Synthesis and anti-Trypanosoma cruzi activity of derivatives from nor-lapachones and lapachones

Article abstract of DOI:10.1016/j.bmc.2008.03.032

New naphthoquinone derivatives were synthesized and assayed against bloodstream trypomastigote forms of Trypanosoma cruzi, the etiological agent of Chagas' disease. The compounds were rationalized based on hybrid drugs and appear as important compounds ag

Full text of DOI:10.1016/j.bmc.2008.03.032

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 5030–5038
Synthesis and anti-Trypanosoma cruzi activity of derivatives
from nor-lapachones and lapachones
a
c
Eufraˆnio N. da Silva Ju´nior,a,b Maria Cecılia B. V. de Souza, Michelle C. Fernandes,
´
Rubem F. S. Menna-Barreto,c Maria do Carmo F. R. Pinto,d Francisco de Assis Lopes,d
Carlos Alberto de Simone,e Carlos Kleber Z. Andrade,b Antoˆnio V. Pinto,d
Vitor F. Ferreiraa and Solange L. de Castroc,*
a
ˆ
´
´
Departamento de Quı´mica Organica, Instituto de Quımica, UFF, 24020-150 Niteroi, RJ, Brazil
bInstituto de Quı´mica, Universidade de Brası´lia, 70910-970 Brası´lia, DF, Brazil
cLaborato´rio de Biologia Celular, Instituto Oswaldo Cruz, FIOCRUZ, 21045-900 Rio de Janeiro, RJ, Brazil
dNu´cleo de Pesquisas em Produtos Naturais, UFRJ, 21944-971 Rio de Janeiro, RJ, Brazil
eInstituto de Quı´mica e Biotecnologia, UFAL, Tabuleiro do Martins, 57072-970 Maceio´, Alagoas, Brazil
Received 31 January 2008; revised 10 March 2008; accepted 12 March 2008
Available online 16 March 2008
Abstract—New naphthoquinone derivatives were synthesized and assayed against bloodstream trypomastigote forms of Trypano-
soma cruzi, the etiological agent of Chagas’ disease. The compounds were rationalized based on hybrid drugs and appear as
important compounds against this parasite. From nor-lapachol were prepared five substituted ortho-naphthofuranquinones, a
non-substituted para-naphthofuranquinone, a new oxyrane and an azide and from a-lapachone a new non-substituted para-napht-
hofuranquinone. Other five substituted ortho-naphthofuranquinones recently designed as cytotoxic, were also evaluated. The most
active compounds were the ortho naphthofuranquinones 3-(4-methoxyphenylamino)-2,3-dihydro-2,2-dimethylnaphtho[1,2-b]furan-
4,5-dione and 3-(3-nitrophenylamino)-2,3-dihydro-2,2-dimethylnaphtho[1,2-b]furan-4,5-dione with trypanocidal activity higher
than that of benznidazole, the standard drug. The compounds were rationalized based on hybrid drugs and appear as important
compounds against T. cruzi. The trypanocidal activity of these substances endowed with redox properties representing a good start-
ing point for a medicinal chemistry program aiming the chemotherapy of Chagas’ disease.
ꢀ 2008 Elsevier Ltd. All rights reserved.
1. Introduction
States.3 The life cycle of T. cruzi involves obligatory pas-
sage through vertebrate and invertebrate hosts, in a ser-
ies of different developmental forms. The bloodstream
trypomastigote ingested by the insect differentiates into
the proliferative epimastigote, which differentiates into
metacyclic trypomastigote on the posterior intestine of
the insect. The metacyclic form invades the vertebrate
host cell, differentiates into the proliferative amastigote
form, which transforms into the trypomastigote form
responsible for the dissemination of the infection. When
T. cruzi is transmitted to man through the feces of tri-
atomines, at bite sites or in mucosa, through blood
transfusion or orally through contaminated food, it in-
vades the bloodstream and lymphatic system and be-
comes established in the muscle and cardiac tissue, the
digestive system and phagocytic cells.4
Chagas’ disease (American trypanosomiasis), caused by
the protozoa Trypanosoma cruzi, is endemic in 21 coun-
tries of the Americas.1 Acute infections are usually
asymptomatic, but the ensuing chronic T. cruzi infec-
tions have been associated with high ratios of morbidity
and mortality.2 Most human infections in the Western
Hemisphere occur through contact with infected blood-
sucking insects of the triatomine species. However, eco-
nomic hardship, political problems, or both, have
spurred migration from endemic countries to developed
ones such as Australia, Canada, Spain, and the United
Keywords: Naphthoquinones; Lapachone; Trypanosoma cruzi; Chagas’
disease; Chemotherapy.
