Hybridization of non-sulfonylurea insulin secretagogue and thiazolidinedione-derived insulin sensitizer

Article abstract of DOI:10.1016/S0960-894X(00)00491-1

Hybrid compounds of non-sulfonylurea insulinotropic agents and thiazolidinedione-derived insulin-sensitizing agents were designed and synthesized. The benzylidenesuccinic acid derivative 24 was equal both to nateglinide in potency of insulin-releasing activity and to pioglitazone in insulin-sensitizing activity. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0960-894X(00)00491-1

Bioorganic & Medicinal Chemistry Letters 10 (2000) 2453±2456
Hybridization of Non-Sulfonylurea Insulin Secretagogue and
Thiazolidinedione-Derived Insulin Sensitizer
Hiroshi Kitajima,* Mitsuharu Nakamura, Hiroki Tamakawa and Nobuharu Goto
Department of Discovery Research, Wel®de Corporation, Shodai-Ohtani 2-chome, Hirakata-shi, Osaka 573-1153, Japan
Received 27 June 2000; accepted 19 August 2000
AbstractÐHybrid compounds of non-sulfonylurea insulinotropic agents and thiazolidinedione-derived insulin-sensitizing agents were
designed and synthesized. The benzylidenesuccinic acid derivative 24 was equal both to nateglinide in potency of insulin-releasing
activity and to pioglitazone in insulin-sensitizing activity. # 2000 Elsevier Science Ltd. All rights reserved.
Chemistry
Introduction
Pioglitazone was selected as the prototype from among
Type 2 diabetes (non-insulin-dependent diabetes melli-
tus) is a progressive metabolic disorder characterized by
defective insulin secretion from pancreatic b-cells and
insulin resistance in peripheral tissues. Accordingly,
both enhancement of insulin secretion and reduction of
insulin resistance may be of importance for its treat-
ment. Combination therapy of sulfonylurea and insulin
sensitizers has been reported to exert an additional
antihyperglycemic e€ect compared with sulfonylurea
alone.1 Therefore, we considered that a compound pos-
sessing both insulinotropic and insulin-sensitizing
activity would be promising anti-diabetic agent.
a number of TZD insulin sensitizers as it has been
reported to have moderate insulinotropic activity.7
Scheme 1 shows the preparation of the nateglinide±pio-
glitazone hybrid molecule. The N-acylated tyrosine 1,
which was prepared by condensation of dl-tyrosine
methyl ester with trans-4-isopropylcyclohexanecarboxylic
acid, was treated with 2-(5-ethyl-2-pyridyl)ethanol
under Mitsunobu reaction conditions. Saponi®cation
with 2 N NaOH gave the desired hybrid molecule 2. The
KAD-1229±pioglitazone hybrid molecule (9, R=5-
ethyl-2-pyridyl) and related compounds were prepared
as shown in Scheme 2. The (E)-benzylidenesuccinate 5
was obtained by Stobe condensation between 4-hydroxy-
benzaldehyde (3) and diethyl succinate (4) in the pre-
sence of 2.5 equiv of NaOEt. Catalytic hydrogenation
of 5 followed by coupling with cis-hexahydroisoindoline
gave the amidoester 7. O-Alkylation of 7 with the tosylate
of 2-(5-ethyl-2-pyridyl)ethanol and subsequent saponi®-
cation a€orded the desired hybrid 9 as a racemate. The
a,b-unsaturated analogue 10 was obtained by omitting
the above catalytic hydrogenation, or alternatively from
the known O-alkylated benzaldehyde 11.8 The optically
pure (S)-isomer of 9 was prepared from 2-(4-benzyloxy)
phenylpropionic acid modi®ed with Evans' chiral aux-
iliary9 (R)-4-benzyl-1,3-oxazolidine-2-one utilizing highly
diastereoselective alkylation of bromoacetate as shown
in Scheme 3. (R)-9 was obtained by using an enantiomer
of the auxiliary.10
The recently developed non-sulfonylurea class of insuli-
notropic agents includes two, nateglinide2 and KAD-
1229,3 which have a b-phenylpropionic acid structure
with amide functionality adjacent to the carboxyl
group. Meanwhile, a series of 5-benzylthiazolidine-2,4-
dione (TZD) compounds (e.g. troglitazone and piogli-
tazone)4 and analogous phenylpropionic acid deriva-
tives5 have been developed as insulin-sensitizing agents.
Of these, the amide-containing b-phenylpropionic acid
AÐthe main metabolite of the isoxazolidinedione insu-
lin sensitizer JTT-501Ðhas been reported as showing
potent insulin-sensitizing activity.6 Intrigued by the
structural similarity between the non-sulfonylurea insu-
lin secretagogues and the insulin sensitizers, we designed
hybrid molecules of these distinct hypoglycemic agents
based on a b-phenylpropionic acid (Chart 1).
Results and Discussion
Compounds were screened for insulin-releasing activity
in HIT-T15 cells in the presence of 16.7 mM of
*Corresponding author. Tel.: +81-72-850-0510; fax: +81-72-867-
4301; e-mail: kitajima_hiroshi@wel®de.co.jp
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00491-1

