Synthesis, antitumor activity and molecular docking study of novel Sulfonamide-Schiff's bases, thiazolidinones, benzothiazinones and their C-nucleoside derivatives

Article abstract of DOI:10.1016/j.ejmech.2009.10.044

A series of sulfapyridine-polyhydroxyalkylidene (or arylidene)-imino derivatives (Schiff's bases) 2a-c and 4a-e were prepared by condensation of 4-amino-N-pyridin-2-ylbenzenesulfonamide (1) with different monosaccharides or with aromatic aldehydes. Treatment of 2a-c with thioglycolic acid led to the formation of the C-nucleosides (3a-c), while treatment of 4a-e with thioglycolic and/or thiosalicylic acids afforded the corresponding 2-arylthiazolidin-4-one or 2-arylbenzothiazin-4-one derivatives 5a-e and/or 6a-e, respectively. Some representative examples of the newly prepared compounds showed considerable cytotoxic effect against breast carcinoma cell line MCF7 and cervix carcinoma cell line HELA in comparison with 5-flurouracil and doxorubicin. AutoDock molecular docking into PTK has been done for lead optimization of the compounds in study as potential PTK inhibitors.

Full text of DOI:10.1016/j.ejmech.2009.10.044

European Journal of Medicinal Chemistry 45 (2010) 572–580
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, antitumor activity and molecular docking study of novel
Sulfonamide-Schiff’s bases, thiazolidinones, benzothiazinones and their
C-nucleoside derivatives
,
a
a
Mohsen M. Kamel a, Hamed I. Ali b, Manal M. Anwar a , Neama A. Mohamed , AbdelMohsen M. Soliman
*
a Medicinal Chemistry Department, National Research Centre, Dokki, Cairo, Egypt
b Pharmaceutical Chemistry Department, Faculty of Pharmacy, Helwan University, Helwan, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of sulfapyridine-polyhydroxyalkylidene (or arylidene)-imino derivatives (Schiff’s bases) 2a–c
and 4a–e were prepared by condensation of 4-amino-N-pyridin-2-ylbenzenesulfonamide (1) with
different monosaccharides or with aromatic aldehydes. Treatment of 2a–c with thioglycolic acid led to
the formation of the C-nucleosides (3a–c), while treatment of 4a–e with thioglycolic and/or thiosalicylic
acids afforded the corresponding 2-arylthiazolidin-4-one or 2-arylbenzothiazin-4-one derivatives 5a–e
and/or 6a–e, respectively. Some representative examples of the newly prepared compounds showed
considerable cytotoxic effect against breast carcinoma cell line MCF7 and cervix carcinoma cell line HELA
in comparison with 5-flurouracil and doxorubicin. AutoDock molecular docking into PTK has been done
for lead optimization of the compounds in study as potential PTK inhibitors.
Received 31 August 2009
Received in revised form
22 October 2009
Accepted 23 October 2009
Available online 11 November 2009
Keywords:
Sugar-Schiff’s base
Thiazolidin-4-one
Benzothiazin-4-one
Antitumor activity
Autodock
Ó 2009 Elsevier Masson SAS. All rights reserved.
Protein tyrosine kinase
1. Introduction
The role of tyrosine kinase in the control of cellular growth and
differentiation is central to all organisms and the tyrosine kinase has
The chemistry of sulfanilamides [1,2], thiazolidinones [3] and
benzothiazines [4] have been of increasing interest since many of
these derivatives produce useful applications as chemotherapeutic
agents especially against pathogenic bacteria and tumor cells. On
the other hand, it has been reported that a wide range of Schiff’s
bases with their reactive azomethine linkage shows interesting
inhibitory activity against experimental tumor cells [5–8]. It is also
suggested that the Schiff’s bases could be hydrolyzed selectively by
the tumor cells to act as alkylating agents at the same time as the
active amine becomes free to act as antimetabolite [9]. Besides, the
Schiff’s bases represent active intermediates to develop various
heterocyclic systems of biological importance as the above
mentioned pyridines, thiazolidines, benzothiazines and their C-
nucleoside analogues. Based on all of these findings, it was of
interest to synthesize some new sulfapyridine-Schiff’s bases and
their cyclic products and/or their C-nucleoside analogues to be
evaluated for their cytotoxic activity.
been found to participate in human neoplastic diseases. Tyrosine
kinase inhibitors and their potentials in the clinical applications are
well documented by dramatic examples such as Gleevec, Iressa and
Herceptin. Several tyrosine kinase inhibitors are undergoing human
trials and several are in the pipeline of drug discovery [10]. Molec-
ular docking has been a focus of attention for many years. Generally
speaking, today’s flexible docking programs such as AutoDock are
able to predict protein–ligand complex structures with reasonable
accuracy and speed [11]. One of the most reliable, robust and
popular energy-based docking packages is AutoGrid/AutoDock
(Morris et al., 1998) because it allows a very efficient docking of
flexible ligands (e.g. substrates, drug candidates, inhibitors, peptides,
etc.) onto receptors (e.g. enzymes, antibodies, nucleic acids, etc.) [12].
2. Chemistry
The discovery of C-nucleosides and continuous study of their
biological activities [13,14] led us to construct compounds con-
taining sulfapyridine Schiff’s bases incorporated into different
aldoses, thiazolidinones, benzothiazines and/ or their C-nucleo-
side analogues which might be of potential anticancer properties
against experimental tumor cell lines. Thus the reaction of
* Corresponding author. Tel.: þ20 123956970; fax: þ20 233370931.
E-mail address: manal.hasan52@yahoo.com (M.M. Anwar).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.10.044

M.M. Kamel et al. / European Journal of Medicinal Chemistry 45 (2010) 572–580
573
sulfapyridine 1 dissolved in DMF containing few drops of acetic
acid with various monosaccharide (aldoses) namely, -arabinose,
-xylose and/ or -mannose dissolved in water, gave the corre-
sponding Schiff’s bases: N-[1- (1,2,3,4-tetrahydroxypentylidene)]-
imino 4-[(pyridinylamino)sulfonyl]benzenes (2a, b) and/ or
N-[1-(1,2,3,4,5- pentahydroxyhexyl idene)- imino-4-[(pyridin-
2-ylamino)sulfonyl]benzene (2c), respectively. Cyclocondensation
of Schiff’s bases 2a–c with thioglycolic acid in dry dioxane,
these analogs, being of sulfapyridine attached to xylose (2a), thia-
zolidinone (3b), sulfapyridine attached to p-methoxyphenyl (4a),
sulfapyridine attached to indole (4e), thiazolidinone attached to
indole (5e), and benzothiazine analogue (6a). It has been noticed
from Table 1 that all of the tested compounds showed significant
antitumor activities and this might be explained that the presence
of the phenyl ring of sulfapyridine moiety provided good affinity
towards the enzyme on account of the force of electrostatic
attraction between the planar phenyl and the target site pocket of
the tumor cells. In comparison to 5-flurouracil, the attachment of
xylose nucleus to sulfapyridine via azomethine linkage in
D
D
D
afforded
the
corresponding
thiazolidinones,
namely;
2-[1-(1,2,3,4- tetrahydroxybutyl)]-3-[4-[(pyridin-2-yl amino)
sulfonyl]phenyl] thiazolidin-4-one (3a,b) and/ or 2-[1-(1,2,3,4,5-
penta- hydroxyl- pentyl)]-3-[4-[(pyridin-2-ylamino)]sulfonyl]-
phenyl]thiazolidin-4-one (3c), respectively (Scheme 1).
