CN114805109A

CN114805109A - Efficient preparation method of fluoro [18F ] safinamide and application of PET (polyethylene terephthalate) developer

Info

Publication number: CN114805109A
Application number: CN202210508969.4A
Authority: CN
Inventors: 和庆钢; 徐洋洋; 张宏; 田梅; 余开武; 古望军; 傅珠荣
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2022-05-10
Filing date: 2022-05-10
Publication date: 2022-07-29

Abstract

The invention discloses a fluorine [18F ]]The method comprises the steps of designing and preparing fluorine at first[18F]The precursor of safinamide is subjected to nucleophilic substitution reaction to realize direct radioactive fluorine labeling on the aromatic ring in the precursor to obtain fluorine [18F ]]Safinamide; the precursor is Mel-SF, SPIAd-SF, SPI5-SF, Me ₃ Sn-SF, or Bpin-SF; prepared fluorine [18F]The safinamide can be used as a PET (positron emission tomography) imaging agent for imaging of a cell line secreting monoamine oxidase B, can also be used for imaging of living animals, can penetrate through a blood brain barrier and realize brain area imaging, can be reversibly combined with multiple targets in vivo, can also be used for imaging of animal in-vitro tissues, and has potential application prospects in the medical fields of medical early diagnosis, adjuvant therapy, pathogenesis research and the like.

Description

Efficient preparation method of fluoro [18F ] safinamide and application of PET (polyethylene terephthalate) developer

Technical Field

The invention relates to radiopharmaceutical development, belongs to the technical field of nuclear medicine, and particularly relates to a high-efficiency preparation method of fluoro [18F ] safinamide, and application of the method as a PET (polyethylene terephthalate) probe with the capability of targeting monoamine oxidase B, wherein the method has potential application prospects in the medical fields of medical early diagnosis, auxiliary treatment, pathogenesis research and the like.

Background

Safinamide is an auxiliary drug which is approved as the Parkinson treatment at present, and can reduce the degradation of in vivo levodopa and exogenously injected levodopa by inhibiting the activity of monoamine oxidase B (monoamine oxidase B), thereby maintaining the in vivo levodopa at a higher level and achieving the effect of treating Parkinson diseases. However, as the research progresses, safinamide also exhibits potassium-sodium channel inhibition, glutamate receptor secretion inhibition, and the like. These effects allow the safinamide to have a good therapeutic effect or to exhibit therapeutic potential in other nervous system diseases than Parkinson's disease, such as depression, Alzheimer's disease, Parkinson's disease, ischemic cerebral infarction, etc. Unfortunately, the research on the application of safinamide in treating parkinson's disease has been approved for wide application in the market for more than ten years from the first clinical experiment, and the main reason for limiting the progress is that the current research means for safinamide mainly focuses on anatomical and other in-vitro means or traumatic in-vivo experiments, and the experiments are long in period, high in consumption and difficult to know the real metabolism, distribution, action and the like of safinamide in the body. This has led to the fact that safinamide, even though it exhibits broader application prospects and greater potential for use, is poorly approved in the short term by other disease areas. Therefore, it is very important to perform noninvasive and real-time in-vivo research on safinamide, so as to rapidly obtain the therapeutic effect, explore mechanism mechanisms of different diseases, shorten research period and the like.

Positron Emission Tomography (PET) is the only new imaging technology that can display biomolecular metabolism, receptor and neuromediator activities in vivo at present, and is now widely used in the aspects of diagnosis and differential diagnosis of various diseases, treatment effect evaluation, organ function research, new drug development, and the like. The PET imaging technology has high sensitivity, high specificity and strong penetrability, and can be used for whole-body imaging, and images of all regions of the whole body can be obtained through one-time whole-body imaging examination. PET is an imaging reflecting molecular metabolism, when the early stage of a disease is in a molecular level change stage, the morphological structure of a lesion area is not abnormal, and MRI and CT examination cannot clearly diagnose, the PET examination can find the focus, can obtain a three-dimensional image, can also carry out quantitative analysis, and realizes early diagnosis, which is incomparable with other current image examinations.

PET probes, also known as PET imaging agents, are radiopharmaceuticals that can be introduced into the body for imaging organs, tissues or molecules. After the radioactive drug is introduced into the body, the radioactive drug can be concentrated in a target organ or tissue, and the radiation emitted by the radioactive drug can be detected by an imaging instrument, so that a distribution image of the drug in the body can be obtained for diagnosing various diseases. The glucose group of the PET probe, which is mainly used in clinical studies, is, for example, 18-fluoro-deoxyglucose (",") ¹⁸ F]FDG) is the most common PET imaging agent in tumor diagnosis and treatmentHave been intensively studied.

Therefore, the safinamide (fluorine 18F safinamide) marked by the 18F nuclide can be used as a PET imaging agent to provide a noninvasive, rapid, sensitive and real-time in-vivo research means for the safinamide research. Due to the short half-life of the radionuclide used in PET imaging agents (half-life of 18F nuclide is 109.8 minutes), it is generally required that the radiosynthesis yield of PET imaging agents can reach more than 10% in order to meet experimental requirements, on one hand, a sufficient radioactive dose is provided, and on the other hand, a sufficiently high radioactive concentration is provided, so that the use time range of the PET imaging agents and the number of experiments which can be scheduled can be prolonged.

Five of the five approaches identified in the present invention are directed to radiolabelling strategies involving direct radionucleophilic substitution of aromatic rings ¹⁸ The high-efficiency synthetic route of the F-labeled safinamide can reach over 10 percent of radioactive synthetic yield. The high affinity capacity for monoamine oxidase B, the distribution in the whole body of a living animal, particularly in a brain area, the ingestion dynamics of the probe and the like are researched through biological experiments at a cell level, a living animal level and an anatomical level, and the application potential of the probe in nervous system diseases such as Alzheimer's disease, Huntington's disease, depression, ischemic cerebral infarction and the like is indicated.

Disclosure of Invention

The invention aims to provide a high-efficiency preparation method of fluoro [18F ] safinamide and application of the same in a PET (polyethylene terephthalate) developer aiming at the defects of the prior art.

