Discovery of potent dipeptidyl peptidase IV inhibitors derived from β-aminoamides bearing substituted [1,2,3]-triazolopiperidines for the treatment of type 2 diabetes

Article abstract of DOI:10.1016/j.bmcl.2011.01.086

A series of novel [1,2,3]-triazolopiperidine derivatives 5a-5y were synthesized and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-4) for the treatment of type 2 diabetes, most of the compounds exhibited excellent in vitro potency (IC₅₀

Full text of DOI:10.1016/j.bmcl.2011.01.086

Bioorganic & Medicinal Chemistry Letters 21 (2011) 1731–1735
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Discovery of potent dipeptidyl peptidase IV inhibitors derived
from b-aminoamides bearing substituted [1,2,3]-triazolopiperidines
for the treatment of type 2 diabetes
Zhenwei Shan a, , Min Peng b, , Houxing Fan c, Qingtao Lu a, Peng Lu c, Chuansheng Zhao c, Yilang Chen c,
⇑
a Department of Medicinal Chemistry, Shandong University of Traditional Chinese Medicine, Jinan, Shandong 250355, China
b Department of Medicinal Chemistry, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
c Department of Medicinal Chemistry, Shanghai Sun-Sail Pharmaceutical Science & Technology Co., Ltd, Shanghai 201203, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel [1,2,3]-triazolopiperidine derivatives 5a–5y were synthesized and evaluated as inhibi-
tors of dipeptidyl peptidase IV (DPP-4) for the treatment of type 2 diabetes, most of the compounds
exhibited excellent in vitro potency (IC50 <50 nM) against DPP-4. Among these, compound 5d with potent
in vitro activity against DPP-4 and good pharmacokinetic profiles exhibited pronounced in vivo efficacy in
an oral glucose tolerance test (OGTT) in ICR mice. On the base of these properties, compound 5d was
selected as a potential new candidate for the treatment of type 2 diabetes.
Received 17 November 2010
Revised 15 January 2011
Accepted 19 January 2011
Available online 22 January 2011
Keywords:
Dipeptidyl peptidase IV inhibitors
Type 2 diabetes
Ó 2011 Elsevier Ltd. All rights reserved.
Triazolopiperidine
Type 2 diabetes is a chronic disease characterized by elevated
plasma glucose in the presence of high endogenous insulin levels,
causing serious debilitating cardiovascular, significant morbidity,
nerve damage and mortality.1 In recent years, inhibition of dipep-
tidyl peptidase IV (DPP-4), a serine protease, has emerged as an
attractive new approach to the treatment of type 2 diabetes. It is
generally accepted that DPP-4 inhibitors exert their beneficial ef-
fects by increasing the levels of active glucagon-like peptide-1
(GLP-1) and glucose-dependent insulinotropic peptide (GIP), both
of which enhance insulin secretion in a glucose-dependent man-
ner.2 Additionally, GLP-1 stimulates insulin biosynthesis, inhibits
glucagon secretion, slows gastric emptying, reduces appetite, and
stimulates the regeneration and differentiation of islet b-cells.
DPP-4 inhibitors increase circulating GLP-1 and GIP levels in hu-
mans, which leads to decreased blood glucose levels, hemoglobin
A1C levels and glucagon levels.3
F
F
OH
F
O
NH2
N
N
N
N
N
H
N
CN
O
CF3
MK-0431:
NVP-LAF237:
Vildagliptin (2)
Sitagliptin (1)
O
OH
N
NC
N
O
H2N
N
N
O
NH2
NC
BMS-477118:
Saxagliptin (3)
SYR-322:
Alogliptin (4)
To date, several DPP-IV inhibitors have obtained approval as a
class of novel antidiabetic agents, the first marketed DPP-4 inhibi-
tor, Sitagliptin 1 was approved by FDA in October 2006 (Fig. 1); Vil-
dagliptin 2 was approved by the European Medicines Agency in
September 2007; Saxagliptin 3 was approved by FDA as a once-dai-
ly treatment for type 2 diabetes to be taken in combination with
diet and exercise.4 Recently, Alogliptin 4 had been launched in Ja-
pan as a potent (IC50 <10 nM) and highly selective DPP-4 inhibitor
Figure 1. Selected DPP-4 inhibitors.
(selectivity >10,000 over DPP-8 and -9).5 DPP-4 inhibitors possess
advantages over alternative diabetes therapies including a lowered
risk of hypoglycemia, a potential for weight loss, and the potential
for the regeneration and differentiation of pancreatic b-cells.6
Since Sitagliptin was identified as a potent, selective and orally
active antidiabetic agent for the treatment of type 2 diabetes,
development of novel antidiabetic agents based on the b-aminoa-
mide backbone of Sitagliptin has attracted the attention of
⇑
Corresponding author. Tel.: +86 21 50278490; fax: +86 21 50278483.
E-mail address: ylchen@sun-sail.cn (Y. Chen).
The authors contributed equally to this work.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.01.086

