Design, synthesis and biological evaluation of 2-mercapto-3- phenethylquinazoline bearing anilide fragments as potential antitumor agents: Molecular docking study

Article abstract of DOI:10.1016/j.bmcl.2013.04.056

A novel series of 2-(3-phenethyl-4(3H)quinazolin-2-ylthio)-N-substituted anilide and substituted phenyl 2-(3-phenethyl-4(3H) quinazolin-2-ylthio)acetate were designed, synthesized and evaluated for their in-vitro antitumor activity. Compound 15 possessed remarkable broad-spectrum antitumor activity which almost sevenfold more active than the known drug 5-FU with GI₅₀ values of 3.16 and 22.60 μM, respectively. Compound 15 exhibited remarkable growth inhibitory activity pattern against renal cancer (GI₅₀ = 1.77 μM), colon cancer (GI₅₀ = 2.02 μM), non-small cell lung cancer (GI₅₀ = 2.04 μM), breast cancer (GI₅₀ = 2.77 μM), ovarian cancer (GI₅₀ = 2.55 μM) and melanoma cancer (GI ₅₀ = 3.30 μM). Docking study was performed for compound 15 into ATP binding site of EGFR-TK which showed similar binding mode to erlotinib.

Full text of DOI:10.1016/j.bmcl.2013.04.056

Bioorganic & Medicinal Chemistry Letters 23 (2013) 3935–3941
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design, synthesis and biological evaluation of 2-mercapto-3-phen-
ethylquinazoline bearing anilide fragments as potential antitumor
agents: Molecular docking study
Ibrahim A. Al-Suwaidan a, Amer M. Alanazi a, Alaa A.-M. Abdel-Aziz a,b, Menshawy A. Mohamed c,d
,
Adel S. El-Azab a,c,
⇑
a Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
b Department of Medicinal Chemistry, Faculty of Pharmacy, University of Mansoura, Mansoura 35516, Egypt
c Department of Organic Chemistry, Faculty of Pharmacy, Al-Azhar University, Cairo 11884, Egypt
d Department of Pharmaceutical Chemistry, College of Pharmacy, Salman Bin Abdulaziz University, AlKharj 11451, Saudi Arabia
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of 2-(3-phenethyl-4(3H)quinazolin-2-ylthio)-N-substituted anilide and substituted phenyl
2-(3-phenethyl-4(3H) quinazolin-2-ylthio)acetate were designed, synthesized and evaluated for their in-
vitro antitumor activity. Compound 15 possessed remarkable broad-spectrum antitumor activity which
Received 9 February 2013
Revised 17 April 2013
Accepted 22 April 2013
Available online 29 April 2013
almost sevenfold more active than the known drug 5-FU with GI50 values of 3.16 and 22.60
lM, respec-
tively. Compound 15 exhibited remarkable growth inhibitory activity pattern against renal cancer
(GI50 = 1.77
(GI50 = 2.77
l
M), colon cancer (GI50 = 2.02
l
M), non-small cell lung cancer (GI50 = 2.04
l
M), breast cancer
Keywords:
Synthesis
Quinazoline
In-vitro antitumor evaluation
NCI
lM), ovarian cancer (GI50 = 2.55
l
M) and melanoma cancer (GI50 = 3.30
lM). Docking study
was performed for compound 15 into ATP binding site of EGFR-TK which showed similar binding mode
to erlotinib.
Ó 2013 Elsevier Ltd. All rights reserved.
Molecular docking
Cancer is continuing to be a major health problem in developed
as well as undeveloped countries.1–5 The great cancer incidence
worldwide increases the search for new, safer and efficient antican-
cer agents, aiming the prevention or the cure of this illness.
