Novel PET (Polyethylene Terephthalate) tracer agent of targeted cannabinoid type 2 receptor and preparation method of novel PET tracer agent

Abstract

The invention provides a novel PET (Polyethylene Terephthalate) tracer agent of a targeted cannabinoid type 2 receptor and a preparation method of the novel PET tracer agent.

Description

Technical Field

[0001] This invention relates to the development and preparation of a lead compound for a novel radiopharmaceutical, belonging to the field of nuclear medicine technology. Specifically, it involves the design of a lead compound that can be prepared from a radionuclide. 18 The F-labeled drug and its preparation method, as well as the ability of the drug to target cannabinoid type 2 receptors and be applied to the early diagnosis, efficacy monitoring, pathological research, drug development and other medical applications / research fields of diseases, especially peripheral related diseases. Background Technology

[0002] Neuroinflammation, as a multifactorial condition, is closely related to many CNS diseases. A deeper understanding of neuroinflammation will help clarify the pathogenesis of CNS diseases and identify potential treatments and interventions. Research data has identified cannabinoid receptor type 2 (CB2R) as a highly promising target. This is because the distribution of CB2R in the CNS is strongly correlated with the distribution of cells such as glial cells, and its expression level is significantly upregulated under conditions of neuroinflammation.

[0003] CB2R is thought to be expressed very low in the central nervous system, but is instead widely present in cells and tissues of the immune, reproductive, cardiovascular, gastrointestinal and respiratory systems. Therefore, it was named the peripheral cannabinoid receptor by some researchers in the early stages of research.

[0004] Recent studies have revealed that while CB2R is poorly detected in normal healthy brains due to its low expression in the CNS, it is significantly upregulated under many pathological conditions, thus meeting the requirements for certain research. For example, low levels of CB2 receptors have been found in microglia, human fetal astrocytes, and human brain microvascular endothelial cells. Significantly enhanced CB2R expression in brain regions, primarily observed in activated microglia, has also been demonstrated in some neurodegenerative diseases such as multiple sclerosis, Down syndrome, and Huntington's disease. Other conditions associated with CB2R expression include traumatic brain injury, neuropathic pain, and HIV-induced encephalitis. Therefore, using PET to study CB2R changes in the CNS in diseases such as neuroinflammation, neurodegeneration, and gliomas will provide more possibilities for personalized diagnosis and treatment monitoring of these diseases. Given the numerous significant changes in CB2R during these disease / physiological processes, CB2R has gained increasing attention as a CNS target.

[0005] Positron Emission Tomography (PET) differs from structural imaging techniques such as Magnetic Resonance Imaging (MRI) and Computed Tomography (CT). PET is a functional imaging technique, a novel imaging technology that can visualize the metabolism of biomolecules, receptors, and neurotransmitters in living organisms. It is widely used in the diagnosis and differential diagnosis of various diseases, efficacy evaluation, organ function research, and new drug development. PET imaging is characterized by high specificity, high sensitivity, and excellent penetration. Therefore, when a disease is in its early stages at the molecular level, and the lesion area has not yet shown structural changes, making a definitive diagnosis impossible with MRI or CT, PET can sensitively detect the location of the lesion, providing three-dimensional imaging information of the patient non-invasively. This facilitates quantitative and qualitative follow-up research and diagnosis, which is currently unmatched by other imaging examinations. The core component of PET is the use of PET imaging agents, also known as PET probes, PET contrast agents, or PET tracers. These are substances labeled with radioactive isotopes that, once inside the body, specifically recognize and bind to specific target organs, tissues, enzymes, proteins, and receptors. After a PET probe enters the body, it accumulates in a specific area, and with the help of signal acquisition equipment and computer imaging software, a three-dimensional image is formed. The most common PET probe is 18-fluoro-deoxyglucose ([ 18 F]FDG is a type of glucose metabolism probe that can specifically image high-energy-consuming glucose regions in the body and has been widely used in tumor diagnosis and treatment.

