Lipopeptidic surfactants. II. Acidic and basic Nα‐lauroyl‐L‐arginine dipeptides from pure amino acids

In this paper, the second part of a systematic study whose aim deals with the influence of the terminal amino acid side chain on the properties of Nα‐lauroyl arginyl dipeptides is reported. Nα‐lauroyl arginyl dipeptides that contain an acidic amino acid (glutamic acid) or a basic amino acid (lysine) as terminal amino acid have been prepared by peptide synthesis methods. These compounds have been synthesized as methyl esters (cationic surfactants) and free α‐carboxylic acids (amphoteric surfactants), and their fundamental surfactant properties and antimicrobial activity have been evaluated. The properties of these compounds have been compared to the properties of the cationic monomer derivative methyl ester of Nα‐lauroyl arginine and of the amphoteric monomer derivative Nα‐lauroyl arginine reported earlier. The compounds are soluble in water and show surface activity, although in the case of the amphoteric Nα‐lauroyl arginyl dipeptide containing glutamic acid these two properties depend on the solution pH. The cationic Nα‐lauroyl arginyl dipeptides are antimicrobial agents. However, only the amphoteric compound containing lysine may be considered antimicrobial.