Design and one-pot synthesis of hybrid thiazolidin-4-one-1,3,5-triazines as potent antibacterial agents against human disease-causing pathogens

Article abstract of DOI:10.1039/c2nj41028a

An efficient and general one-pot reaction to a novel series of hybrid thiazolidine-4-one-1,3,5-triazine derivatives was developed. The easy work-up of the products, rapid reaction, and mild conditions are notable features of this protocol. These molecules were found to exhibit potent activity against a panel of Gram-positive and Gram-negative micro-organisms.

Full text of DOI:10.1039/c2nj41028a

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LETTER
Design and one-pot synthesis of hybrid thiazolidin-4-one-1,3,5-triazines
as potent antibacterial agent against human disease causing pathogens
Sudhir Kumar,a Hans Raj Bhat,a Mukesh Kumar Kumawat,b Udaya Pratap Singha,c*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
An efficient and general one-pot reaction to novel series of
in three parts. The part one was dealt with synthesis of diꢀ
hybrid thiazolidine-4-one-1,3,5-triazine derivatives were 50 substituted 1,3,5ꢀtriazine derivatives 3 (aꢀd), it was furnished by
developed. The easy work-up of the products, rapid reaction,
and mild conditions are notable features of this protocol.
treating two equivalents of distinguished amine with
commercially available 2,4,6ꢀtri chlroro 1,3,5ꢀtriazine in the
10 These molecules were found to exhibit potent activity against
the panel of Gram-positive and Gram-negative micro-
organisms.
presence of base. It was a temperature dependent SNAr
nucleophilic reaction, thus, the reaction was carried out at 0ꢀ5 °C
55 for the first substitution and then refluxing the same mixture to
40ꢀ45 °C for 3ꢀ4 h. The second part of synthesis deals with
amination of mono chloro of diꢀsubstituted 1,3,5ꢀtriazine in the
presence of ammonia to furnish 2,4ꢀdi substitutedꢀ6ꢀamineꢀ1,3,5ꢀ
triazine derivative 4 (a-d). Whereas, the last part of the scheme
Treatment of infections caused by bacterial pathogens is always
15 creating a peril to the healthcare. It becomes more acute due to
the rapid development of resistance against the conventional
chemotherapy.1 Considering the magnitude of ever growing 60 illustrates the oneꢀpot synthesis of hybrid thiazolidinꢀ4ꢀoneꢀ1,3,5ꢀ
antibacterial resistance and high vulnerability against human
population towards them, it is necessary to discover novel
20 chemical entity (NCE) with improved pharmacological profile.
1,3,5ꢀtraizine, a pharmacophore found as a core skeleton in
triazines derivatives 7 (aꢀl). It was afforded via condensationꢀ
cyclisation reaction between amine of diꢀsubstituted 1,3,5ꢀ
triazines, corresponding aldehydes and 2ꢀmercaptoethanethioic Sꢀ
acid. These compounds were taken altogether in a flask and
molecules with diverse biological activity such as antibacterial,2 65 allowed to reflux at 110 °C in the presence of toluene. The
antifungal,3 anticancer,4 antimalarial5 and antiviral6 agents. In our
aim to develop novel antibacterial agents derived from 1,3,5ꢀ
25 triazine, we had reported a novel heterocyclic hybrid skeleton
comprise of thiazole and 1,3,5ꢀtriazine as potent antibacterial
agent.7,8 Prompted by the results, we further carry out the
modification on 1,3,5ꢀtriazine to deliver newer antibacterial
agents with piperazine,9 1,3ꢀthiazine10 1,3,4ꢀthiadiazole11 and 4ꢀ
30 aminoquinoline12. More recently in our previous communication,
we had disclosed that hybrid conjugates of 1,3,5ꢀtriazine were
acted via arrest of bacterial translation. 10
completion of reaction was initially monitored via TLC and the
structures of these molecules were ascertained on the basis of FTꢀ
IR, 1HꢀNMR, mass spectral and elemental analysis (see
supplementary information).
The final compounds were screened against panel of human
disease causing pathogens consists of three Gramꢀpositive and
three Gramꢀnegative strains. The MIC (minimum inhibitory
concentration) of the compounds along with the activity of
reference Cefixime was presented in Table 1. Compounds
75 showed varying degree of antibacterial activity against Gramꢀ
positive pathogens; nevertheless, remarkable activity was also
reported against the Gramꢀnegative bacteria from the entire set of
title hybrid compounds. Marked inhibition pattern was disclosed
by the molecules having mꢀchloro substitution on the phenyl ring
70
Based upon the our earlier observation and extensive
investigation of the structure activity relationship for hybrid
35 1,3,5ꢀtriazine conjugates, it was indicated that 1,3,5ꢀtraizine core
and its pendant substitution is crucial for generation and
escalation of activity. It was further substantiated with the nature 80 tethered to 1,3,5ꢀtriazine against entire set of bacterial strains 7
of the substituent on the other flanked portions of 1,3,5ꢀtraizine
core.
