Modification of the Thioglycosyl-Naphthalimides as Potent and Selective Human O-GlcNAcase Inhibitors

Article abstract of DOI:10.1021/acsmedchemlett.8b00406

β-N-Acetylhexosaminidases are widely distributed exoglycosidases and have attracted significant attention due to their important roles in the field of pesticide and drug discovery. Remarkably, human O-GlcNAcase (hOGA) and human β-N-acetylhexosaminidase (HsHex) possess the same catalytic mechanism but play different physiological actions in vivo. In this Letter, we aim to improve the inhibitory potency and selectivity of previously reported thioglycosyl-naphthalimides against hOGA. The rational compound design led to the synthesis of 13r bearing a 4-piperidylnaphthalimide moiety as a highly potent hOGA inhibitor (K_i = 0.6 μM against hOGA) with good selectivity (K_i > 100 μM against HsHexB). Furthermore, to investigate the basis for the potency and selectivity of 13r against hOGA, the possible inhibitory mechanisms of selected inhibitors (15b, 13b, and 13r) against hOGA and HsHexB were studied using molecular docking and MD simulations. These 4-substituted naphthalimide thioglycosides may potentially serve as useful tools for the further study of the function of hOGA.

Full text of DOI:10.1021/acsmedchemlett.8b00406

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Letter
Modification of the thioglycosyl–naphthalimides as
potent and selective human O-GlcNAcase inhibitors
Shengqiang Shen, Lili Dong, Wei Chen, Xiangdi Zeng, Huizhe Lu, Qing Yang, and Jianjun Zhang
ACS Med. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acsmedchemlett.8b00406 • Publication Date (Web): 15 Nov 2018
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ACS Medicinal Chemistry Letters
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Modification of the thioglycosyl–naphthalimides as potent and
selective human O-GlcNAcase inhibitors
†
†
‡
†
†
,‡,§
Shengqiang Shen, Lili Dong, Wei Chen, Xiangdi, Zeng, Huizhe Lu, Qing Yang,* and Jianjun
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Zhang*,†
†Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
‡Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
§School of Life Science and Biotechnology, Dalian University of Technology, Dalian, China.
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KEYWORDS: Thioglycosides, naphthalimids, human O-GlcNAcase, β-N-acetylhexosaminidase, inhibitor, docking, MD
simulations
ABSTRACT: β-N-acetylhexosaminidases are widely distributed exo-glycosidases and have attracted significant attention due to
their important roles in the field of pesticide and drug discovery. Remarkably, human O-GlcNAcase (hOGA) and human β-N-
acetylhexosaminidase (HsHex) possess the same catalytic mechanism but play different physiological actions in vivo. In this article,
we aim to improve the inhibitory potency and selectivity of previously reported thioglycosyl-naphthalimides against hOGA. The
rational compound design led to the synthesis of 13r bearing a 4-piperidylnaphthalimide moiety as a highly potent hOGA inhibitor
(K
i
= 0.6 μM against hOGA) with good selectivity (K >100 μM against HsHexB). Furthermore, to investigate the basis for the
i
potency and selectivity of 13r against hOGA, the possible inhibitory mechanisms of selected inhibitors (15b, 13b and 13r) against
hOGA and HsHexB were studied using molecular docking and MD simulations. These 4-subtituteds naphthalimide thioglycosides
may potentially serve as useful tools for the further study of the function of hOGA.
