Click-based synthesis and antitubercular evaluation of novel dibenzo[b,d]thiophene-1,2,3-triazoles with piperidine, piperazine, morpholine and thiomorpholine appendages

Article abstract of DOI:10.1016/j.bmcl.2016.04.015

A series of novel piperidine, piperazine, morpholine and thiomorpholine appended dibenzo[b,d]thiophene-1,2,3-triazoles were designed and synthesized utilizing azide-alkyne click chemistry in the penultimate step. The required azide building block 6a-e was

Full text of DOI:10.1016/j.bmcl.2016.04.015

Accepted Manuscript
Click-based synthesis and antitubercular evaluation of novel dibenzo[b,d]thio-
phene- 1,2,3-triazoles with piperidine, piperazine, morpholine and thiomorpho-
line appendages
Lokesh Pulipati, Perumal Yogeeswari, Dharmarajan Sriram, Srinivas Kantevari
PII:
S0960-894X(16)30376-6
DOI:
http://dx.doi.org/10.1016/j.bmcl.2016.04.015
BMCL 23777
Reference:
To appear in:
Bioorganic & Medicinal Chemistry Letters
Received Date:
Revised Date:
Accepted Date:
24 January 2016
24 March 2016
7 April 2016
Please cite this article as: Pulipati, L., Yogeeswari, P., Sriram, D., Kantevari, S., Click-based synthesis and
antitubercular evaluation of novel dibenzo[b,d]thiophene- 1,2,3-triazoles with piperidine, piperazine, morpholine
and thiomorpholine appendages, Bioorganic & Medicinal Chemistry Letters (2016), doi: http://dx.doi.org/10.1016/
j.bmcl.2016.04.015
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Bioorganic & Medicinal Chemistry Letters
Click-based synthesis and antitubercular evaluation of novel dibenzo[b,d]thiophene-
1,2,3-triazoles with piperidine, piperazine, morpholine and thiomorpholine appendages
a
b
b
a,c
Lokesh Pulipati , Perumal Yogeeswari , Dharmarajan Sriram and Srinivas Kantevari
a
Organic Chemistry Division-II (C P C Division), CSIR- Indian Institute of Chemical Technology, Hyderabad-500 007, Telangana, INDIA.
Medicinal Chemistry and Antimycobacterial Research Laboratory, Pharmacy Group, Birla Institute of Technology & Science-Pilani, Hyderabad Campus,
b
Jawahar Nagar, Hyderabad-500078, Telangana, INDIA.
c
Academy of Scientific and innovative Research, CSIR- Indian Institute of Chemical Technology, Hyderabad-500 007, Telangana, INDIA.
ARTICLE INFO
ABSTRACT
Article history:
Received
Revised
Accepted
Available online
A series of novel piperidine, piperazine, morpholine and thiomorpholine appended
dibenzo[b,d]thiophene-1,2,3-triazoles were designed and synthesized utilizing azide-alkyne click
chemistry in the penultimate step. The required azide building block 6a-e was synthesized from
commercial dibenzo[b,d]thiophene in good yields following five step reaction sequence. All the
new analogues 8a-f, 9a-f, 10a-f, 11a-f & 12a-f were characterized by their NMR and mass
spectral analysis. Screening all thirty new compounds for in vitro antimycobacterial activity
against Mycobacterium tuberculosis H37Rv, resulted 8a, 8f and 11e as potent analogues with
MIC 0.78 µg/mL, 0.78 µg/mL & 1.56 µg/mL respectively and has shown lower cytotoxicity.
Interestingly, all six piperazine appended dibenzo[b,d]thiophene-1,2,3-triazoles 11a-f exhibited
Mtb inhibition activity with MIC 1.56 to 12.5 µg/mL. To some extent, the data observed here
indicated Mycobacterium tuberculosis inhibition among the appendages is in the order,
piperazine > thiomorpholine > morpholine.
Keywords:
Dibenzothiophene
Triazole
Piperidine
Piperazine
Antitubercular agents
Click chemistry
2
009 Elsevier Ltd All rights reserved.
The resurgence of tuberculosis (TB) is one of the most serious
public health concerns worldwide. The causative pathogen
Mycobacterium tuberculosis (Mtb) is observed more frequently
dibenzo[b,d]furan,
dibenzo[b,d]thiophene
and
10
N-methyl
1
carbazole tethered substituted 1,2,3-triazoles. Structure-activity
relationships (SAR) revealed that dibenzo[b,d]thiophene tethered
1,2,3-triazoles exhibited M. tuberculosis inhibition at lower
concentrations compared to the corresponding dibenzo[b,d]furan
in immune-compromised individuals suffering from human
2
immune deficiency virus (HIV). According to World Health
3
11
Organization (WHO) Global tuberculosis report 2015, TB killed
and N-methyl carbazole derivatives. These observations led us
890,000 men, 480,000 women and 140,000 children in 2014
to focus on development of dibenzo[b,d]thiophene derived newer
alone, and the disease ranked alongside HIV as a leading killer
worldwide. Interconnected factors, including the high cost of
scaffolds to screen their antitubercular activity
4
drugs and poor patient compliance with long treatment regimen,
often resulted in emergence of both multidrug-resistant (MDR)
5
and extensively drug-resistant (XDR) TB. These resistant
strains, in turn, demand prolonged treatment up to 24 months
with the use of cocktail of 6-8 drugs. However, all these drugs
have different drawbacks such as host toxicity, gradual
6
ineffectiveness against MDR-TB etc. Consequently, there is
desperate need to develop new antitubercular agents to address
the unmet demand for antituberculosis therapeutic goals such as
fast and long-acting, with high potency against TB and latent
Figure 1: Dibenzo[b,d]thiophene derivatives embodied with piperazine and
7
infections.
morpholine units.