2454
H. Kitajima et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2453±2456
glucose11 and for insulin-sensitizing activity by measur-
ing the triglyceride accumulation resulting from insulin-
regulated di€erentiation of 3T3-L1 cells.12 Values in
Table 1 are given as a percentage of nateglinide response
for insulin-releasing activity and of pioglitazone
response for insulin-sensitizing activity.
As indicated in Table 1, simple hybridization was found to
result in decrease of both activities. Although (S)-9
showed almost the same insulinotropic activity as nategli-
nide at a concentration of 10 mM, little insulin-sensitizing
activity was observed. It has been reported that l-tyr-
osine-based insulin sensitizers have more potent activity
Chart 1.
Scheme 1. Synthesis of nateglinide±pioglitazone hybrid molecule. Reagents: (a) trans-4-isopropylcyclohexanecarboxylic acid, WSCD-HOBt; 78%;
(b) 2-(ethyl-2-pyridyl)ethanol, Ph3P, DEAD, THF, 46%; (c) 2 N NaOH, 81%.
Scheme 2. Synthesis of KAD-1229-pioglitazone hybrid molecule and related compounds. Reagents: (a) NaOEt (2.5 equiv), EtOH, re¯ux 72%; (b)
H2±Pd/C, EtOH, 99%; (c) cis-hexahydroisoindoline, WSCD-HOBt, DMF; (d) tosylate of R-(CH2)n-OH, K2CO3, CH3CN, re¯ux; (e) 2 N NaOH; (f)
NaOEt (1.5 equiv), EtOH, re¯ux.
Scheme 3. Synthesis of chiral KAD-1229-pioglitazone hybrid molecule. Reagents: (a) LDA, BrCH2CO2But, THF and then crystallization, 58%; (b)
H2±Pd/C; (c) TFA, 67% (two steps); (d) cis-hexahydroisoindoline, Bop reagent, DMF, 62%; (e) 2-(5-ethyl-2-pyridyl)ethanol, Ph3P, DEAD, THF,
24%; (f) LiOOH, THF, 95%.

H. Kitajima et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2453±2456
2455
than their d-antipodes,5e but also that the l-antipode of
nateglinide shows little correlation with insulinotropic
activity.13 This ®nding suggested that our target hybrid
molecules ought to be achiral ones. Encouragingly, the
benzylidenesuccinic acid compound 10 showed increase
in both activities compared to the saturated racemic 9.
We therefore next synthesized the benzylidenesuccinic
acids 16±24, in which the pyridyl moiety of 10 was sub-
stituted with other aryl- or arylamino groups found in
TZD-based insulin sensitizers. Synthesis of these analo-
gues was carried out in a similar manner to that illu-
strated in Scheme 2.
Table 2 summarizes screening data for the synthesized
benzylidenesuccinic acid hybrid molecules. Replacement
of the pyridyl group of 10 with 4-substituted phenyl or
1-indolyl groups to give 16±19 decreased insulin-sensi-
tizing activity, although insulin-releasing activity was
maintained. In contrast, compounds 20±21, which pos-
sessed N-methylheteroaryl groups derived from BRL-
49653 and its analogues,14 showed increased insulin-
sensitizing activity but with reduced insulinotropic
activity. Substitution with the 5-methyl-2-phenylox-
azolyl group to give 24 successfully increased both
activities. We also prepared compound 25 as a saturated
analogue of 24. Again, the potency of activity was
reduced. This result corroborates the importance of the
a,b-unsaturated structure of benzylidenesuccinic acid
for both activities of the present hybrid molecules.
Table 1. Biological activities of hybrid molecules (R=5-Et-2-pyridyl)
Compound
Insulin-releasinga
activity
Triglyceride accumulationb
(insulin-sensitizing activity)
at 10 mM
at 10 mM
at 1 mM
2
9
33
68
105
1
30
30
11
55
50
2
8
4
17
20
(S)-9
(R)-9
10
136
Nateglinide
Pioglitazone
100
10
40
100
6
100
a% activity of nateglinide. Values are means of four experiments.
b% activity of pioglitazone. Values are means of three experiments.
Table 2. Screening data for benzylidenesuccinic acid hybrid moleculesa
Compound
R
n
Insulin-relasing
activity
Triglyceride
accumulation
at 1 mM
at 10 mM
10
2
136
20
16
17
1
2
130
93
15
5
18
19
20
21
22
23
24
3
2
2
2
2
2
2
130
105
60
4
9
87
60
121
93
83
49
93
145
103
25
85
45
Nateglinide
Pioglitazone
100
10
6
100
aSee footnotes to Table 1.