[0006] The development of drugs targeting cannabinoid type 2 receptors (CB2R) is primarily focused on peripheral drugs, with a very small proportion dedicated to the development of PET tracer lead compounds. This research is still in its early stages, and most tracers suffer from problems such as low affinity, poor selectivity, poor stability, high lipophilicity, and insufficient BBB penetration. Therefore, the development of novel PET tracer lead compounds targeting CB2R, especially those capable of penetrating the brain for CNS-related CB2R studies, remains crucial. Summary of the Invention

[0007] The purpose of this invention is to develop a lead compound that can be labeled with 18-fluoro to specifically target cannabinoid type 2 receptors and to provide its efficient preparation method and application.

[0008] Another objective of this invention is to provide a novel compound that can target cannabinoid receptor type 1 (CB2R) and develop it into a positron emission tomography (PET) molecular probe to meet the requirements of visual diagnosis and treatment.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] This invention provides a compound that has the ability to specifically target and bind to cannabinoid type 2 receptors, but has no affinity for cannabinoid type 1 receptors. Therefore, it can be used to develop tracers that target cannabinoid type 2 receptors, such as PET tracers.

[0011] Specifically, the present invention relates to the molecular formula of the lead compound as follows:

[0012]

[0013] The compound can be prepared using conventional techniques in the art based on its molecular structure.

[0014] Preferably, the present invention provides a compound having the structural formula shown in formula (1):

[0015]

[0016] Furthermore, the present invention also provides a radioactive compound, using the above-mentioned compound as a standard, wherein the fluorine in the alkane chain group is replaced with the radioactive isotope 18F.

[0017] Preferably, the structure of the radioactive compound is as follows (hereinafter referred to as "Formula (1)-PET probe").

[0018]

[0019] Furthermore, the present invention provides the application of the radioactive compound as described above in the preparation of PET imaging agents.

[0020] Preferably, the PET imaging agent is a tracer that targets cannabinoid type 1 receptors.

[0021] More preferably, the PET tracer is used for the diagnosis of peripheral diseases. These peripheral diseases include inflammatory bowel disease, pancreatitis, colon cancer, bile duct cancer, and pancreatic cancer.

[0022] Furthermore, the present invention provides an application as described above, wherein the PET tracer is used to evaluate the efficacy of immunotherapy for cannabinoid type 2 receptor-related diseases.

[0023] Furthermore, the present invention provides a PET tracer, wherein the tracer comprises the radioactive compound of the present invention as described above and a pharmaceutically acceptable carrier. Attached Figure Description

[0024] Figure 1 Cytotoxicity diagram of the lead compound.

[0025] Figure 2 Results of radiochemical purity and identity tests of 3-A-7 after mixing with 3-A-8.

[0026] Figure 3 In vitro stability test diagram of 3-A-7 tracer.

[0027] Figure 4 Whole-body distribution of C57 mice (PET dynamic scan, 0-60 minutes). Detailed Implementation

[0028] Example 1: The specific synthesis steps of the lead compound are as follows:

[0029]

[0030] 1-1 Synthesis Weigh out N,N-diethyl-4-aminobenzaldehyde (2.0 g, 11.29 mmol), dissolve it in methanol, and slowly add p-methoxyaniline (1.38 g, 11.29 mmol). Reflux at 65 °C overnight. TLC analysis shows the reaction is complete, yielding 1.2 g of a yellow solid. 1 H NMR(400MHz, CDCl3)δ:ppm 8.3084(s,1H);7.7110-7.7331(m,2H);7.1564-701865(m,2H);6.8821-6.9243(m,2H); 6.6806-6.7027(m,2H); 3.8208(s,1H); 3.3952-3.4483(m,4H); 1.1854-1.2270(m,6H).

[0031] 1-2 Synthesis Weigh 1-1 (1.0 g, 3.5 mmol) and dissolve it in methanol. Slowly add sodium borohydride (524 mg, 14.18 mmol) under ice bath conditions. Stir for 30 min, remove the ice bath, and react at room temperature for 3 h. TLC analysis shows the reaction is complete, yielding 0.8 g of a yellow solid. 1 H NMR(400MHz, CDCl3)δ:ppm 7.1152-7.1322(m,2H);6.5152-6.6744(m,6H);5.5438(s,1H);4.0099 (s,2H); 3.6063(s,3H); 3.2771-3.2920(m,4H); 1.0327-1.0651(m,6H).

