Modification and biological evaluation of novel 4-hydroxy-pyrone derivatives as non-peptidic HIV-1 protease inhibitors

Article abstract of DOI:10.1007/s00044-010-9307-4

In this study, we have modified 4-hydroxy-pyran-2-ones, especially introduced heteroatoms (S or O) into the substituents, and detected their interactions with the binding pockets of HIV-1 protease (PR). The results indicated that the ethoxyl groups at C-2

Full text of DOI:10.1007/s00044-010-9307-4

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2011) 20:200–209
DOI 10.1007/s00044-010-9307-4
ORIGINAL RESEARCH
Modification and biological evaluation of novel 4-hydroxy-pyrone
derivatives as non-peptidic HIV-1 protease inhibitors
•
Meizi He Ning Yang Chunlai Sun
•
•
•
Xiaojian Yao Ming Yang
Received: 12 July 2009 / Accepted: 13 January 2010 / Published online: 2 February 2010
Ó Springer Science+Business Media, LLC 2010
Abstract In this study, we have modified 4-hydroxy-
pyran-2-ones, especially introduced heteroatoms (S or
O) into the substituents, and detected their interactions with
the binding pockets of HIV-1 protease (PR). The results
indicated that the ethoxyl groups at C-20 and C-50 of the
agents, numerous new and potent HIV PR inhibitors have
been identified (Huff, 1991; Meek, 1992; Thaisrivongs,
1994; Leung et al., 2000), but most of them are pepti-
domimetic compounds and often associates with a low
bioavailability and rapid clearance (West and Fairlie, 1995;
Lebon and Ledecq, 2000). Thus, it is important to design
and identify new non-peptidic structural inhibitors.
Different research groups have synthesized series of
4-hydroxy-pyran-2-one derivatives as HIV-1 PR inhibitors
(Romines and Chrusciel, 1995; Vara Prasad et al., 1999;
Tummino et al., 1996; Thaisrivongs et al., 1996; Lunney
et al., 1994; Skulnick et al., 1995; Tait et al., 1997; Sun
et al., 2005). The pyran-2-one group, 4-hydroxyl group,
and substitution at the 3-position were all necessary for the
HIV-1 PR inhibitory activity. X-ray structural study
showed that there were four internal four pockets (S2, S1,
S1, S2) within HIV-1 PR for the 4-hydroxy-pyran-2-ones to
fill (Thaisrivongs et al., 1996; Lunney et al., 1994; Skul-
nick et al., 1995).
0
0
phenyl ring could enhance the affinities to the S1 and S2
pockets and improve the inhibitory activities. The most
potent compound 10f with an IC50 of 3.5 nM in enzymatic
assay also exhibited good antiviral activity at the cellular
level; it exhibited an EC50 value of 2.9 lM in Simian
immunodeficiency virus-infected CEM cells and sup-
pressed the PR activity in 293T cells using western blot
analysis.
Keywords 4-Hydroxy-pyran-2-ones ꢀ
HIV-1 protease inhibitors ꢀ Anti-SIV activity
Introduction
Great efforts were focused on adding thiosubstitutes to
the C-3 position of 4-hydroxy-pyran-2-ones. As a result,
compound 1 (Fig. 1) was identified to be a potent HIV PR
inhibitor with a very low IC50 value of 1.1 nM (Vara
Prasad et al., 1999). But it showed poor antiviral activity
(EC50 = 15 lM). Compound 2 was the most active one in
vitro (IC50 = 5 nM) because of the hydrogen bond formed
between –COOH and PR residues. However, it exhibited
low antiviral activity in cellular assay due to the high
polarity of the carboxylic acid (Tait et al., 1997). Our
previous study (Sun et al., 2005) has revealed some
4-hydroxy-3-thiosubstituted-pyran-2-ones (compound 3 in
Fig. 1) which showed good antiviral activities in Simian
immunodeficiency virus (SIV)-induced syncytium in
hybrid human B-/T-cell lines (CEM174) (Mahlknecht
et al., 2000).
Human immunodeficiency virus type 1 (HIV-1) protease
(PR), that cleaves the Gag and Gag/Pol polyproteins, is
essential for the formation of mature and infectious virions
(Redshaw, 1994). In an attempt to develop new anti-HIV
M. He ꢀ N. Yang ꢀ C. Sun ꢀ M. Yang (&)
State Key Laboratory of Natural and Biomimetic Drugs, Peking
University Health Science Center, No. 38, Haidian District,
Beijing, People’s Republic of China
e-mail: yangm@bjmu.edu.cn
X. Yao
Laboratory of Molecular Human Retrovirology, Department
of Medical Microbiology, University of Manitoba, 508-745
William Avenue, Winnipeg, MB R3E OJ9, Canada
123

Med Chem Res (2011) 20:200–209
201
Fig. 1 4-Hydroxy-3-
thiosubstituted-pyran-2-ones
and four binding pockets in
HIV-1 PR
OH
OH
S
S
O
2
O
O
1
O
HOOC
'
S1
OH
R2
S1
OH
O
4
R4
3
5
S
2'
2
6
1
O
O
O
R1
5'
R3
S2
'
S2
4
3
Based on those results, we designed the template 4
(Fig. 1). The propyl group at C-6 position was replaced
with a phenyl group which could improve the activity as
previously reported (Tait et al., 1997). For the other sub-
stituent at the C-6 position of the pyrone ring, we inserted
O or S between the aryl group and the heterocycle. We
expected that the heteroatom could form hydrogen bond
and provide suitable polarity to improve the activity. We
also modified at the C-20 and C-50 positions of the phenyl
group located at the C-3 position of the pyrone ring.
Besides various alkyl groups, we introduced O-containing
group to this position, which was rarely studied before.
Overall, we have synthesized a number of 4-hydroxy-
pyran-2-ones derivatives and tested their inhibitory activi-
ties. Furthermore, the structures were docked to the binding
sites of HIV-1 PR using AutoDock3.0 program (Morris
et al., 1998; Huang et al., 2002), to investigate the inter-
action characteristics between respective compound and
HIV-1 PR.
Synthesis
a-Bromoacetophenone was prepared by a-bromination of
acetophenone with CuBr2 (Peter et al., 1998), and then
reacted with thiophenol or naphthol (alpha- or beta-) in the
presence of potassium carbonate, to get the appropriate
ketone (5–7 in Scheme 1) (Wang et al., 1998; Seshadri
et al., 1981). The ketone reacted with the dianion of methyl
acetoacetate to produce compound 8 in Scheme 2. The
method for the synthesis of the dihydropyrone targets (9–
11 in Scheme 2) involved preparation of the 3-bro-
modihydropyrone derivatives with NBS in the dark and
then displacement of the bromide by the appropriately
substituted thiophenol.
