Synthesis and anti-Trypanosoma cruzi activity of naphthoquinone-containing triazoles: Electrochemical studies on the effects of the quinoidal moiety

Article abstract of DOI:10.1016/j.bmc.2013.08.055

In our continued search for novel trypanocidal compounds, twenty-six derivatives of para- and ortho-naphthoquinones coupled to 1,2,3-triazoles were synthesized. These compounds were evaluated against the infective bloodstream form of Trypanosoma cruzi, th

Full text of DOI:10.1016/j.bmc.2013.08.055

Accepted Manuscript
Synthesis and anti-Trypanosoma cruzi activity of Naphthoquinone-containing
Triazoles: Electrochemical studies on the effects of the quinoidal moiety
Emilay B.T. Diogo, Gleiston G. Dias, Bernardo L. Rodrigues, Tiago T.
Guimarães, Wagner O. Valença, Celso A. Camara, Ronaldo N. de Oliveira,
Mauro G. da Silva, Vitor F. Ferreira, Yen Galdino de Paiva, Marilia O.F.
Goulart, Rubem F.S. Menna-Barreto, Solange L. de Castro, Eufrânio N. da Silva
Júnior
PII:
S0968-0896(13)00758-X
http://dx.doi.org/10.1016/j.bmc.2013.08.055
BMC 11071
DOI:
Reference:
To appear in:
Bioorganic & Medicinal Chemistry
Received Date:
Revised Date:
Accepted Date:
15 June 2013
18 August 2013
26 August 2013
Please cite this article as: Diogo, E.B.T., Dias, G.G., Rodrigues, B.L., Guimarães, T.T., Valença, W.O., Camara,
C.A., de Oliveira, R.N., da Silva, M.G., Ferreira, V.F., Paiva, Y.G.d., Goulart, M.O.F., Menna-Barreto, R.F.S., de
Castro, S.L., da Silva Júnior, E.N., Synthesis and anti-Trypanosoma cruzi activity of Naphthoquinone-containing
Triazoles: Electrochemical studies on the effects of the quinoidal moiety, Bioorganic & Medicinal Chemistry (2013),
doi: http://dx.doi.org/10.1016/j.bmc.2013.08.055
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Synthesis and anti-Trypanosoma cruzi activity of Naphthoquinone-containing
Triazoles: Electrochemical studies on the effects of the quinoidal moiety
Emilay B. T. Diogo,a Gleiston G. Dias,a Bernardo L. Rodrigues,a Tiago T. Guimarães,b
Wagner O. Valença,c Celso A. Camara,c Ronaldo N. de Oliveira,c Mauro G. da Silva,d
Vitor F. Ferreira,e Yen Galdino de Paiva,f Marilia O. F. Goulart,f Rubem F. S. Menna-
Barreto,g Solange L. de Castrog and Eufrânio N. da Silva Júniora*
aInstituto de Ciências Exatas, Departamento de Química, UFMG, 31270-901, Belo
Horizonte, MG, Brazil; bNúcleo de Pesquisas de Produtos Naturais, UFRJ, 21941-971,
Rio de Janeiro, RJ, Brazil; cDepartamento de Ciências Moleculares, UFRPE, 52171-
900, Recife, PE, Brazil; dUniversidade Federal de Pernambuco, UFPE, 50670-901,
Recife, PE, Brazil; eInstituto de Quíımica, UFF, 24020-150, Niterói, RJ, Brazil;
fInstituto de Química e Biotecnologia, UFAL, Tabuleiro do Martins, 57072-970,
Maceió, AL, Brazil; gLaboratório de Biologia Celular, IOC, FIOCRUZ, 21045-900, Rio
de Janeiro, RJ, Brazil.
Corresponding author: Tel.: 55 31 34095720; fax: 55 31 34095700.
E-mail address: eufranio@ufmg.br (E.N. da Silva Júnior).
Abstract: In our continued search for novel trypanocidal compounds, twenty-six
derivatives of para- and ortho-naphthoquinones coupled to 1,2,3-triazoles were
synthesized. These compounds were evaluated against the infective bloodstream form
of Trypanosoma cruzi, the etiological agent of Chagas disease. Compounds 17-24, 28-
30 and 36-38 are described herein for the first time. Three of these novel compounds
(28, 29 and 30) were found to be more potent than the standard drug benznidazole, with
IC50/24 h values between 6.8-80.8 µM. Analysis of the toxicity to heart muscle cells led
to LC50/24 h of <125, 63.1 and 281.6 µM for 28, 29 and 30, respectively. Displaying a
selectivity index of 34.3, compound 30 will be further evaluated in vivo. The
electrochemical properties of selected compounds were evaluated in an attempt to find
correlations with trypanocidal activity, and it was observed that more electrophilic
quinones were generally more potent.
Keywords: Lapachol; β-Lapachone; Quinone; Chagas disease; Trypomastigote; Click
chemistry; Electrochemical Parameters.
1

1. Introduction
Chagas disease (CD) is caused by the protozoan Trypanosoma cruzi and affects
approximately eight million individuals in Latin America. Approximately 30-40% of
these patients have, or will develop, cardiomyopathy, digestive mega-syndromes, or
both.1 Although vectorial (Triatoma infestans) and transfusional transmission of CD
have declined steadily as a result of multinational initiatives,2 this disease can also be
orally transmitted through the ingestion of food or liquid contaminated with T. cruzi.
This route of transmission is the cause of regional outbreaks of acute infection in areas
devoid of domiciled insect vectors.3 Several outbreaks of severe acute CD, each
numbering in the hundreds of cases, have been reported in the Amazon Region in recent
decades.4 Most of these outbreaks were the result of oral transmission. The emergence
of CD in non-endemic areas, such as North America and Europe, is another major
concern. This development is due to the immigration of infected individuals and
subsequent transmission via the blood, organ transplantation and congenital routes.5,6
Other challenges remaining to be overcome in the fight against CD include the
development of sustainable public health policies, vector control strategies and
educational approaches.7,8
CD is characterized by a short acute phase defined by patent parasitemia
followed by a long and progressive chronic phase. Up to 40-50% of chronically infected
patients develop progressive cardiomyopathy, motility disturbances of the esophagus
and colon, or all of these symptoms. CD is the most severe parasitic infection of the
heart, which is the organ most often affected in chronic patients.1 The available
chemotherapy for CD is not satisfactory and depends on two nitroheterocyclic agents:
the 5-nitrofuran nifurtimox and the 2-nitroimidazole benznidazole. These compounds
are effective against acute infections, but they show poor activity in the later chronic
phase. These drugs also cause severe off-target effects, have limited efficacy against
different parasite isolates and must be applied in long-term therapy. These drawbacks
justify the urgent effort to identify better drugs for the treatment of CD.9,10 Nearly all
current drug development efforts for CD are in the preclinical research phase, although
Phase II clinical trials with the antifungal drug posaconazole are underway in Latin
America and Spain. A ravuconazole prodrug is also undergoing Phase II studies in
Bolivia.11
2

Plants represent a vast reservoir of phytoconstituents and secondary metabolites
that can be used as templates for the design of semi-synthetic or synthetic compounds.
This approach can lead to the discovery of new candidates for the treatment of neglected
tropical diseases with high therapeutic indices. Naphthoquinones account for the
majority of naturally occurring naphthalenes,12 displaying an assortment of substituents
over a variety of structural motifs. They act as vital links in the electron transport chains
of metabolic pathways and participate in multiple biologically relevant oxidative
processes.13
Naphthoquinones are considered privileged scaffolds in medicinal chemistry due
to their structural properties and biological activities,14 especially against tumor cells
and pathogenic protozoa.15 We have recently described the synthesis and trypanocidal
and leishmanicidal activities of 1,2,3-triazoles based on the lapachone scaffold.16,17a
Modification of the prototype β-lapachone, as shown in Scheme 1, is a relevant strategy
for the development of novel bioactive compounds. The C-ring was modified to afford
nor-β-lapachone and β-lapachone derivatives with pronounced activity against
trypomastigote forms of T. cruzi.16 Other derivatives can be prepared by modification of
the redox centre and the C-ring, as described in Scheme 1: arylamino derivatives of nor-
β-lapachone, imidazoles and oxiranes are important examples of this strategy.16,17,18
Recently, nor-α-lapachone and α-lapachone derivatives were also prepared and shown
to have potent activity against promastigote forms of antimony-sensitive and -resistant
strains of Leishmania infantum (syn. L. chagasi) and L. amazonensis.17a
Several studies have investigated and reported the electrochemical behavior of
quinones. Some correlation has been demonstrated between electrochemical parameters
and disease states.19 The quinone/semiquinone/hydroquinone (Q/SQ-/H2Q) triad is an
important component of many redox systems in biology. It is a vital link in the transfer
of electrons through cells and tissues (Eq. 1-3).20
Electrochemical techniques have been used extensively to provide excellent
insights into the modes of action of various drugs, and these results can inspire the
3

