One-pot, four-component synthesis of novel cytotoxic agents 1-(5-aryl-1,3,4-oxadiazol-2-yl)-1-(1H-pyrrol-2-yl)methanamines

Article abstract of DOI:10.1016/j.ejmech.2014.03.049

A series of N-benzyl-1-(5-aryl-1,3,4-oxadiazol-2-yl)-1-(1H-pyrrol-2-yl) methanamines were synthesized via one-pot reaction of appropriate benzylamine, pyrrole-2-carbaldehyde, (N-isocyanimino)triphenylphosphorane, and a carboxylic acid. The anti-tumor potential of title compounds was tested against several cancer cell lines by using MTT assay. Some tested compounds including 5e, 5p and 5q exhibited comparable or better cytotoxic activity against A549, HT29 or HT1080 cells in comparison to the reference drug doxorubicin. Also, the cytotoxic activity of compounds 5d and 5n against MCF-7 was better than that of doxorubicin. Compound 5n with IC₅₀ value of 4.3 μM was 4-fold more potent than doxorubicin. The structure-activity relationship study revealed that the introduction of halogen atoms on both 5-phenyl ring and N-benzyl part improved the cytotoxic activity against all tested cell lines.

Full text of DOI:10.1016/j.ejmech.2014.03.049

European Journal of Medicinal Chemistry 78 (2014) 151e156
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
One-pot, four-component synthesis of novel cytotoxic agents
1-(5-aryl-1,3,4-oxadiazol-2-yl)-1-(1H-pyrrol-2-yl)methanamines
,
b
a
c
Ali Ramazani a , Mehdi Khoobi , Azar Torkaman , Fatemeh Zeinali Nasrabadi ,
*
Hamid Forootanfar d, Mojtaba Shakibaie d, Mandana Jafari d, Alieh Ameri d, Saeed Emami e,
Mohammad Ali Faramarzi f, Alireza Foroumadi b, Abbas Shafiee b
,
*
a Department of Chemistry, University of Zanjan, P.O. Box 45195-313, Zanjan, Iran
b Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran
14176, Iran
c Department of Chemistry, Payame Noor University, P.O. Box 19395-3697, Tehran, Iran
d Pharmaceutics Research Center, Kerman University of Medical Sciences, Kerman, Iran
e Department of Medicinal Chemistry and Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari,
Iran
f Department of Pharmaceutical Biotechnology, Faculty of Pharmacy and Biotechnology Research Center, Tehran University of Medical Sciences, P.O. Box
14155-6451, Tehran 14176, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of N-benzyl-1-(5-aryl-1,3,4-oxadiazol-2-yl)-1-(1H-pyrrol-2-yl)methanamines were synthesized
via one-pot reaction of appropriate benzylamine, pyrrole-2-carbaldehyde, (N-isocyanimino)triphenyl-
phosphorane, and a carboxylic acid. The anti-tumor potential of title compounds was tested against
several cancer cell lines by using MTT assay. Some tested compounds including 5e, 5p and 5q exhibited
comparable or better cytotoxic activity against A549, HT29 or HT1080 cells in comparison to the refer-
ence drug doxorubicin. Also, the cytotoxic activity of compounds 5d and 5n against MCF-7 was better
Received 29 January 2014
Received in revised form
14 March 2014
Accepted 15 March 2014
Available online 16 March 2014
than that of doxorubicin. Compound 5n with IC50 value of 4.3 mM was 4-fold more potent than doxo-
Keywords:
rubicin. The structureeactivity relationship study revealed that the introduction of halogen atoms on
both 5-phenyl ring and N-benzyl part improved the cytotoxic activity against all tested cell lines.
Ó 2014 Elsevier Masson SAS. All rights reserved.
Anti-cancer agents
Cytotoxic activity
1,3,4-Oxadiazole
Aza-Wittig reaction
Multi-component reactions
1. Introduction
Therefore, the development of novel anticancer agents remains a
major challenge in the field of cancer chemotherapy.
Currently cancer is a main cause of death worldwide. WHO
proposed about 17 million cancer deaths per year with available
cancer therapies by 2030 [1]. Despite many efforts to combat can-
cer, the success for treating the certain types of neoplasm has
shown little progress due their metastasis and aggressiveness [2].
Among the existing cancer therapies, chemotherapy is the most
significant treatment in cancer management [3]. Although several
drugs have been developed for management of cancer, but most of
them show no selectivity to the neoplastic cells, associated with
reduced bioavailability, toxicity and drug-resistance [4e6].
The five-membered ring 1,3,4-oxadiazole is an important het-
erocycle which plays a significant role in organic synthesis [7] and
medicinal chemistry, especially in the field of antimicrobial agents
and chemotherapy. 1,3,4-Oxadiazole derivatives showed broad
spectrum of bioactivities such as antiviral [8], antimicrobial [9,10],
anti-tubercular [11], antifungal [12], and anticancer [13e17].
A series of 2,5-disubstituted-1,3,4-oxadiazoles have been re-
ported by Ouyang et al. [18], and Tuma and co-workers [19] as
tubulin polymerization inhibitors. In vitro studies indicated that
compound 1 (Fig. 1) which interrupts mitotic division in breast
carcinoma and squamous cell tumors were more effective than the
taxane paclitaxel. Moreover, 1,3,4-oxadiazole derivatives possess-
ing 1,4-benzodioxan moiety were described as potential anticancer
agents [20]. Among the synthesized compounds, compound 2
exhibited good inhibitory activity against telomerase. Recently, Liu
et al. reported the antiproliferative and EGFR inhibition properties
* Corresponding authors.
