2-Aryl-3-(1H-azol-1-yl)-1H-indole derivatives: A new class of antimycobacterial compounds - Conventional heating in comparison with MW-assisted synthesis

Article abstract of DOI:10.1002/ardp.200900031

2-Aryl-3-(1H-imidazol-1-yl and 1H-1,2,4-triazol-1-yl)-1H-indole derivatives were synthesized and tested for their in-vitro antifungal and antimycobacterial activities. These indole derivatives were devoid of antifungal activity against the tested strains of Candida spp. Yet, they exhibited an interesting antitubercular activity against Mycobacterium tuberculosis reference strain H₃₇Rv.

Full text of DOI:10.1002/ardp.200900031

716
Arch. Pharm. Chem. Life Sci. 2009, 342, 716–722
Full Paper
2-Aryl-3-(1H-Azol-1-yl)-1H-Indole Derivatives: A New Class of
Antimycobacterial Compounds – Conventional Heating in
Comparison with MW-Assisted Synthesis
Daniele Zampieri1, Maria Grazia Mamolo1, Erik Laurini1, Giuditta Scialino2, Elena Banfi2,
and Luciano Vio1
1 Department of Pharmaceutical Sciences, University of Trieste, Trieste, Italy
2 Department of Life Sciences, Microbiology Section, University of Trieste, Trieste, Italy
2-Aryl-3-(1H-imidazol-1-yl and 1H-1,2,4-triazol-1-yl)-1H-indole derivatives were synthesized and
tested for their in-vitro antifungal and antimycobacterial activities. These indole derivatives were
devoid of antifungal activity against the tested strains of Candida spp. Yet, they exhibited an
interesting antitubercular activity against Mycobacterium tuberculosis reference strain H37Rv.
Keywords: Antifungal activity / Antimycobacterial activity / Indole / MW-assisted synthesis /
Received: February 18, 2009; accepted: March 19, 2009
DOI 10.1002/ardp.200900031
cytochrome. Using genomic DNA from a strain of Mycobac-
Introduction
terium tuberculosis (MT), it was established that a CYP51-
like gene encodes a bacterial sterol 14a-demethylase [9]
(MT P450 14DM CYP51-like) which acts on 14a-methylster-
ols and binds azole antifungal drugs [1, 10, 11]. On the
basis of these considerations and because many imidazole
and triazole derivatives showed potent antifungal activity
associated with good antimycobacterial activity [6, 7,
12, 13], we synthesized a series of 2-aryl-3-(1H-imidazol-1-
yl- and 1H-1,2,4-triazol-1-yl)-1H-indole derivatives 3a–j in
which the azole moiety is linked at the 3-position of the
indole nucleus. The indole moiety is present in only few
derivatives already described for their antifungal activity
[14–16] but none of these compounds has been studied to
evaluate their potential antimycobacterial activity. As a
possible precursor in the synthesis of the corresponding
indole derivatives we also synthesized the 1-[2-(1H-imida-
zol-1-yl)- and (1H-1,2,4-triazol-1-yl)-1-arylethylidene]-2-phe-
nylhydrazine derivatives 2a–j; their features resemble
typical azole antifungal drugs. All the synthesized com-
pounds were tested in vitro for their antifungal and antitu-
bercular activity towards Candida spp. and Mycobacterium
tuberculosis H37Rv. The phenylhydrazone derivatives 2a–j
showed a moderate antifungal and antimycobacterial
Considering the increased incidence of severe opportun-
istic fungal infections in immunocompromised patients
together with the development of drug resistance among
pathogenic strains of Candida spp., there is a great need
for new antifungal compounds. On the other hand, the
increase of tuberculosis due to emergence of MDR (multi-
ple-drug resistant) strains of Mycobacterium tuberculosis
[1–4] together with the increased incidence of severe dis-
seminated infections produced by mycobacteria other
than tuberculosis (MOTT), particularly Mycobacterium
avium [5] in immunocompromised patients, has
prompted the search for new antimycobacterial drugs.
