Quinoxalines Derived from Disaccharides withO-Phenylenediamine under Weakly Acidic Reflux Conditions

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Abstract
Quinoxaline derivatives from disaccharides (isomaltose, maltose, laminaribiose, trehalose and sucrose) and o-phenylenediamine (OPD) under weakly acidic reflux conditions were subjected to GLC and GC-MS analyses. Three high-molecular-weight quinoxaline derivatives (IA-I, -II and -III) were obtained from isomaltose in a yield of 90%, indicating no splitting of the glucosidic linkages. Both low- and high-molecular-weight quinoxaline derivatives were obtained from 5 mm maltose. From 50 mm maltose, a low-molecular-weight quinoxaline, GA-I, was obtained predominantly. Quinoxalines from laminaribiose were both high (LA-I and -II) and low (ATBQ, GA-I, G-l and GA-II) molecular-weight derivatives, in yields of 18% and 48%, respectively. LA-I and -II were stereoisomers, at the C-3 position, of laminaribiose. Trehalose gave no quinoxalines, and sucrose gave only small amounts of low-molecular-weight quinoxalines. From these results, we found that 1,6-linkages of the disaccharides used are most resistant to the OPD degradation, followed by the 1,4- and 1,3-linkages, in that order. Possible pathways for the formation of quinoxalines are proposed.