Synthesis and cytotoxicity evaluation of a series of 3-alkenyl-2-hydroxy-1,4-naphthoquinones obtained by an efficient knoevenagel condensation

Article abstract of DOI:10.21577/0103-5053.20180146

A modified and efficient Knoevenagel condensation procedure was developed to synthesize the title compounds using β-alanine and acetic acid as catalysts, showing good to excellent yields. We used lawsone with suitable aliphatic aldehydes including isobuty

Full text of DOI:10.21577/0103-5053.20180146

http://dx.doi.org/10.21577/0103-5053.20180146
J. Braz. Chem. Soc., Vol. 00, No. 00, 1-11, 2018
Printed in Brazil - ©2018 Sociedade Brasileira de Química
Article
Synthesis and Cytotoxicity Evaluation of a Series of 3-Alkenyl-2-Hydroxy-
1,4-Naphthoquinones Obtained by an Efficient Knoevenagel Condensation
Cibelle C. David,a Antonio C. S. Lins,a Tania M. S. Silva,a Júlia F. Campos,b
Teresinha G. Silva,c Gardenia C. G. Militãoc and Celso A. Camara*,a
aDepartamento de Química, Universidade Federal Rural de Pernambuco, Campus Dois Irmãos,
52171-900 Recife-PE, Brazil
bCentro de Tecnologias Estratégicas do Nordeste, 50740-540 Recife-PE, Brazil
cDepartamento de Antibióticos, Universidade Federal de Pernambuco,
50670-901 Recife-PE, Brazil
A modified and efficient Knoevenagel condensation procedure was developed to synthesize
the title compounds using β-alanine and acetic acid as catalysts, showing good to excellent
yields. We used lawsone with suitable aliphatic aldehydes including isobutyraldehyde, 3-methyl-
butyraldehyde, 2-ethylbutyraldehyde, phenylacetaldehyde, 2-phenyl-propionaldehyde, among
others. These compounds were submitted to cytotoxic screening against three tumor cell lines
presenting good to excellent cytotoxic profiles.
Keywords: 1,4-naphthoquinones, 3-alkenyl-2-hydroxy-1,4-naphthoquinones, lawsone,
Knoevenagel condensation, cytotoxic evaluation
Introduction
Bock et al.5 published an update of this methodology (see
Table 1).
The synthesis of 3-alkenyl-2-hydroxy-1,4-naphtho-
quinones has been a topic of permanent interest in Brazil
and abroad.1,2 These compounds share structural features
with natural lapachol (1), the most abundant quinone found
in the core wood of various Bignoniaceae. Lapachol has a
long tradition of use as a precursor of modified quinones,
particularly for derivatives aimed at trials and screening of
their multipurpose biological profiles.3
Hooker, in 1936,4 published a systematic synthetic
procedure for a series of 3-alkenyl-2-hydroxy-
1,4-naphthoquinones using lawsone (2) with suitable
aliphatic aldehydes with hydrochloric acid as catalyst.
Hooker used propionaldehyde, n-butyraldehyde,
valeraldehyde, heptanaldehyde, phenylacetaldehyde and
hydrocynamaldehyde (3a-f), obtaining the corresponding
products in low to modest yields (23-48%, Table 1). In this
work, Hooker also pointed that he was unable to obtain the
condensation product from isobutyraldehyde, and from
acetaldehyde he notes that a rapid consumption of the
formed product was observed.4 Fifty years later, in 1986,
Using (R)-(+)-citronelal (3 h) in Hooker’s conditions,
a cyclization to furnish only tetracyclic product 5 was
observed (Scheme 1).5 However, changing the catalytic
conditions to basic triethylamine in more polar solvents
as acetonitrile or dimethylformamide (DMF), the
corresponding hydroxy-naphthoquinone (3h) was obtained
with 20 and 28% yield, respectively.5 These findings in the
cyclization of lawsone with (R)-(+)-citronelal were also
previously published by Ferreira et al.6 in 1982.
In the synthesis of tetracyclic vesparione in 1987,
Kopanski et al.7 developed a modified Knoevenagel
procedure to obtain the deoxy-derivative of vesparione (6,
Scheme 2) with 32% yield. The procedure involved a
previously explored oxidative cyclization step using
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)
in both acidic or basic media.8,9 The high yield of
2-cyclopentylidenemethyl-3-hydroxy-1,4-naphthoquinone
(4m, 94%) was obtained by the use of β-alanine/acetic acid
in benzene under reflux, using only two equivalent excess
of aldehyde, compared with five equivalent or higher used
by Hooker.4 Dehydropyranonaphthoquinones (6) could
also be obtained using modified Knoevenagel procedure by
*e-mail: celso.camara@ufrpe.br

2
Synthesis and Cytotoxicity Evaluation of a Series of 3-Alkenyl-2-Hydroxy-1,4-Naphthoquinones
J. Braz. Chem. Soc.
Table 1. Compounds 3a-l obtained by Hooker4 and Bock et al.5
Product
entry
Aldehyde
Condition
(yield / %)
4a (23)4
4b (42)4
4c (43)4,a
4d (35)4
4e (41)4
4f (48)4,a
4g (–)4
1
3a
3b
3c
3d
3e
3f
(i)
2
(i)
3
(i)
4
(i)
5
(i)
6
(i)
7
3g
3h
3i
(i)
(ii)
8
4h (20-28)5
4i (33-36)5
4j (–)5
9
(ii)
10
11
12
3j
(ii) and (iii)
(ii)
3k
3l
4k (30)5
4l (26)5
(ii)
aCrude reaction product without recrystallization.
Scheme 1. Tetracyclic quinone 5 from Hooker condensation using (R)-(+)-citronelal (3 h) by Ferreira et al.6
one-pot condensation-cycloaddition using α,β-unsaturated
aldehydes in the presence of ethylenediamine diacetate in
moderate to good yields.10
in 2006, used methylamine hydrochloride and p-TsOH in
refluxing benzene, obtaining modest yields of 2-hydroxy-3-
alkenyl-1,4-naphthoquinones by the use of propanal (48%,
conversion yield), 2-ethyl-butyraldehyde (44%) and using
naphthopurpurine (7) with propanal (16%).
Using Bock’s basic methodology,5 Nagabhushana et al.,13
in 2001, studied the reaction conditions for the condensation
products between caproaldehyde and lawsone with
triethylamine as catalyst and also under some other different
conditions. Using the optimized conditions they obtained
a best result yield of 43% for the desired 2-hydroxy
3-(1’-hexenyl)-1,4-naphthoquinone.13
Anufriev et al.,11 in 1993, using a modified Hooker’s
methodology with methylamine hydrochloride in ethanol
under reflux synthesized 3-alkenyl-2,5,8-trihydroxy-
1,4-naphthoquinones (8) besides 3,3’-methylene-
bisnaphthazarine (9) from naphthopurpurin (7, Table 2).
Using few aliphatic aldehydes (propionaldehyde,
isobutyraldehyde and valeraldehyde), they observed
mixtures of 8 and 9 and using acetaldehyde or
paraformaldehyde just dimers were formed. Using a similar
approach in the selection of catalysts, Glazunov et al.,12
As a part of a continuous interest of our laboratory in

Vol. 00, No. 00, 2018
David et al.
