Addition of thiols to o-quinone methide: New 2-hydroxy-3- phenylsulfanylmethyl[1,4]naphthoquinones and their activity against the human malaria parasite Plasmodium falciparum (3D7)

Article abstract of DOI:10.1016/j.ejmech.2012.10.052

A series of 36 new phenylsulfanylmethyl[1,4]naphthoquinones (7-42) were synthesized by a three-component reaction that involves lawsone, the appropriate aldehyde and thiols with variable substitution patterns. These reactions involve the in situ generation of o-quinone methides (o-QM) via Knoevenagel condensation and 1,4-nucleophilic addition under conventional heating or microwave irradiation. The new naphthoquinones obtained by this methodology were shown to have moderate to good in vitro antimalarial activity against Plasmodium falciparum (3D7).

Full text of DOI:10.1016/j.ejmech.2012.10.052

European Journal of Medicinal Chemistry 59 (2013) 48e53
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Addition of thiols to o-quinone methide: New 2-hydroxy-3-phenylsulfanylmethyl
[1,4]naphthoquinones and their activity against the human malaria parasite
Plasmodium falciparum (3D7)
,
Abhinay Sharma a, Isabela O. Santos b, Pratibha Gaur a, Vitor F. Ferreira b, Celia R.S. Garcia a
**
,
,
David R. da Rocha b
*
a Universidade de São Paulo, Instituto de Biociências, Departamento de Fisiologia, 05508-900 São Paulo, Brazil
b Universidade Federal Fluminense, Instituto de Química, Departamento de Química Orgânica, 24020-150 Niterói, RJ, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 36 new phenylsulfanylmethyl[1,4]naphthoquinones (7e42) were synthesized by a three-
component reaction that involves lawsone, the appropriate aldehyde and thiols with variable substitu-
tion patterns. These reactions involve the in situ generation of o-quinone methides (o-QM) via Knoevenagel
condensation and 1,4-nucleophilic addition under conventional heating or microwave irradiation. The new
naphthoquinones obtained by this methodology were shown to have moderate to good in vitro antimalarial
activity against Plasmodium falciparum (3D7).
Received 12 September 2012
Received in revised form
25 October 2012
Accepted 30 October 2012
Available online 7 November 2012
Ó 2012 Elsevier Masson SAS. All rights reserved.
Keywords:
Malaria
Plasmodium falciparum
Naphthoquinone
Phenylsulfanylmethyl[1,4]naphthoquinone
Antimalarial
1. Introduction
that are currently in use stem from six drug classes: aminoquino-
lines, arylaminoalcohols, artemisinins, antifolates, antibiotics and
Malaria is an infection caused by a parasite from the genus
Plasmodium [1] that represents a major public health issue due
to the growing resistance to current antimalarial drugs. The
World Health Organization (WHO) estimates that 300e500 million
people are infected annually, and the number of deaths exceeds one
million [2,3]
Plasmodium falciparum is a protozoan parasite with a complex
life cycle, the intraerythrocytic cycle, which is comprised of
well-studied stages: ring, trophozoite and schizonts [4e6]. Despite
the worldwide effort to understand the molecular [7,8] and cellular
mechanisms of infection and develop new lead natural [9e11] and
synthetic compounds to fight the P. falciparum (the causative agent
of human malaria), the disease is still devastating. Additionally,
parasite resistance to classical antimalarial treatments raises the
need for the development of new drugs. The antimalarial agents
inhibitors of the respiratory chain [12]. It is important to highlight
the problem of resistance, which further decreases the available
therapeutic arsenal. Therefore, in the interest of public health, an
urgent need remains for novel drug candidates.
The drug arsenals for fighting malaria include the synthetic
naphthoquinone atovaquone (1) [13]. The molecular structure of
compound 1 was inspired by lapachol (2), which is a natural
naphthoquinone that belongs to a class of alkyl-1,4-naphthoqu-
inones and a large group of important natural and synthetic
compounds that present some biological activity. Lapachol was the
first naphthoquinone discovered to possess antimalarial activity
[14e16], and it was later discovered that its toxicity against the
parasite was due to its interaction with the mitochondrial respira-
tory chain [17]. Indeed, this class of compounds possesses a broad
spectrum of important biological activities, such as antiprotozoal,
antibacterial, pesticidal, and antitumor [18], as well as activity
against the snail Biomphalaria glabrata that is involved in the
transmission of schistosomiasis [19,20], among others [21]. Lapa-
chol (1) occurs as component found in various plant families,
including Bignoniaceae, Leguminosae, Sapotaceae, Scrophulariaceae,
Verbenaceae, Malvaceae, and Proteaceae, and exhibits an impressive
* Corresponding author. Tel.: þ55 2126292229; fax: þ55 2126292136.
