A Complete and Unambiguous 1H and 13C NMR Signals Assignment of para?Naphthoquinones, ortho- And para-Furanonaphthoquinones

Article abstract of DOI:10.21577/0103-5053.20190009

A complete and unambiguous assignment of ¹H and ¹³C nuclear magnetic resonance (NMR) signals of 29 naphthoquinones is reported on the basis of one- and two-dimensional NMR techniques (¹H, ¹³C, ¹H-

Full text of DOI:10.21577/0103-5053.20190009

http://dx.doi.org/10.21577/0103-5053.20190009
J. Braz. Chem. Soc., Vol. 30, No. 6, 1138-1149, 2019
Printed in Brazil - ©2019 Sociedade Brasileira de Química
Article
A Complete and Unambiguous 1H and 13C NMR Signals Assignment of
para‑Naphthoquinones, ortho- and para-Furanonaphthoquinones
,,aa
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a
TTaattiiaanneeFF..BBoorrggaattii,, ** JJoossééDD..ddeeSSoouuzzaaFFiillhhoo aannddAAllaaííddeeBB..ddeeOOlliivveeiirraa
aDepartamento de Produtos Farmaceuticos, Faculdade de Farmacia,
Universidade Federal de Minas Gerais (UFMG),
Av. Antonio Carlos, 6662, Campus Pampulha, 31620-901 Belo Horizonte-MG, Brazil
bDepartamento de Quimica, nstituto de Ciencias s atas,
Universidade Federal de Minas Gerais (UFMG),
Av. Antonio Carlos, 6662, Campus Pampulha, 31620-901 Belo Horizonte-MG, Brazil
A complete and unambiguous assignment of 1H and 13C nuclear magnetic resonance (NMR)
signals of 29 naphthoquinones is reported on the basis of one- and two-dimensional NMR techniques
(1H, 13C, 1H-1H correlated spectroscopy (COSY) and 1H-13C heteronuclear multiple-bond correlation
(HMBC)). This is the first report distinguishing data between para-naphthoquinones, ortho- and
para-furanonaphthoquinones isomers.
Keywords: 1D and 2D NMR, 1H NMR and 13C NMR, naphthoquinones, furanonaphthoquinones
Introduction
Quinones are conjugated cyclic diones oxidatively
derived from aromatic compounds. Natural quinones
are widespread as plant and microorganisms secondary
metabolites disclosing several biological effects such
as antitumor, trypanocidal, anti-inflamatory, antifungal
and leishmanicidal.1-7 Lapachol (1, Figure 1), a
hydroxy prenylnaphthoquinone, was first isolated from
Tabebuia avellanedae, in 1882, by Paternó.8 Since then, it has
been found in several families asVerbenaceae and Proteaceae,
being highly frequent in the Family Bignoniaceae, mainly
in representatives of the Handroanthus genus (Tabebuia) of
which some are known as “ipês” in Brazil.8 Semi-synthetic
derivatives and analogs of lapachol are described with
antitumor, anti-inflammatory and anti-protozoa activities.5,9-15
Furanonaphthoquinones such naphtho[2,3-b]furan-
4,9-dione (2), and naphtho[1,2-b]furan-4,5-dione (3)
(Figure 1) are also found in Bignoniaceae and disclose
several important biological activities, such as anticancer,
antibacterial and anti-inflammatory.16
Figure 1. Structures of lapachol (1), naphtho[2,3-b]furan-4,9-dione (2)
and naphtho[1,2-b]furan-4,5-dione (3).
naphthoquinones (para-FNQs) (6a‑h) (Figure 2) that were
assayed for antiplasmodial activity against the chloroquine-
resistant Plasmodium falciparum W2 strain and for
cytotoxicity to the human hepatoma cell culture (HepG2).
The furanonaphthoquinones (FNQs) were highlighted
as interesting new hits of interest for antimalarial drug
development.17
Spectral analysis of this naphthoquinones were
explored aiming to distinguish between the three
structural classes: NQs, ortho- and para-FNQs as well
as the distinction between the two groups of isomeric
furanonaphthoquinones. Some data on nuclear magnetic
resonance (NMR) spectra of NQs, ortho- and para-FNQs
are found in the literature, although most of them are
restricted to only one isomer, ortho- or para-FNQ2,3,18-21
and previous assignments are revised here.6,22 No
references were found correlating NQs and FNQs data,
as well as no data that allowed the differentiation between
ortho- and para-FNQs isomers.
Recently, we described the synthesis of a series of
naphthoquinones represented by 2-hydroxy-3-(1’-alkenyl)-
1,4-naphthoquinones (NQs) (4a‑h), ortho-furano-
naphthoquinones (ortho-FNQs) (5a‑h) and para-furano-
*e-mail: tatianefborgati@yahoo.com.br

