Aminocarboxylic acids and derivatives thereof

Abstract: There are provided chelating agents particularly useful for the preparation of diagnostic and therapeutic agents for magnetic resonance imaging, scintigraphy, ultrasound imaging, radiotherapy and heavy metal detoxification, said agents being compound of formula (wherein each X may independently represent a carboxyl group or a derivative thereof or a group R₁; each group R₁ may independently represent a hydrogen atom, a hydroxylalkyl group, an optionally mono- or polyhydroxylated alkoxy or alkoxyalkyl group; n, m, q, r are each 2, 3 or 4, with the provisos that at least two nitrogens carry a -CHR₁X moiety, wherein X is a carboxyl group or a derivative thereof, that each -CHR₁X moiety represents other than a methyl group, that at least one -R₁ group represents other than hydrogen and that where all but one -CHR₁X groups are -CH₂COOH, then the remaining -CHR₁X group may not represent a hydroxyethyl, 2-hydroxypropyl or 2,3-dihydroxypropyl group) or a salt or metal chelate thereof.

Description: The present invention relates to certain chelating agents, in particular aminopoly(carboxylic acid or carboxylic acid derivative) compounds, and to the metal chelates thereof. The medical use of chelating agents is well established, for example as stabilizers for pharmaceutical preparations, as antidotes for poisonous heavy metal species and as diagnostic agents for the administration of metal species (e.g. ions or atoms) for diagnostic techniques such as X-ray, magnetic resonance imaging (MRI) or ultrasound imaging or scintigraphy. Aminopoly(carboxylic acid or carboxylic acid derivative) (hereinafter APCA) chelating agents and their metal chelates are well known and are described for example in US-A-2407645(Bersworth), US-A-2387735 (Bersworth), EP-A-71564 (Schering), EP-A-130934 (Schering), EP-A-165728 (Nycomed AS), DE-A-2918842 (Rexolin Chemicals AB) and DE-A-3401052 (Schering). Thus, for example, EP-A-71564 describes paramagnetic metal chelates, for which the chelating agent is nitrilotriacetic acid (NTA), N,N,N',N'-ethylenediaminetetraacetic acid (EDTA), N-hydroxyethyl-N,N',N'-ethylenediamine-triacetic acid (HEDTA), N,N,N',N'',N''-diethylenetriamine-pentaacetic acid (DTPA) and N-hydroxyethylimino-diacetic acid, as being suitable as contrast agents for MRI, contrast being achieved by the effect of the magnetic field of the paramagnetic species (e.g. Gd(III)) with the chelating agents serving to reduce the toxicity and to assist administration of that paramagnetic species. Amongst the particular metal chelates disclosed by EP-A-71564 was Gd DTPA, the use of which as an MRI contrast agent has recently received much attention. The Gd(III) chelate of 1,4,7,10-tetraazacyclododecane-tetraacetic acid (DOTA), referred to in DE-A-3401052 (Schering) and in US-A-4639365 (University of Texas), has also recently received attention in this regard. To improve stability, water solubility and selectivity, relative to the APCA chelating agents described in EP-A-71564, Schering, in EP-A-130934, have proposed the partial substitution for the N-attached carboxyalkyl groups of alkyl, alkoxyalkyl, alkoxycarbonylalkyl or alkylaminocarbonylalkyl groups, where any amide nitrogens may themselves carry polyhydroxyalkyl groups. However, all hitherto known APCA chelating agents and their metal chelates encounter problems of toxicity, stability or selectivity and there is thus a general and continuing need for APCA chelating agents which form metal chelates of reduced toxicity or improved stability. We now propose certain new improved toxicity APCAs, and in particular APCAs which carry hydrophilic groups on the amine nitrogens. Viewed from one aspect, the present invention thus provides APCA chelating agents of formula I (wherein each X may independently represent a carboxyl group or a derivative thereof or a group R₁; each group R₁ may independently represent a hydrogen atom, a hydroxylalkyl group, an optionally mono- or poly-hydroxylated alkoxy or alkoxyalkyl group; n, m, q, r are each 2, 3 or 4, with the provisos that at least two nitrogens carry a -CHR₁X moiety, wherein X is a carboxyl group or a derivative thereof, that each -CHR₁X moiety represents other than a methyl group, that at least one -R₁ group represents other than hydrogen and that where all but one -CHR₁X groups are -CH₂COOH, then the remaining -CHR₁X group may not represent a hydroxyalkyl group) or a salt