Département de chimie moléculaire

Upon treatment of fructose-derived nitrone I with samarium diiodide, with the aim of inducing its umpolung and coupling with electrophiles, an unexpected beta-elimination of the benzyloxy group at C-1 was obsd., yielding nitrone II. The mechanism and scope of this transformation were investigated, from nitrone I and from five other alpha-alkoxy or alpha-acyloxy nitrones. This paper describes the prepn. of new nitrones III and IV from D-fructose; their synthesis demonstrates that acyl-protected nitrones can be prepd. efficiently by intramol. N-alkylation of sugar-derived oximes, a strategy previously developed only for ether- or ketal-protected cyclic nitrones. Nitrones III and IV underwent fast beta-elimination upon treatment with SmI2. Contrastingly, no beta-elimination occurred with nitrones V-VII, suggesting a specific behavior of endocyclic keto nitrones.