Although many classes of drugs are being used for the treatment
of cancer, the need for more potent selective antitumor agents is still
not precluded. Quinazolines are frequently used in medicine be-
cause of their wide spectrum of biological activities.6–23 It is well
known that quinazoline derivatives are potent inhibitors of epider-
mal growth factor receptor (EGFR).24–36 The epidermal growth fac-
tor receptor (EGFR) is cellular trans-membrane tyrosine kinases
that are over-expressed in a significant number of human tumors
(e.g., breast, ovarian, colon, renal, and prostate).37–40 Overexpres-
sion of EGFR family receptors have always been observed in these
tumors, approximately in 60% of all tumors. A number of small mol-
ecule EGFR kinase inhibitors have been evaluated in cancer clinical
trials.24–40 For example, anilinoquinazoline-containing compounds
erlotinib (A) (TarcevaTM),31 gefitinib (B) (IressaTM),28–40 lapatinib
(C) (TykerbTM, also known as GW-572016) and Vandetanib (Zacti-
maTM) were recently approved for the treatment of breast cancer
and non-small-cell lung cancer.32–36 Moreover a series of salicylan-
ilides (D) were synthesized and determined their inhibitory activity
against tyrosine kinases (Fig. 1), some of them indeed proved to be
potent and selective EGFR tyrosine kinase inhibitors (Fig. 1).41 We
have recently studied a series of 4-substituted quinazoline deriva-
tives which were evaluated for their antitumor activities (E)
(Fig. 1).20,21 Owing to our continues studies on quinazoline deriva-
tives as an attractive candidates as antitumor agents, we have de-
signed
a number of new quinazoline derivatives containing
anilide fragments41 (F) and biologically evaluated there in-vitro
antitumor activities (Fig. 1). In the present study, the substitution
pattern at the 2-substituted quinazoline pharmacophores was se-
lected based on different electronic environment which would af-
fect the lipophilicity, and hence the activity of the target
molecules. The objective of forming these hybrids is an attempt to
attain an active antitumor agent with potentiated activity and selec-
tivity toward cancerous cells. Molecular docking methodology was
used to identify the structural features required for the antitumor
properties of these new series. These models are necessary to obtain
a consistent and more precise picture of the biological active mole-
cules at the atomic level and furthermore, provide new insights that
can be used to design novel therapeutic agents.21,42–49 Moreover,
the results of this molecular docking could support the postulation
⇑
Corresponding author. Tel.: +966 1 467 9096; fax: +966 1 467 6383.
E-mail address: adelazaba@yahoo.com (A.S. El-Azab).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.04.056

3936
I. A. Al-Suwaidan et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3935–3941
Large fragment
Fragment replacement
O
O
HN
N
N
Small Lipophilic fragment insersion
N
O
O
S
Erlotinib; A
Cl
N
N
Fragment replacement
Large fragment
F
O
N
CH3
New scaf fold f or small
molecular antitumor
HN
N
Cl
Lipophilic Aromatic insersion
O
O
μg/ml
E; IC50 = 3.35
(MCF-7)
N
Gefitinib;B
Lead optimization
O
Large fragment
Fragment insertion
F
Fragment replacement
HN
N
Cl
O O
S
N
H
O
O
N
N
X
N
O
S
Lapatinib;C
n
Cl
R1
R2
Large fragment insertion
HN
N
H2
R3
O
F;designed quinazolines
OH
Salicylanilide;D
Figure 1. Reported and proposed quinazoline derivatives as antitumor.
that our active compounds may act on the same enzyme target
where EGFR inhibitor acts confirming the molecular design of the
reported class of antitumor agents.
toward numerous cell lines belong to different tumor subpanels.
Consequently, compound 15 was carried over and tested against
a panel of 60 different tumor cell lines at a 5-log dose range.50–52
Three response parameters, GI50, TGI, and LC50 were calculated
for each cell line, using the known drug 5-Fluorouracil (5-FU) as
a positive control. Compound 15 exhibited remarkable growth
Synthesis of 2-mercapto-3-phenethylquinazolin-4(3H)-one (1)
as a key intermediate was achieved by the reaction of anthranilic
acid with 2-phenylethyl isothiocyanate in absolute ethanol
in 78% yield. The reaction of compound 1 with various 2-chloro-
N-substituted phenylacetamide and/or substituted phenyl-2-chlo-
roacetate in anhydrous acetone in the presence of potassium
carbonate gave 2-(quinazolin-2-ylthio)-N-substituted anilide and/
or 2-(quinazolin-2-ylthio) substituted acetate derivatives 2–22 in
84–95% yield (Scheme 1).
inhibitory activity pattern against renal cancer (GI50 = 1.77
colon cancer (GI50 = 2.02 M), non-small cell lung cancer
M), breast cancer (GI50 = 2.77 M), ovarian cancer
M) and melanoma cancer (GI50 = 3.30 M). Com-
lM),
l
(GI50 = 2.04
(GI50 = 2.55
l
l
l
l
pound 15 is almost sevenfold more active than the known drug
5-FU with GI50 values of 3.16 and 22.60 M, respectively (Table 2).