[0032] 1-3 SynthesisWeigh 1-2 (600 mg, 2.11 mmol) and dissolve it in anhydrous dichloromethane. Add N,N-diisopropylethylamine (818.15 mg, 6.63 mmol). Under ice bath conditions, add dropwise anhydrous dichloromethane solution containing 2,4-dimethoxybenzenesulfonyl chloride to the reaction solution. Stir for 10 min, then remove the ice bath and react at room temperature for 16 h to obtain 0.8 g of white solid. 1 H NMR(400MHz, CDCl3)δ:ppm 7.3797-7.4274(m,1H); 6.8968-6.9776(m,4H); 6.7205-6.7499(m,3H); 6.5149-6.5351(m,3H); 4.6894-4.7071(m,2H); 3.9560-3.9709(m,3H); 3.8087-3.8615(m,3H); 3.6320-3.6476(m,3H); 1.2018-1.2563(m,6H); 1.0154-1.0485(m,4H).

[0033]

[0034] 2-1 Synthesis: 2.0 g (11.29 mmol) of N,N-diethyl-4-aminobenzaldehyde was dissolved in methanol, and 1.21 g (11.29 mmol) of p-methylaniline was slowly added. The mixture was refluxed at 65 °C overnight. TLC analysis showed the reaction was complete, yielding 1.6 g of a yellow solid. 1 H NMR(400MHz, CDCl3)δ:ppm 7.2140(s,2H);6.9749-6.9949(m,2H);6.6623(s,1H);6.5639-6.6063(m,2H); 4.1655(s,2H); 3.3376-3.3542(m,4H); 2.2365(s,3H); 1.1429-1.1780(m,6H).

[0035] 2-2 Synthesis Weigh 1.0 g (mmol) and dissolve it in methanol. Slowly add sodium borohydride (mg, 14.18 mmol) under ice bath conditions. Stir for 30 min, remove the ice bath, and react at room temperature for 3 h. TLC analysis shows the reaction is complete, yielding 0.8 g of a yellow solid. 1H NMR(400MHz, CDCl3)δ:ppm 7.2042-7.2246(m,2H);6.9740-6.9947(m,2H);6.6696(s,2H);6.5657-6.5865(m,2H);4.7 779(s,1H); 4.1593(s,2H); 3.3190-3.3715(m,4H); 2.2361(s,3H); 1.1383-1.1735(m,6H).

[0036] 2-3 Synthesis Weigh 1-2 (600 mg, 2.11 mmol) and dissolve it in anhydrous dichloromethane. Add N,N-diisopropylethylamine (818.15 mg, 6.63 mmol). Under ice bath conditions, add dropwise anhydrous dichloromethane solution containing 2,4-dimethoxybenzenesulfonyl chloride to the reaction solution. Stir for 10 min, then remove the ice bath and react at room temperature for 16 h to obtain 0.8 g of white solid. 1 H NMR(400MHz, CDCl3)δ:ppm 7.5932-7.6227(m,2H); 7.0097-7.0279(m,4H); 6.9438-6.9660(m,2H); 6.8580-6.8787(m,2H); 6.5106-6. 5324(m,2H); 4.5899(s,2H); 3.9002(s,3H); 3.2730-3.3256(m,4H); 2.2908(s,3H); 1.0161-1.1412(m,3H).

[0037]

[0038] 3-1 Synthesis p-Fluorobenzaldehyde (2.0 g, 16.11 mmol) and cis-2,6-dimethylmorpholine (1.86 g, 16.15 mmol) were dissolved in N,N-dimethylformamide (20 mL). Potassium carbonate (6.68 g, 48.3 mmol) was added to the reaction flask at room temperature. The reaction mixture was reacted at 120 °C for 12 h. The reaction solution was concentrated under reduced pressure and then diluted with 50 mL of H₂O. The resulting mixture was extracted with ethyl acetate (3 × 50 mL). The combined organic layers were dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography to give a yellow oil (2.9 g). 1 H NMR (400MHz, CDCl3) δ: ppm9.7788 (s, 1H); 7.7426-7.7635 (m, 2H); 6.8929-6.913 7(m,2H); 3.6366-3.7538(m,4H); 2.5420-2.5989(m,2H); 1.2650-1.2802(m,6H).

