Redox Center Modification of Lapachones towards the Synthesis of Nitrogen Heterocycles as Selective Fluorescent Mitochondrial Imaging Probes

Article abstract of DOI:10.1002/ejoc.201700227

We describe herein a synthetic strategy for the synthesis of new fluorescent imidazole and phenazine derivatives synthesized from lapachol, a naturally occurring naphthoquinone isolated from Tabebuia species (ipê tree). The photophysical properties and computational details of these compounds have been studied, aiming at gaining a complete understanding of the potential of these derivatives as probes capable of staining mitochondria selectively. Cell imaging experiments proved the capacity of the imidazole derivatives as selective fluorescent mitochondrial imaging probes. These heterocycles present the same staining patterns as MitoTracker Red, corroborating the potential of these compounds as new mitochondria markers permeable to the cell membrane.

Full text of DOI:10.1002/ejoc.201700227

A Journal of
Accepted Article
Title: Redox Center Modification of Lapachones Toward the Syntheses
of Nitrogenated Heterocycles as Selective Fluorescent
Mitochondrial Imaging Probes
Authors: Fabíola dos Santos, Gleiston G. Dias, Rossimiriam P. de
Freitas, Lucas S. Santos, Guilherme F. de Lima, Hélio A.
Duarte, Carlos A. de Simone, Lidia Rezende, Monique J. X.
Vianna, José R. Correa, Brenno A. D. Neto, and Eufrânio
Nunes da Silva Júnior
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published online in Early View as soon as possible and may be different
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the VoR from the journal website shown below when it is published
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content of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201700227
Link to VoR: http://dx.doi.org/10.1002/ejoc.201700227
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10.1002/ejoc.201700227
European Journal of Organic Chemistry
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Redox Center Modification of Lapachones Toward the Syntheses
of Nitrogenated Heterocycles as Selective Fluorescent
Mitochondrial Imaging Probes
Fabíola S. dos Santos,[a]1 Gleiston G. Dias,[a]1 Rossimiriam P. de Freitas,[a] Lucas S. Santos,[a]
Guilherme F. de Lima,[a] Hélio A. Duarte,[a] Carlos A. de Simone,[b] Lidia M. S. L. Rezende,[c] Monique J.
X. Vianna,[c] José R. Correa,[c] Brenno A. D. Neto[c] and Eufrânio N. da Silva Júnior*[a]
Abstract: This work describes a synthetic strategy for the syntheses
of new fluorescent imidazole and phenazine derivatives synthesized
from lapachol, a naturally occurring naphthoquinone isolated from
Tabebuia species (ipê tree). Photophysical properties and
computational details of these compounds were studied aiming at a
complete understanding of the potential of these derivatives as
probes capable of staining mitochondria selectively. Cell imaging
experiments proved the imidazole derivatives capacity as selective
fluorescent mitochondrial imaging probes. These heterocycles
presented the same staining patterns of MitoTracker red
corroborating the potential of these compounds as new mitochondria
markers permeable to the cell membrane.
derivatives easily obtained from lapachol. These compounds
were observed as superior and selective probes for endocytic
pathway tracking in live cancer cells. Finally, phenazine-based
1,2,3-triazole was efficient for determining Cd2+ ions in
H2O/CH3CN medium. Later, our group have also studied the
indirect
consequences
of
exciplex
states
on
the
phosphorescence lifetime of this phenazinic compound.[13]
Taking into account the large number of possible substituents
and also the easy π-conjugation (beneficial effect for
fluorescence emissions) one may rationalize several new
bioprobes from lapachones.
Fluorescent phenazines[14-16] and their complexes may be
used to stain different cell organelles as well as fluorescent
imidazoles.[17-19] Among the almost uncountable possibilities of
specific staining inside live cells, the mitochondria are organelles
of paramount importance.[20] Known to be the membrane-bound
powerhouse of eukaryotic cells,[21] the dysfunction of this
organelle is related to several diseases[22-24] or apoptotic
processes.[25-27] The specific staining of mitochondria is even
more challenge whether one consider that these organelles vary
the size, morphology, dynamics and quantities from organism to
organism.[28] To follow the mitochondrial dynamics in live cells is
indeed a hard task[29] where fluorescent small molecule probes
are key players toward the understanding and roles of many
factors affecting the mitochondrial regular function.[30]
Due of our interest on the development of new and
selective bioprobes,[31] especially for mitochondrial selective
staining,[32-34] we disclose herein our synthetic strategy in the
syntheses of new fluorescent imidazole and phenazine
derivatives from lapachone toward selective mitochondrial
staining in live cells.
Introduction
Inspiration from nature toward chemical transformations
and new compounds syntheses is virtually unlimited.[1] Versatile
synthons and intermediates may be directly accessed and, in
many cases, multigram access is not a drawback for fine
chemical transformations. β-Lapachone and its derivatives are
among these classes of natural substrates widely used for a
plethora of applications such as organic chemistry
transformation,[2] anticancer agents,[3] trypanocidal[4] and many
others.[5] Lapachol is a naturally occurring naphthoquinones[6]
prone to several chemical modifications, attracting therefore, the
interest for the possibilities of structural diversity and
applications.[7]
The opportunity of generating heterocyclic compounds
from naphthoquinoidal derivatives obtained from lapachones in a
straight fashion is an additional feature to be considered
(Scheme 1A).[8,9] For example, our group have recently
demonstrated the application of this strategy for the synthesis of
fluorescent oxazoles,[10] boron complexes mimic BODIPYs[11]
and phenazine-based 1,2,3-triazole[12] (Scheme 1B). We have
shown that the lipophilic oxazoles are able to use for selective
cellular staining of lipid-based structures. In the same way, we
have designed and prepared boron complexes of oxazole
[a]
Institute of Exact Sciences, Department of Chemistry, Federal
University of Minas Gerais, Belo Horizonte, 31270-901, MG, Brazil.
E-mail: eufranio@ufmg.br
[b]
[c]
[1]
Department of Physics and Informatics, Institute of Physics,
University of São Paulo, São Carlos, 13560-160, SP, Brazil
Institute of Chemistry, University of Brasilia, P.O. Box 4478, Brasilia,
70904970, DF, Brazil.
These authors contributed equally to this work
Supporting information for this article is given via a link at the end of
the document.
Scheme 1. Redox centre modification of lapachones to afford fluorescent
imidazole, oxazoles and phenazine derivatives.