design of next-generation therapeutics. This approach is particularly suitable for
diseases associated with cellular oxidative stress, which is a hallmark of cancer.19-21
Electrochemistry experiments can provide data on the fundamental thermodynamic and
kinetic properties associated with the reactions of quinones and reduced intermediates.
The versatility and functional diversity of quinones are due primarily to the
diverse mid-point potentials that are sensitive to substituent effects, solvent and medium
effects (hydrophilic/lipophilic) and interactions with certain macromolecules (e.g., DNA
and proteins). The electronic properties of quinones are influenced by substituent
groups, hydrogen bonding (H-bonding), hydrophobic and π-stacking interactions and
conformational effects. These factors act in tandem to stabilize or destabilize the
semiquinone radical (under aprotic conditions or during enzymatic one-electron
transfer). They can be correlated to the nature of the anion radical that is formed in vivo
or to the completely reduced species (hydroquinones or modified derivatives).19b,21
In this context, we herein describe the synthesis of para- and ortho-
naphthoquinones bearing 1,2,3-triazole substituents, as well as 1,2,3-triazoles derived
from α-lapachone and nor-α-lapachone. These compounds were evaluated for activity
against trypomastigote forms of T. cruzi. Electrochemical studies of selected
compounds are also presented.
Our synthetic rationale was to combine para and ortho quinoidal moieties with
heterocycles (Schemes 2-4). Derivatives of N-phthalimide have been shown to have
biological significance, including antibacterial,22 antiviral,23 anticancer24 and anti-
hepatitis activity.25 Based on the pharmacological importance of phthalimide analogues,
we synthesized hybrids of 1,4-naphthoquinone and N-phthalimide conjugated through
an aminomethyltriazole linkage. The introduction of a second quinoidal moiety was also
accomplished (Scheme 4) in a hybrid approach to duplicate the effect of the quinone.
Finally, the importance of the redox centre was analyzed by modifying the structure of
nor-β-lapachone-based 1,2,3-triazole to generate compounds similar to phenazine
derivatives (Scheme 5).
Scheme 1.
2. Results and discussion
2.1 Chemistry
4

α-Lapachone and nor-α-lapachone-derived 1,2,3-triazoles were synthesized as
described previously (Scheme 2).17a Lapachol (1) was used to prepare α-lapachone (2),
which was subsequently treated with N-bromosuccinimide in carbon tetrachloride, in
the presence of benzoyl peroxide, to provide 4-bromo-α-lapachone. This bromide was
reacted with sodium azide to yield 4-azido-α-lapachone (3). The 1,2,3-triazoles 4-6
were then obtained from Cu(I)-catalyzed reactions with the appropriate alkynes,
following the methodology described by Sharpless and coworkers (Scheme 2).17b
Lapachol (1) was used to prepare nor-lapachol in two steps as described
previously.26 This derivative was treated with HCl/AcOH to provide nor-α-lapachone
(7). Conversion to 3-bromo-nor-α-lapachone and reaction with sodium azide in
dichloromethane gave the corresponding azide 8, as described previously.17a Triazole
derivatives 9-12 were synthesized from quinone 8 (Scheme 2).
Scheme 2.
A previously described methodology16d,27 was used to prepare para-
naphthoquinones 13-26 (Scheme 3). A series of N-phthalimidoalkylazides was initially
prepared for the synthesis of compounds 13-22. These intermediates were used in click
chemistry reactions with substituted 2-(prop-2-yn-1-ylamine)-naphthoquinone to obtain
the respective triazole compounds in high yields. Compounds 23 and 24 were prepared
by the click reaction among the respective quinone and 1-azido-3-nitrobenzene. Final
compounds were typically isolated as crystalline solids, and all spectroscopic data were
in accordance with the proposed structures shown in Scheme 3. Compounds 17-24 are
described herein for the first time.
Scheme 3.
The last set of naphthoquinoidal compounds was synthesized from the
intermediate azide 27 that we have described previously.16a Naphthoquinones
substituted with a terminal alkyne had been synthesized previously. These compounds
were subjected to click chemistry conditions17b to prepare novel derivatives 28-30 as
shown in Scheme 4. Nor-β-lapachone derivatives 28-30 were isolated in moderate
yields as yellow and orange solids. Known compounds 31-35,16a,d shown in Scheme 4,
5

were included to study their electrochemical properties in comparison with their
trypanocidal activity (vide infra).
Cu-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) is a well established
methodology using Cu(I) as source of catalysis.28 Herein, we described the synthesis of
quinone-based 1,2,3-triazoles using two reaction conditions, the most common using
.
aqueous conditions employing CuSO4 5H2O and sodium ascorbate as reducing agent
and copper(I) iodide in acetonitrile. As recently described by Meldal and Tornøe29 there
is no obvious correlation between method used and yield of reaction. In general,
.
CuSO4 5H2O and sodium ascorbate is preferred due to ease of workup, while, in other
reactions, the copper(I) iodide can be used to improve the rate of reaction. In this
manuscript the classical methodology published by Sharpless and co-workers17b was
used preferentially. In the case of low yields and long reaction time, copper(I) iodide in
acetonitrile or the same condition under ultrasound energy were used.
Scheme 4.
The phenyl substituted 1,2,3-triazole derived from nor-β-lapachone (31) was
described previously and was shown to be 6-fold more potent than the standard drug
benznidazole against trypomastigote forms of T. cruzi.16a Herein we describe the
synthesis of three novel derivatives synthesized from 31 (Scheme 5). Our strategy was
based on modifying the redox centre of 31. We selected modification reactions from
previously published studies on related β-lapachone derivatives, which showed
pronounced activity against T. cruzi.16 Compound 31 was obtained in five steps, in good
overall yield, starting from lapachol (1).16a Intermediate 31 reacted smoothly with
ethane-1,2-diamine or ortho-phenylenediamine in acetic acid30 to furnish compounds 36
and 37 in excellent yields. Oxime 38 was prepared by reaction of 31 with
hydroxylamine in ethanol in the presence of TEA (Scheme 5).31
Scheme 5.
The structures of novel compounds 17-24, 28-30 and 36-38 were determined by
13
1H, C NMR, and IR. The structures were further characterized by comparing their
spectroscopic data with those of similar compounds known in the literature.16a,17a,18
Electrospray ionization mass spectra and combustion analysis data were also obtained.
6

Crystals of 38 suitable for X-ray analysis were obtained, and the structure was solved.
ORTEP-3 projections are shown in Figure 2, and these reveal the Z-stereochemistry.
2.2. Electrochemistry
In a typical measurement, cyclic voltammograms (CV) were recorded first in
aprotic medium (DMF + TBAP, 0.1 mol L-1), at a scan rate of 50 mV s-1. This enabled
determination of the electrochemical reduction behavior of each compound. Initial
cathodic and anodic peak currents were also determined for each compound.
It was not feasible to study all of the quinones in the present work.
Representative compounds were selected to cover each of the structural classes
(Schemes 2-4).
As has been noted, the compounds described here can be divided among three
structural classes: dihydropyran-para-naphthoquinones (4 and 6), para-naphthoquinone
derivatives (16, 25 and 26), and ortho-dihydrofuranones (28, 30-35).
Figure 1 shows the cyclic voltammograms of compounds 4, 6, 16, 25, 26, 28,
and 30-35. All of the quinones exhibited quasi-reversible reduction behavior (Fig. 1).
The major electrochemical parameters for each compound are listed in Table 1.
The relative ease of reduction among the compounds was established by
comparison of their first reduction potentials (Epc1, Table 1, column 2). The relative
reduction potential of the compounds is as follows: 25 > 26 > 34 > 35 > 33 > 28 ~32
~30 > 31 > 6 ~4 > 16.
The values of Eredox were obtained from the equation (Epc1 + Epa1)/2 and are
shown in Table 1. As was expected for quinonoid compounds, the overall CV profiles
are similar to those reported for other quinones. The characteristic profile shows two
couples of cathodic and anodic peaks, represented by diffusional (EpIc α 1/2) quasi-
reversible systems.19b,c The first pair is related to the formation of a radical anion (SQ-,
Eq. 1). The second pair of peaks is broader and ill-defined, as has been observed
previously.19b This broadening may be due to possible disproportionation or
comproportionation reactions.19b
Figure 1.
Table 1.
7

