MANGANESE CHELATE ISOMERS.

Abstract

The invention relates to isomers of chelating compounds and their use as contrast agents in magnetic resonance imaging (MRI) procedures.

Description

MANGANESE CHELATE ISOMERS Field of invention The invention relates to isomers of chelating compounds and their use as contrast agents in magnetic resonance imaging (MRI) procedures. Background of the invention MRI is a medical imaging technique in which areas of the body are visualized by examining the nuclei of selected atoms, particularly hydrogen nuclei. The MRI signal depends on the environment surrounding the visualized nuclei and their longitudinal and transverse relaxation times, T1 and T2. Therefore, if the visualized nucleus is a proton, the intensity of the MRI signal will depend on factors such as proton density and the proton's chemical environment. Contrast agents can be used in MRI to enhance image contrast. They work by affecting the T1, T2, and / or T2* relaxation times and thus influence the contrast in the images. It is known that paramagnetic contrast agents can modify T1, T2, and / or T2* relaxation times, and this effect can be optimized by structurally modifying the paramagnetic metal chelate. The presence and residence time of a water molecule bound to the paramagnetic ion, as well as the rotational correlation time of the contrast agent, are of particular importance. The presence and residence time of a water molecule bound to the paramagnetic ion can be modulated by the choice of the paramagnetic ion and the chelating fraction. The rotational correlation time can be modulated by changing the size of the contrast agent. The solubility of paramagnetic chelates in water is also an important factor when used as a contrast agent for MRI because they are administered to patients in relatively large doses. A highly water-soluble paramagnetic chelate requires a smaller injection volume, making it easier to administer and causing less discomfort. Water-soluble paramagnetic chelates—complexes of a chelating agent and a paramagnetic metal ion—are well-known, for example, the commercially available gadolinium chelates Omniscan™ (GE Healthcare), Dotarem™ (Guerbet), Gadavist™ (Bayer), and Magnevist™ (Bayer). Due to their low molecular weight, they are rapidly distributed into the extracellular space (i.e., the blood and interstitium) when administered into the vasculature. They are also eliminated relatively quickly from the body. An essential property of MRI chelate compounds is that the paramagnetic ion is conserved as much as possible within the chelate structure. The paramagnetic ion released from the chelate in vivo can interfere with biological pathways and potentially induce toxicity. The ability of a chelate to retain the paramagnetic ion (also referred to herein as stability) is a property that can be modulated by the structural design of the chelating moiety. Kinetic stability is of particular interest, measured as a dissociation half-life, which indicates the degree of inertness to altered chemical environments (i.e., endogenous ions). As can be seen from the commercially available agents and the state's approach In the field of MRI, gadolinium is the most widely used paramagnetic metallic ion for MRI chelates due to its favorable relaxivity properties. The concept of "relaxivity" of an MRI agent is well understood by technicians in the field and refers to the ability of magnetic compounds to increase the relaxation rates of surrounding water proton spins. Relaxivity is used to enhance MRI image contrast and to study specific tissue areas where the contrast agent diffuses best or to perform functional MRI. The relaxivity of MRI agents depends on the molecular structure and kinetics of the complex. It is also influenced by temperature, field strength, and the substance in which the contrast agent is dissolved. The stability of the paramagnetic ion within the chelate structure is desirable for gadolinium chelates when used as contrast agents. Therefore, there is a desire to identify new gadolinium chelates with higher levels of stability, particularly in physiological environments. The manganese(II) ion is a paramagnetic species with a high spin number and a long electronic relaxation time, and the potential of a high-relaxability contrast agent based on manganese(II) has been reported in the literature (Toth, E., Advances in Inorganic Chemistry, 2009, 61(09), 63–129). However, certain manganese(II) chelates developed to date have proven to be much less stable compared to the corresponding gadolinium chelates. For example, the manganese chelate DOTA (MnDOTA) is several hundred times less stable compared to the corresponding gadolinium complex Gd-DOTA (Drahos, B., Inorganic Chemistry, 2012(12), 1975–1986). The document WO2011 / 073371 by Andreas Meijer, published on June 23, 2011, describes a molecular design that favors high chelate stability and high relaxivity. This makes these compounds very suitable for use as MRI contrast agents. An exemplary compound from WO2011 / 073371 has the following structure: QQCznn / zznz / E / Yi WO2017 / 220610 by Andreas Meijer et al., published on December 28, 2017, describes manganese chelates that are suitable for use as contrast agents and provide superior properties to other known manganese-based contrast agents. The manganese chelates in WO2017 / 220610 include the compounds of formula (1): Qocznn / zznz / E / YiA or a salt or solvate thereof, where: each R1 is independently selected from the group comprising C1-6 hydroxyalkyl, C1-6 alkyl, C1-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH-C1-6 hydroxyalkyl, or a carbohydrate fraction; each R2 is independently selected from the group comprising Ci20 hydroxyalkyl, C1-6 alkyl or hydrogen; R3 is selected from the group comprising C1-3 alkyl or -(CH2)mC(=O)- NR5R6 where m is an integer from 2-5, and R5 and R6 are defined respectively for R1 and R2; R4 represents 0 to 3 substituents selected from the group comprising hydroxy, C1-6 alkyl and Ci-o hydroxyalkyl; and each n is an integer from 0 to 4; and where the compound of formula I comprises at least two hydroxy groups. There is still a need to develop manganese contrast agents that are stable and suitable for use as contrast agents. Brief description of the invention The present invention relates to the compound of formula IA: or a salt or solvate thereof. In the above formula, each R1 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH-C1-6 hydroxyalkyl, or a carbohydrate moiety. Each R2 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, or hydrogen. R3 is selected from C1-3 alkyl or -(CH2)mC(=O)-NR5R6, where m is an integer from 2-5, where R5 and R6 are independently selected from hydrogen, C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH-C1-6 hydroxyalkyl, or a carbohydrate moiety. R4 represents 0-3 substituents selected from hydroxy, C1-6 alkyl and C1-6 hydroxyalkyl. Each n is an integer from 0 to 4. In one embodiment, the invention involves a composition comprising a compound of formula IA, or a salt or solvate thereof, and a pharmaceutically acceptable excipient. In one embodiment, the composition lacks detectable amounts of a compound of formula IB. QQCznn / zznz / B / Yi (IB) wherein each R1 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH-C1-6 