l
The synthesized compounds 1–22 were subjected to the Na-
tional Cancer Institute (NCI) in-vitro disease-oriented human cells
screening panel assay for in-vitro antitumor activity. A single dose
Regarding the activity toward individual cell lines; Non-small
cell lung; compounds 8, 15 and 16 proved to be susceptible to
the HOP-62 cancer cell line with GI values of 52%, 91% and 49%
respectively. NCI-H522 cell line proved to be selectively sensitive
to compounds 10, 15, 16 and 19 with GI values of 51, lethal, 85%
and 52%, respectively. In addition, compound 15 showed strong
activity against A549/ATCC, NCI-H226, NCI-H23, NCI-H322M and
NCI-H460 cancer cell lines in 76%, lethal, 74%, 73% and lethal
respectively. Respecting colon cancer; compound 15 verified
strong selectively sensitive to colon HCT-116, HCC-2998, COLO
205, HT29, KM12 and SW-620 cancer cell lines in lethal, 71%,
66%, 85%, 93% and 52%, respectively. Concerning CNS cancer; Com-
pounds 5, 8, 15 and 16 showed GI values of 63%, 72%, lethal and
74% to SNB-75 cancer cell line respectively, while compounds 15
and 19 illustrated potent activity against SF-539 cancer cell line
(10 lM) of the test compounds were used in the full NCI 60 cell
lines panel assay which includes nine tumor subpanels namely;
Leukemia, Non-small cell lung, Colon, CNS, Melanoma, Ovarian, Re-
nal, Prostate, and Breast cancer cells.50–52 The data reported as
mean-graph of the percent growth of the treated cells, and pre-
sented as percentage growth inhibition (GI %) caused by the test
compounds (Table 1).
Concerning broad spectrum antitumor activity; the results of
this study demonstrated that compounds 15, 16 and 19 are the
most remarkable broad spectrum antitumor agents. Close exami-
nation of the data presented in Table 1, revealed that compound
15 are the most active member of this study showing effectiveness

I. A. Al-Suwaidan et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3935–3941
3937
R
O
R
HN
O
R
O
O
O
N
SH
O
N
O
S
Cl
N
O
S
N
Cl
HN R
N
acetone,
K CO r.t.
N
O
acetone,
K CO r.t.
2
3,
2
3,
(1)
20: R=H
21: R=4-Cl
22: R=3,4,5-trimethoxy
O
O
O
R
no.
2
H
Cl
HN
O
3
4
5
6
7
8
9
Ph
4-Br-Ph
4-Cl-Ph
4-F-Ph
4-CH -Ph
4-OCH -Ph
acetone,
K CO r.t.
2
3,
3
O
3
p-ethoxy-Ph
O
O
S
O
10 4-acetyl-Ph
11
12
1-naphthyl
Bn
NH
13 4-ethylbenzoate
14 2-trifluromethyl-Ph
15 3,4,5-trimethoxy-Ph
16
17
2-benzoic acid
N
5-bromo-2-benzoic acid
18 5-chloro-2-benzoic acid
N
O
(19)
Scheme 1. Reactions of 2-mercapto-3-phenethylquinazolin-4(3H)-one (1) with various 2-chloro-N-phenylanilide and/or phenyl 2-chloroacetate.
in lethal and 70%, respectively. On the other hand, compound 15
showed lethal activities against CNS U251, SF-295 and SNB-19 can-
cer cell lines and strong activity against SF-268 with GI value of
87%. Regarding Melanoma; compounds 15 and 19 showed selec-
tive activities against LOX IMVI, MALME-3M, UACC-257 cancer cell
lines with GI values of 70%, 59%, 61%, 54%, 77% and 72% respec-
tively. Compound 15 showed moderate sensitivity towards M14,
SK-MEL-28 cancer cell lines with GI values of 68% and 63%, whilst
compound 15 proved to be lethal to MDA-MB-435 and SK-MEL-5
cancer cell lines. Respecting ovarian cancer; compounds 15 and
16 showed moderate activities against Ovarian OVCAR-8 cell line
with GI values of 70% and 61%. Ovarian SK-OV-3 cell line was
responsive to compound 16 with GI value of 53% while compound
15 active against IGROV1 cancer cell line with GI value of 92%.
