Synthesis, tuberculosis inhibitory activity, and SAR study of N-substituted-phenyl-1,2,3-triazole derivatives

Article abstract of DOI:10.1016/j.bmc.2006.08.019

The aim of this work was to describe the synthesis, the in vitro anti-Mycobacterium tuberculosis profile, and the structure-activity relationship (SAR) study of new N-substituted-phenyl-1,2,3-triazole-4-carbaldehydes (3a-l). The reactions of aromatic amin

Full text of DOI:10.1016/j.bmc.2006.08.019

Bioorganic & Medicinal Chemistry 14 (2006) 8644–8653
Synthesis, tuberculosis inhibitory activity, and SAR study
of N-substituted-phenyl-1,2,3-triazole derivatives
a
a
a
b
´
Marilia S. Costa, Nu´bia Boechat, Erica A. Rangel, Fernando de C. da Silva,
Alessandra M. T. de Souza,b Carlos R. Rodrigues,d Helena C. Castro,e Ivan N. Junior,c
Maria Cristina S. Lourenc¸o,c Solange M. S. V. Wardella and Vitor F. Ferreirab,*
a
ˆ
Fundac¸a˜o Oswaldo Cruz, Instituto de Tecnologia em Fa´rmacos, Departamento de Sı´ntese Organica,
Manguinhos, CEP 21041250, Rio de Janeiro, RJ, Brazil
b
ˆ
Universidade Federal Fluminense, Departamento de Quı´mica Organica, Instituto de Quımica,
´
Outeiro de Sa˜o Joa˜o Baptista, CEP 24020-150, Nitero´i, RJ, Brazil
cFundac¸a˜o Oswaldo Cruz, Instituto de Pesquisa Evandro Chagas, Manguinhos, CEP 21040-030, Rio de Janeiro, RJ, Brazil
dUniversidade Federal do Rio de Janeiro, Faculdade de Farma´cia, ModMolQSAR, 24020-150 Rio de Janeiro, Brazil
eUniversidade Federal Fluminense, LABioMol, Departamento de Biologia Celular e Molecular,
Outeiro de Sa˜o Joa˜o Baptista, CEP 24020-150, Nitero´i, RJ, Brazil
Received 5 July 2006; revised 13 August 2006; accepted 15 August 2006
Available online 1 September 2006
Abstract—The aim of this work was to describe the synthesis, the in vitro anti-Mycobacterium tuberculosis profile, and the structure–
activity relationship (SAR) study of new N-substituted-phenyl-1,2,3-triazole-4-carbaldehydes (3a–l). The reactions of aromatic
amine hydrochlorides with diazomalonaldehyde (1) produced several N-substituted-phenyl-1,2,3-triazole-4-carbaldehydes (3a–l)
in moderate-to-good yields. In order to investigate the influence of the difluoromethylene group on the anti-Mycobacterium activity
of these compounds, fluorination of triazoles with DAST converted the corresponding carbaldehyde compounds into new difluo-
romethyl derivatives (4a–l) in excellent yield. Characterization of all compounds was achieved by spectroscopic means and addition-
al for 1-(4-methylphenyl)-1,2,3-triazole-4-carbaldehyde, 3k by X-ray crystallography. Compounds (3a–l) and (4a–l) have been
screened for the inhibitory activity against Mycobacterium tuberculosis H37Rv strain (ATCC 27294) and all of them were able to
inhibit the growth of the bacterium. Interestingly, 3a and 3k exhibited the best inhibition with MIC values of 2.5 lg/mL, similar
to pharmaceuticals currently used in the treatment of tuberculosis. Our SAR study indicated the importance of the hydrogen bond
acceptor subunit (3a–l), the position in the aromatic ring, the planarity of triazole and phenyl rings in these compounds, and a cor-
relation between the uniform HOMO coefficient distribution and the anti-tubercular activity. The significant activity of 3a and 3k
pointed them as promising lead molecules for further synthetic and biological exploration.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
one-third of the world’s population harbors latent infec-
tion of TB and thus declared it as a global emergency.1–3
Tuberculosis (TB) is caused by Mycobacterium tubercu-
losis and remains as a leading cause of mortality world-
wide. Currently, among the infected individuals
approximately eight million develop active TB, and al-
most two million die from this disease. Of the new TB
cases reported, 95% occur in developing countries every
year. World Health Organization estimates that about
The mortality and spread of this disease has been fur-
ther aggravated by its synergy with Human Immunode-
ficiency Virus (HIV).4,5 By destroying the two most
important cells to the containment of tubercle bacilli
(macrophages and CD4-receptor-bearing lymphocytes),
HIV vigorously promotes the progression of recent or
remotely acquired TB infection to active disease.6 The
deadly synergy between TB and HIV has led to a qua-
drupling of TB cases in several African and Asian
countries. In fact it is estimated that eleven million
adults are now co-infected with HIV and tuberculosis
worldwide.3 Thus both the current HIV pandemic
Keywords: Tuberculosis; Diazomalonaldehyde; 1,2,3-Triazoles; Diflu-
oromethylation; DAST.
*
Corresponding author. Tel.: +55 21 26292345; fax: +55 21
26292362; e-mail: cegvito@vm.uff.br
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.08.019

M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
8645
and multidrug-resistant M. tuberculosis have emerged
as major obstacles for treatment and public health con-
trol of tuberculosis.1,2
4-carbaldehydes (3a–l). Since the introduction of fluorine
atom(s) may strongly modify the physical, chemical, and
biological properties in a molecule and thus may increase
its biological activity, in this work we also investigated the
influence of the difluoromethylene group on the antimy-
cobacterial profile of these compounds by synthesizing
N-substituted-phenyl-4-difluoromethyl-1,2,3-triazoles
(4a–l).24,25
Chemotherapy of TB started in the 1940s and since then
some agents have been discovered, including p-amino-
salicylic acid (PAS), isoniazide (INH), pyrazinamide
(PZA), cycloserine, ethionamide, rifampicin, and etham-
butol.7 However, the emergence of multiple drug-resis-
tant (MDR) TB revealed the urgent need for new anti-
tubercular drugs.8
2. Chemistry
Internationally efforts are now being made to develop
new anti-tubercular agents.3 Several studies have indi-
cated the potential of analogues of isoniazide9,10 and
heterocyclic compounds, such as BM212,11,12 as tuber-
culostatic agents. In pursuit of this goal, our research ef-
forts herein have been directed toward the discovery of
new chemical entities that are effective as anti-tuberculo-
sis agents.
