title: Absolute configuration of eremophilanoids by vibrational circular dichroism.
abstract: The absolute configurations (AC) of natural occurring 6-hydroxyeuryopsin (1), of its acetyl derivative 2, and of eremophilanolide 8 were confirmed by comparison of the experimental vibrational circular dichroism (VCD) spectra with theoretical curves generated from density functional theory (DFT) calculations. Initial analyses were carried out using a Monte Carlo searching with the MMFF94 molecular mechanics force field. All MMFF94 conformers were further optimized using DFT at the B3LYP/6-31G(d) level of theory, followed by calculations of their vibrational frequencies at the B3LYP/6-31G(d,p); the VCD spectra of 2 and 8 were also calculated at the B3PW91/DGDZVP level of theory. Good agreement between theoretical and experimental VCD curves unambiguously verified the 4S,5R,6S absolute configuration for 1 and 2, and the 1S,4S,5R,6S,8S,10S configuration for 8.
authors.affiliation: Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala, Col. Santo Tomás, México D.F., 11340 Mexico.
authors.forename: Eleuterio
authors.initials: E
authors.lastname: Burgueño-Tapia
authors.forename: Pedro
authors.initials: P
authors.lastname: Joseph-Nathan
mesh_terms: D002942:Circular Dichroism; D041621:Eremophila Plant / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D011763:Pyrrolizidine Alkaloids / Q000737:chemistry*
chemical_list: D011763:Pyrrolizidine Alkaloids