As further study to develop newer hybrid conjugates of 1,3,5ꢀ
triazine as antibacterial agent with diverse heterocyclic fragment
(aꢀd).Whereas, on isomeric replacement of chloro in aldehyde
portion from para (7a) to ortho (7b) generate the molecule more
potent towards Gramꢀnegative and less active towards the Gramꢀ
positive. On the other hand, introduction of pꢀnitro group (7c) and
40
on the pendant position, we report here the oneꢀpot synthesis and 85 its ortho isomeric counterpart (7d) in aldehyde by keeping the
antibacterial activity of conjugates derived from 1,3,5ꢀtriazineꢀ
thiazolidinone. Our primary objective was to optimize the
45 potency of these compounds against Gramꢀpositive and Gramꢀ
negative organisms.
1,3,5ꢀtriazine portion rigid showed noticeable variation in activity
against the Gramꢀpositive and Gramꢀnegative bacterial strains.
Out of which compound 7d presented highly potent activity
against E. coli than Cefixime as a standard. A marked variation in
The synthesis of designed target compounds were
accomplished via a multiꢀstep synthetic procedure and distributed
90
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Part 2
b
Part 1
H
NH2
H
N
N
N
Cl
Cl
Cl
N
N
H2N
R2
R2
a
+
N
N
N
N
N
N
Cl
NH
NH
R1/R2
R1
R1
5
4(a-d)
3(a-d)
2(a-d)
1
Part 3
H2N
O
H
H
N
N
S
N
N
N
R2
CHO
R2
N
N
O
10
N
N
c
R3
HS
NH
+
+
R3
HN
SH
R1
R1
6
5(a-d)
7 (a-l)
4 (a-d)
Scheme 1 Reagents and condition: a. Various amines, stirring, aq. NaOH, 0ꢀ5 °C; Reflux, aq. NaOH 40ꢀ55°C: b. NH3, reflux, 125ꢀ135 °C; c: Toluene,
15
reflux, 110 °C.
antibacterial profile of the compounds were observed on
introduction of mꢀfluoro in the place of mꢀchloro at the phenyl of
1,3,5ꢀtriazine. Compound 7e, having pꢀchloro on the phenyl of
thiazolidineꢀ4ꢀone showed significant to moderate activity against
conformational state may be responsible for the pronounced
antibacterial activity showed by halogen containing molecules.
Additionally, these compounds perhaps tend to occupy the active
site of molecular targets including the deeper pockets which is
20 entire set of bacterial strains except potent in the case of E. coli 55 necessary to exert potent antibacterial action.
than Cefixime. While, isomeric replacement of pꢀchloro to oꢀ
chloro (7f), makes the molecule more potent towards S. aureus,
mild active towards B. cereus, E. coli, P. vulgaris and no change
against B. subtilis and P. aeruginosa. Extremely potent
We had developed a novel series of hybrid thiazolidineꢀ4ꢀoneꢀ
1,3,5ꢀtriazine derivatives as potent antibacterial agents via
efficient synthetic methodology. Present study suggests the role
of halogenated electron withdrawing groups to generate highly
25 antibacterial activity was disclosed by the compound 7g resulted 60 potent antibacterial agents from the title hybrid skeleton. Our
on introduction of pꢀNO2 in the phenyl tethered to thiazolidineꢀ4ꢀ
one against E. coli and P. vulgaris than Cefixime as standard,
while, no major difference in antibacterial profile was observed
against rest of the strains except B. cereus. Further decline in
optimisation studies on the hybrid derivatives of 1,3,5ꢀtriazine is
underway and reported subsequently in future.
Experimental
30 antibacterial action was reported against E. coli and P. vulgaris 65 All chemical reagents are commercial available, and used without
by compound 7h, with no significant change towards other
microorganisms. On replacement of halogenated electron
withdrawing groups with nonꢀhalogenated (NO2) in the phenyl of
1,3,5ꢀtriazine fragment 7 (iꢀn) makes the molecule significantly
further purification. Melting points of the synthesized compounds
were determined in an open capillary tube Hicon Melting point
apparatus and are uncorrected. Thin layer chromatography (TLC)
was performed on silica gelꢀG coated plates to detect the
35 active against the Gramꢀpositive and mild to moderate against the 70 completion of reaction. The diverse mobile phase was selected in
Gramꢀnegative microorganisms. While, significant activity was
reported by the compounds 7i, 7j and even more potent than
Cefixime against the P. vulgaris and P. aeruginosa by compound
7l.
