Design and synthesis of aryloxyethyl thiocyanate derivatives as potent inhibitors of Trypanosoma cruzi proliferation

Article abstract of DOI:10.1021/jm9905007

As a part of our project directed at the search of new chemotherapeutic agents against American trypanosomiasis (Chagas' disease), several drugs possessing the 4-phenoxyphenoxy skeleton and other closely related structures employing the thiocyanate moiety as polar end group were designed, synthesized, and evaluated as antiproliferative agents against Trypanosoma cruzi, the parasite responsible for this disease. These thiocyanate analogues were envisioned bearing in mind the potent activity shown by 4- phenoxyphenoxyethyl thiocyanate (compound 8) taken as lead drug. This compound had previously proved to be an extremely active growth inhibitor against T. cruzi with IC₅₀ values ranging from the very low micromolar level in epimastigotes to the low nanomolar level in the intracellular form of the parasite. Of the designed compounds, the ethyl thiocyanate drugs connected to nonpolar skeletons, namely, arylthio, 2,4-dichlorophenoxy, ortho-substituted aryloxy, and 2-methyl-4-phenoxyphenoxy (compounds 15, 34, 47, 52, 72, respectively), were shown to be very potent antireplicative agents against T. cruzi. On the other hand, conformationally restricted analogues as well as branched derivatives at the aliphatic side chain were shown to be moderately active against T. cruzi growth. The biological activity of drugs bearing the thiocyanate group correlated quite well with the activity exhibited by their normal precursors, the tetrahydropyranyl ether derivatives, when bonded to the same nonpolar skeleton. Compounds having the tetrahydropyranyl moiety as polar end were proportionally much less active than sulfur-containing derivatives in all cases. Drugs 47 and 72 also resulted to be very active against the amastigote form of the parasite growing in myoblasts; however, they were slightly less active than the lead drug 8. On the other hand, compounds 34 and 52 were almost devoid of activity against myoblasts. Surprisingly, the dithio derivative 15 was toxic for myoblasts.

Full text of DOI:10.1021/jm9905007

1826
J . Med. Chem. 2000, 43, 1826-1840
Design a n d Syn th esis of Ar yloxyeth yl Th iocya n a te Der iva tives a s P oten t
In h ibitor s of Tr ypa n osom a cr u zi P r olifer a tion
Sergio H. Szajnman,‡ Wen Yan,† Brian N. Bailey,† Roberto Docampo,† Eleonora Elhalem,‡ and
J uan B. Rodriguez*,‡
Departamento de Quı´mica Orga´nica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires,
Pabello´n 2, Ciudad Universitaria, RA-1428 Buenos Aires, Argentina, and Laboratory of Molecular Parasitology,
Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign,
2001 South Lincoln Avenue, Urbana, Illinois 61802
Received October 4, 1999
As a part of our project directed at the search of new chemotherapeutic agents against American
trypanosomiasis (Chagas’ disease), several drugs possessing the 4-phenoxyphenoxy skeleton
and other closely related structures employing the thiocyanate moiety as polar end group were
designed, synthesized, and evaluated as antiproliferative agents against Trypanosoma cruzi,
the parasite responsible for this disease. These thiocyanate analogues were envisioned bearing
in mind the potent activity shown by 4-phenoxyphenoxyethyl thiocyanate (compound 8) taken
as lead drug. This compound had previously proved to be an extremely active growth inhibitor
against T. cruzi with IC50 values ranging from the very low micromolar level in epimastigotes
to the low nanomolar level in the intracellular form of the parasite. Of the designed compounds,
the ethyl thiocyanate drugs connected to nonpolar skeletons, namely, arylthio, 2,4-dichlorophe-
noxy, ortho-substituted aryloxy, and 2-methyl-4-phenoxyphenoxy (compounds 15, 34, 47, 52,
72, respectively), were shown to be very potent antireplicative agents against T. cruzi. On the
other hand, conformationally restricted analogues as well as branched derivatives at the
aliphatic side chain were shown to be moderately active against T. cruzi growth. The biological
activity of drugs bearing the thiocyanate group correlated quite well with the activity exhibited
by their normal precursors, the tetrahydropyranyl ether derivatives, when bonded to the same
nonpolar skeleton. Compounds having the tetrahydropyranyl moeity as polar end were
proportionally much less active than sulfur-containing derivatives in all cases. Drugs 47 and
72 also resulted to be very active against the amastigote form of the parasite growing in
myoblasts; however, they were slightly less active than the lead drug 8. On the other hand,
compounds 34 and 52 were almost devoid of activity against myoblasts. Surprisingly, the dithio
derivative 15 was toxic for myoblasts.
In tr od u ction
highly infective metacyclic trypomastigotes that invade
mammalian tissues via wounds provoked by blood-
sucking action. The parasite proliferates intracellularly
as the amastigote, the clinically more important form
of the parasite, which is released as the nondividing
bloodstream trypomastigote forms that invade other
tissues.3,4
American trypanosomiasis (Chagas’ disease), caused
by the kinetoplastid protozoon Trypanosoma cruzi, is
considered by the Word Health Organization to be one
of the important tropical parasitic diseases worldwide
together with malaria and schistosomiasis. This major
health problem afflicts 16-18 million persons in Latin
America, who are infected with T. cruzi.1 At the present
time, it was calculated that around of 2-3 million people
present the typical symptoms that characterize the
chronic stage of American trypanosomiasis producing
45 000 deaths yearly.2 This illness is transmitted in
rural areas to humans and other mammals by Reduviid
bugs, for instance Rhodnius prolixus and Triatoma
infestans,3,4 as a consequence of the blood-sucking
activity of Chagas’ disease vectors on mammals when
feeding in a cyclic process. The parasite occurs in three
main morphological forms in a complex life cycle. It
multiplies within the crop and midgut of Chagas’
disease vectors as the epimastigote form, and it is
released with the insect excrements as the nondividing
In the past few years a tremendous impetus in the
study of T. cruzi biochemistry and physiology has been
observed.5 As a result of these studies, several crucial
enzymes for parasite survival and not present in the
host have been identified as potential targets for the
design of new drugs.6-11 However, the existing chemo-
therapy to control this parasitic infection is based on
old and quite unspecific drugs associated with long-term
treatments and severe side effects. Certainly, the only
two drugs currently in use for clinical treatment of this
disease, nifurtimox (4-([5-nitrofurfurylidene]amino)-3-
methylthiomorpholine 1,1-dioxide) and benznidazole (N-
benzyl-2-nitro-1-imidazoleacetamide), are able to cause
negativization of parasitemia and serology in most of
the cases.12,13 However, they are not specific enough to
all T. cruzi strains to warrant complete cure and hence
the divergence of efficacy observed for both drugs in
different endemic areas.14-17 Due to the chemotherapy
* To whom correspondence should be addressed. Phone: (54 11)
4-576-3385. Fax: (54 11) 4-576-3346. E-mail: J BR@qo.fcen.uba.ar.
‡ Universidad de Buenos Aires.
† University of Illinois at Urbana-Champaign.
10.1021/jm9905007 CCC: $19.00 © 2000 American Chemical Society
Published on Web 04/14/2000

Aryloxyethyl Thiocyanates as Inhibitors of T. cruzi
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9 1827
Ch a r t 1. Current Drugs for Treatment of Chagas’
Disease and Blood Sterilization
Ch a r t 2. Chemical Structures of Three Well-Known
Sterol Biosynthesis Inhibitors That Are Effective
Against T. cruzi
drawbacks, there is significant interest in developing
novel chemotherapeutic approaches against Chagas’
disease based on unique aspects of T. cruzi structure
and metabolism. Moreover, the chronic stage of this
disease leads to irreversible cardiac and digestive
disorders and is the leading cause of heart disease in
Latin America with close to 90 million people at risk.
Many chagasic patients die from heart failure associated
with cardiomyopathy during the chronic phase of the
disease, while in the acute phase myocarditis occurs in
near 60% of patients with an estimated 9% of mortality
occurring in endemic areas.18 In addition, the main way
of transmission in large urban centers takes place by
transfusion of infected blood or through the placenta.
This kind of mechanism is responsible for the occurrence
of Chagas’ disease in countries where this illness is not
endemic. In the past few years, this illness has been
encountered, in the United States, as a consequence of
transfusion of contaminated blood from immigrants.19-21
For that reason, it is very important to have an efficient
agent to eradicate the bloodstream trypomastigotes from
blood banks. Crystal violet (N-{4-bis[[4-(dimethylami-
no)phenyl]methylene]-2,5-cyclohexadien-1-ylidene}-N-
methylmethanaminium chloride), the only drug em-
ployed for blood sterilization and discovered for that
purpose some decades ago,22 cannot be considered as
an ideal drug. In fact, this agent suffers from some
disadvantages, since it was shown to be carcinogenic
in in vivo assays23 (Chart 1).
The above summary emphasizes the urgent need of
new chemotherapeutic and chemoprophylactic agents
that are specific and effective against all strains of the
parasite with less or no toxicity than that produced by
the drugs currently in use for clinical therapy.
Ergosterol biosynthesis proved to be an interesting
target for the design of new drugs not only for fungi but
also for different pathogenic parasites.24 Sterol biosyn-
thesis in parasites differs essentially compared with the
mammalian host due to the final product in the latter
biosynthetic pathway leads to cholesterol.24 Depletion
of endogenous sterols produces inhibition of growth of
the parasite; therefore, selective inhibition of a crucial
enzyme responsible of sterol biosynthesis of the parasite
will slow T. cruzi growth. The blockage of this metabolic
pathway has been extensively studied, and even some
drugs resulted to be potential chemotherapeutic agents
such as the bis triazole derivatives D0870 and SCH
56592 (compounds 4 and 5, respectively) and the triazole
derivative 6, ketoconazole (Chart 2).25-29
We have reported that several compounds structur-
ally related to the well-known insect growth regulator
fenoxycarb30 (N-{2-[(4-phenoxyphenoxy)ethyl]}ethyl car-
bamate) are very active trypanostatic agents. In fact,
slight modifications on the fenoxycab side chain give
drugs 7 and 8 and other closely related compounds,
which are shown to be potent inhibitors against T. cruzi
growth.31-35 The molecule of fenoxycarb had been taken
as lead structure on the basis that Chagas’ disease
vector treated with this compound was less susceptible
to natural infection with T. cruzi than untreated
controls.36 These interesting results led to evaluate
several modified structures, which had previously shown
to be active on the Chagas’ disease vector Triatoma
infestans,37,38 against the parasite establishing a good
correlation between trypanostatic activity and juvenile
hormone action39 and suggesting a mechanism of infec-
tion control. There is strong evidence that the target of
4-phenoxyphenoxy derivatives is the ergosterol biosyn-
thetic pathway. When T. cruzi epimastigotes are treated
with the thiocyanate derivative 8, an accumulation of
low molecular weight metabolites from mevalonate to
squalene is observed (Chart 3).40
Compounds 7 and 8 and other sulfur-containing
derivatives were also effective agents against amastig-
otes,32,41,42 the clinically more relevant form of the
parasite, and as observed for other sterol biosynthesis
inhibitors, they were devoid of capacity to eradicate the
nondividing highly infective trypomastigotes.43
Bearing in mind the ultrapotent activity exhibited by
drug 8 (4 times more active than nifurtimox in epimas-
tigotes and significantly more active in amastigotes,
under the same assays conditions),32 a new set of related
compounds having the aryloxyethyl thiocyanate moiety

1828 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9
Szajnman et al.
group of 11 with pyridinium p-toluenesulfonate46 pro-
duced alcohol 12, which after treatment with tosyl
chloride gave tosylate 13 and the undesired chloride
derivative (compound 14) as a side product. Tosylate 13
reacted with potassium thiocyanate in N,N-dimethyl-
formamide at 100 °C to yield the desired thiocyanate
derivative 15.47 The nitrogen-containing derivatives
(compounds 18, 24, and 25), replacing the oxygen atom
at C-1′ by a nitrogen atom, were prepared following a
similar synthetic approach employing 4-phenoxyaniline
(16) as starting material. Attempts to alkylate the
nitrogen atom of 16 with 2-bromoethyl tetrahydro-2H-
pyran-2-yl ether were unsuccessful; however, the ac-
etanilide derivative 17, with a lower pKa, was easily
N-alkylated by treatment with 2-bromoethyl tetrahydro-
2H-pyran-2-yl ether to afford compound 18 in almost
quantitative yield. Removal of tetrahydropyranyl group
with pyridinium p-toluenesulfonate gave alcohol 19. The
normal precursor to obtain thiocyanate derivatives was
the corresponding tosylate because a good leaving group
at C-1 has to be present; nonetheless an alkyl halide
could be an alternate leaving group. Although 19 could
not be tosylated under the usual conditions, this com-
pound was transformed into the respective chloride
(compound 20) by treatment with triphenylphosphine
in carbon tetrachloride.48,49 Surprisingly, when 20 was
treated with potassium thiocyanate in dimethylforma-
mide it afforded acetate 21 instead of the expected
thiocyanate derivative 25. The formation of compound
21 can be rationalized by the anchimeric assistance of
the neighbor acetate group. Hydrolysis of 21 with
potassium carbonate led to 22 that reacted with triph-
enylphosphine in carbon tetrachloride to give 23 in good
yield. Nucleophilic displacement with potassium thio-
cyanate afforded 24. As preliminary biological assays
had indicated that 18 exhibited similar inhibitory action
as the parent drug 8, it was of interest to prepare the
acetylated analogue of 24. Therefore, compound 24
reacted with acetic anhydride in pyridine to yield 25
(Scheme 1).
Ch a r t 3. Chemical Structures of Two Representative
Inhibitors of T. cruzi Proliferation Structurally Related
to Fenoxycarb Taken as Lead Drug
was designed, synthesized, and biologically evaluated
against T. cruzi cells in order to establish a structure-
activity relationship and to refine the inhibitory action
already observed. It is important to point out that the
tetrahydropyranyl derivatives related to drug 7 are the
common intermediate for the preparation of thiocyan-
ates, so it will be of interest to compare their biological
activity with the final products, that is, the thiocyanate-
containing drugs.
Ra tion a le
The introduction of a sulfur atom at the polar extreme
in a series of 4-phenoxyphenoxyethyl derivatives and
closely related compounds gives rise to extremely potent
inhibitors against T. cruzi proliferation. The replace-
ment of this sulfur atom by an oxygen atom brings about
a dramatic impairing in the biological activity. On the
other hand, the 4-phenoxyphenoxy unit is also very
important to maintain high inhibitory values against
T. cruzi growth, because replacement of the terminal
phenoxy group by methoxy or benzoyl groups has a
marked effect in the biological action producing mod-
erately active drugs.33,34 The preparation of the new
drugs in the present study was motivated by the potent
activity shown by the lead structure 8. The incorpora-
tion of the thiocyanate moiety at the terminal aliphatic
chain of 4-phenoxyphenoxy derivatives and closely
related compounds gives rise to potent growth inhibitors
of T. cruzi. Therefore a new set of related compounds
possessing the aryloxyethyl thiocyanate moieties was
designed, prepared, and evaluated against the epimas-
tigote forms of T. cruzi which is the preferred form to
test new drugs.
Bearing in mind the unusual biological activity ex-
hibited by sulfur-containing derivatives at C-1, it was
likely that minor modifications in the vicinity of this
position would have a strong effect on the biological
activity. The replacement of the oxygen atom between
the phenyl group and the aliphatic side chain (C-2) by
other heteroatoms (sulfur or nitrogen) was the first
modification considered. The designed drugs 11 and 15
were straightforwardly prepared from 4-bromodiphenyl
ether (compound 9). This compound treated with metal-
lic magnesium gave rise to the respective Grignard
reagent that, on reaction with sulfur followed by reduc-
tion with lithium aluminum hydride,44 produced the
respective thiophenol 10 in theoretical yield. Compound
10 was transformed into the tetrahydropyranyl ether
derivative 11 by treatment with 2-bromoethyl tetrahy-
dro-2H-pyran-2-yl ether in a suspension of potassium
hydroxide in dimethyl sulfoxide, via a modified Will-
iamson procedure.45 Cleavage of the tetrahydropyranyl
As a second variation, the replacement of the ethoxy
unit in the lead drug 8 by a methylene group to give
thiocyanate 29 was considered. This drug was easily
prepared from 4-phenoxybenzaldehyde (compound 26).
On reaction with sodium borohydride,50 26 was con-
verted into the alcohol 27, which after treatment with
triphenylphosphine in carbon tetrachloride-acetonitrile
yielded the chloride 28. Compound 28 reacted with
potassium thiocyanate to yield the benzyl thiocyanate
29. To correlate the biological activity of drug 29 with
the tetrahydropyranyl ether analogue, compound 30
was easily prepared by treating alcohol 27 with 3,4-
dihydro-2H-pyran in the presence of pyridinium p-
toluenesulfonate (Scheme 2).
Previous biological assays had indicated that the
tetrahydropyranyl ether 31, in which the aromatic
skeleton was a 2,4-dichlorophenyl group instead of a
4-phenoxyphenyl moiety, was 2-fold more active than
its analogue 7. Then, it was interesting to prepare the
respective thiocyanate derivative from the readily avail-
able compound 31, which after hydrolysis of the tet-
rahydropyranyl group followed by treatment with tosyl
chloride and further nucleophilic attack of potassium
thiocyanate led to drug 34. To study the influence of

