New phthalimide-benzamide-1,2,3-triazole hybrids; design, synthesis, α-glucosidase inhibition assay, and docking study

Article abstract of DOI:10.1007/s00044-020-02522-7

A new series of phthalimide-benzamide-1,2,3-triazole hybrids 8a–k as α-glucosidase inhibitors was designed and synthesized. The biological evaluation of compounds 8a–k against yeast α-glucosidase demonstrated that all they have excellent inhibitory activity in comparison with standard inhibitor acarbose. Among them, the most potent compound was compound 8d with inhibitory activity 18.5-fold more than acarbose. Kinetic study revealed that α-glucosidase inhibition of compound 8d was the competitive type. Furthermore, docking study suggested that compound 8d is more stable than acarbose in the active site of α-glucosidase.

Full text of DOI:10.1007/s00044-020-02522-7

MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research
https://doi.org/10.1007/s00044-020-02522-7
ORIGINAL RESEARCH
New phthalimide-benzamide-1,2,3-triazole hybrids; design,
synthesis, α-glucosidase inhibition assay, and docking study
1 ●
1 ●
2 ●
3 ●
Seyed Esmaeil Sadat-Ebrahimi Abbas Rahmani Maryam Mohammadi-Khanaposhtani Negar jafari
4 ●
4 ●
5 ●
6 ●
7 ●
Somayeh Mojtabavi Mohammad Ali Faramarzi Mehdi Emadi Azadeh Yahya-Meymandi Bagher Larijani
Mahmoud Biglar Mohammad Mahdavi
7 ●
7
Received: 9 January 2020 / Accepted: 11 February 2020
©
Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
A new series of phthalimide-benzamide-1,2,3-triazole hybrids 8a–k as α-glucosidase inhibitors was designed and
synthesized. The biological evaluation of compounds 8a–k against yeast α-glucosidase demonstrated that all they have
excellent inhibitory activity in comparison with standard inhibitor acarbose. Among them, the most potent compound was
compound 8d with inhibitory activity 18.5-fold more than acarbose. Kinetic study revealed that α-glucosidase inhibition of
compound 8d was the competitive type. Furthermore, docking study suggested that compound 8d is more stable than
acarbose in the active site of α-glucosidase.
●
●
●
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Keywords Phthalimide Benzamide 1,2,3-Triazole Hybrid α-Glucosidase
Introduction
α-Glucosidase is a hydrolyzing enzyme that found in the
Supplementary information The online version of this article (https://
doi.org/10.1007/s00044-020-02522-7) contains supplementary
material, which is available to authorized users.
brush border surface of intestine. The main function of this
enzyme is conversion of carbohydrates (polysaccharides
and disaccharides) into absorbable monosaccharide glucose
(Chiba 1997). Therefore, this enzyme is involved in
carbohydrate-related diseases such as diabetes, cancer, viral
infections, and pompe disease (Toeller 1994; Pili et al.
*
*
Mahmoud Biglar
mbiglar@tums.ac.ir
Mohammad Mahdavi
momahdavi@tums.ac.ir
1995; Howe et al. 2013; Shimada et al. 2014). In terms of
prevalence, the most important carbohydrate-related disease
is type 2 diabetes and some of sugar-containing α-glucosi-
dase inhibitors, such as acarbose, miglitol, and voglibose
are successfully used in the treatment of this disease (Fig. 1)
1
Department of Medicinal Chemistry, Faculty of Pharmacy and
Pharmaceutical Sciences Research Center, Tehran University of
Medical Sciences, Tehran, Iran
2
3
4
Cellular and Molecular Biology Research Center, Health Research
Institute, Babol University of Medical Sciences, Babol, Iran
(Van De Laar et al. 2005). However, these inhibitors were
prepared by tedious multistep reactions and their clinical
use is associated with gastrointestinal side effects (Hol-
lander 1992). Thus, the discovery of effective small mole-
cules with convenient synthesis, high inhibitory activity
against α-glucosidase, and low side effects is an attractive
target for pharmaceutical scientists (Taha et al. 2020;
Rafique et al. 2019; Rahim et al 2020; Taha et al. 2015;
Khan et al. 2014).
