Synthesis and hypoglycemic evaluation of substituted pyrazole-4-carboxylic acids.

Article abstract of DOI:10.1016/S0960-894X(02)00380-3

The synthesis and in vivo activities of a series of substituted pyrazole-4-carboxylic acids as hypoglycemic agents are described. Modelization of some potent compounds, comparatively to the metformine, presents certain analogies permitting to predict the design of some novel antidiabetic drugs.

Full text of DOI:10.1016/S0960-894X(02)00380-3

Bioorganic & Medicinal Chemistry Letters 12 (2002) 2105–2108
Synthesis and Hypoglycemic Evaluation of Substituted
Pyrazole-4-carboxylic Acids
Bertrand Cottineau, Patrick Toto, Christophe Marot, Aline Pipaud and
Jacques Chenault*
´ ´ ´
Institut de Chimie Organique et Analytique, Universite d’Orleans, BP 6759, 45067 Orleans Cedex 2, France
Received 9 November 2001; revised 22 April 2002; accepted 14 May 2002
Abstract—The synthesis and in vivo activities of a series of substituted pyrazole-4-carboxylic acids as hypoglycemic agents are
described. Modelization of some potent compounds, comparatively to the metformine, presents certain analogies permitting to
predict the design of some novel antidiabetic drugs. # 2002 Elsevier Science Ltd. All rights reserved.
In recent years, the increase of people suffering from
diabetes in the world had focused the attention toward a
search for novel structural classes of hypoglycemic
agents as thiazolidinediones,1 the alpha-glucosidase
inhibitors,2 the meglitinides,3 the beta-3-adrenergics
agonists,4 the AR inhibitors5 and more recently protein
Acrp 30.6 However, all these drugs present secondary
effects that involve numerous diseases for the patients.
described in literature.9 The regioselective O-alkylatation
of pyrazoles was carried out in two steps. First, the ethyl
1-acetyl-3-hydroxy-1H-pyrazole-4-carboxylate was syn-
thesized by condensation of one equivalent of acetic
acid anhydride in acetic acid. Then reaction of alkyl
halide with pyrazole 2 using potassium carbonate
as base in N,N-dimethylformide at 90 ꢀC lead to the
O-alkylated pyrazoles 3 in high yields. This methodology
does not need a N-deprotection step.10
Actually, the more used hypoglycemic drugs stand sul-
fonylureas7 and more particularly the metformine for
the treatment of diabetes of type II ( NIDDM ).
In a second step, a N1 regioselective alkylation is
obtained by deprotonation of N1-hydrogen using
sodium hydride in THF as solvent and reaction with
different alkyl halides or sulfates and acrylates.11 Com-
pounds 6 were isolated after a classical procedure with
good yields as shown in Table 1. The ethyl 3-hydroxy-1-
methyl-1H-pyrazole-4-carboxylate 7 was obtained by
deprotection of 3-hydroxyl group by boron tribromide
in methylene chloride or hydrogen bromide in glacial
acetic acid before saponification.12
Historically, different substituted pyrazoles8 were
known for their hypoglycemic activity in vivo, but in a
search for novel structural classes of drugs inhibiting the
activity of the ATP-K+ channel of the beta cell pan-
creatic membrane, inducing the production of insulin we
turned our attention to substituted pyrazole-4-carboxylic
acids
All 3-hydroxy or 3-alkoxy-1H-pyrazole-4-carboxylic
acids 4, 5, 8, 9 were obtained after saponification and
acidification of correspondent esters.13 Compounds 4c
and 8(c,g,h,i,k) were obtained as diacids.
Chemistry
All substituted pyrazole-4-carboxylic acids described in
this paper were prepared as shown in Scheme 1 from 1,
which was prepared according to the classical procedure
Evaluation of the Biological Activity
The antidiabetic activity of compounds 4, 5, 8 and 9 has
been determined from a pharmacological test based on
*Corresponding author. Tel.: + 33-2-3849-4588; fax: +33-2-3841-
7281; e-mail: jacques.chenault@univ-orleans.fr
0960-894X/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(02)00380-3

