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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.

International audience; The transglycosylation from raffinose and lactose to Aloc-Ser-OMe is catalyzed respectively by alpha and beta galactosidases. Transglycosylation from cellobiose has been achieved with beta-glucosidase. The simplicity of the enzymatic synthesis, the stereospecificity of the condensations in one-pot reactions and the ease of purification give the method value for large scale preparation of beta-linked derivatives. The protective groups of the serine residue can be cleaved under mild conditions: the ester group has been removed quantitatively by papain catalyzed hydrolysis and the Aloc group by a Pd (0) hydrostannolytic cleavage.