Synthesis, molecular docking and α-glucosidase inhibition of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylacetamides

Article abstract of DOI:10.1016/j.bmcl.2017.01.094

A novel series of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylacetamides 5a–5q have been synthesized and evaluated for their α-glucosidase inhibitory activity. All newly synthesized compounds exhibited potent α-glucosidase inhibitory activity in the range of IC₅₀?=?12.46?±?0.13–72.68?±?0.20?μM, when compared to the standard drug acarbose (IC₅₀?=?817.38?±?6.27?μM). Among the series, compound 5j (12.46?±?0.13?μM) with strong electron-withdrawing nitro group on the arylacetamide moiety was identified as the most potent inhibitor of α-glucosidase. Molecular docking study was carried out to explore the binding interactions of these compounds with α-glucosidase. Our study identifies a novel series of potent α-glucosidase inhibitors for further investigation.

Full text of DOI:10.1016/j.bmcl.2017.01.094

Bioorganic & Medicinal Chemistry Letters 27 (2017) 1115–1118
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis, molecular docking and a-glucosidase inhibition of
2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylacetamides
⇑
Guangcheng Wang , Xin Li, Jing Wang, Zhenzhen Xie, Luyao Li, Ming Chen, Shan Chen, Yaping Peng
College of Chemistry and Chemical Engineering, Hunan Engineering Laboratory for Analyse and Drugs Development of Ethnomedicine in Wuling Mountains, Jishou University,
Jishou 416000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylacetamides 5a–5q have been synthe-
Received 22 November 2016
Revised 16 January 2017
Accepted 30 January 2017
Available online 2 February 2017
sized and evaluated for their
ited potent -glucosidase inhibitory activity in the range of IC50 = 12.46 0.13–72.68 0.20
compared to the standard drug acarbose (IC50 = 817.38 6.27 M). Among the series, compound 5j
(12.46 0.13 M) with strong electron-withdrawing nitro group on the arylacetamide moiety was iden-
tified as the most potent inhibitor of -glucosidase. Molecular docking study was carried out to explore
the binding interactions of these compounds with -glucosidase. Our study identifies a novel series of
potent -glucosidase inhibitors for further investigation.
a
-glucosidase inhibitory activity. All newly synthesized compounds exhib-
a
l
M, when
l
l
a
Keywords:
1,2,4-Triazine
a
a
a-Glucosidase inhibitor
Ó 2017 Elsevier Ltd. All rights reserved.
Molecular docking
Diabetes mellitus (DM) is a group of metabolic diseases charac-
terized by chronic hyperglycemia that leads to long-term
macrovascular and microvascular complications.1,2 Hence, one of
the therapeutic approaches in treating diabetes is to reduce post-
prandial hyperglycemia by inhibiting major carbohydrate
azine moiety have been reported as potent inhibitors of
a
-glucosidase (Fig. 1).18–21
Hence, prompted by these observations and in continuation to
our interest in design and synthesis of novel heterocyclic
compounds,19–21 herein we report for the first time the synthesis
of a series of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylac-
etamides. All synthesized derivatives were tested for their
hydrolyzing enzymes.
a-Glucosidase is the key carbohydrate
hydrolyzing enzymes, located in the brush-border surface mem-
brane of human intestinal cells, which plays an important role in
in vitro
a-glucosidase inhibitory activity. Furthermore, in silico
the carbohydrate digestion.3 Therefore, the inhibition of
a
-glucosi-
molecular docking studies were performed to further investigate
dase is an effective approach in both preventing and treating dia-
the interactions of these compounds with the active site of
betes through controlling the postprandial glucose levels and
a
-glucosidase.
suppressing postprandial hyperglycemia.4 Some
a
-glucosidase
A series of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylac-
inhibitors like acarbose, voglibose, and miglitol, have been used
etamides (5a–5q) were synthesized according to the pathways
described in Scheme 1. 5,6-Diphenyl-1,2,4-triazine-3-thiol 2 was
prepared by condensation of benzil 1 with thiosemicarbazide
under reflux in acetic acid. The commercially available anilines
3a–3q was reacted with 2-chloroacetyl chloride in the presence
of Et3N as base at room temperature to give the corresponding
2-chloro-N-arylacetamides 4a–4q. Finally, condensation of 5,6-
diphenyl-1,2,4-triazine-3-thiol 2 with appropriate 2-chloro-N-ary-
lacetamides 4a–4q in the presence of Et3N in CH3OH to afford the
title compounds (5a–5q) in high yields (68.7–96.3%). The chemical
structures of the title compounds (5a–5q) were confirmed by 1H
NMR, 13C NMR and HRMS. For instance, the 1H NMR spectrum of
compound 5b shown a singlet at d 2.27 ppm was attributed to
the methyl group at the para position of the phenyl moiety. A
two-proton singlet at d 4.07 ppm was attributed to the methylene
protons of ASACH2ACOA. The two-proton double peak at d
in clinic for the treatment of type II diabetes mellitus.4 Thus, dis-
covery and development of new
a-glucosidase inhibitors has
attracted great attention in recent years.
1,2,4-Triazine is an important heterocyclic nucleus, which is
present in many naturally occurring products such as fervenulin,
toxoflavin, and reurhycin (Fig. 1).5 In the last few decades, the
chemistry of 1,2,4-triazines and their derivatives have received
considerable attention owing to their broad spectrum of biological
activities,6,7 including antifungal,8 anticonvulsant,9 anti-HIV,10
anticancer,11 antiinflammatory,12 neuroprotective,13 antiviral,14
antimalarial,15 cyclin-dependent kinase inhibitors,16 antimicro-
bial17 activities. Recently, several compounds containing 1,2,4-tri-
⇑
Corresponding author.
E-mail address: wanggch123@163.com (G. Wang).
http://dx.doi.org/10.1016/j.bmcl.2017.01.094
0960-894X/Ó 2017 Elsevier Ltd. All rights reserved.

