DE3448606C2 - Diagnostic agents, processes for their production and their use - Google Patents

Abstract

A diagnostic agent for use in in-vivo NMR diagnostics is claimed which contains at least one physiologically compatible complex salt from the anion of a complex-forming acid and one or more central ions of an element of atomic numbers 21 to 29, 42, 44 or 58 to 70, wherein the complex-forming acid is linked to a biomolecule from the group of hormones such as insulin, prostaglandins, steriodhormones, amino sugars, peptides, proteins or lipids and optionally one or more physiologically acceptable cations of an inorganic and / or organic base or amino acid optionally with the additives customary in galenics, dissolved or suspended in an aqueous medium.

Description

The invention relates to that characterized in the claims Object.

Complexes or their salts have long been used in medicine, so e.g. B. as an aid to the administration of poorly soluble ions (z. B. iron) and as antidotes (calcium or zinc complexes are preferred) Detoxification in the event of accidental incorporation of heavy metals or their radioactive isotopes. It has now been found to be physiologically acceptable Complex salts from the anion of a complexing acid and one or several central ions of an element of atomic numbers 21 to 29, 42, 44 or 58 to 70 and optionally one or more physiologically harmless cations of an inorganic and / or organic base or Amino acid surprisingly excellent for the production of diagnostic Agents are suitable which are suitable for use in NMR diagnostics.

The element of the above-mentioned atomic number, which the or Forms central ions of the physiologically compatible complex salt for the intended use of the diagnostic according to the invention By means of course not being radioactive.

Is the agent according to the invention for use in NMR diagnostics determined (see European patent application 71 564), this must be the case Central ion of the complex salt to be paramagnetic. These are especially the divalent and trivalent ions of the elements of atomic numbers 21 to 29, 42, 44 and 58 to 70. Suitable ions are, for example, chromium (III) -, Manganese (II) -, iron (III) -, iron (II) -, cobalt (II) -, nickel (II) -, copper (II) -, Praseodymium (III), neodymium (III), samarium (III) and ytterbium (III) ions. Because of their very strong magnetic moment are particularly preferred Gadolinium (III) -, terbium (III) -, dysprosium (III) -, holmium (III) - and erbium (III) - Ion.  

Suitable complexing acids are those which are usually used for Complex formation of the above-mentioned central ions used. Suitable Complex-forming acids are, for example, those that are 3 to 6 Methylenephosphonic acid groups, methylene carbohydroxamic acid groups, Carboxyethylidene groups or especially carboxymethylene groups contain, one or two of which each form a complex supporting nitrogen atom are bound. Are only one or two at a time of the acidic groups bound to a nitrogen atom, the nitrogen is over an optionally substituted ethylene or over up to four, each with a complexing nitrogen or oxygen or Sulfur atom separated ethylene units to another nitrogen atom bound. Preferred complexing acids of this type are those of general formula I according to claim 2.

The complex-forming acids are linked as conjugates with biomolecules which are known to accumulate particularly in the organ or organ part to be examined. Such biomolecules are, for example, hormones such as insulin, prostaglandins, steroid hormones, aminosugars, peptides, proteins or lipids. Of particular note are conjugates with albumins such as human serum albumin; Antibodies, such as monoclonal antibodies specific for tumor-associated antigens or antimyosin. The diagnostic agents formed from this are suitable, for example, for use in tumor and infarct diagnostics. For liver examinations, for example, conjugates or inclusion compounds with liposomes are suitable, which are used, for example, as unilamellar or multilamellar phosphatidylcholine-cholesterol vesicles. The conjugate formation takes place either via a carboxyl group of the complex-forming acid or, in the case of the proteins or peptides, also via one

(CH ₂ ) _p -C ₆ H ₄ -W-

Group as defined in claim 2. At the Conjugation of the complexing acids with proteins, peptides or  Lipids sometimes have several acid residues on the macromolecular biomolecule be bound. In this case, any complex-forming acid residue can Carry central ion.

Suitable complex salts of the general formula I according to claim 2 are, for example, those of the general formula Ia

wherein X, V, R ₁ , R ₂ and R _{3 have} the meaning given in claim 2.

