CA2074171A1 - Chelants - Google Patents

Abstract

2074171 9110645 PCTABS00006 There are provided novel chelating agents useful in the preparation of contrast media for diagnostic imaging or of radiotherapeutic or detoxification compositions.

Description

`~ ~07~171 ~O91/10~5 PCT/EP91/00126 Chelants The present invention relates to certain novel chelating agents, in particular polyamines, and to their uses, especially their medical uses.
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.
Polyamine chela~ing agents, for example 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 (Sal~tar), DE-A-3633245 (Schering), EP-A-263059 (Schering), EP-A-277088 (Schering) and DE-A-3633243 (IDF)-Thus, for example, EP-A-71564 describes paramagnetic metal chelates, for which the chelating agents are nitrilotriacetic acid (NTA), N,N,N',N'-ethylenediamine-tetraacetic acid (EDTA), N-hydroxyethyl-N,N',N~-ethylenediaminetriacetic acid (HEDTA), N,N,N',N",~"- diethylenetriaminepentaacetic acid (DTPA) and N-hydroxyethyl-iminodiacetic 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 tha~ paramagnetic species.
Amongst the particular metal chelates disclosed by .-, . . , - ,., : .
- ,., :., ~. , - , . ' '' ' . . `
:, . ; .,

2 0 7 ~ -I r~
W091/10~5 PCT/EP91/00126 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 (Scherlng) and in US-A-4639365 (University or Texas) and of l-hydroxypropyl-4,7,10-triscarboxymethyl-1,4,7,10-tetraazacyclododecane (HP-DO3A) have also recently received attention in this regard.
To improve stability, water solubility and selectivity, relative to the APCA chelating agents described in E?-A-71564, Schering, in EP-A-130934, have p~oposed the partial substitution for the N-attached carboxvalkyl groups of alkyl, alkoxyalkyl, alkoxycarbonylalkyl or alkylaminocarbonylalkyl groups, where any amide nitrogens may themselves carry polyhydroxyalkyl groups. More recently, to improve compatibility, stability, solubility and selectivity, in EP-A-250358 Schering have proposed a narrow range of compounds having a DTPA-like structure including a bridging alkylene chain.
In the field of hepatobiliary MRI cont~rast agents, where lipophilicity rather than hydrophilicity is desired, Nycomed in EP-A-165728, have proposed the use of paramagnetic chelates of certain anilide group-containing iminodiacetic acids and Lauffer in WO-A-86/06605 has suggested the use of paramagnetic chelates of triaza and tetraaza macrocycles which have fused aryl group on one of the alkylene chains linking the ring nitrogens but are otherwise unsubstituted.
Nycomed, in EP-A-299795, suggest that the toxicity of certain APCA chelating agents and their chelates may be reduced by introducing at least one hydrophilic moiety as a substituent on one or more of the alkylene bridges between the amine nitrogens.

,.
..
"

.

207~7~
~O91/10~5 PCT/EP91/00126

3 --stability selectivity and there is thus a general and continuing need for such polyamine chelatiny agents which form metal chelates of reduced toxicity, impro~ed stability or improved water solubility or having improved biodistribution characteristics.
We now propose a novel class of polyamine chelating agents which incorporate within their structure at least one 5- or 6-membered heterocyclic ring.
Thus viewed from one aspect the present invention provides a compound of formula I

Rl(CR2R )n[X(CR2R )n]~R~ (I) (wherein each X independently represents an oxygen or sulphur atom or a group of formula NA, or (CR2R )nX(CR R )n represents a group of formula -( CR2R3 ) n-l \

E~\J

-(CR2R3)n-E represents COH, NR2, O or S;
each A independently represents a hydrogen atom or a group 'CR2R3)pY, (CR R3)nN[(CR2R3)pY]2 or .-'' WO91/10~5 PCT/EPg1/00126

- 4 -' - ( C 2 R 3 ) R ~

where two (CR2R3)nY groups on different nitrogens, preferably in adjacent groups, may together represent a group -(CR2R )n~;
each Y independently rePresents a group COZ, SO2Z, POZ2, CON(OH)R , CH2SR , CS2R or CSZ; 2 each Z independently represents a group OR or NR2R2;
each G is a 3 or 4 membered chain of carbon atoms and optionally a nitrogen, oxygen or sulphur atom; each J is a 2 or 3 membered chain of carbon atoms and optionally a nitrogen, oxygen or sulphur atom; each n is an integer of 2 to 4, preferably 2 or 3 or in a group (CR2R3)n attached to a moiety Rl which represents a hydrogen atom or a group R4 n may also be zero or 1;
m is an integer of 3 to 8, preferably 3 to 6;
p is an integer of 1 to 3, preferably 1;
each Rl represents a hydrogen atom or a group R4 or together both groups Rl represent a carbon-carbon bond;
each R2 independently represents a hydrogen atom or a C18 alkyl group optionally mono- or poly-substituted by hydroxyl or C18 alkoxy groups or NR2R2 may together represent a nitrogen-attached S to 7 membered saturated heterocyclic ring optionally containing as a further ring heteroatom a nitrogen, oxygen or sulphur atom and optionally substituted by a group R4;
each R3 independently represents a hydrogen atom or a Cl8 alkyl or C13 alkoxy group optionally mono or poly substituted by hydroxy or C1 8 alkoxy groups; and each R4 independently represents a hydrogen atom, a .. . .
: ~ , . -: . ' 2 G 7 ~ 171 r VO91/10~5 PCT/EP9t/00126 halogen atom, a hydroxyl group, an optionally monv- or poly-hydroxylated C18 alkyl, Cl~ alkoxy, (C18 alkoxy)-C
alkyl or poly(Cl8 alkoxy)-C18 alkyl group, a sulphonate group or a group (CR2R3)pY or two groups R~ on the same ring represent a (CR R3)n l [X(CR R )n]m l (CR R )n l group in which case the said ring may be saturated; with the provisos that at least 2 Y groups, preferably at least 3, are present, that where both groups Rl ~ogether form a bond, m is 4 or 5, all n are 2, one X is 2,6-pyridindiyl and the remainder are NCH2COOR2, then a~
least one R2, R3 or R4 is other than hydrogen, and that either at least one X group comprises an aromatic heterocyclic group or both Rl groups together represen' a bond and two (CR2R3)pY groups together represent a i -(CR2R3)n~ group or both Rl groups represent a bond, m is 6 or greater and two X groups separated by at least two other X groups are oxygen or sulphur atoms, and preferably that where m is 3 or 4, all n are 2, one X is 4-substituted-2,6-pyridindiyl, 2,5-furandiyl, 2,5-pyrroldiyl, 2,5-thiophendiyl or l-hydroxy-2,6-phenylene and the remainder are NCH2 COOR2 or NH then at least one R2, R3 or R4 is other than hydrogen) or a chelate comple~:
or salt thereof.
In the compounds of the invention, alkyl or alkylene ~ieties in groups Rl to R4, unless otherwise stated, mG~ be straight chained or branched and preferably contain from l to 6 and most preferably l to 4, carbon atoms. Where substituents may themselves optionally be substituted by hydroxyl or alkoxy groups, this may be monosubstitution or polysubstitution and, in the case of polysubstitution, alkoxy or hvdroxyl substituents may be carried by alkoxy substituen-s.
Where, as is particularly preferred, the compounds of the invention incorporate one or more hydrophilic to R4 groups, these are preferably straight-chained or branched moieties having a carbon atom content of from l to 8, especially preferably l to 6, carbon atoms. The ;; ..
' ~
:. : . .

2~7~171 WO91/10~5 PCT/EP91/00126 hydrophilic groups may be alkoxy, polyalkoxy, hydroxyalkoxy, hydroxypolyalkoxy, polyhydroxyalkoxy, polyhydroxylated polyalkoxy, hydroxyalkyl, polyhydroxyalkyl, alkoxyalkyl, polyalkoxyalkyl, hydro~ylated al~oxyal~yl, polyhydroxylated alkoxyalkyl, hydroxylated polyalkoxyalkyl, or polyhydroxylated polyalkoxyalXyl groups. More preferably however they will be monohydroxyalkyl or polyhydroxyalkyl groups.
The hydrophilic groups serve to increase the hydrophilici~y and reduce the lipophilicity of the metal chelates formed with the chelating agents of the invention and it is preferred that the co~pounds of formula I should contain at least l, conveniently from l to 4, and preferably l, 2 or 3 such hydrophilic groups.
As hydrophilic groups, the compounds of the invention may thus include for example hydroxymethyl, ;/ 2-hydroxyethyl, l,2-dihydroxyethyl, 3-hydroxypropyl, 2,3-dihydroxypropyl, 2,3,4-trihydroxybutyl, l-(hydroxymethyl)-2-hydroxy-ethyl, methoxymethyl, ethoxymethyl, 2-hydroxyethoxymethyl, methoxyethoxymethyl, (2-hydroxy-ethoxy)ethyl, etc, groups.
Particularly preferred compounds of formula I
according to the invention include those of monocyclic structure containing at least 6 ring heteroatoms, those of fused bicyclic structure containing at least two ring heteroatoms in the smaller ring, and those of fused tricyclic or higher polycyclic structure.
In the compounds of the invention, the aromatic groups comprised by X groups preferably are pyridine, pyra~ine, pyrrole, furan, phenol, pyrimidine or thiophene rings, especially pyridine rings. Where in a group X, E is COH, e.g. where X comprises a phenol group, it is especially preferred that an electron withdrawing R4 substituent (e.g. a lower alkyl or halogen such as chlorine or methyl) should be present on the ring, preferably at the para position to the .. . .