different proportion according to the assumed polarity of the
products. The spots was visualised by exposure to the Iodine
vapour. InfraꢀRed (IR) spectra were recorded in KBr on Biored
FTs spectrophotometer and the reported wave numbers are given
40
From the structureꢀactivity relationship studies of hybrid 75 in cmꢀ1. 1H NMR spectra were recorded in DMSO on Bruker
thiazolidineꢀ4ꢀoneꢀ1,3,5ꢀtriazine derivatives, it was confirmed
that isomeric replacements of the substituents may lead to marked
difference in antibacterial profile of the compounds. It is
noteworthy to mention that compounds consists of halogenated
Model D9RXꢀ400MHz spectrometer. Chemical shifts were
reported as δ (ppm) relative to TMS as internal standard. Mass
spectra were obtained on VGꢀAUTOSPEC spectrometer
equipped with electrospray ionization (ESI) sources. Elemental
45 electron withdrawing groups were found as highly active against 80 analysis of C, H and N was performed on a Vario EL III CHNOS
the Gramꢀnegative pathogens and mild towards the Gramꢀ
positive. While, the compounds comprises of nonꢀhalogenated
electron withdrawing group exert mild to moderate activity
against the entire set of the bacterial strains. The increase in
elemental analyzer.
Synthesis of the intermediate compounds 3 (a-d), 4 (a-d)7 was
performed in accordance with earlier reported procedures.
General procedure for the synthesis of title hybrid analogues
50 membrane permeability and alteration of volumetric and 85 7(aꢀl).
2
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2,4ꢀBisꢀ(substitutedꢀphenyl)ꢀ[1,3,5]ꢀtriazineꢀ2,4,6ꢀtriamine 4(a-d)
(0.1mol), substituted benzaldehyde 5 (a-d) (0.1mol) and 2ꢀ
diluted from tube 2 to tube 9 (tube 2–9 containing 125, 62.5,
31.25, 15.62, 7.81, 3.91, 1.95, 0.97 ꢁg/mL, respectively). After
mercaptoethanethioic Sꢀacid 6 (0.1mol) were refluxed in presence 40 this process, each tube was inoculated with 0.1 mL of the
of toluene for 6ꢀ10 h. The product 7(a-l) was filtered, washed
with cold water and recrystallized with ethanol to afford the
corresponding pure product.
bacterial suspension whose concentration corresponded to 0.5
McFarland scale (9 × 108 cells/mL) and each bacterium was
incubated at 37 °C for 24 h at 150 rpm. The final volume in each
tube was 1.0 mL. The incubation chamber was kept humid. At the
45 end of the incubation period, MIC values were recorded as the
lowest concentration of the substance that gave no visible
turbidity, i.e. no growth of inoculated bacteria.
5
Table 1 Minimum Inhibitory Concentration of designed target molecules.
Minimum Inhibitory Concentration (µg/mL)
Gram-positive bacteria Gram-negative bacteria
Compound
Acknowledgement
S.
B.
B.
E. coli P.
vulgaris aeruginosa
125 15.625
P.
50 Authors are thankful to Sam Higginbottom Institute of
Agriculture, Technology & Sciences, Allahabad, India for
providing necessary infrastructural facilities and Sophisticated
Analytical Instrumental Facility (SAIF), Punjab University, India
for providing the spectral data of compounds synthesized herein.
55
aureus subtilis cereus
7a
7b
7c
7d
7e
7f
7g
7h
7i
62.5
125
31.25 31.25 62.5
125
31.25 7.8125 15.625 3.91
31.25 15.625 31.25
31.25 1.95 62.5 15.625
7.8125 31.25 1.95 7.8125 7.8125
15.625 31.25 62.5
31.25 62.5
125
Notes and references
a Department of Pharmaceutical Sciences, Sam Higginbottom Institute of
Agriculture Technology and Sciences, Formerly Allahabad Agricultural
Institute, Deemed to be University, Allahabad 211007, India
60 b Anand College of Pharmacy, Agra 282007, India
c Present Address: Archimedes DoRa5 Visiting Fellow, Institute of
Chemistry, Division of Bio-organic Chemistry, Institute of Chemistry,
University of Tartu, Estonia
15.625 7.8125 125
62.5
62.5
3.91
31.25
7.8125
31.25
62.5
31.25 15.625 15.625 1.95
31.25 15.625 31.25 62.5
15.625 31.25 62.5
31.25 7.8125 15.625 31.25 125
31.25 31.25 31.25 31.25 15.625 31.25
31.25 62.5 31.25 15.625 1.95 1.95
3.91 3.91 7.8125 3.91
1.95
15.625 15.625
7j
31.25
7k
7l
65 †Electronic Supplementary Information (ESI) available: Analytical
details are given in supplementary information
DOI: 10.1039/b000000x/
Cefixime 7.8125 1.95
a Footnote text.
