Cyclic Gd(III) complexes and their preparation and use.

Abstract

Cyclic Gd(III) complexes and their preparation and use are provided. [Solution] The present invention provides a cyclic Gd(III) complex, which has the chemical structure shown in formula I, and takes the ring structure of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, i.e., DOTA, as the parent ring. In formula I, lipophilic groups R' and R'' are introduced into the α-position of phenylacetic acid and the benzene ring structure, respectively. In formula I, the chiral group R is introduced into the DOTA macrocyclic position. The chiral group R increases the rigidity of the macrocyclic structure and improves the stability of the complex. The lipophilic groups R' and R can bind to organic anion transporting polypeptides in hepatocytes, so that the distribution of the cyclic Gd(III) complex as an imaging agent in the liver and gallbladder is greatly improved, i.e., the targeting is high.

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application with application number 202210256593.2, filed with the China Patent Office on March 16, 2022, entitled "Cyclic Gd(III) Complex and Its Preparation Method and Use," the entire contents of which are incorporated herein by reference. [Background technology]

[0002] The present invention relates to the technical field of organic complexes, and in particular to cyclic Gd(III) complexes and their preparation and use.

[0003] Magnetic resonance imaging (MRI) is a technique that uses computer technology and image reconstruction methods to obtain electromagnetic signals through the nuclear magnetic resonance phenomenon of atomic nuclei under the influence of a magnetic field. This imaging technique has the advantage of being harmless to the human body because it does not rely on external radiation, absorption, or reflection, and does not emit gamma rays. Furthermore, MRI has unique advantages in detecting liver cancer, providing multiparameter, multidirectional, and high-contrast soft-tissue imaging. However, MRI detection sensitivity is low, and approximately 40% of MRI detections require the use of contrast agents to improve the detection signal. For MRI detection of the nervous system, this rate is as high as approximately 60%, and approximately 40 million people worldwide use MRI contrast agents each year.

[0004] Currently, most commercially available hepatobiliary-specific MRI contrast agents are linear Gd-DTPA derivatives, such as Gd-EOB-DTPA, Primovist / Eovist, and Primovist. However, the above commercially available Gd-based MRI contrast agents have problems such as poor stability, high levels of metallic gadolinium residue, and poor targeting, posing serious health risks. Therefore, how to provide a stable MRI contrast agent that targets the hepatobiliary system is an urgent problem in the prior art. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a cyclic Gd(III) complex and its preparation and use. The cyclic Gd(III) complex provided by the present invention can be used as an MRI contrast agent targeting the liver and bile, and has the advantages of high stability and targeting ability. [Means for solving the problem]

[0006] In order to achieve the above object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a cyclic Gd(III) complex, having the chemical structure shown in Formula I: TIFF0007721572000001.tif54165 R in the formula I is H, a C1 to C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, and the configuration of R in the formula I is independently S or R; R″ in formula I is in the ortho, meta or para position of the benzene ring; R' and R'' in the formula I are independently H, C1 to C 10 alkyl group, fluorine atom, chlorine atom, bromine atom, iodine atom, -CF3, -CCl3, -CBr3, C1 to C 10 alkoxy groups, -COOH, -R1COOH, -COOR1, -Ph, -NO2, substituted phenyl groups, -R1-Ph, -R1NO2, -OR1-Ph, -CONHR3, TIFF0007721572000002.tif28165-SO2-R4 or -SO-R5, R1 in -R1COOH, -COOR1, -R1-Ph, -R1NO2, and -OR1-Ph is independently a C1 to C5 alkyl group, a substituent of the substituted phenyl group is a C1 to C5 alkyl group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, —CF3, —CCl3, —CBr3, a C1 to C5 alkoxy group, —COOH, —R2COOH, —COOR2, —Ph, —R2NO2, —OR2-Ph, —CONHR2, —SO2-R2, or —SO-R2, and R2 in —R2COOH, —COOR2, —Ph, —R2NO2, —OR2-Ph, —CONHR2, —SO2-R2, and —SO-R2 is independently a C1 to C3 alkyl group; R3, R4, and R5 in -CONHR3, -SO2-R4, and -SO-R5 are independently a C1 to C5 alkyl group or a benzyl group, M in formula I + is a metal cation or a glucosamine cation.

[0008] Preferably, R in formula I is H, -CH3, -CH2CH3, -CH(CH3)2, -CH(CH3)OH, -CH2Ph or -(CH2)4Ph; R' and R'' in formula I are independently H, -COOH, CONHR3, -CF3, -C(CH3)3, -Ph, -NO2, -OBn, TIFF0007721572000003.tif28165-SO2-R4 or -SO-R5, R3, R4 and R5 in the -CONHR3, -SO2-R4 and -SO-R5 are independently a C1 to C5 alkyl group or a benzyl group.

[0009] Preferably, M in formula I + Na + , K. + , Li + Or glucosamine cation.

[0010] The present invention also provides a method for preparing the cyclic Gd(III) complex described in the above technical solution, wherein R in Formula I is H, R' is H, and R'' is TIFF0007721572000004.tif24165, and the preparation method is (1) mixing a compound having a structure represented by formula A-1, DO3A, potassium carbonate, and acetonitrile in a nitrogen atmosphere to carry out a nucleophilic substitution reaction to obtain a compound having a structure represented by formula A-2; (2) mixing the compound having the structure shown in formula A-2 obtained in step (1) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a first reaction precursor; (3) In a nitrogen atmosphere, the first reaction precursor obtained in step (2) is mixed with HATU, dichloromethane, an amine, and DIPEA to carry out a condensation reaction, thereby obtaining a compound having a structure shown in formula A-3; (4) mixing the compound having the structure shown in formula A-3 obtained in step (3) with trifluoroacetic acid to carry out a tert-butyl ester removal reaction to obtain a compound having the structure shown in formula A-4; (5) The compound having the structure shown in formula A-4 obtained in step (4) is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (5) + The solution containing the compound is characterized in that it is a solution of a metal hydroxide or glucosamine. TIFF0007721572000005.tif43165

[0011] Preferably, the temperature for the tert-butyl ester removal reaction in step (4) is room temperature, and the time for the tert-butyl ester removal reaction is 10 to 15 hours.

[0012] The present invention also provides a method for preparing the cyclic Gd(III) complex described in the above technical solution, wherein R in Formula I is H, R' is H, and R'' is H, -COOH, -CF3, -C(CH3)3, -Ph, -NO2 or -OBn, and the preparation method includes: (1) mixing a compound having a structure shown in formula B-1, acetonitrile, DO3A, and potassium carbonate in a nitrogen atmosphere to carry out a nucleophilic substitution reaction to obtain a second reaction precursor; (2) mixing the second reaction precursor obtained in step (1) with hydrochloric acid to carry out a tert-butyl ester removal reaction to obtain a compound having a structure represented by formula B-2; (3) The compound having the structure shown in formula B-2 obtained in step (2) is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (3) + The solution containing the compound is characterized in that it is a solution of a metal hydroxide or glucosamine. TIFF0007721572000006.tif39165

[0013] Preferably, the temperature of the coordination reaction in step (3) is 90 to 110° C., and the time of the coordination reaction is 5 to 7 hours.

[0014] The present invention also provides a method for preparing the cyclic Gd(III) complex described in the above technical solution, wherein R in formula I is a C1-C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, R' is H, and R'' is -COOH, and the preparation method includes: (a) mixing a compound having a structure shown in formula C-1, a compound having a structure shown in formula chiral cyclen, and acetonitrile to carry out a nucleophilic substitution reaction to obtain a compound having a structure shown in formula C-2; (b) in a nitrogen atmosphere, mixing the compound having the structure shown in formula C-2 obtained in step (a), acetonitrile, potassium carbonate, and tert-butyl bromoacetate to carry out a nucleophilic substitution reaction to obtain a compound having the structure shown in formula C-3; (c) mixing the compound having the structure shown in formula C-3 obtained in step (b) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a compound having the structure shown in formula C-4; (d) The compound having the structure shown in formula C-4 obtained in step (c) is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (d) + The solution containing the compound is characterized in that it is a solution of a metal hydroxide or glucosamine. TIFF0007721572000007.tif86165

[0015] Preferably, the temperature of the second nucleophilic substitution reaction in step (b) is room temperature, and the time for the second nucleophilic substitution reaction is 16 to 20 hours.

[0016] The present invention also provides a method for preparing the cyclic Gd(III) complex described in the above technical solution, wherein R in Formula I is a C1-C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, R' is H, and R'' is TIFF0007721572000008.tif24165, and the preparation method is 1) mixing a compound having a structure shown in formula A-1, a compound having a structure shown in formula chiral cyclen, and acetonitrile to carry out a nucleophilic substitution reaction to obtain a compound having a structure shown in formula D-2; 2) in a nitrogen atmosphere, mixing the compound having the structure shown in formula D-2 obtained in step 1), acetonitrile, potassium carbonate, and tert-butyl bromoacetate to carry out a nucleophilic substitution reaction to obtain a compound having the structure shown in formula D-3; 3) mixing the compound having the structure shown in formula D-3 obtained in step 2) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction to obtain a third reaction precursor; 4) In a nitrogen atmosphere, the third reaction precursor obtained in step 3) is mixed with HATU, dichloromethane, an amine compound, and DIPEA to carry out a condensation reaction, thereby obtaining a compound having a structure shown in formula D-4; 5) mixing the compound having the structure shown in formula D-4 obtained in step 4) with trifluoroacetic acid in a nitrogen atmosphere to carry out a tert-butyl ester removal reaction to obtain a compound having the structure shown in formula D-5; 6) The compound having the structure shown in formula D-5 obtained in step 5) is treated with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in step 6) + The solution containing the compound is characterized in that it is a solution of a metal hydroxide or glucosamine. TIFF0007721572000009.tif88165

[0017] Preferably, the temperature of the ester hydrolysis reaction in step 3) is room temperature, and the time of the ester hydrolysis reaction is 4 to 8 hours.

[0018] The present invention also provides a method for preparing the cyclic Gd(III) complex described in the above technical solution, wherein R in formula I is a C1-C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, R' is H, and R'' is H, -CF3, -C(CH3)3, -Ph, -NO2 or -OBn, and the preparation method includes: (1') in a nitrogen atmosphere, a compound having a structure represented by formula E-1, a compound having a structure represented by formula chiral cyclen, and acetonitrile are mixed to carry out a nucleophilic substitution reaction to obtain a compound having a structure represented by formula E-2; (2') in a nitrogen atmosphere, mixing the compound having the structure shown in formula E-2 obtained in step (1'), acetonitrile, potassium carbonate, and ethyl bromoacetate to carry out a nucleophilic substitution reaction to obtain a compound having the structure shown in formula E-3; (3') mixing the compound having the structure shown in formula E-3 obtained in step (2') with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction, and then concentrating, diluting, and adjusting the pH of the product of the ester hydrolysis reaction to obtain a compound having the structure shown in formula E-4; (4') The compound having the structure shown in formula E-4 obtained in step (3') is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (4') + The solution containing the compound is characterized in that it is a solution of a metal hydroxide or glucosamine. TIFF0007721572000010.tif83165

[0019] Preferably, the temperature of the coordination reaction in step (4') is 90 to 110°C, and the time of the coordination reaction is 5 to 7 hours.

[0020] The present invention also provides a pharmaceutical composition of the cyclic Gd(III) complexes described in the above technical solution.

