Synthesis and in vitro activity of novel 2-(benzylthio)-4-chloro-5-(1,3,4- oxadiazol-2-yl)benzenesulfonamide derivatives

Article abstract of DOI:10.1007/s00706-012-0732-6

Two series of novel 4-chloro-2-(benzylthio)-5-(1,3,4-oxadiazol-2-yl) benzenesulfonamides and their N-aroyl derivatives have been synthesized and evaluated for in vitro anticancer activity against the full NCI-60 cell line panel. Most of the compounds exhibited antiproliferative activity. Among them a compound bearing an N-(thien-2-ylcarbonyl) moiety showed broad-spectrum activity with 50% growth inhibition (GI₅₀) values in the range of 2.02-7.82 μM over 50 cell lines. The Author(s) 2012.

Full text of DOI:10.1007/s00706-012-0732-6

Monatsh Chem (2012) 143:975–984
DOI 10.1007/s00706-012-0732-6
ORIGINAL PAPER
Synthesis and in vitro activity of novel 2-(benzylthio)-4-chloro-5-
(1,3,4-oxadiazol-2-yl)benzenesulfonamide derivatives
•
Kamil Brozewicz Jarosław Sławinski
_
´
Received: 10 November 2011 / Accepted: 27 January 2012 / Published online: 2 March 2012
Ó The Author(s) 2012. This article is published with open access at Springerlink.com
Abstract Two series of novel 4-chloro-2-(benzylthio)-
5-(1,3,4-oxadiazol-2-yl)benzenesulfonamides and their
N-aroyl derivatives have been synthesized and evaluated
for in vitro anticancer activity against the full NCI-60 cell
line panel. Most of the compounds exhibited antiprolifer-
ative activity. Among them a compound bearing an
N-(thien-2-ylcarbonyl) moiety showed broad-spectrum
activity with 50% growth inhibition (GI50) values in the
range of 2.02–7.82 lM over 50 cell lines.
A number of structurally novel N-acylbenzenesulfon-
amides have recently been reported either as potent
antitumor agents against a broad spectrum of human tumor
xenografts (colon, lung, breast, ovary, and prostate) in nude
mice [22] (Fig. 2) or clinically investigated drug candidates
with cytostatic activity against malignant tumors such
as Eli Lilly’s tasisulam sodium [23] or Abbott’s
WO-2002024636, ABT-737 [24], and ABT-263 [25] (Fig. 3).
This led us to an assumption that expansion of the
series of 2-mercapto-N-acylbenzenesulfonamide potential
anticancer agents, in which groups of varying size
and electronic properties are placed at positions 2, 5, and
N- of the benzenesulfonamide ring, may shed light
on the structural features contributing to the biological
activities.
Keywords Acylsulfonamides Á
2-Mercaptobenzenesulfonamides Á Antitumor agents Á
Phase-transfer catalysis Á Heterocycles
Introduction
Aryl- and heteroarylsulfonamides are an important class of
therapeutic agents in current medicinal science [1]. Various
arylsulfonamides have been reported to possess anticancer
[2–6] and/or anti-human immunodeficiency virus (HIV)
properties [6, 7]. Our systematic studies on the synthesis
of 1,4,2-benzodithiazine 1,1-dioxides and their subsequent
transformationsinto2-mercaptobenzenesulfonamide(MBSA)
derivatives (Fig. 1) having a variety of heterocyclic ring
systems or acyclic polynitrogen moieties at the sulfonamide
functionality resulted in promising anticancer [8–13], HIV
antiviral [14–16], or antibacterial agents [17] as well as
potent inhibitors of transmembrane cancer-associated
carbonic anhydrase isozymes hCAIX and hCAXII [18, 19].
Results and discussion
Chemistry
Several methods for synthesis of 2-mercaptobenzene-
sulfonamides are known. The simplest and most efficient
method employs the ring-opening reaction of preformed
3-mercapto-1,1-dioxo-1,4,2-benzodithiazine
derivatives
under alkaline conditions [27]. Alternatively, access to
2-mercaptobenzenesulfonamides is provided by direct
reaction of 2-halogenobenzenesulfonamides with sodium
polysulfide (Na2Sx) [28] or conversion of 2-aminoben-
zenesulfonamides via diazonium salt decomposition
utilizing disodium sulfide (Na2S) or potassium ethyl
xanthate [28–30]. Herein, we report a direct synthetic route to
novel 4-chloro-2-benzylthiobenzenesulfonamides and their
N-acylated derivatives. Due to our ongoing research in the field
of biologically active 2-mercaptobenzenesulfonamides with
´
K. Broz_ewicz Á J. Sławinski (&)
Department of Organic Chemistry, Medical University of
´
Gdansk, Al. Gen. J. Hallera 107, 80-416 Gdansk, Poland
e-mail: jaroslaw@gumed.edu.pl
´
123

´
K. Broz_ewicz, J. Sławinski
976
S-R2
NH-R3
The expected 1,3,4-oxadiazoles 1a, 1b were conve-
niently prepared in good yields by the reaction of 2,4-
dichloro-5-sulfamoylbenzhydrazide [31] with orthoesters
in refluxing glacial acetic acid (Scheme 1).
Cl
R1
S
We found that 2,4-dichloro-5-(1,3,4-oxadiazol-2-yl)
benzenesulfonamide (1a) under standard conditions (BnSH/
K2CO3/DMF (N,N-dimethylformamide)/RT) undergoes a
selective SNAr addition–elimination reaction in 2-position.
Moderate yields (14–58%, Table 1, entries 1–4, 6, and 8) of
this reaction led us to optimize the conditions. Higher yields
were observed when tetrabutylammonium bromide (TBAB)
was used as a phase-transfer catalyst, especially in acetoni-
trile/water (300:1, v/v) reaction environment (Table 1,
entry 9). Slight decrease of substrate conversion was
observed in the absence of argon atmosphere (Scheme 1).
The desired N-acylsulfonamides 4a–4j (Scheme 2) were
prepared by carbodiimide-mediated coupling of aromatic
carboxylic acids with sulfonamides [32–34] promoted by
4-(N,N-dimethylamino)pyridine (DMAP) in the appropriate
O
O
Fig. 1 MBSA scaffold [20, 21]
R2
H
N
R1
S
O
O
O
Fig. 2 Acyl sulfonamide antiproliferative (ASAP) scaffold [26]
five-membered rings incorporated in 5-position of the MBSA
scaffold [9], we choose 1,3,4-oxadiazole as our model hetero-
cyclic residue.
