Phenyl β-methoxyacrylates: A new antimalarial pharmacophore

Article abstract of DOI:10.1021/jm990002y

Phenyl β-methoxyacrylates, linked to an aromatic ring via an olefinic bridge, have been identified as novel, potentially inexpensive, antimalarial agents. The compounds are believed to exert their activity by inhibition of mitochondrial electron transport

Full text of DOI:10.1021/jm990002y

560
J . Med. Chem. 2000, 43, 560-568
Articles
P h en yl â-Meth oxya cr yla tes: A New An tim a la r ia l P h a r m a cop h or e
J awad Alzeer, J acques Chollet, Ingrid Heinze-Krauss, Christian Hubschwerlen, Hugues Matile, and
Robert G. Ridley*
Pharma Research, Preclinical Infectious Diseases, F. Hoffmann-La Roche Ltd., CH-4070 Basel, Switzerland
Received J anuary 4, 1999
Phenyl â-methoxyacrylates, linked to an aromatic ring via an olefinic bridge, have been
identified as novel, potentially inexpensive, antimalarial agents. The compounds are believed
to exert their activity by inhibition of mitochondrial electron transport at the cytochrome bc1
complex. A series of compounds have been synthesized to define structure-activity relationships
affecting antimalarial activity. It was found that the â-methoxyacrylate was required ortho to
the linker and the optimal bridge was (E,E)-butadiene. Compounds in which the second aromatic
ring was ortho-substituted or ortho,para-disubstituted gave optimal potency. Several compounds
were identified with potency that is superior to that of chloroquine both in culture and in a
murine malaria model.
In tr od u ction
which have found use as agrochemical agents.11-14 They
have not been previously reported to inhibit human
pathogens, but their ability to inhibit the mitochondrial
respiration process of certain fungal plant pathogens
and insects is widely reported. We rationalized that
â-methoxyacrylates could constitute a new class of
antimalarial agents and proceeded to investigate this
possibility.
A series of â-methoxyacrylates was screened for
antimalarial activity, both in culture against P. falci-
parum-infected erythrocytes, and in a rodent P. berghei
model. Full details of our methodology have been
reported previously.15 Compound 2 was found to have
reasonable antimalarial activity in culture, with a 50%
inhibitory concentration (IC50) against the chloroquine-
resistant P. falciparum strain K1 of 29 ng/mL and an
IC50 against the chloroquine-sensitive P. falciparum
strain NF54 of 5.5 ng/mL. No in vivo activity was
observed in the rodent P. berghei model. Consequently,
we initiated a synthesis program to explore structure-
activity relationships (SAR) of the new lead compound
with the objective of improving the in vitro activity and
obtaining oral in vivo activity.
The rapidly increasing resistance of Plasmodium
falciparum malaria parasites to commonly used inex-
pensive drugs, such as chloroquine and sulfadoxine-
pyrimethamine, and the recent appearance of resistance
to more expensive chemotherapeutic agents and pro-
phylactic drugs, such as mefloquine and halofantrine,
indicate the urgent need for new classes of antimalarial
compounds.1-4
Atovaquone (1) is a hydroxynaphthoquinone analogue
that was recently developed as an antimalarial drug in
combination with proguanil.5,6 This compound is an
analogue of ubiquinone which is a critical component
in mitochondrial electron transfer. It has been demon-
strated that atovaquone inhibits the transfer of elec-
trons at the cytochrome c reductase complex (cyto-
chrome bc1) of malaria parasites.7 This results in the
collapse of the mitochondrial membrane potential in the
parasite.8 A further consequence is the inhibition of
parasite dihydroorotate dehydrogenase, which transfers
electrons to cytochrome bc1 and requires a functional
mitochondrial electron-transport chain.9,10 This enzyme
is a key component in pyrimidine biosynthesis, and due
to its inhibition parasites are no longer able to synthe-
size and replicate their DNA.
In this paper we describe the effects of modifying the
linker, the substituent pattern on the aromatic rings
A + B, and the isosteric replacement of â-methoxyacry-
late. We report here the synthesis and antimalarial
activities of a series of â-methoxyacrylates to define the
optimal structural features of this novel antimalarial
pharmacophore.
Although the atovaquone plus proguanil combination
is effective against malaria, atovaquone’s high cost is
likely to limit its widespread use in disease-endemic
countries, especially those of sub-Saharan Africa. Less-
expensive inhibitors of the malaria cytochrome c reduc-
tase complex might therefore find application as anti-
malarial therapies.
Ch em istr y
Compounds 2 and 7 were prepared from 3a 16 and
4a ,17 respectively, as outlined in Scheme 1. Thus,
nucleophilic displacement of bromine ion 3a with o-
trifluorothiophenol (5) gave the phenylsulfanyl acrylate
2, and a Wittig-Horner reaction between phosphonate
4a and o-(trifluoromethyl)benzaldehyde (6) gave the
ethylene-bridged acrylate 7.
Another class of compounds known to inhibit cyto-
chrome c reductase complex are the â-methoxyacrylates,
* Corresponding author: Robert G. Ridley. Current address: World
Health Organization, Communicable Disease Research and Develop-
ment (CRD), CH-1211 Geneva 27, Switzerland. Tel.: +41-22-791-3884.
Fax: +41-22-791-4854. E-mail: ridleyr@who.int.
10.1021/jm990002y CCC: $19.00 © 2000 American Chemical Society
Published on Web 02/03/2000

Phenyl â-Methoxyacrylates
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4 561
Sch em e 1a
Coupling vinylstannane 24 with vinyl bromide 20 gave
(E,E)-butadiene 26. Butenyne derivative 27 was made
by coupling vinyl bromide 20 with alkyne 23 (Scheme
4) using Pd2[diba]3 and CuI in the presence of trieth-
ylamine.
Although oxime 23 has been reported,20 no final proof
for the assigned Z-stereochemistry of the oxime moiety
was given. To obtain both isomers for comparison by
1H NMR, we attempted to isomerize oxime 23 with
various acids but were unsuccessful. Compound 23
either was recovered unchanged or underwent decom-
position. However, in the reaction of methoxylamine
with acetylene 29, a 6:1 mixture of two isomers was
obtained which could be separated by column chroma-
a
(a) NaH, THF.
1
tography. The major product had an H NMR spectrum
1
identical to that of 23. The major difference in H NMR
Similarly compounds 12, 15a -o, and 18 were made
as depicted in Schemes 2 and 3. The intermediate
aromatic propenals 14a -o were prepared by Wittig
oxopropenylation of the appropriate benzaldehyde de-
rivatives using (1,3-dioxan-2-ylmethyl)tributylphospho-
nium bromide.18 Catalytic hydrogenation converted
butadiene 15a to butane 16.
spectra of both isomers is the chemical shift values of
the acetylenic proton: the minor product resonates at
3.27 ppm, whereas the major product resonates at 3.17
ppm. Irradiation of OMe protons in the 1H NMR spectra
in both isomers, unfortunately, did not show any NOE
effects. However, it is fair to assume that the trimeth-
ylsilyl group on the acetylene in 21 leads to exclusive
formation of the Z-isomer (assigned as 23) due to large
steric repulsion, whereas the smaller proton of acetylene
29 allows also some formation of the E-isomer (assigned
as 30).
Different olefin bridges were also prepared, as out-
lined in Scheme 5. Oximes 23 and 30 were coupled with
bromoalkyne 28, prepared by the dehydrobromination
of dibromoolefin 19 using Ratovelomanana’s condition,21
in the presence of Pd[diba]3/CuI to afford butadiynes 31
and 32, respectively. Treatment of butadiyne 31 with
The methoxyiminoacetate derivatives were made as
shown in Schemes 4 and 5. o-(Trifluoromethyl)benzal-
dehyde (6) was transferred to gem-dibromoolefin 19
which, in turn, was treated with diethyl phosphite in
the presence of triethylamine19 to give monobromoalk-
ene 20 (trans:cis ) 8:1).
Vinylstannane 24 was prepared from 2320 as an
inseparable mixture of E- and Z-isomers (1:1) using the
radical hydrostannylation condition (Bu3SnH/AIBN).
When hydrostannylation was performed in the presence
of Pd(0)/Bu3SnH, only regioisomer 25 was obtained.
