High relaxivity gadolinium chelate compounds for use in magnetic resonance imaging

Abstract

The present invention relates to a new class of high relaxivity extracellular gadolinium chelate complexes, to methods of preparing said compounds, and to the use of said compounds as MRI contrast agents.

Claims

1. An aqueous pharmaceutical solution comprising a tetrameric gadolinium compound of general formula (I), ##STR00072## wherein: R.sup.1 represents, independently from each other, a hydrogen atom or a methyl group; R.sup.2 represents, independently from each other, a substituent selected from the group consisting of: C.sub.1-C.sub.6-alkyl, C.sub.3-C.sub.6-cycloalkyl, C.sub.2-C.sub.6-hydroxyalkyl, (C.sub.1-C.sub.3-alkoxy)-(C.sub.2-C.sub.4-alkyl)-, 2-(2-methoxyethoxy)ethyl, 2-(2-ethoxyethoxy)ethyl, oxetan-3-yl, tetrahydro-2H-pyran-4-yl, and phenyl, wherein said C.sub.1-C.sub.6-alkyl group is optionally substituted, identically or differently, with a phenyl group, wherein the phenyl group is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy, and wherein when R.sup.2 represents phenyl, the phenyl is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy; or a stereoisomer, a tautomer, an N-oxide, a hydrate, a solvate, or a salt thereof, or a mixture of same.

2. The aqueous pharmaceutical solution according to claim 1, wherein: R.sup.1 represents a hydrogen atom; R.sup.2 represents a substituent selected from the group consisting of: C.sub.1-C.sub.6-alkyl, C.sub.3-C.sub.6-cycloalkyl, C.sub.2-C.sub.4-hydroxyalkyl, (C.sub.1-C.sub.3-alkoxy)-(C.sub.2-C.sub.4-alkyl)-, oxetan-3-yl, tetrahydro-2H-pyran-4-yl, and phenyl, wherein said C.sub.1-C.sub.6-alkyl group is optionally substituted, identically or differently, with a phenyl group, wherein the phenyl group is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy, and wherein when R.sup.2 represents phenyl, the phenyl is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy; or a stereoisomer, a tautomer, an N-oxide, a hydrate, a solvate, or a salt thereof, or a mixture of same.

3. The aqueous pharmaceutical solution according to claim 1, wherein: R.sup.1 represents a hydrogen atom; R.sup.2 represents a substituent selected from the group consisting of: C.sub.1-C.sub.6-alkyl, C.sub.3-C.sub.6-cycloalkyl, (C.sub.1-C.sub.3-alkoxy)-(C.sub.2-C.sub.4-alkyl)-, and phenyl, wherein said C.sub.1-C.sub.6-alkyl group is optionally substituted, identically or differently, with a phenyl group, wherein the phenyl group is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy, and wherein when R.sup.2 represents phenyl, the phenyl is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy; or a stereoisomer, a tautomer, an N-oxide, a hydrate, a solvate, or a salt thereof, or a mixture of same.

4. The aqueous pharmaceutical solution according to claim 1, wherein: R.sup.1 represents a hydrogen atom; R.sup.2 represents a substituent selected from the group consisting of: C.sub.1-C.sub.4-alkyl, C.sub.3-C.sub.5-cycloalkyl, (C.sub.1-C.sub.2-alkoxy)-(C.sub.2-C.sub.3-alkyl)-, and phenyl, wherein said C.sub.1-C.sub.4-alkyl group is optionally substituted, identically or differently, with a phenyl group, wherein the phenyl group is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy, and wherein when R.sup.2 represents phenyl, the phenyl is optionally substituted, one, two, or three times, identically or differently, with a halogen atom or a group selected from: C.sub.1-C.sub.3-alkyl, C.sub.1-C.sub.3-haloalkyl, and C.sub.1-C.sub.3-alkoxy; or a stereoisomer, a tautomer, an N-oxide, a hydrate, a solvate, or a salt thereof, or a mixture of same.

5. The aqueous pharmaceutical solution according to claim 1, wherein: R.sup.1 represents a hydrogen atom; R.sup.2 represents a substituent selected from the group consisting of: methyl, ethyl, isopropyl, 2-methylpropyl, benzyl, cyclopropyl, cyclopentyl, 2-methoxyethyl, 2-ethoxyethyl, and phenyl, or a stereoisomer, a tautomer, an N-oxide, a hydrate, a solvate, or a salt thereof, or a mixture of same.

6. The aqueous pharmaceutical solution according to claim 1, wherein the compound has a structure selected from the group consisting of: Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dimethyl-8,8-bis({[(methyl {[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino) acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-diethyl-8,8-bis({[(ethyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}-methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[15-(2-methoxyethyl)-10,10-bis[({[(2-methoxyethyl){[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}amino]acetyl}amino)methyl]-7,13,16-trioxo-5-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-2-oxa-5,8,12,15-tetraazaheptadecan-17-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate, Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[16-(2-ethoxyethyl)-11,11-bis[({[(2-ethoxyethyl){[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}amino]acetyl}amino)methyl]-8,14,17-trioxo-6-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-3-oxa-6,9,13,16-tetraazaoctadecan-18-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-diisopropyl-8,8-bis({[(isopropyl-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]-amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[3-isobutyl-8,8-bis({[(isobutyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}-methyl)-15-methyl-2,5,11-trioxo-13-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]acetyl}-3,6,10,13-tetraazahexadec-1-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dicyclopropyl-8,8-bis({[(cyclopropyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dicyclopentyl-8,8-bis({[(cyclopentyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{2,5,11,14-tetraoxo-3,13-diphenyl-8,8-bis({[(phenyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-amino)acetyl]amino}methyl)-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, and Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dibenzyl-8,8-bis({[(benzyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}-methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl], acetate, or a stereoisomer, a tautomer, an N-oxide, a hydrate, a solvate, or a salt thereof, or a mixture of same.

7. A method of preparing an aqueous pharmaceutical solution of a compound of general formula (I) where R.sup.1 and R.sup.2 are as defined in claim 1, the method comprising: ##STR00073## dissolving the compound of general formula (I) in a sufficient volume of a 10 mM Tris-HCl buffer solution to provide the aqueous pharmaceutical solution having a pH of 7.4 and a final concentration of gadolinium of 5 mmol Gd/L.

8. The method of claim 7, wherein the compound of general formula (I) has a structure selected from the group consisting of: Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dimethyl-8,8-bis({[(methyl {[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino) acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-diethyl-8,8-bis({[(ethyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}-methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[15-(2-methoxyethyl)-10,10-bis[({[(2-methoxyethyl){[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}amino]acetyl}amino)methyl]-7,13,16-trioxo-5-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-2-oxa-5,8,12,15-tetraazaheptadecan-17-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate, Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[16-(2-ethoxyethyl)-11,11-bis[({[(2-ethoxyethyl){[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}amino]acetyl}amino)methyl]-8,14,17-trioxo-6-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-3-oxa-6,9,13,16-tetraazaoctadecan-18-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-diisopropyl-8,8-bis({[(isopropyl-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]-amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[3-isobutyl-8,8-bis({[(isobutyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}-methyl)-15-methyl-2,5,11-trioxo-13-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]acetyl}-3,6,10,13-tetraazahexadec-1-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dicyclopropyl-8,8-bis({[(cyclopropyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dicyclopentyl-8,8-bis({[(cyclopentyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{2,5,11,14-tetraoxo-3,13-diphenyl-8,8-bis({[(phenyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-amino)acetyl]amino}methyl)-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate, and Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dibenzyl-8,8-bis({[(benzyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]amino}-methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl], acetate, or a stereoisomer, a tautomer, an N-oxide, a hydrate, a solvate, or a salt thereof, or a mixture of same.

9. A method of imaging body tissue in a mammal, comprising: administering to the mammal an effective amount of the aqueous pharmaceutical solution according to claim 1 in an amount sufficient to provide from 25 μmol Gadolinium per kilogram body weight and 100 μmol Gadolinium per kilogram body weight; and subjecting the mammal to magnetic resonance imaging.

10. A compound having a structure selected from the group consisting of: Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(methyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(ethyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(2-methoxyethyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(2-ethoxyethyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(isopropyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(isobutyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(cyclopropyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(cyclopentyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(phenyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate; and Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(benzyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate; or a hydrate, a solvate, or a salt thereof, or a mixture of same.

11. A compound having a structure selected from the group consisting of: Gadolinium 2,2′,2″-(10-{2-(methyl)[2-(4-nitrophenoxy)-2-oxoethyl]amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-(ethyl)[2-(4-nitrophenoxy)-2-oxoethyl]amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-{(2-methoxyethyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-{(2-ethoxyethyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-{(isopropyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-{(isobutyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-{(cyclopropyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-{(cyclopentyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; Gadolinium 2,2′,2″-(10-{2-{(phenyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; and Gadolinium 2,2′,2″-(10-{2-{(benzyl)[2-(4-nitrophenoxy)-2-oxoethyl]}amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate; or a hydrate, a solvate, or a salt thereof, or a mixture of same.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 Diffusion of different contrast agents through semipermeable membranes (20 kDa). Dynamic CT measurements were performed to show the ability of different contrast agents to diffuse through a semipermeable membrane. (A) CT images of Example 1-10 in comparison to that of Reference compound 1 (Gadovist®) and 4 (Gadomer). A representative measurement region for the signal evaluation overtime is indicated in the image RC1. (B) CT images of Example 1-10 in comparison to that of Reference compound 1 (Gadovist®) and 4 (Gadomer) after 30 h.

(2) FIG. 2 Signal analysis of dynamic CT diffusion phantom study over time. Signal in Hounsfield units (HU) over time of the dialysis cassette in fetal bovine solution for (A) Example 1-5 and (B) for Example 6-10 compared with Reference compounds 1 and 4. The results demonstrate that contrary to Reference compound 4 (Gadomer) all of the investigated compounds are able to pass the semipermeable membrane (20 kDa).