Phthalimide is a fused heterocyclic structure that formed by
the merger of benzene and pyrrole-2,5-dione. This scaffold was
used as an important block in the design biological active
compounds with properties such as anti-inflammatory,
Department of Pharmaceutical Chemistry٫ Faculty of pharmacy,
University of Kansas, Lawrence, KS 66045, USA
Department of Pharmaceutical Biotechnology, Faculty of
Pharmacy and Biotechnology Research Center, Tehran University
of Medical Sciences, Tehran, Iran
5
6
7
Electrical and Computer Engineering Department, Babol
Noshirvani University of Technology, Babol, Iran
Department of Chemistry, Faculty of Science, University of
Birjand, Birjand, Iran
Endocrinology and Metabolism Research Center, Endocrinology
and Metabolism Clinical Sciences Institute, Tehran University of
Medical Sciences, Tehran, Iran

Medicinal Chemistry Research
anticonvulsant, hypolipidemic, analgesic, and immunomodu-
latory activities (Lima et al. 2002; Bailleux et al. 1994;
Chapman et al. 1979; Antunes et al. 2003; de Oliveira
Cardoso et al. 2015). Furthermore, phthalimide derivative
A is a known inhibitor for α-glucosidase (Dodo et al.
Synthesis of 3-(1,3-dioxoisoindolin-2-yl)benzoic acid 3
A mixture of phthalic anhydride 1 (10 mmol) and 3-
aminobenzoic acid 2 (10 mmol) in acetic acid glycial
(30 mL) was refluxed for 3 h. Then, solvent was decreased
under reduced pressure and water was added to the obtained
mixture. The pure precipitated product 3 was filtered off.
2
008) (Fig. 2). Like phthalimide, 1,2,3-triazole ring
widely used in design new molecules with various bio-
logical activities (Lauria et al. 2014). Recently, our
research group introduced 1,2,3-triazole derivatives B
with significant inhibitory effects against α-glucosidase
Synthesis of 3-(1,3-dioxoisoindolin-2-yl)-N-(prop-2-
yn-1-yl)benzamide 5
(
Fig. 2) (Saeedi et al. 2019). On the other hand, pre-
viously, structures C containing benzamide moiety was
reported as potent α-glucosidase inhibitors (Khan et al.
A mixture of 3-(1,3-dioxoisoindolin-2-yl)benzoic acid 3
(4 mmol), propargylamine 4 (4 mmol), HOBT (4.8 mmol),
EDCI (4.8 mmol), and NEt3 (4.4 mmol) in anhydrous
CH Cl (20 mL) were stirred at room temperature for
2
016) (Fig. 2). Therefore, in this study, in continuation of
our attempts to introduce novel α-glucosidase inhibitors
using molecular hybridization, for the first time, effective
pharmacophore phthalimide and 1,2,3-triazole were
attached together by a benzamide moiety in order to
achieve phthalimide-benzamide-1,2,3-triazole hybrids
2
2
30 min, and then were poured into water and the obtained
mixture was extracted with CH Cl (3 × 15 ml) and organic
2
layer dried over Na SO . Finally, CH Cl was evaporated
2
4
2
2
under reduced pressure and the residue used for the next
8
a–k as new α-glucosidase inhibitors (Saeedi et al. 2019).
reaction with no purification.
Eleven derivatives of the latter scaffold were synthesized
and their in vitro α-glucosidase inhibition and docking
study were also performed.
General procedure for the produce of phthalimide-
benzamide-1,2,3-triazoles 8a–k
In order to do a click reaction in the last step, 3-(1,3-diox-
oisoindolin-2-yl)-N-(prop-2-yn-1-yl)benzamide 5 (1 mmol),
sodium ascorbate, and CuSO .5H O (7 mol%) were added to
Material and methods
4
2
General chemistry
the freshly prepared benzyl azide derivatives 7a–k, and
obtained mixture was stirred at room temperature for
12–14 h. After that, reaction mixture was poured into cru-
shed ice and precipitated products 8a–k were filtered off,
washed with cold water, and purified by recrystallization in
ethyl acetate.