E-mail addresses: aliramazani@gmail.com (A. Ramazani), ashafiee@ams.ac.ir
(A. Shafiee).
http://dx.doi.org/10.1016/j.ejmech.2014.03.049
0223-5234/Ó 2014 Elsevier Masson SAS. All rights reserved.

152
A. Ramazani et al. / European Journal of Medicinal Chemistry 78 (2014) 151e156
O
N
N
O
N
N
N
H
O
O
O
O
S
HN
2
1
N
CF3
N
N
N
N
O
S
O
N
S
N
H2N
F2HC
3
4
N
O
N
R2
HN
N
H
R1
H
5
Fig. 1. Compounds 1e4 with 2,5-disubstituted 1,3,4-oxadiazole structure were reported as cytotoxic agents. Compounds 5 were designed as new potential cytotoxic agents.
of a series of 2-(benzylthio)-5-aryloxadiazole derivatives exempli-
3. Pharmacology
fied by compound 3 [21]. In a study by Puthiyapurayil et al., 1,3,4-
oxadiazole
4
bearing N-methyl-4-(trifluoromethyl)phenyl pyr-
The in vitro effect of synthesized compounds 5aeq on cancer cell
viability was assessed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide) assay [24] against A549 (human
alveolar basal epithelial adenocarcinoma), HT29 (human colorectal
adenocarcinoma), HT1080 (human fibrosarcoma) and MCF-7 (hu-
man breast adenocarcinoma) cell lines. The percent of inhibition for
each concentration of the compounds was calculated comparing to
the control group. The IC50 of each compound was then determined
using the achieved dose-percent of inhibition curve. Each experi-
ment was repeated three times and the results were reported as
azole moiety was introduced as cytotoxic agent [22].
In continuation of our previous works in order to synthesize
novel heterocyclic compounds [23], herein we synthesize a new
series of 1,3,4-oxadiazoles 5 (Fig. 1) as cytotoxic agents.
2. Chemistry
The target compounds 5 were prepared by using one-pot, four-
component reaction in CH2Cl2 (Scheme 1) [23]. The 1:1 imine in-
termediate generated by the condensation reaction of appropriate
benzylamine 6 with pyrrole-2-carbaldehyde (7), was trapped by
(N-isocyanimino)triphenylphosphorane (8) in the presence of
benzoic acid derivatives 9 and led to the formation of 1,3,4-
oxadiazole derivatives 5. The reaction proceeds smoothly and
cleanly under mild and neutral conditions and no side reactions
were observed.
mean ꢀ SD (in
mM).
4. Results and discussion
The cytotoxic activities of target compounds were summarized
in Table 1 as IC50 values of tested compounds.
In general, some compounds showed good activity against
tested cell lines. The IC50 values of compounds against A549 cell
The structures of the products 5 were deduced from their IR, 1H
NMR, 13C NMR spectra, mass spectrometry and elemental analysis.
For example, The 1H NMR spectrum of 5a consists of a singlet for
line demonstrated that compound 5p with IC50 value of 13.3 mM
showed the highest activity comparable to standard drug doxoru-
bicin. Moreover, compounds 5d, 5e and 5q exhibited good cytotoxic
activity against A549 cells. Compound 5p followed by 5e and 5q
the NH proton (
¼ 3.85 ppm), a singlet for the CH proton (
multiplet for the protons of pyrrole (
¼ 6.13e6.18 and 6.80e
6.84 ppm), a singlet for the NH proton of pyrrole (
¼ 9.02 ppm),
and multiplet for the aromatic protons (
¼ 7.27e8.03 ppm). The
d
¼ 2.31 ppm), a singlet for the CH2N group
(d
d
¼ 5.34 ppm), two
d
with IC50 values of 18e20
against HT29 cells. Compounds 5d and 5o possessing IC50 values of
15.2 and 14.7 M against HT1080 had comparable inhibitory ac-
tivity in respect to doxorubicin. The most active compound against
M). It was 4-fold more potent than
mM were the most active compounds
d
d
m
1H decoupled 13C NMR spectrum of 5a shows 16 distinct reso-
nances, the assignment of these signals is given in the experi-
mental section. The 1H and 13C NMR spectra of compounds 5beq
are similar to those of compound 5a, except for the aromatic parts,
which exhibit characteristic signals with appropriate chemical
shifts.
MCF-7 was 5n (IC50 ¼ 4.3
m
doxorubicin. Also, the cytotoxic activity of compound 5d against
MCF-7 cells was better than that of doxorubicin.
A survey on IC50 values of compounds 5aef against all tested cell
lines revealed that compounds 5bef containing halogen

A. Ramazani et al. / European Journal of Medicinal Chemistry 78 (2014) 151e156
153
O
O
R2
NH2
H
R1
+
+
(Ph)3P N N C
+
HN
HO
7
8
6
9
CH2Cl2
r.t., 12 h
N
N
R2
HN
O
N
H
R1
H
5
Scheme 1. One-pot four-component synthesis of 1,3,4-oxadiazoles 5.
substituent on 5-phenyl ring were most potent than unsubstituted
analog 5a. Thus, the substitution of halogen on 5-phenyl ring
significantly increased the cytotoxic activity against all tested cell
lines. The observed results of 3- or 4-chloro derivatives (5b or 5c)
and 3,4-dichloro compound 5d revealed that the introduction of
second chlorine atom on phenyl ring was favorable for cytotoxic
activity.