Aryloxyethyl Thiocyanates as Inhibitors of T. cruzi
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9 1829
Sch em e 1a
Sch em e 3a
a
Reagents: (a) BrCH2CH2OTHP, KOH/DMSO, rt, overnight
(68%); (b) PPTs, MeOH, rt, (42% for 41, 64% for 45, 59% for 50);
(c) ClTs/py, rt, 4 h (40% for 42, 94% for 46, 100% for 51); (d) KSCN,
DMF, 100 °C, 5 h (73% for 43, 62% for 47, 52% for 52).
Sch em e 4a
a
Reagents: (a) i. Mg/I2, THF, 65 °C, 15 min, then rt, 2 h, ii. S8,
3 h, rt, iii. LiAlH4, rt, 30 min (100%); (b) BrCH2CH2OTHP, KOH/
DMSO, rt, 16 h (43% for 11, 90% for 18); (c) PPTs, MeOH, rt, (78%
for 12, 73% for 19); (d) ClTs/py, rt, 4 h (85% for 13, 9% for 14); (e)
KSCN, DMF, 100 °C, 5 h (100% for 15, 95% for 21, 39% for 24,
13% for 29); (f) Ac2O/py, rt, 16 h (98% for 17, 82% for 25); (g) Ph3P/
Cl4C, MeCN, rt, overnight (51% for 20, 70% for 23); (h) K2CO3,
MeOH-H2O, rt, 3 h; (i) NaBH4, EtOH, rt, 2 h (84%); (j) PPTs,
DHP, Cl2CH2, rt, (100%).
a
Reagents: (a) BrCH2CH2OTHP, KOH/DMSO, rt, overnight
(39%); (b) PPTs, MeOH, rt, (100%); (c) ClTs/py, rt, 4 h (75%); (d)
KSCN, DMF, 100 °C, 5 h (54%).
quently, using the halogen-containing derivatives 2-chlo-
ro-4-phenoxyphenoxyethyl and 2-bromo-4-phenoxyphe-
noxyethyl tetrahydropyranyl ethers (compounds 40 and
44, respectively) as starting materials,32 these com-
pounds were converted into the desired thiocyanate
derivatives 43 and 47 following a similar synthetic
approach as depicted for compound 15. The iodine
derivative 52 was prepared from iodophenol 48,32 and
this compound was converted into the tetrahydropyra-
nyl derivative 49, which was transformed into the
desired drug employing a similar method for the prepa-
ration of 15 (Scheme 3).
Sch em e 2a
Since halogen derivatives were very promising drugs
it was decided to introduce a halogen atom at the meta
position (C-3′). In this case, the designed drug was a
simplified model of aryloxyethyl derivatives due to
synthetic difficulties to carry out a substitution in
4-phenoxyphenoxy derivatives at this site. m-Bromophe-
nol (53) was used as starting material. Following the
usual synthetic methodology, 53 reacted with 2-bromo-
ethyl tetrahydro-2H-pyran-2-yl ether to give 54, which
after cleavage of the protective group, tosylation and SN2
reaction with the thiocyanate ion produced drug 57
(Scheme 4).
To study the influence of the relative spatial align-
ment of the phenyl groups on the biological activity, it
was considered that the replacement of the hydrogen
atom at the ortho position in the B ring (C-2′′) would
drive the phenyl groups to adopt a special conformation
by van der Waals interactions. The synthesis of these
kinds of 4-phenoxyphenoxy derivatives was not direct
because the C-2′′ is not activated for an electrophilic
aromatic substitution. Therefore, the required phenol
intermediates (compounds 60, 68, and 76, respectively)
to prepare the designed drugs were synthesized employ-
ing a nucleophilic aromatic substitution, an Ullmann
a
Reagents: (a) BrCH2CH2OTHP, KOH/DMSO, rt, overnight
(77%); (b) PPTs, MeOH, rt, (43% for 32, 78% for 37); (c) ClTs/py,
rt, 4 h (53% for 33, 92% for 38); (d) KSCN, DMF, 100 °C, 5 h (70%
for 34, 63% for 39).
the chlorine atom at C-2′ position on biological activity,
the 4-phenyl group was envisioned. Therefore, employ-
ing 4-chlorophenol (compound 35) as starting material,
this compound was transformed into tetrahydropyranyl
derivative 36, which following a similar protocol as
described for 34 was converted into thiocyanate 39 in
good yield (Scheme 2).
We have recently demonstrated32 that the substitu-
tion of an ortho hydrogen atom of 4-phenoxyphenol by
different groups exhibited a marked influence on bio-
logical activity. It has been found that the inhibitory
potency increases as the substituent size increases.
Then, it was reasonable to consider that the replace-
ment in our lead drug 8 of the hydrogen atom at the
C-2′ position by different halogen atoms would lead to
more active drugs than 8. For the above reasons,
4-phenoxyphenoxyethyl thiocyanates possessing chlo-
rine, bromine, and iodine at C-2′ (drugs 43, 47, and 52,
respectively) were designed and synthesized. Conse-

1830 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9
Szajnman et al.
Sch em e 5a
coupling reaction in this case, as the key step.50 Thus,
3-bromophenol (compound 48) was condensed with
4-nitrochlorobenzene in the presence of cuprous chloride
to afford the nitro derivative 58 in good yield. This
compound was reduced by catalytic hydrogenation
employing palladium on charcoal as catalyst51 to yield
the aniline 59 in very good yield. On reaction with
sodium nitrite in sulfuric acid in the presence of urea,52
59 was transformed into the phenol 60. This modified
Sandmeyer protocol occurred in moderate yield. Fol-
lowing the usual synthetic procedures the intermediate
60 led to compound 61 by treatment with 2-bromoethyl
tetrahydro-2H-pyran-2-yl ether, which after tetrahy-
dropyranyl cleavage, followed by tosylation and further
nucleophilic displacement with potassium thiocyanate
produced the desired thiocyanate 64 in good yield. The
use of a group bigger than a bromine atom to replace
the H-2′′, namely a methyl unit, would give rise to
stronger van der Waals forces than those present in
compound 64 and its precursors. For that reason, it is
quite reasonable to assume that the increment of the
substituent size will lead to an increase in the torsion
angles φC2′′-C1′′-O1′′-C4′, that is, a displacement out of the
plane of one phenyl group with respect to the other one.
Therefore, drugs 69 and 72 were synthesized starting
from o-cresol via the phenol intermediate 70 employing
the same synthetic strategy as depicted for the bromine
derivatives 61 and 64. Finally, the introduction of an
extra methyl group at C-6′′ was also considered in order
to bring about strong van der Waals forces. Then, the
preparation of compound 77 was successfully carried out
employing 2,6-dimethylphenol as starting material;
however, the respective Sandmeyer-type reaction to
produce the corresponding phenol intermediate was not
satisfactory in terms of the yield (Scheme 5).
a
Reagents: (a) 1-chloro-4-nitrobenzene, DMSO/KOH, CuCl, rt,
16 h (71% for 58, 54% for 66, 63% for 74); (b) H2, Pd/C 3 atm, rt,
overnight (91% for 59, 94% for 67, 94% for 75); (c) i. H2SO4/AcOH,
ii. NaNO2, H2O, 0 °C, 20 min, iii. urea, H2O, iv. H2O/H2SO4, reflux
(37% for 60, 26% for 68, 10% for 76); (d) BrCH2CH2OTHP, KOH/
DMSO, rt (60% for 61, 60% for 69, 54% for 77); (e) PPTs, MeOH,
rt (85% for 62, 100% for 70); (f) ClTs/py, rt (95% for 63, 67% for
71); (g) KSCN, DMF, 100 °C (71% for 64, 50% for 72).
Another interesting structural variation was the
preparation of conformationally constrained 4-phenox-
yphenoxy derivatives in order to investigate the influ-
ence of a specific restricted spatial disposition of both
phenyl groups on biological activity. The skeleton of
xanthone (compound 78) would be a suitable template
to prepare these rigid drugs. The C-2 and C-4 positions
of the xanthone ring should be the more active sites for
an electrophilic aromatic substitution reaction because
they are para and ortho with respect to phenoxy group.
However, reaction at the C-2 position would be more
favorable than at C-4 due to absence of steric hindrances
of the incoming electrophile. The nitration reaction at
C-2 to form compound 79 was considered as the key step
for the preparation of the tetrahydropyranyl and thio-
cyanate derivatives built on a rigid template because
the nitro group can be readily converted into the
corresponding phenol intermediate. The substitution of
H-2 by a nitro group was satisfactory and carried out
in detriment of the yield by adding 0.5 equiv of the
nitrating agent (fuming nitric acid in concentrated
sulfuric acid)53 over a cold diluted solution of 1 equiv of
xanthone in concentrated sulfuric acid. Xanthone was
always in excess irrespective of the nitrating agent and
the forming 2-nitroxanthone was less like to react with
Sch em e 6a
a
Reagents: (a) fuming HNO3/H2SO4, 0 °C, 40 min; (b) H2, Pd/C
3 atm, rt, 6 h (91% overall yield from 78, based on the number of
equiv of HNO3 employed); (c) i. H2SO4/AcOH, ii. NaNO2, H2O, 0
°C, 20 min, iii. urea, H2O, iv. H2O/H2SO4, reflux (36%); (d)
BrCH2CH2OTHP, KOH/DMSO, rt (45%); (e) PPTs, MeOH, rt
(100%); (f) ClTs/py, rt (78%); (g) KSCN, DMF, 100 °C (71%).
presence of urea, led to the hydroxy derivative 81.
Treatment of this compound with 2-bromoethyl tetrahy-
dro-2H-pyran-2-yl ether afforded the conformationally
constrained drug 82. After the routine three synthetic
steps, compound 82 was converted into the rigid thio-
cyanate 85 in good yield (Scheme 6).
Since the presence of the thiocyanate group at the
polar end of this family of drugs was hardly responsible
for the ultrapotency observed, it would be predicted that
slight modification in the aliphatic side chain would be
a remarkable effect on biological activity. It was decided
to attach a methyl group at the C-1 position of our lead
drug 8. The replacement of either the pro-R or pro-S
+
the NO2 cation than the starting material 78. Com-
pound 79 was reduced by catalytic hydrogenation to
form the rigid aniline 80 that on reaction with sodium
nitrite in sulfuric acid at low temperature, and in the

