C11/C9 Helical Folding in ab Hybrid Peptides Containing 1-Aminocyclohexane acetic acid (b3,3-Ac6c)

The present study describes the solid-state conformation of ab hybrid peptides, Boc-Leu-b3,3-Ac6c-OH, P1; Boc-Leu-b3,3-Ac6c-Leu-b3,3-Ac6c-OMe, P2; and Boc-Leub 3,3-Ac6c-Leu-b3,3-Ac6c-Leu-OMe, P3. The dipeptide P1 adopts extended conformations, whereas tetrapeptide P2 and pentapeptide P3 favor a helical conformation stabilized by mixed types of C11/C9 intramolecular hydrogen bonds. In peptide P3, the amino group of b3,3-Ac6c(2) and b3,3-Ac6c(4) residues occupies axial orientation, whereas in P2 it occupies axial and equatorial orientations for residues b3,3-Ac6c(2) and b3,3-Ac6c(4), respectively. The self-assembly of P3 forms channels filled with solvent molecules that present interesting patterns