The following complex acids are among others suitable for the preparation of the complex salts of the general formula Ia:
the ethylenediaminetetraacetic acid, the ethylenediaminetetraacethydroxamic acid, the trans-1,2-cyclohexylenediaminetetraacetic acid, the DL-2,3-butylenediamine tetraacetic acid, the DL-1,2-butylenediamine tetraacetic acid, the DL-1,2-propylenediamine tetraacetic acid, the 1,2-diphenylethylenediamine the ethylenedinitrilotetrakis (methanephosphonic acid) and the N- (2-hydroxyethyl) - ethylenediamine triacetic acid.

Further suitable complex salts of the general formula I according to claim 2 are, for example, those of the general formula Ib

wherein X, V, Z, R ₁ and m have the meaning given in claim 2. If Z represents an oxygen atom or a sulfur atom, complex salts with m in the meaning of 1 or 2 are preferred.

The following are suitable for the preparation of the complex salt of the general formula Ib other following complex-forming acids: the diethylene triamine penta acetic acid, triethylene tetramine hexaacetic acid, tetraethylene pentamine heptaacetic acid, the 13,23-dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24- pentaazapentatriacontanedioic acid, the 3,9-bis (1-carboxyethyl) -3,6,9-triaza- undecanedioic acid, the diethylenetriaminepentakis (methylenephosphonic acid), the 1,10-diaza-4,7-dioxadecane-1.1.10.10-tetraacetic acid and the 1.10-diaza-4.7- dithiadecan-1.1.10.10-tetraacetic acid.

Other, complex-forming acids that are used to produce the complex salts of general formula I are, for example: the 1,2,3-tris- [bis- (carboxymethyl) amino -] - propane and the nitrilotris- (ethylene nitrilo) - hexaacetic acid.

If not all acidic hydrogen atoms of the complexing acid the central ion or the central ions are substituted, it is for the purpose It is advisable to increase the solubility of the complex salt, the remaining ones Hydrogen atoms through physiologically harmless cations of inorganic and / or to substitute organic bases or amino acids. Suitable, Inorganic cations are, for example, lithium ion, potassium ion or especially the sodium ion. Suitable cations of organic bases are below other those of primary, secondary or tertiary amines, such as Example ethanolamine, diethanolamine, morpholine, glucamine, N, N-dimethylglucamine or in particular N-methylglucamine. Suitable Cations of amino acids are, for example, those of lysine, arginine or Ornithins.

The complexing acids required for the agent according to the invention are known or can be prepared in a manner known per se.

For example, the production of 13,23-dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24-pentaazapentatriacontanedioic acid takes place in an improvement of that of RA Bulman et. al. in "Natural Sciences", 68, (1981), 483:
17.85 g (= 50 mmol) of 1,5-bis (2,6-dioxomorpholino) -3-azapentane-3-acetic acid are suspended in 400 ml of dry dimethylformamide and after the addition of 20.13 g (= 100 mmol) 11-Amino-undecanoic acid heated to 70 ° C for 6 hours. The clear solution is concentrated in vacuo. The yellow, oily residue is stirred with 500 ml of water at room temperature. An almost white, voluminous solid precipitates, which is suctioned off and washed several times with water. The product obtained is introduced into 200 ml of acetone for further purification and stirred at room temperature for 30 minutes. After suction and drying in vacuo at 50 ° C, 36.9 g (97% of theory) of a white powder with a melting point of 134-138 ° C.

The complexing acids are conjugated with biomolecules also by methods known per se, for example by reaction nucleophilic groups of the biomolecule - such as amino, hydroxy, Thio or imidazole groups with an activated derivative of the complexing Acid.

Examples of activated derivatives of the complexing acids are Acid chlorides, acid anhydrides, activated esters, nitrenes or isothiocyanates in Consider, conversely, it is also possible to use the activated biomolecule with the implement complexing acid.

Substituents of the structure -C ₆ H ₄ N ₂ ⁺ or C ₆ H ₄ NHCOCH ₂ halogen are also suitable for conjugation with proteins.

The preparation of the complex salts is also known in some cases or can be found in be done in a known manner by using the metal oxide or a metal salt (e.g. the nitrate, chloride or sulfate) of the element of Atomic numbers 21 to 29, 42, 44 or 58 to 70 in water and / or one lower alcohol (such as methanol, ethanol or isopropanol) dissolves or suspends  and with the solution or suspension of the equivalent amount of complexing acid added in water and / or a lower alcohol and stir, if necessary with heating or heating to boiling point, until the implementation is finished. If the complex salt formed in If the solvent used is insoluble, it is isolated by filtration. Is it soluble, it can, for example, by evaporating the solution to dryness be isolated by spray drying.

