A tripeptide on treatment with PhNCS (pH = 8.0) followed by heating with dilute HCl afforded a cyclic… · ABC26OR0522
Subject: Organic Chemistry · Chapter: Natural Products · Topic: Natural Products & – General · Exam: GATE 2000-2022 · Marks: 2 · Difficulty: Medium
A tripeptide on treatment with PhNCS (pH = 8.0) followed by heating with dilute HCl afforded a cyclic compound M and a dipeptide. The dipeptide on treatment with PhNCS (pH = 8.0) followed by heating with dilute HCl afforded a cyclic compound N and an acyclic compound O. The CORRECT sequence (from N- to C-terminus) of the tripeptide is M = 
N = 
O = $\mathrm{HO_2C-CH(NH_2)-CH(CH_3)_2}$
N = O = $\mathrm{HO_2C-CH(NH_2)-CH(CH_3)_2}$(a)glycine-phenylalanine-valine
(b)valine-phenylalanine-glycine
(c)glycine-tyrosine-valine
(d)glycine-phenylalanine-alanine
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
The first Edman cycle releases PTH-Gly (M), the second PTH-Phe (N), and valine (O) remains. The sequence is Gly–Phe–Val (a).
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