Enantioselective extraction of unprotected amino acids coupled with racemization

AbstractScalable and economical methods for the production of optically pure amino acids, both natural and unnatural, are essential for their use as synthetic building blocks. Currently, enzymatic dynamic kinetic resolution (DKR) underpins some of the most effective processes. Here we report the development of enantioselective extraction coupled with racemization (EECR) for the chirality conversion of underivatized amino acids. In this process, the catalytic racemization of amino acids in a basic aqueous solution is coupled with the selective extraction of one enantiomer into an organic layer. Back-extraction from the organic layer to an acidic aqueous solution then completes the deracemization of the amino acid. The automation of the EECR process in a recycling flow reactor is also demonstrated. Continuous EECR is made possible by the sterically hindered chiral ketone extractant 5, which prevents the coextraction of the copper racemization catalyst because of its nonplanar geometry. Furthermore, the extractant 5 unexpectedly forms imines with amino acids faster and with greater enantioselectivity than less bulky derivatives, even though 5 cannot participate in intramolecular resonance-assisted hydrogen bonding. These features may allow EECR to challenge the preponderance of enzymatic DKR in the production of enantiomerically enriched amino acids.

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ω-Amino Acid:Pyruvate Transaminase from Alcaligenes denitrificans Y2k-2: a New Catalyst for Kinetic Resolution of β-Amino Acids and Amines

Applied and Environmental Microbiology ◽

10.1128/aem.70.4.2529-2534.2004 ◽

2004 ◽

Vol 70 (4) ◽

pp. 2529-2534 ◽

Cited By ~ 71

Author(s):

Hyungdon Yun ◽

Seongyop Lim ◽

Byung-Kwan Cho ◽

Byung-Gee Kim

Keyword(s):

Amino Acids ◽

Kinetic Resolution ◽

Specific Activity ◽

Expression System ◽

Enantiomeric Excess ◽

Selective Enrichment ◽

Alcaligenes Denitrificans ◽

Keto Acids ◽

Optically Pure ◽

High Stereoselectivity

ABSTRACT Alcaligenes denitrificans Y2k-2 was obtained by selective enrichment followed by screening from soil samples, which showed ω-amino acid:pyruvate transaminase activity, to kinetically resolve aliphatic β-amino acid, and the corresponding structural gene (aptA) was cloned. The gene was functionally expressed in Escherichia coli BL21 by using an isopropyl-β-d-thiogalactopyranoside (IPTG)-inducible pET expression system (9.6 U/mg), and the recombinant AptA was purified to show a specific activity of 77.2 U/mg for l-β-amino-n-butyric acid (l-β-ABA). The enzyme converts various β-amino acids and amines to the corresponding β-keto acids and ketones by using pyruvate as an amine acceptor. The apparent Km and V max for l-β-ABA were 56 mM and 500 U/mg, respectively, in the presence of 10 mM pyruvate. In the presence of 10 mM l-β-ABA, the apparent Km and V max for pyruvate were 11 mM and 370 U/mg, respectively. The enzyme exhibits high stereoselectivity (E > 80) in the kinetic resolution of 50 mM d,l-β-ABA, producing optically pure d-β-ABA (99% enantiomeric excess) with 53% conversion.

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Continuous Diastereomeric Kinetic Resolution—Silybins A and B

Catalysts ◽

10.3390/catal11091106 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1106

Author(s):

David Biedermann ◽

Martina Hurtová ◽

Oldřich Benada ◽

Kateřina Valentová ◽

Lada Biedermannová ◽

...

Keyword(s):

Flow Rate ◽

Kinetic Resolution ◽

Flow Reactor ◽

Scale Up ◽

Acrylic Resin ◽

Optimal Conditions ◽

Continuous Flow Reactor ◽

Resin Beads ◽

Diastereomeric Mixture ◽

Optically Pure

The natural diastereomeric mixture of silybins A and B is often used (and considered) as a single flavonolignan isolated from the fruit extract of milk thistle (Silybum marianum), silymarin. However, optically pure silybin diastereomers are required for the evaluation of their biological activity. The separation of silybin diastereomers by standard chromatographic methods is not trivial. Preparative chemoenzymatic resolution of silybin diastereomers has been published, but its optimization and scale-up are needed. Here we present a continuous flow reactor for the chemoenzymatic kinetic resolution of silybin diastereomers catalyzed by Candida antarctica lipase B (CALB) immobilized on acrylic resin beads (Novozym® 435). Temperature, flow rate, and starting material concentration were varied to determine optimal reaction conditions. The variables observed were conversion and diastereomeric ratio. Optimal conditions were chosen to allow kilogram-scale reactions and were determined to be −5 °C, 8 g/L silybin, and a flow rate of 16 mL/min. No significant carrier degradation was observed after approximately 30 cycles (30 days). Under optimal conditions and using a 1000 × 15 mm column, 20 g of silybin per day can be easily processed, yielding 6.7 and 5.6 g of silybin A and silybin B, respectively. Further scale-up depends only on the size of the reactor.