β-N-acetylhexosaminidases represent an important class of
enzymes found in a number of organisms and are involved in
diverse physiological functions including human autoimmune
naphthalimides22-26. Among these inhibitors, naphthalimide
inhibitors were first found by high-throughput screening , and
one of the compounds M-31850 (1) was determined to exhibit
22
1
-2
3
diseases , fungi cell differentiation , and insect
i
a promising inhibitory potency against HsHex (K value of 3.2
4
22
morphogenesis . Inhibitors of these enzymes are particularly
useful in the regulation of corresponding bioprocesses,
providing benefits in the development of eco-friendly
μM) . Subsequently, non-carbohydrate-based naphthalimide
derivatives, e.g. compound 7a (2) synthesized by Qian and
i
Yang, exhibited a higher inhibitory activity (K value of 0.6
5
23
pesticides or therapeutic drugs. Remarkably, two types of
μM) against HsHex compared to M-31850. Furthermore,
Q1 (3) was found to possess an equally potent inhibitory
activity against both human β-N-acetylhexosaminidase HsHex
significant human β-N-acetylhexosaminidases, namely human
O-GlcNAcase (hOGA, a family GH84 glycoside hydrolase)
and human β-N-acetylhexosaminidase (HsHex, a family GH20
glycoside hydrolase) have been reported as potential
pharmacological targets. These two enzymes follow the
same substrate-assisted catalysis mechanism but play different
(K
i
value of 2.2 μM) and insect β-N-acetylhexosaminidases
24
OfHex1 (K
i
value of 4.3 μM). To improve the selective
6-7
inhibition against OfHex1, Q2 (4) bearing a 4-dimethylamino
group on the naphthalimide unit was designed and exhibited
8
pivotal roles in vivo.
i
K values of 0.3 μM against OfHex1 and more than 100 μM
2
4
against HsHex. The complex crystal structure of OfHex1-Q1
PDB: 3WMB) and OfHex1-Q2 (PDB: 3WMC) revealed that
Human O-GlcNAcase (hOGA) is responsible for catalyzing
the removal of O-GlcNAc from serine or threonine residues in
nucleocytoplasmic proteins. The related O-GlcNAcylation is
(
8
the 4-dimethylaminonaphthalimide moiety of Q2 rotates
approximately 180° (relative to naphthalimide moiety of Q1)
and is tightly bound to the +1 subunit of OfHex1 via π-π
stacking with Trp490.24 On the other hand, relative to Q1 the
added dimethylamino group led to an increase in the steric
mediated by O-GlcNAc transferase (OGT) and O-GlcNAcase
9
(OGA) under tightly regulated conditions . Dysregulation of
O-GlcNAcylation cycling has been found to be closely linked
to diseases such as Alzheimer’s disease (AD)
and obesity . It is worth noting that crystallographic
investigations on hOGA in three recent reports
foundation for hOGA-related drug discovery. Human β-N-
acetylhexosaminidase (HsHex) is found to be implicated in
osteoarthritis and lysosomal storage disorders.
1
0-11
12
, cancer ,
24
13
hindrance for Q2 to bind the -1 subsite of HsHex. These
1
4-16
results suggest that the 4-substituent at naphthalimide moiety
may be crucial for the activity and selectivity of β-N-
acetylhexosaminidases in the naphthalimides. (Figure 1)
laid a solid
1
We
recently
identified
thioglycosyl-naphthalimide
derivatives as promising lead compounds for β-N-
It has already been shown that small molecule inhibitors
with good potency and selectivity towards one of these β-N-
acetylhexosaminidases are of great importance to help in the
acetylhexosaminidase inhibitors2 , in which inhibitor 15b (5,
5-26
K
i
i
= 3.8 μM against hOGA; K = 30.4 μM against HsHexB)
1
7
exhibited a significant inhibitory activity against hOGA and a
treatment of correlated diseases. Inhibitors against β-N-
2
5
1
8
certain degree of selectivity towards these two enzymes . In
addition, structure-activity relationship studies revealed that a
acetylhexosaminidases can be classified as NAG-thiazoline ,
1
9
20
21
PUGNAc ,
Nagstatin ,
iminocyclitols
and
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linker containing five to seven atoms between thioglycosyl
and naphthalimide moiety would be beneficial to the
efficiency against hOGA. Considering the profound effects
hOGA has on disease treatment, we further attempted to
modify thioglycosyl-naphthalimide compounds as potent and
selective hOGA inhibitors. (Figure 1)
thiol 10 could be prepared according to literature procedures
in three steps.27 Subsequently, 10 was reacted with α,ω-
dibromoalkane to furnish the key intermediates 11a-11b in
acetone/water (2:1, v:v). Meanwhile, the naphthalimide
derivatives 8a-8l were obtained according to published
methods (Scheme S1 and Scheme S2). Then, treatment of
bromides 11a-11b with naphthalimides 8a-8l produced the
acetyl-protected 12a-12x. Finally, deacetylation of 12a-12x
via methanol-ammonia catalysis produced the target
compounds 13a-13x in 71-93% yield (Scheme S3).
