Structure-activity relationship of antileishmanials neolignan analogues

Article abstract of DOI:10.1016/j.bmc.2007.08.016

Twenty-two synthetic analogues of neolignans comprising β-ketoethers and β-ketosulfides were obtained from condensation reactions among β-bromoketones and phenols or thiophenols, respectively, in basic solutions, and assayed in vitro for activity against

Full text of DOI:10.1016/j.bmc.2007.08.016

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 15 (2007) 7337–7343
Structure–activity relationship of antileishmanials
neolignan analogues
a
c
b
´
Mario Aveniente, Eduardo F. Pinto, Lourivaldo S. Santos,
Bartira Rossi-Bergmannc and Lauro E. S. Barataa,*
aInstituto de Quı´mica, Universidade Estadual de Campinas, UNICAMP, CP 6154, CEP l3083-970 Campinas, SP, Brazil
bDepartamento de Quı´mica, CCEN, Universidade Federal do Para´, CP 8600, CEP 66075-110 Bele´m, PA, Brazil
cInstituto de Biofı´sica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro (UFRJ), CEP 21949-900 Rio de Janeiro,
RJ, Brazil
Received 18 May 2007; revised 8 August 2007; accepted 9 August 2007
Available online 22 August 2007
Abstract—Twenty-two synthetic analogues of neolignans comprising b-ketoethers and b-ketosulfides were obtained from conden-
sation reactions among b-bromoketones and phenols or thiophenols, respectively, in basic solutions, and assayed in vitro for activity
against intracellular Leishmania amazonensis and Leishmania donovani amastigotes, the causative agents of cutaneous and visceral
leishmaniasis. The highest selective activity was found for compounds with sulfur bridges, whereas b-ketosulphoxides and b-keto-
sulphones had significantly less growth inhibitory activity. Compounds 2-[(4-chlorophenyl)thio]propan-1-one and 1-(3,4-dime-
thoxy)-2-[(4-methylphenyl)thio]propan-1-one were the most potent, inhibiting the growth parasite species by over 90% at
microgram/mL, but only compound 1-(3,4-dimethoxy)-2-[(4-methylphenyl)thio]propan-1-one was selectively toxic to the parasites.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
is further aggravated by the surge of antimonial resis-
tance in some areas where the disease is endemic.6
Therefore, the development of new therapeutic agents
is highly expected.7–10
Leishmaniasis is a spectrum of diseases caused by
intracellular protozoan parasites belonging to the genus
Leishmania. Depending on the immune status of the
host and the parasite species, the disease may manifest
itself in specific or disseminated cutaneous areas (e.g
Leishmania amazonensis), disfiguring mucocutaneous
(Leishmania braziliensis) or fatal visceral leishmaniasis
(e.g. Leishmania donovani).1,2 The disease is endemic in
88 tropical and subtropical countries, where 350 million
people are at risk. There is an estimate of 12 million
already contaminated people, as well as an annual inci-
dence of 2 million cases.3
In search of new drugs against leishmaniasis, potentially
active natural products and their derivatives have been
described, including chalcones present in Glycirrhyza
glabra and Piper aduncum11,12 and quercitrin present in
Kalanchoe pinnata.13 Neolignans form another potential
class of new antileishmanials, which are normally found
in Myristicaceae and other primitive plant families.
They are usually dimers of the oxidative coupling of
allyl and propenyl phenols14,15 while a considerable
number of biological properties, namely antifungal,16
antitrypanosomal,17 antibacterial,18 anti-PAF,19 anti-
tumoral20 and anti-schistosomal21 activities have been
ascribed to them.
So far no vaccine approved for human use is available.4
Despite the recent advances in new antileishmanial com-
pounds, the first-line therapy to all forms of leishmania-
sis still requires multiple, potentially toxic and painful
injections with pentavalent antimonials.5 The problem
We have previously described that a sulfur analogue of a
natural neolignan from the Virola surinamensis (Rol.)
Warb. was very active against L. donovani in vitro.22
In the present work, we evaluate the antileishmanial
activity of novel sulfur and oxygen synthetic analogues.
Since the sensitivity of different parasite species to drugs
Keywords: Leishmania amazonensis; Leishmania donovani; b-Ketoe-
thers; b-Ketosulfides; b-Ketosulfoxides; b-Ketosulfones; Neolignans.
Corresponding author. Tel.: +55 19 3521 3153; fax: +55 19 3521
3023; e-mail: lbarata@iqm.unicamp.br
*
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.08.016

7338
M. Aveniente et al. / Bioorg. Med. Chem. 15 (2007) 7337–7343
may vary considerably,23–25 we proposed to evaluate the
activity of the analogues against parasite species that
cause cutaneous and visceral leishmaniasis.
synthetic neolignans, but did not reveal the degree of
activity on the entire cells which may vary according
to cell membrane permeability or intracellular drug
metabolism.
2. Results and discussion
We have previously shown that general compounds with
a sulfur bond in carbon 8 have higher activity as com-
pared to compounds bearing oxygen bond, as according
to previous studies on L. donovani.22 The synthesis of
those analogues was conducted for substitutions in the
C-8, whose bonding in the C-7 can be rigid or present
free rotation. In the sulfur atom case, it forms bonds
where the free capacity of rotation is greater than oxy-
gen, even considering the size of the atom and electro-
negativity. This may explain the differential biological
activity between sulfurated and oxygenated analogues
1–5.
