Question

The maximum number of dipeptides that could be obtained by reaction of phenylalanine with leucine is .............

Hint:

Dipeptides differ based on the sequence and chirality of constituent amino acids.

Answer 1

Correct Answer: 2

Step 1: Understanding dipeptide formation.
A dipeptide forms when two different amino acids join through a peptide bond. The order of amino acids matters: A–B and B–A are different molecules.
Step 2: Considering chirality of amino acids.
Both phenylalanine and leucine are chiral (each has one stereocenter). Each chiral amino acid exists as L and D enantiomers when considered for maximum possibilities.
Step 3: Counting possible dipeptides.
Two amino acids (A and B) can produce four stereochemically distinct dipeptides:
1. L-Phe–L-Leu
2. L-Leu–L-Phe
3. D-Phe–D-Leu
4. D-Leu–D-Phe
Thus, the maximum number is 4.
Step 4: Conclusion.
Hence, phenylalanine and leucine together can form a maximum of four dipeptides.