2~7~171 ,V091/10~ PCT/EP91/00126 hydroxyl group. "N"-membered aromatic rings attach~d to the linear or cyclic skeleton of the molecule at the 2 and/or "N-l" positions are especially preferred.
Moreover in the compounds according to the lnven~ion, adjacent X groups preferably do not both comprise such aromatic groups. Where the chelants of the invention contain fused saturated heterocyclic rings these preferably are piperazine, or l,4-diazaci~cloheplan_ rings, especially piperazin-l,4-diyl groups.
Particularly preferably one, two or three X groups ; should comprise such aromatic groups, the remaining groups, or all but one remaining X group being N(CR2R3)pY groups. It is especially preferred tha_ groups X comprising no ionizing group Y should be non-adjacent particularly that they should adopt opposed positions in macrocyclic chelants, e.g. as the 1st and 5th X groups in an 8 X ring. Particularly preferred compounds of formula I include those of formulae Ib and Ic IR2R3c~ (IbJ

2R3)n ' J m-2 ~CR2R3)n_1NlCR2R3)n~X(CR2R3)n)m 4NICR2R3) R~ ) R~

, :
SUBSTITUTE SI~EET

..

: , ~ . . .

2~74~7~
WO91/10~5 PCT/EP91/00126 and in particular those of formulae Id to Il.

R~
R~

A A~' (Id) N
R~ R~

(è

R ' ~ N A ' A ' N R 2 R
~J4 J~ R' 1~ 1 A ' R2--NA ' R l~h \~ j~ 2 R ~ R 2 R

--N N ~ ' N A ~ N

.
.' ~' ', , ; ''.'' ` ' ' ";: ' '~

2~7~
WO 91/1064; PCI/EP91/00126 _ g _ ICR2R3 ) (CR2 R3 Jn ~ ( I h ) ( CR2 R3)n '~;~

m-2 ~CR2R3 )n N` N
. / (CR2R3)n \
~ ~ ( li) , ~v ~[72~R3~m v 3 ~R~

( N~ A'~A~t ( Ij) (R2~N~L R2) (R~N~R2)z NA' A'N
(R2~

SUBSTITUTE SltEET

' -207~
WO91/10~ PCTtEP91/00126 R ~A~' ( R 2~i N ~,~R 2) `X~ A~
NA' ,, A'N
( R2~N~:~, (11) R2~X ~R2 (where A' is CHR2Y or hydrogen, z is 1 or 2, t is 1 or 2, v is 0,1,2,3 or 4 and x2 is o or S).
Where a group NR22 in a compound according to the invention is a nitrogen attached heterocyclic ring, it ~ will conveniently be of formula 'A R4 ~ CHR 4 )q - N W

R4 R~

~V~S~ S 8 "~ "

... . ..

2~7~17~
~091/10~5 PCT/EP91/00126 r where q is o,l or 2, and W is CHR4, NR4, O or S, where q is zero W preferably being CHR4. Particularly preferably such groups are of formula ~1 --U C --!l O
/ y --OH
~ or --~ rOY

In the compounds of formula I, the groups Y
preferably r~present carboxylic acid or amide groups, for example groups of formula COOH, CONH2, CONCHR4CHR4W(CHR4)qCHR4, CONHR2 or CONR22 (where R2 is an alkyl or mono or poly hydroxyalkyl group, for example a Cl 6 alkyl group optionally carrying l, 2, 3 or 4 hydroxyl groups). Particularly preferably, in the case where Rl are not bonds terminal X groups will comprise an aromatic heterocyclic group.
Where Y is a carboxyl group, the compounds of formula I can conveniently form salts or chelates in which Y represents -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 or lysine.
In such salts or chelates one or more (but not necessarily all) of the carboxyl groups are transformed into COOM groups.
It is particularly preferred that the number of the ion-forming groups Y 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 compound of formula I (or salt thereof) preferably contains three or six .

2074-1~1 , .
WO91/10~5 PCT/EP91/00126 ion-forming Y groups, for exa~ple -COOH (or -COOM). ~In this way, the metal chelate will be formed as a neutral species, a form preferred since the osmolalities 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 whish 211 the Y groups are -COOH groups or salts or amiaes oî such cGmpounds are especially preferred since compositions containing metal chelates of such compounds can readil~ be s~erilized, for example by au'ocl~vin~.
Included amongst the par.ic~larly pre_êrrêd compounds according to the inven~ion are those of formulae Ib to Ii wherein each R2 represents a hydrogen atom or a mono- or poly-hydroxylated alkyl group, Y
represents a group of formula COZ and Z represents a hydroxyl group or a group NHR ) and metal chelates and salt thereof.
Especially preferred compounds according to the invention include those of the following formulae Im to Iw ~\~o~

NR ~N (Im) R~ ~ O

~R ?` N ~

~R R~N (In) R

, t ,. c . ` !

207~171 , .
iVO 91/10645 PC~r/EP91/00126 R~ ~ (Io) R~ ¦

~ ;

~ ~ ~ (Ip) N NR~ NR~ NR6 N

(/~ N N ~\) r R ~ ~ ~ (Iq) (Ir) , ~R'' ~ , ~J

(Is) N~

'. , `' ,' . .

2074171 -~
WO 91/1064~ PC~/EP91/00126 --~,b~ (It) I`l R~ R ~1 ~ N ~
NRb R~ ~1 R~
~-- ~0~
(Iu) r_~lR R~ ~
' N ~J
R'~
~

Nrf~ ~ ~N
.3 ~ R3O
~X~ x~ (Iv) n OH

R~ k~

~ ----;~ tIW) ~ ~ J

. (where R30 is (CH2)2 or (CH2)3, each r is l or 2, t is l or ~ 2, R is hydrogen or methyl, and R is a carboxymethyl s~ group or derivative thereof, e.g. CH2COOH, CH2CON(CH~)CH2CHOHCH2OH, or CH2CONHR (where R
represents CH~, CH2CHOHCH2OH or CH(CH2OH)2 or a group -CH2CONCH2CHR W(CHR )qCH2 where W represents an oxygen -2~417~
. ' ~091/10~S PCT/EP91/00126 atom or a group CH2 or CHOH, q is 0 or l and R4" is hydrogen or where q is l and W is oxygen each R4 may also represent a Cl 4 hydroxyalkyl group) and the metal chelates and the salts thereof.
Particularly preferred compounds according to the invention include those of formulae Ij to Io wherein R6 is CH2COOH and the chelates, e.g. with Gd3+, and salts thereof.
Viewed from a further aspect, the invention also provides a process for the preparation of the compounds of the invention, said process comprising one or more o^
the following steps:

(a) reacting a compound of formula II

Rl (CR2 R3 )n[X (CR2 R3 )n]mRl (II) (where Rl to R3 are as defined for Rl to R3 or are protected Rl to R groups, and X' is a group X or a protected group X with the proviso that at least one X
group is of formula NH or (CR2 R )pNH2) with a compound of formula III

LV-(cR2 R3 ) ~Y' (III) (where Y' is a group Y or a protected group Y, R2 and R are as hereinbefore defined and Lv is a leaving group for example a halogen atom, e.g. bromine or chlorine or a tosylate group) and if necessary subse~uently removing any protecting groups used; and (b) converting a compound of formula I into a chelate complex or salt thereof.

The compounds of formula II are known from tne literature or may be prepared in a number of ways using 207~71 WO91/lO~S PCT/EP91/00126 .

techniques known from the literature or analogous tG~
literature described techniques. Thus for example such compounds may be prepared by condensing mono or bifunctional heterocyclic compounds of formula IVa or IVb /~ `~ ~ R~ c) Rl ( CR~ R ) n-l (CR R
~(C 2' 3, ~ N (CR R )n_lCoR3 (IVb) (where R2 , R3 and R4 are as defined for R2 to R4 or are protected R2 to R4 groups and R12 is hydrogen, an amine protecting group or a group (CR R )n 1 CoR3 ) with a linking molecule of formula V

H[X"(CR2 R3 )n]iX"H (V) (where i is 1 to 5, R2 and R3 are as hereinbefore defined, mid-chain X" groups, if any are groups X' and end of chain X" groups are oxygen, sulphur or ring nitrogen atoms or, preferably, NH groups) followed if necessary by removal of any protecting groups and if necessary by reduction.
The compounds of formula II may also be prepared by activating starting compounds of formula V, e.g. by tosylation, and condensing the product with a mono or bifunctional heterocyclic compound of formulae VI or VII

2~171 . .~
~091/10~5 PCT/EP91/00126 ,((~R4' (VI) R13 2' 3' Lv 2'R3' R13 N~ ~N-(CR2 R3 )n Lv (VII) (CR R )n (where Rl3 is hydrogen, an amine protecting group or a group (CR2 R3 )nLv), followed by removal of the tosyl and other protecting groups.
Thus for e~ample linear or cyclic compounds of ~ formula II can be prepared using the following reaction ; schemes.
(A) 2CH2CH2NH2 E~h--O O
b~ ~Y
. ~' N~ (b) NaBH4 ~NH HN~
~J~ J

SUBSTITUTF SI~EET

, ~ .

207417~ -W O 91tlO643 PC~r/EP91/00126 (Bl) .
H "~,,H +NH2CH2CH2NH2 ( a) CaCl2 O O

b) NaBH~ /~
Ethanol ~NH HN~
NH HN
~ N ~J

(B2) `1 + /~ CH3CN
~ ` N~bNH2 NH NH2 O O Ambient temperature ., .

[~N N~ N~5~
. NH HN ~ , ~ Na~H
['IN~I~ ~ `~N' Ethano~

NH HN
NH HN
(NH HN) ~ .

SUBSTlTUT' S~EET

.. .. ~ . . ..