Different methods for synthesizing 1,2,3-triazole are de-
scribed in the literature.26 In this work, the cycloaddi-
tion reactions between diazomalonaldehyde (1) and
aniline hydrochlorides in water (2a–l) were effectively
used to prepare the N-substituted-phenyl-1,2,3-tria-
zole-4-carbaldehydes (3a–l) in moderate-to-good
yields.27–29 Then the carbaldehyde moieties in 3a–l were
readily converted into difluoromethyl groups for gener-
ating 4a–l, on treatment with N,N-diethylaminosulfur
trifluoride (DAST).30
1,2,3-Triazoles are an important class of heterocyclic
compounds dueto their wide range of applications includ-
ing as pharmaceutical agents.13 Literature described tria-
zoles as antiplatelet agents,14 dopamine D2 receptor
ligands related to schizophrenia,15 anti-inflammatory
agents,16,17 anticonvulsants,18 b-lactamase inhibitors,19
and antiviral20 and antimicrobial agents.21–23 In this
paper, we describe the synthesis, the in vitro antimycobac-
terial profile, and the structure–activity relationship
(SAR) study of new N-substituted-phenyl-1,2,3-triazole-
3. Pharmacology
In vitro antimycobacterial activities of compounds 3a–l
and 4a–l were assessed against M. tuberculosis H37Rv
strain (ATCC 27294), susceptible to both rifampin and
isoniazide, and were carried out using the Microplate
Alamar Blue assay (MABA), which shows good correla-
Table 1. Comparison of in vitro antimycobacterial activity of compounds 3a–l and 4a–l against drug-sensitive Mycobacterium tuberculosis H37Rv
strain and molecular weight (MW), molecular volume (MV), clogP and polar surface area (PSA), and molecular electronic properties (EHOMO,
ELUMO, dipole moment)
2
3
˚ ˚
clogP PSA (A ) MV (A ) Dipole (debye) EHOMO (eV) ELUMO (eV)
Compound
R
MIC (lg/mL) Inhibition (%) MW
3a
3b
3,5-DiCl
3-CN
4-CN
2.5
20.0
5.0
100
NDa
ND
94
242.06 3.08
198.18 1.20
198.18 1.20
203.20 1.62
203.20 1.62
233.22 1.57
233.22 1.23
207.62 2.36
207.62 2.36
252.07 2.51
187.20 2.12
218.04 1.47
264.06 3.54
220.18 1.72
220.18 1.72
225.19 2.11
225.19 2.11
255.22 2.13
255.22 1.79
229.61 2.77
229.61 2.77
274.06 2.92
209.19 2.38
240.17 1.99
100.97
170.26
168.85
105.59
122.41
NDa
224.63
215.40
215.43
221.88
224.52
251.64
253.53
209.65
209.70
214.49
214.45
220.64
233.83
224.58
224.62
231.08
233.71
218.84
262.62
218.84
218.88
223.68
223.64
229.82
—
2.76
3.81
0.58
6.31
5.71
5.32
6.99
3.76
3.04
2.92
5.28
0.83
2.45
2.95
1.48
5.95
5.01
4.83
3.11
5.13
2.68
2.57
4.80
1.68
—
À7.22
À7.34
À7.31
À6.44
À6.24
À5.94
À6.09
À6.99
À6.81
À6.81
À6.60
À7.45
À7.17
À7.33
À7.25
À6.37
À6.17
À5.87
À6.93
À6.50
À6.74
À6.74
À6.53
À7.49
—
À2.33
À2.39
À2.61
À1.69
À1.84
À1.69
À1.75
À2.17
À2.15
À2.18
À1.92
À2.93
À1.95
À2.11
À2.37
À1.28
À1.28
À1.29
À1.74
À1.30
À1.72
À1.76
À1.40
À2.81
—
3c
3d
2-OCH3
4-OCH3
40.0
10.0
3e
100
59
3f
3g
2,5-(OCH3)2 80.0
3,4-(OCH3)2 80.0
0
123.01
103.72
103.72
103.72
103.72
NDa
3h
3i
3-Cl
4-Cl
10.0
5.0
100
ND
100
100
ND
55
3j
3k
4-Br
5.0
2.5
4-CH3
4-NO2
3,5-DiCl
3-CN
3l
4a
20.0
80.0
80.0
20.0
40.0
10.0
47.91
114.45
113.04
49.78
66.60
NDa
4b
4c
ND
ND
86
4-CN
2-OCH3
4-OCH3
4d
4e
93
74
4f
4g
2,5-(OCH3)2 80.0
3,4-(OCH3)2 80.0
66
54
67.21
47.91
47.91
47.91
47.91
NDa
4h
4i
3-Cl
4-Cl
4-Br
4-CH3
4-NO2
—
80.0
40.0
20.0
40.0
40.0
1.0
ND
75
4j
4k
87
4l
ND
ND
ND
Rifampicin
Ethambutol
—
—
—
—
—
—
—
3.25
—
—
—
—
a ND, not determined.

8646
M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
tion and proportionality with BACTEC radiometric
methods.31–33 This colorimetric method uses the Alamar
Blue–resazurin-based oxidation–reduction indicator to
obtain drug susceptibility measurements for bacteria.
The minimum inhibitory concentration (MIC, lg/mL)
was defined as the lowest drug concentration that pre-
vented a color change from blue (no growth) to pink
(growth). Rifampicin and Ethambutol were used as po-
sitive controls (Table 1).
N1-N2 = 1.367(3)
N1-C5 = 1.350(3)
C4-C5 = 1.371(3)
C4-C12 = 1.463(3)
N2-N3 = 1.312(3)
N3-C4 = 1.370(3)
N1-C6 = 1.435(3)
C12-O1 = 1.211(3)
C5-N1-N2 = 110.55(19) N1-N2-N3 = 107.32(18)
N2-N3-C4 = 108.48(19) N3-C4-C5 = 109.0(2)
C4-C5-N1 = 104.6(2)
C4-C12-O1 = 124.1(2)
C11-C6-N1 = 119.41(19) C7-C6-N1 = 119.51(19)
C5-N1-C6 = 129.0(2) N2-N1-C6 = 120.43(17)
4. Results and discussion
The preparation of diazomalonaldehyde (1) was per-
formed by the procedure described by Stojanovic and
Arnold.28 The reaction of 1 with appropriate aniline
hydrochlorides (2a–l), in aqueous solution, yielded N-
substituted-phenyl-1,2,3-triazole-4-carbaldehydes (3a–l).
The new series of N-substituted-phenyl-4-difluorometh-
yl-1,2,3-triazoles (4a–l) were obtained in 90-98% yields
on reaction of 3 with N,N-diethylaminosulfur trifluoride
(DAST)30 (Scheme 1).
Figure 1. Molecular structure and selected geometric parameters,
o
(A, ), for 1-(4-methylphenyl)-1,2,3-triazole-4-carbaldehyde (3k).
˚
triazole-4-carbaldehyde, 3a and 3k, respectively, showed
the highest activity with 100% inhibition and MIC of
2.5 lg/mL, comparable to the positive controls (Table
1). In addition compounds 3c (R = 4-CN), 3i (R = 4-
Cl), and 3j (R = 4-Br) also presented a potential activity
(MIC = 5.0 lg/mL) as they presented MIC values lower
than 6.25 lg/mL, which is currently the limiting value
for evaluation of new anti-tuberculosis candidates
according to the Global Discovery Program for Novel
Anti-tuberculosis Drugs. The other compounds of this
series and the 4-difluoromethyl derivatives displayed a
lower in vitro activity against M. tuberculosis
(MIC > 6.5 lg/mL). The most effective analogue in 4-
difluoromethyl series was 4e (R = 4-OCH3) with 93%
inhibition at 10.0 lg/mL (Table 1).
Characterizations of 3a–l and 4a–l were generally car-
ried out using microanalysis, EI-MS, IR, 1H NMR,
13C NMR spectroscopy, X-ray diffraction34 and for
4a–l, also by 19F NMR spectroscopy. The 1H NMR
spectrums of 3a–l showed carbaldehyde (CHO) proton
as singlet at d 10.21–10.24 ppm. Further the absence of
this singlet and presence of triplet at d 6.95–6.97
(JHF = 55.5 Hz) on the 1H NMR spectrums of 4a–l indi-
cated conversion from carbaldehyde to difluoromethyl
(CHF2).
In the effort to study the structure–activity relationships
(SAR) of these compounds, we initially evaluated their
hydrophobic pattern, by calculating clogP, molecular
weight (MW) and volume (MV), polar surface area
(PSA) (Table 1), and number of hydrogen bond accep-
tors and donors (not shown).35,36 Our results pointed
all compounds as sufficiently hydrophobic for penetrat-
ing the biological membranes, probably including the
cellular wall of the mycobacterium, as determined by
Lipinski rule of 5 (clogP < 5, molecular weight (MW)
In addition, the crystal structure of 1-(4-methylphenyl)-
1,2,3-triazole-4-carbaldehyde, 3k, grown from water,
was determined by X-ray diffraction. The atom arrange-
ments for 3k are shown in Figure 1, where selected geo-
metric parameters were also included. The 3k crystal
revealed that the two rings are nearly co-planar, with
an angle between the two planar rings of about
7.11(12)ꢁ (Fig. 1).
