scholarly journals α-Amino Acids as Synthons in the Ugi-5-Centers-4-Components Reaction: Chemistry and Applications

Symmetry ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 798 ◽  
Author(s):  
Sveva Pelliccia ◽  
Ilenia Antonella Alfano ◽  
Ubaldina Galli ◽  
Ettore Novellino ◽  
Mariateresa Giustiniano ◽  
...  
Keyword(s):  
Amino Acids ◽  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Organic Reactions ◽  
Peptide Mimetics ◽  
Atom Economy ◽  
Organic Transformations ◽  
Huge Variety ◽  
Gain Access

Since the first reports, the Ugi four-component reaction (U-4CR) has been recognized as a keystone transformation enabling the synthesis of peptide mimetics in a single step and with high atom economy. In recent decades, the U-4CR has been a source of inspiration for many chemists fascinated by the possibility of identifying new efficient organic reactions by simply changing one of the components or by coupling in tandem the multicomponent process with a huge variety of organic transformations. Herein we review the synthetic potentialities, the boundaries, and the applications of the U-4CR involving α-amino acids, where the presence of two functional groups—the amino and the carboxylic acids—allowed a 5-center 4-component Ugi-like reaction, a powerful tool to gain access to drug-like multi-functionalized scaffolds.

Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

2018 ◽  
Author(s):  
Erin Stache ◽  
Alyssa B. Ertel ◽  
Tomislav Rovis ◽  
Abigail G. Doyle
Keyword(s):  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Direct Access ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Synthetic Strategy ◽  
Acyl Radicals ◽  
Benzyl Radicals ◽  
Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

2018 ◽  
Author(s):  
Erin Stache ◽  
Alyssa B. Ertel ◽  
Tomislav Rovis ◽  
Abigail G. Doyle
Keyword(s):  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Direct Access ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Synthetic Strategy ◽  
Acyl Radicals ◽  
Benzyl Radicals ◽  
Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

Quinone C–H Alkylations via Oxidative Radical Processes

Synthesis ◽  
2018 ◽  
Vol 50 (15) ◽  
pp. 2915-2923 ◽  
Author(s):  
Ryan Baxter ◽  
Akil Hamsath ◽  
Jordan Galloway
Keyword(s):  
Amino Acids ◽  
Kinetic Analysis ◽  
Carboxylic Acids ◽  
Functional Groups ◽  
Alkyl Radical ◽  
Radical Initiation ◽  
Radical Processes

A brief survey of radical additions to quinones is reported. Carboxylic acids, aldehydes, and unprotected amino acids are compared as alkyl radical precursors for the mono- or bis- C–H alkylation of several quinones. Two methods for radical initiation are discussed comparing inorganic persulfates and Selectfluor as stoichiometric oxidants. Kinetic analysis reveals dramatic differences in the rate of radical initiation depending on the identity of the radical precursor and oxidant. Synthetic strategies for efficiently producing alkyl-quinones are discussed in the context of selecting optimum radical precursors and initiators depending on quinone identity and functional groups present.

scholarly journals Synthesis of γ-Oxo-α-amino Acids via Radical Acylation with Carboxylic Acids

2020 ◽  
Author(s):  
Kay Merkens ◽  
Francisco José Aguilar Troyano ◽  
Khadijah Anwar ◽  
Adrián Gómez Suárez
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Carboxylic Acids ◽  
Functional Groups ◽  
Photoredox Catalysis ◽  
Average Yield ◽  
Highly Efficient ◽  
Wide Range ◽  
Acyl Radicals

Herein we present a highly efficient, light-mediated, deoxygenative protocol to access g-oxo-a-amino acid derivatives.This radical methodology employs photoredox catalysis, in combination with triphenylphosphine, to generate acyl radicals from readily available (hetero)aromatic and vinylic carboxylic acids. This approach allows for the straightforward synthesis of g-oxo-aamino acids bearing a wide range of functional groups (e.g. Cl, CN, furan, thiophene, Bpin) in synthetically useful yields (~ 60% average yield). To further highlight the utility of the methodology, several deprotection and derivatization reactions were carried out.

scholarly journals Synthesis of γ-Oxo-α-amino Acids via Radical Acylation with Carboxylic Acids

2020 ◽  
Author(s):  
Kay Merkens ◽  
Francisco José Aguilar Troyano ◽  
Khadijah Anwar ◽  
Adrián Gómez Suárez
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Carboxylic Acids ◽  
Functional Groups ◽  
Photoredox Catalysis ◽  
Average Yield ◽  
Highly Efficient ◽  
Wide Range ◽  
Acyl Radicals