O
SH
S
A
5
6
OH
O
O
O
O
Br
B
B
+
OH
O
7
Scheme 1 Reagents and conditions: (A) K2CO3, EtOH, rt; (B)
K2CO3, acetone, reflux
Scheme 2 Regeants and
OH
R2
O
O
O
O
conditions: (A) (i) NaH, (ii) n-
BuLi, dry THF, followed by
ketone addition, 0°C; (B) (i)
NaOH, CH3OH, (ii) H?,
50–70% (for two steps); (C)
NBS, dry t-BuOH, reflux; (D)
corresponding thiophenol,
piperidine, CH2Cl2, 50–65%
(for two steps)
S
A
O
O
OH
O
O
O
R1
B
C,D
R3
R1
9-11(a, b, c,d ,e ,f)
O
O
R1
5-7
8a-c
OH
S
R1
8a
Phenylsulfanylmethyl
8b Naphthalen-1-yloxymethyl
8c
O
O
R1
Naphthalen-2-yloxymethyl
9-11(g)
123

202
Med Chem Res (2011) 20:200–209
Results and discussion
inhibitory activity, we assumed that the observed impres-
sed activity could be due to the inserted heteroatoms. The
compounds were docked into the binding site of HIV-1 PR
structure using AutoDock3.0 program (Morris et al., 1998;
Huang et al., 2002). Figure 2 from docking result showed
that the phenyl group at C-6 position of the pyrone ring
could fit the S1 pocket very well as predicted. On the other
hand, though the other group at C-6 position of the pyrone
ring could insert into the S2 pocket, there was no hydrogen
bond formed by the O or S atom as the –COOH group did.
Instead, the affinity was weakened because of the polarity
caused by the heteroatom when it overlaid into the S2
pocket which is hydrophobic.
The inhibitory activities for HIV PR (Nashed et al., 1989)
were tested and results were listed in Table 1. To further
investigate their inhibitory activities at the cellular level,
we also evaluated the antiviral activities of the compounds
against SIV-induced syncytium in CEM174 cells (Mah-
lknecht et al., 2000). Their EC50, TC50, and TI values are
listed in Table 2. The compounds 9a–d to 11a–d with
phenylthiomethyl or naphthalenyloxymethyl at the C-6
position of the pyrone had high IC50, some of which even
had IC50 higher than 200 nM. Since the phenyl group at the
C-6 position of the pyrone ring was reported to improve the
0
0
To explore the interaction with S1 and S2 pockets, we
modified at the 20 and 50 positions of the phenyl ring
located at the C-3 position of the pyrone ring. The data in
Table 1 showed that the activities were enhanced when the
bulk of the alkyl group at the 20 and 50 positions was
increased. Substitution of the phenyl ring at the 20 position
with Cl group also resulted in an enhanced enzymatic
Table 1 The modification and IC50 values of 4-hydroxy-pyrones
OH
R2
R4
O
O
R1
R3
Table 2 Antiviral activity and cytotoxicity of 4-hydroxy-pyrones
Entry
ECa50 (lM)
TCb50 (lM)
TIc
Entrya R1
R2
R3
R4b
ICc50
(nM)
9a
12.4
13.2
12.6
7.2
10
18.6
19.8
1.5
1.5
9a
H
H
H
H
H
S
S
S
S
S
S
258
240
238
70
9b
9b
CH3
C2H5
Cl
9c
25.0
2.0
S
9c
9d
25.4
3.5
9d
9e
[100
[100
[100
72.0
[10
17.2
[26
6.1
9e
CH3
CH3
196
24
9f
5.8
4.8
11.7
7.1
11
9f
CH3CH2O CH3CH2O
9g
9g
H
H
SCH2 32
10a
10b
10c
10d
10e
10f
10g
11a
11b
11c
11d
11e
11f
11g
IDV
a
10a
10b
10c
10d
10e
10f
10g
11a
11b
11c
11d
11e
11f
11g
a
H
H
S
S
S
S
S
S
159
64
17.3
2.4
CH3
C2H5
Cl
H
20.9
1.9
H
100
59
6.8
8.7
2.9
11
16.9
2.4
O
H
56.9
6.5
CH3
CH3
126
17.1
5.9
CH3CH2O CH3CH2O
3.5
[100
[100
16.5
[9.1
[10
2.3
H
H
SCH2 128
9.8
7.1
4.3
7.6
7.5
4.3
7.9
\0.1
H
H
S
S
S
S
S
S
126
61
22
89
CH3
C2H5
Cl
H
58.9
13.7
3.0
O
H
22.8
H
[100
35.2
13.3
8.2
CH3
CH3
65
CH3CH2O CH3CH2O
9.2
40.7
5.2
H
H
SCH2 73
[100
[1000
All compounds were racemic mixtures. IDV was used as positive
control
EC50 is the effective concentration at which 50% of the CEM cells
are protected from SIV infection and is the average of at least two
runs
b
The S atom was attached to the pyrone ring and CH2 was linked to
the phenyl group when R4 was SCH2
b
TC50 is the concentration that elicits cytotoxicity in 50% of unin-
fected CEM cells
c
IC50 is the effective concentration at which 50% of HIV-1 PR
activity is inhibited and is the average of at least two runs
c
TI, therapeutic index = TC50/EC50
123

Med Chem Res (2011) 20:200–209
203
16
14
12
10
8
µ
6
4
2
0
0
50
100
150
200
250
300
50
IC (nM)
Fig. 3 The antiviral activity of the compounds is correlated with their
PR inhibitory activity
Fig. 2 Molecular modeling of compounds 10f and 11f docked in
HIV-1 PR. Compound 10f was white and 11f was gray. Program
AutoDock3.0 automatically selected the best confirmation among the
stereo isomers
activity (10d versus 10a, 11d versus 11a). The most sig-
nificant modification that dramatically improved the
inhibitory activities was the ethoxyl groups at 20 and 50
positions (9f, 10f, and 11f). Figure 2 from molecular
modeling displayed that the active conformation of 10f
nearly coincided with 11f. Their 20-ethoxyl group and 50-
Fig. 4 Western blot assay with anti-p24 antibody showed convinc-
ingly reduced expression of p24 in 293T cells co-transfected with
pGAGPOL and pGAG which encoded PR and its substrate, respec-
tively, in the cases of 10f and 11f treatments. The cells without co-
transformation were used as blank and IDV was used as positive
control
0
0
ethoxyl group effectively filled the S1 and the S2 pockets
and they could form hydrogen bonds with the residue
0
Asp30 in S2 pocket. These interactions reduced their
docking energy and promoted their inhibitory activities.
