CA1068278A - The (-)-(3-methyl-4-oxo-5-piperidinothiazolidin-2-ylidene)-acetic acid - Google Patents

Abstract

A B S T R A C T

The (-)-(3-methyl-4-oxo-5-piperidino-thiazolidin-2-ylidene)-acetic acid and pharmacologically-compatible salts thereof are obtained by reacting the (+)-(3-methyl-4-oxo-5-N-piperidino-thiazolidin-2-ylidene)-acetic acid with an optically-active base and the racemic mixture thus obtained is separated by fractional crystallization and the separated levorotatory isomer is liberated by means of a weak acid and may subsequently be converted into a salt by treatment with an inorganic or organic acid, base or amino acid.

Description

1~68Z78 The present invention is concerned with the levo-rotary enantiomers of (+)-(3-alkyl-4-oxo-5-N-piperidino-thiazolidin-2-ylidene)-acetic acids which are described in United States Patent Number 3,971,794. Also, encompassed by this invention are the pharmaceutically acceptable salts of the enantiomers, a process for the preparation of the enantiomer and pharmaceutical compositions which contain the enantiomer or at least one pharmaceutically acceptable salt as the pharmaceutically active material.

- From United States Patent Number 3,971,794, it is known that racemic thiazolidine-acetic acid derivatives ; of the general formula:
, ~\
S CH - N H
; HOOC ~ C ¦ I ~
H ~ ~ N ~ ~O (I) -. I
,; Rl ' wherein Rl is a lower alkyl radical, as well as the pharma-cologically-compatible salts thereof, exhibit a diuretic effectiveness.
By lower alkyl is meant straight-chained or ~A: branched alkyl radicals with up to 4 carbon atoms, and ~;' 20 includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl and t-butyl radicals, the methyl radical being preferred.
The racemic compounds of general formula (I) will be noted to have an asymmetric carbon atom in the 5-position.
THE INVENTION
~ e have now found that the levorotary enantiomer of (3-methyl-4-oxo-5-N-piperidino-thiazolidin-2-ylidene)-~x acetic acid (ozolinone~ has a diuretic activity which is twice as strong as the activity for the racemate. We have A; 30 furthermore found that a parallel increase of the tox-icity, which would have been expected with the increase in ,~ ~

