Synthesis, biological evaluation, and docking studies of novel 5,6-diaryl-1,2,4-triazine thiazole derivatives as a new class of α-glucosidase inhibitors

Article abstract of DOI:10.1016/j.bioorg.2018.03.015

A novel 5,6-diaryl-1,2,4-triazine thiazole derivatives (7a-7q) were synthesized and characterized by ¹H NMR and ¹³C NMR and evaluated for their α-glucosidase inhibitory activity. All tested compounds displayed good α-glucosidase inhibitory activity with IC₅₀ values ranging between 2.85 ± 0.13 and 14.19 ± 0.23 μM when compared to the standard drug acarbose (IC₅₀ = 817.38 ± 6.27 μM). Compound 7i (IC₅₀ = 2.85 ± 0.13 μM) exhibited the highest activity among this series of compounds. Molecular docking studies were carried out in order to investigate the binding mode of this class of compounds to α-glucosidase. This study showed that these 5,6-diaryl-1,2,4-triazine thiazole derivatives are a new class of α-glucosidase inhibitors.

Full text of DOI:10.1016/j.bioorg.2018.03.015

Accepted Manuscript
Synthesis, biological evaluation, and docking studies of novel 5,6-diaryl-1,2,4-
triazine thiazole derivatives as a new class of α-glucosidase inhibitors
Guangcheng Wang, Zhiyun Peng, Zipeng Gong, Yongjun Li
PII:
S0045-2068(18)30035-X
https://doi.org/10.1016/j.bioorg.2018.03.015
YBIOO 2305
DOI:
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
14 January 2018
8 March 2018
18 March 2018
Please cite this article as: G. Wang, Z. Peng, Z. Gong, Y. Li, Synthesis, biological evaluation, and docking studies
of novel 5,6-diaryl-1,2,4-triazine thiazole derivatives as a new class of α-glucosidase inhibitors, Bioorganic
Chemistry (2018), doi: https://doi.org/10.1016/j.bioorg.2018.03.015
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Synthesis, biological evaluation, and docking studies
of novel 5,6-diaryl-1,2,4-triazine thiazole derivatives
as a new class of α-glucosidase inhibitors
a,b,c
a,b,c
a,c
b,c,*
Guangcheng Wang , Zhiyun Peng , Zipeng Gong , Yongjun Li
a
Guizhou Provincial Key Laboratory of Pharmaceutics, State Key Laboratory of
Functions and Applications of Medicinal Plants, Guizhou Medical University,
Guiyang 550004, China
b
Guizhou Provincial Engineering Research Center for the Development and
Application of Ethnic Medicine and TCM, Guizhou Medical University, Guiyang
5
50004, China
c
School of Pharmacy, Guizhou Medical University, Guiyang 550004, China
*
Corresponding Author
Tel.: +86 851 86908468
Fax: +86 851 86908468
E-mail address: liyongjun_gmu@163.com; liyongjun026@126.com
1

Abstract.
A novel 5,6-diaryl-1,2,4-triazine thiazole derivatives (7a-7q) were synthesized and
1
13
characterized by H NMR and C NMR and evaluated for their α-glucosidase
inhibitory activity. All tested compounds displayed good α-glucosidase inhibitory
activity with IC50 values ranging between 2.85±0.13 and 14.19±0.23 μM when
compared to the standard drug acarbose (IC50 = 817.38±6.27 μM). Compound 7i (IC50
=
2.85±0.13 μM) exhibited the highest activity among this series of compounds.
Molecular docking studies were carried out in order to investigate the binding mode
of this class of compounds to α-glucosidase. This study showed that these
5
,6-diaryl-1,2,4-triazine thiazole derivatives are a new class of α-glucosidase
inhibitors.
Keywords: Triazine; Thiazole; α-Glucosidase; Molecular docking
2

