Synthesis, characterization, and SAR studies of new (1H-indol-3-yl)alkyl-3- (1H-indol-3-yl)propanamide derivatives as possible antimicrobial and antitubercular agents

Article abstract of DOI:10.1007/s00044-012-0451-x

In this article, we report herein the SAR studies of a series of (1H-indol-3-yl)alkyl-3-(1H-indol-3-yl)propanamide 10(a-j), 11(a-j). The synthesized compounds were evaluated for their preliminary in vitro antibacterial, antifungal activity and were screened for antitubercular activity against Mycobacterium tuberculosis H37Rv strain. The synthesized compounds displayed interesting antimicrobial activity.

Full text of DOI:10.1007/s00044-012-0451-x

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:4437–4454
DOI 10.1007/s00044-012-0451-x
ORIGINAL RESEARCH
Synthesis, characterization, and SAR studies of new (1H-indol-3-
yl)alkyl-3-(1H-indol-3-yl)propanamide derivatives as possible
antimicrobial and antitubercular agents
•
Ranjith Pakkath Karuvalam Rajeesh Pakkath
•
•
•
Karickal Raman Haridas Rathnasamy Rishikesan
Nalilu Suchetha Kumari
Received: 11 October 2012 / Accepted: 21 December 2012 / Published online: 10 January 2013
Ó Springer Science+Business Media New York 2013
Abstract In this article, we report herein the SAR studies
of a series of (1H-indol-3-yl)alkyl-3-(1H-indol-3-yl)pro-
panamide 10(a–j), 11(a–j). The synthesized compounds
were evaluated for their preliminary in vitro antibacterial,
antifungal activity and were screened for antitubercular
activity against Mycobacterium tuberculosis H37Rv strain.
The synthesized compounds displayed interesting antimi-
crobial activity.
heterogeneous bacterial populations in the TB lesions and
perhaps also to insufficient host immunity, treatment with a
combination of drugs must be given for extended periods
of time to prevent reactivation of disease by persisting
bacilli. The increasing problem of MDR-TB has focused
attention on developing new drugs that are not only active
against drug resistant TB, but also shorten the lengthy
therapy. In developing new TB drugs, it is crucial to think
about which target in the tubercle bacillus are good targets.
Heterocyclic compounds play an important role in an
untiring effort aimed at developing new antimicrobial
agents with new mechanism of action. These heterocyclic
compounds well known to possess diverse pharmacological
properties, like anti-inflammatory, anticancer anticonvul-
sant, antimalarial, etc. An extensive literature survey
reveals that apart from these biological activities, some of
the heterocyclic compounds like derivatives of pyrrole
(Mariangela et al., 2009), benzimidazole (Charansingh
et al., 2008), indole (Subramanian et al., 2009), imidazole
(Jyoti et al., 2009), furan (Tangallapally et al., 2004),
benzotriazole (Dixit et al., 2006) showed excellent anti-
mycobacterial properties. In addition, among the hetero-
cyclic compounds, indole derivatives are significant
because of their wide spectrum of biological activities. For
well over 100 years, the synthesis and functionalization of
indole have been a major area of focus for synthetic
organic chemist, and numerous methods for the preparation
of indoles have been developed (Humphrey and Kuethe,
2006a; Tois et al., 2003a; Gribble, 2000; Pindur and Adam,
1998). Among the synthetic methodologies reported so far
for the preparation of the indole analogs, the Fischer indole
synthesis still maintain its prominent role for the large scale
production of biologically active compounds (Siu et al.,
2004). The indole nucleus is an important structure in
numerous natural or synthetic alkaloids and in medicinal
Keywords Indole Á Antibacterial activity Á
Anti fungal activity Á Antimycobacterial
Introduction
Mycobacterium tuberculosis, the causative agent of tuber-
culosis (TB), is a tenacious and remarkably successful
pathogen that has latently infected a third of the world
population. The increasing emergence of drug resistant TB
and HIV infection, which compromises host defense and
allows latent infection to reactivate or render individuals
more susceptible to TB, pose further challenges for effec-
tive control of the disease (Corbett, 2003). Due to the
R. P. Karuvalam Á R. Pakkath Á K. R. Haridas (&)
School of Chemical Sciences, Kannur University, Payyanur
Campus, Edat P.O. Box 670327 Kannur, Kerala, India
e-mail: pkranjith@rediffmail.com; krharidas2001@yahoo.com
R. Rishikesan
Department of Chemistry, PG and Research Centre,
Sri Paramakalyani College, Alwarkurichi,
Tirunelveli 627412, Tamil Nadu, India
N. S. Kumari
Department of Biochemistry, Justice K.S. Hegde Medical
Academy, Deralakatte, India
123

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Med Chem Res (2013) 22:4437–4454
chemistry. The diversity of the structures encountered as
well as their biological and pharmaceutical relevance, have
motivated research aimed at the development of new
economical, efficient, and selective synthetic strategies
particularly for the synthesis of substituted indole rings
(Tois et al., 2003b). The substituted indoles have been
referred to as privileged structures since they are capable of
binding to many receptors with high affinity (Horton et al.,
2003). Therefore, the synthesis and selective functionali-
zation of indoles have been the focus of active research
(Humphrey and Kuethe, 2006b). In this article, we report
herein the SAR studies of a series of (1H-indol-3-yl)alkyl-
3-(1H-indol-3-yl)propanamide derivatives. Among the
numerous indole derivatives, with biologically active
tryptamine and its derivative such as the neurotransmitter
serotonin, and the tissue hormone melatonin constitute
especially important examples (Hibino and Choshi, 2002).
As a part of our research work on the development of
useful synthetic molecules (Ranjith et al., 2010) and for
new antitubercular agents (Ranjith et al., 2012), it has been
planned to introduce two indoles in a single molecular
frame work with active groups like chloro, trifluoro, etc. at
different positions. It has been hoped that the combination
of these active molecules in the new molecular design
would lead to better antimicrobial agents. In this commu-
nication, we report the synthesis ofnewlydesigned (1H-indol-3-
yl)alkyl-3-(1H-indol-3-yl)propanamide (10a–10j), (11a–11j)
(Scheme 3) and evaluated these compounds for the antimicro-
bial and antitubercular activities.
methyl-substituted acid 9 was also prepared in two steps.
5-chloro-1-methyl indole-3-carboxaldehyde treated with
malonic acid to form 8 which on reduction using PtO2 to
form 1-methyl-substituted indole-3-carboxylic acid 9. The
title compounds 10(a–j) and 11(a–j) were then synthesized
(Scheme 3) by coupling of key intermediates in the pres-
ence of EDCI and HOBT (Chan and Cox, 2007). The
spectral data are discussed in ‘‘Experimental’’ section.
Structure activity relationship
In this study, we have mainly concentrated at the region 1
and region 2 (Fig. 1) of the synthesized molecules. Lipo-
philicity of compounds plays a vital role in studying the
biological activity of a compound (Leo et al., 1971). These
properties are seen as an important parameter related to
membrane permeation in biological system. It has been
well established that halogenated particularly –CF3
substituted molecules have got a significant place in
modern medicinal chemistry (Nakayama et al., 2011).
Different substitutions have done at the region 1 of the
synthesized molecules (Table 1), e.g., biological results
showed that compound 10e displayed good activity. One of
the reasons could be the presence of chloro and –OCF3
group attached to the aryl ring increases the lipophilic
nature of the compound, there by making the molecule
more cells permeable. The biological results indicated that
the compound with electron withdrawing group at the ring
at the regions 1 and 2 of the molecule were more active.
The unsubstituted –NH at the region 1 of the molecule
showed the activity (10a, 10b, 10e, 10h, 10i, 10j, 11b, 11i,
and 11j), but after methyl substitution at the region 1 the
activity has been lowered (10d, 10g, 11a, and 11h) and the
dimethyl substituted compounds show minimal activity
(10c, 10f, and 11d). It has been observed that introduction
of –OCF3, chloro substitutions at the ring increases the
lipophilicity of the molecule, there by making the molecule
more cell permeable and hence enhance the potency of the
compounds. Next we shifted our focus on region 2 of the
synthesized molecules, at this region methyl substitution at
the –NH group found to be active. The SAR studies of the
synthesized molecules show that the methyl substitution at
the region 1 of the molecule decreases the activity and
surprisingly the methyl substitution at the region 2 of the
some molecules found to be active (10e, 10j, 11a, 11e, 11g,
and 11i) (Table 2)
Results and discussion
Chemistry
The reaction sequences employed for the synthesis of title
compounds are shown in Schemes 1, 2, and 3, respectively.
The tryptamine derivatives 3(a–e) were prepared by react-
ing substituted indole-3-carboxaldehyde 1 and hydroxyl-
amine hydrochloride in methanol heated to 60 °C to get
indole-3-methyloxime 2(a–e) which on reduction with
raney nickel in alcoholic medium to get 3(a–e). In
Scheme 1 substituted indole carboxaldehyde was conve-
niently converted to 4(a–e) by condensing it with cy-
anomethyltriphenyl phosphorous bromide, which on
reduction using raney nickel heating at 50 °C, 60 psi to
form substituted indole-3-propylamine 5(a–e). In Scheme 2
substituted indole-3-carboxaldehyde 1 was conveniently
converted to 6 by condensing it with ethoxy carbonyl
methyltriphenyl phosphorous bromide, which on reduc-
tion using PtO2 to get 7 which on hydrolysis in alkaline
medium to get indole-3-substituted carboxylic acid 9. The
Biological activity
All the title compounds were subjected to in vitro anti-
bacterial, antifungal, and antitubercular properties follow-
ing standard methods.
