Design, synthesis, and antitumor evaluation of 2,4,6-triaryl pyridines containing chlorophenyl and phenolic moiety

Article abstract of DOI:10.1016/j.ejmech.2012.03.010

We have designed and synthesized a series of 2,4,6-triaryl pyridine derivatives containing chlorophenyl and phenolic moeity at 2- and 4- position of the central pyridine, respectively, resulting in a total of 42 compounds. They were evaluated for topoisom

Full text of DOI:10.1016/j.ejmech.2012.03.010

European Journal of Medicinal Chemistry 52 (2012) 123e136
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European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis, and antitumor evaluation of 2,4,6-triaryl pyridines containing
chlorophenyl and phenolic moiety
Pritam Thapa a, Radha Karki a, Minho Yun a, Tara Man Kadayat a, Eunyoung Lee b, Han Byeol Kwon b,
,
b,
***
Younghwa Na c, Won-Jea Cho d, Nam Doo Kim e, Byeong-Seon Jeong a , Youngjoo Kwon
,
**
,
Eung-Seok Lee a
*
a College of Pharmacy, Yeungnam University, 214-1 Dae-dong, Gyeongsan 712-749, Republic of Korea
b College of Pharmacy, Division of Life & Pharmaceutical Sciences, Ewha Womans University, Seoul 120-750, Republic of Korea
c College of Pharmacy, Cha University, Pochon 487-010, Republic of Korea
d College of Pharmacy, Chonnam National University, Kwangju 500-757, Republic of Korea
e New Drug Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu 706-010, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
We have designed and synthesized a series of 2,4,6-triaryl pyridine derivatives containing chlorophenyl
and phenolic moeity at 2- and 4- position of the central pyridine, respectively, resulting in a total of 42
compounds. They were evaluated for topoisomerase I and II inhibitory activities as well as cytotoxicities
against several human cancer cell lines. Most compounds showed better topoisomerase II inhibitory
activity compared to topoisomerase I inhibitory activity. Compounds 19, 20, 26e28, and 47e50 especially
showed stronger topo II inhibitory activity than etoposide.
Received 16 December 2011
Received in revised form
6 March 2012
Accepted 6 March 2012
Available online 24 March 2012
Ó 2012 Elsevier Masson SAS. All rights reserved.
Keywords:
2,4,6-Triaryl pyridine
Antitumor
Terpyridine
Topoisomerase I and II inhibition
Cytotoxicity
1. Introduction
reported the topoisomerase I and/or II inhibitory activities and
cytotoxicity of various terpyridine derivatives [6].
The discovery of topoisomerase (topo) [1] provided a new
insight into the development of anticancer agents [2]. Topo is
broadly classified into two families, type I and II, based on the break
introduced by enzymes. Topo I breaks a single strand of DNA
whereas topo II breaks both strands of DNA, allowing the release of
torsional strains, which are created during essential biological
processes including DNA replication and transcription [3]. Top-
oisomerase inhibitors, such as camptothecin (topo I inhibitor) [4]
and etoposide (topo II inhibitor) [5], are clinically used for the
treatment of cancer. But due to the severe side effects of current
clinical drugs, the development of a new class of topoisomerase
inhibitors that possess smaller side effects and greater potency is
necessary. Our research group has previously investigated and
Many phenolic or polyphenolic compounds have been reported
to have a wide range of biological activities such as antioxidant [7],
anti-inflammatory [8], chemoprevention [9], antibacterial [10],
antiangiogenic and antitumor [11], and antiviral [12] activities. Of
these, antioxidant activities have been the most heavily studied.
Structureeactivity relationship studies of various isoaurostatin
derivatives have illustrated the importance of the hydroxyl group
for topo I and II inhibitory activities [13]. In addition, recently
reported work by our research group [6k] has provided more
support for the importance of the hydroxyl group in 2,4,6-
trisubstituted pyridines for topoisomerase inhibitory activity and
cytotoxicity. Bulky groups like chlorine tend to occupy all the active
sites of molecular targets, including deeper pockets. Due to the
ability to improve potency, blood brain barrier permeability, and
metabolic and chemical stability, the insertion of halogen atoms is
widely practiced in drug discovery optimization [14]. A previously
discussed role of phenolic moiety and the chlorine atom motivated
us to incorporate these moieties in the synthesized 2,4,6-triaryl
pyridine derivatives.
* Corresponding author. Tel.: þ82 53 810 2827; fax: þ82 53 810 4654.
** Corresponding author. Tel.: þ82 53 810 2814; fax: þ82 53 810 4654.
*** Corresponding author. Tel.: þ82 2 3277 4653; fax: þ82 2 3277 2851.
E-mail addresses: bjeong@ynu.ac.kr (B.-S. Jeong), ykwon@ewha.ac.kr (Y. Kwon),
eslee@yu.ac.kr (E.-S. Lee).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.03.010

124
P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
In this study, forty-two 2,4,6-triaryl pyridine derivatives with
20, 26e28 and 47e50 have shown stronger topo II inhibitory
activity than etoposide both at 100 and 20 M. It is interesting to
chlorophenyl and phenolic moiety, respectively, at 2- and 4- posi-
tion of central pyridine were synthesized on the basis of previous
findings, our research group’s and others, which emphasize the
importance of phenolic moiety and the chlorine atom as shown in
Fig. 1 and Scheme 1.
m
note that most of the compounds with pyridyl moiety at 6-position
of central pyridine did not show good topo II inhibitory activity.
In addition, most compounds showed selectivity for topo II
against topo I which implies biological importance as topo II is the
only enzyme available to disentangle the topological problems in
chromosomes, which arise during the completion of replication,
and to decantenate the replicated chromosomes by introducing
transient double strand breaks [17]. Moreover, topo II participates
in many nuclear processes that generate topological problems.
Most tumor cells are characterized as having chromosome aber-
rations caused by the inefficient decatenation checkpoint [18].
2. Results and discussion
2.1. Synthetic chemistry
Final 2,4,6-triaryl pyridines which contained either 3-
hydroxyphenyl or 4-hydroxyphenyl at 4-position of central pyri-
dine were synthesized in three steps as summarized in Scheme 1. In
the first step, pyridinium iodide salts 2 (R ¼ aeg) were synthesized
by the reaction of appropriate aryl methyl ketones 1 (R ¼ aeg) with
iodine and pyridine for 3 h at 140 ꢀC in the yield of 61.8e98.9%. In
parallel, propenone intermediates 4 (R1 ¼ hej) and 5 (R1 ¼ hej)
were prepared on the basis of the Claisen Schmidt condensation
reaction [15]. 3-Hydroxy or 4-hydroxy benzaldehyde was reacted
with various aryl methyl ketones 3 (R1 ¼ hej) in the presence of
NaOH to give 56.0e86.7% of 4 (R1 ¼ hej) and 5 (R1 ¼ hej). Total of 6
propenone intermediates were synthesized. Pyridinium iodide
salts and propenone intermediates, on the basis of Krönke pyridine
synthesis method [16], were finally reacted in the presence of
NH4OAc for 24 h at 90e110 ꢀC to yield 7.0e78.1% of 2,4,6-triaryl
pyridines (12e53). We have designed and synthesized forty-two
2,4,6-triaryl pyridines as shown in Fig. 2.
2.3. Cytotoxicity
Selected compounds were evaluated for cytotoxicity against
four different human cancer cell lines: HEK293 (human embryonic
kidney cell line), DU145- (human prostate tumor cell line), HCT 15
(human colorectal adenocarcinoma cell line), and T47D (human
breast ductal carcinoma cell line). Selection of compounds was
done on the basis of topo I and II inhibitory activity. Compounds
having moderate to significant topo inhibitory activity were chosen
for the cytotoxicity. The IC50 values of evaluated compounds are as
shown in Table 1 and Table 2.Most of the compounds showed
moderate cytotoxicity, generally IC50 values of 1.48e39 mM.
Comparatively, compounds from series 3 (8, Scheme 1) have
shown weaker cytotoxicity than compounds from other series.
Among the compounds with pyridyl moiety at 6-position of the
central pyridine, evaluated for cytotoxicity, 32 has shown the most
significant cytotoxicity. Although most of the compounds showed
direct correlation between cytotoxicity and topoisomerase inhibi-
tory activity, some compounds did not show direct correlation,
which were common in biological studies in vitro [19].
From the biological results, some structureeactivity relationship
(SAR) was observed. It is revealed that most of the compounds
containing pyridyl moiety at the 6-position of central pyridine
showed little or no topoisomerase inhibitory activity. At the same
time, derivatives with aryl groups other than pyridyl at 6-position
of central pyridine possess moderate to significant topoisomerase
II inhibitory activity. This shows that pyridyl moiety at 6-position of
synthesized compounds is less essential for the topoisomerase
inhibitory activity as compared to other aryl groups. Further
modification at this position is necessary to find more potent top-
oisomerase inhibitors. Moreover, all compounds (26e28 and
47e50) with stronger topoisomerase II inhibitory activity than
2.2. Topo I and II inhibitory activity
We have studied the conversion of supercoiled plasmid DNA to
relaxed DNA by topo I and II in the presence of prepared 2,4,6-
triaryl pyridines 12e53 as shown in Fig. 3 and Fig. 4. Camptothe-
cin and etoposide, well-known topo I and II inhibitors, respectively,
were used as positive controls. Inhibitory activities were evaluated
both at 100
Several compounds 41, 44, 45, 47e49 have shown considerable
topo I inhibitory activity at 100 M. Compound 47 has shown the
most significant topo I inhibitory activity both at 100 M and
20 M, 68.0% and 55.2%, respectively, as compared to 57.8% and
mM and 20 mM.
m
m
m
39.9% of camptothecin. Compounds having the hydroxyl group at
the para position of 4-phenyl ring showed topo I inhibitory activity
whereas entire compounds having hydroxyl group at the meta
position of 4-phenyl were devoid of topo I inhibitory activity except
compound 30 with moderate activity of 30.0% at 100
mM (as
compared to 76.3% of camptothecin). The topo I inhibitory activities
of evaluated compounds are summarized in Table 1 and Table 2.
Most of the compounds 12e15, 19e22, 26e30, 33e36, 40e44,
47e52 have shown significant topo II inhibitory activity at
etoposide both at 100 mM and 20 mM have para-chlorophenyl at the
2-position of the central pyridine except compounds 19 and 20.
This probably indicates that chlorine at the para position of the
phenyl ring is important for the topoisomerase II inhibitory activity
as compared to the ortho and meta positions.
100
mM as summarized in Table 1 and Table 2. Compounds 19,
a
b
Fig. 1. Structure of a. a-terpyridine, b. 2,4,6-triaryl pyridines.

P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
125
Scheme 1. Synthesis of pyridinium iodide salts 2 (R ¼ aeg), propenone intermediates 4 (R1 ¼ hej) and 5 (R1 ¼ hej) and 2,4,6 triaryl pyridines (6e11); Reagents and conditions: i)
iodine (1.0 equiv), pyridine, 3 h, 140 ꢀC, 61.8e98.9% yield; ii) aq. NaOH (3.00 equiv), EtOH, room temperature, 4e12 h, 56.0e86.7% yield; iii) NH4OAc (10.0 equiv), glacial AcOH, 24 h,
90e110 ꢀC, 7.0e78.1% yield.
2.4. Analysis of molecular docking model
interactions with DNA base pairs of topo II active site. The similarity
in superimposed docking model of compound 47 and etoposide
probably demonstrated highly potent activity.
Molecular modeling study was performed using compound
47, which showed strong inhibitory activities both in topo I and
topo II.
3. Conclusions
We investigated the plausible docking model of compound 47
with topo I and topo II. Analysis of the results from the docking
studies suggested hydrogen interactions between compound 47
and the Asp533 residue in the side chain of topo I. In addition, we
also found that the compound 47 structurally overlapped with the
topotecan, and a 4-chlorophenyl and pyridine moiety were located
in the DNA topo I active site. Therefore, the binding of compound
47 on the topo I is highly capable of inhibition of DNA topo I active
site.
Forty-two 2,4,6-triaryl pyridines were designed and synthesized
with chlorophenyl and phenolic moiety at 2- and 4- position of the
central pyridine, respectively, and were evaluated for topo I and II
inhibitory activity and cytotoxicity against several human cancer
cell lines. SAR study led us to conclude that it is highly probable that
furyl, thienyl or phenyl moiety are more essential for top-
oisomerase II inhibitory activity compared to pyridyl moiety at the
6-position of central pyridine. Similarly, most of the compounds
with para-chlorophenyl at the 2-position of central pyridine
showed stronger topo II inhibitory activity than etoposide both at
As shown in Fig. 5, the docking model of compound 47 with topo
II indicated that following interactions are important in the active
site; the hydrogen bonding of Asp 479 and Gly 478, and the
p
-p
100 and 20 mM, which indicates the importance of para-

126
P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
Fig. 2. Structure of the prepared compounds.
Fig. 3. Topoisomerase I inhibitory activity of the prepared compounds 12e53.

