Compounds having the structural formula or a stereoisomer, tautomer, or pharmaceutically acceptable salt or solvate thereof, wherein R 1 ,R 3 and R 4 are variables defined in the specification. The compounds function as aspartyl protease inhibitors and are useful in the treatment of cardiovascular diseases, cognitive and neurodegenerative diseases, and as inhibitors of the Human Immunodeficiency Virus, plasmepsins, cathepsin D and protozoal enzymes.
