Synthesis and trypanocidal activity of 1,4-bis-(3,4,5-trimethoxy-phenyl)-1,4-butanediol and 1,4-bis-(3,4-dimethoxyphenyl)-1,4-butanediol

Article abstract of DOI:10.1016/j.bmc.2006.07.006

Chagas' disease is endemic in Central and South American countries. Specific chemotherapy with nifurtimox or benznidazole has been recommended for treatment of recent infection but they have limited efficacy. The natural products veraguensin (1) and grand

Full text of DOI:10.1016/j.bmc.2006.07.006

Bioorganic & Medicinal Chemistry 14 (2006) 7075–7082
Synthesis and trypanocidal activity of
1,4-bis-(3,4,5-trimethoxy-phenyl)-1,4-butanediol and
1,4-bis-(3,4-dimethoxyphenyl)-1,4-butanediol
Lilian Sibelle Campos Bernardes,a Massuo Jorge Kato,b
a
,a
*
´
Sergio Albuquerque and Ivone Carvalho
a
ˆ ˆ
´
Faculdade de Ciencias Farmaceuticas de Ribeira˜o Preto, Universidade de Sa˜o Paulo, Av. do Cafe,
s/n, 14040-903 Ribeira˜o Preto-SP, Brazil
bInstituto de Quı´mica, Universidade de Sa˜o Paulo, Av. Lineu Prestes, 748, 05508-900 Sa˜o Paulo-SP, Brazil
Received 12 May 2006; revised 23 June 2006; accepted 1 July 2006
Abstract—Chagas’ disease is endemic in Central and South American countries. Specific chemotherapy with nifurtimox or benzni-
dazole has been recommended for treatment of recent infection but they have limited efficacy. The natural products veraguensin (1)
and grandisin (2) have shown potent in vitro activity against trypomastigote parasite (Y strain) with IC50 2.3 lM (1) and 3.7 lM (2).
We report herein the synthesis and in vitro trypanocidal evaluation of symmetrical and unsymmetrical 1,4-diaryl-1,4-diol derivatives
as potential trypanocidal analogs of natural compounds 1 and 2. Among the synthesized products, compounds 1,4-bis-(3,4,5-tri-
methoxyphenyl)-1,4-butanediol (6a) and 1,4-bis-(3,4-dimethoxyphenyl)-1,4-butanediol (6b) showed better activity against Trypano-
soma cruzi trypomastigotes with IC50 100 and 105 lM (Y strain), respectively, and 110 lM (Bolivia strain) for both compounds.
However, the most active compound of this series was 1,4-bis-(3,4-dimethoxyphenyl)butane-1,4-dione (7b) with IC50 10 and
200 lM against Y and Bolivia strains, respectively.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
give sequentially superoxide, hydrogen peroxide, and
hydroxyl radical. These oxygen species are responsible
for damaging parasite cellular components.6 A further
drawback of this therapy involves the drug resistance
and different strains’ susceptibility.
Trypanosoma cruzi is the etiological agent of Chagas’ dis-
ease, a debilitating condition that affects 18–20 million
people in Central and South American countries and
2–3 million have shown clinical symptoms of which
3000 evolve to deaths.1,2 Although various attempts of
treatment had been performed since its discovery, a com-
pletely efficient drug has not been found.3 The currently
available drugs, nifurtimox (4-(5-nitrofurfurylindenami-
no)-3-methylthiomorpholine-1,1-dioxide) (Lampitꢁ, dis-
continued by Bayer) and benznidazole (N-benzyl-2-(2-
nitro-1H-imidazol-1-yl)acetamide) (Rochagan, Roche),
have shown limited efficacy, strong side-effects, and low
effectiveness.4,5 Their high toxicity may involve the
generation of nitroanion radical from reduction of
nitroheteroaryl drugs that further react with oxygen and
Despite being widely transmitted by triatomine insects,
the blood transfusion is a relevant mechanism of the
disease infection and gentian violet (N-[4-bis[[4-(dimeth-
ylamino)-phenyl]methylene]-2,5-cyclohexadien-1-ylidene]
N-methylammonium chloride) has been used as a chemo-
prophylactic agent in blood banks of endemic areas.7
The comparative studies of genomes of T. cruzi are
promising since they can identify characteristics that dis-
tinguish pathogen and host, providing information
about parasite-specific targets for drug discovery.8
Comprising the predicted 22,570 proteins encoded by
genes, the T. cruzi genome sequence was recently
deposited in GenBank/EMBL/DDBJ and it has been
explored to discover new targets.9 The elucidation of
biochemical processes of this protozoan parasite has
led to the identification of very promising targets for
Keywords: 1,4-Diaryl-1,4-diol; 1,4-Diaryl-1,4-diketones; 1,4-Diaryl-
acetylenic-1,4-glycol; Chagas’ disease; Trypanosoma cruzi.
*
Corresponding author. Tel.: +55 16 3602 4709; fax: +55 16 3602
4879; e-mail: carronal@usp.br
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.07.006

7076
L. S. C. Bernardes et al. / Bioorg. Med. Chem. 14 (2006) 7075–7082
the chemotherapy of Chagas’ disease, as exemplified by
trypanothione reductase,10 glutathionyl spermidine syn-
thase,11 dihydroorotate dehydrogenase,12 farnesyl
diphosphate synthase,13 squalene synthase,11 glyceralde-
hyde-3-phosphate dehydrogenase,14 iron superoxide dis-
mutase,15 proline racemase, hexokinase,16 dihydrofolate
reductase,17 prenyltransferases, ornithine decarboxylase,
cysteine, serine, threonine, and metallo proteinases,18
trans-sialidases,19–21 glucose-6-phosphate isomerase,22
DNA topoisomerase,23 hypoxanthine-phosphoribosyl-
transferase, C14D24,25-esterol methyltransferase,24 etc.
Platelet-activating factor-like activity was recently iso-
lated from lipid extract of T. cruzi epimastigotes and
its activity was related to modulation of cell differentia-
tion toward the infectious stage.25 Even though the
mechanisms underlying the differentiation and prolifera-
tion of the parasite are still under investigation, Urbina
et al., 1993, showed that platelet-activating factor (PAF)
antagonist can inhibit the proliferation of both epimas-
tigote and amastigote forms of T. cruzi probably involv-
ing alterations in phospholipids’ composition.
water solubility and biological activity.31 Compounds
4 and 5 are promising derivatives synthesized so far as
they presented IC50 51.2 and 1.5 lM, respectively. Here-
by, we describe our results on the synthesis and in vitro
trypanocidal evaluation of symmetrical and unsymmet-
rical 1,4-diaryl-1,4-diol derivatives, which were designed
by molecular simplification of the lead compounds 1–3
containing a nonrigid scaffold. This synthetic strategy
also allows the use of products and intermediates in
the synthesis of constrained derivatives, such as furan,
pyrroles, thiophenes, and pyrrolidines.