[0021] The present invention also provides the use of the cyclic Gd(III) complex or said pharmaceutical composition according to the above technical solution in nuclear magnetic resonance imaging. [Effects of the Invention]

[0022] The present invention provides a cyclic Gd(III) compound having the chemical structure shown in Formula I, in which the parent ring is the ring structure of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, i.e., DOTA. In Formula I, lipophilic groups R' and R'' are introduced into the α-position of the phenylacetic acid and the benzene ring structure, and a chiral group R is introduced into the DOTA macrocyclic position. The chiral group R increases the rigidity of the macrocyclic structure and improves the stability of the compound. The lipophilic groups R' and R'' can bind to organic anion transporting polypeptides in hepatocytes, thereby significantly improving the distribution of the cyclic Gd(III) complex as a contrast agent in the liver and bile, i.e., improving targeting. The results of the examples show that the hepatobiliary targeting ability of the cyclic Gd(III) complexes provided by the present invention has the optimal relaxivity range for nuclear magnetic resonance imaging, and GdL9 also has a relaxivity suitable for high-field nuclear magnetic resonance imaging. The cyclic Gd(III) complexes have high stability, significantly higher than those of Primovist and Gd-DOTA. After the chiral group R is introduced, the stability of the cyclic Gd(III) complexes is greatly improved, and GdL9 and GdL10 showed no detectable metal ion release within one year, demonstrating their excellent stability and can be used as hepatobiliary MRI contrast agents. [Brief explanation of the drawings]

[0023] [Figure 1] Figure 1 shows MRI images of the liver and bile obtained by detecting the liver and bile of a mouse using the GdL1 complex prepared in Example 1 of the present invention as an MRI contrast agent targeting the liver and bile, where 0 min, 5 min, 10 min, 20 min, 30 min, 1 h, and 2 h are the corresponding detection times after administering GdL1 to the mouse, respectively. [Figure 2] Figure 1 shows MRI images of the liver and bile obtained by detecting the liver and bile of a mouse using the GdL3 complex prepared in Example 3 of the present invention as an MRI contrast agent targeting the liver and bile, where 0 min, 5 min, 10 min, 20 min, 30 min, and 1 h are the corresponding detection times after administering GdL3 to the mouse, respectively. [Figure 3]Figure 1 shows MRI images of the liver and bile obtained by detecting the liver and bile of a mouse using the GdL4 complex prepared in Example 4 of the present invention as an MRI contrast agent targeting the liver and bile, where 0 min, 5 min, 10 min, 20 min, 30 min, 1 h, and 2 h are the corresponding detection times after administering GdL4 to the mouse, respectively. [Figure 4] Figure 1 shows MRI images of the liver and bile obtained by detecting the liver and bile of a mouse using the GdL8 complex prepared in Example 8 of the present invention as an MRI contrast agent targeting the liver and bile, where 0 min, 5 min, 10 min, 20 min, 30 min, 1 h, and 2 h are the corresponding detection times after administering GdL8 to the mouse, respectively. [Figure 5] Figure 1 shows MRI images of the liver and bile obtained by detecting the liver and bile of a mouse using the GdL9 complex prepared in Example 9 of the present invention as an MRI contrast agent targeting the liver and bile, where 0 min, 5 min, 10 min, 20 min, 30 min, and 1 h are the corresponding detection times after administering GdL9 to the mouse, respectively. [Figure 6] This is a hepatobiliary MRI image obtained by detecting the hepatobiliary tissue of a mouse using the GdL10 complex prepared in Example 10 of the present invention as an MRI contrast agent targeting the hepatobiliary tissue, where 0 min, 5 min, 10 min, 20 min, and 30 min are the corresponding detection times after administering GdL10 to the mouse, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention provides a cyclic Gd(III) complex, having the chemical structure shown in Formula I: TIFF0007721572000011.tif50165 R in the formula I is H, a C1 to C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, preferably H, -CH3, -CH2CH3, -CH(CH3)2, -CH(CH3)OH, -CH2Ph or -(CH2)4Ph, and the configuration of R in the formula I is independently S or R; R″ in formula I is in the ortho, meta or para position of the benzene ring; R' and R'' in the formula I are independently H, C1 to C 10 alkyl group, fluorine atom, chlorine atom, bromine atom, iodine atom, -CF3, -CCl3, -CBr3, C1 to C 10 alkoxy groups, -COOH, -R1COOH, -COOR1, -Ph, substituted phenyl groups, -R1-Ph, -R1NO2, -OR1-Ph, -CONHR3, TIFF0007721572000012.tif25165-SO2-R4 or -SO-R5, preferably H, -COOH, CONHR3, -CF3, -C(CH3)3, -Ph, -NO2, -OBn, TIFF0007721572000013.tif24165-SO2-R4 or -SO-R5, and more preferably H, -COOH, -CF3, -C(CH3)3, -Ph, -NO2, -OBn, TIFF0007721572000014.tif25165, R1 in -R1COOH, -COOR1, -R1-Ph, -R1NO2, and -OR1-Ph is independently a C1 to C5 alkyl group, a substituent of the substituted phenyl group is a C1 to C5 alkyl group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, —CF3, —CCl3, —CBr3, a C1 to C5 alkoxy group, —COOH, —R2COOH, —COOR2, —Ph, —R2NO2, —OR2-Ph, —CONHR2, —SO2-R2, or —SO-R2, and R2 in —R2COOH, —COOR2, —Ph, —R2NO2, —OR2-Ph, —CONHR2, —SO2-R2, and —SO-R2 is independently a C1 to C3 alkyl group; R3, R4, and R5 in -CONHR3, -SO2-R4, and -SO-R5 are independently a C1 to C5 alkyl group or a benzyl group, R' in formula I is more preferably H, -COOH, -CF3, -C(CH3)3 or -Ph; M in formula I + is a metal cation or a glucosamine cation, preferably Na + , K. + , Li + Or glucosamine cation.

[0025] In the present invention, the cyclic Gd(III) complex having the chemical structure shown in formula I is preferably TIFF0007721572000015.tif121165.

[0026] The cyclic Gd(III) complexes provided by the present invention can be used as MRI contrast agents targeting the liver and bile, and have the advantages of being highly stable and targetable.

[0027] The present invention also provides a method for preparing the cyclic Gd(III) complexes described in the above technical solution.

[0028] In the present invention, in the formula I, R is H, R' is H, and R'' is TIFF0007721572000016.tif26165, the method for preparing the cyclic Gd(III) complex is (1) mixing a compound having a structure represented by formula A-1, DO3A, potassium carbonate, and acetonitrile in a nitrogen atmosphere to carry out a nucleophilic substitution reaction to obtain a compound having a structure represented by formula A-2; (2) mixing the compound having the structure shown in formula A-2 obtained in step (1) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a first reaction precursor; (3) In a nitrogen atmosphere, the first reaction precursor obtained in step (2) is mixed with HATU, dichloromethane, an amine, and DIPEA to carry out a condensation reaction, thereby obtaining a compound having a structure shown in formula A-3; (4) mixing the compound having the structure shown in formula A-3 obtained in step (3) with trifluoroacetic acid to carry out a tert-butyl ester removal reaction to obtain a compound having the structure shown in formula A-4; (5) The compound having the structure shown in formula A-4 obtained in step (4) is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (5) + The solution containing is a solution of metal hydroxide or glucosamine. TIFF0007721572000017.tif38165

[0029] In the present invention, unless otherwise specified, all raw materials used are conventional commercially available products in the field.

[0030] In the present invention, a compound having the structure shown in formula A-1, DO3A, potassium carbonate, and acetonitrile are mixed in a nitrogen atmosphere to carry out a nucleophilic substitution reaction, thereby obtaining a compound having the structure shown in formula A-2.

[0031] In the present invention, the ratio of the amount of the compound having the structure shown in formula A-1, DO3A, and potassium carbonate is preferably 1:1:(1.5-2.5), more preferably 1:1:(1.8-2.2). In the present invention, controlling the ratio of the amount of the compound having the structure shown in formula A-1, DO3A, and potassium carbonate within the above range is beneficial for reducing by-products.

[0032] In the present invention, the mixing method is not particularly limited, and any conventional technical solution in this field may be used.

[0033] In the present invention, the temperature of the nucleophilic substitution reaction is preferably 60 to 80° C., more preferably 65 to 75° C. The time of the nucleophilic substitution reaction is preferably 12 to 18 hours, more preferably 14 to 17 hours. In the present invention, controlling the temperature and time of the nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula A-2.

[0034] In the present invention, after the nucleophilic substitution reaction is completed, the product of the nucleophilic substitution reaction is concentrated and then subjected to column chromatography to obtain a compound having the structure shown in formula A-2.

[0035] In the present invention, the concentration method is not particularly limited as long as the purpose of removing the solvent is achieved. In the present invention, the eluent used in the column chromatography is preferably a mixed solution of ethyl acetate and methanol in a volume ratio of 5:1.

[0036] In the present invention, after obtaining a compound having a structure represented by formula A-2, the compound having a structure represented by formula A-2 is mixed with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a first reaction precursor.

[0037] In the present invention, the ratio of the amount of the compound having the structure shown in formula A-2 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide is preferably (1-1.5):(3.5-4.5), more preferably (1.1-1.4):(3.8-4.2). In the present invention, controlling the ratio of the amount of the compound having the structure shown in formula A-2 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide within the above range is beneficial for improving the reaction efficiency.

[0038] In the present invention, the mixing method is preferably such that the compound having the structure shown in Formula A-2 is mixed with tetrahydrofuran and methanol in a volume ratio of 1:1 to obtain a mixed solution, and then the mixed solution is mixed with an aqueous solution of lithium hydroxide.

[0039] In the present invention, the temperature of the hydrolysis reaction is preferably room temperature. The time of the hydrolysis reaction is preferably 10 to 15 hours, more preferably 11 to 13 hours. In the present invention, controlling the temperature and time of the hydrolysis reaction within the above ranges is beneficial for improving the yield and purity of the hydrolysis reaction product.

[0040] In the present invention, after the hydrolysis reaction is completed, the hydrolysis reaction product is preferably sequentially concentrated, diluted with water, pH adjusted, and the solvent removed to obtain a first reaction precursor.

[0041] In the present invention, the concentration method is not particularly limited as long as the purpose of removing the solvent is achieved. In the present invention, the method of diluting by adding water is not particularly limited as long as the purpose of dissolving the concentrated product is achieved. In the present invention, the pH value is preferably adjusted to 7 with 1N hydrochloric acid. In the present invention, the solvent removal method is not particularly limited as long as the purpose of removing the solvent is achieved.

[0042] In the present invention, after obtaining the first reaction precursor, the first reaction precursor is mixed with HATU, dichloromethane, an amine, and DIPEA in a nitrogen atmosphere to carry out a condensation reaction, thereby obtaining a compound having the structure shown in Formula A-3.

[0043] In the present invention, the amine is preferably p-ethoxybenzylamine or 3,3-diphenylpropylamine. In the present invention, the ratio of the amounts of the compound having the structure represented by formula A-2, HATU, amine, and DIPEA is preferably (1-1.5):(2-3):(2-3):(2-3), more preferably (1.1-1.4):(2.2-2.8):(2.2-2.8):(2.2-2.8). In the present invention, controlling the ratio of the amounts of the compound having the structure represented by formula A-2, HATU, amine, and DIPEA within the above range is beneficial for improving the yield of the compound having the structure represented by formula A-3.

