Novel series of 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides as potent and selective dipeptidyl peptidase IV inhibitors

Article abstract of DOI:10.1016/j.bmcl.2012.09.099

A series of novel 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides were investigated as dipeptidyl peptidase IV (DPP-4) inhibitors. Introduction of a 4-phenylthiazol-2-yl group showed highly potent DPP-4 inhibitory activity. Among various derivatives, (3R)-3-amino-N-(4-(4-phenylthiazol-2-yl)-tetrahydro-2H- thiopyran-4-yl)-4-(2,4,5-trifluorophenyl)butanamide 1,1-dioxide (30) reduced blood glucose excursion in an oral glucose tolerance test by oral administration.

Full text of DOI:10.1016/j.bmcl.2012.09.099

Bioorganic & Medicinal Chemistry Letters 22 (2012) 7036–7040
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Novel series of 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides
as potent and selective dipeptidyl peptidase IV inhibitors
⇑
Aiko Nitta , Hideaki Fujii, Satoshi Sakami, Mikiya Satoh, Junko Nakaki, Shiho Satoh, Hiroki Kumagai,
Hideki Kawai
Pharmaceutical Research Laboratories, Toray Industries, Inc., 6-10-1 Tebiro, Kamakura, Kanagawa 248-8555, Japan
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 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides were investigated as dipeptidyl
peptidase IV (DPP-4) inhibitors. Introduction of a 4-phenylthiazol-2-yl group showed highly potent
DPP-4 inhibitory activity. Among various derivatives, (3R)-3-amino-N-(4-(4-phenylthiazol-2-yl)-tetrahy-
dro-2H-thiopyran-4-yl)-4-(2,4,5-trifluorophenyl)butanamide 1,1-dioxide (30) reduced blood glucose
excursion in an oral glucose tolerance test by oral administration.
Received 20 August 2012
Revised 24 September 2012
Accepted 26 September 2012
Available online 2 October 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Dipeptidyl peptidase IV
Inhibitor
Diabetes
Glucagon-like peptide 1 (GLP-1),1 which is an incretin secreted
from L cells of the small intestine after ingestion of food, stimulates
insulin biosynthesis and release and inhibits glucagon release. It
also inhibits gastric emptying and regulates islet b-cell mass.2
Dipeptidyl peptidase IV (DPP-4) is a serine protease which selec-
tively cleaves dipeptide derived from the N-terminus of peptides.
One of the important roles of DPP-4 is rapid inactivation of GLP-1.
Inhibition of DPP-4 increases the concentration of endogenous
GLP-1 and, as a result, increases insulin secretion,3 which can ame-
liorate hyperglycemia in type 2 diabetes without any side effects
such as hypoglycemia and exhaustion of b-cells.4
(3R)-N-Boc-b-amino acid using a coupling reagent followed by oxi-
dation using mCPBA. Subsequently, iodides 5 were converted to
biaryls 20–25 by the Suzuki–Miyaura coupling reaction or Migi-
ta-Kosugi-Stille coupling reaction with various heteroaromatics
F
F
NH2 O
N
N
N
H
N
N
HO
CN
F
N
O
Among various DPP-4 inhibitors reported, Sitagliptin,5,6 Vildag-
liptin,7 Saxagliptin,8 Alogliptin,9 Linagliptin,10 and Teneligliptin
have received approval for the treatment of type 2 diabetes from
the FDA and/or the EMEA and/or Japan (Fig. 1).11,12
CF3
Sitagliptin
O
Vildagliptin
O
N
N
N
NH2
NC
We reported the b-amino amide derivatives as DPP-4 inhibi-
tors.13 Structurally, DPP-4 is similar to several other proteases, so
selectivity against other serine proteases is necessary, especially
DPP-8, DPP-9 and QPP.14 Our DPP-4 inhibitors mentioned above
showed good potency but poor selectivity against these enzymes.
In order to improve this weakness, our efforts were focused on mod-
ification of a heteroaryl group of the b-amino amide derivatives. In
this study, we report the synthesis and biological evaluation of an-
other series of 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butana-
mides as potent and selective DPP-4 inhibitors.
N
N
HO
N
N
N
O
NH2
Saxagliptin
Linagliptin
O
N
NH2
O
N
N
N
N
NH
N
N
The series and analogues of 3-amino-N-(4-aryl-1,1-dioxothian-
4-yl)butanamides were prepared by the acylation of amine 4 with
N
S
CN
Alogliptin
O
Teneligliptin
⇑
Corresponding author. Tel.: +81 467 32 9659; fax: +81 467 32 9891.
