A method of radiolabeling a trifluoromethyl terminated olefin 18 F]

Abstract

The application discloses a kind of organic synthesis technical field[ 18 F] radioactive labeling method of trifluoromethyl terminal olefin, under room temperature condition, using 3,3-difluoro allyl sulfonium salt as precursor, 18 F] KF / K222 or[ 18 F] TBAF as fluorination reagent, acetonitrile as solvent, can obtain very high radiochemical yield within 30 seconds, and functional group tolerance is excellent, specific reaction formula is as follows: the method provides a simple and efficient way for producing[ 18 F] trifluoromethylated terminal olefin compound, so that it can be applied to positron emission tomography imaging.The method for constructing 3,3-difluoro allyl sulfonium salt compound is easy to obtain raw materials, low cost, simple operation, safe and controllable, and the obtained product has high radioactivity yield.

Description

Technical Field

[0001] This invention relates to the fields of organic synthesis and molecular imaging probes, specifically to a […]. 18 F] Radiolabeling method for trifluoromethyl terminal alkenes. Background Technology

[0002] PET (Positron emission tomography) is a non-invasive nuclear medicine imaging technique capable of detecting chemical biological processes within organisms, assessing disease status and progression, and evaluating the effectiveness of drug treatments. However, the development of PET technology largely depends on the molecular imaging probes (also known as radiotracers) employed. The successful clinical application of PET molecular imaging probes depends not only on their biological functions but also on the efficiency and practicality of their radiolabeling methods. Fluorine-18 is the most widely used PET radionuclide, possessing excellent physicochemical properties, including a good half-life of 110 minutes and multifunctional bonding capabilities. For example, it can be used in both covalent and non-covalent forms ([... 18 It has F]AlF-NOTA6, a high positron yield (97% β⁺ decay) and a low maximum positron energy of 638 kV.

[0003] The trifluoromethyl (-CF3) group is an important functional group in many drug molecules and drug candidates, and has been shown to improve the efficacy of molecules by enhancing their target binding selectivity, lipophilicity, and metabolic stability. Although [ 18 [F] Trifluoromethylation has made significant progress, but further improvements are needed to address several key limitations: (1) a narrow substrate range, limiting broader applicability; (2) harsh radiation labeling conditions, with increased temperature accelerating the decomposition of both the precursor and the final product; (3) low reactivity of the leaving group in the difluoromethylene precursor; (4) similar polarities between the precursor and product, complicating their separation, especially when using typical halogen exchange processes, which often exacerbates the problem; and (5) low molar reactivity. Late-stage [F] is generally preferred. 18 F] Trifluoromethylation.

[0004] For example, prior art CN 107311877 B discloses a positron-emitting drug [ 18 A novel preparation method for F]FDOPA and its intermediates are described, with the preparation method shown in the following formula.

[0005]

[0006] (1) Compound of Formula I and suitable 18 The reaction at source F produces compound II;

[0007] (2) the compound of formula II is subjected to a deprotection operation to generate 18 F]FDOPA;

[0008] The reaction conditions of step (1) in the above method for synthesizing 18 F]FDOPA are as follows: the compound of formula I is reacted with a suitable 18 F source in an organic solvent, the reaction is carried out in a sealed vessel at 120-140°C for 5-15 minutes, the organic solvent is preferably DMF or DMSO, and the suitable 18 F source is selected from 18 F]KF / K222 or 18 F]Et4NF, and the reaction conditions of step (2) are conventional deprotection operation conditions in organic synthesis, preferably acidic conditions (hydrochloric acid, hydrobromic acid or hydroiodic acid) or conditions selected from the deprotection conditions for synthesizing 18 F]FDOPA in the prior art. However, this method is not suitable for some nitrogen-containing substrates, and the reaction time is too long and the yield is not high.

[0009] Therefore, in order to meet the needs of observing the metabolism of drug molecules in vivo in the treatment of diseases in the clinic, it is necessary to develop a simple and efficient method for rapidly 18 F radiolabeling, which is a promising strategy for reusing biologically active molecules for PET imaging applications. It is of great significance to develop 18 F-labeled drug molecules as PET molecular imaging probes. SUMMARY

[0010] The present application is designed to overcome the shortcomings of the prior art and to provide a method for rapidly obtaining 18 F-trifluoromethylated terminal olefin compounds with high radiochemical yield.

