WO1990008134A1

WO1990008134A1 - Chelating agent derivatives

Info

Publication number: WO1990008134A1
Application number: PCT/EP1990/000078
Authority: WO
Inventors: Torsten Almén; Arne Berg; Jo Klaveness; Pål RONGVED
Original assignee: Nycomed As
Priority date: 1989-01-13
Filing date: 1990-01-15
Publication date: 1990-07-26
Also published as: GB8900732D0; AU5044690A; EP0453507A1; JPH04502919A

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 compounds of formula (I): X-CHR1-NZ-(CHR1)n-A-(CHR1)m-NZ-CHR1-X, wherein each of the groups Z is a group -CHR1X or the groups Z together are a group -(CHR¿1?)q-A'-(CHR?1)¿r-, where A' is an oxygen or sulphur atom or a group N-Y; m, n, q and r are each 2, 3 or 4, preferably 2; and the groups A, X, Y and R1 are as defined herein.

Description

Chelating Agent Derivatives

The present invention relates to certain

chelating agents, in particular aminopoly (carboxylic acid or carboxylic acid derivative) compounds,

and to the salts and 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), DE-A-3401052

(Schering), EP-A-258616 (Salutar), EP-A-277088

(Schering), DE-A-3633243 (Schering), EP-A-287465

(Guerbet) and EP-A-292689 (Squibb). Cyclic APCAs are also well known in the art, for example from

EP-A-287465 (Guerbet) and US-A-4639365 (Sherry).

EP-A-71564, for example, 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 administ ration 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-tetraazacyclododecanetetraacetic acid (DOTA), referred to in DE-A-3401052 (Schering) and in US-A-4639365

(University of Texas), lias 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.

To achieve reduced toxicity, Nycomed, in

EP-A-299795 have proposed APCAs which carry hydrophilic groups on the amine nitrogens or on the alkylene chains linking the amine nitrogens.

Viewed from one aspect, the present invention provides compounds of formula I

X-CHR¹-NZ-(CHR¹)_n-A-(CHR¹)_m-NZ-CHR¹-X (I)

(wherein each of the groups Z is a group -CHR¹X or the groups Z together are a group -(CHR¹)_q-A'- (CHR ¹)_r - , where A' is an oxygen or sulphur atom or a group N-Y;

A is a group N-Y or A- (CHR¹)_m- represents a carbonnitrogen bond or, when the groups Z together are a group -(CHR¹)_q-A'-(CHR¹)_r-, A may also represent an oxygen or sulphur atom;

each Y, which may be the same or different, is a a group -(CHR¹)_pN (CHR¹X)₂ or a group CHR¹X;

each X, which may be the same or different, is a

R ¹ group or a group of formula COD, POD₂, CON (OH) R²,

SO₂D, CH₂SR², CS₂ R² or CSD;

each D which may be the same or different is a group of formula OR ² , NR² ₂ or

where each R¹¹ which may be the same or different is a hydrogen atom, a hydroxyl group or an optionally hydroxylated alkyl group,

s is 0, 1 or 2, and

W is a group CHR¹¹, NR¹¹ or an oxygen atom;

each R¹, which may be the same or different, is a hydrogen atom, a hydroxyalkyl group or an optionally hydroxylated alkoxy or alkoxyalkyl group;

n,m,p,q and r are each 2,3 or 4, preferably 2;

each R² which may be the same or different is a hydrogen atom, an optionally mono or polyhydroxylated alkyl, alkoxyalkyl or polyalkoxyalkyl group;

with the provisos that where s is 0 then in the resulting 5 membered ring W is a CHR ¹¹ group,

at least one nitrogen carries a -CHR₁X moiety wherein

X and R¹ are not the same, that at least one group

X is other than a group R¹ or COD, and that unless the groups Z together are a -(CHR¹)_q-A'-(CHR¹)_r group or A is an N-(CHR¹)_p- N(CHR¹X)₂ group at least one R¹ is other than hydrogen) and salts

and metal chelates thereof.

In the compounds of the invention, alkyl or alkylene moieties in the R ¹, R² and R¹¹ groups may, unless

otherwise stated, be straight-chained or branched

and preferably contain from 1 to 8, especially

preferably from 1 to 6 and most preferably 1 to

4, carbon atoms. Where substituents may optionally be substituted by hydroxyl or alkoxy groups, this

may be mono-substitution or polysubstitution, and

in the case of poly-substitution the hydroxyl or

alkoxy substituents may be carried by alkoxy substituents groups.

