Synthesis of alpha- and beta-biotinylated T-antigen

The T-antigen [beta-D-Gal-(1-->3)-D-Ga1NAc] has been linked to biotin through a C6 spacer arm for the detection of a specific 'T-antigen-lectin' complex at the surface and/or on the migration pathway of melanoma cells. When 4,6-di-O-acetyl-2-azido-2-deoxy-3-O-(2,3,4, 6-tetra-O-acetyl-beta-D-galactopyranosyl)-alpha- or -beta-D-galactopyranosyl halides were treated with N-benzyloxycarbonyl or N-fluorenylmethoxycarbonyl protected aminohexanols (used as the spacer arm), unusual stereoselectivities were observed for the synthesis of the alpha and beta anomers. The synthesis of the alpha anomer could only be achieved, in reasonable yields, with the Schiff base of aminohexanol.