Unsaturated carbohydrates. Part XII. Synthesis and properties of 3-deoxy-α- and -β-D-erythro-hex-2-enopyranoside esters

Abstract

The boron trifluoride catalysed reaction of 1-deoxy-D-arabino-hex-1-enopyranose (2-hydroxyglucal) esters with alcohols afforded alkyl 3-deoxy-D-erythro-hex-2-enopyranoside esters with the α-anomers predominating; several have been isolated crystalline in good yield. Alternatively, crystalline β-anomers have been obtained by the uncatalysed alcoholysis of 2,4,6-tri-O-benzoyl-3-deoxy-1-O-trichloroacetyl-α-D-erythro-hex-2-enose. The nuclear magnetic resonance and optical rotatory dispersion characteristics of the members of the anomeric pairs of unsaturated glycosides are compared.