If acidic groups are still present in the complex salt obtained, it is often useful, the acidic complex salt by means of inorganic and / or organic bases or amino acids, the physiologically harmless Form cations, convert them into neutral complex salts and isolate them. In many cases this is inevitable because the dissociation of the Complex salt by shifting the pH value to neutral so far is suppressed that this makes the insulation more uniform in the first place Products or at least their cleaning is made possible.

The production is expediently carried out with the aid of organic bases or basic amino acids. However, neutralization can also be advantageous using inorganic bases (hydroxides, carbonates or bicarbonates) of Sodium, potassium or lithium.

For example, the acid salts can be used to prepare the neutral salts Complex salts in aqueous solution or suspension as much as desired Add base so that the neutral point is reached. The solution obtained can then concentrated to dryness in vacuo. It is often from Advantage, the neutral salts formed by adding water-miscible Solvents, such as lower alcohols (methanol, ethanol, Isopropanol etc.), lower ketones (acetone etc.), polar ethers (Tetrahydrofuran, dioxane, 1,2-dimethoxyethane etc.) precipitate and so easily isolating and easy to clean crystals. As special It has proven advantageous to have the desired base already during the Add complex formation of the reaction mixture and thereby one Process step to be saved.  

It is often the case that the acidic complex salts contain several free, acidic groups expedient to produce neutral mixed salts, both inorganic and also organic, physiologically harmless cations as counterions contain. This can be done, for example, by using the complexing acid in aqueous suspension or solution with the oxide or salt of the element providing the central ion and half of the elements Neutralization required amount of an organic base, the formed Complex salt isolated, purified if necessary and then to complete Neutralization with the required amount of inorganic base. The The order of adding the base can also be reversed.

The diagnostic agents according to the invention are also produced in a manner known per se, by optionally using the complex salts under Addition of the additives commonly used in galenics suspended in an aqueous medium or dissolves and then sterilizes the solution or suspension. Suitable Additives are, for example, physiologically harmless buffers (such as Example tromethamine hydrochloride), small additions of complexing agents (such as diethylenetriamine-pentaacetic acid) or, if necessary, electrolytes (such as sodium chloride).

In principle, it is also possible to use the diagnostic agents according to the invention can also be produced without isolating the complex salts. In any case, must special care must be taken to avoid chelation make the salts and salt solutions of the invention practical are free of non-complexed, toxic metal ions. This can for example with the help of color indicators such as xylenol orange Control titrations can be guaranteed during the manufacturing process. The invention therefore also relates to processes for producing the Complex compound and its salts. The final security is cleaning of the isolated complex salt.

Are suspensions for oral administration or other purposes Complex salts in water or physiological saline are desired sparingly soluble complex salt with one or more commonly used in galenics  Excipients and / or surfactants and / or flavorings for Flavor correction mixed.

The diagnostic agents according to the invention preferably contain 1 μmol to 1 mole per liter of the complex salt and are usually in amounts of Dosed 0.001 to 5 mmol / kg. They are for oral and parenteral in particular Application determined.

The agents according to the invention meet the diverse requirements for Suitability as a contrast medium for magnetic resonance imaging. They're like that excellently suited for after oral or parenteral application Increasing the signal intensity that obtained with the help of an MRI scanner Enhance image in its meaningfulness. They also show the high Efficacy that is necessary to the body with the smallest possible amounts of foreign substances and the good tolerance that is necessary to maintain the non-invasive nature of the investigation (which in "J. Comput. Tomography", 5, 6: 543-46 (1981), in "Radiology", 144, 343 (1982) and in "Brevet Special de Medicament", No. 484 M (1960) For example, compounds are too toxic). The good water solubility of the agents according to the invention make it possible to produce highly concentrated solutions, thus keeping the volume load of the circuit within reasonable limits and balance the dilution with the body fluid, d. H. NMR diagnostics must be 100 to 1000 times more water-soluble than for NMR spectroscopy. Furthermore, the agents according to the invention do not have only high stability in vitro, but also surprisingly high stability in vivo so that a release or exchange of the in the complexes non-covalently bound, poisonous ions within the 24 hours, in which - as pharmacological studies have shown - the new ones Contrast agents are completely excreted again, only extremely slowly he follows. The conjugates used, for example, for tumor diagnosis Proteins and antibodies already have such a low dose surprisingly high signal amplification, that here solutions accordingly low concentration can be applied.  

