| Popis: |
During the last decade the synthesis and spectroscopic characteristics of nitro compounds have aroused much interest. New synthetic methods have been developed, and the excellence of the nitro group as a chromophore in spectroscopy has been demonstrated. Previous work in this Department has been concerned with the synthesis and spectroscopic properties of secondary nitrosteroids and related compounds. In the present work, this investigation was extended to nitro compounds in the bornane series, and to α-nitroketosteroids and related compounds. Many oximes and ketones were handled as starting materials, and other ketosteroids were available from microbiological studies. These provided a sufficiently wide coverage of the positions on the steroid nucleus to enable studies to be made of the solvent shifts of angular methyl groups in the n.m.r. spectra of the ketones, and of the low field signals and chemical shifts of the angular methyl groups in the n.m.r, spectra of the oximes. Accordingly, the present investigation is divided into four sections. In the first Section, general methods for the preparation of secondary nitro compounds are reviewed, and the preparation, and elucidation of the structures of the 2- and 3-nitrobornanes (l, 2) are described. In Section II methods for preparing α-nitroketones and related compounds are described. Base catalysed nitration of 5αcholestan-3-one, 5α-cholestan-6-one and 5α-cholestan-7-one was carried out. During the preparation of the starting materials used in this section, it was found that the hydroboration of cholest-5-ene in the preparation of the 6-ketone, was not as stereospecific as had been reported. The mixture of 5α- and 5β-6-ketones produced was subjected to an alkaline epimerisation without any change in composition. In view of the fact that the ketone would be used under equilibrating conditions, the material prepared, containing approximately 15% of 5β-cholestan-6-one, was used without further purification. The signals of the angular methyl groups in twenty-six mono-, di- and tri-oxo-steroids, free from other substituents were examined in carbon tetrachloride, deuterochloroform, benzene and pyridine (Section III). In Section IV, a study of the n.m.r. spectra of eight monocyclic mono- and dioximes, eight bicyclic monoterpene oximes and steroid monoximes at the 1, 2, 3, 4, 6, 7 and 17 positions is described. The features of the spectra of the monocyclic oximes were found to be in agreement with those previously reported. |