Aryloxyethyl Thiocyanates as Inhibitors of T. cruzi
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9 1831
Sch em e 7a
at C-1′ by a nitrogen (compound 24) produced a dra-
matic reduction in biological activity compared to our
lead structure 8 with IC50 of 141 µM. The decrease in
the inhibitory action was not so pronounced with
N-acetylated derivatives; certainly, drug 25 exhibited
an IC50 close to 15 µM, 10 times more active than 24,
while its normal tetrahydropyranyl precursor (com-
pound 18) was a moderate inhibitor of T. cruzi growth
(IC50 > 200 µM).
Rep la cem en t of th e Ter m in a l P h en oxy Gr ou p by
a Ch lor in e Atom . The replacement of the terminal
phenoxy group and the H-1′ by chlorine atoms in our
lead drug 8 produced a very active compound. As
predicted by the biological activity previously observed
for compound 31 (IC50 93 µM),32 being almost 50% more
active than compound 7, drug 34 proved to be an
extremely potent trypanostatic agent being 2-fold more
active than 8 with an IC50 of 1.0 µM. In addition at
concentrations as low as 40 µM complete growth arrest
took place. The presence of the chlorine atom at the
ortho position with respect to the ether group seemed
to be very important for biological activity. Removal of
chlorine atom at C-1′ from compound 34 led to drug 39
that was 15 times less active than the dichloride
derivative. Moreover, the precursor tetrahydropyranyl
derivative 36 was almost devoid of inhibitory action.
a
Reagents: (a) KOH, DMSO, S-propylene oxide or R-propylene
oxide, rt, 6 h (20% for 87, 15% for 90); (b) ClTs/py, rt (87% for 88,
84% for 91); (c) KSCN, DMF, 100 °C (58% for 89, 57% for 92).
Ta ble 1. Growth Inhibition against T. cruzi (Epimastigotes)
compd
IC50 (µM)
compd
IC50 (µM)
11
18
24
29
34
39
47
52
57
64
72
82
89
291
211
141
18.7
1.0b
14.1
1.4d
1.8e
<4c
2.9
15
19
25
30
36
43
49
54
61
69
77
85
92
8
0.87a
277
14.4
102
>390
24.5
45
104
138
143
2.7f
>60
25
>60
54
>82
2.2g,32
Sh or ten in g th e Alip h a tic Sid e Ch a in a n d Elim i-
n a tion of th e Oxygen Atom a t C-1′. Although short-
ening of the aliphatic side chain and deleting the oxygen
atom at C-1′ gave place to the very potent drug 29, this
compound was around 10 times less active than lead
structure 8. Unexpectedly, the introduction of the tet-
rahydropyranyl functionality (compound 30) produced
a slight improvement on biological activity (IC50 102 µM)
compared with drug 7.
ketoconazole, 6
3.2
a
b
d
IC90 ) 32 µM. IC90 ) 30 µM. c IC90 ) 27 µM. IC90 ) 18 µM.
e IC90 ) 23 µM. f IC90 ) 3.5 µM. IC90 ) 3.5 µM.
g
hydrogen atoms at C-1 by this function would lead to
chiral compounds. Thus, regioselective ring opening of
S-propylene oxide by treatment with 4-phenoxyphenol
(compound 86) in basic medium lead to optically pure
alcohol 87, which after reaction with tosyl chloride and
further nucleophilic displacement with potassium thio-
cyanate afforded chiral thiocyante 89 in moderate yield.
The enantiomer of 89 was prepared starting from
R-propylene oxide employing the same synthetic se-
quence (Scheme 7).
In t r od u ct ion of a H a logen At om a t t h e C-2′
P osition . Taking into account the increment on biologi-
cal activity when the thiocyanate moiety replaces the
tetrahydropyranyl group when bonded to the same
nonpolar skeleton, and considering that the larger the
substituent, the more active the drug, it was reasonably
expected that an improvement on biological activity
would occur by introducing different groups at C-2′.32
With the exception of chlorine derivative 43, which
exhibited an IC50 of 25 µM, the introduction of a halogen
atom at the ortho position in the 4-phenoxyphenoxy
skeleton produced very active trypanostatic agents. The
normal precursor for the preparation of 43 (drug 40)
had previously exhibited an IC50 of 93 µM, being one of
the most active tetrahydropyranyl ether derivatives ever
prepared.32 Therefore, the introduction of either bromine
or iodine into the lead structure brought about two very
potent anti-T. cruzi agents exhibiting quite similar
biological activities as compound 8. However, the thera-
peutic index for drugs 47 and 52 was not as good as
previously observed for compound 8. These halogen-
containing drugs presented IC90 values of 18 and 23 µM,
respectively, data that are still far from those reported
for 8 (IC90 of 3.5 µM).32
Resu lts a n d Discu ssion
The biological data on the epimastigote form of T.
cruzi cells were very encouraging. Ketoconazole was
used as positive control. The results are presented in
Table 1.
Rep la cem en t of th e Oxygen Atom a t C-1′ by a
Heter oa tom . Replacement of the oxygen atom by a
sulfur atom at the C-1′ position of lead drug 8 led to a
significant improvement on the biological activity. On
the other hand, when the substitution was made with
a nitrogen atom at that position, an important decrease
in the inhibitory action was observed. For instance,
compound 15 exhibited a remarkably high biological
activity on the epimastigote form of the parasite with
an IC50 of 0.9 µM and was 2-fold more active than lead
compound 8 (IC50 2.2 µM).32 This compound was able
to produce 95% inhibition at a concentration of 35 µM.
Contrary to it would be expected, the sulfur-containing
tetrahydropyranyl ether derivative 12 was 2-fold less
active than lead drug 7 (IC50 138 µM).33 Nitrogen-
containing derivatives did not lead to an enhancement
on biological activity. Thus, substitution of the oxygen
Elim in a tion of th e Ter m in a l P h en oxy Moiety
a n d In tr od u ction of a Br om in e Atom a t th e C-3′
P osition . Replacement of a bromine atom at the meta
position (C-3′) with respect to the phenol group together
with elimination of the terminal phenoxy moiety was

1832 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9
Szajnman et al.
Ta ble 2. Growth Inhibition against Intracellular T. cruzi
compd
IC50 (µM)
compd
IC50 (µM)
8
47
72
16.0
64.5
41.7
34
52
>100
>100
myoblasts, while drugs 34 and 52 were devoid of activity
against amastigotes. On the other hand, compounds 47
and 72 were highly active trypanostatic agents but to a
lesser extent than 8 (IC50 16.0 µM) exhibiting IC50
values of 64.5 and 41.7 µM, respectively, under the same
assays conditions based on differential uracil incorpora-
tion54 (see Table 2). In contrast to compound 15, no
toxicity to the host cells, as assessed by phase contrast
microscopy observation of detachment, vacuolation, and
rounding of the cells, was detected using the concentra-
tions of compounds described.
In conclusion, aryloxylethyl thiocyanate derivatives
represent an interesting new family of drugs to control
replication of T. cruzi cells that were rationally designed
and synthesized. Slight modifications in the closeness
to the polar end group produced a marked effect on
inhibitory action. Work aimed at exploiting the potential
usefulness of these thiocyanate derivatives as well as
in vivo studies of the more promising drugs is currently
in progress in our laboratory.
F igu r e 1. Dose-response graph for compounds 8, 47, 52, and
72.
very promising for biological activity. In fact, thiocyan-
ate 57 was a very potent trypanostatic agent with an
IC90 close to 27 µM, activity that correlates quite
properly with the activity exhibited with its precursor,
the tehydropyranyl ether 54.
Str u ctu r a l Va r ia tion s in th e B Rin g. Structural
modifications at the C-2′′ or C-3′′ positions in the B ring
to give thiocyanates 64 and 72 seemed not to have a
significant effect on biological activity. In fact, both of
these drugs exhibited almost the same inhibitory action
as lead drug 8 presenting IC50 values of 2.9 and 2.7 µM,
respectively. In addition, their precursors 61 and 69,
which showed IC50 values of 138 and 143 µM, respec-
tively, were as active as lead compound 7 (IC50 138
µM).32 The above biological data are very meaningful
for drug design because the introduction of different
groups at C-2′′ or C-3′′ is not only somewhat difficult
but also has no significant consequence on biological
activity. Moreover, as we had previously demonstrated
that substitutions at C-4′′ produced an impairment on
the growth inhibitory effect, it can be concluded that
any modification in the B ring will not lead to an
enhancement on biological activity.
Con for m a tion a lly Rigid Ar yloxyeth yl Th iocy-
a n a tes. Aryloxyethyl thiocyanates built on a rigid
template did not present potent action in inhibiting the
proliferation of T. cruzi. Accordingly, although confor-
mationally constrained thiocyanate 85 was a rather
active compound (IC50 54 µM), its inhibitory action was
far from that observed for other thiocyanates deriva-
tives, namely the lead structure 8. In addition, its
precursor (compound 82) showed very modest activity,
which at a concentration of 60 µM merely a 25%
inhibition was observed.
Br a n ch ed Der iva tives of Lea d Dr u g 8. The intro-
duction of a branched side chain at the proximity of the
thiocyante moiety did not improve the biological activity.
On the contrary, neither enantiomer was more active
than 8: the R isomer (compound 89) was 10 times less
active than 8, while its antipode 92 was almost 30 times
less active than our lead drug. A typical dose-response
graph for the more active drugs such as compounds 8,
47, 52, and 72 is illustrated in Figure 1.
The more promising drugs (compounds 15, 34, 47, 52,
and 72, respectively) were assayed against the intrac-
ellular form of the parasite employing compound 8 as
positive control. Compound 15 proved to be toxic for
Exp er im en ta l Section
The glassware used in air- and/or moisture-sensitive reac-
tions was flamed-dried and the experiments were carried out
under a dry nitrogen atmosphere. Unless otherwise noted,
chemicals were commercially available and used without
further purification.
Nuclear magnetic resonance spectra were recorded on
Bruker AC-200 MHz and Bruker AM-500 spectrometers.
Chemical shifts are reported in parts per million (δ) relative
to tetramethylsilane. The 1H NMR spectra are referenced with
respect to the residual CHCl3 proton of the solvent CDCl3 at
7.26 ppm. Coupling constants are reported in hertz (Hz). 13C
NMR spectra were fully decoupled and are referenced to the
middle peak of the solvent CDCl3 at 77.00 ppm. Splitting
patterns are designated as s, singlet; d, doublet; t, triplet; q,
quartet.
Melting points were determined using a Fisher-J ohns
apparatus and are uncorrected. IR spectra were recorded using
a
Nicolet Magna 550 spectrometer. Low-resolution mass
spectra were obtained on a VG TRIO 2 instrument at 70 eV
(direct inlet). High-resolution mass spectrometry (HRMS) were
conducted on a VG ZAB BEqQ spectrometer.
Column chromatography was performed employing E. Mer-
ck silica gel (Kieselgel 60, 230-400 mesh). Analytical thin-
layer chromatography was performed employing 0.2-mm
coated commercial silica gel plates (E. Merck, DC-aluminum
sheets, Kieselgel 60 F254) and was visualized by 254 nm UV
or by immersion into an ethanolic solution of 5% H2SO4.
Elemental analyses were performed by UMYMFOR (Fac-
ultad de Ciencias Exactas y Naturales-CONICET) and Atlantic
Microlab, Norcross, Ga. The results were within (0.4% of the
theoretical values except when otherwise stated.
4-P h en oxyth iop h en ol (10). To a solution of 4-bromophe-
nyl phenyl ether (9; 2.00 g, 8.0 mmol) in tetrahydrofuran (10
mL) were added metallic magnesium (297 mg, 12.2 mmol) and
iodine (30 mg) and the mixture was refluxed for 15 min. The
reaction mixture was allowed to cool to room temperature and
was stirred for 2 h. The resulting dark solution was treated
with sulfur (3.125 g) and the mixture was stirred for an
additional 3 h. Then, the mixture was cooled to 0 °C and was
treated with excess of lithium aluminum hydride (1.0 g). The
reaction mixture was stirred for 30 min. The reaction was
quenched with ethyl acetate (2.0 mL) and the mixture was

Aryloxyethyl Thiocyanates as Inhibitors of T. cruzi
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9 1833
partitioned between methylene chloride (70 mL) and an
aqueous saturated solution of sodium potassium tartrate (100
mL). The aqueous phase was extracted with methylene
chloride (2 × 50 mL), and the combined organic layers were
washed with water (2 × 100 mL), dried (MgSO4), and the
solvent was evaporated. The residue was purified by column
chromatography eluting with hexanes-EtOAc (50:1) to afford
1.61 g (100% yield) of pure compound 10 as a syrup: Rf 0.71
(hexanes-EtOAc, 4:1); IR (film, cm-1) 3447, 3063, 3038, 2567,
1490, 1242, 1170, 828, 760, 690; 1H NMR (CDCl3) δ 3.36 (s, 1
H, -SH), 6.85 (d, J ) 8.7 Hz, 2 H, H-3), 6.91-7.50 (m, 5 H,
aromatic protons), 7.21 (d, J ) 8.7 Hz, 2 H, H-2); 13C NMR
(CDCl3) δ 118.70 (C-2′), 119.55 (C-3), 123.28 (C-4′), 129.68 (C-
2, C-3′), 132.55 (C-1), 155.75 (C-4), 156.97 (C-1′).
2-(4-P h en oxyp h en ylth io)eth yl Th iocya n a te (15). To a
solution of tosylate 13 (530 mg, 1.3 mmol) in anhydrous N,N-
dimethylformamide (5 mL) was added potassium thiocyanate
(520 mg, 5.4 mmol). The reaction mixture was heated at 100
°C for 5 h. The mixture was allowed to cool to room temper-
ature and water (50 mL) was added. The aqueous phase was
extracted with methylene chloride (2 × 50 mL) and the
combined organic layers were washed with an aqueous satu-
rated solution of sodium chloride (5 × 50 mL) and water (2 ×
50 mL). The solvent was dried (MgSO4) and evaporated. The
residue was purified by column chromatography (silica gel)
using a mixture of hexanes-EtOAc (24:1) as eluent to afford
380 mg (100% yield) of pure compound 15 as a yellow pale oil:
Rf 0.58 (hexanes-EtOAc, 4:1); IR (film, cm-1) 3061, 2924, 2853,
2154, 1582, 1485, 1240, 1167, 868, 756, 692; 1H NMR (500
MHz, CDCl3) δ 3.08 (m, 2 H, H-1), 3.20 (m, 2 H, H-2), 6.96 (d,
J ) 8.8 Hz, 2 H, H-3′), 6.97-7.42 (m, 5 H, aromatic protons),
7.40 (d, J ) 8.8 Hz, 2 H, H-2′); 13C NMR (CDCl3) δ 33.26 (C-
1), 35.44 (C-2), 119.23 (C-2′′), 119.42 (C-3′), 123.93 (C-4′′),
129.87 (C-3′′), 132.98 (C-1′), 134.05 (C-2′), 156.34 (C-4′), 157.80
(C-1′′); MS (m/z, relative intensity) 287 (M+, 83), 274 (3), 215
(20), 201 (96), 77 (100); HRMS calcd for (C15H13ONS2) 287.0439,
found 287.0441. Anal. (C15H13ONS2) C, H.
N-(4-P h en oxyph en yl)acetam ide (17). A solution of 4-phe-
noxyaniline (16; 2.00 g, 10.8 mmol) in anhydrous pyridine (3
mL) was treated with acetic anhydride (2 mL). The reaction
mixture was stirred at room temperature overnight. Then, 5%
hydrochloric acid (20 mL) was added and the mixture was
stirred for 1 h. The aqueous phase was extracted with
methylene chloride (2 × 50 mL). The combined organic layers
were washed with 5% HCl (3 × 50 mL), and water (2 × 50
mL). The solvent was dried (MgSO4) and evaporated to afford
2.408 g (98% yield) of pure amide 17 as a brown solid: mp
128-129 °C; IR (KBr, cm-1) 3290, 3258, 3194, 3136, 3067,
1661, 1607, 1549, 1549, 1506, 1489, 1406, 1373, 1315, 1244,
856, 831, 754, 691; MS (m/z, relative intensity) 227 (M+, 66),
185 (100), 156 (11), 108 (75).
N-Acetyl-N-(4-ph en oxyph en yl)am in oeth yl Tetr ah ydr o-
2H-p yr a n -2-yl Eth er (18). A solution of acetate 17 (3.405 g,
15 mmol) in dimethyl sulfoxide (5 mL) was treated with
potassium hydroxide (1.7 g, 30 mmol). The mixture was stirred
at room temperature for 5 min. Then, bromoethyl tetrahydro-
pyranyl ether (3.923 g, 15.75 mmol) was added, and the
solution was stirred at room temperature overnight. The
reaction was worked up as depicted for 11. The product was
purified by column chromatography (silica gel) eluting with
hexanes-EtOAc (7:3) to afford 4.801 g (90% yield) of pure
compound 18 as a yellow oil: IR (film, cm-1) 3292, 3065, 2941,
2870, 1663, 1506, 1489, 1406, 1240, 1072, 1036, 872, 754, 692;
1H NMR (CDCl3) δ 1.52-1.89 (m, 6 H, H-3′′′, H-4′′′, H-5′′′),
1.87 (s, 3 H, COCH3), 3.53 (m, 1 H, H-6′′′a), 3.63 (m, 1 H,
H-6′′′b), 3.60-4.00 (m, 4 H, H-1, H-2), 4.56 (m, 1 H, H-2′′′),
6.95-7.41 (m, 9 H, aromatic protons); 13C NMR (CDCl3) δ 19.37
(C-4′′′), 22.73 (COCH3), 25.34 (C-5′′′), 30.51 (C-3′′′), 48.92 (C-
2), 62.17 (C-6′′′), 64.49 (C-1), 98.64 (C-2′′′), 119.02 (C-2′′), 119.30
(C-3′), 121.56 (C-2′), 123.86 (C-4′′), 129.85 (C-3′′), 138.07 (C-
1′), 156.32 (C-4′), 156.89 (C-1′′); MS (m/z, relative intensity)
355 (M+, 5), 254 (10), 227 (89), 198 (20), 185 (100), 108 (65),
43 (77); HRMS calcd for C21H25O4N 355.1799, found 355.1791
Anal. (C21H25O4N) C, H.
N-Acetyl-N-(4-p h en oxyp h en yl)a m in oeth a n ol (19). To a
solution of compound 18 (3.834 g, 10.8 mmol) in methanol (100
mL) was added pyridinium 4-toluenesulfonate (200 mg). The
mixture was stirred at room temperature for 4 days. The
reaction was worked up as described for 12. The residue was
purified by column chromatography (silica gel) employing a
mixture of hexanes-EtOAc (7:3) as eluent to give 2.155 g (73%
yield) of pure alcohol 19 as a white solid and 900 mg of
unreacted material: mp 90-92 °C; MS (m/z, relative intensity)
271 (M+, 21), 227 (8), 198 (100), 43 (85).
2-(4-P h en oxyp h en ylth io)eth yl Tetr a h yd r o-2H-p yr a n -
2-yl Eth er (11). To a solution of thiophenol 10 (1,046 g, 5.2
mmol) in dimethyl sulfoxide (5.0 mL) was added potassium
hydroxide (1.165 g, 20.4 mmol). The mixture was stirred at
room temperature for 5 min. Then, bromoethyl tetrahydropy-
ranyl ether (1.30 g, 6.2 mmol) was added and the reaction
mixture was stirred at room temperature overnight. The
mixture was partitioned between water (50 mL) and methylene
chloride (50 mL). The aqueous phase was extracted with
methylene chloride (2 × 30 mL). The combined organic layers
were washed with saturated solution of sodium chloride (5 ×
50 mL), dried (MgSO4), and the solvent was evaporated. The
residue was purified by column chromatography (silica gel)
employing a mixture of hexanes-EtOAc (19:1) as eluent to
yield 739 mg (43% yield) of pure compound 11 as a colorless
oil: Rf 0.49 (hexanes-EtOAc, 17:3); IR (film, cm-1) 2942, 2877,
1590, 1498, 1354, 1238, 1122, 1032, 974, 870; 1H NMR (CDCl3)
δ 1.52-1.86 (m, 6 H, H-3′′′, H-4′′′, H-5′′′), 3.09 (t, J ) 6.8 Hz,
2 H, H-2), 3.50 (m, 1 H, H-6′′′a), 3.64 (m, 1 H, H-6′′′b), 3.73-
4.03 (m, 2 H, H-1), 4.61 (distorted t, J ) 3.2 Hz, 1 H, H-2′′′),
6.92 (d, J ) 8.8 Hz, 2 H, H-3′), 6.91-7.39 (m, 5 H, aromatic
protons) 7.37 (d, J ) 8.7 Hz, 2 H, H-2′); 13C NMR (CDCl3) δ
19.37 (C-4′′′), 25.37 (C-5′′′), 30.51 (C-3′′′), 34.76 (C-2), 62.18
(C-6′′′), 66.43 (C-1), 98.87 (C-2′′′), 118.91 (C-2′′), 119.26 (C-3′),
123.42 (C-4′′), 129.74 (C-2′, C-3′′), 132.28 (C-1′), 156.32 (C-4′),
156.94 (C-1′′); MS (m/z, relative intensity) 330 (M+, 1), 250
(19), 248 (20), 141 (20), 85 (100); HRMS calcd for (C19H22O3S)
330.1290, found 330.1289. Anal. (C19H22O3S) C, H.
2-(4-P h en oxyp h en ylth io)eth a n ol (12). To a solution of
compound 11 (720 mg, 2.2 mmol) in methanol (30 mL) was
added pyridinium p-toluenesulfonate (30 mg). The reaction
mixture was stirred at room temperature for 14 h. The mixture
was partitioned between water (70 mL) and methylene chloride
(70 mL). The aqueous phase was extracted with methylene
chloride (2 × 30 mL) and the combined organic layers were
washed with brine (2 × 50 mL), dried (MgSO4), and the solvent
was evaporated to afford 420 mg (78% yield) of pure alcohol
12 as a colorless oil that was use in the next step without
further purification: Rf 0.14 (hexanes-EtOAc, 17:3); IR (film,
cm-1) 3385, 3063, 2947, 2878, 1582, 1483, 1238, 1167, 1045,
756, 692; MS (m/z, relative intensity) 246 (M+, 100), 215 (43),
202 (14), 181 (25), 77 (50).
2-(4-P h en oxyp h en ylth io)eth yl 4-Tolu en esu lfon a te (13)
a n d 2-(4-P h en oxyp h en ylth io)eth yl Ch lor id e (14). To a
solution of alcohol 12 (400 mg, 1.6 mmol) in pyridine (5 mL)
cooled at 0 °C was added p-toluenesulfonyl chloride (389 mg,
5.0 mmol) portionwise, and the mixture was stirred at room
temperature for 4 h. Then, 5% HCl (50 mL) was added and
the reaction mixture was stirred for an additional hour. The
mixture was extracted with methylene chloride (50 mL) and
the organic layer was washed with 5% HCl (3 × 50 mL) and
water (3 × 50 mL). The organic phase was dried (MgSO4) and
the solvent was evaporated to give 550 mg (85% yield) of pure
tosylate 13 as a colorless oil and 39 mg of chloride 14 as a
colorless oil. Compound 13: Rf 0.68 (hexanes-EtOAc, 4:1); IR
(film, cm-1) 2939, 2870, 1584, 1484, 1238, 1132, 1032, 868, 756,
692; MS (m/z, relative intensity) 400 (M+, 18), 278 (20), 201
(73), 77 (100). Compound 14: MS (m/z, relative intensity) 266
(M+, 37), 264 (M+, 100), 215 (27), 201 (34), 108 (10), 129 (18),
181 (12), 77 (77).
N-Acetyl-(4-p h en oxyp h en yl)-2-ch lor oeth yla m in e (20).
To a solution of triphenylphosphine (900 mg, 3.4 mmol) in
carbon tetrachloride (20 mL) and acetonitrile (5 mL) was added
alcohol 19 (650 mg, 2.4 mmol). The reaction mixture was