1
. Introduction.
Diabetes mellitus is recognized as a serious global health problem that is
characterized by high blood glucose levels. α-Glucosidase is
a
carbohydrate-hydrolyzing enzyme which located in the epithelium of the human small
intestine. The inhibition of α-glucosidase activity may retard the digestion of
carbohydrates and thereby reducing the amount of glucose absorbed into the
bloodstream [1]. Thus, α-glucosidase has been considered to be a prominent target in
the management of non-insulin-dependent diabetes mellitus [2] and a number of
α-glucosidase inhibitors (acarbose, voglibose, and miglitol) have been used in the
clinic for many years [3]. However, the clinical use of these compounds was always
limited by high cost and side effects [4]. Therefore, it is very important to discover
new α-glucosidase inhibitors with minor side effects.
1
,2,4-Triazine is a prominent structural core system present in numerous natural and
synthetic biologically active compounds [5, 6]. Many compounds bearing a
,2,4-triazine moiety have been reported in the literature with a variety of
1
pharmacological activities, including anticancer, [7] anticonvulsant, [8]
anti-inflammatory, [9] neuroprotective, [10] anti-HIV, [11] antifungal, [12] antiviral,
[
13] and antimalarial activity [14]. In particular, our previous studies revealed that
,2,4-triazine ring could be used as a useful moiety in the design of new α-glucosidase
1
inhibitors [15-18]. Some of the representative α-glucosidase inhibitors bearing
quinoline moiety as shown in Fig. 1. On the other hand, thiazole derivatives have
3

been reported as anticancer [19], anticonvulsant, [20] antibacterial, [21] and
antidiabetic activity [22]. In recent years, some of the thiazole derivatives have been
reported in the literature to show α-glucosidase inhibitory activity (Fig. 1) [23-25].
Figure 1. Chemical structures of some reported α-glucosidase inhibitors having
1
,2,4-triazine (Blue color) or thiazole (Red color) moiety.
Recently, a novel series of 2-((5,6-diphenyl-1,2,4-triazin-3- yl)thio)-N-arylacetamides
have been synthesized and evaluated for their α-glucosidase inhibitory activity [15]
and compound I was identified as a potent α-glucosidase inhibitor with IC50 value of
1
2.46 ± 0.13 μM (Fig. 2). In addition, Sravanthi et al [22] reported the synthesis of a
series of novel substituted pyrazoles containing indole and thiazole motifs and the
most active compound II shown better antihyperglycemic activity than the standard
drug acarbose (Fig. 2). In the continuous effort to discover new α-glucosidase
inhibitors [17, 26-29], a new series of 5,6-diaryl-1,2,4-triazine thiazole derivatives
were designed and synthesized based on the lead compound I and II (Fig. 2). All the
synthesized compounds were evaluated for their α-glucosidase inhibitory activity.
4

Figure 2. Rational design for the synthesis of novel 5,6-diaryl-1,2,4-triazine thiazole
derivatives
2
. Results and discussion
2
.1. Chemistry.
A general synthesis of 5,6-diaryl-1,2,4-triazine thiazole derivatives (7a-7q) is
exhibited in Scheme 1. Condensation of substituted benzyl (1) with thiosemicarbazide
in reflux acetic acid afforded the corresponding 5,6-diaryl-1,2,4-triazine-3-thiols (2).
The methyl group of commercially available acetophenones (3) were brominated with
NBS in the presence of p-toluenesulfonic acid to give α-bromoacetophenones (4),
which were then reacted with thiourea in ethanol to give 4-arylthiazol-2-amines (5).
The reaction of (5) with 2-chloroacetyl chloride to obtain the intermediates (6).
Finally, 5,6-diaryl-1,2,4-triazine thiazole derivatives (7a-7q) were achieved by
condensation of (6) with (5) at ambient temperature in the presence of triethylamine
as base and methanol as solvent. The structure of synthesized compounds
5

1
13
was characterized by H NMR and C NMR. Moreover, all the title compounds
(
7a-7q) have not yet been reported in the literature.
Scheme 1. (a) AcOH, reflux, 3 h; (b) p-MeC
6
H
4
SO
3
H, NBS, CH
N, CH Cl
3
CN, reflux, 2 h; (c)
thiourea, EtOH, reflux; (d) 2-chloroacetyl chloride, Et
3
2
2
, room temperature,
2
2
2
4 h; (e) Et
3
N, CH OH, room temperature, 2 h.
3
.2. Biological activity
.2.1. α-Glucosidase Inhibition Assay
Newly synthesized 5,6-diaryl-1,2,4-triazine thiazole derivatives (7a-7q) were
evaluated for their α-glucosidase inhibitory activity. The α-glucosidase inhibition
6