*
At present, the only accepted drugs for the treatment
of Chagas’ disease are nifurtimox (Lampitꢁ) and
Corresponding author. Tel.: +55 21 25984534; fax: +55 21
25984577; e-mail: solange@ioc.fiocruz.br
0968-0896/$ - see front matter ꢀ 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2008.03.032

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E. N. da Silva Junior et al. / Bioorg. Med. Chem. 16 (2008) 5030–5038
5031
benznidazole (Rochaganꢁ or Radanilꢁ), effective for
acute infections, but controversy on their use for chronic
patients is due to undesirable side effects, frequently
forcing the abandonment of the treatment, poor indices
of apparent cure, and a lack of consensus about criteria
for parasitological cure.5,6
lapachone were the most active against the three evolu-
tive forms of the parasite, and by ultrastructural, flow
cytometry and biochemical studies, it was shown that
they interfere with the energetic metabolism and DNA
fragmentation.13,14 Our group also reported the synthe-
sis and trypanocidal activity of new naphthofuranqui-
nones obtained from nor-lapachol, 2-hydroxy-3-allyl-
naphthoquinone,15 of heterocyclic oxyranes,16,17 and
[1,2,3]-triazole derivatives of nor-b-lapachone.18 Giving
continuity to our studies on the chemistry of naphtho-
quinones and their activity against T. cruzi, we now fo-
cus on new ortho- and para-naphthoquinone derivatives.
In this context, an intensive effort has been devoted to
finding new prototype compounds among natural and
synthetic sources. Compounds having a quinone core
have promising biological activity. In this regard, naph-
thoquinones have a broad distribution in the plant king-
dom and are involved in several oxidative processes such
as photosynthesis and electron transfer reactions.7 The
1,2- and 1,4-naphthoquinones are considered privileged
structures in medicinal chemistry, with the easiness of
reduction–oxidation of the quinoidal moiety being the
basis for their participation in electron transport and
oxidative-phosphorylation processes. Taking into ac-
count that molecular hybridization8a is a powerful ap-
proach for the design of new compounds based on the
recognition of the pharmacophoric sub-unities in the
molecular structure, we have been searching for new
quinone derivatives as potential anti-T. cruzi com-
pounds exploring the electrophilicity of 1,2-quinoidal
carbonyls by reactions with different heteroatom nucle-
ophilic centers7 (Scheme 1). From the heartwood of
Tabebuia trees (Bigoniaceae) we have extracted lapa-
chol, and prepared about 60 derivatives which were
screened for their trypanocidal effect, using the infective
bloodstream form of T. cruzi.8–12 Among these com-
pounds, three naphthoimidazoles derived from b-
2. Results and discussion
2.1. Chemistry
Lapachol (1) (2-hydroxy-3-(30-methyl-2-butenyl)-1,4-
naphthoquinone) was extracted from the heartwood
of Tabebuia sp. (Tecoma) and purified by a series of
recrystallizations. From this quinone, nor-lapachol
(2) (2-hydroxy-3-(2-methyl-propenyl)-[1,4]-naphthoqui-
none) was obtained by Hooker oxidation.19 The treat-
ment of 2 with HCl/AcOH produced nor-a-lapachone
(3) (2,3-dihydro-2,2-dimethyl[2,3-b]furan-4,9-dione) which
was transformed into 3-bromo-nor-a-lapachone (4) (3-
bromo-2,3-dihydro-2,2-dimethyl[2,3-b]furan-4,9-dione)
as previously described by us.20 Reaction of 4 with so-
dium azide in CH2Cl2 and with aniline gave, respec-
tively, the corresponding azide and arylamino
derivatives 10 and 11. This azidonaphthoquinone 10
O
O
NHPh
N
Ph
N
O
N
O
N
Ph
O
Redox center
modification
O
O
NH
O
N
N
N
O
N
NH
O
Ring
modification
Redox center
modification
O
C
O
O
O
H
N
β-lapachone
Redox center
O
modification and
Ring
modification
H
N
O
OMe
Scheme 1. Examples of trypanocidal compounds obtained from b-lapachone by ring and redox center modifications.

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E. N. da Silva Junior et al. / Bioorg. Med. Chem. 16 (2008) 5030–5038
5032
is a chemically versatile compound, which can be
transformed into triazolequinones. Also, reduction of
the azido group originates the corresponding amine
that can be oxidized to its nitro derivative, which pre-
sents a broad reactivity.
