Regioselective syntheses of new tri- and tetrasaccharides from β-glucobioses by Trichoderma viride β-glucosidase and their structural analyses by NMR spectroscopy

A new β-glucosidase was partially purified from Trichoderma viride cellulase complex. This β-glucosidase hydrolyzed β-(1→2)-, β-(1→3)-, β-(1→4)-, and β-(1→6)-linked glucobioses and catalyzed a transglycosylation reaction of cellobiose to give regioselectively β-d-Glc-(1→6)-β-d-Glc-(1→4)-d-Glc (yield: 18.8%) and β-d-Glc-(1→6)-β-d-Glc-(1→6)-β-d-Glc-(1→4)-d-Glc (3.7%). Furthermore, the enzyme converted laminarabiose and gentiobiose into β-d-Glc-(1→6)-β-d-Glc-(1→3)-d-Glc (15.3%) and β-d-Glc-(1→6)-β-d-Glc-(1→6)-d-Glc (20.2%), respectively. The structures of the products were determined by 1H and 13C NMR spectroscopy. This high regio- and stereoselectivity demonstrated by the enzyme could be applied for oligosaccharide synthesis in general.