MC2418A1 - Process for the preparation of a (-) - (3R) -3-methyl-4- [4- [4- (4-pyridyl) piperazine-1-yl] phenoxy] butyric acid and of a pharmaceutical composition containing it - Google Patents

Description

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chiral compounds such as chiral amino acids. The distinct enantiomers that together form a racemic mixture of enantiomers of a pharmacologically active compound can interact to varying degrees with a chiral macromolecule such as an enzyme or a receptor. Consequently, different enantiomers may possess different activities as enzyme inhibitors or receptor antagonists. Furthermore, the rate and extent of absorption, distribution, metabolism, and excretion observed when an enantiomer is administered to a warm-blooded animal may differ from those observed when the mirror image of the preceding enantiomer is administered, meaning that enantiomers may possess different pharmacokinetic properties.

Furthermore, the stereochemical purity of an organic compound can also be important for the nature and extent of side effects that may occur upon administration of a pharmacologically active compound. Thus, one enantiomer may be a useful compound, while the other enantiomer may cause adverse side effects or toxicity. It has been suggested, for example, that one enantiomer of thalidomide is a safe and effective sedative, while the other enantiomer is responsible for the teratogenic side effect of the racemic mixture.

The optically active compound of the present invention is an optical isomer of the racemic mixture of (3RS)-3-methyl-4-{4-[4-(4-pyridyl)-30-piperazine-l-yl]phenoxy}butyric acid isomers [hereinafter referred to as the (3RS) racemic mixture] which is described, in the form of the trifluoracetic acid salt, in Example 132 of International Patent Application No. WO 95/22 834 and Example 203 of International Patent Application No. WOP 94/22 835. It is disclosed in these documents that these compounds are useful in the treatment of

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The present invention relates to the novel optically active compound consisting of (-)-(3R)-3-methyl-4-{4-[4-(4-pyridyl)piperazine-l-yl]phenoxy}butyric acid [hereinafter referred to as (-)-(3R) compound] and its pharmaceutically acceptable salts, esters, amides, or solvation products. The present invention also relates to methods for preparing the optically active compound, pharmaceutical compositions containing it, and its use in inhibiting cell adhesion, for example, platelet aggregation.

Organic compounds can exist in optically active forms. These compounds have the property of rotating the plane of polarized light within a plane in a dextrorotatory (dextrorotatory) or levorotatory (levorotatory) manner. Classically, an optically active compound has an asymmetric or chiral atom, such as a tetrahedral carbon atom, bonded to four different atoms or groups. The four different atoms or groups can be arranged around the asymmetric carbon atom in only two ways, resulting in two chiral compounds that are structurally related as mirror images of each other. These compounds are called stereoisomers or enantiomers. Enantiomers have identical physical and chemical properties, except that they rotate the plane of polarized light within a plane in equal amounts, but in opposite directions. A racemic mixture is a mixture of equal amounts of a pair of enantiomers. Such a mixture does not cause the plane of polarized light to rotate within a plane.

30 The stereochemical purity of an organic compound can be important in the fields of pharmaceutical chemistry and pharmacology. Many macromolecules, such as enzymes and receptors in the organisms of warm-blooded animals, which are involved in maintaining 35 life, are built from building blocks

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chiral compounds such as chiral amino acids. The distinct enantiomers that together form a racemic mixture of enantiomers of a pharmacologically active compound can interact to varying degrees with a chiral macromolecule such as an enzyme or a receptor. Consequently, different enantiomers may possess different activities as enzyme inhibitors or receptor antagonists. Furthermore, the rate and extent of absorption, distribution, metabolism, and excretion observed when an enantiomer is administered to a warm-blooded animal may differ from those observed when the mirror image of the preceding enantiomer is administered, meaning that enantiomers may possess different pharmacokinetic properties.

Furthermore, the stereochemical purity of an organic compound can also be important for the nature and extent of side effects that may occur upon administration of a pharmacologically active compound. Thus, one enantiomer may be a useful compound, while the other enantiomer may cause adverse side effects or toxicity. It has been suggested, for example, that one enantiomer of thalidomide is a safe and effective sedative, while the other enantiomer is responsible for the teratogenic side effect of the racemic mixture.

The optically active compound of the present invention is an optical isomer of the racemic mixture of {3RS)-3-methyl-4-{4-[4-(4-pyridyl)-30-piperazine-l-yl]phenoxy}butyric acid isomers [hereinafter referred to as the (3RS) racemic mixture], which is described, in the form of the trifluoracetic acid salt, in Example 132 of International Patent Application No. WO 95/22 834 and Example 203 of International Patent Application No. WOP 94/22 835. It is disclosed in these documents that these compounds are useful in the treatment of

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Various diseases involving cell adhesion, for example in the formation of blood thrombi after platelet aggregation. The formation of blood thrombi can lead to diseases such as thrombosis, stroke, thrombotic events accompanying unstable angina, myocardial infarction, atherosclerosis, thromboembolism, and reocclusion during or after thrombolytic therapy.

It is stated that the platelet aggregation-inhibiting effect of the compounds is based on their ability to inhibit the binding of adhesion molecules such as fibrinogen and von Willebrand factor to glycoprotein IIb/IIIa (hereafter referred to as GPIIb/IIIa), which is contained within the membrane of each platelet. Thus, the necessary activation and dimerization of, for example, platelet-supporting fibrinogen, do not occur, and processes such as thrombus formation and platelet aggregation are inhibited.