~07~71 .
1064~ - 19 - PCr/EP91/00126 ~C) ~H 2 2 2 2~H2NH2 R2 P~

N NH NH NH N
(D~
~ (d)TsCl NH2 NH NH2 EthanolTsNH NTs NHTs Wat~r NaOH
(e) K2C03 + ~ _ K NTs NTs NTs K
DMF
Ambient temperature ( VIII ) If) DMF ,~, ,~ (VIII) , ~ 2l~ hours~ ~l! N~
N temperature NTs TsN
Br Br ~ ~N~

(9) HBr/HOAc rH HN s Phenol (E) i~ ~h) DMF
~N N~, (VII) OTs TsO
G~ (IX) Q
~N N~ (9) ~N N~
NTs TsN ~ NH HN
~N~
Ts H
' SUBSTITUTE SHEET

.:

WO91/10~ PCT/EP91/00126 (IX)+ Na+-NTs TsN~Na+ (h) Q 1~
~N N~ ( 9) N N~
LNTS TSNJ [~NH HNJ
\ - \J
;

(G) R~R16 ~ N~N~ CaCl2/Ethanol ' (X) ~N~ NaBH4 ~N~
R~ R16 R16= H orCH3 z= 1 or2 Compounds of formula II containing a ( CR2R3 ) n -N ~ ~ N-( CR2R3 ) n ~

group may be prepared by condensing a linear compound having active groups at each end with a compound of formula ~ ( CR2R3 ) n HN HN
( CR2R3 ) n SUBSTITUTE S!tEET

2~171 .~091/10~ PCT/EP91/00126 for example as follows (H) ~ BocOBoc ~/ \~
NH2 NH NH2NH Nl INH
Boc Boc Boc 1) NaH 1 XI) ( Xl) ., MsON N N OMs 2)C~b~ Boc Boc Boc 0 ~ XII) 3) ~lsC [

H N ,NH ~N~
~XII) Boc--N N-Boc (XIII) Boc N~N
IXIII) ~NH3 (XIV) The active linear compound of formula XII may of course be prepared by other routes, e.g.

SVE3ST1TU~E SH~:ET

207~171 WO91/10~ PCT/EP91/00126 ~BocOBoc ~ MsCl ~_~
H2N OH BocNH OH BocNH OMs t~ i~ A MsCl HO NH OH HO N OH
IXV) XII) MsO N OMs Base Boc NaH

Compounds of formula II containing a ( CR2R3 ) n \
-N N-~ (CR2R3~ /

group can also be prepared by condensing the corresponding compound in which one of these (CR2R3) bridges is missing and the nitrogens carry hydrogens instead with a compound of formula LV-tcR2 R3 )nLv, for example as follows ~ F~
~NH HN) Br(CH2~2Br ~N N~
NH HN NH HN
\J

This is described for example in J.Chem. Soc. Chem.
Commun. 1982,277.
In the reactions mentioned above, a starting material containing more than one heterocyclic ring may of course be used in place of the compound of formulae IVa,IVb,V,VI and VII.

SUBSTITUTE S~ET

2~ 171 ~ `
~091/10~5 PCT/EP91/00126 This is exemplified by the following scheme:
Gf,~_ hb, 0\~ oH

~ /~
~~ H J~ ~
^~ OH O~ OH
rS C~ ~ ~o~, 'S~ ~
f ~ f~ N ~~ ' GTs OTs ' I \ ~L, ~r, N~
rS
~Ts T~ ~ J

~. Nl~
~ ' Combinations and extensions of these procedures may be used to prepare further compounds of formula II, e.g.
by condensing a compound of formula VIIIB
H~X"(CR2 R3 )n]m lX"H (VIIIB) with a compound of formula IX
Lv-(CR2 R3 )n-X'-(CR R )n-Lv (IX) or a compound of formula IXB
Ts-[X"(CR2 R3 )n]m lX" Ts (IXB) 207~171

5 PCT/EP91/00126 with a compound of formula XI

Lv-(CR2 R3 )n-Lv ~XI) followed by removal of the tosyl groups.

This may be illustrated by the reaction schemes:
( ~X) I TsC~ /E~o ~011 /H, . ~ ~`JaH ( ~ Nrs TsN ~ )~
x 1 ~ ) ' r~ c~ r----~r~o~s , (x~

~rST~

, ~ 9 ) HN

(~) ~-0 0 (XII)__ ~

T' N )~ ( N~l Hl`l )-\~/ ~ _ I

2~7~17~
,091/10~; - 25 - P~r/EP91/00126 The precursors of formula II for dimeric macrocyclic chelants - i.e. compounds wherein two R4 groups on a cyclic X group together represent a group ( CR2R3 ) n. 1 [ X ( CR2R3 ) n ~ m- 1 ( CR2R3 ) n 1 ~ C an be prepared for example by a condensation equivalent to those o~ the schemes above usln~ a tetrafunctional precursor for the cyclic X group and bifunctional co-reagents. It may be desirable to utili2e aromatic tetrafunctional precursors and subsequently to reduce the product, e.g. by high pressure catalytlc hydrogenation. Thus compounds of formula II may be prepared ~y the following scheme:
IL~

~ ~ H2/Pd-C H2N~N~NH2 NC N CN Ethanol H2N N NH2 OCH~ CHO
N Boc ,~ ~Nl~J NaBH~
high dilution or 200 mol% template M2 ~NJ~ or H2/Pd-C
( M2+= Cd2+ Ba2+, Pb2+ etc )~ Methanol N N
or ethanol as solvent ~NH~
.
` ~NH~ ~NI~\>
NH H~ NH HN
~¢~ reduction ~NH~

NH HN NH H N
<~NH~ ~,NH

Further reaction schemes for the production of compounds of formula II will be evident to the skilled chemist from the literature, e.g. Tabushi et al. Tetr.

~1 IP~C'`lTl ~Tr .CUF~

.

;.

2~7~71 W091/10~5 PCT/EP9l/00126 . - 26 -Lett. 4339 (1976) and 1049 (1977), Richmann et al. JACS
96: 2268 (1974), Nelson, Pure and Applied Chemistry 52:
461-476 (1980). Moi et al. JACS 110: 6266 (1988), ~
EP-A-287465 (Guerbet), Stetter et al. Tetrahedron ~:
767 (1981), EP- A-232751 (Squibb), J. Chem. Soc. Commun.
277 (1982). Hancock et al. JACS 110: 2788-2794 (1988), Smith et al. JACS 111: 7437-7443 (1989) and the references listed therein.
To introduce a (CR2R )pY group onto a compound of formula II using the precedure of step (a) may be effected in an aqueous, preferably basic, medium, for example by using a halocarboxylic acid Hal(CR2 R3 )p-COOH or a metal, e.g. Li, salt thereof (where Hal is ~romine or chlorine) followed by amidation or esterification of the carboxyl group.
The introduction of (CR2R3)pY moiety other than a carboxylic acid residue may for example be performed as follows:
a) To introduce a phosphonic acid moiety, the general method for synthesis of alpha-aminophosphonic acids described by K.Moedritzer et al. in J.Org.Chem 31: 1603 (1966) may be used.

R17NH CH2O R NCHzPO3H2 ______~

(XVII) (XVIII) (of formula II) (of formula I) (where R17NCH2Y is a compound o. formula I).

: : :
.. ; :-.

,~091/10~5 PCT/EP91/00126 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 Inor~. Chem. 27: 474 (1988) may be used.
~o //o 1~0h11R2 /~
R ~ ~ ~ --- ~ R ~ R O H
~ C O G 1~

(where RlN(CH2COOH)CH2Y is a compound of formula I).

c) To introduce a sulfonic acid moiety, s-~nthesis may be performed by alkylation of an amino function for example with iodomethanesulfonic acid R17NH ICH2S02H Rl NCH2S02H

(XVII) (XXI) Amide derivatives of formula I may produced from the oligo acids by methods analogous to those of EP-A-250358 or of EP-A-299795. Furthermore hydrophilic substituents on the skeleton of the linear or cyclic chelants of formula I may be introduced by methods `~

.
..

2~7 ~7 1 ~t~
WO91/10~5 PCT/EP91/00126 analogous to those of EP-A-299795.
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 Y or Rl to R4 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 metal chelates and salts thereof form a further as?ect o~ the present invention.
The lin~age o_ a compound of formula I to a macromolecule or bac~bone polymer may be effected by any of the conventional methods such as the carbodiimide method, 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 W0-A-89/06979.
Salt and chelate formation may be performed in a conventional manner.
The chelating agents of the formula I (as defined above but with the deletion of the second proviso) 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 uses of these metal chelates form a further aspect of the present invention.

' . ~. . . .

~'74~7~

. .
WO91/10~ PCT/EP91/00126 Salts or chelate complexes of the compounds of the invention containing a heavy metal atom or ion are particularly useful in diagnostic imaging or therap~.
Especially preferred are salts or complexes with metals of atomic numbers 20-32,42-~4,49 and 57 to 83, especially Gd, Dy and Yb. 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 , Mn2 and Dy3 are particularly preferred.
Chelates of ions Ot these m~als s?ecifically listed above with chelants of formula I (defined as above with the exclusion of the second proviso) or their salts with physiologically tolerable counterions are particularly useful for the diagnostic imaging procedures mentioned herein and they and their use are deemed to fall within the scope of the invention and references to chelates of compounds of formula I herein are consequently to be taken to include such chelates.
For use as contrast agents in MRI, 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 For use in scintigraphy and radiotherapy, the ; chelated metal species must of course be radioactive and ` any conventional complexable radioactive metal isotope, ;i such as 99mTc or lllIn for example, may be used. For radiotherapy, the chelating agent may be in the form of a metal chelate with for example l53Sm, 67Cu or 90Y~

i .'' ~ - ~

.