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Results and Discussion
With compound 6 in hands, phenazine P1 was prepared
by the reaction with ortho-phenylenediamine. Next, different
diamines were prepared by using a reductive sulfur extrusion of
substituted 2,1,3-benzothiadiazole (BTD). Initially, π-extended
BTDs were prepared following methodology previously
described with minor modifications.[41] The substitution pattern of
the BTDs was selected aiming electronic conjugation in order to
favor the increase of the fluorescence of the subsequent
phenazines. The sulfur extrusion from 2,1,3-benzothiadiazole
was accomplished by using NaBH4 in the presence of catalytic
amounts of CoCl2•6H2O (1 mol %) as described elsewhere.[42]
With the respective substituted diamines in hands, we have
synthesized phenazines P2 and P3 by the reaction with 6.
Compound P4 was prepared by cross coupling Sonogashira
reaction from dibromide compound P2. All attempts for obtaining
P4 from the respective π-extended diamine prepared by Suzuki
reaction afforded the product in poor yields.
The new fluorescent imidazole and phenazine derivatives
were synthesized as shown in Scheme 2. Quinone-based 1,2,3-
triazole (6) was prepared by using classical click chemistry
methodology and used for the synthesis of the phenazinic
compounds.[35] Initially, lapachol (1),
a natural occurring
naphthoquinone was easily extracted from the heartwood of
Tabebuia sp. (Tecoma),[36] and after recrystallization with
appropriate solvent, generally hexane, yellow crystalline solid of
1 was used for converting into nor-lapachol (2) via Hooker
oxidation reaction.[37] Compound 2 was then treated with
bromine affording 3-bromo-nor-β-lapachone, which was followed
by
dichloromethane to obtain 3-azido-nor-β-lapachone (5) as
previously described.[38] Finally,
click reaction with the
nucleophilic
substitution
with
sodium
azide
in
a
respective alkyne was used to produce compound 6 in good
70% yield. The structures of P5 and 6 were solved by using
crystallographic methods. Bond lengths and angles are in good
agreement with the expected values reported in the literature.[39]
Compound P5 crystallizes with two independent molecules in
the asymmetric unit and two water molecules. For clarity, we are
showing only one molecule in Scheme 2. The naphthalene and
imidazole rings are coplanar and the largest deviation [0.078(2)
Å] from the least-square plane is exhibited by atom C1. The
dihedral angle between the least-square plane calculated
through the atoms of these two rings and [C12-C17] ring is
10.9(3)°. The dihydrofuran ring present a twisted conformation
where the puckering parameters calculated for this conformation
were: q2 = 0.287(1) Å, q3 = 0.581(1) Å, φ2 = 147.9(2)° , Q =
0.648(3) Å , θ2 = 26.36°.[40] For compound 6 the atoms of the
naphthoquinoidal ring are coplanar and the largest deviation
[0.0515(2) Å] from the least-square plane is exhibited by atom
C7. Atoms O1 and O2 lie in the mean least-square plane of the
quinoidal ring with deviations of 0.0319(1) and 0.0156(1)
respectively. Regarding the dihydrofuran ring, the atoms O3, C1
and C12 lie out of the mean least-square plane with deviations
of -0.1626(2) Å, -0.1408(1) Å and -0.4833(1) Å respectively and
this attribute to furan ring an envelope conformation. The
puckering parameters calculated for this conformation were: q2 =
0.251(1) Å and φ2= 122.5(2)°.[40] The dihedral angle between
the least-square plane calculated through the atoms of quinoidal
and triazole rings is 86.05(3)°. The least-square plane calculated
through the atoms [C16-C29] showing almost planarity and the
dihedral angle between this plane and the triazole ring is
Naphthoimidazoles derivatives were synthesized by well-
know methodology described by Pinto and coworkers.[43] Ortho-
quinones were used for the synthesis of the fluorescent
imidazoles P5 and P6. From lapachol (1) and nor-lapachol (2),
the ortho-quinoidal compounds, nor-β-lapachone (3) and β-
lapachone (4) were prepared via acidic cyclization by simple
treatment with sulfuric acid. Quinones 3 and 4 were reacted with
terephthalaldehyde in acetic acid in the presence of ammonium
acetate affording P5 and P6.
Fluorescent phenazine and imidazole derivatives had their
photophysical features studied and results are summarized in
Table 2 (also see Fig. S37-40 in the ESI file). Phenazines P1,
P3 and P4 showed small Stokes shifts and reasonable molar
extinction coefficients with log ε values in the range of 3.79-4.61
mM-1 cm-1. Although we have prepared P2 for preparing P4, we
have also evaluated their photophysical details, but it was not
observed good fluorescence pattern for this nitrogenated
heterocycle. In general, probes P1, P3 and P4 are fluorescent
but these data indicate that π-extended phenazinic systems
were not as efficient as expected to be.
Imidazole derivatives P5 and P6 however displayed large
Stokes shifts. In solvents, as for instance, acetonitrile,
dichloromethane and dimethyl sulfoxide, we have observed
values in the range of 137 to 155 nm. Large molar extinction
coefficients (log ε values in the range of 4.11-4.95 mM-1 cm-1)
were also noted. These data indicates that the P5 and P6 have
desirable photophysical characteristics to be used as
a
fluorescent probes for bioimaging. Photophysical details of the
compounds in Phosphate-Buffered Saline (PBS, pH = 7.1) was
also studied. All the fluorescent probes, with exception of P1,
have shown similar features as observed for all the aprotic and
protic solvents evaluated.
135.95(2)°. All
H
atoms were located by geometric
considerations placed (C–H = 0.93-0.97 Å) and refined as riding
with Uiso(H) = 1.5 Ueq (C-methyl) or 1.2 Ueq (other). An Ortep-3
diagram of the molecules is shown in Scheme 2 and Table 1
shown the main crystallographic data for P5 and 6.
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Table 1. Main crystallographic data.
