Crowned dopa's, their dimers, cyclodimers and polymers: Synthesis and cation complexation

Optically pure protected L‐[3,4‐(1,4,7,10,13‐pentaoxatridecamethylene) phenyl] alanine, its dipeptide, diketopiperazine and homopolymer, protected L‐[3,4‐(1,4,7,10,13,16‐hexaoxahexadecamethylene) phenyl] alanine and its polymer have been synthesized and characterized. These crown ether derivatives complex the potassium and ammonium cations as well as protonated leucine and glycine in tetrahydrofuran and methanol. They are also phase‐transfer agents. The cooperativity of the crown units was studied in detail for the dimeric ligands.