Natural occurrence and preparation of O-acylated 2,3-unsaturated sialic acids.

Three O-acylated, unsaturated sialic acids, N-acetyl-9-O-acetyl-, N-acetyl-9-O-lactoyl-, and 2-deoxy-N-glycoloyl-9-O-lactoyl-2,3-didehydroneuraminic acid (5-acetamido-9-O-acetyl-, 5-acetamido-9-O-lactoyl-, and 2,6-anhydro-3,5-dideoxy-5-glycoloylamido-9-O-lactoyl-D-glycero-D-g alacto-non-2- enonic acid) were isolated from urine or submandibular glands of rat, pig, and cow. Mass spectrometric evidence for the existence of 2,3-unsaturated 9-O-acetyl-N-glycoloylneuraminic acid in porcine urine was also obtained. The sialic acids were purified by dialysis, gel- and ion-exchange chromatography, and preparative thin-layer chromatography. They were analyzed by thin-layer chromatography, high-pressure liquid chromatography, and capillary gas-liquid chromatography-mass spectrometry. For comparison, O-acetylated unsaturated sialic acids were synthesized.