or metal chelate thereof. Viewed from another aspect, the present invention provides compounds of formula I wherein n, m, q and r each have the value 2, or a salt or metal chelate thereof. Particularly preferred compounds of formula I include those of formula (wherein R₁ represents a hydrogen atom, a hydroxyalkyl group, or an optionally mono- or poly-hydroxylated alkoxy or alkoxyalkyl group) or a salt or metal chelate thereof. In the compounds of formula I, each hydrophilic R₁ group, which may be straight-chained or branched, preferably has a carbon atom content of from 1 to 8, especially preferably 1 to 6, carbon atoms. The R₁ groups may be alkoxy, polyalkoxy, polyhydroxy-alkoxy, hydroxyalkoxyalkyl or hydroxypolyalkoxyalkyl groups, but more preferably they will be monohydroxyalkyl or polyhydroxyalkyl groups. The hydrophilic R₁ groups serve to increase the hydrophilicity and reduce the lipophilicity of the metal chelates formed with the chelating agents of the invention and it is preferred that the compounds of formula I should contain at least 1, conveniently from 1 to 12, and preferably 2 to 8 hydrophilic R₁ groups and that in total the hydrophilic R₁ groups should contain about 6 or more hydroxy or ether oxygen atoms. As hydrophilic R₁ groups, the compounds of the invention may thus include for example hydroxymethyl, 2-hydroxyethyl, 1,2-dihydroxyethyl, 3-hydroxypropyl, 2,3-dihydroxypropyl, 2,3,4-trihydroxybutyl, 1-(hydroxymethyl)-2-hydroxy-ethyl, methoxymethyl, ethoxymethyl, 2-hydroxyethoxymethyl, methoxyethoxymethyl, (2-hydroxy-ethoxy)ethyl, etc, groups. The carboxyl derivatives which may be represented by the groups X in the compounds of formula I, may include, for example, amide groups, ester groups and carboxylate salt groups, for example groups of formulae -CONR₂R₃ (wherein R₂ is a hydrogen atom or an optionally hydroxylated alkyl, for example C₁₋₆ alkyl, group and R₃ is a hydrogen atom, a hydroxyl group or an optionally hydroxylated alkyl group), -COOR₄ (wherein R₄ is an optionally hydroxylated alkyl group), and -COOM (wherein M⁺ is a monovalent cation or a fraction of a polyvalent cation, for example an ammonium or substituted ammonium ion or a metal ion, for example an alkali metal or alkaline earth metal ion). Particularly preferably, M⁺ is a cation deriving from an organic base, for example meglumine. It is also particularly preferred that the number of the ion-forming groups X in the compounds of formula I be chosen to equal the valency of the metal species to be chelated by the compound formula I. Thus, for example, where Gd(III) is to be chelated, the chelating agent of formula I preferably contains three ion-forming X groups, for example -COOH or -COOM. In this way, the metal chelate will be formed as a neutral species, a form preferred since the osmotic pressures in concentrated solutions of such compounds are low and since their toxicities relative to their ionic analogues are significantly reduced. Compounds of formula I in which all the carboxyl or carboxyl derivative X groups are -COOH or -COOM groups are especially preferred since compositions containing such metal chelates can readily be sterilized, for example by autoclaving. Included amongst the particularly preferred chelating agents of formula I are the compounds: 1-(5-hydroxy-3-oxapentyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid; 1-(8-hydroxy-3,6-dioxaoctyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid; or a salt or metal chelate thereof. Viewed from a further aspect, the invention provides a process for the preparation of the compounds of formula I, said process comprising one or more of the following steps: (i) reacting a corresponding amine to introduce a -CHR₁X moiety at an amine nitrogen; (ii) converting a carboxyl X moiety in a compound of formula I into a carboxyl derivative thereof or a carboxyl derivative X moiety in a compound of formula I into a carboxyl group; and (iii) converting a compound of formula I into a salt or metal chelate thereof or converting a salt or chelate of a compound of formula I into a compound of formula I. Process step (i) may conveniently be performed by reacting a compound essentially of formula I but having at least one hydrogen atom in place of a -CHR₁X moiety and optionally having in place of X and/or R₁ moieties groups convertible thereto (for example groups convertible by the removal of protecting groups), with a compound of formula III R₂ CHR₁'X' (wherein