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H. Kitajima et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2453±2456
Figure 1. E€ects of compound 24 and nateglinide on insulin release in
HIT-T15 cells. Values represent the meanÆS.E.M. (n=4).
Figure 2. E€ects of compound 24 and pioglitazone on triglyceride
accumulation in 3T3-L1 cells. Values represent meanÆ S.E.M. (n=3).
Charifson, S. P.; Cobb, E. J.; Henke, R. B.; Hull-Ryde, A. E.;
Kazmierski, M. W.; Lake, H. D.; Leesnitzer, M. L.; Lehmann,
M. J.; Lenhard, M. J.; Orband-Miller, A. L.; Gray-Nunez, Y.;
Parks, J. D.; Plunket, D. K.; Tong, W. J. Med. Chem. 1998,
41, 5037. (c) Henke, R. B.; Blanchard, G. S.; Brackeen, F. M.;
Brown, K. K.; Cobb, E. J.; Collins, L. J.; Harrington, W. W.;
Hashim, A. M.; Hull-Ryde, A. E.; Kaldor, I.; Kliwer, A. S.;
Lake, H. D.; Leesnitzer, M. L.; Lehmann, M. J.; Lenhard, M.
J.; Orband-Miller, A. L.; Millar, F. J.; Mook, A. R.; Noble, A.
S.; Oliver, W., Jr.; Parks, D. J.; Plunker, K. D.; Szewczyk, J.
W.; Willson, T. J. Med. Chem. 1998, 41, 5020. (d) Ishikawa,
Y.; Watanabe, K.; Takeno, H.; Tani, T. Arzneim.-Forsch./
Drug Res. 1998, 48, 245. (e) Hulin, B.; Newton, L. S.; Lewis,
D. M.; Glenereux, P. E.; Gibbs, E. M.; Clark, D. E. J. Med.
Chem. 1996, 39, 3897. (f) Buckle, D. R.; Cantello, B. C. C.;
Cawthorne, M. A.; Coyle, P. J.; Dean, D. K.; Faller, A.;
Haigh, D.; Hindley, R. M.; Jefcott, L. J.; Lister, C. A.; Pinto,
I. L.; Rami, H. K.; Smith, D. G.; Smith, S. A. Bioorg. Med.
Chem. Lett. 1996, 6, 2121.
For compound 24, dose-dependency of the activities
was examined. Compound 24 stimulated insulin secre-
tion signi®cantly from concentrations of 3Â10 6 M and
potency was almost the same as that of nateglinide. It
was noteworthy that it displayed greater ecacy than
nateglinide at concentrations of 10 mM or more (Fig. 1).
Compound 24 also exhibited a similar triglyceride-
accumulation pro®le to pioglitazone in 3T3-L1 cells
(Fig. 2).
In summary, we designed and synthesized hybrid mole-
cules of non-sulfonylurea insulin secretagogues and
TZD-derived insulin sensitizers on the basis of their
common structure. We demonstrated that a benzyli-
denesuccinic acid structure plays an important role in
enhancing both insulin-secreting and -sensitizing activ-
ities. In particular, a hybrid molecule with a phenylox-
azolyl group (compound 24)15 exhibited potency in both
insulin-related activities. To the best of our knowledge,
this is the ®rst example of a potent insulin-releasing and
-sensitizing dual agent. Study of the present compounds
in vivo and further optimization are in progress.
6. Shinkai, H.; Onogi, S.; Tanaka, M.; Shibata, T.; Iwao, M.;
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10. Optical purity was determined to be >99% e.e. by HPLC
using a Daicel CHIRALCEL1 AD column. Speci®c rotations,
References and Notes
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(CDCl3, 270MHz) d: 1.30±1.69 (8H, m), 2.14±2.33 (2H, m), 2.38
(3H, s), 2.99 (2H, t, J=6.6 Hz), 3.25±3.53 (6H, m), 4.26 (2H, t,
J=6.6 Hz), 6.90 (2H, d, J=8.6 Hz), 7.29 (2H, d, J=8.6 Hz), 7.36±
7.48 (3H, m), 7.82 (1H, s), 7.93±8.01 (2H, m). FABMS (m/z) 515.