[0011] One object of the present application is to provide a 18 F-trifluoromethylated terminal olefin compound, and the structure of the 18 F-trifluoromethylated terminal olefin compound is shown in formula I:

[0012]

[0013] wherein R1 is selected from 、 、 、 ;

[0014] R2 is selected from methoxy, benzyloxy, 1,3-dioxymethylene, n-butyl, halogen, ester, cyano and ketone.

[0015] Further, the structure of the compound of formula I is selected from:

[0016] .

[0017] The second object of the present application is to provide a compound of formula II 18 A method for radiolabeling of terminal trifluoromethyl olefins, at room temperature, using 3,3-difluoroallyl sulfonium salt of formula A as a precursor, 18 KF / K222 (Fluorine-18-fluoride-potassium 222 complex) or 18 TBAF (Fluorine-18-tetrabutylammonium fluoride) as fluorinating reagent, and acetonitrile as solvent, to generate compound of formula B, the specific reaction formula is as follows:

[0018]

[0019] wherein R is selected from 、 、 、 ;

[0020] R2 is selected from methoxy, benzyloxy, 1,3-dioxymethylene, n-butyl, halogen, ester, cyano and ketone.

[0021] wherein, 18 F] The fluorinating reagent is produced by cyclotron. In radiochemistry experiment, the 18 F] fluorinating reagent is collected after the last bombardment by flushing the target and delivery line with deionized water. 18 F] KF / K222 fluorinating reagent is prepared by dissolving potassium carbonate in a mild mixture of deionized water and Kryptofix® 222 in acetonitrile, trapping the 18 F] fluoride on a pre-conditioned QMA filter cartridge and eluting into a 4 mL vial with a stir bar. The vial is heated in a heating block at 110°C with vigorous stirring. When no liquid is observed, 0.5 mL of anhydrous acetonitrile is added via syringe and the vial is re-heated until dry. This process is repeated twice. Then, an additional 0.5 mL of anhydrous acetonitrile is added and the 18 F] KF / K222 is allowed to suspend for 10 – 20 seconds. Finally, the vial is cooled to room temperature to obtain dry 18 F] KF / K222 complex.

[0022] Further, the 18 F] TBAF fluorinating reagent is prepared by using a mixture of tetrabutylammonium bromide (TBAB), deionized water and acetonitrile for QMA elution, and the preparation scheme is the same as that of 18F] KF / K222 complex.

[0023] Further, the concentration of the compound of formula A is 4 mM to 8 mM.

[0024] Further, the reaction is carried out at 30℃ to 110℃.

[0025] Further, the reaction time is 0.5 to 10 minutes, preferably 0.5 minutes.

[0026] Further, the fluorination reagent is most preferably 18 ] KF / K222 complex.

[0027] Further, the compound of formula A is prepared according to the following method:

[0028] ;

[0029] ;

[0030] The compound of formula D and the compound of formula E are reacted to obtain the compound of formula C, and the compound of formula C and methyl triflate are reacted to obtain the compound of formula A.

[0031] Further, the equivalent ratio of the compound of formula D and the compound of formula E is 1.0:2.0 to 3.0, the reaction solvent is the organic solvent 1,4-dioxane, the reaction is carried out in the presence of potassium hydroxide, the reaction temperature is 120℃, and the reaction time is 12 hours.

[0032] Further, the equivalent ratio of the compound of formula C and methyl triflate is 1:1, the reaction solvent is the organic solvent dichloromethane, and the reaction is carried out at room temperature for 12 hours.

[0033] The third object of the present application is to provide 18 F] Use of a compound of formula A in the preparation of a PET molecular imaging probe.

[0034] This study introduces a method for rapid [ 18 F] trifluoromethylation, which overcomes the challenges of previous radiolabeling methods related to reactivity, temperature control and substrate range limitations, using a difluoroallyl sulfonium salt (DFAS) as a precursor, the reaction is completed within 30 seconds at room temperature, producing a high radiochemical output, this breakthrough greatly improves the feasibility of synthesizing PET imaging agents, and further explores the application of trifluoromethyl-containing compounds in drug research, the method is simple in operation, strong in functional group tolerance, and rapid in kinetic reaction, and is an important tool for expanding [ 18 F] PET tracers.