Although the regioisomers 5b and 5c showed same activity
against HT1080 cells but in the cases of A549 and HT29 cells, 3-
chloro derivative 5b was more active than 4-chloro analog 5c. In
contrast, the cytotoxic activity of 4-chloro isomer 5c against MCF-7
was higher than that of 3-chloro derivative 5b. These findings
indicated that the displacement of chlorine on 5-phenyl ring had
different effect on activity depending on the type of tested cell line.
By comparing the IC50 values of 4-chloro and 4-bromo derivatives
(5c and 5f, respectively), it was revealed that 4-chloro substitution
was more favorable than 4-bromo group against all cell lines. In the
case of methyl substituent on 5-phenyl ring, the 3-metyl analog 5h
displayed better activity against all cell lines respect to the 4-
methyl isomer 5g. The replacement of 4-methyl group with 4-
methoxy substituent (5i vs. 5g) improved the cytotoxic activity
against all cancer cells with the exception of HT29.
compound had a variable pattern. For example, while the MCF-7 is
more susceptible to the compounds 5d, and 5len, but this cell line
is more resistant towards 5fek.
5. Conclusion
We have synthesized a series of N-benzyl-1-(5-aryl-1,3,4-
oxadiazol-2-yl)-1-(1H-pyrrol-2-yl)methanamines via one-pot,
four-component reaction. We believe that the reported method
offers a mild, simple, and efficient route for the preparation of the
2,5-disubstituted 1,3,4-oxadiazole prototype 5. The designed
compounds showed good anti-proliferative activity against
different cell lines. Some tested compounds including 5p, 5e and 5q
exhibited comparable or better cytotoxic activity against A549,
HT29 or HT1080 cells in respect to the reference drug doxorubicin.
Also, the cytotoxic activity of compounds 5d and 5n against MCF-7
were better than that of doxorubicin. Compound 5n with IC50 value
of 4.3 mM was 4-fold more potent than doxorubicin. The alteration
of substituents on 5-phenyl ring and N-benzyl part revealed that
the introduction of halogen atoms on both units improved the
cytotoxic activity against all tested cell lines.
The comparison of cytotoxic activities of compounds 5gej to
those of unsubstituted compound 5a demonstrated that the sub-
stitution of methyl or methoxy group on phenyl ring did not
improve the activity. The introduction of 4-methoxy group on
benzylamine moiety had positive or negative effect on cytotoxic
activity, depending on the type of cell line (compound 5l vs. 5a).
The substitution of 3-chlorophenyl in 4-methoxybenzylamine de-
rivative 5l resulted in more active compound 5m. The cytotoxic
activities of halo-substituted benzyl derivatives 5oeq were better
than those of corresponding non-halogenated analogs. Therefore,
the insertion of halogen atom on benzyl group improved the
cytotoxicity towards all tested cell lines. The observed IC50 values of
3-chlorophenyl derivatives (5b, 5m and 5p) demonstrated that the
3,4-dichlorobenzyl pendent group is more favorable. 4-
Methoxybenzyl derivative 5l showed better activity compared to
the 2-methoxybenzyl isomer 5k.
6. Experimental protocols
6.1. General chemistry
(N-Isocyanimino)triphenylphosphorane (8) was prepared based
on reported procedure [25]. Other starting materials and solvents
were obtained from Merck (Germany) and Fluka (Switzerland) and
were used without further purification. Melting points were
measured on an Electrothermal 9100 apparatus and are uncorrec-
ted. IR spectra were measured on a Jasco 6300 FTIR spectrometer.
1H and 13C NMR spectra (CDCl3) were recorded on a BRUKER DRX-
250 AVANCE spectrometer at 250.1 and 62.9 MHz, and a BRUKER
AVANCE III spectrometer at 400.2 and 100.6 MHz, respectively.
Elemental analyses were performed using a Heraeus CHNeO-Rapid
analyzer. Mass spectra were recorded on a Finnigan MAT 8430 mass
spectrometer operating at an ionization potential of 70 eV. Pre-
parative layer chromatography (PLC) plates were prepared from
Merck silica gel (F254) powder.
The IC50 values of tested compounds against different cell lines
revealed that the relative susceptibilities of cell lines to each

154
A. Ramazani et al. / European Journal of Medicinal Chemistry 78 (2014) 151e156
Table 1
Cytotoxic activity (IC50
,
m
M)a of target compounds 5aeq against different cancer cell lines in comparison with standard drug doxorubicin.
