1,2,3-Selenadiazole thioacetanilides: Synthesis and anti-HIV activity evaluation

Article abstract of DOI:10.1016/j.bmc.2009.07.027

The development of new HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) offers the possibility of generating novel structures of increased potency. Based on the bioisosteric principle, novel series of 1,2,3-selenadiazole thioacetanilide deri

Full text of DOI:10.1016/j.bmc.2009.07.027

Bioorganic & Medicinal Chemistry 17 (2009) 6374–6379
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
1,2,3-Selenadiazole thioacetanilides: Synthesis and anti-HIV activity evaluation
a
b
b
Peng Zhan a, Xinyong Liu a, , Zengjun Fang , Christophe Pannecouque , Erik De Clercq
*
a Institute of Medicinal Chemistry, School of Pharmaceutical Sciences, Shandong University, No. 44 Wenhuaxi Road, Jinan 250012 , PR China
b Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
a r t i c l e i n f o
a b s t r a c t
Article history:
The development of new HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) offers the pos-
sibility of generating novel structures of increased potency. Based on the bioisosteric principle, novel ser-
ies of 1,2,3-selenadiazole thioacetanilide derivatives were designed, and synthesized using an original
synthetic route, structurally confirmed by spectral analysis, and evaluated for their anti-HIV activity in
MT-4 cells. The results showed that only compound 7f possessed potent activity against HIV-1 replication
Received 1 June 2009
Revised 12 July 2009
Accepted 14 July 2009
Available online 18 July 2009
(EC50 = 2.45
against HIV-2 replication.
lM) similar to the prototype series of sulfanyltriazoles. None of the compounds were active
Keywords:
HIV-1
AIDS
Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved.
NNRTIs
Selenadiazole
Anti-HIV-1 activity
1. Introduction
geometry for binding to RT.11 However, new research has also re-
vealed that there are differences in the electronic and conforma-
tional contribution of the five-membered heterocyclic moiety to
the binding of the inhibitors to the HIV-1 RT.13
Human immunodeficiency virus (HIV) infection affects close to
40 million individuals worldwide. Since 1981, when the first case
reports of individuals dying from a rare opportunistic infection
were reported, 20 million people have died from this epidemic.1
Although the introduction of highly active anti-retroviral therapy
(HAART) has dramatically decreased the morbidity and mortality
resulting from the infection with HIV, the AIDS prevalence remains
one of the world’s most serious health problems. In the research of
anti-HIV agents, non-nucleoside reverse transcriptase inhibitors
(NNRTIs) have gained a definitive and important place due to their
unique antiviral potency, high specificity and low toxicity. HIV-1
NNRTIs currently in clinical use have a low genetic barrier to resis-
tance or poor pharmacokinetic properties and, therefore, novel
NNRTIs that are active against virus strains resistant to current
NNRTIs and have good pharmacokinetic properties suitable for
once daily dosing are urgently expected.2–4
When continuing our work on the role of the five-membered
heterocycles in the binding of the inhibitors with the RT, and find-
ing potent HIV replication inhibitors, a novel series of 1,2,3-selen-
adiazole thioacetanilide (STA) derivatives was designed and
synthesized based on the general principle of bioisosterism in
medicinal chemistry.14,15 In the STA analogues, the 1,2,3-selen-
adiazole ring was substituted by the triazole/tetrazole or 1,2,3-
thiadiazole moiety in the corresponding lead compounds (Fig. 2);
the other fragments which were considered to be necessary for
conserving anti-HIV-1 activity, such as the ‘S–CH2–CO–NH’ linker
and the 2-substituted anilides,16 were left unchanged. Besides,
the anilide phenyl ring was also replaced by several substituted
X
X
Since the first report of sulfanyltriazole/tetrazoles (L1–L4,
Fig. 1) as potent HIV-1 NNRTIs, these derivatives have been of great
interest for the development of novel NNRTIs, because of their high
potency and low toxicity against HIV-1 wild-type and drug-resis-
tant strains.5–11 We recently reported that 1,2,3-thiadiazole deriv-
atives efficiently behave as a triazole/tetrazole surrogates (Fig. 2).12
Molecular modeling studies elucidated that the five-membered
heterocycle portion of these inhibitors could simply be acting as
a scaffold which orients the pharmacophores into the proper
N
N
N
N
H
H
N
N
N
S
S
N
R
N
O
O
Y
R
L3. R=2,4,6-TriMe, X=Cl
L1. R=CH3, X=Y=H,
IC50= 5 nM (WT)
EC50= 2.053µM(WT)
L2. R=H, X=Br, Y=CH3
EC50= 0.1 µM(WT)
L4. R-Ph=1-naphthalene, X=NO2
IC50 = 9.5 nM(WT)
IC50 = 766 nM(K103N/Y181C)
EC50= 1.3 µM(K103N/Y181C)
* Corresponding author. Tel: +86 531 88380270; fax: +86 531 88382731.
E-mail address: xinyongl@sdu.edu.cn (X. Liu).