The first step involves in situ preparation of 6, which
then reacts with the desired arylamine (Scheme 2). The
new oxyran 9 (2,2-dimethyl-3-hydro-4-oxanaphtho[2,3-
b]furane-9-spiro-20-oxyrane) was synthesized by addi-
tion of an ethereal solution of freshly prepared diazo-
methane to 3. The reaction of naphthoquinones
leading to oxyrans has been previously described and
their structures were unequivocally established.21–23
The naphthoquinone 5 (2,2-dimethyl-3,4-dihydro-2H-
5,10-dioxy-naphtho[2,3-b]pyrane) was obtained from 1,
through cyclization of its isoprenyl lateral chain in the
presence of HCl/AcOH, by nucleophilic attack of oxy-
gen atom of the hydroxyl group. By reacting 5 with
NBS in the presence of benzoyl peroxide, and CCl4 as
solvent, (8) (4-bromo-3,4-dihydro-2,2-dimethyl-2H-
benzo[g]chromene-5,10-dione) was obtained20 and its
subsequent reaction with aniline gave the new para-
arylaminonaphthoquinone 22 (2,2-dimethyl-4-phenyla-
mino-3,4-dihydro-2H-benzo[g]chromene-5,10-dione). The
reaction of 2 with bromine in CHCl3 originated (6) (3-
bromo-2,3-dihydro-2,2-dimethylnaphtho[1,2-b]furan-4,
5-dione), the starting material for the synthesis of the
naphthoquinone (7) (2,3-dihydro-3-hydroxy-2,2-dimeth-
ylnaphtho[1,2-b]furan-4,5-dione) and of the ortho-aryla-
minonaphthofuranquinones 12–21. The synthesis of
12–15 and 21 was previously reported by our group.24
The formation of arylamino ortho-naphthofuranqui-
nones 12–21 possibly occurs through a carbenium ion,
since the alternative reaction, direct displacement, is less
favorable due to spacial steric hindrance caused by the
two methyl groups.20 The para-naphthofuranquinone
(11)24 and the para-naphthopyranquinone (22), de-
scribed herein for the first time, were obtained in good
yields by a methodology similar to that used for the syn-
thesis of ortho-naphthofuranquinones.
The structures of the synthesized compounds (Scheme 2)
1
were confirmed by spectroscopic techniques, such as H
and 13C NMR, infrared, and electron-impact mass spec-
tra. X-ray crystallography study of the fluoro derivative
21 was performed.
12 - R1, R4 = Me; R2, R3 = H
13 - R1, R3, R4 = H; R2 = Cl
14 - R1, R3, R4 = H; R2 = Br
O
O
O
NH2
R3
6
O
1) NaHSO3
2) Na2CO3
O
R1
R2
O
5a
9a
4
7
8
15 - R1, R3, R4 = H; R2 = NO2
16 - R1, R3, R4 = H; R2 = F
17 - R1, R2, R4 = H; R3 = Cl
18 - R1, R2, R4 = H; R3 = Br
19 - R1, R2, R4 = H; R3 = NO2
20 - R1, R2, R4 = H; R3 = OMe
21 - R1, R2, R4 = H; R3 = F
5
R1
2'
H
N
Br
3a
3
R4
OH
R2
R3
1'
9b
3'
4'
9
O
(6)
O
H
11
(7)
2
O
6'
1
5'
10
R4
Br2
CHCl3
O
O
O
O
O
O
OH
OH
Hooker
Oxidation
HCl
CH3COOH
O
(1)
(2)
(5)
NBS
CCl4
HCl
CH3COOH
benzoyl per.
O
O
NH2
O
O
CH2N2
5ºC
O
O
O
O
O
NH
O
(9)
O
(3)
(22)
O
(8)
Br
O
NBS
CCl4
benzoyl per.
O
NaN3
CH2Cl2
O
N3
O
(10)
O
O
Br
O
(4)
O
NH2
NH
O
(11)
Scheme 2. Synthetic route for preparing the naphthoquinones assayed against trypomastigote forms of T. cruzi.

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E. N. da Silva Junior et al. / Bioorg. Med. Chem. 16 (2008) 5030–5038
5033
Table 1. Crystal data and structure refinement of the fluoro derivative
21
The structure of 21 was solved by direct methods and re-
fined through the interactive blocked-matrix least square
calculations. The refinement was conducted until all
atomic parameters shifts were smaller than their stan-
dard deviations. All H atoms were located by geometric
Crystal data
C
20H15FNO3
Mr = 336.33
Z = 8
Dx = 1.324 Mg mꢀ3
Mo Ka
˚
Orthorhombic, Pcab
˚
a = 8.3124 (2) A
˚
b = 12.2195 (4) A
c = 33.2167 (11) A
considerations placed (C–H = 0.93–0.98 A) and refined
as riding with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl
C). In the final difference Fourier map there are no
l = 0.10 mmꢀ1
T = 293 (2) K
Prism, colorless
0.15 · 0.10 · 0.09 mm
˚
peaks greater than 0.57 Aꢀ3. An Ortep3 diagram of
˚
3
˚
V = 3373.93 (18) A
the molecule is given in Figure 1 and Table 1 displays
the main crystal data and structure refinement for the
compound.