Identification code
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
Compound P5
C23H20N2 O2
744.8
293(2) K
0.71073 Å
monoclinic
C2/c
Compound 6
C29H38N3 O3
476.6
293(2) K
0.71073 Å
triclinic
P-1
a = 32.7465(4) Å
b = 16.3390(3) Å
c = 14.1742(2) Å
α = 90°
β = 93.113(4)°
γ = 90°
a = 7.4250(4) Å
b = 9.6190(6) Å
c = 21.0910(12) Å
α = 87.198(3)°
β = 81.595(4)°
γ = 67.245(4)°
Unit cell dimensions
3
3
Volume
7572.6(3) Å
1374.2(3) Å
Z
8
2
3
3
Density (calculated)
1.31 Mg/m
1.15 Mg/m
-1
-1
Absorption coefficient
F(000)
0.087 mm
3136
0.075 mm
514
3
3
Crystal size
0.34 x 0.21 x 0.15 mm
2.0 to 26.5°
0.20 x 0.18 x 0.12 mm
2.9 to 26.4°
Theta range for data collection
-40≤h≤40, -20≤k≤17,
-17≤l≤17
-7≤h1≤7, -9≤k≤10,
-22≤l≤22
Index ranges
Reflections collected
Independent reflections
Absorption correction
28393
7724 [R(int) = 0.08]
none
7077
3383 [R(int) = 0.08]
none
2
2
Refinement method
Data / restraints / parameters
Full-matrix least-squares on F
Full-matrix least-squares on F
2232 / 0 / 316
4792 / 0 / 505
1.08
2
1.017
Goodness-of-fit on F
Final R indices [I>2sigma(I)]
R1 = 0.09, wR2 = 0.191
R1 = 0.07, wR2 = 0.181
-3
-3
Largest diff. peak and hole
0.98 and -0.64 e.Å
0.483 and -0.470 e.Å
Scheme 2. Synthesis of fluorescent phenazine and oxazole derivatives P1-P6.
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Table 2. Photophysical data (in different solvents) for P1, P3-P6.
Compounds
P1
Solvent
ethyl acetate
acetonitrile
dichloromethane
dimethyl sulfoxide
hexane
λmax. (abs) (nm)
log ε (ε)
4.54 (34512)
4.51 (32044)
4.56 (35923)
4.50 (31762)
4.60 (40028)
4.55 (35400)
4.61 (40720)
nd
λmax. (em) (nm)
Stokes Shift (nm)
425
424
426
429
424
423
427
nd
450
457
448
469
433
470
443
nd
25
33
22
40
9
47
16
nd
methanol
toluene
PBS
ethyl acetate
acetonitrile
dichloromethane
dimethyl sulfoxide
hexane
411
412
413
416
411
411
414
434
3.90 (7904)
3.79 (6198)
3.83 (6738)
3.85 (7132)
3.89 (7848)
3.82 (6700)
3.87 (7366)
3.26 (1827)
554
563
555
572
532
585
547
537
143
151
142
156
121
174
133
103
P3
P4
P5
P6
methanol
toluene
PBS
ethyl acetate
acetonitrile
dichloromethane
dimethyl sulfoxide
hexane
421
420
422
424
421
420
423
425
4.06 (11434)
4.03 (10682)
4.02 (10554)
4.07 (11864)
4.06 (11602)
4.03 (2005)
4.11 (12846)
4.05 (11203)
511
502
514
511
495
528
507
498
90
82
92
87
74
108
84
129
methanol
toluene
PBS
ethyl acetate
acetonitrile
dichloromethane
dimethyl sulfoxide
hexane
401
395
391
394
390
387
395
389
4.41 (25704)
4.50 (31623)
4.55 (35481)
4.56 (36308)
4.43 (26919)
4.39 (24547)
4.48 (30200)
4.02 (10460)
493
543
523
545
424
469
487
498
92
148
132
151
34
82
92
109
methanol
toluene
PBS
ethyl acetate
acetonitrile
dichloromethane
dimethyl sulfoxide
hexane
392
399
401
403
395
390
401
395
4.47 (29512)
4.51 (32359)
4.68 (47863)
4.52 (33113)
4.95 (89125)
4.60 (39808)
4.43 (26915)
4.10 (12496)
503
552
538
558
430
437
488
500
111
153
137
155
35
47
87
105
methanol
toluene
PBS
Quantum yields (in dichloromethane) for P1 and P3-P6 of 0.31, 0.62, 0.57, 0.42 and 0.58, respectively. PBS = Phosphate-Buffered Saline (pH = 7.1).
nd, Not determined. Photophysical data for P1 in PBS was not determined due low solubility in all conditions evaluated.
-
LUMO transition and this transition has
a significant
Calculations based on Density Functional Theory (DFT)
were carried out at B3LYP[44,45]/TZVP level of theory using the RI
approach and the D3 dispersion scheme proposed by Grimme
and coworkers.[46] Each structure was fully optimized using a
convergence criteria of 10-6 Hartree and 10-8 Hartree in the SCF
calculation. Harmonic frequencies were evaluated for each
optimized structure to confirm that it corresponds to a minimum
in the potential energy surface. The orbitals were plotted with
isovalue of 0.02 e Bohr-3. All calculations were carried out in
Orca 3.0.2.[47] DFT calculations were conducted in order to
evaluate the frontier orbitals for P1 and P3-P6, as shown in
Figure 1 and for more details see in the ESI (S41-45). The
excited states were evaluated by TD-DFT calculations using the
similar theory level described above considering 150 transitions.
Our calculations indicate that both HOMO and LUMO orbitals
are dispersed in a long extension of the molecules and are
basically of π type. The aliphatic side did not show any
significant contribution to the frontier orbitals in any molecule, as
expected. The HOMO-LUMO band gap was also evaluated for
each species. P5 showed a band gap of 2.7 eV, P1 was 3.4 eV.
P3, P4 and P6 had band gaps of 3.1 eV. TD-DFT calculations
suggest that the first excited state is maily formed by the HOMO
contribution to the UV-VIS spectra.
Finally, compounds for P1 and P3-P6 had their capacity as
bioimaging probes evaluated against MCF-7 (human breast
adenocarcinoma cells), Caco-2 (human epithelial colorectal
adenocarcinoma cells), PANC-1 (human pancreatic carcinoma,
epithelial-like cells line) and the T47D (human ductal breast
epithelial tumor cells line) and the normal cells HUVEC (human
umbilical vein epithelial cells) cells lineage (Figure 2 and Figures
S46-S52, in the ESI file). As suggested by the photophysical
studies, phenazines P1, P3 and P4 were not efficient to stain
any cellular organelles and could be not visualized inside the
cells.
Compounds P5 and P6 aldehyde-bearing dyes[48] afforded
intense dual fluorescence signals in the ranges of 420-450 nm
(blue) and 510-560 nm (green), and it was detected no naked
eye photobleaching at the standard operational conditions
during the image acquisition process. These compounds were
observed distributed near to the nucleus and slightly diffuse
through the cells cytoplasm. Both samples conditions (live and
fixed cells) showed the same fluorescence pattern. For all
Figures the red arrows are indicating the cells regions stained
for both compounds and it was also observed difference
between fluorescent signal intensities.