Figure 1. Sulfanyltriazole and sulfanyltetrazole lead compounds.5,6,8–10
0968-0896/$ - see front matter Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2009.07.027

P. Zhan et al. / Bioorg. Med. Chem. 17 (2009) 6374–6379
6375
X
X
N
N
H
N
N
Bioisosterism based design
S
S
N
O
O
Y
R
R
X
X
N
S
N
Se
H
H
N
N
N
N
S
S
N
N
O
H
N
O
Y
Y
R
R
R'
N
Y
Original leads
Previously reported NNRTIs by us
Newly designed STA scaffold
Figure 2. Bioisosterism based design of 1,2,3-selenadiazole thioacetanilide (STA) scaffold.
heterocycles to further investigate the structure activity relation-
ship (SAR) in this region. Here, a new approach for the synthesis
of novel STAs (7a–d), as well as the evaluation of their inhibitory
effects on HIV replication in MT-4 cell culture, is reported.
2.2. Anti-HIV evaluation
Compounds 7a–r were evaluated for their in vitro anti-HIV-1
activity by using the IIIB strain for HIV-1 and the ROD strain for
the HIV-2, and monitored by the inhibition of the virus-induced
cytopathic effect in the human T-lymphocyte (MT-4) cells. The re-
sults are listed in Table 1. The compounds nevirapine (NVP), dela-
viridine (DLV), efavirenz (EFV) and zidovudine (azidothymidine,
AZT) were used as reference compounds for comparative purposes.
2. Results and discussion
2.1. Chemistry
Of the title compounds tested, compounds 7f (EC50 = 2.45
l
M), 7h
M), and 7l
M) were found to be the active compounds which
A novel synthetic route of 1,2,3-selenadiazole thioacetanilides
which requires the salt of 5-thiol-1,2,3-selenadiazole as one of
the key intermediates was described as shown in Scheme 1. In this
approach, the commercially available 1-(3,4-dichlorophenyl)etha-
none (1) was utilized as starting material. 2-bromo-1-(3,4-dichlo-
rophenyl)ethanone (2), synthesized by direct bromination of 1,
was reacted with methyl 3-mercaptopropanoate in EtOH at ambi-
ent temperature for several hours to obtain the methyl 3-(1-(3,4-
dichlorophenyl)ethanone)propanoate (3). The compound 4 was
synthesized from semicarbazide by reaction with the compound
3.17 Ring-closure reaction was carried out with selenium dioxide
according to described methods,18–24 producing the methyl 3-(4-
(3,4-dichlorophenyl)- 1,2,3-selenadiazol-5-ylthio)propanoate (5)
which was purified by flash column chromatography. Treatment
of compound 5 with sodium methoxide afforded the desired so-
dium salt of 1,2,3-selenadiazole-5-thiolate 6 as a result of the b-
elimination of the propyl ester group at C5-S group.25 The final
1,2,3-selenadiazole thioacetanilides 7 were synthesized by reac-
(EC50 = 5.42
(EC50 = 5.59
l
l
M), 7i (EC50 = 5.56 lM), 7k (EC50 = 6.65 l
inhibited HIV-1 replication in cell culture. It should be noted that
compound 7f (EC50 = 2.45 M) possesses similar HIV-1 inhibitory
activity compared with the lead compound L1 (EC50 = 2.053 M)
l
l
of the sulfanyltriazole series.11 However, the therapeutic indexes
of the 1,2,3-selenadiazole derivatives are generally low (<10) in
comparison with that of 1,2,3-thiadiazoles.12 This is probably due
to the fact that the introduction of a selenium atom caused a sub-
stantial increase in cytotoxicity. In addition, none of the synthe-
sized compounds was active against HIV-2 (ROD). On the basis of
the chemical structure and the fact that these compounds inhibit
HIV-1, but not HIV-2 replication, these molecules can be proposed
to act as HIV-1 NNRTIs.
3. Conclusion
tion of
6
with various 2-chloro-N-(substituted aromatic
Although the heterocyclic system of 1,2,3-selenadiazoles has
been known for a long time,26 1,2,3-selenadiazole thioacetanilides
(STAs) as bioisoster of 1,2,3-thiadiazole (triazole/tetrazole) thio-
acetanilides, which are novel classes of potential HIV-1 NNRTIs,
group)acetamides in high yield. The structures of all the synthe-
sized compounds were confirmed on the basis of spectral and ana-
lytical data.
O
O
O
S
O
Br
i
ii
iii
O
Cl
Cl
Cl
Cl
Cl
Cl
1
2
3
O
N
Se
N
Se
N Se
NNHCONH2
S
H
N
N
N
N
O
S
R
iv
SNa
S
O
v
vi
O
O
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
4
5
6
7
Scheme 1. Reagents and conditions: (i) Br2/AcOH; (ii) HSCH2CH2COOCH3, Na2CO3, EtOH; (iii) NH2NHCONH2ꢀHCl, AcONa, EtOH; (iv) SeO2/AcOH; (v) CH3ONa/CH3OH; (vi)
ClCH2CONHR, EtOH.