20 As a possible aid in the search for compounds with an improved therapeutic index, it would be desirable to find a compound with increased activity compared to the compounds described in international patent applications No. WO 94/22 834 and 25 WO 94/22 835.

It is also known that there are several categories of molecules with adhesion properties, such as integrins, selectins, and cadherins. Integrins are present on leukocytes and platelets, and selectins are present on leukocytes and endothelial cells. Within each category of molecules with adhesion properties, there are many members. The integrin category includes, for example, GPIIb/IIIa, which binds to fibrinogen; integrin arv/3, which binds to vitronectin; and integrin as(S1), which binds to fibronectin. It is considered

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It has been noted that the most useful therapeutic platelet aggregation inhibitors exhibit selectivity of inhibitory effect between categories of adherent molecules and between members of each category of adherent molecules. Therefore, it would also be desirable to find a compound that possesses this selectivity or greater selectivity than known platelet aggregation inhibitors.

In addition, several categories of GPIIb/IIIa antagonists are known to exist. For example, GPIIb/IIIa antagonists consisting of monoclonal antibodies have been generated. Furthermore, small molecules that inhibit the binding of molecules with adhesion to GPIIb/IIIa are also known, such molecules being described, for example, in U.S. patents Nos. 5,039,805 and 5,084,446, Canadian patent applications Nos. 2,008,161, 2,037,153 and 2,061,661, and by Alig et al., J. Med. Chem. , 1992, 35, 4393. Usually, the structures of these compounds are based on the 20-binding regions of adhesion-bearing molecules, for example, the RGD (arginyl-glycyl-aspartate) amino acid sequence in the fibrinogen structure. It is considered that these compounds can be used to inhibit platelet aggregation and, for example, thrombus formation for a sufficient time to allow the healing of damaged tissue without the harmful aftereffects of excessively vigorous platelet aggregation processes. A theoretical problem concerning the different classes of GPIIb/IIIa antagonists is the possibility that the inhibition of 30 platelet aggregation causes a decrease in the rate of blood clotting and, consequently, an increase in bleeding events and times. Although a slight increase in bleeding times may be acceptable, certain medically significant bleeding events such as intracranial hemorrhage

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could threaten the lives of patients.

Thus, it would be desirable to find a compound having the advantage of the potent GPIIb/IIIa antagonistic activity described for the compound in Example 132 of International Patent Application No. WO 94/22 834, which does not possess, or possesses to a lesser degree, the disadvantages of increased bleeding times and/or adverse medically significant bleeding events associated with known GPIIb/IIIa antagonists. According to the present invention, the optically active compound consisting of (-)-(3R)-3-methyl-4-{4-[4-(4-pyridyl)piperazine-l-yl]-phenoxy}butyric acid, or one of its pharmaceutically acceptable salts, esters, amides, or solvation products, is proposed, practically devoid of the (+)-(3S) stereoisomer.

The compound (-)-(3R) exhibits significantly greater activity as a GBIIb/IIIa antagonist than its corresponding (+)-(3S) isomer (more than 10 times greater activity). The compound (-)-(3R) also displays selectivity of inhibitory effect between categories of binding molecules and between members of these categories. For example, the compound exhibits activity against the binding of GBIIb/IIIa to fibrinogen (pCI0=7.65), but not against the binding of av/?3 to vitronectin (pCI50 less than 4) or the binding of as/31 to fibronectin (pCI50 less than 4).

Consequently, the (-)-(3R) compound is a novel, potent, and selective fibrinogen receptor antagonist that greatly reduces the tendency or possibility of adverse effects such as excessive bleeding associated with the administration of other fibrinogen receptor antagonists, such as the racemic mixture (3RS). The use of the (-)-(3R) compound also suppresses the tendency or possibility of adverse effects associated with the administration of the (+)-(3S) therapeutic compound.

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less effective than a component of the racemic mixture (3RS), the use of the compound (-)-(3R) allows for a clearer structure-activity-toxicity analysis and provides an improved therapeutic index. Therefore, it is desirable to use the compound (-)-(3R) of the present invention instead of the racemic mixture (3RS) of Example 132 of International Patent Application No. WO 94/22 834.

Pharmaceutically acceptable particular salts of the compound (-)-(3R) of the present invention include, for example, salts formed with acids giving physiologically acceptable anions, such as salts formed with mineral acids, for example a hydrohalic acid such as hydrochloric acid or hydrobromide, sulfuric acid or phosphoric acid, and salts formed with organic acids, for example trifluoracetic acid. Other pharmaceutically acceptable salts include, for example, salts formed with inorganic bases such as alkali metal salts and alkaline earth metal salts, for example sodium salts, ammonium salts, and salts formed with organic amines and quaternary bases giving physiologically acceptable cations such as salts formed with methylamine, dimethylamine, trimethyl-25 amine, ethylenediamine, piperidine, morpholine, pyrrolidine, piperazine, ethanolamine, triethanolamine, N-methylglucamine, tetramethylammonium hydroxide and benzyltrimethylammonium hydroxide.

