Glycoconjugates: Design and syntheses of multivalent T-antigen tumor markers.
Creators: name: Baek, Myung-Gi.
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 1998
Subjects: subject: Biology, Cell.

description: The Thomsen-Friedenreich (TF or T) antigen has been known as a carbohydrate disaccharide, Gal-$\beta$-D-(1-3)-$\alpha$-D-GalNAc $\alpha$-linked to serine or threonine in glycoprotein and other mucins. It is widely distributed on common cancers of epithelial cells including breast cancers. Due to difficulties in isolating them from natural sources, various synthetic methods were developed to achieve the synthesis of multivalent carbohydrate haptens in different forms varying in carbohydrate densities, conformations, and interglycosidic distances. The synthesis of the T-antigen and its derivatives and modification of its aglycons having and give different terminal functional groups is described herein. Several glycosyl acceptors were synthesized and subsequent glycosylations were performed with glycosyl donors using TfOMe, TfOAg/2,4,6-collidine, NIS/TfOH, or Hg(CN$\sb2$) as promoters to give $\beta$-(1-3) linked disaccharides. The aglycon was modified to give sulfide bridged spacer arms containing end groups such as alcohol, amine, carboxylic acid, and thiol. Hydroformylation of allyl glycoside using rhodium catalyst afforded linear and branched aldehydes. The synthesis of convergent dendrimers with valencies of between two and six T-antigen residues is described. The synthesis of dendritic cores was based on peptide coupling between N,N$\sp\prime$-bis(acrylamido)acetic acid as a seed molecule and hexamethylene diamine or tris(2-aminoethyl)amine using HOBt/EDC strategy to give tetra- and hexa-valent structures. Conjugate addition of thiolated T-antigen to acrylamido functionality on the seed molecule gave divalent T-antigen in quantitative yield. Tetra- and hexa-valent glycodendrimers bearing T-antigen were prepared by two different methods. First, thiolated T-antigen was added to the acrylamido functions of the dendritic cores. In addition, divalent T-antigen-bearing terminal carboxylic acid was coupled to polyamines using carbodiimide chemistry. N-substituted glycosyl acrylamides were used as monomers to prepare neoglycoproteins and multivalent synthetic polyacrylamide based glycopolymers. Neoglycoproteins were synthesized by coupling N-acryloylated T-antigen residues onto proteins by conjugate addition. This methodology is simple, efficient and requires no additional reagents. Copolyacrylamide were prepared by two strategies. N-acryloylated carbohydrate and acrylamide were copolymerized using ammonium persulfate in aqueous conditions. Alternatively, preactivated poly(N-acryloxysuccinimide) and its analogues containing active esters were prepared. Graff conjugation of monomeric units bearing amino functional group such as carbohydrate hapten, NH$\sb4$OH, and alkyl amines was performed. Binding assays were performed using double radial immunodiffusion and turbidimetric analysis to confirm the ability of the glycoconjugates to bind to protein such as Arachis Hypogaea from peanut lectin. In addition, competitive enzyme linked immunoassays were performed with monoclonal mouse IgG and peroxidase labeled goat anti-mouse IgG conjugates and all glycoconjugates showed enhanced inhibitory potentials. (Abstract shortened by UMI.)