** Corresponding author.
E-mail addresses: cgarcia@usp.br (C.R.S. Garcia), davidrrocha@vm.uff.br (D.R. da
Rocha).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2012.10.052

A. Sharma et al. / European Journal of Medicinal Chemistry 59 (2013) 48e53
49
list of biological activities [22]. Atovaquone (2) is a hydroxynaph-
thoquinone used in combination with proguanil (Malarone) for
prophylaxis and therapy of uncomplicated tropical malaria [6].
Parvaquone (3) and buparvaquone (4) are additional important
3-substituted-2-hydroxy-1,4-naphthoquinones used as drugs for
the treatment of Pneumocystis pneumonia, toxoplasmosis and
malaria, which highlight the importance of this class of compounds
(Fig. 1). Despite efforts toward the discovery of new bioactive
compounds, the number of new cases of malaria continues to
increase worldwide.
New biochemical targets and chemical entities are currently
being researched as potential antimalarials with particular
emphasis on those with low toxicity in normal cells. Based on what
has been described about the chemotherapy of malaria and the
importance of naphthoquinone derivatives, much remains to be
studied in the search for new compounds that are more active and
Fig. 2. Alkyl-and arylsulfanylmethyl[1,4]naphthoquinones structurally related to
lapachol (2).
a good alternative for the synthesis of 2-hydroxy-3-alkyl[1,4]
naphthoquinones or 3-arylsulfanylmethyl[1,4]naphthoquinones
(7e42). These compounds were characterized using spectroscopic
analyses where we can highlight for its unequivocal analysis the
disappearance of the signal relative to the H-3 of 6 in 1H NMR
spectrum proving that the addition was in this site as well as the
appearance of
a singlet around 4 ppm for the CH2 group
selective than compounds
1 and 2. The literature data for
(compounds 7e18) or singlet around 6 ppm for the group CH
(compounds 19e42). In the 13C NMR spectrum we can easily note
the presence of CH2 groups around 28 ppm (compounds 7e18) and
around 50 ppm for the group CH (compounds 19e42), as well as
signs for the carbons from the thiols introduced.
compounds 1 and 2 show their potential as lead compounds for the
development of new bioactive compounds.
The main objective of this work was the development of a new
three-component reaction for the preparation of alkyl-and aryl-
sulfanylmethyl[1,4]naphthoquinones via o-quinone methide
(Fig. 2). The products of the reaction are structurally related to
lapachol (2), and their biological evaluation against the human
malaria parasite Plasmodium falciparum was studied.
2.2. Biology
2.2.1. In vitro culture of Plasmodium falciparum (3D7)
Parasites were cultured and synchronized as previously
described [26]. In brief, parasites were maintained at 1e10% para-
sitemia and 2% hematocrit in RPMI 1640 culture medium supple-
mented with erythrocytes, 10% human serum, 0.16% glucose,
2. Results
2.1. Chemistry
0.2 mM hypoxanthine, 2.1 mM L-glutamine and 22 mg/mL genta-
Compounds 7e42 were obtained by reaction of lawsone with
the appropriate aldehyde to generate the intermediate o-quinone
methide (6) in situ, followed by nucleophilic addition of
a substituted thiol (Scheme 1). This reaction explores the in situ
generation of o-quinone methides (o-QM) via the Knoevenagel
condensation reaction between lawsone (5) and an appropriate
aldehyde followed by 1,4-nucleophilic addition of thiol derivatives
(Scheme 1) [23e25]
mycin. Cultures were incubated at 37 ꢀC, 3% O2, 3% CO2 and 94% N2.
Synchronization of parasites in culture to ring stages was carried
out by repetitive treatment with 5% (w/v) sorbitol. Parasite growth
and parasitemia were monitored by assessing Giemsa-stained
blood smears under the microscope.
2.2.2. Drug treatment
Drug treatment experiments were conducted in 96-well plates
with varying concentrations (100, 20, 4, 0.8, 0.16, 0.032, 0.0064 and
The reactions of an appropriate aldehyde, thiols (RSH) and
lawsone (5) were carried out by using conventional heating (reflux)
or microwave irradiation (150 ꢀC, 20 min). The results are presented
in Table 1. As shown in the data presented in Table 1, it is possible to
use microwave irradiation to prepare compounds 7e18 in higher
yields and with a drastic decrease in reaction time compared to
conventional heating. After this improvement was observed,
compounds 19e42 were prepared using only microwave irradia-
tion and obtained as a racemic mixture (Table 1). After using either
set of reaction conditions, the products were purified by column
chromatography using silica gel and were characterized by spec-
troscopic techniques. This three-component reaction proved to be
0.00128
this assay, 1% parasitemia and 2% hematocrit were set for each well,
and 200 L of RPMI with 10% human serum and drug were added.
mM) of each drug in triplicate for each concentration. For
m
The parasites were exposed to the drug, and the 96-well plates
were incubated for 48 h.
