1-Phenyl-pyrazole derivatives as glucagon inhibitors

The invention discloses certain 1-phenyl-pyrazole derivatives having pharmacological activity in animals and useful as glucagon inhibiting agents. Nearly all of the compounds of this invention are prepared by cyclization of a phenyl hydrazine compound with a 1,1,3,3-tetra-C.sub.1-4 -alkoxy-propane compound.

The present invention relates to the use of certain 1-phenyl pyrazole 
derivatives, and the pharmaceutically acceptable acid addition salts 
thereof, where such may exist, as glucagon-inhibiting agents. 
British Pat. No. 1,368,615 discloses certain pyrazole derivatives useful as 
analgesic and anti-inflammatory agents. In addition, J. of Med. Chem. 7 
pp. 102-105 (1964) is directed to an investigation of the antidiabetic 
activity of certain pyrazole compounds. 
The present invention involves the novel use of the compounds of formula I: 
##STR1## 
wherein R.sub.o is methyl, trifluoromethyl or amino, and 
n is 1 or 2, 
and the pharmaceutically acceptable acid addition salts thereof, with the 
proviso that when n is 2, R.sub.o is methyl, one methyl group being in the 
2-position of the phenyl ring and the other methyl group being in the 3- 
or 4-position of the phenyl ring. 
Preferred compounds of formula I are compounds wherein n is 1 and R.sub.o 
is trifluoromethyl, methyl in the 2-position of the phenyl ring or amino 
in the 2-position of the phenyl ring, and the pharmaceutically acceptable 
acid addition salts thereof. The more preferred compounds of formula I are 
compounds wherein n is 1 and R.sub.o is trifluoromethyl and the compound 
wherein n is 1 and R.sub.o is methyl in the 2-position of the phenyl ring. 
The most preferred compound of formula I is l-o-tolyl-1H-pyrazole. 
All of the compounds of formula I, save for compounds wherein R.sub.o is 
amino, may be prepared by cyclization of a phenyl hydrazine compound of 
formula II: 
##STR2## 
wherein R.sub.o is methyl or trifluoromethyl, and n is 1 or 2, with the 
proviso as set forth above, with a 1,1,3,3-tetra-C.sub.1-4 -alkoxypropane 
compound. The cyclization may be effected by processes known per se for 
the cyclization of hydrazine compounds. Preferably, the cyclization 
involves reacting a compound of formula II, as described above, with a 
1,1,3,3-tetra-C.sub.1-4 -alkoxypropane, more preferably, a 
1,1,3,3-tetra-C.sub.1 or 2 alkoxypropane compound, in the presence of an 
inert, organic solvent such as the lower alkanols, e.g., methanol, 
ethanol, and the like, and an inorganic mineral acid such as sulfuric 
acid, hydrochloric acid and the like, in concentrated form. The 
cyclization is conveniently carried out at temperatures of between 
50.degree. C. and 100.degree. C., preferably, between 80.degree. C. and 
90.degree. C. Reaction times will, of course, vary but it is preferred 
that the reaction be conducted for a period of 1 to 4 hours, more 
preferably, for 2 to 3 hours. 
The compounds of formula I wherein R.sub.o is amino may be prepared by a 
two-step reaction comprising, in a first step, the cyclization of a 
compound of formula III: 
##STR3## 
essentially as described above, to obtain the corresponding ortho-, meta- 
or para-nitrophenyl pyrazole compound which, in a second step, is 
catalytically hydrogenated to obtain the desired amino compound of formula 
I. Thus, the corresponding ortho-, meta- or para-nitrophenyl pyrazole 
compound is reduced in the presence of hydrogen gas under pressure and in 
the presence of a catalyst such as palladium on carbon or platinum oxide 
on carbon. The reaction is carried out in the presence of an inert, 
organic solvent such as the lower alkanols, e.g., methanol, ethanol, and 
the like. The temperature of the reaction is not critical, but it is 
preferred that the reaction be run at temperatures from about 10.degree. 
C. to 80.degree. C., more preferably, from about 20.degree. C. to 
50.degree. C. Reaction times will, of course, vary but it is preferred 
that the reaction be conducted for a period of 1 to 24 hours, more 
preferably, for 16 to 20 hours. 
It will be noted that the above-identified compounds of formula I wherein 
R.sub.o is amino bear a free amino group and can, therefore, form 
pharmaceutically acceptable acid addition salts; it being understood that 
the use of such salts is comprehended as being included within the scope 
of the present invention. 
The products of the above-described reactions may be recovered and purified 
in conventional manner, e.g., by crystallization, distillation or 
chromatographic techniques, such as eluting from a chromatographic column 
or separating on a silica layer. 