Melting points of phthalimide-benzamide-1,2,3-triazoles
8
a–k were measured on a Kofler hot stage apparatus. The
1
13
NMR ( H and C) and IR spectra were obtained by using
a Bruker FT-500 and Nicolet Magna FTIR 550 spectro-
photometer on KBr disks, respectively. Mass spectrum
was performed by an Agilent Technology (HP) mass
spectrometer (ionization potential = 70 eV). Elemental
analysis was measured by an Elementar Analysensystem
GmbH VarioEL CHN mode. Compounds 7a–k were
obtained according to our previous work (Saeedi et al.
N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)-3-(1,3-
dioxoisoindolin-2-yl)benzamide (8a)
Off white solid; yield: 61%, mp = 172–174 °C; IR (KBr):
−1
1
3351, 1709, 1650, 1583, 1385, and 1115 cm . H NMR
2
019).
(500 MHz, CDCl ): 4.30 (brs, 2H), 5.47 (s, 2H), 7.22–7.24 (m,
3
Fig. 1 Structures of well-known
α-glucosidase inhibitors

Medicinal Chemistry Research
Fig. 2 Rational design of
phthalimide-benzamide-1,2,3-
triazole hybrids 8a–k as
potential anti-α-
glucosidase agents
3
3
3
1
H), 7.30–7.35 (m, 3H), 7.53–7.57 (m, 2H), 7.77–7.79 (m,
3-(1,3-dioxoisoindolin-2-yl)-N-((1-(4-fluorobenzyl)-1H-1,2,3-
triazol-4-yl)methyl)benzamide (8d)
13
H), and 7.90–7.94 (m, 4H). C NMR (125 MHz, CDCl ):
3
5.4, 53.1, 123.9, 125.6, 127.0, 128.4, 129.0, 129.2, 129.5,
29.7, 131.6, 132.1, 134.3, 134.7, 135.2, 136.1, 166.5, 166.7,
Off white solid; yield: 81%; mp = 184–186 °C; IR (KBr):
−1
and 170.3. MS (70 eV): m/z = 437.1 [M+]. Anal. Calcd for
C H N O : C, 68.64; H, 4.38; N, 16.01. Found: C, 68.75; H,
3368, 1722, 1650, 1585, 1485, 1380, and 1223 cm . 1H
NMR (500 MHz, CDCl3): 4.62 (brs, 2H), 5.60 (s, 2H),
6.97–6.99 (m, 3H), 7.19–7.21 (m, 2H), 7.50–7.52 (m, 4H),
25 19 5 3
4.51; N, 16.12.
13
7
.77–7.86 (m, 4H), and 8.02–8.04 (m, 1H). C NMR
3
1
-(1,3-dioxoisoindolin-2-yl)-N-((1-(4-methoxybenzyl)-1H-
,2,3-triazol-4-yl)methyl)benzamide (8b)
(125 MHz, CDCl ): 33.2, 52.1, 115.85, 116.0, 123.7, 126.1,
3
127.3, 129.2, 129.6, 130.6, 131.3, 131.8, 134.4, 161.8, 163.9,
and 166.8. MS (70 eV): m/z = 455.3 [M + ]. Anal. Calcd for
C H FN O : C, 65.93; H, 3.98; N, 15.38. Found: C, 65.86;
Off white solid; yield: 75%; mp = 95–97 °C; IR (KBr):
3
25
18
5 3
−
1
1
336, 1726, 1642, 1382, and 1222 cm . H NMR
H, 3.78; N, 13.23.
(
500 MHz, CDCl ): 3.79 (s, 3H), 4.70 (brs, 2H), 5.42 (s,
3
2H), 6.88 (d, J = 8.6 Hz, 2H), 7.10 (brs, 1H), 7.22 (d, J =
8.6 Hz, 2H), 7.55–7.59 (m, 2H), 7.79–7.81 (m, 4H), 7.87 (s,
1
H), and 7.94–7.96 (m, 2H). 13C NMR (125 MHz, CDCl3):
33.5, 53.6, 54.8, 103.88, 104.33, 114.5, 118.4, 120.4,
120.7, 123.9, 125.2, 126.3, 126.7, 129.4, 129.6, 129.8,
131.6, 132.1, 132.9, 134.6, 135.6, 166.9, 179.5, and 190.1.
