Conformational Analysis and Intramolecular Interactions of l‑Proline Methyl Ester and Its N‑Acetylated Derivative through Spectroscopic and Theoretical Studies

This work reports a detailed study regarding the conformational preferences of l-proline methyl ester (ProOMe) and its N-acetylated derivative (AcProOMe) to elucidate the effects that rule their behaviors, through nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies combined with theore...

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Published inThe journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 118; no. 9; pp. 1748 - 1758
Main Authors Braga, Carolyne B, Ducati, Lucas C, Tormena, Cláudio F, Rittner, Roberto
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 06.03.2014
Subjects
Acetylation
Amino acids
Derivatives
Esters
Infrared
Magnetic Resonance Spectroscopy
Mathematical analysis
Molecular Conformation
Nuclear magnetic resonance
Orbitals
Proline - analogs & derivatives
Proline - chemical synthesis
Proline - chemistry
Quantum Theory
Spectroscopy
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Summary:This work reports a detailed study regarding the conformational preferences of l-proline methyl ester (ProOMe) and its N-acetylated derivative (AcProOMe) to elucidate the effects that rule their behaviors, through nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies combined with theoretical calculations. These compounds do not present a zwitterionic form in solution, simulating properly amino acid residues in biological media, in a way closer than amino acids in the gas phase. Experimental 3 J HH coupling constants and infrared data showed excellent agreement with theoretical calculations, indicating no variations in conformer populations on changing solvents. Natural bond orbital (NBO) results showed that hyperconjugative interactions are responsible for the higher stability of the most populated conformer of ProOMe, whereas for AcProOMe both hyperconjugative and steric effects rule its conformational equilibrium.
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ISSN:1089-5639
1520-5215
DOI:10.1021/jp5007632