Azido glycoside primer: a versatile building block for the biocombinatorial synthesis of glycosphingolipid analogues

A lactoside primer, 12-azidododecyl beta -lactoside, was synthesized via the Koenigs-Knorr method by glycosylation of 1,12-dodecyldiol with perbenzoylated lactosyl bromide. The presence of the 2-O-acyl substituent in the donor gave the beta -lactoside, and an excess of acceptor ensured monoglycosylation of the diol. Mesylation of the omega -hydroxyl group in the aglycon, followed by displacement of the mesylate with azide and subsequent O-debenzoylation gave the desired omega -azidododecyl beta -lactoside. The azido glycoside primer was examined in mouse B16 melanoma cells for its feasibility as a building block for oligosaccharide biosynthesis. Uptake of the azido glycoside primer by B16 cells resulted in the sialylation of the galactose residue of the primer to give a glycosylated product having the same glycan as in ganglioside GM3. After 24 h incubation of B16 cells with the primers, the amount of sialylated omega -azidododecyl beta -lactoside primer was 75% of the amount of sialylated n-dodecyl beta -lactoside. However, after 48 h incubation, both primers gave equal amounts of the sialylated products. Interestingly, the remaining azido glycoside primer after 48 h incubation was 5.6-fold greater than that of the alkyl primer, indicating degradation of the alkyl primer to a larger extent than the omega -azido glycoside primer. The facile chemical synthesis and the efficient uptake in cells make the azido glycoside primer a versatile building block for the biocombinatorial synthesis of glycolipid oligosaccharides. (C) 2000 Elsevier Science Ltd. All rights reserved.