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Compound P6 has produced more accentuated
fluorescence emission under the same analysis conditions, as
can be observed in the confocal microscopy images (Figure 3).
However, only the fixed cell samples stained with compound P6
shows specific marker accumulation near to the nuclei. In the
live samples, the staining profile was more diffuse to the cells
cytoplasm, Figure 2. No fluorescent signal could be detected in
cells nuclei at all experimental conditions, which are noted as
black voids inside the cells cytoplasm (Figures 2 and 3). It was
also generated phase contrast image for all samples in order to
verify the cells morphological aspects. It was observed none
morphological alteration for all tested samples related to the
short period of cells incubation with these compounds. However,
the viability test performed based on 24 hours of cells incubation
of these compounds showed different cytotoxic levels depending
on the cell type used during the assay. Only when the samples
were incubated with 10 µM solution, compound P5 produced
more accentuated cytotoxic effect than those observed in
samples treated with P6. None cytotoxic effect could be
detected in normal cell sample HUVEC treated with the tested
compounds at both concentrations. The differences observed
between microscopy results and MTT results could be explained
by the time of incubation. Results suggest that it is necessary
much more than 30 minutes for both compound start to induce
cytotoxicity.
Figure 2. Fluorescent profile of MCF-7 cells, incubated with compound P5.
Images A, B, D and E show the fluorescent signal distribution to cells
cytoplasm in live (A and B) and fixed (D and E) samples. The images C and F
show the normal morphological aspects of these samples by phase contrast
microscopy. The arrowheads (red) show the distribution of fluorescence in
cells cytoplasm. Note the accumulation of fluorescent stain at perinuclear
region for both experimental conditions. The “N” letter was used to identify the
nuclei. Reference scales bar 25 μm were indicated.
Figure 3. Fluorescent profile of MCF-7 cells, incubated with compound P6.
Images A, B, D and E show the fluorescent signal distribution to cells
cytoplasm in live (A and B) and fixed (D and E) samples. The images C and F
show the normal morphological aspects of these samples by phase contrast
microscopy. The arrowheads (red) show the distribution of fluorescence in
cells cytoplasm. Note a more intense fluorescence emission and specific
staining accumulation in perinuclear region in fixed cells sample. The “N” letter
was used to identify the nuclei. Reference scales bar 25 μm were indicated.
Figure 1. Molecular Orbital Diagram for P1, P3-P6 and their respective HOMO
orbital and the first excited state calculated at DFT/B3LYP/TZVP and TD-DFT/
B3LYP/TZVP level of theory, respectively, and plotted using an isovalue of
0.02 e Bohr-3.
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In order to confirm that the observed fluorescent patterns
are correlated with the mitochondria staining it was performed a
cells staining by using MitotrackerTM, which is a widely used
commercial marker of mitochondria. The fluorescent signal
pattern observed in mammal cells using P5 and P6 were
identical to the fluorescent pattern obtained from MitotrackerTM
staining assay. Both compounds and the MitotrackerTM were
observed accumulated near to the cells nuclei and slight
distributed in cells cytoplasm, which is the typical mitochondria
distribution in this line cell model. The results obtained by
MitotrackerTM cells staining confirmed our preview finds that P5
and P6 could stain mitochondria selectively. Figure 4 shows the
cell cytoplasm fluorescence distribution in samples stained with
P5 and P6 (green) and with MitotrackerTM (red). It was also
produced an image from the fluorescence channel overlay from
each tested compound and MitotrackerTM (images B). The
white arrows are indicating the region of staining accumulation in
the cells cytoplasm for both compounds, which is the same
observed by the MitotrackerTM staining. The images created
through the overlay fluorescence channels (Figure 4, images B),
which combined the green emission from compounds P5 or P6
(green) and red emission from (Mitotracker), produced a yellow
color. The yellow color demonstrated that the both signal are
emitted from the same cell region, which means from the
mitochondria. These results demonstrated that the compound
P5 and P6 could be applied as new mitochondria marker,
permeable to the cell membrane. It was also generated phase
contrast image for all samples (images D) in order to verify the
cells morphological aspects and it was observed no
morphological alteration in MCF-7 cells submitted to dual
staining procedures. Finally, we have also accomplished
colocalization analysis (Pearson’s correlation coefficient) with P5
or P6 and MitotrackerTM. Data were inserted in the
Supplementary Information (Figure S54).
4B
Figure 4. Fluorescent profile of MCF-7 cells incubated with compound P5 (4A)
and P6 (4B) plus MitotrackerTM. The images A show the staining profile
obtained from P5 (4A) and P6 (4B) and the images C shows the staining
profile from MitotrackerTM. The white arrows are indicating the perinuclear
staining accumulation for all markers used. Images B were produced by the
overlay of the green and red fluorescence images, the yellow color produced
demonstrate that there is an overlap between the fluorescence emission from
the tested compounds and the MitotrackerTM. The images D shows the
normal morphological aspects of the samples by phase contrast microscopy.
The cells nuclei were identified by “N” letter in images D. Reference scale bar
25 μm.
Conclusions
Five new fluorescent compounds were prepared from lapachol,
a naturally occurring naphthoquinone, easily extracted from ipe
tree. Two of these compounds, imidazole derivatives, were very
efficient to selectively stain mitochondria. To the best of our
knowledge, this is the first report with azoles prepared from a
natural product with highlighted luminescence prepared in only
three or four steps that are able to use as selective
mitochondrial imaging probes. This manuscript opens a new
avenue for the synthesis and application of fluorescent
compounds prepared from natural compounds, as for instance,
lapachones.