Data collection
KappaCCD diffractometer
CCD rotation images,thick
slice scans
3823 independent reflections
2047 reflections with I > 2r(I)
Bond lengths and angles are in good agreement with the
expected values reported in the literature.25 The atoms
of the naphthoquinonic ring are coplanar and the largest
Absorption correction: none Rint = 0.054
17805 measured reflections
hmax = 27.5ꢂ
Refinement
˚
deviation [0.044(3) A] from the least-square plane is
Refinement on F2
R[F2>2r(F2)] = 0.075
wR(F2) = 0.225
S = 1.05
(D/r)max<0.001
exhibited by atom C3. Atoms O1 and C12 of the furane
ring lie in the mean least-square plane of the naphtho-
quinonic ring with deviations of 0.045(2) and
ꢀ3
˚
Dqmax = 0.57 e A ꢀ3
˚
Dqmin = ꢀ0.18 eA
Extinction correction: none
H atoms treated by constrained
refinement
˚
˚
0.035(2) A, respectively, while atom C11 is 0.105(2) A
out of that plane (Fig. 2), and this attribute is a confor-
mation of the pure envelope to furane ring. The packing
parameters calculated for this conformation were:
3823 Reflections
2
226 Parameters
w ¼ 1=½r2ðF 2oÞ þ ð0:1028PÞ
þ0:9409Pꢂ where P ¼ ðF 2o þ 2F c2Þ=3
2
2
26
˚
q = 1.629(2) A and / = 254.5(8)ꢂ.
benznidazole is 103.6 0.6 lM,18 and for crystal violet,
536.0 3.0 lM.8b
The dihedral angle between the least-square plane calcu-
lated through the atoms [C13–C18] of benzene ring and
that of the naphthoquinonic ring is 74.07(1)ꢂ. In the
crystalline packing, molecules are held together by
The synthesis of oxyrans from naphthoquinones was ini-
tially reported by Pinto et al.,21 and more recently the
epoxide obtained from a-lapachone (5) was shown to in-
hibit the proliferation of T. cruzi epimastigotes.17 In this
context, the oxyran 9 was synthesized from nor-a-
lapachone (3), but when assayed against trypomastigote
form was inactive.
strong
N–Hꢁ ꢁ ꢁO
interaction
where
N1–
i
H1 = 0.96,H1ꢁ ꢁ ꢁ;O2 = 2.13 A and N1–H1ÆO2i = 159ꢂ
(i = 1/2 + x, 1/2 ꢀ y, z), forming chains propagated in
the a direction (Fig. 3).
˚
2.2. Trypanocidal activity
The naphthoquinone 7 which presents important activ-
ity against methicillin-resistant bacterial strains27 was
assayed for the first time against T. cruzi and its activity
was only twofold lower than that of benznidazole. While
nor-a-lapachone (3) was inactive against the parasite, its
derivative the azide 10 presented an IC50/
24 h = 179.3 12.0 lM (Table 2). In the same experi-
mental conditions, the corresponding IC50 value for
Comparing the non-substituted arylamino derivatives 11
and 22, we observed the good activity of the para-naph-
thoquinone 22, while 11 was inactive against the para-
site. Also, 22 was more active than the original
quinone, a-lapachone (5), possibly due to the insertion
of the arylamino group, increasing the lipophilicity of
the molecule, which could be associated with a better
penetration through the plasma membrane.
Figure 1. An ellipsoid plot Ortep3 of 21 showing the atom labeling and 50% probability displacement ellipsoids.

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E. N. da Silva Junior et al. / Bioorg. Med. Chem. 16 (2008) 5030–5038
5034
Figure 2. Projection down direction of the naphthoquinonic ring of 21.
Figure 3. View of the crystal packing showing in dotted lines the N1–H1ꢁ ꢁ ꢁO2 interactions of compound 21.
In this paper, we also presented the synthesis of the aryl-
amines 16–20 substituted by electron-withdrawing or
electron-donating groups and the 12–21 were also evalu-
ated against T. cruzi (Table 2). The compounds 15 and 20
were both more active than benznidazole, and were fol-
lowed by 14, 13, and 17 (Fig. 4), while the others presented
IC50 values higher than 800 lM. These two latter aryl-
amines, 13 and 17, were more active than 1 (lapachol),
the original quinone. In the same experimental condition,
the IC50/1 day value for crystal violet is 536.0 3.0 lM.8b
A NO2 group is present both in 15 and in 19, but the latter
compound is much less active, suggesting that the posi-
tion of this group affects the electronic distribution,
mainly at position 4 of the aromatic ring, decreasing the
electronic density of the nitrogen, which may affect the re-
dox potential of the quinone center.
pounds proved to be more active against the T. cruzi
than their original precursor nor-b-lapachone, and such
activity was especially dependent on structural features
and on the substituent position on the furanic ring.18
3. Conclusions
Plants containing naphthoquinones are still employed in
folk medicine,28 and their molecular structure endows
them with redox properties that could interfere in bio-
logical oxidative processes. Naphthofuranquinones dis-
play a wide variety of biological activities, being in
some instances more active than their pyranic counter-
parts. Due to the already described lytic effect upon
bloodstream trypomastigotes of T. cruzi,15 new deriva-
tives were prepared and assayed against the parasite.
