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

Valle, G. ; Crisma, M. ; Toniolo, C. ; Sudhanand, ; Balaji Rao, R. ; Sukumar, M. ; Balaram, P. (1991) Stereochemistry of peptides containing 1-aminocycloheptane-1-carboxylic acid (Ac7c) International Journal of Peptide & Protein Research, 38 (6). pp. 511-518. ISSN 0367-8377

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The crystal structures of four peptides incorporating l-aminocycloheptane-l-carboxylic acid (Ac7c) are described. Boc-Aib-Ac7c-NHMe and Boc-Pro-Ac7c-Ala-OMe adopt ß-turn conformations stabilized by an intramolecular 4 x 1 hydrogen bond, the former folding into a type-I/III β-turn and the latter into a type-II β-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 β-turn conformations in solution.

Item Type:Article
Source:Copyright of this article belongs to Munksgaard International Publishers.
Keywords:L-aminocycloheptane Carboxylic Acid Peptides; α-aminoisobutyryl Peptides; β-turns; H-NMR; IR Studies; Peptide Conformations; X-ray Diffraction
ID Code:91393
Deposited On:21 May 2012 08:41
Last Modified:21 May 2012 08:41

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