The technical scheme adopted by the invention is as follows:

fluoro [18F ] safinamide has the structure shown below:

the preparation method comprises the following steps: first, fluorine 18F is designed and prepared]The precursor of safinamide is subjected to direct radioactive fluorine labeling on an aromatic ring in the precursor through nucleophilic substitution reaction to obtain fluorine [18F ]]Safinamide. The precursor is Mel-SF, SPIAd-SF、SPI5-SF、Me ₃ Sn-SF, or Bpin-SF; the general structural formula is as follows:

the corresponding R is respectively:

the preparation method of the precursor comprises the following steps:

1) the precursor of Mel-SF, SPIAd-SF and SPI5-SF is prepared by the following method:

compound 4A [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-iodophenyl) oxy) benzyl) carbamate ] (1 eq) was dissolved with m-chloroperoxybenzoic acid (1 to 2 eq) using anhydrous organic solution (e.g. tetrahydrofuran, dichloromethane, N-dimethylformamide etc.) with stirring at 40 ℃ to 80 ℃ for 1 hour to 6 hours. The reaction mixture is cooled to room temperature, and potassium hydroxide or sodium hydroxide (5 to 10 equivalents) and 1 to 2 equivalents of mucic acid, spiro [ decane-2, 2'- [1,3] dioxane ] -4',6 '-dione (SPI5), or spiro [ adamantane-2, 2' - [1,3] dioxane ] -4',6' -dione (SPIAd) are added and the reaction is stirred for 30 minutes to 12 hours. Then diluting the reactant with high polar organic solution (such as dichloromethane, methanol, ethyl acetate, etc.), filtering, concentrating the filtrate until solid precipitation occurs, adding 4-20 times volume of low polar organic solution (such as n-hexane, petroleum ether, etc.) to promote solid precipitation, and standing the mixture at-30 deg.C to 0 deg.C for 2-24 hr until all solid precipitation occurs. And filtering and drying the solid to obtain the solid, and finally further purifying the product by column chromatography. The synthetic route is (wherein KOH can also be NaOH):

2)Me ₃ the synthesis method of the Sn-SF precursor comprises the following steps:

compound 4B [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-bromophenyl) oxy) benzyl) carbamate ] (1 equivalent) was dissolved using an anhydrous organic solution (tetrahydrofuran, 1, 4-dioxane, etc.), and hexamethylditin (1 to 8 equivalents) was added under an inert gas atmosphere by replacing an inert gas (e.g., nitrogen, argon) and stirred, followed by triphenylphosphine palladium dichloride (0.01 to 0.5 equivalent) and then catalyzed, and the reaction was carried out under reflux with heating for 2 to 48 hours. After the reaction is finished, cooling and drying to remove the solvent, and purifying the crude product by using a column chromatography.

3) The synthesis method of the Bpin-SF precursor comprises the following steps:

dissolving the compound 4B (1 equivalent) in an anhydrous organic solution (tetrahydrofuran, 1, 4-dioxane, etc.), replacing with an inert gas, sequentially adding potassium acetate (1 to 5 equivalents) and [1,1' -bis (diphenylphosphino) ferrocene ] dichloropalladium (II) (0.01 to 0.5 equivalent) under an inert gas atmosphere, mixing uniformly, adding 4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane (1 to 10 equivalents), and stirring under reflux for 0.5 to 72 hours. Cooling and extracting after the reaction is finished, adding a drying agent (such as anhydrous magnesium sulfate and the like) into the extracted organic phase, drying, filtering, concentrating, and finally purifying by column chromatography.

Bpin-SF precursor, Me ₃ The synthesis route of the Sn-SF precursor is as follows:

in the above technical scheme, a preparation method of a compound 4A, i.e., [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-iodophenyl) oxy) benzyl) carbamate ] ] and a compound 4B, i.e., [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-bromophenyl) oxy) benzyl) carbamate ] ] is as follows:

dissolving the

compound

3A or 3B (1 equivalent) in an anhydrous organic solution (such as tetrahydrofuran, dichloromethane and the like), slowly adding sodium cyanide substances (2 to 4 equivalents) at a low temperature, stirring uniformly, and then heating the mixture to 20 to 30 ℃. Di-tert-butyl dicarbonate (2 to 20 equivalents) is then added slowly and the mixture is stirred further to react. After the reaction was completed, the reaction mixture was cooled to room temperature, and the crude product was transferred to an organic solution by extraction of the organic solution and an aqueous solution and washing. The collected organic solution was dried by adding a drying agent and concentrated by filtration. Finally, the crude product is purified by column chromatography. The structural formulas of the

compounds

3A and 3B are as follows:

the method for radiofluoridation labeling the precursor is as follows:

(1) bombardment H of cyclotron ₂ ¹⁸ O to obtain radionuclide 18F, purifying by ion exchange under the condition of leacheate containing alkali and phase transfer catalyst, or directly transferring into a reaction bottle containing alkali and phase transfer catalyst, and removing water at 80-120 deg.C (anhydrous acetonitrile can be added for removing water by azeotropic method).

(2) Then dissolving a precursor (the concentration of the precursor is 0.5mmol/L to 20mmol/L) by using an anhydrous polar aprotic solution (such as dimethyl sulfoxide, acetonitrile and the like) and adding the precursor into the reactant obtained in the step (1), reacting at 80 ℃ to 160 ℃ for 5 minutes to 40 minutes, ending the reaction and diluting and purifying by a semi-preparative high performance liquid chromatography system. For Me ₃ Sn-SF and Bpin precursors, and optionally adding copper catalyst (such as copper trifluoromethanesulfonate, Cu (OTf)) ₂ (py) ₄ ) And pyridine for catalytic reactions.

The prepared fluorine [18F ] safinamide can be used as a PET (positron emission tomography) imaging agent for imaging of a cell line capable of secreting monoamine oxidase B.

The fluoro [18F ] safinamide can be used as a PET imaging agent for imaging living animals. Furthermore, the PET imaging agent can penetrate blood brain barrier and realize brain area imaging when in live animal imaging, can be combined with multiple targets in vivo, comprises monoamine oxidase B, potassium-sodium ion channel receptor and glutamic acid receptor, is reversible, and can remove the fluorine [18F ] safinamide combined with the target under the competitive action by adding 19-fluorine-safinamide, monoamine oxidase B inhibitor and potassium-sodium ion channel inhibitor.

