Synthesis and anti-mycobacterial activity of novel amino alcohol derivatives

Article abstract of DOI:10.1016/j.ejmech.2011.01.004

Thirteen new hydroxyethylamines have been synthesized from reactions of (2S,3S)Boc-phenylalanine epoxide, piperonylamine and arenesulfonyl chlorides in good yields. These compounds were evaluated as antibacterial agents against Mycobacterium tuberculosis

Full text of DOI:10.1016/j.ejmech.2011.01.004

European Journal of Medicinal Chemistry 46 (2011) 974e978
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and anti-mycobacterial activity of novel amino alcohol derivatives
,
c
,
a
a
a
a
Wilson Cunico a , Claudia R.B. Gomes , Maria L.G. Ferreira , Thaís G. Ferreira , Danielle Cardinot ,
*
Marcus V.N. de Souza a, Maria C.S. Lourenço b
a Instituto de Tecnologia em Fármacos e Farmanguinhos, FioCruz e Fundação Oswaldo Cruz, R. Sizenando Nabuco, 100, Manguinhos, 21041-250, Rio de Janeiro, RJ, Brazil
b Instituto de Pesquisas Clínicas Evandro Chagas, Departamento de Bacteriologia, FioCruz e Fundação Oswaldo Cruz, Av. Brazil, 4365, Manguinhos, Rio de Janeiro, Brazil
c NuQuiA e Núcleo de Química Aplicada, Departamento de Química Orgânica, UFPel, Campus Universitário s/n, 96010-900 Pelotas, RS, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
Thirteen new hydroxyethylamines have been synthesized from reactions of (2S,3S)Boc-phenylalanine
epoxide, piperonylamine and arenesulfonyl chlorides in good yields. These compounds were evaluated as
antibacterial agents against Mycobacterium tuberculosis H37Rv using the Alamar Blue susceptibility test
Received 25 August 2010
Received in revised form
28 December 2010
Accepted 5 January 2011
Available online 13 January 2011
and their activity expressed as the minimum inhibitory concentration (MIC) in mM. Two amino alcohols
displayed significant activity when compared with first line drug ethambutol (EMB). Therefore this class
of compounds could be a good starting point to develop new lead compounds in the treatment of
tuberculosis.
Keywords:
Tuberculosis
Ó 2011 Elsevier Masson SAS. All rights reserved.
Amino alcohols
Hydroxyethylamines
1. Introduction
treatment of tuberculosis show that it does not have the same
target as EMB [10]. It has also been reported that the presence of
Amino alcohols are very important and versatile compounds
with significant applications in many fields, such as in synthetic
and medicinal chemistry. Different compounds containing the
moiety amino alcohols have been synthesized to use in various
diseases [1]. For example, compounds that present hydroxyethyl-
amines core have the capacity to inhibit aspartic protease enzymes
and are widely used as anti-HIV [2,3], antimalarial [4] and anti-
leishmaniose [5] agents. Recently, we reported the synthesis and
antimalarial activity against Plasmodium falciparum of hydrox-
yethypiperazines [6] and hydroxyethylsulfonamides derivatives [7].
The only amino alcohol used in the treatment of tuberculosis (TB)
disease is Ethambutol (EMB). Despite its modest anti-tuberculosis
activity, EMB is used in combination with other front-line anti-
tuberculosis agents mainly owing to its synergy with the other
drugs and also because it’s low toxicity [8].
a hydroxyl group
b to the amine results in an increase in antitu-
bercular potency [8,9]. Moreover, the distance between oxygen
atom and nitrogen atom in EMB is the same distance of both atoms
in hydroxyethylamine structure suggesting good relationship
between both structures (Fig. 1).
Tuberculosis (TB) is a chronic bacterial infection transmitted
through the air. This disease is caused by the bacteria Mycobacte-
rium tuberculosis and mainly affects the lungs (pulmonary TB),
which is responsible for more than 75 percent of cases, but it may
also affect different parts of the body, such as the brain, stomach,
bones, skin, intestine, liver, kidneys, spinal cord and breasts [11,12].
Different factors are responsible for the resurgence of TB, such the
AIDS epidemic, which emerged in the mid-1980s and immigration,
war, famine, homelessness.
A serious problem worldwide in the fight against TB is the rapid
spread of the multidrug-resistant (MDR) TB due to inconsistent or
partial treatment, and the lack of new drugs in the market.
Particularly worrisome is the super bacterium XDR-TB (extensively
drug-resistant tuberculosis), which is resistant to all first and
second line anti-TB drugs. Because of these problems, the World
Health Organization (WHO) declared TB a global health emergency
in 1993. According to statistical data, 9.27 million people world-
wide develop active TB and almost 1.77 million die every year [13].