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Mass fraction assignment of Amino Acids in acidic aqueous solution (CCQM-K78.a)

Metrologia ◽

10.1088/0026-1394/56/1a/08010 ◽

2019 ◽

Vol 56 (1A) ◽

pp. 08010-08010 ◽

Cited By ~ 1

Author(s):

Steven Westwood ◽

Ralf Josephs ◽

Tiphaine Choteau ◽

Adeline Daireaux ◽

Robert Wielgosz ◽

...

Keyword(s):

Aqueous Solution ◽

Amino Acids ◽

Mass Fraction ◽

Acidic Aqueous Solution

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Solid-phase acylating polymer reagents. II. Amino acids acetylation in aqueous solution

Journal of Chemical Technology & Biotechnology ◽

10.1002/jctb.280310146 ◽

1981 ◽

Vol 31 (1) ◽

pp. 341-344 ◽

Cited By ~ 2

Author(s):

Martine Gosselet ◽

Bernard Sebille

Keyword(s):

Aqueous Solution ◽

Amino Acids ◽

Solid Phase

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ChemInform Abstract: Asymmetric Synthesis of Unusual Amino Acids: Synthesis of the Optically Pure Isomers of Indole-Protected β-Methyltryptophan Suitable for Peptide Synthesis.

ChemInform ◽

10.1002/chin.199317235 ◽

2010 ◽

Vol 24 (17) ◽

pp. no-no

Author(s):

L. W. BOTEJU ◽

K. WEGNER ◽

V. J. HRUBY

Keyword(s):

Amino Acids ◽

Asymmetric Synthesis ◽

Peptide Synthesis ◽

Unusual Amino Acids ◽

Optically Pure

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Chiroptical activity of hydroxycarboxylic acids with implications for the origin of biological homochirality

Communications Chemistry ◽

10.1038/s42004-021-00524-z ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Jana Bocková ◽

Nykola C. Jones ◽

Uwe J. Meierhenrich ◽

Søren V. Hoffmann ◽

Cornelia Meinert

Keyword(s):

Amino Acids ◽

Lactic Acid ◽

Organic Molecules ◽

Building Blocks ◽

Aliphatic Chain ◽

Monocarboxylic Acids ◽

Hydroxycarboxylic Acids ◽

Polarised Light ◽

Suitable Target ◽

Anisotropy Spectra

AbstractCircularly polarised light (CPL) interacting with interstellar organic molecules might have imparted chiral bias and hence preluded prebiotic evolution of biomolecular homochirality. The l-enrichment of extra-terrestrial amino acids in meteorites, as opposed to no detectable excess in monocarboxylic acids and amines, has previously been attributed to their intrinsic interaction with stellar CPL revealed by substantial differences in their chiroptical signals. Recent analyses of meteoritic hydroxycarboxylic acids (HCAs) – potential co-building blocks of ancestral proto-peptides – indicated a chiral bias toward the l-enantiomer of lactic acid. Here we report on novel anisotropy spectra of several HCAs using a synchrotron radiation electronic circular dichroism spectrophotometer to support the re-evaluation of chiral biomarkers of extra-terrestrial origin in the context of absolute photochirogenesis. We found that irradiation by CPL which would yield l-excess in amino acids would also yield l-excess in aliphatic chain HCAs, including lactic acid and mandelic acid, in the examined conditions. Only tartaric acid would show “unnatural” d-enrichment, which makes it a suitable target compound for further assessing the relevance of the CPL scenario.

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Lipase Catalyzed Synthesis of Enantiopure Precursors and Derivatives for β-Blockers Practolol, Pindolol and Carteolol

Catalysts ◽

10.3390/catal11040503 ◽

2021 ◽

Vol 11 (4) ◽

pp. 503

Author(s):

Morten Gundersen ◽

Guro Austli ◽

Sigrid Løvland ◽

Mari Hansen ◽

Mari Rødseth ◽

...

