Synthesis of novel pyrrole and pyrrolo[2,3-d]pyrimidine derivatives bearing sulfonamide moiety for evaluation as anticancer and radiosensitizing agents

Article abstract of DOI:10.1016/j.bmcl.2010.08.005

Pyrroles and pyrrolo[2,3-d]pyrimidines were reported to act as potent anticancer agents, in this work, a series of novel 2-substituted-3-cyano-4- phenyl-pyrrole 5, 6, 11-18, and 5-phenyl-pyrrolo[2,3-d]pyrimidine derivatives 7-10, 19-24 bearing either sulfathiazole or sulfapyridine were synthesized. The structures of these compounds were confirmed by elemental analysis, IR, ¹H NMR and mass spectral data. All the newly synthesized compounds were evaluated for their in vitro cytotoxicity against liver and breast cancer cell line (HEPG2 and MCF7). Most of the screened compounds showed interesting cytotoxic activities compared with the used reference drug (doxorubicin). The radiosensitizing ability of some of the synthesized compounds was studied and the results showed an increase in the cell killing effect of γ-radiation after combination with the tested compounds.

Full text of DOI:10.1016/j.bmcl.2010.08.005

Bioorganic & Medicinal Chemistry Letters 20 (2010) 6316–6320
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of novel pyrrole and pyrrolo[2,3-d]pyrimidine derivatives bearing
sulfonamide moiety for evaluation as anticancer and radiosensitizing agents
Mostafa M. Ghorab a, Fatma A. Ragab b, Helmy I. Heiba c, Hanan A. Youssef b, Marwa G. El-Gazzar c,
⇑
a Medicinal, Aromatic and Poisonous Plants Research Center (MAPPRC), College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
b Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Cairo University, Cairo, Egypt
c Department of Drug Radiation Research, National Center for Radiation Research and Technology, PO box 29, Nasr City, Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Pyrroles and pyrrolo[2,3-d]pyrimidines were reported to act as potent anticancer agents, in this work, a
series of novel 2-substituted-3-cyano-4-phenyl-pyrrole 5, 6, 11–18, and 5-phenyl-pyrrolo[2,3-d]pyrimi-
dine derivatives 7–10, 19–24 bearing either sulfathiazole or sulfapyridine were synthesized. The struc-
tures of these compounds were confirmed by elemental analysis, IR, 1H NMR and mass spectral data.
All the newly synthesized compounds were evaluated for their in vitro cytotoxicity against liver and
breast cancer cell line (HEPG2 and MCF7). Most of the screened compounds showed interesting cytotoxic
activities compared with the used reference drug (doxorubicin). The radiosensitizing ability of some of
the synthesized compounds was studied and the results showed an increase in the cell killing effect of
Received 12 May 2010
Revised 17 July 2010
Accepted 3 August 2010
Available online 7 August 2010
Keywords:
Pyrrole
Pyrrolo[2,3-d]pyrimidine
Sulfonamide
Anticancer
c
-radiation after combination with the tested compounds.
Ó 2010 Elsevier Ltd. All rights reserved.
Pyrrole and pyrrolo[2,3-d]pyrimidine derivatives have aroused
recent attention as potent anticancer agents.1–3 Several mecha-
nisms are involved in their cytotoxic activities as being dihydrofo-
late reductase inhibitors,4 tyrosine kinase inhibitors,5 cyclin
dependant kinase inhibitors6 or adenosine receptor antagonist.7
A series of N7-substituted and 5-aryl-pyrrolo[2,3-d]pyrimidines
I–IV represent a class of potent antitumor agents acting as tyrosine
kinase inhibitors.1–3,8 On the other hand, a host of structurally no-
vel sulfonamide derivatives have recently been reported to show
substantial anticancer activity in vitro and/or in vivo.9–14 Since
the discovery of E-7010 V,15 sulfonamides have emerged as an
important class of anticancer agents which interact with a wide
range of different cellular targets as disruption of microtubules
assembly and carbonic anhydrase inhibition,16–18 and some of
these compounds having the NH of the sulfonamide group substi-
tuted by an aryl group showed potent anticancer activity such as
VI, KD5170 VII, and PXD101 VIII.19–21
In the light of these facts and as a continuation of previous work
on anticancer agents,22–29 we report the synthesis of a series of
2-substituted-3-cyano-4-phenyl-pyrrole and 5-phenyl-pyrrol-
o[2,3-d]pyrimidine derivatives substituted at N-pyrrole by either
sulfathiazole or sulfapyridine moiety (Fig. 1) to be screened as anti-
cancer agents. Additionally, some of the synthesized compounds
were evaluated as radiosensitizing agents to prove their ability to
The synthesis of 4-(2-amino-3-cyano-4-phenyl-pyrrol-1-yl)-
benzenesulfonamide derivatives 5 and 6 is described in Scheme
1, where, the reaction of sulfathiazole 1, sulfapyridine 2, with
phenacyl bromide furnished 4-(2-oxo-2-phenyl-ethylamino)-ben-
zenesulfonamide derivatives 3, 4, which upon reaction with mal-
ononitrile in sodium ethoxide gave pyrrole derivatives 5, 6.
(Scheme 1).
Pyrrolo[2,3-d]pyrimidine-4-ones 7, 8 and 4-amino- pyrrolo[2,3-
d]pyrimidines 9, 10 were obtained via condensation of the pyrroles
5 and 6 with formic acid or formamide, respectively. The reactivity
of pyrrole o-amino carbonitriles 5 or 6 towards different nucleo-
philes was studied in order to obtain novel pyrrole or pyrrol-
o[2,3-d]pyrimidines. Thus, interaction of 5 or 6 with urea in
refluxing ethanol containing sodium ethoxide afforded the corre-
sponding pyrrole derivatives 11 or 12, respectively. While their fu-
sion with either urea or thiourea for 15 min yielded the
corresponding pyrrolopyrimidine derivatives 21–24, respectively.
On the other hand, reaction of 5 or 6 with succinic anhydride in
ethanol yielded the corresponding pyrrole derivatives 15 or 16,
respectively. While, under condition of fusion, gave the corre-
sponding pyrrolopyrimidine derivatives 17 or 18, respectively. Fi-
nally, acetylation of 5 or 6 with acetic anhydride for 2 h, afforded
the corresponding monoacetyl pyrrole derivatives 13 or 14, respec-
tively, while, upon conducting the same reaction for long time
(10 h), cyclization occurred to give the corresponding pyrrolopyr-
imidine derivatives 19 or 20, respectively (Scheme 2).
enhance the cell killing effect of c-radiation.
The synthesized compounds were evaluated for their in vitro
cytotoxicity against human liver and breast cancer cell lines
⇑
Corresponding author. Tel./fax: +20 222709209.
E-mail address: marwagalalgazzar@yahoo.com (M.G. El-Gazzar).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.08.005