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Figure 2. Synthesis of 2-hydroxy-3-(1’-alkenyl)-1,4-naphthoquinones (4a‑h), ortho- (5a‑h) and para-furanonaphthoquinones (6a‑h). Reagents and
conditions: (i) CH3COOH, RCH2CHO, HClconc., reflux 40 min; (ii) (a) Hg(OAc)2, CH3COOH, room temperature (rt), 30 min, (b) HCl 2 mol L-1, EtOH,
reflux 15 min; (iii) (a) Hg(OAc)2, CH3COOH, rt, 30 min, (b) HClconc., EtOH, reflux 3 h (adapted from reference 17).
In this article we report signals assignments for
lapachol (1) and all compounds of the series 4, 5 and
6 (Figure 2). A detailed discussion is presented for
compounds 2-hydroxy-3-(1’-hexenyl)-1,4-naphthoquinone
(4d), ortho-2-butylnaphtho[1,2-b]furan-4,5-dione (5d)
and para-2 butylnaphtho[2,3-b]furan-4,9-dione (6d). A
complete and unambiguous assignment of 1H and 13C NMR
chemical shifts was based in a combination of one- and
The 13C spectra were acquired using the spectrometer
frequency of 100 MHz, spectrum resolution of 0.73 Hz,
zgpg 30 pulse program with ns 1024, d1 2s, acquisition
time 0.6815744 s and spectral width 238.9086 ppm.
The 1H-1H COSY contour maps were obtained with a 2 s
relaxation delay, acquisition time 0.1024000 s and spectral
width 24.9930 ppm. The 1H-13C HMBC contour maps were
recorded with a 1.5 s relaxation delay in a 24.9930 ppm
spectral width in F2 and 260.0000 ppm in F1 and acquisition
time 0.1024000 s (F2) and 0.0048928 s (F1).
1
two-dimensional techniques (1H, 13C, H-1H correlated
spectroscopy (COSY) and 1H-13C heteronuclear multiple-
bond correlation (HMBC)).
Results and Discussion
Experimental
The 1H and 13C NMR spectra of all the naphthoquinones
were registered at 400 and 100 MHz, respectively.
Signals assignments were based on chemical shifts (d,
ppm) of 1H and 13C, on the multiplicity patterns of proton
resonances depicted by the J couplings (Hz), and on
The synthesis have been published elsewhere.17 The
2-hydroxy-3-(1’-alkenyl)-1,4-naphthoquinones (4a-h)
were obtained by aldol condensation between commercial
lawsone (Sigma-Aldrich) and different aldehydes
(Figure 2). The furanonaphthoquinones (5a-h and 6a-h)
were formed by oxidative cyclization of the 2-hydroxy-
3-(1’-alkenyl)-1,4-naphthoquinone with Hg(OAc)2
(Figure 2).
1
data of homonuclear H-1H COSY and heteronuclear
1H-13C HMBC. The NMR experiments and the signals
assignments were made for all compounds (1, 4a-h, 5a-h
and 6a-h), and the naphthoquinones 4d, 5d and 6d were
focused for illustrating the 1H and 13C assignments.
The hydrogen signals in the alkenyl chain of
The NMR experiments were performed in CDCl3
solution at 25 ºC on a BrukerAvance DRX400 spectrometer.
Tetramethylsilane (TMS) was used as internal reference and
the program the Bruker’s TopSpin 3.5TM software package
was used to process the NMR row data.
1
compound 4d (Figure 3) were assigned in the H NMR
1
spectrum and confirmed by the H-1H COSY (Figure 4).
A multiplet at d 7.10-7.03 corresponding to H-2’ that
couple to H-1’(d 6.60, d, 3JH,H 16.00), and to H-3’(d 2.30,
q, 2H, 3JH,H 7.00). H-4’ and H-5’ are disclosed as a quintet
at d 1.49 (2H, 3JH,H 7.20) and a sextet at d 1.38 (2H, 3JH,H
7.20), respectively. As expected, H-6’ appears as a triplet
at d 0.93 (3H, 3JH,H 7.20).
1
The H spectra were acquired using the spectrometer
frequency of 400 MHz, spectrum resolution of 0.12 Hz,
zg 30 pulse program with ns 16, d1 1s, acquisition time
4.0894465 s and spectral width 20.0264 ppm. The phase
and baseline were manually corrected and the TMS signal
calibrated at 0.00 ppm. Integration regions of signal were
selected manually.
To assess more information about the structure of
1
naphthoquinone 4d, an H-13C HMBC (Figures 5 and 6)

