Anticancer and radiosensitizing evaluation of some new pyranothiazole- Schiff bases bearing the biologically active sulfonamide moiety

Article abstract of DOI:10.1016/j.ejmech.2012.04.009

The present work reports the synthesis of some new Schiff bases, 5-(substituted benzylideneamino)-6-cyano-7H-7-(4-methoxyphenyl)-2-(4- sulphamoylphenylamino) pyrano[2,3-d]thiazole (5-15). The design of the structures of these compounds complies with the general pharmacophoric requirements for CA inhibiting anticancer drugs. The newly synthesized compounds were evaluated for their in vitro anticancer activity against human breast cancer cell line (MCF7). Most of the screened compounds showed interesting cytotoxic activities compared to doxorubicin as a reference drug. Compounds 4, 6-8 and 11 (IC₅₀: 27.51, 10.25, 9.55, 9.39 and 9.70 μM, respectively) exhibited higher cytotoxic activities than the reference drug doxorubicin (IC₅₀: 32.00 μM). Additionally, the previously mentioned compounds were evaluated again for their ability to enhance the cell killing effect of γ-radiation.

Full text of DOI:10.1016/j.ejmech.2012.04.009

European Journal of Medicinal Chemistry 53 (2012) 403e407
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Anticancer and radiosensitizing evaluation of some new pyranothiazole-Schiff
bases bearing the biologically active sulfonamide moiety
,
c
c
Mostafa M. Ghorab a, Mohamed A. Shaaban b, Hanan M. Refaat b , Helmy I. Heiba , Sara S. Ibrahim
*
a Medicinal, Aromatic and Poisonous Plants Research Center (MAPPRC), College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
b Department of Organic Chemistry, Faculty of Pharmacy, Cairo University, Kasr El-Aini St., Cairo 11562, Egypt
c Department of Drug Radiation Research, National Center for Radiation Research and Technology, 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:
The present work reports the synthesis of some new Schiff bases, 5-(substituted benzylideneamino)-
6-cyano-7H-7-(4-methoxyphenyl)-2-(4-sulphamoylphenylamino) pyrano[2,3-d]thiazole (5e15). The
design of the structures of these compounds complies with the general pharmacophoric requirements
for CA inhibiting anticancer drugs. The newly synthesized compounds were evaluated for their in vitro
anticancer activity against human breast cancer cell line (MCF7). Most of the screened compounds
showed interesting cytotoxic activities compared to doxorubicin as a reference drug. Compounds 4, 6e8
Received 16 January 2012
Received in revised form
3 April 2012
Accepted 7 April 2012
Available online 26 April 2012
and 11 (IC50: 27.51, 10.25, 9.55, 9.39 and 9.70
the reference drug doxorubicin (IC50: 32.00
were evaluated again for their ability to enhance the cell killing effect of
m
m
M, respectively) exhibited higher cytotoxic activities than
M). Additionally, the previously mentioned compounds
-radiation.
Keywords:
Pyranothiazole
Sulfonamides
Carbonic anhydrase inhibitors
Cytotoxicity
g
Ó 2012 Elsevier Masson SAS. All rights reserved.
Radiosensitizing activities
1. Introduction
treatment through reducing the provision of bicarbonate for the
synthesis of nucleotides and other cell components such as
membrane lipids [20]. E7070 II (Fig. 1) is an example of carbonic
anhydrase inhibitors.
