Synthesis of α- and β-biotinylated T-antigen

The T-antigen [β-d-Gal-(1 → 3)-d-GalNAc] 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-β-d-galactopyranosyl)-α- or -β-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 α and β anomers. The synthesis of the α anomer could only be achieved, in reasonable yields, with the Schiff base of aminohexanol.