NOVEL GLYCOSYNTHONS FOR GLYCOCONJUGATE PREPARATION - OLIGOSACCHARYLPYROGLUTAMYLANILIDE DERIVATIVES

The reducing sugar of an oligosaccharide reacting with the a-amino gro up of an amino acid is converted to an N-oligosaccharylamino acid whic h can then be stabilized by N-acylation. Oligosaccharides in solution in N,N-dimethylformamide reacted with alpha-glutamyl-p-nitroanilide at 50 degrees C for a few hours, leading to an N-oligosaccharylglutamyl- p-nitroanilide. Then, the gamma-carboxylic group of the glutamyl moiet y, activated by adding enzotriazol-1-yloxy)tris(dimethylamino)phosphon ium hexafluorophosphate (BOP), reacted with the substituted alpha-amin o group of the glutamyl residue, leading to an N-oligosaccharylpyroglu tamyl-p-nitroanilide within 0.5 h. Such a one-pot two-step reaction wa s shown to be very efficient in the case of a disaccharide such as lac tose, or pentasaccharides such as lacto-N-fucopentaoses, Lewis(a) or L ewis(x). The glycosynthons were characterized by chromatography (HPAEC and HPLC); their molecular mass was determined by electrospray ioniza tion mass spectrometry, and the glycosylamides were shown to have a be ta-anomeric configuration on the basis of their proton NMR. The N-olig osaccharylpyroglutamyl-p-nitroanil are quite stable at room temperatur e over a large pH range. They are easily converted to ligosaccharylpyr oglutamyl-p-isothiocyanatoanilides which can be used to prepare glycoc onjugates such as cationic glycosylated polylysines suitable for speci fically delivering genes or oligonucleotides in a sugar-dependent mann er.