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J. Braz. Chem. Soc.
Figure 3. 1H NMR spectrum of NQ 4d.
Figure 4. 1H-1H COSY contour map of compound 4d.

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contour map was recorded. From that we can conclude
the following: H-1’ (d 6.60, d, JH,H 16.00) shows long-
shows a correlation with the carbon resonances of C-10
at d 132.87 (3JC,H). H-5 is coupled to C-7 at 133.16 and to
C-9 at d 129.62 (3JC,H). The two apparent triplets at d 7.73
and 7.64 were assigned to H-6 and H-7, in this order. The
H-6 signal shows long-range correlation with the carbon
resonances of C-10 at d 132.87 and C-8 at d 126.08 (3JC,H),
while the H-7 signal is correlated with the ones of C-9 at
d 129.62 and C-5 at 127.19 (3JC,H) (Figure 5).
3
range couplings to C-4 at d 184.50, C-2 at d 151.47 and
C-3’ at d 34.95 (3JC,H). H-2’ (d 7.10-7.03, m) is coupled
to C-4’ at 31.45 and to C-3 at d 120.18 (3JC,H) (Figure 5).
3
The H-3’ signal (d 2.30, q, JH,H 7.00) shows long-range
correlations with C-1’ at d 118.80, C-5’ at d 22.55 (3JC,H),
C-2’ at d 144.40 and C-4’ at d 31.45 (2JC,H). H-4’ (d 1.49,
3
quint, JH,H 7.20) is coupled to C-2’ at d 144.40, C-6’ at
Assignments of the heteronuclear correlations observed
d 14.14 (3JC,H), C-5’ at d 22.55 and C-3’ at d 34.95 (2JC,H).
H-5’ (d 1.38, st, 3JH,H 7.20) shows long-range couplings to
C-3’ at d 34.95 (3JC,H) and C-6’ at d 14.14 (2JC,H). Finally,
H-6’ signal (d 0.93, t, 3JH,H 7.20) is correlated to those of
C-4’at d 31.45 (3JC,H) and C-5’at d 22.55 (2JC,H) (Figure 6).
Although carbonyl carbon signals are close they were
assigned with 1H-13C HMBC support (Figure 5) once H-1’
(d 6.60) shows a long-range coupling to the carbonyl carbon
at d 184.50 which is thus attributed to C-4 and, therefore,
the other carbonyl carbon signal at d 181.56 corresponds
undoubtedly to C-1. Opposite assignments were previously
proposed for lapachol (1) that discloses similar situation on
the naphthoquinone moiety.6,22 Long range couplings of the
carbonyl carbons C-1 and C-4 supported the assignment
of the aromatic hydrogens. There is a clear coupling
in the H-13C HMBC contour map for compound 4d are
1
shown in Table 1.
The main difference between NQ and FNQ is the change
of spectral features in 1H NMR spectra around d 7-6. In the
NQ’s (4d) 1H NMR spectra the signal of H-1’, a hydrogen
of alkenyl moiety, is a doublet, while in the FNQs H-1’(5d
and 6d), the only hydrogen in the furan ring, is a singlet
(Figure 7).
1
The ortho-FNQ H NMR spectrum of 5d (Figure 8)
exhibits a triplet at d 2.71 related to 2H-3’ (3JH,H 7.60),
a quintet at d 1.70 refers to 2H-4’ (3JH,H 7.60), a sextet at
d 1.44 relative to 2H-5’ (3JH,H 7.60) and a triplet at d 0.97
corresponds to methyl hydrogens 3H-6’ (3JH,H 7.60).
All these hydrogens were assigned on the basis of the
1H-1H COSY spectrum (Figure 9), where can be observed
that H-3’ is coupled to H-4’, H-4’ to H-5’, and H-5’ to
H-6’. A apparent doublet at d 8.00 and a apparent triplet
3
of C-1 to H-8 (d 8.04, d, JH,H 7.60), and of C-4 to H-5
3
(d 8.11, d, JH,H 7.60) (3JC,H). Furthermore the H-8 signal
Figure 5. Expansion of 1H-13C HMBC contour map (d 6.4-8.3 ppm) of compound 4d.

