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Crystal and molecular structure of Boc-D-Ala-ΔPhe-Gly-ΔPhe-D-Ala-OMe: A 310-helical dehydropeptide

✍ Scribed by M. Rosaria Ciajolo; Angela Tuzi; Claudio R. Pratesi; Adriano Fissi; Osvaldo Pieroni

Publisher
Wiley (John Wiley & Sons)
Year
1990
Tongue
English
Weight
672 KB
Volume
30
Category
Article
ISSN
0006-3525

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✦ Synopsis

Abstract

The crystal and molecular structure of the pentapeptide Boc‐D‐Ala‐ΔPhe‐Gly‐ΔPhe‐D‐Ala‐OMe, containing two dehydrophenylalanine residues, was determined by x‐ray diffraction. The molecule crystallizes in the orthorombic P2~1~2~1~2~1~ space group, with a = 10.439(3), b = 15.319(3) and c = 21.099(4) Å.

In the solid state, the conformation of the pentapeptide is characterized by the presence of two type III′ β‐turns. Thus the peptide assumes a left‐handed 3~10~‐helical conformation, the left sense being due to the D configuration of the alanine residues. The two unsaturated residues are located in the (i + 1) position of the first β‐turn and in the (i + 2) position of the second β‐turn, respectively.

In the crystal, the helical molecules are linked head to tail by hydrogen bonds. Lateral hydrogen bonds are also formed between molecules related by a twofold screw symmetry. This gives rise to a typical mode of packing characterized by infinite helical “chains,” smiliar to the packing found in other oligopeptides that adopt a 3~10~‐helical structure.

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Stabilization of unusual structures in peptides using α,β-dehydrophenylalanine: Crystal and solution structures of Boc–Pro–ΔPhe–Val–ΔPhe–Ala–OMe and Boc–Pro–ΔPhe–Gly–ΔPhe–Ala–OMe
✍ Puniti Mathur; U. A. Ramagopal; S. Ramakumar; N. R. Jagannathan; V. S. Chauhan 📂 Article 📅 2006 🏛 Wiley (John Wiley & Sons) 🌐 English ⚖ 408 KB 👁 1 views

## Abstract The structures of two dehydropentapeptides, Boc–Pro–ΔPhe–Val–ΔPhe–Ala–OMe (**I**) and Boc–Pro–ΔPhe–Gly–ΔPhe–Ala–OMe (**II**) (Boc: __t__‐butoxycarbonyl), have been determined by nuclear magnetic resonance (NMR), circular dichroism (CD), and X‐ray crystallographic studies. The peptide **