Sch em e 2a
a
(a) Pd[PPh3]4, toluene; (b) toluene-4-sulfonic acid, EtOH; (c) CBr4, PPh3, Et2O; (d) NaH, THF.
Sch em e 3a
a
(a) P(OMe)3, toluene; (b) NaH, THF; (c) Pd/C, H2, CH2Cl2.

562 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4
Alzeer et al.
Sch em e 4a
a
(a) CBr4, PPh3; (b) HPO(EtO)2, Et3N; (c) Bu3SnH, AIBN; (d) Pd[PPh3]4, toluene; (e) Et3N, Pd2[diba]3, CuI, toluene.
Sch em e 5a
a
(a) DBU, DMSO; (b) Bu4NF, THF; (c) MeONH2.HCl, NaOAc, MeOH, H2O; (d) Et3N, CuI, Pd2[diba]3; (e) Na2S‚9H2O, MeOEtOH, H2SO4,
MeOH; (f) 10% Pd/C, H2, CH2Cl2.
Na2S‚9H2O in 2-methoxyethanol followed by H2SO4/
MeOH gave thiophene 33. Reduction of both triple bonds
in 30 with H2/Pd yielded 34.
improvement of in vitro activity was observed upon
increasing the length of the linker from two to four
atoms. In some cases this also resulted in a demon-
strable in vivo activity. The (E,E)-butadiene-linker
(compound 15a ) conferred the best activity. Conjugation
through the linker appears beneficial for activity as
indicated by the lower potency of the saturated deriva-
tive 16 in comparison to 15a , in both in vitro and in
vivo models. Substitution of one of the double bonds in
15a by a heterocycle, such as furan in 18, gave deriva-
tives that had good in vitro activity but which were toxic
when applied to mice. Compound 15a exhibited 140-
fold increase in potency against P. falciparum in vitro
compared to the lead compound 2. In correlation with
its excellent in vitro activity, 15a also gave the best
results for in vivo efficacy.
Biologica l Resu lts a n d Discu ssion
All new compounds were evaluated for antimalarial
activity in vitro (i.e. in culture against parasite-infected
erythrocytes) against chloroquine-sensitive (NF54) and
-resistant (K1) strains of P. falciparum. They were also
tested for in vivo efficacy in a rodent P. bergehei model
(both po and sc) using a single-dose application of 50 or
100 mg/kg, 24 h after infection. The dose of those
compounds showing in vivo activity was titrated down
to a dose of 10 mg/kg in order to investigate differences.
The methodology used for these studies has previously
been described in detail.15 If in vivo efficacy in the rodent
model, as measured by growth inhibition (GI) of para-
sites, was >99% compared to control untreated mice 72
h after infection, further studies were undertaken to
determine the effective doses for parasite reduction in
the mice of 50% or 90%, respectively (ED50/90 values).
First we investigated the influence of the linker on
antimalarial activity, keeping the 2-trifluoromethyl
substituent on ring B constant (Table 1). All compounds
in this series showed an enhancement of in vitro activity
over the lead compound 2, against both sensitive (NF54)
and resistant (K1) strains of P. falciparum. Consistent
In the next step, the substituents as well as the
substitution pattern on ring B were optimized, keeping
the (E,E)-butadiene linker constant (Table 2). Replace-
ment of the trifluoromethyl group in 15a with a chloro
substituent did not improve potency but retained some
in vivo activity in contrast to strongly electron-with-
drawing substituents such as the cyano group (15d ).
Compounds having corresponding substituents in the
meta- or para-position (15e-h ) exhibited diminished
potency and had no in vivo activity. A series of disub-
stituted analogues (15i-m ) were also prepared and

Phenyl â-Methoxyacrylates
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4 563
Ta ble 1. Antimalarial Activities of â-Methoxyacrylates with
Different Linkers Against Chloroquine-Sensitive (NF54) and
Chloroquine-Resistant (K1) P. falciparum (in vitro) and
P. berghei (in vivo)a
Ta ble 2. Antimalarial Activities of â-Methoxyacrylates 15,
Containing a Butadiene Linker, Against Chloroquine-Sensitive
(NF54) and Chloroquine-Resistant (K1) P. falciparum (in vitro)
and P. berghei (in vivo)a
a
The dose used in the in vivo experiments was 100 mg/kg. GI,
growth inhibition; tox, toxic; sc, subcutaneous; po, per os.
tested. In general, the o-â-methoxyacrylate derivatives
with o-p-disubstitution pattern on ring B were ex-
tremely potent, in vitro and in vivo. In particular, 15i-k
warranted further investigation.
The substitution pattern on ring A was also evalu-
ated, shifting the â-methoxyacrylate pharmacophore
into meta- and para-positions (Table 3). The results
clearly demonstrated the superiority of o-â-methoxy-
acrylates.
a
For the in vivo experiments the compounds were initially
tested at either 50 or 100 mg/kg. If growth inhibitory activity was
greater than 99%, they were further tested at 10 mg/kg and this
value was recorded.
Ta ble 3. Antimalarial Activities of â-Methoxyacrylates
15l,t,u Against Chloroquine-Sensitive (NF54) and
Chloroquine-Resistant (K1) P. falciparum (in vitro) and
P. berghei (in vivo)
In addition, we investigated structural modifications
in the pharmacophore. Isosteric replacement of carbon
by nitrogen led to methoxyimino analogues such as 26
(Table 4). Many of these compounds gave reasonable
activity in vitro. However, none displayed significant in
vivo activity, and so they were not pursued further.
The ED50/90 values were determined for the most
active compounds, and these are presented, together
with their in vitro IC50 values, in Table 5 and are
compared to both chloroquine and atovaquone. An
outstanding feature of this series is their potent in vitro
activity, surpassing that of chloroquine by a factor of
100. These are among the lowest IC50 values we have
ever recorded. The in vivo potency also exceeds that of
chloroquine in the rodent P. berghei model, but to a
lesser extent. A compound which incorporated both the
butadiene linker and the 2,4-bis-trifluoromethyl sub-
stituents (15i) was found to be the most potent com-
pound of the series with an ED50/90 value of 0.42/1.44
mg/kg (po) and 0.28/0.96 mg/kg (sc). The ED50/90 value
of compound 15i is superior to that of chloroquine by a
factor of 5 but is a factor of 10 lower than that for
atovaquone.
been designed, synthesized, and subjected to pharma-
cological evaluation. Some compounds have been identi-
fied with very potent oral antimalarial activities. SAR
confirmed the role of the â-methoxyacrylate as phar-
mocophore. Several criteria have been established for
the further design of â-methoxyacrylate analogues: i.e.,
(a) o-â-methoxyacrylate on the aromatic ring A, (b) 2,4-
substitution pattern on the aromatic ring B, and (c)
(E,E)-butadiene linker.
Con clu sion
This work has identified a new class of compounds
with antimalarial activity. A series of compounds have

564 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4
Alzeer et al.
Ta ble 4. Antimalarial Activities of R-Methoxyiminoacetates
with Different Linkers Against Chloroquine-Sensitive (NF54)
and Chloroquine-Resistant (K1) P. falciparum (in vitro) and
P. berghei (in vivo)
Melting points were determined on a Buchi 510 apparatus and
are uncorrected. H NMR spectra were recorded on a Bruker
FT AC-250 instrument (250 MHz); chemical shifts are reported
as δ values (ppm) downfield from internal Me4Si in the solvent
shown. IR spectra were recorded on a Nicolet FT IR20 SX
1
spectrophotometer. EI mass spectra were recorded on
Perking Elmer Siex API III instrument.
a
Meth yl (E)-3-Meth oxy-2-[(2-tr iflu or om eth ylp h en ylsu l-
fa n ylm eth yl)p h en yl]a cr yla te (2). Sodium hydride (85%
suspension in mineral oil, 74 mg, 2.62 mmol) was added to a
solution of 2-(trifluoromethyl)thiophenol (190 µL, 1.05 mmol)
in THF (5 mL). The mixture was stirred at room temperature
for 10 min and treated with 3a (250 mg, 0.87 mmol) for 1 h.
