X-Pro peptides: solution and solid-state conformation of benzyloxycarbonyl-(Aib-Pro)methyl ester, a type I β-turn

Venkatachalapathi, Y. V. ; Nair, C. M. K. ; Vijayan, M. ; Balaram, P. (1981) X-Pro peptides: solution and solid-state conformation of benzyloxycarbonyl-(Aib-Pro)methyl ester, a type I β-turn Biopolymers, 20 (6). pp. 1123-1136. ISSN 0006-3525

Full text not available from this repository.

Official URL: http://www3.interscience.wiley.com/journal/1075861...

Related URL: http://dx.doi.org/10.1002/bip.1981.360200604

Abstract

The synthesis of the tetrapeptide benzyloxycarbonyl(α-aminoisobutyryl-L-prolyl)2-methyl ester (Z-(Aib-Pro)2-OMe) and an analysis of its conformation in solution and the solid state are reported. Stepwise synthesis using dicyclohexylcarbodiimide leads to racemization at Pro(2). Evidence for the presence of diastereomeric tetrapeptides is obtained from 270-MHz1H-nmr and 67.89-MHz 13C-nmr. The all-L tetrapeptide is obtained by fractional crystallization from ethyl acetate. The NH of Aib(3) is shown to be involved in an intramo-lecular hydrogen bond by variable-temperature 1H-nmr and the solvent dependence of NH chemical shifts. The results are consistent with a -turn conformation with Aib(1) and Pro(2) at the corners stabilized by a 4 →1 hydrogen bond. The molecule crystallizes in the space group P212121, with a = 8.839, b = 14.938, and c = 22.015 Å. The structure has been refined to an R value of 0.051. The peptide backbone is all-trans, and a 4 →1 hydrogen bond, between the CO group of the urethane moiety and Aib(3) NH, is observed. Aib(1) and Pro(2) occupy the corner positions of a type I β-turn with Φ= -55.4°, = Ψ=-31.3° for Aib(1) and Φ= -71.6°, Ψ= -38° for Pro(2). The tertiary amide unit linking Pro(2) and Aib(3) is significantly distorted from planarity ( Δω= 14.3°).

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons, Inc.
ID Code:4470
Deposited On:18 Oct 2010 07:46
Last Modified:16 May 2011 09:06

Repository Staff Only: item control page