E-mail address: aiko_nitta@nts.toray.co.jp (A. Nitta).
Figure 1. Potent DPP-4 inhibitors.
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.09.099

A. Nitta et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7036–7040
7037
R1
S
O
S
I
S
I
I
S
R2
Boc
ii)
i)
iii)
iv)
v)
NH
O
HO
N
H
H2N
I
Cl
N
H
I
F
I
5a: R1=H, R2=H
1
2
3
4
5b: R1=F, R2=F
R1
F
O
O
R1
F
O
O
R1=H, R2=H, R3=
S
S
R2
Boc
R2
N
N
N
vi, vii)
N
N
NH
O
NH2
O
NH
R3
I
S
S
N
N
H
N
H
25
20
21
22
24
6a: R1=H, R2=H
6b: R1=F, R2=F
N
R1=F, R2=F, R3=
S
23
Scheme 1. Reagents and conditions: (i) 1 equiv n-BuLi/hex, THF, À78 °C, then 4-oxothiane, À78 °C ? rt, 85%; (ii) chloroacetonitrile, concd H2SO4, AcOH, rt; (iii) thiourea,
EtOH/AcOH (5:1), reflux; (iv) N-Boc-b-aminoacid, TsCl, N-methylimidazole, CH3CN, 0 °C-rt, then 4; (v) mCPBA, CH2Cl2, 0 °C; (vi) 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl) pyridine, PdCl2 (dppf), Cs2CO3, dioxane, 80 °C, or 2–3 equiv Het-SnBu3, Pd(PPh3)4, CH3CN, 80 °C or 2–3 equiv Het-SnBu3, Pd-C/CuI/AsPh3, CH3CN, 80 °C, (vii) HCl/MeOH, rt.
R1
F
R1
O
O
S
I
S
S
S
R2
Boc
R2
iii)
iv)
i)
ii)
NH
O
NH2 O
H2N
H2N
R3
N
R3
N
H
N
H
R3
F
N
N
3
N
8a: R1=F, R2=F, R3=
8b: R1=H, R2=H, R3=
8c: R1=H, R2=H, R3=
N
7a: R3=
19: R1=F, R2=F, R3=
26: R1=H, R2=H, R3=
27: R1=H, R2=H, R3=
N
N
N
S
N
S
7b: R3=
7c: R3=
S
N
N
N
N
N
N
S
S
S
Scheme 2. Reagents and conditions: (i) imidazole, CuI, Cs2CO3, dioxane, 1,10-phenanthroline, 110 °C, or 1 equiv Het-SnBu3, Pd(PPh3)4, CH3CN, 80 °C; (ii) N-Boc-b-aminoacid,
TsCl, N-methylimidazole, CH3CN, 0 °C ? rt, then 7; (iii) mCPBA, CH2Cl2, 0 °C; (iv) HCl/MeOH, rt.
O
HO2C
N
EtO2C
N
N
i)
ii)
iii)
Br
S
R
S
R
S
R2
R
R2
R2
R2
R
12a: R2=H, R=4-OMe
12b: R2=H, R=4-Cl
12c: R2=H, R=4-CF3
12d: R2=H, R=2-OMe
12e: R2=H, R=3-CF3
12f: R2=Me, R=H
11a: R2=H, R=4-OMe
11b: R2=H, R=4-Cl
11c: R2=H, R=4-CF3
11d: R2=H, R=2-OMe
11e: R2=H, R=3-CF3
11f: R2=Me, R=H
9a: R2=H, R=4-OMe
9b: R2=H, R=4-Cl
9c: R2=H, R=4-CF3
10a: R2=H, R=4-OMe
10b: R2=H, R=4-Cl
10c: R2=H, R=4-CF3
10d: R2=H, R=2-OMe
10e: R2=H, R=3-CF3
10f: R2=Me, R=H
9d: R2=H, R=2-OMe
9e: R2=H, R=3-CF3
9f: R2=Me, R=H
O
H2N
N
N
v)
vi)
iv)
S
S
R
R
R
14g: R=H
12g: R=H
13g: R=H
13h: R=4-F
14h: R=4-F
12h: R=4-F
N
N
N
vii)
HN
12i
15
viii)
O
H2NHN
R
N
N
O
R
12j: R=H
12k: R=F
12l: R=OMe
16j: R=H
16k: R=F
16l: R=OMe
Scheme 3. Reagents and conditions: (i) ethyl 2-amino-2-thioxoacetate, EtOH, reflux; (ii) NaOH aq., EtOH, rt; (iii) concd HCl, 1,4-dioxane, reflux; (iv) PhMe3NBr3, THF, rt; (v)
Thiourea, EtOH, reflux; (vi) 50% H2SO4, TFA, NaNO2 aq, À15 °C, then H3PO2 aq, À15 °C ? rt; (vii) NaH, MeI, DMF, rt, 59%; (viii) CH(OEt)3, 145 °C.