Approaches on the planning of new trypanocidal com-
pounds based on molecular hybridization were previ-
ously accomplished by our group in order to prepare
new naphthoquinoidal [1,2,3]-triazoles.18 These com-
The substituted arylamino quinones and substituted
naphthoquinones appear as interesting new prototype
compounds and experiments are currently underway in

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E. N. da Silva Junior et al. / Bioorg. Med. Chem. 16 (2008) 5030–5038
5035
Table 2. Activity of the compounds against Y strain trypomastigote
forms of T. cruzi
ter ca 6 nm). Infrared spectra were recorded on a Perkin-
1
Elmer FT-IR Spectrometer. H and 13C NMR were re-
IC50/24 ha (lM)
corded at room temperature using a Varian Unity Plus
300 instrument, in the solvents indicated, with TMS as
internal standard. Chemical shifts (d) are given in ppm
and coupling constants (J) in Hertz. electron-impact
mass spectra (70 eV) were obtained using a MAT8500
instrument and a VG Autospec apparatus (Micromass,
Manchester, UK). The main fragments were described
as a relation between atomic mass units and the charge
(m/z) and the relative abundance in percentage of the
base-peak intensity.
Compounds
1
410.8 53.2b
1281.0 167.0b
>4800b
2
3
c
4
—
>4800b
—
5
6
7
212.3 10.6
—
>4000
8
9
10
179.3 12.0
>4000
11
12
4.2. Synthesis of 3-azido-2,2-dimethyl-2,3-dihydro-naph-
tho[2,3-b]furan-4,9-dione (10)
1756.1 91.8
332.8 23.3
140.8 11.9
86.3 4.6
>4000
13
14
3-Bromo-nor-a-lapachone (4) (307 mg, 1 mmol) in
dichloromethane (25 mL), was treated with an excess
of sodium azide (195 mg, 3 mmol) at room temperature.
The reactional system was stirred for 24 h, filtered and
purified by column chromatography over silica-gel,
using as eluent a gradient mixture of hexane/ethyl ace-
tate (9/1 to 7/3) with increasing polarity. Compound
10 was obtained as an orange solid (123 mg, 0.45 mmol,
45% yield, m.p. 115–116 ꢂC). 1H NMR (300 MHz,
CDCl3) d: 8.16–8.10 (2H, m), 7.80–7.69 (2H, m), 4.84
(1H, s), 1.63 (3H, s), 1.54 (3H, s); 13C NMR (75 MHz,
CDCl3) d: 178.1 (C@O), 159.9 (C@O), 134.5 (CH),
133.2 (CH), 132.6 (C0), 131.5 (C0), 126.5 (CH), 126.2
(CH), 120.7 (C0), 93.9 (C0), 68.2 (CH), 29.5 (CH2),
26.9 (CH3), 21.7 (CH3); IR mmax(cmꢀ1, KBr) 2977–
2851 (CH2, CH3), 1654 (C@O), 1602 (C@O), (2105)
N3; EI HRMS (m/z) 269.08000 Calcd for C14H11N3O3:
269.08004; (m/z) (%) 227.0 (100.00), 199.0 (17.00),
104.0 (14.10), 76.0 (11.20).
15
16
17
18
384.4 52.5
952.5 71.1
857.3 96.4
88.2 6.7
2517.9 169.8
342.0 42.8
103.6 0.6
19
20
21
22
Benznidazole
a Mean SD of at least three independent experiments.
b Ref. 8.
c In situ preparation.
100
50
4.3. Synthesis of 2,2-dimethyl-3-hydro-4-oxanaphtho[2,3-
b]furane-9-spiro-20-oxyrane (9)
13
15
14
17
Bz
The naphthoquinone 3 (228 mg, 1 mmol) and an ethe-
real solution of freshly prepared diazomethane (excess)
were kept at 5oC for 48 h, and then the solvent was evap-
orated under reduced pressure and the residue obtained
was purified by column chromatography over silica-gel,
using as eluent a gradient mixture of hexane/ethyl ace-
tate (9/1 to 7/3) with increasing polarity. Compound 9
was obtained as a yellow solid (145 mg, 0.6 mmol, 60%
20
0
0
200
400
600
800
1000
μM
Figure 4. Graphic representation of the effect of the most active
arylamines naphthoquinones and of benznidazole against bloodstream
trypomastigotes of Trypanosoma cruzi.
