Direct synthesis of unprotected α-amino acids via allylation of hydroxyglycine

2005 ◽  
Vol 83 (6-7) ◽  
pp. 937-942 ◽  
Author(s):  
Masaharu Sugiura ◽  
Chieko Mori ◽  
Keiichi Hirano ◽  
Shū Kobayashi
Keyword(s):  
Amino Acids ◽  
Direct Synthesis ◽  
Glyoxylic Acid ◽  
Cope Rearrangement ◽  
Reaction Conditions ◽  
Stereoselective Reactions ◽  
High Stereoselectivity

Hydroxyglycine, the ammonia adduct of glyoxylic acid, was found to react with various allylboronates in the presence of triethylamine in methanol to give unprotected α-amino acids directly with high stereoselectivity. For instance, the reactions with (E)- and (Z)-crotylboronates afforded the corresponding anti- and syn-crotylated products (isoleucine and alloisoleucine after hydrogenation) with high diastereoselectivity, respectively. Interestingly, it was found that isomerization of the products (γ-adducts to α-adducts) occurred under the reaction conditions in some cases. Control experiments have suggested that the isomerization took place via 2-aza (or azonia) Cope rearrangement of imines derived from γ-adducts and glyoxylic acid.Key words: hydroxyglycine, glyoxylic acid, allylboronates, α-amino acids, allylglycines, isoleucine, alloisoleucine, stereoselective reactions, isomerization, 2-aza (azonia) Cope rearrangement.

scholarly journals Design of Iridium N-Heterocyclic Carbene Amino Acid Catalysts for Asymmetric Transfer Hydrogenation of Aryl Ketones

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 671
Author(s):  
Chad M. Bernier ◽  
Joseph S. Merola
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Enantiomeric Excess ◽  
Transfer Hydrogenation ◽  
Acid Catalysts ◽  
Asymmetric Transfer Hydrogenation ◽  
Reaction Conditions ◽  
Chiral Complexes ◽  
Acetophenone Derivatives ◽  
Aryl Ketones

A series of chiral complexes of the form Ir(NHC)2(aa)(H)(X) (NHC = N-heterocyclic carbene, aa = chelated amino acid, X = halide) was synthesized by oxidative addition of -amino acids to iridium(I) bis-NHC compounds and screened for asymmetric transfer hydrogenation of ketones. Following optimization of the reaction conditions, NHC, and amino acid ligands, high enantioselectivity was achieved when employing the Ir(IMe)2(l-Pro)(H)(I) catalyst (IMe = 1,3-dimethylimidazol-2-ylidene), which asymmetrically reduces a range of acetophenone derivatives in up to 95% enantiomeric excess.

scholarly journals Recent Advances in Rapid Synthesis of Non-proteinogenic Amino Acids from Proteinogenic Amino Acids Derivatives via Direct Photo-Mediated C–H Functionalization

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5270
Author(s):  
Zhenbo Yuan ◽  
Xuanzhong Liu ◽  
Changmei Liu ◽  
Yan Zhang ◽  
Yijian Rao
Keyword(s):  
Amino Acids ◽  
Direct Synthesis ◽  
Environmentally Friendly ◽  
Powerful Method ◽  
Rapid Synthesis ◽  
Conservation Of Energy ◽  
Mild Conditions ◽  
Recent Advances ◽  
Recent Developments

Non-proteinogenic amino acids have attracted tremendous interest for their essential applications in the realm of biology and chemistry. Recently, rising C–H functionalization has been considered an alternative powerful method for the direct synthesis of non-proteinogenic amino acids. Meanwhile, photochemistry has become popular for its predominant advantages of mild conditions and conservation of energy. Therefore, C–H functionalization and photochemistry have been merged to synthesize diverse non-proteinogenic amino acids in a mild and environmentally friendly way. In this review, the recent developments in the photo-mediated C–H functionalization of proteinogenic amino acids derivatives for the rapid synthesis of versatile non-proteinogenic amino acids are presented. Moreover, postulated mechanisms are also described wherever needed.

scholarly journals A New Route to Non-Natural Aryl-Containing Amino Acids and Their Precursors from Thiophenes

2003 ◽  
Vol 2003 (9) ◽  
pp. 527-528 ◽  
Author(s):  
Krishna Gopal Dongol ◽  
Shuntaro Mataka ◽  
Thies Thiemann
Keyword(s):  
Amino Acids ◽  
Reaction Conditions

Thiophenes may be converted to substituted arenes by oxidative cycloaddition to alkynes or by oxidative cycloaddition to alkenes with subsequent oxidative SO-extrusion. Cyano- and acetylamino-groups do not interfere in the reaction and are stable under the reaction conditions. This transformation can be used as a novel route to non-natural aryl-containing amino acids.