[0044] In the present invention, the mixing method is preferably such that the first reaction precursor is mixed with HATU and dichloromethane to obtain a mixed solution, and then the mixed solution is mixed with the amine and DIPEA.

[0045] In the present invention, the temperature of the condensation reaction is preferably room temperature. The time of the condensation reaction is preferably 3 to 6 hours, more preferably 3.5 to 5 hours. In the present invention, controlling the temperature and time of the condensation reaction within the above ranges is beneficial in reducing side reactions.

[0046] In the present invention, after the condensation reaction is completed, the product of the condensation reaction is added with dichloromethane, washed with water, dried, concentrated and subjected to column chromatography in this order to obtain a compound having the structure shown in formula A-3.

[0047] In the present invention, the method of adding dichloromethane is not particularly limited as long as it achieves the purpose of sufficient dissolution. In the present invention, the method of washing with water is not particularly limited as long as it achieves the purpose of removing water-soluble impurities. In the present invention, the method of drying is not particularly limited as long as it achieves the purpose of removing water. In the present invention, the method of concentration is not particularly limited as long as it achieves the purpose of removing organic solvents. In the present invention, the method of column chromatography is not particularly limited as long as it achieves the purpose of separating and purifying to obtain a compound having the structure shown in Formula A-3.

[0048] In the present invention, after obtaining a compound having the structure shown in formula A-3, the compound having the structure shown in formula A-3 is mixed with trifluoroacetic acid to carry out a tert-butyl ester removal reaction, thereby obtaining a compound having the structure shown in formula A-4.

[0049] In the present invention, the ratio of the amount of the compound having the structure represented by formula A-3 to the volume of trifluoroacetic acid is preferably (0.9-1.5):(3.3-5), more preferably (1-1.3):(3.5-4.5). In the present invention, controlling the ratio of the amount of the compound having the structure represented by formula A-3 to the volume of trifluoroacetic acid within the above range is beneficial for improving the yield of the compound having the structure represented by formula A-4.

[0050] In the present invention, the mixing method is not particularly limited as long as the purpose of uniformly mixing the components is achieved.

[0051] In the present invention, the temperature of the tert-butyl ester removal reaction is room temperature, and the time of the tert-butyl ester removal reaction is 10 to 15 hours, more preferably 11 to 13 hours. In the present invention, controlling the temperature and time of the tert-butyl ester removal reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by formula A-4.

[0052] In the present invention, after the completion of the tert-butyl ester removal reaction, the product of the tert-butyl ester removal reaction is successively subjected to evaporation to dryness to remove trifluoroacetic acid and separation to obtain a compound having a structure represented by formula A-4.

[0053] In the present invention, the method for evaporating trifluoroacetic acid to dryness is not particularly limited, as long as the objective of removing trifluoroacetic acid is achieved. In the present invention, the separation equipment is preferably reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited, as long as the objective of separating and purifying to obtain a compound having the structure shown in Formula A-4 is achieved.

[0054] In the present invention, after obtaining the compound having the structure shown in formula A-4, the compound having the structure shown in formula A-4 is reacted with a gadolinium source, water, M + The resulting solution is mixed with a solution containing Gd(III) to carry out a coordination reaction, yielding a cyclic Gd(III) complex.

[0055] In the present invention, the ratio of the amount of the compound having the structure shown in Formula A-4 to the amount of the gadolinium source is preferably 1: 1. In the present invention, controlling the ratio of the amount of the compound having the structure shown in Formula A-4 to the amount of the gadolinium source within the above range is beneficial for improving the yield of the cyclic Gd(III) complex.

[0056] In the present invention, the M + The solution containing M is a solution of metal hydroxide or glucosamine. In the present invention, the metal hydroxide is preferably NaOH, KOH or LiOH. In the present invention, the solution containing M + The concentration of the solution containing M is preferably 1N. In the present invention, the mixing method is to mix a compound having a structure shown in Formula A-4 with a gadolinium source and water to obtain a mixed solution, and then add M + Preferably, the pH value of the mixed solution is adjusted to 7 with a solution containing

[0057] In the present invention, the temperature of the coordination reaction is preferably 90 to 110°C, more preferably 95 to 105°C. The time of the coordination reaction is preferably 5 to 7 hours, more preferably 5.5 to 6.5 hours. In the present invention, controlling the temperature and time of the coordination reaction within the above ranges is beneficial for improving the yield of the cyclic Gd(III) complex.

[0058] In the present invention, after the coordination reaction is completed, it is preferable to separate the product of the coordination reaction to obtain a cyclic Gd(III) complex.

[0059] In the present invention, the separation equipment is preferably a reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0060] In the present invention, when R is H, R' is H, and R'' is H, -COOH, -CF3, -C(CH3)3, -Ph, -NO2 or -OBn in the formula I, the method for preparing the cyclic Gd(III) complex is as follows: (1) mixing a compound having a structure shown in formula B-1, acetonitrile, DO3A, and potassium carbonate in a nitrogen atmosphere to carry out a nucleophilic substitution reaction to obtain a second reaction precursor; (2) mixing the second reaction precursor obtained in step (1) with hydrochloric acid to carry out a tert-butyl ester removal reaction to obtain a compound having a structure represented by formula B-2; (3) The compound having the structure shown in formula B-2 obtained in step (2) is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (3) + The solution containing is a solution of metal hydroxide or glucosamine. TIFF0007721572000018.tif38165

[0061] In the present invention, a compound having the structure shown in formula B-1, acetonitrile, DO3A, and potassium carbonate are mixed in a nitrogen atmosphere to carry out a nucleophilic substitution reaction, thereby obtaining a second reaction precursor.

[0062] In the present invention, the ratio of the amounts of the compound having the structure shown in formula B-1, DO3A, and potassium carbonate is preferably 1:1:(1.5-2.5), more preferably 1:1:(1.8-2.2). In the present invention, controlling the ratio of the amounts of the compound having the structure shown in formula B-1, DO3A, and potassium carbonate within the above range is beneficial for improving the yield of the product of the nucleophilic substitution reaction.

[0063] In the present invention, the mixing method is not particularly limited, and any conventional technical solution in this field may be used.

[0064] In the present invention, the temperature of the nucleophilic substitution reaction is preferably 60 to 80° C., more preferably 65 to 75° C. The time of the nucleophilic substitution reaction is preferably 15 to 19 hours, more preferably 16 to 18 hours. In the present invention, controlling the temperature and time of the nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the product of the nucleophilic substitution reaction.

[0065] In the present invention, after the nucleophilic substitution reaction is completed, the product of the nucleophilic substitution reaction is successively filtered and concentrated.

[0066] In the present invention, the method of filtration is not particularly limited as long as it achieves solid-liquid separation.In the present invention, the method of concentration is not particularly limited as long as it achieves the purpose of removing the solvent.

[0067] In the present invention, after the second reaction precursor is obtained, the second reaction precursor is mixed with hydrochloric acid to carry out a tert-butyl ester removal reaction, thereby obtaining a compound having a structure represented by formula B-2.

[0068] In the present invention, the mixing method is not particularly limited as long as the objective of uniformly mixing each component is achieved. In the present invention, the concentration of the hydrochloric acid is preferably 6N. In the present invention, the ratio of the amount of the compound having the structure represented by formula B-1 to the volume of hydrochloric acid is preferably 1 mmol:(5-7) mL.

[0069] In the present invention, the temperature of the tert-butyl ester removal reaction is preferably 100 to 120°C, more preferably 105 to 110°C. The time of the substitution reaction is preferably 15 to 19 hours, more preferably 16 to 18 hours. In the present invention, controlling the temperature and time of the tert-butyl ester removal reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula B-2.

[0070] In the present invention, after the completion of the tert-butyl ester removal reaction, it is preferable to separate the product of the tert-butyl ester removal reaction to obtain a compound having a structure represented by formula B-2.

[0071] In the present invention, the separation equipment is preferably a reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0072] In the present invention, after obtaining the compound having the structure shown in formula B-2, the compound having the structure shown in formula B-2 is reacted with a gadolinium source, water, M + The resulting solution is mixed with a solution containing Gd(III) to carry out a coordination reaction, yielding a cyclic Gd(III) complex.

[0073] In the present invention, the ratio of the amount of the compound having the structure shown in formula B-2 to the amount of the gadolinium source is preferably 1:1. + The solution containing M is a solution of metal hydroxide or glucosamine. In the present invention, the metal hydroxide is preferably NaOH, KOH or LiOH. In the present invention, the solution containing M +The concentration of the solution containing M is preferably 1N. In the present invention, the mixing method is to mix a compound having a structure shown in Formula B-2 with a gadolinium source and water to obtain a mixed solution, and then add M + Preferably, the pH value of the mixed solution is adjusted to 7 with a solution containing

[0074] In the present invention, the temperature of the coordination reaction is 90 to 110°C, more preferably 95 to 105°C. The time period of the coordination reaction is 5 to 7 hours, more preferably 5.5 to 6.5 hours. In the present invention, controlling the temperature and time period of the coordination reaction within the above ranges is beneficial for improving the yield of the cyclic Gd(III) complex.

[0075] In the present invention, after the coordination reaction is completed, it is preferable to separate the product of the coordination reaction to obtain a cyclic Gd(III) complex.

[0076] In the present invention, the separation equipment is preferably a reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0077] In the present invention, in the formula I, when R is a C1-C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, R' is H, and R'' is -COOH, the method for preparing the cyclic Gd(III) complex compound is as follows: (a) mixing a compound having a structure shown in formula C-1, a compound having a structure shown in formula chiral cyclen, and acetonitrile to perform a first nucleophilic substitution reaction to obtain a compound having a structure shown in formula C-2; (b) in a nitrogen atmosphere, mixing the compound having the structure shown in formula C-2 obtained in step (a), acetonitrile, potassium carbonate, and ethyl bromoacetate to carry out a second nucleophilic substitution reaction to obtain a compound having the structure shown in formula C-3; (c) mixing the compound having the structure shown in formula C-3 obtained in step (b) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a compound having the structure shown in formula C-4; (d) The compound having the structure shown in formula C-4 obtained in step (c) is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (d) + The solution containing is a solution of metal hydroxide or glucosamine. TIFF0007721572000019.tif83165

[0078] In the present invention, a compound having a structure shown in formula C-1, a compound having a structure shown in formula chiral cyclen, and acetonitrile are mixed to perform a first nucleophilic substitution reaction, thereby obtaining a compound having a structure shown in formula C-2.

[0079] In the present invention, the mixing method is not particularly limited as long as the purpose of uniformly mixing the components is achieved.

[0080] In the present invention, the ratio of the amount of the compound having the structure shown in the formula C-1 to the amount of the compound having the structure shown in the formula chiral cyclen is preferably 1:1.

[0081] In the present invention, the temperature of the first nucleophilic substitution reaction is preferably room temperature. The time of the substitution reaction is preferably 16 to 20 hours, more preferably 17 to 19 hours. In the present invention, controlling the temperature and time of the first nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula C-2.

[0082] In the present invention, after the first nucleophilic substitution reaction is completed, the product of the first nucleophilic substitution reaction is sequentially subjected to first solvent removal, dissolution, first extraction, pH adjustment, second extraction, and second solvent removal to obtain a compound having a structure shown in Formula C-2.

