The cis-trans isomerization of N-methyl-α,β-dehydroamino acids

Dehydroamino acids with the methylated N‐terminal peptide group occur in natural small cyclic peptides. The structural analysis was used to investigate the cis‐trans isomerization of the N‐terminal tertiary amide group of diamides: Ac‐(Z)‐Δ(Me)Abu‐NHMe (1), Ac‐(Z)‐Δ(Me)Phe‐NHMe (2), Ac‐(E)‐Δ(Me)Phe‐...

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Published in:Biopolymers 2012, Vol.98 (5), p.466-478
Main Authors: Siodłak, Dawid, Macedowska-Capiga, Agnieszka, Broda, Małgorzata A., Kozioł, Anna E., Lis, Tadeusz
Format: Article
Language:English
Subjects:
Acetonitriles - chemistry
Acids - chemistry
Amides - chemistry
Chloroform - chemistry
Crystallography, X-Ray
dehydroamino acids
dehydropeptide
Magnetic Resonance Spectroscopy
Models, Molecular
Molecular Conformation
N-methylation
Peptides - chemical synthesis
Peptides - chemistry
Spectroscopy, Fourier Transform Infrared
Stereoisomerism
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Summary:Dehydroamino acids with the methylated N‐terminal peptide group occur in natural small cyclic peptides. The structural analysis was used to investigate the cis‐trans isomerization of the N‐terminal tertiary amide group of diamides: Ac‐(Z)‐Δ(Me)Abu‐NHMe (1), Ac‐(Z)‐Δ(Me)Phe‐NHMe (2), Ac‐(E)‐Δ(Me)Phe‐NHMe (3), Ac‐Δ(Me)Ala‐NHMe (4), and Ac‐(Me)Ala‐NHMe (5). The compounds were analyzed in the solid state by an X‐ray crystallography (1–3), and in the solution by FTIR (MeCN and CHCl3) and NMR (DMSO‐d6 and CDCl3) methods (1–5). In the solid state, the studied compounds adopt the cis configuration of N‐terminal amide. In solution, this configuration also prevails for the dehydroamino acids 1–4, in contrast to the saturated analog 5. The results indicate that N‐methyldehydroamino acids present a promising tool to induce the cis configuration of the amide bond. © 2012 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 98: 466–478, 2012.
ISSN:0006-3525
1097-0282
DOI:10.1002/bip.22082