N
N
R2
HN
O
N
R1
H
H
Compound
R1
R2
A549
HT29
HT1080
MCF-7
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
H
H
H
H
H
H
H
H
H
187.0 ꢀ 6.3
62.2 ꢀ 3.1
73.8 ꢀ 2.7
25.5 ꢀ 0.7
27.5 ꢀ 0.8
87.2 ꢀ 4.1
744.5 ꢀ 36.3
430.5 ꢀ 11.3
326.5 ꢀ 13.9
296.5 ꢀ 8.8
362.5 ꢀ 11.8
277.5 ꢀ 8.8
77.5 ꢀ 1.8
53.94 ꢀ 0.5
52.8 ꢀ 2.6
13.3 ꢀ 0.8
17.3 ꢀ 0.8
13.6 ꢀ 0.5
198.1 ꢀ 13.5
48.3 ꢀ 2.4
54.5 ꢀ 2.0
41.7 ꢀ 1.9
20 ꢀ 0.7
231.0 ꢀ 9.0
41.1 ꢀ 2.4
41.0 ꢀ 1.0
15.2 ꢀ 0.5
25.6 ꢀ 0.9
70.6 ꢀ 3.1
909.3 ꢀ 44.1
311.1 ꢀ 15.2
169.5 ꢀ 8.4
418.5 ꢀ 12.9
278.5 ꢀ 8.9
174.6 ꢀ 7.9
84.6 ꢀ 0.9
51.9 ꢀ 2.2
14.7 ꢀ 0.7
25.1 ꢀ 1.8
45.3 ꢀ 2.9
15.4 ꢀ 0.6
216.4 ꢀ 13.6
56.7 ꢀ 2.6
46.2 ꢀ 2.2
13.9 ꢀ 0.6
21.7 ꢀ 1.0
96.6 ꢀ 4.1
1118.2 ꢀ 53
480.3 ꢀ 10.8
460.5 ꢀ 13.9
471.0 ꢀ 9.4
441.1 ꢀ 10.1
141.6 ꢀ 6.1
41.7 ꢀ 3.0
4.3 ꢀ 1.8
3-Cl
4-Cl
3,4-Cl2
2,4-Cl2-5-F
4-Br
4-Me
3-Me
4-OMe
2,4-(OMe)2
H
H
3-Cl
4-Br
4-OMe
3-Cl
58.3 ꢀ 5.0
248.7 ꢀ 12.0
201.5 ꢀ 3.5
343.8 ꢀ 16.7
392.4 ꢀ 11.9
392.4 ꢀ 9.8
285.6 ꢀ 9.7
95.6 ꢀ 2.7
49.5 ꢀ 2.2
39.4 ꢀ 1.8
18 ꢀ 0.9
H
H
2-OMe
4-OMe
4-OMe
4-Me
4-F
28.9 ꢀ 1.3
19.0 ꢀ 3.4
31.0 ꢀ 2.1
16.9 ꢀ 0.6
3,4-Cl2
3,4-Cl2
5q
4-Br
20 ꢀ 0.4
Doxorubicin
16.0 ꢀ 0.6
a
Each experiment was repeated three times and the results were reported as mean ꢀ SD.
6.2. General procedure for the preparation of compounds 5aeq
To a magnetically stirred solution of appropriate benzylamine 6
6.2.3. N-Benzyl-1-[5-(4-chlorophenyl)-1,3,4-oxadiazol-2-yl]-1-
(1H-pyrrol-2-yl)methanamine (5c)
Brown powder; yield: 83%; m.p. 129e131 ꢁC; IR (KBr): 3416,
(1 mmol), pyrrole-2-carbaldehyde
7
(1 mmol) and (N-iso-
2922, 2852, 1608, 1484, 1094 cmꢂ1 1H NMR (250.0 MHz, CDCl3):
;
cyanimino)triphenylphosphorane 8 (1 mmol) in CH2Cl2 (5 mL) was
added dropwise a solution of benzoic acid derivatives 9 (1 mmol) in
CH2Cl2 (5 mL) over 15 min. The mixture was stirred at room tem-
perature for 12 h. Then, the solvent was removed under reduced
pressure, and the viscous residue was purified by preparative thin
layer chromatography (PTLC) (silica gel F254), eluting with petro-
leum ethereethyl acetate (4:1).
d 2.21 (1H, s, NH amine), 3.87 (2H, s, CH2), 5.35 (1H, s, CH), 6.19e
6.21 (2H, m, 2CH pyrrole), 6.85 (1H, dd, 4JHH ¼ 2.0 Hz, 3JHH ¼ 4.0 Hz,
CH pyrrole), 7.27e7.37 (5H, m, CH Ar), 7.49 (2H, d, 3JHH ¼ 8.4 Hz, CH
3
Ar), 7.97 (2H, d, JHH ¼ 8.4 Hz, CH Ar), 8.98 (1H, s, NH pyrrole). 13
C
NMR (62.5 MHz, CDCl3): d 51.22, 51.77, 107.87, 108.67, 118.66, 127.45,
128.27, 128.33, 128.61, 129.44, 122.16, 126.85, 138.16, 138.83, 164.33,
166.27. Anal. Calcd for C20H17ClN4O: C, 65.84; H, 4.70; N, 15.36;
Found: C, 66.71; H, 4.59; N, 15.49.
6.2.1. N-Benzyl-1-(5-phenyl-1,3,4-oxadiazol-2-yl)-1-(1H-pyrrol-2-
yl)methanamine (5a)
6.2.4. N-Benzyl-1-[5-(3,4-dichlorophenyl)-1,3,4-oxadiazol-2-yl]-1-
(1H-pyrrol-2-yl)methanamine (5d)
Brown powder; yield: 85%; m.p. 103e105 ꢁC; IR (KBr): 3299,
2923, 2852, 1552, 1450, 705 cmꢂ1
;
1H NMR (250.0 MHz, CDCl3):
Brown powder; yield: 87%; m.p. 144e146 ꢁC; IR (KBr): 3416,
d
2.31 (1H, s, NH amine), 3.85 (2H, s, CH2), 5.34 (1H, s, CH), 6.13e
2922, 2852, 1634, 1455, 729 cmꢂ1
;
1H NMR (400.2 MHz, CDCl3):
2
6.18 (2H, m, 2CH pyrrole), 6.80e6.84 (1H, m, CH pyrrole), 7.27e8.03
d
2.49 (1H, s, NH amine), 3.87 and 3.95 (2H, ABq, JHH ¼ 13.2 Hz,
(10H, m, CH Ar), 9.02 (1H, s, NH pyrrole). 13C NMR (62.5 MHz,
CH2), 5.41 (1H, s, CH), 6.21 (2H, s, 2CH pyrrole), 6.88 (1H, s, CH
CDCl3):
d
51.18, 51.77, 107.79, 108.59, 118.57, 126.98, 127.37, 128.31,
pyrrole), 7.29e8.13 (8H, m, CH Ar), 9.13 (1H, s, NH pyrrole). 13C NMR
128.56, 129.00, 131.80, 123.70, 127.03, 138.93, 165.09, 166.12. Anal.