N-((1-(4-chlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-3-(1,3-
dioxoisoindolin-2-yl)benzamide (8e)
Off white solid; yield: 82%; mp = 190–192 °C; IR (KBr):
−
1 1
3321, 1709, 1652, 1584, 1483, 1389, and 1115 cm . H
NMR (500 MHz, CDCl ): 4.52 (brs, 2H), 5.45 (s, 2H), 7.19
3
Anal. Calcd for C H N O : C, 66.80; H, 4.53; N, 14.98.
Found: C, 66.63; H, 4.9442; N, 15.06.
(d, J = 7.5 Hz, 2H), 7.32 (d, J = 7.5 Hz, 2H), 7.53–7.58 (m,
3H), 7.78–7.79 (m, 4H), 7.89 (s, 1H), and 7.93–7.94 (m,
2
6
21
5
4
1
3
2
H). C NMR (125 MHz, CDCl ): 35.0, 53.0, 117.3,
3
3
-(1,3-dioxoisoindolin-2-yl)-N-((1-(2-fluorobenzyl)-1H-1,2,3-
123.9, 125.3, 126.7, 129.3, 129.4, 129.6, 131.6, 132.1,
132.8, 134.2, 134.6, 135.1, 139.5, 162.1, 165.3, and 166.9.
Anal. Calcd for C H ClN O : C, 63.63; H, 3.84; N, 14.84.
triazol-4-yl)methyl)benzamide (8c)
2
5
18
5
3
Off white solid; yield: 63%; mp = 169–171 °C; IR (KBr):
Found: C, 63.81; H, 3.97; N, 14.72.
−
1 1
3
334, 1722, 1657, 1586, 1437, 1381, and 1221 cm . H
NMR (500 MHz, CDCl ): 4.80 (brs, 2H), 5.59 (s, 2H),
N-((1-(2,6-dichlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-3-
3
7
.14–7.26 (m, 3H), 7.33–7.36 (m, 3H), 7.51–7.54 (m, 3H),
(1,3-dioxoisoindolin-2-yl)benzamide (8f)
13
and 7.70–7.79 (m, 5H). C NMR (125 MHz, CDCl ): 32.4,
3
5
1
1
1
3.1, 116.0, 116.2, 121.4, 124.0, 125.1, 125.7, 127.0,
29.5, 129.7, 131.4, 131.6, 132.1, 134.7, 160.7, 161.6, and
67.1. Anal. Calcd for C H FN O : C, 65.93; H, 3.98; N,
Off white solid; yield: 85%; mp = 201–203 °C; IR (KBr):
3322, 1727, 1647, 1540, 1436, and 1222 cm . H NMR
−1
1
(500 MHz, CDCl ): 4.69 (brs, 2H), 5.80 (s, 2H), 7.24–7.28 (m,
25
18
5
3
3
5.38. Found: C, 66.08; H, 3.84; N, 15.49.
1H), 7.49–7.56 (m, 2H), 7.77–7.83 (m, 2H), 7.82 (d, J =

Medicinal Chemistry Research
13
7
.6 Hz, 1H), 7.88 (brs, 1H), and 7.91–7.93 (m, 2H). C NMR
3-(1,3-dioxoisoindolin-2-yl)-N-((1-(3-nitrobenzyl)-1H-1,2,3-
(
125 MHz, CDCl ): 36.4, 53.1, 123.9, 125.5, 126.9, 129.0
triazol-4-yl)methyl)benzamide (8j)
3
(2C), 129.4, 129.6, 129.9, 131.2, 131.6, 132.0, 133.4, 134.7,
1
35.3, 136.9, 166.4, and 167.0. Anal. Calcd for
Off white solid; yield: 58%; mp = 110–112 °C; IR (KBr):
3342, 1721, 1649, 1585, 1382, 719 cm− .1H NMR
(500 MHz, CDCl3): 4.72 (brs, 2H), 5.62 (s, 2H),
1
C H Cl N O : C, 59.30; H, 3.38; N, 13.83. Found: C, 59.44;
H, 3.51; N, 13.69.