P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
127
Fig. 4. Topoisomerase II inhibitory activity of the prepared compounds 12e53.
chlorophenyl moiety for topoisomerase II inhibitory activity.
4. Experimental
Analysis of molecular docking model revealed that binding pattern
of compound 47 with topo I and II were similar to that of topotecan
and etoposide, respectively.
Compounds used as starting materials and reagents were
obtained from Aldrich Chemical Co., Junsei or other chemical
Table 1
Topo I and II inhibitory activities, and cytotoxicity of the prepared compounds 12e32.
Compounds
Topo I (% inhibition)
100
Topo II (% inhibition)
100
IC50 (mM)
m
M
20
m
M
m
M
20
m
M
cHEK293
dDU145
eHCT15
fT47D
gAdriamycin
1.34 ꢁ 0.32
1.21 ꢁ 0.11
1.01 ꢁ 0.14
1.76 ꢁ 0.06
2.60 ꢁ 0.31
2.72 ꢁ 0.51
1.86 ꢁ 0.06
ND
1.10 ꢁ 0.09
1.21 ꢁ 0.24
1.06 ꢁ 0.08
1.48 ꢁ 0.04
1.70 ꢁ 0.29
1.97 ꢁ 0.26
1.63 ꢁ 0.08
ND
1.03 ꢁ 0.03
1.17 ꢁ 0.25
1.38 ꢁ 0.01
2.93 ꢁ 0.16
2.79 ꢁ 0.31
2.50 ꢁ 0.06
2.23 ꢁ 0.14
ND
1.05 ꢁ 0.11
2.39 ꢁ 0.10
1.53 ꢁ 0.12
2.92 ꢁ 0.04
3.99 ꢁ 0.12
2.44 ꢁ 0.96
2.01 ꢁ 0.20
ND
hEtoposide
76.8/84.5a/71.6b
44.5/22.4a/32.1b
iCamptothecin
46.6/70.3a/76.3b
3.2
2.7
0
0
0
23.1
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
83.0
78.9
77.1
77.9
19.1
0
23.0
10.7
15.7
8.6
ND
ND
0
0
ND
ND
ND
ND
ND
ND
ND
ND
0.7
ND
11.5
7.6
26.2
5.5
0.4
27.6
0
7.1
15.1
11.7
27.1
30.0
2.8
8.0
81.1
80.4
80.1
70.1
2.4
49.1
39.0
15.4
4.8
ND
ND
3.12 ꢁ 0.13
3.15 ꢁ 0.04
3.18 ꢁ 0.01
2.53 ꢁ 0.07
ND
2.75 ꢁ 0.20
2.65 ꢁ 0.02
3.33 ꢁ 0.27
2.02 ꢁ 0.07
ND
2.55 ꢁ 0.11
2.61 ꢁ 0.15
2.51 ꢁ 0.03
2.46 ꢁ 0.44
ND
3.70 ꢁ 0.13
3.41 ꢁ 0.25
3.54 ꢁ 0.23
3.57 ꢁ 0.01
ND
0
ND
ND
ND
ND
ND
ND
ND
ND
13.9
76.3
75.5
71.6
63.8
59.4
40.4
51.7
ND
53.0
54.2
38.3
16.7
13.1
10.6
12.9
11.62 ꢁ 0.62
11.83 ꢁ 0.16
11.21 ꢁ 0.48
8.19 ꢁ 1.01
14.02 ꢁ 2.70
39.45 ꢁ 0.97
2.89 ꢁ 0.13
11.23 ꢁ 0.73
11.59 ꢁ 0.29
11.57 ꢁ 0.39
11.36 ꢁ 0.14
8.09 ꢁ 0.76
26.76 ꢁ 2.72
2.51 ꢁ 0.09
8.11 ꢁ 0.17
9.28 ꢁ 1.14
8.85 ꢁ 0.26
10.20 ꢁ 0.68
13.53 ꢁ 0.51
16.75 ꢁ 0.74
2.63 ꢁ 0.36
11.29 ꢁ 0.00
10.45 ꢁ 0.77
11.49 ꢁ 0.60
10.54 ꢁ 1.96
13.94 ꢁ 0.14
18.08 ꢁ 1.25
3.33 ꢁ 0.20
ND
ND
ND: Not determined.
Each data represents mean ꢁ S.D. from three different experiments performed in triplicate.
a
Value for compounds 19e25.
Compounds 26e32.
HEK293: human embryonic kidney cell line.
DU145: human prostate tumor.
HCT15 human colorectal adenocarcinoma.
T47D: Human breast ductal carcinoma.
Adriamycin: positive control for cytotoxicity.
Camptothecin: positive control for topo I and cytotoxicity.
b
c
d
e
f
g
h
i
Etoposide: positive control for topo II and cytotoxicity.

128
P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
Table 2
Topo I and II inhibitory activities, and cytotoxicity of the prepared compounds 33e53.
Compounds
Topo I (% inhibition)
100
Topo II (% inhibition)
100
IC50 (mM)
m
M
20
m
M
m
M
20
m
M
cHEK293
dDU145
eHCT15
fT47D
gAdriamycin
1.51 ꢁ 0.04
1.27 ꢁ 0.15
1.20 ꢁ 0.15
3.93 ꢁ 0.15
5.22 ꢁ 0.25
5.93 ꢁ 0.88
4.31 ꢁ 0.16
ND
1.28 ꢁ 0.09
1.33 ꢁ 0.16
1.19 ꢁ 0.06
2.80 ꢁ 0.32
4.19 ꢁ 0.71
3.89 ꢁ 0.50
5.30 ꢁ 0.21
ND
1.13 ꢁ 0.14
1.10 ꢁ 0.03
1.32 ꢁ 0.17
4.99 ꢁ 0.77
5.43 ꢁ 0.52
5.83 ꢁ 0.60
5.46 ꢁ 0.06
ND
1.49 ꢁ 0.07
1.58 ꢁ 0.05
1.03 ꢁ 0.10
5.46 ꢁ 0.42
5.87 ꢁ 0.87
6.11 ꢁ 0.23
5.48 ꢁ 0.20
ND
hEtoposide
84.9/76.8a/67.5b
44.6/20.9a/20.0b
iCamptothecin
51.4/64.7a/57.8b
13.6
2.2
4.1
3.9
5.2
0.9
9.9
0
52.4
26.0
25.5
59.4
55.2
29.2
68.0
38.8
47.7
15.8
12.7
18.8
5.9
34.0a/39.9b
ND
ND
ND
ND
ND
ND
ND
ND
0
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
77.5
78.3
80.5
77.8
21.1
0
5.5
8.2
29.2
7.7
ND
ND
ND
0.5
0
0
0
0
0
ND
44.6
22.0
67.1
36.2
13.1
11.9
ND
ND
ND
ND
ND
ND
ND
ND
ND
0
76.8
72.4
83.7
71.3
67.5
46.9
0
80.9
77.2
83.6
84.1
66.7
59.1
2.4
2.82 ꢁ 0.08
2.72 ꢁ 0.05
2.67 ꢁ 0.05
2.88 ꢁ 0.15
25.41 ꢁ 2.04
25.66 ꢁ 0.97
ND
4.81 ꢁ 0.18
4.52 ꢁ 0.27
4.86 ꢁ 0.51
5.72 ꢁ 0.28
27.15 ꢁ 0.74
27.45 ꢁ 1.16
ND
5.36 ꢁ 0.29
5.74 ꢁ 0.30
6.22 ꢁ 0.90
5.75 ꢁ 0.61
35.20 ꢁ 2.64
22.94 ꢁ 0.17
ND
7.27 ꢁ 0.03
7.66 ꢁ 0.22
6.94 ꢁ 0.54
7.28 ꢁ 0.69
22.54 ꢁ 0.96
22.76 ꢁ 0.74
ND
6.10 ꢁ 0.07
5.05 ꢁ 0.62
5.76 ꢁ 0.16
8.02 ꢁ 0.88
28.15 ꢁ 2.08
21.31 ꢁ 0.77
ND
6.92 ꢁ 0.38
6.47 ꢁ 0.22
6.24 ꢁ 0.42
7.02 ꢁ 0.47
21.34 ꢁ 1.93
20.72 ꢁ 0.86
ND
4.79 ꢁ 0.33
5.35 ꢁ 0.26
7.39 ꢁ 0.33
5.22 ꢁ 0.45
27.91 ꢁ 0.46
25.66 ꢁ 0.97
ND
4.27 ꢁ 0.01
6.45 ꢁ 0.44
5.49 ꢁ 0.48
6.26 ꢁ 0.21
25.91 ꢁ 0.20
29.30 ꢁ 3.28
ND
ND
ND
0
0
ND
55.2
0
30.7
ND
ND
ND
ND
ND: Not determined.
Each data represents mean ꢁ S.D. from three different experiments performed in triplicate.
a
Value for compounds 40e46.
Compounds 47e53.
HEK293: human embryonic kidney cell line.
DU145: human prostate tumor.
HCT15 human colorectal adenocarcinoma.
T47D: Human breast ductal carcinoma.
Adriamycin: positive control for cytotoxicity.
Camptothecin: positive control for topo I and cytotoxicity.
b
c
d
e
f
g
h
i
Etoposide: positive control for topo II and cytotoxicity.
companies, and utilized without further purification. HPLC grade
acetonitrile (ACN) and methanol were purchased from Burdick and
Jackson, USA. Thin-layer chromatography (TLC) and column chro-
matography (CC) were performed with Kieselgel 60 F254 (Merck) and
silica gel (Kieselgel 60, 230e400 mesh, Merck) respectively. Since all
the compounds prepared contain aromatic rings, they were visual-
ized and detected onTLC plates with UV light (short wave, long wave
or both). NMR spectra were recorded on a Bruker AMX 250
(250 MHz, FT) for 1H NMR and 62.5 MHz for 13C NMR, and chemical
a flow rate of 200 mL/min, where mobile phase A was 100% distilled
water with 20 mM ammonium formate (AF) and mobile phase B was
100% acetonitrile (ACN). MS ionization conditions were: Sheath gas
flow rate: 40 arb, aux gas flow rate: 0 arb, I spray voltage: 5.3 kV,
capillary temperature: 275 ꢀC, capillary voltage: 27 V, tube lens
offset: 45 V. Retention time was given in minutes.
4.1. General method for preparation of 2 (R ¼ aeg)
shifts were calibrated according to TMS. Chemical shifts (d) were
Aryl methyl ketones 1 (R ¼ aeg) was treated with pyridine and
equivalent amount of iodine. The mixture was then refluxed at
140 ꢀC for 3 h. Precipitate occurred during reaction was cooled to
room temperature, filtered and washed with cold pyridine, and was
dried overnight to yield 61.8e98.9% of 2 (R ¼ aeg). Compounds
were used without further purification.
recorded in ppm and coupling constants (J) in hertz (Hz). Melting
points were determined in open capillary tubes on electrothermal
1A 9100 digital melting point apparatus and were uncorrected.
HPLC analyses were performed using two Shimadzu LC-10AT
pumps gradient-controlled HPLC system equipped with the Shi-
madzu system controller (SCL-10A VP) and photo diode array
detector (SPD-M10A VP) utilizing the Shimadzu Class VP program.
4.2. General method for the preparation of 4 (R1 ¼ hej) and 5
(R1 ¼ hej)
Sample volume of 10
m 5 mM
L was injected in Waters X-TerraÒ
reverse-phase C18 column (4.6 ꢂ 250 mm) with a gradient elution
of 50%e100% of B in A for 10 min followed by 100%e50% of B in A
for 20 min at a flow rate of 1.0 mL/min at 254 nm UV detection,
where mobile phase A was doubly distilled water with 50 mM
ammonium formate (AF) and B was 90% ACN in water with 20 mM
AF. Purity of compound is described as percent (%).
Aryl methyl ketones
3
(R1
¼
hej) (1.00 equiv) and 3-
hydroxybenzaldehye (1.00 equiv) or 4-hydroxybenzaldehyde
(1.00 equiv) were dissolved in ethanol (10 mL). After complete
dissolution, aqueous NaOH (3.00 equiv, 10 mL) was added slowly to
the reaction mixture at room temperature. The reaction mixture
was stirred for 4e12 h. After completion, reaction was terminated
by the addition of 6 M HCl solution. The compound was extracted
with EtOAc, washed with H2O, saturated aqueous NaCl solution,
dried over MgSO4 (1 spatula), and filtered. The organic layer was
concentrated to yield a yellow solid. It was further purified by silica
gel column chromatography using EtOAc and n-hexane as eluents
ESI LC/MS analyses were performed with a Finnigan LCQ
AdvantageÒ LC/MS/MS spectrometry utilizing XcaliburÒ program.
For ESI LC/MS, LC was performed with a 1
a Waters Atlantis T3, 3
with a gradient elution from 20% to 100% of B in A for 6.5 min fol-
mL injection volume on
m reverse-phase C18 column (2.1 ꢂ 50 mm)
m
lowed by 100%e20% of B in A for 6 min and 20% of B in A for 2.5 min at

