Formation of dimethyl acetals of d-glucose, d-xylose, and l-idose in the presence of strontium ions

The dimethyl acetals of d -glucose, d -xylose, and l -idose were prepared in 15–25% yield by Fischer glycosidation in the presence of strontium or calcium chloride, whereas no dimethyl acetal was isolated in the absence of these cations. Complexing of these dimethyl acetals with cations was indicated by n.m.r. spectra and by electrophoresis. From the reaction of l -idose, the two (previously unknown) methyl l -idofuranosides were isolated.