Organic Chemistry
7th Edition
ISBN: 9780321918765
Author: Bruice
Publisher: PEARSON EDUCATION (COLLEGE)
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Textbook Question
Chapter 22, Problem 72P
Propose a mechanism for the rearrangement of the thiazoline obtained from the reaction of Ed man's reagent with a peptide to a PTH-amino acid (page 1014). (Hint: Thioesters are very reactive toward nucleophiles.)
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Another method to form a peptide bond involves a two-step process:[1] Conversion of a Boc-protected amino acid to a p-nitrophenyl ester.[2] Reaction of the p-nitrophenyl ester with an amino acid ester.a. Why does a p-nitrophenyl ester “activate” the carboxy group of the first amino acid to amide formation? b. Would a p-methoxyphenyl ester perform the same function? Why or why not?
The reaction of ninhydrin with an -amino acid occurs in several steps
(a) The first step is loss of water to give a triketone. Show the mechanism of the reaction and the structure of the triketone.(b) The second step is formation of an imine by reaction of the amino acid with the triketone. Show its structure. (c) The third step is a decarboxylation. Show the structure of the product and the mechanism of the decarboxylation reaction.
(d) The fourth step is hydrolysis of an imine to yield an amine and an aldehyde. Show the
structures of both products.
(e) The final step is formation of the purple anion. Show the mechanism of the reaction
Show how phenylalanine can be prepared by reductive amination of an α-ketocarboxylic acid.
Chapter 22 Solutions
Organic Chemistry
Ch. 22.1 - a. Explain why, when the imidazole ring of...Ch. 22.2 - a. Which isomer(R)-alanine or (S)-alanineis...Ch. 22.2 - Prob. 4PCh. 22.3 - Prob. 5PCh. 22.3 - Prob. 6PCh. 22.3 - Draw the predominant form for glutamate in a...Ch. 22.3 - a. Why is the pKa of the glutamate side chain...Ch. 22.4 - Explain why the pI of lysine is the average of the...Ch. 22.4 - Calculate the pI of each of the following amino...Ch. 22.4 - a. Which amino acid has the lowest pI value? b....
Ch. 22.4 - Prob. 13PCh. 22.5 - What aldehyde is formed when valine is treated...Ch. 22.5 - Prob. 15PCh. 22.5 - Prob. 16PCh. 22.5 - Prob. 17PCh. 22.5 - Prob. 18PCh. 22.6 - Why is excess ammonia used in the preceding...Ch. 22.6 - Prob. 20PCh. 22.6 - What amino acid is formed using the...Ch. 22.6 - Prob. 22PCh. 22.6 - What amino acid is formed when the aldehyde used...Ch. 22.7 - Esterase is an enzyme that catalyzes the...Ch. 22.8 - Draw the tetrapeptide Ala-Thr-Asp-Asn and indicate...Ch. 22.8 - Prob. 26PCh. 22.8 - Prob. 27PCh. 22.8 - Which bonds in the backbone of a peptide can...Ch. 22.9 - What is the configuration about each of the...Ch. 22.9 - Glutathione is a tripeptide whose function is to...Ch. 22.10 - What dipeptides would be formed by heating a...Ch. 22.10 - Suppose you are trying to synthesize the dipeptide...Ch. 22.10 - Show the steps in the synthesis of the...Ch. 22.10 - a. Calculate the overall yield of bradykinin when...Ch. 22.11 - Show the steps in the synthesis of the...Ch. 22.13 - Prob. 36PCh. 22.13 - In determining the primary structure of insulin,...Ch. 22.13 - A decapeptide undergoes partial hydrolysis to give...Ch. 22.13 - Explain why cyanogen bromide does not cleave on...Ch. 22.13 - Indicate the peptides produced from cleavage by...Ch. 22.13 - Prob. 42PCh. 22.13 - Three peptides were obtained from a trypsin...Ch. 22.14 - Prob. 44PCh. 22.15 - How would a protein that resides in the nonpolar...Ch. 22.16 - a. Which would have the greatest percentage of...Ch. 22 - Prob. 47PCh. 22 - Glycine has pK2 values of 2.34 and 9.60. At what...Ch. 22 - Prob. 49PCh. 22 - Prob. 50PCh. 22 - Aspartame (its structure is on page 1007) has a pl...Ch. 22 - Draw the form of aspartate that predominates at...Ch. 22 - A professor was preparing a manuscript for...Ch. 22 - Prob. 54PCh. 22 - Determine the amino acid sequence of a polypeptide...Ch. 22 - Prob. 56PCh. 22 - Which is the more effective buffer at...Ch. 22 - Identify the location and type of charge on the...Ch. 22 - Draw the product obtained when a lysine side chain...Ch. 22 - After the polypeptide shown below was treated with...Ch. 22 - Treatment of a polypeptide with 2-mercaptoethanol...Ch. 22 - Show how aspartame can be synthesized using DCCD.Ch. 22 - -Amino acids can be prepared by treating an...Ch. 22 - Reaction of a polypeptide with carboxypeptidase A...Ch. 22 - a. How many different octapeptides can be made...Ch. 22 - Glycine has pKa values of 2.3 and 9.6. Do you...Ch. 22 - A mixture of 15 amino acids gave the fingerprint...Ch. 22 - Write the mechanism for the reaction of an amino...Ch. 22 - Prob. 69PCh. 22 - Show how valine can be prepared by a. a...Ch. 22 - A chemist wanted to test his hypothesis that the...Ch. 22 - Propose a mechanism for the rearrangement of the...Ch. 22 - A normal polypeptide and a mutant of the...Ch. 22 - Determine the amino acid sequence of a polypeptide...
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- Show how phenylalanine can be prepared by reductive amination of an a-ketocarboxylic acid.arrow_forwardShow how you could prepare the following -amino acids from the appropriate carboxylic acids: (a) Phenylalanine (b) Valinearrow_forwardThe reaction of ninhydrin with an -amino acid occurs in several steps (a) The first step is loss of water to give a triketone. Show the mechanism of the reaction andthe structure of the triketonearrow_forward
- An unknown decapeptide was isolated and characterized. Complete hydrolysis of this peptide gave : F(2), A,G,C,K,N,T, W and V. Treatment with carboxypeptidase releases A. Reaction with Edman’s reagent gave PTH-T and a nonapeptide. The nonapeptide was treated with trypsin and gave 2 peptides: (V-C-G-A) and (N-FF-W-K). Give the sequence of amino acid in the decapeptide.arrow_forwardA nonapeptide released by globulins in the blood in response to a waspsting. Hydrolysis gives the following amino acids: 2 Arg, Gly, 2 Phe, 3 Pro, and Ser.Edman degradation gives phenylthiohydantoin of Arg. Cleavage with carboxypeptidase gives Arg. Partial hydrolysis gives the following di- and tripeptides: Phe-Ser, Pro-GlyPhe, Pro-Pro, Ser-Pro-Phe, Phe-Arg, and Arg-Pro. What is the amino acid sequence of this peptide?arrow_forward
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