After treatment with acetic acid, the reaction mixture was
diluted with ethyl acetate and brine. The organic phase was
separated and dried over Na2SO4. Evaporation of the solvent
afforded 2 (330 mg, 98%) as white crystals: mp 92-93 °C; IR
1
(KBr) 2924, 1708, 1634 cm-1; MS (EI) 350 (M - MeOH); H
NMR (250 MHz, CDCl3) δ 3.70 (s, 3H, MeO), 3.83 (s, 3H, MeO),
4.04 (2H, s), 7.11 (1H, d), 7.25 (6H, m), 7.60 (1H, s), 7.62 (1H,
d) ppm.
Meth yl (E)-2-[2-[(E)-2-(2-Tr iflu or om eth ylp h en yl)vin yl]-
p h en yl]-3-m eth oxya cr yla te (7). Sodium hydride (21 mg,
0.88 mmol) was added to a cooled (0 °C) solution of 4a (233
mg, 0.74 mmol) in THF (2 mL). The cooling bath was removed
and the mixture stirred at room temperature for 20 min.
o-(Trifluoromethyl)benzaldehyde (6) (97 µL, 0.81 mmol) was
added and the mixture heated to 60 °C for 4 h. The reaction
mixture was allowed to cool to room temperature, treated with
acetic acid (1 mL), diluted with ethyl acetate, washed with
brine, and dried over Na2SO4. Evaporation of the solvent and
purification of the residue by column chromatography (7:1
hexane/ethyl acetate eluant) afforded 7 (100 mg, 37%) as white
crystals: mp 99-100 °C; IR (KBr) 1705, 1629 cm-1; MS (EI)
Ta ble 5. ED50/90 on P. berghei (in vivo) and Antimalarial
Activities Against Chloroquine-Sensitive (NF54) and
Chloroquine-Resistant (K1) P. falciparum (in vitro) of the Most
Active Compounds Compared to Chloroquine and Atovaquone
1
62 (M); H NMR (250 MHz, CDCl3) δ 3.67 (s, 3H, MeO), 3.79
(s, 3H, MeO), 7.00 (1H, d, J ) 16 Hz), 7.25 (5H, m), 7.50 (1H,
t), 7.62 (1H, s), 7.64 (3H, m) ppm.
Meth yl (E)-3-Meth oxy-2-{(E)-2-[3(R)- a n d 3-(S)-(tetr a -
h yd r op yr a n -2-yloxy)p r op en yl]p h en yl}a cr yla te (9). Tet-
rakis(triphenylphosphine)palladium (58 mg, 0.05 mmol) was
added to a solution of (E)-tributyl-[3(RS)-(tetrahydropyran-2-
yloxy)propenyl]stannane (2.2 g, 5.1 mmol) and 8 (1.38 g, 5.1
mmol) in toluene (20 mL). The mixture was stirred at 110 °C
for 2 days, cooled to room temperature, extracted with toluene,
washed with brine, and dried over Na2SO4. Evaporation of the
solvent and purification of the residue by column chromatog-
raphy (9:1 hexane/ethyl acetate eluant) afforded 9 (884 mg,
52%) as white crystals: mp 66-68 °C; IR (KBr) 1711, 1633
cm-1; MS (EI) 216 (M - MeOH - dihydropyran); 1H NMR (250
MHz, CDCl3) δ 1.8 (6H, m), 3.47 (1H, m), 3.67 (3H, s), 3.80
(3H, s), 3.90 (1H, m), 4.17 (1H, dd, J ) 12, 6.8 Hz), 4.55 (1H,
dd, J ) 12, 5.0 Hz), 4.70 (1H, t), 6.22 (1H, ddd, J ) 16.0, 6.8,
5.0 Hz), 6.6, (1H, d, J ) 16.0 Hz), 7.1 (1H, d), 7.26 (1H, m),
7.57 (1H, d) ppm.
Literature evidence suggests that â-methoxyacrylates
act on the cytochrome bc1 complex similarly to atova-
quone.11-14 Preliminary data also confirm that they act
by this mechanism against malaria parasites (Arnulf
Dorn, unpublished data).
The recent success of atovaquone in combination with
proguanil as a malaria therapy6 further demonstrates
that the â-methoxyacrylates, either alone or in combi-
nation, could become valuable antimalarial drugs. The
compounds have the notable advantage over atovaquone
of a less-expensive synthetic route. Thus, whereas
atovaquone-proguanil is limited to high-cost therapy,
and potentially prophylaxis, â-methoxyacrylates have
the potential for use in poorer populations, such as in
sub-Saharan Africa.
Meth yl (E)-2-[2-[(E)-3-Hydr oxypr open yl]ph en yl]-3-m eth -
oxya cr yla te (10). Toluene-4-sulfonic acid monohydrate (1.11
g, 0.4 mmol) was added to a solution of 9 (4.86 g, 14 mmol) in
ethanol (70 mL). The mixture was stirred for 6 h and
neutralized with saturated K2CO3 solution. The solvent was
evaporated and the residue treated with ethyl acetate. The
organic phase was separated, washed with brine, and dried
over Na2SO4. Evaporation of the solvent afforded 10 (3.4 g,
93%) as white crystals: mp 78-80 °C; IR (KBr) 1683, 1619
1
cm-1; MS (EI) 216 (M - MeOH); H NMR (250 MHz, CDCl3)
δ 1.52 (OH, t, J ) 6.0 Hz), 3.67 (3H, s), 3.8 (3H, s), 4.26 (2H,
m), 6.3 (1H, td, J ) 15.0, 6.0 Hz), 6.55 (1H, d, J ) 15.0 Hz),
7.1 (1H, d, J ) 8.0 Hz), 7.25 (2H, m), 7.58 (1H, d), 7.59 (1H, s)
ppm.
Meth yl (E)-2-[2-[(E)-3-Br om op r op en yl]p h en yl]-3-m eth -
oxya cr yla te (11). A solution of 10 (3.84 g, 14 mmol) in diethyl
ether (60 mL) was added to a solution of carbon tetrabromide
(6.26 g, 18.2 mmol) and triphenylphosphine (4.96 g, 18.2 mmol)
in diethyl ether (30 mL). The resulting white suspension was
stirred for 20 h and filtered through a pad of Celite. Evapora-
On the basis of the studies outlined here, compounds
15i-k were selected for further investigations, which
will be reported elsewhere.
Exp er im en ta l Section
Gen er a l Meth od s. TLC was performed on silica gel plates
(Merck, silica gel 60 F254). Column chromatography was
carried out with Merck silica gel, 40-63 µm, 230-400 mesh.

Phenyl â-Methoxyacrylates
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4 565
tion of the solvent and purification of the residue by column
chromatography (9:2 hexane/ethyl acetate eluant) afforded 11
(3 g, 63%) as white crystals: mp 88 °C; IR (KBr) 1708, 1632
cm-1; MS (EI) 231 (M - Br); 1H NMR (250 MHz, CDCl3) δ
3.69 (3H, s), 3.83 (3H, s), 4.12 (2H, d, J ) 7.5 Hz), 6.32 (1H,
td, J ) 15.0 Hz), 6.62 (1H, d, J ) 15.0 Hz), 7.1 (1H, d, J ) 8.0
Hz), 7.25 (2H, m), 7.58 (1H, d), 7.6 (1H, s) ppm.
by column chromatography (8:2 hexane/ethyl acetate elvant)
afforded 15i (245 mg, 33%) as white crystals: mp 176-177
°C; IR (KBr) 1703, 1630 cm-1; MS (EI) 456 (M); 1H NMR (250
MHz, CDCl3) δ 3.69 (3H, s), 3.82 (3H, s), 6.76 (1H, d, J ) 15.0
Hz), 6.97 (3H, m), 7.15 (1H, dd, J ) 2.0, 8.0 Hz), 7.3 (2H, m),
7.63 (1H, s), 7.7 (1H, d, J ) 8.0 Hz), 7.75 (1H, d, J ) 8.0 Hz),
7.83 (1H, d, J ) 8.0 Hz), 7.87 (1H, s) ppm.