OH
OH
H3CO
H3CO
OCH3
OBn
H3CO
H3CO
OCH3
OBn
O
O
OCH3
OCH3
OCH3
OCH3
4
5
2. Results and discussion
The synthesis of 1,4-bis-(3,4,5-trimethoxyphenyl)-1,4-
butanediol (6a) and 1,4-bis-(3,4-dimethoxyphenyl)-1,4-
butanediol (6b) hinges on either 1,4-diaryl-1,4-diketones
7a and 7b or 1,4-diarylacetylenic-1,4-glycols 8a and 8b
formation, respectively, accessible from the corresponding
a,b-unsaturated arylketone32–34 and modified arylalde-
hyde or arylaldehyde and arylacetylenic derivatives,35,36
followed by reduction of carbonyl or acetylenic groups,
respectively.
The screening of potential trypanocidal compounds
from plant extracts and natural products has provided
a diverse class of compounds illustrated by naphthoqui-
nones, terpenoids, isoflavonoids, and alkaloids, which
may interfere with the redox equilibrium and cause oxi-
dative stress.23,26,27
The Brazilian plants Virola surinamensis and Piper
solmsianum from Amazon and Atlantica Forests,
respectively, have proved to be a rich source of tetra-
hydrofuran neolignans such as veraguensin 2,5-bis(3,4-
dimethoxyphenyl)tetrahydro-3,4-dimethylfuran (1) and
Preparations of 7a and 7b were attempted under var-
ious reaction conditions with sodium cyanide or 3-eth-
yl-5-(2-hydroxyethyl)-4-methylthiazolium bromide (ETB)
to promote the Michael conjugate addition of substi-
tuted aldehydes (9a–e) to a,b-unsaturated arylketones
(10a,b, Stetter reaction).33,37,38 Using the former ap-
proach, we were unsuccessful in attempts to accom-
plish this reaction under a variety of conditions. On
the other hand, condensation was achieved using
ETB to generate the intermediate carbanion in the
presence of triethylamine, as outlined in Scheme 1.
The reaction was performed with different solvents,
such as dioxane/EtOH, DMF/EtOH, and EtOH, that
afforded compound 7a in 21%, 12%, and 10% yields,
respectively, whereas for compound 7c the best yield
was 38% in a mixture of DMF/EtOH. Although the
yields were not high, the targets diaryl-1,4 dicarbonyl
7a–e were directly accessed from readily available
starting materials under relatively mild conditions.
The problems faced in this reaction may be due to
the reduced reactivity of the aldehydes 9a and 9b
grandisin
2,5-bis(3,4,5-trimethoxyphenyl)tetrahydro-
3,4-dimethylfuran (2), which show potent in vitro
activity against trypomastigote parasite.28 Based on
experiments involving the Y strain of T. cruzi, com-
pounds 1 and 2 were able to produce lysis of parasites
with IC50 2.3 and 3.7 lM, respectively, while gentian
violet showed a value of IC50 31 lM. Although the
compounds are very effective, their high lipophilicity
is a serious limitation to carry on in vivo assays.
Furthermore, compound 1 is a competitive PAF-re-
ceptor antagonist in experiments performed with
PAF isolated from human and rabbit platelets
(IC50 1.1 lM).29 This result was further investigated
by Hwang et al., 1985, to synthesize new derivatives
with the diaryl-tetrahydrofuran analogues without
the methyl substituents. From this series, compound
3 exhibited a potent and orally active platelet-activat-
ing factor (PAF)-specific and competitive receptor
antagonist (IC50 20.0 nM).30
H3CO
H3CO
OCH3
OCH3
H3CO
H3CO
OCH3
OCH3
O
O
O
H3CO
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
1
2
3
We have been interested in the synthesis of analogues of
natural products 1 and 2, containing appropriate chem-
ical modifications to afford products with improved
due to the donor effect of the OMe group at para-
position of the ring. Indeed, several works that had
been reported32,34,39,40 focus on reactions that have

L. S. C. Bernardes et al. / Bioorg. Med. Chem. 14 (2006) 7075–7082
7077
R2
R2
R3
R4
R3
O
OH
O
CHO
R2
R3
R1
R1
R1
NaBH4
ETB
Et3N
R4
+
OH
O
H3CO
H3CO
H3CO
R4
OCH3
OCH3
OCH3
10a: R1=OCH3
10b: R1=H
6a: R1=R2=R3=R4=OCH3
6b: R1=R2=H ,R3=R4=OCH3
7a: R1=R2=R3=R4=OCH3
7b: R1=R2=H ,R3=R4=OCH3
7c: R1=R2=R4=H ,R3=OH
9a: R2=R3=R4=OCH3
9b: R2=H ,R3=R4=OCH3
9c: R2=R4=H ,R3=OH
7d: R1=R2=H ,R3=O H, R4=OCH3
7e: R1=R2=R4=O CH3,R3=OBn
9d: R2=H ,R3= OH, R4=OCH3
9e: R2=H ,R3=O Bn,R4=OCH3
Scheme 1. Conjugate addition of modified aldehydes 9a–e to a,b-unsaturated arylketones 10a,b, mediated by ETB with triethylamine as a catalyst to
give diaryl-1,4 dicarbonyl 7a–e, followed by reduction.
halogens (iodine or bromine) incorporated at meta-posi-
tion to deactivate the carbonyl group of the arylaldehyde
and facilitate the addition of cyanide or thiazolium ions.
The 1H and 13C NMR spectral data of all products were
in accordance with the structure, showing for compound
7a a chemical shift at d 7.24, for ortho-aromatic hydro-
gens, d 3.86 and 3.87 for methoxyl groups, and d 3.37
related to a-carbonyl methylene group.
required starting a,b-unsaturated arylketones 10a and
10b were easily obtained from b-amino-arylcarbonyl
derivatives, which in turn involve the classical Mannich
reaction,34 we investigated, therefore, a direct approach
using the readily available reagents 12a and 12b,
Scheme 2. Thus, treatment of benzaldehyde 13 with
sodium cyanide, followed by 12a or 12b, gave the dike-
tones 14a and 14b with 36 and 48% yield, respectively,
1
whose H NMR data showed the same chemical shift
The diketones 7a and 7b were reduced with sodium
borohydride to give the corresponding diols 6a and 6b
with 38 and 45% yields, respectively. The 1H NMR
showed two sets of nonequivalent hydrogens for both
compound 6a (d 1.90–1.70 for the methylene group
and d 4.64–4.54 for methyne carbinols) and compound
6b (d 2.00–1.90 and 2.40–2.30 for the methylene group,
and d 5.13 and 4.94 for methyne carbinols), indicating
the presence of diastereomeric isomers rather than the
symmetrical meso structure. It could be argued that an
intramolecular hydride transfer from an alkoxymetal
hydride intermediate to the remaining carbonyl group
may give a preferential trans-diol relationship.41
for methylene groups at d 3.45. Comparatively, the
similar procedure attempting to convert compounds
9a and 9b or even p-hydroxybenzaldehyde into diaryl
diketones was unsuccessful, as expected. Reduction of
compounds 14a,b afforded 1,4-diaryl-1,4-diols 15a,b.
