A novel strategy for unambiguous determination of inner esterification sites of ganglioside lactones

A method is described which is suitable for protection of all free hydroxyl groups of a glycosphingolipid under conditions which will not cleave ester linkages, including inner ester linkages characteristic of ganglioside lactones. The protecting methoxyethoxymethyl group is stable in alkaline media, surviving permethylation procedures which introduce a methyl ether at all sites previously acylated. Hydrolysis, reduction, and acetylation then yield alditol acetate derivatives which can be analyzed by conventional GC-MS to locate the methyl ether groups. The method is used to locate the inner esterification site of GM3 lactone.