Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic Table
  • C07F5/003—Compounds containing elements of Groups 3 or 13 of the Periodic Table without C-Metal linkages
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K49/00—Preparations for testing in vivo
  • A61K49/06—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations
  • A61K49/08—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by the carrier
  • A61K49/10—Organic compounds
  • A61K49/101—Organic compounds the carrier being a complex-forming compound able to form MRI-active complexes with paramagnetic metals
  • A61K49/106—Organic compounds the carrier being a complex-forming compound able to form MRI-active complexes with paramagnetic metals the complex-forming compound being cyclic, e.g. DOTA
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D255/00—Heterocyclic compounds containing rings having three nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D249/00 - C07D253/00
  • C07D255/02—Heterocyclic compounds containing rings having three nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D249/00 - C07D253/00 not condensed with other rings
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D257/00—Heterocyclic compounds containing rings having four nitrogen atoms as the only ring hetero atoms
  • C07D257/02—Heterocyclic compounds containing rings having four nitrogen atoms as the only ring hetero atoms not condensed with other rings
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D259/00—Heterocyclic compounds containing rings having more than four nitrogen atoms as the only ring hetero atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D405/00—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom
  • C07D405/14—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom containing three or more hetero rings

Definitions

• the present invention relates to a compound and a production method thereof, a metal complex and a production method thereof, and an MRI contrast agent.
• Magnetic resonance imaging is a method for obtaining an image of a tissue or structure or the like in the living body using nuclear magnetic resonance in a magnetic field.
• the signal strength of magnetic resonance (MR) depends on the longitudinal relaxation time (Tl) , transverse relaxation time (T2) and the like. Consequently, the contrast of the resulting image may be increased by controlling Tl or T2.
• gadolinium complex which is stabilized by coordinating an organic ligand to a gadolinium ion, has been used as a contrast agent, and many proposals have been made regarding it (refer to U.S. Patent No. 5,695,739, U.S. Patent No. 5,798,092, U.S. Patent No. 6,039,931, U.S. Patent No. 6,149,890 and U.S.
• Tl-reducing effect of Gd 3+ is considered to depend on the coordination of a free water molecule to Gd 3+ .
• a gadolinium complex which is generally used as an MRI contrast agent, forms a chelate complex by the coordination of 7 or 8 coordinating functional groups (N or COOH) in a ligand to Gd 3+ .
• N or COOH coordinating functional groups
• Gd 3+ is a metal ion in a nine-coordination geometry, it is more likely that the Tl-reducing ability intrinsic to Gd 3+ is not sufficiently derived from such a general gadolinium complex. This point is the same as in the case of a complex using a metal ion other than Gd 3+ .
• an object of the present invention is to provide a metal complex that exhibits a Tl-reducing effect superior to that of a conventional one, a compound which is a ligand used for the metal complex and an intermediate compound used for the production of the metal complex.
• another object of the present invention is to provide an MRI contrast agent which exhibits a Tl-reducing effect superior to that of a conventional MRI contrast agent.
• a compound with a cyclic structure according to the present invention is characterized by being a compound represented by the following Formula (A) :
• n is an integer of 1 or more
• k is an integer of 3 or more and 8 or less
• R represents a group represented by the following Formula (1):
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR ,10 (R ,10 is H, an aryl group or an alkyl group) , R is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR ,10 (R 10 is H, an aryl group or an alkyl group) , m is an integer of 1 or more, and R 2 and R 3 are an end-group
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or
• R 10 is H, an aryl group or an alkyl group
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 4 and R 5 are each independently H, OH, COOH, NH 2 , an alkyl group which may have a substituent or an alkoxyl group which may have a substituent) , or an end- group with a five-ring structure represented by the following Formula (2-2) :
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 6 and R 7 are each independentlyH, an alkyl group which may have a substituent or
• a metal complex of the present invention is characterized in that the compound in the above Formula (A) is bonded to a metal ion with a Tl-reducing effect by a coordination bond.
• a contrast agent of the present invention is characterized by containing the metal complex as a contrast component.
