Immobilized Pseudomonas sp lipase: A powerful biocatalyst for asymmetric acylation of (+/-)-2-amino-1-phenylethanols with vinyl acetate

Pseudomonas sp. lipase was immobilized onto glutaraldehyde-activated Florisil (R) support via Schiff base formation and stabilized by reducing Schiff base with sodium cyanoborohydride. The immobilization performance was evaluated in terms of bound protein per gram of support (%) and recovered activity (%). A 4-factor and 3-level Box-Behnken design was applied for the acylation of (+/-)-2-(propylamino)-1-phenylethanol, a model substrate, with vinyl acetate and the asymmetric acylations of other (+/-)-2-amino-1-phenylethanols with different alkyl substituents onto nitrogen atom such as (+/-)-2-(methylamino)-1-phenylethanol, (+/-)-2-(ethylamino)-1-phenylethanol, (+/-)-2-(butylamino)-1-phenylethanol and (+/-)-2-(hexylamino)-1-phenylethanol were performed under the optimized conditions. The optimal conditions were bulk water content of 1.8%, reaction temperature of 51.5 degrees C, initial molar ratio of vinyl acetate to amino alcohol of 1.92, and immobilized lipase loading of 47 mg mL(-1). (R)-enantiomers of tested amino alcohols were preferentially acylated and the reaction purely took place on the hydroxyl group of 2-amino-1-phenylethanols. The increase of alkyl chain length substituted onto nitrogen atom caused an increase in the acylation yield and ee values of (S)-enantiomers. Enantiomeric ratio values were >200 for all the reactions. Our results demonstrate that the immobilized lipase is a promising biocatalyst for the preparation of (S)-2-amino-1-phenylethanols and their corresponding (R)-esters via O-selective acylation of (+/-)-2-amino-1-phenylethanols with vinyl acetate. (C) 2013 Elsevier Ltd. All rights reserved.