Concise syntheses of immunostimulating glycolipids, α-galactosyl ceramides

Structure-activity relationship studies of novel glycosphingolipids that stimulate natural killer T-cells

KRN7000, an anticancer drug candidate developed by Kirin Brewery Co. in 1995, is an α-galactosyl ceramide. It is a ligand making a complex with CD1d protein, and it stimulates invariant natural killer T (NKT) cells, which are one of the lineages of immunocytes. NKT cells activated by recognition of the CD1d/KRN7000 complex with its invariant T-cell receptor (TCR) can induce both protective and regulatory immune responses. To determine the recognition and activation mechanisms of NKT cells and to develop drug candidates more effective than KRN7000, a large number of analogs of KRN7000 have been synthesized. Some of them show potent bioactivities and have the potential of being utilized as therapeutic agents. In this review, structure-activity relationship studies of novel glycolipids which stimulate NKT cells efficiently are summarized.

Catalytic stereoselective glycosidation with glycosyl diphenyl phosphates: rapid construction of 1,2-cis-alpha-glycosidic linkages

A commercially available 0.1 M solution of HClO(4) in dioxane has been shown to catalyze the glycosidation of glycosyl diphenyl phosphates. The per-O-benzyl-protected glucosyl and galactosyl donors and the 3,4,6-tri-O-acetyl-2-azido-2-deoxygalactosyl donor each react with a range of acceptor alcohols in the presence of 0.05-0.2 equiv of HClO(4) in dioxane/Et(2)O (1:1) to afford glycosides in good yields with good to excellent alpha selectivities. The synthetic utility of this glycosidation method was demonstrated by a stereoselective synthesis of the alpha-galactosylceramide KRN7000, an activator of natural killer (NK) T cells through CD1d molecules.