Synthesis and biological evaluation of alkenyldiarylmethane HIV-I non-nucleoside reverse transcriptase inhibitors that possess increased hydrolytic stability

Article abstract of DOI:10.1021/jm070382k

Non-nucleoside inhibitors of HIV reverse transcriptase (NNRTIs), albeit not the mainstays of HIV/AIDS treatment, have become increasingly important in highly active antiretroviral therapy (HAART) due to their unique mechanism of action. Several years ago

Full text of DOI:10.1021/jm070382k

4854
J. Med. Chem. 2007, 50, 4854-4867
Synthesis and Biological Evaluation of Alkenyldiarylmethane HIV-1 Non-Nucleoside Reverse
Transcriptase Inhibitors That Possess Increased Hydrolytic Stability
Matthew D. Cullen,† Bo-Liang Deng,† Tracy L. Hartman,‡ Karen M. Watson,‡ Robert W. Buckheit, Jr.,‡
Christophe Pannecouque,§ Erik De Clercq,§ and Mark Cushman*,†
Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, and the Purdue Cancer
Center, Purdue UniVersity, West Lafayette, Indiana 47907, Imquest Biosciences, 7340 ExecutiVe Way, Suite R, Frederick, Maryland 21704, and
Rega Institute for Medical Research, Katholieke UniVersiteit LeuVen, B-3000 LeuVen, Belgium
ReceiVed March 31, 2007
Non-nucleoside inhibitors of HIV reverse transcriptase (NNRTIs), albeit not the mainstays of HIV/AIDS
treatment, have become increasingly important in highly active antiretroviral therapy (HAART) due to their
unique mechanism of action. Several years ago our group identified the alkenyldiarylmethanes (ADAMs)
as a potent and novel class of NNRTIs; however, the most active compounds were found to be metabolically
unstable. Subsequent work has led to the synthesis of 33 analogues, with improved metabolic profiles,
through the replacement of labile esters with various heterocycles, nitriles, and thioesters. As a result, a
number of hydrolytically stable NNRTIs were identified with anti-HIV activity in the nanomolar concentration
range. Furthermore, an improved pharmacophore model has been developed based on the new ADAM series,
in which a salicylic acid-derived aryl ring is oriented cis to the side chain and the aryl ring that is trans to
the side chain contains a hydrogen bond acceptor site within the plane of the ring.
Introduction
immense structural diversity;6 however, only three NNRTIs
(nevirapine,7 delavirdine,8 and efavirenz9) have been approved
for clinical use by the FDA. NNRTIs exert their antiretroviral
effects through binding at an allosteric site close to (ap-
proximately 10 Å away), but separate from the nucleoside
binding site (polymerase active site). This dual mode of
inhibition available for RT typically results in a synergistic,
therapeutic effect when NNRTIs are coupled with NRTIs in
retroviral therapy.10 Unfortunately, aggressive treatment with
NNRTIs results in the rapid emergence of RT mutants that
exhibit cross-resistance to multiple NNRTIs.11 Should a patient
relapse after HAART fails to halt the progression of AIDS,
treatment of the resulting multi-drug-resistant (MDR) HIV is
problematic in that extreme dosing and constant exchange of
antiretrovirals is required, which produces serious side effects
and severe, acute toxicities.12 The emergence of MDR HIV
strains, as a result of antiretroviral therapy, has developed into
a serious medical issue because there are no efficient therapeu-
tics to combat them. In response, potent NNRTIs capable of
inhibiting MDR forms of RT are urgently needed, and this area
of research has the potential to make great contributions to AIDS
therapy.
In the 25 years since the initial discovery that acquired
immunodeficiency syndrome (AIDSa) is caused by the human
immunodeficiency virus (HIV), the disease has grown into a
global pandemic. At the end of 2005, the Joint United Nations
Programme on HIV/AIDS (UNAIDS) reported more than 4
million new cases of HIV infection for the year, bringing the
worldwide number of HIV-infected individuals up to more than
40 million.1 Given the rate at which HIV infection is spreading,
despite the current number of AIDS therapeutics and vast
resources being poured into AIDS research, it is quite clear that
curbing the spread of AIDS is becoming one of the most
challenging medical problems of the century.
Highly active antiretroviral therapy (HAART) is the first line
of defense against development of AIDS. The regimen has been
successful in reducing the morbidity and mortality associated
with AIDS progression to a level at which the disease can be
treated as a chronic ailment with associated drug toxicities.2-4
The success of HAART lies in the combined use of an HIV
protease inhibitor and several reverse transcriptase inhibitors
(RTIs). Typically, the RTIs employed are nucleoside or nucle-
otide analogues (NRTIs) that act as chain terminators for
developing viral DNA chains being reverse transcribed by
reverse transcriptase (RT). However, another class of RTIs, the
non-nucleoside reverse transcriptase inhibitors (NNRTIs), have
been experiencing increased use in HAART over the past several
years.5
Several years ago, our group discovered a novel class of
NNRTIs based on an alkenyldiarylmethane (ADAM) scaffold
while investigating the ability of cosalane analogues to inhibit
the attachment of HIV-1 to CD4+ cells.13-15 The initial lead
compounds exhibited low micromolar inhibition of HIV-1
cytopathicity, and, after a few years of investigation, ADAMs
1 and 2 were identified as sub-micromolar inhibitors of HIV-1
RT, which also exhibited minimal losses in potency against
clinically relevant RT mutants K103N and L100I.16 Unfortu-
nately, it was discovered that conversion of the methyl esters
present in the ADAMs to carboxylic acids results in complete
loss of antiviral activity, which compromises the ADAMs as
potential therapeutic agents because ester hydrolysis is expected
to occur readily in vivo.15-17 The focus of the project therefore
shifted toward improving the hydrolytic stability of the ADAMs
The NNRTI class of HIV-1 antiretroviral agents is reported
to consist of over thirty different scaffolds, which exhibit
* To whom correspondence should be addressed. E-mail: cushman@
pharmacy.purdue.edu. Phone: 765-494-1465. Fax: 765-494-6790.
† Purdue University.
‡ ImQuest Biosciences, Inc.
§ Katholieke Universiteit Leuven.
a Abbreviations: AIDS, acquired immunodeficiency syndrome; AZT,
azidothymidine; DIAD, diisopropylazodicarboxylate; HAART, highly active
anti-retroviral therapy; HIV, human immunodeficiency virus; NNRTI, non-
nucleoside reverse transcriptase inhibitor; RT, reverse transcriptase.
10.1021/jm070382k CCC: $37.00 © 2007 American Chemical Society
Published on Web 09/06/2007

Alkenyldiarylmethane HIV-1 NNRTIs
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20 4855
while maintaining their antiviral potency, and we have been
making progress toward this objective.18-20
Design
Given the recent assertion that performing molecular model-
ing studies on novel NNRTIs without an experimentally
determined NNRTI-RT crystal structure complex is problematic,
and because our own attempts to explain the SAR of ADAMs
based on hypothetical models of protein complexes have been
frustrating,18,21 we opted to forego traditional structure-based
drug design in favor of synthesizing an array of compounds
that incorporate several of our current leads for improving the
hydrolytic stability of ADAMs. Past SAR work on ADAMs
indicated that conversion of the labile esters to traditional
bioisosteres, such as amides,15,22 ketones,16,18 carbamates,16 and
oxazolidinones,19,22 usually yielded analogues with significantly
reduced or no detectable antiviral activity. In contrast, thioester
replacements on the aryl rings surprisingly provide the desired
increase in hydrolytic stability at the expense of only a 6-fold
loss in potency.18 We have also reported that replacing the esters
and adjacent methoxy groups on the aryl rings with a number
of hydrolytically stable heterocycles (as shown in ADAMs 3
and 4) or a simple nitrile moiety effectively increases the half-
RT and to protect infected cells from the cytopathic effects of
three HIV strains (HIV-1 strains RF and IIIB, and HIV-2 strain
ROD). The more potent analogues identified in the series were
also tested for cytoprotective activity against HIV-1 strains
bearing the K103N and Y181C mutations. In addition, the
metabolic half-lives of a subset of ADAMs in rat plasma were
determined to ensure that the hydrolytic stability of the proposed
compounds had, in fact, increased relative to the parent
compounds.
Results and Discussion
lives of analogues in rat plasma and occasionally maintains the
anti-HIV potency of the parent compounds.20,23 The side chain
ester SAR indicates that this region of the ADAMs is more
amenable to change, relative to the rest of the molecule;
however, conservation of electrostatic potential and hydrogen
bond acceptor sites appears to be necessary for achieving high
potency. As such we sought to replace the remaining side chain
ester with a hydrolytically stable heterocycle (such as an
alkylated tetrazole or 1,3,4-oxadiazole), which possesses a
similar electrostatic potential surface, volume, and number of
hydrogen bond acceptor sites as an ester. Although the antiviral
activity of the target compounds may not necessarily be
governed by the “sum of the fragments” composing them, we
believed that the serial array strategy was the best option
available for combining our various leads to produce potent
antiviral agents.
Chemistry. Over the course of the project, a variety of routes
have been established for the synthesis of ADAMs, including
a solid-phase based strategy.16,23,24 Of the options available we
chose the route that utilized a series of metal-mediated cross-
coupling reactions to stitch ADAMs together from a series of
simple, common precursors because it particularly suited our
array design. All of the ADAMs reported here were synthesized
from common precursors via the same methodology; thus a
general, rather than a detailed, scheme is presented for the
synthesis of ADAMs 5-37 (Scheme 1). Briefly, Sonogashira
coupling of aryl halide 38 with terminal alkyne 39 afforded the
highly functionalized alkyne intermediate 40, which when
treated with tributyltin hydride and a catalytic amount of Pd-
(PPh3)4 yields stannane 41. To complete the synthesis of the
ADAM scaffold, a Stille coupling between stannane 41 and aryl
halide 42 provided the desired target compound 43.
Herein we report the synthesis of a serial array of 33 new
ADAMs 5-37, which led to the discovery of several antiviral
agents with low micromolar and sub-micromolar activities. The
new ADAMs were evaluated for their ability to inhibit HIV-1
The conditions reported for all reactions in Scheme 1 were
general and provided the desired products in good yields
(typically >70%), regardless of the substrates used. With respect

4856 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20
Cullen et al.
Scheme 1a
Scheme 2a
a
Reagents and conditions: (a) KOH, MeOH, reflux; (b) (i) SOCl2,
reflux; (ii) NaSCH3, benzene, rt; (c) H2NOH-HCl, EtOH, reflux; (d) PPh3,
DIAD; (e) NaN3, Et3N-HCl, toluene, reflux; (f) cat. Bu4NBr, K2CO3,
Me2SO4, EtOAc/H2O; (g) Ac2O, reflux.
of oxime intermediate 54 was accomplished with triphenylphos-
phine and DIAD to afford isoxazole 48.
Alkynes 59-64 were synthesized from their corresponding
nitriles, 55 and 56, via tetrazole intermediates. Treatment of
commercially available nitriles 55 and 56 with triethylamine
hydrochloride and sodium azide afforded the cycloaddition
products 57 and 58, respectively. The tetrazole intermediates
57 and 58 conveniently served as common precursors for both
the methylated tetrazole and oxadiazole-bearing side chains via
application of different reaction conditions. Alkylation of
tetrazoles 57 and 58 proceeded smoothly with dimethyl sulfate
and potassium carbonate under biphasic catalysis conditions to
afford mixtures of the 1H and 2H methylated products (59 mixed
with 61 and 60 mixed with 62), which were easily separated
a
Reagents and conditions: (a) cat. PdCl2(PPh3)2, cat. CuI, Et3N, THF,
rt; (b) cat. Pd(PPh3)4, Bu3SnH, THF, 0 °C to rt; (c) cat. CuI or 1 equiv. of
CuI, cat. Pd(PPh3)4, CsF, DMF, 60 °C.
to the Stille coupling, it was found that the cross-coupling could
be performed in the presence of copper(I) iodide in either
catalytic or stoichiometric amounts; however, the two conditions
required reaction times of 4-24 h (depending on the substrates)
or 15 min, respectively. Although copper is a heavy metal and
use of its associated reagents in excess amounts should be
avoided due to toxicity concerns, the Stille couplings were
performed on a sufficiently small scale that using stoichiometric
amounts of the metal did not present a significant hazard. As
such, the majority of the Stille couplings utilized a full
equivalent of copper(I) iodide in an effort to enhance coupling
yields and reaction times.
1
via chromatography on silica and distinguished by H NMR
chemical shifts of the methyl groups. Alternatively, a mixture
of acetic anhydride and tetrazole 57 or 58 could be heated at
reflux to obtain the desired oxadiazole intermediates 63 and
64, respectively.
Of the common aryl “building blocks” presented in Scheme
1, the syntheses of intermediates 44,19 46,23 47,19 and 4919 have
been previously reported and benzonitriles 50 and 51 are
commercially available. The syntheses of aryl intermediates 45
and 48 are presented in Scheme 2, in addition to the alkyne
intermediates 59-64, which were required for the initial
Sonogashira couplings, as depicted by alkyne 39. Access to
thioester 45 was conveniently achieved through another aryl
building block, ester 44. Saponification of 44 was effected
through heating a mixture of the ester and potassium hydroxide
in methanol at reflux to afford benzoic acid 52. Treatment of
acid 52 with thionyl chloride to obtain the corresponding acyl
chloride intermediate, followed by esterification with sodium
thiomethoxide in benzene, afforded thioester 45. Synthesis of
isoxazole 48 began with formation of oxime 54 from salicylic
aldehyde 53 via condensation with hydroxylamine. Cyclization
Biological Results and Discussion. The antiviral activity of
the ADAMs was evaluated by determining their ability to inhibit
the enzymatic activity of HIV-1 RT in Vitro and protect HIV-
infected cells from the cytopathic effects of three viral strains
(HIV-1 strains RF and IIIB, and HIV-2 strain ROD). In addition,
cytotoxicities for the ADAMs were recorded and their metabolic
half-lives in rat plasma (Sigma, St. Louis, MO) were determined.
The results of the antiviral and metabolic investigations on
ADAMs 5-37 are presented in Table 1. Associated data for
ADAMs 1-4 and two clinically approved NNRTIs (nevirapine
and efavirenz) are included for comparison.
Unsurprisingly, a wide range of inhibitory activities were
exhibited by the array of ADAMs; however, the array design
was surprisingly successful at affording a large number of
moderately potent NNRTIs. Of the 33 ADAMs under investiga-
tion, 74% of the compounds displayed IC50 values lower than

