Chapter 24: Q25P (page 1289)
Show how you would synthesize Leu-Gly-Ala-Val-Phe starting with Fmoc-Ala-Val-Phe— P
Short Answer
The synthesis of Leu-Gly-Ala-Val-Phe starting from Fmoc-Ala-Val-Phe-P is given as follows:


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Chapter 24: Q25P (page 1289)
Show how you would synthesize Leu-Gly-Ala-Val-Phe starting with Fmoc-Ala-Val-Phe— P
The synthesis of Leu-Gly-Ala-Val-Phe starting from Fmoc-Ala-Val-Phe-P is given as follows:


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There are many methods for activating a carboxylic acid in preparation for coupling with an amine. The following method converts the acid to an N-hydroxysuccinimide (NHS) ester.

(a) Explain why an NHS ester is much more reactive than a simple alkyl ester.
(b) Propose a mechanism for the reaction shown.
(c) Propose a mechanism for the reaction of the NHS ester with an amine, R-NH2
Show how you would use the Strecker synthesis to make isoleucine. What stereochemistry would you expect in your synthetic product?
Peptides often have functional groups other than free amino groups at the N terminus and other than carboxyl groups at the C terminus.
(a) A tetrapeptide is hydrolyzed by heating with 6 M, and the hydrolysate is found to contain Ala, Phe, Val, and Glu. When the hydrolysate is neutralized, the odor of ammonia is detected. Explain where this ammonia might have been incorporated in the original peptide.
(b) The tripeptide thyrotropic hormone releasing factor(TRF) has the full name pyroglutamylhistidylprolinamide. The structure appears here. Explain the functional groups at the N terminus and at the C terminus.

(c)On acidic hydrolysis, an unknown pentapeptide gives glycine, alanine, valine, leucine and isoleucine. No odor of ammonia is detected when the hydrolysate is neutralized. Reaction with phenyl isothiocyanate followed by mild hydrolysis gives nophenylthiohydantoin derivative. Incubation with carboxypeptidase has no effect. Explain these findings.
Draw the complete structures of the following peptides:
(a) Thr-Phe-Met (b) Serylarginylglycylphenylalanine (c) IMQDK (d) ELVIS
Show the third and fourth steps in the sequencing of oxytocin. Use figure 24-14 as a guide.
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