207~
W091/10~ PCTtEP9l/00126 ~ - 30 -For use in detoxification of heavy metals, the chelating agent must be in weak complex or 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 char~e, 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, su~stituted ammonium, alkali metal or alkallne earth metal (e.g. calcium) cation or an anion deriving from an inor~anic or organic acid. In this regard, meglumine salts are particulzrly preferred.
Viewed rrom a further aspect, the present invention provides a diagnostic or therapeutic composition comprising a metal chelate, whereof the chelating entity is the residue of a compound of formula I 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 ~ormulation aids, for example stablizers, antioxidants, osmolality adjusting agents, buffers, pH adjusting agents, etc. and may ~e in a form suitable for parenteral or enteral administration, for example injection or infusion or "~ ' . :.;, : , , . 20~171 ~091/10~ PCT/EP91/00126 ~ - 31 -administration directly into a body cavity having an external escape duct, for example the gastrointestinal tract, the bladder or the uterus. Thus the compositlon;
of the present invention may be in conventional pharmaceutical administration forms such as tablets, capsules, powders, solutions, suspensions, dispersions, syrups, suppositories, etc; however, solutions, suspensions and dispersions in physiologically acceptable carrier media, for example water for injections, will generally be preferred.
The compounds according to the invention may therefore ~e formulated for administration using physiologically acceptable carriers or excipients in a manner fully within the skill OI the 2-_. For example, the compounds, optionally with the addition of pharmaceutically acceptable excipients, may be suspended or dissolved in an aqueous medium, with the resulting solution or suspension then being sterilized. Suitable additives include, for example, physiologically biocompatible buffers (as for example, tromethamine hydrochloride), additions (e.g., O.Ol to lO mole percent) of chelants (such as, for example, DTPA, DTPA-bisamide or non-complexed chelants of formula I) or calcium chelate complexes (as for example calcium D-'A, CaNaDTPA-bisamide, calcium salts or chelates of chelants of formula I), or, optionally, additions (e.g., l to 50 mole percent) of calcium of sodium salts (for example, calcium chloride, calcium ascor~ate, calcium gluconate or calcium lactate combined with metal chelate complexes of chelants formula I and the like).
If the compound~ are to be formulated in suspension form, e.g., in water or physiological saline for oral administration, a small amount of soluble chelate may -e mixed with one or more of the inactive ingredients traditionally present in oral solutions and/or surfactants and/or aromatics for flavouring.
.

207~171 ", . ..
WO91~10~ PCT/EP91/00126 For MRI and for X-ray imaging of some portions of the body the most preferred mode for administering metal chelates as contrast agents is parentral, e.g., intravenous administration. Parenterally administrable forms, e.g., intravenous solutions, should be sterile and free from physiologically unacceptable agents, and should have low os~olality to minimize irritation or other adverse effects upon administration, and thus the contrast medium should preferably be isotonic or slightly hypertonic. Suitable vehicles include aqueous vehicles customarily used for administering parenteral solutions such as Sodium Chloride Injection, Ringer's Injection, Dextrose Injection, Dextrose and Sodium Chloride InJe_tior., Lactated Rin~er's Injection and other solutions such as are described in Remington's Pharmaceutical Sciences, 15th ed., Easton: Mack Publishing Co., pages. 1405-1412 and 1461-1487 (1975) and The Nati~nal Formulary XIV, 14th ed. Washington:
American Pharmaceutical Association (1975). The solutions can contain preservatives, antimicrobial agents, buffers and antioxidants conventionally used for parenteral solutions, excipients and other additives which are compatible with the chelates and which will not interfere with the manufacture, storage or use of products.
Where the diagnostic or therapeutic agent comprises a chelate or salt of a toxic metal species, e.g. a heavy metal ion, it may be desirable to include within the formulation a slight excess of the chelating agent, e.g. as discussed by Schering in ~E-A-3640708, or more preferably a slight excess of the calcium salt of such a chelating agent. 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 : ' ' ' , .' ' ,.~ : . '' ~7~t'71 ~091/10~; PCT/EP91/00126 more concentrated form for dilution prior to administration. The diagnostic agent of the invention may conveniently be administered in amounts of from ~10 3 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 ~e 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, whlch method comprises administering to said body a diagnos~ic agen~ accordin~
to the present invention and generating an X-ray, MR, ultrasound or scintigraphic image of at least a part said body.
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 accorqing 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 generationl detoxification or radiotherapy practised on the human or non-human animal body.

' ' ~' .
' ::
, . .

207 ~
f "~, WO91/lO~S PCT/EP9t/00126 Viewed from a still further aspect, the present invention provldes a process ~or the preparation of the metal chelates o~ the invention which process comprises admixing in a solvent a compound of formula I or a salt (e.g. the sodium salt) or chelate therecf together with an at least sparingly soluble compound of said metal, for example a chloride, oxide, acetate 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 accept2ble salt thereof, together wilh at least one pharmaceutical or veterinary carrie- or excipien~.
Viewed from a yet still rurther 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 weak complex or 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 Examples. All ratios and percentages given herein are by weight and all temperatures are in degrees Celsius unless otherwise indicated.

, :, ' , :: - ' ~O91/10~5 PCT/EP91/00126 Exam~le 1 [l8]N6H8o4(Py)2 ~q ~N~
HOOC--N N rCOOH

~N N~
HOOC--I~,N~ COOH
~J

~ (a) Ca2~ ~2 Cl-.3H20 .. , 1~1 ~Ca[18~N6H4(PY)2]Cl2 3H20 i To a stired solution of 2,6-diformyl-pyridine (1.306 g, 9.662 mmol) and calcium chloride dihydrate (0.71 g, 4.83 mmol) in 80 mL of methanol was added ethylenediamine (0.646 mL, 9.662 mmol). The solut on was refluxed for 3 hours, stirred at ambient temperature for 15 hours, and stripped to dryness. The resulting solid was taken up in lO mL of ethanol, and ethyl acetate added until precipitation ceased, giving 2.214 g (94%) of the title SUBSTITUTE SH1~ET

.

, ~ ' , . .
.. . .

2074171 ~s~
WO9l/10~5 PCT/EP9l/00126 product as the trihydrate.
lH NMR(MeOD): ~ 3.9(s, 8H), 7.85-8.23(m, 6H), 8.67(s, 4H).

(b) [l8]N6H8(PY)2 ~1 ~ ' H ~
J
NH HN
~,~J

To a stirred solution of [Ca~18]N6H~(py)2]C12.3H2O
(500mg, 0.93 mmol) in 50 ml of ethanol at ambient temperature was added sodiu~ borohydride (0.2184 mg, 5.58 mmol). The mixture was refluxed for 3 hours, stirred at ambient temperature overnight, stripped to dryness, and diluted with 100 mL of water. The water layer was extracted with methylene chloride (2 x 250 mL) and the combined organic layers dried over K2CO2.
Evaporation of the solvent gave 162 mg (52%) of the title ~roduct as a white solid.
1H NMR (MeOD) :C 2.73(s, 8H), 2.80-3.0(br s, 4H), 3.78(s, 8H), 6.90-7.60(m, 6H).

;.. , , ~, . . . .
.
. -, ;; ~ ' '' '' - ' ' ': ' r ~ 2 ~ 7 1 ~091/10~5 PCT/EP91/00126 (c) r 181N6_8o4(py)2 [18]N6H8(py)2 (162 mg, 0.49 mmol) in 50 mL of ethanol/water (1/1) is placed in a 100 mL three nec}
round-botto~ flask equipped with two addition funnels, pH electrode, thermometer, and stir bar. NaOH (199 mg, 4.98 mmol) and BrCH2C02H (346 mg, 2.49 mmol) are each dissolved in 10 mL of water and the resulting solutions placed in the two addition funnels. The solution of NaOH is added to the amine solution to bring the p~: to 10.5. The temperature is raised to 50C and the BrCH2CO2H and NaOH solutions are added concurrentl~ ove~
a 24 hour period maintaining the pH at 'l during th~
addition. When the pH no longer drops, the reac~ic..
mixture is stirred at 75C for 4 hours, cooled to ambient temperature and stripped to dyness. The solid is taken up in 5 mL of water, the pH adjusted to 3 and the solution applied to AG50-X8(200-400 mesh, H ) resin and the titl~ ~roduct eluted with lN NH40H.

.: Exam~le 2 ~ [18](Me)4N6H404(py)2 ~N
~,ooc ¦ ¦ ~coo~
: ~N

H O O C ~ C C ^ I I
~'J

`: _ ~ , ." .' ., `
.~ '~ ' ` :'' ~' . .

20741'71 W091/10~5 PCT/EP91/00126 (a) [Ca[l8](Me)4N6(py)2]cl2.6H2o C u 1 ~ ) 2 C I . 6 H ~ O

J~N~
I ~,J

To a stirred solution of 2,6-diacetyl-pyrldine (~o.o g, 0.306 mol) and calcium chloride dihydrate (22.49 g, 0.153 mol) in 600 mL of methanol was added ethylenediamine (20.42 mL, 0.306 mol). The solution was heated at 55-C for 3 hours and then stirred at 25C for 15 hours and stripped to dryness to leave a pale yellow-orange solid. The addition of ethanol (200 ml) followed by methylene chloride (200 mL) produced 60 g (66%) of a pale yellow solid isolated as the hexahydrate. 1H NMR (MeOD) :~ 2.56(s, 12~), 3.98(s, 8H), 8.18-8.26(m, 6H). FAB Mass Spectrum, m/z : 449 (MH -Cl), 413 (MH -2Cl).

[18](Me)4N6H4(PY)2 2H2o 1~1 ,N H H 'I

` ~ H H 1 ,1~,~.1 .

- ~

``

2 ~ 7 1 ^' WO91/10~5 PCT/EP91/00126 To a stirred solution of [Ca[18](Me)4N6(py)2]C12.6H20 (20 g, 33.9 mmol) in 600 mL of ethanol at ambient temperature was added sodium borohydride (9.2 g, 242~
mmol). The mixture was refluxed for 6 hours, cooled to ambient temperature, stripped to dryness and diluted with 100 mL of water. After adjusting the pH to 10, the water layer was extracted with methylene chloride (3 x 200 mL) and the combined organic layer dried over K2CG3.
Evaporation of the solvent gave a pale yellow solid which was triturated with ether and collected by suction filtration to glve 8.61 g (58%) of the title product as the dihydrate. H NMR (CDC13) :~ 1.24-1.52 (m, 12H), ~.1-2.8 (m, 12H), 2.7-2.9 (m, 4H), 6.9-7.7 (ll~l 6H).
FAB Mass Spectrum, m/z : 383 (MH ).

