Cytostatic activity of novel 4′-aminochalcone-based imides

Article abstract of DOI:10.1016/j.bmcl.2007.05.094

A series of nine 1-(4-((E)-3-arylacryloyl)phenyl)-1H-pyrrole-2,5-diones 3a-i (4′-aminochalcone-based maleimides) was synthesized as candidate cytotoxic agents. The efficacy of these potential cytotoxics were evaluated against three representative cell lin

Full text of DOI:10.1016/j.bmcl.2007.05.094

Bioorganic & Medicinal Chemistry Letters 17 (2007) 4545–4550
Cytostatic activity of novel 40-aminochalcone-based imides
Amitabh Jha,a,* Chandrani Mukherjee,a Alfred J. Rolle,a Erik De Clercq,b
Jan Balzarinib and James P. Stablesc
aDepartment of Chemistry, Acadia University, Wolfville, NS, Canada B4P 2R6
bRega Institute for Medical Research, Kathiolieke Universiteit Leuven, B-3000 Leuven, Belgium
cNational Institute of Neurological Disorders and Stroke, Rockville, MD 20852, USA
Received 16 April 2007; revised 29 May 2007; accepted 30 May 2007
Available online 7 June 2007
Abstract—A series of nine 1-(4-((E)-3-arylacryloyl)phenyl)-1H-pyrrole-2,5-diones 3a–i (40-aminochalcone-based maleimides) was
synthesized as candidate cytotoxic agents. The efficacy of these potential cytotoxics were evaluated against three representative cell
lines and more than half of the drug candidates proved to exhibit significant cytostatic activity in vitro. QSAR studies using statis-
tical analyses on several physicochemical parameters and IC50 values resulted in a few very important correlations which will aid in
later the amplification of the project. Representative test compounds were well tolerated by mice in in vivo survival and toxicity
studies.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Chemists have long sought a ‘magic bullet’ for the treat-
ment of cancer, a compound that will selectively kill can-
cerous cells without affecting the normal cells. A number
of chalcones (i.e., 1,3-diaryl-2-propen-1-ones) have dem-
onstrated cytotoxic and anticancer properties because of
their preferential reactivity toward cellular thiols in con-
trast to amino and hydroxy groups found in nucleic
acids.1–4 Hence, these compounds may be free from
the problems of mutagenicity and carcinogenicity that
are associated with a number of alkylating agents used
in cancer chemotherapy.
ophilic addition involving reactive thiols of key
regulatory enzymes.
Pharmacological activity of cyclic imides, a type of cyc-
lic a,b-unsaturated ketones, has been extensively ex-
plored,9–14 such as the F-ring of the indolocarbazole
antitumor drug NB-506 (Fig. 1) which was found to in-
crease the cytotoxicity, DNA binding, and topoisomer-
ase
I
inhibition activities.14 N-Methyl maleimide
(NMM, Fig. 1) and N-ethyl maleimide (NEM, Fig. 1)
are also examples of potent thiol-alkylators of topoiso-
merase II and have been widely investigated.5,15,16
Thiol-alkylators such as chalcones are most commonly
associated with enzymes; in particular, topoisomerase
II which is unusually rich in cysteine residues.5 Topoi-
somerases participate in DNA replication by facilitating
cleavage of the DNA template. Any interruption in this
intricate process can lead to potentially lethal DNA
strand breaks, which may induce apoptosis.6 The affinity
of thiol-alkylators for topoisomerase II, a regulator of
DNA topology, offers a means of selectivity.7,8 In the
case of thiol-alkylators, such as a,b-unsaturated ke-
tones, inhibition of tumor growth arises through nucle-
The present work was aimed at investigating the cyto-
toxic efficacy of novel electrophilic thiol-alkylators
related to 40-aminochalcone (1). We have reported the
cytotoxic potencies of 40-aminochalcones (1a–d, g;
Fig. 1) and 40-aminochalcone maleamic acids (2a–g;
Fig. 1) against human Molt 4/C8 and CEM T-lympho-
cytes as well as murine P388 and L1210 leukemic cells.17
The molecules 3a–i (Fig. 1) are derived from the hybrid-
ization of two kinds of a,b-unsaturated ketones (Mi-
chael acceptors), a chalcone and a maleimide, both of
which have shown notable anti-cancer properties inde-
pendently.5,15–20 Our design seeks to optimize the
potency of single Michael acceptors by providing multi-
ple sites of reactivity toward cellular thiols. Importantly,
these mild alkylating agents address the issue of
Keywords: Chalcone; Maleimides; Cytostatic activity; Thiol-alkylators;
QSAR.