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J. Braz. Chem. Soc.
Figure 6. Expansion of 1H-13C HMBC contour map (d 0.9-2.4 ppm) of compound 4d.
Table 1. 1H NMR chemical shifts (d), multiplicities, coupling constants (J) and heteronuclear correlations observed in the HMBC for compound 4d
1H (d, multiplicity, 3JH,H / Hz)
H-5 (8.11, d, J 7.60)
H-6 (7.73, t, J 7.40)
H-7 (7.64, t, J 7.40)
H-8 (8.04, d, J 7.60)
H-1’ (6.60, d, J 16.00)
H-2’ (7.10-7.03, m)
3J 13C (d / ppm)
C-4 (184.50); C-7 (133.16); C-9 (129.62)
C-8 (126.08); C-10 (132.87)
C-5 (127.19); C-9 (129.62)
C-1 (181.56); C-10 (132.87)
C-2 (151.47); C-3’(34.95); C-4 (184.50)
C-4’(31.45)
2J 13C (d / ppm)
−
−
−
−
−
C-3 (120.18)
C2’(144.40); C4’(31.45)
C-3’(34.95); C-5’(22.55)
C-6’ (14.14)
C-5’ (22.55)
H-3’ (2.30, q, J 7.00)
H-4’ (1.49, quint, J 7.20)
H-5’ (1.38, st, J 7.20)
H-6’ (0.93, t, J 7.20)
C-1’(118.80); C-5’(22.55)
C-2’ (144.40); C-6’(14.14)
C-3’(34.95)
C-4’(31.45)
s: singlet; d: doublet; t: triplet; q:quartet; quint: quintet; s: sextet.
at d 7.40 corresponding to H-8 (3JH,H 7.70) and H-7 (3JH,H
to differentiate between the two carbonyl carbons because
H-1’shows long-range coupling to C-2 at d 174.60 (3JC,H).
So, the other carbonyl carbon signal is related to C-1
(d 180.89). Besides, H-1’ is coupled to C-4 at d 159.65
(3JC,H) and C-3 at d 122.68 (2JC,H), allowing to distinguish
1
7.70), respectively, (Figure 8) and from H-1H COSY
contour map these hydrogens are coupling to each other
(Figure 9). A multiplet at d 7.64-7.58 is related to H-5
and H-6.
Aiming to confirm the 5d chemical shifts assignments a
heteronuclear correlation contour map 1H-13C HMBC was
recorded (Figure 10) and the following informations were
derived from it. From the singlet at d 6.42 corresponding
to H-1’, the only hydrogen in the furan ring, it is possible
3
them from aromatic carbons. H-3’ (d 2.71, t, JH,H 7.60)
shows long-range couplings to C-2’ at d 160.49, C-4’ at
d 29.71 (2JC,H), C-1’at d 103.84 and C-5’at d 22.28 (3JC,H).
The signal of H-4’ (d 1.70, quint, 3JH,H 7.60) is correlated
with the carbon resonances of C-2’ at d 160.49, C-6’ at

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d 13.85 (3JC,H), C-3’ at d 27.70 and C-5’ at d 22.28 (2JC,H).
H-5’ (d 1.44, st, JH,H 7.60) shows long-range couplings
to C-4’ at d 29.71 and C-6’ at d 13.85 (2JC,H). The signal
of H-6’ (d 0.97, t, 3JH,H 7.60) is correlated with the carbon
resonances of C-4’ at d 29.71 (3JC,H) and C-5’ at d 22.28
(2JC,H) (Figure 11).
3
Figure 7. Difference between 1H NMR spectra of compounds 4d, 5d and 6d.
Figure 8. 1H NMR spectrum of compound 5d.