[0039] 3-2 Synthesis Compound 3-1 (1.0 g, 4.56 mmol) was weighed and dissolved in methanol. p-Methoxyaniline (561 mg, 4.56 mmol) was slowly added, and the mixture was refluxed at 65 °C overnight. TLC analysis showed the reaction was complete, yielding 1.6 g of a yellow solid. 1 H NMR(400MHz, CDCl3)δ:ppm 8.3596(s,1H);7.7714-7.7910(m,2H);7.1885-7.2094(m,2H);6.9069-6.9440(m,4H);3.8263(s,3 H); 3.7439-3.8080 (m, 2H); 3.5810-3.6100 (m, 2H); 2.4854-2.5413 (m, 2H); 1.2736-1.2888 (m, 6H).

[0040] 3-3 Synthesis Weigh out 3-2 (600 mg, 1.84 mmol) and dissolve it in methanol. Add sodium borohydride (278.4 mg, 7.36 mmol). Stir for 10 min under ice bath conditions, then remove the ice bath and react at room temperature for 3 h to obtain 540 mg of yellow solid. 1 H NMR(400MHz, CDCl3)δ:ppm 7.1837-7.2050(m,2H);7.0097-7.0279(m,4H);6.7987-6.8201(m,2H);6.6909-6.7130(m,2H);6.5214-6.5236(m,2H);4.1 090(s,2H);3.6930-3.7648(m,2H);3.6678(s,3H);3.3507-3.3780(m,2H);2.3011-2.3567(m,2H);1.1767-1.1924(d,6H).

[0041] 3-4 Synthesis Weigh 3-3 (500 mg, 1.53 mmol) and dissolve it in anhydrous dichloromethane. Add N,N-diisopropylethylamine (789 mg, 6.12 mmol). Under ice bath conditions, add an anhydrous dichloromethane solution containing 3-methoxybenzenesulfonyl chloride (379.4 mg, 1.8 mmol) dropwise to the reaction mixture. After stirring for 10 min, remove the ice bath and react at room temperature for 16 h to obtain 190 mg of yellow solid. 1H NMR (400MHz, CDCl3) δ:ppm 7.5086-7.5491(m,2H); 7.2671-7.2943(m,1H); 7.1800-7.1997(m,1H) ;7.0307-7.0526(m,3H);6.8827-6.9050(m,2H);6.7774-6.8115(m,4H) ;4.6208(s,2H);3.7868(s,3H);3.6887(s,3H);3.5846-3.6543(m,2H); 3.4950-3.5251(m,2H); 2.1389-2.1947(m,2H); 1.1112-1.1267(d,2H).

[0042]

[0043] 4-1 Synthesis Weigh out 2.0 g (11.29 mmol) and dissolve it in methanol. Slowly add p-methylaniline (1.21 g, 11.29 mmol), reflux at 65 °C overnight, and check by TLC. The reaction is complete, yielding 1.6 g of a yellow solid. 1 HNMR(400MHz,CDCl3)δ:ppm 8.3005(s,1H);7.7208-7.7420(m,2H);7.0882-7.1740(m,4H);6.6839-6.7 005(m,2H); 3.3987-3.4512(m,4H); 2.3551(s,3H); 1.1883-1.2234(m,6H).

[0044] 4-2 Synthesis Weigh 4-1 (1.0 g, mmol) and dissolve it in methanol. Slowly add sodium borohydride (mg, 14.18 mmol) under ice bath conditions. Stir for 30 min, remove the ice bath, and react at room temperature for 3 h. TLC analysis shows the reaction is complete, yielding 0.8 g of a yellow solid. 1 H NMR(400MHz, CDCl3)δ:ppm 7.1551-7.1761(m,2H);6.8265-6.8705(m,4H);6.4634-6.4841(m,2H);5.8109-5.8402(m, 1H); 4.0819-4.0967(m,2H); 3.0569-3.0832(m,4H); 2.1164(s,3H); 1.5080-1.6001(m,6H).