hydroxyalkyl, or a carbohydrate moiety. Each R2 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, or hydrogen. R3 is selected from C1-3 alkyl or -(CH2)mC(=O)-NR5R6, wherein m is an integer from 2-5, wherein R5 and R6 are independently selected from hydrogen, C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH-C1-6 hydroxyalkyl, or a carbohydrate moiety. R4 represents 0-3 substituents selected from hydroxy, C1-6 alkyl and C1-6 hydroxyalkyl. Each n is an integer from 0 to 4. In one embodiment, the invention involves a method of imaging a patient comprising administering the contrast agent, or contrast agent composition, followed by acquiring an MRI image of the patient. In one embodiment, the invention involves a method for manufacturing the imaging agent as described above. The method may involve enantioselective synthesis, or isomerization of compounds of formula (1A) to compounds of formula (1B). Brief description of the drawings Figure 1 shows the predicted stereoisomers of Mn chelate-5. Figure 2 shows the HPLC chromatographs for (a) Mn chelate-5 synthesized without stereochemical control, (b) (fi,S)-Mn chelate-5, (c) (fi,fí)-Mn chelate-5, (d) (S,S)-Mn chelate-5, and (e) (S,fí)-Mn chelate-5. Figure 3 shows the percentage dechelation of Mn chelate-5 stereoisomers in human serum Figure 4 shows the percentage of Mn-5 chelate remaining as a function of time for (a) (R,R)Mn-5 chelate (diamonds), (b) (S,S)Mn-5 chelate (squares), (c) (S,phi)Mn-5 chelate (circles), and (d) (phi,S)Mn-5 chelate (triangles) when incubated in the presence of xs. ZnCh at pH = 4 and 40°C. Figure 5 shows the % ID (injected dose) / organ 7 days after injection of a dose of 0.62 mmol of Mn chelate-5 / kg containing ~30 pmol of Mn-5 chelate-54 (a) synthesized without stereochemical control (filled bars), (b) a 1:1 mixture of isomers of and S,S)-Mn chelate-5 (lattice bars), and (c) (ñ,S)-Mn chelate-5 (checkered bars). Figure 6 shows the chelate-10 structure of Mn. Figure 7 shows the chelate-15 structure of Mn. Figure 8 shows the percentage of Mn chelate remaining as a function of time for (R,S)Mn chelate-5 (circles), a 1:1 mixture of (R,R and S,S)Mn chelate-5 isomers (X), group A of Mn chelate-10 isomers (triangles) and group B of Mn chelate-10 isomers (diamonds). Figure 9 shows the synthetic route to isomerically pure chelates according to the embodiments of the invention. Figure 10 is an exemplary chromatogram showing the separation of manganese-containing proteins from the intact chelate. Detailed description of the invention To describe and highlight more clearly and concisely the objective of the claimed invention, definitions and exemplary forms are provided below for specific terms used throughout this specification and claims. Any examples of specific terms herein should be considered non-limiting. The terms “comply” or “comprises” have their conventional meaning throughout this application and imply that the agent or composition must have the essential characteristics or components listed, but that others may also be present. The term “comply” includes as a preferred subset “consist essentially of,” which means that the composition has the listed components without any other characteristics or components being present. A “salt” according to the invention includes physiologically acceptable acid addition salts such as those derived from mineral acids, for example, hydrochloric, hydrobromic, phosphoric, metaphosphoric, nitric and sulfuric acids, and those derived from organic acids, for example, tartaric, trifluoroacetic, citric, malic, lactic, fumaric, benzoic, glycolic, gluconic, succinic, methanesulfonic and para-toluensulfonic acids. A suitable “solvate” according to the invention is selected from ethanol, water, saline solution, physiological buffer solution, and glycol. The term “alkyl”, individually or in combination, means a straight-chain or branched-chain alkyl radical having the general formula CnEEn+i. Examples of such radicals include methyl, ethyl, and isopropyl. The term “hydroxyl” refers to the -OH group. The term “hydroxyalkyl” refers to an alkyl group as defined above that QQCznn / zznz / E / Yi comprises one or more hydroxyl substituents as defined above. The term “aryl” refers to a functional group or substituent derived from an aromatic ring, generally an aromatic hydrocarbon, examples of which include phenyl and pyridyl. In one embodiment of the aryl groups of the present invention, there are 6-membered aromatic rings with between 0 and 3 heteroatoms selected from O, N, and S. The term “halogen” or “halo” means a substituent selected from fluorine, chlorine, bromine, or iodine. The term “hydroxy” refers to the -OH group. The term “chelate fraction” refers to a substituent that is a metal chelate, whereas the term “metal chelate” refers to a coordination complex in which a metal ion is bound to a surrounding array of molecules or anions comprising a chelating agent. A “chelating agent” is defined herein as an organic compound capable of forming coordinate bonds with a paramagnetic metal ion through two or more donor atoms. In a common chelating agent suitable for the present invention 2-6, and preferably 4-6, the metal donor atoms are arranged such that (having a non-coordinated structure of carbon atoms or non-coordinating heteroatoms linking metal donor atoms) 5- or 6-membered rings are produced. Examples of suitable donor atom types where the metal ion is a paramagnetic metal ion include amines, thiols, amides, oximes, and phosphines. In one embodiment, the metal ion is manganese. In one respect, the invention involves a compound of formula IA: QQCznn / zznz / B / Yi R3 (IA) or a salt or solvate thereof. In this formula, each R1 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH-C1-6 hydroxyalkyl, or a carbohydrate moiety; each R2 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, or hydrogen; R3 is selected from C1-3 alkyl or -(CH2)mC(=O)-NR5R6, where m is an integer from 2-5, where R5 and R6 are independently selected from hydrogen, C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH-C1-6 hydroxyalkyl, or a carbohydrate moiety; R4 represents 0-3 substituents selected from hydroxy, C1-6 alkyl and C1-6 hydroxyalkyl; and, each n is an integer from 0 to 4. The following process illustrates the stereoselective synthesis of the (R,R) and (S,S) isomers of Mn chelate-5. (fi,fi)-Mn chelate-5 was synthesized from deprotected 2-fragment cyclic chelate (compound III) via bis-alkylation with (S)-5-benzyl-1-tere-butyl 2-(methylsulfonyloxy)pentanedioate to produce protected (fi,fij)-C5 2-fragment Mn chelate (compound V). The protected (fi,ñ)-C5 2-fragment Mn chelate was deprotected under acidic conditions, the Mn was chelated, and the amino alcohol (D-glucamine) was coupled, yielding (fi,fi)-Mn chelate-5. (S,S)-Mn chelate-5 was synthesized from deprotected 2-fragment cyclic chelate (compound III) via bis-alkylation with 2-(methylsulfonyloxy)pentanedioate of (fi)-5-benzyl 1-tere-butyl to produce protected Mn (S,S)-chelate C5 of 2 segments (compound VI). (S,^-chelate C5 of 2 Mn fragments was converted to Mn (S,S)-chelate-5 using the method described above for the synthesis of (fi). / ^-chelate-S of Mn. The following process illustrates the stereoselective synthesis of the (S,R) and (R,S) isomers of Mn chelate-5. (S, / 3)-Mn chelate-5 and ( / 3,S)-Mn chelate-5 were synthesized from deprotected 2-fragment cyclic chelate by monoalkylation with (S)-5-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanedioate followed by alkylation with ( / ^-S-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanedioate to produce 2-fragment (fi,S)-Mn C5 chelate (Compound VII). The 2-fragment (n,S)-Mn C5 chelate was deprotected under acidic conditions and the Mn was chelated to produce a mixture of 2-fragment (S, / ?)