Probing multidrug-resistance and protein-ligand interactions with oxatricyclic designed ligands in HIV-1 protease inhibitors

Article abstract of DOI:10.1002/cmdc.201000318

A healthier HAART: We report the design, synthesis, biological evaluation, and X-ray crystallographic analysis of a new class of HIV-1 protease inhibitors. Compound 4 proved to be an extremely potent inhibitor toward various multidrug-resistant HIV-1 variants, representing a near 10-fold improvement over darunavir (DRV). Compound 4 also blocked protease dimerization with at least 10-fold greater potency than DRV.

Full text of DOI:10.1002/cmdc.201000318

MED
DOI: 10.1002/cmdc.201000318
Probing Multidrug-Resistance and Protein–Ligand Interactions with
Oxatricyclic Designed Ligands in HIV-1 Protease Inhibitors
Arun K. Ghosh,*[a] Chun-Xiao Xu,[a] Kalapala Venkateswara Rao,[a] Abigail Baldridge,[a] Johnson Agniswamy,[b]
Yuan-Fang Wang,[b] Irene T. Weber,[b] Manabu Aoki,[c] Salcedo Gomez Pedro Miguel,[c] Masayuki Amano,[c] and
Hiroaki Mitsuya[c, d]
The introduction of HIV-1 protease inhibitors (PIs) into highly
active antiretroviral therapy (HAART) in 1996 had a critical
impact in decreasing HIV-related morbidity and mortality.[1]
Indeed, HAART regimens with PIs initially suppressed HIV-1
replication in patients to undetectable HIV-1 RNA levels in
plasma.[2] However, one of the serious shortcomings of current
treatments is the rapid emergence of drug-resistant HIV
strains.[3] There is an urgent need for improved PIs for the
treatment of the increasing number of treatment-experienced
patients harboring multidrug-resistant HIV-1 strains.[4,5]
We recently reported a number of PIs that were developed
by incorporating structure-based designed novel nonpeptide
ligands/scaffolds that target the HIV-1 protease substrate bind-
ing site.[6–17] One of the PIs, darunavir (1, DRV, Figure 1), was
first approved for HIV/AIDS patients harboring drug-resistant
HIV who do not respond to other antiretroviral drugs.[11] Re-
cently, DRV has received full approval for all HIV/AIDS patients,
including children infected with HIV-1.[12] DRV has a stereo-
Figure 1. Structure of darunavir (DRV, 1) and protease inhibitors 2–4.
chemically defined fused bis-tetrahydrofuran (bis-THF) moiety
as the P2 ligand.[7,8] The X-ray crystal structures of the com-
plexes of both 1- and 2-bound HIV-1 protease revealed exten-
sive protein–ligand hydrogen bonding interactions involving
the backbone of HIV-1 protease throughout the active site.[13,14]
In particular, both oxygen atoms of the P2 bis-THF ligand are
involved in hydrogen bonding with Asp29 and Asp30 back-
bone NH groups.[15] In addition, the bicyclic ligand appears to
fill the hydrophobic pocket at the S2 subsite. The P2 bis-THF
ligand is responsible for the superior drug-resistance properties
of both DRV (1) and TMC-126 (2). In our preliminary investiga-
tion, we chose to incorporate para-methoxysulfonamide as the
P2’ ligand owing to its marked hydrogen bonding interaction
in the S2’ site. To combat drug resistance, our inhibitor design
strategies focused on maximizing inhibitor interactions with
the HIV-1 protease active site, particularly by promoting exten-
sive hydrogen bond interactions with the protein backbone
atoms.[15] We have recently shown that the enhancement of
’backbone binding’ leads to the design of PIs that maintain full
potency against a panel of multidrug-resistant HIV-1 variants.[17]
Based on our examination of the protein–ligand crystal struc-
ture of DRV-bound HIV-1 protease, we have further speculated
that the incorporation of another tetrahydrofuran ring on the
bis-THF ligand would provide additional ligand–binding site in-
teractions. Particularly, it appears that the ligand oxygen atoms
can effectively maintain backbone hydrogen bonding with
Asp29 and Asp30, and can fill the hydrophobic pocket effec-
tively. This in turn could further improve drug-resistance prop-
erties of the PIs. Such oxatricyclic ligands could have a variety
of possible stereochemical motifs, including syn-syn-syn (SSS-
type) and syn-anti-syn (SAS-type) isomers. Our X-ray crystal
structure-based preliminary modeling suggested that the SAS-
type ligand-based inhibitor 4 would make enhanced interac-
tions in the S2 subsite relative to the SSS-derived inhibitor 3
(Figure 1).