2.2.3. Flow cytometry analysis
Flow cytometry analysis was performed according the proce-
dure already published [27]. In brief, after 48 h incubation, the
plates were centrifuged at 3000 rpm for 5 min, and RPMI was
removed. Any traces of drug were washed away with PBS (pH 7.2e
7.4). The sample was incubated with 2% formaldehyde in PBS for
24 h to fix the parasite. After fixation, the samples were washed
with PBS again. Permeabilization and staining was performed with
0.1% Triton-X100 and 5 nM YoYo-1 dye (Molecular Probes) [28] by
incubating the sample reaction mixtures at 37 ꢀC for 30 min. Par-
asitemia and the proportions of parasites at each drug concentra-
tion for all drugs tested and control samples (without drug
treatment) were determined from dot plots [side scatter (SSC)
versus fluorescence] of 105 cells acquired on a FACS Calibur flow
cytometer using BD CellQuest Pro software (Becton & Dickinson
Inc.). YOYO-1 was excited with a 488 nm Argon laser, and fluores-
cence emission was collected at 520e530 nm. Parameters subject
to adjustment of the FACS Calibur flow cytometer were forward
scatter (FSC) (log scale, Eꢁ1), SSC (log scale, 269), and FL-1 (log
Fig. 1. Natural and synthetic bioactive naphthoquinones.

50
A. Sharma et al. / European Journal of Medicinal Chemistry 59 (2013) 48e53
Scheme 1. General scheme for preparing the 2-hydroxy-3-alkyl[1,4]naphthoquinones or 3-arylsulfanylmethyl[1,4]naphthoquinones under conventional heating or microwave
irradiation.
scale, 530), and the compensation parameters were FL1-0.8% FL2
and FL1-23.6% FL2.
using a comparative structural. All compounds proved active
against Plasmodium falciparum (3D7); the vast majority revealed
IC50 values <20
R1 and R2 were the most active. Among the ten most active
compounds (IC50 < 10 M), 40% displayed a p-nitro group on the
mM, and the compounds with two phenyl groups at
2.2.4. Statistical analysis
GraphPad Prism (GraphPad Software) software was used for
statistical analysis to calculate IC50 values. At least three indepen-
dent experiments were performed for each experimental condition.
m
phenyl ring as a substituent at R1. The most active compound (34)
has an electron withdrawing substituent at R1 and an electron
donating substituent at R2. The less active compound (38) has two
nitro groups on the phenyl rings at R1 and R2. The results show that
a strongly electron withdrawing substituent at R1 and an electron
donor at R2 are necessary for better antimalarial activity. This same
trend can be observed in the 4-MeO series (34, 10 and 22), which is
more active than 4-MeS series (35, 23 and 11).
3. Results
3.1. Rationale
Taking into consideration that the naphthoquinone core
remains the same in all the assayed compounds, we analyzed them
3.2. Drug screening
Table 1
2-Hydroxy-3-alkyl or 3-arylsulfanylmethyl[1,4]naphthoquinones 7e42 prepared by
conventional heating (7e18) and microwave irradiation (7e42).
