Synthesis, antitumor activity and docking of 2,3-(substituted)-1,4-naphthoquinone derivatives containing nitrogen, oxygen and sulfur

Article abstract of DOI:10.5935/0103-5053.20150157

Eleven 2,3-(substituted)-1,4-naphthoquinone derivatives were synthesized in yields ranging from 52-89percent. These derivatives were evaluated for their cytotoxic effects on human lungs (H460), triple-negative breast (MDA-MB-231) and ovarian (A2780) cancer cell lines. Compounds 5f and 8 showed IC₅₀ values of 3.048 × 10^-5 mol L^-1 and 4.24 × 10^-6 mol L^-1 for H460; 5c and 8 showed IC₅₀ values of 2.16 × 10^-5 mol L^-1 and 1.60 × 10^-5 mol L^-1 for MDA-MB-231, and 5g and 8 showed IC₅₀ values of 2.68 × 10^-6 mol L^-1 and 3.89 × 10^-6 mol L^-1 for A2780. Additionally, we conducted a docking study with the four most active compounds and the therapeutic targets PI3K and topoisomerase II showing the pharmacophoric conformation of these compounds.

Full text of DOI:10.5935/0103-5053.20150157

http://dx.doi.org/10.5935/0103-5053.20150157
J. Braz. Chem. Soc., Vol. 26, No. 9, 1804-1816, 2015.
Printed in Brazil - ©2015 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Article
A
Synthesis, Antitumor Activity and Docking of 2,3-(Substituted)-1,4-Naphthoquinone
Derivatives Containing Nitrogen, Oxygen and Sulfur
Maicon Delarmelina,a Renata D. Daltoé,c Murilo F. Cerri,c Klesia P. Madeira,c
Leticia B. A. Rangel,c Valdemar Lacerda Júnior,a Wanderson Romão,b Alex G. Tarantod
and Sandro J. Greco*,a
aLaboratório de Síntese Orgânica & Medicinal and bLaboratório de Petroleômica e Química Forense,
Departamento de Química, Universidade Federal do Espírito Santo, 29075-910 Vitória-ES, Brazil
cLaboratório de Biologia Celular do Câncer Humano, Departamento de Ciências Farmacêuticas,
Universidade Federal do Espírito Santo, 29040-090 Vitória-ES, Brazil
dLaboratório de Modelagem Molecular, Universidade Federal de São João Del-Rei,
35501-296 Divinópolis-MG, Brazil
Eleven 2,3-(substituted)-1,4-naphthoquinone derivatives were synthesized in yields ranging
from 52-89%. These derivatives were evaluated for their cytotoxic effects on human lungs (H460),
triple-negative breast (MDA-MB-231) and ovarian (A2780) cancer cell lines. Compounds 5f and 8
showed IC50 values of 3.048 × 10-5 mol L-1 and 4.24 × 10-6 mol L-1 for H460; 5c and 8 showed IC50
values of 2.16 × 10-5 mol L-1 and 1.60 × 10-5 mol L-1 for MDA-MB-231, and 5g and 8 showed IC50
values of 2.68 × 10-6 mol L-1 and 3.89 × 10-6 mol L-1 forA2780.Additionally, we conducted a docking
study with the four most active compounds and the therapeutic targets PI3K and topoisomerase II
showing the pharmacophoric conformation of these compounds.
Keywords: 1,4-naphthoquinone, antineoplastic activity, topoisomerase, PI3K, nucleophilic
substitution
Introduction
These data show that quinone derivatives can have multiple
antineoplastic mechanisms, leading our group to postulate
that some of them might, as well as, inhibit the activity of
Notwithstanding, the progress observed in cancer
treatments in the past decades, epidemiology data, clearly
point to urgent new therapeutic approaches to control the
disease. Improvements in the quality of life and overall
survival rates of cancer patients strongly rely on the
development of novel compounds with promising anticancer
activity, such as natural or synthetic substances containing
the quinone nuclei. The antineoplastic properties and the
mechanism of action of quinone derivatives (Figure 1) have
been widely studied and it is known that quinone derivatives
can inhibit the activity of topoisomerase and telomerase
through DNA alkylation or intercalation, inhibiting the
heat shock protein HSP90.1 In particular, the anticancer
properties of quinone derivatives seem to be mainly due
to the induction of oxidative stress caused by reactive
oxygen species, such as superoxide, generated from the
reduction of the quinone nucleus by cellular reductases.1
*e-mail: sandrogreco.ufes@gmail.com
Figure 1. Quinones with antineoplastic activity.