[0083] In the present invention, the method for removing the first solvent is not particularly limited, as long as the purpose of removing the organic solvent is achieved. In the present invention, the reagent used for the dissolution is preferably ethyl acetate. In the present invention, the reagent used for the first extraction is preferably 1N hydrochloric acid. The number of times of the first extraction is preferably three. In the present invention, the method for adjusting the pH value is preferably adjusting the pH value to 10 with potassium carbonate solvent. In the present invention, the reagent used for the second extraction is preferably dichloromethane. The number of times of the first extraction is preferably three. In the present invention, the method for removing the second solvent is not particularly limited, as long as the purpose of removing the organic solvent is achieved.

[0084] In the present invention, after obtaining a compound having the structure shown in formula C-2, the compound having the structure shown in formula C-2, acetonitrile, potassium carbonate, and ethyl bromoacetate are mixed in a nitrogen atmosphere to carry out a second nucleophilic substitution reaction, thereby obtaining a compound having the structure shown in formula C-3.

[0085] In the present invention, the mixing is preferably carried out by mixing a compound having the structure shown in Formula C-2 with acetonitrile to obtain a mixed solution, and then adding potassium carbonate and tert-butyl bromoacetate to the mixed solution in that order.

[0086] In the present invention, the ratio of the amounts of the compound having the structure represented by formula C-2, potassium carbonate, and tert-butyl bromoacetate is preferably 1:(4.9-5.3), more preferably 1:(5-5.2). In the present invention, controlling the ratio of the amounts of the compound having the structure represented by formula C-2, potassium carbonate, and tert-butyl bromoacetate within the above range is beneficial for improving the yield of the compound having the structure represented by formula C-3.

[0087] In the present invention, the temperature of the second nucleophilic substitution reaction is room temperature. The duration of the substitution reaction is 16 to 20 hours, more preferably 17 to 19 hours. In the present invention, controlling the temperature and duration of the second nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula C-3.

[0088] In the present invention, after the second nucleophilic substitution reaction is completed, the product of the second nucleophilic substitution reaction is preferably subjected to filtration, concentration and column chromatography to obtain a compound having a structure represented by formula C-3.

[0089] In the present invention, the filtration method is not particularly limited as long as the purpose of solid-liquid separation is achieved. In the present invention, the concentration method is not particularly limited as long as the purpose of solvent removal is achieved. In the present invention, the eluent used in the column chromatography is preferably a mixed solution of ethyl acetate and methanol in a volume ratio of 10:1.

[0090] In the present invention, after obtaining a compound having a structure represented by formula C-3, the compound having a structure represented by formula C-3 is mixed with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a compound having a structure represented by formula C-4.

[0091] In the present invention, the ratio of the amount of the compound having the structure shown in Formula C-3 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide is preferably (1-1.5):(3.5-4.5), more preferably (1.1-1.4):(3.8-4.2). In the present invention, controlling the ratio of the amount of the compound having the structure shown in Formula C-3 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide within the above range is beneficial for improving the yield of the compound having the structure shown in Formula C-4.

[0092] In the present invention, the mixing method is preferably such that the compound having the structure shown in Formula C-3 is mixed with tetrahydrofuran and methanol in a volume ratio of 1:1 to obtain a mixed solution, and then the mixed solution is mixed with an aqueous solution of lithium hydroxide.

[0093] In the present invention, the temperature of the hydrolysis reaction is preferably room temperature. The time of the hydrolysis reaction is preferably 4 to 8 hours, more preferably 5 to 7 hours. In the present invention, controlling the temperature and time of the hydrolysis reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula C-4.

[0094] In the present invention, after the hydrolysis reaction is completed, the product of the hydrolysis reaction is preferably concentrated, diluted with water, pH adjusted, and separated to obtain a compound having the structure shown in formula C-4.

[0095] In the present invention, the concentration method is not particularly limited as long as the objective of removing the solvent is achieved. In the present invention, the method of diluting by adding water is not particularly limited as long as the objective of dissolving the concentrated product is achieved. In the present invention, the pH value is preferably adjusted to 7 with 1N hydrochloric acid. In the present invention, the separation equipment is preferably reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the objective of separating and purifying to obtain a compound having the structure shown in Formula C-4 is achieved.

[0096] In the present invention, after obtaining a compound having the structure shown in formula C-4, the compound having the structure shown in formula C-4 is mixed with a solution containing a gadolinium source, water, and M+ to carry out a coordination reaction, thereby obtaining a cyclic Gd(III) complex.

[0097] In the present invention, the ratio of the amount of the compound having the structure shown in formula C-4 to the amount of the gadolinium source is preferably 1:1. + The solution containing M is a solution of metal hydroxide or glucosamine. In the present invention, the metal hydroxide is preferably NaOH, KOH or LiOH. In the present invention, the solution containing M + The concentration of the solution containing M is preferably 1N. In the present invention, the mixing method is to mix a compound having a structure shown in formula C-4 with a gadolinium source and water to obtain a mixed solution, and then add M + Preferably, the pH value of the mixed solution is adjusted to 7 with a solution containing

[0098] In the present invention, the temperature of the coordination reaction is preferably 90 to 110°C, more preferably 95 to 105°C. The time of the coordination reaction is preferably 5 to 7 hours, more preferably 5.5 to 6.5 hours. In the present invention, controlling the temperature and time of the coordination reaction within the above ranges is beneficial for improving the yield of the cyclic Gd(III) complex.

[0099] In the present invention, after the coordination reaction is completed, it is preferable to separate the product of the coordination reaction to obtain a cyclic Gd(III) complex.

[0100] In the present invention, the separation equipment is preferably a reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0101] In the present invention, in the formula I, R is a C1 to C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, R' is H, R'' is TIFF0007721572000020.tif28165, the method for preparing the cyclic Gd(III) complex is 1) mixing a compound having a structure shown in formula A-1, a compound having a structure shown in formula chiral cyclen, and acetonitrile to carry out a first nucleophilic substitution reaction to obtain a compound having a structure shown in formula D-2; 2) In a nitrogen atmosphere, the compound having the structure shown in formula D-2 obtained in step 1) is mixed with acetonitrile, potassium carbonate, and tert-butyl bromoacetate to carry out a second nucleophilic substitution reaction, thereby obtaining a compound having the structure shown in formula D-3; 3) mixing the compound having the structure shown in formula D-3 obtained in step 2) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction to obtain a third reaction precursor; 4) In a nitrogen atmosphere, the third reaction precursor obtained in step 3) is mixed with HATU, dichloromethane, an amine compound, and DIPEA to carry out a condensation reaction, thereby obtaining a compound having a structure shown in formula D-4; 5) mixing the compound having the structure shown in formula D-4 obtained in step 4) with trifluoroacetic acid in a nitrogen atmosphere to carry out a tert-butyl ester removal reaction to obtain a compound having the structure shown in formula D-5; 6) The compound having the structure shown in formula D-5 obtained in step (5) is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in step 6) + The solution containing is a solution of metal hydroxide or glucosamine. TIFF0007721572000021.tif91165

[0102] In the present invention, a compound having a structure shown in Formula A-1, a compound having a structure shown in Formula chiral cyclen, and acetonitrile are mixed to carry out a first nucleophilic substitution reaction, thereby obtaining a compound having a structure shown in Formula D-2.

[0103] In the present invention, the mixing method is not particularly limited as long as the purpose of uniformly mixing the components is achieved.

[0104] In the present invention, the ratio of the amount of the compound having the structure shown in the formula A-1 to the amount of the compound having the structure shown in the formula chiral cyclen is preferably 1:1.

[0105] In the present invention, the temperature of the first nucleophilic substitution reaction is preferably 70 to 90° C., more preferably 75 to 85° C. The time of the substitution reaction is preferably 6 to 8 d, more preferably 6.5 to 7.5 d. In the present invention, controlling the temperature and time of the first nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula D-2.

[0106] In the present invention, after the first nucleophilic substitution reaction is completed, it is preferable to sequentially subject the product of the first nucleophilic substitution reaction to concentration and column chromatography.

[0107] In the present invention, the concentration method is not particularly limited as long as the purpose of removing the solvent is achieved. In the present invention, the eluent used in the column chromatography is preferably a mixed solution of ethyl acetate and methanol in a volume ratio of 5:1.

[0108] In the present invention, after obtaining a mixture having the structure shown in formula D-2, a compound having the structure shown in formula D-2, acetonitrile, potassium carbonate, and tert-butyl bromoacetate are mixed in a nitrogen atmosphere to carry out a second nucleophilic substitution reaction, thereby obtaining a compound having the structure shown in formula D-3.

[0109] In the present invention, the ratio of the amounts of the compound having the structure represented by formula D-2, potassium carbonate, and tert-butyl bromoacetate is preferably 1:(4.9-5.3), more preferably 1:(5-5.2). In the present invention, controlling the ratio of the amounts of the compound having the structure represented by formula D-2, potassium carbonate, and tert-butyl bromoacetate within the above range is beneficial for improving the yield of the compound having the structure represented by formula D-3.

[0110] In the present invention, the temperature of the second nucleophilic substitution reaction is preferably room temperature. The time of the substitution reaction is preferably 16 to 20 hours, more preferably 17 to 19 hours. In the present invention, controlling the temperature and time of the second nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula D-3.

[0111] In the present invention, after the second nucleophilic substitution reaction is completed, the product of the second nucleophilic substitution reaction is preferably filtered, concentrated and subjected to column chromatography to obtain a compound having a structure shown in formula D-3.

[0112] In the present invention, the filtration method is not particularly limited as long as the purpose of solid-liquid separation is achieved. In the present invention, the concentration method is not particularly limited as long as the purpose of solvent removal is achieved. In the present invention, the eluent used in the column chromatography is preferably a mixed solution of ethyl acetate and methanol in a volume ratio of 20:1.

[0113] In the present invention, after obtaining a compound having a structure represented by formula D-3, the compound having a structure represented by formula D-3 is mixed with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction, thereby obtaining a third reaction precursor.

[0114] In the present invention, the ratio of the amount of the compound having the structure shown in Formula D-3 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide is preferably (1.5-2):(4.9-5.5), more preferably (1.6-1.8):(5-5.2). In the present invention, controlling the ratio of the amount of the compound having the structure shown in Formula D-3 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide within the above range is beneficial for improving the yield of the product of the ester hydrolysis reaction.

[0115] In the present invention, the mixing method is preferably such that the compound having the structure shown in Formula D-3 is mixed with tetrahydrofuran and methanol in a volume ratio of 1:1 to obtain a mixed solution, and then the mixed solution is mixed with an aqueous solution of lithium hydroxide.

[0116] In the present invention, the temperature of the ester hydrolysis reaction is room temperature. The time of the ester hydrolysis reaction is 4 to 8 hours, more preferably 5 to 7 hours. In the present invention, controlling the temperature and time of the ester hydrolysis reaction within the above ranges is beneficial for improving the yield of the product of the ester hydrolysis reaction.

[0117] In the present invention, after the ester hydrolysis reaction is completed, the product of the ester hydrolysis reaction is preferably concentrated, diluted with water, pH adjusted, and the solvent removed to obtain a third reaction precursor.

[0118] In the present invention, the concentration method is not particularly limited as long as the purpose of removing the solvent is achieved. In the present invention, the method of diluting by adding water is not particularly limited as long as the purpose of dissolving the concentrated product is achieved. In the present invention, the pH value is preferably adjusted to 7 with 1N hydrochloric acid. In the present invention, the solvent removal method is not particularly limited as long as the purpose of removing the solvent is achieved.

[0119] In the present invention, after obtaining the third reaction precursor, the third reaction precursor is mixed with HATU, dichloromethane, an amine compound, and DIPEA in a nitrogen atmosphere to carry out a condensation reaction, thereby obtaining a compound having the structure shown in Formula D-4.

