Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
1-C-Nitroglycals. Preparation and Reaction with Some Nitrogen NucleophilesAcetylation of the 1-deoxy-1-nitromannopyranoses 2 and 6 was accompagnied by spontanous β-elimination to give the 1-C-nitroglucals 3 and 7, respectively, while acetylation of the gluco- and galacto-configurated 1-deoxy-1-nitropyranoses 8 and 14 gave the acetates 9 and 15, respectively (Scheme 1). The acetylation of the ribo- and arabino-configurated 1-deoxy-1-nitrofuranoses 19 and 21 also occurred without β-elimination to give the acetates 20 and 22, respectively (Scheme 2). Mild base treatment of the previously described O-acetylnitro-β-D-glucose 4, the O-acetylnitro-β-D-pyranoses 9 and 15, and the O-acetylnitro-β-D-furanoses 17, 20, and 22 gave the 1-C-nitroglycals 3, 10, 16, 18 and 23, respectively (Scheme 1 and 2). The previously obtained 1-C-nitroglucal 3 was deacetylated by treatment with MeOH in the presence of KCN or sodium m-nitrophenolate to give the free nitroglucal 5. Deacetylation of the benzylidene protected 1-C-nitroglucal 10 (MeOH, NaOMe) gave the 4,6-O-benzylidene-1-C-nitroglucal 11 and traces of the 2-O-methyl-1-C-nitromannoses 12 and 13. The UV, IR, 1H-NMR and 13C-NMR spectra of the 1-C-nitroglycals are discussed. In solution, the 1-C-nitroglycals 1, 5, 7, 10, 11, and 16 adopt approximately a 4H5- and 3 a flattened 4H5 conformation. The structure of 5 was established by X-ray analysis. In the solid state, 5 adopts a sofa conformation, which is stabilized by an intramolecular H-bond. The β-addition of NH3 to the 1-C-nitroglucals 7 and 10 was followed by an O→ N acetyl migration to give exclusively anomeric pairs of the N-acetyl-1-nitromannosamine derivatives 24/25 and 26/27, respectively (Scheme 3). The β-addition of methylamine, octadecylamine, and tryptamine to the 1-C-nitroglucal 11 also stereoelectronically controlled and gave the crystalline N-alkyl-1-nitromannosamines 28, 29, and 30, respectively. The stereoelectronically controlled β-addition of NH3 to the 1-C-nitrogalactal 16, followed by acetylation, yielded exclusively the talosamine derivative 31, while the reversible β-addition of azide ions to 16 gave the anomeric 2-azido-1-nitrogalactoses 32 and 33. The β-addition of azide ions to the 1-C-nitroglucal 1 led to the 2-azido-1-nitromannose 34. In the presence of excess formaldehyde, this addition was followed by a Henry reaction. Chromatography of the crude product was accompagnied by solvolytic removal of the NO2 group to give the 3-azidomannoheptulose 35 in high yields (Scheme 4).
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