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Delarmelina et al.
1805
the phosphatidylinositol 3-kinase (PI3K). This suggestion
may open an avenue to use of quinone derivatives as
target therapies against PI3K-related pathways, which are
frequently regulated in several human cancers, promoting
cellular proliferation, differentiation and drug resistant
phenotype, among other carcinogenic properties.2
It has been established that many of the biological effects
of quinone derivatives depend on their 1,4-naphthoquinone
pharmacophore group. Such is the case for antitumor,
antiproliferative, antibacterial, anti-inflammatory,
antimalarial, antiviral, antifungal and antileishmanial
compounds.3 Moreover, the incorporation of nitrogen
and sulfur atoms on C2 and C3 of the 1,4-naphthoquinone
core has led to the formation of compounds with diverse
biological activities, including anticancer activity.3
Thus, considering the importance of the substitution of
C2 and C3 of the naphthoquinone core for various biological
activities, the literature has provided numerous examples that
2,3-dichloro-1,4-naphthoquinone reacts with nucleophiles to
form monosubstituted and disubstituted products and, more
commonly, a mixture of both, depending on the softness of
the nucleophile used.4-10 However, reactions carried out with
electron donor groups such as amines replace just one of the
chlorine atoms due to the increasing of the electron density
in the naphthoquinone core.11 The second replacement
happens when the withdrawing electrons effect is imposed
on the naphthoquinone ring or a catalyst, normally containing
palladium, is employed in the reaction.2
Melting points were determined using Fisatom
430D equipment. Infrared (IR) spectra were recorded
on Bomem FTLA2000-102-ABB spectrometer. The H
1
nuclear magnetic resonance (NMR) and 13C NMR spectra
were obtained on a Vary VNMRS spectrometer model
400 (400 MHz) with tetramethylsilane (TMS) as internal
standard. NMR analyses of compounds 5a-g, 6a-c and 8
were performed in chloroform deuterated (99.8%) with
1% (v/v) of TMS and stabilized with silver foil (Cambridge
Isotope Laboratories, Inc.).
Mass spectra were recorded on ultra-high resolution and
accuracy mass spectrometer (model 9.4 T Solarix, Bruker
Daltonics), operated in both ionization modes: positive and
negative electrospray ionization with Fourier transform
ion clyclotron resonance mass spectrometry, ESI(+) and
ESI(−)-FT-ICR MS spectra were acquired with resolving
power of m/Dm50% ca. 500000, in which Dm50% is the
full peak width at half-maximum peak height of m/z 400
and a mass accuracy < 1 ppm. It provides an unambiguous
molecular formula assignment for singly charged molecular
ions such as [M − H]+ or [M + H]− and DBE (double bound
equivalents) values.
Compounds 5b and 6b were partially soluble in
most common deuterated solvents used in NMR and
accurate 13C NMR spectra could not be obtained for these
compounds.
Synthesis of compounds 5a-g
Herein, we present the 2,3-(substituted)-1,4-
naphthoquinone derivatives containing nitrogen, oxygen
and sulfur atoms, obtained from 2,3-dichloro-1,4-
naphthoquinone 1, 2-methoxy-1,4-naphthoquinone 2 and
1,4-naphthoquinone 3 (Figure 2) and the respective in vitro
biological assays for their potential antiproliferative activity.
Importantly, the active antineoplastic substances seem to act
by multiple cellular pathways, which is an effective strategy
to avoid the occurrence of the chemoresistant phenotype
frequently observed in tumor cells.
2-Chloro-3-[(pyridin-2-ylmethyl)amino]naphthoquinone (5a)
A suspension of 2,3-dichloro-1,4-naphthoquinone 1
(0.2270 g, 1.0 mmol), methanol (10 mL), picolylamine 4a
(155 µL, 1.5 mmol) and triethylamine (153 µL, 1.1 mmol)
was stirred for 2 h at room temperature. The product was
filtered, washed with cold methanol to obtain 5a as an
orange colored solid (0.2624 g, 88%); melting point (m.p.):
156-157 °C (literature: 126-127 °C);12 1H NMR (400 MHz,
CDCl3) d 8.65 (d, 1H, J 4.9 Hz, Py-H), 8.15 (dd, 1H,
J 7.7 Hz, 1.3, H-8), 8.06 (dd, 1H, J 7.6 Hz, 1.4, H-5), 7.82 (s,
1H, N-H), 7.75-7.69 (m, 2H, H-6,7), 7.63 (td, 1H, J 7.6 Hz,
1.3, Py-H), 7.29 (d, 1H, J 7.9 Hz, Py-H), 7.30-7.22 (m, 1H,
Py-H), 5.19 (d, 2H, J 5.0 Hz, CH2); 13C NMR (101 MHz,
CDCl3) d 180.57, 176.78, 155.10, 149.04, 144.39, 136.87,
134.77, 132.65, 132.40, 129.96, 126.77, 126.71, 122.66,
121.72, 48.60; EI-FT-ICRMS (M+) calcd. for C16H11ClN2O2:
299.0587; found: 299.0583 (DBE = 12).
Figure 2. Substrates for synthesis of the desired compounds.
Experimental
General information
2-[(3-Aminopropyl)amino]-3-chloronaphthoquinone (5b)
A suspension of 2,3-dichloro-1,4-naphthoquinone
1 (0.2270 g, 1.0 mmol), methanol (10 mL),
1,3-diaminopropane 4b (167 µL, 2 mmol) was stirred for
All solvents and reagents were commercially purchased
and were used without any treatment.

