Design, synthesis, and antibiofilm activity of 2-arylimino-3-aryl-thiazolidine-4-ones

Article abstract of DOI:10.1016/j.bmcl.2010.03.013

A series of novel 2-arylimino-3-aryl-thiazolidine-4-ones was designed, synthesized and tested for in vitro antibiofilm activity against Staphylococcus epidermidis. Among them tested, some compounds with carboxylic acid groups showed good antibiofilm activity. The antibiofilm concentration of 1x was 6.25 μM. The structure-activity relationships revealed that incorporation of 2-phenylfuran moiety could greatly enhance antibiofilm activity of thiazolidine-4-one.

Full text of DOI:10.1016/j.bmcl.2010.03.013

Bioorganic & Medicinal Chemistry Letters 20 (2010) 2461–2464
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design, synthesis, and antibiofilm activity of 2-arylimino-3-aryl-thiazolidine-4-
ones
b
a
a
a
Bin Pan a, Ren-Zheng Huang b, Shi-Qing Han a, , Di Qu , Ming-Li Zhu , Ping Wei , Han-Jie Ying
*
a College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing 210009, China
b Key Laboratory of Medical Molecular Virology of Ministry of Education and Ministry of Pulic Health, Institute of Medical Microbiology and Institutes of Biomedical
Sciences, Shanghai Medical School of Fudan University Box 228, Shanghai 200032, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel 2-arylimino-3-aryl-thiazolidine-4-ones was designed, synthesized and tested for in vitro
antibiofilm activity against Staphylococcus epidermidis. Among them tested, some compounds with car-
boxylic acid groups showed good antibiofilm activity. The antibiofilm concentration of 1x was
Received 19 November 2009
Revised 25 February 2010
Accepted 4 March 2010
Available online 7 March 2010
6.25
lM. The structure–activity relationships revealed that incorporation of 2-phenylfuran moiety could
greatly enhance antibiofilm activity of thiazolidine-4-one.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Thiazolidine
Antibiofilm activity
Bacterial infections are now known to predominately exist in a
biofilm growth state that confers both enhanced virulence and
defensive properties to the bacterium.1 Bacteria that reside within
the biofilm state also are inherently more resistant to many antibi-
otics and biocides that would often lead to their eradication.2,3 Gi-
Lys542; the hydrophobic moieties of the inhibitors fit into the
two hydrophobic cavities. In our research, a series of 2-arylimi-
no-3-aryl-thiazolidine-4-ones (Table 1) with hydroxyl groups, es-
ter functional and carboxylic acid groups were designed and
synthesized to expect their good hydrogen bonding capacity.
Moreover, from the literature survey it was revealed that some
derivatives of thiazolo[2,3-b]dihydropyrimidinone possessing 2-
phenylfuran moiety were reported to be potent antibacterial and
antifungal activities.5 Based on these observations, 2-phenylfuran
moiety was introduced into thiazolidione core structure (1l–o
and 1u–x).
ven the breadth of biofilm mediated infections, there is
significant need for new and potent antibiofilm modulators.
a
Recently, several compounds had been documented which had
moderate biofilm inhibitory activities against RP62A,4 a strain of
the Staphylococcus epidermidis. It was also shown that these com-
pounds elicited their effects through inhibition of the YycG histi-
dine kinase, which was an important two-component system
(TCS) control protein. All these inhibitors from a variety of struc-
tural classes included benzamides, furans, pyrimidinones, and thia-
zolidiones. Among these inhibitors, a typical compound 2, which
had a thiazolidione core substituted by aromatic ring, showed po-
tent antibiofim activity, displayed low cytotoxicity on mammalian
cells and was not hemolytic. The biofilm inhibitory activity of 2
was even better than that of vancomycin, one of the antibiotics
usually used in multidrug-resistant staphylococci associated infec-
tions. In this Letter, we presented our further research results on
this related compound class, thiazolidione, exemplified by the gen-
eral structure 1. (Fig. 1).
A simple one-pot reaction consisting of aniline or substituted
aniline, carbon disulfide, water, and triethanolamine catalysed by
Lac Sulfur,6 gave 1,3-diarylthiourea (3–7) in good yield. Formation
According to the interaction model which had been studied by
Qin et al.4 a four-point pharmacophore could be figured out for
describing the binding of the inhibitors: each inhibitor had two
hydrogen bond acceptors, hydrogen bonding to Asn503 and
* Corresponding author. Tel.: +86 25 83587334; fax: +86 25 83587326.
E-mail address: hanshiqing@njut.edu.cn (S.-Q. Han).
Figure 1. Thiazolidione core structure.
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.03.013