Met h yl (E)-3-Met h oxy-2-[2-[(E)-3-(2-t r iflu or om et h yl-
p h en ylsu lfa n yl)p r op en yl]p h en yl]a cr yla te (12). Sodium
hydride (85% suspension in mineral oil, 24 mg, 0.85 mmol)
was added to a solution of 5 (81 mg, 0.45 mmol) in THF (1
mL). The mixture was stirred for 10 min and treated with 11
(127 mg, 0.38 mmol). After stirring 10 min, acetic acid was
added and diluted with ethyl acetate. The organic phase was
washed with brine and dried over Na2SO4. Evaporation of the
solvent afforded 12 (147 mg, 0.36 mmol, 95%) as a colorless
oil: IR (neat) 2948, 1708, 1633, 1593 cm-1; MS (EI) 408 (M);
1H NMR (250 MHz, CDCl3) δ 3.65 (3H, s), 3.73 (2H, d), 3.77
(3H, s), 6.2 (1H, dt), 6.4 (1H, d), 7.11 (1H, d), 7.25 (4H, m),
7.48 (2H, m), 7.53 (1H, s), 7.62 (1H, d) ppm.
Meth yl (E)-2-[3-(Dim eth oxyph osph or ylm eth yl)ph en yl]-
3-m eth oxya cr yla te (4b). 4a 17 was prepared according to the
method described for 4b. At room temperature, a catalytic
amount of 2,2′-azobis(isobutyronitrile) was added to a solution
of methyl 2-(3-methylphenyl)-3-methoxyacrylate (4 g, 19.4
mmol) and N-bromosuccinimide (3.9 g, 21.3 mmol) in carbon
tetrachloride (100 mL). The mixture was refluxed for 4 h,
cooled to 0 °C, and filtered. The filtrate was evaporated and
the residue dissolved in toluene (2.5 mL). Trimethyl phosphite
(2.5 mL, 21.3 mmol) was added and the solution heated 20 h
under reflux. The solvent was evaporated and the product was
purified by column chromatography (ethyl acetate) to afford
4b (850 mg, 14%) as white crystals:1H NMR (250 MHz, CDCl3)
δ 3.17 (2H, d, J ) 21.0 Hz), 3.64 (3H, s), 3.68 (3H, s), 3.73
(3H, s), 3.85 (3H, s), 7.26 (4H, m), 7.55 (1H, s) ppm.
The following compounds were obtained similarly.
Meth yl (E)-3-m eth oxy-2-{2-[(E,E)-4-(2-tr iflu or om eth -
ylp h en yl)bu ta -1,3-d ien yl]p h en yl}a cr yla te (15a ): MS (EI)
1
388 (M); H NMR (250 MHz, CDCl3) δ 3.69 (3H, s), 3.81 (3H,
s), 6.67 (1H, d, J ) 15.0 Hz), 6.95 (3H, m), 7.15 (1H, dd, J )
2.0, 8.0 Hz), 7.28 (3H, m), 7.5 (1H, t, J ) 8.0 Hz), 7.62 (1H, s),
7.63 (1H, d, J ) 8.0 Hz), 7.73 (2H, m) ppm.
Meth yl (E)-3-m eth oxy-2-[2-(E,E)-(4-p h en ylbu ta -1,3-d i-
en yl)p h en yl]a cr yla te (15b): MS (EI) 320 (M); 1H NMR (250
MHz, CDCl3) δ 3.69 (3H, s), 3.81 (3H, s), 6.66 (2H, m), 6.93
(2H, m), 7.2 (6H, m), 7.43 (2H, d), 7.62 (1H, s), 7.68 (1H, d,
J ) 8.0 Hz) ppm.
Met h yl (E)-2-{2-[(E,E)-4-(2-ch lor op h en yl)b u t a -1,3-d i-
en yl]p h en yl}-3-m eth oxya cr yla te (15c): MS (EI) 354 (M);
1H NMR (250 MHz, CDCl3) δ 3.69 (3H, s), 3.81 (3H, s), 6.69
(1H, d, J ) 15.0 Hz), 6.9-7.4 (9H, m), 7.58 (1H, d, J ) 8.0
Hz), 7.62 (1H, s), 7.63 (1H, d, J ) 8.0 Hz) ppm.
Meth yl (E)-2-[2-[(E,E)-4-(2-cyan oph en yl)bu ta-1,3-dien yl]-
p h en yl]-3-m eth oxya cr yla te (15d ): mp 161-162 °C; IR (KBr)
1706, 1628 cm-1; MS (EI) 345 (M); 1H NMR (250 MHz, CDCl3)
δ 3.69 (3H, s), 3.82 (3H, s), 6.74 (1H, d, J ) 15.0 Hz), 7.0 (3H,
m), 7.18 (1H, d, J ) 8.0 Hz), 7.3 (3H, m), 7.55 (1H, t, J ) 8.0
Hz), 7.6 (1H, d, J ) 8.0 Hz), 7.63 (1H, s), 7.7 (2H, d) ppm.
Meth yl (E)-2-{2-[(E,E)-4-(3-flu or oph en yl)bu ta-1,3-dien yl]-
p h en yl}-3-m eth oxya cr yla te (15e): MS (EI) 338 (M); 1H
NMR (250 MHz, CDCl3) δ 3.69 (3H, s), 3.82 (3H, s), 6.59 (1H,
d, J ) 15.0 Hz), 6.64 (1H, d, J ) 15.0 Hz), 6.9 (3H, m), 7.18
(3H, m), 7.22 (3H, s), 7.62 (1H, s), 7.66 (1H, d, J ) 8.0 Hz)
ppm.
Meth yl (E)-2-[4-(dim eth oxyph osph or ylm eth yl)ph en yl]-
3-m eth oxya cr yla te (4c) was obtained analogously to 4b: 1H
NMR (250 MHz, CDCl3) δ 3.15 (2H, d, J ) 21.0 Hz), 3.66 (3H,
s), 3.7 (3H, s), 3.73 (3H, s), 3.84 (3H, s), 7.28 (4H, m), 7.54
(1H, s) ppm.
Meth yl (E)-3-m eth oxy-2-{2-[(E,E)-4-(3-tr iflu or om eth -
ylp h en yl)bu ta -1,3-d ien yl]p h en yl}a cr yla te (15f): MS (EI)
1
388 (M); H NMR (250 MHz, CDCl3) δ 3.69 (3H, s), 3.82 (3H,
s), 6.67 (1H, d, J ) 15.0 Hz), 6.77 (1H, d, J ) 14.0 Hz), 6.93
(2H, m), 7.14 (1H, dd, J ) 2.0, 8.0 Hz), 7.28 (2H, m), 7.45 (2H,
d), 7.55 (1H, d), 7.63 (1H, s), 7.66 (2H, d) ppm.
(E)-3-(2-Ch lor o-4-flu or op h en yl)p r op en a l (14l). Sodium
methoxide (266 mg, 4.92 mmol) was added to a solution of (1,3-
dioxan-2-ylmethyl)tributylphosphonium bromide (5.7 mL, 1 M
in DMF, 5.7 mmol) and 2-chloro-4-fluorobenzaldehyde (600 mg,
3.78 mmol) in 10 mL of THF. The mixture was heated 6 h at
90 °C and poured into water. The phases were separated and
the aqueous phase was extracted with diethyl ether. The
combined organic phases were washed with brine and dried
over Na2SO4. The solvent was evaporated and the residue was
dissolved in THF (10 mL) and treated with 2 N HCl (10 mL).
After stirring for 45 min at room temperature, THF was
evaporated under reduced pressure, and the remaining aque-
ous solution was extracted with diethyl ether. The organic
phase was washed with brine and dried over Na2SO4. Evapo-
ration of the solvent and purification of the residue by column
chromatography (2:1 hexane ethyl acetate eluant) afforded 14l
(385 g, 55%) as colorless crystals: mp 83 °C; IR (KBr) 1689,
1598 cm-1; MS (EI) 180 (M); 1H NMR (250 MHz, CDCl3) δ 6.65
(1H, dd, J ) 7.5, 15.0 Hz), 7.07 (1H, td), 7.21 (1H, dd, J ) 3.0,
8.0 Hz), 7.66 (1H, dd, J ) 5.0, 7.5 Hz), 7.9 (1H, d, J ) 15 Hz),
9.75 (1H, d, J ) 7.5 Hz) ppm.