The fluoro [18F ] safinamide can also be used as a PET imaging agent for ex vivo tissue imaging of animals by autoradiography.

The invention has the beneficial effects that:

the invention provides a route for preparing the fluorine [18F ] safinamide in a radioactive mode, corresponding reaction steps and parameters, and the routes can obtain a radioactive yield of more than 10% so as to provide enough radioactive dose and radioactive concentration to meet various experimental requirements.

② there are 5 precursors for radioactive preparation of fluoro [18F ] safinamide, there are 3 synthetic routes. This facilitates the selection of appropriate precursors and synthetic routes for the needs of the fluoro [18F ] safinamide, depending on the actual production conditions.

The invention discloses the biological experiment result information of the fluorine 18F safinamide on the cell layer, the living animal layer and the animal in-vitro tissue layer for the first time, and the invention can be used as an imaging research means of multi-layer information of users.

Experiments prove that the fluorine [18F ] safinamide disclosed by the invention retains many characteristics of 19-fluorine-safinamide, and therefore, the fluorine [18F ] safinamide can be used as an imaging research means of 19-fluorine-safinamide.

The biological experiment result of the fluorine 18F safinamide disclosed by the invention shows that the fluorine 18F safinamide has the properties of combining monoamine oxidase B and a potassium-sodium ion channel receptor, penetrating a blood brain barrier, combining reversibility in vivo and the like, and combines the current research situations of some diseases, particularly nervous system diseases, so that the fluorine 18F safinamide as a PET (positron emission tomography) imaging agent can be applied to the aspects of drug screening, curative effect monitoring, early disease diagnosis, pathogenesis research and the like of the diseases such as Alzheimer, Huntington chorea, Parkinson's disease, depression, ischemic cerebral infarction and the like.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings.

FIG. 1 radiolabelled precursors of fluoro [18F ] safinamide

FIG. 2 fluorine [18F ]]The synthetic process of the safinamide radioactive labeling precursor (A) Mel-SF, SPIAd-SF and SPI 5-SF; (B) me ₃ Sn-SF&Bpin-SF。

FIG. 3 fluorine [18F ]]1H-NMR spectra of each molecule in the synthetic process of the safinamide radioactive labeling precursor (A)4A, (B)4B, (C) Mel-SF, (D) SPIAd-SF, (E) SPI5-SF, (F) Me ₃ Sn-SF，(G)Bpin-SF

FIG. 4 fluorine [18F ]]The radioactive synthesis process of safinamide based on different precursors (A) Mel-SF, SPIAd-SF, SPI 5-SF; (B) me ₃ Sn-SF；(C)Bpin-SF

FIG. 5 optimization of the experimental conditions for the radiolabelling of fluoro [18F ] safinamide with Mel-SF, SPIAd-SF, SPI5-SF in (A) base dosage and species selection, (B) precursor species and dosage selection, (C) reaction time and temperature selection, (D) reaction solvent selection

FIG. 6 radioactivity control of Fluo [18F ] safinamide (A) radioactivity chemical purity and identity test (B) stability of injection test

FIG. 7 summary of uptake of fluoro [18F ] safinamide into astrocyte U87, breast cancer MCF-7, and safinamide-pretreated astrocyte

FIG. 8 systemic distribution of fluoro [18F ] safinamide in Sprague Dawley rats (PET dynamic Scan) FIG. 9(A) brain area distribution of fluoro [18F ] safinamide in Sprague Dawley rats (PET dynamic Scan), (B) and corresponding activity/time curves

FIG. 10 displacement of fluoro [18F ] safinamide in Sprague Dawley rats (A) brain area distribution (PET dynamic scan), (B) and corresponding activity/time curves

FIG. 11 distribution of fluoro [18F ] safinamide in ex vivo tissues in C57 mice (autoradiography)

Detailed Description

The technical scheme of the invention is further explained in detail by the attached drawings and the specific examples, and all reagents can be purchased unless otherwise specified.

The structure of fluoro [18F ] safinamide is as follows:

the invention designs and determines an efficient preparation method thereof, wherein the structure of the related marking precursor is specifically shown in figure 1;

the synthetic routes of the respective precursors are shown in FIG. 2, and the present invention will be further described below with reference to some specific examples in order to better illustrate the synthesis of the respective precursors.

Preparation of molecule 4A [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-iodophenyl) oxy) benzyl) carbamate ] ] and molecule 4B [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-bromophenyl) oxy) benzyl) carbamate ] ]:

the

molecule

3A or 3B (1 equivalent) is dissolved in an anhydrous organic solution (such as tetrahydrofuran, dichloromethane, etc.), sodium cyanide material (2 to 4 equivalents) is slowly added at low temperature, and after stirring well, the mixture temperature is raised to 20 to 30 ℃. Di-tert-butyl dicarbonate (2 to 20 equivalents) is then added slowly and the mixture is stirred further to react. After the reaction was completed, the reaction mixture was cooled to room temperature, and the crude product was transferred to an organic solution by extraction of the organic solution and an aqueous solution and washing. The collected organic solution was dried by adding a drying agent and concentrated by filtration. Finally, the crude product is purified by column chromatography.

Example 1:

3A (615mg, 1.5mmol) was dissolved in anhydrous tetrahydrofuran (10mL) and then sodium hydride (60% dispersed in mineral oil, 132mg, 3.3mmol) was added dropwise to the solution at 0 ℃ and stirred for 1 h. The reaction mixture was heated to 25 ℃, di-tert-butyl dicarbonate (1.63g, 24mmol) was added slowly and the mixture was stirred for an additional 2 hours. Finally, the reaction mixture was quenched with water and extracted with ethyl acetate. The organic solution was then washed successively with water, 1M HCl and brine and the organic portion was collected, the final organic solution was Na2SO4 was dried, filtered and concentrated. The product was finally purified by silica gel column chromatography (5-50% ethyl acetate/petroleum ether) to give a colourless solid (4A, 170mg, 0.28mmol, 68% yield). ¹ H NMR(400MHz,Chloroform-d)δ7.67(d,J＝1.8Hz,1H),7.54(dt,J＝7.8,1.5Hz,1H),7.26(dd,J＝7.8,1.5Hz,1H),7.13–6.96(m,3H),6.80(dd,J＝8.3,4.6Hz,2H),4.86(s,2H),4.69–3.70(m,3H),1.33(d,J＝4.1Hz,18H),1.21(d,J＝7.0Hz,3H)ppm.

