Background of the invention

The invention is concerned with the in vivo diagnosis of dementia of the Alzheimer type (DAT). DAT is a progressive neurodegenerative disorder that affects a significant part of the human population over the age of 60 years. It is well known that DAT is associated with a depletion of GABA _B receptor sites in the central nervous system, especially in the brain. Specifically, it has been ascertained by post-mortem investigations of DAT patients, that the number of baclofen-sensitive GABA _B receptor sites in outer layers of cortex and in several regions of the hippocampus of the DAT-affected brain is reduced by 60% to 70%. A diagnostic mean allowing in vivo assessment of this DAT-associated depletion of GABA _B receptor sites would provide a diagnostic method to positively identify DAT patients and might possibly even offer a means for early diagnosis of DAT.

Detailed Description of the invention

The present invention provides a class of [ ³ H]- and [ ¹¹ C]-labeled GABA _B receptor antagonists exhibiting a strong and specific interaction with that receptor site. [ ³ H]-labeled labeled GABA _B receptor antagonist according to the invention are useful for ex vivo autoradiographic localization and assessment of GABA _B receptor sites in the mammal central nervous system preparations. [ ¹¹ C]-labeled GABA _B receptor antagonist can be utilized for in vivo localization and assessment of GABA _B receptor sites in the mammal central nervous system by means of Positron Emission Tomography (PET). As ¹¹ C has a very short half-life, the invention also provides a class of unlabelled precursors and a process for transforming these in the corresponding ¹¹ C-labelled PET ligands. The resulting PET ligands can be administered by intravenous injection or infusion and thus provides a novel diagnostic method for early diagnosis of DAT in human.

Specifically, the invention relates to novel hydroxylated or alkoxylated N.P-aralkylphosphinic acid derivatives of the formula I

wherein

Ri denotes an aliphatic, cycloaliphatic or aromatic group,

R ₂ and R ₅ , independently of each other, represent hydrogen or an aliphatic group,

R ₃ denotes hydrogen or hydroxy and R ₄ denotes hydrogen or R ₃ and R together represent oxo,

R ₆ denotes hydrogen or [ ³ H]- or [ ¹¹ C]-labeled alkyl,

R ₇ denotes hydrogen, lower alkyl, lower alkoxy, halogen, carboxy, carbamoyl or cyano, and wherein one of Xi and X ₂ represents a group of the formula >N- and the other represents a group of the formula >P(=O)(OH)-, and to their salts, to process for the manufacture of compounds of the formula I, wherein R ₆ denotes hydrogen, and to their use as intermediates, to a process for the conversion of compounds of the formula I, wherein R ₆ denotes hydrogen into compounds of the formula I in which R ₆ denotes [ ³ H]- or [ ¹ C]-labeled alkyl, and to the use of compounds of the formula

I wherein R ₆ denotes [ ³ H]- or [ ¹ C]-labeled alkyl, and their pharmaceutically acceptable salts as a tool for localization and assessment of GABA _B receptor sites in the mammal central nervous system by means of ex vivo autoradiography or in vivo Positron Emission

Tomography (PET).

Depending on whether asymmetric carbon atoms are present, the compounds of the invention can be present as mixtures of isomers, especially as racemates, or in the form of pure isomers, especially optical antipodes. For example, compounds of the formula I, wherein R ₃ denotes hydroxy, can be present either in the form of the S-enantiomer or in the form of the R-enantiomer, the S-enantiomer being preferred, or as an mixture of both enantiomers. Similarly, compounds of the formula I, wherein either of R ₂ and R ₅ is different from hydrogen, may be present in the form of the S-enantiomer or in the form of the R- enantiomer, the R-enantiomer being preferred when X _t is a group of the formula >NH-, or as an mixture of both enantiomers. Compounds of the formula I having more than one asymmetric carbon atom, for example, those wherein R ₂ is different from hydrogen and R ₃

is hydrogen, can be present in the form of one individual enantiomer having S.S-, R,R-, S,R- or R,S-configuration or diastereomers having S,S- or S.R-configu ration or R,S- or Re¬ configuration, or in the form of an enantiomeric or diastereomeric mixture of two or more of these enantiomers or diastereomers.

Aliphatic groups are, for example, lower alkyl, but may also be lower alkenyl or lower alkynyl or, in the case of R _1f mono- or di-lower alkoxyalkyl.

Cycloaliphatic groups are, for example, 5- to 7-membered cycloalkyl groups, such as cyclopentyl, cyclohexyl or cycloheptyl.

Aromatic groups are, for example, phenyl or naphthyl groups which are unsubstituted or mono-, di- or trisubstituted by lower alkyl, lower alkoxy, halogen, trifluoromethyl, carboxy, carbamoyl or cyano.

Lower alkyl is, for example, d-C -alkyl such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl or tertiary butyl but may also be a pentyl, hexyl of heptyl group.

[ ³ H]-I_abeled alkyl is, for example, [ ³ H]-labeled methyl, i.e. C[ ³ H] ₃ , but may also be a labeled C ₂ -C ₄ -alkyl group such as [ ³ H]-labeled ethyl, [ ³ H]-labeled propyl, [ ³ H]-labeled isopropyl, [ ³ H]-labeled butyl or [ ³ H]-labeled secondary or tertiary butyl.

[ ¹¹ C]-Labeled alkyl is, for example, [ ¹¹ C]-labeled methyl, i.e. [ ¹¹ C]H ₃ , but may also be a [ ¹¹ C]- labeled C ₂ -C -alkyl group such as [ ¹¹ C]-labeled ethyl, [ ¹¹ C]-labeled propyl, [ ¹¹ C]-labeled isopropyl, [ ¹¹ C]-labeled butyl or [ ¹¹ C]-labeled secondary or tertiary butyl.

Lower alkoxy is, for example, Cι-C ₄ -alkoxy such as methoxy, ethyloxy, propyloxy, isopropyl- oxy, butyloxy, secondary butyloxy or tertiary butyloxy.

Lower alkenyl is, for example, C ₂ -C ₄ -alkenyl, such as vinyl or allyl.

Lower alkynyl is, for example, C ₂ -C ₄ -alkynyl such as propargyl.

Lower alkoxyalkyl is, for example, Cι-C -alkoxy-d-C ₄ -alkyl such as methoxy methyl, 2- methoxyethyl, 3-methoxypropyl, ethoxymethyl, 2-ethoxyethyl, 3-ethoxypropyl or propyl- oxymethyl.

Di-lower alkoxyalkyl is, for example, di-Cι-C -alkoxy-Cι-C ₄ -alkyl such as dimethoxymethyl, 1- dimethoxyethyl, 1-diethoxymethyl or 1-diethoxyethyl.

Salts of compounds having salt-forming groups are especially acid addition salts, salts with bases or, where several salt-forming groups are present, can also be mixed salts or internal salts.

