Arzu Uyanik

Improvement of catalytic activity of lipase from Candida rugosa via sol–gel encapsulation in the presence of calix(aza)crown

Lipase from Candida rugosa (CRL) was encapsulated within a chemically inert sol-gel support in the presence of calix(aza)crowns as the new additives. The catalytic activity of the encapsulated lipases was evaluated both in the hydrolysis of p-nitrophenyl palmitate (p-NPP) and the enantioselective hydrolysis of racemic Naproxen methyl ester. It has been observed that the percent activity yields of the calix(aza)crown based encapsulated lipases were higher than that of the free lipase. Improved enantioselectivity was observed with the calix(aza)crown-based encapsulated lipases as compared to encapsulated free lipase. The reaction of Naproxen methyl ester resulted in 48.4% conversion for 24h and 98% enantiomeric excess for the S-acid, corresponding to an E value of >300 (E=166 for the encapsulated free enzyme). Moreover, the encapsulated lipases were still retained about 18% of their conversion ratios after the sixth reuse in the enantioselective reaction.

L-proline derivatives based on a calix[4]arene scaffold as chiral organocatalysts for the direct asymmetric aldol reaction in water

Abstract A new series of water-compatible proline catalysts (4–6) derived from calixarene bearing a hydrophobic nature have been synthesised. It was found that the compound 4 was a highly efficient organocatalyst for aldol reactions occurred in the water. Under optimised reaction conditions, high yields (up to 82%), good enantioselectivities (ee up to 81%) and high diastereoselectivities (dr up to 91:9) were obtained.

Chiral Calix[4]arenes-Bearing Prolinamide Functionality as Organocatalyst for Asymmetric Direct Aldol Reactions in Water

ABSTRACT The chiral calix[4]arene derivative (6) bearing an L-prolinamido group has been designed and proved to be a water compatible efficient organocatalysts for a direct enantioselective aldol reaction. Compound 6 catalyzes the aldol reaction of cyclohexanone and a variety of aromatic aldehydes yielding anti-aldol products in high yield with enantioselectivities of up to 93% and diastereoselectivity of up to 95:5.

Enhancing Effect of Calix[4]arene Amide Derivatives on Lipase Performance in Enantioselective Hydrolysis of Racemic Arylpropionic Acid Methyl Esters

Calix[4]arene amide derivatives were employed as new additives within the sol-gel encapsulation of lipase from Candida rugosa (CRL) to improve its catalytic properties. Evaluation of catalytic activity of the encapsulated lipases was acheived by enantioselective hydrolysis of both racemates, Naproxen methyl ester and 2-phenoxypropionic acid methyl ester, in aqueous buffer solution/isooctane reaction system. Results show that enantioselectivity was improved by using calix[4]arene amide derivatives-based encapsulated lipases. The reaction of naproxen methyl ester resulted in 47.6% conversion (x) in 24 h with 88.9% enantiomeric excess of substrate (ees), analogous to an enantioselectivity (E) value of 297 (E = 137 for the encapsulated free enzyme). The conversion of 2-phenoxypropionic acid methyl ester, obtained was 48.4% with E value of 327, enantiomeric excess of substrate (ees) of 92% for the reaction time of 1 h (E = 211 for the encapsulated free enzyme).

Functional Group Effects of New Calixarene Derivatives on Catalytic and Enantioselective Behavior of Lipase

ABSTRACT In this study, two new calixarene derivatives bearing thiourea and carbamate moieties were synthesized and characterized. Moreover, thiourea- and carbamate-bridged calixarene derivatives with Fe3O4 magnetic nanoparticle were employed for the first time as the convenient additives in the encapsulation process of lipase. The results of catalytic activity and enantioselectivity of the encapsulated lipases in the hydrolysis reaction of racemic flurbiprofen methyl ester indicate that both of the encapsulated lipases (Enc-TuC[4]@Fe3O4 and Enc-CbC[4]@Fe3O4) exhibit higher conversion and enantioselectivity compared to the free-encapsulated lipase (Enc-Lipase). However, the highest affinities result was obtained when the encapsulated lipase (Enc-CbC[4]@Fe3O4) was used in the kinetic resolution reaction of racemic flurbiprofen methyl ester.