Novel indazole non-nucleoside reverse transcriptase inhibitors using molecular hybridization based on crystallographic overlays

Article abstract of DOI:10.1021/jm801322h

A major problem associated with non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the treatment of HIV is their lack of resilience to mutations in the reverse transcriptase (RT) enzyme. Using structural overlays of the known inhibitors efaviren

Full text of DOI:10.1021/jm801322h

J. Med. Chem. 2009, 52, 1219–1223
1219
Novel Indazole Non-Nucleoside Reverse Transcriptase Inhibitors Using Molecular Hybridization
Based on Crystallographic Overlays†
Lyn H. Jones,*,‡ Gill Allan,| Oscar Barba,‡ Catherine Burt,# Romuald Corbau,§ Thomas Dupont,‡ Thorsten Kno¨chel,3
Steve Irving, Donald S. Middleton,‡ Charles E. Mowbray,‡ Manos Perros,§ Heather Ringrose,O Nigel A. Swain,‡
Robert Webster,| Mike Westby,§ and Chris Phillips
DiscoVery Chemistry, DiscoVery Biology, Pharmacokinetics, Dynamics, and Metabolism, Structural Biology, Molecular Informatics and
Structure-Based Design, Sandwich Laboratories, Pfizer Global Research and DeVelopment, Ramsgate Road, Sandwich,
Kent CT13 9NJ, United Kingdom
ReceiVed September 10, 2008
A major problem associated with non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the treatment
of HIV is their lack of resilience to mutations in the reverse transcriptase (RT) enzyme. Using structural
overlays of the known inhibitors efavirenz and capravirine complexed in RT as a starting point, and structure-
based drug design techniques, we have created a novel series of indazole NNRTIs that possess excellent
metabolic stability and mutant resilience.
Introduction
caused by mutations in RT that can retain viable enzymatic
function. The so-called first-generation NNRTIs such as nevi-
rapine, delavirdine, and efavirenz (Figure 1) are very susceptible
to single-point resistance mutations within RT and therefore
significant efforts in this field have focused on developing
second-generation NNRTIs with an improved mutant profile.2
For example, treatment with efavirenz, the market leader in this
class, can result in drug resistant virus due to the emergence of
the K103N mutation in the NNRTI binding pocket of the
enzyme.3 Etravirine (Figure 1) is a recently launched second-
generation NNRTI drug that retains activity against the clinically
relevant mutations of RT, particularly K103N and Y181C.4
However, there is still a need for additional novel chemical
substrate that provides opportunities for delivering broad
spectrum activity against mutant HIV. Our key aim has been
the design and development of novel and potent NNRTIs that
retain potent activity (within 10-fold of wild-type) against the
most clinically relevant mutations, particularly K103N, thus
reducing their intrinsic susceptibility to these mutations.
Capravirine (Figure 1) is a second-generation NNRTI which
exhibits an improvement over the marketed NNRTIs with regard
to its spectrum of activity against drug-resistant strains of HIV,
including K103N.5 We decided that capravirine was an ap-
propriate starting point for our design of novel NNRTIs due to
its excellent mutant profile and we reasoned that a hybrid of
the well-established efavirenz template with that of capravirine
(molecular hybridization6), facilitated by structure-based drug
Approximately 33 million people are living with HIV/AIDS
worldwide, and 2.5 million people were newly infected with
the virus in 2007.1 HIV slowly attacks and destroys the immune
system, leaving an individual open to other infections that
eventually result in death. There is no cure for HIV infection,
but a number of drugs slow or halt disease progression.
However, HIV can rapidly become resistant to any single
antiretroviral drug, therefore a combination of three or more
drugs are usually required to effectively suppress the virus. This
is known as highly active antiretroviral therapy (HAART).
Reverse transcriptase (RTa) is an essential enzyme in the
infectious lifecycle of HIV, and inhibition of this enzyme has
shown utility in the treatment of HIV. Several inhibitors of RT
are used as components of HAART. However, established drugs
called non-nucleoside reverse transcriptase inhibitors (NNRTIs),
which bind to an allosteric pocket outside the catalytic site, are
particularly vulnerable to the development of viral resistance
†
PDB code 2JLE for cocrystal 6 and K103N.