Pharmaceutically acceptable esters of the compound (-)-(3R) of the present invention include, for example, esters consisting of derivatives of the carboxylic acid group in the compound of the present invention, for example esters formed with alcohols such as C1-C6 alcohols (e.g. methanol, ethanol, propanol and tert-obutanol), indanol,

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1 ' adamantol, (alkanoyl in Cj to C6) -oxy- (alcohols in Cj to C4) (for example pivaloyloxymethanol) and (alkoxy in C, to C4 )-carbonyl-(alcohols in Cx to C4) (for example methoxy-carbonylmethanol).

5 Particular pharmaceutically acceptable amides of the compound (-)-(3R) of the present invention include, for example, amides consisting of derivatives of the carboxylic acid group in the compound of the present invention, for example amides formed with amines such as ammonia, C: to C4 alkylamines (for example methylamine), di-(C2 to C4 alkyl)-amines (for example dimethylamine, N-ethyl-N-methylamine and diethylamine), (Cx to C4 alkoxy)-(C2 to C4 alkyl)-amines (for example 2-methoxyethylamine), phenyl-(Cx to C4 alkyl)-amines (for example benzylamine) and amino acids (for example glycine or one of its esters). Thus, particular amides of the (-)-(3R) compound of the present invention include N-methyl-, N,N-dimethyl-, N-ethyl-N-methyl-, and N,N-diethyl-butyramides. 20 Particular pharmaceutically acceptable solvation products of the (-)-(3R) compound of the present invention include, for example, hydrates, such as a hemihydrate, monohydrate, dihydrate, or trihydrate, or a hydrate in another proportion. 25 The expression "practically devoid of stereo-

The term "(+)-(3S) isomer", as previously used, means that there is at least 90% by weight of the (-)-(3R) isomer and an amount equal to or less than 10% by weight of the corresponding (+)-(3S) isomer. Advantageously, there is at least 95% by weight of the (-)-(3R) isomer and an amount equal to or less than 5% by weight of the (+)-(3S) isomer. Preferably, there is at least 99% by weight of the (-)-(3R) isomer and an amount equal to or less than 1% by weight of the (+)-(3S) isomer.

35 The compound (-)-(3R) of the present invention, or

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One of its pharmaceutically acceptable salts, esters, amides, or solvation products may be prepared by any process known in practice for the preparation of such a compound. Suitable methods include an asymmetric synthesis involving a suitable chiral intermediate and resolution of the racemic mixture (3RS). These methods represent a further feature of the present invention and include the following:

10 a) Reaction of 4-[4-(4-pyridyl)piperazine-1-yl]-

phenol, or one of its reactive derivatives, with the chiral intermediate consisting of (3R)-4-hydroxy-3-methylbutyric acid or one of its esters, or one of its reactive derivatives.

The reaction is carried out suitably in the presence of a strong base, such as an alkali metal hydride, for example sodium hydride. Suitable solvents include amides, such as dimethylformamide. The reaction is carried out suitably at a temperature within the range of 0 to 100°C. Suitable esters of the chiral intermediate consisting of (3R)-4-hydroxy-3-methylbutyric acid include, for example, methyl, ethyl, propyl, and tert-butyl esters. Suitable reactive derivatives include, for example, (3R)-4-halogeno-3-25 methylbutyric acid or one of its esters (e.g., a methyl or ethyl ester) such as the 4-chloro and 4-bromo functional derivatives, (3R)-4-alkanesulfonyloxy-3-methylbutyric acid or one of its esters (e.g., a methyl or ethyl ester) such as the 4-30 functional derivative methanesulfonyloxy, or (3R)-4-arylsulfonyloxy-3-methylbutyric acid or one of its esters (e.g., a methyl or ethyl ester) such as the 4-(jd-toluenesulfonyloxy) functional derivative.

b) Reaction of a compound of formula I

%

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O

in which L represents a leaving atom or group, with the chiral intermediate consisting of (3R)-3-methyl-4-[4-(piperazine-1-yl)phenoxy]butyric acid, or one of its acid addition salts.

Examples of L values include a halogen, such as chlorine or bromine, and the cyano group.

Examples of acid addition salts of 1' acid(3R)-3-methyl-4-[4-(piperazine-l-yl)-phenoxy]butyri-10 include, for example, hydrochlorides.

The reaction can be suitably carried out at a temperature within the range of -10 to 120°C, preferably from 10 to 100°C. Suitable solvents include, for example, ethers such as tetrahydrofuran 15 and dioxane, amides such as dimethylformamide, nitriles such as acetonitrile, halogenated hydrocarbons such as dichloromethane, alcohols such as ethanol, and water.

In some cases, for example when an acid addition salt of (3R)-3-methyl-4-[4-(piperazine-l-yl)phenoxy]butyric acid is used as a starting material, the reaction can be advantageously carried out in the presence of a base. Examples of suitable bases include tertiary amines, such as triethylamine, and hydroxides, carbonates, and bicarbonates of alkali metals, such as sodium or potassium hydroxide, carbonate, or bicarbonate.

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c) Decomposition of an ester of formula II

in which R represents a protecting group of the carboxyl function.

5 R can represent any classic carboxyl group that can be removed without interfering with other parts of the molecule. Examples of carboxyl group protectants include alkyl groups at Cx to C6 (such as the methyl, ethyl, propyl, or tert-butyl group), the phenyl group, and the benzyl group. The phenyl group in any of these groups may optionally bear one or two halogen substituents, alkyl groups at C1 to C4, alkoxy groups at C4, or nitro substituents.

