The invention comprises compounds for selectively inhibiting glycosidases, prodrugs of the compounds, and pharmaceutical compositions containing the compounds or prodrugs of the compounds. The invention also comprises animal models and methods of making the animal models for studying diseases and disorders related to deficiency or overexpression of O-GIcNAcase, accumulation or deficiency of O-GIcNAc, and treatment of such diseases and disorders. The invention also comprises methods of treating such diseases and disorders. The invention also comprises methods of making the compounds, and methods of making selective glycosidase inhibitors.