Enantiospecific synthesis of 2-[<sup>18</sup>F]fluoro-<scp>l</scp>-phenylalanine and 2-[<sup>18</sup>F]fluoro-<scp>l</scp>-tyrosine by isotopic exchange
作者:Johnny Castillo Meleán、Johannes Ermert、Heinz H. Coenen
DOI:10.1039/c0ob00440e
日期:——
2-[18F]Fluoro-L-phenylalanine and 2-[18F]fluoro-L-tyrosine have been developed as promising radiopharmaceuticals for molecular imaging using positron emission tomography (PET). However, the lack of a convenient radiosynthetic pathway has limited their practical use. In this work a new three-step nucleophilic synthesis of these compounds starting from [18F]fluoride is described. Corresponding precursors (1a and 1b) were 18F-fluorinated by isotopic exchange, followed by the removal of an activating formyl group with Rh(PPh3)3Cl and subsequent hydrolysis of protecting groups in acidic medium. All reactions were carried out using both conventional and microwave heating. Conventional heated reactions yielded the desired products 2-[18F]Fphe and 2-[18F]Ftyr in 43% and 49% whereas radiochemical yields of 34% and 43%, respectively, were obtained when they were heated by microwaves. Under optimized conditions the enantiomeric purity was ≥94% for both radiopharmaceuticals.
2-[18F]氟-L-苯丙氨酸和2-[18F]氟-L-酪氨酸是使用正电子发射断层扫描(PET)进行分子成像的有前景的放射性药物。然而,由于缺乏便捷的放射性合成途径,限制了它们的实际应用。在这项工作中,描述了从[18F]氟化物开始对这些化合物进行新的三步亲核合成。相应的前体(1a和1b)通过同位素交换进行18F氟化,然后用Rh(PPh3)3Cl除去活化的甲酰基,然后在酸性介质中水解保护基团。所有反应都使用常规加热和微波加热进行。常规加热反应分别获得了43%和49%的所需产物2-[18F]Fphe和2-[18F]Ftyr,而微波加热时分别获得了34%和43%的放射化学产率。在优化的条件下,两种放射性药物的对映体纯度均≥94%。