assay had been carried out using baker’s yeast α-glucosidase enzyme. The result in
Table 1 showed that compounds (7a-7q) displayed a variable degree of α-glucosidase
inhibitory activity with IC50 values ranging between 2.85±0.13 and 14.19±0.23 μM,
when compared to the standard drug acarbose (IC50 = 817.38±6.27 μM). Compound
7
i (IC50 = 2.85±0.13 μM) having Br at R
1
and CH
3
O at R showed the highest activity
2
among this series of compounds (7a-7q). Compared the inhibitory activity of (7a-7f)
with (7g-7q), the result was shown that the introduction of the electron-withdrawing
group (F or Br) at R
was observed that by changing substituents at R
activity of compounds. However, the introduction of various substituents at R
resulted in a slight increase or decrease of the biological activity, which indicated that
the substituents at R are not important for activity.
1
, results in the increase the inhibitory activity. From this study, it
1
greatly influence the biological
2
2
Table 1. α-Glucosidase inhibitory activity of novel 5,6-diaryl-1,2,4-triazine thiazole
derivatives (7a-7q)
Compounds
R
1
R
2
IC50 (μM)
14.19±0.23
11.81±0.19
7.37±0.24
10.0±0.22
8.35±0.18
7.24±0.21
7
7
a
H
H
H
H
H
H
H
b
CH
3
7
c
CH
3
O
7
d
F
7
e
Cl
Br
7
f
7

7
7
g
Br
Br
Br
Br
Br
F
H
4.61±0.17
3.72±0.15
2.85±0.13
2.97±0.12
3.42±0.14
10.08±0.23
6.70±0.18
9.15±0.21
7.14±0.18
4.58±0.14
3.17±0.11
817.38±6.27
h
CH
3
7
i
CH
3
Cl
Br
H
O
7
j
7
k
7
l
7
m
F
CH
3
7
n
o
p
q
F
F
7
F
Cl
Br
F
7
7
F
Br
Acarbose
.2.2. Molecular docking study
2
Molecular docking was performed to investigate the binding mode of this class of
compounds to α-glucosidase using software Autodock VINA 1.1.2 [30]. Since the 3D
structure of α-glucosidase is still unavailable, the homology model was built based on
the known crystal structures of the Saccharomyces cerevisiae isomaltase (PDB ID:
3
AJ7) as described in our previous report [17]. The theoretical binding mode between
7
i and Saccharomyces cerevisiae α-glucosidase was shown in Fig. 3. Compound 7i
adopted a “U-shaped” conformation in the pocket of the α-glucosidase. The
substituted phenyl groups of 7i were located at the hydrophobic pocket, surrounded
8

by the residues Phe-157, Phe-177, Leu-218, Pro-240, and Ala-278, forming a stable
hydrophobic binding. Detailed analysis showed that the 4-methoxyphenyl group of 7i
formed π-π stacking and CH-π interactions with the residues His-239 and Phe-157,
respectively. Moreover, one of the 4-bromophenyl group of 7i formed π-π stacking
interactions with the residues Tyr-71 and Phe-177, respectively, while the other
4
-bromophenyl group formed CH-π interaction with the residue Phe-300. In addition,
one of the 4-bromophenyl group of 7i formed the cation-π interaction with the residue
Arg-439 and formed anion-π interactions with the residues Asp-68, Asp-214, Glu-276,
and Asp-349, respectively. It was shown that the residue Asp-349 (bond length: 3.2 Å)
formed a hydrogen bond with 7i, which was the main interaction between 7i and
α-glucosidase. All these interactions helped 7i to anchor in the binding site of the
α-glucosidase. These results confirmed the interaction between 7i and the active site
of α-glucosidase.
9

Figure 3. The binding mode of compound 7i docked with α-glucosidase.
. Conclusion.
3
A novel series of 5,6-diaryl-1,2,4-triazine thiazole derivatives (7a-7q) have been
synthesized and evaluated for their α-glucosidase inhibitory activity. All tested
compounds displayed good α-glucosidase inhibitory activity. Among the series,
compound 7i was found to be the most potent α-glucosidase inhibitor with IC50 value
of 2.85±0.13 μM, as compared to standard acarbose (IC50 = 817.38±6.27 μM).
Consequently, molecular docking study confirmed the interaction between 7i and the
active site of α-glucosidase.
4
. Experimental section.
4
.1. Chemistry
10