Alkenyldiarylmethane HIV-1 NNRTIs
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20 4857
CC50 (µM)c
Table 1. Antiviral Activity and Hydrolysis Half-Lives of ADAMs 1-37
EC50 (µM)b
half-life
IC50
t1/2 ( SD
compound
(µM)a
HIV-1RF
HIV-1IIIB
HIV-2ROD
CEM-SS
MT-4
(min)d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
0.30
0.30
0.02
0.91
53
67
95
7.7
71
32
29
24
7.4
0.39
1.0
> 100
0.90
9.2
2.6
9.3
6.3
7.7
90
33
> 100
55
48
6.7
0.47
> 100
0.52
3.2
36
5.2
> 100
7.7
0.001
0.01
0.03
0.04
NAe
2.9
0.30
0.60
0.09
0.02
NAe
NAe
NAe
1.5
NAe
25
13
32
91
160
17
1.1
5.0
7.0
1.4
34
6.2 ( 0.4
5.8 ( 0.9
1.3 ( 0.09
NTf
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
4.7
5.1
0.50
9.6
33
1.6
7.4
40
13
4.5
28
7.7
2.8
3.2
8.1
2.1
18
5.9
2.7
5.5
38
6.6
1.2
17
1.3
1.2
5.3
5.7
6.0
12
24 ( 3.2
NTf
NAe
2.4
NTf
42 ( 3.2
3.3 ( 0.07
78 ( 4.1
113.5 ( 0.7
45 ( 1.4
219.5 ( 9.2
331 ( 20
NTf
2.3
3.2
37
NAe
NAe
3.0
NAe
NAe
2.0
3.9
8.1
16
41
6.4
13
5.9
4.4
19
12
8.4
45
NT
14
1.6
37
3.8
3.2
4.4
7.0
9.9
36
3.0
2.7
0.36
0.43
NAe
0.52
6.4
0.60
NAe
2.1
0.42
0.44
NAe
0.81
3.7
0.69
1.4
3.2
NTf
1090 ( 302
NTf
739 ( 25
221 ( 43
NTf
NAe
NAe
NTf
2.6
NTf
NAe
NAe
NAe
NAe
NAe
1.3
0.14
0.76
0.83
0.36
NAe
NAe
NAe
NAe
NAe
0.053
0.001
NTf
NAe
NAe
NAe
NAe
NAe
2.2
5.9
NTf
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NAe
NTf
NTf
NTf
NTf
76 ( 4.2
864 ( 29
NTf
0.05
0.97
0.50
0.60
NAe
NAe
NAe
NAe
NAe
0.015
0.005
221 ( 43
45 ( 7.1
NTf
8.9
5.5
0.78
12
7.2
4.8
36
33
34
35
36
7.7
1.1
25
8.2
7.6
15
NTf
NTf
NTf
37
0.45
NT
NT
41.5 ( 2.1
nevirapine
efavirenz
NTf
6.0
NTf
a Inhibitory activity versus HIV-1 RT with poly(rC).oligo(dG) as the template primer. b EC50 is the 50% inhibitory concentration for inhibition of the
cytopathic effect of HIV-1RF in CEM-SS cells, HIV-1IIIB in MT-4 cells, or HIV-2ROD in MT-4 cells. c CC50 is the cytotoxic concentration required to induce
cell death for 50% of the mock infected CEM-SS or MT-4 cells. d The metabolic half-life of the compound when it was incubated with rat plasma; determined
from a minimum of two replicates. e Not Active. f Not Tested.
50 µM. Even more encouraging was the observation that 53%
of the array displayed RT IC50 values in the low micromolar to
nanomolar range (less than 10 µM), with the lowest IC50 of
0.39 µM being assigned to ADAM 14. Unfortunately, although
53% of the compounds in the array were at least low micromolar
inhibitors of HIV-1 RT enzymatic activity in Vitro, many failed
to satisfactorily protect HIV-infected cells from the cytopathic
effects of the virus because either they were less potent in a
cellular system (example: ADAM 37) or possessed pronounced
cytotoxicities (example: ADAM 34). Despite the overall
drawbacks observed for many of the compounds, ADAMs 14
and 29 exhibited sub-micromolar antiviral and RT inhibitory
activities. Yet, 14 and 29 were both 5- to 400-fold less potent
in the cytoprotective assays than the clinically approved NNRTIs
nevirapine and efavirenz, indicating that the potency of the
ADAMs still has room for improvement. As is typical of most
NNRTIs, all of the target compounds were inactive against HIV-
2, with the exception of ADAMs 19 and 23.
poorly inhibit RT activity in Vitro, such as 6 and 9, but are
relatively potent antivirals in the cellular assays. These observa-
tions led to the conclusion that ADAMs likely interact with
additional cellular and/or viral entities to produce their cytotoxic
and antiviral effects. In the development of new therapeutics,
emergence of drug-related toxicities is expected; however, when
the toxicity increases along with the drug potency, the thera-
peutic target and source of toxicity likely possess similar
pharmacophores, which complicates drug development efforts.
In regard to non-RT, antiviral therapy targets, there are several
other HIV replication proteins, such as integrase or TaT, and
HIV-associated cellular pathways through which ADAMs might
be affecting the HIV lifecycle. To address these issues,
additional investigations are being performed to identify other
molecular entities through which ADAMs may exert their
antiviral and cytotoxic effects.
During prior investigations, ADAMs 1 and 2 displayed
zero- to 5-fold loss in antiviral activity against NNRTI-resistant
HIV-1 bearing the K103N and Y188C RT mutations, yet their
potency was significantly reduced (20-fold or more) when in
the presence of the Y181C mutation. It was believed that, in
general, other ADAM analogues would exhibit similar patterns
in antiviral activity against these same mutations. In light of
Over the course of this project, the ADAMs have exhibited
undesirable cytotoxic properties, which narrow their therapeutic
windows; unfortunately, as ADAM RT inhibitory activity has
improved, the compounds have typically become more cyto-
toxic. Also, compounds have occasionally been identified that

4858 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20
Cullen et al.
Figure 1. The general SAR observed for ADAMs as generated from past studies.
Figure 2. New pharmacophore model for the design of potent ADAM-based NNRTIs.
this information, cytoprotective activities for ADAMs 11, 13-
15, 17-19, 21, 22, 28, 29, 31, 32, 34, and 37, the fifteen most
potent RT inhibitors in this study, were determined for CEM-
SS cells that had been infected with NNRTI-resistant HIV-1
strains, which were engineered to express the K103N and
Y181C RT mutations.25,26 As expected, all fifteen analogues
were inactive (EC50 > 100 µM) in the cytoprotection assay for
the Y181C mutant, mirroring the attenuation in antiviral activity
reported for ADAMs 1 and 2. Unexpectedly, only ADAMs 14,
19, 29, 31, and 32 were found to inhibit the cytopathic effects
of the K103N HIV-1 mutant with EC50 values of 0.8, 1.0, 0.4,
1.2, and 2.3 µM, respectively, which reflected only a 2- to 8-fold
loss in antiviral potency for these analogues relative to their
activities against wild-type HIV-1RF in CEM-SS cells. The
remaining analogues showed no cytoprotective activity against
the K103N mutant (EC50’s > 50 µM). The antiviral potency of
nevirapine was reduced by four and five times in the Y181C
and K103N mutant assays, respectively.
After noting the salient information obtained from the antiviral
evaluations, a closer examination of the data yields a new
pharmacophore model for potent ADAM-based NNRTIs (Figure
2). In comparing the structures of the most potent RT inhibitors
in the array (ADAMs 14, 15, 17, 29, and 31) with earlier leads
3 and 4, one notices that the compounds share many structural
similarities. First, the inhibitors contain a salicylic acid-derived
aryl ring cis to the side chain. Second, the compounds have
chain lengths of either two or three methylene units, although
the longer three methylene unit side chain is optimal. Third,
the aryl ring trans to the side chain contains a pendant functional
group, at the three or four position, with a hydrogen bond
acceptor site in the plane of the ring. In addition, on the basis
of past and current SAR data, the side chain must contain a
small functional group capable of accepting hydrogen bonds.
This new model more narrowly defines the structural features
that are required for potent RT inhibitory in the ADAM series;
however, the accuracy of the new model needs to be validated
by future work.
Metabolic Stability Studies. The basis of our research has
been toward improving the metabolic stability of the lead
compounds, so that we may continue the development of new,
potential antivirals. To ensure that the ester bioisosteres were,
in fact, improving the hydrolytic stability of the array, a
metabolic stability assay was employed to determine the ADAM
half-lives in rat plasma.18 Rat plasma was utilized because
esterase activity in rodents is reported to be significantly higher
than that of humans, so ADAMs displaying moderately short
or longer half-lives in the assay should, a fortiori, be particularly
stable to similar forms of metabolism in humans. A panel of
ADAMs, which included the most active compounds from the
array, was subjected to the metabolism assay, and the calculated
half-lives are presented in Table 1, along with the antiviral data.
After surveying the metabolism data, it is evident that the
ester bioisosteres successfully increased the metabolic half-lives
of the analogues relative to the lead compounds, albeit to varying
degrees. In some cases, incorporation of the bioisosteres afforded
ADAMs with several hour long half-lives (example: ADAM
17), but for others the increase in half-life was modest at best,
resulting in compounds whose metabolic profiles are not much
better than those of the original leads (example: ADAM 37).
However, many of the potent inhibitors, notably nanomolar
inhibitor 29, exhibited half-lives of at least 3 h, which should
translate into a longer half-life in a human system with similar
metabolic processes.
The inclusion of ester bioisosteres in the ADAM system
clearly does not render all compounds resistant to hydrolysis,
and the rate of metabolism for each compound appears to be
based on its individual structure. This observation is not
surprising because the metabolic enzymes would be expected

Alkenyldiarylmethane HIV-1 NNRTIs
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20 4859
from a FinniganMAT XL95. Analytical HPLC analyses performed
to aid in the establishment of compound purity were completed on
a Waters binary HPLC system (model 1525, 20 µL injection loop)
equipped with a Waters dual wavelength absorbance UV detector
(model 2487) set for 254 nM. The mobile phases consisted of 8:2
(v/v) acetonitrile-water or 8:2 (v/v) THF-water, and the Symmetry
HPLC column (4.6 mm × 150 mm) was packed with C18 silica
from Waters. All yields reported refer to isolated yields. The
structures of all of the intermediates for the general synthetic scheme
(Scheme 1) that are referenced in experimental procedures, but are
not explicitly shown in the body of the paper, can be found in the
Supporting Information.
to have their own sets of structure-activity relationships for
the ADAM class of compounds. However, for the ADAM-rat
esterase system, ester stability is modulated by the overall
ADAM structure to the extent that an ADAM bearing an ester
(ADAM 13) can exhibit a longer metabolic half-life than one
whose esters have been replaced with bioisosteres (ADAM 32).
In fact, compounds with very similar structures can have
significantly different metabolic half-lives (ADAM 31 versus
32).
Conclusions
General Procedure for the Synthesis of Alkenyldiaryl-
methanes via Stille Cross-Coupling of Stannanes with Aryl
Halides. A mixture of stannane 41 (1 equiv) and aryl halide 42
(1.2 equiv) in anhydrous DMF (2-3 mL) was sparged with argon
for 10 min and maintained under an argon atmosphere. Cesium
fluoride (3.5 equiv), Pd(PPh3)4 (0.1 equiv), and copper(I) iodide
(0.2-1 equiv) were quickly added to the reaction mixture, which
was again placed under an argon atmosphere. The reaction mixture
was stirred at 60 °C, under an argon atmosphere, for 1-24 h until
the stannane starting material had been consumed. The system was
allowed to cool to room temperature, and the reaction mixture was
sonicated at room temperature for 30 s, after being diluted with a
mixture of ethyl acetate (5 mL), methanol (1 mL), and water (1
mL). The reaction mixture was loaded onto a short column of silica
(10-20 mL), and the products were eluted with ethyl acetate (50-
75 mL). The eluate was then washed with a basic, aqueous solution
(pH ) 10) of 1 M EDTA (2 × 20 mL) and an aqueous solution
saturated with ammonium chloride (2 × 20 mL). The phases were
separated, and the organic phase was dried over magnesium sulfate,
filtered, and condensed in vacuo to afford the crude products. The
crude products were separated by column chromatography to obtain
the desired ADAM product, and, if necessary, additional purification
methods were applied.
The incorporation of ester bioisosteres into an array of
ADAMs led to the successful development of several low
micromolar and sub-micromolar inhibitors of HIV-1 reverse
transcriptase that exhibited increased metabolic stability in rat
plasma relative to their parent analogues. Among the inhibitors
synthesized, ADAM 14 proved to be the most potent inhibitor
of RT in Vitro, exhibiting an IC50 of 0.39 µM. However, ADAM
29 displayed similar RT inhibitory activity (IC50 ) 0.47 µM)
to 14, yet also exhibited superior cytoprotective and metabolic
stability profiles, making it a better candidate for future
development. Unfortunately, the ADAM class of NNRTIs
exhibit cytotoxic properties and the relative cytotoxicity of the
compounds tends to increase as the RT inhibitory potency
increases. Regardless of the apparent toxicities associated with
the analogues produced in this study, the antiviral activity of
the ADAMs still falls short of current FDA-approved NNRTIs,
and additional studies are required to improve their potencies.
Additionally, the ADAMs produced in this study were
incapable of inhibiting the cytopathic effects of HIV-1 bearing
the Y181C RT mutation, clearly indicating that these analogues
are not suitable for treating drug-resistant HIV bearing this
particular mutation. However, in relation to the K103N RT
mutation, five compounds were identified that retained antiviral
activity, exhibiting only 2- to 8-fold reductions in potency. On
the basis of this investigation and past ADAM studies, another
viral or cellular entity may play a role in the antiviral properties
of the ADAMs, and therefore additional studies are being
performed to identify other potential mechanisms for the
antiviral activity and cytotoxicity of the ADAMs. Antiviral data
obtained for the array also led to the development of a new
pharmacophore model, which will serve an important role in
the development of future ADAM-based NNRTIs.
Methyl 2-Methoxy-5-[1-(4-methoxy-3-methyl-5-methoxycar-
bonyl-phenyl)-4-(2-methyl-2H-tetrazol-5-yl)-but-1-enyl]-3-me-
thylbenzoate (5). The general Stille coupling procedure was
followed using stannane 69 (375 mg, 0.619 mmol), iodide 44 (255
mg, 0.833 mmol), cesium fluoride (338 mg, 2.23 mmol), Pd(PPh3)4
(75 mg, 0.065 mmol), and copper(I) iodide (26 mg, 0.137 mmol)
in anhydrous DMF (6 mL). The reaction mixture was stirred for
17 h. The crude products were separated by column chromatography
(100 mL of silica gel, 2 in. diameter) using an ethyl acetate-
hexanes gradient (50-80%). The product was isolated and purified
again by column chromatography (80 mL of silica gel, 2 in.
diameter) using an ethyl acetate-hexanes gradient (20-66%). The
desired ADAM product was isolated as a clear oil (255 mg, 83%):
IR (neat) 2951, 2862, 2004, 1729, 1600, 1577, 1480, 1436, 1379,
Experimental Section
1
1298, 1260, 1228, 1173, 1135, 1123, 1008 cm-1; H HMR (300
Unless noted, all 1H NMR spectra were obtained at 300 MHz in
CDCl3, using the deuterated solvent as the internal standard for
chemical shifts. In the cases where a solvent other than CDCl3 was
utilized, the alternative solvent was used as the internal standard,
with the calibration set according to the residual solvent peak as
reported by Nudelman and co-workers.27 A Perkin-Elmer 1600
series FT-IR spectrometer was used to record infrared spectra of
all compounds, and flash chromatography was performed on 230-
400 mesh silica. Preparative TLC separations utilized Analtech
Uniplates with glass supported silica (20 × 20 cm, 2000 µm
thickness) and UV indicator (254 nm). The progress of reactions
was monitored with Baker-flex silica gel IB2-F plates (0.25 mm
thickness). Melting points are uncorrected. Unless specifically
mentioned, chemicals and solvents were of minimum reagent grade
and used as obtained from commercial sources without further
purification. Anhydrous tetrahydrofuran was prepared by distillation
from sodium ketyl radical. The hydrolytic stability assay utilized
lyophilized rat plasma (LOTs 052K7609 and 065K7555) from
Sigma Chemical Co., St. Louis, MO. Elemental analyses were
performed at the Purdue University Microanalysis Laboratory. High-
resolution mass spectra for all ionization techniques were obtained
MHz, CDCl3) δ 7.44 (d, J ) 2.4 Hz, 1 H), 7.37 (d, J ) 2.4 Hz, 1
H), 7.08 (d, J ) 1.8 Hz, 1 H), 7.06 (d, J ) 1.8 Hz, 1 H), 6.01 (t,
J ) 7.5 Hz, 1 H), 4.30 (s, 3 H), 3.90 (s, 3 H), 3.89 (s, 3 H), 3.87
(s, 3 H), 3.80 (s, 3 H), 3.00 (t, J ) 7.5 Hz, 2 H), 2.57 (q, J ) 7.5
Hz, 2 H), 2.30 (s, 3 H), 2.25 (s, 3 H); ESIMS m/z (relative intensity)
517 (MNa+, 100). Anal. (C26H30N4O6) C, H, N.
2-Methoxy-5-[1-(4-methoxy-3-methyl-5-methylsulfanylcarbo-
nyl-phenyl)-4-(2-methyl-2H-tetrazol-5-yl)-but-1-enyl]-3-methyl-
thiobenzoic Acid S-Methyl Ester (6). The general Stille coupling
procedure was followed using stannane 73 (144 mg, 0.232 mmol),
iodide 45 (95 mg, 0.299 mmol), cesium fluoride (135 mg, 0.889
mmol), Pd(PPh3)4 (27 mg, 0.023 mmol), and copper(I) iodide (15
mg, 0.079 mmol) in anhydrous DMF (2 mL). The reaction mixture
was stirred for 15 h. The crude products were absorbed onto silica
gel (2 mL) and separated by column chromatography (80 mL of
silica gel, 2 in. diameter) using an ethyl acetate-hexanes gradient
(33-66%). The desired product was isolated as a highly viscous,
pale yellow oil (57 mg, 47%): IR (neat) 2298, 2857, 2824, 1673,
1644, 1593, 1574, 1478, 1417, 1379, 1307, 1244, 1199, 1156, 1133,
1039, 1001 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.37 (d, J ) 2.4
Hz, 1 H), 7.32 (d, J ) 2.1 Hz, 1 H), 7.08 (dd, J ) 2.1, 0.6 Hz, 1