The required intermediates 8a and 8b were obtained by
condensation of arylaldehydes with acetylide anion
derived from either lithium acetylide complexed with
ethylenediamine, lithium or magnesium acetylides.35,36
In this approach, we intended to use stronger nucleo-
philes such as acetylide anions to convert readily
available aldehydes into acetylenic carbinols, whose
transformation of the sp terminal carbon allows genera-
tion of structural variety of symmetrical and unsymmet-
rical 1,4-diarylacetylenic-1,4-glycols. Thus, addition of
lithium acetylide complexed with ethylenediamine to
3,4,5-trimethoxylbenzaldehyde (9a) or 3,4-dimethoxyl-
benzaldehyde (9b) gave acetylenic carbinols 16a and
16b, which were further treated with n-butyllithium to
afford the corresponding carbanion and alkoxy dianions
in THF. Condensation of these intermediates with the
same aldehydes 9a or 9b at low temperature provided
1,4-diarylacetylenic-1,4-glycols 8a and 8b in 59% and
45% yield, respectively (Scheme 3). These compounds
were characterized on the basis of their spectral proper-
ties, which showed two sets of signals for carbinol
hydrogens of compounds 8a and 8b, respectively, at d
5.38, 5.39 and d 5.41, 5.42. These structures were further
confirmed by their 13C NMR spectra, with carbinol and
acetylenic carbons, respectively, at d 64.92 and 86.67,
86.73 for compound 8a, and d 64.80 and 86.78 for
compound 8b.
It is worth noting that, in preliminary experiments using
different starting material with ETB, such as 3-indolcar-
boxaldehyde instead of substituted benzaldehyde, we
found that the amino group of the heterocycle was
preferentially added to the double bond of a,b-unsaturat-
ed arylketone, giving compounds 11a and 11b (45%). The
1H NMR spectrum showed all characteristic signals,
which consist of d 8.24–6.77, related to the aromatic
and heteroaromatic hydrogens,
d 4.62 and 3.45
representing the methylene groups, and the methoxyl
and aldehyde hydrogen, respectively, at d 3.87–3.84 and
9.90.
O
CHO
R
N
H3CO
OCH3
11a:R=H
11b:R=OCH3
Concerning the reaction with lithium acetylide complex,
several heteroarylaldehydes and arylaldehydes with
different substitution patterns were investigated.
However, the yields of the corresponding acetylenic car-
binols were disappointing owing to the high instability
During this investigation, additional experiments were
conducted on unsubstituted arylaldehydes to confirm
the influence of methoxyl substituents. Since the

7078
L. S. C. Bernardes et al. / Bioorg. Med. Chem. 14 (2006) 7075–7082
O
O
OH
R
CHO
R
R
(CH ) NH(CH )
2 2
3 2
NABH
NaCN
DMF
4
+
O
OH
H CO
3
H CO
3
H CO
3
OCH
3
13
OCH
3
OCH
3
14a: R=OCH
14b: R=H
12a: R=OCH
12b: R=H
3
15a:R=OCH
15b: R=H
3
3
Scheme 2. Preparation of unsymmetrical diaryl diols 15a,b from diaryl diketones 14a,b by replacement of the amino group of compounds 12a,b by
aldehyde 13, via a carbanion cyanohydrin.
R
OH
OH
OCH3
OCH3
R
R
H2
HC C(en)Li
i. n-BuLi
9a:R=OCH3
9b:R=H
6a:R=OCH3
6b:R=H
ii. ArCHO
PtO2
H3CO
H3CO
OH
OCH3
OCH3
16a:R=OCH3
16b:R=H
8a:R=OCH3
8b:R=H
Scheme 3. Preparation of symmetrical acetylenic glycols 8a,b, via addition of acetylenic carbinols 16a and 16b to arylaldehydes.
of the acetylide reagent under storage and handling, as
well self-condensation of aldehydes.
Table 1. In vitro activities of natural products 1 and 2, and synthesized
compounds against bloodstream trypomastigotes of Trypanosoma
cruzi Y and Bolivia strainsa,b
Furthermore, an attempt to repeat the reaction sequence
for the preparation of 8a and 8b by condensation of the
acetylenic carbinol monoanion, obtained from 16a or
16b by reaction with tert-butyldimethylsilyl chloride
(TBSCl) followed by treatment with n-butyllithium, led
to recovery of the starting materials.
Compound
IC50 (lM)
Y strain
Bolivia strain
Gentian violet
1
31
2.3
33
—
2
3.7
—
—
4
51.2
1.5
5
—
The preparation of acetylenic derivatives was earlier dis-
cussed in several reviews pointing out the efficient use of
ethylmagnesium halides or alkyl lithium to abstract
ethynyl proton.36,42 Considering that acetylene gas does
not form the monolithium or mono-Grignard acetylide
in ether because of their immediate conversion into acet-
ylide dianion, we envisaged that using this solvent the
acetylenic glycols 8a and 8b could be straightforwardly
obtained. Contrary to our expectations, neither dilithi-
um nor di-Grignard acetylide afforded satisfactory re-
sults on attempted condensation of 9a or 9b, giving
poor yields of acetylenic carbinols (ꢀ20%) and products
(ꢀ8%) besides recovery of the starting materials (ꢀ40%).
6a
6b
7a
7b
7e
100
105
110
110
210
10
1870
200
110
110
140
140
8a
8b
14a
14b
15a
15b
16a
16b
520
420
3.5 · 106
2.1 · 106
1080
1180
180
3.5 · 106
7.4 · 105
1900
230
450
440
760
a Positive control, gentian violet, concentration of 250 lg/mL.
b Negative control, mice blood infected + 5.0% of DMSO.
Hydrogenation of compounds 8a and 8b in the presence
of palladium-carbon gave only by-products that com-
prise a butane chain bridge instead of a 1,4-butanediol
between the two aryl groups.43 On the other hand, the
reduction performed with platinum oxide35 allowed
isolation of products 6a and 6b with 73% and 41% yield,
respectively.
diaryl-1,4 dicarbonyl intermediate 7b, with IC50
10 lM, had better activity against Y strain when com-
pared to natural products 1 and 2. Regarding the 1,4-
diarylacetylenic-1,4-glycols, compound 8a was the most
active with IC50 110 and 140 lM for Y and Bolivia
strains, respectively.
