Synthesis, Conformational Analysis, and the Glycosidic Coupling Reaction of Substituted 2,7-Dioxabicyclo[4.1.0]Heptanes: 1,2-Anhydro-3,4-di-O-Benzyl-β-L-arabinopyranose

Abstract

Abstract The title 1,2-anhydro sugar (8) was synthesized from l-arabinose. The key intermediate for the synthesis was 2-O-acetyl-3,4-di-O-benzyl-α-l-arabinopyranosyl fluoride (7) which was transformed into the target compound by ring closure with potassium tert-butoxide. Comparison of the observed vicinal coupling constants with the results obtained from calculations by molecular mechanics for 8 suggested that the conformation of the pyranose ring was close to a half chair 5 H 4. The 1,2-anhydro sugar 8 was highly reactive; its condensation with 1,2:3,4-di-O-isopropylidene-α-d-galactopyranose in the absence of any Lewis catalysts afforded disaccharide derivatives in a reasonable yield, and in the presence of molecular sieves gave a quantitative yield of disaccharides, in which α-linked disaccharide predominated.