Stereochemistry of peptides containing 1-aminocycloheptane-1-carboxylic acid (Ac7c)

Int J Pept Protein Res. 1991 Dec;38(6):511-8. doi: 10.1111/j.1399-3011.1991.tb01534.x.

Abstract

The crystal structures of four peptides incorporating 1-aminocycloheptane-1-carboxylic acid (Ac7c) are described. Boc-Aib-Ac7c-NHMe and Boc-Pro-Ac7c-Ala-OMe adopt beta-turn conformations stabilized by an intramolecular 4----1 hydrogen bond, the former folding into a type-I/III beta-turn and the latter into a type-II beta-turn. In the dipeptide esters, Boc-Aib-Ac7c-OMe and Boc-Pro-Ac7c-OMe, the Ac7c and Aib residues adopt helical conformations, while the Pro residue remains semi-extended in both the molecules of Boc-Pro-Ac7c-OMe found in the asymmetric unit. The cycloheptane ring of Ac7c residues adopts a twist-chair conformation in all the peptides studied. 1H-NMR studies in CDCl3 and (CD3)2SO and IR studies in CDCl3 suggest that Boc-Aib-Ac7c-NHMe and Boc-Pro-Ac7c-Ala-OMe maintain the beta-turn conformations in solution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acids / chemistry
  • Amino Acids, Cyclic*
  • Magnetic Resonance Spectroscopy
  • Molecular Sequence Data
  • Oligopeptides / chemistry*
  • Protein Conformation
  • Spectrophotometry, Infrared
  • Stereoisomerism
  • X-Ray Diffraction

Substances

  • Amino Acids
  • Amino Acids, Cyclic
  • Oligopeptides
  • 1-aminocycloheptanecarboxylic acid