compound 2b gave antitumor activity against HELA (IC50: 3.56
mL); about one third that of 5-flurouracil (IC50:1.01 g/mL), but the
activity against MCF7 (IC50: 1.68 g/mL) was one half that of the
reference compound (IC50: 0.67 g/mL). The antitumor activity of
thiazolidinone analogue 3b against HELA increased (IC50: 2.01 g/
mL), while the activity against MCF7 decreased to be about one
fourth of the activity of the comparing drug (IC50: 2.68 g/mL). Also,
mg/
m
Also, reaction of sulfapyridine 1 with different aromatic alde-
hydes, namely; p-anisaldehyde, 3,4-dimethoxybenzaldehyde, 2-
hydroxy-4-methoxybenzaldehyde, 3,4,5-trimethoxybenzal- dehyde
and/ or indol-3-carboxaldehyde in the presence of few drops of acetic
acid, afforded Schiff’s bases, namely; N-(substituted arylidene)-
imino-4-[(pyridin-2-ylamino)sulfonyl]benzenes (4a–e), respec-
tively. Compounds 4a–e were reacted with thioglycolic acid and/ or
thiosalicylic acid to give the corresponding 2-aryl- 3-[4-[(pyridin-2-
ylamino)sulfonyl]phenyl] thiazolidin-4-ones (5a–e) and/or 2-aryl-
3-[4-[(pyridin-2-ylamino)sulfonyl]phenyl]-2,4-dihydr- obenzo[e]
[1,3]thiazin-4-ones (6a–e), respectively (Scheme 2).
m
m
m
m
combining sulfapyridine moiety with p-methoxyphenyl via azo-
methine linkage in derivative 4a enhances the antitumor activity
against both types of carcinoma cell lines HELA and MCF7 to be very
close to that gained by the comparing drug (IC50: 1.88 and 0.74
mL, respectively). The benzothiazine analogue 6a showed more
slight increase in the activity against HELA (IC50: 1.48 g/mL), but
the activity against MCF7 decreased (IC50: 1.61 g/mL). The deriv-
m/
m
m
ative 4e containing indole moiety attached to sulfapyridine through
3. Results and discussion
azomethine linkage induced antitumor activity against HELA of
about one half that of 5-flurouracil (IC50: 2.82
MCF7 of about one third that of the comparing drug (IC50: 2.28
mL). The cyclized analogue bearing thiazolidinone ring 5e exhibited
increase in the antitumor activity against both HELA (IC50:1.95 g/
mL) and MCF7 (IC50: 1.07 g/mL). It is noteworthy that, comparing
to doxorubicin (IC50: 8.72 and 7.71 g/mL against HELA and MCF7,
respectively), all of the tested derivatives showed much higher
antitumor activity against both types of carcinoma cell lines (IC50
0.74–3.56 g/mL).
m
g/mL) and against
3.1. Biological evaluation
mg/
Chemotherapy is a major therapeutic approach for the both
localized and metastasized cancers. In the present work, six of the
newly synthesized compounds 2b, 3b, 4a, 4e, 5e, 6a were selected
to evaluate their in vitro growth inhibitory activities against two
human cultured cell lines, which are cervix carcinoma cell line
(HELA) and breast carcinoma cell lines (MCF7) in comparison to the
known anticancer drugs: 5-flurouracil and doxorubicin as reference
drugs. The six compounds selected being, 2a, 3b, 4a, 4e, 5e, and 6a
were carefully selected to be representatives for all the newly
synthesized 21 derivatives. And covering all structural variations in
m
m
m
:
m
Considering the structure activity relationship (SAR) of the
aforementioned selected compounds, they exhibited narrow range
of variation of IC50, being [0.74–3.56]
mg/ml. This indicate that SAR of
Aldoses
60oC, 2h
CHR
N
N
NHSO2
NH2
N
NHSO2
1
(2a-c)
HSCH2COOH
Dioxane, r.t.
R
S
N
N
NHSO2
O
(3a-c)
3a, R =
3b, R =
3c, R =
HO
HO
HO
OH
OH
HO
OH
HO
OH
OH
OH
HO
OH
Scheme 1.

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M.M. Kamel et al. / European Journal of Medicinal Chemistry 45 (2010) 572–580
ArCHO
N
NHSO2
NH2
N
NHSO2
N
CHAr
(4a-e)
1
COOH
SH
HSCH2COOH
Dry dioxane,
anh. Na2SO4
Ar
Ar
N
S
S
N
NHSO2
N
N
NHSO2
O
O
(5a-e)
(6a-e)
OCH3
OCH3
OCH3
OCH3
a: Ar =
b: Ar =
c: Ar =
HO
OCH3
OCH3
OCH3
d: Ar =
e: Ar =
N
H
Scheme 2.
these compounds mainly depends on their main structural feature
of: 4-[(pyridin-2-ylamino) sulfonyl]benzene which is considered as
the pharmacophoric moiety. Whereas, the attached fragment being
alkylidene imino (2a–c), thiazolidin-4-one (3a–c) and (5a–e), ary-
lidene imino (4a–e), and benzo[e][1,3]thiazin-4-ones (6a–e) play
a minor role in structure activity relationship, namely as auxiliary
group for the antitumor activity.
program AutoDock 3.0.5 [15] was used to evaluate the binding free
energies as potential inhibitors into the target PTK macromolecule.
3.2.1. Validation of the accuracy of AutoDock
As cited in literature [10] if the RMSD (root mean square devi-
ation) of the best docked conformation is ꢀ2.0 Å from the bound
ligand in the experimental crystal, the used scoring function is
successful. Therefore, the docked results were compared to the
crystal structure of the bound ligand–protein complex. The
obtained success rates of AutoDock (Morris et al., 1998) were highly
excellent as cited in Table 2. The STI-571 ligand (Imatinib or Glee-
vec), 4-(4-methylpiperazin-1-ylmethyl)-N-[4-methyl-3-(4-pyr-
idin-3-yl-pyrimidin-2-ylamino)phenyl]ben-zamide, was docked
into its c-Kit receptor PTK (pdb code:1t46). The RMSD of the docked
ligand was 0.25 Å as it seems exactly superimposed on the native
3.2. Molecular docking study
Both pharmaceutical companies and university laboratories have
been active to develop compounds which can inhibit tyrosine kinase
activity in the expectation that the potent and selective inhibitors
would represent a new class of therapeutics for cancers as well as
other proliferative diseases. Therefore, PTK inhibitors can be applied
aptly as a new mode of cancer therapy. Depending on the above
mentioned idea, herein we investigated the AutoDock binding
affinities of the synthesized sulfonylbenzenes, sulfonylphenylth-
iazolidinones, and sulf- onylphenylbenzo[e] [1,3]thiazinones into
PTK. Towards optimization of the aforementioned lead compounds
of the promising antitumor activities, the advanced docking
bound one. Moreover, the obtained binding free energy (
DGb) was
quite low being ꢁ18.43 kcal/mol. The docked ligand (yellow stick)
exhibited hydrogen bonds with almost same atoms of amino acids
involved with the native ligand (ball and stick, colored by element).