P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
129
Fig. 5. Molecular docking model of compound 47 with topo I and topo II. (a) Hydrogen bonds between the compound 47 and topo I are denoted by dashed line. (b) Superimposed
binding model of topotecan and compound 47. (c) Hydrogen bonds between the compound 47 and topo II are denoted by dashed line (blue color). (d) superimposed binding model
of anticancer drug etoposide. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
to yield compounds 4 (R1 ¼ hej) and 5 (R1 ¼ hej) as yellow solid in
56.0e86.7% yield.
and glacial acetic acid (4.00 mL) to yield 85 mg (11.9%, 0.23 mmol)
as a white solid, Rf ¼ 0.31 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
187.2e187.9 ꢀC, purity: 99.6%, retention time: 9.12 min; [MH]þ:
358.32 (100%), [MHþ2]: 360.33 (32.6%).
4.3. General method for the preparation of 12e53
1H NMR (250 MHz, DMSO-d6)
d 9.72 (s, 1H, 4-phenyl 3-OH),
8.22 (dd, J ¼ 8.1, 1.5 Hz, 2H, 6-phenyl H-2, H-6), 8.16 (d, J ¼ 1.1 Hz,
1H, pyridine H-3), 7.81 (d, J ¼ 1.1 Hz, 1H, pyridine H-5), 7.79e7.75
(m, 1H, 2-phenyl H-6), 7.63e7.59 (m, 4H, 2-phenyl H-3, 6-phenyl
H-3, H-4, H-5), 7.51e7.47 (m, 2H, 2-phenyl H-4, H-5), 7.36e7.29
(m, 3H, 4-phenyl H-2, H-5, H-6), 6.93e6.90 (m, 1H, 4-phenyl H-
2,4,6-triaryl pyridines 12e53 were synthesized according to the
Krohnke synthesis method [16]. Previously synthesized propenone
intermediates 4 (R1 ¼ hej) or 5 (R1 ¼ hej) were reacted with
pyridinium iodide salts 2 (R ¼ aeg) in the presence of anhydrous
ammonium acetate (10.0 equiv) and glacial acetic acid. The mixture
was heated at 90e110 ꢀC for 24 h. The reaction mixture was then
extracted with ethyl acetate, washed with water and saturated
aqueous NaCl solution. The organic layer was dried with magne-
sium sulfate and filtered. The filtrate was concentrated under
reduced pressure and dried in vacuum pump, which was then
purified by silica gel column chromatography with the gradient
elution of ethyl acetate and n-hexane to afford solid compounds
12e53 in 7.0e78.1% yield.
4). 13C NMR (62.5 MHz, DMSO-d6)
d 158.27, 156.84, 156.76, 149.12,
139.14, 139.05, 138.81, 132.06, 131.56, 130.47, 130.37, 130.25,
129.46, 128.93, 127.21, 127.21, 120.94, 118.16, 116.99, 116.54,
114.14.
4.3.2. 3-(2-(2-Chlorophenyl)-6-(thiophen-2-yl)pyridin-4-yl)phenol (13)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ h) (0.52 g, 2.00 mmol, 1.00 equiv), 2 (R ¼ b) (0.66 g,
2.00 mmol, 1.00 equiv), NH4OAc (1.54 g, 20.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 227 mg (31.2%, 0.63 mmol)
as a white solid, Rf ¼ 0.28 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
136.9e137.8 ꢀC, purity: 99.2%, retention time: 8.90 min; [MH]þ:
364.26 (100%), [MHþ2]: 366.27 (32.6%).
4.3.1. 3-(2-(2-Chlorophenyl)-6-phenylpyridin-4-yl)phenol (12)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ h) (0.52 g, 2.00 mmol, 1.00 equiv), 2 (R ¼ a) (0.65 g,
2.00 mmol, 1.00 equiv), NH4OAc (1.54 g, 20.00 mmol, 10.00 equiv)

130
P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
1H NMR (250 MHz, DMSO-d6)
d
9.72 (br,1H, 4-phenyl 3-OH), 8.16
4.3.6. 3-(6-(2-Chlorophenyl)-2,30-bipyridin-4-yl)phenol (17)
(d, J ¼ 1.1 Hz, 1H, pyridine H-3), 8.04 (dd, J ¼ 3.6, 0.8 Hz, 1H, 6-
thiophene H-3), 7.77e7.69 (m, 2H, pyridine H-5, 2-phenyl H-6),
7.66e7.59 (m, 2H, 2-phenyl H-3, 6-thiophene H-5), 7.51e7.46 (m,
2H, 2-phenyl H-4, H-5), 7.35e7.31 (m, 3H, 4-phenyl H-2, H-5, H-6),
7.19 (dd, J ¼ 4.9, 3.7 Hz, 1H, 6-thiophene H-4), 6.93e6.91 (m, 1H, 4-
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ h) (0.52 g, 2.00 mmol, 1.00 equiv), 2 (R ¼ f) (0.66 g,
2.00 mmol, 1.00 equiv), NH4OAc (1.54 g, 20.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 185 mg (25.8%, 0.52 mmol)
as a white solid, Rf ¼ 0.26 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
218.1e218.5 ꢀC, purity: 99.5%, retention time: 7.76 min; [MH]þ:
359.32 (100%), [MHþ2]: 361.32 (32.6%).
phenyl H-4).13C NMR (62.5 MHz, DMSO-d6)
d 158.23,156.56,152.58,
149.01, 144.56, 138.72, 138.69, 131.89, 131.54 130.44, 130.25, 128.93,
128.64, 127.65, 126.20, 121.15, 120.61, 118.08, 116.19, 115.19, 114.09.
1H NMR (250 MHz, DMSO-d6)
d 9.75 (s, 1H, 4-phenyl 3-OH), 9.41
(d, J ¼ 1.8 Hz, 1H, 2-pyridine H-20), 8.67e8.57 (m, 2H, 2-pyridine H-
40, H-60), 8.28 (s, 1H, pyridine H-3), 7.88 (s, 1H, pyridine H-5),
7.82e7.78 (m, 1H, 6-phenyl H-6), 7.65e7.61 (m, 1H, 6-phenyl H-3),
7.54e7.48 (m, 3H, 6-phenyl H-4, H-5, 2-pyridine H-50), 7.38e7.32
(m, 3H, 4-phenyl H-2, H-5, H-6), 6.92 (d, J ¼ 7.4 Hz, 1H, 4-phenyl
4.3.3. 3-(2-(2-Chlorophenyl)-6-(thiophen-3-yl)pyridin-4-yl)phenol (14)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ c) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 157 mg (43.1%, 0.43 mmol)
as a white solid, Rf ¼ 0.28 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
188.7e189.1 ꢀC, purity: 95.8%, retention time: 8.91 min; [MH]þ:
364.26 (100%), [MHþ2]: 366.27 (32.6%).
H-4). 13C NMR (62.5 MHz, DMSO-d6)
d 158.30, 157.05, 154.66,
150.28, 149.36, 148.48, 138.90, 138.82, 134.68, 134.27, 132.16, 131.58,
130.52, 130.32, 127.75, 123.99, 121.56, 118.28, 117.54, 116.68, 114.26.
1H NMR (250 MHz, DMSO-d6)
d
9.72 (s, 1H, 4-phenyl 3-OH), 8.35
4.3.7. 3-(6-(2-Chlorophenyl)-2,40-bipyridin-4-yl)phenol (18)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ h) (0.52 g, 2.00 mmol, 1.00 equiv), 2 (R ¼ g) (0.66 g,
2.00 mmol, 1.00 equiv), NH4OAc (1.54 g, 20.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 195 mg (27.2%, 0.54 mmol)
as a white solid, Rf ¼ 0.19 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
223.8e224.2 ꢀC, purity: 99.9%, retention time: 7.77 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.34 (32.6%).
(dd, J ¼ 2.9, 1.2 Hz, 1H, 6-thiophene H-2), 8.12 (d, J ¼ 1.2 Hz, 1H,
pyridine H-3), 7.89 (dd, J ¼ 5.0, 1.2 Hz, 1H, 6-thiophene H-4),
7.76e7.73 (m, 1H, 2-phenyl H-6), 7.73 (d, J ¼ 0.9 Hz, 1H, pyridine H-
5), 7.67e7.59 (m, 2H, 2-phenyl H-3, 6-thiophene H-5), 7.50e7.47
(m, 2H, 2-phenyl H-4, H-5), 7.34 (d, J ¼ 4.9 Hz, 2H, 4-phenyl H-5,
H-6), 7.28 (s, 1H, 4-phenyl H-2), 6.93e6.90 (m, 1H, 4-phenyl H-4).
13C NMR (62.5 MHz, DMSO-d6)
d 158.24, 156.67, 153.47, 148.95,
142.04, 139.13, 138.97, 132.02, 131.54, 130.44, 130.33, 130.22, 127.63,
127.15, 126.92, 124.96, 120.45, 118.10, 116.89, 116.52, 114.10.
1H NMR (250 MHz, DMSO-d6)
d 9.74 (s, 1H, 4-phenyl 3-OH), 8.72
(d, J ¼ 5.6 Hz, 2H, 2-pyridine H-20, H-60), 8.34 (s, 1H, pyridine H-3),
8.21 (d, J ¼ 5.6 Hz, 2H, 2-pyridine H-30, H-50), 7.94 (s,1H, pyridine H-
5), 7.79e7.77 (m, 1H, 6-phenyl H-6), 7.63e7.61 (m, 1H, 6-phenyl H-
3), 7.53e7.49 (m, 2H, 6-phenyl H-4, H-5), 7.38e7.32 (m, 3H, 4-
phenyl H-2, H-5, H-6), 6.92 (d, J ¼ 7.1 Hz, 1H, 4-phenyl H-4). 13C
4.3.4. 3-(2-(2-Chlorophenyl)-6-(furan-2-yl)pyridin-4-yl)phenol (15)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ h) (0.52 g, 2.00 mmol, 1.00 equiv), 2 (R ¼ d) (0.63 g,
2.00 mmol, 1.00 equiv), NH4OAc (1.54 g, 20.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 427 mg (61.4%, 1.22 mmol)
as a yellow solid, Rf ¼ 0.27 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
166.4e167.0 ꢀC, purity: 96.5%, retention time: 8.51 min; [MH]þ:
348.27 (100%), [MHþ2]: 350.26 (32.6%).
NMR (62.5 MHz, DMSO-d6)
d 158.92, 157.78, 154.95, 151.49, 150.12,
146.33, 139.40, 139.26, 132.72, 132.20, 131.21, 131.15, 130.93, 128.36,
123.15, 122.02, 118.89, 118.51, 117.38, 115.88.
4.3.8. 3-(2-(3-Chlorophenyl)-6-phenylpyridin-4-yl)phenol (19)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ a) (0.48 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 335 mg (62.5%, 0.94 mmol)
as a white solid, Rf ¼ 0.27 (ethyl acetate/n-hexane 1 : 4 v/v). mp.:
158.8e158.9 ꢀC, purity: 95.9%, retention time: 9.79 min; [MH]þ:
358.32 (100%), [MHþ2]: 360.33 (32.6%).
1H NMR (250 MHz, CDCl3)
d
7.88 (d, J ¼ 1.5, 1H, pyridine H-3),
7.70e7.66 (m, 2H, pyridine H-5, 2-phenyl H-6), 7.54 (d, J ¼ 1.0 Hz,1H,
6-furan H-5), 7.48e7.44 (m, 1H, 2-phenyl H-3), 7.38e7.29 (m, 4H, 2-
phenyl H-4, H-5, 4-phenyl H-5, H-6), 7.18 (d, J ¼ 3.4 Hz,1H, 6-furan H-
3), 7.14e7.13 (m, 1H, 4-phenyl H-2), 6.88 (ddd, J ¼ 7.6, 2.3, 1.1 Hz, 1H,
4-phenyl H-4), 6.54 (dd, J ¼ 3.4,1.8 Hz,1H, 6-furan H-4), 5.80 (br,1H,
4-phenyl 4-OH). 13C NMR (62.5 MHz, CDCl3)
d 157.17, 156.25, 153.42,
149.67, 148.76, 143.42, 139.75, 138.92, 132.32, 131.72, 130.28, 130.07,
129.73, 126.95, 121.31, 119.46, 116.22, 115.40, 114.08, 112.15, 109.32.
1H NMR (250 MHz, DMSO-d6)
d 9.70 (br,1H, 4-phenyl 3-OH), 8.37
(br, 1H, 2-phenyl H-2), 8.31e8.28 (m, 3H, 2-phenyl H-6, 6-phenyl H-
2, H-6), 8.19 (s,1H, pyridine H-3), 8.14 (s,1H, pyridine H-5), 7.60e7.47
(m, 5H, 2-phenyl H-4, H-5, 6-phenyl H-3, H-4, H-5), 7.44e7.32 (m,
3H, 4-phenyl H-2, H-5, H-6), 6.94e6.90 (m, 1H, 4-phenyl H-4). 13C
4.3.5. 3-(6-(2-Chlorophenyl)-2,20-bipyridin-4-yl)phenol (16)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ e) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 203 mg (56.8%, 0.56 mmol)
as a gray solid, Rf ¼ 0.20 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
189.4e189.8 ꢀC, purity: 98.8%, retention time: 8.58 min; [MH]þ:
359.33 (100%), [MHþ2]: 361.33 (32.6%).
NMR (62.5 MHz, DMSO-d6)
d 158.84, 157.47, 155.72, 150.86, 141.78,
139.80, 139.48, 146.61, 131.44, 130.92, 130.14, 129.83, 129.62, 127.80,
127.43, 126.43, 118.98, 118.01, 117.77, 117.17, 115.03.
4.3.9. 3-(2-(3-Chlorophenyl)-6-(thiophen-2-yl)pyridin-4-yl)
phenol (20)
1H NMR (250 MHz, DMSO-d6)
d
9.75 (s, 1H, 4-phenyl 3-OH), 8.74
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ b) (0.66 g,
2.00 mmol, 2.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 287 mg (52.6%, 0.79 mmol)
as a white solid, Rf ¼ 0.26 (ethyl acetate/n-hexane 1 : 4 v/v). mp.:
104.1e104.3 ꢀC, purity: 95.0%, retention time: 9.65 min; [MH]þ:
364.29 (100%), [MHþ2]: 366.29 (32.6%).
(d, J ¼ 4.7 Hz, 1H, 2-pyridine H-60), 8.61 (d, J ¼ 1.4 Hz, 1H, pyridine
H-3), 8.45 (d, J ¼ 7.9 Hz, 1H, 2-pyridine H-30), 7.96 (td, J ¼ 7.7, 1.7 Hz,
1H, 2-pyridine H-40), 7.93 (d, J ¼ 1.4 Hz, 1H, pyridine H-5), 7.81e7.78
(m, 1H, 6-phenyl H-6), 7.65e7.61 (m, 1H, 6-phenyl H-3), 7.54e7.49
(m, 3H, 6-phenyl H-4, H-5, 2-pyridine H-50), 7.36e7.28 (m, 3H, 4-
phenyl H-2, H-5, H-6), 6.93e6.89 (m, 1H, 4-phenyl H-4). 13C NMR
(62.5 MHz, DMSO-d6)
d
158.36, 156.73, 155.93, 155.14, 149.57,
1H NMR (250 MHz, DMSO-d6)
d 9.68 (s, 1H, 4-phenyl 3-OH), 8.31
148.96, 138.90, 138.79, 137.63, 132.08, 131.60, 130.70, 130.49, 130.29,
127.69, 124.69, 122.35, 121.09, 117.87, 116.74, 113.75.
(s, 1H, 2-phenyl H-2), 8.25e8.22 (m, 1H, 2-phenyl H-6), 8.13 (s, 1H,
pyridine H-3), 8.11 (s, 1H, pyridine H-5), 8.05 (d, J ¼ 3.6 Hz, 1H, 6-