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Synthesis, Antitumor Activity and Docking of 2,3-(Substituted)-1,4-Naphthoquinone Derivatives
J. Braz. Chem. Soc.
7 h at room temperature. The product was filtered, washed
with cold methanol to give 5b as a reddish orange solid
(0.2356 g, 89%); m.p.: 215 °C (with decomposition);
1H NMR (400 MHz, CDCl3) d 8.14 (dd, 1H, J 7.6 Hz,
1.0, H-8), 8.02 (dd, 1H, J 7.7 Hz, 1.0, H-5), 7.73 (td, 1H,
J 7.6 Hz, 1.3, H-6 ), 7.63 (td, 1H, J 7.5 Hz, 1.2, H-7), 6.13
(bs, 1H, N-H), 4.00 (dd, 2H, J 13.5 Hz, 6.8, H2N-CH2), 3.72
(dd, 1H, J 14.0 Hz, 7.0, HN-CH2), 2.91 (t, 1H, J 6.4 Hz,
HN-CH2), 2.12 (dt, 1H, J 13.9 Hz, 7.1, CH2), 1.83 (dt,
1H, J 12.9 Hz, 6.6, CH2); EI-FT-ICRMS (M+) calcd. for
C13H13ClN2O2: 265.0744; found: 265.0739 (DBE = 8).
1H NMR (400 MHz, CDCl3) d 8.07 (dd, 2H, J 5.7 Hz, 3.3,
H-5,8), 7.69 (dd, 2H, J 5.7 Hz, 3.3, H-6,7), 3.30 (s, 4H,
S-CH2); 13C NMR (101 MHz, CDCl3) d 178.60, 140.74,
133.74, 131.56, 126.90, 26.99; EI-FT-ICRMS (M+) calcd.
for C12H8S2O2: 249.0044; found: 249.0037 (DBE = 8);
[M + Na]+: 270.9863; found: 270.9856 (DBE = 8).
2-Chloro-3-[(mercaptomethyl)thio]naphthoquinone (5f)
A suspension of 2,3-dichloro-1,4-naphthoquinone 1
(0.2270g, 1.0mmol), methanol(10mL), 1,2-ethanedithiol4e
(210 µL, 2.5 mmol) was stirred for 1 h at room temperature.
Then, water was added (15 mL) slowly and stirred for
12 h. The product was filtered, washed with cold water
to give 5f as a purple solid (0.2164 g, 66%); m.p.: 125 °C
(with decomposition; literature: 196 °C);5 1H NMR
(400 MHz, CDCl3) d 8.22-8.17 (m, 2H, H-5,8), 8.15-8.10
(m, 2H, H-6,7), 3.59-3.42 (m, 4H, S-CH2), 1.62 (s, 1H,
SH); 13C NMR (101 MHz, CDCl3) d 186.55, 186.44,
135.08, 134.81, 133.55, 131.17, 128.44, 128.42, 75.35,
42.40, 39.84; EI-FT-ICRMS (M+) calcd. for C12H9ClS2O2:
284.9811; found: 284.9804 (DBE = 7).
2-Chloro-3-((2-hydroxyethyl)amino)naphthalene-1,4-dione
(5c)
A suspension of 2,3-dichloro-1,4-naphthoquinone 1
(0.2270 g, 1.0 mmol), methanol (10 mL), 2-aminoethanol 4c
(121 µL, 2.0 mmol) was stirred for 24 h at room temperature.
The product was filtered, washed with cold water to give
5c as an orange solid (0.2240 g, 89%); m.p.: 139-140 °C
(literature: 147 °C);13 1H NMR (400 MHz, CDCl3) d 8.14
(dd, 1H, J 7.7 Hz, 0.9, H-8), 8.03 (dd, 1H, J 7.7 Hz, 1.0,
H-5), 7.73 (td, 1H, J 7.6 Hz, 1.3, H-7), 7.63 (td, 1H, J 7.6 Hz,
1.3, H-6), 6.42 (bs, 1H, N-H), 4.06 (dt, 2H, J 10.7 Hz, 5.3,
CH2-OH ), 3.93 (dd, 2H, J 10.1 Hz, 5.0, CH2-NH), 1.81
(bs, 1H, J 4.7 Hz, CH2-OH); 13C NMR (101 MHz, CDCl3)
d 180.42, 176.86, 144.42, 134.92, 132.58, 132.51, 129.81,
126.84, 126.82, 61.97, 46.57; EI-FT-ICRMS (M+) calcd.
for C12H10ClNO3: 252.0427; found: 252.0419 (DBE = 8);
[M + Na]+: 274.0247; found: 274.0238 (DBE = 8).
2,3-Bis[(2-hydroxyethyl)thio]naphthoquinone (5g)
A suspension of 2,3-dichloro-1,4-naphthoquinone 1
(0.2270 g, 1.0 mmol), acetone (5 mL), 2-mercaptoethanol 4f
(210 µL, 2.0 mmol) was stirred for 1 h at room temperature.
Then, water was added (10 mL) slowly and stirred for 24 h.
The product was filtered, washed with cold water to obtain
5g as an orange solid (0.1614 g, 52%); m.p.: 111-113 °C
(literature: 117-118 °C);16 1H NMR (400 MHz, CDCl3)
d 8.07 (dd, 2H, J 5.7 Hz, 3.3, H-5,8), 7.72 (dd, 2H, J 5.7 Hz,
3.3, H-6,7), 3.79 (q, 4H, J 4.9 Hz, CH2-OH), 3.47-3.37 (m,
4H, S-CH2), 2.71 (s, 2H, CH2-OH); 13C NMR (101 MHz,
CDCl3) d 178.88, 148.99, 133.81, 132.85, 127.18, 61.94,
38.20; EI-FT-ICRMS (M+) calcd. for C14H14S2O4: 309.0255;
found: 309.0260 (DBE = 7).
2-Chloro-3-methoxynaphthalene-1,4-dione (5d)
A suspension of 2,3-dichloro-1,4-naphthoquinone 1
(0.2270 g, 1.0 mmol), methanol (10 mL) and triethylamine
(153 µL, 1.1 mmol) was stirred for 3 h at room temperature.
The product was filtered, washed with cold water to give
5d as a yellow solid (0.1794 g, 81%); m.p.: 144-147 °C
(literature: 140 °C);14 1H NMR (400 MHz, CDCl3)
d 8.17-8.12 (m, 1H, H-8), 8.11-8.07 (m, 1H, H-5), 7.79-7.72
(m, 2H, H-6,7), 4.32 (s, 3H, OCH3); 13C NMR (101 MHz,
CDCl3) d 179.68, 178.59, 156.76, 134.35, 133.92, 131.03,
130.78, 128.29, 126.97, 126.86, 61.87; EI-FT-ICRMS
(M+) calcd. for C11H7ClO3; [M + Na]+: 244.9981; found:
244.9972 (DBE = 8).
Synthesis of compounds 6a-c
2-[(Pyridin-2-ylmethyl)amino]naphthoquinone (6a)
A suspension of 2-methoxy-1,4-naphthoquinone 2
(0.0941 g, 0.5 mmol), methanol (10 mL), picolylamine 4a
(180 µL, 2.0 mmol) and triethylamine (84 µL, 0.6 mmol)
was stirred for 24 h at room temperature. Then, water was
slowly added (20 mL) and stirred for 24 h. The product
was filtered, washed with cold methanol to obtain 6a as an
orange solid (0.1506 g, 58%); m.p.: 146-148 °C (literature:
153-155 °C);17 1H NMR (400 MHz, CDCl3) d 8.63 (dd, 1H,
J 4.9 Hz, 0.7, Py-H), 8.12-8.07 (m, 2H, H-5,8), 7.78-7.66 (m,
2H, H-6,7), 7.63 (td, 1H, J 7.5 Hz, 1.2, Py-H), 7.29 (d, 1H,
J 8.7 Hz, Py-H), 7.29-7.22 (m, 1H, Py-H), 7.16 (s, 1H, NH),
2,3-Dihydronaphtho[2,3-b][1,4]dithiine-5,10-dione (5e)
A suspension of 2,3-dichloro-1,4-naphthoquinone 1
(0.2270 g, 1.0 mmol), methanol (10 mL), 1,2-ethanedithiol 5e
(149 µL, 2.0 mmol) was stirred for 12 h at 50 °C. The solution
was allowed to cool and the obtained product was filtered
and washed with cold methanol to give 5e as a dark red solid
(0.1522 g, 62%); m.p.: > 230 °C (literature: > 250 °C);15