Sulfonamides are currently an important group of organic
compounds that possess several types of biological activities [1e4]
including anticancer activity [5e10]. The anticancer activity of
sulfonamides was found to take place through a variety of mecha-
nisms such as cell cycle perturbation in the G1phase, disruption of
microtubule assembly, angiogenesis inhibition, and functional
suppression of the transcriptional activator NF-Y, and carbonic
anhydrase inhibition [11e14] which was reported to be the most
prominent mechanism [15]. Carbonic anhydrases (CAs) are zinc
metalloenzymes that catalyze the reversible hydration of carbon
dioxide to give bicarbonate and a proton. CAs are involved in pH
regulation, secretion of electrolytes, respiration [16,17], biosynthetic
reactions which require CO2/bicarbonate as substrate such
as gluconeogenesis, lipogenesis, ureagenesis, and pyrimidines
synthesis [18]. The catalytic domain of CAs contains an active site
Zn2þ; a strong Lewis acid that binds to and activates a substrate H2O
molecule to catalyze the reversible hydration reaction of carbon
dioxide. The hydration of CO2 does not proceed at an appreciable rate
under physiological conditions in the absence of CA enzymes [19]. CA
inhibition has been found to have an important role in cancer
Furthermore, among the compounds that had shown significant
anticancer activity were the thiazole derivatives [21e26]. Also,
combination of several pyranothiazole with sulfonamide moiety was
reported to have significant anticancer activity [27e29]. In addition,
Schiff bases are important class of compounds in medicinal and
pharmaceutical field that show vast biological applications including
antitumor activity [30,31]. In the light of these facts, and in a hope to
obtain some novel compounds with significant anticancer activity,
this work reports the synthesis of a novel series of Schiff base deriv-
atives containing pyranothiazole bearing a sulfonamide moiety and
the testing of these compounds for their in vitro anticancer activity.
We also aimed to evaluate the most potent compounds for their
in vitro anticancer activity in combination with g-radiation, to eval-
uate their ability to enhance the cytotoxic activity of g-radiation.
2. Result and discussion
2.1. Chemistry
The newly synthesized compounds were obtained starting
with 4-(4-oxo-4,5-dihydrothiazol-2-ylamino)benzenesulfonamide
* Corresponding author. Tel.: þ20 02 3639307; fax: þ20 02 3635140.
E-mail address: hanan-refaat@hotmail.com (H.M. Refaat).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.04.009

404
M.M. Ghorab et al. / European Journal of Medicinal Chemistry 53 (2012) 403e407
subclinical metastases and if the primary local tumor is effectively
treated by radiotherapy. In this regard, no interaction between
radiotherapy 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 radio-
resistant phase cells, eliminating hypoxic cells or inhibiting the
accelerated repopulation of tumor cells. Virtually, all chemothera-
peutic agents have the ability to sensitize cancer cells to the lethal
effects of ionizing radiation [33]. The ability of the most five active
compounds 4, 6e8 and 11 to enhance the cell killing effect of
Fig. 1. Compound E7070, a sulfonamide compound in advanced clinical trials as
anticancer agent.
g
-irradiation was studied. Compounds 4, 6e8 and 11 exhibited
(IC50: 27.51, 10.25, 9.55, 9.39 and 9.70 M, respectively) when
used alone (Table 1). The IC50 values were decreased to 14.76,
9.11, 8.72, 8.72 and 7.55 M when the cells were treated with
compound 4, 6e8 and 11 in combination with a single dose of
-radiation at a dose level of 8 Gy (Table 2). The survival curve
for MCF7 cell line for compound 11 alone and in combination with
-irradiation is illustrated in (Fig. 2).
m
3, which was prepared according to the reported procedure [32], by
refluxing the N-chloroacetyl derivative 2 with ammonium thiocy-
anate in ethanol, through intramolecular cyclization and elimina-
tion of 1 mol of ammonium chloride. Treatment of compound 3
with 2-(4-chlorobenzylidene) malononitrile in ethanol containing
a catalytic amount of piperidine, as a base catalyst, resulted in
intramolecular cyclization affording the 4-(5-amino-6-cyano-7-
(2-methoxyphenyl)-7H-pyrano[2,3-d]thiazol-2-ylamino) benzene-
sulfonamide 4. The structure of compound 4 was confirmed by its
microanalytical and spectral data; where the IR spectrum showed
bands at 2187 attributed to the presence of (C^N) group and the 1H
m
g
g
3. Conclusion
The objective of the present study was to synthesize and inves-
tigate the anticancer activity of new Schiff bases of pyrano[2,3-d]
thiazole containing a free sulfonamide moiety. Some of the new
synthesized compounds 4, 6e8 and 11 showed promisinganticancer
activity against human breast cancer cell line [MCF7]. Also,
combination of these active compounds with radiation resulted in
a remarkable increase of their potency toward cancer cells.