(3) FIG. 3: Representative MR-Angiograms (maximum intensity projection) for

(4) B (middle): example compound 6 at 25 μmol/kg, compared to

(5) C (right): reference compound 1 (Gadovist) at standard dose (100 μmol/kg), and

(6) A (left): reference compound 1 (Gadovist) at reduced dose (25 μmol/kg).

(7) No qualitative difference in the vascular contrast was found for the example compound 6 at 25 μmol/kg compared to the reference compound 1 at 100 μmol/kg. The vascular contrast at the reduced dose of the reference compound is considerable lower.

(8) FIG. 4: Signal enhancement at representative vascular regions (mean±standard deviation) for example compound 6 at 25 μmol/kg compared to reference compound 1 (Gadovist) at standard dose (100 μmol/kg) and reduced dose (25 μmol/kg). No significant difference exist between compound 6 compared to the standard dose of the reference compound, while significantly (p<0.001) higher signal enhancements were found compared to the reduced dose of the reference compound.

EXPERIMENTAL SECTION

Abbreviations

(9) TABLE-US-00001 ACN acetonitrile AUC area under the curve bw body weight CDCl.sub.3 chloroform-d CPMG Carr-Purcell-Meiboom-Gill (MRI sequence) C.sub.Gd concentration of the compound normalized to the Gadolinium Cl.sub.tot total clearance d day(s) D.sub.2O deuterium oxide DAD diode array detector DCM dichloromethane DMSO dimethylsulfoxide DMSO-d.sub.6 deuterated dimethylsulfoxide ECCM extracellular contrast media EI electron ionisation ELSD evaporative light scattering detector ESI electrospray ionisation FBS fetal bovine serum h hour HCOOH formic acid HPLC high performance liquid chromatography HU Hounsfield units IR inversion recovery kDa kilo Dalton LCMS liquid chromatography-mass spectroscopy ICP-MS inductively coupled plasma mass spectrometry MRI magnetic resonance imaging MRT mean residence time MS mass spectrometry m multiplet min minute(s) NMR nuclear magnetic resonance spectroscopy: chemical shifts (δ) are given in ppm. q quartet r.sub.i (where i = 1, 2) relaxivities in L mmol.sup.−1 s.sup.−1 R.sub.t retention time s singlet RC reference compound R.sub.i (where i = 1, 2) relaxation rates (1/T.sub.1,2) R.sub.i(0) relaxation rate of the respective solvent T.sub.1,2 relaxation time T Tesla t triplet t.sub.1/2 α plasma half-life, compartment V1 t.sub.1/2 β plasma half-life, compartment V2 t.sub.1/2 γ plasma half-life, compartment V3 TFA trifluoroacetic acid THF tetrahydrofuran TI inversion time UPLC ultra performance liquid chromatography V1 + V2 volume, compartments V1 + V2 V.sub.c (V1) volume, central compartment V1 V.sub.d,ss volume of distribution at steady state
Materials and Instrumentation

(10) The chemicals used for the synthetic work were of reagent grade quality and were used as obtained.

(11) All reagents, for which the synthesis is not described in the experimental section, are either commercially available, or are known compounds or may be formed from known compounds by known methods by a person skilled in the art.

(12) .sup.1H-NMR spectra were measured in CDCl.sub.3, D.sub.2O or DMSO-d.sub.6, respectively (room temperature, Bruker Avance 400 spectrometer, resonance frequency: 400.20 MHz for .sup.1H or Bruker Avance 300 spectrometer, resonance frequency: 300.13 MHz for .sup.1H. Chemical shifts are given in ppm relative to sodium (trimethylsilyl)propionate-d.sub.4 (D.sub.2O) or tetramethylsilane (DMSO-d.sub.6) as external standards (δ=0 ppm).

(13) The compounds and intermediates produced according to the methods of the invention may require purification. Purification of organic compounds is well known to the person skilled in the art and there may be several ways of purifying the same compound. In some cases, no purification may be necessary. In some cases, the compounds may be purified by crystallization. In some cases, impurities may be stirred out using a suitable solvent. In some cases, the compounds may be purified by chromatography, particularly flash column chromatography, using for example prepacked silica gel cartridges, e.g. Biotage SNAP cartridges KP-Sil® or KP-NH® in combination with a Biotage autopurifier system (SP4® or Isolera Four®) and eluents such as gradients of hexane/ethyl acetate or DCM/methanol. In some cases, the compounds may be purified by preparative HPLC using for example a Waters autopurifier equipped with a diode array detector and/or on-line electrospray ionization mass spectrometer in combination with a suitable prepacked reverse phase column and eluents such as gradients of water and acetonitrile which may contain additives such as trifluoroacetic acid, formic acid or aqueous ammonia.

(14) Examples were analyzed and characterized by the following HPLC based analytical methods to determine characteristic retention time and mass spectrum:

(15) Method 1: UPLC (ACN-HCOOH):

(16) Instrument: Waters Acquity UPLC-MS SQD 3001; column: Acquity UPLC BEH C18 1.7 μm, 50×2.1 mm; eluent A: water+0.1% formic acid, eluent B: acetonitrile; gradient: 0-1.6 min 1-99% B, 1.6-2.0 min 99% B; flow 0.8 mL/min; temperature: 60° C.; injection: 2 μl; DAD scan: 210-400 nm; ELSD.

(17) Method 2: LC-MS:

(18) Instrument: Agilent 1290 UHPLCMS Tof; column: BEH C 18 (Waters) 1.7 μm, 50×2.1 mm; eluent A: water+0.05 vol-% formic acid (99%), eluent B: acetonitrile+0.05% formic acid; gradient: 0-1.7 min 98-10% A, 1.7-2.0 min 10% A, 2.0-2.5 min 10-98% A, flow 1.2 mL/min; temperature: 60° C.; DAD scan: 210-400 nm.

EXAMPLE COMPOUNDS

Example 1

Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dimethyl-8,8-bis({[(methyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)-acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetate

(19) ##STR00014##

Example 1-1

Tert-butyl N-(bromoacetyl)-N-methylglycinate

(20) ##STR00015##

(21) A stirred suspension of 30.00 g (165.1 mmol, 1 eq.) tert-butyl N-methylglycinate hydrochloride (1:1) and 44.82 g (346.8 mmol, 2.1 eq.) N,N-diisopropyl ethylamine in 250 ml dichloromethane was cooled to −70° C. After slow addition of 35.67 g (176.7 mmol, 1.07 eq.) bromoacetyl bromide, dissolved in 70 ml dichloromethane, the reaction mixture was warmed over night to room temperature. The organic layer was washed twice with 0.1 M aqueous hydrochloric acid, with saturated aqueous sodium bicarbonate solution and with half saturated sodium chloride solution. After drying over sodium sulfate, the solvent was evaporated under reduced pressure yielding 34.62 g (79%, 130.1 mmol) of the title compound.

(22) .sup.1H-NMR (400 MHz, DMSO-d.sub.6): δ=1.36-1.47 (m, 9H), 2.80-3.08 (m, 3H), 3.94-4.47 (m, 4H) ppm.

(23) LC-MS (ES.sup.+): m/z=266.1 and 268.1 (M+H).sup.+; R.sub.t=0.91 and 0.94 min.

Example 1-2

Tert-butyl N-methyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetyl}glycinate

(24) ##STR00016##

(25) To a solution of 6.98 g (13.56 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate {CAS No. [122555-91-3]; see B. Jagadish et al., THL 52(17), 2058-2061 (2011)} in 175 ml acetonitrile were added 5.62 g (40.69 mmol, 3 eq.) potassium carbonate and 3.80 g (13.56 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-methylglycinate (example 1-1). The resulting reaction mixture was stirred over night at 60° C. After filtration, the solution was evaporated under reduced pressure to dryness. The residue was purified by chromatography yielding 6.63 g (70%, 9.48 mmol) of the title compound.

(26) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.38-1.50 (m, 36H), 1.90-4.00 (m, 29H) ppm.

(27) LC-MS (ES.sup.+): m/z=700.5 (M+H).sup.+; R.sub.t=1.01 min.

Example 1-3

N-methyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-glycine

(28) ##STR00017##

(29) 12.29 g (17.56 mmol) Tert-butyl N-methyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 1-2) were dissolved in 300 ml formic acid. The solution was stirred for two hours at 80° C. After evaporation under reduced pressure, the residue was dissolved in 600 ml water and was washed repeatedly with dichloromethane. The aqueous layer was dried by lyophilization yielding 8.04 g (96%, 16.90 mmol) of the title compound.

(30) .sup.1H-NMR (400 MHz, D.sub.2O): δ=2.81-2.94 (m, 3H), 2.95-4.05 (m, 26H) ppm.

(31) LC-MS (ES.sup.+): m/z=476.2 (M+H).sup.+; R.sub.t=0.22 min.

Example 1-4

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(methyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate

(32) ##STR00018##

(33) 2.03 g (4.28 mmol, 1 eq.) N-Methyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclodo-decan-1-yl]acetyl}glycine (example 1-3) were dissolved in 42 ml water. 697.8 mg (1.925 mmol, 0.45 eq.) Gadolinium(III) oxide were added and the resulting reaction mixture was stirred for 7.5 hours at 100° C. After cooling to room temperature, 260 mg of activated charcoal were added and the black suspension was stirred over night at room temperature. The filtrated solution was dried by lyophilization. The residue was dissolved in 50 ml water and the pH was adjusted to 2.4 by adding Dowex 50 W-X2 (H.sup.+ form). The final product was isolated by lyophilization yielding 2.09 g (78%, 3.32 mmol).

