Chemo-enzymatic synthesis of amino acid-based surfactants |
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Authors: | Rao Valivety Paula Jauregi Iqbal Gill Evgeny Vulfson |
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Affiliation: | (1) FMS Department, BBSRC Institute of Food Research, Earley Gate, Whiteknights Rd., RG6 6BZ Reading, United Kingdom |
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Abstract: | The application of lipases to the synthesis of amino acid-based surfactants was investigated. Low yields (2–9%) were obtained in the acylation of free amino acids, such as l-serine and l-lysine, as well as their ethyl esters and amides with fatty acids, owing in part to low miscibility of the reactants. When the N-carbobenzyloxy (Cbz)-l-amino acids were used in an effort to improve miscibility of the amino acid derivatives with the acyl donor, a dramatic improvement was observed for N-Cbz-l-serine (92% yield) but not for N α-Cbz- or N ζ-Cbz-l-lysine (7 and 2% yield, respectively). As an alternative, and efficient synthesis of N ζ-acyl-l-lysines was developed, based on the regiospecific chemical acylation of copper(II) lysinate. In pursuit of a general route to amino acid-fatty acid surfactants, the utility of a polyol linker was investigated. Thus, the glycerol ester of N α′ N ζ-di-Cbz-l-lysine was prepared and evaluated as a substrate for acylation. As expected, this and other glycer-1-yl esters of N-protected amino acids were excellent substrates for lipase-catalyzed acylation. Their reaction with myristic acid in the presence of Novozyme resulted in the regioselective acylation of the primary hydroxyl group of the glycerol moiety to afford the corresponding 1-O-(N-Cbz-l-aminoacyl)-3-O-myris-toylglycerols with conversions of 50–90%. These were readily deprotected to give a range of 1-O-(aminoacyl)-3-O-myristoyl-glycerols with overall yields of 27–71%. |
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Keywords: | Amidation amino acids copper(II) lysinate enzymatic synthesis fatty acids glycerol ester lipase regioselectivity solvent-free acylation surfactants |
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