R₂ is a leaving group, for example a nucleophilically displaceable group such as a halogen atom, preferably a bromine atom; and R₁' and X', which are not both hydrogen atoms, are as defined for R₁ and X or are groups convertible thereto, for example by deprotection). As protecting groups, conventional protecting groups may be used, for example groups such as are described by T.W. Greene in "Protective Groups in Organic Synthesis", John Wiley & Sons, 1981. For the protection of hydroxyl groups, particular mention may be made however of the utility of benzyl protecting groups which are stable over a wide pH range but are readily removed by hydrogenolysis as described by T.W. Greene. Polyhydroxyalkyl groups may for example alternatively be protected in the form of cyclic polyether groups, for example as 2,2-dimethyl-1,3-dioxa-cyclopent-4-yl groups, as such cyclic polyether groups can be opened by acid hydrolysis to leave the unprotected polyhydroxyalkyl group. Thus for example, introduction of a -CHR₁X moiety may be effected by reacting an amine of formula II (wherein R₃ is a hydrogen atom or a -CHR₁'X' group; X' and R₁' are as hereinbefore defined for X and R₁ or are groups convertible thereto; n, m, q, and r are as hereinbefore defined; with the provisos that at least one R₃ moiety is a hydrogen atom, that at least two amine nitrogens carry a hydrogen atom or a -CHR₁'X' moiety in which X' is convertible to a carboxyl group or a derivative thereof, and that each -CHR₁'X' moiety is other than a methyl group) with a compound of formula III (as defined above), followed if necessary by converting R₁' or X' to R₁ or X. The process of step (i) is particularly preferably effected by reacting a compound of formula II (in which any hydroxyl moieties are protected) with bromoacetic acid or a derivative thereof, for example the sodium salt or an ester, followed by deprotection of the hydroxyl moieties. To introduce -CHR₁X groups wherein R₁ is hydroxy or hydroxyalkyl, alternative compounds of formula III, such as 3-bromo-oxacyclopentan-2-one, Hal.CH₂CH₂OH, Hal CH₂CHOHCH₂OH or R₅-O-CH₂-CHHal-COOH (wherein Hal is a halogen atom such as a bromine atom and R₅ is a protecting group) may of course be used. Thus for the process of step (i) the following preferred starting compounds of II may be used: (wherein each R₁'' is a protected hydroxyalkyl group, for example a -CH₂-O-CH₂-Phenyl group or a 2,2-dimethyl-1,3-dioxa-cyclopent-4-yl group, A₁ is a group -N-CHR₁'X' (for example a -N-CH₂COOH group) and R₆ is a group -CHR₁'X' or a moiety convertible thereto). In the starting compounds of formulae IIi and IIj, protected hydroxyalkyl groups attached to the alkylene chains between amine nitrogens are preferably benzyl protected groups and the nitrogen-attached protected hydroxyalkyl groups in -CHR₁'X' moieties are preferably in the form of cyclic polyethers. The preparation of starting compounds of formulae IIi and IIj, which compounds themselves form further aspects of the present invention, may for example be by the following procedures: The cyclic compounds of formula IIi may be prepared by peptide condensation followed by reduction of the amide carbonyl groups, substantially as described by J. Tabushi et al. in Tetr. Lett. (1976) 4339 and (1977) 1049. The reaction may be performed according to the following scheme: The starting compound (1) is described by A. Bongini et al. in J. Chem. Soc., Perkin Trans. 1, (1985) 935. It can be converted by benzyl protection of the remaining alcohol group and by ammonolysis to compound (2) and then condensation of compounds (1) and (2) and subsequent acid hydrolysis can yield compound (4) The starting compound (24), wherein A₁ is an amine group, may be prepared by alkylation of an iminodiacetic acid derivative and the ether and thioether starting compounds may be prepared analogously by formylation of the corresponding starting materials, for example as described by W. Rasshofer et al. in Chem. Ber. 112 (1979) 2095. Compounds of formula IIi are particularly preferred starting materials as they may be used to form non-ionic or mono-ionic chelates with trivalent metal ions according to the selection of A₁. The cyclic compounds of formula IIj may be prepared by the well known routes for the preparation of cyclic polyamines. Thus, in a method analogous to that described by J.E. Richmann et al. in J. Am. Chem. Soc. 96 (1974) 2268, compound (4) may be tosylated and the resultant