Total Synthesis of Sialyl Inositol Phosphosphingolipids CJP-2, CJP-3, and CJP-4 Isolated from Feather Star Comanthus japonica

The first total synthesis of three echinodermatous sialyl inositol phosphosphingolipids, which exhibit unusual neuritogenic activity in the absence of nerve growth factor, are reported. Highlights of the syntheses include 9-O-methylation on sialic acid, inter-residual amide bond formation between sialic acid residues, and highly stereo- and regioselective sialylation of inositol. A key phosphodiester linkage between the mono-, di-, and trisialyl inositols and ceramide was formed at a late state employing the phosphoramidite method.