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A Complete and Unambiguous 1H and 13C NMR Signals
J. Braz. Chem. Soc.
Figure 9. 1H-1H COSY contour map of compound 5d.
Figure 10. Expansion of 1H-13C HMBC contour map (d 6.2-8.0 ppm) of compound 5d.
1
In the H-13C HMBC contour map (Figure 10) the
signal of H-8 (d 8.00) shows a long-range correlation
with the ones of C-1 at d 180.89, C-10 at d 128.78, C-6 at
d 135.46 (3JC,H) and C-7 at d 130.55 (2JC,H). The H-7 signal
(d 7.40) is correlated with those of C-5 at 122.15 and
C-9 at d 128.92 (3JC,H). Assignments of the heteronuclear

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1145
Figure 11. Expansion 1H-13C HMBC contour map (d 0.8-3.0 ppm) of compound 5d.
1
correlations observed in the H-13C HMBC contour map
at d 28.20 and C-5’ at d 22.34 (2JC,H). H-5’ (d 1.43, st, 3JH,H
7.50) shows long-range couplings to C-3’ at d 29.20 (3JC,H
and C-6’ at d 13.83 (2JC,H). The H-6’ signal (d 0.96, t, 3JH,H
7.50) is correlated with the carbon resonances for C-4’ at
d 29.68 (3JC,H) and C-5’ at d 22.34 (2JC,H).
The signals at d 8.20-8.17, 8.15-8.13 and 7.75-7.69
refer to the benzenoid hydrogens of the naphthoquinone
moiety H-5 (m), H-8 (m) and H-6/7 (m), respectively. In
the HMBC contour map (Figure 13) H-5 shows long range
coupling to C-4 (d 181.06) (3JC,H) and the same for H-8
to C-1 (d 173.23) (3JC,H), as expected. On the other hand,
HMBC correlations for C9, C10, C6 and C7 are not clearly
shown in the spectrum and their assignments were based
on similarities with 4d that is a NQ, structurally closer to
6d because of the carbonyl carbons positions.
for compound 5d are shown in Table 2.
)
1
Finally, in the H NMR spectrum of para-FNQ 6d
(Figure 12) the singlet at d 6.60 is related to H-1’, the
only hydrogen in the furan ring and it shows long-range
correlation (1H-13C HMBC contour map) (Figures 13 and 14)
to the carbonyl carbon C-4 (d 181.06) (3JC,H). Thus the other
carbonyl carbon at d 173.23 corresponds to C-1. Therefore
H-1’signal is correlated with those of C-2 at d 151.72 (3JC,H),
C-3 at d 131.95 and C-2’ at d 164.99 (2JC,H). H-3’ signal
3
(d 2.81, t, JH,H 7.60) shows long-range correlation with
the carbon resonance of C-2’ at d 164.99, C-4’ at d 29.68
(2JC,H), C-1’ at d 104.30 and C-5’ at d 22.34 (3JC,H). H-4’
signal (d 1.75, quint, 3JH,H 7.60) is correlated with the carbon
resonances to C-2’ at d 164.99, C-6’ at d 13.83 (3JC,H), C-3’
Table 2. 1H NMR chemical shifts (d), multiplicities, coupling constants (J) and heteronuclear correlations observed in the HMBC for compound 5d
1H (d, multiplicity, 3JH,H / Hz)
H-7 (7.40, at, J 7.70)
H-8 (8.00, ad, J 7.57)
H-1’ (6.42, s)
3J 13C (d / ppm)
C-5 (122.15); C-9 (128.92)
C-1 (180.89); C-6 (135.46); C-10 (128.78)
C-2 (174.60); C-4 (159.65)
C-1’(103.84); C-5’(22.28)
C-2’ (160.49); C-6’(13.85)
−
2J 13C (d / ppm)
−
C-7 (130.55)
C-3 (122.68)
H-3’ (2.71, t, J 7.60)
H-4’ (1.70, quint, J 7.60)
H-5’ (1.44, st, J 7.60)
H-6’ (0.97, t, J 7.60)
C-2’ (160.49); C-4’(29.71)
C-3’(27.70); C-5’(22.28)
C-4’(29.71); C-6’(13.85)
C-5’(22.28)
C-4’(29.71)
s: singlet; ad: apparent doublet; at: apparent triplet; t: triplet; quint: quintet; st: sextet.