1116
G. Wang et al. / Bioorganic & Medicinal Chemistry Letters 27 (2017) 1115–1118
Fig. 1. Chemical structures of some 1,2,4-triazine natural products and a-glucosidase inhibitors containing 1,2,4-triazine moiety.
Scheme 1. Reagents and conditions: (a) thiosemicarbazide, AcOH, reflux, 3 h; (b) 2-chloroacetyl chloride, Et3N, CH2Cl2, room temperature, 24 h; (c) Et3N, CH3OH, room
temperature, 2 h.
7.04 ppm (J = 7.6 Hz) was attributed to CH protons of the phenylac-
etamide. The ten aromatic protons of 5,6-diphenyl-1,2,4-triazine
and two aromatic protons of phenylacetamide were appeared as
multiplet in the region of d 7.29–7.46 ppm and d 7.51–7.56 ppm.
The proton of ANHACOA were appeared at 9.04 as a singlet signal.
The above analysis clearly confirmed that the 1H NMR spectrum of
the synthesized compound 5b was in agreement with the designed
structure. Moreover, in 13C NMR spectrum of compound 5b, the
number of signals equals the number of different carbons in the
molecule.
enzyme interactions, the 3D structure of a-glucosidase was built
by homology modeling methods using modeller 9.15 homology
modeling software (http://salilab.org/modeller/). The protein
sequence of
a-glucosidase in FASTA format was retrieved from
Uniprot (Uniprot id: P53341). The crystallographic structure of Sac-
charomyces cerevisiae isomaltase (PDB ID: 3AJ7, Resolution 1.30 Å)
with 72.4% of sequence identity with the target was selected as the
template for homology modeling.24 The quality of homology model
All newly synthesized compounds 5a–5q were evaluated for
Table 1
their in vitro
shown that all compounds exhibited potent
inhibitory activity in the range of IC50 = 12.46 0.13–
72.68 0.20 M, when compared to the standard drug acarbose
(IC50 = 817.38 6.27
M22,23) (Table 1). Among all the tested mole-
cules, compound 5i (14.09 0.14 M), 5j (12.46 0.13 M) and 5n
(15.99 0.18 M) displayed outstanding inhibitory activity than
the standard drug acarbose. Compounds 5k, 5l, 5m, 5o and 5p also
displayed potent -glucosidase inhibitory activity with IC50 values
of 36.79 0.15, 28.03 0.18, 26.27 0.23, 34.94 0.19,
a-glucosidase inhibitory activity. The results were
a-Glucosidase inhibitory activity and binding energies of 2-((5,6-diphenyl-1,2,4-
triazin-3-yl)thio)-N-arylacetamides (5a–5q).
a
-glucosidase
l
l
l
l
l
a
Compound
R
IC50
(
l
M)a
Binding energy (kcal/mol)
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
5q
Acarbose
H
4-Me
3-Me
2-Me
2,4-Me2
2-NO2-4-Me
2-NO2-4-MeO
4-F
71.09 0.22
52.01 0.19
42.54 0.21
72.68 0.20
67.24 0.24
45.65 0.17
46.98 0.19
50.63 0.21
14.09 0.14
12.46 0.13
36.79 0.15
28.03 0.18
26.27 0.23
15.99 0.18
34.94 0.19
25.25 0.20
49.44 0.19
817.38 6.27
À8.5
À8.9
À9.1
À8.3
À9.2
À9.0
À9.2
À8.8
À10.3
À10.7
À9.6
À9.2
À9.5
À10.2
À9.4
À9.8
À9.0
À6.8
25.25 0.20, respectively. Furthermore, all other tested com-
pounds shown moderate inhibitory activity with IC50 value of
71.09 0.22, 52.01 0.19, 42.54 0.21, 72.68 0.20, 67.24 0.24,
45.65 0.17, 46.98 0.19, 50.63 0.21 and 49.44 0.19
respectively.
lM,
Among the series, compound 5j (12.46 0.13
electron-withdrawing nitro group on the arylacetamide moiety
was identified as the most potent inhibitor of -glucosidase. Addi-
tionally, 5i (14.09 0.14 M) with para-chloro substitution on the
lM) with strong
4-Cl
a
4-NO2
2,4-Cl2
2,5-Cl2
4-EtO
2-EtO
3-CF3
l
phenyl ring, was found to be the second most active compound. In
summary, it was observed that the difference of substitution on the
arylacetamide ring greatly influence the inhibitory activity of this
class of compounds. In order to verify these observations, molecu-
lar docking study was performed.
4-PhO
4-MeO
The X-ray crystal structure of Saccharomyces cerevisiae
a-glu-
a
cosidase has never been reported. To understand the ligand-
Acarbose is standard for a-glucosidase inhibition activity.