NMR spectrum showed a peak at
d 4.70 ppm attributed to the
presence of C-4 pyran H (Scheme 1).
Treatment of compound 4 with aromatic aldehydes in acetic acid
yielded the corresponding Schiff bases 5e15. The structures of
synthesized compounds 5e15 were supported from their microan-
alytical and spectral data. The 1H NMR spectra of compounds 5e15
displayed the disappearance of NH2 absorption of the precursor 4
4. Experimental
and the presence of singlets at the range d 8.23e8.79 ppm for (N]
CHe), in addition to the presence of the expected methoxyphenyl
and sulphamoylphenyl protons signals together with other signals
assigned to N-substituted benzylidene groups (Scheme 2).
4.1. Chemistry
Melting points are uncorrected and were determined on a Stuart
melting point apparatus (Stuart Scientific, Redhill, UK). Elemental
analysis (C, H, N) were performed on PerkineElmer 2400 analyser
(PerkineElmer, Norwalk, CT, USA) at the microanalytical laboratories
oftheFacultyofScience, CairoUniversity. Allcompoundswerewithin
ꢀ0.4% of the theoretical values. The IR spectra (KBr) were measured
on Shimadzu IR 110 spectrophotometer (Shimadzu, Koyoto, Japan),
1H NMR spectra were obtained on a Bruker proton NMR-Avance 300
(300 MHz) (Bruker, Munich, Germany), in DMSO-d6 as a solvent,
using tetramethylsilane (TMS) as internal standard. Mass spectra
were run on JEOL JMS AX-500 mass spectrometer (JEOL JMS, Tokyo,
Japan). All reactions were monitored by thin layer chromatograph
(TLC) using precoated Aluminum sheets Silica gel Merck 60 F254 and
were visualized by UV lamp (Merck, Darmstadt, Germany).
2.2. In vitro anticancer screening
The newly synthesized compounds were evaluated for their
in vitro cytotoxic activity against human breast cancer cell line,
MCF7. Doxorubicin, which is one of the most effective anticancer
agents, was used as the reference drug in this study. The relation-
ship between surviving fraction and drug concentration was
plotted to obtain the survival curve of breast cancer cell line
(MCF7). The response parameter calculated was the IC50 value,
which corresponds to the concentration required for 50% inhibition
of cell viability. Table 1 shows the in vitro cytotoxic activity of the
synthesized compounds. Most of the synthesized compounds
exhibited significant activity compared to the reference drug.
From the analysis of Table 1, it was found that all compounds
showed significant antitumor activities. Interestingly, compounds
4.1.1. 2-Chloro-N-(4-sulfamoylphenyl)acetamide (2)
M.p.: 215e217 ꢁC as reported [31].
6e8 and 11 (IC50: 10.25, 9.55, 9.39 and 9.70
exhibited 3.1e3.4 fold more potent antitumor activity than doxo-
rubicin (IC50: 32.00 M). Further, the key compound 4 (IC50: 27.5
M) showed better cytotoxicity than doxorubicin. Compounds 9,
10 and 13 (IC50: 28.85, 23.48, 28.85 M) showed also better activity
mM, respectively)
4.1.2. 4-(4-Oxo-4,5-dihydrothiazol-2-ylamino)benzenesulfonamide
(3)
m
1
m
Compound 3 was prepared by another method.
A mixture of compound 2 (2.48 g, 0.01 mol) and ammonium
thiocyanate (0.76 g, 0.01 mol) in ethanol (50 mL) was refluxed for
1 h. The solid obtained was crystallized from dioxane. M.p.:
244e246 ꢁC as reported [11].
m
than doxorubicin. While compound 5, 12, 14 and 15 showed slightly
lower activity than that of doxorubicin.
