Iodine promoted glycosylation with glycosyl iodides:: α-glycoside synthesis

Glycosidation of fully acetylated glucopyranosyl iodide with methanol under the influence of iodine gave a-glucoside selectively. Use of less reactive acceptors led to the formation of alpha/beta-mixtures. Glycosylations with fully benzoylated glucosyl iodide yielded beta-glucosides only. In contrast, iodine-promoted glycosylation of serine and threonine with 2-azido-2-deoxy-glycosyl iodides, easily obtained in three steps, proceeded smoothly, resulting in only alpha-linked products in high yield in most cases.