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Subsequently, these target compounds were evaluated for
their inhibitory potency against hOGA and HsHexB by using
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4
-MU-GlcNAc as a substrate. The corresponding results are
listed in Table 1 and Table 2. Analysis of 13a-13x to assess
the inhibitory activity against hOGA showed that the 4-
subtituted on the naphthalimide moiety exhibited a significant
influence on the inhibitory activity. Specifically, the halogen
substituents (Cl, Br) in 4-position on the naphthalimides (13a-
1
3h) could slightly increase in inhibitory activity against
hOGA compared to that of naphthalimides not bearing any 4-
2
5
substituents (15b ). However, compounds bearing a methoxy
substituent (13u-13x) exhibited a minor activity decrease, and
compounds bearing the nitro group (13i-13l) and
dimethylamino group (13m-13p) demonstrated a significantly
weakened inhibitory effect. It is suggested that the size of the
Figure 1. Design of 4-subtituted naphthalimide thioglycosides for
hOGA.
4
-substituents may be the main factor to affect the inhibitory
potency against hOGA rather than the electronic properties. In
particular, the presence of smaller functional groups (Cl, Br)
In this paper, we retained the frame structure of
resulted in
naphthalimides bearing OCH
In contrast, the presence of an electron-donating group
N(CH ) and electron-withdrawing group (NO ) resulted in
a
more effective inhibitory potency than
2
5
thioglycosyl-naphthalimides and selected the length of the
linker with five to seven atoms. Then, we focused on studying
the influences of the 4-substituent group (on the naphthalimide
moiety) on the inhibitory activity and selectivity against
hOGA (Figure 1). Initially, our strategy involved the synthesis
of a handful of 4-subtituted naphthalimide thioglycosides and
the measurement of the inhibition rates (or IC50 values)
towards hOGA and HsHex. This way, we could evaluate the
potency of these thioglycosides rapidly and avoid unnecessary
synthesis of a large number of compounds with uncertain
activity. Thus, two thioglycosyl-naphthalimides, namely 13m
3
, NO , and N(CH substituents.
2
3 2
)
(
3
)
2
2
the same inhibitory activity. A special case was thioglycosyl-
naphthalimides bearing piperidyl group (13q-13t) that featured
a larger substituent than the dimethylamino group but
exhibited the highest inhibitory potency against hOGA (13r,
i
K = 0.6 μM). Presumably, the larger 4-piperidyl moiety may
have led to a greater rotation of 4-piperidylnaphthalimide to
tightly bind to the relevant hydrophobic domain near the
active pocket when interacting with hOGA. Furthermore, the
relationship of inhibitory activity against hOGA and the
flexible linker between the glycosyl and naphthalimide groups
(bearing a 4-dimethylamino group) and 13c (bearing a 4-
bromo group), were synthesized and compared with the
25
previously evaluated compounds 15a and 15d. As shown in
(
values of m, n) exhibited a certain regularity. The inhibitors
3b, 13f, 13r, 13v containing both thioethyl (m=2) and 3-
aminopropyl-naphthalimide (n=3) exhibited a higher potency
25
Table S1, in contrast to reference 15a , even though 13m
1
showed a decreased potency against hOGA (IC50 = 25.0 μM),
it possessed good selectivity (IC50 >100 μM against HsHexB).
In additon, 13c was demonstrated to be approximately seven
(e.g. 13r > 13q, 13s, 13t, Table 1).
2
5
The HsHexB inhibition of 13a-13x (Table 1 and Table 2)
times more potent than 15d , with an IC50 value of 3.7 μM.
