Replacement of α-hydrogen atom of α-amino acids with alkyl substituents affords α, α-disubstituted α-amino acids, which are non-proteinogenic amino acids. This kind of modification changes the conformational freedom of peptides containing such residues. 2-Aminoisobutyric acid (dimethylglycine, Aib) is a natural product, isolated as a component of peptaibol antibiotics, and is widely used among peptide chemists for the construction of helical secondary structure. Contrary to 3
10-helical structure of Aib homopeptides, the conformation of homopeptides prepared from diethylglycine or dipropylglycine is a fully planar C
5-conformation. Besides achiral α, α-disubstituted α-amino acids, the conformation of homopeptides prepared from chiral α-methylated or α-ethylated α, α-disubstituted α-amino acids was recently reported. The conformation of homopeptides prepared from chiral α-methylated α, α-disubstituted amino acids is the 3
10-helical structure and the screw sense of helicity (
P) or (
M) depends on the chirality of quaternary carbon center of amino acids, while that of α-ethylated α, α-disubstituted amino acids is the fully planar C
5-conformation. The application of α, α-disubstituted α-amino acids for the design of biologically active peptides and catalytic peptides is also described.
抄録全体を表示