3
Scheme 2. Two-step synthesis of 3,4-dehydropyrano-1,4-naphthoquinones using Knoevenagel conditions in the obtention of 2-hydroxy-3-alkenyl-
1,4-naphthoquinone.7
Table 2. Condensation of 2-hydroxy-naphtharazin with selected aliphatic aldehydes yielding mixtures of expected alkenyls 8 and dimers 911
R
R1
CH3
8 / %
15
9 / %
29
H
H
(CH2)2CH3
CH3
36
22
CH3
H
22
17
H
–
97
obtaining a range of 2-hydroxy-3-alkenyl-1,4-naphtho-
quinones (4) from suitable aliphatic aldehydes and
lawsone (2) under simple Knoevenagel conditions, we chose
to perform a preliminary systematic study of experimental
conditions to improve product yields, but also to find a
general method to synthesize those interesting compounds.
As pointed above, the use of modified Knoevenagel catalysts
and water scavenger could reduce undesired reactions
like lawsone dimerization and side chain acid cyclization,
common side reactions in this type of condensation.14 Finally,
the synthesized compounds were subjected to an evaluation
screening for their potentials as antitumor lead compounds
against different cancer cell lines. In this study, the
biological screening also included a comparison with some
other available furan and pyran derived hydroxymethyl-
1,4-naphthoquinones obtained previously in our group by an
acid catalyzed Prins cyclization of lapachol and norlapachol
with paraformaldehyde and the newly corresponding acetyl
derivatives.
Experimental
General information
Air- and moisture-sensitive reactions were carried
out under argon atmosphere. Reagents were purchased
from Sigma-Aldrich, Dinâmica or Vetec and distilled
or used without further purification. Reactions were
monitored by thin layer chromarography (TLC) analysis
on precoated silica gel plates (Merck, Kieselgel 60
GF254) and compounds were visualized with UV light.
Column chromatography was performed on silica gel 60
(70-230 mesh, Merck). Melting points were measured
in open capillary tubes in a Quimis apparatus and are
uncorrected. The infrared (IR) spectra were recorded on an
IFS66 Bruker spectrophotometer using KBr discs orVarian
Mercury 640IR with attenuated total reflectance (ATR).
High resolution mass spectrometry (HRMS) analyses were
performed on a matrix assisted laser desorption ionization-

4
Synthesis and Cytotoxicity Evaluation of a Series of 3-Alkenyl-2-Hydroxy-1,4-Naphthoquinones
J. Braz. Chem. Soc.
tandem time of flight (MALDI-TOF/TOF)Autoflex III 10,
using positive reflected mode. Nuclear magnetic resonance
(NMR) spectra were recorded on a Varian Unity Plus-400
spectrometer (1H at 400 MHz and 13C at 100 MHz),
200 MHz Varian Mercury or Anasazi (90 MHz for 1H and
22.5 MHz for 13C), using CDCl3 or dimethyl sulfoxide-d6
(DMSO-d6) as solvents, and calibrated for the solvent signal.
Chemical shifts are expressed in parts per million (ppm) and
coupling constants are given in Hz.Assignments are based
on correlation spectroscopy (COSY) and heteronuclear
single quantum coherence (HSQC) experiments.
2-Hydroxy-3-butenyl-[1,4]naphthoquinone (C14H12O3) (4b)
Orange solid; mp 99 C (lit. 101.5 C);4 1H NMR
(200 MHz, CDCl3) d 8.09 (ddd, 1H, J 7.4, 1.4, 0.8 Hz),
8.05 (ddd, 1H, J 7.4, 1.4, 0.6 Hz), 7.81 (s, 1H), 7.80 (dt,
1H, J 7.4, 1.4 Hz), 7.70 (dt, 1H, J 7.6, 1.8 Hz), 7.30 (dt,
1H, J 16.2, 6.8 Hz), 6.70 (dt, 1H, J 16.2, 1.6 Hz), 2.29 (dq,
2H, J 7.2, 1.4 Hz), 1.19 (t, 3H, J 7.4 Hz); 13C NMR (APT)
(50 MHz, CDCl3) d 184.3, 181.3, 151.2, 145.4, 134.8,
133.0, 132.6, 129.4, 127.0, 125.9, 118.7, 117.7, 28.0, 13.3;11
IR (KBr) νmax / cm-1 3330, 3072, 2964, 2933, 2876, 1652,
1592, 1459, 1372, 1341, 1263; HRMS (MALDI) calcd.:
229.0859, found: 229.0851.
o
o
Synthesis
2-Hydroxy-3-pentenyl-[1,4]naphthoquinone (C15H14O3) (4c)
Orange solid; mp 95-98 oC (lit. 98-98.5 oC);4 1H NMR
(200 MHz, CDCl3) d 8.08 (dd, 1H, J 7.2, 1.6 Hz), 8.01
(dd, 1H, J 7.4, 1.8 Hz), 7.70 (dt, 1H, J 7.6, 1.8 Hz), 7.66
(s, 1H), 7.62 (dt, 1H, J 7.4, 1.4 Hz), 7.03 (dt, 1H, J 16.2,
7.0 Hz), 6.57 (dt, 1H, J 16.4, 1.2 Hz), 2.24 (dq, 2H, J 7.2,
1.2 Hz), 1.49 (sex, 2H, J 7.2 Hz), 0.93 (t, 3H, J 7.4 Hz);11
13C NMR (50 MHz, CDCl3) d 184.3, 181.4, 151.2, 144.0,
134.8, 133.0, 132.6, 129.4, 127.0, 125.9, 118.8, 118.7,
37.1, 22.3, 13.8; IR (KBr) νmax / cm-1 3454, 3330, 2959,
2930, 2869, 1652, 1632, 1607, 1460, 1375, 1278; HRMS
(MALDI) calcd.: 243.1016, found: 243.1001.
The compounds 10a (β-lapachone) and 10b
(nor-β-lapachone) were obtained as described by literature
methods from lapachol and norlapachol, respectively.15
Synthesis of 3-alkenyl-2-hydroxy-1,4-naphthoquinones
compounds (4)
Method A: in a flask, it was added lawsone 2 (0.2 g,
1.2 mmol), β-alanine (0.03 g, 0.33 mmol) and toluene
(40 mL), followed by glacial acetic acid (0.017 g,
0.28 mmol) and the corresponding aldehyde (2.3 mmol).
The reaction system was kept under reflux using a
Dean-Stark apparatus. The reaction was monitored by TLC
for about 1 h. The solvent was removed and the compound
was purified by crystallization in EtOH/H2O (4e, 4g, 4i,
4j) or by column chromatography with silica gel and
hexanes:ethyl acetate 90:10 as eluent (4a, 4b, 4c, 4p).
Method B: in a flask, it was added lawsone (2, 0.2 g,
1.2 mmol), β-alanine (0.06 g, 0.67 mmol) and toluene
(40 mL), followed by glacial acetic acid (0.034 g,
0.56 mmol) and the corresponding aldehyde (2.3 mmol).
The reaction system was kept under reflux using Dean-Stark
apparatus. Inspection of the progress of the reaction was
made by TLC for about 1 h. The solvent was removed and
the compound was purified by column chromatography
with silica gel and hexanes:ethyl acetate 90:10 as eluent.