2.3. Radiosensitizing activity
4.1.3. 5-Amino-6-cyano-7-(4-methoxyphenyl)-7H-2-
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
(4-sulphamoylphenylamino) pyrano[2,3-d]thiazole (4)
A mixture of compound 3 (2.71 g, 0.01 mol) with 2-(4-methoxy
benzylidene) malononitrile (0.01 mol) in ethanol (30 mL) containing

M.M. Ghorab et al. / European Journal of Medicinal Chemistry 53 (2012) 403e407
405
O
O
NH2
HN C
Cl
Cl
Cl
NH4SCN
O
O
N
S
DMF/ r.t
reflux ,ethanol
S
NH
Ar
O
NH2
SO2NH2
SO2NH2
3
1
2
CN
CN
Ar= C6H4OCH3 -4
Ar
O
H
CN
O
S
N
H
N
S
O
NH2
NH2
4
Scheme 1. Preparation of compound 4.
piperidine (1 mL) was refluxed for 8 h. The reaction mixture was
filtered and the filtrate was poured onto ice cold water. The solid
obtained was crystallized from dioxane to give compound 4: yield,
70%;m.p.:150e152 ꢁC. IR(KBr, cmꢂ1): 3333, 3217 (NH, NH2), 3075(CH
arom.), 2936, 2850 (CH aliph.), 2187 (C^N), 1593 (C]N), 1330, 1159
(C^N), 1595 (C]N), 1329, 1165 (SO2). 1H NMR (DMSO-d6)
d
: 3.78 [s,
3H, OCH3], 4.70 [s, 1H, CH pyran], 6.60e7.80 [m, 14 H,
AreH þ SO2NH2], 8.00 [s, 1H, NH, D2O exchangeable], 8.54 [s, 1H,
CH]N]. MS (m/z): 580 [M þ 3] (0.26), 578 [M þ 1] (0.78), 149 (100).
(SO2). 1H NMR (DMSO-d6)
d: 3.78 [s, 3H, OCH3], 4.70 [s,1H, CH pyran],
4.1.4.3. 5-(4-Chlorobenzylideneamino)-6-cyano-7H-7-(4-
7.05e7.90 [m, 10H, AreH þ SO2NH2], 8.20 [s, 1H, NH, exchangeable
with D2O], 10.00 [s, 2H, NH2 exchangeable with D2O]. MS (m/z): 456
[M þ 1] (28.41), 277 (100).
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thia-
zole (7). Yield, 67%; m.p.: 206e208 ꢁC. IR (KBr, cmꢂ1): 3331, 3273,
3226 (NH, NH2), 3039 (CH arom.), 2934, 2851 (CH aliph.), 2201
(C^N), 1603 (C]N), 1331, 1170 (SO2). 1H NMR (DMSO-d6)
d: 3.78 [s,
4.1.4. 5-(Substituted benzylideneamino)-6-cyano-7H-7-(4-
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]
thiazole (5e15)
A mixture of compound 4 (0.45 g, 0.001 mol) and the appro-
priate aromatic aldehyde (0.001 mol) in acetic acid (20 mL) was
refluxed for 5 h. The reaction mixture was then poured onto cold
water; the obtained solid was recrystallized from dioxane.
3H, OCH3], 4.10 [s, 1H, CH pyran], 7.06e7.07 [m, 2 H, AreH], 7.15 [d,
2 H, J ¼ 7.8 Hz, AreH], 7.34 [s, 2 H, SO2NH2, D2O exchangeable], 7.49
[d, 2 H, AreH], 7.62 [d, 2 H, AreH],7.77 [d, 2 H, J ¼ 7.8 Hz, AreH],
7.80 [m, 2 H, AreH], 8.00 [s, 1H, NH, D2O exchangeable], 8.23 [s,
1H, CH]N].
