Myrmekioside A, which was isolated from the marine sponge Myrmekioderma sp. as a member of the family of natural mono-O-alkyl-diglycosylglycerols, and which has a strong reversion effect on the tumor cell morphology of ras-transformed cells at 5 μg/mL, was synthesized for the first time in 17 steps and 14 % overall yield. The β-glycosidic linkages in myrmekioside A were successfully constructed by the neighbouring-group-participation approach using trichloroacetimidates and thioglycosides as glycosyl donors. The 2R absolute configuration at C-2 of the glycerol backbone was derived from (S)-1,2-isopropylideneglycerol (8). This synthetic approach may be applicable to the preparation of other myrmekioside analogues featuring different sugars and alkyl chains for further structure–activity relationship studies.

A highly efficient and practical total synthesis of the sulfated ganglioside SM1a, a kind of human epithelial carcinoma antigen identified in mammalian kidney, has been accomplished for the first time. The characteristic sequence of SM1a, β-D-Galp-(13)-β-D-NHAcGalp-(14)-β-D-(3-O-sulfate)-Galp-(14)-β-D-Glcp-ceramide was assembled by a [3+2] convergent approach. A key trisaccharide building block was formed from a new galactose acceptor 7 containing a potential sulfated site, GalNHTroc donor 6, and galactose donor 4. The cyclic glucosyl ceramide was glycosylated with trisaccharide trichloroacetimidate 2 to give the protected ganglioside backbone in good yield. Selective sulfonation at the 3-OH of the Gal residue followed by global deprotection gave the target molecule SM1a.