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degree of effectiveness, could not be ascertained.
This discovery is most surprising since a differ-ence of action in the case of enantiomers of diuretically-active substances has not previously been reported with the exception of the steroid aldosterone antagonists, the working mechanism of which is quite different. It was also not known previous to our invention that there are chiral receptors or stereo-specifically-controlled working ; mechanisms for diuretics. Therefore, prochiral active materials used for influencing diuresis, as for example mefruside or metolazone, have been commercially available only in their racemate form.
By subjecting the racemate ozolinone to a rela-tively simple racemate separation, it is now possible to practically double the therapeutic activity of the race-mate. This is of great importance for the safety of a i pharmaceutical and must be regarded as being a decisive technical advance in the case of a diuretic which must normally be administered over a comparatively long period of therapy.
The preparation of the levorotary enantiomer of (3-methyl-4-oxo-5-N-piperidino-thiazolidin-2-ylidene)-acetic acid, i.e. (-)-ozolinone, takes place by the fractional crystallization of a diastereomeric salt of the racemate, prepared according to United States Letters , Patent Numbered 3,971,794 (Example 1), with an optically active base, such as, for example, l-ephedrin or l-lysine.
As the solvent for the fractional crystalli-zation, there can be used, when employing chlorinated hydrocarbons, for example, chloroform, carbon tetra-chloride, dichloroethane or trichloroethylene, or mixtures '~ with those organic solvents in which the diastereomeric salts are ~paringly soluble. These include, for example, open-chained and cyclic ethers, as for example, diethyl ether, tetrahydrofuran and dioxan, lower esters, such as :~ ethyl acetate, or ketones, such as acetone. The corre-` - 2 -., ~ ..
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10~8Z78 sponding lysine salts are preferably dissolved in water and fractionally precipitated with lower alcohols, such as ethanol or isopropanol, or with lower ketones, such as acetone. With the two above-mentioned adjuvant bases, (-)-ozolinone forms a sparingly soluble salt and can thus be separated from (+)-ozolinone, which remains in solution.
The (-)-ozolinone can be obtained in optically pure form by further recrystallizations from the solvents or solvent mixtures employed for the fractional precipitation.
In order to obtain the (-)-ozolinone from its salt, the salts are treated with a weak acid, preferably with dilute aqueous acetic acid and chloroform, to dis-solve the (-)-ozolinone in the chloroform fraction. The (-)-ozolinone is obtained, after washing with water, by distilling off the solvent and precipitating the compound with, for example, petroleum ether or benzine.
(-)-Ozolinone has a specific rotation of ~ ~23 = -225 (c. = 1 in chloroform/methanol 1:1); its ; melting point is 10C. below that of the racemate. The infra-red spectrum also shows a marked difference in com-parison with the racemate. The good lipid-solubility of (-)-ozolinone is also noticeable. Whereas the racemate ~; only has a solubility of 0.2% in chloroform and of 0.01~
in diethyl ether, the solubility of the levorotary enanti-:
omer in chloroform is about 20% and in diethyl ether 0.3%.
The better lipid solubility of (-)-ozolinone is surprising ' and is possibly the reason for its increased pharmacologi-cal effectiveness.
The properties of the (-)-ozolinone enantiomer and its method of preparation are demonstrated by the following examples which are to illustrate, but not iimit, the present invention.

(-)-Ozolinone71-ephedrine salt ; 165.2 g. (1 mol) l-ephedrine and 256.3 g.
~ (l mol) (+)-3-methyl-4-oxo-5-N-piperidino-thiazolidine-2-:., . . , : .. . : . , . , : .. . .

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ylidene)-acetic acid ~)-ozolinon ~ are dissolved in 3000 ml. chloroform and filtered and 3000 ml. diethyl ether are added to the clear filtrate, whereafter the solution is left to stand overnight. The following day, the crystals are filtered off with suction and subsequently washed with 500 ml. of a mixture of chloroform/diethyl ether (1:1) and dried at 45C. The yield of (l)-ozolinone salt is about 205 g.
For purification, the ephedrine salt is dis-solved in 2050 ml. chloroform and recrystallized by the addition of 2050 ml. diethyl ether. The yield is about 180 g. (about 85% of theory); ~ ~D ~ -98 (c. = 0.5% in chloroform); m.p. 110-115C.
(+)-Ozolinone-l-ephedrine salt The combined mother liquors are substantially concentrated in a rotary evaporator and the residue is dissolved in 2000 ml. chloroform. The salt is brought to crystallization by the addition of 2000 ml. diethyl ether.
The crystals are filtered off with suction, subsequently washed with 500 ml. chloroform/diethyl ether (1:2) and dried at 45C. By repeated reprecipitation (3 or 4 times) from a five-fold amount of chloroform and a tenfold amount of diethyl ether, the salt is purified to such an extent that the optical rotation is ~ D ~ +83 (c. = 0.5% in chloroform). The yield is about 105 g. (about 50~ of theory); m.p. 137 - 140C.
Ozolinone ~y ;~ 180 g. (0.43 mole) (-)-ozolinone-1-ephedrine ^ salt are introduced, with good stirring, into a solution 3Q of 50 ml. (0.87 mole) glacial acetic acid in 3000 ml. dis-i~ tilled water and stirred for 1 hour, followed by ex-~-~ traction with 1000 ml. chloroform. The chloroform phase is separated off, washed with water and dried over anhydrous magnesium sulphate, whereafter the solution is ~ concentrated in a rotary evaporator to one third and the ;~ (-)-ozolinone is brought to crystallization by the ;~
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1C~8278 addition of 2000 ml. petroleum ether. The crystals are filtered off with suction, subsequently washed with petroleum ether and dried at 45C. The yield is about 70 g. (63% of theory); m.p. 145C. (decomp.); ~ ~D = 224.9 (c. = 1% in chloroform/methanol 1:1).
(+)-Ozolinone From (+)-ozolinone l-ephedrine salt there is prepared (~)-ozolinone in the same manner; yield about 63%
of theory; m.p. 145C. (decomp.); ~ ~ D = +225.6 (c. = 1%
in chloroform/methanol 1:1).