M. M. Ghorab et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6316–6320
6317
O
NH
NH2
N
N
N
H
NH2
N
N
N
N
N
N
N
N
H
N
SO2
O
N
H
N
N
NH2
N
OH
H
I
II
III
IV
R
N
SO2NH
O
N
N
N
N
S
S
S
O2
HN
O
S
O
MeO
O
N
H
N
N
O
OH
Cl
V
VI
VII
O
O2
S
N
H
NHOH
VIII
H2N
H2N
O
Ph
CN
R1
Ph
Ph
Ph
N
N
NH
R2
X
N
H
N
N
N
N
N
N
SO2NHR
SO2NHR
21-24
SO2NHR
SO2NHR
9, 10
5, 6, 11-18
7, 8, 19, 20
O
N
; R1= NH2, NHCONH2, NHCOCH3, NHCOCH2CH2COOH,
; R2= H, CH3
X= O, S
R=
,
;
N
S
N
O
Figure 1. Structure of the target compounds.
Ph
CN
NH2
bicin. From Table 1 we can observe that, for the liver cell line
(HEPG2), considering the pyrrole series 5, 6, 11–18, the pyrrole
derivatives 5 and 6 showed increased activity (IC50 = 5.36 and
Ph
NH2
HN
CN
CN
PhCOCH2Br
O
N
EtOH
5.3
6.75
(IC50 = 5.23
tion 2 of the pyrrole ring showed increase in activity especially
for compounds 14 (IC50 = 3.49 M), 15 (IC50 = 3.75 M), and 16
(IC50 = 3.75 M) which are the most potent compounds in this ser-
l
l
M) when compared to compounds 3 and 4 (IC50 = 6.78 and
M) and they were found to be nearly as active as doxorubicin
M). While, substitution on the amino group at posi-
NaOEt
SO2NHR
1, 2
SO2NHR
3, 4
l
SO2NHR
5, 6
l
l
N
S
,
l
R=
N
ies. Concerning the pyrrolo[2,3-d]pyrimidine derivatives 7–10,
19–24, the most potent of this series were compounds 19
Scheme 1.
(IC50 = 3.39
the breast cell line (MCF7), The O-amino carbonitriles 5 and 6 were
the most potent in the pyrrole series (IC50 = 3.49 and 4.6 M) and
they were found to be more potent than doxorubicin
lM), 20 (IC50 = 3.15 lM), and 21 (IC50 = 3.49 lM). For
(HEPG2 and MCF7) and some of the tested compounds were equi-
potent while the others were more potent compared with doxoru-
l