Keyword(s):

Building Block ◽

Kinetic Resolution ◽

Enantiomeric Excess ◽

Catalytic Amount ◽

Building Blocks ◽

Β Blocker ◽

Β Blockers ◽

Optical Rotations ◽

Reported Data ◽

By Products

Sustainable methods for producing enantiopure drugs have been developed. Chlorohydrins as building blocks for several β-blockers have been synthesized in high enantiomeric purity by chemo-enzymatic methods. The yield of the chlorohydrins increased by the use of catalytic amount of base. The reason for this was found to be the reduced formation of the dimeric by-products compared to the use of higher concentration of the base. An overall reduction of reagents and reaction time was also obtained compared to our previously reported data of similar compounds. The enantiomers of the chlorohydrin building blocks were obtained by kinetic resolution of the racemate in transesterification reactions catalyzed by Candida antarctica Lipase B (CALB). Optical rotations confirmed the absolute configuration of the enantiopure drugs. The β-blocker (S)-practolol ((S)-N-(4-(2-hydroxy-3-(isopropylamino)propoxy)phenyl)acetamide) was synthesized with 96% enantiomeric excess (ee) from the chlorohydrin (R)-N-(4-(3-chloro-2 hydroxypropoxy)phenyl)acetamide, which was produced in 97% ee and with 27% yield. Racemic building block 1-((1H-indol-4-yl)oxy)-3-chloropropan-2-ol for the β-blocker pindolol was produced in 53% yield and (R)-1-((1H-indol-4-yl)oxy)-3-chloropropan-2-ol was produced in 92% ee. The chlorohydrin 7-(3-chloro-2-hydroxypropoxy)-3,4-dihydroquinolin-2(1H)-one, a building block for a derivative of carteolol was produced in 77% yield. (R)-7-(3-Chloro-2-hydroxypropoxy)-3,4-dihydroquinolin-2(1H)-one was obtained in 96% ee. The S-enantiomer of this carteolol derivative was produced in 97% ee in 87% yield. Racemic building block 5-(3-chloro-2-hydroxypropoxy)-3,4-dihydroquinolin-2(1H)-one, building block for the drug carteolol, was also produced in 53% yield, with 96% ee of the R-chlorohydrin (R)-5-(3-chloro-2-hydroxypropoxy)-3,4-dihydroquinolin-2(1H)-one. (S)-Carteolol was produced in 96% ee with low yield, which easily can be improved.

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Synthesis, Characterization and Evaluation of Peptide Nanostructures for Biomedical Applications

Molecules ◽

10.3390/molecules26154587 ◽

2021 ◽

Vol 26 (15) ◽

pp. 4587

Author(s):

Fanny d’Orlyé ◽

Laura Trapiella-Alfonso ◽

Camille Lescot ◽

Marie Pinvidic ◽

Bich-Thuy Doan ◽

...

Keyword(s):

Amino Acids ◽

Biomedical Applications ◽

Chemical Reactivity ◽

Physical Stability ◽

Chemical Properties ◽

Building Blocks ◽

Imaging Probes ◽

Therapeutic Molecules

There is a challenging need for the development of new alternative nanostructures that can allow the coupling and/or encapsulation of therapeutic/diagnostic molecules while reducing their toxicity and improving their circulation and in-vivo targeting. Among the new materials using natural building blocks, peptides have attracted significant interest because of their simple structure, relative chemical and physical stability, diversity of sequences and forms, their easy functionalization with (bio)molecules and the possibility of synthesizing them in large quantities. A number of them have the ability to self-assemble into nanotubes, -spheres, -vesicles or -rods under mild conditions, which opens up new applications in biology and nanomedicine due to their intrinsic biocompatibility and biodegradability as well as their surface chemical reactivity via amino- and carboxyl groups. In order to obtain nanostructures suitable for biomedical applications, the structure, size, shape and surface chemistry of these nanoplatforms must be optimized. These properties depend directly on the nature and sequence of the amino acids that constitute them. It is therefore essential to control the order in which the amino acids are introduced during the synthesis of short peptide chains and to evaluate their in-vitro and in-vivo physico-chemical properties before testing them for biomedical applications. This review therefore focuses on the synthesis, functionalization and characterization of peptide sequences that can self-assemble to form nanostructures. The synthesis in batch or with new continuous flow and microflow techniques will be described and compared in terms of amino acids sequence, purification processes, functionalization or encapsulation of targeting ligands, imaging probes as well as therapeutic molecules. Their chemical and biological characterization will be presented to evaluate their purity, toxicity, biocompatibility and biodistribution, and some therapeutic properties in vitro and in vivo. Finally, their main applications in the biomedical field will be presented so as to highlight their importance and advantages over classical nanostructures.

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