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Experimental and theoretical NMR and IR studies of the side-chain orientation effects on the backbone conformation of dehydrophenylalanine residue

✍ Scribed by Aneta M. Buczek; Tomasz Ptak; Teobald Kupka; Małgorzata A. Broda

Publisher
John Wiley and Sons
Year
2011
Tongue
English
Weight
285 KB
Volume
49
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

Conformation of N‐acetyl‐(E)‐dehydrophenylalanine N′, N′‐dimethylamide (Ac‐(E)‐ΔPhe‐NMe~2~) in solution, a member of (E)‐α, β‐dehydroamino acids, was studied by NMR and infrared spectroscopy and the results were compared with those obtained for (Z) isomer. To support the spectroscopic interpretation, the ϕ, ψ potential energy surfaces were calculated at the MP2/6‐31 + G(d,p) level of theory in chloroform solution modeled by the self‐consistent reaction field‐polarizable continuum model method. All minima were fully optimized by the MP2 method and their relative stabilities were analyzed in terms of π‐conjugation, internal H‐bonds and dipole interactions between carbonyl groups. The obtained NMR spectral features were compared with theoretical nuclear magnetic shieldings, calculated using Gauge Independent Atomic Orbitals (GIAO) approach and rescaled to theoretical chemical shifts using benzene as reference. The calculated indirect nuclear spin‐spin coupling constants were compared with available experimental parameters. Copyright © 2011 John Wiley & Sons, Ltd.

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