Amino sugar

For galactal, addition of azide to the double bond will preferentially occur from equatorial direction because of steric hindrance at the top face caused by axial group at C-4.

Glycals may also be converted into amino sugars by nitration followed by treatment with thiophenol (Michael addition) to furnish a thioglycoside donor.

This is a versatile donor and can react with simple or carbohydrate alcohols to establish the glycosidic linkage, with reduction and N-acetylation of nitro group will give the targeted product.

This methodology makes the introduction of both natural and non-natural amide functionalities at C-2 possible and more importantly with glycosidic bond formation at the same time in a one-pot procedure.

One aspect of this problem is that displacements at the C2 position tend to be slow as it is adjacent to the anomeric centre; this is particularly true for glycosides with axially-oriented aglycones.