Theoretical and experimental NMR study of protopine hydrochloride isomers.
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%.
Tousek
Jaromír
J
Department of Theoretical and Physical Chemistry, Faculty of Science, Masaryk University, Kotlárská 2, CZ-611 37 Brno, Czech Republic. tousek@chemi.muni.cz
Malináková
Katerina
K
Dostál
Jirí
J
Marek
Radek
R
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
D053119:Benzophenanthridines; D001600:Berberine Alkaloids; D002247:Carbon Isotopes; D011522:Protons; C009093:protopine