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B. Pan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2461–2464
Table 1
Anti-bacteria and antibiofilm activities of 2-arylimino-3-aryl-thiazolidine-4-ones
Compound
R1
R2
S. epidermidis RP62A MICa
(
lM)
S. epidermidis RP62A MBCb
(
lM)
Antibiofilm concentrationc
(lM)
1a
1b
1c
1d
1e
1f
1g
1h
1i
H
H
4-N(CH3)2–Ph–
3-OCH3–4-OH–Ph–
4-OH–Ph-
3-OCH3–4-OH–Ph–
4-OH–Ph–
3-OH–Ph–
3-OCH3–4-OCH2COOCH3–Ph–
4-OCH2COOCH3–Ph–
3-OCH3–4-OCH2COOCH3–Ph–
4-OCH2COOCH3–Ph–
3-OCH2COOCH3–Ph–
>200d
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
2-CH3
2-CH3
2-CH2CH3
2-CH2CH3
H
2-CH3
2-CH3
2-CH2CH3
2-CH2CH3
1j
1k
1l
2-CH3
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
1m
1n
1o
2-CH2CH3
4-CH3
4-OCH3
1p
1q
1r
1s
1t
H
2-CH3
2-CH3
2-CH2CH3
2-CH2CH3
3-OCH3–4-OCH2COOH–Ph–
4-OCH2COOH–Ph–
3-OCH3–4-OCH2COOH–Ph–
4-OCH2COOH–Ph–
>200
>200
>200
50
>200
>200
>200
100
>200
>200
>200
100
3-OCH2COOH–Ph–
50
100
100
1u
1v
2-CH3
12.5
12.5
6.25
25
25
25
25
2-CH2CH3
4-CH3
25
1w
12.5
1x
2
4-OCH3
6.25
50
25
6.25
100
2-CH2CH3
3-OCH3–4-OCH2COOH–Ph–
100
a
MIC assays for the antibacterial activities of the compounds were performed according to the broth microdilution (in tubes) method of the Clinical and Laboratory
Standards Institute (CLSI) of America.14
b
MBC of the compounds was obtained by subculturing 100 ll from each negative (no visible bacterial growth) tube from the MIC assay, onto substance-free Mueller–
Hinton agar plates. The plates were incubated at 37 °C for 24 h, and the MBC was defined as the lowest concentration of compounds which produced subcultures growing no
more than five colonies on each plate.
c
In the Antibiofilm concentration experiment, overnight culture of S. epidermidis strain RP62A was diluted 1:10 in TSB (OD600 = 0.6–0.8), then was diluted 1:200 in MH.
The bacterial suspension was inoculated into the wells of sterile 96-well polystyrene microtiter plates (Falcon) incubated at 37 °C for 6 h. The plates with young biofilm were
washed gently four times with sterile PBS before adding fresh TSB containing the various concentration compounds, and incubated at 37 °C for 16 h.
d
The initiate dilution was 200 lM.
of thiazolidiones (8–12) from the five disubstitued symmetrical
thioureas was accomplished in EtOH with chloracetic acid and
NaOAc7 (Scheme 1). The 3-(5-formylfuran-2-yl)benzoic acid 138
was obtained according to the known method, then an esterifica-
tion of 13 with methanol in the presence of sulfuric acid gave
the 149 (Scheme 2).