Antifungal azole derivatives synthesized by us [6–8]
inhibited the fungal cytochrome P450-dependent 14a-
demethylase (P450 14DM CYP51) but exhibit also antitu-
bercular activity which was attributed to a similar inhibi-
tory interaction with the corresponding mycobacterial
Correspondence: Maria Grazia Mamolo, Department of Pharmaceutical
Sciences, Piazzale Europa 1, University of Trieste, Piazzale Europa 1,
34127 Trieste, Italy.
E-mail: mamolo@units.it
Fax: +3904052572
Abbreviations: microwave irradiation (MW); multiple-drug resistant
(MDR); mycobacteria other than tuberculosis (MOTT); Mycobacterium tu-
berculosis (MT)
* A preliminary account of this work was presented at XIX Joint Meeting
on Medicinal Chemistry, Verona (IT), September 14-18, 2008.
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Arch. Pharm. Chem. Life Sci. 2009, 342, 716–722
Indole Derivatives as Antimycobacterial Compounds
717
Table 1. Antifungal and antimycobacterial activities of compounds 2a–j and 3a–j.
Comp.
X
Ar
C.A. 685 MIC
(lg/mL)
C.G. 66 MIC
(lg/mL)
M.tuberculosis H37Rv
MIC (lg/mL)
Miconazole
Amphotericin B
Rifampicin
2a
0.06 – 0.12
1–1
resistant
2–4
–
A32
A64
0.5
32
8
CH
8
A64
3a
2b
3b
CH
CH
CH
CH
8
A64
32
A64
16
4
2c
3c
8
A64
32
A64
16
8
2d
3d
16
A64
A32
A64
A64
8
2e
3e
8
A64
32
A64
16
2
2f
3f
N
N
N
16
64
32
64
16
8
2g
3g
16
A64
32
A64
32
4
2h
3h
8
A64
32
A64
32
8
2i
3i
N
N
16
A64
32
A64
32
8
2j
3j
16
A64
A32
A64
32
4
activity. On the other hand, indole derivatives 3a–j exhib-
ited a remarkable antimycobacterial activity but were
devoid of antifungal activity (Table 1).
Moreover, we compare two synthetic methods to
obtain the indole compounds 3a–j: reflux heating and
microwave irradiation (MW). The use of a microwave
reactor ensures a significant increase in reaction yields
and an easier work-up as well as a decrease in reaction
time (Table 2).
Results and discussion
The indole derivatives 3a–j, characterized by the pres-
ence of imidazole or triazole substituents at the position
3 of the indole moiety, have been synthesized by Fischer
indole synthesis using two synthetic procedures namely,
conventional reflux synthesis and microwave irradiation
(MW). Fischer indole synthesis is well known and largely
described, as well as the use of a microwave oven for this
kind of reaction. Several solvents and catalyst can be
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D. Zampieri et al.
Arch. Pharm. Chem. Life Sci. 2009, 342, 716–722
Table 2. Yields of compounds 3a–j under reflux (method A) or using MW irradiation (method B).
Comp
X
Ar
Time
(Reflux) (h)
Purification
(Reflux)
Yield
(Reflux) (%)
Time
(MW) (h)
Purification
(MW)
Yield
(MW) (%)
3a
CH
22
AcOEta)
2.4
1
AcOEta)
43.4
3b
3c
CH
CH
10
AcOEta)
8.0
2.0
1
1
AcOEta)
38.0
35.3
20.5
AcOEt / EtOH
9.5 : 0.5a)
AcOEt / EtOH
9.5 : 0.5a)
3d
CH
24
AcOEt/Hexane 3.4
10 : 10a)
1
AcOEt/Hexane 39.3
10 : 10a)
3e
3f
CH
N
18.5
20
AcOEta)
4.3
12
1
1
1
AcOEta)
47.3
57.6
68.2
Hexaneb)
Ethyl etherb)
Ethyl etherb)
3g
N
13.5
AcOEt/Hexane 3.9
4 : 6a)
3h
3i
N
9.5
AcOEta)
14.7
1
Ethyl etherb)
67.2
N
N
21
46
AcOEt/Hexane 3.6
8 : 2a)
1
1
Ethyl etherb)
Ethyl etherb)
58.3
72.3
3j
AcOEt/Hexane 2.0
4 : 6a)
a)
Dry-flash chromatography.