4860 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20
Cullen et al.
H), 7.05 (dd, J ) 2.1, 0.6 Hz, 1 H), 6.02 (t, J ) 7.2 Hz, 1 H), 4.30
(s, 3 H), 3.86 (s, 3 H), 3.80 (s, 3 H), 3.02 (t, J ) 7.5 Hz, 2 H), 2.59
(q, J ) 7.5 Hz, 2 H), 2.44 (s, 3 H), 2.43 (s, 3 H), 2.32 (s, 3 H),
2.26 (s, 3 H); ESIMS m/z (relative intensity) 549 (MNa+, 9), 526
(MH+, 37), 497 (MH+ - SCH3 + H2O, 100), 479 (MH+ - SCH3,
24). Anal. (C26H30N4O4S2) C, H, N.
mg, 0.143 mmol) in anhydrous DMF (7 mL). The reaction mixture
was stirred for 21 h. The crude products were separated by column
chromatography (110 mL of silica gel, 2 in. diameter) using an
ethyl acetate-hexanes gradient (50-100%), and the desired product
was further purified by preparative thin layer chromatography using
50% ethyl acetate-hexanes as the eluant (developed twice). The
product was isolated as a very viscous, opaque oil (239 mg, 65%):
IR (neat) 2930, 2866, 2004, 1730, 1679, 1645, 1595, 1570, 1479,
(Z)-Methyl 2-Methoxy-5-[1-(4-methoxy-3-methyl-5-methyl-
sulfanylcarbonyl-phenyl)-4-(2-methyl-2H-tetrazol-5-yl)-but-1-
enyl]-3-methylbenzoate (7). The general Stille coupling procedure
was followed using stannane 69 (225 mg, 0.372 mmol), iodide 45
(183 mg, 0.568 mmol), cesium fluoride (199 mg, 1.30 mmol), Pd-
(PPh3)4 (50 mg, 0.043 mmol), and copper(I) iodide (18 mg, 0.096
mmol) in anhydrous DMF (4 mL). The reaction mixture was stirred
for 16 h. The crude products were absorbed onto silica (3 mL) and
separated by column chromatography (100 mL of silica, 2 in.
diameter) using an ethyl acetate-hexanes gradient (20-50%). The
product was isolated as a yellow oil (141 mg, 74%): IR (neat)
3642, 2950, 2004, 1729, 1675, 1646, 1594, 1575, 1479, 1435, 1379,
1
1435, 1379, 1296, 1253, 1229, 1125, 1049, 1004 cm-1; H NMR
(300 MHz, CDCl3) δ 7.39 (d, J ) 2.1 Hz, 1 H), 7.36 (d, J ) 2.4
Hz, 1 H), 7.09 (d, J ) 2.1 Hz, 1 H), 7.06 (d, J ) 2.4 Hz, 1 H),
6.00 (t, J ) 7.5 Hz, 1 H), 3.90 (s, 3 H), 3.88 (s, 3 H), 3.80 (s, 3 H),
2.92 (t, J ) 7.5 Hz, 2 H), 2.57 (q, J ) 7.5 Hz, 2 H), 2.48 (s, 3 H),
2.43 (s, 3 H), 2.32 (s, 3 H), 2.27 (s, 3 H); ESIMS m/z (relative
intensity) 511 (MH+, 94), 481 (MH+ - SCH3 + H2O, 100). Anal.
(C27H30N2O6S) C, H, N.
(Z)-Methyl 5-[1-(3-Cyanophenyl)-4-(5-methyl-[1,3,4]oxadia-
zol-2-yl)-but-1-enyl]-2-methoxy-3-methylbenzoate (11). The gen-
eral Stille coupling procedure was followed using stannane 71 (200
mg, 0.330 mmol), bromide 50 (83 mg, 0.429 mmol), cesium fluoride
(177 mg, 1.17 mmol), Pd(PPh3)4 (6 mg, 0.033 mmol), and copper-
(I) iodide (13 mg, 0.066 mmol) in anhydrous DMF (3 mL). The
reaction mixture was stirred for 16 h. The crude products were
absorbed onto silica (2 mL) and purified by column chromatography
(100 mL of silica, 2 in. diameter) using an ethyl acetate-hexanes
gradient (50-100%). The product was isolated as a clear oil (103
mg, 75%): IR (neat) 3065, 2950, 2851, 2229, 2003, 1728, 1596,
1571, 1480, 1436, 1379, 1299, 1256, 1230, 1199, 1154, 1125, 1007
1
1296, 1253, 1229, 1208, 1150, 1125, 1051, 1005 cm-1; H HMR
(300 MHz, CDCl3) δ 7.38 (s, 1 H), 7.37 (s, 1 H), 7.08 (d, J ) 1.8
Hz, 1 H), 7.06 (d, J ) 1.8 Hz, 1 H), 6.02 (t, J ) 7.2 Hz, 1 H), 4.30
(s, 3 H), 3.90 (s, 3 H), 3.87 (s, 3 H), 3.80 (s, 3 H), 3.00 (t, J ) 7.2
Hz, 2 H), 2.58 (q, J ) 7.2 Hz, 2 H), 2.43 (s, 3 H), 2.31 (s, 3 H),
2.26 (s, 3 H); ESI HRMS m/z calcd for C26H30N4O5S [MNa+]
533.1835, found 533.1840; ESIMS m/z (relative intensity) 533
(MNa+, 100), 481 (MH+ - SCH3 + H2O, 76).
(Z)-5-[1-(3-Cyanophenyl)-4-(2-methyl-2H-tetrazol-5-yl)-but-
1-enyl]-2-methoxy-3-methylbenzoic Acid Methyl Ester (8). The
general Stille coupling procedure was followed using stannane 69
(155 mg, 0.256 mmol), bromide 50 (65 mg, 0.357 mmol), cesium
fluoride (161 mg, 1.06 mmol), Pd(PPh3)4 (32 mg, 0.028 mmol),
and copper(I) iodide (11 mg, 0.058 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 13.5 h. The crude products
were absorbed onto silica (5 mL) and separated by column
chromatography (100 mL of silica, 2 in. diameter) using an ethyl
acetate-hexanes gradient (33-50%). The product was isolated as
a clear oil (94 mg, 88%): IR (neat) 3063, 2951, 2858, 2229, 1728,
1597, 1575, 1480, 1436, 1418, 1396, 1380, 1300, 1256, 1231, 1199,
1154, 1125, 1008 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.51 (dt, J
) 7.2, 1.5 Hz, 1 H), 7.44-7.34 (m, 4 H), 7.04 (d, J ) 1.8 Hz, 1
H), 6.14 (t, J ) 7.5 Hz, 1 H), 4.30 (s, 3 H), 3.91 (s, 3 H), 3.89 (s,
3 H), 3.02 (t, J ) 7.5 Hz, 2 H), 2.61 (q, J ) 7.5 Hz, 2 H), 2.32 (s,
3 H); ESIMS m/z (relative intensity) 440 (MNa+, 100), 364 (MH+
- C2H2N2, 67). Anal. (C23H23N5O3) C, H, N.
Methyl 2-Methoxy-5-[1-(4-methoxy-3-methyl-5-methoxycar-
bonylphenyl)-4-(5-methyl-[1,3,4]oxadiazol-2-yl)-but-1-enyl]-3-
methylbenzoate (9). The general Stille coupling procedure was
followed using stannane 71 (522 mg, 0.862 mmol), iodide 44 (356
mg, 1.16 mmol), cesium fluoride (461 mg, 3.03 mmol), Pd(PPh3)4
(99 mg, 0.086 mmol), and copper(I) iodide (47 mg, 0.247 mmol)
in anhydrous DMF (6 mL). The reaction mixture was stirred for
17 h. The crude products were separated by column chromatography
(125 mL of silica, 2 in. diameter) using an ethyl acetate-hexanes
gradient (20-100%). The desired product was further purified by
preparative thin layer chromatography using 50% ethyl acetate-
hexanes as the eluant (developed 4 times). The desired ADAM
product was isolated as a pale, yellow oil (284 mg, 67%): IR (neat)
3000, 2950, 2851, 1729, 1596, 1570, 1480, 1436, 1298, 1260, 1228,
1173, 1135, 1123, 1007 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.42
(d, J ) 2.4 Hz, 1 H), 7.38 (d, J ) 2.1 Hz, 1 H), 7.08 (d, J ) 2.1
Hz, 1 H), 7.05 (d, J ) 2.1 Hz, 1 H), 5.98 (t, J ) 7.2 Hz, 1 H), 3.89
(s, 3 H), 3.88 (s, 3 H), 3.86 (s, 3 H), 3.80 (s, 3 H), 2.91 (t, J ) 7.5
Hz, 2 H), 2.56 (dt, J ) 7.5, 7.2 Hz, 2 H), 2.47 (s, 3 H), 2.30 (s, 3
H), 2.24 (s, 3 H); CIMS m/z (relative intensity) 495 (MH+, 100),
463 (MH+ - HOCH3, 73). Anal. (C27H30N2O7) C, H, N.
1
cm-1; H NMR (300 MHz, CDCl3) δ 7.52 (dt, J ) 7.2, 1.5 Hz, 1
H), 7.46-7.35 (m, 4 H), 7.05 (d, J ) 1.8 Hz, 1 H), 6.12 (t, J ) 7.2
Hz, 1 H), 3.97 (s, 3 H), 3.90 (s, 3 H), 2.94 (t, J ) 7.2 Hz, 2 H),
2.61 (q, J ) 7.2 Hz, 2 H), 2.48 (s, 3 H), 2.33 (s, 3 H); ESI HRMS
m/z calcd for C24H23N3O4 [MNa+] 440.1586, found 440.1580;
ESIMS m/z (relative intensity) 440 (MNa+, 100).
(Z)-Methyl 5-[1-(4-Cyanophenyl)-4-(5-methyl-[1,3,4]oxadia-
zol-2-yl)-but-1-enyl]-2-methoxy-3-methylbenzoate (12). The gen-
eral Stille coupling procedure was followed using stannane 71 (541
mg, 0.894 mmol), bromide 51 (213 mg, 1.17 mmol), cesium fluoride
(481 mg, 3.17 mmol), Pd(PPh3)4 (104 mg, 0.090 mmol), and
copper(I) iodide (34 mg, 0.178 mmol) in anhydrous DMF (6 mL).
The reaction mixture was stirred for 15 h. The crude products were
purified by column chromatography (100 mL of silica gel, 2 in.
diameter) using an ethyl acetate-hexanes gradient (50-100%), and
the desired product was isolated as a very viscous, pale yellow oil
(363 mg, 87%): IR (neat) 2950, 2868, 2225, 1731, 1599, 1570,
1503, 1480, 1435, 1409, 1380, 1300, 1258, 1230, 1195, 1169, 1126,
1
1007 cm-1; H NMR (300 MHz, CDCl3) δ 7.62 (dt, J ) 8.4, 1.8
Hz, 2 H), 7.33 (dt, J ) 8.7, 1.8 Hz, 2 H), 7.27 (d, J ) 2.4 Hz, 1
H), 7.13 (d, J ) 1.8 Hz, 1 H), 3.87 (s, 3 H), 3.83 (s, 3 H), 2.99 (t,
J ) 7.2 Hz, 2 H), 2.59 (dt, J ) 7.5, 7.2 Hz, 2 H), 2.44 (s, 3 H),
2.31 (s, 3 H); CIMS m/z (relative intensity) 418 (MH+, 100), 386
(MH+ - OCH3, 69). Anal. (C24H23N3O4) C, H, N.
(Z)-5-[1-(2,7-Dimethyl-3-oxo-2,3-dihydrobenzo[d]isoxazol-5-
yl)-4-(5-methyl-[1,3,4]oxadiazol-2-yl)-but-1-enyl]-2-methoxy-3-
methylbenzoic Acid Methyl Ester (13). The general Stille coupling
procedure was followed using stannane 71 (160 mg, 0.264 mmol),
iodide 49 (98 mg, 0.339 mmol), cesium fluoride (154 mg, 1.01
mmol), Pd(PPh3)4 (31 mg, 0.027 mmol), and copper(I) iodide (13
mg, 0.068 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 20 h. The crude products were absorbed onto silica
(4 mL) and separated by column chromatography (80 mL of silica,
2 in. diameter) using an ethyl acetate-hexanes gradient (50-100%).
The product was isolated as an off-white solid (76 mg, 60%): mp
135-136 °C; IR (CHCl3) 3469, 2949, 2862, 2236, 1997, 1729,
1690, 1614, 1596, 1570, 1490, 1437, 1399, 1378, 1298, 1257, 1227,
1168, 1147, 1121, 1008 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.38
(d, J ) 2.1 Hz, 1 H), 7.36 (d, J ) 1.8 Hz, 1 H), 7.28 (s, 1 H), 7.05
(d, J ) 1.5 Hz, 1 H), 6.02 (t, J ) 7.2 Hz, 1 H), 3.90 (s, 3 H), 3.89
(s, 3 H), 3.66 (s, 3 H), 2.92 (t, J ) 7.5 Hz, 2 H), 2.59 (q, J ) 7.5
Hz, 2 H), 2.48 (s, 3 H), 2.35 (s, 3 H), 2.31 (s, 3 H); ESI HRMS
m/z calcd for C26H27N3O6 [MNa+] 500.1798, found 500.1797;
(Z)-Methyl 2-Methoxy-5-[1-(4-methoxy-3-methyl-5-methyl-
sulfanylcarbonylphenyl)-4-(5-methyl-[1,3,4]oxadiazol-2-yl)-but-
1-enyl]-3-methylbenzoate (10). The general Stille coupling pro-
cedure was followed using stannane 71 (433 mg, 0.715 mmol),
iodide 45 (312 mg, 1.02 mmol), cesium fluoride (383 mg, 2.52
mmol), Pd(PPh3)4 (85 mg, 0.074 mmol), and copper(I) iodide (28