Vol. 26, No. 9, 2015
Delarmelina et al.
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5.78 (s, 1H, H-4), 4.49 (d, 2H, J 5.2 Hz, NH-CH2); 13C NMR
(101 MHz, CDCl3) d183.08, 181.70, 154.51, 149.49, 147.76,
136.91, 134.67, 133.57, 132.04, 130.60, 126.31, 126.17,
122.81, 121.67, 101.74, 47.03; EI-FT-ICRMS (M+) calcd.
for C16H12N2O2: 265.0977; found: 265.0971 (DBE = 12);
[2M + H]+: 529.1876; found: 529.1869 (DBE = 24);
[M + Na]+: 287.0796; found: 287.0790 (DBE = 12) and
[2M + Na]+: 551.1695; found: 551.1687 (DBE = 24).
from hot water to obtain 7 as a yellow solid (0.7937g, 73%);
m.p.: 179-180 °C (literature: 183 °C);19 1H NMR (400 MHz,
CDCl3) d 8.19-8.04 (m, 2H, H-5,8), 7.81-7.68 (m, 2H,
H-6,7), 6.19 (s, 1H, H-4), 3.92 (s, 3H, OCH3).
Synthesis of compound 8
2-((2-Hydroxyethyl)thio)naphthalene-1,4-dione (8)
A solution of 1,4-naphthoquinone 3 (0.0941 g,
0.5 mmol), acetone (2.5 mL) and 2-mercaptoethanol 4f
(70 µL, 1.0 mmol) was stirred for 0.5 h at room temperature.
The crude mixture was then purified by chromatography
(15-25% ethyl acetate:hexane) to obtain product 8 as a
yellow solid (0.0449 g, 77%); m.p.: 124-127 °C; 1H NMR
(400 MHz, CDCl3) d 8.14-8.04 (m, 2H, H-5, 8), 7.79-7.66
(m, 2H, H-6,7), 6.71 (s, 1H, H-4), 3.98 (dd, 2H, J 10.7 Hz,
5.4, CH2-OH), 3.10 (t, 2H, J 6.1 Hz, S-CH2), 2.06 (s,
1H, CH2-OH); 13C NMR (101 MHz, CDCl3) d 182.04,
181.59, 154.21, 134.42, 133.40, 132.09, 131.84, 127.44,
126.92, 126.59, 59.73, 33.26; ESI(+)FT-ICRMS calcd. for
C12H10O3S [M + Na]+: 257.0248; found: 257.0244; [2M +
Na]+: 491.0599; found 491.0596.
2-[(3-Aminopropyl)amino]naphthoquinone (6b)
A suspension of 2-methoxy-1,4-naphthoquinone 2
(0.0941 g, 0.5 mmol), methanol (10 mL), 1,3-diamino-
propane 4b (83 µL, 1 mmol) and triethylamine (84 µL,
0.6 mmol) was stirred for 24 h at room temperature. Then,
water was slowly added (20 mL) and stirred for 7h. The
product was filtered, washed with cold methanol to obtain
6b as an orange solid (0.1335 g, 58%); m.p.: 124-126 °C;
1H NMR (400 MHz, CDCl3) d 8.10 (dd, 1H, J 7.7 Hz,
1.2, H-8), 8.05 (dd, 1H, J 7.7 Hz, 1.2, H-5), 7.74 (td, 1H,
J 7.6 Hz, 1.4, H-6), 7.63 (td, 1H, J 7.6 Hz, 1.3, H-7), 5.91
(s, 1H, NH), 5.76 (s, 1H, H-4), 3.35 (dd, 2H, J 6.6 Hz,
CH2-NH2), 2.11 (dt, 2H, J 6.9 Hz, NH-CH2), 1.25 (s, 2H,
CH2); EI-FT-ICRMS (M+) calcd. for C13H15N2O2: 231.1133;
found: 231.1118 (DBE = 8).
In vitro antineoplastic activity evaluation
2-((2-Hydroxyethyl)amino)naphthalene-1,4-dione (6c)
A suspension of 2-methoxy-1,4-naphthoquinone 2
(0.1881 g, 1.0 mmol), methanol (10 mL), 2-aminoethanol4c
(121 µL, 2.0 mmol) was stirred for 32 h at room
temperature. The solution was cooled and the product
was filtered, washed with cold methanol to obtain 6c as an
orange solid (0.1642 g, 76%); m.p.: 156-157 °C (literature:
146-147 °C);18 1H NMR (400 MHz, CDCl3) d 8.08 (ddd,
2H, J 18.6 Hz, 7.7, 1.0, H-5,8), 7.73 (td, 1H, J 7.6 Hz, 1.3,
H-6), 7.62 (td, 1H, J 7.6 Hz, 1.3, H-7), 6.22 (s, 1H, NH),
5.77 (s, 1H, H-4), 3.93 (dd, 2H, J 10.2 Hz, 5.0, CH2-OH),
3.37 (dd, 1H, J 10.8 Hz, 5.5, NH-CH2), 1.79 (t, 1H,
J 5.1 Hz, CH2-OH); 13C NMR (101 MHz, CDCl3) d 183.10,
181.73, 148.09, 134.77, 132.06, 126.33, 126.19, 101.16,
77.33, 77.21, 77.01, 76.69, 60.05, 44.39; EI-FT-ICRMS
(M+) calcd. for C12H11NO3; [M + Na]+: 240.0637; found:
240.0628; [2M + Na]+: 457.1376; found: 457.1364.
The in vitro cytotoxicity activity of the synthesized
compounds was carried out against three human cancer
cell lines of solid tumors namely H460 (non-small cell lung
cancer/large cell lung cancer), A2780 (epithelial ovarian
carcinoma) and MDA MB-231(triple negative breast cancer).
Cells were cultured in Roswell Park Memorial Institute
(RPMI) medium supplemented with 10% of fetal bovine
serum (FBS) and antibiotics, at 37 ºC in 5% of CO2. For
dimethyl thiazolyl diphenyl tetrazolium bromide (MTT)
assay,20 the cells were plated in 96-well culture dishes at
7.5 × 104 cell/well, and allowed to recover for 24 h, then,
treated for 24 h in a dose-dependent manner with each
tested compound at concentrations of 10-4, 10-5, 10-6, 10-7 and
10-8 mol L-1. After, was used MTT (5 mg mL-1) to evaluate
the cellular metabolic viability. The absorbance at 630 nm
was measured on a spectrophotometer (MR-96A, Bioclin).
Control treatments were performed with chemotherapy
standard. The results are representatives of three
independent experiments, mean and standard-deviation
of the absorbances were used to calculate cell metabolic
viability, and the IC50 using PrismaGraphPad version 5.1.
Synthesis of compound 7
2-Methoxynaphthalene-1,4-dione (7)
2-Hidroxy-1,4-naphthoquinone (1.000 g, 5.7 mmol)
was dissolved in methanol (50 mL) containing concentrated
chloridric acid (0.8 mL). The reaction mixture was
maintained under reflux for 4 h. Then, the solution was
allowed to cool and the product was filtered and recrystallized
Docking
The docking studies were performed in AutoDock
Vina software21 with the ligand and the enzymes PI3Kγ