4A
Experimental Section
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 mm, 60 Å). Infrared spectra were recorded on an FTIR
Spectrometer IR Prestige-21 Shimadzu. 1H and 13C NMR spectra were
recorded at 303 K using a Bruker AVANCE DRX400 spectrometer. All
samples for NMR were prepared in CDCl3 containing TMS as internal
reference. Chemical shifts (δ) are given in ppm and coupling constants
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(J) in hertz. High resolution mass spectra (electrospray ionization) were
obtained using a MicroTOF Ic – Bruker Daltonics instrument.
as an orange solid (166 mg, 0.7 mmol, 70% yield); mp 111-112 ºC. 1H
NMR (400 MHz, CDCl3, 303 K) δ: 8.16 (dd, J = 7.4 and 1.2 Hz, 1H), 7.81-
7.66 (m, 3H), 7.21 (s, 1H), 5.92 (s, 1H), 2.69-2.60 (t, J = 8.0 Hz, 2H),
1.73 (s, 3H), 1.68-1.53 (m, 2H), 1.34-1.18 (m, 20H), 1.16 (s, 3H), 0.86 (t,
3H, J = 6.9 Hz). 13C NMR (100 MHz; CDCl3, 303 K) δ: 180.1, 174.4,
171.1, 148.3, 134.8, 133.2, 131.5, 129.9, 126.7, 125.5, 120.1, 111.4,
96.0, 66.6, 44.3, 31.9, 29.6, 29.6, 29.6, 29.5, 29.3, 29.3, 29.2, 27.6, 25.6,
22.6, 21.0, 14.0. EI/HRMS (m/z) [M+H]+: 478.3065. Cald for
[C29H40N3O3]+: 478.3069.
General procedure for the extraction of lapachol (1) from the
heartwood of Tabebuia sp. (Tecoma): A saturated aqueous sodium
carbonate solution was added to the sawdust of ipê tree. Upon observing
rapid formation of lapachol sodium salt, hydrochloric acid was added,
allowing the precipitation of lapachol. Then, the solution was filtered and
a yellow solid was obtained. This solid was purified by recrystallizations
with hexane.
Nor-lapachol (2) was synthesized by Hooker oxidation
methodology and data are consistent with those reported in the
literature.[11,49] Compound 2 was obtained as an orange solid (160 mg,
0.7 mmol, 70% yield); mp 121-122 ºC. 1H NMR (400 MHz, CDCl3, 303 K)
δ: 8.13 (ddd, J = 7.5, 1.5 and 0.5 Hz, 1H), 8.10 (ddd, J = 7.5, 1.5 and 0.5
Hz, 1H), 7.76 (td, J = 7.5, 7.5 and 1.5 Hz, 1H), 7.69 (td, J = 7.5, 7.5 and
1.5 Hz, 1H), 6.03-5.99 (m, 1H), 2.0 (d, J = 1.5 Hz, 3H), 1.68 (d, J = 1.2
Hz, 3H). 13C NMR (100 MHz, CDCl3, 303 K) d: 184.7, 181.5, 151.1, 143.6,
134.9, 133.0, 132.9, 129.5, 126.9, 126.0, 120.9, 113.6, 26.5, 21.7.
General procedure for the synthesis of nor-β-lapachone (3)
and β-lapachone (4). Sulfuric acid was slowly added to lapachol (1) or
nor-lapachol (2) (1 mmol) until complete dissolution of the quinone. Then,
the solution was poured into ice and the precipitate formed was filtered
and washed with water. Lapachones (3) and (4) were recrystallized in an
appropriate solvent, as for instance, ethanol. Compound 3 and 4 were
obtained as an orange solids. Nor-β-lapachone (3): Nor-β-lapachone was
obtained as an orange solid (216 mg, 95% yield); m.p. 169-171 ºC. 1H
NMR (400 MHz, CDCl3, 303 K) δ: 8.05-803 (m, 1H), 7.66-7.52 (m, 3H),
2.93 (s, 2H), 1.60 (s, 6H). 13C NMR (100 MHz, CDCl3, 303 K) δ: 181.3,
175.6, 168.7, 134.4, 131.8, 130.9, 129.2, 127.9, 124.5, 115.0, 93.7, 39.3,
28.4. Data are consistent with those reported in the literature.[50] β-
lapachone (4): (240 mg, 99% yield); mp 153-155 ºC. 1H NMR (400 MHz,
CDCl3, 303 K) δ: 8.06 (dd, J = 7.6 and 1.4 Hz, 1H), 7.81 (dd, J = 7.8 and
1.1 Hz, 1H), 7.65 (ddd, J = 7.8, 7.6 and 1.4 Hz, 1H), 7.51 (td, J = 7.6, 7.6
and 1.1 Hz, 1H), 2.57 (t, J = 6.7 Hz, 2H), 1.86 (t, J = 6.7 Hz, 2H), 1.47 (s,
6H). 13C NMR (100 MHz, CDCl3, 303 K) δ: 179.8, 178.5, 162.0, 134.7,
132.6, 130.6, 130.1, 128.5, 124.0, 112.7, 79.3, 31.6, 26.8, 16.2. Data are
consistent with those reported in the literature.[51]
Synthesis of 3-azido-2,2-dimethyl-2,3-dihydronaphtho[1,2-
b]furan-4,5-dione (5). To a solution of nor-lapachol (2) (228 mg, 1.0
mmol) in 25 mL of dichloromethane, 2 mL of bromine was added. The
bromo intermediate precipitated immediately as an orange solid. After
removal of bromine, an excess of sodium azide (2 mmol) was added in
CH2Cl2 and the mixture was stirred overnight. The crude reaction mixture
was poured into 50 mL of water. The organic phase was extracted with
organic solvent, dried over sodium sulfate, filtered, and evaporated under
reduced pressure. Compound 5 was obtained as an orange solid (263
mg, 0.98 mmol, 98% yield); mp 200-202 ºC. 1H NMR (400 MHz, CDCl3,
303 K) δ: 8.14 (ddd, J = 6.9, 2.1 and 0.9 Hz, 1H), 7.72-7.65 (m, 3H), 4.77
(s, 1H), 1.67 (s, 3H), 1.55 (s, 3H). 13C NMR (100 MHz, CDCl3, 303 K) δ:
180.3, 175.2, 170.2, 134.5, 132.7, 131.1, 113.5, 129.5, 125.1, 126.7,
95.5, 67.3, 27.1, 21.9. Data are consistent with those reported in the
literature.[52]
General Procedure for the synthesis of the phenazines. In a 25
mL flask, quinone 6 (0.5 mmol), sodium acetate (0.95 mmol), the
respective diamine (0.55 mmol) in 3 mL of glacial acetic acid were added.
The reaction medium was agitated at room temperature and monitored
by thin layer chromatography. After, the crude reaction was poured into
water and the precipitate formed was filtrate and then purified by column
chromatography on silica gel eluted with an increasing polarity gradient
mixture of hexane and ethyl acetate.
2,2-dimethyl-1-(4-tridecyl-1H-1,2,3-triazol-1-yl)-1,2-
dihydrobenzo[a]furo[2,3-c]phenazine (P1). Compound P1 was
obtained as yellow solid (186 mg, 0.34 mmol, 68% yield); mp 151-153 ºC.
