(Chemical Equation Presented) Conformation analysis and synthesis of 2, a hydrolytically stable mimetic of the tumour antigen, GM3 lactone ganglioside (1 a), is reported (see figure for superimposed images of 1 a and 2). The interaction between 2 and wheat germ agglutinin lectin showed that 2 is a veritable mimetic of a sialyl-containing saccharide. DOPC/DOPE liposomes containing thioether 3 were also prepared and characterized; these could prove to be promising carriers for the production of monoclonal antibodies.