During the last two decades, several natural products from
plants or microbes and their synthetic derivatives reported
exhibiting significant Mycobacterium tuberculosis inhibition
Recently it is realized that compounds containing piperidine,
piperazine and morpholine has immediate relevance in binding to
various biological targets and possess clinical applications in the
8
12
activity. Among such molecules, the lichen secondary metabolite
therapy of functional diseases. For example, dibenzo[b,d]
Usnic acid with dibenzofuran architecture displayed favourable
mycobacterial inhibition, but its myocardial toxicity did not
thiophene derivatives I-IV embodied with piperazine and
morpholine units (Figure 1) showed DNA-dependent protein
kinase (DNA-PK) inhibition and some of these derivatives are in
9
permit further development as an antitubercular drug. Taking this
clue, we recently reported antimycobacterial activity of various
13
clinical trials.
—
——
Corresponding author; Tel.: +91-4027191437; fax: +91-4027198933; e-mail: kantevari@yahoo.com, kantevari@gmail.com.
1

Huisgen 1,3-dipolar cycloaddition reaction of suitably modified
azide intermediates 6a-e with various alkynes 7a-e (Figure 4).
Figure 4: Alkynes used in the present study.
Figure 2: Clinical antitubercular agents embodied with piperidine,
piperazine, morpholine, and thiomorpholine units.
In clinical antitubercular agents V-XV(Figure 2) pharmacophoric
morpholine, thiomorpholine, piperidine or piperazine units play
14
vital role in the inhibition of M. tuberculosis. Continuing our
efforts on the development of newer and potent antitubercular
agents, we envisaged that, maneuvering dibenzothiophene-1,2,3-
triazoles appended with morpholine, thiomorpholine, piperidine
or piperazines in single molecular frame could deliver new
scaffolds for screening against Mycobacterium tuberculosis
20
(
Mtb). Here we described click chemistry based efficient
Scheme 1: Synthesis of dibenzo[b,d]thiophene azides 6a-e.
Initiating synthesis, commercially available dibenzo[b,d]
thiophene was acetylated using acetyl chloride and anhydrous
synthesis of novel piperidine, piperazine, morpholine and
thiomorpholine appended dibenzo[b,d]thiophene-1,2,3-triazoles
in excellent yields. Screening all thirty new compounds for in
vitro activity against M. tuberculosis H37Rv (Mtb) resulted in
three compounds 8a, 8f and 11e as promising lead analogues
with MIC ranging from 0.78 to 1.56 µg/mL and has shown lower
cytotoxicity.
11
AlCl
-acetyl dibenzo[b,d]thiophene (1), in 70% yield. α-Bromination
of 1 is initially carried out with commonly used reagents;
3
in chloroform by following literature procedure to yield
2
1
6a
16b
molecular bromine, N-bromosuccinimide (NBS) and cupric
bromide,
1
6c
16d
NBS–PTSA
varying reaction conditions.
Unfortunately, all these reactions were sluggish, leading to
complex mixtures of poly-brominated compounds along with
very low yields (< 5%) of desired product 2. An extensive
literature search on α-bromination of methyl ketones revealed a
1
7
report on the use of NH
4
Br/ Oxone as a reagent. When carried
Br/ Oxone, in MeOH at
out the reaction of 1 with equimolar NH
4
reflux gave crude reaction mixture mainly containing mono α-
brominated product 2. Purification of crude mixture over silica
gel column chromatography (hexane: ethyl acetate; 9:1) gave 2-
18
bromo-1-(dibenzo[b,d]thiophen-2-yl) ethanone (2) in 81% yield.
With α-bromo derivative 2 in hand, we next reacted with various
cyclic amines (piperidine 3a, morpholine 3b, thiomorpholine 3c,
Boc-protected pyrazine 3d and 2-(piperazin-1-yl)ethanol 3e)
Figure 3: Design strategy of dibenzothiophene-1,2,3-triazole derivatives with
2 3
using K CO as a base in DMF at room temperature resulted in
piperidine, morpholine, thiomorpholine, and piperazines appendages.
1
5
poor yields of 3a-e. After series of attempts using various reaction
conditions and bases, the reaction of 2 with 3a-e in the presence
of triethylamine in dry dichloromethane at room temperature
A more holistic approach for design strategy would be
through, i) correlation of the structural features of widely used
drugs (figure 1); ii) identification of common pharmacophoric
unit(s) and iii) incorporate them to generate newer scaffolds with
envisaged activity profile. With the fact that piperidine,
piperazine, morpholine and thiomorpholine are prominent in TB
drugs (Figure 2), a design strategy is formulated to inculcate
these units into the dibenzo[b,d]thiophene-1,2,3-triazole
architecture (Figure 3). The method adopted for the synthesis of
desired compounds (Scheme 1) is based on the copper catalyzed
18
delivered desired products 4a-e in excellent yields (82-88%).
Reduction of ketones 4a-e with NaBH in methanol, chloroform
1:1) produced alcohols 5a-e. Attempts for the preparation of
azides 6a-e from alcohols 5a-e were unsuccessful using TMSN
in nitromethane in the presence of InCl catalyst. After series of
reactions, the azido compounds 6a-e obtained in moderate yields
4
(
3
3
(35-43%) using Mitsunobu conditions [i.e., triphenyl phosphine,
2

diisopropyl azodicarboxylate (DIAD) and diphenyl phosphoryl
azide (DPPA) in THF] and unreacted alcohols 5a-e were
recovered from the reaction mixture. After continued efforts
varying reaction conditions the reaction of alcohols 5a-e with
diphenyl phosphoryl azide (DPPA) and diazabicyclo undecane
When compared to first line anti-TB drugs all the compounds
found to be less potent than Isoniazid (0.1 µg/mL). Three
compounds 8a, 8f (MIC 0.78 µg/mL) and 11e (MIC 1.56 µg/mL)
exhibited greater in vitro potency than standard drugs Ethambutol
and Pyrazinamide. Two compounds 8c and 11d (MIC 3.13
µg/mL) is equipotent to standard drug Ethambutol and more
potent than Pyrazinamide. Among other dibenzo[b,d]thiophene-
1,2,3-triazole derivatives, five compounds 9c, 10c, 11b-c and 12f
exhibited MIC 6.25 µg/mL, and another seven derivatives 10b,
10e, 11a, 11f, 12a, and 12d-e exhibited MIC 12.5 µg/mL and are
more potent than Pyrazinamide.