25
17
2 5 3
7
.50–7.51 (m, 2H), 7.54–7.58 (m, 4H), 7.79–7.94
N-((1-(3-bromobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-3-(1,3-
(m, 6H), and 8.14–8.19 (m, 2H). 13C NMR (125 MHz,
dioxoisoindolin-2-yl)benzamide (8g)
CDCl3): 35.1, 51.4, 123.2, 123.9, 124.0, 125.4, 126.9
(
2C), 129.6, 129.8, 130.4, 131.6 (2C), 132.1, 134.1,
Off white solid; yield: 79%; mp = 146–148 °C; IR (KBr):
134.8, 135.1, 136.5, 148.6, 166.5, and 167.1. Anal. Calcd
for C H N O : C, 62.24; H, 3.76; N, 17.42. Found: C,
−1 1
3321, 1722, 1639, 1585, 1483, 1389, and 1115 cm . H NMR
2
5
18
6
5
(
500 MHz, CDCl ): 4.67 (s, 2H), 5.42 (s, 2H), 7.14 (d, J =
62.13; H, 3.89; N, 17.33.
3
7.5 Hz, 1H), 7.20 (t, J = 7.7 Hz, 1H), 7.39 (s, 1H), 7.43–7.44
(m, 2H), 7.51 (t, J = 7.7 Hz, 1H), 7.55 (d, J = 7.7 Hz, 1H),
3-(1,3-dioxoisoindolin-2-yl)-N-((1-(4-nitrobenzyl)-1H-1,2,3-
7
.61–7.63 (m, 1H), 7.77–7.78 (m, 2H), 7.81 (d, J = 7.2 Hz,
triazol-4-yl)methyl)benzamide (8k)
13
1H), 7.88 (s, 1H), and 7.90–7.92 (m, 2H). C NMR
(
1
1
125 MHz, CDCl ): 35.5, 53.5, 123.1, 123.9, 124.0, 125.4,
26.7, 126.9, 129.5, 129.7, 130,8, 131.2, 131.6, 132.02,
32.08, 134.7, 134.8, 135.2, 136.7, 166.5, and 167.0. MS
Off white solid; yield: 83%; mp = 199–201 °C; IR (KBr):
3
−
1
3309, 1711, 1648, 1594, 1520, 1386, 1114, and 717 cm .
1
H NMR (500 MHz, CDCl ): 4.73 (brs, 2H), 5.62 (s, 2H),
3
(
70 eV): m/z = 515.1 [M+]. Anal. Calcd for C H BrN O :
7.16–7.18 (m, 1H), 7.40 (d, J = 7 Hz, 2H), 7.55–7.59 (m,
2H), 7.81–7.86 (m, 5H), 7.93–7.95 (m, 2H), and 8.21 (d,
25
18
5 3
C, 58.15; H, 3.51; N, 13.56. Found: C, 58.26; H, 3.62; N,
1
1
3
3.41.
J = 7.0 Hz, 2H). C NMR (125 MHz, CDCl ): 35.7, 53.9,
3
124.3, 124.7, 125.6, 127.0, 129.1, 129.9, 130.0, 131.9,
N-((1-(4-bromobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-3-(1,3-
dioxoisoindolin-2-yl)benzamide (8h)
132.5, 135.0, 135.3, 141.7, 148.5 (2C), 166.8, 167.4, and
170.2. MS (70 eV): m/z = 482.6 [M+]. Anal. Calcd for
C H N O : C, 62.24; H, 3.76; N, 17.42. Found: C, 62.11;
2
5
18
6
5
Off white solid; yield: 78%; mp = 196–198 °C; IR (KBr):
H, 3.87; N, 17.57.
