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Magazine Chapter 29: Q23. (page 1172)
Devise a synthesis of each peptide from amino acid starting materials: (a) Leu鈥揤al; (b) Ala鈥揑le鈥揋ly.
Short Answer
Expert verified
a.
Protecting Groups
Synthesis of Leu-Val
b.
Synthesis of Ala-Ile-Gly
Step by step solution
01
The structure of Leucine and Valine
The amino acids, Leucine and Valine, exist as shown:
The structure of Leu-Val dipeptide is:
02
The synthesis of Leu-Val dipeptide
The synthesis of Leu-Val dipeptide involves the following steps:
- Protect the amine group in Leucine by reacting with Boc.
- Protect the carboxylic acid group in -Val as a benzyl ester.
- Then both are allowed to react to form the required dipeptide in the presence of DCC.
- In the last step, the protecting groups should be removed.
Protecting Groups
Synthesis of Leu-Val
03
Synthesis of Ala-Ile-Gly
The amine group is protected with Boc(t-butyloxycarbonyl) group, and the carboxylic acid group is protected with benzyl alcohol in the presence of mild acid.
- First, in Ala, the amine group is protected with Boc.
- Next, the 鈥揅OOH group in Ile amino acid is protected with benzyl alcohol.
- Next, these two amino acids are allowed to react with each other then an amide group is formed, a dipeptide of Ala-Ile with protecting groups.
- The carboxylic acid group in glycine is protected. This amino acid is allowed to react with the dipeptide.
Thus, the required tripeptide will be obtained.
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