1
9
(DBU) in THF produced azides 6a-e quantitative yields. For
example, the reaction of alcohol 5a with 1.5 equivalents of DPPA
and DBU in tetrahydrofuran at room temperature stirring for 12h
gave azide 6a in 82% yield. Similarly, following optimized
conditions all the azides 6b-e was obtained from the respective
alcohols 5b-e in 82-92% yield. Boc deprotection of 6d refluxing
in methanolic HCl resulted in azide 6f in 92% yield. A tert-butyl
silyloxy group of 6e was also deprotected using TBAF in THF at
RT under standard reaction conditions to give azide 6g in 85%
yield. All compounds 2, 4a-d, 5a-e, and 6a-g, were fully
Table 1: Synthesis of novel dibenzo[b,d]thiophene-1,2,3-triazole derivatives
a
8a-f, 9a-f, 10a-f, 11a-f & 12a-f.
1
13
characterized by their IR, H, C NMR and mass (ESI & HRMS)
18,19
spectral analysis.
b
c
S.No
Azide
Alkyne
7a
7b
7c
7d
7e
7f
Triazole
8a
Yield (%)
85
88
89
84
88
81
82
85
88
80
84
86
84
86
90
81
85
84
88
84
88
80
82
81
82
83
86
78
82
80
CLogP
6.69
7.33
8.66
6.65
7.48
6.82
5.52
6.12
7.44
5.44
6.26
5.6
1
2
3
4
5
6
7
8
9
8b
6a
8c
Reagents and conditions: (i) MeOH, Conc. HCl, reflux, 6h, 92% (ii) TBAF,
THF, RT, 5h, 85%.
8d
8e
Scheme 2: Synthesis of Azides 6g-f.
8f
7a
7b
7c
7d
7e
7f
9a
To build the desired triazole analogues, the azide building
9b
blocks 6a-c & 6f-g were reacted with selected aromatic and
6b
6c
6d
6e
9c
2
0
aliphatic alkynes 7a-f utilizing click chemistry (Table 1). For
example, azide 6a was reacted with phenyl acetylene (7a) in
1
1
1
1
1
1
1
1
1
0
9d
1
2
3
4
5
6
7
8
9e
4 2
presence of CuSO .5H O and sodium ascorbate in t-butanol and
9f
water (1:1, v/v) gave 1-(2-(dibenzo[b,d]thiophen-2-yl)-2-(4-
phenyl-1H-1,2,3-triazol-1-yl)ethyl)piperidine (8a) in 85% yield.
In general, click reaction without catalyst is thermodynamically
favored requires heating; leading to the formation of both 1,4- or
7a
7b
7c
7d
7e
7f
10a
10b
10c
10d
10e
10f
11a
11b
11c
11d
11e
11f
12a
12b
12c
12d
12e
12f
6.26
6.85
8.18
6.17
7.0
1,5-disubstituted triazoles. However, in catalytic version, copper
catalyst greatly enhances the reactivity of alkyne through
complexation and promotes the reaction to proceed at room
6.34
5.07
5.71
7.04
5.03
5.86
5.2
2
0b
19
7a
7b
7c
7d
7e
7f
temperature. This catalytic process, drives reaction extremely
regioselective towards 1,4-disubstituted triazoles over 1,5-
2
0
2
0c
21
disubstiueted triazoles and explains the observed regiosectivity
2
2
2
2
2
3
4
5
in the preparation of triazole 8a. Under similar conditions, all the
azides 6a-c & 6f-g were reacted with alkynes 7a-f to generate a
library of thirty triazoles 8a-f, 9a-f, 10a-f, 11a-f & 12a-f in
excellent to good yields (Table 1). All new derivatives 8a-f, 9a-f,
7a
7b
7c
7d
7e
7f
4.14
4.65
5.98
3.96
4.79
4.14
1
13
26
27
1
0a-f, 11a-f & 12a-f were fully characterized by their H &
C
21
NMR, IR and Mass (ESI-MS & HR-MS) spectral data. ClogP
required assessing the lipophilic character of new analogs was
calculated using Chembiodraw 12.0 programme (Table 1).
All the synthesized dibenzo[b,d]thiophene-1,2,3-triazole
derivatives 8a-f, 9a-f, 10a-f, 11a-f & 12a-f were screened for
their in vitro antimycobacterial activity against M. tuberculosis
H37Rv (ATCC27294) by agar dilution method. Isoniazid,
Ethambutol and pyrazinamide were as positive controls and for
comparison. The minimum inhibitory concentration (MIC)
determined for each compound, was measured as the minimum
concentration of compound required for complete inhibition of
bacterial growth. Summarized in figure 5 are MIC (µg/mL) of all
the new molecules 8a-f, 9a-f, 10a-f, 11a-f & 12a-f and standard
drugs for complete inhibition of bacterial growth. Thirty new
compounds screened showed in vitro inhibitory activity against
Mtb with MIC ranging from 0.78 - 50.0 µg/mL.
2
2
3
8
9
0
a
Azides 6a-f (1.0 mmol), Aromatic & aliphatic acetylenes (1.1 mmol),
CuSO
mLb).
4 2 2
.5H O & Sodium ascorbate (20 mol%), t-BuOH:H O (1:1, v/v, 8
2
2
Isolated yield.
Calculated using Chembiodraw 12.0.
c
The safety profile of antitubercular active dibenzo[b,d]
thiophene-1,2,3-triazole derivatives with MIC ≤12.5 µg/mL were
assessed by testing in vitro cytotoxicity against Human
Embryonic Kidney (HEK-293T) cells using 3-(4,5-dimethyl
23
thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.
Figure 6 described percentage inhibition of seventeen analogues
at 50 μg/mL concentration. Most of the tested compounds
demonstrated excellent safety profile with very low inhibitory
potential. The promising antitubercular compounds 8a, 8f and
3

Figure 5: Antitubercular activity of dibenzo[b,d]thiophene-1,2,3-triazole derivatives 8a-f, 9a-f, 10a-f, 11a-f & 12a-f.
x= Isoniazid; y=Ethambutol; z= Pyrazinamide]
[
Figure 6: Percentage inhibition of dibenzo[b,d]thiophene-1,2,3-triazole derivatives on HEK-293T cells at a concentration of 50μg/mL.