In this work, 22 compounds (18 new) oxygenated or sul-
phurated neolignan analogues (Schemes 1 and 2) were
synthesized, while the activities against both intracellu-
lar amastigotes of L. amazonensis and L. donovani were
compared. Synthetic procedures for neolignans were
adapted from our previous work22 through the conden-
sation reaction of a-bromoketones with a phenol or thi-
ophenol derivative, leading to
a
keto-neolignan
analogue (b-ketoethers or b-ketosulphides), compounds
1–15 (Scheme 1), in 72–91% yield. Compounds were
purified by PTLC and purity done by GC–MS. For
the determination of the structures, spectroscopic meth-
ods were used, such as: mass spectrometry, high resolu-
We found that, in general, L. donovani and L. amazonen-
sis were differently sensitive to most of the synthetic neo-
lignans, and that L. amazonensis was more susceptible
than L. donovani to compounds 3, 7, 15, 16, 20 and
21, while compounds 1, 2, 6, 8, 11, 13 and 17–19 showed
similar activity (Table 1). The reference drug meglumine
antimoniate (Glucantime) was equally active against
both species (26–28%). The differential drug sensitivity
among Leishmania species may be due to differential
metabolism or biosynthetic pathways.23
1
tion mass spectrometry, H and 13C nuclear magnetic
1
resonance and infrared spectroscopy. H NMR and IR
data of the compounds 11, 12, 13 and 15 are in concor-
dance with the literature.22 13C NMR data of these com-
pounds are described for the first time in this work.
Sulfur analogues presented greater activity when com-
pared to oxygenated compounds of the same series.22
Based on those previous results, we intended to associ-
ate the structure with biological activity (SAR), to find
new active molecules. Several physicochemical proper-
ties were calculated for a group of synthetic substances
for which the biological activities against Leishmania
are known.26 The methodology used was very helpful
in providing information to the parasite target of the
Table 1 also shows that compounds 3, 16–18, 20 and 22
did not inhibit the growth of L. donovani, that the com-
pounds 1, 4–8, 15 and 19–21 were potentially more ac-
tive than the control drug against L. amazonensis, and
that sulfurated compounds 11 and 13 were the most ac-
tive, inhibiting the growth of both parasites in 94.1–
100% at 80 lg/mL.
Compound 11 has a group Cl in position 40 (ring B),
whereas compound 13 has CH3 in position 40 (ring B)
and OCH3 in positions 3 and 4 (ring A). Compounds
9, 12 and 14 were extremely toxic to macrophages, prob-
ably due to the presence of the OCH3group in positions
3 and 4 (ring A) (e.g. 12 and 14) and NH2 in position 40
(e.g. 9). The presence of chlorine in 40 was associated
with low toxicity to mammalian cells, as Cl-containing
compounds 6, 11, 15–17, 19 and 21 were very well toler-
ated by the macrophages. Interestingly, compound 15
containing both OCH3 in positions 3 and 4 and Cl in po-
sition 40 had significantly less activity against L. dono-
vani (22% inhibition) although some activity was
maintained against L. amazonensis (63% inhibition).
As an attempt to improve the permeation through mac-
rophage and parasite membranes, the alcohols 19–21
1
and acetate 22 were synthesized. The H NMR spectra
of 19–21, presented multiplets (d 3.22, 3.17 and 3.22)
in reference to the coupling between H-8 with H-7 and
H-9.
The acetate 22 was evidenced through the absorption
band in the IR spectrum at 1736 cmꢀ1 corresponding
to the stretch of the carbonyl esther group (OAC@O),
typical of saturated aliphatic esthers. The 1H NMR
Scheme 1. Synthesis of b-ketoethers 1–5 and b-ketosulfides 6–15.
Reagents and conditions: (i) phenol derivatives, K2CO3, MeCOEt, D;
(ii) thiophenolderivatives, K2CO3, MeCOEt, D.

M. Aveniente et al. / Bioorg. Med. Chem. 15 (2007) 7337–7343
7339
Scheme 2. Synthesis of b-ketosulphoxide 16, b-ketosulphones 17 and 18, alcohols 19–21, and acetate 22. Reagents and conditions: (i) m-CPA,
anhydrous THF, RT,1 h; (ii) HOOAc, anhydrous THF, RT, 24 h; (iii) NaBH4, MeOH/THF, RT, 30 min; (iv) Ac2O, MeCOEt, pyridine D, 24 h.
spectrum of acetate 22 presented a singlet (d 1.93) corre-
sponding to the methyl protons of OAc group, and also
a doublet in low field (d 5.67) referent to H-7, adjacent
to the OAc group, resulting from the coupling between
H-7 and H-8. The H NMR spectrum of the starting
compound 19 presented a doublet (d 4.32) referent to
H-7, resulting from the coupling between H-7 and H-8.
the 22 synthesized substances were active against at least
one of the parasite species (growth inhibition P 50% at
80 lg/mL). The most active compounds were 11 and 13,
which presented Cl or CH3 in position 40 of the ring B.
The presence of Cl, but not CH3, is crucial for the selec-
tive toxicity. The presence of the group OCH3 as in 9
and/or the removal of the group Cl resulting in molecule
12 generated an extremely toxic substance for the mac-
rophages. These results extend our previous observa-
tions on the selective and potent activity of sulfur
neolignan analogues seen on L. donovani, the causative
agent of visceral leishmaniasis to L. amazonensis, which
causes disseminated cutaneous leishmaniasis, a very dif-
ficult disease to treat, in men. The wide action spectrum
of compound 11within Leishmania species suggests that
it may act on a common parasite target, and may serve
as a new lead compound for the treatment of all forms
of leishmaniasis.
1
We found that the replacement of ketone group in the
position 7 by OH (e.g. 20 and 21) or acetate (e.g. 22) sig-
nificantly decreased the activity against both Leishmania
species, as compared to 13, 15 and 19, respectively. This
is much more drastic when comparing 13–20.
It is worth mentioning that in the same concentration
compounds 11 and 13 were more active than Glucan-
time (meglumine antimoniate), which is the first-line
drug for the treatment of all forms of leishmaniasis; nev-
ertheless, 13 was toxic to macrophages.
4. Experiment
3. Conclusions
4.1. General methods
The results shown here demonstrated that despite the
lower toxicity of the oxygenated analogues of the natu-
ral neolignans surinamensin and virolin against mam-
malian cells,14 they were much less active against
leishmania parasites than the sulfurated analogues.