Such salts are formed, for example, by compounds of formula I having an acid group, for example a carboxy group, and are, for example, salts thereof with suitable bases, such as non-toxic metal salts derived from metals of groups la, lb, Ma and lib of the Periodic Table of the Elements, for example alkali metal salts, especially lithium, sodium or potassium salts, or alkaline earth metal salts, for example magnesium or calcium salts, also zinc salts or ammonium salts, as well as salts formed with organic amines, such as unsubstituted or hydroxy-substituted mono-, di- or tri-alkylamines, especially mono-, di- or tri-lower alkyl- amines, or with quaternary ammonium bases, for example with methyl-, ethyl-, diethyl- or triethyl-amine, mono-, bis- or tris-(2-hydroxy-lower alkyl)amines, such as ethanol-, diethanol- or triethanol-amine, tris(hydroxymethyl)methylamine or 2-hydroxy-tert-butylamine, N,N-di- lower alkyl-N-(hydroxy-lower alkyl)-amine, such as N,N-dimethyl-N-(2-hydroxyethyl)-amine, or N-methyl-D-glucamine, or quaternary ammonium hydroxides, such as tetrabutylammonium hydroxide.

The compounds of formula I having a basic group, for example an amino group, can form acid addition salts, for example with suitable inorganic acids, for example hydrohalic acids, such as hydrochloric acid or hydrobromic acid, or sulfuric acid with replacement of one or both protons, phosphoric acid with replacement of one or more protons, e.g. orthophos- phoric acid or metaphosphoric acid, or pyrophosphoric acid with replacement of one or more protons, or with organic carboxylic, sulfonic, sulfo or phosphonic acids or N- substituted sulfamic acids, for example acetic acid, propionic acid, glycolic acid, succinic acid, maleic acid, hydroxymaleic acid, methylmaleic acid, fumaric acid, malic acid, tartaric acid, gluconic acid, glucaric acid, glucuronic acid, citric acid, benzoic acid, cinnamic acid,

mandelic acid, salicylic acid, 4-aminosalicylic acid, 2-phenoxybenzoic acid, 2-acetoxy- benzoic acid, embonic acid, nicotinic acid or isonicotinic acid, as well as with amino acids, such as the α-arnino acids mentioned hereinbefore, and with methanesulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, ethane-1 ,2-disulfonic acid, benzenesulfonic acid, 4-methylbenzenesulfonic acid, naphthalene-2-sulfonic acid, 2- or 3- phosphoglycerate, glucose-6-phosphate, or N-cyclohexylsulfamic acid (forming cyclamates) or with other acidic organic compounds, such as ascorbic acid. Compounds of formula I having acid and basic groups can also form internal salts.

For isolation and purification purposes it is also possible to use pharmaceutically unacceptable salts.

Compounds of the formula I, wherein R denotes phenyl substituted, inter alia, by hydroxy and/or wherein R ₆ denotes hydrogen, have previously generically been disclosed in the art, but have hitherto not been described specifically. Also compounds of the formula I, wherein Ri denotes phenyl substituted, inter alia, by lower alkoxy, such as methoxy and/or R ₆ denotes lower alkoxy, such as methoxy, have previously generically been disclosed and specifically described in the art. These previously known compounds have been proposed and suggested as GABA _B receptor antagonists useful as nootropic and/or antiepileptic medicaments.

It has also been known in the prior art that GABA _B and GABA _A hippocampal receptor changes in histologically verified cases of DAT can be assessed post mortem by quantitative autoradiography of the binding of [ ³ H] -GABA (γ-aminobutyric acid) to GABAβ and GABAA receptor sites. It has also been reported in the prior art as being conceivable that the loss of GABA _B receptors associated with DAT could be measured utilizing a positron-labeled derivative of baclofen which compound also interacts with the GABA _B receptor site and is available commercially as a muscle relaxant. However, the interaction of baclofen with GABA _B receptor sites is not strong and or specific enough to render this compound appropriate for this purpose. Furthermore, no viable method has been suggested to positron-label this compound.

It has now been found that compounds of the formula I wherein R ₆ denotes hydrogen, are selectively alkylated at the phenolic hydroxy group. This finding is highly suφrising as hydroxy compounds of the formula I possess reactive sites expected to be at least equally reactive toward alkylating agents as the phenolic hydroxy group -OR ₆ such as the nitrogen atom of the >NH- group Xi or X ₂ and/or the hydroxy group of the >P(=O)(OH)- group X ₂ or Xi and when present, hydroxy R ₃ and carboxy R ₇ and/or carboxy as a substituent of R _L

It is also suφrising that this conversion inclusive of elaborate purification steps is completed within 30 minutes, typically in about 15 minutes and that a resulting positron labeled compound of the formula I in which R ₆ denotes [ ¹¹ C]-labeled alkyl, cross the blood-brain barrier on systemic administration and bind to the GABA _B receptor side quickly enough to complete the PET-investigation before a significant loss of positron-emitting activity can occur.

The invention relates in the first line to compounds of the formula I, wherein

Ri denotes lower alkyl, lower alkenyl, lower alkynyl, lower alkoxyalkyl or di-lower alkoxyalkyl,

5- to 7-membered cycloalkyl or phenyl or naphthyl groups which are unsubstituted or mono-, di- or trisubstituted by lower alkyl, lower alkoxy, halogen, trifluoromethyl, carboxy, carbamoyl or cyano,

R ₂ and R ₅ , independently of each other, represent hydrogen, lower alkyl, lower alkenyl or lower alkynyl,

R ₃ denotes hydrogen or hydroxy and R ₄ denotes hydrogen or R ₃ and R together represent oxo,

R ₆ denotes hydrogen or [ ³ H]- or [ ¹¹ C]-labeled labeled alkyl,

R ₇ denotes hydrogen, lower alkyl, lower alkoxy, halogen, carboxy, carbamoyl or cyano, and wherein one of Xi and X ₂ represents a group of the formula >N- and the other represents a group of the formula >P(=O)(OH)-, and to their salts.

The invention especially relates to compounds of the formula la

wherein

R _T denotes phenyl or phenyl mono-, di- or trisubstituted by d-C ₄ alkyl, such as methyl, d-

C ₄ alkoxy, such as methoxy, halogen, trifluoromethyl, carboxy, carbamoyl or cyano,

R ₂ represents Cι-C alkyl, such as methyl,

R ₆ denotes hydrogen or [ ³ H]- or [ ¹¹ C]-labeled Cι-C ₄ alkyl, such as C[ ³ H] ₃ or [ ¹¹ C]H ₃ and

R ₇ denotes hydrogen, Cι-C alkyl, such as methyl, Cι-C ₄ alkoxy, such as methoxy, halogen, carboxy, carbamoyl or cyano, and to their salts.

