1,2,3-thiadiazole thioacetanilides. Part 2: Synthesis and biological evaluation of a new series of 2-{[4-(3,4-dichlorophenyl)-1,2,3-thiadiazol-5-yl] sulfanyl}acetanilides as HIV-1 inhibitors

Article abstract of DOI:10.1002/cbdv.200900197

As part of our studies to discover new HIV-1 reverse transcriptase inhibitors, a series of 3,4-dichlorophenyl substituted 1,2,3-thiadiazole thioacetanilide (TTA=[(1,2,3-thiadiazole-5-yl)sulfanyl]-acetanilide) derivatives were synthesized, and in vitro ant

Full text of DOI:10.1002/cbdv.200900197

CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
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1,2,3-Thiadiazole Thioacetanilides
Part 21)
Synthesis and Biological Evaluation of a New Series of 2-{[4-(3,4-Dichlorophenyl)-
1,2,3-thiadiazol-5-yl]sulfanyl}acetanilides as HIV-1 Inhibitors
by Peng Zhana), Xin-Yong Liu*a), Zhen-Yu Lia), Zeng-Jun Fanga), Christophe Pannecouqueb),
and Erik De Clercqb)
a) Institute of Medicinal Chemistry, School of Pharmaceutical Sciences, Shandong University,
No. 44 Wenhuaxi Road, Jinan 250012, P. R. China
(phone: þ8653188380270; fax: þ8653188382731; e-mail: xinyongl@sdu.edu.cn)
b) Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven
As part of our studies to discover new HIV-1 reverse transcriptase inhibitors, a series of 3,4-
dichlorophenyl substituted 1,2,3-thiadiazole thioacetanilide (TTA¼[(1,2,3-thiadiazole-5-yl)sulfanyl]-
acetanilide) derivatives were synthesized, and in vitro anti-HIV activity was evaluated. The results
revealed that nearly half of the compounds show moderate-to-good inhibitory potency against HIV-1. In
particular, compound 7f is highly potent, with an EC50 value of 0.95ꢀ0.33 mm. The preliminary structure–
activity relationship among the newly synthesized congeners is discussed.
Introduction. – Among the drugs approved by the U.S. Food and Drug Admin-
istration (FDA) for the treatment of AIDS, non-nucleoside reverse transcriptase
inhibitors (NNRTIs) are a mainstay of therapy for treating human immunodeficiency
type 1 virus (HIV-1)-infected patients. However, the effectiveness of NNRTIs can be
hampered by the development of drug resistance and severe side-effect in the long-
term administration. As a consequence, there is a great need for additional drugs to
further optimize and improve the efficacy of long-term HIV treatment [2–6].
Among the structurally diverse HIV-1 NNRTIs, substituted azole-thioacetanilide
scaffolds have been of much interest for the development of novel NNRTIs because of
their high potency and low toxicity against HIV-1 wild-type and resistant strains [7–
13]. In previous articles, we described our early efforts toward the design and synthesis
of 1,2,3-thiadiazole thioacetanilide (TTA¼[(1,2,3-thiadiazole-5-yl)sulfanyl]acetani-
lide) derivatives as potent HIV-1 inhibitors. Especially, some 2,4-dichlorophenyl
substituted TTAs proved to be highly effective in inhibiting HIV-1 replication at
nanomolar or low micromolar concentrations [1][14].
It is worth noting that halogenated phenyl rings were regarded as ubiquitous
moieties in numerous NNRTI molecules, and the substitution pattern of halogens has a
significant influence on the overall protein-ligand binding affinity and anti-HIVactivity
[15][16].
1
)
For Part 1, see [1].
ꢀ 2010 Verlag Helvetica Chimica Acta AG, Zꢁrich

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CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
Fig. 1. Design of a new series of 1,2,3-thiadiazole thioacetanilides
In view of this factor, and in continuation of our work, we report here the synthesis
and anti-HIV activity evaluation of a new series of TTA derivatives in which the 2,4-
dichlorophenyl residue linked with the 1,2,3-thiadiazole moiety was replaced by a 3,4-
dichlorophenyl substituent (Fig. 1), with the goal of further exploration of the
structure–activity relationship of this region and the discovery of new more potent
HIV-1 inhibitors.
Results and Discussion. – 1. Chemistry. A modified synthetic route of 1,2,3-
thiadiazole thioacetanilides which requires the salt of 1,2,3-thiadiazole-5-thiol as one of
the key intermediates was described as shown in the Scheme. In this approach, the
commercially available 1-(3,4-dichlorophenyl)ethanone (1) was utilized as starting
material. 2-Bromo-1-(3,4-dichlorophenyl)ethanone (2), synthesized by direct bromi-
nation of 1, was reacted with methyl 3-sulfanylpropanoate in EtOH at ambient
temperature for several hours to obtain the methyl 3-{[2-(3,4-dichlorophenyl)-2-
oxoethyl]sulfanyl}propanoate (3). Compound 4 was prepared by the reaction of 3 with
semicarbazide. Hurd and Mori-type ring-closure reaction of 4 with SOCl2 was carried
out according to the similar methods reported [17–19], to give methyl 3-{[4-(3,4-
dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}propanoate (5), which was purified by
flash chromatography. Treatment of 5 with MeONa afforded the desired sodium salt of
1,2,3-thiadiazole-5-thiolate 6 as a result of the b-elimination of the propanoate group at
the C(5)ꢁS group [20]. The target compounds, i.e., 1,2,3-thiadiazole thioacetanilides 7,
were obtained by the reaction of 6 with various 2-chloro-N-(substituted aryl)aceta-
mides in high yield. All synthesized compounds were characterized by their IR, MS,
and NMR data, which confirmed the proposed structures.
It should be pointed out that we previously reported a synthetic method for TTAs
[1] which requires the [(4-aryl-1,2,3-thiadiazol-5-yl)sulfanyl]acetic acid, produced by
hydrolysis reaction, as the key intermediate. In the last step, the desired thioacetani-
lides were obtained by finicky acylation reaction of the [(4-aryl-1,2,3-thiadiazol-5-
yl)sulfanyl]acetic acid with various substituted anilines in the presence of PCl5.
However, this route did not give satisfactory results due to the low overall yield and
complicated procedure in these two reaction steps. Fortunately, the modified method
disclosed herein not only improved the overall yield, but also provides possibilities of
further development of TTA derivatives with mild reaction conditions and simple
operations.

CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
1719
Scheme
i) Br2/AcOH. ii) HSCH2CH2COOMe, Na2CO3, EtOH. iii) NH2NHCONH2 ·HCl, AcONa, EtOH. iv)
SOCl2. v) MeONa/MeOH. vi) ClCH2CONHR, EtOH.
2. Anti-HIV Evaluation. All newly synthesized compounds, 7a–7r, were evaluated
on MT-4 cells infected with HIV-1 (IIIB) and HIV-2 (ROD) for anti-HIV activity and
cytotoxicity, in comparison with nevirapine (NVP), delaviridine (DLV), efavirenz
(EFV), and zidovudine (azidothymidine, AZT) used as reference drugs for compa-
rative purposes, and the results, expressed as CC50, EC50, and SI, are summarized in the
Table.
As can be seen from the Table, seven of the newly synthesized 3,4-dichlorophenyl-
containing TTA analogues were active against HIV-1 replication with a wide range of
EC50 values from 0.95ꢀ0.33 to 12.8ꢀ2.04 mm; compound 7f was most promising in this
series, with an EC50 value of 0.95ꢀ0.33 mm. However, these analogues showed less
potency compared with the corresponding compounds reported in the literature [13],
suggesting the detrimental effect of having a 2,4-dihalogenphenyl substituent attached
to the thiadiazole.
The nature of the substituent at the 2-position of the anilide phenyl ring also
influenced the anti-HIV-1 activity of the new congeners. As could be seen for the 2-
substituted anilides, 7a, 7b, 7d, 7g, 7i, and 7j, the inhibitory activity changed with the
nature of the substituent in 2-position. Here, the most-potent compound was the 2-NO2

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CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
Table. Anti-HIV Activities, Cytotoxicities, and Selectivity Indices of 2-{[4-(3,4-Dichlorophenyl)-1,2,3-
thiadiazol-5-yl]sulfanyl}acetamide Derivatives 7a–7r
R
EC50 [mm]a)
HIV-1 IIIB
>302
CC50 [mm]b) SIc)
HIV-1 IIIB HIV-2 ROD
HIV-2 ROD
7a
7b
7c
7d
7e
2-Fluorophenyl
2-Chlorophenyl
2-Chloropyridin-3-yl
2-Bromophenyl
2-Bromo-4-methyl-
phenyl
>302
>302
>290
>290
>263
ꢂ1
>23
>71
>29
13
ꢂ1
ꢂ1
ꢂ1
ꢂ1
<1
12.4ꢀ8.64 >290
4.10ꢀ0.07 >290
8.96ꢀ4.31 >263
12.8ꢀ2.04 >165
165ꢀ13.0
7f
4-Acetyl-2-bromo-
phenyl
0.95ꢀ0.33 >149
149ꢀ23.7
159
<1
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
7q
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
2.31ꢀ1.59 >235
4.46ꢀ2.46 >190
235ꢀ18.2
190ꢀ4.35
101
43
<1
<1
ꢂ1
ꢂ1
<1
<1
ꢂ1
ꢂ1
ꢂ1
<1
<1
>305
>305
>315
>244
>37.5
>295
>295
>315
>206
>25.9
>305
ꢂ1
ꢂ1
<1
<1
ꢂ1
ꢂ1
ꢂ1
<1
<1
>315
>244
>37.5
>295
>295
>315
>206
>25.9
>315
244ꢀ23.4
37.5ꢀ9.75
>295
>295
>315
206ꢀ24.0
25.9ꢀ1.13
123ꢀ62.3
7r
3-(Methoxycarbonyl)- >123
thien-2-yl
>123
<1
<1
NVPd)
DLVd)
EFVd)
AZTd)
0.208
0.320
0.00440
0.0151
>15.0
>3.83
>6.34
>93.6
>72
>12
>1434
>6192
a) EC50: concentration of compound required to achieve 50% protection of MT-4 cell from HIV-1
induced cytotoxicity, as determined by the MTT method. b) CC50: concentration required to reduce the
viability of mock-infected cells by 50%, as determined by the MTT method. c) SI: selectivity index (CC50/
EC50). The SI values: ꢂ 1 stand for ꢃ1 or <1. d) The antiviral properties of these compounds were
previously described [1]. NVP¼nevirapine; DLV¼delaviridine; EFV¼efavirenz; AZT¼azidothymi-
dine.
derivative 7g, followed by the 2-Br derivative 7d and the corresponding Cl derivative
7b; the 2-F and 2-Me analogues (7a and 7i, resp.), and 2-H (7j) were devoid of any
antiviral activity completely.

CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
1721
In addition, the effect of substituents at other positions of the anilide phenyl ring
was examined; it was found that two compounds with a 4-Me substituent on the anilide
phenyl ring were less potent than their analogues (7d vs. 7e; 7g vs. 7h).
It is important to indicate that a dramatic improvement of the biological profiles
was obtained by the introduction of a 4-Ac substituent (i.e., 7f) or an N-atom at C(3)
(i.e., 7c) of the anilide phenyl ring, indicating that hydrophilic or polar substituents in
the 4 (or 3)-position of the anilide phenyl ring might be beneficial for strengthening the
antiviral profile.
Meanwhile, all title compounds were evaluated for their capability to inhibit HIV-2
replication in MT-4 cells. However, none was found effective. On the basis of this fact
and the chemical structure, these molecules can be proposed to act as genuine NNRTIs.
3. Molecular-Modeling Analysis. Molecular modeling provided a complex structure
of compound 7f bound in the WT NNRTI binding pocket (Fig. 2). Overall, compound
7f shares a similar binding conformation with sulfanyltriazole- [7][13] and sulfanyl-
tetrazole-based NNRTIs [11–13]. Particularly, the anilide moiety of 7f lies under the
Pro236 residue along the enzyme/solvent interface, and the 4-acetyl moiety points
toward the solvent-exposed region, as such, this region (3 or 4-position) should be
amenable to functionalization with polar, hydrophilic substituents, which was
consistent with our SAR conclusion.
Fig. 2. Model of 7f docked into the RT non-nucleoside binding site using AutoDock Vina (http://
vina.scripps.edu). Three-dimensional coordinates of the HIV-1 RT/GW564511 (a benzophenone based
NNRTI) complex (PDB code: 3DLG) were used as the input structure for docking calculations because
of the high degree of similarity between sulfanyltriazole/tetrazole leads and benzophenones [7][13].