(c) rl8lrMe)4--H40-(pv)2 ~;
[18](Me)4N6H404(py)2.2H20 (8-00 g, 19 mmol) in 250 ml of j ethanol/water (1/1) was placed in a 500 ml three neck ; round-bottom flask equipped with two addition funnels, i pH electrode, thermometer, and stir bar. NaOH (7.66 g, 191 mmol) and BrCH2C02H (13.28 g, 95.6 mmol) were each dissolved in 30 ml of water and the resulting solutions placed in the two addition funnels. The solution of NaOH was added to the amine solution to bring the pH to 10.5. The temperature was raised to 50C and the BrCH2C02H and NaOH solutions were added concurrently over a 24 hour period maintaining the pH at 11 during the addition. When the pH no longer dropped the reaction mixture was stirred at 75C for 4 hours, cooled to ambient temperature and stripped to dryness. The solid was dissolved in 30 ml of water and adjusted to pH
3 using lN NaOH. The solution was applied to AG50-X8 (200-400 mesh, H ) resin and the product eluted with lN
NH40H to yield 10.93 g of the title product as the ammonium salt.

207~17~
W09ltlO~ PCT/EP91/00126 13c N~R(D20) :~ (ppm) 15.58, 48.83, 54.26, 60.97, 121.24, 137.5, 159.80, 172.52.

Example 3 [12]N403(py) H!:)OC I~C;~Or /N N
~ '~\' ~Oi3H

a) 2 6-Di(bromomethyl~pvridine 2,6-Di(hydroxymethyl)pyridine (10.0 g; 71.8 mmol) and hydrobromic acid (42% solution in water; lOo mi, 70 mmol) were heated under reflux for 2 hours. The resulting solution was cooled to 0C, neutralized by slow addition of a 40% w/w solution of sodium hydroxide in water (87 ml), diluted with water (200 ml) and extracted with dichloromethane (5xlOO ml). The combined organic phases were concentrated in vacuo to yield a red solid (about 10 g). This was chromatographed on silica gel (170 g) and eluted with dichloromethane to yield 3.75 g (20%) of the title ~roduct.
H NMR(CDC13):~ 7.69(t, lH), 7.35(d, 2H), ~.51(s, ~H).

':: , ,` , ,: . ' .
, .
.. . . . . .
.. . ... .

- 2~7~171 ~O91/10~5 PCT/EP91/00126 . - 41 -b) [12~N4(py)(Ts)3 ~,1 1'--~ N ,~A~l 1`1 T s T s N
>
\ ~ ,/

R5~_ ~ A

To ~ solution of the tritosylate of diethylenetriamine (4.59 g; 8.113 mmol) in dimethylformamide (100 mL) heated at llO C, was added NaH (60% dispersion: 0.75 g) under a nitrogen atompshere. The resultant, white suspension, and also a solution of 2,6-ditbromo-methyl)pyridine (1.5 g; 8.113 mmol) in DMF (80 ml) at 110C were dripped separately and simultaneously into DMF (100 mL) also maintained at 110C. After 2 1/2 hours of vigorous stirring at this temperature, the solution was cooled and then concentrated to dryness in vacuo. Water (150 ml) was added and the beige precipitate collected by suction filtration.
Dichloromethane (250 mL) was added to the solid, followed by water (200 mL), and after sha~ing the organic phase collected via a separating funnel. The aqueous phase was extracted with dichloromethane (2X100 mL) and the combined organic fractions dried ~MgS0~) and concentrated in vacuo to a solid (about 5.6g).
Purification on silica gel (200 g) eluting with 2a74l7l WO91/10~5 PCTtEP91/00126 chloroform/acetone (95:5) afforded the title product as a white crystalline solid (2.43 g; 45%).
lH NMR(CDC13) :~ 7.24-7.74(m, 15H); 4.26 (s, 3.3(t, 4H); 2.71(s, 4H); 2.4(d, 9H).

Route B

2,6-Di(bromomethyl)pyridine (5.0 g; 19 mmol; 0.86 eq) in dimethylformamide (200 ml) was dripped over a period o-10 hours into a mixture of the tritosylate of diethylenetriamine (12.72 g; 22 mmol) and pot2ssiu~
carbonate (7.154 g; 58 mmol~ in DMF (3,~ mLj, s~irring a~ 25C. After stirring for 15 hours 2_ 2~c _he e~cess potassium carbonate was removed by suc~ion filtration and the filtrate concentrated to about 120 mL. water (250 mL) was added and the white precipitate removed by suction filtration and washed with water until the ensuing filtrate was neutral pH. Excess tritosylate was precipitated by adding chloroform to the solid residue, the precipitate was removed by suction filtration and the filtrate concentrated in vacuo to a white solid (16 g). This solid was chromatographed on silica gel (600 g) and eluted with chloroform to yield 12.3 g of the title ~roduct (97% with respect to 2,6-dibromomethylpyridine; 82~ with respect to diethylenetriamine tritosylate).
lH NMR(CDC13):~ 7.24-7.74(m, 15H); 4.26(s, 4H); 3.30(t, 4H); 2.71(s, 4H): 2.40(d, 9H).

: . . , : .
' ''' ' ` . ';: ' , '" - . . .
: ' , ' ' :

20~17~
,~/0 91tlO645 P~/EP91/00126 (c) [12]N4(py) ~`1 NH HN
~\_ ,,N~

H

A mixture of [12]N~,(py) (Ts)3 (56-6 g; 84 mmol) and phenol (90 g) in a solution of HBr in acetic acid (30 w/w; 1000 mL) was stirred at 80C for 48 hours. The reaction mixture was allowed to cool and was then poured into ice-water (1000 mL). With vigorous stirring, diethylether (1500 mL) was added, followed by ethanol (1500 mL). After 5 minutes, the mixture was allowed to stand, whereupon a white precipitate began to settle.
The solid was removed by suction filtration, washed with ethanol and dried under vacuum. The off-white solid (about 38 g) was dissolved in water (100 mL) and pa~sed through a bed of AG lX-8 anion-exchange resin (hydroxide form, 560 g). The water was then removed by roto-evaporation to yield the title product as a white solid (15 g; 8S%).
lH NMR(D2O) :~ 7.5(t, lH); 7.0(d, 2H); 3.76(s, 4H);
2.60(s, 4H); 1.8(s, 4H).
Mass Spectrum : (M+H ) 207.3.

(d) ~12]N4O3(py~

Chloroacetic acid (24 g; 254 mmol) in water (500 ml) was adjusted to pH 7 with NaOH solution. This was added dropwise to a solution of [12]N4(py) (15.00 g; 727 mmol) in water maintained at a temperature of 95C. During 2a7~7l WO91/10~5 PCT/EP91/00126 the addition, the pH is maintained at pH 9-10 by the addition of lN NaOH solution. When addition was complete, the reaction mixture was adjusted to p~l 3 using lN HCl solution and concentrated to a solid.
Water (150 mL) was added, the pH readjusted to p~ 7 and the sample applied to a bed of AG lX-8 anion-exchange resin (100-200 mesh, acetate form, 1.5 L). The columr.
was eluted with an aqueous acetic acid solution to yield 10.2 g (37~) of the title ~roduct.
H NMR(D2O) :~ 7.72(t, lH); 7.2(d, 2~ .56(s, ~H);
3.78(s, 4H); 2.76(s, 4H).

-~ Exam~le 4 1 4 7 10.13-Pentaazabicvclo~11.2.21he~tadecane-4 7.10-trislacetic acid) ([151N503(pip!) -rN N~
- HOOC ~ ~ COOH
N N
~\~N~
, ~OOH

a) N,5~Ul~L~Q~yLlethanolamine ~, , To a solution of tosyl chloride (100 g, 520 mmol) in 5G
ml of dry pyridine, was added dropwise ethanolamine (15 ml, 250 mmol) in 65 ml of pyridine. The temperature was held below 5C, and vigorous stirring was maintained together with a steady flow of nitrogen gas. After the addition was completed, the mixture was allowed to stir at ambient temperature overnight. The solution was then cooled to 5C, and 500 mL of ice-water was added slowly.

~ ' ' ,' .~` -WO91/10~ PCT/EP91/00126 Precipitated solid was separated by filtration andwashed with water. Crystallization from methanol ~150 ml) gave 56.4 g (62~) of the title produc .
H NMR(CDCl3):~ 2.45(s, 3H), 2.6(s, 3H), 3.2(m, 2H), 4.l(t, 2H), 5.0(t, lH), 7.3-7.7(m, 8H).

b) N-Tosylaziridine - To a vigorously stirred suspension of N,O-bis(tosyl)-ethanolamine (40 g, 110 mmol) in S00 ml of toluene was added KOH (20% solution in wàter, 140 ml) over a period of 0.5 hour. After stirring for an additional 2 hours, the water phase was removed, and the organic layer was washed with water (3 x 150 ml) and dried over MgSO4.
After filtration, toluene was evaporated to give 20.1 g (92.5%) of the title ~roduct.
H NMR(CDCl3):~ 2.4(s, 4H), 2.5(s, 3H), 7.4(d, 2H), 7.8(d, 2H).

c) N,N'-Bis(N-tosylaminoethyl)piperazine ' I~ ' .