7038
A. Nitta et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7036–7040
Table 1
DPP-4 inhibiting activity and selectivity of compound
R1
F
O
O
S
R2
NH2 O
R3
N
H
R1
R2
R3
IC50 (lM)
a
Compound
DPP-4
QPP
DPP-8
DPP-9
17
18
19
20
21
22
23
24
25
26
27
H
F
F
H
F
F
H
H
0.57
28.4
6.7
4.6
ND
ND
ND
1.7
ND
34.6
ND
ND
49.0
13.6
5.0
ND
ND
ND
6.3
ND
45.4
ND
ND
9.0
3.0
0.083
0.012
0.49
1-Imidazolyl
4-Pyridyl
2-Thiazolyl
5-Thiazolyl
5-Thiazolyl
4-Pyrazolyl
1-Methyl-5-imidazolyl
2-Methyl-5-thiazolyl
2-Piperidyl-5-thiazolyl
1.7
ND
ND
ND
0.94
ND
11.2
ND
ND
H
H
H
F
H
H
H
H
H
H
H
F
H
H
H
H
0.39
0.041
0.0078
0.33
0.084
0.28
0.25
a
ND = no data.
followed by acidic deprotection (Scheme 1).15 Amine 3 from 1,3-
diiodobenzene 1 was prepared by the Ritter reaction: tertiary alco-
hol 2 derived from 4-oxothiane was converted to chloroacetamide
3 followed by dechloroacylation using thiourea.16 On the other
hand, amine 4 was directly converted to biarylamines 7 by the
Buchwald reaction with imidazole or the Migita-Kosugi-Stille cou-
pling reaction with stannyl thiazoles followed by acylation, oxida-
tion and deprotection (Scheme 2). The analogues 28–42 having a
direct bond with dioxothiane and the azoles were prepared from
4-oxothiane and substituted phenyl azoles 12, as shown in Scheme
3 followed by the synthetic route reported previously.13 Phenyl-
thiazols 12a–h were prepared by two methods from commercially
available 2-bromo-1-phenylethanones 9 or acetophenones 13.
De-esterification of ethyl 4-phenylthiazole-2-carboxylates 10 was
carried out by hydrolysis followed by decarboxylation. Deamina-
tion of 4-phenylthiazol-2-amines 14 was carried out by the Sand-
meyer reaction.17,18 Imidazole 12i and oxadiazoles 12j–l were
prepared by methylation of 15 and cyclization of benzohydrazides
16, respectively.19
Firstly, the synthesized compounds were evaluated for the
inhibition of DPP-4 derived from human colonic carcinoma cells
(Caco-2).20 The results of 4-phenyl-1,1-dioxothiane derivatives
Table 2
DPP-4 inhibiting activity and selectivity compound
R1
O
O
S
R2
NH2 O
N
H
R3
F
R1
R2
R3
IC50 (lM)
a
Compound
DPP-4
QPP
DPP-8
DPP-9
17
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
H
H
H
F
H
H
F
F
F
F
H
H
F
F
F
H
H
H
F
H
H
F
F
F
F
H
H
F
F
F
Ph
0.57
0.19
28.4
85.2
22.0
2.7
8.6
ND
ND
ND
ND
ND
29.4
45.4
ND
ND
ND
49.0
45.8
9.6
9.0
37.6
8.6
7.7
7.0
ND
ND
ND
ND
ND
8.8
17.4
ND
ND
ND
ND
2-Thiazolyl
4-Phenylthiazol-2-yl
4-Phenylthiazol-2-yl
4-(3-Methoxyphenyl)thiazol-2-yl
4-(4-Methoxyphenyl)thiazol-2-yl
4-(2-Methoxyphenyl)thiazol-2-yl
4-(4-Chlorophenyl)thiazol-2-yl
4-(4-(Trifluoromethyl)phenyl)thiazol-2-yl
4-(3-(Trifluoromethyl)phenyl)thiazol-2-yl
4-(4-Fluorophenyl)thiazol-2-yl
5-Methyl-4-phenylthiazol-2-yl
5-Phenyl-1,3,4-oxadiazol-2-yl
5-(3-Fluorophenyl)-1,3,4-oxadiazol-2-yl
5-(3-Methoxyphenyl)-1,3,4-oxadiazol-2-yl
1-Methyl-4-phenyl-1H-imidazol-2-yl
0.060
0.016
0.024
0.67
0.059
1.1
0.11
0.19
0.10
0.072
0.094
0.055
0.050
0.16
4.1
16.0
ND
ND
ND
ND
ND
9.2
20.9
ND
ND
ND
ND
F
F
ND
a
ND = no data.