To overcome the problems with available treatments, new drugs
to treat TB are urgently required, specifically more potent therapies,
Lee et al. [9] reported that the 1,2-ethylenediamine moiety is the
EMB pharmacophore due the possibility of chelate formation with
divalent metal ions such copper, and that the best 1,2-diamine
synthesized was 35-fold more active than EMB. However, results
of advanced studies of this 1,2-ethylenediamine derivative for
* Corresponding author. Instituto de Tecnologia em Fármacos e Farmanguinhos,
FioCruz e Fundação Oswaldo Cruz, R. Sizenando Nabuco, 100, Manguinhos, 21041-
250, Rio de Janeiro, RJ, Brazil. Tel.: þ55 53 3275 7358.
E-mail address: wjcunico@yahoo.com.br (W. Cunico).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.01.004

W. Cunico et al. / European Journal of Medicinal Chemistry 46 (2011) 974e978
975
for 4 h without any purification as an oil (Scheme 2). Table 1 shows
the yields, melting points and LCeMS data for compounds 3, 4, 5aef
and 6aee.
OH R4
N
H
N
R2
R3
H
N
HO
HO
H
R2
N
H
OH
All the compounds were identified by 1H, 13C NMR and by
LCeMS data. In the proton nuclear magnetic resonance spectra (1H
NMR), the signals of hydrogen for the synthesized compounds were
verified on the basis of their chemical shifts, multiplicities and
coupling constants (Table 2). 2D-NMR techniques (HMBQ, HMQC
N
H
R4
N
R3
ethambutol
hydroxyethylamine core
Fig. 1. Ethambutol and hydroxyethylamine-based structures.
O
O
OH
OH
ii
H2N
N
H
O
O
O
O
O
4
t-BuO NH
OH
O
NH2
O
t-BuO NH
N
i
+
H
O
O
93%
O
3
O
t-BuO NH
N
2
1
S
O
iii
5e
R = NO2
5a-e
iv
5f
R
R = NH2
Scheme 1. Reaction and conditions: i: IPA, reflux, 16 h; ii: TFA/CH2Cl2 (1/3), r.t., 4 h; iii: Et3N, DMF, ArSO2Cl, CH2Cl2, r.t., 4 h; iv: H2, Pd/C 10%, EtOH, r.t., 16 h.
with fewer side effects, to be used in shorter treatment regimens
and to be employed to treat MDR TB and latent disease. In this
context and in the course of our investigations on hydroxyethyl-
amine derivatives [6,7], the aim of this work is the synthesis and in
vitro activity of novel hydroxyethylsulfonamide-based compounds,
against M. tuberculosis.
and COSY) helped us to assign the correct signals of compounds. For
the hydroxyethylamine core, the protons H1 appears as two
double-doublets more shielded than the protons H4, which also
shows two double-doublets. The two multiplets in the 1H NMR
spectra in the range of
and H3 protons. The 13C NMR spectra exhibited CH signals at
72e71 ppm for C3 (CeOH) and at 56e60 ppm for C2 (CeNH).
d 3.59 to 3.37 ppm were assigned to the H2
d
d
The CH2 signals for C4 and C1 appears at
35e38 ppm, respectively.
d 49e55 ppm and
2. Results and discussion
2.1. Chemistry
2.2. Anti-mycobacterial activity
The target compounds 3, 4, 5aef and 6aee were prepared as
outlined in Scheme 1 and Scheme 2. The selective ring-opening of
the (2S,3S)Boc-phenylalanine epoxide 1 with piperonilamine 2 in
reflux of isopropanol afforded the hydroxyethylamine intermediate
3, which was coupled with arenesulfonyl chlorides by using trie-
thylamine, CH2Cl2 and DMF (catalytic concentration) at room
temperature to give the hydroxyethylsulfonamides 5aee in good
yields (Scheme 1). The compound 5f was prepared by reduction
reaction of nitro group of compound 5e with H2 Pd/C 10% using
ethanol in quantitative yield. We also synthesized the amino
alcohol 4 after deprotection of tert-butoxycarbonil group with tri-
fluoroacetic acid and CH2Cl2 (1/3) mixture at room temperature in
quantitative yield (Scheme 1).
The results of anti-mycobacterial activity of all compounds 3, 4,
5aef and 6aee is shown in Table 3. The intermediates 3 and 4
showed poor activity suggesting that the sulfonamide moiety was
important to activity. Clearly, the presence of amino alcohol moiety
on hydroxyethylsulfonamides 6aee is crucial for anti-mycobacte-
rial activity since the presence of the carbamate moiety (tert-
butoxycarbonyl group) leads to loss of activity (5aef). This infor-
mation was in according with literature reported once reduced
Table 1
Yields and selected physical properties of compounds 3, 4, 5aef and 6aee.
