Textbook Question
Propose a mechanism for the rearrangement of the thiazoline obtained from the reaction of Edman's reagent with a peptide to a PTH-amino acid. (Hint: Thioesters are very reactive toward nucleophiles.)
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Ch. 21 - Amino Acids, Peptides, and Proteins
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 22, Problem 75d
Show how valine can be prepared by
d. a N-phthalimidomalonic ester synthesis.
Verified step by step guidance1
Step 1: Understand the N-phthalimidomalonic ester synthesis. This method involves the use of diethyl malonate, phthalimide, and a suitable alkyl halide to synthesize α-amino acids. The phthalimide group protects the amine functionality during the reaction.
Step 2: Start with the N-phthalimidomalonic ester. This compound is prepared by reacting diethyl malonate with phthalimide in the presence of a base such as potassium carbonate (K₂CO₃).
Step 3: Perform the alkylation step. Treat the N-phthalimidomalonic ester with isopropyl bromide (CH₃-CHBr-CH₃) in the presence of a strong base like sodium ethoxide (NaOEt). This step introduces the isopropyl group, which is the side chain of valine.
Step 4: Hydrolyze and decarboxylate. Hydrolyze the ester groups using aqueous acid or base to form the corresponding dicarboxylic acid. Then, heat the compound to decarboxylate one of the carboxylic acid groups, forming the intermediate α-amino acid with the phthalimide group still attached.
Step 5: Remove the phthalimide protecting group. Treat the intermediate with hydrazine (NH₂NH₂) to remove the phthalimide group, yielding valine as the final product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
N-phthalimidomalonic Ester Synthesis
N-phthalimidomalonic ester synthesis is a method used to synthesize amino acids, particularly through the reaction of phthalimide with malonic ester. This reaction involves the formation of a phthalimide derivative that can undergo hydrolysis and decarboxylation to yield the desired amino acid. The process is notable for its ability to introduce a side chain to the amino acid, making it a valuable tool in organic synthesis.
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Synthesis of Amino Acids: N-Phthalimidomalonic Ester Synthesis Example 2
Valine Structure and Properties
Valine is an essential branched-chain amino acid characterized by its isopropyl side chain. It plays a crucial role in protein synthesis and is important for muscle metabolism and tissue repair. Understanding valine's structure helps in recognizing how it can be synthesized through various organic reactions, including the N-phthalimidomalonic ester synthesis.
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Decarboxylation in Organic Synthesis
Decarboxylation is a chemical reaction that involves the removal of a carboxyl group from a molecule, releasing carbon dioxide. In the context of amino acid synthesis, decarboxylation is often a key step that transforms intermediates into the final amino acid product. This reaction is essential for converting malonic acid derivatives into amino acids like valine, as it helps in forming the correct carbon skeleton.
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Related Practice
Textbook Question
Show how valine can be prepared by
c. a reductive amination.
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Textbook Question
Dithiothreitol reacts with disulfide bridges in the same way that 2-mercaptoethanol does. With dithiothreitol, however, the equilibrium lies much more to the right. Explain.
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Textbook Question
Show how valine can be prepared by
a. a Hell–Volhard–Zelinski reaction.