The invention relates more especially to compounds of the formula lb

wherein

Ri denotes unsubstituted phenyl,

R ₅ denotes d-dalkyl, such as methyl,

R ₆ denotes hydrogen or [ ³ H]- or [ ¹¹ C]-labeled Cι-C ₄ alkyl, such as C[ ³ H] ₃ or [ ¹¹ C]H ₃ , and

R ₇ denotes hydrogen, C ₁ -C alkoxy, such as methoxy, carboxy, carbamoyl or cyano, and to their salts.

The invention relates even more especially to compounds of the formula Ic

(Ic),

wherein

Ri denotes phenyl monosubstituted by carboxy, carbamoyl or cyano, mono- or di¬ substituted by halogen and/or trifluoromethyl or disubstituted by halogen or trifluoromethyl and carboxy, carbamoyl or cyano, R ₂ represent Cι-C alkyl, such as methyl,

R _β denotes hydrogen or [ ³ H]- or [ ¹¹ C]-labeled C,-C ₄ alkyl, such as C[ ³ H] ₃ or [ ¹¹ C]H ₃ , and R ₇ denotes hydrogen, and to their salts.

The invention relates to specifically to compounds of the formula I described in the Examples herein and to their salts.

The process for the preparation of the compounds of formula I, wherein R ₆ denotes hydrogen, provided according to the invention is characterized in that in a compound of formula II

wherein R is a hydroxy-protecting group,

R _a is a group Ri or a group Ri in which a carboxy group is present in a carboxy-protected form,

R _b is hydrogen, hydroxy or protected hydroxy, and R _c is hydrogen or R and R _c together represent oxo,

R is a group R ₇ or protected carboxy, one of X _a and X represents a group of the formulae >N(H) or >N(R _β ) and the other one represents a group of the formulae >P(=O)(OH) or >P(=O)(OR ₍ ),

R _β denotes an amino protecting group,

Ri denotes a hydroxy-protecting group and

Rι _> R ₂ , s and R ₇ have the meanings indicated under formula I, or in a salt thereof, the hydroxy-protecting group R and any carboxy-protecting group R _d , any carboxy-protecting group which may be present in R _a , any hydroxy-protecting group R ₍ , any hydroxy-protecting group which may be present in R _b , and a amino-protecting group R _β is removed and, if

desired, a resulting compound is converted into a different compound of formula I, an isomeric mixture obtainable according to the process is separated into its components and the preferred isomer is separated off and/or a free compound obtainable according to the process is converted into a salt or a salt obtainable according to the process is converted into the corresponding free compound.

Hydroxy-protecting groups R, R ₍ or such groups present in R _b are, for example, optionally lower alkyl-, lower alkoxy-, halogen- and/or nitro-substituted a-phenyl-lower alkyl such as benzyl, α,α-diphenyl-lower alkyl such as α,α-diphenylmethyl or α,α,α-triphenyl-lower alkyl such as trityl groups or silyl groups such as tri-lower alkylsilyl, such as trimethylsilyl, tributylsilyl, or tertiary-butyl(dimethyl)silyl. Preferred as hydroxy-protecting groups R are lower alkyl such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl or tertiary butyl, and optionally lower alkyl-, lower alkoxy-, halogen- and/or nitro-substituted a-phenyl-lower alkyl groups. Hydroxy-protecting groups Ri may also be aromatic groups, for example, optionally lower alkyl-, lower alkoxy-, halogen- and/or nitro-substituted phenyl, lower alkenyl or especially lower alkyl such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl or tertiary butyl.

Carboxy-protecting groups are, for example, optionally lower alkyl-, lower alkoxy-, halogen- and/or nitro-substituted phenyl, α-phenyl-lower alkyl such as benzyl, α,α-diphenyl-lower alkyl such as α,α-diphenylmethyl or α,α,α-triphenyl-lower alkyl such as trityl groups or silyl groups such as tri-lower alkylsilyl, such as trimethylsilyl, tributylsilyl, or tertiary- butyl(dimethyl)silyl, lower alkenyl or especially lower alkyl such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl or tertiary butyl.

Amino-protective groups R _β are, for example, acyl groups derived from a lower alkanoic acid or from a semi-ester of carbonic acid such as lower alkanoyl, especially formyl, or lower alkoxycarbonyl, especially tertiary-butyloxycarbonyl, also silyl groups such as tri-lower alkylsilyl, such as trimethylsilyl, tributylsilyl, or tertiary-butyl(dimethyl)silyl.

α-Phenyl-lower alkyl groups which are preferred as hydroxy-protecting groups R, also α- phenyl-lower alkyl groups Ri or such groups present in R can easily be removed by conventional reductive de-protecting methods, such as treatment with hydrogen in the

presence of an hydrogenation catalyst, for example, of palladium on charcoal, preferably in a lower alkanol such as methanol or ethanol.

The replacement and conversion of other protective groups involved may be effected in succession or simultaneously in accordance with methods known perse, for example, by treatment with a suitable basic or acidic agent, such as an alkali metal hydroxide, for example sodium hydroxide or lithium hydroxide, an alkali metal halide, especially an alkali metal bromide or iodide, such as lithium bromide or sodium iodide, thiourea, an alkali metal thiophenolate, such as sodium thiophenolate, or a protonic acid or a Lewis acid, such as a mineral acid, for example hydrochloric acid, or a tri-lower alkylhalosilane, for example trimethylchlorosilane. The replacement reaction can be effected in the absence or presence of a solvent and, if necessary, with heating or with cooling in a closed vessel and or under an inert gas atmosphere. The replacement of hydroxy-protecting groups such as groups R, the R protecting group, for example a silyl or alkyl group, in compounds of formula II by hydrogen can also be carried out by treatment with an acid under hydrolytic conditions, especially with a mineral acid, such as a hydrohalic acid, for example hydrochloric acid, which is used in dilute or concentrated aqueous form, or by treatment with an organic silyl halide, such as trimethylsilyl iodide or bromide, and, if necessary, by subsequent hydrolysis. The reaction is preferably carried out at elevated temperature, for example by maintaining the reaction mixture at reflux temperature, and, where appropriate, using an organic diluent in a closed vessel and/or under an inert gas atmosphere. Amino-protecting groups can be removed by known processes which are chosen in accordance with the type of amino- protecting group, for example by solvolytic or hydrogenolytic processes, for example hydrolysis in the presence of an acid or base, acidolysis, for example treatment with trifluoroacetic acid, treatment with hydrazine, or hydrogenolysis in the presence of a metallic hydrogenation catalyst, or by some other suitable process.

All protecting groups can be replaced by hydrogen in a single step. It is, however, preferred to remove first any optional protective groups and subsequently the group R.