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B. Cottineau et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2105–2108
blood glyceamia measure. The results obtained are
summarized in Table 2.
on 10 rats at the same time, for each compounds at each
concentration. The results of the present study Table 2
indicate that compounds 4a emerges as the best
hypoglycemic agent in the series.
Tests were realized from Wistar rats suffering from dia-
betes of type II, which had been brought about by the
administration of stepozocin in moderate dose. The
glyceamia had been determined on plasma before treat-
ment (J0), then 2h after the first administration (J1) and
2h after the last administration for 4 days chronic
treatment (J4). During the test time, the glucose con-
tribution from the intestine was negligible, as the rats
had eaten nothing for 4 h. As the blood samples were
taken at the extremity of the tail, the tests were realized
Molecular Modeling
Molecular modeling studies of 4a were performed using
Sybyl software version 6.514 running on Silicon Gra-
phics workstations. The low-energy conformation of 4a
superimposed to metformine Figure 1 permits us to
think that it can act as this last compound.
Scheme 1.
Table 1. Esters and acids derivatives of pyrazoles
Compd
R1
R2
% Ester yield
Compd
% Acid yield
1
2
H
H
H
COCH3
H
H
H
CH3
90
95
80
90
90
68
95
82
64
77
84
62
65
67
90
90
67
90
5
—
4a
4b
4ca
9a
9b
9ca
9d
9e
85
—
68
75
94
100
78
80
90
95
97
80
56
88
92
88
63
80
3a
3b
3c
6a
6b
6c
6d
6e
6f
6g
6h
6i
CH3
C6H5CH2
2-CN-[1,10-biphenyl]-40-(CH2)
CH3
C6H5CH2
CH3
CH3
C6H5CH2
2-CN–[1,10-biphenyl]-40–(CH2)
CH2¼CH–CH2
(CH3)2C¼CH–CH2
CH3
CH3
C6H5CH2
C6H5CH2
C6H5CH2
C6H5CH2
C6H5CH2
C6H5CH2
C6H5CH2
H
9f
CH3CH2OOC–CH2
CH3OOC–(CH2)2
CH3CH2OOC–(CH2)3
Tetrazole—CH2
2-CN–[1,10-biphenyl]-40–(CH2)
(4-Cl-phenyl)–NH-CO–(CH2)2
CH3
9ga
9ha
9ia
9j
6j
6k
6l
9ka
9l
7
8
aCompounds obtained as diacids.