−1
1
3315, 1709, 1651, 1585, 1388, and 1115 cm . H NMR
(
500 MHz, CDCl ): 4.39 (brs, 2H), 5.44 (s, 2H), 7.12 (d, J =
Biological evaluations
3
7
7
7
1
1
.8 Hz, 2H), 7.48 (d, J = 7.8 Hz, 2H), 7.55–7.59 (m, 2H),
.79–7.80 (m, 3H), 7.80–7.82 (m, 2H), 7.88 (s, 1H), and
In vitro α-glucosidase inhibition of phthalimide-benza-
mide-1,2,3-triazoles 8a–k, kinetic analysis of the most
potent compound 8d, and docking study of the standard
drug and the most potent compounds 8d and 8c in the
active site of α-glucosidase were performed exactly
according to our previous work (Adib et al. 2018).
.93–7.95 (m, 2H). 13C NMR (125 MHz, CDCl ): 33.9, 52.6,
3
23.0, 123.9, 125.3, 126.7, 129.4, 129.6, 129.8, 131.6, 132.1,
32.3, 134.5, 164.7, and 166.95 (2C). Anal. Calcd for
C H BrN O : C, 58.15; H, 3.51; N, 13.56. Found: C, 58.27;
H, 3.43; N, 13.68.
25
18
5 3
3
-(1,3-dioxoisoindolin-2-yl)-N-((1-(2-nitrobenzyl)-1H-1,2,3-
triazol-4-yl)methyl)benzamide (8i)
Results and discussion
Off white solid; yield: 62%; mp = 177–179 °C; IR (KBr):
Chemistry
−
1 1
3
311, 1662, 1585, 1388, and 1112, 720 cm . H NMR
(
(
(
5
1
1
6
500 MHz, CDCl ): 4.74 (brs, 2H), 5.93 (s, 2H), 7.04
The synthesis route for the production of phthalimide-benza-
mide-1,2,3-triazoles 8a–k has been depicted in Scheme 1. At
first, phthalic anhydride 1 and 3-aminobenzoic acid 2 in acetic
acid glycial were refluxed for 3 h to afford 3-(1,3-dioxoi-
soindolin-2-yl)benzoic acid 3. The latter compound was con-
verted to 3-(1,3-dioxoisoindolin-2-yl)-N-(prop-2-yn-1-yl)
benzamide 5 in the presence of propargylamine 4, HOBT/
EDCI, and NEt in anhydrous CH Cl at room temperature.
3
brs, 1H), 7.50–7.55 (m, 4H), 7.77–7.90 (m, 6H), 8.11
1
3
d, J = 7.3 Hz, 1H). C NMR (125 MHz, CDCl ): 35.5,
3
1.6, 124.2, 125.8, 125.9 (2C), 127.1, 129.7, 130.0 (2C),
30.1, 130.5, 130.7, 131.9, 132.3, 134.8, 135.0, 135.3,
47.8, 166.7, and 167.3. Anal. Calcd for C H N O : C,
2
5
18
6
5
2.24; H, 3.76; N, 17.42. Found: C, 62.38; H, 3.59;
N, 17.69.
3
2
2

Medicinal Chemistry Research
Scheme 1 Synthesis of phthalimide-benzamide-1,2,3-triazoles 8a–k
Table 1 In vitro α-glucosidase
inhibitory activities of
phthalimide-benzamide-1,2,3-
triazoles 8a–k
Compound
R
IC50 (µM)
Compound
R
IC50 (µM)a
8a
8b
8c
8d
8e
8f
H
92.7 ± 1.6
131.3 ± 2.2
48.7 ± 0.8
40.5 ± 0.6
83.7 ± 1.2
109.6 ± 1.9
8g
3-Br
89.5 ± 1.4
116.5 ± 2.0
54.1 ± 0.9
68.3 ± 1.0
77.5 ± 1.1
750.0 ± 10.0
4-OCH3
2-F
8h
4-Br
8i
2-NO2
3-NO2
4-NO2
–
4-F
8j
4-Cl
8k
2,6-Dichloro
Acarbose
aValues are the mean ± SD. All experiments were performed at least three times
Compound 5 was an appropriate prone to be participated in
Pharmacology
click reaction in order to construct 1,2,3-triazole ring (Kolb
et al. 2001). For this purpose, different benzyl chloride/bromide
derivatives 6a–k and sodium azide reacted in the presence
NEt in the mixture of H O and t-BuOH (1:1) at room tem-
In vitro α-glucosidase inhibitory activity
Anti-α-glucosidase activity of phthalimide-benzamide-1,2,3-
triazoles 8a–k were screened by using α-glucosidase isolated
from Saccharomyces cerevisiae (yeast). The obtained results
demonstrated that all the title compounds exhibited excellent
activity against α-glucosidase. These compounds were
3
2
perature to afford the fresh azide derivatives 7a–k. Finally,
compound 5, CuSO .5H O, and sodium ascorbate were added
4
2
to the azide derivatives 7a–k at room temperature for 12–14 h
at 60 °C to give the corresponding products 8a–k.