These findings suggested that the 4-subtituted group on the
naphthalimide moiety exhibited a vital role in influencing the
selectivity and potency of thioglycosyl-naphthalimides against
hOGA. (Figure S1)
revealed similar properties. The inhibitory potency of these
compounds was also closely related to the size of 4-
substituents residing on naphthalimide. The greater inhibitory
25
activity of 13b relative to 15b suggested that a slight
increase in size of the 4-subtituted on naphthalimide (from H
to Br) could improve the binding affinity to HsHexB.
However, upon increasing the size from halogen substituents
The list of observations desribed herein prompted us to
further study the substituent residing in 4-position on the
naphthalimide scaffold. Halogen substituents (Cl, Br),
2 3 2
(Cl, Br) to NO , N(CH ) and piperidyl substituents, a loss in
electron-donating groups (OCH
3
3
, N(CH )2), an electron-
activity was observed. These results show that a large
substituent in this position may result in steric hindrance,
ultimately decreasing the access of the inhibitors to enter the
active pocket of the enzyme (HsHexB features a shallow
withdrawing group (NO ) and a larger substituent (piperidyl)
2
were introduced to the structure and the relationship between
the inhibtory activity and the size or electronic properties of
the substituents of these thioglycoside inhibitors were
evaluated. In doing so, another 22 4-subtituted naphthalimide
thioglycosides with the linker containing five to seven atoms
24
substrate-binding pocket ). It is worth mentioning that 13r did
not inhibit HsHexB but exhibited a hOGA inhibitory activity
in the nanomolar range, which means in comparison with the
classic inhibitor NGT, the thioglycosyl-naphthalimide 13r
(m = 2, 3; n = 2, 3) were synthesized. As shown in Scheme 1,
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Scheme 1. Synthesis of 4-subtituted thioglycosyl-naphthalimides 13a-13xa
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a
Reagents and conditions: (i) tert-butyl (n-amino-alkyl) carbamate, EtOH; (ii) DCM, CF
3
COOH; (iii) dimethylamine, 2-methoxyethanol
, DCM, H O;
for 7g, 7h; piperidine, 2-methoxyethanol for 7i, 7j; MeOH, K
vii) 8a-8l, K CO , acetone, H O; (viii) K CO , CH CN; (ix) NH
exhibted considerable inhibitory potency and with excellent
2
CO
3
for 7k, 7l; (iv) AcCl; (v) thiourea, acetone; (vi) Na
2
S
2
O
5
2
(
2
3
2
2
3
3
3
, MeOH. m, n, R are defined in Table 1.
group extended out from the active pocket and interacted with
residues of related hydrophobic domains. We then compared
selectivity for hOGA (Table 2).
25
the binding modes of 15b (Figure S6a) and 13b (Figure S6c)
Considering these interesting enzyme inbition results of
5b , 13b, and 13r (Table 2), we further studied how hOGA
25
with hOGA. The results indicated that the hydrogen atom of
NH in the 2-acetamido group of 13b could establish key
interactions with the catalytic residues G67 and W278 via
hydrogen bonds and the 4-bromonaphthalimide moiety of 13b
rotated to the residue W679 to form a strong π-π stacking
1
and HsHexB could recognize these compounds at the atomic
level. Firstly, the dixon plots of 15b , 13b, and 13r against
25
hOGA and HsHexB were investigated (Figure S2). The data
revealed that these active thioglycosyl-naphthalimides were
competitive inhibitors and could specifically bind to the active
pocket of the enzymes. Then, density functional theory (DFT)
using the B3LYP/6-31G(d) basis set was performed to
optimize the structures of 15b , 13b, and 13r using the
Gaussian 16 program (Figure S4). Subsequently, molecular
docking with these optimized structures into the binding site
of hOGA and HsHexB, respectively, were carried out using
the complex crystal structure of hOGA-PUGNAc-type
inhibitor (PDB ID: 5M7T) and HsHexB-NGT (PDB ID:
1NP0) . In an effort to shed further light on the appropriate
interaction mode of 15b , 13b, and 13r when bound to hOGA
and HsHexB, we further implemented MD simulations of 30
ns, using structures generated from the docking. As shown in
Figure 2a and Figure 2b, the root-mean-square deviations
2
5
interaction as compared to 15b . These interactions may have
resulted in the 4-fold increase in hOGA inhibitory potency
when compared with 15b25 and 13b. For the binding mode of
2
5
13r (Figure S6e), a significant conformational difference
25
relative to 15b
and 13b could be observed. The
naphthalimide moiety with a larger 4-piperidyl group of 13r
moved into the new hydrophobic domain, which was
composed of F223, E677, P678, F681, W679, and the
piperidyl group could then establish Van der Waals
interactions with E677, P678 (Figure S6e). In addition,
affected by the 4-piperidylnaphthalimide moiety, the glycosyl
moiety in 13r entered more deeply into the hOGA pocket and
the conformation of glycosyl rotated clockwise around 80°,
relative to the glycosyl moiety in 15b25 (Figure 2c).