The guided synthesis based on biological activity of sul-
fur analogues produced compounds with high antileish-
manial activity. Seven (5, 7, 8, 11, 13, 15 and 19) out of
1H NMR (300 and 500 MHz) and 13C NMR (75 and
125 MHz) spectra were recorded on either a Varian
Gemini 300BB or Varian INOVA-500 spectrometer.
Chemical shifts were reported in ppm from tetramethyl-
silane on the d scale. IR spectra were recorded in chloro-
form solution and measured with a Bomen model MB
series II spectrophotometer. HRMS were measured

7340
M. Aveniente et al. / Bioorg. Med. Chem. 15 (2007) 7337–7343
Table 1. Activity of neolignan analogues against intracellular amastig-
otes of L. amazonensis and L. donovani (80lg/mL)
4.2.1. 2-Phenoxy-1-phenylethanone (1). Yield: 75%; col-
ourless crystals; mp 72–74 ꢁC; IR (CHCl3): 3058, 2899,
1706 (C@O), 1600, 1301 cmꢀ1 1H NMR (500 MHz,
;
Compound
Toxicity to MØs L. donovani L. amazonensis
CDCl3): d 5.29 (s, 2H, H-8), 6.79–8.19 (m, 10H, H-
Ar). 13C NMR (125 MHz, CDCl3): d 70.7, 114.7,
121.6, 128.1, 128.8, 129.5, 133.8, 134.5, 157.9, 194.5.
MS m/z (+EI): 212 (M+, 26), 105 (100), 91 (5), 77 (35);
HRMS (+EI) (M)+; found: 212.08369; (M)+ calcd for
C14H12O2 212.08373.
1
—
—
40.0 0.0
5.8 0.5
44.0 0.4
8.8 2.0
17.7 0.8
37.9 0.0
34.2 0.3
38.8 0.0
50.5 2.5
78.1 0.4
nd
2
3
—
—
0
0
4
49.9 0.8
50.0 0.5
37.2 0.4
0.0 0.4
70.2 2.5
nd
5
—
—
6
7
—
—
8
4.2.2. 1-(4-Chlorophenyl)-2-[2-(methylthio)phenoxy]etha-
none (2). Yield: 75%; colourless crystals; mp 104–106 ꢁC;
IR (CHCl3): 3063, 2920, 1702 (C@O), 1589, 1475, 1445,
9
10
+++
—
28.8 2.1
94.1 3.0
nd
0
0.6
11
12
—
100
nd
0
1
1400, 1280 cmꢀ1; H NMR (300 MHz , CDCl3): d 2.44
+++
++
+++
—
(s, 3H, H-20), 5.25 (s, 2H, H-8), 6.75–8.02 (m, 8H, H-
Ar). 13C NMR (75 MHz, CDCl3): d 14.7, 111.8, 122.4,
125.8, 126.5, 127.9, 129.1, 129.9, 132.8, 140.3, 154.6,
193.6. MS m/z (+EI): 292 (M+,82), 153 (85), 139 (100)
111 (20), 77 (7); HRMS (+EI) (M)+; found: 292.03287;
(M)+ calcd for C15H13ClSO2 292.03259.
13
14
100
nd
0
100
nd
0
15
16
22.0
0
63.3
0
—
—
0
0
0
0
20.7 0.5
0.0 0.2
7.0 0.3
50.6 2.0
40.6 0.7
36.1 0.6
17
18
0
0
—
—
19
20
45.2 3.8
—
—
0
0
0
0.6
0.9
0
4.2.3. 2-(4-Chlorophenoxy)-1-(3,4-dimethoxyphenyl)etha-
none (3). Yield: 78%; colourless crystals; mp 94–97 ꢁC;
IR (CHCl3): 3015, 2907, 2835, 1686 (C@O), 1594,
21
22
—
—
0
28.2 0.5
0
Meglumine
antimoniate*
26.0 0.0
1
1516, 1262, 1152 cmꢀ1; H NMR (500 MHz, CDCl3):
d 3.92 (s, 3H, CH3O), 3.95 (s, 3H, CH3O), 5.20 (s, 2H,
H-8), 6.75–7.67 (m, 7H, H-Ar). 13C NMR (125 MHz,
CDCl3): d 55.9, 70.7, 110.1, 110.2, 116.0, 122.6, 126.4,
127.5, 129.3, 149.2, 154.0, 156.6, 192.6. MS m/z (+EI):
306 (M+, 10), 165 (100), 151 (43); HRMS (+EI) (M)+;
found: 306.06599; (M)+ calcd for C16H15ClO4
306.06589.
All compounds were tested in quadruplicate at 80 lg/mL. The results
are expressed as inhibition of parasite growth (100 minus % controls
cultured in medium alone). Controls were always P 1500 amastigotes
per 100 total macrophages. Means SD. nd, not determined. *Glu-
cantime, control antileishmanial drug. Toxicity to macrophages were
evaluated under light microscopy:
Key:
—, more than 80% macrophages (MØs) healthy and spreaded.
++, more than 80% macrophages rounded up.
+++, more than 80% macrophages disrupted or detached.
4.2.4. 2-(2,6-Dimethoxyphenoxy)-1-(3,4-dimethoxyphe-
nyl)propan-1-one (4). Yield: 87%; colourless crystals;
mp 93–95 ꢁC; IR (CHCl3): 2939, 2839, 1673 (C@O),
using a direct inlet system VG AUTO SPEC spectrom-
eter. Electrothermal melting point apparatus are uncor-
rected. Preparative thin-layer chromatography (PTLC)
used silica gel plates (Merck, 60 PF-254).
