Synthesis of Uridine 5′-(α-D-Fucopyranosyl Diphosphate) and (Digitoxigenin-3β-yl)-β-D-Fucopyranoside and Enzymatic β-D-Fucosylation of Cardenolide Aglycones in Digitalis lanata1

The phosphorylation of 2,3,4-tri-O-acetyl-α-D-fucopyranose with o-phenylene phosphochloridate yielded α-D-fucopyranosyl phosphate which was used for condensation with uridine 5′-monophosphomorpholidate to give uridine 5′-(α-D-fucopyranosyl diphosphate) (UDP-α-D-fucose). A crude enzyme preparation from young leaves of Digitalis lanata EHRH has been shown to catalyze the transfer of D-fucose from synthetic UDP-α-D-fucose to cardenolide aglycones, such as digitoxigenin. The reaction product was identified and characterized by chemical synthesis, HPLC, and spectral methods as the 3 β-O-β-D-fucopyranoside of digitoxigenin (digiproside).