Efficient synthesis and antimicrobial activity of some novel S-β-d-glucosides of 5-aryl-1,2,4-triazole-3-thiones derivatives

Article abstract of DOI:10.1016/j.bmcl.2013.02.038

A series of 3-S-β-d-glucosides-4-arylideneamino-5-aryl-1,2,4-triazoles were rationally designed and synthesized according to the principle of superposition of bioactive substructures by the combination of 1,2,4-triazole, Schiff base and glucosides. The structures of the target compounds have been characterized by ¹H NMR, ¹³C NMR, IR, MS and HRMS. All the newly synthesized compounds have been evaluated for their antimicrobial activities in vitro against Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 8099) as well as Monilia albican (ATCC 10231). The bioactive assay showed that most of the tested compounds displayed variable inhibitory effects on the growth of the Gram-positive bacterial strain (Staphylococcus aureus), Gram-negative bacterial strains (Escherichia coli) and fungal strains (Monilia albican). All the target compounds exhibited better antifungal activity than antibacterial activity. Especially, compounds 6b, 6c, 6f, 6j, 6k and 6l showed excellent activity against fungus Monilia albican with MIC values of 16 μg/mL.

Full text of DOI:10.1016/j.bmcl.2013.02.038

Bioorganic & Medicinal Chemistry Letters 23 (2013) 1997–2000
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Efficient synthesis and antimicrobial activity of some novel
S-b-D-glucosides of 5-aryl-1,2,4-triazole-3-thiones derivatives
b
a
a
a
a
Dan Ji a, JunRui Lu a, , BoWei Lu , ChunWei Xin , JiangBei Mu , JianFa Li , ChunYong Peng ,
⇑
XiuRong Bao a
a College of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China
b College of Chemistry & Chemical Engineering, Xiamen University, Xiamen 361005, 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 3-S-b-D-glucosides-4-arylideneamino-5-aryl-1,2,4-triazoles were rationally designed and syn-
Received 25 September 2012
Revised 25 January 2013
Accepted 6 February 2013
Available online 14 February 2013
thesized according to the principle of superposition of bioactive substructures by the combination of
1,2,4-triazole, Schiff base and glucosides. The structures of the target compounds have been characterized
by 1H NMR, 13C NMR, IR, MS and HRMS. All the newly synthesized compounds have been evaluated for
their antimicrobial activities in vitro against Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC
8099) as well as Monilia albican (ATCC 10231). The bioactive assay showed that most of the tested com-
pounds displayed variable inhibitory effects on the growth of the Gram-positive bacterial strain (Staph-
ylococcus aureus), Gram-negative bacterial strains (Escherichia coli) and fungal strains (Monilia albican). All
the target compounds exhibited better antifungal activity than antibacterial activity. Especially, com-
pounds 6b, 6c, 6f, 6j, 6k and 6l showed excellent activity against fungus Monilia albican with MIC values
Keywords:
5-Aryl-1,2,4-triazole-3-thiones
S-b-D-glucosides
Schiff bases
Synthesis
of 16 lg/mL.
Antimicrobial activity
Ó 2013 Elsevier Ltd. All rights reserved.
1,2,4-Triazoles nucleus and their derivatives have emerged rap-
idly with the advance of modern heterocyclic chemistry, promising
a variety of medical applications such as antibacterial, antifungal,
anticancer, antitumor, anticonvulsant, anti-inflammatory and
analgesic properties.1–6 Several compounds possessing 1,2,4-tria-
zole nucleus are clinically used drugs, for example, fluconazole, itr-
aconazole and terconazole.7,8 These drugs act by displacing
Schiff bases have also been reported a broad range of biological
activities, including antifungal, antibacterial, antimalarial, antipro-
liferative, anti-inflammatory, antiviral and antipyretic properties.13
Schiff base hydrazone ligands containing 1,2,4-triazole nucleus
have aroused great interest in chemistry and biology for many
years due to their facile synthesis and wide applications.14
Prompted by these observations and in continuation of search
for bioactive molecules, we designed and synthesized a series of
lanosterol from cytochrome P45014
and, in this manner, block
a
DM
the biosynthesis of ergosterol, an essential component of the fun-
gal cell membrane. Cytochrome P45014 oxidatively removes
novel 3-S-b-D-glucosides-4-arylideneamino-5-aryl-1,2,4-triazoles.
