Electrochemical O-glycosylation of primary alcohols with O-protected thioglycosides was performed in the presence of a small amount of sodium trifluoromethansulfonate (12.5 mol % to glycosyl acceptor) as a supporting electrolyte. The reaction was successfully carried out in an undivided cell to give O-glycosides in good yields with a high electro-efficiency (ca. I F/mol) at 15 degrees C in acetonitrile. (C) 2007 Elsevier Ltd. All rights reserved.