Synthesis and biological evaluation of heteroaryldiamides and heteroaryldiamines as cytotoxic agents, apoptosis inducers and caspase-3 activators

Article abstract of DOI:10.1002/ardp.200500220

The work described here involved the synthesis and biological evaluation of new heteroaryldiamides and heteroaryldiamines. A new general model in which the structures can be adjusted has been applied in this study. Three different structural units can be distinguished: a central nucleus and two symmetric terminal units. The central element is either an aliphatic chain of varying length and flexibility, piperazine, or a polyamine nucleus. However, the terminal units are pyridine, quinoline, indole, benzene or pyrido[2,3-d] pyrimidine with different substituents. The antitumoural activities of the compounds were evaluated in vitro by examining their cytotoxic effects against human breast, colon, and bladder cancer cell lines. Compounds that showed cytotoxic activity were subjected to both apoptosis and caspase-3 assays. With regard to selectivity, the cytotoxicity was also determined in cell cultures of two nontumoural lines. The most promising compounds are 4c, 5c and 7, which are amino-pyridinium, quinolyl-N-oxide, and pyridyl derivatives, respectively, and these reveal a significant in vitro cytotoxicity in at least two of the three cell lines tested. These compounds induced apoptosis and also produced a rapid dose-dependent increase in the caspase-3 level in HT-29 cells. Other encouraging profiles were found, such as those presented by 1k and 8d, which are cytotoxic and apoptotic but do not provoke an increase in the level of caspase-3, or those presented by 2f, 3c and 4a, which are slightly cytotoxic but do not show any other significant activity. The different types of behaviour of each compound are not necessarily parallel in the three cell lines tested.

Full text of DOI:10.1002/ardp.200500220

182
Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Full Paper
Synthesis and Biological Evaluation of Heteroaryldiamides and
Heteroaryldiamines as Cytotoxic Agents, Apoptosis Inducers
and Caspase-3 Activators
Mikel Echeverrꢀa1, Beatriz Mendꢀvil1, Lucꢀa Cordeu2, Elena Cubedo2, Jesffls Garcꢀa-Foncillas2,
Marꢀa Font3, Carmen Sanmartꢀn1, Juan Antonio Palop1
1 Secciꢀn de Sꢁntesis, Departamento de Quꢁmica Orgꢂnica y Farmacꢃutica, University of Navarra, Pamplona,
Spain
2 Laboratorio de Biotecnologꢁa y Genꢀmica, ꢄrea de Terapia Celular, Clꢁnica Universitaria, University of
Navarra, Pamplona, Spain
3 Secciꢀn de Modelizaciꢀn Molecular, Departamento de Quꢁmica Orgꢂnica y Farmacꢃutica, University of
Navarra, Pamplona, Spain
The work described here involved the synthesis and biological evaluation of new heteroaryldi-
amides and heteroaryldiamines. A new general model in which the structures can be adjusted
has been applied in this study. Three different structural units can be distinguished: a central
nucleus and two symmetric terminal units. The central element is either an aliphatic chain of
varying length and flexibility, piperazine, or a polyamine nucleus. However, the terminal units
are pyridine, quinoline, indole, benzene or pyrido[2,3-d]pyrimidine with different substituents.
The antitumoural activities of the compounds were evaluated in vitro by examining their cytoto-
xic effects against human breast, colon, and bladder cancer cell lines. Compounds that showed
cytotoxic activity were subjected to both apoptosis and caspase-3 assays. With regard to selectiv-
ity, the cytotoxicity was also determined in cell cultures of two nontumoural lines. The most
promising compounds are 4c, 5c and 7, which are amino-pyridinium, quinolyl-N-oxide, and pyri-
dyl derivatives, respectively, and these reveal a significant in vitro cytotoxicity in at least two of
the three cell lines tested. These compounds induced apoptosis and also produced a rapid dose-
dependent increase in the caspase-3 level in HT-29 cells. Other encouraging profiles were found,
such as those presented by 1k and 8d, which are cytotoxic and apoptotic but do not provoke an
increase in the level of caspase-3, or those presented by 2f, 3c and 4a, which are slightly cytotoxic
but do not show any other significant activity. The different types of behaviour of each com-
pound are not necessarily parallel in the three cell lines tested.
Keywords: Heteroaryldiamides / Heteroaryldiamines / Cytotoxicity / Apoptosis / Caspase-3 /
Received: October 6, 2005; accepted: December 1, 2005
DOI 10.1002/ardp.200500220
fits of these compounds are limited due to the fact that
Introduction
cancer is still one of the most common causes of mortal-
ity. The study of cellular proliferation kinetics in
tumours has provided important information on the
genetic changes that are involved in several types of can-
cer [1]. The cellular death programme disorder is also
included in this group due to its determinant activity in
tumourgenesis processes [2, 3].
In recent years, a number of chemotherapeutic agents
have been developed for clinical use. However, the bene-
Correspondence: Prof. Juan Antonio Palop, Departamento de Quꢁmica
Orgꢂnica y Farmacꢃutica, Universidad de Navarra, Irunlarrea 1, E-31008
Pamplona, Spain.
E-mail: jpalop@unav.es
Fax: + 34 948 425-649
There are two types of cellular death: necrosis and
apoptosis. It has been demonstrated that apoptosis is
i 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Symmetrical Diamides and Diamines as Apoptosis Inducers
183
inhibited in major tumours and this results in an uncon-
trolled cellular increase in carcinogenic tissue. This pro-
liferation disorder is not only produced by the outbreak
of the mitosis rate but can also be produced by the con-
siderable decrease in the rate of cellular death. Therefore,
gaining knowledge concerning the biochemistry and
molecular apoptotic pathways is extremely important
for the discovery and development of new therapeutic
strategies in cancer [4–9]. The use of the apoptotic
mechanism as a target in cancer research is a complex
issue, but most previous studies have revealed that the
cystein-protease family (namely caspases) are activated in
apoptotic pathways [10, 11]. These systems are probably
the most important effect-provoking molecules related
to the induction of apoptosis and all of them are synthe-
sised in the form of inactive precursors (proenzymes)
that are subsequently activated by self-proteolysis (auto-
catalytic cleavage) or other proteases [12].
A review of the literature enabled the selection of new
molecules with different chemical groups for the present
work. Structural analysis was then carried out on com-
pounds with recognized efficacy in cancer treatment and
most of their mechanisms of action are intimately
related with the induction of apoptosis and/or caspase
activation. Among the many structural groups identi-
fied, the following were selected for this study:
Figure 1. General formula of newly synthesised compounds.
a result, we present the synthesis of new compounds that
are based on this general formula (Fig. 1).
