Facile synthesis of 1,3-thiazolidin-4-ones as antitubercular agents

Article abstract of DOI:10.1016/j.bmcl.2016.02.056

We have developed, highly efficient, one-pot, solvent-free, [Et₃NH][HSO₄] catalyzed multicomponent reaction protocol for the synthesis of 1,3-thiazolidin-4-ones in excellent yields. For the first time, the 1,3-thiazolidin-4-ones were evaluated in vitro for their antimycobacterial activity against Mycobacterium tuberculosis dormant MTB H37Ra and Mycobacterium bovis BCG strains. Among the synthesized basic 1,3-thiazolidin-4-ones, particularly the compounds 4c, 4d, 4e, 4f, 4h, 4i and 4j displays promising antitubercular activity along with no significant cytotoxicity against the cell lines MCF-7, A549 and HCT-116.

Full text of DOI:10.1016/j.bmcl.2016.02.056

Accepted Manuscript
Facile Synthesis of 1,3-Thiazolidin-4-ones as Antitubercular Agents
Dnyaneshwar D. Subhedar, Mubarak H. Shaikh, Manisha A. Arkile, Amar
Yeware, Dhiman Sarkar, Bapurao B. Shingate
PII:
S0960-894X(16)30168-8
DOI:
http://dx.doi.org/10.1016/j.bmcl.2016.02.056
BMCL 23610
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
6 December 2015
3 February 2016
19 February 2016
Please cite this article as: Subhedar, D.D., Shaikh, M.H., Arkile, M.A., Yeware, A., Sarkar, D., Shingate, B.B.,
Facile Synthesis of 1,3-Thiazolidin-4-ones as Antitubercular Agents, Bioorganic & Medicinal Chemistry Letters
(2016), doi: http://dx.doi.org/10.1016/j.bmcl.2016.02.056
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Facile Synthesis of 1,3-Thiazolidin-4-ones as Antitubercular Agents
Dnyaneshwar D. Subhedar,a Mubarak H. Shaikh,a Manisha A. Arkile,b Amar Yeware,b Dhiman
Sarkar,b Bapurao B. Shingate*a
aDepartment of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, 431
004, India
bCombichem Bioresource Center, Organic Chemistry Division, CSIR-National Chemical
Laboratory, Pune 411 008
E-mail:* bapushingate@gmail.com (B. B. Shingate)
*Corresponding author. Tel.: (91)-240-2403312; Fax: (91)-240-2403113
Abstract:
We have developed, highly efficient, one-pot, solvent-free, [Et3NH][HSO4] catalyzed
multicomponent reaction protocol for the synthesis of 1,3-thiazolidin-4-ones in excellent yields.
For the first time, the 1,3-thiazolidin-4-ones were evaluated in vitro for their antimycobacterial
activity against Mycobacterium tuberculosis dormant MTB H37Ra and M. Bovis BCG strains.
Among the synthesized basic 1,3-thiazolidin-4-ones, particularly the compounds 4c, 4d, 4e, 4f,
4h, 4i and 4j displays promising antitubercular activity along with no significant cytotoxicity
against the cell lines MCF-7, A549 and HCT-116.
Keywords: Antitubercular; Cytotoxicity; Green protocol; Multicomponent reaction.
1

Multicomponent reactions (MCRs) permit rapid access to combinatorial libraries of
complex molecules, particularly in drug discovery. Multicomponent reactions and ionic liquids is
a perfect synergy for eco-compatible heterocyclic synthesis.1 1,3-Thiazolidin-4-ones are
important class of compounds due to their biological profiles like antimicrobial,2 antitubercular,3
anti-inflammatory,4 HIV inhibitors,5 anti-hypertensive,6 anticonvulsant,7 anti-hepatitis,8 anti-
hyperglycemic,9 antioxidant,10 antifungal11 and antiproliferative12 activity. Thiazolones are also
display promising biological activities.13
Owing to the potential importance of a 1,3-thiazolidin-4-ones as a key moiety in life
sciences and pharmaceuticals, various protocols have been developed using various methods and
catalysts such as ZnCl2,14a DCC,14b HBTU,14c [bmim][PF6],14d silica gel,14e [BmIm]OH,14f
Hunig's base,14g ferrite,14h sodium sulfate,14i molecular sieves,14j nano-Fe3O4@SiO2,14k
montmorillonite K-10,14l baker’s yeast,14m and DBSA.14n However, most of these methods suffer
from one or more drawbacks such as low yields, long reaction times, harsh reaction conditions or
tedious workup procedures.
Recently, the utility of Acidic Bronsted Ionic Liquid (ABIL), particularly
[Et3NH][HSO4]15 has received considerable attention because, it is an inexpensive, non-toxic
catalyst as well as solvent for many organic transformations in excellent yields. Very recently,
we have utilized [Et3NH][HSO4] for the synthesis of α-amino-phosphonates in excellent yields.16
To the best of our knowledge and literature survey, there is no report for the antitubercular
activity of basic skeletons of 1,3-thiazolidin-4-one derivatives and also use of [Et3NH][HSO4] as
catalyst for their synthesis.
In view of the diverse therapeutic activity of 1,3-thiazolidin-4-ones and continuation of
our work on efficient synthesis and bioevaluation of highly functionalized heterocyclic
2