-Mn C5 chelate and n,S)-Mn C5 chelate. The mixture of 2-fragment (S,n)-Mn C5 chelate Mn and (phi,S)-chelate C5 of 2 Mn fragments was combined with amino alcohol (D-glucamine) to produce a mixture of Mn (S,phi)-chelate-5 and Mn (ñ,S)-chelate-5 that was separated by C18 chromatography.Furthermore, (fi,S)-Mn chelate-5 was synthesized by heating a mixture of (S,ñ)-C5 chelate of 2 Mn fragments and (ñ,S)-C5 chelate of 2 Mn fragments at 90°C until the isomerization of (S,fí)-C5 chelate of 2 Mn fragments to (ñ,S)-C5 chelate of 2 Mn fragments was complete, and then (fi,S)-C5 chelate of 2 Mn fragments was coupled with an amino alcohol (D-glucamine) to produce (ñ, ^)-Mn chelate-5. As can be seen by a person skilled in the art, the described method for the stereoselective synthesis of the Mn chelate-5 isomers is applicable to the stereoselective synthesis of the compounds described by formulas IA and IB. The Mn-5 chelate was synthesized without stereochemical control at the macrocycle attachment sites. In the absence of stereochemical control, four isomers were expected to be present, as shown in Figure 1. The (S,n) and (R,S) isomers can interconvert via dechelation and rechelation of the metal. The designations R and S represent the stereochemistry at the macrocycle attachment points. Figure 2a shows the HPLC analysis results of the Mn chelate-5 synthesized without stereochemical control. Subsequently, Mn(S,S)-chelate-5 and Mn(S,S)-chelate-5 were synthesized enantioselectively as illustrated in Figure 9. The HPLC analysis results of Mn(S,S)-chelate-5 are shown in Figure 2c and the HPLC analysis results of Mn(S,S)-chelate-5 are shown in Figure 2d. The enantioselective synthesis of Mn(S,S)-chelate-5 and Mn(S,S)-chelate-5 was carried out as illustrated in Figure 9. The HPLC analysis results of Mn(S,S)-chelate-5 are shown in Figure 2b and the HPLC analysis results of Mn(S,S)-chelate-5 are shown in Figure 2e. The stability of Mn-5 chelate in transmetalation with Zn was evaluated with 2 mM Mn-5 chelate at pH = 4 in the presence of 100 times excess Zn (200 mM ZnCl₂ in 15 mM ammonium formate, pH = 4 at 40°C). Figure 3 shows the percentage of Mn-5 chelate remaining as a function of time for QQCznn / zznz / E / Yi (phi,phi)-Mn chelate-5 (diamonds), (S,S)-Mn chelate-5 (open squares), (S,ff)-Mn chelate-5 (circles), and (phi,S)-Mn chelate-5 (triangles). Surprisingly, the data in Figure 3 show a significantly slower transmetalation rate for the (phi,S)-Mn chelate-5 isomer and a significantly faster transmetalation rate for the (S,phi)-Mn chelate-5 isomer, suggesting a difference in the intensity of Mn chelation depending on the stereochemistry of the chelate. The stability of Mn-5 chelate stereoisomers in human serum was evaluated in vitro by monitoring the transfer of Mn from the chelate to blood proteins using a method that employs size exclusion chromatography combined with online detection of manganese-containing species by ICP-MS. Figure 3 shows the percentage of chelation during the 2-day total incubation time at 37°C.There is a significant difference between the (S,phi)-chelate-5 isomer of Mn (upper curve, less stable) and the (phi,S)-chelate-5 isomer of Mn (lower curve, more stable), according to the results obtained in the study of Zn transmetalation. The in vivo stability of the different isomer groups was assessed through radioactive biodistribution of 54Mn, as Mn released in vivo is known to be retained in the brain, bones, and liver. The amount of Mn released in vivo was evaluated for Mn-5 chelate synthesized without stereochemical control, a 1:1 mixture of (phi,phi)-Mn-5 chelate and (S,S)-Mn-5 chelate isomers, and group B of (phi,S)-Mn-5 chelate using 54Mn-labeled material added to non-radiolabeled material. The 1:1 mixture of (phi,phi)-Mn-5 chelate and (S,S)-Mn-5 chelate isomers was chosen because the two isomers were expected to have comparable stability based on their similar transmetalation rates. Rats were dosed with 0.62 mmol of Mn-5 chelate / kg containing ~30 pmol of 54Mn-5 chelate. The animals were sacrificed 7 days after injection, organs of interest were harvested, and the remaining 54Mn in the organs was measured using a gamma counter.Figure 4 is a graph showing % ID (injected dose) / organ 7 days after injection of a 0.62 mmol / kg dose of Mn-5 chelate containing ~30 pmol of 54Mn-5 chelate. Bars containing dashed lines represent % ID / organ at or below the limit of detection for the study. The results of the statistical comparison of % ID for each organ are summarized as p-values ​​using a one-way Games-Howell ANOVA or a two-way t-test, as appropriate for each organ. Surprisingly, the data in Figure 4 show significantly less remaining Mn in vivo 7 days post-injection for (fi,S)-Mn chelate-5 than for the 1:1 mixture of (S,S)-Mn chelate-5 and ( / Tfij)-Mn chelate-S or Mn chelate-5 synthesized without stereochemical control in brain and bone, which is consistent with lower in vivo Mn release. This is consistent with Zn transmetalation data and further supports the conclusion that the intensity of Mn chelation is a function of chelate stereochemistry. This is further supported by the higher level of Mn detected in the kidney for (fi,S)-Mn chelate-5, since more intact Mn chelate-5 will pass through the kidney. Since Mn-chelate-5 contains 10 additional stereocenters in the glucamine side chain besides the 2 alpha stereocenters in the macrocycle, Mn-chelate-10 (Figure 5) was synthesized without stereochemical control using racemic 3-amino-1,2-propanediol, and C18 chromatography provided the Mn-chelate-10 isomer A and the Mn-chelate-1Oa isomer B. Zn transmetalation was carried out with QQCznn / zznz / E / Yi the Mn-10 chelate isomer A and the Mn-10a chelate isomer B using the conditions described above (Figure 9). Surprisingly, group A of Mn chelate-10 isomers, Mn (S,S)-chelate-5, and Mn (fi.F^-chelate-S) were transmetalated with Zn at the same rate, as were group B of Mn chelate-10 and Mn (R,S)-chelate-5 isomers. These data show that both the identity and stereochemistry of the side fragment do not affect the strength of Mn chelation, whereas the stereochemistry at the alpha site in the macrocycle is essential for determining the stability of the Mn chelate. Based on the data presented above, it is reasonable to assume that alpha stereochemistry of (R,S) and / or (S,R) in the macrocycle is preferable with respect to the stability of the Mn chelate compared to alpha stereochemistry of (R,R) and (S,S) in the macrocycle. The following examples, Ex. 1-8, describe the preparation of precursors of the present invention. Examples 9-23 describe compounds according to various embodiments of the present invention. Example 1 Synthesis of N,N'-((methyllazanedyl)bis(ethane-2,1-diethyl))bis(4-methylbenzenesulfonamide) (compound I). In TsHNT ^NHTs Compound I A 1 L round-bottom flask fitted with a magnetic stir bar was charged with N-tosylaziridine (49 g, 248 mmol) and AcN (450 ml). Aqueous 41% methylamine (12 ml, 121 mmol) was added and the mixture was stirred at room temperature for 36 h. A second aliquot of N-tosylaziridine (1.7 g, 8.62 mmol) was added and the mixture was stirred at room temperature for an additional 48 h. The solvent was removed under vacuum and the crude residue was recrystallized from EtOH to produce 45 g (87%) of the desired product as a white solid.1H NMR (400 MHz, DMSO-D6, δ) 7.68 (4H, m), 7.36 (6H, m), 2.75 (4H, t), 2.38 (6H, s), 2.22 (4H, t), 1.93 (3H, s). Example 2 Synthesis of 2 protected cyclic fragment chelate (compound II). Compound II QQCznn / zznz / E / Yi A 12 L three-necked round-bottom flask equipped with a reflux condenser and a mechanical stirrer was charged with N,N'-((methyllazanedi)bis(ethane-2,1-di)bis(4-methylbenzenesulfonamide) (93 g, 218.5 mmol) and AcN (8.3 L). 