(34) LC-MS (ES.sup.+): m/z=630.0 (M+H).sup.+; R.sub.t=0.25 and 0.28 min.

Example 1-5

Gadolinium 2,2′,2″-[10-(2-{methyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(35) ##STR00019##

(36) 2.09 g (3.32 mmol, 1 eq.) Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(methyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 1-4) and 922.0 mg (6.64 mmol, 2 eq.) 4-nitrophenol were dissolved in 6 ml formamide and 4 ml THF. The solution was cooled to 0° C. and 628.0 mg (4.98 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide, dissolved in 280 μl THF, were slowly added. The resulting reaction mixture was stirred for 5 hours at 0-5° C. Dropwise addition of 45 ml THF precipitated the desired product. 2.47 g (94%, 3.13 mmol) of title compound were isolated by filtration.

(37) LC-MS (ES.sup.+): m/z=752.5 (M+H).sup.+; R.sub.t=0.59 and 0.62 min.

Example 1

(38) 30.9 mg (0.111 mmol, 1 eq.) 2,2-Bis(ammoniomethyl)propane-1,3-diaminium tetrachloride [see W. Hayes et al., Tetrahedron 59 (2003), 7983-7996 and S. Dutta et al., Inorg. Chem. Communications 13(9), 1074-1080 (2010)] were dissolved in 16 mL DMSO. After addition of 115.0 mg (0.888 mmol, 8 eq.) N,N-diisopropylethylamine and 1.0 g (1.332 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{methyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 1-5), the resulting reaction mixture was stirred and heated for 8 hours at 50° C. The cooled solution was concentrated under reduced pressure. The concentrate was poured under stirring in an excess of ethyl acetate, the formed precipitate was filtered off and was dried in vacuo. The solid was dissolved in 30 ml 0.01 M aqueous sodium hydroxide solution and the pH was adjusted to 12 by adding of 1 M aqueous sodium hydroxide solution. After stirring for 1 hour at pH=12, the pH was adjusted to 7 by adding 1 M aqueous hydrochloric acid. The resulting solution was filtered, was ultrafiltrated with water using a 1 kDa membrane and the final retentate was lyophilized. The crude product was purified by RP-chromatography yielding 219 mg (77%, 0.085 mmol) of the title compound.

(39) UPLC (ACN-HCOOH): R.sub.t=0.39 min.

(40) MS (ES.sup.+): m/z (z=2)=1290.3 (M+H).sup.2+, m/z (z=3)=860.8 (M+H).sup.3+, m/z (z=4)=646.5 (M+H).sup.4+.

Example 2

Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-diethyl-8,8-bis({[(ethyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]-amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclododecan-1-yl]acetate

(41) ##STR00020##

Example 2-1

Tert-butyl N-ethylglycinate

(42) ##STR00021##

(43) 31.21 g (160.0 mmol) Tert-butyl bromoacetate, dissolved in 160 ml THF, were dropped in 800 ml of a 2 Methanamine solution in THF. The reaction mixture was stirred over night at room temperature. THF was distilled off, the residue was dissolved in dichloromethane and the organic layer was washed twice with 0.1 M aqueous sodium hydroxide solution, was dried over sodium sulfate and was evaporated yielding 23.4 g (92%, 147.0 mmol) of the title compound.

(44) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.11 (t, 3H), 1.46 (s, 9H), 1.59 (s, 1H), 2.63 (q, 2H), 3.29 (s, 2H) ppm.

Example 2-2

Tert-butyl N-(bromoacetyl)-N-ethylglycinate

(45) ##STR00022##

(46) The compound was synthesized according to the procedure described in example 1-1 starting from 23.20 g (145.7 mmol, 1 eq.) tert-butyl N-ethylglycinate (example 2-1), 20.15 g (155.9 mmol, 1.07 eq.) N,N-diisopropyl ethylamine, and 31.47 g (155.9 mmol, 1.07 eq.) bromoacetyl bromide yielding 40.6 g (100%, 145 mmol).

(47) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.08-1.29 (m, 3H), 1.42-1.53 (m, 9H), 3.41-3.53 (m, 2H), 3.77-4.02 (m, 4H) ppm.

(48) LC-MS (ES.sup.+): m/z=280.0 and 282.0 (M+H).sup.+; R.sub.t=1.01 min.

Example 2-3

Tert-butyl N-ethyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate

(49) ##STR00023##

(50) The compound was synthesized according to the procedure described in example 1-2 starting from 18.00 g (34.97 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 14.50 g (104.91 mmol, 3 eq.) potassium carbonate, and 9.80 g (34.97 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-ethylglycinate (example 2-2) yielding 24.8 g (100%, 34.8 mmol).

(51) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.02-1.23 (m, 3H), 1.39-1.54 (m, 36H), 1.65-4.90 (m, 28H) ppm.

(52) LC-MS (ES.sup.+): m/z=714.6 (M+H).sup.+; R.sub.t=1.01 min.

Example 2-4

N-ethyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine

(53) ##STR00024##

(54) The compound was synthesized according to the procedure described in example 1-3 starting from 24.83 g (34.78 mmol) tert-butyl N-ethyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 2-3) in 515 ml formic acid yielding 18.33 g (108%, 37.44 mmol).

(55) .sup.1H-NMR (400 MHz, D.sub.2O): δ=0.93-1.22 (m, 3H), 2.90-4.15 (m, 28H) ppm.

(56) LC-MS (ES.sup.+): m/z=490.2 (M+H).sup.+; R.sub.t=0.29 min.

Example 2-5

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(ethyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate

(57) ##STR00025##

(58) The compound was synthesized according to the procedure described in example 1-4 starting from 17.02 g (34.77 mmol, 1 eq.) N-ethyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 2-4) and 5.67 g (15.65 mmol, 0.45 eq.) gadolinium(III) oxide yielding 22.90 g (102%, 35.57 mmol).

(59) LC-MS (ES.sup.+): m/z=645.1 (M+H).sup.+; R.sub.t=0.31 and 0.39 min.

Example 2-6

Gadolinium 2,2′,2″-[10-(2-{ethyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(60) ##STR00026##

(61) The compound was synthesized according to the procedure described in example 1-5 starting from 4.25 g (6.60 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(ethyl)-amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 2-5), 1.84 g (13.20 mmol, 2 eq.) 4-nitrophenol, and 1.25 g (9.90 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 5.05 g (100%, 6.6 mmol).

(62) LC-MS (ES.sup.+): m/z=766.0 (M+H).sup.+; R.sub.t=0.63 and 0.65 min.

Example 2

(63) The compound was synthesized according to the procedure described in example 1 starting from 151.5 mg (0.545 mmol, 1 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 563.0 mg (4.36 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 5.00 g (6.54 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{ethyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 2-6) yielding 413 mg (29%, 0.16 mmol).

(64) UPLC (ACN-HCOOH): R.sub.t=0.41 min.

(65) MS (ES.sup.+): m/z (z=2)=1318.0 (M+H).sup.2+, m/z (z=3)=878.9 (M+H).sup.3+.

Example 3

Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[15-(2-methoxyethyl)-10,10-bis[({[(2-methoxyethyl){[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}amino]acetyl}amino)methyl]-7,13,16-trioxo-5-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-2-oxa-5,8,12,15-tetraazaheptadecan-17-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate

(66) ##STR00027##

Example 3-1

Tert-butyl N-(bromoacetyl)-N-(2-methoxyethyl)glycinate

(67) ##STR00028##

(68) The compound was synthesized according to the procedure described in example 1-1 starting from 3.73 g (19.71 mmol, 1 eq.) tert-butyl N-(2-methoxyethyl)glycinate [see J. T. Suh et al., J. Med. Chem. 1985(28), 57-66], 2.73 g (21.09 mmol, 1.07 eq.) N,N-diisopropyl ethylamine, and 4.26 g (21.09 mmol, 1.07 eq.) bromoacetyl bromide yielding 6.10 g (100%, 19.67 mmol).

(69) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.43-1.52 (m, 9H), 3.26-3.36 (m, 3H), 3.49-3.64 (m, 4H), 3.78-4.00 (m, 2H), 4.01-4.16 (m, 2H) ppm.

(70) LC-MS (ES.sup.+): m/z=310.0 and 312.0 (M+H).sup.+; R.sub.t=1.04 min.

Example 3-2

Tert-butyl N-(2-methoxyethyl)-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetra-azacyclododecan-1-yl]acetyl}glycinate

(71) ##STR00029##

(72) The compound was synthesized according to the procedure described in example 1-2 starting from 4.33 g (8.41 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 3.49 g (25.24 mmol, 3 eq.) potassium carbonate, and 2.61 g (8.41 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-(2-methoxyethyl)glycinate (example 3-1) yielding 5.81 g (84%, 7.04 mmol).

(73) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.36-1.55 (m, 36H), 1.89-4.95 (m, 33H) ppm.

(74) LC-MS (ES.sup.+): m/z=744.5 (M+H).sup.+; R.sub.t=1.09 min.

Example 3-3

N-(2-methoxyethyl)-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}glycine

(75) ##STR00030##

(76) The compound was synthesized according to the procedure described in example 1-3 starting from 5.80 g (7.80 mmol) tert-butyl N-(2-methoxyethyl)-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 3-2) in 120 ml formic acid yielding 4.19 g (93%, 7.26 mmol).

(77) .sup.1H-NMR (400 MHz, D.sub.2O): δ=2.70-3.98 (m, 31H), 3.99-4.07 (m, 2H) ppm.

(78) LC-MS (ES.sup.+): m/z=520.2 (M+H).sup.+; R.sub.t=0.32 min.