Therefore, even with the heteroatom-containing substitu-
ents on the pyrone, the derivatives 10f and 11f exhibited
good inhibitory activity with the IC50 below 10 nM.
We also inserted a methylene group between the S atom
and the phenyl group (9g–11g) (Table 1). The prolonged
linker yielded a modest enhancement in the binding affinity
with the enzyme relative to compounds 9a–11a.
western bolt analysis (Chien et al., 2006). As shown in
Fig. 4, the p24 protein expression level was decreased in
the presence of 10f and 11f, indicating that the activity of
PR was inhibited by these compounds in 293T cells. These
results provide evidence that compounds 10f and 11f would
be a promising HIV-1 PR inhibitor because of potent
enzyme inhibitory activity and antiviral activity.
As shown in Table 2, Compound 10f with an enzyme
IC50 of 3.5 nM exhibited a significant antiviral activity
(EC50 = 2.9 lM), whereas the majority of the derivatives
showed modest or low EC50 values (Table 2). Furthermore,
we calculated the correlation between PR inhibitory
activity and antiviral activity, which showed a correlation
value of 0.85 (P \ 0.05).
To test whether these compounds are indeed targeting
viral PR (Fig. 3), we co-transfected 293T cells with HIV
Gag/Pol and Gag expressing plasmids (pGAGPOL and
pGAG), in the presence of different compounds. Since,
during HIV morphogenesis, the Gag and Gag–Pol precur-
sor need to be cleaved by viral PR to generate different
structural and enzymatic proteins including Gagp24, we
can easily test the effect of different compounds on PR’s
activity by measuring Gagp24 level in the cells by anti-p24
Conclusion
In conclusion, we modified the 4-hydroxy-pyran-2-one,
especially introduced heteroatoms into the substituents to
detect the interaction with the binding pockets. The results
indicated that the heteroatom (S or O) at the C-6 position of
the pyrone was disadvantageous to fit the S2 pocket,
whereas ethoxyl groups at C-20 and C-50 of the phenyl ring
0
0
could enhance the affinities to the S1 and S2 pockets and
improve the inhibitory activity. The most potent compound
10f which inhibited HIV-1 PR in vitro (IC50 = 3.5 nM)
also exhibited significant antiviral activity in a cell-based
SIV infection assay with an EC50 value at 2.9 lM and
inhibited the PR activity in 293T cells.
123

204
Med Chem Res (2011) 20:200–209
5,6-Dihydro-4-hydroxy-6-phenyl-6-
Experimental section
((phenylthio)methyl)pyran-2-one (8a)
General
Methyl acetoacetate (3.4 ml, 32 mmol) was added drop-
wise to a slurry of hexane-washed sodium hydride (0.84 g,
35 mmol) in anhydrous THF at 0°C and the reaction stirred
at 0°C for 15 min. n-Butyllithium (15 ml, 2.4 mol/l) was
then added at 0°C and the reaction stirred at 0°C for
15 min. Compound 5 (3.42 g, 15 mmol) in THF was added
to the dianion, and the reaction was stirred at 0°C for
30 min, and then allowed to warm to room temperature.
The mixture was stirred for 16 h at room temperature.
Water or 0.1 N NaOH was added to the reaction mixture
and stirred for 30 min. After extracting with Et2O, the
aqueous layer was cooled to 0°C and acidified with 6 N
HCl to pH 1–2. The aqueous layer was extracted with
EtOAc (39 30 ml). The organic extracts were combined,
dried over MgSO4, and concentrated. After being purified
by column chromatography (silica gel, petroleum ether/
ethyl acetate = 5:1), 8a was obtained as an off-white solid,
2.04 g, mp 122–124°C, yield = 43.5%. EI-MS m/z: 312
(M?), 189, 123. 1H NMR(CDCl3) d3.26 (1H, d,
J = 22.5 Hz, CH2), 3.28 (1H, d, J = 22.5 Hz, CH2), 3.33
(1H, d, J = 10.5 Hz, CH2), 3.36 (1H, d, J = 10.5 Hz,
CH2), 3.55 (1H, d, J = 17.4 Hz, SCH2), 3.57 (1H,d,
J = 17.4 Hz, SCH2), 7.19–7.42 (10H, m, Ar–H).
All reactions were performed with commercially available
reagents and they were used without further purification.
Solvents were dried by standard methods and stored over
molecular sieves. All reactions were monitored by thin-
layer chromatography and viewed with UV light. Melting
points were determined on an XA-4 instrument. All the
title compounds were characterized by 1H NMR spectra on
a Varian 300 MHz photometer using the solvents descri-
bed. Chemical shifts were reported in parts per million
relative to tetramethylsilane for deteriorated water (D2O).
Signals were quoted as s (singlet), d (doublet), t (triplet), q
(quartet), and m (multiplet). Mass spectra were measured
on a VG-ZAB-HS spectrometer or an ABI QSTAR
spectrometer.
1-Phenyl-2-(phenylthio)ethanone (5)
a-Bromoacetophenone (5.6 g, 28 mmol) was stirred in
ethanol (100 ml) with anhydrous K2CO3 (4.2 g, 30 mmol).
Benzenethiol (3.3 g, 30 mmol) was added, and stirring was
continued for 1 h. The reaction mixture was filtered and
diluted with CHCl3 (200 ml), and the organic layer was
washed with H2O (49 50 ml). The CHCl3 solution was
dried (Na2SO4), filtered, and concentrated on a rotary
evaporator under reduced pressure. The product was re-
crystallized (petroleum ether/ethyl acetate = 50:1) to give
5.5 g (87% yield) of the title compound. mp 53–55°C.
(Seshadri et al., 1981)
5,6-Dihydro-4-hydroxy-6-((naphthalen-1-
yloxy)methyl)-6-phenylpyran-2-one (8b)
Compound 8b was prepared in the same way as 8a,
yield = 62%, mp 154–156°C. EI-MS m/z: 346 (M?), 158,
144. 1H NMR (CDCl3) d3.42 (1H, d, J = 17.4 Hz, CH2), 3.81
(1H, d, J = 17.4 Hz, CH2), 4.23 (1H, d, J = 10.2 Hz, OCH2),
4.46 (1H, d, J = 10.2 Hz, OCH2), 5.51 (1H, s, CH=COH),
6.73 (1H, d, J = 7.2 Hz, Ar–H), 7.27–7.59 (9H, m, Ar–H),
7.79–7.82 (1H, m, Ar–H), 8.17–8.20 (1H, m, Ar–H).