1593, 1514, 1480, 1421 cmꢀ1 1H NMR (500 MHz,
;
CDCl3): d 1.87 (d, 3H, J = 6.84 Hz, H-8), 4.03 (s, 6H,
2CH3O), 4.22 (s, 3H, CH3O), 4.24 (s, 3H, CH3O), 5.60
(q, 1H, J = 6.84 Hz, H-8), 6.75–7.67 (m, 6H, H-Ar);
13C NMR (125 MHz, CDCl3): d 18.2, 55.7, 55.8, 55.9,
80.7,105.2, 109.8, 111.5, 123.7, 124.0, 128.3, 136.0,
148.8, 153.1, 153.4, 197.4. MS m/z (+EI): 346 (M+,
39), 165 (100), 181 (57), 143 (2), 77 (8); HRMS (+EI)
4.2. General procedure for b-ketoethers and b-ketosulp-
hides (1–15)
A solution of 1.03 equivalent of phenol or thiophenol
derivatives and 1.80 equivalents of anhydrous K2CO3
in anhydrous ethyl methyl ketone (4.5 mL of solvent/
mmol of phenol or thiophenol derivative) was stirred
for 10 min at room temperature. After this period, a
solution of a-bromoketone in anhydrous ethyl methyl
ketone (1.5 mL of solvent/mmol of ketone) was added
dropwise and the mixture was stirred and refluxed for
3–6 h. The solution was cooled at room temperature, fil-
tered, and the residue washed with CH2Cl2. The solution
was concentrated in vacuum (to eliminate the ethyl
methyl ketone), diluted with H2O, and extracted thor-
oughly with CH2Cl2 (4·). Organic extracts were com-
bined, washed with water, 5% NaHCO3 solution,
NaCl saturated solution, dried over Na2SO4 and then
filtered and concentrated in vacuum. The b-ketoethers
and b-ketosulphides were purified by preparative thin-
layer chromatography (PTLC) or crystallization with
MeOH, affording a 72–91% yield.
(M)+;
C19H22O6346.14164.
found:
346.14157;
(M+)
calcd
for
4.2.5.
1-(3,4-Dimethoxyphenyl)-2-{2-methoxy-4-[(1E)-
prop-1-en-1-yl]phenoxy}propan-1-one (5). Yield: 81%;
colourless crystals; mp 97-99 ꢁC; IR (CHCl3): 2933,
2840, 1683 (C@O), 1594, 1511, 1465, 1511 cmꢀ1 1H
;
NMR (500 MHz, CDCl3): d 1.72 (d, 3H, J = 6.85 Hz,
H-9), 1.84 (dd; 3H, J = 6.52 Hz and J = 1.56 Hz, H-
90), 3.86 (s, 3H, CH3O), 3.92 (s, 3H, CH3O), 3.94 (s,
3H, CH3O), 5.41 (q, 1H, J = 6.85 Hz, H-8), 6.08 (dq,
1H, J = 15.69 Hz and J = 6.55 Hz, H-80), 6.19 (dd, 1H,
J = 15.72 Hz and J = 1.54 Hz, H-70), 6.75–7.67 (m, 6H,
H-Ar). 13C NMR (125 MHz, CDCl3): d 18.6, 19.5,
56.0, 56.1, 56.3, 109.7, 110.3, 111.5, 116.0, 118.8,
123.9, 124.6, 127.5, 130.7, 132.7, 146.2, 149.2, 153.8,
197.9. MS m/z (+EI): 356 (M+, 53), 191 (2), 165 (100),
77 (2); HRMS (+EI) (M)+; found: 356.16247; (M+)
calcd for C21H24O5 356.16237.

M. Aveniente et al. / Bioorg. Med. Chem. 15 (2007) 7337–7343
7341
4.2.6. 2-[(4-Chlorophenyl)thio]-1-phenylethanone (6).
Yield: 79%; colourless crystals; mp 74-76 ꢁC; IR
135.5, 136.1, 195.9. HRMS (+EI) (M+); found:
276.03747; (M+) calcd for C15H13ClSO 276.03756.
(CHCl3): 2944, 2900, 1685 (C@O), 1474, 1389 cmꢀ1
;
1H NMR (300 MHz, CDCl3): d 4, 25 (s, 2H, H-8),
7.24–7.99 (m, 8H, H-Ar). 13C NMR (75 MHz, CDCl3):
d 41.2, 129.2, 129.5, 129.9, 130.3, 130.9, 132.4, 132.9,
133.6, 133.8, 140.3, 193.0. MS m/z (+EI): 262 (M+,
17), 157 (2), 143 (2), 105 (100), 77 (43), 51 (11); HRMS
(+EI) (M)+; found: 262.02205; (M+) calcd for
C14H11ClSO 262.02191.
4.2.12. 1-(3,4-Dimethoxyphenyl)-2-(phenylthio)propan-1-
one (12). Yield: 89%; colourless crystals; mp 61–62 ꢁC;
1
IR and H NMR lit.22 13C NMR (75 MHz, CDCl3): d
17.4, 46.0, 55.9, 56.0, 109.9, 110.9, 123.0, 128.4, 128.6,
128.9, 134.1, 149.0, 153.3, 195.2. HRMS (+EI) (M+);
found: 302.09764; (M+) calcd for C17H18SO3 302.09767.
4.2.13. 1-(3,4-Dimethoxyphenyl)-2-[(4-methylphenyl)thio]pro-
pan-1-one (13). Yield: 90%; colourless crystals; mp 76–
77 ꢁC; IR and 1H NMR lit.22 13C NMR (75 MHz, CDCl3):
d 17.1, 21.1, 45.9, 55.8, 56.0, 109.9, 110.9, 123.0, 128.2, 128.6,
129.6, 134.8, 138.7, 148.9, 153.1, 195.0. HRMS (+EI) (M+);
found: 316.11339; (M+) calcd for C18H20SO3 316.11332.
4.2.7.