2
˚
All 24 compounds were active against M. tuberculosis
although 3a–l derivatives were significantly more effec-
tive than 4a–l series (Table 1). This result indicated that
the fluorine atom mostly negatively affected the anti-
tubercular activity of these compounds. Interestingly
1-(3,5-dichlorophenyl)- and 1-(4-methylphenyl)-1,2,3-
6500, and PSA 6140 A , number of hydrogen bond
acceptors <10 and donors <5).35 The only exceptions
2
were 3b and 3c with PSA of 170.26 and 168.85 A (Table
˚
1). Importantly the analysis of hydrogen donors and
acceptors showed that 3a–l and 4a–l series differed from
the number of hydrogen bond acceptors (carbaldehyde
replaced at R1) (not shown). Since 3a–l derivatives were
more active than 4-difluoromethyl derivatives (4a–l), the
carbaldehyde group seems to be important to the inter-
action with the target receptor and consequently influ-
ences the inhibitory profile of these compounds (Fig. 2
and Table 1).
CHO
CHF2
N
N
N
N
NH3Cl
R
N2
N
N
a
b
H
H
+
O
O
R
R
1
4a-l
2a-l
3a-l
In the conformational analysis of all compounds using
molecular mechanics methods, the structures were
minimized and equilibrium geometry was obtained
using semi-empirical AM1 method. They were submit-
ted to a Single Point calculation on the base of DFT
methods at B3lYP/6-31G* level.37 Then structural and
electronic properties of the compounds such as
Scheme 1. Synthesis of 1,2,3-triazole derivatives 3a–l and 4a–l.
Reagents and conditions: (a) H2O, rt, 24 h, 60–80%; (b) DAST,
DCM, rt, 24 h, 90–98%. [(a) R = 3,5-diCl; (b) R = 3-CN; (c) R = 4-CN;
(d) R = 2-OCH3; (e) R = 4-OCH3; (f) R = 2,5-(OCH3); (g) R = 3,4-
(OCH3); (h) R = 3-Cl; (i) R = 4-Cl; (j) R = 4-Br; (k) R = 4-CH3; (l)
R = 4-NO2].

M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
8647
Figure 2. Comparison of molecular electrostatic potential energy isosurfaces (MEP) and LUMO density of carbaldehydes (3a–l) and fluoride
derivatives (4a–l) (A) MEP superimposed onto total electron density of 0.002 e/au3. The color code is in the range of À65.0 (deepest red) to À23.0
(deepest blue) kcal/mol. (B) LUMO density encoded onto a van der Waals surface (isodensity 0.002 e/au3) with the LUMO’s absolute density
coefficient mapped from deepest red (0.00) to deepest blue (0.03).
HOMO and LUMO (energy, coefficient orbital and
density), and dipole moment were calculated to gain
insight about their role in modulating the antimicrobi-
al activity studied. The overall analysis of HOMO and
LUMO energy values of the 3a–l and 4a–l series
revealed that both widely varied (HOMO À5.94 to
À7.45 eV and À5.87 to À7.49 eV, and LUMO À1.69
to À2.93 eV and À1.28 to À2.81 eV, respectively) but
without any clear or direct correlation with the
antimycobacterial activity (Table 1). Similarly, the
dipole moment did not show any further clue about
the biological activity profile of these series, excluding
this feature as crucial for displaying the studied
activity.
The individual analysis of the compounds of the more
active series with carbaldehyde at R1 (3a–l) revealed
the dipole moment vector directed from phenyl ring to
the triazole moiety, except for 3c and 3l, which presented
electron-withdrawing groups in para-position (not
shown). The addition of a methyl substituent, a weak
electron-donating group, at para-position of aromatic
ring (3k) led to a slight negative potential (red region)
on the ring and a high inhibitory activity as can be ob-
served in the three-dimensional MEP (Fig. 2). The com-
pound also showed distribution of HOMO through
both rings, although most of them concentrate in the
aromatic ring, which may have pointed it as the most
likely region for stacking interactions with the target
(Fig. 3A). In fact the overall analysis of HOMO orbital
coefficient distribution of 3a–l in comparison to MIC
values revealed the importance of its uniform distribu-
tion along the molecule instead of its concentration on
one part of it for the biological activity evaluated
(Fig. 3).
In this work, the electron density/LUMO was taken into
consideration where the blue and red areas around
atoms indicate a large and a small LUMO values,
respectively. Our results showed that 4a–l derivatives
have the most intense blue, which represents the largest
high orbital density, compared to 3a–l series. The
LUMO density of 3a–l series is concentrated over phen-
yl ring compared to the 4-difluoromethyl derivatives
(4a–l), in which it is distributed along the structure
(Fig. 2). This result pointed the LUMO electronic densi-
ty mainly on the topside of the 3a–l derivatives structure
is important for displaying a significant antimycobacte-
rial activity.
The evaluation of the stereoelectronic effects when the
oxygen is present in the para substituent (3e) revealed
that although a methoxy analogue may allow the par-
ticipation of the free electron pairs on the oxygen by
resonance and the increase of the electron density in
the aromatic system, the compound 3e exhibited a 4-
fold decrease in activity (Table 1). The addition of
an extra methoxy group at meta-positions led to an
even less active compound (3g) revealing the impor-
tance of the volume in this context (Fig. 2). Adding
methoxy at ortho-position (3d) there was a 16-fold loss
of activity and a 28ꢁ-torsion of the aromatic ring out
of the plane also called as ortho-effect in the literature,
which currently affects the biological activity of the
compound, herein seen as a deleterious effect. Impor-
tantly, there was a significant loss of activity when
an extra methoxy group (3f) was added (Table 1).
The 3f and 3g results suggested that a high molecular
volume (MV) may compromise the interaction with
The molecular electrostatic potential map (MEP) is an
alternative approach for understanding the electrostatic
contribution to binding between receptor and drugs.
The SAR studies involving the MEP of these derivatives
pointed that the introduction of fluorine atom(s) modi-
fied the molecular electrostatic distribution in 4a–l,
which presented a lower biological profile (Fig. 2 and
Table 1). Therefore, the loss of this negative region on
the top of the molecule by the addition of the fluorine
seemed to be deleterious to the anti-tubercular activity
of these compounds.

8648
M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
Figure 3. Comparison of HOMO coefficient distribution and MIC of 3a–l derivatives (A), and druglikeness value (B) and theoretical toxicity risks of
presenting mutagenic, tumorigenic, and reproductive effects (C) of the most active compounds and isoniazide using Osiris program (http://
www.organic-chemistry.org/prog/peo/druglikeness.html). The scale of side effects ranges from low (0–1) to high (2–3) toxicity profile.
the target (Table 1). In addition, the presence of ste-
reoelectronic effects depending on the position of the
aromatic ring could also affect the biological activity
(Fig. 2 and Table 1).
in one side of the molecule may lead to weak com-
pounds (Fig. 3A).
Currently, there are many approaches that assess drug-
likeness to compounds based on topological descriptors,
fingerprints of molecular druglikeness, structural keys or
other properties as clogP and molecular weights.38 In
case of Osiris program, the occurrence frequency of each
fragment is determined within the collection of traded
drugs and within the supposedly non-druglike collection
of Fluka compounds. On that case a value between À5
and 5 indicates that the molecule contains predominant-
ly fragments, which are frequently present in commer-
cial drugs. In this work we used the Osiris program
for calculating the fragment-based druglikeness of the
most active compounds (3a, 3c, 3i, 3j, and 3k) also using
isoniazide, a tuberculostatic drug, as positive control for
the calculation due to its structural closeness with our
derivatives. Interestingly, only 3c (MIC = 5.0 lg/ml)
presented a non-potential druglikeness while 3i present-
ed the best value among them including isoniazide
(Fig. 3B). In agreement, 3c presented the worst predic-
tion of one of the toxicity risks (mutagenic, tumorigenic,
and reproductive effects) calculated for these most active
compounds using the Osiris Property Explorer (http://
www.organic-chemistry.org/). The predicted mutagenic
profile of 3c is a direct indication of its non-potential
druglikeness. The low theoretical mutagenic, tumorigen-
ic, and reproductive effects of the other compounds (3i,
3j, and 3k) indicated a low risk drug-like profile; similar
to isoniazide that in the analyzed aspects was also safe.