Crystallization.
b)
used but absolute ethanol and HCl (conc.) seems to be the
The indole derivatives 3a–j have been tested for their
optimal combination with an easier work-up. The use of antifungal and antimycobacterial activity. Target of
MW-irradiation ensures a significant increase in reaction azole antifungal drugs are enzymes involved in the bio-
yields and a decrease in reaction time. In Table 2, we synthesis of ergosterol, specifically the lanosterol 14a-
reported the comparison between two synthetic methods demethylase P450-dependent (P450 14DM, CYP 51). The
to obtain compounds 3a–j. Reaction time was drastically tertiary nitrogen of the imidazole cycle or the nitrogen
decreased and yields were strongly enhanced (from 2 to atom at position 4 of the triazole ring bind the sixth coor-
15% of traditional heating, to 35 to 72% with MW). More- dination position of the heme iron of the lanosterol 14a-
over, the use of MW-irradiation reduces the formation of demethylase and the N1-linked moiety binds the amino
by-products, as documented by TLC.
acid sequence of the enzyme. The inhibition of P450
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Arch. Pharm. Chem. Life Sci. 2009, 342, 716–722
Indole Derivatives as Antimycobacterial Compounds
719
Scheme 1. Synthesis of compounds 3a–j.
14DM increases the normal levels of methylated sterols,
ergosterol depletion, and inhibition of cellular growth
[17].
Figure 1. Zinoconazole and compounds 2a–j.
From the obtained results, however, the indole deriv-
atives 3a–j (Table 1), containing azole residues, were
devoid of antifungal activity against the tested strains of
Candida spp. Surprisingly, compounds 3a–j, in which
azole moieties are present, were characterized by a very
interesting antimycobacterial activity (Table 1) against
Mycobacterium tuberculosis H37Rv, with MIC values ranging
from 2 to 8 lg/mL. The higher antimycobacterial activity
was exhibited by the indole derivatives 3b and 3e and by
the triazole derivatives 3g and 3j, both characterized by
the higher level of lipophilicity.
The antitubercular activity of the compounds may be
due to the inhibition of the Mycobacterium sterol 14a-
demethylase P450 dependent (MT P450 14DM, CYP 51-
like) [9], whereas the lack of antifungal activity may be
due to the incapacity of the indole component to bind
the enzymatic protein of fungal P450 DM, even if Candida
albicans CYP-51 and MT CYP 51-like share a sequence
homology of 40% with 22% identical residues [18]. How-
ever, it is possible that the antimycobacterial activity of
compounds 3a–j depends on a mechanism which does
not involve a coordination bond of the azole nitrogen
atom with the heme iron of mycobacterial P450 DM. A
preliminary molecular modeling of compounds and MT
P450 complexes is in progress. Phenylhydrazone deriv-
atives 2a–j (Scheme 1) have been synthesized as possible
intermediates in the synthesis of the corresponding
indole derivatives 3a–j. However, it was impossible to
obtain compounds 3a–j with a reasonable yield through
this synthetic approach. In compounds 2a–j, the 1-aryl-2-
(1H-azol-1-yl)-ethane moiety, present in many azole anti-
fungal drugs, is linked through an azomethyne linkage
to phenylhydrazine. These features characterize the anti-
fungal drug zinoconazole (Fig. 1), which exhibits antifun-
gal activity against some strains of Candida albicans, with
MIC values in the range of 6.2 - 12.5 lg/mL [19]. The phe-
nylhydrazone derivatives 2a–j exhibit a similar antifun-
gal activity towards a strain of Candida albicans 685, with
MIC values of 8 and 16 lg/mL (Table 1). The activity
against a strain of Candida glabrata 66 miconazole-resist-
ant was moderate, revealing MIC values of 32 lg/mL for
almost all the compounds. The antimycobacterial activ-
ity of derivatives 2a–j against Mycobacterium tuberculosis
resembles their activity towards C. albicans 685 (Table 1),
with MIC values of 16 and 32 lg/mL, suggesting that the
mechanism of action may be dependent on the coordina-
tion of the azole nitrogen atom with heme iron of the
fungal 14a-demethylase (P450 14DM-CYP 51) and myco-
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Yield: 35%; m.p.: 174–1778C; I.R.(nujol, cm– 1): 3222; 1H-NMR
(CDCl3 / TMS) d: 5.30 (s, 2H, CH2), 6.90–8.00 (m, 13H, arom. and
imidazole), 8.45 (broad sign., 1H, NH disappearing on deutera-
tion); MS m/z: 277 [M + H+]. Anal. calcd. for C17H16N4 (MW: 276.34):
C, 78.89: H, 5.84; N, 20.27. Found: C, 73.72; H, 5.67; N, 20.10.
