title: 13C GIAO DFT calculation as a tool for configuration prediction of N-O group in saturated heterocyclic N-oxides.
abstract: Tropane, tropinone, pseudopelletierine and cocaine were oxidized in situ in a nuclear magnetic resonance (NMR) tube providing mixtures of exo/endo N-oxides. Observed (13)C chemical shifts were correlated with values calculated by gauge-including atomic orbitals density functional theory (DFT) OPBE/6-31G* method using DFT B3LYP/6-31G* optimized geometries. The same method of (13)C chemical shift calculation was applied on series of methyl-substituted 1-methylpiperidines and their epimeric N-oxides described in literature. The results show that using this undemanding calculation method enables assignment of configuration of N-O group in N-epimeric saturated heterocyclic N-oxides. The approach enables assigning of the configuration with high degree of certainty even if NMR data of only one isomer are available. An improved method of in situ oxidation of starting amines in an NMR tube is also described.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, Flemingovo nám. 2, CZ-166 10 Prague 6, Czech Republic.
authors.forename: Radek
authors.initials: R
authors.lastname: Pohl
authors.forename: Francisc
authors.initials: F
authors.lastname: Potmischil
authors.forename: Martin
authors.initials: M
authors.lastname: Dračínský
authors.forename: Václav
authors.initials: V
authors.lastname: Vaněk
authors.forename: Lenka
authors.initials: L
authors.lastname: Slavětínská
authors.forename: Miloš
authors.initials: M
authors.lastname: Buděšínský
mesh_terms: D002247:Carbon Isotopes; D003042:Cocaine / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry; D011237:Predictive Value of Tests; D013237:Stereoisomerism; D014326:Tropanes / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D003497:Cyclic N-Oxides; D010880:Piperidines; D014326:Tropanes; C008195:isopelletierine; D003042:Cocaine; D009584:Nitrogen; D010100:Oxygen