2-(Naphthalen-1-yloxy)-1-phenylethanone (6)
a-Bromoacetophenone (5.6 g, 28 mmol) was stirred in
acetone (100 ml) with anhydrous K2CO3 (4.2 g, 30 mmol).
naphthalen-1-ol (4.4 g, 30 mmol) was added, and the
mixture was refluxed for 2 h. The reaction mixture was
quenched with water and allowed to reach room tempera-
ture. The aqueous layer was extracted with Et2O (49
50 ml). The combined organic fraction was washed (1 N
NaOH), dried (Na2SO4), filtered, and concentrated on a
rotary evaporator under reduced pressure. The product was
recrystallized to give 6.2 g (85% yield) of the title com-
pound. mp 71–73°C (Wang et al., 1998).
5,6-Dihydro-4-hydroxy-6-((naphthalen-2-
yloxy)methyl)-6-phenylpyran-2-one (8c)
Compound 8c was prepared in the same way as 8a, yield =
1
67%, mp 100–102°C. EI-MS m/z: 346 (M?), 158, 144. H
NMR (CDCl3) d3.32 (1H, d, J = 17.4 Hz, CH2), 3.79 (1H,
d, J = 17.4 Hz, CH2), 4.14 (1H, d, J = 10.2 Hz, OCH2),
4.39 (1H, d, J = 10.2 Hz, OCH2), 5.73 (1H, s, CH=COH),
7.05–7.77 (12H, m, Ar–H).
5,6-Dihydro-4-hydroxy-6-phenyl-3-(phenylthio)-6-
2-(Naphthalen-3-yloxy)-1-phenylethanone (7)
((phenylthio)methyl)pyran-2-one (9a)
Compound 7 was prepared in the same way as 6,
yield = 83%, mp 101–104°C (Wang et al., 1998).
Compound 8a (624 mg, 2 mmol) was stirred in t-BuOH
(50 ml) with NBS (356 mg, 2 mmol) in the dark. The
123

Med Chem Res (2011) 20:200–209
205
reaction mixture was refluxed for 2 h. The solvent was
evaporated, and the residue was partitioned between CHCl3
and water. The aqueous layer was extracted with CHCl3
(49 30 ml). The combined organic layer was washed with
brine, dried (Na2SO4), and concentrated. The crude product
was dissolved in CHCl3 (50 ml). To the solution, ben-
zenethiol (230 mg, 2.1 mmol) was added. The mixture was
cooled to 0°C (ice bath) and piperidine (0.2 ml) was added.
The reaction mixture was stirred at room temperature for
2 h. Water was added and the aqueous layer was extracted
with CHCl3 (29 15 ml). The combined organic layer was
washed with brine, dried (Na2SO4), and concentrated. After
being purified by column chromatography (silica gel,
dichloromethane/methanol = 100:1), 9a was obtained as
an off-white solid, 353 mg, yield = 42%, mp 173–175°C.
EI-MS m/z: 420 (M?), 312, 105. 1H NMR (CDCl3) d: 3.38
(1H, d, J = 14.1 Hz, CH2), 3.43 (1H, d, J = 17.7 Hz,
SCH2), 3.58 (1H, d, J = 17.7 Hz, SCH2), 3.64 (1H, d,
J = 14.1 Hz, CH2), 6.55 (2H, d, J = 7.5 Hz, Ar–H),
6.93–7.19 (3H, m, Ar–H), 7.19–7.50 (10H, m, Ar–H).
d, J = 17.4 Hz, SCH2), 3.59 (1H, d, J = 17.4 Hz, SCH2),
3.62 (1H, d, J = 13.8 Hz, CH2), 6.65 (1H, t, J = 6.6 Hz,
Ar–H), 6.90 (1H, t, J = 6.6 Hz, Ar–H), 7.10–7.52 (12H,
m, Ar–H).
3-(2,5-Dimethylphenylthio)-5,6-dihydro-4-hydroxy-6-
phenyl-6-((phenylthio)methyl)pyran-2-one (9e)
9e was obtained as an off-white solid, 466 mg, yield =
52%, mp 156–158°C. EI-MS m/z: 448 (M?), 325. 1H NMR
(CDCl3) d 1.91 (3H, s, CH3), 2.28 (3H, s, CH3), 3.38 (1H,
d, J = 13.8 Hz, CH2), 3.41 (1H, d, J = 17.4 Hz, SCH2),
3.62 (1H, d, J = 13.8 Hz, CH2), 3.64 (1H, d, J = 17.4 Hz,
SCH2), 6.78 (1H, d, J = 7.8 Hz, Ar–H), 6.98 (1H, d,
J = 7.8 Hz, Ar–H), 7.21–7.48 (11H, m, Ar–H).
3-(2,5-Diethoxyphenylthio)-5,6-dihydro-4-hydroxy-6-
phenyl-6-((phenylthio)methyl)pyran-2-one (9f)
9f was obtained as an off-white oil, 588 mg, yield = 54%.
EI-MS m/z: 508 (M?), 464, 385. 1H NMR (CDCl3) d
1.34–1.42 (6H, m, CH3CH2O), 3.18 (1H, d, J = 17.4 Hz,
SCH2), 3.34 (1H, d, J = 14.1 Hz, CH2), 3.47 (1H, d,
J = 17.4 Hz, SCH2), 3.53 (1H, d, J = 14.1 Hz, CH2),
3.87–3.99 (4H, m, CH3CH2O), 6.74 (2H, d, J = 2.7 Hz),
6.99 (2H, d, J = 2.7 Hz), 7.14–7.49 (9H, m).
3-(o-Tolylthio)-5,6-dihydro-4-hydroxy-6-phenyl-6-
((phenylthio)methyl)pyran-2-one (9b)
The compound was obtained in the same way from 2-
methylbenzenethiol and compound 8a in the same proce-
dure for 9a. 9b was obtained as an off-white solid, 443 mg,
yield = 51%, mp 162–163°C. EI-MS m/z: 434 (M?), 325,
3-(Benzylthio)-5,6-dihydro-4-hydroxy-6-phenyl-6-
1
311. H NMR (CDCl3) d 1.25 (s, 3H, CH3), 3.36 (d, 1H,
((phenylthio)methyl)pyran-2-one (9g)
J = 13.8 Hz, CH2), 3.43 (d, 1H, J = 17.4 Hz, SCH2), 3.57
(d, 1H, J = 17.4 Hz, SCH2), 3.62 (d, J = 13.8 Hz, CH2),
6.58 (s, 1H, Ar–H), 6.96 (s, 1H, Ar–H), 7.05 (d, 1H,
J = 7.2 Hz, Ar–H), 7.15–7.58 (m, 11H, Ar–H).
