Quinoxaline derivatives derived from isomaltooligosaccharides with o-phenylenediamine under deoxygenated and heated alkaline conditions.

Abstract

Quinoxaline derivatives derived from isomaltooligosaccharides and o-phenylenediamine (OPD) were studied by ion-exchange chromatography. Under deoxygenated and heated alkaline conditions, the formation of quinoxaline from α-1,6-glucan with OPD proceeded from the reducing-end glucose residue in a complicated way, and the mechanism mainly involved the following processes: 1) formation of quinoxaline derivatives of high molecular weight as a condensation with OPD and 1,2-dicarbonyl compounds at the reducing-end residue of the glucan. 2) formation of several kinds of quinoxaline derivatives of low molecular weight from the reducing-end residue of 1,6-linked glucan as liberated glucose; as a consequence, the one glucose unit smaller 1,6-linked chain was liberated and again reacted with OPD. The rate of decomposition gradually decreased during the liberation of about 7 glucose residues from the reducing end. The characteristics and probable stoichiometry of this alkaline degradation of α-1,6-glucans are discusse...