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

摘要

Pseudomonas sp. lipase was immobilized onto glutaraldehyde-activated Florisil~® 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)-l-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)-l -phenylethanol were performed under the optimized conditions. The optimal conditions were bulk water content of 1.8%, reaction temperature of 51.5 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-l -phenylethanols and their corresponding (R)-esters via O-selective acylation of (±)-2-amino-l-phenylethanols with vinyl acetate.