B. Cottineau et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2105–2108
2107
Table 2. Glyceamia evolution%
B. C. C.; Cawthorne, M. A.; Cottam, G. P.; Duff, P. T.;
Haigh, D.; Hindley, R. M.; Lister, C. A.; Smith, S. A.;
Thurlby, P. L. J. Med. Chem. 1994, 37, 3977.
Compd
J1a
J4b
2. (a) Taylor, R. H. In New Antidiabetic Drugs; Bailey, C. J.,
Flatt, P. R., Eds.; Smith-Gordon: Nishimura, 1990; p 119. (b)
Ikenone, T.; Okazaki, K.; Fujitani, S.; Tschiya, Y.; Akiyoshi,
M.; Maks, T.; Kondo, N. Biol. Pharm. Bull. 1997, 20, 354. (c)
Bols, M. Acc. Chem. Res. 1998, 31, 1.
3. Grell, W.; Hurnans, R.; Griss, G.; Sauter, R.; Rupprecht,
E.; Mark, M.; Luger, P.; Nar, H.; Wittneben, H.; Muller, P.
J. Med. Chem. 1998, 41, 5219.
4. (a) Kordick, C. P.; Reitz, A. B. J. Med. Chem. 1999, 42,
181. (b) Smith, S. A.; Sennett, M. V.; Cawthorne, M. A. In
New Antidiabetic Drugs; Bailey, C. J., Flatt, P. R., Eds.;
Smith-Gordon: Nishimura, 1990, p 117.
5. (a) Costantino, L.; Rastelli, G.; Cignarella, G.; Vianello, P.;
Barlocco, D. Opin. Ther. Pat. 1997, 7, 843. (b) Mylari, B. L.;
Larson, E. R.; Beyer, T. A.; Zembrowski, W. J.; Adlinger,
C. E.; Dee, M. F.; Siegel, T. W.; Singleton, D. H. J. Med.
Chem. 1991, 34, 108.
6. Fruebis, J.; Tsao, T.-S.; Javorski, S.; Ebbets-Reed, D.;
Erickson, M. R.; Yen, F. T.; Bihain, B. E.; Lodish, H. F. Proc.
Natl. Acad. Sci. U.S.A. 2001, 98, 2005.
7. (a) Campbell, I. W. In New Antidiabetic Drugs; Bailey, C.
J., Flatt, P. R., Eds.; Smith-Gordon: Nishimura, 1990; p 33.
(b) Jacot, E.; Assal, J. Ph. Pharmacologie; Schoderet, M., Eds.,
Frison-Roche: Slaktine, 1992; p 481.
20 mg/kgc
200 mg/kgc
20 mg/kgc
200 mg/kgc
5
4a
4b
4c
9a
9b
9c
9d
9e
9f
9g
9h
9i
9j
9k
ꢁ127
ꢁ19
1
ꢁ7
ꢁ7
ꢁ6
ꢁ5
3
ꢁ9
ꢁ20
ꢁ24
ꢁ11
ꢁ10
ꢁ5
ꢁ10
1
2
ꢁ8
ꢁ4
ꢁ1
0
ꢁ5
ꢁ14
1
ꢁ15
ꢁ5
ꢁ10
ꢁ9
ꢁ3
5
6
3
ꢁ8
ꢁ5
0
ꢁ3
ꢁ11
ꢁ4
ꢁ4
ꢁ8
ꢁ3
ꢁ1
0
ꢁ5
ꢁ16
0
2
ꢁ6
ꢁ7
ꢁ3
ꢁ7
ꢁ10
ꢁ10
ꢁ12
4
ꢁ3
ꢁ13
ꢁ1
ꢁ2
ꢁ4
ꢁ19
ꢁ12
ꢁ2
ꢁ3
ꢁ6
ꢁ7
ꢁ3
9l
ꢁ19
ꢁ16
—ꢁ24
8
Metformine
—
a2h after the first administration.
b2h after the last administration for 4 days chronic treatment.
cDose of compound/kg of rat.
8. (a) Gerritsen, G. C.; Dulin, W. E.; Kalamazoo, P. D. Dia-
betes 1965, 14, 102. (b) Smith, D. L.; Forist, A. A.; Dulin,
W. E. J. Med. Chem. 1965, 350.
9. (a) Sanghvi, Y. S.; Udadhhya, K. G.; Dalley, N. K.;
Robins, R. K.; Revankar, G. R. Nucleosides and Nucleotides
1987, 6, 737. (b) Willson, T. M.; Henke, B. R.; Momtahen,
T. M.; Garrison, D. T.; Moore, L. B.; Geddie, N. G.; Baer,
P. G. Bioorg. Med. Chem. Lett. 1996, 6, 1047.
10. Experimental procedure and datas for 3a: Compound 1
(9 g, 60 mmol) was dissolved in acetic acid (150 mL). To the
resulting solution was added acetic anhydride (5.4 mmol,
60 mL). The reaction mixture was stirred at room temperature
for 3 h. Then the solvent was evaporated under reduced pres-
sure. The precipitate was washed with water and then collected
on a filter to give the pyrazole 2 10.1 g (95%) as white needles;
mp 138 ꢀC ; 1H NMR (CDCl3) d 1.4 (t, J=7.15 Hz, 3H, CH3),
2.7 (s, 3H, COCH3), 4.4 (q, J=7.15 Hz, 2H, CH2), 4.7 (s, 1H,
OH), 8.5 (s, 1H, H5) ; 13C NMR (CDCl3) d 14.2( CH3), 21.7
Figure 1. Superposition of 5a and metformine.
The introduction of different pharmacophors moiety 9e
or 9l shows no more activity comparatively to com-
pound 4a. These results and a study by modelization
permit us to propose a new compound which was in
progress and represent an important breakthrough in
the design of structurally new compounds as potential
therapeutics for the treatment of NIDDM and diabetes.
(COCH3), 61.6 (CH2), 103.6 (C4), 134 (C5), 163.2(C ), 164.5
3
(COOCH2), 169.2(N COCH3) ; IR (KBr) n 3117 (OH), 1740
(COCH3), 1695 (COOCH2) cmꢁ1. MS 199 (M+H, 70). Anal.
calcd for C8H10N2O4 : C, 59.69 ; H, 4.55 ; N, 12.00. Found :
C, 59.74 ; H, 4.53 ; N, 11.97. A solution of ethyl 1-acetyl-3-
hydroxy-1H-pyrazole-4-carboxylate
2 (2g, 10 mmol) and
potassium carbonate (1.4 g, 10 mmol) in anhydrous DMF
(50 mL) was stirred at room temperature during 30 min.
Methylsulfate (12mmol) in DMF (20 mL) was added dropwise
over 15 min and the reaction mixture was warmed for 20 h at
70 ꢀC. The solvent was evaporated under vaccum, the residue
was dissolved in water and extracted with ethyl acetate (2 ꢂ
100 mL). The combined organic layers were dried (MgSO4)
and concentrated. The resultant crude product was crystallized
in diisopropyl ether to give (1,6 g) of the corresponding O-
methylated product 3a. (93% yield). White solid; mp 110 ꢀC;
1H NMR (CDCl3) d 1.35 (t, J=7.1 Hz, CH2CH3), 1.8 (s, 1H,
NH), 4 (s, 3H, OCH3), 4.3 (q, J=7.1 Hz, CH2CH3), 7.9 (s, 1H,
H5) ; 13C NMR (CDCl3) d 15 (CH3), 56.9 (OCH3), 60.4 (CH2),
99.6 (C4), 134.5 (C5), 163.3 (C3), 163.5 (COOCH2) ; IR (KBr)
n 3257 (NH), 1667 (C¼O) cmꢁ1. MS 171 (M+H, 90).
Acknowledgements
We thank G. Moinet and Society Merck-Lipha at
Chilly-Mazarin for their financial support and in vivo
evaluations.
References and Notes
1. (a) Colca, J. R.; Morton; D. R. In New Antidiabetic Drugs;
Bailey, C. J., Flatt, P. R., Eds.; Smith-Gordon: Nishimura, 1990,
p 255. (b) Solida, T.; Mizuno, K.; Imamiya, E.; Sugiyama, Y.;
Fujita, T.; Kawamatsu, Y. Chem. Pharm. Bull. 1982, 30, 3580.
(c) Solida, T.; Mizuno, K.; Momore, Y.; Ikeda, H.; Fujita, T.;
Meguro, T. J. Med. Chem. 1992, 35, 2617. (d) Cantello,
11. Experimental procedure and datas for 6a. To a stirred
suspension of sodium hydride (1.5 g, 35.2mmol) in anhydrous
tetrahydrofurane (30 mL) was added dropwise a solution of