product may then be cyclized with a di(protected hydroxyalkyl) amine, which may itself be prepared from compound (18). Compounds of formula (17) may be produced by mono-protection of aminopropandiol at the primary hydroxyl group and may be mono or di-alkylated using a glycidol ether. The mono and di-alkylation products may be separated by distillation. Thus the compounds of formula IIj may for example be prepared by the following scheme: Compound (27) may be prepared from compound (18) by a method analogous to that described by M. Hediger et al. in J. Chem. Soc, Chem Commun (1978) 14 and by J. Pless et .al. in Chem. Abs 71 (1969) 49569x. Various detosylation methods for step (p) are known, as described for example by W. Rasshofer et al. in Liebigs Ann Chem. (1977) 1344. The group R₆ may be a protecting group resistant to the detosylation conditions allowing the possibility of substituting the nitrogen to which it is attached with a carboxymethyl derivative, etc. Reaction of starting compounds of formula IIi and IIj with sodium bromoacetate and subsequent deprotection of the protected groups by acid hydrolysis or by hydrogenolysis will yield corresponding compounds of formulae I I and IJ: Further compounds of formula I may be prepared in a similar fashion by the process of step (i). Thus for example a compound of formula IP (where R''₁ is as defined for R₁ but does not represent a hydrogen) can be produced by reacting a compound of formula IIP (where X''' is a protected carboxyl group, e.g. an ethoxycarbonyl group) with a compound of formula Hal.CH₂R''₁ (where Hal is a halogen atom) followed by deprotection of the X''' groups, e.g. by saponification. In this way for example compounds of formula IP in which R₁'' is 2-hydroxyethyl or 2,3-dihydroxy propyl can be produced by reaction of a compound of formula IIP in which X''' is -COOC₂H₅ with Cl.CH₂CH₂OH or ClCH₂CHOHCH₂OH respectively. The starting compound of formula IIP can be prepared by reaction of a 1,4,7,10-tetraazacyclododecane having one amine nitrogen protected by a protecting group, e.g. a benzyl group, with a compound HalCH₂X''', e.g. ethyl bromoacetate, and subsequently removing the protecting group, e.g. using standard debenzylation conditions. The chelating agents of the present invention are particularly suitable for use in detoxification or in the formation of metal chelates, chelates which may be used for example in or as contrast agents for in vivo or in vitro magnetic resonance (MR), X-ray or ultrasound diagnostics (e.g. MR imaging and MR spectroscopy), or scintigraphy or in or as therapeutic agents for radiotherapy, and such metal chelates form a further aspect of the present invention. For use as an MR-diagnostics contrast agent, the chelated metal species is particularly suitably a paramagnetic species, the metal conveniently being a transition metal or a lanthanide, preferably having an atomic number of 21-29, 42, 44 or 57-71. Metal chelates in which the metal species is Eu, Gd, Dy, Ho, Cr, Mn or Fe are especially preferred and Gd³⁺ and Mn²⁺ are particularly preferred. For such use, the paramagnetic metal species is conveniently non-radioactive as radioactivity is a characteristic which is neither required nor desirable for MR-diagnostics contrast agents. For use as X-ray or ultrasound contrast agents, the chelated metal species is preferably a heavy metal species, for example a non-radioactive metal with an atomic number greater than 37. For use in scintigraphy and radiotherapy, the chelated metal species must of course be radioactive and any conventional complexable radioactive metal isotope, such as 99m Tc or ¹¹¹In for example, may be used. For radiography, the chelating agent may be in the form of a metal chelate with for example ⁶⁷Cu. For use in detoxification of heavy metals, the chelating agent must be in salt form with a physiologically acceptable counterion, e.g. sodium, calcium, ammonium, zinc or meglumine, e.g. as the sodium salt of the chelate of the compound of formula I with zinc or calcium. Where the metal chelate carries an overall charge, such as is the case with the prior art Gd DTPA, it will conveniently be used in the form of a salt with a physiologically acceptable counterion, for example an ammonium, substituted ammonium, alkali metal or alkaline earth metal cation or an anion deriving from an inorganic or organic acid. In this regard, meglumine salts are particularly preferred. Viewed from a further