Example 3-4

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(2-methoxyethyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate

(79) ##STR00031##

(80) The compound was synthesized according to the procedure described in example 1-4 starting from 4.19 g (8.07 mmol, 1 eq.) N-(2-methoxyethyl)-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 3-3) and 1.32 g (3.63 mmol, 0.45 eq.) gadolinium(III) oxide yielding 5.09 g (84%, 6.80 mmol).

(81) LC-MS (ES.sup.+): m/z=675.1 (M+H).sup.+; R.sub.t=0.37 and 0.42 min.

Example 3-5

Gadolinium 2,2′,2″-[10-(2-{(2-methoxyethyl)[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(82) ##STR00032##

(83) The compound was synthesized according to the procedure described in example 1-5 starting from 4.57 g (6.78 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(2-methoxyethyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 3-4), 1.89 g (13.57 mmol, 2 eq.) 4-nitrophenol, and 1.28 g (10.17 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 5.26 g (97.5%, 6.62 mmol).

(84) LC-MS (ES.sup.+): m/z=796.1 (M+H).sup.+; R.sub.t=0.65 and 0.67 min.

Example 3

(85) The compound was synthesized according to the procedure described in example 1 starting from 169.1 mg (0.61 mmol, 1 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 629.0 mg (4.86 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 5.80 g (7.30 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{(2-methoxyethyl)[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 3-5) yielding 462 mg (39%, 0.17 mmol).

(86) UPLC (ACN-HCOOH): R.sub.t=0.44 min.

(87) MS (ES.sup.+): m/z (z=2)=1377.7 (M+H).sup.2+, m/z (z=3)=919.7 (M+H).sup.3+.

Example 4

Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[16-(2-ethoxyethyl)-11,11-bis[({[(2-ethoxyethyl){[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}amino]acetyl}amino)methyl]-8,14,17-trioxo-6-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-3-oxa-6,9,13,16-tetraazaoctadecan-18-yl]-1,4,7,10-tetraazacyclododecan-1-yl}acetate

(88) ##STR00033##

Example 4-1

Tert-butyl N-(2-ethoxyethyl)glycinate

(89) ##STR00034##

(90) The compound was synthesized according to the procedure described in example 2-1 starting from 8.00 g (89.75 mmol, 10 eq.) 2-ethoxyethanamine and 1.75 g (8.98 mmol, 1 eq.) tert-butyl bromoacetate yielding 1.84 g (91%, 8.15 mmol).

(91) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.20 (t, 3H), 1.46 (s, 9H), 1.95 (s, 1H), 2.78 (t, 2H), 3.33 (s, 2H), 3.50 (q, 2H), 3.53 (t, 2H) ppm.

Example 4-2

Tert-butyl N-(bromoacetyl)-N-(2-ethoxyethyl)glycinate

(92) ##STR00035##

(93) The compound was synthesized according to the procedure described in example 1-1 starting from 1.80 g (8.86 mmol, 1 eq.) tert-butyl N-(2-ethoxyethyl)glycinate (example 4-1), 1.23 g (9.47 mmol, 1.07 eq.) N,N-diisopropyl ethylamine, and 1.91 g (9.47 mmol, 1.07 eq.) bromoacetyl bromide yielding 2.94 g (102%, 9.07 mmol).

(94) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.13-1.21 (m, 3H), 1.43-1.51 (m, 9H), 3.42-3.52 (m, 2H), 3.53-3.64 (m, 4H), 3.76-4.20 (m, 4H) ppm.

(95) LC-MS (ES.sup.+): m/z=324.0 and 326.0 (M+H).sup.+; R.sub.t=1.14 min.

Example 4-3

Tert-butyl N-(2-ethoxyethyl)-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]acetyl}glycinate

(96) ##STR00036##

(97) The compound was synthesized according to the procedure described in example 1-2 starting from 4.60 g (8.94 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 3.71 g (26.83 mmol, 3 eq.) potassium carbonate, and 2.90 g (8.94 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-(2-ethoxyethyl)glycinate (example 4-2) yielding 6.04 g (89%, 7.97 mmol).

(98) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.11-1.22 (m, 3H), 1.34-1.55 (m, 36H), 1.66-5.00 (m, 32H) ppm.

(99) LC-MS (ES.sup.+): m/z=758.8 (M+H).sup.+; R.sub.t=1.02 min.

Example 4-4

N-(2-ethoxyethyl)-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}glycine

(100) ##STR00037##

(101) The compound was synthesized according to the procedure described in example 1-3 starting from 6.04 g (7.97 mmol) tert-butyl-(2-ethoxyethyl)-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 4-3) in 125 ml formic acid yielding 4.49 g (106%, 8.41 mmol).

(102) .sup.1H-NMR (400 MHz, D.sub.2O): δ=0.99-1.09 (m, 3H), 2.64-4.45 (m, 32H) ppm.

(103) LC-MS (ES.sup.+): m/z=534.2 (M+H).sup.+; R.sub.t=0.41 min.

Example 4-5

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(2-ethoxyethyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate

(104) ##STR00038##

(105) The compound was synthesized according to the procedure described in example 1-4 starting from 4.48 g (8.40 mmol, 1 eq.) N-(2-ethoxyethyl)-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 4-4) and 1.37 g (3.78 mmol, 0.45 eq.) gadolinium(III) oxide yielding 5.56 g (96%, 8.08 mmol).

(106) LC-MS (ES.sup.+): m/z=689.9 (M+H).sup.+; R.sub.t=0.41 and 0.46 min.

Example 4-6

Gadolinium 2,2′,2″-[10-(2-{(2-ethoxyethyl)[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxo-ethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(107) ##STR00039##

(108) The compound was synthesized according to the procedure described in example 1-5 starting from 4.93 g (7.17 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(2-ethoxyethyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 4-5), 2.00 g (14.35 mmol, 2 eq.) 4-nitrophenol, and 1.36 g (10.76 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 5.05 g (87%, 6.24 mmol).

(109) LC-MS (ES.sup.+): m/z=810.3 (M+H).sup.+; R.sub.t=0.72 and 0.74 min.

Example 4

(110) The compound was synthesized according to the procedure described in example 1 starting from 158.4 mg (0.57 mmol, 1 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 589.0 mg (4.56 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 5.53 g (6.84 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{(2-ethoxyethyl)[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 4-6) yielding 365 mg (23%, 0.13 mmol).

(111) UPLC (ACN-HCOOH): R.sub.t=0.51 min.

(112) MS (ES.sup.+): m/z (z=2)=1406.5 (M+H).sup.2+, m/z (z=3)=938.3 (M+H).sup.3+.

Example 5

Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-diisopropyl-8,8-bis({[(isopropyl-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)-acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetate

(113) ##STR00040##

Example 5-1

Tert-butyl N-isopropyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetyl}glycinate

(114) ##STR00041##

(115) The compound was synthesized according to the procedure described in example 1-2 starting from 5.05 g (9.81 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 4.07 g (29.43 mmol, 3 eq.) potassium carbonate, and 2.89 g (9.81 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-isopropylglycinate [see J. M. Kim et al., Carbohydrate Research, 298(3), 173-179 (1997)] yielding 6.83 g (86%, 8.44 mmol).

(116) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.00-1.26 (m, 6H), 1.34-1.56 (m, 36H), 1.68-5.00 (m, 27H) ppm.

(117) LC-MS (ES.sup.+): m/z=728.6 (M+H).sup.+; R.sub.t=1.04 min.

Example 5-2

N-isopropyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-glycine

(118) ##STR00042##

(119) The compound was synthesized according to the procedure described in example 1-3 starting from 6.83 g (9.38 mmol) tert-butyl N-isopropyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 5-1) in 140 ml formic acid yielding 5.17 g (109%, 10.27 mmol).

(120) .sup.1H-NMR (400 MHz, D.sub.2O): δ=0.94-1.25 (m, 6H), 2.50-4.42 (m, 27H) ppm.

(121) LC-MS (ES.sup.+): m/z=504.2 (M+H).sup.+; R.sub.t=0.41 min.

Example 5-3

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(isopropyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate

(122) ##STR00043##

(123) The compound was synthesized according to the procedure described in example 1-4 starting from 5.17 g (10.27 mmol, 1 eq.) N-isopropyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 5-2) and 1.68 g (4.62 mmol, 0.45 eq.) gadolinium(III) oxide yielding 6.16 g (91%, 9.36 mmol).

(124) LC-MS (ES.sup.+): m/z=659.1 (M+H).sup.+; R.sub.t=0.39 and 0.42 min.

Example 5-4

Gadolinium 2,2′,2″-[10-(2-{isopropyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(125) ##STR00044##

(126) The compound was synthesized according to the procedure described in example 1-5 starting from 5.63 g (8.56 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(iso-propyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 5-3), 2.38 g (17.12 mmol, 2 eq.) 4-nitrophenol, and 1.62 g (12.84 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 6.26 g (94%, 8.04 mmol).

(127) LC-MS (ES.sup.+): m/z=779.4 (M+H).sup.+; R.sub.t=0.63 and 0.68 min.

Example 5

(128) The compound was synthesized according to the procedure described in example 1 starting from 161.7 mg (0.58 mmol, 1 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 752.0 mg (4.65 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 6.80 g (8.72 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{isopropyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 5-4) yielding 262 mg (17%, 0.097 mmol).

(129) UPLC (ACN-HCOOH): R.sub.t=0.44 min.

(130) MS (ES.sup.+): m/z (z=2)=1347.5 (M+H).sup.2+, m/z (z=3)=897.9 (M+H).sup.3+.