1
1e exhibited 25.42%, 20.60% and 18.92% inhibition
scaffolds (Panels A-C & E), the Mtb inhibition activity is varied
large extent on substituents attached to the triazole unit. For
example, among piperidine appended analogues 8a-f; Mtb
inhibition activity (MIC: 0.78 µg/mL) was best observed with
attached phenyl group (8a) or with four carbon aliphatic chain
(8f). Substitutions on phenyl unit in 8b-e reduced Mtb inhibition
activity with MIC ranging up to 50 µg/mL. Interestingly, when
replaced piperidine unit of 8a & 8f with morpholine and
thiomorpholine, Mtb inhibition activity was reduced large extent
with MIC 25.0- 50.0 µg/mL (9a, 9f in panel B and 10a, 10f in
respectively at 50 μg/mL. The results clearly indicated that potent
analogs 8a, 8f and 11e are less toxic and are suitable for further
mechanistic evaluations.
On structure-activity relationship (SAR), we have not found
the best correlation in SAR among the synthesized analogues but
indicated some interesting patterns. To describe SAR in general
(
figure 5); we observed Mtb inhibition activity for all the
dibenzo[b,d]thiophene-1,2,3-triazoles having piperazine unit
11a-f) with MIC 1.56 to 12.5 µg/mL (Panel D). In other
(
4

panel C; figure 5). Similarly, triazole appended with
thiomorpholine proves to be effective appendage compared to
morpholine (Panels B &C). Compounds with the 2-hydroxylethyl
group attached to piperazine, 12a-f, reduced the lipophilicity
Moreira, C. T.; Oliveira, A. L.; Comar, J. F.; Peralta, R. M.; Bracht, A.
Chem. Biol. Interact. 2013, 203, 502. (d) Honda, N. K.; Pavan, F. R.;
Coelho, R. G.; de Andrade Leite, S. R.; Micheletti, A. C.; Lopes, T. I.;
Misutsu, M. Y.; Beatriz, A.; Brum, R. L.; Leite, C. Q. Phytomedicine,
2
010, 17, 328.
(
CLogP, table 1), with a marginal reduction in Mtb inhibition
10. (a) Surineni, G.; Yogeeswari, P.; Sriram, D.; Kantevari, S. Bioorg. Med.
Chem. Lett. 2015, 25, 485. (b) Yempala, T.; Sridevi, J. P.; Yogeeswari,
P.; Sriram, D.; Kantevari, S. Eur. J. Med. Chem. 2014, 71, 160. (c)
Addla, D.; Jallapally, A.; Gurram, D.; Yogeeswari, P.; Sriram, D.;
Kantevari, S. Bioorg. Med. Chem. Lett. 2014, 24, 1974. (d) Addla,
D.; Jallapally, A.; Gurram, D.; Yogeeswari, P.; Sriram, D.; Kantevari, S.
Bioorg. Med. Chem. Lett. 2014, 24, 233. (e) Yempala, T.; Sridevi, J. P.;
Yogeeswari, P.; Sriram, D.; Kantevari, S. Bioorg. Med. Chem. Lett. 2013,
activity (Panel E). To some extent, all these observations
indicated Mtb inhibition activity pattern among the appendages is
in the order, piperazine > thiomorpholine > morpholine.
In conclusion we have synthesized a series of novel
piperidine, piperazine, morpholine and thiomorpholine appended
dibenzo[b,d]thiophene-1,2,3-triazoles 8a-f, 9a-f, 10a-f, 11a-f &
2
3, 5393. (f) Yempala, T.; Sriram, D.; Yogeeswari, P.; Kantevari, S.
1
2a-f utilizing click chemistry. The required azide building
Bioorg. Med. Chem. Lett., 2012, 22, 7426. (g) Kantevari, S.; Yempala, T.;
Yogeeswari, P.; Sriram, D.; Sridhar, B.; Bioorg. Med. Chem. Lett. 2011,
blocks 6a-g is synthesized from commercial dibenzo[b,d]
thiophene in good yields following reaction sequence described
in scheme-1 & 2. All the new analogues were fully characterized
by their NMR and mass spectral data. Screening all thirty new
derivatives 8a-f, 9a-f, 10a-f, 11a-f & 12a-f against M.
tuberculosis H37Rv (Mtb) resulted in three compounds 8a, 8f and
2
1, 4316. (h) Kantevari, S.; Patpi, S. R.; Addla, D.; Putapatri, S. R.;
Sridhar, B.; Yogeeswari, P.; Sriram, D. ACS Comb. Sci. 2011, 13, 427. (i)
Kantevari, S.; Yempala, T.; Surineni, G.; Sridhar, B.; Yogeeswari, P.;
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1
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1
1e are active antitubercular agents with lower cytotoxicity
profile compared to the other evaluated compounds. Interestingly,
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dibenzo[b,d]thiophene-1,2,3-triazoles appended with piperazine
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1
11a-f exhibited potency with MIC 1.56 to 12.5 µg/mL. To some
extent, the data observed here indicated Mtb inhibition among the
appendages in the order, piperazine > thiomorpholine >
morpholine. The results described here demonstrate the potential
utility of dibenzo[b,d]thiophene-1,2,3-triazole derivatives as
antitubercular agents. With new anti-TB agents desperately
needed, we believe that the analogues reported in this work will
help global efforts for identification of potential lead
antimycobacterial agents for further development.
