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

• An immobilized lipase was prepared for the asymmetric acylation of 2-amino-1-phenylethanols.
• A facile approach is provided for preparation of enantiopure (S)-2-amino-1-phenylethanols.
• The yield of acylation affects from increasing length of alkyl substituents on nitrogen atom.
• The acylation reaction purely takes places on the hydroxyl group of 2-amino-1-phenylethanols.
• Only (R)-enantiomers of 2-amino-1-phenylethanols are acylated by the immobilized lipase.

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)-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 °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.