All starting materials and reagents were purchased from commercial suppliers. TLC
was performed on 0.20 mm Silica Gel 60 F254 plates (Qingdao Ocean Chemical
Factory, Shandong, China). Nuclear magnetic resonance spectra (NMR) were
recorded on a Bruker spectrometer (400 MHz) with TMS as an external reference and
reported in parts per million.
4
.1.1. General produce for the synthesis of novel 5,6-diaryl-1,2,4-triazine thiazole
derivatives (7a-7q)
A mixture of (2) (1 mmol), (6) (1 mmol) and Et N (2 mmol) in methanol (10 mL) was
3
stirred at room temperature for 2 h. After the completion of the reaction (monitored by
TLC), the mixture was poured into 50 mL of water and extracted with 50 mL of ethyl
acetate for three times. The combined organic layers were dried (Na
and evaporated. The residue was purified by chromatography to give the title product
7a-7q).
.1.2.
7a)
2
SO4), filtered
(
4
2-((5,6-Diphenyl-1,2,4-triazin-3-yl)thio)-N-(4-phenylthiazol-2-yl)acetamide
(
1
Yellow solid (58 %); H NMR (d
6
-DMSO, 400 MHz) δ: 4.40 (s, 2H), 7.14-7.24 (m,
3
H), 7.34-7.47 (m, 10H), 7.64 (s, 1H), 7.91 (d, 2H, J = 7.6 Hz), 12.68 (s, 1H, NH);
1
3
C NMR (d -DMSO, 100 MHz) δ: 34.6, 108.7, 126.1, 128.3, 128.7, 128.9, 129.2,
6
1
1
4
29.3, 129.7, 129.8, 130.1, 131.2, 134.8, 135.3, 135.6, 149.5, 154.7, 156.0, 158.3,
67.0, 169.7.
.1.3. 2-((5,6-Diphenyl-1,2,4-triazin-3-yl)thio)-N-(4-(p-tolyl)thiazol-2-yl)acetamide
11

(7b)
1
Yellow solid (63 %); H NMR (d
6
-DMSO, 400 MHz) δ: 2.33 (s, 3H), 4.39 (s, 2H),
7
7
3
1
4
2
.19 (t, 2H, J = 8.0 Hz), 7.24 (d, 2H, J = 8.0 Hz), 7.33-7.45 (m, 8H), 7.56 (s, 1H),
1
3
.79 (d, 2H, J = 8.4 Hz), 12.64 (s, 1H, NH); C NMR (d -DMSO, 100 MHz) δ: 21.3,
6
4.6, 101.0, 107.8, 125.9, 126.1, 128.7, 128.9, 129.4, 129.7, 129.8, 130.1, 131.2,
35.2, 135.6, 137.6, 149.5, 154.7, 156.0, 158.2, 166.9, 169.8.
.1.4.
-((5,6-Diphenyl-1,2,4-triazin-3-yl)thio)-N-(4-(4-methoxyphenyl)thiazol-2-yl)acetami
de (7c)
Yellow solid (67 %); H NMR (d
1
6
-DMSO, 400 MHz) δ: 3.79 (s, 3H), 4.39 (s, 2H),
6
7
5
1
4
2
.99 (d, 2H, J = 8.8 Hz), 7.20 (t, 2H, J = 8.0 Hz), 7.33-7.45 (m, 8H), 7.47 (s, 1H),
1
3
.83 (d, 2H, J = 8.8 Hz), 12.63 (s, 1H, NH); C NMR (d -DMSO, 100 MHz) δ: 34.6,
6
5.6, 106.6, 114.6, 127.5, 127.6, 128.7, 128.9, 129.7, 129.8, 130.1, 131.2, 135.3,
35.6, 149.4, 154.7, 156.0, 158.2, 159.5, 166.9, 169.8.
.1.5.
-((5,6-Diphenyl-1,2,4-triazin-3-yl)thio)-N-(4-(4-fluorophenyl)thiazol-2-yl)acetamide
(7d)
1
Yellow solid (59 %); H NMR (d
6
-DMSO, 400 MHz) δ: 4.40 (s, 2H), 7.20 (t, 2H, J =
8
1
2
.0 Hz), 7.28 (t, 2H, J = 8.4 Hz), 7.33-7.44 (m, 8H), 7.62 (s, 1H), 7.93-7.97 (m, 2H),
1
3
2.68 (s, 1H, NH); C NMR (d
6
-DMSO, 100 MHz) δ: 34.6, 108.4, 116.0 (d, 2C, J =
1.4 Hz), 128.1 (d, 2C, J = 8.0 Hz), 128.7, 128.9, 129.7, 129.8, 130.1, 131.2, 131.4 (d,
12