1732
Z. Shan et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1731–1735
researchers from both academic and industrial fields.7 According to
some reported structure–activity relationships (SARs) studies of
DPP-4 inhibitors, we knew that substitution of alkyl around b-ami-
noamide backbone was found to be detrimental to potency, alkyl
substitutions along with other modifications such as lengthening,
shortening, or tethering were also proved to be ineffective. We
therefore became interested in modifying the 3-(trifluoro-
methyl)-[1,2,4]-triazolopiperazine group of Sitagliptin 1 to various
C-4 substituted [1,2,3]-triazolopipera-zine group (Fig. 2). Herein,
we report our efforts towards the synthesis, SARs and biological
The synthesis of substituted [1,2,3]-triazolopiperdine inter-
mediates began by converting azide 68 to 7a–7c through intramo-
lecular cycloaddition reaction (Scheme 1). Treatment of 7a with
NBS in CH3CN afforded 8a, while 7b underwent standard hydroly-
sis reaction to give 8b. Compound 8a was treated with correspond-
ing Boronates via Suzuki–Miyaura couplings9 to generate 9a–9l or
with corresponding Stannane agents via Stille couplings10 to afford
9m–9p. Compound 8b readily underwent Swern oxidation11 to
give 10, which was reacted with DAST to obtain difluoromethy
9q or with TosMIC to afford fused oxazol-5-yl 9r.12 Meanwhile,
8b was treated with iodine in 2,2,2-trifluoroethanol to form 11,13
which was substituted by methanol, ammonium hydroxide and
dimethylamine to afford 9s–9u, respectively.
properties of
a series of potent DPP-4 inhibitors derived
from b-aminoamides bearing substituted [1,2,3]-triazolopiperdine
groups.
F
F
F
F
O
O
NH2
NH2
R
1
4
N
N
N
N
N
3
2
4
F
N
F
N
1
N
3
2
CF3
5
1 Sitagliptin
Figure 2. Design of substituted [1,2,3]-triazolopiperdine derivatives as DPP-4 inhibitors.
R
Boc
N3
R
Boc
N
a
N
N
N
N
7a: R = H
6
7b: R = CH2OAc
7c: R = Me
b
c
8a: R = Br
8b: R = CH2OH
9g: R1 = Ph-4-SO2Me
9a: R1 = Ph
d
R
9b: R1 = Ph-4-F
9c: R1 = Ph-4-Cl
9h: R1 = Ph-4-CO2Me
9i: R1 = Ph-4-CONMe2
Boc
N
R1
OH
N
B
N
N
9d: R1 = Ph-4-CF3 9j: R1 = Ph-4-CONH2
OH
9k: R1 = 2-Pyridine
9l: R1 = 4-Pyridine
9e: R1 = Ph-4-CN
9f: R1 = Ph-3-MeO
Br
Boc
N
N
N
N
R
8a
9m: R2 = 2-furanyl
9n: R2 = 3-furanyl
9o: R2 = 2-thienyl
9p: R2 = 3-thienyl
Boc
N
R
2SnBu3
e
N
N
N
CF2
N
H
g
Boc
N
N
O
N
f
Boc
9q
N
N
N
N
N
O
10
h
OH
Boc
Boc
N
N
Boc
N
N
N
N
N
N
9r
N
8b
F F
O
N
F
O
N
R
9s: R = OCH3
9t: R = NH2
9u: R = NMe2
O
Boc
j
i
N
N
N
N
N
11
Scheme 1. Reagents and conditions: (a) DMSO, 150 °C; (b) NBS, CH3CN (51% yield); (c) LiOH, MeOH/H2O (80% yield); (d) Pd(PPh3)4, K2CO3, dioxane/H2O; (e) Pd(PPh3)4,
toluene; (f) (COCl)2, DMSO, DIPEA, CH2Cl2, À78 °C (78% yield); (g) DAST, CH2Cl2 (51% yield); (h) TosMIC, MeOH, K2CO3, reflux (59% yield); (i) CF3CH2OH, I2, K2CO3 (35% yield);
(j) CH3OH, reflux (for 9s, 45% yield); NH3H2O, rt (for 9t, 86% yield); NH(CH3)2, K2CO3 (for 9u, 98% yield).

