Phosphite-Mediated Peptide Bond Formation through Fragment Condensation

Area of Science:

• Organic Chemistry
• Peptide Chemistry
• Green Chemistry

Background:

• Triaryl phosphites are emerging as sustainable reagents for condensation reactions, especially in peptide bond formation.
• Peptide fragment condensation is a key strategy for synthesizing oligopeptides, which are prevalent in bioactive molecules.
• A major challenge in peptide synthesis is epimerization at stereocenters, often caused by oxazolone formation during C-terminal activation.

Purpose of the Study:

• To investigate the utility of triaryl phosphites, specifically tri(p-tolyl)phosphite, in oligopeptide synthesis via fragment condensation.
• To evaluate the epimerization-suppressing capabilities of this method during peptide fragment coupling.
• To assess the compatibility of the method with various peptide sequences and functional groups.

Main Methods:

• Application of tri(p-tolyl)phosphite for peptide fragment condensation.
• Synthesis of various oligopeptides, including those with diverse functional groups and unprotected side chains.
• Validation of the method through the multi-step synthesis of a specific hexapeptide.

Main Results:

• Tri(p-tolyl)phosphite effectively suppressed epimerization during peptide fragment condensation.
• The method demonstrated broad applicability to peptides with diverse functional groups, including sensitive ones.
• Successful synthesis of hexapeptide-10 in 10 steps with a 55% overall yield was achieved, validating the approach.
• Compatibility with certain unprotected amino acid side chains was observed.

Conclusions:

• Triaryl phosphite-mediated peptide fragment condensation is a robust and efficient method for oligopeptide synthesis.
• This approach minimizes epimerization, a critical issue in peptide chemistry.
• The method's compatibility and efficiency make it suitable for synthesizing complex bioactive peptides and improving operational efficiency in peptide synthesis.