*
Corresponding author. Tel.: +1 902 585 1515; fax +1 902 585 1414;
e-mail: ajha@acadiau.ca
0960-894X/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.05.094

4546
A. Jha et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4545–4550
OH
OH
H2N
R2
R1
HN
N
F
α'
O
O
β'
β'
O
1a-d,g
O
O
HN
OH
R2
R1
N R
O
α
C
OH
OH
A
E
B
N
D
O
β
β
N
α'
O
O
2a-i
NMM, R=CH3
NEM, R=CH2CH3
H
C
R2
R1
O
N
α
B
HO
A
O
OH
O
3a-i
NB-506
Figure 1. Molecular structures of NMM, NEM, NB-506, and 40-aminochalcone derivatives 1–3. The aryl substituents in series 1–3 are as follows: a:
R1 = R2 = H; b: R1 = H, R2 = Cl; c: R1 = R2 = Cl; d: R1 = H, R2 = CH3; e: R1 = H, R2 = OCH3; f: R1 = R2 = OCH3; g: R1 = H, R2 = NO2; h:
R1 = H, R2 = CO2H; i: R1 = R2 = –OCH2O–.
genotoxicity that is characteristic of non-specific cellular
alkylators.
toxicity for malignant cells. In particular, if cytotoxicity
was influenced by the chemical reactivity of the enone
group, a correlation between the IC50 values of 3a–i
and Hammett r values and/or partial atomic charges
on electrophilic carbons should emerge.
Series 3a–i are second generation derivatives aimed at
enhancing the cytotoxic potency of compounds in series
2. Drawbacks of the compounds in series 2 include ion-
ization of the maleamic carboxylic acid which slows
their transmembrane movement.17 In series 3, the malea-
mic carboxylate of series 2 was replaced by the malei-
mide functionality. The retained chalcone moiety
allows tuning of electronic and steric properties as well
as lipophilic character. Although both series of com-
pounds (2 and 3) have two electrophilic alkene sites
(b-carbon atom and either the a0 or b0-carbons, Fig. 1)
susceptible to Michael additions involving cellular thi-
ols, compounds of series 3 are expected to show en-
hanced electrophilicity owing to maleimide moiety.
Maleimide ring is anti-aromatic (4p electrons) and
strained (bond angles ꢀ108ꢁ as opposed to 120ꢁ for
sp2 C), and is therefore less stable. Thiolation of malei-
mide ring will not only release some angular strain, but
it will also result into an aromatic system when viewed
in enolic form. The two electrophilic a,b-unsaturated ke-
tones will likely allow sequential alkylation of two reac-
tive thiols by a single agent. Sequential chemical insults
result in enhanced cytotoxicity against tumor cells rela-
tive to healthy cells.21 Hence the compounds in series 3
should have the potential to display preferential cyto-
The target compounds were prepared as shown in
Scheme 1. Claisen-Schmidt condensation of 40-acetyl-
N-maleanilinic acid and various aryl aldehydes under
basic conditions afforded the 40-aminochalcone-malea-
mic acids 2a–i.17 The reaction between 40-aminoace-
tophenone and maleic anhydride produced the
precursor 40-acetyl-N-maleanilinic acid.22 The desired
chalcone-imides 3a–i were obtained on dehydration of
40-aminochalcone-maleamic acids 2a–i. New com-
pounds viz. 2h, 2i, and 3a–i were completely character-
ized based on their spectroscopic data.23
All the compounds in chalcone-imide series 3 were eval-
uated against human Molt 4/C8 and CEM T-lympho-
cytes as well as against L1210 leukemia cells following
a literature procedure.24 These data are presented in
Table 1. The clinically approved cytotoxic drug
Alkeranꢂ (i.e., melphalan) was used as a reference drug
which is also known to sequentially conjugate with sulf-
hydryl groups.25 Three representative compounds (3b,
3e, and 3h) were also evaluated in short-term survival
and neurotoxicity assays in mice.
R2
R1
H
H
O
N
R2
R1
O
N
O
O
OHC
aq. KOH
HO
HO
O
2a-i
O
O
NaOAc, Ac2O
N
R2
R1
O
O 3a-i
Scheme 1. Synthetic scheme for preparing compounds 2a–i and 3a–i. R1 and R2 substituents are indicated in Figure 1 legend.

A. Jha et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4545–4550
4547
Table 1. Cytostatic potency of compounds 3a–i against human Molt 4/
C8 and CEM T-lymphocytes and murine L1210 cell lines
logical pH and temperature. This resulted in formation
of di-benzylthio adduct (4, Scheme 2)23c which qualita-
tively substantiates our claim of sequential chemical in-
sult by these types of compounds to cellular thiols.
Compound
IC50 (lM)
L1210
Molt 4/C8
CEM
3a
3b
8.6 2.2
7.3 0.4
6.5 0.9
1.5 0.7
9.8 6.7
157 0.7
>500
9.5 0.1
7.5 1.0
8.8 0.5
2.4 0.6
7.9 0.5
202 36
>500
9.8 0.3
7.5 0.3
7.7 0.7
4.1 2.7
8.4 0.3
The disparity in activity in highly related compounds
(Table 1) required a systematic quantitative structure-
activity relationship (QSAR)27 study to understand the
effect of structural and electronic properties of the mol-
ecule on cytostatic potency. Physicochemical parameters
of the molecule and/or aromatic substituents such as cal-
culated partial charge,28 calculated partition coefficients
(cLogP),28 Hammett r,29 Hansch p29, and molar refrac-
tivity (MR)29 were used for statistical correlation stud-
ies. The calculated atomic charges at various
electrophilic carbon atoms of compounds 3a–i are pre-
sented in Table 2. The partial atomic charges on carbons
designated a0 and b0 (Fig. 1 and Table 2) were found to
be nearly identical across the series presumably because
substitutions on aromatic ring A have little or no elec-
tronic effect on these carbons, therefore these values
were not used for QSAR studies.