In our design we emphasized the strategy of combining three mol-
ecules, 1,2,4-triazole nucleus, Schiff base and glycosyl, in one
frame. The newly synthesized compounds 6a–6l was screened
for their in vitro antibacterial activities against Escherichia coli,
Staphylococcus aureus and Monilia albican. The bioactive assay
showed that most of the tested compounds displayed variable
inhibitory effects on the growth of the Gram-positive bacterial
strain, Gram-negative bacterial strains and fungal strains.
The route employed for synthesis of the target compounds is
shown in Scheme 1. Hydrazides (1a and 1b) and potassium aroyl
dithiocarbazate (2a and 2b) were obtained by the reported meth-
od.15,16 The salt 2 underwent ring closure with an excess of hydra-
zine hydrate to give the key intermediate 4-amino-1,2,4-triazole-
3-thione 3. The ring closure reaction may have a nucleophilic sub-
stitution–elimination mechanism (Scheme 2). The ring closure
reaction mechanism is discussed as Scheme 2. The Schiff base
4a–4l were produced by reaction of 4-amino-1,2,4-triazole-3-thi-
a
DM
the 14-
a-methyl group of lanosterol by oxygenization and
NADPH.9
On the other hand, glycosylsulfanyl heterocycles have attracted
much attention because of their biological activity and in particular
because of their inhibition of the activity of enzymes.10,11 They
have excellent chemoselectivity in glycosylation processes as both
donors and acceptors, particularly via reaction processes that in-
volve active and latent glycosylation protocols.10 The synthesis
and investigation of biological activity of 1,2,4-triazole glycosides
have been stimulated by the finding that Ribavirin, b-D-ribofurano-
syl-1,2,4-triazole-3-carboxamide, is remarkable in its broad
spectral activity against DNA and RNA viruses.12
⇑
Corresponding author. Tel.: +86 138 2137 8020 (J.L.).
E-mail addresses: jidan13820890973@163.com (D. Ji), lujunrui@tjut.edu.cn
(JunRui Lu).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.02.038

1998
D. Ji et al. / Bioorg. Med. Chem. Lett. 23 (2013) 1997–2000
R
O
catalyst. 2,3,4,6-Tetra-O-acetyl-a-D-glucopyranosyl bromide com-
R
pound 5 was obtained by the reported method.17 Compounds
4a–4l and 5 were used as starting materials to prepare new func-
NH2
N
H
COOCH3
N2H4.H2O
Reflux
CS2/KOH
tionalized 1,2,4-triazoleS-b-
compounds 4a–4l with 1.2 M equiv of 2,3,4,6-tetra-O-acetyla-
-glucopyranosyl bromide 5 afforded a chromatographically
separable product, namely, 3-(2,3,4,6-tetra-O-acetyl-b- -glucopyr-
D-glucosides. Thus, glucosidation of
1a-1b
R
R
O
H
N
NH
S
a-D
N
N
S-K+
D
N2H4.H2O
N
H
anosyl-1-thio)-4-arylideneamino-5-aryl-1,2,4-triazoles 6a–6l. To
optimize the synthetic reaction condition for compounds 6a–6l,
we tested a mild inorganic base (KOH) and two kinds of organic
base (pyridine and triethylamine), potassium hydroxide proved
to be the most effective one, giving the desired compounds in bet-
ter yield and as the single product.
S
HCl
NH2
2a-2b
3a-3b
R
N NH
CHO
R1
S
N
N
R
N
N
R3
R2
SH
N
R 1
R 2
The structures of all newly synthesized compounds were char-
Reflux
NH2
R 3
4a-4l
acterized by IR, 1H NMR, 13C NMR, MS and HRMS studies.