1834 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9
Szajnman et al.
stirred at room temperature overnight. The solvent was
evaporated and the residue was purified by column chroma-
tography (silica gel) eluting with hexanes-EtOAc (7:3) to
afford 355 mg (51% yield) of pure chloride 20 as a pale yellow
oil: Rf 0.52 (hexanes-EtOAc, 1:1); MS (m/z, relative intensity)
291 (M+, 2), 289 (M+, 6), 271 (20), 247 (5), 211 (10), 198 (100).
(4-P h en oxyp h en yl)a m in oeth yl Aceta te (21). A mixture
of chloride 20 (154 mg, 0.53 mmol) and potassium thiocyanate
(500 mg, 5.1 mmol) in N,N-dimethylformamide (3 mL) was
stirred at 100 °C for 6 h. The mixture was treated as depicted
for 15. The product was purified by column chromatography
(silica gel) eluting with hexanes-EtOAc (9:1) to afford 130 mg
(95% yield) of pure acetate 21 as a colorless oil: Rf 0.56
(hexanes-EtOAc, 7:3); MS (m/z, relative intensity) 271 (M+,
24), 211 (13), 198 (100).
2-[(4-P h en oxyp h en yl)a m in o]eth a n ol (22). A solution of
acetate 21 (250 mg, 0.93 mmol) in methanol-water (10:3) (13
mL) was treated with potassium carbonate. The reaction
mixture was stirred at room temperature for 3 h. The mixture
was partitioned between water (50 mL) and methylene chloride
(70 mL). The aqueous phase was extracted with methylene
chloride (2 × 50 mL). The combined organic layers were
washed with brine (3 × 70 mL), dried (MgSO4), and the solvent
was evaporated to afford 200 mg (87% yield) of pure amino
alcohol 22 as a white solid: Rf 0.24 (hexanes-EtOAc, 7:3); MS
(m/z, relative intensity) 229 (M+, 29), 198 (100).
was quenched by careful addition of 5% HCl (2 mL). The
mixture was partitioned between water (50 mL) and methyene
chloride (70 mL). The organic layer was washed with water
(3 × 50 mL), dried (MgSO4), and the solvent was evaporated
to afford 876 mg (84% yield) of pure alcohol 27 as a white
solid: mp 94-96 °C; Rf 0.61 (hexanes-EtOAc, 3:2); IR (KBr,
cm-1) 3358, 3059, 2930, 2881, 1590, 1526, 1489, 1245, 1005,
845, 697; MS (m/z, relative intensity) 200 (M+, 100), 183 (18),
171 (19), 153 (21), 107 (44), 94 (54), 77 (66).
4-P h en oxyp h en ylm eth yl Ch lor id e (28). To a solution of
triphenylphosphine (450 mg, 1.71 mmol) in carbon tetrachlo-
ride-acetonitrile (1:1, 20 mL) was added alcohol 23 (314 mg,
1.6 mmol). The reaction mixture was stirred at room temper-
ature overnight. The solvent was evaporated and the residue
was suspended in hexane (50 mL) and filtered off and the
solvent was evaporated. The chloride 24 resulted to be
unstable and was used in the next step without further
purification.
4-P h en oxyp h en ylm eth yl Th iocya n a te (29). The above
extract was dissolved in anhydrous dimethylformamide (3 mL)
and was treated with potassium thiocyanate (500 mg, 5.1
mmol). The mixture was stirred at 100 °C for 3 h. The reaction
was quenched as depicted for 15. The residue was purified by
column chromatography (silica gel) eluting with hexanes-
EtOAc to give 50 mg of pure compound 25 (13% yield) as a
yellow pale solid: mp 52-53 °C; IR (film, cm-1) 3056, 2995,
2933, 2154, 1595, 1516, 1493, 1460, 1430, 1239, 1110, 1076;
1H NMR (CDCl3) δ 4.15 (s, 2 H, H-1), 6.97-7.39 (m, 9 H,
aromatic protons); 13C NMR (CDCl3) δ 38.01 (C-1), 118.86 (C-
3′), 119.45 (C-2′′), 123.88 (C-4′′), 128.67 (C-1′), 129.87 (C-3′′),
130.50 (C-2′), 156.38 (C-4′), 158.15 (C-1′′); MS (m/z, relative
intensity) 241 (M+, 4), 183 (100), 155 (10), 91 (22), 77 (40);
HRMS calcd for C14H11ONS 241.0561, found 241.0569. Anal.
(C14H11ONS‚0.1C6H14) C, H, N, S.
(()-4-P h en oxyp h en ylm eth yl Tetr a h yd r o-2H-p yr a n -2-
yl Eth er (30). To a solution of alcohol 27 (158 mg, 0.79 mmol)
in anhydrous methylene chloride (50 mg) were added pyri-
dinium 4-toluenesulfonate (20 mg) and 3,4-dihydro-2H-pyran
(1 mL). The reaction mixture was stirred at room temperature
overnight. The organic phase was washed with water (3 × 50
mL), dried (MgSO4), and the solvent was evaporated. The
residue was purified by column chromatography (silica gel)
eluting with hexanes-EtOAc (19:1) to give 224 mg (100%
yield) of pure compound 30 as a colorless oil: Rf 0.41 (hex-
anes-EtOAc, 4:1); IR (film, cm-1) 2943, 2869, 1589, 1508, 1489,
1238, 1134, 1038, 871, 692; 1H NMR (CDCl3) δ 1.56-1.88 (m,
6 H, H-3′′′, H-4′′′, H-5′′′), 3.51-3.59 (m, 1 H, H-6′′′a), 3.87-
3.96 (m, 1 H, H-6′′′b), 4.46 (d, J ) 11.8 Hz, 1 H, H-1a), 4.72
(distorted t, J ) 3.4 Hz, 1 H, H-2′′′), 4.75 (d, J ) 11.9 Hz, 1 H,
H-1b); 13C NMR (CDCl3) δ 19.34 (C-4′′′), 25.47 (C-5′′′), 30.57
(C-3′′′), 62.13 (C-6′′′), 68.38 (C-1), 97.73 (C-2′′′), 118.76 (C-3′),
118.79 (C-2′′), 123.16 (C-4′′), 129.42 (C-1′), 129.67 (C-3′′), 133.18
(C-2′), 156.69 (C-4′), 157.29 (C-1′′); MS (m/z, relative intensity)
284 (M+, 37), 183 (100), 85 (72). Anal. (C18H20O3) C, H.
(2-Ch lor oeth yl)(4-p h en oxyp h en yl)a m in e (23). To a so-
lution of triphenylphosphine (400 mg, 1.5 mmol) in carbon
tetrachloride (20 mL) and acetonitrile (5 mL) was added amino
alcohol 22 (200 mg, 0.87 mmol). The mixture was stirred at
room temperature for 16 h. Then, the solvent was evaporated
and the residue was purified by column chromatography (silica
gel) eluting with hexanes-EtOAc (9:1) to give 152 mg (70%
yield) of pure compound 23 as a colorless oil: IR (film, cm-1
)
2957, 2835, 1589, 1508, 1489, 1233, 868, 835, 754, 692; MS
(m/z, relative intensity) 249 (M+, 10), 247 (M+, 31), 198 (100).
4-P h en oxyp h en yla m in oeth yl Th iocya n a te (24). A solu-
tion of compound 23 (150 mg, 0.6 mmol) in anhydrous
dimethylformamide (3 mL) was treated with potassium thio-
cyanate (200 mg, 2.1 mmol). The mixture was stirred at 100
°C for 6 h. the reaction was worked up as depicted for 15. The
residue was purified by column chromatography (silica gel)
employing hexanes-EtOAc (19:1) as eluent to afford 63 mg
(39% yield) of pure compound 24 as a white solid and 72 mg
of unreacted chloride 23: Rf 0.09 (EtOAc); IR (KBr, cm-1) 2918,
1
2851, 2156, 1491, 1244, 1171, 1094, 1032, 827, 667; H NMR
(CDCl3) δ 3.26 (t, J ) 6.7 Hz, 2 H, H-1), 4.04 (t, J ) 6.7 Hz, 2
H, H-2), 7.01 (d, J ) 8.8 Hz, 2 H, H-2′), 7.02-7.32 (m, 5 H
aromatic protons), 7.34 (d, J ) 8.6 Hz, 2 H, H-3′); 13C NMR
(CDCl3) δ 26.83 (C-1), 54.39 (C-2), 118.75 (C-2′′), 119.32 (C-
3′), 123.27 (C-4′′), 125.19 (C-2′), 129.66 (C-3′′), 135.72 (C-1′),
154.45 (C-4′), 157.05 (C-1′′); MS (m/z, relative intensity) 270
(M+, 100), 243 (4), 215 (9), 210 (10), 198 (16), 84 (74); HRMS
calcd for (C15H14ON2S) 270.0826, found 270.0827. Anal. (C15H14
-
ON2S‚H2O) C, H.
2,4-Dich lor op h en oxyeth a n ol (32). A solution of com-
pound 31 (746 mg, 2.6 mmol) in methanol (30 mL) was treated
with pyridinium 4-toluenesulfonate (20 mg). The mixture was
stirred at room temperature overnight. The reaction was
worked up as described for 12. The residue was purified by
column chromatography eluting with hexanes-EtOAc (9:1) to
afford 230 mg (43% yield) of pure compound 32 as a colorless
oil: Rf 0.14 (hexanes-EtOAc, 4:1); IR (film, cm-1) 3238, 2932,
1487, 1389, 1267, 1107, 1063, 930, 829, 799; MS (m/z, relative
intensity) 210 (M+, 5), 208 (M+, 27), 206 (M+, 42), 166 (18),
164 (97), 162 (100)
N-Acet yl-(4-p h en oxyp h en yl)-2-t h iocya n oet h yla m in e
(25). A solution of compound 24 (30 mg, 0.11 mmol) in pyridine
(3 mL) was treated with acetic anhydride (2 mL). The reaction
mixture was treated as depicted for 17. The product was
purified by column chromatography (silica gel) eluting with
hexanes-EtOAc (4:1) to afford 28 mg (82% yield) of pure
compound 25 as a colorless oil: Rf 0.55 (EtOAc); 1H NMR
(CDCl3) δ 1.89 (s, 3 H, C(O)CH3); 3.20 (t, J ) 6.9 Hz, 2 H,
H-2), 4.03 (t, J ) 6.8 Hz, 2 H, H-1), 7.02-7.43 (m, 9 H,
aromatic protons); 13C NMR (CDCl3) δ 26.84 (C-1), 27.41 (C(O)-
CH3), 52.53 (C-2), 118.67 (C-2′′), 119.33 (C-3′), 123.75 (C-4′′),
126.03 (C-2′), 129.85 (C-3′′), 155.70 (C-4′), 156.68 (C-1′′); MS
(m/z, relative intensity) 312 (M+, 17), 297 (7), 270 (10), 198
(90), 43 (100); HRMS calcd for (C17H16O2N2S) 312.0933, found
312.0929.
2,4-Dich lor op h en oxyeth yl 4-Tolu en esu lfon a te (33). To
a solution of alcohol 31 (230 mg, 1.1 mmol) in pyridine (3 mL)
was added portionwise tosyl chloride (254 mg, 1.3 mmol) at 0
°C, and the reaction mixture was stirred at room temperature
for 4 h. The reaction was quenched as depicted for compound
11. The residue was purified by column chromatography (silica
gel) eluting with hexanes-EtOAc (9:1) to yield 190 mg (53%
yield) of pure tosylate 33 as a colorless oil: IR (film, cm-1) 1599,
4-P h en oxyp h en ylm eth a n ol (27). A solution of 4-phenoxy-
benzaldehyde (26; 1.00 g, 5.2 mmol) in absolute ethanol (20
mL) was treated with sodium borohydride (210 mg) and the
mixture was stirred at room temperature for 2 h. The reaction

