Contribution of the reaction pathways involved in the isomerization of monosaccharides by alkali

✍ Scribed by Hassan S. El Khadem; Sofiane Ennifar; Horace S. Isbell

• Book ID: 102992363
• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 572 KB
• Volume: 169
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(87)80238-0

✦ Synopsis

The isomerization of eight hexoses and four pentoses, in aqueous KOH at pH 11.5 under nitrogen, was monitored by l.c. on cation (Pb2+)-exchange and reverse-phase columns. The primary epimerization reaction of pentoses and hexoses accounts for -90% of the saccharides found in solution after one week. The remaining saccharides were formed in part by fragmentation and recombination. This is indicated by the formation of hexoses (glucose and sorbose) during the isomerization of pentoses, and by the simultaneous formation of 3-and 4-epimeric hexuloses from hexoses. The aldol reaction responsible for the formation of hexoses (glucose, fructose, and sorbose) from glyceraldehyde at pH 11.5 was found to be fast (t,, = 2 h), which accounts for the rapid fragmentation and recombination observed.