Convenient synthesis of mixed S–Se-linked pseudodisaccharides by sulfur and selenium exchange

A one-pot reaction methodology has been developed for the preparation of mixed S–Se-linked pseudodisaccharides by the treatment of glycosyl halides with a combination sodium sulfide nonahydrate (Na2S⋅9H2O) and carbon disulfide (CS2) in the presence of alkyl and glycosyl diselenides. The reaction condition is fast, odourless, high yielding and suitable for scale-up synthesis. Exclusive formation of anomerically beta-linked products was obtained from anomeric glycosyl bromides.