Squaric esters as peptide stapling reagents

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Biochemistry

Background:

• Peptide stapling is crucial for stabilizing peptide secondary structures.
• Developing efficient and selective methods for peptide stapling is an ongoing challenge.

Purpose of the Study:

• To introduce squaric esters as novel bifunctional reagents for peptide stapling.
• To demonstrate the versatility and stability of squaric amide staples.

Main Methods:

• Utilized squaric esters for selective reactions with amine-containing side chains on peptides.
• Performed peptide stapling on solid-phase synthesis platforms.
• Analyzed stapled peptide structure and stability using circular dichroism and acid-cleavage tests.

Main Results:

• Squaric esters effectively formed stable squaric amide staples under mild conditions.
• Peptide stapling occurred at various positions with diverse amine linkers (e.g., Lysine, ornithine).
• Stapled peptides exhibited enhanced helicity and stability against strong acid treatment.

Conclusions:

• Squaric esters are efficient bifunctional reagents for selective peptide stapling.
• The resulting squaric amide staples enhance peptide helicity and structural stability.
• This methodology provides a valuable approach for peptide engineering and therapeutic development.