B. Pan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2461–2464
2463
Scheme 1. Reagents and conditions: (a) CS2, LacÁSulfur, triethanolamine, water, reflux, 6 h; (b) ClCH2COOH, NaOAc, absolute alcohol, reflux, 10 h.
Scheme 2. Reagents and conditions: (a) concentrated HCl, H2O, NaNO2, 0–5 °C, 30 min; 2-furanaldehyde, CuCl2Á2H2O, H2O, acetone, rt, 2 d; (b) methanol, H2SO4 (catalytic),
reflux, 4 h.
Scheme 3. Synthetic routes for representative targets. Reagents and conditions: (a) 4-hydroxybenzaldehyde, piperidine, absolute alcohol, 60 °C, 3 h; (b) BrCH2COOCH3,
acetone, reflux, 4 h; (c) K2CO3, water, methanol, reflux, 10 h; (d) 14, piperidine, absolute alcohol, 60 °C, 3 h.
Starting from intermediates 8–12, various types of derivatives
featuring different aryl fragments could be prepared. The synthesis
of some representative examples was described in Scheme 3. An al-
dol condensation of 4-hydroxy benzaldehyde with equivalent
amount of precursors 9 or 10 in EtOH was taken place in the pres-
ence of piperidine gave 1c or 1e without incident.10 When equiva-
lent amount of 1c or 1e and methyl bromoacetate were mixed in
acetone with K2CO3 and refluxed for 4 h, compound 1h or 1j were
formed.11 The desired compound 1q and 1s were prepared by
hydrolization of 1h or 1j in methanol and water, catalyzed by
K2CO3. 1o and 1x were synthesized in the same manner.12
that of vancomycin (88 l
M).4 It revealed that the 3-(5-methylfu-
ran-2-yl) benzoic acid substitution group obviously improved the
activity of 2-arylimino-3-aryl-thiazolidine-4-one. The change, that
rigidity of 1u–x is enhanced when the 3-(5-formylfuran-2-yl)ben-
zoic acid moiety was incorporated into the scaffold, probably, led
the thiazolidiones bind to the target protein more easily. The
anti-bacteria and antibofilm activities may be also dependent on
the substitution of the benzene ring (R1). While 2-substitued inhib-
itors (1q–t, 1u and 1v) were relatively weak antibiofilm agents,
their 4-substitued counterparts (1w and 1x) were the most potent
inhibitors among the synthesized compounds.
Subsequently, the minimal inhibitory concentration (MIC), min-
imal bactericidal concentration (MBC) and antibiofilm concentra-
tion assay of compounds were determined against S. epidermidis
using a standard tube-dilution assay (Table 1). Among tested com-
pounds, the antibiofilm activity of 1s–x was superior or compara-
ble to that of 2. Moreover, the data of 1u–x13 was even superior to
Unliked the good activity of 1s–x against S. epidermidis, the 1j–
o showed no activity, the ester functional group of R2 in these com-
pounds might be the main reason which led the anti-bacteria and
antibiofilm activities disappeared. In addition, compounds 1b–f
which contained hydroxy group of R2 exhibited no activities too.
The results showed that compounds contained carboxylic acid

