Synthesis and cytotoxic activities of 2-(4-(2-heterocycloethoxy)phenyl)-1, 2,4-triazolo[1,5-a] pyridines

Article abstract of DOI:10.2174/157017811795038377

Nine 2-(4-(2-heterocycloethoxy)phenyl)-1,2,4-triazolo[1,5-a] pyridines have been synthesized. The structures of all products were confirmed by ¹H NMR and HRMS. The cytotoxic activities of these compounds were evaluated against human ovary cance

Full text of DOI:10.2174/157017811795038377

180
Letters in Organic Chemistry, 2011, 8, 180-183
Synthesis and Cytotoxic Activities of 2-(4-(2-heterocycloethoxy)phenyl)-
1,2,4-triazolo[1,5-a] Pyridines
Guolin Zhang* and Jun Chen
Department of Medicinal Chemistry, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058,
P. R. China
Received July 19, 2010: Revised November 10, 2010: Accepted February 10, 2011
Abstract: Nine 2-(4-(2-heterocycloethoxy)phenyl)-1,2,4-triazolo[1,5-a] pyridines have been synthesized. The structures
1
of all products were confirmed by H NMR and HRMS. The cytotoxic activities of these compounds were evaluated
against human ovary cancer cell line (HO-8910) in vitro by MTT method. The preliminary results showed that compound
4e (IC50 0.11mM) and compound 4f (IC50 0.11mM) exhibited moderate activity against the cancer cell line when
compared with Cisplatin.
Keywords: Synthesis, cytotoxic, 1,2,4-triazolo[1,5-a] pyridines.
2-Aryl-1,2,4-triazolo[1,5-a]pyridines have been found to
have pregnancy interceptive activity [1]. The mechanism of
pregnancy interceptive activity was cell apoptosis to cause
luteolysis [2]. Because tumor cells grow vigorously like
embryo cells, we had synthesized 2-(substituted) phenyl
1,2,4- triazolo[1,5-a] pyridines and their cytotoxic activities
had been evaluated in the recent paper [3]. We founded that
2-(4-benzyloxyphenyl)-8- methyl-1, 2, 4-triazolo [1, 5-a]
pyridine and 2-(4- benzyloxyphenyl)-5-methyl-1, 2, 4-
triazolo [1, 5-a] pyridine exhibited stronger activity against
the cancer cell line when compared with Cisplatin. However,
they have very low solubility, which hinder them from clinic
application.
compounds 3, which on treatment with the various
heterocycles gave target compounds 4a-4i. Physical
properties and HRMS [M+] data of 4a-4i were summarized
in Table 1.
The cytotoxic activities of 4a-4i were evaluated against
human ovary cancer cell line (HO-8910) in vitro by MTT
method [6]. The results were summarized in Table 1. The
IC50 value represents the drug concentration (mM) required
to inhibit the cell growth by 50%. The preliminary results
showed that some synthetic compounds exhibited activities
against human ovary cancer cell line (HO-8910) in vitro. The
most potent compounds were 5-methyl-2-(morpholino-4-
yl)ethyloxy phenyl-1, 2, 4-triazolo [1, 5-a] pyridine 4e and 8-
methyl-2-(morpholino-4-yl)ethyloxyphenyl-1,2, 4-triazolo
[1, 5-a] pyridine 4f. Their IC50 values were 0.11mM and
0.11mM respectively. The cytotoxic activities of compounds
were affected by the sort of heterocycle (4a,4c,4e,4h), the
compound with morpholine (4e) had more potent cytotoxic
activity. 5-Methyl substituted compounds and 8-methyl
substituted compounds almost had same cytotoxic activities
(4a vs 4b, 4c vs 4d, 4e vs 4f), 7-methyl substituted
compound had less cytotoxic activity (4g vs 4e and 4f).
Heterocycles, such as piperazine, piperidine and
morpholine are frequently introduced to compounds to
improve their hydrophilic character. Heterocycles also play
an important role in the optimization of leading compound.