P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
131
thiophene H-3), 7.68 (d, J ¼ 4.4 Hz, 1H, 6-thiophene H-5), 7.60e7.42
(m, 2H, 2-phenyl H-4, H-5), 7.45e7.32 (m, 3H, 4-phenyl H-2, H-5, H-
6), 7.21 (dd, J ¼ 4.9, 2.7 Hz, 1H, 6-thiophene H-4), 6.94e6.91 (m, 1H,
4.3.13. 3-(6-(3-Chlorophenyl)-2,30-bipyridin-4-yl)phenol (24)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ i) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ f) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 277 mg (77.4%, 0.77 mmol)
as a white solid, Rf ¼ 0.30 (ethyl acetate/n-hexane 1 : 1v/v). mp.:
193.4e193.8 ꢀC, purity: 99.5%, retention time: 8.35 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.34 (32.6%).
4-phenyl H-4). 13C NMR (62.5 MHz, DMSO-d6)
d 158.81, 155.37,
153.21, 150.79, 145.37, 141.17, 139.49, 134.60, 131.48, 130.92, 129.96,
129.60, 129.37, 127.30, 126.91, 126.25, 118.94, 117.38, 117.23, 116.23,
115.00.
4.3.10. 3-(2-(3-Chlorophenyl)-6-(thiophen-3-yl)pyridin-4-yl)
phenol (21)
1H NMR (250 MHz, DMSO-d6)
d 9.68 (s, 1H, 4-phenyl 3-OH), 9.47
(d, J ¼ 1.3 Hz,1H, 2-pyridine H-20), 8.68e8.64 (m, 2H, 2-pyridine H-40,
H-60), 8.38 (s, 1H, 6-phenyl H-2), 8.32e8.29 (m, 1H, 6-phenyl H-6),
8.25 (s,1H, pyridine H-3), 8.24 (s,1H, pyridine H-5), 7.59e7.49 (m, 4H,
2-pyridine H-50, 4-phenyl H-2, 6-phenyl H-4, H-5), 7.41e7.36 (m, 2H,
4-phenyl H-5, H-6), 6.95e6.91 (m, 1H, 4-phenyl H-4). 13C NMR
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ i) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ c) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 229 mg (63.1%, 0.63 mmol)
as a white solid, Rf ¼ 0.26 (ethyl acetate/n-hexane 1 : 4 v/v). mp.:
116.9e117.2 ꢀC, purity: 95.5%, retention time: 9.61 min; [MH]þ:
364.29 (100%), [MHþ2]: 366.29 (32.6%).
(62.5 MHz, DMSO-d6) d 158.17, 155.34, 154.59, 150.38, 150.25, 148.41,
140.84, 138.87, 134.61, 134.23, 133.96, 130.81, 130.26, 129.30, 126.82,
125.85, 123.97, 118.41, 117.79, 117.67, 116.59, 114.47.
1H NMR (250 MHz, DMSO-d6)
d 9.71 (s, 1H, 4-phenyl 3-OH),
8.45 (s, 1H, 6-thiophene H-2), 8.36 (s, 1H, 2-phenyl H-2),
8.27e8.23 (m, 1H, 2-phenyl H-6), 8.11 (s, 1H, pyridine H-3), 8.09 (s,
1H, pyridine H-5), 7.98 (d, J ¼ 4.8 Hz, 1H, 6-thiophene H-4), 7.68
(dd, J ¼ 4.2, 3.1 Hz, 1H, 6-thiophene H-5), 7.55e7.54 (m, 2H, 2-
phenyl H-4, H-5), 7.45e7.35 (m, 3H, 4-phenyl H-2, H-5, H-6),
6.92 (d, J ¼ 7.4 Hz, 1H, 4-phenyl H-4). 13C NMR (62.5 MHz, DMSO-
4.3.14. 3-(6-(3-Chlorophenyl)-2,40-bipyridin-4-yl)phenol (25)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ i) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ g) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 273 mg (76.1%, 0.76 mmol)
as a white solid, Rf ¼ 0.22 (ethyl acetate/n-hexane 1 : 1v/v). mp.:
211.7e211.9 ꢀC, purity: 99.9%, retention time: 8.37 min; [MH]þ:
359.35 (100%), [MHþ2]: 361.36 (32.6%).
d6)
d 158.10, 154.86, 153.40, 150.01, 142.02, 140.99, 139.02, 133.88,
130.66, 130.16, 129.07, 127.05, 126.85, 126.68, 125.65, 124.98,
118.20, 117.23, 116.51, 116.42, 114.28.
1H NMR (250 MHz, DMSO-d6)
d 9.69 (s, 1H, 4-phenyl 3-OH), 8.75
(d, J ¼ 5.4 Hz, 2H, 2-pyridine H-20, H-60), 8.38 (s, 1H, 6-phenyl H-2),
8.29e8.26 (m, 5H, pyridine H-3, H-5, 2-pyridine H-30, H-50, 6-
phenyl H-6), 7.57e7.54 (m, 2H, 6-phenyl H-4, H-5), 7.49e7.46 (m,
1H, 4-phenyl H-2), 7.39e7.33 (m, 2H, 4-phenyl H-5, H-6), 6.95e6.92
4.3.11. 3-(2-(3-Chlorophenyl)-6-(furan-2-yl)pyridin-4-yl)phenol (22)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ i) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ d) (0.63 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 112 mg (32.2%, 0.32 mmol)
as a white solid, Rf ¼ 0.27 (ethyl acetate/n-hexane 1 : 4 v/v). mp.:
166.8e166.9 ꢀC, purity: 98.9%, retention time: 9.26 min; [MH]þ:
348.28 (100%), [MHþ2]: 350.27 (32.6%).
(m, 1H, 4-phenyl H-4). 13C NMR (62.5 MHz, DMSO-d6)
d 158.19,
155.42, 154.24, 150.53, 145.66,140.69,138.71, 133.99,130.82, 130.28,
129.40, 126.84, 125.86, 121.32, 118.68, 118.41, 118.16, 116.67, 114.49.
4.3.15. 3-(2-(4-Chlorophenyl)-6-phenylpyridin-4-yl)phenol (26)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ a) (0.48 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 403 mg (75.3%, 1.13 mmol)
as a white solid, Rf ¼ 0.30 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
195.9e196.1 ꢀC, purity: 96.7%, retention time: 9.81 min; [MH]þ:
358.32 (100%), [MHþ2]: 360.32 (32.6%).
1H NMR (250 MHz, DMSO-d6)
d 9.69 (s, 1H, 4-phenyl 3-OH),
8.33 (s, 1H, 2-phenyl H-2), 8.26e8.23 (m, 1H, 2-phenyl H-6), 8.12
(d, J ¼ 0.8 Hz, 1H, pyridine H-3), 7.90 (s, 2H, pyridine H-5, 6-furan
H-5), 7.75e7.53 (m, 2H, 2-phenyl H-4, H-5), 7.39e7.32 (m, 4H, 6-
furan H-3, 4-phenyl H-2, H-5, H-6), 6.92 (d, J ¼ 7.5 Hz, 1H, 4-
phenyl H-4), 6.70 (dd, J ¼ 3.3, 1.6 Hz, 1H, 6-furan H-4). 13C
NMR (62.5 MHz, DMSO-d6)
d 158.20, 155.23, 153.14, 149.90,
149.26, 144.64, 140.67, 138.75, 133.92, 130.75, 130.38, 129.29,
126.76, 125.75, 118.10, 116.76, 116.65, 115.08, 114.08, 112.58,
109.93.
1H NMR (250 MHz, DMSO-d6)
d 9.71 (s, 1H, 4-phenyl 3-OH), 8.35
(d, J ¼ 8.6 Hz, 2H, 2-phenyl H-2, H-6), 8.30 (dd, J ¼ 8.2, 1.5 Hz, 2H, 6-
phenyl H-2, H-6), 8.14 (s, 1H, pyridine H-3), 8.12 (s, 1H, pyridine H-
5), 7.58 (d, J ¼ 8.6 Hz, 2H, 2-phenyl H-3, H-5), 7.54e7.49 (m, 3H, 6-
phenyl H-3, H-4, H-5), 7.41e7.35 (m, 3H, 4-phenyl H-2, H-5, H-6),
6.94e6.91 (m, 1H, 4-phenyl H-4). 13C NMR (62.5 MHz, DMSO-d6)
4.3.12. 3-(6-(3-Chlorophenyl)-2,20-bipyridin-4-yl)phenol (23)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ i) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ e) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 175 mg (48.8%, 0.48 mmol)
as a yellow solid, Rf ¼ 0.22 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
186.7e187.1 ꢀC, purity: 100%, retention time: 9.19 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.34 (32.6%).
d
158.21,156.71,155.34,150.15,139.25,138.85,137.77,134.29,130.34,
129.50, 128.96, 128.91, 127.15, 118.30, 117.06, 116.79, 116.49, 114.34.
4.3.16. 3-(2-(4-Chlorophenyl)-6-(thiophen-2-yl)pyridin-4-yl)
phenol (27)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ b) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 418 mg (76.6%, 1.15 mmol)
as a white solid, Rf ¼ 0.30 (ethyl acetate/n-hexane 1 : 3 v/v).
mp.188.8e189.3 ꢀC, purity: 97.4%, retention time: 9.67 min; [MH]þ:
364.26 (100%), [MHþ2]: 366.26 (32.6%).
1H NMR (250 MHz, DMSO-d6)
d 9.70 (s, 1H, 4-phenyl 3-OH), 8.73
(d, J ¼ 4.0 Hz, 1H, 2-pyridine H-60), 8.61e8.58 (m, 2H, pyridine H-3,
2-pyridine H-30), 8.40 (s, 1H, 6-phenyl H-2), 8.34e8.31 (m, 1H, 6-
phenyl H-6), 8.29 (d, J ¼ 1.3 Hz, 1H, pyridine H-5), 8.01 (td,
J ¼ 7.7, 1.7 Hz, 1H, 2-pyridine H-40), 7.58e7.50 (m, 3H, 6-phenyl H-4,
H-5, 2-pyridine H-50), 7.41e7.34 (m, 3H, 4-phenyl H-2, H-5, H-6),
6.92 (d, J ¼ 7.6 Hz, 1H, 4-phenyl H-4). 13C NMR (62.5 MHz, DMSO-
1H NMR (250 MHz, DMSO-d6)
d 9.69 (s, 1H, 4-phenyl 3-OH), 8.28
d6)
d
158.26, 155.91, 155.14, 155.03, 149.97, 149.51, 140.81, 138.88,
(d, J ¼ 8.6 Hz, 2H, 2-phenyl H-2, H-6), 8.11 (d, J ¼ 1.0 Hz,1H, pyridine
H-3), 8.05 (dd, J ¼ 3.8, 1.0 Hz, 1H, 6-thiophene H-3), 8.03 (d,
J ¼ 1.0 Hz, 1H, pyridine H-5), 7.67 (dd, J ¼ 5.0, 1.0 Hz, 1H, 6-
137.68, 133.99, 130.80, 130.48, 129.29, 126.80, 125.81, 124.69, 121.07,
118.51, 118.05, 117.13, 116.68, 113.95.

