Convenient synthesis of β-galactosyl nucleosides using the marine β-galactosidase from Aplysia fasciata

A convenient synthesis of β-galactosyl derivatives of antiviral and anticancer nucleosides, which utilizes the purified β-galactosidase activity from the hapatopancreas of Aplysia fasciata, is reported. All reactions were extremely stereo- and regioselective, since only anomerically pure 5′-O-β-galactosyl conjugates were formed. 5′-O-β-Galactosyl-5-fluorouridine was synthesized with a 60% yield and 5′-O-β-galactosyl-3′-azido-3′-deoxythymidine, the derivative of the anti-HIV drug, was obtained in 43% yield.