3c
3d
3e
3f
3g
220
>500
1
3h
3i
135 99
160 99
2.13 0.03
178
214 47
6
133 97
258 69
2.47 0.03
Alkeranꢂa
3.24 0.79
a The data for Alkeranꢂ are reproduced from the Eur. J. Med. Chem.
35, 970 (2000).
Human Molt 4/C8 and CEM T-lymphocyte cell lines
were chosen to obtain an appreciation of the toxicity
of these compounds toward human mutated cells. The
murine L1210 cytotoxicity assay is regarded as a predic-
tor of clinically useful anticancer drugs.26 From the data
in Table 1, the following observations were made: first,
nearly half of the compounds (3a–e) displayed notewor-
thy cytostatic activity against the three cell lines.
Although slightly inferior to Alkeranꢂ, compounds
3a–c and 3e showed cytotoxic potencies of the same or-
der of magnitude. Second, compound 3d was as potent
as Alkeranꢂ against all three cell lines when standard
deviations were taken into consideration. There was a
strong correlation of the cytostatic potency between
the three tumor cell lines. This observation points to a
common molecular mechanism of cytostatic activity
that is present across three different tumor cell lines.
Compounds 3f–i were essentially inactive. With compa-
rable IC50 values for the cytostatic potential of com-
pounds 3a–c and their precursors 1a–c,17 the presence
of maleimido group on 3a–c did not appear to signifi-
cantly influence the bioactivity. However, the tolyl ana-
log 3d was found to be 6.9, 3.5, and 2.1 times more
active than the corresponding 40-aminochalcone analog
1d for L1210, Molt 4/C8, and CEM lymphocytic cell
lines, respectively.
Linear and semilogarithmic correlations were gener-
ated30 for the IC50 of each cell line and physicochemical
parameters using statistical analysis. The only significant
correlations obtained are tabulated in Table 3. The va-
lue of P in the range 0.1–0.05 shows a trend toward sig-
nificance, while values <0.05 are indicative of significant
correlation. The magnitude of coefficient r indicates the
extent of correlation (the closer the values to 1, the bet-
ter), while the sign indicates whether the correlation is
positive or negative. It was logical to assume that adding
electron-withdrawing groups appropriately placed
would increase the potency of 3a–i since electron-with-
Table 2. Atomic charges of chalcone-imides
Compound
Partial atomic charges (esu)
a
b
a0
b0
3a
3b
3c
3d
3e
3f
ꢁ0.252
ꢁ0.246
ꢁ0.241
ꢁ0.256
ꢁ0.262
ꢁ0.248
ꢁ0.214
ꢁ0.248
ꢁ0.250
0.007
0.003
ꢁ0.133
ꢁ0.134
ꢁ0.133
ꢁ0.135
ꢁ0.134
ꢁ0.135
ꢁ0.132
ꢁ0.133
ꢁ0.134
ꢁ0.136
ꢁ0.134
ꢁ0.135
ꢁ0.137
ꢁ0.137
ꢁ0.135
ꢁ0.134
ꢁ0.134
ꢁ0.135
ꢁ0.002
0.014
0.021
0.005
ꢁ0.027
0.005
0.005
To obtain experimental support for the assertion that
these compounds act via thiolation of sulfhydryl-rich
proteins such as topoisomerase 2a, a representative
example, 3a, was reacted with two equivalents of benzyl
mercaptan under aqueous buffered condition at physio-
3g
3h
3i
O
N
O
HS
S
N
O
O
O
S
O
4
3a
Scheme 2. Formation of thiol adduct 4. Reagents and condition: pH 7.4 MOPS buffer, DMSO, 37 ꢁC.

4548
A. Jha et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4545–4550
Table 3. Pearson correlation between IC50 values of chalcone-based
imides 3a–i and the physicochemical parameters
of 300 mg/kg and after 4 h of sample injection. Neuro-
toxicity was measured using the rotating rod proce-
dure33; in addition, mice were observed for other
pathological symptoms. Neurological deficit displayed
after 0.5 h (in parentheses are the number of animals dis-
playing neurotoxicity/total number of animals, dose of
compound) namely 3b (1/8, 100; 2/4, 300) and 3h (1/8,
100; 2/4, 300). The neurotoxicity displayed after 4 h by
the compound, namely 3h, is (1/4, 100; 2/2, 300). The
mice which received the dose of 300 mg/kg of 3h for
4 h succumbed to death. No neurotoxicity was observed
for 3e, suggesting that the 4-methoxy analog 3e was well
tolerated, while the presence of the 4-COOH analog 3h
appeared to be detrimental.