Gen er a l P r oced u r e for th e P r ep a r a tion of Com p ou n d s
of Typ e 15: Meth yl (E)-2-[2-(E,E)-[4-(2,4-Bis-tr iflu or o-
m et h ylp h en yl)b u t a -1,3-d ien yl]p h en yl]-3-m et h oxya cr y-
la te (15i). Sodium hydride (85% suspension in mineral oil,
90 mg, 3.18 mmol) was added to a cooled (0 °C) solution of 4a
(500 mg, 1.6 mmol) in THF (10 mL). The mixture was stirred
for 20 min at room temperature and treated with (E)-3-(2,4-
bis-trifluoromethylphenyl)propenal22 (426 mg, 1.6 mmol) in
THF (2 mL). The mixture was stirred for a further 30 min at
room temperature and heated under reflux for 2 h. The solvent
was evaporated and the residue taken up in ethyl acetate. The
solution was washed with brine and water and dried over Na2-
SO4. Evaporation of the solvent and purification of the residue
Meth yl (E)-2-{2-[(E,E)-4-(3-br om op h en yl)bu ta -1,3-d i-
en yl]p h en yl}-3-m eth oxya cr yla te (15g): MS (EI) 399 (M);
1H NMR (250 MHz, CDCl3) δ 3.69 (3H, s), 3.82 (3H, s), 6.55
(1H, d, J ) 15.0 Hz), 6.65 (1H, d, J ) 15.0 Hz), 6.8 (2H, m),
7.2 (6H, m), 7.57 (1H, s), 7.62 (1H, s), 7.66 (1H, d, J ) 8.0 Hz)
ppm.
Met h yl (E)-2-{2-[(E,E)-4-(4-ch lor op h en yl)b u t a -1,3-d i-
en yl]p h en yl}-3-m eth oxya cr yla te (15h ): MS (EI) 354 (M);
1H NMR (250 MHz, CDCl3) δ 3.69 (3H, s), 3.82 (3H, s), 6.62
(1H, d, J ) 15.0 Hz), 6.66 (1H, d, J ) 15.0 Hz), 6.85 (1H, d,
J ) 15.0 Hz), 6.9 (1H, d, J ) 15.0 Hz), 7.16 (1H, d, J ) 8.0
Hz), 7.3 (6H, m), 7.63 (1H, s), 7.67 (1H, d, J ) 8.0 Hz) ppm.
Meth yl (E)-2-[2-[(E,E)-4-(2,4-d ich lor op h en yl)bu ta -1,3-
d ien yl]p h en yl]-3-m eth oxya cr yla te (15j): mp 125-126 °C;
IR (KBr) 1702, 1627 cm-1; MS (EI) 348 (M); 1H NMR (250
MHz, CDCl3) δ 2.30 (3H, s), 2.35 (3H, s), 3.69 (3H, s), 3.81
(3H, s), 6.60 (1H, d, J ) 15.0 Hz), 6.8 (3H, m), 7.0 (2H, m),
7.13 (1H, d, J ) 8.0 Hz), 7.3 (2H, m), 7.46 (1H, d, J ) 8.0 Hz),
7.62 (1H, s), 7.7 (1H, d, J ) 8.0 Hz) ppm.
Meth yl (E)-2-[2-[(E,E)-4-(2,4-d im eth ylp h en yl)bu ta -1,3-
d ien yl]p h en yl]-3-m eth oxya cr yla te (15k ): mp 125-126 °C;
IR (KBr) 1702, 1627 cm-1; MS (EI) 348 (M); 1H NMR (250
MHz, CDCl3) δ 2.30 (3H, s), 2.35 (3H, s), 3.69 (3H, s), 3.81
(3H, s), 6.60 (1H, d, J ) 15.0 Hz), 6.8 (3H, m), 7.0 (2H, m),
7.13 (1H, d, J ) 8.0 Hz), 7.3 (2H, m), 7.46 (1H, d, J ) 8.0 Hz),
7.62 (1H, s), 7.7 (1H, d, J ) 8.0 Hz) ppm.
Meth yl (E)-2-[2-[(E,E)-4-(2-ch lor o-4-flu or op h en yl)bu ta -
1,3-d ien yl]p h en yl]-3-m eth oxya cr yla te (15l): mp 163-165
°C; IR (KBr) 1707, 1629 cm-1; MS (EI) 372 (M); 1H NMR (250
MHz, CDCl3) δ 3.69 (3H, s), 3.82 (3H, s), 6.63 (1H, d, J ) 15.0
Hz), 6.9 (4H, m), 7.1 (1H, dd, J ) 2.0, 8.0 Hz), 7.18 (1H, dd,

566 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4
Alzeer et al.
J ) 2.0, 8.0 Hz), 7.3 (2H, m), 7.6 (1H, dd, J ) 6.0, 8.0 Hz),
7.63 (1H, s), 7.8 (1H, d, J ) 8.0 Hz) ppm.
Meth yl (Z)-Meth oxyim in o-[2(E a n d Z)-(2-tr ibu tylsta n -
n a n ylvin yl)p h en yl]a ceta te (1:1) (24). Tributyltin hydride
(0.56 mL, 2.1 mmol) was added to a solution of 23 (151 mg,
0.7 mmol) and a catalytic amount of 2,2′-azobis(isobutyroni-
trile) in toluene (0.5 mL). The mixture was stirred 3.5 h at 80
°C, the solvent was evaporated under reduced pressure, and
the residue was purified by column chromatography (9:1
hexane/ethyl acetate eluant) and afforded 24 (155 mg, 44%)
as a yellowish liquid: IR (neat) 1731, 1600 cm-1; MS (CI) 525
(M + NH4)+, 508 (M); 1H NMR (250 MHz, CDCl3) δ 0.84 (30H,
m), 1.3 (12H, m), 1.54 (12H, m), 3.81 (3H, s), 3.84 (3H, s), 4.0
(3H, s), 4.03 (3H, s), 6.2 (1H, d, J ) 14.0 Hz), 6.7 (1H, d, J )
19.0 Hz), 6.8 (1H, d, J ) 19 Hz), 7.15 (3H, m), 7.33 (5H, m),
7.6 (1H, d) ppm.
Meth yl (E)-3-m eth oxy-2-[2-[(E,E)-4-(3-m eth oxy-2-n itr o-
p h en yl)bu ta -1,3-d ien yl]p h en yl]a cr yla te (15m ): mp 65-66
°C; IR (KBr) 1707, 1632 cm-1; MS (EI) 395 (M); 1H NMR (250
MHz, CDCl3) δ 3.68 (3H, s), 3.82 (3H, s), 3.89 (3H, s), 6.47(1H,
d, J ) 15.0 Hz), 6.7 (1H, d, J ) 15.0 Hz), 6.81 (1H, d,
J ) 15.0 Hz), 6.9 (1H, d, J ) 15.0 Hz), 6.91 (1H, d), 7.07 (1H,
d, J ) 8.0 Hz), 7.3 (4H, m), 7.62 (1H, s), 7.64 (1H, d, J ) 8.0
Hz) ppm.
Meth yl (E)-2-{3-(E,E)-{[4-(2,4-bistr iflu or om eth ylp h en -
yl)bu ta -1,3-d ien yl]p h en yl}-3-m eth oxya cr yla te (15n ): mp
1
130 °C; IR (KBr) 1703, 1629 cm-1; MS (EI) 456 (M); H NMR
(250 MHz, CDCl3) δ 3.7 (3H, s), 3.83 (3H, s), 6.71 (1H, d, J )
15.0 Hz), 6.75 (1H, d, J ) 15.0 Hz), 6.9 (1H, d, J ) 15.0 Hz),
6.93 (1H, d, J ) 15.0 Hz), 7.09 (1H, d, J ) 8.0 Hz), 7.3 (2H,
m), 7.64 (1H, s), 7.7 (1H, d, J ) 8.0 Hz), 7.74 (1H, s), 7.83 (2H,
s) ppm.