Default parameters were used as described in the AutoDock manual unless otherwise specified. The
docking result of 7f is shown by PyMOL.

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CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
Conclusions. – A novel series of TTA congeners with a 3,4-dichlorophenyl
substituent attached to the thiadiazole core were synthesized and evaluated for their
anti-HIV activities. The bioassay results revealed that seven of the title compounds
show moderate-to-good inhibitory potency against HIV-1. In particular, compound 7f
was highly potent, with an EC50 value of 0.95ꢀ0.33 mm. Based upon preliminary SAR
studies, some structural requirements for high potency against HIV-1 were identified.
These results provided useful indicators for guiding the further rational design of new
TTA analogues as more active and selective HIV-1 inhibitors.
Research work in the authorsꢂ laboratory has been supported by the National Natural Science
Foundation of China (NSFC No. 30371686, No. 30772629, and No. 30873133), the Key Project of The
International Cooperation, the Ministry of Science and Technology of China (2003DF000033), and the
Research Fund for the Doctoral Program of Higher Education of China (070422083). We are grateful to
Kristien Erven and Kris Uyttersprot for technical assistance.
Experimental Part
General. Solvents were of reagent grade and, when necessary, were purified and dried by standard
methods. Concentration of the reaction solns. involved the use of rotary evaporator under reduced
pressure. TLC: silica gel GF254 plates for TLC (Merck); spots were visualized by I2 vapor or by
irradiation with UV light (254 nm). Flash column chromatography (FC): column packed with silica gel
60 (SiO2, 230–400 mesh; Qingdao Marine Chemical Inc., P. R. China). M.p.: WRS-1 digital melting-point
apparatus; uncorrected. IR Spectra: Nexus 470 FT-IR spectrometer. 1H- and 13C-NMR spectra: Brucker
Avance-600 spectrometer in the indicated solvents; chemical shifts in d units, with TMS as internal
reference. MS: LC Autosampler Device: Standard G1313A instrument. HR-MS: Accela UPLC-LTQ
Orbitrap Mass Spectrometer.
Synthesis of Sodium 4-(3,4-Dichlorophenyl)-1,2,3-thiadiazole-5-thiolate (6). To a soln. of 1-(3,4-
dichlorophenyl)ethanone (1; 18.9 g, 0.1 mol) in glacial AcOH (80 ml) was added at r.t. a soln. of Br2
(16.0 g, 0.1 mol) in glacial AcOH (30 ml) over a period of 30 min. The mixture was stirred at r.t. for 6 h
(monitored by TLC). Then, the mixture was poured into ice water (100 g), the separated solid was
filtered, washed with cold H2O, and dried in air to give crude 2-bromo-1-(3,4-dichlorophenyl)ethanone
(2) as a white solid, which was used without any further purification.
Compound 2 (0.1 mol) was added to a mixture of methyl 3-sulfanylpropanoate (11.4 ml, 0.1 mol) and
Na2CO3 (5.3 g, 0.05 mol) in 100 ml of EtOH. The mixture was stirred at r.t. for 12 h. The solvent was
evaporated under reduced pressure. The residue was then diluted with CH2Cl2 (100 ml), washed
successively with 0.1m aq. HCl, aq. sat. NaHCO3, H2O, and brine. The org. layer was dried (Na2SO4),
filtered, and concentrated under reduced pressure to afford crude product 3 as a pale yellow oil. ESI-MS:
307.3 ([Mþ1]þ ).
A mixture of semicarbazide hydrochloride (12.2 g, 0.12 mol) and AcONa (8.2 g, 0.1 mol) was
dissolved in abs. EtOH (50 ml). The mixture was heated for 60 min under reflux, and then filtered while
hot to remove precipitated NaCl. The filtrate was then mixed with compound 3 (30 g, 0.1 mol), and the
resulting mixture was heated to reflux, a few drops of conc. HCl were added. Heating under reflux with
continuous removal of the generated H2O was continued overnight. Finally, the mixture was cooled and
filtered. The obtained solid was washed successively with H2O and Et2O, and dried to give 4 (28.8 g,
79%). White solid. M.p. 209–2118. ESI-MS: 364.1 ([Mþ1]þ ).
To a suspension of hydrazone 4 (3.6 g, 0.01 mol) in 10 ml dry CH2Cl2, SOCl2 (10 ml) was added with
vigorous stirring in an ice bath. The mixture was allowed to warm up to r.t. under continuous stirring.
Monitoring of the reaction progress with TLC showed that the reaction was complete after more than
10 h at which time the solvent was removed under vacuum. The residue was diluted with AcOEt (50 ml),
filtered, and the filtrate was evaporated to give a residue, which was chromatographed on SiO2 using
AcOEt/petroleum ether 1:4. The fractions were collected and evaporated, to give 5 (2.34 g, 67%). White
solid. M.p. 97–998. IR (KBr): 2959, 2929, 2850, 1738 (C¼O), 1436 (N¼N), 1249, 1198, 742 (CꢁS).

CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
1723
1H-NMR (600 MHz, (D6)DMSO): 8.10 (s, 1 arom. H); 7.86–7.87 (m, 2 arom. H); 3.61 (s, MeO); 3.42 (t,
J¼5.4, CH2ꢁS); 2.83 (t, J¼5.4, CH2). ESI-MS: 349.2 ([Mþ1]þ ).
A soln. of MeONa (0.54 g, 0.01 mol) in 15 ml of MeOH was added to a soln. of 5 (3.5 g, 0.01 mol) in
100 ml of MeOH. After about 1 h, the soln. was concentrated in vacuo to ca. 10 ml. Dry CH2Cl2 (50 ml)
was added, causing precipitation of a white solid. This solid was collected, washed with CH2Cl2, giving the
desired sodium 4-(3,4-dichlorophenyl)-1,2,3-thiadiazole-5-thiolate (6; 2.57 g, 90%). White powder. M.p.
153–1558.
General Procedure for the Synthesis of the 2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-
acetamides 7a–7r. To a soln. of 6 (1.05 mmol, 0.3 g) in EtOH (30 ml) was added 2-chloro-N-
arylacetamide (1.0 mmol). The mixture was stirred at r.t. overnight. Upon completion of the reaction, the
solvent was evaporated, leaving a residue, which was treated with CH2Cl2 (30 ml) and washed with H2O
(3ꢂ30 ml). The org. layer was dried over anh. Na2SO4, the drying agent was filtered off, and the solvent
was removed in vacuo. The residue was purified by recrystallization using EtOH to yield the title
compounds 7a–7r.
