Secondary structure in ring-constrained gamma-peptides

ORGN 115

M. Khurram Qureshi, Abhishek Kothari, ak508@cam.ac.uk, and Martin D Smith, mds44@cam.ac.uk. Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge CB2 1EW, United Kingdom
The conformational properties of oligomeric ring-constrained gamma-amino acids have been examined in solution (predominantly by NMR in organic solvents), and in the solid phase by X-ray studies. This has demonstrated that conformation is dependant upon the ring size of the backbone constraint. Cyclopropane gamma-peptides adopt an extended structure and assemble into sheet structures stabilized by intermolecular C-H…O hydrogen bonds; this motif may also be used to design hairpin turn structures. In contrast, oligomers with a five or six-membered backbone constraints populate well-defined bend-ribbon type conformations stabilized by intramolecular hydrogen bonds in solution.