Ovarian OVCAR-4 cell line receptive to compounds 19, 20 and 21
with GI values of 51%, 59% and 59% respectively, additionally com-
pound 15 demonstrated lethal activities to OVCAR-3 and SK-OV-3
cancer cell lines. Relating to renal cancer; renal CAKI-1 cancer cell
line was sensitively selective to compound 19 with GI value of 74%.
Additionally, compound 15 showed certain activity against renal
RXF 393 and SN12C cancer cell lines with GI values of 55% and
75%, as well lethal to renal 786-0, A498, ACHN, TK-10 and UO-
31cancer cell lines. Prostate PC-3 and DU-145 cancer cell lines
proved to be selectively sensitive to compound 15 with GI value
of 59% and 55%, respectively. Pertaining to breast cancer; breast
HS 578T cancer cell line convinced responsive to compounds 15
and 19 with GI values of 64% and 67% respectively. Compounds 5
and 19 showed GI effectiveness against breast T-47D and MDA-
MB-231/ATCC cancer cell lines with values of 56% and 67%, respec-
tively. Concurrently, compound 15 showed remarkable potency
against breast MDA-MB-468 cancer cell line with GI value of
71%, at the same time as showed lethal activities against breast
BT-549, T-47D and MDA-MB-231/ATCC cancer cell lines (Table 1).
The antitumor activity correlation of the newly synthesized
compounds revealed that compounds 2, 3, and 18 devoid any potent
antitumor activities. Replacement of the hydrogen atom
of amino function of 2-(4-oxo-3-phenethyl-3,4-dihydroquinazo-
lin-2-ylthio)acetamide (2) or phenyl ring of 2-(4-oxo-3-phen-
ethyl-3,4-dihydroquinazolin-2-ylthio)-N-phenylacetamide
(3)
with variety of substituted phenyl produced (N-substituted
phenyl)acetamide analogs with variable potency. The presence of
electron withdrawing or electron donating groups at aromatic ring
of compound 3 afforded N-(4-substituted phenyl)-2-(4-oxo-3-
phenethyl-3,4-dihydroquinazolin-2-ylthio)acetamides (5–10) with
improvement of the antitumor activity as shown in compound 3
matched up to compounds 5–10. Introduction of electron donating
group such as 3,4,5-trimethoxy moiety at aromatic ring of com-
pound 3 produced N-(3,4,5-trimethoxyphenyl)acetamide 15 and
N-(3,4,5-trimethoxyphenyl)propanamide 19 with enhancement of
the antitumor activities compared to compounds containing unsub-
stituted phenyl or electron withdrawing group (3–6). The length
of the carbon chain linking of the N-substituted anilide proved cru-
cial and manipulated the antitumor activity; accordingly one
carbon length favored the antitumor activities such as 2-(4-oxo-3-
phenethyl-3,4-dihydroquinazolin-2-ylthio)-N-(3,4, 5-trimethoxy-
phenyl)acetamide (15) rather than two carbon lengths like

3938
I. A. Al-Suwaidan et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3935–3941
Table 1
Percentage growth inhibition (GI %) of in vitro subpanel tumor cell lines at 10
lM concentration.
