α/β-Chimera peptide synthesis with cyclic β-sugar amino acids: the efficient coupling protocol

Area of Science:

• Peptide Chemistry
• Organic Synthesis
• Biochemistry

Background:

• Peptide synthesis traditionally involves α-amino acids.
• Incorporating cyclic β-Sugar Amino Acids (β-SAA) into peptide structures presents unique synthetic challenges.
• Developing efficient methods for β-SAA incorporation is crucial for expanding peptide diversity.

Purpose of the Study:

• To report the solid-phase synthesis of -GXXG- chimera peptides incorporating cyclic β-Sugar Amino Acids (β-SAA).
• To systematically investigate and compare different coupling strategies and reagents for β-SAA incorporation.
• To identify the optimal conditions for efficient synthesis of β-SAA containing peptides.

Main Methods:

• Solid-phase synthesis of chimera peptides using Fmoc-protected amino acids.
• Utilizing cyclic β-Sugar Amino Acids (β-SAA) with furanoid and pyranoid structures.
• Comparative analysis of coupling reagents (PyBOP, HATU, HOBt) and conditions.
• Time-resolved 1H-NMR spectroscopy to assess Fmoc-protected active ester formation and stability.

Main Results:

• Successful synthesis of -GXXG- chimera peptides containing furanoid and pyranoid β-SAA.
• PyBOP was identified as the optimal coupling reagent for both β-SAA prototypes.
• Time-resolved 1H-NMR confirmed PyBOP's superiority in forming stable active esters.

Conclusions:

• The optimized solid-phase synthesis strategy enables efficient construction of β-SAA containing peptides.
• This methodology provides a viable route for synthesizing diverse β-SAA containing homo- and heterooligomers.
• The findings advance the field of peptide chemistry by facilitating the incorporation of non-canonical amino acids.