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Molecules 2014, 19(4), 4695-4707;

Molecular Disorder in (‒)-Encecanescin

Laboratorio de Productos Naturales, Área de Química, Departamento de Preparatoria Agrícola AP 74 Oficina de Correos Chapingo, Universidad Autónoma Chapingo, Km. 38.5 Carretera México-Texcoco, Texcoco 56230, Estado de México, Mexico
Departamento de Química, CINVESTAV-IPN, Apdo. Postal 14-740, México D.F. 07000, Mexico
Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, Colonia Santo Tomás, Delegación Miguel Hidalgo, México D.F. 11340, Mexico
Departamento de Química Orgánica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán D.F. 04510, Mexico
Authors to whom correspondence should be addressed.
Received: 20 January 2014 / Revised: 3 April 2014 / Accepted: 4 April 2014 / Published: 15 April 2014
(This article belongs to the Section Molecular Diversity)
PDF [943 KB, uploaded 18 June 2014]


(‒)-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 24 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. View Full-Text
Keywords: encecanescin; DFT calculations; X-ray diffraction; FTIR and NMR spectra encecanescin; DFT calculations; X-ray diffraction; FTIR and NMR spectra

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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.

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