Conformational Analysis of Helical Peptides Incorporating Azepane-Based β-Amino Acids Prepared by an...

Area of Science:

• Chemical Synthesis
• Peptide Chemistry
• Structural Biology

Background:

• Unnatural amino acids are crucial for designing novel peptide structures and functions.
• Developing efficient synthesis methods for non-canonical amino acids is essential for peptide research.
• Understanding the conformational preferences of amino acids in peptides informs biomaterial design.

Purpose of the Study:

• To synthesize cis-5-aminoazepane-4-carboxylic acid (cis-AAzC) using an improved method.
• To investigate the conformational behavior of cis-AAzC within unnatural peptide sequences.
• To evaluate the impact of cis-AAzC on peptide helical propensity and aqueous solubility.

Main Methods:

• Ultrasound-assisted reductive amination for cis-AAzC synthesis.
• Incorporation of cis-AAzC into 1:1 α/β-peptides and β-peptides.
• Circular dichroism spectroscopy to analyze secondary structures.
• X-ray crystallography to determine peptide crystal structures.

Main Results:

• An optimized ultrasound-assisted method enhanced cis-AAzC synthesis yield and reduced solvent use.
• cis-AAzC incorporation induced the 11/9-helix in 1:1 α/β-peptides.
• cis-AAzC promoted the 12/10-helix in β-peptides, increasing aqueous solubility.
• Azepane moiety functionalization was tolerated without compromising helical propensity.

Conclusions:

• cis-5-aminoazepane-4-carboxylic acid is a valuable building block for helical peptides.
• The developed synthesis method is efficient and environmentally conscious.
• cis-AAzC-containing peptides exhibit unique helical structures and improved solubility, with potential applications in biomaterials.