The compounds 1a–n, 2a–f, 3a–e, 4a–c, 5a–c, and
6a–b (Table 1–2) include symmetrical amide derivatives
with pyridine, quinoline and indole units connected by
central apolar chains of variable length and flexibility.
The aromatic end units are in some cases functionalized
by N-oxide, N-methyl, N-amino, halogen, thereby modify-
ing the electronic distribution, polarity and ability to
form hydrogen bonds. The derivatives 7 and 8c–d
include amine and polyamine derivatives with the aim of
evaluating the influence of the replacement of amides
for amines in the target activity. By contrast, the deriv-
atives 8a–b, recently published [31], include the flat and
rigid pyrido[2,3-d]pyrimidine bicycle functionalized in
positions 2 and 4 by amine aliphatic chains with pyridine
and indole aromatic end groups in the central nucleus.
Results
1) p-deficient monocyclic aromatic systems, such as
pyridine [13, 14] or bicyclic aromatic systems, such as qui-
noline [15, 16], indole [17, 18] and pyrido[2,3-d]pyrimi-
dine [19, 20] at the ends of the molecule;
2) Amide groups directly linked to the heterocycle or
near to it [21, 22] – these are attached to apolar chains of
variable length and flexibility [23, 24];
Chemistry
The synthesis of the diamides 1a–n and 2a–f was carried
out according to Schemes 1a and 1b, by reaction between
acyl chlorides, obtained by the corresponding carboxylic
acid by heating under reflux with thionyl chloride, and
the appropriate amines in the presence of equimolecular
amounts of triethylamine. In the case of the acyl chlor-
ides prepared for compounds 2a–f, chloroform was
added as a solvent in order to provide milder conditions
and avoid halogenation of the quinoline ring.
Compounds 3a–e were obtained from the correspond-
ing derivatives 1 by treatment with methyl iodide in
refluxing ethanol. Derivatives 4a–c were obtained from
derivatives 1 by treatment with hydroxylamine-O-sulfo-
nic acid (potassium salt) in refluxing water, with metha-
nol as co-solvent (Scheme 1a). HI was then added to
obtain the desired dihydroiodide salts. Compound 4c was
obtained as a sulfate.
3) Groups that are capable of participating in oxide-
reduction processes, such as N-oxides [25], or are capable
of altering molecular polarity and the possibility of form-
ing hydrogen bonds, such as N-amino and N-methyl
groups [26]. It was also noted that many of the molecules
studied possess a high degree of symmetry [27–30].
In designing new structures, a general pattern derived
from the reference literature has been adopted. This pat-
tern, while flexible in geometry and chemical structure,
basically responds to molecules which contain three enti-
ties: a central nucleus made up of a cyclic or linear ali-
phatic chain of variable length and flexibility, two identi-
cal lateral arms connected to the centre by a variable
functional group. In the work described here, an attempt
was made to confirm the usefulness, in terms of cytotoxic
activity and apoptosis induction, of certain structural
parameters relative to the described model. These struc-
tural considerations were combined with our experience
in the study and preparation of this kind of molecules. As
Compounds 5a–c (Scheme 1b) were obtained from the
corresponding compounds 2 by treatment with 3-chloro-
peroxybenzoic acid. The use of dichloromethane/chloro-
form as the solvent allowed N-oxidation of the quinoline
ring without modification of the amide group.
Compounds 6a–b were obtained by reaction of the cor-
responding diamine with 2-ethoxycarbonylindole in
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184
M. Echeverrꢀa et al.
Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Table 1. Experimental data for new compounds 1–6.
Ref
Z
Position
W
Yield
[%]
M. p.
[8C]
Recrystallisation
Solvent
C.H.N.
1a
1b
1c
1d
1e
1f
1g
1h
1i
Pyridyl
Pyridyl
Pyridyl
Pyridyl
Pyridyl
Pyridyl
Pyridyl
(6-Cl)-Pyridyl
(6-Cl)-Pyridyl
(6-Cl)-Pyridyl
Pyridyl-N-oxide
Pyridyl-N-oxide
3
3
3
3
3
3
2
3
3
3
3
3
3
3
3
3
3
2
2
2
3
3
3
3
3
3
3
3
2
2
2
2
2
–(CH2)4 –
1,4-piperazine
–(CH2)3 –
52
38
31
202-3
198-9
157-8
A300
129-30
148-9
165-6
300
EtOH
EtOH
EtOH
MeOH
AcOEt
EtOH
CHCl3/EtOH
EtOH
EtOH
C16H18N4O2
C16H16N4O2
C15H16N4O2
C18H20N4O2
C17H20N4O2
C20H26N4O2
C15H16N4O2
C18H18Cl2N4O2
C16H14Cl2N4O2
C16H16Cl2N4O2
C16H18N4O4
C16H16N4O4
C15H16N4O4
1,4-cyclohexanediamine 36
–(CH2)5 –
–(CH2)8 –
–(CH2)3 –
1,4-cyclohexanediamine 57
1,4-piperazine
–(CH2)4 –
–(CH2)4 –
1,4-piperazine
–(CH2)3 –
1,4-cyclohexanediamine
–(CH2)3 –
1,4-piperazine
–(CH2)5 –
1,4-piperazine
–(CH2)3–
–(CH2)2–
–(CH2)4 –
1,4-piperazine
–(CH2)3 –
1,4-cyclohexanediamine 21
–(CH2)5 –
–(CH2)4 –
1,4-piperazine
–(CH2)3 –
7
40
23
77
55
22
17
6
245-6
200-1
248-9
281-2
206-7
A300
200-1
268-9
179-80
197-8
118-9
214-5
226-7
A300
220-1
A300
159-60
195-6
224-5
264-5
290-3
269-70
157-8
A300
A300
1j
1k
1l
EtOH
MeOH/H2O
EtOH/H2O
MeOH
MeOH/H2O
n-Hexane/EtOH
MeOH/CH2Cl2
EtOH
1m Pyridyl-N-oxide
1
1n
2a
2b
2c
2d
2e
2f
3a
3b
3c
3d
3e
4a
4b
4c
5a
5b
5c
6a
6b
Pyridyl-N-oxide
Quinolyl
Quinolyl
Quinolyl
Quinolyl
8
C18H20N4O4 N /3 H2O
66
73
67
24
23
35
50
51
40
C23H20N4O2
C24H20N4O2
C25H24N4O2
C24H20N4O2
MeOH
Quinolyl
Quinolyl
n-Hexane/2-Propanol C23H20N4O2
CH2Cl2
C22H18N4O2
1-Methyl-pyridinium
1-Methyl-pyridinium
1-Methyl-pyridinium
1-Methyl-pyridinium
1-Methyl-pyridinium
1-Amino-pyridinium
1-Amino-pyridinium
1-Amino-pyridinium
Quinolyl-N-oxide
Quinolyl-N-oxide
Quinolyl-N-oxide
Indolyl
EtOH/H2O
EtOH/H2O
EtOH/H2O
EtOH/H2O
EtOH
MeOH
MeOH
MeOH
CH2Cl2/MeOH
EtOH
C18H24I2N4O2
C18H22I2N4O2
C17H22I2N4O2
C20H26I2N4O2
C19H26I2N4O2
C16H22I2N6O2
C16H20I2N6O2
C15H20N6O6S N /2 H2O
C24H20N4O4
C22H18N4O4
C23H20N4O2
13
14
13
7
1
1,4-piperazine
–(CH2)2 –
–(CH2)3 –
–(CH2)3 –
1,4-piperazine
8
89
13
26
13
EtOH
Washed with MeOH C21H20N4O2
Washed with MeOH C22H20N4O2
Indolyl
Table 2. Experimental data for new compounds 7–8.