1
1
4
C, J = 3.0 Hz), 135.2, 135.6, 148.4, 154.7, 156.0, 158.4, 161.1 (d, 1C, J = 243.4 Hz),
67.0, 167.7.
.1.6.
N-(4-(4-Chlorophenyl)thiazol-2-yl)-2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)acetamide
7e)
Yellow solid (72 %); H NMR (d
.0 Hz), 7.35-7.45 (m, 8H), 7.50 (d, 2H, J = 8.8 Hz), 7.71 (s, 1H), 7.92 (d, 2H, J = 8.4
(
1
6
-DMSO, 400 MHz) δ: 4.40 (s, 2H), 7.19 (t, 2H, J =
8
1
3
Hz), 12.70 (s, 1H, NH); C NMR (d
6
-DMSO, 100 MHz) δ: 34.6, 109.4, 127.9, 128.7,
1
1
4
28.9, 129.3, 129.7, 129.8, 130.1, 131.2, 132.8, 133.6, 135.2, 135.6, 148.2, 154.7,
56.0, 158.5, 167.1, 169.7.
.1.7.
N-(4-(4-Bromophenyl)thiazol-2-yl)-2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)acetamide
7f)
Yellow solid (51 %); H NMR (d
.0 Hz), 7.33-7.44 (m, 8H), 7.63 (d, 2H, J = 8.8 Hz), 7.72 (s, 1H), 7.85 (d, 2H, J = 8.8
(
1
6
-DMSO, 400 MHz) δ: 4.40 (s, 2H), 7.19 (t, 2H, J =
8
1
3
Hz), 12.70 (s, 1H, NH); C NMR (d
6
-DMSO, 100 MHz) δ: 34.6, 109.5, 121.4, 128.2,
1
1
4
2
28.7, 128.9, 129.7, 129.8, 130.1, 131.2, 134.0, 135.2, 135.6, 148.2, 154.7, 156.1,
58.5, 167.1, 169.7.
.1.8.
-((5,6-Bis(4-bromophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-phenylthiazol-2-yl)acetamid
e (7g)
13

1
Yellow solid (49 %); H NMR (d
6
-DMSO, 400 MHz) δ: 4.38 (s, 2H), 7.32-7.35 (m,
3
H), 7.39-7.46 (m, 6H), 7.59 (d, 2H, J = 8.8 Hz), 7.63 (s, 1H), 7.91 (d, 2H, J = 7.6
1
3
Hz), 12.68 (s, 1H, NH); C NMR (d
6
-DMSO, 100 MHz) δ: 34.6, 108.7, 123.7, 125.2,
1
1
4
2
26.2, 128.3, 129.2, 131.8, 131.9, 132.0, 132.2, 134.3, 134.6, 134.7, 149.5, 153.7,
55.3, 158.3, 167.0, 170.1.
.1.9.
-((5,6-Bis(4-bromophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(p-tolyl)thiazol-2-yl)acetami
de (7h)
Yellow solid (68 %); H NMR (d
1
6
-DMSO, 400 MHz) δ: 2.33 (s, 3H), 4.37 (s, 2H),
7
1
.24 (d, 2H, J = 8.0 Hz), 7.32 (d, 2H, J = 8.8 Hz), 7.41 (t, 4H, J = 8.4 Hz), 7.55 (s,
13
H), 7.60 (d, 2H, J = 8.4 Hz), 7.79 (d, 2H, J = 8.4 Hz), 12.65 (s, 1H, NH); C NMR
(
d
6
-DMSO, 100 MHz) δ: 21.3, 34.6, 107.8, 123.7, 125.2, 126.1, 129.8, 131.8, 131.9,
1
4
2
32.0, 132.1, 132.2, 134.3, 134.6, 137.6, 149.6, 153.7, 155.3, 158.2, 166.9, 170.1.
.1.10.
-((5,6-Bis(4-bromophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(4-methoxyphenyl)thiazol-2-
yl)acetamide (7i)
Yellow solid (55 %); H NMR (d
1
6
-DMSO, 400 MHz) δ: 3.79 (s, 3H), 4.37 (s, 2H),
6
1
.99 (d, 2H, J = 8.8 Hz), 7.32 (d, 2H, J = 8.4 Hz), 7.41 (t, 4H, J = 8.4 Hz), 7.46 (s,
13
H), 7.60 (d, 2H, J = 8.8 Hz), 7.83 (d, 2H, J = 8.8 Hz), 12.63 (s, 1H, NH); C NMR
-DMSO, 100 MHz) δ: 34.6, 55.6, 106.7, 114.6, 123.7, 125.2, 127.5, 127.6, 131.8,
31.9, 132.0, 132.2, 134.3, 134.6, 149.4, 153.7, 155.3, 158.2, 159.5, 166.9, 170.1.
(
d
6
1
14