[0120] In the present invention, the amine compound is preferably p-ethoxybenzylamine or 3,3-diphenylpropylamine. In the present invention, the ratio of the amounts of the compound having the structure represented by Formula D-3, HATU, the amine compound, and DIPEA is preferably (1.5-2):(3.2-3.6):(3.2-3.6):(3.2-3.6), more preferably (1.6-1.8):(3.3-3.5):(3.3-3.5):(3.3-3.5). In the present invention, controlling the ratio of the amounts of the compound having the structure represented by Formula D-3, HATU, the amine compound, and DIPEA within the above range is beneficial for improving the yield of the compound having the structure represented by Formula D-4.

[0121] In the present invention, the mixing method is preferably such that the third reaction precursor is mixed with dichloromethane to obtain a mixed solution, and the mixed solution is mixed with HATU, an amine compound, and DIPEA.

[0122] In the present invention, the temperature of the condensation reaction is preferably room temperature. The time of the condensation reaction is preferably 3 to 6 hours, more preferably 3.5 to 5 hours. In the present invention, controlling the temperature and time of the condensation reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula D-4.

[0123] In the present invention, after the condensation reaction is completed, the product of the condensation reaction is preferably subjected to solvent removal and column chromatography in that order to obtain a compound having a structure represented by formula D-4.

[0124] In the present invention, the method for removing the solvent is not particularly limited as long as the purpose of removing the organic solvent is achieved. In the present invention, the eluent used in the column chromatography is preferably a mixed solution of ethyl acetate and methanol in a volume ratio of 10:1.

[0125] In the present invention, after obtaining a compound having the structure shown in formula D-4, the compound having the structure shown in formula D-4 is mixed with trifluoroacetic acid in a nitrogen atmosphere to carry out a tert-butyl ester removal reaction, thereby obtaining a compound having the structure shown in formula D-5.

[0126] In the present invention, the ratio of the amount of the compound having the structure represented by formula D-4 to the volume of trifluoroacetic acid is preferably (0.8-1.2):(3.3-5), more preferably (0.9-1.1):(3.5-4.5). In the present invention, controlling the ratio of the amount of the compound having the structure represented by formula D-4 to the volume of trifluoroacetic acid within the above range is beneficial for improving the yield of the compound having the structure represented by formula D-5.

[0127] In the present invention, the mixing method is not particularly limited as long as the purpose of uniformly mixing the components is achieved.

[0128] In the present invention, the temperature of the tert-butyl ester removal reaction is preferably room temperature. The time of the tert-butyl ester removal reaction is preferably 10 to 15 hours, more preferably 11 to 13 hours. In the present invention, controlling the temperature and time of the tert-butyl ester removal reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula D-5.

[0129] In the present invention, after the completion of the tert-butyl ester removal reaction, the product of the tert-butyl ester removal reaction is sequentially concentrated and separated to obtain a compound having the structure shown in formula D-5.

[0130] In the present invention, the concentration method is not particularly limited as long as the purpose of solvent removal is achieved. In the present invention, the separation equipment is preferably reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0131] In the present invention, after obtaining the compound having the structure shown in formula D-5, the compound having the structure shown in formula D-5 is reacted with a gadolinium source, water, M + The resulting solution is mixed with a solution containing Gd(III) to carry out a coordination reaction, yielding a cyclic Gd(III) complex.

[0132] In the present invention, the ratio of the amount of the compound having the structure shown in the formula D-5 to the amount of the gadolinium source is preferably 1:1. + The solution containing M is a solution of metal hydroxide or glucosamine. In the present invention, the metal hydroxide is preferably NaOH, KOH or LiOH. In the present invention, the solution containing M + The concentration of the solution containing M is preferably 1N. In the present invention, the mixing method is to mix a compound having a structure shown in Formula D-5 with a gadolinium source and water to obtain a mixed solution, and then add M + Preferably, the pH value of the mixed solution is adjusted to 7 with a solution containing

[0133] In the present invention, the temperature of the coordination reaction is preferably 90 to 110°C, more preferably 95 to 105°C. The time of the coordination reaction is preferably 5 to 7 hours, more preferably 5.5 to 6.5 hours. In the present invention, controlling the temperature and time of the coordination reaction within the above ranges is beneficial for improving the yield of the cyclic Gd(III) complex.

[0134] In the present invention, after the coordination reaction is completed, it is preferable to separate the product of the coordination reaction to obtain a cyclic Gd(III) complex.

[0135] In the present invention, the separation equipment is preferably a reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0136] In the present invention, when, in the formula I, R is a C1-C4 alkyl group, -CH2OH, -CH(CH3)OH, -CH2CH2OH, -CH2Ph, -(CH2)2Ph, -(CH2)3Ph, -(CH2)3NH2 or -(CH2)4Ph, R' is H, and R'' is H, -CF3, -C(CH3)3, -Ph, -NO2 or -OBn, the method for preparing the cyclic Gd(III) complex is as follows: (1') in a nitrogen atmosphere, a compound having a structure represented by formula E-1, a compound having a structure represented by formula chiral cyclen, and acetonitrile are mixed to carry out a first nucleophilic substitution reaction to obtain a compound having a structure represented by formula E-2; (2') in a nitrogen atmosphere, mixing the compound having the structure shown in formula E-2 obtained in step (1'), acetonitrile, potassium carbonate, and tert-butyl bromoacetate to carry out a second nucleophilic substitution reaction to obtain a compound having the structure shown in formula E-3; (3') mixing the compound having the structure shown in formula E-3 obtained in step (2') with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction, and then sequentially concentrating, diluting, and adjusting the pH of the product of the ester hydrolysis reaction to obtain a compound having the structure shown in formula E-4; (4') The compound having the structure shown in formula E-4 obtained in step (3') is reacted with a gadolinium source, water, M + and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex, M in the step (4') + The solution containing is a solution of metal hydroxide or glucosamine. TIFF0007721572000022.tif87165

[0137] In the present invention, a compound having a structure represented by Formula E-1, a compound having a structure represented by Formula chiral cyclen, and acetonitrile are mixed in a nitrogen atmosphere to carry out a first nucleophilic substitution reaction, thereby obtaining a compound having a structure represented by Formula E-2.

[0138] In the present invention, the mixing method is not particularly limited as long as the purpose of uniformly mixing the components is achieved.

[0139] In the present invention, the ratio of the amount of the compound having the structure shown in the formula E-1 to the amount of the compound having the structure shown in the formula chiral cyclen is preferably 1:1.

[0140] In the present invention, the temperature of the first nucleophilic substitution reaction is preferably room temperature. The time of the substitution reaction is preferably 15 to 22 hours, more preferably 17 to 20 hours. In the present invention, controlling the temperature and time of the first nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula E-2.

[0141] In the present invention, after the first nucleophilic substitution reaction is completed, it is preferable to sequentially subject the product of the first nucleophilic substitution reaction to concentration and column chromatography.

[0142] In the present invention, the concentration method is not particularly limited as long as the purpose of removing the solvent is achieved. In the present invention, the eluent used in the column chromatography is preferably a mixed solution of ethyl acetate and methanol in a volume ratio of 5:1.

[0143] In the present invention, after obtaining a compound having the structure shown in formula E-2, the compound having the structure shown in formula E-2, acetonitrile, potassium carbonate, and ethyl bromoacetate are mixed in a nitrogen atmosphere to carry out a second nucleophilic substitution reaction, thereby obtaining a compound having the structure shown in formula E-3.

[0144] In the present invention, the ratio of the amounts of the compound having the structure represented by formula E-2, potassium carbonate, and ethyl bromoacetate is preferably 1:(4.9-5.3), more preferably 1:(5-5.2). In the present invention, controlling the ratio of the amounts of the compound having the structure represented by formula E-2, potassium carbonate, and tert-butyl bromoacetate within the above range is beneficial for improving the yield of the compound having the structure represented by formula E-3.

[0145] In the present invention, the temperature of the second nucleophilic substitution reaction is preferably room temperature. The time of the substitution reaction is preferably 16 to 20 hours, more preferably 17 to 19 hours. In the present invention, controlling the temperature and time of the second nucleophilic substitution reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula E-3.

[0146] In the present invention, after the second nucleophilic substitution reaction is completed, the product of the second nucleophilic substitution reaction is preferably filtered, concentrated and subjected to column chromatography to obtain a compound having a structure shown in formula E-3.

[0147] In the present invention, the filtration method is not particularly limited as long as the purpose of solid-liquid separation is achieved. In the present invention, the concentration method is not particularly limited as long as the purpose of solvent removal is achieved. In the present invention, the eluent used in the column chromatography is preferably a mixed solution of ethyl acetate and methanol in a volume ratio of 10:1.

[0148] In the present invention, after obtaining a compound having the structure represented by formula E-3, the compound having the structure represented by formula E-3 is mixed with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction, and then the product of the ester hydrolysis reaction is concentrated, diluted, and pH adjusted sequentially to obtain a compound having the structure represented by formula E-4.

[0149] In the present invention, the ratio of the amount of the compound having the structure shown in Formula E-3 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide is preferably (1-1.5):(3.5-4.4), more preferably (1.1-1.4):(3.6-4.1). In the present invention, controlling the ratio of the amount of the compound having the structure shown in Formula E-3 to the amount of lithium hydroxide in the aqueous solution of lithium hydroxide within the above range is beneficial for improving the yield of the compound having the structure shown in Formula E-4.

[0150] In the present invention, the mixing method is preferably such that the compound having the structure shown in Formula E-3 is mixed with tetrahydrofuran and methanol in a volume ratio of 1:1 to obtain a mixed solution, and then the mixed solution is mixed with an aqueous solution of lithium hydroxide.

[0151] In the present invention, the temperature of the ester hydrolysis reaction is preferably room temperature. The time of the ester hydrolysis reaction is preferably 4 to 8 hours, more preferably 5 to 7 hours. In the present invention, controlling the temperature and time of the ester hydrolysis reaction within the above ranges is beneficial for improving the yield of the compound having the structure represented by Formula E-4.

[0152] In the present invention, the concentration method is not particularly limited as long as the purpose of removing the solvent is achieved. In the present invention, the method of diluting by adding water is not particularly limited as long as the purpose of dissolving the concentrated product is achieved. In the present invention, the pH value is preferably adjusted to 7 with 1N hydrochloric acid.

[0153] In the present invention, after the pH adjustment is completed, the product obtained by the pH adjustment is preferably separated to obtain a compound having the structure shown in formula E-4.

[0154] In the present invention, the separation equipment is preferably a reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0155] In the present invention, after obtaining the compound having the structure shown in formula E-4, the compound having the structure shown in formula E-4 is reacted with a gadolinium source, water, M + The resulting solution is mixed with a solution containing Gd(III) to carry out a coordination reaction, yielding a cyclic Gd(III) complex.

[0156] In the present invention, the ratio of the amount of the compound having the structure shown in formula E-4 to the amount of the gadolinium source is preferably 1:1. + The solution containing M is a solution of metal hydroxide or glucosamine. In the present invention, the metal hydroxide is preferably NaOH, KOH or LiOH. In the present invention, the solution containing M + The concentration of the solution containing M is preferably 1N. In the present invention, the mixing method is to mix a compound having a structure shown in Formula E-4 with a gadolinium source and water to obtain a mixed solution, and then add M + Preferably, the pH value of the mixed solution is adjusted to 7 with a solution containing

[0157] In the present invention, the temperature of the coordination reaction is 90 to 110°C, more preferably 95 to 105°C. The time period of the coordination reaction is 5 to 7 hours, more preferably 5.5 to 6.5 hours. In the present invention, controlling the temperature and time period of the coordination reaction within the above ranges is beneficial for improving the yield of the cyclic Gd(III) complex.