Example 2:

similarly, 4B was prepared by replacing 3A with 3B in an equimolar amount in example 1, and the same procedure was repeated to finally obtain 4B as a colorless oily substance. ¹ H NMR(400MHz,Chloroform-d)δ7.59(t,J＝1.8Hz,1H),7.46(dt,J＝7.9,1.6Hz,1H),7.34(dt,J＝7.8,1.3Hz,1H),7.25(p,J＝4.8Hz,3H),6.99–6.88(m,2H),5.01(s,2H),4.90–3.89(m,3H),1.71(d,J＝2.8Hz,2H),1.46(d,J＝4.3Hz,18H),1.34(d,J＝7.0Hz,3H),1.31–1.22(m,1H).

The preparation of 3A/3B is available on the basis of the prior art, one of which is shown in FIG. 2, starting with 1A/1B.

② Synthesis of precursors Mel-SF, SPIAd-SF, SPI5-SF

Compound 4A (1 equivalent) and m-chloroperoxybenzoic acid (1 to 2 equivalents) were dissolved with stirring using an anhydrous organic solution (e.g., tetrahydrofuran, dichloromethane, N-dimethylformamide, etc.), and stirred at 40 ℃ to 80 ℃ for 1 hour to 6 hours. The reaction mixture is cooled to room temperature and added with potassium hydroxide or sodium hydroxide (5 to 10 equivalents) and 1 to 2 equivalents of Mesox acid/spiro [ decane-2, 2'- [1,3] dioxane ] -4',6 '-dione (SPI 5)/spiro [ adamantane-2, 2' - [1,3] dioxane ] -4',6' -dione (SPIAd) and stirred for 30 minutes to 12 hours. And then diluting the reactant by using a high-polarity organic solution (such as dichloromethane, methanol, ethyl acetate and the like), filtering, concentrating the filtrate until solid precipitation occurs, adding a low-polarity organic solution (such as n-hexane, petroleum ether and the like) with the volume of 4-20 times to promote solid precipitation, and standing the mixture at the low temperature of-30-0 ℃ for 2-24 hours until all the solid is precipitated. And filtering and drying the solid to obtain the solid, and finally further purifying the product by column chromatography.

Example 3:

in a closed reaction flask, compound 4A (1 eq) was stirred with 85% m-chloroperoxybenzoic acid (1.1 eq) in Dichloromethane (DCM) for 80 minutes at 40 ℃. After cooling to room temperature, KOH (7 eq) and mucic acid (1.3 eq) were added and stirred for a further 45 minutes. The reaction mixture was then diluted with DCM and filtered through filter paper. The solvent of the collected organic phase was removed under reduced pressure at 35 ℃ until the first solid precipitated. Then, hexane was slowly added, and the mixture was left standing at-20 ℃ for 12 hours to complete precipitation. The solid was collected by filtration, washed with n-hexane, and dried in air and vacuum. The crude product was finally purified by silica gel column chromatography (SiO2, 40-100% ethyl acetate/petroleum ether) to give Mel-SF precursor.

Mel-SF (41% yield, white solid): ¹ H NMR(400MHz,Chloroform-d)δ7.86–7.76(m,1H),7.69–7.57(m,1H),7.47–7.36(m,1H),7.25–7.05(m,2H),6.92(t,J＝7.6Hz,2H),5.03(d,J＝37.9Hz,2H),4.90–3.80(m,3H),1.72(s,6H),1.49–1.41(m,18H),1.33(dd,J＝7.1,3.0Hz,3H)ppm.

the same method can prepare SPIAd-SF precursor and SPI5-SF precursor

SPIAd-SF (33% yield, yellowish solid): ¹ H NMR(400MHz,Chloroform-d)δ7.83(s,1H),7.75–7.69(m,1H),7.52(d,J＝7.8Hz,1H),7.35(t,J＝7.9Hz,1H),7.18–6.95(m,3H),6.82(d,J＝8.6Hz,2H),5.00(s,2H),4.79–3.92(m,3H),2.36(s,2H),2.09(d,J＝12.6Hz,4H),1.78(s,2H),1.64(s,4H),1.39(d,J＝12.6Hz,18H),1.26(d,J＝7.0Hz,3H)ppm.

SPI5-SF (36% yield, yellow solid): ¹ H NMR(400MHz,Chloroform-d)δ7.81(d,J＝1.7Hz,1H),7.68(dt,J＝7.9,1.5Hz,1H),7.40(dt,J＝7.8,1.3Hz,1H),7.14(t,J＝7.8Hz,3H),6.94(d,J＝6.6Hz,2H),5.01(s,2H),4.95–3.78(m,3H),2.40–2.21(m,2H),2.18(d,J＝7.5Hz,2H),1.98(td,J＝4.5,2.2Hz,2H),1.95–1.88(m,2H),1.48(d,J＝4.3Hz,18H),1.35(d,J＝7.1Hz,3H).

③ precursor Me ₃ Sn-SF Synthesis

The compound 4B (1 equivalent) is dissolved in an anhydrous organic solution (tetrahydrofuran, 1, 4-dioxane, etc.), hexamethyl ditin (1 to 8 equivalents) is added under the protection of an inert gas by replacing the inert gas (such as nitrogen and argon) and stirred, then triphenylphosphine palladium dichloride (0.01 to 0.5 equivalent) is added for catalysis, and the mixture is heated, refluxed and stirred for 2 to 48 hours to fully react. After the reaction is finished, cooling and drying to remove the solvent, and purifying the crude product by using a column chromatography.