O
O
O
O
O2N
S
O
O
N
S
S
H
N
Br
N
H
Cl
Cl
Na
F
Tasisulam sodium (LY573636-sodium)
WO-2002024636
O
F3C
S
O
NO2
H
H
N
N
N
N
N
N
S
S
H
H
N
S
O
H
H
N
S
O
O
O
N
N
O
O
Cl
Cl
O
ABT-263
ABT-737
Fig. 3 Tasisulam sodium (LY573636-sodium): clinically evaluated (phase II/III in metastatic melanoma) antitumor N-acylsulfonamide; pan-Bcl
family inhibitors targeting Bcl-2, Bcl-w, and Bcl-xL: WO-2002024636, ABT-737, and ABT-263 [23–25]
R1
OEt
OEt
Scheme 1
Cl
Cl
S
Cl
N
Cl
S
OEt
H
N
NH2
NH2
O
R1
H2N
AcOH
O
O
O
O
O
N
1a, R = H
1b, R = Me
R2
HS
2a
2b
2c
2d
R2
Cl
N
S
S
R1
R2
H
H
Me
H
H
Cl
Me
Cl
K2CO3
NH2
O
N
R1
Solvent, RT, 18 h
O
O
2a-2d
123

Synthesis and in vitro activity
977
activity. Sulfonamides 2a and 2c showed significant
selectivity toward leukemia cell line CCRF-CEM (Fig. 4),
whereas 2d appears to be substantially inactive.
Table 1 Reaction of 2,4-dichloro-5-(1,3,4-oxadiazol-2-yl)benzene-
sulfonamide (1a) with benzyl mercaptan and optimization of the
reaction conditions
HOP-92, non-small cell lung cancer, and renal cancer
A498 cell lines reveal some insight into structure–activity
relationship (SAR). Cytostatic activity of 2a–2c toward
those cell lines increases when CLogP and calculated molar
refractivity (CMR) of the compound increase (Table 2).
Over a series of N-(thien-2-ylcarbonyl)benzenesulfon-
amide derivatives (4c–4g), substitution on the heterocyclic
(4e, 4f: R1 = Me) or benzylthio (4d, 4f: R2 = Cl) moiety
decreases activity significantly. It seems interesting that
closely related six-membered N-heteroaroyl derivatives
(4a, 4b, and 4h) showed no activity, which renders 4c as a
lead for further optimization.
HS
Cl
N
Cl
S
Cl
N
S
S
K2CO3
NH2
O
NH2
O
Solvent, RT, 18h
O
O
O
O
N
N
1a
2a
Entry
Solvent
BnSH/mmol
K2CO3/mmol
Yielda/%
1
2
3
4
5
6
7
8
9
EtOH
DMF
DMF
DMF
1.0
1.0
2.0
1.0
1.0
1.0
1.0
1.0
1.0
1.2
Trace
32
1.2
2.2
27
2.2
2.2 (cat.)b
41
Compound 4c (NSC 754633) which satisfied predeter-
mined threshold inhibition criteria was selected for the NCI
five-dose (0.01–100 lM) assay and exhibited remarkable
anticancer activity against most of the tested cell lines
representing nine different subpanels (Table 3). Only NCI/
ADR-RES (adriamycin-resistant cell line) expressing high
levels of MDR1 and Pgp-170 glycoprotein [36, 37] was
found to be insensitive at the highest tested concentration
(100 lM). The obtained data revealed some subpanel
sensitivity toward renal, central nervous system (CNS), and
breast cancer cell lines (subpanel selectivity ratio:
1.04–1.46). The CNS cancer subpanel showed highest
sensitivity with mean GI50 value of 3.24 lM and mean
concentration causing total growth inhibition at 12.68 lM
level. It is worth mentioning that the cytotoxic effect of 4c
was less pronounced in the leukemia subpanel [50% lethal
concentration (LC50) for all tested leukemia cell
lines [100 lM]. A relatively large difference in mean
cytostatic (mean-graph GI50 = 4.27 lM) and cytotoxic
(mean-graph LC50 = 58.88 lM) indicators could be pro-
jected to potential low toxicity against normal cells
resulting in a broad therapeutic index.
DMF/H2O
DMSO
55
2.2
2.2 (cat.)b
2.2
14
DMSO/H2O
MeCN
33
58
MeCN/H2O
2.2 (cat.)a
81
Reaction conditions: 5 cm3 solvent at room temperature (ca. 25 °C)
under argon atmosphere
DMSO dimethylsulfoxide
a
Isolated yield of 2a
(n-Bu4 N)? Br- (0.01 mmol)
b
solvent. In some cases crystalline 4-(N,N-dimethyl-
amino)pyridinium N-heteroaroylsulfonamidates (3a–3c)
were isolated and characterized, which by treatment with 10%
(w/v) ethanolic p-toluenesulfonic acid (p-TSA) solution were
converted to the desired N-acylsulfonamides 4a–4c.
In vitro biological activity
Compounds 2a–2d and 4a–4j submitted to National Cancer
Institute (NCI) were evaluated for their in vitro anticancer
R2
R2
R1
R2
Ar
(a)
(b)
ArCOOH
EDCI or DCC
DMAP, MeCN or THF
3a 4a
,
H
H
H
H
H
H
H
Cl
H
Cl
H
H
H
H
2-Pyrazinyl
2-Pyridinyl
2-Thienyl
Cl
N
S
S
Cl
N
S
S
3b, 4b
3c, 4c
4d
H
NH2
N
Ar
O
O
R1
R1
10% p-TSA/MeCN
or
10% p-TSA/EtOH
O
O
O
O
O
2-Thienyl
N
N
4a-4j
4e
2a-2d
Me
Me
H
2-Thienyl
R2
4f
2-Thienyl
4g
5-Cl-2-thienyl
3-Pyridinyl
4-Cl-Ph
4h
H
Cl
N
S
4i
H
(a)
HN
(b)
4j
H
3,4,5-(MeO)3Ph
N
Ar
O
Me
R1
S
N
O
O
O
N
Me
3a 3c
-
Scheme 2
123

´
K. Broz_ewicz, J. Sławinski
978
Fig. 4 Differential cytotoxicity graph for 2a and 2c revealing NCI-60
panel selectivity/resistance pattern expressed in % growth. Sulfona-
mides 2a and 2c show significant selectivity toward CCRF-CEM
human T cell lymphoblast-like cell line. For each agent the difference
between mean % growth and % growth of each cell line for that agent
is determined, to yield positive values for cell lines more sensitive
than average (bars projecting above the horizontal axis) and negative
values for cell lines less sensitive than average (bars projecting below
the horizontal axis). Mean graph midpoint (the origin of the abscissa)
for 2a is 98.22% and for 2c is 92.12%
activity. The discovered N-acylbenzenesulfonamide 4c
shows promising anticancer activity toward 50 human can-
cer cell lines and could be considered as a lead for further
optimization.
Table 2 CLogP and CMR molecular descriptors of 2a–2d
Compd.
Growth (%)
HOP-92
CLogPa
CMRa
A498
2a
2b
2c
2d
62.58
57.35
48.61
84.54
94.43
59.49
56.18
91.46
1.86852
2.13752
2.58152
2.85052
9.5054
9.9692
9.9968
10.4606
Experimental
¨
Melting points were determined with a Boetius apparatus.