Many of the compounds of formulae II and III are either known and obtained 
by methods described in the literature, or where not known, may be 
obtained by methods analogous to those described in the literature. 
As previously indicated, pharmaceutically acceptable acid addition salts 
(i.e., those salts which do not significantly increase the toxicity of the 
basic compound) of the compounds of formula I, where such may exist, are 
included within the scope of this invention. Included are salts with 
inorganic acids, e.g., the hydrochloride, hydrobromide, hydroiodide, 
phosphate (including hydrogen phosphates) metaphosphate, sulfates 
(including hydrogen sulfate) and perchlorate salts. 
The compounds of formula I, and their pharmaceutically acceptable acid 
addition salts, are useful as glucagon inhibiting agents in the treatment 
of diabetes as indicated by a lowering of plasma glucagon levels in 
alloxan diabetic rats. Adult male rats, each weighing between 200 and 400 
g., are injected intravenously with 50-100 mg./kg. of alloxan and, after 5 
days, are tested for the presence of urinary glucose (Clinistix). The 
selection of animals is determined according to the degree of urine 
Clinistix reaction, i.e., only animals with a positive urine response 
(deep purple color of Clinistix within 15 seconds) are used. The rats are 
divided into two groups, viz., the "insulin" group, wherein the rats are 
intramuscularly administered 1 unit/kg. body weight of insulin and the 
"test compound" group, wherein the rats are dosed orally with 100 mg./kg. 
body weight of the test compound. After two hours, the animals in each 
group are sacrificed and 2 to 5 mls. of blood are collected and the plasma 
separated. The plasma is stored frozen until assayed for glucagon, at 
which time plasma levels of glucagon are determined using 
radioimmunological techniques. Similar tests are run simultaneously with a 
"negative control" group comprising non-diabetic rats which received only 
the alloxan. 
For the above-mentioned use, the compounds of formula I and their 
pharmaceutically acceptable salts may be administered orally or 
parenterally as such or admixed with conventional pharmaceutical carriers. 
They may be administered orally in such forms as tablets, dispersible 
powders, granules, capsules, syrups and elixirs, and parenterally as 
solutions, e.g., a sterile injectable aqueous solution. The compositions 
for oral use may contain one of more conventional adjuvants, such as 
sweetening agents, flavoring agents, coloring agents and preserving 
agents, in order to provide an elegant and palatable preparation. Tablets 
may contain the active ingredient in admixture with conventional 
pharmaceutically acceptable excipients, e.g., inert diluents, such as 
calcium carbonate, sodium carbonate, lactose and talc, granulating and 
disintegrating agents, e.g., starch and alginic acid, binding agents, 
e.g., starch, gelatin and acacia, and lubricating agents, e.g., magnesium 
stearate, stearic acid and talc. The tablets may be uncoated or coated by 
known techniques to delay disintegration and adsorption in the 
gastrointestinal tract and thereby provide a sustained action over a 
longer period. Similarly, suspensions, syrups and elixirs may contain the 
active ingredient in admixture with any of the conventional excipients 
utilized in the preparation of such compositions, e.g., suspending agents 
such as methylcellulose, tragacanth and sodium alginate; wetting agents 
such as lecithin, polyoxyethylene stearate and polyoxyethylene sorbitan 
monooleate; and preservatives such as ethyl-p-hydroxybenzoate. Capsules 
may contain the active ingredient alone or admixed with an inert solid 
diluent, e.g., calcium carbonate, calcium phosphate and kaolin. The 
injectable compositions are formulated as known in the art. These 
pharmaceutical preparations may contain up to about 90% of the active 
ingredient in combination with the carrier or adjuvant. 
The precise dosage of a compound of formula I, or a pharmaceutically 
acceptable acid addition salt thereof, to be employed depends upon several 
factors including the severity of the condition being treated, the mode of 
administration and the particular compound employed. However, in general, 
satisfactory results in lowering the glucagon level in plasma are obtained 
when a compound of formula I, or a pharmaceutically acceptable acid 
addition salt thereof, is administered at a daily dosage of from about 50 
milligrams to about 300 milligrams per kilogram of animal body weight, 
preferably given orally and in divided doses three times a day, more 
preferably, before each meal, or in sustained release form. For most large 
mammals, the total daily dosage is from about 250 milligrams to about 3000 
milligrams. Unit dosage forms suitable for internal use comprise from 
about 50 milligrams to about 3000 milligrams, more usually 50 to 1500 
milligrams of the active compound in intimate admixture with a solid or 
liquid, pharmaceutically acceptable carrier. 