• a compound, which is useful as a raw material compound for the synthesis of a compound of the above Formula (A) according to the present invention is characterized by being represented by the following Formula (3) :
• R 1 is any of an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• m is an integer of 1 or more
• R 2 and R 3 is an integer of 1 or more
• R 1 is any an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 4 and R 5 are each independently H, OH, COOH, NH 2 ,
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 6 and R 7 are each independentlyH, an alkyl group which may have a substituent or
• a method for producing a compound of the above Formula (A) according to the present invention is characterized by comprising at least a step of reacting a cyclic structure compound represented by the following Formula (B) and a compound represented by the above Formula (3) :
• n is an integer of 1 or more and k is an integer of 3 to 8.
• a method for producing a metal complex according to the present invention is characterized by comprising at least a step of coordinating the compound represented by the above Formula (A) to a metal ion with a Tl-reducing effect .
• FIG. 1 shows Tl relaxation time measurement data of a sample water prepared by adding 10% heavy water to an aqueous solution of 0.13 mM complex (R)-Il, as measured by using a 500 MHz NMR apparatus in Example 4.
• FIG. 2 shows Tl relaxation time measurement data of a sample water prepared by adding 10% heavy water to an aqueous solution of 0.13 mM Gd (DTPA), as measured by using a 500 MHz NMR apparatus in Comparative Example 1.
• DTPA 0.13 mM Gd
• FIG. 3 shows Tl relaxation time measurement data of a sample water prepared by adding 10% heavy water to an aqueous solution of 0.13 mM GdCl 3 , as measured by using a 500 MHz NMR apparatus in Comparative Example 1.
• FIG. 4 shows Tl relaxation time measurement data of an aqueous solution of 1.3 mM, 0.65 mM, 0.325 mM, 0.13 mM, 0.026 mM, and 0.013 mM complex (R)-Il and purified water, as measured by a 7T MRI apparatus in Example 5.
• FIG. 5 shows a graph of the relation between the concentration of the complex (R)-Il and 1/Tl in Example 5.
• FIG. 6 shows Tl relaxation time measurement data of water for an aqueous solution of 1.3 mM GdCl 3 and an aqueous solution of 1.3 mM Gd (DTPA), as measured by a 7T MRI apparatus in Comparative Example 2.
• FIG. 7 shows a graph of the relation of the concentration between the Gd (DTPA) and 1/Tl in Comparative Example 2.
• FIG. 8 shows an MRI image of a phantom of an aqueous solution of complex (R)-Il (1.3 mM) , GdCl 3 (1.3 mM) and Gd (DTPA) (1.3 and 0.5 mM) and water, as measured by changing the TR using 7T MRI apparatus.
• FIGS. 9A and 9B shows MRI images of a mouse as measured by using a 7T MRI apparatus in Example 6;
• FIG. 9A shows an image before the administration of a complex, and
• FIG. 9B shows an image after the administrasion of a Gd triamine 2nd G-12-ol-dendrimer complex (11) .
• FIGS. 1OA and 1OB shows ESI-TOS MS spectra of the 2nd Generation-chiral-acetonide tetraamine dendrimer (R)- 9a synthesized in Example 9.
• a compound with a cyclic structure according to the present invention is represented by the following Formula (A) :
• a unit comprising -N- (CH 2 ) n ⁇ is serially repeated in predetermined numbers and both ends are bonded to form a structure comprising a ring chain.
• a core site is formed by the cyclic structure, and multiple Ns in the ring chain of the core site form a coordination site of a metal ion.
• n in the Formula (A) is an integer of 1 or more and k is an integer from 3 to 8. Further, the value of n may be different for each -N- (CH 2 ) n - • R in Formula (A) is a side chain to the core site and has a structure with the following Formula (1) :
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group)
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• m is an integer of 1 or more
• R 2 and R 3 are an end-group represented by
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may- have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 4 and R 5 are each independently H, OH, COOH, NH 2
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded together
• R 8 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 9 is H, an alkyl group, a halogenated alkyl group, an alkoxyl group, an aryl group, an aryloxy group, a silyl group, a silyloxy group or COOR 10
• R 10 is H, an aryl group or an alkyl group
• R 6 and R 7 are each independently H, an alkyl group which may have a substituent or
• the substituent on R 1 that increases the water-solubility of the finally obtained metal complex is preferred.