SAR based on HOP-92 and A498 cell line screen at 10 lM concen-
tration of the test agent
Infrared (IR) spectra were taken using a Thermo Mattson
Satellite FTIR spectrophotometer, 1H and 13C nuclear
magnetic resonance (NMR) were taken with a Varian
Gemini 200 MHz or Varian Unity Plus 500 MHz spec-
trometer. Chemical shifts are reported in ppm (d). The
results of elemental analyses for C, H, and N were in
agreement with the calculated values within 0.4% range.
Column chromatography was carried out on silica gel
Fluka Silica gel 60 (0.035–0.070 mm). The starting 2,4-
dichloro-5-sulfamoylbenzhydrazide was obtained from
commercially available 2,4-dichloro-5-sulfamoylbenzoic
acid according to methods described previously [31].
a
Molecular descriptors calculated using BioByte software package
[35]
COMPARE [38, 39] analysis at the NCI of compound 4c
showed moderate Pearson correlation coefficient (PCC =
0.446–0.549) with DNA interfering agents such as actino-
mycin D, echinomycin, bruceantin, chromomycin A3, or
didemnin B (Table 4).
Conclusions
We designed a new and efficient method of obtaining
substituted 2-mercaptobenzenesulfonamides from readily
available 2,4-dichlorobenzenesulfonamides under opti-
mized mild phase-transfer catalysis conditions. This
approach offers easy and quick isolation of the products and
preparative-scale synthesis. Novel 2-mercaptobenzene-
sulfonamides and their structurally diverse N-(hetero)aroyl
derivatives were evaluated for in vitro antiproliferative
General procedure for the synthesis of 1a, 1b
A mixture of 2.84 g 2,4-dichloro-5-sulfamoylbenzhydrazide
(10 mmol) and the appropriate orthoester (60 mmol) in
30 cm3 glacial AcOH was refluxed for 7–12 h. After cooling
to room temperature, stirring was continued overnight. The
precipitate was filtered off, washed with cold EtOH and
petroleum ether, and purified by crystallization from EtOH.
123

Synthesis and in vitro activity
979
Table 3 In vitro antiproliferative data (lM) for 4c (NSC 754633)
against the full NCI cell lines panel derived from nine clinically
isolated human cancer types described by three parameters: molar
concentration of the compound causing 50% net cell growth inhibi-
tion (GI50), total growth inhibition (TGI), and 50% net cell death
Table 3 continued
Subpanel Cell line
GI50/lM
TGI/ LC50
lM lM
/
Conc. Subpanel SSRd TGI- LC50
-
per
MIDb
MIDe MIDf
(LC50
)
cell
line
Subpanel Cell line
GI50/lM
TGI/ LC50
lM lM
/
a
a
Conc. Subpanel SSRd TGI- LC50
-
UACC-257
UACC-62
13.6
10.9
83.5
a
–
–
–
per
cell
line
MIDb
8.27
MIDe MIDf
Ovarian cancer
IGROV1
19.60
0.22 31.02 60.09
a
10.2
2.29
2.10
16.4
2.55
39.0
4.37
3.86
46.6
7.74
–
a
a
a
a
a
a
a
Leukemia
0.52 83.57
a
–
–
–
–
–
–
–
OVCAR-3
8.34
7.08
CCRF-CEM
3.08
12.9
3.19
3.69
23.4
3.33
–
OVCAR-4
a
a
HL-60(TB)
K-562
–
OVCAR-5
–
29.3
72.1
OVCAR-8
36.6
a
a
a
MOLT-4
RPMI-8226
SR
NCI/ADR-
RES
–
–
–
a
–
a
SK-OV-3
Renal cancer
786-0
3.65
15.6
68.6
–
4.09
1.04 33.44 72.36
Non-small cell lung cancer
A549/ATCC
EKVX
4.52
0.94 31.10 71.33
a
2.64
3.18
10.9
3.65
2.39
3.57
2.68
3.68
6.47
a
–
–
–
2.04
6.01
3.19
3.14
5.07
7.25
7.82
2.29
3.90
4.82
36.2
9.48
13.7
a
a
a
A498
–
–
a
ACHN
–
HOP-62
36.2
a
–
a
CAKI-1
18.3
5.14
15.5
5.77
16.3
80.4
14.6
75.3
34.6
74.0
HOP-92
–
a
RXF 393
SN12C
NCI-H226
NCI-H23
NCI-H322M
NCI-H460
NCI-H522
Colon
25.0
a
–
–
a
–
a
TK-10
90.8
5.42
17.1
–
UO-31
20.7
a
Prostate cancer
PC-3
5.44
2.93
0.78 56.15 84.05
a
–
a
7.54
3.33
–
–
6.70
0.64 36.74 64.73
DU-145
12.3
68.1
COLO 205
HCC-2998
HCT-116
HCT-15
2.61
21.1
4.01
10.5
3.11
3.69
1.88
6.84
a
38.3
a
Breast cancer
MCF7
1.46 25.04 83.77
–
–
a
3.22
2.02
17.7
6.10
–
16.1
69.8
8.97
51.6
3.88
71.1
a
–
MDA-MB-
231/ATCC
54.0
HT29
35.7
a
–
a
HS 578T
BT-549
T-47D
2.26
4.02
2.80
7.04
a
–
–
KM12
a
–
SW-620
7.99
a
7.02
12.4
–
CNS cancer
SF-268
3.24
1.32 12.68 36.39
MDA-MB-468 3.30
4.27
48.6
2.07
3.40
3.40
6.75
1.96
1.85
5.32
14.6
3.95
44.3
4.25
3.67
23.4
51.4
27.1
MG-MIDc
21.38 58.88
SF-295
a
SF-539
Parameter not determined in five-dose assay, thus assumed 100 lM
for the purpose of midpoint calculations
a
SNB-19
–
b
Subpanel GI50 midpoint = average sensitivity of subpanel cell lines
toward the test agent
SNB-75
9.18
7.27
U251
c
Mean-graph GI50, TGI, and LC50 midpoints = average sensitivity
of all cell lines toward the test agent
Melanoma
LOX IMVI
5.87
0.73 51.09 88.23
a
a
a
a
3.09
–
–
–
–
d
Subpanel selectivity ratio = subpanel MID:MG-MID
MALME-3 M 6.79
M14 4.51
MDA-MB-435 2.90
25.1
a
e
Subpanel TGI midpoint
–
f
Subpanel LC50 midpoint
10.8
8.73
21.4
10.3
75.0
49.2
69.9
SK-MEL-2
SK-MEL-28
SK-MEL-5
2.64
5.50
2.91
a
–
123

´
K. Broz_ewicz, J. Sławinski
980
2-Benzylthio-4-chloro-5-(1,3,4-oxadiazol-2-yl)benzenesul-
fonamide (2a, C15H12ClN3O3S2)
Table 4 COMPARE correlation coefficients (PCC) calculated using
compound 4c (NSC 754633) as seed, tested in US NCI-60 cell lines
in vitro screen
Starting from 1.47 g 1a and 0.62 g benzyl mercaptan.