Independent Dependent
Type
Molt4 IC50 Linear
CEM IC50 Linear
L1210 IC50 Linear
r Coefficient P value
Charge b
cLogP
ꢁ0.795
ꢁ0.776
ꢁ0.836
0.010
0.014
0.005
Molt4 IC50 Semi-log ꢁ0.657
0.055
0.045
0.044
CEM IC50
L1210 IC50 Semi-log ꢁ0.681
Molt4 IC50 Semi-log ꢁ0.674
Semi-log ꢁ0.677
Hansch p
0.046
0.042
0.036
CEM IC50 Semi-log ꢁ0.685
L1210 IC50 Semi-log ꢁ0.700
In conclusion, the present investigation revealed 40-
aminochalcone-based maleimides as potential leads for
development of novel cytotoxics. Compound 3d proved
at least as potent as the reference drug Alkeranꢂ against
L1210, Molt C4/8, and CEM cells. QSAR results also
provide useful suggestions for modifying the parent
model. The in vivo toxicity experiments reveal that the
chalcone imides are not general biocidal agents. Sub-
stantial structural modifications of chalcone-imides have
important potential for further drug development as
anti-cancer agents.
drawing groups increase the electrophilicity of the con-
jugated unsaturated ketones and, therefore, promote
the attack by biological nucleophiles. A negative corre-
lation of IC50 with partial charge on b-carbon atom (Ta-
ble 3) indicates a decrease in IC50 of chalcone-imides
with rise in electrophilicity of the b-carbon atom. Based
on values in Table 2, it can be noted that in case of 3a–i,
attack by cellular nucleophiles will take place formerly
at the b-carbon atom followed by a0 or b0-carbon atoms
of the imide ring. This explains the possibility of com-
pounds in series 3 undergoing a cascade of chemical
alkylations using cellular nucleophilic thiols.
Negative correlation of both cLogP and Hansch p with
cytostatic activity infers that when lipophilicity in-
creases, the IC50 decreases leading to improved cytotox-
icity. This is clearly evident from the lack of cytostatic
activity in dimethoxy, nitro, carboxy, and methylenedi-
oxy substituted polar compounds (3f–i, respectively)
presumably because of their difficulty in crossing the li-
pid membrane of cancerous cells. Therefore, adding
more hydrophobic groups would be a good start for fur-
ther analog preparation.
Acknowledgments
The authors thank the following agencies for financial
support, namely the Nova Scotia Health Research
Foundation (A.J.), Research Corporation, USA (A.J.),
and Fonds voor Wetenschappelijk Onderzoek-Vlaand-
eren (J.B., E.D.C.). Appreciation is extended to Mrs.
Lizette van Berckelaer for conducting the Molt 4/C8,
CEM, and L1210 assays, and the National Institute of
Neurological Disorders and Stroke, USA, for undertak-
ing the short-term toxicity studies in mice.
It is recognized that a number of tumors are slightly
more acidic than the corresponding healthy cells due
to increased anaerobic glycolysis in malignant cells.31
Therefore, compounds 3a–i can potentially hydrolyze
(chemically/enzymatically) to their chalcone maleamic
acid (2) counterparts. The contention, whether the ob-
served activity was due to the parent compounds per
se or due to their possible hydrolyzed products, was con-
sidered. We have recently reported the cytotoxicity of
these chalcone maleamic acids (2a–g)17 which are the
synthetic precursors to compounds 3a–g (Scheme 1).
When compared to the reported cytotoxic potential of
precursor 2a–e, cyclization to imide clearly results in sig-
nificantly increased potency in compounds 3a–e; the ob-
served cytotoxicity, therefore, is not due to the
hydrolyzed products.
References and notes
1. Yit, C. C.; Das, N. P. Cancer Lett. 1994, 82, 65.
2. Satomi, Y. Int. J. Cancer 1993, 55, 506.
3. (a) Wattenberg, L. W.; Coccia, J. B.; Galhaith, A. R.
Cancer Lett. 1994, 83, 165; (b) De Vincenzo, R.; Ferlini,
C.; Distefano, M.; Gaggini, C.; Riva, A.; Bombardelli, E.;
Morazzoni, P.; Valenti, P.; Belluti, F.; Ranelletti, F. O.;
Mancuso, S.; Scambia, G. Cancer Chemother. Pharmacol.
2000, 46, 305.
4. (a) Edwards, M. L.; Stemerick, D. M.; Sunkara, S. P.
J. Med. Chem. 1990, 33, 1948; (b) Achanta, G.; Mod-
zelewska, A.; Feng, L.; Khan, S. R.; Huang, P. Mol.
Pharmacol. 2006, 70, 426.
5. Chen, G. L.; Yang, L.; Rowe, T. C.; Halligan, B. D.;
Tewey, K. M.; Liu, L. F. J. Biol. Chem. 1984, 259, 13560.
6. Wang, H.; Yong, M.; Allan, Y.; Chen, N. Z.; Edmond, J.
L. V.; Liu, L. F. Biochemistry 2001, 40, 3316.
7. Wang, J. C. Annu. Rev. Biochem. 1996, 65, 635.
8. Holden, J. A. Curr. Med. Chem. Anti-Cancer Agents 2001,
1, 1.