[a] Prof. Dr. A. K. Ghosh, Dr. C.-X. Xu, Dr. K. V. Rao, A. Baldridge
Department of Chemistry and Medicinal Chemistry
Purdue University, 560 Oval Drive, West Lafayette, IN 47907 (USA)
Fax: (+1)765-496-1612
E-mail: akghosh@purdue.edu
[b] J. Agniswamy, Y.-F. Wang, Prof. Dr. I. T. Weber
Department of Biology, Molecular Basis of Disease
Georgia State University, Atlanta, GA 30303 (USA)
The synthesis of the oxatricyclic tris-THF ligand with an SSS
configuration was carried out as shown in Scheme 1. Optically
active bis-THF derivatives 6 and 7 were conveniently prepared
in multi-gram quantities from dihydrofuran 5 in a three-step
sequence followed by lipase-catalyzed optical resolution as de-
scribed previously.[18,19] Optically active alcohol 7 was treated
with triphenylphosphine and iodine in the presence of imida-
zole to provide the corresponding iodide. Treatment of the re-
[c] M. Aoki, S. G. P. Miguel, M. Amano, Dr. H. Mitsuya
Departments of Hematology and Infectious Diseases
Kumamoto University School of Medicine, Kumamoto 860-8556 (Japan)
[d] Dr. H. Mitsuya
Experimental Retrovirology Section, HIV and AIDS Malignancy Branch
National Cancer Institute, Bethesda, MD 20892 (USA)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cmdc.201000318.
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Scheme 1. Synthesis of the syn-syn-syn tris-THF ligand 12.
sulting iodide with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)
furnished volatile bicyclic enol ether 8. Reaction of 8 with N-io-
dosuccinimide (NIS) and propargyl alcohol in dichloromethane
at 0–238C afforded iodoether 9 in 58% yield over three
steps.[18] Radical cyclization of 9 with tri(n-butyl)tin hydride in
the presence of azobisisobutyronitrile (AIBN) in toluene at
reflux provided tricyclic olefin 10. The relative stereochemistry
of the tricyclic core was established by extensive NMR experi-
ments (COSY, NOESY). Ozonolysis of the olefin, followed by l-
selectride reduction of the resulting ketone furnished endo-al-
Scheme 2. Synthesis of the syn-anti-syn tris-THF alcohol 18.
thiocarbamate, and 2) treatment of the resulting thiocarba-
mate with tri(n-butyl)tin hydride in the presence of AIBN in tol-
uene at reflux to provide olefin 17 in 75% yield over two
steps.[23] The stereochemistry of olefin 17 was established by
1H NMR spectroscopy. Olefin 17 was converted into endo-alco-
hol 18 by ozonolysis of the olefin followed by sodium borohy-
dride reduction of the resulting ketone to furnish 18 as a
single isomer. Mosher ester analysis[24] revealed high optical
purity (99% ee).
1
cohol 12 as a single isomer (by H NMR analysis).
