RESUMO
2R-(-)-6-Hydroxytremetone (C13H14O3) is a bioactive metabolite isolated from Xenophyllum poposum (Phil.) V.A. Funk. (ex. Werneria poposa Phil.), a member of the Asteraceae. Various pharmacological properties attributed by popular medicine to benzofurane derivatives prompted their physical and chemical characterization. The obtained substance was characterized by melting point, optic rotation, ultraviolet spectrum, 1HRMN, 13CRMN, infrared spectroscopy, and thermo-analytical techniques. The molecular structure of 2R-(-)-6-hydroxytremetone was determined by single crystal X-rays diffraction methods. The substance crystallizes in the monoclinic space group P2(1) with a = 8.767(2) A, b = 5.423(1) A, c = 24.301(4) A, beta = 90.52(2) degrees , and two independent but very similar molecules of the same handedness per asymmetric unit (Z = 4). Both molecules have the phenyl ring and its attached oxydryl and methyl ketone groups nearly co-planar to one another and are stabilized by a strong OH ... Oketone intra-molecular bond (Ohydroxyl ... Oketone distances of 2.529 and 2.536 A; O-H ... Oketone angles of 146.4 and 143.9 degrees , respectively).
Assuntos
Asteraceae/química , Benzopiranos/química , Benzopiranos/isolamento & purificação , Varredura Diferencial de Calorimetria , Cristalografia por Raios X , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Rotação Ocular , Componentes Aéreos da Planta/química , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
The molecular structure of 2-isopropyl-5-methyl-1,4-benzoquinone, C(6)O(2)H(2) (CH(3))(3)CH, has been optimized using methods based on density functional theory (DFT) and Moller-Plesset second-order perturbation theory (MP2). As regards C(6)O(2)H(2) (CH(3))(3)CH, two populated conformations with C(1) (trans) and C(s) (cis) symmetries are obtained, the former being more stable than the latter. The theoretical data indicate that although both anti and cis conformers are possible by rotation about the C-C bond, the preferred conformation is trans. The effects governing the torsion barriers and preferred conformations were analyzed at B3LYP/6-311++G** level. The atoms in molecules (AIM) theory and natural bond orbital (NBO) analysis was applied to the cis and trans conformers in order to detect intramolecular contacts. Furthermore, the infrared spectra for the gas and solid phases and the Raman spectrum for the solid one, were recorded and the observed bands assigned to the vibrational modes.