Example 6

Tetragadolinium {4,10-bis(carboxylatomethyl)-7-[3-isobutyl-8,8-bis({[(isobutyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)acetyl]-amino}methyl)-15-methyl-2,5,11-trioxo-13-{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-3,6,10,13-tetraazahexadec-1-yl]-1,4,7,10-tetraaza-cyclododecan-1-yl}acetate

(131) ##STR00045##

Example 6-1

Tert-butyl N-isobutyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetyl}glycinate

(132) ##STR00046##

(133) The compound was synthesized according to the procedure described in example 1-2 starting from 13.73 g (26.67 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 11.06 g (80.01 mmol, 3 eq.) potassium carbonate, and 8.22 g (26.67 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-isobutylglycinate [see U. K. Saha et al., Tetrahedron Letters 36(21), 3635-3638 (1995)] yielding 13.47 g (65%, 17.25 mmol).

(134) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=0.80-1.04 (m, 6H), 1.24-1.57 (m, 36H), 1.61-4.40 (m, 29H) ppm.

(135) LC-MS (ES.sup.+): m/z=742.5 (M+H).sup.+; R.sub.t=1.17 min.

Example 6-2

N-isobutyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-glycine

(136) ##STR00047##

(137) The compound was synthesized according to the procedure described in example 1-3 starting from 13.47 g (18.15 mmol) tert-butyl N-isobutyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 6-1) in 270 ml formic acid yielding 8.79 g (94%, 17.00 mmol).

(138) .sup.1H-NMR (400 MHz, D.sub.2O): δ=0.71-0.92 (m, 6H), 1.67-1.97 (m, 1H), 2.96-4.03 (m, 28H) ppm.

(139) LC-MS (ES.sup.+): m/z=518.8 (M+H).sup.+; R.sub.t=0.44 min.

Example 6-3

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(isobutyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate

(140) ##STR00048##

(141) The compound was synthesized according to the procedure described in example 1-4 starting from 8.79 g (16.98 mmol, 1 eq.) N-isobutyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 6-2) and 2.77 g (7.64 mmol, 0.45 eq.) gadolinium(III) oxide yielding 9.62 g (76%, 12.89 mmol).

(142) LC-MS (ES.sup.+): m/z=673.1 (M+H).sup.+; R.sub.t=0.43 and 0.48 min.

Example 6-4

Gadolinium 2,2′,2″-[10-(2-{isobutyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(143) ##STR00049##

(144) The compound was synthesized according to the procedure described in example 1-5 starting from 9.12 g (13.57 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(isobutyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 6-3), 3.78 g (27.15 mmol, 2 eq.) 4-nitrophenol, and 2.57 g (20.36 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 9.67 g (81%, 10.98 mmol).

(145) LC-MS (ES.sup.+): m/z=794.3 (M+H).sup.+; R.sub.t=0.74 min.

Example 6

(146) The compound was synthesized according to the procedure described in example 1 starting from 269.0 mg (0.97 mmol, 0.9 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 1.11 g (8.58 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 10.21 g (12.88 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{isobutyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 6-4) yielding 674 mg (25%, 0.245 mmol).

(147) UPLC (ACN-HCOOH): R.sub.t=0.54 min.

(148) MS (ES.sup.+): m/z (z=2)=1373.4 (M+H).sup.2+, m/z (z=3)=916.0 (M+H).sup.3+.

Example 7

Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dicycopropyl-8,8-bis({[(cyclo-propyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-amino)acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetra-azacyclododecan-1-yl]acetate

(149) ##STR00050##

Example 7-1

Tert-butyl N-(bromoacetyl)-N-cyclopropylglycinate

(150) ##STR00051##

(151) The compound was synthesized according to the procedure described in example 1-1 starting from 1.98 g (11.56 mmol, 1 eq.) tert-butyl N-cyclopropylglycinate [see J. T. Suh et al., J. Med. Chem. 28(1), 57-66 (1985)], 1.60 g (12.37 mmol, 1.07 eq.) N,N-diisopropyl ethylamine, and 2.50 g (12.37 mmol, 1.07 eq.) bromoacetyl bromide yielding 3.24 g (96%, 11.09 mmol).

(152) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=0.83-1.00 (m, 4H), 1.46 (s, 9H), 2.95-3.04 (m, 1H), 4.00 (s, 2H), 4.16 (s, 2H) ppm.

(153) LC-MS (ES.sup.+): m/z=292.3 and 294.3 (M+H).sup.+; R.sub.t=1.09 min.

Example 7-2

Tert-butyl N-cyclopropyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]acetyl}glycinate

(154) ##STR00052##

(155) The compound was synthesized according to the procedure described in example 1-2 starting from 5.00 g (9.71 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 4.03 g (29.14 mmol, 3 eq.) potassium carbonate, and 2.84 g (8.41 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-cyclopropylglycinate (example 7-1) yielding 6.38 g (91%, 8.79 mmol).

(156) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=0.63-1.02 (m, 4H), 1.35-1.54 (m, 36H), 1.75-4.50 (m, 27H) ppm.

(157) LC-MS (ES.sup.+): m/z=726.7 (M+H).sup.+; R.sub.t=0.98 min.

Example 7-3

N-cyclopropyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}glycine

(158) ##STR00053##

(159) The compound was synthesized according to the procedure described in example 1-3 starting from 6.38 g (8.79 mmol) tert-butyl N-cyclopropyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 7-2) in 132 ml formic acid yielding 4.70 g (107%, 9.37 mmol).

(160) .sup.1H-NMR (400 MHz, D.sub.2O): δ=0.67-0.88 (m, 4H), 2.71-2.79 (m, 1H), 2.88-4.31 (m, 26H) ppm.

(161) LC-MS (ES.sup.+): m/z=502.2 (M+H).sup.+; R.sub.t=0.34 min.

Example 7-4

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(cyclopropyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate

(162) ##STR00054##

(163) The compound was synthesized according to the procedure described in example 1-4 starting from 4.68 g (9.33 mmol, 1 eq.) N-cyclopropyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 7-3) and 1.52 g (4.20 mmol, 0.45 eq.) gadolinium(III) oxide yielding 5.46 g (89%, 8.33 mmol).

(164) LC-MS (ES.sup.+): m/z=657.1 (M+H).sup.+; R.sub.t=0.41 min.

Example 7-5

Gadolinium 2,2′,2″-[10-(2-{cyclopropyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(165) ##STR00055##

(166) The compound was synthesized according to the procedure described in example 1-5 starting from 4.95 g (7.55 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(cyclopropyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 7-4), 2.10 g (15.10 mmol, 2 eq.) 4-nitrophenol, and 1.43 g (11.32 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 5.76 g (98%, 7.41 mmol).

(167) LC-MS (ES.sup.+): m/z=778.0 (M+H).sup.+; R.sub.t=0.66 min.

Example 7

(168) The compound was synthesized according to the procedure described in example 1 starting from 188.2 mg (0.68 mmol, 1 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 700.0 mg (5.42 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 6.31 g (8.12 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{cyclopropyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 7-5) yielding 627 mg (35%, 0.234 mmol).

(169) UPLC (ACN-HCOOH): R.sub.t=0.44 min.

(170) MS (ES.sup.+): m/z (z=2)=1343.4 (M+H).sup.2+, m/z (z=3)=895.8 (M+H).sup.3+

Example 8

Tetragadolinium[4,10-bis(carboxylatomethyl)-7-{3,13-dicyclopentyl-8,8-bis({[(cyclo-pentyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-amino)acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetra-azacyclododecan-1-yl]acetate

(171) ##STR00056##

Example 8-1

Tert-butyl N-(bromoacetyl)-N-cyclopentylglycinate

(172) ##STR00057##

(173) The compound was synthesized according to the procedure described in example 1-1 starting from 5.24 g (26.29 mmol, 1 eq.) tert-butyl N-cyclopentylglycinate [see J. T. Suh et al., J. Med. Chem. 28(1), 57-66 (1985)], 3.64 g (28.13 mmol, 1.07 eq.) N,N-diisopropyl ethylamine, and 5.68 g (28.13 mmol, 1.07 eq.) bromoacetyl bromide yielding 8.40 g (89%, 23.61 mmol).

(174) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.21-2.12 (m, 17H), 3.73-3.86 (m, 2H), 3.94 (s, 2H), 4.14-4.87 (m, 1H) ppm.

(175) LC-MS (ES.sup.+): m/z=320.1 and 322.1 (M+H).sup.+; R.sub.t=1.25 min.

Example 8-2

Tert-butyl N-cyclopentyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraaza-cyclododecan-1-yl]acetyl}glycinate

(176) ##STR00058##

(177) The compound was synthesized according to the procedure described in example 1-2 starting from 8.07 g (15.68 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 6.50 g (47.03 mmol, 3 eq.) potassium carbonate, and 5.02 g (15.68 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-cyclopentylglycinate (example 8-1) yielding 8.95 g (76%, 11.87 mmol).

(178) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.33-1.51 (m, 36H), 1.55-5.00 (m, 35H) ppm.

(179) LC-MS (ES.sup.+): m/z=754.5 (M+H).sup.+; R.sub.t=1.15 min.

Example 8-3

N-cyclopentyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}glycine

(180) ##STR00059##

(181) The compound was synthesized according to the procedure described in example 1-3 starting from 8.94 g (11.86 mmol) tert-butyl N-cyclopentyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 8-2) in 180 ml formic acid yielding 6.20 g (74%, 8.78 mmol).

(182) LC-MS (ES.sup.+): m/z=530.2 (M+H).sup.+; R.sub.t=0.40 and 0.46 min.

Example 8-4

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(cyclopentyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate

(183) ##STR00060##

(184) The compound was synthesized according to the procedure described in example 1-4 starting from 6.20 g (11.71 mmol, 1 eq.) N-cyclopentyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 8-3) and 1.91 g (5.27 mmol, 0.45 eq.) gadolinium(III) oxide yielding 7.21 g (90%, 10.54 mmol).

(185) LC-MS (ES.sup.+): m/z=685.0 (M+H).sup.+; R.sub.t=0.44 and 0.50 min.