1
yield, m.p. 120–122 ꢂC). H NMR (300 MHz, CDCl3)
d: 8.05–7.94 (2H, m), 7.74–7.71 (2H, m), 2.86 (1H, dd,
J = 12.9, 0.9 Hz), 2.36 (1H, dd, J = 5.6, 0.9 Hz), 2.0–
1.96 (2H, m), 1.43 (3H, s), 1.27 (3H, s); 13C NMR
(75 MHz, CDCl3) d: 192.8 (C@O), 191.9 (C0), 134.0
(CH), 133.9 (CH), 132.7 (C0), 132.3 (C0), 127.1 (CH),
94.4 (C0), 75.6 (C0), 47.3 (CH2), 41.7 (CH2), 41.4
(CH2), 27.5 (CH3), 27.2 (CH3); IR mmax(cmꢀ1, KBr)
2932–2969 (CH2, CH3), 1682 (C@O); EI HRMS (m/z)
242.09430. Calcd for C15H14O3: 242.09429; (m/z) (%)
227.0 (100.00), 242.0 (47.00), 76.0 (35.10), 104.0 (29.00).
our laboratories to investigate their mode of action,
especially free-radicals generation, possibly opening
new perspectives to the development of more potent
and selective trypanocidal drugs.
4. Experimental protocols
4.1. General procedures
Melting points were obtained on a Reichert micro hot-
stage and are uncorrected. Analytical grade solvents
were used. Column chromatography was performed on
silica-gel (Acros Organics 0.035–0.070 mm, pore diame-
4.4. General procedures for preparation of 16–20
To a solution of nor-lapachol (2) (228 mg, 1 mmol) in
25 mL of chloroform, 2 mL of bromine (6 mg, 38 mmol)

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E. N. da Silva Junior et al. / Bioorg. Med. Chem. 16 (2008) 5030–5038
5036
was added. The bromo intermediate 6 (3-bromo-2,2-
dimethyl-2,3-dihydro-naphtho[1,2-b]furan-4,5-dione)
precipitated immediately as an orange solid. Over this
mixture, an excess of the appropriate arylamine was
added and, then, the mixture was stirred for 30 min.
After addition of 50 mL of water, the organic phase
was separated and washed with 10% HCl (3 · 50 mL),
dried over sodium sulfate, filtered, and concentrated un-
der reduced pressure. The arylamino derivative was
purified by column chromatography over silica-gel,
using as eluent a gradient mixture of hexane/ethyl ace-
tate (9/1 to 7/3) with increasing polarity.
(C@O), 169.9 (C0), 146.5 (C0), 131.4 (C0), 127.5 (C0),
115.1 (C0), 110.0 (C0), 96.9 (C0), 134.8 (CH), 132.8
(CH), 132.2 (CH), 129.7 (CH), 125.3 (CH), 114.9
(CH), 61.9 (CH), 27.6 (CH3), 21.9 (CH3); IR
m
max(cmꢀ1, KBr) 3365 (R2NH), 1689 (C@O), 1646
(C@O); MS (70 eV, m/z) (%) 43.05 (6.58), 75.10
(4.53), 76.10 (8.78), 77.10 (5.21), 104.10 (4.14), 128.10
(7.04), 142.95 (4.33), 156.95 (5.82), 171.00 (6.44),
199.20 (10.96), 209.20 (6.31), 227.15 (100.00), 228.20
(17.60), 397.05 (4.47).
4.4.4. 3-(4-Nitro-phenylamino)-2,2-dimethyl-2,3-dihydro-
naphtho[1,2-b]furan-4,5-dione (19). Using an excess of 4-
nitro-phenylamine, 19 was obtained as a red solid
4.4.1. 3-(3-Fluoro-phenylamino)-2,2-dimethyl-2,3-dihydro-
naphtho[1,2-b]furan-4,5-dione (16). Using an excess of 3-
fluoro-phenylamine, 16 was obtained as a red solid
1
(254 mg, 0.70 mmol, 70% yield, m.p. 248–250 ꢂC). H
0
0
NMR (300 MHz, CDCl3) d: 8.03 (H3 and H5 , d,
1
0
0