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Synthesis, Antitumor Activity and Docking of 2,3-(Substituted)-1,4-Naphthoquinone Derivatives
J. Braz. Chem. Soc.
(PDB ID: 1E7U) and topoisomerase II (PDB ID: 1QZR).
The 3D structures of the compounds were obtained after
semi-empirical PM6 optimization.22 Docking was performed
covering an 18 × 10 ×12Å box size, centered on ligand.After
validation of the method with the crystallographic ligands,
interaction studies with new compounds were performed.
For the synthesis of compound 5a (entry 1, Table 1),
triethylamine was used with the nucleophile and methanol
as the solvent to facilitate the precipitation of the
product, which was obtained with high purity and in an
excellent yield.12 The synthesis of 5b (entry 2, Table 1)
followed a similar methodology, except for the absence
of triethylamine. Moreover, to the best of our knowledge,
the preparation of compound 5b has not been reported
before.
Results and Discussion
Chemistry
In turn, compounds 5c (entry 3, Table 1) was
synthesized under milder conditions than that previously
published and yet resulted in better yields. Compound 5c
was synthesized by Brun et al.,13 reacting 2,3-dichloro-1,4-
naphthoquinone, 2-ethanolamine and Et3N, in diethyl ether
solution, obtaining a 46% yields. In the present work, the
same product was obtained with a yield of 89% by using
methanol as the solvent and excess of nucleophile. The
substance 5d (entry 4, Table 1) was prepared before using
Initially, we carried out monosubstitution of the
2,3-dichloronaphthoquinone 1 with nitrogen nucleophiles
(picolylamine 4a, 1,2-diaminopropane 4b and
2-aminoethanol 4c), oxygen nucleophile (methanol 4d),
and sulfur nucleophiles (1,2-ethanedithiol 4e and
2-mercaptoethanol 4f) using the various experimental
conditions compiled in Table 1.
Table 1. Synthesis of substituted naphthoquinone derivatives from 2,3-dichloro-1,4-naphthoquinone 1
Entry No.
1
Nucleophile
Solvent
CH3OH
Base
Et3N
time / h
Product
Yield / %
88
O
H
N
N
4a
2
Cl
O
5a
O
H
N
NH2
2
3
4
5
4b
4c
4d
4e
CH3OH
CH3OH
CH3OH
CH3OH
not used
not used
Et3N
7
24
3
89
89
81
62
Cl
O
5b
O
O
H
N
OH
Cl
5c
O
O
OCH3
Cl
5d
O
S
not used
12
S
O
5e
O
S
SH
6
7
4e
4f
(CH3)2CO/ H2O
(CH3)2CO/ H2O
not used
not used
12
24
66
52
Cl
O
5f
O
S
OH
OH
S
O
5g

Vol. 26, No. 9, 2015
Delarmelina et al.
1809
a solution of 2,3-dichloro-1,4-naphthoquinone and sodium
methoxide in methanol, where methoxide acted as the
nucleophile.14 In this work, compound 5d was synthesized
with a yield of 81% using a solution of 2,3-dichloro-1,4-
naphthoquinone, methanol and Et3N, where methanol was
the nucleophile and the solvent, simultaneously.
product was obtained, which is likely due to the increased
hardness and lower nucleophilicity of the hydroxyl group
of 2-mercaptoethanol. The monosubstituted product was
not obtained by this methodology.
Subsequently, several attempts were made to develop a
simple and effective novel methodology that would enable
us to obtain the disubstituted compounds from the products
5a and 5f using, initially, nucleophiles 4a and 4e (Table 2).
Preparation of the compound 5f by reacting 1 with
1,2-ethanedithiol 4e (entry 6, Table 1) was particularly
challenging since we failed to reproduce the previously
described method of nucleophilic substitution in water.4
Therefore, we enacted several experimental modifications,
including different solvents (water, ethanol, methanol and
acetone), variable temperatures (reactions were carried
out at room temperature (r.t.) and under reflux, different
bases such as K2CO3 and Et3N and reaction times ranging
from 1-48 h. However, due to the softness and the high
nucleophilicity of 4e, the disubstituted cyclized product
5e15 (entry 5, Table 1) was systematically obtained from
an intramolecular nucleophilic substitution (Scheme 1).
Heat and the use of the Et3N base favored generation of the
product. The desired compound 5f was obtained only when
the reaction was carried out in a mixture of acetone:water
at r.t. with excess nucleophile.
Table 2. Tested methods to obtain the disubstituted product from 4a and 4e
Entry No.
Solvent
CH3OH
CH3OH
CH3OH
C2H5OH
C2H5OH
H2O
Temperature / oC time / h
Catalyst
not used
AgNO3
AgNO3
AgNO3
AgNO3
AgNO3
AgNO3
AgNO3
AgNO3
AlCl3
1
r.t.
r.t.
1
2
24
24
24
24
24
24
24
24
24
24
72
24
24
12
24
3
65
4
r.t.
5
78
6
r.t.
7
H2O
50
8
CH3OH/ H2O
C2H5OH / H2O
H2O
50
9
50
10
11
12
13
14
15
16
r.t.
H2O
50
AlCl3
(H3C)2CO
H3CCN
H2O
56
AlCl3
r.t.
AlCl3
50 oC
r.t.
CeCl3.7H2O
CeCl3/NaI
CeCl3/NaI
H3CCN
H3CCN
82 oC
r.t.: room temperature.
In attempt to render the chlorine atom a better leaving
group, we added AgNO3 to the reactional solution, aiming
at the complexation of the Ag+ ions with the chlorine atom
(entries 2-9, Table 2);23 the same rationale applies for the
use of AlCl3, a Lewis acid with an affinity for oxygen
and halogen atoms (entries 10-13, Table 2). However,
the two methodologies proved to be unsatisfactory. Next,
CeCl3 was used to impose an electron withdrawing effect
on the quinone ring by complexation with the carbonyl
group and, thus, increasing the electrophilicity of C3 and
facilitating the nucleophile attack (entry 14, Table 2).
Again, an unsatisfactory result was obtained. We next tried
to complete the second nucleophilic substitution under
Finkelstein conditions using NaI to replace the remaining
chlorine by iodine, which is a better leaving group (entries
15 and 16, Table 2). Nonetheless, we did not succeed in
obtaining the desired disubstituted products.
Scheme 1. Substitution mechanisms affording 5e and 5f.
In order to obtain the monosubstituted product from 1
and 2-mercaptoethanol 4f, a reaction was carried out under
the same optimized conditions as previously described
for the formation of 5f. However, the disubstituted
product 5g was formed (entry 7, Table 1) from a double
intermolecular nucleophilic substitution. No alicyclic
To evaluate the importance of the chlorine at the carbon
atom C3, as well as, the nitrogen substituent at the C2 in the
5a-cproductsforantitumoractivity, nucleophilicsubstitution

