含1-氨基环庚烷-1-羧酸（Ac7c）的肽的立体化学

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

作者信息

Valle G, Crisma M, Toniolo C, Rao R B, Sukumar M, Balaram P

机构信息

Department of Organic Chemistry, University of Padova, Italy.

出版信息

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

DOI:10.1111/j.1399-3011.1991.tb01534.x

PMID:1819586

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.

摘要

描述了四种包含1-氨基环庚烷-1-羧酸（Ac7c）的肽的晶体结构。Boc-Aib-Ac7c-NHMe和Boc-Pro-Ac7c-Ala-OMe呈现由分子内4→1氢键稳定的β-转角构象，前者折叠成I/III型β-转角，后者折叠成II型β-转角。在二肽酯Boc-Aib-Ac7c-OMe和Boc-Pro-Ac7c-OMe中，Ac7c和Aib残基呈现螺旋构象，而在不对称单元中发现的Boc-Pro-Ac7c-OMe的两个分子中，Pro残基均保持半伸展状态。在所有研究的肽中，Ac7c残基的环庚烷环呈现扭船式构象。在CDCl3和(CD3)2SO中的1H-NMR研究以及在CDCl3中的IR研究表明，Boc-Aib-Ac7c-NHMe和Boc-Pro-Ac7c-Ala-OMe在溶液中保持β-转角构象。