Yield: 1.55 g (81%); m.p.: 153–154 °C; Rf = 0.64 (ben-
Rank NSC
Number of cell lines PCC
Compd
ꢀ
zene/EtOH = 4:1); IR (KBr): m = 3,435, 3,332, 3,142,
1
2
3
4
5
6
7
8
3053 59
0.549 Actinomycin D
0.547 Bactobolin
1
2,926, 1,590, 1,532, 1,495, 1,450, 1,350, 1,161 cm-1; H
325014 58
526417 56
305884 58
165563 56
267469 58
58514 55
325319 57
NMR (500 MHz, DMSO-d6): d = 4.54 (s, 2H, SCH2),
7.29–7.32 (m, 1H, Ar–H), 7.36–7.39 (m, 2H, Ar–H),
7.52–7.54 (m, 2H, Ar–H), 7.73 (s, 2H, SO2NH2), 7.84 (s,
1H, H-3), 8.42 (s, 1H, H-6), 9.48 (s, 1H, Ar–H) ppm; 13C
NMR (50 MHz, DMSO-d6): d = 36.16, 118.23, 127.88,
128.89, 129.12, 129.61, 130.29, 135.19, 135.57, 139.55,
143.08, 155.18, 161.33 ppm.
0.520 Echinomycin
0.517 Acodazole HCl
0.511 Bruceantin
0.493 Deoxydoxorubicin
0.455 Chromomycin A3
0.446 Didemnin B
For definitions and methods of calculation of the correlation coeffi-
cient from the COMPARE analysis, see Ref. [39]
2-Benzylthio-4-chloro-5-(5-methyl-1,3,4-oxadiazol-2-yl)-
benzenesulfonamide (2b, C16H14ClN3O3S2)
Starting from 1.54 g 1b and 0.62 g benzyl mercaptan. Yield:
2,4-Dichloro-5-(1,3,4-oxadiazol-2-yl)benzenesulfonamide
(1a, C8H5Cl2N3O3S)
Starting from 8.89 g triethyl orthoformate. Yield: 2.42 g
1.54 g (78%); m.p.: 208–210 °C; Rf = 0.67 (benzene/
ꢀ
EtOH = 4:1); IR (KBr): m = 3,429, 3,246, 2,924, 2,854,
1,624, 1,591, 1,577, 1,558, 1,525, 1,495, 1,347, 1,165 cm-1
;
(82%); m.p.: 195–197 °C; Rf = 0.59 (benzene/EtOH =
1H NMR (500 MHz, DMSO-d6): d = 2.58 (s, 3H, CH3),
4.50 (s, 2H, SCH2), 7.27–7.30 (m, 1H, Ar–H), 7.34–7.37 (m,
2H, Ar–H), 7.44–7.46 (m, 2H, Ar–H), 7.74 (s, 2H, SO2NH2),
7.78 (s, 1H, H-3), 8.35 (s, 1H, H-6) ppm; 13C NMR (50 MHz,
DMSO-d6): d = 10.87, 36.23, 118.89, 127.87, 128.70,
128.96, 129.14, 129.26, 129.33, 129.47, 129.60, 133.49,
135.70, 137.31, 145.04, 161.70, 164.32 ppm.
ꢀ
4:1); IR (KBr): m = 3,323, 3,229, 3,165, 3,100, 1,359,
1,340, 1,168 cm-1 1H NMR (200 MHz, DMSO-d6):
;
d = 7.97 (s, 2H, SO2NH2), 8.20 (s, 1H, H-3), 8.56 (s,
1H, H-6), 9.54 (s, 1H, Ar–H) ppm; 13C NMR (50 MHz,
DMSO-d6): d = 121.84, 131.12, 134.09, 134.56, 136.02,
140.83, 155.47, 160.89 ppm.
2,4-Dichloro-5-(5-methyl-1,3,4-oxadiazol-2-yl)benzenesul-
fonamide (1b, C9H7Cl2N3O3S)
Starting from 9.73 g triethyl orthoacetate. Yield: 2.13 g
4-Chloro-2-(4-chlorobenzylthio)-5-(1,3,4-oxadiazol-2-yl)-
benzenesulfonamide (2c, C15H11Cl2N3O3S2)
Starting from 1.47 g 1a and 0.79 g 4-chlorobenzyl mer-
captan. Yield: 1.58 g (76%); m.p.: 185–187 °C; Rf = 0.63
(69%); m.p.: 217–219 °C; Rf = 0.61 (benzene/EtOH =
ꢀ
4:1); IR (KBr): m = 3,305, 3,205, 3,094, 1,579, 1,542,
ꢀ
(benzene/EtOH = 4:1); IR (KBr): m = 3,248, 3,156, 3,087,
1
1,460, 1,354, 1,174 cm-1; H NMR (200 MHz, DMSO-
2,918, 2,858, 1,589, 1,530, 1,490, 1,440, 1,350, 1,333,
1,162 cm-1; 1H NMR (500 MHz, DMSO-d6): d = 4.55 (s,
2H, SCH2), 7.42–7.44 (m, 2H, Ar–H), 7.55–7.57 (m, 2H,
Ar–H), 7.73 (s, 2H, SO2NH2), 7.84 (s, 1H, H-3), 8.42 (s,
1H, H-6), 9.48 (s, 1H, Ar–H) ppm; 13C NMR (50 MHz,
DMSO-d6): d = 35.29, 118.41, 128.84, 129.32, 130.29,
131.42, 132.49, 134.86, 135.20, 139.74, 142.55, 155.19,
161.29 ppm.
d6): d = 2.64 (s, 3H, CH3), 7.95 (s, 2H, SO2NH2), 8.18 (s,
1H, H-3), 8.51 (s, 1H, H-6) ppm; 13C NMR (50 MHz,
DMSO-d6): d = 10.93, 122.02, 130.75, 134.08, 134.21,
135.74, 140.77, 161.04, 165.08 ppm.
General procedure for the synthesis of 2a–2d
To a suspension of the appropriate 2,4-dichloroben-
zenesulfonamide 1a, 1b (5 mmol) in 30 cm3 MeCN and
0.1 cm3 water, 1.52 g K2CO3 (11 mmol) and 0.016 g
TBAB (0.05 mmol) were added. The obtained reaction
mixture was vigorously stirred under an argon atmosphere,
and slowly the appropriate mercaptan (5 mmol) was added
dropwise. After 24 h of stirring at room temperature, the
reaction mixture was concentrated under reduced pressure
to dryness, and 15 cm3 EtOH was added. The precipitate
was filtered off and suspended in 30 cm3 water, stirred for
30 min, and filtered off. The crude product was purified by
crystallization from EtOH.