[0045] 4-3 SynthesisWeigh 1-2 (600 mg, 2.11 mmol) and dissolve it in anhydrous dichloromethane. Add N,N-diisopropylethylamine (818.15 mg, 6.63 mmol). Under ice bath conditions, add dropwise anhydrous dichloromethane solution containing 2,4-dimethoxybenzenesulfonyl chloride to the reaction solution. Stir for 10 min, then remove the ice bath and react at room temperature for 16 h to obtain 0.8 g of white solid. 1 H NMR (400MHz, CDCl3) δ:ppm 7.5932-7.6227(m,2H); 7.1892-7.2105(m,2H); 6.8723-6.8939(m,2H );6.6579-6.6801(m,2H);6.5067-6.5290(m,2H);5.6307-5.6614(m, 1H);4.0725-4.0874(m,2H);3.6566-3.6921(m,2H);3.6101(s,3H);3 .5118-3.5385(m,2H); 2.1670-2.2227(m,2H); 1.1132-1.1488(d,6H).

[0046] Example 2: Cell Experiment

[0047] (1) Cell resuscitation and culture

[0048] CHO cell lines were cultured using a complete culture medium prepared with DMEM high-glucose medium, 10% FBS, streptomycin (100 μg / ml), and penicillin (100 U / ml). After being frozen in liquid nitrogen, the CHO cells were quickly thawed by continuous shaking in a 37°C water bath. The cell suspension was then transferred to a 15 mL centrifuge tube, and 5 mL of the aforementioned culture medium was added. The cell clumps were dispersed by pipetting, and the 15 mL tube was centrifuged at 13000 rpm for 5 minutes. The supernatant was discarded, and the complete culture medium was added. The cells were gently dispersed and mixed, then seeded into cell culture dishes or flasks and incubated at 37°C with 5% CO2.

[0049] (2) Cell transfection (hCB1R-CHO, hCB2R-CHO)

[0050] CHO cells were transfected with DNA plasmids to obtain hCB1R-CHO and hCB2R-CHO cell lines, respectively, with high expression of hCB1R and hCB2R. 2.5 μg of DNA plasmid was diluted with 125 μL of Opti-MEM I medium, and 12.5 μL of EndoFectin Max transfection reagent was diluted with 112.5 μL of medium. Both dilutions were incubated at room temperature for 5 minutes. After incubation, the two dilutions were gently mixed and incubated at room temperature for another 20 minutes to allow for the formation of the DNA-Endofectin complex. The DNA-Endofectin complex was added dropwise to six-well plates containing CHO cells, and the plates were agitated during the process to ensure even distribution of the transfection reagent. After culturing for 72 hours in a 37°C, 5% CO2 incubator, puromycin (1 μg / ml) was added for cell selection, and the selected cells were then subjected to proliferation culture.

[0051] (3) IC 50 test

[0052] Observe the cell density and growth status of the proliferating cells under a microscope. If the cell density reaches approximately 90%, proceed to the next step. Pour the cell culture medium into a waste container, add a small amount of PBS along the side of the flask, gently shake the flask to ensure the PBS fully contacts the cells, rinse, and pour the PBS into the waste container. Remove any remaining PBS with a pipette. Add trypsin to cover the bottom of the culture flask and incubate for about 2 minutes. Observe the cells under a microscope; they should be dispersed into individual round cells, with gaps between them, moving in a sand-like manner, and suspended in the culture medium. Add 4 mL of complete culture medium to stop the digestion. Repeatedly pipette the bottom of the flask and the cells to ensure they are fully suspended and transfer them to a centrifuge tube. Wash the culture flask again with a small amount of PBS, and combine the two washes into one tube. Centrifuge the cells at 400g for 5 minutes. Discard the supernatant from the centrifuged cell solution, gently tap the cell pellet to disperse it, add 1 mL of culture medium and mix well, then add another 1 mL of culture medium to dilute and mix thoroughly. For cell counting, take 20 μL of cell suspension, add 20 μL of trypan blue staining solution, mix well, and then take 20 μL of the mixture and add it to the cell counting chamber for counting. Dilute the cell suspension to 2E4 / mL according to the obtained concentration.