* To whom correspondence should be addressed. Phone: +44 (0)130-
4644256. Fax: +44 (0)1304651821. E-mail: Lyn.Jones@pfizer.com.
‡
Discovery Chemistry.
Discovery Biology.
Pharmacokinetics, Dynamics and Metabolism.
§
|
Structural Biology.
Molecular Informatics and Structure-Based Design.
Current address: Protein Crystallography (ZD-A/ZFA), Merck KgaA,
#
3
Frankfurter Strasse 250, D-64293 Darmstadt, Germany.
O
Current address: Hamilton Robotics Ltd, Knights Court, Solihull
Parkway, Birmingham Business Park B37 7WY, United Kingdom.
a Abbreviations: AcOH, acetic acid; APCI, atmospheric pressure chemical
ionization; CCD, charge-coupled device; CPV, capravirine; DCM, dichlo-
romethane; DMF, N,N-dimethylformamide; DMSO, dimethyl sulfoxide;
EDTA, ethylenediaminetetraacetic acid; EFV, efavirenz; Et, ethyl; EtOAc,
ethyl acetate; FCC, flash column chromatography; HAART, highly active
antiretroviral therapy; Hheps, human hepatocytes; HLM, human liver
microsomes; HMBC, heteronuclear multiple bond correlation; HSQC,
heteronuclear single quantum coherence; IC50, half-maximal (50%) inhibi-
tory concentration; IR, infrared; LCMS, liquid chromatography mass
spectrometry; MeCN, acetonitrile; mL, milliliter; µL, microliter; NBS,
N-bromosuccinimide; NOE, nuclear Overhauser effect; Me, methyl; MeOH,
methanol; MOI, multiplicity of infection; mp, melting point; nd, not
determined; nM, nanomolar; NMR, nuclear magnetic resonance; NNRTI,
non-nucleoside reverse transcriptase inhibitors; RPMI, Roswell Park Memo-
rial Institute medium; RT, reverse transcriptase; THF, tetrahydrofuran;
tBuOH, tert-butanol; TTP, thymidine-5′-triphosphate; wt, wild-type.
Figure 1. Existing NNRTIs.
10.1021/jm801322h CCC: $40.75
2009 American Chemical Society
Published on Web 01/28/2009

1220 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 4
Scheme 1. Synthesis of 3-Methyl Indazolesa
Brief Articles
Scheme 3. Modification of the Indazole 3-Positiona
a Reagents and conditions: (a) Boc2O, K2CO3, DMF, 40°C, 96%; (b)
NBS, VAZO, CCl4, reflux, 96%; (c) MeNH2, THF, 66°C, 40%; (d) MeOH,
NEt3, 80°C, 50%.
a Reagents and conditions: (a) 3,5-dicyanofluorobenzene, K2CO3, DMF,
80°C, 45%; (b) SO2Cl2, AcOH, 70°C, 35%; (c) Selectfluor, MeCN, rt, 56%.
Scheme 4. Modification of the 7-Positiona
Scheme 2. Synthesis of 3-Ethyl Indazolesa
a Reagents and conditions: (a) N2H4.H2O, ethylene glycol, 140°C, 92%;
(b) 3,5-dicyanofluorobenzene, K2CO3, DMF, 75°C, 23%; (c) Selectfluor,
MeCN, rt, 41%.
a Reagents and conditions: (a) Br2, AcOH, rt, 92%. (b) (i) Tributylvi-
nyltin, Pd2(dba)3, P(o-tolyl)3, dioxane, reflux; (ii) OsO4, NMO, tBuOH/THF/
H2O then NaIO4; (iii) NaBH4, MeOH, 45% over 3 steps.
Scheme 5. Synthesis of 3-Phenoxy Derivative 16a
design, could create a novel starting point which may furnish
analogues with the desired potency and resilience to RT
mutations.
Synthetic Chemistry
a Reagents and conditions: (a) 3,5-dicyanofluorobenzene, K2CO3, DMF,
75°C, 35%.