4.1.4.4. 5-(3-Bromobenzylideneamino)-6-cyano-7H-7-(4-
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thia-
zole (8). Yield, 54%; m.p.: 228e230 ꢁC. IR (KBr, cmꢂ1): 3320, 3260,
3210 (NH, NH2), 3057 (CH arom.), 2933, 2846 (CH aliph.), 2197
4.1.4.1. 5-(Benzylideneamino)-6-cyano-7H-7-(4-methoxyphenyl)-
2-(4-sulphamoylphenylamino)pyrano[2,3-d]thiazole (5). Yield, 51%;
m.p.: 188e190 ꢁC. IR (KBr, cmꢂ1): 3250, 3203, 3150 (NH, NH2), 3065
(CH arom.), 2938, 2848 (CH aliph.), 2201 (C^N), 1598 (C]N), 1320,
1162 (SO2). MS (m/z): 543 [Mþ] (1.91), 169 (100).
(C^N), 1603 (C]N), 1328, 1144 (SO2). 1H NMR (DMSO-d6)
d: 3.85 [s,
3H, OCH3], 4.45 [s, 1H, CH pyran], 7.05e7.90 [m, 14 H,
AreH þ SO2NH2 at 7.32 D2O exchangeable], 8.2 [s, 1H, NH, D2O
exchangeable], 8.50 [s, 1H, CH]N].
4.1.4.2. 5-(2-Chlorobenzylideneamino)-6-cyano-7H-7-(4-
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thia-
zole (6). Yield, 47%; m.p.: 180e182 ꢁC. IR (KBr, cmꢂ1): 3329, 3251,
3211 (NH, NH2), 3071 (CH arom.), 2932, 2843 (CH aliph.), 2203
4.1.4.5. 6-Cyano-5-(4-fluorobenzylideneamino)-7H-7-(4-
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thia-
zole (9). Yield, 63%; m.p.: 108e110 ꢁC. IR (KBr, cmꢂ1): 3334, 3208,
OCH3
OCH3
H
H
AcOH
CN
O
S
NH2
S
N
CN
N
O
S
NH2
H
N
S
N
H
N
ArCHO
+
O
O
NH2
O
O
Ar
4
5-15
5:Ar= C6H4
11:Ar= 4-(C6H4)NO2
12:Ar= 4-(C6H4)N(CH3)2
CH=CH-C H
6:Ar= 2-(C6H4)Cl
7:Ar= 4-(C6H4)Cl
8:Ar= 3-(C6H4)Br
9:Ar= 4-(C6H4)F
13:Ar=
6
5
14:Ar= 4-(C6H4)OH
15:Ar= piperonyl
10:Ar= 2,4-(C6H3)Cl2
Scheme 2. Preparation of Schiff bases 5e15.

406
M.M. Ghorab et al. / European Journal of Medicinal Chemistry 53 (2012) 403e407
Table 1
In vitro anticancer screening of the synthesized compounds against human breast
cell line (MCF7).
Cpd. Compound concentration (
no.
m
M)
IC50
M)
(
m
10 (
mM)
25 (m
M)
50 (m
M)
100 (mM)
Surviving fraction (mean ꢀ SE)a
DOX 0.551 ꢀ 0.026 0.480 ꢀ 0.003 0.139 ꢀ 0.005 0.130 ꢀ 0.016 32.00
4
5
6
7
8
9
10
11
12
13
14
15
0.810 ꢀ 0.022 0.550 ꢀ 0.019 0.331 ꢀ 0.013 0.350 ꢀ 0.015 27.51
0.825 ꢀ 0.013 0.668 ꢀ 0.021 0.307 ꢀ 0.007 0.271 ꢀ 0.017 33.55
0.541 ꢀ 0.003 0.323 ꢀ 0.020 0.360 ꢀ 0.018 0.460 ꢀ 0.015 10.25
0.443 ꢀ 0.017 0.251 ꢀ 0.012 0.355 ꢀ 0.020 0.290 ꢀ 0.009
0.435 ꢀ 0.009 0.233 ꢀ 0.006 0.371 ꢀ 0.018 0.309 ꢀ 0.011
9.55
9.39
0.845 ꢀ 0.013 0.551 ꢀ 0.021 0.380 ꢀ 0.003 0.443 ꢀ 0.017 28.85
0.693 ꢀ 0.023 0.503 ꢀ 0.033 0.377 ꢀ 0.010 0.391 ꢀ 0.015 23.48
0.480 ꢀ 0.010 0.327 ꢀ 0.016 0.313 ꢀ 0.005 0.381 ꢀ 0.007
9.70
0.792 ꢀ 0.021 0.701 ꢀ 0.031 0.347 ꢀ 0.017 0.378 ꢀ 0.018 36.24
0.828 ꢀ 0.020 0.601 ꢀ 0.019 0.242 ꢀ 0.013 0.370 ꢀ 0.026 28.85
0.872 ꢀ 0.025 0.638 ꢀ 0.016 0.370 ꢀ 0.030 0.307 ꢀ 0.005 34.50
0.814 ꢀ 0.008 0.660 ꢀ 0.025 0.419 ꢀ 0.023 0.393 ꢀ 0.006 38.25
Fig. 2. Interaction map of E7070 with the active site of hCA II showing similar inter-
actions as those previously reported.
