Synthèses et epimérisation de déoxy-spiro C-1 sucres

Abstract

2-Deoxy and 2,3-dideoxy-3-oxo-butyl-β-D-glycopyranosides were synthesized starting from tri-O-acetyl-D-glucal. These β compounds undergo Norrish II type photocyclization giving the corresponding hydroxyspiroketals without stereoselectivity but with greater reactivity than the α derivatives. Acidic epimerization of these spiro C-1 sugars leads to the α anomers in accord with known stereoelectronic effects.