[0053] 100 μL of diluted cell suspension was seeded into 96-well plates, and the plates were incubated at 37°C with 5% CO2 for 24 h. Different concentrations of the test drug were added to the 96-well plates, and the plates were incubated for 48 h. After incubation, 10 μL of CCK-8 solution was added to each well, and the plates were incubated for 3 h. The absorbance at 450 nm was measured using a microplate reader. A dose-response curve was constructed with log(0.78125 μM, 1.5625 μM, 3.125 μM, 6.25 μM, 12.5 μM, 25 μM, 50 μM, 100 μM) on the x-axis and cell viability on the y-axis to calculate the IC50. 50 value.

[0054] (3) IC 50 result Figure 1 As shown, the data indicates that IC with molecular formula 2-3 50 The smallest is 17.12, and the most cytotoxic is found in the IC50 of molecular formulas 3-4 and 4-3. 50 It has the highest cytotoxicity, the lowest cytotoxicity, and the best targeting effect on cannabinoid type II receptors. In addition, the molecular structure of molecule 3-4 is easy to modify, making it a very good potential PET tracer lead compound for targeting cannabinoid type II receptors.

[0055] Example 3: Synthesis of PET probes

[0056] Based on molecular formula 3-4, this invention designs and synthesizes a PET probe precursor, with the following reaction route and structural formula 3-A-6.

[0057]

[0058]

[0059] 3-A-3 Synthesis 4-(2,6-dimethylmorpholino)benzaldehyde (1.27 g, 5.8 mmol) and 4-benzyloxyaniline (1.156 g, 5.8 mmol) were dissolved in methanol (40 mL). Two drops of acetic acid were added, and the mixture was stirred at room temperature for 2 hours. TLC (petroleum ether: ethyl acetate = 2:1) showed a new spot. The reaction mixture was then moved to an ice bath at 0 °C and stirred. Sodium borohydride (438.8 mg, 11.6 mmol) was added, and the mixture was stirred in an ice bath for 30 minutes. After the reaction was completed, the mixture was filtered and dried to give 2.076 g of a gray-green solid product. ¹H NMR: δ 7.69 (2H), 7.35 (5H), 7.30 (2H), 6.93 (2H), 6.67 (2H), 5.53 (1H), 5.06 (2H), 4.48 (2H), 4.31 (2H), 4.07 (4H), 1.29 (6H).

[0060] 3-A-4 Synthesis 4-Benzyloxy-N-(4-(2,6-dimethylmorpholino)benzyl)aniline (2.076 g, 5.16 mmol) was dissolved in dichloromethane (40 mL), followed by the addition of N,N-diisopropylethylamine (1.334 g, 10.32 mmol). A 10 mL solution of m-methoxybenzenesulfonyl chloride (1.173 g, 5.676 mmol) in dichloromethane was slowly added dropwise to the solution in an ice bath at 0 °C. After the addition was complete, the ice bath was removed, and the reaction mixture was stirred at room temperature for 16 hours. TLC (petroleum ether:ethyl acetate = 4:1) showed new spots. The mixture was extracted three times with water and separated, washed twice with saturated sodium chloride solution, dried over anhydrous sodium sulfate, filtered, and the solvent was removed under vacuum to obtain the crude product. The crude product was purified by silica gel chromatography using a gradient elution of petroleum ether:ethyl acetate at ratios of 15:1 to 3:1 to give 1.44 g of a yellow solid. 1H NMR: δ7.82(1H),7.75(1H),7.69(2H),7.44(2H),7.35(5H),6.96(1H),6.93(2H),6. 87(1H),6.67(2H),5.06(2H),4.48(2H),4.35(2H),4.07(4H),3.84(3H),1.29(6H).

