SE467256B - / R- (E) / - 4- (3-PHOSPHONO-2-PROPENYL) -2-PIPERAZINE CARBOXYLIC ACID, PROCEDURES FOR PREPARING THIS AND A PHARMACEUTICAL COMPOSITION CONTAINING COMPOSITIONS - Google Patents

Description

15 20 25 30 35 467 256 or chloroform, at room temperature. The subsequent hydrolysis can be carried out under mild conditions.

When R is aryl (C 1-6) alkyl, aryl is suitably an optionally substituted phenyl group, where suitable substituents include lower alkyl or lower alkoxy groups.

The compound of formula I including its salts can also be obtained in the form of its hydrates, especially monohydrates. hydrates, in particular the monohydrate, also form part of the invention.

The compound of formula II can be prepared as shown in the following reaction scheme: CH 2 H 2 6 5 H 2 C 3 H 5 (c) 3 cu 3 L / N 1) (-) - menthol E 1 / ______________>; L. 'l u H' t! COOCZHS 2) separation of I too GQCSHS diastereoisomers Üüc5H5 [HJ CH Q OR Lai / c 3 p: | OR * få cH3 C143 +: LY ß "* coiß '" H CH (° 2 "s) s" 3 O ef "1 Q \ °“ m3 N cnå / czag II é-- [É H: g * coo 10 The compound of formula I can form cationic salts and acid addition salts, such salts being readily prepared by standard methods Cationic salts include, but are not limited to, ammonium, sodium, potassium, calcium, piperidinium salts. Acid addition salts include, but are not limited to, those formed with hydrochloric acid, hydrobromic acid, sulfuric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoroacetic acid.

The hydrate, in particular the monohydrate, of the compound of formula I has particularly interesting physicochemical and other properties- e.g. ease with which it is purified per, in terms of solubility, as well as stability. The hydrate can be obtained by crystallizing the compound of formula I from an aqueous medium, e.g. as described in Example e), for example from water / methanol.

In the following example, all temperatures are given in degrees Celsius and uncorrected. The EKJDZÛ values are also uncorrected.

Example: [R- (E) -4- (3-Phosphono-2-Dronenyl) -2-Diperazinecarboxylic acid a): RL-1A-alpha-ethyl-2-ilzmethoxylate 4-Dibenzyl-2-piperazinecarboxylic acid ethyl ester (prepared according to E. Helv.

Chim. Acta go (1962) 2383) and 458 g of C

Jucker and E. Rissi, Approximately 700 ml of the solvent is then slowly removed by distillation and replaced continuously with new portions of toluene (the reaction is monitored by TLC, room temperature and treated with 1.25 l of 2N aqueous HCl and 6 ethyl acetate / hexane 1 : 3). The mixture is cooled to 1 diethyl ether and stirred thoroughly for 1 hour. The crystalline precipitate is filtered off and washed with diethyl ether and 0.1N aqueous HCl. The crude product is recrystallized from ethanol / 0.2N aqueous to give the hydrochloride hydrate of the title compound, culD2 ° = + 1s, s ° ce = 1.2 l of cacl3> ernellee, which is used without further purification in subsequent steps. b> LRL-2-2iesraainkarbßzvlsxra L1B, _2§._5E>; 5; me fi xl; 2; 210 g of the product from step a) in 2 l of ethanol and 10.5 g of Pd / C (10%) are hydrogenated for 7 hours at room temperature and normal pressure, then filtered and evaporated in a vacuum. The residue is treated with ethanolic HCl, then the precipitate is filtered off and washed with ethanol / diethyl ether (1: 1). The product is recrystallized from water / methanol / ethyl acetate to give the dihydrochloride of the title compound, m.p. 225226 °, EQJDZÛ = -52.0 ° (c = 1.34 in water). The dihydrochloride is treated with diethyl ether / aqueous ammonia, then the organic phase is evaporated to dryness to give the title compound, m.p. 50-52 °, ca1D2 ° = 56.70 <= = 1.05 1 cnc13>.