Compounds 2b–j have been prepared in an analogous way.
bacterium 14a-demethylase (MT P450 14DM-CYP 51-like),
respectively.
This research was carried out with the financial support of the
Italian M.U.R.S.T. (60%).
The authors have declared no conflict of interest.
N-[1-(4-Bromophenyl)-2-(1H-imidazol-1-yl)ethylidene]-N9-
phenyl-hydrazine 2b
Yield: 34%; m.p.: 185–1898C; I.R.(nujol, cm– 1): 3206; 1H-NMR
(CDCl3 / TMS) d: 5.28 and 5.42 (s, 2H, CH2), 6.88–8.04 (m, 12H,
arom. and imidazole), 8.50 (broad sign., 1H, NH disappearing on
deuteration); MS m/z: 355 [M + H+], 357 [M + H+ + 2]. Anal. calcd.
for C17H15N4Br (MW: 355.23): C, 57.48: H, 4.26; N, 15.77. Found: C,
57.44; H, 4.22; N, 15.73.
Experimental
Chemistry
Melting points were determined with a Bꢀchi 510 capillary appa-
ratus, and are uncorrected (Bꢀchi, Switzerland). Infrared spectra
in nujol mulls were recorded on a Jasko FT 200 spectrophotome-
ter Jasko, Tokyo, Japan. Proton nuclear magnetic resonance (1H-
NMR) spectra were determined on a Varian Gemini 200 spec-
trometer (Varian, Palo Alto, CA, USA), chemical shifts are
reported as d (ppm) in CDCl3 solution (0.05% v/v TMS), DMSO-d6
and CD3OD. Reaction courses and product mixtures were rou-
tinely monitored by thin-layer chromatography (TLC) on silica
gel precoated F254 Merck plates (Merck, Germany). Column chro-
matography and flash-dry chromatography were performed
using silica gel 70–230 mesh and 15–40 mesh, respectively. ESI-
MS spectra were obtained on a PE-API I spectrometer (Applied
Biosystems, Inc. USA) by infusion of a solution of the sample in
MeOH. Elemental analyses (C, H, N) were performed on a Carlo
Erba analyzer (Carlo Erba, Milan, Italy) and were within l 0.3 of
the theoretical value. Microwave irradiations were performed
using a CEMm (Discoverm-Labmate”; CEM SRL, Italy) reactor.
The synthesis of compounds 3a–j (Scheme 1), was carried out
via a two-steps reaction which involved a N-alkylation of imida-
zole or 1,2,4-triazole with para-substituted 2-bromoacetophe-
nones to afford the corresponding 1-aryl-2-(1H-imidazol-1-yl) or
(1H-1,2,4-triazol-1-yl)-ethanones 1a–j in accordance with the lit-
erature procedure [6, 8]. The indole derivatives 3a–j were
obtained through the classical Fischer cyclization (Scheme 1) by
reacting compounds 1a–j and phenylhydrazine in ethanol with
acid catalyst (HCl) under reflux or using the microwave reactor.
The simple condensation of compounds 1a–j with phenylhydra-
zine gave the corresponding intermediate phenylhydrazone
derivatives 2a–j. The attempt to obtain the indole derivatives
3a–j from the corresponding phenylhydrazone 2a–j was unsuc-
cessful.
