The enzymatic transglycosylation of biologically active compounds-mainly vitamins, nucleosides, sugar alcohols and some alvcosides-is described . A highly purified dextransucrase, from Streptococcus bovis catalyzed the transglucosylation reaction from sucrose to acceptors such as riboflavin, maltooligosaccharides and hydrogenated maltooligosaccharides. A crystalline a-glucosidase, from Mucor javanicus, exhibiting high riboflavin-a-glucoside-synthesizing activity also glucosylated various sugar alcohols and sucrose through the transfer of glucosyl residues from soluble starch, resulting 1-O-(α-glucosyl)-ribitol and 6G-a-glucosyl-sucrose were isolated in crystalline and white powder forms . respectively. Two O-glycosylpyridoxines (4'- and 5'-) were formed when disaccharides and pyridoxine were incubated with various glycosidases. Moreover, O-β-glucosylpyridoxines were accumulated in germinating seeds of various plants cultured on a pyridoxine solution and in plant calluses and cells grown on sucrose media containing pyridoxine . The formation of O-β-galactosylpyridoxines and fructosylpyridoxine was observed in the cultured broth of Sporobolomyces and Aspergillus grown on media containing pyridoxine and lactose (and sucrose), respectively, nearly 90% conversion of pyridoxine into, β-galactosylpyridoxine being observed . A new derivative of L-ascorbic acid, 5-O- (α-glucosyl) -L-ascorbic acid, was synthesized from maltose and L-ascorbic acid by the Asp . niger a-glucosidase. The yield of a-glucosyl-L-ascorbic acid from L-ascorbic acid was about 50%. New derivatives of nucleosides, a series of 3'- and 5'-glycosylnucleosides, were isolated in crystalline forms from incubation mixtures containing glycosyl donors, nucleosides (adenosine, i nosine and uridine) and various glycosidases . We found that Sporobolomyces yielded large amounts of the l-galactosides of 5-bromouridine and arabinosylcytosine in lactose cultures with these nucleosides. Some glycosides, such as rutin and esculin, functioned as acceptors for a-glucosyl residues of maltose in the presence of the a-glucosidases from Ms javanicus and pig liver. 3'-O-(a-glucosyl)- esculin and 4'-O-(a-glucosyl)-esculin were isolated in crystalline forms . The above-mentioned glycosylated compounds have advantages over the original compounds in their solubility in water, stability as to UV light, heat and air oxidation, reduction of a bitter taste, and resistance to enzymatic action.