Z. Shan et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1731–1735
1733
O
N
O
F3C
CF3
EtO
OEt
EtOOC
CF3
H
N
N
N
N
N3
Cbz
N
N
a
NHCbz
NHCbz
12
13a
13b
O
N
F3C
OEt
O
CF3
CF3
N
c
b
HN
N
N
N
HN
N
N
N
N
NH2
14a
14b
15v
Scheme 2. A novel synthetic method for 15v. Reagents and conditions: (a) toluene, rt, overnight (97% yield); (b) 10% Pd/C, H2, rt; reflux (35% yield, 2 steps); (c) LiAlH4, THF
(43% yield).
F
Boc
F
HN
O
R
R
OH
Boc
a
HN
16
N
F
F
F
N
N
N
N
N
N
b
7a, 7c, 9
15
HX
NH2
F
F
Boc
O
F
F
HN
O
c
R
R
N
N
N
N
N
N
N
N
5a-5p, 5r-5y
17
d
5q
5p
Scheme 3. Reagents and conditions: (a) TFA, CH2Cl2; (b) HOBT, EDC, TEA, CH2Cl2, rt; (c) CF3COOH, CH2Cl2; HX, rt; (d) LiOH, TEA, CH2Cl2.
As shown in Scheme 2, trifluoromethyl intermediate 15v was
readily synthesized from azide 12 in three steps. Cycloaddition of
azide 12 with ethyl 4,4,4-trifluorobut-2-ynoate in toluene to give
a mixture of isomers (13a and 13b). Without further purification,
the mixture of 13a and 13b directly underwent deprotection of
Cbz group by catalytic hydrogenation, followed by filtration and
refluxing overnight to form 14a and 14b, which were treated with
1 M HCl to afford the pure 14a in organic phase, finally, the desired
intermediate 14a reacted with LAH to yield trifluoro-methyl 15v.
After removal of N-protected Boc group of previously prepared
intermediate amines 7a, 7c, 9 (shown in Scheme 1), the resulting
amino 15 were treated with b-amino acid 16 under the typical
HOBT/EDC condensation conditions14 followed by deprotection of
Boc group to afford the target compounds 5a–5p and 5r–5y
(Scheme 3), while compound 5q was obtained from compound
5p by hydrolysis reaction. All the target compounds were con-
firmed by 1H NMR and MS (ESI) data.15
which showed improved potency against DPP-4 than simple alkyl
analogues 5a–d, electron-withdrawing groups may be favorable
to potency, especially compound 5e (IC50 = 15.09 nM) displayed
more potent activity than Sitagliptin. Unfortunately, compound
5e did not have the required solution stability to warrant further
evaluation.
To further improve the potency of this series of compounds,
(un)substituted phenyl analogues 5h–5r were synthesized, all
compounds except compound 5k exhibited potent activity with
IC50 <50 nM, methyl benzoate derivative 5p showed the most po-
tent activity with IC50 of 12.4 nM. To further study, compounds
5s–5y with different heteraryl substitutents were prepared. Among
these, 2-furyl derivative 5u showed more potent activity than the
other heteraryl derivatives, but there is not significant difference
between them, compounds 5u (IC50 = 15.8 nM) and 5y (IC50
17.83 nM) showed more potent activity than Sitagliptin (IC50
19.4 nM).
=
=
Inhibitory potency of the synthesized compounds was mea-
sured by monitoring the hydrolytic reaction of Ala-Pro-amidom-
ethyl-coumarin (Ala-Pro-AMC) by human DPP-4 with Sitagliptin
as positive control, and the results are reported as concentrations
for 50% inhibition (IC50). As shown in Table 1, most of the com-
pounds exhibited excellent in vitro potency (IC50 <50 nM) against
DPP-4. The C4-unsubstituted compound 5a exhibited the weakest
activity with IC50 of 89.5 nM; while substituted 5a with simple al-
kyl group (compounds 5b–5d) resulted in superior activity to com-
pound 5a, especially compound 5c was similar in potency to
Sitagliptin with IC50 of 22.53 nM. Introduction of methoxycarbonyl
or amide substitutents to compound 5a afforded compounds 5e–g,
Selected compounds (5c, 5d, 5f, 5q, 5t, 5u and 5y) were further
subjected to pharmacokinetic properties study in healthy male rats
(200–220 g weight, four rats in each group), the test compounds
were administered orally at the dose of 20 mg/kg. The results seen
in Table 2. Trifluoromethyl derivative 5d exhibited favorable phar-
macokinetic profiles with moderate half-life (2.53 h) and excellent
AUC (4559 ng/mL h). Compounds 5c and 5t exhibited accepted
pharmacokinetic properties, while compounds 5f and 5u were
unfavorable.
Furthermore, compounds 5c, 5d and 5t, exhibited excellent
in vitro potency and favorable pharmacodynamic profiles, were
chosen for the assessment of their ability to improve oral glucose

