Textbook Question
Show how you would synthesize any of the standard amino acids from each starting material. You may use any necessary reagents.
(c)
Ch. 24 - Amino Acids, Peptides, and Proteins
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 24, Problem 31c,d
Show how you would convert alanine to the following derivatives. Show the structure of the product in each case.
(c) N-benzyloxycarbonyl alanine
(d) tert-butyloxycarbonyl alanine
Verified step by step guidance1
Step 1: Begin with the structure of alanine, which is an amino acid with the formula CH₃CH(NH₂)COOH. Alanine has both an amino group (-NH₂) and a carboxylic acid group (-COOH).
Step 2: For part (c), N-benzyloxycarbonyl alanine, the goal is to protect the amino group (-NH₂) by converting it into an N-benzyloxycarbonyl group. This is typically achieved using benzyl chloroformate (C₆H₅CH₂OCOCl) in the presence of a base such as Na₂CO₃ or NaHCO₃. The reaction proceeds via nucleophilic attack of the amino group on the carbonyl carbon of benzyl chloroformate.
Step 3: Write the structure of the product for part (c). The amino group (-NH₂) is now protected as -NHCOOCH₂C₆H₅, while the carboxylic acid group (-COOH) remains unchanged. The structure of N-benzyloxycarbonyl alanine is CH₃CH(NHCOOCH₂C₆H₅)COOH.
Step 4: For part (d), tert-butyloxycarbonyl alanine, the goal is to protect the amino group (-NH₂) by converting it into a tert-butyloxycarbonyl (Boc) group. This is typically achieved using di-tert-butyl dicarbonate ((Boc)₂O) in the presence of a base such as Na₂CO₃ or NaHCO₃. The reaction proceeds via nucleophilic attack of the amino group on the carbonyl carbon of the Boc reagent.
Step 5: Write the structure of the product for part (d). The amino group (-NH₂) is now protected as -NHCOO(C(CH₃)₃), while the carboxylic acid group (-COOH) remains unchanged. The structure of tert-butyloxycarbonyl alanine is CH₃CH(NHCOO(C(CH₃)₃))COOH.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Amino Acid Structure
Amino acids, like alanine, have a central carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain (R group). Understanding the structure of alanine is crucial for recognizing how modifications, such as protecting groups, can be added to the amino or carboxyl functional groups during chemical reactions.
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Charged Amino Acids
Protecting Groups
Protecting groups are temporary modifications used in organic synthesis to prevent certain functional groups from reacting during a chemical transformation. In the case of N-benzyloxycarbonyl (Z) and tert-butyloxycarbonyl (Boc) derivatives, these groups protect the amino group of alanine, allowing for selective reactions at the carboxyl group or other sites without interference.
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Reactions of Amino Acids
The conversion of alanine to its derivatives involves specific organic reactions, such as acylation or alkylation. For N-benzyloxycarbonyl alanine, the reaction typically involves the introduction of the benzyloxycarbonyl group through coupling reactions, while tert-butyloxycarbonyl alanine is formed using the Boc group, which is often introduced via a reaction with di-tert-butyl dicarbonate. Understanding these reactions is essential for predicting the structures of the final products.
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Related Practice
Textbook Question
Suggest a method for the synthesis of the unnatural D enantiomer of alanine from the readily available L enantiomer of lactic acid.
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Textbook Question
Aspartame (Nutrasweet®) is a remarkably sweet-tasting dipeptide ester. Complete hydrolysis of aspartame gives phenyl alanine, aspartic acid, and methanol. Mild incubation with carboxypeptidase has no effect on aspartame. Treatment of aspartame with phenyl isothiocyanate, followed by mild hydrolysis, gives the phenylthiohydantoin of aspartic acid. Propose a structure for aspartame.
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Textbook Question
Show how you would convert alanine to the following derivatives. Show the structure of the product in each case.
(a) alanine isopropyl ester
(b) N-benzoylalanine
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Textbook Question
Show how you would synthesize any of the standard amino acids from each starting material. You may use any necessary reagents.
(b)
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Textbook Question
Show how you would use the Strecker synthesis to make tryptophan. What stereochemistry would you expect in your synthetic product?
1
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