The starting materials of formula II can be prepared by methods known perse, for example reacting compounds of the formulae III and IV

wherein R _g denotes α,α-di-lower alkoxy-lower alkyl such as 1 ,1-diethoxyethyl and Y _t represents reactive esterified hydroxy such as halogen, preferably in the presence of sodium hydride in tetrahydrofuran, removing the group R _g form the resulting compound of the formula V

for example, by reaction with a tri-lower alkylsilylhalide such as trimethylchlorosilane in dichloromethane/ethanol, reaction the resulting compound of the formula

with a compound of the formula VII

for example, in tetrahydrofuran and the presence of a tri-lower alkylsilylhalide such as trimethylchlorosilane and of a tri-lower alkylamine such as triethylamine, or first with a compound of the formula VIII

Y\

and subsequently, in the presence of Hϋnig's base in ethanol with a compound of the formula IX

and optionally removing an amino-protective group R _β , a hydroxy-protective group present in Rb, a carboxy-protective group Rd or a carboxy-protective group present in R„ or an amino-protective group R _β or optionally converting cyano R ₇ or cyano as a substituent of R _a into Carbamoyl and or carboxy. Compounds of the formula II are thus obtained, wherein X _a denotes a group of the formulae >N(H) or >N(R _β ) and X _b denotes a group of the formulae >P(=O)(OH) or >P(=O)(OR,).

Similarly, compounds of the formula II, wherein X _a denotes a group of the formulae >P(=O)- (OH) or >P(=O)(OR and Xt _> denotes a group of the formulae >N(H) or >N(R _β ), are obtained according to the following scheme:

(llla) (IVa) (Va) (Via)

(Villa) (IXa)

Resulting compounds of formula I can be converted in a manner known per se into other compounds of formula I.

For example, cyano R ₇ or cyano as a substituent of Ri into carbamoyl and/or carboxy, analogous as described hereinbefore.

Resulting salts can be converted into the free compounds in a manner known per se, for example by treatment with a base, such as an alkali metal hydroxide, a metal carbonate or metal hydrogen carbonate, or ammonia, or another of the salt-forming bases mentioned at the beginning, or with an acid, such as a mineral acid, for example with hydrochloric acid, or another of the salt-forming acids mentioned at the beginning.

Resulting salts can be converted into different salts in a manner known ger≤e; for example, acid addition salts can be converted by treatment with a suitable metal salt, such as a sodium, barium or silver salt, of another acid in a suitable solvent in which an inorganic salt being formed is insoluble and is thus excluded from the reaction equilibrium, and base salts can be converted by freeing the free acid and converting into a salt again.

The compounds of formula I, including their salts, may also be obtained in the form of hydrates or may include the solvent used for crystallization.

Owing to the close relationship between the novel compounds in free form and in the form of their salts, hereinbefore and hereinafter the free compounds and their salts a«"e also optionally to be understood as being the corresponding salts and free compounds, respectively, where appropriate and where the context so allows.

Resulting diastereomeric mixtures and mixtures of racemates can be separated in known manner into the pure diastereomers and racemates, respectively, on the basis of the physico-chemical differences between their constituents, for example by chromatography and/or fractional crystallization.

Resulting racemates can also be resolved into the optical antipodes by known methods, for example by recrystallization from an optically active solvent, with the aid of microorganisms or, by reaction of the resulting diastereomeric mixture or racemate with an optically active

auxiliary compound, for example according to the acidic, basic or functionally modifiable groups contained in compounds of formula I, with an optically active acid, base or an optically active alcohol, into mixtures of diastereomeric salts or functional derivatives, such as esters, separation of the same into the diastereomers from which the desired enantiomer can be freed in customary manner. Suitable bases, acids and alcohols for the puφose are, for example, optically active alkaloid bases, such as strychnine, cinchonine or brucine, or D- or L-(1-phenyl)ethylamine, 3-pipecoline, ephedrine, amphetamine and similar bases that can be obtained by synthesis, optically active carboxylic or sulfonic acids, such as quinic acid or D- or L-tartaric acid, D- or L-di-o-toluoyltartaric acid, D- or L-malic acid, D- or L- mandelic acid, or D- or L-camphorsulfonic acid, or optically active alcohols, such as bomeol or D- or L-(1-phenyl)ethanol.

The invention relates also to those forms of the process according to which a compound obtainable as intermediate at any stage of the process is used as starting material and the remaining steps are carried out, or a starting material is used in the form of a salt or, especially, is formed under the reaction conditions.

The invention relates also to the novel starting materials which have been specifically developed for the preparation of the compounds according to the invention, especially the group of starting materials that lead to the compounds of formula I mentioned at the beginning as being preferred, to the processes for their preparation and to their use as intermediates.

The process for the conversion of compounds of the formula I, wherein R ₆ denotes hydrogen into compounds of the formula I in which R ₆ denotes [ ³ H]- or [ ¹¹ C]-labeled alkyl, according to the invention is characterized in that a reactive ester such as a halide, preferably the iodide, of a [ ³ H]- or [ ¹¹ C]-labeled alkanoi, preferably C[ ³ H] ₃ I or [ ¹¹ C]H ₃ I, is, in dimethylsulfoxide and in the presence of an approximately 5- to approximately 10-fold, preferably approximately 7.5- to 8.5-fold, suφlus of a approximately 3- to approximately 5- molar-, preferably approximately 4- molar, aqueous solution of an alkalimetal hydroxide, preferably sodium hydroxide, at a temperature of approximately 60° to approximately 100° C, reacted for approximately 2 to approximately 10, preferably for approximately 5, minutes with an approximately 5- to approximately 20-fold, preferably approximately 10-fold surplus of compound of the formula I, wherein R ₆ denotes hydrogen, and that the reaction mixture

is subsequently neutralized by adding the required amount, for example, the approximately 5- to approximately 10-fold, preferably approximately 7.5- to 8.5-fold, molar amount of a approximately 3- to approximately 5-moiar, preferably approximately 4- molar aqueous solution of a mineral acid such as sulfuric acid or a hydrohalide acid, preferably hydrochloric acid, such as to obtain solution of the corresponding compound of the formula I, wherein R ₆ denotes [ ³ H]- or [ ¹¹ C]-labeled d-d alkyl, preferably C[ ³ H] ₃ or [ ¹¹ C]H ₃ .

The following Examples serve to illustrate the invention; temperatures are given in degrees Celsius and pressures in mbar.

