Department of Chemistry - Radiochemistry, University of Helsinki, Helsinki, Finland.
Department of Chemistry - Radiochemistry, University of Helsinki, Helsinki, Finland; Department of Ecochemistry and Radioecology, Faculty of Natural Sciences, University of Ss. Cyril and Methodius in Trnava, Trnava, Slovakia.
Nucl Med Biol. 2018 Dec;67:27-35. doi: 10.1016/j.nucmedbio.2018.10.001. Epub 2018 Oct 15.
F-fluoroglycosylation via oxime formation is a chemoselective and mild radiolabeling method for sensitive molecules. Glycosylation can also improve the bioavailability, in vivo kinetics, and stability of the compound in blood, as well as accelerate clearance of biomolecules. A typical synthesis procedure for F-fluoroglycosylation with [F]FDG (2-deoxy-2-[F]fluoro-d-glucose) and [F]FDR (5-deoxy-5-[F]fluoro-d-ribose) involves two HPLC (high performance liquid chromatography) purifications: one after F-fluorination of the carbohydrate to remove its labeling precursor, and a second one after the oxime formation step to remove the aminooxy precursor. The two HPLC purifications can be time consuming and complicate the adaptation of the synthetic strategy in nuclear medicine applications and automated synthesis. We have developed a procedure in which SPE (solid phase extraction) and resin purification methods replace both of the needed HPLC purification steps.
We used [F]FDR and [F]FDG as prosthetic groups to radiolabel two aminooxy-modified model molecules, a tetrazine and a PSMA (prostate specific membrane antigen) inhibitor. After fluorination, the excess carbohydrate precursor was removed by derivatizing it with 4,4'-dimethoxytrityl chloride (DMT-Cl). The DMT moiety increases the hydrophobicity of the unreacted precursor making the separation from the fluorinated precursor possible with simple C18 Sep-Pak cartridge. For removal of the aminooxy precursor, we used a commercially available aldehyde resin (AminoLink, Thermo Fisher Scientific). C18 Sep-Pak SPE cartridge was used to separate [F]FDR and [F]FDG from the F-fluoroglycoconjugate end product.
[F]FDR and [F]FDG were efficiently purified from their precursors, free fluorine-18, and other impurities. The aldehyde resin quantitatively removed the unreacted aminooxy precursors after the oxime formation. The fluorine-18 labeled oxime end products were obtained with high radiochemical purity (>99%) and molar activity (>600 GBq μmol).
We have developed an efficient cartridge purification method for producing high molar activity F-glycoconjugates synthesized via oxime formation.
通过肟形成的 F-氟代糖基化是一种对敏感分子具有化学选择性和温和的放射性标记方法。糖基化还可以提高化合物在血液中的生物利用度、体内动力学和稳定性，并加速生物分子的清除。使用 [F]FDG（2-脱氧-2-[F]氟代-d-葡萄糖）和 [F]FDR（5-脱氧-5-[F]氟代-d-核糖）进行 F-氟代糖基化的典型合成过程包括两个 HPLC（高效液相色谱）纯化步骤：一个是在碳水化合物进行 F-氟化后，去除其标记前体；另一个是在肟形成步骤后，去除氨氧基前体。这两个 HPLC 纯化步骤可能会很耗时，并使核医学应用和自动化合成中的合成策略的适应复杂化。我们开发了一种使用 SPE（固相萃取）和树脂纯化方法替代这两个所需的 HPLC 纯化步骤的方法。
我们使用 [F]FDR 和 [F]FDG 作为前体，放射性标记两个氨氧基修饰的模型分子，一个是四嗪和一个 PSMA（前列腺特异性膜抗原）抑制剂。氟化后，通过用 4,4'-二甲氧基三苯甲基氯（DMT-Cl）衍生化去除过量的碳水化合物前体。DMT 部分增加了未反应的前体的疏水性，使得可以使用简单的 C18 Sep-Pak 小柱从氟代前体中分离出来。对于氨氧基前体的去除，我们使用了一种市售的醛树脂（AminoLink，Thermo Fisher Scientific）。C18 Sep-Pak SPE 小柱用于从 F-氟代糖缀合物终产物中分离 [F]FDR 和 [F]FDG。
[F]FDR 和 [F]FDG 从其前体、游离氟-18 和其他杂质中得到有效纯化。肟形成后，醛树脂定量去除了未反应的氨氧基前体。通过肟形成获得了具有高放射化学纯度（>99%）和摩尔活性（>600GBqμmol）的氟-18 标记的肟终产物。
我们开发了一种用于通过肟形成合成高摩尔活性 F-糖缀合物的高效小柱纯化方法。