6376
P. Zhan et al. / Bioorg. Med. Chem. 17 (2009) 6374–6379
Table 1
Anti-HIV activities, cytotoxicities and selectivity indices of 2-(4-(3,4-dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)acetamide derivatives (7a–r)
N
Se
H
N
N
S
R
O
Cl
Cl
EC50
No.
R
(l
M)a
CC50
(l
M)b
SIc
HIV-1
IIIB
HIV-2
ROD
HIV-1
IIIB
HIV-2
ROD
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
7q
2-Fluorophenyl
2-Chlorophenyl
>26.95
>23.41
>24.80
>23.62
P8.71
2.45 1.08
P6.84
5.42 2.41
5.56 1.92
P6.07
6.65 1.33
5.59 1.05
>12.84
>7.00
>31.36
>8.68
>10.23
>22.00
0.208
0.32
0.0044
0.0151
>26.95
>23.41
>24.80
>23.62
>22.94
>18.95
>26.59
>26.34
>22.31
>19.04
>13.32
>16.79
>12.84
>7.00
26.95 3.66
23.41 4.73
24.80 2.19
23.62 1.95
22.94 3.43
18.95 4.02
26.59 3.20
26.34 7.85
22.31 3.65
19.04 4.06
13.32 4.33
16.79 1.78
12.84 5.58
7.00 3.63
31.36 0.14
8.68 6.49
10.23 7.47
22.00 3.96
>15.02
<1
<1
<1
<1
63
8
64
5
4
63
2
3
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
2-Chloropyridin-3-yl
2-Bromophenyl
2-Bromo-4-methylphenyl
4-Acetyl-2-bromophenyl
2-Nitrophenyl
4-Methyl-2-nitrophenyl
o-Tolyl
Phenyl
p-Tolyl
4-Chlorophenyl
2,3-Dimethylphenyl
2,6-Dimethylphenyl
Pyridin-2-yl
Thiazol-2-yl
5-Methylbenzo[d]thiazol-2-yl
3-Methyl acetate-thiophen-2-yl
>31.36
>8.68
>10.23
>22.00
7r
NVPd
DLVd
EFVd
AZTd
>72
>12
>1434
>6192
>3.827
>6.336
>93.55
Bold entries stand for active compounds.
a
EC50: concentration of compound required to achieve 50% protection of MT-4 cell against HIV-1-induced cytotoxicity, as determined by the MTT method.
CC50: concentration required to reduce the viability of mock-infected cells by 50%, as determined by the MTT method.
SI: selectivity index (CC50/EC50). The SI values: ꢁ1 stand for P1 or <1.
b
c
d
The antiviral properties of these compounds were previously described.12
have not been investigated so far. In this article the target com-
chromatography was performed on column packed with Silica
Gel 60 (230–400 mesh). Solvents were reagent grade and, when
necessary, were purified and dried by standard methods. Concen-
tration of the reaction solutions involved the use of rotary evapo-
rator at reduced pressure.
pounds was prepared by a creative route, in which, key intermedi-
ate of the sodium salt of 5-thiol-1,2,3-selenadiazole was described
in detail. The designed and synthesized compounds were evalu-
ated for their inhibition of HIV-induced (HIV-1 IIIB, HIV-2 ROD)
cytopathogenicity in MT-4 cell culture. The results showed that
some compounds, such as 7f (EC50 = 2.45 lM), possess similar
4.2. General procedure for the synthesis of sodium 4-(3,4-
dichlorophenyl)-1,2,3- selenadiazole-5-thiolate (6)
HIV-1 inhibitory activity compared with that of sulfanyltriazole
series, but most of these derivatives exhibited decreased anti-
HIV-1 specificity due to a significantly increased cytotoxicity, and
none of them were active against HIV-2 replication. Although the
pharmacological results are not very encouraging, this study pro-
vides useful information to further design new anti-HIV agents.
To a solution of 1-(3,4-dichlorophenyl)ethanone (1, 18.9 g,
0.1 mol) in glacial acetic acid (80 ml) was added at room tempera-
ture a solution of Br2 (16.0 g, 0.1 mol) in glacial acetic acid (30 ml)
over a period of 30 min. The reaction mixture was stirred at room
temperature for 6 h (monitored by TLC), and then the mixture was
poured into ice water (100 g). The separated solid was filtrated,
washed with cold water and dried to give crude 2-bromo-1-(3,4-
dichlorophenyl)ethanone (2) as white solid, which was used with-
out any further purification.