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Med Chem Res (2013) 22:4437–4454
4439
H2N
HON
R3
B
R3
R2
R2
N
N
R1
R1
2(a-e)
A
3(a-e)
R1=H,CH3
R1=H,CH3
R2=H,CH3
R2=H,CH3
R3=Cl,OCF3
CHO
R2
R3=Cl,OCF3
H2N
R3
N
R1
C
1
CN
R1=H,CH3
R2=H,CH3
R3=Cl,OCF3
R3
D
R3
R2
R2
N
N
R1
R1
4(a-e)
5(a-e)
R1=H,CH3
R1=H,CH3
R2=H,CH3
R3=Cl,OCF3
R2=H,CH3
R3=Cl,OCF3
Scheme 1 (A) NH2OHÁHCl, C2H5OH/Na2CO3 60 °C, 3 h. (B) Raney Ni/NH4OH, methanol, 5 h. (C) Cyanomethyltriphenylphosphoniumbromide,
DBU, toluene, 110 °C, 15 h. (D) Raney Ni, CH3OH, 50 °C, 10 h
COOEt
COOEt
Cl
F
Cl
N
R1
N
R1
7
6
E
G
CHO
Cl
N
H
COOH
R1
COOH
1
R1=H,CH3
Cl
I
Cl
R2
N
N
R1
R1
8(a,b)
9(a,b)
R1=H,CH3
R1=H,CH3
Scheme 2 (E) Ethoxycarbonylmethyltriphenylphosphoniumbromide, DBU, toluene, 120 °C, 20 h. (F) PtO2, Methanol, H2, 12 h. (G) Ethanol,
NaOH, 0 °C. (H) Malonic acid, pyridine, piperidine, 115 °C, 14 h. (I) PtO2, H2, Methanol, 8 h
123

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Med Chem Res (2013) 22:4437–4454
R1
N
H2N
R2
R3
R3
Cl
R
J
R2
HN
+
N
R1
O
3(a-e)
R1=H,CH3
N
COOH
10(a-J)
R2=H,CH3
R3=Cl,OCF3
H2N
Cl
N
R
9(a,b)
R=H,CH3
Cl
N
HN
R2
N
J
O
+
R1
R3
R2
R3
N
R
R1
5(a-e)
R1=H,CH3
11(a-J)
R2=H,CH3
R3=Cl,OCF3
Scheme 3 (J) EDCl/HOBT, TEA, dichloromethane, 25 °C, 3 h
Fig. 1 Selected regions for the
SAR studies
Cl
N
HN
R2
Region 1
O
N
R1
R3
R
Region 2
Antibacterial activity
Antifngal activity
Antibacterial activity of the title compounds was investi-
gated against five different bacterial strains, Staphylococ-
cus aureus, Streptococcus pyogenes, Pseudomonas
aeruginosa, Klebsiella pneumoniae, and Escherichia coli
using ciprofloxacin as reference, by serial dilution method.
Table 2 depicts the antibacterial screening results (MIC,
lg/mL) of final compounds, 10(a–j) and 11(a–j).
Antifungal activity of the title compounds was investigated
against five different strains, Aspergillus flavus, Aspergillus
fumigatus, Penicillium marneffei (recultured), Trichophy-
ton mentagrophytes (recultured), and Candida albicans
using Ciclopirox olamine as reference, by serial dilution
method. Table 3 depicts the antifungal screening results
(MIC, lg/mL) of final compounds, 10(a–j) and 11(a–j).
123

Med Chem Res (2013) 22:4437–4454
4441
Table 1 Characterization data of synthesized compounds 10(a–j) and 11(a–j)
Compounds
Structure
Mol. formula
Mol. wt
MP (°C)
Yield (%)a
79
10a
C21H17ClF3N3O2
435.8
213–215
H
N
OCF3
Cl
HN
O
HN
H
N
10b
C22H19ClF3N3O2
449.8
ND
80
OCF3
Cl
HN
O
HN
N
10c
10d
10e
10f
C23H21ClF3N3O2
463.8
261–263
209–211
235–237
ND
86
68
70
79
OCF3
Cl
HN
O
HN
Cl
N
C21H19Cl2N3O
400.3
Cl
HN
O
HN
Cl
H
N
C22H19ClF3N3O2
449.8
OCF3
HN
O
N
N
C24H23ClF3N3O2
477.9
OCF3
Cl
HN
O
N
123

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Med Chem Res (2013) 22:4437–4454
Table 1 continued
Compounds
Structure
Mol. formula
Mol. wt
MP (°C)
Yield (%)a
63
10g
C22H21Cl2N3O
414.3
254–256
N
Cl
Cl
HN
O
N
H
10h
10i
10j
C20H17Cl2N3O
386.2
219–221
66
73
80
N
Cl
Cl
HN
O
HN
H
N
C23H21ClF3N3O2
463.9
ND
OCF3
Cl
N
HN
O
H
N
C21H19Cl2N3O
400.3
208–210
Cl
Cl
HN
O
N
11a
C24H25Cl2N3O
442.4
249–251
71
Cl
HN
N
O
N
Cl
11b
C24H23ClF3N3O2
478.0
283–285
74
Cl
HN
NH
O
HN
F3CO
123

Med Chem Res (2013) 22:4437–4454
4443
Table 1 continued
Compounds
Structure
Mol. formula
Mol. wt
MP (°C)
Yield (%)a
83
11c
C22H21Cl2N3O
414.3
264–266
Cl
HN
NH
O
HN
Cl
Cl
11d
C25H25ClF3N3O2
491.9
ND
89
HN
N
O
HN
Cl
F3CO
11e
C24H23ClF3N3O2
477.69
ND
68
HN
NH
O
N
F3CO
11f
C23H21ClF3N3O2
463.8
254–256
82
Cl
HN
NH
O
HN
Cl
F3CO
11g
C26H27ClF3N3O2
505.9
ND
86
HN
N
O
N
F3CO
11h
C23H23Cl2N3O
428.3
238–240
73
Cl
HN
N
O
HN
Cl
123

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Med Chem Res (2013) 22:4437–4454
Table 1 continued
Compounds
Structure
Mol. formula
Mol. wt
MP (°C)
Yield (%)a
79
11i
C23H23Cl2N3O
428.3
241–243
Cl
HN
NH
O
N
Cl
11j
C24H23ClF3N3O2
477.9
ND
81
Cl
HN
NH
O
HN
F3CO
ND Not detected
a
Isolated yield after column purification
Table 2 Antibacterial activity data of the synthesized compounds 10(a–j) and 11(a–j)
Compounds
MIC in lg/mL and zone of inhibition in mm
S. aureus
(ATCC 25923)
E. coli
(ATCC 24922)
P. aeruginosa
(ATCC 27853)
K. pneumoniae
(recultured)
S. pyogenes
10a
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
12.5 (11–15)
25 (\10)
6.25 (16–20)
12.5 (11–15)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
25 (\10)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
25 (\10)
6.25 (16–20)
25 (\10)
12.5 (11–15)
6.25 (16–20)
25 (\10)
10b
10c
25 (\10)
10d
12.5 (11–15)
6.25 (16–20)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
25 (\10)
6.25 (16–20)
6.25 (16–20)
25 (\10)
10e
6.25 (16–20)
25 (\10)
10f
10g
12.5 (11–15)
6.25 (16–20)
25 (\10)
25 (\10)
10h
6.25 (16–20)
25 (\10)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
25 (\10)
10i
10j
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
25 (\10)
25 (\10))
11a
25 (\10)
6.25 (16–20)
11b
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
25 (\10)
11c
25 (\10)
25 (\10)
25 (\10))
11d
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
25 (\10)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
6.25 (22–30)
25 (\10)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
12.5 (11–15)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
1.56 (21)
11e
12.5 (11–15)
6.25 (16–20)
25 (\10)
11f
11g
11h
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
25 (\10)
11i
6.25 (16–20)
6.25 (16–20)
6.25 (30–40)
12.5 (11–15)
6.25 (16–20)
6.25 (23–27)
11j
Ciprofloxacin (standard)
MIC values were evaluated at concentration ranging between 1.56 and 25 lg/mL. The figures in the table show the MIC values in lg/mL and
corresponding zone of inhibition in mm inside the bracket. MIC (lg/mL) = minimum inhibitory concentration, i.e., the lowest concentration to
completely inhibit bacterial growth
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Med Chem Res (2013) 22:4437–4454
4445
Table 3 Antifungal activity data of the synthesized compounds 10(a–j) and 11(a–j)
Compounds
MIC in lg/mL and zone of inhibition in mm
A. flavus
(NCIM no. 524)
A. fumigatus
(NCIM no. 902)
P. marneffei
(recultured)
T. mentagrophytes
(recultured)
Candida
albicans
10a
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
25 (\10)
6.25 (16–20)
25 (\10)
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
12.5 (11–15)
25 (\10)
6.25 (16–20)
25 (\10)
6.25 (16–20)
25 (\10)
10b
10c
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
25 (\10)
12.5 (11–15)
6.25 (16–20)
25 (\10)
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
12.5 (11–15)
25 (\10)
10d
10e
10f
6.25 (16–20)
25 (\10)
10g
25 (\10)
12.5 (11–15)
25 (\10)
10h
25 (\10)
6.25 (16–20)
25 (\10)
6.25 (16–20)
25 (\10)
25 (\10)
10i
25 (\10)
25 (\10)
12.5 (11–15)
6.25 (16–20)
25 (\10)
10j
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
25 (\10)
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
25 (\10)
6.25 (16–20)
25 (\10)
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
6.25 (16–20)
25 (\10)
11a
11b
6.25 (16–20)
6.25 (16–20)
6.25 (16–20)
25 (\10)
6.25 (16–20)
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
25 (\10)
11c
11d
11e
12.5 (11–15)
25 (\10)
25 (\10)
11f
25 (\10)
6.25 (16–20)
25 (\10)
11g
6.25 (16–20)
12.5 (11–15)
6.25 (16–20)
25 (\10)
12.5 (11–15)
6.25 (16–20)
12.5 (11–15)
25 (\10)
25 (\10)
11h
25 (\10)
25 (\10)
25 (\10)
6.25 (16–20)
11i
25 (\10)
25 (\10)
11j
25 (\10)
6.25 (25–30)
25 (\10)
6.25 (25–30)
12.5 (11–15)
6.25 (20–27)
25 (\10)
6.25 (20)
Ciclopirox olamine
6.25 (27–33)
MIC values were evaluated at concentration ranging between 6.25 and 25 lg/mL. The figures in the table show the MIC values in lg/mL and
corresponding zone of inhibition in mm inside the bracket. MIC (lg/mL) = minimum inhibitory concentration, i.e., the lowest concentration to
completely inhibit bacterial growth
Antitubercular study
10a, 10e, 10h, 10i, 10j, 11b, 11f, 11i, and 11j showed good
activity against K. pneumoniae.
