1,721,031 research outputs found
Chemo-enzymatic deracemization methods for the preparation of enantiopure non-natural alpha-amino acids
No full textThe complete transformation of a racemate into one single enantiomer is defined as a deracemization. In amino acid chemistry, chemo-enzymatic deracemization is possible due to the ease of racemization of alpha-amino acids and the numerous enantioselective enzymatic systems operating on this class of compounds. Deracemization by dynamic kinetic resolution is a process in which the enantioselective catalyst is coupled with a second one promoting racemization of the reagent but not of the product. Deracemization by stereo-inversion is a convergent process in which the transformed
isomer is finally converted into its enantiomer. These transformations can be applied for the preparation of enantiomerically pure alpha-amino acids of non-natural configuration or of l-alpha-amino acid of non-natural structure
Characterization of a novel amine transaminase from Halomonas elongata
Full text linkChiral amines are indispensable building blocks in the production of biologically active compounds. They are fundamental for the pharmaceutical industry, both as active molecules themselves and as chiral auxiliaries in asymmetric synthesis; however, the available synthetic strategies often present disadvantages. ω-Transaminases (ω-TAs) appear as an attractive alternative by driving the stereoselective amination of prochiral ketones. HEWT is a novel amine transaminase from the moderate halophilic bacterium, Halomonas elongata DSM 2581, which is highly (S)-selective, being able to fully convert (S)-1-phenylethylamine to acetophenone and showing no activity with the corresponding (R)-1-phenylethylamine. HEWT has a broad substrate scope, active with a range of amino donors and acceptors, and naturally accepts isopropylamine (IPA) as amino donor in asymmetric synthesis providing a 41% conversion of pyruvate in 24 h at 37 °C starting with 1:1 molar ratio between the reagents. HEWT also accepts ortho-xylylenediamine as amino donor in for amine synthesis, in particular, with benzaldehyde yielding high conversions between 90 and 95%. The enzyme is also tolerant to the presence of cosolvents up to 20% making it a promising candidate for industrial applications.Science Foundation Irelan
Transphosphatidylation of phospholipids in presence of ionic liquids
No full textNatural and synthetic phospholipids (PLs) have attracted considerable interest for the multiple scientific and practical applications which follow from their amphiphilic properties. PLs are the focus of biomedical research because of their possible use as pharmaceuticals, food additives, cosmetics, in liposome technology, in gene transfer therapy and in drug delivery systems. However, the investigations and applications rely upon the availability of a great number of purified PLs which can be obtained by semisynthesis from natural sources or from synthetic precursors. The aim of this work is to investigate innovative reaction media such as ionic liquids (ILs) for enzymatic PLs transformations in order to obtain a higher selectivity in the enzymatic transphosphatidylation reactions of natural phosphatidylcholine catalyzed by phospholipase D (PLD) from Streptomyces PMF. We have tested the stability and the activity of this PLD in various commercial ILs. We illustrate the encouraging preliminary results of the use of ILs as co-solvents in transesterification reactions with different alcohols. The presence of ILs seems to drive the reaction towards transphosphatidylation with high depression of competitive hydrolysis. We believe that the results here illustrated can stimulate further study on PLs biotransformations in ILs
Multi-step chemo-enzymatic synthesis of azelaic and pelargonic acids from the soapstock of high-oleic sunflower oil refinement
Full text linkSoapstock recovery and manipulation represent one of the most burdensome aspects of the vegetable seed oil refining industry. In particular, soapstock splitting requires high amounts of concentrated acid and produces a low-value mixture of triglycerides and free fatty acids (oleins or acid oil), as well as huge volumes of acidulated wastewater. Oleins are currently converted into biodiesel or supplied to biodigesters, but alternative procedures to afford high-value products are sought after by the vegetable seed oil industry. In this paper, the valorization of soapstock from high-oleic sunflower oil refinement is investigated by biocatalytic methods. First, lipases are used to catalyze an efficient soapstock splitting, and reduce the environmental load of the procedure. Then, the high content of oleic acid (60-80%) is exploited by promoting its oxidative cleavage. Self-epoxidation of oleic acid by lipase-mediated perhydrolysis in the presence of H2O2 affords the corresponding epoxide, which is subsequently hydrolyzed to the diol derivative and oxidized to commercially valuable azelaic and pelargonic acids. The cleavage is performed using only sodium hypochlorite as an inexpensive and efficient oxidant. Epoxidation and glycol cleavage are optimized by a statistical approach and implemented under continuous-flow conditions to increase yields and productivity
Synergy between catalysts: enzymes and bases. DKR of non-natural amino acids derivatives
No full textA double catalyst system (protease + base) is applied for the dynamic kinetic resolution (DKR) of amino acid thioesters in hydrolysis, transesterification or transamidation, allowing to obtain L-N-Boc-aminoacids, esters or amides in high yields and ee. This approach not only obviates the tedious recycling steps of the undesired remaining enantiomer, but, more importantly, the enantiomeric excess of the product (ee) is independent of the extent of conversion, and the process becomes more enantiospecific compared to a kinetic resolution. Substrates of different α-C acidity can be transformed by selecting the base of appropriate strength. Conditions have been found to extend the DKR of phenylglycine thioesters to the whole set of aminoacids thioesters fully representative of natural and non-natural amino acid structures
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