ChemInform Abstract: FOLDED AND EXTENDED STRUCTURES OF HOMOOLIGOPEPTIDES FROM α,α‐DIALKYLATED α‐AMINO ACIDS. AN INFRARED ABSORPTION AND PROTON NUCLEAR MAGNETIC RESONANCE STUDY

Context‐dependent conformation of diethylglycine residues in peptides

“…The α‐aminoisobutyryl (Aib) residue has been widely used in the design of β‐turn and helical conformations (1–3). In the case of the higher homologs of Aib like α,α‐diethylglycine (Deg), α,α‐dipropylglycine (Dpg), both fully extended (C 5 ) and folded helical conformations have been characterized in crystal structures (4–15). Theoretical calculations suggest that for the higher dialkyl glycines the minima in the C 5 and the helical region are of comparable energy.…”

De novo design: backbone conformational constraints in nucleating helices andβ‐hairpins

“…A particularly interesting feature of the higher α,α‐dialkylated glycine residues (α,α‐diethylglycine, Deg; α,α‐di‐ n ‐propylglycine, Dpg and α,α‐di‐ n ‐butylglycine, Dbg) is their tendency to adopt fully extended C 5 (φ~180°, ψ~180°) conformations. This property was first noted by Toniolo, Benedetti & Hardy in their studies of oligomers of Deg ( 21, 22). Theoretical calculations reveal that in these higher dialkylglycines the minima in the helical (φ~ ± 60°, ψ~ ± 30°) and fully extended (φ~180°, ψ~180°) regions of conformational space are energetically comparable ( 23), in contrast to Aib, where the minima in the helical region are substantially deeper ( 9).…”