4-Chloro-2-(4-chlorobenzylthio)-5-(5-methyl-1,3,4-oxa-
diazol-2-yl)benzenesulfonamide (2d, C16H13Cl2N3O3S2)
Starting from 1.54 g 1b and 0.79 g 4-chlorobenzyl mer-
captan. Yield: 1.79 g (83%); m.p.: 250–252 °C; Rf = 0.68
ꢀ
(benzene/EtOH = 4:1); IR (KBr): m = 3,363, 3,239, 2,925,
2,853, 1,636, 1,587, 1,574, 1,559, 1,520, 1,493, 1,456,
1,349, 1,167 cm-1
;
1H NMR (500 MHz, DMSO-d6):
d = 2.59 (s, 3H, CH3), 4.51 (s, 2H, SCH2), 7.41–7.43
(m, 2H, Ar–H), 7.47–7.49 (m, 2H, Ar–H), 7.76–7.77 (m,
3H, H-3 and SO2NH2), 8.35 (s, 1H, H-6) ppm; 13C NMR
(50 MHz, DMSO-d6): d = 10.87, 35.36, 119.03, 128.78,
123

Synthesis and in vitro activity
981
128.94, 129.48, 131.27, 132.50, 133.51, 134.94, 137.44,
144.62, 161.67, 164.34 ppm.
4-(N,N-Dimethylamino)pyridinium 2-benzylthio-4-
chloro-5-(1,3,4-oxadiazol-2-yl)-N-(thien-2-ylcarbonyl)-
benzenesulfonamidate (3c, C27H24ClN5O4S3)
General procedure for the synthesis of 2-benzylthio-
4-chloro-5-(1,3,4-oxadiazol-2-yl)-
4-(N,N-dimethylamino)pyridinium
Starting from 0.141 g thiophene-2-carboxylic acid. Yield:
0.295 g (48%); m.p.: 201–202 °C; Rf = 0.16 (benzene/
ꢀ
EtOH = 4:1); IR (KBr): m = 3,214, 3,090, 2,924, 1,649,
N-acylbenzenesulfonamidates 3a–3c
1,591, 1,565, 1,315, 1,138 cm-1 1H NMR (200 MHz,
;
DMSO-d6): d = 3.17 (s, 6H, N(CH3)2), 4.33 (s, 2H,
SCH2), 6.94–6.98 (m, 3H, Ar–H), 7.18–7.21 (m, 3H, Ar–
H), 7.36–7.38 (m, 3H, Ar–H), 7.49–7.50 (m, 2H, H-3 and
Ar–H), 8.18–8.22 (m, 2H, Ar–H), 8.44 (s, 1H, H-6), 9.43
(s, 1H, Ar–H), 13.18 (br s, 1H, NH?) ppm; 13C NMR
(50 MHz, DMSO-d6): d = 35.75, 107.20, 116.90, 127.31,
127.49, 128.66, 128.90, 129.04, 129.31, 129.56, 132.09,
133.14, 136.22, 139.51, 142.21, 143.27, 145.46, 154.93,
157.14, 161.81, 165.81 ppm.
To the appropriate carboxylic acid (1.1 mmol) in 5 cm3 dry
MeCN, 0.212 g 1-ethyl-3-(3-dimethylaminopropyl)carbo-
diimide hydrochloride (EDCI, 1.1 mmol) was added and
stirred for 5 min. 2a (0.382 g, 1 mmol) and 0.256 g DMAP
(2.1 mmol) were added, and the reaction mixture was
stirred at room temperature overnight. The precipitate was
filtered off and washed with cold MeCN and MeOH. The
crude salt was purified by crystallization from MeOH.
4-(N,N-Dimethylamino)pyridinium 2-benzylthio-
4-chloro-5-(1,3,4-oxadiazol-2-yl)-N-(pyrazine-2-carbonyl)-
benzenesulfonamidate (3a, C27H24ClN7O4S2)
General procedure for the synthesis of
N-acylbenzenesulfonamides 4a–4c
Starting from 0.137 g pyrazine-2-carboxylic acid. Yield:
To a suspension of the appropriate pyridinium salt 3a–3c
(0.5 mmol) in 5 cm3 EtOH, 2 cm3 10% p-TSA solution in
EtOH was added and stirred at room temperature for 1 h.
The precipitate was filtered off and washed with EtOH and
water.
0.338 g (55%); m.p.: 209–210 °C; Rf = 0.14 (benzene/
ꢀ
EtOH = 4:1); IR (KBr): m = 3,198, 3,109, 3,056, 2,924,
1
1,646, 1,612, 1,589, 1,562, 1,498, 1,323, 1,142 cm-1; H
NMR (200 MHz, DMSO-d6): d = 3.17 (s, 6H, N(CH3)2),
4.35 (s, 2H, SCH2), 6.94–6.98 (m, 2H, Ar–H), 7.19–7.22
(m, 3H, Ar–H), 7.32–7.37 (m, 2H, Ar–H), 7.58 (s, 1H, H-
3), 8.20–8.23 (m, 2H, Ar–H), 8.49 (s, 1H, H-6), 8.62–8.63
(m, 2H, Ar–H), 9.09 (s, 1H, Ar–H), 9.44 (s, 1H, Ar–H),
13.22 (br s, 1H, NH?) ppm; 13C NMR (50 MHz, DMSO-
d6): d = 35.76, 107.14, 117.12, 127.52, 127.67, 128.64,
129.25, 132.10, 133.50, 136.12, 139.51, 141.52, 143.23,
144.00, 145.22, 145.57, 150.80, 154.98, 157.13, 161.75,
167.83 ppm.
2-Benzylthio-4-chloro-5-(1,3,4-oxadiazol-2-yl)-N-
(pyrazine-2-carbonyl)benzenesulfonamide
(4a, C20H14ClN5O4S2)
Yield: 0.242 g (99%); m.p.: 294–296 °C; Rf = 0.10 (ben-
ꢀ
zene/EtOH = 4:1); IR (KBr): m = 3,485, 3,364, 3,298,
3,203, 2,871, 1,612, 1,585, 1,549, 1,492, 1,450, 1,362,
1,159 cm-1; 1H NMR (500 MHz, DMSO-d6): d = 4.51 (s,
2H, SCH2), 7.08–7.17 (m, 3H, Ar–H), 7.29–7.31 (m, 2H,
Ar–H), 7.89 (s, 1H, H-3), 8.58 (s, 1H, H-6), 8.81 (s, 1H,
Ar–H), 8.94 (s, 1H, Ar–H), 9.08 (s, 1H, Ar–H), 9.47 (s, 1H,
Ar–H) ppm; 13C NMR (50 MHz, DMSO-d6): d = 35.98,
118.54, 127.81, 128.61, 129.27, 129.74, 133.91, 135.58,
136.99, 143.88, 144.09, 144.87, 148.89, 155.25, 161.03,
163.39, 163.44 ppm.