[0035] The present application has the following advantages: (1) the F-18 labeling of trifluoromethyl olefins is realized for the first time; (2) the obtained product has potential application in nuclear medicine research and development. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 For part[ 18 F]trifluoromethyl olefin compound. DETAILED DESCRIPTION

[0037] The following will be further described in detail through specific embodiments:

[0038] Example 1: Preparation of 18 F]trifluoromethyl olefin compound

[0039] (1) Preparation of (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compound

[0040] The intermediate (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compound of the present application is prepared according to the following route:

[0041]

[0042] Into a 25-mL reaction tube, potassium hydroxide (1.5 equivalents) and trifluoromethyl olefin (formula E) (2.0-3.0 equivalents) were added. The reaction mixture was vacuumed and backfilled with argon (3 cycles). Then organic solvent 1,4-dioxane (2.5 mL) and 2-phenylethanethiol (formula D) (0.5 mmol, 1.0 equivalent) were added, and the tube was sealed. The reaction mixture was heated to 120°C in an oil bath with stirring for 12 hours. After cooling to room temperature, the reaction was quenched with saturated aqueous ammonium chloride solution. The organic layer was separated, and the aqueous layer was extracted twice with organic solvent ethyl acetate. The combined organic layer was washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated. Purification was performed by silica gel column chromatography (eluent: petroleum ether or a mixture of petroleum ether-ethyl acetate) to obtain the (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compound of formula C.

[0043] The structure, characterization and yield of each formula C (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compound obtained in this example are shown in Table 1.

[0044] Table 1. Structure, characterization and yield of (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compound.

[0045]

[0046] (2) Preparation of 3,3-difluoroallyl sulfide triflate

[0047] The labeled precursor 3,3-difluoroallyl sulfide triflate compound of the present application is prepared according to the following route.

[0048]

[0049] Into a 25 mL reaction tube was added a (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compound (1.05 equivalents, 0.5 mole per liter in dichloromethane) of Formula C. Then, methyl triflate (MeOTf) (1.0 equivalent) was added dropwise at room temperature. The reaction mixture was stirred at room temperature overnight. After removing part of the solvent, diethyl ether was added until a large amount of solid precipitated. The solid was filtered and washed with diethyl ether three times to obtain a 3,3-difluoroallyl sulfide triflate compound (Formula A).

[0050] Using (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compounds of different structures in Table 1, 3,3-difluoroallyl sulfide triflate compounds of different structures shown in Table 2 were prepared, respectively. For example, when the structure of the (2-arylallyl-3,3-difluoro)(phenethyl)sulfane compound is , the structure of each 3,3-difluoroallyl sulfide triflate compound obtained is .

[0051] The structure, characterization, yield, and Table 2 of each 3,3-difluoroallyl sulfide triflate compound obtained in this example are shown in Table 2.

[0052] Table 2. Structure, characterization, yield of 3,3-difluoroallyl sulfide triflate compounds.

[0053]

[0054] (3) Preparation of trifluoromethyl terminal olefin compound

[0055] The trifluoromethyl terminal olefin compound is prepared according to the following route.

[0056] Route 1: Preparation of trifluoromethyl terminal olefin compound.

[0057]

[0058] Into a 25 mL reaction tube was added aryl boronic acid (1 mmol, 1.0 equiv), potassium carbonate (4.0 mmol, 4.0 equiv), palladium (II) bis(triphenylphosphine) dichloride (0.03 mmol, 3 mol%), and the air was removed under vacuum and replaced with argon (3 times). Subsequently, tetrahydrofuran (3.0 mL) was added, followed by 2-bromo-3,3,3-trifluoropropene (1.5 mmol, 1.5 equiv), potassium carbonate aqueous solution (2.0 M, 2.0 mL) and sealed. The solution was heated to 60ºC in an oil bath for 12 hours, after which the mixture was cooled to room temperature. Extraction with ethyl acetate and water, the organic layer was separated and washed with brine, the combined organic layers were dried over anhydrous sodium sulfate, filtered, and concentrated. Purification by silica gel column chromatography (eluent: petroleum ether or a mixture of petroleum ether-ethyl acetate) afforded the trifluoromethyl terminal olefinic compound.

[0059] Scheme 2: Preparation of trifluoromethyl terminal olefinic compounds.

