Synthesis and in vitro anti-hepatitis B virus activities of 4-aryl-6-chloro-quinolin-2-one and 5-aryl-7-chloro-1,4-benzodiazepine derivatives

Article abstract of DOI:10.1016/j.bmcl.2008.05.065

A series of 4-aryl-6-chloro-quinolin-2-ones and 5-aryl-7-chloro-1,4-benzodiazepine were synthesized and assayed for their in vitro anti-hepatitis B virus activities and cytotoxicities for the first time. Some of the tested compounds were active against HBsAg and HBeAg secretion in Hep G2.2.15 cells. Compound 5c showed IC₅₀ of 0.074 and 0.449 mM on HBsAg and HBeAg secretions, respectively, which were 10 times higher than that of its analog 4c and led to better selective index (SI) values (SI = 23.2 and 3.4, respectively).

Full text of DOI:10.1016/j.bmcl.2008.05.065

Bioorganic & Medicinal Chemistry Letters 18 (2008) 3787–3789
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and in vitro anti-hepatitis B virus activities of 4-aryl-6-chloro-
quinolin-2-one and 5-aryl-7-chloro-1,4-benzodiazepine derivatives
Pi Cheng a,b, Quan Zhang a,b, Yun-Bao Ma a, Zhi-Yong Jiang a, Xue-Mei Zhang a, Feng-Xue Zhang c,
Ji-Jun Chen a,
*
a State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, PR China
b Graduate School of Chinese Academy of Sciences, Beijing 100039, PR China
c Institute of Tropical Medicine Sciences, Guangzhou University of Traditional Chinese Medicines, Guangzhou, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 4-aryl-6-chloro-quinolin-2-ones and 5-aryl-7-chloro-1,4-benzodiazepine were synthesized
and assayed for their in vitro anti-hepatitis B virus activities and cytotoxicities for the first time. Some
of the tested compounds were active against HBsAg and HBeAg secretion in Hep G2.2.15 cells. Compound
5c showed IC50 of 0.074 and 0.449 mM on HBsAg and HBeAg secretions, respectively, which were 10
times higher than that of its analog 4c and led to better selective index (SI) values (SI = 23.2 and 3.4,
respectively).
Received 25 January 2008
Revised 21 April 2008
Accepted 9 May 2008
Available online 20 May 2008
Keywords:
Ó 2008 Elsevier Ltd. All rights reserved.
4-Aryl-6-chloro-quinolin-2-one
5-Aryl-7-chloro-1,4-benzodiazepine
Anti-HBV activity
Hepatitis B virus (HBV) infection is still a major health problem
around the world, particularly in Asia. Approximately 350 million
people are chronic carriers of HBV worldwide, even though effec-
tive vaccines have been available for the last 20 years.1 Worldwide
deaths from liver cancer caused by HBV infection probably exceed
1 million per year.2 Nowadays, at least two different treatment op-
tions, including interferon and nucleoside analogs such as lamivu-
dine, are considered as antiviral therapy for chronic hepatitis B
infection.3 However, the side effects of interferon and the viral
resistance of nucleoside analogs make the current treatment regi-
mens far from satisfactory.4–6 To circumvent the existing therapeu-
tic difficulties, novel compounds with unique modes of actions are
still urgently needed.
4-Aryl-quinoline-2-ones are inhibitors of acyl coenzyme A and
cholesterol acyltransferase and are potent openers of the high con-
ductance, calcium-activated K+-channels.7 As a part of our contin-
uous search for active anti-HBV leads from natural sources and
synthetic compounds,8–10 a rational screening suggested that 4-
aryl-6-chloro-quinolin-2-one (4a, Fig. 1) possessed moderate activ-
ity to inhibit the production of HBV surface antigen (HBsAg) in
HBV-infected Hep G2.2.15 cells with selective index (SI) value of
2.6 (IC50 = 0.458 mM). Considering the diversity of the structures
of non-nucleoside HBV inhibitors,11–13 we decided to investigate
the biological properties of 4-aryl-6-chloro-quinolin-2-ones and
their analogs as potential anti-HBV agents.
In this paper, we report the synthesis of several 4-aryl-6-chloro-
quinolin-2-ones and 5-aryl-7-chloro-1,4-benzodiazepines, which
were mainly modified at C-3 of 4a to 3-substituted-quinolin-2-
ones, and at ring A to ring expanded 5-aryl-7-chloro-1,4-benzodi-
azepines (Fig. 1). The synthesized compounds were evaluated for
their in vitro anti-HBV activities for the first time.
The synthetic route of two kinds of target compounds was sum-
marized in Scheme 1. 4-Aryl-6-chloro-quinolin-2-ones and 5-aryl-
7-chloro-1,4-benzodiazepines shared the same synthetic precursor
2-aminobenzophenones (3, Scheme 1). The synthesis of com-
pounds 3 by a variety of methods has been reviewed.14 Based on
the complex-induced proximity effect,15the majority of com-
pounds 3 were prepared by the reaction of aryl esters with
ortho-lithiated Boc protected 3-chloro-aniline (2) via the formation
R1
R1
R2
5
4
6
Cl
Cl
Cl
N
3
3
A
R3
N
H
O
N
H
O
N
O
H
5-aryl-7-chloro-1,4-
benzodiazepine
3-substituted-4-aryl-6-chloro-
quinolin-2-one
4a
Figure 1. Structures of 4a, 3-substituted-quinolin-2-one, and 5-aryl-1,4-
benzodiazepine.
* Corresponding author. Tel./fax: +86 871 5223265.
E-mail address: chenjj@mail.kib.ac.cn (J.-J. Chen).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.05.065