Where a group D in a compound according to

the invention is a nitrogen-attached heterocyclic

ring, it particularly preferably is of formula:

Particularly preferred compounds of formula

I include those of formula la

X-CHR¹-NZ-(CHR¹)₂-NY-(CHR¹)₂-NZ-CHR¹-X (la)

(wherein each group Z is a group -CHR¹X or the

groups Z together are a group -(CHR¹)₂-A'-(CHR¹)₂-;

each Y, which may be the same or different, is

a group - (CHR¹)₂-N(CHR¹X) ₂ or -CHR¹X;

and A',X and R¹ are as hereinbefore defined)

and metal chelates and salts thereof.

In the compounds of the present invention, it is particularly preferred that one or more of the

-CHR¹- groups in the bridges between the amine

nitrogens, i.e. in the groups (CHR¹)_n, (CHR¹)_m,

(CHR¹) , (CHR¹) and (CHR¹) , should carry a hydrophilic R¹ group. Prior art APCAs, such as DTPA or DOTA

for example, possess certain hydrophobic areas

which cause the metal chelates produced from such

chelating agents to present relatively lipophilic

and hydrophobic zones.

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, polyhydroxyalkoxy, hydroxlated polyalkoxy, polyhydroxylated

polyalkoxy, hydroxylated alkoxyalkyl, hydroxylated polyalkoxyalkyl, polyhydroxylated alkoxyalkyl or

polyhydroxylated polyhydroxyalkyl 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 1 to 4 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 the invention may include, for example, amide groups, ester groups and carboxyl groups, for example groups of formulae

-CONR ²R³ (wherein R² is a hydrogen atom or an optionally hydroxylated alkyl, for example C_1-6 alkyl, group and R ³ is a hydrogen atom, a hydroxyl group or

an optionally hydroxylated alkyl group),

. (where W represents an

oxygen atom or a group CH₂ or CHOH, s is 0 or 1

and R ¹¹ is hydrogen or where s is 1 and W is oxygen R¹¹ may also represent a C_1-4 hydroxy-alkyl group),

-COO R⁴ (wherein R⁴ is an optionally hydroxylated alkyl group). Compounds wherein all but one X

group is a carboxyl or a salt or amide thereof

are particularly preferred. Moreover compounds

wherein terminal amine nitrogens, i.e those carrying two CHR¹X groups, carry a CHR¹X group in which

X is an amide are also preferred. Compounds of

formula I wherein one or more X groups are carboxyl groups may form salts or chelate complexes, which are also compounds according to the present invention, in which one or more (but not necessarily all)

such carboxyl groups are converted to -COOM groups

(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 or lysine. 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.

To improve complex stability and thereby reduce the toxicity of the complexes, use of other complexing moieties than acetic acid residues may be advantageous. The choice of complexing groups will be dependent upon the metal and complex in accordance to the theory of hard and soft acids and bases (HSAB theory).

Included amongst the particularly preferred chelating agents of formula I are the compounds of formulae lb, Ic, Id, Ie and If:

(wherein A' is oxygen or sulphur and at least one

of the the X groups is other than a COD or R¹ group, preferably wherein at least two, more preferably

3 or 4 of the X groups are ion-forming groups (for

example -COOH or -COOM groups), preferably wherein

at least one and especially preferably at least

two R¹ groups are hydrophilic groups, and particularly preferably wherein at least one R¹ group in each

-(CHR¹)₂ moiety is a hydrophilic R¹ group).

Preferred compounds of formula I include certain compounds of formulae lb to If wherein each moiety

-CHR¹X is of formula -CH₂X" wherein X" is other

than a group R ¹.

The following are particular examples of

preferred compounds according to the invention )

and chelates, especially Gd ³⁺ chelates, and salts, e.g. Na⁺ salts, 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 moieity 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 chelate thereof or converting a salt or chelate of a compound of formula I into a compound of formula I.

The introduction of a CHR¹X moiety at an amino

function may for example be performed as follows: a) To introduce a phosphonic acid moiety, the general method of synthesis of alpha-aminophosphonic acids described by K. Moedritzer et al. in J.Org.Chem. 31 (1966) 1603 may be used.

(where R *₂NCHR¹X is a compound of formula I) b) To introduce a hydroxamic acid moiety, the general method for transformation of an activated acid derivative into hydroxamic acid described by P.N. Turowski et al. in Inorg. Chem. 27 (1988) 474 may be used.