compounds,17 herein, we would like to report a facile synthesis and antitubercular activity of 1,3-
thiazolidin-4-ones against dormant MTB H37Ra and M. Bovis BCG strains for the first time.
The synthesis of 1,3-thiazolidin-4-ones 4a-u via cyclocondensation of Schiff’s base
(obtained in situ from aldehydes and anilines) with thioglycolic acid in the presence of
[Et3NH][HSO4] as catalyst under solvent free conditions is outlined in Scheme 1.
Scheme 1. [Et3NH][HSO4]-catalyzed synthesis of 1,3-thiazolidin-4-ones 4a-u.
In our initial endeavour, we have performed the reaction of aniline 1a (1 mmol),
benzaldehyde 2a (1 mmol) with thioglycolic acid 3 (1 mmol) using 20 mol% of [Et3NH][HSO4]
at 80 °C in various solvents and solvents-free condition also. According to the study, it has been
found that a solvent-free condition is more efficient over using solvents with respect to the
reaction time and yield of the desired 1,3-thiazolidin-4-one (Table 1).
Again, we have screened the concentration of [Et3NH][HSO4] as a catalyst. In the
absence of catalyst, the desired product 4a was obtained in trace amount (Table S1, supporting
information). After varying the concentration 5, 10, 15, 20 and 25 mol%, the product 4a was
obtained in 40, 62, 85, 94 and 94% yield, respectively (Table S1, supporting information). It
indicates that, 20 mol% catalyst is suitable for better yield of product 4a.
3

Table 1
Screening of solventsa
Entry
Solvent
Yield (%)b
1
2
3
4
5
6
7
8
9
EtOH
MeOH
H2O
57
60
47
CH2Cl2
CH3CN
THF
52
62
50
DMF
53c
66c
94d
PhMe
Solvent-free
aReaction conditions: aniline 1a (1 mmol), benzaldehyde 2a (1 mmol), thioglycolic acid 3 (1
b
mmol) and 20 mol% [Et3NH][HSO4] at reflux temperature of solvents after 30 min. Isolated
yields. c,dReaction were performed at 120 and 80 °C, respectively.
We have also studied the recyclability and reuse of catalyst [Et3NH][HSO4] for the
subsequent experiments under similar reaction conditions. After completion of the reaction, the
reaction mixture was poured on ice cold water and the product was extracted using ethylacetate
solvent. The filtrate was subjected for evaporation of water to get viscous liquid, which on
cooling afforded ionic liquid. It was then reused at least five consecutive cycles without much
appreciable loss in its catalytic activity. The recyclability data demonstrates the high stability of
the catalyst under the reaction conditions (Table S2, supporting information).
In addition to this, we have also compared the present protocol for the synthesis of 1,3-
thiazolidin-4-ones is better than earlier reported methods (Table 2).
4

Table 2
Comparison of our results with previously reported data for the synthesis of (4a)
Reaction
Entry
Catalyst
Time/h
Yielda (%)
Ref.
condition
THF/rt
1
2
3
4
5
6
7
8
DCC
SiO2
1
91
78
97
85
55
72
75
94
14b
14e
DCM/rt
7
MCM-41
110 ºC
12
14f
HClO4-SiO2
H2SO4-SiO2
TfOH-SiO2
Bi(SCH2COOH)3
[Et3NH][HSO4]
PhMe/100 ºC
PhMe/100 ºC
PhMe/100 ºC
70 ºC
5
18a
5
18a
5
2
18a
18b
80 ºC
30 min
This work
aIsolated yield.
With this optimized reaction condition, i.e. 20 mol% [Et3NH][HSO4] catalyst at 80 °C for
30 min, we have utilized19 this protocol for the synthesis of highly functionalized 1,3-thiazolidin-
4-ones 4a-u from corresponding aniline 1a-e, aromatic aldehyde 2a-h and thioglycolic acid 3 in
excellent yield (Scheme 1). We have also described the plausible mechanism for the formation
of 1,3-thiazolidin-4-ones 4a-u (Scheme S1, supporting information). This method offers several
advantages like milder reaction condition, shorter reaction time, cleaner reaction, high yield and
simple experimental and isolation procedures, making it an useful route for the synthesis of 1,3-
thiazolidin-4-ones.
Antitubercular activity evaluation of the synthesized 1,3-thiazolidin-4-ones, 4a-u were
determined by measuring growth of inhibition against avirulant strain of dormant MTB H37Ra
(ATCC 25177) and M. bovis BCG (ATCC 35743) in liquid M. pheli medium.
5