C) LR;; 2; Pipsra2incarb2-acrylic acid 113._2§._53); 5; methxl; 2; <1-methylecyclocloberyl ester to a stirred solution of 11.3 g of the free base from step b) and 5.9 ml triethylamine in 90 ml of tetrahydrofuran is added at -30 ° within 30 minutes 10.7 g of 3-bromopropen-2-ylphosphonic acid diethyl ester (prepared according to K. Hemmi, H. Takeno, M. Hashimoto and T. Kamiya, Chem. Pharm. Bull gg (1982), 111) in 45 ml of tetrahydrofuran. Stirring is continued at -25 ° for 20 hours. After filtering the precipitate, the solution is concentrated under reduced pressure, and the resulting syrup is chromatographed on silica gel using dichloromethane with the addition of increasing concentration of a mixture in a ratio of 1:19 of concentrated aqueous ammonia / ethanol, which concentration reaches 10% after 2 hours. The fraction eluted with dichloromethane / concentrated aqueous ammonia / ethanol in the ratio 200: 1: 19 (rf = 0.35) is isolated and concentrated in vacuo to give the title compound as an oil, EKJDZÛ = - 56.00 (c = 1.3 in 2N HCl). Treatment of the product with ethanolic HCl / ether gives the dihydrochloride, m.p. 157-1ss °, raJD2 ° = -4a, 2 ° = cc = 1.4 1 2N Hcl). d> LR; <â> _l ~ i-L3.: D.i_ei2. ° ši ioafinxlztprøeenyl> jnviperazinkarb; To a stirred solution of 5.79 g of the product from step c) in 58 ml of absolute CH 2 Cl 2 is added at -30 ° within 30 minutes 22.8 ml of a solution of boron trichloride in 1.2 dichloroethane (about 2.2M) . The reaction mixture is stirred for 1 hour at -25 ° and 3.5 hours at 0 °.

At 0 ° C, 50 ml of water are added, and the mixture is neutralized by the addition of 2N aqueous NaOH and partitioned between H 2 O and CH 2 Cl 2. The aqueous phase is evaporated to dryness in vacuo, then the residue is taken up in CHCl 3, filtered, dried (Na 2 SO 4) and evaporated to dryness in vacuo to give the title compound, which was used without further purification in the next step.

An analytical sample is purified by HPLC (Nucleosil RP-B, H 2 O / cH 3 OH 3: 2) to give foam cu1D2 ° = -13, o ° <3 = 1.1 in 0.5 HCl). 339 MHz (1N-NMR (C , 2.35 <1H, axd, J = 11.3 x 3.6 Hz), 2.52 - 2.53 <1H, m), 2.77 <1H, axax, J = 12.1 x 9, 0 x 3.3 Hz), 2.33 <1H, axdxd, J = 11.3 z 3.3 x 1.7 Hz), 2.99 c1H, ax, J = 12.1 x 3.9 Hz) , 3.10 - 3.15 <2H, m), 3.33 <1H, axa, J = 3.3 x 3.3 Hz), 3.97 <4H, axq, J = 3.6 x 7, 0 Hz), 5.50 <2H, bran), 5.33 <1H, dxaxt, J = 21.5 x 17.1 x 2.1 Hz), 6.52, dxdxt, J = 22.0 x 17 , 1 x 5.6 Hz). 9) LR: 3 - EO3fena-Z ~ 2r2PenII-2-2iaeraincarbøëvlßxra 3.9 g of the crude product from step d) are dissolved in 300 ml of absolute CH 16 hours. The reaction mixture is evaporated, the residue is taken up in H 2 O, stirred for 1 hour and filtered. The pH of the solution is adjusted to 6 by adding Dowex 1x4 (OH form), and the mixture is placed on top of a column containing Dowex 1x4 (acetate form). Elution with a gradient of water-based acetic acid (0.05 to 0.25N) gives a foam when concentrated to dryness in vacuo. This foam is crystallized from H 2 O / CH 3 OH and recrystallized from H 2 O / C 2 H 5 OH to give the title compound as the monohydrate, m.p. 206 ° (dec.). ca1D2 ° = -21.3 ° <3 = 1.1 1 2N Hcl). The absolute configuration is derived from a chemical correlation with D-asparagine and is confirmed by X-ray structure analysis.

The compound of formula I exhibits valuable pharmacological activity and is therefore suitable for use as a pharmaceutical. In particular, the compound possesses lu- e.g. for therapy. teinizing hormone (LH) and testosterone secretion inhibitory activity in the following tests: Adult male rats of the Wistar strain (SIV, Kissleg, West Germany, 200-300 g) receive the test compound intraperitoneally. 2 hours later, the rats are killed by decapitation and blood samples are taken. Serum LH is measured using a bioassay based on testosterone production by dispersed, collagenase-treated rat interstitial Leydig cells exposed to LH-containing serum or rat LH standard; serum testosterone is measured using radioimmunoassay (125-JT, cis, Medipro Teufen, Switzerland) (cf. E. del Pozo, A Podesta, A Solano, J. Cslaf, M. Marko, in: Biorythms and Stress in the Physiopathology of Repro - duction, P. Pancheri and L. Zichella (Eds), Hemisphere Publishing Co. Washington, 389-398 (1988) l.