Three representative compounds 3b, 3e, and 3h were
also examined for murine toxicity in vivo following liter-
ature procedure.32 These compounds were injected
intraperitoneally into mice at doses of 30, 100, and
300 mg/kg. After the administration of the compounds,
the animals were observed for 0.5 and 4 h. Mortality
was observed only in case of compound 3h at a dose
9. Andricopulo, A. D.; Yunes, R. A.; Nunes, R. J.; Savi, A.
ˆ
O. S.; Correa, R.; Cruz, A. B.; Cechinel Filho, V. Quim.
Nova 1998, 21, 573.

A. Jha et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4545–4550
4549
10. (a) Pradoa, S. R. T.; Filhob, V. C.; Buzzib, F. C.; Correab,
R.; Cadena, S. M. C. S.; de Oliveira, M. B. M. Z.
Naturforsch., C 2004, 59, 663; (b) Marrian, D. H.;
Friedmann, E.; Ward, J. L. Biochemistry 1953, 54, 5.
15 min. After completion of reaction the mixture was
allowed to cool to room temperature and the reaction
mixture quenched with ice cold water. The precipitate was
filtered and dried, and the crude product was purified by
column chromatography using DCM as eluent. Analytical
data for 3a: yield 17%; mp 197–200 ꢁC; 1H NMR (DMSO-
d6): d 7.25 (2H, s, pyrrole-Hs), 7.47–7.49 (3H, m, Ar-H),
7.58 (2H, d, J = 8.5 Hz, Ar-H), 7.78 (1H, d, J = 15.7 Hz,
E-vinylic-H), 7.90–7.93 (2H, m, Ar-H), 7.98(1H, d,
J = 15.7 Hz, E-vinylic-H), 8.28 (2H, d, J = 8.5 Hz, Ar-
H); 13C NMR (DMSO-d6): d 122.83, 127.17, 129.82,
130.07, 131.62, 135.47, 135.77, 136.58, 137.06, 145.17,
170.43, 189.32; IR (KBr): m 3435, 3083, 1704, 1662, 1604,
1384, 1307 cmꢁ1; UV–vis (MeOH): kmax 220, 318 nm;
HRMS Calcd: 303.0895, found: 303.0899. For 3b: yield
56%; mp 175–177 ꢁC; 1H NMR (DMSO-d6): d 6.93 (2H, s,
pyrrole-Hs), 7.42 (2H, d, J = 8.2 Hz, Ar-H), 7.51(1H, d,
J = 15.7 Hz, E-vinylic-H), 7.58–7.63 (4H, m, Ar-H), 7.80
(1H, d, J = 15.9 Hz, E-vinylic-H), 8.13 (2H, d, J = 8.4 Hz,
Ar-H); 13C NMR (DMSO-d6): d 119.64, 123.56, 127.15,
129.84, 130.11, 131.39, 131.52, 135.78, 136.94, 143.65,
170.42, 189.18; IR (KBr): m 3427, 3071, 1716, 1660, 1608,
1384, 1305 cmꢁ1; UV–vis (MeOH): kmax 204, 226, 324 nm;
HRMS Calcd: 337.0505, found: 337.0501. For 3c: yield
94%; 207–210 ꢁC; 1H NMR (DMSO-d6): d 7.25 (2H, s,
pyrrole-Hs), 7.59 (2H, d, J = 8.5 Hz, Ar-H), 7.71–7.77
(2H, m, Ar-H, E-vinylic-H), 7.89–7.92 (1H, m, Ar-H), 8.09
(1H, d, J = 15.6 Hz, E-vinylic-H), 8.29–8.31 (3H, m, Ar-
H); 13C NMR (DMSO-d6): d 124.80, 127.15, 130.12,
130.22, 131.09, 131.90, 132.70, 133.68, 135.80, 136.41,
136.74, 136.79, 142.30, 170.43, 189.02; IR (KBr): m 3427,
11. Andricopulo, A. D.; Muller, L. A.; Cechinel Filho, V.;
¨
Cani, G. S.; Roos, J. F.; Correa, R.; Santos, A. R. S.;
Nunes, R. J.; Yunes, R. A. Farmaco 2000, 55, 319.
12. Kovac, A.; Wilson, R. A.; Besra, G. S.; Filipic, M.; Kikelj,
D.; Gobec, S. J. Enzyme Inhib. Med. Chem. 2006, 21, 391.
13. Hall, I. H.; Wong, O. T.; Chapman, J. M. Anticancer
Drugs 1995, 6, 147.
14. Bailly, C.; Qu, X.; Chaires, J. B.; Colson, P.; Houssier, C.;
Ohkubo, M.; Nishimura, S.; Yoshinari, T. J. Med. Chem.
1999, 42, 2927.
15. Yellaturu, C. R.; Manjula, B.; Neeli, I.; Rao, G. N. J. Biol.
Chem. 2002, 227, 40148.