• the substituent on R 1 is preferably a group that is not coordinated to a central metal during the formation of a metal complex.
• the substituent on R 1 is preferably an ether group.
• R-*- include an arylene group such as a phenylene group, a naphthalenediyl group, an anthracenediyl group and the like, and an arylene group with an ether group as a substituent such as an oxyphenylene group and the like; an alkyl group such as a methylene group, an ethylene group, a propylene group, a butylene group and the like; an alkyl group with an ether group as a substituent such as an oxymethylene group, an oxyethylene group, an oxypropylene group, an oxybutylene group and the like; and a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded, such as a methylenephenylene group, an oxymethylenephenylene group, an oxyphenylenemethylene group and the like.
• n 1 or more
• the preferred range is 1 or more and 8 or less.
• R 4 or R 5 is an alkyl group or an alkoxy group
• the preferred carbon number is 1 or more and 3 or less.
• R 6 or R 7 is an alkyl group, the preferred carbon number is 1 or more and 3 or less.
• the substituents which R 4 , R 5 , R 6 and R 7 may have include halogen, NH 3 , COOH and the like.
• R 8 is an alkyl group, a halogenated alkyl group and or alkoxyl group
• the preferred carbon number is 1 or more and 3 or less.
• the aryl portion is preferably a phenyl group.
• the silyl portion is preferably either a trimethylsilyl group or a trimethoxysilyl group.
• R 10 is either an aryl group or an alkyl group, the carbon number is preferably 1 or more and 3 or less.
• the methylene group side of a next repeating unit containing R 1 is bonded, and the bonding is repeated according to the value of m.
• the next repeating unit is bonded to at least one of position b of the R 2 side and position c of the R 3 side at position a of the methylene group side. Further, the repeating unit is bonded depending on the value of m and elongation of the side chain is ultimately stopped in a state where R 2 and R 3 are bonded to the ends.
• R 1 is an arylene group which may have a substituent, an alkylene group which may have a substituent or a group in which an arylene group which may have a substituent and an alkylene group which may have a substituent are bonded, and is independent for each repeating unit when there are several of the above repeating units.
• R 1 may be different in each repeating unit.
• an end- group with R 2 and R 3 represents an end-group that is independent of each end-group and is represented by the above-described Formula (2-1) or Formula (2-2) . Of these, a group in which R 1 in each repeating unit is the same and each end-group is the same is preferred.
• the coordination site of the compound in Formula (A) may be coordinated to a metal ion with a Tl-reducing effect to obtain a metal complex that is useful as a contrast component (effective component) of a contrast agent.
• the metal ion with a Tl-reducing effect includes any of a lanthanoid ion, a manganese ion, a chromium ion, an iron ion and the like.
• an MRI contrast agent may be prepared by using at least one of these metal complexes as an effective component.
• X is a halogen atom and m, R 1 to R 3 , R 8 and R 9 are defined in the same manner as in Formula (1)
• the compound represented by the Formula (A) may be produced by a method comprising at least one step of reacting a cyclic structure compound represented by the following Formula (B) with a compound represented by Formula (3) .
• a metal complex may be produced according to the present invention by a method that includes at least one step of coordinating the compound of the Formula (A) to a metal ion having the Tl- reducing effect.
• an asymmetric dihydroxylation is preferably used for the synthesis of a compound in Formula (3) .
• a commercially available one may be used as a compound in which k is 3 or more and 6 or less.
• a compound in which k is 7 or 8 may be synthesized by a well-known synthetic method (For the former, for example, Atkins, T. J.; Richman, J. E.; Dettle, W. F. Org. Synth. 1978, 58, 86.
• Bianchi A.; Mangani, S.; Micheloni, M.; Nanini, V.; Orioli, P.; Paoletti, P.; Seghi, B. Inorg. Chem. 1985, 24, 1182.
• a compound in which n is different for each (-NH (CH 2 J n -) may be obtained by purchasing a commercially available product or through synthesis.
• a cycloamine that includes (-NH (CH 2 ) 2 ⁇ ) and (-NH (CH 2 ) 3-) in which k is 4 is available commercially.
• the value (that is, the number of atoms constituting a ring) represented by k(n+l) is preferably ! or more and 24 or less.
