Abstract: (‒)-Encecanescin (1) has been isolated from the leaves of Eupatorium aschembornianum. Two conformers are present in the crystal structure as a result of molecular disorder. The structure of 1 was established by 1H- and 13C-NMR spectroscopy in CDCl3 solution using 2D NMR techniques (gHSQC, gHMBC and NOESY). A Monte Carlo random search using molecular mechanics followed by the geometry optimization of each minimum energy structure using density functional theory (DFT) calculations at the B3LYP/6–31G* level and a Boltzmann analysis of the total energies generated accurate molecular models describing the conformational behavior of 1. The three most stable conformers 2–4 of compound 1 were reoptimized at the B3LYP/6-311++G(d,p) level of theory using CHCl3 as a solvent. Correlations between the experimental 1H- and 13C-NMR chemical shifts (δexp) have been found, and the GIAO/B3LYP/6-311++G(d,p) calculated magnetic isotropic shielding tensors (σcalc) for conformers 2 and 3, δexp = a + b σcalc, are reported. A good linear relationship between the experimental and calculated NMR data has been obtained for protons and carbon atoms.
Keywords: encecanescin; DFT calculations; X-ray diffraction; FTIR and NMR spectra
This is an open access article distributed under the
Creative Commons Attribution License which permits unrestricted use, distribution,
and reproduction in any medium, provided the original work is properly cited.
Export to BibTeX
MDPI and ACS Style
Reyes-Trejo, B.; Guerra-Ramírez, D.; Zuleta-Prada, H.; Santillán, R.; Sánchez-Mendoza, M.E.; Arrieta, J.; Reyes, L. Molecular Disorder in (‒)-Encecanescin. Molecules 2014, 19, 4695-4707.
Reyes-Trejo B, Guerra-Ramírez D, Zuleta-Prada H, Santillán R, Sánchez-Mendoza ME, Arrieta J, Reyes L. Molecular Disorder in (‒)-Encecanescin. Molecules. 2014; 19(4):4695-4707.
Reyes-Trejo, Benito; Guerra-Ramírez, Diana; Zuleta-Prada, Holber; Santillán, Rosa; Sánchez-Mendoza, María E.; Arrieta, Jesús; Reyes, Lino. 2014. "Molecular Disorder in (‒)-Encecanescin." Molecules 19, no. 4: 4695-4707.