2-Hydroxy-3-styryl-[1,4]naphthoquinone (C18H12O3) (4e)
o
o
Orange crystals; mp 163-165 C (lit. 167-168 C);4
1H NMR (200 MHz, CDCl3) d 8.13 (ddd, 1H, J 7.4, 1.6,
0.4 Hz), 8.04 (ddd, 1H, J 7.0, 1.4, 0.6 Hz), 7.93 (d, 1H,
J 17 Hz), 7.73 (dt, 1H, J 7.2, 1.4 Hz), 7.65 (dt, 1H, J 7.2,
1.6 Hz), 7.57 (ddd, 2H, J 7.6, 1.6, 0.4 Hz), 7.36 (d, 1H,
J 16.6 Hz), 7.36 (m, 3H); 13C NMR (APT) (50 MHz, CDCl3)
d 184.0, 180.9, 151.8, 139.1, 137.7, 134.8, 133.1, 132.6,
129.5, 128.6, 128.5, 127.1, 127.0, 125.9, 118.6, 117.3;
IR (KBr) νmax / cm-1 3312, 3061, 3027, 2929, 1651, 1592,
1451, 1372, 1262; HRMS (MALDI) calcd.: 277.0859,
found: 277.0857.
2-Hydroxy-3-(3-phenyl-propenyl)-[1,4]naphthoquinone
(C19H14O3) (4f)
2-Hydroxy-3-propenyl-[1,4]naphthoquinone (C13H10O3) (4a)
Orange solid; mp 131-133 C (lit. 135.2-135.7 C);4
1H NMR (400 MHz, CDCl3) d 8.11 (dd, 1H, J 7.8, 1.2 Hz),
8.05 (dd, 1H, J 7.4, 1.6 Hz), 7.74 (dt, 1H, J 7.8, 1.6 Hz),
7.67 (dt, 1H, J 7.8, 1.2 Hz), 7.07 (dq, 1H, J 16.0, 7.0 Hz),
6.62 (dq, 1H, J 16.0, 1.6 Hz), 1.98 (dd, 3H, J 7.0, 1.6 Hz);
13C NMR attached proton test (APT) (100 MHz, CDCl3)
d 184.2, 181.4, 151.2, 138.8, 134.8, 133.0, 132.7, 129.4,
127.0, 125.9, 119.9, 118.6, 20.5; IR (ATR) νmax / cm-1 3227,
2977, 1654, 1591, 1458, 1365, 1260; HRMS (MALDI)
calcd.: 215.0703, found: 215.0713.
Orange crystals; mp 121-124 oC (lit. 140.5-141.5 oC);4
1H NMR (400 MHz, CDCl3) d 8.11 (ddd, 1H, J 7.6, 7.1,
1.2, 0.5 Hz), 8.05 (ddd, 1H, J 7.3, 1.5, 0.5 Hz), 7.74 (dt, 1H,
J 7.6, 1.4 Hz), 7.67 (ddt, 1H, J 7.6, 7.4, 1.2 Hz), 7.33-7.16
(m, 6H), 6.72 (dt, 1H, J 16.3, 1.5 Hz), 3.63 (dd, 2H, J 7.1,
1.2 Hz); 13C NMR (APT) (100 MHz, CDCl3) d 184.1, 181.3,
151.5, 141.6, 139.6, 135.0, 133.1, 132.7, 129.4, 128.7,
128.5, 127.0, 126.3, 126.0, 119.8, 118.3, 41.3; IR (KBr)
o
o
ν
max / cm-1 3280, 3063, 2926, 2856, 1651, 1597, 1459, 1380,
1257; HRMS (MALDI) calcd.: 290.0937, found: 290.0956.

Vol. 00, No. 00, 2018
David et al.
5
2-Hydroxy-3-(2-methyl-propenyl)-[1,4]naphthoquinone
2-Hydroxy-3-(2-phenyl-propenyl)-[1,4]naphthoquinone
(C19H14O3) (4q)
(C14H12O3) (4g)
Orange crystals; mp 114-117 C (lit. 119-120 C);16
1H NMR (200 MHz, DMSO-d6) d 8.05-7.96 (m, 2H),
7.90-7.76 (m, 2H), 5.87 (m, 1H), 1.91 (d, 3H, J 1.2 Hz),
1.58 (d, 3H, J 0.8 Hz); 13C NMR (APT) (50 MHz,
DMSO-d6) d 185.2, 182.1, 155.0, 141.0, 135.5, 134.1,
133.0, 131.1, 126.8, 126.6, 121.5, 116.0, 27.0, 22.4;
IR (KBr) νmax / cm-1 3363, 3074, 2969, 2927, 2863,
1647, 1592, 1453, 1377, 1275; HRMS (MALDI) calcd.:
229.0859, found: 229.0865.
Orange crystals; mp 142-144 oC (lit. 141.2-143.6 oC);18
1H NMR (400 MHz, CDCl3) d 8.15 (dd, 1H, J 7.6, 1.4 Hz),
8.11 (dd, 1H, J 7.6, 1.5 Hz), 7.77 (ddt, 1H, J 7.6, 1.5,
0.7 Hz), 7.70 (ddt, 1H, J 7.6, 1.5, 0.7 Hz), 7.58 (m, 2H),
7.38-7.27 (m, 3H), 6.62 (m, 1H), 2.08 (m, 3H); 13C NMR
(APT) (100 MHz, CDCl3) d 184.5, 181.4, 151.3, 144.1,
142.5, 135.0, 133.1, 133.0, 129.6, 128.3, 127.8, 127.0,
126.2, 126.2, 120.8, 116.0, 19.5; IR (KBr) νmax / cm-1 3374,
3081, 2957, 2929, 2859, 1664, 1638, 1595, 1459, 1326,
1276, 1255; HRMS (MALDI) calcd.: 290.0937, found:
290.0933.
o
o
2-Hydroxy-3-(3-methylbut-1-enyl)-[1,4]naphthoquinone
(C15H14O3) (4i)
o
o
Red crystals; mp 107-110 C (lit. 118-119 C);17
1H NMR (200 MHz, CDCl3) d 8.08 (ddd, 1H, J 7.2, 1.8,
0.8 Hz), 8.01 (dd, 1H, J 7.4, 1.4 Hz), 7.77 (s, 1H), 7.70
(dt, 1H, J 7.6, 1.8 Hz), 7.62 (dt, 1H, J 7.4, 1.4 Hz), 7.02
(dd, 1H, J 16.4, 7.2 Hz), 6.57 (dd, 1H, J 16.4, 1.2 Hz),
2.51 (m, 1H), 1.09 (d, 6H, J 6.6 Hz); 13C NMR (APT)
(50 MHz, CDCl3) d 184.3, 181.3, 151.2, 150.5, 134.9,
133.0, 132.7, 129.4, 127.0, 125.9, 118.7, 115.9, 33.4,
22.2;11 IR (KBr) νmax / cm-1 3323, 2958, 2926, 2867, 1656,
1631, 1592, 1461, 1372, 1279; HRMS (MALDI) calcd.:
243.1016, found: 243.1030.