[0061] 3-A-5 Synthesis N-(4-(benzyloxy)phenyl)-N-(4-(2,6-dimethylmorpholino)benzyl)-3-methoxybenzenesulfonamide (1.44 g, 2.51 mmol) was dissolved in 120 ml of methanol and 40 ml of tetrahydrofuran. Then, 150 mg of palladium on carbon (10%) was added, and the reaction was carried out under hydrogen for 16 hours. TLC (petroleum ether: ethyl acetate = 2:1) showed new spots. The solvent was removed by rotary evaporation under vacuum to obtain the crude product. The crude product was purified by silica gel chromatography using gradient elution with petroleum ether: ethyl acetate at ratios of 10:1 to 2:1 to obtain 640 mg of a pale yellow oily product. 1HNMR: δ7.82(1H),7.75(1H),7.69(2H),7.44(2H),6.96(1H),6.87(1H),6.67( 2H),6.66(2H),5.37(1H),4.48(2H),4.35(2H),4.07(4H),3.84(3H),1.29(6H).

[0062] 3-A-6 SynthesisN-(4-(2,6-dimethylmorpholino)benzyl)-N-(4-hydroxyphenyl)-3-methoxybenzenesulfonamide (450 mg, 0.93 mmol) was dissolved in 15 ml of acetonitrile. Then, cesium carbonate (1215 mg, 3.73 mmol) was added to the solution and the mixture was stirred for 15 minutes. 1,2-bis(toluenesulfonyloxy)ethane (1382 mg, 3.73 mmol) was then added and the mixture was stirred overnight at 45 °C. TLC (petroleum ether: ethyl acetate = 2:1) showed new spots. The mixture was extracted with water / ethyl acetate three times, washed twice with saturated sodium chloride solution, dried over anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation under vacuum to obtain the crude product. The crude product was purified by silica gel chromatography using a gradient elution of petroleum ether: ethyl acetate from 8:1 to 2:1 to obtain 450 mg of a white oily product. 1H NMR: δ7.82(1H),7.79(2H),7.75(1H),7.69(2H),7.44(2H),7.33(2H),6.96(1H),6.93(2H),6.87(1 H),6.67(2H),4.48(2H),4.35(2H),4.13(2H),4.07(4H),3.84(3H),3.79(2H),2.35(3H),1.29(6H).

[0063] This invention discloses a radioactive PET tracer as shown in Formula 3-A-7 and a PET tracer standard as shown in Formula 3-A-8.

[0064]

[0065] The main steps of the radiochemical process are:

[0066] Bombard the target water with a CYPRISHM-12 cyclotron [ 18 On O]H2O, through the 18O(p,n)18F reaction, […] 18 F] Fluoride ions.

[0067] Captured by QMA anion exchange column [ 18 [F] fluoride ions. The [18F] fluoride ions adsorbed on the QMA column were eluted into the reaction flask using eluent. Anhydrous acetonitrile was added to the reaction flask, followed by azeotropic evaporation of the solution in the reaction flask for 4 minutes at 110°C and a nitrogen flow rate of 50 mL / min. Anhydrous acetonitrile was then added to repeat the drying process. Finally, thoroughly dried [F] fluoride ions were obtained. 18 F] Fluorine source. Dry [F] is added to the reaction flask. 18 [F] A fluorine source was added to the precursor dissolved in anhydrous acetonitrile. The reaction was then carried out under sealed conditions at 110°C for 5 min. After the reaction was complete, the reaction flask was cooled to 40°C. A 5 μL sample was taken using a pipette, and the composition of the crude product solution was analyzed by analytical radio-HPLC.