These results indicated the high accuracy of the AutoDock simu-
lation in comparison with the biological methods [16].
3.2.2. AutoDock binding affinities of the synthesized compounds
into PTK
The binding affinity was evaluated by the binding free energies
Table 1
(DGb, kcal/mol), inhibition constants (Ki), hydrogen bonding, and
Effect of some selected sulfapyridine derivatives on MCF7 and HELA tumor cell lines.
RMSD values. The compounds which revealed the highest binding
affinities, i.e., lowest binding free energies, within PTK and the
hydrogen bond interactions into the target macromolecule are
represented in Table 2. These compounds include: (2a–c), (3a–3c),
(4a–e), (5a–e) and (6a–e). As shown in Table 2, the compounds
Compound
IC50 [mg/ml]
MCF7
HELA
5-Fluorouracil (5-FU)
Doxorubicin (Dox)
0.67
6.71
1.68
2.68
0.74
2.28
1.07
1.61
1.01
8.72
3.56
2.01
1.88
2.82
1.95
1.48
2b
3b
4a
4e
5e
6a
exhibiting the lowest binding free energy are compound 2a (DGb:
ꢁ8.84 kcal/mol) which exhibited four hydrogen bonds with
Glu640, Asp810, and Cys673 and RMSD: 3.80 Å, compound 4a,
(
D
Gb: ꢁ9.07 kcal/mol) which exhibited one hydrogen bonds with
Thr670, and RMSD: 0.99 Å, compound 4c (
D
Gb: ꢁ8.99 kcal/mol)

M.M. Kamel et al. / European Journal of Medicinal Chemistry 45 (2010) 572–580
575
Table 2
The best docking results based on the binding free energies (
between compounds and amino acids in PTK, and RMSD from the co-crystallized STI ligand.
D
Gb) and inhibition constants (Ki) of compounds docked into PTK, the distances and angles of hydrogen bonds
Compound
DGb (kcal/mol)
Ki
Hydrogen bonds between atoms of compounds and amino acids
RMSD (Å)
Atom of compound
Amino acid
Distance (Å)
Angle (ꢂ)
1
ꢁ7.43
ꢁ7.88
ꢁ6.80
ꢁ8.84
3.59E-06
1.67E-06
1.03E-05
3.31E-07
SO2NH
Arabinose-OH
SO2NH
SO2NH
SO2NH
Mannose-OH
Mannose-O
(Arabinose)-4-OH
(Xylose)-2-OH
Thiazole-S
HNSO2
SO2NH
SO2NH
Pyridine-N
HNSO2
SO2NH
Pyrrole-NH
SO2NH
Pyridine-N
OH of Thr670
O]C of Val668
O]C of Glu640
O]C of Glu640
O]C of Asp810
O]C of Cys673
HN of Cys673
O]C of Ile789
O]C of 810
HO of Thr670
HO of Thr670
O]C of Asp810
O]C of Glu640
HN of Asp810
HN of Lys623
O]C of His790
O]C of Cys673
O]C of Asp810
HN of Asp810
–
1.92
2.34
1.97
193
127.0
140.8
128.4
109.9
138.5
134.0
145.8
121.1
136.1
123.8
112.5
131.7
123.8
171.7
106.0
148.3
123.7
149.6
110.9
–
5.34
1.78
3.20
3.80
2a
2b
2c
2.39
2.16
1.65
2.07
2.08
2.39
2.45
2.35
2.21
1.94
2.247
1.907
2.17
1.96
2.40
–
2.33
2.08
1.91
2.05
1.81
1.86
2.256
–
3a
3b
3c
4a
4b
ꢁ5.43
ꢁ5.90
ꢁ7.68
ꢁ9.07
ꢁ8.36
1.04E-04
4.77E-05
2.35E-06
7.40E-07
2.58E-07
9.05
6.87
0.80
0.993
4.91
4c
4d
4e
ꢁ8.99
ꢁ8.57
2.58E-07
5.26E-07
1.19E-08
3.74
4.10
3.70
ꢁ10.81
5a
5b
ꢁ8.39
ꢁ8.16
7.05E-07
1.05E-06
0.80
4.23
SO2NH
HNSO2
OH
SO2NH
SO2NH
SO2NH
HNSO2
–
O]C of Glu640
HN of Asp810
O]C of Asp810 1.91
O]C of Glu640
O]C of Asp810
O]C of Asp810
HN of Asp810
–
107.3
153.8
134.3
112.6
123.4
153.1
108.9
–
5c
5d
ꢁ6.57
ꢁ7.20
1.54E-05
5.32E-06
7.24
5.55
5e
6a
6b
6c
6d
6e
STI
ꢁ8.65
ꢁ8.07
ꢁ7.64
ꢁ7.27
ꢁ5.88
ꢁ8.54
ꢁ18.43
4.57E-07
1.22E-06
2.51E-06
4.72E-06
4.87E-05
5.53E-07
3.08E-14
5.87
6.82
8.27
7.96
6.59
8.20
0.25
o-aryl-OH
O]C of Asp810
2.06
146.3
Pyrrole-NH
N3N
NH(H79)
O(O29)
O]C of Ile789
HN of Cys673
OF of Thr670
HN of Asp810
1.78
1.66
1.86
2.01
142.6
161.0
147.2
133.3
which exhibited one hydrogen bonds with Lys623 and RMSD:
3.74 Å, compound 4e (
Gb: ꢁ10.81 kcal/mol) which exhibited three
hydrogen bonds with Cys 673 and Asp810, and RMSD: 3.70 Å, and
compound 5e (
The overall correlation between the growth inhibitory
activities (IC50 g/mL) of the synthesized sulfonylbenzenes, sulfo-
nylphenylthiazolidinones and sulfonyl- phenylbenzo[e] [1,3]thiazi-
none against tumor cells and the binding affinities predicted by
AutoDock was fairly good for some compounds.
D
, m
D
Gb: ꢁ8.65 kcal/mol) which exhibited one hydrogen
bond with Asp810 and RMSD: 5.87 Å.