Aryloxyethyl Thiocyanates as Inhibitors of T. cruzi
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9 1835
1481, 1452, 1356, 1294, 1190, 1032, 930, 812, 665; MS (m/z,
relative intensity) 362 (M+, 5) 360 (M+, 8), 199 (86), 155 (48),
91 (100).
2-Ch lor o-4-p h en oxyp h en oxyeth a n ol (41). A solution of
compound 40 (635 mg, 1.8 mmol) in methanol (20 mL) was
treated with pyridinium p-toluenesulfonate (30 mg). The
mixture was treated as described for the preparation of
compound 12. The residue was purified by column chroma-
tography (silica gel) eluting with hexanes-EtOAc (9:1) to
afford 200 mg (42% yield) of pure compound 41 as a colorless
oil: IR (film, cm-1) 3385, 3076, 2941, 1596, 1491, 1266, 1216,
1057, 913, 758, 695; MS (m/z, relative intensity) 266 (M+, 20),
264 (M+, 60), 222 (26), 220 (96), 84 (49), 77 (60), 49 (100).
2-Ch lor o-4-p h en oxyp h en oxyeth yl 4-Tolu en esu lfon a te
(42). A solution of alcohol 41 (180 mg, 0.68 mmol) in pyridine
(3 mL) was treated with tosyl chloride (250 mg, 1.3 mmol).
After the usual treatment the residue was purified by column
chromatography (silica gel) eluting with hexanes-EtOAc (19:
1) to give 113 mg (40% yield) of pure 42 as a colorless oil: MS
(m/z, relative intensity) 420 (M+, 6), 418 (M+, 15), 221 (4), 219
(10), 199 (100), 155 (31), 91 (86), 77 (47).
2,4-Dich lor op h en oxyeth yl Th iocya n a te (34). A solution
of compound 33 (178 mg, 0.5 mmol) in dimethylformamide (2
mL) was treated with potassium thiocyanate (300 mg, 3.1).
The mixture was stirred at 100 °C for 6 h and was worked up
as depicted for 15. The residue was purified by column
chromatography (silica gel) employing hexanes-EtOAc (9:1)
as eluent to afford 90 mg (70% yield) of pure compound 34 as
a colorless oil: IR (film, cm-1) 3074, 2933, 2880, 2156, 1585,
1
1483, 1389, 1288, 1250, 1105, 1063, 1024, 870, 804, 731; H
NMR (CDCl3) δ 3.37 (t, J ) 5.9 Hz, 2 H, H-1), 4.34 (t, J ) 5.9
Hz, 2 H, H-2), 6.88 (d, J ) 8.8 Hz, 1 H, H-6′), 7.21 (dd, J )
8.8, 2.5 Hz, 1 H, H-5′), 7.39 (d, J ) 2.5 Hz, 1 H, H-3′); 13C
NMR (CDCl3) δ 32.99 (C-1), 67.30 (C-2), 114.97 (C-6′), 124.24
(C-2′), 127.07 (C-4′), 127.64 (C-5′), 130.15 (C-3′); 152.19 (C-1′);
MS (m/z, relative intensity) 251 (M+, 3), 249 (M+, 12), 247 (M+,
17), 166 (1), 164 (8), 162 (12), 137 (2), 135 (9), 133 (15), 86
(100). Anal. Calcd for (C9H7ONCl2S: C 43.57, H 2.84, N 5.64,
S 12.92. Found: C 43.80, H 2.31, N 5.39, S 12.53.
4-Ch lor op h en yleth yl Tetr a h yd r o-2H-p yr a n -2-yl Eth er
(36). A solution of 4-chlorophenol (35; 386 mg, 3.0 mmol) in
dimethyl sulfoxide (3 mL) was treated with potassium hydrox-
ide (350 mg, 6.2 mmol) and bromoethyl tetrahydropyranyl
ether (650 mg, 3.1 mmol). The mixture was stirred at room
temperature overnight. After the usual workup, the residue
was purified by column chromatography (silica gel) using
hexanes-EtOAc (19:1) as eluent to afford 592 mg (77% yield)
of pure compound 36 as a yellow oil: IR (film, cm-1) 2943,
2874, 1597, 1492, 1456, 1284, 1248, 1140, 1080, 1036, 989, 824,
667; 1H NMR (CDCl3) δ 1.55-1.81 (m, 6 H, H-3′′, H-4′′, H-5′′),
3.55 (m, 1 H, H-6′′a), 3.77-4.03 (m, 3 H, H-1, H6′′b), 4.06-
4.15 (m, 2 H, H-2), 4.69 (distorted t, J ) 3.5 Hz, 1 H, H-2′′),
6.85 (d, J ) 8.9 Hz, 2 H, H-2′), 7.21 (d, J ) 8.9 Hz, 2 H, H-3′);
13C NMR (CDCl3) δ 19.32 (C-4′′), 25.36 (C-5′′), 30.45 (C-3′′),
62.15 (C-6′′), 65.72 (C-1), 67.75 (C-2), 98.99 (C-2′′), 115.98 (C-
2′), 125.63 (C-4′), 129.19 (C-3′), 157.52 (C-1′); MS (m/z, relative
intensity) 258 (M+, 5), 256 (M+, 14), 129 (64), 85 (100), 73 (58).
Anal. (C13H17O3Cl) C, H.
4-Ch lor op h en oxyeth a n ol (37). To a solution of compound
36 (500 mg, 2.0 mmol) in methanol (20 mL) was added
pyridinium 4-toluenesulfonate (30 mg). The mixture was
stirred at room temperature for 16 h. The reaction was
quenched as depicted for compound 12. The product was
purified by column chromatography (silica gel) eluting with
hexanes-EtOAc (9:1) to afford 260 mg (78% yield) of pure
alcohol 37 as a colorless oil: IR (film, cm-1) 3370, 2934, 2876,
1597, 1493, 1452, 1287, 1246, 1092, 1053, 916, 824, 667; MS
(m/z, relative intensity) 174 (M+, 20) 172 (M+, 63), 130 (46),
128 (100).
4-Ch lor op h en oxyeth yl 4-Tolu en esu lfon a te (38). A solu-
tion of alcohol 37 (195 mg, 1.13 mmol) in pyridine (3 mL) was
treated with tosyl chloride (300 mg, mmol) according to the
general procedure. The product was purified by column chro-
matography (silica gel) eluting with hexanes-EtOAc (19:1) to
afford 301 mg (92% yield) of pure tosylate 38 as a colorless
oil: MS (m/z, relative intensity) 328 (M+, 1), 326 (M+, 3), 199
(35), 172 (19), 155 (26), 128 (97), 91 (100).
2-Ch lor o-4-p h en oxyp h en oxyeth yl Th iocya n a te (43). To
a solution of tosylate 42 (120 mg, 0.29 mmol) in dimethylfor-
mamide (3 mL) was added potassium thiocyanate (300 mg,
mmol). The reaction was heated at 100 °C with vigorous
stirring for 6 h. The reaction was quenched as depicted for
15. The residue was purified by column chromatography (silica
gel) eluting with hexanes-EtOAc (9:1) to afford 65 mg (73%
yield) of pure compound 43 as a colorless oil: IR (film, cm-1
)
2918, 2850, 2156, 1481, 1217, 1055, 1024, 924, 876, 824, 961;
1H NMR (CDCl3) δ 3.38 (t, J ) 5.9 Hz, 2 H, H-1), 4.34 (t, J )
5.9 Hz, 2 H, H-2), 6.91-7.38 (m, 8 H, aromatic protons); 13C
NMR (CDCl3) δ 33.26 (C-1), 68.10 (C-2), 116.06 (C-2′), 118.26
(C-5′), 118.51 (C-6′), 121.38 (C-3′), 123.49 (C-4′′), 124.63 (C-
2′′), 129.84 (C-3′′), 149.64 (C-4′), 152.09 (C-1′), 157.16 (C-1′′);
MS (m/z, relative intensity) 307 (M+, 7), 305 (M+, 20), 221 (13),
219 (36), 86 (42), 77 (100). Anal. (C15H12O2NSCl) C, H.
2-Br om o-2-p h en oxyp h en yleth a n ol (45). Compound 45
was prepared from 44 (510 mg, 1.3 mmol) following the method
of preparation described for 12. Purification by column chro-
matography eluting with hexanes-EtOAc (17:1) gave 256 mg
(64% yield) of pure alcohol 45 as a colorless oil: Rf 0.20
(hexanes-EtOAc, 4:1); IR (film, cm-1) 3391, 2930, 2858, 1589,
1490, 1457, 1217, 1047, 870, 750; MS (m/z, relative intensity)
310 (M+, 93), 308 (M+, 100), 266 (68), 264 (69), 157 (25), 77
(75).
2-Br om o-4-p h en oxyp h en ylet h yl 4-Tolu en esu lfon a t e
(46). Alcohol 45 (220 mg, 0.71 mmol) was treated with tosyl
chloride according to the general procedure. After the usual
workup, 310 mg (94% yield) of pure product as colorless oil
were isolated that were used in the next step without further
purification: Rf 0.30 (hexanes-EtOAc, 4:1); IR (film, cm-1
)
3067, 2953, 2876, 1589, 1496, 1360, 1267, 1215, 1020, 910, 814,
754, 692; MS (m/z, relative intensity) 464 (M+, 6), 462 (M+,
6), 310 (15), 308 (13), 266 (33), 264 (33), 199 (86), 155 (32), 91
(73), 77 (100).
2-Br om o-4-p h en oxyp h en oxyeth yl Th iocya n a te (47).
Compound 46 (273 mg, 0.60 mmol) was treated with potassium
thiocyanate as depicted for compound 13. Purification by
column chromatography (silica gel) employing hexanes-EtOAc
(9:1) as eluent afforded 130 mg (62% yield) of pure 47 as a
colorless oil: Rf 0.36 (hexanes-EtOAc, 4:1); IR (film, cm-1
)
3067, 2934, 2877, 2156, 1587, 1483, 1265, 1215, 1070, 1043,
4-Ch lor op h en oxyeth yl Th iocya n a te (39). A solution of
tosylate 38 (250 mg, 0.77 mmol) in dimethylformamide (3 mL)
was treated with potassium thiocyanate (500 mg, 5.1 mmol)
according to the method of preparation of 15. After the usual
workup, the product was purified by column chromatography
(silica gel) eluting with hexanes-EtOAc (19:1) to afford 105
mg (63% yield) of pure compound 39 as a colorless oil: IR (film,
cm-1) 2941, 2878, 2156, 1597, 1491, 1464, 1283, 1244, 1171,
1
1022, 910, 874, 756, 699; H NMR (CDCl3) δ 3.37 (t, J ) 5.9
Hz, 2 H, H-1), 4.33 (t, J ) 5.9 Hz, 2 H, H-2), 6.88-7.37 (m, 8
H, aromatic protons); 13C NMR (CDCl3) δ 33.26 (C-1), 67.98
(C-2), 113.40 (C-2′), 115.60 (C-2′′), 118.43 (C-5′), 119.01 (C-6′),
123.46 (C-4′′), 124.34 (C-3′), 129.83 (C-3′′), 150.59 (C-4′), 152.28
(C-1′), 157.24 (C-1′′); MS (m/z, relative intensity) 351 (M+, 69),
349 (M+, 66), 265 (60), 263 (61), 128 (19), 86 (32), 77 (100).
Anal. (C15H12O2NSBr) C, H.
1
1092, 1030, 824, 664; H NMR (CDCl3) δ 3.30 (t, J ) 5.8 Hz,
2 H, H-1), 4.26 (t, J ) 5.8 Hz, 2 H, H-2), 6.85 (d, J ) 9.0 Hz,
2 H, H-2′), 7.25 (d, J ) 9.0 Hz, 2 H, H-3′); 13C NMR (CDCl3) δ
33.07 (C-1), 66.12 (C-2), 115.94 (C-2′), 126.66 (C-4′), 129.45 (C-
3′), 156.37 (C-1′); MS (m/z, relative intensity) 215 (M+, 10),
213 (M+, 28), 128 (13), 99 (17), 86 (100). Anal. (C9H8ONSCl)
C, H.
2-Iod o-4-p h en oxyp h en oxyeth yl Tetr a h yd r o-2H-p yr a n -
2-yl Eth er (49). Iodophenol 48 (225 mg, 0.72 mmol) was
treated with bromoethyl tetrahydropyranyl ether as depicted
for compound 11. The residue was purified by column chro-
matography (silica gel) employing a mixture of hexanes-
EtOAc (19:1) as eluant to afford 216 mg (68% yield) of pure