Based on the encouraging results from the antibacterial
screening, title compounds were further tested for their
in vitro antimycobacterial activity against M. tuberculosis
H37Rv, Mycobacterium smegmatis (ATCC 19420),
Mycobacterium fortuitum (ATCC 19542), and MDR-TB
strains using isoniazid and rifampicin as standards. The
screening results of in vitro antimycobacterial activity of
the final compounds are tabulated in Table 4.
The investigation of antifungal screening (Table 3)
revealed that all the newly synthesizes compounds showed
moderate to good inhibition at 1.56–25 lg/mL in DMSO.
Compounds 10a, 10b, 10d, 10j, 11b, 11c, and 11g showed
good activity against A. flavus and P. marneffei. Com-
pounds 10a, 10d, 10f, 10h, 10j, 11b, 11c, and 11h showed
good activity against T. mentagrophytes and A. fumigatus.
Compounds 10a, 10c, 10d, 10j, 11b, 11c, 11e, and 11i
showed good activity against C. albicans. Further, the
preliminary antimycobacterial screening of the title com-
pounds was carried out at 1, 10, and 100 lg/mL concen-
trations against three different TB strains and also against
MDR-TB strain. From the result, it was noticed that the
compounds 10a, 10b, 10e, 10h, 10i, 10j, 11a, 11b, 11d,
11e, 11g, 11i, and 11j were active between 1 and 10 lg/mL
concentrations against M. tuberculosis H37Rv strain. The
active compounds from the preliminary investigation were
further subjected to second level of testing. The compounds
Biological results
The investigation of antibacterial screening (Table 2)
revealed that all the newly synthesizes compounds showed
moderate to good inhibition at 1.56–25 lg/mL in DMSO.
Compounds 10a, 10e, 10h, 11b, 11f, 11i, and 11j showed
good activity against E. coli and P. aeruginosa. Com-
pounds 10b, 10e, 10j, 11b, 11e, and 11j showed good
activity against S. aureus and S. pyogenes. Compounds
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Med Chem Res (2013) 22:4437–4454
Table 4 Antitubercular activity data of the synthesized compounds 10(a–j) and 11(a–j)
Compounds
Preliminary in vitro screening results, MIC (lg/mL)
Second level screening results, MIC (lg/mL)
d
MTBa
MSb
MFc
%
MTB
MS
MF
MDR-TB
10a
1
1
10
90
95
1.25
0.625
5
1.25
10
–
1.25
10
–
[50
6.25
[50
[50
6.25
[50
[50
6.25
[50
6.25
25
10b
10c
1
10
10
[100
[100
1
10
[100
10
\90
90
10d
10e
10
1.25
0.625
5
–
10
10
–
1
10
95
1.25
–
10f
[100
[100
1
10
[100
10
\90
\90
90
10g
[100
1
10
10
1.25
1.25
10
10
10
–
10
10
1.25
10
–
10h
10i
10
0.625
1.25
0.625
5
1
1
10
90
10j
1
10
10
95
11a
10
10
[100
10
\90
\90
0
11b
11c
10
10
2.5
10
–
[50
–
[100
10
[100
[100
10
[100
10
–
11d
11e
90
10
–
10
10
–
[50
6.25
–
1
10
95
0.625
–
10
–
11f
[100
10
[100
[100
[100
10
[100
[100
[100
[100
10
0
11g
\90
0
1.25
–
–
–
1.25
–
11h
11i
[100
10
–
–
\90
95
2.5
2.5
10
50
1.5
–
2.5
11j
1
10
0.625
0.7
10
12.5
1.5
12.5
12.5
25
Isoniazid
Rifampicin
0.7
0.5
50
12.5
1.5
95
1.5
95
0.5
‘‘–’’ Not detected
a
Mycobacterium tuberculosis H37Rv
b
c
d
Mycobacterium smegmatis (ATCC 19420)
Mycobacterium fortuitum (ATCC 19542)
Percentage of inhibition against M. tuberculosis H37Rv
which were active at 100 lg/mL concentration were not
taken for further studies. The second level testing was
carried out at concentrations 0.3125, 0.625, 1.25, 2.5, and
5 lg/mL. Amongst the tested compounds 10b, 10e, 10h,
10j, 11e, and 11j are active at 0.625 lg/mL concentra-
tions against M. tuberculosis H37Rv strain and com-
pounds 10a, 10d, 10i, 11d, and 11g are active at 1.25 lg/
mL concentrations. Similarly, the target molecules 10a,
10e, 10h, and 10i displayed significant activity at 1.25 lg/
mL against M. smegmatis (ATCC 19420). It is interesting
to note that most of the compounds showed either
enhanced activity or activity in line with the reference
compound isoniazid against M. fortuitum (ATCC 19542).
Further, the compounds 10b, 10e, 10h, 10j, and 11e
showed promising activity against the MDR-TB strain at
6.25 lg/mL. These are just initial screening results to
check the antimicrobial potential, since this is established
and further work would be done to understand their
mechanism of action.
Conclusion
We herein report the successful synthesis of (1H-in-
dol-3-yl)alkyl-3-(1H-indol-3-yl)propanamide 10(a–j) and
11(a–j). They have been characterized by spectral studies.
All the title compounds have been investigated for their
antimicrobial and antimycobacterial activities, the investi-
gation of antibacterial and antifungal screening revealed
that all the newly synthesizes compounds showed moderate
to good inhibition at 1.56–25 lg/mL in DMSO. Com-
pounds 10a, 10b, 10e, 10h, 10j, 11b, 11f, 11i, and 11j
exhibited comparatively good activity against the tested
bacterial strains. Compounds 10a, 10d, 10j, 11b, and 11c
exhibited comparatively good activity against the five
fungal strains. Further, the compounds 10b, 10e, 10h, 10j,
and 11e displayed significant activity against M. tubercu-
losis H37Rv strain. Furthermore, the target molecules 10a,
10e, 10h, and 10i displayed significant activity at 1.25 lg/
mL against M. smegmatis (ATCC 19420). Similarly, the
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Med Chem Res (2013) 22:4437–4454
4447
compounds 10b, 10e, 10h, 10j, and 11e showed substantial
activity against the MDR-TB strain at 6.25 lg/mL. The
halogen and trifluoro-substituted aromatic compounds will
improve the lipophilic nature of the compound at the same
time methyl-substituted compound would act as an electron
donors. In addition, the presence of an amide group would
be the essential element for hydrogen bonding with
receptor. The above mentioned properties of these phar-
macophores would be responsible for the promising
activities of the title compounds. The scaffold synthesized
in the research work can be taken for further derivatization
in order to find the lead in these series.
9.1 (s, 1H, OH), 11.26 (d, 1H, NH); 13C d ppm (DMSO,
400 MHz) = 102.1, 112.9, 119.6, 121.9, 127.0, 127.5,
131.3, 133.9, 148.7; LC/MS (ESI–MS) m/z = 195.49
(M?1).
5-Chloro-2-methyl-1H-indole-3-carbaldehyde oxime
Appearance, pale yellow solid (mp = 192–194 °C); 1H
NMR (DMSO, 400 MHz) d ppm = 3.2 (d, 3H, CH3), 6.8 (s,
1H, CH), 6.83 (s, 1H, ArH), 7.21 (d, 1H, ArH), 7.28 (d, 1H,
ArH), 7.29 (s, 1H, ArH), 9.1 (s, 1H, OH); 13C d ppm (DMSO,
400 MHz) = 42.3, 102.3, 112.9, 119.6, 121.9,126.8, 127.6,
134.4, 134.8, 148.1; LC/MS (ESI–MS) m/z = 209.72
(M?1).
Experimental
5-Trifluoromethoxy-1H-indole-3-carbaldehyde oxime
General
1
Appearance, yellow oil; H NMR (DMSO, 400 MHz) d
All reagents were purchased from Aldrich. Solvents used
were extra dried. Final purifications were carried out using
Quad biotage Flash purifier (A Dyax Corp. Company).
Microwave-assisted syntheses were performed in Biotage
initiator. TLC experiments were performed on alumina
backed silica gel 40 F254 plates (Merck, Darmstadt, Ger-
many). The plates were illuminated under UV (254 nm) and
molesybidinic acid. All 1H and 13C NMR spectra were
recorded on a Bruker AM-300 (300.12 MHz) and AM-400
(400.13 MHz), Bruker Biospin Corp., Germany. Molecular
weights of unknown compounds were checked by LCMS
6200 series Agilent Technology. Chemical shifts are repor-
ted in ppm (d) with reference to internal standard TMS. The
signals are designated as follows: s, singlet; d, doublet;
t, triplet; m, multiplet.
ppm = 6.78 (d, 1H, ArH), 6.80 (s, 1H, CH), 7.30 (s, 1H,
ArH), 7.46 (d, 1H, ArH), 7.52(d, 1H, ArH), 9.12 (S, 1H, OH),
11.26 (d, 1H, NH); 13C d ppm (DMSO, 400 MHz) = 102.1,
102.8, 109.6, 112.1, 121.8, 127.1, 127.8, 130.8, 148.2, 155.6;
LC/MS (ESI–MS) m/z = 245.25 (M?1).