Product
R
m.p.a (ꢀC)
Yieldb (%)
LC/MS m/z (%)
The amino alcohols 6aee were prepared in excellent yields from
reaction of hydroxyethylsulfonamides 5aee with a solution of tri-
fluoroacetic acid and methylene chloride (1/3) at room temperature
3
4
e
148e149
oil
92
95
93
71
89
72
76
91
79
66
68
68
61
415.2 (Mþ þ 1, 100)
315.2 (Mþ þ 1, 100)
673.0 (Mþ þ K, 100)
623.2 (Mþ þ K, 51)
607.1 (Mþ þ K, 100)
611.2 (Mþ þ K, 100)
e
5a
5b
5c
5d
5e
5f
6a
6b
6c
6d
6e
Br
189e190
160e161
175e177
159e161
194e195
oil
oil
oil
oil
oil
OMe
Me
F
NO2
NH2
Br
OMe
Me
F
O
O
O
O
638.2 (Mþ
þ
K, 94)
O
5
OH
OH
3
535.2 (Mþ þ 1, 100)
532.1 (Mþ þ 1, 98)
484.2 (Mþ þ 1, 100)
473.1 (Mþ þ 1, 100)
500.1 (Mþ þ 1, 100)
415.2 (Mþ þ 1, 100)
O
O
t-BuO NH
N
2
H2N
N
i
S
R
S
R
O
4
O
61-79%
1
5a-e
NO2
oil
6a-e
a
melting points are uncorrected.
yields of purified compounds.
b
Scheme 2. Reaction and conditions: i: TFA/CH2Cl2 (1/3), r.t., 4 h.

976
W. Cunico et al. / European Journal of Medicinal Chemistry 46 (2011) 974e978
Table 2
Selected 1H and 13C NMR data of compounds 3, 4, 5aef and 6aee.
d
(ppm) for 1H NMR (JH-H Hz) and 13C NMR (JC-F Hz)a
3
4
7.27e7.19 (m; 2H); 7.17e7.15 (m; 3H); 6.92 (s; 1H); 6.83 (d; 1H; J ¼ 7.9); 6.75 (d; 1H; J ¼ 7.8); 6,66 (d; 1H; J ¼ 9.1; OH); 5.96 (s; 2H; OCH2O); 4.79 (br; 1H; NH);
3.59 (s; 2H; H5); 3.59e3.56 (m; 1H; H2); 3.45e3.44 (m; 1H; H3); 2.97 (dd; 1H; J ¼ 13.8; 2J ¼ 3.1H4a); 2.55 (dd; 1H; J ¼ 13.6; 2J ¼ 3.5; H4b); 2.49 (dd; J ¼ 11.9; 2J
¼ 6.5; H1a); 2.44 (dd; 1H; J ¼ 11.9; 2J ¼ 7.4; H1b); 1.24 (s; 9H; C(CH3)3).
155.3 (C]O); 147.2, 145.8, 139.8, 134.9, 129.1, 127.9, 125.6, 121.0, 108.4, 107.8 (aryl); 100.6 (OCH2O); 77.3 (C(CH3)3); 72.0 (C3); 55.1 (C2); 52.8 (C5); 51.6
(C4); 36.1
(C1); 28.2 (C(CH3)3).
7.19e6.55 (m; 5H); 6.92 (s; 1H); 6.83 (d; 1H; J ¼ 7.9); 6.75 (d; 1H; J ¼ 7.8); 6.66 (d; 1H; J ¼ 9.1; OH); 5.96 (s; 2H; OCH2O); 4.79 (br; 1H; NH); 3.59 (s; 2H; H5);
3.59e3.55 (m; 1H; H2); 3.44e3.43 (m; 1H; H3); 2.97 (dd; 1H; J ¼ 13.8; 2J ¼ 3.1H4a); 2.55 (dd; 1H; J ¼ 13.6; 2J ¼ 3.5; H4b); 2.49 (dd; J ¼ 11.9; 2J ¼ 6.5; H1a);
2.44 (dd; 1H; J ¼ 11.9; 2J ¼ 7.4; H1a).
147.2, 145.8, 139.8, 134.9, 129.7, 129.2, 127.5, 121.0, 108.4, 107.8 (aryl); 100.6 (OCH2O); 72.0 (C3); 55.1 (C2); 52.8 (C5); 51.6 (C4); 36.1 (C1).