Preparation Example 1 : 3-(1-(ffl-r3-f4-Hydroxybenzyhphosphinyl-2-(S^-hydroxy-propyl - aminolethylrbenzoic acid

To a solution of 1.02 g (2.5 mmol) of ethyl 3-Λ/-[1-( ?)-(3-cyanophenyl)-ethylamino]-2-(S)- hydroxypropyl-4-hydroxybenzylphosphinate in 4 ml of absolute ethanol is added 6.5 ml of 2 M sodium hydroxide and the solution refluxed for 24 hours. The clear solution is evaporated to dryness and the residue is dissolved in 30 ml of water and extracted twice with 10 ml of diethyl ether. The pH of the aqueous layer is adjusted to 1 with 3.3 ml of 4 M hydrochloric acid. This acidic aqueous layer is evaporated and the residue co-evaporated with water (3 x 10 ml) and isopropanol (5 ^χ 10 ml) to give a white solid which is extracted with 350 ml of hot isopropanol in a Soxhlet apparatus. The isopropanol extract is treated with 1 ml propylene oxide at room temperature, during 24 hours under stirring crystallization occurred. The crystals are filtered and the filtrate is concentrated to 200 ml and stirred 20 hours at room temperature. The solid is collected by filtration and dried to give 100 mg (10%) of the title compound as a white solid; melting point 169-172 °C; ¹ H NMR (300 MHz, CD ₃ OD) δ 8.14 (s, 1 H, H _AT ), 8.06 (d, J = 7 Hz, 1 H, HAT), 7.67 (d, J = 7 Hz, 1 H, H _AT ), 7.55 (appears as t, J = 7 Hz, 1 H, H _AT ), 7.11 (appears as d, J = 7 Hz, 2H, H _Ar ) 6.79 (d, J = 7 Hz, 2H, H _AT ), 4.32 (q, J = 7 Hz, 1 H, NCHCH ₃ ), 4.10-4.00 (m, 1 H, CHOH), 3.00-2.75 (m, 4H, N-CH ₂ and P-CH ₂ -Ph), 1.87-1.58 (m, 2H, P-CH ₂ ), 1.65 (d, J = 7 Hz, 3H, CH ₃ ) ppm; ³¹ P NMR (121 MHz, CD ₃ OD) δ 37.8 ppm; Anal. Calculated for Cι ₉ H ₂₄ NOβP,(1.10 H ₂ O): C, 55.24; H, 6.62; N, 3.39; P, 7.48. Found: C, 55.24; H, 6.40; N, 3.39; P, 7.5.

[α]g° = + 7.2° (c = 0.235 in Methanol).

The starting material may be obtained as follows:

ai Ethyl 4-Benzyloxybenzyl-1.1-diethoxyethylphosphinate

Sodium hydride,55% dispersion in oil (4.8 g, 110 mmol) is washed with dry pentane and suspended in 50 ml of dry tetrahydrofuran under argon. A solution of 22.8 g (100 mmol) of ethyl 1 ,1 -diethoxyethylphosphinate in 50 ml of dry tetrahydrofuran is added over the period of 0.5 hour maintaining the temperature between 20 and 25 °C by cooling in an ice bath. After the addition is complete the suspension is stirred for 2 hours at room temperature before the dropwise addition of a solution of 24 g (103 mmol) of p-benzyloxybenzylchloride in 50 ml of dry tetrahydrofuran. The reaction mixture is stirred for 48 hours at room temperature, 200 ml of water is then added and the reaction mixture is extracted twice with 200 ml dichloromethane. The organic layer is removed, dried over magnesium sulphate, filtered and the solvent evaporated to give an oil. Distillation in high vacuum afforded 33.8 g (83%) of the title compound as a colourless oil: boiling point 180-190 °C / 10 ^'1 mbar; ¹ H NMR (360 MHz, CDCI ₃ ) δ 7.45-7.20 (m, 7H, H _AT ), 6.92 (d, J = 7 Hz, 2H, H _Ar ), 5.05 (s, 2H, Ph- CH ₂ -O), 4.12-3.96 (m, 2H, ester CH ₂ ), 3.82-3.60 (m, 4H, acetal CH ₂ ), 3.17-3.03 (m, 2H, CH ₂ -P), 1.45 (d, J = 12 Hz, 3H, P-C-CH ₃ ), 1.24-1.14 (m, 9H, CH ₃ ) ppm.

bι Ethyl 4-Hydroxybenzyl-1.1 -diethoxyethylphosphinate

A solution of 20.0 g (49.2 mmol) of ethyl 4-benzyloxybenzyl-1 ,1 -diethoxyethylphosphinate in 250 ml of tetrahydrofuran containing 9.9 g (98 mmol) triethylamine and 4 g of 10% Pd/C is hydrogenated for 2.5 hours at room temperature and normal pressure. The catalyst is removed by filtration and the solvent evaporated in vacuo to give a oil which crystallized from a mixture of diethylether and pentane. Filtration afforded 14.58 g (93.7%) of the title compound; melting point 76-77 °C; ¹ H NMR (360 MHz, CDCI ₃ ) δ 8.13 (s, 1H, Ph-OH), 7.02 (dd, J = 2 and 7 Hz, 2H, H ), 6.57 (d, J = 7 Hz, 2H, H _AT ), 4.12-4.03 (m, 2H, ester CH ₂ ), 3.83- 3.63 (m, 4H, acetal CH ₂ ), 3.13 (dd, J = 11 and 15 Hz, 1 H, CH ₂ -P), 3.13 (t, J = 15 Hz, 1 H, CH ₂ -P), 1.52 (d, J = 12 Hz, 3H, P-C-CH ₃ ), 1.27-1.18 (m, 9H, CH ₃ ) ppm.

c) Ethyl 4-Hydroxybenzylphosphinate

A solution of 15.94 g (50.4 mmol) of ethyl 4-hydroxybenzyl-1 ,1 -diethoxyethylphosphinate in 220 ml of 10% ethanol in dichloromethane is treated with 8.3 g (75.6 mmol) of trimethyl¬ chlorosilane under argon. The clear solution is stirred at room temperature for 24 hours and

evaporated to dryness to give a oil. This is diluted with 200 ml dichloromethane and extracted with 200 ml of water. The aqueous layer is extracted twice with dichloromethane and the organic layer is removed, dried over magnesium sulfate, filtered and the solvent removed to give a oil. Crystallization in diethylether/dichloromethane gives 8.97 g (89%) of the title compound; melting point 82-83 °C; ¹ H NMR (360 MHz, CDCI ₃ ) δ 7.36 (s, 1 H, Ph- OH), 7.06 (appears as d, J = 543 Hz, 1 H, P-H), 7.02 (dd, J = 2 and 7 Hz, 2H, H _AT ), 6.67 (d, J = 7 Hz, 2H, H _AT ), 4.23-4.02 (m, 2H, ester CH ₂ ), 3.18-3.03 (m, 2H, CH ₂ -P), 1.34 (t, J = 7 Hz, 3H, CH ₃ ) ppm.