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(2-fluorophenyl)acetamide (7a). Yield:
0.29 g (69%). Light yellow needle crystals. M.p. 167–1698. IR (KBr): 3254 (NH), 1656 (C¼O), 1539,
1490, 1458 (N¼N), 760 (CꢁS). 1H-NMR (600 MHz, CDCl3): 11.01 (s, NH); 8.18 (t, J¼8.4, 1 arom. H’);
8.09 (d, J¼2.4, 1 arom. H); 7.88 (dd, J¼1.8, 7.8, 1 arom. H); 7.59 (d, J¼7.8, 1 arom. H); 7.14–7.17 (m, 3
arom. H’); 3.90 (s, CH2ꢁS). 13C-NMR (150 MHz, CDCl3): 165.8 (C¼O); 154.5 (thiadiazole); 154.3, 152.7
1
(d, JCF ¼243.8, arom. C); 149.7 (thiadiazole); 131.9; 131.7; 131.2; 130.9; 129.9; 128.4; 125.8, 125.8 (d,
3
4
3JCF ¼8.1, arom. C); 125.5, 125.4 (d, JCF ¼11.4, atom. C); 124.5, 124.5 (d, JCF ¼3.45, atom. C); 123.8,
115.6, 115.5 (d, JCF ¼19.5, arom. C); 41.4 (CH2ꢁS). ESI-MS: 414.3 ([Mþ1]þ ), 416.2. HR-ESI-MS:
2
412.9637 (C16H10Cl2FN3OSþ2 ; calc. 412.9626).
N-(2-Chlorophenyl)-2-{[4-(3,4-dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}acetamide (7b).
Yield: 0.32 g (73%). White crystals. M.p. 163–1658. IR (KBr): 3252 (NH), 1648 (C¼O), 1588, 1540,
1445 (N¼N), 1186, 751 (CꢁS). 1H-NMR (600 MHz, CDCl3): 8.47 (s, NH); 8.25 (d, J¼8.4, 1 arom. H);
8.09 (d, J¼1.8, 1 arom. H); 7.82 (dd, J¼8.4, 1.8, 1 arom. H); 7.59 (d, J¼2.4, 1 arom. H’); 7.36 (d, J¼7.8, 1
arom. H’); 7.29–7.27 (m, 1 arom. H’); 7.11–7.09 (m, 1 arom. H’); 3.93 (s, CH2ꢁS). 13C-NMR (150 MHz,
CDCl3): 163.3 (C¼O); 156.5 (thiadiazole); 145.7 (thiadiazole); 133.9; 133.5; 130.9; 130.5; 130.2; 129.3;
123.0; 127.8; 125.9; 123.2; 121.6; 42.0 (CH2ꢁS). ESI-MS: 430.3 ([Mþ1]þ ), 432.2. HR-ESI-MS: 428.9346
(C16H10Cl3N3OSþ2 ; calc. 428.9331).
N-(2-Chloropyridin-3-yl)-2-{[4-(3,4-dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}acetamide (7c).
Yield: 0.29 g (68%). White needle crystals. M.p.: 161–1638. IR (KBr): 3233 (NH), 1662 (C¼O),
1
1532, 1400 (N¼N), 1077, 818, 752 (CꢁS). H-NMR (600 MHz, CDCl3): 8.62 (d, J¼8.4, 1 pyridine-H);
8.46 (s, NH); 8.17 (dd, J¼1.8, J¼4.2, 1 pyridine-H); 8.10 (d, J¼1.8, 1 arom. H); 7.82 (dd, J¼1.8, 8.4, 1
arom. H); 7.61 (d, J¼8.4, 1 arom. H); 7.29–7.27 (m, 1 pyridine-H); 3.93 (s, CH2ꢁS). 13C-NMR
(150 MHz, (D6)DMSO): 166.3 (C¼O); 154.7 (thiadiazole); 149.5 (thiadiazole); 145.8; 142.9; 133.8;
131.9; 131.7; 131.3; 131.2; 130.8; 129.9; 128.4; 123.5; 41.3 (CH2ꢁS). ESI-MS: 431.2 ([Mþ1]þ ), 433.2,
435.1. HR-ESI-MS: 429.9292 (C15H9Cl3N4OSþ2 ; calc. 429.9283).
N-(2-Bromophenyl)-2-{[4-(3,4-dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}acetamide (7d).
Yield: 0.36 g (75%). White powder. M.p. 159–1618. IR (KBr): 3219 (NH), 1651 (C¼O), 1533, 1436
(N¼N), 748 (CꢁS). 1H-NMR (600 MHz, CDCl3): 8.52 (s, NH); 8.25 (d, J¼7.8, 1 arom. H’); 8.10 (d, J¼
1.8, 1 arom. H); 7.83 (dd, J¼1.8, 7.8, 1 arom. H); 7.60 (d, J¼7.8, 1 arom. H); 7.52 (d, J¼7.8, 1 arom. H’);
7.34–7.32 (m, 1 arom. H’); 7.03 (dt, J¼1.8, 7.8, 1 arom. H’); 3.93 (s, CH2ꢁS). 13C-NMR (150 MHz,
(D6)DMSO): 165.6 (C¼O); 154.5 (thiadiazole); 149.7 (thiadiazole); 135.5; 132.8; 131.9; 131.7; 131.2;
130.9; 129.9; 128.4; 128.1; 127.5; 126.9; 117.7; 41.2 (CH2ꢁS). ESI-MS: 474.2 ([Mþ1]þ ), 476.2, 478.2. HR-
ESI-MS: 472.8834 (C16H10BrCl2N3OSþ2 ; calc. 472.8826).
