Application of p.m.r. spectroscopy in the sequencing of oligosaccharides containing 1-carboxyethylidene substituents

1-Carboxyethylidene acetals (formed by pyruvic acid) are labile to acid. Consequently, when an aqueous solution of an acidic oligosaccharide is examined by p.m.r. spectroscopy at 95°, the acetal is progressively hydrolyzed. The spectrum then reflects the presence of two compounds, one with, and one without, an acetal substituent, and this causes certain signals to be twinned2 2 The word "twin" is deliberately chosen, in order to avoid confusion with "doublet". The character of each signal, i.e., singlet, doublet, multiplet, etc., is maintained, but is accompanied by a twin having a small difference in chemical shift.. The protons affected may be not only on the acetalated sugar unit but also on neighboring residues. Analysis of these spectral changes aids in the sequencing of the oligosaccharide. The potential of the method is illustrated by a study of the acetalated, acidic hexasaccharide obtained from the capsular polysaccharide of Klebsiella serotype K46 by action of φ46 bacteriophage endoglucanase. © 1984.