The antimalarial activities of the new synthetic compounds
were evaluated against P. falciparum (3D7)-infected RBC cells in
culture. Drug treatment experiments were conducted in 96-well
plates with varying concentrations of each drug, which were
tested in triplicate for each concentration. For this assay, 1% para-
Compound R1
R2
Heathing Microwavec IC50 values
(%)
(%)
(mM)
34
16
39
12
9
4-NO2C6H4 4-CH3OC6H4
3-CH3C6H4
4-NO2C6H4 2-CH3C6H4
e
46
84
77
84
71
65
79
58
83
77
54
60
78
71
33
52
45
83
49
52
60
64
79
63
78
68
60
49
76
85
44
40
89
72
81
53
3.1
5.4
6.6
6.8
7.0
7.5
7.5
8.7
H
71a
e
sitemia and 2% hematocrit were set for each well, and 200 mL of
RPMI with 10% human serum and drug was added. The parasites
were exposed to drug for 48 h. After fixation in 2% formaldehyde,
permeabilization and staining were performed by adding Triton X-
100 and YoYo-1 dye. The samples were then subjected to FACS
analysis, and IC50 values were calculated. Among all of the screened
H
H
4-CH3C6H4
4-FC6H4
73
62a
e
37
32
21
10
15
40
19
22
30
26
35
33
14
17
31
27
23
24
41
8
11
25
29
36
7
42
20
18
28
13
38
4-NO2C6H4 4-HOC6H4
4-NO2C6H4 4-ClC6H4
e
eC6H5
H
H
4-FC6H4
e
4-CH3OC6H4 78b
9.3
9.7
drug compounds, 34 (IC50 ¼ 3.1
m
M) was found to be most effective
2-CH3C6H4
65a
e
against the parasite (with IC50 < 5
mM). Other drugs also showed
4-NO2C6H4 3-CH3C6H4
10.7
11.2
13.6
13.8
13.9
14.3
14.3
14.4
14.5
16.8
17.6
18.2
18.4
19.9
20.0
22.3
25.0
26.1
27.0
27.1
27.8
31.6
31.8
34.2
49.9
56.9
eC6H5
eC6H5
eC6H5
eC6H5
eC6H5
4-CH3OC6H4
Propyl
e
good activity against the malaria parasite (Table 1).
e
e
4. Conclusion
4-NO2C6H4
e
4-NO2C6H4 4-CH3SC6H4
4-NO2C6H4 4-FC6H4
e
e
A new three-component method for the synthesis of 2-hydroxy-
3-phenylsulfanylmethyl[1,4]naphthoquinones was developed
and used to synthesize a series of 36 new phenylsulfanylmethyl
[1,4]naphthoquinones. This three-component reaction explored
the in situ the generation of o-quinone methides (o-QM) via the
Knoevenagel condensation between lawsone and the appropriate
aldehyde followed by nucleophilic addition of a thiol. The reac-
tions were evaluated under both conventional heating and micro-
wave irradiation. The microwave conditions produced several
compounds with higher yields and shorter reaction times. The new
naphthoquinones obtained by this methodology were evaluated for
their in vitro antimalarial activity against P. falciparum (3D7).
Most were active, although none of them showed a biological
profile better than the control drugs. The most active compounds
H
H
4-NO2C6H4
2-Naphthyl
71b
33
e
4-NO2C6H4 eC6H5
eC6H5
eC6H5
eC6H5
2-CH3C6H4
4-CH3SC6H4
4-MeC6H4
e
e
e
4-NO2C6H4 2-Naphthyl
e
H
H
4-ClC6H4
4-CH3C6H4
4-HOC6H4
2-Naphthyl
4-CH3C6H4
eC6H5
57a
49b
e
eC6H5
eC6H5
4-NO2Ph
H
e
e
52a
e
4-NO2C6H4 Propyl
eC6H5
eC6H5
eC6H5
H
4-ClC6H4
Propyl
3-CH3C6H4
4-HOC6H4
e
63a
e
from this study (IC50 < 10
mM) have a p-nitro phenyl group as
72b
e
a substituent at R1.
4-NO2C6H4 4-NO2C6H4
a
Reaction time 24 h.
5. Experimental section
b
c
Reaction time 48 h.
Internal temperature 150 ꢀC, reaction time 20 min. Atovaquone (IC50 value was
Melting points were obtained on a Fisher Johns apparatus and
are reported as uncorrected values. Analytical grade solvents were
3 nM for 3D7) and Chloroquine (IC50 value was 100 nM for 3D7) were used as
positive controls for the present study.

A. Sharma et al. / European Journal of Medicinal Chemistry 59 (2013) 48e53
51
used. Column chromatography was performed on silica gel (Acros
Organics 0.035e0.070 mm, pore diameter of approximately 6 nm).
Infrared spectra were recorded on an ABB FTLA2000-100 spec-
trometer. 1H and 13C NMR spectra were recorded at room temper-
ature using a Varian VNMRS 300 MHz instrument in the solvents
indicated in their monographs with TMS as the internal standard.