The trypanocidal activity of products and intermediates
was evaluated against two T. cruzi strains, Bolivia and
Y, with distinct parasitemic level. The results are depict-
ed in Table 1 which shows IC50 values ranging from
10 lM to inactive compounds. Products 6a and 6b
showed similar activity against both strains with IC50
100–110 lM that represents an interesting activity for
these series of compounds. On the other hand, the
In summary, we report a convenient synthesis of new
analogues of natural products veraguensin (1) and gran-
disin (2) containing nonrigid structures. The final prod-
ucts 6a and 6b, comprising a 1,4-diaryl-1,4-diol structure
with different patterns of substitution, were successfully
prepared from 1,4-diaryl-1,4-diketones or 1,4-diaryl
acetylenic-1,4-glycols in moderate yields in spite of the

L. S. C. Bernardes et al. / Bioorg. Med. Chem. 14 (2006) 7075–7082
7079
low reactivity of the reactants. Except for the 1,4-diaryl-
1,4-diketone 7b, the target products and intermediates
were less active than the previous tetrahydrofuran neo-
lignan leads 1–5, revealing that the central tetrahydrofu-
ran ring and the methoxyl groups attached to both
aromatic rings of the natural products may play a criti-
cal role toward the parasite inhibitory activity.
(s, 6H, OCH3), 3.89 (s, 6H, OCH3), 6.85 (d, 2H,
Jortho 8.3, H-9, H-90), 7.50 (d, 2H, Jmeta 2.0, H-6, H-
60), 7.65 (dd, 2H, Jortho 8.3, Jmeta 2.0, H-10, H-100);
13C NMR (100 MHz): d 32.70 (C-2, C-3), 56.40
(OCH3), 56.50 (OCH3), 110.50, 110.60, 123.20, 130.50,
149.40, 153.70 (C–Ar).
3.4. 1-(4-Hydroxyphenyl)-4-(3,4-dimethoxyphenyl)-
butane-1,4-dione (7c)
3. Experimental
It was prepared as described above from compound 10b
(100.0 mg, 0.52 mmol), 4-hydroxybenzaldehyde (9c)
(95.0 mg, 0.57 mmol), the catalyst 3-ethyl-5-(2-hydroxyeth-
yl)-4-methylthiazolium bromide (9.0 mg, 0.035 mmol), and
triethylamine (0.1 mL, 0.7 mmol) in DMF/EtOH
(1.0 mL, 1:1, v/v). Purification by chromatography (sili-
ca gel Merck, 230–400 mesh, 7:3 hexane/ethyl acetate)
3.1. Materials and methods
1H and 13C NMR spectra were measured on a Bruker
DPX-400 (400 and 100 MHz) using CDCl3 (Aldrich)
as solvent and TMS as internal standard. Chemical
shifts were reported in d units (ppm) and coupling con-
stants (J) in Hz. IR spectra were recorded on a Nicolete
Protege FT460 spectrophotometer. TLC was performed
on silica gel (E. Merck) SIL G-25UV254 and com-
pounds on developed plates were detected either by
viewing with a UV lamp (254 nm), or by spraying with
a 10% sulfuric acid, 1.5% molybdic acid, 1% ceric sulfate
spray followed by heating to 150 ꢂC. Column chroma-
tography was performed on Kieselgel 60 (70–230 mm
mesh, E. Merck).
gave
a
yellow solid (62.0 mg, 38%); 1H NMR
(400 MHz/CDCl3): d 3.29–3.39 (m, 4H, J 4.0, CH2–
CH2), 3.86, 3.89 (s, 2· 3H, OCH3), 6.81 (d, 2H,
Jortho 8.8, H–Ar), 6.85 (d, 1H, Jortho 8.5, H–Ar), 7.49
(d, 1H, Jmeta 2.0, H–Ar), 7.66 (dd, 1H, Jortho 8.5, Jmeta
2.0, H–Ar), 7.82 (d, 2H, Jortho 8.8, H–Ar).
3.5. 1-(3-Methoxy-4-hydroxyphenyl)-4-(3,4-dimethoxy-
phenyl)butane-1,4-dione (7d)
3.2. 1,4-Bis-(3,4,5-trimethoxyphenyl)butane-1,4-dione
(7a)
It was prepared as described above from compound 10b
(148.0 mg, 0.77 mmol), 3-hydroxy-4-methoxybenzalde-
hyde (9d) (129.0 mg, 0.85 mmol), the catalyst 3-ethyl-5-
(2-hydroxyethyl)-4-methylthiazolium bromide (13.0 mg,
0.051 mmol), and triethylamine (0.12 mL, 0.85 mmol) in
dioxane/EtOH (1.0 mL, 8:2, v/v). Purification by chroma-
tography (silica gel Merck, 230–400 mesh, 7:3 hexane/
ethyl acetate) gave a yellow oil (10.0 mg, 5%); 1H
A mixture of compound 10a (100.0 mg, 0.45 mmol),
3,4,5-trimethoxybenzaldehyde (9a) (97.0 mg, 0.5 mmol),
the catalyst 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazoli-
um bromide (7.0 mg, 0.03 mmol), and triethylamine
(0.1 mL, 0.5 mmol) in dioxane/EtOH (1.0 mL, 8:2,
v/v), under nitrogen atmosphere, was heated at reflux.
Another portion (7.0 mg) of thiazolium salt was added
at the end of 10 and 20 h, and the mixture refluxed for
a total of 30 h. The solution was evaporated, and the
residue was dissolved with dichloromethane. The organ-
ic layer was washed with saturated NaCl solution and
water. The organic layer was dried over anhydrous
Na2SO4, filtered, and evaporated under vacuum. The
compound 7a was purified by flash column chromatog-
raphy (silica gel Merck, 230–400 mesh, 7:3 hexane/ethyl
acetate) to give a yellow solid (132.2 mg, 36%); 1H NMR
(400 MHz/CDCl3): d 3.37 (s, 4H, H-2, H-3), 3.86 (s, 6H,
OCH3), 3.87 (s, 12H, OCH3), 7.24 (s, 4H, H-6, H-10, H-
60, H-100); 13C NMR (100 MHz): d 32.90 (C-2, C-3),
56.71 (OCH3), 61.37 (OCH3), 105.98, 132.39, 143.06,
153.49, 198.03 (C–Ar).