4
2
.1.11.
-((5,6-Bis(4-bromophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(4-chlorophenyl)thiazol-2-yl
)
acetamide (7j)
1
Yellow solid (60 %); H NMR (d
6
-DMSO, 400 MHz) δ: 4.38 (s, 2H), 7.31 (d, 2H, J =
8
1
3
1
4
2
.4 Hz), 7.39-7.42 (m, 4H), 7.49 (d, 2H, J = 8.4 Hz), 7.60 (d, 2H, J = 8.4 Hz), 7.69 (s,
1
3
H), 7.92 (d, 2H, J = 8.8 Hz), 12.69 (s, 1H, NH); C NMR (d -DMSO, 100 MHz) δ:
6
4.6, 109.4, 123.7, 125.2, 127.9, 129.2, 131.8, 131.9, 132.0, 132.2, 132.8, 133.6,
34.3, 134.6, 148.2, 153.8, 155.3, 158.5, 167.1, 170.0.
.1.12.
-((5,6-Bis(4-bromophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(4-bromophenyl)thiazol-2-yl
)
acetamide (7k)
1
Yellow solid (52 %); H NMR (d
6
-DMSO, 400 MHz) δ: 4.38 (s, 2H), 7.31 (d, 2H, J =
8
1
3
1
4
2
.4 Hz), 7.39-7.42 (m, 4H), 7.59 (d, 2H, J = 8.4 Hz), 7.63 (d, 2H, J = 8.4 Hz), 7.70 (s,
1
3
H), 7.85 (d, 2H, J = 8.4 Hz), 12.69 (s, 1H, NH); C NMR (d -DMSO, 100 MHz) δ:
6
4.6, 109.5, 121.4, 123.7, 125.2, 128.2, 131.8, 131.9, 132.0, 132.2, 133.9, 134.3,
34.6, 148.3, 153.7, 155.3, 158.5, 167.0, 170.0.
.1.13.
-((5,6-Bis(4-fluorophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-phenylthiazol-2-yl)acetamide
(
7l)
Yellow solid (68 %); H NMR (d
.8 Hz), 7.23 (t, 2H, J = 8.4 Hz), 7.33 (t, 1H, J = 7.2 Hz), 7.42-7.52 (m, 6H), 7.63 (s,
1
6
-DMSO, 400 MHz) δ: 4.40 (s, 2H), 7.06 (t, 2H, J =
8
15