For
example,
5-Methyl-2-(morpholino-4-yl)-ethyloxy-
phenyl-1,2,4- triazolo [1, 5-a] pyridine has growth inhibitory
activities against fungi[4] and 5-methyl-2- (piperazin-1-yl)-
ethyloxyphenyl-1,2,4- triazolo [1, 5-a] pyridine has cytotoxic
activities against cancer cell lines[5]. Thus, we designed and
synthesized 2-(4-(2-hetero cycloethoxy) phenyl)-1,2,4-
triazolo [1,5-a] pyridines in order to increase their solubility
and find new compounds which have stronger cytotoxic cell
activity.
EXPERIMENTAL
Melting points were recorded on a BUCHI melting point
B-540 apparatus and were uncorrected. 1HNMR spectral
were determined in CDCl3 on
a
Bruker 400MHz
RESULTS AND DISCUSSION
spectrometer with SiMe4 as the internal standard. J values
are given in Hz. Mass spectral data were recorded on a
Bruker Esquir 3000 plus instrument. HRMS data were
obtained on a Bruker FT-ICR-MS Apex III apparutas.
Scheme 1 outline the synthetic sequences employed in
our laboratories for preparation of 4a-4i. Compounds 1 were
prepared by the procedure of the previous paper in our
laboratory [3]. Hydrogenation of 1 by 10% Pd/C afforded
compounds 2. 2 were coupled to 1,2-dibromo ethane to form
General Procedure for the Synthesis of 2-hydroxyphenyl-
1, 2, 4-triazolo [1, 5-a] Pyridines 2
*Address correspondence to this author at the Department of Medicinal
Chemistry, College of Pharmaceutical Sciences, Zhejiang University,
Hangzhou, 310058, P. R. China; Tel: 8657188208450;
2.80 g 2-(4-Benzyloxyphenyl)-1, 2, 4-triazolo [1, 5-a]
pyridines 1, 0.28 g 10% Pd/C and 30 ml DMF were added to
a 50 ml round-bottomed flask. After three vacuum/hydrogen
Fax: 8657188208450; E-mail: guolinzhang@zju.edu.cn
1570-1786/11 $58.00+.00
© 2011 Bentham Science Publishers Ltd.

Synthesis and Cytotoxic Activities
Letters in Organic Chemistry, 2011, Vol. 8, No. 3
181
H3C
H3C
10%Pd/C
H2
BrCH2CH2Br
N
N
N
N
NaOH
OH
OCH2C6H5
N
N
1
2
H3C
HN
N
N
H3C
OCH2CH2
N
N
N
N
OCH2CH2Br
N
4a-4b
HN
X R
H3C
3
N
N
OCH2CH2
N
N
X
R
4c-4i
Scheme 1.
Table 1. Physical Analytical Data and IC50 of Compounds 4a-4i
Compound
HRMS [M+] Calcd
Found
IC50
(mM)
Mp (°C)
Molecular
Formula
4a
46-48
C19H22N4O
C19H22N4O
C20H24N4O
C20H24N4O
C19H22N4O2
322.1794
322.1794
336.1950
336.1950
338.1743
322.1797
*
H3C
N
N
OCH2CH2
N
N
4b
4c
4d
4e
96-98
78-80
322.1792
336.1952
336.1951
338.1745
*
CH3
N
N
OCH2CH2
N
N
0.18
0.18
0.11
H3C
N
N
OCH2CH2
N
N
76-78
CH3
N
N
OCH2CH2
N
N
134-136[4]
H3C
N
N
OCH2CH2
N
N
O

182 Letters in Organic Chemistry, 2011, Vol. 8, No. 3
Zhang and Chen
(Table 1). Contd…..
HRMS [M+] Calcd
Found
IC50
(mM)
Compound
Mp (°C)
Molecular
Formula
4f
80-82
C19H22N4O2
338.1743
338.1742
0.11
0.27
CH3
N
N
OCH2CH2
N
O
N
4g
102-104
C19H22N4O2
338.1743
338.1745
CH3
N
N
N
OCH2CH2
N
O
4h
4i
92-94[5]
C19H23N5O
337.1903
351.2059
337.1902
351.2057
0.47
0.37
0.04
H3C
N
N
N
OCH2CH2
N
NH
79-81
C20H25N5O
CH3
N
N
OCH2CH2
N
N
N
CH3
cisplatin
*The IC50 values were more than 1.5mM.
cycles to remove air from the reaction flask, the reaction
mixture was stirred at room temperature under hydrogen.
