Helix-Forming Carbohydrate Amino Acids

• Published in: Journal of organic chemistry Vol. 70; no. 6; pp. 2082 - 2090
• Main Authors: Claridge, Timothy D. W., Long, Daniel D., Baker, Christopher M., Odell, Barbara, Grant, Guy H., Edwards, Alison A., Tranter, George E., Fleet, George W. J., Smith, Martin D.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18-03-2005
• Subjects: Amino Acids - chemistry; Carbohydrates - chemistry; Carbohydrates with 4, 5, 6, ... C atoms, dissacharides and oligosaccharides; Carbohydrates. Nucleosides and nucleotides; Chemistry; Exact sciences and technology; Models, Chemical; Molecular Conformation; Organic chemistry; Polymers - chemical synthesis; Preparations and properties; Protein Structure, Secondary; Spectrophotometry, Infrared; Molecular rigidity; Chemical solution; Chloroform; Oside; NMR spectrometry; Oligomer; Secondary structure; Infrared spectrometry; Organic solvent; Aminoacid; Circular dichroism spectrometry; Tetramer; Helical structure; C-Glycoside; Conformation; Hydrogen bond
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo0480040

The solution-phase conformational properties of tetrameric and octameric chains of C-glycosyl α-d-lyxofuranose configured tetrahydrofuran amino acids (where the C-2 and C-5 substituents on the tetrahydrofuran ring are trans to each other) were examined using NMR and IR and CD in organic solvents. Studies by NMR and IR demonstrated that in chloroform solution, the tetramer 7 does not adopt a hydrogen-bonded conformation whereas the octamer 10 populates a well-defined helical secondary structure stabilized by 16-membered (i, i − 3) interresidue hydrogen bonds, similar to a π-helix. Circular dichroism studies in trifluoroethanol are consistent with this conformation for the octamer 10, and also indicate that the tetramer 7 adopts a rigid conformation not stabilized by hydrogen bonds.