9g was obtained as an off-white solid, 373 mg, yield =
43%, mp 136–138°C EI-MS m/z: 434 (M?), 311. 1H NMR
(CDCl3) d 3.05 (1H, d, J = 17.4 Hz, SCH2), 3.33 (2H, s,
SCH2), 3.49 (1H, d, J = 7.5 Hz, CH2), 3.54 (1H, d,
J = 7.5 Hz, CH2), 3.72 (1H, d, J = 17.4 Hz, SCH2), 6.55
(2H, d, J = 6.6 Hz, Ar–H), 7.17–7.50 (13H, m, Ar–H).
3-(2-Ethylphenylthio)-5,6-dihydro-4-hydroxy-6-
phenyl-6-((phenylthio)methyl)pyran-2-one (9c)
9c was obtained as an off-white solid, 488 mg, yield =
54%, mp 105–107°C. MS (EI) m/z: 448 (M?), 325, 311. 1H
NMR (CDCl3) d 1.22 (3H, t, J = 7.5 Hz, CH2CH3),
2.68–2.75 (2H, m, CH2CH3), 3.38 (1H, d, J = 14.1 Hz,
CH2), 3.44 (1H, d, J = 17.4 Hz, SCH2), 3.60 (1H, d,
J = 17.4 Hz, SCH2), 3.65 (1H, d, J = 14.1 Hz, CH2), 6.58
(1H, s, Ar–H), 6.98 (1H, d, J = 6.6 Hz, Ar–H), 7.05 (1H,
d, J = 6.6 Hz, Ar–H), 7.17–7.31 (5H, m, Ar–H), 7.33–7.47
(6H, m, Ar–H).
5,6-Dihydro-4-hydroxy-6-((naphthalen-1-
yloxy)methyl)-6-phenyl-3-(phenylthio)pyran-2-one
(10a)
Compound 8b (692 mg, 2 mmol) was stirred in t-BuOH
(50 ml) with NBS (356 mg, 2 mmol) in the dark. The
reaction mixture was refluxed for 2 h. The solvent was
evaporated, and the residue was partitioned between CHCl3
and water. The aqueous layer was extracted with CHCl3
(49 30 ml). The combined organic layer was washed with
brine, dried (Na2SO4), and concentrated. The crude product
was dissolved in CHCl3 (50 ml). To the solution, ben-
zenethiol (230 mg, 2.1 mmol) was added. The mixture was
cooled to 0°C (ice bath) and piperidine (0.2 ml) was added.
The reaction mixture was stirred at room temperature for
2 h. Water was added and the aqueous layer was extracted
3-(2-Chlorophenylthio)-5,6-dihydro-4-hydroxy-6-
phenyl-6-((phenylthio)methyl)pyran-2-one (9d)
9d was obtained as an off-white solid, 368 mg, yield =
1
40%, mp 83–85°C. EI-MS m/z: 454 (M?), 331, 311. H
NMR (CDCl3) d 3.36 (1H, d, J = 13.8 Hz, CH2), 3.42 (1H,
123

206
Med Chem Res (2011) 20:200–209
3-(2,5-Dimethylphenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-1-yloxy)methyl)-6-phenylpyran-
2-one (10e)
with CHCl3 (29 15 ml). The combined organic layer was
washed with brine, dried (Na2SO4), and concentrated. After
being purified by column chromatography (silica gel,
dichloromethane/methanol = 150:1), 10a was obtained as
an off-white solid, 505 mg, yield = 55%, mp 164–166°C.
Yield = 56%. mp 176–178°C, EI-MS m/z: 482 (M?), 325,
339. 1H NMR (300 MHz, CDCl3) d 1.92 (s, 3H, CH3), 2.31
(s, 3H, CH3), 3.58 (d, 1H, J = 17.7 Hz, CH2), 3.92 (d, 1H,
J = 17.7 Hz, CH2), 4.25 (d, 1H, J = 9.9 Hz, OCH2), 4.50
(d, 1H, J = 9.9 Hz, OCH2), 6.74–6.80 (m, 2H, Ar–H), 6.95
(d, 1H, J = 7.2 Hz, Ar–H), 7.36–7.41 (m, 2H, Ar–H),
7.45–7.52 (m, 6H, Ar–H),7.66 (d, 2H, J = 6.6 Hz, Ar–H),
7.76–7.81 (m, 2H, Ar–H).
1
EI-MS m/z: 454 (M?), 346, 144. H NMR (CDCl3) d 3.10
(d, 1H, J = 20.4 Hz, CH2), 3.46 (d, 1H, J = 20.4 Hz,
CH2), 3.59 (d, 1H, J = 17.4 Hz, OCH2), 3.89 (d, 1H,
J = 17.4 Hz, OCH2), 6.60 (d, 1H, J = 7.2 Hz, Ar–H),
6.74–6.78 (m, 1H, Ar–H), 6.96–7.06 (m, 2H, Ar–H),
7.30–7.36 (m, 1H, Ar–H), 7.46–7.57 (m, 10H, Ar–H), 7.63
(m, 1H, Ar–H), 7.80 (m, 1H, Ar–H).
3-(2,5-Diethoxyphenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-1-yloxy)methyl)-6-phenylpyran-
2-one (10f)
3-(o-Tolylthio)-5,6-dihydro-4-hydroxy-6-((naphthalen-
1-yloxy)methyl)-6-phenylpyran-2-one (10b)
Yield = 55%. mp 151–153°C. EI-MS m/z: 468 (M?), 311,
144. H NMR (CDCl3) d 2.38 (3H, s, CH3), 3.61 (1H, d,
1
Yield = 51%. mp 142–144°C. EI-MS m/z: 542 (M?), 346,
498. H NMR (CDCl3) d 1.35–1.43 (6H, m, CH3CH2O),
1
J = 17.7 Hz, CH2), 3.90 (1H, d, J = 17.7 Hz, CH2), 4.28
(1H, d, J = 9.9 Hz, OCH2), 4.57 (1H, d, J = 9.9 Hz,
OCH2), 6.60 (1H, s, Ar–H), 6.77 (1H, d, J = 7.5 Hz, Ar–
H), 6.96 (1H, d, J = 7.2 Hz, Ar–H), 7.05 (1H, d,
J = 7.2 Hz, Ar–H), 7.38 (1H, t, J = 7.8 Hz, Ar–H),
7.41–7.59 (7H, m, Ar–H), 7.64–7.67 (3H, m, Ar–H),
7.79–7.82 (1H, m, Ar–H).
