12-Epinapelline and its N-oxide fromAconitum baicalense

12-Epinapelline and its N-oxide have been isoated from the epigeal part ofAconitum baicalense Turcz. ex Rapaics (A. Czekanovskyi Steinb.). The structures of these compounds have been determined with the aid of two-dimensional¹H and¹³C NMR spectroscopy, and IR and mass spectrometry. Irkutsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 888–892. November–December, 1993.     

Alkaloids ofPetilium eduardi. Petine and petine N-oxide

Two new alkaloids — petine and petine N-oxide — have been isolated from the bulbs of Petilium eduardi. Their structures have been established on the basis of spectral characteristics and chemical transformations.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, FAX (3712) 89-14-75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 524–528, July–August, 1994.     

Alkaloids ofNitraria komarovii XVII. Peganine N-oxide, N-allylschoberine, and dehydronitramidine

Three new alkaloids have been isolated from the epigeal part ofNitraria komarovii — peganine N-oxide, N-allylschoberine, and dehydronitramidine. Their structures have been determined on the basis of chemical transformations and spectral results.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 780–783, November–December, 1994.     

Synthesis of 5-benzyl-3-hydroxypyridine and its N-oxide

Conclusions The acylation of benzene with 5-bromonicotinoyl chloride gave 5-bromo-3-benzoylpyridine in high yield, the Kizhner reduction of which led to the synthesis of 3-hydroxy-5-benzylpyridine in good yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.1, pp.222–224, January, 1976.The authors thank N. M. Émanuél' for his constant interest in the work.     

Severine N-oxide and korsemine fromKorolkowia sewerzowii

Korsevine and the new alkaloids severine N-oxide and korsemine have been isolated from the combined alkaloids ofKorolkowia sewerzowii Regel. On the basis of the results of a study of the IR and NMR spectra of the alkaloids and also of a correlation with korseveriline and korsevine it has been established that base (I) is severine N-oxide and korsemine has the structure of korsevine 3-D-glucopyranoside.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 823–826, November–December, 1979.     

Structure of the new diterpene alkaloid zeraconine and its N-oxide

The structures of the new diterpene alkaloid zeraconine and its N-oxide, isolated fromAconitum zeravschanicum, have been established on the basis of spectral characteristics and chemical transformations.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 407–411, May–June, 1987.     

Electronic structures of pyridine N-oxide and 4-nitrosopyridine N-oxide

The -electron structure of pyridine N-oxide was calculated by the Pariser-Parr-Pople method, the effect of -polarization of the NO bond upon the valence state ionization potentials and electron affinities being taken into account. By the aid of these results, the -electron structure of 4-nitrosopyridine N-oxide was studied by the composite system method. The calculated transition energies and oscillator strengths can satisfactorly explain the observed electronic absorption spectrum. The 372 m band was ascribed to the charge-transfer transition from the oxygen atom of the NO group to the nitroso group via the pyridine nucleus.     

Electrophilic substitution reactions in 2, 3-dimethylquinoxaline and its N-oxide

The reaction of 2, 3-dimethylquinoxaline and its mono-N-oxide with aromatic aldehydes and nitroso and diazo compounds has been studied. It has been found that the introduction of the N-oxide group increases the reactivity of a methyl group in the -position with respect to it. Some properties of the compounds obtained have been studied.     

Cation-radical of pyridine N-oxide and its reactions with C?H bonds

Visible absorption spectrum for the cation-radical of pyridine N-oxide pyO⁺ obtained in the oxidation of the appropriate N-oxide by the photo-excited triplet state of chloranil, has a wide maximum at =430–460 nm. pyO⁺ reacts with cyclohexane, methanol or toluene with the formation of intermediate complexes. Equilibrium constants of their formation K×10^–2 dm³/mol amount to 0.1, 1.0 and 2.0, respectively. The (pyO⁺...RH) complex readily reacts with O₂, and in the absence of O₂ its decomposition is independent of the hydrocarbon nature.

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- N- (pyO⁺) N- . pyO⁺ , =430–460 . , pyO⁺ , , , (×10^{–2 3}/) 0,1, 1,0 2,0. , .

     

Pyridine N-oxide and pyridine-d5 N-oxide: an electrospray/tandem mass spectrometric study carried out at high mass resolution

A mass spectrometric study of pyridine N-oxide and pyridine-d5 N-oxide was carried out with a hybrid quadrupole/time-of-flight (TOF) mass spectrometer coupled with an electrospray (ES) source. In addition to the observation of protonated, sodiated, and proton-bound dimers of pyridine N-oxide and pyridine-d5 N-oxide, mass scans revealed the presence of several doubly-charged ion species. Doubly-charged ions of m/z 191 were identified as diprotonated tetramers of pyridine N-oxide; a structure has been proposed for the diprotonated tetramer and its energy relative to that of protonated pyridine N-oxide has been obtained from geometry optimizations. The principal ion species observed were subjected to collision-induced dissociation; accurate mass measurements were made of each fragment ion so as to determine its elemental composition. On the basis of mass spectrometric evidence, it is suggested that dissociation of pyridine N-oxide may occur during the ES process and the resulting fragments become embedded in doubly-charged ions. The proton affinity for both pyridine N-oxide and pyridine-d5 N-oxide was calculated; the difference between these proton affinities was compared with an experimentally determined difference between the proton affinities of pyridine N-oxide and pyridine-d5 N-oxide.