Synthetic applications of glucose isomerase: isomerisation of C-5-modified (2R,3R,4R)-configured hexoses into the corresponding 2-ketoses

Immobilised glucose isomerase (EC 5.3.1.5) accepted various (2R,3R,4R)-configured hexoses such as 5-deoxy-d-ribo-hexose, 5-azido-5-deoxy-d-allose, as well as the corresponding epimer at C-5, 5-azido-5-deoxy-l-talose, as substrates. From the resulting azidodeoxyketoses, 5-azido-5-deoxy-d-psico- and -l-tagatopyranose, the powerful d-galactosidase inhibitors 2,5-dideoxy-2,5-imino-d-galactitol and -d-altritol were obtained in one additional step.