Medicinal Chemistry Research
a)
b)
1
0
8
6
4
2
0
30
20
10
0
Concentration of Inhibitor
0
1
2
4
µM
0 µM
5 µM
0 µM
-
1.5
-1.0
-0.5
0.0
0.5
1.0
-1
1
/[S](PNPG, mM )
-
60
-40
-20
0
20
40
60
-
10
Compound (8d )
Fig. 3 a Lineweaver–Burk plots for the inhibition of α-glucosidase by compound 8d and (b) the secondary plot between Km and various
concentrations of compound 8d
around 18.5–5.7 (range of IC50 values = 40.5 ± 0.6–131.3 ±
.2 µM) folds more potent than standard drug acarbose
IC = 750.0 ± 10.0 µM). As can be seen the chemistry
the halogenated derivatives were 2,6-dichloro derivative
2
(
8f (IC = 109.6 ± 1.9 µM) and 4-bromo derivative 8h
5
0
(IC = 116.5 ± 2.0 µM).
5
0
50
section, in order to achieve optimal α-glucosidase inhibitor,
we altered the substituents on the pendant phenyl ring.
As can be seen in the Table 1, among the synthesized
compounds, the most potent compound was 4-fluoro deri-
vative 8d (IC = 40.5 ± 0.6 µM). Changing the position of
Kinetic study
The kinetic analysis of α-glucosidase inhibition by the
most potent compound 8d was performed in order to
5
0
the fluorine atom in the phenyl ring from 4-position to 2-
position, as in compound 8c (the second most potent com-
pound with IC = 48.7 ± 0.8 µM), slightly diminished the
determine the mechanism of inhibition and K value of this
i
compound. As can be seen in Fig. 3a, with increasing the
concentration of inhibitor (compound 8d), the value of
Vmax remained constant and the value of Km increased.
This finding indicated that compound 8d acted as com-
petitive inhibitor of α-glucosidase. Moreover, the plot of
Km versus different concentrations of inhibitor gave an
5
0
inhibitory activity. Moreover, inhibitory activities of
-substituted derivatives and un-substituted compound
demonstrated that 4-fluoro derivative 8d (IC = 40.5 ±
4
50
0
.6 µM), 4-nitro derivative 8k (IC = 77.5 ± 1.1 µM), and
50
4
-chloro derivative 8e (IC = 83.7 ± 1.2 µM) with strong
estimate of K (Inhibition constant) value of 37 μM for
50
i
electron withdrawing substituents have more inhibitory
compound 8d (Fig. 3b).
activity in comparison with compound 8a (IC = 92.7 ±
50
1.6 µM) with un-substituted phenyl ring, compound
Docking study
8
h (IC = 116.5 ± 2.0 µM) with weak electron withdrawing
5
0
substituent Br, and compound 8b (IC = 131.3 ± 2.2 µM)
with strong electron donating substituent methoxy (order of
In order to gain further insight into the inhibitory activities
of the synthesized compounds against α-glucosidase, we
investigated the binding modes of the standard drug acar-
bose and the most potent compounds 8d and 8c in the active
site of target enzyme by using docking calculations (Adib
et al. 2018). Figure 4 shows the binding mode between
acarbose and α-glucosidase. This drug interacted with the
residues Ser308, Glu304, Thr307, Val305, Thr301, Gln322,
Arg312, His279, His239, and Asn241.