25.6 g. (0.1 mole) (+)-(3-methyl-4-oxo-5-N-^ piperidino-thia7olidin-2-ylidene)-acetic acid and 16.0 g.
~0.105 mole) l-lysine are dissolved in 80 ml. distilled water and the solution is subsequently filtered. 400 ml.
isopropanol are then added thereto and the mixture is left to stand overnight. The following day, the crystals are filtered off with suction and then washed with a little 80% isopropanol. The yield is 13 g. (63% of theory) of the l-lysine salt; ~ ~ D = -71.9 (c. = 1% in water); m.p.
175C.
12 g. (0.03 mole) of this salt are introduced, ` with good stirring, into a mixture of 3.6 ml. (0.06 mole) glacial acetic acid and 200 ml. water and stirred for 30 minutes. Extraction is then carried out with 80 ml.
chloroform, the chlo~oform phase is washed with water and, after drying with anhydrous sodium sulphate, concentrated in a vacuum to one third. By the addition of 150 ml.
petroleum ether, the (-)-ozolinone is subsequently caused ' 3a to crystallize. The crystals are filtered off with s suction, then washed with petroleum ether and dried at ^i~ 40Co The yield is 4.8 g. (63% of theory); m.p. 145C.
;~ (decomp.); ~ ~ D = -225.6 (c. = 1% in chloroform/methanol .. `,-', 1: 1) .
The (-)-ozolinone according to the present ' invention, as well as the pharmacologically-compatible ;..

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1068;~'7~3 salts thereof, can be administered enterally or par-enterally in liquid or solid form. As injection medium, it is especially preferred to use water which contains the additives usual in the case of injection solutions, such as stabilizing agents, solubilizing agents or buffers.
Such additives include, for example, ethanol, complex-forming agents such as ethylenediamine-tetraacetic acid and the non-toxic salts thereof, tartrate and citrate buffers and high molecular weight polymers for example liquid polyethylene oxide for viscosity regulation. Solid carrier materials include, for example, starch, lactose, mannitol, methyl cellulose, talc, highly dispersed silicic acid, high molecular weight fatty acids for example stearic acid, gelatine, agar-agar, calcium phosphate, mag--~ nesium stearate, animal and vegetable fats and solid high molecular weight polymers such as polymers such as poly-ethylene glycols. Compositions for oral administration ~ can, if desired, contain flavoring and sweetening agents.
<~ The dosage obvîously depends upon the nature and severity of the condition to be treated. The individual dosage is usually between 5 and 250 mg. whereas the sub-cutaneously or intravenously administered individual dosage can be from about 5 to 100 mg.
The present invention also provides a process for the preparation of levorotary ozolinone, wherein (+)-ozolinone is converted into a diastereomeric salt by means `~ of an optically-active base, this salt is then fractional-ly crystallized and the desired levorotary ozolinone is obtained from the salt by means of a weak acid.
The present invention is also concerned with the use of (-)-ozolinone for the preparation of highly ef-fective diuretics.
~ ~-)-Ozolinone can be used as a diuretic in the -~ form of the free amino acid or also in the form of a salt - with a physiologically-compatible base, acid or amino acid.
As acids, there can be used those normally employed for . ~, .
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salt formation, such as hydrochloric acid, sulphuric acid, phosphoric acid or comparatively strong organic acids, such as acetic acid, fumaric acid, succinic acid, ascorbic acid and the like. Salt-forming bases include non-toxic amines and amino acids, as well as alkali metal carbonates and hydroxides.
The following comparative experiments demon-strate the clear advantage of (-)-ozolinone in comparison with (+)-ozolinone and the racemate.
I. Acute toxicity The acute toxicity of (-)-ozolinone was de-termined on male rats. The substance was administered as a suspension in tragacanth. The statistical calculation of the LD50 was carried out by means of the probit analy-sis according to E. Weber.
In the following Table I, there are given not only the found values but also the LD50 values for (+)-'! ozolinone in male and female rats:
TABLE I
:, test compound animal mg/kg. ¦~ oAII~e~ce lower upper . (-)-ozolinonemale rats 1202 1112 1300 '~
male rats 1450 1237 1700 (+)-ozolinone female rats 1260 1042 1525 The acute toxicity of (-)-ozolinone is only slightly greater than that of the racemate; it follows -from this that the therapeutic quotient of (-)-ozolinone in the case of rats is twice as great as that of the racemate.