G. Wang et al. / Bioorganic & Medicinal Chemistry Letters 27 (2017) 1115–1118
1117
was verified by PROCHECK (http://services.mbi.ucla.edu/PRO-
CHECK/). The result was shown that the model could be used to
study the interactions between this class of compounds and the
CH-p interactions with the residues Tyr-71 and Phe-157. It was
shown that the Glu-276 (bond length: 3.3 Å) formed a hydrogen
bond with 5a, which was the main interaction between 5a and
active site of
a
-glucosidase.21
a
-glucosidase. On the other hand, molecular docking study of the
standard drug acarbose with -glucosidase was also performed
(Fig. 2B). Acarbose adopted a U-shaped conformation in the pocket
of the -glucosidase. The results were shown that compound 5a
To investigate the binding mode of these compounds with
a
-
a
glucosidase, molecular docking study was carried out by using
Autodock VINA 1.1.2.25 The theoretical binding mode between 5a
a
and Saccharomyces cerevisiae
Compound 5a adopted a F-shaped conformation in the pocket of
the -glucosidase. One of the o-diphenyl group of 5a bind at the
bottom of the -glucosidase pocket and made a high density of
van der Waals contacts, whereas the phenylamino group of 5a
was positioned near the entrance of the pocket and made only a
few contacts. Detailed analysis showed that o-diphenyl group of
5a formed arene-cation interaction with the residue Arg-312, and
a
-glucosidase was shown in Fig. 2A.
(binding energy was about À8.5 kcal molÀ1 and a hydrogen bond
with Glu-276) has similar binding affinity as compared to standard
drug acarbose (binding energy was about À6.8 kcal molÀ1 and
three hydrogen bonds with Asp-68, Gln-181 and Asp-349).
In order to increase the activity of 5a, a nitro group was intro-
duced to 4-position of the phenylamino group of 5a to obtain 5j.
Compound 5j was docked to the binding pocket of the Saccha-
a
a
romyces cerevisiae a-glucosidase, and the theoretical binding mode
Fig. 2. Compound 5a (A) and acarbose (B) were docked to the binding pocket of the Saccharomyces cerevisiae a-glucosidase.
Fig. 3. (A) Compound 5j was docked to the binding pocket of the Saccharomyces cerevisiae
Saccharomyces cerevisiae -glucosidase (overlapped).
a-glucosidase. (B) Compounds 5a and 5j were docked to the binding pocket of the
a

