Synthesis of spacer-arm, lipid, and ethyl glycosides of the terminal trisaccharide [alpha-D-Gal-(1----4)-beta-D-Gal-(1----4)-beta-D-GlcNAc] portion of the blood-group P1 antigen: preparation of neoglycoproteins.

The title compounds were prepared via the acetylated 2-bromoethyl beta-glycoside (5) of alpha-D-Gal-(1----4)-beta-D-Gal-(1----4)-beta-D-GlcNAc by displacement of bromide ion with methyl 3-mercaptopropionate, octadecanethiol, and hydrogen, respectively. Silver triflate-promoted glycosylation of 2-bromoethyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranoside with 2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl) -alpha-D-galactopyranosyl bromide gave 5. The spacer-arm glycoside derived from methyl 3-mercaptopropionate was coupled to bovine serum albumin and key-hole limpet haemocyanin to give neoglycoproteins.