~N N~
/
, ~ ~
N H T s T s N H

Piperazine (22.0 g, 255 mmol) and N-tosylaziridine (105.5 g, 530 mmol) were refluxed in 650 ml of acetonitrile for .8 hours. After the solution had been cooled to ambient temperature, the precipitated product was separated by filtration, washed with cold 20~ ~ 7 ~
WO91~10~ PCT/EP9t/00126 acetonitrile and dried in vacuo to yield 83.7 g (68%~ of the title product.
H NMR(CDCl3):~ 2.5(s, 6H), 2-4(t~ 4H), 2.~(t~ 4H)~, 2.3(s, 8H).

d) 4 7.10-Tris(tosyl)-1 4 7.10 13-pentaazabicvclo-r 11 . 2.2]-heptadecane N,N'-Bis(N-tosylaminoethyl)piperazine (4.0 g, 8.7 mmol) was dissolved in 200 ml of DMF, and Cs2CO3 (6.0 g, lo.
mmol) was added. The mixture was stirred under a nitrogen atmosphere at 110C for 2 hours before ~,N-bis(tosyloxyethyl)amine (~.9 g, 8.6 mmol - p-epar~i as described by Guerbet in EP-A-287465) in 80 mi of DlIF
was added dropwise over 0.5 hour. Stirring at llO'C was maintained for an additional 3 hours. The reaction mixture was evaporated to dryness. The resulting solid was stirred in C~2Cl2 overnight. Undissolved material was filtered, and the solution was evaporated to dryness. The resulting solid was stirred in acetone for 19 hours. The precipitated product was separated by filtration to yield 1.3 g t21~) of the title product.
3C NMR(CDCl3):~ 21.8, 47.8, 49.6, 50.3, 57.9, 127.6, 130.1, 136.0, 143.8.

e) 1,4,7,_10 13-Pentaazabicyclo L11.2.2lhePtadecane HBr in acetic acid (32~ w/w, 82 ml) was added to a mixture of phenol (4.3 g, 46 mmol) and 4,7,10-tris(tosyl)-1,4,7,10,13-pentaazabicyclo[11.2.2]hepta-decane (2.06 g, 3 mmol). The solution was stirred at 70'C for 24 hours. The temperature was raised to 85~C, and stirring was continued for 5.5 hours. The solution was allowed to cool to ambient temperature.
Precipitated solid was collected and triturated with ether and cold ethanol. The solid was then dissolved in water and passed down a Dowex AGI-8X column. Water was . . . , ~
, ., " .

,~091/10~ PCT/EP91/00126 , - 47 -removed. Drying of the solid overnight yielded 0.32 g (50%) of the title_ roduct.
H NMR(CDCl3):~ 2.4(br s, 12H), 2.7(br s,l2H) f) 1,4,7,10,13-Pentaazabicyclo[11.2.2lheptadcane-4,7,10-tris(acetic acid) (rlSlN5O3(pip)) :.
Bromoacetic acid (2.57 g, 19 mmol) is disolved in water, and LioH (0.77 g, 19 mmol) is carefully added at 5C.
This solution is added to a solution of 1,4,?,10,13-pentaazabicyclo[11.2.2]heptadecane (1.3 g, 5.4 mmol) in water (2.5 ml). The mixture is heated to

6~'C, whlle the pH is held between 9 and 10 with addition of 4 M LioH. After 2 hours, the temperature is increased to 80C. Stirring is maintained at this temperature for 45 minutes following the addition of LioH. The m .ture is then cooled to ambient temperature and neutralized with HBr. The volume is reduced to 2 ml, and then the mixture is loaded onto a Dowex l-X8 column (acetate, 50-lO0 mesh). The material is eluted with deionized water, then lN, 2N, 3N and 4N acetic acid. Fractions containing product are concentrated by rotary evaporation, and repeatedly reconcentrated with several portions of deionized water until the title ~roduct is obtained as an acetate-free solid.

,~ .

.
, ;, ~ , .

, 207~171 WO91/10~5 PCT/EP91/00126 .

Example 5 [15]N503(py)2 H~OC ~ ~OOH

. . ._ The title compound is prepared from 2,6-di(hydroxymethyl)-pyridine, reacted with HBr to form 2-bromomethyl-6-hydroxy-methylpyridine, condensed with 2-aminomethyl-6-hydroxy-methylpyridine, then pertosylated and cyclized with the sodium salt of bistosyl- ethylenediamine, detosylated with HBr and acetic acid and alkylated with chloroacetic acid (see Scheme (I)).

Example 6 N.N"-Bisfpvrid-2-vl-methyl)-diethylenetriamlne-N.N',N"-triacetic acid(Bis(~y)DTTA) HOOC~ ~ ~ rCOOh f=~l~ N N~

~N C O O H ~_ . ~ '' , ' .. .. . ..
: ' ` ' ` ' ,.,.. ' ` ~ .~, . : ' ':' - ` .
. .' ~ ! , .

,' 207~71 WO91/10~5 PCT/EP91/00126 a) N N''-Bis(pyrid-2-yl-methYl)diethylenetriamine Diethylenetriamine (76 g, 0.75 mol) and pyridine-2- ~
carboxaldehyde (174 g, 1.62 mol) in 2.5 L of absolute ethanol were heated for 2 hours at 50C with stirring.
After the reaction mixture was cooled to ambient temperature, 25 g of 10% palladium on charcoal was added and the schiff base hydrogenated at slightly greater than 1 atmosphere of hydrogen, over a 48-hour period.
The catalyst was removed by filtration, the filtrate adjus~e~ to pH ~. with HC1 gas and then lowered to pH l using 12 N HCL. The resulting precipitate was removed by suction filtration, washed with absolute ethanol until the washings were colourless, and recrystallized from 95% ethanol. This hydrochloride salt was then dissolved in 500 mL of water and neutralized with 5 N
NaOH, then raised to pH 12.5, and the free base, the title compound, was extracted with methylene chloride (4 x 500 mL). The methylene chloride solution was dried to give 136 g (65%) of a pale yellow oil. NMR (D2O): ~ 2.46 (s, 8H), 3.55 (s, 4H), 7.10 (m, 4H), 7.55 (t, J=12.5 Hz, 2H), 8.25 (d, J=10 Hz, 2H), 7.50 (t, J=10 Hz, 2H), 8.40 (d, J=10 Hz, 2H). (Preparation of the trihydrochloride salt is also described in Inorg. Chem. 17: 889 (1978)).

b) N.N''-Bis(pyrid-2-yl-methyl)-N.N'.N " -tris(t-butYlcarboxvmethvl)diethvlenetriamine To a solution of N, N''-bis(pyrid-2-yl-methyl)diethylenetriamine (23.6 g, 82.6 mmol) and diisopropylethylamine (53.4 g, 0.4 mol) in 1.2 L of methylene chloride at ambient temperature was added dropwise t-butylbromoacetate (50 g, 0.2 mol) in 300 mL
of methylene chloride. After being stirred for 24 hours, the solution was evaporated to dryness and placed under vacuum for 2 hours to remove excess diisopropylethylamine. The crude solid was taken up in ' `' ' :

2~7~17:~ `

WO91/10~5 PCT/EP91/00126 1.5 L of methylene chloride, washed with 0.2 N NaOH, water t2 x 250 mL), brine (200 mL) and dried (MgSO4).
The methylene chloride was removed, 200 mL oP ethyl ~
acetate added and this solution passed through 300 g of silica gel in a B~chner funnel using EtOAc to elute the product. The pure fractions (TLC: methanol:CH2Cl2 (3:7) were combined to give 40.6 g t79.5%) of the title compound. NMR (CDCl3) S 1.26 (s, 9H), ~ 1.31 (s, 18H), 2.62 (s, 8H), 3.12 (s, 2H), 3.17 (s, 4H), 3.78 (s, 4H),

7.02 (t, J=10 Hz, 2H), 7.35 (d, J=10 Hz, 2H).

c) N N''-Bis(pyrid-2-yl-methyl~diethYlenetriamine-N N' N " -triacetic acid The tris(t-butylcarboxymethyl)ester (24.89g, 0.1 mol) of step (b) was dissolved in a solution of 600 mL of methylene chloride containing 380 mL of trifluoroacetic acid. The solution was stirred for 48 hours, evaporated under reduced pressure and diluted with 50 mL of water.
This solution was applied to 200 mL of AG50-X8 (H~ form, 100-200 mesh) and after washing with water until neutral, the product was eluted with lN NH40H. After removal of NH40H solution, the product was taken up in 24 mL of water, and the solution was adjusted to pH 10 and then applied to AGl-X8 (acetate, 100-200 mesh). The column was washed with three bed volumes of water and the product eluted with 2 N HOAc to-give 12.0 g (69%) of the title product after several lyophilizations. NMR
(D20) ~ 3.02 (t, J=6 Hz, 4H), 3.08 (t, J=6 Hz, 4H), 3.14 (s, 4H), 3.41 (s, 2H), 4.08 (s, 4H), 7.52 tm, 4H), 8.05 (t, J=10 Hz, 4H), 8.40 (d, J=10 Hz, 2H).

: , ..

20~4171 ~O91/10~ - 51 - PCT/EP91/00126 Examp l e 7 [ 17 ] N503 (pip) ~N N

~N N
H O O C ~ C O O H

COOH

The title compound is prepared from 1,4-di(3-aminopropyl)-piperazine and di(hydroxyethyl)~.~ine by the method of Scheme (J) followed by alkylation with bromoacetic acid.

Exam~e &

[12]N4O2(pip) ~N N

--N N--HOOC-- \-- ` CO

_ . _ .~ , : ' . ` ' ` ` '. ~ .. `' `

2~7~71 WO91/10~ PCT/EP91/00126 A) The title com~ound is prepared by reaction of 1,4,7,10-tetraazacyclododecane and 1,2-dibromoethane (according to the method of J. Chem. Soc. Chem. Commun.
227 (1982)), followed by alkylation with bromoacetic acid.

B) The title compound is prepared by reaction of the bis-tosylate of 1l4-di(hydroxyethyl)piperazine with the sodium salt of bistosyl~ ethylenediamine by the method of Scheme (F), followed by alkylation with bromoacetic acid.

E~amF~e g [14]N~O2(pip) ~N NJ
HOOC~ --/ ~COOH

The title c~om~ound is prepared by reaction of the sodium salt of the bistosylate of 1,4-di(3-aminopropyl)-piperazine with mesylated ethan-1,2-diol by the method of scheme (K), followed by alkylation with bromoacetic acid.