16. Jensen, L. H.; Renodon-Corniere, A.; Wessel, I.; Langer,
S. W.; Søkilde, B.; Carstensen, E. V.; Sehested, M.; Jensen,
P. B. Mol. Pharmacol. 2002, 61, 1235.
17. Dimmock, J. R.; Jha, A.; Zello, G. A.; Allen, T. M.;
Santos, C. L.; Balzarini, J.; De Clercq, E.; Manavathu, E.
K.; Stables, J. P. Pharmazie 2003, 58, 227.
18. Dimmock, J. R.; Kandepu, N. M.; Hetherington, M.;
Quail, J. W.; Pugazhenthi, U.; Sudom, A. M.; Chaman-
khah, M.; Rose, P.; Pass, E.; Allen, T. M.; Halleran, S.;
Szydlowski, J.; Mutus, B.; Tannous, M.; Manavathu, E.
K.; Myers, T. M.; De Clercq, E.; Balzarini, J. J. Med.
Chem. 1998, 41, 1014.
19. Go, M. L.; Wu, X.; Liu, X. L. Curr. Med. Chem. 2005, 12,
483.
20. Dimmock, J. R.; Elias, D. W.; Beazely, M. A.; Kandepu,
N. M. Curr. Med. Chem. 1999, 6, 1125.
3071, 1720, 1637, 1608, 1384, 1305 cmꢁ1
; UV–vis
21. Dimmock, J. R.; Kandepu, N. M.; Nazarali, A. J.;
Motaganahalli, N. L.; Kowalchuk, T. P.; Pugazhenthi,
U.; Prisciak, J. S.; Quail, J. W.; Allen, T. M.; LeClerc, R.;
Santos, C. L.; De Clercq, E.; Balzarini, J. J. Med. Chem.
2000, 43, 3933.
(MeOH): kmax 204, 207 nm; HRMS Calcd: 371.0116,
found: 371.0093. For 3d: yield 50%; mp 178–181 ꢁC; 1H
NMR (DMSO-d6): d 3.37 (3H, s, CH3), 7.24 (2H, s,
pyrrole-Hs), 7.28 (2H, d, J = 8.1 Hz, Ar-H), 7.56 (2H,
d,J = 8.5 Hz, Ar-H), 7.75 (1H, d, J = 15.8 Hz, E-vinylic-
H), 7.80 (2H, d, J = 8.1 Hz, Ar-H), 7.80 (1H, d,
J = 15.6 Hz, E-vinylic-H), 8.26 (2H, d, J = 8.5 Hz, Ar-
H); 13C NMR (DMSO-d6): d 21.97, 121.75, 127.11, 129.86,
130.00, 130.43, 132.78, 135.75, 136.49, 137.18, 141.71,
145.22, 170.43, 189.22; IR (KBr): m 3427, 3071, 1716, 1660,
22. (a) Barakat, M. Z.; Shehab, S. K.; El-Sadr, M. M.
J. Chem. Soc. 1957, 4133; (b) Lui, K. C.; Chen, T.; Jan, H.;
Shih, C. J. Chin. Chem. Soc. 1973, 20, 163.
1
23. (a) Analytical data for 2h: yield 60%, mp 195–200 ꢁC, H
NMR (DMSO-d6): d 6.38 (1H, d, J = 12.0 Hz, Z-vinylic-
H), 6.60 (1H, d, J = 12.0 Hz, Z-vinylic-H), 7.76 (1H, d,
J = 15.6 Hz, E-vinylic-H), 7.84 (2H, d, J = 8.5 Hz, Ar-H),
7.91–8.03 (4H, m, Ar-H), 8.07 (1H, d, J = 15.6 Hz, E-
vinylic-H), 8.19 (2H, d, J = 8.5 Hz, Ar-H), 11.00 (1H, s,
NHCO); 13C NMR (DMSO-d6): d 123.20, 128.53, 133.22,
134.06, 134.36, 135.25, 136.34, 136.76, 143.24, 146.34,
147.77, 168.03, 171.19, 171.45, 191.84; IR (KBr): m 3447,
1734, 1718, 1700, 1696, 1603, 1560, 1384, 1326 cmꢁ1; UV–
vis (MeOH): kmax 310 nm; ESI-MS (MꢁH)ꢁ Calcd:
365.09, found: 363.90. For 2i: yield 79%; mp 198–200 ꢁC;
1H NMR (DMSO-d6): d 6.12 (2H, s, OCH2O), 6.36 (1H, d,
J = 12.0 Hz, Z-vinylic-H), 6.54 (1H, d, J = 12.0 Hz, Z-
vinylic-H), 7.00 (1H, d, J = 8.1 Hz, Ar-H), 7.15–7.60 (2H,
m, Ar-H), 7.64–7.95 (5H, m, E-vinylic-H, Ar-H), 8.17 (1H,
d, J = 8.6 Hz, Ar-H), 10.74 (1H, s, NHCO); 13C NMR
(DMSO-d6): d 102.51, 107.78, 109.39, 119.62, 120.73,
126.71, 130.15, 130.68, 131.21, 132.36, 133.73, 143.83,
144.38, 148.96, 150.35, 164.56, 167.86, 188.26; IR (KBr): m
3447, 3286, 3208, 3118, 1709, 1647, 1631, 1593, 1534, 1500,
1608, 1384, 1305 cmꢁ1
; UV–vis (MeOH): kmax 231,