a
Each value is the mean of three experiments ꢀ standard error.
7.33 [s, 2H, SO2NH2, D2O exchangeable], 7.41e7.64 [m, 4H, AreH],
7.71e7.95 [m, 4H, AreH], 8.20 [s, 1H, NH D2O exchangeable], 8.50
3188 (NH, NH2), 3032 (CH arom.), 2934, 2849 (CH aliph.), 2198
(C^N), 1603 (C]N), 1331, 1171 (SO2). 1H NMR (DMSO-d6)
d: 3.78
[s, 1H, CH]N]. 13C NMR (DMSO-d6)
d: 29.32, 55.86, 77.61, 114.75,
[s, 3H, OCH3], 4.80 [s, 1H, CH pyran], 6.81 [d, 2H, J ¼ 9.6 Hz,
AreH], 7.06 [d, 2H, J ¼ 9.6 Hz, AreH], 7.13 [d, 2H, J ¼ 9.6 Hz,
AreH], 7.32 [s, 2H, SO2NH2, D2O exchangeable], 7.49 [d, 2H,
J ¼ 9.6 Hz, AreH], 7.55e7.80 [m, 4H, AreH], 8.10e8.20 [s, 1H,
NH, D2O exchangeable], 8.79 [s, 1H, CH]N]. 13C NMR (DMSO-d6)
116.37, 117.22, 127.16, 127.49, 128.82, 129.73, 130.12, 130.19, 132.32,
146.84, 158.13, 160.92, 161.13, 163.56, 169.27. MS (m/z): 587 [M ꢂ 1]
(0.34), 76 (100).
4.1.4.8. 6-Cyano-5-(4-(dimethylamino)benzylideneamino)-7H-7-(4-
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thia-
zole (12). Yield, 43%; m.p.: 162e164 ꢁC. IR (KBr, cmꢂ1): 3333, 3267,
3213 (NH, NH2), 3071 (CH arom.), 2935, 2846 (CH aliph.), 2205
d
: 26.25, 55.91, 73.09, 114.46, 115.01, 115.38, 120.72, 126.25, 126.75,
127.13, 127.52, 130.09, 130.65, 131.92, 132.36, 140.56, 158.95,
160.92, 161.48, 167.97, 173.37. MS (m/z): 560 [M ꢂ 1] (0.33), 63
(100).
(C^N), 1597 (C]N), 1378, 1169 (SO2). 1H NMR (DMSO-d6)
d: 3.10 [s,
6H, 2CH3], 3.80 [s, 3H, OCH3], 4.25 [s, 1H, CH pyran], 6.80 [d, 2H,
J ¼ 9.0 Hz, AreH], 7.06 [d, 2H, J ¼ 7.2 Hz, AreH], 7.12 [d, 2H,
J ¼ 7.2 Hz, AreH], 7.36 [s, 2H, SO2NH2, D2O exchangeable], 7.56
[d, 2H, J ¼ 8.1 Hz, AreH], 7.60 [d, 2H, J ¼ 8.1 Hz, AreH], 7.69 [d,
2H, J ¼ 9.0 Hz, AreH], 7.80 [s, 1H, NH, D2O exchangeable], 8.30 [s,
1H, CH]N].