132
P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
thiophene H-5), 7.59 (d, J ¼ 8.6 Hz, 2H, 2-phenyl H-3, H-5),
7.42e7.31 (m, 3H, 4-phenyl H-2, H-5, H-6), 7.20 (dd, J ¼ 5.0, 3.8 Hz,
1H, 6-thiophene H-4), 6.94e6.90 (m, 1H, 4-phenyl H-4). 13C NMR
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 420 mg (78.1%, 1.17 mmol)
as a white solid, Rf ¼ 0.26 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
236.9e237.6 ꢀC, purity: 99.2%, retention time: 8.40 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.34 (32.6%).
(62.5 MHz, DMSO-d6)
d 158.16, 155.12, 152.54, 150.08, 144.79,
138.93, 137.22, 134.38, 130.29, 128.95, 128.86, 128.72, 126.16, 118.22,
116.56, 116.39, 115.27, 114.27.
1H NMR (250 MHz, DMSO-d6)
d 9.70 (br, 1H, 4-phenyl 3-OH),
9.47 (d, J ¼ 1.5 Hz, 1H, 2-pyridine H-20), 8.67e8.63 (m, 2H, 2-
pyridine H-40, H-60), 8.36 (d, J ¼ 8.6 Hz, 2H, 6-phenyl H-2, H-6),
8.22 (d, J ¼ 0.9 Hz, 1H, pyridine H-3), 8.18 (s, 1H, pyridine H-5),
7.59e7.52 (m, 3H, 6-phenyl H-3, H-5, 2-pyridine H-50), 7.47e7.32
(m, 3H, 4-phenyl H-2, H-5, H-6), 6.94e6.91 (m, 1H, 4-phenyl H-
d 158.20, 155.64, 154.53, 150.33,
150.25, 148.41, 138.98, 137.51, 134.57, 134.41, 134.25, 130.30, 128.95,
123.94, 118.36, 117.47, 117.32, 116.59, 114.42.
4.3.17. 3-(2-(4-Chlorophenyl)-6-(thiophen-3-yl)pyridin-4-yl)
phenol (28)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ c) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 396 mg (72.6%, 1.09 mmol)
as a white solid, Rf ¼ 0.31 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
203.7e204.0 ꢀC, purity: 98.20%, retention time: 9.61 min; [MH]þ:
364.27 (100%), [MHþ2]: 366.27 (32.6%).
4). 13C NMR (62.5 MHz, DMSO-d6)
4.3.21. 3-(6-(4-Chlorophenyl)-2,40-bipyridin-4-yl)phenol (32)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ g) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 250 mg (46.5%, 0.70 mmol)
as a white solid, Rf ¼ 0.23 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
227.5e228.1 ꢀC, purity: 99.8%, retention time: 8.43 min; [MH]þ:
359.36 (100%), [MHþ2]: 361.36 (32.6%).
1H NMR (250 MHz, DMSO-d6)
d 9.68 (s, 1H, 4-phenyl 3-OH), 8.41
(dd, J ¼ 3.0, 1.0 Hz, 1H, 6-thiophene H-2), 8.33 (d, J ¼ 8.6 Hz, 2H, 2-
phenyl H-2, H-6), 8.06 (s, 2H, pyridine H-3, H-5), 7.96 (dd, J ¼ 5.0,
0.7 Hz, 1H, 6-thiophene H-4), 7.67 (dd, J ¼ 5.0, 2.9 Hz, 1H, 6-
thiophene H-5), 7.57 (d, J ¼ 8.6 Hz, 2H, 2-phenyl H-3, H-5),
7.42e7.31 (m, 3H, 4-phenyl H-2, H-5, H-6), 6.93e6.90 (m, 1H, 4-
phenyl H-4). 13C NMR (62.5 MHz, DMSO-d6)
d 158.16, 155.19,
153.39, 150.00, 142.14, 139.17, 137.68, 134.22, 130.26, 128.85, 127.09,
126.91, 124.95, 118.21, 116.97, 116.45, 116.22, 114.28.
1H NMR (250 MHz, DMSO-d6)
d 9.71 (br, 1H, 4-phenyl 3-OH),
8.75 (d, J ¼ 5.9 Hz, 2H, 2-pyridine H-20, H-60), 8.36 (d, J ¼ 8.6 Hz, 2H,
6-phenyl H-2, H-6), 8.30e8.24 (m, 4H, pyridine H-3, H-5, 2-
pyridine H-30, H-50), 7.58 (d, J ¼ 8.5 Hz, 2H, 6-phenyl H-3, H-5),
7.47e7.32 (m, 3H, 4-phenyl H-2, H-5, H-6), 6.95e6.92 (m, 1H, 4-
4.3.18. 3-(2-(4-Chlorophenyl)-6-(furan-2-yl)pyridin-4-yl)phenol (29)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ d) (0.47 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 256 mg (49.0%, 0.74 mmol)
as a yellow solid, Rf ¼ 0.33 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
212.5e212.6 ꢀC, purity: 95.3%, retention time: 9.27 min; [MH]þ:
348.28 (100%), [MHþ2]: 350.28 (32.6%).
phenyl H-4). 13C NMR (62.5 MHz, DMSO-d6)
d 158.20, 155.71,
154.14, 150.47, 145.75, 138.81, 137.35, 134.50, 130.31, 128.97, 121.32,
118.36, 117.86, 116.66, 114.43.
4.3.22. 4-(2-(2-Chlorophenyl)-6-phenylpyridin-4-yl)phenol (33)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ a) (0.65 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 115 mg (32.2%, 0.32 mmol)
as a white solid, Rf ¼ 0.30 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
106.9e108.0 ꢀC, purity: 100%, retention time: 8.92 min; [MH]þ:
358.31 (100%), [MHþ2]: 360.32 (32.6%).
1H NMR (250 MHz, DMSO-d6)
d 9.70 (s, 1H, 4-phenyl 3-OH), 8.30
(d, J ¼ 8.6 Hz, 2H, 2-phenyl H-2, H-6), 8.06 (s,1H, pyridine H-3), 7.88
(s, 2H, pyridine H-5, 6-furan H-5), 7.57 (d, J ¼ 8.6 Hz, 2H, 2-phenyl
H-3, H-5), 7.36e7.29 (m, 4H, 4-phenyl H-2, H-5, H-6, 6-furan H-3),
6.94e6.90 (m, 1H, 4-phenyl H-4), 6.70 (dd, J ¼ 3.3, 1.7 Hz, 1H, 6-
furan H-4). 13C NMR (62.5 MHz, DMSO-d6)
d 158.22, 155.57,
153.24,149.85,149.25,144.59,138.86,137.36,134.39,130.42,128.89,
118.06, 116.65, 116.43, 114.78, 114.04, 112.57, 109.83.
1H NMR (250 MHz, CDCl3)
d
8.10 (dd, J ¼ 6.7, 1.5 Hz, 2H, 6-phenyl
H-2, H-6), 7.87 (d, J ¼ 1.4 Hz, 1H, pyridine H-3), 7.76 (d, J ¼ 1.3 Hz,
1H, pyridine H-5), 7.74e7.73 (m, 1H, 2-phenyl H-6), 7.63 (d,
J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.53e7.42 (m, 4H, 2-phenyl H-3,
6-phenyl H-3, H-4, H-5), 7.40e7.35 (m, 2H, 2-phenyl H-4, H-5), 6.93
(d, J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5), 5.63 (br, 1H, 4-phenyl 4-OH).
4.3.19. 3-(6-(4-Chlorophenyl)-[2,20-bipyridin]-4-yl)phenol (30)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ e) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 317 mg (58.9%, 0.88 mmol)
as a white solid, Rf ¼ 0.22 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
234.4e235.3 ꢀC, purity: 99.6%, retention time: 9.19 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.34 (32.6%).
13C NMR (62.5 MHz, CDCl3)
d 157.82, 157.03, 156.69, 148.75, 139.48,
139.37, 132.35, 131.79, 130.84, 130.15, 129.58, 128.99, 128.70, 128.55,
127.22, 126.97, 120.93, 117.00, 116.04.
4.3.23. 4-(2-(2-Chlorophenyl)-6-(thiophen-2-yl)pyridin-4-yl)
phenol (34)
1H NMR (250 MHz, DMSO-d6)
d 9.72 (s,1H, 4-phenyl 3-OH), 8.73,
(d, J ¼ 3.7 Hz, 1H, 2-pyridine H-60), 8.60e8.56 (m, 2H, pyridine H-3,
2-pyridine H-30), 8.38 (d, J ¼ 8.6 Hz, 2H, 6-phenyl H-2, H-6), 8.24 (d,
J ¼ 1.2 Hz, 1H, pyridine H-5), 8.00 (td, J ¼ 7.8, 1.7 Hz, 1H, 2-pyridine
H-40), 7.58 (d, J ¼ 8.6 Hz, 2H, 6-phenyl H-3, H-5), 7.50 (ddd, J ¼ 7.4,
4.8, 0.9 Hz,1H, 2-pyridine H-50), 7.38e7.33 (m, 3H, 4-phenyl H-2, H-
5, H-6), 6.93e6.90 (m, 1H, 4-phenyl H-4). 13C NMR (62.5 MHz,
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ b) (0.66 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 221 mg (60.1%, 0.60 mmol)
as a white solid, Rf ¼ 0.31 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
169.8e169.9 ꢀC, purity: 100%, retention time: 8.83 min; [MH]þ:
364.28 (100%), [MHþ2]: 366.26 (32.6%).
DMSO-d6)
d 158.28. 155.87, 155.34, 155.21, 149.94, 149.53, 138.99,
137.63, 137.48, 134.40, 130.53, 128.95, 124.69, 121.04, 118.16, 118.01,
116.84, 116.67, 113.92.
1H NMR (250 MHz, CDCl3)
d
7.74 (d, J ¼ 1.4 Hz, 1H, pyridine H-3)
7.69e7.64 (m, 3H, pyridine H-5, 2-phenyl H-6, 6-thiophene H-3),
7.55 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.46e7.42 (m, 1H, 2-
phenyl H-3), 7.38e7.29 (m, 3H, 2-phenyl H-4, H-5, 6-thiophene
H-5), 7.08 (dd, J ¼ 5.0, 3.7 Hz, 1H, 6-thiophene H-4), 6.90 (d,
J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5), 5.25 (s, 1H, 4-phenyl 4-OH). 13C
4.3.20. 3-(6-(4-Chlorophenyl)-2,30-bipyridin-4-yl)phenol (31)
The compound was synthesized as described in section 4.3 with
4 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ f) (0.49 g,