N-(2-Bromo-4-methylphenyl)-2-{[4-(3,4-dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}acetamide
(7e). Yield: 0.44 g (89%). White needle crystals. M.p. 163–1658. IR (KBr): 3224 (NH), 3030, 2977, 2916,
1646 (C¼O), 1535, 1488 (N¼N), 830, 817, 743 (CꢁS). 1H-NMR (600 MHz, CDCl3): 8.57 (s, NH); 8.41
(d, J¼1.8, 1 arom. H); 8.08 (dd, J¼1.8, 8.4, 1 arom. H); 7.82 (d, J¼8.4, 1 arom. H); 7.60 (d, J¼8.4, 1
arom. H’); 7.34 (s, 1 arom. H’); 7.12 (dd, J¼1.8, 8.4, 1 arom. H’); 3.91 (s, CH2ꢁS); 2.31 (s, Me). 13C-NMR
(150 MHz, (D6)DMSO): 166.2 (C¼O); 155.2 (thiadiazole); 150.5 (thiadiazole); 138.1; 133.6; 133.5;

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CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
132.6; 132.4; 131.9; 131.6; 130.6; 129.4; 129.1; 127.5; 118.4; 41.8 (CH2ꢁS); 20.7 (Me). ESI-MS: 488.2
([Mþ1]þ ), 490.2. HR-ESI-MS: 486.8990 (C17H12BrCl2N3OSþ2 ; calc. 486.8982).
N-(4-Acetyl-2-bromophenyl)-2-{[4-(3,4-dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}acetamide
(7f). Yield: 0.37 g (72%). Light yellow needle crystals. M.p. 165–1678. IR (KBr): 3194 (NH), 1674
1
(C¼O), 1672 (C¼O), 1531, 1392 (N¼N), 1261, 816, 743 (CꢁS). H-NMR (600 MHz, CDCl3): 8.69 (s,
NH); 8.40 (d, J¼8.4, 1 arom. H’); 8.14 (d, J¼1.8, 1 arom. H); 8.08 (d, J¼2.4, 1 arom. H’); 7.89 (dd, J¼1.8,
8.4, 1 arom. H); 7.81 (dd, J¼2.4, 8.4, 1 arom. H’); 7.59 (d, J¼8.4, 1 arom. H); 3.94 (s, CH2ꢁS); 2.58 (s,
Me). 13C-NMR (150 MHz, (D6)DMSO): 195.8 (C¼O); 166.0 (C¼O); 154.7 (thiadiazole); 149.4
(thiadiazole); 139.5; 134.7; 132.6; 131.8; 131.6; 131.2; 130.7; 129.9; 128.4; 128.0; 125.0; 116.0; 41.4
(CH2ꢁS); 26.6 (Me). ESI-MS: 516.1 ([Mþ1]þ ), 518.1, 520.2. HR-ESI-MS: 514.8939
(C18H12BrCl2N3O2Sþ2 ; calc. 514.8931).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(2-nitrophenyl)acetamide (7g). Yield:
0.34 g (76%). Light yellow needle crystals. M.p. 157–1598. IR (KBr): 3339 (NH), 1690 (C¼O), 1500
(NO2), 1438 (N¼N), 1349 (NO2), 1278, 742 (CꢁS). 1H-NMR (600 MHz, CDCl3): 11.12 (s, NH); 8.67 (d,
J¼8.4, 1 arom. H’); 8.23 (dd, J¼1.8, 8.4, 1 arom. H’); 8.10 (d, J¼1.8, 1 arom. H); 7.88 (dd, J¼1.8, 8.4, 1
arom. H); 7.71–7.69 (m, 3 arom. H’); 7.59 (d, J¼8.4, 1 arom. H); 7.27–7.25 (m, 2 arom. H’); 3.83 (s,
CH2ꢁS). 13C-NMR (150 MHz, (D6)DMSO): 165.7 (C¼O); 154.6 (thiadiazole); 149.5 (thiadiazole);
142.4; 134.2; 131.9; 131.7; 131.2; 130.8; 130.4; 129.9; 128.5; 126.0; 125.5; 125.0; 41.2 (CH2ꢁS). ESI-MS:
441.3 ([Mþ1]þ ), 443.2. HR-ESI-MS: 439.9582 (C16H10Cl2N4O3Sþ2 ; calc. 439.9571).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(4-methyl-2-nitrophenyl)acetamide
(7h). Yield: 0.32 g (70%). Light yellow needle crystals. M.p. 148–1508. IR (KBr): 3342 (NH), 2973, 2926,
1690 (C¼O), 1517 (NO2), 1453 (N¼N), 1346 (NO2), 761 (CꢁS). 1H-NMR (600 MHz, CDCl3): 10.99 (s,
NH); 8.53–8.51 (m, 1 arom. H’); 8.11 (d, J¼1.8, 1 arom. H); 8.03 (s, 1 arom. H’); 7.83 (dd, J¼1.8, 8.4, 1
arom. H); 7.58 (d, J¼8.4, 1 arom. H); 7.48 (d, J¼8.4, 1 arom. H’); 3.90 (s, CH2ꢁS); 2.41 (s, Me).
13C-NMR (150 MHz, (D6)DMSO): 160.6 (C¼O); 154.6 (thiadiazole); 149.6 (thiadiazole); 142.3; 136.1;
134.6; 131.9; 131.7; 131.2; 130.9; 129.9; 128.5, 127.9; 125.5; 124.9; 41.1 (CH2ꢁS); 20.0 (Me). ESI-MS:
455.3 ([Mþ1]þ ), 457.2. HR-ESI-MS: 453.9737 (C17H12Cl2N4O3Sþ2 ; calc. 453.9728).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(2-methylphenyl)acetamide (7i). Yield:
0.32 g (79%). White solid. M.p. 192–1958. IR (KBr): 3258 (NH), 3050, 2968, 2922, 2852, 1644 (C¼O),
1539, 1459 (N¼N), 1252, 1224, 751 (CꢁS). 1H-NMR (600 MHz, CDCl3): 9.69 (s, NH); 8.10 (s, J¼1.8, 1
arom. H); 7.82 (dd, J¼1.8, 8.4, 1 arom. H); 7.71 (d, J¼8.4, 1 arom. H’); 7.61 (d, J¼8.4, 1 arom. H); 7.22 (t,
J¼7.8, 1 arom. H’); 7.18 (t, J¼8.4, 1 arom. H’); 7.12 (t, J¼1.8, 1 arom. H’); 3.94 (s, CH2ꢁS); 2.11 (s, Me).