At the outset, we desired a facile and reliable method for the
preparation of 4-aryloxyindazoles, which would allow us to
prepare a variety of related analogues in this series. Our strategy
for their preparation involved the arylation of 4-hydroxy
indazoles using an electron-deficient aryl fluoride as the key
step. Treatment of the known 4-hydroxyindazole 97 with
commercially available 3,5-dicyanofluorobenzene provided the
desired adduct 1 in modest yield (Scheme 1). Chlorination and
fluorination of 1 provided derivatives 5 and 6, respectively
(structures confirmed by NOE and C-H correlation NMR
experiments: see Supporting Information).
Similar chemistry was used to prepare the 3-ethyl indazole
derivatives (Scheme 2). Treatment of the known resorcinol 108
with hydrazine at high temperature effected transformation to
indazole 11. Arylation provided 2, and fluorination of this
derivative yielded 7. Further modifications to the 3-position of
the indazole were readily achieved by radical bromination of
derivative 12, which was reacted with methylamine and
methanol to provide 3 and 4, respectively (Scheme 3).
Modification of the 7-position of the indazole was realized
using a selective bromination of 1, (14 structure confirmed by
NOE: see Supporting Information), followed by a Stille reaction
to install the ethylene group, followed by oxidative cleavage
and reduction of the resulting aldehyde to provide derivative 8
(Scheme 4). Commercially available 3-indazolinone 15 was
arylated with 3,5-dicyanofluorobenzene (in the same manner
as 9) to furnish 16 (Scheme 5).
capravirine-RT complex (1EP4, Supporting Information),
described previously by Stuart and Stammers, sheds light on
the structural components responsible for its resilience to drug
resistant mutations.9 A key feature is the hydrogen bonding
network capravirine makes with the peptide backbone of the
NNRTI allosteric binding pocket. Two of these hydrogen bonds
are between the carbamate group and the peptide main chain
of residues K103 and P236. A third bond is formed between
N3 of capravirine and the main chain of residue K101, which
is mediated by a bridging water molecule. Interestingly, both
the N-H and carbonyl groups of the cyclic carbamate substitu-
ent of efavirenz form direct hydrogen bonds with the K101 main
chain atoms (1FKO, Supporting Information) without the need
for a bridging water.10
Another key attribute of the capravirine-RT structure is an
optimized edge-to-face π-interaction between the 3,5-dichlo-
rophenyl substituent of capravirine and the indole moiety of
the highly conserved residue W229. Indeed, the rational design
of NNRTIs to interact specifically with W229 to improve mutant
resilience has also been suggested by Balzarini and De Clercq11
and was recently utilized in the development of pyrroloben-
zoxazepine NNRTIs by Campiani and co-workers.12 A crystal-
lographic overlay of efavirenz and capravirine within the binding
site is shown in Figure 2. This overlay nicely illustrates the
key differences between these NNRTIs in the location and nature
of the group, which occupies the lipophilic pocket created by
W229, Y188, and Y181 in the allosteric binding site. Our initial
aim was to transpose the 3,5-disubsituted phenyl moiety present
in capravirine to a novel bicyclic template (similar to but distinct
Target Design
Our starting point was an analysis of the published X-ray
cocrystal structures of efavirenz and capravirine with RT to
investigate the relation between structure and function. The

Brief Articles
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 4 1221
Table 1. Potency of Indazole Derivatives against the Wild-Type
Reverse Transcriptase Enzyme
compd
R
R1
R2
wt IC50/nMa
1
2
3
4
5
6
7
8
H
H
H
H
Cl
F
Me
Et
MeNHCH2
MeOCH2
Me
Me
Et
Me
H
H
H
H
H
H
H
332 (108)
112 (2.2)
>30000
1670 (3240)
399 (195)
50 (8.5)
Figure 2. Crystallographic overlay of efavirenz (gold) and capravirine
(pink) with RT (protein removed for clarity).
F
H
25 (9.6)
71 (2.0)
CH2OH
a Values are geomeans of three experiments. Standard deviations are in
brackets.