As shown in Table 1, compounds 25 and 26 (Figs. 1d and 1e) are most easily
reduced. The direct attachment of the electron-withdrawing triazole affects the
electrochemical behavior of the para-quinones in a way that facilitates electron transfer.
On the other hand, the presence of an electron-donating amine group increases the
barrier to reduction of compound 16 (Fig. 1c). This compound presents two additional
waves at more negative potentials (Epc3 and Epc4, Fig. 1c, Table 1, column 4). A full
description of the electrodic mechanism is beyond the scope of the present paper and
will be described elsewhere. It is noticeable that nor-β-lapachone ortho-quinones
derivatives (31-35, Figs. 1h-l) are more easily reduced than are the α-lapachone-derived
1,2,3-triazoles (4 and 6, Figs. 1a and 1b), as has been shown previously.19b The CV of
compound 34, which shows the lowest negative potential in this series, displayed
additional waves that can be attributed to an additional electron-withdrawing nitro
group (Fig. 1k). The behavior of this compound is characterized by three waves. The
first wave arises from single electron transfer to the quinone system. The second is
attributable to a combined system, with two close electron transfers: one to the
semiquinone and the other to the nitroaromatic group, generating a nitro radical anion.
The third wave is related to further reduction of the nitroaromatic system.
The presence of two quinone systems in 28 and 30 (Figs. 1f and 1g) leads to CV
curves displaying considerably more complex features. These curves show at least four
cathodic waves and corresponding anodic waves. It is clear from comparison with the
CV of compound 16 that the first wave is related to the reduction of the ortho-quinone.
2.3. X-ray analysis
The Ortep-3 diagram of 38 is shown in Figure 2, and Table 2 lists the major
crystallographic parameters. Compound 38 crystallizes in the non-centrosymmetric
space group P21, with one molecule in the asymmetric unit. The bond lengths and
angles are in good agreement with expected values, based on each atomic type.
Although the statistical and structural parameters indicate that the structure is well
solved, the Flack parameter indicates that the absolute structure cannot be resolved from
this analysis. The crystal structure reveals one intramolecular hydrogen bond (O1 – H10
…
O2) that forms a six-membered ring. Three main planes may be defined through the
molecule. Plane 1 is formed by the quinoidal ring (atoms C1 to C10, as O1, O2 and N4).
8

It is interesting to note that atoms C11 and O3 of the furan ring are close to plane 1
(distances equal to 0.059 (4) Ǻ 0.044(A) A), while atom C12 is more distant from this
plane (0.238(5) Ǻ). Plane 2 is formed by atoms N1, N2, N3, C13 and C14. Nitrogen N1
of this plane is bonded to the chiral C11 atom of plane 1. The distance between C11 and
plane 2 is equal to 0.018 (5) Ǻ, indicating that these atoms belong to both planes. Plane
3 is defined through the benzene ring (atoms C15 to C20). The angle between planes 1
and 2 is equal to 85.75(7)°, while the angle between planes 2 and 3 is equal to
18.91(18)°. This suggests that the phenyl ring and the triazole group are approximately
coplanar. The crystal packing is stabilized by intermolecular C-H…N and C-H…O
interactions, involving atoms C13, N2 and N3 of the triazole ring (Table 3).
Figure 2.
Table 2.
Table 3.
2.4. Biological Activity
We have recently described the introduction of 1,2,3-triazole and arylamino
groups into naphthoquinoidal structures; some of these substances were identified as
potent trypanocidal compounds.16 In that work, we demonstrated that 1,4-
naphthoquinones and β-lapachones derivatized with a 1,2,3-triazole had efficacy as
novel trypanocidal compounds.
In the present study, we have evaluated four classes of compounds for activity
against T. cruzi. These include α- (4-6) and nor-α-lapachone-derived 1,2,3-triazoles (9-
12), aminomethylnaphthoquinones conjugated to N-phthalimide via triazole linkers (13-
22), nor-β-lapachone-derived 1,2,3-triazole-conjugated aminoquinones (28-30) and
derivatives of nor-β-lapachone bearing phenazine and oxime moieties (36-38).
Previously published data are included in Table 4 and the associated footnote to enable
comparison.16a,d
The first class of compounds, α-lapachones linked to 1,2,3-triazoles (para-
quinones, Scheme 2), was synthesized from α-lapachone (2) and nor-α-lapachone (7).
We sought to evaluate the effect of the 1,2,3-triazole ring on the trypanocidal activity of
9

these compounds. This strategy had previously been shown to be effective for
derivatives of nor-β-lapachone (ortho-quinones). Unfortunately, compounds 4-6 and 9-
12 were inactive against trypomastigote forms of T. cruzi, with IC50/24 h values greater
than 500 µM for all derivatives (Table 4).
The hybrids of 1,4-naphthoquinone and N-phthalimide (13-22) were prepared
from brominated, chlorinated or unsubstituted quinones with spacers of one, two or
three carbon atoms between the 1,2,3-triazole ring and the N-phthalimido group
(Scheme 3). Compounds 13-22 were inactive against T. cruzi, as all showed IC50/24 h
values greater than 4000 µM. Compounds 23 and 24 were also inactive (Table 4).
The last class of naphthoquinoidal compounds described herein was designed to
couple ortho-quinone to para-quinoidal structures (Scheme 4). Compounds 28-30 were
isolated in moderate yields as yellow and orange crystalline solids. Our approach
proved to be effective, and 28, 29 and 30 showed IC50/24 h values of 80.8, 6.8 and 8.2
µM, respectively (Table 4). The compounds 29 and 30 were about 15 times more potent
than benznidazole, the drug used for the treatment of Chagas disease. A hypothesis for
the potent trypanocidal activity is that the union of ortho- and para-quinoidal moieties
can generate high concentrations of reactive oxygen species, in general related to
activity of this class of compounds. Analysis of the toxicity to heart muscle cells gave
the LC50/24h values of <125, 63.1 and 281.6 µM for 28, 29 and 30, respectively,
corresponding to selectivity indexes (SI) of < 1.5, 9.3 and 34.3. As preconized in the
workshop “Experimental Models in Drug Screening and Development for Chagas
Disease” organized by Fiocruz and Drugs for Neglected Diseases Initiative (DNDi)32
establishing a protocol for drug screening, compound 30 will be submitted to in vivo
experiments using T. cruzi-infected mice. These results highlight the potential of these
compounds as novel trypanocidal agents.
To evaluate the importance of redox centers primarily as releasers of ROS, we
prepared a series of compounds by modifying the scaffold of the previously described
trypanocidal nor-β-lapachone derivative 31 (Scheme 5).16a Compounds 36-38 were
evaluated against trypomastigote forms of T. cruzi, but none were found to be active
(Table 4).
Table 4.
10

A comparison of the data in Tables 1 and 4 (Figure 3) reveals a trend: more
electrophilic quinones, that is, those with less negative values for Epc1, (Epc1 > -0.6 V
vs. Ag/AgCl, Table 1) were more potent trypanocidal compounds. Compound 33 was
the lone exception to this trend.
Figure 3.
Electrochemical experiments (analytical and preparative) and electrochemical
(thermodynamic and kinetic) parameters are useful in biomedical chemistry, particularly
in elucidating the mechanisms of biological electron-transfer processes. Such analyses
can be useful in the design of putatively bioactive lead compounds for which the
mechanism of action is based on redox reactions leading to oxidative stress.21a
3. Conclusions
We evaluated twenty-six compounds, and three were identified as potent
trypanocidal agents. These compounds were more active than the anti-T. cruzi drug
benznidazole, the current therapeutic standard. As compound 29 was fifteen-fold more
active than benznidazole, it is a promising candidate for further investigation. The
electrochemical properties of selected compounds were studied, and important
correlations were found with trypanocidal activity.
4. Experimental Section
4.1. Chemistry
Melting points were obtained on Thomas Hoover and are uncorrected.
Analytical grade solvents were used. Column chromatography was performed on silica
gel (SiliaFlash G60 UltraPure – 60-200 µm, 60 Å). Infrared spectra were recorded on an
1
FTIR Spectrometer IR Prestige-21 - Shimadzu. H- and 13C-NMR were recorded at
room temperature using a Bruker AVANCE DRX200, Varian Mercury 300 and Varian
Mercury 400 MHz, in the solvents indicated, with TMS as internal reference. Chemical
shifts (δ) are given in ppm and coupling constants (J) in Hertz. High resolution mass
spectra (electrospray ionization) were obtained using a MicroTOFIc - BrukerDaltonics.
Elemental analysis was performed using a CE Instruments (Thermo-Fisher) EA 1110
11