1836 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9
Szajnman et al.
compound 49 as a colorless oil: Rf 0.45 (hexanes-EtOAc, 4:1);
IR (film, cm-1) 3063, 2941, 1872, 1587, 1479, 1456, 1265, 1219,
1140, 1034, 891, 814, 750, 692; 1H NMR (CDCl3) δ 1.50-1.80
(m, 6 H, H-3′′′, H-4′′′, H-5′′′), 3.56 (m, 1 H, H-6′′′a), 3.83-4.07
(m, 3 H, H-1, H-6′′′b), 4.17 (distorted t, J ) 4.7 Hz, 2 H, H-2),
4.80 (distorted t, J ) 3.1 Hz, 1 H, H-2′′′), 6.82 (d, J ) 8.9 Hz,
1 H, H-6′), 6.92-7.09 (m, 4 H, aromatic protons), 7.25-7.34
(m, 2 H, aromatic protons), 7.46 (d, J ) 2.8 Hz, 1 H); 13C NMR
(CDCl3) δ 19.22 (C-4′′′), 25.40 (C-5′′′), 30.50 (C-3′′′), 62.05 (C-
6′′′), 65.60 (C-1), 69.53 (C-2), 86.74 (C-2′), 99.02 (C-2′′′), 113.07
(C-6′), 117.91 (C-2′′), 120.18 (C-5′), 122.95 (C-4′′), 129.67 (C-
3′), 130.35 (C-3′′), 151.02 (C-4′), 154.14 (C-1′′), 157.80 (C-1′);
MS (m/z, relative intensity) 440 (M+, 10), 356 (2), 312 (23),
129 (100); HRMS calcd for (C19H21O4I) 440.0485, found 440.0483.
Anal. (C19H21IO4) C, H.
2-Iod o-4-p h en oxyp h en oxyeth a n ol (50). Compound 49
(190 mg, 0.43 mmol) was treated with pyridinium 4-toluene-
sulfonate as depicted for the preparation of 12 to give 91 mg
(59% yield) of pure alcohol 50 as a colorless oil: Rf 0.16
(hexanes-EtOAc, 4:1); IR (film, cm-1) 3366, 3065, 3034, 2936,
2874, 1475, 1456, 1265, 1217, 1074, 1043, 889, 816, 750, 692;
MS (m/z, relative intensity) 356 (M+, 59), 312 (97), 264 (12),
230 (16), 220 (20), 186 (30), 77 (100).
yielded 205 mg (75% yield) of pure tosylate 56 as a colorless
oil: Rf 0.29 (hexanes-EtOAc, 4:1); IR (film, cm-1) 3067, 2953,
1591, 1574, 1476, 1456, 1360, 1177, 1096, 1074, 1022, 928, 816,
775, 664; MS (m/z, relative intensity) 372 (M+, 24), 370 (M+,
23), 199 (100), 155 (84), 91 (87).
3-Br om op h en oxyeth yl Th iocya n a te (57). Tosylate 56
(200 mg, 0.43 mmol) reacted with potassium thiocyanate as
depicted for 13. Purification by column chromatography (silica
gel) eluting with hexanes-EtOAc (19:1) afforded 60 mg (54%
yield) of pure compound 57 as a colorless oil: Rf 0.47 (hex-
anes-EtOAc, 4:1); IR (film, cm-1) 2924, 2853, 2156, 1589, 1474,
1283, 1227, 1067, 1030, 901, 860, 679; 1H NMR (CDCl3) δ 3.30
(t, J ) 5.8 Hz, 2 H, H-1), 4.28 (t, J ) 5.8 Hz, 2 H, H-2), 6.85
(dt, J ) 6.3, 2.9 Hz, 1 H, H-6′), 7.07-7.20 (m, 3 H, aromatic
protons); 13C NMR (CDCl3) δ 33.06 (C-1), 66.01 (C-2), 113.50
(C-6′), 118.03 (C-5′), 122.87 (C-3′), 124.87 (C-4′), 130.69 (C-5′),
158.48 (C-1′); MS (m/z, relative intensity) 259 (M+, 99), 257
(M+, 100), 201 (6), 199 (7), 187 (10), 185 (11), 174 (27), 172
(28), 157 (20), 155 (20), 145 (20), 143 (21), 86 (89). Anal. (C9H8-
ONSBr) C, H.
3-Br om op h en yl 4-Nitr op h en yl Eth er (58). A solution of
3-bromophenol (53; 1.73 g, 10 mmol) in dimethyl sulfoxide (10
mL) was treated with potassium hydroxide (600 mg, 11 mmol).
The mixture was stirred at room temperature for 10 min.
Then, 4-chloronitrobenzene (1.57 g, 10 mmol) and cuprous
chloride (50 mg) were added and the mixture was stirred at
room temperature overnight. The reaction was worked up as
depicted for 11. The product was purified by column chroma-
tography (silica gel) eluting with hexanes-EtOAc (50:1) to
afford 2.099 g (71% yield) of pure compound 58 as a colorless
oil: Rf 0.20 (hexanes-EtOAc, 19:1); IR (film, cm-1) 1580, 1516,
1489, 1341, 1240, 1111, 1061, 895, 847, 775, 750, 671; MS (m/
z, relative intensity) 295 (M+, 100), 293 (M+, 92), 265 (14), 263
(13), 168 (54), 157 (16), 155 (19), 139 (41), 128 (33).
2-Iodo-4-ph en oxyph en oxyeth yl 4-Tolu en esu lfon ate (51).
Alcohol 50 (80 mg, 0.22 mmol) was treated with tosyl chloride
as described for the preparation of 13 affording 119 mg (100%
yield) of pure tosylate 51 as a colorless oil: Rf 0.35 (hexanes-
EtOAc, 4:1); IR (film, cm-1) 2924, 2872, 1477, 1456, 1267, 1217,
1176, 1022, 928, 891, 816, 777; MS (m/z, relative intensity)
510 (M+, 16), 311 (13), 199 (100), 155 (34), 91 (82).
2-Iod o-4-p h en oxyp h en oxyet h yl 4-Th iocya n a t e (52).
Compound 51 (110 mg, 0.22 mmol) was treated with potassium
thiocyanate as depicted for 15. The residue was purified by
column chromatography (silica gel) eluting with hexanes-
EtOAc (19:1) to give 45 mg (52% yield) of pure compound 52
4-(3-Br om op h en oxy)a n ilin e (59). A solution of compound
58 (1.5 g, 5.1 mmol) in ethyl acetate (50 mL) in the presence
of palladium on charcoal (100 mg) was treated with hydrogen
at 3 atm, and the mixture was stirred at room temperature
overnight. The mixture was filtered, and the solvent was
evaporated to give 1.220 g (91% yield) of pure amine 59 as a
pale yellow oil that was used as such in the next step: Rf 0.61
(hexanes-EtOAc, 4:1); IR (film, cm-1) 2824, 2594, 2575, 1570,
1504, 1485, 1246, 1198, 831, 779, 692; MS (m/z, relative
intensity) 265 (M+, 5), 263 (M+, 5), 185 (100), 156 (17), 108
(99), 80 (69).
as a colorless oil: Rf 0.31 (hexanes-EtOAc, 4:1); IR (film, cm-1
)
3063, 3040, 2926, 2876, 2154, 1585, 1481, 1387, 1267, 1215,
1070, 1038, 878, 816, 773, 692; 1H NMR (CDCl3) δ 3.39 (t, J )
5.9 Hz, 2 H, H-1), 4.31 (t, J ) 5.9 Hz, 2 H, H-2), 6.81 (d, J )
8.9 Hz, 1 H, H-6′), 6.93-7.13 (m, 4 H, aromatic protons), 7.29-
7.37 (m, 2 H, aromatic protons), 7.46 (d, J ) 2.8 Hz, 1 H, H-3′);
13C NMR (CDCl3) δ 33.31 (C-1), 67.90 (C-2), 87.04 (C-2′), 113.80
(C-6′), 118.28 (C-2′′), 120.11 (C-5′), 123.33 (C-4′′), 129.80 (C-
3′), 130.31 (C-3′′), 152.17 (C-4′), 152.94 (C-1′′), 157.39 (C-1′);
MS (m/z, relative intensity) 397 (M+, 69), 311 (45), 128 (74),
77 (100). Anal. (C15H12O2NSI) C, H.
4-(3-Br om op h en oxy)p h en ol (60). To a solution of amine
59 (1.00 g, 3.8 mmol) in glacial acetic acid (12 mL) was added
sulfuric acid (3.6 mL). The mixture was cooled at 0 °C, and a
solution of sodium nitrite (350 mg, 5.2 mmol) in water (2 mL)
was added dropwise. The reaction mixture was stirred at 0
°C for 20 min. Then, urea (120 mg) and cold water (12 mL)
was added. This mixture was kept at 0 °C and was carefully
added to a boiling mixture of water (25 mL) and concentrated
sulfuric acid (6 mL). After the addition was complete the
reaction was stirred for an additional 10 min at the boiling
temperature. The mixture was allowed to cool and was
partitioned between water (100 mL) and methylene chloride
(70 mL). The aqueous phase was extracted with methylene
chloride 2 × 70 mL), and the combined organic layers were
washed with brine (2 × 50 mL), dried (MgSO4), and the solvent
was evaporated. The residue was purified by column chroma-
tography eluting with hexanes-EtOAc (9:1) to yield 374 mg
(37% yield) of pure phenol 60 as a colorless oil: Rf 0.32
(hexanes-EtOAc, 4:1); IR (film, cm-1) 3377, 1592, 1508, 1489,
1362, 1217, 1096, 1070, 847, 815, 692; MS (m/z, relative
intensity) 266 (M+, 11), 264 (M+, 12), 186 (100), 157 (21), 129
(14), 109 (25).
3-Br om oph en oxyeth yl Tetr ah ydr o-2H-pyr an -2-yl Eth er
(54). Compound 54 was prepared from 3-bromophenol (53; 500
mg, 2.89 mmol) according to the method of preparation for
compound 11. The residue was purified by column chroma-
tography (silica gel) employing hexanes-EtOAc (9:1) as eluent
to yield 336 mg (39% yield) of pure compound 54 as a colorless
oil: Rf 0.34 (hexanes-EtOAc, 4:1); IR (film, cm-1) 2941, 2871,
1591, 1572, 1476, 1067, 1034, 991, 872, 772, 681; 1H NMR
(CDCl3) δ 1.54-1.87 (m, 6 H, H-3′′, H-4′′, H-5′′), 3.42-3.57 (m,
1 H, H-6′′a), 3.74-4.08 (m, 3 H, H-1, H-6′′b), 4.13 (t, J ) 4.6
Hz, 2 H, H-2), 4.69 (distorted t, J ) 3.2 Hz, 1 H, H-2′′), 6.80-
7.20 (m, 5 H, aromatic protons); 13C NMR (CDCl3) δ 19.29 (C-
4′′), 25.38 (C-5′′), 30.46 (C-3′′), 62.13 (C-6′′), 65.68 (C-1), 67.71
(C-2), 98.97 (C-2′′), 113.74 (C-6′), 118.06 (C-2′), 122.69 (C-3′),
123.89 (C-4′), 130.41 (C-5′), 158.70 (C-1′); MS (m/z, relative
intensity) 302 (M+, 25), 300 (M+, 28), 200 (10), 174 (16), 172
(18), 129 (35), 101 (66), 85 (100). Anal. (C12H15BrO2) C, H.
3-Br om op h en oxyeth a n ol (55). Alcohol 55 was prepared
from ether 54 (233 mg, 0.77 mmol) as described for 12.
Evaporation of the solvent afforded 170 mg (100% yield) of
pure alcohol 55 (colorless oil) that was used as such in the
next step: Rf 0.08 (hexanes-EtOAc, 4:1); IR (film, cm-1) 3356,
2934, 2874, 1589, 1574, 1476, 1287, 1231, 1051, 928, 768, 681;
MS (m/z, relative intensity) 218 (M+, 22), 216 (M+, 24), 174
(95), 172 (100), 157 (18), 155 (17), 93 (31).
4-(3-Br om op h en oxy)p h en oxyeth yl Tetr a h yd r o-2H-p y-
r a n -2-yl Eth er (61). Phenol 60 (359 mg, 1.36 mmol) was
condensed with bromoethyl tetrahydropyranyl ether (358 mg,
1.7 mmol) as described for 11. The product was purified by
column chromatography (silica gel) employing hexanes-EtOAc
(19:1) as eluent to afford 320 mg (60% yield) of pure compound
61 as a colorless oil: Rf 0.24 (hexanes-EtOAc, 10:1); 1H NMR
3-Br om op h en oxyeth yl 4-Tolu en esu lfon a te (56). Alcohol
55 (160 mg, 0.74 mmol) was treated with tosyl chloride
described for 13. Evaporation of the solvent of the solvent