Figure 3. Molecular hybridization of capravirine and efavirenz to create
the indazole template.
groups at the 3-position of the indazole would avoid reactive
metabolite formation by this mechanism. From the structural
overlaps shown in Figure 2, we also noticed that a group here
would overlap well with the CF3-substituent in efavirenz and
the isopropyl group in the 4-position of capravirine. Indeed,
increasing the size of this substituent from a methyl to an ethyl
group to provide 2 not only increased the potency 3-fold (Table
1), 2 was also negative in the reactive metabolite assay. Further
elaboration of this substituent was pursued due to synthetic
tractability, but we quickly discovered that increasing the size
of this substituent even further resulted in significant potency
reductions (3 and 4).
from the dihydrobenzoxazinone template of efavirenz), while
ensuring the π-interaction with the immutable W229 residue
could be retained. In particular, we were keen to avoid the chiral
center present in efavirenz, thus reducing synthetic complexity,
so the indazole template appeared to be ideally suited for our
purposes because it could satisfy these structural criteria (Figure
3). Additionally, the N-H moiety of the indazole should
undergo hydrogen bonding with the main chain of residue K101,
similar to that in the efavirenz complex.
Additionally, from the crystallographic overlay in Figure 2,
it was apparent that a hydrophobic group in the 5-position of
the indazole would overlap well with the chloro-subsitituent in
efavirenz. Interestingly, a chlorine atom at this position had
minimal effect on potency (Table 1, compound 5), but the
smaller fluorine substituent improved the potency nearly 7-fold
(compound 6: see below for an explanation). Incorporating an
ethyl group into the 3-position to provide 7 further improved
the potency as we expected. Additionally, both 6 and 7 were
negative in the reactive metabolite assay.
We were then able to cocrystallize 6, as a representative from
this series, with K103N RT as shown in Figure 4.18 Derivative
6 makes the important edge-to-face π-interactions with the
immutable W229 residue, and the indazole N-H undergoes a
hydrogen bond with the peptide main chain of residue K101,
thus satisfying both design features that were in our original
plan.19 The benzene ring also appears to make a face-to-face
π-interaction with the Y188 residue, an interaction that has also
been reported recently by Tucker and co-workers for a series
of meta-cyanophenoxy-containing NNRTI derivatives.20
Table 2 shows the potency of derivatives 6 and 7 against the
clinically relevant K103N and Y181C RT mutations (we have
included efavirenz and capravirine for reference). Their balanced
mutant profile (potencies within 10-fold of wild-type) and potent
antiviral activity vindicates our original strategy. Interestingly,
the highly mutable residue Y181 adopts a “down” position
(Figure 4), analogous to a series of benzophenone NNRTIs
recently reported by Stammers and co-workers, which appears
to result from a steric clash between the meta-substituent on
the A ring and the Y181 tyrosine. The resilience of these
derivatives to the Y181C mutation may be due to a reduction
in the aromatic stacking interactions with this residue, and that
Results and Discussion
From the structural overlap shown in Figure 2, we noticed
that the most favorable position for the incorporation of the 3,5-
disubstituted benzene moiety into the indazole template would
be the 4-position as this is closest to the location of this group
in capravirine. For synthetic expedience, the first analogue we
prepared in this series was 1 (Scheme 1). We have previously
shown that a 3,5-dicyanophenoxy group can be incorporated
into NNRTIs,13 and amenable synthetic chemistry facilitated
its incorporation into the indazole template. In fact, the
replacement of the hydrophobic chlorine atoms with nitrile
moieties (∆LogP ∼ -2 from Rekker fragments)14 and removing
the metabolically vulnerable sulfur atom with the more polar
oxygen, creates a more “druggable” starting point for our design
due to the expected improvements in metabolic stability and
solubility associated with reducing lipophilicity (see below).15
Pleasingly, 1 possessed encouraging potency against wild-
type RT (Table 1). To test the importance of the location of
this moiety in the indazole template, we appended this group
to the 3-position to provide 16, but this derivative is ap-
proximately 100-fold less potent than 1 (wild-type RT IC50 38
µM), thus illustrating the usefulness of the structural overlays.
However, we found that 1 formed a reactive metabolite
conjugate that could be trapped with glutathione following
incubation with human liver microsomes (HLMs), a feature that
has been linked with hepato- and idiosyncratic toxicity.16
Although the structure of this conjugate was not further
characterized, there is an obvious similarity with 3-methyl
indole, which exhibits toxicity due to H-atom abstraction from
the methyl group, followed by single electron oxidation to form
the electrophilic imine-methide.17 We reasoned that alternative

1222 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 4
Brief Articles
augment resilience to mutations in RT. The 7-position of the
indazole would appear to be the optimal location for a hydrogen-
bonding group and derivative 8, which contains a hydroxymethyl
substituent at this position, displays a significant improvement
in potency over 1 (∼5-fold, Table 1). Interestingly, this
derivative is >10-fold less potent against K103N (Table 2),
unlike compounds 6 and 7, and therefore optimization of the
peptide-backbone hydrogen-bonding capacity would be required
to address the apparent mutant vulnerability in this strategy.