2-Methyl-5-trifluoromethoxy-1H-indole-3-carbaldehyde
oxime
Appearance, white solid (mp = 197–199 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.38 (d, 3H, CH3), 6.62 (S,
1H, ArH), 6.64 (d, 1H, ArH), 6.92 (S, 1H, CH), 7.12 (d,
1H, ArH), 11.26 (S, 1H, NH), 9.12 (S, 1H, OH); 13C d ppm
(DMSO, 400 MHz) = 13.1, 102.6, 103.1, 109.8, 112.4,
122.2, 127.6, 127.82, 131.2, 149.4, 156.2; LC/MS (ESI–
MS) m/z = 259.21 (M?1).
General procedure for the preparation of compounds
2(a–e)
1,2-Dimethyl-5-trifluoromethoxy-1H-indole-3-
carbaldehyde oxime
5-Chloro indole-3-carboxaldehyde (5 g, 0.0278 mol) and
hydroxylamine (2.9 g, 0.0417 mol) were dissolved in eth-
anol (200 mL) and stirred vigorously for 3 h at 60 °C. The
reaction completion was monitored by TLC. After the
completion, saturated Na2CO3 solution was added to bring
the reaction mass to an alkaline medium. Concentrated the
ethanol and the crude obtained were recrystalized in ethyl
acetate/hexane. The yield of the compound obtained from
this reaction is from 85 to 90 %. The spectral data of
compounds 2(a–e) are given below.
1
Appearance, semi solid; H NMR (DMSO, 400 MHz) d
ppm = 2.47 (s, 3H, CH3), 3.82 (s, 3H, CH3), 6.41 (s, 1H,
ArH), 6.92 (d, 1H, ArH), 6.96 (d, 1H, ArH), 7.01 (s, 1H,
CH), 9.34 (s, 1H, OH); 13C
d
ppm (DMSO,
400 MHz) = 7.6, 36.4, 104.1, 105.0, 110.6, 114.24, 123.2,
129.2, 130.4, 141.3, 149.7, 156.1; LC/MS (ESI–MS) m/
z = 273.3 (M?1).
General procedure for the preparation of (1H-indol-3-
yl)methanamine derivatives 3(a–e)
5-Chloro-1H-indole-3-carbaldehyde oxime
The indole-3-methyloxime (4 g, 0.0205 mol) was dis-
solved in methanol (40 mL) and added ammonium
hydroxide (8 mL), and raney nickel (5.9 g, 0.1025 mol),
the reaction mass was stirred for 5 h at ambient
Appearance, off white solid (mp = 186–188 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 6.8 (s, 1H, CH), 7.1 (d, 1H,
ArH), 7.38 (d, 1H, ArH), 7.46 (d, 1H, ArH), 7.6 (s, 1H, ArH),
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Med Chem Res (2013) 22:4437–4454
temperature. The reaction completion was monitored by
TLC. After the completion, the reaction mass was filtered
through Celite and concentrated the methanol, the crude
product recrystalized in ethyl acetate/hexane. The spectral
data of compounds 3(a–e) are given below.
CH3), 3.6 (m, 3H, CH3), 3.8 (t, 2H, CH2), 5.6 (s, 1H, ArH),
6.5 (d, 1H, ArH), 6.7 (d, 1H, ArH); 13C d ppm (DMSO,
400 MHz) = 13.0, 39.2, 43.8, 102.3, 109.6, 109.8, 112.6,
121.9, 128.6, 129.5, 132.6, 155.9; LC/MS (ESI–MS) m/
z = 259.2 (M?1); Anal. Calcd for C12H13F3N2O; C, 55.81;
H, 5.07; N, 10.85; Found C, 55.99; H, 5.28; N, 10.94.
5-Chloro-1H-indole-3-methanamine
General procedure for the preparation of compounds
1
Appearance, colorless oil; H NMR (DMSO, 400 MHz) d
4(a–e)
ppm = 1.9(t, 2H, NH2), 3.8 (t, 2H, CH2), 6.8 (s, 1H, ArH), 7.1
(d, 1H, ArH), 7.2 (d, 1H, ArH), 7.2 (d, 1H, ArH), 11.26 (d, 1H,
NH); 13C d ppm (DMSO, 400 MHz) = 45.6, 110.2, 110.2,
119.2,121.4,123.0,127.7,129.3,134.5;LC/MS(ESI–MS)m/
z = 181.2 (M?1). Anal. Calcd for C9H9ClN; C, 59.84; H,
5.02; N, 15.51; Found C, 59.98; H, 5.12; N, 15.58.
5-Chloroindole-3-carboxaldehyde (5 g, 0.027 mol), cyanom-
ethyltriphenyl phosphoniumbromide (21.82 g, 0.055 mol),
and DBU (8.37 g, 0.055 mol) were dissolved in toluene
(70 mL). The reaction mass was refluxed for 15 h at 110 °C.
The reaction completion was monitored by TLC. After com-
pletion, charged (20 mL) of water and the product formed
were extracted in ethylacetate. The organic layer was washed
with water and was dried over sodium sulfate and concentrated
under vacuum and the products obtained were purified by
column chromatography on a silica gel (230–400 mesh) using
ethyl acetate (20–40 %) in petroleum ether as eluant to afford
4a–4e. The spectral data of compounds 4(a–e) are given
below.
5-Chloro-1-methyl-1H-indole-3-methanamine
Appearance, off white solid (mp = 110–112 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 1.9 (t, 2H, NH2), 3.8 (t, 2H,
CH2), 3.6 (d, 3H, CH3), 6.4 (s, 1H, ArH), 6.7 (s, 1H, ArH),
6.9 (d, 1H, ArH), 7.3 (d, 1H, ArH); 13C d ppm (DMSO,
400 MHz) = 42.6, 46.9, 112.5, 112.5, 119.3, 121.87,
126.5, 126.7, 129.0, 135.9; LC/MS (ESI–MS) m/z = 195.6
(M?1). Anal. Calcd for C10H11ClN2; C, 61.70; H, 5.7; N,
14.39; Found C, 61.98; H, 5.86; N, 14.83.
3-(5-Chloro-1H-indole-3yl)acrylonitrile
Appearance, pale yellow solid (mp = 134–136 °C); 1H
NMR (DMSO, 400 MHz) d ppm = 5.92 (d, 1H, CH), 7.02
(d, 1H, ArH), 7.14 (d, 1H, ArH), 7.28 (s, 1H, ArH), 7.42 (d,
1H, CH), 9.46 (d, 1H, ArH), 11.26 (d, 1H, NH); 13C d ppm
(DMSO, 400 MHz) = 104.6, 111.2, 112.6, 118.4, 119.94,
122.4, 127.9, 128.4, 130.6, 133.9, 147.3; LC/MS (ESI–MS)
m/z = 203.6 (M?1).
5-Trifluoromethoxy-1H-indole-3-methanamine
Appearance, white solid (mp = 156–158 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 1.9 (t, 2H, NH2), 3.8 (t, 2H,
CH2), 6.8 (s, 1H, ArH), 7.1 (d, 1H, ArH), 6.7 (d, 1H, ArH),
6.7 (d, 1H, ArH), 10.0 (d, 1H, NH); 13C d ppm (DMSO,
400 MHz) = 46.5, 102, 112.0, 112.5, 120.0, 122.1, 122.2,
123.0, 128.6, 129.0; LC/MS (ESI–MS) m/z = 231.1
(M?1). Anal. Calcd for C10H9F3N2O; C, 52.18; H, 3.94; N,
12.17; Found C, 52.39; H, 4.02; N, 12.31.
3-(5-Chloro-1-methyl-1H-indole-3yl)acrylonitrile
1
Appearance, yellow oil; H NMR (DMSO, 400 MHz) d
ppm = 3.82 (d, 3H, CH3), 5.92 (d, 1H, CH), 6.84 (s, 1H,
ArH), 6.92 (d, 1H, ArH), 7.32 (d, 1H, ArH), 7.43 (d, 1H,
CH), 8.97 (s, 1H, ArH); 13C d ppm (DMSO, 400 MHz) =
42.9, 104.6, 111.2, 112. 4, 118.4, 119.9, 122.4, 127.9,
128.4, 135.9, 136.2, 147.3; LC/MS (ESI–MS) m/
z = 217.62 (M?1).
2-Methyl-5-trifluoromethoxy-1H-indole-3-methanamine
1
Appearance, yellow liquid; H NMR (DMSO, 400 MHz) d
ppm = 1.9 (t, 2H, NH2), 2.2 (d, 3H, CH3), 3.8 (t, 2H, CH2), 6.3
(s, 1H, ArH), 6.7 (d, 1H, ArH), 6.74 (d, 1H, ArH), 11.26 (s, 1H,
NH); 13C d ppm (DMSO, 400 MHz) = 16.0, 43.5, 102.1,
109.5, 109.9, 112.3, 121.7, 128.4, 128.5, 131.4, 155.7; LC/MS
(ESI–MS) m/z = 245.2 (M?1). Anal. Calcdfor C11H11F3N2O;
C, 54.10; H, 4.54; N, 11.47; Found C, 54.28; H, 4.62; N, 11.68.
