CHARACTERIZATION OF HEMIACETAL BONDS FORMED AFTER PERIODATE-OXIDATION OF HETEROGLYCANS

The location of inter-residue, cyclic hemiacetals formed following the periodate oxidation of four representative heteroglycans has been determined by methylation analysis of the periodate-oxidized glycans. The cyclic hemiacetals led to the protection of hydroxyl groups during methylation in methyl sulfoxide, and their positions were located by analysis of the resulting di- and mono-methyl ethers. Such derivatives were not observed upon methylation analysis of the native and the periodate-oxidized-borohydride-reduced glycans. Inter-residue hemiacetals were thus identified in all oxidized glycans, between aldehydic groups at C-2 or C-3 of oxidized residues and hydroxyl groups at C-3 or C-2 of adjacent, unoxidized residues. Selective removal of 6-O-substituents from oxidized residues resulted in a decreased ability of the latter to form the inter-residue hemiacetals. Analysis of the types and proportions of the methyl ethers resulting from inter-residue hemiacetal formation may also yield structural information on the glycan. © 1979.