4-(N,N-Dimethylamino)pyridinium 2-benzylthio-4-
chloro-5-(1,3,4-oxadiazol-2-yl)-N-(pyridine-2-carbonyl)-
benzenesulfonamidate (3b, C28H25ClN6O4S2)
Starting from 0.135 g pyridine-2-carboxylic acid. Yield:
0.219 g (36%); m.p.: 217–219 °C; Rf = 0.22 (benzene/
ꢀ
EtOH = 4:1); IR (KBr): m = 3,195, 3,107, 2,924, 1,646,
1
1,607, 1,588, 1,562, 1,496, 1,324, 1,141 cm-1; H NMR
2-Benzylthio-4-chloro-5-(1,3,4-oxadiazol-2-yl)-N-
(pyridine-2-carbonyl)benzenesulfonamide
(4b, C20H14ClN5O4S2)
(200 MHz, DMSO-d6): d = 3.16 (s, 6H, N(CH3)2), 4.32 (s,
2H, SCH2), 6.91–6.95 (m, 2H, Ar–H), 7.18–7.21 (m, 3H,
Ar–H), 7.31–7.32 (m, 2H, Ar–H), 7.41–7.45 (m, 1H, Ar–
H), 7.57 (s, 1H, H-3), 7.78–7.86 (m, 1H, Ar–H), 7.94–7.98
(m, 1H, Ar–H), 8.23–8.26 (m, 2H, Ar–H), 8.50 (s, 1H,
H-6), 8.55–8.57 (m, 2H, Ar–H), 9.45 (s, 1H, Ar–H), 13.20
(br s, 1H, NH?) ppm; 13C NMR (50 MHz, DMSO-d6):
d = 35.80, 107.05, 117.09, 123.74, 125.21, 127.49, 127.65,
128.63, 129.26, 132.30, 133.45, 136.04, 136.91, 139.89,
141.62, 143.21, 148.68, 154.99, 155.48, 157.00, 161.77,
169.37 ppm.
Yield: 0.241 g (99%); m.p.: 173–175 °C; Rf = 0.40 (ben-
ꢀ
zene/EtOH = 4:1); IR (KBr): m = 3,138, 2,924, 2,854,
1,730, 1,647, 1,590, 1,530, 1,496, 1,450, 1,347,
1,174 cm-1 1H NMR (200 MHz, DMSO-d6): d = 4.47
;
(s, 2H, SCH2), 7.02–7.19 (m, 3H, Ar–H), 7.26–7.30 (m,
2H, Ar–H), 7.82 (s, 1H, H-3), 7.88–7.95 (m, 1H, Ar–H),
8.12–8.16 (m, 1H, Ar–H), 8.26–8.35 (m, 1H, Ar–H), 8.57
(s, 1H, H-6), 8.76–8.78 (m, 1H, Ar–H), 9.47 (s, 1H, Ar–H)
ppm; 13C NMR (50 MHz, DMSO-d6): d = 35.82, 118.20,
123

´
K. Broz_ewicz, J. Sławinski
982
124.54, 127.67, 128.58, 128.79, 129.19, 129.30, 133.37,
135.73, 136.07, 136.66, 141.76, 143.52, 146.77, 147.41,
155.18, 161.20, 162.66 ppm.
2,925, 2,854, 1,658, 1,591, 1,577, 1,525, 1,495, 1,453,
1,361, 1,176 cm-1
;
1H NMR (500 MHz, DMSO-d6):
d = 2.62 (s, 3H, CH3), 4.50 (s, 2H, SCH2), 7.21–7.23
(m, 1H, Ar–H), 7.28–7.31 (m, 1H, Ar–H), 7.34–7.37 (m,
2H, Ar–H), 7.44–7.46 (m, 2H, Ar–H), 7.79 (s, 1H, H-3),
7.97–7.98 (m, 1H, Ar–H), 8.15–8.16 (m, 1H, Ar–H), 8.50
(s, 1H, H-6) ppm; 13C NMR (50 MHz, DMSO-d6):
d = 10.87, 36.39, 118.83, 127.98, 128.56, 129.02,
129.56, 132.56, 132.64, 133.06, 133.48, 135.35, 135.48,
136.27, 147.66, 160.11, 161.39, 164.43 ppm.
2-Benzylthio-4-chloro-5-(1,3,4-oxadiazol-2-yl)-N-(thien-2-
ylcarbonyl)benzenesulfonamide (4c, C20H14ClN3O4S3)
Yield: 0.244 g (99%); m.p.: 282–284 °C; Rf = 0.12 (ben-
ꢀ
zene/EtOH = 4:1); IR (KBr): m = 3,382, 3,354, 3,253,
3,106, 1,614, 1,601, 1,579, 1,565, 1,549, 1,332, 1,318,
1,176 cm-1; 1H NMR (200 MHz, DMSO-d6): d = 4.51 (s,
2H, SCH2), 7.30–7.76 (m, 12H, H-3 and Ar–H), 8.35 (s,
1H, H-6) ppm; 13C NMR (50 MHz, DMSO-d6): d = 36.26,
118.90, 119.01, 126.03, 127.87, 128.46, 128.72, 128.96,
129.25, 129.50, 132.64, 135.75, 137.16, 137.65, 144.38,
155.74, 159.68 ppm.