2,6-Bis(chloromethyl)pyridine (38.5 g, 218.5 mmol) was added, and the resulting solution was heated to 80°C for 16 h. The reaction mixture was cooled to room temperature, and the solvent was removed under vacuum until crystallization began. The resulting crystals were collected by vacuum filtration to yield 86.9 g (75%) of the desired product as a white solid (ESI: m / z = 530 (M + H)+). Example 3 Synthesis of chelate of 2 unprotected cyclic fragments (compound III). QQCznn / zznz / E / Yi Compound III A 1 L round-bottom flask with three necks, fitted with a mechanical stirrer, was charged with protected cyclic 2-fragment chelate (150 g, 284 mmol) and concentrated sulfuric acid (250 mL, 4.69 mol) and heated to 100°C for 15 h. The solution was poured onto ice, and the pH was adjusted to 7.4 by adding 50 wt% NaOH in water, resulting in the formation of a white solid. AcN (200 mL) was added, and the white solid was removed by vacuum filtration. The filtrate was evaporated to dryness, producing a brown froth. The foam was dissolved in water (200 ml) and purified with Amberlite A26 resin in its hydroxide form to produce 61 g (98%) of the desired product as a light brown solid.1H NMR (400 MHz, AcN-D3, δ) 7.56 (1H, m), 7.03 (2H, m), 3.76 (4H, s), 2.47 (4H, m), 2.19 (3H, s), 1.95 (4H, s). Example 4 Synthesis of a C5 chelate of 2 protected Mn fragments (compound IV). A 500 mL round-bottom flask fitted with a magnetic stir bar was charged with unprotected 2-fragment cyclic chelate (20.0 g, 90.8 mmol) and AcN (160 mL). Diisopropylethylamine (38.7 mL, 217 mmol) and dimethyl 2-bromopentanedioate (47.7 g, 199.7 mmol) were added, and the resulting solution was stirred at 65°C for 20 h. Diisopropylethylamine (9.75 mL, 54.6 mmol) and dimethyl 2-bromopentanedioate (11.8 g, 49.4 mmol) were added, and the resulting solution was stirred at 65°C for an additional 19 h. The solvent was removed under vacuum until a red oil was obtained. The oil was dissolved in water (300 ml) and washed with EtOAc (300 ml). The EtOAc layer was extracted with water (twice at 50 ml) and combined with the initial aqueous layer. The water was then removed under vacuum until a red-colored oil was obtained, which was used without further purification. Example 5 Synthesis of (phy.^-C5 chelate of 2 protected Mn fragments (compound V). Qocznn / zznz / E / YiA A 50 mL round-bottom flask fitted with a magnetic stir bar was charged with unprotected 2-fragment cyclic chelate (1.01 g, 4.58 mmol), potassium carbonate (1.58 g, 11.5 mmol), and NaCl (10 mL). (S)-5-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanedioate (Levy, SG et al. Org. Proc. Res. Dev. 2009, 13, 535-542) (2.60 g, 6.98 mmol) was dissolved in NaCl (2 mL) and then added to the stirred suspension. This mixture was heated in an oil bath at 50°C for 21 h. An additional amount of (S)-5-benzyl-1-tere-butyl 2-(methylsulfonyloxy)pentanedioate (1.71 g, 4.59 mmol, in 2 ml of AcN) and potassium carbonate (317 mg, 2.29 mmol) was added, and heating was continued for an additional 47 h. The reaction was cooled to room temperature and filtered through a 0.45 pm PTFE filter.The solids were rinsed with acetonitrile (5 times at 5 mi) and the combined filtrates were concentrated under reduced pressure, which provided a red-colored oil that was obtained without further purification (ESI: m / z = 774 (M + H)+). Specific rotation: [o]27d = +12.1° (c=0.00404, acetonitrile);1H NMR (CDCI3, 500 MHz) δ 1.40-1.45 (m, 10H), 1.49 (s, 9H), 1.55-1.64 (m, 1.65-1.6H), (m, 1H), 1.85-1.95 (m, 2H), 1.95-2.04 (m, 1H), 2.04-2.10 (m, 2H), 2.83-2.87 (m, 3H), 2.93-2.98 (m, 1H), 3.05-3.2.98 (m, 1H), 3.05-1.78 (m, 3H), J.7. = 17.4 Hz, 1H), 3.70 (d, J= 16.9 Hz, 1H), 4.00 (d, J = 16.9 Hz, 1H), 4.03-4.14 (m, 2H), 4.25 (d, J = 17.6 Hz, 1H), 4.88 (4.4.8 Hz), (d, J= 7.6 Hz, 1H), 6.99 (d, J = 7.6 Hz, 1H), 7.15-7.20 (m, 2H), 7.20-7.23 (m, 2H), 7.28-7.34 (m, 6H), 7.49 (t, J= 7.6 Hz, 1.4Hz), 1H);13C NMR (CDCI3, 125 MHz) δ 25.5, 26.6, 28.3, 28.4, 30.4, 30.6, 33.9, 46.7, 52.9, 53.6, 54.3, 54.7, 65.7, 66.3. 66.8, 67.9, 82.5, 82.6, 120.2, 120.6, 126.0, 128.5, 128.6, 128.7, 135.7, 135.8, 138.5, 159.8, 160.9, 170.7, 171.3, 172.1, 172.2. Example 6 Synthesis of a protected 2-Mn fragment (S,S)-chelate C5 (compound VI). A 10 mL round-bottom flask fitted with a magnetic stir bar was charged with unprotected 2-fragment cyclic chelate (0.210 g, 0.953 mmol), potassium carbonate (0.329 g, 2.38 mmol), and NaCl (6 mL). (α)-5-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanedioate (prepared from D-glutamic acid: Levy, SG et al. Org. Proc. Res. Dev. 2009, 13, 535-542) (0.888 g, 2.38 mmol) was dissolved in NaCl (2 mL) and then added to the stirred suspension. This mixture was heated in an oil bath at 50°C for 67 h. The reaction was cooled to room temperature and concentrated under reduced pressure. The residue was divided between water and dichloromethane (20 mL each). The layers were separated, and the aqueous layer was subsequently extracted with dichloromethane (twice at 10 mL). The combined organic compounds were extracted with water (twice at 20 mL) and then dried over anhydrous sodium sulfate. The dried organic layer was filtered through a 0.5 mm PTFE filter.45 pm and the filtrate was concentrated at reduced pressure, which yielded a yellow-colored oil that was carried out without further purification (ESI: m / z = 774 (M + H)+). Example 7 Synthesis of (F?,S)-C5 chelate of 2 protected Mn fragments (Compound Vil). QQCznn / zznz / B / Yi A 10 mL round-bottom flask fitted with a magnetic stir bar and a nitrogen inlet was charged with unprotected 2-fragment cyclic chelate (278 mg, 1.26 mmol) and isopropanol (4 mL). Diisopropylethylamine (522 mL, 3.07 mmol) was added, followed by (S)-5-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanoate (prepared from L-glutamic acid: Levy, SG et al. Org. Proc. Res. Dev. 2009, 13, 535-542) (407 mg, 0.87 mmol) and additional isopropanol (1 mL). The resulting solution was placed under nitrogen and heated in an oil bath at 50°C for 48 h. An additional amount of (S)-5-benzyl-1-tere-butyl 2-(methylsulfonyloxy)pentanedioate (222 mg, 0.596 mmol) and diisopropylethylamine (215 ml, 1.26 mmol) was added, and heating continued for an additional 21 h. The reaction was cooled to room temperature and concentrated under reduced pressure. The residue was diluted with 15 ml of dichloromethane and 30 ml of water.The layers were separated, and the aqueous layer was extracted with 15 mL of dichloromethane. The combined organic compounds were washed with 30 mL of water and then dried over sodium sulfate. The dried organic compounds were filtered through a #1 filter, and the resulting filtrate was concentrated under reduced pressure. The residual material was purified on a C18 column using a gradient elution (AcN / 2 mM HCl, 10:90 to 80:20) to produce 260 mg (43%) of the intermediate (fij-monoalkylate (ESI: m / z = 497 (M + H)+). A 10 mL round-bottom flask equipped with a magnetic stir bar and a nitrogen inlet was charged with the monoalkyl intermediate (260 mg, 0.524 mmol) and acetonitrile (5 mL). Potassium carbonate (219 mg, 1.58 mmol) was added, followed by (fi)-5-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanoate (prepared from D-glutamic acid: Levy, SG et al. Org. Proc. Res. Dev. 2009, 13). 