Ref
Z
n
W
Yield
[%]
M. p.
[08C]
Recrystallisation
Solvent
C.H.N.
7
8a
2-Pyridyl
2-Pyridyl
1
2
1,4-piperazine
2,4-diaminopyrido-
pyrimidine
37
15
94-5
156-7
n-Hexane/CH2Cl2
AcOEt/2-propanol
C16H20N4
C21H21N7
8b
8c
8d
3-Indolyl
2
2,4-diaminopyrido-
pyrimidine
1,4-bis(3-aminopropyl)-
piperazine
–NH–(CH2)3 –NH–
(CH2)4 –NH–(CH2)3 –NH–
10
30
9
162-3
268-9
284-5
n-Hexane/MeOH
EtOH/MeOH
C27H25N7 N HCl
Pyrido[2,3-d]pyrimidyl
C24H30N10 N 2HCl
Pyrido[2,3-d]pyrimidyl 3
Washed with boiling C24H32N10 N 3HI
acetic acid
refluxing methanol with sodium cyanide as the catalyst
(Scheme 2).
Compound 7 was obtained by direct reaction of pipera-
zine with the alkyl halide in refluxing ethanol in the pre-
sence of K2CO3 (Scheme 3).
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Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Symmetrical Diamides and Diamines as Apoptosis Inducers
185
Scheme 4. Synthesis route of compounds 8a–b and 8c–d.
replaced with chloro-substituents by treatment with
refluxing phosphorus oxychloride. N,N-dimethylforma-
mide was added as a catalyst to the reaction of the diol
because substitution in position 2 is less favored [32]. In
the third step, the chloro-substituents were replaced by
the corresponding amines in the presence of equimolecu-
lar amounts of triethylamine. In the case of compound
8d, which was obtained by reaction of 4-chloropyrido[2,3-
d]pyrimidine and 1,4-butanediamine, the addition of KI
was necessary in order to facilitate the substitution of pri-
mary amines rather than secondary amines.
Scheme 1. a) Synthesis route of compounds 1a–n, 3a–e and
4a–c. b) Synthesis route of compounds 2a–f and 5a–c.
Scheme 2. Synthesis route of compounds 6a, b.
Scheme 3. Synthesis route of compound 7.
Biological evaluation
Cytotoxicity
The cytotoxic activities of the synthesised compounds
were determined on three human cancer cell lines
[breast (MD-MBA-231), bladder (T-24) and colon (HT-29)]
using the neutral red assay [33]. The survival percentage
was determined after a period of 72 h at screening con-
centrations of 100 and 20 lM, using the survival percen-
tage obtained from the cells treated only with the solvent
The synthesis of compounds 8a–b and 8c–d was car-
ried out in three steps (Scheme 4). 2-Aminonicotinic acid
was condensed with an excess of urea or formamide to (DMSO at 0.5%) as a reference. The results are expressed
as the average of assays carried out in triplicate. IC50
values were calculated for those compounds that showed
afford pyrido[2,3-d]pyrimidine-2,4-diol and pyrido[2,3-
d]pyrimidine-4-ol, respectively. The hydroxyl groups were
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186
M. Echeverrꢀa et al.
Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Table 3. Biological profile for the most active compounds.
Ref
Z
Position
W
IC50 [lM]
Apoptosis in cell line
Caspase-3
% survivala) % survivalb)
(a)
(b)
(c)
(a)
(b)
(c)
d)
1k
1m
2a
2f
3a
3c
4a
4c
5c
6a
Pyridyl-N-oxide
Pyridyl-N-oxide
Quinolyl
3
3
3
2
3
3
3
3
2
2
– (CH2)4 –
– (CH2)3 –
– (CH2)3 –
– (CH2)3 –
– (CH2)4 –
– (CH2)3 –
– (CH2)4 –
– (CH2)3 –
– (CH2)3 –
– (CH2)3 –
18.0
25.0
31.0
49.0
36.4
42.3
55.1
25.8
7.9
nac)
47.9
na
na
na
na
na
49.2
37.8
na
35.5
na
na
na
na
62.8
na
na
50.5
78.0
0.009
1.8
1.6
1.3
1.5
1.6
1.5
na
2.0
2.6
–
–
1.8
–
–
–
–
na
–
–
na
1.9
3.3
na
100
65
90
48
82
73
64
89
90
86
64
nd
1.5
–
+(MD-MBA-231) 100
+(MD-MBA-231) 100
na
+(MD-MBA-231)
na
Quinolyl
–
–
–
–
100
95
82
100
95
95
1-Methyl-pyridinium
1-Methyl-pyridinium
1-amino-pyridinium
1-amino-pyridinium
Quinolyl-N-oxide
Indolyl
na
1.7
2.9
–
++(HT-29)
++(HT-29)
na
nde)
na
0.291
75
nd
camptothecin
0.014
2.6
2.6
(a) Cell line: MD-MBA-231, (b) Cell line: HT-29m (c) Cell line: T-24.
a)
Survival percentage in CRL-8799 cell line (concentration: the highest IC50 value obtained from the three tumoural lines).
Survival percentage in CRL-11233 cell line (concentration: the highest IC50 value obtained from the three tumoural lines).
na = no activity observed after 48 h incubation at the highest IC50 found.
– = apoptosis assay not pertinent because compound is not cytotoxic.
nd = no data.
b)
c)
d)
e)
Table 4. Biological profile for the most active compounds.