6318
M. M. Ghorab et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6316–6320
O
Ph
NH
H2N
Ph
CN
O
Ph
N
N
N
NH2
N
N
N
N
H
N
7, R=
8, R=
S
N
N
11, R=
12, R=
9, R=
S
S
SO2NHR
N
SO2NHR
10, R=
N
N
SO2NHR
2
HCONH2
2
H2N
Ph
CN
O
Ph
N
X
Ph
CN
NH2
X
CH3
N
N
H
N
H2N NH2
N
N
AC2O
2 Hrs
, X=O
, X=O
, X=S
, X=S
H
21, R=
N
S
N
Fusion
13, R=
14, R=
S
22, R=
23, R=
24, R=
N
SO2NHR
N
SO2NHR
N
SO2NHR
5, 6
S
N
O
O
O
O
Fusion O
O
O
Ph
NH
Ph
CN
O
CH3
OH
Ph
CN
N
O
N
N
H
O
N
N
N
N
19, R=
20, R=
S
O
SO2NHR
N
SO2NHR
N
SO2NHR
N
15, R=
S
17, R=
18, R=
Scheme 2.
S
16, R=
N
N
(IC50 = 3.22
l
M), while, substitutions on the amino group resulted
and chemotherapy is required. The other idea is the enhancement of
radiation effects. Cytotoxic agents can enhance radiation effects by
direct enhancement of the initial radiation damage by incorporating
drugs into DNA, inhibiting cellular repair, accumulating cells in a
radiosensitive phase or eliminating radioresistant phase cells, elim-
inating hypoxic cells or inhibiting the accelerated repopulation of
tumor cells. Virtually, all chemotherapeutic agents have the ability
to sensitize cancer cells to the lethal effects of ionizing radiation.30
Consequently, the ability of some of the most potent compounds re-
sulted from in vitro cytotoxic activity 14, 15, 16, and 21, to enhance
in a drop in their anticancer activity which may give an idea about
the possible importance of the free amino group on activity. Final-
ly, for the pyrrolopyrimidine derivatives, the most potent com-
pounds were 22 (IC50 = 3.9
lM), 23 (IC50 = 3.12 lM), and 24
(IC50 = 3.8 M). Considering the activity on both cell lines when
l
using either sulfathiazole or sulfapyridine, the activity doesn’t
change significantly which indicate that these sulfonamides may
be equipotent on both cell lines. These preliminary results of bio-
logical screening of the tested compounds could offer an encourag-
ing framework in this field that may lead to the discovery of potent
anticancer agent.
The rationale for combining chemotherapy and radiotherapy is
based mainly on two ideas, one being spatial cooperation, which is
effective if chemotherapy is sufficiently active to eradicate subclin-
ical metastases and if the primary local tumor is effectively treated
by radiotherapy. In this regard, no interaction between radiotherapy
the cell killing effect of c-irradiation was studied. From Tables 2 and
3 and Figure 2, we can observe that the effect of radiation alone was
not significant when compared to control group which contains the
cell lines without radiation or drug. On the other hand, the surviving
fraction of the tested compounds decreased significantly from the
control after being subjected to radiation which indicate the syner-
gism due to combining drugs with radiation.