5a 7.80e7.76 (m; 2H); 7.74e7.73 (m; 2H); 7.23e7.18 (m; 2H); 7.16e7.11 (m; 3H); 6.83 (d; 1H; J ¼ 8.4); 6.77 (s; 1H) 6.76 (d; 1H; J ¼ 7.1); 6.62 (d; 1H; J ¼ 9.0; OH);
5.99 (d; 2H; J ¼ 2.7; OCH2O); 4.99 (d; 1H; J ¼ 6.5; NH); 4.45 (d; 1H; J ¼ 15.4; H5a); 4.29 (d; 1 H; J ¼ 15.4; H5b); 3.50e3.42 (m; 2H; H2, H3); 3.01 (dd; 1H; J
¼ 14.7; 2J
¼ 8.6; H4a); 2.90 (dd; 1H; J ¼ 13.8; 2J ¼ 2.8; H4b); 2.51e2.48 (m; 1H; H1a); 2.44 (dd; 1H; J ¼ 13.6; 2J ¼ 10.8; H1b); 1.21 (s; 9H; C(CH3)3).
155.2 (C]O); 147.2, 146.6, 139.6, 139.4, 132.1, 130.1, 129.1, 129.1, 128.9, 127.8, 126.4, 125.6, 121.8, 108.4, 107.9 (aryl); 100.9 (OCH2O); 77.4 (C(CH3)3); 71.5 (C3);
54.9 (C2); 50.9 (C5); 50.2 (C4); 35.3 (C1); 28.1 (C(CH3)3).
5b 7.76 (d; 2H; J ¼ 8.8); 7.22 (t; 2H; J ¼ 7.4); 7.17e7.13 (m; 3H); 7.09 (d; 2H; J ¼ 8.8); 6.81 (d; 1H; J ¼ 7.8); 6.76 (s; 1H); 6.75 (d; 1H; J ¼ 7.9); 6.71 (d; 1H; J ¼ 8.8;
OH); 5.97 (d; 2H; J ¼ 2.4; OCH2O); 4.92 (d; 1H; J ¼ 6.1; NH); 4.38 (d; 1H; J ¼ 15.5; H5a); 4.26 (d; 1H; J ¼ 15.4; H5b); 3.84 (s; 3H; OMe); 3.53e3.46 (m; 2H;
H2, H3); 3.35e3.30 (m; 1H; H4a); 2.95e2.89 (m; 2H; H4b, H1a); 2.46 (dd; 1H; J ¼ 13.5; 2J ¼ 10.6; H1b); 1.23 (s; 9H; C(CH3)3).
162.3 (aryl); 155.2 (C]O); 147.2, 146.4, 139.5, 131.6, 130.5, 129.2, 129.1, 127.8, 125.6, 121.7, 114.3, 108.5, 107.9 (aryl); 100.9 (OCH2O); 77.4 (C(CH3)3); 71.9 (C3);
55.6 (OCH3); 54.8 (C2); 51.2 (C5); 50.4 (C4); 35.1 (C1); 28.1 (C(CH3)3).
5c 7.70 (d; 2H; J ¼ 8.1); 7.38 (d; 2H; J ¼ 8.0); 7.25e7.20 (m; 2H); 7.15e7.12 (m; 3H); 6.81 (d; 1H; J ¼ 8.4); 6.75 (s; 1H); 6.74 (d; 1H; J ¼ 7.8); 6.59 (d; 1H; J
¼ 9.0; OH); 5.97 (d; 2H; J ¼ 2.3; OCH2O); 4.94 (d; 1H; J ¼ 6.3; NH); 4.39 (d; 1H; J ¼ 15.4; H5a); 4.27 (d; 1H; J ¼ 15.4; H5b); 3.51e3.42 (m; 2H; H2, H3); 3.35e3.31
(m; 1H; H4a); 2.96e2.87 (m; 2H; H4b, H1a); 2.46 (dd; 1H; J ¼ 13.8; 2J ¼ 10.5; H1b); 2.40 (s; 3H; CH3); 1.22 (s; 9H; C(CH3)3).
155.2 (C]O); 147.3, 146.5, 143.0, 139.5, 137.1, 130.5, 129.7, 129.2, 127.9, 127.0, 125.7, 121.8, 108.5, 108.0 (aryl); 100.9 (OCH2O); 77.5 (C(CH3)3); 71.9 (C3); 54.9
(C2); 51.2 (C5); 50.5 (C4); 35.1 (C1); 28.1 (C(CH3)3); 21.0 (CH3).