The synthesis of tris-THF ligand with a SAS ring fused system
is shown in Scheme 2. Optically active (3S,3aR,6aS)-bis-THF al-
cohol ent-7 was readily obtained by saponification of acetate
derivative 6. It was converted into bicyclic enol ether ent-8 as
described above. This enol ether was exposed to acetone-free
dimethyldioxirane (DMDO)[20] in dichloromethane at ꢀ788C to
provide the corresponding epoxide. Treatment of the resulting
epoxide with a catalytic amount of sodium methoxide (10%)
in methanol provided epoxide-opened product 13 as a single
diastereomer.[21] The depicted stereochemistry of 13 was fully
supported by extensive NMR studies. Dess–Martin oxidation[22]
of 13 followed by l-selectride reduction of the resulting
ketone provided endo-alcohol 14 as a single isomer in 68%
yield over two steps. To append the third oxacyclic ring, alco-
hol 14 was first acylated, and the resulting acetate was treated
with trimethylsilyl trifluoromethanesulfonate (TMSOTf) and
propargyl alcohol, which afforded acetals 15 and 16 as a 4:1
mixture of diastereomers. The isomers could not be separated
at this stage; however, removal of the acetate provided the
corresponding alcohols, which were readily separated by
column chromatography. The major diastereomeric alcohol
was converted into tricyclic olefin 17 in a two-step sequence
involving: 1) reaction of alcohol with thiocarbonyldiimidazole
(TCDI) in dichloroethane (DCE) to provide the corresponding
The synthesis of tris-THF-containing PIs is shown in
Scheme 3. Optically active tris-THF ligand alcohols 12 and 18
were converted into the corresponding para-nitrophenyl car-
bonates 19 and 20 by treatment with para-nitrophenyl chloro-
formate and N-methylmorpholine (NMM). Treatment of amine
21,[25] synthesized previously, with activated carbonate 19 or
20 in the presence of diisopropylethylamine (DIPEA) provided
PIs 3 and 4 in 65% yield.
Inhibitor 3 shows potent inhibitory activity (Ki =60 pm). In
comparison, inhibitor 4 (GRL-0519A, Figure 1) has a Ki value of
5.9 pm, a 10-fold improvement over 3. Both PIs 3 (IC50 =
3.5 nm) and 4 (IC50 =1.8 nm) also showed excellent antiviral ac-
tivity against the wild-type HIV-1LAV. PI 4 (GRL-0519A) was the
most potent against a laboratory HIV-1 strain, HIV-1LAI, with an
EC50 value of 1.8 nm and a favorable cytotoxicity profile (CC50 =
44.6 mm) as examined by using MT-2 cells as target cells, pro-
ducing a selectivity index (CC50/EC50) of 24778.
We next examined GRL-0519A against a variety of primary
HIV-1 strains, which were isolated from patients with AIDS who
had failed a number of anti-HIV therapeutic regimens after re-
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values and fold differences ranging between 0.291 and
0.521 mm, and from 9 to 16, respectively. GRL-0519A exerted
the greatest potency among the three agents against wild-
type HIV-1ERS104pre, with an EC50 value of 0.6 nm. GRL-0519A was
less potent against the variants, with EC50 values ranging from
0.9 to 4.3 nm, and the fold difference was 2–7 relative to wild-
type HIV-1 (Table 1). Importantly, GRL-0519A is more potent
than DRV by a factor of 5.9–14 in comparing absolute concen-
trations of EC50 values.
Dimerization of HIV-1 protease subunits is an essential pro-
cess for the acquisition of proteolytic activity, which plays a
critical role in the maturation and replication of the virus.[29]
We previously demonstrated that a group of compounds, in-
cluding DRV and TPV, inhibit the dimerization of HIV-1 protease
monomer subunits as examined by a FRET-based HIV-1 expres-
sion assay that uses cyan (CFP) and yellow fluorescent protein
(YFP)-tagged protease monomers; other conventional FDA-ap-
proved PIs such as APV failed to block dimerization.[30] As
shown in Figure 2, the average CFPA/B ratio determined in the
cells transfected and cultured in the absence of drug was 1.1ꢁ
0.13, indicating that protease dimerization efficiently occurred.
