Design, synthesis and biological evaluation of novel pyrimidinedione derivatives as DPP-4 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2018.05.022

A series of novel pyrimidinedione derivatives were designed and evaluated for in vitro dipeptidyl peptidase-4 (DPP-4) inhibitory activity and in vivo anti-hyperglycemic efficacy. Among them, the representative compounds 11, 15 and 16 showed excellent inhibitory activity of DPP-4 with IC₅₀ values of 64.47 nM, 188.7 nM and 65.36 nM, respectively. Further studies revealed that compound 11 was potent in vivo hypoglycemic effect. The structure–activity relationships of these pyrimidinedione derivatives had been discussed, which would be useful for developing novel DPP-4 inhibitors as treating type 2 diabetes.

Full text of DOI:10.1016/j.bmcl.2018.05.022

Bioorganic&MedicinalChemistryLettersxxx(xxxx)xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design, synthesis and biological evaluation of novel pyrimidinedione
derivatives as DPP-4 inhibitors
Ning Lia,b,c,d, Li-Jun Wanga,b,d, Bo Jianga,b,d, Shu-Ju Guoa,b,d, Xiang-Qian Lia,b,d, Xue-Chun Chene,
⁎
Jiao Luoa,b,c,d, Chao Lia,b,c,d, Yi Wange,⁎, Da-Yong Shia,b,c,d,
a
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, China
b
c
University of Chinese Academy of Sciences, Beijing 100049, China
Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China
College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
d
e
A R T I C L E I N F O
A B S T R A C T
Keywords:
A series of novel pyrimidinedione derivatives were designed and evaluated for in vitro dipeptidyl peptidase-4
(DPP-4) inhibitory activity and in vivo anti-hyperglycemic efficacy. Among them, the representative compounds
11, 15 and 16 showed excellent inhibitory activity of DPP-4 with IC50 values of 64.47 nM, 188.7 nM and
65.36 nM, respectively. Further studies revealed that compound 11 was potent in vivo hypoglycemic effect. The
structure–activity relationships of these pyrimidinedione derivatives had been discussed, which would be useful
for developing novel DPP-4 inhibitors as treating type 2 diabetes.
Pyrimidinedionederivatives
DPP-4 inhibitor
Molecular hybrid
SARs
Type 2 diabetes
Diabetes is a major global problem nowadays. It currently affects
nearly 425 million people worldwide in 2017, and this number will rise
to 700 million in 2045.1 Glucagon-like peptide-1 (GLP-1) and glucose-
dependent insulinotropic polypeptide (GIP) are both incretin hormones
increasing insulin biosynthesis and therefore contributing to glycemic
control.2,3 However, both hormones are rapidly inactivated by the
serine protease DPP-4, leading to limiting their therapeutic practicality.
The idea of inhibiting DPP-4 was developed as a promising new therapy
for type 2 diabetes mellitus (T2DM) 20 years ago.4 To date, twelve DPP-
4 inhibitors (sitagliptin, vildagliptin, saxagliptin, alogliptin, linagliptin,
anagliptin, gemigliptin, teneligliptin, evogliptin, omarigliptin, tre-
lagliptin and gosogliptin) have been approved for the treatment of
T2DM (Fig. 1).5 Yet, there is still strong enthusiasm in developing novel
DPP-4 inhibitors since some undesirable side effects exist in current
drugs.6
Bromophenols are a set of natural products widely distributed in
seaweed, most of which exhibit many biological activities, including
hypoglycemic effect, anticancer, antioxidant, antimicrobial and other
potent bioactivities.7 In our previous study, a variety of bromophenols
(Fig. 2), isolated from the red marine algae of the Rhodomelaceae fa-
mily or synthesized derivatives, showed potent hypoglycemic effects in
vitro and in vivo.8–11 Herein, bromophenols are used as potent hy-
poglycemic agents and are considered as part of a new therapeutic
strategy for treatment of type 2 diabetes.
The fully understanding of the interaction between DPP-4 enzyme
and the bioactive substances plays a significant role in designing novel
DPP-4 inhibitors. From the binding models we found that pyr-
imidinedione forms π-π interactions with Tyr547, which undergoes a
conformational change in the S1 subsite; in addition, the cyanobenzyl
group or the butynyl group binds to the S1 subsite.12,13 Moreover,
aminopiperidine is crucial for DPP-4 inhibitory activity, which forms
salt bridge with Glu205, Glu206 and Tyr662 in S2 pocket.14,15
Synergistic activity is often attributed to molecular hybrids with
different pharmacophores. Apart from pyrimidinedione core, we de-
termined bromophenol, butynyl group, fluorocyanobenzyl or (R)-3-
aminopiperidine as substituents. The widespread application of fluorine
in drug design benefits from distinctive properties, including lipophi-
licity, eletrophilicity, metabolic stability, chemical stability, et al.16 In
view of these observations, a novel series of pyrimidinedione deriva-
tives were designed and evaluated for in vitro DPP-4 inhibitory activity.
Among these pyrimidinedione derivatives, compound 11 showed the
most potent inhibitory activity of DPP-4 and was potent in vivo hy-
poglycemic effect. Structure-activity relationships (SARs) of these pyr-
imidinedione derivatives are also discussed in this paper.
It has been reported about the synthesis of benzyl bromide in our
previous reports, as shown in Scheme 1
17–19
The synthetic route of
⁎
Corresponding authors at: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China (Da-Yong Shi); College of
Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China (Yi Wang).
E-mail addresses: mysky@zju.edu.cn (Y. Wang), shidayong@qdio.ac.cn (D.-Y. Shi).
https://doi.org/10.1016/j.bmcl.2018.05.022
Received 30 March 2018; Received in revised form 2 May 2018; Accepted 9 May 2018
0960-894X/©2018PublishedbyElsevierLtd.
Pleasecitethisarticleas:Li,N.,Bioorganic&MedicinalChemistryLetters(2018),https://doi.org/10.1016/j.bmcl.2018.05.022