[0060]

[0061] Into a 25 mL reaction tube was added aryl boronic acid (1 mmol, 1.0 equiv), potassium carbonate (4.0 mmol, 4.0 equiv), palladium (II) bis(triphenylphosphine) dichloride (0.03 mmol, 3 mol%), and the air was removed under vacuum and replaced with argon (3 times). Subsequently, tetrahydrofuran (3.0 mL) was added, followed by 2-bromo-3,3,3-trifluoropropene (1.5 mmol, 1.5 equiv), potassium carbonate aqueous solution (2.0 M, 2.0 mL) and sealed. The solution was heated to 60ºC in an oil bath for 12 hours, after which the mixture was cooled to room temperature. Extraction with ethyl acetate and water, the organic layer was separated and washed with brine, the combined organic layers were dried over anhydrous sodium sulfate, filtered, and concentrated. Purification by silica gel column chromatography (eluent: petroleum ether or a mixture of petroleum ether-ethyl acetate) afforded the trifluoromethyl terminal olefinic compound.

[0062] The structure, characterization, yield, and the like of each of the trifluoromethyl terminal olefinic compounds obtained in this example are shown in Table 3.

[0063] Table 3. Structure, characterization, yield of trifluoromethyl terminal olefinic compounds.

[0064]

[0065] Example 2: Preparation of 18 F] trifluoromethyl terminal olefinic compound

[0066] (1) Preparation using a radionuclide accelerator [ 18 F] Fluoridating reagent

[0067] [ 18 F] The fluorinating agent is produced using a Siemens Eclipse (RDS111) cyclotron accelerator via... 18 O (p, n) 18 Produced by the F reaction. In radiochemical experiments, [ 18 F] The fluorinating agent (approximately 1.5 - 2.0 GBq) was collected after rinsing the target and delivery lines with 1 mL of deionized water following the previous bombardment.

[0068] preparation[ 18 F]KF / K222 Fluorination reagent.

[0069] A mild mixture of potassium carbonate dissolved in deionized water (2.1 mg, 140 μL) and Kryptofix® 222 dissolved in formonitrile (5.7 mg, 460 μL) was prepared. 18 [F] Fluoride was retained on the pretreated QMA filter cartridge and eluted into a 4 mL vial equipped with a stir bar. The vial was heated vigorously at 110°C in a heating block for azeotropic drying. When no liquid was observed, 0.5 mL of anhydrous acetonitrile was added via syringe, and the vial was reheated until dry. This process was repeated twice. Then another 0.5 mL of anhydrous acetonitrile was added to make [ 18 [F]KF / K222 suspended for 10–20 seconds. Finally, the vial was cooled to room temperature to obtain a dry [ 18 F]KF / K222 complex.

[0070] preparation[ 18 F]TBAF fluorination reagent.

[0071] In addition to QMA elution using a mixture of 82 μL tetrabutylammonium bicarbonate (TBAB, 20%, w / w), 62 μL deionized water, and 556 μL acetonitrile, it was also performed according to […]. 18 The same scheme as F]KF / K222 was used to prepare dried [ 18 F]TBAF solution.

[0072] (2) Synthesis 18 F] Trifluoromethyl terminal olefins

[0073]

[0074] All radiochemical operations were performed under ambient air conditions. 2 μmol of 3,3-difluoroallyl thiotrifluoromethanesulfonate as substrate and 0.5 mL of anhydrous acetonitrile were added to a 4 mL vial equipped with a stir bar. For each experiment, 10–100 μL of aliquots (approximately 111–222 MBq) of […] were added. 18 F]KF / K222 fluorination reagent. Cap the reaction flask and stir the mixture for 30 seconds. Then, dilute the reaction mixture with approximately 1 mL of anhydrous acetonitrile. Spot 3–5 μL aliquots onto a TLC plate and develop using an acetonitrile / water (95:5) solvent system to determine the radiochemical conversion rate (RCC). Separate aliquots of the crude product (typically 20–40 MBq) by high-performance liquid chromatography and collect the fractions with […]. 18 F] indicates the fraction corresponding to the product.

[0075] Using the 3,3-difluoroallyl thiotrifluoromethanesulfonate compounds with different structures shown in Table 2 of Example 1, products with different structures were prepared. 18 F] Trifluoromethyl-terminated olefin compounds. For example, when 3,3-difluoroallyl thiotrifluoromethanesulfonate compounds are... At that time, the product obtained [ 18 The structure of F] trifluoromethyl-terminated olefins is as follows: .