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2'78 II. Diuretic effectiveness The diuretic action of (-)-ozolinone was tested on rats and dogs. In the case of rats, administration was intragastrally in the form of a suspension in tragacanth.
In the case of dogs, an aqueous solution of the compound was administered intragastrally. The results are given in the following Table II (rat experiments) and Table III
(dog experiments):
TABLE II
:: _ _ 10 dosage urine excretion mg/kg blank value (+)-ozoli- (+)-ozoli- (-)-ozoli-i.g. (NaCl) none none none ml/kg ml/kg ml/kg ml/kg 4.7 28 28 28 18 9.38 28 28 38 40 18.75 28 30 40 62 37.5 28 35 50 68 75.0 28 38 55 85 150.0 28 58 75 90 300.0 28 42 95 115 The superiority of (-)-ozolinone clearly follows from the experimental results. Even in very high dosages, levorotatory (+)-ozolinone only has a weakly diuretic ` action.
TABLE III
:;
., dosage urine excretion mg/kg blank value (+)-ozolinone(-)-ozolinone ; i.g. (NaCl) ml/kg ml/kg ml/kg ~ 16 17 42 53 .,- 32 17 _ 47 62 :
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The substantially higher diuretic activity of (-)-ozolinone clearly follows from the experimental results. In the lower dosages, it is twice as high as that of the racemate and already manifests itself at a dosage where the racemate and already manifests itself at a dosage where the racemate scarcely shows any effective-ness.

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Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as Eollows:

1. Process for the preparation of (-)-(3-methyl-4-oxo-5-N-piperidino-thiazolidin-2-ylidene)-acetic acid and of the pharmacologically-compatible salts thereof, wherein (?)-(3-methyl-4-oxo-5-N-piperidino-thiazolidin-2-ylidene)-acetic acid is reacted with an optically-active base and the racemic mixture so obtained is separated by fractional crystallization and the separated levorotatory isomer is liberated by means of a weak acid and, if desired, subsequently converted into a salt with an inor-ganic or organic acid, base or amino acid.

2. Process according to Claim 1, wherein 1-ephedrine is used as the optically-active base and the desired levorotatory isomer is precipitated and/or re-crystallized from a solution of the diastereomeric salt in a chlorinated hydrocarbon with a low molecular weight alcohol, ether or ketone.

3. Process according to Claim 1, wherein 1-lysine is used as the optically-active base and the desired levorotatory isomer is precipitated and/or re-crystallized from an aqueous solution of the diastereo-meric salt with a lower alcohol or ketone.

4. (-)-(3-Methyl-4-oxo-5-piperidino-thiazolidin-2-ylidene)-acetic acid and the pharmacologically-compati-ble salts thereof, whenever prepared by the process according to any of Claims 1, 2 or 3.