Novel di- O-acetylated GM3s from equine erythrocytes, one containing 4,9-di- O-acetyl- N-glycolylneuraminic acid and another containing 4- O-acetyl- N-glycolylneuraminic acid and [formula omitted

Abstract

A novel GM3 O-acetylated at C-4 and at C-9 of N-glycolylneuraminic acid (4,9-di- O-Ac GM3), together with a second GM3 O-acetylated at O-4 of the neuraminic acid and O-6 of d-galactose (4,6′-di- O-Ac GM3) were isolated from equine erythrocytes as a mixture in approximate 1:1 ratio. These two major species were chromatographically inseparable. Their structures, especially the positions of the acetoxy group(s), were determined by means of 1D- and 2D- 1H NMR and fast atom bombardment-MS as well as by gas chromatography-MS of partially O-methylated O-trimethylsilylated monosaccharides derived from the di- O-Ac GM3s. In addition, 4- O-Ac GM3 was chemically mono- O-acetylated with trimethyl orthoacetate under acidic conditions, giving exclusively 4,9-di- O-Ac GM3, the NMR and mass spectra of which were used as references to confirm the 4,9-di- O-acetylated structure of the naturally-occurring GM3.