5.1.2.3. 2-Hydroxy-3-(((4-fluorophenyl)thio)methyl)naphthalene-
1,4-dione (9). The reaction produced compound 9 in 71% as a light
brown solid. m.p. 105 ꢀC. IR (KBr) nmax (cmꢁ1) 1583 (C]C), 1643
(C]O), 3353 (OH). 1H NMR (CDCl3, 300 MHz)
d (J in Hz): 8.12 (ddd,
1H, J ¼ 7.6, 1.5, 0.5, H-8), 8.08 (ddd, 1H, J ¼ 7.6, 1.5, 0.5 H-5), 7.78
(ddd, 1H, J ¼ 7.6, 7.4, 1.5, H-6), 7.70 (ddd, 1H, J ¼ 7.6, 7.4, 1.5, H-7),
7.47 (ddd, 2H, J ¼ 8.8, 2.3, 2.0, H-ortho-aryl), 6.95 (ddd, 2H, J ¼ 8.8,
2.3, 2.0, H-meta-aryl), 4.04 (s, 2H, CH2) ppm. 13C NMR (CDCl3,
75 MHz): 183.2 (C-4), 181.1 (C-1), 162.4 (C-40-aryl), 153.1 (C-2),135.1
(C-7), 134.4 (C-20 and C-60-aryl), 133.1 (C-6), 132.7 (C-10-aryl), 132.7
(C-8a), 115.7 (C-30 and C-50-aryl), 129.3 (C-4a), 127.0 (C-5), 126.3 (C-
8), 120.1 (C-3), 28.5 (CH2). Anal. Calcd. for C17H11FO3S: C, 64.96; H,
3.53, (Exp. C, 64.97; H, 3.51).
Chemical shifts (d) are given in ppm, and coupling constants (J) are
reported in Hertz. High-resolution mass spectra (electrospray
ionization) were obtained using a QTOF Micro (Waters, Manchester,
UK) mass spectrometer (HRESIMS). The ions in the mass spectra
were described as mass-to-charge ratio (m/z) and the relative
abundance in percentage of the base peak intensity. All the
compounds were drawn using CS ChemDraw Ultra version 10.0.
Compounds 7e42 were prepared using an Anton Paar monowave
300 microwave reactor.
5.1.2.4. 2-Hydroxy-3-(((4-methoxyphenyl)thio)methyl)naphthalene-
1,4-dione (10). The reaction produced the compound 10 in 83% as
a brown solid. m.p. 127 ꢀC. IR (KBr) nmax (cmꢁ1) 1586 (C]C), 1644
5.1. Chemistry
(C]O), 3343 (OH). 1H NMR (CDCl3, 300 MHz)
d (J in Hz): 8.12 (dd,
5.1.1. General procedure for preparing 7e18 under conventional
heating
1H, J ¼ 7.8, 1.0, H-8), 8.07 (dd, 1H, J ¼ 7.8, 1.0, H-5), 7.77 (ddd, 1H,
J ¼ 7.3, 7.3, 1.0, H-6), 7.69 (ddd, 1H, J ¼ 7.3, 7.3, 1.0, H-7), 7.42 (d, 2H,
J ¼ 8.8, H-ortho-aryl), 6.78 (d, 2H, J ¼ 8.8, H-meta-aryl), 3.99 (s, 2H,
CH2), 3.77 (s, 3H, OCH3) ppm. 13C NMR (CDCl3, 75 MHz): 183.2 (C-4),
181.1 (C-1),159.5 (C-40-aryl),153.0 (C-2),135.0 (C-7),135.0 (C-20 and
C-60-aryl), 133.0 (C-6), 132.6 (C-8a), 129.3 (C-4a), 126.9 (C-5), 126.2
(C-8), 126.2 (C-10-aryl), 120.4 (C-3), 114.3 (C-30 and C-50-aryl), 55.2
(OCH3), 29.1 (CH2) ppm. Anal. Calcd. for C18H14O4S: C, 66.24; H, 4.32
(Exp. C, 66.46; H, 4.36).
Compound 5 (500 mg, 2.9 mmol), the appropriate aldehyde
(5.8 mmol, 2 eq.) and the alkyl-or arylthiol (ReSH) (5.8 mmol, 2 eq.)
dissolved in ethanol (15 mL) were added to a 25 mL round-bottom
flask equipped with a reflux condenser. The mixture was refluxed
for 24e48 h (see Table 1), and the solvent was subsequently evap-
orated under reduced pressure. The residual solid was purified by
column chromatography on silica gel and eluted with an increasing
polarity gradient mixture of hexane and ethyl acetate (9/1 to 7/3).
5.1.2.5. 2-Hydroxy-3-(((4-(methylthio)phenyl)thio)methyl)naphtha-
lene-1,4-dione (11). The reaction produced the compound 11 in 68%
as a orange solid. m.p.120 ꢀC. IR (KBr) nmax (cmꢁ1) 1585 (C]C),1641
5.1.2. General procedure for preparing 7e42 under microwave
irradiation
A 10 mL microwave tube was loaded with 5 (500 mg, 2.9 mmol),
the appropriate aldehyde (5.8 mmol, 2 eq.), the alkyl-or arylthiol
(5.8 mmol, 2 eq.) and ethanol (5 mL). The mixture was irradiated for
20 min at 150 ꢀC (internal temperature), and the solvent was then
evaporatedunderreducedpressure.Theresidualsolidwaspurifiedby
column chromatography on silica gel and eluted with an increasing
polarity gradient mixture of hexane and ethyl acetate (9/1 to 7/3).
