title: Ac10c: a medium-ring, cycloaliphatic Calpha,alpha-disubstituted glycine. Incorporation into model peptides and preferred conformation.
abstract: Two complete series of N-protected oligopeptide esters to the pentamer level from 1-amino-cyclodecane-1-carboxylic acid (Ac10c), an alpha-amino acid conformationally constrained through a medium-ring Calphai <--> Calphai cyclization, and either the L-Ala or Aib residue, along with the N-protected Ac10c 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 1H NMR techniques. Furthermore, the molecular structures of two derivatives (Z-Ac10c-OH and Fmoc-Ac10c-OH) and two peptides (the dipeptide ester Z-Ac10c-L-Phe-OMe and the tripeptide ester Z-Aib-Ac10c-Aib-OtBu) were determined in the crystal state using X-ray diffraction. The experimental results support the view that beta-bends and 3(10)-helices are preferentially adopted by peptides rich in Ac10c, the third largest cycloaliphatic C(alpha,alpha)-disubstituted glycine known. This investigation allowed us to complete a detailed conformational analysis of the whole 1-amino-cycloalkane-1-carboxylic acid (Ac(n)c, with n = 3-12) series, which represents the prerequisite for our recent proposal of the 'Ac(n)c scan' concept.
authors.affiliation: Biopolymer Research Center, CNR, Department of Organic Chemistry, University of Padova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Moretto
authors.forename: F
authors.initials: F
authors.lastname: Formaggio
authors.forename: M
authors.initials: M
authors.lastname: Crisma
authors.forename: C
authors.initials: C
authors.lastname: Toniolo
authors.forename: M
authors.initials: M
authors.lastname: Saviano
authors.forename: R
authors.initials: R
authors.lastname: Iacovino
authors.forename: R M
authors.initials: RM
authors.lastname: Vitale
authors.forename: E
authors.initials: E
authors.lastname: Benedetti
mesh_terms: D018360:Crystallography, X-Ray; D003500:Cyclization; D005998:Glycine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry; D011487:Protein Conformation; D012996:Solutions / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D009842:Oligopeptides; D012996:Solutions; D005998:Glycine