Example 4:

compound 4B (282mg, 0.500mmol) was added to a two-necked flask, dissolved in 5mL of 1, 4-dioxane, degassed, and purged with nitrogen. Hexamethylditin (193 μ l, 0.930mmol) and triphenylphosphine palladium dichloride (3.9mg) were added. The mixture was heated to 65 ℃ and stirred for 12 hours. The mixture was rotary evaporated to dryness and purified by silica gel column chromatography (0-80% ethyl acetate/n-hexane, 1% by volume triethylamine) to give the product (Me) as a yellow oil ₃ Sn-SF, 21% yield). ¹ H NMR(400MHz,Chloroform-d)δ8.80(s,1H),7.35–7.18(m,6H),6.88–6.72(m,2H),5.14–5.02(m,2H),4.68(q,J＝6.8Hz,1H),4.35(dt,J＝12.5,1.0Hz,1H),4.28(dt,J＝12.4,0.9Hz,1H),1.46(d,J＝2.8Hz,18H),1.38(d,J＝6.8Hz,3H),0.78(s,9H).

Synthesis of precursor Bpin-SF

Example 5:

under a nitrogen atmosphere, compound 4B (4.8g, 8.7mmol), potassium acetate (2.55g, 26mmol), [1,1' -bis (diphenylphosphino) ferrocene]Palladium (II) dichloride (0.63g, 0.87mmol) and 4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane (4.39g) were dissolved in 1, 4-dioxane (40ml), stirred at 80 ℃ under nitrogen for 2h, then cooledCooling to room temperature. Water (30ml) was added to the solution, and the mixture was extracted with ethyl acetate (3X 20 ml). The combined organic phases were concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography (0-40% ethyl acetate/n-hexane) to give a clear gum (62% yield). ¹ H NMR(300MHz,Chloroform-d)δ7.59–7.47(m,2H),7.40–7.21(m,4H),6.89–6.80(m,2H),5.19–5.03(m,2H),4.68(q,J＝6.8Hz,1H),4.41–4.30(m,1H),4.30–4.22(m,1H),1.46(d,J＝2.2Hz,18H),1.41(d,J＝6.8Hz,3H),1.24(d,J＝15.1Hz,12H).

Hydrogen spectrum of nuclear magnetic resonance: FIG. 3 shows the 1H-NMR chart of each molecule. FIG. 3 fluorine [18F ]]1H-NMR spectra of each molecule in the synthetic process of the safinamide radioactive labeling precursor (A)4A, (B)4B, (C) Mel-SF, (D) SPIAd-SF, (E) SPI5-SF, (F) Me ₃ Sn-SF，(G)Bpin-SF

Different fluorines [18F ] are designed according to different precursors]The radioactive synthesis process of safinamide is shown in fig. 4. The method comprises the following steps: bombardment H of cyclotron ₂ ¹⁸ O to obtain the radionuclide 18F, purifying by an ion exchange method (by using leacheate containing alkali and a phase transfer catalyst), or directly transferring into a reaction bottle containing the alkali and the phase transfer catalyst; removing water at 80-120 deg.C (anhydrous acetonitrile can be added during volatilization process, and azeotropic method is used for removing water). The precursor (0.5mmol/L to 20mmol/L) was then dissolved using an anhydrous polar aprotic solution (e.g. dimethyl sulfoxide, acetonitrile, DMF, DMA, etc.) and added to the reaction flask for Me ₃ Sn-SF and Bpin precursors, and optionally adding copper catalyst (such as copper trifluoromethanesulfonate, Cu (OTf)) ₂ (py) ₄ ) And pyridine is used for catalytic reaction, the reaction lasts for 5 to 40 minutes at 80 to 160 ℃, and the reaction is diluted and purified by a semi-preparative high performance liquid chromatography system.

Example 6:

the radioactive synthesis process based on Mel-SF, SPIAd-SF and SPI5-SF comprises the following steps:

bombarding oxygen-enriched water H by a cyclotron ₂ ¹⁸ O to obtain 18F ions, and adsorbing with anion exchange column (QMA) ¹⁸ F ion, 0.8mL acetonitrile in 1mL H ₂ An eluent of O, 10mg TEAB ¹⁸ The F ion was eluted from the QMA column and transferred to a reaction flask, azeotropically removed with 1mL of anhydrous acetonitrile and the azeotropic step repeated three times until drying was complete. 3mg of the labeled precursor compound Mel-SF, SPIAd-SF or SPI5-SF prepared in example 1 was added, dissolved in 1mL of anhydrous acetonitrile, and reacted at 120 ℃ for 15min with heating. Adding 1mL of 6M hydrochloric acid aqueous solution into the obtained crude product solution, and carrying out hydrolysis reaction at 110 ℃ for 10min to obtain the target compound fluorine [18F ]]A crude solution of safinamide.

Example 7:

based on Me ₃ The radioactive synthesis process of Sn-SF comprises the following steps:

bombarding oxygen-enriched water H by a cyclotron ₂ ¹⁸ O to obtain 18F ions, and adsorbing with anion exchange column (Chromafix 30-PS-HCO3) ¹⁸ F ion, the column was activated by washing with 5mL ethanol, 5mL of 90mg/mL potassium triflate solution, and 5mL deionized water in that order before use. Then, the adsorbed fluoride ions were eluted into the reaction flask using 1mL of an eluent (0.45 mL of potassium trifluoromethanesulfonate 10mg/mL, 0.05mL of 1mg/mL of an aqueous potassium carbonate solution and 0.5mL of anhydrous acetonitrile). Azeotropic removal of water was performed using 1mL of anhydrous acetonitrile and the azeotropic step was repeated three times until drying was complete. 3mg of the labelled precursor compound Me from example 1 were added ₃ Sn-SF, 0.4mL of anhydrous Dimethylacetamide (DMA), 0.1mL of a 1M solution of pyridine DMA, and 0.067mL of a 0.2M solution of copper trifluoromethanesulfonate DMA were mixed thoroughly, and then heated at 110 ℃ for 20 min. Then cooling to room temperature, adding 1mL of 6M hydrochloric acid aqueous solution, and carrying out hydrolysis reaction at 110 ℃ for 10min to obtain the target compound fluorine [18F ]]A crude solution of safinamide.