1118
G. Wang et al. / Bioorganic & Medicinal Chemistry Letters 27 (2017) 1115–1118
Fig. 4. (A) Compounds 5h and 5i were docked to the binding pocket of the Saccharomyces cerevisiae a-glucosidase (overlapped). (B) Compounds 5m and 5n were docked to
the binding pocket of the Saccharomyces cerevisiae
a-glucosidase (overlapped).
between 5j and Saccharomyces cerevisiae
a-glucosidase was shown
Acknowledgments
in Fig. 3A. The interaction between 5j and
a
-glucosidase was nearly
the same as the precursor 5a. The only difference was that the
introduced nitro group formed a hydrogen bond with the residue
Arg-312, with the length of 3.5 Å, which made 5j was more active
This work was supported by National Natural Science Founda-
tion of China (81660574), Hunan Provincial Natural Science Foun-
dation of China (2015JJ3099) and Scientific Research Fund of
Hunan Provincial Education Department (15B194).
than 5a against
To explain the activity order of 5h, 5i, 5m and 5n against
cosidase, these compounds were docked into the binding site of
a-glucosidase (Fig. 3B).
a
-glu-
a
-
A. Supplementary material
glucosidase. The theoretical binding modes of 5h, 5i, 5m and 5n
were nearly the same as 5a (Fig. 4). The only difference between
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2017.01.
094.
5h and 5i was that the chlorine atom of 5i formed a Cl-
p interac-
tion with residue His-239, which made 5i was more active than
5h against a-glucosidase (Fig. 4A). The estimated binding energies
were À8.8 kcal molÀ1 for 5h and À10.3 kcal molÀ1 for 5i, respec-
tively, which was consistent with the results of the in vitro anti-
References
1. Lopez-Candales A. J Med (Westbury). 2001;32:283.
a
-glucosidase assay (Table 1). In addition, the difference between
2. Deshpande AD, Harris-Hayes M, Schootman M. Phys Ther. 2008;88:1254.
3. Hirsh AJ, Yao SYM, Young JD, Cheeseman CI. Gastroenterology. 1997;113:205.
4. Joshi SR, Standl E, Tong N, Shah P, Kalra S, Rathod R. Expert Opin Pharmacother.
2015;16:1959.
5. Yoneda F, Nagamatsu T. Tetrahedron Lett. 1973;14:1577.
6. Kumar R, Sirohi TS, Singh H, et al. Mini-Rev Med Chem. 2014;14:168.
7. Arshad M, Khan TA, Khan MA. Int J Pharm Sci Res. 2014;5:149.
8. Sangshetti JN, Shinde DB. Bioorg Med Chem Lett. 2010;20:742.
9. Ahuja P, Siddiqui N. Eur J Med Chem. 2014;80:509.
5m and 5n was that the C@O group of 5n formed an extra hydro-
gen bond with the residue His-279, with the length of 2.3 Å, which
made 5n was more active than 5m against a-glucosidase (Fig. 4B).
The estimated binding energies were À9.5 kcal molÀ1 for 5m and
À10.2 kcal molÀ1 for 5n, respectively, which was consistent with
the results of the in vitro a-glucosidase inhibitory activity (Table 1).
In summary, the above molecular simulations give us rational
explanation of the interactions between this class of compounds
and
10. Zhan P, Li X, Li Z, et al. Bioorg Med Chem Lett. 2012;22:7155.
11. Krauth F, Dahse H-M, Ruettinger H-H, Frohberg P. Bioorg Med Chem.
2010;18:1816.
a-glucosidase, which provided valuable information for fur-
12. Irannejad H, Kebriaieezadeh A, Zarghi A, et al. Bioorg Med Chem. 2014;22:865.
13. Irannejad H, Amini M, Khodagholi F, et al. Bioorg Med Chem. 2010;18:4224.
14. Rusinov VL, Egorov IN, Chupakhin ON, Belanov EF, Bormotov NI, Serova OA.
Pharm Chem J. 2012;45:655.
ther development of
A novel series of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-
arylacetamides 5a–5q have been synthesized and evaluated for
a
-glucosidase inhibitors.
15. Ban K, Duffy S, Khakham Y, et al. Bioorg Med Chem Lett. 2010;20:6024.
16. Popowycz F, Fournet G, Schneider C, et al. J Med Chem. 2009;52:655.
17. Abd El-Moneim M, Hasanen JA, El-Deen IM, Abd El-Fattah W. Res Chem
Intermed. 2015;41:3543.
18. Rahim F, Ullah K, Ullah H, et al. Bioorg Chem. 2015;58:81.
19. Wang G, Wang J, He D, Li X, Li J, Peng Z. Bioorg Med Chem Lett. 2016;26:2806.
20. Wang G, Wang J, He D, Li X, Li J, Peng Z. Heterocycles. 2016;92:1430.
21. Wang G, Peng Z, Wang J, Li X, Li J. Eur J Med Chem. 2017;125:423.
22. Rahim F, Malik F, Ullah H, et al. Bioorg Chem. 2015;60:42.
23. Niaz H, Kashtoh H, Khan JAJ, et al. Eur J Med Chem. 2015;95:199.
24. Yamamoto K, Miyake H, Kusunoki M, Osaki S. FEBS J. 2010;277:4205.
25. Trott O, Olson AJ. J Comput Chem. 2010;31:455.
their
pounds exhibited potent
range of IC50 = 12.46 0.13–72.68 0.20
the standard drug acarbose (IC50 = 817.38 6.27
docking study was performed to understand the interaction pat-
tern of these compounds at the binding site of -glucosidase
enzyme. Hence, this study identified compound 5j could be used
a
-glucosidase inhibitory activity. All newly synthesized com-
-glucosidase inhibitory activity in the
M, when compared to
M). Molecular
a
l
l
a
as lead molecules for further research to discover more potent
glucosidase inhibitors.
a-