Table 3
In vitro antitubercular activity against dormant MTB H37Ra and M. Bovis BCG
MTB H37Ra
M. Bovis BCG
Compounds
Structures
Anti TB IC90 Anti TB IC50 Anti TB IC90 Anti TB IC50
(µg/mL)
>30
(µg/mL)
>30
(µg/mL)
>30
(µg/mL)
20.7
4a
4b
>30
24.0
28.7
>30
2.2
>30
>30
>30
>30
>30
>30
4c
17.3
4d
>30
>30
19.8
5.6
>30
>30
>30
>30
4e
4f
6

>30
>30
27.5
25.2
>30
>30
4.2
6.8
8.9
>30
>30
>30
>30
>30
>30
>30
8.7
4g
4h
4i
20.9
>30
>30
4j
4k
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
4l
4m
4n
7

>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
29.8
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
4o
4p
4q
4r
4s
4t
4u
-
-
0.043 ± 0.15 0.0018 ± 0.009 0.041 ± 0.01 0.0016±0.002
0.075 ± 0.25 0.0025±0.0007 0.045 ± 0.02 0.0023 ±0.001
RP
INH
RP: rifampicin; INH: isoniazid.
8

In a preliminary screening (Table S3 and S4, supporting information ), the
antimycobacterial activity of compounds was assessed at concentrations of 30, 10 and 3 μg/mL
using an established XTT Reduction Menadione assay (XRMA) antitubercular screening
protocol20 using first-line antitubercular drugs rifampicin and isoniazid as reference standards
and the results are presented in Table 3.
The diversely functionalized 1,3-thiazolidin-4-one 4a-u, in particular the compounds 4c,
4f, 4h, 4i and 4j exhibited IC50 values of 2.2, 5.6, 4.2, 6.8 and 8.9 µg/mL, respectively, against
dormant MTB H37Ra, which indicates that, these may be promising antitubercular agents.
However, the only compound 4h active against M. Bovis BCG strain with IC50 value 8.7 µg/mL.
These findings inspired us to evaluate their cytotoxicity. Hence, all of the 1,3-thiazolidin-4-one
derivatives 4a-u were evaluated for their cytotoxicity against MCF-7, A549 and HCT-116 cell
lines using in vitro MTT assay21 (primary screening data, Table S5-S7, supporting information).
Particularly, the selected compounds 4a, 4c, 4d, 4e, 4f, 4h, 4i, 4j and 4u were found to be non
toxic against cell lines at the maximum concentration evaluated (Table S8, supporting
information).
Again, the most active antitubercular compounds 4a, 4c, 4d, 4e, 4f, 4h, 4i and 4j, were
also evaluated for antibacterial activity against Gram-negative and Gram-positive bacteria. These
compounds does not displays promising antibacterial activity against the tested strains, (Table
S9, supporting information).
In conclusion, highly efficient and safer protocol has been developed for the synthesis of
1,3-thiazolidin-4-ones via one-pot three-component cyclocondensation of anilines, aryl
aldehydes, thioglycolic acid using 20 mol% of [Et3NH][HSO4] as a catalyst in excellent yields.
The synthesized 1,3-thiazolidin-4-ones were evaluated in vitro for their antimycobacterial
9

activity, cytotoxicity and antimicrobial activity, shows that these compounds are highly selective
towards dormant MTB H37Ra and M. Bovis BCG strains.
Acknowledgments
The authors D.D.S. and M.H.S. are very much grateful to the Council for Scientific and
Industrial Research (CSIR), New Delhi for the award of Senior Research Fellowship. Authors
are also thankful to the University Grants Commission, Department of Science & Technology,
New Delhi for financial support under UGC-SAP and DST-FIST schemes.
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19 General procedure for one-pot synthesis of 1,3-thiazolidin-4-ones: A mixture of anilines (1
mmol), benzaldehydes (1 mmol), thioglycolic acid (1 mmol) and [Et3NH][HSO4] 20 mol%
was magnetically stirred at 80 °C. The progress of the reaction was monitored by TLC
using ethyl acetate:hexane as a solvent system. The reaction mixture was quenched with
crushed ice and extracted with ethyl acetate (2 × 25 mL). The organic extracts were washed
with brine (2 × 25 mL) and dried over anhydrous sodium sulphate. The solvent was
evaporated under reduced pressure to afford the corresponding crude compounds. The
obtained crude compounds were recrystallized using ethanol.
13

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Graphical Abstract
Facile Synthesis of 1,3-Thiazolidin-4-ones as Antitubercular Agents
Dnyaneshwar D. Subhedar, Mubarak H. Shaikh, Manisha A. Arkile, Amar Yeware, Dhiman
Sarkar, Bapurao B. Shingate*a
One-pot three component reactions, environmentally benign with high catalytic
activity and antitubercular activities.
15