1810
Synthesis, Antitumor Activity and Docking of 2,3-(Substituted)-1,4-Naphthoquinone Derivatives
J. Braz. Chem. Soc.
Table 3. Synthesis of monosubstituted derivatives 6a-c from 2-methoxy-1,4-naphthoquinone 7
Entry No.
1
Nucleophile
Solvent
CH3OH
time / h
24
Product
Yield / %
58
O
H
N
N
4a
O
6a
O
H
N
NH2
2
3
4b
4c
CH3OH
CH3OH
7
58
76
O
6b
O
O
H
N
OH
32
6c
reactions at r.t. with 2-methoxy-1,4-naphthoquinone 7
using the 4a picolylamine, 1,2-diaminopropane 4b
and 2-aminoethanol 4c nucleophiles, were carried out
(Table 3). The compounds 6a17 and 6c18,24 were obtained in
good-to-moderate yields by nucleophilic substitution of the
methoxyl group in the 2-methoxy-1,4-naphthoquinone 7 by
picolylamine and ethanolamine, respectively (Scheme 2).
The compound 6b was synthesized following the same
method, but using 1,3-diaminopropane as the nucleophile
and methanol as the solvent, at room temperature.
Moreover, to the best of our knowledge, the preparation
of compound 6b has not been reported before.
sulfur atom in the position 2 of the naphthoquinone core,
we then tried to obtain these products by the oxidative
Michael addition.
This methodology, which is well recommended,
employs cerium(III), copper(II), nickel(II) or gold(III)
salts as Lewis acids to promote the Michael addition type
in the naphthoquinone, with moderate-to-good results
when primary and secondary aliphatic and aromatic amines
were used.6,24-27A comprehensive study of the methods was
carried out by Lisboa et al.,25 who obtained better yields
when Cu(OAc)2.H2O and acetic acid was used at 60 °C.
Interestingly, recent studies have described simplified
methods to carry out the referred reaction without the
need for a metal, which promotes the oxidative addition
of quinone, but using methanol, ethanol, ethanol:water, or
even water only as solvents.4,14,28-31
Initially, theoxidativeMichaelreactionwastestedbetween
the 2-mercaptoethanol 4f and the 1,4-naphthoquinone 3,
using Cu(OAc)2.H2O as the oxidant and acetic acid or
ethanol as solvent, as described in the literature.6 However,
in both cases, a complex mixture of products was formed,
making them difficult to isolate and purify. Subsequently,
the reaction was performed using oxygen as the oxidizing
agent and water or ethanol as the solvent. The reaction was
performed at room temperature and under reflux, but again
the desired product could not be obtained.
Only when acetone was used as the solvent, at r.t.,
compound 8 was obtained in a 77% yield (Scheme 3). The
occurrence of oxidative addition in absence of an external
oxidizing agent can be explained by the oxidizing ability of
1,4-naphthoquinone, which can assist in the formation of
the desired product, as described by Taylor et al.,32 is worth
emphasizing that, to the best of our knowledge, compound 8
has never been before described in the literature.
Scheme 2. Mechanism for nucleophilic substitution on 2-methoxy-1,4-
naphthoquinone.
The 2-methoxy-1,4-naphthoquinone 7 was prepared by
methylation of 2-hidroxy-1,4-naphthoquinone via heating
in methanol and hydrochloric acid, as described in the
literature.19
The reaction of 2-methoxy-1,4-naphthoquinone was
also tested with the sulfur nucleophiles 4e and 4f; however,
distinct from the observation with nitrogen nucleophiles,
the reactions with sulfur nucleophiles resulted in a complex
mixture of products which were difficultly separated and it
was not possible to obtain the desired product. A possible
undesired reaction in this system is the oxidative Michael
addition.
Because we failed to substitute the methoxyl group
in 7 by the sulfur nucleophiles 4e and 4f to obtain the
corresponding monosubstituted product containing the

Vol. 26, No. 9, 2015
Delarmelina et al.
1811
Table 4. IC50 values for human lung (H460), triple-negative breast (MDA-
MB-231) and ovarian (A2780) cancer cell lines
IC50 / mol L-1
Compound
H460
MDA-MB-231
A2780
a
Cisplatin
8.586 × 10-5
3.441 × 10-5
−
4.01 × 10-5
a
a
Etoposide
−
−
a
a
1.7 × 10-4
−
Scheme 3. Synthesis of naphthoquinone derivatives 8.
Doxorubicine
−
a
Paclitaxel
−
1 × 10-6
1.36 × 10-5
3.04 × 10-4
2.43 × 10-4
6.29 × 10-5
4.97 × 10-5
The aforementioned optimized oxidative Michael
addition was employed with 1,2-ethanedithiol 4e as the
nucleophile; however, the respective product was not
obtained. We also tested hydrated copper acetate in acetic
acid or water; nonetheless, the strategy was proven to be
ineffective.
b
5a
5b
5c
5d
5e
5f
1.960 × 10-4
5.008 × 10-4
1.293 × 10-4
2.292 × 10-4
1.861 × 10-4
3.048 × 10-5
4.410 × 10-5
7.595 × 10-4
6.635 × 10-4
2.334 × 10-4
4.24 × 10-6
−
8.6 × 10-4
2.13 × 10-5
6.08 × 10-5
1.1 × 10-3
1.3 × 10-4
4.28 × 10-5
9.4 × 10-4
7.8 × 10-4
b
−
3.38 × 10-5
2.68 × 10-6
2.77 × 10-5
1.91 × 10-5
5g
6a
6b
6c
8
In vitro antineoplastic activity
Over the past years, efforts of our research group have
been devoted to synthesizing and proving the antineoplastic
efficacy of various naphthoquinone derivatives in several
human cancer cell lines, such as lung cancer H460 and
A549, ovarian cancer A2780, triple negative breast cancer
MDA-MB-231 and promyelocytic leukemia HL-60, which
are representative cancers with poor prognoses.
In the present study, the in vitro cytotoxicity of the
synthesized compounds 5a-5g, 6a-6c and 8 was assessed, by
a standard colorimetric assay (the MTT method)20 to estimate
IC50 values, in three human cancer cell lines of solid tumors:
H460 (non-small cell lung cancer/large cell lung cancer),
A2780 (epithelial ovarian carcinoma) and MDA MB-231
(triple negative breast cancer). For internal experimental
controls, the lineages were treated with routinely prescribed
chemotherapy agents: etoposide, cisplatin for lung cancer
line cell H460, cisplatin and paclitaxel for epithelial
ovarian carcinoma A2780, paclitaxel, and doxorubicin for
MDA MB-231 (triple negative breast cancer).All cells were
treated continuously for 24 h in a dose-dependent fashion.
The results are listed in Table 4.
When analyzing the proliferation of the lung cancer
cell line H460, we noted that compound 8 was 10 times
more potent than the control drugs at inhibiting H460
proliferation. On the other hand, compounds 5f and 5g
showed cytotoxic activities similar to the controls. Thus,
the compound containing a sulfur atom at the C2 carbon
of the naphthoquinone was the most potent drug against
the type of lung cancer studied, suggesting that the drug
might serve as an alternative, but yet efficient, therapeutic
strategy to fight this deadly disease.
b
b
−
−
1.603 × 10-5
3.89 × 10-6
aRoutinely prescribed as chemotherapy agents; bno antiproliferative
activity.
than paclitaxel at controlling the cell proliferative activity.
Nonetheless, among the tested compounds, substance 8
was the most potent. Of interest, compound 5c, which
contains a nitrogen substituent at the C2 position of the
naphthoquinone, was potent against the proliferation of
the cancer at the same order of magnitude as compound 8.
These observations are of remarkable clinical interest since
triple negative breast cancer still challenges the field of
medicine due to its low overall survival rates. These low
rates are caused, in part, by the relapse of resistant clones,
despite the initial satisfactory response to chemotherapy,
thus leading to an overall low index of survival.33
The in vitro screening for ovarian cancer A2780
antiproliferation revealed that compounds 8 and 5g were
10 times more potent than paclitaxel. Other compounds,
such as 6a and 6b, exhibited activities similar to paclitaxel,
but were more potent than cisplatin against the disease.
Overall, and as discussed above, these findings are of
major clinical interest since ovarian cancer cells are either
refractory or acquire resistant phenotypes, accounting
for ovarian cancer second position in the ranking of the
most frequent causes of deaths related to gynecological
cancers in the world.
Interestingly, we noted that when alkyl groups
containing sulfur atom are present at C2 of the carbon
atom of the naphthoquinone core, the resulting compounds
are more potent against human cancers than compounds
For the triple negative breast cancer cell line,
MDA MB-231, all tested compounds were less potent