[0158] In the present invention, after the coordination reaction is completed, it is preferable to separate the product of the coordination reaction to obtain a cyclic Gd(III) complex.

[0159] In the present invention, the separation equipment is preferably a reversed-phase liquid chromatography. In the present invention, the separation method is not particularly limited as long as the purpose of separation and purification is achieved.

[0160] In the present invention, the reversed-phase liquid chromatography can effectively separate the Gd(III) complex, the ligand, and the inorganic salt, thereby obtaining a highly pure Gd(III) complex for nuclear magnetic resonance imaging.

[0161] The present invention also provides a pharmaceutical composition comprising the cyclic Gd(III) complex described in the above technical solution.

[0162] The present invention also provides a use of the cyclic Gd(III) complex or the pharmaceutical composition in nuclear magnetic resonance imaging, wherein the cyclic Gd(III) complex or the pharmaceutical composition is preferably used as a nuclear magnetic resonance imaging contrast agent targeting the liver and bile.

[0163] The following will clearly and completely describe the technical solutions of the present invention with reference to the embodiments of the present invention. The described embodiments are only some of the embodiments of the present invention, and are not all of the embodiments. Based on the embodiments of the present invention, any other embodiments that can be conceived by those skilled in the art without any creative effort fall within the technical scope of the present invention.

[0164] Example 1

[0165] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where R is H, R' is H, and R'' is The compound TIFF0007721572000023.tif22165 is designated as complex GdL1.

[0166] Preparation method: TIFF0007721572000024.tif62165(1) The compound having the structure shown in formula A-1 (1.0 g, 3 mmol), DO3A (1.6 g, 3 mmol), and potassium carbonate (0.6 g, 6 mmol) were dissolved in 20 mL of acetonitrile, heated to 70°C under nitrogen protection, and stirred to carry out a nucleophilic substitution reaction for 16 hours. The product of the nucleophilic substitution reaction was concentrated and the resulting mixture was purified by silica gel column chromatography (ethyl acetate:methanol = 5:1) to obtain the compound having the structure shown in formula A-2, with a yield of 76%. 1H NMR(400MHz,CDCl3)δ(ppm):8.00(d,2H,J=8.40Hz),7.54(d,2H,J=8.40Hz),4.52(s,1 H),3.92(s,3H),3.33(s,2H),3.18(s,3H),2.80(m,15H),1.48(s,20H),1.43(s,16H). 13 C NMR(100MHz,CDCl3)δ(ppm)171.26,171.09,170.86,166.93,143.16,129.46,129.38,129.10,81.65,80.81,77 .41,77.09,76.77,69.45,56.24,56.10,52.37,52.08,52.05,49.32,31.27,29.73,28.28,28.22,28.19,28.09. (2) The compound (1.0 g, 1.3 mmol) having the structure shown in Formula A-2 obtained in step (1) was dissolved in tetrahydrofuran / methanol (10 mL, 1:1) to obtain a mixture. Lithium hydroxide (0.1 g, 4.0 mmol) was dissolved in 1 mL of water to obtain a lithium hydroxide solution, and the mixture was added to the lithium hydroxide solution. The mixture was stirred at room temperature to carry out an ester hydrolysis reaction for 12 hours. The product of the ester hydrolysis reaction was concentrated, diluted with 5 mL of water, and the pH was adjusted to 7 with 1 N hydrochloric acid solution. The solvent was then evaporated to dryness to obtain a first reaction precursor. (3) HATU (1.0 g, 2.6 mmol) and 30 mL of dichloromethane were added to the first reaction precursor obtained in step (2). After complete dissolution, p-ethoxybenzylamine (0.4 g, 2.6 mmol) and DIPEA (0.3 g, 2.6 mmol) were added. The condensation reaction was continued for 4 hours under nitrogen protection and stirring. 70 mL of dichloromethane was added to the condensation product, which was then washed three times with water. The organic phase was dried and concentrated. The compound having the structure shown in formula A-3 was purified by silica gel column chromatography in an 80% yield. (4) 4 mL of trifluoroacetic acid was added to the compound (1.0 g, 1.1 mmol) having the structure shown in Formula A-3 obtained in step (3), and the mixture was stirred at room temperature to carry out a tert-butyl ester removal reaction for 12 hours. The trifluoroacetic acid product of the tert-butyl ester removal reaction was evaporated to dryness, and the product was separated and purified by reverse phase liquid chromatography to obtain a compound having the structure shown in Formula A-4. (5) The compound having the structure shown in formula A-4 obtained in step (4) (0.2 g, 0.3 mmol) and GdCl3·6H2O (111 mg, 0.3 mmol) were dissolved in 10 mL of water, the pH was adjusted to 7 with 1 N sodium hydroxide solution, and the mixture was heated to 100 °C to carry out the coordination reaction for 6 h. The product of the coordination reaction was separated by reversed-phase preparative liquid chromatography to obtain complex GdL1.

[0167] Example 2

[0168] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where R is H, R' is H, and R'' is The compound TIFF0007721572000025.tif24165 is designated as complex GdL2.

[0169] Preparation method: TIFF0007721572000026.tif42165

[0170] The complex GdL2 was prepared according to the method of Example 1. HPLC-MS (ESI - )calculated for C 38 H 43 GdN5O9,[M] = 871.23,found 871.25.

[0171] The difference from Example 1 is that in step (2), p-ethoxybenzylamine is replaced with 3,3-diphenylpropylamine.

[0172] Example 3

[0173] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where the compound of Formula I in which R is H, R' is H, and R'' is -NO2 is designated as complex GdL3.

[0174] Preparation method: TIFF0007721572000027.tif27165(1) In a nitrogen atmosphere, a compound (1.5 g, 5 mmol) having the structure shown in formula B-1 was dissolved in 30 mL of acetonitrile, and DO3A (2.6 g, 5 mmol) and potassium carbonate (1.4 g, 10 mmol) were added. The mixture was heated to 70°C and stirred for 17 hours to carry out a nucleophilic substitution reaction. The product of the nucleophilic substitution reaction was concentrated, filtered, evaporated to dryness, and concentrated to obtain the second reaction precursor. (2) The second reaction precursor obtained in step (1) and 30 mL of a 6N hydrochloric acid solution were heated to 100°C and refluxed, and the tert-butyl ester removal reaction was carried out for 17 hours with continuous stirring. The product of the tert-butyl ester removal reaction was separated and purified by reverse-phase semi-preparative liquid phase separation to obtain a compound having the structure shown in Formula B-2. 1 H NMR(400MHz,D2O)δ(ppm):8.07(d,2H,J=8.52Hz),7.61(d,2H,J=8.52Hz),5.24(s,1H),4.10-2.30(m,25H). 13 C NMR(100MHz,D2O)δ 178.85,176.45,175.50,170.44,170.16,168.41,147.19,144.20,131.10,129.85,124.52,123.54,65.54,60. 63,57.00,56.07,55.16,54.71,54.05,51.89,51.68,50.79,49.94,49.36,48.31,46.55,45.83,43.58,42.51. (3) The compound having the structure shown in Formula B-2 obtained in step (2) (0.2 g, 0.4 mmol) and GdCl3·6H2O (148 mg, 0.4 mmol) were dissolved in 10 mL of water, the pH was adjusted to 7 with 1N sodium hydroxide solution, and the mixture was heated to 100 °C for 6 hours to carry out the coordination reaction. The product of the coordination reaction was separated by reversed-phase preparative liquid chromatography to obtain the complex GdL3. HPLC-MS (ESI- )calculated for C 22 H 27 GdNO 10 [M] - 679.10,found 679.12.

[0175] Example 4

[0176] The cyclic Gd(III) complex has the chemical structure shown in Formula I, and the compound of Formula I in which R is H, R' is H, and R'' is -H is designated as complex GdL4.

[0177] Preparation method: TIFF0007721572000028.tif27165

[0178] The complex GdL4 was prepared according to the method of Example 3. HPLC-MS (ESI - )calculated for C 22 H 28 GdN4O8,[M] - 634.11,found 634.11.

[0179] The difference from Example 3 is that in the step (1), a compound having a chemical structure represented by formula B-1, in which R is H, R' is H, and R'' is H, is used as a raw material.

[0180] Example 5

[0181] The cyclic Gd(III) complex has the chemical structure shown in Formula I, and the compound of Formula I in which R is H, R' is H, and R'' is -OBn is designated as complex GdL5.

[0182] Preparation method: TIFF0007721572000029.tif34165

[0183] The complex GdL5 was prepared according to the method of Example 3. HPLC-MS (ESI - )calculated for C 29 H 34GdN4O9[M] - 740.16,found 740.20.

[0184] The difference from Example 3 is that in the step (1), a compound having a chemical structure represented by formula B-1, in which R is H, R' is H, and R'' is -OBn, is used as a raw material.

[0185] Example 6

[0186] The cyclic Gd(III) complex has the chemical structure shown in Formula I, and the compound of Formula I in which R is H, R' is H, and R'' is -Ph is designated as complex GdL6.

[0187] Preparation method: TIFF0007721572000030.tif33165

[0188] The complex GdL6 was prepared according to the method of Example 3. HPLC-MS (ESI - )calculated for C 28 H 32 GdN4O8,[M] - 710.15,found 710.20.

[0189] The difference from Example 3 is that in the step (1), a compound having a chemical structure represented by formula B-1, in which R is H, R' is H, and R'' is -Ph, is used as a raw material.

[0190] Example 7

[0191] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where the compound of Formula I in which R is H, R' is -Ph, and R'' is H is designated complex GdL7.

[0192] Preparation method: TIFF0007721572000031.tif28165

[0193] The complex GdL7 was prepared according to the method of Example 3. HPLC-MS (ESI- )calculated for C 28 H 32 GdN4O8,[M] - 710.15,found 710.17.

[0194] The difference from Example 3 is that in the step (1), a compound having a chemical structure represented by formula B-1, in which R is H, R' is H, and R'' is -Ph, is used as a raw material.

[0195] Example 8

[0196] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where the compound of Formula I in which R is -CH2CH3, R' is H, and R'' is -COOH is designated complex GdL8.