CHNS-O elemental analyzer. All the compounds were nominated using the program CS
ChemDraw Ultra version 10.0.
4.2. General procedure for the synthesis of compounds 17-24
Method A: In a flask containing 3 mL acetonitrile, it was added 0.5 mmol of the
appropriate azides, followed by 0.6 mmol of the appropriate alkynes and finally 11 mg
(0.06 mmol) of copper(I) iodide. The reaction was left under magnetic stirring at 28 °C
under argon atmosphere, for a reaction time ranging from 19-24 h. The end of the
reaction was monitored by TLC with dichloromethane as eluent. The solvent was then
removed under reduced pressure and the reaction mixture was purified on a silica gel
column as a gradient mixture of hexane/ethyl acetate or dichloromethane/ethyl acetate
with increasing polarity. Method B: In a flask containing 2 mL of DMF, it was added
0.5 mmol of the appropriate azides, followed by 0.6 mmol of the appropriate alkynes,
11 mg (0.06 mmol) of copper(I) iodide and finally 1 drop of Et3N. The reaction was left
under ultrasound energy at 28 °C, during 30 min. After the end of the reaction
monitored by TLC with dichloromethane, the mixture was purified as described in
method A. Method C: The same procedures described in Method A, but 2 mL DMF,
one drop Et3N were added and the reaction was left under magnetic stirring for 60 min
as monitored by TLC. Method D: The same procedures described in method A, 2 mL
of DMF were added, and the reaction was left under magnetic stirring for 60 min as
monitored by TLC.
4.2.1. 2-((4-(((3-Chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)methyl)isoindoline-1,3-dione (17)
Using method D, compound 17 was obtained as an orange solid (200 mg, 0.44
mmol, 87% yield); mp 170-172 ºC. IR νmax(cm-1, KBr): 3324, 3140, 2955, 1775, 1712,
1
1672, 1605, 1573, 1507, 1403, 1363, 1330, 1293, 1136, 1048, 953, 717. H NMR (400
MHz, CDCl3) δ: 8.12 (dd, 1H, J = 1.2 and 8.0 Hz), 8.01 (dd, 1H, J = 1.2 and 8.0 Hz),
7.91-7.89 (m, 3H), 7.78-7.76 (m, 2H), 7.70 (td, 1H, J = 1.6 and 7.3 Hz), 7.61 (td, 1H, J
= 1.6 and 7.3 Hz), 6.41 (br s, 1H, NH), 6.20 (s, 2H), 5.14 (d, 2H, J = 6.4 Hz). 13C NMR
(100 MHz, CDCl3) δ: 177.6, 174.1, 163.8, 142.4, 141.4, 132.4, 132.1, 132.0, 128.8,
127.4, 124.2, 124.1, 121.6, 121.4, 120.5, 120.3, 47.2, 37.6. Anal. Calcd for
12

C22H14ClN5O4 0.3 x H2O: C, 58.30; H, 3.25; N, 15.45. Found: C, 58.48; H, 3.21; N,
15.24.
4.2.2. 2-(2-(4-(((3-Chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)ethyl)isoindoline-1,3-dione (18)
Using method D, compound 18 was obtained as a red solid (200 mg, 0.44 mmol,
71% yield); mp 197-199 ºC. IR νmax(cm-1, KBr): 3313, 3141, 1774, 1715, 1678, 1605,
1
1572, 1525, 1425, 1391, 1356, 1298, 1139, 1049, 943, 720. H NMR (400 MHz,
CDCl3) δ: 8.15 (d, 1H, J = 7.6 Hz), 8.04 (d, 1H, J = 7.6 Hz), 7.79-7.61 (m, 7H), 6.41
(br s, 1H, NH), 5.13 (d, 2H, J = 5.6 Hz), 4.69 (t, 2H, J = 6.4 Hz), 4.15 (t, 2H, J = 6.0
13
Hz). C NMR (100 MHz, CDCl3) δ: 180.3, 167.5, 134.8, 134.3, 132.6, 131.7, 126.8,
123.6, 48.2, 40.3, 37.7. Anal. Calcd for C23H16ClN5O4 0.35 x H2O: C, 59.01; H, 3.49; N,
15.16. Found: C, 59.38; H, 3.64; N, 14.56.
4.2.3. 2-(3-(4-(((3-Chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)propyl)isoindoline-1,3-dione (19)
Using method D, compound 19 was obtained as a red solid (200 mg, 0.44 mmol,
94% yield); mp 179-181 ºC. IR νmax(cm-1, KBr): 3313, 3141, 1774, 1712, 1678, 1602,
1571, 1525, 1435, 1293, 1139, 1049, 716. 1H NMR (400 MHz, acetone-d6) δ: 7.93-7.60
(m, 2H), 7.70-7.61 (m, 7H), 6.94 (br s, 1H, NH), 5.01 (d, 2H, J = 5.9 Hz), 4.37 (t, 2H, J
13
= 7.0 Hz), 3.59 (t, 2H, J = 6.7 Hz), 2.18 (qt, 2H, J = 7.0 Hz). C NMR (100 MHz,
acetone-d6) δ: 181.7, 175.2, 167.3, 143.9, 134.1, 133.4, 131.9, 125.9, 122.2, 121.9, 46.9,
39.6, 34.3. Anal. Calcd for C24H18ClN5O4: C, 60.57; H, 3.81; N, 14.72. Found: C,
60.38; H, 3.69; N, 14.45.
4.2.4. 2-((4-(((3-Bromo-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)methyl)isoindoline-1,3-dione (20)
Using method C, compound 20 was obtained as a red solid (200 mg, 0.40 mmol,
88% yield); mp 155-157 ºC. IR νmax(cm-1, KBr): 3250, 3123, 1778, 1725, 1675, 1596,
1
1567, 1401, 1361, 1329, 1292, 1132, 1045, 783, 737. H NMR (400 MHz, acetone-d6)
δ: 8.13 (s, 1H), 8.07-7.65 (m, 8H), 7.02 (br s, 1H, NH), 6.25 (s, 2H), 5.20 (d, 2H, J = 5.1
13

Hz). 13C NMR (100 MHz, acetone-d6) δ: 179.4, 174.9, 165.9, 144.6, 134.4, 134.2,
131.9, 131.1, 130.9, 125.9, 122.9, 122.6, 49.4, 39.8. Anal. Calcd for C22H14BrN5O4: C,
53.68; H, 2.87; N, 14.23. Found: C,53.62; H, 2.97; N,13.86.
4.2.5. 2-(2-(4-(((3-Bromo-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)ethyl)isoindoline-1,3-dione (21)
Using method C, compound 21 was obtained as a red solid (200 mg, 0.40 mmol,
90% yield); mp 169-170 ºC. IR νmax(cm-1, KBr): 3314, 3274, 3129, 1772, 1714, 1591,
1565, 1397, 1286, 1124, 1024, 939, 722. 1H NMR (300 MHz, CDCl3) δ: 8.14 (dd, 1H,
J = 1.5 and 7.5 Hz), 8.03 (dd, 1H, J = 1.5 and 7.5 Hz), 7.79-7.77 (m, 2H), 7.76 (s, 1H),
7.72-7.61 (m, 4H), 6.48 (br s, 1H, NH), 5.14 (br s, 2H), 4.70 (t, 2H, J = 5.9 Hz), 4.15 (t,
13
2H, J = 5.9 Hz). C NMR (100 MHz, CDCl3) δ: 180.0, 176.5, 167.6, 146.2, 144.8,
134.7, 134.3, 132.5, 132.2, 131.6, 130.0, 127.0, 126.9, 123.6, 122.5, 48.2, 40.6, 37.7.
Anal. Calcd for C23H16BrN5O4: C, 54.56; H, 3.19; N,13.85. Found: C, 54.46; N, 3.58;
H, 13.48.
4.2.6. 2-(3-(4-(((3-Bromo-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)propyl)isoindoline-1,3-dione (22)
Using method C, compound 22 was obtained as a red solid (200 mg, 0.40 mmol,
70% yield); mp 168-170 ºC. IR νmax(cm-1, KBr): 3219, 3137, 1770, 1711, 1680, 1600,
1
1566, 1389, 1290, 1131, 1054, 715. H NMR (300 MHz, CDCl3) δ: 8.13 (dd, 1H, J =
0.9 and 6.9 Hz), 8.04 (dd, 1H, J = 1.2 and 7.5 Hz), 7.85-7.80 (m, 3H), 7.76-7.60 (m,
4H), 6.57 (br s, 1H, NH), 5.17 (d, 2H, J = 5.1 Hz), 4.41 (t, 2H, J = 6.6 Hz), 3.74 (t, 2H,
13
J = 6.9 Hz), 2.35 (qt, 2H, J = 6.3 Hz). C NMR (100 MHz, CDCl3) δ: 180.2, 176.8,
168.6, 146.5, 135.0, 134.5, 132.8, 132.4, 132.1, 130.2, 127.3, 127.2, 123.7, 48.2, 40.9,
35.2, 29.6. Anal. Calcd for C24H18BrN5O4: C, 55.40, H, 3.49, N, 13.46. Found: C, 55.61,
H, 3.82, N, 13,37.
4.2.7. 2-(((1-(3-Nitrophenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)naphthalene-1,4-
dione (23)
14