Consequently, the key interactions could be observed due to
the formation of hydrogen bonds between the catalytic residue
N313 and the hydrogen atom in NH of the acetamido group in
13r (Figure S6e). On the basis of these observations, 13r
possessed the most appropriate binding conformation for
hOGA of these reported compounds, and thus exhibited the
highest inhibitory potency.
21
2
9
2
5
(
RMSDs) of all structures between receptors and ligands were
ultimately maintained around 2.0-3.0 Å. These data showed
that equilibrated and converged stages were reached in these
simulations. Besides, it could be observed that the hOGA and
HsHexB receptors exhibited some larger fluctuations located
at the loop areas of the proteins (Figure S5), which was in
agreement with the high conformational flexibility of the
1
4
25
glycoprotein.
In vitro assays revealed that 15b , 13b, and 13r displayed a
Superimposition of the conformations of 15b25 (green
8.0-, 2.0- and more than 167-fold higher selectivity for hOGA
as compared to HsHexB (Table 2). Therefore, we sought to
investigate this significant selectivity throughout the MD
colored carbon atoms), 13b (yellow colored carbon atoms),
and 13r (cyan colored carbon atoms) with hOGA at 30 ns of
MD simulations are shown in Figure 2c. The glycosyl moiety
from these three inhibitors was found to be tightly bound to
the -1 subsite (active pocket) of hOGA and the naphthalimide
2
5
simulations. The conformations of the inhibitors 15b , 13b,
and 13r combined in the active pocket of HsHexB at 30 ns of
MD simulations were extracted as shown in Figure 2d.
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Table 1. Structures and hOGA as well as HsHexB
Table 2. Inhibition constants and selectivity ratios of
representative compounds for hOGA
(μM)
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2
3
4
5
6
7
8
9
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1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
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5
5
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inhibition rate of target compounds 13a-13x at
concentration of 20 μM
a
K
i
Selectivity
ratio for
Compd
hOGA
HsHexB
2.6 ± 0.0
1.8 ± 0.1
5.1 ± 0.3
4.4 ± 0.1
1.2 ± 0.0
1.6 ± 0.1
1.6 ± 0.2
1.8 ± 0.2
Nd
hOGA
2.2
1
3a
1.2 ± 0.0