• a compound represented by the Formula (A) according to the present invention is a compound that can become a ligand of a chelate complex.
• the specifically preferred embodiment of the compound includes, for example, a compound of the following Formula (5) .
• the important point is in that at least one of the end-most ends (hereinafter simply referred to as an "end") of the end portions is other than COOH.
• an end When a complex is formed, it is considered that COOH is strongly coordinated to a central metal ion such as Gd 3+ and the like.
• a central metal ion such as Gd 3+ and the like.
• the Tl-reducing effect of a central metal is considered to be impaired.
• a structure represented by the above Formula (2-2) is selected as an end portion of the side chain, before being used as a ligand, it is preferably dihydroxylated by hydrolyzing at least part of it.
• the end portion of the side chain may be arbitrarily designed depending on the kind of central metal ion or the structure of other portions of the ligand or the like. With regard to relatively difficult coordination to the central metal ion, an OH group is preferably selected as at least one of the ends.
• n or k of the core of a cyclic structure represented by Formula (B) a suitable value may be selected primarily depending on the kind of central metal ion.
• the preferred value of k is an integer of 3 or more and 5 or less.
• the preferred value of n is an integer of 2 or more and 4 or lees.
• m in the Formula (1) is an integer of 1 or more and preferably 1 or more and 9 or less.
• the first compound may be an optically active compound. This is the same as in the case of the following compounds.
• a second compound of the present invention is a metal complex with a structure in which the above first compound is coordinated to a metal ion.
• a metal ion an ion with a Tl-reducing effect is selected.
• a metal ion can include lanthanoid ion, manganese ion, chromium ion and iron ion, and gadolinium ion is preferable .
• the second compound of the present invention has an excellent Tl-reducing effect because many free water molecules can get close to the central metal ion compared to the conventional complex for an MRI contrast agent.
• the Tl-reducing effect may be increased by reducing the mobility of the molecules of a complex themselves. Such reduction of the mobility of the molecules themselves may be achieved by increasing the molecular weight of the molecules of a complex, especially a ligand. Since the second compound of the present invention has a considerably large molecular weight compared to a complex for a commercially available MRI contrast agent, the Tl-reducing effect is further increased due to the reduction of the mobility of the molecules of a complex themselves. Further, when the second complex is used as an MRI contrast agent, the stability of the complex itself is one of the important performance factors. The second compound of the present invention contributes to the stability of the complex itself by a protecting effect due to the high cubic bulk of the ligand.
• the present invention is an excellent method for synthesizing a ligand with such a large molecular weight both uniformly and selectively.
• a third compound of the present invention is a compound represented by the Formula (3) described previously. This compound can be used as an intermediate for the synthesis of the compound in Formula (1). (For Synthesizing a Ligand)
• a side chain represented by the Formula (3) is synthesized, and this is then reacted with a compound represented by the Formula (B) to form the core of a cyclic structure.
• an asymmetric dihydroxylation is preferred. The specific technique is described later in the Examples.
• Kondo et al. “H. -T. Chang, C-T. Chen, T. Kondo, G. Siuzdak, and K. B. Sharpless, Asymmeteric Dihydroxylation Enables Rapid Construction of Chiral Dendrimers, Agnew. Chem. , 35, 182 (1996)” is used as a reference.
• only a single diastereomer may be synthesized by using asymmetric dihydroxylation .
• An MRI contrast agent of the present invention contains the above-mentioned metal complex (second compound of the present invention) .
• the second compound of the present invention may be used alone as an MRI contrast agent and may be mixed with other compounds and the like which can function as a contrast component for use as an MRI contrast agent.
• the second compound may be used by mixing it with a carrier or diluent where necessary.
• the second compound of the present invention since it has an excellent Tl-reducing effect, it is suitable as an MRI contrast agent.
• the second compound should preferably have a structure with increased water-solubility (specifically, a water-soluble group such as an ether group, a COOH group and the like should be introduced as mentioned above) .