5d 7.89 (dd; 2H; J ¼ 8.7; 2J ¼ 5.2); 7.41 (t; 2H; J ¼ 8.8); 7.23e7.20 (m; 2H); 7.16e7.11 (m; 3H); 6.82 (d; 1H; J ¼ 4.0); 6.76 (s; 1H); 6.75 (d; 1H; J ¼ 7.4); 6.62 (d; 1H;
J ¼ 8.9; OH); 5.98 (d; 2H; J ¼ 2.4; OCH2O); 4.99 (d; 1H; J ¼ 6.4; NH); 4.44 (d; 1H; J ¼ 15.4; H5a); 4.29 (d; 1H; J ¼ 15.4; H5b); 3.55e3.43 (m; 2H; H2 and H3); 2.99
(dd; 1H; J ¼ 14.8; 2J ¼ 8.7; H1a); 2.90 (d; 1H; J ¼ 13.5; J ¼ ¼ 3.0; H4a); 2.49e2.47 (m; 1H; H4b); 2.42 (dd; 1H; J ¼ 14.8; 2J ¼ 9.8; H1b); 1.21 (s; 9H; C(CH3)3).
3
164.2 (d; J ¼ 250.0; aryl)); 155.2 (C]O); 147.3; 146.6; 139.5; 136.7; 130.2; 130.0 (d; JCF ¼ 9.0); 129.2; 127.9; 125.7; 121.8; 116.3 (d; 2J ¼ 22.3); 108.5; 108.0
(aryl); 101.0 (OCH2O); 77.5 (C(CH3)3); 71.6 (C3); 54.9 (C2); 50.9 (C5); 50.2 (C4); 35.3 (C1); 28.1 (C(CH3)3).
5e 8.37 (d; 2H; J ¼ 8.8); 8.08 (d; 2H; J ¼ 8.8); 7.23e7.21 (m; 2H); 7.15e7.11 (m; 3H); 6.85 (d; 1H; J ¼ 7.9); 6.79 (s; 1H); 6.78 (d; 1H; J ¼ 7.9); 6.62 (d; 1H;
J ¼ 9.0; OH); 5.99 (d; 2H; J ¼ 3.3; OCH2O); 4.99 (d; 1H; J ¼ 6.6; NH); 4.56 (d; 1H; J ¼ 15.3; H5a); 4.33 (d; 1H; J ¼ 15.4; H5b); 3.52e3.38 (m; 2H; H2, H3); 3.11
(dd; 1H; J ¼ 14.8; 2J ¼ 8.8; H4a); 2.90 (dd; 1H; J ¼ 13.2; 2J ¼ 3.2; H4b); 2.50e2.48 (m; 1H; H1a); 2.43 (dd; 1H; J ¼ 13,7; 2J ¼ 10.8; H1b); 1.21 (s; 9H; C(CH3)3).
155.2 (C]O); 149.5, 147.4, 146.7, 146.1, 139.4, 129.8, 129.8, 129.3, 129.1, 128.6, 127.9, 125.7, 124.4, 121.9, 108.5, 108.1 (aryl); 101.1 (OCH2O); 77.5 (C(CH3)3);
71.2 (C3); 54.9 (C2); 50.7 (C5); 50.1 (C4); 35.4 (C1); 28.1 (C(CH3)3).
5f 7.44 (d; 2H; J ¼ 8.6); 7.23e7.18 (m; 2H); 7.16e7.13 (m; 3H); 6.80 (d; 1H; J ¼ 7.7); 6.75 (s; 1H); 6.74 (d; 1H; J ¼ 8.0). 6.61 (d; 2H); 6.55 (d; 1H; J ¼ 9.0; OH); 5.99
(s; 2 H; NH2); 5.97 (d; 2H; J ¼ 2.4; OCH2O); 4.83 (d; 1H; J ¼ 6.0; NH); 4.29 (d; 1H; J ¼ 15. 4; H5a); 4.18 (d; 1H; J ¼ 15.3; H5b); 3.57e3.44 (m; 2H; H2, H3); 3.30
(dd; 1H; J ¼ 14.6; 2J ¼ 3.2; H4a); 2.90 (dd; 1H; J ¼ 13.8; 2J ¼ 2.6; H4b); 2.80 (dd; 1H; J ¼ 14.4; 2J ¼ 8.0; H1a); 2.47e2.45 (m; 1H; H1b); 1.23 (s; 9H; (C(CH3)3);
1.10 (s; 2H; NH2).
155.1 (C]O); 152.7, 147.1, 146.2, 139.5, 130.9, 129.0, 128.8, 127.7, 124.3, 121.5, 112.6, 112.6, 108.4, 107.7 (aryl); 100.7 (OCH2O); 77.3 (C(CH3)3); 72.1 (C3); 54.7
(C2); 51.4 (C5); 50.5 (C4); 34.9 (C1); 28.0 (C(CH3)3).