Alkenyldiarylmethane HIV-1 NNRTIs
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20 4861
ESIMS m/z (relative intensity) 500 (MNa+, 100), 464 (MH+
OCH3 + OH, 33). Anal. (C26H27N3O6) C, H, N.
-
gradient (50-100%). The desired product was isolated as a pale,
yellow oil (67 mg, 62%): IR (neat) 2929, 2862, 2230, 1775, 1675,
1641, 1610, 1596, 1570, 1547, 1495, 1477, 1448, 1418, 1394, 1316,
1284, 1240 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.35 (d, J ) 2.1
Hz, 1 H), 7.17 (s, 1 H), 7.16 (s, 1 H), 7.05 (d, J ) 2.1 Hz, 1 H),
6.01 (t, J ) 7.5 Hz, 1 H), 4.13 (s, 3 H), 3.87 (s, 3 H), 2.95 (t, J )
7.5 Hz, 2 H), 2.61 (q, J ) 7.5 Hz, 2 H), 2.48 (s, 3 H), 2.45 (s, 3
H), 2.44 (s, 3 H), 2.32 (s, 3 H); ESIMS m/z (relative intensity) 516
(MNa+, 100). Anal. (C26H27N3O5S) C, H, N.
(Z)-2-Methoxy-5-[1-(3-methoxy-7-methyl-benzo[d]isoxazol-5-
yl)-4-(5-methyl-[1,3,4]oxadiazol-2-yl)-but-1-enyl]-3-methylben-
zoic Acid Methyl Ester (14). The general Stille coupling procedure
was followed using stannane 71 (144 mg, 0.238 mmol), iodide 47
(106 mg, 0.367 mmol), cesium fluoride (142 mg, 0.935 mmol),
Pd(PPh3)4 (29 mg, 0.024 mmol), and copper(I) iodide (13 mg, 0.068
mmol) in anhydrous DMF (2 mL). The reaction mixture was stirred
for 20 h. The crude products were absorbed onto silica (3 mL) and
separated by column chromatography (100 mL of silica, 2 in.
diameter) using an ethyl acetate-hexanes gradient (33-100%). The
product was isolated as a clear oil (106 mg, 93%): IR (neat) 2948,
1730, 1596, 1570, 1547, 1495, 1436, 1395, 1318, 1284, 1256, 1202,
1143, 1120, 1048, 1008 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.39
(d, J ) 2.1 Hz, 1 H), 7.17 (s, 1 H), 7.15 (s, 1 H), 7.06 (d, J ) 2.1
Hz, 1 H), 6.01 (t, J ) 7.2 Hz, 1 H), 4.13 (s, 3 H), 3.90 (s, 3 H),
3.88 (s, 3 H), 2.93 (t, J ) 7.2 Hz, 2 H), 2.59 (q, J ) 7.5 Hz, 2 H),
2.48 (s, 3 H), 2.45 (s, 3 H), 2.31 (s, 3 H); ESIMS m/z (relative
intensity) 500 (MNa+,100). Anal. (C26H27N3O6) C, H, N.
(E)-5-[1-(3,7-Dimethyl-2-oxo-2,3-dihydrobenzooxazol-5-yl)-4-
(5-methyl-[1,3,4]oxadiazol-2-yl)-but-2-enyl]-2-methoxy-3-meth-
ylbenzoic Acid Methyl Ester (15). The general Stille coupling
procedure was followed using stannane 71 (197 mg, 0.325 mmol),
iodide 46 (136 mg, 0.470 mmol), cesium fluoride (178 mg, 1.17
mmol), Pd(PPh3)4 (42 mg, 0.036 mmol), and copper(I) iodide (14
mg, 0.066 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 22 h. The crude products were absorbed onto silica
(5 mL) and purified by column chromatography (60 mL of silica,
1 in. diameter) using ethyl acetate as the eluant. The desired product
was further purified by preparative thin layer chromatography using
ethyl acetate as the eluant (developed twice). The product was
isolated from the plate and purified again by preparative thin layer
chromatography using 66% ethyl acetate-hexanes as the eluant
(developed three times). The pure product was isolated as a glassy,
amber solid (80 mg, 52%): mp 43-47 °C; IR (CHCl3) 2949, 1776,
1728, 1641, 1619, 1596, 1570, 1475, 1437, 1368, 1334, 1299, 1229,
1196, 1141, 1120, 1064, 1008 cm-1; 1H NMR (300 MHz, CDCl3)
δ 7.39 (d, J ) 2.1 Hz, 1 H), 7.06 (d, J ) 2.4 Hz, 1 H), 6.73 (s, 1
H), 6.56 (d, J ) 2.0 Hz, 1 H), 5.98 (t, J ) 7.2 Hz, 1 H), 3.92 (s,
3 H), 3.88 (s, 3 H), 3.34 (s, 3 H), 2.94 (t, J ) 7.2 Hz, 2 H), 2.59
(q, J ) 7.2 Hz, 2 H), 2.47 (s, 3 H), 2.32 (s, 6 H); ESI HRMS m/z
calcd for C26H27N3O6 [MNa+] 500.1798, found 500.1794; ESIMS
m/z (relative intensity) 500 (MNa+, 100).
(Z)-S-Methyl 5-(1-(2,7-Dimethyl-3-oxo-2,3-dihydrobenzo[d]-
isoxazol-5-yl)-4-(5-methyl-1,3,4-oxadiazol-2-yl)but-1-enyl)-2-
methoxy-3-methylbenzothioate (18). The general Stille coupling
procedure was followed using stannane 75 (162 mg, 0.261 mmol),
iodide 49 (99 mg, 0.342 mmol), cesium fluoride (150 mg, 0.987
mmol), Pd(PPh3)4 (29 mg, 0.024 mmol), and copper(I) iodide (16
mg, 0.084 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 15 h. The crude products were purified by column
chromatography (60 mL of silica, 1.5 in. diameter) using ethyl
acetate as the eluant. The desired product was recrystallized from
acetone-hexanes (1:3) to afford an off-white solid (84 mg, 65%):
mp 123-124 °C; IR (CHCl3) 2929, 2868, 2238, 1689, 1643, 1615,
1596, 1592, 1490, 1436, 1377, 1308, 1243, 1226, 1192, 1155, 1126,
1
1042, 1000 cm-1; H NMR (300 MHz, methanol-d4) δ 7.47 (s, 1
H), 7.29 (s, 1 H), 7.24 (d, J ) 1.8 Hz, 1 H), 7.16 (s, 1 H), 6.19 (t,
J ) 7.5 Hz, 1 H), 3.85 (s, 3 H), 3.68 (s, 3 H), 3.01 (t, J ) 7.2 Hz,
2 H), 2.60 (q, J ) 7.5 Hz, 2 H), 2.46 (s, 3 H), 2.43 (s, 3 H), 2.38
(s, 3 H), 2.34 (s, 3 H); ESIMS m/z (relative intensity) 516 (MNa+,
100), 464 (MH+ - SCH3 + H2O, 81). Anal. (C26H27N3O5S) C, H,
N.
(E)-S-Methyl 5-(1-(3,7-Dimethyl-2-oxo-2,3-dihydrobenzo[d]-
oxazol-5-yl)-4-(5-methyl-1,3,4-oxadiazol-2-yl)but-1-enyl)-2-meth-
oxy-3-methylbenzothioate (19). The general Stille coupling pro-
cedure was followed using stannane 75 (118 mg, 0.190 mmol),
iodide 46 (68 mg, 0.235 mmol), cesium fluoride (107 mg, 0.704
mmol), Pd(PPh3)4 (23 mg, 0.020 mmol), and copper(I) iodide (8
mg, 0.042 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 14 h. The crude products were purified by preparative
thin layer chromatography using 66% ethyl acetate-hexanes as the
eluant (developed 4 times). The product was isolated as a clear oil
(39 mg, 43%): IR (CHCl3) 2925, 2853, 2252, 1772, 1641, 1597,
1
1571, 1463, 1376, 1318, 1246, 1153, 1045 cm-1; H NMR (300
MHz, CDCl3) δ 7.35 (d, J ) 2.1 Hz, 1 H), 7.05 (d, J ) 1.8 Hz, 1
H), 6.73 (s, 1 H), 6.56 (d, J ) 1.5 Hz, 1 H), 5.98 (t, J ) 7.5 Hz,
1 H), 3.87 (s, 3 H), 3.34 (s, 3 H), 2.95 (t, J ) 7.5 Hz, 2 H), 2.61
(q, J ) 7.5 Hz, 2 H), 2.48 (s, 3 H), 2.45 (s, 3 H), 2.32 (s, 6 H);
ESIMSm/z(relativeintensity)516(MNa+,100).Anal.(C26H27N3O5S)
C, H, N.
S,S′-Dimethyl 5,5′-(4-(5-Methyl-1,3,4-oxadiazol-2-yl)but-1-
ene-1,1-diyl)bis(2-methoxy-3-methylbenzothioate) (16). The gen-
eral Stille coupling procedure was followed using stannane 75 (165
mg, 0.266 mmol), iodide 45 (114 mg, 0.354 mmol), cesium fluoride
(160 mg, 1.05 mmol), Pd(PPh3)4 (32 mg, 0.029 mmol), and copper-
(I) iodide (17 mg, 0.089 mmol) in anhydrous DMF (3 mL). The
reaction mixture was stirred for 18.5 h. The crude products were
purified by column chromatography (100 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-66%). The
product was isolated as a beige oil (81 mg, 59%): IR (neat) 2928,
2867, 1995, 1793, 1674, 1644, 1595, 1570, 1476, 1419, 1378, 1362,
(Z)-S-Methyl 5-(1-(3-Cyanophenyl)-4-(5-methyl-1,3,4-oxadia-
zol-2-yl)but-1-enyl)-2-methoxy-3-methylbenzothioate (20). The
general Stille coupling procedure was followed using stannane 75
(138 mg, 0.222 mmol), bromide 50 (61 mg, 0.340 mmol), cesium
fluoride (132 mg, 0.869 mmol), Pd(PPh3)4 (90 mg, 0.078 mmol),
and copper(I) iodide (33 mg, 0.173 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 14 h. The crude products
were purified by column chromatography (100 mL of silica, 1.5
in. diameter) using an ethyl acetate-hexanes gradient (50-100%),
and the desired product was further purified by preparative thin
layer chromatography using 2:1 ethyl acetate-hexanes as the eluant.
The product was isolated as a clear film (21 mg, 22%): IR (neat)
3065, 2928, 2851, 2229, 1674, 1643, 1596, 1570, 1478, 1416, 1390,
1
1307, 1244, 1193, 1159, 1133, 1045, 1001 cm-1; H NMR (300
MHz, CDCl3) δ 7.35 (dd, J ) 6.6, 2.4 Hz, 2 H), 7.09 (m, 1 H),
7.06 (m, 1 H), 6.01 (t, J ) 7.5 Hz, 1 H), 3.87 (s, 3 H), 3.80 (s, 3
H), 2.93 (t, J ) 7.5 Hz, 2 H), 2.58 (q, J ) 7.5 Hz, 2 H), 2.49 (s,
3 H), 2.43 (s, 3 H), 2.39 (s, 3 H), 2.33 (s, 3 H), 2.27 (s, 3 H);
ESIMS m/z (relative intensity) 549 (MNa+, 100), 497 (MH+
SCH3 + H2O, 59). Anal. (C27H30N2O5S2) C, H, N.
-
1374, 1313, 1278, 1239, 1178, 1133, 1041, 1000 cm-1; H NMR
1
(300 MHz, CDCl3) δ 7.54-7.32 (m, 5 H), 7.04 (d, J ) 1.8 Hz, 1
H), 6.12 (t, J ) 7.5 Hz, 1 H), 3.88 (s, 3 H), 2.95 (t, J ) 7.5 Hz, 2
H), 2.62 (q, J ) 7.5 Hz, 2 H), 2.49 (s, 3 H), 2.43 (s, 3 H), 2.34 (s,
3 H); ESIMS m/z (relative intensity) 456 (MNa+, 100), 404 (MH+
- SCH3 + H2O, 23). Anal. (C24H23N3O3S) C, H, N.
(Z)-S-Methyl 5-(1-(4-Cyanophenyl)-4-(5-methyl-1,3,4-oxadia-
zol-2-yl)but-1-enyl)-2-methoxy-3-methylbenzothioate (21). The
general Stille coupling procedure was followed using stannane 75
(162 mg, 0.261 mmol), bromide 51 (64 mg, 0.340 mmol), cesium
fluoride (179 mg, 1.18 mmol), Pd(PPh3)4 (33 mg, 0.031 mmol),
(Z)-S-Methyl 2-Methoxy-5-(1-(3-methoxy-7-methylbenzo[d]-
isoxazol-5-yl)-4-(5-methyl-1,3,4-oxadiazol-2-yl)but-1-enyl)-3-me-
thylbenzothioate (17). The general Stille coupling procedure was
followed using stannane 75 (140 mg, 0.225 mmol), iodide 47 (84
mg, 0.291 mmol), cesium fluoride (127 mg, 0.836 mmol), Pd(PPh3)4
(28 mg, 0.024 mmol), and copper(I) iodide (13 mg, 0.068 mmol)
in anhydrous DMF (3 mL). The reaction mixture was stirred for
14 h. The crude products were purified by column chromatography
(60 mL of silica, 1.5 in. diameter) using an ethyl acetate-hexanes