(C]O), 3338 (OH). 1H NMR (CDCl3, 300 MHz)
d (J in Hz): 8.13 (d, 1H,
J ¼ 7.8, H-8), 8.08 (dd,1H, J ¼ 7.8, H-5), 7.77 (dd,1H, J ¼ 7.3, 7.3, H-6),
7.70 (dd, 1H, J ¼ 7.3, 7.3, H-7), 7.39 (d, 2H, J ¼ 8.3, H-ortho-aryl), 7.13
(d, 2H, J ¼ 8.3, H-meta-aryl), 4.06 (s, 2H, CH2), 2.45 (s, 3H, CH3) ppm.
13C NMR (CDCl3, 75 MHz): 183.3 (C-4), 181.0 (C-1), 153.1 (C-2), 137.8
(C-40-aryl), 135.1 (C-7), 133.1 (C-6), 132.6 (C-8a), 132.2 (C-20 and C-
60-aryl), 131.8 (C-10-aryl), 129.3 (C-4a), 127.0 (C-30 and C-50-aryl),
126.7 (C-5), 126.2 (C-8), 120.1 (C-3), 27.9 (CH2), 15.3 (CH3) ppm.
Anal. Calcd. for C18H14O3S2: C, 63.13; H, 4.12 (Exp. C, 63.05; H, 4.07).
5.1.2.1. 2-Hydroxy-3-((phenylthio)methyl)naphthalene-1,4-dione (7).
The reaction produced compound 7 in 85% as a orange solid. m.p.
125 ꢀC. IR (KBr) nmax (cmꢁ1) 1588 (C]C),1639 (C]O), 3330 (OH). 1H
5.1.2.6. 2-Hydroxy-3-((p-tolylthio)methyl)naphthalene-1,4-dione
(12). The reaction produced the compound 12 in 84% as a orange
solid. m.p. 122 ꢀC. IR (KBr) nmax (cmꢁ1) 1593 (C]C), 1637 (C]O),
NMR (CDCl3, 300 MHz)
d
(J in Hz): 8.14 (d, 1H, J ¼ 7.8, H-8), 8.08 (m,
1H, J ¼ 7.8, H-5), 7.77 (ddd, 1H, J ¼ 7.8, 7.8, 1.5, H-6), 7.70 (ddd, 1H,
J ¼ 7.8, 7.8, 1.5, H-7), 7.48e7.47 (m, 2H, H-ortho-aryl), 7.27e7.24 (m,
2H, H-meta-aryl), 7.22e7.19 (m, 1H, H-para-aryl), 4.11 (s, 2H, CH2)
ppm. 13C NMR (CDCl3, 75 MHz): 183.3 (C-4), 181.1 (C-1), 153.1 (C-2),
135.6 (C-10-aryl), 135.1 (C-7), 133.1 (C-6), 132.6 (C-8a), 131.1 (C-20
and C-60-aryl), 129.3 (C-4a), 128.7 (C-30 and C-50-aryl), 126.9 (C-5),
126.8 (C-40-aryl), 126.2 (C-8), 120.1 (C-3), 27.3 (CH2) ppm. Anal.
Calcd. for C17H12O3S: C, 68.90; H, 4.08 (Exp. C, 68.94; H, 4.24).
3309 (OH). 1H NMR (CDCl3, 300 MHz)
d (J in Hz): 8.13 (dd, 1H,
J ¼ 7.8, 1.0, H-8), 8.07 (dd, 1H, J ¼ 7.8, 1.0, H-5), 7.77 (ddd, 1H, J ¼ 7.3,
7.3, 1.0, H-6), 7.70 (ddd, 1H, J ¼ 7.3, 7.3, 1.0, H-7), 7.37 (d, 2H, J ¼ 8.3,
H-ortho-aryl), 7.06 (d, 2H, J ¼ 8.3, H-meta-aryl), 4.06 (s, 2H, CH2),
2.30 (s, 3H, CH3) ppm. 13C NMR (CDCl3, 75 MHz): 183.3 (C-4), 181.1
(C-1), 153.0 (C-2), 137.1 (C-10-aryl), 135.1 (C-7), 133.1 (C-6), 132.7 (C-
8a),131.9 (C-20 and C-60-aryl), 131.8 (C-40-aryl), 129.5 (C-30 and C-50-
aryl), 129.3 (C-4a), 127.0 (C-5), 126.2 (C-8), 120.3 (C-3), 28.0 (CH2),
21.1 (CH3) ppm. Anal. Calcd. for C18H14O3S: C, 69.66; H, 4.55 (Exp. C,
69.70; H, 4.48).
