Design, synthesis and evaluation of potent G-protein coupled receptor 40 agonists

Article abstract of DOI:10.1016/j.cclet.2015.09.002

GPR40 has emerged as an attractive drug target for the treatment of type 2 diabetes due to its role in the enhancement of insulin secretion with glucose dependency. With the aim to improve the metabolic and safety profiles, a series of novel phenylpropionic acid derivatives were synthesized. Extensive structural optimization led to identification of compounds 22g and 23e as potent GPR40 agonists with moderate liver microsomal stability. All the discovery supported further exploration surrounding this scaffold.

Full text of DOI:10.1016/j.cclet.2015.09.002

Chinese Chemical Letters 27 (2016) 159–162
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
Original article
Design, synthesis and evaluation of potent G-protein coupled receptor
40 agonists
a,
Jing Huang a,1, Bin Guo b,1, Wen-Jing Chu b, Xin Xie c, Yu-She Yang b, , Xian-Li Zhou
*
*
a School of Life Science and Engineering, Southwest Jiao Tong University, Chengdu 610031, China
b State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
c CAS Key Laboratory of Receptor Research, The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences,
Shanghai 201203, China
A R T I C L E I N F O
A B S T R A C T
Article history:
GPR40 has emerged as an attractive drug target for the treatment of type 2 diabetes due to its role in the
enhancement of insulin secretion with glucose dependency. With the aim to improve the metabolic and
safety profiles, a series of novel phenylpropionic acid derivatives were synthesized. Extensive structural
optimization led to identification of compounds 22g and 23e as potent GPR40 agonists with moderate
liver microsomal stability. All the discovery supported further exploration surrounding this scaffold.
ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
Received 11 February 2015
Received in revised form 10 May 2015
Accepted 12 August 2015
Available online 21 September 2015
Keywords:
GPR40
Anti-diabetic
Agonist
Phenylpropionic acid derivative
1. Introduction
clinical trials, exemplified by TAK-875, AMG-837 and LY2881835
(Fig. 1) [6]. Unfortunately, these compounds have been terminated
The prevalence of type 2 diabetes (T2DM) is now a serious
global health burden. The total number of people suffering from
diabetes is expected to grow from 171 million in 2000 to
366 million by 2030 [1]. Despite some medications are available
for treatment of T2DM, current therapy is often associated with
weight gain and hypoglycemia (sulfonylureas), also with other
adverse effects such as gastrointestinal discomfort or edema
[2]. Therefore, there still remains a significant unmet need for new
effective, oral anti-diabetic agents that improve glycemic control
while maintaining an excellent safety profile.
due to safety concerns [6]. By analyzing their structures, we find
that there is a common structural moiety of benzyloxy fragment in
these compounds. This may cause poor oral pharmacokinetic
profiles (PK) and potential safety concern due to benzaldehyde
moiety resulted from metabolic oxidation at the benzyl position
[7]. Therefore, as an effort to identify novel GPR40 agonists with
improved PK and safety profiles, we designed a series of new
linkers between the left phenyl (B ring) and phenylpropanoic acid
to avoid benzyl oxidation. This paper described the synthesis and
biological evaluation of a series of novel phenylpropanoic acid
derivatives as potential GPR40 agonists (Fig. 2).
The G protein-coupled receptor 40 (GPR40, also known as FFA1)
primarily expressed in pancreatic
b-cells and enteroendocrine
cells of the small intestine [3]. When activated by medium to long
chain fatty acids, GPR40 elicits enhanced insulin secretion only in
the presence of elevated glucose but does not affect insulin
secretion at low glucose levels [4,5]. This alluring mechanism to
treat type 2 diabetes presents that small molecule agonists of
GPR40 may serve as novel insulin secretagogues with little or no
risk of hypoglycemia. In recent years, a number of potent GPR40
agonists have been reported and some of them have progressed to
2. Experimental
The synthetic routes of compounds 7 and 13 are outlined in
Scheme 1. Condensation of compounds 4a and b with propargyl
bromide in the presence of potassium carbonate as a base afforded
5a and b. Compounds 6 and 10 were obtained by Sonogashira
cross-coupling reaction of 5a and b and appropriate aromatic
bromides [8]. Deprotection of 10 in THF with tetrabutylammonium
fluoride and further esterification with triflic anhydride gave
11. Suzuki-Miyaura cross-coupling of 11 with 3-methoxybenze-
neboronic acid provided 12. Basic hydrolysis of intermediates 6
and 12 afforded the corresponding carboxylic acids 7 and 13,
respectively.
*
Corresponding authors.
E-mail addresses: ysyang@simm.ac.cn (Y.-S. Yang), xxbiochem@163.com
(X.-L. Zhou).
1
These authors contributed equally to this work.
http://dx.doi.org/10.1016/j.cclet.2015.09.002
1001-8417/ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.

