÁO/Leu768 (distance:

5376
P.-C. Lv et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5374–5377
Table 1
Chemical structures and EGFR TK inhibitory activity of compounds 4–45
R1
A
B
I
N
R2
N
II
N
S
C
R3
Compd
R1
R2
R3
EGFR (IC50
,
lM)
Compd
R1
R2
R3
EGFR (IC50, lM)
4
5
6
7
8
9
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
3,4-2CH3
4-Br
4-Br
4-Br
4-Br
4-Br
4-Br
4-Br
—
4-F
4-Cl
4-Br
4-CH3
4-OCH3
4-OH
4-NO2
4-F
4-H
4-H
4-H
4-H
4-H
4-H
4-H
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-H
4-H
4-H
4-H
4-H
4-H
4-H
—
1.73 0.12
2.36 0.28
1.84 0.16
2.67 0.31
3.08 0.42
1.92 0.19
3.85 0.56
0.06 0.009
0.19 0.012
0.37 0.026
1.04 0.11
0.82 0.057
0.97 0.064
0.63 0.049
11.24 1.68
9.37 0.83
8.95 0.78
19.64 2.15
10.17 1.46
22.36 2.34
15.72 1.82
0.03 0.007
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
—
4-Br
4-Br
4-Br
4-Br
4-Br
4-Br
4-Br
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
—
4-F
4-Cl
4-Br
4-CH3
4-OCH3
4-OH
4-NO2
4-F
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-H
4-H
4-H
4-H
4-H
4-H
4-H
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
—
24.16 2.74
17.84 1.89
25.74 2.83
28.17 2.91
19.83 1.94
21.52 2.46
24.37 2.72
5.71 0.61
4.94 0.43
5.56 0.56
7.48 0.70
6.92 0.69
5.35 0.48
8.63 0.73
5.07 0.52
7.78 0.68
6.31 0.57
4.68 0.38
6.27 0.49
7.66 0.81
8.43 0.94
—
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Erlotinib
4-Cl
4-Br
4-Cl
4-Br
4-CH3
4-OCH3
4-OH
4-NO2
4-F
4-CH3
4-OCH3
4-OH
4-NO2
4-F
4-Cl
4-Br
4-Cl
4-Br
4-CH3
4-OCH3
4-OH
4-NO2
—
4-CH3
4-OCH3
4-OH
4-NO2
—
2.35 Å, angle: 127.5°), NIIÁ Á ÁO/Gln767 (distance: 1.82 Å, angle:
121.8°) and SÁ Á ÁN/Cys751 (distance: 2.87 Å, angle: 97.3°). The mod-
eling also suggested that there was a
p-cation interaction between
the thiazole ring of compound 11 and Lys828.
p-Cation interaction
energies are of the same order of magnitude as hydrogen bonds or
salt bridges and play an important role in stabilizing the three
dimensional structure of a protein.29 Also, the binding model of erl-
otinib and EGFR was introduced to make a comparison, which is
shown in Figure 2. As illustrated in Figure 2, one nitrogen atom
of the quinazoline skeleton forms a hydrogen bond with Met769,
and the other quinazoline nitrogen atom is not within H-bonding
distance of the Thr766 side chain, but a water molecule bridges
this gap.30
In addition, we also selected the top seven compounds 11–17
which had better EGFR inhibitory activity to test their in vitro anti-
proliferative activity against human tumor cell line (MCF-7). The
results are showed in Table 2. We can see from Table 2 that com-
pound 11 exhibited significant antiproliferative activity against
Figure 1. Molecular docking modeling of compound 11 with EGFR kinase. The
H-bonds are displayed as green dot lines. Compound 11 was nicely bound to the
EGFR kinase with three hydrogen bonds: NIÁ Á ÁO/Leu768 (distance: 2.35 Å, angle:
127.5°), NIIÁ Á ÁO/Gln767 (distance: 1.82 Å, angle: 121.8°) and SÁ Á ÁN/Cys751 (dis-
MCF-7 with IC50 of 0.07
control erlotinib (IC50 = 0.02
played good antiproliferative activity against MCF-7 with IC50
ranging from 0.16 to 1.47 M. In particular, compound 11 demon-
strated significant EGFR inhibitory activity and potent antiprolifer-
l
M, which was comparable to the positive
lM). Compounds 12–17 also dis-
l
tance: 2.87 Å, angle: 97.3°). The modeling also suggested that there was a
interaction between the thiazole ring of compound 11 and Lys828.
p-cation

P.-C. Lv et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5374–5377
5377
Acknowledgments
This work was supported by the China Postdoctoral Science
Foundation (20100481122) and the Jiangsu National Science Foun-
dation (No. BK2009239).
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Top
compounds
MCF-7
(IC50, lM)
11
12
13
14
15
16
17
Erlotinib
0.07 0.008
0.16 0.02
0.26 0.03
0.68 0.07
0.92 0.09
1.47 0.12
0.43 0.05
0.02 0.005
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S.; Graneto, M. J.; Lee, L. F.; Malecha, J. W.; Miyashiro, J. M.; Rogers, R. S.; Rogier,
D. J.; Yu, S. S.; Anderson, G. D.; Burton, E. G.; Cogburn, J. N.; Gregory, S. A.;
Koboldt, C. M.; Perkins, W. E.; Seibert, K.; Veenhuizen, A. W.; Zhang, Y. Y.;
Isakson, P. C. J. Med. Chem. 1997, 40, 1347.
ative activity, and could act as a potential anticancer agent deserv-
ing further study.
In conclusion, fourty-two thiazolyl-pyrazoline derivatives that
may function as inhibitors of EGFR kinases were prepared, and
some of them exhibited potent EGFR inhibitory. Compound 11 dis-
played the most potent EGFR inhibitory activity with IC50 of
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0.06 lM, which was comparable to the positive control erlotinib.
Molecular docking study indicated that compound 11 was nicely
bound to the EGFR kinase with three hydrogen bonds. Compounds
11 also exhibited significant antiproliferative activity against MCF-
28. Lv, P.-C.; Zhou, C.-F.; Chen, J.; Liu, P.-G.; Wang, K.-R.; Mao, W.-J.; Li, H.-Q.; Yang,
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7 with IC50 of 0.07 lM, which was comparable to the positive con-
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trol. Therefore, compound 11 would be a potent anticancer agent
with significant EGFR TK inhibitory activity.