4862 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20
Cullen et al.
1
and copper(I) iodide (18 mg, 0.091 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 24 h. The crude products
were purified by column chromatography (80 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-66%), and
the desired product was further purified by preparative thin layer
chromatography using 50% ethyl acetate-hexanes as the eluant.
The product was isolated as colorless, opaque oil (20 mg, 17%):
IR (neat) 2929, 2226, 1674, 1641, 1597, 1570, 1502, 1476, 1409,
1312, 1231, 1136, 1040, 1001 cm-1; 1H NMR (300 MHz, CDCl3)
δ 7.55 (d, J ) 8.4 Hz, 2 H), 7.32-7.25 (m, 3 H), 7.04 (d, J ) 2.1
Hz, 1 H), 6.19 (t, J ) 7.5 Hz, 1 H), 3.87 (s, 3 H), 2.95 (t, J ) 7.5
Hz, 2 H), 2.63 (q, J ) 7.5 Hz, 2 H), 2.48 (s, 3 H), 2.45 (s, 3 H),
2.33 (s, 3 H); ESI HRMS m/z calcd for C24H23N3O3S [MNa+]
456.1358, found 456.1362; ESIMS m/z (relative intensity) 456
(MNa+, 100), 404 (MH+ - SCH3 + H2O, 21).
(Z)-S-Methyl 5-(1-(Benzo[d]isoxazol-5-yl)-4-(5-methyl-1,3,4-
oxadiazol-2-yl)but-1-enyl)-2-methoxy-3-methylbenzothioate (22).
The general Stille coupling procedure was followed using stannane
75 (118 mg, 0.190 mmol), iodide 48 (75 mg, 0.306 mmol), cesium
fluoride (112 mg, 0.737 mmol), Pd(PPh3)4 (24 mg, 0.021 mmol),
and copper(I) iodide (40 mg, 0.210 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 45 min. The crude
products were purified by column chromatography (60 mL of silica,
1.5 in. diameter) using an ethyl acetate-hexanes gradient (50-
100%). The product was isolated as yellow oil (20 mg, 23%): IR
(CDCl3) 2928, 2862, 2227, 1672, 1643, 1598, 1569, 1508, 1473,
1416, 1301, 1244, 1226, 1139 cm-1; 1H NMR (300 MHz, methanol-
d4) δ 7.30 (d, J ) 2.1 Hz, 1 H), 7.28 (d, J ) 2.4 Hz, 1 H), 7.24 (d,
J ) 2.4 Hz, 2.4 Hz), 7.21 (d, J ) 1.8 Hz, 1 H), 7.12 (dd, J ) 2.1,
0.6 Hz, 1 H), 6.86 (d, J ) 8.7 Hz, 1 H), 6.08 (t, J ) 7.5 Hz, 1 H),
3.84 (s, 3 H), 2.98 (t, J ) 7.2 Hz, 2 H), 2.55 (q, J ) 7.2 Hz, 2 H),
2.45 (s, 3 H), 2.43 (s, 3 H), 2.33 (s, 3 H); ESI HRMS m/z calcd for
C24H23N3O4S [MH+] 450.1488, found 450.1490; ESIMS m/z
(relative intensity) 450 (MH+, 51), 420 (MH+ - SCH3 + H2O,
100).
(Z)-S-Methyl 5-(1-(3,7-Dimethyl-2-oxo-2,3-dihydrobenzo[d]-
oxazol-5-yl)-4-(5-methyl-1,3,4-oxadiazol-2-yl)but-1-enyl)-2-meth-
oxy-3-methylbenzothioate (23). The general Stille coupling pro-
cedure was followed using stannane 79 (213 mg, 0.362 mmol),
iodide 45 (139 mg, 0.434 mmol), cesium fluoride (202 mg, 1.33
mmol), Pd(PPh3)4 (46 mg, 0.040 mmol), and copper(I) iodide (15
mg, 0.070 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 3.5 h. The crude products were absorbed onto silica
(15 mL) and purified by column chromatography (60 mL of silica,
1.5 in. diameter) using an ethyl acetate-hexanes gradient (50-
100%). The desired product was further purified by preparative
thin layer chromatography using 70% ethyl acetate-toluene as the
eluant. The product was isolated as a white, microcrystalline solid
after being exposed to high vacuum conditions (92 mg, 51%):
mp: 50-53 °C; IR (neat) 2928, 2857, 1779, 1674, 1640, 1618,
1595, 1473, 1420, 1375, 1350, 1298, 1248, 1220, 1177, 1156, 1121,
1057, 1030, 1000 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.35 (d, J
) 2.4 Hz, 1 H), 7.12 (d, J ) 2.4 Hz, 1 H), 6.68 (s, 1 H), 6.52 (s,
1 H), 6.04 (t, J ) 7.5 Hz, 1 H), 3.80 (s, 3 H), 3.37 (s, 3 H), 2.92
(t, J ) 7.5 Hz, 2 H), 2.57 (q, J ) 7.5 Hz, 2 H), 2.43 (s, 3 H), 2.39
(s, 3 H), 2.27 (s, 3 H); ESIMS m/z (relative intensity) 516 (MNa+,
100), 494 (MH+, 29), 464 (MH+ - SCH3 + H2O, 81). Anal.
(C26H27N3O5S) C, H, N.
(E)-S-Methyl 2-Methoxy-5-(1-(3-methoxy-7-methylbenzo[d]-
isoxazol-5-yl)-4-(5-methyl-1,3,4-oxadiazol-2-yl)but-1-enyl)-3-me-
thylbenzothioate (24). The general Stille coupling procedure was
followed using stannane 83 (164 mg, 0.278 mmol), iodide 45 (178
mg, 0.553 mmol), cesium fluoride (153 mg, 1.01 mmol), Pd(PPh3)4
(33 mg, 0.029 mmol), and copper(I) iodide (55 mg, 0.288 mmol)
in anhydrous DMF (3 mL). The reaction mixture was stirred for
45 min. The crude products were purified by column chromatog-
raphy (60 mL of silica, 1.5 in. diameter) using an ethyl acetate-
hexanes gradient (55-66%). The product was isolated from the
column as an orange, amorphous solid (115 mg, 84%): IR (neat)
2928, 2862, 1675, 1644, 1614, 1595, 1570, 1547, 1498, 1475, 1423,
1389, 1350, 1311, 1251, 1233, 1195, 1181, 1157, 1121, 1042, 1001
cm-1; H NMR (300 MHz, CDCl3) δ 7.34 (d, J ) 2.4 Hz, 1 H),
7.19 (s, 1 H), 7.10 (d, J ) 1.5 Hz, 1 H), 7.00 (s, 1 H), 6.06 (t, J )
7.5 Hz, 1 H), 4.17 (s, 3 H), 3.80 (s, 3 H), 2.92 (t, J ) 7.5 Hz, 2 H),
2.56 (q, J ) 7.5 Hz, 2 H), 2.49 (s, 3 H), 2.47 (s, 3 H), 2.41 (s. 3
H), 2.26 (s, 3 H); ESI HRMS m/z calcd for C26H27N3O5S [MH+]
494.1750, found 494.1742; ESIMS m/z (relative intensity) 516
(MNa+, 13), 494 (MH+, 15), 464 (MH+ - SCH3 + H2O, 100).
(E)-S-Methyl 5-(1-(2,7-Dimethyl-3-oxo-2,3-dihydrobenzo[d]-
isoxazol-5-yl)-4-(5-methyl-1,3,4-oxadiazol-2-yl)but-1-enyl)-2-
methoxy-3-methylbenzothioate (25). The general Stille coupling
procedure was followed using stannane 87 (134 mg, 0.228 mmol),
iodide 45 (88 mg, 0.273 mmol), cesium fluoride (123 mg, 0.810
mmol), Pd(PPh3)4 (27 mg, 0.023 mmol), and copper(I) iodide (49
mg, 0.257 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 1 h. The crude products were purified by column
chromatography (40 mL of silica, 1.5 in. diameter) using ethyl
acetate as the eluant. The product was isolated from the column as
an orange oil (86 mg, 76%): IR (neat) 2926, 2855, 1778, 1692,
1615, 1595, 1570, 1493, 1477, 1438, 1376, 1301, 1251, 1224, 1193,
1121, 1047 1000 cm-1; H NMR (300 MHz, CDCl3) δ 7.41 (d, J
1
) 1.2 Hz, 1 H), 7.33 (d, J ) 2.4 Hz, 1 H), 7.09 (d, J ) 2.4 Hz, 2
H), 6.05 (t, J ) 7.5 Hz, 1 H), 3.80 (s, 3 H), 3.70 (s, 3 H), 2.92 (t,
J ) 7.5 Hz, 2 H), 2.56 (q, J ) 7.5 Hz, 2 H), 2.49 (s, 3 H), 2.42 (s,
3 H), 2.38 (s, 3 H), 2.26 (s, 3 H); ESIMS m/z (relative intensity)
516 (MNa+, 8), 494 (MH+, 48), 464 (MH+ - SCH3 + H2O, 100).
Anal. (C26H27N3O5S) C, H, N.
(E)-S-Methyl 5-(1-(3-Cyanophenyl)-4-(5-methyl-1,3,4-oxadia-
zol-2-yl)but-1-enyl)-2-methoxy-3-methylbenzothioate (26). The
general Stille coupling procedure was followed using stannane 91
(138 mg, 0.261 mmol), iodide 45 (128 mg, 0.397 mmol), cesium
fluoride (157 mg, 1.03 mmol), Pd(PPh3)4 (37 mg, 0.032 mmol),
and copper(I) iodide (54 mg, 0.284 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 1 h. The crude products
were purified by column chromatography (50 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-66%). The
desired product was isolated as a yellow oil (85 mg, 75%): IR
(neat) 3063, 2929, 2860, 2229, 1674, 1639, 1595, 1570, 1477, 1418,
1356, 1304, 1227, 1183, 1130, 1049, 999 cm-1; H NMR (300
1
MHz, CDCl3) δ 7.64 (dt, J ) 7.8, 1.5 Hz, 1 H), 7.52 (t, J ) 7.8
Hz, 1 H), 7.39 (tt, J ) 7.8, 1.5 Hz, 2 H), 7.30 (d, J ) 2.4 Hz, 1 H),
7.07 (d, J ) 1.8 Hz, 1 H), 6.11 (t, J ) 7.5 Hz, 1 H), 3.81 (s, 3 H),
2.94 (t, J ) 7.5 Hz, 2 H), 2.55 (q, J ) 7.5 Hz, 2 H), 2.50 (s, 3 H),
2.43 (s, 3 H), 2.27 (s, 3 H); ESIMS m/z (relative intensity) 434
(MH+, 8), 404 (MH+ - SCH3 + H2O, 100). Anal. (C24H23N3O3S)
C, H, N.
(E)-S-Methyl 5-(1-(4-Cyanophenyl)-4-(5-methyl-1,3,4-oxadia-
zol-2-yl)but-1-enyl)-2-methoxy-3-methylbenzothioate (27). The
general Stille coupling procedure was followed using stannane 95
(118 mg, 0.223 mmol), iodide 45 (102 mg, 0.317 mmol), cesium
fluoride (131 mg, 0.862 mmol), Pd(PPh3)4 (28 mg, 0.024 mmol),
and copper(I) iodide (43 mg, 0.226 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 1 h. The crude products
were purified by column chromatography (60 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-66%). The
desired product was isolated as an orange oil (74 mg, 77%): IR
(neat) 2929, 2856, 2227, 1733, 1674, 1643, 1595, 1570, 1503, 1476,
1421, 1357, 1303, 1251, 1222, 1178, 1136, 1109, 1048, 999 cm-1
1H NMR (300 MHz, CDCl3) δ 7.69 (d, J ) 8.1 Hz, 2 H), 7.30 (d,
J ) 2.4 Hz, 1 H), 7.24 (d, J ) 8.1 Hz, 2 H), 7.08 (d, J ) 2.1 Hz,
1 H), 6.10 (t, J ) 7.5 Hz, 1 H), 3.80 (s, 3 H), 2.93 (t, J ) 7.5 Hz,
2 H), 2.56 (q, J ) 7.5 Hz, 2 H), 2.48 (s, 3 H), 2.42 (s, 3 H), 2.27
(s, 3 H); ESI HRMS m/z calcd for C24H23N3O3S [MH+] 434.1538,
found 434.1529; ESIMS m/z (relative intensity) 434 (MH+, 16),
404 (MH+ - SCH3 + H2O, 100).
;
S,S′-Dimethyl 5,5′-(5-(5-Methyl-1,3,4-oxadiazol-2-yl)pent-1-
ene-1,1-diyl)bis(2-methoxy-3-methylbenzothioate) (28). The gen-
eral Stille coupling procedure was followed using stannane 77 (213
mg, 0.335 mmol), iodide 45 (131 mg, 0.402 mmol), cesium fluoride
(215 mg, 1.42 mmol), Pd(PPh3)4 (78 mg, 0.067 mmol), and copper-
(I) iodide (13 mg, 0.068 mmol) in anhydrous DMF (3 mL). The
reaction mixture was stirred for 13.5 h. The crude products were