A representative formulation suitable for oral administration three times a 
day, preferably before each meal, for lowering the glucagon level is a 
capsule prepared by standard encapsulating techniques which contains the 
following: 
______________________________________ 
Ingredients Weight (mg.) 
______________________________________ 
1-o-tolyl-1H--pyrazole 
100 
inert solid diluent (e.g., starch, 
lactose, kaolin, etc.) 
200 
Total 300 
______________________________________ 
The following examples are for purposes of illustration only and are not 
intended to in any way limit the scope of the invention.

EXAMPLE 1 
1-o-tolyl-1H-pyrazole 
##STR4## 
Into a 1 liter, 2-neck flask, fitted with a condenser and a magnetic 
stirrer, is successively added 90.0 g. (0.570 M.) of o-tolyl-hydrazine 
hydrochloride hydrate, 100 ml. of water, 63 ml. of 100% ethanol and 139.0 
g. (0.633 M.) of 1,1,3,3-tetraethoxypropane. The reaction mixture is then 
heated slowly to between 80.degree. C. and 90.degree. C., and after 
maintaining the mixture at this temperature range for a period of about 3 
hours, the reaction mixture is quenched on ice water and extracted with 
ethylacetate/ether. After drying the organic solution over anhydrous 
sodium sulfate, the solvents are evaporated to obtain a very dark liquid. 
Distillation in an air oven at a temperature between 
110.degree.-120.degree. C. and a pressure of 1 mm. of Hg. yielded a light 
yellow oil (Yield: 83%). 
Diabetic rat test -60%-100 mg./kg. (aver. of 4 runs) 
EXAMPLE 2 
1-(m-trifluoromethylphenyl)-pyrazole 
##STR5## 
Into a 500 ml., 2-neck flask, fitted with a condenser and a magnetic 
stirrer, is successively added 35.2 g. (0.2 M.) of m-trifluoromethylphenyl 
hydrazine, 15 ml. of water, 20 ml. of 100% ethanol, 16.5 ml. of 
concentrated hydrochloric acid (slowly) and 44.0 g. (0.2 M.) of 
1,1,3,3-tetraethoxypropane. The reaction mixture is then heated slowly to 
between 80.degree. C. and 90.degree. C., and after maintaining the mixture 
at this temperature range for a period of between 2 and 3 hours, the 
reaction mixture is cooled, quenched on ice water, extracted with 
ethylacetate and washed several times with water. After drying the organic 
solution over sodium sulfate, the solvent is evaporated on a rotary 
evaporator to obtain a very dark liquid which is then distilled at 
70.degree. to 80.degree. C. and a pressure of about 100 microns to yield a 
light yellow oil (Yield: 80%). 
Diabetic rat test -62%-100 mg./kg. (aver. of 4 runs) 
EXAMPLE 3 
Following essentially the procedure of Example 2, and using in place of 
m-trifluoromethylphenyl hydrazine, an equivalent amount of: 
(a) p-tolyl hydrazine, 
(b) o-trifluoromethylphenyl hydrazine, 
(c) 2,4-dimethylphenyl hydrazine, or 
(d) 2,3-dimethylphenyl hydrazine, 
there is obtained 
(a) 1-p-tolyl-1H-pyrazole, m.p. 30.degree.-32.degree. C. 
(Yield: 63%) 
-15%-100 mg./kg. 
(b) 1-(o-trifluoromethylphenyl)-pyrazole, an oil 
(Yield: 83%) 
-45%-100 mg./kg. 
(c) 1-(2,4-dimethylphenyl)-pyrazole, an oil 
(Yield: 76%) 
-25%-100 mg./kg. (aver. of 2 runs), and 
(d) 1-(2,3-dimethylphenyl)-pyrazole, an oil 
(Yield: 49%) 
-32.5%-100 mg./kg. (aver. of 3 runs), respectively. 
EXAMPLE 4 
1-(o-aminophenyl)-pyrazole 
##STR6## 
Into a Parr hydrogenation apparatus is successively added 20 g. (0.106 M.) 
of 1-(o-nitrophenyl)-pyrazole and 150 ml. of methanol and the resultant 
solution is hydrogenated in the presence of 1.0 g. of hydrogenation 
catalyst (10% Pd on active charcoal) at between 40 and 50 p.s.i. of 
hydrogen pressure at room temperature. After the theoretical uptake of 
hydrogen is achieved, the reaction mixture is filtered to remove the 
palladium and the solvent is removed on a rotary evaporator. Ether is then 
added to the resultant mixture and after removing the precipitated solids 
by filtration, the solvent is evaporated to yield a light amber colored 
oil (Yield: 90%). 
Diabetic rat test -33%-100 mg./kg.