(wherein R N(CH₂COOH) CHR¹X is a compound of formula I). c) To introduce a sulfonic acid moiety, synthesis may be performed by alkylation of an amino function for example with iodomethanesulfonic acid

R₂ ^*NH ICH₂SO₃H R^*NCH₂SO₃H

→

(II) (VI) d) To introduce a thiol group, synthesis may be made by functional group transformation for example from corresponding alcohols by reaction with phosphorus pentasulfide (BP 917921) or from corresponding halides with KHS (see Chem.Ber 86

(1953) 825).

R₂ ^*NCH₂CH₂OH P₂S₅ R₂ ^*NCH₂CH₂SH

→

(VII) (VIII)

e) To produce thiocarboxylic acids, dithiocarboxylic acids and derivatives thereof, carboxylic esters

can be converted to both thioesters and dithioesters for example with phosphorus pentasulfide (see J.W

Scheren: Synthesis (1973) 149) or Lawesson's reagents (see Cava et al.: Tetrahedron 41(22) (1985 5061).

(where R⁺X is a compound of formula I)

Lawesson's reagents may also be used in a general

method for conversion of carboxamides into thiocaboxamides (see Catfa et al. : Tetrahedron 41 (22) (1985) 5061):

Cyano groups may also be converted into thioesters or dithioesters (see Janssen: "The Chemistry of

Carboxylic Acids and Esters", Ed. S. Patai, Interscience, N.Y., 1969, Chapter 15)

(where X² represents an oxygen or sulphur atom). f) A carboxylic acid, CHR¹COOH, functional group may be introduced by reaction between an amine

of formula II and for example a compound of formula

XVIII

L CHR^1'X'

(XVIII) where L is a leaving group, for example a halogen atom such as chlorine, bromine or iodine, and R^1' is a group R¹ as described above or a group convertible thereto and X' is a COOH moiety or a group convertible thereto.

Transformation of a carboxylic acid into

a derivative thereof may readily be performed as

described in the literature (e.g. by esterification, amide formation etc.). In the preparation of the compounds of the

invention, it may be desirable or necessary to

protect functional groups such as carboxylic acids and alcohols in the starting compound, e.g. the

amine of formula II. This might be done as described in the literature (see for example T. Greene, "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 XIX

(wherein R ³ is a hydrogen atom or a -CHR^1'X³ group;

X³ is as defined for X or is a group convertible

thereto; R^1' is as defined above; each group Z'

is a group -CHR ^1'X³ or an R³ moiety or together

the groups Z' are a -(CHR^1')_q-A"' -(CHR^1')_r- bridging group where A"' is an oxygen or sulphur atom or

a group -N-Y' where Y' is an R³ moiety or a group

-(CHR^1')_p-N(R³)₂; and A" is a group -N-Y' or -A"-

(CHR^1')_m- is a carbon-nitrogen bond or, where the

groups Z' together form a bridging group, A" may also represent an oxygen or sulphur atom; with the proviso that at least one R³ moiety is a hydrogen atom.

Thus for the process of step (i) the following preferred starting compounds of formula II may be used:

(wherein each R ^1" is an optionally protected hydroxyalkyl or hydroxyalkoxyalkyl group, for example a -CH₂-

O-CH₂-Phenyl group or a 2, 2-dimethyl-1,3-dioxacyclopent-4-yl group, A ² is a sulphur or oxygen

atom or a group -N-CHR ^{1 '} X³ and R⁶ is a group -CHR^1' X³ or a moiety convertible thereto). In the starting compounds of formulae IIa to IIo, optionally protected hydroxyalkyl groups attached to the alkylene chains between amine nitrogens are preferably benzyl protected groups and the nitrogen-attached protected hydroxyalkyl groups in -CHR ^1' X³ moieties are preferably in the

form of cyclic polyethers.

The preparation of starting compounds of

formulae IIa to IIo, may for example be by the

following procedures:

Compounds of formula IIa may be prepared

by 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) which is of formula IIa.

Compounds of formula lib may be prepared from compounds of formula IIa by reductive amination, for example as described by R.F. Borch in J. Org.

Chem. 34 (1969) 627, using a protected aldehyde

prepared for example as described by C. Hubschwerlen in Synthesis (1986) 962. The reaction may for

example follow the scheme: Compounds of formulae IIm and IIn may be

prepared analogously to compounds of formulae IIa and lib by omitting the condensation step (b) in

the above scheme.

Compounds of formula lie may be prepared

analogously to compounds of formula IIa by condensation of compounds (1) and (2) and subsequent acid hydrolysis, for example according to the scheme:

Compounds of formulae IIm and IIn may be

the above scheme.