N. Li et al.
Bioorganic&MedicinalChemistryLettersxxx(xxxx)xxx–xxx
Fig. 1. Marketed DPP-4 inhibitors.
transformed into 3 through the N-alkylation. Compound 4 was obtained
by a process of replacing the 6-chloro group with (R)-3-(Boc-Amino)
piperidine. Finally, removal of Boc with TFA produced the final com-
pounds 5–22.
The inhibitory effects of compounds on DPP-4 activity were eval-
uated based on fluorescent probe.22 In this part, we found that three
compounds 11, 15, 16 showed potent inhibitory activity of DPP-4 at
100 nM with inhibitory rate of (100.12
0.54)%, (95.59
3.7)%,
(98.84 0.66)%, respectively (Table 1). As shown in Fig. 3, com-
pounds 11, 15 and 16 exhibited potent DPP-4 inhibitory activity, with
IC50 values of 64.47 nM, 188.7 nM and 65.36 nM.
Fig. 2. Structures of bromophenol possessing hypoglycemic effect.
From the data of Table 1, we found that the degree of bromination
of these compounds may have a close relationship with their DPP-4
inhibitory activity. For example, the number of bromine of compounds
11–14 gradually increases from 0 to 3. However, the DPP-4 inhibition
rates of compounds 11–14 decrease from 100.12% to 0.66%. Similarly,
compounds 6–8 were less potent than compound 5. It could be found
compounds 5–22 is depicted in Scheme 220,21 Briefly, the synthesis of
pyrimidinedione derivatives was started from commercially available
compound 1. After alkylation of material 1 with 1-bromo-2-butyne or 2-
cyanobenzo-5-fluorobenzyl bromide, the resulting precursor 2 was
Scheme 1. Reagents and conditions (a):Br2, CH3OH, 0 °C; (b): CH3I, K2CO3, DMF, rt; (c): Br2, CH3COOH, Fe, 60 °C; (d): NBS, H2SO4, 0 °C; (e): NaBH4, CH3OH, 0 °C;
(f):PBr3, Et3N, CH2Cl2, 0 ∼ 15 °C;
2

