Synthèse de sucres aminés ramifiés III . Synthèse et réactions de 1′α‐amino‐nitrile dérivé du di‐O‐isopropylidène‐1,2:5,6‐α‐ D ‐ ribo ‐hexofurannosul‐3‐ose

The addition of cyanohydric acid to 1,2:5,6‐di‐O‐isopropylidene‐α‐ D ‐ ribo ‐hexofurannos‐3‐ulose can be sterically controlled. Under kinetic conditions, the allo cyanohydrine epimer is formed, under thermodynamic conditions, the gluco epimer is formed. The configuration of these two products is proved by their chemical reactions. Hydration followed by hydrolysis of the nitrile group of the allo epimer (O‐acetyl derivative) gives the 3‐C‐carboxy‐1,2‐O‐isopropyloidene compound. This product forms the corresponding γ or δ‐lactone with hydroxyl ( 5 ) or ( 6 ). On the other hand, after hydrolysis of 5,6‐isopropylidene, the 3‐O‐acetyl derivative of the gluco epimer gives an acetyl migration from position 3 to position 5 and finally to position 6. By reaction of the allo epimer with NH 3 and CN − , an aminonitrile is formed. The allo configuration is deduced from the above mentioned reaction and from IR. and NMR. data. Several acetylated and trifluoracetylated derivatives of these products are described. The oxidation of the nitrile group to the amide group is possible with both epimeric cyanohydrines and the amino‐nitrile.