Calcd for C20H18N4O: C, 72.71; H, 5.49; N, 16.96; Found: C, 72.56; H,
5.67; N, 16.73.
(100.6 MHz, CDCl3): d 51.25, 51.78, 107.92, 108.70, 118.74, 126.00,
127.47, 128.32, 128.62, 128.69, 131.25, 123.45, 126.45, 133.68, 136.37,
138.75, 163.33, 166.57. Anal. Calcd for C20H16Cl2N4O: C, 60.16; H,
4.04; N, 14.03; Found: C, 60.32; H, 4.16; N, 14.36.
6.2.2. N-Benzyl-1-[5-(3-chlorophenyl)-1,3,4-oxadiazol-2-yl]-1-
(1H-pyrrol-2-yl)methanamine (5b)
6.2.5. N-Benzyl-1-[5-(2,4-dichloro-5-fluorophenyl)-1,3,4-
oxadiazol-2-yl]-1-(1H-pyrrol-2-yl)methanamine (5e)
Brown powder; yield: 90%; m.p. 81e83 ꢁC; IR (KBr): 3416, 2922,
2852,1637,1122, 613 cmꢂ1; 1H NMR (250.0 MHz, CDCl3):
d
2.20 (1H,
Brown powder; yield: 86%; m.p. 107e109 ꢁC; IR (KBr): 3417,
s, NH amine), 3.87 (2H, s, CH2), 5.36 (1H, s, CH), 6.19e6.21 (2H, m,
2CH pyrrole), 6.85 (1H, dd, 4JHH ¼ 2.4 Hz, 3JHH ¼ 4.4 Hz, CH pyrrole),
7.28e8.02 (9H, m, CH Ar), 8.97 (1H, s, NH pyrrole). 13C NMR
2922, 2851, 1634, 1457, 1085, 730 cmꢂ1 1H NMR (400.2 MHz,
;
CDCl3):
d 2.33 (1H, s, NH amine), 3.85 and 3.89 (2H, ABq,
2JHH ¼ 13.6 Hz, CH2), 5.39 (1H, s, CH), 6.18e6.21 (2H, m, 2CH pyr-
(62.5 MHz, CDCl3):
d 51.24, 51.79, 107.90, 108.69, 118.69, 125.10,
role), 6.85 (1H, dd, 4JHH ¼ 2.8 Hz, 3JHH ¼ 5.0 Hz, CH pyrrole), 7.28e
3
126.98, 127.46, 128.34, 128.62, 130.41, 131.90, 125.30, 126.77, 135.20,
138.79, 164.00, 166.43. Anal. Calcd for C20H17ClN4O: C, 65.83; H,
4.70; N, 15.36; Found: C, 65.54; H, 5.08; N, 15.14.
7.38 (3H, m, CH Ar), 7.64 (2H, d, JHH ¼ 8.4 Hz, CH Ar), 7.80 (2H, d,
3JHH ¼ 8.4 Hz, CH Ar), 9.01 (1H, s, NH pyrrole). 13C NMR (100.6 MHz,
CDCl3):
d 51.26, 51.78, 107.96, 108.68, 118.76, 127.46, 128.33, 128.61,

A. Ramazani et al. / European Journal of Medicinal Chemistry 78 (2014) 151e156
155
133.01, 118.46 (d, 2JCF ¼ 24.9 Hz, CH), 125.50, 126.56, 138.77, 140.96,
(1H, s, NH pyrrole). 13C NMR (100.6 MHz, CDCl3):
d
51.09, 51.67,
1
156.58 (d, JCF ¼ 249.7 Hz, C), 161.93, 166.98. Anal. Calcd for
55.57, 55.96, 98.98, 105.33, 107.72, 108.37, 118.81, 127.28, 128.37,
128.51, 131.63, 105.90, 127.33, 139.11, 159.37, 163.76, 165.24. MS: m/z
(%) ¼ 390 (1), 285 (94), 165 (78), 106 (87), 91 (100), 77 (69), 57 (35).
Anal. Calcd for C22H22N4O3: C, 67.68; H, 5.68; N, 14.35; Found: C,
67.49; H, 5.51; N, 14.58.
C
20H15Cl2FN4O: C, 57.57; H, 3.62; N, 13.43; Found: C, 57.33; H, 3.81;
N, 13.64.