Compound 8 also retained excellent in vitro metabolic stability
in human liver microsomes (Table 2). Metabolic stability was
also assessed in vitro in human hepatocytes (HHeps), which
retain phase 2 metabolic capabilities. Unfortunately, 8 was found
to have poor stability in hepatocytes relative to 6 and 7 (Table
2) and therefore this derivative did not warrant further profiling.
Conclusion
We have used molecular hybridization of existing NNRTIs
to efficiently create a new series of indazole derivatives that
possess potent activity against both wild-type and clinically
relevant mutations of the RT enzyme. Specifically, compounds
6 and 7, fashioned using structure-based drug design, also
possess potent antiviral activity and retain excellent in vitro
metabolic stability. Because of the expense of HAART therapy,
we have also addressed potential cost of goods issues in our
design from the outset by pursuing a synthetically expedient
series, which avoids chiral centers. These studies provide a
proof-of-concept for the utility of molecular hybridization in
the creation of novel leads as inhibitors of RT. Further
development of this series will be reported in due course.
Figure 4. Cocrystal structure of 6 with K103N RT (2JLE). Highlighted
residues: W229 (red); Y188 (green); Y181 (blue).
Table 2. Enzyme and Antiviral Potency and Metabolic Stability of
Indazole Derivatives Capravirine and Efavirenz
wt IC50/ K103N
Y181C
wt AV
HLM
HHeps
compd
nMa
IC50/nMa IC50/nMa IC50/nMa T1/2/mins T1/2/mins
6
7
8
50 (8.5) 384 (30)
25 (9.6) 183 (80)
145 (83) 14 (8.4)
>120
>120
>120
7.5
>360
>360
11
nd
nd
32 (16)
4.6 (1.1)
14 (3.7)
0.5 (0.5)
0.4 (0.4)
71 (2.0) 1268 (565) ndb
CPV 47 (35) 68 (60)
EFV 14 (6.0) 364 (212) 40 (21)
61 (66)
nd
a Values are geomeans of at least three experiments. Standard deviations
are in brackets. 6, 7, and 8 were not cytotoxic, CC50 > 100 µM. b nd ) not
determined.
Experimental Section
The syntheses of compounds 1, 5, and 6 are described below as
representatives of the series. Detailed syntheses of all other
compounds, and procedures for the assays, crystallizations, and
molecular modeling, are to be found in the Supporting Information.
5-(3-Methyl-1H-indazol-4-yloxy)-isophthalonitrile (1). 3-Meth-
yl-4-hydroxyindazole (7.0 g, 47.3 mmol) was dissolved in DMF
(100 mL), and potassium carbonate (6.5 g, 47.3 mmol) was added
and stirred for 10 min before the addition of 3,5-dicyanofluoroben-
zene (6.9 g, 47.3 mmol). The mixture was then heated at 80 °C for
24 h, cooled to room temperature and concentrated in vacuo, then
diluted with EtOAc, brine was added, and the layers separated, dried
(MgSO4), filtered, and concentrated under reduced pressure. The
residue was purified by FCC (silica gel, 40% EtOAc/pentane) and
crystallized from diethyl ether to yield the title compound as a white
solid (5.8 g, 45%); mp 188-189 °C. 1H NMR (400 MHz, CDCl3)
7.62 (s, 1H), 7.48 (s, 2H), 7.40-7.35 (m, 2H), 6.67-6.63 (m, 1H),
2.48 (s, 3H). APCI MS m/z 275 [M + H]+. LCMS CI m/z 275 [M
+ H]+ >95%. Anal. (C16H10N4O) C, H, N.
5-(5-Chloro-3-methyl-1H-indazol-4-yloxy)-isophthalonitrile (5).