[0197] Preparation method: TIFF0007721572000032.tif65165(a) Compound C-1 (1.0 g, 3.5 mmol) and the compound having the structure shown in formula (1.0 g, 3.5 mmol) were mixed and dissolved in 20 mL of acetonitrile. The mixture was stirred at room temperature to perform the first nucleophilic substitution reaction for 18 h. After evaporating the solvent of the product of the first nucleophilic substitution reaction to dryness, 50 mL of ethyl acetate was added and the mixture was dissolved. The aqueous phase was adjusted to pH 10 with potassium carbonate, and then separated with dichloromethane (30 mL x 3). The organic phases were combined and evaporated to dryness to obtain the compound having the structure shown in formula C-2. (b) In a nitrogen atmosphere, the compound having the structure shown in formula C-2 obtained in step (a) (1.0 g, 2 mmol) was dissolved in 20 mL of acetonitrile, and potassium carbonate (1.4 g, 10.2 mmol) and tert-butyl bromoacetate (1.7 g, 10.2 mmol) were added sequentially. The mixture was stirred and subjected to a second nucleophilic substitution reaction for 18 hours. The products of the second nucleophilic substitution reaction were filtered, concentrated, and purified by silica gel column chromatography (ethyl acetate:methanol = 10:1) to obtain a compound having the structure shown in formula C-3. (c) The compound having the structure shown in Formula C-3 obtained in step (b) (1.0 g, 1.3 mmol) was dissolved in tetrahydrofuran / methanol (10 mL, 1:1), and an aqueous solution of lithium hydroxide prepared by dissolving lithium hydroxide (0.1 g, 4 mmol) in 1 mL of deionized water was added. The mixture was stirred at room temperature and hydrolyzed for 6 hours. The product of the hydrolysis reaction was concentrated, and then 10 mL of water was added. The pH was adjusted to neutral with 1N hydrochloric acid solution. The product was further purified by reverse phase liquid chromatography to obtain a compound having the structure shown in Formula C-4. 1 H NMR(400MHz,D2O)δ(ppm):7.82(d,2H,J=8.48Hz),7.30(d,2H,J=8.48Hz),4.78(s,1H),4.20-3.62(m,7H),3.41(s,2H),3.32-3.10(m ,6H),2.89(m,6H),2.58(d,1H,J=11.84Hz),2.20-1.82(m,4H),1.37(m,3H),1.10-0.65(m,12H),0.47(t,3H,J=7.08Hz),0.24(s,1H). (d) The compound having the structure shown in formula C-4 obtained in step (c) (0.2 g, 0.3 mmol) and GdCl3·6H2O (111 mg, 0.3 mmol) were dissolved in 10 mL of water, the pH was adjusted to 7 with 1N sodium hydroxide solution, and the mixture was heated to 100 °C for 6 h. The coordination reaction product was separated by reversed-phase preparative liquid chromatography to obtain the complex GdL9. HPLC-MS (ESI) - )calculated for C 31 H 44 GdN4O10[M] - 790.23,found 790.30.

[0198] Example 9

[0199] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where R is -CH2CH3, R' is H, and R'' is The compound TIFF0007721572000033.tif19165 is designated as complex GdL9.

[0200] Preparation method: TIFF0007721572000034.tif651651) A compound having the structure shown in Formula A-1 (1.0 g, 3 mmol) and a compound having the structure shown in Formula chiral cyclen (0.9 g, 3 mmol) were dissolved in 30 mL of acetonitrile, and the reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 7 days to carry out the first nucleophilic substitution reaction. The product of the first nucleophilic substitution reaction was concentrated and then purified by silica gel column chromatography (ethyl acetate:methanol = 5:1) to obtain a compound having the structure shown in Formula D-2. 2) In a nitrogen atmosphere, the compound having the structure shown in Formula D-2 obtained in Step 1) (1.6 g, 3 mmol), potassium carbonate (2.1 g, 15 mmol), and tert-butyl bromoacetate (2.9 g, 15 mmol) were dissolved in 20 mL of acetonitrile, stirred, and allowed to undergo a second nucleophilic substitution reaction for 18 hours. The product of the second nucleophilic substitution reaction was filtered, concentrated, and then purified by silica gel column chromatography (ethyl acetate:methanol = 20:1) to obtain a compound having the structure shown in Formula D-3. 1 H NMR(400MHz,CDCl3)δ(ppm):7.95(d,2H,J=7.92Hz),7.46(d,2H,J=7.92Hz),4.51(s,1H),3.21 -2.69(m,14H),2.37(m,1H),2.20(m,2H),1.80(m,1H),1.72-1.10(m,51H),1.01-0.75(m,14H). 13C NMR(100MHz,CDCl3)δ(ppm)172.62,171.90,171.75,166.70,143.16,129.99,129.31,129.21,80. 85,80.25,80.08,79.79,77.51,77.19,76.87,63.29,60.24,57.50,56.92,56.58,56.10,54.03,53 .40, 52.68, 52.41, 51.89, 51.75, 51.49, 50.89, 47.08, 31.85, 29.62, 29.59, 29.28, 28.03, 27.95, 27.83, 27.14, 23.65, 23.11, 23.00, 22.73, 22.62, 20.92, 14.14, 14.07, 12.26, 11.92, 11.70, 11.63. 3) The compound (1.0 g, 1.7 mmol) having the structure shown in Formula D-3 obtained in Step 2) was dissolved in tetrahydrofuran / methanol (10 mL, 1:1), and lithium hydroxide (122 mg, 5.1 mmol) was dissolved in 1 mL of water. The solution was then added to the above solution and stirred at room temperature to carry out the ester hydrolysis reaction for 6 hours. The product of the ester hydrolysis reaction was concentrated, and then 10 mL of water was added. The pH was adjusted to neutral with 1N hydrochloric acid solution, and the solvent was evaporated to dryness to obtain the third reaction precursor. 4) In a nitrogen atmosphere, the third reaction precursor obtained in step 3) was mixed with 20 mL of dichloromethane, and then HATU (1.3 g, 3.4 mmol), p-ethoxybenzylamine (0.5 g, 3.4 mmol), and DIPEA (0.4 g, 3.4 mmol) were added sequentially. The mixture was stirred at room temperature to carry out the condensation reaction for 4 hours. The product of the condensation reaction was evaporated to dryness and then purified by silica gel column chromatography (ethyl acetate:methanol=10:1) to obtain a compound having the structure shown in formula D-4. 5) In a nitrogen atmosphere, the compound (1.0 g, 1.0 mmol) having the structure shown in Formula D-4 obtained in Step 4) above was dissolved in 4 mL of trifluoroacetic acid, and the mixture was stirred at room temperature under nitrogen protection to carry out a tert-butyl ester removal reaction for 12 hours. The product of the tert-butyl ester removal reaction was concentrated and then separated and purified by reverse-phase preparative high-performance liquid chromatography to obtain a compound having the structure shown in Formula D-5. 6) The compound having the structure shown in formula D-5 obtained in step 5) (0.3 g, 0.4 mmol) and GdCl3·6H2O (148 mg, 0.4 mmol) were dissolved in 10 mL of water, the pH was adjusted to neutral with 1 N sodium hydroxide solution, and the mixture was heated to 100 °C to carry out the coordination reaction for 6 h. The product of the coordination reaction was separated by reversed-phase preparative high-performance liquid chromatography to obtain complex GdL9.

[0201] Example 10

[0202] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where the compound of Formula I in which R is -CH2CH3, R' is H, and R'' is -NO2 is designated complex GdL10.

[0203] Preparation method: TIFF0007721572000035.tif53165(1') In a nitrogen atmosphere, the compound having the structure shown in formula E-1 (1.0 g, 3.5 mmol) was dissolved in 20 mL of acetonitrile, and then the compound having the structure shown in formula chiral cyclen (1.0 g, 3.5 mmol) was added and stirred at room temperature to carry out the first nucleophilic substitution reaction for 18 hours. The product of the first nucleophilic substitution reaction was concentrated and then purified by silica gel column chromatography (ethyl acetate:methanol = 5:1) to obtain the compound having the structure shown in formula E-2, with a yield of 81%. (2') In a nitrogen atmosphere, the compound having the structure shown in Formula E-2 obtained in step (1') (1.0 g, 2.0 mmol), potassium carbonate (1.4 g, 10 mmol), and ethyl bromoacetate (1.7 g, 10 mmol) were dissolved in 20 mL of acetonitrile, and the mixture was stirred at room temperature to carry out a second nucleophilic substitution reaction for 18 hours. The product of the second nucleophilic substitution reaction was filtered, concentrated, and then purified by silica gel column chromatography (ethyl acetate:methanol = 10:1) to obtain a compound having the structure shown in Formula E-3 in a yield of 73%. 1 H NMR(400MHz,D2O)δ(ppm):7.97(m,2H),7.31(m,2H),5.25(s,1H),4.35-2.31(m,16H),2.05-0.08(m,20H).13 C NMR(100MHz,D2O)δ(ppm):189.90,189.09,178.06,175.74,175.36,174.73,174.28,173.69,173.17,171.01,168.59,168. 42,168.36,166.80,166.51,166.44,164.94,164.30,153.96,147.63,147.56,147.21,141.00,131.88,131.23,129.57,12 4.48,123.85,118.82,63.04,62.69,62.47,61.24,60.88,59.70,58.82,57.61,55.30,52.43,51.54,51.22,48.96,48.21, 47.62,44.23,42.10,20.65,18.49,18.04,13.10,12.76,11.56,11.12,10.66,10.20,10.12,9.91,9.80,9.70.HPLC-MS(ESI - )Calculated for C 30 H 48 N5O 10 [M+H] + 638.33,found 638.37. (3') The compound having the structure shown in Formula E-3 obtained in Step (2') (1.0 g, 1.3 mmol) was dissolved in tetrahydrofuran / methanol (10 mL, 1:1), and an aqueous solution of lithium hydroxide prepared by dissolving lithium hydroxide (0.1 g, 4 mmol) in 1 mL of deionized water was added. The mixture was stirred at room temperature for 6 hours to carry out the ester hydrolysis reaction. The product of the ester hydrolysis reaction was concentrated, and then 10 mL of water was added. The pH was adjusted to 7 with 1N hydrochloric acid solution. The mixture was purified by reverse-phase preparative high-performance liquid chromatography to obtain a compound having the structure shown in Formula E-4. (4') The compound having the formula E-4 structure obtained in step (3') and GdCl3·6H2O (111 mg, 0.3 mmol) were dissolved in 10 mL of water, the pH was adjusted to 7 with 1N sodium hydroxide solution, and the mixture was heated to 100 °C for 6 h. The coordination reaction product was separated by reversed-phase preparative liquid chromatography to obtain the complex GdL10. HPLC-MS (ESI -)Calculated for C 30 H 43 GdNO 10 [M] - 719.23,found 719.21.

[0204] Example 11

[0205] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where R is —CH2CH3, R' is H, and R'' is —C(CH3)3, and is designated as complex GdL11.

[0206] Preparation method: TIFF0007721572000036.tif62165

[0207] The complex GdL11 was prepared according to the method of Example 10. HPLC-MS (ESI - )Calculated for C 34 H 52 GdN4O8[M]802.30,found 802.33.

[0208] The difference from Example 10 is that in the step (1'), a compound having the chemical structure shown in E-1, in which R'' is -C(CH3)3, is used as a starting material.

[0209] Example 12

[0210] The cyclic Gd(III) complex has the chemical structure shown in Formula I, where the compound of Formula I in which R is -CH2CH3, R' is H, and R'' is -CF3 is designated as complex GdL12.

[0211] Preparation method: TIFF0007721572000037.tif61165

[0212] The complex GdL12 was prepared according to the method of Example 10. HPLC-MS (ESI - )Calculated for C 31 H43 F3GdN4O8[M] - :814.23,found 814.25.

[0213] The difference from Example 10 is that in the step (1'), a compound having a chemical structure represented by formula E-1, in which R'' is -CF3, is used as a starting material.

[0214] Detection 1: Relaxation rate parameters of some complexes were detected using 1.5T, 3T and 7T nuclear magnetic resonance instruments, and the results are shown in Table 1.

[0215] TIFF0007721572000038.tif54165

[0216] As can be seen from Table 1, the cyclic Gd(III) complexes provided by the present invention have an optimal relaxivity range for nuclear magnetic resonance imaging, and GdL9 also has a relaxivity suitable for high-field nuclear magnetic resonance imaging.