In the same assay, in the presence of DRV at 0.1 and 1 mm, the
average CFPA/B ratios determined were 0.93ꢁ0.07 and 0.81ꢁ
0.11, respectively, indicating that DRV effectively inhibits pro-
tease dimerization at those concentrations. However, the aver-
age ratios were greater than 1.0 at 0.001 and 0.01 mm, indicat-
ing that no dimerization inhibition occurred at these lower
DRV concentrations, in line with the data we previously report-
ed.[30] We next examined whether GRL-0519A can block pro-
tease dimerization under exactly the same conditions in the
FRET-based HIV-1 expression assay. When the ratios were de-
termined in the cells transfected and cultured in the presence
of GRL-0519A at 0.01, 0.1, and 1 mm, the average values were
0.96ꢁ0.07, 0.84ꢁ0.09, and 0.84ꢁ0.11, respectively, indicating
that GRL-0519A can block protease dimerization more potent-
ly, by at least 10-fold, relative to
Scheme 3. Synthesis of inhibitors 3 and 4.
ceiving 9–11 anti-HIV-1 drugs over the previous 32–83 months,
and who proved to be highly resistant to multiple PIs.[9,26]
These primary strains contain 9–14 amino acid substitutions in
the protease-encoding region of the HIV-1 genome which
have been reported to be associated with HIV-1 resistance
against various PIs.[27] The substitutions identified include
Leu10!Ile (L10I; 6 of 6 isolates), M46I/L (6 of 6), I54V (4 of 6),
L63P (6 of 6), A71V/T (5 of 6), V82A (6 of 6), and L90M (4 of 6)
(see the footnote of Table 1).
Darunavir (DRV) is more potent against wild-type HIV-
1ERS104pre (EC50 =0.005 mm) than amprenavir (APV),[28] which has
an EC50 value of 0.032 mm. DRV was moderately less active
against a panel of multidrug-resistant HIV-1 variants, with EC50
values ranging from 0.011 to 0.031 mm. The fold difference in
EC50 values was 2–6 relative to its EC50 value against HIV-
1
ERS104pre. APV was less active against the variants, with EC50
DRV.
The X-ray crystal structure of
wild-type HIV-1 protease co-crys-
tallized with GRL-0519A was re-
fined at the near-atomic resolu-
tion of 1.27 ꢁ (PDB ID: 3OK9).
The structure comprises the pro-
tease dimer and the inhibitor in
two orientations related by a
1808 rotation with 55/45% occu-
pancies. The protease dimer
structure is essentially identical
to that in the protease–DRV
complex[31] with an RMSD of
0.16 ꢁ on Ca atoms. The inhibi-
tor is bound in the active site
cavity through a series of hydro-
gen bond interactions and
weaker CH···O interactions with
the main-chain atoms of the HIV-
Table 1. Antiviral activity of GRL-0519A (4), amprenavir (APV), and darunavir (DRV) against multidrug-resistant
clinical isolates in PHA-PBMs.[a]
EC50 [mm]
Virus
GRL-0519A
APV
DRV
HIV-1ERS104pre (wild-type: X4)
HIV-1MDR/B (X4)
HIV-1MDR/C (X4)
0.0006ꢁ0.0002
0.032ꢁ0.006
0.005ꢁ0.002
0.0043ꢁ0.0012 (7)
0.0009ꢁ0.0002 (2)
0.0027ꢁ0.0012 (5)
0.0022ꢁ0.0001 (4)
0.0027ꢁ0.0006 (5)
0.0028ꢁ0.0001 (5)
0.521ꢁ0.203 (16)
0.357ꢁ0.040 (11)
0.485ꢁ0.073 (15)
0.488ꢁ0.009 (15)
0.291ꢁ0.128 (9)
0.419ꢁ0.122 (13)
0.028ꢁ0.008 (6)
0.011ꢁ0.004 (2)
0.031ꢁ0.002 (6)
0.031ꢁ0.002 (6)
0.016ꢁ0.006 (3)
0.024ꢁ0.007 (5)
HIV-1MDR/G (X4)
HIV-1MDR/TM (X4)
HIV-1MDR/MM (R5)
HIV-1MDR/JSL (R5)
[a] The amino acid substitutions identified in the protease-encoding region of HIV-1ERS104pre, HIV-1B, HIV-1C, HIV-
1G, HIV-1TM, HIV-1MM, HIV-1JSL compared with the consensus type B sequence cited from the Los Alamos data-
base include L63P; L10I, K14R, L33I, M36I, M46I, F53I, K55R, I62V, L63P, A71V, G73S, V82A, L90M, I93L; L10I,
I15V, K20R, L24I, M36I, M46L, I54V, I62V, L63P, K70Q, V82A, L89M; L10I, V11I, T12E, I15V, L19I, R41K, M46L, L63P,
A71T, V82A, L90M; L10I, K14R, R41K, M46L, I54V, L63P, A71V, V82A, L90M, I93L; L10I, K43T, M46L, I54V, L63P,
A71V, V82A, L90M, Q92K; and L10I, L24I, I33F, E35D, M36I, N37S, M46L, I54V, R57K, I62V, L63P, A71V, G73S,
V82A, respectively. HIV-1ERS104pre served as a source of wild-type HIV-1. The EC50 values were determined by
using PHA-PBMs as target cells, and the inhibition of p24 gag protein production by each drug was used as an
endpoint. The numbers in parentheses represent the fold change in EC50 value for each isolate relative to the
IC50 value for wild-type HIV-1ERS104pre. All assays were conducted in duplicate, and the data shown represent
mean values ꢁSD derived from the results of two or three independent experiments.