Compounds 4-amino-1,2,4-triazole-3-thiones 3 may exist in
tautomeric equilibrium in solution, which enables two possible
configurations of the sulfide group as thione and thiol (Fig. 1), in
the present study, the thione structure was dominated in the solid
state. These constitutional isomers were distinguished by usual
spectroscopic methods of IR and 1H NMR. The appearance of a
C@S absorption peak in the region 1248–1260 cmÀ1 indicated that
the triazoles are in their thione form. The 1H NMR spectra of com-
pounds 3 (measured in DMSO-d6) exhibited the NH signals (NH
function of the triazoline ring) as a singlet at 13.86 ppm which also
supports the proposed thione structure18. A signal in the region
5.62 ppm, integrating to two protons, was assigned to NH2 protons.
The structures of compounds 4a–4l were confirmed on the basis
of both microanalysis and spectral data. These compounds exist in
the tautomeric forms in the solid state as indicated by their IR
spectra similarly as compounds 3. The 1H NMR spectra of these
compounds (measured in DMSO-d6) support the predominant
2,4-dihydrothione structure (NH signals of these compounds ap-
peared as a singlet at d 14.14–14.20, consistent with related re-
ported thione structures.18–20) Furthermore, their proton NMR
spectra lacked singlets characteristic of NH2 protons, and showed
new singlet characteristic for –N@CH– proton recorded in the
range of 9.14–9.96 ppm (integration for one proton) confirmed
the conversion of compounds 3 into 4-arylideneamino-5-aryl-
1,2,4-triazoles-3-thhone derivatives 4a–4l.
OAc
O
R
N N
AcO
AcO
SH
N
N
AcO
Br
5
R1
R2
KOH/H2O/CH3COCH3
R3
OAc
OAc
R
N N
O
S
N
N
A
OAc
AcO
R1
R2
B
R3
6a-6l
a:R=OH,R1=Cl,R2=H,R3=H; b:R=OH,R1=OH,R2=Br,R3=Br;
c:R=OH,R1=OH,R2=H,R3=Br d:R=OH,R1=H,R2=H,R3=H;
e:R=OH,R1=OH,R2=H,R3=H; f:R=OH,R1=OH,R2=H,R3=Cl;
g:R=H,R1=OH,R2=H,R3=H;
i:R=H,R1=Cl,R2=H,R3=H;
h:R=H,R1=H,R2=H,R3=H;
j:R=H,R1=OH,R2=Br,R3=Br;
k:R=H,R1=OH,R2=H,R3=Cl; l:R=H,R1=OH,R2=H,R3=Br;
Scheme 1. Synthetic pathway of compounds 6a–6l.
-
O
R
H
N
S-K+
O
H
R
S-K+
N
N
N
+H2N
H2N
NH2
H
The structures identification for compounds 6a–6l was based on
S
H
S
NH2
spectroscopic and chemical evidences. The S-b-D-configuration of
compounds 6a–6l is supported by their 1H NMR data, which re-
vealed the anomeric proton signal around d 5.4 with a coupling
constant value of 9.9–10.5 Hz consistent with the reported data
H
R
S-
N
HN
OH
HO
H
N
R
S-K+
S-K+
for S-b-D
glycosides.21 In the IR spectra, the disappearance of a
NH +
NH2
N
H
C@S absorption peak in the region 1252–1278 cmÀ1 also supports
the proposed structure. Meanwhile, four singlets in the region of d
1.91–2.13 were attributed to four acetyl groups.
HN
S
NH2
H
N
The in vitro minimum inhibitory and bactericidal concentra-
tions (MICs and MBCs) of compounds against Gram-positive,
Gram-negative bacteria as well as fungi were determined by the
method of National Committee for Clinical Laoratory (NCCLS).22
The in vitro minimal inhibitory concentration and bactericidal con-
centration values are summarized in Table 1. Fluconazole triclosan
and gentamicin were used as standard drugs.
HN
NH
HN
R
HO
-H +
S
HO
R
NH +
NH2
S
N
NH2
NH
N
R
MICs and MBCs of tested compounds showed that most of the
compounds displayed better antifungal activity than antibacterial
activity. However, it was revealed that all newly synthesized com-
pounds exhibited poor antibacterial activity compared to that of
the control drugs triclosan and gentamicin.
S
-H2O
N
NH2
Scheme 2. Representative postulated mechanism of ring closure reaction for
synthesis of compound 3.