N-[1-(4-Chlorophenyl)-2-(1H-imidazol-1-yl)ethylidene]-N9-
phenyl-hydrazine 2c
Yield: 40%; m.p.: 188–1918C; I.R.(nujol, cm– 1): 3213; 1H-NMR
(CDCl3 / TMS) d: 5.42 (s, 2H, CH2), 6.84–8.00 (m, 12H, arom. and
imidazole), 10.30 (broad sign., 1H, NH disappearing on deutera-
tion); MS m/z: 311 [M + H+], 313 [M + H+ + 2]. Anal. calcd. for
C17H15N4Cl (MW: 310.77): C, 65.70: H, 4.86; N, 18.03. Found: C,
65.48; H, 4.64; N, 17.81.
N-[2-(1H-Imidazol-1-yl)-1-(4-methylphenyl)ethylidene]-
N9-phenyl-hydrazine 2d
Yield: 47%; m.p.: 197–2038C; I.R.(nujol, cm– 1): 3222; 1H-NMR
(CDCl3 / TMS) d: 2.40 (s, 3H, CH3), 5.20 (s, 2H, CH2), 6.94–7.81 (m,
12H, arom. and imidazole), 8.90 (broad sign., 1H, NH disappear-
ing on deuteration); MS m/z: 291 [M + H+]. Anal. calcd. for
C18H18N4 (MW: 290.36): C, 74.46: H, 6.25; N, 19.30. Found: C,
74.34; H, 6.43; N, 19.18.
N-[1-(2-Biphenyl-4-yl)-2-(1H-imidazol-1-yl)ethylidene]-N9-
phenyl-hydrazine 2e
Yield: 57%; m.p.: 195–1998C; I.R.(nujol, cm– 1): 3222; 1H-NMR
(DMSO-d6) d: 5.49 (s, 2H, CH2), 6.88–7.92 (m, 17H, arom. and imid-
azole), 10.30 (broad sign., 1H, NH disappearing on deuteration);
MS m/z: 353. Anal. calcd. for C23H20N4 (MW: 352.43): C, 78.38: H,
5.72; N, 15.90. Found: C, 78.18; H, 5.52; N, 15.70.
N-[1-Phenyl -2-(1H-1,2,4-triazol-1-yl)-ethylidene]-N9-
phenyl-hydrazine 2f
Yield: 44%; m.p.: 168–1708C; I.R.(nujol, cm– 1): 3220; 1H-NMR
(CDCl3 / TMS) d: 5.44 (s, 2H, CH2), 7.00–7.87 (m, 10H, arom.), 8.05
(s, 1H, H5 triazole), 8.21 (s, 1H, H3 triazole), 9.76 (broad sign., 1H,
NH disappearing on deuteration); MS m/z: 278 [M + H+]. Anal.
calcd. for C16H15N5 (MW: 277.32): C, 69.29: H, 5.45; N, 25.25.
Found: C, 69.04; H, 5.20; N, 25.00.
N-[2-(1H-Imidazol-1-yl)-1-phenylethylidene]-N'-phenyl-
hydrazine 2a
A
solution of 1-phenyl-2-(1H-imidazol-1-yl)-ethanone (2.0 g,
11.0 mmol) in 50 mL of ethanol, was treated with a few drops of
acetic acid. To the stirred solution, phenylhydrazine (1.19 g,
11.0 mmol) in 20 mL of absolute ethanol was added dropwise
and the reaction mixture was heated at reflux for 7 h. There-
after, the solvent was removed under reduced pressure and the
residue was extracted with CHCl3 (36100 mL) and the organic
phase was washed with distilled water. The collected organic
phases were dried over sodium sulphate, filtered, and evapo-
rated under reduced pressure. The residue was crystallized from
absolute ethanol.