535-542) (252 mg, 0.676 mmol).The resulting solution was placed under nitrogen and heated in an oil bath at 50°C for 48 h. An additional amount of (fi)-5-benzyl-1-tere-butyl 2-methylsulfonyloxypentanedioate (97 mg, 0.260 mmol) was added, and heating continued for an additional 48 hours. The reaction was cooled to room temperature, diluted with acetonitrile, and filtered through a 0.45 µm filter. The yellow filtrate was concentrated under reduced pressure. The residue was dissolved in 1:1 acetonitrile:water (4 mL) and purified on a C18 column using a gradient elution (AcN / 2 mM HCl, 10:90 to 80:20) to yield 310 mg (76%, 32% in two steps) of the desired product (ESI: m / z = 774 (M + H)+); Specific rotation: [o]24d = +1.9° (c=0.044, acetonitrile);1H NMR (CDCfe, 500 MHz) δ 1.38 (s, 18H), 1.37-1.45 (m, 2H), 1.69-1.80 (m, 4H), 1.80-1.89 (m, 2H), 2.63 (bs, 3H), 2.89-3.02 (m, 4H), 3.03-3.08 (m, 2H), 3.08-3.14 (m, 2H), 3.47 (d, J= 17.5 Hz, 2H), 3.96 (bs, 2H), 4.15 (d, J = 17.5 Hz, 2H), 4.79 (s, 4H), 6.90 (d, J= 7.5 Hz, 2H), 7.03–7.08 (m, 4H), 7.14–7.19 (m, 6H), 7.41 (t, J = 7.5 Hz (1C 1C), 18); (CDCh, 125 MHz) δ 26.1, 27.8, 28.0, 30.0, 52.1, 52.7, 53.4, 66.0, 67.4, 82.0, 119.8, 128.2, 128.3., 128.2, 128.3. 170.9, 171.8. Example 8 Synthesis of (phy^-chelate C5 from 2 deprotected Mn fragments (compound VIII). Shop / sell / E / Yii A 100 mL round-bottom flask equipped with a magnetic stir bar, reflux condenser, and nitrogen inlet was charged with C5(n,fí)-chelate of two protected Mn fragments (3.64 g, 4.71 mmol) and dioxane (20 mL). One-M HCl (20 mL, 20.0 mmol) was added, and the mixture was placed under a nitrogen atmosphere and heated to 50°C. After 5 days, concentrated HCl (1.7 mL, 20.4 mmol) was added, and heating was continued. After 3 days, the reaction was cooled to room temperature, and the solution was extracted with ethyl acetate (twice at 25 mL). The pH of the resulting aqueous layer was adjusted to approximately 8 with KOH, and this solution was concentrated under reduced pressure. Methanol (25 mL) was added to the residue, and the mixture was stirred. The resulting suspension was filtered through a 0.45 µm PTFE filter. The filtrate was concentrated under reduced pressure to produce a brown foam, which was carried out without further purification. Example 9 Synthesis of C5 (S,S)-chelate of 2 unprotected Mn fragments (compound IX). A 100 mL round-bottom flask equipped with a magnetic stir bar, reflux condenser, and nitrogen inlet was charged with (S,S)-C5 chelate of two protected Mn fragments (0.713 g, 0.922 mmol) and dioxane (5 mL). Water (3.75 mL) was added, followed by concentrated HCl (1.25 mL, 15.0 mmol), and the mixture was placed under a nitrogen atmosphere and heated to 50°C. After 30 hours, the reaction was cooled to room temperature, and the solution was extracted with ethyl acetate (twice at 10 mL). The combined organic extracts were re-extracted with water (10 mL). The pH of the resulting aqueous layer was adjusted to approximately 8 with KOH granules, and this solution was concentrated under reduced pressure. Methanol (25 mL) was added to the residue, and the mixture was stirred. The resulting suspension was filtered through a 0.45 pm PTFE filter.The filtrate was concentrated at reduced pressure to provide the desired product, which was carried out without further purification (ESI: m / z = 481 (M + H)+). Example 10 Synthesis of (F?,S)-C5 chelate of 2 unprotected Mn fragments (compound X). KOV° °<^0K Α'Ά A' η ko^JX <ok0XX0Compuesto X A 10 mL round-bottom flask equipped with a magnetic stir bar, reflux condenser, and nitrogen inlet was charged with (n,S)-C5 chelate of two protected Mn fragments (189 mg, 0.245 mmol) and dioxane (2.5 mL). Water (1.25 mL) was added, followed by concentrated HCl (1.25 mL), and the mixture was placed under a nitrogen atmosphere and heated to 50°C for 40 h. The reaction was cooled to room temperature, and the solution was diluted with water (15 mL) and ethyl acetate (10 mL). The layers were separated, and the aqueous layer was extracted with ethyl acetate (twice to 10 mL). The pH of the resulting aqueous layer was adjusted to approximately 7 with KOH, and this solution was concentrated under reduced pressure. Methanol (25 mL) was added to the residue, and the mixture was stirred. The resulting suspension was filtered through a 0.45 pm PTFE filter. The filtrate was concentrated under reduced pressure, providing the unprotected chelate, which was carried out without further purification (ESI: m / z = 481 (M + H)+). Example 11 Synthesis of C5 chelate of 2 Mn fragments (compound XI). aocznn / zznz / E / Yii Composite XI A 1 L round-bottom flask fitted with a magnetic stir bar was charged with C5 chelate of two protected Mn fragments (48.7 g, 90.8 mmol) and water (450 mL). Sodium hydroxide (29.1 g, 726 mmol) was added, and the mixture was stirred at room temperature for 2 h. The reaction mixture was washed with EtOAc (250 mL), and the layers were separated. The aqueous layer was washed again with EtOAc (twice at 100 mL), and the aqueous layer was collected. Manganese chloride tetrahydrate (19.6 g, 99 mmol) was added to the aqueous solution. The pH was adjusted to 7.1 with 6 M NaOH, and the mixture was stirred at room temperature for 17 h and then at 90°C for 2.5 h. After cooling to room temperature, the pH was adjusted to 10.1 with 50 wt% aqueous NaOH, and a fine brown precipitate formed. The precipitate was removed by centrifugation at 3000 rcf for 20 min, and the supernatant was collected and evaporated to dryness under vacuum. The residue was ground with 127 mL of MeOH at 40°C for 1.5 h.The insoluble white solid was removed by centrifugation at 3000 rcf for 30 min. The supernatant was evaporated to dryness under vacuum to produce a whitish solid that was purified in C18 silica gel (3% AcN in water) to produce 36.8 g (75%) of the desired product as a whitish solid (ESI: m / z = 534 (M + H)+). QQCznn / zznz / E / Yi Example 12 Synthesis of (F?,F?)