Example 8:

the radioactive synthesis process based on the Bpin-SF comprises the following steps:

bombarding oxygen-enriched water H by a cyclotron ₂ ¹⁸ O to obtain 18F ions, and adsorbing with anion exchange column (QMA) ¹⁸ F ion, 0.8mL acetonitrile in 1mL H ₂ An eluent of O, 10mg TEAB ¹⁸ F ions were eluted from the QMA column and transferred to a reaction flask using 1mL of anhydrous acetonitrileAzeotropic removal of water, azeotropic step repeated three times until drying was complete. 1-3mg of the labeled precursor compound Bpin-SF prepared in example 1, 0.15mL of 1M Cu (OTf) ₂ (py) ₄ 1mL of anhydrous DMA solution, and the reaction was heated at 140 ℃ for 20 min. Adding 1mL of 6M hydrochloric acid aqueous solution into the obtained crude product solution, and carrying out hydrolysis reaction at 110 ℃ for 10min to obtain the target compound fluorine [18F ]]A crude solution of safinamide.

The resulting crude product solution was subjected to a semi-preparative liquid chromatography purification process:

to the crude product reaction solutions obtained in examples 6, 7, and 8, respectively, 2.5mL of a solution (30% acetonitrile, 70% water) was added for dilution, followed by purification using a semi-preparative high performance liquid chromatography system (column C18, 250mm x 10mm, 4.6um particle size) under chromatography conditions (5mL/min, 30% -80% acetonitrile/0.1% aqueous TFA), and the purified product was transferred to a sterile vial, diluted with 40mL of deionized water, and adsorbed by a Waters Sep-Pak C18 column. The product was then eluted from the reagent loading module using 0.5ml ethanol and 4.5 ml saline. The final solution of fluoro [18F ] safinamide was passed through a sterile membrane filter (Millex LG, 0.20um) and stored in another sterile vial as an injection for subsequent experiments.

The radioactive yield (RCY) of the synthesis process can basically reach 10%; furthermore, we have made extensive optimization of the synthesis conditions for the various radiosynthesis processes described above to maximize the radioactive yield to better meet the dose requirements of biological experiments. Wherein the radioactive yield of the SPIAd-SF-based fluorine [18F ] safinamide radioactive labeling process can reach more than 25% through optimization, and the specific synthesis conditions are as follows:

10mg TEAB was used in the leacheate; the precursor is 15mgSPIAd-SF, the polar aprotic solution adopts DMSO solution, and the radioactive reaction condition is 120 ℃ and 15 min; the remainder of the example 6 gave the highest radioactive yield of 25.6. + -. 4.2% (decay corrected) and a molar activity of 286.2. + -. 31.5 GBq/umol. All manipulations, including radiosynthesis and purification, took 88. + -.4 minutes in total. Correspondingly, when the leacheate is 7mg of TEAB, the precursor is 2mg of SPIAd-SF, the polar aprotic solution is N, N-dimethylacetamide solution, and the radioactive reaction is carried out under the conditions of 120 ℃ and 10min, the radioactive yield is only 4-9%.

When the precursor is Me ₃ The radioactive synthesis optimization process of Sn-SF is as follows: the leacheate used was 3 to 5mg of potassium trifluoromethanesulfonate, 0.05mg of potassium carbonate, 3 to 8mg of precursor, the polar aprotic solution was DMA solution, the radioactive reaction temperature was 110 to 125 ℃ for 10 to 30min, the rest of the conditions were the same as in example 7, the radioactive yield can exceed 10%, and the molar activity was 166 GBq/umol. All operations, including radiosynthesis and purification, took 94 to 106 minutes.

When the precursor is Bpin-SF, the radioactive synthesis optimization process comprises the following steps: 6mg TEAB, 10mg precursor, 0.25mL Cu (OTf) was used in the leacheate ₂ (py) ₄ The solution, polar aprotic solution is DMA solution, and radioactive reaction is carried out at 155 ℃ for 10 min; the highest radioactive yield of 11-17% (n-5, decay corrected) was obtained with a molar activity of 182 GBq/umol. All manipulations, including radiosynthesis and purification, took 101 minutes.

Aiming at the prepared fluorine [18F ] safinamide injection, in order to ensure that the quality of the injection meets the experimental requirements, a high performance liquid chromatography system is used for quality control. The results are shown in FIG. 6.

First, it was confirmed that the retention time difference between the product of fluoro [18F ] safinamide (black line in fig. 6A) and 19-fluoro-safinamide (red line in fig. 6A) was within 0.1 minute by mixing the injection with non-radioactive safinamide (red line) and co-injecting into HPLC analysis. At the same time, the radiochemical purity of the fluoro [18F ] safinamide purified in radio HPLC is over 99%. Proves that the preparation of the fluoro [18F ] safinamide is successful and the purity meets the requirement

② the newly prepared fluorine 18F safinamide injection is stirred at 37 ℃ for 0, 30, 90 and 180 minutes (550rpm), 1/10 volume of solution is taken out at each time point, 10 percent ethanol physiological saline solution is added for dilution, and the radioactive chemical purity analysis is carried out in a high performance liquid chromatography system with a radioactive NaI detector, finally, the fluorine 18F safinamide injection is proved to have extremely high stability (the radioactive chemical purity is higher than 98 percent) all the time within 180 minutes.

Example 9:

cell experiments have shown that the prepared fluoro [18F ] safinamide can be used to image monoamine oxidase B-secreting cell lines. Astrocyte U87, which produces monoamine oxidase B-monoamine oxidase B, and breast cancer MCF-7, which does not produce monoamine oxidase B-monoamine oxidase B, were used as controls in the experiment. The results of the experiment are shown in FIG. 7.

The uptake of fluoro [18F ] safinamide by U87 astrocyte cells (uptake rate 2.01%) that produce monoamine oxidase B was approximately four times that of MCF-7 breast cancer cells (uptake rate 0.53%) that do not produce monoamine oxidase B. This result indicates that the fluoro [18F ] safinamide has a high affinity for monoamine oxidase B, which is consistent with the properties of safinamide. Meanwhile, U87 cells pretreated with 100ug/mL safinamide showed significantly reduced radioisotope probe uptake (uptake 0.59%) compared to U87 cells, and showed similar levels to MCF-7 cells. This indicates that the binding site of fluorine [18F ] safinamide is identical to that of safinamide and that there is an upper limit on the binding capacity.

Example 10:

we performed the first in vivo experiment with fluoro [18F ] safinamide to obtain information on the distribution, aggregation, migration, metabolism, etc. of fluoro [18F ] safinamide in living organisms. Uptake by major organs is shown in figure 8.

