Chapter 29: Q16. (page 1166)
How many different tripeptides can be formed from three different amino acids?
Short Answer
Two different tripeptides can be formed from three different amino acids.
Chapter 29: Q16. (page 1166)
How many different tripeptides can be formed from three different amino acids?
Two different tripeptides can be formed from three different amino acids.
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Draw the amino acids and peptide fragments formed when the decapeptide A-P-F-L-K-W-S-G-R-G is treated with each reagent or enzyme: (a) chymotrypsin; (b) trypsin; (c) carboxypeptidase; (d)
Devise a synthesis of threonine from diethyl acetamidomalonate.
Draw the organic products formed in each reaction.




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.

Why does a p-nitrophenyl ester “activate” the carboxy group of the first amino acid to amide formation?
Would a p-methoxyphenyl ester perform the same function? Why or why not?

Draw the structure of leu-enkephalin, a pentapeptide that acts as an analgesic and opiate, and has the following sequence: Tyr–Gly–Gly–Phe–Leu. (The structure of a related peptide, met-enkephalin,
appeared in Section 22.6B.)
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