It is important to notice that the toxicity predicted
herein neither is a fully reliable toxicity prediction, nor
guarantees that these compounds are completely free
of any toxic effect. However it reinforced the promising
profile of these compounds for further experimental
investigation.
Replacement of a nitrile at para-position (3c) led to
significant changes in MV and an increase of the
inhibitory potential compared to the methoxy ana-
logues (Table 1). The transposition of the substituent
to a meta-position (3b) led to an 8-fold drop in activ-
ity and dislocation of HOMO to the carbaldehyde
moiety (Fig. 3). This result reinforced the importance
of the para-position in the ring for the biological
activity.
Substitution of NO2 at para-position (3l) decreased
four times the inhibitory potential of the compound,
compared to its analogues (3c). Since NO2 is a high
electron-withdrawing group, the dislocation of HOMO
to the carbaldehyde moiety was observed (Fig. 3A).
Setting a weak electron-withdrawing group, as Cl
(3i) or Br (3j), at para-position increased the lipophil-
icity but decreased the activity 4-fold compared to the
most active (Table 1). The addition of chlorine at
meta-position of compound 3h decreased the activity
two times, which pointed the position as important
as the electronic and lipophilic features. Interestingly,
the addition of an extra chlorine substituent at posi-
tion 5 (3a) led to the highest inhibitory activity, and
a similar MEP, HOMO orbital coefficient and LUMO
density compared to compound (3k) (Fig. 2 and Table
1). Apparently there is a clear correlation between the
HOMO coefficient distribution and the biological pro-
file of these molecules (Fig. 3A). This correlation is
characterized by a broad HOMO distribution through
the molecule structure for displaying significant anti-
microbial profile while the location of this coefficient

M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
8649
5. Conclusion
(125 MHz; CDCl3/Me4Si): d 119.3, 123.0, 129.8, 136.6,
137.3, 148.3, 184.6 (HC@O); EIMS (m/z): 241 (M+;
18%); 212 (M+À29; 100%); Anal. Calcd for
C9H5Cl2N3O: C, 44.66; H, 2.07; N, 17.36. Found: C,
44.66; H, 2.07; N, 17.36.
To summarize, herein we described two series of 1,2,3-
triazoles compounds with antimycobacterial profile.
The in vitro anti-tuberculosis screening of these series
showed that all compounds were active, although in
general the triazole-4-carbaldehyde derivatives (3a–l)
were more effective than the 4-difluoromethyl deriva-
tives (4a–l). Our SAR study indicated the importance
of the hydrogen bond acceptor subunit (3a–l), the posi-
tion in the aromatic ring, the planarity of triazole and
phenyl rings and the uniform HOMO coefficient distri-
bution in these compounds for the anti-tubercular activ-
ity. Although the Osiris risk alerts are not a fully reliable
toxicity prediction, the theoretical low-toxicity profile of
these compounds reinforces the significant activity of 3i,
3j, and 3k and pointed them as promising lead molecules
for further synthetic and biological exploration.
6.1.1.3. 1-(3-Cyanophenyl)-1H-1,2,3-triazole-4-carbal-
dehyde (3b). Obtained in 80% yield as white solid crys-
tals; mp 177–179 ꢁC; IR (KBr) mmax (cmÀ1) 3130, 2839,
1
2234 (CN), 1697 (C@O); H NMR (500 MHz; CDCl3/
Me4Si): d 7.75 (t, 1H, J = 8.0 Hz, 0.5 Hz; arom.); 8.06
(ddd, 1H, J = 1.2, 8.0 Hz; arom.); 7.84 (dt, 1H,
J = 1.0, 8.0 Hz; arom.); 8.15 (t, 1H, J = 2.0 Hz; arom.);
8.61 (s, 1H, triazole); 10.24 (s, 1H, HC@O); 13C NMR
(125 MHz; CDCl3/Me4Si): d 114.6, 117.0 (CN), 124.7,
133.1, 124.1, 131.2, 122.9, 136.7, 148.0, 184.6 (HC@O);
EIMS (m/z): 198 (M+, 9%); 169 (M+À29; 100%); Anal.
Calcd for C10H6N4O: C, 60.60; H, 3.05; N, 28.27.
Found: C, 60.60; H, 3.05; N, 28.27.
6. Experimental protocol
6.1. Chemistry
6.1.1.4. 1-(4-Cyanophenyl)-1H-1,2,3-triazole-4-carbal-
dehyde (3c). Obtained in 75% yield as white solid crys-
tals; mp 178–179 ꢁC; IR (KBr) mmax (cmÀ1) 3116, 2865,
1
2232 (CN), 1697 (C@O); H NMR (500 MHz; DMSO-
Melting points were determined with a Buchi Model B-
545 instrument and are uncorrected. Infrared (IR) spectra
were recorded on a Perkin-Elmer model 1420 FT-IR
d6/Me4Si): d 8.14 (d, 2H, J = 9.0 Hz; arom.); 8.24 (d,
2H, J = 9.0 Hz; arom.); 9.71 (s, 1H, triazole); 10.14 (s,
1H, HC@O); 13C NMR (125 MHz; DMSO-d6/Me4Si):
d 111.8, 117.8 (CN), 126.4, 121.1, 134.2, 138.8, 147.6,
184.6 (HC@O); EIMS (m/z): 198 (M+, 10%); 169
(M+À29; 100%); Anal. Calcd for C10H6N4O: C, 60.60;
H, 3.05; N, 28.27. Found: C, 60.60; H, 3.05; N, 28.27.
1
Spectrophotometer in KBr pellets. H and 13C NMR
spectra were recorded on Bruker Advance 500 plus
400.00 and 500.00 MHz, employing tetramethylsilane as
the internal reference at room temperature. 19F NMR
spectra were recorded on Brucker UltraShield plus
376.0 MHz, employing CFCl3 as internal reference at
room temperature. The chemical shifts (d) are reported
in parts per million and the coupling constant (J) in hertz.
Mass spectra were recorded on CGMS (Hewlett Packard
Model AT-6890N) autosampler/direct injection (EI/CI).
Reactions were routinely monitored by thin-layer chro-
matography (TLC) on silica gel precoated F254 Merck
plates. Microanalyses were performed on Perkin-Elmer
Model 2400 instrument and all values were within
0.4% of the calculated compositions. Chemicals em-
ployed were obtained from commercial supplies and used
without purifications, unless otherwise stated.
6.1.1.5. 1-(2-Methoxyphenyl)-1H-1,2,3-triazole-4-car-
baldehyde (3d). Obtained in 66% yield as yellow solid; mp
108–109 ꢁC; IR (KBr) mmax (cmÀ1) 3157, 2979, 1685
1
(C@O); H NMR (500 MHz; CDCl3/Me4Si): d 3.93 (s,
OCH3); 7.15 (m, 2H, arom.); 7.47 (ddd, 1H, J = 1.5,
8.0 Hz; arom.); 7.87 (dd,1H, J = 1.5, 6.5, 8.0 Hz; arom.);
8.72 (s, 1H, triazole); 10.24 (s, 1H, HC@O); 13C NMR
(125 MHz; CDCl3/Me4Si): 56.0 (OCH3); 112.3, 125.2,
121.3, 130.9, 127.3, 147.3, 150.8, 185.3 (HC@O); EIMS
(m/z): 203 (M+; 38%); 174 (M+À29; 30%); 77 (M+À126;
100%); Anal. Calcd for C10H9N3O2: C, 59.11; H, 4.43;
N, 20.69. Found: C, 59.11; H, 4.43; N, 20.68.
