Synthesis of oligosaccharides by cycloaddition. Part II. Free and protected O-hexopyranosyl-(1 → 3)-D-glucoses with the α-D-allo-, α-D-altro-, α-L-altro-, β-L-altro-, and α-D-galacto-configurations
Abstract
O-α-D-Altropyranosyl-(1 → 3)-D-glucose (8), O-α-L-altropyranosyl-(1 → 3)-D-glucose, and O-β-L-altro-pyranosyl-(1 → 3)-D-glucose have been prepared from the products of cycloaddition of butyl glyoxylate to 3-O(buta-1,3-dienyl)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose. Configurational inversion in one step allowed the preparation of O-α-D-galactopyranosyl-(1 → 3)-D-glucose (27) and O-α-D-allopyranosyl-(1 → 3)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (26).