As shown in Fig. 1, the molecular docking study revealed
the binding affinities of the synthesized 2-[(2S,3R,4R)1-
(1,2,3,4-tetrahydroxy butyl)]-3-[4- [(pyridin-2-ylamino)sulfonyl]
phenyl]thiazolidin-4-one (3a), N-(o-hydroxy-p-methoxy phenyl-
arylidene)-imino-4-[(pyridin-2-ylamino)sulfonyl]benzenes
(4c),N-(indol-3-ylarylidene)-imino-4-[(pyridin-2-ylamino)sulfo-
nyl]benzenes (4e), and 2-(indol-3-yl)-3-[4-[(pyridin-2-ylamino)-
sulfonyl]phenyl]thiazolidin-4-ones (5e); into PTK. Where
compounds 4c,e exhibited the highest binding free energies being
Considering the growth inhibition against HELA cells, it was
noticed that the correlation between IC50 of 2b, 4a, 5e and 6a and
their AutoDock binding free energies revealed a reasonable corre-
lation coefficient (R2) of 0.652 (not represented). Whereas, the
growth inhibition against MCF7 cells revealed an excellent corre-
lation with AutoDock binding free energies for compounds 2b, 3b,
4a, 5e, and 6a of correlation coefficient (R2) value of 0.897 as shown
in Fig. 3.
(
D
Gb: ꢁ8.99 and ꢁ10.81 kcal/mol, respectively) with 1–3 hydrogen
4. Conclusion
bonds with Lys623, Cys673, and Asp810 mainly via their sulfamoyl
moiety. Whereas compound 3a revealed the poor binding affinity
In this study, eight novel sulfapyridine-polyhydroxyalkylidene
(arylidine)-imino derivatives (Schiff’s bases) 2a–c and 4a–e were
synthesized by reacting the key starting sulfapyridine with
different monosacharides and/or aromatic aldehydes. Further
condensation of 4a–e and 2a–c with thioglycolic acid afforded the
corresponding thiazolidin-4-one derivatives 5a–e and their C-
nucleoside analogues 3a–c, respectively. Additionally, treatment of
the hydrazone derivatives 4a–e with thiosalicylic acid gave the
corresponding benzothiazine-4-one derivatives 6a–e. In vitro
growth inhibitory activities of compounds 2b, 3b, 4a, 4e, 5e, 6a
against (HELA) and (MCF7) cell lines revealed significant potential
antitumor activity. Best results were gained by compound 4a since
it showed approximately similar potency against HELA and MCF7
with binding free energy being (
D
Gb: ꢁ5.43 kcal/mol) which predict
its weak biological antitumor activity (not measured yet), but it may
be similar to its analog namely sulfonylphenylthiazolidin-4-one
(3b) of IC50 against HELA cells (Cervix carcinoma) and MCF7 cells
(breast carcinoma) being 2.01 and 2.68
Fig. 2 illustrates differential binding affinities on docking of
compound 3b; (
mg/ml, respectively.
DGb: ꢁ5.90 kcal/mol) which docked shifted from
the main binding pocket of PTK in another region of the binding site
along with STI-ligand and compound 4a; exhibited one hydrogen
bond, docked in almost superimposed manner with the native
ligand STI. This different binding mode of these compounds may
explain their good correlation with their antiproliferative activity
against HELA cells and MCF7 cells as cited in biology results.
(IC50: 1.88 and 0.74 m/mL, respectively) to that of 5-flurouracil

576
M.M. Kamel et al. / European Journal of Medicinal Chemistry 45 (2010) 572–580
Fig. 1. Comparative binding affinities of compounds (3a, 4c, 4e, and 5e; colored by element, ball and stick) into PTK. Where compounds 4c, e exhibited the highest binding energy
with 1–3 hydrogen bonds. The binding pocket of PTK is shown in transparent solid surface with labeled amino acids and the STI ligand is shown as yellow line. The settled hydrogen
bonds are shown as green dotted lines.
(IC50:1.01
zine analogue 6a exhibited significant potency against HELA (IC50
1.48 g/mL). Fortunately, all of the tested compounds showed
higher antitumor activity against both types of carcinoma cell lines
(IC50: 0.74–3.56 g/mL) than that obtained by doxorubicin IC50
8.72 and 7.71 g/mL against HELA and MCF7, respectively.
m
g/mL and 0.67
m
g/mL, respectively). Also its benzothia-
The AutoDock investigation of the synthesized analogs, (2a–c),
(3a–c), (4a–e), (5a–e) and (6a–e) was carried out for molecular
modeling study. Thus, they were docked within c-kit protein
tyrosine kinase. The overall correlation between the growth
:
m
m
:
inhibitory activities (IC50
, mg/mL) of the synthesized compounds
m
against tumor cells and the binding affinities predicted by
Fig. 2. Differential binding affinities of compounds (3b; blue, stick) and (4a; ball and stick) into PTK. Where compounds 4a exhibited the higher binding energy being (
ꢁ9.07 kcal/mol). Whereas compound 3b exhibited ( Gb: ꢁ5.90 kcal/mol). The binding pocket of PTK is shown in wire mesh view with labeled amino acids and the STI ligand as
yellow line. The settled hydrogen bonds are shown as green dotted lines.
DGb:
D

M.M. Kamel et al. / European Journal of Medicinal Chemistry 45 (2010) 572–580
577
J ¼ 6.4 Hz, 1H, 20-OH) and 7.10–8.43 (m, 10H, aromatic, 10H and NH
protons). MS, m/z (%): M at 381(5).
5.1.1.2. 2b (From xylose). Yield 75%, mp 144 ꢂC (C2H5OH/ H2O). Anal.
calcd. for C16H19N3O6S (381.42): C, 50.38; H, 5.02; N, 11.01; S, 8.40.
Found: C, 50.00; H, 4.89; N, 11.50; S, 8.21. IR (KBr, cmꢁ1): 3343–3295
(broad, OH, NH),1620 (C]N) and 1330 & 1140 (SO2).1H NMR (DMSO-
d6,
d
ppm): 3.35–3.65 (m, 4H, 50-H, 50-H, 40-H, 50-OH), 4.2 (m, 1H,
20-H), 4.35–4.58 (m, 3H, 30-H, 30-OH, 40-OH), 4.97 (d, J ¼ 6.4 Hz,1H, 20-
OH) and 7.10–8.43 (m, 10H, aromatic, 10H and NH protons).
N-[1-(E)-(1,2,3,4,5-Pentahydroxyhexylidene)]-imino-4-[
(pyridin-2-yl amino) sulfonyl]benzenes 2c
5.1.1.3. 2c (From mannose). Yield 70%, mp 150 (C2H5OH/ H2O).
Anal. calcd. for C17H21N3O7S (411.45): C, 49.62; H, 5.14; N, 10.21; S,
7.79. Found: C, 49.33; H, 4.81; N, 10.01; S, 7.52. IR (KBr, cmꢁ1):
34389–3213 (broad, OH, NH), 1619 (C]N) and 1320 & 1140 (SO2).