Ref
Z
n
W
IC50 [lM]
Apoptosis in cell line
Caspase-3
%
%
survivala) survivalb)
(a)
(b)
(c)
(a)
(b)
(c)
d)
7
2-Pyridyl
2-Pyridyl
3-Indolyl
Pyrido[2,3-d]pyrimidyl
1
2
2
3
1,4-piperazine
2,4-diaminopyridopyrimidine na
2,4-diaminopyridopyrimidine 5.1
15.3
28.9
68.0
3.0
nac))
na
7.7
2.4
–
na
na
5.4
1.5
3.0
3.0
2.6
–
–
++(HT-29)
+(HT-29)
++(HT-29)
na
80
100
56
62
nd
58
8a
8b
8d
100
nde)
68
na
2.7
3.3
– NH – (CH2)4 – NH –
9.2
0.29
15.4
62.7
camptothecin
0.014 0.009 2.6
nd
nd
(a) Cell line: MD-MBA-231, (b) Cell line: HT-29, (c) Cell line: T-24.
a)
Survival percentage in CRL-8799 cell line (concentration: the highest IC50 value obtained from the three tumoural lines).
Survival percentage in CRL-11233 cell line (concentration: the highest IC50 value obtained from the three tumoural lines).
na = no activity observed after 48 h incubation at the highest IC50 found.
– = apoptosis assay not pertinent because compound is not cytotoxic.
nd = no data.
b)
c)
d)
e)
survival levels of a45% (100 lM). The results obtained for Apoptosis and Caspase-3
the most active compounds are shown in Tables 3–4. Once the active compounds in the cytotoxicity assay had
With regard to selectivity, the cytotoxicity was deter- been identified, the compounds were subjected to a test
mined in cell cultures of two nontumoural lines, one of aimed at determining whether or not they also act as
breast (CRL-8799) and another of liver (CRL-11233). The inducers of apoptosis and/or activators of caspase-3.
same experimental procedure was used in these cytotoxi-
city assays with nontumoural lines. For each compound, Apoptosis
the highest IC50 value obtained from the three tumoural The ability of the selected compounds to induce apopto-
lines was selected as the test concentration. The results sis in cell cultures (lines MD-MBA-231, HT-29 and T-24),
obtained are expressed in survival percentage at this con- was assessed [31] by using the Cell Death Detection ELISA
centration because we only expect a rough measure Plus Kit from Roche Biochemical (Roche Diagnostics, Bar-
about selectivity of these compounds.
celona, Spain); this cellular test detects nucleosomes in
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Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Symmetrical Diamides and Diamines as Apoptosis Inducers
187
cytoplasm prior to disintegration of the plasma mem- least one of the tested cell lines. The results for the most
brane, a well-known hallmark of apoptosis. The test con- active compounds are summarised in Tables 3–4.
centrations correspond to the IC50 values determined in
the cytotoxicity assay; the incubation time was of 24 h. Cytotoxicity
The results express the number of times in which the cul- The structure-activity relationships that are considered
ture containing the test compound surpasses the control useful for improving the activity were established on the
culture in its ability to induce DNA fragmentation, with basis of the results from the biological assays carried out
a relative value of 1 assigned to the level of apoptosis on the compounds prepared from the aforementioned
detected in the control culture. A result was considered design. These relationships have already been applied in
positive when the level of DNA fragmentation obtained this study but, more importantly, they are useful in the
was at least double the values obtained for the corre- planning of future studies. These conclusions can be sum-
sponding control cultures, which were treated only with marised as follows:
the solvent. The results obtained for the selected com-
In general, the amide derivatives that contain aliphatic
pounds and the reference substance (camptothecin) are chains as the central linking unit with pyridine, N-alkyl
shown in Tables 3–4.
and N-amines as the terminal groups have moderate cyto-
toxic activity. The N-oxidation of the pyridinic nitrogen
causes an increase in activity in comparison to the analo-
Caspase-3
The compounds that showed cytotoxicity were subjected gous reduced compounds in cases where the central
to the caspase-3 assay because caspase-3 is considered to chains have 3 or 4 carbon atoms. Compounds 1k and 1m
be one of the principal executing caspases in which all of were cytotoxic, especially on cellular line MD-MBA-231
the biochemical routes involved in the apoptosis (18.0 and 25.0 lM, respectively).
response converge. The Active-Caspase-3 FITC Mab apop-
The compounds with central chains of 3 carbon atoms
tosis kit from Pharmingen (San Diego, CA, USA) was used that separate the heterocyclic end units and are located
[31]. This test detects the quantity of caspase-3 dimerized in the 2-position with respect to the heteroatom gave rise
in the apoptotic cells, by means of the number of cells to the best results. In particular, 5c was active on MD-
that contain the dimerized and activated form of cas- MBA-231, HT-29 and T-24 lines (7.9, 37.8 and 50.5 lM,
pase-3 after treatment with a cytotoxic compound. The respectively). It is worth noting that in this derivative the
test allows confirmation of the involvement of this quinolinic nitrogen is also in the N-oxide form.
enzyme in the cell death process. The range of effective
Replacement of the amide group by a polyamine, a
measurements for this enzyme was found to be between structure highlighted by numerous literature references
14 and 48 h. We have selected 48 h because at this time [34] on cancer therapy, made reach the desired markedly
all the enzyme is activated. Therefore, for the most active higher activity levels and, therefore, this system appears
compounds, measurements are taken at 14, 24 and 48 h, to be a very interesting central block in terms of increas-
in order to detect other forms of cell death, and the ing the activity. These results, considering the small
obtained values were compared with those of control number of structures tested (7, 8c and 8d), justify future
cells incubated without the test compounds. The test con- research in this area.
centrations correspond to the IC50 values determined in
In order to study the degree of selectivity of the cyto-
the cytotoxicity assay. The results of this semi-quantita- toxic activity of the compounds under investigation,
tive assay are expressed using the following symbols: (na) assays using healthy cells were carried out on some repre-
when an increase was not detected in caspase-3 level with sentative examples. The compounds selected were those
respect to the control, (+) when an increase of approxi- that showed activity in tumoural cells. The healthy cells
mately 50% was detected, and (++) when an increase of corresponded to CLR-8799 and CLR-11233, and the survi-
100% or more was observed (Tables 3–4). This is consid- val values were between 95 and 100% for 1k, 1m, 2a, 2f,
ered to be preliminary data for the determination of the 3a, 4a, 4c, 5c, and 8a in at least one of the tested lines.
mechanism of action.