1
3
1
3
1
1
H), 7.90 (d, 2H, J = 8.4 Hz), 12.69 (s, 1H, NH); C NMR (d -DMSO, 100 MHz) δ:
6
4.6, 108.7, 115.7 (d, 2C, J = 21.8 Hz), 115.9 (d, 2C, J = 21.7 Hz), 126.1, 128.3,
29.2, 131.6 (d, 1C, J = 3.1 Hz), 131.9 (d, 1C, J = 3.1 Hz), 132.1 (d, 2C, J = 8.6 Hz),
32.7 (d, 2C, J = 9.0 Hz), 134.7, 149.4, 153.9, 155.2, 158.3, 162.0 (d, 2C, J = 245.6
Hz), 162.6 (d, 2C, J = 248.3 Hz), 167.0, 169.8.
4
2
.1.14.
-((5,6-Bis(4-fluorophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(p-tolyl)thiazol-2-yl)acetami
de (7m)
Yellow solid (65 %); H NMR (d
1
6
-DMSO, 400 MHz) δ: 3.79 (s, 3H), 4.38 (s, 2H),
6
8
.99 (d, 2H, J = 8.8 Hz), 7.06 (t, 2H, J = 8.8 Hz), 7.44-7.51 (m, 5H), 7.83 (d, 2H, J =
1
3
.8 Hz), 12.64 (s, 1H, NH); C NMR (d
6
-DMSO, 100 MHz) δ: 34.6, 55.6, 106.6,
114.6, 115.7 (d, 2C, J = 21.9 Hz), 115.9 (d, 2C, J = 21.6 Hz), 127.5, 127.6, 131.6 (d,
1
8
C, J = 2.9 Hz), 131.9 (d, 1C, J = 2.9 Hz), 132.1 (d, 2C, J = 8.6 Hz), 132.7 (d, 2C, J =
.9 Hz), 149.3, 153.9, 155.2, 158.2, 159.5, 162.0 (d, 2C, J = 245.7 Hz), 162.6 (d, 2C,
J = 248.5 Hz), 166.9, 170.0.
4
2
.1.15.
-((5,6-Bis(4-fluorophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(4-methoxyphenyl)thiazol-2-
yl)acetamide (7n)
Yellow solid (57 %); H NMR (d
.8 Hz), 7.22-7.30 (m, 4H), 7.44-7.51 (m, 4H), 7.61 (s, 1H), 7.93-7.96 (m, 2H), 12.68
1
6
-DMSO, 400 MHz) δ: 4.39 (s, 2H), 7.06 (t, 2H, J =
8
1
3
(
s, 1H, NH); C NMR (d -DMSO, 100 MHz) δ: 34.6, 108.5, 115.7 (d, 2C, J = 22.1
6
16

Hz), 115.9 (d, 2C, J = 21.7 Hz), 116.0 (d, 2C, J = 21.6 Hz), 128.1 (d, 2C, J = 8.1 Hz),
31.3 (d, 1C, J = 3.0 Hz), 131.6 (d, 1C, J = 3.0 Hz), 131.9 (d, 1C, J = 3.2 Hz), 132.1
d, 2C, J = 8.6 Hz), 132.7 (d, 2C, J = 9.0 Hz), 148.4, 153.9, 155.3, 158.4, 161.1 (d, 2C,
J = 245.7 Hz), 162.0 (d, 2C, J = 245.7 Hz), 162.6 (d, 2C, J = 248.3 Hz), 167.0, 169.8.
1
(
4
2
.1.16.
-((5,6-Bis(4-fluorophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(4-chlorophenyl)thiazol-2-yl)
acetamide (7o)
Yellow solid (73 %); H NMR (d
.8 Hz), 7.24 (t, 2H, J = 8.8 Hz), 7.44-7.51 (m, 6H), 7.69 (s, 1H), 7.91 (d, 2H, J = 8.4
1
6
-DMSO, 400 MHz) δ: 4.39 (s, 2H), 7.05 (t, 2H, J =
8
1
3
Hz), 12.70 (s, 1H, NH); C NMR (d
6
-DMSO, 100 MHz) δ: 34.6, 109.4, 115.7 (d, 2C,
J = 21.8 Hz), 115.9 (d, 2C, J = 21.7 Hz), 127.8, 129.2, 131.6 (d, 1C, J = 3.0 Hz),
1
1
31.9 (d, 1C, J = 3.1 Hz), 132.1 (d, 2C, J = 8.5 Hz), 132.7 (d, 2C, J = 8.9 Hz), 132.8,
33.6, 148.2, 153.9, 155.3, 158.5, 162.0 (d, 2C, J = 245.7 Hz), 162.6 (d, 2C, J = 248.2
Hz), 167.1, 169.7.
4
2
.1.17.
-((5,6-Bis(4-fluorophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(4-bromophenyl)thiazol-2-yl)
acetamide (7p)
Yellow solid (64 %); H NMR (d
1
6
-DMSO, 400 MHz) δ: 4.40 (s, 2H), 7.05 (t, 2H, J =
8
1
3
.8 Hz), 7.24 (t, 2H, J = 8.8 Hz), 7.44-7.51 (m, 4H), 7.62 (d, 2H, J = 8.8 Hz), 7.69 (s,
1
3
H), 7.85 (d, 2H, J = 8.4 Hz), 12.70 (s, 1H, NH); C NMR (d
6
-DMSO, 100 MHz) δ:
4.6, 109.5, 115.7 (d, 2C, J = 21.8 Hz), 115.9 (d, 2C, J = 21.7 Hz), 121.4, 128.1,
17