1-(4-Chlorophenyl)-2-[(4-chlorophenyl)thio]etha-
none (7). Yield: 88%; colourless crystals; mp 118–
119 ꢁC; IR (CHCl3): 2922, 1672 (C@O), 1587,
1389 cmꢀ1 1H NMR (300 MHz, CDCl3): d 4.20 (s,
;
2H, CH2-8), 7.20–7.93 (m, 8H, H-Ar). 13C NMR
(75 MHz, CDCl3): d 40.9, 129.2, 129.5, 129.9, 130.3,
130.9, 132.4, 132.9, 133.6, 133.8, 140.3, 193.0. MS m/z
(+EI): 296 (M+, 20), 157 (12), 139 (100), 111 (40), 75
(25); HRMS (+EI) (M)+; found: 295.98296; (M+) calcd
for C14H10Cl2SO 295.98294.
4.2.14. 2-[(4-Aminophenyl)thio]-1-(3,4-dimethoxyphenyl)pro-
pan-1- one (14). Yield: 91%; dark orange oil; IR
(CHCl3): 3455 (NAH), 3371 (NAH), 3233 (NAH),
1654 (C@O), 1594, 1418 cmꢀ1 1H NMR (300 MHz,
;
CDCl3): d 1.46 (d, 3H, J = 6.84 Hz, H-9), 3.80 (2H, bs,
NH2), 3.92 (s, 3H, CH3O), 3.96 (s, 3H, CH3O), 4.44
(q, 1H, J = 6.84 Hz, H-8), 6.44–7.73 (m, 7H, H-Ar).
13C NMR (125 MHz, CDCl3): d 16.8, 46.1, 55.9, 56.1,
109.9, 111.0, 115.3, 123.07, 125.7, 128.9, 133.9, 134.3,
137.5, 147.1, 148.9, 153.1, 195.1. MS m/z (+EI): 317
(M+, 26), 207 (4), 194 (3), 165 (100), 152 (43), 137 (8),
124 (32), 107 (7), 94 (15), 80 (20), 69 (3), 59 (27), 44 (29).
4.2.8. 1-Phenyl-2-(phenylthio)propan-1-one (8). Yield:
82%; yellow oil; IR (CHCl3): 3059, 2974, 2928, 1680
1
(C@O), 1596, 1372 cmꢀ1; H NMR (500 MHz, CDCl3):
d 1.54 (d, 3H, J = 6.86 Hz, H-9), 4.63 (q, 1H,
J = 6.86 Hz, H-8), 7.20–8.00 (10H, m, H-Ar). 13C
NMR (125 MHz, CDCl3): d 17.0, 46.1, 127.4, 128.4,
128.6, 128.8, 128.9, 129.0, 129.9, 130.1, 130.3, 131.7,
133.0, 134.6, 135.6, 196.3. MS m/z (+EI): 242 (M+,
34), 137 (100), 105 (57), 77 (52), 65 (10), 51 (20); HRMS
(+EI) (M+); found: 242.07653; (M+) calcd for C15H14SO
242.07654.
4.2.15. 2-[(4-Chlorophenyl)thio]-1-(3,4-dimethoxyphenyl)pro-
pan-1-one (15). Yield: 87%; colourless crystals; mp 83–
1
84 ꢁC; IR and H NMR lit.22 13C NMR (75 MHz,
CDCl3): d 17.0, 45.5, 55.7, 56.0, 110.0, 110.9, 123.1,
128.5, 129.1, 134.9, 135.9, 149.2, 153.5, 195.0. HRMS
(+EI) (M+); found: 336.05871; (M+) calcd for
C17H17ClSO3 336.05869.
4.2.9. 2-[(4-Methylphenyl)thio]-1-phenylpropan-1-one (9).
Yield: 75%; yellow oil; IR (CHCl3): 3061, 3030, 2972,
2925, 1679 (C@O), 1595, 1330 cmꢀ1
;
1H NMR
(300 MHz, CDCl3): d 1.55 (d, 3H, J = 6.83 Hz, H-9),
2.38 (s, 3H, H-40), 4.61 (q, 1H, J = 6.83 Hz, H-8),
7.13–8.03 (9H, m, H-Ar). 13C NMR (75 MHz, CDCl3):
d 16.8, 46.0, 128.6, 128.6, 129.1, 129.9, 133.2, 135.1,
135.5, 136.1, 195.9. MS m/z (+EI): 256 (M+, 32), 151
(100), 136 (6), 123 (19), 105 (32), 77 (32), 65 (3), 51
(8); HRMS (+EI) (M+); found: 256.09229; (M+) calcd
for C16H16SO 256.09219.
4.3. Procedure to obtain mixture b-ketosulphoxides (16)
To a solution of 100 mg (0.36 mmol) of 2-[(4-chlorophe-
nyl)thio]-1-phenylpropan-1-one (11) in anhydrous THF
(3.6 mL), 55 mg (0.40 mmol) of m-chloroperbenzoic
acid (m-CPA) in anhydrous THF (1.2 mL) was added
dropwise during 10 min. The reaction mixture was stir-
red for 1 h at room temperature, diluted with distilled
water and extracted with diethyl ether (4· 15 mL). The
organic layers were collected, washed with a 5% aqueous
sodium hydrogen carbonate solution (15 mL), saturated
with NaCl solution (15 mL) and then dried over
Na2SO4and evaporated to dryness. The residue was
purified by PTLC, with continuous elution in hexane:
EtOAc (7:3) and crystallized from MeOH, giving a
mixture of two diastereomeric sulphoxides a:b (1:1).
4.2.10. 2-[(4-Aminophenyl)thio]-1-phenylpropan-1-one (10).
Yield: 72%; dark orange oil; IR (CHCl3): 3853 (NAH),
3750 (NAH), 3682 (NAH), 3113, 1673 (C@O), 1595,
1371 cmꢀ1 1H NMR (300 MHz, CDCl3): d 1.46 (d,
;
3H, J = 6.79 Hz, H-9), 3.82 (2H, bs, NH2), 4.45 (q,
1H, J = 6.84 Hz, H-8), 6.50–7.99 (m, 9H, H-Ar). 13C
NMR (125 MHz, CDCl3): d 16.2, 46.1, 115.3, 128.7,
128.8, 128.8, 133.0, 136.2, 137.9, 147.9, 196.5, 200.7.