Apoptosis and Caspase-3
Eight compounds showed notable activity (>1.50) in indu-
cing apoptosis against the tested cell tumoural lines. The
Discussion
best apoptosis inducer was compound 7, which has a
The study described here included the synthesis of 36 value of 5.4 in HT-29 and 2.4 in MD-MBA-231. Other inter-
new compounds – however, reference is only made to esting compounds are 8d (3.0 in HT-29 and 2.7 in T-24)
those that showed a certain degree of cytotoxicity in at and 5c (2.9 in HT-29 and 2.6 in MD-MBA-231). Camptothe-
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188
M. Echeverrꢀa et al.
Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
cin, which was used as a reference, gives values between gress about the structure-activity relationships. Com-
2.6 and 3.3 for these same cell lines. pounds that showed cytotoxicity were evaluated in apop-
Certain compounds, particularly 1m, 2a and 3a, caused tosis and caspase-3 assays. Progressive design of the struc-
notable increases in the caspase-3 levels in the MD-MBA- tures enabled us to obtain some lead derivatives, such as
231 cell line and compounds 4c, 5c and 7 caused higher 1m, 3a, 4c, 5c, and 7 which have the desired cytotoxic
increases in HT-29. This fact is of great interest given the activity, proapoptotic behaviour and caspase-3 activator
characteristics of this enzyme; the enzyme is considered characteristics. These compounds show a similar biologi-
to be one of the principal executing caspases, in which cal profile even though they have a markedly different
all of the biochemical routes involved in the apoptosis structure. The best apoptosis inducer found in this study
response converges.
is compound 7, which shows an apoptosis value of 5.4
Analysis of the results obtained from the biological against HT-29 cell line and is also cytotoxic and a caspase-
evaluation shows different preliminary profiles in the 3 activator in the same cell line. It is envisaged that tak-
behaviour of the products, thereby suggesting the exis- ing these lead compounds as a starting point will enable
tence of diverse mechanisms of action. For example, com- more potent analogues to be generated.
pounds 1k, 2f, 3c, 6a, and 8d are cytotoxic and apoptotic
The precise mechanism of action of some of these
in at least one of the tested lines and yet do not modify derivatives is currently under investigation in our labora-
the levels of caspase-3. This indicates cell death by apopto- tory. The ability of some of these compounds to cause
sis, in which caspase plays no part whatsoever. Such accumulation of caspase-3 will be taken into account
behaviour is similar to that shown by irofulven [35], an even though comparable structures in literature have
agent used in the treatment of prostate cancer. This com- the ability to bind tightly but reversibly to DNA by inter-
pound binds to DNA and protein targets, forming a calation between the base pairs of the double helix [25,
macromolecular adduct. This binding interferes with 36, 37]. Optimisation of the design of these compounds
DNA replication (S-phase arrest) and cell division of from a structure-activity relationship point of view, as
tumour cells, leading to apoptotic cell death. Finally, well as the elucidation of their mechanisms of action,
derivatives 1m, 2a, 3a, 4c, 5c, and 7 are cytotoxic, apopto- could very well lead to the development of novel types of
tic and activators of caspase-3 in at least one of the tested antineoplastic drug.
cell lines. In addition 1m, 3a, 4c, and 5c have survival
values in the range 95-100% in the nontumoural CRL-
8799 cell line, thereby perfectly fitting our target com- of Navarra Research Plan (Plan de Investigaciꢀn de la Universi-
pound profile. dad de Navarra, PIUNA) and the Ministry of Science and Tech-
The authors wish to express their gratitude to the University
The general trend on which the design of these struc- nology (Spain), FPU Program, for financial support.
tures is based has proven to be valid in obtaining the
desired activity. However, it must be stressed that the
model still requires some adjustment and refinement in
order to obtain the most potent structures. It is clear that
Experimental
the synthesis of more analogues is required to obtain a
Chemistry
good structure-activity relationship, but the initial
results presented here have strengthened our interest in
these structures in the search for the target activity.
Melting points were determined with Mettler FP82 and FP80
apparatus (Mettler-Toledo, Greifense, Switzerland) and are not
corrected. 1H-NMR spectra were recorded on either a Bruker AC-
200E or a Bruker 400 UltrashieldTM spectrometer (Bruker, Rhein-
stetten, Germany) using TMS as the internal standard. The IR
spectra were obtained using a Thermo Nicolet FT-IR Nexus
(Thermo Electron Corporation, Waltham, MA, USA) on KBr pel-
lets. Elemental microanalyses were obtained using an Elemental
Analyzer (LECO model CHN-900; LECO Corporation, St. Joseph,
MI, USA,) on vacuum-dried samples and were an an accepteable
range of l0.4% for all compounds. Silica gel 60 (0.040–0.063
mm) 1.09385.2500 (Merck, Darmstadt, Germany) was used for
Column Chromatography and Alugramm SIL G/UV254 (Layer: 0.2
mm) (Macherey-Nagel, Dꢀren, Germany) was used for Thin Layer
Chromatography. Chemicals were purchased from E. Merck,
Scharlau (F.E.R.O.S.A., Barcelona, Spain), Panreac Quꢁmica S.A.
(Montcada i Reixac, Barcelona, Spain), Sigma-Aldrich Quꢁmica,
S.A., (Alcobendas, Madrid, Spain), Acros Organics (Janssen Phar-
maceuticalaan 3a, Geel, Belgium), and Lancaster (Bischheim-
Conclusion
We have completed the synthesis and biological evalua-
tion of 36 novel heteroaryldiamides and heteroaryldia-
mines as potential antineoplastic agents, apoptosis indu-
cers and caspase-3 activators. These compounds were
studied in an in vitro cytotoxicity assay against three can-
cer cell lines: breast (MD-MBA-231), colon (HT-29) and
bladder (T-24). Most of the synthesised compounds
showed low cytotoxicity against three human cancer cell
lines although these data have been useful to make pro-
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Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Symmetrical Diamides and Diamines as Apoptosis Inducers
189
Table 5. IR and 1H-NMR data for selected compounds.
Ref.
1k
1m
2a
2f
IR [cm – 1
]
1H-NMR [J in Hz]
3305, 3072,
a) 1.55 ( brs, 4H, CH2); 3.30 ( brs, 4H, CH2); 7.50 (dd, J5-4 = 8, J5-6 = 6, 2H, H5, H59); 7.79 (d, J4-5 = 8, 2H, H4, H49); 8.34 (d, J6-5 = 6, 2H, H6, H69); 8.55 (s, 2H, H5,
3000 – 2850, 1636
3308, 3074, 2928,
2883, 1642
H59); 8.74 ( brs, 2H, NH, NH9).
a)
1.79 (q, J = 7, 2H, CH2); 3.32 (m, 4H, CH2); 7.55 (dd, J5-4 = 8, J5-6 = 6, 2H, H5, H59); 7.76 (d, J4-5 = 8, 2H, H4, H49); 8.34 (d, J6-5 = 6, 2H, H6, H69); 8.57 (s, 2H, H2,
H29); 8.75 (t, J = 5, 2H, NH, NH9).