[0076] The implementation example obtained [ 18 The structures of F]trifluoromethyl-terminated olefins are shown below:

[0077]

[0078] The untreated sample obtained in Example 1 18 Using F-labeled trifluoromethyl-terminated olefin compounds as reference standards, the results obtained in Example 2 were calculated using high-performance liquid chromatography. 18 F] Trifluoromethyl-terminated olefin compounds. The radioactivity of the crude and separated products was measured to calculate the radiochemical yield (RCY). Both the crude and separated products were supplemented with... 19 F is a pure compound.

[0079] The chromatographic conditions for high performance liquid chromatography (HPLC) are as follows:

[0080] High performance liquid chromatography conditions 1: analytical

[0081] The HPLC was performed using a GL Sciences Inertsustain® C18 column (5 μm, 150 × 4.6 mm). Mobile phase A consisted of 0.1% TFA in water, and mobile phase B consisted of 0.1% TFA in acetonitrile. The flow rate was 1.0 mL / min, and the wavelength was 280 nm. The elution gradient for HPLC was: 0–2 min (10% B), 2–12 min (10% B to 90% B), 12–13 min (90% B), 13–16 min (90% B to 10% B), and 16–20 min (10% B).

[0082] High performance liquid chromatography conditions 2: semi-preparative

[0083] The HPLC was performed using a Shimadzu Shim-Pack PRC-ODS LC column (15 μm, 250 × 20 mm). Mobile phase A consisted of 0.1% TFA in water, and mobile phase B consisted of 0.1% TFA in acetonitrile. The flow rate was 16.0 mL / min, and the wavelength was 280 nm. The elution gradients for HPLC were: 0–6.5 min (15% B to 75% B), 6.5–8.5 min (75% B), 8.5–9.5 min (75% B to 95% B), 9.5–11.5 min (95% B), 11.5–14 min (95% B to 15% B), and 14–20 min (15% B).

[0084] This embodiment contains [ 18 The radiogenic yield results of trifluoromethyl-terminated olefin compounds are as follows: Figure 1 As shown. Analysis was performed by HPLC. All radiochemical yields (RCYs) were decay-corrected and reported as isolated RCYs.

[0085] The purification methods described above are all conventional methods in this field. For example, when using thin-layer chromatography and column chromatography, the developing solvent can be a single solvent or a mixed solvent, such as petroleum ether or a mixture of petroleum ether and ethyl acetate.

[0086] The features mentioned above in this invention, or the features mentioned in the embodiments, can be combined arbitrarily. All features disclosed in this specification can be used in any compositional form, and each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0087] The above-mentioned are only embodiments of the present application, and the common knowledge of specific structures and characteristics in the scheme is not described too much. It should be pointed out that for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, which will not affect the effect and practicality of the patent. The protection scope claimed in this application should be subject to the content of its claims, and the specific implementation mode and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. A kind of [ 18 The radioactive labeling method for trifluoromethyl-terminated alkenes, characterized in that, At room temperature, using compound 3,3-difluoroallyl sulfonium salt as precursor, 18 F] KF / K222 complex or 18 F] TBAF as fluorination reagent, acetonitrile as solvent, to generate compound of formula B, the specific reaction formula is as follows: ； wherein R is selected from , , , ; R2 is selected from the group consisting of methoxy, benzyloxy, 1,3-dioxymethylene, n-butyl, halogen and cyano.

2. The marking method according to claim 1, characterized in that: The concentration of the compound of formula A is 4 mM to 8 mM.

3. The marking method according to claim 2, characterized in that: The reaction is carried out at 30°C to 110°C.

4. The marking method according to any one of claims 1 to 3, characterized in that: The compound of formula A is prepared according to the following method: The compound of formula D and the compound of formula E are reacted to obtain the compound of formula C, and the compound of formula C is reacted with methyl trifluoromethyl sulfonate to obtain the compound of formula A.

5. The marking method according to claim 4, characterized in that: The equivalent ratio of the compound of formula D and the compound of formula E is 1.0:2.0 to 3.0, the reaction solvent is the organic solvent 1,4-dioxane, the reaction is carried out in the presence of potassium hydroxide, the reaction temperature is 120°C, and the reaction time is 12 hours.

6. The marking method according to claim 5, characterized in that: The equivalent ratio of the compound of formula C and methyl trifluoromethyl sulfonate is 1:1, the reaction solvent is the organic solvent dichloromethane, the reaction is carried out at room temperature, and the reaction time is 12 hours.

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