The Rearrangement Reaction of Some Acetylated Unsaturated 2-Acetamidoaldose Derivatives. Selective Removal of one N-Acetyl Group from 2-(N-acetylacetamido) Compounds

Two pairs of anomers, the l ,4,6-tri-0-acetyl-2-(N-acetylacetamido)- 2,3-dideoxy-o-hex-2-enopyranoses of the erythro- (II and III) and the threo- series (IV and VI) have been prepared and character; ized. The molecular conformation of these substances has been discussed on the basis of their NMR spectral characteristics. It is suggested that the a-anomers II and IV adopt the H~ conformation as the favorable one, while the B-anomers III and VI most probably tend to take a slightly modified H~ conformation. A convenient preparative method for selective removal of one N-acetyl group from 0-acetylated N-acetylacetamido compounds is described. The reaction can be carried out in aqueous dioxane solution at room temperature in the presence of an ammonium salt at pH ca. 9