6.1.1. General procedures
6.1.1.6. 1-(4-Methoxyphenyl)-1H-1,2,3-triazole-4-car-
baldehyde (3e). Obtained in 76% yield as white solid; mp
158–161 ꢁC; IR (KBr) mmax (cmÀ1) 3157, 2979, 1685
6.1.1.1. General procedure for the preparation of
N-substituted-phenyl-1,2,3-triazole-4-carbaldehydes (3a–
l). A solution of diazomalonaldehyde (1) (5.0 mmol) in
water (30 mL) was added dropwise to a stirred solution
of an aniline hydrochloride (2a–l) (4.5 mmol) in water
(5 mL). The reaction mixture was stirred for 24 h at
room temperature, the solid was collected, washed with
cold water, and recrystallized from ethanol/water. The
following compounds were prepared according to this
general procedure.
1
(C@O); H NMR (500 MHz; CDCl3/Me4Si): d 3.89 (s,
OCH3); 7.06 (ddd, 2H, J = 4.5, 9.0 Hz, arom.); 7.66
(ddd, 2H, J = 4.5, 9.0 Hz, arom.); 8.46 (s, 1H, triazole);
10.21 (s, 1H, HC@O); 13C NMR (125 MHz; CDCl3/
Me4Si): 55.7 (OCH3), 123.0; 129.4, 122.4, 115.0, 148.5,
160.5, 185.1 (HC@O); EIMS (m/z): 203 (M+; 39%);
174 (M+À29; 40%); 132 (M+À71; 100%); Anal. Calcd
for C10H9N3O2: C, 59.11; H, 4.43; N, 20.69. Found:
C, 59.11; H, 4.43; N, 20.69.
6.1.1.2. 1-(3,5-Dichlorophenyl)-1H-1,2,3-triazole-4-
carbaldehyde (3a). Obtained in 73% yield as white solid;
6.1.1.7. 1-(2,5-Dimethoxyphenyl)-1H-1,2,3-triazole-4-
carbaldehyde (3f). Obtained in 73% yield as yellow solid;
mp 89 ꢁC; IR (KBr) mmax (cmÀ1) 3369, 2929, 1697
mp 156–158 ꢁC; IR (KBr) mmax (cmÀ1) 3126, 3085, 1690
1
(C@O); H NMR (500 MHz; CDCl3/Me4Si): d 7.52 (d,
1H, J = 1.5 Hz, arom.); 7.75 (d, 2H, J = 1.5 Hz; arom.);
1
(C@O); H NMR (500 MHz; CDCl3/Me4Si): d 3.85 (s,
8.75 (s, 1H, triazole); 10.22 (s, 1H, HC@O); 13C NMR
OCH3); 3.88 (s, OCH3); 7.01 (dd, 1H, J = 3.0, 9.0 Hz;

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M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
1
arom.); 7.06 (d, 1H, J = 9.0 Hz); 7.49 (d, 1H, J = 3.0,
9.0 Hz; arom.); 8.79 (s, 1H, triazole); 10.23 (s, 1H,
HC@O); 13C NMR (125 MHz; CDCl3/Me4Si): d 55.7
(OCH3), 123.0, 129.4, 122.4, 115.0, 148.5, 160.5, 185.1
(HC@O); EIMS (m/z): 233 (M+; 45%); 204 (M+À29;
40%); 162 (M+À71; 100%); Anal. Calcd for
C11H11N3O3: C, 56.65; H, 4.75; N, 18.02. Found: C,
56.64; H, 4.77; N, 18.02.
(C@O); H NMR (500 MHz; CDCl3/Me4Si): d 2.45 (s,
1H, CH3); 7.36 (d, 2H, J = 8.0 Hz, arom.); 7.64 (d,
2H, J = 8.0 Hz, arom.); 8.49 (s, 1H, triazole); 10.22 (s,
1H, HC@O); 13C NMR (125 MHz; CDCl3/Me4Si): d
21.1 (CH3), 140.1, 133.8, 130.5, 123.0, 120.7, 148.0,
185.1 (HC@O); EIMS (m/z): 187 (M+; 20%); 158
(M+À29; 52%); 130 (M+À57; 100%); Anal. Calcd for
C10H9N3O: C, 64.16; H, 4.85; N, 22.45. Found: C,
64.16; H, 4.85; N, 22.44.
6.1.1.8. 1-(3,4-Dimethoxyphenyl)-1H-1,2,3-triazole-4-
carbaldehyde (3g). Obtained in 80% yield as yellow solid;
mp 170–171 ꢁC; IR (KBr) mmax (cmÀ1) 3131, 2970, 1693
6.1.1.13. 1-(4-Nitrophenyl)-1H-1,2,3-triazole-4-carbal-
dehyde (3l). Obtained in 80% yield as yellow solid;
mp185–186 ꢁC; IR (KBr) mmax (cmÀ1) 3136; 1696
1
(C@O); H NMR (500 MHz; CDCl3/Me4Si): d 3.96 (s,
1
OCH3); 3.98 (s, OCH3); 6.99 (d,1H, J = 8.5 Hz, arom.);
7.23 (dd, 1H, J = 2.5, 8.5 Hz, arom.); 7.36 (d, 1H,
J = 2.5 Hz, arom.); 8.49 (s, 1H, triazole); 10.21 (s, 1H,
HC@O); 13C NMR (125 MHz; CDCl3/Me4Si): d 56.2
(OCH3); 56.3 (OCH3); 105.0, 111.2, 112.8, 129.5,
123.1, 148.0, 149.9, 150.1, 185.1 (HC@O); EIMS (m/z):
233 (M+; 50%); 204 (M+À29; 9%); 162 (M+À71;
100%); Anal. Calcd for C11H11N3O3: C, 56.65; H,
4.75; N, 18.02. Found: C, 56.65; H, 4.75; N, 18.02.
(C@O); 1524 (NO2); H NMR (500 MHz; DMSO-d6/
Me4Si): d 8.31 (d, 2H, J = 8.8 Hz); 8.48 (d, 2H,
J = 8.8 Hz; arom.); 9.78 (s, 1H, triazole); 10.15 (s, 1H,
HC@O); 13C NMR (125 MHz; CDCl3/Me4Si): d 121.4,
125.4, 126.7, 140.2, 147.2, 147.7, 184.8 (HC@O); EIMS
(m/z): 218 (M+; 9%); 189 (M+À29; 100%); Anal. Calcd
for C9H6N4O3: C, 49.55; H, 2.77; N, 25.60. Found: C,
49.56; H, 2.77; N, 25.58.
6.1.1.14. General procedure for the preparation of N-
substituted-phenyl-4-difluoromethyl-1,2,3-triazoles (4a–l).
A solution of a N-substituted-phenyl-1,2,3-triazole-4-
carbaldehyde (7.5 mmol) in dichloromethane (15 mL)
was added dropwise to DAST (2 equiv) at room tem-
perature. The reaction mixture was stirred for 24 h at
room temperature, poured onto a saturated sodium
bicarbonate solution at 0 ꢁC, and extracted with
dichloromethane. The combined organic layers were
washed with brine, dried over sodium sulfate, filtered,
and the filtrate concentrated under reduced pressure.
The solid residue was purified by column chromatog-
raphy using chloroform as eluent. The following com-
pounds were prepared according to this general
procedure.