Alkenyldiarylmethane HIV-1 NNRTIs
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20 4863
purified by column chromatography (60 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-66%). The
product was isolated as an orange oil (126 mg, 70%): IR (neat)
2929, 2866, 1675, 1644, 1595, 1570, 1476, 1421, 1378, 1362, 1308,
(Z)-S-Methyl 5-(1-(4-Cyanophenyl)-5-(5-methyl-1,3,4-oxadia-
zol-2-yl)pent-1-enyl)-2-methoxy-3-methylbenzothioate (32). The
general Stille coupling procedure was followed using stannane 77
(171 mg, 0.269 mmol), bromide 51 (71 mg, 0.390 mmol), cesium
fluoride (173 mg, 1.14 mmol), Pd(PPh3)4 (36 mg, 0.031 mmol),
and copper(I) iodide (26 mg, 0.135 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 30 min. The crude
products were purified by column chromatography (100 mL of
silica, 1.5 in. diameter) using an ethyl acetate-hexanes gradient
(50-66%). The product was isolated from the column as a yellow
oil (71 mg, 59%): IR (neat) 2931, 2867, 2226, 1674, 1643, 1599,
1
1244, 1228, 1192, 1154, 1133, 1043, 1002 cm-1; H NMR (300
MHz, CDCl3) δ 7.39 (d, J ) 2.4 Hz, 1 H), 7.36 (d, J ) 1.8 Hz, 1
H), 7.08 (m, 2 H), 5.99 (t, J ) 7.5 Hz, 1 H), 3.87 (s, 3 H), 3.80 (s,
3 H), 2.80 (t, J ) 7.5 Hz, 2 H), 2.47 (s, 3 H), 2.45 (s, 3 H), 2.43
(s, 3 H), 2.32 (s, 3 H), 2.27 (s, 3 H), 2.22 (q, J ) 7.5 Hz, 2 H),
1.93 (p, J ) 7.5 Hz, 2 H); ESIMS m/z (relative intensity) 563
(MNa+, 100), 533 (MH+, 9). Anal. (C28H32N2O5S2) C, H, N.
(Z)-S-Methyl 2-Methoxy-5-(1-(3-methoxy-7-methylbenzo[d]-
isoxazol-5-yl)-5-(5-methyl-1,3,4-oxadiazol-2-yl)pent-1-enyl)-3-
methylbenzothioate (29). The general Stille coupling procedure
was followed using stannane 77 (411 mg, 0.647 mmol), iodide 47
(231 mg, 0.779 mmol), cesium fluoride (443 mg, 2.92 mmol), Pd-
(PPh3)4 (78 mg, 0.067 mmol), and copper(I) iodide (29 mg, 0.152
mmol) in anhydrous DMF (6 mL). The reaction mixture was stirred
for 15 h. The crude products were absorbed onto silica (20 mL)
and purified by column chromatography (100 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-100%). The
desired product was isolated as an amorphous, yellow solid (212
mg, 65%): IR (neat) 2930, 2867, 1675, 1642, 1614, 1596, 1570,
1547, 1494, 1477, 1455, 1424, 1394, 1315, 1275, 1240, 1223, 1042
1
1570, 1503, 1476, 1409, 1231, 1179, 1136, 1043, 1000 cm-1; H
NMR (300 MHz, methanol-d4) δ 7.64 (dd, J ) 6.9, 1.8 Hz, 2 H),
7.37 (dd, J ) 6.6, 1.8 Hz, 2 H), 7.28 (d, J ) 2.1 Hz, 1 H), 7.17 (d,
J ) 2.1 Hz, 1 H), 6.33 (t, J ) 7.5 Hz, 1 H), 3.84 (s, 3 H), 2.85 (t,
J ) 7.5 Hz, 2 H), 2.46 (s, 3 H), 2.42 (s, 3 H), 2.33 (s, 3 H), 2.25
(q, J ) 7.5 Hz, 2 H), 1.96 (p, J ) 7.5 Hz, 2 H); ESIMS m/z (relative
intensity) 448 (MH+, 11), 418 (MH+ - SCH3 + H2O, 100). Anal.
(C25H25N3O3S) C, H, N.
(Z)-S-Methyl 5-(1-(3,7-Dimethyl-2-oxo-2,3-dihydrobenzo[d]-
oxazol-5-yl)-5-(5-methyl-1,3,4-oxadiazol-2-yl)pent-1-enyl)-2-meth-
oxy-3-methylbenzothioate (33). The general Stille coupling pro-
cedure was followed using stannane 81 (160 mg, 0.266 mmol),
iodide 45 (127 mg, 0.394 mmol), cesium fluoride (144 mg, 0.948
mmol), Pd(PPh3)4 (38 mg, 0.033 mmol), and copper(I) iodide (56
mg, 0.294 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 1.5 h. The crude products were purified by column
chromatography (60 mL of silica, 1.5 in. diameter) using an ethyl
acetate-hexanes gradient (50-80%). The desired product was
isolated as a yellow oil (81 mg, 60%): IR (neat) 3534, 2929, 2865,
1779, 1771, 1674, 1641, 1618, 1570, 1471, 1421, 1389, 1375, 1351,
1
cm-1; H NMR (300 MHz, CDCl3) δ 7.38 (d, J ) 2.1 Hz, 1 H),
7.19 (s, 1 H), 7.18 (s, 1 H), 7.09 (d, J ) 2.1 Hz, 1 H), 6.01 (t, J )
7.5 Hz, 1 H), 4.15 (s, 3 H), 3.89 (s, 3 H), 2.83 (t, J ) 7.5 Hz, 2 H),
2.48 (s, 3 H), 2.47 (s, 3 H), 2.46 (s, 3 H), 2.33 (s, 3 H), 2.26 (q, J
) 7.5 Hz, 2 H), 1.95 (p, J ) 7.5 Hz, 2 H); ESIMS m/z (relative
intensity) 508 (MH+, 5), 478 (MH+ - SCH3 + H2O, 100), 460
(MH+ - SCH3, 13). Anal. (C27H29N3O5S) C, H, N.
1
1298, 1242, 1229, 1171, 1153, 1120 cm-1; H NMR (300 MHz,
(Z)-S-Methyl 5-(1-(2,7-Dimethyl-3-oxo-2,3-dihydrobenzo[d]-
isoxazol-5-yl)-5-(5-methyl-1,3,4-oxadiazol-2-yl)pent-1-enyl)-2-
methoxy-3-methylbenzothioate (30). The general Stille coupling
procedure was followed using stannane 77 (154 mg, 0.242 mmol),
iodide 49 (90 mg, 0.311 mmol), cesium fluoride (134 mg, 0.882
mmol), Pd(PPh3)4 (32 mg, 0.028 mmol), and copper(I) iodide (50
mg, 0.263 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 1 h. The crude products were purified by column
chromatography (60 mL of silica, 1.5 in. diameter) using an ethyl
acetate-hexanes gradient (50-100%). The desired product was
isolated as a yellow oil (90 mg, 73%): IR (neat) 3479, 2929, 2868,
1693, 1681, 1646, 1596, 1570, 1489, 1434, 1401, 1377, 1242, 1226,
CDCl3) δ 7.37 (d, J ) 2.7 Hz, 1 H), 7.11 (d, J ) 2.7 Hz, 1 H),
6.71 (s, 1 H), 6.55 (s, 1 H), 6.02 (t, J ) 7.5 Hz, 1 H), 3.80 (s, 3 H),
3.38 (s, 3 H), 2.79 (t, J ) 7.5 Hz, 2 H), 2.46 (s, 3 H), 2.43 (s, 3 H),
2.39 (s, 3 H), 2.27 (s, 3 H), 2.18 (q, J ) 7.5 Hz, 2 H), 1.92 (p, J
) 7.5 Hz, 2 H); ESI HRMS m/z calcd for C27H29N3O5S [MH+]
508.1906, found 508.1908; ESIMS m/z (relative intensity) 508
(MH+, 14), 478 (MH+ - SCH3 + H2O, 100), 460 (MH+ - SCH3,
33).
(E)-S-Methyl 2-Methoxy-5-(1-(3-methoxy-7-methylbenzo[d]-
isoxazol-5-yl)-5-(5-methyl-1,3,4-oxadiazol-2-yl)pent-1-enyl)-3-
methylbenzothioate (34). The general Stille coupling procedure
was followed using stannane 85 (123 mg, 0.204 mmol), iodide 45
(106 mg, 0.329 mmol), cesium fluoride (125 mg, 0.823 mmol),
Pd(PPh3)4 (25 mg, 0.022 mmol), and copper(I) iodide (42 mg, 0.221
mmol) in anhydrous DMF (3 mL). The reaction mixture was stirred
for 1 h. The crude products were purified by column chromatog-
raphy (60 mL of silica, 1.5 in. diameter) using an ethyl acetate-
hexanes gradient (50-66%). The desired product was isolated as
a yellow, amorphous solid (81 mg, 60%): IR (neat) 2930, 1675,
1
1126, 1043 cm-1; H NMR (300 MHz, methanol-d4) δ 7.47 (s, 1
H), 7.30 (s, 2 H), 7.18 (s, 1 H), 6.17 (t, J ) 7.5 Hz, 1 H), 3.84 (s,
3 H), 3.70 (s, 3 H), 2.86 (t, J ) 7.5 Hz, 2 H), 2.45 (s, 3 H), 2.42
(s, 3 H), 2.39 (s, 3 H), 2.33 (s, 3 H), 2.24 (q, J ) 7.5 Hz, 2 H),
1.95 (p, J ) 7.5 Hz, 2 H); ESI HRMS m/z calcd for C27H29N3O5S
[MH+] 508.1906, found 508.1904; ESIMS m/z (relative intensity)
530 (MNa+, 100).
(Z)-S-Methyl 5-(1-(3-Cyanophenyl)-5-(5-methyl-1,3,4-oxadia-
zol-2-yl)pent-1-enyl)-2-methoxy-3-methylbenzothioate (31). The
general Stille coupling procedure was followed using stannane 77
(92 mg, 0.145 mmol), bromide 50 (41 mg, 0.225 mmol), cesium
fluoride (87 mg, 0.572 mmol), Pd(PPh3)4 (18 mg, 0.018 mmol),
and copper(I) iodide (16 mg, 0.084 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 30 min. The crude
products were purified by column chromatography (60 mL of silica,
1 in. diameter) using an ethyl acetate-hexanes gradient (50-66%),
and the desired product was further purified via preparative thin
layer chromatography using 66% ethyl acetate-hexanes as the
eluant (developed twice). The pure product was obtained as a light,
yellow oil (33 mg, 51%): IR (neat) 3063, 2930, 2866, 2228, 1995,
1726, 1675, 1643, 1595, 1570, 1478, 1416, 1394, 1378, 1239, 1175,
1133, 1043, 1000 cm-1; 1H NMR (300 MHz, methanol-d4) δ 7.61-
7.55 (m, 2 H), 7.47-7.45 (m, 2 H), 7.29 (s, 1 H), 7.18 (s, 1 H),
6.26 (t, J ) 7.5 Hz, 1 H), 3.84 (s, 3 H), 2.85 (t, J ) 7.5 Hz, 2 H),
2.45 (s, 3 H), 2.43 (s, 3 H), 2.33 (s, 3 H), 2.25 (q, J ) 7.5 Hz, 2
H), 1.96 (p, J ) 7.5 Hz, 2 H); ESIMS m/z (relative intensity) 470
(MNa+, 52), 418 (MH+ - SCH3 + H2O, 100), 400 (MH+ - SCH3,
76). Anal. (C25H25N3O3S) C, H, N.
1
1596, 1570, 1548, 1498, 1389, 1233, 1042 cm-1; H NMR (300
MHz, CDCl3) δ 7.36 (d, J ) 2.1 Hz, 1 H), 7.22 (s, 1 H), 7.09 (d,
J ) 2.1 Hz, 1 H), 7.04 (s, 1 H), 6.05 (t, J ) 7.5 Hz, 1 H), 4.17 (s,
3 H), 3.80 (s, 3 H), 2.77 (t, J ) 7.5 Hz, 2 H), 2.47 (s, 3 H), 2.45
(s, 3 H), 2.42 (s, 3 H), 2.26 (s, 3 H), 2.12 (q, J ) 7.5 Hz, 2 H),
1.91 (p, J ) 7.5 Hz, 2 H); ESI HRMS m/z calcd for C27H29N3O5S
[MH+] 508.1906, found 508.1905; ESIMS m/z (relative intensity)
508 (MH+, 8), 408 (MH+ - SCH3 + H2O, 100).
(E)-S-Methyl 5-(1-(2,7-Dimethyl-3-oxo-2,3-dihydrobenzo[d]-
isoxazol-5-yl)-5-(5-methyl-1,3,4-oxadiazol-2-yl)pent-1-enyl)-2-
methoxy-3-methylbenzothioate (35). The general Stille coupling
procedure was followed using stannane 89 (127 mg, 0.211 mmol),
iodide 45 (116 mg, 0.360 mmol), cesium fluoride (138 mg, 0.908
mmol), Pd(PPh3)4 (27 mg, 0.023 mmol), and copper(I) iodide (45
mg, 0.236 mmol) in anhydrous DMF (3 mL). The reaction mixture
was stirred for 45 min. The crude products were purified by column
chromatography (60 mL of silica, 1.5 in. diameter) using an ethyl
acetate-hexanes gradient (50-100%). The desired product was
isolated as a yellow oil (80 mg, 75%): IR (neat) 2929, 2865, 1694,
1682, 1644, 1615, 1596, 1570, 1493, 1477, 1439, 1422, 1395, 1365,

