title: High-resolution proton NMR studies of gangliosides. III. Elucidation of the structure of ganglioside GM3 lactone.
abstract: Ganglioside GM3 lactone (1) was prepared in 95% yield from the parent ganglioside by incubation at 25 degrees C for 4 days in glacial acetic acid. Inspection of the 500 MHz proton NMR spectra of 1 and its precursor in dimethylsulfoxide-d6-deuterium oxide at 30 degrees C revealed a large deshielding (+1.42 ppm) of the H-2 resonance of the galactosyl residue. This suggests that 1 must be the lactone formed by esterification of the sialic acid carboxyl group with the C-2 hydroxyl of the galactosyl residue. Consideration of all the NMR data leads to a specific structure proposal in which 1 has a highly rigid structure. Interesting features of the structure include a hydrophobic inner surface and a semicircular outer edge of seven-oxygen atoms, which may have physiological importance.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002855:Chromatography, Thin Layer; D005679:G(M3) Ganglioside / Q000031:analogs & derivatives / Q000032:analysis*; D005732:Gangliosides / Q000032:analysis*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation
chemical_list: D005679:G(M3) Ganglioside; D005732:Gangliosides; C047143:ganglioside GM3 lactone