Conformationally constrained compounds of structure: ##STR00001## which mimic the secondary structure of .beta.-strand regions of biologically active peptides and proteins are disclosed. Such .beta.-strand mimetic structures have utility over a wide range of fields, including use as diagnostic and therapeutic agents that inhibit protease, kinase and the like. Libraries containing the .beta.-strand mimetic structures of this invention are also disclosed as well as methods for screening the same to identify biologically active members.