Selective Deprotonated Amide Activation of Dehydroalanine for Peptide Modification

Area of Science:

• Organic Chemistry
• Peptide Chemistry
• Synthetic Methodology

Background:

• Dehydroalanine (Dha) is a non-canonical amino acid found in various natural products.
• Functionalization of the Dha double bond is challenging due to its unique electronic properties.
• Mild and selective methods for modifying peptides containing Dha are needed.

Purpose of the Study:

• To develop a novel deprotonated amide activation strategy for dehydroalanine.
• To establish a remote functionalization reaction for the Dha double bond.
• To demonstrate the compatibility of the new method with peptide synthesis.

Main Methods:

• Deprotonation of the amide hydrogen in dehydroalanine.
• Utilizing diaryliodonium salts for intermolecular charge transfer.
• Performing reactions under mild conditions compatible with peptide backbones.

Main Results:

• A unique deprotonated amide activation of dehydroalanine was discovered.
• A novel remote functionalization reaction of the Dha double bond was developed.
• The reaction demonstrated good chemoselectivity and site-selectivity.
• The method proved compatible with various peptide structures.

Conclusions:

• The developed method provides a facile route for the remote functionalization of dehydroalanine in peptides.
• Mechanistic studies revealed an electron-rich enamine intermediate and an intermolecular charge transfer process.
• This work expands the toolkit for peptide modification and the synthesis of complex biomolecules.