2-Cyclopent-1-enyl-3-hydroxy-[1,4]naphthoquinone
(C15H12O3) (4r)
Orange crystals; mp 111-113 oC; 1H NMR (400 MHz,
CDCl3) d 8.10 (ddd, 1H, J 7.8, 1.2, 0.8 Hz), 8.05 (ddd, 1H,
J 7.8, 1.2, 0.8 Hz), 7.73 (ddt, 1H, J 7.8, 1.6, 0.8 Hz), 7.65
(ddt, 1H, J 7.4, 1.6, 0.8 Hz), 6.53 (m, 1H), 2.85 (ddd, 1H,
J 7.4, 4.3, 2.0 Hz), 2.83 (ddd, 1H, J 7.4, 4.3, 2.0 Hz), 2.55
(ddd, 1H, J 7.0, 4.7, 2.4 Hz), 2.53 (ddd, 1H, J 7.0, 4.7,
13
2.4 Hz), 1.94 (qui, 2H, J 7.8, 7.4 Hz); C NMR (APT)
(100 MHz, CDCl3) d 184.1, 181.5, 151.7, 138.9, 134.9,
133.7, 133.2, 132.8, 129.1, 127.0, 125.8, 119.7, 35.6, 33.6,
23.4; IR (KBr) νmax / cm-1 3325, 3081, 2962, 2930, 2873,
1651, 1591, 1461, 1365, 1245; HRMS (MALDI) calcd.:
240.0781, found: 240.0780.
2-(2-Ethyl-but-1-enyl)-3-hydroxy-[1,4]naphthoquinone
(C16H16O3) (4j)
Yellow crystals; mp 99-100 oC (lit. 91-93 oC);5 1H NMR
(400 MHz, CDCl3) d 8.12 (dd, 1H, J 7.6, 1.4 Hz), 8.09 (dd,
1H, J 7.6, 1.4 Hz), 7.75 (dt, 1H, J 7.6, 1.2 Hz), 7.69 (dt,
1H, J 7.6, 1.2 Hz), 7.48 (sl, 1H), 5.90 (s, 1H), 2.30 (dq, 2H,
J 7.4, 1.4 Hz), 2.05 (q, 2H, J 7.4 Hz), 1.16 (t, 3H, J 7.4 Hz),
1.01 (t, 3H, J 7.6 Hz); 13C NMR (APT) (100 MHz, CDCl3)
d 184.7, 181.5, 153.6, 151.4, 134.9, 133.0, 132.9, 129.5,
126.9, 126.0, 121.2, 111.1, 28.9, 26.4, 12.6, 12.1; IR (KBr)
Synthesis of 10b and 11b
In a preheated flask filled with formic acid (25 mL), it
was added paraformaldehyde (1.32 g, 44.3 mmol) followed
by corresponding lapachol or norlapachol (22 mmol). The
o
reaction was heated for 2 h at 90 C, and water (50 mL)
was added and the mixture was kept under reflux for
12 h. The reaction mixture was cooled, neutralized with
Na2CO3 saturated solution and the resulting precipitate
was submitted to vacuum filtration. The compounds
were purified by column chromatography with silica
gel using mixtures of dichlorometane:hexanes and
dichloromethane:ethyl acetate with increasing polarity.
ν
max / cm-1 3439, 2965, 2935, 2876, 1663, 1643, 1593, 1459,
1332, 1273; HRMS (MALDI) calcd.: 257.1172, found:
257.1181.
2-Hydroxy-3-hexenyl-[1,4]naphthoquinone (C16H16O3) (4p)
o
o
1
Orange solid; mp 83-85 C (lit. 82-83 C);4 H NMR
(90 MHz, CDCl3) d 8.09 (dd, 1H, J 6.9, 2.2 Hz), 8.02
(dd, 1H, J 6.9, 2.2 Hz), 7.82-7.53 (m, 2H), 7.08 (dt, 1H,
J 16.4, 6.9 Hz), 6.58 (dt, 1H, J 16.1, 1.1 Hz), 2.30 (dq, 2H,
J 6.6, 1.1, 0.7 Hz), 1.64-1.18 (m, 4H), 1.00-0.84 (m, 3H,
J 6.6 Hz); 13C NMR (22.73 MHz, CDCl3) d 184.7, 181.9,
151.8, 144.6, 135.3, 133.4, 127.5, 126.4, 119.2, 35.2, 31.7,
22.9, 14.4; IR (KBr) νmax / cm-1 3449, 3268, 2959, 2927,
2858, 1654, 1632, 1608, 1593, 1458, 1371, 1265; HRMS
(MALDI) calcd.: 257.1172, found: 257.1188.
3-Hydroxymethyl-2,2-dimethyl-3,4-dihydro-2H-benzo
[h]chromene-5,6-dione (C16H16O4) (10b)
o
1
Orange crystals (51%); mp 147-150 C; H NMR
(200 MHz, CDCl3) d 7.96 (dd, 1H, J 7.6, 1.2 Hz), 7.74 (dd,
1H, J 7.6, 1.0 Hz), 7.59 (ddd, 1H, J 8, 7.6 Hz), 7.67 (dd, 1H,
J 8, 7.6 Hz), 3.82 (dd, 1H, J 11, 5.2 Hz), 3.60 (dd, 1H, J 7,
11 Hz), 3.01 (br, 1H), 2.74 (dd, 1H, J 5.6, 17.6 Hz), 2.27
(dd, 1H, J 17.6, 11 Hz), 2.01 (m, 1H, J 5.2, 5.6, 7, 11 Hz),
13
1.56 (s, 3H), 1.30 (s, 3H); C NMR (APT) (50.3 MHz,

6
Synthesis and Cytotoxicity Evaluation of a Series of 3-Alkenyl-2-Hydroxy-1,4-Naphthoquinones
J. Braz. Chem. Soc.
CDCl3) d 179.7, 178.4, 161.9, 134.8, 132.1, 130.7, 129.9,
128.4, 124.1, 112.4, 81.7, 71.0, 62.6, 27.5, 21.9, 19.6; IR
(KBr) νmax / cm-1 3072, 2982, 1737, 1695, 1607, 1572, 1457,
1392, 1293, 1232, 1132, 1092, 1034, 984, 934; HRMS
(MALDI) calcd.: 273.1121, found: 273.1119.
(s, 3H), 1.58 (s, 3H); 13C NMR (APT) (100 MHz, CDCl3)
d 180.9, 175.4, 170.5, 169.0, 134.5, 132.2, 130.9, 129.4,
127.5, 124.8, 114.3, 94.7, 61.5, 47.9, 29.6, 22.2, 20.8; IR
(KBr) νmax / cm-1 2099, 2901, 1734, 1695, 1611, 1567, 1490,
1402, 1379, 1243, 1120, 1082; HRMS (MALDI) calcd.:
301.1071, found: 301.1074.
3-Hydroxymethyl-2,2-dimethyl-2,3-dihydro-naphtho
[1,2-b]furan-4,5-dione (C15H14O4) (11b)
In vitro citotoxicity assay
o
1
Dark red crystals (76%); mp 122-124 C; H NMR
(400 MHz, CDCl3) d 8.03 (d, 1H, J 7.5 Hz), 7.66 (m, 2H),
7.58 (m, 1H), 4.03 (sl, 1H), 3.85 (dd, 1H, J 11, 8.4 Hz),
3.78 (dd, 1H, J 11, 4.3 Hz), 3.35 (dd, 1H, J 8.3, 4.6 Hz),
1.65 (s, 3H), 1.47 (s, 3H); 13C NMR (APT) (100 MHz,
CDCl3) d 181.0, 176.4, 170.5, 134.6, 132.4, 130.7, 129.2,
127.3, 124.9, 117.4, 95.4, 61.3, 52.4, 29.1, 22.2; IR (KBr)
The human lung carcinoma cell line (NCI-H292),
human larynx carcinoma cell line (HEP-2) and breast
adenocarcinoma (MCF-7) were purchased from the
Adolfo Lutz Institute, São Paulo, Brazil. A Dulbecco’s
Modified Eagle’s medium (DMEM), enriched with 10%
of fetal bovine serum, 1% of L-glutamine and 1% of
antibiotics (penicillin and streptomycin), was used for
cell cultivation and to perform the tests. The cytotoxic
activity was investigated using the 3-(4,5-dimethylthiazole-
2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.19
Cell suspensions were diluted to 105 cells mL-1, suitably
prepared and distributed in plates of culture with 96 wells
ν
max / cm-1 3362, 2968, 2926, 1645, 1591, 1456, 1376, 1343,
1275, 1213, 1163; HRMS (MALDI) calcd.: 259.0965,
found: 259.0961.