6a 7.77 (d; 2H; J ¼ 8.7); 7.73 (d; 2H; J ¼ 8.7); 7.28e7.23 (m; 2H); 7.19e7.16 (m; 3H); 6.85 (d; 1H; J ¼ 7.4); 6.78 (s; 1H); 6.75 (d; 1H; J ¼ 8.0); 5.99 (s; 2H;
OCH2O); 4.75 (d; 1H; J ¼ 5.7; NH); 4.41 (d; 1H; J ¼ 15.5; H5a); 4.34 (d; 1H; J ¼ 15.4; H5b); 3,45 (dd; 1H; J ¼ 14.5; 2J ¼ 2.4; H4a); 3.42e3.37 (m; 1H; H2); 3.12
(dd; 1H; J ¼ 14.8; 2J ¼ 8.7: H1a); 2.71 (dd; 1H; J ¼ 14.4; 2J ¼ 3.0; H4b); 2.30 (dd; 1H; J ¼ 14.7; 2J ¼ 9.8; H1b); 1.27 (br; 2H; NH2).
147.2, 146.5, 139.8, 139.5, 132.2, 130.4, 129.2, 128.9, 128.1, 126.3, 125.8, 121.7, 108.4, 107.9 (aryl); 100.9 (OCH2O); 72.2 (C3); 56.1 (C2); 51.4 (C5); 49.9
(C4); 36.7 (C1).
6b 7.76 (d; 2H; J ¼ 8.9); 7.27e7.24 (m; 2H); 7.20e7.14 (m; 3H); 7.09 (d; 2H; J ¼ 8.9); 6.83 (d; 1H; J ¼ 7.9); 6.74 (d; 1H; J ¼ 7.9); 5.98 (s; 2H; OCH2O); 4.70
(d; 1H; J ¼ 5.6; NH); 4.32 (s; 2H; H5); 3.85 (s; 3H; OCH3); 3.44e3.40 (m; 2H; H2, H3); 3.04 (dd; 1H; J ¼ 13.9; 2J ¼ 8.0, H4a); 2.74e2.70 (m; 2H; H4b, H1a);
2.29 (dd; 1H; J ¼ 14.1; 2J ¼ 9.6, H1b); 1.17 (br; 2H; NH2).
162.3, 147.2, 146.4, 139.9, 131.5, 130.8, 129.2, 129.1, 128.0, 125.7, 121.6, 114.3, 108.4, 107.9 (aryl); 100.9 (OCH2O); 72.5 (C3); 56.0 (OCH3); 55.6 (C2); 51.6 (C5);
50.2 (C4); 36.3 (C1).
6c 7.70 (d; 2H; J ¼ 8.2); 7.39 (d; 2H; J ¼ 8.0); 7.27e7.24 (m; 2H); 7.20e7.17 (m; 2H); 6.75 (d; 1H; J ¼ 7.9); 6.73 (s; 1H); 6.72 (dd; 1H; J ¼ 6.9; 2J ¼ 1.2); 5.98
(s; 2H; OCH2O); 4.78 (br; 1H; NH); 4.32 (s; 2H; H5); 3.46e3.41 (m; 2H; H2, H3); 3.04 (dd; 1H; J ¼ 15.1; 2J ¼ 9.0; H4a); 2.79e2.76 (m; H4b, H1a); 2.40 (s; 3H;
CH3); 2.32 (dd; 1H; J ¼ 14.3; 2J ¼ 8.6; H1b); 1.24 (br; 2H; NH2).
147.4, 146.7, 143.3, 139.9, 137.1, 131.0, 129.9, 129.4, 128.4, 127.2, 126.1, 121.9, 108.7, 108.1 (aryl); 101.1 (OCH2O); 72.5 (C3); 56.1 (C2); 51.9 (C5); 50.4 (C4);
38.7 (C1); 21.2 (CH3).
6d 7.90e7.86 (m; 2H); 7.40 (t; 2H; J ¼ 8.8); 7.27e7.22 (m; 2H); 7.19e7.14 (m; 3H); 6.83 (d; 1H; J ¼ 7.9); 6.77 (s; 1H); 6.74 (d; 1H; J ¼ 8.0); 5.99 (s; 2H;
OCH2O); 4.74 (d; 1H; J ¼ 5.2; NH); 4.40 (d; 1H; J ¼ 15.5; H5a); 4.35 (d; 1H; J ¼ 15.4; H5b); 3.45 (dd; 1H; J ¼ 14.5; 2J ¼ 2.7; H4a); 3.41e1.32
(m; 2H; H2, H3); 3.11 (d; 1H; J ¼ 14.5; 2J ¼ 8.6; H4b); 2.76e2.69 (m, 1H; H1a); 2.30 (dd; 1H; J ¼ 14.2; 2J ¼ 10.0; H1b); 1.28 (br; 2H; NH2).