Using method B, compound 23 was obtained as an orange solid (200 mg, 0.54
mmol, 78% yield); mp 234-235 ºC. IR νmax(cm-1, KBr): 3298, 3132, 1673, 1640, 1590,
1526, 1350, 1260, 1046, 804, 721. 1H NMR (400 MHz, DMSO-d6) δ: 8.94 (s, 1H), 8.68
(br s, 1H, NH), 8.38 (dd, 1H, J = 2.0 and 8.0 Hz), 8.30 (dd, 1H, J = 2.0 and 8.4 Hz),
8.02-7.71 (m, 6H), 5.80 (s, 1H), 4.62 (d, 2H, J = 4.8 Hz). 13C NMR (100 MHz, DMSO-
d6) δ: 181.4, 181.3, 148.4, 148.1, 144.7, 137.0, 134.6, 132.9, 132.1, 131.3, 130.3, 125.9,
125.7, 125.2, 122.8, 121.7, 114.5, 100.6, 37.3. Anal. Calcd for C19H13N5O4: C, 60.80;
H, 3.49; N, 18.66. Found: C, 60.83, H, 3.84, N, 18.86.
4.2.8.
2-Bromo-3-(((1-(3-nitrophenyl)-1H-1,2,3-triazol-4-
yl)methyl)amino)naphthalene-1,4-dione (24)
Using method A, compound 24 was obtained as an orange solid (200 mg, 0.44
mmol, 86% yield); mp 175-176 ºC. IR νmax(cm-1, KBr): 3298, 3132, 1673, 1640, 1590,
1526, 1350, 1260, 1046, 804, 721. 1H NMR (400 MHz, DMSO-d6) δ: 8.91 (s, 1H), 8.68
(br s, 1H, NH), 8.37 (d, 1H, J = 8.0 Hz), 8.29 (d, 1H, J = 8.4 Hz), 7.99 (d, 1H, J = 7.6
13
Hz), 7.88-7.74 (m, 5H), 5.16 (d, 2H, J = 6.4 Hz). C NMR (100 MHz, DMSO-d6) δ:
179.6, 175.3, 148.4, 147.4, 147.0, 137.1, 134.6, 132.6, 131.4, 131.3, 130.1, 126.5,
126.0, 125.8, 122.8, 121.3, 114.5. Anal. Calcd for C19H12BrN5O4, 0.45 x H2O: C, 49.36;
H, 2.81; N, 15.15. Found: C,49.72; H, 3.18, N, 14.78.
4.2.9.
3-(4-(((1,4-Dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-1,2,3-
triazol-1-yl)-2,2-dimethyl-2,3-dihydronaphtho[1,2-b]furan-4,5-dione (28)
Using method A, compound 28 was obtained as a yellow solid (220 mg, 0.7
mmol, 65% yield); mp 218-220 ºC. IR νmax(cm-1, KBr): 3352 (NH), 1671 (C=O), 1654
(C=O), 1605 (C=O), 1565 (C=O). 1H NMR (400 MHz, DMSO-d6) δ: 8.26 (s, 1H), 8.02
(d, 1H, J = 7.34 Hz), 7.97-7.93 (m, 1H), 7.92-7.86 (m, 2H), 7.84-7.76 (m, 3H), 7.76-
7.67 (m, 2H), 6.01 (s, 1H), 5.68 (s, 1H), 4.45 (d, 2H, J = 5.98 Hz), 1.65 (s, 3H), 0.97 (s,
3H). 13C NMR (100 MHz, DMSO-d6) δ: 181.9, 180.1, 174.9, 170.1, 148.6, 143.4,
135.2, 135.1, 133.4, 133.3, 132.7, 132.1, 130.7, 129.1, 126.9, 126.3, 125.7, 125.4,
123.9, 111.6, 101.0, 95.6, 66.5, 38.0, 27.3, 21.0. EI-HRMS (m/z) [M+H]+: 481.1424.
Calcd for [C27H20N4O5H]+: 481.1512.
15

4.2.10. 3-(4-(((3-Bromo-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)-2,2-dimethyl-2,3-dihydronaphtho[1,2-b]furan-4,5-dione (29)
Using method A, compound 29 was obtained as an orange solid 196 mg, 0.5
mmol, 70% yield); mp 167-168 ºC. IR νmax(cm-1, KBr): 3348 (NH), 1671 (C=O), 1651
(C=O), 1608 (C=O), 1565 (C=O). 1H NMR (400 MHz, DMSO-d6) δ: 8.21 (s, 1H), 8.01
(d, 1H, J = 7.26 Hz), 7.94-7.88 (m, 2H), 7.84-7.75 (m, 3H), 7.74-7.68 (m, 3H), 5.99 (s,
1H), 4.99 (d, 2H, J = 6.36 Hz), 1.65 (s, 3H), 0.97 (s, 3H). 13C NMR (100 MHz, DMSO-
d6) δ: 180.1, 175.8, 174.9, 170.2, 168.7, 147.2, 145.6 135.1, 133.4, 133.1, 132.1, 131.8,
130.4, 129.1, 127.0, 126.4, 125.4, 123.4, 123.3, 111.7, 95.6, 40.3, 27.3, 21.0. EI-HRMS
(m/z) [M+H]+: 559.0532. Calcd for [C27H19BrN4O5H]+: 559.0617.
4.2.11. 3-(4-(((3-Chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)methyl)-1H-
1,2,3-triazol-1-yl)-2,2-dimethyl-2,3-dihydronaphtho[1,2-b]furan-4,5-dione (30)
Using method A, compound 30 was obtained as an orange solid (211 mg, 0.5
mmol, 82% yield); mp 194 - 195 ºC. IR νmax(cm-1, KBr): 3355 (NH), 1671 (C=O), 1615
(C=O), 1605 (C=O), 1565 (C=O). 1H NMR (400 MHz, DMSO-d6) δ: 8.24 (s, 1H), 8.02
(d, 1H, J = 6.94 Hz), 7.95-7.90 (m, 2H), 7.86-7.76 (m, 4H), 7.76-7.70 (m, 2H), 6.02 (s,
1H), 4.98 (d, 2H, J = 6.65 Hz), 1.67 (s, 3H), 0.99 (s, 3H). 13C NMR (100 MHz, DMSO-
d6) δ: 180.4, 180.2, 175.9, 174.9, 170.1, 145.8, 135.3, 135.1, 133.4, 133.2, 132.1, 132.1,
130.3, 129.1, 127.0, 126.9, 126.2, 125.4, 123.3, 111.7, 95.6, 66.5, 40.3, 27.3, 21.0. EI-
HRMS (m/z) [M+H]+: 515.1022. Calcd for [C27H19ClN4O5H]+: 515.1122.
4.2.12.
2,2-Dimethyl-3-(4-phenyl-1H-1,2,3-triazol-1-yl)-2,3-
dihydrobenzo[f]furo[2,3-h]quinoxaline (36)
Nor-β-lapachone-based 1,2,3-triazole 31 (200 mg, 0.54 mmol) was reacted with
an excess of ethylenediamine (65 mg, 1.08 mmol) in 30 mL toluene. The reaction was
stirred under reflux in a Dean-Stark apparatus till the total consumption of the reagents
as monitored by TLC. The solvent was evaporated under reduced pressure. The residue
obtained was purified by column chromatography on silica gel using an increasing
polarity mixture of hexane/ethyl acetate as eluent. Compound 36 was obtained as a
yellow solid (162 mg, 0.41 mmol, 77% yield, mp 235-238 ºC); IR (KBr) 1595 (C=N),
16