3-(5-(Trifluoromethoxy)-1H-indole-3yl)acrylonitrile
1
Appearance, semi solid; H NMR (DMSO, 400 MHz) d
ppm = 5.92 (d, 1H, CH), 6.64 (s, 1H, ArH), 6.54 (d, 1H,
1,2-Dimethyl-5-trifluoromethoxy-1H-indole-3-
methanamine
ArH), 6.73 (d, 1H, ArH), 7.42 (d, 1H, CH), 9.46 (d, 1H,
ArH, 11.26 (d, 1H, NH); 13C
d ppm (DMSO,
400 MHz) = 103.4, 104.6, 109.2, 110.2, 112.6, 118.3,
123.6, 128.4, 129.1, 131.2, 146.9, 156.5; LC/MS (ESI–MS)
m/z = 253.31 (M?1).
1
Appearance, yellow solid (mp = 174–176 °C); H NMR
(DMSO, 400 MHz) d ppm = 1.9 (t, 2H, NH2), 2.4 (m, 3H,
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Med Chem Res (2013) 22:4437–4454
4449
6.81 (s, 1H, ArH), 6.90 (d, 1H, ArH), 7.34 (d, 1H, ArH), 13C d
ppm (DMSO, 400 MHz) = 28.2, 33.6, 42.6, 43.6, 112.4,
113.4, 120.1, 123.1, 126.9, 127.4, 129.1, 136.8; LC/MS(ESI–
MS) m/z = 223.9 (M?1); Anal. Calcd for C12H15ClN2; C,
64.71; H, 6.79; N, 12.58; Found C, 64.77; H, 6.82; N, 12.64.
3-(2-Methyl-5-(trifluoromethoxy)-1H-indole-
3yl)acrylonitrile
Appearance, white solid (mp = 166–168 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.42 (d, 3H, CH3), 5.92 (d,
1H, CH), 6.13 (s, 1H, ArH), 6.62 (d, 1H, ArH), 6.68 (d, 1H,
ArH), 7.46 (d, 1H, CH), 11.26 (s, 1H, NH); 13C d ppm
(DMSO, 400 MHz) = 12.6, 103.4, 104.6, 109.24, 105.6,
112.6, 118.3, 123.6, 128.4, 129.1, 131.2, 146.9, 156.5; LC/
MS (ESI–MS) m/z = 268.23 (M?1).
3-(5-(Trifluoromethoxy)-1H-indol-3-yl)propane-1-amine
1
Appearance, yellow oil; H NMR (DMSO, 400 MHz) d
ppm = 1.91 (m, 2H, CH2), 2.12 (t, 2H, NH2), 2.53 (t, 2H,
CH2),2.74(m, 2H, CH2), 6.92(d, 1H, ArH), 6.72(s, 1H, ArH),
6.81 (d, 1H, ArH), 7.24 (d, 1H, ArH), 11.26 (d, 1H, NH); 13C d
ppm (DMSO, 400 MHz) = 28.2, 33.6, 42.6, 103.4, 110.1,
111.2, 113.2, 122.6, 123.6, 129.8, 129.9, 156.3; LC/MS (ESI–
MS) m/z = 259.29; Anal. Calcd for C12H13F3N2O; C, 55.81;
H, 5.07; N, 10.85; Found C, 55.92; H, 5.13; N, 10.81.
3-(1,2-Dimethyl-5-(trifluoromethoxy)-1H-indole-
3yl)acrylonitrile
Appearance, white solid (mp = 172–174 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.42 (s, 3H, CH3), 3.78 (s,
3H, CH3), 5.92 (d, 1H, CH), 5.84 (s, 1H, ArH), 6.82 (d, 1H,
ArH), 6.42 (d, 1H, ArH), 7.46 (d, 1H, CH); 13C d ppm
(DMSO, 400 MHz) = 7.1, 37.2, 103.4, 104.6, 109.2,
105.6, 112.6, 118.3, 123.6, 129.2, 129.3, 141.4, 146.9,
156.5; LC/MS (ESI–MS) m/z = 283.31 (M?1).
3-(2-Methyl-5-(trifluoromethoxy)-1H-indol-3-yl)propane-
1-amine
1
Appearance, semi solid; H NMR (DMSO, 400 MHz) d
ppm = 1.91 (m, 2H, CH2), 2.12 (t, 2H, NH2), 2.42 (d, 3H,
CH3), 2.53 (t, 2H, CH2), 2.74 (m, 2H, CH2), 6.31 (s, 1H,
ArH), 6.76 (d, 1H, ArH), 6.94 (d, 1H, ArH), 11.26 (s, 1H,
NH); 13C d ppm (DMSO, 400 MHz) = 12.6, 21.2, 33.6,
42.1, 103.1, 109.6, 110.1, 113.4, 122.1, 129.6, 129.9,
132.4, 156.5; LC/MS (ESI–MS) m/z = 273.27 (M?1);
Anal. Calcd for C13H15F3N2O; C, 57.35; H, 5.55; N, 10.29;
Found C, 57.42; H, 5.59; N, 10.26.
General procedure for the preparation of 3-(1H-indol-3-
yl)propan-1-amine derivatives 5(a–e)
The above 4(a–e) prepared compounds (3 g, 0.0148 mol)
were dissolved in methanol (60 mL) and raney nickel
(4.35 g, 0.074 mol) was added, and the reaction mass was
stirred at 50 °C for 10 h under hydrogen atmosphere at
60 psi pressure. The reaction completion was monitored by
TLC. After completion, the reaction mass was filtered
through Celite. Concentrated the methanol and the crude
obtained were purified by column chromatography on a
silica gel (230–400 mesh) using ethyl acetate (40–50 %) in
petroleum ether as eluant to afford 5(a–e). The yield of the
compound obtained from this reaction is from 40 to 50 %.
3-(1,2-Dimethyl-5-(trifluoromethoxy)-1H-indol-3-
yl)propane-1-amine
1
Appearance, semi solid; H NMR (DMSO, 400 MHz) d
ppm = 1.91 (m, 2H, CH2), 2.12 (t, 2H, NH2), 2.42 (d, 3H,
CH3), 2.53 (t, 2H, CH2), 2.74 (m, 2H, CH2), 3.84 (s, 3H,
CH3), 5.92 (s, 1H, ArH), 6.62 (d, 1H, ArH), 6.92 (d, 1H,
ArH); 13C d ppm (DMSO, 400 MHz) = 6.0, 21.2, 34.3,
36.2, 42.6, 102.4, 109.1, 110.6, 113.4, 122.9, 129.7, 130.6,
134.1, 156.4; LC/MS (ESI–MS) m/z = 287.32; Anal.
Calcd for C14H17F3N2O; C, 58.73; H, 5.99; N, 9.78; Found
C, 58.82; H, 6.03; N, 9.81.
3-(5-Chloro-1H-indol-3-yl)propane-1-amine
Appearance, brown oil; 1H NMR (DMSO, 400 MHz) d
ppm = 1.91 (m, 2H, CH2), 2.12 (t, 2H, NH2), 2.53 (t, 2H,
CH2), 2.74 (m, 2H, CH2), 6.92 (d, 1H, ArH), 7.20 (d, 1H,
ArH), 7.28(d, 1H, ArH), 7.32(s, 1H, ArH), 11.26(d, 1H, NH);
13C d ppm (DMSO, 400 MHz) = 26.9, 33.6, 42.6, 111.8,
113.1, 120.1, 122.1, 123.1, 126.9, 129.1, 135.3; LC/MS (ESI–
MS) m/z = 209.68 (M?1); Anal. Calcd for C11H13ClN2; C,
63.31; H, 6.28; N, 13.42; Found C, 63.39; H, 6.32; N, 13.49.
Procedure for the preparation of ethyl-3-(5-chloro-1H-
indol-3-yl)acrylate (6)
5-Chloro indole-3-carboxaldehyde (20 g, 0.0278 mol) and
ethoxycarbonylmethyl triphenylphosphoniumbromide (95.6 g
0.222 mol), and DBU (33.8 g, 0.222 mol) were dissolved in
toluene (300 mL) and refluxed at 120 °C for 20 h. The
reaction was monitored by TLC. After completion, toluene
was concentrated under vacuum. Crude obtained was purified
by column chromatography on a silica gel (230–400 mesh)
3-(5-Chloro-1-methyl-1H-indol-3-yl)propane-1-amine
Appearance, brown oil; 1H NMR (DMSO, 400 MHz) d
ppm = 1.91 (m, 2H, CH2), 2.12 (t, 2H, NH2), 2.53 (t, 2H,
CH2),2.74(m, 2H, CH2), 3.84(d, 3H, CH3), 6.55(s, 1H, ArH),
123

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using ethyl acetate (10–20 %) in petroleum ether as eluant to
afford 9 as an off white solid; 1H NMR (DMSO, 400 MHz) d
ppm = 1.42 (t, 3H, CH3), 4.23 (m, 2H, CH2), 6.42 (d, 1H,
CH), 6.99 (d, 1H, ArH), 7.22 (d, 1H, ArH), 7.28 (s, 1H, ArH),
7.82 (d, 1H, CH), 9.43 (d, 1H, ArH), 11.26 (d, 1H, NH).
reaction was monitored by TLC. After the completion, meth-
anol was concentrated under vacuum. Crude obtained was
purified by column chromatography on a silica gel (230–400
mesh) using ethyl acetate (40–50 %) in petroleum ether as
eluant to afford 9(a, b).
Procedure for the preparation of ethyl 3-(5-chloro-1H-
indol-3-yl)propanoate (7)
3-(5-Chloro-1H-indol-3yl)propanoic acid (9a)
Appearance, colorless liquid; 1H NMR (DMSO, 400 MHz)
d ppm = 2.59 (t, 2H, CH2), 2.92 (t, 2H, CH2), 6.92 (d, 1H,
ArH), 7.21 (d, 1H, ArH), 7.26 (d, 1H, ArH), 7.28 (s, 1H,
ArH), 10.46 (d, 1H, NH), 11.96 (s, 1H, COOH); 13C d ppm
(DMSO, 400 MHz) = 26.8, 39.2, 111.2, 113.6, 119.8,
122.3, 123.9, 127.3, 129.2, 135.4, 178.2; LC/MS (ESI–MS)
m/z = 224.69 (M?1); Anal. Calcd for C11H10ClNO2; C,
59.07; H, 4.51; N, 6.26; Found C, 59.11; H, 4.53; N, 6.64.