1734
Z. Shan et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1731–1735
Table 1
a
400
350
300
250
200
150
100
50
Inhibitory properties of substituted [1,2,3]-triazolopiperazine analogues 5a–5y
vehicle
5c 3mg/kg
5d 3mg/kg
5t 3mg/kg
Control
HX
NH2
F
F
O
R
N
N
F
N
N
a
Compd
R
HX
DPP-IV IC50 (nM)
0
5a
5b
5c
5d
5e
5f
5g
5h
5i
H
CH3
CF2H
CF3
Fumaric acid
HCl
HCl
Fumaric acid
HCl
HCl
89.50
77. 06
22.53
50.66
15.09
29.92
52.34
37.54
45.20
46.89
75.35
30.03
46.61
36.43
26.64
12.40
33.78
33.17
28.60
33.25
-60
0
20
40
60
120
Time (min)
b
400
350
300
250
200
150
100
50
CO2Me
CO2NH2
CO2NMe2
Ph
Ph-4-F
Ph-4-Cl
Ph-4-CF3
Ph-4-CN
Ph-3- CO2Me
Ph-4-CONH2
Ph-4-CONMe2
Ph-4-CO2Me
Ph-4-COOH
Ph-4-SO2Me
4-Pyr
vehicle
5c 10mg/kg
5d 10mg/kg
5t 10mg/kg
Control
HCl
H3PO4
H3PO4
HCl
HCl
HCl
HCl
HCl
HCl
H3PO4
HCl
5j
5k
5l
5m
5n
5o
5p
5q
5r
5s
5t
0
-60
0
20
40
60
120
Time (min)
HCl
HCl
Fumaric acid
c
35000
30000
25000
20000
15000
10000
5000
0
2-Pyr
0%
O
inh.
5u
5v
HCl
15.80
26.17
22.76
19%
inh.
27%
inh.
O
100%
Fumaric acid
HCl
inh.
S
S
5w
control
vehicle
Compound 5d (mg/kg)
3
10
5x
Fumaric acid
Fumaric acid
47.27
O
N
Figure 3. (a,b) Effect of compounds 5c, 5d and 5t (3, 10 mg/kg) on glucose levels
after an oral glucose tolerance test; (c) the suppression of glucose AUC was
calculated from 0 to 120 min. Data are represented as mean SEM (n = 7–10/
group).
5y
17.83
19.40
1
a
Means of at least three experiments; standard derivatives are 20%.
5d with potent in vitro activity against DPP-4 and good pharmaco-
kinetic profiles exhibited pronounced in vivo efficacy in an oral
glucose tolerance test (OGTT) in ICR mice. On the base of these
properties, compound 5d was selected as a potential new candi-
date for the treatment of type 2 diabetes, and further study of com-
pound 5d against a panel of related peptidases, including DPP7,
DPP8, DPP9, POP and FAP is underway in our laboratory.
Table 2
Pharmacokinetic properties of the selected compoundsa
Entry
Compd
Cmax (ng/mL)
Tmax (h)
t1/2 (h)
AUC0–t (ng/mL h)
1
2
3
4
5
6
7
5c
5d
5f
5q
5t
695
965
231
600
484
255
475
1.00
0.88
0.63
0.38
1.38
1.00
1.88
2.27
2.53
2.23
2.18
2.67
1.87
1.35
2524
4559
871
1128
2509
730
Acknowledgments
5u
5y
1643
The authors are thankful for the financial support from Shang-
hai Municipal Natural Science Foundation (Project 09431901800).
a
All PK was measured in rats (n = 4) at 20 mg/kg dose. Cmax, maximal concen-
tration when dosed orally; Tmax, time of maximum concentration; t1/2, terminal
half-life when dose orally; AUC, area under curve. For structures, see Table 1.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2011.01.086.
tolerance in ICR mice. Results on an oral glucose tolerance test
(OGTT) and corresponding pharmacodynamic (PD) studies in ICR
mice are shown in Figure 3, Each of compounds or water (vehicle)
was orally administered 60 min prior to an oral dextrose challenge
(5.0 mg/kg), compound 5d significantly reduced peak blood glu-
cose excursion.
In summary, we described the synthesis, SARs and biological
evaluations of a novel series of [1,2,3]-triazolopiperidine deriva-
tives as highly potent DPP-IV inhibitors. Among these, compound
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15. (a) All new compounds were characterized by 1H NMR and LC-MS prior to
submission for biological evaluation. (b) Compound 5d: 1H NMR (400 MHz,
CD3OD, 5d fumarate salt): d 7.33–7.39 (m, 1H), 7.19–7.25 (m, 1H), 6.66 (s, 1H),
5.04–5.10 (d, 1H), 4.90–4.93 (d, 1H), 4.53–4.58 (m, 1H), 4.47–4.50 (m, 1H),
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C
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13.03.