Textbook Question
The first amino acid in the pentapeptide of Figure 26.50, Pyr, is not one of the 20 amino acids in Table 26.1. Based on the following structure of Pyr, from which natural amino acid is it likely derived?
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Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 25, Problem 18b
Provide a synthesis of the following amino acids using a combination of the HVZ and amination reactions.
b. Leu
Verified step by step guidance1
Identify the starting material: Begin with a carboxylic acid that has a similar carbon skeleton to leucine. For leucine, you can start with isovaleric acid (3-methylbutanoic acid).
Apply the Hell-Volhard-Zelinsky (HVZ) reaction: Treat the isovaleric acid with bromine (Br2) and phosphorus tribromide (PBr3) to brominate the alpha position of the carboxylic acid, forming an alpha-bromo acid.
Prepare for amination: Convert the alpha-bromo acid into an alpha-amino acid by treating it with ammonia (NH3). This step involves a nucleophilic substitution where the bromine atom is replaced by an amino group.
Ensure stereochemistry: If necessary, use a chiral auxiliary or a chiral catalyst to ensure the correct stereochemistry of the amino acid, as leucine is chiral.
Finalize the synthesis: Purify the product to obtain leucine, ensuring that the amino acid is in its correct L-configuration, which is the naturally occurring form in proteins.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
HVZ Reaction
The Hell-Volhard-Zelinsky (HVZ) reaction is a halogenation process used to introduce a halogen atom, typically bromine, at the alpha position of a carboxylic acid. This reaction involves the use of phosphorus tribromide (PBr3) and bromine (Br2) to convert the carboxylic acid into an alpha-bromo acid, which is a key intermediate for further transformations.
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Amino Acid Synthesis: HVZ Method Concept 1
Amination Reaction
Amination is a chemical process that introduces an amino group (-NH2) into a molecule. In the context of synthesizing amino acids, amination typically involves the conversion of an alpha-bromo acid into an amino acid by replacing the bromine atom with an amino group, often using ammonia or an amine as the nucleophile.
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03:46Buchwald-Hartwig Amination Reaction
Synthesis of Leucine
Leucine synthesis involves creating the specific structure of this branched-chain amino acid. Starting with a suitable precursor, such as isovaleric acid, the HVZ reaction introduces a bromine atom at the alpha position. Subsequent amination replaces the bromine with an amino group, yielding leucine, which is characterized by its isobutyl side chain.
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Related Practice
Textbook Question
Why are conjugated molecules like the product of the ninhydrin reaction brightly colored?
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Textbook Question
Give the pKa value of the following compounds.
b.
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Textbook Question
Calculate the equilibrium constant for the reaction of ethylamine and propanoic acid. Which side is favored?
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Textbook Question
Although there is free rotation around most σ bonds, rotation is restricted around the C--N bond of an amide. Explain why this is true.
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Textbook Question
Provide a mechanism for the protection of the amine as the benzylcarbamate shown in Figure 26.33(a). <IMAGE>
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