13C-NMR (150 MHz, (D6)DMSO): 165.2 (C¼O); 154.4 (thiadiazole); 150.0 (thiadiazole); 135.6; 131.9;
131.7; 131.7; 131.3; 130.9; 130.4; 129.9; 128.4; 126.1; 125.7; 124.8; 41.3 (CH2ꢁS); 17.7 (Me). ESI-MS:
410.3 ([Mþ1]þ ), 412.3. HR-ESI-MS: 408.9885 (C17H13Cl2N3OSþ2 ; calc. 408.9877).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-phenylacetamide (7j). Yield: 0.32 g
(80%). White needle crystals. M.p. 143–1458. IR (KBr): 3272 (NH), 1663 (C¼O), 1539, 1442
(N¼N), 742 (CꢁS). 1H-NMR (600 MHz, CDCl3): 10.37 (s, NH); 8.09 (d, J¼1.8, 1 arom. H); 7.82 (dd, J¼
1.8, 8.4, 1 arom. H); 7.59 (d, J¼8.4, 1 arom. H); 7.40 (d, J¼7.8, 2 arom. H’); 7.34 (dt, J¼8.4, 2 arom. H’);
7.17 (dt, J¼8.4, 1 arom. H’); 3.87 (s, CH2ꢁS). 13C-NMR (150 MHz, (D6)DMSO): 164.1 (C¼O); 155.1
(thiadiazole); 150.4; 149.0 (thiadiazole); 147.7; 137.6; 133.5; 131.2; 130.3; 130.0; 127.4; 121.8; 117.5; 41.3
(CH2ꢁS). ESI-MS: 396.3 ([Mþ1]þ ), 398.3. HR-ESI-MS: 394.9732 (C16H11Cl2N3OSþ2 ; calc. 394.9721).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(4-methylphenyl)acetamide (7k).
Yield: 0.36 g (89%). White needle crystals. M.p. 175–1778. IR (KBr): 3270 (NH), 3053, 2961, 2920,
1646 (C¼O), 1539, 1432 (N¼N), 816, 741 (CꢁS). 1H-NMR (600 MHz, CDCl3): 10.31 (s, NH); 8.08 (d,
J¼1.8, 1 arom. H); 7.81 (dd, J¼1.8, 8.4, 1 arom. H); 7.59 (d, J¼8.4, 1 arom. H); 7.27 (d, J¼8.4, 2 arom.
H’); 7.12 (d, J¼8.4, 2 arom. H’); 3.85 (s, CH2ꢁS); 2.32 (s, Me). 13C-NMR (150 MHz, (D6)DMSO): 163.4
(C¼O); 154.5 (thiadiazole); 151.6; 149.6 (thiadiazole); 148.8; 138.0; 131.5; 131.9; 130.4; 129.9; 128.1;
120.0; 113.2; 42.1 (CH2ꢁS); 21.1 (Me). ESI-MS: 410.3 ([Mþ1]þ ), 412.3. HR-ESI-MS: 408.9884
(C17H13Cl2N3OSþ2 ; calc. 408.9877).
N-(4-Chlorophenyl)-2-{[4-(3,4-dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}acetamide (7l). Yield:
0.32 g (74%). White needle crystals. M.p. 171–1738. IR (KBr): 3261 (NH), 1669 (C¼O), 1531, 1491
(N¼N), 825, 744 (CꢁS). 1H-NMR (600 MHz, CDCl3): 10.39 (s, NH); 8.08 (d, J¼2.4, 1 arom. H); 7.81

CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
1725
(dd, J¼2.4, 8.4, 1 arom. H); 7.60 (d, J¼8.4, 1 arom. H); 7.35 (d, J¼9, 2 arom. H’); 7.30 (d, J¼9, 2 arom.
H’); 3.86 (s, CH2ꢁS). 13C-NMR (150 MHz, (D6)DMSO): 166.1 (C¼O); 154.7 (thiadiazole); 151.4; 149.6
(thiadiazole); 148.1; 138.4; 131.7; 131.2; 130.8; 129.9; 128.4; 119.9; 113.5; 41.7 (CH2ꢁS). ESI-MS: 430.3
([Mþ1]þ ), 432.3. HR-ESI-MS: 428.9343 (C16H10Cl3N3OSþ2 ; calc. 428.9331).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(2,3-dimethylphenyl)acetamid (7m).
Yield: 0.31 g (72%). White powder. M.p. 197–1998. IR (KBr): 3252 (NH), 3032, 2977, 2917, 2853,
1642 (C¼O), 1536, 1426 (N¼N), 755 (CꢁS). 1H-NMR (600 MHz, CDCl3): 9.74 (s, NH); 8.09 (d, J¼1.8,
1 arom. H); 7.82 (dd, J¼1.8, 8.4, 1 arom. H); 7.61 (d, J¼8.4, 1 arom. H); 7.38 (d, J¼7.8, 1 arom. H’); 7.12–
7.11 (m, 1 arom. H’); 7.07–7.04 (m, 1 arom. H’); 3.84 (s, CH2ꢁS); 2.28 (s, Me); 2.00 (s, Me). 13C-NMR
(150 MHz, (D6)DMSO): 167.8 (C¼O); 154.9 (thiadiazole); 151.3; 149.9 (thiadiazole); 146.6; 137.9;
133.6; 131.8; 129.4; 128.8; 126.5; 120.5; 117.5; 42.6 (CH2ꢁS); 21.2 (Me); 19.9 (Me). ESI-MS: 424.3 ([Mþ
1]þ ), 426.2. HR-ESI-MS: 423.0047 (C18H15Cl2N3OS2þ ; calc. 423.0034).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(2,6-dimethylphenyl)acetamide (7n).