332 nm; HRMS Calcd: 317.1052, found: 317.1050. For
1
3e: yield 99%; 165–167 ꢁC; H NMR (DMSO-d6): d 3.88
(3H, s, OCH3), 6.97 (2H, d, J = 8.6 Hz, Ar-H), 7.28 (2H, s,
pyrrole-Hs), 7.41 (1H, d, J = 15.7 Hz, E-vinylic-H), 7.56–
7.65 (4H, m, Ar-H), 7.82 (1H, d, J = 15.7 Hz, E-vinylic-
H), 8.13 (2H, d, J = 8.4 Hz, Ar-H); 13C NMR (DMSO-d6):
d 56.27, 115.31, 120.29, 127.13, 129.93, 131.76, 135.76,
136.37, 137.37, 145.17, 170.45, 189.11; IR (KBr): m 3431,
3093, 1712, 1660, 1608, 1384, 1304, 1030 cmꢁ1; UV–vis
(MeOH): kmax 204, 235, 347 nm; HRMS Calcd: 333.1001,
1
found: 333.0989. For 3f: 92%; mp 200–201 ꢁC; H NMR
(DMSO-d6): d 3.83 (6H, s, OCH3), 7.25 (2H, s, pyrrole-
Hs), 7.41 (2H, d, J = 8.4 Hz, Ar-H), 7.86 (1H, d,
J = 15.6 Hz, E-vinylic-H), 7.58–7.63 (4H, m, Ar-H), 8.26
(1H, d, J = 15.3 Hz, E-vinylic-H), 7.58 (2H, d, J = 8.4 Hz,
Ar-H); 13C NMR (DMSO-d6): d 56.48, 56.61, 111.65,
112.43, 120.37, 124.97, 127.11, 128.30, 129.94, 135.77,
136.37, 137.41, 145.69, 149.89, 152.26, 170.45, 189.14; IR
1384, 1360, 1262, 1243, 1177, 1033, 847, 834, 802 cmꢁ1
;
(KBr): m 3447, 2926, 1718, 1654, 1605, 1384, 1015 cmꢁ1
;
UV–vis (MeOH): kmax 362 nm; ESI-MS (MꢁH)ꢁ Calcd:
365.09, found: 363.90; (b) General procedure for synthesis
of compounds 3a–i. A mixture of anhydrous NaOAc
(5 mmol) and acetic anhydride (20 mmol) was heated at
90 ꢁC with stirring until all NaOAc had dissolved. The
appropriate 40-aminochalcone maleamic acid analog 2a–i
was added and stirred at the noted temperature range for
UV–vis (MeOH): kmax 204, 235, 347 nm; HRMS Calcd:
363.1106, found: 363.1117. For 3g: 40%; mp 200–202 ꢁC;
1H NMR (DMSO-d6): d 7.25 (2H, s, pyrrole-Hs), 7.61
(2H, d, J = 8.5 Hz, Ar-H), 7.86 (1H, d, J = 15.7 Hz, E-
vinylic-H), 8.15–8.21 (3H, m, E-vinylic-H and Ar-H),
8.30–8.33 (4H, d, J = 8.6 Hz, Ar-H); 13C NMR (DMSO-
d6): d 124.83, 126.85, 127.18, 130.28, 130.81, 135.81,

4550
A. Jha et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4545–4550
136.62, 136.91, 142.00, 142.22, 149.00, 170.41, 189.14; IR
(KBr): m 3427, 3071, 1716, 1660, 1608, 1384, 1305 cmꢁ1
127.83, 128.09, 128.43, 128.89, 129.00, 129.19, 129.33 (2C),
;
129.66, 136.10, 136.80, 136.95, 138.23, 141.92, 173.54,
175.58, 196.11; IR (KBr): m 3054, 1720, 1691, 1603, 1494,
1421, 1377, 1265, 1178, 895 cmꢁ1; UV–vis (MeOH): kmax
254 nm; HRMS calculated for C33H29NO3S2Na+
574.1481, found: 574.1450.
UV–vis kmax (MeOH): 219, 222, 328 nm; HRMS Calcd:
348.0746, found: 348.0745. For 3h: yield 82%; 270–273 ꢁC;
1H NMR(DMSO-d6): d 7.25 (2H, s, pyrrole-Hs), 7.59 (2H,
d, J = 8.2 Hz, Ar-H), 7.81 (1H, d, J = 15.6 Hz, E-vinylic-
H), 8.09 (1H, d, J = 15.7 Hz, E-vinylic-H), 8.02 (4H, m, E-
vinylic-H and Ar-H), 8.30 (2H, d, J = 8.4 Hz, Ar-H); 13C
NMR (DMSO-d6): d 124.98, 127.17, 129.84, 130.18,
130.59, 133.07, 135.79, 136.76, 136.82, 139.98, 143.65,
167.72, 170.42, 189.22; IR (KBr): m 3427, 3080, 1715, 1664,
24. Balzarini, J.; De Clercq, E.; Mertes, M. P.; Shugar, D.;
Torrence, P. F. Biochem. Pharmacol. 1982, 31, 3673.