Fig. 3. Correlation between the binding free energy (
6a against MCF7 tumor cell lines.
DGb) and IC50 of 2b, 3b, 4a, 5e and
AutoDock was fairly good for some compounds, namely; 2b, 4a, 5e
and 6a against HELA tumor cell lines, with the correlation coeffi-
cient (R2) of 0.652. While the correlation between IC50 of
compounds 2b, 3b, 4a, 5e and 6a against MCF7 tumor cell lines was
excellent correlation being with correlation coefficient (R2) value of
0.897. These computationally studied compounds may be prom-
ising candidates for further investigation.
1H NMR (DMSO-d6, ppm): 3.24–3.44 (m, 2H, 60-H, 600-H), 3.56 (m,
d
3H, 50-H, 40-H, 60-OH), 4.13 (d, 1H, J ¼ 6.2 Hz, 50-OH), 4.35 (d, 1H,
J ¼ 6.5 Hz, 40-OH), 4.40 (m, 3H, 20-H, 30-H, 30-OH), 4.73 (d, J ¼ 6.7 Hz,
1H, 20-OH), and 7.10–8.42 (m, 10H, aromatic, 10H and NH protons).
MS, m/z (%): (M þ 1) at 411 (0.7).
5.1.2. 2-[1-(1,2,3,4-Tetrahydroxybutyl)]-[4-[(pyridin-2-y
lamino)sulfonyl]phenyl]thiazo- lidin-4-ones (3a, b)
5. Experimental
General procedure: A solution of compounds 2a, b (10 mmol) and
mercaptoacetic acid (2 mL, 20 mmol) in dioxane (20 mL) was stir-
red at room temperature for two days. The solvent was evaporated
under vacuum and the residue was washed with 4 N Na2CO3
solution then with water. The separated solid was filtered off,
washed with water till carbonate free then with cold ethanol then
ether and dried under vacuum at room temperature to give
compounds 3a, b.
5.1. Chemistry
All melting points are uncorrected and were recorded on an open
glass capillaries using an Electrothermal IA 9000 digital melting
point apparatus and are uncorrected. Analytical data were obtained
from the Microanalytical Unit, Cairo University, Egypt. IR spectra
(KBr discs) were recorded on a Perkin Elmer 1430 spectrophotom-
eter. 1H NMR spectra were measured with Joel 270 MHz in DMSO-d6
and the chemical shifts were recorded in ppm relative to TMS. The
mass spectra were recorded on GCMC-QP 1000 EX Shimadzo Gas
Chromatography MS spectrometer, Japan E.I.70 ev. Follow-up of the
reactions and checking the purity of the compounds were made by
TLC on silica gel pre-coated aluminum sheets (Type 60F254, Merck,
Darmstadt, Germany) and the spots were detected by exposure to
UV lamp at l254 nanometer for few seconds.
5.1.2.1. 3a (From arabinose). Yield 75%, mp 180 ꢂC (C6H6). Anal.
calcd. For C18H21N3O7S2 (455.52): C, 47.46; H, 4.64; N, 9.22; S, 14.07.
Found: C, 47.12; H, 4.32; N, 9.00; S, 14.00. IR (KBr, cmꢁ1): 3435–3210
(broad, OH, NH), 1705 (C]0) and 1617(C]N). 1H NMR (DMSO-d6,
d
ppm): 3.38 (s, 2H, CH2, thiazolidinone ring), 3.30–3.60 (m, 4H, 40-
H, 400-H, 30-H, 40-OH), 4.25 (m, 1H, 1’H), 4.35–4.65 (m, 3H, 20-H,
20-OH, 30-OH), 4.95 (d, , J ¼ 6.4 Hz, 1H, 10-OH), 5.91 (s, 1H, CH,
thiazolidinone ring) and 7.09–8.43 (m, 8H, aromatic and NH
protons). MS, m/z (%): (M þ 1) at 456 (10).
5.1.1. N-[1-(E)-Polyhydroxyalkylidene]-imino-4-[(pyridin-2-
ylamino) sulfonyl] benzenes (2a–c)
General procedure: A mixture of sulfapyridine 1 (2.5 g; 10 mmol)
dissolved in ethanol (5 mL) and DMF (5 mL) and the respective
monosacaride, namely; arabinose, xylose and/ or mannose (D-
series) (10 mmol) dissolved in water (1.0 mL) containing few drops
of acetic acid, was heated on a water bath at 60 ꢂC for 2 h. The solid
that separated after cooling was filtered off, washed with water
followed with cold ethanol and dried to give compounds 2a–c,
respectively.
5.1.2.2. 3b (From xylose). Yield %70, mp 148 ꢂC (C6H6). Anal. calcd.
For C18H21N3O7S2 (455.52): C, 47.46.00; H, 4.64; N, 9.22; S, 14.07.
Found: C, 47.23; H, 4.43; N, 8.89; S,14.34. IR (KBr, cmꢁ1): 3435–3210
(broad, OH and NH), 1705 (C]O) and 1617 (C]N). 1H NMR (DMSO-
d6,
d
ppm): 3.30–3.61 (m, 4H, 30-H, 40-H, 400-H, 40-OH), 3.38 (s, 2H,
CH2, thiazolidinone ring), 4.25 (m, 1H, 1’H), 4.35–4.65 (m, 3H, 20-H,
20-OH, 30-OH), 4.95 (d, J ¼ 6.4 Hz, 1H, 10-OH), 5.95 (s, 1H, CH, thia-
zolidinone ring) and 7.10–8.50 (m, 9H, aromatic and NH protons).
MS, m/z (%): M at 455 (10).
N-[1-(E)-1,2,3,4-Tetrahydroxypentylidene]-imino-4-[(pyridin-
2-ylamino)sulfonyl] benzenes (2a,b)
5.1.2.3. 2-[1-(1,2,3,4-Pentahydroxypentyl)]-[4-[(pyridin-2-ylamino)-
sulfonyl]phenyl] thiazolidin-4-one (3c). A solution of compound 2c
(2 g; 0.01 mol) and mercaptoacetic acid (2 mL; 0.02 mol) in dioxane
(20 mL) was stirred at room temperature for two days. The solvent
was evaporated under vacuum and the residue was washed with 4 N
Na2CO3 solution, then with water. The separated solid was filtered
off, washed with water till carbonate free, then with cold ethanol
followed by ether and dried under vacuum at room temperature to
give the compound 3c.
5.1.1.1. 2a (From arabinose). Yield 80%, mp 156 ꢂC (C2H5OH/H2O).
