ANALYSIS OF OLIGOSACCHARIDES CONTAINING 2-DEOXY-ALPHA-ARABINO-HEXOSYLRESIDUES BY THE REDUCTIVE-CLEAVAGE METHOD

A mixture of oligosaccharides containing (1 --> 4)-linked 2-deoxy-alph a-D-arabino-hexosyl (''2-deoxyglucosyl'') and (1 --> 4)-linked alpha-D -glucosyl residues (1) was analyzed by reduction, permethylation (pere thylation), degradation to monomers, and GLC-MS. Degradation was perfo rmed either by hydrolysis with subsequent reduction, by methanolysis, or by reductive cleavage, always followed by acetylation. Reductive cl eavage turned out to be the method of choice for the acid-labile 2-deo xy sugars. The main degradation product formed during acid hydrolysis of 2-deoxy-D-arabino-hexosyl residues yielded, after reduction and ace tylation, (4R,S)-6-O-acetyl-2,3,5-trideoxyhexono-1,4-lactone (7). By m ethanolysis, in addition to the expected methyl glycosides, methyl 2,3 ,5-trideoxy-6-O-methyl-4-hexulosonate (12) is formed as a by-product. For determination of the distribution of chain lengths, the permethyla ted oligomers were separated by reversed-phase HPLC. For peak assignme nt, one isolated oligomer was investigated by FABMS and H-1 NMR spectr oscopy. The average degree of polymerization (dp) calculated from the HPLC chromatogram is in good agreement with the reductive-cleavage res ults.