Herein we present a highly efficient, light-mediated, deoxygenative protocol to access g-oxo-a-amino acid derivatives.This radical methodology employs photoredox catalysis, in combination with triphenylphosphine, to generate acyl radicals from readily available (hetero)aromatic and vinylic carboxylic acids. This approach allows for the straightforward synthesis of g-oxo-aamino acids bearing a wide range of functional groups (e.g. Cl, CN, furan, thiophene, Bpin) in synthetically useful yields (~ 60% average yield). To further highlight the utility of the methodology, several deprotection and derivatization reactions were carried out.

scholarly journals Synthesis of γ-Oxo-α-amino Acids via Radical Acylation with Carboxylic Acids

2020 ◽  
Author(s):  
Kay Merkens ◽  
Francisco José Aguilar Troyano ◽  
Khadijah Anwar ◽  
Adrián Gómez Suárez
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Carboxylic Acids ◽  
Functional Groups ◽  
Photoredox Catalysis ◽  
Average Yield ◽  
Highly Efficient ◽  
Wide Range ◽  
Acyl Radicals

Herein we present a highly efficient, light-mediated, deoxygenative protocol to access g-oxo-a-amino acid derivatives.This radical methodology employs photoredox catalysis, in combination with triphenylphosphine, to generate acyl radicals from readily available (hetero)aromatic and vinylic carboxylic acids. This approach allows for the straightforward synthesis of g-oxo-aamino acids bearing a wide range of functional groups (e.g. Cl, CN, furan, thiophene, Bpin) in synthetically useful yields (~ 60% average yield). To further highlight the utility of the methodology, several deprotection and derivatization reactions were carried out.

Asymmetric Synthesis of Fused Tetrahydroquinolines via Intramolecular Aza-Diels-Alder Reaction of ortho-Quinone Methide Imines

Synthesis ◽  
2021 ◽  
Author(s):  
Fabian Hofmann ◽  
Cornelius Gärtner ◽  
Martin Kretzschmar ◽  
Christoph Schneider
Keyword(s):  
Asymmetric Synthesis ◽  
Alder Reaction ◽  
Single Step ◽  
Diels Alder ◽  
Quinone Methide ◽  
Bronsted Acid ◽  
Atom Economy ◽  
Diels Alder Reaction ◽  
Brönsted Acid ◽  
Chiral Bronsted Acid

Aza-Diels Alder reactions are straightforward processes in the construction of N-heterocycles, featuring inherent atom-economy and stereospecificity. Intramolecular strategies allow formation of bicyclic core structures with up to three stereocenters within a single step. Herein, this concept is combined with the chemistry of chiral Brønsted acid-bound ortho-quinone methide imines generating a range of interesting fused tetrahydro-quinolines in a diastereo- and enantioselective manner.

scholarly journals Non-Enzymatic Desymmetrization Reactions in Aqueous Media

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 720
Author(s):  
Satomi Niwayama
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Functional Groups ◽  
Organic Compounds ◽  
Recent Progress ◽  
Aqueous Media ◽  
Building Blocks ◽  
Organic Reactions ◽  
Environmentally Benign ◽  
Enzymatic Desymmetrization

Symmetric organic compounds are generally obtained inexpensively, and therefore they can be attractive building blocks for the total synthesis of various pharmaceuticals and natural products. The drawback is that discriminating the identical functional groups in the symmetric compounds is difficult. Water is the most environmentally benign and inexpensive solvent. However, successful organic reactions in water are rather limited due to the hydrophobicity of organic compounds in general. Therefore, desymmetrization reactions in aqueous media are expected to offer versatile strategies for the synthesis of a variety of significant organic compounds. This review focuses on the recent progress of desymmetrization reactions of symmetric organic compounds in aqueous media without utilizing enzymes.

The potential mechanism of atmospheric new particle formation involving amino acids with multiple functional groups

2021 ◽  
Author(s):  
Jiarong Liu ◽  
Ling Liu ◽  
Hui Rong ◽  
Xiuhui Zhang
Keyword(s):  
Amino Acids ◽  
Aspartic Acid ◽  
Functional Groups ◽  
Atmospheric Aerosols ◽  
Potential Role ◽  
Particle Formation ◽  
Potential Mechanism ◽  
New Particle Formation

Amino acids are recognized as significant components of atmospheric aerosols. However, its potential role in the atmospheric new particle formation (NPF) is poorly understood, especially aspartic acid (ASP), one of...

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