160
J. Huang et al. / Chinese Chemical Letters 27 (2016) 159–162
Fig. 1. Structures of representative GPR40 agonists.
Fig. 2. Design of phenylpropanoic acid derivatives with new linker.
Scheme 1. Synthesis of compounds 7 and 13. Reagents and conditions: (a) K2CO3, DMF, propargyl bromide, 80 8C, 88%–91%; (b) 5a and 2-bromophenylacetonitrile, Na2PdCl4,
CuI, H2O, TMEDA, 2-(di-tert-butylphosphino)-1-phenylindole, 80 8C, 62%; (c) 1 mol/L LiOH aq., MeOH, r.t., 82%–87%; (d) TBSCl, TEA, THF, r.t., 92%; (e) 5b and 9, Na2PdCl4, CuI,
H2O, TMEDA, 2-(Di-tert-butylphosphino)-1-phenylindole, 80 8C, 76%; (f) TBAF, THF, r.t., 94%; (g) triflic anhydride; pyridine, DCM, 92%; (h) 3-methoxybenzeneboronic acid,
2 mol/L Na2CO3, LiCl, Pd(PPh3)4, 85 8C, 75%.
Compounds 16, 22a–g and 23a–e were synthesized according
to Scheme 2. The preparation of compound 16 began with the
conversion of compound 14 to 15, which was followed by
Sonogashira coupling with 25 and basic hydrolysis. Compounds
17a–c were protected by benzyl bromide and then coupled with
pinacolborane to give boronic esters 19a–c. Suzuki coupling of
19a–c with appropriate aromatic bromides provided 20a–
f. Compounds 21a–f were yielded by deprotection of intermediates
20a–f and then alkylation of the phenols. Sonogashira coupling of
21a–f with group 24 or 25, and followed by final basic hydrolysis
resulted in 22a–g. Compounds 23a–e were synthesized from the
intermediate 21f and 26a–e [9] according to the synthesis
procedures of 22a–g.
moiety with propinyloxy group to avoid benzyl oxidation. First we
investigated the effect of different connection position of
propinyloxy with two phenyl rings (A ring and B ring) on the
GRP40 agonistic activity (Table 1). Docosa-hexaenoic acid (DHA),
the endogenous ligand for GPR40, was selected as positive control.
The results indicated that compounds with linker L2 showed more
potent GPR40 agonistic activity than those with linker L1
(compound 7 vs. 16; 13 vs. 22a). Accordingly, we chose compound
22a as a new lead compound for further chemical optimization and
focused our investigation to the substituents on the phenyl ring
and b-position to the carboxylic function (Table 2). The CF3 (22b)
substituent provided a significant decrease in agonistic activity.
When introduced the same tail as seen in compound TAK-875, the
derivative (22c) showed slightly weaker potency than compound
22a. So we kept the methoxy group as the favorable substituent at
the 500-position of C ring. Then a fluoro group was introduced into
3. Results and discussion
Agonist activities of the synthesized compounds were mea-
sured with Calcium flux assay in GPR40-transfected HEK293 cells
[10]. As a starting modification effort, we exchanged benzyloxy
the 2-position of the A ring, which increased the activity
significantly (22d). We next turned our attention to optimize
the biphenyl group. About 2-fold increase in potency was observed

