Title: Analysis of anomeric configurations in glyceroglycolipids and glycosphingolipids by chromium trioxide oxidation
Abstract:Acetylation and CrO3 oxidation in acetic acid (Angyal and James, Aust./.Chern.23: [1209][1210][1211][1212][1213][1214][1215][1216][1217][1218][1219][1220][1221] 1970) was applied to 18 different glyce...Acetylation and CrO3 oxidation in acetic acid (Angyal and James, Aust./.Chern.23: [1209][1210][1211][1212][1213][1214][1215][1216][1217][1218][1219][1220][1221] 1970) was applied to 18 different glyceroglycolipids and glycosphingolipids of known structure.The lipids studied contained from one to five pyranosic monosaccharide units including a-and 8-linked glucose, galactose, mannose, and N-acetylgalactosamine and 8linked N-acetylglucosamine. Monosaccharides bound to the lipids through &glycosidic linkages reacted to the extent of 80-9770, but in the case of a-glycosidic linkages the oxidation proceeded only to the extent of 0-676.A partial reaction was ob- served in lipids in which a given monosaccharide unit was present in both anomeric forms.Therefore, oxidation with CrOs allows the determination of anomeric configurations in simple glycolipids.Samples of only 100-300 r g are required.Treatment with CrO3 in acetic acid oxidizes acetylated hexopyranosides, in which the aglycone occupies an equatorial position, giving acetylated 5-hexulosonates (1) (Fig. 1).The corresponding anomers in which the aglycone occupies an axial position are oxidized only very slowly.Thus, the &glycosidic hexopyranoside units of natural glycolipids should be oxidized, whereas the corresponding a-glycosidic units should not.The possibility of using this difference in the analysis of anomeric configurations of natural lipids has been studied by Hoffman, Lindberg, and Svensson (2), who analyzed a bacterial lipopolysaccharide, and by Laine and Renkonen (3), who studied some mannose-containing sphingolipids.The present report shows that the C r 0 3 treatment oxidizes almost completely all @-glycosidically linked glucose, galactose, mannose, N-acetylglucosamine, and N-acetylgalactosamine units in simple glycero-and sphingolipids, whereas the a-glycosidically linked monosaccharide units appear to resist the oxidation. MATERIALS AND METHODSThe pure glycolipids studied are listed in Table 1.CrO3 oxidation of acetylated glyceroglycolipids was car-Read More