1346 (C=C), 1070 (C-O), 767 (C-H) cm-1. 1H NMR (400 MHz, CDCl3) δ: 9.28 (dd, 1H
J = 8.11 and 0.73 Hz), 8.74 (d, 1H, J = 2.16 Hz), 8.67 (d, 1H, J = 2.16 Hz), 8.25 (dd,
1H, J = 7.86 and 0.89 Hz), 7.95-7.84 (m, 2H), 7.71-7.67 (m, 2H), 7.34-7.28 (m, 2H),
7.26-7.22 (m, 2H), 6.63 (s, 1H), 1.80 (s, 3H), 1.34 (s, 3H). 13C NMR (100 MHz,
CDCl3)δ: 158.1, 146.1, 144.9, 141.0, 140.6, 138.2, 132.3, 130.3, 129.6, 129.5, 129.0,
128.8, 127.9, 125.2, 125.1, 124.7, 122.6, 122.5, 121.5, 109.8, 92.2, 67.7, 27.0, 21.1.
4.2.13.
2,2-Dimethyl-1-(4-phenyl-1H-1,2,3-triazol-1-yl)-1,2-
dihydrobenzo[a]furo[2,3-c]phenazine (37)
Nor-β-lapachone-based 1,2,3-triazole 31 (150 mg, 0.4 mmol) was reacted with
ortho-phenylenediamine (41 mg, 0.44 mmol) and sodium acetate (62 mg, 0.76 mmol)
in 25 mL glacial acetic acid. The reaction was stirred at room temperature for 2 h. The
reaction was shed over cold water and the precipitate filtered using Buchner funnel. The
solid obtained was purified by column chromatography on silica gel using an increasing
polarity mixture of hexane/ethyl acetate as eluent. Compound 37 was obtained as a
yellow solid (195 mg, 0.44 mmol, 82% yield, mp 224-227 ºC); IR (KBr) 1597 (C=N),
1346 (C=C), 1049 (C-O), 763 (C-H) cm-1.1H NMR (400 MHz, CDCl3) δ: 9.48 (d, 1H, J
= 8.16 Hz), 8.31-8.26 (m, 1H), 8.26-8.21 (m, 1H), 8.06-8.01 (m, 1H), 7.98-7.93 (m,
1H), 7.92-7.86 (m, 1H), 7.78-7.72 (m, 2H), 7.70-7.66 (m, 2H), 7.31-7.25 (m, 3H), 7.24-
13
7.18 (m, 1H), 6.73 (s, 1H), 1.83 (s, 3H), 1.36 (s, 3H). C NMR (100 MHz, DMSO-d6)
δ: 160.2, 146.6, 142.2, 142.2, 141.1, 139.9, 132.9, 131.2, 131.0, 130.8, 130.5, 129.8,
129.6, 129.2, 129.1, 129.1, 128.6, 126.1, 125.5, 125.4, 124.3, 123.5, 121.8, 109.4, 93.1,
68.2, 27.5, 21.6.
4.2.14. (Z)-5-(Hydroxyimino)-2,2-dimethyl-3-(4-phenyl-1H-1,2,3-triazol-1-yl)-2,3-
dihydronaphtho[1,2-b]furan-4(5H)-one (38)
Nor-β-lapachone-based 1,2,3-triazole 31 (200 mg, 0.54 mmol) was reacted with
hydroxylamine hydrochloride (120 mg, 1.68 mmol), sodium acetate (89 mg, 1.08
mmol) and catalytic triethylamine in 30 mL methanol. The reaction was stirred under
reflux overnight. The solvent was evaporated under reduced pressure. The residue
obtained was purified by column chromatography on silica gel using an increasing
polarity mixture of hexane/ethyl acetate as eluent. Compound 38 was obtained as a
17

yellow solid (129 mg, 0.33 mmol, 62% yield, mp 222-225 ºC); IR (KBr) 3449 (OH),
1609 (C=O), 1524 (C=N), 972 (N-O) cm-1. 1H NMR (400 MHz, CDCl3) δ: 8.41 (d, 1H,
J = 8.09 Hz), 7.90 (d, 1H, J = 7.75 Hz), 7.81 (d, 2H, J = 7.55 Hz), 7.73 (t, 1H, J = 7.67
Hz), 7.66-7.58 (m, 2H), 7.40 (t, 2H, J = 7.53 Hz), 7.32 (t, 1H, J = 7.53 Hz), 6.10 (s,
13
1H), 1.78 (s, 3H), 1.27 (s, 3H). C NMR (100 MHz, CDCl3) δ: 202.5, 170.9, 149.4,
147.0, 131.7, 129.7, 129.6, 128.9, 128.8, 128.5, 126.2, 126.0, 125.1, 123.3, 123.3,
123.1, 118.7, 103.0, 89.9, 60.3, 23.1, 23.1.
4.3. Trypanocidal activity
Stock solutions of the compounds were prepared in dimethyl sulfoxide (DMSO),
with the final concentration of the latter in the experiments never exceeding 0.1%.
Preliminary experiments showed that concentrations of up to 0.5%, DMSO have no
deleterious effect on the parasites. Bloodstream trypomastigotes of the Y strain were
obtained at the peak of parasitaemia from infected albino mice, isolated by differential
centrifugation and resuspended in Dulbecco's modified Eagle medium (DME) to a
parasite concentration of 107 cells/mL in the presence of 10% of mouse blood. This
suspension (100 µL) was added in the same volume of each compound previously
prepared at twice the desired final concentrations. Cell counts were performed in
Neubauer chamber and the trypanocidal activity was expressed as IC50, corresponding
to the concentration that leads to lysis of 50% of the parasites.
4.4. Toxicity to heart muscle cells
The cytotoxicity assays were performed using primary cultures of heart muscle
cells (HMC). Briefly, hearts of 18-day-old mouse embryos were fragmented and
dissociated with trypsin and collagenase in phosphate buffered saline (PBS pH 7.2), as
previously established.33 For these experiments, 6x104 cardiomyocytes in 100 mL of
RPMI-1640 medium (pH 7.2) plus 10% foetal bovine serum and 2 mM glutamine were
added to each well of a 96-well microtiter plate and incubated for 24 h at 37°C. The
treatment with 28-30 was performed in fresh supplemented medium without phenol red
(200 µL/well) for 24 h at 37°C. After this period, 110 µL of the medium was discarded
and 10 µL of PrestoBlue (Invitrogen) was added to complete the final volume of 100
µL. Thus, the plate was incubated for 5 h and the measurement was performed at 570
18

and 600 nm, as recommended by the manufacturer. The results were expressed as the
difference in the percentage of reduction between treated and untreated cells being the
LC50 value, corresponds to the concentration that leads to damage of 50% of the
mammalian cells.
4.5. X-Ray analysis
X-ray data were collected at 150 K using MoK (0.71073 A) on an Agilent –
Gemini diffractometer equipped with a CCD area detector. The CrysAlisPro software
package34 was used for data collection and data reduction. The data were corrected
empirically for absorption using spherical harmonics using the SCALE3 ABSPACK35
scaling algorithm. The structure was solved by direct methods using SHELXS-9736 and
refined by full-matrix least squares on F2 using SHELXL-97.37 All non-hydrogen atoms
were successfully refined using anisotropic displacement parameters. Hydrogen atoms
were found in the Fourier difference synthesis and fixed. Crystallographic data for the
structure were deposited in the Cambridge Crystallographic Data Centre, with number
CCDC 926844.
4.6. Electrochemical Studies
Cyclic voltammetry (CV) experiments were performed with a conventional
undivided three electrode cell using an Autolab PGSTAT-30 potentiostat (Echo
Chemie, Utrecht, the Netherlands) coupled to a microcomputer, interfaced by GPES 4.9
software. Glassy carbon (GC) (diameter = 3 mm) as the working electrode, a Pt wire as
the counter electrode and the reference electrode an Ag|AgCl, Cl− (saturated) were used.
The GC electrode was cleaned up by polishing with alumina on a polishing felt (BAS
polishing kit). The solvent used in aprotic media studies, DMF, was distilled under
reduced pressure after stirring with anhydrous copper sulfate. In CV experiments, the
scan rate varied from 10 to 500 mV s-1. All experiments were conducted at room
temperature (25 ± 2 °C) and purging an inert gas (Argon). Electrochemical reduction in
aprotic media (DMF + TBAP 0.1 mol L-1) was performed in the absence of oxygen.
Each compound (1 x 10-3mol L-1) was added to the supporting electrolyte and the
solution was deoxygenated with argon before the measurements by cyclic voltammetry.
4.7. Statistical analysis
19