1812
Synthesis, Antitumor Activity and Docking of 2,3-(Substituted)-1,4-Naphthoquinone Derivatives
J. Braz. Chem. Soc.
containing nitrogen atoms. It is worthwhile pointing out
that the most active compounds with substituents at the
C2 position of the naphthoquinone core have either –OH
or –SH groups in their terminal alkyl chain.
were redocked with their receptors in order to validate the
efficiency of the docking calculations (Figure 4).
Docking
As previously discussed, PI3K is frequently mutated
in human cancers, thus enabling constitutive activation of
PI3K-related pathways, as in PI3K/AKT/mTOR pathways.
Because the genotype facilitates carcinogenesis and cancer
progression,34 targeting PI3K, as well as, its effect or
molecules have attracted the attention of cancer research
groups in both academia and the pharmaceutical industry.
Indeed, there are a few examples in clinical trials now;
nonetheless, many have failed to confer sustained disease
remission. Therefore, the generation of novel anti-PI3K
molecules is urgent. Recently, the elucidation of the crystal
structure of PI3Kγ and their complexes with Wortmannim
and LY294002 ligands have facilitated the rational design
of new inhibitors of the enzyme. Its crystal structure was
obtained from the Protein Data Bank (PDB) under code
1E7U (Figure 3). Docking studies were conducted in order
to analyze the conformation and binding energy through
the AutoDock Vina software.21
Figuurree4.4C. rCysrtyaslltoagllroagphraicplhiigcanldigsandsre(dgorcekye)d alingdanrde.d(ao)cWkeodrtmliagnannidm.
(1a)E:7rUed-KWWoTrt:mPDanBn)imand(1(Eb7) Ude-xKrWazTox:PaDneB()1QanZdR(-bC)D: Xgr:ePeDnBd)e.xrazoxane
(1QZR-CDX:PDB).
Next, the control drugs Etoposide, a topoisomerase II
inhibitor, and Wortmannim, a PI3K inhibitor compound
described in the literature,37,38 were superimposed on the
binding site of the enzyme, the adenosine triphosphate
(ATP) cleft, via the same method. Note that the chemical
structure of the ligand was fully optimized using the
parametric method 6 (PM6) semi-empirical method.22
As a result, we obtained the superposition of the ligand
in the active site of PI3Kγ by calculating the interaction
energy ligand/receptor (Table 5). The same procedures
of molecular modeling calculations were used for all
naphthoquinone derivatives.
Docking studies were also conducted in relation to
topoisomerase II, another target of great importance
in the study and development of new naphthoquinone
substances with potential antineoplastic activity.35,36 The
crystal structure of this protein was obtained from the PDB
under code 1QZR.
The results obtained for the tested compounds (Table 5)
indicated interaction energies close to crystallographic
reference structures, especially 5a and 6a against PI3Kγ
and 6c against topoisomerase II. These results lead us to
suppose that the anticancer mechanism of action to these
naphthoquinone derivatives occur through PI3K and
topoisomerase II inhibition, as widely reported previously.2
The docking studies are able to identify the best
pose of ligands into the binding site. Figure 5 depicts
the intermolecular interaction between Wortmannim and
6a against the binding site of PI3K enzyme performing
van der Waals interactions with Lys808, Pro810, Trp812,
Ile831, Ile879, Glu880, Ile881, Asp950, Phe961, Ile967
amino acids; electrostatic interactions with Met804,
Val882, Lys883, Met953, Asp964, Tyr867; and hydrogen
bonds with Val882, Lys883, Tyr867, Asp964 amino acids
(Figure 6a).
Figure 3. Crystallographic structure representation of PI3K (1E7U) (a)
and topoisomerase II (1QZR) (b).
PI3K and topoisomerase II were prepared with
their respective ligands, dexrazoxane and Wortmannim,
according to the protocol described in the literature.21
Grid boxes with dimensions of 18 × 10 × 12 Å for
both receptors and coordinates x = 23.426, y = 62.986
and z = 20.716 (PI3K) and x = 28.166, y = 33.408 and
z = 32.263 (topoisomerase II), both centered in the ligand,
were constructed to fully cover the active site of the
enzymes. Immediately after, the crystallographic ligands
Likewise, the most active compound by docking, 6a,
can complex by van der Waals interactions with Ser806,
Pro810, Glu880, Lys833, Ile879,Val882, Met953, Phe961,
Ile963 amino acids; electrostatic interactions with Met804,
Tyr867,Asp964 amino acids. No hydrogen bonds could be
observed in these compounds. However, new derivatives
with acceptor hydrogen bond can improve the active by
an interaction with Tyr867, similar to Wortmannim. In
addition, Figure 6c shows the cluster of all ligands in the