When the reaction was deemed complete by TLC, the
mixture was filtrated and the filtration was diluted with 100
ml water. The solid was collected by vacuum filtration,
washed twice with 30 ml water and dried under vacuum. The
product was carried on to the next step without further
purification.
(d, J=8.8Hz,1H), 8.28(d, J=8.8Hz , 2H); ms: m/z 331(M+),
333 (M++2).
2-Bromoethyloxyphenyl-7-methyl-1,2,4- triazolo [1, 5-a]
pyridine (3b)
This compound was obtained as a white solid. yield,
87.9%; mp 126~128°C; 1H nmr: 2.50 (s, 3H), 3.68 (t,
J=6.3Hz, 2H), 4.37 (t, J=6.3Hz, 2H), 6.83 (dd, J=6.9Hz,
J=1.1Hz, 1H), 7.02 (d, J=8.7Hz , 2H), 7.53 (s, 1H), 8.22 (d,
J=8.7Hz, 2H), 8.44 (d, J=6.9Hz , 1H); ms: m/z 331(M+), 333
(M++2).
General Procedure for the Synthesis of 2-bromoethyloxy
phenyl-1, 2, 4-triazolo [1, 5-a] Pyridines 3
2-Bromoethyloxyphenyl-8-methyl-1, 2, 4-triazolo [1, 5-a]
pyridine (3c)
1.50 g (6 mmol) 2-Hydroxyphenyl-1, 2, 4-triazolo [1, 5-
a] pyridines 2, 6.76 g (36 mmol) BrCH2CH2Br, 2.4 g NaOH,
3.6 ml water and 0.1 g TBAB were added to a 25 ml round-
bottomed flask. The reaction mixture was stirred at reflux
temperature. When the reaction was deemed complete by
TLC, the mixture was cooled and diluted with 50 ml CH2Cl2
and 50 ml water. The CH2Cl2 layer was washed with water
(3 ꢀ 30ml), dried over anhydrous Na2SO4 and evaporated to
dryness under reduced pressure. The residue was purified by
column chromatography (ethyl acetate: petroleum ether =
1:2) to afford the target compound.
This compound was obtained as a white solid. yield,
1
87.9%; mp 112~114°C; H nmr: 2.69 (s, 3H), 3.68 (t,
J=6.3Hz, 2H), 4.36 (t, J=6.3Hz, 2H), 6.89 (dd, J=6.9Hz,
J=1.1Hz, 1H), 7.01 (d, J=8.7Hz , 2H), 7.25 (d, J=6.9Hz, 1H),
8.23 (d, J=8.7Hz, 2H), 8.42 (d, J=6.9Hz , 1H); ms: m/z
331(M+), 333 (M++2).ms: m/z 239 (M+).
General Procedure for the Synthesis of 2-(4-(2-hetero
cycloethoxy) phenyl-1,2,4- triazolo [1,5-a] Pyridines 4
2-Bromoethyloxyphenyl-5-methyl-1,2,4- triazolo [1, 5-a]
pyridine (3a)
0.25 g (0.75 mmol) 2-Bromoethyloxyphenyl-1, 2, 4-
triazolo [1, 5-a] pyridines 3, 5 mmol heterocycle and 5 ml
CHCl3 were added to a 25 ml round-bottomed flask. The
reaction mixture was stirred at room temperature. When the
reaction was deemed complete by TLC, the mixture was
diluted with 50 ml CH2Cl2 and 50 ml water. The CH2Cl2
layer was washed with water (3 ꢀ 30ml), dried over
This compound was obtained as a white solid. yield,
85.8%; mp 123~125°C; 1H nmr: 2.84 (s, 3H), 3.68 (t,
J=6.3Hz, 2H), 4.37 (t, J=6.3Hz, 2H), 6.83 (d, J=7.1Hz, 1H),
7.03 (d, J=8.8Hz , 2H), 7.45 (t, J=7.1Hz, J=8.8Hz, 1H), 7.64

Synthesis and Cytotoxic Activities
Letters in Organic Chemistry, 2011, Vol. 8, No. 3
183
anhydrous Na2SO4 and evaporated to dryness under reduced
pressure. The residue was purified by column
chromatography ( methanol: CH2Cl2 = 1:20) to afford the
target compound.
