Tandem Exploitation of Helix pomatia Glycosyltransferases: Facile Syntheses of H‐Antigen‐Bearing Oligosaccharides

Snails from the family Helicidae produce in their albumen glands a highly branched galactan, which consists almost exclusively of D ‐ and L ‐galactose. The D ‐Gal residues are glycosydically β(1→6)‐ or β(1→3)‐linked, whereas the L ‐Gal moieties are attached α(1→2). Up until the present time, two β(1→6)‐ D ‐galactosyl transferases and one α(1→2)‐ L ‐galactosyl transferase have been identified in a membrane preparation of these glands. These were used to synthesise various oligosaccharides by successive addition of the NDP‐activated (NDP=nucleoside‐5′‐diphosphate) D ‐Gal or L ‐Fuc moieties, up to a heptasaccharide by starting from the disaccharide D ‐Gal‐β(1→3)‐ D ‐Gal‐β(1→OMe. Even larger oligosaccharides up to a tridecasaccharide were obtained by starting with the hexasaccharide D ‐Gal‐[β(1→3)‐ D ‐Gal] 4 ‐β(1→4)‐ D ‐Glc as an acceptor substrate. This tandem exploitation process has high potential for the easy introduction of D ‐Gal and L ‐Fuc residues into a great variety of oligosaccharides, which can be used in ligand/acceptor studies.