Synthesis of 10c and 11c
In a round bottom flask with 10a or 11a (200 mg), it
was added acetic anhydride (1 mL, 10.6 mmol) followed
by pyridine (1 mL, 12.4 mmol). After 2.5 h, after TLC
inspection, the product was precipitated in ice-water and
submitted to vacuum filtration and column chromatography
with silica gel using mixtures of dichlorometane:hexanes
and dichloromethane:ethyl acetate with increasing polarity.
o
(225 μL in each well), then incubated at 37 C in a
humid atmosphere with 5% of CO2. After 24 h, 25 μL of
either the synthesized compounds or the reference drugs
(doxorubicine and cisplatin) were added to each well. The
plates were incubated again at 37 oC for 72 h. Then, 25 μL
of MTT solution (5 mg mL-1) were added to each well, and
the mixture was incubated at 37 oC for 2 h. At the end of
this period, the culture medium with the MTT excess was
aspirated and after that, 100 μL of DMSO were added to
each well to dissolve the formazan crystals.20 The optical
density (OD) of the wells was measured at 540 nm and
compared to the control (cells with medium only). The
data represent the mean of two experiments in triplicate and
were expressed as means standard deviation (SD).21 The
concentration at which 50% survival of cells was observed
(IC50), the effective concentration causing 50% decrease in
cell viability (EC50) and their 95% confidence intervals were
determined from nonlinear regression using the program
SigmaPlot version 11.22
3-[(Acetyloxy)methyl]-2,2-dimethyl-3,4-dihydro-2H-benzo
[h]chromene-5,6-dione (C18H18O5) (10c)
Purified by chromatography using silica gel with
hexanes:ethyl acetate 6:4 yielding an yellow solid (54%);
mp 91-92 oC; 1H NMR (400 MHz, CDCl3) d 7.97 (dd, 1H,
J 7.8, 1.6 Hz), 7.73 (dd, 1H, J 7.8, 1.6 Hz), 7.59 (dt, 1H,
J 7.8, 1.6 Hz), 7.45 (dt, 1H, J 7.4, 1.2 Hz), 4.23 (dd, 1H,
J 11.4, 5.1 Hz), 3.88 (dd, 1H, J 11.3, 7.4 Hz), 2.74 (dd,
1H, J 17.6, 5.4 Hz), 2.28 (dd, 1H, J 17.6, 9.4 Hz), 2.15
(m, 1H), 2.02 (s, 3H), 1.54 (s, 3H), 1.32 (s, 3H); 13C NMR
(APT) (100 MHz, CDCl3) d 179.3, 178.2, 170.6, 134.7,
130.7, 129.9, 128.4, 124.0, 111.8, 80.6, 64.0, 39.2, 27.2,
21.9, 20.7, 19.8; IR (KBr) νmax / cm-1 3068, 2975, 1714,
1643, 1614, 1587, 1488, 1403, 1334, 1275, 1177, 1107,
1076; HRMS (MALDI) calcd.: 315.1227, found: 315.1229.
Results and Discussion
The preliminary data found by the present method in
the synthesis of norlapachol 4g showed a 95% yield, and
resulted in patent filing.14 In this method, benzene was
substituted by toluene, a greener and safer solvent with a
higher boiling point. As far as we know, this remarkable
result is better than any previously reported in the literature.
For example, the classic Hooker’s oxidative degradation of
natural lapachol 1 to obtain norlapachol 4g results in yields
3-[(Acetyloxy)methyl]-2,2-dimethyl-2,3-dihydro-naphtho
[1,2-b]furan-4,5-dione (C17H16O5) (11c)
Purified by recristallization from EtOH/H2O yielding
o
1
brownish crystals (86%); mp 140-141 C; H NMR
(400 MHz, CDCl3) d 8.08 (d, 1H, J 7.2 Hz), 7.61 (m,
3H), 4.51 (dd, 1H, J 11.2, 4.0 Hz), 4.24 (dd, 1H, J 11.6,
9.2 Hz), 3.49 (dd, 1H, J 9.2, 4.0 Hz), 2.04 (s, 3H), 1.59

Vol. 00, No. 00, 2018
David et al.
7
around 50%.16 Initially, we planned to use the inexpensive
n-butyraldehyde as a model to observe the importance of
some reaction conditions employed in original Kopanski
methodology (Table 3), in particular the proportion of
acetic acid/β-alanine catalyst, the amount of aldehyde, the
substitution of acetic acid by p-TsOH, and the substitution
of β-alanine by triethylamine or L-proline (Table 3).
also unsuccesful. The reaction seems to be sensitive to the
amount of acid and β-alanine, however, all the reactions
with excess acid catalysis results in the formation of the
bis-adduct dimer of lawsone, a polar product visible by
TLC inspection that was studied in a previous article
by our group.23 We chose to compare this modification
of the original Kopanski procedure (named method A,
entry 3), with this new method B (entry 9, Table 3) in a
series of experiments conducted to verify the scope of the
method with a range of suitable aldehydes. These results
are shown in Table 4, and we planned to submit initially
the available propionaldehyde (3a), n-butyraldehyde
(3b), n-valeraldehyde (3c), phenylacetaldehyde
(3e), n-hexanaldehyde (3p), isobutyraldehyde (3g),
isovaleraldehyde (3i) and 2-ethylbutyraldehyde (3j) to
condense with lawsone (2) using both conditions A and
B that differ only by B using twice the amount of catalyst
that A uses (Table 4). The best yields were obtained in
either method for the more substituted alkyl, specially
those with an extra alkyl at alpha position (see entries
6-8). This should reflect an easier elimination step at the
formation of a more stable substituted double bond. This
effect could be extended to the stabilization of the double
bond by conjugation with a phenyl group (entry 4). The
use of twice the amount of catalyst in method B should
give better and more consistent yields without exceptions.
Table 3. Variation in conditions for the condensation of lawsone 2 with
n-butyraldehyde
entry
1
AcOH / mmol
β-Alanine / mmol
Yielda / %
0
0.25
–
–
2
0.28
0.28
0.28
0.56
0.28
0.56
1.12
1.12
0.56
0.56
0.56
–
23
3
0.25
0.50
0.25
0.25
0.50
1.00
0.50
1.00
–
64
4
62
5
57
6
35b
81
7
8
50
9
49
Table 4. Knoevenagel condensation reaction conditions and yields using
methods A and B with suitable aldehydes
10
11
12
13
67
22c
28d
32e
–
0.50
aIsolated yield after chromatographic column; b4 mmol of n-butyraldehyde;
c0.5 mmol N(Et)3; d0.5 mmol p-TsOH; e0.56 mmol L-proline.All reactions
performed in 1 h reflux, using 40 mL of toluene in a Dean-Stark apparatus,
and 2 mmol of n-butyraldehyde.