Indazole 1 (50 mg, 0.18 mmol) was dissolved in acetic acid (1
mL), SO2Cl2 (30 µL, 0.36 mmol) was added and stirred at 70 °C
for 6 h, cooled to room temperature, concentrated in vacuo, diluted
with DCM, washed with saturated aqueous sodium bicarbonate,
dried (MgSO4), filtered, and concentrated under reduced pressure.
The residue was purified by FCC (silica gel, 25% EtOAc/pentane)
to yield the title compound as a white solid (22 mg, 35%). 1H NMR
(400 MHz, CD3OD) 7.87 (s, 1H), 7.52-7.44 (m, 4H), 2.39 (s, 3H).
NOE and C-H correlation experiments included in Supporting
Information. APCI MS m/z 309 [M + H]+. LCMS CI m/z 309 [M
+ H]+ >95%. Anal. (C16H9N4OCl) C, H, N.
Figure 5. Overlay of 6 (gray; from cocrystal structure Figure 4, protein
removed for clarity) and the energy minimized structure for 5 (blue).
efficient binding can still be achieved due to optimized
interactions elsewhere (for example, the edge-to-face π-bond
with W229).21
The conformation of compound 6 shown in Figure 4 was
used as a template to generate an energy minimized structure
for the chloro-derivative 5 (see Experimental Section), and the
indazole rings of compounds 5 and 6 were then overlaid (Figure
5). As one might predict, the larger chlorine atom causes a flip
and twist of the phenoxy group away from the halogen, implying
that the conformation required for optimal binding is sterically
less favored for 5 and may explain why this derivative is less
potent than 6.
We also noticed the potential for incorporating hydrogen-
bonding groups into the benzene ring of the indazole template
to mimic the carbamate substituent present in capravirine, which
is apparent in the overlay shown in Figure 2. We felt these
additional interactions may not only improve potency, but also
5-(5-Fluoro-3-methyl-1H-indazol-4-yloxy)-isophthalonitrile (6).
Indazole 1 (100 mg, 0.34 mmol) was dissolved in MeCN (1 mL),
Selectfluor (120 mg, 0.34 mmol) added, and the mixture stirred at
room temperature for two days. Brine was then added and the
mixture extracted with EtOAc, dried (MgSO4), filtered, and

Brief Articles
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 4 1223
(10) Ren, J.; Milton, J.; Weaver, K. L.; Short, S. A.; Stuart, D. I.; Stammers,
D. K. Structural Basis for the Resilience of Efavirenz (DMP-266) to
Drug Resistance Mutations in HIV-1 Reverse Transcriptase. Structure
2000, 8, 1089–1094.
(11) Pelemans, H.; Esnouf, R.; De Clercq, E.; Balzarini, J. Mutational
Analysis of Trp-229 of Human Immunodeficiency Virus Type 1
Reverse Transcriptase (RT) Identifies This Amino Acid Residue as a
Prime Target for the Rational Design of New Non-Nucleoside RT
Inhibitors. Mol. Pharm. 2000, 57, 954–960.
(12) Fattorusso, C.; Gemma, S.; Butini, S.; Huleatt, P.; Catalanotti, B.;
Persico, M.; De Angelis, M.; Fiorini, I.; Nacci, V.; Ramunno, A.;
Rodriquez, M.; Greco, G.; Novellino, E.; Bergamini, A.; Marini, S.;
Coletta, M.; Maga, G.; Spadari, S.; Campiani, G. Specific Targeting
Highly Conserved Residues in the HIV-1 Reverse Transcriptase Primer
Grip Region. Design, Synthesis and Biological Evaluation of Novel,
Potent and Broad Spectrum NNRTIs with Antiviral Activity. J. Med.
Chem. 2005, 48, 7153–7165.
(13) (a) Jones, L. H.; Allan, G.; Corbau, R.; Hay, D.; Middleton, D. S.;
Mowbray, C. E.; Newman, S.; Perros, M.; Randall, A.; Vuong, H.;
Webster, R.; Westby, M.; Williams, D. Optimization of 5-aryloxy-
imidazole non-nucleoside reverse transcriptase inhibitors. ChemMed-
Chem 2008, 3, 1756–1762. (b) Jones, L. H.; Randall, A.; Barba, O.;
Selby, M. Synthetic chemistry-led creation of a difluorinated biaryl
ether non-nucleoside reverse transcriptase inhibitor. Org. Biomol.
