Turn-Induction in Peptides Incorporating Novel Cyrene-Derived α,α-Disubstituted Amino Acid

Area of Science:

• Organic Chemistry
• Peptide Chemistry
• Structural Biology

Background:

• α,α-disubstituted amino acids are valuable peptide building blocks.
• Exploring novel amino acid structures expands chemical diversity.
• Cyrene-derived amino acids (H-Cyr-OH) present a unique structural motif.

Purpose of the Study:

• To introduce cyrene-derived α,α-disubstituted amino acids (H-Cyr-OH) into peptides.
• To investigate the conformational properties of Cyr monomers and dimers.
• To assess the potential of Cyr residues in peptide secondary structure formation.

Main Methods:

• Multiple component Ugi reaction for peptide synthesis.
• X-ray crystallography for solid-state conformational analysis.
• NMR spectroscopy for solution-state conformational analysis.

Main Results:

• Cyr monomers exhibited conformational preferences for left- and right-handed α-helices in the solid state.
• Cyr dimers formed a distorted type III β-turn in the solid state.
• Solution-state analysis indicated Cyr residues can adopt central positions in γ-turns.

Conclusions:

• The Cyr residue displays conformational flexibility, supporting α-, β-, and γ-turns.
• H-Cyr-OH serves as a novel chiral α,α-disubstituted amino acid.
• Cyr residues offer potential for exploring new chemical space in peptide design.