The compound of formula I inhibits LH and testosterone secretion at the dose of 3.2 mg / kg i.p. significant. (¿) - 4- (3-Phosphono-2-propenyl) -2-piperazinecarboxylic acid (hereinafter referred to as the CPP), corresponding to the racemate of the compound of formula I, has at 3.2 mg / kg i.p. no effect on LH secretion and only weakly inhibits testosterone secretion.

In female rats, the compound of formula I inhibits LH-dependent spontaneous ovulation in the following tests (cf. M. Marko and E.

Flückiger, Neuroendocrinology gg, 228-231 (1980)]: Female rats of the Wistar strain (SIV, Kissleg, West Germany, 200-300 g) with regular 4-day cycles receive the test substance intraperitoneally during proestrus at 13.00 and 15.00.

The next day at 9.00, when the rats are in estrus, they are killed, and the oviducts are examined microscopically and counted. Ovulation is considered to be inhibited only if no ova can be counted. The compound of formula I (tested in the form of the monohydrate) significantly inhibits spontaneous ovulation, as it is administered at doses of 2 x 3.2 mg / kg i.p. (at time 13.00 3.2 mg / kg i.p. and at time 15.00 3.2 mg / kg i.p.). The CPP spontaneously inhibits ovulation very weakly when administered at doses of 2 x 3.2 mg / kg i.p. under the same experimental conditions.

The compound of formula I is therefore suitable for use in the treatment of disorders or diseases with an etiology associated with or modulated by LH secretion or with an etiology in which physiological regulation of LH secretion is involved, e.g. in the treatment of prostate hypertrophy, in the treatment of menopausal syndrome and in the treatment of breast and prostate cancer. For this use, a suitable daily dose is in the range of from about 1 to about 800 mg of the compound, which is conveniently administered in divided doses 2 to 4 times a day in unit dosage form containing e.g. from about 0.25 to about 400 mg of the compound or in a sustained release form.

Ii! The compound of formula I exhibits muscle relaxing activity in conscious rabbit at doses from 0.01 to 0.05 mg / kg [H.J. 266, 467-468 (1970)]. In this test, the monohydrate of the compound with i.v. Teschendorf et al., Arch.Exp.Pharmacol. formula I 50% inhibition of reflex muscle tone after administration of 0.02 mg / kg i.v., while the CPP inhibits reflex muscle tone by 47 X after administration of 0.5 mg / kg i.v.; the compound of formula I is about 25 times more active than the corresponding racemate.

The compound of formula I is therefore suitable for use in e.g. treatment of increased muscle tone, in the treatment of painful muscle spasms, which can be attributed to static and functional disorders of the lumbar or cervical spine or after surgery or in the treatment of spasticity, e.g. due to cerebrovascular multiple sclerosis, diseases of the spinal cord, accidents, cerebral trauma or cerebral palsy. For this use, a suitable daily dose ranges from about 1 to about 800 mg of the compound, which is conveniently administered in divided doses 2 to 4 times a day in unit dosage form containing e.g. from about 0.25 to about 400 mg of the compound or in a sustained release form.

Furthermore, the compound of formula I reduces ischemia-induced neuronal damage and concomitant symptoms according to the occlusion model of the middle cerebral artery (MCA) in rats at a dose of Ejfr. A.Tamura 130 mg / kg s.c. and especially at 3 x 10 mg / kg i.p. et al., J. Cereb. Blood Flow Metabol. ¿, 53-60 (1981), A. Sauter, M. Rudin, Stroke il, 1228-1234 (1986)]. The area of the tissue that has been subjected to infarction is measured using MCID image analysis software (developed by Imaging Research Inc.) in 5 horizontal 20 μm thick discs sectioned at several levels and stained with cresyl violet. The total volume of the brain that exhibits ischemic damage is estimated by adding the 5 areas obtained from these 5 discs. Infarct size determined histologically 5 days after occlusion of MCA is reduced by more than 20% after treatment with 3 x 10 mg / kg i.p. of the monohydrate of the compound of formula I (first injection immediately after MCA occlusion, second and third after 8 and 16 hours, respectively.