6.2.6. N-Benzyl-1-[5-(4-bromophenyl)-1,3,4-oxadiazol-2-yl]-1-
(1H-pyrrol-2-yl)methanamine (5f)
Brown powder; yield: 87%; m.p. 139e141 ꢁC; IR (KBr): 3299,
6.2.11. N-(2-Methoxybenzyl)-1-(5-phenyl-1,3,4-oxadiazol-2-yl)-1-
(1H-pyrrol-2-yl)methanamine (5k)
2923, 2852, 1552, 1450, 705 cmꢂ1 1H NMR (250.1 MHz, CDCl3):
;
d
2.41 (1H, s, NH amine), 3.83 (2H, s, CH2), 5.32 (1H, s, CH), 6.18 (2H,
Brown powder; yield: 82%; m.p. 106e108 ꢁC; IR (KBr): 3439,
s, 2CH pyrrole), 6.82e6.83 (1H, m, CH pyrrole), 7.27e7.32 (5H, m,
CH Ar), 7.61 (2H, d, 3JHH ¼ 8.5 Hz, CH Ar), 7.32 (2H, d, 3JHH ¼ 8.5 Hz,
2926, 2836, 1443, 1161, 1085, 707 cmꢂ1 1H NMR (400.2 MHz,
;
CDCl3):
d 2.70 (1H, s, NH amine), 3.83 (3H, s, OCH3), 3.83 and 3.93
CH Ar), 9.15 (1H, s, NH pyrrole). 13C NMR (62.5 MHz, CDCl3):
d
51.17,
(2H, ABq, JHH ¼ 13.6 Hz, CH2), 5.38 (1H, s, CH), 6.19e6.20 (2H, m,
2
51.74, 107.91, 108.57, 118.77, 127.42, 128.36, 128.59, 132.36, 122.51,
126.56, 126.81, 138.80, 164.39, 166.33. Anal. Calcd for C20H17BrN4O:
C, 58.69; H, 4.19; N, 13.69; Found: C, 59.37; H, 4.30; N, 13.51.
2CH pyrrole), 6.85e8.04 (10H, m, CH Ar and CH pyrrole), 9.14 (1H, s,
NH pyrrole). 13C NMR (100.6 MHz, CDCl3):
d 47.17, 51.80, 55.28,
107.69, 108.53, 110.34, 118.39, 120.50, 126.97, 128.82, 128.97, 130.34,
131.74, 123.79, 126.83, 127.22, 157.72, 165.00, 166.29. Anal. Calcd for
6.2.7. N-Benzyl-1-[5-(4-methylphenyl)-1,3,4-oxadiazol-2-yl]-1-
(1H-pyrrol-2-yl)methanamine (5g)
C21H20N4O2: C, 69.98; H, 5.59; N, 15.55; Found: C, 70.22; H, 5.33; N,
15.30.
Brown powder; yield: 89%; m.p. 107e109 ꢁC; IR (KBr): 3415,
2922, 2852, 1617, 1499, 1120, 728 cmꢂ1
;
1H NMR (250.1 MHz,
6.2.12. N-(4-Methoxybenzyl)-1-(5-phenyl-1,3,4-oxadiazol-2-yl)-1-
(1H-pyrrol-2-yl)methanamine (5l)
CDCl3):
d 2.20 (1H, s, NH amine), 2.45 (CH3), 3.86 (2H, s, CH2), 5.35
(1H, s, CH), 6.19e6.20 (2H, m, 2CH pyrrole), 6.85 (1H, dd,
4JHH ¼ 2.0 Hz, 3JHH ¼ 4.0 Hz, CH pyrrole), 7.26e7.36 (5H, m, CH Ar),
7.31(2H, d, 3JHH ¼ 8.0 Hz, CH Ar), 7.92 (2H, d, 3JHH ¼ 8.0 Hz, CH Ar),
Brown powder; yield: 90%; m.p. 107e109 ꢁC; IR (KBr): 3415,
2924, 2836, 1613, 1449, 1031,730 cmꢂ1 1H NMR (400.2 MHz,
;
CDCl3):
d
¼ 2.97 (1H, s, NH amine), 3.77 (3H, s, OCH3), 3.75 and 3.80
9.04 (1H, s, NH pyrrole). 13C NMR (62.5 MHz, CDCl3):
d
21.66, 51.18,
(2H, ABq, JHH ¼ 14.0 Hz, CH2), 5.36 (1H, s, CH), 6.17e6.18 (2H, m,
2
51.76, 107.81, 108.58, 118.57, 126.97, 127.40, 128.36, 128.59, 129.73,
120.92, 127.07, 138.93, 142.42, 165.27, 165.83. Anal. Calcd for
2CH pyrrole), 6.81e6.85 (1H, m, CH pyrrole), 7.24e8.03 (9H, m, CH
Ar), 9.43(1H, s, NH pyrrole). 13C NMR (100.6 MHz, CDCl3):
d 50.63,
C
21H20N4O: C, 73.23; H, 5.85; N, 16.27; Found: C, 73.51; H, 5.56; N,
51.60, 55.27, 107.72, 108.61, 113.97, 118.50, 127.00, 129.03, 129.58,
131.83, 123.71, 127.08, 130.95, 158.94, 165.09, 166.13. Anal. Calcd for
16.51.
C21H20N4O2: C, 69.98; H, 5.59; N, 15.55; Found: C, 70.55; H, 5.23; N,
6.2.8. N-Benzyl-1-[5-(3-methylphenyl)-1,3,4-oxadiazol-2-yl]-1-
(1H-pyrrol-2-yl)methanamine (5h)
15.72.