4.1.4.6. 6-Cyano-5-(2,4-dichlorobenzylideneamino)-7H-7-(4-
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thia-
zole (10). Yield, 77%; m.p.: 84e86 ꢁC. IR (KBr, cmꢂ1): 3330, 3266,
3189 (NH, NH2), 3079 (CH arom.), 2928, 2858 (CH aliph.), 2207
(C^N), 1585 (C]N), 1377, 1168 (SO2). 1H NMR (DMSO-d6)
d: 3.78 [s,
3H, OCH3], 4.45 [s, 1H, CH pyran], 7.03 [d, 2H, J ¼ 6.9 Hz, AreH], 7.06
[d, 2H, J ¼ 6.9 Hz, AreH], 7.33 [s, 2H, SO2NH2, D2O exchangeable],
7.55e7.59 [m, 4H, AreH], 7.71 [s, 1H, AreH], 7.80 [d, 1H,
J ¼ 6.4 Hz, AreH], 7.84 [d, 1H, J ¼ 6.4 Hz, AreH], 8.20 [s, 1H, NH, D2O
4.1.4.9. 6-Cyano-7H-(7-(4-methoxyphenyl)-5-(3-phenylallylidene)
amino)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thiazole
(13). Yield, 39%; m.p.: 92e94 ꢁC. IR (KBr, cmꢂ1): 3311, 3190, 3152
(NH, NH2), 3035 (CH arom.), 2931, 2846 (CH aliph.), 2202 (C^N),
exchangeable], 8.50 [s, 1H, CH]N]. 13C NMR (DMSO-d6)
d: 26.25,
1593 (C]N), 1331, 1165 (SO2). 1H NMR (DMSO-d6)
d: 3.83 [s, 3H,
55.91, 73.09, 114.46, 115.01, 115.38, 120.72, 126.25, 126.75, 127.13,
127.52, 130.09, 130.65, 131.92, 132.36, 140.56, 158.95, 160.92,
161.48, 167.97, 173.37.
OCH3], 4.30 [s, 1H, CH pyran], 6.82, 6.90 [2d, 2H, J ¼ 8.5 Hz,
CH ¼ CH], 7.08e7.16 [m, 4H, AreH], 7.37 [s, 2H, SO2NH2, D2O
exchangeable], 7.51 [m, 1H, AreH], 7.59 [d, 2H, J ¼ 6.8 Hz, AreH],
7.61 [d, 2H, J ¼ 6.8 Hz, AreH], 7.72e7.78 [m, 4H, AreH], 8.15 [s,
1H, NH, D2O exchangeable], 8.30 [s, 1H, CH]N].
4.1.4.7. 6-Cyano-7H-7-(4-methoxyphenyl)-5-(4-
nitrobenzylideneamino)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]
thiazole (11). Yield, 75%; m.p.: 198e200 ꢁC. IR (KBr, cmꢂ1): 3339,
3224, 3150 (NH, NH2), 3068 (CH arom.), 2937, 2842 (CH aliph.),
4.1.4.10. 6-Cyano-5-(4-hydroxybenzylideneamino)-7H-7-(4-
methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-d]thia-
zole (14). Yield, 46%; m.p.: 170e172 ꢁC. IR (KBr, cmꢂ1): 3333, 3267,
2201 (C^N), 1595 (C]N), 1336, 1165 (SO2). 1H NMR (DMSO-d6)
d:
3.80 [s, 3H, OCH3], 4.25 [s, 1H, CH pyran], 6.96e7.22 [m, 4H, AreH],
Table 2
In vitro anticancer screening of compounds 4, 5bed and 5g against human breast cell line (MCF7) in combination with radiation.
Cpd. no.