• the second compound has a structure in which the water- solubility is not too increased and the lipid-solubility is increased to some extent, the retention properties in the liver can be improved and the contrast effect in the liver can be increased. Examples (Example 1)
• the reaction mixture was returned to room temperature by removing the cooling bath, 225 g of sodium sulfite (Na 2 SO 3 ) was added, and the mixture was stirred for one hour or less. After stirring was complete, the yellow organic layer was concentrated by an evaporator. The water layer was extracted with ethyl acetate. To the residue obtained after the evaporator was added the extracted solution, and the mixture was concentrated once again by the evaporator. Thereafter, the residue was recrystallized from a mixed solvent of hexane and ethyl acetate. After recrystallization, the resulting product was filtered off to obtain a colorless needle crystal. The filtrate was concentrated once again, and then subjected to recrystallization. The resulting crystals were all collected and recrystallized several times to obtain a product (R) -2.
• sodium sulfite Na 2 SO 3
• a dendrimer was synthesized according to the following scheme. 1. Synthesis of 2nd Generation-chiral acetonide triamine dendrimer (R) -9
• the Tl relaxation time measurement was performed using a broadband probe on a 500 MHz NMR apparatus (Avance 500 manufactured by Bruker Biospin K. K.). The Tl relaxation times were measured at 27 0 C using an inversion recovery method.
• a Gd triamine 2nd G-12-ol-dendrimer complex (R)-Il was dissolved in 1 ml of ultrapure water to prepare an aqueous solution in which the concentration of complex (R)-Il was 24.05 itiM.
• the concentration of complex (R)-Il was determined from the Gd concentration by inductive coupled plasma emission spectrometry (ICP emission spectrometry) .
• the aqueous solution was diluted with ultrapure water and heavy water so that the concentration of complex (R)-Il was 0.13 mM and the concentration of heavy water was 10%, and the resulting aqueous solution was used as an NMR measurement sample.
• FIG. 1 shows the Tl time measurement data of water of the prepared sample. The data shown in FIG. 1 clarified that the Tl time of water of the complex (R)-Il aqueous solution was 429 ms .
• a GdCl 3 aqueous solution was prepared by dissolving commercially available GdCl 3 1 GH 2 O in ultrapure water and heavy water so that the concentration of GdCl 3 was adjusted to 0.13 mM and the concentration of heavy water was adjusted to 10%, and used as an NMR measurement sample.
• a Gd (DTPA) aqueous solution was prepared by diluting a commercially available Gd (DTPA) aqueous solution (630 mM) with ultrapure water and heavy water so that the concentration of Gd (DTPA) was adjusted to 0.13 mM and the concentration of heavy water was adjusted to 10%, and used as an NMR measurement sample, FIG.
• FIG. 2 shows the Tl time measurement data of water for the Gd (DTPA) aqueous solution sample
• FIG. 3 shows the same data for the GdCl 3 aqueous solution sample.
• the Tl relaxation time of water for the Gd (DTPA) aqueous solution sample determined from the data shown in FIG. 2 was 1333 ms, which is considerably longer than the Tl relaxation time of complex (R)-Il. This result suggests that complex (R)-Il of the present invention has considerably greater Tl-reducing ability than Gd (DTPA) which is a commercially available MRI contrast agent.
• Tl time of water for the GdCl 3 aqueous solution (0.13 mM) determined from the data shown in FIG. 3 was 712 ms, which is greater than the Tl relaxation time of complex (R)-Il shown in Example 4. This suggests that complex (R)-Il has greater Tl relaxation ability than GdCl 3 .
• Table 1 summarizes the Tl relaxation time of water for each of the above samples.
• Aqueous solutions of six different concentrations (1.3 mM, 0.65 mM, 0.325 mM, 0.13 mM, 0.026 mM and 0.013 mM) were prepared by dissolving complex (R) -11 in ultrapure water, and each of the aqueous solutions was placed into an Eppendorf tube and used directly as a measurement sample.
• FIG. 4 shows the Tl relaxation time measurement data for complex (R)-Il at each concentration
• Table 2 shows the Tl relaxation time and Tl relaxation rate (1/Tl) of water at each concentration determined from the Tl relaxation time measurement data
• FIG. 5 shows a graph of the concentration vs 1/Tl of the complex (R)-Il As shown in FIG. 5, 1/Tl and the sample concentration showed an excellent linear relationship. Based on the value of the slope, the Tl relaxation ability of complex (R)-Il, rl was 23.649 (L/mmol • s) . Table 2
• the Tl relaxation time was measured in the same manner as in Example 5.