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1
1
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8. Synthesis of 2-bromo-1-(dibenzo[b,d]thiophen-2-yl)ethanone (2):
Oxone (14.9 g, 2.4 mmol) was added to the well stirred solution of 2-
Acknowledgments
We thank CSIR for research fellowship to LP and IICT-CSIR for
research facilities, encouragement and financial support to SK as part of
4
acetyl dibenzothiophene 1 (5g, 2.2 mmol) and NH Br (2.30 g, 2.4 mmol)
in methanol (80 mL) and the reaction mixture was allowed to stir at reflux
for 1.5 h. After completion of the reaction, as monitored by TLC, the
reaction mixture was quenched with aqueous sodiumthiosulphate and
extracted with chloroform (3x25 mL). Finally, the combined organic
layer was washed with water, dried over anhydrous sodium sulfate,
filtered and concentrated under vacuum yielded a crude residue, which
was further purified by column chromatography over silica gel to afford
th
CSIR-12 FYP projects [ORIGIN, CSC 0108; DENOVA, CSC0205].
References and notes
1
.
(a) Getahun, H.; Matteelli, A.; Chaisson, R.E.; Raviglione, M. N. Engl. J.
Med., 2015, 372, 2127. (b) Hermosilla, S.; El-Bassel, N.; Aifah, A.;
Terlikbayeva, A.; Zhumadilov, Z.; Berikkhanova, K.; Darisheva, M.;
Gilbert, L.; Schluger, N.; Galea, S. Public Health. 2015, 129, 569.
1
pure product 2 as colourless solid. Yield: 5.4 g, 81%; m.p: 96-98 °C; H
NMR (300 MHz, CDCl
3
) δ 8.82-8.73 (s, 1H), 8.31-8.18 (m, 1H), 8.12-
2
.
(a) Zumla. A.; George, A.; Sharma, V.; Herbert, R. H.; Baroness, M. I.;
Oxley, A.; Oliver, M. Lancet Glob Health. 2015, 3, 10. (b) Ronacher, K.;
Joosten, S.A.; van Crevel, R.; Dockrell, H.M.; Walzl, G.; Ottenhoff, T.
H. Immunol. Rev. 2015, 264, 121. (c) Koch, A.; Mizrahi, V.; Warner, D.
F. Emerg. Microbes Infect. 2014, 3, 17. (d) Delogu, G.; Sali, M.; Fadda,
G. Mediterr J Hematol Infect Dis. 2013, 5, e2013070. (e) Upadhyaya, S.
K.; Dixit, S. M.; Shrestha, S.; Dangol, S. D.; Pokhrel, D.; Banjara,
S.; Shrestha, K. S.; Hengoju, S.; Dahal, B. K. J. Sci. Eng. Technol. 2013,
8
.01 (m, 2H), 8.00-7.84 (m, 2H), 7.59-7.47 (m, 2H), 4.60-4.51 (m, 2H);
13
C NMR (75 MHz, CDCl
3
): δ 190.6, 145.2, 139.4, 135.5, 134.6, 130.0,
1
1
27.4, 126.3, 124.8, 122.7, 122.0, 121.7, 31.0; IR (KBr): 3403, 2923,
674, 1581, 1426, 1242, 1072, 765, 738 cm ; MS (EI): m/z 304 (M)
BrOS.
-
1
+
Calcd for C14H
8
Synthesis of piperidine, morpholine thiomorpholine and piperazine
appended ketones 4a-e: To a mixture of 3a-e (6.5 mmol) and
triethylamine (1.1 mL, 7.8 mmol) in dry dichloromethane (20 mL) was
added the appropriately 2-bromo-1-(dibenzo[b,d]thiophen-2-yl)ethanone
9
, 181.
3
4
.
.
http://www.who.int/tb/publications/global_report/gtbr2015_executive_su
mmary.pdf
(a) Millard, J.; Ugarte-Gil, C.; Moore, D.A. BMJ, 2015, 350. http://dx.
doi.org/ 10.1136/bmj.h882. (b) Kumar, K.; Abubakar, I. Clin. Med. 2015,
2
(2.0 g, 6.5 mmol) at 0 °C under a nitrogen atmosphere. The mixture was
stirred vigorously for 0.5 h at the same temperature and then diluted with
water (5 mL). The mixture was extracted with chloroform (3×10 mL), the
organic layers were combined, washed with water (2×10 mL), dried over
anhydrous Na SO and concentrated under vacuum yielded a crude
2 4
residue, which was further purified by column chromatography over
6
, 37.
5
.
(a) van Zyl, L.; du Plessis, J.; Viljoen, J.; Tuberculosis, 2015, 95, 629. (b)
Zumla, A.; Chakaya, J.; Centis, R.; D'Ambrosio, L.; Mwaba, P.;Bates, M.
Kapata, N.; Nyirenda, T.; Chanda, D.; Mfinanga, S.; Hoelscher, M.;
Maeurer, M.; Migliori, G.B. Lancet Respir. Med. 2015, 3, 220.
Dartois, V. Nat Rev Microbiol. 2014, 12(3), 159.
silica gel to afford pure products 4a-e.
1
1
-(Dibenzo[b,d]thiophen-2-yl)-2-(piperidin-1-yl)ethanone (4a): Yield:
.72 g, 85%; syrup; H NMR (300 MHz, CDCl ) δ 8.89 (s, 1H), 8.28-8.11
3
1
6
7
.
.
(
m, 2H), 7.97-7.80 (m, 2H), 7.55-7.45 (m, 2H), 3.91-3.86 (m, 2H), 2.65-
(a) Manjunatha, U. H.; Smith, P. W. Bioorg. Med. Chem. 2015, 23(16),
13
2
.57 (m, 4H), 1.71-1.64 (m, 4H), 1.52-1.45 (m, 2H); C NMR (75 MHz,
CDCl ): δ 196.4, 144.4, 139.4, 135.3, 135.1, 132.6, 127.2, 126.0, 124.7,
22.7, 122.3, 121.7, 121.6, 65.6, 54.7, 25.7, 23.8; IR (KBr) 3132, 2932,
5
2
087. (b) Zuniga, E. S.; Early, J.; Parish, T. Future Microbiol. 2015; 10,
17. (c) Schito, M.; Maeurer, M.; Kim, P.; Hanna, D.; Zumla, A. Clin.
3
1
1
Infect. Dis. 2015, 3, S95.
-1
+
467, 1431, 1223, 1156, 764, 731, 694 cm ; MS (ESI) m/z 310 (M+H) ;
8
9
.