Yielda of 4 / %
From the data of Table 3, we conclude that the acetic
acid or β-alanine alone were not effective as catalysts
(entries 1 and 2), but the use of the mixture (entry 3) results
in a good yield of 64%. Increase of acid alone or β-alanine,
however (entries 4 and 5, respectively), did not contribute
to further increase the observed yields.An increase of two-
fold in the aldehyde drops the yield (entry 6), probably
caused by competition for self-condensation; however, the
increase of catalyst in a 4:1:1 proportion of aldehyde:acetic
acid:β-alanine results in the best yield of 81% (entry 7).
Increasing two-fold the proportion of either catalyst or both
(entries 8, 9 and 10) drops the observed yield. Changing
the acetic acid by triethylamine or p-toluenesulfonic
acid (entries 11 and 12) also drops the yield. The use of
a known condensation catalyst L-proline (entry 13) was
entry
3
R
R1
Method Ab Method Bb
1
a
b
c
e
f
H
CH3
CH2CH3
CH2CH2CH3
Ph
15
64
41
83
–
17
81
70
95
47
85
86
96
76
85
36
2
H
3
H
4
H
5
H
CH2Ph
6
g
i
CH3
CH3
95
90
74
47
–
7
H
CH2CH3
H
CH(CH3)2
CH2CH3
CH2(CH2)2CH3
Ph
8
j
9
p
q
r
10
11
CH3
cyclopentanone
–
aYields after column chromatography; bsee Experimental section.

8
Synthesis and Cytotoxicity Evaluation of a Series of 3-Alkenyl-2-Hydroxy-1,4-Naphthoquinones
J. Braz. Chem. Soc.
At a glance we could see that method B was generally
in the condensation of the alkene quinone side chain
and the formaldehyde by a Prins reaction,28,29 followed
by in situ cyclization, in 76 and 51% yield, respectively.
The corresponding acetates 10c and 11c were obtained
by straightforward acetylation procedure in 86 and 54%
yield, respectively.
Concerning the biological activity, the title compounds
4e, 4i, 4j, and 4p were previously tested together
for antifungal activity,30 4g and 4i for molluscicidal
activity,31,32 4g for antimycobacterial activity,33 4b, 4g and
4i for trypanocidal activity,34 4g and 4i for leishmanicial
activity,35,36 and 4e was evaluated for cytotoxicity,37
antifungal30 and anticancer activities.24 Although the
majority of the title compounds were known and tested
elsewhere, they were all tested together in the present study
for cytotoxic screening against tumor cell lines HEP-2,
MCF-7 and NCI-H292 (Table 5).
Concerning the inhibition of growth of HEP-2 tumor
cells, the compounds alkenyl-1,4-naphthoquinone series
4b, 4c, 4i, 4j, 4p and 4q showed the highest percentuals of
inhibition, superior to those from lapachol 1 and reference
compound doxorubicin (Table 5). Compound 4c showed
a higher percentual of inhibition (95.6%) against (HEP-2)
cell lines when compared to 4j with 94.1%, 4p with 94%,
4b with 93.5%, 4i with 93% and 4q with 91.2%. In this
series the norlapachol 4g showed the lowest inhibition
percentual (27.3%) (Table 5). Concerning the MCF-7cell
line tested the only compound with high activity was
4j with 77.9% inhibition, showing a better profile than
the isomer with a linear alkyl side chain 4p with 53.6%
inibition (Table 5). Notably, in these experimental trials
the compound norlapachol 4g did not inhibit the growth
of MCF-7 cells or of NCI-H292. In NCI-H292, the highest
inhibition for the alkenyl-1,4-naphthoquinones 4 were 85.9,
85.7 and 85.3% for compounds 4i, 4j and 4r, respectively
(Table 5). The presence of an additional phenyl ring in
compounds 4e, 4f and 4q did not improve the biological
profile. From the data on Table 5 we could see that the series
of alkenyl-1,4-naphthoquinones 4 showed a remarkable
selectivity to the larynx tumor cell lines, when compared
to other tumor cell lines.
better than the previous one, varying from an excelent
yield of 95 and 96% for phenylaceltadehyde (3e) and
2-ethylbutyraldehyde (3j) (entries 4 and 8), respectively,
to good yields (85, 86 and 85%) for isobutyraldehyde
(3g), isovaleraldehyde (3i) and 2-phenyl-propionaldehyde
(3q) (entries 6, 7 and 10), respectively. Linear alkyl
aldehydes are also otained in good yields of 70 and 76%,
respectively, for n-valeraldehyde (3c) and n-hexanaldehyde
(3p) (entries 3 and 9), representing better yields than those
afforded using method A. The 3-phenyl-propionaldehyde
(3f) and even the cyclopentanone (3r) furnish modest
yields of 47 and 36% (entries 5 and 11, Table 4),
respectively, using method B. These last two precursors
and 2-phenyl-propionaldehyde (3q) did not react (entries 5,
10 and 11) at the conditions used in method A by TLC
inspection. However, the method did not improve the yield
of propionaldehyde (3a), entry 1. With the aid of some
minor condition modifications, as the use of β-alanine
alone as catalyst with 2 h reaction time, we are able to
improve almost twice the yield of 3a to 31%. We believe
that the extremely low boiling point of propionaldehyde
could explain the observed low yield. The compound
2-phenyl-propionaldehyde (3q) was only recently described
and synthesized by the aid of a Pd-catalyzed hydroxy-
involved enolate-type reaction with lawsone and suitable
alkenes. Previously, this type of functionalization of a
2-hydroxy-naphthoquinone used labor-intensive alkylation
conditions24 or phenyliodonium ylides BF3 catalyzed
cross coupling.25 Although Knoevenagel condensations
with acyclic or cyclic ketones as enolates are common,26
it is noteworthy that in our report the cyclopentanone
yielding compound 4r was used almost always as an
electrophile,27 and as far as we know, this compound is
new. The similar reaction with cyclohexanone gives no
results with the sort of different modifications described
before in this work.
The synthesis of the furan (10b) and pyran (11b)
3-hydroxymethyl-1,4-naphthoquinones were performed
by the reaction of lapachol 1 or norlapachol 4g with
paraformaldehyde in formic acid (Scheme 3), resulting
Scheme 3. The synthesis of the furan (10b) and pyran 3-hydroxymethyl-1,4-naphthoquinones (11b) and corresponding acetates 10c and 11c from
lapachol (1) and norlapachol 4g.

Vol. 00, No. 00, 2018
David et al.
9
Table 5. Cell growth inhibition percentual of the 3-alkenyl-2-hydroxy-
1,4-naphthoquinones (4) and cyclic derivatives 10a-c and 11a-c at
25 μg mL-1 in the three tumor cell lines
for 10c in HEP-2 cell lines to 92.7% for 11c in NCI-H292
cell lines. The acetylation of the hydroxymethyl groups
enhances the observed activities in all tested cell lines,
either in pyran 10b or furan 11b series (Table 5).