1
protease (Figure 3A). The
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three conserved water molecules that surround the
guanidine side chain of Arg8’. The hydrogen bond
and van der Waals interactions of the third THF re-
strain the Arg8’ side chain in a single conformation,
thus preventing the formation of an alternate confor-
mation observed in the DRV complex. Furthermore,
the third THF ring packs neatly against the P1 phenyl
group of the inhibitor with better internal hydropho-
bic contacts than are possible for bis-THF in DRV. The
ring stereochemistry (SSS-type) in the tris-THF ligand
of 3 would not be able to make similar hydrophobic
contacts. Thus, the tris-THF ring of GRL-0519A (4) fills
the substrate binding cavity better than the bis-THF
ligand of DRV, anchors Arg87 at the dimer interface,
and forms new CH···O and conserved water-mediated
interactions with the flaps and the base of the sub-
strate binding cavity.
Figure 2. Inhibition of HIV-1 protease dimerization by GRL-0519A. Changes in emission
intensity ratios in the presence of DRV or GRL-0519A are shown. COS7 cells were co-
transfected with a pair of HIV-PRCFP and HIV-PRYFP, and CFPA/B ratios were determined. The
mean values of the ratios are shown as horizontal bars. The results of statistical evalua-
tion of the changes in the CFPA/B ratios determined in the presence or absence of DRV or
GRL-0519A are as follows: the CFPA/B ratios in the absence of drug (CFPA/BNoDrug) vs. the
CFPA/B ratios in the presence of 0.001 mm DRV (CFPA/B0.001DRV), p=0.94; CFPA/B
vs.
,
1.0DRV
,
NoDrug
vs. CFPA/B
CFPA/B0.01DRV, p=0.15; CFPA/B
vs. CFPA/B0.1DRV, p=0.0042; CFPA/B
In conclusion, we designed and synthesized novel
oxatricyclic [3(R), 3aS, 4aS, 6aR, 7aS] and [3(R), 3aS,
4aR, 6aS, 7aS] ligands and incorporated these ligands
in the (R)-hydroxyethyl sulfonamide isostere.[16] The
orientation, ring size, and stereochemistry are all criti-
cal to the potency of the oxatricyclic ligand-derived
inhibitors. The ligands were synthesized with defined
stereochemistry in optically active forms. Incorpora-
tion of a syn-syn-syn-fused tris-THF led to inhibitor 3,
NoDrug
NoDrug
p=0.0004; CFPA/B
p=0.0077; CFPA/B
vs. CFPA/B0.001GRL-519, p=0.947; CFPA/B
vs. CFPA/B0.1GRL-519, p=0.0003; CFPA/B
vs. CFPA/B
vs. CFPA/B
NoDrug
NoDrug
0.01GRL-519
,
NoDrug
NoDrug
1.0GRL-519
75/219gag
p=0.0002; CFPA/B0.01DRV vs. CFPA/B0.01GRL-519, p=0.013. Panel A: HIVWT vs. rHIVWTpro
,
p=0.53; HIVWT vs. rHIVWTpro12/75/219/309/409gag, p=0.0080; HIVWT vs. rHIVWTpro219/409gag, p=0.22;
75/219gag
219/409gag
rHIVWTpro
p=0.15; rHIVWTpro
vs. rHIVWTpro12/75/219/309/409gag, p=0.0065; rHIVWTpro75/219gag vs. rHIVWTpro
,
vs. rHIVWTpro219/409gag, p=0.0018. Panel B: HIVWT vs.