Particularly low doses (below 1 mg / kg) and therefore lower concentrated solutions (1 µmol / l to 5 mmol / l) as specified in EP 71564, are used for organ-specific NMR diagnostics such. B. for the detection of Tumors and heart attacks.

The following exemplary embodiments serve to explain the Invention.  

example 1

Preparation of the disodium salt of the gadolinium III complex of 13,23-dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24-pentaazapentatriacontane diacid,

C ₃₆ H ₆₀ GdN ₅ O ₁₂ .2Na

15.2 g (= 20 mmol) 13,23-dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24- pentaazapentatriacontanediacid are suspended in 400 ml of water and opened 95 ° C warmed. 7.43 g (= 20 mmol) of gadolinium III chloride hexahydrate, dissolved in 60 ml of water are slowly added dropwise. It'll be 2 hours at this Temperature maintained and then to neutralize the resulting Hydrochloric acid mixed with 60 ml of 1 n sodium hydroxide solution.

After the reaction is complete (test with xylenol orange), the resultant Precipitate filtered and washed with water until free of chloride. 17.60 g are obtained (96% of theory) of a water-soluble, white powder of melting point 290-292 ° C.

Gadolinium III complex of 13,23-dioxo-15,18,21-tris (carboxymethyl) - 12,15,18,21,24-pentaazapentatriacontanedioic acid.

analysis

(Calculated):
C 47.30; H 6.84; N 7.66; Gd 17.20;
(Found):
C 47.131; H 6.83; N 7.60; Gd 17.06.

14.6 g (= 16 mmol) of the gadolinium III complex thus obtained are in Suspend 200 ml of water and dropwise with 31.4 ml of 1N sodium hydroxide solution transferred. After 1 hour, a clear solution is obtained, which is filtered and is then concentrated in vacuo. After drying in a vacuum at 80 ° C 13.2 g (87% of theory) of a readily water-soluble white powder are obtained melting point 279-285 ° C.  

analysis

(Calculated):
C 45.13; H 6.31; N 7.31; Gd 16.41; Na 4.80;
(Found):
C 45.20; H 6.12; N 7.28; Gd 16.26; Na 4.75.

In the same way, the di-N-methylglucamine salt of the gadolinium III complex of 13,23-dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24 is used with N-methylglucamine instead of sodium hydroxide solution -pentaazapentatriacontan-diacid, C ₅₀ H ₉₆ GdN ₇ O ₂₂ obtained.

Example 2 Preparation of a solution of the di-sodium salt of the gadolinium III complex the 13,23-dioxo-15,18,21-tris- (carboxymethyl) -12,15,18,21,24- pentaazapentatriacontane diacid

392.0 g (= 400 mmol) of the salt described in Example 1 are in 500 ml Water p. i. slurried and by filling with water p. i. to 1000 ml below light warming solved. The solution is bottled and heat sterilized.

Example 3 Preparation of a solution of the di-N-methylglucamine salt of gadolinium III Complex of 13,23-dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24- pentaazapentatriacontane diacid

130.4 g (= 100 mmol) of the salt listed in Example 1 are in 250 ml Water p. i. slurried and loosened with warming. You fill with water p. i. to 500 ml, fill the solution into ampoules and heat sterilize.

Example 4 Preparation of a solution of the gadolinium III complex from the conjugate of Diethylenetriamine-pentaacetic acid with human serum albumin

To 20 ml of a solution of 3 mg of the protein in 0.05 molar Sodium bicarbonate buffer (pH 7-8) 10 mg 1,5-bis (2,6-dioxomorpholino) -3- azapentane-3-acetic acid added. The mixture is left at room temperature for 30 minutes stir and then dialyze against a 0.3 molar sodium phosphate buffer. Then add 50 mg of gadolinium III acetate and cleanse through Gel chromatography on a Sephadex G25 column. The fraction obtained is sterile filtered and filled into multivials. Freeze drying turns a preservable dry preparation received.

