Synthesis of 6"-triazole-substituted α-GalCer analogues as potent iNKT cell stimulating ligands

We report the synthesis of a small series of 6"-triazol-1-yl-substituted α-GalCer analogues by late-stage conversion of the 6"-OH to an azide group, copper-catalyzed azide-alkyne cycloaddition and final deprotection. When evaluated for their capacity to induce IL-2 secretion in vitro, all compounds proved equally potent or superior to α-GalCer. The S.A.R suggests that the improved antigenic activity is mainly triggered by the triazole functionalization in se. While the introduction of selected substitutuents at C-4 of this heterocyclic ring is tolerated, this generally fails to further improve antigenicity.