Yield: 0.32 g (76%). Light yellow solid. M.p. 211–2138. IR (KBr): 3227 (NH), 3021, 2957, 2919, 2852,
1
1653 (C¼O), 1533, 1484, 1431 (N¼N), 1222, 766, 744 (CꢁS). H-NMR (600 MHz, CDCl3): 10.02 (s,
NH); 8.10 (d, J¼1.8, 1 arom. H); 7.83 (dd, J¼1.8, 8.4, 1 arom. H); 7.61 (d, J¼8.4, 1 arom. H); 7.12 (d, J¼
7.8, 1 arom. H’); 7.06 (d, J¼7.8, 1 arom. H’); 3.97 (s, CH2ꢁS); 2.10 (s, 2 Me). 13C-NMR (150 MHz,
(D6)DMSO): 166.9 (C¼O); 155.5 (thiadiazole); 150.1; 149.3 (thiadiazole); 147.5; 137.2; 132.2; 131.9;
130.9; 128.6; 127.9; 120.0; 114.6; 41.9 (CH2ꢁS); 22.8 (Me). ESI-MS: 424.3 ([Mþ1]þ ), 426.3. HR-ESI-
MS: 423.0051 (C18H15Cl2N3OSþ2 ; calc. 423.0034).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(pyridin-2-yl)acetamide (7o). Yield:
0.30 g (75%). Light yellow needle crystals. M.p. 171–1738. IR (KBr): 3218 (NH), 1689 (C¼O), 1586,
1542, 1446 (N¼N), 1436 (N¼N), 1318, 1163, 785, 743 (CꢁS). 1H-NMR (600 MHz, CDCl3): 8.80 (s, NH);
8.27 (d, J¼4.2, 1 pyridine-H); 8.13 (d, J¼8.4, 1 pyridine-H); 8.09 (d, J¼2.4, 1 arom. H); 7.82 (dd, J¼2.4,
9.0, 1 arom. H); 7.76–7.73 (m, 1 pyridine-H); 7.58 (d, J¼9.0, 1 arom. H); 7.11 (dd, J¼4.8, 7.2, 1 pyridine-
H); 3.88 (s, CH2ꢁS). 13C-NMR (150 MHz, (D6)DMSO): 166.1 (C¼O); 154.7 (thiadiazole); 151.4; 149.6
(thiadiazole); 148.1; 138.4; 131.9; 131.6; 131.2; 130.8; 129.9; 128.4; 119.9; 113.5; 41.7 (CH2ꢁS). ESI-MS:
397.2 ([Mþ1]þ ), 399.2. HR-ESI-MS: 395.9685 (C15H10Cl2N4OSþ2 ; calc. 395.9673).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(1,3-thiazol-2-yl)acetamide (7p). Yield:
0.26 g (65%). Light yellow powder. M.p. 221–2238. IR (KBr): 3435 (NH), 1686 (C¼O), 1590, 1432
(N¼N), 1327, 1162, 817, 713 (CꢁS). 1H-NMR (600 MHz, CDCl3): 12.51 (s, NH); 8.13 (d, J¼1.8, 1 arom.
H); 7.89 (dd, J¼1.8, 8.4, 1 arom. H); 7.85 (d, J¼8.4, 1 arom. H); 7.50 (d, J¼3.6, 1 thiazole-H); 7.28 (d, J¼
3.6, 1 thiazole-H); 4.29 (s, CH2ꢁS). 13C-NMR (150 MHz, (D6)DMSO): 166.8 (C¼O); 157.3; 153.2
(thiadiazole); 149.1 (thiadiazole); 143.5; 133.3; 131.4; 131.9; 130.4; 129.9; 128.4; 109.8; 40.3 (CH2ꢁS).
ESI-MS: 403.1 ([Mþ1]þ ), 405.2. HR-ESI-MS: 401.9245 (C13H8Cl2N4OSþ3 ; calc. 401.9237).
2-{[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}-N-(5-methyl-1,3-benzothiazol-2-yl)aceta-
mide (7q). Yield: 0.37 g (78%). Light yellow lamellar crystals. M.p. 198–2008. IR (KBr): 3319 (NH),
2971, 2924, 2853, 1698 (C¼O), 1607, 1554, 1464 (N¼N), 1159, 740 (CꢁS). 1H-NMR (600 MHz, CDCl3):
12.68 (s, NH); 8.14 (d, J¼1.8, 1 arom. H); 7.90 (dd, J¼1.8, 8.4, 1 arom. H); 7.84 (d, J¼8.4, 1 arom. H);
7.77 (s, 1 arom. H’); 7.65 (d, J¼8.4, 1 arom. H’); 7.27 (d, J¼8.4, 1 arom. H’); 4.33 (s, CH2ꢁS); 2.50 (s, Me).
13C-NMR (150 MHz, (D6)DMSO): 166.4 (C¼O); 156.5; 155.1 (thiadiazole); 149.0 (thiadiazole); 146.4;
133.3; 132.0; 131.7; 131.2; 130.7; 130.0; 128.5; 127.6; 121.4; 120.4; 56.0; 40.7 (CH2ꢁS); 21.0 (Me). ESI-
MS: 467.3 ([Mþ1]þ ), 469.2. HR-ESI-MS: 465.9564 (C18H12Cl2N4OSþ3 ; calc. 465.9550).
Methyl 2-[({[4-(3,4-Dichlorophenyl)-1,2,3-thiadiazol-5-yl]sulfanyl}acetyl)amino]thiophene-3-car-
boxylate (7r). Yield: 0.36 g (79%). White needle crystals. M.p. 181–1838. IR (KBr): 3300 (NH), 1671
(C¼O), 1575 (C¼O), 1447 (N¼N), 1294, 779, 741 (CꢁS). 1H-NMR (600 MHz, CDCl3): 10.93 (s, NH);
8.14 (d, J¼1.8, 1 arom. H); 8.03 (d, J¼6.0, 1 thiophene-H); 7.84 (dd, J¼1.8, 8.4, 1 arom. H); 7.58 (d, J¼
8.4, 1 arom. H); 7.50 (d, J¼6.0, 1 thiophene-H); 3.90 (s, CH2ꢁS); 3.87 (s, MeO). 13C-NMR (150 MHz,
(D6)DMSO): 164.9 (C¼O); 163.1 (C¼O); 155.2 (thiadiazole); 149.0 (thiadiazole); 142.5; 133.1; 132.0;
131.6; 131.2; 130.7; 130.0; 128.5; 122.2; 111.5; 52.1; 41.5 (CH2ꢁS). ESI-MS: 460.2 ([Mþ1]þ ), 462.2. HR-
ESI-MS: 458.9355 (C16H11Cl2N3O3Sþ3 ; calc. 458.9340).
Anti-HIVActivity Assays. Evaluation of the antiviral activity of the compounds against HIV-1 strain
(IIIB) and HIV-2 strain (ROD) in MT-4 cells was performed using the MTT (¼ 3-(4,5-dimethylthiazol-2-

1726
CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
yl)-2,5-diphenyl-2H-tetrazolium bromide) assay as previously described [21][22]. Stock solns. (10ꢂ final
concentration) of test compounds were added in 25 ml 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. Serial 5-fold dilutions of test compounds were made directly in flat-bottomed 96-well
microtiter trays using a Biomek 3000 robot (Beckman instruments, Fullerton, CA). Untreated control
HIV- and mock-infected cell samples were included for each sample.
