Synthesis and Evaluation of N-Acetyl-2-amino-2-deoxy-alpha-D-galactosyl 1-Thio-7-oxaceramide, a New Analogue of alpha-D-Galactosyl Ceramide

The N-acetyl-2-amino-2-deoxy-alpha-D-galactopyranosyl 1-thio-7-oxaceramide 1 was synthesized by substituting the 7-oxasphingosine triflate 3 with alpha-D-N-acetyl-1-thiogalactosamine (2). The triflate 3 was obtained from azide 4. Thiol 2 was prepared according to a known procedure from alpha-D-galactosamine hydrochloride. As compared to ceramide (Cer), 1 is neither a substrate of ceramide kinase (CerK), consistent with the absence of the C(1)-OH group, nor an inhibitor of Cer phosphorylation by CerK. While 1 partially displaced CD1d-bound lipids, it failed to stimulate invariant natural killer T (iNKT) cells when presented by human CD1d-transfected cells. These results suggest that 1 binds weakly to recombinant CD1d, but does not form immunogenic complexes with CD1d.