Compounds of formula IIe may be prepared

Compounds of formula IId may be prepared analogously to compounds of formula lIb by reductive amination of compounds of formula IIe, for example following the scheme:

Compounds of formula IIe may be prepared by the following scheme:

Compounds of formula Ilf may be prepared analogously to compounds of formula IIe using a triamide starting material:

The alpha-formylation described above may be performed using the method described in J. Med. Chem. 8 (1965) 220.

Alternatively, compounds of formulae IIe

and Ilf may be prepared by replacing the formylation step (e) by reaction with chloromethylbenzylalcohol (available from Fluka) to yield the starting compounds (15) and (16) for the reduction step (f):

The direct insertion of benzyl-protected

hydroxymethyl groups may be performed as described in Org. Syn. 52 (1972) 16. Compounds of formula IIg may be prepared by the following scheme:

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. The mono-alkylation product, compound (18), is used in the preparation of compounds of formula Ilg

and the dialkylation product, compound (22) below, may be used in the preparation of compounds of

formula Ilh. The mono-alkylated compound (18)

may be converted to compound (20), which is of

formula Ilg, by oxidation and subsequent reductive amination or by halogenation and subsequent amination.

Compounds of formula Ilh may be prepared analogously to the compounds of formula Ilg, for example according to the scheme:

Compounds of formula IIo can be prepared analogously to compounds of formula Ilg by omitting the initial mono-/di-alkylation step (h). 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 (24), wherein A² 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 A². 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, compounds of formula IIa 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). 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.

Alternatively, a tetrapeptide or a protected tetrapeptide may be reduced, and the corresponding tetraamine may be cyclized in a way similar to that described by M.K.Moi et al. in J.Am.Chem. Soc. 110 (1988) 6266.

Compounds of formula Ilk may be prepared

by a reaction scheme substantially as follows:

The starting compound (33) is described by Y. Ohfune et al. in Tetr. Lett. (1984) 1071. Protection of the alcohol function as a benzyl ether gives

compound (34) which alternatively can be obtained by reducing the commercially available serine ester, compound (35), as described in Chem. Pharm. Bull.

23 (1975) 3081. Reductive amination of compound

(34) yields compound (36) from which the BOC (t- butyloxycarbonyl) groups may be removed by acid

hydrolysis to yield compound (37) which is of formula Ilk. Compounds of formula Ilg may be prepared

by alkylation of compounds of formula Ilk, for

example with 2-(2,2-dimethyl-1,3-dioxa-cyclopent- 4-yl)-ethylamine. This reaction would generally

be performed as a reductive amination. The asymmetric compounds of formula III may be prepared by peptide condensation of protected amino acids followed reduction of the amide carbonyl groups, for example using the following scheme:

Reductive amination of O-benzyl serine with glyceraldehyde acetal gives compound (39) and coupling of compound (39) with the ethyl ester of O-benzyl protected ser ine gives the dipeptide compound (40 ) (see J. Martinez et al. Int . J. Peptide Protein

Res . 12 (1978 ) 277 ) . Amidation of compound (40 ) with a protected amino alcohol gives compound (41) which may be reduced to compound (42) using lithium aluminium hydride , as described by J. E. Nordlander et al . in J. Org. Chem. 49 (1984) 133. Compound (42) is a compound of formula III. if the amidation step (w) is omitted, reduction of compound (40)

will give further asymmetric compounds of formula II.

The cyclic compounds of formula I may also be prepraed by methods analogous to those described by Guerbet in EP-A-287465. Thus a compound of

formula IIi may be formed by reacting a polyamine of formula (43)

T-N- (CHR^{1 "})₂-NT- (CHR^{1 "})₂-NT (43) with an amine of formula (44)

L-(CHR^1")₂-NY³-(CHR^1")₂-L (44)

(where T represents a displaceable group such as a tosyl, mesyl or benzenesulphonyl group, L represent a leaving group such as a halogen atom, e.g. chlorine, bromine or iodine, and Y³ represents a group T

or CHR ^1"X³) to yield a compound of formula IIi

where A ² is N-CH^R1"X³. Subsequent reaction with

an ether or thioether of formula (45)

L(CHR¹")₂X²-(CHR^1")₂L (45) (where X² represents an oxygen or sulphur atom)

can yield the corresponding cyclic ether or thioether.

Insertion of CHR¹X moieties in compounds

of formulae IIa to IIo may be performed as described above to give compounds of formula I. However

to insert different CHR¹X moieties in the same

molecule it may be desirable or necessary to selectively protect different amine nitrogen, e.g. by conventional methods.

