The cause of discrepancies in the literature regarding the specificity of immobilized Candida antarctica lipase B in the acylation of oligosaccharides was examined. Molecular sieves, generally used to control the water content during acylation reactions, turned out to have an important role in this. It was proven that molecular sieves alone can catalyze the acylation of fructose oligomers using vinyl laurate, leading to multiple substitution of the oligomers. This effect was the most profound at conditions unfavorable for the enzyme, because this resulted in a relatively high concentration of the chemically produced adducts. The enzyme alone catalyzed the formation of monosubstituted oligomers. It was proven that even solvent pre-drying by molecular sieves already causes the release of catalyzing compounds to the liquid, leading to subsequent catalysis. These findings should be taken into account when applying molecular sieves in this type of reactions in the future. Molecular sieves could, moreover, be used as a catalyst when multiple substitution is desired.
- regioselective acylation
- organic media
ter Haar, R., Schols, H. A., van den Broek, L. A. M., Saglam, D., Frissen, A. E., Boeriu, C. G., & Gruppen, H. (2010). Molecular sieves provoke multiple substitutions in the enzymatic synthesis of fructose oligosaccharide–lauryl esters. Journal of Molecular Catalysis. B, Enzymatic, 62(2), 183-189. https://doi.org/10.1016/j.molcatb.2009.10.008