1H NMR (400 MHz, CDCl3, 303 K) δ: 9.46 (dd, J = 8.0 and 0.7 Hz, 1H),
8.32-8.27 (m, 1H), 8.21 (dd, J = 7.8 and 0.9 Hz, 1H), 8.09-8.03 (m, 1H),
7.91 (dtd, J = 24.7, 7.3 and 1.3 Hz, 2H), 7.80-7.73 (m, 2H), 6.87 (s, 1H),
6.66 (s, 1H), 2.64-2.48 (m, 2H), 1.80 (s, 3H), 1.56-1.43 (m, 2H), 1.29 (s,
3H), 1.26-1.05 (m, 20H), 0.87 (t, J = 6.9 Hz, 3H). 13C NMR (100 MHz,
CDCl3, 303 K) δ: 148.0, 140.9, 140.4, 133.2, 130.3, 130.0, 129.8, 129.6,
128.7, 126.1, 124.1, 123.2, 120.1, 108.9, 92.9, 68.4, 31.9, 29.6, 29.6,
29.5, 29.5, 29.4, 29.3, 29.2, 29.0, 27.5, 25.6, 22.6, 21.3, 14.1. EI/HRMS
(m/z) [M+H]+: 550.3518. Cald for [C35H44N5O]+: 550.3545.
9,12-dibromo-2,2-dimethyl-1-(4-tridecyl-1H-1,2,3-triazol-1-yl)-
1,2-dihydrobenzo[a]furo[2,3-c]phenazine (P2). Compound P2 was
obtained as yellow solid (264 mg, 0.37 mmol, 75% yield); mp 142-143 ºC.
1H NMR (400 MHz, CDCl3, 303 K) δ: 9.52 (d, J = 7.7 Hz, 1H), 8.25 (d, J =
7.3 Hz, 1H), 7.99-7.88 (m, 4H), 6.99 (s, 1H), 6.68 (s, 1H), 2.61 (t, J = 7.3
Hz, 2H), 1.87 (s, 3H), 1.60-1.46 (m, 2H), 1.37 (s, 3H), 1.28-1.07 (m, 20H),
0.89 (t, J = 6.9 Hz, 3H). 13C NMR (100 MHz, CDCl3, 303 K) δ: 161.3,
147.8, 142.4, 141.6, 140.6, 138.0, 133.1, 132.5, 131.6, 130.7, 130.2,
127.0, 124.5, 124.2, 123.4, 123.4, 120.3, 108.8, 93.3, 68.5, 31.9, 29.6,
29.6, 29.6, 29.5, 29.4, 29.3, 29.2, 29.0, 28.0, 25.6, 22.6, 21.6, 14.0.
EI/MS (m/z) [M+H]+: 706. Cald for [C35H42Br2N5O]+: 706.
9,12-bis(4-methoxyphenyl)-2,2-dimethyl-1-(4-tridecyl-1H-1,2,3-
triazol-1-yl)-1,2-dihydrobenzo[a]furo[2,3-c]phenazine
(P3).
Compound P3 was obtained as yellow solid (296 mg, 0.39 mmol, 78%
yield); mp 163-165 ºC. 1H NMR (400 MHz, CDCl3, 303 K) δ: 9.21-9.15 (m,
1H), 8.20-8.14 (m, 1H), 7.92-7.79 (m, 6H), 7.30 (d, J = 8.7 Hz, 2H), 7.15
(d, J = 8.7 Hz, 2H), 6.97 (d, J = 8.7 Hz, 2H), 6.87 (s, 1H), 6.53 (s, 1H),
3.97 (s, 3H), 3.94 (s, 3H), 2.61 (t, J = 7.7 Hz, 2H), 1.75 (s, 3H), 1.59-1.45
(m, 2H), 1.28 (s, 3H), 1.23-1.02 (m, 20H), 0.86 (t, J = 6.9 Hz, 3H). 13C
NMR (100 MHz, CDCl3, 303 K) δ: 160.0, 159.2, 148.0, 140.5, 140.2,
139.6, 139.1, 138.4, 138.0, 133.5, 132.2, 131.7, 131.3, 130.1, 129.7,
129.5, 128.5, 126.4, 124.2, 123.0, 119.8, 113.7, 113.4, 108.9, 92.7, 68.6,
55.4, 55.4, 31.9, 29.6, 29.6, 29.5, 29.5, 29.4, 29.4, 29.3, 29.2, 29.1, 27.7,
25.6, 22.6, 21.5, 14.0. EI/HRMS (m/z) [M+H]+: 762.4344. Cald for
[C49H56N5O3]+: 762.4383.
2,2-dimethyl-3-(4-tridecyl-1H-1,2,3-triazol-1-yl)-2,3-
dihydronaphtho[1,2-b]furan-4,5-dione (6). Click chemistry procedure
was used for preparing compound 6 as previously classical methodology
described by Sharpless and Fokin with minor modifications.[35] In a 25 mL
2,2-dimethyl-9,12-bis(phenylethynyl)-1-(4-tridecyl-1H-1,2,3-
triazol-1-yl)-1,2-dihydrobenzo[a]furo[2,3-c]phenazine (P4). In a 25 mL
schlenk tube were added P2 (0.07 mmol), phenylacetylene (0.28 mmol),
Pd(Ph3)2Cl2 (0.05 mmol), triphenylphosphine (0.1 mmol) and copper(I)
iodide (0.05 mmol). The tube was evacuated and backfilled with nitrogen.
Triethylamine (5.0 mL) was added under nitrogen, and the tube was
locked. The tube was immersed in an oil bath (90 °C) and stirred for 12 h.