.
(a) Jimenez-Arellanes, M. A.; Gutiérrez-Rebolledo, G.; Rojas-Tome, S.;
Meckes-Fischer, M. J. Infect. Dis. Ther. 2014, 2, 185. (b) García, A.;
Bocanegra-Garcia, V.; Palma-Nicolas, J. P.; Rivera, G. Eur. J. Med.
Chem. 2012, 49, 1.
(a) Araujo, A. A.; de Melo, M. G.; Rabelo, T. K.; Nunes, P. S.; Santos, S.
L.; Serafini, M. R.; Santos, M. R.; Quintans-Júnior, L. J.; Gelain, D. P.;
Nat. Prod. Res. 2015, 29, 2167. (b) Yokouchi, Y.; Imaoka, M.; Niino, N.;
Kiyosawa, N.; Sayama, A.; Jindo, T. Toxicol. Pathol. 2015, 43, 424 (c)
+
HR-MS (ESI): Calcd. for
10.12601.
19
C H20NOS (M+H) : 310.12572, found:
3
Synthesis of piperidine, morpholine thiomorpholine and piperazine
appended alcohols 5a-e: To the solution of 4a-e (4 mmol) in methanol
and chloroform, sodium borohydride (8 mmol) was added at 0 °C and
stirred at RT for 1 h. The crude reaction mixture was evaporated under
vacuum, water (15 mL) and dichloromethane (2×25 mL) were added, and
5

1
the organic layer was separated, washed with H
2
O, dried over anhydrous
piperidine (8a): Yield: 0.33 g, 85%; m.p. 194-196 °C; H NMR (500
MHz, CDCl ) δ 8.17-8.10 (m, 2H), 7.94-7.76 (m, 5H), 7.50-7.37 (m, 5H),
Na SO , and filtered. The residue thus obtained after rotary evaporation
2
4
3
was chromatographed over silica gel column and eluted with hexane/ethyl
7.34-7.27 (m, 1H), 6.11-6.03 (m, 1H), 3.69-3.60 (m, 1H), 3.21 (dd, J=
acetate to give 5a-e as thick syrupy liquid. 1-(Dibenzo[b,d]thiophen-2-
yl)-2-(piperidin-1-yl)ethanol (5a): Yield: 1.14 g, 92%; syrup; H NMR
13.0, 5.0 Hz, 1H), 2.69-2.42 (m, 4H), 1.60-1.49 (m, 4H), 1.48-1.35 (m,
1
13
2H); C NMR (75 MHz, CDCl
3
) δ 147.3, 139.7, 139.4, 135.8, 134.9,
(
3
500 MHz, CDCl
3
) δ 8.26-8.15 (m, 2H), 7.89-7.78 (m, 2H), 7.49-7.42 (m,
134.7, 130.6, 128.7, 127.9, 127.0, 125.6, 125.4, 124.4, 123.1, 122.8,
121.6, 120.1, 119.5, 63.1, 54.7, 25.9, 24.0; IR (KBr) 3132, 2932, 1467,
H), 5.42-5.34 (m, 1H), 3.20-3.07 (m, 4H), 2.98-2.90 (m, 2H), 1.96-1.83
1
3
-1
+
(m, 4H), 1.66-1.58 (m, 2H); C NMR (125 MHz, CDCl
3
) δ 139.6, 138.9,
1431, 1223, 1156, 764, 731, 694 cm ; MS (ESI) m/z 439 [M+H] ; HR-
MS (ESI) Calcd for C27 S: 439.19509, found: 439.19400. 4-(2-
1
6
38.2, 135.5, 135.3, 126.5, 124.6, 124.1, 122.6, 122.4, 121.5, 118.7, 68.6,
7.1, 54.3, 26.0, 24.1; IR (KBr) 3421, 2933, 1429, 1070, 763, 733 cm ;
27 4
H N
-
1
(Dibenzo[b,d]thiophen-2-yl)-2-(4-phenyl-1H-1,2,3-triazol-1-yl)ethyl)
+
1
MS (ESI) m/z 312 [M+H] ; HR-MS (ESI) Calcd for C19
12.14166, found: 312.14042.
H
22NOS:
morpholine (9a): Yield: 0.36 g, 82%; m.p. 90-92 °C; H NMR (300
3
MHz, CDCl
3
) δ 8.19-8.06 (m, 2H), 7.92-7.76 (m, 5H), 7.51-7.27 (m, 6H),
1
9. (a) Thompson, A. S.; Humphrey, G. R.; DeMarco, A. M.; Mathre, D. J.;
Grabowski, E. J. J. J. Org. Chem., 1993, 58 (22), 5886.
5.98 (dd, J= 8.8, 5.4 Hz, 1H), 3.69-3.57 (m, 5H), 3.2 (dd, J= 13.5, 5.4
Hz, 1H), 2.69-2.45 (m, 4H); C NMR (75 MHz, CDCl ) δ 147.4, 139.7,
3
1
3
(
b) Synthesis of azide derivatives 6a-e: A mixture of alcohol (5a-e) (3.0
139.6, 135.8, 134.8, 134.1, 130.4, 128.7, 127.0, 125.5, 125.3, 124.4,
123.2, 122.7, 121.6, 120.0, 119.4, 66.7, 62.8, 62.5, 53.6; IR (KBr) 2962,
mmol) and diphenyl phosphoryl azide (DPPA) (4.5 mmol) were dissolved
in dry THF. To the mixture at 0 C, under N
diazabicyclo[5.4.0]undec-7-ene (DBU) (4.5 mmol). The reaction was
warmed to room temperature and stirred until complete. The resulting two
o
-1
2
was added neat 1,8-
2857, 2807, 1666, 1458, 1429, 1116, 1076, 764, 732, 696 cm ; MS (ESI)
+
m/z 441 [M+H] ; HR-MS (ESI) Calcd for C26
H
24
N
4
ONaS: 463.15630,
found: 463.15561. 4-(2-(Dibenzo[b,d]thiophen-2-yl)-2-(4-phenyl-1H-
phase mixture was washed with H
separated, dried over anhydrous Na
2
O (2x10 mL). The organic layer was
SO , and filtered. The residue thus
1,2,3-triazol-1-yl)ethyl)thiomorpholine (10a): Yield: 0.37 g, 84%; m.p.