J=5.6Hz, 2H), 3.78 (t, J=4.5Hz, 4H), 4.21 (t, J=5.6Hz, 2H),
6.90 (d, J=6.9Hz, 1H), 7.03 (d, J=8.6Hz, 2H), 7.27 (d,
J=6.9Hz, 1H), 8.24 (d, J=8.6Hz, 2H), 8.45(d, J=6.9Hz, 1H ).
7-Methyl-2-(morpholino-4-yl)-ethyloxyphenyl-1, 2, 4-
triazolo [1, 5-a] pyridine (4g)
5-Methyl-2-(pyrrolidin-1-yl)ethyloxyphenyl-1, 2, 4- triazolo
[1, 5-a] pyridine (4a)
This compound was obtained as a pale yellow solid.
1
yield, 97%; H nmr: 2.48 (s, 3H), 2.62 (br, 4H), 2.84 (t,
This compound was obtained as a pale yellow solid.
1
J=5.6Hz, 2H), 3.75 (t, J=4.3Hz, 4H), 4.19 (t, J=5.6Hz, 2H),
6.80 (d, J=6.9Hz, 1H), 7.01 (d, J=8.4Hz, 2H), 7.47 (s, 1H),
8.19 (d, J=8.4Hz, 2H), 8.43 (d, J=6.9Hz, 1H).
yield, 99%; H nmr: 1.87 (br, 4H), 2.74 (br, 4H), 2.83 (s,
3H), 3.00(t, J=5.7Hz, 2H), 4.23(t, J=5.7Hz, 2H), 6.81 (dd,
J=0.6Hz, J=7.0Hz, 1H), 7.02 (d, J=8.6Hz, 2H), 7.42 (t,
J=7.0Hz, J=8.6Hz, 1H), 7.60 (d, J=8.6Hz, 1H), 8.24(d,
J=8.6Hz, 2H ).
5-Methyl-2-(piperazin-1-yl)-ethyloxyphenyl-1, 2, 4- triazolo
[1, 5-a] pyridine (4h)
8-Methyl-2-(pyrrolidin-1-yl)ethyloxyphenyl-1, 2, 4- triazolo
[1, 5-a] pyridine (4b)
This compound was obtained as a pale yellow solid.
yield, 97%; H nmr: 2.64 (br, 4H), 2.84~2.87 (m, 5H), 2.98
1
(m, 4H), 3.10 (br, 1H), 4.20 (t, J=5.7Hz, 2H), 6.81 (d,
J=7.0Hz, 1H), 7.02 (d, J=8.8Hz, 2H), 7.43 (t, J=7.0Hz,
J=8.6Hz, 1H), 7.62 (d, J=8.8Hz, 1H), 8.27 (d, J=8.6Hz, 2H).
This compound was obtained as a pale yellow solid.
yield, 97%; mp 96~98°C; H nmr: 1.84 (br, 4H), 2.68 (m,
7H),2.96 (t, J=5.9Hz, 2H), 4.20 (t, J=5.9Hz, 2H), 6.87 (t,
J=6.9Hz, 1H), 7.02 (d, J=8.8Hz, 2H), 7.24 (d, J=6.9Hz, 1H),
8.21 (d, J=8.8Hz, 2H), 8.43 (d, 1H, J=6.9Hz ).
1
5-Methyl-2-(4-methylpiperazin-1-yl)-ethyloxyphenyl-1, 2,
4-triazolo [1, 5-a] pyridine (4i)
5-Methyl-2-(piperidin-1-yl)-ethyloxyphenyl-1, 2, 4- triazolo
[1, 5-a] pyridine (4c)
This compound was obtained as a pale yellow solid.
yield, 98%; 1H nmr: 2.31 (s, 3H), 2.54 (br, 8H), 2.67 (s, 3H),
2.86 (t, J=5.8Hz, 2H), 4.18 (t, J=5.8Hz, 2H), 6.87 (t,
J=6.9Hz, 1H), 7.01 (d, J=8.8Hz, 2H), 7.24 (d, J=6.9Hz, 1H),
8.21(d, J=8.8Hz, 2H), 8.42 (d, J=6.9Hz, 1H).