The results obtained on Gram-negative bacteria showed that
compounds 6b (MIC = 16
l
g/mL, MBC = 16
lg/mL) and 6j
(MIC = 16 g/mL, MBC = 16
l
lg/mL) exhibited much higher activi-
one derivative 3 with appropriate aryl aldehydes heated under re-
ties than the other compounds,while compound 6g showed weak
flux in ethanol containing a few drops of hydrochloric acid as a
activity against Escherichia coli.

D. Ji et al. / Bioorg. Med. Chem. Lett. 23 (2013) 1997–2000
1999
Figure 1. Schematic representation of thione-thiol tautomerism of triazoles.
Table 1
In vitro antimicrobial activities for some synthetic compounds 6a–6l expressed as MIC and MBC (
l
g/mL)
Compd.
Gram-negative bacteria
Gram-positive bacteria
Staphylococcus aureus
Fungus
MIC
Escherichia coli
Monilia albican
MIC
MBC
MIC
MBC
MBC
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
128
16
128
128
64
128
—
128
128
16
128
16
128
256
64
256
—
128
128
16
128
32
64
128
128
128
64
64
128
16
64
32
128
32
32
16
16
32
64
16
32
32
64
16
16
16
2
64
32
16
32
64
32
64
64
64
16
32
16
4
128
256
128
128
128
64
128
32
128
32
128
128
128
2
128
128
128
4
Fluconazole
Triclosan
Gentamicin
16
4
2
32
4
2
32
4
64
4
2
4
MIC: minimum inhibitory concentration (the lowest concentration that inhibited the bacterial growth). MBC: minimum bactericidal concentration (the lowest concentration
at which no bacterial growth was observed).
—: Indicates the compound has no activity.
The results mentioned in Table 1 indicated that compounds 6b,
6j and 6i have shown a promising antibacterial activity against
Staphylococcus aureus with MIC values of 32, 16 and 32 lg/mL,
1,2,4-triazoles. All the compounds 6a–6l were tested for their
in vitro antibacterial activity against Staphylococcus aureus (ATCC
6538), Escherichia coli (ATCC 8099) and for their antifungal activity
against fungus Monilia albican (ATCC 10231). Most of the
synthesized compounds exhibited moderate to good activity to-
wards Gram positive and Gram negative bacteria as well as fungi
respectively.
The MICs of antifungal results revealed that compounds 6b, 6c,
6f, 6j, 6k and 6l showed excellent activity with MIC values of
16
l
g/mL than rest of the compounds.
species. Compounds 6b (MIC = 16
(MIC = 16 g/mL, MBC = 16 g/mL) appeared more effective
against Escherichia coli than the other compounds (MIC = 64–
128 g/mL). From structure–activity relationship, we can conclude
that glycosylation improved the biological activity of these com-
pounds against Gram negative bacteria. The introduction of halo-
gen atoms (–Br) into the pharmacophore structure increased the
antimicrobial activity. Introduction of –OH group at R1 on B ring
decreased in activity against Monilia albican.
lg/mL, MBC = 16 lg/mL) and 6j
From the in vitro antimicrobial activity data, preliminary struc-
l
l
ture–activity relationship of the synthesized compounds 6a–6l
was studied. The compounds 6a–6l exhibited good antibacterial
activity against bacteria Staphylococcus aureus, Escherichia coli
and antifungal activity against fungi Monilia albican. All the com-
pounds exhibited better antifungal activity than antibacterial
activity.
l
Meanwhile, the halogen substituents on the phenyl ring A as
well as B in compounds 6a–6l affected the antibacterial activity
to a certain extent. The presence of an electron-withdrawing sub-
stituent(R2 = R3 = Br) on the phenyl ring B is beneficial for antibac-
terial activity, such as compound 6j, which showed better activity
against Escherichia coli, and also registered higher inhibitory effect
against Staphylococcus aureus and Monilia albican than most of the
other compounds. To compare the antimicrobial activity of the
bromine and chlorine moiety on the phenyl ring, we find com-
Acknowledgment
We are grateful to the National Natural Science Foundation of
China (21176194, 20976135) for financial support.