1
2
4
182-184 °C; H NMR (300 MHz, CDCl
3
) δ 8.21-8.07 (m, 2H), 7.93-7.75
obtained after rotary evaporation was chromatographed over silica gel
column and eluted with hexane/ethyl acetate to give 6a-e. 4-(2-Azido-2-
(m, 5H), 7.54-7.28 (m, 6H), 6.11-5.93 (m, 1H), 3.75 (dd, J= 13.5, 9.0 Hz,
1H), 3.28 (dd, J= 13.5, 4.5 Hz, 1H), 3.02-2.77 (m, 4H), 2.61 (t, J= 4.5
Hz, 4H); C NMR (75 MHz, CDCl ) δ 147.5, 139.7, 139.6, 135.8, 134.7,
3
1
3
(
dibenzo[b,d]thiophen-2-yl)ethyl)piperidine (6a): Yield: 0.82 g, 82%;
1
m.p. 42-44 °C; H NMR (500 MHz, CDCl
.80 (m, 2H), 7.52-7.36 (m, 3H), 4.86 (dd, J= 9.8, 3.7 Hz, 1H), 2.82 (dd,
J= 13.4, 9.8 Hz, 1H), 2.66-2.42 (m, 5H), 1.71-1.56 (m, 4H), 1.52-1.37 (m,
3
) δ 8.23-8.07 (m, 2H), 7.89-
134.0, 130.3, 128.7, 128.1, 127.1, 125.5, 125.3, 124.5, 123.2, 122.7,
121.6, 120.0, 119.7, 62.9, 62.7, 55.0, 27.6; IR (KBr) 2919, 2801, 1463,
7
-
1
+
1428, 1227, 1126, 763, 729, 692 cm ; MS (ESI) m/z 457 [M+H] ; HR-
MS (ESI) Calcd for C26 : 457.15151, found: 457.15008. 1-(2-
13
2
1
2
H); C NMR (100 MHz, CDCl
3
) δ 139.8, 139.0, 135.7, 135.3, 135.1,
25 4 2
H N S
26.9, 125.3, 124.4, 122.9, 122.8, 121.6, 119.8, 65.8, 63.3, 54.9, 25.9,
(Dibenzo[b,d]thiophen-2-yl)-2-(4-phenyl-1H-1,2,3-triazol-1-yl)ethyl)
-
1
1
4.2; IR (KBr) 3060, 2930, 2086, 1488, 1295, 1187, 958, 766 cm ; MS
piperazine (11a): Yield: 0.37 g, 88%; m.p. 144-146 °C; H NMR (500
+
(ESI) m/z 337 [M+H] ; HR-MS (ESI) Calcd for C19
H
21
N
4
S: 337.14814,
3
MHz, CDCl ) δ 8.32-8.23 (m, 2H), 8.18-8.11 (m, 2H), 7.88-7.82 (m, 2H),
found: 337.14757.
7.50-7.44 (m, 3H), 7.19 (dd, J= 8.5, 2.5 Hz, 1H), 7.10 (td, J= 8.5, 2.5 Hz,
1H), 5.99 (dd, J= 5.1, 3.9 Hz, 1H), 3.60 (dd, J= 9.1,4.5 Hz, 1H), 3.19
(dd, J= 13.5, 5.1 Hz, 1H), 2.89-2.77 (m, 4H), 2.66-2.57 (m, 2H), 2.54-
2
2
0. (a) Musumeci, F.; Schenone. S.; Desogus, A.; Nieddu, E.; Deodato,D.;
Botta, L. Curr Med Chem. 2015, 22(17), 2022. (b) Verma, S. Int. J. Drug
Dev. & Res. 2015, 7(4), 18. (c) Pasini, D. Molecules, 2013, 18, 9512.
1. Synthesis of 1-(2-azido-2-(dibenzo[b,d] thiophen-2-yl)ethyl)piperazine
1
3
3
2.45 (m, 2H); C NMR (75 MHz, CDCl ) δ 147.4, 139.7, 139.6, 135.8,
134.8, 134.2, 130.5, 128.7, 128.0, 127.1, 125.6, 125.4, 124.5, 123.2,
122.8, 121.6, 120.1, 119.4, 62.9, 62.7, 54.2, 45.7; IR (KBr) 3424, 2924,
(
6f): To a solution of 12 (2.5 mmol) dissolved in methanol (20 mL) was
added one drop Conc.HCl. The reaction mixture was stirred at reflux for
h and then cooled to room temperature. The solvent was removed by
evaporation and mixture was extracted with chloroform (3×15 mL),
washed with saturated aqueous NaHCO solution, and water and then
dried over anhydrous Na SO . The residue thus obtained after rotary
-
1
2853, 1647, 1460, 1429, 1315, 1077, 762, 731, 695 cm ; MS (ESI) m/z
+
6
26 26 5
440 [M+H] ; HR-MS (ESI) Calcd for C H N S: 440.19034, found:
440.18917. 2-(4-(2-(Dibenzo[b,d]thiophen-2-yl)-2-(4-phenyl-1H-1,2,3-
3
triazol-1-yl)ethyl) piperazin-1-yl)ethanol (12a): Yield: 0.41 g, 82%;
1
2
4
m.p. 90-92 °C; H NMR (300 MHz, CDCl
3
) δ 8.21-8.08 (m, 2H), 7.95-
evaporation was chromatographed over silica gel column and eluted with
hexane/ethyl acetate to give 6f as a syrup. Yield: 0.78 g, 92%; syrup; H
7.79 (m, 5H), 7.59-7.26 (m, 6H), 5.98 (dd, J= 9.0, 5.0 Hz, 1H), 3.75-3.58
(m, 3H), 3.33-3.58 (m, 2H), 2.99-2.58 (m, 9H); C NMR (75 MHz,
1
13
NMR (500 MHz, CDCl
3
) δ 8.22-8.07 (m, 2H), 7.50-7.45 (m, 2H), 7.50-
6
DMSO-d ) δ 146.1, 138.9, 138.4, 135.2, 135.1, 134.6, 130.7, 128.8,
7
.44 (m, 2H), 7.41-7.37 (m, 1H), 4.86 (dd, J= 9.6, 3.8 Hz, 1H), 2.99-2.82
127.7, 127.2, 126.0, 125.0, 124.7, 123.2, 123.0, 122.0, 120.7, 120.5, 61.4,
60.9, 59.5, 57.5, 57.4, 52.5; IR (KBr) 3405, 2925, 2850, 1661, 1425,
1
3
(m, 5H), 2.68-2.49 (m, 5H); C NMR (75 MHz, CDCl
3
) δ 139.6, 139.0,
35.6, 134.9, 134.7, 126.8, 125.1, 124.2, 122.8, 122.6, 121.4, 119.6, 65.2,
2.9, 54.0, 45.4; IR (KBr) 3394, 2934, 2492, 2079, 1426, 1272, 1110,
-
1
+
1
6
8
1225, 1158, 1022, 852, 765, 725 cm ; MS (ESI) m/z 506 [M+Na] ; HR-
MS (ESI) Calcd for C28 ONaS: 506.19850, found: 506.19766.