-C5 chelate of 2 Mn fragments (compound XII). N Mη N L ^N^ J Compound XII A 25 mL round-bottom flask fitted with a magnetic stir bar was charged with (fi,fi)-C5 chelate of two Mn fragments (2.98 g, 4.71 mmol) and water (12 mL). Manganese chloride tetrahydrate (1.41 g, 7.12 mmol) was added to the aqueous solution. The pH was adjusted to 6.5 with 50% aqueous KOH and stirred at room temperature for 5 h. The pH was then adjusted to 10 with KOH(s) and the mixture was stirred overnight. The brown suspension was filtered through a 0.45 µm PTFE filter containing celite (4.9 cm² x 1.8 cm). The pH of the filtrate was adjusted to 7.3 with cHCl (20 mL) and this material was concentrated under reduced pressure. The residual material was combined with methanol (25 ml) and stirred. The resulting suspension was filtered through a 0.45 µm PTFE filter and the solid was rinsed several times with methanol. The filtrate was concentrated under reduced pressure and the residual material was purified on a C18(AcN / water) column to produce 1.09 g (43%) of the desired product (ESI: m / z = 534 (M + H)+). Example 13 Synthesis of (S,S)-C5 chelate of 2 Mn fragments (compound XIII). N Mη N Compound XIII In a procedure identical to its diastereomer, (S,S)-chelate C5 of 2 Mn fragments (0.092 g, 0.17 mmol) yielded 0.101 g (68%) of the expected product (ESI: m / z = 860 (M + H)+). Specific rotation: [a]24D = -3.0° (c=0.018, water). Example 14 Synthesis of (ñ,S)-C5 chelate of 2 Mn fragments (compound XIV). QQCznn / zznz / E / Yi A 5 mL round-bottom flask fitted with a magnetic stir bar was charged with unprotected (fi,S)-C5 chelate of two Mn fragments (180 mg, 0.284 mmol) and water (4 mL). Manganese chloride tetrahydrate (115 mg, 0.581 mmol) was added to the aqueous solution. The pH of the solution was adjusted from 6.0 to 6.4 with 50% aqueous KOH and stirred at room temperature for 4 days. The pH was then adjusted to 10 with KOH(s) and the mixture was stirred overnight. The brown suspension was filtered through a 0.45 µm PTFE filter containing Celite (4.9 cm² x 1.8 cm). The pH of the filtrate was adjusted to 7.2 with cHCl (8 µL) and this material was concentrated under reduced pressure. The residual material was combined with methanol (25 ml) and stirred. The resulting suspension was filtered through a 0.45 µm PTFE filter and the solid was rinsed several times with methanol.The filtrate was concentrated under reduced pressure and the residual material was purified on a C18 column, eluting with water to produce 94 g (62%) of the desired product (ESI: m / z = 534 (M + H)+). Example 15 Synthesis of Mn chelate-5 (compound XV). A 50 mL two-necked flask fitted with a magnetic stir bar was charged with D-glucamine (0.713 g, 3.94 mmol) and water (19.7 mL). The pH of the resulting solution was adjusted to 7.4 with 1.0 M HCl, and C5 chelate of two Mn fragments (1.00 g, 1.87 mmol) was added, followed by EDCl-HCl (0.848 g, 4.42 mmol) and HOBt hydrate (0.121 g, 0.787 mmol). The pH was maintained at 6 by adding 1.0 M HCl or 1.0 M NaOH as needed while stirring at room temperature for 8 h. D-glucamine (0.359 g, 1.98 mmol) and EDCI-HCl (0.433 g, 2.26 mmol) were added, and the pH was maintained at 6 while stirring at room temperature for 16 h. The reaction solution was evaporated to dryness under vacuum, and the crude product was purified on C18 silica gel (100% water to 20% AcN in water) to produce 0.782 g (48%) of the desired product as a light yellow solid (ESI: m / z = 860 (M + H)+). Example 16 Synthesis of Mn (fi,fi)-chelate-5 (computer XVI). QQCznn / zznz / E / Yi A 25 mL flask equipped with a magnetic stir bar was charged with Mn 2-fragment C5 chelate (1.06 g, 2.04 mmol), D-glucamine (0.833 g, 4.60 mmol), HOBt hydrate (0.016 g, 0.10 mmol), and water (8.2 mL). The pH of the resulting solution was adjusted to 6.2 with concentrated HCl. EDCl-HCl (0.924 g, 4.82 mmol) was added, and the pH was maintained between 6 and 6.5 by adding concentrated HCl as needed while stirring at room temperature for 23 h. The reaction solution was diluted with water (30 mL) and purified by sequentially passing the solution through an IR-120 (Na) ion-exchange column followed by an IR-400 (Cl) ion-exchange column. The crude product was purified in C18 silica gel (2% AcN in water to 50% AcN in water) to produce 1.42 g (81%) of the desired product as a light yellow foam (ESI: m / z = 860 (M + H)+). Specific rotation: [a]26D = -19.7° (c=0.0129, water). Example 17 Synthesis of (S,S)-chelate-5 of Mn (compound XVII). In a procedure identical to its diastereomer, (S,S)-chelate C5 of 2 Mn fragments (0.092 g, 0.17 mmol) yielded 0.101 g (68%) of the expected product (ESI: m / z = 860 (M + H)+). Specific rotation: [a]24D = -3.0° (c=0.018, water). Example 18 Synthesis of (phi,S)-Mn chelate-5 (compound XVIII). OH OH EITHER. OH OH Compound XVIII N Mη N LJ O OH OH OH OH Qocznn / zznz / E / YiA A 5 mL flask fitted with a magnetic stir bar was charged with Mn(fi,S)-chelate-1a (60 mg, 0.112 mmol), D-glucamine (50 mg, 0.276 mmol), HOBt hydrate (4.6 mg, 0.030 mmol), and water (3 mL). The pH of the resulting solution was adjusted to 6 with concentrated HCl (40 mL). EDCl-HCl (52 mg, 0.271 mmol) was added, and the mixture was stirred at room temperature. Additional amounts of EDCl were added after 6 h (44 mg, 0.230 mmol), 24 h (40 mg, 0.209 mmol), and 30 h (50 mg, 0.261 mmol). The reaction solution was diluted with water (3 ml) and purified by sequentially passing the solution through an IR-120 (Na) ion exchange column followed by an IR-400 (Cl) ion exchange column. The crude product was purified on a C18 column using a gradient elution (AcN / water, 0:100 to 10:90) to produce 23 mg of Mn(S,fi)-chelate-5 (24%, 42% of) and 40 mg of Mn(fi,S)-chelate-5 (42%, 91% of) (ESI: m / z = 860 (M + H)+). Example 19 Isomerization of (S,fi)-C5-chelate of 2 Mn fragments to (fi,S)-C5 of 2 Mn fragments. A mixture of Mn(fi,S)-chelate-1a and Mn(S,ñ)-chelate-1a (59 mg, 0.111 mmol) was dissolved in water (1 ml). This mixture was sealed in a glass flask and heated at 90°C for 42 h. After this heating period, HPLC showed a collapse of the two peaks into one peak. (ESI: m / z = 534 (M + H)+). Example 20 Synthesis of (fi,S)-chelate-5 of Mn prepared from (S,ñ)-chelate C5 of 2 isomerized Mn fragments. To an HPLC flask containing (n,S)-Mn chelate-1a (59 mg, 0.111 mmol) and water (1 mL), D-glucamine (49 mg, 0.270 mmol) and HOBt hydrate (5 mg, 0.032 mmol) were added. The pH of the resulting solution was adjusted to 5.7 with concentrated HCl (35 mL). EDCl-HCl (53 mg, 0.276 mmol) was added, and the mixture was stirred at room temperature for 22 h. More EDCl (23 mg, 0.120 mmol) was added, and the reaction was stirred for an additional 42 h. The reaction solution was diluted with water (3 mL) and purified by sequentially passing the solution through an IR-120 (Na) ion-exchange column followed by an IR-400 (Cl) ion-exchange column. The crude product was purified on a C18 column using a gradient elution (AcN / water, 0:100 to 10:90) to produce 12 mg (37%, 74% of) of the desired isomer (R,S) as an off-white solid (ESI: m / z = 860 (M + H)+). Example 21 Synthesis of Mn chelate-10 (compound XIX). Qocznn / zznz / E / YiA rac-3-aminopropane-1,2-diol (0.190 g, 2.08 mmol) was dissolved in H2O (10.4 ml) in a 25 ml two-necked round-bottom flask fitted with a magnetic stir bar and a pH probe. The resulting solution was adjusted to pH 7.1 with 1.0 M HCl and Mn chelate-1a (0.603 g, 0.996 mmol) followed by EDCl-HCl (0.473 g, 2.47 mmol) and then HOB1 hydrate (0.063 g, 0.466 mmol). The pH was maintained at 6 by the addition of 1.0 M HCl or 1.0 M NaOH as needed while stirring at room temperature for 7.5 