50
activity: F > NO > Cl > H > Br > OCH ). 4-Methoxy deriva-
2
3
tive 8b also was the less active compound among the syn-
thesized compounds. The tired most potent compound was 2-
NO derivative 8i (IC = 54.1 ± 0.9 µM). Movement of NO
2
50
2
group of 2-position to 3 or 4-position led to decrease in
inhibitory activities as observed in the compounds 8j (IC =
5
0
6
8.3 ± 1.0 µM) and 8k (IC = 77.5 ± 1.1 µM), respectively. It
50
is worthy to note that in the cases of 3-nitro derivative 8j
4-Fluoro and 3-Fluoro derivatives 8d and 8c were
found to be more active than other synthesized inhibitors.
The superposed structure of acarbose and the most potent
compound 8d revealed that the latter compound as well
fitted in the active site of α-glucosidase (Fig. 5).
(
IC = 68.3 ± 1.0 µM) and 3-bromo derivative 8g (IC =
5
0
5
0
89.5 ± 1.4 µM), compound 8j with stronger electron with-
drawing substituent has more inhibitory effect than compound
with weaker electron withdrawing substituent (compound
8
j vs. compound 8g). This pattern was also observed in the
As can be seen in Fig. 6a, pendant 4-fluorophenyl
moiety of compound 8d interacted with Arg312,
4-substituted derivatives. The less active compounds among

Medicinal Chemistry Research
Fig. 4 (a) The 3D and (b) 2D predicted binding modes of acarbose in the active site pocket
2
-Fluoro substituent of pendant phenyl moiety in the
second most potent 8c interacted with Phe157, Asp408,
and Asn412 and phenyl ring of this moiety formed a
hydrophobic interaction with Arg312 (Fig. 6b). The latter
amino acid also interacted with 1,2,3-triazole ring via a
hydrogen bond and a hydrophobic interaction. Phenyl ring
of benzamide moiety of compound 8c established a π–π
interaction with His279 and a π–anion interaction with
Glu304. Furthermore, Glu304 also formed a π–anion
interaction with phthalimide ring.
Calculation of binding energies of acarbose and the
most active compounds 8d and 8c predicted that our new
compounds with binding energies −9.17 and −9.12 can
be attached to active site of α-glucosidase easier than
standard drug acarbase with binding energies =
−
4.04 kcal/mol. These results are in agreement with
Fig. 5 Acarbose (gray) and the most potent compound 8d (pink)
superimposed in the active site pocket
in vitro α-glucosidase inhibition evaluation (Table 1).
Conclusion
Asp349, and Gln350 through fluoro substituent and
Arg439 through phenyl ring. Residue Arg312 also
formed a hydrophobic interaction with 1,2,3-triazole ring
of compound 8d. The latter ring also established a
π–lone pair interaction with Phe157. Carbonyl unit of
benzamide moiety formed a hydrogen bond with His239.
Furthermore, phthalimide moiety of compound 8d cre-
ated the following interactions with active site: a π–anion
interaction with Glu304 and two hydrophobic interac-
tions with Pro309.
In this paper, we combined phthalimide and 1,2,3-triazole
derivatives by benzamide linker to design new potent α-
glucosidase inhibitors. Designed phthalimide-benzamide-
1,2,3-triazole hybrids 8a–k were synthesized by click
reaction and evaluated again yeast α-glucosidase.
Obtained results demonstrated that all the title compounds
were more potent than standard inhibitor and the most
potent compound 8d was a competitive inhibitor into α-
glucosidase. Furthermore, docking study was performed

Medicinal Chemistry Research
Fig. 6 Predicted binding modes of compounds (a) 8d and (b) 8c in the active site pocket
in order to predict possible interaction modes and binding
energies of the standard drug and the most potent com-
pounds in the active site of α-glucosidase.
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Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
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