Abstract
Amphiphiles of symmetrical bis-quaternary ammonium salts possessing ammonium groups, with methyl as head group, dodecyl and aralkyl as hydrophobic groups, and connected by an alkanediyl were synthesized. Aralkyls are p-heptylbenzyl and 8-phenyloctyl (corresponding ammonium salts are designated “phenylene type” and “phenyl type”, respectively). The effect of a benzene ring in the hydrophobic chain on the hydrolytic and substrate recognizing activity of amino acid esters were examined. The phenyl type showed higher hydrolytic rate, particularly so in the case of phenylalanine and methionine esters, than the corresponding ammonium salts having no benzene ring (“alkyl type”). The phenylene type was less active compared to an alkyl type and hydrolyzed only phenylalanine ester. The position of benzene ring is thus a significant determinant of hydrolytic rate and substrate recognition. The orientation or formation of a molecular assembly as well as the uptaken site of a substrate are also affected by this position.