3788
P. Cheng et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3787–3789
NH2
H
N
O
NHBoc
O
NH2
Cl
a
b
c
Cl
Cl
Cl
R1
4a: R1 = H
R1
3
1
2
4
R1 = 2-F
3a: R1 = H
3b:
3c:
4b:
R1 = 2-Cl
e
R1 = 2-F
R1 = 2-Cl
4c:
d
H
H
N
O
H
N
O
NHCOCH2Cl
N
O
OAc
O
g
f
Cl
Cl
OH
N
N
Cl
Cl
R1
R1
8a: R1 = H
6a: R1 = H
7a: R1 = H
R1
R1
5a: R1 = H
6b:
6c:
R1 = 2-F
R1 = 2-F
7b:
7c:
R1 = 2-F
1 = 2-Cl
8b:
R1 = 2-F
5b:
6
h
R
1 = 2-Cl
R1 = 2-Cl
8
5
8c:
R1 = 2-Cl
R
7
5c:
i
H
N
O
H
N
H
N
H
O
O
N
O
_
O
j
Cl
N
k
N
Cl
Cl
NHAc
R1
Cl
NH2
R1
Cl
+
R1
R1
11a: R1 = H
11b:
11c:
9a: R1 = H
12a: R1 = H
12b:
12c:
R1 = 2-F
R
R1 = 2-F
9b:
11
9
R
1 = 2-F
12
R1 = 2-Cl
10
1 = 2-Cl
1 = 2-Cl
9c:
R
Scheme 1. Synthesis of target compounds. Reagents and conditions: (a) (Boc)2O, DIEA, DCM; (b) À78 °C, 2.2 equiv tert-BuLi, then add R1-PhCOOMe at À40 °C and warm up to
0 °C, then 3 N HCl, EtOH, reflux, in three steps; (c) 0 °C, LiHMDS, EtOAc; (d) 0 °C, LiHMDS, c-valerolactone; (e) ClCH2COCl, DIEA, toluene; (f) HMTA, NH4OAc, EtOH, reflux; (g)
I2, K2S2O 8, KOAc, AcOH, 70 °C; (h) m-CPBA, DCM; (i) pyridine, reflux; (j) NH2NH2ÁH2O, EtOH, reflux; (k) pyridine, Ac2O, 70 °C.
Table 1
of dianion species with tert-BuLi (2.2 equiv) followed by deprotec-
tion of Boc group (Scheme 1).16 A tandem amidation/Knoevengel
Anti-HBV activity, cytotoxicity, and selectivity index of compounds 4–5, 7–9, and 11–
12a
condensation of readily prepared compounds 3 with ethyl acetate
HBsAgc
HBeAgd
IC50 (mM)
b
Compound
CC50 (mM)
or c-valerolactone gave compounds 4 and 3-hydroxyl ethyl substi-
tuted compounds (5) in good yields, respectively.17
e
f
IC50 (mM)
SI
SI
As shown in Scheme 1, chloroacetylation of compounds 3 with
chloroacetyl chloride in the presence of N,N-diisopropylethylamine
(DIEA) in dichloromethane (DCM) gave the corresponding N-(chlo-
roacetyl)-2-aminobenzophenone derivatives (6). Due to our inter-
est to examine whether the ring expanded 1,4-benzodiazepine
could have an effect on potential anti-HBV activities, compounds
7 were afforded by the reaction of intermediates 6 with hexameth-
ylenetetramine (HMTA) in EtOH in the presence of NH4OAc. In
addition, compounds 7 were further transferred to compounds 8
as racemates and compounds 9 by acetoxylation reaction of 3-po-
sition of 1,4-benzodiazepine ring18 and epoxidation of the C@N
double bond,19 respectively.
4a17
4b
1.25
>5.46
6.00
>4.91
>2.99
1.72
0.485
2.84
2.6
>1.9
8.0
>16
>16
23
<1
<1
<1
2.3
2.2
<1
1.3
1.8
<1
6.0
14
1.0
1.1
<1
>4.14
2.22
<1
>2.4
<1
>5.2
>5.5
3.4
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
4c
0.752
0.300
0.187
0.074
0.255
0.294
0.076
0.292
0.160
0.167
0.728
0.195
0.355
0.067
0.056
0.341
0.208
0.141
0.129
11.7
>6.00
0.950
0.545
0.449
0.835
5.36
4.08
>4.26
1.22
5a20
5b
5c
7a
7b
0.221
0.183
0.076
0.678
0.344
0.154
0.946
0.346
0.302
0.399
0.767
0.341
0.239
0.044
0.208
30.0
7c
8a18
8b
8c
1.94
9a21,22
9b23
9c23
11a24À26
11b27
11c28
12a28À30
12b
12c
>3.28
>3.26
4.49
>3.99
>3.61
>5.47
1.87
0.079
0.080
25.9
Upon heating a solution of compounds 6 in anhydrous pyridine
at reflux for 30 min, the initially formed a-pyridinium salt under-
went cyclodehydration to afford intermediates 10, which were fur-
ther hydrolyzed with hydrazine hydrate in ethanol at reflux for 2 h
to provide the desired compounds 11. The acetamide derivatives
(12) of 11 were further prepared by a protocol using excess Ac2O
in pyridine at 70 °C.
Target compounds 4–5, 7–9, and 11–12 were evaluated for their
cytotoxicities and anti-HBV activities, namely the ability to inhibit
the secretion of HBsAg and HBV e antigen (HBeAg) in HBV-infected
Hep G2.2.15 cells using lamivudine (3TC) as a positive control.
Although some of the synthesized compounds were already
known or published to have other biological activities before,20–
30 14 of them exhibited inhibitory effect on the secretion of HBsAg
(SI > 1), and five compounds possessed inhibitory effect on the
secretion of HBeAg (Table 1). 4-Aryl-6-chloro-quinolin-2-ones
derivatives 4a–c showed lower cell cytotoxicities, and their IC50
<1
2.6
1.2
1.6
2.6
3TCg
a
All values are the mean of two independent experiments.
CC50: 50% cytotoxic concentration.
HBsAg: HBV surface antigen.
HBeAg: HBV e antigen.
IC: 50% effective concentration.
b
c
d
e
f
SI (selective index) = CC50/IC50
3TC: lamivudine, an antiviral agent used as positive control.
.
g
values on inhibition of HBsAg secretion were 0.485, 2.863, and
0.752 mM, respectively (SI = 2.6, >1.9, 8.0). In addition, compound

