Aggregation Behavior of Amphiphiles Functionalized with Dipeptide Segments and Enantioselective Ester Hydrolysis in Their Bilayer Membranes

Article abstract of DOI:10.1246/bcsj.58.172

Four amphiphiles having dipeptide segments, which consist of one histidyl residue and another amino acid residue, and the dihexadecyl moiety for the double-chain segment (N⁺C5AlaHis2C16, N⁺C5LeuHis2C16, N⁺C5PheHis2C16, and N⁺C5HisAla2C16) were synthesized, and the aggregate morphology of them was characterized by electron microscopy and differential scanning calorimetry.The amphiphiles, which have the histidyl residue bound to the dihexadecylamine component (N⁺C5AlaHis2C16, N⁺C5LeuHis2C16, and N⁺C5PheHis2C16) formed both multi- and single-walled aggregates in the aqueous dispersion state, while their sonicated solutions involved only single-walled vesicles.On the other hand, the amphiphile, which has the alanyl residue bound to the dihexadecylamine component (N⁺C5HisAla2C16) afforded tubular aggregates in the aqueous dispersion.The hydrolysis of enantiomeric esters of various hydrophobic nature, which was carried out in the single-walled vesicles, showed relatively small enantioselectivity.The reasons for such catalytic performance of the vesicles were discussed from the kinetic and mechanistic viewpoints; the kinetic analysis being carried out on the basis of the organic pseudo-phase concept.