Meth yl (Z)-Meth oxyim in o-[2-(1-tr ibu tylsta n n a n ylvi-
n yl)p h en yl]a ceta te (25). Tributyltin hydride (0.16 mL, 0.46
mmol) was added to a solution of tetrakis(triphenylphosphine)-
palladium (27 mg, 0.023 mmol) and 23 (100 mg, 0.46 mmol)
in THF (2 mL). The mixture was stirred 20 min at room
temperature, diluted with ethyl acetate, washed with brine,
and dried over Na2SO4. Evaporation of the solvent and
purification of the residue by column chromatography (9:1
hexane/ethyl acetate eluant) afforded 25 (200 mg, 85%) as a
Meth yl (E)-2-{4-(E,E)-[4-(2,4-bistr iflu or om eth ylph en yl)-
bu ta-1,3-dien yl]ph en yl}-3-m eth oxyacr ylate (15o): IR (neat)
1706, 1627 cm-1; MS (EI) 456 (M); 1H NMR (250 MHz, CDCl3)
δ 3.75 (3H, s), 3.88 (3H, s), 6.82 (1H, d, J ) 15.0 Hz), 6.95
(3H, m), 7.34 (2H, d), 7.45 (2H, d), 7.57 (1H, s), 7.76 (1H, d,
J ) 8.0 Hz), 7.83 (1H, d, J ) 8.0 Hz), 7.88 (1H, s) ppm.
Meth yl (E)-3-Meth oxy-2-[2-[4-(2-tr iflu or om eth ylp h en -
yl)bu tyl]p h en yl]a cr yla te (16). 15a (100 mg, 0.25 mmol) in
CH2CL2 was hydrogenated over Pd/C at room temperature and
pressure. Filtration of the catalyst and evaporation of the
solvent afforded 16 (100 mg, 99%) as a colorless oil: IR (neat)
1710, 1635 cm-1; MS (EI) 392 (M); 1H NMR (250 MHz, CDCl3)
δ 1.62 (4H, m), 2.5 (2H, m), 2.79 (2H, m), 3.65 (3H, s), 3.75
(3H, s), 7.1 (1H, d), 7.25 (5H, m), 7.4 (1H, d), 7.54 (1H, s), 7.6
(1H, d) ppm.
Meth yl (E)-3-Meth oxy-2-[2-[(E)-2-[5-(2-tr iflu or om eth -
ylp h en yl)fu r a n -2-yl]vin yl]p h en yl]a cr yla te (18). Sodium
hydride (85% suspension in mineral oil, 60 mg, 2.1 mmol) was
added to a cooled (0 °C) solution of 4a (250 mg, 0.79 mmol) in
THF (5 mL). The mixture was stirred 30 min at room
temperature and cooled to 0 °C before the addition of 17 (191
mg, 0.79 mmol). The mixture was maintained 18 h at 4 °C.
The reaction mixture was warmed to room temperature,
treated with acetic acid (1 mL), and diluted with ethyl acetate.
The organic phase was washed with brine and dried over Na2-
SO4. Evaporation of the solvent and purification of the residue
by column chromatography (1:9 hexane/CH2Cl2 eluant) af-
forded 18 (184 mg, 54%) as a yellow oil: IR (neat) 1708, 1632
cm-1; MS (EI) 428 (M); 1H NMR (250 MHz, CDCl3) δ 3.97 (3H,
s), 3.81 (3H, s), 6.42 (1H, d), 6.7 (1H, d), 6.88 (1H, J ) 16.0
Hz), 7.17 (1H, d), 7.3 (4H, m), 7.6 (1H, t), 7.64 (1H, s), 7.78
(3H, m) ppm.
1
colorless oil: IR (neat) 1730, 1602 cm-1; MS (EI) 508 (M); H
NMR (250 MHz, CDCl3) δ 0.87 (15H, m), 1.3 (6H, m), 1.54 (6H,
m), 3.80 (3H, s), 4.02 (3H, s), 5.4 (1H, d, J ) 2.5 Hz), 5.7 (1H,
d, J ) 2.5 Hz), 7.0 (1H, d), 7.2 (2H, m), 7.32 (1H, d) ppm.
Meth yl (Z)-Meth oxyim in o-{2-[(E,E)-4-(2-tr iflu or om eth -
ylp h en yl)bu ta -1,3-d ien yl]p h en yl}a ceta te (26). Tetrakis-
(triphenylphosphine)palladium (21 mg, 0.02 mmol) was added
to a solution of 20 (151 mg, 0.6 mmol) and 24 (304 mg, 0.6
mmol) in toluene (5 mL). The mixture was heated 5 h at 110
°C, cooled to room temperature, diluted with toluene, washed
with brine, and dried over Na2SO4. Evaporation of the solvent
and purification of the residue by column chromatography (3:2
hexane/ethyl acetate eluant) afforded 26 (48 mg, 21%) as a
brown oil: IR (neat) 1734, 1610 cm-1; MS (EI) 389 (M); 1H
NMR (250 MHz, CDCl3) δ 3.87 (3H, s), 4.06 (3H, s), 6.5 (1H,
d, J ) 15.0 Hz), 6.9 (1H, d, J ) 15.0 Hz), 7.0 (2H, m), 7.16
(1H, d, J ) 8.0 Hz), 7.4 (4H, m), 7.71 (1H, d, J ) 8.0 Hz), 7.72
(2H, d) ppm.
Meth yl (Z)-Meth oxyim in o-{2-[(E)-4-(2-tr iflu or om eth -
ylp h en yl)bu t-3-en -1-yn yl]p h en yl}a ceta te (27). Triethyl-
amine (0.22 mL, 1.6 mmol), copper(I) chloride (3 mg, 0.015
mmol), and tris(dibenzylideneacetone)dipalladium chloroform
(18 mg, 0.018 mmol) were added to a solution of 23 (129 mg,
0.59 mmol) and 20 (179 mg, 0.71 mmol) in toluene (2 mL).
After stirring 4 h at 110 °C, the mixture was cooled to room
temperature and treated with NH4Cl solution (4 mL) for 10
min. The phases were separated and the aqueous phase was
extracted with toluene. The combined organic phases were
washed with brine and dried over Na2SO4. Evaporation of the
solvent and purification of the residue by column chromatog-
raphy (7:3 hexane/ethyl acetate eluant) afforded 27 (28 mg,
12%) as orange crystals: mp 104-107 °C; IR (KBr) 2220, 1744,
1601 cm-1; MS (EI) 387 (M); 1H NMR (250 MHz, CDCl3) δ 3.88
(3H, s), 4.04 (3H, s), 6.38 (1H, d, J ) 15.0 Hz), 7.4 (5H, m), 7.6
(2H, m), 7.69 (2H, d) ppm.
1-(2,2-Dibr om ovin yl)-2-(tr iflu or om eth yl)ben zen e (19).
A solution of carbon tetrabromide (10.8 g, 32 mmol) in CH2-
Cl2 (10 mL) was added dropwise to a stirred, cooled (-10 °C)
solution of triphenylphosphine (16.5 g, 64 mmol) in CH2Cl2
(40 mL). The resulting orange suspension was stirred 15 min
at -10 °C. A solution of 2-(trifluoromethyl)benzaldehyde (2.83
g, 16 mmol) in CH2Cl2 (10 mL) was added. The resulting brown
solution was stirred for 30 min at -10 °C. Triethylamine (3
mL) and a solution of Na2CO3 (2 mL) were added dropwise.
The mixture was diluted with diethyl ether (100 mL) and
filtered through a short pad of silica gel (eluted with hexane).
Evaporation of the solvent afforded 19 (5.29 g, 98%) as a
1-(Br om oeth yn yl)-2-(tr iflu or om eth yl)ben zen e (28). 1,8-
Diazabicyclo[5.4.0]undec-7-ene (1.83 mL, 12.3 mmol) was
added dropwise to a stirred solution of 19 (2 g, 6.15 mmol) in
DMSO (5 mL). The reaction mixture was stirred 45 min at 15
°C, cooled to 0 °C, and treated with 1 N HCl. The mixture was
diluted with diethyl ether, the phases were separated, and the
organic layer was washed with brine and water and dried over
Na2SO4. Evaporation of the solvent and purification of the
residue by column chromatography (7:1 hexane/ethyl acetate
eluant) afforded 28 (1.364 g, 90%) as a colorless oil: IR (neat)
2210, 1319 cm-1; MS (EI) 249 (M); 1H NMR (250 MHz, CDCl3)
δ 7.45 (2H, m), 7.6 (2H, m) ppm.