15 The decomposition can be carried out using any of the classical reagents and any of the conditions known in practice for transforming carboxylic esters into carboxylic acids. Thus, for example, the decomposition can be carried out by base-catalyzed hydrolysis, 20 using, for example, an alkali metal hydroxide such as lithium, potassium, or sodium hydroxide, or a tertiary amine such as triethylamine in the presence of water. Base-catalyzed hydrolysis can be carried out in the presence of a solvent such as an alcohol, 25 for example, methanol or ethanol, or an ether such as tetrahydrofuran or dioxane. Alternatively, the

O. »

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Decomposition can be carried out by acid-catalyzed hydrolysis, for example, using an aqueous solution of acetic acid or trifluoracetic acid. The temperature is suitably within the range of -10 to 100°C, or, for example, 10 to 50°C. When the alcohol residue is a tert-butyl residue, this residue can be removed by heating, for example, at a temperature within the range of 80 to 150°C, alone or in the presence of a suitable diluent such as diphenyl ether or diphenyl-10-sulfone. A benzyl group can be removed by catalytic hydrogenation, for example, by palladium hydrogenation of carbon at a temperature within the range of -10 to 100°C in the presence of a solvent such as an alcohol, for example, methanol or ethanol. 15 d) Resolution of the racemic mixture (3RS) of the acid

(3RS)-3-methyl-4-{4-[4-(4-pyridyl)piperazine-1-yl]phenoxy}-butyric.

The resolution of the butyric acid derivative consisting of the racemic mixture (3RS) can be carried out by a conventional method, for example, by forming a salt with an optically active base followed by separation, for example, by fractional crystallization, of the two salts thus produced and regeneration of the separated (-)-(3R) and (+)-(3S) compounds by acidifying the separated salts. The resolution of the butyric acid derivative consisting of the racemic mixture (3RS) can also be carried out by the conventional method of forming a pair of diastereomeric esters by reaction with an optically active alcohol, separating the esters, for example, by chromatography, and regenerating the distinct (-)-(3R) and (+)-(3S) compounds by hydrolysis of the separated esters. An analogous route involving the preparation of a pair of diastereomeric amides can also be used.

The preparation of the (-)-(3R) compound and chiral intermediates is described in the non-limiting examples.

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attached, which are provided for illustrative purposes only.

Some of the chiral intermediates defined previously are novel; thus, in accordance with another aspect of the present invention, a compound consisting of tert-butyl (3R)-3-methyl-4-hydroxybutyrate, or one of its reactive derivatives, practically devoid of the (3S) stereoisomer is proposed. One particular reactive derivative that may be mentioned is tert-butyl (3R)-3-methyl-4-(p-toluene-10 suifonyloxy)butyrate.

The expression "virtually devoid of the (3S) stereoisomer," as used previously, has the same definition as that mentioned in relation to the (-)-(3R) compound of the present invention. When a pharmaceutically acceptable salt of the (-)-(3R) compound of the present invention is required, it can be obtained, for example, by reacting said compound with a suitable acid or base using a conventional method. When a pharmaceutically acceptable ester or amide of the (-)-(3R) compound of the present invention is required, it can be obtained, for example, by reacting said compound with a suitable alcohol or amine in an appropriate manner using a conventional method.

The ability of the compound (-)-(3R) of the present invention to inhibit platelet aggregation and to inhibit the binding of fibrinogen to GPIIb/IIIa can be demonstrated using the conventional test methods (a) and (b) described in International Patent Application No. WO 94/22 834, test methods which are cited by reference in this document.

The compound (-)-(3R) of the present invention has activity against adenosine diphosphate (ADP)-induced aggregation of human platelets with a pA2 of 7.3, and against the binding of fibrinogen to GPIIb/IIIa with a pCI50 of 7.65.

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As described above, the compound (-)-(3R) of the present invention can be used in the therapeutic or preventive treatment of diseases in which cell adhesion (particularly platelet aggregation) is involved, for example, venous or arterial thrombosis (e.g., pulmonary embolism, stroke, and thrombotic events accompanying unstable angina and transient ischemic attack), myocardial infarction, atherosclerosis, thromboembolism, and reocclusion during or after thrombolytic therapy. The compounds may also be useful for preventing reocclusion and restenosis after percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting. It should also be noted that the compounds may be useful in the treatment of other diseases mediated by the binding of molecules with adhesion to GPIIb/IIIa, for example, cancer.

In accordance with another aspect of the present invention, it is proposed to use the compound (-)-(3R), or one of its pharmaceutically acceptable salts, esters, amides or solvation products, practically devoid of the stereoisomer (+)-(3S), as a pharmaceutical substance.

In accordance with a further aspect of the present invention, a method is proposed for inhibiting platelet aggregation in a warm-blooded animal requiring such treatment, which includes administering an effective amount of the compound (-)-(3R), or one of its pharmaceutically acceptable salts, esters, amides or solvation products, practically devoid of the stereoisomer (+)-(3S).

In accordance with another aspect of the present invention, a method is proposed for inhibiting the binding of fibrinogen to GPIIb/IIIa in a warm-blooded animal requiring such treatment, which includes the administration

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of an effective amount of the compound (-)-(3R), or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, practically devoid of the stereoisomer ( + ) -(3S) .

5 In accordance with a further aspect of the present invention, a method is proposed for inhibiting thrombotic events accompanying unstable angina in a warm-blooded animal requiring such treatment, which includes administering an effective 10% amount of the compound (-)-(3R), or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, practically devoid of the stereoisomer (+)-(3S).

