Synthesis of doubly bridged p-tert-butyl-calix[6]arene containing hard and soft ion binding sites

A conformationally preorganized, Cs-symmetrical p-tert-butyl-calix[6]-1,4-crown-4-2,6-dioxo-diazacrown-4 with hard and soft ion binding sites at the lower rim is synthesized. The binding sites may complex alkali metal ions or transition metal ions selectively.