4. Experimental
4.1. Chemistry
All melting points were determined on a micromelting point
apparatus and are uncorrected. Infrared spectra (IR) were recorded
with a Nexus 470FT-IR Spectrometer. 1H NMR spectra were ob-
tained on a Brucker Avance-600 NMR-spectrometer in the indi-
cated solvents. Chemical shifts are expressed in d units and TMS
as internal reference. Mass spectra were taken on a LC Autosampler
Device: Standard G1313A instrument. TLC was performed on Silica
Gel GF254 for TLC (Merck) and spots were visualized by iodine va-
pors or by irradiation with UV light (254 nm). Flash column
2-Bromo-1-(3,4-dichlorophenyl)ethanone (2, 0.1 mol) was
added to a mixture of methyl 3-mercaptopropanoate (11.4 ml,
0.1 mol) and Na2CO3 (5.3 g, 0.05 mol) in 100 ml EtOH. The reaction
mixture was stirred at room temperature for 12 h. The solvent was
evaporated under reduced pressure. The residue was then diluted
with CH2Cl2 (100 ml), washed successively with aqueous 0.1 M
HCl solution, aqueous saturated NaHCO3, water and brine. The or-
ganic layer was dried (Na2SO4), filtered and concentrated under re-
duced pressure to afford crude product 3 as a light yellow oil.

P. Zhan et al. / Bioorg. Med. Chem. 17 (2009) 6374–6379
6377
A mixture of semicarbazide hydrochloride (12.2 g, 0.12 mol)
4.3.2. N-(2-Chlorophenyl)-2-(4-(3,4-dichlorophenyl)-1,2,3-
and sodium acetate (8.2 g, 0.1 mol) was dissolved in anhydrous
ethanol (50 ml). The mixture was heated for 60 min under reflux,
and then filtered while hot to remove precipitated sodium chlo-
selenadiazol-5-ylthio)acetamide (7b)
White solid, yield: 75.2%. Mp: 119–121 °C. 1H NMR (DMSO-d6,
ppm) d: 9.84 (s, 1H, NH), 8.13 (d, 1H, J1 = 1.8 Hz, PhH), 7.86 (dd,
1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH), 7.84 (d, 1H, J2 = 8.4 Hz, PhH),
7.66 (d, 1H, J1 = 7.8 Hz, Ph0H), 7.50 (d, 1H, J1 = 7.8 Hz, Ph0H), 7.32
(t, 1H, Ph0H), 7.20 (t, 1H, Ph0H), 4.09 (s, 2H, S–CH2). IR (KBr,
ride. The filtrate was then mixed with compound
3 (30 g,
0.1 mol), and the resulting mixtures were heated to reflux, a few
drops of concentrated hydrochloric acid were added. Heating un-
der reflux with continuous removal of the generated water was
continued overnight. Finally, the reaction solution was cooled
and filtered. The obtained solid was washed successively with
water and diethyl ether and dried to give compound 4 as white so-
lid, yield: 78.5%, mp: 209–211 °C.
cmꢂ1): 3261 (
752
m
NH), 1642 (
mC@O), 1590, 1530, 1441 (mN@N), 1311,
(
mC–Se). MS (ESI): m/z 478.0 (M+1), 479.9 (M+3).
C16H10Cl3N3OSSe (476.88).
4.3.3. N-(2-Chloropyridin-3-yl)-2-(4-(3,4-dichlorophenyl)-1,2,3-
selenadiazol-5-ylthio)acetamide (7c)
To
a magnetically stirred solution of hydrazone 4 (3.6 g,
White crystal, yield: 84.7%. Mp: 129–131 °C. 1H NMR (DMSO-d6,
ppm) d: 10.00 (s, 1H, NH), 8.20 (dd, 1H, J = 1.2 Hz, J = 2.1 Hz, pyri-
dine-H), 8.13 (dd, 1H, J = 1.8 Hz, J = 3.0 Hz, pyridine-H), 8.12 (d,
1H, J1 = 1.8 Hz, PhH), 7.88 (dd, 1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH),
7.83 (d, 1H, J2 = 8.4 Hz, PhH), 7.42 (dd, 1H, J = 4.8 Hz, J = 8.4 Hz, pyr-
10 mmol) in acetic acid (50 ml) was added selenium dioxide
(1.0 equiv) at room temperature. The reaction mixture was al-
lowed to stand at 65–70 °C until the disappearance of hydrazone
4 (about 8 h, monitored by TLC). The selenium deposited on the
cooling was removed by filtration, and the filtrate was poured over
ice water and extracted with dichloromethane (3 ꢁ 50 ml). The
combined organic layers were washed with saturated sodium
hydrogen carbonate solution and dried using anhydrous sodium
sulfate. The solvent was removed under reduced pressure, and
the crude product was purified by column chromatography using
silica gel with 1:4 acetic ether/petroleum ether as eluent to give
methyl 3-(4-(3,4-dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)pro-
panoate (5), which was recrystallised from ethanol as red solid.
Yield: 42.7%. Mp: 105–107 °C. 1H NMR (DMSO-d6, ppm) d: 8.05
(d, 1H, J1 = 2.4 Hz, PhH), 7.82 (m, 2H, PhH), 3.62 (s, 3H, OCH3),
3.41 (t, 2H, S–CH2), 2.83 (t, 2H, CH2). IR (KBr, cmꢂ1): 2944, 2906,
idine-H), 4.09 (s, 2H, S–CH2). IR (KBr, cmꢂ1): 3283 (
C@O), 1526, 1431 ( N@N), 1394, 752 (
m
NH), 1674
(m
m
mC–Se). MS (ESI): m/z 477.1
(M+), 479.1 (M+2). C15H9Cl3N4OSSe (477.87).
