54638-10-7

Upstream product

• 108-05-4 vinyl acetate 
• 6032-29-7 (+/-)-2-pentanol 
• 108-22-5 Isopropenyl acetate 
• 141-78-6 ethyl acetate 
• 626-38-0 2-Pentyl acetate 
• 64-19-7 acetic acid 

Relevant academic research and scientific papers

Discovery and Redesign of a Family VIII Carboxylesterase with High (S)-Selectivity toward Chiral sec-Alcohols

Highly enantioselective lipase has been widely utilized in the preparation of versatile enantiopure chiral sec-alcohols through kinetic or dynamic kinetic resolution. Lipase is intrinsically (R)-selective, and it is difficult to obtain (S)-selective lipase. Recent crystal structures of a family VIII carboxylesterase have revealed that the spatial array of its catalytic triad is the mirror image of that of lipase but with a catalytic triad that is distinct from lipase. We, therefore, hypothesized that the family VIII carboxylesterase may exhibit (S)-enantioselectivity toward sec-alcohols similar to (S)-selective serine protease, whose catalytic triad is also spatially arrayed as its mirror image. In this study, a homologous enzyme (carboxylesterase from Proteobacteria bacterium SG_bin9, PBE) of a known family VIII carboxylesterase (pdb code: 4IVK) was prepared, which showed not only moderate (S)-selectivity toward sec-alcohols such as 3-butyn-2-ol and 1-phenylethyl alcohol but also (R)-selectivity toward particular sec-alcohols among the substrates explored. Furthermore, the (S)-selectivity of PBE has been significantly improved by rational redesign based on molecular modeling. Molecular modeling identified a binding pocket composed of Ser381, Ala383, and Arg408 for the methyl substituent of (R)-1-phenylethyl acetate and suggested that larger residues may increase the enantioselectivity by interfering with the binding of the slow-reacting enantiomer. As predicted, substituting Ser381with larger residues (Phe, Tyr, and Trp) significantly improved the (S)-selectivity of PBE toward all sec-alcohols explored, even the substrates toward which the wild-type PBE exhibits (R)-selectivity. For instance, the enantioselectivity toward 3-butyn-2-ol and 1-phenylethyl alcohol was improved from E = 5.5 and 36.1 to E = 2001 and 882, respectively, by single mutagenesis (S381F).

Highly Focused Library-Based Engineering of Candida antarctica Lipase B with (S)-Selectivity Towards sec-Alcohols

Candida antarctica lipase B (CALB) is one of the most extensively used biocatalysts in both academia and industry and exhibits remarkable (R)-enantioselectivity for various chiral sec-alcohols. Considering the significance of tailor-made stereoselectivity in organic synthesis, a discovery of enantiocomplementary lipase mutants with high (R)- and (S)-selectivity is valuable and highly desired. Herein, we report a highly efficient directed evolution strategy, using only 4 representative amino acids, namely, alanine (A), leucine (L), lysine (K), tryptophan (W) at each mutated site to create an extremely small library of CALB variants requiring notably less screening. The obtained best mutant with three mutations W104V/A281L/A282K displayed highly reversed (S)-selectivity towards a series of sec-alcohol with E values up to 115 (conv. 50%, ee 94%). Compared with the previously reported (S)-selective CALB variant, W104A, a single mutation provided less selectivity, while the synergistic effects of three mutations in the best variant endow better (S)-selectivity and a broader substrate scope than the W104A variant. Structural analysis and molecular dynamics simulation unveiled the source of reversed enantioselectivity. (Figure presented.).

Enzymatic kinetic resolution of aliphatic sec-alcohols by LipG9, a metagenomic lipase

Bioprospection for new enantioselective enzymes for application in organic synthesis is a prominent area of investigation in biocatalysis. In this context, here we present the evaluation of an immobilized lipase isolated from a metagenomic library (LipG9) for the enzymatic kinetic resolution (EKR) of aliphatic sec-alcohols, which are still challenging substrates, since low enantioselectivity values are usually observed for these resolutions. LipG9 was successfully employed in EKR of aliphatic alcohols, which were resolved with satisfactory conversions (19-59%) and enantiomeric excesses for alcohols (26-88%) and esters (30-96%) by transesterification reactions, demonstrating that its performance is equal to or better than commercially available enzymes for the same reaction.

Escherichia coli BioH: A highly enantioselective and organic solvent tolerant esterase for kinetic resolution of sec-alcohols

Escherichia coli BioH, which is obligatory for biotin synthesis, was found to be an organic solvent tolerant esterase with high enantioselectivity for the kinetic resolution of sec-alcohols using free enzyme powder. With this esterase, a variety of racemic sec-alcohols were efficiently resolved with ee values of up to 99%.

Preparation of passion fruit-typical 2-alkyl ester enantiomers via lipase-catalyzed kinetic resolution

The preparation of ester enantiomers (acetates, butanoates, hexanoates and octanoates) of the secondary alcohols 2-pentanol, 2-heptanol and 2-nonanol via lipase-catalyzed kinetic resolutions was investigated. Conversion rates and stereochemical courses of esterification and hydrolysis reactions catalyzed by commercially available enzyme preparations were followed for the homologous series of these passion fruit-typical 2-alkyl esters by capillary gas chromatography using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)- β-cyclodextrin as chiral stationary phase. An efficient method was developed to prepare the ester enantiomers via lipase-catalyzed esterifications: optically pure (R)-2-alkyl esters (ee > 99.9%) were obtained by esterification of the racemic alcohols with enantioselective Candida antarctica lipase B (immobilized) as catalyst. The subsequent esterification of the unreacted alcohols using lipase from Candida cylindracea yielded the optically enriched (S)-esters (ee > 81.4%). The separation of the products via liquid solid chromatography using a mixture of silica gel and aluminum oxide (basic) resulted in high chemical purities and yields (> 40 mol %).

Catalytic properties of lipases immobilized on various mesoporous silicates

Lipases SP525, AK, LIP, and PS were immobilized on three kinds of mesoporous silicates (FMS, PESO, and SBA) with diameters of 27 to 92 A. The amount of lipase activity adsorbed on these supports was related to the pore size of the silicate. Enantioselectivities of immobilized lipases were similar to those of free lipases, and recycling could be done in both aqueous and organic solvents.

Structure of Solvent Affects Enantioselectivity of Lipase-Catalyzed Transesterification

Lipase-catalyzed transesterification of (rac)-6-methyl-5-hepten-2-ol (sulcatol) with vinyl acetate has been studied in various solvents and the effect of solvent on the enantioselectivity has been discussed from the viewpoint of molecular shape of the solvent.Alkanes and ethers are selected as solvents.Enantioselectivity of a reaction in a structurally linear solvent is higher than that in the corresponding branched chain solvent.Furthermore, the enantioselectivity decreases specifically with the increase in the ring size of solvent molecule.Thus, lipase recognizes not only the structure of substrate but also that of solvent.