4-Chloro-2-(4-chlorobenzylthio)-5-(5-methyl-1,3,4-
oxadiazol-2-yl)-N-(thien-2-ylcarbonyl)-
benzenesulfonamide (4f, C21H15Cl2N3O4S3)
To a solution of 0.128 g thiophene-2-carboxylic acid
(1 mmol) in 5 cm3 dry tetrahydrofuran (THF), 0.206 g
1,3-dicyclohexylcarbodiimide (DCC, 1 mmol) was added
and stirred for 5 min at room temperature. 2d (0.430 g,
1 mmol) and 0.184 g DMAP (1.5 mmol) were added and
stirred at room temperature for 48 h. By-products were
filtered out and washed thoroughly with THF. The filtrate
was acidified with 2 cm3 10% p-TSA/EtOH and concen-
trated under reduced pressure, and the resulting oily residue
was chromatographed with AcOEt/petroleum ether (1:1) on
silica gel column giving pure 4f. Yield: 0.135 g (25%);
m.p.: 134–136 °C; Rf = 0.22 (benzene/EtOH = 4:1); IR
4-Chloro-2-(4-chlorobenzylthio)-5-(1,3,4-oxadiazol-2-yl)-
N-(thien-2-ylcarbonyl)benzenesulfonamide
(4d, C20H13Cl2N3O4S3)
To a solution of 0.128 g thiophene-2-carboxylic acid
(1 mmol) in 3 cm3 dry MeCN, 0.192 g EDCI (1 mmol)
was added and stirred at room temperature for 5 min. 2c
(0.416 g, 1 mmol) and 0.184 g DMAP (1.5 mmol) were
added and stirred at room temperature for 18 h. The
reaction mixture was acidified with 2 cm3 10% p-TSA/
MeCN and concentrated under reduced pressure, and the
residue was chromatographed with CH2Cl2/MeOH/AcOH
(97:1:2) on silica gel column giving pure 4d. Yield:
0.248 g (47%); Rf = 0.16 (benzene/EtOH = 4:1); m.p.:
ꢀ
(KBr): m = 3,422, 2,925, 2,855, 1,654, 1,575, 1,523, 1,490,
1
1,360, 1,261, 1,169 cm-1; H NMR (200 MHz, DMSO-
d6): d = 2.63 (s, 3H, CH3), 4.52 (s, 2H, SCH2), 7.20–7.24
(m, 1H, Ar–H), 7.39–7.51 (m, 4H, Ar–H), 7.77 (s, 1H,
H-3), 7.97–7.99 (m, 2H, Ar–H), 8.15–8.17 (m, 1H, Ar–H),
8.51 (s, 1H, H-6) ppm; 13C NMR (50 MHz, DMSO-d6):
d = 10.58, 35.22, 118.62, 128.30, 128.48, 128.71, 131.06,
132.34, 132.76, 133.20, 134.27, 135.18, 135.97, 146.95,
159.82, 161.06, 164.15 ppm.
ꢀ
205–207 °C; IR (KBr): m = 3,164, 3,094, 2,841, 1,678,
1
1,591, 1,526, 1,491, 1,450, 1,352, 1,262, 1,170 cm-1; H
NMR (200 MHz, DMSO-d6): d = 4.55 (s, 2H, SCH2),
7.08–7.12 (m, 2H, Ar–H), 7.23–7.27 (m, 1H, Ar–H), 7.32–
7.37 (m, 2H, Ar–H), 7.44–7.46 (m, 1H, Ar–H), 7.90 (s, 1H,
H-3), 7.97–8.00 (m, 1H, Ar–H), 8.53 (s, 1H, H-6), 9.48 (s,
1H, Ar–H) ppm; 13C NMR (50 MHz, DMSO-d6):
d = 35.02, 118.77, 128.57, 129.02, 129.97, 131.00,
131.35, 132.37, 133.00, 134.08, 134.90, 135.32, 135.43,
136.59, 136.95, 142.89, 155.23, 159.97, 160.99 ppm.
2-Benzylthio-4-chloro-N-(5-chlorothien-2-ylcarbonyl)-5-
(1,3,4-oxadiazol-2-yl)benzenesulfonamide
(4g, C20H13Cl2N3O4S3)
To a solution of 0.164 g 5-chlorothiophene-2-carboxylic
acid (1 mmol) in 5 cm3 dry MeCN, 0.192 g EDCI
(1 mmol) was added and stirred at room temperature for
5 min. 2a (0.382 g, 1 mmol) and 0.184 g DMAP
(1.5 mmol) were added and stirred at room temperature
for 12 h. The obtained solution was acidified with 2 cm3
10% p-TSA/MeCN and stirred under cooling (ice bath) for
2 h. The precipitated white solid was filtered off and
purified by crystallization from MeCN. Yield: 0.268 g
(51%); m.p.: 254–255 °C; Rf = 0.12 (benzene/EtOH =
2-Benzylthio-4-chloro-5-(5-methyl-1,3,4-oxadiazol-2-yl)-
N-(thien-2-ylcarbonyl)benzenesulfonamide
(4e, C21H16ClN3O4S3)
To a solution of 0.128 g thiophene-2-carboxylic acid
(1 mmol) in 3 cm3 dry MeCN, 0.192 g EDCI (1 mmol)
was added and stirred for 5 min. 2b (0.396 g, 1 mmol) and
0.184 g DMAP (1.5 mmol) were added and stirred at room
temperature for 18 h. The obtained solution was concen-
trated under reduced pressure, and 2 cm3 10% p-TSA/
EtOH was added with vigorous stirring. The obtained
suspension was left in the refrigerator overnight. The
formed crystalline solid was filtered off and washed with
cold EtOH. Yield: 0.213 g (42%); m.p.: 230–231 °C;
ꢀ
4:1); IR (KBr): m = 3,160, 3,098, 2,924, 2,855, 2,717,
1,683, 1,592, 1,559, 1,531, 1,472, 1,351, 1,328,
1,168 cm-1 1H NMR (500 MHz, DMSO-d6): d = 4.51
;
(s, 2H, SCH2), 7.15–7.22 (m, 3H, Ar–H), 7.24–7.25 (s, 1H,
ꢀ
Rf = 0.17 (benzene/EtOH = 4:1); IR (KBr): m = 3,098,
Ar–H), 7.33–7.35 (m, 2H, Ar–H), 7.83 (s, 1H, H-3), 7.87
123

Synthesis and in vitro activity
983
(s, 1H, Ar–H), 8.49 (s, 1H, H-6), 9.46 (s, 1H, Ar–H) ppm;
13C NMR (50 MHz, DMSO-d6): d = 35.64, 118.22,
127.52, 128.39, 128.81, 129.01, 129.37, 132.56, 133.56,
134.98, 135.25, 135.75, 136.51, 136.62, 143.19, 154.91,
159.11, 160.73 ppm.
130.41, 130.80, 134.00, 134.79, 135.39, 136.95, 138.61,
143.69, 155.24, 161.03, 164.52 ppm.
