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 28
Provide a mechanism for the protection of the amine as the benzylcarbamate shown in Figure 26.33(a). <IMAGE>
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Identify the amine group in the molecule that needs to be protected. The amine group typically contains a nitrogen atom bonded to hydrogen atoms or alkyl groups.
Select the protecting group for the amine. In this case, the benzylcarbamate group is used, which is derived from benzyl chloroformate.
React the amine with benzyl chloroformate. This reaction typically occurs in the presence of a base, such as triethylamine, to neutralize the hydrochloric acid byproduct and facilitate the formation of the carbamate linkage.
The mechanism involves the nucleophilic attack of the nitrogen atom of the amine on the carbonyl carbon of the benzyl chloroformate, forming a tetrahedral intermediate.
The intermediate collapses, expelling the chloride ion and forming the benzylcarbamate-protected amine. This step completes the protection of the amine group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Amine Protection
Amine protection is a strategy used in organic synthesis to temporarily mask the reactivity of an amine group. This is crucial when multiple functional groups are present, and selective reactions are needed. Protecting groups, like benzylcarbamate, are introduced to prevent unwanted reactions at the amine site, allowing for selective transformations elsewhere in the molecule.
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Acetal Protecting Group
Benzylcarbamate Formation
Benzylcarbamate is a common protecting group for amines, formed by reacting an amine with benzyl chloroformate. This reaction typically involves nucleophilic attack by the amine on the carbonyl carbon of benzyl chloroformate, followed by the release of hydrochloric acid. The resulting benzylcarbamate is stable under a variety of conditions, making it a versatile choice for protection.
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Reaction Mechanism
Understanding the reaction mechanism involves detailing the step-by-step process by which reactants are converted to products. For amine protection with benzylcarbamate, the mechanism includes nucleophilic attack, formation of a tetrahedral intermediate, and subsequent elimination of a leaving group. This mechanistic insight is essential for predicting reaction outcomes and troubleshooting synthetic challenges.
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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
Calculate the equilibrium constant for the reaction of ethylamine and propanoic acid. Which side is favored?
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Textbook Question
Draw the following amino acids in all possible protonation states as you move from high pH to low pH.
b. His
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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 synthesis of the following amino acids using a combination of the HVZ and amination reactions.
b. Leu
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