In accordance with another aspect of the present invention, a method is proposed for inhibiting platelet aggregation in a warm-blooded animal requiring such treatment with a strong simultaneous reduction of the adverse effects associated with the administration of the racemic mixture (3-RS), which includes the administration of an effective amount of the compound (-)-(3R), or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, practically devoid of the stereoisomer (+)-(3S).

In accordance with another aspect of the present invention, it is proposed to use the compound (-)-(3R), or one of its pharmaceutically acceptable salts, esters, amides or sol-25 vatation products, practically devoid of the stereoisomer (+)-(3S), for the production of a drug intended for the prevention or treatment of a disease involving platelet aggregation.

In accordance with a further aspect of the present invention, it is proposed to use the compound (-)-(3R), or one of its pharmaceutically acceptable salts, esters, amides or solvation products, practically devoid of the stereoisomer (+)-(3S), for the production of a drug intended for the prevention or treatment of a disease involving the binding of fibrinogen to GPIIb/IIIa.

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In accordance with another aspect of the present invention, it is proposed to use the compound (-)-(3R), or one of its pharmaceutically acceptable salts, esters, amides or solvation products, practically devoid of the stereoisomer (+)-(3S), for the production of a drug intended for the prevention or treatment of thrombotic events accompanying unstable angina.

In general, the compound (-)-(3R) of the present invention is administered for this purpose orally, 10 rectally, topically, intravenously, subcutaneously or intramuscularly or by inhalation, such that a dose in the range of 0.01 to 50 mg/kg body weight is provided, depending on the route of administration, the age and sex of the patient and the severity 15 of the condition to be treated.

The compound (-)-(3R) of the present invention will generally be used in the form of a pharmaceutical composition comprising the compound (-)-(3R) or one of its pharmaceutically acceptable salts, esters, amides, or solvation products, practically devoid of the (+)-(3S) stereoisomer, mixed with a pharmaceutically acceptable diluent or carrier. Such a composition is proposed as a further feature of the present invention and can be supplied in various dosage forms. For example, it can be in the form of tablets, capsules, solutions, or suspensions for oral administration; in the form of creams or ointments or a transdermal (transcutaneous) patch for topical administration; in the form of a suppository for rectal administration; in the form of a sterile solution or suspension for administration by intravenous or intramuscular injection; or in the form of an aerosol or a solution or suspension for a nebulizer, for administration by inhalation. and in powder form, in combination with pharmaceutically acceptable inert solid diluents such as lactose,

CFI

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for administration by insufflation.

Depending on the route of administration, the composition may include, for example, 0.1 to 99.9% by weight of the compound (-)-(3R) of the present invention.

5. Pharmaceutical compositions can be obtained by conventional operating procedures using pharmaceutically acceptable diluents and supports well known in practice. Tablets and capsules for oral administration can be suitably formed with an enteric coating, comprising, for example, cellulose acetate phthalate, to minimize contact of the compound (-)-(3R) of the present invention with the acids present in the stomach.

The compound (-)- (3R) of the present invention can 15 be co-administered or co-formulated with one or more agents known for their interest in the diseases or conditions for which treatment is envisaged, for example a known platelet aggregation inhibitor (e.g. aspirin, a thromboxane antagonist or a thromboxane-20 synthetase inhibitor), a lipid-lowering agent, an antihypertensive agent, a thrombolytic agent (such as streptokinase, urokinase, prourokinase, tissue plasminogen activator and its derivatives), a beta-adrenergic blocking agent or a vasodilator may also be usefully present 25 in a pharmaceutical composition of the present invention intended for use in the treatment of a cardiac or vascular disease or condition.

In addition to its use in medical therapy, the compound (-)-(3R) of the present invention is also useful as a pharmacological tool in the development and standardization of test systems for evaluating the effects of adhesion molecules in laboratory animals such as cats, dogs, rabbits, monkeys, rats, and mice, as part of the search for new therapeutic agents. The compound (-)-

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17

(3R) of the present invention can also be used, due to its platelet aggregation-inhibiting properties, to facilitate blood storage and to maintain the viability of blood and blood vessels in warm-blooded animals (or parts thereof) undergoing artificial extracorporeal circulation, for example, during limb or organ transplantation. When used for this purpose, the compound (-)-(3R) of the present invention is generally administered in such a way that a constant concentration within the range, for example, of 0.1 to 10 mg per liter is achieved in the blood.

The present invention is now illustrated by the following non-limiting examples in which, unless otherwise indicated:

(i) the concentrations and evaporations were carried out by rotary evaporation under vacuum;

ii) the operations were carried out at room temperature, i.e. in the range of 18 to 26 °C;

iii) Column chromatography was performed on silica gel (Merck 7736) available from E Merck and Co., Darmstadt, Germany;

(iv) yields are mentioned for illustrative purposes only and are not necessarily the maximum yields that can be achieved by carefully adjusting the implementation of the process;

(v) Proton NMR spectra were usually determined at 200 MHz or 250 MHz using tetramethylsilane (TMS) as an internal standard, and are expressed as chemical shifts (delta values) in parts per million relative to TMS using the

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Classical abbreviations for the designation of the main peaks: s, singlet; m, multiplet; t, triplet; l, broad; d, doublet, - and vi) the following abbreviations have been used for particular organic solvents: THF for tetrahydrofuran, DMF for N,N-dimethylformamide and DMSO for dimethyl sulfoxide.