This compound was obtained as a pale yellow solid.
1
yield, 99%; H nmr: 1.49 (br, 2H), 1.67 (br, 4H), 2.60 (br,
4H), 2.83 (s, 3H), 2.86 (t, J=5.9Hz, 2H), 4.22 (t, J=5.9Hz,
2H), 6.80 (d, J=7.0Hz, 1H), 7.02 (d, J=8.8Hz, 2H), 7.41 (t,
J=7.0Hz, J=8.8Hz, 1H), 7.60 (d, J=8.8Hz, 1H), 8.25 (d, 2H,
J=8.8Hz ).
ACKNOWLEDGEMENT
The project was supported by Zhejiang Provincial
Natural Science Foundation of China (Y4090024).
8-Methyl-2-(piperidin-1-yl)-ethyloxyphenyl-1, 2, 4- triazolo
[1, 5-a] pyridine (4d)
This compound was obtained as a pale yellow solid.
yield, 98%; H nmr: 1.47 (br, 2H), 1.64 (br, 4H), 2.56 (br,
1
REFERENCES
4H), 2.68 (s, 3H), 2.83 (t, J=6.0Hz, 2H), 4.20 (t, J=6.0Hz,
2H), 6.86 (d, J=6.9Hz, 1H), 7.01 (d, 2H, J=8.7Hz), 7.25 (d,
J=6.9Hz, 1H), 8.22 (d, J=8.7Hz, 2H), 8.42(d, J=6.9Hz, 1H ).
[1]
Liu, T.; Hu, Y. Z. Non-steroidal pregnancy- terminating agents:
design, synthesis and structure–activity relationships of 2-aryl-
1,2,4- triazolo[1,5-a]pyridine. Bioorg. Med. Chem. Lett. 2002,
12(17), 2411-2413.
[2]
[3]
[4]
Yang, B.; Cao, L.; Fang, R. Y.; Gu, Z. P. Luteolytic effects of
DL111-IT in pregnant rats. Eur. J. Pharmac., 1999, 380(2-3), 145-
152.
Zhang, G.; Hu, Y. Synthesis and antitumor activities of 2-(4-(2-
heterocycloethoxy)phenyl)-1,2, 4-triazolo[1,5-a] pyridines. J.
Heterocycl. Chem., 2007, 44, 919-922.
Luo, Y.; Hu, Y. Synthesis and antifungal activity of 2-aryl-1,2,4-
triazolo[1,5-a] pyridine derivatives. Arch. Pharm. Chem. Life Sci.,
2006, 339, 262-266.
Tao, X.; Hu, Y. Synthesis and antitumor activity of 2-aryl-1,2,4-
triazolo[1,5-a] pyridine derivatives. Med. Chem., 2010, 6, 65-69.
Lin, S.; Liu, H.; Yan, W.; Zhang, L.; Bai, N.; Ho, C. T. Design,
synthesis, and anti-tumor activity of (2-O-alkyloxime-3-phenyl)-
propionyl- 1-O-acetylbritannilactone esters. Bioorg. Med. Chem.,
2005, 13(8), 2783-2789.
5-Methyl-2-(morpholino-4-yl)-ethyloxyphenyl-1, 2, 4-
triazolo [1, 5-a] pyridine (4e)
This compound was obtained as a pale yellow solid.
1
yield, 97%; H nmr: 2.62 (br, 4H), 2.83~2.86 (m, 5H), 3.76
(t, J=4.5Hz, 4H), 4.20 (t, J=5.6Hz, 2H), 6.81 (d, J=7.0Hz,
1H), 7.02 (d, J=8.7Hz, 2H), 7.42 (t, J=7.0Hz, J=8.8Hz, 1H),
7.61 (d, J=8.8Hz, 1H), 8.25 (d, J=8.8Hz, 2H ).
[5]
[6]
8-Methyl-2-(morpholino-4-yl)-ethyloxyphenyl-1, 2, 4-
triazolo [1, 5-a] pyridine (4f)
This compound was obtained as a pale yellow solid.
1
yield, 98%; H nmr: 2.64 (br, 4H), 2.71 (s, 3H), 2.87 (t,