Ethyl-3-(5-chloro-1H-indol-3-yl)acrylate (3 g, 0.012 mol)
and PtO2 (2.7 g, 0.012 mol) were dissolved in methanol
(30 mL) and stirred under hydrogen atmosphere for 12 h. The
reaction was monitored by TLC. After completion, methanol
was concentrated under vacuum. Crude obtained was purified
by column chromatography on a silica gel (230–400 mesh)
using ethyl acetate (10–20 %) in petroleum ether as eluant to
afford 10 as an off white solid; 1H NMR (DMSO, 400 MHz) d
ppm = 1.42(t, 3H, CH3), 2.67(t, 2H, CH2), 2.85(t, 2H, CH2),
4.22 (m, 2H, CH2), 6.94 (d, 1H, ArH), 7.21 (d, 1H, ArH), 7.32
(d, 1H, ArH), 7.34 (s, 1H, ArH), 11.26 (d, 1H, NH).
3-(5-Chloro-1-methyl-1H-indol-3yl)propanoic acid (9b)
Appearance, white solid (mp = 180–082 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.48 (t, 2H, CH2), 2.69 (t,
2H, CH2), 3.68 (s, 3H, CH3), 6.48 (s, 1H, ArH), 6.97 (s,
1H, ArH), 7.01 (d, 1H, ArH), 7.08 (d, 1H, ArH), 11.96 (s,
1H, COOH); 13C d ppm (DMSO, 400 MHz) = 26.3, 36.4,
43.4, 111.4, 112.6, 120.1, 122.4, 125.9, 126.8, 130.2,
136.3, 176.6; LC/MS (ESI–MS) m/z = 238.69 (M?1);
Anal. Calcd for C12H12ClNO2; C, 60.64; H, 5.09; N, 5.89;
Found C, 60.68; H, 5.11; N, 5.92.
General procedure for the preparation of ethyl 3-(5-
chloro-1H-indol-3-yl)acrylate derivatives 8(a, b)
5-Chloro indole-3-carboxaldehyde (5 g, 0.027 mol) and
malonic acid (3.18 g, 0.031 mol) were dissolved in pyridine
(50 mL) and piperidine (5 mL). The reaction mixture was
heated at 115 °C for 14 h. The reaction was monitored by
TLC. After completion, the reaction mixture was extracted
with ethyl acetate (50 mL), the organic layer was separated
and concentrated under reduced pressure to afford 8(a, b).
The spectral data of compounds 8(a, b) are given below.
General procedure for the preparation of compounds
10(a–j) and 11(a–j)
A mixture of 3-(5-chloro-1H-indol-3-yl)propanoic acid
(0.5 g, 0.0022 mol), EDCl (0.0034 mol), HOBT(0.022 mol),
triethylamine (0.93 mL, 0.0066 mol), and dichloromethane
(5.0 mL) were stirred vigorously for 10 min at 25 °C. Then
amine (0.0022 mol) in dichloromethane was added slowly to
the reaction mixture. The reaction mass was stirred at 25 °C
for 3 h. The reaction completion was monitored by TLC.
After completion, the reaction mass was diluted with dichlo-
romethane, washed with 10 % NaHCO3 (10 mL), brine
solution. The organic layer was dried over anhydrous sodium
sulfate and concentrated under reduced pressure. The crude
product was purified on a Biotage parallel column purifier
using ethyl acetate:petroleum ether (3:1) as eluant to metha-
nol:methylene chloride (2–6 %). The spectral data of com-
pounds 10(a–j) and 11(a–j) are given below.
3-(5-Chloro-1H-indole-3yl)acrylicacid (8a)
1
Appearance, off white solid; H NMR (DMSO, 400 MHz)
d ppm = 6.52 (d, 1H, CH), 6.98 (d, 1H, ArH), 7.24 (d, 1H,
ArH), 7.28 (s, 1H, ArH), 7.81 (d, 1H, CH), 9.42 (d, 1H,
ArH), 10.46 (d, 1H, NH), 12.01 (s, 1H, COOH).
3-(5-Chloro-1-methyl-1H-indole-3yl)acrylicacid (8b)
1
Appearance, off white solid; H NMR (DMSO, 400 MHz)
d ppm = 3.42 (s, 3H, CH3), 6.52 (d, 1H, CH), 6.86 (d, 1H,
ArH), 7.18 (d, 1H, ArH), 7.22 (s, 1H, ArH), 7.69 (d, 1H,
CH), 8.97 (s, 1H, ArH), 12.01 (s, 1H, COOH).
General procedure for the preparation of ethyl 3-(5-
chloro-1H-indol-3-yl)propanoate derivatives 9(a, b)
3-(5-Chloro-1H-indol-3-yl)-N-((5-(trifluoromethoxy)-1H-
indol-3-yl)methyl)propanamide (10a)
Ethyl-3-(5-chloro-1H-indol-3-yl)acrylic acid (3 g, 0.013 mol)
and PtO2 (3.07 g, 0.013 mol) were dissolved in methanol
(30 mL) and stirred under hydrogen atmosphere for 8 h. The
Appearance, white solid (mp = 213–215 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.45 (t, 2H, CH2), 2.71
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4451
(t, 2H, CH2), 4.34 (d, 2H, CH2), 6.69 (s, 1H, ArH), 6.80 (d,
2H, ArH), 7.12 (d, 1H, ArH), 7.20 (m, 4H, ArH), 9.2 (t, 1H,
NH), 10.32 (d, 2H, NH); 13C NMR (DMSO, 400 MHz) d
ppm = 27.4, 36.1, 36.4, 103.7, 108.6, 110.9, 111.2, 112.8,
118.3, 120.8, 122.1, 125.8, 128.5, 129.2, 134.2, 152.3,
172.1; LC/MS (ESI–MS) m/z = 436.9 (M?1).
(t, 2H, CH2), 3.62 (s, 3H, CH3), 4.36 (s, 2H, CH2), 6.40
(s, 1H, ArH), 6.74 (s, 1H, ArH), 6.81 (d, 1H, ArH), 6.88
(s, 2H, ArH), 6.91 (d, 1H, ArH), 7.12 (d, 1H, ArH), 7.31
(d, 1H, ArH), 9.23 (t, 1H, NH), 10.32 (d, 1H, NH); 13C d
ppm (DMSO, 400 MHz) = 27.4, 36.1, 36.4, 42.4, 103.7,
108.6, 110.9, 111.2, 112.8, 118.3, 120.8, 122.1, 124.9,
125.8, 128.0, 128.5, 129.2, 134.2, 152.3, 172.1; LC/MS
(ESI–MS) m/z = 450.8 (M?1).
3-(5-Chloro-1H-indol-3-yl)-N-((2-methyl-5-
(trifluoromethoxy)-1H-indol-3-yl) methyl)
propanamide (10b)
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-
((1,2-dimethyl-5-(trifluoromethoxy)-1H-indol-3-
yl)methyl)propanamide (10f)
Appearance, brown oil; 1H NMR (DMSO, 400 MHz) d
ppm = 2.11(s, 3H, CH3), 2.45(t, 2H, CH2), 2.71(t, 2H, CH2),
4.34 (d, 2H, CH2), 6.69 (s, 1H, ArH), 6.80 (d, 2H, ArH), 7.12
(d, 1H, ArH), 7.20(m, 4H, ArH), 9.2 (t, 1H, NH), 10.30 (s, 1H,
NH), 10.32 (d, 1H, NH); 13C NMR (DMSO, 400 MHz) d
ppm = 12.6, 27.4, 36.1, 36.4, 103.7, 108.6, 110.9, 111.2,
112.8, 118.3, 120.8, 122.1, 125.8, 128.5, 129.2, 131.3, 134.2,
152.3, 172.1; LC/MS (ESI–MS) m/z = 450.91 (M?1).
Appearance, brown semisolid; 1H NMR (DMSO, 400 MHz)
d ppm = 2.31 (s, 3H, CH3), 2.48 (t, 2H, CH2), 2.74 (t, 2H,
CH2), 3.61 (s, 6H, CH3), 4.38 (d, 2H, CH2), 5.87 (s, 1H, ArH),
6.38 (s, 1H, ArH), 6.54 (d, 1H, ArH), 6.80 (d, 1H, ArH), 6.84
(s, 1H, ArH), 6.88(d, 1H, ArH), 7.34(d, 1H, ArH), 9.21(t, 1H,
NH); 13C d ppm (DMSO, 400 MHz) = = 5.6, 28.1, 31.6,
35.8, 36.4, 42.4, 103.7, 108.6, 110.9, 111.2, 112.0, 112.8,
118.3, 120.8, 122.1, 125.8, 126.4, 128.5, 129.2, 131.3, 134.2,
152.3, 172.1; LC/MS (ESI–MS) m/z = 479.2 (M?1).
