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|Type:||Artigo de periódico|
|Title:||H-1 NMR and theoretical studies on the conformational equilibrium of tryptophan methyl ester|
|Abstract:||Selected (3)J(HH) coupling constants and theoretical calculations were used to explain the conformational equilibrium of L-tryptophan methyl ester (Trp-OMe) in several solvents. The obtained (3)J(H alpha H beta) values did not exhibit any significant variability and thus indicate that there are no conformational population variations for the side chain of the Trp-O-Me depending on the solvent. Moreover, the potential energy surfaces obtained at the B3LYP/cc-pVDZ theoretical level produced eight energy minima that were analysed by QTAIM and NBO methods. It was possible to conclude that the Trp-OMe conformational preferences were due to hyperconjugative effects involving the nonbonding electron pairs of the main chain nitrogen atom and certain antibonding orbitals (sigma(C4-C13)*, sigma(C1-C4)* and sigma(C4-H12)*) and also to the steric effects from the nonbonding electron pairs of oxygen atoms and the main and side chain of this system. (C) 2013 Elsevier B.V. All rights reserved.|
|Subject:||Tryptophan methyl ester|
|Editor:||Elsevier Science Bv|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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