The Total Synthesis of Immunostimulant α-Galactosylceramides from Naturally Configured α-Galactoside Raffinose

The total synthesis of absolute anomeric confirmation α-galactosylceramide analogues from raffinose is described. Using the naturally occurring α-galactoside raffinose as the starting material, the easily maneuverable protocol without glycosylation reactions ensured the critical α-linkage in the product and simplified the synthetic procedures. The immunostimulatory activities of the new α-galactosylceramides were validated by both <i>in vitro</i> and <i>in vivo</i> NKT cell stimulation assays.