Subpanel tumor cell lines
% Growth inhibition (GI %)a
2
3
5
6
7
8
9
10
12
13
15
16
18
19
20
21
22
Leukemia
HL-60(TB)
MOLT-4
nt
nt
17
–
nt
nt
25
26
–
–
nt
nt
nt
10
nt
nt
nt
nt
nt
nt
nt
nt
nt
nt
nt
nt
27
40
11
23
nt
nt
nt
nt
Non-small cell lung cancer
A549/ATCC
EKVX
HOP-62
NCI-H226
NCI-H23
NCI-H322M
NCI-H460
12
10
–
16
16
–
–
11
–
16
29
40
24
21
13
32
45
23
24
–
21
29
42
–
25
25
52
–
13
19
36
31
–
23
11
11
29
29
22
16
12
27
31
51
17
25
36
13
10
26
29
28
27
34
45
25
13
23
23
26
76
35
91
L
74
73
L
46
25
49
26
26
19
41
85
–
20
–
–
–
–
–
–
29
34
45
10
28
28
17
52
12
nt
nt
–
10
36
–
16
–
11
26
–
28
10
13
25
–
–
nt
–
–
–
12
17
–
–
–
14
25
14
37
15
22
22
19
25
–
–
10
–
37
NCI-H522
31
L
Colon cancer
COLO 205
HCC-2998
HCT-116
HCT-15
HT29
KM12
SW-620
–
––
–
–
–
–
–
15
–
–
15
–
23
16
–
–
–
19
10
10
–
15
–
13
10
–
–
–
13
–
–
–
–
16
–
10
–
12
–
–
–
27
20
–
22
–
14
–
12
11
11
71
66
L
11
85
93
52
35
–
–
–
–
–
–
–
–
20
–
–
–
21
–
–
–
–
–
25
–
–
–
20
48
–
37
21
12
18
14
45
12
11
10
21
40
18
18
39
14
–
–
–
–
14
11
11
10
16
11
–
–
–
–
–
–
–
–
–
–
CNS cancer
SF-268
SF-295
SF-539
SNB-19
SNB-75
U251
–
–
–
–
12
–
40
32
41
30
63
25
–
13
–
–
–
19
12
19
22
12
11
47
21
10
41
72
29
25
–
–
–
21
27
32
21
–
20
41
10
28
27
38
17
38
24
33
25
–
36
39
28
87
49
L
73
L
33
18
44
40
74
nt
–
–
–
–
20
–
26
10
70
12
38
25
16
20
–
–
28
nt
–
–
–
–
28
–
–
13
–
–
12
26
–
–
–
–
–
17
L
Melanoma
LOX IMVI
MALME-3M
M14
MDA-MB-435
SK-MEL-28
SK-MEL-5
UACC-257
UACC-62
11
–
10
–
–
13
–
23
–
–
13
10
22
18
34
18
11
18
–
–
16
–
14
17
–
17
22
22
17
20
–
11
37
10
14
–
–
–
–
25
13
21
23
23
25
36
28
17
14
14
19
12
22
–
22
23
21
16
14
21
29
29
70
59
68
L
63
L
38
18
12
35
17
35
35
21
–
–
–
–
–
–
–
–
54
77
40
38
42
31
72
30
16
16
13
19
–
–
11
19
14
–
–
–
–
–
–
11
–
–
–
–
–
–
–
23
–
–
–
–
–
–
–
40
25
10
11
10
14
13
61
25
16
25
29
Ovarian cancer
IGROV1
–
–
–
–
–
–
14
36
32
14
–
39
21
43
16
–
–
–
–
20
–
–
–
27
–
18
10
–
21
–
–
–
29
–
20
23
25
10
42
33
17
39
10
13
–
40
19
14
31
13
10
15
37
19
19
92
L
42
29
23
–
61
34
53
–
–
–
–
–
–
–
21
11
51
–
28
13
44
10
–
59
–
23
22
28
15
–
59
–
–
10
28
11
–
–
–
–
OVCAR-3
OVCAR-4
OVCAR-5
OVCAR-8
NCI/ADR-RES
SK-OV-3
–
–
–
–
–
–
47
35
70
64
L
–
40
15
25
–
25
11
–
20
–
Renal cancer
786-0
A498
–
11
–
–
–
–
–
–
13
–
–
–
–
21
13
10
–
–
–
–
13
21
–
10
–
–
–
12
12
13
–
–
–
15
–
–
–
21
19
14
–
L
L
L
nt
55
75
L
16
26
34
–
25
–
–
10
–
17
–
–
29
37
21
74
12
16
17
22
13
18
10
–
–
16
–
–
10
–
27
–
–
–
–
–
10
16
22
13
19
–
ACHN
34
12
–
–
–
22
42
22
13
19
28
30
16
–
13
–
38
32
16
20
20
33
10
28
–
10
–
CAKI-1
RXF 393
SN12C
TK-10
–
–
–
26
–
10
19
–
–
18
–
–
UO-31
–
31
10
L
16
37
Prostate cancer
PC-3
DU-145
–
–
10
–
30
12
16
–
14
–
–
–
–
–
20
11
29
13
10
10
59
55
–
30
–
–
25
–
14
25
–
–
–
Breast cancer
MCF7
MDA-MB-231/ATCC
HS 578T
BT-549
T-47D
19
35
–
–
13
18
30
37
45
nt
56
36
18
22
16
10
25
23
23
23
41
–
44
29
11
39
49
10
–
12
25
–
–
15
10
16
39
33
–
19
14
21
37
37
–
20
–
12
48
33
12
17
18
49
L
64
L
L
71
21
45
45
10
27
14
–
–
–
10
–
33
66
67
13
47
27
15
15
–
–
14
–
34
33
41
15
14
–
34
20
–
10
26
–
–
–
–
–
–
MDA-MB-468
13
–
Nt, not tested; –, GI <10%; L, GI >100%.