0.9 ± 0.0
3.5 ± 0.1
2.2 ± 0.1
2.0 ± 0.1
0.8 ± 0.1
0.7 ± 0.1
2.1 ± 0.1
8.3 ± 0.5
0.6 ± 0.0
3.2 ± 0.0
6.7 ± 0.3
1.6 ± 0.1
13b
13c
2.0
1.5
substituent group
Inhibition rate (%)
hOGA
Compd
R
Br
m
2
2
3
3
2
2
3
3
2
2
3
3
2
2
3
3
2
2
3
3
2
2
3
3
2
n
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
3
HsHexB
73.3 ± 3.5
70.5 ± 3.9
60.6 ± 1.4
65.0 ± 1.3
73.8 ± 2.7
70.8 ± 1.6
75.2 ± 3.2
74.3 ± 4.2
13.8 ± 1.8
8.0 ± 1.0
0.0
1
3d
13e
3f
3g
13h
3j
2.0
1
3a
3b
13c
3d
3e
13f
3g
3h
13i
3j
3k
3l
13m
3n
3o
13p
3q
3r
13s
3t
3u
3v
13w
3x
5ba
73.2 ± 2.0
84.7 ± 1.4
75.7 ± 1.7
59.2 ± 1.2
66.1 ± 1.5
83.3 ± 0.6
83.6 ± 2.3
68.9 ± 1.7
25.1 ± 2.1
55.0 ± 1.8
25.6 ± 2.6
20.0 ± 0.6
32.6 ± 1.8
40.9 ± 1.6
26.6 ± 3.0
28.2 ± 2.3
36.7 ± 1.8
87.6 ± 1.3
67.5 ± 2.5
49.1 ± 3.3
56.4 ± 1.8
73.1 ± 1.4
34.3 ± 3.1
68.0 ± 0.9
82.4 ± 0.1
0
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0.6
1
Br
1
2.0
Br
1
2.3
1
Br
0.9
1
Cl
1
>12.0
>167
>31.2
8.4
Cl
1
3r
3s
Nd
1
Cl
1
Nd
1
Cl
13u
56.2 ± 0.3
22.1 ± 0.0
24.7 ± 0.4
NO
NO
NO
NO
2
2
2
2
1
1
3v
3x
13.8
1.6
1
15.9 ± 0.5
1
15ba
NGT
3.8 ± 0.0
30.4 ± 0.1
8.0
1
0.0
0.18b
0.19c
1.1
N(CH
N(CH
N(CH
N(CH
3
3
3
3
)
)
)
)
2
2
2
2
0.0
aStructure and K
values of 15b were taken from ref [25]. Data
b
i
c
1
0.0
was taken from ref [28]. Data was taken from ref [22]. Nd: not
determined (less than 50% inhibition at 100 μM).
1
0.0
0.0
hOGA. Furthermore, it is important to note that inhibitor 13r
showed notable differences in its position and conformation
with HsHexB (Figure 2d). Both of the glycosyl and
naphthalimide moieties of 13r moved away from the active
pocket (Figure S6f) resulting in contact loss with HsHexB.
Accordingly, 13r exhibited a significantly higher selectivity
against hOGA as compared to HsHexB.
1
piperidyl
piperidyl
piperidyl
piperidyl
OMe
0.0
1
0.0
0.0
1
0.0
1
22.5 ± 1.1
47.9 ± 2.3
39.0 ± 2.8
45.2 ± 1.6
38.7 ± 0.8
Table 3. Results of binding free energy calculated using the
MM/GBSA method.
1
OMe
OMe
Ki (μM)
ΔGGBTOT（kcal/mol）
Compd
1
OMe
hOGA
HsHexB
30.4
hOGA
-27.9
-30.2
-32.4
HsHexB
-25.1
1
H
15ba
3.8
0.9
0.6
aStructure and inhibition rate data of compound 15b were taken
from ref [25].
1
3b
3r
1.8
-27.4
1
>100
-16.7
2
5
Compounds 15b , 13b, and 13r exhibited significant
a
differences in binding patterns. The binding mode between
Both structure and K
ref [31].
