Investigations in the fie ld of substituted furanurona ldehydes steric directivity of the nitromethane condensation
Summary1. The condensation of the anomeric methyl 2,3-di-O-benzyl-D-xylofuranosiduronaldehydes with nitromethane has been studied.2. It has been shown that the position of the substituent at the glycosidic center has an influence on the steric directivity of this reaction.3. The structure of the 6-nitro-6-deoxyhexofuranosides synthesized has been confirmed by their conversion into known derivatives of methyl D-glucofuranosides.
Darstellung von 5‐Aminozuckern und deren Umwandlung in Pyridinderivate
Derivate der 5.6-Diamino-5.6-didesoxy-D-glucose und -L-idose wurden durch Ammoniak-Anlagerung an das Nitroolefin VI und Hydrierung der erhaltenen Nitrozucker dargestellt. 5.6-Diacetamino-5.6-didesoxy-D-glucose und -L-idose bevorzugen die Furanoseform. Nach Abspaltung der N-Acetylreste zu den freien 5.6-Diaminozuckern wird das intermediare Auftreten einer „Piperidinose-Form” angenommen, welche bei den 5.6-Diamino-5.6-didesoxy-hexosen unter spontaner Abspaltung von 3 Mol Wasser und Aromatisierung in 2-Aminomethyl-5-hydroxy-pyridin ubergeht. 5-Acetamino-5.6-didesoxy-6-nitro-L-idofuranose liefert bei Abspaltung der N-Acetylgruppe am C-Atom 5 in entsprechender Reaktion 5-Hydroxy-2-nitromethyl-pyridin.
AN ASYMMETRIC SYNTHESIS OF D- AND L-MANNOSAMINE
The addition of ammonia to the ethylenic bond of D-arabo-tetraacetoxy-1-nitrohexene-1 was stereospecific and formed a crystalline product, 1-nitro-1-deoxy-N-acetyl-D-mannosaminol. Application of the Nef reaction to this compound gave 2-amino-2-deoxy-D-mannose, which was isolated as the crystalline pentaacetate and further characterized as the hydrochloride by deacetylation with hydrochloric acid. In the deacetylation of the pentaacetate with barium methoxide, however, an abnormal epimerization occurred to yield N-acetyl-D-glucosamine.L-Mannosamine pentaacetate was synthesized in a similar manner from L-arabo-tetra-acetoxy-1-nitrohexene-1.