(a) The mechanism using curved arrows to show the flow of electrons is to be suggested for the given cyclization reaction. (b) A stepwise mechanism is to be written for the hydrolysis of the conjugate acid of the iminolactone to corresponding lactone that cleaves the peptide chain. Concept Introduction: Cyanogen bromide adds to the sulfur atom of the methionine residue forming a sulfonium ion. The sulfonium ion cyclizes to form an iminolactone. Iminolactone undergoes hydrolysis, cleaving the bond between nitrogen and the ring carbon. This results in the peptide chain being cleaved between carbonyl of the methionine residue and the next amino acid.

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Chapter 26, Problem 44P

Interpretation Introduction

Interpretation:

(a) The mechanism using curved arrows to show the flow of electrons is to be suggested for the given cyclization reaction.

(b) A stepwise mechanism is to be written for the hydrolysis of the conjugate acid of the iminolactone to corresponding lactone that cleaves the peptide chain.

Concept Introduction:

Cyanogen bromide adds to the sulfur atom of the methionine residue forming a sulfonium ion.

The sulfonium ion cyclizes to form an iminolactone.

Iminolactone undergoes hydrolysis, cleaving the bond between nitrogen and the ring carbon. This results in the peptide chain being cleaved between carbonyl of the methionine residue and the next amino acid.

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