Example 1

(-)-(3R)-3-methvl-4-(4-f4-(4-pyridyl)-piperazine-1-vilphenoxy)butyric acid hydrochloride

Sodium hydride (60% dispersion in mineral oil, 2.44 g) was added to a stirred suspension of 4-[4-(4-pyridyl)piperazine-1-yl]phenol (15.5 g) in anhydrous DMF (120 mL), and the mixture was stirred for 45 minutes. Tert-butyl(3R)-3-methyl-4-(p-toluene-tallow onyloxy)butyrate (20 g) was added, and the mixture was stirred for 20 hours. The mixture was evaporated, and the residue was divided between dichloromethane and water. The organic phase was washed with water, filtered through phase-separation paper (Whatman IPS), and evaporated. The residue was triturated under diethyl ether. The solid substance thus obtained was recrystallized in ethyl acetate, which yielded tert-butyl (-)-(3R)-3-methyl-4-{4-[4-(4-pyridyl)piperazine-1-yl]phenoxy}butyrate (10.6 g).

P.F. 112-113°C;

[alpha]D = -5.5° (concentration = 1 g/100 ml of mehanol; 20°C);

NMR (CDC13) ô 8.3 (2 H, d), 6.89 (4 H, m), 6.7 (2 H, m), 3.79 (2 H, d), 3.46 (4 H, m), 3.28 (4 H, m), 2.31-2.53 (2 H, m), 2.08-2.21 (1 H, m), 1.44 (9 H, s), 1.07 (3 H, d).

A mixture of (-)-(3R)-3-methyl-4-{4-[4-(4-pyridyl)piperazine-1-yl]phenoxy} tert-butyl butyrate

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(10.53 g) and an aqueous solution of hydrochloric acid (IN) (250 mL) were stirred for 44 hours. An aqueous solution of sodium hydroxide (IN) (250 mL) was added, and the mixture was cooled to 5°C. The mixture was filtered, and the filtrate was evaporated. Water (150 mL) was added, and the resulting precipitate was isolated and washed successively with water, acetone, and diethyl ether. The substance thus obtained was stirred with an aqueous solution of hydrochloric acid (IN) (25 mL) for 16 hours. The mixture was cooled to 5°C and filtered. The solid substance thus obtained was washed successively with water, acetone and diethyl ether and was dried, which gave the hydrochloride of (-)-(3R)-3-methyl-4-{4-[4-(4-pyridyl)-piperazine-l-yl]phenoxy}butyric acid (7.9 g). 15 P.F. 203-205°C;

[alpha]D = -6.2° (concentration = 1 g/100 ml of methanol; 20°C);

NMR (d6DMSO) 0 13.8 (1H, 1), 12.1 (1 H, 1), 8.27 (2 H, d), 7.28 (2 H, d), 6.9 (4 H, m), 3.8 (6 H, m), 3.18 20 (4 H, t), 2.45 (1 H, m), 2.23 (1 H, m), 2.12 (1 H, m), 1.0 (3 H, d);

m/e 356 (M+H)+ ;

Calculated for C20H2SN3O3. HCl. H2O:

C. 58.5; H. 6.8; N. 10.2; 2 5 Found: C. 58.3; H. 6.9; N. 10.2 %.

The necessary chiral starting material was prepared as follows:

Sodium bis(trimethylsilyl)amide (1 M in THF, 170 mL) was added dropwise to a solution of (4S)-4-isopropyl-3-propionyloxazolidine-2-one (J. Am. Chem. Soc., 1981, 103, 2127; 2.4 g) in anhydrous THF (500 mL) that had been cooled to -70°C and placed under an argon atmosphere. The addition rate was adjusted so that the temperature of the reaction mixture did not rise above -67°C. The resulting solution was

20

The solution was stirred at -70°C for 30 minutes. Tert-butyl bromacate (42.3 g) was added dropwise, and the solution was stirred at -70°C for 3 hours. The solution was then allowed to warm to room temperature. The solvent was evaporated, and the residue was divided between diethyl ether and water. The organic phase was separated, filtered through phase separation paper (Whatman IPD), and evaporated. The residue was triturated under hexane at -40°C, yielding a solid (21.6 g). A second fraction of solid (4.4 g) was obtained by evaporating the solution obtained with hexane and purifying the residue by silica gel filtration chromatography, starting with hexane and passing through a 1/10 ethyl acetate/hexane mixture. The two batches of solid substance were combined and recrystallized in hexane, giving (4S)-3-[(2R)-3-tertiobutoxy-carbonyl-2-methylpropionyl]-4-isopropyloxazolidine-2-one (22.5 g).

P.F. 64-65°C;

NMR (CDC13) <5 4.41 (1 H, m), 4.21 (2 H, m), 4.12 (1 H, m), 2.79 (1 H, m), 2.28-2.4 (2 H, m), 1.41 (9 H, s), 1.16 (3 H, d), 0.9 (6 H, m).

