3-Fluoro-1-((thiazol-4-yl)ethynyl)benzenes constitute an important class of high-affinity metabotropic glutamate subtype 5 receptor (mGluR5) ligands, some of which have been labeled with fluorine-18 (t1/2 = 109.7 min), to provide radioligands for molecular imaging of brain mGluR5 in living animal and human subjects with positron emission tomography (PET). Labeling in the 3-fluoro position of such ligands can be achieved through aromatic nucleophilic substitution of a halide leaving group with [18F]fluoride ion when a weakly activating m-nitrile group is present, but is generally very low yielding (<8%). Here we used a microfluidic reaction platform to show that greatly enhanced (up to 6-fold) radiochemical yields can be achieved from suitably synthesized diaryliodonium tosylate precursors. The presence of a m-nitrile or other activating group is not required. Similar conditions were adopted in a more conventional automated radiochemistry platform having a single-pot reactor, to produce mGluR5 radioligands with useful radioactivities for PET imaging.
3-
氟-1-((
噻唑-4-基)
乙炔基)苯系物是一类重要的高亲和性代谢谷
氨酸亚型 5 受体(mGluR5)
配体,其中一些已用
氟-18(t1/2 = 109.7 分钟)标记,为正电子发射断层扫描(PET)对活体动物和人体脑部 mGluR5 进行分子成像提供了放射性
配体。当存在弱活化间腈基团时,可通过芳香族亲核取代卤化物离去基团与[18F]
氟离子来实现此类
配体 3-
氟位置的标记,但通常产率很低(<8%)。在这里,我们利用微流体反应平台证明,通过适当合成二芳碘对甲苯磺酸盐前体,可大大提高放射化学产率(高达 6 倍)。无需存在间腈或其他活化基团。在具有单锅反应器的更传统的自动化放射化学平台中也采用了类似的条件,以生产具有 PET 成像有用放射性活性的 mGluR5 放射性
配体。