(253 mg, 0.75 mmol, 75% yield, m.p. 221–225 ꢂC). H
J = 9.0 Hz), 6.78 (H2 and H6 , d, J = 9.0 Hz), 7.84–
7.71 (H6 or H9; H7 and H8, m), 7.42 (H6 or H9, d,
J = 9.0 Hz), 4.96 (H3, d, J = 8.3 Hz), 1.65 (H10 or
H11, s), 1.45 (H10 or H11, s); 13C NMR (75 MHz,
DMSO-d6) d: 180.7 (C@O), 175.0 (C@O), 168.4 (C0),
154.0 (C0), 136.6 (C0), 131.2 (C0), 127.2 (C0), 114.8
(C0), 95.8 (C0), 133.0 (CH), 129.0 (CH), 135.2 (CH),
126.5 (CH), 124.8 (CH), 112,5 (CH), 59.4 (CH), 26.8
NMR (300 MHz, CDCl3) d: 8.10 (1H, ddd, J = 7.5,
1.5, 0.7 Hz), 7.74–7.61 (3H, m), 7.10 (1H, m), 6.42
(1H, m), 6.38 (1H, dd, J = 8.0, 2.1), 6.26 (1H, dt,
J = 11.2, 2.4 Hz), 4.78 (1H, s), 1.68 (3H, s), 1.58 (3H,
s); 13C NMR (75 MHz, CDCl3) d: 180.7 (C@O), 175.2
(C@O), 169.5 (C0), 163.8 (d, J = 243 Hz), 148.9 (C0),
134.5 (CH), 132.5 (CH), 131.1 (C0), 130.3 (d,
J = 16.0 Hz), 129.4 (CH), 127.2 (C0), 114.7 (C0), 124.9
(CH), 108 (d, J = 2.3 Hz), 104.5 (d, J = 23.8 Hz), 99.8
(d, J = 24.9 Hz), 96.5 (C0), 61.5 (CH), 27.2 (CH3), 21.6
(CH3), 21.5 (CH3); IR
m
max(cmꢀ1
,
KBr) 3343
(R2NH), 1644 (C@O), 1599 (C@O); MS (70 eV, m/z)
(%) 39.00 (5.13), 43.05 (7.68), 50.05 (4.34), 76.10
(10.16), 77.10 (5.83), 104.10 (4.18), 114.95 (5.35),
128.10 (7.89), 171.15 (4.43), 199.20 (10.14), 203.20
(4.53), 209.20 (5.45), 227.20 (100.00), 228.25 (15.72),
364.20 (4.86).
(CH3); IR
m , KBr) 3364 (R2NH), 1641
max(cmꢀ1
(C@O), 1611 (C@O); EI HRMS (m/z) 337.11140. Calcd
for C20H16FNO3: 337.11142; (m/z) (%) 227.0 (100.00),
337.0 (15.00), 199.0 (10.10).
4.4.2. 3-(4-Chloro-phenylamino)-2,2-dimethyl-2,3-dihydro-
naphtho[1,2-b]furan-4,5-dione (17). Using an excess of 4-
chloro-phenylamine, 17 was obtained as a red solid
(317 mg, 0.9 mmol, 90% yield, m.p. 210–214 ꢂC). 1H
NMR (300 MHz, CDCl3) d: 8.1 (H6 or H9, ddd,
J = 7.9, 2.2, 0.7 Hz), 7.72–7.60 (H6 or H9; H7 and H8,
4.4.5. 3-(4-Methoxy-phenylamino)-2,2-dimethyl-2,3-dihy-
dro-naphtho[1,2-b]furan-4,5-dione (20). Using an excess
of 4-methoxy-phenylamine, 20 was obtained as a brown
solid (218 mg, 0.6 mmol, 60% yield, m.p. 190–194 ꢂC).
1H NMR (300 MHz, CDCl3) d: 6.48 (H3 and H5 , d,
0
0
0
0
J = 9.0 Hz), 6.54 (H2 and H6 , d, J = 8.3 Hz), 7.73–
7.60 (H6 or H9; H7 and H8, m), 7.42 (H6 or H9, dd,
J = 8.1, 1.3 Hz), 4.71 (H3, s), 1.65 (H10 or H11, s), 1.59
(H10 or H11, s), 3.74 (CH3, s); 13C NMR (75 MHz,
DMSO-d6) d: 180.9 (C@O), 175.4 (C@O), 168.4 (C0),
152.3 (C0), 141.5 (C0), 131.3 (C0), 127.4 (C0), 115.4
(C0), 96.8 (C0), 134.5 (CH), 132.4 (CH), 129.4 (CH),
125.0 (CH), 114.8 (CH), 114,3 (CH), 55.7 (CH), 62.5
(CH3), 27.3 (CH3), 21.7 (CH3); IR mmax(cmꢀ1, KBr)
3357 (R2NH), 1693 (C@O), 1641 (C@O) MS (70 eV,
m/z) (%) 39.05 (4.95), 41.05 (6.23), 43.05 (9.49), 76.10
(6.45), 77.10 (8.85), 104.05 (4.24), 108.10 (8.58), 122.10
(4.80), 123.10 (6.17), 128.05 (9.06), 153.10 (5.10),
157.10 (5.37), 171.05 (7.01), 199.15 (15.28), 209.10
(11.03), 227.10 (100.00), 228.20 (17.13), 306.15
(0.53),349.25 (21.04).