3295, 3068,
a) 1.91 (q, J = 7, 2H, CH2); 3.45 (m, 4H, CH2); 7.68 (dd, J6-5 = 8, J6-7 = 8, 2H, H6, H69); 7.86 (dd, J7-6 = 8, J7-8 = 8, 2H, H7, H79); 8.07 (d, J5-6 = 8, 2H, H5, H59); 8.07
(d, J8-7 = 8, 2H, H8, H89); 8.81 (s, 2H, H4, H49); 8.89 (t, J = 5, 2H, NH, NH9); 9.28 (s, 2H, H2, H29).
3000 – 2900, 1634
3396, 3068, 2940,
1665
b)
3.84 (d, J = 6, 4H, CH2); 7.58 (dd, J6-5 = 8, J6-7 = 8, 2H, H6, H69); 7.72 (dd, J7-6 = 8, J7-8 = 8, 2H, H7, H79); 7.84 (d, J5-6 = 8, 2H, H5, H59); 8.07 (d, J8-7 = 8, 2H, H8, H89);
8.28 (d, 2H, H4, H49); 8.28 (d, 2H, H3, H39); 8.65 ( brs, 2H, NH, NH9).
3a
3c
3212, 3064, 1660
a) 1.64 ( brs, 4H, CH2); 3.38 ( brs, 4H, CH2); 4.41 (s, 6H, CH3); 8.25 (dd, J5-4 = 8, J5-6 = 5, 2H, H5, H59); 8.89 (d, J4-5 = 8, 2H, H4, H49); 9.09 (t, J = 5, 2H, NH, NH9);
9.09 (d, J6-5 = 5, 2H, H6, H69); 9.39 (s, 2H, H2, H29).
3262, 3040, 2952,
1660
3258, 3062, 1656
a) 1.89 (q, J = 7, 2H, CH2); 3.43 (m, 4H, CH2); 4.42 (s, 6H, CH3); 8.26 (dd, J5-4 = 8, J5-6 = 5, 2H, H5, H59); 8.89 (d, J4-5 = 8, 2H, H4, H49); 9.12 (t, J = 8, 2H, NH, NH9);
9.12 (d, J6-5 = 5, 2H, H6, H69); 9.40 (s, 2H, H2, H29).
4a
4c
a) 1.61 ( brs, 4H, CH2); 3.35 ( brs, 4H, CH2); 8.12 (dd, J5-4 = 8, J5-6 = 6, 2H, H5, H59); 8.61 (d, J4-5 = 8, 2H, H4, H49); 8.61 (s, 4H, NH2, NH29); 8.86 (d, J6-5 = 6, 2H, H6,
H69); 9.14 (s, 2H, H2, H29); 9.14 ( brs, 2H, NH, NH9).
3214, 3072, 1655
a) 1.94 (q, J = 6, 2H, CH2); 3.48 (t, J = 6, 4H, CH2); 8.02 (dd, J5-4 = 8, J5-6 = 6, 2H, H5, H59); 8.58 (d, J4-5 = 8, 2H, H4, H49); 8.80 (d, J6-5 = 6, 2H, H6, H69); 9.06 (s, 2H,
H2, H29).
5c
3414, 3053, 3000 – b) 2.19 (q, J = 6, 2H, CH2); 3.82 (m, 4H, CH2); 7.77 – 7.99 (dd, 2H, H6, H69); 7.77 – 7.99 (dd, 2H, H7, H79); 7.77 – 7.99 (d, 2H, H5, H59); 7.77 – 7.99 (d, 2H, H8,
2900, 1656
H89); 8.53 (d, J4-3 = 8, 2H, H4, H49); 8.75 (d, J3-4 = 8, 2H, H3, H39); 11.83 ( brs, 2H, NH, NH9).
6a
3400, 3290, 3100 – c) 1.62 ( brs, 4H, CH2); 3.14 ( brs, 2H, CH2); 7.02 (dd, J6-5 = 8, J6-7 = 8, 2H, H6, H69); 7.10 (s, 2H, H3, H39); 7.16 (dd, J5-4 = 8, J5-6 = 8, 2H, H5, H59); 7.41 (d, J4-5 = 8,
3000, 3000 – 2900, 2H, H4, H49); 7.59 (d, J7-6 = 8, 2H, H7, H79); 8.50 (t, J = 5, 2H, NH, NH9 amide); 11.53 (s, 2H, NH, NH9 indole).
1623
7
3150 – 3000, 3000 – d) 2.57 ( brs, 8H, CH2); 3.68 (s, 4H, CH2); 7.12 (dd, J5-4 = 8, J5-6 = 5, 2H, H5, H59); 7.39 (d, J3-4 = 8 2H, H3, H39); 7.62 (dd, J4-3 = 8, J4-5 = 8, 2H, H4, H49); 8.54 (d, J6-5
=
2750
3254, 3100 – 3000, b) 3.15 ( brs, 4H, CH2-pyridine); 3.96 ( brs, 4H, CH2-N); 7.11 ( brs, 1H, H6 pyridopyrimidine); 7.19 (dd, J5-4 = 8, J5-6 = 5, 2H, H5, H59 pyridine); 7.23 (d, J3-4 = 8,
3000 – 2900 2H, H3, H39 pyridine); 7.56 ( brs, 1H, H5 pyridopyrimidine); 7.64 (dd, J4-3 = 8, J4-5 = 8, 2H, H4, H49 pyridine); 8.54 ( brs, 1H, H7 pyridopyrimidine); 8.57 (d,
6-5 = 5, 2H, H6, H69 pyridine); 7.00 – 7.92-8.29 – 8.71 (dd- brs- brs- brs, 2H, NH, NH9)
3415, 3300, 3100 – b) 3.01 (t, 2H, CH2-indole); 3.10 (t, 2H, CH2-indole); 3.74 (m, 2H, CH2-N); 3.85 (m, 2H, CH2-N); 6.86 (dd, J5-4 = 8, J5-6 = 8, 1H, H5 indole); 6.97 (dd, J59-49 = 8, J59-69
5, 2H, H6, H69).