25. Dulik, D. M.; Fenselau, C.; Hilton, J. Biochem. Pharma-
col. 1986, 35, 3405.
26. Suffness, M.; Douros, J.. In Cancer Research, Volume
XVI, Part A; De Vita, V. T., Jr., Busch, H., Eds.;
Academic Press: New York, 1979; p 84.
27. Patrick, G. L. In An Introduction to Medicinal Chemistry,
3rd ed.; Oxford University Press: New York, 2005; p 271.
28. The charge density calculations (extended Huckel method)
and partition coefficients (cLogP) were obtained by
Chem3Dꢂ computer program (version 8.0) after energy
minimization of the molecules using MOPAC. Chem3Dꢂ
is obtainable from Cambridge Soft Corporation, Cam-
bridge, MA, USA.
29. (a) Hansch, C.; Leo, A. In Substituent Constant for
Correlation Analysis in Chemistry and Biology; John Wiley
and Sons: New York, 1979; p 49; (b) Hansch, C.; Leo, A.
In Exploring QSAR; American Chemical Society: Wash-
ington, DC, 1995.
30. Linear and semilogarithmic correlations were generated for
IC50 values for each cell line and physicochemical param-
eters using commercial software package Minitab Release
14.20ꢂ, Statistical software, 1972–2005 ꢀ Minitab Inc.
31. Wike-Hooley, J. L.; van der Berg, A. P.; van der Zee, J.;
Reinhold, H. S. Eur. J. Cancer Clin. Oncol. 1985, 21, 785.
32. Stables, J. P.; Kupferberg, H. J. In Molecular and Cellular
Targets for Antiepileptic Drugs; Avanzini, G. A., Tanga-
nelli, P., Avoli, M., Eds.; John Libbey: London, 1997; p
191.
33. Dunham, M. S.; Miya, T. A. J. Am. Pharm. Assoc. Sci.
1957, 46, 208, The recommendations of the National
Research Council Publication ‘Guide for the Care and Use
of Laboratory Animals’ were followed in regard to the
housing, feeding, and handling of the mice used in these
experiments.
1609, 1384, 1292 cmꢁ1
; UV–vis (MeOH): kmax 205,
322 nm; HRMS Calcd: 347.0793, found: 347.0790. For
3i: yield 34%; mp 197–198 ꢁC; 1H NMR (DMSO-d6): d
6.06 (2H, s, OCH2O), 6.88–7.20 (3H, m, Ar-H), 7.28 (2H,
s, pyrrole-Hs), 7.38 (1H, d, J = 15.6 Hz, E-vinylic-H), 7.58
(2H, d, J = 8.4 Hz, Ar-H), 7.78 (1H, d, J = 15.3 Hz, E-
vinylic-H), 8.13 (2H, d, J = 8.4 Hz, Ar-H); 13C NMR
(DMSO-d6): d 102.56, 107.85, 109.43, 120.73, 127.00,
127.12, 129.97, 130.03, 135.77, 136.43, 137.29, 145.19,
148.99, 150.56, 170.44, 189.01; IR (KBr): m 3447, 3071,
1714, 1650, 1608, 1384, 1305 cmꢁ1; UV–vis (MeOH): kmax
269 nm; HRMS Calcd: 347.0793, found: 347.0778; (c)
Synthesis
of
1-(4-(3-(benzylthio)-3-phenylpropa-
noyl)phenyl)-3-(benzylthio)pyrrolidine-2,5-dione (4). To
a suspension of 3a (0.59 mmol) in MOPS (3-(N-morpho-
lino)propanesulfonic acid) buffer (100 mM, 10 ml, pH 7.4)
and DMSO (1 mL), benzyl mercaptan (1.20 mmol) was
added and the resulting mixture stirred at 37 ꢁC for 72 h.
Reaction mixture was worked up by adding water (75 ml)
and extracting with ethyl acetate (3· 25 ml). Organic layer
was dried over anhyd Na2SO4 and concentrated to give
crude product which was purified by column chromatog-
raphy (13% EtOAc–hexane eluent) as colorless oil in 50%
yield. Analytical data for 4: 1H NMR d (CDCl3): 2.57 and
2.64 (1H, 2d, J = 3.6 Hz each, CHaHb), 3.15 and 3.22 (1H,
dd, J = 9.3 and 18.9 Hz, CHaHb), 3.50 (2H, m, CH2), 3.55
(2H, d, J = 8.4 Hz, CH2), 3.64 and 3.68 (1H, 2d,
J = 3.6 Hz each, CH), 3.92 and 4.29 (1H each, d,
J = 13.8 Hz each, CH0aHb0 ), 7.24–7.46 (17H, m, ArH),
7.97 (2H, d, J = 8.4 Hz, ArH); 13C NMR d (CDCl3):
30.12, 35.89, 36.50, 37.66, 44.51, 45.74, 126.71, 127.46,