The present invention provides compounds of formula (I) the stereoisomers and prodrugs thereof, and the pharmaceutically acceptable salts of the compounds, stereoisomers, and prodrugs, wherein R.sup.1, R.sup.2, and R.sup.3 are as defined herein; pharmaceutical compositions thereof; combinations thereof; and uses thereof in the treatment of, inter alia, conditions, diseases, and symptoms including, inter alia, Alzheimer's Disease, cancer, dementia, depression, diabetes, hair loss, schizophrenia, and stroke.