0
m), 7.13 (H3 and H5 , dd, J = 6.7, 2.1 Hz), 6.5 (H2
0
0
0
and H6 , dd, J = 6.7, 2.1 Hz), 4.75 (H3, d, J = 5.7 Hz),
1.66 (H10 or H11, s), 1.56 (H10 or H11, s); 13C NMR
(75 MHz, CDCl3) d: 180.8 (C@O), 175.3 (C@O), 169.6
(C0), 145.8 (C0), 134.6 (CH), 132.6 (CH), 131.1 (C0),
129.5 (CH), 129.1 (CH), 127.2 (C0), 125.0 (CH), 122.6
(C0), 114.6 (C0), 114.1 (CH), 96.6 (C0), 61.7 (CH), 27.3
(CH3), 21.7 (CH3); IR mmax (cmꢀ1, KBr) 3365 (R2NH),
1689 (C@O), 1647 (C@O); MS (70 eV, m/z) (%) 39.05
(4.10), 41.05 (4.62), 43.05 (7.02), 50.05 (3.17), 51.05
(3.15), 75.15 (6.05), 76.10 (6.77), 77.10 (5.37), 102.15
(4.06), 110.95 (4.08), 126.85 (7.32), 152.10 (6.06),
171.10 (5.81), 199.10 (12.48), 209.20 (6.73), 227.15
(100.00), 228.25 (15.41).
4.4.3. 3-(4-Bromo-phenylamino)-2,2-dimethyl-2,3-dihydro-
naphtho[1,2-b]furan-4,5-dione (18). Using an excess of 4-
bromo-phenylamine, 18 was obtained as a red solid
(270 mg, 0.67 mmol, 67% yield, m.p. 207–210 ꢂC). H
4.5. 2,2-Dimethyl-4-phenylamino-3,4-dihydro-2H-
benzo[g]chromene-5,10-dione (22)
1
0
0
NMR (300 MHz, CDCl3) d: 7.25 (H3 and H5 , dd,
The bromo derivative 8 (307 mg, 1 mmol) obtained
from a-lapachone (5)20 was dissolved in 5 mL of ani-
line (5.1 g, 58 mmol) and the mixture was left under
stirring for 30 min. After addition of 50 mL of water,
the organic phase was extracted with dichloromethane,
washed with 10% HCl (3 · 50 mL), dried over sodium
0
0
J = 6.7, 2.1 Hz), 6.46 (H2 and H6 , dd, J = 6.7,
2.1 Hz), 7.72–7.60 (H6 or H9; H7 and H8, m), 8.1 (H6
or H9, ddd, J = 7.9, 2.2, 0.7 Hz), 4.75 (H3, d,
J = 5.7 Hz), 1.66 (H10 or H11, s), 1.56 (H10 or H11, s);
NMR (75 MHz, CDCl3) d: 181.3 (C@O), 175.6

´
E. N. da Silva Junior et al. / Bioorg. Med. Chem. 16 (2008) 5030–5038
5037
sulfate filtered, concentrated under reduced pressure
Acknowledgments
This research was supported by grants from the Conse-
and was purified by column chromatography over sil-
ica-gel, using as eluent a gradient mixture of hexane/
ethyl acetate (9/1 to 7/3) with increasing polarity.
´
lho Nacional de Desenvolvimento Cientıfico e Tec-
nologico (CNPq), DECIT/SCTIE/MS, FIOCRUZ,
´
Compound 22 was obtained as
a
brown solid
(233 mg, 0.7 mmol, 70% yield, m.p. 175–178 ꢂC). 1H
NMR (300 MHz, CDCl3) d: 2.31 (1H, dd, J = 14.2,
4.1 Hz), 2.06 (1H, dd, J = 14.4, 5.6 Hz), 4.72 (1H,
dd, J = 5.6, 4.3 Hz), 7.28–7.23 (2H, m), 6.89–6.81
(3H, m), 8.13-8.07 (2H, m), 7.77–7.68 (2H, m), 1.55
(3H, s), 1.50 (3H, s); 13C NMR (75 MHz, CDCl3) d:
183.4 (C@O), 179.8 (C@O), 155.1 (C0), 146.6 (C0),
134.1 (C0), 132.9 (CH), 132.0 (C0), 130.7 (C0), 129.2
(CH), 126.2 (CH), 126.0 (CH), 118.8 (C0), 118.3
(CH), 113.8 (CH), 79.0 (C0), 43.3 (CH), 37.4 (CH2),
18.6 (CH3), 26.1 (CH3); IR mmax(cmꢀ1, KBr) 3381
(R2NH), 1686 (C@O), 1607 (C@O); EI HRMS (m/z)
333.13650. Calcd for C15H14O3: 333.13649; (m/z) (%)
333.0 (100.00), 241.0 (53.20), 223.0 (50.00), 93.0
(41.50).
Fundac¸a˜o Carlos Chagas Filho de Amparo a Pesquisa
`
do Rio de Janeiro (FAPERJ), CAPES, UFRJ, UnB,
UFAL, and UFF.
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