RCAI-61 and related 6′-modified analogs of KRN7000: Their synthesis and bioactivity for mouse lymphocytes to produce interferon-γ in vivo

We synthesized ten new analogs of 6′-modified KRN7000 (A): RCAI-58, 61, 64, 83, 85-87, 113, 119, and 125. They could be synthesized by α-selective galactosylation of ceramide 9 with the 6-modified d-galactopyranosyl fluorides (8a-8f) or l-arabinopyranosyl fluoride (17), or by etherification of the known alcohol 19. Bioassay of the ten analogs demonstrated that RCAI-61 (1, 6′-O-methylated analog of A) was the most potent immunostimulant among them, and could induce the production of a large amount of IFN-γ even at a low concentration in mice in vivo.