• a GdCl 3 aqueous solution was prepared by dissolving commercially available GdCl 3 - 6H 2 O in ultrapure water so that the concentration was adjusted to 1.3 mM
• Gd (DTPA) aqueous solutions were prepared by diluting a commercially available Gd (DTPA) aqueous solution (630 mM) with ultrapure water so that the concentration was adjusted to 2.0, 1.3, 1.0, 0.5 and 0.25 mM, respectively.
• Each of the aqueous solutions was placed into an Eppendorf tube and used directly as a measurement sample.
• Tl relaxation time measurement for the GdCl 3 aqueous solution (1.3 mM) and Gd (DTPA) aqueous solution (1.3 mM)
• Table 3 shows a summary of the Tl relaxation time determined from the results.
• the Tl relaxation time of water for the Gd (DTPA) aqueous solution was 205.653 ms, which is a considerably longer than the Tl relaxation time (32.116 ms) of water for complex (R)-Il at the same concentration as determined in Example 5.
• the Tl relaxation ability was determined at 24 0 C using Gd (DTPA) aqueous solutions of 2.0, 1.0, 0.5 and 0.25 mM by a saturation recovery spin echo method, and as a result rl was 4.661 (L/mmol-s) (FIG. 7) .
• the rl of Gd (DTPA) was approximately one-fifth of the rl (23.649 (L/mmol-s)) of complex (R)-Il determined in Example 5, and it was clear that complex (R)-Il of the present invention had a Tl-reducing ability that was about five-fold higher than that of the MRI contrast agent Gd (DTPA), which is currently commercially available.
• FIG. 8 shows MRI images of each sample (complex (R)- 11 (1.3 mM) , GdCl 3 (1.3 m) , Gd (DTPA) (1.3 and 0.5 mM) and water) obtained by a saturation recovery spin echo method.
• complex (R)-Il gives a greate contrast than Gd (DTPA) . Therefore, complex (R)-Il of the present invention has a high Tl relaxation ability that is superior to that of a commercially available contrast agent as a positive MRI contrast agent. (Example 6)
• FIG. 9A shows the T ⁇ -weighted image of the mouse before the administration of complex (R)-Il
• FIG. 9B shows the T ⁇ -weighted image of the mouse after the administration of complex (R)-Il.
• a high contrast was obtained, especially in the liver site
• the Tl time was measured in the same manner as in
• Example 4 except that the NMR measurement sample was changed to an FBS (fetal bovine serum) solution of the complex (R) -11 (FBS concentration: 80%, heavy water concentration: 10%, H 2 O concentration: 10%) .
• FBS fetal bovine serum
• the Tl time was measured in the same manner as in Comparative Example 1 except that the NMR measurement sample was changed to an FBS (fetal bovine serum) solution of GdCl 3 or Gd (DTPA) (FBS concentration: 80%, heavy water concentration: 10%, H 2 O concentration: 10%).
• FBS fetal bovine serum
• DTPA Gd
• the number of the coordinated water molecules was estimated by removing background from XAFS spectra and performing fitting using Fourier transformation or Fourier inverse transformation. Further, the XAFS spectra were obtained by a transmission method using an ion chamber for a pellet (in a powder state) of the complex ((R)-Il) and a fluorescence method using a multi-element semiconductor detector for an aqueous solution of the complex ((R)-Il), respectively.
• fitting was performed without fixing the proximal coordination number to 9 the following results were obtained.
• the coordination number of 0 was 6.99 and the distance between atoms of Gd and O was 2.421 A, and in an aqueous solution (3 inM) the coordination number of 0 was 9.77 and the distance between atoms of Gd and O was 2.430 A.
• the XAFS analysis was performed for Gd (DTPA) and Gd (DOTA), and the coordination number of water molecule was 1.
• Tl relaxation time of complex (R)-IIa was measured by 7T MRI in the same manner as in Example 4.
• a metal complex which exhibits a Tl-reducing effect superior to that of a conventional compound and an MRI contrast agent containing the metal complex.

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