aspect, the present invention provides a diagnostic or therapeutic agent comprising a metal chelate, whereof the chelating entity is the residue of a compound according to the present invention, together with at least one pharmaceutical or veterinary carrier or excipient, or adapted for formulation therewith or for inclusion in a pharmaceutical formulation for human or veterinary use. Viewed from another aspect, the present invention provides a detoxification agent comprising a chelating agent according to the invention in the form of salt with a physiologically acceptable counterion, together with at least one pharmaceutical or veterinary carrier or excipient, or adapted for formulation therewith or for inclusion in a pharmaceutical formulation for human or veterinary use. The diagnostic and therapeutic agents of the present invention may be formulated with conventional pharmaceutical or veterinary formulation aids, for example stablizers, antioxidants, osmolality adjusting agents, buffers, pH adjusting agents, etc. and may be in a form suitable for parenteral or enteral administration, for example injection or infusion or administration directly into a body cavity having an external escape duct, for example the gastrointestinal tract, the bladder or the uterus. Thus the agent of the present invention may be in a conventional pharmaceutical administration form such as a tablet, capsule, powder, solution, suspension, dispersion, syrup, suppository, etc; however, solutions, suspensions and dispersions in physiologically acceptable carrier media, for example water for injections, will generally be preferred. Where the agent is formulated for parenteral administration, the carrier medium incorporating the chelate or the chelating agent salt is preferably isotonic or somewhat hypertonic. For MR-diagnostic examination, the diagnostic agent of the present invention, if in solution, suspension or dispersion form, will generally contain the metal chelate at concentration in the range 1 micromole to 1.5 mole per litre, preferably 0.1 to 700mM. The diagnostic agent may however be supplied in a more concentrated form for dilution prior to administration. The diagnostic agent of the invention may conveniently be administered in amounts of from 10 ⁻⁴ to 1 mmol of the metal species per kilogram of body weight. For X-ray examination, the dose of the contrast agent should generally be higher and for scintigraphic examination the dose should generally be lower than for MR examination. For radiotherapy and detoxification, conventional dosages may be used. Viewed from a further aspect, the present invention provides a method of generating enhanced images of the human or non-human animal body, which method comprises administering to said body a diagnostic agent according to the present invention and generating an X-ray, MR-diagnostics, ultrasound or scintigraphic image of at least a part thereof. Viewed from a further aspect, the present invention provides a method of radiotherapy practised on the human or non-human animal body, which method comprises administering to said body a chelate of a radioactive metal species with a chelating agent according to the invention. Viewed from a further aspect, the present invention provides a method of heavy metal detoxification practised on the human or non-human animal body, which method comprises administering to said body a chelating agent according to the invention in the form of a salt with a physiologically acceptable counterion. Viewed from a still further aspect, the present invention provides a process for the preparation of the metal chelates of the invention which process comprises admixing in a solvent a compound of formula I or a salt (e.g. the sodium salt) or chelate thereof together with an at least sparingly soluble compound of said metal, for example a chloride, oxide or carbonate. Viewed from a yet still further aspect, the present invention provides a process for the preparation of the diagnostic or therapeutic agent of the present invention, which comprises admixing a metal chelate according to the invention, or a physiologically acceptable salt thereof, together with at least one pharmaceutical or veterinary carrier or excipient. Viewed from a yet still further aspect, the present invention provides a process for the preparation of the detoxification agent of the invention, which comprises admixing a chelating agent according to the invention in