Chem. 2007, 5, 3431–3433. (c) Jones, L. H.; Dupont, T.; Mowbray,
C. E.; Newman, S. A Concise and Selective Synthesis of Novel
5-Aryloxyimidazole NNRTIs. Org. Lett. 2006, 8, 1725–1727. (d)
Jones, L. H.; Mowbray, C. E. A concise synthesis of trifluormethyl-
substituted 4-aryloxy pyrazoles. Synlett 2006, 9, 1404–1406.
(14) Rekker, R. The Hydrophobic Fragmental Constant; Elsevier: Am-
sterdam, 1977.
concentrated under reduced pressure. The residue was purified by
FCC (silica gel, 20% EtOAc/toluene) to yield the title compound
as a white solid (56 mg, 56%). H NMR (500 MHz, DMSO-d6)
13.01 (s, 1H), 8.19 (s, 1H), 7.88 (s, 2H), 7.45 (dd, J 9.3, 3.8 Hz,
1H), 7.41 (dd, J 9.6, 9.3 Hz, 1H), 2.30 (s, 3H). 13C NMR (125
MHz, DMSO-d6) 158.2, 147.6, 140.0, 139.5, 131.2, 130.5, 123.4,
116.5, 114.4, 109.2, 13.1. C-H correlation experiments included
in Supporting Information. 19F NMR (376 MHz, CDCl3) -141.0.
APCI MS m/z 293 [M + H]+. LCMS CI m/z 293 [M + H]+ >95%.
Anal. (C16H9FN4O) C, H, N.
1
Acknowledgment. We thank Michael Kinns and Torren
Peakman for NOE and C-H correlation NMR experiments. We
also thank Ian Burr, Alex Martin, and Amy Thomas for
determining the potencies of these compounds and Iain Gardner
for proof reading this manuscript.
Supporting Information Available: Detailed syntheses of all
compounds (except 1, 5, and 6), NOE and C-H correlation spectra
of 5, 6, 14, combustion analyses of 1-8 and 16. Procedures for
the enzyme and antiviral assays and molecular modeling details.
X-ray diffraction data for 6 with K103N RT. Structures of efavirenz
and capravirine with RT and overlays of compound 6 with efavirenz
and capravirine. This material is available free of charge via the
Internet at http://pubs.acs.org.
(15) Bu, H.-Z.; Pool, W. F.; Wu, E. Y.; Raber, S. R.; Amantea, M. A.;
Shetty, B. V. Metabolism and excretion of capravirine, a new non-
nucleoside reverse transcriptase inhibitor, alone and in combination
with ritonavir in healthy volunteers. Drug Metab. Dispos. 2004, 32,
689.
(16) Evans, D. C.; Watt, A. P.; Nicoll-Griffith, D. A.; Baille, T. A. Drug-
Protein Adducts: An Industry Perspective on Minimizing the Potential
for Drug Bioactivation in Drug Discovery and Development. Chem.
Res. Toxicol. 2004, 17, 3–16.
(17) Kalgutkar, A. S.; Gardner, I.; Obach, R. S.; Shaffer, C. L.; Callegari,
E.; Henne, K. R.; Mutlib, A. E.; Dalvie, D. K.; Lee, J. S.; Nakai, Y.;
O’Donnell, J. P.; Boer, J.; Harriman, S. P. A comprehensive listing
of bioactivation pathways of organic functional groups. Curr. Drug
Metab. 2005, 6, 161–225.
(18) Coordinates have been deposited with the PDB and have the assigned
code 2JLE.
(19) The crystallographic overlay of 6 with capravirine and efavirenz fits
perfectly the predicted binding mode: see Supporting Information.
(20) Tucker, T. J.; Saggar, S.; Sisko, J. T.; Tynebor, R. M.; Williams, T. M.;
Felock, P. J.; Flynn, J. A.; Lai, M.-T.; Liang, Y.; McGaughey, G.;
Liu, M.; Miller, M.; Moyer, G.; Munshi, V.; Perlow-Poehnelt, R.;
Prasad, S.; Sanchez, R.; Torrent, M.; Vacca, J. P.; Wan, B.-L.; Yan,
Y. The design and synthesis of diaryl ether second generation HIV-1
non-nucleoside reverse transcriptase inhibitors (NNRTIs) with en-
hanced potency versus key clinical mutations Bioorg. Med. Chem.