Anal. calcd. for C16H19N3O6S (381.42): C, 50.38; H, 5.02; N, 11.01; S,
8.40. Found: C, 50.49; H, 5.30; N, 11.43; S, 8.00. IR (KBr, cmꢁ1):
3435–3210 (broad, OH, NH), 1617 (C]N) and 1336 &1140 (SO2). 1H
NMR (DMSO-d6,
4.25 (m, 1H, 20H), 4.35–4.65 (m, 3H, 30-H, 30-OH, 40-OH), 4.95 (d,
d
ppm): 3.30–3.60 (m, 4H, 50-H, 500-H, 40-H, 50-OH),

578
M.M. Kamel et al. / European Journal of Medicinal Chemistry 45 (2010) 572–580
5.1.2.3.1. 3c (From mannose). Yield %75, mp 260 ꢂC (C6H6). Anal.
1335 & 1150 (SO2). 1H NMR (DMSO-d6,
d ppm): 7.12–8.5 (m, 13H,
calcd. For C19H23N3O8S2 (485.54): C, 47.00; H, 4.77; N, 8.65; S, 13.20.
Found: C, 47.40; H, 4.79; N, 8.32; S, 13.00. IR (KBr, cmꢁ1): 3332 (OH),
3221 (NH), 1699 (C]O) and 1620 (C]N). 1H NMR (DMSO-d6,
aromatic and 1H (N]CH)) and 6.3,11.8 (2s,2H, 2NH, exchangeable
with D2O). MS, m/z (%): M at 376 (5).
d
ppm): 3.25–3.45 (m, 4H, 50-H, 500-H, 40-H, 30-H), 3.37 (s, 2H, CH2,
5.1.4. 2-Substituted aryl-3-[4-[(pyridin-2-ylamino)sulfonyl]phenyl]
thiazolidin-4-ones (5a–e)
General procedure: The foregoing method is the same as
described for the preparation of C- nucleosides 3a–c, using the
Schiff’s bases 4a–e instead of 2a–c derivatives.
thiazolidinone ring), 3.75 (t, 1H, 50-OH), 4.25 (m, 2H, 40-OH, 30-OH),
4.50 (m, 3H, 1-H, 20-H, 20-OH), 4.73 (d, J ¼ 6.7 Hz, 1H, 10- OH), 5.9 (s,
1H, CH, thiazolidine ring) and 7.11–8.51(m, 8H, aromatic and NH
protons).
5.1.3. N-(Substituted arylidene)-imino-4-[(pyridin-2-
ylamino)sulfonyl benzenes (4a–e)
5.1.4.1. 2-(p-Methoxyphenyl)-3-[4-[(pryridin-2-ylamino)sulfonyl]
phenyl]-thiazolidin-4-one (5a). Yield 75%, mp 120 ꢂC (C2H5OH).
Anal. calcd. For C21H19N3O4S2 (441.53): C, 57.12; H, 4.33; N, 9.51; S,
14.52. Found: C, 57.32; H, 4.01; N, 9.21; S,14.23. IR (KBr, cmꢁ1): 3100
(NH), 1710 (C]O), 1620 (C]N) and 1322,1150(N–SO2). 1H NMR
(DMSO-d6, d ppm): 3.32 (s, 2H, CH2, thizolidine), 3.95 (s, 3H, OCH3),
4.40 (s, 1H, CH, thiazolidine), 7.30–7.80 (m, 12H, aromatic) and
10.01 (s, 1H, NH, exchangeable with D2O). MS, m/z (%): M at 441(5).
General procedure:
A mixture of the aromatic aldehydes,
namely; p-anisaldehyde, 3,4-dimethoxybenzaldehyde, 2-hydroxy-
4-methoxybenzaldehyde, 3,4,5-trimethoxybenzaldehyde and/ or
indole-3-carboxaldehyde (10 mmol) and sulfapyridine (2.5 g;
10 mmol) in ethanol (30 mL) containing few drops of glacial acetic
acid was refluxed for 3 h. Then the hot mixture was filtered off.
After cooling the filtrate was diluted with 50 mL of water and the
resulting precipitate was filtered off and recrystallized from the
appropriate solvent to give 4a–c, respectively.
5.1.4.2. 2-(3,4-Dimethoxyphenyl)-3-[4-[(pyridin-2-ylamino)sulfonyl]-
phenyl] thiazolidin-4-one (5b). Yield 75%, mp 107 ꢂC (C2H5OH).
Anal. calcd. For C22H21N3O5S2 (471.56): C, 56.03; H, 4.48; N, 8.91; S,
13.59. Found: C, 56.21; H, 4.51; N, 8.72; S, 13.32. IR (KBr, cmꢁ1):
3122 (NH), 1700 (C]O), 1620 (C]N) and 1322, 1153 (N–SO2). MS,
m/z (%): (M þ 1) at 472 (1.5).
5.1.3.1. N-(p-Methoxyphenylidene)-imino-4-[(pyridin-2-ylamino)
sulfonyl] benzene (4a). Yield 75%, mp 160 ꢂC (CH3COOH). Anal.
calcd. for C19H17N3O3S (367.43): C, 62.10; H, 4.66; N, 11.43; S, 8.72.
Found: C, 62.22; H, 4.32; N,11.75; S, 8.42. IR (KBr, cmꢁ1): 3220 (NH),
1627 (C]N), 1520 (C]N, pyridine) and 1330 & 1153 (SO2). 1H NMR
(DMSO-d6, d ppm): 3.90 (s, 3H, OCH3), 6.97–8.44 (m, 12H, aromatic
and 1H (N]CH) protons) and 11.72 (S, 1H, NH, exchangeable with
D2O).
5.1.4.3. 2-(2-Hydroxy-4-methoxyphenyl)-3-[4-(pyridin-2-ylamino)-
sulfonyl] phenyl]thiazolidin-4-one (5c). Yield 70%, mp 170 ꢂC
(CH3OH). Anal. calcd. For C21H19N3O5S2 (457.53): C, 55.12; H ,4.18;
N, 9.18; S, 14.01. Found: C, 55.00; H, 4.00; N, 9.11; S, 14.32. 1H NMR
(DMSO-d6,
d ppm): 3.35 (s, 2H, CH2, thiazolidine), 3.90 (s, 3H,
5.1.3.2. N-(3,4-Dimethoxyphenylidene)-imino-4-[(pyridin-2-yla-
mino) sulfonyl] benzene (4b). Yield 70%, mp 172 ꢂC (CH3COOH).
Anal. calcd. For C20H19N3O4S (397.46): C, 60.43; H, 4.81; N, 10.57; S,
8.06. Found: C, 60.10; H, 5.00; N, 10.72; S, 7.98. IR (KBr, cmꢁ1): 3220
(NH), 1628 (C]N), 1520 (C]N, pyridine) and 1333 & 1154 (SO2). 1H
NMR (DMSO-d ppm): 3.98 (s, 6H, 2(OCH3)), 6.95–8.50 (m, 11H,
aromatic and 1H (N]CH)) and 11.50 (s, 1H, NH, exchangeable with
D2O). MS, m/z (%): M at 379 (5).