P. Cheng et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3787–3789
3789
4b showed inhibitory activity on HBeAg secretion with an SI value
Acknowledgments
of >2.4 (IC50 = 2.22 mM). Compounds 5a–c, derived from hydroxyl
ethyl introduction to C-3 of compounds 4, exhibited increased sup-
pressant properties of the secretion of HBsAg and HBeAg. Espe-
cially, compound 5c showed IC50 of 0.074 and 0.449 mM on
HBsAg and HBeAg secretion, respectively, which were 10 times
lower than its analog 4c and led to greatly increased SI values
(SIHBsAg = 23, SIHBeAg = 3.4). It was worth noting that compounds
5a–c all possessed relative low cell cytotoxicities and good SI
values on inhibitory effect of HBeAg secretion.
The authors are grateful to the staff of analytical group of the
State Key Laboratory of Phytochemistry and Plant Resources in
West China, Kunming Institute of Botany, Chinese Academy of Sci-
ences, for measurements of all spectra. This work was financially
supported by Xibu Zhiguang Joint-Scholarship, guided project of
Chinese Academy of Sciences (No. KSCX1-YW-R-24) and National
Natural Science Foundation of China (No. 30672522).
Compared with the quinolin-2-one derivatives, 1,4-benzodiaze-
pines 7–9 showed increased cell cytotoxicities with slightly chan-
ged activities of inhibition on HBsAg secretion and reduced
suppressant properties on the secretion of HBeAg. Thus, their
anti-HBV SI values were suboptimal and only compounds 8a–b
and 9a–b exhibited SIHBsAg values of 2.3, 2.2, 1.3, and 1.8. Com-
pounds 7–9 were all inactive to inhibit HBeAg secretion. Interest-
ingly, according to Helena and colleagues’ research, the 3-amino
substituted 1,4-benzodiazepines, analogs of compounds 8, were
identified as anti-hepatitis C infection agents.31
The introduction of amino group to C-3 of compounds 4 in-
creased both cytotoxicities and activities on inhibition of HBsAg
secretion (compound 11a vs 4a, 11b vs 4b, 11c vs 4c). The SIHBsAg
values of compounds 11a and 11b were 6.0 and 13.6, respectively
(IC50 = 0.067 and 0.056 mM). However, compounds 11 lost the
properties to inhibit HBeAg secretion compared with compounds
5. N-acetylation of compounds 11a–c gave derivatives 12a–c. Com-
pounds 12b (IC50 = 0.079 mM) and 12c (IC50 = 0.080 mM) were the
most active analogs to inhibit the secretion of HBeAg. However,
these two compounds were more toxic in Hep G2.2.15 cells, and
only compound 12b showed an SIHBeAg value of 2.6.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2008.05.065.
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In summary, a series of 4-aryl-6-chloro-quinolin-2-ones and
5-aryl-7-chloro-1,4-benzodiazepines were synthesized and
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