Example 8-5

Gadolinium 2,2′,2″-[10-(2-{cyclopentyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(186) ##STR00061##

(187) The compound was synthesized according to the procedure described in example 1-5 starting from 6.70 g (9.80 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(cyclopentyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 8-4), 2.73 g (19.60 mmol, 2 eq.) 4-nitrophenol, and 1.86 g (14.70 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 7.08 g (90%, 8.79 mmol).

(188) LC-MS (ES.sup.+): m/z=806.1 (M+H).sup.+; R.sub.t=0.71 and 0.77 min.

Example 8

Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dicyclopentyl-8,8-bis({[(cyclo-pentyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-amino)acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetra-azacyclododecan-1-yl]acetate

(189) The compound was synthesized according to the procedure described in example 1 starting from 130.4 mg (0.47 mmol, 0.6 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 808.0 mg (6.25 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 7.55 g (9.38 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{cyclopentyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 8-5) yielding 222 mg (17%, 0.08 mmol).

(190) UPLC (ACN-HCOOH): R.sub.t=0.56 min.

(191) MS (ES.sup.+): m/z (z=2)=1400.0 (M+H).sup.2+, m/z (z=3)=933.0 (M+H).sup.3+

Example 9

Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{2,5,11,14-tetraoxo-3,13-diphenyl-8,8-bis({[(phenyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-acetyl}amino)acetyl]amino}methyl)-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetra-azacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraaza1cyclododecan-1-yl]acetate

(192) ##STR00062##

Example 9-1

Tert-butyl N-phenyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetyl}glycinate

(193) ##STR00063##

(194) The compound was synthesized according to the procedure described in example 1-2 starting from 9.00 g (17.49 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 7.25 g (52.46 mmol, 3 eq.) potassium carbonate, and 5.74 g (17.49 mmol, 1 eq.) tert-butyl N-(bromoacetyl)-N-phenylglycinate [see C. Roy et al., Organic Letters 15(9), 2246-2249 (2013)] yielding 7.74 g (58%, 10.16 mmol).

(195) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.30-1.64 (m, 36H), 1.67-4.78 (m, 26H), 7.22-7.26 (m, 2H), 7.36-7.46 (m, 3H) ppm.

(196) LC-MS (ES.sup.+): m/z=763.5 (M+H).sup.+; R.sub.t=1.11 min.

Example 9-2

N-phenyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}-glycine

(197) ##STR00064##

(198) The compound was synthesized according to the procedure described in example 1-3 starting from 7.20 g (9.45 mmol) tert-butyl N-phenyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 9-1) in 144 ml formic acid yielding 5.54 g (109%, 10.31 mmol).

(199) .sup.1H-NMR (400 MHz, D.sub.2O): δ=2.65-4.42 (m, 26H), 7.12-7.59 (m, 5H) ppm.

(200) LC-MS (ES.sup.+): m/z=538.2 (M+H).sup.+; R.sub.t=0.45 min.

Example 9-3

Gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(phenyl)amino]-2-oxoethyl}-1,4,7,10-tetra-azacyclododecane-1,4,7-triyl)triacetate

(201) ##STR00065##

(202) The compound was synthesized according to the procedure described in example 1-4 starting from 5.54 g (10.31 mmol, 1 eq.) N-phenyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 9-2) and 1.68 g (4.64 mmol, 0.45 eq.) gadolinium(III) oxide yielding 7.10 g (100%, 10.26 mmol).

(203) LC-MS (ES.sup.+): m/z=693.1 (M+H).sup.+; R.sub.t=0.51 min.

Example 9-4

Gadolinium 2,2′,2″-[10-(2-{[2-(4-nitrophenoxy)-2-oxoethyl](phenyl)amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(204) ##STR00066##

(205) The compound was synthesized according to the procedure described in example 1-5 starting from 3.93 g (5.68 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[(carboxymethyl)(phenyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 9-3), 1.58 g (11.36 mmol, 2 eq.) 4-nitrophenol, and 1.08 g (8.52 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 4.06 g (88%, 4.99 mmol).

(206) LC-MS (ES.sup.+): m/z=814.3 (M+H).sup.+; R.sub.t=0.77 min.

Example 9

(207) The compound was synthesized according to the procedure described in example 1 starting from 129.4 mg (0.47 mmol, 1 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 481.0 mg (3.72 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 4.54 g (5.59 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{[2-(4-nitrophenoxy)-2-oxoethyl](phenyl)amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 9-4) yielding 663 mg (50%, 0.23 mmol).

(208) UPLC (ACN-HCOOH): R.sub.t=0.61 min.

(209) MS (ES.sup.+): m/z (z=2)=1415.0 (M+H).sup.2+, m/z (z=3)=944.4 (M+H).sup.3+.

Example 10

Tetragadolinium [4,10-bis(carboxylatomethyl)-7-{3,13-dibenzyl-8,8-bis({[(benzyl{[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}amino)-acetyl]amino}methyl)-2,5,11,14-tetraoxo-15-[4,7,10-tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]-3,6,10,13-tetraazapentadec-1-yl}-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetate

(210) ##STR00067##

Example 10-1

Tert-butyl N-benzyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetyl}glycinate

(211) ##STR00068##

(212) The compound was synthesized according to the procedure described in example 1-2 starting from 16.00 g (31.09 mmol, 1 eq.) tri-tert-butyl 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate, 12.89 g (93.26 mmol, 3 eq.) potassium carbonate, and 10.64 g (31.09 mmol, 1 eq.) tert-butyl N-benzyl-N-(bromoacetyl)glycinate [see U. Saha et al., THL 36(21), 3635-3638 (1995)] yielding 19.32 g (80%, 24.9 mmol).

(213) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=1.29-1.61 (m, 36H), 1.77-5.14 (m, 28H), 7.12-7.40 (m, 5H) ppm.

(214) LC-MS (ES.sup.+): m/z=776.6 (M+H).sup.+; R.sub.t=1.11 min.

Example 10-2

N-benzyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine

(215) ##STR00069##

(216) The compound was synthesized according to the procedure described in example 1-3 starting from 18.80 g (24.23 mmol) tert-butyl N-benzyl-N-{[4,7,10-tris(2-tert-butoxy-2-oxoethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycinate (example 10-1) in 376 ml formic acid yielding 14.14 g (106%, 25.63 mmol).

(217) .sup.1H-NMR (400 MHz, D.sub.2O): δ=2.80-4.19 (m, 26H), 4.44-4.58 (m, 2H), 7.12-7.45 (m, 5H) ppm.

(218) LC-MS (ES.sup.+): m/z=552.2 (M+H).sup.+; R.sub.t=0.49 min.

Example 10-3

Gadolinium 2,2′,2″-(10-{2-[benzyl(carboxymethyl)amino]-2-oxoethyl}-1,4,7,10-tetraaza-cyclododecane-1,4,7-triyl)triacetate

(219) ##STR00070##

(220) The compound was synthesized according to the procedure described in example 1-4 starting from 14.10 g (25.56 mmol, 1 eq.) N-benzyl-N-{[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetyl}glycine (example 10-2) and 4.17 g (11.50 mmol, 0.45 eq.) gadolinium(III) oxide yielding 17.05 g (85%, 21.74 mmol).

(221) LC-MS (ES.sup.+): m/z=707.1 (M+H).sup.+; R.sub.t=0.45 and 0.53 min.

Example 10-4

Gadolinium 2,2′,2″-[10-(2-{benzyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate

(222) ##STR00071##

(223) The compound was synthesized according to the procedure described in example 1-5 starting from 6.50 g (9.21 mmol, 1 eq.) gadolinium 2,2′,2″-(10-{2-[benzyl(carboxymethyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate (example 10-3), 2.56 g (18.42 mmol, 2 eq.) 4-nitrophenol, and 1.74 g (13.81 mmol, 1.5 eq.) N,N′diisopropyl carbodiimide yielding 6.42 g (84%, 7.76 mmol).

(224) LC-MS (ES.sup.+): m/z=828.2 (M+H).sup.+; R.sub.t=0.78 min.

Example 10

(225) The compound was synthesized according to the procedure described in example 1 starting from 191.9 mg (0.69 mmol, 1 eq.) 2,2-bis(ammoniomethyl)propane-1,3-diaminium tetrachloride, 714.0 mg (5.52 mmol, 8 eq.) N,N-diisopropyl ethylamine, and 6.85 g (8.28 mmol, 12 eq.) gadolinium 2,2′,2″-[10-(2-{benzyl[2-(4-nitrophenoxy)-2-oxoethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]triacetate (example 10-4) yielding 738 mg (35%, 0.24 mmol).

(226) UPLC (ACN-HCOOH): R.sub.t=0.61 min.

(227) MS (ES.sup.+): m/z (z=2)=1442.6 (M+H).sup.2+, m/z (z=3)=961.9 (M+H).sup.3+

(228) Reference Compound 1

(229) Gadovist® (gadobutrol, Bayer AG, Leverkusen, Germany)

(230) Reference Compound 2

(231) Magnevist® (gadopentetate dimeglumine, Bayer AG, Leverkusen, Germany)

(232) Reference Compound 3

(233) Primovist® (gadoxetate disodium, Bayer AG, Leverkusen, Germany)

(234) Reference Compound 4

(235) Gadomer-17 was synthesized as described in EP0836485B1, Example 1k.

(236) In Vitro and In Vivo Characterization of Example Compounds

(237) Examples were tested in selected assays one or more times. When tested more than once, data are reported as either average values or as median values, wherein the average value, also referred to as the arithmetic mean value, represents the sum of the values obtained divided by the number of times tested, and the median value represents the middle number of the group of values when ranked in ascending or descending order. If the number of values in the data set is odd, the median is the middle value. If the number of values in the data set is even, the median is the arithmetic mean of the two middle values.