OCH3), 4.42 (s, 1H, CH, thiazolidine), 7.51–8.00 (m, 11H, aromatic)
and 10.11 & 10.50 (2s, 2H, NH and OH, exchangeable with D2O).
5.1.4.4. 2-(3,4,5-Trimethoxyphenyl)-3-[4-(pyridin-2-ylamino)sulfonyl]
phenyl]thiazolidin- 4-one (5d). Yield 70%, mp 155 ꢂC (C2H5OH).
Anal. calcd. for C23H23N3O6S2 (501.58): C, 55.07; H, 4.62; N, 8.37; S,
12.78. Found: C, 54.89; H, 4.43; N, 8.12; S, 12.42. IR (KBr, cmꢁ1):
3150 (NH), 1700 (C]O), 1625 (C]N) and 1320, 1153 (N–SO2). 1H
NMR (DMSO-d6, dppm): 3.32 (s, 2H, CH2, thiazolidine), 3.85 (s, 9H,
5.1.3.3. N-(2-Hydroxyl-4-methoxyphenylidene)-imino-4-[(pyridin-2-
ylamino)sulfonyl] benzene (4c). Yield 70%, mp 199 ꢂC
(CH3CH(OH)CH3/ pet. ether). Anal. calcd. for C19H17N3O4S,
(383.43): C, 59.51; H, 4.46; N, 10.95; S, 8.36. Found: C, 59.65; H,
4.21; N, 10.75; S, 8.64. IR (KBr, cmꢁ1): 3435 (OH), 3210 (NH),
1617 (C]N), 1524 (C]N, pyridine) and 1335 & 1151 (SO2). 1H
NMR (DMSO-d6, dppm): 3.80 (s, 3H, OCH3), 6.90–8.61 (m, 11H,
aromatic and 1H (N]CH)), 11.70 (s, 1H, NH, exchangeable with
D2O) and 12.52 (s, 1H, OH, exchangeable with D2O).
3(OCH3)), 4.42 (s, 1H, CH2, thiazolidine), 7.22–8.53 (m, 10H,
aromatic) and 10.02 (s, 1H, NH, exchangeable with D2O).
5.1.4.5. 2-(3-Indolyl)-3-[4-(pyridin-2-ylamino)sulfonyl]phenyl]th-
iazolidin-4-one (5e). Yield 65%, mp 180 ꢂC (C2H5OH). Anal. calcd. for
C22H18N4O3S2 (450.54): C, 58.64; H, 4.02; N, 12.43; S, 14.23. Found:
C, 58.71; H, 4.21; N,12.19; S, 14.43. IR (KBr, cmꢁ1): 3211, 3123 (2NH),
1698 (C]O), 1620(C]N) and 1325, 1151 (N–SO2). MS, m/z (%): M at
450 (10).
5.1.3.4. N-(3,4,5-Trimethoxyphenylidene)-imino-4-[(pyridin-2-y
lamino) sulfonyl]benzene (4d). Yield 75%, mp 283.3 ꢂC
(CH3CH(OH)CH3/ pet. ether). Anal. calcd. for C21H21N3O5S,
(427.49): C, 59.00; H, 4.95; N, 9.82; S, 7.50. Found: C, 59.32; H,
5.22; N, 9.52; S, 7.21. IR (KBr, cmꢁ1): 3212 (NH), 1620 (C]N),
1526 (C]N, pyridine) and 1335 & 1152(SO2). 1H NMR (DMSO-d6,
5.1.5. 2-(Substituted aryl)-3-[4-[(pyridin-2-ylamino)sulfonyl]-
phenyl]-2,4-dihydrobenzo[e][1,3]thiazin-4-ones (6a–e)
General procedure: The foregoing method for the preparation of
the arylthiazolidinones 5a–e was applied to prepare the benzo-
thiazines 6a–e except that thiosalicylic acid was used instead of
thioglycolic acid.
d
ppm): 3.85 (s, 9H, 3(OCH3)), 7.10–8.57 (m, 10H, aromatic and
1H (N]CH) protons) and 11.8 (s, 1H, NH, exchangeable with
D2O).
5.1.5.1. 2-(p-Methoxyphenyl)-3-[4-[(pyridin-2-ylamino)sulfonyl]-
phenyl]-2,4dihydrobenzo [e][1,3]thiazin-4-one (6a). Yield 72%, mp
283 ꢂC (C2H5OH). Anal. calcd. for C26H21N3O4S2 (503.61): C, 62.01;
H, 4.20; N, 8.34; S,12.73. Found: C, 62.17; H, 4.28; N, 8.05; S,12.41. IR
(KBr, cmꢁ1): 3394 (NH), 1675 (C]O), 1626 (C]N), 1529 (C]C) and
d ppm): 3.51 (s, 1H, CH,
benzothiazine), 3.85 (s, 3H, OCH3), 7.3–8.3 (m, 16H, aromatic) and
10.11 (s, 1H, NH, exchangeable with D2O).
5.1.3.5. N-(3-Indolmethylidene)-imino-4-[(pyridin-2-ylamino)-
sulfonyl] benzene (4e). Yield 70%, mp 199 ꢂC (CH3CH(OH)CH3/ pet.
ether). Anal. calcd. for C20H16N4O2S (376.45): C, 63.81, H; 4.28; N,
14.88; S, 8.51. Found: C, 63.52; H, 4.35; N, 14.54; S, 8.21. IR (KBr,
cmꢁ1): 3212, 3190 (NH), 1620 (C]N), 1520 (C]N, pyridine) and
1322, 1157 (N–SO2). 1H NMR (DMSO-d6,

M.M. Kamel et al. / European Journal of Medicinal Chemistry 45 (2010) 572–580
579
5.1.5.2. 2-(3,4-Dimethoxyphenyl)-3-[4-[(pyridin-2-ylamino)sulfo-
nyl]phenyl]-2,4-dihydro- benzo[e][1,3]thiazin-4-one (6b). Yield 70%,
mp 295 ꢂC (C2H5OH). Anal. calcd. for C27H23N3O5S2 (533.63): C,
60.77; H, 4.34; N, 7.87; S, 12.01.Found: C, 60.59; H, 4.52; N, 7.65; S,
12.31. IR (KBr, cmꢁ1): 3325 (NH), 1670 (C]O), 1620 (C]N), 1529
(C]C) and 1359, 1153 (N–SO2). MS, m/z (%): M at 533 (4.2).
5.3.1. Preparation of ligands and target protein tyrosine kinase
The compounds involved in this study as ligands include (2a–c),
(3a–c), (4a–e), (5a–e) and (6a–e) were studied for their binding
activities into PTK. The three dimensional structures of the afore-
mentioned compounds were constructed using Chem3D ultra 8.0
software [Chemical Structure Drawing Standard; Cambridge Soft
corporation, USA (2003)], then they were energetically minimized
by using MOPAC with 100 iterations and minimum RMS gradient of
0.10. The crystal structure of c-Kit receptor protein-tyrosine kinase in
complex with STI-571 (Imatinib or Gleevec) was extracted from the
RCSB Protein Data Bank http://www.rcsb.org/pdb/Welcome.do. All
bound waters, ligand were removed from the protein. For the target,
the amino acids of the ligand binding site were defined using data in
pdbsum http://www.ebi.ac.uk/thorntonsrv/databases/pdbsum/.