Brown powder; yield: 89%; m.p. 99e101 ꢁC; IR (KBr): 3445,
6.2.13. N-(4-Methoxybenzyl)-1-[5-(3-chlorophenyl)-1,3,4-
oxadiazol-2-yl]-1-(1H-pyrrol-2-yl)methanamine (5m)
Brown powder; yield: 90%; m.p. 86e88 ꢁC; IR (KBr): 3413, 2925,
2922, 2852, 1635, 1619, 1551, 699 cmꢂ1 1H NMR (400.2 MHz,
;
CDCl3): d 2.44 (3H, s, CH3), 2.54 (1H, s, NH amine), 3.87 (2H, s, CH2),
5.38 (1H, s, CH), 6.20e6.21 (2H, m, 2CH pyrrole), 6.86 (1H, dd,
2850, 1637, 1406, 1103, 773 cmꢂ1 1H NMR (400.2 MHz, CDCl3):
;
4JHH ¼ 2.4 Hz, 3JHH ¼ 4.4 Hz, CH pyrrole), 7.27e7.86 (9H, m, CH Ar),
d
2.42 (1H, s, NH amine), 3.79 (3H, s, OCH3), 3.80 and 3.85 (2H, ABq,
9.18 (1H, s, NH pyrrole). 13C NMR (100.6 MHz, CDCl3):
d
29.72, 51.19,
2JHH ¼ 13.2 Hz, CH2), 5.38 (1H, s, CH), 6.19 (2H, s, 2CH pyrrole),
6.81e8.03 (9H, m, CH Ar and CH pyrrole), 9.08 (1H, s, NH pyrrole).
51.76, 107.79, 108.62, 118.55, 124.16, 127.41, 127.51, 128.34, 128.59,
128.94, 132.66, 123.55, 127.05, 138.90, 138.94, 165.30, 165.98. MS:
m/z (%) ¼ 258 (50), 185 (18), 139 (20), 106 (95), 91 (100), 71 (67), 57
(98). Anal. Calcd for C21H20N4O: C, 73.23; H, 5.85; N, 16.27; Found:
C, 73.50; H, 5.61; N, 16.48.
13C NMR (100.6 MHz, CDCl3):
d 50.65, 51.62, 55.26, 107.81, 108.63,
113.96, 118.63, 125.08, 126.95, 129.57, 130.39, 131.86, 125.30, 126.87,
130.86, 135.16, 158.94, 163.95, 166.50. Anal. Calcd for C21H19ClN4O2:
C, 63.88; H, 4.85; N, 14.19; Found: C, 63.71; H, 4.60; N, 14.29.
6.2.9. N-Benzyl-1-[5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl]-1-
(1H-pyrrol-2-yl)methanamine (5i)
6.2.14. N-(4-Methylbenzyl)-1-[5-(4-bromophenyl)-1,3,4-oxadiazol-
2-yl]-1-(1H-pyrrol-2-yl)methanamine (5n)
Brown powder; yield: 88%; m.p. 96e98 ꢁC; IR (KBr): 3415, 2923,
Yellow powder; yield: 86%; m.p. 136e138 ꢁC; IR (KBr): 3431,
2851, 1616, 1172, 1026 cmꢂ1
;
1H NMR (250.0 MHz, CDCl3):
d
2.34
2921, 2852, 1603, 1480, 826 cmꢂ1 1H NMR (250.1 MHz, CDCl3):
;
(1H, s, NH amine), 3.88 (2H, s, CH2), 3.90 (3H, s, OCH3), 5.34 (1H, s,
d 2.30 (3H, s, CH3), 2.41 (1H, s, NH amine), 3.80 (2H, s, CH2), 5.31(1H,
4
CH), 6.19e6.20 (2H, m, 2CH pyrrole), 6.84 (1H, dd, JHH ¼ 2.0 Hz,
s, CH), 6.13e6.17 (2H, m, 2CH pyrrole), 6.79e6.82 (1H, m, CH pyr-
role), 7.11 (2H, d, 3JHH ¼ 8.5 Hz, CH Ar), 7.20 (2H, d, 3JHH ¼ 7.0 Hz, CH
Ar), 7.61 (2H, d, 3JHH ¼ 7.0 Hz, CH Ar), 7.81 (2H, d, 3JHH ¼ 8.5 Hz, CH
3JHH ¼ 4.0 Hz, CH pyrrole), 7.01 (2H, d, 3JHH ¼ 9.2 Hz, CH Ar), 7.27e
7.37 (5H, m, CH Ar), 7.97(2H, d, 3JHH ¼ 9.2 Hz, CH Ar), 9.02 (1H, s, NH
pyrrole). 13C NMR (62.5 MHz, CDCl3):
108.58, 114.46, 118.54, 127.39, 128.35, 128.59, 128.79, 116.19, 127.12,
138.93, 162.41, 165.07, 165.57. Anal. Calcd for C21H20N4O2: C, 69.98;
H, 5.59; N, 15.55; Found: C, 69.66; H, 5.82; N, 15.32.
d
¼ 51.18, 51.74, 55.48, 107.78,
Ar), 9.08 (1H, s, NH pyrrole). 13C NMR (62.5 MHz, CDCl3):
d 21.06,
50.91, 51.67, 107.81, 108.56, 118.65, 128.27, 128.35, 129.24, 132.33,
122.54, 126.50, 126.88, 135.75, 137.05, 164.32, 166.36. Anal. Calcd for
C21H19BrN4O: C, 59.58; H, 4.52; N,13.24; Found: C, 59.72; H, 4.27; N,
13.51.