12/75/219/309/409gag
rHIVWTpro75/219gag, p=0.65; HIVWT vs. rHIVWTpro12/75/219/309/409gag, p<0.0001; HIVWT vs.
rHIVWTpro219/409gag, p<0.0001.
major conformation of the inhibitor forms hydrogen bonding
interactions of its urethane NH group with the carbonyl
oxygen of Gly27. The oxymethyl oxygen of the tris-THF inter-
acts with the amide of Asp30, and the second THF oxygen
forms hydrogen bonds with the amides of Asp29, Asp30, and
the carboxylate side chain of Asp30. In addition, water-mediat-
ed interactions connect the inhibitor carbonyl oxygen and sul-
fonamide oxygen with the amides of Ile50 and 50’ in the flaps,
and link the inhibitor P2’ aromatic ring with the amide of
Asp30’. Similar interactions are shared by the protease–DRV
complex, and are considered responsible for the high affinity
of DRV for HIV protease and its potency against drug-resistant
HIV-1 variants.[31]
which has significantly decreased enzyme inhibitory and antivi-
ral potency relative to DRV. However, the tris-THF ligand with a
syn-anti-syn fusion provided inhibitor GRL-0519A (4), which has
remarkable enzyme inhibitory and antiviral activity. Of particu-
lar interest, GRL-0519A displayed potent activity against a vari-
ety of multidrug-resistant clinical HIV-1 strains, with EC50 values
ranging from 0.6 to 4.3 nm, a nearly 10-fold improvement over
darunavir. Moreover, GRL-0519A blocked protease dimerization
at least 10-fold more potently than DRV. An X-ray crystal struc-
ture of GRL-0519A-bound HIV-1 protease revealed molecular
insight into the ligand–binding site interactions responsible for
its potency against wild-type and mutant viruses. It appears
that the first and second THF rings of the tris-THF ligand with
a syn-anti-syn configuration maintain key backbone hydrogen
bonding interactions similar to the bis-THF ligand of darunavir.
The third THF ring oxygen makes water-mediated hydrogen
bonds with Asp29, Arg8’, and Gly27. In addition, the ring fills
the hydrophobic pocket in the S2 subsite and also stacks
nicely behind the P1 phenylmethyl substituent at the S1 sub-
site. Therefore, our basic design strategy has shown to be ex-
tremely powerful and is well worth further experimentation.
The majority of differences are confined in the interactions
of the third THF moiety in GRL-0519A. The third THF ring
forms CH···O interactions with Gly48 in the protease flap and
water-mediated hydrogen bonds with conserved residues at
the dimer interface as shown in Figure 3B. The third THF ring
forms CH···O and water-mediated interactions with the carbon-
yl and amide of Gly48 that may stabilize the flexible flap con-
formation. The oxygen at the opposite side of the THF ring
forms a hydrogen bond with a conserved water molecule and
stabilizes a network of hydrogen bonds and ionic interactions
connecting Arg8’ from the other subunit with the side chains
of Asp29 and Arg87, as well as with the main-chain carbonyl
oxygen atoms of Thr26 and Gly27 in the characteristic catalytic
triplet (Asp25-Thr26-Gly27) of aspartic proteases. The ionic and
hydrogen bonding interactions of Arg8’ with Asp29 and Arg87
are conserved among HIV protease structures and are impor-
tant components of the dimer interface.[32,33] Also, the oxygen
of the third THF ring interacts with a semicircular network of
Acknowledgements
This research was supported by grants from the National Insti-
tutes of Health (GM53386, A.K.G. and GM62920, I.W.). This work
was also supported by the Intramural Research Program of the
Center for Cancer Research, National Cancer Institute, National
Institutes of Health and in part by a Grant-in-aid for Scientific Re-
search (Priority Areas) from the Ministry of Education, Culture,
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[6] A. K. Ghosh, J. F. Kincaid, W. Cho, D. E. Walters, K. Krishnan, K. A. Hussain,
Y. Koo, H. Cho, C. Rudall, L. Holland, J. Buthod, Bioorg. Med. Chem. Lett.
1998, 8, 687–690.