Chelants of formula I may be used as the

basis for bifunctional chelants or for polychelant compounds, that is compounds containing several

independant chelant groups, by substituting for

one X or R¹ group a bond or linkage to a macromolecule or polymer, e.g. a tissue specific biomolecule or a backbone polymer such as polylysine or polyethyleneimine which may carry several chelant groups and may

itself be attached to a macromolecule to produce

a bifunctional-polychelant. Such macromolecular

derivatives of the compounds of formula I and the

salts and metal chelates thereof form a further

aspect of the present invention.

The linkage of a compound of formula I to

a macromolecule or backbone polymer may be effected

by any of the conventional methods such as the

mixed anhydride procedure of Krejcarek et al. (see

Biochemical and Biophysical Research Communications

77: 581 (1977)), the cyclic anhydride method of

Hnatowich et al. (see Science 220: 613 (1983) and

elsewhere), the backbone conjugation techniques

of Meares et al. (see Anal. Biochem. 142: 68

(1984) and elsewhere) and Schering (see EP-A-331616

for example) and by the use of linker molecules

as described for example by Nycomed in WO-A-89/06979.

Compounds of formula I thus produced may

be converted by conventional techniques to salts

or chelate complexes thereof.

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.

Salts or chelate complexes of the compounds

of the invention containing a heavy metal atom

or ion are particularly useful in diagnostic imaging

or therapy. Especially preferred are salts or

complexes with metals of atomic numbers 20-32,

42-44, 49 and 57-83. 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 Gd ³⁺, Mn²⁺ and Dy³⁺ 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, preferably greater than 50, e.g. Dy ³⁺

For use in scintigraphy and radiotherapy,

the chelated metal species must of course be radioactive and any conventional complexable radioactive metal isotope, such as ^99mTc or ¹¹¹In for example, may

be used. For radiography, the chelating agent

may be in the form of a metal chelate with for

examplie 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

a weak complex or 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.

Where the diagnostic or therapeutic agent

comprises a chelate or salt of a toxic metal species, for example a heavy metal ion, or atom, it may

be desirable to include within the formulation

a slight excess of the chelating agent, e.g. as

discussed by Schering in DE-A-3640708.

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 3 mmol of the metal species per

kilogram of body weight, e.g. about 1 mmol Dy/kg

bodyweight.

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 weak complex or salt with a

physiologically acceptable counterion.

Viewed from a yet further aspect, the present invention also provides the use of the compounds, especially the metal chelates, according to the invention for the manufacture of diagnostic or therapeutic agents for use in methods of image generation, detoxification or radiotherapy practised on the human or non-human animal body.

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 disclosures of all of the documents mentioned herein are incorporated by reference.

The present invention will now be illustrated further by the following non-limiting Example.

All ratios and percentages given herein are by

weight and all temperatures are in degrees Celsius

unless otherwise indicated.

Example 1

2,6-Bishydroxymethyldiethylenetriaminepenta

(methylenephosphonic acid)

1,5-Diamino-1,5-dibenzloxymethyl-3-azapentane (0.5g, 1.46 mmol) was dissolved in cone. HCl (1 ml), and

an aqueous solution of phosphorous acid (0.72g/8.8

mmol) was added. The solution was heated to reflux temperature, and a 35% aqueous formaldehyde solution

(1.4 ml/17.6 mmol) was added dropwise. The solution was kept at 100 °C for 30 minutes. The solvent

was removed by evaporation and the residue was

dissolved in methanol/water and precipitated with

isopropanol to give a yellow oil, identified as

2,6-bis (benzyloxymethyl) diethylenetriaminepenta (methylenephosphonic acid) (FAB-MS, [M+1]=814). This product was dissolved in methanol/water, and 10% palladium

on carbon (2.89 g) and ammonium formiate (0.68

g/10.8 mmol) was added. The mixture was stirred

at 50 °C for three hours, and kept at ambient temperature overnight. The catalyst was filtered off, and

the solution evaporated to dryness. The residue

was dissolved in water and loaded on a strong cation exchanger and eluted with aqueous ammonia (6M).

The title compound was isolated as a white powder.