3-(5-Chloro-1H-indol-3-yl)-N-((1,2-dimethyl-5-
(trifluoromethoxy)-1H-indol-3-yl) methyl)
propanamide (10c)
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-((5-chloro-1-
Appearance, off white solid (mp = 261–263 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.11 (s, 3H, CH3), 2.45 (t, 2H,
CH2), 2.71 (t, 2H, CH2), 3.64 (s, 3H, CH3), 4.34 (d, 2H, CH2),
5.84 (s, 1H, ArH), 6.52 (d, 1H, ArH), 6.81 (d, 2H, ArH), 7.22
(m, 3H, ArH), 9.24 (t, 1H, NH), 10.30 (d, 1H, NH), 10.32 (d,
1H, NH); 13C NMR (DMSO, 400 MHz) d ppm = 5.6, 28.1,
31.6, 36.1, 36.4, 103.7, 108.6, 110.9, 111.2, 112.8, 118.3,
120.8, 122.1, 122.9, 125.8, 128.5, 129.2, 131.3, 134.2, 152.3,
172.1, LC/MS (ESI–MS) m/z = 464.7 (M?1).
methyl-1H-indol-3-yl) methyl)propanamide (10g)
1
Appearance, brown solid (mp = 254–256 °C); H NMR
(DMSO, 400 MHz) d ppm = 2.48 (t, 2H, CH2), 2.74
(t, 2H, CH2), 3.61 (s, 6H, CH3), 4.38 (d, 2H, CH2), 6.34
(s, 2H, ArH), 6.82 (s, 2H, ArH), 6.89 (d, 2H, ArH), 7.28
(d, 2H, ArH), 9.24 (t, 1H, NH); 13C d ppm (DMSO,
400 MHz) = 28.4, 36.8, 38.1, 42.4, 111.2, 112.5, 119.3,
121.6, 126.5, 126.8, 129.2, 135.7, 173.7; LC/MS (ESI–MS)
m/z = 415.2 (M?1).
N-((5-Chloro-1-methyl-1H-indol-3-yl)methyl)-3-(5-chloro-
1H-indol-3yl)propanamide (10d)
3-(5-Chloro-1H-indol-3-yl)-N-((5-chloro-1H-indol-3-
yl)methyl)propanamide (10h)
Appearance, white solid (mp = 209–211 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.45 (t, 2H, CH2), 2.71
(t, 2H, CH2), 3.62 (s, 3H, CH3), 4.31 (s, 2H, CH2), 6.41
(s, 1H, ArH), 6.83 (s, 1H, ArH), 6.89 (d, 1H, ArH), 7.11
(d, 1H, ArH), 7.21 (m, 3H, ArH), 7.29 (d, 1H, ArH), 9.16
(t, 1H, NH), 10.32 (d, 1H, NH); 13C d ppm (DMSO,
400 MHz) = 28.1, 36.8, 38.1, 42.4, 110.9, 112.5, 119.3,
121.6, 122.9, 126.5, 126.9, 128.9, 129.2, 134.6, 135.7,
173.7; LC/MS (ESI–MS) m/z = 401.1 (M?1).
Appearance, White solid (mp = 219–221 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 2.48 (t, 2H, CH2), 2.74 (t, 2H,
CH2), 4.38 (d, 2H, CH2), 6.82 (d, 2H, ArH), 7.10 (d, 2H,
ArH), 7.18 (m, 2H, ArH), 7.20 (d, 2H, ArH), 9.24(t, 1H, NH),
10.34 (d, 2H, NH); 13C d ppm (DMSO, 400 MHz) = 28.1,
36.8, 37.6, 110.9, 112.1, 112.6, 119.3, 121.6, 122.9, 126.5,
129.2, 134.7, 173.7; LC/MS (ESI–MS) m/z = 388.1 (M?1).
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-
((2-methyl-5-(trifluoromethoxy)-1H-indol-3-yl)
methyl)propanamide (10i)
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-((5-
(trifluoromethoxy)-1H-indol-3-yl) methyl)
propanamide (10e)
Appearance, pale yellow liquid; 1H NMR (DMSO,
400 MHz) d ppm = 2.32 (s, 3H, CH3), 2.48 (t, 2H, CH2),
2.74 (t, 2H, CH2), 3.72 (s, 3H, CH3), 4.38 (d, 2H, CH2), 6.22
1
Appearance, brown solid (mp = 235–237 °C); H NMR
(DMSO, 400 MHz) d ppm = 2.45 (t, 2H, CH2), 2.71
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Med Chem Res (2013) 22:4437–4454
(s, 1H, ArH), 6.38 (s, 1H, ArH), 6.89 (d, 3H, ArH), 7.10 (s,
1H, ArH), 7.28 (d, 1H, ArH), 9.21 (t, 1H, NH), 10.32 (s, 1H,
NH); 13C d ppm (DMSO, 400 MHz) = 12.1, 28.4, 31.3,
36.8, 42.4, 102.1, 109.1, 109.6, 111.2, 112.0, 112.6, 119.3,
121.3, 121.9, 126.3, 126.8, 128.5, 129.2, 131.3, 135.7, 155.6,
173.7; LC/MS (ESI–MS) m/z = 465.2 (M?1).
(s, 2H, ArH), 7.21 (m, 4H, ArH), 7.28 (s, 2H, ArH), 9.20
(t, 1H, NH), 10.32 (d, 2H, NH); 13C d ppm (DMSO,
400 MHz) = 26.8, 28.1, 30.2, 36.8, 39.2, 110.9, 112.5,
119.3, 121.6, 122.9, 126.8, 128.9, 134.6, 172.8; LC/MS
(ESI–MS) m/z = 416.1 (M?1).
3-(5-Chloro-1H-indol-3-yl)-N-(3-(1,2-dimethyl-5-
(trifluoromethoxy)-1H-indol-3-yl)propyl)
propanamide (11d)
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-((5-chloro-1H-
indol-3-yl)methyl)propanamide (10j)
1
Appearance- White solid (mp = 208–210 °C); H NMR
Appearance, semisolid; 1H NMR (DMSO, 400 MHz) d
ppm = 1.86 (m, 2H, CH2), 2.36 (s, 3H, CH3), 2.48 (t, 4H,
CH2), 2.69 (t, 2H, CH2), 3.34 (m, 2H, CH2), 3.64 (s, 3H,
CH3), 6.02 (s, 1H, ArH), 6.48 (d, 1H, ArH), 6.81 (d, 1H,
ArH), 6.84 (d, 1H, ArH), 7.22 (d, 2H, ArH), 7.26 (s, 1H,
ArH), 9.26 (t, 1H, NH), 10.34 (d, 1H, NH); 13C d ppm
(DMSO, 400 MHz) = 5.9, 20.6, 28.1, 30.5, 35.9, 36.8, 39.2,
102.1, 108.6, 109.6, 110.9, 112.1, 112.5, 119.3, 121.1, 121.9,
122.9, 126.8, 128.3, 128.9, 129.7, 132.6, 134.6, 154.8, 172.8;
LC/MS (ESI–MS) m/z = 493.1 (M?1).
(DMSO, 400 MHz) d ppm = 2.48 (t, 2H, CH2), 2.74 (t, 2H,
CH2), 3.72 (s, 3H, CH3), 4.38 (d, 2H, CH2), 6.38 (s, 1H,
ArH), 6.80 (s, 1H, ArH), 6.82 (d, 1H, ArH), 6.89 (d, 1H,
ArH), 7.19 (d, 2H, ArH), 7.24 (s, 1H, ArH), 7.28 (d, 1H,
ArH), 9.22 (t, 1H, NH), 10.32 (d, 1H, NH); 13C d ppm
(DMSO, 400 MHz) = 28.4, 36.8, 37.8, 42.4, 111.2, 112.1,
112.6, 119.3, 121.6, 122.9, 126.5, 126.8, 128.9, 129.4, 134.6,
135.7, 173.7; LC/MS (ESI–MS) m/z = 401.4 (M?1).
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-(3-(5-chloro-1-
methyl-1H-indol-3-yl) propyl)propanamide (11a)
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-(3-(5-
(trifluoromethoxy)-1H-indol-3-yl)propyl)
propanamide (11e)
Appearance, off white solid (mp = 249–251 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 1.86 (m, 2H, CH2), 2.48
(t, 4H, CH2), 2.78 (t, 2H, CH2), 3.26 (m, 2H, CH2), 3.68
(s, 6H, CH3), 6.48 (s, 2H, ArH), 6.92 (s, 2H, ArH), 7.06
(d, 2H, ArH), 7.41 (d, 2H, ArH), 9.28 (t, 1H, NH); 13C d ppm
(DMSO, 400 MHz) = 27.1, 28.4, 30.2, 36.8, 39.2, 42.4,
111.2, 112.5, 119.3, 121.6, 126.2, 126.8, 129.2, 135.7,
172.8; LC/MS (ESI–MS) m/z = 443.5 (M?1).
Appearance, semisolid; 1H NMR (DMSO, 400 MHz) d
ppm = 1.86 (m, 2H, CH2), 2.48 (t, 4H, CH2), 2.70 (t, 2H,
CH2), 3.28 (m, 2H, CH2), 3.62 (s, 3H, CH3), 6.38 (s, 1H,
ArH), 6.72 (d, 1H, ArH), 6.78 (s, 1H, ArH), 6.82 (d, 1H,
ArH), 6.88 (s, 1H, ArH), 7.28 (d, 3H, ArH), 9.24 (t, 1H, NH),
10.35 (s, 1H, NH); 13C d ppm (DMSO, 400 MHz) = 26.8,
28.4, 30.2, 36.8, 39.2, 42.4, 102.1, 109.6, 112.0, 112.6, 119.3,
121.3, 121.8, 122.9, 126.1, 126.7, 128.2, 128.9, 129.6, 135.7,
155.6, 172.8; LC/MS (ESI–MS) m/z = 479.1 (M?1).