The comparison between the IC50 values for T. cruzi was performed by ANOVA
followed by the Student-Newman-Keuls and Mann-Whitney tests (p < 0.05).
Conflict of interest
Authors declare no conflict of interest.
Acknowledgements
This research was funded by grants from the Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq) Project Universal – MCTI/CNPq nº
14/2012
(480719/2012-8),
FAPEMIG
APQ-04166-10,
PRONEM-FACEPE
(1232.1.06/10), CENAPESQ-UFRPE, PRONEX/FAPEAL/CNPq and CAPES. Dr. E.N.
da Silva Júnior also thanks the Programa Institucional de Auxílio à Pesquisa de
Doutores Recém-Contratados and Universidade Federal de Minas Gerais. The authors
would like to thank Professors Bruno C. Cavalcanti and Claudia Pessoa for the support
with the biological assays.
References
1. Rassi Júnior, A.; Rassi, A.; Rezende, J. M. Infect. Dis. Clin. North Am. 2012, 26,
275.
2. Schofield, C. J.; Jannin, J.; Salvatella, R. Trends Parasitol. 2006, 22, 583.
3. Shikanai-Yasuda, M. A.; Carvalho, N. B. Clin. Infect. Dis. 2012, 54, 845.
4. Coura, J. R.; Junqueira, A. C. Mem. Inst. Oswaldo Cruz 2012, 107, 145.
5. Schmunis, G. A.; Yadon, Z. E. Acta Trop. 2010, 115, 14.
6. Coura, J. R. ; Viñas, P. A. Nature 2010, 465, S6.
7. Dias, J. C. P. ; Prata, A. ; Correia, D. Rev. Soc. Bras. Med. Trop. 2008, 41, 193.
8. Abad-Franch, F.; Santos, W. S.; Schofield, C. J. Acta Trop. 2010, 115, 44.
9. Guedes, P. M. M.; Silva, G. K.; Gutierrez, F. R. S.; Silva, J. S. Expert Rev. Anti
Infect. Ther. 2011, 9, 609.
10. Soeiro, M. N. C.; de Castro, S. L. Open Med. Chem. J. 2011, 5, 21.
20

11. DNDi 2012 New letter Chagas Disease Clinical Research Plataform, dez 2012
http://www.dndi.org.br/images/stories/img_videos/NEWSLETTERChagasEd2%20
(1)(1).pdf, accessed 12/6/2012.
12. (a) Salas, C. O.; Faúndez, M.; Morello, A.; Maya, J. D.; Tapia, R. A. Curr. Med.
Chem. 2011, 18, 144. (b) Pieretti, S.; Haanstra, J. R.; Mazet, M.; Perozzo, R.;
Bergamini, C.; Prati, F.; Fato, R.; Lenaz, G.; Capranico, G.; Brun, R.; Bakker, B.
M.; Michels, P. A. M.; Scapozza, L.; Bolognesi, M. L.; Cavalli, A. PLoS Negl.
Trop. Dis. 2013, 7, e2012.
13. O’Brien, P. J. Chem. Biol. Interact. 1991, 80, 1.
14. Constantino, L.; Barlocco, D. Curr. Med. Chem. 2006, 13, 65.
15. Pinto, A. V.; de Castro, S. L. Molecules, 2009, 14, 4570.
16. (a) da Silva Júnior, E. N.; Menna-Barreto, R. F. S.; Pinto, M. C. F. R.; Silva, R. S.
F.; Teixeira, D. V.; Souza, M. C. B. V.; de Simone, C. A.; de Castro, S. L.;
Ferreira, V. F.; Pinto, A. V. Eur. J. Med. Chem. 2008, 43, 1774. (b) da Silva
Júnior, E. N.; Guimarães, T. T.; Menna-Barreto, R. F. S.; Pinto, M. C. F. R.; de
Simone, C. A.; Pessoa, C.; Cavalcanti, B. C.; Sabino, J. R.; Andrade, C. K. Z.;
Goulart, M. O. F.; de Castro, S. L.; Pinto, A. V. Bioorg. Med. Chem. 2010, 18,
3224.(c) da Silva Júnior, E. N.; de Moura, M. A. B. F.; Pinto, A. V.; Pinto, M. C.
F. R.; Souza, M. C. B. V.; Araújo, A. J.; Pessoa, C.; Costa-Lotufo, L. V.;
Montenegro, R. C.; de Moraes, R. C.; Goulart, M. O. F.; Ferreira, V. F. J. Braz.
Chem. Soc. 2009, 20, 635. (d) da Silva Júnior, E. N.; Melo, I. M. M.; Diogo, E. B.
T.; Costa, V. A.; Souza Filho, J. D.; Valença, W. O.; Camara, C. A.; Oliveira, R.
N.; Araujo, A. S.; Emery, F. S.; Santos, M. R.; de Simone, C. A.; Menna-Barreto,
R. F. S.; de Castro, S. L. Eur. J. Med. Chem. 2012, 52, 304.
17. (a) Guimarães, T. T.; Pinto, M. C. F. R.; Lanza, J. S.; Melo, M. N.; do Monte-Neto,
R. L.; de Melo, I. M. M.; Diogo, E. B. T.; Ferreira, V. F.; Camara, C. A.; Valença,
W. O.; de Oliveira, R. N.; Frézard, F.; da Silva Júnior, E. N. Eur. J. Med. Chem.
2013, 63, 523. (b) Rostovtsev, V. V.; Green, G. L.; Fokin, V. V.; Sharpless, K. B.
Angew. Chem., Int. Ed. 2002, 41, 2596.
18. (a) Pinto, A. V.; Neves Pinto, C.; Pinto, M. C. F. R.; Santa Rita, R.; Pezzella, C. A.
C.; de Castro, S. L. Arzneim-Forsch. 1997, 47, 74; (b) Neves-Pinto, C.; Dantas, A.
P.; Moura, K. C. G.; Emery, F. S.; Polequevitch, P. F.; Pinto, M. C. F. R.; de
Castro, S. L.; Pinto, A. V. Arzneim-Forsch. 2000, 50, 1120. (c) Pinto, A. V.; Cruz,
21

F. S.; Pellegrino, J.; Mello, R. T. Trans. Roy. Soc. Trop. Med. Hyg. 1977, 71, 133.
(d) da Silva Júnior, E. N.; de Souza, M. C. B. V.; Fernandes, M. C.; Menna-
Barreto, R. F. S.; Pinto, M. C. F. R.; Lopes, F. A.; de Simone, C. A.; Andrade, C.
K. Z.; Pinto, A. V.; Ferreira, V. F.; de Castro, S. L. Bioorg. Med. Chem. 2008, 16,
5030.
19. (a) Goulart, M. O. F.; Zani, C. L.; Tonholo, J.; Freitas, L. R.; de Abreu, F. C.;
Oliveira, A. B.; Raslan, D. S.; Starling, S.; Chiari, E. Bioorg. Med. Chem. Lett.
1997, 7, 2043. (b) Paulino, M.; Alvareda, E. M.; Denis, P. A.; Barreiro, E. J.;
Sperandio da Silva, G. M.; Dubin, M.; Gastellú, C.; Aguilera, S.; Tapia, O. Eur. J.
Med. Chem. 2008, 43, 2238. (c) Pérez-Silanes, S.; Devarapally, G.; Torres, E.;
Moreno-Viguri, E.; Aldana, I.; Monge, A.; Crawford, P. W. Helv. Chim. Acta,
2013, 96, 217.
20. Song, Y.; Buettner, G. R. Free Radic. Biol. Med. 2010, 49, 919.
21. (a) Hillard, E. A.; de Abreu, F. C.; Ferreira, D. C. M.; Jaouen, G.; Goulart, M. O. F.;
Amatore, C. Chem. Commun. 2008, 2612. (b) Araújo, A. J.; de Souza, A. A.; da
Silva Júnior, E. N.; Marinho-Filho, J. D. B.; de Moura, M. A. B. F.; Rocha, D. D.;
Vasconcellos, M. C.; Costa, C. O.; Pessoa, C.; de Moraes, M. O.; Ferreira, V. F.; de
Abreu, F. C.; Pinto, A. V.; Montenegro, R. C.; Costa-Lotufo, L. V.; Goulart, M. O.
F. Toxicol. in vitro. 2012, 26, 585. (c) Cavalcanti, B.; Barros, F. W. A.; Cabral, I.;
Ferreira, J.; Magalhães, H.; Júnior, H.; da Silva Júnior, E. N.; de Abreu, F. C.;
Costa, C. O.; Goulart, M. O. F.; Moraes, M. O.; Pessoa, C. Chem. Res. Toxicol.
2011, 24, 1560. (d) Ferreira, D. C. M.; Tapsoba, I.; Arbault, S.; Bouret, Y.;
Moreira, A. M. S.; Pinto, A. V.; Goulart, M. O. F.; Amatore, C. ChemBioChem.
2009, 10, 528.
22. Ceric, H.; Šindler-Kulyk, M.; Kovacevic, M.; Peric, M.; Ivkovic, A. Z. Bioorg. Med.
Chem. 2010, 18, 3053.
23. Spallarossa, A.; Cesarini, S.; Ranise, A.; Bruno, O.;Schenone, S.; La Colla, P.;
Collu, G.; Sanna, G.; Secci, B.; Loddo, R. Eur. J. Med. Chem. 2009, 44, 1650.
24. Banik, B. K.; Banik, I.; Becker, F. F. Bioorg. Med. Chem. 2005, 13, 3611-3622.
25. Li, Y. F.; Wang, G. F.; He, P. L.; Huang, W. G.; Zhu, F. H.; Gao, H. Y.; Tang, W.;
Luo, Y.; Feng, C. L.; Shi, L. P.; Ren, Y. D.; Lu, W.; Zuo, J. P. J. Med. Chem. 2006,
49, 4790.
26. Fieser, L. F.; Fieser, M. J. Am. Chem. Soc. 1948, 70, 3215.
22