5.1.2.2. 2-Hydroxy-3-(((4-chlorophenyl)thio)methyl)naphthalene-
1,4-dione (8). The reaction produced compound 8 in 78% as
a orange solid. m.p. 177 ꢀC. IR (KBr) nmax (cmꢁ1) 1589 (C]C), 1637
(C]O), 3265 (OH). 1H NMR (DMSO-d6, 300 MHz)
d
(J in Hz): 8.13
5.1.2.7. 2-Hydroxy-3-(((4-hydroxyphenyl)thio)methyl)naphthalene-
1,4-dione (13). The reaction produced the compound 13 in 78% as
a dark red solid. m.p. 177 ꢀC. IR (KBr) nmax (cmꢁ1) 1579 (C]C), 1634
(dd,1H, J ¼ 7.6,1.3, H-8), 8.08 (dd,1H, J ¼ 7.6,1.3, H-5), 7.78 (ddd,1H,
J ¼ 7.6, 7.6, 1.5, H-6), 7.70 (ddd, 1H, J ¼ 7.6, 7.6, 1.5, H-7), 7.40 (ddd,
2H, J ¼ 8.6, 2.6, 2.0, H-ortho-aryl), 7.22 (ddd, 2H, J ¼ 8.6, 2.6, 2.0, H-
meta-aryl), 4.08 (s, 2H, CH2) ppm. 13C NMR (DMSO-d6, 75 MHz):
183.0 (C-4), 180.6 (C-1), 156.2 (C-2), 135.4 (C-10-aryl), 134.6 (C-7),
133.2 (C-6), 131.6 (C-8a), 131.0 (C-20 and C-60-aryl), 130.9 (C-40-aryl),
129.9 (C-4a), 128.7 (C-30 and C-50-aryl), 125.7 (C-5), 125.7 (C-8),
119.2 (C-3), 26.4 (CH2) ppm. Anal. Calcd. for C17H11ClO3S: C, 61.73;
H, 3.35 (Exp. C, 61.78; H, 3.33).
(C]O), 3320 (OH). 1H NMR (DMSO-D6, 300 MHz)
d (J in Hz): 7.97
(dd, 1H, J ¼ 7.5, 1.1, H-8), 7.94 (dd, 1H, J ¼ 7.5, 1.1, H-5), 7.83 (ddd, 1H,
J ¼ 7.5, 7.5, 1.7, H-6), 7.78 (ddd, 1H, J ¼ 7.5, 7.5, 1.4, H-7), 7.22 (ddd,
2H, J ¼ 8.8, 3.0, 2.2, H-ortho-aryl), 6,66 (ddd, 2H, J ¼ 8.8, 3.0, 2.2,
H-meta-aryl), 3.86 (s, 2H, CH2) ppm. 13C NMR (DMSO-d6, 75 MHz):
183.2 (C-4), 180.9 (C-1), 157.2 (C-40-aryl), 155.8 (C-2), 134.8 (C-7),
134.2 (C-20 and C-60-aryl), 133.4 (C-6), 131.8 (C-10-aryl), 131.8 (C-8a),

52
A. Sharma et al. / European Journal of Medicinal Chemistry 59 (2013) 48e53
125.8 (C-30 and C-50-aryl), 120.3 (C-4a), 120.3 (C-3), 116.4 (C-5),
116.0 (C-8), 28.7 (CH2) ppm. m.p. 144 ꢀC, Anal. Calcd. for C17H12O4S:
C, 65.37; H, 3.87 (Exp. C, 64.82; H, 3.80).
J ¼ 7.8, 1.0, H-8), 8.09 (dd, 1H, J ¼ 7.8, 1.0, H-5), 7.77 (ddd, 1H, J ¼ 7.4,
7.4,1.0, H-6), 7.70 (dd,1H, J ¼ 7.4, 7.4,1.0, H-7), 3.70 (s, 2H, CH2), 2.58
(t, 2H, J ¼ 7.4, CH2CH2CH3), 1.66 (st, 2H, J ¼ 7.4, CH2CH2CH3), 0.98 (t,
3H, J ¼ 7.4, CH2CH2CH3) ppm. 13C NMR (CDCl3, 75 MHz): 183.7 (C-
4), 181.3 (C-1), 152.9 (C-2), 135.0 (C-7), 133.1 (C-6), 132.7 (C-8a),
129.3 (C-4a),126.9 (C-5), 126.2 (C-8), 121.8 (C-3), 34.7 (CH2CH2CH3),
23.4 (CH2CH2CH3), 22.8 (CH2), 13.5 (CH2CH2CH3) ppm. Anal. Calcd.
for C14H14O3S : C, 64.10; H, 5.38 (Exp. C, 64.07; H, 5.39).
