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 beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)- [beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-beta -D- GlcOMe (1) was obtained on a 0.1-mmol scale by enzymic bigalactosylation of the tetrasaccharide beta-D-GlcpNAc-(1----3)-[beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-b eta- D-GlcOMe by the use of an immobilised multi-enzyme system which regenerated UDP-alpha-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 beta-D-GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-b eta- D-Galp-(1----4)-beta-D-GlcOMe.