Synthesis of pyroglutamic acid fatty esters through lipase-catalyzed esterification with medium chains alcohols

The lipase-catalyzed synthesis of fatty alcohol esters of pyroglutamic acid (pGlu) was investigated. The results showed that, a strategy involving ethyl pyroglutamic ester intermediate was advantageous since this compound had a better solubility in the chosen solvent than the free pyroglutamic acid. The effects of the enzyme load, type of solvent, substrates molar ratio and fatty alcohol type were studied. It was shown that the most optimized reaction conditions were the ones using a 10% (w/w) quantities of Candida antarctica lipase with acetonitrile as solvent and a molar ratio of substrates corresponding to a 1:5 excess of fatty alcohols. Under such conditions, octyl, decyl and dodecyl esters of pyroglutamic acid were obtained in satisfactory yields between 65 and 70% with good reaction kinetics within 24 h.