4.3.4. N-(2-Bromophenyl)-2-(4-(3,4-dichlorophenyl)-1,2,3-
selenadiazol-5-ylthio)acetamide (7d)
White solid, yield: 74.5%. Mp: 135–137 °C. 1H NMR (DMSO-d6,
ppm) d: 9.80 (s, 1H, NH), 8.14 (d, 1H, J1 = 1.8 Hz, PhH), 7.88 (dd,
1H, J1 = 1.8 Hz, J2 = 7.8 Hz, PhH), 7.85 (d, 1H, J2 = 7.8 Hz, PhH),
7.65 (dd, 1H, Ph0H), 7.55 (dd, 1H, Ph0H), 7.36 (dt, 1H, Ph0H), 7.14
(dt, 1H, Ph0H), 4.10 (s, 2H, S–CH2). IR (KBr, cmꢂ1): 3231 (
m
NH),
C–Se). MS (ESI): m/z 521.9
(M+1), 523.9 (M+3). C16H10BrCl2N3OSSe (520.83).
2840, 1739 (mC@O), 1485, 1432 (mN@N), 1244, 1174, 798, 667. MS
(ESI): m/z 397.1 (M+1). C12H10Cl2N2O2SSe (395.9).
1647 (mC@O), 1530, 1436 (mN@N), 750 (m
A solution of sodium methoxide (0.54 g, 0.01 mol) in 15 ml of
methanol was added to a solution of methyl 3-(4-(3,4-dichloro-
phenyl)-1,2,3-selenadiazol-5-ylthio)propanoate (5) (4.4 g, 0.01
mol) in 100 ml of methanol. After about 1 h, the reaction solution
was evaporated in vacuo to about 10 ml. Fifty milliliters of dry
methylene chloride was added, causing precipitation of a red solid.
This solid was collected, washed with methylene chloride, giving
the desired product sodium 4-(3,4-dichlorophenyl)-1,2,3-selen-
adiazole-5-thiolate (6), yield: 87.8%. Mp: 151–155 °C.
4.3.5. N-(2-Bromo-4-methylphenyl)-2-(4-(3,4-dichlorophenyl)-
1,2,3-selenadiazol-5-ylthio)acetamide (7e)
Light yellow solid, yield: 84.5%. Mp: 142–144 °C. 1H NMR
(DMSO-d6, ppm) d: 9.73 (s, 1H, NH), 8.13 (d, 1H, J1 = 1.8 Hz, PhH),
7.55 (dd, 1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH), 7.85 (d, 1H, J2 = 8.4 Hz,
PhH), 7.48 (s, 1H, Ph0H), 7.40 (d, 1H, J = 9.0 Hz, Ph0H), 7.16 (dd,
1H, Ph0H), 4.07 (s, 2H, S–CH2), 2.28 (s, 3H, CH3). IR (KBr, cmꢂ1):
3231 (mNH), 3026, 2982, 2918, 1647 (mC@O), 1530, 1488 (mN@N),
746 ( C–Se). MS (ESI): m/z 535.9 (M+1), 538.0 (M+3). C17H12BrCl2-
N3OSSe (534.84).
m
4.3. General procedure for the synthesis of 2-(4-(3,4-
dichlorophenyl)-1,2,3-selenadiazol-5-ylthio) acetamide (7a–r)
4.3.6. N-(4-Acetyl-2-bromophenyl)-2-(4-(3,4-dichlorophenyl)-
1,2,3-selenadiazol-5-ylthio)acetamide (7f)
To the solution of sodium 4-(3,4-dichlorophenyl)-1,2,3-
selenadiazole-5-thiolate (6) (1.05 mmol, 0.35 g) in ethanol (30 ml)
was added 2-chloro-N-(substituted aromatic group)acetamides
(1.0 mmol). The reaction mixture was stirred at room temperature
overnight. Upon completion of the reaction, the solvent was evapo-
rated, leaving a residue which was treated with methylene chloride
(30 ml) and washed with water (3 ꢁ 30 ml). The organic layer was
dried over anhydrous sodium sulfate, filtered off, and then evapo-
rated in vacuo. The obtained residue was purified by recrystalliza-
tion using ethanol to yield the title compounds (7a–r).
White solid, yield: 85.7%. Mp: 165–167 °C. 1H NMR (DMSO-d6,
ppm) d: 9.82 (s, 1H, NH), 8.15 (d, 1H, J3 = 1.8 Hz, Ph0H), 8.12 (d,
1H, J1 = 1.8 Hz, PhH), 7.92 (dd, 1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH),
7.86 (dd, 1H, J3 = 1.8 Hz, J4 = 9.0 Hz, Ph0H), 7.84 (d, 1H, J4 = 9.0 Hz,
Ph0H), 7.82 (d, 1H, J2 = 8.4 Hz, PhH), 4.10 (s, 2H, S–CH2), 2.50 (s,
3H, CH3). IR (KBr, cmꢂ1): 3223 (
1520, 1388 ( N@N), 1261, 741 (
m
NH), 1680(
mC@O), 1664 (mC@O),
m
mC–Se). MS (ESI): m/z 562.1 (M+),
564.1 (M+2). C18H12BrCl2N3O2SSe (562.84).