1. ECDC ꢂ EMEA Joint Technical Report. The bacterial challenge:time
70
75
80
to react. 2009, EMEA ꢂ 576176 ꢂ 2009.
10
2. Gahtori P, Ghosh SK. J. Enzyme Inhib. Med. Chem. 2012, 27, 281.
3. Singh, UP, Bhat, HR, Gahtori, P. J. Mycol. Med. 2012, 22, 134.
4. Kumar, R, Gupta, L, Pal, P, Khan, S, Singh, N, Katiyar, SB, Meena,
S, Sarkar, J, Sinha, S, Kanaujiya, JK, Lochab, S, Trivedi, AK,
Chauhan, PM. Eur. J. Med. Chem. 2010, 45, 2265.
5. Gahtori, P, Ghosh, SK, Parida, P, Prakash, A, Gogoi, K, Bhat, HR,
Singh, UP. Exp. Parasitol. 2012, 130, 292
6. Lozano, V, Aguado, L, Hoorelbeke, B, Renders, M, Camarasa, MJ,
Schols, D, Balzarini, J, SanꢀFélix, A, PérezꢀPérez, MJ. J Med
Chem. 2011, 54, 5335.
Antibacterial Screening
Minimum Inhibitory Concentration
All the synthesized compounds were screened for their minimum
15 inhibitory concentration (MIC, ꢁg/mL) against selected Gramꢀ
positive organisms viz. Bacillus subtilis (NCIMꢀ2063), Bacillus
cereus (NCIMꢀ2156), Staphylococcus aureus (NCIMꢀ2079) and
Gramꢀnegative organism viz. Escherichia coli (NCIMꢀ2065),
Proteus vulgaris (NCIMꢀ2027) and Pseudomonas aeruginosa
20 (NCIMꢀ2036), by the broth dilution method as recommended by
the National Committee for Clinical Laboratory Standards with
minor modifications.13 Cefixime was used as standard
antibacterial agent. Solutions of the test compounds and reference
drug were prepared in dimethyl sulfoxide (DMSO) at
25 concentrations of 125, 62.5, 31.25, 15.62, 7.81, 3.91, 1.95, 0.97
ꢁg/mL. Ten tubes were prepared in duplicate with the second set
being used as MIC reference controls (16–24 h visual). After
sample preparation, the controls were placed in a 37 °C incubator
and read for macroscopic growth (clear or turbid) the next day.
30 Into each tube, 0.8 mL of nutrient broth was pipette (tubes 2–7),
tube 1 (negative control) received 1.0 mL of nutrient broth and
tube 10 (positive control) received 0.9 mL of nutrient. Tube 1, the
negative control, did not contain bacteria or antibiotic. The
positive control, tube 10, received 0.9 mL of nutrient broth since
35 it contained bacteria but not antibiotic. The test compound were
dissolved in DMSO (125 ꢁg/mL), 0.1 mL of increasing
concentration of the prepared test compounds which are serially
7. Singh, UP, Singh, RK, Bhat, HR, Subhashchandra, YP, Kumar, V,
Kumawat, MK, Gahtori, P. Med. Chem. Res. 2011, 20, 1603.
8. Gahtori, P, Gosh, SK, Singh, B, Singh UP, Bhat HR, Uppal A. Saudi
Pharm. J. 2011, 20, 35.
85 9. Ghosh, SK, Singh, UP, Bhat, HR, Gahtori, P. Lett. Drug Des. Disc.
2012, 9, 329.
10. Singh, UP, Pathak, MK, Bhat, HR, Gahtori, P, Singh, RK. Chem.
Biol. Drug Des. 2012, 80, 572.
11. Singh, UP, Dubey, V, Bhat, HR. Chem. Biol. Drug Des. 2012, 80,
90
95
598.
12. Bhat, HR, Gupta, SK, Singh UP. RSC Adv. 2012, 2, 12690ꢀ12695.
13. National Committee for Clinical Laboratory Standards. (1982)
Standard Methods for Dilution Antimicrobial Susceptibility Test for
Bacteria Which Grow Aerobically. Villanova: NCCLS; p. 242.
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Graphical Abstract
A novel series of hybrid thiazolidine-4-one-1,3,5-triazine conjugates was developed as potent
antibacterial agents through facile one-pot synthetic route.