Utilisation d'ylides du phosphore en chimie des sucres VII. Synthèse de sucres ramifiés des types «streptose» et «apiose». Communication préliminaire

Abstract

Abstract A new high‐yielding route to branched‐chain sugars of the streptose or the apiose type having at the branching point a configuration epimeric with that which would be obtained by the classical synthesis using Grignard reagents is described. The main steps are the preparation of branched‐chain unsaturated cyano sugars by reaction of cyanomethylene triphenylphosphorane with keto sugars and the cis ‐dihydroxylation (KMnO 4 ) of the so obtained cyano sugars. The cis and the trans isomers of a series of cyanovinylidenic sugars have been separated and the stereodependence of the long‐range coupling constants in this class of compounds has been examined.