M. M. Ghorab et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6316–6320
6319
Table 1
100
Anticancer screening of the newly synthesized compounds
against human liver cell line (HEPG2) and human breast cell
line (MCF7)
before radiation
after radiation
80
60
40
20
0
Compound
Cytotoxicitya,b (IC50) (
lM)
HEPG2
MCF7
3
4
5
6
6.78
6.75
5.36
5.3
8.89
7.56
3.49
4.6
control
5 uM
12.5 uM 25 uM
40 uM
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
5.3
6.21
5.32
6.45
6.34
8.05
7.34
7.24
11.82
9.12
8.32
6.71
9.93
5.8
4.67
4.24
4.09
4.02
4.12
4.02
3.49
3.75
3.75
4.56
5.36
3.39
3.15
3.49
4.3
Compound concentrations
Figure 2. The effect of radiation on anticancer activity of different concentrations of
compound 16 on HEPG2 cell line.
From the above results, we can conclude that administration of
the tested compounds on human liver and breast (HEPG2 and
MCF7) cell lines showed promising cytotoxic activity especially
on liver cell line, while, combining these compounds with radiation
at the same concentrations enhances their activity which demon-
strates the importance of the combination therapy for the patients
with cancer to decrease the side effects of both drugs and radiation.
5.1
8.32
3.9
3.12
3.8
23
24
4.12
4.1
Supplementary data
Doxorubicin
5.23
3.22
a
IC50, compound concentration required to inhibit
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.08.005.
tumor cell proliferation by 50%.
b
Values are means of three experiments.
Table 2
Statistical analysis of the results of in vitro anticancer activity of compounds 5, 14, 15, 16, 21 against human liver or breast cell line (HEPG2 and MCF7)
Cell line
Compd no.
Control (cells only)
Drug (
l
M)
25
Means SE (% change)#
5
12.5
40
HEPG2
14
15
16
21
5
1.526 0.05680
(100%)
1.526 0.05680
(100%)
1.5139 0.03894
(100%)
1.526 0.05680
(100%)
1.063 0.1006*
(30.34%)
0.71 0.03384*
(53.47%)
0.5683 0.009735*
(62.7%)
0.4587 0.02338*
(69.9%)
1.144 0.0788**
(25.03%)
0.9217 0.08055*
(39.6%)
0.9773 0.1336*
(35.95%)
0.7693 0.09242*
(49.58%)
0.967 0.06185*
(15.12%)
0.6007 0.01299*
(60.3%)
0.4227 0.05646*
(72%)
0.3333 0.01299*
(78%)
1.185 0.0543**
(22.34%)
0.7987 0.04421*
(47.66%)
0.5503 0.01810*
(63.9%)
0.555 0.08602*
(63.6%)
MCF7
1.3613 0.05082
(100%)
1.207 0.02674**
(11.3%)
0.7823 0.01598*
(42.5%)
0.391 0.03029*
(71.3%)
0.379 0.01801*
(72%)
Each value is the mean of three values SE.
#
Percentage of change from control group.
Significant difference from control group at p <0.05.
Non-significant difference from control group at p <0.05.
*
**
Table 3
Statistical analysis of the results of in vitro anticancer activity of compounds 5, 14, 15, 16, 21 against human liver or breast cell line (HEPG2 and MCF7) after irradiation
Cell line
Compd no.
Control (cells only)
Control (radiation)
Drug Irradiated (
25
lM)
5
12.5
40
Means SE (% change)#
HEPG2
14
15
16
21
5
1.526 0.05680 (100%)
1.2022 0.03297**
(21.2%)
0.6497 0.04890*
(57.42%)
0.466 0.01537*
(69.46%)
0.2667 0.03464*
(82.5%)
0.2763 0.03552*
(81.9%)
1.526 0.05680
(100%)
1.5139 0.03894
(100%)
1.526 0.05680
(100%)
1.3613 0.05082
(100%)
1.2022 0.03297**
(21.2%)
0.6 0.09200*
(60.6%)
0.4167 0.03034*
(72.6%)
0.4287 0.04051*
(71.8%)
0.3133 0.02671*
(79.4%)
1.2303 0.04683**
(18.73%)
0.281 0.09250*
(81.4%)
0.2363 0.07980*
(84.4%)
0.162 0.004583*
(89.2%)
0.1847 0.02278*
(87.7%)
1.2022 0.03297**
(21.2%)
0.584 0.02835*
(61.73%)
0.47 0.02793*
(69.2%)
0.3307 0.03992*
(78.3%)
0.278 0.02553*
(81.7%)
MCF7
1.261 0.03745**
(7.3%)
0.796 0.03629*
(41.5%)
0.4727 0.08178*
(65.3%)
0.241 0.03759*
(82.3%)
0.1937 0.03320*
(85.8%)
Each value is the mean of three values SE.
#
Percentage of change from control group.
Significant difference from control group at p <0.05.
Non-significant difference from control group at p <0.05.
*
**

6320
M. M. Ghorab et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6316–6320
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