Utilisation d'ylides du phosphore en chimie des sucres. XV. Synthèse de sucres à insaturation terminale

Abstract

Abstract Treatment of 3‐O‐benzyl‐1, 2‐O‐isopropylidene‐3‐O‐methyl‐α‐ D ‐ xylo ‐pentodialdlo‐1,4‐furanose and 2,5‐anhydro‐3,4‐O‐isopropylidene‐ aldehydo ‐ D ‐ribose with moderately stable and stable phosphonium ylides led to the corresponding terminal‐unsaturated sugars obtained as a mixture of cis and trans isomers. The cis:trans ratios were determined by 1 H‐NMR. and (or) GLC. They showed that steric factors play an important role in the control of the stereochemistry of these reactions.