After, the solvent was evaporated and the product purified by column
chromatography on silica gel using a mixture of hexane/ethyl acetate. P4
was obtained as a orange solid (280 mg, 0.37 mmol, 75% yield); mp 132-
134 ºC; 1H NMR (400 MHz, CDCl3, 303 K) δ: 9.58 (d, J = 7.9 Hz, 1H),
.
flask containing 15 mL of CH2Cl2/H2O (1:1), Cu(OAc)2 H2O (10 mg, 0.08
mmol) and sodium ascorbate (30 mg, 0.15 mmol), was added 3-azido-
nor-β-lapachone (135 mg, 0.5 mmol) and 1-pentadecyne (217 mg, 0.28
mL, 1.0 mmol). The mixture was stirred at room temperature, and, the
reaction was monitored by thin layer chromatography. The aqueous
phase was extracted with CH2Cl2, dried over anhydrous Na2SO4 and
concentrated under reduced pressure. The residue was purified by
column chromatography using as eluent a mixture of hexane/ethyl
acetate, with a gradient of increasing polarity. The product was obtained
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700227
European Journal of Organic Chemistry
FULL PAPER
8.23 (d, J = 7.5 Hz, 1H), 8.01-7.94 (m, 3H), 7.90 (t, J = 7.1 Hz, 1H), 7.79
(d, J = 6.5 Hz, 2H), 7.61 (d, J = 7.2 Hz, 2H), 7.52-7.43 (m, 5H), 7.42-7.36
(m, 1H), 6.90 (s, 1H), 6.73 (s, 1H), 2.58-2.47 (m, 2H), 1.82 (s, 3H), 1.48-
1.37 (m, 2H), 1.32 (s, 3H), 1.29-1.00 (m, 20H), 0.86 (t, J = 6.8 Hz, 3H).
13C NMR (100 MHz, CDCl3, 303 K) δ: 160.9, 147.7, 142.5, 142.0, 141.0,
140.1, 133.1, 133.1, 132.2, 131.9, 130.3, 130.0, 128.7, 128.7, 128.5,
128.4, 126.5, 124.4, 123.8, 123.5, 123.3, 123.3, 123.0, 120.3, 108.9,
98.0, 97.5, 93.4, 87.0, 86.2, 68.4, 31.9, 29.6, 29.6, 29.6, 29.5, 29.4, 29.3,
29.2, 28.8, 27.8, 25.5, 22.6, 21.4, 14.0. EI/HRMS (m/z) [M+H]+: 750.4146.
Cald for [C51H52N5O]+: 750.4171.
temperature and fixed in formaldehyde 3.7% for 30 minutes. The
samples were washed again three times in PBS 1X (pH 7.4) at room
temperature and the coverslips were mounted over glass slides using
ProLong Gold Antifade (Invitrogen, OR, USA) according to the
manufacturer’s recommendations. The fixed samples were first washed
three times in PBS 1X (pH 7.4) and then fixed with formaldehyde 3.7%
for 30 minutes. After fixative procedure the samples were washed three
times in PBS 1X (pH 7.4) at room temperature and incubated for 30
minutes in 1 µM of P5 or P6 solution at room temperature. The samples
were washed three times in PBS 1X (pH 7.4) at room temperature and
the coverslips were mounted over glass slides using ProLong Gold
Antifade (Invitrogen, OR, USA) according to the manufacturer’s
recommendations. The negative control was performed by incubation of
the samples in 0.02% of DMSO, which was the diluent used. The
samples were analyzed using a Leica Confocal Microscopy TCS SP5
and excited using 488 nm wavelength laser emission. All assays were
performed in triplicate and it was done three repetitions for each cell
sample and experimental condition.
Cell viability assay. The same cell lineages used in fluorescence
detection assay were incubated with P5 or P6 solutions at 1 or 10 μM for
24 hours and analyzed by standard MTT (3-[4, 5-dimethylthiazol-2-yl]-2,
5-diphenyltetrazolium bromide) assay, following the manufacture
recommendations (R&D System Inc, MN, USA). Briefly, 3 x 103 of each
cell line were seeded in 96 well plate and maintained overnight a 37 °C.
These samples were incubated in 1 or 10 μM of P5 or P6 solutions for 24
hours. Cells incubated with 0.02% of DMSO solution (compound solvent)
at the same conditions and cells maintained only in culture medium were
used as diluent control and negative control respectively. The samples
were incubated with 150 μL of MTT solution (0.5 mg/mL) in cell culture
medium for 4h, in the dark at 37 °C. MTT is reduced by metabolically
active cells to insoluble purple formazan dye crystals which were
accumulated inside the cells cytoplasm. The MTT solution was removed
and was add 200 μL of DMSO in all samples in order to solubilize the
formazan dye crystals. The plate was read in spectrophotometer
Spectramax M5 (Molecular Devices, CA, USA) and the optimal
wavelength for absorbance was 570 nm. The MTT assay was performed
in triplicate and also was made three independent assays. The cell
viability inhibition was determined by evaluation of MTT result obtained
for test samples compared with the control samples in the same
conditions, following the expression [Survival % = [(Tested Sample –
Blanc)/(Control Sample – Blanc)] x 100. The data was statically analyzed
by ANOVA one way test followed to Dunnett’s post test.
4-(6,6-dimethyl-3,4,5,6-tetrahydrobenzo[7,8]chromeno[5,6-
d]imidazol-2-yl)benzaldehyde (P5). To a solution of β-lapachone (1.0
mmol, 242 mg) in acetic acid (10 mL), terephthalaldehyde (3.0 mmol, 402
mg) was added, and the mixture was heated to 70 ºC; at this point,
ammonium acetate (20.0 mmol, 1.54 g) was slowly added, and reflux
was maintained for 2h. At the end of the reaction, after addition into cold
water, a yellow precipitate was formed and filtered under reduced
pressure. The precipitate was also washed with distilled water and a
solution of sodium bicarbonate. Finally, it was purified by column
chromatography using as eluent a mixture of hexane/ethyl acetate, with a
gradient of increasing polarity, as previously described. Compound P5
was obtained as a yellow solid (220 mg, 0.6 mmol, 62% yield); mp 271-
272 ºC. 1H NMR (400 MHz, CDCl3/DMSO-d6, 303 K) δ: 10.00 (s, 1H),
8.49 (d, J = 7.7 Hz, 1H), 8.42 (d, J = 7.9 Hz, 2H), 8.26 (d, J = 7.8 Hz, 1H),
7.92 (d, J = 7.9 Hz, 2H), 7.54 (t, J = 7.7 Hz, 1H), 7.44 (t, J = 7.8 Hz, 1H),
3.11 (t, J = 5.9 Hz, 2H), 1.99 (t, J = 5.9 Hz, 2H), 1.46 (s, 6H). 13C NMR
(100 MHz, CDCl3/DMSO-d6, 303 K) δ: 191.2, 146.9, 145.2, 136.1, 135.3,
129.6, 126.2, 125.5, 123.5, 122.3, 121.1, 103.7, 74.0, 31.7, 26.3, 18.4.
EI/HRMS (m/z) [M+H]+: 357.1584. Cald for [C23H20N2O2]+: 357.1558.