3-(4-oxo-3-phenethyl-3,4-dihydroquinazolin-2-ylthio) N-(3,4,5-
trimethoxyphenyl)propanamide (19). Replacement of acetamide
function of N-(4-chlorophenyl)-2-(4-oxo-3-phenethyl-3,4-dihy-
droquinazolin-2-ylthio)acetamide (5) and 2-(4-oxo-3-phen
ethyl-3,4-dihydroquinazolin-2-ylthio)-N-(3,4,5-trimethoxyphenyl)
acetamide (15) by acetate function produced 4-chlorophenyl-2-(4-
oxo-3-phenethyl-3,4-dihydroquinazolin-2-ylthio)acetate (21) and
3,4,5-trimethoxyphenyl-2-(4-oxo-3-phenethyl-3,4-dihydroquinazo-

I. A. Al-Suwaidan et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3935–3941
3939
Table 2
Compound 15 median growth inhibitory (GI50
,
l
M), total growth inhibitory (TGI,
l
M) and median lethal (LC50
,
l
M) concentration of in-vitro subpanel tumor cell lines.
MG-MIDb
Compound
Supbanel tumor cell linesa
Activity
I
II
III
IV
V
VI
2.55
52.03
84.50
61.4
c
VII
VIII
IX
15
GI50
TGI
LC50
GI50
TGI
c
c
c
2.04
43.09
c
c
c
c
2.02
c
c
8.4
c
2.73
13.45
75.03
72.1
c
|3.30
76.60
94.47
70.6
c
1.77
3.63
54.18
45.6
c
4.98
c
c
22.7
c
c
2.77
44.06
81.86
76.4
c
3.16
25.0
77.6
22.60
c
5-FU
15.1
c
c
LC50
c
c
c
c
c
c
c
a
b
c
I, leukemia; II, non-small cell lung cancer; III, colon cancer; IV, CNS cancer; V, melanoma; VI, ovarian cancer; VII, renal cancer; VIII, prostate cancer; IX, breast cancer.
Full panel mean-graph midpoint ( M).
Compound showed values >100 M.
l
l
Figure 2. Docking of the erlotinib inhibitor and compound 15 into the active site of epidermal growth factor receptor.
lin-2-ylthio)acetate (22) with a dramatically reduction of the antitu-
mor activities. Substitution of ethoxy group of N-(4-ethoxyphenyl)-
2-(4-oxo-3-phenethyl-3,4-dihydroquinazolin-2-ylthio) acetamide
(9) by methoxy group gave N-(4-methoxyphenyl)-2-(4-oxo-3-phen-
ethyl-3,4-dihydroquinazolin-2-ylthio)acetamide (8) with develop-
ment of the antitumor activities. Displacement of chlorine atom of
5-chloro-2-(2-(4-oxo-3-phenethyl-3,4-dihydroquinazolin-2-ylthio)
acetamido)benzoic acid (18) produced 2-(2-(4-oxo-3-phenethyl-3,4-
dihydroquinazolin-2-ylthio)acetamido)benzoic acid (16) with
improvement of the antitumor activities. The carbon bridge linking
potentiate the antitumor activity of N-benzyl-2-(4-oxo-3-phen-
ethyl-3,4-dihydroquinazolin-2-ylthio)acetamide (12) compared to
2-(4-oxo-3-phenethyl-3,4-dihydroquinazolin-2-ylthio)-N-phenyl-
acetamide (3).

3940
I. A. Al-Suwaidan et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3935–3941
Figure 3. Docking of the PLX4032 inhibitor and compound 15 into the V600E-B-RAF kinase domain.
