An apparatus for safe and convenient handling of anhydrous, liquid hydrogen fluoride at controlled temperatures and reaction times. Application to the generation of oligosaccharides from polysaccharides

β-d-Gal-(1 → 4)-β-d-GlcNAc-OC₆H₄NO₂-p (p-nitrophenyl N-acetyl-β-lactosaminide) and β-d-Gal-(1 → 6)-β-d-GlcNAc-OC₆H₄NO₂-p (p-nitrophenyl N-acetyl-β-isolactosaminide) were regioselectively synthesized from lactose and p-nitrophenyl 2-acetamido-2-deoxy-glucopyranoside, employing transglycosylation by the β-d-galactosidase from Bacillus circulans and by controlling the concentration of organic solvent in the reaction system. The (1 → 4)-linked disaccharide was formed exclusively when the concentration of organic solvent was high, whereas the (1 → 6)-linked isomer was produced with a low concentration. Further utilization of the transglycosylation by the enzyme led to the regioselective formation of β-d-Gal-(1 → 4)-d-GalNAc and β-d-Gal-(1 → 4)-β-d-GalNAc-OC₆H₄NO₂-p. With the enzyme, β-d-galactosyl transfer occurred preferentially at the O-4 position of GlcNAc and GalNAc, regardless of the configuration of the hydroxyl group.