Hydrogen peroxide (30%, 4 mL) and lithium hydroxide monohydrate (6.38 g) were added successively to a stirred mixture of (4S)-3-[(2R)-3-tertiobutoxycarbonyl-2-methylpropionyl]-4-isopropyloxazolidin-2-one (22.5 g), water (280 mL), and THF (800 mL) that had been cooled to 5°C. The resulting mixture was stirred at 5°C for 3 hours. A saturated aqueous solution of sodium metabisulfite was added to destroy the excess hydrogen peroxide, and the solvent was evaporated. The residue was subjected to extraction with dichloromethane. The aqueous solution was acidified by the addition of an aqueous solution of citric acid and subjected to extraction with dichloromethane. The extracts were combined and washed.

21

with water and filtered through paper for phase separation. The filtrate was evaporated, giving 1-tert-butyl (3R)-3-methylsuccinate, in the form of an oil (12.9 g).

5 NMR (CDC13) ô 2.9 (1 H, m), 2.64 (1 H, m), 2.37

(1 H, m), 1.4 (9 H, s), 1.23 (3 H, d).

A borane-dimethyl sulfide complex (10 M, 10.3 mL) was added over 15 min to a stirred mixture of (3R)-3-methylsuccinate of 1-tert-butyl 10 (12.9 g) and THF (200 mL) that had been cooled to -10°C and placed under an argon atmosphere. The mixture was stirred at -10°C for 30 min. It was then allowed to warm to room temperature and stirred for 1 hour. The mixture was cooled again to 5°C, and methanol (50 mL) was added in portions. It was allowed to warm to room temperature and stirred for 30 min. The mixture was evaporated, and the residue was divided between dichloromethane (100 mL) and water (100 mL). The organic phase was filtered through 20 paper for phase separation and was evaporated, giving tert-butyl (3R)-4-hydroxy-3-methylbutyrate, in the form of an oil (11 g).

NMR (CDCI3) δ 3.55 (2 H, m), 2.1-2.4 (3 H, m), 1.46 (9 H, s), 0.98 (3 H, d).

25 p-Toluenesulfonyl chloride (13.2 g) was

Added in portions to a stirred mixture of tert-butyl (3R)-4-hydroxy-3-methylbutyrate (11 g), triethylamine (21 mL), and dichloromethane (120 mL), the mixture was stirred for 20 hours. The mixture was successively washed with water and dilute aqueous sodium carbonate. The organic solution was filtered through phase-separation paper and evaporated, yielding tert-butyl (3R)-3-methyl-4-(p-toluenesulfonyloxy)butyrate, as an oil (20 g). NMR (CDCI3) α 7.6 (2H,d), 7.33 (2H,d), 3.92

9i

22

(2 H, d), 2.45 (3 H, s), 2.18-2.47 (2 H, m), 2.0-2.15 (1 H, m), 1.42 (9 H, s), 0.95 (3 H, d).

Example 2

Examples of suitable pharmaceutical dosage forms to allow therapeutic or prophylactic use of the compound of the present invention include the following, which can be obtained by conventional operating procedures well known in practice:

a) Tablet 1 mg/tablet 10 Active ingredient 1.0

Lactose European Pharmacopoeia 93.25

Croscarmellose sodium 4.0

Corn starch paste 0.75 (aqueous paste at 5% by weight/volume)

15 Magnesium stearate 1.0

b) Tablet II mg/tablet Active ingredient 50 Lactose (European Pharmacopoeia) 223.75 Croscarmellose sodium 6.0

20 Corn starch 15.0

Polyvinylpyrrolidone 2.25 (aqueous paste at 5% by weight/volume)

Magnesium stearate 3.0

c) Tablet III mq/tablet 25 Active ingredient 100

Lactose European Pharmacopoeia 182.75

Croscarmellose sodium 12.0

Corn starch paste 2.25 (aqueous paste at 5% by weight/volume)

3.0 Magnesium stearate 3.0

d) Capsule mg/capsule Active ingredient 10 Lactose (European Pharmacopoeia) 4 8 8.5 Magnesium stearate 1.5

23

e )

Injectable preparation

Active ingredient

(acid addition salt)

Sodium chloride

Purified water per 1.0 ml mcr/ml 1.0

9.0

5

Example 3

The following description describes a study of the effects of the compound (-)-(3R) of the present invention and the corresponding racemic mixture (3RS) in rats. Four groups of ten Alderley Park Wistar rats (each group comprising five male and five female rats) were administered orally to the racemic mixture (3RS) at daily doses of 0, 25, 100, or 500 mg/kg. Administration was continued for a total duration of seven 15-day periods. The animals were euthanized and examined. Adverse effects were noted in the livers of six rats in the group of ten rats receiving the 500 mg/kg/day dose.

(Each group comprised five male and five female rats.) Twenty animals were administered orally the compound (-)-(3R) of the present invention at daily doses of 0, 50, 250, and 1000 mg/kg. The highest dose was not tolerated. After four or five days, four of the animals in this group were killed. The remaining six animals were administered 500 mg/kg/day for the remainder of the study. Administration continued for a total of 14 days. The animals were killed and examined. No adverse effects were observed in the livers of the group of rats receiving 250 mg/kg/day. No adverse effects on the liver were also noted in the six animals that received 1000 mg/kg/day for three or four days and then 500 mg/kg/day for ten or eleven days.

The compound (-)-(3R) of the present invention has no significant adverse effect on the rat liver at 500 mg/kg/day.

Four groups of ten rats at Alderley Park Wistar

Based on these observations, we note that

24

This implies that the (-)-(3R) compound is less toxic than the racemic mixture (3RS).