The compound is therefore suitable for use in the prophylaxis and therapy of conditions associated with cerebral ischemia, e.g. stroke. For this use, a suitable daily dose is in the range of about 25 to about 800 mg of the compound, which is conveniently administered in divided doses 2 to 4 times a day in unit dosage form containing e.g. from about 5 to about 400 mg of the compound or in a sustained release form.

Furthermore, the compound of formula I has a strong selective and competitive antagonistic effect on NMDA (N-methyl-D-aspartic acid) receptors. Thus, the monohydrate of the compound of formula I inhibits NMDA-induced depolarizations upon analysis on isolated spinal cord from frog [P.L. Herrling, Neuroscience ¿g, 417-426 (19B5)] with a pA2 value of 6.8, the CPP with a pA2 value of 6.2, so the compound of formula I is thus about 4 times as active as the corresponding racemat. CPF I (¿) -3- (2-carboxypiperazin--4-yl) propyl-1-phosphonic acid, which is the compound disclosed in British Patent Application 2,157,685, has a pA2 value of 5.8.

In NMDA-induced sodium effluent assay on right brain slices [Luini A., Goldberg O. + Teichberg V.I., Proc. Natl. Acad.

Sci. USA Zå, 3250-3254 (1981) J, the monohydrate of the compound of formula I has a pA2 value of 6.5 and the CPP has a pA2 value of 6.2, the compound of formula I being approximately twice as active as the corresponding racemate. CPP has a pA2 value of 6.0.

The selectivity for the NMDA antagonistic effect is shown by the fact that it is inactive, which also applies to the CPP and CPP, in the test for quisqualate- and kainate-induced sodium outflow up to a concentration of 1 mM.

As a result of its NMDA receptor antagonism, the compound of formula I is suitable for use in the treatment of anxiety, schizophrenia and depression or of CNS degenerative disorders or diseases, such as Huntington's, Alzheimer's or Parkinson's disease. For these uses, a suitable daily dose ranges from about 25 to about 800 mg of the compound, which is conveniently administered in divided doses 2 to 4 times a day in unit dosage form containing e.g. from about 6 to about 400 mg of the compound or in a sustained release form As a result of its NMDA receptor antagonism, the compound of formula I is further suitable for use in the treatment of fw 10 15 20 25 30 35 467 256 "pretreated groups. about 6 female mice (18-26 g, OF-1, Sandoz, Basel) with the test substance intraperitoneally. 30 minutes later, they are exposed to 400 mg / kg s.c. of NMDA in the neck area and kept under observation for 30 minutes. The latency for the appearance of the first signs of convulsions, for the first tonic convulsions and for differences in the occurrence of deaths are noted. The significance of any is determined using the Mann-Whitney U-test ES. Siegel, Non-parametric Statistics, McGraw-Hill, New York 1956]. The threshold dose is the minimum dose at which there is a significant inhibition of convulsive symptoms. The threshold dose for the compound of formula I (tested in the form of monohydrate) is approximately 5 mg / kg i.p., for CPP 10 mg / kg i.p.

As a result of its anti-convulsive activity, the compound of formula I is suitable for use in the treatment of epilepsy. For this use, a suitable daily dose ranges from about 25 to about 800 mg of the compound, which is conveniently administered in divided doses 2 to 4 times a day in unit dosage form containing e.g. from about 6 to about 400 mg of the compound or in a sustained release form.

In addition, the compound of formula I exhibits analgesic activity in in vitro isolation of rat spinal cord tail using capsaicin (0.8-1 μM) as chemically harmful stimulus-inducing depolarizing ventral root responses EM. Yanagisawa et ¿Q§, 231-239 (1984)]. the compound of formula I reduces the chemical stimulus al., European J. Pharmacol. The monohydrate of 75-80% at a concentration of 10 μM.

The compound of formula I is therefore suitable for use in relieving pain. For this use, a suitable daily dose is in the range of from about 25 to about 800 mg of the compound, which is conveniently administered in divided doses 2 to 4 times a day in unit dosage form containing e.g. from about 8 to about 400 mg of the compound or in a sustained release form.

In addition, the compound of formula I as well as the corresponding racemate has no effects on the blood pressure and cardiac activity of anesthetized cat at a dose up to 10 mg / kg i.v .. In pilot toxicity tests on dogs for 4 weeks, 3 mg / kg / day i.v. of the compound of formula I well. 10 15 20 25 30 35 gt 467 256 tinnitus. For this use, a suitable daily dose ranges from about 25 to about B00 mg of the compound, which is conveniently administered in divided doses 2 to 4 times a day in unit dosage form containing e.g. from about 6 to about 400 mg of the compound or in a sustained release form.