N-[1-(4-Bromophenyl)-2-(1H-1,2,4-triazol-1-yl)
ethylidene]-N9-phenyl-hydrazine 2g
Yield: 56%; m.p.: 187–1908C; I.R.(nujol, cm– 1): 3216; 1H-NMR
(CDCl3 / TMS) d: 5.25 (s, 2H, CH2), 6.90–7.66 (m, 9H, arom.), 7.94
(s, 1H, H5 triazole), 8.10 (s, 1H, H3 triazole), 9.82 (broad sign., 1H,
NH disappearing on deuteration); MS m/z: 356 [M + H+], 358 [M +
H+ + 2]. Anal. calcd. for C16H14N5Br (MW: 356.23): C, 53.95: H, 3.96;
N, 19.66. Found: C, 54.05; H, 4.06; N, 19.76.
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Arch. Pharm. Chem. Life Sci. 2009, 342, 716–722
Indole Derivatives as Antimycobacterial Compounds
721
Anal. calcd. for C17H12BrN3 (MW: 338.20): C, 60.37; H, 3.58; N,
12.42. Found: C, 60.45; H, 3.42; N, 12.51.
N-[1-(4-Chlorophenyl)-2-(1H-1,2,4-triazol-1-yl)
ethylidene]-N9-phenyl-hydrazine 2h
Yield: 54%; m.p.: 165–1708C; I.R.(nujol, cm– 1): 3232; 1H-NMR
(CDCl3 / TMS) d: 5.40 (s, 2H, CH2), 6.97–7.78 (m, 9H, arom.), 8.05
(s, 1H, H5 triazole), 8.20 (s, 1H, H3 triazole), 9.77 (broad sign., 1H,
NH disappearing on deuteration); MS m/z: 312 [M + H+], 314 [M +
H+ + 2]. Anal. calcd. for C16H14N5Cl (MW: 311.77): C, 61.64: H, 4.53;
N, 22.46. Found: C, 61.77; H, 4.66; N, 22.59.
2-(4-Chlorophenyl)-3-(1H-imidazol-1-yl)-1H-indole 3c
M.p.: 220–2228C; I.R.(Nujol, cm– 1): 3151; 1H-NMR (CD3OD / TMS)
d: 7.09–7.51 (m, 11H, 3H imid., 8H arom.); 7.74 (s, 1H, NH disap-
pearing on deuteration); MS m/z: 294 [M + H+], 296 [M + H+ + 2].
Anal. calcd. for C17H12ClN3 (MW: 293.75): C, 69.51; H, 4.12; N,
14.30. Found: C, 69.40; H, 4.35; N, 14.17.
N-[1-(4-Methylphenyl)-2-(1H-1,2,4-triazol-1-yl)
3-(1H-Imidazol-1-yl)-2-(4-methylphenyl)-1H-indole 3d
M.p.: A2358C; I.R.(Nujol, cm– 1): 3145; 1H-NMR (CD3OD / TMS) d:
2.36 (s, 3H, CH3); 7.12–7.63 (m, 11H, 3H imid., 8H arom.); 8.59 (s,
1H, NH disappearing on deuteration); MS m/z: 274 [M + H+]. Anal.
calcd. for C18H15N3 (MW: 273.33): C, 79.10; H, 5.53; N, 15.37.
Found: C, 79.02; H, 5.35; N, 15.27.
ethylidene]-N9-phenyl-hydrazine 2i
Yield: 54%; m.p.: 110–1128C; I.R.(nujol, cm– 1): 3217; 1H-NMR
(CDCl3 / TMS) d: 2.41 (s, 3H, CH3), 5.29 and 5.46 (s, 2H, CH2), 6.87–
7.90 (m, 9H, arom.), 7.98 and 8.05 (s, 1H, H5 triazole), 8.30 and
8.36 (s, 1H, H3 triazole), 9.80 (broad sign., 1H, NH disappearing
on deuteration); MS m/z: 292 [M + H+]. Anal. calcd. for C17H17N5
(MW: 291.35): C, 70.08: H, 5.88; N, 24.04. Found: C, 70.03; H, 5.83;
N, 23.99.