MS m/z (+EI): 257 (M+, 26), 152 (100), 124 (60), 105
(29), 93 (29), 77 (64), 66 (16), 59 (57), 51 (32); HRMS
(+EI) (M+); found: 257.08743; (M+) calcd for
C15H15NOS 257.08695.
4.3.1. 2-[(4-Chlorophenyl)sulfinyl]-1-phenylpropan-1-one
(16). Yield: 45; colourless crystals; mp 114–117 ꢁC; IR
(CHCl3): 1675 (C@O), 1578, 1474, 1448, 1048 (S=O),
1
1593, 1387, 1342 cmꢀ1; H NMR (300 MHz, CDCl3):
4.2.11. 2-[(4-Chlorophenyl)thio]-1-phenylpropan-1-one (11).
d a-isomer 1.33 (d, 3H, J = 6.84 Hz, H-9), 4.89 (q, 1H,
J = 7.06 Hz, H-8), 7.24–8.02 (m, 9H, H-Ar); b-isomer
1.68 (d, 3H, J = 7.07 Hz, H-9), 4.60 (q, 1H, J = 6.8 Hz,
H-8), 7.24–8.02 (m, 9H, H-Ar). 13C NMR (75 MHz,
1
Yield: 85%; colourless crystals; mp 71 ꢁC; IR and H
NMR lit.22 13C NMR (125 MHz, CDCl3): d 16.8, 46.0,
128.2, 128.6, 128.6, 129.0, 129.1, 129.9, 133.2, 135.1,

7342
M. Aveniente et al. / Bioorg. Med. Chem. 15 (2007) 7337–7343
CDCl3): d 17.0, 45.5, 55.9, 56.0, 110.0, 111.0, 123.1,
128.5, 129.1, 134.9, 135.9, 149.2, 153.5, 195.0. MS m/z
(+EI): 292 (M+, 15), 165 (100), 151 (12), 123 (7); HRMS
(+EI) (M+) found 292.03249; (M+) calcd for
C15H13ClSO2 292.03248.
3062, 2969, 1475, 1452, 1388 cmꢀ1; 1H NMR (500 MHz,
CDCl3): d 1.02 (d, 3H, J = 6.99 Hz, H-9), 3.11 (1H, s,
OH), 3.22 (dq, 1H, J = 8.47 Hz and J = 6.97 Hz, H-8),
4.32 (d, 1H, J = 8.52 Hz, H-7), 7.19–7.36 (m, 9H, H-
Ar). 13C NMR (125 MHz, CDCl3): d 17.0, 53.1, 125.9,
126.8, 127.4, 128.0, 128.1, 129.1, 129.2, 130.9, 133.7,
134.16, 134.8, 139.1. MS m/z (+EI): 278 (M+, 5) 165
(100), 151 (12), 123 (7); HRMS (+EI) (M+); found:
278.05321; (M+) calcd for C15H15ClSO 278.05321.
4.4. General procedure for b-ketosulphones (17 and 18)
To a b-ketosulphide solution in anhydrous THF (10 mL
solvent/mmol of b-ketosulphide), peracetic acid (2.20
equivalent) was added dropwise in anhydrous THF
(3 mL of the solvent/mmol of the peracid) during
10 min. The reaction was stirred at room temperature
for 24 h. Distilled water was added, extracted with
diethyl ether (4·). The organic layers were combined,
washed with water, 5% NaHCO3 solution, saturated
with NaCl solution and then dried over Na2SO4. The
solvent was removed in vacuum. The residue was puri-
fied by PTLC and crystallization.
4.5.2.
threo-1-(3,4-Dimethoxyphenyl)-2-[(4-methylphe-
nyl)thio]propan-1-ol (20). Yield: 88%; colourless crys-
tals; mp 120–123 ꢁC; IR (CHCl3): 3494 (OH), 2969,
2866, 1592 cmꢀ1
;
1H NMR (300 MHz, CDCl3): d
1.04 (d, 3H, J = 6.94 Hz, H-9), 2.37 (3H, s, H-40)
3.17 (dq, 1H, J = 8.90 Hz and J = 6.98 Hz, H-8),
3.48 (s, 1H, OH), 3.87 (s, 3H, CH3O), 3.88 (s, 3H,
CH3O), 4.27 (d, 1H, J = 8.99 Hz, H-7), 6.70–7.47 (m,
7H, H-Ar). 13C NMR (75 MHz, CDCl3): d 17.0,
53.1, 125.9, 126.8, 127.4, 128.0, 128.1, 129.1, 129.2,
130.9, 133.7, 134.2, 134.8, 139.1. MS m/z (+EI): 318
(M+,1) 167 (67), 152 (100), 139 (56), 91 (18), 77
(16); HRMS (+EI) (M+) found 318.12896; (M+) calcd
for C18H22SO3 318.12897.