Lett. 2008, 18, 2959-2966. These authors observed a notable reduction
in potency for their lead compound against the clinically rare mutation
Y181L, presumably due to interactions between the compound and
the Y188 residue. We cannot rule out a similar mutant vulnerability
as we have not measured Y188 mutant potencies.
(21) Ren, J.; Chamberlain, P. P.; Stamp, A.; Short, S. A.; Weaver, K. L.;
Romines, K. R.; Hazen, R.; Freeman, A.; Ferris, R. G.; Andrews,
C. W.; Boone, L.; Chan, J. H.; Stammers, D. K. Structural basis for
the improved drug resistance profile of new generation benzophenone
non-nucleoside HIV-1 reverse transcriptase inhibitors. J. Med. Chem.
2008, 51, 5000–5008.
References
(1) UNAIDS/WHO UNAIDS/WHO 2007 AIDS Epidemic Update, 2007.
(2) De Clercq, E. Non-Nucleoside Reverse Transcriptase Inhibitors
(NNRTIs): Past, Present and Future. Chem. BiodiVersity 2004, 1, 44–
64.
(3) Bacheler, L.; Jeffrey, S.; Hanna, G.; D’Aquila, R.; Wallace, L.; Logue,
K.; Cordova, B.; Hertogs, K.; Larder, B.; Buckery, R.; Baker, D.;
Gallagher, K.; Scarnati, H.; Tritch, R.; Rizzo, C. Genotypic Correlates
of Phenotypic Resistance to Efavirenz in Virus Isolates from Patients
Failing Non-Nucleoside Reverse Transcriptase Inhibitor Therapy.
J. Virol. 2001, 75, 4999–5008.
(4) Haubrich, R.; Gubernick, S.; Yasothan, U.; Kirkpatrick, P. Etravirine.
Nat. ReV. Drug DiscoVery 2008, 7, 287.
(5) Fujiwara, T.; Sato, A.; El-Farrash, M.; Miki, S.; Abe, K.; Isaka, Y.;
Kodama, M.; Wu, Y.; Chen, L. B.; Harada, H.; Sugimoto, H.;
Hatanaka, M.; Hinumi, Y. S-1153 Inhibits Replication of Known Drug-
Resistant Strains of Human Immunodeficiency Virus Type 1. Anti-
microb. Agents Chemother. 1998, 42, 1340–1345.
(6) Viegas-Junior, C.; Danuello, A.; Bolzani, V.; Barreiro, E. J.; Fraga,
C. A. M. Molecular Hybrization: A Useful Tool in the Design of New
Drug Prototypes. Curr. Med. Chem. 2007, 14, 1829–1852.
(7) Boehm, H.-J.; Boehringer, M.; Bur, D.; Gmuender, H.; Huber, W.;
Klaus, W.; Kostrewa, D.; Kuehne, H.; Luebbers, T.; Meunier-Keller,
N.; Mueller, F. Novel Inhibitors of DNA Gyrase: 3D Structure Based
Biased Needle Screening, Hit Validation by Biophysical Methods, and
3D Guided Optimization. A Promising Alternative to Random
Screening. J. Med. Chem. 2000, 43, 2664–2674.
(8) Bobik, A.; Holder, G. M.; Ryan, A. Inhibitors of Hepatic Mixed
Function Oxidase. 3. Inhibition of Hepatic Microsomal Aniline
Hydroxylase and Aminopyrine Demethylase by 2,6- and 2,4-Dihy-
droxyphenyl Alkyl Ketones and Related Compounds. J. Med. Chem.
1977, 20, 1194–1199.
(9) Ren, J.; Nichols, C.; Bird, L. E.; Fujiwara, T.; Sugimoto, H.; Stuart,
D. I.; Stammers, D. K. Binding of the Second Generation Non-
Nucleoside Inhibitor S-1153 to HIV-1 Reverse Transcriptase Involves
Extensive Main Chain Hydrogen Bonding. J. Biol. Chem. 2000, 275,
14316–14320.
JM801322H