4864 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20
Cullen et al.
1
1303, 1251, 1224, 1191, 1173, 1154, 1123 cm-1; H NMR (300
under an argon atmosphere, for 3-24 h. The reaction mixture was
concentrated in vacuo, and the remaining residue was absorbed onto
silica. The products were separated by column chromatography to
obtain the desired alkyne product, and, if necessary, additional
purification methods were applied.
MHz, CDCl3) δ 7.43 (d, J ) 0.9 Hz, 1 H), 7.34 (d, J ) 2.4 Hz, 1
H), 7.11 (s, 1 H), 7.08 (d, J ) 1.8 Hz, 1 H), 6.03 (t, J ) 7.5 Hz,
1 H), 3.80 (s, 3 H), 3.70 (s, 3 H), 2.77 (t, J ) 7.5 Hz, 2 H), 2.42
(s, 3 H), 2.38 (s, 3 H), 2.35 (s, 3 H), 2.26 (s, 3 H), 2.19 (q, J ) 7.5
Hz, 2 H), 1.91 (p, J ) 7.5 Hz, 2 H); ESIMS m/z (relative intensity)
530 (MNa+, 27), 478 (MH+ - SCH3 + H2O, 100). Anal.
(C27H29N3O5S) C, H, N.
5-Iodo-2-methoxy-3-methylthiobenzoic Acid S-Methyl Ester
(45). A flask was charged with benzoic acid 52 (251 mg, 0.859
mmol) and thionyl chloride (3.4 mL). The flask was fitted with a
condenser and the system heated at reflux, under argon, for 40 min.
The system was allowed to cool to room temperature, and the
reaction mixture was azeotropically condensed in vacuo with
benzene (2 mL). More benzene (3 mL) was added, and the reaction
mixture was concentrated again to azeotrope any remaining thionyl
chloride (this step was repeated two more times). A white solid
was obtained after concentrating the reaction mixture (occasionally
the material is a yellow oil). The solid was dissolved in benzene
(3 mL), and sodium thiomethoxide (77 mg, 1.10 mmol) was added
to the solution. The heterogeneous mixture was stirred at room
temperature for 15 h and was then diluted with ethyl acetate (5
mL) and water (5 mL). The phases were separated, and the aqueous
phase was extracted with ethyl acetate (3 × 15 mL). Organic
extracts were combined, dried over magnesium sulfate, filtered, and
condensed in vacuo to afford an oil. The product was purified by
column chromatography (30 mL of silica, 0.5 in. diameter) using
5% ethyl acetate-hexanes as the eluant. The product was isolated
as a clear oil (215 mg, 78%): IR (neat) 3066, 2926, 1995, 1674,
(E)-S-Methyl 5-(1-(3-Cyanophenyl)-5-(5-methyl-1,3,4-oxadia-
zol-2-yl)pent-1-enyl)-2-methoxy-3-methylbenzothioate (36). The
general Stille coupling procedure was followed using stannane 93
(86 mg, 0.159 mmol), iodide 45 (68 mg, 0.211 mmol), cesium
fluoride (106 mg, 0.698 mmol), Pd(PPh3)4 (21 mg, 0.018 mmol),
and copper(I) iodide (40 mg, 0.210 mmol) in anhydrous DMF (2
mL). The reaction mixture was stirred for 1 h. The crude products
were purified by column chromatography (60 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-66%). The
product was isolated from the column as an orange, viscous oil
(51 mg, 72%): IR (neat) 3060, 2930, 2862, 2229, 1995, 1674, 1643,
1596, 1570, 1478, 1418, 1307, 1252, 1227, 1173, 1130, 1048, 1000
cm-1; H NMR (300 MHz, CDCl3) δ 7.63 (dt, J ) 7.5, 1.5 Hz, 1
1
H), 7.51 (t, J ) 7.5 Hz, 1 H), 7.43-7.38 (m, 2 H), 7.32 (d, J ) 2.4
Hz, 1 H), 7.06 (d, J ) 1.8 Hz, 1 H), 6.08 (t, J ) 7.5 Hz, 1 H), 3.81
(s, 3 H), 2.79 (t, J ) 7.5 Hz, 2 H), 2.77 (s, 3 H), 2.48 (s, 3 H), 2.27
(s, 3 H), 2.18 (q, J ) 7.5 Hz, 2 H), 1.93 (p, J ) 7.5 Hz, 2 H);
ESIMS m/z (relative intensity) 470 (MNa+, 41), 448 (MH+, 18),
418 (MH+ - SCH3 + H2O, 100). Anal. (C25H25N3O3S) C, H, N.
(E)-S-Methyl 5-(1-(4-Cyanophenyl)-5-(5-methyl-1,3,4-oxadia-
zol-2-yl)pent-1-enyl)-2-methoxy-3-methylbenzothioate (37). The
general Stille coupling procedure was followed using stannane 97
(179 mg, 0.330 mmol), iodide 45 (158 mg, 0.490 mmol), cesium
fluoride (222 mg, 1.46 mmol), Pd(PPh3)4 (42 mg, 0.036 mmol),
and copper(I) iodide (50 mg, 0.352 mmol) in anhydrous DMF (3
mL). The reaction mixture was stirred for 1 h. The crude products
were purified by column chromatography (60 mL of silica, 1.5 in.
diameter) using an ethyl acetate-hexanes gradient (50-66%), and
the desired product was isolated as a highly viscous, yellow oil
(103 mg, 70%): IR (neat) 2930, 2868, 2227, 1674, 1643, 1596,
1
1642, 1565, 1465, 1414, 1255, 1173, 1039 cm-1; H NMR (300
MHz, CDCl3) δ 7.83 (dd, J ) 2.4, 0.6 Hz, 1 H), 7.65 (dd, J ) 2.4,
0.6 Hz, 1 H), 3.80 (s, 3 H), 2.46 (s, 3 H), 2.28 (s, 3 H); EIMS m/z
(relative intensity) 322 (M+, 2), 275 (M+ - SCH3, 100). Anal.
(C10H11IO2S) C, H.
5-Iodobenzo[d]isoxazole (48). An oven-dried flask (25 mL) was
charged with oxime 54 (180 mg, 0.684 mmol), triphenylphosphine
(192 mg, 0.720 mmol), and anhydrous THF (4 mL). The flask was
maintained under an argon atmosphere, and diisopropylazodicar-
boxylate (DIAD) (0.14 mL, 0.719 mmol) was added dropwise. The
reaction mixture was stirred at room temperature for 1 h before
more triphenylphosphine (30 mg) and DIAD (0.5 mL) were added.
After the reaction mixture was stirred for another hour, the mixture
was condensed in vacuo and the remaining residue was loaded onto
a short column of silica (20 mL, 0.5 in. diameter). The product
was eluted with 20% ethyl acetate-hexanes (80 mL), and the eluate
was condensed in vacuo to afford a yellow solid. The material was
recrystallized from acetone and hexanes to afford the product as a
white, crystalline solid (77 mg, 46%): mp 102-103 °C; IR (CDCl3)
3085, 3056, 1995, 1896, 1782, 1755, 1724, 1621, 1597, 1506, 1435,
1570, 1500, 1476, 1418, 1305, 1251, 1221, 1136, 1048 cm-1; H
1
NMR (300 MHz, CDCl3) δ 7.67 (dd, J ) 6.6, 1.5 Hz, 2 H), 7.31
(d, J ) 2.4 Hz, 1 H), 7.26 (dd, J ) 6.6, 1.5 Hz, 2 H), 7.06 (d, J )
1.8 Hz, 1 H), 6.09 (t, J ) 7.5 Hz, 1 H), 3.80 (s, 3 H), 2.79 (t, J )
7.5 Hz, 2 H), 2.47 (s, 3 H), 2.43 (s, 3 H), 2.26 (s, 3 H), 2.19 (q, J
) 7.5 Hz, 2 H), 1.93 (p, J ) 7.5 Hz, 2 H); ESIMS m/z (relative
intensity) 448 (MH+, 42) 447 (M+, 51), 418 (MH+ - SCH3 +
H2O, 100), 400 (MH+ - SCH3, 37). Anal. (C25H25N3O5S) C, H,
N.
1
1417, 1269, 1254, 1224, 1167, 1133 cm-1; H NMR (300 MHz,
CDCl3) δ 8.65 (d, J ) 0.9 Hz, 1 H), 8.10 (d, J ) 1.8 Hz, 1 H),
7.82 (dd, J ) 8.7, 1.5 Hz, 1 H), 7.42 (d, J ) 8.7 Hz, 1 H); CIMS
m/z (relative intensity) 246 (MH+, 100). Anal. (C7H4INO) C, H,
N.
General Procedure for the Synthesis of Stannane Intermedi-
ates via Palladium-Catalyzed Hydrostannation of Alkynes. A
solution of alkyne 40 (1 equiv) in anhydrous THF (0.02-0.05 M)
was cooled in an ice bath, sparged with argon for 15 min, and
maintained under an inert atmosphere at 0 °C. The catalyst, Pd-
(PPh3)4 (0.01 equiv), was added to the THF solution, followed by
tributyltin hydride (1.2-1.5 equiv). The heterogeneous reaction
mixture was stirred at 0 °C, under an argon atmosphere, for 30
min to 2 h. If the reaction had not reached completion after
approximately 2 h, the reaction mixture was allowed to warm to
room temperature and stirred for an additional 1-24 h. The reaction
mixture was concentrated in vacuo, and the remaining residue was
absorbed onto silica. The products were separated by column
chromatography to obtain the stannane product, and, if necessary,
additional purification methods were applied.
General Procedure for the Synthesis of Functionalized Alkyne
Intermediates via the Sonogashira Coupling Reaction of Aryl
Halides with Terminal Alkynes. A mixture of alkyne 39 (1.2-
1.5 equiv), aryl halide 38 (1 equiv), and triethylamine (2.5 equiv)
in anhydrous THF (0.1-0.5 M) was cooled in an ice bath, sparged
with argon for 15 min, and maintained under an inert atmosphere.
After being allowed to warm back to room temperature, PdCl2-
(PPh3)2 (0.1 equiv) and copper(I) iodide (0.2 equiv) were added.
The heterogeneous reaction mixture was stirred at room temperature,
5-Iodo-2-methoxy-3-methylbenzoic Acid (52). A flask was
charged with ester 4419 (266 mg, 0.869 mmol) and methanol (40
mL). Solid potassium hydroxide (506 mg, 9.02 mmol) was added,
and the reaction mixture was stirred until all of the solids had
dissolved. The flask was fitted with a condenser, and the system
was heated at reflux, under an argon atmosphere, for 19 h. The
system was allowed to cool to room temperature, and the reaction
mixture was condensed in vacuo to afford a yellow oil. The oil
was partitioned between water (10 mL) and ethyl acetate (20 mL),
followed by separation of the two phases. The aqueous phase was
cooled in an ice bath and acidified to a pH of 1, via slow addition
of concentrated hydrochloric acid, to produce a white precipitate.
The precipitate was extracted with ethyl acetate (3 × 20 mL), and
the combined organic phases were washed with brine (1 × 30 mL),
dried over magnesium sulfate, filtered, and condensed in vacuo to
afford a white, fluffy solid (248 mg, 85%): mp 163-165 °C; IR
(KBr) 3434, 2947, 2560, 1673, 1567, 1467, 1299, 1252, 1223, 1170,
1
996 cm-1; H NMR (300 MHz, CDCl3) δ 8.27 (d, J ) 2.4 Hz, 1
H), 7.76 (d, J ) 1.8 Hz, 1 H), 3.92 (s, 3 H), 2.34 (s, 3 H); ESIMS
m/z (relative intensity) 291 (M- - H, 100). Anal. (C9H9IO3) C, H.

