Rapid, traceless and facile peptide cyclization enabled by tetrazine-thiol exchange

Area of Science:

• Chemical Biology
• Medicinal Chemistry
• Synthetic Chemistry

Background:

• Cyclic peptides offer superior stability and binding affinity compared to linear peptides.
• Traditional peptide cyclization methods require complex protecting groups or specific ligation strategies.
• Developing efficient and mild cyclization techniques is crucial for peptide-based therapeutics.

Purpose of the Study:

• To introduce a novel, rapid, and traceless method for in situ peptide cyclization.
• To demonstrate the utility of chemoselective tetrazine-thiol exchange for peptide cyclization.
• To highlight the advantages of this method for generating cyclic peptide libraries.

Main Methods:

• Incorporation of N-terminal sulfide-bearing unsymmetric tetrazines into peptides using solid-phase peptide synthesis.
• Spontaneous tetrazine-thiol exchange reaction with internal cysteines at pH 6.5.
• Assessment of cyclized peptide stability under various conditions, including excess free thiols.

Main Results:

• The tetrazine-thiol exchange reaction proceeds rapidly and tracelessly under mild, acidic conditions.
• The method is orthogonal to standard solid-phase peptide synthesis and trifluoroacetic acid cleavage.
• Generated cyclic peptides exhibit high stability, even in the presence of competing thiols.

Conclusions:

• Chemoselective tetrazine-thiol exchange is a powerful and efficient tool for in situ peptide cyclization.
• This method simplifies cyclic peptide synthesis and is compatible with library generation.
• The approach holds significant potential for accelerating drug discovery and development efforts.