[7] A. K. Ghosh, D. Shin, L. Swanson, K. Krishnan, H. Cho, K. A. Hussain, D. E.
Walters, L. Holland, J. Buthod, Farmaco 2001, 56, 29–32.
[8] A. K. Ghosh, P. Ramu Sridhar, N. Kumaragurubaran, Y. Koh, I. T. Weber, H.
Mitsuya, ChemMedChem 2006, 1, 939–950.
[9] K. Yoshimura, R. Kato, M. F. Kavlick, A. Nguyen, V. Maroun, K. Maeda,
K. A. Hussain, A. K. Ghosh, S. V. Gulnik, J. W. Erickson, H. Mitsuya, J. Virol.
2002, 76, 1349–1358.
[10] Y. Koh, H. Nakata, K. Maeda, Antimicrob. Agents Chemother. 2003, 47,
3123–3129.
[11] The US Food and Drug Administration (FDA) approved Darunavir on
June 23, 2006: FDA approved new HIV treatment for patients who do not
respond to existing drugs: http://www.fda.gov/newsEvents/Newsroom/
PressAnnouncements/2006/ucm108676.htm.
[12] On October 21, 2008 the FDA granted traditional approval to Prezista
(darunavir), co-administered with ritonavir and with other antiretroviral
agents, for the treatment of HIV-1 infection in treatment-experienced
adult patients. In addition to the traditional approval, a new dosing
regimen for treatment-naꢃve patients was approved.
[13] Y. Tie, A. Y. Kovalevsky, P. Boross, Y. F. Wang, A. K. Ghosh, J. Tozser, R. W.
Harrison, I. T. Weber, Proteins Struct. Funct. Bioinf. 2007, 67, 232–242.
[14] A. Y. Kovalevsky, Y. Tie, F. Liu, P. I. Boross, Y. F. Wang, S. Leshchenko, A. K.
Ghosh, R. W. Harrison, I. T. Weber, J. Med. Chem. 2006, 49, 1379–1387.
[15] A. K. Ghosh, B. D. Chapsal, I. T. Weber, H. Mitsuya, Acc. Chem. Res. 2008,
41, 78–86.
[16] A. K. Ghosh, P. R. Sridhar, S. Leshchenko, A. K. Hussain, J. Li, A. Y. Kova-
levsky, D. E. Walters, J. E. Wedekind, V. Grum-Tokars, D. Das, Y. Koh, K.
Maeda, H. Gatanaga, I. T. Weber, H. Mitsuya, J. Med. Chem. 2006, 49,
5252–5261.
[17] A. K. Ghosh, S. Leshchenko-Yashchuk, D. D. Anderson, A. Baldridge, M.
Noetzel, H. B. Miller, Y. Tie, Y. F. Wang, Y. Koh, I. T. Weber, H. Mitsuya, J.
Med. Chem. 2009, 52, 3902–3914.
[18] A. K. Ghosh, Y. Chen, Tetrahedron Lett. 1995, 36, 505–508.
[19] A. K. Ghosh, J. F. Kincaid, D. E. Walters, J. Med. Chem. 1996, 39, 3278–
3290.
[20] M. Gibert, M. Ferrer, F. Sꢄnchez-Baeza, A. Messeguer, Tetrahedron 1997,
53, 8643–8650.
[21] F. P. Boulineau, A. Wei, Org. Lett. 2004, 6, 119–121.
[22] D. B. Dess, J. C. Martin, J. Am. Chem. Soc. 1991, 113, 7277–7287.
[23] E. J. Corey, A. K. Ghosh, Tetrahedron Lett. 1988, 29, 3205–3208.