HIV-1 (IIIB) [23] or HIV-2 (ROD) [24] stock (50 ml) 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 compound on uninfected cells in order to
assess the cytotoxicity of the test compound. Exponentially growing MT-4 cells [25] were centrifuged for
5 min at 1000 rpm and the supernatant was discarded. The MT-4 cells were resuspended at 6ꢂ105 cells/
ml, and 50-ml volumes were transferred to the microtiter tray wells. Five days after infection, the viability
of mock- and HIV-infected cells was examined spectrophotometrically by the MTT assay.
The MTT assay is based on the reduction of yellow coloured MTT (Acros Organics, Geel, Belgium)
by mitochondrial dehydrogenase of metabolically active cells to a blue-purple formazan that can be
measured spectrophotometrically. The absorbances were read in an eight-channel computer-controlled
photometer (Multiscan Ascent Reader, Labsystems, Helsinki, Finland), at two wavelengths (540 and
690 nm). All data were calculated using the median OD (optical density) value of tree wells. The 50%
cytotoxic concentration (CC50) was defined as the concentration of the test compound that reduced the
absorbance (OD540) of the mock-infected control sample by 50%. The concentration achieving 50%
protection from the cytopathic effect of the virus in infected cells was defined as the 50% effective
concentration (EC50).
REFERENCES
[1] P. Zhan, X. Liu, Y. Cao, Y. Wang, C. Pannecouque, E. De Clercq, Bioorg. Med. Chem. Lett. 2008, 18,
5368.
[2] E. De Clercq, Chem. Biodiversity 2004, 1, 44.
[3] E. De Clercq, Int. J. Biochem. Cell Biol. 2004, 36, 1800.
[4] E. De Clercq, J. Med. Chem. 2005, 48, 1297.
[5] E. De Clercq, Nat. Rev. Drug Discovery 2007, 6, 1001.
[6] P. Zhan, X. Liu, Z. Li, Curr. Med. Chem. 2009, 16, 2876; P. Zhan, X. Liu, Z. Li, C. Pannecouque, E.
De Clercq, Curr. Med. Chem. 2009, 16, 3903.
[7] Z. Wang, B. Wu, K. L. Kuhen, B. Bursulaya, T. N. Nguyen, D. G. Nguyen, Y. He, Bioorg. Med. Chem.
Lett. 2006, 16, 4174.
[8] M. De La Rosa, H. W. Kim, E. Gunic, C. Jenket, U. Boyle, Y.-H. Koh, I. Korboukh, M. Allan, W.
Zhang, H. Chen, W. Xu, S. Nilar, N. Yao, R. Hamatake, S. A. Lang, Z. Hong, Z. Zhang, J.-L.
Girardet, Bioorg. Med. Chem. Lett. 2006, 16, 4444.
[9] Z. Zhang, W. Xu, Y.-H. Koh, J. H. Shim, J.-L. Girardet, L. T. Yeh, R. K. Hamatake, Z. Hong,
Antimicrob. Agents Chemother. 2007, 51, 429.
[10] E. Muraglia, O. D. Kinzel, R. Laufer, M. D. Miller, G. Moyer, V. Munshi, F. Orvieto, M. C. Palumbi,
G. Pescatore, M. Rowley, P. D. Williams, V. Summa, Bioorg. Med. Chem. Lett. 2006, 16, 2748.
[11] J. A. OꢂMeara, A. Jakalian, S. LaPlante, P. R. Bonneau, R. Coulombe, A.-M. Faucher, I. Guse, S.
Landry, J. Racine, B. Simoneau, B. Thavonekham, C. Yoakim, Bioorg. Med. Chem. Lett. 2007, 17,
3362.
[12] A. Gagnon, M. H. Amad, P. R. Bonneau, R. Coulombe, P. L. DeRoy, L. Doyon, J. Duan, M.
Garneau, I. Guse, A. Jakalian, E. Jolicoeur, S. Landry, E. Malenfant, B. Simoneau, C. Yoakim,
Bioorg. Med. Chem. Lett. 2007, 17, 4437.
[13] P. Zhan, Z. Li, X. Liu, E. De Clercq, Mini-Rev. Med. Chem. 2009, 9, 1014.
[14] X. Liu, P. Zhan, C. Pannecouque, E. De Clercq, Antiviral Res. 2009, 82, A44.
[15] Y. Lu, T. Shi, Y. Wang, H. Yang, X. Yan, X. Luo, H. Jiang, W. Zhu, J. Med. Chem. 2009, 52,
2854.

CHEMISTRY & BIODIVERSITY – Vol. 7 (2010)
1727
[16] G. Campiani, A. Ramunno, G. Maga, V. Nacci, C. Fattorusso, B. Catalanotti, E. Morelli, E.
Novellino, Curr. Pharm. Des. 2002, 8, 615.
[17] C. D. Hurd, R. I. Mori, J. Am. Chem. Soc. 1955, 77, 5359.
[18] W. V. Curran, M. L. Sassiver, J. H. Boothe, E.P. 104403, 1984; Chem. Abstr. 1984, 101, 90945.
[19] E. W. Thomas, E. E. Nishizawa, D. C. Zimmermann, D. J. Williams, J. Med. Chem. 1985, 28, 442.
[20] Y. A. Al-Soud, N. A. Al-Masoudi, E. De Clercq, C. Pannecouque, Heteroatom Chem. 2007, 18, 333.
[21] R. Pauwels, J. Balzarini, M. Baba, R. Snoeck, D. Schols, P. Herdewijn, J. Desmyter, E. De Clercq, J.
Virol. Methods 1988, 20, 309.
[22] C. Pannecouque, D. Daelemans, E. De Clercq, Nat. Protoc. 2008, 3, 427.
[23] M. Popovic, M. G. Sarngadharan, E. Read, R. C. Gallo, Science 1984, 224, 497.
[24] F. Barre-Sinoussi, J. C. Chermann, F. Rey, M. T. Nugeyre, S. Chamaret, J. Gruest, C. Dauguet, C.
Axler-Blin, F. Vezinet-Brun, C. Rouzioux, W. Rozenbaum, L. Montagnier, Science 1983, 220, 868.
[25] I. Miyoshi, H. Taguchi, I. Kobonishi, S. Yoshimoto, Y. Ohtsuki, Y. Shiraishi, T. Akagi, Gann Monogr.
Cancer Res. 1982, 28, 219.
Received June 19, 2009