164.2 (d; J ¼ 249.0), 147.2, 146.6, 139.8, 136.6, 130.5, 130.0 (d; 3J ¼ 9.1), 129.2, 128.1, 125.7, 121.6, 116.2 (d; 2J ¼ 22.2), 108.4, 107.9 (aryl); 100.9 (OCH2O); 72.3
(C3); 56.1 (C2); 51.3 (C5); 49.9 (C4); 35.3 (C1)
6e 8.35 (d; 2H; J ¼ 8.8); 8.06 (d; 2H; J ¼ 8.8); 7.26e7.23 (m; 2H); 7.17e7.14 (m; 3H); 6.85 (d; 1H; J ¼ 7.8); 6.81 (d; 1H; J ¼ 1.3); 6.77 (dd; 1H; J ¼ 6.0; 2J ¼ 1.3); 5.99
(d; 2H; J ¼ 2.5; OCH2O); 4.76 (d; 1H; J ¼ 5.3; NH); 4.5 (d; 1H; J ¼ 15.4; H5a); 4.39 (d; 1H; J ¼ 15.4; H5b); 3.49 (dd; 1H; J ¼ 14.4; 2J ¼ 1.9; H4a); 3.22 (dd; 1H;
J ¼ 14.5; 2J ¼ 9.0; H4b); 2.75e2.67 (m; 3H; H2, H3, H1a); 2.30 (dd; J ¼ 14.4; 2J ¼ 10.3; H1b); 1.27 (br; 2H; NH2).
149.4, 147.3, 146.6, 146.0, 139.7, 130.1, 129.2, 128.5, 128.1, 125.8, 124.3, 121.7, 108.4, 108.0 (aryl); 101.0 (OCH2O); 71.9 (C3); 56.1 (C2); 51.2 (C5); 49.7 (C4);
38.8 (C1).
a
NMR Spectra in DMSO-d6/TMS.
basicity of amino group results in a loss of activity. [9] The amino
alcohol moiety on hydroxyethylsulfonamides 6aee is more closely
to ethambutol structure than carbamate moiety of hydrox-
yethylsulfonamides 5aee. The best results were obtained for amino
alcohols 6a, 6b and 6c, especially for amino alcohol 6a (R ¼ Br) that
M). The compound with
the strongly electron withdrawing nitro (6e) did not show activity,
exhibit the highest activity (MIC ¼ 23.5
m
suggesting that the substituent in the phenyl ring is important for

W. Cunico et al. / European Journal of Medicinal Chemistry 46 (2011) 974e978
977
Table 3
3.4. General procedure for the preparation of compound 5f
The in vitro activity of compounds 3, 4, 5aef and 6aee against Mycobacterium
tuberculosis H37Rv strain (ATCC 27294, susceptible to ethambutol).
To a stirred solution of nitro compound 5e (0.57 mmol) in
absolute ethanol (15 mL) under a blanket of nitrogen was added
10% palladium on activated charcoal (5 mg). The reaction was
evacuated, placed under a hydrogen atmosphere and stirred over-
night. The reaction mixture was filtered through Celite and the
solvent was removed under reduced pressure to yield brown oil.
The residue was purified by chromatography on silica, eluting with
3:1 hexane/ethyl acetate.
Comp.
R
MIC (
m
M)
logP
3
4
e
241
318
5.152
1.409
7.114
6.362
6.754
5.381
6.264
6.469
3.371
2.619
3.010
1.638
2.521
0.35
e
5a
5b
5c
5d
5e
5f
6a
6b
6c
6d
6e
EMB
Br
>500
>500
>500
>500
>500
>500
23.5
51.6
106
211
>500
15.9
OMe
Me
F
NO2
NH2
Br
OMe
Me
F
NO2
e
3.5. General procedure for the preparation of compounds 4 and
6aee
Trifluoracetic acid (1.5 mL, 20 mmol) was added to a solution of
the compounds 3 or 5aee (2 mmol) in CH2Cl2 (6 mL). After 4 h at
room temperature, the solvent was removed in high vacuum. The
residue was dissolved in EtOAc (20 mL), washed with 5% NaHCO3
aqueous solution, H2O, brine and dried over MgSO4. The solvent
was removed to afford the compounds 4 or 6aee, respectively,
without any further purification.
the biological activity. Three other compounds (3, 4, and 6d)
exhibited low activity (MIC up to 200 M). The more active
compounds are at least 1.5e6 times less active than EMB
M), their IC50 values are in the micromolar concen-
m
(MIC ¼ 15.9
m
tration range comparable to recently reported results [10] and
could be a start point to find new compounds with better antitu-
bercular activity. Lipophilicities of the compounds 3, 4, 5aef, 6aee
and the standard drug EMB, which were expressed as logP values,
were determined using logP method through online http://www.
molinspiration.com/cgi-bin/properties site, as show in Table 3.
