Synthesis, metal-binding properties and polypeptide solubilization of ‘crowned’ arborols

Abstract

The first dendritic crown ether polymers (‘crowned’ arborols: G1, G2 and G3) have been synthesized and characterized. The convergent synthetic method was found to be more convenient than the divergent synthetic method. The building block in the branch was prepared from N-benzyloxycarbonyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane and 3,5-bis(ethoxycarbonylmethoxy)benzoyl chloride. Since the basic repeating unit is the amino dicarboxylic acid, one can utilize the methods developed for peptide synthesis. Final products were obtained in moderate yields by coupling of each generational fragment with a core (benzene-1,3,5-tricarbonyl trichloride) followed by reduction of all amide linkages to tertiary amine linkages by borane–dimethyl sulfide. The complexation ability of these ‘crowned’ arborols was estimated by two-phase solvent extraction of alkali picrate salts. We found that some of these arborols can solubilize proteins in organic solvents.