Aryloxyethyl Thiocyanates as Inhibitors of T. cruzi
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9 1837
H-1, H-6′′′b), 3.99-4.15 (m, 2 H, H-2), 4.71 (distorted t, J )
(CDCl3) δ 1.50-1.91 (m, 6 H, H-3′′′, H-4′′′, H-5′′′), 3.54 (m, 1
H, H-6′′′a), 3.74-3.95 (m, 3 H, H-1, H-6′′′b), 3.98-4.15 (m, 2
H, H-2), 4.69 (distorted t, J ) 3.3 Hz, 1 H, H-2′′′), 6.77-7.38
(m, 8 H, aromatic protons); 13C NMR (CDCl3) δ 19.25 (C-4′′′),
25.32 (C-3′′′), 30.40 (C-5′′′), 62.01 (C-6′′′), 65.75 (C-1), 67.86
(C-2), 98.84 (C-2′′′), 115.73 (C-6′′), 117.52 (C-2′), 120.57 (C-3′),
122.31 (C-2′′), 125.49 (C-3′′), 129.45 (C-4′′), 132.36 (C-5′′),
155.11 (C-4′), 157.64 (C-1′), 158.35 (C-1′′); MS (m/z, relative
intensity) 394 (M+, 9) 392 (M+, 10), 266 (9), 264 (9), 129 (100),
85 (70); HRMS calcd for (C19H21O4Br) 392.0623, found 392.0619.
4-(3-Br om op h en oxy)p h en oxyeth a n ol (62). Compound
61 (302 mg, 0.77 mmol) was reacted with pyridinium 4-tolu-
enesulfonate according to the procedure of 12 and was purified
by column chromatography (silica gel) eluting with hexanes-
EtOAc (9:1) to give 203 mg (85% yield) of pure alcohol 62 as a
white solid: mp 49-50 °C; Rf 0.44 (hexanes-EtOAc, 4:1); IR
(KBr, cm-1) 3292, 2930, 2872, 1587, 1506, 1491, 1248, 1221,
1107, 1074, 1053, 891; MS (m/z, relative intensity) 310 (M+,
16), 308 (M+, 17), 266 (19), 264 (22), 230 (100), 186 (98).
4-(3-Br om op h en oxy)p h en oxyeth yl 4-Tolu en esu lfon a te
(63). Alcohol 62 (178 mg, 0.58 mmol) was treated with
4-toluenesulfonyl chloride as depicted for 13 affording 254 mg
3.2 Hz, 1 H, H-2′′′), 6.77-7.24 (m, 8 H, aromatic protons); 13
C
NMR (CDCl3) δ 16.16 (PhMe), 19.37 (C-4′′′), 25.42 (C-3′′′), 30.52
(C-5′′′), 62.17 (C-6′′′), 65.90 (C-1), 68.04 (C-2), 98.99 (C-2′′′),
115.82 (C-6′′), 118.11 (C-2′), 119.17 (C-4′′), 123.09 (C-3′), 126.92
(C-5′′), 129.24 (C-2′′), 131.26 (C-3′′), 151.29 (C-4′), 154.62 (C-
1′), 155.75 (C-1′′); MS (m/z, relative intensity) 328 (M+, 1), 256
(7), 129 (40), 85 (100); HRMS calcd for (C20H24O4) 328.1675,
found 328.1680.
4-(2-Meth ylp h en oxy)p h en oxyeth a n ol (70). Ether 69
(405 mg, 1.2 mmol) was treated as described for the prepara-
tion of 12. After the usual workup and evaporation of the
solvent afforded 333 mg (100% yield) of pure alcohol 70 as a
colorless oil: Rf 0.19 (hexanes-EtOAc, 3:1); IR (film, cm-1
)
3362, 2934, 2868, 1585, 1506, 1460, 1299, 1229, 1203, 1118,
1088, 1052, 880, 834, 762; MS (m/z, relative intensity) 244 (M+,
35), 200 (38), 172 (24), 128 (100).
4-(2-Meth ylph en oxy)p h en oxyeth yl 4-Tolu en esu lfon a te
(71). Alcohol 70 (207 mg, 0.85 mmol) was treated with tosyl
chloride as depicted for 13. The product was purified by column
chromatography (silica gel) using hexanes-EtOAc (9:1) as
eluent to afford 227 (67% yield) of pure tosylate 71 as a
colorless oil and 30 mg of unreacted alcohol 70: Rf 0.32
(hexanes-EtOAc, 3:1); IR (film, cm-1) 2928, 1510, 1492, 1456,
1365, 1233, 1172, 1027930, 822, 774, 665; MS (m/z, relative
intensity) 398 (M+, 28), 199 (100), 155 (40), 91 (95).
(95% yield) of pure tosylate 63 as a colorless oil: IR (film, cm-1
2924, 2874, 1597, 1504, 1484, 1362, 1228, 1177, 1022, 934, 821,
777, 664; MS (m/z, relative intensity) 464 (M+, 10), 462 (M+,
10), 384 (31), 199 (100), 155 (47), 91 (87)
)
4-(3-Br om op h en oxy)p h en oxyeth yl Th iocya n a te (64).
Tosylate 63 (219 mg, 0.47 mmol) was reacted with potassium
thiocyanate as described for 15. The product was purified by
column chromatography employing hexanes-EtOAc (19:1) to
afford 116 mg (71% yield) of pure compound 57 as a colorless
oil: Rf 0.38 (hexanes-EtOAc, 3:1); IR (film, cm-1) 2934, 2870,
2156, 1587, 1503, 1489, 1219, 1070, 1032, 866, 842, 827, 692;
1H NMR (CDCl3) δ 3.31 (t, J ) 5.8 Hz, 2 H, H-1), 4.29 (t, J )
5.8 Hz, 2 H, H-2), 6.80-7.09 (m, 6 H, aromatic protons), 7.27-
7.41 (m, 2 H, aromatic protons); 13C NMR (CDCl3) δ 33.29 (C-
1), 66.41 (C-2), 115.94 (C-6′′), 117.86 (C-2′), 120.69 (C-3′),
122.69 (C-2′′), 125.63 (C-3′′), 129.61 (C-4′′), 132.52 (C-5′′),
153.92 (C-4′), 157.37 (C-1′), 158.07 (C-1′′); MS (m/z, relative
intensity) 351 (M+, 18), 349 (M+, 18), 271 (50), 265 (14), 263
(16), 185 (100), 157 (17), 155 (15), 129 (38); HRMS calcd for
(C15H12O2NSBr) 348.9772, found 348.9779.
2-Meth ylp h en yl 4-Nitr op h en yl Eth er (66). A mixture of
o-cresol (65; 2.60 g, 24 mmol) and 4-chloronitrobenzene (3.78
g, 24 mmol) was treated as depicted for 58. The product was
purified by column chromatography (silica gel) eluting with
hexane to afford 3.024 g (54% yield) of pure compound 66 as
a colorless oil: Rf 0.43 (hexanes-EtOAc, 4:1); MS (m/z, relative
intensity) 229 (M+, 100), 212 199, 182 168 153 91.
4-(2-Meth ylp h en oxy)a n ilin e (67). Compound 66 (2.891
g, 12.6 mmol) was reacted with hydrogen as depicted for 59
affording 2.365 g (94% yield) of pure aniline 67 as a colorless
oil that was used as such in the next step: Rf 0.13 (hexanes-
EtOAc, 4:1); IR (film, cm-1) 3441, 3371, 2934, 2859, 1629, 1521,
1489, 1242, 1204, 1109, 875, 837, 748; MS (m/z, relative
intensity) 199 (M+, 100), 108 (81), 93 (81).
4-(2-Met h ylp h en oxy)p h en ol (68). Compound 68 was
prepared following a similar protocol depicted for 60 starting
from aniline 67 (1.60 g, 8.0 mmol) and was purified by column
chromatography (silica gel) eluting with hexanes-EtOAc (24:
1) to yield 417 mg (26% yield) of pure phenol 68 as a colorless
oil: Rf 0.59 (hexanes-EtOAc, 3:1); IR (film, cm-1) 3350, 1510,
1495, 1468, 1233, 1112, 828, 774; MS (m/z, relative intensity)
200 (M+, 100), 107 (70), 94 (50), 90 (50), 65 (70).
4-(2-Meth ylp h en oxy)p h en oxyeth yl Th iocya n a te (72).
Tosylate 71 (196 mg, 0.68 mmol) was treated with potassium
thiocyanate as depicted for 15. The residue was purified by
column chromatography (silica gel) eluting with hexanes-
EtOAc (93:7) to afford 97 mg (50% yield) of pure thiocyanate
72 as a colorless oil: Rf 0.12 (hexanes-EtOAc, 9:1); IR (film,
cm-1) 3067, 2927, 2869, 2161, 1588, 1512, 1471, 1301, 1235,
1207, 1120, 1044, 880, 833, 763; 1H NMR (CDCl3) δ 2.26 (s, 3
H, PhMe), 3.29 (t, J ) 5.8 Hz, 2 H, H-1), 4.26 (t, J ) 5.8 Hz,
2 H, H-2), 6.81 (dd, J ) 7.9, 1.3 Hz, 1 H), 6.87 (mAB, 4 H,
H-2, H-3), 6.97-7.24 (m, 3 H, aromatic protons); 13C NMR
(CDCl3) δ 16.08 (PhMe), 33.28 (C-1), 66.47 (C-2), 115.88 (C-
6′′), 118.43 (C-2′), 119.04 (C-4′′), 123.38 (C-3′), 126.97 (C-5′′),
129.24 (C-2′′), 131.31 (C-3′′), 152.12 (C-4′), 153.28 (C-1′), 155.27
(C-1′′); MS (m/z, relative intensity) 285 (M+, 34), 213 (35), 199
(38) 86 (100); HRMS calcd for (C16H15O2NS) 285.0824, found
285.0829. Anal. Calcd for C16H15O2NS: C 67.34, H 5.30, N 4.91,
S 11.23. Found: C 66,27, H 5.14, N 5.03, S 11.17.
2,6-Dim eth ylp h en yl 4-Nitr op h en yl Eth er (74). 2,6-Dim-
ethylphenol (73; 3.30 g, 25 mmol) was reacted with 4-chlo-
ronitrobenzene (3.87, 22 mmol) according to the method of
preparation of 58. The product was purified by column
chromatography (silica gel) eluting with hexane-Cl2CH2 (24:
1) to yield 3.356 g (63% yield) of pure compound 74 as a green
solid: Rf 0.56 (hexane-CH2Cl2, 1:1); mp 51-52 °C; IR (KBr,
cm-1) 3448, 2927, 1605, 1529, 1488, 1342, 1237, 1178, 1107,
851, 786, 757; MS (m/z, relative intensity) 243 (M+, 100), 226
(16), 196 (17), 105 (43), 77 (45).
4-Am in op h en yl 2,6-Dim eth ylp h en yl Eth er (75). Nitro
derivative 74 (1.95 g, 8.02 mmol) was hydrogenated as depicted
for 59 affording 1.60 g (94% yield) of pure compound 74 as a
white solid: mp 88-90 °C; Rf 0.20 (hexanes-EtOAc, 4:1); IR
(KBr, cm-1) 3434, 3368, 3348, 3230, 3059, 2953, 2921, 1637,
1506, 1473, 1274, 1216, 1091, 867, 841, 782; MS (m/z, relative
intensity) 213 (M+, 100), 108 (42), 93 (57).
2,6-Dim eth ylp h en oxyp h en ol (76). Amino derivative 75
(1.30 g, 6.10 mmol) was treated as described for the prepara-
tion of 60. The residue was purified by column chromatography
(silica gel) eluting with hexanes-EtOAc (19:1) to afford 125
mg (10% yield) of pure phenol 76 as a colorless oil: Rf 0.26
(hexanes-EtOAc, 4:1); MS (m/z, relative intensity) 214 (M+,
100), 121 (55).
4-(2-Meth ylp h en oxy)p h en oxyeth yl Tetr a h yd r o-2H-p y-
r a n -2-yl Eth er (69). Phenol 68 (505 mg, 2.5 mmol) was
condensed with bromoethyl tetrahydropyranyl ether according
to the procedure of 13 and was purified by column chroma-
tography (silica gel) employing hexanes-EtOAc (97:3) as
eluent to give 584 mg (60% yield) of pure ether 69 as a colorless
oil: Rf 0.62 (hexanes-EtOAc, 3:1); IR (film, cm-1) 3059, 2954,
2881, 1597, 1506, 1493, 1453, 1215, 1196, 1045, 986, 828, 775;
1H NMR (CDCl3) δ 1.52-1.86 (m, 6 H, H-3′′′, H-4′′′, H-5′′′),
2.27 (s, 3 H, PhMe), 3.53 (m, 1 H, H-6′′′a), 3.75-3.94 (m, 3 H,
2,6-Dim eth ylp h en oxyp h en yl Tetr a h yd r o-2H-p yr a n -1-
yl Eth er (77). Compound 76 (110 mg, 0.51 mmol) was treated
with bromoethyl tetrahydropyranyl ether as described for 11.
The product was purified by column chromatography (silica
gel) eluting with hexanes-EtOAc (19:1) to afford 94 mg (54%
yield) of pure compound 77 as a colorless oil: Rf 0.43 (hex-

