Adaptation of Zemplen's conditions for a simple and highly selective approach to methyl 1,2-trans glycosides

1,2-trans methyl glycosides can be readily obtained from peracetylated sugars through their initial conversion into glycosyl iodide donors and subsequent exposure of these latter to a slight excess of sodium methoxide in methanol. Under these conditions a varied set of mono- and disaccharide precursors afforded the corresponding 1,2-trans glycosides with concomitant de-O-acetylation in satisfying yields (in the range 59-81%). A similar approach also proved effective when using GlcNAc glycosyl chloride as the donor.