Highly Selective Artificial Cholesteryl Crown Ether K + ‐Channels

The bacterial KcsA channel conducts K + cations at high rates while excluding Na + cations. Herein, we report an artificial ion‐channel formed by H‐bonded stacks of crown‐ethers, where K + cation conduction is highly preferred to Na + cations. The macrocycles aligned along the central pore surround the K + cations in a similar manner to the water around the hydrated cation, compensating for the energetic cost of their dehydration. In contrast, the Na + cation does not fit the macrocyclic binding sites, so its dehydration is not completely compensated. The present highly K + ‐selective macrocyclic channel may be regarded as a biomimetic of the KcsA channel.