In an analogous manner, the corresponding solution is obtained with immunoglobulin the complex conjugates.

Example 5 Preparation of a solution of the gadolinium III complex from the conjugate of Diethylenetriamine-pentaacetic acid (DTPA) with monoclonal antibody

To 20 µl of a solution of 0.3 mg monoclonal antibody in 0.05 molar Sodium bicarbonate buffer (pH 7-8) 1 mg of a mixed DTPA Anhydrides (obtained, for example, from DTPA and isobutyl chloroformate) and Stirred for 30 minutes at room temperature. Dialyze against 0.3 molar Sodium phosphate buffer and add 2 mg to the antibody fraction obtained of the gadolinium III complex of ethylenediamine tetraacetic acid (EDTA). To Purification by gel chromatography on Sephadex G25 is the sterile filtered Solution filled in multivials and freeze-dried.

Using the mixed anhydride of trans-1,2-diaminocyclohexane tetraacetic acid (CDTA) is obtained in a similar way a solution of corresponding Gadolinium III complex news of the CDTA antibody.

Using the manganese-II complex of ethylenediamine tetraacetic acid is obtained analogously to the manganese-II complexes with DTPA or CDTA coupled antibody.  

Example 6 Preparation of a solution of the gadolinium III complex from the conjugate of the 1- Phenyl-ethylenediamine-tetraacetic acid with immunoglobulin

According to the one described in "J. Med. Chem.", 1974, Vol. 17, p. 1307 Procedure is a 2% solution of the protein in a 0.12 molar Sodium bicarbonate solution containing 0.01 mol ethylenediamine tetraacetic acid, cooled to + 4 ° C and fresh with the proportion equivalent to the protein prepared, ice-cold diazonium salt solution of 1- (p-aminophenyl) - ethylenediamine-tetraacetic acid added dropwise. You let go overnight Stir + 4 ° C (pH 8.1) and then dialyze against a 0.1 molar Sodium citrate solution. After dialysis is complete, the solution of the conjugate with an excess of gadolinium III chloride and removed ultrafiltered by ions. Finally, the sterile-filtered solution in multivials bottled and freeze-dried.

Example 7 Preparation of a colloidal dispersion of an Mn-CDTA-lipid conjugate

0.1 mmol distearoylphosphatidylethanolamine and 0.1 mmol bisanhydride der Trans-1,2-diaminocyclohexanetetraacetic acid are dissolved in 50 ml of water Stirred for 24 hours at room temperature. 0.1 mmol of manganese II carbonate are added and stir again at room temperature for 6 hours. After cleaning over a Sephadex G50 column, the sterile-filtered solution is filled into multivials and freeze-dried.

Analogously, a colloidal dispersion of the Gadolinium-DTPA-lipid conjugate obtained.  

Example 8 Preparation of gadolinium-DTPA-loaded liposomes

Following the procedure described in "Proc. Natl. Acad. Sci.", U.S.A. 75, 4194 The procedure is a lipid mixture of 75 mol% egg phosphatidylcholine and 25 mol% cholesterol as a dry substance. Of this 500 mg dissolved in 30 ml diethyl ether and added dropwise in an ultrasonic bath 3 ml of a 0.1 molar solution of the di-N-methylglucamine salt of gadolinium III complex of diethylenetriamine-pentaacetic acid in water p. i. transferred. After the solution has been added completely, the ultrasonication is still set 10 minutes away and then concentrated in the Rotavapor. The gel-like residue is in 0.125 molar sodium chloride solution suspended and repeated at 0 ° C Centrifuge (20,000 g / 20 minutes) non-encapsulated contrast media shares exempt. Finally, the liposomes thus obtained are multivial freeze-dried. The application takes place as a colloidal dispersion in 0.9 weight percent saline.

