A versatile strategy for the synthesis of crown ether-bearing heterocycles: Discovery of calcium-selective fluoroionophore

Heterocycles have been modified in various ways in the search for new functions, but few examples are known of crown ethers incorporating heterocycles in macro-ring systems. Here we report a simple and versatile synthesis of crown ether-bearing heterocycles. An acylurea moiety in the heterocycles is efficiently transformed to 'crown ether' of various ring sizes. The products included a Ca²⁺-selective fluoroionophore. Our simple methodology is expected to provide many novel functional heterocyclic compounds, including fluoroionophores and candidate pharmaceuticals.