The invention provides compounds of formula (I) ##STR00001## 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; and use thereof in the treatment of, inter alia, conditions, diseases, and symptoms such as diabetes, dementia, Alzheimer's Disease, stroke, schizophrenia, depression, hair loss, and cancer.