SYNTHESIS OF TRISACCHARIDE AND TETRASACCHARIDE HAPTENS RELATED TO THE ASIALO FORMS OF THE GANGLIOSIDES GM2 AND GM1

Synthesis of .beta.DGalNAc(1 .fwdarw. 4).beta.DGal(1 .fwdarw. 4).beta.DGlc-O(CH2)8COOCH3 (21) and .beta.DGal(1 .fwdarw. 3).beta.DGalNAc(1 .fwdarw. 4).beta.DGal(1 .fwdarw. 4).beta.DGlc-O(CH2)8COOCH3 (33) are presented starting from .beta.DGal(1 .fwdarw. 4).beta.DGlc-O(CH2)8COOCH3 (1) and D-galactose. Improvements in the preparations of D-galactal triacetate and tri-O-acetyl-2-azido-2-deoxy-.alpha.-D-galactopyranosyl bromide are reported. The syntheses proceeded by way of the tri-O-acetyl-2-deoxy-2-phthalimido-.beta.-D-galactopyranosyl and 4,6-di-O-acetyl-3-O-(tetra-O-acetyl-.beta.-D-galactopyranosyl)-2-deoxy-2-phthalimido-.beta.-D-galactopyranosyl bromides, which, in turn, were prepared from the corresponding allyl glycosides. The 13C chemical shifts for the tri- and tetrasaccharide portions of 21 and 33 are assigned from the chemical shifts that were observed for the C atoms in the disaccharides which make up these structures. The trisaccharide 21 only very weakly inhibited the agglutination of human A red cells by the lectin of Dolichos biflorus. The tetrasaccharide 33 was inactive.