title: Determination of the absolute configurations of natural products via density functional theory calculations of vibrational circular dichroism, electronic circular dichroism and optical rotation: the schizozygane alkaloid schizozygine.
abstract: The development of density functional theory (DFT) methods for the calculation of vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and transparent spectral region optical rotation (OR) has revolutionized the determination of the absolute configurations (ACs) of chiral molecules using these chiroptical properties. We report the first concerted application of DFT calculations of VCD, ECD, and OR to the determination of the AC of a natural product whose AC was previously undetermined. The natural product is the alkaloid schizozygine, isolated from Schizozygia caffaeoides. Comparison of DFT calculations of the VCD, ECD, and OR of schizozygine to experimental data leads, for each chiroptical technique, to the AC 2R,7S,20S,21S for the naturally occurring (+)-schizozygine. Three other alkaloids, schizogaline, schizogamine, and 6,7-dehydro-19beta-hydroxyschizozygine, have also been isolated from S. caffaeoides and shown to have structures closely related to schizozygine. Assuming a common biosynthetic pathway, their ACs are defined by that of schizozygine.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA. pstephen@usc.edu
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Stephens
authors.forename: Jian-Jung
authors.initials: JJ
authors.lastname: Pan
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Devlin
authors.forename: Marie
authors.initials: M
authors.lastname: Urbanová
authors.forename: Josef
authors.initials: J
authors.lastname: Hájícek
mesh_terms: D029062:Apocynaceae / Q000737:chemistry; D001688:Biological Products / Q000737:chemistry*; D002942:Circular Dichroism; D004583:Electrons; D026121:Indole Alkaloids / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared; D014732:Vibration
chemical_list: D001688:Biological Products; D026121:Indole Alkaloids; C519431:schizozygane; C509580:schizozygine