6.1.1.9. 1-(3-Chlorophenyl)-1H-1,2,3-triazole-4-carb-
aldehyde (3h). Obtained in 73% yield as yellow solid;
mp 129–130 ꢁC; IR (KBr) mmax (cmÀ1) 3127, 2874,
1701 (C@O); 1H NMR (500 MHz; CDCl3/Me4Si): d
7.51 (m, 2H, arom.); 7.85 (t, 1H, J = 1.5, 3.0 Hz, arom.);
7.68 (ddd, 1H, J = 1.5, 3.0, 8.0 Hz, arom.); 8.55 (s, 1H,
triazole); 10.23 (s, 1H, HC@O); 13C NMR (125 MHz;
CDCl3/Me4Si): d 118.8, 121.2, 123.0, 129.5, 131.1,
135.9, 136.9, 148.2, 184.8 (HC@O); EIMS (m/z): 207
(M+; 18%); 178 (M+À29; 92%); 111 (M+À96; 100%);
Anal. Calcd for C9H6ClN3O: C, 52.05; H, 2.91; N,
20.24. Found: C, 52.05; H, 2.92; N, 20.24.
6.1.1.10. 1-(4-Chlorophenyl)-1H-1,2,3-triazole-4-carb-
aldehyde (3i). Obtained in 75% yield as white solid; mp
159–161 ꢁC (lit.14 155–156 ꢁC); IR (KBr) mmax (cmÀ1
)
6.1.1.15.
1-(3,5-Dichlorophenyl)-4-(difluoromethyl)-
1
3127; 2874; 1701 (C@O); H NMR (500 MHz; CDCl3/
Me4Si): d 7.56 (2H, d, J = 1.5, 3.0 Hz; arom.); 7.74
(2H, d, J = 7.0 Hz; arom.); 8.53 (1H, s, triazole); 10.22
(1H, s, HC@O); 13C NMR (125 MHz; CDCl3/Me4Si):
d 22.0, 123.0, 130.2, 134.6, 135.8, 148.2, 184.9 (HC@O);
EIMS (m/z): 207 (M+; 32%); 178 (M+À29; 100%); Anal.
Calcd for C9H6ClN3O: C, 52.05; H, 2.91; N, 20.24.
Found: C, 52.06; H, 2.91; N, 20.25.
1H-1,2,3-triazole (4a). Obtained in 98% yield as
white solid; mp 83–85 ꢁC; IR (KBr) mmax (cmÀ1) 3160,
1042, 1H NMR (500 MHz; CDCl3/Me4Si): d 6.95 (t,
1H, CHF2, J = 54.5 Hz); 7.72 (d, 1H, J = 1.5 Hz;
arom.); 7.49 (dd,1H, J = 1.0, 1.5 Hz; arom.); 7.72 (d,
1H, J = 1.5 Hz; arom.); 8.24 (s, 1H, triazole); 13C
NMR (125 MHz; CDCl3/Me4Si): d 109.6 (t, CHF2,
J = 235.3 Hz); 119.2, 123.0, 129.5, 136.5, 137.6, 143.9
(t, J = 29.8 Hz); 19F NMR (376.0 MHz, CDCl3/CFCl3):
d À117.6 (2F, CHF2); EIMS (m/z): 263 (M+; 73%); 235
(M+À28; 30%); 234 (M+À29; 100%); Anal. Calcd for
C9H5Cl2F2N3: C, 40.94; H, 1.91; N, 15.91. Found: C,
40.94; H, 1.91; N, 15.91.
6.1.1.11. 1-(4-Bromophenyl)-1H-1,2,3-triazole-4-carb-
aldehyde (3j). Obtained in 76% yield as white solid; mp
190–191 ꢁC; IR (KBr) mmax (cmÀ1) 3098; 2851; 1698
1
(C@O); H NMR (500 MHz; CDCl3/Me4Si): d 7.68 (d,
2H, J = 9.0 Hz, arom.); 7.72 (d, 2H, J = 9.0 Hz, arom.);
8.54 (s, 1H, triazole); 10.22 (s, 1H, HC@O); 13C NMR
(125 MHz; CDCl3/Me4Si): d 122.2, 122.9, 123.7, 133.2,
135.1, 148.2, 184.9 (HC@O); EIMS (m/z): 253 (M+;
11%); 224 (M+À29; 32%); 116 (M+À137; 100%); Anal.
Calcd for C9H6BrN3O: C, 42.88; H, 2.40; N, 16.67.
Found: C, 42.87; H, 2.41; N, 16.67.
6.1.1.16.
1-(3-Cyanophenyl)-4-(difluoromethyl)-1H-
1,2,3-triazole (4b). Obtained in 97% yield as white solid;
mp 119–120 ꢁC; IR (KBr) mmax (cmÀ1) 3156, 2235 (CN),
1042; 1H NMR (500 MHz; CDCl3/Me4Si): d 6.97 (t, 1H,
CHF2, J = 54.5 Hz); 8.12 (dd, 1H, J = 1.5, 2.0 Hz;
arom.); 8.06 (ddd,1H, J = 1.0, 2.0, 3.0, 8.5 Hz, arom.);
7.81 (dd, 1H, J = 1.0, 7.0 Hz, arom.); 7.74 (d, 1H,
J = 8.0 Hz; arom.) 8.33 (s, 1H, triazole); 13C NMR
6.1.1.12. 1-(4-Methylphenyl)-1H-1,2,3-triazole-4-carb-
aldehyde (3k). Obtained in 86% yield as white solid; mp
105–106 ꢁC; IR (KBr) mmax (cmÀ1) 3136, 2842, 1696
(125 MHz; CDCl3/Me4Si): 109.6 (t, CHF2,
J = 237.3 Hz); 114.4, 117.1 (CN); 120.0, 124.0, 124.7,
d

M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
8651
131.1, 132.8, 137.0, 143.9 (t, J = 29.5 Hz); 19F NMR
(376.0 MHz, CDCl3/CFCl3): d À112.9 (2F, CHF2);
EIMS (m/z): 220 (M+; 24%); 192 (M+À28; 20%); 191
(M+À29; 63%); 173 (M+À47; 52%); 128 (M+À92;
45%); 102 (M+À118; 100%); Anal. Calcd for
C10H6F2N4: C, 54.55; H, 2.75; N, 25.45. Found: C,
54.55; H, 2.75; N, 25.45.
142.3 (t, J = 29.1 Hz) 144.7, 153.9; 19F NMR
(376.0 MHz, CDCl3/CFCl3):
d
À112.2 (2F,CHF2);
EIMS (m/z): 255 (M+; 60%); 227 (M+À28; 8%); 226
(M+À29; 5%); 212 (M+À43; 100%); Anal. Calcd for
C11H11F2N3O2: C, 51.77; H, 4.34; N, 16.46. Found: C,
51.77; H, 4.34; N, 16.46.