In addition, the compound of formula I exhibits anti-convulsive activity in electroshock-induced convulsions in mice [E.A.

J.Am.Pharm.Assoc.Scient.Ed. go, 201 (1949) and J. Phar- Exptl. 319 (1952) J. In this test, OF-1, Swinyard, receives macol. Therap. 106, groups of 6 male mice (18-26 g, Basel) the test substance After 1, Sandoz, intraperitoneally. For 2 and 4 hours, a 200 ms long shock of 50 mA is applied via electrodes in the cornea, which electrodes are lubricated with electrolyte jelly. This supra-maximal shock produces tonic extensor convulsions in all extremities. Inhibition of the extension in the hind paw is taken as a sign of protective effect.

After examination of several dose levels, the threshold dose is determined. The threshold dose at 1 hour, which is the dose required for pre-CPP. to inhibit the extension of the hind paw, is (img / kg i.p. the formula I (monohydrate) and 3-10 mg / kg i.p.

The literature dose dose for CPP is 10 mg / kg i.p ..

The following table indicates the inhibition of the hind paw extension expressed in% for the compound of formula I in comparison with the corresponding racemate: Dose 1 Inhibition of E-shock mg / kg induced hind paw extension i.p. 1 hour 2 hours 4 hours Compound of formula I - 1 67 * 67 * 33 monohydrate 2.5 83 * 83 * 67 * 3 100 * 100 * 83 * CPP 1 20 50 25 3 33 67 * 17 10 67 * 80 * 80 * Fischer test, comparison group versus substance group, * p <= 0.05.

As shown in the table, the compound of formula I has higher anti-convulsion activity than the corresponding racemate, as it is tested against electroshock-induced convulsions in mice.

The compound of formula I further inhibits N-methyl-D-aspartic acid (NMDA) -induced convulsions in mice. In this test 10 15 20 25 30 35 il 467 256 As can be seen from the above test results, the strong LH secretion inhibitory activity is accompanied, the marked (25-fold) increase in the muscle relaxing activity as well as the two- to four-fold NMDA receptor antagonistic activity for the compound of formula I compared with the corresponding racemate not by a corresponding increase in the side effects, e.g. cardiovascular effects.

The compound of formula I may be administered as such or in the form of its pharmaceutically acceptable salts. Such salts have the same order of magnitude of activity as the compound of formula I.

According to the present invention there are further provided pharmaceutical compositions which comprise the compound of formula I or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable carrier or diluent.

The compound of formula I may be administered by any conventional route, in particular enterally, preferably orally or parenterally. The compound of formula I may be administered as such or mixed with conventional pharmaceutical carriers. For example, for oral administration, e.g. in the form of tablets or capsules, the compound of formula I may be mixed with conventional pharmaceutically acceptable excipients, e.g. inert diluents such as lactose, mannitol, calcium sulfate, microcrystalline cellulose; disintegrants, e.g. starch, sodium carboxymethylcellulose, sodium carboxymethyl starch, alginic acid, crospovidone; binders such as cellulose derivatives (methyl, hydroxymethyl, hydroxypropylmethyl), povidone, gelatin; lubricants, e.g. silica, stearic acid, magnesium or calcium stearate; hydrogenated oils, such as castor oil, glycerol esters, e.g. palmitostearate and / or flavoring, coloring and sweetening agents. The tablets may be uncoated or coated by known techniques to delay the disintegration and absorption in the gastrointestinal tract and thereby provide delayed action for a longer period. Parenteral compositions are preferably in the form of a sterile injectable aqueous solution. Such aqueous solutions should be suitably buffered, if required, and made isotonic with sufficient saline. Optionally, a preservative may be added, such as benzyl alcohol. A unit dose may contain from about 0.25 to about 400 mg of the compound of formula I or a pharmaceutically acceptable salt thereof.

The pharmaceutical compositions can be prepared according to conventional techniques.

For the preparation of tablets, the compound of formula I may be mixed with lactose and granulated with water, 0.51 sodium alginate or 5% hydroxypropyl methylcellulose solution. The dried granulate is compressed into tablets in the presence of about 20% corn starch and 1% magnesium stearate. In this way, e.g. tablets of the following composition: šgmgggggtgg Tablet weight (mg) Compound of formula I - monohydrate 50 Lactose 97 Maize starch 40 Hydroxypropylmethylcellulose 10 Magnesium stearate 2 Silica 1 200 tablet one to four times a day.