di Ethyl 3-Chloro-2-fff^- 0-tι1methylsilvπ-hydroxyDroDyl-4-hvdroxybenzylDhosDhinate A solution of 4.0 g (20 mmol) of ethyl 4-hydroxybenzylphosphinate in 60 ml of dry tetrahydrofuran under argon is treated with 6.5 g (65 mmol) of triethylamine at room temperature and a solution of 5.08 g (47 mmol) of trimethylchlorosilane in 10 ml of dry tetrahydrofuran by dropwise addition over 20 minutes. After 2 hours stirring at room temperature the resulting suspension is filtered under argon and the filtrate evaporated to dryness to give the P(lll) intermediate as a colourless oil. This is treated sequentially with 0.45 g (3.3 mmol) of anhydrous zinc chloride and 2.6 g (28 mmol) of at room temperature. A very exothermic reaction occurred, which is allowed to subside, before heating to 80 °C for 24 hours. After cooling to room temperature the reaction mixture is diluted with dichloromethane and extracted twice with 100 ml of water. The organic layer is dried over magnesium sulfate, filtered and the solvent removed to give in approximately quantitative yield a mixture (8.35 g) of ethyl 3-Chloro-2-(/7)-(0-trimethylsilyl)-hydroxypropyl- 4-benzyloxybenzylphosphinate and the bis-O _r O-trimethylsilylether. This mixture is used for the preparation of ethyl 3-Chloro-2-( )-hydroxypropyl-4-hydroxybenzylphosphinate without further purification because of the instability of the phenolic trimethylsilylether. Thick layer chromatography from a aliquot of this mixture using dichloromethane/petrolether/ethanol/methanol (50:40:8:3) as eluant gives the title compound as a 1 :1 mixture of diastereomers (Rf = 0.40); ¹ H NMR (300 MHz, CDCI ₃ ) δ 8.39 (broad s, 1H, Ph-OH), 7.08-7.00 (m, 2H, H _Ar ), 6.70-6.60 (m, 2H, H _AT ), 4.40-4.25 (m, 1 H, CH- OTMS), 4.12-3.90 (m, 2H, ester CH ₂ ), 3.60-3.50 (m, 2H, CH ₂ CI), 3.22-3.02 (m, 2H, Ph-CH ₂ - P), 2.16-2.02 (m, 2H, P-CH ₂ ), 1.33-1.22 (m, 3H, CH ₃ ), 0.21 (s, 9H, OTMS) ppm; ³¹ P NMR (121 MHz, CDCI ₃ ) δ 48.7 and 48.5 ppm.

e) Ethyl 3-Chloro-2-( 7l-hvdroxypropyl-4-hvdroxybenzylphosphinate (7c)

A solution of 7.65 g (=18 mmol) of the crude mixture of ethyl 3-Chloro-2-(r7)-(0-trimethyl- silyl)-hydroxypropyl-4-hydroxybenzylphosphinate and the corresponding bis-O.O- trimethylsilylether in 50 ml of methanol containing 2% acetic acid is stirred at room temperature for 24 hours and evaporated to dryness to give a oil. Chromatography on silica gel using dichloromethane/petrolether/ethanol/methanol (50:50:3:3) gives 2.34 g (44% calculated from ethyl 4-hydroxybenzyl-1 ,1 -diethoxyethylphosphinate) of the title compound as an oily 1 :1 mixture of diastereomers; ¹ H NMR (300 MHz, CDCI ₃ ) δ 7.90 (broad s, 1 H, Ph- OH), 7.12-7.02 (m, 2H, H^), 6.72-6.64 (m, 2H, H _AT ), 4.38-4.22 (m, 1 H, CH-OH), 4.15-3.94 (m, 2H, ester CH ₂ ), 3.57-3.49 (m, 2H, CH ₂ CI), 3.22-3.08 (m, 2H, Ph-CH ₂ -P), 2.08-1.93 (m, 2H, P-CH ₂ ), 1.33-1.24 (m, 3H, CH ₃ ) ppm; ³¹ P NMR (121 MHz, CDCI ₃ ) δ 51.2 and 50.1 ppm.

f) Ethyl 3-/V-[1 -(ff)-f3-Cyanophenyl)-ethylaminol-2- S)-hydroxypropyl-4-hydroxybenzyl- phosphinate

A mixture of 2.3 g (7.8 mmol) of ethyl 3-chloro-2-(r9)-hydroxypropyl-4-hydroxybenzyl- phosphinate (7c), 1.4 g (9.6 mmol) of 1-(fl)-t7>cyanophenyl-ethylamine, 1.06 g (8 mmol) of Hϋnig's base and 10 ml of ethanol is heated to reflux for 7 days. The mixture is then cooled to room temperature and the volatile material removed in vacuo. The reaction mixture is extracted with dichloromethane-water at different pH. The first dichloromethane extracts at pH between 1 and 4 which contained only few very impure title compound, are eliminated. The further dichloromethane extract (pH between 6 and 9) are combined, washed with water, dried over magnesium sulfate, filtered and the solvent removed to give a oil. Chromatography on silica gel using dichloromethane/petrolether/ethanol/methanol (10:10:1 :1 ) gives 2.4 g (50%) of the title compound as an oily 1 :1 mixture of diastereomers; ¹ H NMR (300 MHz, CDCI ₃ ) δ 7.62 (appears as s, 1 H, H _Ar ), 7.58-7.50 (m, 2H, H _AT ), 7.42 (appears as t, J = 7 Hz, H, H _Ar ), 7.03 (dd, J = 1.5 and 7 Hz, 2H, H _Ar ), 6.65 (d, J = 7 Hz, 2H, H _Ar ), 4.15-3.95 (m, 3H, CHOH and ester CH ₂ ), 3.86-3.69 (m, 2 NCHMe and NH), 3.14-3.06 (m, 2H, Ph-CH ₂ -P), 2.51 (dd, J - 8 and 12 Hz, 1 H, CH ₂ -N), 2.40 (dt, J = 3 and 12 and 12 Hz, 1 H, CH ₂ -N), 1.95-1.68 (m, 2H, P-CH ₂ ), 1.38-1.22 (m, 3H, CH ₃ ) ppm; ³ P NMR (121 MHz, CDCI ₃ ) δ 51.8 and 50.9 ppm.

The 1-(ft)-m-cyanophenyl-ethylamine used as starting material may be obtained as follows:

q\ 1 -(fln+W3-CvanoDhenvn-ethylamine

26 g (180 mmol) of 1-(3-cyanophenyl)ethylamine and 31 g (180 mmol) of N-acetyl-L-leucine are dissoved in 1.25 L of hot ethanol. On cooling, a solid precipitat4e4s which is recrystallized trice from ethanol. The 1-(S)-(-)-(3-cyanophenyl)ethyiamine thus obtained is discarded. The mother-liquors are combined, concentrated by evaporation under reduced pressure to 25 ml and triturated with a solution of 6.79 g (34.25 mmol) of (-)-camphanic acid in 155 ml of ethanol is treated The resulting salt is left to crystallize overnight at room temperature and collected by filtration. This is recrystallized twice from ethanol (100 ml and 60 ml respectively) to give 2.73 g (46%) of 1-(ff)-(+)-(t7vcyanophenyl)-ethylamine-(-)- camphanic salt; melting point 205-207 °C.