Yield 244, M.P. greater than 350 °C. ¹H-NMR (90

MHz, D₂O) : 2.2-3.0 ppm (m), 3.4-3.8 ppm (m). Example 2

4,8-Bishydroxymethyl-3,6,9-triscarboxymethyl-3,6,9-triazaunedecane-1,11-bis-(N-methylhydroxamic acid) a) 4,8-Bisbenzyloxymethyl-3,6,9-triscarboxymethyl-3,6,9-triazaunedecane-1,11-bis-(N-methylhydroxamic acid)

1,5-Bisbenzyloxy-1,5-bis(2,6-dioxomorpholino)-3-azapentan-3-aceticacid (0.20 g, 0.34 mmol) was dissolved in DMA (2 ml) and N-methylhydroxylamine (0.28 g, 3.4 mmol) in DMA (1.5ml) was added. The mixture was stirred at ambient temperature under nitrogen for 24 hours. The solvent was evaporated, and the product was isolated as a yellw oil. Yield 0.22 g, 95%. FAB/MS : 692 (M+l) b) 4,8-Bishydroxymethyl-3,6,9-triscarboxymethyl-3,6,9-triazaunedecane-1,11-bis-(N-methylhydroxamic acid)

4,8-Bisbenzyloxymethyl-3,6,9-triscarboxymethyl- 3,6,9-triazaunedecane-1,11-bis-(N-methylhydroxamic acid) (0.23 g, 0.34 mmol) was dissolved in methanol (20 ml) and ammonium formiate (0.16 g, 2.5 mmol) was added. 10% palladium on carbon (0.44 g) was added under argon. The suspension was kept at

50°C for 3 hours, filtered and evaporated and the 4 ,8-bishydroxy-methyl-3,6,9-triscarboxymethyl-3,6,9- triazaunedecane-1,11-bis-(N-methylhydroxamic acid) was isolated. Yield: 0.15 g (90%). FAB/MS: 512 (M+1).

Example 3

1,5-Bisamino-1,5-bishydroxymethyl-3-azapentanepenta (methylphosphonic acid) a) 1,5-Bisamino-1,5-bisbenzyloxymethyl-3-azapentanepenta(methylphosphonic acid)

1,5-Bisamino-1,5-bisbenzyloxymethyl-3-azapentane

(0.20 g, 0.58 mmol) (prepared in acordance with

WO-A-89/00557) was dissolved in 6M hydrochloric

acid (1 ml) and phosphorous acid (0.48 g, 5.8 mmol) dissolved in water (1 ml) was added. The temperature was increased to 80°C and formaldehyde (37%) in

water (0.35 g, 11.6 mmol) was added. The solvent

was evaporated and the 1,5-bisamino-1,5-bisbenzyloxymethyl-3-azapentanepenta-(methylphosphonic acid) was isolated. Yield 0.47 g, 99%, FAB-MS: 814 (M+1). b) 1,5-Bisamino-1,5-bishydroxymethyl-3-azapentanepenta (methylphosphonic acid)

1,5-Bisamino-1,5-bisbenzyloxymethyl-3-azapentanepenta (methylphosphonic acid) (0.47 g, 0.58 mmol)

is dissolved in methanol (20 ml), and ammonium

formiate (0.54 g, 8.6 mmol) is added. 10% palladium on carbon (1.5 g) is added under argon. The suspension is kept at 50°C for 6 hours, filtered and evaporated and the 1,5-bisamino-1,5-bishydroxymethyl-3-azapentanpenta

(methylphosphonic acid) is isolated. FAB-MS: 634

(M+1).

Example 4

1,5-Bisamino-1,5-bishydroxymethyl-3-azapentanepenta (methylsulphonic acid), pentasodium salt a) 1,5-Bisamino-1,5-bisbenzyloxymethyl-3-azapentanepenta-(methylsulphonic acid), pentasodium salt.

1,5-Bisamino-1,5-bisbenzyloxymethyl-3-azapentane

(0.3 g, 0.87 mmol) (prepared in accordance with

WO-A-89/00557) was dissolved in 2ml 50% methanol in water and sodiumhydroxymethylensulphonate (0.6 g, 4.457 mmol) was added. The mixture was stirred at 50 °C for 3 hours, the solvent was evaporated and the title product isolated. Yield: 0.8 g,

99%. b) 1,5-Bisamino-1,5-bishydroxymethyl-3-azapentanepenta (methylsulphonic acid), pentasodium salt.

1,5-Bisamino-1,5-bisbenzyloxymethyl-3-azapentanepenta (methylsulphonic acid) (0.1 g, 0.11 mmol) was dissolved in methanol (20 ml), and ammonium formiate (50 mg , 0.8 mmol) was added . 10% palladium on carbon (140 mg) was added under nitrogen. The suspension was kept at 50 °C for 3 hours, filtered and evaporated and the title product was isolated. Yield: 72 mg, 90 %. Melting pointy 350°C.