Capsules may contain the active agent alone or mixed with an inert solid excipient, e.g. as mentioned above.

Capsules containing the ingredients listed below can be prepared by conventional techniques and administered in a dose of one capsule one to four times a day.

Components Kagsel weight (mg) Compound of formula I - monohydrate 50 Inert solid excipient (maize starch, lactose, aerosil, magnesium stearate) 250 Similarly, tablets and capsules containing 25 mg and 100 mg of the compound of formula I can be prepared.

The following injectable solution is prepared with the indicated amount of active agent using conventional techniques. The injectable solution is suitable for once-daily administration. f'w 10 15 20 25 30 35 13 467 256 Components Sterile injectable solution Weight (mg / ml) Compound of formula I - monohydrate 25 Sodium chloride 7.0 Potassium dihydrogen phosphate 3.63 Disodium hydrogen phosphate 5.68 Benzyl alcohol 9.0 Water for injection q.s. to 1 ml.

The solutions can be filtered through a 0.2 μm sterile filter and aseptically filled into ampoules. The ampoules are gassed with carbon dioxide.

The present invention also relates to the compound of formula I or a pharmaceutically acceptable salt thereof for use as a pharmaceutical, e.g. for use in the treatment of disorders or diseases associated with LH secretion; treatment of increased muscle tone; treatment of conditions associated with cerebral ischemia; treatment of anxiety, schizophrenia, depression or CNS degenerative disorders; treatment of tinnitus; treatment of epilepsy or to relieve pain.

Accordingly, the present invention provides a method of treating disorders or diseases associated with LH secretion; treatment of increased muscle tone; treatment of conditions associated with cerebral ischemia; treatment of anxiety, schizophrenia, depression or CNS degenerative disorders; treatment of tinnitus; treatment of epilepsy or to relieve pain in an individual, which comprises administering a therapeutically effective amount of the compound of formula I or a pharmaceutically acceptable salt thereof to an individual in need of such treatment.

The present invention further relates to the compound of formula I or a pharmaceutically acceptable salt thereof for use in the manufacture of a pharmaceutical composition for use in the treatment of disorders or diseases associated with LH secretion, increased muscle tone, conditions associated with cerebral ischemia, anxiety. , schizophrenia, depression, CNS degenerative disorders, tinnitus or epilepsy or to relieve pain.

Claims (8)

10 15 20 25 30 467 256 14 PATENT REQUIREMENTS A compound in the form of [R- (E)] - 4- (3-phosphono--2-propenyl) -2-piperazinecarboxylic acid of formula I: OH few? r I E "i .JfH" "coou s.) or a salt thereof. A compound according to claim 1 in the form of its monohydrate or a salt thereof. A compound according to claim 1 or 2 or a pharmaceutically acceptable salt thereof for use as a pharmaceutical. A compound according to claim 3 for use in the treatment of diseases or disorders associated with LH secretion, increased muscle tone, conditions associated with cerebral ischemia, anxiety, schizophrenia, depression, CNS degenerative disorders, tinnitus or epilepsy or to relieve pain. Process for the preparation of [R--2-propenyl] -2-piperazinecarboxylic acid of formula I. OH f ”I Ön f N (NLH" “coon or a salt thereof, characterized in that a compound of formula II is dealkylated: = 10 15 20 25 30 35 15 467 256 o on * | o: n F wherein R is (C 1-4) alkyl or aryl (C 1-4) alkyl, and optionally forms a salt thereof. Use of [R- (E) 1-4- (3-phosphono-2-propenyl) -2-piperazinecarboxylic acid of the formula I: OH is a "K sx E" ii thereof, for the preparation of a pharmaceutical composition for use in the treatment of disorders or diseases associated with LH secretion, increased muscle tone, conditions associated with cerebral ischemia, anxiety, schizophrenia, depression, CNS degenerative disorders, tinnitus, epilepsy or for the relief of pain . A pharmaceutical composition comprising [R- (E)] - 4- (3-phosphono-2-propenyl) -2-piperazinecarboxylic acid of formula I OH. p = o GH f (LH N. "coon or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable diluent or carrier therefor. 467 256 16 A pharmaceutical composition according to claim 7, wherein the compound I is in the form of its monohydrate or salt.