NMR (400 MHz/CDCl3):
d
3.34–3.36 (s, 4H,
CH2–CH2), 3.87 (s, 3H, OCH3), 3.88 (s, 3H, OCH3),
3.89 (s, 3H, OCH3), 6.85 (d, 1H, Jortho 8.3, ArH), 6.91
(d, 1H, Jortho 8.3, H–Ar), 7.50 (d, 2H, Jmeta 2.0, ArH),
7,60 (dd, 1H, Jortho 8.3, Jmeta 2.0, ArH), 7.65 (dd, 1H, Jortho
8.8, Jmeta 2.0, ArH); 13C NMR (100 MHz): d 30.10, 32.70
(C-2, C-3), 56.40, 56.50 (OCH3), 110.25, 110.42, 110.54,
114.28, 123.22, 123.88, 130.17, 130.44, 146.95, 149.36,
150.78, 153.69, (C–Ar), 197.85, 197.93 (C@O).
3.6. 1-(3,4,5-Trimethoxyphenyl)-4-(3,5-dimethoxyphenyl-
4-O-benzyl)butane-1,4-dione (7e)
It was prepared as described above from compound
10a (30.0 mg, 0.14 mmol), 1-(3,5-dimethoxy-4-O-ben-
zyl)benzaldehyde (9e) (44.0 mg, 0.16 mmol), the catalyst
3-ethyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide
(3.0 mg, 0.01 mmol), and triethylamine (0.2 mL,
1.0 mmol) in DMF/EtOH (1.0 mL, 1:1, v/v). Purification
by chromatography (silica gel Merck, 230–400 mesh, 7:3
hexane/ethyl acetate) gave a yellow solid (62.0 mg, 38%);
1H NMR (400 MHz/CDCl3): d 3.36 (s, 4H, CH2–CH2),
3.82 (s, 6H, OCH3), 3.86 (s, 3H, OCH3), 3.87 (s, 6H,
OCH3), 5.05 (s, 2H, OCH2Ph), 7.19 (s, 2H, ArH), 7.21
(s, 2H, ArH), 7.24–7.30 (m, 3H, ArH:OBn), 7.40 (dd,
2H, Jortho 8.1, Jmeta 1.5, ArH:OBn); 13C NMR
(100 MHz): d 34.23, 34.28 (C-2, C-3), 58.06, 58.07,
62.72 (OCH3), 107.36, 129.80, 129.97, 130.20, 133.89,
3.3. 1,4-Bis-(3,4-dimethoxyphenyl)butane-1,4-dione (7b)
It was prepared as described above from compound 10b
(100.0 mg, 0.52 mmol), 3,4-dimethoxybenzaldehyde (9b)
(95.0 mg, 0.57 mmol), the catalyst 3-ethyl-5-(2-hydroxyeth-
yl)-4-methylthiazolium bromide (9.0 mg, 0.035 mmol), and
triethylamine (0.1 mL, 0.7 mmol) in dioxane/EtOH
(1.0 mL, 8:2, v/v). Purification by chromatography (sili-
ca gel Merck, 230–400 mesh, 7:3 hexane/ethyl acetate)
gave
(400 MHz/CDCl3): d 3.36 (s, 4H, H-2 and H-3), 3.87
a
yellow solid (54.0 mg, 29%); 1H NMR

7080
L. S. C. Bernardes et al. / Bioorg. Med. Chem. 14 (2006) 7075–7082
139.06, 143.25, 144.44, 154.85, 155.17 (C–Ar), 199.40
(C@O).
61.24 (OCH3), 64.89 (C-3), 75.25 (C-1), 83.80 (C-2),
103.98, 136.04, 138.37, 153.73 (C–Ar).
3.7. 1-(Phenyl)-4-(3,4,5-trimethoxyphenyl)butane-1,4-
dione (14a)
3.10. 1-(3,4-Dimethoxyphenyl)prop-2-in-1-ol (16b)
It was prepared as described above from lithium acety-
lide ethylenediamine (555.0 mg, 6.0 mmol) and com-
pound 9b (200.0 mg, 1.2 mmol). Purification by
chromatography (silica gel Merck, 230–400 mesh, 1:1
hexane/ethyl acetate) gave a yellow solid (141.0 mg,
A solution of benzaldehyde (13) (97.0 mg, 0.5 mmol),
NaCN (60.3 mg, 1.2 mmol) in DMF (2.5 mL), under
nitrogen atmosphere, was heated at 40 ꢂC for 30 min.
After that, a mixture of 3-(N,N-dimethylamine)-1-
(3,4,5-trimethoxyphenyl)prop-1-one (12a) (130.6 mg,
1.2 mmol) in DMF (3.0 mL) was poured slowly into
the solution. The reaction mixture was stirred for 24 h.
The reaction mixture was cooled in an ice water and
quenched with water, and the aqueous layer was extract-
ed with ethyl ether. The organic layer was washed with
brine, water, dried over anhydrous Na2SO4, filtered,
and evaporated under vacuum. The compound 14a was
purified by flash column chromatography (silica gel
Merck, 230–400 mesh, 8:2 hexane/ethyl acetate) to give
1
61%); IR mmax (cmꢁ1): 3.237 (OH), 2.109 (C„C); H
NMR (400 MHz/CDCl3): d 2.69 (d, 1H, J 2.3, H-1),
3.90 (s, 3H, OCH3), 3.92 (s, 3H, OCH3), 5.45 (s, 1H,
H-3), 6.87 (d, 1H, Jortho 8.6, H-8), 7.09–7.14 (m, 2H,
H-9 and H-5); 13C NMR (100 MHz): d 56.28, 56.35
(OCH3), 64.67 (C-3), 75.10 (C-1), 83.98 (C-2), 110.15,
111.30, 119.44, 133.07, 149.50, 149.63 (C–Ar).
3.11. 1,4-Bis-(3,4,5-trimethoxyphenyl)but-2-in-1,4-diol
(8a)
a white solid (132.2 mg, 36%); IR mmax (nujol/cmꢁ1
)
1675 (C@O); 1H NMR (400 MHz/CDCl3): d 3.45 (t, 4H,
J 4.0, CH2–CH2), 3.93 (d, 9H, J 1.3, OCH3), 7.31 (s, 2H,
ArH), 7.48 (t, 2H, Jortho 7.0, Jmeta 1.5, ArH), 7.59 (tt,
1H, Jortho 7.0, Jmeta 1.5, ArH), 8.05 (dd, 2H, Jortho 8.0,
Jmeta 1.5, ArH).