Alkenyldiarylmethane HIV-1 NNRTIs
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20 4865
2-Hydroxy-5-iodobenzaldehyde Oxime (54). A solution of
aldehyde 53 (472 mg, 1.90 mmol) in ethanol (10 mL) was heated
at 70 °C, and an aqueous solution of hydroxylamine hydrochloride
(3.70 g, 53.3 mmol in 15 mL of water) was added. The reaction
mixture was stirred for 1 h and then cooled to room temperature.
The reaction mixture was diluted with water (50 mL), and the
resulting heterogeneous mixture was extracted with ethyl acetate
(3 × 30 mL). The combined organic extracts were dried over
magnesium sulfate, filtered, and condensed in vacuo to afford the
product as a white solid (489 mg, 98%): mp 134-135 °C; IR
(CDCl3) 3416, 3137, 2945, 2225, 1873, 1769, 1640, 1616, 1555,
47-49 °C; IR (CHCl3) 3684, 3622, 3019, 2977, 2895, 2400, 1520,
1476, 1424, 1218, 1046, 928 cm-1; 1H NMR (300 MHz, CDCl3) δ
4.07 (s, 3 H), 3.10 (t, J ) 7.2 Hz, 2 H), 2.78 (dt, J ) 7.2, 2.7 Hz,
2 H), 2.02 (t, J ) 2.7 Hz, 1 H); CIMS m/z (relative intensity) 137
(MH+, 100). Anal. (C6H8N4) C, H, N.
5-But-3-ynyl-2-methyl-2H-tetrazole (61). IR (neat) 3290, 2958,
1
2925, 2119, 1497, 1440, 1395, 1330, 1194 1038 cm-1; H NMR
(300 MHz, CDCl3) δ 4.31 (s, 3 H), 3.12 (t, J ) 7.5 Hz, 2 H), 2.69
(dt, J ) 7.5, 2.7 Hz, 2 H), 1.98 (t, J ) 2.7 Hz, 1 H); CIMS m/z
(relative intensity) 137 (MH+, 100). Anal. (C6H8N4) C, H, N.
1-Methyl-5-pent-4-ynyl-1H-tetrazole (60) and 2-Methyl-5-
pentyl-4-ynyl-2H-tetrazole (62). A saturated aqueous solution of
potassium carbonate (25 mL) was added to a mixture of tetrazole
58 (1.52 g, 0.011 mol), tetrabutylammonium bromide (373 mg, 1.16
mmol), and dimethyl sulfate (1.60 mL, 0.017 mol) in ethyl acetate
(25 mL). The biphasic mixture was stirred vigorously at room
temperature for 7 h. The phases were separated, and the organic
phase was washed with water (1 × 20 mL) and brine (1 × 20
mL), dried over magnesium sulfate, filtered, and condensed in vacuo
to afford a brown oil. The products were purified by column
chromatography (40 mL of silica, 1 in. diameter) using 50% ethyl
acetate-hexanes as the eluant. Tetrazoles 60 (593 mg, 36%) and
62 (825 mg, 50%) were isolated as clear oils. The physical constants
determined for 60: IR (neat) 3920, 3465, 3285, 2955, 2873, 2116,
1633, 1526, 1468, 1455, 1434, 1415, 1349, 1332, 1286, 1239, 1152,
1
1477, 1429, 1359, 1288, 1255, 1181 cm-1; H NMR (300 MHz,
CDCl3) δ 9.74 (s, 1 H), 8.14 (s, 1 H), 7.55 (dd, J ) 8.7, 2.1 Hz, 1
H), 7.47 (d, J ) 2.1 Hz, 1 H), 7.19 (s, 1 H), 6.76 (d, J ) 8.7 Hz,
1 H); EIMS m/z (relative intensity) 263 (M+, 100), 245 (M+
H2O, 27). Anal. (C7H6NIO2) C, H, N.
-
5-But-3-ynyl-1H-tetrazole (57). A flask was charged with nitrile
55 (8.449 g, 0.107 mol) and toluene (100 mL). Triethylamine
hydrochloride (29.49 g, 0.214 mol) was added to the flask, followed
by sodium azide (14.05 g, 0.216 mol). The flask was fitted with a
condenser, and the system was heated at reflux for 9.5 h. During
the course of the reaction a second, black layer formed at the bottom
of the flask. The system was allowed to cool to room temperature,
and the reaction mixture was diluted with water (35 mL). The
phases were separated, and the organic phase was extracted with
water (3 × 10 mL). Aqueous extracts were combined and
acidified to a pH of 1 through the addition of concentrated
hydrochloric acid. The acidified extracts were stored at 5 °C for
several hours to obtain a white precipitate. The precipitate was
extracted with ethyl acetate (200 mL), and the organic phase was
dried over magnesium sulfate, filtered, and condensed in vacuo to
afford the product as an off-white solid (5.734 g, 49%). An
analytical sample was prepared by recrystallization from ethyl
acetate-hexanes (1:4): mp 59-61 °C; IR (CHCl3) 3684, 3617,
3412, 3308, 3020, 2978, 2897, 2400, 2243, 1885, 1602, 1520, 1476,
1
1095, 1034 cm-1; H NMR (300 MHz, CDCl3) δ 4.03 (s, 3 H),
3.00 (t, J ) 7.5 Hz, 2 H), 2.35 (dt, J ) 6.6, 2.7 Hz, 2 H), 2.06 (p,
J ) 6.6 Hz, 2 H), 2.02 (t, J ) 2.7 Hz, 1 H); CIMS m/z (relative
intensity) 151 (MH+, 100). Anal. (C7H10N4) C, H, N.
2-Methyl-5-pentyl-4-ynyl-2H-tetrazole (62). IR (neat) 3921,
3291, 2957, 2870, 2116, 1496, 1435, 1395, 1348, 1329, 1295, 1191,
1
1078, 1032 cm-1; H NMR (300 MHz, CDCl3) δ 4.30 (s, 3 H),
3.01 (t, J ) 7.5 Hz, 2 H), 2.31 (dt, J ) 6.9, 2.7 Hz, 2 H), 2.01 (p,
J ) 7.2 Hz, 2 H), 1.99 (t, J ) 2.7 Hz, 1 H); CIMS m/z (relative
intensity) 151 (MH+, 100). Anal. (C7H10N4) C, H, N.
1
1423, 1219 1046, 929 cm-1; H NMR (300 MHz, acetone-d6) δ
2-But-3-ynyl-5-methyl-[1,3,4]oxadiazole (63). A flask was
charged with tetrazole 57 (1.50 g, 12.3 mmol) and acetic anhydride
(25 mL). The flask was fitted with a condenser, and the system
was heated at reflux for 20 h. The system was allowed to cool to
room temperature, and the reaction mixture was concentrated in
vacuo to afford a black-yellow residue. The residue was dissolved
in ethyl acetate (30 mL), and the organic solution was washed with
an aqueous solution saturated with sodium bicarbonate (3 × 20
mL) and brine (1 × 10 mL). The organic phase was dried over
magnesium sulfate, filtered, and condensed in vacuo to afford a
brown oil. The product was purified by column chromatography
(100 mL of silica, 2 in. diameter) using an ethyl acetate-hexanes
gradient (50-66%). The desired product was isolated as a clear
oil (834 mg, 50%): IR (CHCl3) 3690, 3606, 3309, 3155, 2984,
2902, 2254, 1817, 1793, 1732, 1643, 1598, 1572, 1471, 1382, 1096,
3.20 (t, J ) 7.2 Hz, 2 H), 2.73 (dt, J ) 7.2, 2.7 Hz, 2 H), 2.41 (t,
J ) 2.7 Hz, 1 H); CIMS m/z (relative intensity) 123 (MH+, 100).
Anal. (C6H6N4) C, H, N.
5-Pent-4-ynyl-1H-tetrazole (58). A flask (100 mL) was charged
with nitrile 56 (1.12 mL, 0.011 mol) and toluene (20 mL).
Triethylamine hydrochloride (4.41 g, 0.032 mol) and sodium azide
(2.06 g, 0.032 mol) were added to the solution, and the resulting
mixture was heated at reflux for 9 h. As the reaction progressed, a
black liquid formed at the bottom of the reaction vessel. The system
was allowed to cool to room temperature, and the reaction mixture
was extracted with water (4 × 10 mL). Aqueous extracts were
combined and acidified to a pH of 1 by adding concentrated
hydrochloric acid. The aqueous phase was extracted with ethyl
acetate (4 × 20 mL), and the combined organic extracts were dried
over magnesium sulfate, filtered, and condensed in vacuo to afford
a yellow oil that, when triturated with hexanes, solidified to a low
melting point solid (1.259 g, 84%): mp 24-26 °C; 1H NMR (300
MHz, DMSO-d6) δ 3.31 (s, 1 H), 2.95 (t, J ) 7.5 Hz, 2 H), 2.84
(t, J ) 2.7 Hz, 1 H), 2.25 (dt, J ) 7.2, 2.7 Hz, 2 H), 1.87 (p, J )
7.2 Hz, 2 H); CIMS m/z (relative intensity) 137 (MH+, 100). Anal.
(C6H8N4) C, H, N.
5-But-3-ynyl-1-methyl-1H-tetrazole (59) and 5-But-3-ynyl-2-
methyl-2H-tetrazole (61). A flask was charged with tetrazole 57
(1.504 g, 12.3 mmol) and ethyl acetate (30 mL). Tetrabutylammo-
nium bromide (419 mg, 1.30 mmol) and dimethyl sulfate (1.74 mL,
18.4 mmol) were added to the flask, followed by an aqueous
solution (30 mL) saturated with potassium carbonate (14.40 g). The
biphasic mixture was stirred vigorously for 16 h, and then the phases
were separated. The organic phase was dried over magnesium
sulfate, filtered, and condensed in vacuo to afford a yellow oil.
The products were separated by column chromatography (75 mL
of silica gel, 2 in. diameter column) using 50% ethyl acetate-
hexanes as eluant. Two methylated tetrazole products were isolated
after column chromatography: solid 59 (553 mg, 33%) and liquid
61 (792 mg, 47%). The physical constants determined for 59: mp
1
912 cm-1; H NMR (300 MHz, CDCl3) δ 3.03 (t, J ) 7.3 Hz, 2
H), 2.67 (dt, J ) 7.2, 2.7 Hz, 2 H), 2.46 (s, 3 H), 2.43 (t, J ) 2.7
Hz, 1 H); CIMS m/z (relative intensity) 137 (MH+, 100). Anal.
(C7H8N2O) C, H, N.
2-Methyl-5-pent-4-ynyl-[1,3,4]oxadiazole (64). A solution of
tetrazole 58 (3.16 g, 0.023 mol) in acetic anhydride (22 mL) was
heated at reflux for 24 h and then allowed to cool to room
temperature. The mixture was diluted with water (30 mL) and
basified to a pH of 8 through the addition of concentrated
ammonium hydroxide. The mixture was extracted with ether (3 ×
40 mL) and ethyl acetate (1 × 30 mL). The organic extracts were
combined, washed with brine (1 × 40 mL), dried over magnesium
sulfate, and condensed in vacuo to afford a yellow oil. The crude
products were purified by column chromatography (100 mL of
silica, 2 in. diameter) using an ethyl acetate-hexanes gradient (33-
50%). The product was isolated as a yellow oil (2.44 g, 91%): IR
(neat) 3453, 3290, 2942, 2873, 2648, 2117, 1725, 1702, 1597, 1571,
1
1435, 1394, 1367, 1348, 1330, 1278, 1224, 1043 cm-1; H NMR
(300 MHz, CDCl3) δ 2.95 (t, J ) 7.5 Hz, 2 H), 2.50 (s, 3 H), 2.34
(dt, J ) 6.9, 2.7 Hz, 2 H), 2.06-1.99 (m, 3 H); CIMS m/z (relative
intensity) 151 (MH+, 100). Anal. (C8H10N2) C, H, N.

4866 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20
Cullen et al.
(8) Dueweke, T. J.; Poppe, S. M.; Romero, D. L.; Swaney, S. M.; So,
A. G.; Downey, K. M.; Althaus, I. W.; Reusser, F.; Busso, M.;
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Hogg, R. S.; Yip, B.; Harris, M.; Montessori, V.; O’Shaughnessy,
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HIV Potency with Lipophilicity in a Series of Cosalane Analogs
Having Normal Alkenyl and Phosphodiester Chains as Cholestane
Replacements. J. Med. Chem. 1996, 39, 508-514.
(14) Cushman, M.; Golebiewski, M.; Buckheit, R. W., Jr.; Graham, L.;
Rice, W. G. Synthesis and Biological Evaluation of an Alkenyl-
diarylmethane (ADAM) Which Acts as a Novel Non-Nucleoside
HIV-1 Reverse Transcriptase Inhibitor. Bioorg. Med. Chem. Lett.
1995, 5, 2713-2716.
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W. G.; Fliakas-Boltz, V.; Buckheit, R. W., Jr. Synthesis and
Biological Evaluation of Certain Alkenyldiarylmethanes as Anti-
HIV-1 Agents Which Act as Non-Nucleoside Reverse Transcriptase
Inhibitors. J. Med. Chem. 1996, 39, 3217-3227.
RT Inhibition Assay. The ability of target compounds to inhibit
the enzymatic activity of recombinant HIV-1 RT (p66/51 dimer)
was evaluated as previously described.15,28 Briefly, inhibition of
purified HIV-1 reverse transcriptase was determined by the amount
of 32P labeled GTP incorporated into a nascent DNA strand, with
a poly(rC)oligo(dG) homopolymer primer, in the presence of
increasing concentrations of the target compounds.
In Vitro Antiviral Assays. The antiviral activities of the target
compounds were determined for the HIV strains HIV-1RF, HIV-
1
1
IIIB, and HIV-2ROD. Evaluation of antiviral activity against HIV-
RF was determined in infected CEM-SS cells while using the XTT
cytoprotection assay, as previously described.28 Evaluation of
antiviral activity against the HIV-1IIIB and HIV-2ROD strains was
performed in infected MT-4 cells using the previously described
MTT assay.18,29 Cytoprotective evaluations against the engineered
HIV strains bearing Y181C and K103N RT mutations were
performed as previously reported.25,26
In Vitro Hydrolytic Stability Assay Utilizing Rat Plasma. The
compounds of interest were tested for their hydrolytic stability in
solutions of reconstituted rat plasma using methods that have been
previously reported.18 The internal standard used was 1,1-diphe-
nylethylene, and two different batches of rat plasma had to be
utilized for the experiments (LOTs 052K7609 and 065K7555). A
control compound was tested in both batches of rat plasma to ensure
that the hydrolysis rates of the two batches were approximately
equivalent. The aliquot supernatants were analyzed using a Waters
binary HPLC system (model 1525, 20 µL injection loop) and a
Waters dual wavelength absorbance UV detector (model 2487) set
for 254 nM. Data were collected and processed using the Waters
Breeze software (version 3.3) on a Dell Optiplex GX280 personal
computer. The mobile phase consisted of 8:2 (v/v) acetonitrile/
water, and the Symmetry HPLC column (4.6 mm x 150 mm) was
packed with C18 Silica from Waters. The column was maintained
at room temperature during the analyses. The reported half-lives
for the compounds are averages calculated from a minimum of two
replicates. Half-lives for the individual replicates were calculated
from regression curves fitted to plots of the compound concentration
versus time.
(16) Casimiro-Garcia, A.; Micklatcher, M.; Turpin, J. A.; Stup, T. L.;
Watson, K.; Buckheit, R. W.; Cushman, M. Novel Modifications in
the Alkenyldiarylmethane (ADAM) Series of Non-Nucleoside Re-
verse Transcriptase Inhibitors. J. Med. Chem. 1999, 42, 4861-4874.
(17) Cushman, M.; Casimiro-Garcia, A.; Hejchman, E.; Ruell, J. A.;
Huang, M.; Schaeffer, C. A.; Williamson, K.; Rice, W. G.; Buckheit,
R. W., Jr. New Alkenyldiarylmethanes with Enhanced Potencies as
Anti-HIV Agents Which Act as Non-Nucleoside Reverse Tran-
scriptase Inhibitors. J. Med. Chem. 1998, 41, 2076-2089.
(18) Silvestri, M. A.; Nagarajan, M.; De Clercq, E.; Pannecouque, C.;
Cushman, M. Design, Synthesis, Anti-HIV Activities, and Metabolic
Stabilities of Alkenyldiarylmethane (ADAM) Non-Nucleoside
Reverse Transcriptase Inhibitors. J. Med. Chem. 2004, 47, 3149-
3162.
Acknowledgment. This investigation was made possible by
funding from the National Institutes of Health, DHHS, through
Grant RO1-AI-43637, and research was conducted in a facility
constructed with the financial support of a Research Facilities
Improvement Program grant, No. C06-14499, also from the
National Institutes of Health.
(19) Deng, B. L.; Hartman, T. L.; Buckheit, R. W.; Pannecouque, C.; De
Clercq, E.; Fanwick, P. E.; Cushman, M. Synthesis, Anti-HIV
Activity, and Metabolic Stability of New Alkenyldiarylmethane
HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors. J. Med.
Chem. 2005, 48, 6140-6155.
(20) Deng, B. L.; Hartman, T. L.; Buckheit, R. W.; Pannecouque, C.; De
Clercq, E.; Cushman, M. Replacement of the Metabolically Labile
Methyl Esters in the Alkenyldiarylmethane Series of Non-Nucleoside
Reverse Transcriptase Inhibitors with Isoxazolone, Isoxazole, Ox-
azolone, or Cyano Substituents. J. Med. Chem. 2006, 49, 5316-
5323.
(21) Das, K.; Lewi, P. L.; Hughes, S. H.; Arnold, E. Crystallography and
the Design of Anti-AIDS Drugs: Conformational Flexibility and
Positional Adaptability Are Important in the Design of Non-
Nucleoside HIV-1 Reverse Transcriptase Inhibitors. Prog. Biophys.
Mol. Biol. 2005, 88, 209-231.
(22) Xu, G.; Micklatcher, M.; Silvestri, M.; Hartman, T. L.; Burrier, J.;
Osterling, M. C.; Wargo, H.; Turpin, J. A.; Buckheit, R. W., Jr.;
Cushman, M. The Biological Effects of Structural Variation at the
Meta Position of the Aromatic Rings and at the End of the Alkenyl
Chain in the Alkenyldiarylmethane Series of Non-Nucleoside Reverse
Transcriptase Inhibitors. J. Med. Chem. 2001, 44, 4092-4113.
(23) Deng, B. L.; Cullen, M. D.; Zhou, Z. G.; Hartman, T. L.; Buckheit,
R. W.; Pannecouque, C.; De Clercq, E.; Fanwick, P. E.; Cushman,
M. Synthesis and Anti-HIV Activity of New Alkenyldiarylmethane
(ADAM) Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
Incorporating Benzoxazolone and Benzisoxazole Rings. Bioorg. Med.
Chem. 2006, 14, 2366-2374.
Supporting Information Available: Schemes and experimental
procedures pertaining to synthetic intermediates not presented; syn-
thesis of compound 4; analytical HPLC traces and data; elemental
analysis results for compounds and intermediates. This material is
available free of charge via the Internet at http://pubs.acs.org.
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