P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
133
NMR (62.5 MHz, CDCl3)
138.91, 132.21, 131.75, 130.07, 129.54, 129.39, 128.32, 127.88, 127.42,
126.91, 124.75, 120.70, 115.90, 115.06.
d
158.00, 156.68, 152.64, 148.90, 144.74,
and glacial acetic acid (3.00 mL) to yield 136 mg (38.0%, 0.38 mmol)
as a brown solid, Rf ¼ 0.25 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
114.8e115.6 ꢀC, purity: 97.8%, retention time: 7.58 min; [MH]þ:
359.31 (100%), [MHþ2]: 361.32 (32.6%).
4.3.24. 4-(2-(2-Chlorophenyl)-6-(thiophen-3-yl)pyridin-4-yl)
phenol (35)
1H NMR (250 MHz, DMSO-d6)
d 9.90 (s, 1H, 4-phenyl 4-OH), 9.40
(s,1H, 2-pyridine H-20), 8.65 (d, J ¼ 3.5 Hz,1H, 2-pyridine H-60), 8.57
(d, J ¼ 7.9 Hz, 1H, 2-pyridine H-40), 8.27 (s, 1H, pyridine H-3), 7.87 (s,
1H, pyridine H-5), 7.86 (d, J ¼ 8.2 Hz, 2H, 4-phenyl H-2, H-6),
7.78e7.75 (m, 1H, 6-phenyl H-6), 7.62e7.60 (m, 1H, 6-phenyl H-3),
7.56e7.75 (m, 3H, 6-phenyl H-4, H-5, 2-pyridine H-50), 6.92 (d,
J ¼ 8.5 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR (62.5 MHz, DMSO-d6)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ c) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 165 mg (45.5%, 0.46 mmol)
as a white solid, Rf ¼ 0.31 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
188.7e189.4 ꢀC, purity: 99.4%, retention time: 8.79 min; [MH]þ:
364.28 (100%), [MHþ2]: 366.27 (32.6%).
d
159.21, 157.06, 154.44, 150.10, 148.98, 148.36, 139.14, 134.64,
134.43, 132.03, 131.59, 130.38, 130.24, 128.89, 127.73, 127.65, 123.94,
120.57, 116.52, 116.17.
1H NMR (250 MHz, CDCl3)
d 9.05 (br, 1H, 4-phenyl 4-OH), 7.93
(dd, J ¼ 3.0, 1.2 Hz, 1H, 6-thiophene H-2), 7.71 (d, J ¼ 1.5 Hz, 1H,
pyridine H-3), 7.68e7.61 (m, 3H, pyridine H-5, 2-phenyl H-6, 6-
thiophene H-4), 7.55 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6),
7.47e7.43 (m, 1H, 2-phenyl H-3), 7.36e7.23 (m, 3H, 2-phenyl H-4,
H-5, 6-thiophene H-5), 6.89 (d, J ¼ 8.7 Hz, 2H, 4-phenyl H-3, H-5).
4.3.28. 4-(6-(2-Chlorophenyl)-2,40-bipyridin-4-yl)phenol (39)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ g) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 79 mg (22.0%, 0.22 mmol)
as a brown solid, Rf ¼ 0.19 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
118.3e119.1 ꢀC, purity: 96.7%, retention time: 7.62 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.33 (32.6%).
13C NMR (62.5 MHz, CDCl3)
d 158.01, 156.88, 153.66, 149.04, 141.97,
139.19, 132.25, 131.59., 130.00, 129.53, 129.40, 128.30, 126.85,
126.37, 126.12, 123.87, 120.54, 116.64, 115.89.
4.3.25. 4-(2-(2-Chlorophenyl)-6-(furan-2-yl)pyridin-4-yl)phenol (36)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ d) (0.63 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 117 mg (33.6%, 0.34 mmol)
as a white solid, Rf ¼ 0.33 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
207.7e208.1 ꢀC, purity: 97.5%, retention time: 8.35 min; [MH]þ:
348.27 (100%), [MHþ2]: 350.28 (32.6%).
1H NMR (250 MHz, DMSO-d6)
d 9.93 (s, 1H, 4-phenyl 4-OH), 8.71
(d, J ¼ 6.0 Hz, 2H, 2-pyridine H-20, H-60), 8.32 (d, J ¼ 1.2 Hz, 1H,
pyridine H-3), 8.20 (dd, J ¼ 4.6, 1.5 Hz, 2H, 2-pyridine H-30, H-50),
7.92 (d, J ¼ 1.2 Hz,1H, pyridine H-5), 7.87 (d, J ¼ 8.6 Hz, 2H, 4-phenyl
H-2, H-6), 7.78e7.74 (m, 1H, 6-phenyl H-6), 7.64e7.60 (m, 1H, 6-
phenyl H-3), 7.51e7.60 (m, 2H, 6-phenyl H-4, H-5), 6.93 (d,
J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR (62.5 MHz, DMSO-d6)
d
159.29, 157.17, 154.14, 150.45, 149.14, 145.91, 139.03, 132.02, 131.61,
1H NMR (250 MHz, CDCl3)
d
9.02 (br,1H, 4-phenyl 4-OH), 7.83 (d,
130.46, 130.26, 128.92, 127.67, 127.58, 121.55, 121.37, 116.92, 116.20.
J ¼ 1.6 Hz, 1H, pyridine H-3), 7.61e7.54 (m, 1H, 2-phenyl H-6), 7.57
(d, J ¼ 1.6 Hz, 1H, pyridine H-5), 7.55 (d, J ¼ 8.8 Hz, 2H, 4-phenyl H-
2, H-6), 7.49 (dd, J ¼ 1.6, 0.6 Hz, 1H, 6-furan H-5), 7.45e7.41 (m, 1H,
2-phenyl H-3), 7.33e7.28 (m, 2H, 2-phenyl H-4, H-5), 7.10 (d,
J ¼ 3.4 Hz, 1H, 6-furan H-3), 6.88 (d, J ¼ 8.7 Hz, 2H, 4-phenyl H-3, H-
5), 6.48 (dd, J ¼ 3.8, 1.8 Hz, 1H, 6-furan H-4). 13C NMR (62.5 MHz,
4.3.29. 4-(2-(3-Chlorophenyl)-6-phenylpyridin-4-yl)phenol (40)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ a) (0.48 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 93 mg (17.4%, 0.26 mmol)
as a white solid, Rf ¼ 0.29 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
210.3e210.4 ꢀC, purity: 95.2%, retention time: 9.67 min; [MH]þ:
358.33 (100%), [MHþ2]: 360.33 (32.6%).
CDCl3)
d 158.11, 156.99, 153.32, 149.45, 148.88, 143.21, 139.05,
132.24, 131.52, 129.92, 129.61, 129.09, 128.28, 126.86, 120.54, 115.88,
114.68, 112.03, 109.05.
1H NMR (250 MHz, CDCl3)
d 9.25 (br,1H, 4-phenyl 4-OH), 8.05 (s,
4.3.26. 4-(6-(2-Chlorophenyl)-2,20-bipyridin-4-yl)phenol (37)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ e) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (3.00 mL) to yield 91 mg (25.4%, 0.25 mmol)
as a yellow solid, Rf ¼ 0.17 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
238.9e240.5 ꢀC, purity: 99.1%, retention time: 8.39 min; [MH]þ:
359.35 (100%), [MHþ2]: 361.35 (32.6%).
1H, 2-phenyl H-2), 8.03 (d, J ¼ 8.1 Hz, 2H, 6-phenyl H-2, H-6),
7.93e7.09 (m, 1H, 2-phenyl H-6), 7.75 (d, J ¼ 1.2 Hz, 1H, pyridine H-
3), 7.70 (d, J ¼ 1.2 Hz, 1H, pyridine H-5), 7.53 (d, J ¼ 8.6 Hz, 2H, 4-
phenyl H-2, H-6), 7.42e7.37 (m, 3H, 6-phenyl H-3, H-4, H-5),
7.33e7.31 (m, 2H, 2-phenyl H-4, H-5), 6.87 (d, J ¼ 8.5 Hz, 2H, 4-
phenyl H-3, H-5). 13C NMR (62.5 MHz, CDCl3)
d 158.04, 157.57,
155.87, 150.07, 141.35, 139.28, 134.54, 129.78, 129.58, 128.96, 128.75,
128.57, 128.25, 127.10, 126.99, 125.08, 117.04, 116.55, 115.87.
1H NMR (250 MHz, DMSO-d6)
d 9.92 (br, 1H, 4-phenyl 4-OH),
8.73 (d, J ¼ 4.0 Hz, 1H, 2-pyridine H-60), 8.60 (d, J ¼ 1.5 Hz, 1H,
pyridine H-3), 8.43 (d, J ¼ 7.9 Hz, 1H, 2-pyridine H-30), 7.95 (td,
J ¼ 7.7, 1.7 Hz, 1H, 2-pyridine H-40), 7.90 (d, J ¼ 1.5 Hz, 1H, pyridine
H-5),7.78e7.75 (m, 1H, 6-phenyl H-6), 7.77 (d, J ¼ 8.6 Hz, 2H, 4-
phenyl H-2, H-6), 7.64e7.60 (m, 1H, 6-phenyl H-3), 7.51e7.45 (m,
3H, 6-phenyl H-4, H-5, 2-pyridine H-50), 6.93 (d, J ¼ 8.6 Hz, 2H, 4-
4.3.30. 4-(2-(3-Chlorophenyl)-6-(thiophen-2-yl)pyridin-4-yl)
phenol (41)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ b) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 80 mg (14.6%, 0.22 mmol)
as a white solid, Rf ¼ 0.26 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
216.2e216.8 ꢀC, purity: 95.2%, retention time: 9.54 min; [MH]þ:
364.27 (100%), [MHþ2]: 366.27 (32.6%).
phenyl H-3, H-5). 13C NMR (62.5 MHz, DMSO-d6)
d 159.17, 156.72,
155.80, 155.37, 149.51, 148.76, 139.16, 137.57, 132.02, 131.64, 130.39,
130.25, 128.57, 127.88, 127.66, 124.58, 121.52, 121.08, 116.35, 115.92.
1H NMR (250 MHz, CDCl3)
d 9.52 (br,1H, 4-phenyl 4-OH), 8.04 (s,
4.3.27. 4-(6-(2-Chlorophenyl)-2,30-bipyridin-4-yl)phenol (38)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ h) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ f) (0.33 g,
1.00 mmol, 1.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
1H, 2-phenyl H-2), 7.93e7.90 (m, 1H, 2-phenyl H-6), 7.75e7.63 (m,
3H, pyridine H-3, H-5, 6-thiophene H-3), 7.54 (d, J ¼ 8.4 Hz, 2H, 4-
phenyl H-2, H-6), 7.36e7.32 (m, 3H, 6-thiophene H-5, 6-phenyl H-
4, H-5), 7.06 (dd, J ¼ 4.8, 3.8 Hz, 1H, 6-thiophene H-4), 6.89 (d,

