Two Positional Isomers of Sialylheptasaccharides Isolated from the Urine of a Patient with Sialidosis

We describe the structures of two positional isomers of sialylheptasaccharide iso-lated from the urine of a patient with sialidosis with partial deficiency of /3-galacto-sidase. Based on structural studies including compositional sugar analysis, exogly-cosidase digestion, chemical ionization mass spectrometry, proton nuclear magnetic resonance spectrometry, and methylation analysis, their structures were deduced to be as follows: 1. AcNeua2->6Gal/31->4GlcNac/?l->2Manal—3(Manal- » 6)Man/51 —4GIcNac 2. AcNeua2->6Gal/91-»4GlcNac/?l->2Manal-»6(Manal->3)Man/31-»4GlcNac Sialyloligosaccharide 1 has previously been found in the urine and liver of patients with mucolipidosis I and II and sialidosis, but sialyloligosaccharide 2 has not been found yet in human urine. These two sialyloligosaccharides could not be com-pletely separated by any chromatographic procedures tested. The analytical tech-niques, including methylation study and NMR spectroscopy, could not clearly detect the differences between them. However, a-mannosidase treatment gave important information for the structural analyses of these sialyloligosaccharides