Ac10c: a medium-ring, cycloaliphatic C-alpha-alpha-disubstituted glycine. Incorporation into model peptides and preferred conformation

Two complete series of N-protected oligopeptide esters to the pentamer level from 1-amino-cyclodecane-1-carboxylic acid (Ac(10)c), an alpha -amino acid conformationally constrained through a medium-ring C-i(alpha)C-i(alpha) cyclization, and either the L-Ala or Aib residue, along with the N-protected Ac(10)c monomer and homo-dimer alkylamides, were synthesized using solution methods and fully characterized. The preferred conformation of these model peptides was assessed in deuterochloroform solution using FT-IR absorption and H-1 NMR techniques