Ab initio and DFT search for conformational transition states of N-formyl-L-prolinamide

Abstract

The ω cis-trans isomers, backbone conformers (α-L, ε-L and γ-L) and syn-anty ring puckered structures of formyl L-prolinamide were studied at the RHF/3-21G, RHF/6-31G(d) and RB3LYP/6-31G(d) level of theory. In addition single point calculations using a more accurate and extended basis set (aug-cc-PVDZ) were carried out. The barrier heights for cis-trans isomerization fell in the range of 19.58 to 24.6 Kcal/mol and those for the interconversion between backbone conformations were in the range of 0.61-5.56 Kcal/mol. The barrier heights for syn-anty ring puckering were found within 1.79 to 7.46 Kcal/mol at the aug-cc-pVDZ//RHF/3-21G level of theory.

Empleando cálculos RHF/3-21G, RHF/6-31G(d) y RB3LYP/6-31G(d) se estudiaron los isómeros ω cis-trans, los conformeros de la cadena principal (α-L, ε-L y γ-L) y las estructuras plegadas syn-anty del anillo para la formil L-prolinamida. Además se realizaron cálculos de punto único empleando un grupo de bases más flexible (aug-cc-PVDZ). Las alturas de las barreras para la isomerización cis-trans fueron encontradas en el rango de 0,61-5,56 Kcal/mol. El valor de la barrera para el arrugado del anillo syn-anty se encontró entre 1,79 to 7,46 Kcal/mol al nivel de teoría aug-cc-pVDZ// RHF/3-21G.