Surface active molecules: preparation and properties of long chain n^α‐acyl‐l‐α‐amino‐ω‐guanidine alkyl acid derivatives

Abstract

Synopsis A new route for the synthesis of long chain N(alpha)-acyl-l-alpha-amino-omega-guamdine alkyl acid derivatives, with cationic or amphoteric character has been established. The general formula of these compounds is shown below. A physico-chemical and antimicrobial study of these products as a function of the alkyl ester or sodium salt (R), the straight chain length of the fatty acid residue (x) and the number of carbons between the omega-guanidine and omega-carboxyl group (n) has been investigated. The water solubility, surface tension, critical micelle concentration (c.m.c.) and minimum inhibitory concentration (MIC) against Gram-positive and Gram-negative bacteria (including Pseudomonas) has been determined. Dicyclohexylcarbodiimide has been used to condense fatty acids and alpha-amino-omega-guanidine alkyl acids. In these conditions protection of the omega-guanidine group is not necessary. The main characteristic of this synthetic procedure is the use of very mild experimental conditions (temperature, pH) to form the amide linkage which leads to pure optical compounds in high yield in the absence of electrolytes. The results show that some structural modifications, particularly the protection of the carboxyl group, promote variations of the surfactant and antimicrobial properties. Only those molecules with the blocked carboxyl group (cationic molecules, where R = Me, Et or Pr) showed a good surfactant and antimicrobial activity. When the carboxyl group was unprotected (amphoteric molecules, where R = Na(+)) the resulting compounds were inactive.

Modeling of Equilibrium Adsorption and Surface Tension of Cationic Gemini Surfactants

“…In this article, the equilibrium tension data of C 3 (LA) 2 , C 6 (LA) 2 , and C 9 (LA) 2 are fitted to several equilibrium tension models of increasing complexity (11). Certain available tension data for the cationic gemini surfactants suggest counterintuitive adsorption behavior, such as surfactant adsorption decreasing with increasing subphase salinity at a given surfactant concentration, and hence deserve scrutiny and testing via modeling and possible future experimentation.…”

“…The synthesis occurs under mild temperature and pH conditions and results in a high yield of optically pure compounds with little or no undesirable byproducts. The methyl ester of N α -lauroyl arginine (LAM) was shown to have the highest activity in both antimicrobial and physicochemical studies in comparison to similar monomeric lipoaminoacid surfactants of differing hydrocarbon chain length (2). The phase behavior of LAM in aqueous solution has been thoroughly examined and is similar to that of other monomeric cationic surfactants (3,4).…”

“…Increasing concerns about surfactant toxicity and environmental issues prompted the development of a new synthesis pathway for, and the re-evaluation of, several cationic amino acid surfactant derivatives by the Department of Surfactant Technology in Barcelona, Spain (2)(3)(4)(5). The synthesis occurs under mild temperature and pH conditions and results in a high yield of optically pure compounds with little or no undesirable byproducts.…”

“…The purity of the final surfactant products was estimated to exceed 99%, and the phase, tension, and aggregation behavior of the bis(Args), or C n (LA) 2 where n is the number of carbon atoms in the spacer chain, has been investigated (5-7). Additionally, these cationic gemini surfactants are characterized by two cmc's.…”

Development of Arginine Based Monopeptides as Cationic Surfactants from Pure Amino Acid

“…Long chain N α -acyl amino acids have been studied by many groups with the aim to obtain mild surfactants for preservative applications [1,2]. Cation ic surfactants derived fro m the condensation of fatty acids and esterified dibasic amino acids, such as fro m lauric acid and arg in ine, in particu lar the Et ester of the lau ramide of the argin ine monohydrochloride (LA E), may be used for the p rotection against the growth of the microorganisms.…”