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 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 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 Morpholin-2-one Derivatives via Intramolecular Acid-Catalyzed Hydroamination

Synthesis ◽  
2019 ◽  
Vol 51 (07) ◽  
pp. 1643-1648 ◽  
Author(s):  
David Knight ◽  
Thomas Wirth ◽  
Abdul Hadi Aldmairi
Keyword(s):  
Amino Acids ◽  
Catalytic Amount ◽  
Practical Method ◽  
Trifluoromethanesulfonic Acid ◽  
Reaction Conditions ◽  
Available N ◽  
Metal Free ◽  
Acid Catalyzed

Substituted morpholin-2-one derivatives were readily obtained in two steps starting from commercially available N-protected amino acids. In a metal-free and practical method, a catalytic amount of trifluoromethanesulfonic acid was sufficient to generate morpholinones under mild reaction conditions in an intramolecular hydroamination reaction in good to excellent yields.

scholarly journals Advances in Chemistry of Isothiocyanate-derived Colourants

2009 ◽  
Vol 27 (Special Issue 1) ◽  
pp. S207-S210
Author(s):  
K. Cejpek ◽  
J. Velíšek
Keyword(s):  
Amino Acids ◽  
Essential Oils ◽  
Maillard Reaction ◽  
Heterogeneous Group ◽  
Model Systems ◽  
Alkaline Media ◽  
Reaction Conditions ◽  
Condensation Products ◽  
Amino Compounds ◽  
Methylene Group

This study is focused on the reactions of isothiocyanates (ITCs) in the presence of amino compounds leading to coloured structures <I>via</I> substituted 2-thiohydantoins. A series of complementary experiments has been done and appropriate reaction conditions and structural prerequisites have been defined. Low-molecular colourants isolated and characterised from the model systems can be sorted into three groups. Yellow to red diastereomeric dehydrodimers of 2-thiohydantoin derivatives that contain an acidic methylene group are formed in mixtures consisted of ITCs and amino acids with &alpha;-methylene group in mild acidic to mild alkaline systems. The condensation products of the 2-thiohydantoins with reactive aromatic or heterocyclic carbaldehydes from the Maillard reaction, essential oils etc. comprise a heterogeneous group of mostly yellow colourants. Blue compounds of two types are structurally more complicated structures that arise from <I>N</I>-substituted amino acids and ITCs in alkaline media.

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.

Oxidations of some α-amino acids under mitsunobu reaction conditions

1988 ◽  
Vol 29 (37) ◽  
pp. 4661-4664 ◽  
Author(s):  
Teodozyj Kolasa ◽  
Marvin J. Miller
Keyword(s):  
Amino Acids ◽  
Mitsunobu Reaction ◽  
Reaction Conditions
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