~7l7l ~: .
,~09l~l0643 PCT/EP91/00126 Example 10 [15~N502(py) (pip) ~ G~
~N N~
HOOC~ ~` COCH
N N
\\r/N`~/'/
~ ~,J

'' The title compound is prepared by reaction of 2,6-diformyl-pyridine with 1,4-di(2-aminoethyl)piperazine by ~ the method of scheme (G), followed by alkylation with :~ bromoacetic acid.

Example 11 ~15](Me)2N5O2(py)(pip) ,,--N N~, HOOC ( ~ COOH
--~N N
"~, " N~

, " ,'J
~, ,!

~ ' , ' ' . ' ` ' ,'' ~ ,. ,' ' ~ ' ~0~171 WO91/10~5 PCT/EP91/00126 The titl Q ompound is prepared by reaction of 2,6-diacetyl-pyridine with 1,4-di(2-aminoethyl)piperazine by the method of scheme (G), followed by alkylation with bromoacetic acid.

Example 12 [ l~ ] N502 (py) (pip) N !i ~

HQQ'' ~ ,/ CQOH

The title com~ound is prepared by reaction of 2,6-diformyl-pyridine with 1,4-di(3-aminopropyl)piperazine by the method of scheme (G), followed by alkylation with bromoacetic acid.

.
: ' - - .:
~ ` ~ , ' ,': : ' :: . :,. .

2 ~ ~t ~
~091/10~5 PCT/EP91/00126 Example 13 [17](Me)2N5O2(py)(pip) ~N N~

HOOC~ ~ COOH
~N NJ

:;
The title com~ound is prepared by reaction of 2,6-diacetyl-pyridine with 1,4-di(3-aminopropyl)piperazine by the method of scheme (G), followed by alkylation with bromoacetic acid.

Example 14 [24]N8H86(PY)2 ~q HOOC ~ ~ COOH
. ~ ~
~N N~
N N
HOOC~ ~, N~ COOH

SU~3S~17UTE SH~:T

wo~l0l7 ~ 17 1 - 56 - PCT/EP9l/OUI26 : (a) J
~N H H N, ~N N l ~J

Tetraimine and bisimine/bisimidazolidine To a solution of diethylenetriamine (0.76 g, 7.40 mmol) in 200 mL of acetonitrile at ambient temperature diformylpyridine (1.00 g, 7.40 mmol) in 130 mL of acetonitrile was added dropwise over 4 hours. The solution was stirred overnight and the white precipitate formed was removed by filtration, and washed with acetonitrile to yield 1.21 g (81%) of the tetraimine and bisimine/bisimidazolidine ti~l~L~ _ucts as a mixture (about 1:1). 1H NMR (CD30D): ~ 2.5 - 3.75 (m, 17 H);
4.25 (s, 3 H); 7.25 - 7.75 (m, 6 H). FAB mass spectrum, m/z. 405.

': : ' : ~

2~7~171 WO91~10~5 PCT/EP91/00126 . - 57 -(b) [24]N8H8(py)2 ~NH HN, . I "i ~N H H N~
"`

~ N HH t~
,J
~'J

The tetraimine:bisimine/bisimidazolidine (3.00 g, 7.42 mmol) was added to a suspension of sodium borohydride (1.17 g, 31 mmol) in 100 mL of ethanol. The mixture was stirred for 1 hour at ambient temperature, refluxed for 0.5 hours, and then stirred overnight at ambient temperature. The reaction mixture was then stripped to dryness, 20 mL of water was added and the product was extracted with chloroform (6 x 100 mL), and dried (MgS04) to give 2.70 g (88% yield) of the title com~ound as a pale yellow oil. lH NMR (CD30D): ~ 2.55 (br s, 16H,); ~
3.71 (s, 8H); 7.10 (d, J = lO Hz, 4H); ~ 7.55 (t, J = lO
Hz, 2H). .

.- ... . . ..

2n7~l~7l WO91/10~5 PCT/EP91/00126 (cj [24]N8H806(PY)2 HOOC ~ l COOH

,~ t~
" HOOC ~ U COOH

H O O C~ J C O O H
~J

`:
The amine (1.34 g, 3.24 mmol) of step (b) and diisopropylethylamine (3.55 g, 25.9 mmol) were dissolved in 125 mL of methylene chloride and to this was added neat t-butylbromoacetate (4.11 g, 3.40 mL, 21.06 mmol) all at once. The reaction mixture was stirred overnight at ambient temperature, refluxed for 0.5 hour, cooled, and stripped to dryness. The resulting oil was taken up in 400 mL of methylene chloride, washed with water (2 x 100 mL), brine (100 mL) and dried (MgSO4). The product was purified by silica gel chromatography, eluting with methamol: CH2Cl2 (5:95) to yield the hexa-t-butyl ester.
H NMR (CDCl3): 1.36 (br s, 54H); ~ 2.61 (br s, 16H);
3.20 (br s, 12H); ~ 3.75 (br s, 8H); ~ 7.15-7.25 (m, 6H). The material was taken up in 100 mL of methylene chloride and 100 mL of trifluoroacetic acid, stirred overnight and stripped to dryness. The resulting thic~
oil was taken up in 20 mL of water, the pH adjusted to 10.9 using SN NaOH and the solution applied to AGl-X8, (OAc- form) resin and the product eluted with 0.1 N HOAc to yield, after recrystallization from water, 194 mg of the title product. 1H NMR (D20): ~ 2.90 (s, 8H); ~ 3.15 (s, 4H); ~ 3.25 (s, 8H); ~ 3.55 (s, 8H), ~ 4.35 (s, 8H);

. ' .,'~ ~', .

' ' ' ~ , ~ ., ~ .. .. .

2~7~171 , .
WO91/10~5 PCT/EP91/00126 ~ 7.15 (d, J = 10 Hz, 4H); ~ 7.55 (t, J = 10 Hz, 2H).
FAB mass spectrum, m/z: 761.

Example 15 rGdrl81N6Q4 (py) 21Na 5 mL of a 100 mM aqueous solution of [18jN6O4(py)2 (Example 1) and 5 mL of a 100 m~l aqueous solution of GdC13 are mixed thoroughly and the pH is adjusted to pH
6.9 with lN NaOH to yield the title ~roduct.

Exam~le 16 rGd[181(Me)4N6H4O4(~Y)2 5 mL of a lOO mM aqueous solution of [18](Me)4N6O4(py)2 (Example 2) and 5 mL of a lO0 mM aqueous solution of GdC13 are mixed thoroughly and the pH is adjusted to pH
6.9 with lN NaOH to yield the title ~roduct.

The Tl relaxivity in mMls1, measured in water at 10 MHz and 37 C was 1.7.

ExamPle 17 Gd[l21N4(Py)o3 1.902 g (5 mmol) of [12]N403(py) (E~ample 3) was dissolved in water (3 ml). Gd2O3(915 mg; 1.01 eq) was added and the volume made up to 8 ml with water. This was then stirred for 2 hours at 100~C. Using Xylenol orange as an indicator, further [12]N403(py) was added in small aliquots until a negative test result was 2~7~7:L
WO91/10~5 PCT/EP91/00126 achieved. A titration of excess ligand with GdC13 was used to check for less than 0.05% ligand excess. The solution was then diluted to 10 ml with water to pro~uce a 350 mM solution of Gd[12]N403(py). Finally the pH was adjusted to 6.2 ~ith lM ~1aOH.

The Tl and T2 relaxivities of the chelate, in mMlsl measured in water at 10MHz and 37C were respectively 6.99 and 6.23.

Example ~8 Gd[151N_23(~

To a suspension of 1,4,7,10,13-pentaazabicyclo[11.2.2]-heptadecane-4,7,10-tris(acetic acid) (1.0 g, 2.4 mmol) (Example 4) in water (1 ml) is added Gd2O3 (0.24 g, 1.2 mmol) with stirring. The mixture is heated at 75C
overnight. Evaporation to dryness gives the title product.

.
Example 19 (Mn r 181(Me)4_6H4O4(~y)2)Na2 The title compound is prepared analogously to that of Example 16 by reaction of the chelant of Example 2 with MnC12.

.

"' ' "' ' ' ~' , 207~171 . .
WO91/10~ PCT/EP91/00126 Example 20 GdBis(py)DTTA

N,N"-Bis(pyrid-2-yl-methyl)diethylenetriamine~
triacetic acid (2,8719 g, 6.25 mmol) (the compound of Example 6) and gadolinium oxide (1.1328 g, 3.125 mmol) were combined in 15 mL of water and heated at 95C for 4 hours to provide a solution of the desired comple~.
Relaxivity (water) at 10 MHz, 37~C : R1 = 3.65 ~M1sec and R2 = 3.57 mMl secl.

Exam~le 21 (CaBis(py)DTTA~ Na The title com~ound is prepared analogously to that of Example 16 by reaction of the chelant of Example 6 with . CaC12.

Example 22 ,.
Composition comprising GdBis(py)DTTA and CaNa ; Bis(py)DTTA
-- --The compounds of Examples 20 and 21 are admixed in a 95:5 (by weight) ratio and dispersed in water for injections to a Gd content of 400 mM.

2a7~l7l WO91/l0~5 PCT/EP9l/00126 Example 23 Gdtl71N5O3(PiP~

The title chelate is prepared analogously to that of Example 16 by reaction of the chelant of Example 7 with GdC13.

E~am~le 24 Mn[121,~~02 The titl~ c~elate is prepared analogous'y to that o-Example 16 by reaction of the chelanl of Example 8 with MnC12, , Example 25 MnL14~N402 (pip) The title chelate is prepared analogously to that of Example 16 by reaction of the chelant of Example 9 with MnC12 .

Example 26 Mn~5]N5O2(py~tpip) The title chelate is prepared analogously to that of Example 16 by reaction of the chelant of Example 10 with MnC12.

..