Compound
HEP-2a / %
86.6 3.5
90.8 2.8
62.8 5.2
93.5 0.1
95.6 1.5
84.5 1.5
85.0 1.4
27.3 1.8
93.0 0.5
94.1 0.0
94.0 2.0
91.2 0.5
86.8 0.1
96.0 1.1
97.6 0.8
99.0 0.8
98.8 0.2
97.4 0.9
94.4 3.8
MCF-7a / %
59.5 1.7
50.8 4.5
55.2 7.3
26.1 1.9
46.3 1.4
57.5 1.8
58.9 1.0
0.0 0.0
NCI-H292a / %
92.9 1.5
59.8 4.2
26.2 5.3
79.8 1.7
81.7 3.4
80.6 0.8
78.7 1.9
0.0 0.0
In order to determine the half maximal inhibitory
concentration (IC50) values (μM) displayed in Table 6, we
decided to adopt a threshold for using only compounds
with at least 75% inhibition in all cell lines tested (at
25 mg mL-1 concentration). Thus, compounds 4j, 10a-c
and 11a-c are those satisfying this criterion as can be
observed from the data in Table 5. The 3-alkenyl-2-hydroxy-
1,4-naphthoquinone compound 4j was shown to be the least
cytotoxic for all tested cell lines (Table 6). For the MCF-7
tumor cell line, compounds 11a-c were more active than
10a-c, β-nor-lapachone (11a) being more cytotoxic than 11b,
11c, and even more cytotoxic than the positive control. All
tested cyclized compounds showed a remarkable citotoxic
profile against the breast MCF-7 tumor cell line, ranging
from 0.10 μM for 11a to 5.51 μM for 10b. Also in this
tumor cell line, the hydroxymethyl 10b/11b and acetate
derivatives 10c/11c resulted in decreased cytotoxicity
when compared to the parent compounds β-lapachone (10)
and β-nor-lapachone (11), although 10c did not result in
changes to the observed activity (Table 6). The tumor cell
lines NCI-H292 and HEP-2 showed more sensitivity to the
acetylated derivative 10c, with IC50 of 2.26 and 6.81 μM,
respectively, and also for the less active 11c, with IC50 values
of 11.13 and 13.6 μM, respectively. In general, the tested
compounds showed remarkable and consistent citotoxicity
in tested cancer cell lines, although the compounds presented
high inhibitory effect in the growth of Buffalo green monkey
kidney (BGMK) cells used to access the selectivity, which
means a non-selective effect and high cytoxicity for the
Doxorubicin
1
4a
4b
4c
4e
4f
4g
4i
5.1 1.4
85.9 0.3
85.7 2.3
83.3 0.3
63.3 1.4
85.3 1.2
95.0 2.9
98.2 1.3
96.8 2.3
97.6 0.0
97.7 1.8
92.7 1.7
4j
77.9 3.5
53.6 5.7
50.8 0.9
41.6 3.4
96.9 0.3
98.5 0.0
98.4 0.4
98.7 0.5
94.7 5.5
96.1 0.1
4p
4q
4r
10a
10b
10c
11a
11b
11c
aInhibitory concentration percentage (IC%) standard deviation. HEP-2:
human larynx carcinoma cell line; MCF-7: breast adenocarcinoma cell
line; NCI-H292: human lung carcinoma cell line.
A very different scenario is obtained when the cyclized
derivatives 10a-c and 11a-c were compared with the open
chain alkenyl 1,4-naphthoquinones 4, with all compounds
showing excellent profiles of inhibition, ranging from 99%
Table 6. Cytotoxic activity expressed as IC50 of compounds 4j, 10a-c and 11a-c against tumor cell lines
Cell line IC50 / μM
Compound
MCF-7
18.75 (16.01-22.26)
2.72 (2.02-3.71)
5.51 (4.81-6.47)
2.73 (2.61-2.83)
0.10 (0.07-0.15)
0.46 (0.38-0.62)
0.60 (0.5-0.7)
0.36 (0.18-0.44)
ND
NCI-H292
15.62 (12.5-20.31)
17.68 (12.56-24.87)
14.48 (9.70-21.54)
2.26 (5.95-7.13)
12.28 (10.70-14.07)
11.27 (9.37-13.56)
11.13 (10.03-12.36)
0.36 (0.18-0.92)
ND
HEP-2
BGMK
4j
ND
ND
10a
11.69 (9.33-14.62)
14.63 (12.20-17.57)
6.81 (5.89-7.86)
10.74 (10.04-11.53)
13.25 (9.72-18.06)
13.60 (11.63-15.93)
1.28 (0.55-2.57)
ND
8.26 (7.35-9.54)
4.55 (3.12-6.65)
6.21 (4.84-7.92)
4.78 (3.33-6.92)
9.18 (4.76-17.59)
5.83 (5.3-6.4)
> 46.04
10b
10c
11a
11b
11c
Doxorubicin
Cisplatin
8.10 (6.26-10.43)
Data are presented as half maximal inhibitory concentration (IC50) values and 95% confidence intervals obtained by nonlinear regression for all cell lines.
Doxorubicin was used as positive control. Only compounds with an IC50 value lower than 5 μg mL-1 for at least one cell line were considered active.
MCF-7: breast adenocarcinoma cell line; NCI-H292: human lung carcinoma cell line; HEP-2: human larynx carcinoma cell line; BGMK: Buffalo green
monkey kidney cell line; ND: not determined.

10
Synthesis and Cytotoxicity Evaluation of a Series of 3-Alkenyl-2-Hydroxy-1,4-Naphthoquinones
J. Braz. Chem. Soc.
series tested, except for the series of cyclic furan-1,4-
naphthoquinone and 3-hydroxymethyl derivatives 11a-c,
which showed a good selectivity index for MCF-7.
3. Brandão, G. C.; Missias, F. C. R.; Arantes, L. M.; Soares, L.
F.; Roy, K. K.; Doerksen, R. J.; de Oliveira, A. B.; Pereira, G.
R.; Eur. J. Med. Chem. 2018, 145, 191.
4. Hooker, S. C.; J. Am. Chem. Soc. 1936, 58, 1163.
5. Bock, K.; Jacobsen, N.; Terem, B.; J. Chem. Soc., Perkin Trans.
1 1986, 659.
Conclusions
In this work a very efficient Knoevenagel procedure
was presented for the obtention of 2-hydroxy-3-alkenyl-
1,4-naphthoquinones (4) from lawsone (2) and suitable
aldehydes, using β-alanine and acetic acid as catalysts.
The method runs with overall good yields in a systematic
fashion. Some of the parameters briefly studied here could
be easily altered resulting in improved reaction yields,
especially when using non-linear chain aldehydes. We
also presented the synthesis of a series of furan and pyran-
derived hydroxymethyl-1,4-naphthoquinones obtained
by an acid catalyzed Prins cyclization of lapachol and
norlapachol and corresponding acetyl derivatives. The
2-hydroxy-3-alkenyl-1,4-naphthoquinone (4) series was in
general less cytotoxic than the cyclized furan- and pyran-
naphthoquinones 10/11. The β-nor-lapachone (11a) was
the most active compound in the MCF-7 tumor cell line. In
general, the furan- (β-nor-lapachone) (11) derivatives were
more active than pyran-β-lapachone (10), and the presence
of the hydroxyl and acetate groups decreased the cytotoxicity
of β-lapachone and β-nor-lapachone.Also the 2-(2-ethyl-but-
1-enyl)-3-hydroxy-[1,4]naphthoquinone (4j) was shown to
be the less cytotoxic for all tumor cell lines tested.
6. Ferreira, V. F.; Coutada, L. C.; Pinto, M. C. F. R.; Pinto, A. V.;
Synth. Commun. 1982, 12, 195.