the form of a salt with a physiologically acceptable counterion together with at least one pharmaceutical or veterinary carrier or excipient. The present invention will now be illustrated further by the following non-limiting Examples. All ratios and percentages given herein are by weight and all temperatures are in degrees Celsius unless otherwise indicated. Example 1 1-(5-Hydroxy-3-oxapentyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid (a) 1,4,7,10-Tetraazacyclododecane-4.7.10-triacetic acid tri-t-butyl ester Sodium acetate (1.23 g, 15 mmol) was added to a stirred suspension of 1,4,7,10 tetraazacyclododecane (0.864 g, 5 mmol) (prepared in accordance with J. Am. Chem. Soc. 96 2268 (1974) and Liebigs Ann. Chem. 1340 (1977)) in N , N -dimethylacetamide (DMA) (15 ml) at ambient temperature. A solution of bromoacetic acid t -butyl ester (2.93 g, 15 mmol) in DMA (8 ml) was added dropwise to the stirred mixture, and the mixture was stirred at ambient temperature for 6 days. The solvent was evaporated and 1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid tri-t-butyl ester was purified by flash chromotography on a silica column with chloroform:methanol 8:2 as eluent. Yield 1.8 g (70%). White solid, m.p. 165-175°C. (b) 1-(5-Hydroxy-3-oxapentyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid 1,4,7,10-Tetraazacyclododecane-4,7,10-triacetic acid tri- t -butyl-ester (515 mg, 1 mmol) was dissolved in dimethylformamide (3 ml). Sodium iodide (15 mg, 0.1 mmol), triethylamine (233 mg, 2.5 mmol) and 2(2-chloroethoxy)ethanol (313 mg, 3.5 mmol) were added to the stirred mixture at ambient temperature. The mixture was stirred for 18 hours at ambient temperature. The temperature was then raised to 100°C and kept there for 1 hour. The solvent was then evaporated and the residue dissolved in a mixture of dichloromethane (4.5 ml) and trifluoroacetic acid (4.5 ml). The mixture was stirred for 2 hours at ambient temperature and the solvent was then evaporated. The residue was dissolved in water (8 ml), and this aqueous solution was washed with ether (6x4 ml). The aqueous solution was acidified and the title compound was isolated as a hygroscopic white powder after evaporation of the water. Yield 325 mg (75%), FAB MS: 435(M+1). The structure was confirmed by ¹HNMR and ¹³C NMR. Example 2 1-(8-Hydroxy-3,6-dioxaoctyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid 1,4,7,10-Tetraazacyclododecane-4,7,10-triacetic acid tri- t -butyl ester (129 mg, 0.25 mmol) (Example 1(a)) was dissolved in dimethylformamide (1 ml). Sodium iodide (7.5 mg, 0.5 mmol), triethylamine (76 mg, 0.75 mmol) and 2-[2-(2-chloroethoxy)-ethoxy]-ethanol (85 mg, 0.5 mmol) were added to the stirred mixture at ambient temperature. The mixture was stirred at ambient temperature for 90 minutes the temperature was then raised to 100°C and kept there for 1 hour. The solvent was evaporated, and the residue was dissolved in dichloromethane (2 ml) and washed with water (1 ml). Trifluoroacetic acid (2 ml) was added to the organic phase and the mixture was stirred at ambient temperature for 1 hour. The solvents were evaporated and the residue dissolved in water (4 ml). The aqueous solution was acidified, the water was evaporated and the title compound was isolated as a hygroscopic white powder. Yield 77 mg (64%). The structure was confirmed by ¹HNMR and ¹³CNMR. Example 3 Gd(III) chelate of 1-(5-hydroxy-3-oxa-pentyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid 1-(5-Hydroxy-3-oxapentyl)-1,4,7,10-tetraazacyclododecane -4,7,10-triacetic acid (400 mg) (Example 1) was dissolved in water (15 ml) and the pH was adjusted to 5.9. Gadolinium acetate tetrahydrate (203 mg, 0.5 mmol) was added and the mixture was stirred at 60°C for 12 hours. The cooled aqueous solution was eluted through a mixed ion exchanger, the water was evaporated and the title compound was isolated as a white powder. Yield 212 mg (72%). Example 4 Fe(III) chelate of 1-(8-hydroxy-3,6-dioxaoctyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid 1-(8-Hydroxy-3,6-dioxaoctyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid (72 mg, 0.15 mmol) (Example 2) was dissolved in water (5 ml). Iron (III) chloride (24.3 mg, 0.15 mmol) was dissolved in water (5 ml), and added to the above solution. The pH was adjusted to 4 and the mixture was stirred at 100°C for 30 minutes. The water was evaporated and the title compound isolated as a brown hygroscopic powder. Yield 77 mg (97%).

