Effects of substituent and temperature on enantioselectivity for lipase-catalyzed esterification of 2-(4-substituted phenoxy) propionic acids in organic solvents

Enzyme-catalysed one-pot synthesis of 4H-pyrimido[2,1-b] benzothiazoles and their application in subcellular imaging

Enzymes, which provide more efficient and eco-friendly strategies for various functional molecules' construction than traditional chemo-catalysts, were utilized for the synthesis of 4H-pyrimido[2,1-b] benzothiazole derivatives. Reported herein is a trypsin-catalysed three- component Biginelli reaction of aldehyde, β-ketoester and 2-amino benzothiazole in one pot, affording a streamlined pathway to diverse ring-fused pyrimidines. In addition to using commercially available aromatic aldehydes as substrates, acetaldehyde, the chemical liquid with rather low boiling point and difficult to handle above room temperature, is utilized to further extend the range of substrates. It was verified that most of the tested substrates exhibited satisfactory reactivity. In addition, several substrates indicated AIE (Aggregation-Induced Emission) property and have been investigated as potential biomarkers.

Molecular bioimprinting of lipases with surfactants and its functional consequences in low water media

Lipases from Thermomyces lanuginosa (TLL), Candida rugosa (CRL) and Burkholderia cepacia (BCL) were obtained in the 'open lid' form by adding surfactant molecules like n-octyl-β-d-glucopyranoside (OG), hexadecyl trimethyl ammonium bromide (CTAB), Bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and triton X-100 for this purpose. The enzymes were 'dried' by precipitating with 4× (v/v) excess of organic solvents. The imprint surfactant molecules were removed by extensive washing with organic solvents. TLL imprinted with 0.05% CTAB showed 11-fold increase in the transesterification activity and was a better preparation to kinetically resolve (±)-1-phenylethanol. Fluorescence emission spectra confirmed that Trp89 of the lid was indeed affected during bioimprinting. With CRL, bioimprinting with OG gave 7-fold increase in the transesterification rates and resulted in reversal of enantioselectivity of CRL and gave R-phenylethyl acetate instead of the S-product as with the unimprinted precipitate. Bioimprinted BCL was also a 7-fold better catalyst for transesterification as well as enantioselectivity.

Kinetic modeling of lipase catalyzed hydrolysis of (R/S)-1-methoxy-2-propyl-acetate as a model reaction for production of chiral secondary alcohols

The Candida antarctica lipase B catalyzed kinetic resolution of (R/S)-1-methoxy-2-propyl-acetate was studied as a model system for the biocatalytic production of chiral secondary alcohols. For this purpose, a kinetic model is proposed involving both enantiomers of this reaction using model discrimination and parameter identification. Starting from a ping-pong bi-bi mechanism, a simplified model with sensitive parameters was derived for the R- and S-enantiomer, respectively. It was validated at pH 7.0, using time-course measurements at varying temperatures (30-60 degrees C) and initial substrate conditions (0.05-1.5 M). This model was then used for mechanistic interpretation of the kinetic resolution on a biochemical level. The effect of temperature on kinetic parameters and enantiomeric ratio was investigated and compared to findings from the field of molecular modeling to obtain a better understanding of the reaction system for process design. Values of 21.2 and 9.7 kJmol-1 were determined for the enthalpic (DeltaR-S DeltaH ++ degrees) and the entropic (-T x DeltaR-S DeltaS ++ degrees) contribution of the difference in transition state energy of both enantiomers at 30 degrees C. High enantiomeric ratio's (E of 47-110) especially at lower temperatures, in addition to enzyme activity at a wide pH range, indicate this biotransformation is a promising example for the industrial production of chiral secondary alcohols.

Lipases as practical biocatalysts

Lipases are the most used enzymes in synthetic organic chemistry, catalyzing the hydrolysis of carboxylic acid esters in aqueous medium or the reverse reaction in organic solvents. Recent methodological advancements regarding practical factors affecting lipase activity and enantioselectivity are reviewed. Select practical examples concerning the use of lipases in the production of chiral intermediates are also highlighted.