[0068] The crude product solution was diluted with an aqueous solution of acetonitrile, and then purified using Elite P230 semi-preparative liquid chromatography (HPLC). The radioactivity changes of the fraction were monitored using a Bioscan FC3500A radioactive probe. The chromatographic conditions were as follows: a Phenomenex Synergi Hydro-RP reversed-phase column; mobile phase A was 1‰ trifluoroacetic acid aqueous solution; mobile phase B was acetonitrile solvent; flow rate was 5 mL / min; mobile phase B was changed from 50% to 85%; detection wavelength was 254 nm; and a Bioscan FC3500A radioactive probe was used. The fraction containing the purified product collected from the semi-preparative HPLC was diluted with 40 mL of deionized water and adsorbed onto a Sep-Pak C18 column to adsorb the PET tracer. The C18 column was then washed sequentially with 0.6 mL of ethanol, 0.4 mL of ethanol, and 7.6 mL of 10 mg / mL ascorbic acid saline solution, with the 0.6 mL ethanol eluent discarded. The resulting 8 mL PET tracer solution was then filtered through a sterile membrane and transferred to a sterile sample vial for later use. The entire process took approximately 60 minutes, with a final uncorrected radioactivity yield ranging from 18% to 39%.

[0069] To ensure the quality of the prepared radioactive PET probe met experimental requirements, quality control was performed using high-performance liquid chromatography (HPLC). The PET probe 3-A-7 was mixed with standard 3-A-8 and co-injected into an analytical HPLC system. Analysis confirmed that the retention time difference between the product PET probe 3-A-7 and standard 3-A-8 was within 0.1 minutes. Simultaneously, the radiochemical purity of 3-A-7 exceeded 99%. This demonstrates the successful preparation of PET probe 3-A-7 and that its purity met the requirements.

[0070] A small amount of the newly prepared 3-A-7 injection solution was added to 10 times the volume of C57 mouse serum. The mixture was stirred at 37°C (550 rpm) for 0, 15, 30, 60, 120, and 180 minutes. At each time point, 1 / 10 volume of the solution was taken out and diluted with 10% ethanol saline solution. The radiochemical purity was analyzed using a high-performance liquid chromatography system equipped with a radioactive gamma ray detection probe. The results showed that the 3-A-7 injection solution maintained extremely high stability throughout the 180-minute period.

[0071] Example 4: Whole-body effects experiment of PET probe

[0072] The distribution, aggregation, migration, and metabolism of 3-A-7 in live C57 mice were obtained using microPET / CT imaging in small animals. The results showed that the imaging agent was highly uptaken in the liver, intestine, spleen, bladder, and kidneys, with a small amount uptake in the brain. Simultaneously, no bone uptake was observed during the scanning process, verifying that the probe did not undergo radioactive defluorination in live C57 mice, indicating that the probe maintained extremely high metabolic stability in vivo. These results demonstrate that the PET probe 3-A-7 disclosed in this invention successfully labeled radionuclides while retaining affinity for cannabinoid type 2 receptors. 18 F, when the research target is related to cannabinoid type 2 receptor, it can be used as a PET imaging agent in the fields of disease diagnosis, pathological research, and efficacy evaluation, such as helping to significantly reduce the consumption of human and material resources and accelerate research progress or drug development.

Claims

1. A compound, characterized in that, The structural formula of the compound is as follows:

2. A radioactive compound, characterized in that, Using the compound of claim 1 as a standard, wherein the fluorine in the group is replaced by a radioactive isotope. 18 F.

3. The radioactive compound as described in claim 2, characterized in that, The structural formula of the radioactive compound is as follows:

4. The use of the radioactive compound as described in claim 2 or 3 in the preparation of PET imaging agents.

5. The application as described in claim 4, characterized in that, The PET imaging agent is a tracer that targets cannabinoid type 1 receptors.

6. The application as described in claim 4 or 5, characterized in that, The PET tracer is used for the diagnosis of peripheral diseases.

7. The application as described in claim 6, characterized in that, The peripheral diseases mentioned include inflammatory bowel disease, pancreatitis, colon cancer, bile duct epithelial carcinoma, and pancreatic cancer.

8. The application as described in claim 4 or 5, characterized in that, The PET tracer was used to evaluate the efficacy of immunotherapy for cannabinoid type 2 receptor-related diseases.

9. A PET tracer, characterized in that, This includes the radioactive compound of claim 3 and a pharmaceutically acceptable carrier.

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