4-(5,5-dimethyl-4,5-dihydro-3H-furo[3',2':3,4]naphtho[1,2-
d]imidazol-2-yl)benzaldehyde (P6). To a solution of nor-β-lapachone
(1.0 mmol, 228 mg) in acetic acid (10 mL), terephthalaldehyde (3.0 mmol,
402 mg) was added, and the mixture was heated to 70 ºC; at this point,
ammonium acetate (20.0 mmol, 1.54 g) was slowly added, and reflux
was maintained for 3h. At the end of the reaction, after addition into cold
water, a yellow precipitate was formed and filtered under reduced
pressure. The precipitate was also washed with distilled water and a
solution of sodium bicarbonate.[43,53] Finally, it was purified by column
chromatography using as eluent a mixture of hexane/ethyl acetate, with a
gradient of increasing polarity. Compound P6 was obtained as a yellow
solid (205 mg, 0.6 mmol, 60% yield); mp 268-269 ºC. 1H NMR (400 MHz,
CDCl3/DMSO-d6, 303 K) δ: 10.00 (s, 1H), 8.55 (d, J = 7.4 Hz, 1H), 8.40
(d, J = 7.8 Hz, 2H), 8.03 (d, J = 7.7 Hz, 1H), 7.92 (d, J = 7.8 Hz, 2H), 7.54
Co-staining P5, P6 and Mitotracker. In order to confirm the
morphological evidence that the compounds P5 or P6 was accumulated
(t, J = 7.4 Hz, 1H), 7.44 (t, J = 7.7 Hz, 1H), 3.38 (s, 2H), 1.61 (s, 6H). 13
C
NMR (100 MHz, CDCl3/DMSO-d6, 303 K) δ: 191.5, 151.8, 147.3, 136.2,
135.7, 129.9, 126.4, 125.7, 123.9, 122.5, 121.9, 118.9, 106.6, 87.5, 42.0,
28.4. EI/HRMS: (m/z) [M+H]+: 343.1448. Cald for [C22H18N2O2]+:
343.1339.
in mitochondria, it was performed a co-staining assay with each
compound and the commercial mitochondria marker MitotrackerTM
(ThermoFisher Scientific, NY, USA). Briefly, 3 x 105 MCF-7 cells (human
breast adenocarcinoma cell), were seeded on 13 mm round glass
coverslips on the bottom of a 24-well plate, allowed to adhere overnight
and washed three times with serum-free medium for removal of non-
adherent cells. After reaching confluence, the samples were incubated
for 30 minutes at 37 °C with 1 µM of P5 or P6 plus 100 nM of
MitotrackerTM. The samples were washed three times in PBS
(Phosphate Buffer Saline), pH 7.4 at 37 °C and the cells were fixed in
3.7% formaldehyde solution for 30 minutes at room temperature. The
samples were washed three times in PBS and the coverslips were
mounted over glass slides using ProLong Gold Antifade (Invitrogen, OR,
USA) according to the manufacturer’s recommendations. The samples
were analyzed using a Leica Confocal Microscopy TCS SP5. All assays
were performed in triplicate and it was done in three independent
repetitions
Biology. Cell culture. MCF-7 (human breast adenocarcinoma cell),
Caco2 (human epithelial colorectal adenocarcinoma cells), PANC-1
(human pancreatic carcinoma, epithelial-like cell line) and the T47D
(human ductal breast epithelial tumor cell line) and the normal cell
HUVEC (human umbilical vein epithelial cell) were used in this work. The
cells were maintained in appropriated culture medium as recommended
by ATCC (American Type Culture Collection), supplemented with 10% of
fetal bovine serum plus 100 IU/mL penicillin and 100 µg/mL streptomycin
at 37 °C in 5% CO2 atmosphere.
Fluorescence detection assay. Cells were seeded on 13mm round
glass coverslips on the bottom of a 24-well plate, allowed to adhere
overnight and washed three times with serum-free medium for removal of
non-adherent cells. After reaching confluence, the cells were separated
in two samples (live samples and fixed samples). The live samples were
incubated for 30 minutes in 1 µM of P5 or P6 solution at 37 °C. These
samples were washed three times with PBS 1X (pH 7.4) at room
X-ray. The structures of the title compounds has been determined from
X- ray diffraction on an Enraf-Nonius Kappa-CCD diffractometer (95 mm
CCD camera on κ-goniostat) using graphite monochromated MoKα
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700227
European Journal of Organic Chemistry
FULL PAPER
radiation (0.71073 Å), at room temperature. Data collections were carried
out using the COLLECT software[54] up to 50° in 2θ. Final unit cell
parameters were based on 12320 reflections for P5 and 3373 reflections
for 6. Integration and scaling of the reflections, correction for Lorentz and
polarization effects were performed with the HKL DENZO-SCALEPACK
system of programs.[55] The structures of compounds were solved by
direct methods with SHELXS-97.[56] The models were refined by full-
matrix least squares on F2 using SHELXL-97.[57] The program ORTEP-
3[58] was used for graphic representation and the program WINGX[59] to
prepare materials for publication. The reference number is CCDC
1529639 and 1530427. Copies of the available material can be obtained,
free of charge on application to the Director, CCDC, 12 Union Road,
Cambridge CH21EZ, UK (fax: +44-1223-336-033 or e-mail:
deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
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Acknowledgements
This research was funded by grants from CNPq (PVE
401193/2014-4), FAPEMIG (Edital 01/2014), Chamada universal
MCTI/CNPq Nº 01/2016 and 474797/2013-9, Programa
Pesquisador Mineiro PPM-X FAPEMIG, CAPES, FAPDF,
FINATEC, DPP-UnB, INCT-Transcend group. Prof. C.A.S. would
like to thank the Institute of Physics of University of São Paulo
(São Carlos), for kindly allowing the use of the KappaCCD
diffractometer.
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Mitochondrial Heterocyclic Probes*
Fabíola S. dos Santos et al. and
Eufrânio N. da Silva Júnior*
Page No. – Page No.
Redox Center Modification of
Lapachones Toward the Syntheses of
Nitrogenated Heterocycles as
Selective Fluorescent Mitochondrial
Imaging Probes
A synthetic strategy for the syntheses of new fluorescent imidazole and phenazine
derivatives prepared from naturally occurring naphthoquinones as selective
fluorescent mitochondrial imaging probes is reported. These heterocycles
presented the same staining patterns of MitoTracker red corroborating the potential
of these compounds as new mitochondria markers permeable to the cell
membrane.
*Heterocycles and Mitochondrial Imaging Probes
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