Synthesis of glycero amino acid-based surfactants. Part 1. Enzymatic preparation of rac-1-O-(N-a-acetyl-L-aminoacyl)glycerol derivatives

An enzymatic procedure for the selective synthesis of a number of N-alpha-p rotected amino acid glyceryl esters is presented. Using N-alpha-Boc-arginin e as a model substrate, changes in product yield are examined for the follo wing reaction variables: aqueous buffer content, pH. biocatalyst configurat ion (free or deposited), enzyme concentration and synthetic approach (therm odynamically or kinetically controlled synthesis). The best yields (61-89%) are obtained at 50 degreesC in glycerol containing a range of aqueous buff er from 0 to 10% (v/v). Readily available industrial proteases and lipases are used as catalysts. The method allowed us to selectively acylate one of the primary hydroxy groups of the glycerol with the carboxylate groups of t he amino acid. In the case of aspartic acid and glutamic acid, selective es terification of the alpha -carboxylate group is achieved. None of the enzym es tested could differentiate between the two enantiotopic hydroxymethyl gr oups of glycerol, giving diastereoisomeric mixtures in all cases.