H-1 NMR and theoretical studies on the conformational equilibrium of tryptophan methyl ester

Autor(es)

Duarte, Claudimar J. ^[1] ; Cormanich, Rodrigo A. ^[1] ; Ducati, Lucas C. ^[2] ; Rittner, Roberto ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Chem, BR-13083970 Campinas, SP - Brazil

^[2] Univ Sao Paulo, Inst Chem, BR-05513970 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Molecular Structure; v. 1050, p. 174-179, OCT 24 2013.
• Citações Web of Science: 8

Resumo

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. (AU)

• Processo FAPESP: 11/01170-1 - Estudos físico-químicos de compostos orgânicos: interações de longa distância e análise conformacional de compostos organofluorados
• Beneficiário: Rodrigo Antonio Cormanich
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 12/03933-5 - Equilíbrios conformacionais e interações intramoleculares em uma série de aminoácidos: abordagem teórica e experimental
• Beneficiário: Roberto Rittner Neto
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 11/11098-6 - Análise conformacional de alguns ésteres metílicos de aminoácidos e seus N-acetil-derivados.
• Beneficiário: Claudimar Junker Duarte
• Modalidade de apoio: Bolsas no Brasil - Doutorado