h. Rac-3-aminopropane-1,2-diol (0.095 g, 1.04 mmol) and EDCI-HCl (0.453 g, 2.36 mmol) were added and the pH was maintained at 6 while stirring at room temperature for 15 h. The reaction solution was evaporated to dryness under vacuum and the crude product was purified on C18 silica gel (100% water to 20% AcN in water) to produce 0.280 g (41%) of the desired product as a light yellow solid (ESI: m / z = 680 (M + H)+). Example 22 Synthesis of the Mn-10 chelate-10 isomer group A and isomer group B. Mn-10 chelate was synthesized as described above and the 2 isomer groups were separated and isolated on C18 silica gel (100% water to 20% AcN in water) as light yellow solids (ESI: m / z = 680 (M + H)+). Example 23 Synthesis of Mn-15 chelate (compound XX). Compound XX Ethanolamine (5.153 g, 84.4 mmol) was dissolved in H₂O (50 mL) in a 250 mL three-necked round-bottom flask equipped with a magnetic stir bar and a pH probe. Manganese chelate-1a (20.107 g, 37.7 mmol) was added, followed by HOBt hydrate (0.289 g, 1.89 mmol). The pH was adjusted to 6.3 with concentrated HCl, and EDCl-HCl (16.966 g, 88.5 mmol) was added. The pH was maintained between 6.0 and 6.5 while stirring at room temperature for 2.5 h. The reaction solution was diluted with water (280 mL) and purified by sequentially passing the solution through an IR-120 (Na) ion-exchange column followed by an IR-400 (Cl) ion-exchange column. The resulting crude material was purified in C18 silica gel (5% AcN to 20% AcN in water) to produce 16.05 g (69%) of the desired product as a light yellow solid (ESI: m / z = 620 (M + H)+). Example 24 Synthesis of group A isomers and group B isomers of Mn chelate-15. Mn chelate-15 was synthesized as described above and the 2 isomer groups were separated and isolated on C18 silica gel (5% AcN to 20% AcN in water) as light yellow solids (ESI: m / z = 620 (M + H)+). Example 25 General method for measuring relaxivity r1 and r2. Manganese-containing chelates were dissolved in water at concentrations ranging from 5 to 0 mM Mn. Relaxation times T1 and T2 were measured at 60 MHz and 40°C using a Brüker mq60 relaxometer. Linear fits (R2 > 0.99 in all cases) of 1 / T1 or 1 / T2 as a function of Mn concentration provided values ​​for r1 or r2, respectively. Table 1. Relaxivity r1 and r2 in human serum at 60 MHz and 37°C. QQCznn / zznz / E / Yi Compound r1 (mM-'s-1) r2 (mM-'s-1) Mn Chelate-5 6.0 15.4 1:1 Mixture of (R,R) & (S,S)-Mn Chelate-5 5.9 15.2 (ñ,S)-Mn Chelate-5 6.0 15.4 Method for evaluating transmetalation with Zn. Mn chelates were dissolved in aqueous solutions containing 200 mM ZnCb and 15 mM ammonium formate at any pH 4 to produce a Mn chelate concentration of approximately 2 mM. The resulting solutions were incubated at 40°C with mixing, and aliquots were periodically analyzed by HPLC. The percentage of manganese-containing chelate remaining in the solution was measured by integration at 265 nm. Method for the preparation of Mn-54-labeled chelate for biodistribution studies. A 3 mL glass flask equipped with a magnetic stir bar was filled with manganese-containing chelate (1 mg) and 1.0 M ammonium formate, pH 4 (0.5 mL). Then, 54MnCl2 in 1.0 M HCl (~500 pCi) was added, and the resulting solution was heated at 40°C for 16 h. The resulting solution was purified by preparative HPLC to remove unchelated Mn. The radioactive fraction was collected and evaporated to dryness under vacuum. The radioactive residue was absorbed into water containing non-radioactive Mn chelate (0.310 M) such that ~30 pCi of radioactivity was formulated at a dose of 0.620 mmol Mn / kg with an injection volume of 2 mL / kg. General Method for Mn-54 Biodistribution Studies. The experimental protocol was adapted to the Guidelines for the Care and Use of Laboratory Animals and was approved by the institutional IACUC. Female Sprague-Dawley rats (130–150 g) were housed in standard cages, provided with ad libitum access to standard commercial food and water, and maintained on a 12-hour light-dark cycle in temperature- and humidity-controlled rooms. Prior to injection of Mn-54-labeled chelates, the rats were anesthetized with 3% inhaled isoflurane (EZ Anesthesia Systems). The injection site was prepared with alcohol swabs, and a temporary 27-gauge catheter was inserted into a tail vein. ~30 pCi of Mn-54 labeled chelate formulated with non-radioactive Mn chelate was dosed at 0.620 mmol of non-radioactive Mn chelate / kg to an injection volume of 2 ml / kg injected at a rate of 1 ml / min.After injection, the animals were housed individually in wire cages with filter paper until the first urine was collected. Rats were housed in standard cages for the long term. Seven days after injection, the animals were euthanized by CO2 immersion, and the organs and tissues of interest were removed and tested for radioactivity using a Wizard 2480 gamma counter (Table 2). Table 2. %ID ± standard deviation for tissues 7 days after injection of a 0.62 mmol Mn / kg dose containing ~30 pCi of chelate labeled with 54Mn. Qocznn / zznz / E / Yii Tissue Mn chelate-5a 1:1 mixture of (R,R) & (S,S)-Mn chelate-5b (F?,S)-Mn chelate-5b Brain 0.005 ± 0.0004% 0.005 ± 0.001% 0.002 ± 0.0004% Pituitary gland < LOD < LOD < LOD Olfactory bulb < LOD < LOD < LOD Liver 0.093 ± 0.008% 0.082 ± 0.009% 0.091 ± 0.013% Kidney 0.053 ± 0.006% 0.027 ± 0.003% 0.112 ± 0.023% Spleen < LOD < LOD 0.002 ± 0.0002% Bladder < LOD < LOD 0.002 ± 0.0003% Heart < LOD 0.002 ± 0.0004% 0.002 ± 0.0002% Lungs 0.003 ± 0.0004% 0.003 ± 0.001% 0.003 ± 0.0003% Muscle < LOD < LOD < LOD Skin < LOD < LOD < LOD Blood < LOD < LOD < LOD Femur 0.004 ± 0.001% 0.004 ± 0.0006% 0.002 ± 0.0004% aLoD = 0.002% ID, n =4;bLoD = 0.001% ID, n = 4 Example 26 The following method was used to measure the dissociation of manganese from manganese chelate in human serum. Human serum obtained from clotted blood (Sigma-Aldrich, 1900 µL) was mixed with an aqueous solution of manganese chelate (2 mM, 100 µL). The mixture was incubated at 37°C. At specific time points, 200 µL aliquots of the test sample were mixed with saline solution (400 µL) and analyzed by size exclusion chromatography (metal-free HPLC equipped with a column with a separation range of 5,000–500,000 Da) combined with online detection of manganese-containing species by ICP-SF-MS. The percentage of chelation was measured as the percentage of the area of ​​the high-molecular-weight fraction (protein). At regular intervals, EDTA solution was run through the system to ensure low background metal ion levels. Human serum was incubated with Mn(lI) acetate and injected to identify the position of Mn-binding components in the high molecular weight region of the chromatogram. Figure 10 illustrates the chromatographic separation of protein-bound manganese from intact manganese chelate into the slowly releasing low molecular weight fraction. In this assay, four different Mn chelate-5 stereoisomers (Mn, SS, SR, and RS) were analyzed. Table 3 shows the percentage of dechelation measured by quantitative detection of protein-bound manganese at time points 3, 24, and 49 h after the start of the experiment. Table 3. Percentage of dechelation of Mn chelate-5 stereoisomers in human serum QQCznn / zznz / E / Yi Mn-5 chelate isomer / Incubation time (h) RR SS SR RS 3 0.6 0.3 2.0 0.04 24 2.7 1.6 12.7 0.11 49 3.6 2.4 15.1 0.16

