Diverse classes of anion transporters have been developed, most of which focus on the transmembrane chloride transport due to its significance in living systems. Fluoride transport has, to some extent, been overlooked despite the importance of fluoride channels in bacterial survival. Here, we report the design and synthesis of a cyclic azapeptide (a peptide-based N-amidothiourea, 1), as a transporter for fluoride transportation through a confined cavity that encapsulates fluoride, together with acyclic control compounds, the analogs 2 and 3. Cyclic receptor 1 exhibits more stable β-turn structures than the control compounds 2 and 3 and affords a confined cavity containing multiple inner –NH protons that serve as hydrogen bond donors to bind anions. It is noteworthy that the cyclic receptor 1 shows the capacity to selectively transport fluoride across a lipid bilayer on the basis of the osmotic and fluoride ion-selective electrode (ISE) assays, during which an electrogenic anion transport mechanism is found operative, whereas no transmembrane transport activity was found with 2 and 3, despite the fact that 2 and 3 are also able to bind fluoride via the thiourea moieties. These results demonstrate that the encapsulation of an anionic guest within a cyclic host compound is key to enhancing the anion transport activity and selectivity.

已经开发出多种类型的阴离子转运蛋白，由于其在生命系统中的重要性，大多数都集中于跨膜氯化物的转运。尽管氟化物通道在细菌存活中很重要，但氟化物的运输在一定程度上被忽略了。在这里，我们报告环状氮杂肽（基于肽的ñ-氨基硫脲 1个），作为氟化物通过密闭氟化物的密闭腔中的转运蛋白，以及无环控制化合物，类似物 2 和 3。环受体1个 表现出比对照化合物更稳定的β-转角结构 2 和 3并提供一个包含多个内部–NH质子的密闭腔，这些质子充当氢键供体以结合阴离子。值得注意的是，环状受体1个 在渗透和氟化物离子选择电极（ISE）分析的基础上，显示出通过脂质双层选择性地运输氟化物的能力，在此期间发现了一种电致阴离子运输机制，而没有发现跨膜运输活性 2 和 3，尽管事实是 2 和 3也能够通过硫脲部分结合氟化物。这些结果表明，将阴离子客体包封在环状主体化合物中是增强阴离子转运活性和选择性的关键。