Control
Irradiated (8 Gy)
Compound concentration (
m
M) þ irradiation (8 Gy)
IC50 (mM)
Surviving fraction (mean ꢀ SE)a
10
25
50
100
4
6
7
8
1.000
1.000
1.000
1.000
1.000
0.927 ꢀ 0.02
0.927 ꢀ 0.02
0.927 ꢀ 0.02
0.927 ꢀ 0.02
0.927 ꢀ 0.02
0.618 ꢀ 0.01*
0.453 ꢀ 0.017*
0.311 ꢀ 0.013*
0.319 ꢀ 0.02*
0.403 ꢀ 0.01*
0.346 ꢀ 0.02*
0.237 ꢀ 0.012*
0.217 ꢀ 0.02*
0.211 ꢀ 0.016*
0.201 ꢀ 0.02*
0.171 ꢀ 0.01*
0.135 ꢀ 0.015*
0.170 ꢀ 0.01*
0.119 ꢀ 0.015*
0.100 ꢀ 0.012*
0.201 ꢀ 0.01*
0.119 ꢀ 0.007*
0.201 ꢀ 0.008*
0.235 ꢀ 0.01*
0. 130 ꢀ 0.009*
14.76
9.11
8.72
8.72
7.55
11
*Significant difference from control group at p < 0.001.
a
Each value is the mean of three values ꢀ Standard Error.

M.M. Ghorab et al. / European Journal of Medicinal Chemistry 53 (2012) 403e407
407
3221 (NH, NH2), 3079 (CH arom.), 2934, 2846 (CH aliph.), 2202
(C^N), 1598 (C]N), 1336, 1169 (SO2). 1H NMR (DMSO-d6)
: 3.80
[s, 3H, OCH3], 4.50 [s, 1H, CH pyran], 6.82e7.81 [m, 14 H,
AreH þ SO2NH2], 8.09 [s, 1H, NH, D2O exchangeable], 8.30 [s, 1H,
CH]N], 9.90 [s, 1H, OH, D2O exchangeable].
a dose level of 8 Gy with a dose rate of 1 Gy/min. The surviving
fraction was measured 1 h after subjection to radiation [35]. The
surviving fractions were expressed as means ꢀ standard error. The
results were analyzed using 1-way ANOVA test and the percentage
of change in the surviving fraction from control for each compound
was calculated considering the control as 100% in the surviving
fraction. The results are given in Table 2.
d
4.1.4.11. 5-((Benzo [1,3-b] dioxol-5-ylmethylene)amino)-6-cyano-
7H-7-(4-methoxyphenyl)-2-(4-sulphamoylphenylamino)pyrano[2,3-
d]thiazole (15). Yield, 71%; m.p.: 122e124 ꢁC. IR (KBr, cmꢂ1): 3333,
3227, 3171 (NH, NH2), 3073 (CH arom.), 2935, 2849 (CH aliph.),
Appendix A. Supplementary material
2206 (C^N), 1597 (C]N), 1333, 1169 (SO2). 1H NMR (DMSO-d6)
d:
Supplementary data related to this article can be found online at
doi:10.1016/j.ejmech.2012.04.009.
3.80 [s, 3H, OCH3], 4.60 [s, 1H, CH pyran], 6.28 [s, 2H, CH2], 6.61 [d,
2H, J ¼ 6.8 Hz, AreH], 6.92 [d, 2H, J ¼ 6.8 Hz, AreH], 7.08 [d, 2H,
J ¼ 8.5 Hz, AreH at C-6 & C-7], 7.38 [d, 1H, J ¼ 5.0 Hz, AreH at C-4],
7.28 [s, 2H, SO2NH2, D2O exchangeable], 7.58 [d, 2H, J ¼ 7.2 Hz,
AreH], 7.62 [d, 2H, J ¼ 7.2 Hz, AreH], 8.10 [s, 1H, NH, D2O
exchangeable], 8.30 [s, 1H, CH]N].
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the results are given in Table 1.
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which corresponds to the concentration required for 50% inhibition
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4.2.3. Radiosensitizing activity
The most active compounds 4, 6e8 and 11 resulted from the
in vitro anticancer screening, were selected for further screening
in combination with
This study was conducted to evaluate the ability of the most
biologically active compounds to enhance the cell killing effect of
radiation. Cells were subjected to a single dose of -radiation at
g-radiation.
g-
g