27. da Silva, M. T.; de Oliveira, R. N.; Valença, W. O.; Barbosa, F. C. G.; da Silva, M.
G.; Camara, C. A. J. Braz. Chem. Soc. 2012, 23, 1839.
28. Hein, J. E.; Fokin, V. V. Chem. Soc. Rev., 2010, 39, 1302.
29. Meldal, M.; Tornøe, C. W. Chem. Rev. 2008, 108, 2952.
30. Silva, R. S. F.; Pinto, M. C. F. R.; Goulart, M. O. F.; de Souza Filho, J. D.; Neves
Júnior, I.; Lourenço, M. C. S.; Pinto, A. V. Eur. J. Med. Chem. 2009, 44, 2334.
31. Emery, F. S.; Silva, R. S. F.; de Moura, K. C. G.; Pinto, M. C. F. R.; Amorim, M.
B.; Malta, V. R. S.; Santos, R. H. A.; Honório, K. M.; da Silva, A. B. F.; Pinto, A.
V. An. Acad. Bras. Cienc. 2007, 79, 29.
32. Romanha, A. J.; de Castro, S. L.; Soeiro, M. N.; Lannes-Vieira, J.; Ribeiro, I.;
Talvani, A.; Bourdin, B.; Blum, B.; Olivieri, B.; Zani, C.; Spadafora, C.; Chiari, E.;
Chatelain, E.; Chaves, G.; Calzada, J. E.; Bustamante, J. M.; Freitas-Júnior, L. H.;
Romero, L. I.; Bahia, M. T.; Lotrowska, M.; Soares, M.; Andrade, S. G.; Armstrong,
T.; Degrave, W.; Andrade, Z. A.; Mem Inst Oswaldo Cruz. 2010, 105, 233.
33. Meirelles, M. N.; de Araujo-Jorge, T. C.; Miranda, C. F.; de Souza, W.; Barbosa, H.
S.; Eur. J. Cell Biol. 1986, 41, 198.
34. CRYSALISPRO, Agilent Technologies, Version 1.171.35.21 (release 20-01-2012
CrysAlis171 .NET.
35. SCALE3 ABSPACK scaling algorithm. CrysAlis, Agilent Technologies, Version
1.171.35.21 (release 20-01-2012 CrysAlis171 .NET).
36. Sheldrick, G. M.; SHELXS-97, Program for the Solution of Crystal Structures,
University of Göttingen, Germany, 1997.
37. Sheldrick, G. M.; SHELXL-97, Program for the Refinement of Crystal Structures,
University of Göttingen, Germany, 1997.
23

Tables
Table 1. Major electrochemical parameters of the quinones (c = 1 x 10-3 mol L-1), in
DMF/TBAP, 0.1 mol L-1,  = 50 mV s-1.
Compound
Epc1
(V)
Eredox
(V)
Epc2
(V)
Additional waves
(V)
_
-1.143
-1.110
4
-0.630
-0.623
-0.807
-0.286
-0.291
-0.511
-0.521
-0.535
-0.515
-0.510
-0.493
-0.506
-0.586
-0.581
-0.761
-0.244
-0.252
-0.467
-0.475
-0.472
-0.454
-0.464
-0.444
-0.457
_
6
16
25
26
28
30
31
32
33
34
35
-1.348
-0.930
-1.993, -2.436
_
-0.940
_
-0.799
-0.648
-0.965, -1.311
-0.999, -1.216
-1.055
-0.950
-
_
-0.925
_
-1.441
_
-1.001
-0.935
1

Table 2. Crystal data and structure refinement for compound 38.
Empirical formula
Formula weight
C22H18N4O3
386.41
Temperature
150(2) K
Wavelength
0.71073 Å
Crystal system, space group
Unit cell dimensions
Monoclinic, P21
a = 5.6099(2) Å
b = 11.3548(5) Å
α = 90°
 = 96.641(4)°
c = 14.5658(7) Å γ = 90°
Volume
921.61(7) Å3
Z, Calculated density
Absorption coefficient
F(000)
2, 1.392 Mg/m3
0.095 mm-1
404
Crystal size
0.087 x 0.170 x 0.188 mm3
Theta range for data collection
Limiting indices
Reflections collected
Independent reflections
2.28 to 29.42°
-7<=h<=7, -14<=k<=14, -19<=l<=18
4789
3346 [R(int) = 0.0275]
Completeness to theta = 26.32° 99.95 %
Absorption correction
Max. and min. transmission
Refinement method
Semi-empirical from equivalents
1 and 0.93
Full-matrix least-squares on F2
Data / restraints / parameters 3346 / 1 / 272
Goodness-of-fit on F2
1.107
R1 = 0.0465, wR2 = 0.1163
R1 = 0.0598, wR2 = 0.1342
0.292 and -0.315 e.Å-3
Final R indices [I>2(I) ]
R indices (all data)
Largest diff. peak and hole
2

Table 3. Intermolecular interaction parameters (A, º) for compound 38.
A-H...B
d(A-B)
3.364(4)
3.297(4)
3.477(3)
d(A-H)
0.963(3)
0.977(3)
0.984(3)
d(H…A)
2.665(2)
2.588(2)
2.527(2)
<(DHA)
129.8(2)
C181-H181…N3
C192-H192…N2
C13-H13…O2
129.51(19)
162.24(19)
Symmetry operators: (1) –x, -0.5+y, 2-z; (2) 1-x, -0.5+y, 2-z; (3) -1+x, y, z
3

Table 4. Activity of compounds against the trypomastigote form of T. cruzi.
IC50/24 ha (μM)
Compound
Lapachol (1)b
α-Lapachone (2)b
410.8 ± 53.5
>4800
4-Azido-α-lapachone (3)
318.2 ± 31.8
>2000
4
>4000
5
>500
6
Nor-α-lapachone (7)c
>4800
3-Azido-nor-α-lapachone (8)c
179.3 ± 12.0
>1500
9
>2000
10
>4000
11
>4000
12
>4000
13
>4000
14
>4000
15
16
>4000
>4000
17
>4000
18
>4000
19
>4000
19
>4000
20
>4000
21
>4000
22
>4000
23
>4000
24
25d
26d
10.9 ± 1.8
45.8 ± 5.1
50.2 ± 3.8
80.8 ± 6.5
6.8 ± 0.7
3-Azido-nor-β-lapachone (27)c
28
29
4

8.2 ± 0.7
17.3 ± 2.0
20.8 ± 1.9
359.2 ± 11.1
21.8 ± 3.1
39.6 ± 4.0
>4000
30
31a
32c
33c
34c
35c
36
37
>1500
>3200
38
Benznidazolec
Crystal violetc
103.6 ± 0.6
536.0 ± 3.0
aMean ± SD of at least three independent experiments. bRef. 18d. cRef. 16a. dRef. 16d.
5

Figures and Schemes
Scheme 1. Structural modification of the prototype β-lapachone and nor-β-lapachone.
Scheme 2. α-Lapachone- and nor-α-lapachone-derived 1,2,3-triazoles 4-6 and 9-12.
Scheme 3. 1,4-Naphthoquinone-derived 1,2,3-triazoles 13-26.
Scheme 4. Nor-β-lapachone-derived 1,2,3-triazoles 28-35. aRef. 16a,d.
Scheme 5. Preparation of 1,2,3-triazoles 36-38 derived from nor-β-lapachone based on
compound 31.
Figure 1. Cyclic voltammograms of naphthoquinones 4, 6, 9, 16, 25, 26, 28, 30-35 (c =
1 x 10-3 mol L-1). DMF/TBAP (0.1 mol L-1), glassy carbon electrode, cathodic direction,
v = 50 mV.
Figure 2. ORTEP-3 projection of compound 38 showing atom labeling and
displacement ellipsoids drawn at the 50% probability level.
Figure 3. Graph correlating the values of Epc1 of each quinone with its trypanocidal
activity (bloodstream trypomastigote forms), represented by IC50/24 h ( M)
1