8a
J
8b
8d
3000, 3000 – 2900
= 8, 1H, H59 indole); 7.03 ( brs, 1H, H6 pyridopyrimidine); 7.03 ( brs, 2H, H6, H69 indole); 7.14 ( brs, 1H, H29 indole); 7.19 ( brs, 1H, H2 indole); 7.33 (d, J5-6
= 8, 1H, H5 pyridopyrimidine); 7.35 (d, J7-6 = 8, 2H, H7, H79 indole); 7.57 (d, J4-5 = 8, 2H, H4, H49 indole); 8.63 (d, J7-6 = 5, 1H, H7 pyridopyrimidine); 10.80 (
brs, 2H, NH, NH9 indole); 7.96 – 8.40 – 8.52 – 9.55 ( brs, 3H, NH, NH‘,HCl).
3270, 3124, 3100 – b) 1.59 ( brs, 4H, CH2); 1.97 (m, 4H, CH2); 2.94 ( brs, 4H, CH2); 3.00 ( brs, 4H, CH2-NH-CH2); 3.63 ( brs, 4H, CH2-NH-pyridopyrimidine); 7.60 (dd, J6-5 = 8, J6-7
3000, 2986, 2950,
2838
= 4, 2H, H6, H69); 8.35 ( brs, 4H, NH-HI); 8.65 (s, 2H, H2, H29); 8.68 (d, J5-6 = 8, 2H, H5, H59); 8.79 ( brs, 2H, NH-pyridopyrimidine, NH9-pyridopyrimidine);
9.01 (d, J7-6 = 4, 2H, H7, H79).
a)
b)
c)
d)
200 MHz, DMSO-d6.
400 MHz, DMSO-d6.
200 MHz, CDCl3.
400 MHz, CDCl3.
Strasbourg, France). The spectroscopic properties of the most
active compounds are summarised in Table 5.
mine (12.6 mmol) and triethylamine (3.50 mL, 25.2 mmol) in
dry chloroform and the mixture was stirred at room tempera-
ture for 1 h. The mixture was then heated under reflux for 5 h.
The solvent was removed and the residue was suspended in
water (100 mL). The resulting solid was filtered off, washed with
water and recrystallized.
General procedures for N,N9-alkyl-diyldinicotinamides
and related compounds
Method A, for compounds 1a–g
A solution of nicotinic acid (1a–f) or isonicotinic acid (1g)
(4.00 g, 32.5 mmol) in thionyl chloride (15-20 mL) was stirred
and heated under reflux for 2 h. The solvent was removed and
the residue was suspended in dry chloroform (30 mL). Triethyla-
mine was then added (4.52 mL, 32.5 mmol). The resulting solu-
tion was added dropwise at room temperature over 1 h to a mix-
ture of the appropriate diamine (16.2 mmol) and triethylamine
(4.52 mL, 32.5 mmol) in dry chloroform. After completion of the
addition, the mixture was heated under reflux for 5 h. The sol-
vent was removed and the resulting residue was subjected to the
purification method described below for each compound.
Method C, for compounds 1k–n
A solution of nicotinic acid N-oxide (4.00 g, 28.7 mmol) in thio-
nyl chloride (15–20 mL) was stirred and heated under reflux for
3 h. The solvent was removed under reduced pressure. The resi-
due was suspended in dry chloroform (30 mL) and triethylamine
was added (4.00 mL, 28.7 mmol). The resulting solution was
added dropwise to a mixture of the appropriate diamine
(14.4 mmol) and triethylamine (4.00 mL, 28.7 mmol) in dry
chloroform and the mixture was stirred at room temperature
for 1 h. The mixture was then heated under reflux for 5 h. The
solvent was removed and the resulting residue was subjected to
the purification method described for each compound.
Method B, for compounds 1h–j
A solution of 6-chloronicotinic (1h) and (1i) or 2-chloronicotinic
acid (1j) (4.00 g, 25.2 mmol) in thionyl chloride (15–20 mL) was
stirred and heated under reflux for 2 h. The solvent was removed
and the residue was suspended in dry chloroform (30 mL).
Triethylamine was then added (3.50 mL, 25.2 mmol). This solu-
tion was added dropwise to a mixture of the appropriate dia-
General procedure for N,N9-alkyl-diyldiquinoline-
carboxamide and related 2a–f
A solution of 3-quinolinic acid (2a–c) or 2-quinolinic acid (2d–f)
(2.00 g, 11.5 mmol) and thionyl chloride (15–20 mL) in dry
chloroform (50 mL) was stirred and heated under reflux for 2 h.
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M. Echeverrꢀa et al.
Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
The solvent was removed and the residue was suspended in dry
chloroform (30 mL). Triethylamine (1.61 mL, 11.6 mmol) was
added to the residue. This solution was added dropwise to a mix-
ture of the appropriate diamine (5.8 mmol) and triethylamine
(1.61 mL, 11.6 mmol) in dry chloroform and the mixture stirred
at room temperature for 1 h. The mixture was then heated
under reflux for 4 h and the solvent was removed. For com-
pounds 2a–d and 2f, the residue was suspended in water
(100 mL) and the solid filtered off. The resulting solid was
washed with boiling water (4625 mL) and recrystallized from
the solvent described for each compound.
3.8 mmol) in ethanol (50 mL) was stirred and heated under
reflux for 72 h. The solvent was removed and the resulting resi-
due was dissolved in water (40 mL). 5N KOH (10 mL) was added
until a basic pH was achieved. The solution was extracted with
dichloromethane (3630 mL). The combined extracts were
washed with water (2625 mL) and dried over anhydrous sodium
sulfate. The solvent was removed and the residue was recrystal-
lized.
Preparation of pyrido[2,3-d]pyrimidin-4-ol
A mixture of 2-aminonicotinic acid (8.00 g, 57.9 mmol) and for-
mamide (16.0 g, 355 mmol) was pulverized and heated at 1708C
(2 h at this temperature). The mixture was allowed to cool to
room temperature and water (50 mL) was added. The solid was
filtered off and washed with water (2610 mL). The solid was
recrystallized from water to give pyrido[2,3-d]pyrimidin-4-ol.
Yield 55%. IR: 3422, 3100–3000, 3000–2900. 1H-NMR (400 MHz,
DMSO-d6, d): 7.56 (dd, J6-5 = 8 Hz, J6-7 = 5 Hz, 1H, H6); 8.32 (s, 1H, H2);
8.51 (d, J5-6 = 8 Hz, 1H, H5); 8.95 (d, J7-6 = 5 Hz, 2H, H7); 12.55 ( brs,
1H, OH). Anal. Calcd. for C7H5N3O (%): C, 57.16; H, 3.40; N, 28.56;
found (%): C, 56.88; H, 3.42; N, 28.89.
