The use of an immobilised cyclic multi-enzyme system to synthesise branched penta- and hexa-saccharides associated with blood-group I epitopes

The branched hexasaccharide β- d-Gal p-(1→4)-β- d-Glc pNAc-(1→3)-[β- d-Gal p-(1→4)-β- d-Glc pNAc-(1→6)]- β- d-Gal p-(1→4)-β- d-GlcOMe ( 1 was obtained on a 0.1-mmol scale by enzymic bigalactosylation of the tetrasaccharide β- d-Glc pNAc-(1→3)-[β]- d-Glc pNAc-(1→6)]-β- d-Gal p-(1→4)-β- d-GlcOMe by the use of an immobilised multi-enzyme system which regenerated UDP-α- d-galactose in situ. The formation of 1 proceeded in two steps. An intermediate compound was identified on the basis of 1H- and 13C-n.m.r. data as the pentasaccharide β- d-Glc pNAc-(1→3)-[β- d-Gal p-(1→4)-β- d-Glc pNAc-(1→6)]-β- d-Gal d- (1→4)-β- d-GlcOMe.