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B. Pan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2461–2464
group (R2) were more likely to have anti-bacteria and antibofilm
activities.
5. Mithun, A.; Bantwal, S. H.; Nalilu, S. K. Eur. J. Med. Chem. 2007, 42, 380.
6. Ramadas, K.; Janarthanan, N.; Velmathi, S. Synth. Commun. 1997, 27, 2255.
7. Sule, E.; Ilknur, D. J. Org. Chem. 2007, 72, 2494.
8. Livio, R.; Vesna, T. K.; David, W. B.; Grace, K. Z. Molecules 2003, 8, 342.
9. Narges, H.; Latifeh, N.; Hooman, S.; Mhsen, A.; Nasrin, S.; Mohammad, A. F.;
Abbas, S. Bioorg. Med. Chem. Lett. 2007, 17, 6354.
10. Rosaria, O.; Rosanna, M.; Rosella, C. Bioorg. Med. Chem. 2007, 15, 7618.
11. (a) Rosanna, M.; Rosaria, O.; Rosella, C.; Maria, G. V.; Dietmar, R.; Theodora, S.;
Thierry, L. Bioorg. Med. Chem. Lett. 2007, 17, 3886; (b) Rosanna, M.; Paolo, P.;
Rosaria, O.; Michela, J.; Rosella, C.; Giampaolo, M.; Theodora, S.; Thierry, L.;
Maria, G. V.; Guido, C. Bioorg. Med. Chem. 2007, 15, 5137.
12. Wang, S. F.; Ye, Y. H.; Zhang, Z.; Tan, R. X. Ultrason. Sonochem. 2006, 13, 28.
13. The selected data of representative compounds 1u–x were as follows:
compound 1u: light yellow solid; 1H NMR (300 MHz, DMSO-d6): d 8.23 (s,
1H, CH), 7.93–7.91 (d, 1H, furan-H), 7.83–7.81 (d, 1H, furan-H), 7.69–6.96 (m,
12H, Ph-H), 2.25 (s, 3H, CH3), 2.05 (s, 3H, CH3); HRMS m/z 495.1372 [calcd for
C29H23N2O4S (M+H)+, 495.1373]; compound 1v: white yellow solid; 1H NMR
(300 MHz, DMSO-d6): d 8.24 (s, 1H, CH), 7.93–7.91 (d, 1H, furan-H), 7.85–7.83
(d, 1H, furan-H), 7.70–6.97 (m, 12H, Ph-H), 2.60–2.55 (q, 2H, CH2), 2.42–2.37
(q, 2H, CH2), 1.19–1.14 (t, 3H, CH3), 1.01–0.96 (t, 3H, CH3); EI-HRMS: calcd for
C31H26N2O4S (M+), 522.1613; found, 522.1614; compound 1w: light yellow
solid; 1H NMR (300 MHz, DMSO-d6): d 8.27 (s, 1H, CH), 7.94–7.92 (d, 1H, furan-
H), 7.87–7.85 (d, 1H, furan-H), 7.64–6.91 (m, 12H, Ph-H), 2.38 (s, 3H, CH3), 2.34
(s, 3H, CH3); compound 1x: light yellow solid; 1H NMR (300 MHz, DMSO-d6): d
8.30 (s, 1H, CH), 7.94–7.92 (d, 1H, furan-H), 7.89–7.87 (d, 1H, furan-H), 7.64–
6.99 (m, 12H, Ph-H), 3.82 (s, 3H, OCH3), 3.79 (s, 3H, OCH3).
In conclusion, new 2-arylimino-3-aryl-thiazolidine-4-ones
were designed and synthesized. Incorporation of a 2-phenylfuran
moiety had been found to greatly enhance antibiofilm activity. In
addition, the chain length and the substituted position of R1 also
influenced antibiofilm activity and the carboxylic acid group of
R2 was indispensable. All these results suggested that the thiazo-
lidione scaffold was clearly a good chemotype for exploration of
antibiofilm drugs. Further studies on these compounds and optimi-
zation of their structures leading to novel analogues with superior
biological properties are on going in our laboratories.
Acknowledgment
This work was supported by National Natural Science Founda-
tion of China (Grant No. 20942006).
References and notes
14. Clinical and Laboratory Standards Institute. (2006). Methods for dilution
antimicrobial susceptibility tests for bacteria that grow aerobically, 7th ed.
Approved standard M7–A7. Clinical and Laboratory Standards Institute,
Wayne, PA.
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