1
colorless oil: IR (neat) 1316, 1170 cm-1; MS (EI) 330 (M); H
NMR (250 MHz, CDCl3) δ 7.46 (1H, m), 7.6 (4H, m) ppm.
1-(2-Br om ovin yl)-2-(tr iflu or om eth yl)ben zen e (20). A
solution of 19 (989 mg, 3 mmol) and diethyl phosphite (0.75
mL, 6 mmol) in triethylamine (0.83 mL, 6 mmol) was stirred
4 h at 5 °C. The mixture was diluted with hexane, washed
with brine, and dried over Na2SO4. Evaporation of the solvent
and purification of the residue by column chromatography
(hexane) afforded 20 (674 mg, 90%) as a colorless liquid: IR
Meth yl (2-Eth yn ylp h en yl)oxoa ceta te (29). A solution of
21 (400 mg, 1.5 mmol) in THF (2 mL) was added dropwise to
a cooled (0 °C) solution of tetrabutylammonium fluoride (146
mg, 0.46 mmol) in THF (5 mL). After 5 min NH4Cl (5 mL)
1
(neat) 1600, 940 cm-1; MS (EI) 251 (M); H NMR (250 MHz,
CDCl3) δ 6.78 (1H, d, J ) 14.0 Hz), 7.4 (3H, m), 7.63 (2H, m)
ppm.

Phenyl â-Methoxyacrylates
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4 567
solution was added and the mixture stirred for 10 min at room
temperature. The mixture was diluted with ethyl acetate, the
phases were separated, and the organic layer was washed with
NH4Cl solution and water and dried over Na2SO4. Evaporation
of the solvent afforded 29 (263 mg, 91%) as an orange oil: IR
(neat) 3274, 2130, 1741, 1983 cm-1; MS (EI) 188 (M); 1H NMR
(250 MHz, CDCl3) δ 3.42 (1H, s), 3.93 (3H, s), 7.6 (3H, m),
7.85 (1H, d) ppm.
Meth yl (Z a n d E)-(2-Eth yn ylp h en yl)-m eth oxyim in oa c-
eta te (23 a n d 30). Methoxylamine hydrochloride (1.63 g, 18.3
mmol) and anhydrous sodium acetate (1.54 g, 18.3 mmol) were
added to a solution of 29 (431 mg, 2.3 mmol) in MeOH (10
mL) and water (1 mL). After stirring 4 h at room temperature
the solvent was evaporated under reduced pressure. The
residue was dissolved in ethyl acetate; the organic phase was
washed with brine and water and dried over Na2SO4. Evapo-
ration of the solvent and separation of the mixture by column
chromatography (7:3 hexane/ethyl acetate eluant) afforded 23-
(Z) (366 mg, 74%) and 30-(E) (50 mg, 10%). Data for 30: IR
(neat) 3281, 2120, 1740 cm-1; MS (EI) 217 (M); 1H NMR (250
MHz, CDCl3) δ 3.27 (1H, s), 3.85 (3H, s), 4.06 (3H, s), 7.4 (2H,
m), 7.5 (1H, d), 7.62 (1H, d) ppm.
mL hypoxanthine, and titrated in duplicates over a 64-fold
range. After addition of the parasite cultures with an initial
parasitemia of 0.75% in a 2.5% erythrocyte suspension, the
test plates were incubated under the conditions described
above in humidified modular chambers. Growth of the para-
sites was measured by the incorporation of radiolabeled [3H]-
hypoxanthine added 16 h prior to the termination of the test.
Fifty percent inhibitory concentrations (IC50) were estimated
by linear interpolation.27
The compounds were tested in vitro against the chloroquine-
resistant strain K1 (Thailand) and the sensitive strain NF54
(airport strain of unknown origin).
In vivo a n tim a la r ia l a ctivity on P . ber gh ei: The com-
pounds were tested in vivo as described earlier.28 Male albino
mice (IBM:MORO(SPF); Fullinsdorf), weighing 25 ( 2 g, were
infected intravenously with 2 × 107 P. berghei (strain ANKA)
infected erythrocytes from a donor mouse on day 0 of the
experiment. The compounds to be tested were solubilized (or
suspended) in 7% Tween-80, 3% ethanol in H2O, to the desired
concentration and injected sc or given po to different groups
of mice (0.01 mL/g-mouse, 3 mice/group). The mice were
treated at day 1 (24 h after the infection). At day 3 (48 h after
the treatment), bloodsmears of all the animals were prepared
and stained with Giemsa. The degree of infection (parasitemia
expressed in % infected erythrocytes) was determined micro-
scopically. The difference of the mean infection rate of the
control group ()100%) to the test group was calculated and
expressed as percent reduction. The ED50/90 was calculated by
nonlinear fitting with the J MP statistical program (Statistical
Analysis Institute, Cary, NC).
Met h yl (Z)-m et h oxyim in o-{2-[4-(2-t r iflu or om et h yl-
p h en yl)bu ta -1,3-d iyn yl]p h en yl}a ceta te (31): prepared ac-
cording to the method described for 27; mp 72-74 °C; IR (KBr)
1
2210, 1738, 1602 cm-1; MS (EI) 385 (M); H NMR (250 MHz,
CDCl3) δ 3.91 (3H, s), 4.1 (3H, s), 7.3 (1H, d), 7.4 (4H, m), 7.65
(3H, m) ppm.
Met h yl (E)-m et h oxyim in o-{2-[4-(2-t r iflu or om et h yl-
p h en yl)bu ta -1,3-d iyn yl]p h en yl}a ceta te (32): prepared ac-
cording to the method described for 27; IR (neat) 1741, 1603
cm-1; MS (EI) 385 (M); 1H NMR (250 MHz, CDCl3) δ 3.96 (3H,
s), 4.08 (3H, s), 7.4 (21H, m), 7.5 (2H, m), 7.7 (4H, m) ppm.
Met h yl (Z)-Met h oxyim in o-{2-[5-(2-t r iflu or om et h yl-
p h en yl)th iop h en e-2-yl]p h en yl}a ceta te (33). Sodium sul-
fide nonahydrate (195 mg, 0.8 mmol) was added to a solution
of 31 (63 mg, 0.16 mmol) in 2-methoxyethanol (1.5 mL). The
mixture was heated 1 h at reflux, the solvent was removed
under reduced pressure, and MeOH (2 mL) and H2SO4 (0.1
mL) were added. The mixture was heated 20 min at reflux
and cooled to room temperature and the solvent evaporated.
The residue was diluted with ethyl acetate, washed with K2-
CO3 solution and brine, and dried over Na2SO4. The solvent
was removed under reduced pressure, the residue was dis-
solved in CH2Cl2, and charcoal (0.5 g) was added. The mixture
was stirred 1 h at room temperature and filtered through a
pad of Celite. Evaporation of the solvent and purification of
the residue by column chromatography (7:1 hexane/ethyl
acetate eluant) afforded 33 (30 mg, 44%) as a brown oil: IR
(neat) 1730, 1603 cm-1; MS (EI) 419 (M); 1H NMR (250 MHz,
CDCl3) δ 3.73 (3H, s), 4.03 (3H, s), 6.93 (1H, d, J ) 2.5 Hz),
7.0 (1H, d, J ) 2.5 Hz), 7.31-7.59 (7H, m), 7.75 (1H, d, J )
7.5 Hz) ppm.
Ack n ow led gm en t. We thank Dr. S. Trah for pro-
viding us with compounds 13 and 15a -c,e-h and Mr.
Ph. Cueni for supplying us with intermediates 3a and
4a . We also thank N. Benedetti, D. Zulauf, and A.
Soederberg for excellent technical assistance and Dr. W.
Arnold, Mr. W. Meister, and A. Bubendorf for spectral
data.
Refer en ces
(1) Barat, L. M.; Bloland, P. B. Drug resistance among malaria and
other parasites. Infect. Dis. Clin. North Am. 1997, 11, 969-987.
(2) Lobel, H. O.; Kozarsky, P. E. Update on prevention of malaria
for travelers. J . Am. Med. Assoc. 1997, 278, 1767-1771.
(3) Warhurst, D. C. Drug-resistant malaria: laboratory and field
investigations. J . Pharm. Pharmacol. 1997, 49, 3-7.