1
1
31.6 (d, 1C, J = 3.0 Hz), 131.9 (d, 1C, J = 3.2 Hz), 132.1 (d, 2C, J = 7.8 Hz), 132.2,
32.7 (d, 2C, J = 8.9 Hz), 133.9, 148.2, 153.9, 155.2, 158.5, 162.0 (d, 2C, J = 245.3
Hz), 162.6 (d, 2C, J = 248.4 Hz), 167.1, 169.7.
4
2
.1.18.
-((5,6-Bis(4-bromophenyl)-1,2,4-triazin-3-yl)thio)-N-(4-(4-fluorophenyl)thiazol-2-yl)
acetamide (7q)
Yellow solid (57 %); H NMR (d
1
6
-DMSO, 400 MHz) δ: 4.48 (s, 2H), 7.26-7.34 (m,
1
3
4
H), 7.39-7.42 (m, 4H), 7.60-7.62 (m, 3H), 7.93-7.97 (m, 2H), 12.67 (s, 1H, NH); C
NMR (d -DMSO, 100 MHz) δ: 34.6, 108.5, 116.0 (d, 2C, J = 21.4 Hz), 123.7, 125.2,
6
1
1
4
28.1 (d, 2C, J = 8.2 Hz), 131.3 (d, 1C, J = 3.0 Hz), 131.8, 131.9, 132.0, 132.2, 134.3,
34.6, 148.4, 153.8, 155.3, 158.4, 161.1 (d, 2C, J = 243.1 Hz), 167.0, 170.1.
.2. In vitro assay of α-glucosidase inhibitory activity
α-Glucosidase inhibitory activity was assayed by using 0.1 M phosphate buffer (pH
o
6
.8) at 37 C. The enzyme (0.1 U/mL) in phosphate buffer saline was incubated with
o
various concentrations of test compounds at 37 C for 15 min. Then 1.25 mM
p-nitrophenyl α-D-glucopyranoside was added to the mixture as a substrate. After
o
further incubation at 37 C for 30 min. The absorbance was measured
spectrophotometrically at 405 nm. The sample solution was replaced by DMSO as a
control. Acarbose was used as a positive control.
4
.3.Molecular docking
Molecular docking study was performed to investigate the binding mode between the
18

compound 7i and α-glucosidase using Autodock vina 1.1.2 [30]. The 3D structure of
α-glucosidase for Saccharomyces cerevisiae was predicted using homology modeling
in our previous report [17]. The 3D structure of the compounds were obtained by
ChemBioDraw Ultra 14.0 and ChemBio3D Ultra 14.0 softwares. The AutoDockTools
1
.5.6 package [31, 32] was employed to generate the docking input files. The search
grid of α-glucosidase was identified as center_x: -19.676, center_y: -7.243, and
center_z: -21.469 with dimensions size_x: 15, size_y: 15, and size_z: 15. The value of
exhaustiveness was set to 20. For Vina docking, the default parameters were used if it
was not mentioned. The best-scoring pose as judged by the Vina docking score was
chosen and visually analyzed using PyMoL 1.7.6 software (http://www.pymol.org/).
Conflict of Interest
The authors confirm that this article content has no conflict of interest.
Acknowledgments
This work was supported by Guizhou Youth Project (201511), Guizhou Science and
Technology Department Platform Talent Project (20165613/5677), Key Technology R
&
D Program of Guizhou Province ([2017]2845), Joint Foundation of Guizhou
Province Department of Science and Technology and Guizhou Medical University
[2016]7346).
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22

Graphical abstract
23

Highlights
►
A novel series of 5,6-diaryl-1,2,4-triazine thiazole derivatives were designed and
synthesized.
►
►
►
►
The IC50 in the range of 2.85±0.13 - 14.19±0.23 μM.
Compound 7i was found to be the most active compound.
The structure-activity relationship has been discussed.
Molecular docking study was carried out.
24