A solution of compound 16a (77.0 mg, 0.35 mmol) in
anhydrous THF, under nitrogen atmosphere, was cooled
to 0 ꢂC and n-BuLi (2.1 M, 0.33 mL) was added and stir-
red for 40 min. After that, the temperature was lowered to
ꢁ78 ꢂC and a solution of 3,4,5-trimethoxybenzaldehyde
(9a) (34.0 mg, 0.17 mmol) in anhydrous THF (0.5 mL)
was added. The reaction mixture was stirred at ꢁ78 ꢂC
for 3 h when monitoring by TLC (hexane/ethyl acetate
1:1) showed completion. The reaction mixture was
quenched with saturated aqueous NH4Cl and extracted
with ethyl ether. The organic layer was dried over anhy-
drous Na2SO4. Removal of the solvent under reduced
pressure followed by purification on silica gel (Merck,
230–400 mesh, hexane/ethyl acetate 1:1) afforded the
compound 8a as a yellow solid (43.0 mg, 43%); 1H
NMR (400 MHz/CDCl3): d 3.73 (s, 12H, OCH3), 3.75
(s, 6H, OCH3), 5.38 (d, 2H, H-1, H-4), 6.66 (d, 4H, H-6,
H-10, H-60, H-100); 13C NMR (100 MHz): d 56.50,
61.22 (OCH3), 64.92 (C-1, C-4), 86.67, 86.73 (C-2, C-3),
104.04, 136.48, 136.51, 138.24, 153.66 (C–Ar).
3.8. 1-(Phenyl)-4-(3,4-dimethoxyphenyl)butane-1,4-dione
(14b)
It was prepared as described above from compound 13
(148.4 mg, 1.4 mmol), NaCN (68.6 mg, 1.4 mmol), and
3-(N,N-dimethylamine)-1-(3,4-dimethoxy-phenyl)prop-
1-one (12b) (300.0 mg, 1.3 mmol). Purification by chro-
matography (silica gel Merck, 230–400 mesh, 8:2
hexane/ethyl acetate) gave a white solid (181.1 mg,
48.0%); IR mmax (nujol/cmꢁ1) 1684, 1667 (C@O); NMR
1H (400 MHz/CDCl3): d 3.44 (t, 4H, J 4.0, CH2–CH2),
3.93, 3.95 (s, 2· 3H, OCH3), 6.91 (d, 1H, Jortho 8.0,
ArH), 7.48 (t, 2H, Jortho 7.0, Jmeta 1.5, ArH), 7.57 (m, 2H,
ArH), 7.71(dd, 1H, Jortho 8.0, Jmeta 2.0, ArH), 8.05(dd, 2H,
Jortho 8.0, Jmeta 1.5, ArH).
3.12. 1,4-Bis-(3,4-dimethoxyphenyl)but-2-in-1,4-diol (8b)
3.9. 1-(3,4,5-Trimethoxyphenyl)pro-2-in-1-ol (16a)
It was prepared as described above from compound 16b
(77.0 mg, 0.4 mmol), n-BuLi (2.1 M, 0.33 mL), and 2,4-
dimethoxybenzaldehyde 9b (33.3 mg, 0.2 mmol). Purifi-
cation by chromatography (silica gel Merck, 230–400
mesh, 8:2 hexane/ethyl acetate) gave a yellow oil
(32.0 mg, 45%); 1H NMR (400 MHz/CDCl3): d 3.77
(s, 6H, OCH3), 3.79 (s, 6H, OCH3), 5.41 (d, 2H, J 3.7,
H-1, H-4), 6.75 (d, 2H, Jortho 8.8, H-9, H-90), 6.98–7.02
(m, 4H, H-6, H-10, H-60, H-100); 13C NMR
(100 MHz): d 56.26, 56.35 (OCH3), 64.80 (C-1, C-4),
86.78 (C-2, C-3), 110.28, 111.28, 119.43, 133.37,
133.38, 149.46, 149.55 (C–Ar).
A
mixture of lithium acetylide ethylenediamine
(470.0 mg, 5.1 mmol) in DMSO (4.0 mL) was added to
solution of 3,4,5-trimethoxybenzaldehyde (9a)
a
(500.0 mg, 2.5 mmol) in DMSO (2.0 mL), under nitro-
gen atmosphere. The mixture was stirred for 1 h at room
temperature when monitoring by TLC (hexane/ethyl
acetate 1:1) showed completion. The reaction mixture
was cooled, quenched with saturated aqueous NH4Cl,
and extracted with ethyl ether. The organic layer was
dried over anhydrous Na2SO4. Removal of the solvent
under reduced pressure followed by purification on silica
gel (Merck, 230–400 mesh, hexane/ethyl acetate 1:1)
afforded the compound 16a as
a
yellow solid
3.13. 1,4-Bis-(3,4,5-trimethoxyphenyl)-1,4-butane diol
(6a)
(113.2 mg, 20%); IR mmax (cmꢁ1): 3.242 (OH), 2.117
1
(C„C); H NMR (400 MHz/CDCl3): d 2.25 (d, 1H, J
6.0, OH), 2.71 (d, 1H, J 2.2, H-1), 3.86 (s, 6H, OCH3),
3.91 (s, 3H, OCH3), 5.44 (dd, 1H, J 2.2 and 6.0, H-3),
6.81 (s, 2H, H-5, H-9); 13C NMR (100 MHz): d 56.51,
3.13.1. Method 1. To a stirred solution of 7a (11.0 mg,
26 mmol) in tetrahydrofuran (0.7 mL) and methanol
(1.4 mL) was added dropwise sodium borohydride

L. S. C. Bernardes et al. / Bioorg. Med. Chem. 14 (2006) 7075–7082
7081
(2.0 mg, 0.05 mmol) in water (0.5 mL). The reaction
mixture was stirred at room temperature for 6 h when
monitoring by TLC (hexane/ethyl acetate 1:1) showed
completion. The reaction mixture was cooled in an ice-
water bath and quenched with water, and the aqueous
layer was extracted with ethyl acetate. The organic layer
was dried over anhydrous Na2SO4. Removal of the sol-
vent under reduced pressure followed by purification on
silica gel (Merck, 230–400 mesh, hexane/ethyl acetate
1:1) afforded the compound 6a as a white oil (4.2 mg,
38%); 1H NMR (400 MHz/CDCl3): d 1.70–1.90 (m,
4H, CH2–CH2), 3.75 (s, 3H, OCH3), 3.78 (s, 12H,
OCH3), 4.55-4.65 (m, 2H, H-1, H-4), 6.48 (s, 4H, H-6,
H-60, H-10, H-100); 13C NMR (100 MHz): d 38.40,
38.50 (CH2), 58.60, 63.20 (OCH3), 71.00, 77.20, 77.30,
106.30, 106.40, 140.10, 144.70, 144.80, 156.50 (C–Ar).
parasites was counted after 24 h, according to the proce-
dure described by Brener.45 Infected blood with the
same volume of DMSO was used as control and gentian
violet was used as positive control (250.0 lg/mL). After
total lysis, all samples were inoculated in healthy mice in
order to detect a possible parasitemy.