3-(5-Chloro-1H-indol-3-yl)-N-(3-(2-methyl-5-
(trifluoromethoxy)-1H-indol-3-yl) propyl)
propanamide (11b)
3-(5-Chloro-1H-indol-3-yl)-N-(3-(5-(trifluoromethoxy)-
Appearance, off white solid (mp = 283–285 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 1.86 (m, 2H, CH2), 2.36
(s, 3H, CH3), 2.48 (t, 4H, CH2), 2.68 (t, 2H, CH2), 3.24
(m, 2H, CH2), 6.28 (s, 1H, ArH), 6.76 (d, 2H, ArH), 6.84
(d, 1H, ArH), 7.21 (d, 2H, ArH), 7.24 (s, 1H, ArH), 9.26
(t, 1H, NH), 10.34 (s, 1H, NH), 10.36 (d, 1H, NH); 13C d
ppm (DMSO, 400 MHz) = 12.4, 20.3, 28.1, 30.5, 36.8,
39.2, 102.1, 108.4, 109.4, 110.5, 112.0, 112.5, 119.3,
121.1, 121.7, 122.9, 126.8, 128.2, 128.7, 129.4, 131.3,
134.6, 155.6, 172.8; LC/MS (ESI–MS) m/z = 479.2 (M?1).
1H-indol-3-yl) propyl)propanamide (11f)
Appearance, white solid (mp = 254–256 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 1.86 (m, 2H, CH2), 2.48 (t, 4H,
CH2), 2.70 (t, 2H, CH2), 3.28 (m, 2H, CH2), 6.72 (d, 1H,
ArH), 6.76 (s, 1H, ArH), 6.82 (d, 1H, ArH), 6.88 (s, 1H,
ArH), 7.27 (d, 3H, ArH), 7.29 (s, 1H, ArH), 9.24 (t, 1H, NH),
10.34 (d, 2H, NH); 13C d ppm (DMSO, 400 MHz) = 26.8,
28.1, 30.2, 36.8, 39.2, 102.1, 109.6, 110.9, 112.1, 112.9,
119.3, 121.5, 121.9, 122.8, 126.8, 128.2, 128.7, 129.4, 134.6,
154.8, 172.8; LC/MS (ESI–MS) m/z = 464.9 (M?1).
3-(5-Chloro-1H-indol-3-yl)-N-(3-(5-chloro-1H-indol-3-
yl)propyl)propanamide (11c)
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-(3-(1,2-dimethyl-
5-(trifluoromethoxy)-1H-indol-3-yl)propyl)propanamide (11g)
1
Appearance, brown solid (mp = 264–266 °C); H NMR
(DMSO, 400 MHz) d ppm = 2.02 (m, 2H, CH2), 2.21
(t, 4H, CH2), 2.48 (t, 2H, CH2), 3.42 (d, 2H, CH2), 6.88
1
Appearance, yellow oil; H NMR (DMSO, 400 MHz) d
ppm = 1.86 (m, 2H, CH2), 2.31 (s, 3H, CH3), 2.48 (t, 4H,
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Antibacterial studies
CH2), 2.76 (t, 2H, CH2), 3.24 (m, 2H, CH2), 3.64 (s, 6H,
CH3), 5.87 (s, 1H, ArH), 6.38 (s, 1H, ArH), 6.54 (d, 1H,
ArH), 6.76 (d, 1H, ArH), 6.84 (s, 1H, ArH), 6.92 (d, 1H,
ArH), 7.32 (d, 1H, ArH), 9.26 (t, 1H, NH); 13C d ppm
(DMSO, 400 MHz) = 5.9, 20.6, 28.4, 30.5, 35.9, 36.8, 39.2,
42.4, 102.1, 108.6, 109.5, 112.2, 112.1, 112.5, 119.3, 121.4,
121.9, 126.4, 126.8, 128.7, 129.1, 129.6, 132.6, 135.7, 154.9,
172.6; LC/MS (ESI–MS) m/z = 506.8 (M?1).
The synthesized compounds were screened for their anti-
bacterial activity against E. coli (ATCC 25922), S. aureus
(ATCC 25923), P. aeruginosa (ATCC 27853), and K.
pneumoniae (recultured), and S. pyogenes bacterial strains
by serial plate dilution method (Barry, 1980). Serial dilu-
tions of the drug in Mueller–Hinton broth were taken in
tubes and their pH was adjusted to 5.0 using phosphate
buffer. A standardized suspension of the test bacterium was
inoculated and incubated for 16–18 h at 37 °C. The mini-
mum inhibitory concentration (MIC) was noted by seeing
the lowest concentration of the drug at which there was no
visible growth. A number of antimicrobial disks are placed
on the agar for the sole purpose of producing zone of
inhibition in the bacterial lawn. Twenty milliliters of agar
media was poured into each petri dish. Excess of suspen-
sion was decanted and plates were dried by placing in an
incubator at 37 °C for an hour. Using an agar punch, wells
were made on these seeded agar plates and MIC of the test
compounds in dimethylsulfoxide (DMSO, 400 MHz) were
added into each labeled well. A control was also prepared
for the plates in the same way using solvent DMSO. The
petri dishes were prepared in triplicate and maintained at
37 °C for 3–4 days. Antibacterial activity was determined
by measuring the diameter of the inhibition zone. Activity
of each compound was compared with ciprofloxacin as
standard. MIC (lg/mL) and zone of inhibition (mm) were
determined for all the synthesized compounds and the
corresponding results are summarized in Table 2.
N-(3-(5-Chloro-1-methyl-1H-indol-3-yl)propyl)-3-(5-
chloro-1H-indol-3-yl)propanamide (11h)
Appearance, white solid (mp = 238–240 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 1.89 (m, 2H, CH2), 2.21
(t, 4H, CH2), 2.48 (t, 2H, CH2), 3.42 (d, 2H, CH2), 3.66
(s, 3H, CH3), 6.35 (s, 1H, ArH), 6.82 (d, 1H, ArH), 6.84
(s, 1H, ArH), 6.92 (d, 1H, ArH), 7.18 (d, 3H, ArH), 7.29
(d, 1H, ArH), 9.21 (t, 1H, NH), 10.32 (d, 2H, NH); 13C d
ppm (DMSO, 400 MHz) = 27.1, 28.1, 30.2, 36.8, 39.2,
42.4, 110.9, 111.2, 112.5, 119.3, 121.6, 122.9, 126.5,
126.8, 128.9, 129.4, 134.6, 135.7, 172.9; LC/MS (ESI–MS)
m/z = 429.5 (M?1).
3-(5-Chloro-1-methyl-1H-indol-3-yl)-N-(3-(5-chloro-1H-
indol-3-yl)propyl)propanamide (11i)
Appearance, off white solid (mp = 241–243 °C); 1H NMR
(DMSO, 400 MHz) d ppm = 1.86 (m, 2H, CH2), 2.46
(t, 4H, CH2), 2.70 (t, 2H, CH2), 3.36 (m, 2H, CH2), 3.64
(s, 3H, CH3), 6.38 (s, 1H, ArH), 6.72 (d, 1H, ArH), 6.82
(s, 1H, ArH), 6.90 (d, 1H, ArH), 7.16 (d, 2H, ArH), 7.25
(s, 1H, ArH), 7.32 (d, 1H, ArH), 9.21 (t, 1H, NH), 10.34
(d, 1H, NH); 13C d ppm (DMSO, 400 MHz) = 26.8, 28.4,
30.2, 36.8, 39.4, 42.4, 110.9, 111.2, 112.5, 119.3, 121.6,
122.9, 126.5, 126.9, 128.8, 129.6, 134.6, 135.7, 172.9; LC/
MS (ESI–MS) m/z = 429.5 (M?1).
Antifungal studies
Newly prepared compounds were screened for their anti-
fungal activity against A. flavus (NCIM No. 524), Aspergil-
lus fumigarus (NCIM No. 902), P. marneffei (recultured),
and T. mentagrophytes (recultured), and C. albicans in
DMSO by serial plate dilution method (Verma et al., 1998).
Sabourands agar media was prepared by dissolving peptone
(1 g), D-glucose (4 g) and agar (2 g) in distilled water
(100 mL) and adjusting the pH to 5.7. Normal saline was
used to make a suspension of spore of fungal stain for law-
ning. A loopful of particular fungal strain was transferred to
3 mL saline to get a suspension of corresponding species.
Twenty milliliters of agar media was poured into each petri
dish. Excess of suspension was decanted and plates were
dried by placing in incubator at 37 °C for 1 h. Using a punch,
wells were made on these seeded agar plates MICs of the test
compounds in DMSO were added into each labeled well. A
control was also prepared for the plates in the same way using
solvent DMSO. The petri dishes were prepared in triplicate
and maintained at 37 °C for 3–4 days. Antifungal activity
was determined by measuring the diameter of the inhibition
3-(5-Chloro-1H-indol-3-yl)-N-(3-(2-methyl-5-
(trifluoromethoxy)-1H-indol-3-yl)propyl)
propanamide (11j)
1
Appearance, semi solid; H NMR (DMSO, 400 MHz) d
ppm = 1.86 (m, 2H, CH2), 2.32 (s, 3H, CH3), 2.48 (t, 4H,
CH2), 2.72 (t, 2H, CH2), 3.26 (m, 2H, CH2), 6.26 (s, 1H,
ArH), 6.72 (d, 2H, ArH), 6.81 (d, 1H, ArH), 7.14 (d, 1H,
ArH), 7.20 (d, 1H, ArH), 7.22 (s, 1H, ArH), 9.22 (t, 1H,
NH), 10.32 (s, 1H, NH), 10.36 (d, 1H, NH); 13C d ppm
(DMSO, 400 MHz) = 12.6, 20.6, 28.4, 30.4, 36.8, 39.7,
102.1, 108.3, 109.6, 110.9, 112.1, 112.6, 119.3, 121.4,
121.8, 122.9, 126.8, 128.0, 128.5, 128.9, 131.3, 134.6,
154.8, 172.8; LC/MS (ESI–MS) m/z = 479.1 (M?1).
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