An in vivo PET study of fluoro [18F ] safinamide was first performed on Sprague-dawley (sd) rats to examine the biodistribution of fluoro [18F ] safinamide and to further understand the in vivo mechanism and metabolic information of safinamide. SD rats were injected intravenously with fluoro [18F ] safinamide at the tail, followed by a 3 minute CT scan to locate the rats, followed by a 90 minute dynamic PET scan. The obtained PET image fused with the matched CT image is shown in fig. 8. We delineate the region of interest (ROI) and quantify these PET imaging data by normalizing the uptake value (SUV ═ ROI radioactivity concentration/total body radioactivity concentration). It is particularly noteworthy that bone uptake detected during PET scanning was negligible and this region also showed a systemic lowest SUV of 0.0573, confirming that the fluoro [18F ] safinamide was not or very little defluorinated in vivo. We then used the SUV of the bone as a baseline and calculated the SUV ratio (labeled SUVROI/bone) for the ROI and bone.

The highest uptake of fluoro [18F ] safinamide (SUVROI/bone ═ 11.99) was observed in the bladder, consistent with the metabolic pathway of safinamide, since the elimination of safinamide proceeds mainly through bladder metabolism. Similarly, some fluoro [18F ] safinamides may also be found in the small intestine region (SUVROI/bone ═ 1.69) 33. Furthermore, high uptake of fluoro [18F ] safinamide was observed in the liver, kidney and pancreas, corresponding to SUVROI/bone values of 6.56, 6.43 and 5.00, respectively. A certain amount of fluoro [18F ] safinamide (SUVROI/bone ═ 2.35) can also be found in the lungs. The heart showed similar uptake levels as bone (SUVROI/bone ═ 1.15). According to literature reports, a large amount of monoamine oxidase B is found in the liver and pancreas in peripheral tissues of rats; some monoamine oxidase B is also produced in the renal cortex and ureters of the kidney and lungs, and is observed in small or negligible amounts in the heart, spleen and muscles. Thus, these uptake states that the distribution and abundance of fluoro [18F ] safinamide in rat peripheral tissues is closely related to monoamine oxidase B, indicating that fluoro [18F ] safinamide and monoamine oxidase B have high affinity in these regions.

Example 11:

monoamine oxidase B information of the brain region is most difficult to obtain by conventional means and is the region that best highlights the advantages of PET in vivo detection. Furthermore, monoamine oxidase B changes in the brain region are closely related to many important neurological disorders. We explored the distribution of the tracer in the brain region and determined a time-activity curve (TAC), disclosing its kinetic characteristics in the brain region.

As shown in fig. 9B, the radioactivity level in the rat brain was relatively high early in the PET scan (10 minutes ago), and then was effectively cleared. The SUV then slowly declined and remained stable after 30 minutes. This TAC means that fluoro [18F ] safinamide enters the rat brain, but most of the fluoro [18F ] safinamide is not well accumulated and is rapidly cleared from the brain with metabolism; the remaining tracer accumulated in the brain and was believed to reflect the actual binding site of fluoro [18F ] safinamide in rat brain.

Several representative slices of the dynamic PET image are shown in fig. 9A. Based on the SUV of the rat brain ROI, the radioactivity of the cerebellar gray matter was lowest. To more conveniently compare SUVs, the SUV ratio between the ROI and cerebellum, labeled SUV, was calculated _{ROI/cerebellum} . The results indicate that fluorine [18F ] is found in the hippocampus, septum, thalamus, striatum, cingulate cortex, septum accumbens, amygdala and medial prefrontal cortex]Safinamide (SUV) _{ROI/cerebellum} Over 1.5). There are also several radiotracers (SUVs) in the midbrain, pontine, hypothalamus, medulla, pituitary and parietal cortex, peripheral frontal cortex, auditory cortex, islet cortex and somatosensory cortex (SUVs) _{ROI/cerebellum} Between 1.3 and 1.5).

In addition, the distribution and abundance mode of the fluorine [18F ] safinamide in the brain of the rat is not single target, and the distribution and abundance mode has the binding capacity for multiple targets in the brain. On the one hand, a large amount of fluoro [18F ] safinamide is seen in regions rich in monoamine oxidase B, such as hippocampus, amygdala, striatum, septum, medial prefrontal cortex and thalamus. On the other hand, radioactive tracers are also observed in the areas of the cingulate cortex, the orbitofrontal cortex, the auditory cortex, and the like. Monoamine oxidase B is relatively rare in these regions, with a large number of potassium/sodium channel receptors and glutamate distributed. The distribution pattern of the above-mentioned fluoro [18F ] safinamide is consistent with the multi-target mode of action of safinamide reported in recent studies. This point is also the first time that verification is achieved through a non-invasive real-time monitoring means of the living body.

Example 12:

in the field of PET imaging agents, whether the combination of a tracer and a target is reversible or not depends on whether the tracer has a high signal-to-noise ratio, excellent image accuracy and a rapid kinetic curve. To this end we disclose reversible binding experiments (i.e. displacement experiments) of fluoro [18F ] safinamide in vivo experiments. The results are shown in FIG. 10.

To further verify the reversibility of the binding of fluoro [18F ] safinamide and the identity of fluoro [18F ] safinamide to the binding site associated safinamide, a replacement experiment was performed in which SD rats were injected with safinamide mesylate solution as a competitor during PET scan (to increase the solubility of safinamide). As shown in fig. 10B, safinamide mesylate injection decreased the whole brain SUV by more than 50% and remained on a slightly decreasing trend in subsequent PET scans. This result indicates that the binding of fluoro [18F ] safinamide in rat brain is reversible, and that the binding site of fluoro [18F ] safinamide is highly identical to that of safinamide. This is more intuitively demonstrated by figure 10A that the extent of probe aggregation in the high uptake region is significantly reduced and in a continuously decreasing trend after injection of safinamide mesylate.

Example 13:

in order to verify the accuracy of the fluorine [18F ] safinamide in PET living body detection, in-vitro dissection and autoradiography scanning are carried out on partial experimental mice, the accuracy is illustrated by comparing the PET experimental result with the autoradiography result, and an autoradiography image is shown in figure 11.