6.1.1.21. 4-(Difluoromethyl)-1-(3,4-dimethoxyphenyl)-
1H-1,2,3-triazole (4g). Obtained in 95% yield as
white solid; mp 62–63 ꢁC; IR (KBr) mmax (cmÀ1) 3160,
1035; 1H NMR (500 MHz; CDCl3/Me4Si): d 3.96 (s,
6H, OCH3); 6.95 (t, 1H, CHF2, J = 54.3 Hz); 6.97
(d,1H, J = 9.0 Hz, arom.); 7.33 (d, 1H, J = 2.5 Hz;
arom.); 7.18 (dd, 1H, J = 2.5, 8.5 Hz, arom.); 8.16 (s,
1H, triazole); 13C NMR (125 MHz; CDCl3/Me4Si): d
56.2, 110.0 (t, CF2H, J = 234.5 Hz); 120.7, 111.1,
112.8, 105.1, 129.9, 143.2 (t, J = 29.0 Hz); 149.8; 19F
6.1.1.17. 1-(4-Cyanophenyl)-4-(difluoromethyl)-1H-
1,2,3-triazole (4c). Obtained in 98% yield as white solid;
mp 126–128 ꢁC; IR (KBr) mmax (cmÀ1) 3139, 2235 (CN),
1040; 1H NMR (500 MHz; CDCl3/Me4Si): d 6.97 (t, 1H,
CHF2, J = 54.5 Hz); 7.89 (dd, 2H, J = 2.0, 7.0 Hz;
arom.); 7.96 (dd, 1H, J = 1.5, 7.0 Hz; arom.); 8.35 (s,
1H, triazole); 13C NMR (125 MHz; CDCl3/Me4Si): d
109.7 (t, CHF2, J = 235.0 Hz); 114.4, 117.1 (CN),
120.0, 124.0, 124.7, 131.1, 132.8, 137.0, 143.9 (t,
J = 29.1 Hz); 19F NMR (376.0 MHz, CDCl3/CFCl3): d
À112.9 (2F, CHF2); EIMS (m/z): 220 (M+; 42%); 192
(M+À28; 42%); 191 (M+À29; 100%); Anal. Calcd for
C10H6F2N4: C, 54.55; H, 2.75; N, 25.45. Found: C,
54.55; H, 2.75; N, 25.45.
NMR (376.0 MHz, CDCl3/CFCl3):
d
À112.2
(2F,CHF2); EIMS (m/z): 255 (M+; 60%); 277 (M+À28;
8%); 226 (M+À29; 5%); 208 (M+À47; 6%); Anal. Calcd
for C11H11F2N3O2: C, 51.77; H, 4.34; N, 16,46. Found:
C, 51.77; H, 4.34; N, 16.46.
6.1.1.18. 4-(Difluoromethyl)-1-(2-methoxyphenyl)-1H-
1,2,3-triazole (4d). Obtained in 96% yield as white solid;
mp 65–66 ꢁC; IR (KBr) mmax (cmÀ1) 3160, 1035; 1H
NMR (400 MHz; CDCl3/Me4Si): d 3.92 (d, 1H, OCH3,
J = 4.0 Hz); 6.97 (t, CHF2,J = 72.0 Hz); 7.12 (d, 2H,
J = 8.0 Hz, arom.); 7.46 (ddd, 1H, J = 4.0; 8.0 Hz;
arom.); 7.79 (d, 1H, J = 8.0 Hz, arom.); 8.07 (s, 1H, tri-
azole); 13C NMR (100 MHz; CDCl3/Me4Si): d 56.0
(OCH3); 110.3 (t, CHF2, J = 235.0 Hz); 112.3, 124.4,
121.3, 125.4, 130.6, 151.0, 137.0, 142.2; 19F NMR
6.1.1.22. 1-(3-Chlorophenyl)-4-(difluoromethyl)-1H-
1,2,3-triazole (4h). Obtained in 93% yield as white solid;
mp 57–58 ꢁC; IR (KBr) mmax (cmÀ1) 3146, 1042; 1H
NMR (500 MHz; CDCl3/Me4Si): d 6.96 (t, 1H, CHF2,
J = 54.5 Hz); 7.8 (d, 1H, J = 1.5 Hz, arom.); 7.66
(dd,1H, J = 1.2, 7.5 Hz, arom.); 7.65 (m); 8.24 (s, 1H,
triazole); 13C NMR (125 MHz; CDCl3/Me4Si): d 109.8
(t, CF2H, J = 236.5 Hz); 120.5, 118.8, 121.1, 131.0,
135.4, 137.2, 143.6 (t, J = 28.1 Hz); 135.8; 19F NMR
(376.0 MHz, CDCl3/CFCl3): d À112.6 (2F, CHF2);
EIMS (m/z): 229 (M+ 60%); 200 (Mꢀ+À29; 72%); 182
(Mꢀ+À47; 60%); 137 (Mꢀ+À92; 50%); 111 (Mꢀ+À118;
100%); Anal. Calcd for C9H6ClF2N3: C, 47.08; H,
2.62; N, 18.30. Found: C, 47.08; H, 2.62; N, 18.29.
(376.0 MHz, CDCl3/CFCl3):
d
À112.1 (2F,CHF2);
EIMS (m/z): 225 (M+; 90%); 196 (M+À29; 18%); 191
(M+À29; 100%); Anal. Calcd for C10H9F2N3O: C,
53.33; H, 4.03; N, 18.66. Found: C, 53.34; H, 4.04; N,
18.66.
6.1.1.23. 1-(4-Chlorophenyl)-4-(difluoromethyl)-1H-
1,2,3-triazole (4i). Obtained in 95% yield as white solid;
6.1.1.19. 4-(Difluoromethy)-1-(4-methoxyphenyl)-1H-
1,2,3-triazole (4e). Obtained in 97% yield as white
solid; mp 98–100 ꢁC; IR (KBr) mmax (cmÀ1) 3097, 1051,
1023; 1H NMR (500 MHz; CDCl3/Me4Si): d 3.89 (s,
OCH3); 6.95 (t, 1H, CHF2, J = 55.0 Hz); 7.04 (dd, 2H,
J = 2.0, 7.0 Hz; arom.); 7.63 (dd, 2H, J = 2.0, 7.0 Hz;
arom.); 8.14 (s, 1H, triazole); 13C NMR (125 MHz;
1
mp 122–124 ꢁC; IR (KBr) mmax (cmÀ1) 3150, 1046; H
NMR (500 MHz; CDCl3/Me4Si): d 6.95 (t, 1H, CF2H,
J = 54.5 Hz); 7.71 (d, 2H, J = 7.0 Hz, arom.); 7.54 (d,
2H, J = 7.0 Hz, arom.); 8.21 (s, 1H, triazole); 13C
NMR (125 MHz; CDCl3/Me4Si): d 109.9 (t, CF2H,
J = 236.5 Hz); 120.5, 134.9, 135.4, 122.0, 130.1, 143.7
(t, C4, J = 28.1 Hz); 19F NMR (376.0 MHz, CDCl3/
CFCl3): d À112.5 (2F, CHF2); EIMS (m/z): 229 (M+;
60%); 220 (M+À29; 68%); 182 (M+À47; 80%); 137
(M+À92; 67%); 111 (M+À118; 100%) Anal. Calcd for
C9H6ClF2N3; C, 47.08; H, 2.63; N, 18.30. Found: C,
47.07; H, 2.64; N, 18.30.
CDCl3/Me4Si):
d 55.6 (OCH3); 110.1 (t, CHF2,
J = 234.7 Hz); 115.0, 120.6, 122.5, 160.3, 129.8, 143.2
(t, J = 29.1 Hz); 19F NMR (376.0 MHz, CDCl3/CFCl3):
d À112.2 (2F, CHF2); EIMS (m/z): 225 (M+; 36%); 197
(M+À28; 15%); 182 (M+À43; 100%); Anal. Calcd for
C10H9F2N3O: C, 53.33; H, 4.03; N, 18.66. Found: C,
53.33; H, 4.03; N, 18.66.