[24] J. A. Dale, D. L. Dull, H. S. Mosher, J. Org. Chem. 1969, 34, 2543–2549.
[25] A. K. Ghosh, S. Gemma, A. Baldridge, Y. F. Wang, A. Y. Kovalevsky, Y. Koh,
I. T. Weber, H. Mitsuya, J. Med. Chem. 2008, 51, 6021–6033.
[26] K. Yoshimura, R. Kato, K. Yusa, M. F. Kavlick, V. Maroun, A. Nguyen, T.
Mimoto, T. Ueno, M. Shintani, J. Falloon, M. Masur, H. Hayashi, J. Erick-
son, H. Mitsuya, Proc. Natl. Acad. Sci. USA 1999, 96, 8675–8680.
[27] C. de Mendoza, V. Soriano, Curr. Drug Metab. 2004, 5, 321–328.
[28] E. E. Kim, C. T. Baker, M. D. Dwyer, M. A. Murcko, B. G. Rao, R. D. Tung,
M. A. Navia, J. Am. Chem. Soc. 1995, 117, 1181–1182.
[29] A. Wlodawer, M. Miller, M. Jaskꢅlski, B. K. Sathyanarayana, E. Baldwin,
I. T. Weber, L. M. Selk, L. Clawson, J. Schneider, S. B. Kent, Science 1989,
245, 616–621.
[30] Y. Koh, S. Matsumi, D. Das, M. Amano, D. A. Davis, J. Li, S. Leshchenko,
A. Baldridge, T. Shioda, R. Yarchoan, A. K. Ghosh, H. Mitsuya, J. Biol.
Chem. 2007, 282, 28709–28720.
Figure 3. A) X-ray crystal structure of the HIV-1 protease–GRL-0519A com-
plex. The major orientation of the inhibitor is shown. The inhibitor carbon
atoms are shown in cyan, water molecules are red spheres, and the hydro-
gen bonds are indicated by dotted lines. B) Polar interactions of the third
THF group with the protease; hydrogen bonds are indicated by dotted
lines, and CH···O interactions by dashed lines.
Sports, Science, and Technology of Japan (Monbu Kagakusho), a
Grant for Promotion of AIDS Research from the Ministry of
Health, Welfare, and Labor of Japan (Kosei Rohdosho: H15-AIDS-
001), and the Grant to the Cooperative Research Project on Clini-
cal and Epidemiological Studies of Emerging and Reemerging In-
fectious Diseases (Kumamoto University) of Monbu-Kagakusho.
Keywords: dimerization inhibitors · HIV-1 protease · multidrug
resistance · oxatricyclic ligands · X-ray crystallography
[31] Y. Tie, P. I. Boross, Y. F. Wang, L. Gaddis, A. K. Hussain, S. Leshchenko,
A. K. Ghosh, J. M. Louis, R. W. Harrison, I. T. Weber, J. Mol. Biol. 2004,
338, 341–352.
[1] C. Flexner, N. Engl. J. Med. 1998, 338, 1281–1292.
[2] K. A. Sepkowitz, N. Engl. J. Med. 2001, 344, 1764–1772.
[3] L. Waters, M. Nelson, Int. J. Clin. Pract. 2007, 61, 983–990.
[4] D. Pillay, K. Bhaskaran, S. Jurriaans, M. Prins, B. Masquelier, F. Dabis, R.
Gifford, C. Nielsen, C. Pedersen, C. Balotta, G. Rezza, M. Ortiz, C. de Men-
doza, C. Kꢂcherer, G. Poggensee, J. Gill, K. Porter, CASCADE Virology
Collaboration, AIDS 2006, 20, 21–28.
[32] R. Ishima, Q. Gong, Y. Tie, I. T. Weber, J. M. Louis, Proteins 2010, 78,
1015–1025.
[33] I. T. Weber, J. Biol. Chem. 1990, 265, 10492–10496.
Received: July 28, 2010
Revised: August 27, 2010
[5] S. Yerly, L. Kaiser, E. Race, J. P. Bru, F. Clavel, L. Perrin, Lancet 1999, 354,
729–733.
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