~07 ~ 171 ,. ~
WO91/10~5 PCT/EP91/00126 Example 2?

Mn r 151 (Me) 2N52 (t~y~ (E)ip) The title chelate is prepared analo~o~sly to that of Example 16 by reaction of the chelant of Example 11 ~titn MnCl2.
.

Claims (19)

Claims

1. A compound of formula I
R1(CR2R3)n[X(CR2R3)n]mR1 (I) (wherein each X independently represents an oxygen or sulphur atom or a group of formula NA, or (CR2R3)nX(CR2R3)n represents a group of formula E represents COH,NR2,O or S;
each A independently represents a hydrogen atom or a group (CR2R3)pY, (CR2R3)nN[(CR2R3)pY]2 or where two (CR2R3)nY groups on different nitrogens, may together represent a group -(CR2R3)n-;
each Y independently represents a group COZ, SO2Z, POZ2, CON(OH)R2, CH2SR2, CS2R2 or CSZ;
each Z independently represents a group OR or NR2R2;
each G is a 3 or 4 membered chain of carbon atoms and optionally a nitrogen, oxygen or sulphur atom;
each J is a 2 or 3 membered chain of carbon atoms and optionally a nitrogen, oxygen or sulphur atom;
each n is an i teger of 2 to 4, or in a group (CR2R3)n attached to a moiety R1 which represents a hydrogen atom or a group R4 n may also be zero or 1;
m is an integer of 3 to 8;
p is an integer of 1 to 3;
each R1 represents a hydrogen atom or a group R4 or together both groups R1 represent a carbon-carbon bond;
each R2 independently represents a hydrogen atom or a C1-8 alkyl group optionally mono- or poly-substituted by hydroxyl or C1-8 alkoxy groups or NR2R3 may together represent a nitrogen-attached 5 to 7 membered saturated heterocyclic ring optionally containing as a further ring heteroatom a nitrogen, oxygen or sulphur atom and optionally substituted by a group R4;
each R3 independently represents a hydrogen atom or a C1-8 alkyl or C1-8 alkoxy group optionally mono or poly substituted by hydroxy or C1-8 alkoxy groups; and each R4 independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally mono- or poly-hydroxylated C1-8 alkyl, C1-8 alkoxy, (C1-8 alkoxy)-C1-8 alkyl or poly(C1-8 alkoxy)-C1-8 alkyl group, a sulphonate group or a group (CR2R3)pY or two groups R4 on the same ring represent a (CR2R3)n-1 [X(CR2R3)n]m-1 (CR2R3)n-1 group in which case the said ring may be saturated; with the provisos that at least 2 Y groups, are present, that where both groups R1 together form a bond, m is 4 or 5, all n are 2, one X is 2,6-pyridindiyl and the remainder are NCH2COOR2, then at least one R2, R3 or R4 is other than hydrogen, and that either at least one X group comprises an aromatic heterocyclic group or both groups together represent a bond and two (CR2R3)pY
groups together represent a -(CR2R3)n- group or both R1 represent a bond, m is 6 or greater and two X groups separated by at least two other X groups are oxygen or sulphur atoms) or a chelate complex or salt thereof.

2. A compound of formula I as claimed in claim 1 wherein both R1 groups together represent a bond and at least one pair of -(CR2R3)p Y groups together represent a -(CR2R3)n- group, or a chelate complex or salt thereof.

3. A compound of formula I as claimed in claim 1 wherein both R1 groups together represent a bond and at least two moieties (CR2R3)n X (CR2R3)n represent heteroaromatic groups of formula which incorporate at least one ring heteroatom, or a chelate complex or salt thereof.

4. A compound of formula I as claimed in claim 1 wherein both R1 groups together represent a bond, m is at least 6 and two X groups separated by at least two other X groups are oxygen or sulphur atoms, or a chelate complex or salt thereof.

5. A compound of formula I as claimed in any one of claims 1 to 4 wherein each n is 2 or 3, each p is 1, and at least 3 Y groups are present, or a chelate complex or salt thereof.

6. A compound of formula I as claimed in any one of claims 1 to 5 comprising at least one hydrophilic R1, R2 R3 or R4 group, or a chelate complex or salt thereof.

7. A compound of formula I as claimed in any one of claims 1 to 6 of formula Ie, If, Ig, Ih, Ii, Ij, Ik or Il (Ie) (If) (Ig) (Ih) (Ii) (Ij) (Ik) (Il) (where A' is CHR2Y or hydrogen, z is 1 or 2, t is 1 or 2, v is 0, 1, 2, 3 or 4 and each X2 is oxygen or sulphur and R2, R3, R4, X, n, m and Y are as defined in claims 1 to 6), or a chelate complex or salt thereof.

8. A compound of formula I as claimed in any one of claims 1 to 7 of formula In, Io, Ip, Iq, Ir, Is, It, Iu, Iv or IW

(In) (Io) (Ip) (Iq) (Ir) (Is) (It) (Iu) (Iv) (Iw) (where R30 is trimethylene or ethylene, each r is 1 or 2, t is 1 or 2, R2" is hydrogen or methyl and each R6 is a group CH2COZ or CH2CON(OH)R2, and each X2 is oxygen or sulphur), or a chelate complex or salt thereof.

9. A chelate complex as claimed in any one of claims 1 to 8 wherein the chelated species is a paramagnetic or heavy metal ion, or a salt thereof.

10. A diagnostic or therapeutic agent comprising a metal chelate, whereof the chelating entity is the residue of a compound of formula I

R1(CR2R3)n[X(CR2R3)n]mR1 (wherein each X independently represents an oxygen or sulphur atom or a group of formula NA, or (CR2R3)nX(CR2R3)n represents a group of formula E represents COH, NR2, O or S;
each A independently represents a hydrogen atom or a group (CR2R3)pY, (CR2R3)nN[(CR2R3)pY]2 or where two (CR2R3)n Y groups on different nitrogens, may together represent a group -(CR2R3)n-; each Y
independently represents a group COZ, SO2Z, POZ2, CON(OH)R2, CH2SR2, CS2R2 or CSZ; each Z independently represents a group OR2 or NR2R2; each G is a 3 or 4 membered chain of carbon atoms and optionally a nitrogen, oxygen or sulphur atom; each J is a 2 or 3 membered chain of carbon atoms and optionally a nitrogen, oxygen or sulphur atom; n is an integer of 2 to 4, or in a group (CR2R3)n attached to a moiety R1 which represents a hydrogen atom or a group R4 n may also be zero or 1; m is an integer of 3 to 8; p is an integer of 1 to 3; each R1 represents a hydrogen atom or a group R4 or together both groups R1 represent a carbon-carbon bond; each R2 independently represents a hydrogen atom or a C1-8 alkyl group optionally mono- or poly-substituted by hydroxyl or C1-8 alkoxy groups or NR2R2 may together represent a nitrogen-attached 5 to 7 membered saturated heterocyclic ring optionally containing as a further ring heteroatom a nitrogen, oxygen or sulphur atom and optionally substituted by a group R4; each R3 independently represents a hydrogen atom or a C1-8 alkyl or C1-8 alkoxy group optionally mono or poly substituted by hydroxy or C1-8 alkoxy groups; and each R4 independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally mono- or poly-hydroxylated C1-8 alkyl, C18 alkoxy, (C1-8 alkoxy) C1-8 alkyl or poly(C1-8 alkoxy) C1-8 alkyl group, a sulphonate group or a group (CR2R3)pY or two groups R4 on the same ring represent a (CR2R3)n-1 [X(CR2R3)n]m-1 (CR2R3)n-1 group in which case the said ring may be saturated; with the provisos that at least 2 Y groups, are present, and that either at least one X group comprises an aromatic heterocyclic group Q both R1 groups together represent a bond and two (CR2R3)pY groups together represent a -(CR2R3)n- group or both R1 represent a bond, m is 6 or greater and two X groups separated by at least two other X groups are oxygen or sulphur atoms.

11. A composition as claimed in claim 10 wherein the chelating entity is the residue of a compound of formula I as defined in any one of claims 1 to 8.

12. A magnetic resonance imaging contrast enhancing composition as claimed in either of claims 10 and 11 wherein the chelated metal species is selected from the paramagnetic ions of Eu, Gd, Dy, Ho, Cr, Mn and Fe.

WO 91/10645 PCT/EP91/00126 i3. A detoxification agent comprising a weak complex or salt of a compound of formula I (as defined in any one of claims 1 to 8 and 10) with a physiologically acceptable counterion, together with at least one pharmaceutical carrier or excipient.

14. A process for the preparation of compounds as claimed in any one of claims 1 to 9 said process comprising one or more of the following steps:

(a) reacting a compound of formula II

R1'(CR2'R3')n[X'(CR2'R3')n]mR1' (II) (where R1 to R3 are as defined for R1 to R3 in claim 1 or are protected R1 to R3 groups, and X' is a group X as defined in claim 1 or a protected group X, with the proviso that at least one X group is of formula NH or (CR2'R3')pNH2) with a compound of formula III

Lv-(CR2'R3')p-Y' (III) (where Y' is a group Y as defined in claim 1 or a protected group Y, p is as defined in claim 1, R2 and R3 are as hereinbefore defined and Lv is a leaving group) and if necessary subsequently removing any protecting groups used; and (b) converting a compound of formula I into a chelate complex or salt thereof.

15. A process as claimed in claim 14 for the preparation of metal chelate complexes of compounds of formula I which process comprises 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.

16. 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 any one of claims 10 to 12 and generating an X-ray, MR, ultrasound or scintigraphic image of at least a part of said body.

17. 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 of formula I as defined in any one of claims 1 to 8 and 10.

18. A method of heavy metal detoxification practised on the human or non-human animal body, which method comprises administering to said body a weak complex or salt with a physiologically acceptable counterion of a compound of formula I as defined in any one of claims 1 to 8 and 10.

19. The use of compounds of formula I and chelates and salts as defined in any one of claims 1 to 10 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.