A. Nitta et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7036–7040
7039
and selectivity against the other proteases. Among these deriva-
tives, oral administration of compound 30 reduced the blood glu-
cose excursion in OGTT. Further optimization of the derivatives is
now being investigated.
vehicle
350
300
250
200
150
100
50
30 (1mg/kg)
30 (3mg/kg)
30 (10mg/kg)
References and notes
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0
- 30
0
30
60
90
120
Time (min)
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Zhang, X. M.; Bollaert, W.; Lambeir, A. M.; Durinx, C.; Goossens, F.; Haemers, A.
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Deacon, C. F. Curr. Opin. Investig. Drugs 2005, 6, 419.
Figure 2. Effect of 30 in OGTT in ICR mice.
are shown in Table 1. Compounds 19 (IC50 = 0.012
(IC50 = 0.084 M) with imidazolyl substituents at the phenyl group
were more potent than unsubstituent derivatives 18
(IC50 = 0.083 M) and 17 (IC50 = 0.57 M) respectively. Thiazol-
5-yl derivatives 22 (IC50 = 0.041 M) and 23 (IC50 = 0.0078 M)
resulted in an increase in the inhibitory effects of DPP-4 against
thiazol-2-yl derivative 21 (IC50 = 0.39 M). For compounds 20
M), 26 (IC50 = 0.28 M) and 27
M), a substitution on the phenyl group did not exhibit
lM) and 25
l
l
l
l
l
l
7. (a) Villhauer, E. B.; Brinkman, J. A.; Naderi, G. B.; Burkey, B. F.; Dunning, B. E.;
Prasad, K.; Mangold, B. L.; Russell, M. E.; Hughes, T. E. J. Med. Chem. 2003, 46,
2774; (b) Ahrén, B. Expert Opin. Investig. Drugs 2006, 15, 431.
(IC50 = 0.49
(IC50 = 0.25
l
l
M), 24 (IC50 = 0.33
l
l
8. (a) Augeri, D. J.; Robl, J. A.; Betebenner, D. A.; Magnin, D. R.; Khanna, A.;
Robertson, J. G.; Wang, A.; Simpkins, L. M.; Taunk, P.; Huang, Q.; Han, S.-P.;
Abboa-Offei, B.; Cap, M.; Xin, L.; Tao, L.; Tozzo, E.; Welzel, G. E.; Egan, D. M.;
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C.; Kwon, C.; Zhao, G.; Magnin, D. R.; Augeri, D. J.; Gungor, T.; Rotella, D. P.; Sun,
Z.; Liu, Y.; Slusarchyk, W. S.; Marcinkeviciene, J.; Robertson, J. G.; Wang, A.;
Robl, J. A.; Atwal, K. S.; Zahler, R. L.; Parker, R. A.; Kirby, M. S.; Hamann, L. G.
Bioorg. Med. Chem. Lett. 2007, 17, 6476.
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Navre, M.; Shi, L.; Skene, R. J.; Asakawa, T.; Takeuchi, K.; Xu, R.; Webb, D. R.;
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sufficient effects.
Table 2 shows the evaluation results of 4-heteroaryl-1,1-dioxo-
thiane derivatives. Exchange of the phenyl group of compound 17
for the 2-thiazolyl group resulted in compound 28 (IC50 = 0.19 lM)
and improved DPP-4 inhibition potency. Addition of phenyl substi-
tuent to the thiazole ring of 28 exhibited excellent DPP-4 potency
of compound 29 (IC50 = 0.060
ously,13 the 2,4,5-trifluoro group on the left phenyl ring of 29
had very effective inhibitory activity (30: IC50 = 0.016 M). Intro-
lM). As for the SAR reported previ-
l
duction of substitutions on the 4-phenylthiazol-2-yl group was
examined in selected compounds 31–38. Compound 31 with a
3-methoxy substituent on the phenyl group exhibited some
improvements in potency over unsubstituted and other substi-
tuted derivatives (31: IC50 = 0.024 lM); however, it showed low
DPP-4 inhibitory activity in human plasma in vitro (data not
shown). Oxadiazole derivatives 39–41 and an imidazole derivative
42 did not exhibit very good activity.