29 5
H N
-
1
+
96, 765 cm ; MS (ESI) m/z 338 [M+H] ; HR-MS (ESI) Calcd for
S: 338.14339, found: 338.14305. 2-(4-(2-Azido-2-(dibenzo[b,d]
thiophen-2-yl)ethyl)piperazin-1-yl)ethanol (6g): To a solution of 11
2.0 g, 4.04 mmol) in dry THF (20 mL) was added TBAF (1.05 g, 5.28
22. Antitubercular evaluation assay: Two-fold serial dilutions (50.0, 25.0,
2.5, 6.25, 3.13, 1.56, 0.78 and 0.4 µg/mL) of each test compounds 5a-l,
6a-l and drugs were prepared and incorporated into Middlebrook 7H11
agar medium with OADC Growth Supplement. Inoculum of M.
tuberculosis H37Rv ATCC 27294 was prepared from fresh Middlebrook
7H11 agar slants with OADC (oleic acid, albumin, dextrose and catalase;
Difco) Growth Supplement adjusted to 1 mg/mL (wet weight) in Tween
18 20 5
C H N
(
0
mmol) at 0 C. After being stirred for about 5 h at room temperature, the
mixture was quenched with water (25 mL) and extracted with EtOAc
(
3×15 mL). The combined organic layers were dried over anhydrous
−
2
7
sodium sulfate, filtered and concentrated in vacuum. The residue was
purified by flash column chromatography to give 6g as a syrup. Yield:
1
80 (0.05%) saline diluted to 10 to give a concentration of ~ 10 cfu/mL.
A 5 μL amount of bacterial suspension was spotted into 7H11 agar tubes
containing 10-fold serial dilutions of drugs per mL. The tubes were
incubated at 37 °C, and final readings were recorded after 28 days. This
method is similar to that recommended by the National Committee for
Clinical Laboratory Standards for the determination of MIC in triplicate.
23. Evaluation of cytotoxicity: Antitubercular active compounds with MIC
≤ 12.5 μg/mL were further examined for toxicity in a HEK-293T cell line
at the concentration of 50 µg/mL. After 72 h of exposure, viability was
assessed on the basis of cellular conversion of MTT into a formazan
product using the Promega Cell Titer 96 non-radioactive cell proliferation
assay.
1
.3 g, 85%; syrup; H NMR (500 MHz, CDCl
3
) δ 8.23-8.12 (m, 1H), 8.08
(d, J= 1.3 Hz, 1H), 7.92-7.81 (m, 2H), 7.54-7.42 (m, 2H), 7.37 (dd, J=
8
3
1
1
2
.3, 1.5 Hz, 1H), 4.85 (dd, J= 9.6, 3.7 Hz, 1H), 3.64 (t, J= 5.2 Hz, 2H),
13
3
.30-3.21 (m, 2H), 2.91-2.54 (m, 12H); C NMR (75 MHz, CDCl ) δ
39.6, 139.1, 135.7, 134.9, 134.5, 126.9, 125.2, 124.4, 123.0, 122.7,
21.5, 119.7, 64.3, 63.1, 59.1, 58.5, 57.2, 52.7; IR (KBr) 3408, 2924,
-
1
+
082, 1419, 1275, 1026, 874, 756 cm ; MS (ESI) m/z 382 [M+H] ; HR-
OS: 382.17000, found: 382.16961.
24 5
MS (ESI) Calcd for C20H N
Synthesis of dibenzo[b,d]thiophene-1,2,3-triazole derivatives 8a-f, 9a-
f, 10a-f, 11a-f & 12a-f: To the mixture of azido compounds (6a-c & 6f-g)
(1.00 mmol) and alkynes 7a-f (1.1 mmol) in t-butanol & water (1:1, v/v,
8
mL), CuSO .5H O (20 mol %) and sodium ascorbate (20 mol %) were
4
2
Supplementary Material
added, stirred at RT for 5-6 h. After completion (TLC), the reaction
mixture was extracted with ethyl acetate (2 x 10 mL) and water (5 mL).
The organic layer was separated, dried over anhydrous Na SO and
2 4
evaporated under vacuum. The crude product obtained was purified by
silica gel column chromatography using ethyl acetate: hexane (1:2) as
eluent to obtain corresponding dibenzo[b,d]thiophene-1,2,3-triazole
derivatives 8a-f, 9a-f, 10a-f, 11a-f & 12a-f as colorless solids. 1-(2-(Di
benzo[b,d]thiophen-2-yl)-2-(4-phenyl-1H-1,2,3-triazol-1-yl)ethyl)
1
13
Copies of H, C NMR and mass spectra of all the compounds 2, 4a-d,
a-e, 6a-g, 8a-f, 9a-f, 10a-f, 11a-f and 12a-f can be obtained free of
charge from the internet.
5
6