Supplementary data
pound 6c (R3 = Br, MIC = 64
against Staphylococcus aureus than compound 6f (R3 = Cl,
MIC = 128
g/mL). While, the antifungi activity of 6e (R1 = OH,
MIC = 64
lg/mL) showed higher inhibitory effect
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2013.
02.038.
l
l
g/mL) and 6d (R1 = H, MIC = 32
lg/mL) indicate the
introduction of –OH group at R1 decrease the activity compared
References and notes
to non –OH group at R1.
In conclusion, in this study we described an efficient method for
the preparation of 3-S-b-D-glucosides-4-arylideneamino-5-aryl-
1. Turan-Zitouni, G.; Kaplancıklı, Z. A.; Yıldız, M. T.; Chevallet, P.; Kaya, D. Eur. J.
Med. Chem. 2005, 40, 607.

2000
D. Ji et al. / Bioorg. Med. Chem. Lett. 23 (2013) 1997–2000
2. Sumangala, V.; Boja Poojary; Chidananda, N.; Arulmoli, T. Eur. J. Med. Chem.
2012, 54, 59.
14. Mari, S. K.; Dasappa, J. P.; Boja, P.; K. Subrahmanya, B.; Bantwal, S. H.; Nalilu,
S. K. Bioorg. Med. Chem. 2006, 14, 7482.
3. Mavrova, A. T.; Wesselinova, D.; Tsenov, Y. A.; Denkova, P. Eur. J. Med. Chem.
2009, 44, 63.
15. Neeraj, U.; Sanjay, K.; Pawan, P.; Kamal, S.; Pradeep, M. Med. Chem. Res. 2012,
21, 1967.
4. Bakr F Abdel-Wahab; Ehab Abdel-Latif, H.A.M., Eur. J. Med. Chem. 2012, 52,
263.
16. Akhtar, T.; Hameed, S.; Khan, K. M.; Choudhary, M. I. Med. Chem. 2008, 4, 539.
17. Martos, M. B.; Körösy, F. Nature 1950, 165, 369.
5. Almasirad, A.; Tabatabai, S. A.; Faizi, M.; Kebriaeezadeh, A.; Mehrabi, N.;
Dalvandi, A. Bioorg. Med. Chem. Lett. 2004, 14, 6057.
6. Amir, M.; Shikha, K. Eur. J. Med. Chem. 2004, 39, 535.
7. Sztanke, M.; Tuzimski, T.; Rzymowska, J.; Pasternak, K.; Szerszen, M. K. Eur. J.
Med. Chem. 2008, 43, 404.
18. Ragenovic, K. C.; Dimova, V.; Kakurinov, V.; Molnar, D. G.; Buzarovska, A.
Molecules 2001, 6, 815.
19. Ergeuc, N.; Llhan, E.; Ötük, G. Pharmazie 1992, 47, 59.
20. Rollas, S.; Karakus, S.; Durgun, B. B.; Kiraz, M.; Erdeniz, H. Farmaco 1996, 51,
811.
8. Haber, J. Cas. Lek. Cesk. 2001, 140, 596.
9. Pallav, D. P.; Maulik, R. P.; Bela, K.; Erika, K., et al. Eur. J. Med. Chem. 2010, 45,
2214.
10. El Ashry, E. S. H.; Ahmed, A. K.; Atta, I. A., et al. Carbohydr. Res. 2009, 344, 725.
11. El Ashry, E. S. H.; Awad, L. F.; Atta, I. A. Tetrahedron 2006, 62, 2943.
12. Nasser, S. A. M. K. Carbohydr. Res. 2006, 341, 2187.
13. Przybylski, P.; Huczynski, A.; Pyta, K.; Brzezinski, B.; Bartl, F. Curr. Org. Chem.
2009, 13, 124.
21. Nasser, S. A. M. K. Carbohydr. Res. 2006, 341, 2187.
22. National Committee for Clinical Laboratory Standards, Methods for dilution
antimicrobial susceptibility tests for bacteria that grow aerobically, 5th ed.;
Approved standard M7–A5. National Committee for Clinical Laboratory
Standards: Wayne, Pa, Vol. 20, no. 2, 2000.