Secondly, since inhibition of DPP-8 and DPP-9 was suggested to
be connected to toxicity,21 some inhibitors showing high DPP-4
inhibitory effects were tested for their selectivity profiles against
the DPP-4 homologues DPP-8, DPP-9 and also QPP. These data
are presented in Tables 1 and 2. Among the tested compounds,
selectivity for DPP-4 of 19, 23 and 25 in Table 1, and 28–31 and
38 in Table 2 over the related enzymes exceeded 100-fold.
Thirdly, mouse plasma DPP-4 activity was measured after oral
administration of compounds 19, 23 and 30, which was metaboli-
cally stable in humans and mice (data not shown) and exhibited
potent DPP-4 inhibition and high selectivity. Compounds 19 and
23 did not inhibit plasma DPP-4 activity at 100 mg/kg and
30 mg/kg, respectively, because the bioavailability of both 19 and
23 was lower (data not shown). On the other hand, DPP-4 inhibi-
tory activity of compound 30 in mouse plasma was observed in a
dose-dependent manner. Finally, when 1, 3, or 10 mg/kg of com-
pound 30 was administered orally to ICR mice, blood glucose
excursion in an oral glucose tolerance test (OGTT) was reduced
in a dose-dependent manner (Fig. 2).22
14. Augustyns, K.; Veken, P. V.; Senten, K.; Haemers, A. Curr. Med. Chem. 2005, 12,
971.
15. (a) Dondoni, A.; Mastellari, A. R.; Medici, A.; Negrini, E.; Pedrini, P. Synthesis
1986, 7579; (b) Elguero, J.; Jaramillo, C.; Pardo, C. Synthesis 1997, 563.
16. Jirgensons, A.; Kauss, V.; Kalvinsh, I.; Gold, M. R. Synthesis 2000, 12,
1709.
17. (a) Cadogan, J. I. G.; Molina, G. A. J. Chem. Soc., Perkin Trans. 1 1973, 541; (b)
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20. An extract from Caco-2 was used as the source of DPP-4 in the assay. The cell
extract was prepared from cells solubilized in lysis buffer (10 mM, Tris–HCl
(pH 8.0), 0.15 M NaCl, 0.04 U aprotinin, 0.50% Nonidet-P40), which were then
centrifuged at 18,500 g for 1 h at 4 °C to remove the cell debris. The assay was
conducted by adding 5
volume of 135 L in an assay buffer (25 mM Tris–HCl (pH 7.4), 0.14 M NaCl,
10 mM KCl, 1% (w/v) BSA) to 96-well flat-bottomed plates. The reaction was
initiated by adding 15 L of 0.4 mM substrate (Ala-Pro-AFC). The reaction was
run for 20 min at 37 °C, and then 10 L of 25% acetic acid was added to stop the
reaction. Fluorescence was measured using Fusion (excitation 380 nm;
lg of solubilized Caco-2 protein, diluted to a final
l
l
l
In conclusion, the novel series of 3-amino-N-(4-aryl-1,1-dioxo-
thian-4-yl)butanamidesexhibited marked DPP-4 inhibitory activity
a

7040
A. Nitta et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7036–7040
emission 485 nm). The test compounds and solvent controls were added to the
assay buffer.
Dimare, M. T.; Wu, W.; Liu, Y.; Maw, H.; Zhou, Y.; Li, Y.; Jin, Z.; Sudmeier, J. L.;
Lai, J. H.; Bachovchin, W. W. J. Med. Chem. 2008, 51, 6005.
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Chan, C.-C.; Edmondson, S.; Feeney, W. P.; He, H.; Ippolito, D. E.; Kim, D.; Lyons,
K. A.; Ok, H. O.; Patel, R. A.; Petrov, A. N.; Pryor, K. A.; Qian, X.; Reigle, L.; Woods,
A.; Wu, J. K.; Zaller, D.; Zhang, X.; Zhu, L.; Weber, A. E.; Thornberry, N. A.
Diabetes 2005, 54, 2988; (b) Burkey, B. F.; Hoffmann, P. K.; Hassiepen, U.;
Trappe, J.; Juedes, M.; Foley, J. E. Diabetes Obes. Metab. 2008, 10, 1057; (c)
Connolly, B. A.; Sanford, D. G.; Chiluwal, A. K.; Healey, S. E.; Peters, D. E.;
22. The mice were orally administered a vehicle (distilled water, 10 mL/kg) or 30
(10, 3, 1 mg/kg; 10 mL/kg). The blood glucose concentration was determined
by a glucometer from blood taken from a nick in the tail, 30 min after the
treatment. The mice were then orally challenged with glucose (2 g/kg; 10 mL/
kg). The blood glucose levels were determined from tail bleeds taken at
intervals of 20, 40, 60, and 120 min after the glucose challenge.