(4) White, N. J . Antimalarial drug resistance. The pace quickens.
J . Antimicrob. Agents Chemother. 1992, 30, 571-585.
(5) Hudson, A. T. Atovaquone - a novel broad-spectrum anti-
infective drug. Parasitol. Today 1993, 9, 66-68.
(6) Looarccsuwan, S.; Viravan, C.; Webster, H. K.; Kyle, D. E.;
Hutchinson, D. B.; Canfield, C. J . Clinical studies of atovaquone,
alone or in combination with other antimalarial drugs, for
treatment of acute uncomplicated malaria in Thailand. Am. J .
Trop. Med. Hyg. 1996, 54, 62-66.
Meth yl (Z)-m eth oxyim in o-{2-[4-(2-tr iflu or om eth ylph en -
yl)bu tyl]p h en yl}a ceta te (34): prepared according to the
method described for 16; IR (neat) 1729, 1607 cm-1; MS (EI)
(7) Fry, M.; Pudney, M. Site of action of the antimalarial hydroxy-
naphthoquinone, 2-[trans-4-(4′-chlorophenyl)cyclohexyl]-3-hydroxy-
1,4-naphthoquinone (566C80). Biochem. Pharmacol. 1992, 43,
1545-1553.
1
362 (M - MeO); H NMR (250 MHz, CDCl3) δ 1.55 (4H, m),
2.5 (2H, t), 2.8 (2H, m), 3.83 (3H, s), 3.99 (3H, s), 7.1 (1H, d),
7.3 (5H, m), 7.4 (1H, t), 7.6 (1H, d) ppm.
(8) Srivastava, I. K.; Rottenberg, H.; Vaidya, A. B. Atovaquone, a
broad spectrum antiparasitic drug, collapses mitochondrial
membrane potential in a malarial parasite. J . Biol. Chem. 1997,
272, 3961-3966.
In Vitr o Mea su r em en t of P . fa lcipa r u m P a r a site
Gr ow th In h ibition . P . fa lcipa r u m con tin u ou s cu ltu r es:
Asynchronous stock cultures were maintained in suspension
cultures.23 The culture medium was a variation24 of that
described by Trager and J ensen.25 It consisted of RPMI 1640
supplemented with 0.5% AlbuMAX (Gibco BRL), 25 mM
HEPES, 25 mM NaHCO3 (pH 7.3), 50 µg/mL hypoxanthine,
and 50 µg/mL neomycin. Human type A+ erythrocytes served
as host cells. The cultures were kept at 37 °C in an atmosphere
of 3% O2, 4% CO2, and 93% N2 ppm.
P a r a site gr ow th in h ibition in vitr o: Drug testing was
carried out essentially as described by Desjardins et al.26 in
96-well microtiter plates. The compounds were dissolved by
sonication in DMSO (5 mg/mL), prediluted in the culture
medium described above but containing an additional 0.5 µg/
(9) Gutteridge, W. E.; Dave, D.; Richards, W. H. G. Conversion of
dihydroorotate to orotate in parasitic protozoa. Biochim. Biophys.
Acta 1979, 582, 390-401.
(10) Ittarat, I. A. W.; Meshnick, S. R. The effects of antimalarials on
the Plasmodium falciparum dihydroorotate dehydrogenase. Exp.
Parasitol. 1994, 79, 50-56.
(11) Clough, J . M. The strobilurins, oudemansins and myxothiazols,
fungicidal derivatives of â-methoxyacrylic acid. Nat. Prod. Rep.
1993, 565-574.
(12) Thierbach, G.; Reichenbach, H. Myxothiazol, a new inhibitor of
the cytochrome b-c1 segment of the respiratory chain. Biochim.
Biophys. Acta. 1981, 638, 282-289.
(13) Brandt, U.; Haase, U.; Scha¨gger, H.; von J agow, G. Significance
of the “Rieske” iron-sulphur protein for formation and function
of the ubiquinol-oxidation pocket of mitochondrial cytochrome c
reductase (bc1 complex). J . Biol. Chem. 1991, 266, 19958-19964.

568 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 4
Alzeer et al.
(14) Xia, D.; Yu, C.-A.; Kim, H., et al. Crystal structure of the
cytochrome bc1 complex from bovine heart mitochondria. Science
1997, 277, 60-66.
(22) Blackburn, C.; Childs, R.; Cremer, D.; Gauss, J . Stereomutation
of Methoxycarbenium ions. J . Am. Chem. Soc. 1985, 107, 2442-
2448.
(23) Ponnudurai, T.; Lensen, A.; Meis, J .; Meuwissen, J . Synchroni-
zation of Plasmodium falciparum gametocytes using an auto-
mated suspension culture system. Parasitol. Oct. 1986, 93, 263-
274.
(24) Dorn, A.; Stoffel, R.; Matile, H.; Bubendorf, A.; Ridley, R. G.
Malarial haemozoin/beta-haematin supports haem polymeriza-
tion in the absence of protein. Nature 1995, 374, 269-371.
(25) Trager, W.; J ensen, J . B. Human malaria parasites in continuous
culture. Science 1976, 193, 673-675.
(26) Desjardin, R. E.; Canfield, C. J .; Haynes, D.; Chulay, J . D.
Quantitative assessment of antimalarial activity in vitro by a
semiautomated microdilution technique. Antimicrob. Agents
Chemother. 1979, 16, 710-718.
(27) Huber, W.; Koella, J . C. A comparison of three methods of
estimating EC50 in studies of drug resistance of malaria
parasites. Acta Tropica 1993, 55, 257-261.
(28) Ridley, R. G.; Matile, H.; J aquet, C.; Dorn, A.; Hofheinz, W.;
Leupin, W.; Masciadri, R.; Theil, F.-P.; Richter, W. F.; Girometta,
M.-A.; Guenzi, A.; Urwyler, H.; Gocke, E.; Potthast, J .-M.; Csato,
M.; Thomas, A.; Peters, W. Antimalarial activity of the bisquino-
line trans-N1,N2-bis-(7-chloroquinolin-4-yl)-cyclohexane-1,2-di-
amine: comparison of two stereoisomers and detailed evaluation
of the S,S enantiomer, Ro 47-7737. Antimicrob. Agents Chemo-
ther. 1997, 41, 677-686.
(15) Ridley, R. G.; Hofheinz, W.; Matile, H.; J aquet, C.; Dorn, A.;
Masciadri, R.; J olidon, S.; Richter, W. F.; Guenzi, A. 4-Amino-
quinoline analogues of chloroquine with shortened side chains
retain activity against chloroquine-resistant P. falciparum.
Antimicrob. Agents Chemother. 1996, 40, 1846-1854.
(16) Clough, J .; Godfrey, C. R. A.; De Fraine, P. J .; Hutchings, M.
G.; Anthony, V. M. Methyl 3-methoxy-2-phenylpropenoate de-
rivatives useful as plant fungicides and plant growth regulators,
their fungicidal compositions, and processes and intermediates
for their preparation. Eur. Pat. Appl. EP 278595.
(17) Brayer, J .; Cadiergue, J .; Mourioux, G.; Tessier, J . Preparation
of 2-thiazolyl-3-alkoxyacrylates and analogues as agricultural
fungicides. Eur. Pat. Appl. EP 402246.
(18) Spangler, C.; McCoy, R. Preparation of conjugated aromatic
polyenals by Wittig oxopropenylation. Synth. Commun. 1988,
18, 51-59.
(19) Hiroa, T.; Masunaga, T.; Ohshiro, Y.; Agawa, T. Reduction of
gem-dibromides with diethylphosphite. J . Org. Chem. 1981, 46,
3745-3747.
(20) Wingert, H.; Hellendahl, B.; Kirstgen, R.; Sauter, H.; Ammer-
mann, E.; Lorenz, G. Acetylenic derivatives and their use as
plant-protective agents. Eur. Pat. Appl. EP 582925.
(21) Ratovelomanana, V.; Rollin, Y.; Gebehenne, C.; Gosmini, C.;
Perichon, J . DBU/DMSO Promoted dehydrobromination of 1,1-
dibromoolefins. A general synthesis of 1-bromoaromatic alkynes
under mild conditions. Tetrahedron Lett. 1994, 35, 4777-4780.
J M990002Y