3.37 (1H, d, J = 17.4 Hz, CH2), 3.74 (1H, d, J = 17.4 Hz,
CH2), 3.90–3.99 (4H, m, CH3CH2O), 4.20 (1H, d,
J = 9.9 Hz, OCH2), 4.42 (1H, d, J = 9.9 Hz, OCH2),
6.70–6.79 (3H, m, Ar–H), 7.07 (1H, d, J = 2.7 Hz, Ar–H),
7.28–7.38 (4H, m, Ar–H), 7.43–7.54(6H, m, Ar–H),
7.77–7.80 (1H, m, Ar–H).
3-(Benzylthio)-5,6-dihydro-4-hydroxy-6-((naphthalen-
3-(2-Ethylphenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-1-yloxy)methyl)-6-phenylpyran-2-one
(10c)
1-yloxy)methyl)-6-phenylpyran-2-one (10g)
Yield = 45%. mp 167–169°C. EI-MS m/z: 468 (M?), 144,
1
91. H NMR (CDCl3) d 3.22 (1H, d, J = 17.4 Hz, CH2),
Yield = 57%. mp 102–104°C. EI-MS m/z: 482 (M?), 339,
325. 1H NMR (CDCl3) d 1.27 (3H, t, J = 7.5 Hz,
CH2CH3), 2.72–2.80 (2H, m, CH2CH3), 3.62 (1H, d,
J = 17.7 Hz, CH2), 3.91 (1H, d, J = 17.7 Hz, CH2), 4.30
(1H, d, J = 9.9 Hz, OCH2), 4.55 (1H, d, J = 9.9 Hz,
OCH2), 6.59 (1H, t, J = 7.5 Hz, Ar–H), 6.79 (1H, d,
J = 7.5 Hz, Ar–H), 6.98–7.03 (1H, Ar–H), 7.05 (1H, d,
J = 7.5 Hz, Ar–H), 7.38 (2H, t, J = 8.1 Hz, Ar–H),
7.47–7.55 (6H, m, Ar–H), 7.67–7.70 (3H, m, Ar–H),
7.81–7.84 (1H, m, Ar–H).
3.56 (2H, m, SCH2), 3.80 (1H, d, J = 17.4 Hz, CH2), 4.17
(1H, d, J = 9.3 Hz, OCH2), 4.41 (1H, d, J = 9.3 Hz,
OCH2), 6.72 (1H, d, J = 7.2 Hz, Ar–H), 6.90 (2H, s, Ar–
H), 7.19–7.32 (6H, m, Ar–H), 7.44–7.60 (7H, m, Ar–H),
7.81 (1H, s, Ar–H).
5,6-Dihydro-4-hydroxy-6-((naphthalen-2-
yloxy)methyl)-6-phenyl-3-(phenylthio)pyran-
2-one (11a)
Compound 8c (692 mg, 2 mmol) was stirred in t-BuOH
(50 ml) with NBS (356 mg, 2 mmol) in the dark. The
reaction mixture was refluxed for 2 h. The solvent was
evaporated, and the residue was partitioned between CHCl3
and water. The aqueous layer was extracted with CHCl3
(49 30 ml). The combined organic layer was washed with
brine, dried (Na2SO4), and concentrated. The crude product
was dissolved in CHCl3 (50 ml). To the solution, ben-
zenethiol (230 mg, 2.1 mmol) was added. The mixture was
cooled to 0°C (ice bath) and piperidine (0.2 ml) was added.
The reaction mixture was stirred at room temperature for
2 h. Water was added and the aqueous layer was extracted
3-(2-Chlorophenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-1-yloxy)methyl)-6-phenylpyran-2-one
(10d)
Yield = 39%. mp 173–175°C. EI-MS m/z: 488 (M?), 345,
1
331. H NMR (CDCl3) d 3.11 (1H, d, J = 20.4 Hz, CH2),
3.46 (1H, d, J = 20.4 Hz, CH2), 4.25 (1H, d, J = 10.2 Hz,
OCH2), 4.54 (1H, d, J = 10.2 Hz, OCH2), 6.78 (1H, d,
J = 7.5 Hz, Ar–H), 7.03–7.09 (2H, m, Ar–H), 7.27–7.34
(2H, m, Ar–H), 7.47–7.54 (10H, m, Ar–H), 7.78–7.85 (1H,
m, Ar–H).
123

Med Chem Res (2011) 20:200–209
207
with CHCl3 (29 15 ml). The combined organic layer was
washed with brine, dried (Na2SO4), and concentrated. After
being purified by column chromatography (silica gel,
dichloromethane/methanol = 150:1), 11a was obtained as
an off-white solid, 488 mg, yield = 53%. mp 182–184°C.
CH3), 3.47 (1H, d, J = 17.7 Hz, CH2), 3.91 (1H, d,
J = 17.7 Hz, CH2), 4.15 (1H, d, J = 10.2 Hz, OCH2),
4.44 (1H, d, J = 10.2 Hz, OCH2), 6.79 (1H, d, J = 7.8 Hz,
Ar–H), 6.95 (1H, d, J = 7.8 Hz, Ar–H), 7.08 (1H, s, Ar–
H), 7.16–7.20 (1H, m, Ar–H), 7.27–7.49 (5H, m, Ar–H),
7.61–7.79 (6H, m, Ar–H).
1
EI-MS m/z: 454 (M?), 311, 297. H NMR (CDCl3) d 3.46
(1H, d, J = 17.7 Hz, CH2), 3.88 (1H, d, J = 17.7 Hz,
CH2), 4.17 (1H, d, J = 10.2 Hz, OCH2), 4.46 (1H, d,
J = 10.2 Hz, OCH2), 6.63 (2H, d, J = 7.2 Hz, Ar–H),
6.97–7.08 (4H, m, Ar–H), 7.15–7.19 (1H, m, Ar–H),
7.35–7.48 (5H, m, Ar–H), 7.60–7.78 (5H, m, Ar–H).
3-(2,5-Diethoxyphenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-2-yloxy)methyl)-6-phenylpyran-
2-one (11f)
Yield = 53%. mp 135–137°C. EI-MS m/z: 542 (M?), 498,
1
3-(o-Tolylthio)-5,6-dihydro-4-hydroxy-6-((naphthalen-
2-yloxy)methyl)-6-phenylpyran-2-one (11b)
385. H NMR (CDCl3) d 1.35–1.44 (6H, m, CH3CH2O),
3.24 (1H, d, J = 17.7 Hz, CH2), 3.73 (1H, d, J = 17.7 Hz,
CH2), 3.89–3.99 (4H, m, CH3CH2O), 4.10 (1H, d,
J = 10.2 Hz, CH2), 4.34 (1H, d, J = 10.2 Hz, CH2),
6.71–6.77 (2H, m, Ar–H), 7.02–7.12 (3H, m, Ar–H),
7.33–7.42 (5H, m, Ar–H), 7.48–7.51 (3H, m, Ar–H),
7.65–7.77 (2H, m, Ar–H).