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B. Cottineau et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2105–2108
pyrazole 3a (6 g, 35.2mmol) in anhydrous tetrahydrofurane
(20 mL). The solution was stirred for 30 min at room tem-
perature then methyl iodide (5.3 mL, 84.5 mmol) was added
and the solution was stirred for 2h at room temperature.
Water is added and the mixture was extracted with ethyl ace-
tate, the organique layer was dried on magnesium sulfate and
evaporated under reduced pressure to give the pyrazole 6a in
NMR (DMSO-d6) d 1.4 (t, J=7.15 Hz, 3H, CH3), 3.8 (s, 3H,
NCH3), 4.3 (q, J=7.15 Hz, 2H, CH2), 7.5 (s, 1H, H5), 9 (s, 1H,
OH); 13C NMR (DMSO-d6) d 14.5 (CH3), 39.6 (NCH3), 60.6
(CH2), 97.5 (C4), 102.2 (C5), 163.2(C ), 165.2( COOCH2); IR
3
(KBr) n 3117 (OH), 1708 (COOCH2) cmꢁ1. MS 170 (M+H, 70).
13. Experimental procedure and datas for the acid 4a. A
solution of 3a 5,5 g (32mmol) in 10% NaOH (150 mL) and
EtOH (80 mL) was refluxed for 20 h. After evaporation of
EtOH, the solution was cooled to 10 ꢀC and acidified to pH 1
with 10% HCl. The precipitated solid 6a was collected by fil-
tration, washed with water and dried to give (3.1 g) white nee-
68% yields. White solid; mp 80 ꢀC; H NMR (CDCl3) d 1.28
1
(t, J=7.1 Hz, CH2CH3), 3.7 (s, 3H, NCH3), 4 (s, 3H, OCH3),
4.2(q, J=7.1 Hz, CH2CH3), 7.6 (s, 1H, H5) ; 13C NMR
(CDCl3) d 15 (CH3), 39.9 (NCH3), 57.1 (OCH3), 60.4 (CH2),
96.7 (C4), 135.7 (C5), 163 (C3), 163.2( COOCH2) ; IR (KBr) n
1667 (C¼O) cmꢁ1. MS 185 (M+H, 90).
dles. 68% yield; mp>270 ꢀC; H NMR (DMSO-d6) d 3.8 (s,
1
3H, OCH3), 7.9 (s, 1H, H5) ; 13C NMR (DMSO-d6) d 55.6
(OCH3), 98.2(C 4), 134.4 (C5), 162(C 3), 163.4 (CO) ; IR (KBr)
n 3100–3300 (COOH+NH), 1670 (CO) cmꢁ1, MS 143
(M+H, 82). Anal. calcd for C5H6N2O3: C, 42.26; H, 4.26; N,
19.71. Found: C, 43.30; H, 4.32; N, 19.64.
12. Experimental procedure and datas for 7. A solution of
pyrazole 6a (10 g, 55 mmol) in a 33% solution of hydrogen
bromide in glacial acetic acid (50 mL) was reflux for 4 h. Then
the solvent was evaporated under reduced pressure. The pre-
cipitate was washed with water and collected on a filter to give
the pyrazole 7 8.5 g (90%) as white needles; mp 156 ꢀC; 1H
14. SYBYL-6,5; Tripos Associates, Inc: 1699, South Hanley
Road, St Louis, MO 63144, USA.