Claims (14)

1. Diagnostic agent for use in in-vivo NMR diagnostics, containing at least one physiologically compatible complex salt from the Anion of a complexing acid and one or more Central ion (s) of an element of atomic numbers 21 to 29, 42, 44 or 58 to 70, the complexing acid with a biomolecule from the Group of hormones is linked and possibly one or more physiologically acceptable cation (s) of an inorganic and / or organic base or amino acid optionally with those in galenics usual additives, dissolved or suspended in an aqueous medium. 2. Diagnostic agent according to claim 1, containing at least one physiologically compatible complex salt of the general formula I.
wherein
X represents the radicals -COOY, -PO ₃ HY or -CONHOY with Y in the meaning of a hydrogen atom, a metal ion equivalent and / or a physiologically acceptable cation of an inorganic or organic base or amino acid and in which R _{1 represents} hydrogen atoms or methyl groups and

• a) A the group
  represents what
  X has the meaning given above,
  R ₂ and R ₃ together represent a trimethylene group or a tetramethylene group or hydrogen atoms, lower alkyl groups, phenyl groups, benzyl groups,
  m represents the numbers 1, 2 or 3,
  Z is an oxygen atom or a sulfur atom or the group
  NCH ₂ X or NCH ₂ CH ₂ OR ₄
  with X in the meaning given above and R ₄ in the meaning of a lower alkyl group and wherein
  V has the same meaning as X, or the groups
  -CH ₂ OH or -COB
  with B in the meaning of a protein or lipid residue or an -NH (CH ₂ ) _n X residue, with X in the meaning given above and n in the meaning of the numbers 1 to 12, with the provisos that at least one group - COB is present in the molecule and that at least two of the substituents Y are metal ion equivalents of an element of atomic numbers 21 to 29, 42, 44 or 58 to 70 or
• b) A represents the group -CHR ₂ -CHR ₃ -, wherein
  R _{2 is} a hydrogen atom and R _{3 is} a group
  - (CH ₂ ) _p -C ₆ H ₄ -W protein
  mean with p in the meaning of 0 or 1, W in the meaning of - NN-,
  -NHCOCH ₂ - or -NHCS and protein in the meaning of a protein residue and
  V has the same meaning as X, or the group
  -CH ₂ OH
  means, with the proviso that at least two of the substituents Y are metal ion equivalents of an element of atomic numbers 21 to 29, 42, 44 or 58 to 70.

3. Diagnostic agent according to claim 1 and 2, characterized by contains di-N-methylglucamine salt of the gadolinium (III) complex 13,23-dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24-pentaazapenta triacontanedioic acid. 4. Diagnostic agent according to claim 1 and 2, characterized by contains a gadolinium (III) complex of the conjugate of Diethylenetriamine-pentaacetic acid with immunoglobulin. 5. Diagnostic agent according to claim 1 and 2, characterized by contains a gadolinium (III) complex of the conjugate of Diethylenetriamine-pentaacetic acid with human serum albumin. 6. Diagnostic agent according to claim 1 and 2, characterized by contains the conjugate with the gadolinium (III) complex of Diethylenetriamine-pentaacetic acid with monoclonal antibody. 7. Diagnostic agent according to claim 1 and 2, characterized by contains a manganese (II) complex of the conjugate of trans-1,2- Cyclohexylenediamine tetraacetic acid with monoclonal antibody. 8. Diagnostic agent according to claim 1 and 2, characterized by contains a manganese (II) complex of the lipid conjugate of trans-1,2- Cyclohexylenediamine tetraacetic acid. 9. Diagnostic agent according to claim 1 and 2, characterized by a content of with the gadolinium (III) complex of diethylenetriaminepentaacetic acid  loaded liposomes. 10. Diagnostic agent according to claim 1 and 2, characterized by contains a di-sodium salt of the gadolinium (III) complex of 13.23- Dioxo-15,18,21-tris (carboxymethyl) -12,15,18,21,24-pentaazapenta triacontanedioic acid. 11. Diagnostic agent according to claim 1 and 10, characterized characterized that it contains 1 µmol to 5 mmol complex salt per liter. 12. A method for producing the diagnostic agent according to claim 1 to 11, characterized in that one in water or physiological salt solution dissolved or suspended complex salt with the in galenicals, additives in one for intravascular or oral Application brings appropriate form. 13. Use of the complex salts of the general formula I
wherein X, A, V and R _{1 have} the meaning given in claims 2 and 3, with the proviso that at least two Y represent a metal ion equivalent of an element of atomic numbers 21 to 29, 42, 44 or 58 to 70, the remaining ones, if any Y represent hydrogen atoms and / or cations of an inorganic or organic base or amino acid, in NMR diagnostic agents. 14. Diagnostic agent according to claim 1, characterized in that as Biomolecule insulin, prostaglandins, steroid hormones, amino sugar, peptides, Proteins and lipids serve.