Claims: A compound of formula (wherein each X may independently represent a carboxyl group or a derivative thereof or a group R₁; each group R₁ may independently represent a hydrogen atom, a hydroxylalkyl group, an optionally mono- or poly-hydroxylated alkoxy or alkoxyalkyl group; n, m, q, r are each 2, 3 or 4, with the provisos that at least two nitrogens carry a -CHR₁X moiety, wherein X is a carboxyl group or a derivative thereof, that each -CHR₁X moiety represents other than a methyl group, that at least one -R₁ group represents other than hydrogen and that where all but one -CHR₁X groups are -CH₂COOH, then the remaining -CHR₁X group may not represent a hydroxyalkyl group) or a salt or metal chelate thereof. A compound as claimed in claim 1 wherein n, m, q and r each have the value 2, or a salt or metal chelate thereof. A compound as claimed in either of claims 1 and 2 of formula (wherein R₁ represents a hydrogen atom, a hydroxyalkyl group, or an optionally mono- or poly-hydroxylated alkoxy or alkoxyalkyl group) or a salt or metal chelate thereof. A compound as claimed in claim 1 being 1-(5-hydroxy-3-oxapentyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid; 1-(8-hydroxy-3,6-dioxaoctyl)-1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid; or a salt or metal chelate thereof. A chelate as claimed in any one of claims 1 to 3 being a chelate of a paramagnetic metal species. A diagnostic or therapeutic agent comprising a metal chelate, whereof the chelating entity is the residue of a compound of formula I as defined in claim 1, together with at least one pharmaceutical or veterinary carrier or excipient. A detoxification agent comprising a chelating agent as claimed in claim 1 in the form of a salt with a physiologically acceptable counterion, together with at least one pharmaceutical or veterinary carrier or excipient. A process for the preparation of compounds as claimed in claim 1, said process comprising at least one of the following steps: (i) reacting an amine of formula II (wherein R₃ is a hydrogen atom or a -CHR₁'X' group; X' and R₁' are as defined for X and R₁ in claim 1 or are groups convertible thereto; n, m, q, and r are as defined in claim 1; with the provisos that at least one R₃ moiety is a hydrogen atom, that at least two amine nitrogens carry a hydrogen atom or a -CHR₁'X' moiety in which X' is convertible to a carboxyl group or a derivative thereof, and that each -CHR₁'X' moiety is other than a methyl group) to introduce a -CHR₁X moiety (where R₁ and X are as defined in claim 1) at an amine nitrogen, followed if necessary by converting R₁' or X' to R₁ or X; (ii) converting a carboxyl X moiety in a compound of formula I into a carboxyl derivative or a carboxyl derivative X moiety in a compound of formula I into a carboxyl group; and (iii) converting a compound of formula I into a salt or metal chelate thereof or converting a salt or chelate of a compound of formula I into a compound of formula I. Use of a compound of formula I or a salt or metal chelate thereof for the manufacture of a diagnostic or therapeutic agent for use in a method of image generation, detoxification or radiotherapy practised on the human or non-human animal body. A method of generating enhanced images of the human or non-human animal body, which method comprises administering to said body a diagnostic agent as claimed in claim 6 and generating an X-ray, MR-diagnostics, ultrasound or scintigraphic image of at least a part thereof. A process for the preparation of a metal chelate as claimed in claim 1, said process comprising admixing in a solvent a compound of formula I, or a salt or chelate thereof, together with a compound of said metal at least sparingly soluble in said solvent. A process for the preparation of a diagnostic or therapeutic agent as claimed in claim 6 said process comprising admixing a metal chelate as claimed in claim 1 together with at least one pharmaceutical or veterinary carrier or excipient. A process for the preparation of a detoxification agent as claimed in claim 7, said process comprising admixing a chelating agent as claimed in claim 1 in the form of a salt with a physiologically acceptable counterion together with at least one pharmaceutical or veterinary carrier or excipient.

Inventors: ALMEN TORSTEN, BERG ARNE, KLAVENESS JO, RONGVED PAL, THOMASSEN TERJE, ALMEN, TORSTEN, BERG, ARNE, KLAVENESS, JO, RONGVED, PAL, THOMASSEN, TERJE
Applicants: NYCOMED IMAGING AS
Application year: 1988
Main classification: C07D257
IPC codes: C07D257, A61K51, A61K47