Notes on improved procedures for the chemical modification and degradation of glycosphingolipids

Some simplified and efficient procedures are described for the following chemical modifications of glycophingolipids. 1) The olefinic bond of the ceramide moiety of the acetylated glycolipid was quantitatively oxidized with osmium tetroxide and periodic acid. Treatment of the resulting glycolipid aldehyde with sodium methodixe resulted in the release of the intact oligosaccharide. The yield of oligosaccharides under the new conditions was much higher than previously found. 2) The olefinic bond was also oxidized to a carboxyl function by either of two methods: a) the aldehyde group resulting from the above oxidation was further oxidized with performic acid; and b) the olefinic bond of the fully acetylated glycolipid was oxidized directly to the acid by potassium permanganate in acetone. 3) The methyl ester of the carboxyl group of the sialic acid in gangliosides can be formed with diazomethane in methanol-ether after treatment of the gangliosides with Dowex-50 (H+ form). Possible uses of these glycolipid modifications are discussed.