5.1.2.8. 2-Hydroxy-3-(((4-nitrophenyl)thio)methyl)naphthalene-1,4-
dione (14). The reaction produced the compound 14 in 83% as a light
brown solid. m.p.189 ꢀC. IR (KBr) nmax (cmꢁ1) 1503 (N]O),1578 (C]
C),1643 (C]O), 3307 (OH).1H NMR (DMSO-D6, 300 MHz)
d (J in Hz):
8.10 (ddd, 2H, J ¼ 9.2, 2.6, 2.2, H-meta-aryl), 7.97 (ddd,1H, J ¼ 7.6,1.5,
0.4, H-8), 7.93 (ddd,1H, J ¼ 7.6,1.5, 0.4, H-5), 7.80 (ddd,1H, J ¼ 7.5, 7.5,
1.5, H-6), 7.70 (ddd, 2H, J ¼ 7.5, 7.5,1.5, H-7), 7.62 (ddd, 2H, J ¼ 9.2, 2.6,
2.2, H-ortho-aryl), 4.19 (s, 2H, CH2) ppm. 13C NMR (DMSO-d6,
75 MHz): 181.5 (C-4),179.8 (C-1),149.1 (C-2),144.0 (C-40-aryl and C-
10-aryl), 133.0 (C-8a), 134.5 (C-7), 132.2 (C-6), 130.2 (C-4a), 126.3 (C-
20 and C-60-aryl), 125.6(C-5), 125.5 (C-8), 123.6 (C-30 and C-50-aryl),
115.6 (C-3), 26.6 (CH2) ppm. Anal. Calcd. for C17H11NO5S: C, 59.82; H,
3.25; N, 4.10, (Exp. C, 59.92; H, 3.35; N, 4.22).
Acknowledgments
Fellowships granted to AS; PG, V.F.F. CRSG and I.O.S. by CNPq
(Brazil) and D.R.R. CAPES-FAPERJ are gratefully acknowledged. This
work was partially supported by CNPq grant 471588/2009-1,
FAPERJ-PRONEX grant number 110.574/2010. Pronex Malaria
CNPqeMS-FAPESP and INBQmed to CRSG.
Appendix A. Supplementary data
5.1.2.9. 2-Hydroxy-3-((o-tolylthio)methyl)naphthalene-1,4-dione
(15). The reaction produced the compound 15 in 77% as a brown
solid. m.p. 97e99 ꢀC. IR (KBr) nmax (cmꢁ1) 1583 (C]C), 1643 (C]O),
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2012.10.052.
3361 (OH). 1H NMR (CDCl3, 300 MHz)
d (J in Hz): 8.13 (ddd, 1H,
J ¼ 7.6, 1.5, 0.6, H-8), 8.08 (ddd, 1H, J ¼ 7.6, 1.5, 0.5, H-5), 7.77 (ddd,
1H, J ¼ 7.6, 7.6, 1.5, H-6), 7.70 (ddd, 1H, J ¼ 7.4, 7.4, 1.5, H-7), 7.48e
7.35 (m, 2H, H-30 and H-40-aryl), 7.18e7.07 (m, 2H, H-50 and H-60-
aryl), 4.06 (s, 2H, CH2), 2.43 (s, 3H, CH3) ppm. 13C NMR (CDCl3,
75 MHz): 183.2 (C-4),181.0 (C-1),153.2 (C-2),139.3 (C-10-aryl),135.1
(C-7), 134.7 (C-20-aryl), 133.0 (C-6), 132.6 (C-8a), 131.4 (C-30-aryl),
130.0 (C-60-aryl), 129.2 (C-4a), 127.0 (C-5), 126.9 (C-50-aryl), 126.2
(C-8),126.2 (C-40-aryl),119.8 (C-3), 26.4 (CH2), 20.5 (CH3) ppm. Anal.
Calcd. for C18H14O3S: C, 69.66; H, 4.55 (Exp. C, 69.62; H, 4.58).
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A. Sharma et al. / European Journal of Medicinal Chemistry 59 (2013) 48e53
53
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a-
b