2-Benzylthio-4-chloro-5-(1,3,4-oxadiazol-2-yl)-N-
(3,4,5-trimethoxybenzoyl)benzenesulfonamide
(4j, C25H22ClN3O7S2)
2-Benzylthio-4-chloro-5-(1,3,4-oxadiazol-2-yl)-N-
(pyridine-3-carbonyl)benzenesulfonamide
(4h, C21H15ClN4O4S2)
To a suspension of 0.233 g 3,4,5-trimethoxybenzoic acid
(1.1 mmol) in 5 cm3 dry MeCN, 0.227 g DCC (1.1 mmol)
was added and stirred at room temperature for 5 min. 2a
(0.382 g, 1 mmol) and 0.184 g DMAP (1.5 mmol) were
added and stirred at room temperature for 20 h. The
precipitate was filtered off and suspended in 5 cm3 EtOH,
acidified with 2 cm3 10% p-TSA/EtOH, and stirred under
cooling (ice bath) for 5 min. The crude product was filtered
off and purified by crystallization from EtOH. Yield:
0.366 g (64%); m.p.: 245–247 °C; Rf = 0.29 (benzene/
To a suspension of 0.135 g pyridine-3-carboxylic acid
(1.1 mmol) in 5 cm3 dry MeCN, 0.212 g EDCI (1.1 mmol)
was added and stirred for 5 min at room temperature. 2a
(0.382 g, 1 mmol) and 0.184 g DMAP (1.5 mmol) were
added and stirred for 18 h at room temperature. The
precipitate was filtered off, washed with MeCN, and then
suspended in 1 cm3 EtOH, acidified with 1 cm3 10%
p-TSA/EtOH, and stirred for 2 h at room temperature. The
precipitate was filtered off, washed with EtOH, and purified
by extraction of contaminants with hot MeCN. Yield:
0.122 g (25%); m.p.: 282–284 °C; Rf = 0.30 (benzene/
ꢀ
EtOH = 4:1); IR (KBr):m = 3,442, 3,158, 3,092, 2,962,
2,931, 2,841, 1,697, 1,595, 1,526, 1,511, 1,460, 1,331,
1,162 cm-1; 1H NMR (200 MHz, DMSO-d6): d = 3.73 (s,
3H, OCH3), 3.78 (s, 6H, 2OCH3), 4.56 (s, 2H, SCH2),
7.16–7.36 (m, 7H, Ar–H), 7.90 (s, 1H, H-3), 8.59 (s, 1H,
H-6), 9.49 (s, 1H, Ar–H) ppm; 13C NMR (50 MHz, DMSO-
d6): d = 36.01, 56.38, 60.45, 106.49, 118.49, 125.99,
127.87, 128.74, 129.39, 134.16, 134.79, 135.32, 136.94,
142.05, 143.73, 152.93, 155.25, 161.05, 164.81 ppm.
ꢀ
EtOH = 4:1); IR (KBr): m = 3,436, 3,096, 3,060, 2,926,
1
1,633, 1,589, 1,565, 1,520, 1,495, 1,355, 1,135 cm-1; H
NMR (200 MHz, DMSO-d6): d = 4.47 (s, 2H, SCH2),
7.20–7.33 (m, 5H, Ar–H), 7.73–7.78 (m, 2H, H-3 and
Ar–H), 8.49–8.55 (m, 2H, H-6 and Ar–H), 8.85–8.87 (m,
1H, Ar–H), 8.09 (s, 1H, Ar–H), 8.47 (s, 1H, Ar–H) ppm;
13C NMR (50 MHz, DMSO-d6): d = 35.88, 117.98,
125.11, 127.74, 127.96, 128.74, 129.29, 131.77, 133.19,
135.59, 135.76, 137.50, 139.95, 143.52, 146.76, 149.56,
155.14, 161.32, 164.82 ppm.
NCI in vitro anticancer screen
As of early 2007 all compounds submitted to the NCI-60
cell screen are tested initially at a single high dose (10 lM)
in the full NCI-60 cell panel representing human leukemia,
melanoma and lung, colon, brain, breast, ovary, kidney,
and prostate cancers. Briefly, the compounds were solubi-
lized in DMSO and added at a single concentration, and the
cell culture was incubated for 48 h at 37 °C, 5% CO2, 95%
air, and 100% relative humidity. End points were deter-
mined by colorimetric sulforhodamine B (SRB) assay [40].
Results for each compound were reported as a mean-graph
of the percent growth of the treated cells relative to the no-
drug control, and relative to the time-zero number of cells.
This allows detection of both growth inhibition (values
between 0 and 100) and lethality (values less than 0) [41].
According to Developmental Therapeutics Program (DTP)
anticancer screening paradigm, after obtaining the results
for one-dose assay, careful analysis of DTP screening data
was performed and compound 4c (NSC 754633) which
satisfied predetermined threshold inhibition criteria was
selected for the NCI five-dose (0.01–100 lM) assay. The
results were used to create dose–response curves (log10 of
sample concentration versus % growth), and three response
parameters (GI50, TGI, and LC50) were calculated for each
cell line. GI50 measures the growth inhibitory power of the
2-Benzylthio-4-chloro-N-(4-chlorobenzoyl)-5-
(1,3,4-oxadiazol-2-yl)benzenesulfonamide
(4i, C22H15Cl2N3O4S2)
To a solution of 0.172 g 4-chlorobenzoic acid (1.1 mmol)
in 5 cm3 dry MeCN, 0.227 g DCC (1.1 mmol) was added
and stirred at room temperature for 5 min. 2a (0.382 g,
1 mmol) and 0.184 g DMAP (1.5 mmol) were added and
stirred at room temperature for 72 h. By-products were
filtered out and washed thoroughly with MeCN. The filtrate
was concentrated under reduced pressure to dryness.
MeOH (2 cm3) was added, and the obtained mixture was
slowly acidified with 5 M hydrochloric acid. The formed
precipitate was filtered off and washed with EtOH and
water. The crude product was purified by crystallization
from EtOH. Yield: 0.292 g (56%); m.p.: 275–277 °C;
ꢀ
Rf = 0.25 (benzene/EtOH = 4:1); IR (KBr):m = 3,162,
3,080, 2,929, 2,854, 1,698, 1,592, 1,531, 1,492, 1,462,
1,348, 1,168 cm-1
;
1H NMR (500 MHz, DMSO-d6):
d = 4.56 (s, 2H, SCH2), 7.14–7.21 (m, 3H, Ar–H),
7.32–7.36 (m, 2H, Ar–H), 7.57–7.62 (m, 2H, H-3 and
Ar–H), 7.88–7.95 (m, 3H, Ar–H), 8.57 (s, 1H, H-6), 9.48
(s, 1H, Ar–H) ppm; 13C NMR (50 MHz, DMSO-d6):
d = 35.99, 118.53, 127.90, 128.80, 128.99, 129.36, 129.51,
123

´
K. Broz_ewicz, J. Sławinski
984
´
21. Kuo CL, Assefa H, Kamath S, Brzozowski Z, Sławinski J,
test agent, TGI signifies a cytostatic effect, and LC50 sig-
nifies a cytotoxic effect.
Sa˛czewski F, Buolamwini JK, Neamati N (2004) J Med Chem
47:385
22. Corbett TH, White K, Polin L, Kushner J, Paluch J, Shih C,
Grossman CS (2003) Investig New Drug 21:33
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liams RR, De Alwis DP, Zimmermann A, Brown MP, Ilaria RL
Jr, Millward MJ (2011) Cancer. doi:10.1002/cncr.26068
Acknowledgments The authors are very grateful to Dr. Joel Morris,
Chief of Drug Synthesis and Chemistry Branch (DSCB), National
Cancer Institute (Bethesda, MD) for the in vitro screening.
Open Access This article is distributed under the terms of the
Creative Commons Attribution License which permits any use, dis-
tribution, and reproduction in any medium, provided the original
author(s) and the source are credited.
ˇ ´
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