Helical Peptide-Foldamers Having a Chiral Five-Membered Ring Amino Acid with Two Azido Functional Groups

A chiral five-membered ring α,α-disubstituted
α-amino
acid (R,R)-Ac5cdN3 having two azido functional groups has been designed and synthesized.
The cyclic amino acid (R,R)-Ac5cdN3 could be efficiently converted into several
cyclic amino acids with various two 1,2,3-triazole functional groups.
(R,R)-Ac5cdN3 homochiral peptides (up to hexapeptide) and (R,R)-Ac5cdN3-containing l-Leu-based
peptides were prepared, and their conversion of azido functional groups
into triazole groups was completed. The preferred conformation of
oligomers, before and after the “click reaction”, together
with the azido gauche effect of amino acid residues
were studied using FT-IR absorption, CD, 1H NMR, and X-ray
crystallographic analysis. The cyclic amino acid (R,R)-Ac5cdN3 could be used
as a helical conformation controlling residue and also has a versatile
functionalizing site in its oligopeptides.