i
values of compound 15b were taken from
2
5
1
5b
and HsHexB (Figure S6b) showed that the
2
5
naphthalimide group of 15b was bound to the active pocket
of HsHexB via lesser interactions with W405, W489, E490
and the glycosyl moiety extended out from the pocket. In
To further explore the cause of the inhibitory potency and
selectivity against hOGA, we performed binding free energy
2
5
analyses of 15b , 13b, and 13r using the MM/GBSA
calculation methods and combined with MD simulations. The
predicted energy values for MD trajectories from the last 4 ns
can be found summarized in Table 3, exhibiting suitable
consistence with the experimental hOGA and HsHexB
2
5
comparison with 15b , as shown in Figure S6d, the glycosyl
moiety from 13b was found to be tightly bound to the active
pocket via strong H-bonding interactions with residues R211,
D290, E355, D354, E288. However, the naphthalimide group
formed additional π-π stacking interactions with W489 outside
of the pocket. These binding modes were coherent with the
observed structure-activity relationship trend between 15b25
and 13b, and, as a result, the increase in HsHexB inhibitory
potency of 13b led to the selectivity loss as compared to
25
inhibitory activities of 15b , 13b, and 13r.
In summary, we reported the molecular design, synthesis,
and inhibitory activities against hOGA and HsHexB of 4-
substituteds
naphthalimide
thioglycoside
derivatives.
Compared to our previously reported naphthalimide
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a)
(b)
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0
(c)
(d)
2
5
Figure 2. Predicted binding mechanism of thioglycosyl-naphthalimides 15b , 13b, and 13r with hOGA (PDB ID:5M7T) and HsHexB
PDB ID:1NP0) revealed by molecular docking and MD simulations. RMSD changes of 15b , 13b, and 13r in complex with hOGA (a)
and HsHexB (b), respectively, during MD simulations. Binding modes of 15b , 13b, and 13r with (c) hOGA and (d) HsHexB at 30 ns of
MD simulations. 15b is shown in green, 13b is shown in yellow, and 13r is shown in cyan (colored by element).
2
5
(
2
5
25
thioglycosides, the 4-subtituent group exerted a vital
influence on both the potency and selectivity against hOGA.
Particularly thioglycoside 13r bearing a 4-piperidyl group
exhibited the highest potency with a K
against hOGA and also exhibited excellent selectivity over
HsHexB (K >100 μM). Furthermore, molecular docking and
MD simulations studies allowed us to rationalize the
differences in potency and selectivity of the thioglycosyl-
naphthalimides for hOGA. Taken in concert, the novel hOGA
inhibitors reported here may find future applications as
potential leads for the development of new therapeutic agents
used in the treatment of hOGA-related diseases.
Author Contributions
The manuscript was written through contributions of all authors.
All authors have given approval to the final version of the
manuscript.
i
value of 0.6 μM
i
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
We acknowledge the financial support by the National Natural
Science Foundation (21772230, 31425021) of China,
and the National Key R&D Program (2018YFD0200100) of
China.
ASSOCIATED CONTENT
Supporting Information
ABBREVIATIONS
MD, molecular dynamics; DCM, dichloromethane; 4-MU-
GlcNAc, 4-methylumbelliferyl N-acetyl-β-D-glucosaminide;
NGT, NAG-thiazoline.
The Supporting Information is available free of charge on the
ACS Publications website.
Experimental procedures, enzymatic studies, molecular docking
and MD simulations studies, and H NMR and C NMR
spectrum. (PDF)
1
13
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β-N-acetylhexosaminidases are widely distributed exo-glycosidases and have attracted significant attention due to their
important roles in the field of pesticide and drug discovery. Remarkably, human O-GlcNAcase (hOGA) and human β-N-
acetylhexosaminidase (HsHex) possess the same catalytic mechanism but exhibit different physiological activities in vivo. In
this article, we aim to improve the inhibitory potency and selectivity of previously reported thioglycosyl-naphthalimides
against hOGA. Rational compound design led to the synthesis of 13r bearing a 4-piperidylnaphthalimide moiety as a highly
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potent hOGA inhibitor (K = 0.6 μM against hOGA) with good selectivity (K >100 μM against HsHexB). Furthermore, to
investigate the basis for the potency and selectivity of 13r against hOGA, the possible inhibitory mechanisms of selected
inhibitors (15b, 13b and 13r) against hOGA and HsHexB were studied using molecular docking and MD simulations. These
4-subtituted naphthalimide thioglycosides may potentially serve as useful tools for the further study of the function of hOGA.
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