(238) Examples were synthesized one or more times. When synthesized more than once, data from assays represent average values or median values calculated utilizing data sets obtained from testing of one or more synthetic batch.

Example A

(239) Relaxivity Measurements at 1.4 T

(240) Relaxivity measurements at 1.41 T were performed using a MiniSpec mq60 spectrometer (Bruker Analytik, Karlsruhe, Germany) operating at a resonance frequency of 60 MHz and a temperature of 37° C. The T.sub.1 relaxation times were determined using the standard inversion recovery (IR) method with a fixed relaxation delay of at least 5×T.sub.1. The variable inversion time (TI) was calculated automatically by the standard software of the MiniSpec mq60 (8 steps). The T.sub.2 measurements were done by using a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, applying a relaxation delay of at least 5×T.sub.1.

(241) Each relaxivity measurement was performed using three different Gd concentrations (3 concentrations between 0.05 and 2 mM). The T.sub.1 and T.sub.2 relaxation times of the example compounds 1 to 10 were measured in different media for example in water and human plasma. Human plasma preparation: For each experiment fresh blood was taken from a volunteer using 10 mL citrate-tubes (Sarstedt S-Monovette 02.1067.001, 10 mL, Citrate). The 10 mL citrate-tubes were carefully inverted 10 times to mix blood and anticoagulant and centrifuged for 15 minutes at 1811 g at room temperature (Eppendorf, Centrifuge 5810R).

(242) The relaxivities r.sub.i (where i=1, 2) were calculated on the basis of the measured relaxation rates R.sub.i in water and plasma:
R.sub.i═R.sub.i(0)+r.sub.i[C.sub.Gd],
where R.sub.i(0) represent the relaxation rate of the respective solvent and C.sub.Gd the concentration of the compound normalized to the Gadolinium. The Gadolinium concentrations of the investigated solutions were verified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS Agilent 7500a, Waldbronn, Germany).

(243) The determined relaxivity values are summarized in Table 1.

(244) TABLE-US-00002 TABLE 1 Relaxivities of investigated compounds in water and human plasma at 1.41 T and relaxivities of Reference compounds 1-4 (RC1-RC4) at 1.5 T in water. All values were measured at 37° C., are normalized to Gd and given in L mmol.sup.−1 s.sup.−1. Example r.sub.1 human r.sub.2 human No r.sub.1 water* r.sub.2 water* plasma* plasma* 1 10.1 11.5 11.7 14.3 2 10.4 11.8 11.6 14.1 3 10.3 11.7 11.7 14.5 4 11.1 12.6 12.5 15.1 5 11.1 12.8 13.1 16.4 6 11.6 13.6 14.1 17.5 7 10.6 12.1 12.1 15.1 8 11.7 13.5 14.1 17.6 9 11.0 12.7 12.0 14.9 10 11.5 13.3 13.3 17.0 RC1{circumflex over ( )} 3.3 3.9 5.2 6.1 RC2{circumflex over ( )} 3.3 3.9 4.1 4.6 RC3{circumflex over ( )} 4.7 5.1 6.9 8.7 RC4{circumflex over ( )} 17.3 22 16 19 *values are depicted in L mmol.sup.−1 s.sup.−1 {circumflex over ( )}Relaxivities from reference compounds from Rohrer et. al. at 1.5 T (Invest. Radiol. 2005; 40, 11: 715-724) and in bovine plasma (Kreaber GmbH, Pharmaceutical Raw Material, Ellerbek, Germany) instead of human plasma
Relaxivity Measurements at 3.0 T

(245) Relaxivity measurements at 3.0 T were performed with a whole body 3.0 T MRI Scanner (Philips Intera, Philips Healthcare, Hamburg, Germany) using a knee-coil (SENSE-Knee-8, Philips Healthcare, Hamburg, Germany). The sample tubes (CryoTube™ Vials, Thermo Scientific 1.8 mL, Roskilde, Denmark) were positioned in 3 rows of 4 and 5 tubes in a plastic holder in a box filled with water. The temperature was adjusted to 37° C. For the MRI sequence the shortest possible echo-time (TE) with 7.46 milliseconds was used. The inversion times were chosen to optimize the sequence to measure T.sub.1 values corresponding to the estimated T.sub.1 range of all relaxation times of contrast media containing solutions. The following inversion times (TIs) were applied: 50, 100, 150, 200, 300, 500, 700, 1000, 1400, 2100, 3200, and 4500 milliseconds. The sequence was run with a constant relaxation delay of 3.4 seconds after the registration of the last echo (variable TR in the range from 3450 to 7900 milliseconds). For details of the fit procedure, see Rohrer et.al. (Invest. Radiol. 2005; 40, 11: 715-724). The experimental matrix of the phantom measurement was 320×320.

(246) The relaxivities were evaluated using three different concentrations of each compound (3 concentrations between 0.05 and 2 mM).

(247) The T.sub.1 relaxation times of Example compounds were measured in water and human plasma. Human plasma preparation: For each experiment fresh blood was taken from a volunteer using 10 mL citrate-tubes (Sarstedt S-Monovette 02.1067.001, 10 mL, Citrate). The 10 mL citrate-tubes were carefully inverted 10 times to mix blood and anticoagulant and centrifuged for 15 minutes at 1811 g at room temperature (Eppendorf, Centrifuge 5810R).

(248) The relaxivities r.sub.i (where i=1, 2) were calculated on the basis of the measured relaxation rates R.sub.i in water and plasma:
R.sub.i═R.sub.i(0)+r.sub.i[C.sub.Gd],
where R.sub.i(0) represent the relaxation rate of the respective solvent and C.sub.Gd the concentration of the compound normalized to the Gadolinium (Table 2).

(249) TABLE-US-00003 TABLE 2 Relaxivities (normalized to Gd) in water and human plasma at 3.0 T and 37° C. [L mmol.sup.−1 s.sup.−1] Example No r.sub.1 water* r.sub.1 human plasma* 1 9.1 ± 0.1 10.3 ± 0.2 2 9.4 ± 0.1 11.3 ± 0.1 3 9.5 ± 0.1 10.9 ± 0.1 4 10.1 ± 0.2 11.3 ± 0.01 5 10.2 ± 0.1 11.6 ± 0.4 7 9.7 ± 0.1 11.1 ± 0.1 8 10.7 ± 0.1 12.0 ± 0.4 RC1{circumflex over ( )} 3.2 ± 0.3 5.0 ± 0.3 RC2{circumflex over ( )} 3.1 ± 0.3 3.7 ± 0.2 RC3{circumflex over ( )} 4.3 ± 0.3 6.2 ± 0.3 RC4{circumflex over ( )} 13.0 ± 0.7 13 ± 1 *Average ± standard deviation, values are depicted in L mmol.sup.−1 s.sup.−1 n.d. = not determined

Example B

(250) Pharmacokinetic Parameters

(251) Pharmacokinetic parameters of Example 6 were determined in male rats (Han-Wistar, 235-270 g, n=3). The compound was administered as a sterile aqueous solution (53.8 mmol Gd/L) as a bolus in the tail vein of the animals. The dose was 0.1 mmol Gd/kg. Blood was sampled 1, 3, 5, 10, 15, 30, 60, 90, 120, 240, 360, 480, and 1440 min post injection and the Gd concentration was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS Agilent 7500a, Waldbronn, Germany). The blood level was converted to plasma concentrations by division by 0.625 (plasma fraction of rat blood, assuming strictly extracellular distribution). As a control, 3 animals (Han-Wistar, 248-289 g), were treated in the same way with Reference Compound 1 (Gadovist®), a low molecular weight contrast agent.

(252) The fit of the obtained data to a three compartment model (Phoenix-WinNonlin) yielded the pharmacokinetic parameters which are shown in Table 3.

(253) The pharmacokinetic of example Example 6 is very similar to that of the reference compound 1.

(254) TABLE-US-00004 TABLE 3 Pharmacokinetic parameters of blood plasma levels Reference Example 6 Compound 1 Parameter unit mean SD mean SD t½ α Half-life, compartment V1 [min] 2.45 0.84 1.80 0.3 t½ β Half-life, compartment V2 [min] 22.4 2.6 22.1 2.1 t½ γ Half-life, compartment V3 [min] 1041 202 780 187 MRT Mean residence time [min] 40.7 5.4 40.5 4.2 AUC∞ Area under the curve (to infinity) [μmol/l * min] 10801 1170 11334 1346 V.sub.c Volume, central compartment [l/kg] 0.98% 0.11% 1.16% 0.20% (V1) V1 V2 Volume, compartment V2 [l/kg] 0.12 0.02 0.16 0.03 V1 + Volume, compartments V1 + V2 [l/kg] 0.14 0.03 0.11 0.01 V2 V.sub.d,ss Volume of distribution at steady [l/kg] 0.27 0.01 0.26 0.02 state Cl.sub.tot Total Clearance [ml/min * kg] 0.40 0.02 0.38 0.03

Example C

(255) Chemical Stability

(256) Example 1 was separately dissolved in 10 mMTris-HCl buffer, pH7.4 at a final concentration of 5 mmol Gd/L. An aliquot was removed and the rest of the clear and colorless solution was autoclaved at 121° C. for 20 min. After autoclaving, the solution was still clear and colorless. The aliquot removed before and after autoclaving was analyzed by HPLC-ICP-MS to determine the integrity of the compound.

(257) HPLC: Column: Hypercarb 2.5 mm×15 cm. Solvent A: 0.1% formic acid in water. Solvent B: acetonitrile. Gradient from 100% Ato5% A+95% B in 10 min. Flow 1 ml/min. Detection by ICP-MS, tuned to .sup.158Gd. The chromatograms, displaying the intensity of the detected Gd, were visually compared. No changes in the chromatograms before and after autoclaving were detected. The compound was stable during the autoclaving procedure.

