Structure of benzyloxycarbonyl-L-alanyl-α-aminoisobutyl-α-aminoisobutylic acid

✍ Scribed by Tooru Taga; Masato Itoh; Katsunosuke Machida; Tetsuro Fujita; Terumi Ichihara

• Book ID: 102764620
• Publisher: Wiley (John Wiley & Sons)
• Year: 1990
• Tongue: English
• Weight: 570 KB
• Volume: 29
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360290616

✦ Synopsis

Abstract

The x‐ray diffraction study of the C‐terminally unprotected tripeptide benzyloxycarbonyl‐L‐alanyl‐α‐aminoisobutyl‐α‐aminoisobutylic acid (Z‐L‐Ala‐Aib‐Aib‐OH) has shown that the molecule adopts a consecutive type III β‐turn, which characterizes a right‐handed 3~10~ helix. A very weak 4 → 1 intramolecular hydrogen bond with the long NO distance of 3.32 Å, and a unique “oxy analogue” of the 4 → 1 hydrogen bond with the OO distance of 2.77 Å, were observed. The stability of the observed conformation with the asymmetric Aib residues was theoretically evaluated by a conformation‐energy calculation. The stereochemical characteristics of Aib and Ala residues were made clear by a comparison of the conformations of the short peptides containing both Aib and Ala residues.