4.3.7. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-N-
(2-nitrophenyl)acetamide (7g)
4.3.1. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-N-
(2-fluorophenyl)acetamide (7a)
Light yellow solid, yield: 84.0%. Mp: 129–131 °C. 1H NMR
(DMSO-d6, ppm) d: 10.60 (s, 1H, NH), 8.12 (d, 1H, J1 = 1.8 Hz,
PhH), 7.98 (d, 1H, J = 7.8 Hz, Ph0H), 7.86 (dd, 1H, J1 = 1.8 Hz,
J2 = 9.0 Hz, PhH), 7.83 (d, 1H, J2 = 9.0 Hz, PhH), 7.71 (t, 1H, Ph0H),
7.62 (d, 1H, J = 8.4 Hz, Ph0H), 7.40 (t, 1H, Ph0H), 4.07 (s, 2H, S–
White lamellar crystal, yield: 80.3%. Mp: 141–143 °C. 1H NMR
(DMSO-d6, ppm) d: 10.08 (s, 1H, NH), 8.14 (d, 1H, J1 = 1.8 Hz,
PhH), 7.88 (dd, 1H, J1 = 1.8 Hz, J2 = 4.2 Hz, PhH), 7.86 (m, 1H, Ph0H),
7.83 (d, 1H, J2 = 4.2 Hz, PhH), 7.26 (m, 1H, Ph0H), 7.15 (m, 2H, Ph0H),
4.18 (s, 2H, S–CH2). IR (KBr, cmꢂ1): 3275 (
1542, 1487, 1457 ( N@N), 755 (
464.1 (M+3). C16H10Cl2FN3OSSe (460.91).
mNH), 1663 (mC@O), 1647,
CH2). IR (KBr, cmꢂ1): 3336 (
N@N), 1340 ( sNO2), 1275, 741 (
491.0 (M+3). C16H10Cl2N4O3SSe (487.9).
m
NH), 1696 (
mC@O), 1500 (masNO2), 1435
m
mC–Se). MS (ESI): m/z 462.0 (M+1),
(m
m
m
C–Se). MS (ESI): m/z 489.1 (M+1),

6378
P. Zhan et al. / Bioorg. Med. Chem. 17 (2009) 6374–6379
4.3.8. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-N-
(4-methyl-2-nitrophenyl)acetamide (7h)
1434 (mN@N), 1215, 769, 740 (mC–Se). MS (ESI): m/z 472.1 (M+1),
474.0 (M+3). C18H15Cl2N3OSSe (470.95).
Yellow crystal, yield: 71.6%. Mp: 138–140 °C. 1H NMR (DMSO-
d6, ppm) d: 10.50 (s, 1H, NH), 8.11 (d, 1H, J1 = 1.8 Hz, PhH), 7.86
(dd, 1H, J1 = 1.8 Hz, J2 = 7.8 Hz, PhH), 7.83 (d, 1H, J2 = 7.8 Hz,
PhH), 7.80 (s, H, Ph0H), 7.51 (m, 2H, Ph0H), 4.05 (s, 2H, S–CH2),
4.3.15. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-
N-(pyridin-2-yl)acetamide (7o)
White solid, yield: 85.4%. Mp: 139–141 °C. 1H NMR (DMSO-d6,
ppm) d: 10.74 (s, 1H, NH), 8.31 (m, 1H, pyridine-H), 8.12 (d,1H,
J1 = 1.8 Hz, PhH), 7.94 (d, 1H, J = 8.4 Hz, pyridine-H), 7.86 (dd, 1H,
J1 = 1.8 Hz, J2 = 7.8 Hz, PhH), 7.80 (d, 1H, J2 = 7.8 Hz, PhH), 7.76
(m, 1H, pyridine-H), 7.12 (dd, 1H, J = 4.8 Hz, J = 9.6 Hz, pyridine-
2.50 (s, 3H, CH3). IR (KBr, cmꢂ1): 3352 (
mas NO2), 1453 ( N@N), 1350 (ms NO2), 1292, 755 (m
m
NH), 1689 (
mC@O), 1514
(
m
C–Se). MS (ESI):
m/z 501.3 (M+), 503.2 (M+2). C17H12Cl2N4O3SSe (501.92).
4.3.9. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-N-
o-tolylacetamide (7i)
H), 4.02 (s, 2H, S–CH2). IR (KBr, cmꢂ1): 3248 (
1577, 1552, 1436 ( N@N), 1314, 777, 752 (
m
NH), 1655 (
mC@O),
m
mC–Se). MS (ESI): m/z
White powder, yield: 84.7%. Mp: 165–167 °C. 1H NMR (DMSO-
d6, ppm) d: 9.63 (s, 1H, NH), 8.14 (d, 1H, PhH), 7.87 (m, 2H, PhH),
7.35 (d, 1H, J = 8.4 Hz, Ph0H), 7.20 (d, 1H, J = 7.8 Hz, Ph0H), 7.16 (t,
1H, Ph0H), 7.10 (t, 1H, Ph0H), 4.11 (s, 2H, S–CH2), 2.15 (s, 3H,
443.2 (M+), 445.2 (M+2). C15H10Cl2N4OSSe (443.91).