3.6. Anti-mycobacterial activity
The anti-mycobacterial activities of compounds 3, 4, 5aef and
6aee have been assessed against M. tuberculosis ATTC 27294 using
the micro plate Alamar Blue assay (MABA) [14] (Table 3). This
methodology is nontoxic, uses a thermally-stable reagent and
shows good correlation with proportional and BACTEC radiometric
methods [15,16]. The method is described as follows: 200 ml of
sterile deionized water was added to all outer-perimeter wells of 96
sterile well plates (falcon, 3072: Becton Dickinson, Lincoln Park, NJ)
to minimize evaporation of the medium in the test wells during
incubation. The 96 plates received 100 mL of the Middlebrook 7H9
broth (Difco laboratories, Detroit, MI, USA) and successive dilution
of the compounds was made directly on the plate. The final drug
3. Experimental
3.1. Materials and methods
Unless otherwise indicated, common reagents and solvents
were used as obtained from commercial suppliers without further
purification. All melting points were determined on a Buchi
Melting Point B-545 and are uncorrected. 1H and 13C NMR spectra
were recorded using a Bruker DRX 400 spectrometer (1H at
400.14 MHz and 13C at 100.61 MHz) or with a Bruker Avance 500
spectrometer (1H at 500.13 MHz and 13C at 125.75 MHz) in DMSO-
d6 containing TMS as in internal standard. The low resolution LC/
MS analyses were performed on an LC/MS micromass ZMD using
chloroform/methanol 1:1 as mobile phase with flux of 0.3 mL/min.
The analyses used Electrospray Ionization technique on positive ion
mode. Samples were introduced by the standard direct insertion
probe method.
concentrations tested were 0.01e20.0
m
g/mL. Plates were covered
ꢀ
and sealed with parafilm and incubated at 37 C for five days.
25 mL of a freshly prepared 1:1 mixture of Alamar Blue (Accumed
International, WestlakeOhio) reagent and 10% tween 80 was then
added to the plate and incubated for 24 h. A blue color in the well
was interpreted as no bacterial growth, and a pink color was scored
as growth. The minimal inhibition concentration (MIC) was defined
as the lowest drug concentration, which prevented a color change
from blue to pink.
3.2. General procedure for the preparation of compound 3
4. Conclusion
Epoxide 1 (1.6 mmol) and piperonylamine 2 (1.5 mmol) were
dissolved in isopropanol (10 mL) and stirred under reflux for 16 h.
After this period, the solvent was removed by evaporation and the
crude product was purified by crystallization in methanol/water
(7:3).
In conclusion, the synthesis of thirteen hydroxyethylamines
derivatives 3, 4, 5aef and 6aee were easily performed with good
yields. All compounds were tested against M. tuberculosis and three
of them (6aec) exhibit significant activity when compared with
first line drug ethambutol (EMB) with amino alcohol 6a (R ¼ Br)
3.3. General procedure for the preparation of compounds 5aee
showing the best activity (MIC ¼ 23.5
mM). It suggests that these
amino alcohols could be a good start point to find new lead
The compound 3 was dissolved in CH2Cl2 (10 mL) and then TEA
(2.2 mmol) and DMF (0.2 mmol) were added. The mixture was
stirred for 30 min over nitrogenous atmosphere, arenesulfonyl
chloride (2.0 mmol) was added portion wise and stirred over 8 h.
The organic layer was washed with 5% HCl aqueous solution, water,
brine and dried over MgSO4. The solvent was removed in high
vacuum and the products 5aee were obtained after recrystalization
in hot hexane.
compounds.
Acknowledgements
The authors gratefully acknowledge Farmanguinhos for the
financial support of the research. We also thank CIEE-RJ (D.C. and
T.G.F.) and CNPq (W.C. and M.V.N.S.).

978
W. Cunico et al. / European Journal of Medicinal Chemistry 46 (2011) 974e978
(b) W. Cunico, C.R.B. Gomes, V. Facchinetti, M. Moreth, C. Penido,
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