[0217] Detection 2: Performance detection as an MRI contrast agent targeting the hepatic and biliary tract

[0218] Figure 1 shows hepatobiliary MR imaging images obtained by detecting MRI of a mouse using the GdL1 complex prepared in Example 1 as a hepatobiliary targeting MRI contrast agent, where 0 min, 5 min, 10 min, 20 min, 30 min, 1 h, and 2 h are the corresponding detection times after administering GdL1 to the mouse, respectively. As can be seen from Figure 1, the GdL1 complex has hepatobiliary targeting ability. Figure 2 shows hepatobiliary MR imaging images obtained by detecting MRI of a mouse using the GdL3 complex prepared in Example 3 as a hepatobiliary-targeting MRI contrast agent, where 0 min, 5 min, 10 min, 20 min, 30 min, and 1 h are the corresponding detection times after GdL3 administration to the mouse, respectively. As can be seen from Figure 2, the GdL3 complex has a strong hepatobiliary targeting ability and is suitable for hepatobiliary imaging. Figure 3 shows hepatobiliary MR imaging images obtained by detecting MRI of a mouse using the GdL4 complex prepared in Example 4 as a hepatobiliary-targeting MRI contrast agent, where 0 min, 5 min, 10 min, 20 min, 30 min, 1 h, and 2 h are the corresponding detection times after GdL4 administration to the mouse, respectively. As can be seen from Figure 3, the GdL4 complex has a high hepatobiliary targeting ability and is suitable for hepatobiliary imaging. Figure 4 shows hepatobiliary MR imaging images obtained by detecting MRI of a mouse using the GdL8 complex prepared in Example 8 as a hepatobiliary targeting MRI contrast agent, where 0 min, 5 min, 10 min, 20 min, 30 min, 1 h, and 2 h are the corresponding detection times after administering GdL8 to the mouse, respectively. As can be seen from Figure 4, the GdL8 complex has hepatobiliary targeting ability. Figure 5 shows hepatobiliary MR imaging images obtained by detecting MRI of a mouse using the GdL9 complex prepared in Example 9 as a hepatobiliary targeting MRI contrast agent, where 0 min, 5 min, 10 min, 20 min, 30 min, and 1 h are the corresponding detection times after GdL9 administration to the mouse, respectively. As can be seen from Figure 5, the GdL9 complex has hepatobiliary targeting ability. Figure 6 shows the hepatobiliary MR imaging images obtained by detecting MRI of a mouse using the GdL10 complex prepared in Example 10 as a hepatobiliary targeting MRI contrast agent, where 0 min, 5 min, 10 min, 20 min and 30 min are the corresponding detection times after administering GdL10 to the mouse, respectively. As can be seen from Figure 6, the GdL10 complex has very strong hepatobiliary targeting ability and very good imaging effect.

[0219] Detection 3: Detection of partial complex stability

[0220] The stability of the compounds in an acidic solution of pH 1 was determined by high-performance liquid chromatography. GdL2, GdL9, and GdL10 were dissolved in an acidic solution of pH 1 and placed at room temperature (298 K, 25 °C). The decay of the compounds over time was then tested by high-performance liquid chromatography to determine the half-life (t 1 / 2 The half-life of Primovist and Gd-DOTA has been reported in the literature.

[0221] TIFF0007721572000039.tif25165

[0222] Table 2 shows that the cyclic Gd(III) complexes provided by the present invention have high hepatobiliary targeting ability and high stability. After the chiral group R is introduced, the stability of the cyclic Gd(III) complexes is greatly improved, significantly higher than that of Primovist and Gd-DOTA. GdL9 and GdL10 show excellent stability, with no detectable metal ion release within one year.

[0223] As can be seen from the examples, the cyclic Gd(III) complexes provided by the present invention have an optimal relaxivity range for nuclear magnetic resonance imaging, and GdL9 also has a relaxivity suitable for high-field nuclear magnetic resonance imaging. The cyclic Gd(III) complexes also have high stability, significantly higher than Primovist and Gd-DOTA. After the chiral group R is introduced, the stability of the cyclic Gd(III) complexes is greatly improved, and GdL9 and GdL10 show no detectable metal ion release within one year, demonstrating excellent stability.

[0224] The above description of the embodiments is merely intended to aid in understanding the method and core idea of the present invention. Those skilled in the art may make minor improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications are also within the scope of protection of the claims of the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be realized in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cyclic Gd(III) complex having the chemical structure shown in Formula I: R in the formula I is H or C2-C ４ an alkyl group (wherein R'' is a C 1 to C 10 alkyl group, -CF 3 , -COOH or -NO ２ If R is C2 to C ４ wherein the configuration of R in formula I is independently S or R; R″ in formula I is in the para position of the benzene ring; In the formula I, R' is H or -Ph, and R'' is C １ ~C １０ an alkyl group of —CF ３ , -COOH, -NO ２ , -OR １ - Ph, and The -OR １ -R in Ph １ is independently C １ ~C ５ is an alkylene group of the formula M in formula I ＋ is a cyclic Gd(III) complex characterized in that the cation is a metal cation or a glucosamine cation.

2. M in formula I ＋ is Na ＋ , K. ＋ , Li ＋ 2. The cyclic Gd(III) complex according to claim 1, characterized in that the cation is a glucosamine cation.

3. The cyclic Gd(III) complex according to claim 1, which is any one of the following formulae GdL1, GdL2, GdL5, and GdL7 to GdL12.

4. In the formula I, R is H, R' is H, and R'' is and the preparation method comprises: (1) mixing a compound having a structure represented by formula A-1, DO3A, potassium carbonate, and acetonitrile in a nitrogen atmosphere, and carrying out a nucleophilic substitution reaction to obtain a compound having a structure represented by formula A-2; (2) mixing the compound having the structure shown in Formula A-2 obtained in step (1) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a first reaction precursor; (3) in a nitrogen atmosphere, mixing the first reaction precursor obtained in step (2) with HATU, dichloromethane, an amine, and DIPEA to carry out a condensation reaction to obtain a compound having a structure shown in Formula A-3; (4) mixing the compound having the structure shown in formula A-3 obtained in step (3) with trifluoroacetic acid to carry out a tert-butyl ester removal reaction to obtain a compound having the structure shown in formula A-4; (5) The compound having the structure shown in formula A-4 obtained in step (4) is reacted with a gadolinium source, water, M ＋ and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex. M in the step (5) ＋ The method for preparing a cyclic Gd(III) complex according to any one of claims 1 to 3, characterized in that the solution containing is a solution of a metal hydroxide or glucosamine.

5. In the formula I, R is H, R' is H, and R'' is -OBn, and the preparation method comprises: (1) mixing a compound having a structure shown in Formula B-1, acetonitrile, DO3A, and potassium carbonate in a nitrogen atmosphere to carry out a nucleophilic substitution reaction to obtain a second reaction precursor; (2) mixing the second reaction precursor obtained in step (1) with hydrochloric acid to carry out a tert-butyl ester removal reaction to obtain a compound having a structure shown in formula B-2; (3) The compound having the structure shown in formula B-2 obtained in step (2) is reacted with a gadolinium source, water, M ＋ and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex. M in the step (3) ＋ The method for preparing a cyclic Gd(III) complex according to any one of claims 1 to 3, characterized in that the solution containing is a solution of a metal hydroxide or glucosamine.

6. In the formula I, R is C2 to C ４ wherein R' is H and R'' is -COOH, and said preparation method comprises: (a) mixing a compound having a structure shown in formula C-1, a compound having a structure shown in formula chiral cycle, and acetonitrile to perform a first nucleophilic substitution reaction to obtain a compound having a structure shown in formula C-2; (b) in a nitrogen atmosphere, mixing the compound having the structure shown in formula C-2 obtained in step (a), acetonitrile, potassium carbonate, and tert-butyl bromoacetate to perform a second nucleophilic substitution reaction to obtain a compound having the structure shown in formula C-3; (c) mixing the compound having the structure shown in formula C-3 obtained in step (b) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out a hydrolysis reaction, thereby obtaining a compound having the structure shown in formula C-4; (d) The compound having the structure shown in formula C-4 obtained in step (c) is reacted with a gadolinium source, water, M ＋ and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex. M in the step (d) ＋ The method for preparing a cyclic Gd(III) complex according to any one of claims 1 to 3, characterized in that the solution containing is a solution of a metal hydroxide or glucosamine.

7. In the formula I, R is C １ ~C ４ where R' is H and R'' is an alkyl group of the formula and the preparation method comprises: 1) mixing a compound having a structure shown in formula A-1, a compound having a structure shown in formula chiral cycle, and acetonitrile to perform a first nucleophilic substitution reaction to obtain a compound having a structure shown in formula D-2; 2) in a nitrogen atmosphere, mixing the compound having the structure shown in formula D-2 obtained in step 1), acetonitrile, potassium carbonate, and tert-butyl bromoacetate to carry out a second nucleophilic substitution reaction to obtain a compound having the structure shown in formula D-3; 3) mixing the compound having the structure shown in formula D-3 obtained in step 2) with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction to obtain a third reaction precursor; 4) in a nitrogen atmosphere, mixing the third reaction precursor obtained in step 3) with HATU, dichloromethane, an amine compound, and DIPEA to carry out a condensation reaction to obtain a compound having a structure shown in formula D-4; 5) mixing the compound having the structure shown in formula D-4 obtained in step 4) with trifluoroacetic acid in a nitrogen atmosphere to carry out a tert-butyl ester removal reaction to obtain a compound having the structure shown in formula D-5; 6) The compound having the structure shown in formula D-5 obtained in step 5) is reacted with a gadolinium source, water, M ＋ and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex. M in step 6) ＋ The method for preparing a cyclic Gd(III) complex according to any one of claims 1 to 3, characterized in that the solution containing is a solution of a metal hydroxide or glucosamine.

8. In the formula I, R is C2 to C ４ where R' is H and R'' is -CF ３ , -C(CH ３ ) ３ , -NO ２ or -OBn, and the preparation method is (1') in a nitrogen atmosphere, a compound having a structure represented by formula E-1, a compound having a structure represented by formula chiral cycle, and acetonitrile are mixed to carry out a first nucleophilic substitution reaction to obtain a compound having a structure represented by formula E-2; (2') in a nitrogen atmosphere, mixing the compound having the structure shown in formula E-2 obtained in step (1'), acetonitrile, potassium carbonate, and ethyl bromoacetate to carry out a second nucleophilic substitution reaction to obtain a compound having the structure shown in formula E-3; (3') mixing the compound having the structure shown in formula E-3 obtained in step (2') with an aqueous solution of tetrahydrofuran, methanol, and lithium hydroxide to carry out an ester hydrolysis reaction, and then sequentially concentrating, diluting, and adjusting the pH of the product of the ester hydrolysis reaction to obtain a compound having the structure shown in formula E-4; (4') The compound having the structure shown in formula E-4 obtained in step (3') is reacted with a gadolinium source, water, M ＋ and mixing the resulting solution with a solution containing the compound to carry out a coordination reaction to obtain a cyclic Gd(III) complex. M in the step (4') ＋ The method for preparing a cyclic Gd(III) complex according to any one of claims 1 to 3, characterized in that the solution containing is a solution of a metal hydroxide or glucosamine.

9. A pharmaceutical composition comprising the cyclic Gd(III) complex of any one of claims 1 to 3.

10. Use of the cyclic Gd(III) complex according to any one of claims 1 to 3 in nuclear magnetic resonance imaging.

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