4.3.16. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-
N-(thiazol-2-yl)acetamide (7p)
CH3). IR (KBr, cmꢂ1): 3266 (
1459 ( N@N), 756 (
m
NH), 3049, 2986, 1638 (
m
C@O), 1538,
Yellow solid, yield: 64.7%. Mp: 191–193 °C. 1H NMR (DMSO-d6,
ppm) d: 12.3 (s, 1H, NH), 8.11 (d, 1H, J1 = 1.8 Hz, PhH), 7.85 (dd, 1H,
J1 = 1.8 Hz, J2 = 8.4 Hz, PhH), 7.79 (d, 1H, J2 = 8.4 Hz, PhH), 7.47 (d,
1H, J = 3.6 Hz, thiazole-H), 7.25 (d, 1H, J = 3.6 Hz, thiazole-H), 4.00
m
mC–Se). MS (ESI): m/z 458.1 (M+1), 460.1 (M+3).
C17H13Cl2N3OSSe (456.93).
4.3.10. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-
N-phenylacetamide (7j)
(s, 2H, S–CH2). IR (KBr, cmꢂ1): 3436 (
1434 ( N@N), 1320, 1301, 1164, 1153, 741 (
m
NH), 1678 (
mC@O), 1554,
m
mC–Se). MS (ESI): m/z
Light yellow crystal, yield: 69.8%. Mp: 138–140 °C. 1H NMR
(DMSO-d6, ppm) d: 10.29 (s, 1H, NH), 8.13 (d, 1H, J1 = 1.8 Hz,
PhH), 7.87 (dd, 1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH), 7.84 (d, 1H,
J2 = 8.4 Hz, PhH), 7.50 (d, 2H, J = 4.8 Hz, Ph0H), 7.31 (dt, 2H, Ph0H),
7.07 (dt, 1H, Ph0H), 4.06 (s, 2H, S–CH2). IR (KBr, cmꢂ1): 3269
423.0 (Mꢂ28), 451.1 (M+), 453.0 (M+3). C13H8Cl2N4OS2Se (449.87).
4.3.17. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-
N-(5-methylbenzo[d]thiazol-2-yl)acetamide (7q)
White crystal, yield: 57.8%. Mp: 162–164 °C. 1H NMR (600 MHz,
DMSO-d6, ppm) d: 12.64 (s, 1H, NH), 8.13 (d, 1H, J1 = 1.8 Hz, PhH),
7.89 (dd, 1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH), 7.85 (d, 1H, J2 = 8.4 Hz,
PhH), 7.76 (s, 1H, Ph0H), 7.63 (d, 1H, J = 8.4 Hz, Ph0H), 7.24 (d, 1H,
J = 8.4 Hz, Ph0H), 4.31 (s, 2H, S–CH2), 2.49 (s, 3H, CH3). IR (KBr,
(mNH), 1658 (mC@O), 1541, 1441 (mN@N), 741(mC–Se). MS (ESI): m/z
444.2 (M+1), 446.1 (M+3). C16H11Cl2N3OSSe (442.92).
4.3.11. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-
N-p-tolylacetamide (7k)
cmꢂ1): 3414 (
1430 ( N@N), 736 (
C18H12Cl2N4OS2Se (513.9).
m
NH), 2969, 2921, 2853, 1684 (
mC@O), 1607, 1552,
White solid, yield: 87.2%. Mp: 144–146 °C. 1H NMR (DMSO-d6,
ppm) d: 10.21 (s, 1H, NH), 8.12 (d, 1H, J1 = 1.8 Hz, PhH), 7.86 (dd,
1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH), 7.83 (d, 1H, J2 = 8.4 Hz, PhH),
7.38 (d, 2H, J = 8.4 Hz, Ph0H), 7.12 (d, 2H, J = 8.4 Hz, Ph0H), 4.05 (s,
m
mC–Se). MS (ESI): m/z 513.2 (M+), 515.2 (M+2).
4.3.18. Methyl 2-(2-(4-(3,4-dichlorophenyl)-1,2,3-selenadiazol-
5-ylthio)acetamido)thiophene -3-carboxylate (7r)
2H, S–CH2), 2.25 (s, 3H, CH3). IR (KBr, cmꢂ1): 3273 (
mNH), 3035,
2979, 2919, 1639 (
m
C@O), 1537, 1431 (
m
N@N), 816, 737 ( C–Se). MS
m
White solid, yield: 75.6%. Mp: 122–124 °C. 1H NMR (DMSO-d6,
ppm) d: 10.28 (s, 1H, NH), 8.10 (d, 1H, J1 = 1.8 Hz, PhH), 7.86 (d,
1H, J = 5.4 Hz, thiophene-H), 7.82 (dd, 1H, J1 = 1.8 Hz, J2 = 7.8 Hz,
PhH), 7.78 (d, 1H, J = 5.4 Hz, thiophene-H), 7.75 (d, 1H,
J2 = 7.8 Hz, PhH), 4.07 (s, 2H, S–CH2), 3.83 (s, 3H, OCH3). IR (KBr,
(ESI): m/z 458.1 (M+1), 460.1 (M+3). C17H13Cl2N3OSSe (456.93).