It goes without saying that the present invention has been described only for explanatory purposes, but in no way as limiting, and that many modifications can be made to it without going out of its scope.

25

Claims (19)

DEMANDS 1. An optically active compound, characterized in that it consists of (-)-(3R)-3-methyl-4-{4-[4-(4-pyridyl)piperazine-1-yl]phenoxybutyric acid, or one of its salts, 5 pharmaceutically acceptable esters, amides or solvation products, practically devoid of the (+)-(3S) stereoisomer. 2. Optically active compound according to claim 1, characterized in that it contains at least 90% 10 weight of the (-)-(3R) isomer and an amount equal to or less than 10% by weight of the corresponding (+)-(3S) isomer. 3. Optically active compound according to claim 1, characterized in that it contains at least 95% by weight of the (-)-(3R) isomer and an equal or lesser amount of 15 greater than 5% by weight of the corresponding ( + )- (3S) isomer. 4. Optically active compound according to claim 1, characterized in that there is at least 99% by weight of the (-)-(3R) isomer and an amount equal to or less than 1% by weight of the corresponding (+)-(3S) isomer. 20 5. Optically active compound according to any one of claims 1 to 4, characterized in that the pharmaceutically acceptable salt is in the form of a hydrochloride. 6. Optically active compound according to one 25 any of claims 1 to 4, characterized in that the pharmaceutically acceptable ester is in the form of a methyl, ethyl, propyl or tert-butyl ester. 7. Optically active compound according to any one of claims 1 to 4, characterized in that 3 0 1'pharmaceuticalally acceptable amide is in the form of an N-methyl-, N,N-dimethyl-, N-ethyl-N-methyl- or N,N-diethyl-butyramide. 8. Optically active compound according to any one of claims 1 to 4, characterized in that the 35 pharmaceutically acceptable solvation product is under 26 form of a hydrate. 9. A process for preparing the optically active compound, or one of its pharmaceutically acceptable salts, esters, amides or solvation products, according to any one of the preceding claims, characterized in that it comprises: a) the reaction of 4-[4-(4-pyridyl)piperazine-1-yl]phenol, or one of its reactive derivatives, with the chiral intermediate consisting of (3R)-4-hydroxy-3-methyl- 10 butyric or one of its esters, or one of its reactive derivatives; b) the reaction of a compound of formula I / * in which L represents an atom or group 15 starting, with the chiral intermediate consisting of (3R)-3-methyl-4-[4-(piperazine-l-yl)-phenoxy]butyric acid, or one of its acid addition salts; c) the decomposition of an ester of formula II 20 in which R represents a protecting group of the carboxyl function; d) the resolution of the racemic mixture (3RS), consisting of 1' acid (3RS)-3-methyl-4-{4-[4-(4-pyridyl)pipe- cfj ■ 27 razine-1-yl]phenoxy}butyric; and, when a pharmaceutically acceptable salt of the (-)-(3R) compound is required, the reaction of the resulting compound with a suitable acid or base; and, when a pharmaceutically acceptable ester or amide of the (-)-(3R) compound is required, the reaction of the resulting compound with a suitable alcohol or amide. 10. Optically active compound, characterized in that it consists of (3R)-3-methyl-4-hydroxybutyrate of 10 tert-butyl, or one of its reactive derivatives, practically devoid of the (3S) stereoisomer. 11. Compound according to claim 10, characterized in that the reactive derivative consists of tert-butyl (3R)-3-methyl-4-(p-toluenesulfonyloxy)butyrate. 15 12. Pharmaceutical composition, characterized in that it comprises the optically active compound, or one of its pharmaceutically acceptable salts, esters, amides, or solvation products, according to any one of claims 1 to 8, mixed with a diluent or carrier 20 pharmaceutically acceptable. 13. Medicinal product for inhibiting platelet aggregation in a warm-blooded animal, characterized in that it comprises an effective amount of the optically active compound, or of one of its salts, esters, amides or solva- products 25 pharmaceutically acceptable formulations, according to any one of claims 1 to 8. 14. Drug for inhibiting platelet aggregation in a warm-blooded animal with a strong simultaneous reduction of adverse effects associated with administration of 30 racemic mixture (3RS), characterized in that it comprises an effective amount of the optically active compound, or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, according to any one of claims 1 to 8. 35 15. Drug to inhibit the binding of 28 GPIIb/IIIa fibrinogen in a warm-blooded animal, characterized in that it comprises an effective amount of the optically active compound, or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, according to any one of claims 1 to 8. 16. Drug for inhibiting thrombotic events accompanying unstable angina in a warm-blooded animal, characterized in that it comprises an effective amount of the optically active compound, or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, according to any one of claims 1 to 8. 17. Use of the optically active compound, or of one of its pharmaceutically acceptable salts, esters, amides or solvation products according to any one of claims 1 to 8, characterized in that it is intended for the production of a medicinal product for the prevention or treatment of a disease involving platelet aggregation. 18. Use of the optically active compound, or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, according to any one of claims 1 to 8, characterized in that it is intended for the production of a drug for the prevention or treatment of a disease involving the binding of fibrinogen to GPIIb/IIIa. 19. Use of the optically active compound, or of one of its pharmaceutically acceptable salts, esters, amides or solvation products, according to any one of claims 1 to 8, characterized in that it is intended for the production of a drug for the prevention or treatment of thrombotic events accompanying unstable angina.