J. Huang et al. / Chinese Chemical Letters 27 (2016) 159–162
161
Scheme 2. Synthesis of compounds 16, 22a–g and 23a–e. Reagents and conditions: (a) K2CO3, DMF, propargyl bromide, 80 8C, 81%–86%; (b) 25, Na2PdCl4, CuI, 2-(di-tert-
butylphosphino)-1-phenylindole, H2O, TMEDA, 80 8C, 86%; (c) 1 mol/L LiOH aq., MeOH, r.t., 62%–91% (2steps); (d) BnBr, K2CO3, DMF, 50 8C, 95%–97%; (e) Potassium acetate,
Pd(dppf)Cl2, 1,4-dioxane, bis(pinacolato)diboron, 85 8C, 90%–96%; (f) Pd(PPh3)4, Cs2CO3, appropriate aromatic bromides, 85 8C, 84%–92%; (g) Pd/C, H2, Etethyl acetate, r.t.,
96%–98%; (h) 24 or 25, Na2PdCl4, CuI, 2-(Di-tert-butylphosphino)-1-phenylindole, H2O, TMEDA, 80 8C, 56%–82%; (i) 21f and 26a–e, Na2PdCl4, CuI, 2-(di-tert-butylphosphino)-
1-phenylindole, H2O, TMEDA, 80 8C, 51%–67%.
when the methyl group was moved from 30-positon of B ring to 200-
position of C ring (22e). Unfortunately, the agonistic activity
drastically decreased when incorporation another fluoro group in
Table 2
GPR40 agonistic activities of compounds 22a–g and 23a–e.
the B ring (22f). Replacement of the methyl of 22f with a fluoro
R2
R4
group in the C ring led to 2-fold improvement on potency (22g).
R5
2
A
R
O
B
5'
C
5''
Table 1
O
GPR40 agonistic activities of compounds 7, 13, 16 and 22a.
R1
R3
OH
a
Compound R1
R2
R3
R4
R5
R
EC50
(
m
mol/L)
22a
22b
22c
22d
22e
22f
CH3 CH3 CH3O
CH3 CH3 CF3
H
H
H
H
H
H
H
F
H
2.60
H
10.72
2.64
CH3 CH3 CH3SO2(CH2)3O
CH3 CH3 CH3O
H
H
0.951
0.526
0.913
0.266
H
F
H
H
H
H
H
H
H
H
CH3O
CH3O
CH3O
CH3O
CH3O
CH3O
CH3O
CH3O
CH3
F
H
CH3
F
F
H
22g
23a
23b
23c
23d
23e
DHA
H
H
H
H
H
H
F
H
a
Compound
L
EC50
(
mmol/L)
F
H
H
H
H
H
methoxy-
ethoxy-
ethyl-
>10
0.692
>10
7
L1
L1
L2
L2
>10
>10
F
13
F
16
1.22
2.60
F
cyclopropyl- >10
1-propinyl- 0.268
14.86
22a
DHA
F
14.86
a
a
Calcium flux assay in GPR40-transfected HEK293 cells. Means of two
Calcium flux assay in GPR40-transfected HEK293 cells. Means of two
experiments.
experiments.

162
J. Huang et al. / Chinese Chemical Letters 27 (2016) 159–162
Table 3
potent GPR40 agonists with EC50 0.266
mmol/L and 0.268 mmol/L,
Liver microsomal stability of compounds 22g and 23ea.
respectively. Additionally, both compounds showed moderate
metabolic stability in liver microsomal stability assay. All these
finding support further exploration based on this scaffold and the
optimization results will be reported in due course.
c
Compound
Species
Microsomal
Clint (mL/min/mg
b
t1/2 (min)
protein)
22g
23e
Human
Mouse
Human
Mouse
53.4
56.2
40.7
46.6
39
38
52
45
Acknowledgment
a
0.33 mg/mL microsomal protein, NADP+-regenerating system,[inhibitor],
This work was supported by grants from the National Natural
Science Foundation of China (No. 2140222).
0.1 mmol/L, incubation at 37 8C, samples taken at 0, 7, 17, 30, and 60 min,
determination of parent compound by MS.
b
t1/2: elimination half-life in rat liver microsomes.
c
Clint: intrinsic body clearance.
Appendix A. Supplementary data
In order to reduce the potential for
acid head, a series of small residues were introduced into the
position [10]. As shown in Table 2 (compound 23a–e), the activity
on the GPR40 varied significantly with different groups at the
b-oxidation of the propionic
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.cclet.2015.09.002.
b
-
b
-
References
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ethyl, or cyclopropyl groups were introduced (compound 23a, 23c
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were tolerant. The most potent alkyne derivative 23e displayed
comparable agonistic activity with compound 22g.
To evaluate the metabolic stability, compounds 22g and 23e
were subjected to the human and mouse liver microsomal stability
assays. As shown in Table 3, both compounds displayed moderate
metabolic stability with an acceptable clearance and half-life.
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Inconclusion,toimprovethepharmacokineticandsafetyprofiles
of the reported benzyloxy-like GPR40 agonists, a series of novel
phenylpropionic acid analogs were designed and synthesized with
redesignlinker between the B ring and phenylpropionic acid moiety.
TheirGPR40agonisticactivitieswerethenevaluatedinHEK293cells
stably expressing human GPR40. The results showed that oxypro-
pinyl (L2) was a preferred linker. Around this new structure,
comprehensive chemical modification was carried on. By focusing
investigationtothesubstituentsonthephenylringand
b-positionof
propionic acid, compounds 22g and 23e were identified as the most