2-(Biphenyl-4-yl)-3-(1H-imidazol-1-yl)-1H-indole 3e
M.p.: A2358C; I.R.(Nujol, cm– 1): 3139; 1H-NMR (CD3OD / TMS) d:
7.20–7.87 (m, 16H, 3H imid., 13H arom.); 9.29 (s, 1H, NH disap-
pearing on deuteration); MS m/z: 336 [M + H+]. Anal. calcd. for
C23H17N3 (MW: 335.40): C, 82.36; H, 5.11; N, 12.53. Found: C,
82.14; H, 5.37; N, 12.58.
N-[1-(2-Biphenyl-4-yl)-2-(1H-1,2,4-triazol-1-yl)
ethylidene]-N9-phenyl-hydrazine 2j
Yield: 52%; m.p.: 180–1848C; I.R.(nujol, cm– 1): 3235; 1H-NMR
(CDCl3 / TMS) d: 5.46 (s, 2H, CH2), 6.98–7.94 (m, 14H, arom.), 8.06
(s, 1H, H5 triazole), 8.23 (s, 1H, H3 triazole), 9.76 (broad sign., 1H,
NH disappearing on deuteration); MS m/z: 354 [M + H+]. Anal.
calcd. for C22H19N5 (MW: 353.42): C, 74.77: H, 5.42; N, 19.82.
Found: C, 74.94; H, 5.59; N, 19.99.
2-Phenyl-3-(1H-1,2,4-triazol-1-yl)-1H-indole 3f
M.p.: 188–1908C; I.R.(Nujol, cm– 1): 3141; 1H-NMR (CD3OD / TMS)
d: 47.10–7.60 (m, 9H arom.); 8.08 (s, 1H, NH disappearing on
deuteration); 8.30 (s, 1H, H3 triaz.); 8.54 (s, 1H, H5 triaz.); MS m/z:
261 [M + H+]. Anal. calcd. for C16H12N4 (MW: 260.29): C, 73.83; H,
4.65; N, 21.52. Found: C, 73.96; H, 4.88; N, 21.41.
General procedure for the synthesis of derivatives 3a–j
*
Method A: To an ethanolic solution of ethanone derivatives
1a–j (200 mg), few milliliter of HCl conc. and a slight excess
of phenylhydrazine were added. The reaction mixture was
heated under reflux for several hours (Table 2). The cooled sol-
ution was evaporated under reduced pressure and the residue
was treated with water, then neutralized with NaOH solution,
and filtered. The residue obtained was dissolved in the mini-
mum amount of ethyl acetate and purified by dry-flash chro-
matography.
2-(4-Bromophenyl)-3-(1H-1,2,4-triazol-1-yl)-1H-indole 3g
M.p.: 200–2028C; I.R.(nujol, cm– 1): 3149; 1H-NMR (CD3OD / TMS)
d: 7.10–7.55 (m, 9H, 8H arom., 1H, NH disappearing on deutera-
tion); 8.31 (s, 1H, H3 triaz.); 8.56 (s, 1H, H5 triaz.); MS m/z: 339 [M +
H+], 341 [M + H+ + 2]. Anal. calcd. for C16H11N4Br (MW: 339.19): C,
56.66; H, 3.27; N, 16.52. Found: C, 56.55; H, 3.40; N, 16.41.
2-(4-Chlorophenyl)-3-(1H-1,2,4-triazol-1-yl)-1H-indole 3h
M.p.: 205–2078C; I.R.(Nujol, cm– 1): 3142; 1H-NMR (CD3OD / TMS)
d: 7.13–7.55 (m, 9H, 8H arom., 1H, NH disappearing on deutera-
tion); 8.57 (s, 1H, H3 triaz.); 9.46 (s, 1H, H5 triaz.); MS m/z: 295 [M +
H+], 297 [M + H+ + 2]. Anal. calcd. for C16H11N4Cl (MW: 294.74): C,
65.20; H, 3.76; N, 19.01. Found: C, 65.35; H, 3.90; N, 18.91.
*
Method B: The same procedure but using an equimolar
amount of phenylhydrazine was followed by carrying out the
reaction in a sealed tube with the use of microwave oven. The
reaction was performed at 120–1408C (300 W and 5 bar) with
a complete cycle of 1 hour. The compounds were purified by
dry-flash chromatography or by crystallization from diethyl
ether and the yields of derivatives 3a–j were greatly improved
and reaction times were reduced (Table 2).