Vol. 26, No. 9, 2015
Delarmelina et al.
1813
Figure66..PhPahramrmacaocpohpohroicricconcfoonrfmoarmtioantiofndeoxfradzeoxnraezionn(ae);in6c(ian);(b6)canidn
c(blu)satenrdocfluaslltenraopfhtahlloqnuapinhothnoeqdueirniovanteivdeesriavnadtivdeesxrianztohneebiinndthinegbisnitdeinogf
stoitpeooisfotmopeoraissoemIeI,rainsewIhIi(cch).dexrazone is highlighted in yellow in (c).
Table 5. Interaction energies of compounds 5a-5g, 6a-6c, 8, Wortmannim,
dexrazone and etoposide against respective molecular targets
Figure 5. Pharmacophoric conformation of Wortmannim in (a); 6a in (b)
and cclluusstteerrooffalalllnanpahpthhtohqouqiunionnoenededrievraivtiavteivseisn athnedbWinodritnmgasnitneimof iPnI3thKe,
bininwdhinicghsiWteoortfmPaIn3nKim(c)is. highlighted in yellow in (c).
Interaction Energy / (kcal mol-1)
Compound
PI3Kγ
−7.7
−
Topoisomerase II
Wortmannim
−
−7.8
binding site. As can be seen, the naphthalene complex
is very similar to Wortmannim into the binding site of
phosphatidylinositol 3-kinase (PI3K), suggesting this
molecular target as a receptor of naphthoquinones.
Dexrazone
Etoposide
−
−8.1
5a
5b
5c
5d
5e
5f
−7.7
−6.7
−6.5
−7.0
−7.0
−6.5
−6.1
−7.9
−6.8
−6.7
−6.6
−4.0
−6.9
−7.1
−6.6
−5.2
−4.8
−4.8
−5.0
Similarly, to PI3K enzyme, Figure 6 shows the
intermolecular interaction between dexrazone, and 6c. As
can be seen, dexrazone performs van der Waals interactions
with Tyr28, Tyr144, Leu148 amino acids; electrostatic
interactions with Thr27, His28, Asn142 amino acids; and
hydrogen bond with Gln365 amino acid, all for both chains
of enzyme (a and b) (Figure 6a). Similarly, compound 6c
can complex through van derWaals interactions with Thr27,
Tyr144, Gln365 amino acids; electrostatics interaction
with Gln17, His20, Thr27, Tyr28, Asn142; a hydrogen
bond can be observed between 6c and Thr27 (Figure 6b).
Finally, Figure 6c shows a cluster formed by dexrazone
and naphthoquinones. These results suggest that these
compounds can inhibit the topoisomerase II.
5g
6a
6b
6c
8
−7.5
−7.8
−7.2
8 can highlight the electrostatic interaction between the
naphthoquinone carbonyl core and amino acids from the
Asp964 residue of the PI3K protein (Figure 7).
Another important interaction occurs between –SH
and –OH substituents and the C2 naphthoquinone carbon
In addition, the naphthoquinone derivatives 5c, 5f, and

1814
Synthesis, Antitumor Activity and Docking of 2,3-(Substituted)-1,4-Naphthoquinone Derivatives
J. Braz. Chem. Soc.
Figure 8.PPhhaarrmmaaccoopphhoorriiccccoonnffoorrmmaattiioonnooffeetotoppoossididee(gargeaein)statghaeinasctttihve
asictteivoefstihte toofptohiesotompeoriassoemIeIr.ase II.
Figure 7. Interaction between PI3Kγ and compounds 5c, 5f, 5g and 8.
with different amino acid residues, such as the electrostatic
interaction with the Lys833 to compound 5c and the
hydrogen bonds with Asp950 and Lys833 with 5g and 8,
respectively. The other interactions of these compounds
are van der Waals interactions with different amino acid
residues.
The docking of etoposide against the active site of
topoisomerase II showed a hydrogen bond between the
hydroxyl group and Gly365, electrostatic interactions with
the Gly17, Thr27, Tyr28, and van der Waals interactions
with Tyr144, as shown in Figure 8.
Naphthoquinone derivatives have in general similar
interactions to those presented in the docking etoposide,
where the major amino acid residues responsible for
this interaction have been Gly365, Gly17, Thr27, Tyr28
and Tyr144 (Figure 9). This similarity likely reflects the
interaction energies between naphthoquinone derivatives and
etoposide when topoisomerase II is the therapeutic target.
Compound 5c showed two important hydrogen bonds,
the amino and hydroxyl groups from the side chain of the
substituent (ethanolamine) with the tyrosine amino acid
residues glycine 28 and 17. Furthermore, an electrostatic
interaction with threonine 27 was observed.
Figure 9. Interactions between topoisomerase II and compounds 5c, 5f,
5g and 8.

Vol. 26, No. 9, 2015
Delarmelina et al.
1815
Compounds 5f and 5g showed the same hydrogen
bonds with etoposide described for the amino acid
residue Gly365. However, the group that was responsible
for this interaction in 5f (5g) was the naphthoquinone
carbonyl core (the terminal hydroxyl substituent from
mercaptoethanol). Besides these interactions, compound
5g showed an electrostatic interaction with the amino
acid threonine 27. Compound 8 showed two electrostatic
interactions with the amino acid residues Gly17 and Tyr144.
van der Waals interactions were also observed with Gly365
and Tyr28.
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Eur. J. Org. Chem. 2014, 24, 5318; Duchowicz, P. R.; Bennardi,
D. O.; Bacelo, D. E.; Bonifazi, E. L.; Rios-Luci, C.; Pádron,
J. M.; Burton, G.; Misico, R. I.; Eur. J. Org. Chem. 2014, 24,
2318.
Conclusions
In this work, we have described novel and highly
efficient methodologies for preparation of eleven
1,4-naphthoquinone derivatives 5a-g, 6a-c and 8
containing substituents in positions 2 and/or 3 in yields
ranging from 38% to 89%. The following compounds
showed greater in vitro antitumor activity: 5f and 8
against human lung cancer lines H460; 5c and 8 against
triple-negative breast cancer lines MDA-MB-231; 5g and
8 against ovarian cancer lines A2780. The clinical drugs
tested in H460, etoposide and cisplatin; and in A2780,
cisplatin and paclitaxel, showed higher values of IC50
compared with the results obtained for synthesized novel
compounds, thus, pointing to the higher antineoplastic
potency of the latter. The structure/activity relationship
of these compounds showed that bioisosteric substitution
for sulfur atoms at the carbon C2 in naphthoquinone core,
or hydroxyl groups in the substituent chain, are primarily
responsible for the biological activity of the compounds.
The docking analysis revealed that a possible therapeutic
target of these substances are topoisomerase II and PI3K.
These compounds have shown to be promising drug
candidates to combat human cancer.
Supplementary Information
Supplementary data (Figures S1-S36) are available free
of charge at http://jbcs.sbq.org.br as PDF file.
4. Tandon,V. K.; Maurya, H. K.; Tetrahedron Lett. 2009, 50, 5896.
5. Tandon,V. K.; Maurya, H. K.;Verma, M. K.; Kumar, R.; Shukla,
P. K.; Eur. J. Med. Chem. 2010, 45, 2418.
Acknowledgments
6. Benites, J.; Valderrama, J. A.; Bettega, K.; Pedrosa, R. C.;
Calderon, P. B.; Verrax, J.; Eur. J. Med. Chem. 2010, 45, 6052.
7. Tandon, V. K.; Maurya, H. K.; Mishra, N. N.; Shukla, P. K.;
Bioorg. Med. Chem. Lett. 2011, 21, 6398.
The authors thank FAPES, CNPq and CAPES for the
financial support.
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Submitted: March 18, 2015
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