134
P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
J ¼ 8.4 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR (62.5 MHz, CDCl3)
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 74 mg (13.9%, 0.21 mmol)
as a white solid, Rf ¼ 0.23 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
261.3e261.4 ꢀC, purity: 99.9%, retention time: 8.24 min; [MH]þ:
359.36 (100%), [MHþ2]: 361.36 (32.6%).
d
158.05, 155.45, 152.50, 149.94, 144.68, 140.70, 134.36, 129.63,
129.10, 128.65, 128.04, 127.69, 127.38, 126.79, 124.81, 124.53, 116.01,
115.69, 114.94.
4.3.31. 4-(2-(3-Chlorophenyl)-6-(thiophen-3-yl)pyridin-4-yl)
phenol (42)
1H NMR (250 MHz, DMSO-d6)
d 9.92 (s, 1H, 4-phenyl 4-OH), 9.47
(s, 1H, 2-pyridine H-20), 8.68e8.64 (m, 2H, 2-pyridine H-40, H-60),
8.39 (s, 1H, 6-phenyl H-2), 8.32e8.29 (m, 1H, 6-phenyl H-6), 8.26 (s,
1H, pyridine H-3), 8.25 (s, 1H, pyridine H-5), 7.98 (d, J ¼ 8.5 Hz, 2H,
4-phenyl H-2, H-6), 7.59e7.54 (m, 3H, 2-pyridine H-50, 6-phenyl H-
4, H-5), 6.93 (d, J ¼ 8.5 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ c) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 332 mg (60.9%, 0.91 mmol)
as a white solid, Rf ¼ 0.28 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
198.5e199.6 ꢀC, purity: 95.9%, retention time: 9.51 min; [MH]þ:
364.29 (100%), [MHþ2]: 366.27 (32.6%).
(62.5 MHz, DMSO-d6)
d 159.25, 155.27, 154.51, 150.24, 149.96,
148.43, 141.06, 134.63, 134.43, 133.98, 130.84, 129.29, 129.10, 127.81,
126.83, 125.87, 124.02, 116.82, 116.70, 116.04.
1H NMR (250 MHz, DMSO-d6)
d 9.87 (br, 1H, 4-phenyl 4-OH),
8.41 (dd, J ¼ 3.0, 1.2 Hz, 1H, 6-thiophene H-2), 8.35 (s, 1H, 2-phenyl
H-2), 8.29e8.26 (m, 1H, 2-phenyl H-6), 8.11 (s, 1H, pyridine H-3),
8.09 (s, 1H, pyridine H-5), 7.97 (dd, J ¼ 5.0, 1.2 Hz, 1H, 6-thiophene
H-4), 7.92 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.67 (dd, J ¼ 4.9,
3.0 Hz, 1H, 6-thiophene H-5). 7.58e7.52 (m, 2H, 2-phenyl H-4, H-5),
6.93 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR (62.5 MHz,
4.3.35. 4-(6-(3-Chlorophenyl)-2,40-bipyridin-4-yl)phenol (46)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ g) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 95 mg (17.7%, 0.27 mmol)
as a white solid, Rf ¼ 0.19 (ethyl acetate/n-hexane 1 : 1 v/v). mp.:
309.2e309.5 ꢀC, purity: 96.7%, retention time: 8.29 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.36 (32.6%).
DMSO-d6)
d 159.07, 154.77, 153.35, 149.55, 142.26, 141.20, 133.89,
130.69,129.04,128.84,127.96,127.05,126.93,126.69,125.68,124.85,
116.30, 115.97, 115.60.
1H NMR (250 MHz, DMSO-d6)
d 9.95 (s, 1H, 4-phenyl 4-OH), 8.74
(d, J ¼ 5.5 Hz, 2H, 2-pyridine H-20, H-60), 8.38 (s, 1H, 6-phenyl H-2),
8.30e8.26 (m, 5H, pyridine H-3, H-5, 2-pyridine H-30, H-50, 6-
phenyl H-6), 7.98 (d, J ¼ 8.5 Hz, 2H, 4-phenyl H-2, H-6), 7.57e7.55
(m, 2H, 6-phenyl H-4, H-5), 6.93 (d, J ¼ 8.5 Hz, 2H, 4-phenyl H-3,
4.3.32. 4-(2-(3-Chlorophenyl)-6-(furan-2-yl)pyridin-4-yl)phenol (43)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ d) (0.47 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 160 mg (30.6%, 0.46 mmol)
as a white solid, Rf ¼ 0.29 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
183.7e190.0 ꢀC, purity: 95.9%, retention time: 9.15 min; [MH]þ:
348.28 (100%), [MHþ2]: 350.28 (32.6%).
H-5). 13C NMR (62.5 MHz, DMSO-d6)
d 159.33, 155.34, 154.16,
150.56, 150.11, 145.89, 140.91, 134.02, 130.86, 129.38, 129.14, 127.67,
126.85, 150.88, 121.36, 117.68, 117.22, 116.07.
4.3.36. 4-(2-(4-Chlorophenyl)-6-phenylpyridin-4-yl)phenol (47)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ j) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ a) (0.65 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (5.00 mL) to yield 25 mg (7.0%, 0.07 mmol) as
a white solid, Rf ¼ 0.26 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
252.9e253.4 ꢀC, purity: 98.2%, retention time: 9.70 min; [MH]þ:
358.32 (100%), [MHþ2]: 360.30 (32.6%).
1H NMR (250 MHz, DMSO-d6)
d 9.92 (s, 1H, 4-phenyl 4-OH), 8.32
(s, 1H, 2-phenyl H-2), 8.26e8.22 (m, 1H, 2-phenyl H-6), 8.11 (d,
J ¼ 0.9 Hz, 1H, pyridine H-3), 7.91 (d, J ¼ 0.9 Hz, 1H, pyridine H-5),
7.87 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.85 (s, 1H, 6-furan H-5),
7.55e7.52 (m, 2H, 2-phenyl H-4, H-5), 7.32 (d, J ¼ 3.3 Hz,1H, 6-furan
H-3), 6.92 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5), 6.69 (dd, J ¼ 3.3,
1.7 Hz, 1H, 6-furan H-4). 13C NMR (62.5 MHz, DMSO-d6)
d 159.23,
155.13, 153.35, 149.53, 149.25, 144.55, 140.88, 133.93, 130.77, 129.25,
128.82, 127.75, 126.77, 125.76, 116.12, 115.90, 114.23, 112.60, 109.79.
1H NMR (250 MHz, DMSO-d6)
d 9.88 (br, 1H, 4-phenyl 4-OH),
8.35 (d, J ¼ 8.6 Hz, 2H, 2-phenyl H-2, H-6), 8.29 (d, J ¼ 6.9 Hz, 2H, 6-
phenyl H-2, H-6), 8.14 (s, 1H, pyridine H-3), 8.12 (s, 1H, pyridine H-
5), 7.91 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.58 (d, J ¼ 8.6 Hz, 2H,
2-phenyl H-3, H-5), 7.50e7.43 (m, 3H, 6-phenyl H-3, H-4, H-5), 6.93
(d, J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR (62.5 MHz, DMSO-
4.3.33. 4-(6-(3-Chlorophenyl)-[2,20-bipyridin]-4-yl)phenol (44)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ e) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 103 mg (19.1%, 0.29 mmol)
as a white solid, Rf ¼ 0.17 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
222.4e222.7 ꢀC, purity: 99.5%, retention time: 9.06 min; [MH]þ:
359.36 (100%), [MHþ2]: 361.36 (32.6%).
d6)
d 159.09, 156.60, 155.21, 149.69, 139.02, 137.94, 134.14, 129.36,
128.87, 128.14, 127.09, 116.09, 116.04, 115.82.
4.3.37. 4-(2-(4-chlorophenyl)-6-(thiophen-2-yl)pyridin-4-yl)
phenol (48)
1H NMR (250 MHz, DMSO-d6)
d
9.92 (s, 1H, 4-phenyl 4-OH), 8.72
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ j) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ b) (0.66 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (5.00 mL) to yield 48 mg (13.4%, 0.13 mmol)
as a white solid, Rf ¼ 0.24 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
230.4e230.5 ꢀC, purity: 99.7%, retention time: 9.58 min; [MH]þ:
364.28 (100%), [MHþ2]: 366.28 (32.6%).
(d, J ¼ 3.7 Hz, 1H, 2-pyridine H-60), 8.58 (s, 2H, pyridine H-3, 2-
pyridine H-30), 8.39 (s, 1H, 6-phenyl H-2), 8.32e8.29 (m, 1H, 6-
phenyl H-6), 8.27 (s, 1H, pyridine H-5), 8.00 (td, J ¼ 7.6, 1.3 Hz,
1H, 2-pyridine H-40), 7.87 (d, J ¼ 8.5 Hz, 2H, 4-phenyl H-2, H-6),
7.56e7.49 (m, 3H, 2-pyridine H-50, 6-phenyl H-4, H-5), 6.94 (d,
J ¼ 8.5 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR (62.5 MHz, DMSO-d6)
d
159.21, 155.83, 155.38, 154.91, 149.71, 149.51, 141.02, 137.68,
1H NMR (250 MHz, CDCl3)
d 8.59 (s, 1H, 4-phenyl 4-OH), 8.04
134.00, 130.83, 129.26, 128.77, 127.98, 126.80, 125.83, 124.65, 121.11,
117.67, 116.31, 116.22.
(d, J ¼ 8.6 Hz, 2H, 2-phenyl H-2, H-6), 7.69 (d, J ¼ 1.2 Hz, 1H,
pyridine H-3), 7.65 (dd, J ¼ 4.4, 1.0 Hz, 1H, 6-thiophene H-3), 7.64
(d, J ¼ 1.0 Hz, 1H, pyridine H-5), 7.56 (d, J ¼ 8.6 Hz, 2H, 4-phenyl
H-2, H-6), 7.41 (d, J ¼ 8.6 Hz, 2H, 2-phenyl H-3, H-5), 7.37 (dd,
J ¼ 5.0, 0.9 Hz, 1H, 6-thiophene H-5), 7.09 (dd, J ¼ 5.0, 3.8 Hz, 1H,
6-thiophene H-4), 6.92 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5). 13C
4.3.34. 4-(6-(3-Chlorophenyl)-2,30-bipyridin-4-yl)phenol (45)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ i) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ f) (0.49 g,

