alpha,beta-unsaturated sugar delta-lactones; Preparation and conjugate addition of hydroxylamines and hydrazines

Oxidation of 2,3-unsaturated glycosides with hydrogen peroxide in the prese nce of molybdenum trioxide as catalyst provides corresponding alpha,beta-un saturated sugar delta-lactones via the anomeric hydroperoxide stage. Conjug ate addition of N-substituted hydroxylamines and hydrazines to these delta- enealdonolactones proceeds anti to the C-6 carbon atom. The adducts undergo rearrangement consisting in opening of the lactone ring and formation of 3 -substituted isoxazolidin-5-one or 5-substituted pyrazolidin-3-one, respect ively. Introduction of a leaving group to the polyol side chain of both het erocycles induces further rearrangements.