4.3.12. N-(4-Chlorophenyl)-2-(4-(3,4-dichlorophenyl)-1,2,3-
selenadiazol-5-ylthio)acetamide (7l)
Yellow solid, yield: 81.9%. Mp: 142–144 °C. 1H NMR (DMSO-d6,
ppm) d: 10.41 (s, 1H, NH), 8.12 (d, 1H, J1 = 1.8 Hz, PhH), 7.86 (dd,
1H, J1 = 1.8 Hz, J2 = 8.4 Hz, PhH), 7.82 (d, 1H, J2 = 8.4 Hz, PhH),
7.52 (d, 2H, J = 9 Hz, Ph0H), 7.36 (d, 2H, J = 9 Hz, Ph0H), 4.02 (s,
cmꢂ1): 3288 (
779, 742
m
NH), 1668 (
mC@O), 1574 (mC@O), 1447 (mN@N), 1287,
(
mC–Se). MS (ESI): m/z 508.0 (M+1), 510.0 (M+3).
C16H11Cl2N3O3S2Se (506.88).
2H, S–CH2). IR (KBr, cmꢂ1): 3248 (
N@N), 751(
m
NH), 1665 (
m
C@O), 1545, 1490
4.4. Anti-HIV activity assays
(m
mC–Se). MS (ESI): m/z 478.0 (M+1), 479.9 (M+3).
C16H10Cl3N3OSSe (476.88).
Evaluation of the antiviral activity of the compounds against
HIV-1 strain IIIB and HIV-2 strain (ROD) in MT-4 cells was per-
formed using the MTT assay as previously described.27,28 Stock
solutions (10 ꢁ final concentration) of test compounds were
4.3.13. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-
N-(2,3-dimethylphenyl)acetamide (7m)
White solid, yield: 74.7%. Mp: 161–163 °C. 1H NMR (DMSO-d6,
ppm) d: 9.70 (s, 1H, NH), 8.14 (s, 1H, PhH), 7.87 (d, 1H, PhH),
7.86 (s, 1H, PhH), 7.10 (d, 1H, J = 7.8 Hz, Ph0H), 7.05 (d, 1H,
J = 7.8 Hz, Ph0H), 7.02 (t, 1H, Ph0H), 4.10 (s, 2H, S–CH2), 2.23 (s,
added in 25 ll volumes to two series of triplicate wells so as
to allow simultaneous evaluation of their effects on mock-
and HIV-infected cells at the beginning of each experiment. Se-
rial fivefold dilution of test compounds were made directly in
flat-bottomed 96-well microtiter trays using a Biomek 3000 ro-
bot (Beckman instruments, Fullerton, CA). Untreated control
HIV- and mock-infected cell samples were included for each
sample.
3H, CH3), 2.02 (s, 3H, CH3). IR (KBr, cmꢂ1): 3250 (
m
NH), 3053,
2983, 2918, 1645 (mC@O), 1540, 1431 (mN@N), 750 (mC–Se). MS (ESI):
m/z 472.1 (M+1), 474.0 (M+3). C18H15Cl2N3OSSe (470.95).
4.3.14. 2-(4-(3,4-Dichlorophenyl)-1,2,3-selenadiazol-5-ylthio)-
N-(2,6-dimethylphenyl)acetamide (7n)
HIV-1(IIIB)29 or HIV-2 (ROD)30 stock (50
lL) at 100–300 CCID50
(cell culture infectious dose) or culture medium was added to
either the infected or mock-infected wells of the microtiter tray.
Mock-infected cells were used to evaluate the effect of test com-
pound on uninfected cells in order to assess the cytotoxicity of
the test compound. Exponentially growing MT-4 cells31 were
White solid, yield: 80.2%. Mp: 136–138 °C. 1H NMR (DMSO-d6,
ppm) d: 9.63 (s, 1H, NH), 8.14 (s, 1H, PhH), 7.88 (m, 2H, PhH),
7.06 (m, 3H, Ph0H), 4.13 (s, 2H, S–CH2), 2.07 (s, 6H, CH3). IR (KBr,
cmꢂ1): 3234 (
mNH), 3023, 2979, 2922, 1648 (mC@O), 1530, 1471,

P. Zhan et al. / Bioorg. Med. Chem. 17 (2009) 6374–6379
6379
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Research work in the authors’ laboratory has been supported by
the National Natural Science Foundation of China (NSFC Nos.
30371686, 30772629, 30873133), Key Project of The International
Cooperation, Ministry of Science and Technology of China
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