Example 5

Gadolinium (III) chelate of 4,8-bis (hydroxymethyl)-3,6,9-triscarboxymethyl-3,6,9-triazaundecane-1,11-bis-(N-methylhydroxamic acid)

4,8-Bishydroxymethyl-3,6,9-triscarboxymethyl-3,6,9- triazaundecane-1,11-bis-(N-methylhydroxamic acid) (0.61 g, 0.12 mmol) was dissolved in water (5 ml), gadolinium (III) chloride (42 mg, 0.12 mml) was added and the pH was adjusted to 5 with 1M sodium hydroxide. The mixture was stirred at ambient temperature for 1 hour and the solvent evaporated. The residue was stirred in methanol, filtered, evaporated and the title product was isolated.

Yield: 0.64 g (80 %). Melting point 180-190°C. Example 6

Dysprosium (III) chelate of 4,8-Bishydroxymethyl-3,6,9-triscarboxymethyl-3,6,9-triazaundecane-1,11-bis-(N-methylhydroxamic acid).

4,8-Bishydroxymethyl-3,6,9-triscarboxymethyl-3,6,9-triazaundecane-1,11-bis(N-methylhydroxamic acid) (0.61 g, 0.12 mmol) was dissolved in water (5 ml), and dysprosium (III) oxide (22 mg, 0.06 mmol) was added. The suspension was stirred at 80 °C for 5 hours, filtered, the solvent was evaporated and the title product was isolated. Yield: 0.72 g, 90%. FAB/MS: 673 (M+1).

Example 7

Sodium salt of the tri-gadolinium (III) chelate of 1,5-bisamino-1,5-bisbenzyloxymethyl-3-azapentanepenta(methylphosphonic acid)

1,5-Bisamino-1,5-bisbenzyloxymethyl-3-azapentanepenta (methylphosphonic acid) (0.09 g, 0.14 mmol) is dissolved in water (10 ml), the pH is adjusted to 6 with 0.1 M sodium hydroxide and gadolinium (III) oxide (0.078 g, 0.21 mmol) is added. The suspension is stirred at 80°C overnight, filtered and evaporated.

Example 8

Preparation of a solution containing the gadolinium (III) chelate of 4,8-bis (hydroxymethyl)-3,6,9-triscarboxymethyl-3,6,9-triazaunedecane-1,11-bis-(N-methylhydroxamic acid)

The gadolinium(III) chelate of 4,8-bis (hydroxymethyl)-3,6,9-triscarboxymethyl-3,6,9-triazaunedecane-1,11-bis-(N-methylhydroxamic acid) (6.65 g, 10 mmol)

(Example 5) was dissolved in 20 ml of distilled water. The solution was filtered, placed in a

20 ml vial and autoclaved. The solution contained 0.5 mmol gadolinium per ml.

Claims

CLAIMS :

1. A compound of formula I

X-CHR¹-NZ-(CHR¹)_n-A-(CHR¹)_m-NZ-CHR¹-X (I)

(wherein each of the groups Z is a group -CHR¹X

or the groups Z together are a group -(CHR¹)_q-A'- (CHR ¹)_r-, where A' is an oxygen or sulphur atom

or a group N-Y;

A is a group N-Y or A- (CHR¹)_m- represents a carbonnitrogen bond or, when the groups Z together are

a group -(CHR¹)_q-A' -(CHR¹)_r-, A may also represent an oxygen or sulphur atom;

each Y, which may be the same or different, is a

a group -(CHR¹)_pN (CHR¹X)₂ or a group CHR¹X;

each X, which may be the same or different, is a

R ¹ group or a group of formula COD, POD₂, CON (OH) R² , SO₂D, CH₂SR ², CS₂ R² or CSD;

each D which may be the same or different is a

group of formula OR ², NR² ₂ or

where each R¹¹ which may be the same or different

is a hydrogen atom, a hydroxyl group or an optionally hydroxylated alkyl group,

s is 0, 1 or 2, and

W is a group CHR¹¹, NR¹¹ or an oxygen atom;

each R¹, which may be the same or different, is

a hydrogen atom, a hydroxyalkyl group or an optionally hydroxylated alkoxy, alkoxyalkyl or polyalkoxyalkyl group; n,m,p,q and r are each 2,3 or 4; each R² which may be the same or different is a

hydrogen atom, an optionally mono or polyhydroxylated alkyl, alkoxyalkyl or polyalkoxyalkyl group;

with the provisos that where s is 0 then in the

resulting 5 membered ring W is a CHR¹¹ group, that at least one nitrogen carries a -CHR₁X moiety wherein

X and R¹ are not the same, that at least one group

X is other than a group R or COD, and that unless the groups Z together are a -(CHR¹)_q-A¹- (CHR¹)_r

group or A is an N-(CHR ¹)_p- N(CHR¹X)₂ group at

least one R ¹ is other than hydrogen) or a metal

chelate or salt thereof.

