title: Theoretical and experimental NMR study of protopine hydrochloride isomers.
abstract: The 1H and 13C NMR chemical shifts of cis- and trans-protopinium salts were measured and calculated. The calculations of the chemical shifts consisted of conformational analysis, geometry optimization (RHF/6-31G** method) and shielding constants calculations (B3LYP/6-31G** method). Based on the results of the quantum chemical calculations, two sets of experimental chemical shifts were assigned to the particular isomers. According to the experimental results, the trans-isomer is more stable and its population is approximately 68%.
authors.affiliation: Department of Theoretical and Physical Chemistry, Faculty of Science, Masaryk University, Kotlárská 2, CZ-611 37 Brno, Czech Republic. tousek@chemi.muni.cz
authors.forename: Jaromír
authors.initials: J
authors.lastname: Tousek
authors.forename: Katerina
authors.initials: K
authors.lastname: Malináková
authors.forename: Jirí
authors.initials: J
authors.lastname: Dostál
authors.forename: Radek
authors.initials: R
authors.lastname: Marek
mesh_terms: D053119:Benzophenanthridines; D001600:Berberine Alkaloids / Q000032:analysis* / Q000737:chemistry*; D002247:Carbon Isotopes; D003198:Computer Simulation; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D011522:Protons
chemical_list: D053119:Benzophenanthridines; D001600:Berberine Alkaloids; D002247:Carbon Isotopes; D011522:Protons; C009093:protopine