[α]g° = - 5.9° (c = 0.985 in H ₂ O).

Preparation Exam ^p le 2: 3-(1-ι^-r3-(4-Hydroxybenzvnphosphinyl-2-(5ϊ-hydroxy-propyl - amino1ethyl}benzoic acid

A solution of 202 mg (0.42 mmol) of 3-{1-( )-[3-(4-benzyloxyoxybenzyl)phosphinyl-2-(S)- hydroxy-propyl-amino]ethyl}benzoic acid in 20 ml of methanol containing 40 mg 10% Pd/C is hydrogenated for 3.5 hours at room temperature and normal pressure. The catalyst is removed by filtration and the solvent evaporated in vacuo to give a solid. Chromatography on silica gel using ethanol-methanol 1:1 gives 65 mg (39%) of the title compound as a white solid, with identical physical and spectroscopic properties.

The starting material may be obtained as follows:

a) Ethyl 4-Benzyloxybenzylphosphinate

A solution of 19.29 g (47.5 mmol) of ethyl 4-benzyloxybenzyl-1,1 -diethoxyethylphosphinate in 275 ml of 10% ethanol in dichloromethane is treated with 7.8 g (71.3 mmol) of trimethyl¬ chlorosilane under argon. The clear solution is stirred at room temperature for 24 hours and evaporated to dryness to give a oil. This is diluted with 200 ml dichloromethane and extracted with 200 ml of water. The aqueous layer is extracted twice with dichloromethane and the organic layer is removed, dried over magnesium sulfate, filtered and the solvent removed to give a oil. Crystallization in hexane gives 13.21 g (96%) of the title compound;

melting point 81 -82 °C; ¹ H NMR (360 MHz, CDCI ₃ ) δ 7.45-7.30 (m, 5H, H _AT ), 7.16 (dd, J = 2 and 7 Hz, 2H, H _Ar ), 7.02 (appears as d, J = 543 Hz, 1 H, P-H), 6.94 (d, J = 7 Hz, 2H, H _AT ), 5.06 (s, 2H, Ph-CH ₂ -O), 4.20-3.98 (m, 2H, ester CH ₂ ), 3.13 (d, J = 17 Hz, 2H, CH ₂ -P), 1.32 (t, J = 7 Hz, 3H, CH ₃ ) ppm.

Ethyl 3-Chloro-2-fffl-(0-trimethylsilvπ-hvdroχypropyl-4-benzylox ybenzylphosphinate A solution of 11.4 g (39.3 mmol) of ethyl 4-benzyloxybenzylphosphinate in 70 ml of dry tetrahydrofuran under argon is treated with 5.0 g (49 mmol) of triethylamine at room temperature and a solution of 4.9 g (45 mmol) of trimethylchlorosilane in 10 ml of dry tetrahydrofuran by dropwise addition over 20 minutes. After 2 hours stirring at room temperature the resulting suspension is filtered under argon and the filtrate evaporated to dryness to give the P(lll) intermediate as a colourless oil. This is treated sequentially with 0.79 g (5.7 mmol) of anhydrous zinc chloride and 4.8 g (61 mmol) of (fl)-epichlorohydrin at room temperature. A very exothermic reaction occurred, which is allowed to subside, before heating to 80 °C for 24 hours. After cooling to room temperature the reaction mixture is diluted with dichloromethane and extracted twice with 100 ml of water. The organic layer is dried over magnesium sulfate, filtered and the solvent removed to give the title compound in quantitative yield; ¹ H NMR (300 MHz, CDCI ₃ ) δ 7.46-7.28 (m, 5H, H _Ar ), 7.23-7.16 (m, 2H, H _Ar ), 6.97- 6.89 (d, J = 7 Hz, 2H, H _Ar ), 5.05 (s, 2H, Ph-CH ₂ -O), 4.40-4.20 (m, 1 H, CH- OTMS), 4.10-3.88 (m, 2H, ester CH ₂ ), 3.70-3.49 (m, 2H, CH ₂ CI), 3.16-3.06 (m, 2H, Ph-CH ₂ - P), 2.14-1.90 (m, 2H, P-CH ₂ ), 1.31-1.20 (m, 3H, CH ₃ ), 0.22 and 0.20 (s, 9H, OTMS) ppm; ³¹ P NMR (121 MHz, CDCI ₃ ) δ 47.8 and 46.9 ppm.

cl Ethyl 3-Chloro-2-(ffl-hvdroxypropyl-4-benzyloxybenzylphosphinate A solution of 17.9 g (39.3 mmol) of Ethyl 3-chloro-2-( )-(0-trimethylsilyl)-hydroxypropyl-4- benzyloxybenzylphosphinate in 100 ml of methanol containing 2% acetic acid is stirred at room temperature for 24 hours and evaporated to dryness to give 15.3 g (100%) of the title compound as a 1 :1 mixture of diastereomers; ¹ H NMR (300 MHz, CDCI ₃ ) δ 7.46-7.28 (m, 5H, H _AT ), 7.24-7.14 (m, 2H, H _Ar ), 6.99- 6.89 (d, J = 7 Hz, 2H, H _Ar ), 5.05 (s, 2H, Ph-CH ₂ -O), 4.45-3.95 (m, 3H, CHOH and ester CH ₂ ), 3.60-3.55 (m, 2H, CH ₂ CI), 3.25-3.10 (m, 2H, Ph- CH ₂ -P), 2.10-1.83 (m, 2H, P-CH ₂ ), 1.35-1.22 (m, 3H, CH ₃ ) ppm; ³¹ P NMR (121 MHz, CDCI ₃ ) δ 51.0 and 49.7 ppm.

d) Ethyl 3-ΛH 1 -fffl-(3-Cyanophenyl)ethylaminol-2-(S)-hydroxypropyll-(4-ben zyloxybenzyl)- phosphinate

A mixture of 8.8 g (23 mmol) of ethyl 3-chloro-2-( )-hydroxypropyl-4- benzyloxybenzylphosphinate, 4.0 g (27 mmol) of 1-(r7)-m-cyanophenyl-ethylamine, 3.2 g (25 mmol) of Hϋnig's base and 30 ml of ethanol is heated to reflux for 7 days. The mixture is then cooled to room temperature and the volatile material removed in vacuo. The residue is diluted with 100 ml dichloromethane and extracted with 100 ml of 1 M aqueous hydrochloric acid which permits to eliminated the non-reacted primary amine and the Hϋnig's base. The organic layer is washed with water, dried over magnesium sulfate, filtered and the solvent removed to give a oil. Chromatography on silica gel using dichloromethane-petrolether-ethanol-methanol 10:10:1 :1 gives 6.12 g (58%) of the title compound as an oily 1 :1 mixture of diastereomers; ¹ H NMR (200 MHz, CDCI ₃ ) δ 7.66-7.60 (m, 1 H, H _Ar ), 7.58-7.47 (m, 2H, H _Ar ), 7.47-7.27 (m, 6H, H _AT ), 7.23-7.11 (m, 2H, H _AT ), 6.96- 6.87 (m, 2H, H _AT ), 5.03 and 5.02 (s, 2H, Ph-CH ₂ -O), 4.40-3.65 (m, 7H, CHOH and ester CH ₂ and NCHMe and OCH ₃ ), 3.20-3.12 (m, 2H, Ph-CH ₂ -P), 2.58-2.42 (m, 1 H, CH ₂ -N), 2.34 (dd, J - 4 and 11.5 Hz, 1 H, CH ₂ -N), 1.90-1.55 (m, 2H, P-CH ₂ ), 1.38-1.18 (m, 3H, CH ₃ ) ppm; ³¹ P NMR (121 MHz, CDCI ₃ ) δ 51.3 and 50.3 ppm.