Acknowledgments
The authors acknowledge Fundac¸a˜o de Amparo a
Pesquisa do Estado de Sa˜o Paulo—FAPESP for finan-
ˆ
cial support and fellowship, Dr. Monica Tallarico Pupo,
Dr. Norberto Peporine Lopes, Dr. Zuleika Rothschild,
and Ms. Peterson de Andrade for valuable contribution
on this manuscript.
3.13.2. Method 2. A mixture of compound 8a (32.0 mg,
0.076 mmol), PtO2 (3.0 mg) in MeOH was stirred in the
presence of H2 (gas) at room temperature until uptake
was completed (3 h). The reaction mixture was then fil-
tered in celite pad and the solvent was removed under
reduced pressure to gave the compound 6a as a white
oil (23.4 mg, 72%).
References and notes
1. Beard, C. B.; Pye, G.; Steurer, F. J.; Rodriguez, R.;
Campman, R.; Peterson, A. T.; Ramsey, J.; Wirtz, R. A.;
Robinson, L. E. Emerg. Infect. Dis. 2003, 9, 103–105.
2. Bryan, C. F.; Tegtmeier, G. E.; Rafik, N.; Markham, L.
E.; Murillo, D.; Nelson, P. W.; Shield, C. F.; Warady, B.
A.; Aeder, M. I. Clin. Transplant. 2004, 18, 12–15.
3.14. 1,4 -Bis-(3,4-dimethoxyphenyl)-1,4-butane diol (6b)
´
3. Muelas-Serrano, S.; Le-Senne, A.; Fernandez-Portillo, C.;
Nogal, J. J.; Ochoa, C.; Gomez-Barrio, A. Mem. Inst.
´
3.14.1. Method 1. It was prepared as described above
from compound 7b (42.5 mg, 0.12 mmol), sodium boro-
hydride (6.5 mg, 0.17 mmol). Purification by chroma-
tography (silica gel Merck, 230–400 mesh, 8:2 hexane/
ethyl acetate) gave a white oil (19.3 mg, 45%); 1H
NMR (400 MHz/CDCl3): d 1.90–2.00 (m, 2H, CH2),
2.30–2.40 (m, 2H, CH2), 3.79 (s, 3H, OCH3), 3.81 (s,
6H, OCH3), 3.84 (s, 3H, OCH3), 4.94 (t, 1H, J 5.0,
CHOH), 5.13 (t, 1H, J 5.0, CHOH), 6.78 (d, 2H,
Jortho 8.0, H-9, H-90), 6.85–6.92 (m, 4H, H-6, H-10, H-
60, H-100); 13C NMR (100 MHz): d 34.50, 36.00 (CH2),
56.30, 56.40 (OCH3), 81.40, 81.50, 109.40, 110.00,
111.40, 111.50, 118.30, 118.60, 136.00, 136.60, 148.60,
148.70, 149.40, 149.50 (C–Ar).
Oswaldo Cruz 2002, 9, 553–557.
4. Urbina, J. A.; Payares, G.; Sanoja, C.; Molina, J.; Lira,
R.; Brener, Z.; Romanha, A. J. Int. J. Antimicrob. Agents
2003, 21, 39–48.
5. Guedes, P. M. M.; Fietto, J. L. R.; Lana, M.; Bahia, M. T.
Anti-Infect. Agents Med. Chem. 2006, 5, 175–186.
6. Williams, D. A.; Lemke, T. L. Foye’s Principles of
Medicinal Chemistry, 5th ed.; Lippincott Williams &
Wilkins: New York, 2002.
7. Faria, T. J.; Fonseca e Silva, L. G.; Souza Filho, J. D.;
Chiari, E.; Olveira, A. B. J. Braz. Chem. Soc. 2005, 16,
1415–1419.
8. WHO data obtained from <http://www.who.ch/>.
9. Atwood, J. A.; Weatherly, D. B.; Minning, T. A.; Bundy,
B.; Cavola, C.; Opperdoes, F. R.; Orlando, R.; Tarleton,
R. L. Science 2005, 309, 473–476.
10. Paulino, M.; Iribarne, F.; Durbin, M.; Aguilera-Morales,
S.; Tapia, O.; Stoppani, A. O. M. Mini-Rev. Med. Chem.
2005, 5, 499–519.
11. Linares, G. E. G.; Ravaschino, E. L.; Rodriguez, J. B.
Curr. Med. Chem. 2006, 13, 335–360.
12. Sariego, I.; Annoura, T.; Nara, T.; Hashimoto, M.;
Tsubouchi, A.; Iizumi, K.; Makiuchi, T.; Murata, E.;
Kita, K.; Aoki, T. Parasitol. Int. 2006, 55, 11–16.
13. Gabelli, S. B.; McLellan, J. S.; Jason, S.; Montalvetti, A.;
Oldfield, E.; Do Campo, R.; Amzel, L. M. Proteins 2006,
62, 80–88.
3.14.2. Method 2. A mixture of compound 8b (50.0 mg,
0.014 mmol), PtO2 (3.0 mg) in MeOH was stirred in the
presence of H2 (gas) at room temperature until uptake
was completed (3 h). The reaction mixture was then fil-
tered in celite pad and the solvent was removed under
reduced pressure to gave the compound 6b as a yellow
oil (20.6 mg, 41%).
3.15. Biological assays
14. Alvim, J., Jr.; Dias, R. L. A.; Castilho, M. S.; Oliva, G.;
Correa, A. G. J. Braz. Chem. Soc. 2005, 16, 763–773.
15. Villagran, M. E.; Marin, C.; Rodriguez-Gonzalez, I.; De
Diego, J. A.; Sanchez-Moreno, M. Am. J. Trop. Med.
2005, 73, 510–516.
16. Hudock, M. P.; Sanz-Rodriguez, C. E.; Song, Y.;
Chan, J. M. W.; Zhang, Y.; Odeh, S.; Kosztowski, T.;
Leon-Rossel, A.; Concepcion, J. L.; Yardley, V.; Croft,
S. L.; Urbina, J. A.; Oldfield, E. J. Med. Chem. 2006,
49, 215–223.
The bioassays were carried out using blood collected by
cardiac puncture of albino Swiss mice on the parasitemy
peak after infection with Y strain (seventh day) and with
Bolivia strain (14th day) of T. cruzi.44 The infected
blood was diluted to the concentration of 2 · 106 try-
pomastigotes per mL. The assays were performed on
titration microplates (96 wells) with 190 lL of blood in
triplicate. The compounds were solubilized in dimethyl
sulfoxide (DMSO) and diluted in blood to give 5.0,
25.0, 50.0, and 100.0 lg/mL as final concentrations.