2-(4-Methylphenyl)-3-(1H-1,2,4-triazol-1-yl)-1H-indole 3i
M.p.: 185–1878C; I.R.(nujol, cm– 1): 3146; 1H-NMR (CD3OD / TMS)
d: 2.35 (s, 3H, CH3); 7.09–7.51 (m, 9H, 8H arom., 1H, NH disap-
pearing on deuteration); 8.31 (s, 1H, H3 triaz.); 8.53 (s, 1H, H5
triaz.); MS m/z: 275 [M + H+]. Anal. calcd. for C17H14N4 (MW:
274.32): C, 74.43; H, 5.14; N, 20.42. Found: C, 74.30; H, 5.20; N,
20.25.
3-(1H-Imidazol-1-yl)-2-phenyl-1H-indole 3a
M. p.: 160–1628C; I.R.(Nujol, cm– 1): 3146; 1H-NMR (CD3OD / TMS)
d: 7.08–7.51 (m, 12H, 3H imid., 8H arom.); 7.72 (s, 1H, NH disap-
pearing on deuteration); MS m/z: 260 [M + H+]. Anal. calcd. for
C17H13N3 (MW: 259.31): C, 78.74; H, 5.05; N, 16.20. Found: C,
78.87; H, 5.19; N, 16.08.
2-(Biphenyl-4-yl)-3-(1H-1,2,4-triazol-1-yl)-1H-indole 3j
M.p.: 219–2218C; I.R.(nujol, cm– 1): 3152; 1H-NMR (CD3OD / TMS)
d: 7.10–7.66 (m, 14H, 13H arom., 1H, NH disappearing on deute-
ration); 8.32 (s, 1H, H3 triaz.); 8.59 (s, 1H, H5 triaz.); MS m/z: 337 [M
+ H+]. Anal. calcd. for C22H16N4 (MW: 336.39): C, 78.55; H, 4.79; N,
16.66. Found: C, 78.33; H, 4.66; N, 16.78.
2-(4-Bromophenyl)-3-(1H-imidazol-1-yl)-1H-indole 3b
M.p.: 230–2328C; I.R.(Nujol, cm– 1): 3142; 1H-NMR (CD3OD / TMS)
d: 7.18–7.76 (m, 11H, 3H imid., 8H arom.); 9.04 (s, 1H, NH disap-
pearing on deuteration); MS m/z: 338 [M + H+], 340 [M + H+ + 2].
i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

722
D. Zampieri et al.
Arch. Pharm. Chem. Life Sci. 2009, 342, 716–722
[4] I. Bastian, R. Colebuuders, Drugs 1999, 58, 633–661.
Microbiology
Both series of derivatives 2a–j and 3a–j were evaluated for their
antifungal activity against Candida albicans 685 and Candida
glabrata 66, both clinical isolates; their antitubercular activity
was evaluated against the reference strain Mycobacterium tubercu-
losis H37Rv. Stock solutions of chemicals were prepared in DMSO
at a concentration of 2 mg/mL. Antifungal activity was always
evaluated by reference methods (NCCLS, 1997); miconazole and
amphotericin B were chosen as a standard in antifungal activity
measurements, each MIC was determined twice in duplicate
experiments after 24 and 48 h incubation time. Antitubercular
activity was evaluated by MRA, a recently developed, one-week
duration, micro-dilution Resazurin assay [20]. The minimum
inhibitory concentration, MIC, was defined as the lowest drug
concentration that prevented Resazurin colour change from
blue to pink and was determined by visual inspection twice in
duplicate experiments; viable counting from control wells and
from test wells performed onto agar plates confirmed bacterici-
dal and bacteriostatic activity of the compounds. Rifampicin
was used as a standard in antitubercular activity measurements,
having a MIC of 0.5 lg/mL; DMSO was also evaluated and was
always devoid of inhibiting activity up to the concentration of
2% (v/v). The antimicrobial activity of the compounds 2a–j and
3a–j is reported in Table 1.
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i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com