Example 0D

(258) Gd-Complex Stabilities in Human Plasma at 37° C. 15 d

(259) Example 1 was separately dissolved in human plasma at 1 mmol Gd/L. As a reference for released Gd.sup.3+0.1 mmol/L Gadolinium chloride (GdCl.sub.3) was dissolved in human plasma. The plasma samples were incubated for 15 days at 37° C. under 5% CO.sub.2 atmosphere to maintain the pH at 7.4. Aliquots were taken at the start and end of the incubation. The amount of Gd.sup.3+ released from the complexes was determined by HPLC-ICP-MS. Column: Chelating Sepharose (HiTrap, 1 mL). Solvent A: 10 mM BisTris-HCl pH 6.0. Solvent B: 15 mM HNO.sub.3. Gradient: 3 min at 100% A, from 3 to 10 min at 100% B. Flow 1 mL/min. Detection by ICP-MS, tuned to .sup.158Gd. The chromatograms, displaying the intensity of the detected Gd, were evaluated by peak area analysis. The size of the peak of Gd.sup.3*, eluting after the change from solvent A to B, was recorded. For Example 1 the increase of this peak and thus the release of Gd.sup.3+ after 15 days was below the limit of quantification (<0.1% of the injected total amount of Gadolinium). Example 1 is stable under physiological conditions.

Example E

(260) Water Solubility

(261) The exploratory water solubilities of the compounds were determined at room temperature (20° C.) in 0.5 mL buffer solution (10 mM Tris-HCl) in the microcentrifuge tubes (Eppendorf, 2.0 mL safe-lock caps). The solid compounds were added stepwise to the buffer solution. The suspension was mixed using a shaker (Heidolph Reax 2000) and treated 5 min in an ultrasound bath (Bandelin, Sonorex Super RK255H). The results are summarized in Table 4.

(262) TABLE-US-00005 TABLE 4 Solubilities of compounds in water at 20° C. (pH 7.4). Example Solubility No [mg/100 mL] 1 >1000 2 >1000 3 >1000 4 >1000 5 >1000 6 >1000 7 >1000 8 >1000 9 >1000 10 >1000

Example F

(263) Contrast-Enhanced Magnetic Resonance Angiography (CE-MRA)

(264) The potential of a significant dose reduction in CE-MRA was shown by an intraindividual comparison of 100 μmol Gadolinium per kilogram body weight [100 μmol Gd/kg bw], which is comparable to the human standard dose and a low dose protocol using 25 μmol Gadolinium per kilogram body weight in an animal model. Reference compound 1 (Gadovist), as an approved representative of the Gadolinium-based MRI contrast agents, was used in both dose protocols (100 μmol Gd/kg bw and 25 μmol Gd/kg bw) and compared to example compound 6 (25 μmol Gd/kg bw).

(265) The contrast-enhanced magnetic resonance angiography study was performed at a clinical 1.5 T Scanner (Magnetom Avanto Fit, Siemens Healthcare, Erlangen, Germany). For optimal signal exploitation, a spine in combination with a body-flex coil was used for the data acquisition. The study was performed on male New Zealand white rabbits (weight 3.6-3.9 kg, n=4, Charles River Kisslegg). The animals received all 3 contrast protocols within one imaging session. The order of the contrast protocols was randomized between the animals.

(266) All animals are initially anesthetized using a body weight-adjusted intramuscular injection of a mixture (1+2) of xylazine hydrochloride (20 mg/mL, Rompun 2%, Bayer Vital GmbH, Leverkusen, Germany) and ketamine hydrochloride (100 mg/mL, Ketavet, Pfizer, Pharmacia GmbH, Berlin, Germany) using 1 mL/kg body weight. The continuous anesthesia of the intubated animals (endotracheal tube, Rueschelit Super Safe Clear, cuff 3.0 mm, Willy Ruesch AG, Kernen, Germany) is achieved by the intravenous injection of 0.9 mg propofol per kilogram per hour (10 mg/mL, Propofol-Lipuro 1%, B. Braun Melsungen AG, Melsungen, Germany). The continuous intravenous injection is performed using a MR infusion system (Continuum MR Infusion System, Medrad Europe B. V., AE Beek, Germany). The tracheal respiration (SV 900C, Maquet, Rastatt, Germany) is performed with 55% oxygen, forty breaths per minute, and a breathing volume of 4 mL per kilogram body weight per minute.

(267) Based on a localizer MRI sequence oriented in coronal, axial, and sagittal directions the anatomic course of the aorta is acquired. A small intravenous test bolus (0.2 mL, Reference compound 1 followed by 1.3 mL saline) was administered to determine the time to peak interval (descending aorta) using a test bolus sequence. The MRA delay time between the start of the contrast injection and the start of image acquisition was calculated by subtracting the time to k-space center from the time to peak interval. For MRA a 3D FLASH sequence (TR=3.3 ms, TE=1.2 ms, flip=25°) was acquired before and after injection of the contrast agent considering the delay time. Both measurements were performed within expiratory breath hold. The time interval for the intraindividual comparison between the different contrast agent applications was twenty to thirty minutes.

(268) FIG. 3 displays representative MR-Angiograms (maximum intensity projection) for

(269) B (middle): example compound 6 at 25 μmol/kg, compared to

(270) C (right): reference compound 1 (Gadovist) at standard dose (100 μmol/kg), and

(271) A (left) reference compound 1 (Gadovist) at reduced dose (25 μmol/kg).

(272) No qualitative difference in the vascular contrast was found for the example compound 6 at 25 μmol/kg compared to the reference compound 1 at 100 μmol/kg. The vascular contrast at the reduced dose of the reference compound is considerable lower.

(273) Quantitative image evaluation was performed on the subtraction images (post contrast-baseline). Regions of interest were placed in the carotid artery (left and right), the ascending aorta, the descending aorta (thoracic level, liver level, kidney level, bifurcation level), and the renal arteries (left and right).

(274) The respective signal enhancements for all regions are shown in FIG. 4. For the example compound 6 similar signal enhancements were found at 25% of the dose of the reference compound 1. At identical doses the signal enhancement of the example compound 6 was significantly higher. That demonstrated the high efficacy of example compound 6 and the potential for significant dose reduction in contrast enhance MRA.

Example G

(275) Dynamic CT Diffusion Phantom Study

(276) As indicated in Example A the Reference compound 4 has a relaxivity which is in a similar range as the compounds of the present invention. Following intravenous injection, all clinically approved small monomer GBCAs (gadopentetate dimeglumine, gadoterate meglumine, gadoteridol, gadodiamide, gadobutrol, and gadoversetamide) distribute in the blood and extravascular/extracellular space by passive distribution (Aime S et. al., J. Magn. Reson. Imaging. 2009; 30, 1259-1267). Contrast agents with a high protein binding, for example gadofosveset trisodium with a prolonged period in the blood vessels caused by the reversible binding to HSA, or large hydrodynamic sizes as for example Reference compound 4 are hindered to pass the vessel wall. For good imaging results a fast diffusion through the vessel walls is required due to the fast renal excretion of GBCAs.

(277) The described dynamic CT diffusion study compares the ability of Examples 1-10 and Reference compounds 1 and 4 to pass a semipermeable membrane (20 kDa). A 128-row clinical CT device (SOMATOM Definition, 128; Siemens Healthcare, Forchheim, Germany) was used to monitor the diffusion through a semipermeable membrane at 100 kV and 104 mA. Single measurements were performed at 0 min, 1 min, 2 min, 3 min, 5 min, 10 min, 15 min, 20 min, 30 min, 45 min, 60 min, 2 h, 3 h, 5 h, 7 h, 22 h, 24 h, 30 h after placing the dialysis cassette (Slide-A-Lyser, 20,000 MWCO, 0.1-0.5 mL Capacity, Thermo Scientific, Roskilde, Denmark) filled with contrast agent in fetal bovine serum solution (FBS, Sigma, F7524). The images were reconstructed with a slice thickness of 2.4 mm and a B30 convolution kernel. The used concentration in the dialysis cassettes of the investigated Examples 1-10 and Reference compounds 1 and 4 was 20 mmol Gd/L.

(278) The imaging results for all investigated Examples and the Reference compounds 1 and 4 for the time points 0 min and 30 h after placing the cassettes in the FBS solution are depicted in FIG. 1. For image analysis, regions of interest were manually drawn on 1 centrally located slice for each time point (a representative measurement region is indicated in FIG. 1: Image RC1). The results of the Hounsfield units (HU) of the analyzed regions over time are shown in FIG. 2. The calculated diffusion half-lifes of the investigated Examples and Reference compounds are summarized in Table 4.

(279) TABLE-US-00006 TABLE 4 Diffusion half-live through a semipermeable membrane (20 kDa) Example Diffusion half-live (20 kDa) No [h] 1 10.4 2 13.3 3 11.6 4 10.1 5 10.8 6 15.0 7 14.0 8 10.5 9 15.1 10 15.0 RC 1 2.1 RC 4 No diffusion

(280) The FIG. 1 and the calculated half-life data show, similar to the Reference compound 1 (Gadovist®) and in contrast to the Reference compound 4, that the Examples 1-10 are able to pass the semipermeable membrane. Furthermore the data of the investigated compounds show contrary to other high relaxivity agents, which have a high protein binding or very slow tumbling rates (e.g. Reference compound 4), that the compounds of the present invention have hydrodynamic dimensions which can overcome barriers in a timely manner. These findings indicate the ability of the compounds of the invention to overcome barriers as for example endothelial walls in the vascular system, which is a requirement for whole body imaging.

High relaxivity gadolinium chelate compounds for use in magnetic resonance imaging

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C07D257/02

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A61K49/124

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A61K49/106

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C07D403/14

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