Resolution of Racemic Aryloxy-Propan-2-yl Acetates via Lipase-Catalyzed Hydrolysis: Preparation of Enantiomerically Pure/Enantioenriched Mexiletine Intermediates and Analogs

Abstract

The lipase kinetic resolution (KR) of aryloxy-propan-2-yl acetates, via hydrolysis, produced enantiomerically pure/enantioenriched mexiletine intermediates and analogs. Racemic acetates rac-1-(2,6-dimethylphenoxy)propan-2-yl acetate (rac-5a), rac-1-(2,4-dimethylphenoxy)propan-2-yl acetate (rac-5b), rac-1-(o-tolyloxy)propan-2-yl acetate (rac-5c) and rac-1-(naphthalen-1-yloxy)propan-2-yl acetate (rac-5d) were used as substrates. A preliminary screening (24 h, phosphate buffer pH 7.0 with 20% acetonitrile as co-solvent, 30 °C and enzyme: substrate ratio of 2:1, m:m) was carried out with twelve lipases using acetate 5a as substrate. Two enzymes stood out in the KR of 5a, the Amano AK lipase from Pseudomonas fluorescens and lipase from Thermomyces lanuginosus (TLL) immobilized on Immobead 150. Under these conditions, both the (R)-1-(2,6-dimethylphenoxy)propan-2-ol [(R)-4a] and the remaining (S)-1-(2,6-dimethylphenoxy)propan-2-yl acetate [(S)-5a] were obtained with enantiomeric excess (ee) > 99%, 50% conversion and enantiomeric ratio (E) > 200. The KR study was expanded to racemic acetates 5b-d, leading to the corresponding chiral remaining acetates with ≥ 95% ee, and the alcohols 4b-d with ≥ 98% ee, and conversion values close to 50%. The best conditions for KRs of rac-5b-d involved the use of lipase from P. fluorescens or TLL immobilized on Immobead 150, 24 or 48 h and 30 °C. These intermediates had their absolute configurations determined using 1H NMR spectroscopy (Mosher’s method), showing that the KRs of these acetates obeyed the Kazlauskas’ rule. Molecular docking studies corroborated the experimental results, indicating a preference for the hydrolysis of (R)-5a-d.

Lipase from Yarrowia lipolytica: Prospects as an Industrial Biocatalyst for Biotechnological Applications

“…In general, lipases are enzymes with the potential to break ester bonds in fats and oils, resulting in fatty acids and glycerol [30]. Thus, applying these enzymes will be possible in different areas of industry, such as the production of detergents, biofuels, and even the food industry [4,[31][32][33][34][35][36][37]. This diversity of applications is made possible due to the versatility of these biomolecules.…”

The Effects of Buffer Nature on Immobilized Lipase Stability Depend on Enzyme Support Loading

“…Lipases are among the most utilized enzymes in academic and applied research [1][2][3][4] due to their high stability under different media and conditions and their high versatility (catalyzing hydrolysis [5][6][7][8], esterifications [9][10][11][12], transesterifications [13][14][15], acidolysis [16][17][18][19][20], interesterifications [21,22], amidations [23][24][25][26], etc.). Lipases have a broad specificity, accepting substrates with very different structures, but in many instances exhibiting a high specificity or regio-or enantio-selectivity [27][28][29][30][31].…”