The synthetic potential of Almond beta-glucosidase and Jack bean alpha-mannosidase in the presence of high amounts of beta-mercaptoethanol as glycosyl acceptor for the synthesis of beta-mercaptoethyl-glycosides was studied. The regioselectivity, O-glycosylation and/or S-glycosylation, and the stereoselectivity were analyzed with the reverse hydrolysis and the transglycosylation methods. With both enzymes, high yields of condensation are obtained without the use of chemical protective groups.