2. A compound of formula I as claimed in claim

1 wherein each D is a group of formula OR ² or NR² ₂ and each R ² is a hydrogen atom or an optionally

hydroxylated alkyl group, or a chelate or salt

thereof.

3. A compound as claimed in claim 1 wherein

from at least one group D is of formula

M

or a metal chelate or salt thereof.

4. A compound as claimed in claim 1 of formula la X-CHR¹-NZ-(CHR¹)₂-NY-(CHR¹)₂-NZ-CHR¹-X (la)

(wherein each group Z is a group -CHR¹X or the

groups Z together are a group -(CHR¹)₂-A'-(CHR¹)₂-; each Y, which may be the same or different, is

a group - (CHR¹)₂-N(CHR¹X)₂ or -CHR¹X; and A',X and R¹ are as defined in either of claims 1 and 2) or a metal chelate or salt thereof.

5. A compound as claimed in any of claims 1 to 4 being of formula lb, Ic, Id, Ie, or If

(wherein A' if present is oxygen or sulphur and at least one X group is other than a COD or R¹ group), or a metal chelate or salt thereof.

6. A compound as claimed in any of claims 1 to 5 wherein one or more of the -CHR¹- groups in the bridges between the amine nitrogens carries a hydrophilic R¹ group.

7. A compound as claimed in any of claims 1 to 6 wherein all but one X group is a carboxyl group or a salt or amide thereof.

8. A compound as claimed in any one of claims

1 to 7 being a metal chelate of a compound of formula

I or a salt thereof.

9. A compound as claimed in claim 8 wherein the number of ion-forming groups X is such that the metal chelate formed is a neutral species.

10. A compound as claimed in either of claims 8 and 9 wherein the chelated metal species is a paramagnetic metal ion having an atomic number of 21-29, 42,44 or 57-71.

11. A compound as claimed in claim 10 wherein said paramagnetic metal ion is selected from ions of Eu, Gd, Dy, Ho, Cr, Mn and Fe.

12. A compound as claimed in either of claims 10 and 11 wherein said paramagnetic metal ion is selected from Gd³⁺, Mn and Dy³⁺.

13. A compound as claimed in either one of claims 8 and 9 wherein the chelated metal species is a heavy metal ion having an atomic number greater than 37.

14. A compound as claimed in either one of claims 8 and 9 wherein the chelated metal species is a radioactive metal ion.

15. A process for the preparation of compounds as claimed in claim 1, said process comprising one or more of the following steps: (i) reacting a corresponding amine to introduce

a -CHR ¹X moieity at an amine nitrogen;

(ii) converting a carboxyl X moiety in a compound

(iii) converting a compound of formula I into a

salt or chelate thereof or converting a salt

or chelate of a compound of formula I into

a compound of formula I.

16. A diagnostic or therapeutic agent comprising

a physiologically acceptable metal chelate as claimed in any of claims 1 to 12 or a physiologically acceptable salt thereof together with at least one pharmaceutical or veterinary carrier or excipient.

17. A detoxification agent comprising a chelating

agent as claimed in any one of claims 1 to 7, in

the form of a weaker complex or salt with a physiologically acceptable counterion, together with at least one

pharmaceutical or veterinary carrier or excipient.

18. A method of generating images of the human

or non-human animal body, said method comprising

administering to said body a compound or diagnostic

agent as claimed in any of claims 8 to 14 and 16

and generating an X-ray, MR-diagnostics, ultrasound

or scintigraphic image of at least a part of said

body.

19. A method of radiotherapy practised on the

human or non-human animal body, which method comprises administering to said body a compound as claimed

in claim 14.

20. 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 as claimed in any of claims 1 to 7 in the form of a weak complex or salt with a physiologically acceptable counterion.

21. The use of compounds as claimed in any of claims 1 to 14 for the manufacture of diagnostic or therapeutic agents for use in methods of image generation, detoxification or radiotherapy practised on the human or non-human animal body.

22. A process for the preparation of the metal chelates as claimed in any of claims 1 to 14 said process comprising admixing in a solvent a compound of formula I or a salt or chelate thereof together with an at least sparingly soluble compound of said metal.