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

2004 ◽  
Vol 70 (4) ◽  
pp. 2529-2534 ◽  
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.

scholarly journals Synthesis of new Cα-tetrasubstituted α-amino acids

2009 ◽  
Vol 5 ◽  
Author(s):  
Andreas A Grauer ◽  
Burkhard König
Keyword(s):  
Amino Acids ◽  
Secondary Structure ◽  
Aromatic Aldehydes ◽  
Building Blocks ◽  
Reaction Conditions ◽  
Peptide Backbone ◽  
Aliphatic Aldehydes ◽  
New Class ◽  
Cyclic Amino Acids

Cα-Tetrasubstituted α-amino acids are important building blocks for the synthesis of peptidemimetics with stabilized secondary structure, because of their ability to rigidify the peptide backbone. Recently our group reported a new class of cyclic Cα-tetrasubstituted tetrahydrofuran α-amino acids prepared from methionine and aromatic aldehydes. We now report the extension of this methodology to aliphatic aldehydes. Although such aldehydes are prone to give aldol products under the reaction conditions used, we were able to obtain the target cyclic amino acids in low to moderate yields and in some cases with good diastereoselectivity.

scholarly journals Isolation of Free Amino Acids via Enzymatic Hydrolysis of Tobacco-Derived F1 Protein

2018 ◽  
Vol 28 (4) ◽  
pp. 179-190
Author(s):  
Mehdi Ashraf-Khorassani ◽  
William M. Coleman ◽  
Michael F. Dube ◽  
Larry T. Taylor
Keyword(s):  
Amino Acids ◽  
Enzymatic Hydrolysis ◽  
Free Amino Acids ◽  
Free Amino ◽  
Protein Concentration ◽  
Enzyme Concentration ◽  
Enzymatic Conversion ◽  
Reaction Conditions ◽  
Analytical Methodology ◽  
Hydrolysis Of

SummaryFree amino acids have been isolated via optimized enzymatic hydrolysis of F1 tobacco protein using two cationic resins (Amberlite IR120 and Dowex MAC-2). Optimized enzymatic conversions of the protein as a result of systematic variations in conditions (e.g., time, temperature, pH, enzyme type, enzyme concentration, anaerobic/aerobic environments, and protein concentration) employing commercially available enzymes, were consistently higher than 50% with qualitative amino acid arrays that were consistent with the known composition of tobacco F1 protein. Amberlite IR120 was shown to have a much higher efficiency and capacity for isolation of amino acids from standard solutions and from hydrolysate when compared with the results using Dowex MAC-2. Two columns packed with conditioned Amberlite IR120 (120 × 10 mm,12–15 g resin) and (200 × 25.4 mm, 60–65 g resin) were used to isolate two batches (2.5–3.0 mg and 13–15 mg) of free amino acids, respectively. A relatively inexpensive analytical methodology was developed for rapid analysis of the free amino acids contained within the enzyme hydrolysate. Commercially available enzymes, when employed in optimized reaction conditions, are very effective for enzymatic conversion of tobacco F1 protein to free amino acids.

Peroxovanadates and Its Bio-Mimicking Relation with Vanadium Haloperoxidases

2016 ◽  
pp. 197-219
Author(s):  
Pranjal Saikia ◽  
Saitanya Kumar Bharadwaj ◽  
Abu Taleb Miah
Keyword(s):  
Amino Acids ◽  
Active Site ◽  
High Efficiency ◽  
Recombinant Enzymes ◽  
Vanadium Compounds ◽  
Reaction Conditions ◽  
The Cost ◽  
Major Emphasis ◽  
Protein Active Site

Vanadium Haloperoxidases (VHPOs) have been used in a variety of biotransformations showing remarkable stereoselectivity and regiospecificity. The high efficiency of the enzyme is influenced by the protein active site and the role of certain amino acids in activation of vanadium(V)-bound peroxide for halide oxidation. The use of natural or recombinant enzymes, or biomimetic vanadium compounds brings up issues regarding the cost of production and reaction conditions. In this chapter, the primary intent is to provide a simple and clear picture of functional mimicking nature of peroxovanadium compounds with haloperoxidases enzymes to the readers. Major emphasis would be given to examine the reactivity of the vanadium haloperoxidases with mechanism.

scholarly journals Conversion of CO2 into Chloropropene Carbonate Catalyzed by Iron (II) Phthalocyanine Hypercrosslinked Porous Organic Polymer

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4598
Author(s):  
Eva M. Maya ◽  
Antonio Valverde-González ◽  
Marta Iglesias
Keyword(s):  
Heterogeneous Catalyst ◽  
Direct Synthesis ◽  
Cyclic Carbonate ◽  
Organic Polymer ◽  
Iron Loading ◽  
Reaction Conditions ◽  
Porous Organic Polymer ◽  
Commercial Iron ◽  
Excellent Stability ◽  
Efficient Heterogeneous Catalyst

Commercial iron (II) phthalocyanine (FePc) was knitted with biphenyl using a Friedel–Crafts reaction to yield a micro-meso porous organic polymer (FePc-POP) with a specific surface area of 427 m2/g and 5.42% of iron loading. This strategy allowed for the direct synthesis of a heterogeneous catalyst from an iron containing monomer. The catalytic system, formed by the knitted polymer containing FePc and DMAP (4-dimethylamino pyridine) as base, results in an efficient heterogeneous catalyst in the cycloaddition of CO2 to epichlorohydrin to selectively obtain the corresponding cyclic carbonate. Thus, a TON (mmol substrate converted/mmol catalysts used) value of 2700 was reached in 3 h under mild reaction conditions (solvent free, 90 °C, 3 bar of CO2). The catalyst does not exhibit leaching during the reactions, which was attributed to the excellent stability of the metal in the macrocycle.

Sign in / Sign up

Export Citation Format

Share Document