1838 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9
Szajnman et al.
anes-EtOAc, 4:1); 1H NMR (CDCl3) δ 1.53-1.85 (m, 6 H,
H-3′′′, H-4′′′, H-5′′′), 2.12 (s, 6 H, PhMe), 3.51 (m, 1 H, H-6′′′a),
3.75-4.00 (m, 3 H, H-1, H-6′′′b), 4.02-4.12 (m, 2 H, H-2), 4.69
(distorted t, J ) 2.9 Hz, 1 H, H-2′′′), 6.65 (d, J ) 9.2 Hz, 2 H,
H-2), 6.82 (d, J ) 9.1 Hz, 2 H, H-3), 7.05 (m, 3 H, aromatic
protons); 13C NMR (CDCl3) δ 16.29 (PhMe), 19.33 (C-4′′′), 25.39
(C-3′′′), 30.48 (C-5′′′), 62.12 (C-2′′′), 65.90 (C-1), 68.05 (C-2),
98.93 (C-2′′′), 115.14 (C-2′), 115.77 (C-3′), 124.81 (C-4′′), 128.91
(C-3′′), 131.50 (C-2′′), 151.53 (C-4′), 152.11 (C-1′), 153.39 (C-
1′′); MS (m/z, relative intensity) 342 (M+, 26), 214 (32), 129
(100); HRMS calcd for (C21H26O4) 342.1831, found 342.1834.
2-Nitr oxa n th on e (79). To a solution of xanthone (78; 5.00
g, 25.5 mmol) in concentrated sulfuric acid (14 mL) cooled at
0 °C was added dropwise fuming nitric acid (0.9 mL, 12.8
mmol) in concentrated sulfuric acid (3 mL). The reaction
mixture was stirred at 0 °C for 40 min. The mixture was
poured onto crushed ice. The solid was filtered off and was
washed with cold water until pH 7. The residue was used as
such in the next step without further purification. An analyti-
cal sample was purified by column chromatography (silica gel)
eluting with hexanes-EtOAc (4:1) as eluent to afford pure
compound 79 as a white solid: mp 195-198 °C; Rf 0.50
(toluene); IR (KBr, cm-1) 1668, 1614, 1533, 1462, 1348, 833,
770, 746, 669; 1H NMR (CDCl3) δ 7.34-7.58 (m, 3 H, H-5, H-7),
7.64 (d, J ) 9.1 Hz, 1 H, H-4), 7.81 (m, 1 H, H-6), 8.35 (dd, J
) 8.0, 1.6 Hz, 1 H, H-8), 8.55 (dd, J ) 9.2, 2.8 Hz, 1 H, H-3),
9.21 (d, J ) 2.8 Hz, 1 H, H-1); 13C NMR (CDCl3) δ 118.21 (C-
5), 119.66 (C-4), 121.43 (C-8a), 123.56 (C-7), 123.92 (C-9a),
125.27 (C-4), 126.75 (q), 126.97 (C-3), 129.01 (C-8), 135.89 (C-
6), 155.88 (C-5a), 159.20 (C-4a); MS (m/z, relative intensity)
241 (M+, 36), 196 (100), 168 (49), 139 (88).
(dd, J ) 8.0, 1.7 Hz, 1 H, H-8′); 13C NMR (CDCl3) δ 19.35 (C-
4′′), 25.43 (C-3′′), 30.53 (C-5′′), 62.20 (C-2′′), 65.73 (C-1), 68.22
(C-2), 99.02 (C-2′′), 107.04 (C-1′), 117.94 (C-5′), 119.31 (C-4′),
121.31 (C-8a′), 122.13 (C-9a′), 123.68 (C-7′), 125.32 (C-3′), 126.70
(C-8′), 134.53 (C-6′), 151.06 (C-4a′), 155.35 (C-2′), 156.15 (C-
5a′); MS (m/z, relative intensity) 340 (M+, 9), 240 (26), 225 (20),
212 (62), 155 (11), 139 (21), 129 (26), 85 (80), 73 (74), 41 (100);
HRMS calcd for (C20H20O5) 340.1311, found 340.1315.
2-(2-Hyd r oxyeth -1-yl)xa n th on e (83). The tetrahydropy-
ranyl group of compound 82 (150 mg, 0.44 mmol) was cleaved
as described for 12 to give 112 mg (100% yield) of pure alcohol
83 as a white solid: mp 119-120 °C; IR (KBr, cm-1) 3428,
2943, 1651, 1617, 1488, 1467, 1326, 1219, 1151, 1074, 1049,
919, 753; 1H NMR (CDCl3) δ 2.13 (s, 1 H, -OH), 4.02 (distorted
t, J ) 4.5 Hz, 2 H, H-1), 4.22 (distorted t, J ) 4.5 Hz, 2 H,
H-2), 7.36-7.51 (m, 4 H, aromatic protons), 7.68-7.76 (m, 2
H, H-2), 8.24 (dd, J ) 8.0, 1.7 Hz, 1 H, H-8′); 13C NMR (CDCl3)
δ 61.34 (C-1), 69.94 (C-2), 106.95 (C-1′), 117.94 (C-5′), 119.53
(C-4′), 121.23 (C-8a′), 122.12 (C-9a′), 123.76 (C-7′), 125.05 (C-
3′), 126.67 (C-8′), 134.65 (C-6′), 151.17 (C-4a′), 155.00 (C-2′),
156.13 (C-5a′), 177.02 (C-9′); MS (m/z, relative intensity) 256
(M+, 31), 225 (17), 212 (100), 197 (7), 184 (24), 155 (10).
2-[2-(4-Tolu en esu lfon yloxy)eth -1-yl]xa n th on e (84). Al-
cohol 83 (100 mg, 0.39 mmol) was treated with tosyl chloride
(110 mg, 0.58 mmol) as described for 13 to afford 125 mg of
pure tosylate 84 (78% yield) as a white solid: IR (KBr, cm-1
)
2967, 2941, 1662, 1619, 1495, 1473, 1222, 1175, 1148, 1071,
1
1029; H NMR (CDCl3) δ 2.43 (s, 3 H, PhMe), 4.25 (m, 2 H,
H-2), 4.40 (m, 2 H, H-1), 7.19-7.25 (m, 1 H, aromatic protons),
7.34 (d, J ) 8.2 Hz, 2 H, H-3′′), 7.38-7.57 (m, 4 H, aromatic
protons), 7.83 (d, J ) 8.2 Hz, 2 H, H-2′′), 7.67-7.75 (m, 2 H,
H-), 8.31 (dd, J ) 8.0, 1.6 Hz, 1 H, H-8′); 13C NMR (CDCl3) δ
21.56 (PhMe), 66.03 (C-1), 67.93 (C-2), 106.84 (C-1′), 117.91
(C-5′), 119.52 (C-4′), 121.12 (C-8a′), 121.93 (C-9a′), 123.78 (C-
7′), 124.98 (C-3′), 126.57 (C-8′), 127.96 (C-2′′), 129.85 (C-3′′),
134.65 (C-6′), 144.97 (C-1′′), 151.20 (C-4a′), 154.27 (C-2′), 156.03
(C-5a′), 176.77 (C-9′); MS (m/z, relative intensity) 410 (M+, 26),
211 (22), 199 (96), 155 (52), 91 (100).
2-Am in oxa n th on e (80). A suspension of compound 79 in
ethyl acetate (100 mL) in the presence of palladium on charcoal
as catalyst (200 mg) was treated with hydrogen at 3 atm in a
Parr apparatus. The mixture was shaken at room temperature
for 6 h. The mixture was filtered and the solvent was
evaporated. The residue was purified by column chromatog-
raphy (silica gel) employing hexanes-EtOAc as eluent to afford
2.465 g (46% yield from xanthone, 91% yield taken the
equivalents of nitric acid used) of pure compound 80 as a
yellow solid: mp 190-192 °C; IR (KBr, cm-1) 3412, 3321, 1641,
1618, 1593, 1491, 1466, 1327, 1209, 1147, 881, 756, 625; Rf
2-(2-Th ia cya n oeth -1-yl)xa n th on e (85). A solution of to-
sylate 84 (114 mg, 0.28 mmol) in dimethylformamide (3 mL)
was treated with potassium thiocyanate (300 mg, 3.1 mmol)
as depicted for 15. After the usual treatment, the product was
purified by column chromatography employing a mixture of
hexanes-EtOAc (19:1) as eluent to afford 59 mg (71% yield)
of pure thiocyanate 75 as a white solid: mp 140-141 °C; IR
(KBr, cm-1) 2924, 2852, 2153, 1647, 1616, 1495, 1465, 1320,
1
0.72 (hexanes-EtOAc, 1:1); H NMR (CDCl3) δ 7.18 (dd, J )
8.8, 2.8 Hz, 1 H, H-3), 7.32-7.55 (m, 3 H, H-1, H-7, H-5), 7.37
(d, J ) 8.9 Hz, 1 H, H-4), 7.72 (m, 1 H, H-6), 8.29 (dd, J ) 8.0,
1.5 Hz, 1 H, H-8), 8.48 (s, 1 H, H-); 13C NMR (CDCl3-CD3OD,
20%) δ 108.45 (C-1), 117.78 (C-5), 118.67 (C-4), 120.85 (C-8a),
121.82 (C-9a), 123.27 (C-7), 124.08 (C-3), 126.13 (C-8), 134.43
(C-6), 143.24 (C-2), 156.07 (C-5a), 168.52 (C-4a), 177.80 (C-9);
MS (m/z, relative intensity) 211 (M+, 59), 196 (15), 69 (100).
1
1235, 1219, 1161, 1028, 888, 755; H NMR (CDCl3) δ 3.40 (t,
J ) 5.7 Hz, 2 H, H-1), 4.46 (t, J ) 5.7 Hz, 2 H, H-2), 7.36-
7.52 (m, 4 H, aromatic protons), 7.70-7.78 (m, 2 H, aromatic
protons), 8.31 (dd, J ) 9.0, 1.6 Hz, 1 H, H-8′); 13C NMR (CDCl3)
δ 33.12 (C-1), 66.46 (C-2), 106.92 (C-1′), 117.89 (C-5′), 119.69
(C-4′), 121.05 (C-8a′), 121.95 (C-9a′), 123.74 (C-7′), 124.94 (C-
3′), 126.48 (C-8′), 134.64 (C-6′), 151.63 (C-4a′), 154.04 (C-2′),
155.97 (C-5a′), 176.66 (C-9′); MS (m/z, relative intensity) 297
(M+, 82), 274 (24), 211 (100), 184 (25), 155 (47); HRMS calcd
for (C16H11O3NS) 297.0460, found 297.0459.
2-Hyd r oxyxa n th on e (81). A solution of compound 80 (770
mg, 3.65 mmol) in glacial acetic acid (10 mL) was treated as
described for the preparation of 60 to afford 280 mg (36% yield)
of pure compound 81 as a red solid: Rf 0.10 (hexanes-EtOAc,
3:2); mp 176-177 °C; IR (KBr, cm-1) 3312, 1659, 1628, 1487,
1460, 1348, 1237, 1153, 1109, 876, 821, 788, 757, 626; 1H NMR
(CDCl3) δ 7.32-7.61 (m, 6 H, aromatic protons), 7.73 (m, 1 H,
H-6), 8.28 (dd, J ) 8.0, 1.5 Hz, H, H-8); 13C NMR (CDCl3) δ
108.69 (C-1), 117.72 (C-5), 118.97 (C-4), 120.58 (C-8a), 121.70
(C-9a), 123.38 (C-7), 124.47 (C-3), 126.00 (C-8), 134.56 (C-6),
150.09 (C-4a), 153.37 (C-2), 156.02 (C-5a); MS (m/z, relative
intensity) 212 (M+, 54), 184 (9), 69 (46), 55 (85), 43 (100).
2-[2-(Tet r a h yd r o-2H -p yr a n -2-yl)oxyet h -1-yl]xa n t h o-
n e (82). A solution of phenol 81 (270 mg, 1.3 mmol) in methyl
sulfoxide (3 mL) was treated as depicted for 11. The product
was purified by column chromatography eluting with hex-
anes-EtOAc (19:1) to afford 200 mg (45% yield) of pure
compound 82 as a white solid: mp 92-93 °C; Rf 0.42 (hex-
anes-EtOAc, 3:2); 1H NMR (CDCl3) δ 1.55-1.81 (m, 6 H, H-3′′,
H-4′′, H-5′′), 3.53 (m, 1 H, H-6′′a), 3.80-3.97 (m, 2 H, H-6′′b,
H-1a), 4.10 (dt, J ) 11.3, 4.5 Hz, 1 H, H-1b), 4.27 (t, J ) 5.4
Hz, 2 H, H-2), 4.72 (t, J ) 3.3 Hz, 1 H, H-2′′), 7.32-7.41 (m, 3
H, aromatic protons), 7.47 (d, J ) 8.0 Hz, 1 H, H-4′), 7.68 (dd,
J ) 7.0, 1.6 Hz, 1 H, H-5′), 7.73 (d, J ) 2.4 Hz, 1 H, H-1′), 8.34
(S)-1-(4-P h en oxyp h en oxy)p r op a n -2-ol (87). A solution
of 4-phenoxyphenol (86; 1.0 g, 5.4 mmol) in methyl sulfoxide
(3 mL) was treated with S-propylene oxide (320 mg, 0.4 mL,
5.5 mmol) and the mixture was stirred at room temperature
for 6 h. The reaction mixture was quenched as depicted for
11, and the residue was purified by column chromatography
employing a mixture of hexanes-EtOAc (19:1) as eluent to give
266 mg (20% yield) of alcohol 87 as a white solid: Rf 0.51
(toluene-EtOAc, 4:1); mp 67-69 °C; [R]D +18.2 (c 1.0, CHCl3).
(S)-1-(4-P h en oxyp h en oxy)p r op a n -2-yl
4-Tolu en e-
su lfon a te (88). Alcohol 87 (266 mg, 1.09 mmol) was treated
with tosyl chloride as depicted for 13. After the usual workup,
283 mg (87% yield) of pure tosylate 88 were obtained as a
colorless oil: Rf 0.67 (toluene-EtOAc, 4:1); [R]D -26.1 (c 1.7,
chloroform); mp 102-104 °C; IR (KBr, cm-1) 3065, 2984, 2926,
2874, 1597, 1504, 1489, 1364, 1225, 1190, 1045, 928, 903, 768,
665, 555; MS (m/z, relative intensity) 398 (M+, 26), 213 (33),
185 (23), 155 (100), 91 (83).

Aryloxyethyl Thiocyanates as Inhibitors of T. cruzi
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 9 1839
(R)-1-(4-P h en oxyph en oxy)pr opan -2-yl Th iocyan ate (89).
Compound 88 (283 mg, 0.71 mmol) was reacted with potassium
thiocyanate according to the method of preparation of 15 and
was purified by column chromatography (silica gel) eluting
with hexanes-EtOAc (19:1) to afford 117 mg (58% yield) of
pure 89 as a colorless oil: [R]D -28.5 (c 1.0, chloroform); IR
(film, cm-1) 3063, 2974, 2934, 2870, 2153, 1589, 1504, 1489,
1390, 1219, 1022, 843, 750, 692, 511; 1H NMR (CDCl3) δ 1.62
(d, J ) 6.9 Hz, 3 H, H-3), 3.63 (m, 1 H, H-2), 4.11 (d, J ) 6.1
Hz, 2 H, H-1), 6.86-7.09 (m, 7 H, aromatic protons), 7.26-
7.34 (m, 2 H, aromatic protons); 13C NMR (CDCl3) δ 18.14 (C-
3), 43.51 (C-2), 71.42 (C-1), 115.89 (C-2′′), 117.82 (C-2′), 120.70
(C-3′), 122.69 (C-4′′), 129.62 (C-3′′), 151.18 (C-4′), 154.06 (C-
1′), 158.13 (C-1′′); MS (m/z, relative intensity) 285 (M+, 6), 272
(11), 251 (3), 186 (23), 87 (100); HRMS calcd for (C16H15O2NS)
285.0824, found 285.0828. Anal. (C16H15O2NS) C, H, N, S.
(R)-1-(4-P h en oxyp h en oxy)p r op a n -2-ol (90). 4-Phenox-
yphenol (86; 900 mg, 4.8 mmol) was treated with R-propylene
oxide (280 mg, 0.35 mL, 4.8 mmol) as depicted for 87. The
product was purified by column chromatography (silica gel)
eluting with hexanes-EtOAc (19:1) to yield 175 mg (15% yield)
of pure alcohol 90 as a white solid: Rf 0.51 (toluene-EtOAc,
4:1); mp 69-71 °C; [R]D -19.0 (c 1.0, CHCl3).
Ack n ow led gm en t. The authors thank the National
Research Council of Argentina (CONICET), the ANP-
CyT (PICT 06-00000-00579), and the Universidad de
Buenos Aires (Grant TX-073) for partial financial sup-
port, UMYMFOR for spectra, and the NIH for Grant
AI23259 to R.D. We also thank Mr. Paul J . Klopfenstein
for technical assistance.
Su p p or tin g In for m a tion Ava ila ble: NMR spectral data
for compounds 12-14, 17, 19-23, 27, 28, 32, 33, 35, 37, 38,
41, 42, 45, 46, 50, 51, 55, 56, 58-60, 62, 63, 66, 68, 70, 71,
74-76, 87, and 88 and tables of data needed to calculate
percent inhibition. This material is available free of charge
via the Internet at http://pubs.acs.org.
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(R)-1-(4-P h en oxyp h en oxy)p r op a n -2-yl
4-Tolu en e-
su lfon a te (91). Alcohol 90 (132 mg, 0.5 mmol) was trans-
formed into tosylate 91 (colorless oil) in quantitative yield as
depicted for 88: [R]D + 26.2 (c 1.0, chloroform); mp 101-103
°C.
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mmol) in 55% yield as depicted for 89: [R]D +28.4 (c 0.3,
chloroform); HRMS calcd for (C16H15O2NS) 285.0824, found
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Dr u g Scr een in g. Biological assays on epimastigotes were
performed as previously described.32
T. cruzi epimastigotes (Y strain) were grown in 20-mL
screw-cap tubes at 28 °C in a liquid medium containing brain-
heart infusion (37 g/L), hemin chlorohydrate (20 mg/L) (dis-
solved in 50% triethanolamine) and 10% newborn calf serum.
The initial inoculum contained (2-3) × 106 cells/mL (as
determined by counting in a Neubauer chamber) in a final
volume of 1 mL. The concentration of cells was determined by
measuring the absorbance of the culture medium containing
parasites at 600 nm against a blank with culture medium
alone. Each drug was tested at four different concentrations
(1, 10, 50 and 100 µg/mL) each one in quadruplicate. Drugs
were dissolved in ethanol. A control without drug was done
with each group that was tested.
To calculate percent inhibition, the following formula was
used: 100 - [(∆Ad × 100)/∆Ac] ) percent inhibition, where
∆Ac and ∆Ad are the differences in the absorbance of control
cultures and drug-treated cultures, respectively, at the begin-
ning and end of the experiment. The maximum amount of
solvent used (1% ethanol) did not have any significant effect
on the epimastigotes growth. The values of IC50 were estimated
by linear and polynomial regression.
Experiments on the intracellular form of the parasite were
conducted on T. cruzi-infected L6E9 myoblasts (Y strain) as
described before.54 L6E9 myoblasts were exposed to 2000 rads
of γ radiation and plated on 75-cm2 flasks at a density of 1.2
× 107 cells/flask in DMEM containing 20% fetal calf serum
in a total volume of 10 mL. After 24 h of incubation at 35 °C,
the cells were exposed to a suspension of 5 × 107 trypomas-
tigotes/flask in DMEM containing 20% fetal calf serum for 2
h, then cultures were washed twice with Dulbecco′ PBS and
the culture medium was replaced. Different concentrations of
drugs were added to the cultures that were labeled with 1.0
µCi of [5,6-3H]uracil and incubated for an additional 72 h.
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inhibition of [3H]uracil incorporation (parasite proliferation)
was calculated employing the following formula: inhibition
percent ) [(A - B)/A] × 100, where A is the mean counts per
minute of infected control-treated myoblasts and B is the mean
counts per minute of infected drug-treated myoblasts.
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