4.4.1. 2-[(4-Chlorophenyl)sulfonyl]-1-phenylpropan-1-one
(17). Yield: 45%; colourless crystals; mp 119–120 ꢁC; IR
(CHCl3): 675, 1681 (C@O), 1582, 1475, 1450, 1320
(O@S@O), 1151 (O@S@O) cmꢀ1
;
1H NMR
(500 MHz,CDCl3): d 1.57 (d, 3H, J = 6.93 Hz, H-9),
5.17 (q, 1H, J = 6.93 Hz, H-8), 7.24–8.03 (m, 9H, H-
Ar). 13C NMR (125 MHz, CDCl3): d 13.3, 53.4, 65.02,
128.9, 129.1, 129.2, 131.3, 136.0, 141.2, 192.4. MS m/z
(+EI): 308 (M+,1), 105 (100), 51 (11); HRMS (+EI)
4.5.3. threo-2-[(4-Chlorophenyl)thio]-1-(3,4-dimethoxy-
phenyl)propan-1-ol (21). Yield: 96%; colourless crystals;
mp 123–125 ꢁC; IR (CHCl3): 3422 (OH), 3062, 2969,
1
1475, 1452, 1388 cmꢀ1; H NMR (500 MHz, CDCl3):
(M+)
C15H13ClSO3308.02739.
found
308.02733;
(M+)
calcd
for
d 1.02 (d, 3H, J = 6.95 Hz, H-9), 1.54 (s, 1H, OH),
3.18 (dq, 1H, J = 8.54 Hz and J = 6.96 Hz, H-8),
3.79 (s, 3H, CH3O), 3.80 (s, 3H, CH3O), 4.26 (d,
1H, J = 8.61 Hz, H-7), 7.19–7.36 (m, 7H, H-Ar). 13C
NMR (125 MHz, CDCl3): d 17.1, 53.1, 125.9, 126.8,
127.4, 128.0, 128.1, 129.1, 129.2, 130.9, 133.7, 134.2,
134.8, 139.1. MS m/z (+EI): 338 (M+,1), 167 (67),
152 (100), 137 (56), 91 (6), 77 (11); HRMS (+EI)
(M+) found 338.07428; (M+) calcd for C17H19ClSO3
338.07434.
4.4.2. 1-(3,4-Dimethoxyphenyl)-2-[(4-methylphenyl)sulfo-
nyl]propan-1-one (18). Yield: 45%; colourless crystals;
mp 125–126 ꢁC; IR (CHCl3): 3023, 2940, 1700 (C@O),
;
1371 (O@S@O), 1162 (O@S@O) cmꢀ1 1H NMR
(500 MHz, CDCl3): d 1.54 (d, 3H, J = 6.91 Hz, H-9),
2.42 (s, 3H, H-40),3.92 (s, 3H, CH3O), 3.95 (s, 3H,
CH3O), 5.10 (q, 1H, J = 6.93 Hz, H-8), 6.87–7.70 (m,
7H, H-Ar). 13C NMR (125 MHz, CDCl3): d 13.4, 21.6,
56.0, 56.1, 64.6, 110.0, 110.8, 124.6, 129.4, 129.4,
129.8, 133.0, 145.2, 149.1, 154.2, 190.7. MS m/z (+EI):
348 (M+, 15), 165 (100), 151 (12), 123 (7); HRMS
(+EI) (M+) found 348.10330; (M+) calcd for
C18H20SO5 348.10315.
4.5.4. threo-2-[(4-Chlorophenyl)thio]-1-phenylpropyl ace-
tate (22). One-hundred milligrams (0.36 mmol) of threo-
1-phenyl-2-(40-chlorothiophenoxy)-1-propanol (19), 59 mg
(0.58 mmol) of acetic anhydride and 74 mg (0.94 mmol)
of pyridine in anhydrous methyl ethyl ketone (20 mL)
were stirred under heating at 80 ꢁC during 24 h. After
this period, the solution was washed with 5% HCl solu-
tion (3·), water, and then dried over Na2SO4. After fil-
tration and evaporation under reduced pressure, the
product was purified by PTLC with continuous elution
in hexane:EtOAc (9:1), giving the acetylated derivative
(22). Yield: 78%; colourless oil; IR (CHCl3): 3063,
4.5. General procedure for reduction with NaBH4
To a solution of NaBH4 (2.02 equivalent) in MeOH
(1 mL solvent/0.13 mmol), the b-ketosulphide in THF
(1 mL solvent/0.04 mmol) was slowly added. The mix-
ture was stirred at room temperature for 30 min. Water
was added and extracted with ethyl ether (4·). The or-
ganic extracts were combined, washed with distilled
water, 5% NaHCO3 solution, saturated with NaCl solu-
tion and then dried over Na2SO4. Filtration and evapo-
ration under reduced pressure afforded a mixture of
diastereomeric alcohols erythro:threo. The major prod-
uct (threo) was obtained by PTLC with continuous elu-
tion in hexane:EtOAc (9:1).
2971, 1736 (OAc), 1476, 1371 cmꢀ1
;
1H NMR
(500 MHz, CDCl3): d 1.05 (d, 3H, J = 6.8 Hz, H-9),
1.93 (s, 3H, OAc) 3.49 (qt, J = 7.18 Hz, 1H, H-8), 5.67
(1H, d, J = 7.3 Hz, H-7), 7.15–7.39 (9 H, m, H-Ar).
13C NMR (125 MHz, CDCl3): d 17.0, 46.1, 127.1,
127.4, 128.5, 128.6, 128.6, 128.9, 130.1, 130.3, 131.7,
133.0, 134.5, 135.6, 196.2. MS m/z (+EI): 320 (M+, 5),
260 (27), 171 (77), 149 (20), 136 (8), 117 (17), 107 (65),
43 (100), 91 (11), 77 (13), 59 (11). HRMS (+EI) (M+)
found 320.06369; (M+) calcd for C17H17ClSO2
320.06378.
4.5.1. threo-2-[(4-Chlorophenyl)thio]-1-phenylpropan-1-ol
(19). Yield: 95%; colourless oil; IR (CHCl3): 3422 (OH),

M. Aveniente et al. / Bioorg. Med. Chem. 15 (2007) 7337–7343
7343
7. Boeck, P.; Falca˜o, C. A. B.; Leal, P. C.; Yunes, R. A.;
Cechinel-Filho, V.; Torres-Santos, E. C.; Rossi-Bergman,
B. Bioorg. Med. Chem. 2006, 14, 1538.
8. Kapou, A.; Nikolas, P. B.; Nikos, A.; Calogeropoulou, T.;
Koufaki, M.; Scoulica, E.; Nikolaropoulos, S. S.; Mavro-
moustakos, T. Bioorg. Med. Chem. 2007, 15, 1252.
