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| Hauptseite > Publikationsdatenbank > 4-Iodophenyl-[18F]fluorosulfate as a versatile building block for Pd-catalyzed cross-coupling reactions |
| Hauptseite > Publikationsdatenbank > 4-Iodophenyl-[18F]fluorosulfate as a versatile building block for Pd-catalyzed cross-coupling reactions |
| Conference Presentation (After Call) | FZJ-2024-03441 |
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2023
Abstract: Introduction: Growing demand for positron emission tomography(PET) probes necessitates access to a wide range of 18F-labeled complexmolecules. However, many of such compounds cannot be directlyradiofluorinated using existing methods and should be labeledindirectly, using 18F-fluorinated building blocks. Recently a novelradiolabeling method based on ultrafast sulfur 18F/19F exchange (18FSuFEx)was published.[1,2] In this work, we evaluated the suitability of4-iodophenyl-[18F]fluorosulfate ([18F]1) prepared by this method as abuilding block for indirect radiolabeling via different Pd-catalyzedcross-coupling reactions.Methods: [18F]1 was synthesized according to the optimized 18FSuFExlabeling method[2], by eluting [18F]F– with BnEt3NCl (0.7 mL,2.2 mM) in MeOH, followed by evaporation of MeOH and the additionof a solution of 1 in MeCN. Aliquots of the reaction mixturewere eitherdirectly used for subsequent cross-coupling reactions (generalprocedure 1 (GP1)) or [18F]1 was first isolated by SPE as solution inEtOH or dioxane. Aliquots of these solutions were used for crosscoupling(GP2). Suzuki-Miyaura reactions with 4-biphenyl-boronicacid were performed according to GP1 using solutions of the substrate(10 mM) and Pd(OAc)2 (5 mM) in dioxane (100 μL of each), oraccording to GP2 by eluting [18F]1 with 1.5 mL EtOH, diluting analiquot of this solution (250 μL) with H2O (350 μL), and adding sat.NaHCO3 (50 μL) followed by solutions of the substrate (10 mM) and Pd(OAc)2 (10 mM) in dioxane (50 μL of each). Stille cross coupling with 4-biphenyltrimethylstannane was performed according to GP2 byeluting [18F]1 with 1.0 mL dioxane and combining an aliquot(250 μL) with solutions of the substrate (10 mM), CuI (10 mM) andPd(OAc)2 (5 mM) in dioxane (100 μL of each). S-Arylation of Boc-Cys-OMe as a representative substrate was performed according to GP1using solutions of the substrate (10 mM) and XantPhos Pd G3 (130 nM)in MeCN (100 μL of each). Sonogashira reaction with propargyl aminewas performed according to GP2 by eluting [18F]1 with 0.5 mL dioxane,diluting an aliquot (100 μL) with EtOH (200 μL), and adding solutionsof the substrate (42 mM, 100 μL), CuI (10 mM, 50 μL), Pd-catalyst(5 mM, 100 μL) and DBU (10 mM, 100 μL) in dioxane. Radiochemicalconversions (RCCs) were determined by HPLC.Results: [18F]1 (10–500 MBq) was obtained from 1 (20 μg,66 nmol) in RCCs of >85% and activity yields of 50–70% within 20–25 min. Subsequent Suzuki-Miyaura cross-coupling reactions afforded1,1′:4,1″terphenyl-4-yl [18F]fluorosulfate ([18F]2) in RCCs of 73–96%after 20–30 min at 40 °C (GP1) or 63–93% after 25 min at r.t. (GP2). TheStille reaction delivered [18F]2 in an RCC of 91 ± 1% after 20 min at r.t. SArylationof Boc-Cys-OMe furnished Boc-Cys(SPh-p-OSO2[18F]F)-OMe([18F]3) in 93 ± 3% RCC after 20 min at 40 °C. The Sonogashira reactiongave 4-(propargylamino)phenyl [18F]fluorosulfate ([18F]4) in a RCC of73% after 15 min at 90 °C.Conclusion: [18F]1 is a versatile building block for indirectradiolabeling via different Pd-catalyzed cross coupling reactions.Acknowledgements: This work was supported by the GermanResearch Foundation (DFG grant ZL 65/4–1).References[1] Zheng Q., et al., J. Am. Chem. Soc. 2021, 142, 10, 3753–3763.[2] Walter N. et al., Eur. J. Med. Chem. 2022, 237, 114383.
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