N. Li et al.
Bioorganic&MedicinalChemistryLettersxxx(xxxx)xxx–xxx
Scheme 2. Reagents and conditions (a):R’Br, DIPEA, DMF, rt; (b) RBr, K2CO3, KI, DMF, rt; (c): (R)-3-(Boc-Amino)piperidine, K2CO3, DMF, 90 °C, N2 protection; (d):
CH2Cl2, TFA, rt.
that their inhibitory rates decreased with the increase of the degree of
bromination on phenol moiety. Furthermore, the degree of bromination
of these compounds may have a close relationship with their lipid/
water partition coefficient (Log P). For example, the DPP-4 inhibition
rates of compounds 5–8 decrease from 86.8% to -0.87% with the in-
crease of Log P. In addition, the compounds (11, 16) with fluor-
ocyanobenzyl substituent were more active than the compounds (5, 10)
with butynyl group (Table 1). SAR studies showed that fluor-
ocyanobenzyl was crucial since it formed a hydrogen bond with
Arg125. Moreover, π-π interaction also explained its enhanced binding
affinity (Fig. 4).
To further study the hypoglycemic effect of compound 11, blood
glucose levels were measured during 4 weeks treatment.11 In order to
improve the solubility, the succinate salt of compound 11 was prepared
according to the method of Hu et al.23 The dynamic effects of com-
pound 11 on water intake and body weight were recorded during four
weeks treatment in BKS db mice. There was no difference in water in-
take and body weight at the baseline (Fig. 5A and B). As shown in
Fig. 5A, there was a decrease trend in mean water intake from the
second week in compound 11- or metformin-treated group. However,
both compound 11 and metformin had no effect on body weight of BKS
db mice (Fig. 5B). A lot of abdominal fat was developed in BKS db mice
at the fourth week (Fig. 5C). Compound 11 or metformin was unable to
block the increased ratio of abdominal fat (Fig. 5D). In comparison with
BKS mice, diabetic BKS db mice exhibited hyperglycaemia with blood
levels of about 30 mM (Fig. 6). A trend towards decrease in blood
glucose levels was revealed in compared with vehicle and compound
11/metformin-treated groups. The blood glucose levels were reduced
from the second week in both compound 11 and metformin treated
group (Fig. 6). These results reveal that compound 11 has anti-diabetic
potency with an effective blood glucose-lowing effect.
In summary, a series of pyrimidinedione derivatives were designed
and evaluated for in vitro DPP-4 inhibitory activity and in vivo anti-
hyperglycemic efficacy. The preliminary SARs analysis exhibits that: (a)
hydrophobic property was important for the inhibitory activity of DPP-
4. Lipid/water partition coefficient may affect their inhibitory activity
Table 1
Inhibition of DPP-4 by compounds 5–22 at 100 nM.
Compound
R
R′
Log P
Inhibitory rate%
IC50/nM
a
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
3,4-Dimethoxybenzyl
3-Bromo-4,5-dimethoxybenzyl
2,3-Dibromo-4,5-dimethoxybenzyl
2,3,6-Tribromo-4,5-dimethoxybenzyl
3,5-Dimethylbenzyl
3,5-Difluorobenzyl
3,4-Dimethoxybenzyl
3-Bromo-4,5-dimethoxybenzyl
2,3-Dibromo-4,5-dimethoxybenzyl
2,3,6-Tribromo-4,5-dimethoxybenzyl
3,5-Dimethylbenzyl
3,5-Difluorobenzyl
Ethyl
Butynyl
Butynyl
Butynyl
Butynyl
Butynyl
Butynyl
Fluorocyanobenzyl
Fluorocyanobenzyl
Fluorocyanobenzyl
Fluorocyanobenzyl
Fluorocyanobenzyl
Fluorocyanobenzyl
Butynyl
Butynyl
Butynyl
Butynyl
Fluorocyanobenzyl
Fluorocyanobenzyl
1.55
2.38
3.21
4.04
2.78
2.12
2.66
3.49
4.32
5.15
3.89
3.23
0.41
0.90
2.15
3.82
3.26
4.93
86.8
28.54
2.7
−0.87
3.61
72.98
100.12
73.89
8.9
2.1
2.03
10.64
2.14
16.56
18.8
0.54
24.03
9.42
14.95
3.7
0.66
1.2
5.63
3.26
2.61
10.6
–
–
–
–
–
–
64.47
–
–
–
188.7
65.36
–
–
–
–
–
–
0.66
95.59
98.84
21.49
10.16
47.51
5.54
15.78
−25.27
100.49
Propyl
Hexyl
Decyl
Hexyl
21
22
Sitagliptin
Decyl
17.51
1.17
37.96
a
The IC50 value was not measured.
3

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Fig. 3. Dose-dependent inhibition of DPP-4 by compounds 11, 15, 16.
Fig. 6. Hyperglycaemic effect of compound 11. Data are expressed as
mean SD (n = 8). *p < 0.05 versus BKS db group.
Fig. 4. Compound 11 in the active site of DPP-4 with key interactions.
Fig. 5. Effects of 4 weeks treatment with compound 11 on mean water intake and body weight. (A): the water intake in BKS db mice during 4 weeks treatment with
vehicle, compound 11 and metformin, and in BKS mice treated with vehicle. Data are expressed as mean SD (n = 4). *p < 0.05 (compound 11 group versus BKS
db group). (B), (C) and (D): the body weight, abdominal fat weight and the fat ratio at the fourth week respectively. Data are expressed as mean
SD (n = 8).
#p < 0.05 versus BKS group.
4

N. Li et al.
Bioorganic&MedicinalChemistryLettersxxx(xxxx)xxx–xxx
of DPP-4; (b) the inhibitory rates increase with the decrease of the
number of bromine atoms on phenol moiety; (c) the alkyl side chain
could affect the DPP-4 inhibitory activity. (d) fluorocyanobenzyl was
crucial for the inhibitory activity of DPP-4. Among them, the re-
presentative compounds 11, 15 and 16 showed strong inhibitory ac-
tivity of DPP-4 with IC50 values of 64.47 nM, 188.7 nM and 65.36 nM,
respectively. Further studies revealed that compound 11 are potent in
vivo hypoglycemic effect. Potentially, compound 11 is a promising DPP-
4 inhibitor and worth further development.
A. Supplementary data
Supplementary data associated with this article can be found, in the
online version, at http://dx.doi.org/10.1016/j.bmcl.2018.05.022.
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