el 3-(1-(ffl-r3-f4-Benzyloxyoxybenzvnphosphinyl-2-fS)-hvdroxy-p ropyl-amino1ethyllbenzoic

_______

To a solution of 3.1 g (6.3 mmol) of ethyl 3-N{1-( )-(3-cyanophenyl)ethylamino]-2-(S)- hydroxypropyl}-(4-benzyloxybenzyl)-phosphinate in 7.5 ml of absolute ethanol is added 15 ml of 2 M sodium hydroxide and the solution refluxed for 24 hours. The clear solution is evaporated to dryness and the residue is dissolved in 200 ml of water and the pH is adjusted to 5 with 1M hydrochloric acid. After extraction with diethylether (2 x 50 ml) the organic layers is washed with water (2 x 50ml) and the pH of the combined aqueous layers is adjusted to 3 with 1 M hydrochloric acid. The resulting suspension is stirred at room temperature for 4 hours and the solid collected by filtration, dried in high vacuum to give 2.15 g (78%) of the title compound as a white solid; melting point 138-141 °C; ¹ H NMR (300 MHz, CD ₃ OD) δ 8.15 (s, 1 H, HAT), 8.07 (d, J = 7 Hz, 1 H, H _Ar ), 7.68 (d, J = 7 Hz, 1 H, H _Ar ), 7.56 (appears as t, J = 7 Hz, 1 H, H _Ar ), 7.43-7.17 (m, 7H, H _Ar ) 6.90 (d, J = 7 Hz, 2H, H _A r), 5.04 (s, 2H, Ph-CH ₂ -O), 4.32 (q, J = 7 Hz, 1 H, NCHCH ₃ ), 4.23-4.12 (m, 1 H, CHOH), 2.96- 2.76 (m, 4H, N-CH ₂ and P-CH ₂ -Ph), 1.88-1.58 (m, 2H, P-CH ₂ ), 1.63 (d, J = 7 Hz, 3H, CH ₃ )

ppm; ³¹ P NMR (121 MHz, CD ₃ OD) δ 36.7 ppm; Anal. Calculated for CaβH∞NOeP.O .01 H ₂ O): C, 62.25; H, 6.43; N, 2.79; P, 6.17. Found: C, 62.3; H, 6.2; N, 2.8; P, 5.9. [α]p° = -2.4° (c = 0.51 in Methanol).

Preparation Example 3: 4-ri-(/7,-(3-Benzylphosphinyl-2-(SVhvdroxy-propyl-amino)ethv n-3- hydroxy-benzamide

The title compound is prepared in a similar manner as described in Preparation Examples 1 and 2.

Preparation Example 4: 3-ri-ffπ-(3.4-Dichlorophenvπethylamino-2-f5)-hvdroxy-f4-hy droxy- benzvOphosphinic acid

The title compound is prepared in a similar manner as described in Preparation Examples 1 and 2.

Application Example 1 : 3-π-(flH3-(4-f ¹ C1Methoxybenzyhphosphinyl-2-(_fl-hydroxy-propyl- aminolethyDbenzoic acid (9a)

In a septum-equipped vial 5 mg (12.7 μmol) of 3-{1-(fl)-[3-(4-Hydroxybenzyl)phosphinyl-2- (S)-hydroxy-propyl-amino]ethyl}benzoic acid are dissolved in 250 μL dimethylsulfoxide. After the addition of 25 μL (100 μmol) of 4 M aqueous sodium hydroxide the mixture is stirred for 5 minutes at room temperature. 7 μL (1.12 μmol) of a 0.16 M solution of [11 Cjmethyl iodide, i.e. [ ¹¹ C]H ₃ I, in dimethylsulfoxide is added and the reaction mixture is heated to 80 °C for 5 minutes and cooled to room temperature. 25 μL of 4M aqueous hydrochloric acid are added and the solvent is removed by evaporation in vacuo. The resulting title compound is purified by HPLC (t _R = 9 min) using a Nucleosil-C18 column (5 μm, 12.5 x 0.8 cm) and water with sodium dihydrogenphosphate (50 mmol/L)/acetonitrile (90:10) as mobile phase with a flow rate of 4 ml/mn, UV detection, λ = 215 nm.

Application Example 2: 3-(1-(flH3-(4-f ³ HlyMethoxybenzv0phosphinyl-2-(5Vhydroxy-propyl- aminolethyllbenzoic acid (9a)

The title compound is prepared analogously as described in Application Example 2 utilizing [ ³ H] ₃ methyl iodide, i.e. C[ ³ H] ₃ I. It is purified by HPLC (t _R = 9 min) using a Nucleosil-C18

column (5 μm, 12.5 x 0.8 cm) and water with sodium dihydrogenphosphate (50 mmol/L)- /acetonitrile (90:10) as mobile phase with a flow rate of 4 ml/mn, UV detection, λ = 215 nm.

Application Example 3: 4-ri-f 7,-(3-BenzylPhosphinyl-2-(S ⁾ -hvdroxy-propyl-aminolethyll 3- f ³ H1ymethoxy-benzamide

The title compound is prepared in a similar manner as described in Preparation Examples 1 and 2.

Application Example 4: 4-r ( ^" r7H3-Benzylphosphinyl-2-(SVhvdroxy-propyl-amino)ethyll 3- r ¹¹ C1-methoxy-benzamide

The title compound is prepared in a similar manner as described in Preparation Examples 1 and 2.

Preparation Example 5: 3-f1 -fffl-(3.4-Dichlorophenvπethylamino-2-f_)-hvdroxy-(4-[ ³ H1fi- methoxybenzyl)phosphinic acid

The title compound is prepared in a similar manner as described in Preparation Examples 1 and 2.

Preparation Example 6: 3-ri-f 7>-f3.4-Dichlorophenvnethylamino-2-(_>,-hvdroxy-(4-r ¹¹ C1- methoxy benzyhphosphinic acid

The title compound is prepared in a similar manner as described in Preparation Examples 1 and 2.