5.1.5.3. 2-(2-Hydroxy-4-methoxyphenyl)-3-[4-[(pyridin-2-ylamino)
sulfonyl] phenyl]-2,4-dihydrobenzo[e][1,3]thiazin-4-one (6c). Yield
75%, mp 300 ꢂC (CH3OH). Anal. calcd. for C26H21N3O5S2 (519.61): C,
60.10; H, 4.07; N, 8.08; S, 12.34. Found: C, 59.85; H, 4.21; N, 7.92; S,
12.00. IR (KBr, cm1): 3415, 3233 (OH, NH), 1668 (C]O),1620 (C]N),
1529 (C]C) and 1359, 1151 (N–SO2). 1H NMR (DMSO-d6,
d ppm):
3.62 (s, 1H, CH, benzothiazine), 3.95 (s, 3H, OCH3), 7.3–8.5 (m, 15H,
aromatic) and 10.2 & 12.01 (2s,2H, NH and OH, exchangeable with
D2O).
5.3.2. Grid generation and run of molecular docking
The grid maps representing the native ligand in the actual
docking target site were calculated with AutoGrid. The grids were
chosen to be sufficiently large to include not only the active site but
also significant portions of the surrounding surface. The three
dimensional grids, 60 Å grid size (x, y, z) with a spacing of 0.375 Å,
were created. The cubic grid box was centered in the catalytic active
region and encompassed the binding site where the ligands were
embedded. Then automated docking studies were carried out using
AutoDock version 3.0.5. [15] of the three different search algorithms
offered by AutoDock, the GA-LS search algorithm (Genetic algorithm
with local search) was chosen to search for the best conformers. The
parameters were set using the software ADT (Autodock Tool Kit) on
PC which is associated with Autodock 3.0.5. For all docking param-
eters, default values were used with 10 independent docking runs for
each docking case.
5.1.5.4. 2-(3,4,5-Trimethoxyphenyl)-3-[4-[(pyridin-2-ylamino)sulfo-
nyl]phenyl]-2,4-dihyd- robenzo[e][1,3]thiazin-4-one (6d). Yield 72%,
mp > 300 ꢂC (C2H5OH). Anal. calcd. for C28H25N3O6S2 (563.66): C,
59.66; H, 4.47; N, 7.45; S, 11.37. Found: C, 59.42; H, 4.41; N, 7.22; S,
11.00. IR (KBr, cmꢁ1): 3313 (NH), 1675 (C]O), 1623 (C]N) and
1350, 1150 (N–SO2). MS, m/z (%): M at 563 (5).
5.1.5.5. 2-(3-Indolyl)-3-[4-[(pyridin-2-ylamino)sulfonyl]phenyl]-2,4-
dihydrobenzo[e] [1,3 thiazin-4-one (6e). Yield 70%, mp 299 ꢂC
(C2H5OH). Anal. calcd. for C27H20N4O3S2 (512.62): C, 63.26; H, 3.93,
N, 10.93; S, 12.51. Found: C, 63.49; H, 4.20; N, 10.65; S, 12.31. IR (KBr,
cmꢁ1): 3320, 3211 (2NH), 1670 (C]O), 1620 (C]N) and 1359, 1151
(N–SO2). 1H NMR (DMSO-d6,
d ppm): 3.56 (s, 1H, CH, benzothia-
zine), 7.5–8.4 (m, 17H, aromatic) and 10.82 & 11.10 (2s, 2H, 2NH).
MS, m/z (%): M at 512 (6).
5.3.3. Molecular modeling and analysis of the docked results
There are two kinds of free energies output by Autodock. One is
the binding free energy that includes the intermolecular energy and
torsional free energy, and the other the docking energy [15]. We used
only the binding free energy of the first type as the criterion for
ranking. Cluster analysis was performed on the docked results using
a root mean square (RMS) tolerance of 0.5. Each of the clusters that
exhibited significant negative interaction energies was examined by
Accelrys, DS Visualizer v2.0. [Accelrys Inc., San Diego, CA (2007)] to
determine their binding orientations, molecular modeling, evalua-
tion of the hydrogen bonds and for measuring RMSD, which was
measured as distance between the centroids of the docked inhibitor
and the native ligand. The mode of interaction of the native ligand
within PTK was used as a standard docked model as well as for RMSD
calculation. The correct hydrogen bond interaction was considered
according to Taylor et al., [18] who showed that C–H/O in crystals
contacts occur within certain distance (3.0–4.0 Å) and angle (C–H/
O, 90–180ꢂ) ranges. However, the more linear hydrogen bond is
likely to be stronger [19]. Moreover, there is general agreement that
for carbonyl acceptors, the H/O]C angle is distributed around 120ꢂ.
Therefore, in our modeling results we consider the hydrogen bond
angle ꢃ100ꢂ to be of a reasonable strength.
5.2. Biological screening
Preliminary experiments were done using the human cervix
carcinoma cell tumor lines and breast carcinoma cell lines to iden-
tify the potential toxicity of six selected newly synthesized
compounds (2b, 3b, 4a, 4e, 5e and 6a) in comparison to the known
anticancer drugs 5-Flurouracil and Doxorubicin by SRB using the
method Skehan et al. (1990) [17] as follows: Cells were plated in
96-multiwell plate (104 cells/ well) for 24 h before treatment with
compounds to allow attachment of cell to the wall of the plate.
Different concentration of the compound under test (0.0, 1, 2.5, 5
and 10 g/ml) were added to the cell monolayer triplicate wells
which were prepared for each individual dose. Monolayer cells were
incubated with the compounds for 48 h at 37 ꢂC and in atmosphere
of 5% CO2. After 48 h, cells were fixed, washed and stained with
Sulfo-Rhodamine-B stain. Excess stain was washed with acetic acid
and attached stain was recovered with Tris EDTA buffer. Color
intensity was measured in an ELISA reader. The relation between
surviving fraction and drug concentration is plotted to get the
survival curve of each tumor cell line after the specified compound.
Acknowledgement
5.3. Molecular docking study
The authors thank the Microanalytical Unit, Cairo University,
Egypt for microanalytical data,IR, H1NMR and Mass spectra.
The advanced docking program AutoDock 3.0.5. [15] was used to
evaluate the binding free energy of the inhibitors within the
macromolecules. AutoDock performs the task of the docking. First,
the ligand moves randomly in any one of six degrees of freedom,
namely; 3 translation degrees and 3 rotation degrees, and the
energy of the new ligand ‘‘state’’ is state, the new one is automat-
ically accepted as the next step in docking.
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