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A Complete and Unambiguous 1H and 13C NMR Signals
J. Braz. Chem. Soc.
Figure 12. 1H NMR spectrum of compound 6d.
Figure 13. Expansion 1H-13C HMBC contour map (d 6.5-8.4 ppm) of compound 6d.
All the hydrogens and heteronuclear correlations
observed in the HMBC for compound 6d are shown in
Table 3.
by 1H-13C HMBC data. In para-FNQ (6d) signals of the
two carbonyl carbons C-1 and C-4 exhibit long-range
correlation to the hydrogen resonances for H-8 and H-5
(Figure 13), respectively, whereas in ortho-FNQ (5d) only
The isomers ortho- and para-FNQ can be distinguished

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1147
Figure 14. Expansion 1H-13C HMBC contour map (d 0.9-2.9 ppm) of compound 6d.
Table 3. 1H NMR chemical shifts (d), multiplicities, coupling constants (J) and heteronuclear correlations observed in the HMBC for compound 6d
1H (d, multiplicity, 3JH,H / Hz)
H-5 (8.20-8.17, m)
3J 13C (d / ppm)
C-4 (181.06)
2J 13C (d / ppm)
−
H-8 (8.15-8.13, m)
C-1 (173.23)
−
H-1’ (6.60, s)
C-2 (151.72); C-4 (181.06)
C-1’(104.30); C-5’(22.34)
C-2’ (164.99); C-6’(13.83)
C-3’ (29.20)
C-2’ (164.99); C-3 (131.95)
C-4’(29.68); C-2’ (164.99)
C-3’(28.20); C-5’(22.34)
C-6’(13.83)
H-3’ (2.81, t, J 7.60)
H-4’ (1.75, quint, J 7.60)
H-5’ (1.43, st, J 7.50)
H-6’ (0.96, t, J 7.50)
C-4’(29.68)
C-5’(22.34)
s: singlet; t: triplet; quint: quintet; s: sextet; m: multiplet.
H-8 shows long-range correlation of carbon resonance
for carbonyl carbon C-1 (Figure 10). Therefore in NQs
the chemical shifts of carbonyl carbon C-4 ranged from
d 184.31 to 184.53 and were higher than those of C-1
(d 181.17-181.61) while in the para-FNQs the differences
in chemical shifts of C-4 ( 180.88-181.10) and C-1
(d 171.64-173.30) are still higher. These data might be
related to the resonance effect between the oxygen bonded
to C-2 and the C-4 carbonyl (Figure 15). However in the
ortho-FNQs the chemical shift of the carbonyl carbon C-1
(d 180.76-183.91) was higher than that of C-2 (d 174.44-
180.92) probably because the resonance effect is more
effective between the C-1 carbonyl and the oxygen bonded
to C-4 (Figure 15). From the chemical shifts of para- and
ortho-FNQs it is clear that the substituents at C-2’ in the
furan ring have practically no influence in the shielding
of the hydrogens and carbons of the naphthoquinone
moiety.
Conclusions
In this work we have shown the complete and
1
unambiguous assignments of H and 13C chemical shifts
of 2-hydroxy-3-(1’-alkenyl)-1,4-naphthoquinones (NQs),
naphtho[1,2-b]furan-4,5-diones (ortho-FNQs) and
naphtho[2,3-b]furan-4,9-diones (para-FNQs), as discussed

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A Complete and Unambiguous 1H and 13C NMR Signals
J. Braz. Chem. Soc.
Figure 15. Resonance structures for compounds 4d, 5d and 6d.
for 4d, 5d and 6d, respectively. It was observed that the
nature of the substituents at C-3 in the NQs and at C-2’
in the furan ring in the FNQs do not affect significantly
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1
the H and 13C chemical shifts of the naphthoquinone
system. As far as we are concerned, this is the first report
on the distinction between NQs and FNQs by NMR data.
The results described for ortho- and para-FNQs isomers
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1
can be used as a model for H and 13C assignments
of compounds possessing the naphthoquinones and
furanonaphthoquinones system.
Supplementary Information
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R.; ARKIVOC 2007, 6, 145.
Supplementary information (assignment tables of all
hydrogen and carbon signals shifts, and copies of the H
and 13C NMR spectra of compounds 1, 4a‑h, 5a‑h and
6a‑h) is available free of charge at http://jbcs.sbq.org.br
as a PDF file.
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1
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Acknowledgments
11. deAndrade-Neto, V. F.; Goulart, M. O.; da Silva Filho, J. F.; da
Silva, M. J.; Pinto, M. C.; Pinto, A. V.; Zalis, M. G.; Carvalho,
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To Fundaço deAmparo a Pesquisa do Estado de Minas
Gerais/FAPEMIG for financial support and fellowships to
T. F. B. (PCRH/FAPEMIG).
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Submitted: October 31, 6018
Published online: January 12, 6019
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