6.1.1.24. 1-(4-Bromophenyl)-4-(difluoromethyl)-1H-
1,2,3-triazole (4j). Obtained in 95% yield as white solid;
6.1.1.20. 4-(Difluoromethyl)-1-(2,5-dimethoxyphenyl)-
1H-1,2,3-triazole (4f). Obtained in 98% yield as
white solid; mp 78–79 ꢁC; IR (KBr) mmax (cmÀ1) 3169,
1027; 1H NMR (500 MHz; CDCl3/Me4Si): d 3.89 (s,
OCH3); 6.95 (t, 1H, CHF2, J = 55.0 Hz); 7.04 (dd, 2H,
J = 2.0, 7.0 Hz; arom.); 7.63 (dd, 2H, J = 2.0,7.0 Hz;
arom.); 8.14 (s, 1H, triazole); 13C NMR (125 MHz;
CDCl3/Me4Si): d 55.9 (OCH3); 56.5 (OCH3); 110.3 (t,
CF2H, J = 230.0 Hz); 113.6, 116.2, 124.4, 121.1, 127.3,
1
mp 141–144 ꢁC; IR (KBr) mmax (cmÀ1) 3152, 1043; H
NMR (500 MHz; CDCl3/Me4Si): d 6.94 (t, 1H, CF2H,
J = 68.0 Hz); 7.64 (d, 2H, J = 11.0 Hz, arom.); 7.69 (d,
2H, J = 11.0 Hz, arom.); 8,20 (s, 1H, triazole); 13C
NMR (125 MHz; CDCl3/Me4Si): d 109.5 (t, CF2H,
J = 233.2 Hz); 120.4, 135.5, 122.2, 133.6, 133.1, 143.7
(t, J = 28.5 Hz). 19F NMR (376.0 MHz, CDCl3/CFCl3):
d À112.5 (2F, CHF2); EIMS (m/z): 273 (M+; 85%); 245

8652
M. S. Costa et al. / Bioorg. Med. Chem. 14 (2006) 8644–8653
(M+À28; 33%); 226 (M+À49; 60%); 181 (M+À94; 50%);
154 (M+À119; 83%); 166 (M+À109; 100%); Anal. Calcd
for C9H6BrF2N3: C, 39.44; H, 2.04; N, 15.33. Found: C,
39.45; H, 2.01; N, 15.32.
the equilibrium geometry was obtained in vacuum using
a semi-empirical AM1 module. In order to evaluate the
electronic properties of the AM1 minimal energy con-
formations, they were submitted to a single-point calcu-
lation using DFT method with a 6-31-G* basis set of the
SPARTAN’04 package. The three-dimensional isosur-
faces of the molecular electrostatic potential maps
(MEPs) at the van der Waals contact surface represent-
ed electrostatic potentials superimposed onto a surface
of constant electron density (0.002 e/au3). They were
generated in a range from À65 to +23 kcal/mol. These
color-coded isosurface values provide an indication of
the overall molecular size and location of negative
(red) or positive (blue) electrostatic potentials. The elec-
tronic properties (HOMO’s energy, HOMO orbital
coefficients’ distribution, LUMO density, dipole mo-
ment, dipole moment vector, and lipophilicity-clogP)
were calculated for all compounds. Theoretical logP
(clogP) and polar superficial area (PSA) were calculated
at SYBYL program v.6.8.
6.1.1.25. 4-(Difluoromethyl)-1-(4-methylphenyl)-1H-
1,2,3-triazole (4k). Obtained in 93% yield as white solid;
mp 96–97 ꢁC; IR (KBr) mmax (cmÀ1) 3162, 1031, 3152,
1043; 1H NMR (500 MHz; CDCl3/Me4Si): d 2.43 (s,
1H, CH3); 6.94 (t, 1H, CF2H, J = 54.5 Hz); 7.31 (d,
2H, J = 8.8 Hz; arom.); 7.60 (d, 2H, J = 8.8 Hz, arom.);
8,18 (s, 1H, triazole); 13C NMR (125 MHz; CDCl3/
Me4Si): d 20.5 (CH3); 109.5 (t, CF2H, J = 233.4 Hz);
119.9, 139.1, 133.6, 129.8, 120.1, 142.7 (t, J = 28.5 Hz);
19F NMR (376.0 MHz, CDCl3/CFCl3): d À112.3 (2F,
CHF2); EIMS (m/z): 209 (M+; 42%); 180 (M+À29;
68%);162 (M+À47; 40%); 130 (M+À79; 42%); 91
(M+À118; 100%); Anal. Calcd for C10H9F2N3; C,
57.41; H, 4.34; N, 20.09. Found: C, 57.41; H, 4.34; N,
20.08.
6.1.1.26. 4-(Difluoromethyl)-1-(4-nitrophenyl)-1H-
1,2,3-triazole (4l). Obtained in 93% yield as white solid;
6.4. Crystal structure analysis of 1-(4-methylphenyl)-
1,2,3-triazole-4-carbaldehyde (3k)
mp 161–163 ꢁC; IR (KBr) mmax (cmÀ1) 3142, 1526, 1341,
1
1039; H NMR (500 MHz; CDCl3/Me4Si): d 6.98 (t,1H,
Room temperature data were collected on a Bruker
SMART area CCD diffractometer whilst low tempera-
ture data were collected on an Enraf Nonius Kap-
paCCD diffractometer at the UK’s EPSRC X-ray
crystallographic service, based at the University of
Southampton. The structure was solved by direct meth-
ods with SHELXS-97 and refined using SHELXL-9739
in the triclinic spacegroup P-1.Crystal data:
C10H9N3O, colorless, M = 187.20, T = 120 K, mono-
CF2H, J = 54.5 Hz); 8.02 (d, 2H, J = 7.5 Hz, arom.);
8.47 (d, 2H, J = 7.5 Hz, arom.); 8.35 (s, 1H, triazole);
13C NMR (125 MHz; CDCl3/Me4Si): d 109.6 (t,
CF2H, J = 236.9 Hz); 120.5, 120.9, 125.6, 140.5, 144.2,
147.7. 19F NMR (376.0 MHz, CDCl3/CFCl3):
d
À113.0 (2F, CHF2); EIMS (m/z): 240 (M+; 30%); 212
(M+À28; 40%); 211 (M+À29; 32%); 193 (M+À47;
18%); 166 (M+À74; 28%); 76 (M+À164, 100%); Anal.
Calcd for C9H6F2N4 O2: C, 45.01; H, 2.53; N, 23.33.
Found: C, 45.01; H, 2.53; N, 23.33.
clinic, space group Pc, a = 3.8806(3), b = 12.6636(12),
˚
3
˚
c = 9.1604(9) A, b = 101.292(6)ꢁ, V = 441.45(7) A ,
Z = 2, Dx = 1.408 mg/m3, monochromatic Mo-Ka radi-
ation, k = 0.71073 A, l = 0.096 mmÀ1. Supplementary
˚
6.2. Antimycobacterial assay
data are available from the CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK, fax: +44 1223 366 033, e-
mail: deposit@ccdc.ac.uk or on the web www: http://
www.ccdc.cam.ac.uk on request, quoting the Deposition
No. CCDC 602817.
Two hundred microliters of sterile deionized water was
added to all outer-perimeter wells of sterile 96-well
plates (Falcon, 3072: Becton–Dickinson, Lincoln Park,
NJ) to minimize evaporation of the medium in the test
wells during incubation. The 96 well-plates received
100 lL of the Middlebrook 7H9 broth (Difco Laborato-
ries, Detroit, MI, USA) and a serial dilution of the com-
pounds 3a–l and 4a–l was made directly on the plate.
The final drug concentrations tested were 1.0–100.0 lg/
mL. The plates were sealed with Parafilm and incubated
at 37 ꢁC for five days. After this time, 25 lL of a freshly
prepared 1:1 mixture of 10· Alamar Blue (Accumed
International, Westlake Ohio) reagent and 10% Tween
80 was added to the plate and reincubated at 37 ꢁC for
24 h, and the colors of all wells were recorded.
Acknowledgments
Fellowships granted by CAPES and to by CNPq
(Brazil) are gratefully acknowledged. This work was
partially supported by CNPq, FAPERJ, FUJB, and
UFF. The authors thank Dr. Floriano Paes Silva Junior
´
´
´
´
from Laboratorio de Bioquımica de Proteınas e Peptıde-
os of Instituto Oswaldo Cruz (FIOCRUZ) for the calcu-
lation of cLOGP, PSA, and MV parameters.
6.3. Molecular modeling and SAR studies
References and notes
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