The result shows that the in vitro systemic distribution condition of the fluorine [18F ] safinamide in the animal body weight is basically consistent with the condition obtained by PET, and the fluorine [18F ] safinamide is used for replacing part of in vitro experiments or other traditional laboratories, so that the method is feasible, is beneficial to greatly reducing the consumption of manpower and material resources, and quickens the development process of the safinamide as a medicament for treating other diseases. Also proves the application value of the fluorine [18F ] safinamide in the fields of disease diagnosis, pathological research, curative effect evaluation and the like.

Claims

1. A high-efficiency preparation method of fluoro [18F ] safinamide is characterized in that firstly, a precursor of the fluoro [18F ] safinamide is designed and prepared, and then, direct radioactive fluorine labeling is realized on an aromatic ring in the precursor through nucleophilic substitution reaction to obtain the fluoro [18F ] safinamide; the structure of said fluoro [18F ] safinamide is as follows:

the precursor is Mel-SF, SPIAd-SF, SPI5-SF, Me ₃ Sn-SF, or Bpin-SF; the general structural formula is as follows:

the corresponding R is respectively:

2. the efficient process for the preparation of fluoro [18F ] safinamide according to claim 1, wherein the process for the preparation of precursors of Mel-SF, SPIAd-SF and SPI5-SF comprises:

dissolving 1 equivalent of a compound 4A [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-iodophenyl) oxy) benzyl) carbamate ] ] and 1-2 equivalents of m-chloroperoxybenzoic acid in an anhydrous organic solution by stirring, and stirring at 40-80 ℃ for 1-6 hours; cooling the reaction mixture to room temperature, adding 5-10 equivalents of potassium hydroxide or sodium hydroxide and 1-2 equivalents of Medsulfonic acid, spiro [ decane-2, 2'- [1,3] dioxane ] -4',6 '-dione (SPI5), or spiro [ adamantane-2, 2' - [1,3] dioxane ] -4',6' -dione (SPIAd), and stirring for reaction for 30 minutes to 12 hours; then diluting the reactant by using a high-polarity organic solution, filtering, concentrating the filtrate until solid is separated out, adding a low-polarity organic solution with the volume of 4-20 times to promote the solid to be separated out, standing the mixture at-30 ℃ to 0 ℃ for 2-24 hours until all the solid is separated out, filtering and drying the solid to obtain the solid, and finally further purifying the product by column chromatography;

the anhydrous organic solution is tetrahydrofuran, dichloromethane or N, N-dimethylformamide; the high-polarity organic solution is dichloromethane, methanol or ethyl acetate; the low-polarity organic solution is n-hexane or petroleum ether.

3. The fluorine [18F ] of claim 1]A process for the efficient preparation of safinamide, characterized in that Me ₃ The synthesis method of the Sn-SF precursor comprises the following steps:

dissolving 1 equivalent of a compound 4B [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-bromophenyl) oxy) benzyl) carbamate ] ] in an anhydrous organic solution, replacing inert gas, adding 1-8 equivalents of hexamethylditin under the protection of the inert gas, stirring, adding 0.01-0.5 equivalent of triphenylphosphine palladium dichloride for catalysis, heating, refluxing and stirring for 2-48 hours for full reaction, cooling after the reaction is finished, drying to remove the solvent, and purifying a crude product by using a column chromatography;

the anhydrous organic solution is tetrahydrofuran or 1, 4-dioxane; the inert gas is nitrogen or argon.

4. The method for efficiently producing fluoro [18F ] safinamide according to claim 1, wherein the synthesis of Bpin-SF precursor comprises:

dissolving 1 equivalent of a compound 4B [ tert-butyl (S) - (1- ((tert-butoxycarbonyl) amino) -1-oxopropan-2-yl) (4- ((3-bromophenyl) oxy) benzyl) carbamate ] ] in an anhydrous organic solution, carrying out inert gas replacement, sequentially adding 1 to 5 equivalents of potassium acetate and 0.01 to 0.5 equivalent of [1,1' -bis (diphenylphosphino) ferrocene ] dichloropalladium (II) in an inert gas atmosphere, uniformly mixing, adding 1 to 10 equivalents of 4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane, and carrying out reflux stirring for 0.5 to 72 hours; cooling and extracting after the reaction is finished, adding a drying agent into the extracted organic phase for drying, filtering, concentrating, and finally purifying by column chromatography;

5. The method for efficiently producing fluoro [18F ] safinamide according to claim 1, wherein the method for radiofluorinating the precursor comprises:

(1) bombardment H of cyclotron ₂ ¹⁸ O to obtain radionuclide 18F, purifying by an ion exchange method under the condition of leacheate containing alkali and a phase transfer catalyst, or directly transferring the radionuclide 18F into a reaction bottle containing the alkali and the phase transfer catalyst; then removing water at 80-120 ℃;

(2) then dissolving a precursor by using an anhydrous polar aprotic solution, wherein the concentration of the precursor is 0.5mmol/L to 20mmol/L, adding the precursor into the reactant obtained in the step (1), reacting at 80 ℃ to 160 ℃ for 5 minutes to 40 minutes, finishing the reaction, diluting and purifying by using a semi-preparative high performance liquid chromatography system; for Me ₃ Sn-SF and Bpin precursors, and a copper catalyst and pyridine are added into reactants respectively for catalyzing the reaction.

6. Use of the prepared fluoro [18F ] safinamide according to claim 1 as PET imaging agent for imaging of cell lines secreting monoamine oxidase B.

7. Use of the prepared fluoro [18F ] safinamide according to claim 1 as PET imaging agent for live animal imaging.

8. Use according to claim 7, wherein the PET imaging agent, when subjected to in vivo animal imaging, is capable of penetrating the blood-brain barrier and enabling brain area imaging, is capable of binding in vivo to multiple targets, including monoamine oxidase B, potassium sodium channel receptors, glutamate receptors, and said binding is reversible, and wherein the fluoro [18F ] safinamide already bound to the target is competitively detached from binding to the target by the addition of 19-fluoro-safinamide, a monoamine oxidase B inhibitor, a potassium sodium channel inhibitor.

9. Use of the fluoro [18F ] safinamide according to claim 1 for the preparation of a fluoro [18F ] safinamide for ex vivo tissue imaging of an animal by autoradiography as a PET imaging agent.