SciCombinator

Discover the most talked about and latest scientific content & concepts.

Chirality-Driven Folding of Short beta-Lactam Pseudopeptides

The Journal of organic chemistry | 12 Dec 2012

JM Aizpurua, C Palomo, E Balentov√°, A Jimenez, E Andreieff, M Sagartzazu-Aizpurua, JI Miranda and A Linden
Abstract
Novel enantiopure pseudopeptide models containing a central -(beta-lactam)-(Aa)- scaffold characterized by the combined presence of an alpha-alkyl-alpha-amino-beta-lactam (i+1) residue and a alpha-substituted (i+2) amino acid have been readily synthesized from alpha-alkyl serines. The conformational analysis of such beta-lactam pseudopeptides conducted in CDCl3 and DMSOd6 solutions using 1D and 2D-NMR techniques revealed an equilibrium between beta-II turn and gamma-turn conformers, which was ultimately modulated by the relative configuration of the -(beta-lactam)-(Aa)- residues. Long range chiral effects on the alpha-lactam pseudopeptide conformers were also found when two (i) and (i+3) chiral residues were attached to the termini of a central -(beta-lactam)-(Aib)- segment. In such mimetics, heterochiral (i) and (i+3) residues reinforced a beta-II turn conformer, whereas homochiral corner residues stabilized an overlapped beta-II/ beta-I double turn motif. No beta-hairpin nucleation was observed in any instance. In good agreement with the conformers found in solution, beta-turned and open structures were also characterized by X-ray crystallography. Relative stabilities of the different conformers were estimated computationally at a B3LYP/6-31++G** calculation level and, finally, a conformation equilibrium model based on steric inter-residual interactions around the -(beta-lactam)-(i+2)- segment was proposed to account for the observed chiral effects.
Tweets*
2
Facebook likes*
0
Reddit*
0
News coverage*
0
Blogs*
0
SC clicks
1
Concepts
Cyclohexane conformation, Amino acid, Folding, Isomer, Steric effects, Stereochemistry, Conformational isomerism
MeSH headings
-
comments powered by Disqus

* Data courtesy of Altmetric.com