Molecular docking studies; The level of antitumor activities of
MMFF94 force field60 till the gradient convergence 0.01 kcal/mol
was reached. The binding energies of compound 15 and erlotinib
docked into the active site of EGFR were À27.21 and À24.00 kcal/
mol, respectively (Fig. 2). These docking studies have revealed that
the quinazoline ring binds to a narrow hydrophobic pocket in the
N-terminal domain of EGFR-TK where N-1 of the quinazoline ring
interacts with the backbone NH of Met-769 via a hydrogen bond.
Similarly, a water (HOH-10) molecule-mediated hydrogen bonding
interaction is observed among the N-3 and S-atom of the quinazo-
line ring, Thr-830 and Thr-766 side chain. These interactions re-
vealed the importance of quinazoline ring for binding and the
subsequent inhibitory capacity. Compound 15 complexed with
EGFR-TK in a fashion similar to erlotinib and showed the occur-
rence of three hydrogen bonds with Met-769 (2.99 Å) and HOH-
10 (2.90 Å, 2.44 Å) mediated hydrogen bonding interaction with
Thr-830 side chain (2.75 Å) and Thr-766 side chain (3.10 Å). More-
over the anilide trimethoxyphenyl fragment showed two addi-
tional hydrogen bonds with Gly-695 (2.90 Å, 2.77 Å). On the
other hand, the binding energies of compound 15 and PLX4032
docked into the active site of V600E-BRAF kinase were À39.89
and À36.11 kcal/mol, respectively (Fig. 3). The docking study has
revealed that the ligand 15 has bound in the active site of one of
the compound 15 over breast cancer, colon, renal, small lung and
melanoma cancer cells, in which epidermal growth factor receptor
(EGFR) and GG V600E-B-RAF kinase is highly expressed,37–40,53
prompted us to perform molecular docking into the ATP binding
site of EGFR and V600E-B-RAF kinase to predict if this compound
15 has analogous binding mode to the EGFR and V600E-B-RAF ki-
nase inhibitors. We assumed that the active target compound 15
might demonstrates antiproliferative activities against breast can-
cer, colon, renal, small lung and melanoma cell lines through inhi-
bition of EGFR and V600E-B-RAF respectively. Compound 15 was
docked into receptor active site of both EGFR and V600E-B-RAF ki-
nase along with their inhibitors. All the calculations were per-
formed using MOE 2008.10 software54 installed on 2.0G Core 2
Duo. The crystal structure of epidermal growth factor receptor
with erlotinib (Tarceva™) (PDB code: 1M17)37–40,55–57 and the
crystal structure of V600E-BRAF kinase in complex with PLX4032
(PDB code: 3OG7)53,58,59 were obtained from protein data bank
(PDB). The automated docking program of MOE 2008.10 was used
to dock compound 15 along with the inhibitors erlotinib and
PLX4032 into ATP binding site of EGFR and domain of V600E-BRAF
kinase, respectively. The complexes were energy-minimized with a

I. A. Al-Suwaidan et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3935–3941
3941
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the protomers in the protein dimer through the formation of seven
hydrogen bonds with Gln-530 (2.17 Å), Cys-532 (2.01, 3.17 Å), Lys-
483 (2.55 Å), Phe-595 (3.21 Å) and Gly-596 (3.17 Å, 2.87 Å). More-
over there are one arene
tween the binding site and the ligand. The arene
p
–
p
and two CH-arene interactions be-
interaction
p–p
occurred between quinazoline fragment and Trp-531 while CH–
arene interaction occurred between the phenethyl fragment and
Ile-463 and Val-471.
In conclusion, an interesting class of novel 2-mercapto-3-phen-
ethyl-4(3H)-quinazolinone analogs were designed, synthesized
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(10 lM) of the test compounds were used in the National Cancer
Institute (NCI) 60 cell lines panel assay. The results of this study
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remarkable broad spectrum antitumor agents. Additionally; the re-
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the most broad-spectrum antitumor activities; consequently com-
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helped in understanding the various interactions between the li-
gands and enzyme active sites; thereby help to design novel potent
inhibitors. Further optimizations of antitumor and pharmacoki-
netic profiling of these series are currently ongoing.
Acknowledgments
´
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The authors extend their appreciation to the Deanship of Scien-
tific Research at King Saud University for funding the work through
the research group project No. RGP-VPP-163. The authors would
like to express their gratitude and thanks to the National Cancer
Institute (NCI), Bethesda Maryland, USA, http://dtp.cancer.gov/
for doing the antitumor testing of the new compounds.
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