Yield = 51%. mp 92–94°C. EI-MS m/z: 468 (M?), 346,
1
144. H NMR (CDCl3) d 2.33 (3H, s, CH3), 3.48 (1H, d,
J = 17.7 Hz, CH2), 3.90 (1H, d, J = 17.7 Hz, CH2), 4.18
(1H, d, J = 10.2 Hz, OCH2), 4.48 (1H, d, J = 10.2 Hz,
OCH2), 6.64 (1H, t, J = 7.2 Hz, Ar–H), 6.95 (1H, t,
J = 7.2 Hz, Ar–H), 7.03–7.09 (2H, m, Ar–H), 7.17–7.21
(1H, m, Ar–H), 7.36–7.50 (5H, m, Ar–H), 7.62–7.70 (4H,
m, Ar–H), 7.75–7.79 (2H, m, Ar–H).
3-(Benzylthio)-5,6-dihydro-4-hydroxy-6-((naphthalen-
2-yloxy)methyl)-6-phenylpyran-2-one (11g)
Yield = 52%. mp 137–139°C. EI-MS m/z: 468 (M?), 311,
1
3-(2-Ethylphenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-2-yloxy)methyl)-6-phenylpyran-
2-one (11c)
144. H NMR (CDCl3) d 3.13 (1H, d, J = 17.7 Hz, CH2),
3.57 (2H, m, SCH2), 3.76 (1H, d, J = 17.7 Hz, CH2), 4.10
(1H, d, J = 9.9 Hz, OCH2), 4.35 (1H, d, J = 9.9 Hz,
OCH2), 6.72 (1H, d, J = 9.9 Hz, Ar–H), 6.84–6.87 (2H, m,
Ar–H), 7.05–7.17 (7H, m, Ar–H), 7.43–7.48 (5H, m, Ar–
H), 7.50–7.53 (2H, m, Ar–H).
Yield = 56%. mp 150–152°C. EI-MS m/z: 482 (M?), 346,
325. 1H NMR (CDCl3) d 1.23 (3H, t, J = 7.5 Hz,
CH2CH3), 2.70–2.78 (2H, m, CH2CH3), 3.47 (1H, d,
J = 17.7 Hz, CH2), 3.89 (1H, d, J = 17.7 Hz, CH2), 4.18
(1H, d, J = 10.2 Hz, OCH2), 4.46 (1H, d, J = 10.2 Hz,
OCH2), 6.60 (1H, t, J = 7.2 Hz, Ar–H), 6.99–7.20 (4H, m,
Ar–H), 7.35–7.49 (5H, m, Ar–H), 7.61–7.78 (6H, d, Ar–H).
PR inhibition assay
The tested compounds were dissolved in 4.0 ll DMSO and
incubated with HIV-1 PR in 200 ll buffer (0.1 M MES,
0.2 M NaCl, 5 mM EDTA, pH5.5) for 10 min. Enzymatic
assays were initiated by the addition of PR substrate (Lys-
Ala-Arg-Val-Leu-Phe(NO2)-Glu-Ala-Met).The hydrolysis
of the substrate resulted in a linear increase in UV absor-
bance at 310 nm over a 30-min period (Nashed et al.,
1989). The IC50 was defined as the compounds concen-
tration required to inhibit the final absorbance by 50% and
was the average of at least two runs. Indinavir (IDV) was
used as the positive control.
3-(2-Chlorophenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-2-yloxy)methyl)-6-phenylpyran-
2-one (11d)
Yield = 41%. mp 73–75°C. EI-MS m/z: 488 (M?), 346,
1
144. H NMR (CDCl3) d 3.47 (1H, d, J = 17.7 Hz, CH2),
3.90 (1H, d, J = 17.7 Hz, CH2), 4.17 (1H, d, J = 10.2 Hz,
OCH2), 4.47(1H, d, J = 10.2 Hz, OCH2), 6.71 (1H, s, Ar–
H), 7.00–7.24 (6H, m, Ar–H), 7.36–7.47 (5H, m, Ar–H),
7.62–7.79 (4H, m, Ar–H).
Anti-SIV assay
3-(2,5-Dimethylphenylthio)-5,6-dihydro-4-hydroxy-6-
((naphthalen-2-yloxy)methyl)-6-phenylpyran-
2-one (11e)
Inhibition of SIV-induced syncytium in CEM174 cell
culture was measured in a 96-well microplate containing
2 9 105 CEM cells/ml infected with 100 TCID50 of SIV
per well and containing appropriate dilutions of the tested
compounds. After 5 days of incubation at 37°C in 5% CO2-
containing humidified air, CEM giant (syncytium) cell
Yield = 60%. mp 73–75°C. EI-MS m/z: 482 (M?), 346,
1
425. H NMR (CDCl3) d 1.92 (3H, s, CH3), 2.30 (3H, s,
123

208
Med Chem Res (2011) 20:200–209
mode and its application in the design of related analogs. J Med
Chem 37:2664–2677
formation was examined microscopically. The EC50 was
defined as the concentration required to protect CEM cells
against the cytopathogenicity of SIV by 50%. The TC50
was the concentration that elicits cytotoxicity in 50% of
uninfected CEM cells under some conditions.
Mahlknecht U, Deng C, Lu MC, Greenough TC, Sullivan JL, O’Brien
WA, Herbein G (2000) Resistance to apoptosis in HIV-infected
CD4? T lymphocytes is mediated by macrophages: role for Nef
and immune activation in viral persistence. J Immunol 165:
6437–6446
Meek TD (1992) Inhibitors of HIV-1 protease. J Enzym Inhib
6:65–98
Western immunoblot assay
Morris GM, Goodsell DS, Halliday RS, Huey R, Hart WE, Belew RK,
Olson AJ (1998) Automated docking using a Lamarckian genetic
algorithm and an empirical binding free energy function.