Claims

1. A compound of formula IA: R3 QQCznn / zznz / B / Yi (IA) or a salt or solvate thereof, wherein: each R1 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH C1-6 hydroxyalkyl, or a carbohydrate moiety; each R2 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl or hydrogen; R3 is selected from C1-3 alkyl or -(CH2)mC(=O)-NR5R6, where m is an integer from 2-5, where R5 and R6 are independently selected from hydrogen, C1-20 hydroxyalkyl, C16 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)NH-C1-6 hydroxyalkyl, or a carbohydrate fraction; R4 represents 0-3 substituents selected from hydroxy, C1-6 alkyl and Ci-θ hydroxyalkyl; and each n is an integer from 0 to 4.

2. The compound according to claim 1, wherein the compound comprises at least two hydroxy groups.

3. The compound according to claim 1, wherein the compound is of formula IA.

4. The compound according to claim 1, wherein the compound is of formula IA, each R1 is C1-20 hydroxyalkyl; R3 is methyl; R2 and R4 are hydrogen; and n is 2.

5. The compound according to claim 1, wherein each R1 is a C1-20 hydroxyalkyl.

6. The compound according to claim 1, wherein R3 is methyl.

7. The compound according to claim 1, wherein R2 and R4 are hydrogen.

8. The compound according to claim 1, where n is 2.

9. The compound according to claim 1, wherein each R1 is independently C3-9 hydroxyalkyl.

10. The compound according to claim 1, wherein each R1 is independently C3-6 hydroxyalkyl.

11. The composition comprising a compound of formula IA: R3 QQCznn / zznz / E / Yi (IA) or a salt or solvate thereof, and a pharmaceutically acceptable excipient, wherein: each R1 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH C1-6 hydroxyalkyl, or a carbohydrate moiety; each R2 is independently selected from C1-20 hydroxyalkyl, C1-6 alkyl, or hydrogen; R3 is selected from C1-3 alkyl or -(CH2)mC(=O)-NR5R6, where m is an integer from 2-5, where R5 and R6 are independently selected from hydrogen, C1-20 hydroxyalkyl, C1-6 alkyl, C3-6 aryl optionally substituted with one or more substituents selected from halo and -C(=O)-NH C1-6 hydroxyalkyl, or a carbohydrate fraction; R4 represents 0-3 substituents selected from hydroxy, C1-6 alkyl and Ci-θ hydroxyalkyl; and each n is an integer from 0 to 4.

12. The composition according to claim 11, wherein the compound of formula IA comprises at least two hydroxy groups.

13. The composition according to claim 11, wherein the compound lacks detectable amounts of the compound of formula (IB): R3 (IB) or a salt or solvate thereof.

14. The composition according to claim 11, wherein the composition further comprises Mn chelates having (R,R) and (S,S) stereochemistry.

15. The composition according to claim 11, wherein each R1 is a C1-20 hydroxyalkyl.

16. The composition according to claim 11, wherein R3 is methyl.

17. The composition according to claim 11, wherein R2 and R4 are hydrogen.

18. The composition according to claim 11, wherein n is 2.

19. The composition according to claim 11, wherein each R1 is independently QQCznn / zznz / B / Yi C3-9 hydroxyalkyl.

20. The composition according to claim 11, wherein each R1 is independently C3-6 hydroxyalkyl.

21. A method of obtaining images of a patient comprising administering the compound according to claim 1 to a patient in need, followed by acquiring an MRI image of the patient.

22. A method of obtaining images of a patient comprising administering the composition according to claim 11 to a patient in need, followed by acquiring an MRI image of the patient.

23. An enantioselective synthesis method of the compound of formula (1A) according to claim 1, comprising: (a) monoalkylation using a first enantiomer of 5-benzyl-1-ferc-butyl 2-(methylsulfonyloxy)pentandioate of a compound of formula (III) (ni); (b) followed by alkylation of the compound of step (a) with a second enantiomer of 5-benzyl-1-ferc-butyl 2-(methylsulfonyloxy)pentandioate, wherein the second enantiomer is opposite to the first enantiomer; (c) reacting the product of step (b) with Mn; and (d) reacting the product of step (c) with an amino alcohol.

24. An enantioselective synthesis method of a composition containing the compound of formula (1A) according to claim 11, comprising: (a) monoalkylation using a first enantiomer of 5-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanedioate of a compound of formula (III) Qocznn / zznz / E / YiA (ni); (b) followed by alkylation of the compound of step (a) with a second enantiomer of 5-benzyl-1-tert-butyl 2-(methylsulfonyloxy)pentanedioate, wherein the second enantiomer is opposite to the first enantiomer; (c) reacting the product of step b) with Mn; and (d) reacting the product of step c) with an amino alcohol.

25. The composition according to claim 24, wherein the method results in a composition comprising the compound of formula (IA).

26. A method for manufacturing the composition according to claim 11, wherein the method comprises: heating a composition comprising the compound of formula (1B): (IB) or a salt or solvate thereof; wherein the heating is for a time and temperature sufficient to convert substantially all of the compound of formula (1B) into the compound of formula (1A).

27. The method according to claim 26, wherein the resulting composition lacks detectable amounts of the compound of formula (1B).