The plates were incubated at 4 ꢂC and the number of
17. Gilbert, I. H. Biochim. Biophys. Acta 2002, 1587, 249–
257.

7082
L. S. C. Bernardes et al. / Bioorg. Med. Chem. 14 (2006) 7075–7082
18. Cazzulo, J. J. Med. Chem. Rev. 2005, 2, 495–503.
19. Yoshida, N. An. Acad. Bras. Cienc. 2006, 78, 87–111.
20. Demir, O.; Roitberg, A. Abstracts of Papers, 231st ACS
National Meeting, Atlanta, GA, United States, March 26–
30, 2006.
21. Neres, J.; Bonnet, P.; Bryce, R. A.; Kotian, P. L.;
Buschiazzo, A.; Alzari, P.; Douglas, K. T. Abstracts of
Papers, 231st ACS National Meeting, Atlanta, GA,
United States, March 26–30, 2006.
22. Broutin, H.; Tarrieu, F.; Tibayrenc, M.; Oury, B.;
Barnabe, C. Exp. Parasitol. 2006, 113, 1–7.
23. Coura, J. R.; De Castro, S. L. Mem. Inst. Oswaldo Cruz
2002, 97, 3–24.
33. Raghavan, S.; Anuradha, K. Tetrahedron Lett. 2002, 43,
5181–5183.
34. Ponpipom, M. M.; Hwang, S.-B.; Doebber, T. W.; Acton, J.
J.; Alberts, A. W.; Biftu, T.; Brooker, D. R.; Bugianesi, R.
L.; Chabala, J. C.; Gamble, N. L.; Graham, D. W.; Lam,
M.-H.; Wu, M. S. Biochem. Biophys. Res. Commun. 1988,
50, 1213–1220.
´
35. Arau´jo, A. L. S. M. Estudo sobre a sıntese de cuparanos.
Tese de Doutorado, FFCLRP, Universidade de Sa˜o
Paulo: Ribeira˜o Preto, 2004.
36. Brandsma, L. Preparative Acetylenic Chemistry, 1st ed.;
Elsevier Publishing Company: Amsterdam, 1971, p. 15.
37. Bernardes, L. S. C. Lignanas tripanocidas naturais: prep-
´
24. Sttopani, A. O. M. Medicina (Buenos Aires) 1999,
59(Suppl. II), 147–165.
arac¸a˜o de analogos e estudo de relac¸a˜o estrutura-atividade.
Dissertac¸a˜o de Mestrado, FCFRP-USP, Universidade de
Sa˜o Paulo: Ribeira˜o Preto, 2002.
38. Stetter, H.; Heinrich, K. Angew. Chem., Int. Ed. Engl.
1974, 13, 539.
39. Sahoo, S. P.; Graham, D. W.; Acton, J.; Biftu, T.;
Bugianesi, R. L.; Girotra, N. N.; Kuo, C. H.; Ponpipom,
M. M.; Doebber, T. W.; Wu, M. S.; Hwang, S. B.; Lam,
M. H.; Macintyre, D. E.; Bach, T. J.; Luell, S.; Meurer,
R.; Davies, P.; Alberts, A. W.; Chabala, J. C. Bioorg. Med.
Chem. Lett. 1991, 1, 327–332.
25. Gomes, M. T.; Monteiro, R. Q.; Grillo, L. A.; Leite-
Lopes, F.; Stroeder, H.; Ferreira-Pereira, A.; Alviano, C.
S.; Barreto-Bergter, E.; Castro-Faria Neto, H.; Cunha e
Silva, N. L.; Almeida, I. C.; Soares, R. M. A.; Lopes, A.
H. Int. J. Parasitol. 2006, 36, 165–173.
26. Tempone, A. G.; Borborema, S. E. T.; De Andrade, H. F.,
Jr.; De Amorin Gualda, N. C.; Yogi, A.; Carvalho, C. S.;
Bachiega, D.; Lupo, F. N.; Bonotto, S. V.; Fischer, D. C.
H. Phytomedicine 2005, 12, 382–390.
27. Rubio, J.; Calderon, J. S.; Flores, A.; Castro, C.;
Cespedes, C. L. J. Biosci. 2005, 60, 711–716.
28. Lopes, N. P.; Chicaro, P.; Kato, M. J.; Albuquerque, S.;
Yoshida, M. Planta Med. 1998, 68, 667–669.
29. Biftu, T.; Gamble, N. F.; Doebber, T.; Hwang, S. B.;
Shen, T. Y.; Snyder, J.; Springer, J. P.; Stevenson, R.
J. Med. Chem. 1986, 29, 1917–1921.
40. Girotra, N. N.; Biftu, T.; Ponpipom, M. M.; Acton, J. J.;
Alberts, A. W.; Bach, T. N.; Ball, R. G.; Bugianesi, R. L.;
Parsons, W. H.; Chabala, J. C.; Davies, P.; Doebber, T. W.;
Doherty, J.; Graham, D. W.; Hwang, S.-B.; Kuo, C. H.;
Lam, M.-H.; Luell, S.; Macintyre, D. E.; Meurer, R.;
Roberts, C. D.; Sahoo, S. P.; Wu, M. S. J. Med. Chem. 1992,
35, 3474–3482.
30. Hwang, S. B.; Lam, M. H.; Biftu, T.; Beattie, T. R.; Shen,
T. Y. J. Biol. Chem. 1985, 260, 15639–15645.
41. Biftu, T.; Hazra, B. G.; Stevenson, R. J. Chem. Soc.,
Perkin Trans. 1 1979, 2276.
31. Nihei, K.; Konno, K.; Bernardes, L. S. C.; Lopes, N. P.;
Albuquerque, S.; Carvalho, I.; Pupo, M. T.; Martins, R.
C. C.; Kato, M. J. Arkivock 2004, vi, 112–126.
32. Cai, X.; Scanell, R. T.; Yaeger, D.; Hussoin, Md. S.;
Killian, D. B.; Qian, C.; Eckman, J.; Hwang, S.-B.;
Garahan, L.; Yeh, C. G.; Ip, S. H.; Shen, T. Y. J. Med.
Chem. 1998, 41, 1970–1979.
42. Sudweeks, W. B.; Broadbent, H. S. J. Org. Chem. 1975,
40, 1131–1136.
43. Rylander, P. N. Hydrogenation Methods; Academic Press:
New York, 1985 (Chapter 3).
44. Silva, L. H. P.; Nussenzweig, V. Fol. Clin. Biol. 1953, 20,
191–198.
45. Brener, Z. Rev. Inst. Med. Trop. 1962, 4, 389–396.