9. Kaur, K.; Patel, S. R.; Patil, P.; Jain, M.; Khan, S. I.;
Jacob, M. R.; Ganesan, S.; Tekwani, B. L.; Jain, R.
Bioorg. Med. Chem. 2007, 15, 915.
5. Antileishmanial activity
The in vitro sensitivity of L. donovani (LD-1S/MHOM/
SD/00-strain 1S) and L. amazonensis (MHOM/BR/75-
Josefa) amastigotes to test compounds was determined
in a mouse peritoneal macrophage model, using a mod-
ification of the method described by Neal & Croft.27
Mouse peritoneal macrophages were isolated from
BALB/c mice and seeded in 16-well tissue-culture cham-
ber slides (Labtek Products, Miles Laboratories) at
2 · 105 cells per 0.1 mL DMEM/chamber. The cells were
maintained at 37 ꢁC in a 4% CO2/air mixture for 2 hours
and then infected with 8 · 105 stationary-phase culture
promastigotes of L. donovani or L. amazonensis in
0.1 mL DMEM containing 5% heat-inactivated foetal
calf serum, 50lg/mL streptomycin and 5 U/mL penicil-
lin for 4 h.
10. Davis, A. J.; Kedzierski, L. Curr. Opin. Invest. Drugs 2005,
6, 163.
11. Chen, M.; Christensen, S. B.; Theander, T. G.; Kharazmi,
A. Antimicrob. Agents Chemother. 1994, 38, 1339.
12. Torres-Santos, E. C.; Moreira, D. L.; Kaplan, M. A. C.;
Meirelles, M. N.; Rossi-Bergmann, B. Antimicrob. Agents
Chemother. 1999, 43, 1234.
13. Muzitano, M. F.; Cruz, E. A.; Almeida, A. P.; Da-Silva, S.
A. G.; Kaiser, C. R.; Guette, C.; Rossi-Bergmann, B.;
Costa, S. S. Planta Med. 2006, 72, 81.
14. Barata, L. E. S.; Gottlieb, O. R.; Ru´veda, E. A.; Baker, P.
M. Phytochemistry 1978, 17, 783.
15. Syrja¨nen, K.; Brunow, G. Tetrahedron 2001, 57, 365.
16. Zacchino, S.; Rodriguez, G.; Pezzenati, G.; Giannini, F.;
Enriz, R. J. Ethnopharmacol. 1998, 62, 35.
17. Lopes, N. P.; Chicaro, P.; Kato, M. J.; Albuquerque, S.;
Yoshida, M. Planta Med. 1998, 64, 667.
18. Lima, E. O.; Maia, R. F.; Barbosa, R. C. S. B. C.; Xavier-
Filho, L.; Paulo, M. Q.; Santos, L. S.; Barata, L. E. S.
The cultures were then washed with pre-warmed saline
to remove free parasites and non-adherent cells, and
0.2 mL test compounds or Glucantime (Rhodia, Meglu-
mine antimoniate), used as a reference drug, was added
in quadruplicate to infected macrophages at 80 lg/mL.
After 48 h, the macrophage monolayers were fixed with
methanol and stained with Giemsa. The total number of
amastigotes per 200 cells was determined and the results
were expressed as percentage growth inhibition (100
minus the percentage of parasites in relation to controls
cultured in the absence of any drug). The toxicity to
macrophages was scored according to the degree of cell
disruption in Giemsa-stained cultures.
ˆ
´
Cienc. Cult. e Saude 1987, 9, 55.
19. Barata, L. E. S.; Santos, L. S.; Fernandes, A. M. A. P.;
Ferri, P. H.; Paulo, M. Q.; Neal, R.; Jourdan, M. C.
Abstracts of II Brazilianisch-Deustsches Symposium fu¨r
Naturstoffchemie, Hannover, 1991, 18.
20. Song, S. Y.; Lee, I.; Park, C.; Lee, H.; Hahm, J. C.; Kang,
W. K. Int. J. Mol. Med. 2005, 16, 517.
21. Alves, C. N.; Barroso, L. P.; Santos, L. S.; Jardim, I. N. J.
Braz. Chem. Soc. 1998, 9, 577.
References and notes
22. Barata, L. E. S.; Santos, L. S.; Ferri, P. H.; Phillipson, J.
D.; Paine, A.; Croft, S. L. Phytochemistry 2000, 55, 589.
23. Neal, R. A.; Allen, S.; McCoy, N.; Olliaro, P.; Croft, S. L.
J. Antimicrob. Chemother. 1995, 35, 577.
1. Herwaldt, B. L. Lancet 1999, 354, 1191.
2. Croft, S. L.; Coombs, G. H. Trends Parasitol. 2003, 19,
502.
3. Desjeux, P. Comp. Immunol. Microbiol. Infect. Dis. 2004,
27, 305.
24. Moreira, E. S. A.; Petrillo-Peixoto, M. L. Braz. J. Med.
Biol. Res. 1991, 24, 459.
4. Coler, R. N.; Reed, S. G. Trends Parasitol. 2005, 21,
244.
5. Raht, S.; Trivellin, A.; Imbrunito, T. R.; Tomazela, D. M.;
Jesus, M. N.; Marzal, P. C.; Junior, H. F. A.; Tempone,
A. G. Quim. Nova 2003, 26, 550.
25. Rangel, H.; Dagger, F.; Hernandez, A.; Liendo, A.; Urbina,
J. A. Antimicrob. Agents Chemother. 1996, 40, 2785.
26. Costa, M. C. A.; Barata, L. E. S.; Takahata, Y. J. Mol.
Struct.—Theochem. 1999, 464, 281.
27. Neal, R. A.; Croft, S. L. J. Antimicrob. Chemother. 1984,
14, 463.
6. Jha, T. K. Indian J. Med. Res. 2006, 123, 389.