General procedure for bis(1-methylpyridinium)diiodide
derivatives 3a–e
A solution of 1a, 1b, 1c, 1d or 1e (1.7 mmol) and iodomethane
(0.60 mL, 9.0 mmol) in ethanol (40 mL) was stirred and heated
under reflux for 96 h. The mixture was cooled to 08C and the
solid filtered off. The solid was washed with ethanol (2610 mL)
and recrystallized.
General procedure for bis(1-aminopyridinium) derivatives
4a–c
Preparation of 4-chloropyrido[2,3-d]pyrimidine
A solution of hydroxylamine-O-sulfonic acid (0.26 g, 2.2 mmol)
and 85% KOH (0.15 g, 2.2 mmol) in water (10 mL) was added to a
solution of the appropriate compound (1a, 1b or 1c; 1.0 mmol)
in water (7 mL) and methanol (3 mL). The mixture was stirred
and heated to 608C. The mixture was then heated under reflux
for 18 h, cooled and washed with dichloromethane (2615 mL).
Concentrated HI was added until pH 1–2 was attained. The sol-
vent was removed and the residue was dissolved in boiling 2-pro-
panol and then filtered. The resultant solid was suspended in
boiling isopropanol, filtered off, dissolved in boiling methanol,
cooled and then refiltered. The solvent was removed and the
resulting solid was isolated and recrystallized.
A solution of pyrido[2,3-d]pyrimidin-4-ol (0.75 g, 5.1 mmol) in
phosphorus oxychloride (40 mL) was stirred and heated under
reflux for 1 h. The solvent was removed under reduced pressure
and ice (50 g) was added to the resulting residue. The solution
was extracted with chloroform (10640 mL). The combined
extracts were washed with water (2680 mL) and dried over
anhydrous sodium sulfate. The solvent was removed and 4-chlor-
opyrido[2,3-d]pyrimidine (0.84 g) was obtained and used imme-
diately without further purification.
N,N9-[Piperazine-1,4-diylbis(propane-3,1-diyl)]dipyrido-
[2,3-d]pyrimidin-4-aminedihydro-chloride 8c
A solution of 4-chloropyrido[2,3-d]pyrimidine (0.84 g, 5.1 mmol),
triethylamine (0.70 mL, 5.1 mmol) and 1,4-bis(3-aminopropyl)pi-
perazine (0.51 g, 2.5 mmol) in chloroform (50 mL) was stirred
and heated under reflux for 48 h [38]. The solvent was removed.
The resulting residue was suspended in ethanol (50 mL), the
solid filtered off, washed with ethanol (3620 mL) and recrystal-
lized.
General procedure for diquinoline-dioxide derivatives
5a–c
A
solution of 3-chloroperoxybenzoic acid (77%, 0.18 g,
0.81 mmol) in dichloromethane (15 mL) was added dropwise to
a stirred solution of the appropriate compound (2d, 2e or 2f;
0.40 mmol) in dry chloroform (15 mL). The mixture was stirred
for 10 h at room temperature. A second quantity of 3-chloroper-
oxybenzoic acid (0.09 g, 0.4 mmol) was then added and the solu-
tion was stirred for 8 h. The mixture was washed with a solution
of K2CO3 (10%; 2620 mL) and water (2620 mL). The organic
layer was dried over anhydrous sodium sulfate, the solvent was
removed and the residue was recrystallized.
N,N9-Bis[3-(pyrido[2,3-d]pyrimidin-4-
ylamino)propyl]butane-1,4-diamine 8d
A solution of 4-chloropyrido[2,3-d]pyrimidine (0.84 g, 5.1 mmol),
triethylamine (0.70 mL, 5.1 mmol), KI (0.86 g, 5.1 mmol) and
spermine (0.51 g, 2.5 mmol) in chloroform (50 mL) was stirred
and heated under reflux for 48 h [38]. The mixture was filtered.
The solid was washed with water (2610 mL), suspended in boil-
ing methanol and filtered off. The solid was suspended in boil-
ing acetic acid, filtered and washed with boiling acetic acid
(10620 mL).
General procedure for indole derivatives 6a and 6b
A stirred mixture of ethyl 1H-indole-2-carboxylate (1.00 g,
5.28 mmol), the appropriate diamine (2.6 mmol) and sodium
cyanide (25 mg, 0.53 mmol) in methanol (10 mL) was heated to
608C for 96 h. The solution was filtered and the solid was washed
with boiling methanol (6620 mL). The solvent was removed and
the resulting residue was suspended in methanol (30 mL) and
the solid filtered off.
Biological evaluation
Evaluation of cytotoxic potential against human cancer
1,4-Bis(pyridin-2-ylmethyl)piperazine 7
A solution of 2-chloromethylpyridine hydrochloride (1.25 g,
7.62 mmol), K2CO3 (1.57 g, 11.4 mmol) and piperazine (0.33 g,
cell lines
An assay utilizing neutral red [33] staining was employed. Cells
were cultured in McCoy medium for HT-29 and T-24 cell lines
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Arch. Pharm. Chem. Life Sci. 2006, 339, 182–192
Symmetrical Diamides and Diamines as Apoptosis Inducers
191
and Leibovitz medium for MD-MBA-231 cell line supplemented
with 10% heat-inactivated FCS and 1% penicillin/streptomycin.
For this assay, cells were obtained from 80–90% confluent T-75
flasks by detaching the cells with PBS/EDTA. 100 lM of cells were
seeded at a density of 206103/well in 96-well plates (MicrotestTM
96 FALCONm; Becton Dickinson S.A., Madrid, Spain), but only the
60 inner wells were used in order to avoid any border effects.
Cells were allowed to attach to the bottom of the wells for 12 h
prior to the addition of the compounds. Compounds were
diluted in complete medium. The plating density permitted sev-
eral rounds of cell proliferation before confluent monolayers
were formed. After 3 days of incubation, 0.05 mL of neutral red
solution (0.05 mg /mL diluted in saline) was added to the cells in
the existing growth medium (0.2 mL) for 1 h 30 min at 378C. The
plates were flicked and 0.1 mL of 0.05 M sodium phosphate
(monobasic) in 50% ethanol was added. The plates were vortexed
in a plate shaker, incubated for 10 minutes at room temperature
and read using a plate reader at 540 nm absorbance. Data were
calculated as a percentage of total absorbance found for cells in
non-drug-treated wells.
compound. The test concentrations correspond to the IC50 values
determined in the cytotoxicity assay.
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