7. Kopanski, L.; Karbach, D.; Selbitschka, G.; Steglich, W.; Liebigs
Ann. Chem. 1987, 793.
8. Gilles, R. G. F.; Roos, G. H. P.; Tetrahedron Lett. 1975, 47,
4159.
9. Ameer, F.; Giles, R. G. F.; Green, I. R.; Pearce, R.; Synth.
Commun. 2004, 34, 1247.
10. Lee, Y. R.; Choi, J. H.; Trinh, D. T. L.; Kim, N. W.; Synthesis
2005, 18, 3026.
11. Anufriev, V. F.; Chizhova, A.Y.; Denisenko, V. A.; Novikov, V.
L.; Russ. J. Org. Chem. 1993, 29, 1671.
12. Glazunov, V. P.; Berdyshev, D. V.; Yakubovskaya, A. Y.;
Porkhilo, N. D.; Russ. J. Org. Chem. 2006, 55, 1729.
13. Nagabhushana, K.; Ameer, F.; Green, I. R.; Synth. Commun.
2001, 31, 719.
14. Pinheiro, S. M.; Silva, T. M. S.; Camara, C. A.; Br PI 10 2012
019793-6 A2 2015.
15. Silva Jr., E. N.; Souza, M. C.; Pinto, A. V.; Pinto, M. C.;
Goulart, M. O.; Barros, F. W.; Pessoa, C.; Costa-Lotufo. L. V.;
Montenegro, R. C.; Moraes, M. O.; Ferreira,V. F.; Bioorg. Med.
Chem. 2007, 15, 7035.
16. Fieser, L. F.; Fieser, M.; J. Am. Chem. Soc. 1948, 70, 3215.
17. Oliveira, A. B.; Raslan, D. S.; Khuong-Huu, F.; Tetrahedron
Lett. 1990, 31, 6873.
Supplementary Information
Supplementary information is available free of charge
at http://jbcs.sbq.org.br as PDF file.
18. Wang, N.; Wu, X.; Qin, T.; Zhou, J.; You, Q.; Zhang, X.; RSC
Adv. 2016, 6, 104126.
19. Alley, M. C.; Scudiero, D. A.; Monsk, A.; Hursey, M. I.;
Czerwinski, M. J.; Fine, D. L.; Abbott, B. J.; Mayo, J. G.;
Shoemaker, R. H.; Boyd, M. R.; Cancer Res. 1988, 48, 589.
20. Mosmann, T.; J. Immunol. Methods 1983, 16, 55.
21. Berridge, M. V.; Tan, A. S.; McCoy, K. D.; Wang, R.;
Biochemica 1996, 4, 14.
Acknowledgments
The authors thank CAPES, CNPq and FACEPE
(PRONEMAPQ 0741.11.06/14) for financial support, and
the Central Analítica of DQF-UFPE and CENAPESQ-
UFRPE for the use of facilities. C. A. C. thanks Eduardo
J. Oliveira (UFVJM) for useful suggestions.
22. Systat Software; SigmaPlot version 11; Systat Software, San
Jose, CA, USA, 2008.
23. Araújo, M. V.; Souza, P. S. O.; Queiroz, A. C.; Matta, C. B.
B.; Leite, A. B.; Silva, A. E.; França, J. A. A.; Silva, T. M. S.;
Camara, C.A.;Alexandre-Moreira, M. S.; Molecules 2014, 19,
15180.
References
1. Gomes, S. L. S.; Militão, G. C. G.; Costa, A. M.; Pessoa, C. O.;
Costa-Lotufo, L. V.; Cunha-Junior, E. F.; Torres-Santos, E. C.;
Costa, P. R. R.; da Silva, A. J. M.; J. Braz. Chem. Soc. 2017,
28, 1573.
24. Fiorito, S.; Epifano, F.; Bruyere, C.; Mathieu, V.; Kiss, R.;
Genovese, S.; Bioorg. Med. Chem. Lett. 2014, 24, 454.
25. Malamidou-Xenikaki, E.; Tsanakopoulou, M.; Chatzistefanou,
M.; Litina, D. H.; Tetrahedron 2015, 71, 5650.
26. Chinchkar, S. M.; Patil, J. D.: Korade, S. N.; Gokavi, G. S.;
Shejawal, R. V.; Pore, D. M.; Lett. Org. Chem. 2017, 14, 403.
2. de Oliveira, R. N.; da Silva, M. G.; da Silva, M. T.; Melo, V.
N.;Valença, W. O.; da Paz, J.A.; Camara, C.A.; J. Braz. Chem.
Soc. 2017, 28, 681.

Vol. 00, No. 00, 2018
David et al.
11
27. Ce, S.; Zhen-Chu, C.; Qin-Guo, Z.; Synthesis 2003, 555.
34. Souza, N. B.;Andrade, I. M.; Carneiro, P. F.; Jardim, G. A. M.;
Melo, I. M. M.; Silva, E. N.; Krettli,A. U.; Mem. Inst. Oswaldo
Cruz 2014, 109, 546.
28. Camara, C. A.; Pinto, A. C.; Vargas, M. D.; Zukerman-
Schpector, J.; Tetrahedron 2002, 58, 6135.
29. Barbosa, T. P.; Camara, C. A.; Silva, T. M. S.; Martins, R. M.;
Pinto, A. C.; Vargas, M. D.; Biorg. Med. Chem. Lett. 2005, 13,
6464.
35. Guimarães, T. T.; Pinto, M. C. F. R.; Lanza, J. S.; Melo, M. N.;
Monte-Neto, R. L.; Melo, I. M. M.; Diogo, E. B. T.; Ferreira,
V. F.; Camara, C. A.; Valença, W. O.; Oliveira, R. N.; Frézard,
F.; Silva Jr., E. N.; Eur. J. Med. Chem. 2013, 63, 523.
36. Lima, N. M. F.; Correia, C. S.; Leon, L. L.; Machado, G. M.
C.; Madeira, M. F.; Santana, A. E. G.; Goulart, M. O. F.; Mem.
Inst. Oswaldo Cruz 2004, 99, 757.
30. Jacobsen, N.; Wengel, A.; Pestic. Sci. 1986, 17, 686.
31. Santos, A. F.; Ferraz, P. A. L.; Pinto, A. V.; Pinto, M. C. F. R.;
Goulart, M. O. F.; Sant’Ana, A. E. G.; Int. J. Parasitol. 2000,
30, 1199.
32. Lima, N. M. F.; Santos, A. F.; Porfírio, Z.; Goulart, A. O. F.;
Sant’Ana, A. E. G.; Acta Trop. 2002, 83, 43.
37. Cushion, M. T.; Chen, F.; Kloepfer, N.; Antimicrob. Agents
Chemother. 1997, 41, 379.
33. Carneiro, P. F.; Pinto, M. C. F. R.; Coelho, T. S.; Cavalcanti, B.
C.; Pessoa, C.; de Simone, C. A.; Nunes, I. K. C.; de Oliveira,
N. M.; de Almeida, R. G.; Pinto, A. V.; de Moura, K. C. G.; da
Silva, P. A.; da Silva Jr., E. N.; Eur. J. Med. Chem. 2011, 46,
4521.
Submitted: April 14, 2018
Published online: July 31, 2018
This is an open-access article distributed under the terms of the Creative Commons Attribution License.