J Comput Chem 19:1639–1662
Nashed NT, Louis JM, Sayer JM, Wondrak EM, Mora PT, Oroszlan
S, Jerina DM (1989) Continuous spectrophotometric assay for
retroviral protease of HIV-1 and AMV. Biochem Biophy Res
Commun 163:1079–1085
The confluent 293T cells were trypsinized and seeded onto
a 6-well plate 24 h prior to transfection with plasmids
pGAG and pGAGPOL (Chien et al., 2006). 12 h after
transfection by standard calcium phosphate precipitation
method, the culture medium was removed and the cells
were washed twice with phosphate-buffered saline. Then
fresh medium was added together with diluted compounds
at a final concentration of 20 lM. After 48 h post-trans-
fection, the medium was collected and ultra-filtrated (cut-
ting off molecular weight: 30 kDa). The filtration was
mixed with the cells which were scratched form the plate
on ice base. The equal amounts of samples were subjected
to SDS–PAGE and were transferred onto nitrocellulose
membrane. The membrane was blocked with 5% gelatin in
tris-buffered saline containing 0.05% Tween 20 (TBST),
followed by incubation with the HRP-conjugated anti-p24
monoclonal antibody (Beijing Perfect Biotechnology, Ltd.,
Beijing, People’s Republic of China) at a 1:500 dilution in
5% gelatin-TBST for 1 h on a rocking platform at room
temperature. The membranes were then washed thrice
(10 min each) with TBST. The HRP activity was deter-
mined with diaminobenzidine. IDV was used as positive
control.
Peter M, Knudsen LB, Wiberg FC, Carr RD (1998) Discovery and
structure–activity relationship of the first non-peptide competi-
tive human glucagon receptor antagonists.
41:5150–5157
J Med Chem
Redshaw S (1994) Inhibitors of HIV proteinase. Exp Opin Invest
Drugs 3:273–286
Romines KR, Chrusciel RA (1995) 4-Hydroxypyrones and related
templates as nonpeptidic HIV protease inhibitors. Curr Med
Chem 2:825–838
Seshadri R, Pegg WJ, Israel M (1981) Reaction of halomethyl ketones
with thiols and selenols: substitution vs reduction. J Org Chem
46:2596–2598
Skulnick HI, Johnson PD, Howe W, Tomich PK, Chong KT,
Watenpaugh KD, Janakiraman MN, Hinshaw RR, Zipp GL,
Ruwart MJ, Schwende FJ, Zhong WZ, Padbury GE, Dalga RJ,
Shiou L, Possert PL, Rush BD, Wilkinson KF, Howard GM,
Toth LN, Williams MG, Kakuk TJ, Cole SL, Zaya RM, Lovasz
KD, Morris JK, Romines KR, Thaisrivongs S, Aristoff PA
(1995) Structure-based design of sulfonamide-substituted non-
peptidic HIV protease inhibitors. J Med Chem 38:4968–4971
Sun CL, Pang RF, Zhang H, Yang M (2005) Design, synthesis, and
biological evaluation of novel 4-hydroxypyrone derivatives as
HIV-1 protease inhibitors. Bioorg Med Chem Lett 15:3257–3262
Tait BD, Domagala JM, Ellsworth EL, Gajda C, Hagen SE, Hamilton
H, Vara Prasad JVN, Ferguson D, Graham N, Hupe D, Nouhan
C, Tummino PJ, Humblet C, Lunney EA, Pavlovsky A, Rubin
RJ, Baldwin ET, Bhat TN, Erickson JW, Gulnik S, Liu BS
(1997) 4-Hydroxy-5, 6-dihydropyrones. 2. Potent non-peptide
inhibitors of HIV protease. J Med Chem 40:3781–3792
Thaisrivongs S (1994) HIV protease inhibitors. Annu Rep Med Chem
29:133–144
Thaisrivongs S, Romero DL, Tommasi RA, Janakiraman MN,
Strohbach JW, Turner SR, Biles C, Morge RR, Johnson PD,
Aristoff PA, Tomich PK, Lynn JC, Horng MM, Chong KT,
Hinshaw RR, Howe WJ, Finzel BC, Watenpaugh KD (1996)
Structure-based design of HIV protease inhibitors: 5,6-dihydro-
4-hydroxy-2-pyrones as effective, nonpeptidic inhibitors. J Med
Chem 39:4630–4642
Tummino PJ, Vara Prasad JVN, Ferguson D, Nouhan C, Graham N,
Domagala JM, Ellsworth E, Gajda C, Hagen SE, Lunney EA,
Para KS, Tait BD, Pavlovsky A, Erickson JW, Gracheck S,
McQuade TJ, Hupe DJ (1996) Discovery and optimization of
nonpeptide HIV-1 protease inhibitors. Bioorg Med Chem 4:
1401–1410
Acknowledgment This study was supported by the National Sci-
ence Foundation of China (No. 30670415).
References
Chien AI, Liao WH, Yang DM, Wang CT (2006) A domain directly
C-terminal to the major homology region of human immunode-
ficiency type 1 capsid protein plays a crucial role in directing
both virus assembly and incorporation of Gag-Pol. Virology
348:84–95
Huang XQ, Xu LS, Luo XM, Fan KN, Ji RY, Pei G, Chen KX, Jiang
HL (2002) Elucidating the inhibiting mode of AHPBA deriva-
tives against HIV-1 protease and building predictive 3D-QSAR
models. J Med Chem 45:333–343
Huff JR (1991) HIV protease: a novel chemotherapeutic target for
AIDS. J Med Chem 34:2305–2314
Lebon F, Ledecq M (2000) Approaches to the design of effective
HIV-1 protease inhibitors. Curr Med Chem 7:455–477
Leung D, Abbenante G, Fairlie DP (2000) Protease inhibitors: current
status and future prospects. J Med Chem 43:305–341
Lunney EA, Hagen SE, Domagala JM, Humblet C, Kosinski J, Tait
BD, Warmus JS, Wilson M, Ferguson D, Hupe D, Tummino PJ,
Baldwin ET, Bhat TN, Liu B, Erickson JW (1994) A novel
nonpeptide HIV-1 protease inhibitor: elucidation of the binding
Vara Prasad JVN, Boye FE, Domagala JM, Ellsworth EL, Gajda C,
Hamilton HW, Hagen SE, Markoski LJ, Steinbaugh BA, Tait
BD, Humblet C, Lunney EA, Pavlovsky A, Rubin JR,
Ferguson D, Graham N, Holler T, Hupe D, Nouhan C,
Tummino PJ, Urumov A, Zeikus E, Zeikus G, Gracheck SJ,
123

Med Chem Res (2011) 20:200–209
209
Saunders JM, VanderRoest S, Brodfuehrer J, Iyer K, Sinz M,
Gulnik SV (1999) Nonpeptidic HIV protease inhibitors
possessing excellent antiviral activities and therapeutic indices.
PD 178390: a lead HIV protease inhibitor. Bioorg Med Chem
7:2775–2800
Wang TC, Lee KH, Chen YL, Liou SS (1998) Synthesis and
anticancer evaluation of certain c-aryloxymethyl-a-methylene-c-
phenyl-c-butyrolactones. Bioorg Med Chem Lett 8:2773–2776
West ML, Fairlie DP (1995) Targeting HIV-1 PR: a test of drug-
design methodologies. Trends Pharmacol Sci 16:67–75
123