6.2.10. N-Benzyl-1-[5-(2,4-dimethoxyphenyl)-1,3,4-oxadiazol-2-
yl]-1-(1H-pyrrol-2-yl)methanamine (5j)
6.2.15. N-(4-Fluorobenzyl)-1-[5-(4-methoxyphenyl)-1,3,4-
oxadiazol-2-yl]-1-(1H-pyrrol-2-yl)methanamine (5o)
Orange powder; yield: 86%; m.p. 98e100 ꢁC; IR (KBr): 3441,
2922, 2852, 1613, 1455, 1119, 721 cmꢂ1
;
1H NMR (400.2 MHz,
Orange powder; yield: 87%; m.p. 93e95 ꢁC; IR (KBr): 3417, 1613,
CDCl3):
d
2.90 (1H, s, NH amine), 3.85 (2H, s, CH2), 3.90 (3H, s,
1499, 1027, 836 cmꢂ1 1H NMR (250.1 MHz, CDCl3):
; d 2.30 (1H, s,
OCH3), 3.92 (3H, s, OCH3), 5.37 (1H, s, CH), 6.16e6.19 (2H, m, 2CH
pyrrole), 6.81 (1H, s, CH pyrrole), 7.27e7.84 (8H, m, CH Ar), 9.39
NH amine), 3.79 (2H, s, CH2), 3.86 (3H, s, OCH3), 5.29 (1H, s, CH),
6.16e6.17 (2H, m, 2CH pyrrole), 6.79e6.82 (1H, m, CH pyrrole),

156
A. Ramazani et al. / European Journal of Medicinal Chemistry 78 (2014) 151e156
6.95e7.95 (8H, m, CH Ar), 9.23 (1H, s, NH pyrrole). 13C NMR
Acknowledgments
(62.5 MHz, CDCl3):
d 50.37, 51.68, 55.44, 107.78, 108.53, 114.44,
118.58, 132.00, 115.31 (d, 2JCF ¼ 21.3 Hz, CH), 129.90 (d, 3JCF ¼ 8.1 Hz,
This work was supported by grants from the Iran National Sci-
ence Foundation (INSF), Research Council of Tehran University of
Medical Sciences and University of Zanjan.
1
CH), 116.13, 127.01, 134.71, 162.40, 162.00 (d, JCF ¼ 251.6 Hz, C),
165.04, 165.46. Anal. Calcd for C21H19FN4O2: C, 66.66; H, 5.06; N,
14.81; Found: C, 66.49; H, 5.21; N, 14.63.
Appendix A. Supplementary data
6.2.16. N-(3,4-Dichlorobenzyl)-1-[5-(3-chlorophenyl)-1,3,4-
oxadiazol-2-yl]-1-(1H-pyrrol-2-yl)methanamine (5p)
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2014.03.049.
Brown powder; yield: 84%; m.p. 96e98 ꢁC; IR (KBr): 3445, 2923,
2851, 1637, 1467, 1092, 794 cmꢂ1
;
1H NMR (400.2 MHz, CDCl3):
2
d
2.37 (1H, s, NH amine), 3.82 (2H, ABq, JHH ¼ 14.4 Hz, CH2), 5.34
References
(1H, s, CH), 6.21(2H, s, CH pyrrole), 6.87 (1H, s, CH pyrrole), 7.16e
7.99 (7H, m, CH Ar), 9.08 (1H, s, NH pyrrole). 13C NMR (100.6 MHz,
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130.14, 130.45, 132.00, 126.28, 127.30, 131.35, 132.61, 135.23, 139.20,
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6.2.17. N-(3,4-Dichlorobenzyl)-1-[5-(4-bromophenyl)-1,3,4-
oxadiazol-2-yl]-1-(1H-pyrrol-2-yl)methanamine (5q)
Brown powder; yield: 85%; m.p. 98e101 ꢁC; IR (KBr): 3417, 2924,
2851, 1602, 1480, 1030, 792 cmꢂ1 1H NMR (400.2 MHz, CDCl3):
;
d
2.19 (1H, s, NH amine), 3.82 and 3.86 (2H, ABq, 2JHH ¼ 14 Hz, CH2),
5.34 (1H, s, CH), 6.21 (2H, s, 2CH pyrrole), 6.87e6.88 (1H, m, CH
pyrrole), 7.17e7.48 (3H, m, CH Ar), 7.66 (2H, d, 3JHH ¼ 8.4 Hz, CH Ar),
7.89 (2H, d, 3JHH ¼ 8.4 Hz, CH Ar), 9.03 (1H, s, NH pyrrole). 13C NMR
(100.6 MHz, CDCl3):
d 50.00, 51.86, 108.21, 108.71, 118.99, 127.59,
128.36, 130.15, 130.45, 132.43, 122.39, 126.35, 126.71, 132.03, 132.13,
139.25, 164.33,166.27. MS: m/z (%) ¼ 390 (1), 285 (94), 165 (78), 106
(87), 91 (100), 77 (69), 57 (35). MS: m/z (%) ¼ 478 (3), 303 (100), 183
(50), 159 (65), 140 (68), 94 (48), 57 (45). Anal. Calcd for
C
20H15BrCl2N4O: C, 50.24; H, 3.16; N, 11.72; Found: C, 50.41; H, 3.37;
N, 11.51.
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compound in DMEM media containing DMSO (0.5% v/v) and added
into desired well and incubated for another 24 h. Negative control
was provided by addition of same volume of DMEM medium to
related well. Doxorubicin was used as positive control. Thereafter,
the media were removed and 20
MTT (5 mg/mL) was added to each well followed by incubation for
further 4 h and insertion of DMSO (100 L) to dissolve formazan
mL DMEM medium containing
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m
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crystal. The optical density of each well was subsequently
measured at 570 nm using Synergy 2 multi-mode microplate
reader (BioTek, USA) [24].