P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
135
NMR (62.5 MHz, CDCl3)
135.03, 129.79, 128.74, 128.28, 128.22, 127.89, 127.57, 124.59,
115.94, 114.89.
d
155.90, 152.63, 149.97, 145.19, 137.53,
as a white solid, Rf ¼ 0.39 (ethyl acetate/n-hexane 2 : 1 v/v). mp.:
310.9e311.9 ꢀC, purity: 95.75%, retention time: 8.29 min; [MH]þ:
359.32 (100%), [MHþ2]: 361.34 (32.6%).
1H NMR (250 MHz, DMSO-d6)
d 9.89 (s, 1H, 4-phenyl 4-OH), 9.47
4.3.38. 4-(2-(4-Chlorophenyl)-6-(thiophen-3-yl)pyridin-4-yl)
phenol (49)
(d, J ¼ 1.6 Hz, 1H, 2-pyridine H-20), 8.66e8.65 (m, 2H, 2-pyridine H-
40, H-60), 8.35 (d, J ¼ 8.6 Hz, 2H, 6-phenyl H-2, H-6), 8.22 (s, 1H,
pyridine H-3), 8.19 (s, 1H, pyridine H-5), 7.94 (d, J ¼ 8.6 Hz, 2H, 4-
phenyl H-2, H-6), 7.59e7.55 (m, 3H, 2-pyridine H-50, 6-phenyl H-
3, H-5), 6.93 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ j) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ c) (0.66 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (5.00 mL) to yield 84 mg (23.1%, 0.23 mmol)
as a white solid, Rf ¼ 0.25 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
233.5e233.8 ꢀC, purity: 100%, retention time: 9.56 min; [MH]þ:
364.27 (100%), [MHþ2]: 366.28 (32.6%).
(62.5 MHz, DMSO-d6)
d 159.17, 155.52, 154.39, 150.15, 149.86,
148.38, 137.68, 134.50, 134.40, 134.28, 128.96, 128.91, 127.89, 123.91,
116.46, 116.32, 116.03.
1H NMR (250 MHz, DMSO-d6)
d
9.87 (br, 1H, 4-phenyl 4-OH),
4.3.42. 4-(6-(4-chlorophenyl)-2,40-bipyridin-4-yl)phenol (53)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ g) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (4.00 mL) to yield 156 mg (29.1%, 0.44 mmol)
as a white solid, Rf ¼ 0.24 (ethyl acetate/n-hexane 2 : 1 v/v). mp.:
327.6e328.6 ꢀC, purity: 95.62%, retention time: 8.37 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.34 (32.6%).
8.40 (dd, J ¼ 3.0,1.1 Hz,1H, 6-thiophene H-2), 8.33 (d, J ¼ 8.6 Hz, 2H,
2-phenyl H-2, H-6), 8.07 (s, 2H, pyridine H-3, H-5), 7.96 (dd, J ¼ 5.0,
0.9 Hz, 1H, 6-thiophene H-4), 7.90 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2,
H-6), 7.66 (dd, J ¼ 5.0, 3.0 Hz, 1H, 6-thiophene H-5), 7.57 (d,
J ¼ 8.6 Hz, 2H, 2-phenyl H-3, H-5), 6.93 (d, J ¼ 8.6 Hz, 2H, 4-phenyl
H-3, H-5). 13C NMR (62.5 MHz, DMSO-d6)
d 159.05, 155.08, 153.30,
149.50, 142.34, 137.86, 134.10, 128.83, 128.05, 127.03, 126.94, 124.74,
116.01, 115.27.
1H NMR (250 MHz, DMSO-d6)
d 9.91 (s, 1H, 4-phenyl 4-OH), 8.73
(d, J ¼ 6.0 Hz, 2H, 2-pyridine H-20, H-60), 8.36 (d, J ¼ 8.6 Hz, 2H, 6-
phenyl H-2, H-6), 8.27e8.24 (m, 4H, pyridine H-3, H-5, 2-pyridine
H-30, H-50), 7.94 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.58 (d,
J ¼ 8.6 Hz, 2H, 6-phenyl H-3, H-5), 6.94 (d, J ¼ 8.6 Hz, 2H, 4-phenyl
4.3.39. 4-(2-(4-Chlorophenyl)-6-(furan-2-yl)pyridin-4-yl)phenol (50)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ j) (0.26 g, 1.00 mmol, 1.00 equiv), 2 (R ¼ d) (0.63 g,
2.00 mmol, 2.00 equiv), NH4OAc (0.77 g, 10.00 mmol, 10.00 equiv)
and glacial acetic acid (5.00 mL) to yield 49 mg (14.2%, 0.14 mmol)
as a white solid, Rf ¼ 0.27 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
238.3e238.5 ꢀC, purity: 96.47%, retention time: 9.18 min; [MH]þ:
348.27 (100%), [MHþ2]: 350.27 (32.6%).
H-3, H-5). 13C NMR (62.5 MHz, DMSO-d6)
d 159.25, 155.60, 154.05,
150.47, 150.01, 145.90, 137.54, 134.39, 129.00, 128.93, 127.73, 121.28,
117.30, 116.86, 116.05.
1H NMR (250 MHz, DMSO-d6)
d
9.90 (s, 1H, 4-phenyl 4-OH), 8.29
4.4. Pharmacology
(d, J ¼ 8.6 Hz, 2H, 2-phenyl H-2, H-6), 8.06 (d, J ¼ 1.1 Hz, 1H, 6-furan
H5), 7.88 (s, 1H, pyridine H-3), 7.87 (s, 1H, pyridine H-5), 7.84 (d,
J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.56 (d, J ¼ 8.6 Hz, 2H, 2-phenyl
H-3, H-5), 7.29 (d, J ¼ 3.1 Hz,1H, 6-furan H-3), 6.93 (d, J ¼ 8.6 Hz, 2H,
4-phenyl H-3, H-5), 6.68 (dd, J ¼ 3.3, 1.7 Hz, 1H, 6-furan H-4). 13C
4.4.1. DNA topoisomerase I inhibition in vitro
DNA topo I inhibition assay was determined following the
previously reported method [6k]. The test compounds were dis-
solved in DMSO at 20 mM as stock solution. The activity of DNA
topo I was determined by assessing the relaxation of supercoiled
DNA pBR322. The mixture of 100 ng of plasmid pBR322 DNA and 1
unit of recombinant human DNA topoisomerase I (TopoGEN INC.,
USA) was incubated with and without the prepared compounds at
37 ꢀC for 30 min in the relaxation buffer (10 mM TriseHCl (pH 7.9),
150 mM NaCl, 0.1% bovine serum albumin, 1 mM spermidine, 5%
NMR (62.5 MHz, DMSO-d6)
d 159.17, 155.45, 153.43, 149.46, 149.20,
144.44, 137.55, 134.28, 128.85, 128.70, 127.85, 116.13, 115.55, 113.91,
112.53, 109.63.
4.3.40. 4-(6-(4-Chlorophenyl)-[2,20-bipyridin]-4-yl)phenol (51)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ e) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (5.00 mL) to yield 341 mg (63.5%, 0.95 mmol)
as a white solid, Rf ¼ 0.18 (ethyl acetate/n-hexane 1 : 3 v/v). mp.:
249.8e245.1 ꢀC, purity: 100%, retention time: 9.09 min; [MH]þ:
359.34 (100%), [MHþ2]: 361.34 (32.6%).
glycerol). The reaction in the final volume of 10
mL was terminated
by adding 2.5 L of the stop solution containing 5% sarcosyl,
m
0.0025% bromophenol blue and 25% glycerol. DNA samples were
then electrophoresed on a 1% agarose gel at 15 V for 7 h with
a running buffer of TAE. Gels were stained for 30 min in an aqueous
solution of ethidium bromide (0.5 mg/mL). DNA bands were visu-
alized by transillumination with UV light and were quantitated
1H NMR (250 MHz, DMSO-d6)
d
9.92 (s, 1H, 4-phenyl 4-OH), 8.73
(dd, J ¼ 4.6, 0.6 Hz, 1H, 2-pyridine H-60), 8.59e8.56 (m, 2H, 2-
pyridine H-30, pyridine H-3), 8.37 (d, J ¼ 8.5 Hz, 2H, 6-phenyl H-
2, H-6), 8.23 (d, J ¼ 0.8 Hz, 1H, pyridine H-5), 7.99 (td, J ¼ 7.6, 1.5 Hz,
1H, 2-pyridine H-40), 7.85 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-2, H-6), 7.59
(d, J ¼ 8.5 Hz, 2H, 6-phenyl H-3, H-5), 7.49 (dd, J ¼ 7.1, 5.0 Hz, 1H, 2-
pyridine H-50), 6.94 (d, J ¼ 8.6 Hz, 2H, 4-phenyl H-3, H-5). 13C NMR
using AlphaImagerÔ (Alpha Innotech Corporation).
4.4.2. DNA topoisomerase II inhibition in vitro
DNA topo II inhibitory activity of compounds were measured
as follows [6k]. The mixture of 200 ng of supercoiled pBR322
plasmid DNA and 1 unit of human DNA topoisomerase IIa (Usb
(62.5 MHz, DMSO-d6)
d
159.17, 155.79, 155.44, 155.23, 149.68,
Corp., USA) was incubated without and with the prepared
compounds in the assay buffer (10 mM TriseHCl (pH 7.9) con-
taining 50 mM NaCl, 5 mM MgCl2, 1 mM EDTA, 1 mM ATP, and
149.51, 137.69, 137.62, 134.31, 128.94, 128.69, 128.07, 125.62, 121.07,
117.32, 116.25, 116.04.
15
tion in a final volume of 20
L of 7 mM EDTA. Reaction products were analyzed on 1%
m
g/mL bovine serum albumin) for 30 min at 30 ꢀC. The reac-
4.3.41. 4-(6-(4-chlorophenyl)-2,30-bipyridin-4-yl)phenol (52)
The compound was synthesized as described in section 4.3 with
5 (R1 ¼ j) (0.39 g, 1.50 mmol, 1.00 equiv), 2 (R ¼ f) (0.49 g,
1.50 mmol, 1.00 equiv), NH4OAc (1.16 g, 15.00 mmol, 10.00 equiv)
and glacial acetic acid (5.00 mL) to yield 220 mg (40.8%, 0.61 mmol)
mL was terminated by the addition of
3
m
agarose gel at 25 V for 4 h with a running buffer of TAE. Gels were
stained for 30 min in an aqueous solution of ethidium bromide
(0.5
mg/mL). DNA bands were visualized by transillumination

136
P. Thapa et al. / European Journal of Medicinal Chemistry 52 (2012) 123e136
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AlphaImagerÔ (Alpha Innotech Corporation).
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Cancer cells were cultured according to the supplier’s instruc-
tions. Cells were seeded in 96-well plates at a density of 2e4 ꢂ 104
cells per well and incubated for overnight in 0.1 mL of media
supplied with 10% Fetal Bovine Serum (Hyclone, USA) in 5% CO2
incubator at 37 ꢀC. On day 2, after FBS starvation for 4 h, culture
medium in each well was exchanged with 0.1 mL aliquots of
medium containing graded concentrations of compounds. On day
(b) L.X. Zhao, Y.S. Moon, A. Basnet, E.K. Kim, Y. Jahng, J.G. Park, T.C. Jeong,
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42e47;
4, each well was added with 5 mL of the cell counting kit-8 solution
(Dojindo, Japan) then incubated for additional 4 h under the same
condition. The absorbance of each well was determined by an
Automatic Elisa Reader System (Bio-Rad 3550) at 450 nm wave-
length. For determination of the IC50 values, the absorbance read-
ings at 450 nm were fitted to the four-parameter logistic equation.
The compounds such as adriamycin, etoposide, and camptothecin
were purchased from Sigma and used as positive controls.
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Y. Na, W.J. Cho, Y. Kwon, E.S. Lee, Bioorg. Med. Chem. 18 (2010) 2245e2254;
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4.5. Modeling method
Docking was carried out using GLIDE software [20]. The
compound 47 was minimized using Impact then subjected for
docking against 2 molecular targets including topo I and topo II
(PDB ID : 1K4T and 3QX3) using Glide extra-precision (XP). The grid
enclosing box was centered to the active sites of corresponding 3D-
structure of the reference ligands.
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Acknowledgments
This research was supported by the Basic Science Research
Program through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education, Science and Technology
(2009-0066925, 2010-0002646, and 2011-0001170) and by the
Ewha Global Top5 Grant 2011 of Ewha Womans University.
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