1-N-Iminosugars:  Potent and Selective Inhibitors of β-Glycosidases

A series of 1-N-iminosugars were synthesized to supply the need for glycosidase inhibitors that are both highly potent and selective for β-glycosidases. Designed on the basis of the transition-state model of the β-glucosidase reaction, these iminosugar inhibitors differ from the currently available inhibitors in possessing a nitrogen atom at the anomeric position of the pyranose ring, thereby generating a positive charge on the anomeric position rather than on the ring oxygen of the sugar. Their syntheses, starting with a readily available carbohydrate derivative, involve (i) introduction of an amino functionality as an azido group, (ii) formation of a 1-N-iminopyranose ring with reductive amination, and (iii) stereoselective introduction of a hydroxymethyl or methyl group and were accomplished in a highly stereoselective and efficient manner. The inhibitory potencies of the 1-N-iminosugars were evaluated against several α- and β-glycosidases, and they were found to be extremely potent and highly specific against the corresponding β-glycosidases, with Ki values in the nanomolar range.