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.
Early Cretaceous Feathers from Victoria
Unusually well preserved fossil feathers from Lower Cretaceous (VaIanginian-Aptian) claystones at Koonwarra, Victoria, are the oldest (c. 110-125 million years) bird remains yet found in the southern hemisphere, They are among the oldest bird remains known in the world, being antedated only by the toothed Archaeopteryx from the late Jurassic of Bavaria, and being more or less the same age as Gallornis from the Lower Cretaceous of France. The Victorian fossil feathers are evidence for essentially worldwide distribution of birds soon after the beginning of the Cretaceous, if not before. The feathers could conceivably have come from toothed birds.